Title of Invention

A DEVICE FOR COOKING/EXTRUSION OF FOODS/FOOD MATERIALS USING STEAM

Abstract

A device for canying out cooking and/or extrusion of food materials using stCaJn comprises a steam piston and cylinder arrangement wherein said material is placed in an annular cl1amber locatcd between said cylinder, the pistorirod and a step(shoulder) provided thereon. Said arrangement is located in a housing that is connectible to a stearn source or itself constitutes said source. In onc embodiment, t.Jle dcvice is a pressure cooker \vith said arrangement provided in the lid tllcrcof. Such a lid usable with an existing pressure cooker vessel constirutes anothcr embodiment. Material cxtrudcd from tlle top of said chaJnber collects in a removable annular bowl located on said lid. Cooking is by both indirect stcam and by direct steam injected into said cl1amber tllrough said rod the vent at tllC top of which is closed'hcn build-up of steam pressure is required for extrusion Various altcmvc constructions arc described.

Full Text

This invention relates to a device for cooking and/or extrusion of foods and food materials using steam In this specification, unless the context requires otherwise, the term food is used to refer to food materials that are substantially ready for consumption while the term "food materials" is used to refer to materials that are not so ready, such as for example, the starting materials of food processes or materials that are the intermediate products thereof In the claims hereinbelow, the term "foods" is used to cover both said foods and food materials discussed hereinabove. This is in the interests of conciseness. In this specification, the terms "lid" and "cover" in reference to a pressure cooker are used interchangeably. The starting point in many food processes is a paste, dough or batter. TTie device of the invention is adapted to process any of the three, namely pastes, doughs and batters. In this specification, therefore said three terms, pastes, doughs and batters are used interchangeably particularly \^en they are used in reference to the device of the invention, although the three may differ somewhat from each other in their characteristics. A paste, dough or batter is prepared by mixing a flour with water and/or other liquid materials. Powdered food products are also used for this purpose and in case of some foods said paste, dough or batter is made by the wet grinding of a food material, for example, cereals. Various cereals such as rice, wheat, maize, pulses, millets and others are used in the preparation of different pastes, doughs and batters. The three are also derived from fruits, fruit pulps and vegetables, for example, potatoes, plantains, tapioca and others. In the making of pastes, doughs and batters, other constituents are added as required or desired, for example, salt, spices, oils and fats, preservatives, colouring agents, flavouring materials and others. Most societies have traditional foods comprising dried doughs, the object of the drying being to enhance the shelf like thereof, that is, to make them suitable for long periods of storage. Prior to said drying said doughs are usually converted into a form that is suitable for quick and thorough drying and that is also convenient for cooking and consumption and furthermore, appealing to the consumer. Said traditional conversion processes usually involve flattening the dough into sheets and cutting thereof, or rolling into discs or other shapes or extruding into strands or other profiles/sections. Pasta products are an example of such dried doughs, which are extruded into a number of shapes/sections. Thus, extrusion is an important operation in food processes and for this purpose, various extruders and extrusion machines have been developed over the years for both domestic and industrial appUcations. Dried doughs are, of course, not ready for consumption and actually require a cooking operation such as steaming, frying, boiling, roasting or others before consuming. Such extruded dried doughs that require a cooking operation before consumption are referred to, hereinbelow, as first group products. TTiere are some food processes, traditional and others, wherein the food material undergoes cooking prior to extrusion, giving a product which is substantially ready for consumpticMi. The object here is to have a freshly cooked and extruded product and the purpose of the extrusion step is not for fecilitating quick drying but to offer the product in a convenient and attractive shape and form. An example of such products is Sevai, which is a widely consumed snack food in Asia. Such cooked and extruded products are referred to hereinbelow as second group products and the extent of cooking therein may be full or partial. Sevai is made from a batter prepared by the wet grinding of rice. Prior to the wet grinding operation, the rice is soaked in water for some time. The processing steps in sevai making are: i. soakingof rice in water; ii. wet grinding of the soaked rice to give a batter^aste); iii. shallow frying the batter; iv. moulding of said batter into handful size, or larger, balls; v. steam cooking of said balls; and vi. extruding said steam cooked balls to give the sevai produrt. The wet grinding of rice is done either manually in stone grinders or in mechanical power operated wet grinders, both being available in domestic and larger capacities. The object of shallow fiying is to reduce the moisture in the batter somewhat and to reduce the stickiness thereof Said moulding is carried out by hand. Said steam cooking at domestic level is carried out by placing said balls in a stack of trays provided with suitable indentations/cavities for placing the balls therein. Said stack is introduced and placed in a deep vessel in which said balls are subjected to steam cooking, the steam being generated by the boiling of water in the vessel. At industrial kitchen level also, similar steam cooking equipment is used which is a scaled-up version of the domestic variety. In a variation of this equipment, steam is not produced within the equipment but in a boiler system independent of the equipment and supplied thereto by a steam line/pipe. Said steam cooking is also done in pressure cookers, vdiich are provided with suitable accessory tray stacks for the purpose. Such pressure cookers are available both in domestic and industrial capacities, hi the final step, the steam-cooked balls are charged into an extruder and extruded to give sevai. In domestic extruders, a piston-like member is manually pushed down either directly or through a screw means. At industrial level similar extruders of larger capacities are used or alternatively, screw extruders are used. The industrial extruders are mostly power-operated. In industrial manufacture of said first group products, large-scale extruders involving high extrusion pressures are employed. Also, the material in such extruders is heated by steam either indirectly or by direct injection or both. Cooking is either full or partial as required. Heating facilitates extrusion and also provides a certain amount of e?q}ansion of the product upon extrusion. Such products are referred to as expanded products and said first group products that are produced partly or fiiUy cooked are referred to as modified first group products hereinbelow. The device of the invention is adapted for cooking alone, or extrusion alone of any of the products mentioned hereinabove or other products. It is also adapted for cooking followed by extrusion of products such of said second group, said modified first group and the expansion products. The device is also adapted for carrying out extrusion followed by cooking, that is, for making products such as Idiappam. Briefly, the device of the invention comprises a steam piston and cylinder system wherein an annular space around the piston rod thereof forms a chamber wherein the operations of cooking and/or extrusion are carried out. Said system is housed in a housing that is detachably connected to or connectable to, a source of steam. Said source of steam may comprise the vessel part of a domestic or industrial pressure cooker or a vessel which is generally similar to said vessel part of a domestic or industrial pressure cooker or a vessel of any type wherein boiling of water can be carried out to produce steam under pressure. For said cooking, indirect steam heating is provided and furthermore, optionally direct injection of steam into said chamber is also provided. The extrusion is carried out by moving said piston under steam pressure, suitable openings/holes/apertures being provided for the purpose at the upper part of said chamber. In one arrangement provided by the invention, said housing is attached to a steam line, vviiich, for the purposes of this invention constitutes a said steam source. It will be observed that while the device of the invention is suitable for carrying out a single operation of cooking or extrusion, maximum advantage thereof is realised when the device is used for twin operations, such as cooking followed by extrusion. In the case of extrusion followed by cooking, similar benefits are realised but to a lesser extent. As would be expected, the use of a single piece of equipment of the device of the invention for two operations offers considerable comfort as it eliminates the painfiil manual extrusion besides cost benefits and time saving in manufacture. At domestic level operations, the significant benefits are operational speed and convenience. A further advantage is that the device of the invention requires only a single energy source for its operation, namely, steam that is used both for cooking and to provide motive power for the extrusion. Thus, the device of the invention is adapted for, and is suitable for any of the following operation modes: i. cooking alone, with steam; ii. extrusion alone, with steam under pressure; iii. cooking followed by extrusion, the former by steam and the latter by means of steam under pressure; iv. extrusion followed by cooking, the former by steam under pressure and the latter by steam heating. This versatility and capacity for carrying out dual operations are novel features and highlights of this invention. The central feature of this invention, namely, the development of a piston-cylinder system for food processing is novel. Specifically, the provision of a chamber within said system for carrying out said food processing operations is novel. Further the capability of the device of the invention to carry out two food processing operations, namely, cooking and extrusion is novel. The development of said chamber such that both said operations can be carried out therein is another novel feature of the invention. The provision of additional direct heating by steam during cooking is novel. The most practical and advantageous orientation for the device of the invention would appear to be the one wherein said system axis is substantially vertical. Other orientations although feasible do not offer the convenience and advantages of the vertical orientation. In view of this, in the description hereinbelow, only the vertical orientation is considered; references to vertical being construed as substantially vertical. This is without limitation to the scope of the invention. Thus all locational references in this specification such as top, bottom, above, below, upper, lower and others are in the context of said vertical orientatirai. References such as "inner", "outer" imply " radially inner" and "radially outward" respectively and are in reference to said system axis unless otherwise required by the context thereof To summarise, the chief advantage of the device of the invention is that two food processing operations, namely, cooking and extrusion can be carried out in a single piece of equipment and more particularly in one place, that is, in said chamber. Considerable savings in human effort and operational cost benefits arise fi-om this. A further advantage is that the device of the invention requires just one source of power/energy for operation. A still further advantage is the option of direct steam heating of the food materials during the cooking operation in addition to indirect steam heating. TTie fourth advantage is that the device of the invention is particularly suited and adapted for products of said second group, in general, and for sevai making in particular both at domestic and large-scale level. The fifth advantage is that said process of sevai making is greatly simplified when used with the device of the invention. Thus, these inventors have developed a novel process of sevai making wherein said operations of cooking and extrusion are carried out in the device of the invention. Said novel process eliminates several steps present in the prior art process and offers considerable benefits with regard to ease of manufacture, equipment costs, manufacturing costs and rate of production, and is easily adaptable for domestic and large-scale operation. According to one aspect of the invention, therefore, there is provided a device for carrying out cooking and/or extrusion operations on food(s) using steam, comprising: i. a steam cylinder system located in a housing, said system comprising a piston, a piston rod attached to or integral therewith, a cylinder and an end cover thereof; ii. an annular space aroimd said piston rod forming a chamber wherein said operations may be carried out; iii. extrusion holes/openings/apertures on said end cover or an upper part of said chamber or both; iv. stopping means for preventing movement of said piston during cooking operations; V. retaining means for preventing movement of said piston out of said cylinder at the bottom end thereof; and vi. limit means for limiting the upward travel of said piston during operation, said housing being attached to, or attachable to a source of steam. According to a second aspect of the invention, therefore, there is provided a Ud/cover for a pressure cooker, inter alia, comprising means for carrying out cooking and/or extrusion operations on food(s) using steam, said means comprising: i. a steam cylinder system located in a housing, said housing being attached to or integral with said cover and said system comprising a piston, a piston rod attached to or integral therewith, a cylinder and an end cover thereof; ii. an annular space around said piston rod forming a chamber wherein said operations may be carried out; iii. extrusion holes/openings/apertures on said end cover or an upper part of said chamber or both; iv. stopping means for preventing movement of said piston during cooking operations; V. retaining means for preventing movement of said piston out of said cylinder at the bottom end thereof; and vi. limit means for limiting the upward travel of said piston during operation, said cover being attached to, or attachable to a said vessel part of a pressure cooker.. According to a third aspect of the invention, therefore, there is provided a pressure cooker comprising a lid/cover having, inter aha, means for carrying out cooking and/or extrusion operations on food(s) using steam, said means comprising: i. a steam cylinder system located in a housing, said housing being attached to or integral with said cover and said system comprising a piston, a piston rod attached to or integral therewith, a cylinder and an end cover thereof; ii. an annular space around said piston rod forming a chamber wherein said operations may be carried out; iii. extrusion holes/openings/apertures on said end cover or an upper part of said chamber or both; iv. stopping means for preventing movement of said piston during cooking operations; V. retaining means for preventing movement of said piston out of said cylinder at the bottom end thereof; and vi. limit means for limiting the upward travel of said piston during operation. Within the scope of the invention a large number of design alternatives and arrangements are feasible and these are described hereinbelow. In one embodiment of the invention, said housing is connectable to an industrial or domestic pressure cooker. In this arrangement the vessel part of a pressure cooker is detached from the lid thereof and said housing of the device of the invention is detachably connectable to said vessel part, said connecting/attaching means being of suitable design to engage and attach therewith. Said vessel part constitutes a steam source in so fer as it is adapted for holding water and heating it by means of a suitable heat source such as gas, electricity or others to produce steam under pressure. The device of the invention \dien attached to a said vessel part also performs the function of the lid thereof and therefore comprises the attachments/fittings normally found on the hds of pressure cookers such as pressure controlling/releasing valves, safely rehef valves/plugs, gasket release systems and others. It will be noted that during operation, the device of the invention together with a said vessel part also performs the further, it will be noted that different embodiments of the invention provide for said cooking operation to be performed in the device of the invention with steam at substantially atmospheric pressure or at a pressure above atmospheric. To ensure proper operation, therefore, it is essential that said fittings are provided on the device of the invention. Said pressure controlling means on pressure cookers are generally weight loaded type valves and these are provided on the device of the invention. Alternatively, any of the other pressure control means available in the art may be used, hi the specification further hereinbelow, the terms "vessel" and "vessel part" in reference to pressure cookers are used interchangeably. The type of said connecting/attaching means most commonly used in pressure cookers is the twist-lock arrangement. In a twist-lock joint, one part, for example said vessel comprises a plurality of radially outwardly extending tongues at the periphery thereof The other part, for example the vessel lid has correspondingly located but radially inwardly extending tongues. When said lid is placed over said vessel and turned such that said two sets of tongues are ahgned with each other, the closure of said vessel is achieved against pressure. Suitable stops are provided if required to ensure said alignment. Several other closure systems are found in the art such as swing bolt system, flange system, threaded systems, various clamping systems and others. The device of the invention can be adapted to the use of any of said connecting means so as to match the arrangements provided on different types of pressure cookers found qn the market. That is, the device of the invention can be made to match any said vessel both with respect to the connecting means required to attach therewith and with respect to the dimensions thereof. In another constmction of the invention, the housing of the invention is attached to a vessel that is generally similar to said vessel part of a pressure cooker and constitutes said steam source for the device of the invention. Thus, the assembly of the device of the invention and said vessel together constitute a special pressure cooker version of the device of the invention. If an ordinary pressure cooker lid were additionally provided with said special version the assembly would be able to function both as an ordinary pressure cooker as also as said special pressure cooker providing cooking and/or extrusion facilities. The device of the invention in this version thereof is provided with said pressure control means, safety relief means and others as required in any pressure cooker. In another embodiment of the invention, the device of the invention is ccmnectible to a steam line, said steam line constituting a source of steam for the puiposes of this invention. The configuration of the piston rod of the cylinder-piston system of the device of the invention is an important consideration. Said piston rod is of stepped construction, a said step(shoulder) being such as to support said food material(s) being processed. Thus, said shoulder forms the floor of said chamber, the sides thereof being formed by said cylinder wall and said piston rod and the top by said end cover. Upward movement of said piston would push the food material(s) against said end cover causing the extrusion thereof through suitable said holes/apertures/openings provided at the top part of said chamber. Within the scope of the invention, said holes may be located upon said cylinder or said end cover or both. Said stepped rod may comprise one or more said st^s. Heat for cooking of the food materials in said chamber during operation comes from steam present in the housing. The heat flows through the cylinder wall and into the food material. If steam could access the interior of said piston rod that would provide additional heat transfer as heat would then flow into the food material from below through said shoulder and also from the side through the wall of the piston rod. This would considerably accelerate the cooking process and reduce the time for the cook*— ~"~-"«+;"^" This invention therefore, provides for two further embodiments, one comprising an ordinary piston rod wherein said access is not possible and the other wherein said piston rod is hollow, that is, it comprises a suitably sized cavity providing said access for the steam from the housing. In the former, said piston rod could even be of solid construction. The construction of the device of the invention not having said access is associated as mentioned, with a considerable disadvantage with regard to the heat transfer aspect. In the interest of conciseness, therefore, this embodiment is not discussed any further in this specification and the description hereinbelow is limited to the case of the piston rod wherein said access is provided. This is without limitation to the scope of the invention. In another embodiment of the invention, said piston rod comprises an internal passage going right through that is, all the way from the bottom to the top thereof In addition to providing said access, this construction of the device of the invention fiirther offers the option of venting of the steam at the top of the piston rod. In this arrangement, in addition to the availability of said facility for additional heat transfer a further option of direct steam heating is available. This is explained hereinbelow. Said opening provided at the top of said rod is used for: i. venting the steam; and/or ii. mounting of a weight loaded or other type of pressure control valve; and/or iii. mounting of a deflector means by means of which steam can be directed downwards into said chamber for the purpose/airect steam heating of the food materials therein as and when desired. Said deflector means is a hood-like component which is placed over and above said outlet (opening) at the top of the piston rod. When said deflector is in position, steam flows past said end cover and into the top of said chamber. Suitable clearances are provided between said end cover and piston rod for the flow of steam into said chamber. This is further elaborated hereinbelow. Said deflector means are a novel development of the invention. The steam used for said direct heating in said chamber is vented through said extrusion holes thereafter. The attachment and detachment of said deflector means to and from said piston-cylinder assembly is an easy operation and provides a control over the direct heating operation, that is, on the duration of said heating operation. As mentioned hereinabove, said pisttm rod is of stepped configuration such as to provide said step (shoulder) for supporting the food material to be processed. Said step (shoulder) forms the floor of said chamber. It is within the scope of the invention to provide said support by constructions other than said step, for example, by providing a suitable ledge-type member attached to or integral with said piston rod. In such a construction, said ledge member would extend from said rod to said cylinder and constitute the floor of said chamber. It will be observed that said ledge(or said shoulder) constitutes a piston in so far as, during operation it exerts a force upon the food materials in said chamber and pushing them towards and against said end cover. Thus, the piston-cylinder assembly of the device of the invention also constitutes a double-piston system wherein two pistons are mounted on a common piston rod and wherein steam acts on one said piston and the other acts on the food material in said chamber. The former is referred to as the steam piston and the latter as the chamber piston in the specification hereinbelow. In the embodiments shown, this invention has provided a stuped configuration for said cylinder also, the object thereof being to provide greater area for said steam piston in contrast to said chamber piston. The consideration here is the ratio of the active areas of said steam piston and said chamber piston. The greater the value of this ratio the greater would be the value of the extrusion pressure realised for a particular value of the steam pressure in the housing. TTius, there are two approaches, one wherein said steam piston area is maximised with a view to minimising said steam pressure in the housing and the other wherein said steam pressure is fixed at a comparatively higher value. The former is more appropriate for domestic apphcations of the device of the invention and the latter for industrial applications thereof Where a lower value of said ratio is acceptable such as in said industrial applications the difference in said two active areas would be less. In the limit, when the value of said ratio is substantially imity said two active areas would be substantially equal. Hiis is the configuration where said two pistons are substantially of the same diameter. This configuration of a non-stepped said cylinder is within the scope of the invention. Said chamber comprises said annular space as mentioned hereinabove and volume thereof depends on the two diameters and height of said annular space. In turn, said two diameters dq)end on the design values of diameter of said steam piston, said ratio and said piston rod diameter. By suitable selection of these parameters, a wide range of value? is obtainable for the volume of said chamber. The inner and outer surfaces of said annular space are cylindrical but within the scope of the invention other configurations are feasible but not quite practical. The chamber surfaces which come in contact with said food materials may be given any of the treatments known in the art. Some of the possible treatment systems for reducing/preventing the sticking of the food materials to said surfaces during cooking/extrusion are: i. synthetic non-stick coating like PTFE (Teflon); ii. hard-chrome plating; and iii, bumishing to a bright finish. Said surfaces may be treated either v^^ole or in part by any of said systems. In the embodiments described in detail hereinbelow said surfaces have been given a teflon coating. The invention provides for said piston-cylinder system to be located in a housing and attached thereto. In one construction provided by the invention, said attachment is made at two locations, one at the top of said housing and cylinder and the other at said step in the cylinder. At the top, the upper edges of said housing and cylinder are attached to each other by crimping. Corresponding to said step in the cylinder, a step is also provided in the housing such that in the region of said steps both said housing and cylinder are oriented substantially horizontal and parallel to each other. The two are riveted together in said region, said rivets being set in a circle around said system axis. At the position of each said rivet, said cylinder comprises a rising dimpled portion the object of which is to provide the required spacing between said cylinder and housing. Said rivets are positioned at the centre points of said dimples. Said dimples-rivets arrangement which combines the function of attachment means and provision of spacing is novel. Said spacing is required to ensure easy flow and circulation of steam in the housing. Other means of said attachment and locations thereof are within the scope of the invention. Within the scope of the invention said housing may be of any of several configurations and may be without said step thereof The invention has made another construction wherein hollow cylindrical spacers are placed between said housing and cylinder to ensure the required spacing therebetween. Said rivets for attachment of said cylinder and housing are located within said hollow spacers. This construction provides cost benefits by the elimination of said dimples but has the drawback of a somewhat larger inventory of parts. Greater magnitudes of said spacing are possible by the use of said hollow spacers than is possible with the dimpled arrangement. Other methods of said attachment and locations thereof are within the scope of the invention. The arrangement comprising said combination of spacers and rivets is novel. A hole is provided in each said rivet extending from one end to the other thereof Said holes form conduits (passages) for flow of air from the air space located in said piston-cylinder assembly beneath said step in the cylinder. This air space is bounded by the cylinder wall on the outside, said piston rod on the inside and said cylinder step and steam piston above and below respectively. Air in said space requires to be vented during the upward motion of said steam piston and in the return motion thereof, it is necessary to let in air into said space. Said holes facilitate this venting and inspiration of air. Rivets provided with said holes are a novel feature of this invention. Other methods provided by the art for said venting and inspiration are within the scope of the invention. It will be noted that the art provides a wide range of joining methods for attachment of one part, component, portion of a device to another. These are welding, brazing, soldering, crimping, by fasteners, adhesive bonding, riveting, and others and as applied to the device of the invention are within the scope thereof. It will also be observed that in the device of the invention several parts/components, for example, said cylinder, have been broken down, or divided into two or more sub-parts/sub-components. Said divisions are governed by factors such as costs, ease of manufacturing and maintenance and others. The use of any said joining method in respect of said sub-parts/sub-components is within the scope of the invention. Said divisions can be carried out in different ways/configurations and these are within the scope of the invention. In this description, two constructions of said piston rod have been discussed. Both constructions provide said access for steam to the interior of said rod the difference being that in one an outlet for steam is provided at the top thereof but not in the other. Said constructions are referred to hereinbelow, as A type and B type piston rods the former having said outlet but not the latter. The steam space in the device of the invention comprises the space in the housing and that within said rod, A or B type. In addition, said steam space also includes the space in said vessel. Thus, said steam space comprises the space in said rod and housing and furthermore in said vessel as applicable. When the steam pressure is required to be built up for the extrusion process, said vent(s) if any are closed. Pressure control means is required to maintain the steam pressure in said steam space and to release the same at the end of said extrusion operation. Said means may be provided on said housing or at the top of said rod or both. Any of the pressure control means of the art may be employed. But, it has been found that weight loaded pressure control/release valves of the type found on pressure cookers are very suitable and convenient for the purpose. In this arrangement, a tubular post (outlet) is provided at the top of said rod, which performs the function of a vent when required and which also comprises a seating for the mounting of the weight assembly of a said weight loaded valve. In one construction of the invention, steam is maintained at substantially atmospheric pressure in the housing during said cooking process and in another embodiment said cooking is carried out with steam under pressure. In both these arrangements, it is necessary to provide stopping means to prevent upward movement of said steam piston during the cooking operation. Said stopping means may be any of the ones known in the art. This invention has provided a novel stopping means comprising one or more vertically oriented pins interposed between said rod and deflector means. In the embodiments described hereinbelow and having said A-type rods said stopping means comprise six numbers of stopping pins located in a circle at the top of said rod. During qjeration, when the cooking is completed said deflector means is removed setting the piston free to move. At this point, said weight assembly is placed in position, which causes the pressure to build up in the device. Under the action of the developing positive steam pressure, said piston starts to move upwards. Said stopping means are also applicable to B-type piston rods but as in this case said deflector means would not be present, a different abutment must be provided for said pins. Said abutment must be removed or discontinued when it is desired to commence the extrusion operation. When the device of the invention is required to carry out cooking also under steam pressure, this invention provides for a release means for the piston assembly. This may be in addition to, or in lieu of said stopping means. Said release means allow gradual release of said piston. It may be borne in mind that in this arrangement said piston is being subjected to an upward force throughout said cooking operation and at the commencement of the extrusion operation. Other release means of the art are within the scope of the invention. Said release means are required to be adopted for both A and B arrangements but, in addition, for said A type rods a steam release valve is required for release of steam for said direct heating. Said piston-cylinder system is also provided with retaining means the purpose of which is to prevent said steam piston from sliding out of the cylinder at the lower end thereof. This would cause said piston to fall into said housing/vessel. Said retaining means is generally similar to the circlips used for retaining shafts and comprises a wire component having a certain amount of resilience. The outer ends thereof are pulled in and said means is aUgned at the bottom of said cylinder and released. Upon release, said outer ends engage with, and sit in a groove formed at the lower end of said cylinder. The engagement and release of said retaining means is easily carried out by one hand. In an alternative arrangement, a U-shaped hair pin type component provides the retaining function. It is inserted into holes provided at said lower end at two places thereon that are substantially diametrically opposite each other. In yet another arrangement, a stool-like member is placed in said vessel/housing to support and retain the steam piston. The advantage of the grooved arrangement is that said groove lends a certain amount of stiffiiess to said lower end which is important as said lower end would tend to get knocked around during use/washing of the device of the invention. On the other hand, a grooveless piston has a simpler profile fi-omthe point of view of manufacturing. A drawback of said hair pin type device is that it is prone to distortion and of said stool arrangement is that said vessels of different dimensions would require different sized stools. Said wire-type retaining means and U-shaped hairpin retainer means are novel as also said stool arrangement. It is essential to provide limit means to prevent said steam piston from going beyond the designed uppermost point of travel thereof In the arrangements comprising said stuped cylinders, said step (shoulder) forms said limit means. Stop at the limiting point is achieved when said steam piston, or a component mounted thereon, abuts the under-surface of said cylinder shoulder or a component attached thereto. Said end cover is neither attached to said housing nor to said cylinder and in the embodiments it is merely in contact therewith. Said end cover is urged upwards by the steam pressure in said chamber in the case where direct steam heating is employed. During extrusion also, said end cover is subjected to an upward force. Proper anchoring of said aid cover needs to be provided. In the device of the invention, said anchoring is provided by a rec^tacle (receiving vessel) which in turn is anchored on said housing by means of a twist-lock or other type of joint. Said receiving vessel is provided for collecting the extruded food material and comprises a ring-shaped bowl which slips over the top of said piston rod and is positioned such as to receive the extruded food material coming out of said extrusion holes. Said receptacle therefore comprises an outer and an inner circular wall. The top of said inner circular wall is formed into a tubulju" rim, which abuts and presses on a flange provided on said end cover. Thus the engagement of said rim and flange provides a firm anchoring for said end cover. As mentioned, said rim comprises a hollow tubular ring, which is formed by rolling the upper edge of said inner circular wall. Other constructions of said bowl-end cover engagement, of said rim construction and of said bowl-housing attachment are within the scope of the invention. Said rim-flange engagement method of anchoring is novel. In view of its anchoring function, said receptacle is required to be feirly heavy unlike if the function thereof was to merely hold the extruded food material. A light-weight receptacle is desirable and therefore, this invention provides for an alternative construction wherein said anchoring is provided by a component which has the general shape of a hollow truncated cone such that it can be slipped over and positioned around said housing-cylinder assembly at the top part thereof Said conical component is provided with said rim and said twist-lock arrangement respectively at the upper and lower portions thereof Said cone is also provided with two or more handles, preferably at, or near, the base thereof for turning it and twist-locking it to said housing. As in the previous construction, anchoring is by said rim-flange engagement. Said cone member just comprises framework (grid-work) so as to minimise the weight thereof Said receiving vessel in this arrangement is quite lightweight and can be of metal or plastics. This anchoring means is also novel. Preferably, said receiving vessel is of plastics because the extruded material is liable to stick to a metal surface. This is because at the moment of contact of said extruded material and the metal surface of the receptacle, quenching occurs. Said cooled extruded material tends to be sticky and somewhat difficult to handle. Said quenching is minimised/avoided in said plastics receptacles. Another possible method of eliminating this stickiness is by way of coating the recg)tacle surface with a special non-stick coating process like PTFE (Teflon). This is within the scope of the invention. Sealing/packing is required at several points in the device of the invention. Said points are: i. between said end cover and piston rod (seal 1); ii. between said end cover and said cylinder-housing assembly (Seal 2); iii. between said piston rod and cylinder in the region of said piston rod shoulder (Seal 3); and iv. between said piston and cylinder (Seal 4). The purpose of seal 1 is to prevent extrusion of the food material through the clearance between said end cover and piston rod. Seal 1 has a generally V-shaped profile such that under the effect of fluid pressure the arms of the Y flay outwards. Seal 1 is integrally moulded with said end cover. During said direct heating phase, steam is required to flow from the space above said end cover into the space below, or within said end cover, that is, into said chamber. For this purpose, one or more flats(chamfers) are provided on the cylindrical surface of said piston rod, said flats being positioned in the zone of said seal 1. During the extrusion operation, right at the commencement of the movement of said piston rod, said flats pass out of the zone of seal 1. With this, the contact of said seal 1 with said cylindrical surface is complete and extrusion of the food material past said end cover is prevented. TTie purpose of seal 2 is to prevent extrusion of food material at the place where said end cover abuts said cylinder-housing assembly. Seal 2 is also integrally moulded with said end cover. The purpose of seal 3 is to prevent the food material from flowing into the clearance between said cylinder and piston rod towards said air space when said extrusion operation is in progress. Seal 3 comprises an 0-ring. The purpose of seal 4 is to prevent leakage of steam past the piston into said air space. Seal 4 also has a generally V-shaped profile and is provided with a lip/locking part which is required to sit in a matching circumferential slot on said steam piston. The requirement of placing said lip into said slot ensures that seal 4 is installed the right way around with the mouth of the V facing the pressure zone, that is, said steam source. The provision of said locking feature is of particular relevance for domestic application of the device of the invention and is novel. A further seal is required at the joint between said housing and vessel. In the embodiments described hereinbelow, said joint is of the twist-lock type and comprises a V-profile ring seal. Said seals may comprise an 0-ring profile or a V-profile or others available in the art and may be loosely mounted or integrally moulded/attached to their respective components or attached therewith by other methods. All such variations are within the scope of the invention. A number of food grade materials of construction are available in the art for said seals. Examples are: silicone rubbers, natural rubber, nitrile rubbers, polyurethanes and others. These and others are within the scope of the invention. As mentioned hereinabove, said deflection means comprise a hood-like component that sits on said end cover and aroimd the top of said piston rod. Said deflector means is attached to said end cover by means of a pair of resilient straps provided with hook ends which lock into brackets located on said end cover. The resiliency of said straps provides the necessary force between the edge of said deflector means and the surface of said end cover resulting in an effective steam seal therebetween. A number of materials are available in the art for construction of the device of the invention. Apart fi-om a few components, most of the device of the invention in the embodiments described hereinbelow is of metallic construction and the metallic parts of the embodiments thereof described herein are generally of aluminium alloy construction. Materials of construction such as brass and others are within the scope of the invention. Various said design altematives and arrangements within the scope of the invention have been considered and elaborated hereinabove. This invention provides different combinations thereof to suit different applications, different scales of operation and other factors. ITie embodiments described hereinbelow incorporate some said combinations. These are: Embodiment liThis embodiment comprises a device for cooking and/or extrusion of food materials wherein said housing is detachably attachable/connectable to a said vessel part of a domestic or industrial pressure cooker. The device incorporates a piston comprising said passage and said shoulder. Attachment means between said housing and cylinder comprise said rivets and dimples. Air release and inspiration is by means of said holes in rivets. Attachment of said housing to vessel and said receptacle to housing is by means of twist-lock arrangements. Said extrusion holes are located on said end cover. The device comprises said outlet, weight loaded valve, deflection means, stopping means, flats, wire clip type retaining means and said limit means formed by said cylinder shoulder. This embodiment is particularly suitable for domestic use and can be adapted for the various sizes and makes of pressure cookers available in the market, hi this embodiment, cooking is with steam that is at substantially atmospheric pressure. This embodiment is described in detail further hereinbelow. Embodiment 2; This embodiment comprises the device of the invention detachably attached to, that is, complete with said vessel part, which constitutes the steam source. Thus this embodiment corresponds to a said special purpose pressure cooker and is generally similar to embodiment 1. This embodiment, therefore can be easily visualised and the operation thereof understood by reference to the description of embodiment 1 hereinabove and the detailed description of embodiment 1 further hereinbelow. It must be stressed that said design variations and said combinations other than mentioned hereinabove which are within the art or which can conceived by persons in the art are within the scope and spirit of the invention. In order to provide a clearer understanding of the invention and without limitation to the scqje thereof a few embodiments thereof are described in detail hereinbelow with respect to the drawings accompanying the provisional specification wherein: Fig. 1 shows the sectional elevation of embodiment 1 of the device of the invention; Fig. 2 shows the sectional elevation of embodiment 2 of the device of the invention; Fig, 3 shows detail of end cover region of embodiments 1 and 2; Fig. 4 shows detail of deflector means of embodiments 1 and 2; and Fig. 5 shows detail of retaining means of embodiments 1 and 2. In this specification, references to accompanying drawings are intended to be to the drawings accompanying the provisional specification. Referring to Figs. 1,3,4 and 5 which illustrate embodiment 1, reference numeral 1 denotes said piston and cylinder system comprising piston 2, piston rod 3, and cylinder 4 with end cover 5 thereof System 1 is housed in housing 6 that is provided with coimecting/attaching means 9 for attachment of the housing to a said vessel 8 of a domestic or industrial pressure cooker. The configuration of assembly 7 of said system 1 and housing 6 is like that of a lid of a pressure cooker with said system 1 attached/integral thereto. Said attachment means 9 is of the twist-lock type which is the most commonly used in pressure cookers but can be of other types to suit said vessel 8. Vessel 8 constitutes the source of steam and holds water therein which upon heating generates steam. Said piston-cylinder system 1 comprises a plurality of dimpled portions 10 abutting said housing 6. Cylinder 4 is attached to housing 6 by means of rivets 11 located at dimpled portions 10. Dimples 10 are provided to ensure a communicating space between cylinder 4 and housing 6 such that steam flows and circulates easily from aroimd the bottom end 12 to the top end 13 thereof Cylinder 4 and housing 6 are also attached to each other at the top by a crimped joint 14. End cover 5 sits over and around the crimped joint 14, a gasket 15 being provided thereat for pressure sealing and for preventing escape of material during extrusion. It will be observed that end cover 5 is not attached to top end 13 of cylinder 4. Receptacle (receiving vessel) 16 which comprises a ring shaped bowl is provided for collecting the extruded food product. The food material upon extrusion fi-om holes 17 located in said end cover 5 drops into receptacle 16. Said receptacle 16 is attached to housing 6 by means of a tVvist-lock system 18 located on housing 6. End cover 5 is also referred to as a die plate in view of the extrusion holes thereof and is neither attached to cylinder 4 nor to housing 6 and to hold it in place against the force of extrusion and pressure of steam it is provided with a ledge (flange) 19 which engages with rim 20 of receptacle 16. Said engagement prevents end cover 5 from detaching itself from the system either due to the steam pressure during said direct steam heating or due to extrusion pressure during the extrusion operation. Steam could be under slight gauge pressure in space 21 located at top of chamber 26 during the cooking operation. Details of end cover 5 and of the attachment thereof to housing 6 and cylinder 4 and engagement with receptacle 16 are shown in Fig. 4 wdiich clearly shows flange 19, gaskets 15,29 and other parts. At the lower end of cylinder 4 is located a circular groove 22, wherein sit the wire ends 24 of a spring loaded retaining means 23. Retaining means 23 is a generally longitudinal member, the ends 24 of which engage in said groove 22 under spring pressure. Mounting and release of retaining means 23 is easily carried out manually. The purpose of retaining means is to support piston 2 and prevent it from moving out of the cylinder 4 from the bottom thereof and dropping into vessel 8. Details of retaining means are shown in Fig. 6. Said retaining means are a novel feature of this invention. Piston rod 3 is of a stepped construction and comprises a shoulder 25 which forms the bottom of chamber 26 which holds the food materials to be cooked and/or extruded. The contact surfaces of chamber 26 have been given a teflon coating to give them a non-stick property. Piston rod 3 is furthermore, hollow and provides a passage for steam all the way to the top thereof At the top of piston rod 3 is located a tubular post 27 which commimicates with said passage and comprises said outlet. Tubular post 27 is part of a weight loaded valve system generally of the type found on domestic pressure cookers. The other part of said weight loaded valve thereof sits on valve seat 28 on tubular post 27 and comprises one or more weight(s) which can be added or removed as desired. Said other part is placed on seat 28 when it is desired to build up steam pressure in vessel 8 for the extrusion process. Gasket 29 provides sealing between end cover 5 and piston rod 3. Another gasket 30 provides sealing between cylinder 4 and rod 3 so that during extrusion, food material does not flow into aimular space 31 which is bounded by lower part 32 of cylinder 4, lower part 33 of piston rod 3 and piston 2. The air contained in annular space 31 is required to be released/vented during upward travel of piston 2 during extrusion. Said air is vented by means holes 34 in rivets 11, as holes 34 communicate with space 31 and the atmosphere. Cylinder 4 is also of stepped construction and the shoulder (ledge) 35 thereof constitutes said limit means, which defmes the uppermost point of travel of piston 2. Chamber 26 which holds the food materials to be processed comprises the annular space bounded by upper part 37 of cylinder 4 on the outside, by upper part 38 of piston rod 3 on the inside, shoulder 25 on piston rod 3 and end cover 5. Said closure/deflector means 39 is a hood shaped member which sits atop piston rod 3 and tubular post 27 thereof The function of deflector means 39 is to prevent escape of steam from said post 27 into the atmosphere and direct it into top portion 21 of chamber 26. It was mentioned that gasket 29 seals said top portion space 21. This is true generally for all positions of piston 2 and piston rod 3 except for the lowermost position thereof When piston 3 is in the lowermost position gasket 29 faces a set of chamfers(flats) 41 located on the face of piston rod 3. It is the clearances between circular gasket 29 and said flats 41 that provides the passage for steam from deflector means 39 into top space 21 of chamber 26. Deflector means 39 is anchored on end cover 5 by means of resilient arms 42 the hook ends whereof engage and lock with brackets 44 located on the upper surface of end cover 5. Pressure generated by said resilient arms 42 provides the seal between the deflector means 39 and the upper surfece of end cover 5. Said locking arrangement is designed for easy and quick locking and release. This is another novel feature of the invention. Gasket 45 provides sealing between piston 2 and cylinder 4 and comprises a lip/locking part 46. Gasket 45 has a V-profile and when in position said locking part 46 engages with circumferential slot 47 of piston 2. Said engagement is provided to ensure that gasket 45 is placed correctly, that is, with the mouth thereof facing the pressure zone, namely, the vessel. As mentioned hereinabove, the joint 9 between said housing and vessel is of the twist-lock type and comprises gasket 48. Gasket 48 has a V-profile and is located in the joint 9 sudi that the mouth thereof faces the pressure zone. For operating the device, it is attached to vessel 8 by means of twist-lock arrangement 9. Next, receptacle 16, deflector means 39, end cover 5 and said weight part of the weight loaded valve are removed from the device and food material(s) to be cooked and extruded are placed in chamber 26. End cover 5 is placed in position and locked in place by mounting receptacle 16 which is attached to the housing 6 by means of twist lock system 18. End cover 5 is locked in position through engagement of rim 20 with flange 19. The device of the invention, together with vessel 8 is now placed on a source of heat that heats the water in vessel 8 to generate steam. The steam provides heat for cooking of the food materials in chamber 26. The heat from steam passes through the cylinder wall into the food material providing indirect heating. Similarly, heat flows from steam through the piston rod wall into the food material. This source of heating is also indirect. Steam passes through piston rod 3 coming out through said tubular post 27. Steam then passes past said chamfers 41 entering the space 21 located at the top of chamber 26. Here, the steam causes direct heating of the food materials. Uncondensed steam exits through holes 17 in end cover 5. During the cooking stage, the pressure of steam in vessel 8 and housing 6 remains substantially atmospheric. However, there is a tendency for said piston 2 to rise under the slight gauge pressure of steam. This tendency is counter-acted by one or more stopping pin(s) 43 located in said deflector means. The stopping pins 43 restrain the piston 2 from rising up. For the extrusion operation, steam under pressure is required. So the deflector means 39 is removed and said weight part placed on the tubular post 27. Pressure begins to build up in vessel 8 and housing 5 causing piston 2 to rise. As the piston moves upwards, food material in chamber 26 is pushed against end cover 5. This causes extrusion of the food material through holes 17. During the process of upward movement of piston 2 air in annular space 31 is pushed out through holes 34 in rivets 11. When the extrusion is complete said weight part (said other part of weight loaded valve) is removed to release the pressure in vessel and housing 6. As the steam pressure drops piston 2 retums back to its lowermost position. At this point, receptacle 16 is removed, followed by end cover 5. Receptacle 16 is emptied if required. A fresh batch of food material is charged into chamber 26 and the cycle repeated. Embodiment 2 is illustrated by Figs. 2,3,4 and 5. As mentioned hereinabove, said vessel part is part of this embodiment. That is, the device of the invention is detachably attached to a said vessel part and together they constitute this embodiment. It will be observed that this embodiment constitutes a specialised pressure cooker wherein normal cooking operations can be carried out in the vessel part thereof and in addition, cooking and/or extrusion operations if desired, in said system forming part of the specialised lid/cover of the pressure cooker. In all other respects, the construction of this embodiment is generally similar to that of embodiment 1 and reference is invited to the detailed description of the construction of embodiment 1 hereinabove for the necessary details and explanation. The operation of the device of embodiment 2 is also generally identical to that of embodiment 1 and reference can be made to the detailed description given hereinabove of the operation of embodiment 1. Various embodiments and variations other than described above which are within the art are within the scope and spirit of the invention. We claim; 1. A device for carrying out cooking and/or extrusion operations on food(s) using steam, .f comprising: i. a steam cylinder system located in a housing, said system comprising a piston, a piston rod attached to or integral therewith, a cylinder and an end cover thereof; ii. an annular space around said piston rod forming a chamber wherein said operations may be carried out; iii. extrusion holes/openings/apertures on said end cover or an upper part of said chamber or both; iv. stopping means for preventing movement of said piston during cooking operations; V. retaining means for preventing movement of said piston out of said - cylinder at the bottom end thereof; and vi. limit means for limiting the upward travel of said piston during operation, said housing being detachably attached to, or connectible(attechable) to a source of steam. 2. The device as claimed in the preceding claim 1 wherein said housing is connectible to a source of steam such as a steam line. 3. The device as claimed in the preceding claim I wherein said housing is in the configuration of a cover(lid) that is detachably attachable to a vessel member that is adapted to hold, and boil, water therein such as to produce steam, and furthermore, to carry ou"t pressure cooking operations therein, said vessel member being either the vessel v part of a known pressure cooker or similar thereto. 4. The device as claimed in the preceding claim I wherein said housing comprises both said cover(lid) and said vessel member, the former being detachably attached to the latter, the said latter being adapted to hold and boil, water therein so as to generate steam, and furthermore, to carry out pressure cooking operation therein, and being generally similar to, or identical to, the vessel part of a known pressure cooker. 5. The device as claimed in any of the preceding claims 3 and 4 wherein said a known pressure cooker is a domestic pressure cooker. 6. The device as claimed in any of the preceding claims 1 to 5 wherein said detachable attachment is of the twist-lock type. 7. The device as claimed in any of the preceding claims 1 to 6 wherein said housing fiirther comprises a receiving vessel(receptacle) for receiving said food(s)/food material(s) upon extrusion. 8. The device as claimed in the preceding claim 7 whetein said receptacle is of generally annular/ring shaped configuration. 9. The device as claimed in the preceding claim 8 wherein said receptacle is mounted upon a supporting member attached to said housing. 10. The device as claimed in the preceding claim 9 wherein said attachment of the supporting member to said housing is by twist-lock means. 11. The device as claimed in any of the preceding claims 7 and 8 wherein said receptacle is mounted directly on said housing and attached thereto preferably through twist lock means. 12. The device as claimed in any of the preceding claims 9 and 10 wherein said end cover is anchored in position by said supporting member. 13. The device as claimed in any of the preceding claims 7, 8 and 11 wherein said end cover is anchored in position by/on said receptacle. t 14 The device as claimed in any of the preceding claims 7 to 13 wherein said receptacle is of generally plastics construction. 15. The device as claimed in any of the preceding claims 7 to 13 wherein said receptacle is of generally metallic construction the contact parts thereof being optionally provided with a nonstick coaling such as of polytctrafluorocthylenc. 16. The device as claimed in any of the preceding claims 1 to 15 wherein said piston rod is of generally stepped configuration comprising one or more stepped portions, one said stepped .f portion constituting said chamber. 17. The device as claimed in the preceding claim 16 wherein the contact parts of said chamber optionally comprise a non-stick coating such as of polytetrafluwoethylene. 18. The device as claimed in any of the preceding claims 16 and 17 wherein said cylinder is of" generally stepped configuration comprising one or more stepped portions(segments). - 19. The device as claimed in the preceding claim 18 wherein one said segment constitutes substantially the swept volume(space) swept by said piston during operation. 20. The device as claimed in the preceding claim 19 wherein an upper part of said segment constitutes said limit means that provide said upper limit of travel of said piston either direct or through an intermediate component that may be resilient or otherwise. 21. The device as claimed in any of the preceding claims 1 to 20 wherein said housing and cylinder are attached to each other by rivet means. 22. The device as claimed in the preceding claim 21 wherein the spacing between said housing and cylinder for the f!ow/circulation-of-steam-therewithin-is provided by a plurality of dimples or spacers or bodi, said dimples being located upon said housing or cylinder or both. 23. The device as claimed in the preceding claim 22 wherein some, more or all of said rivet means are located at said dimples or spacers or both. 24. The device as claimed in any of the preceding claims 21 to 23 wherein passage(s) are provided in one or more said rivet means such as to permit ijispiration and expiration of air from said swept space during operation of said piston. 25. The device as claimed in any of the preceding claims ! to 24 wherein said piston is hollow and compiises steam oiitiet(s) at the tipper portion thereof 26. The device as claimed in the preceding claim 25 wherein said outlet(s) comprise a tubular post adapted to function also as a weight-loaded pressure controlling/releasing valve by the mounting of the weight(s) thereof up 27. The device as claimed in any of the preceding claims 25 and 26 further comprising deflector means for directing steam issuing from said outlet(s) to said chamber for direct steam cooking of the cotents thereof during operation. 28. The device as claimed in the preceding claim 27 wherein said stopping means comprise one or more pins abutting, or attached to said deflection means. 29. The device as claimed in any of the preceding claims I to 28 wherein said retaining means comprise a longitudinal member the ends whereof can be retracted gainst spring pressure and released to engage with slots, groove(s), hooks or other such means located on said cylinder. 30. The device as claimed in any ofthe preceding claims 1 to 29, wherein the sealing gasket between said piston and cylinder comprises a lip portion that engages with a groove upon said piston such as to ensure the correct mounting of said gasket. 31. A device for carrying out cooking and/or extrusion operations on food{s) using steam, substantially as herein described-with reference to and as illustrated inthe Figs. 1,3,4 and 5 of the accompanying drawings. 32. A device for canying out cooking and/or extrusion operations on food(s) using steam, substantially as herein described with reference to and as illustrated in the Figs. 2,3,4 and 5 of the accompanying drawings.

Documents:

0455-mas-2001 abstract duplicate.pdf

0455-mas-2001 abstract.pdf

0455-mas-2001 claims duplicate.pdf

0455-mas-2001 claims.pdf

0455-mas-2001 correspondence others.pdf

0455-mas-2001 correspondence po.pdf

0455-mas-2001 description (complete) duplicate.pdf

0455-mas-2001 description (complete).pdf

0455-mas-2001 drawings duplicate.pdf

0455-mas-2001 drawings.pdf

0455-mas-2001 form-1.pdf

0455-mas-2001 form-19.pdf

0455-mas-2001 form-26.pdf

0455-mas-2001 form-5.pdf