GB2110758A

GB2110758A - Actuator with contaminant excluding seal

Info

Publication number: GB2110758A
Application number: GB08233948A
Authority: GB
Inventors: Norman Dagger; Ian Joseph
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1981-12-02
Filing date: 1982-11-29
Publication date: 1983-06-22
Also published as: ES517881A0; DE3274226D1; EP0082611B1; IN159277B; EP0082611B2; ES8400948A1; EP0082611A1; GB2110758B

Description

GB 2 110 758A 1

SPECIFICATION

Fluid pressure operable actuators spigot 13. Between the end of the rod 11 and the capping piece 12 suitable shims 14 are inserted to establish a pre-determined clearance between the capping piece 12 and the inward end 15 of a rod 16 connected to a twin wedge (not shown) of a braking mechanism. In order to provide for alignment of the rod 11 within the bore of the tube 6, the rod 11 is provided with an annular groove 17 spaced from a similar outwardly positioned annular groove 18 provided in the capping piece 12. These annular grooves serve to locate an annular packing member 19 and an outwardly positioned packing member 20 The invention relates to fluid pressure opera- 70 ble actuators and relates especially but not exclusively to tube-mounted air pressure oper able brake actuators.

Air pressure operable actuators for brakes are known which comprise a housing with a diaphragm which divides the housing into a pressure chamber and a non-pressure cham ber. When the pressure chamber has fluid pressure applied to it, the diaphragm acts upon an output rod via a push plate. It is 80 relative to the rod 11.

usual moreover for the general alignment of Referring to Fig. 2 one such packing mem the output rod to be provided for by gluing or ber is shown on an enlarged scale and from otherwise attaching the diaphragm to the this illustration it will be seen that the packing push plate but despite this provision, the member 19 is designed firstly to be located alignment achieved thereby is by no means 85 on the rod by engagement of the inward precise. Further, where such an actuator is annular projection 21 thereof with the respec required to operate in a hostile environment tive annular groove 17 on the rod. Secondly, such as at the underside of a vehicle, it is by virtue of the portion 22 of substantial desirable to prevent contamination which may thickness the packing member provides a lo enter the vented non-pressure chamber of the 90 cating action whereby the rod is positioned actuator from being communicated to the centrally within the bore of the tube. Thirdly, brake mechanism being actuated by the push by virtue of the radially outward directed rod. reduced thickness portion 23 having a greater In accordance with the invention, a fluid natural diameter 'D' than the diameter 'd' of pressure operable diagpragm actuator has a 95 the solid portion 22, this provides a scraping housing (1, 2) a push rod (11) extending action within the bore of the tube to reduce outwardly of the housing via the bore of a the possibility of transmission of contaminants tube (6) characterised by the push rod having along the tube from the non- pressure chamber located thereon at least one packing member of the actuator to the operated brake mecha (1 g), which is guidingly slideable in the tube 100 nism. The packing members are preferably and contaminant sealing means carried with formed of hard wearing resilient moulded ma the packing member for protecting the outterial incorporating carbon granules for provid ward end of the tube against contaminants ing self lubrication and the life time of which passing thereto from the actuator. is adequate in relation to specified service In order that the invention may be more 105 intervals for such actuators. The packing clearly understood and readily put into effect, member 20 is substantially the same as mem the same will be further described for example ber 19. In order to avoid the possibility of with reference to the accompanying drawing pressure gradients being set up during opera of which: tion of the actuator, between the non-pressure Figure 1 illustrates in sectional diagramma- 110 chamber and the brake mechanism to the left tic view an actuator in accordance with the of the packing member 20 the scraping por invention and, tion 23 of the packing members 19 and 20 Figure 2 illustrates on an enlarged scale a are arranged to be less than gas tight so that packing member for use in an actuator such although they are effective to exclude contam- as shown in Fig. 1. 115 inants they do not result in appreciable pump Referring to Fig. 1 this illustrates a dia- ing action. Alternatively, small leakage paths phragm pneumatic actuator comprising a may be designed into the mouldings of the housing formed of a first part 1 and a second two packing members.

part 2 between which the peripheral bead 3 If it is not required to provide for adjust- of a diaphragm 4 is clamped by a clamping 120 ment of the effective length of the rod 11, the ring 5. Welded into an aperture of the part 1 capping piece 12 can be dispensed with and there is a tube 6 the inner end 7 of which the length of the rod correspondingly in extends inwardly of the actuator. creased to a fixed nominal length. In such a The outboad end 8 of the tube is welded to case, the annular groove 20 in the capping a mounting flange 9 whereby the assembly is 125 piece will now be formed near the outward mounted upon a brake mechanism. Within end of the rod 11 for locating the packing the actuator a push plate 10 is mounted on member 20.

the inboard end of a tubular push rod 11 with

Claims

an outboard capping piece 12 mounted into CLAIMS the end of the tubular

rod by means of a short 130 1. A fluid pressure operable diaphragm 2 GB 2 110 758A 2 actuator having a housing, a push rod extending outwardly of the housing via the bore of the tube, characterised by the push rod having located thereon at least on packing mem- ber, which is guidingly slideable in the tube and contaminant sealing means carried with the packing member for protecting the outward end of the tube against contaminants passing thereto from the actuator.
2. A fluid pressure operable diaphragm actuator as claimed in claim 1, characterised by the push rod having a further packing member located thereon outwardly of and spaced from the first mentioned packing member.
3. A fluid pressure operable diaphragm actuator as claimed in claim 2 characterised by a further sealing means carried with the further packing member.
4. A fluid pressure operable diaphragm actuator as claimed in claims 1, 2 or 3 characterised by the sealing means being so positioned on the rod that the inward end thereof clears the inward end of the tube in the fully retracted position of the actuator rod.
5. A fluid pressure operable diaphragm actuator as claimed in claims 1, 2, 3 or 4 characterised by respective sealing means being integral with the or each packing member.
6. A fluid pressure operable diaphragm actuator as claimed in claim 5 characterised by the or each packing member comprising an annular member with a solid portion and a radially outwardly directed reduced thickness portion the outer diameter of which is greater than that of the solid portion.
7. A fluid pressure operable diaphragm actuator substantially as described therein with reference to Fig. 1 or Fig. 1 and Fig.

of the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess Et Son (Abingdon) Ltd-1 983. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.

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