Title of Invention

MODIFIED DISTRIBUTOR VALVE WITH PRESSURE LIMITED FEATURE

Abstract

ABSTRACT APPLICATION NO.MAS/1639/97 DATED 23/07/1997 TITLE : MODIFIED SITRIBUTOR VALVE (C3W1 - P) WITH PRESSURE LIMITING FEATURE An improved distributor valve in an air brake system in railway vehicles like locomotives, wagonas and passemnger coaches to achieve qulek charging function and pressure limitinfg function, such that quick brake application is achieved form the very start of the braking function, by anabling a quick charge of comparessed air into the brake cylinder and to move the piston outward against the heavy resistance offered by various linkage mechanisam called 'Brake Nigging'. The invention persists retro- filsent on those valves serving in the field.

Full Text

This invention relates to an improved air brake system with Distributor Valve which Is very critical in railway vehicles Hke locomotives, wagons and passenger coaches, BACKGROUND OF THE INVENHON Frequent cases of wheel sliding due to higher brake cylinder pressure in coaches of high speeds trains with air-brakes were observed. As per field trials and consequent reports It was found that even for a slight increase ten brake pipe pressure above 5 kg/cm2 the brake cylinder pressure exceeded 3.8 kg/cm2. The result was skidding of wheels. So attempts were made to develop a feature in the Distributor Valve which wit! restrict the maximum cylinder pressure to 3,8 kg/cm 2. More particularly, the improved version of Pressure Limiting Feature relates to consistent performance of the Distributor Vaive within the safe specified value. This invention also relates to achieving excellent braking (unction within the specified parameters like brake application time, brake release time, charging of reservoirs, build-up of maximum power etc, The Invention relates to new design feature termed "Pressure Limiting Feature" In the Distributor Valve, The design involves two objectives - 1. To control the effect of variation in the reference pressure maintained by tha control rsservoirs and consequently avoid the severe braking force and minimize the wheel skidding, 2. Secondly, to restrict the compressed air pressure delivered by the Distributor Valve to the maximum preset limit of 3,8 Kg/Sq. Cm. Irrespective of the level of reference pressure maintained in the control reservoirs. The design is related to specification laid down by RDSO governing the type of Distributor Valve to be used In passenger coach brake system i.e. specification no, Q2-ABR-94- Appendix A2 - Serial No. 5.2.9, This specification states that — S.2.9. - The Distributor Valve shall have in-built pressure limiting feature for unil^rm maximum brake cylinder pressure of 3.8 ±_ 0,1 Kg/cm2 irrespective of Increase In brake pipe pressure of S Ko/cm2. BASIC PRIHCIPUE PF OPERATIOH OF BRAWNq SYSTEM i- Air brakes In railway vehicles have replaced the vacuum brakes in vehicles like bcomotlves, wagons and passenger coaches. The basic air brake system adopted In wagons and the passenger coaches by and large is the same but for the usage of a facility to feed the air reservoirs in the coaches continuously to ensure Inexhaustibility of the brake power in passenger coaches, The Distributor Valve is the unit on each car which performs the function of distributing compressed air into various pipes at various pressure according to the signals issued by the driver. When the brake pipe is charged to a particular value (say 5 bar) as set on Automatic brake valve In the locomotive, the control reservoir connected to every Distributor Valve on each coach also gets charged to the same value, (i.e. 5 bar) When a drop 1.5 kg/sq. cm is made in brake pipe pressure, the Distributor Valve charges brake cylinder to 3,8 4^0,1 bar drawing air from the auxiliary reservoirs. But any further reduction in brake pipe pressure, will not increase the brake cylinder pressure. The is achieved by the special feature on the main valve portion of the Distributor Valve which controls the maximum brake cylinder pressure = 0.76 times Control Reservoir pressure. So if Brake Pipe pressure Is = 5 bar and the Control Reservoir Pressure is also = 5 bar, the maximum Brake Cylinder Pressure = 0,76 X 5 only = 3.8 kg/sq.cm only. Comparing the overall similar design approach between the Distributor Valves used for wagon braking and passenger coach braking. The main concept of design for the wagon brake control is to 'Brake the loads'. Whereas In atr braked passenger coaches, the design approach is to 'Brake the Speed' BRAKE THE LOADS: Wagons carry a higher pay load at comparatively slower speeds, say 80 -100 Kmph. The thrust in brake design Is to stop these heavily loaded vehicles. BRAKE THE SPEED: In passenger coaches, the pay load is almost constant and does not vary appreciably whether the coach is full or empty and is comparatively lower than (Vhat a wagon can carry, This runs at higher speeds like 140 Kmph and above. Braking at such speed may at times result in locking of the wheels and :onsequent skidding relating to intensity of brake power generated by the distributor Vaive and a few more externa! factors. The external factors which sre InRuential are Condition of rail / Presence of foliage and other fine abrasive iust on the tracks, presence of water film on the tracks etc. 3BJECT OF THE INVENTION As such the main objective of this Invention is brake 'The Speeds' without unning the risk of skidding. The skidding phenomen observed generally in ailways Is known as 'Brake Binding', This Is very much detrimental to )assenger safety firstly and damage to wheel surface secondly. The Distributor Valve assembly according to the invention provides for a better and desired performance of the valve by achieving efficient braking function vide - 1. quick charging function and 2. pressure limiting function. The basic design of Distributor Valve involves various groups of sub¬assemblies of components fitted in a common housing to execute the co¬ordinated functions of braking. The Distributor Valve used is a pneumatic device. As such this valve reacts to pressure fiuctuatlons in comparison to a reference pressure stored In a small reservoir of 6 L volume called, "Control Reservoir". Hence if the very reference pressure rises to above the preset level, the same valve, will deliver higher compressed air pressure for the braking function. The reference pressure tn the Control Reservoir will rise to higher levels - in the following instances: - 1. V^hen the driver releases the brakes completely In one stroke at his brake valve in the locomotive. The high-pressure surge caused due to the release of brake suddenly leads to increase in preset reference pressure in the control reservoir. 2. V^hen the train is decoupled from one locomotive and coupled to a second locomotive-during a long Journey i.e. when the train is detached from a "lower level" electric locomotive and attached to a 'higher level' diesel locomotive, then the control reservoir In the coaches of the train start receiving the higher pressure, delivered by the new locomotive attached. Thus subsequent brake applications in the train may tend to be more severe, because the very reference pressure in the control reservoirs has risen to higher levels. Since this variation in the reference pressure maintained by the control reservoirs is not possible to be detected, there is always a strong likelihood for delivery of more severe braking force than designed and consequential wheel bidding. It is obvious ttnat the Control Reservoir pressure should be maintained at S kg/sq.cm, to get a maximum brake cylinder pressure of 3.8 kg/sq.cm. To achieve this, Brake Pipe should be maintained at 5 kg/sq.cm. this can be maintained as long as Automatic brake vaive is functioning alright and the Brake Pipe gauge in front of the driver is properly calibrated. In casej the Brake Pipe gauge reads 5 kg/sq.cm when the acutual pressure is 6 kg/sq,cm., then during a subsequent service brake application, the brake pipe is reduced by Automatic brake valve by 1.5 kg/sq.cm only so the Brake cylinder pressure on a service brake application will be 3.8 +_kg/sq.cm only. But a further reduction of brake pipe to over-reduction and emergency would rasuit in a maximum Brake Cylinder pressure of 0,75 times the Brake Pipe Pressure I.e. 0,76 X 6 = 4.56 kg/sq.cm, The invention's main objective Is to avoid this and achieve Controlled Pressure Limiting feature. DESCRIPTION OF THE IMVEWTION WITH REFEREWCE TO DRAWINfiS =. The invention will now be described with reference to the accompanying drawings which are as follows : Fig. 1 is a sectional view of the Distributor Valve as per the o!d design -highlighting the components which have been removed / modified in the new design according to the invention. Fig.2 is a sectional view of the Distributor Valve according to the invention, part by part highlighting the newly added items and Items which are modified as per the invention. Fig,3 is the functional arrangement of the modified portion. The brake cylinder pressure from main va[veC19) Is connected to chamber A. Normally when there Is no charging to Brake cylinder, the control spring(2) remains Hilly expanded and the supply valve seat(20) is unseated, So, when the main valve(19) charges Brake cylinder, the same finds its way into Brake cylinder passage 'B' through the unseated supply valveC?). The brake cylinder pressure from chamber B also charges into chamber 'C below the dtaphragm(5) through a restricted opening. When the pressure in chamber 'C develops a force equal to that of the spring force, the dlaphragm(5) unit moves up, This allows the vaive(7) to seat on supply valve, thus cutting off the excess brake cylinder pressure from going to chamber 'B' and from the brake cylinder. When the brake gets released, the valve moves down because of imbalance aeated by the venting of pressure form below the valve. Further release takes place at the main valve as in the existing design of Distributor Valve. The Distributor Valve assembly consists of number of machined components placed in a common house. The group of components --'-- LIST - A 1. - Cap Part - No. 1 2. Spring Pert- No,2 3. Guide Part-No. 3 7. Valve Part- No.7 8. Spring Part- No.S 9. Choke Part- No. 12 13. Plug Part-No. 13 14. '0' Ring Part-No. 14 have been deleted and LIST - B 1. Clamping flange Part - No. 1 2. Regulating Spring Part-No. 2 3. Guide Inshot Part- No.3 4. s, Diaphragm Clamp Diaphragm Part- No.4 Part - No. 5 6. Plug 7. Valve 8, Spring 12, Cap 13. Circlip 0 15 14 Spring Seat Top 15. Stem Adjusting 16. Spring Housing 17, Spring Seat Bottom 18. Circlip 0 15 Part- No.6 Part-No. 7 Part-No. 8 Part- No. 12 Part- No. 13 Part- No. 14 Part- No. 15 Part- No. 16 Part-No, 17 Part-No. 18 have been added in the modified version of the Distributor Valve. DETAILED DESCRIPTION OF THE INVENTION As per the invention and with reference to fig 3, the body of the Distributor Valve Is modified suitably to fit the new set of components, permitting retrofitment on those valves serving in the field. The original feature performed by the List - A group of components is termed INSHOT feature. As the name indicates, this feature permits a quick charge of compressed air into the brake cylinder to move the piston outward against the heavy resistance offered by the various linkage mechanisms called '"BRAKE RIGGING". Thus a quick brake application is achieved even from the very start of the braking function. As per the invention^ this group of components of List A have been removed and newiy designed components and partially re-designed as mentioned in List B are incorporated to adiieve ; 1. the Quick charging ; 2. Pressure Umittng Function in the Control Valve. Now we describe the invention and as illustrated in Fig 3, a Distributive Valve with a pressure limiting function and quick charging function comprising of:- a chamber A communicating with the brake cylinder pipe, a chamber B communicating with the brake cylinder, a chamber C being in free communication with chamber B, an inlet valve inter-posed between chamber A and chamber B to define a passage connecting between chamber A and chamber B, a valve seat positioned In chamber A adjacent to the Inlet valve to define the vale seating^ a control spring bias means fitted onto the vafve seat for biasing the valve away from the valve seating, a diaphragm positioned above chamber C and exposed to pressure in chamber C for flexing movement of said control spring by exerting upward force, such that when there is no charging to brake cylinder the control spring remains fijily expanded, such that when control spring remains fully expanded the supply valve sea is unseated, such ^at the supply valve seat Is unseated and main valve charges brake cylinder, pressure moves Into the brake cylinder passage B through the unseated supply valve, such that the cylinder pressure from brake cylinder passage B charges into chamber C through a restricted opening until the pressure diamber C is less than control spring force, such that v^hen pressure in chamber C develops a force equal to the spring force, the diaphragm is pushed up, such that when diaphragm is pushed up, the spring means is biased thereby seating the valve so as to cut off the communication between chamber A and chamber B, such that said diaphragm is exposed to said chamber B whereby when said chamber 6 is subject to pressure within, the said diaphragm will be subject to a force upwards, thereby biasing the spring also upwards, raising the said seat towards the valve and thereby closing the communication between chamber A and chamber B, DESIGN AND FUNCTIONING OF PRESSURE UNITING FEATURE IN C3W I- P DISTRIBUTOR VALVES CONSTRUCTION AND FUNCTION OF CHAMBER A, BAND C. Pressure Limiting Feature is a sub assembly of some components arranged in a particular way in the body casting of the C3W/ l-P Distributor Valve. Chamber A is a built-in "as cast" cored passage in the body casting of the Distributor Valve. In this cored passage, compressed air charges In the direction of arrow marl applied in the train, The chamber A has a threaded hole into which Plug (6) is screwed-in in such a way that compressed air cannot leak through the threaded Joint between Plug (6) and body of Distributor Valve. Before tightening the Plug (6) into the Body, Spring (8) is dropped into the recess in the Body and Valve Finished (7) is Kept on the Spring (8) in such a way that Valve Finished (7) is "kept floated up" by the Spring, When the Plug (6) is lightened into the Body, the Spring (8) will lift the Vaive Finished (7) upwards until the rubber bonded surface of the Valve Finished (7) abuts the projection in the underside of Plug (6). In this condition, the Spring (8) is designed to exert an adequate force on the Valve Finished (7) to hold it pressed against the projection in the underside of Plug (6) always. Thus compressed air charging into chamber A cannot escape from chamber A since the threaded joint in Plug (6) as well as the rubber bonded surface in Valve Finished (7) will not allow any leakage of compressed air into the top side (chamber 8). Cup (10) is fixed with an 0 Ring (9) and dropped into the Body recess to seat on a narrow edge in the Body. Diaphragm (5) is pre-assembled into the flanked recess of Guide (3) which Is fixed with 0 Ring (11) in the groove made in the shaft portion, The Guide (3) thus assembled with rubber components is inserted into the Cup (10) In such a way that ths shaft portion touches the metallic recess In Valve Finished (7). After placing Guide (3) as above, Diaphragm clamp (4) is pressed into position on Diaphragm (5) and 0 Ring (9) to hold the assembly intact. Clamping Flange (1) which has a threaded portion is screwed tightly into the Body in such a way that Diaphragm damp (A) \s held in position and hence the other parts already placed into the valve. Regulator Spring (2) is fixed on the spigot projection made in Guide (3). Stem adjusting is fixed in spnng Housing through the recess from inside and held in position by a Circllp (13) fixed on the outer surface. Spring Seat top (14) Is screwed into the threaded portion of Stem adjusting (15) to almost half the length of its thread. In this condition, this sub¬assembly of parts is placed on Regulator Spring (2) and the entire Spring Housing (16) screwed tightly Into the Clamping Flange (1). Under the action of Regulating Spring (2), Guide (3) will not be able to stay free but will be pushed down as much as the spring force at the height to which Spring Seat top (14) is kept screwed on Stem adjusting (15). In this condition, under the force of the Regulator Spring (2), Guide (3) will push open Valve Finished (7), compressing the spring (8) underneath. QUICK CHARGING When a brake is applied, compressed air from the Auxiliary Reservoir flows over into the Brake Cylinder through the passage A In which Vaive Finished (7) is kept open by Guide (3) under the action of Regulator Spring (2), Valve Finished (7) has square edges which allow free and unrestricted passage of compressed air around Its edges- Wlth the Valves finished (7) pushed open, compressed air, during the brake application, quickly surges past the recess provided on the edges of Valve Finished (7) and from there into chamber B through the open hole around the shaft portion of Guide (3). This air from chamber B goes to the Brake Cylinder to make an instant brake application, PRESSURE LIMITING As and when the compressed air pressure In the chamber B and hence in the Brake Cylinder rises gradually, the same compressed air also charges into the underside of Diaphragm (5) In chamber C through a hole made in Cup (10), Since the Diaphragm does not allow the compressed air to leak away, compressed air pressure builds up in chamber C also in the same as it is building up in the Brake Cylinders and chamber B. However, the pressure build-up in chamber C is slightly delayed than the rate at which it builds up in chamber B since the hole made in the Cup (10) is sized sufficiently small to restrict the flow of compressed air from chamber B to chamber C. Under the action of compressed air in chamber C, Diaphragm (S) starts lifting up, also carrying with it the flanked Guide (3). The force generated by the compressed air wilt try to overcome the downward force of the Regulator Spring (2) gradually and when both the forces become equal, the Guide Itself is lifted physically compressing the Regulator Spring (2) and taking the Guide upwards. Along with this lifting Guide (3), Valve Finished (7) also lifts up under the action of the Spring (8) until the rubber bonded face of Vaive Finished (8) touches the projection In the underside of Plug (6). At this point, the compressed air cannot escape into chamber B from A any further since Valve Finished (7) has sealed off the passage for compressed air flow, When this happens, the pressure in chamber B cannot rise any more. If the pressure is not adequate for the braking purpose, the Guide (3) can be forced down again to open the Valve Finished (8) a little more by turning the Stem adjusting (IS) which in turn causes the Spring Seat top (14) to move down the threaded portion of Stem adjusting (15), When the Spring Seat top (14) moves down, it will compress the Regulator Spring (2) more than what it had earlier. When the downward force exerted by the Regulator Spring (2) is thus increased, Guide (3) again gets pushed down a little more even against the upward force exerted by compressed air in chamber C on Diaphragm (5). When Valve Finished (7) is opened again as above, more compressed air will charge past the rubber surface of Valve Finished (7) into chamber B rising the pressure in Brai Thus by screwing In the Stem adjusting (IS), more compressed air pressure can be developed in chamber B and at each level of the Spring force of Regulator Spring (2), the compressed air pressure will always balance and would maintain the steady state. The actiustment of St«m acUusting (13) is made In such a way that the maximum presaura in chambar B Is limited to 3.8 Kg/cm^. Even !f the pressure in chamber A is more than 3.8 kg/cm^ say 5 kg/cm^, with an accurate adjustment of Stem adjusting (13), Valve Finished (7) wiil always seal off the passage of compressed air from chamber A to B at 3.8 kg/cm2 pressure in chamber B, thus "limiting the pressure". After properly calibrating the Stem adjusting (15) in such a way to get a Tiaximum Brake Cylinder pressure of 3.8 kg/cm^, Cap (12) is screwed on Spring -iousing (15) tightly to prevent access to Stem adjusting (15) lest the calibration Jhould be tampered by unauthorized people when the Valve is in service, lETROFITMENT In sheet 2 of 3 of the drawings attached, it can be seen that the parts of he Pressure Limiting Feature can be retrofitted into the same Body of the C3W -P DV by replacing the parts of the standard InshoE Valve which the DV is Jesigned with originally. The retrofltment facility Is designed with an aim to supply the "conversion :it" to the users of the C3W l-P DVs so that they can change their stock and eaiize the advantage of Pressure Limiting Feature which they desire. The sketch in sheet 1 to 3 shows both the standard Inshot Valve lonflguration and the Pressure Limiting Feature configuration closely for a better :omparison and would highlight the design adeptness with which the Pressure .imiting Feature is made to fit into the same place where the original Inshot 'aive components were being fixed. n this invention the principle advantages are listed below ;- Ease of adoptability since the new feature is built-in. 2. Restriction of compressed air pressure deiivered by the Control Valve to the maximum preset limit of 3.8 kg, sq/cm, irrespective of the level of reference pressure maintained in the Control Reservoirs. 3. Over ail performance of the Control Valve is within desired value in practice. 4. Existing Control Valve can be converted by retrofitment kit. 5. More safe for passengers. Prototype Control Valves with this new Pressure Limits Feature have been tested in the In-House Test facility center and have proved successful. The design is evolved in such a way that it is possible to convert all existing Control Valves in the Inventory and those that have already been put in service in Indian Railways by way of Retrofitment Conversion kits. 2. A distributive valve with a pressure limiting function and quick charging function comprising of:- 3 Chamber A communicating with the brake cylinder pipe, a chamber B communicating with the brake cylinder a chamber C being in free communication with chamber B, an inlet valve inter-posed between chamber A and chamber B to define a passage connecting between chamber A and chamber B, a valve seat positioned in chamber A adjacent to the inlet valve to define the vale seating, a control spring bias means fitted onto the valve seat for biasing the valve away from the valve seating, a diaphragm positioned above chamber C and exposed to pressure in chamber C for flexing movement of said control spring by exerting upward force, such that when there is no charging to brake cylinder the control spring remains lljliy expanded, such that when control spring remains fully expanded the supply valve sea Is unseated, such that the supply valve seat is unseated and main valve charges brake cylinder, pressure moves into the brake cylinder passage B through the unseated supply valve, such that the cylinder pressure from brake cylinder passage B charges into chamber C through a restricted opening until the pressure chamber C is less than control spring force, such that when pressure in chamber C develops a force equal to the spring force, the diaphragm is pushed up, such that when diaphragm is pushed up, the spring means is biased thereby seating the valve so as to cut off the communication between chamber A and chamber B, such that said diaphragm is exposed to said chamber B whereby when said chamber B is subject to pressure within, the said diaphragm will be subject to a force upwards, thereby biasing the spring also upwards, raising the said seat towards the valve and thereby closing the communication between chamber A and chamber B.

Documents:

1639-mas-1997 abstract granted.pdf

1639-mas-1997 claims granted.pdf

1639-mas-1997 description(complete) granted.pdf

1639-mas-1997 drawings granted.pdf

1639-mas-97 abstract.pdf

1639-mas-97 claims-duplicate.pdf

1639-mas-97 claims.pdf

1639-mas-97 correspondence-others.pdf

1639-mas-97 correspondence-po.pdf

1639-mas-97 description (complete)-duplicate.pdf

1639-mas-97 description (complete).pdf

1639-mas-97 drawings-duplicate.pdf

1639-mas-97 drawings.pdf

1639-mas-97 form-1.pdf

1639-mas-97 form-13.pdf

1639-mas-97 form-19.pdf

1639-mas-97 form-26.pdf

1639-mas-97 form-29.pdf

1639-mas-97 form-3.pdf

1639-mas-97 form-62.pdf