GB1599008A

GB1599008A - Push plates

Info

Publication number: GB1599008A
Application number: GB20043/78A
Authority: GB
Original assignee: Bendix Westinghouse Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1978-05-17
Filing date: 1978-05-17
Publication date: 1981-09-30
Also published as: AR217156A1; IT7968020A0; JPS54150560A; BR7902954A; ZA791959B; EP0006285A1; AU4669879A

Description

PATENT SPECIFICATION

( 11) 00 ( 21) Application No 20043/78 ( 22) Filed 17th May 1978

( 44) Complete Specification Published 30th September 1981

Rev ( 51) INT CL 3 B 21 D 53/88 08 ( 52) Index at Acceptance:

B 3 A 18 200 E FID 152 170 244 246 W ( 72) Inventor(s): ARNOLD COOKE ( 54) PUSH PLATES ( 71) We, BENDIX WESTINGHOUSE LIMITED, a Company incorporated under the Laws of Great Britain, of Douglas Road, Kingswood, Bristol, England, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to push plates and relates especially but not exclusively to push plates for fluid pressure operable brake actuators.

A fluid pressure operable brake actuator which employs a diaphragm is conventionally constructed by clamping a circular diaphragm at its periphery between two body parts, the diaphragm thus forming a boundary between a pressure chamber and a non-pressure chamber.

Extending from the non-pressure chamber there is provided an actuator push-rod on the inner end of which there is a push plate The push plate provides the area against which pressure acts via the diaphragm In operation, in the case of an air brake actuator, the pressure chamber is supplied with air brake pressure from a reservoir by a relay valve or control valve and the push-rod is connected to a brake linkage.

Hitherto push plates for brake actuators have been made by punching discs of appropriate diameter from 1/4 or 5/16 " sheet mild steel, the discs then being machined and surfaced to a quality high enough not to impair the life of the co-operating diaphragm The thickness of the discs must also be sufficiently great to be substantially undistorted by the forces exerted by the fluid pressure in the pressure chamber of the actuator.

According to the present invention there is provided a method of manufacturing push plates wherein laminar discs are produced and the discs being provided with radial stiffening members.

Advantageously, the discs may be produced in quantity by punching from sheet material and the shapes thereby produced between the discs providing radial stiffening members.

In order that the invention may be more clearly understood and readily carried into effect, the same will be further described by way of example with reference to the accompanying drawings which Figure 1 illustrates a typical fluid pressure 1 599 008 ( 19) operable brake actuator, Figure 2 illustrates an area of a sheet showing a number of discs and remaining material 5 after the punching of discs from the sheet and Figure 3 illustrates at (a), (b), (c) and (d), successive stages in the construction of a push plate in accordance with the invention.

Referring to Figure 1, the fluid pressure 6 operable actuator shown therein is shown in its unpressurised condition The actuator comprises a main body denoted by reference 1 and a pressure plate denoted by reference 2, each being formed of pressed steel and clamped together with the periphery of a reinforced rubber diaphragm 3 by means of a pressed steel clamping ring 4 Extending from an aperture in the non-pressure plate 1, a threaded pushrod 6 is provided at its inner end with a push 7 plate 7 urged against the diaphragm 3 by a light return spring 8 bearing against the end wall of the non-pressure housing The pressure plate 2 is provided with an inlet boss 9 for the connection of the pipe work for applying fluid pressure to the actuator and the non-pressure housing is provided with a breathing aperture and mounting studs 11 and 12 as shown.

In operation, when compressed air is introduced at the inlet boss 9, the diaphragm 3 moves the push-rod assembly outwards with a force proportional to its effective area and the fluid pressure As the air pressure is reduced or removed, the return spring moves the push-rod assembly back to the released position.

The push plate 7 is conventionally constructed as mentioned in the foregoing from 1/4 ' or 5/16 " mild steel plate which is subsequently machined and finished to prevent the working life of the diaphragm 3 from being impaired 5 The thickness of the push plate is required to be sufficiently substantial such that it is not susceptible to deformation under the effect of the fluid pressure in the actuator.

By virtue of the present invention, the push 5 plate 7 may be constructed from substantially thinner material than that referred to above by punching the push plates from sheet material of up to half the thickness and utilising elements which normally form part of the waste material resulting from the punching of discs from a sheet, for providing radial reinforcing ribs.

Referring to Figure 2, this shows a typical area of a sheet of mild steel from which a numS i O i 5 ro 1 599 008 ber of discs such as denoted by references 21 to 26 are to be punched It will be seen that if the discs are punched from orthogonal rows, elements such as the shaded area 27 normally constitute waste material but are usefully utilisable by the present invention.

The first step in production of such push plates therefore consists in the punching of pilot holes such as 28 the punching of such pilot holes being followed by the provision of further holes 29 in pairs to occur between one disc and the next in each direction These further holes enable the elements such as 27 to be immediately separated on the subsequent punching operation when the discs themselves are punched out Referring to Figure 3, at (a) is shown a disc and the cruciform waste material.

Figure 3 shows at (b) a disc after being subjected to two stages of drawing to effect a curled edge.

Figure 3 shows at (c) the method whereby by clamping between two mandrels and rotation between shaped rollers, the curled edge is rolled The centre aperture is then countersunk.

Thereafter, the cruciform piece is located as shown in Figure 3 at (d) with its aperture coaxial with the aperture in the disc and spot welded to form a complete push plate After painting to inhibit and protect against eventual rusting, the push plate is ready for mounting on an end spigot of an actuator push-rod by riveting or in other suitable manner.

Possible advantages of the present invention arise out of the economy of material used owing to the reduced thickness of the sheet stock from which the discs are initially punched, machining cutting or polishing of the discs to produce the quality surface which is necessary for co-operation with actuator diaphragms may be avoided owing to the edge profile produced by rolling.

Claims

WHAT WE CLAIM IS:-

1 A method of manufacturing push plates 45 wherein laminar discs are produced and the discs being provided with radial stiffening members.

2 A method as claimed in claim 1, wherein the discs are produced in quantity by punching 50 from sheet material and the shapes thereby produced between the punched discs being employed to provide said radial stiffening members.

3 A method as claimed in claim 2 wherein 55 prior to punching the discs the sheet material is punched to provide separating apertures to permit immediate separation of said shapes on punching of the discs.

4 A method as claimed in claim 2 or 3, 60 wherein prior to punching the discs, centre holes are punched in location of centres for said shapes and discs in orthogonal rows.

A method as claimed in claim 2, 3 or 4, including the step of curling the peripheries of 65 the discs to produce rounded edges.

6 A method as claimed in claim 5, wherein said shapes are spot welded into position within the curled peripheries.

7 A push plate manufactured in accordance 70 with any preceding claim.

8 A push plate according to claim 7 substantially as described herein with reference to Figure 3 of the accompanying drawings.

9 A fluid pressure actuator having a push 75 plate as claimed in claim 7 or 8.

A.R TURNER, Chartered Patent Agent Agent for the Applicants 80 Printed for Her Majesty's Stationery Office by MULTIPLEX techniques ltd, St Mary Cray, Kent 1981 Published at the Patent Office, 25 Southampton Buildings, London WC 2 l AY, from which copies may be obtained.