Title of Invention

A STRAIGHT GRIPPING ATTACHMENT DEVICE FOR PRINTING MACHINE

Abstract

The present invention relates to a straight gripping attachment device comprising: a gripper shaft (1) having a lever (8) mounted on its one end to be fitted into the machine characterized in that said gripper shaft (1) having a plurality of bearing blocks (2), slats (7) fitted on to the said bearing blocks (2) and pads (6) mounted on the said slats (7) so that the gripping surface of the pads (6) is angular to the mounting surface of the device, a plurality of cotllers (5) fitted tightly on the said gripping shaft (1) between the bearing blocks (2), each of the said colters (5) has gripper holder (3), gripper (4) fitted to the said gripper holder (3), coil springs (12) provided intermittently on the said gripper shaft (1), whereas pads (6), slats (7) and bearing blocks (2) are being stationery relative to the gripper shaft (1) while grippers (4), gripper holders (3) and colters (5) have angular movement. Fig. 3

Full Text

The invention relates to a straight gripping attachment device for use in printing machines to replace pincer gripper to convert perfection machines to straight machine. More specifically the present invention relates to straight gripping attachment/ assembly having tapered pads that are angular to the mounting surface of the cylinder to convert perfection printing machines to straight machines. The conversion is without changing any setting on the drive side of the machine and without any drilling, tapping or any kind of machining in the original component. BACKGROUND OF THE INVENTION In sheet-printing machines, the sheets which are to be printed are removed from a stack of paper and are then fed, via conveying devices, such as conveying suckers, suction belts or grippers, to one or more successive printing stations, in which monochrome or multi-colored printed images are transferred to the sheets. The finished, printed sheets are then placed on a stack. In sheet-fed rotary offset machines, the sheets are guided, held by grippers, from printing unit to printing unit alternately via impression cylinders and guide drums downstream of the cylinders, the impression cylinders, together with the associated blanket cylinders of a printing unit, forming the respective printing stations. Due to the high levels of precision required for the gripper devices and the remaining moving parts, the outlay on the device which is needed to produce high-quality multicolored printing in the rotary offset sheet-printing machines is comparatively high. A known printing unit can include a plate cylinder, a blanket cylinder and an impression cylinder, all of which have a single, common diameter. Such a unit can also include three sheet-transfer drums and may be of the type disclosed in German Patent No. 1761 780. The impression cylinder of each printing unit of such a machine and the sheet-transfer drums or transfer drums that are arranged between two printing units are also of the same single diameter and are not intended for the turning of the sheets to be printed. The guidance of the sheets during the transport thereof through the sheet-fed rotary printing machine is performed in a region underneath the transfer cylinders or transfer drums, and if a reversing or turning device is used, by which the sheets are temporarily stored on a storage drum, underneath the storage drum, by respective pneumatic sheet-guiding devices. The sheet-guiding devices are formed of at least approximately planar guide plates, which are disposed at a spaced distance from the path of movement of the gripper devices of the drums and/or cylinders, and which are equipped with a large number of slit nozzles or air jets. Blast air emerging from the air jets at least approximately tangentially to the surface of the guiding devices, in that regard, produces a carrying air cushion which holds the respective sheet at a well-defined spaced distance above the guide surface. The sheet is guided on a circular path which extends radially outside the ideal path of movement, as a result of which a disruptive effect called "sheet pushing or sliding" occurs during the transfer of the leading edge of the sheet from a transfer drum to the gripper devices of the impression cylinder disposed downstream from the transfer drum. That disruptive effect can be attributed to the fact that the speed of the sheet on the radially outward-lying path of movement is greater than the speed of the gripper devices of the impression cylinder, which hold the leading edge of the sheet, due to which the rear or trailing part of the sheet must be braked in the region before the printing nip, and therefore leads to pushing or sliding of the sheets before the printing nip. In the conventional sheet-fed rotary offset printing machines gripping pads are mounted perpendicular to the mounting surface and their surface is parallel to the mounting surface. They are often rectangular in shape and have a coating on them. U.S. Pat. No. 3,951,177 discloses a gripping device essentially consisting of a pneumatic suction movable nozzle, which must be capable of effecting a rotary and traverse motion in a plane perpendicular to the plane of the fabric being manufactured and parallel to the warp yarns, in order to bring the nozzle into the cutting zone and to cause it to follow the motion of the sley of the loom. Patent no. GBM 6 949 816, describes a sheet guiding drum or cylinder in which, besides gripping the forward or leading edge of the sheet, suction air is used to suck the gripped sheet against the cylinder surface, for better guidance. Furthermore grippers or suckers are provided for holding the rear or trailing edge of the sheet being transferred. Such devices are employed in perfector presses or printing machines capable of printing either on a single side or on both sides of a sheet. German patents 1 155 145 and 1 611 241 describe various embodiments of sheet guiding drums or cylinders of this type. They are distinguished particularly in that the sheet which is held by grippers at the forward or leading edge thereof, is sucked in at the rear or trailing edge thereof and is retained under slight tension acting in a direction opposite to the direction of rotation. The tension is produced by adjusting holding devices that engage the rear or trailing edge of the sheet. A crease-free and wrinkle-free sheet transfer to the sheet reversing or turn-over cylinder of the perfector press is sought to be achieved by the foregoing heretofore known constructions. GB372729 describes carriers and forwarders; gripper mechanism.--In a sheet-feeding mechanism for the oscillating cylinder of a printing-machine of the kind in which the sheets are taken from stops on a feed-board by grippers on an oscillating member and are transferred to grippers of the cylinder as this cylinder moves forward to effect the printing, the member is controlled in such manner as to prevent inaccuracies in the transfer of the sheet even after a long period of usage. To this end toothed gearing is avoided in the oscillating mechanism for the shaft of the member, and as the sheet is moved towards the grippers the shaft is controlled by a cam operating on a roller on a lever fixed to the shaft which is spring-controlled by means of springs acting on rods pivoted to arms fixed to each end of the shaft. When the roller moves off the high part of the cam, levers fixed to the shaft engage abutments, on the sides of the cylinder, and these control the motion of the sheet-transfer grippers while the sheet is being taken by the grippers. The members are cut away at parts corresponding to the transfer grippers, and the abutments, are timed to take control of the grippers at the time they reach these cut-away parts. The member is returned to its sheet-receiving position by the high part of the cam. EP0158129 describes Sheet-fed rotary printing machine of in-line construction for single-sided multi-colour printing or perfecting comprising at least one reversing device as well as devices for processing paper and cardboard, each printing unit featuring, besides a plate cylinder and a blanket cylinder, an impression cylinder being an at least double-sized in diameter and a sheet transfer drum wherein one or several impression cylinders can be converted into storage drums each having at least two sheet-carrying surfaces, and wherein a sheet transfer drum following a respective convertible impression cylinder is designed as a reversing cylinder having at least two pincer gripper systems. Generally there are two types of sheet fed offset printing machines available in the market: Straight machines do printing on one side of the paper in one go and Perfection machines can give dual printing in one go with slight adjustments in perfection unit. Pincer gripper is most important assembly of the perfection mechanism. Pincer gripper is mounted on perfection cylinder. Its main function is to hold the paper from one cylinder and transfer it to other. In straight printing it holds the paper from the front edge from the previous cylinder and delivers it to next cylinder for one side printing. In perfection printing it holds the paper from the tail end of the previous cylinder and delivers it to next cylinder turning the paper upside down for dual printing. This intricate functioning of dual printing results in faster wear & tear of pincer gripper assembly. This assembly is usually required to be replaced or repaired after a period of 3 - 5 years. More over the users who do not desire dual printing find it costly and difficult to maintain. Many users in Asia buy second hand perfection printing machines specially small scale units which use these machines for straight printing. Frequent replacement of Pincer gripper in Perfection machine is a great financial burden on them. It is accordingly an object of the invention to provide a device for conveying sheets in a printing machine which overcomes the above-mentioned disadvantages of the prior art in which the sheets are conveyed to the printing drums without it being necessary to use complex mechanical moving parts. In one embodiment the present invention comprises of tapered pads mounted on slats which give an angular gripping surface to the assembly. Alternately slats can be tapered to give an angular gripping surface to the assembly. The pads are coated with any conventional coatings preferably tungsten carbide coating to achieve hardness and due roughness and also to reduce wear. The object of the present invention is to provide a device which has a longer life simple mechanism. Yet other object of the present invention is to provide a low cost device which has at least 50% of the price of Pincer gripper and easy to maintain. Another object of the present invention is to provide device which has tapered pads that are angular to the mounting surface. Yet another object of the invention is to provide a device which can replace Princer Gripper without any drilling, tapping or any other kind of machining in the original component Accordingly the present invention relates to a straight gripping attachment device comprising: a gripper shaft (1) having a lever (8) mounted on its one end to be fitted into the machine, a pair of cam followers (9) mounted on the said lever (8), a pair of cams (10) nearly superimposed on each other associated to the said cam followers (9) characterized in that said gripper shaft (1) having a plurality of bearing blocks (2) at short intervals in such a manner so as to give the said gripper shaft (1) a free movement without axial movement, slats (7) fitted on to the said bearing blocks (2) and pads (6) mounted on the said slats (7) so that the gripping surface of the pads (6) is angular to the mounting surface of the device, a plurality of collers (5) fitted tightly on the said gripping shaft (1) between the bearing blocks (2), each of the said collers (5) has gripper holder (3) attached to it with hex screw and gripping spring (14), gripper (4) fitted to the said gripper holder (3), coil springs (12) provided intermittently on the said gripper shaft (81) having its one end attached to slats (7), whereas pads (6), slats (7) and bearing blocks (2) are being stationery relative to the gripper shaft (1) while grippers (4), gripper holders (3) and collers (5) have angular movement. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS FIG. 1 shows the existing princer gripper assembly. FIG. 2 shows the various parts of the straight gripper attachment. FIG. 3 shows the straight gripper attachment/assembly. FIG. 4 shows the one segment of the straight gripper attachment/assembly. DETAILED DESCRIPTION OF THE INVENTION The invention relates to a straight gripping attachment device for use in printing machines to replace pincer gripper to convert perfection machines to straight machine. As shown in Fig. 1 the existing pincer gripper assembly comprises of two gripper shafts. The outer shaft (1A) is hollow and other shaft (2A) is inserted in the outer shaft. There are two gears (3A, 4A) at each end to drive the inner and the outer shafts. Both the shafts are governed by four cams (5A) at each end via gear and rack arrangement. Fig. 2 shows that the device of present invention has mainly the following parts: 1.Gripper Shaft: Gripper shaft acts as a support to the entire assembly which is mounted on it. 2. Bearing Blocks: Bearing Blocks are mounted on the main cylinder of the machine. The main function of the bearing blocks is to hold and give free movement to the gripper shaft 3. Gripper Holder: Gripper is mounted on a gripper holder which has free movement on the gripper shaft and creates pressure between gripper & pad 4. Gripper/gripping member: The main function of the gripper is to grip or hold the paper from one unit to the other unit. 5. Coller: Coller act as a support to the gripper holder. It is fixed on the gripper shaft. 6. Pad: Caps the gripping of the paper is between gripper and pad. 7. Slats: The main function of Slats is to hold the pads. 8. Lever: Lever is mounted at on end of the gripper shaft. It transfers angular movement to the gripper shaft. 9. Cam Follower: Cam follower is mounted on the lever and it follows the path of the cam. 10. Cam: Cam controls the opening and closing of grippers. 11. Hub: Hub holds the cam and remains stationery with respect to the printing machine. 12. Coil spring are to press the cam follower on the cam and to give drive angular movement to the gripper shaft when cam follower moves from higher to lower radius. 13. Tensioners to controf the tension of the coil springs 14. Gripping springs are to provide pressure between grippers and pad General hardwares like, nuts bolts, screws, washers, circlips etc., are also used. As shown in Fig. 3 In the device of the present invention comprises of a plurality of bearing blocks (2) arranged horizontally across the whole assembly. A number of slats (7) are fitted on these bearing blocks (2) with threaded bolts on which pads (6) are mounted. These pads (6) are tapered at one end so as to give an inclined gripping surface to the assembly. Alternately the slats (7) can have the tapered ends to have an inclined surface of the pads (6) The pads (6) are mounted on the slats with threaded bolts and are tightly fitted. To have a firm gripping and to reduce wear, pads (6) are given a hard and rough surface by a coating of Tungsten Carbide or any other conventional material. A gripper shaft (1) is fitted with the bearing blocks (2) with the bearings such that the said gripper shaft (1) has free movement with bearing blocks (2) without axial movement. A Lever (8) is mounted at the one end of the gripper shaft (1). A plurality of collers (5) and gripper holders (3) are provided at short intervals on the gripper shaft (1). Collers (5) are tightened on the shaft (1) with threaded nuts and bolts and all the collers (5) are aligned. However gripper holders (3) have free movement with the shaft and are joined with hex screws and gripper springs (14) with the collers (5). Gripper's/gripping members (4) are fitted on the gripper holder (3). Coil springs (13) are also provided intermittently. Coil springs (12) are mounted with the help of tensioners (13) on the gripping shaft and have its one end connected to the slats (7). The lever (8) has two cam followers (Fig 2). which are associated to a pair of cams (10). Cams (10) are mounted on the side of main bearing housing with hub (11) and are substantially superimposed. The cam followers follow the path of the cams. One Cam is adjusted to tune the closing of the Grippers and other is to tune the opening of the grippers. Cam-hub remains stationary with respect to the complete machine. Bearing blocks (2) are mounted on the tapped hole available on the original cylinder or in other words it is mounted on the same place from where the Pincer Gripper assembly has been removed. Pads (6), slats (7), bearing blocks (2) are stationary with respect to the complete assembly. Gripper (4), gripper holder (3) and collers (5) have angular movement. This angular movement closes and opens the grippers (4). Sheet is gripped between gripper/gripping member (4) and pad (6). This angular movement is governed by the cam (10) through lever and cam follower. Each printing unit comprises a plate cylinder, a blanket cylinder and an impression cylinder, all of a single diameter, as well as three sheet-transfer cylinders. Two of the sheet-transfer cylinders are of single diameter and one is of the double diameter for printing jobs using a one-sided printing process. Whereas the device is mounted on the cylinder the pads (6) are angular to the mounting surface of the cylinder, this cylinder moves. From lower radius to higher radius cam (10) gives the drive to the cam follower (9), lever (8), and gripper shaft (1) to bring back the Lever (8) from higher radius to lower radius of the cam (10). This movement facilitates the closing and opening and transferring of the sheet from one unit to the next unit. While the assembly functions the gripping members (4) move and the pads (6) remain stationery. In operation as the sheet is moved towards the grippers the movement of the gripping shaft (1) is controlled by a pair of cams (10) operating on cam followers (9) on a lever (8) fitted to the shaft {1} which is spring-controlled. When the cam followers (9) move to the higher radius of the cam(10), lever (8) fitted to the shaft (1) gives angular movement to the assembly while the sheet is being taken by the grippers. The sheet is gripped between grippers (4) and pads (6). It is then lifted off the circumferential surface of the impression cylinders with the aid of grippers (4) in order for the front edge to be transferred to a downstream sheet-guiding cylinder It is also possible to replace the straight gripping attachment/assembly with the original pincer gripper to convert straight machine back to perfection machine. Numerous modifications and variations in practice of the invention are expected to occur to those skilled in the art upon consideration of the foregoing descriptions of preferred embodiments thereof. Consequently, only such limitations should be placed on the invention as appear in the following claims I claim: 1. A straight gripping attachment device comprising: a gripper shaft (1) having a lever (8) mounted on its one end to be fitted into the machine, a pair of cam followers (9) mounted on the said lever (8), a pair of cams (10) nearly superimposed on each other associated to the said cam followers (9) characterized in that said gripper shaft (1) having a plurality of bearing blocks (2) at short intervals in such a manner so as to give the said gripper shaft (1) a free movement without axial movement, slats (7) fitted on to the said bearing blocks (2) and pads (6) mounted on the said slats (7) so that the gripping surface of the pads (6) is angular to the mounting surface of the device, a plurality of collers (5) fitted tightly on the said gripping shaft (1) between the bearing blocks (2), each of the said collers (5) has gripper holder (3) attached to it with hex screw and gripping spring (14), gripper (4) fited o the said gripper holder (3), coil springs (12) provided intermittently on the said gripper shaft (81) having its one end attached to slats (7), whereas pads (6), slats (7) and bearing blocks (2) are being stationery relative to the gripper shaft (1) while grippers (4), gripper holders (3) and collers (5) have angular movement. 2. A straight gripping attachment device as claimed in claim 1 wherein said pads (6) are tapered at one end to provide inclined gripping surface. 3. A straight gripping attachment device as claimed in claim 1 wherein said bearing blocks (2) are aligned and arranged horizontally across the whole assembly. 4. A straight gripping attachment device as claimed in claim 1 wherein said collers (5) are tightened to the gripper shaft (1) with nuts and bolts and are aligned. 5. A straight gripping attachment device as claimed in claim 1 wherein said bearing blocks (2) are mounted on the tapped hole available on the original cylinder. 6. A straight gripping attachment device as claimed in claim 1 wherein said cam followers (9) are associated to the cams (10) to follow the path of the cam (10). 7. A straight gripping attachment device as claimed in claim 5 wherein said cam followers (9) move to a higher radius of the cams (10), lever (8) fitted to the shaft (1) gives angular movement to the assembly. 8. A straight gripping attachment device as claimed in claim 1 wherein said cams (10) are mounted on one side of the bearing housing with hub whereas one cam (10) is adjusted to tune the closing of the grippers and other is to tune the opening of the grippers. 9. A straight gripping attachment device as claimed in claim 1 wherein said coil springs (12) are mounted with help of tensioners (13) of the said gripping shaft (1) having its end connected to its shafts.. 10. A straight gripping attachment device substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

577-DEL-2006-Abstract-(19-01-2009).pdf

577-del-2006-abstract.pdf

577-DEL-2006-Claims-(19-01-2009).pdf

577-del-2006-claims.pdf

577-DEL-2006-Correspondence-Others-(19-01-2009).pdf

577-del-2006-correspondence-others.pdf

577-DEL-2006-Description (Complete)-(19-01-2009).pdf

577-del-2006-description(complete).pdf

577-del-2006-drawings.pdf

577-DEL-2006-Form-1-(19-01-2009).pdf

577-del-2006-form-1.pdf

577-DEL-2006-Form-2-(19-01-2009).pdf

577-del-2006-form-2.pdf

577-del-2006-form-26.pdf

577-del-2006-form-3.pdf

577-del-2006-form-9.pdf