GB2188108A

GB2188108A - Clutch for air compressor assembly

Info

Publication number: GB2188108A
Application number: GB08606993A
Authority: GB
Inventors: Michael Charles Christmas
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1986-03-20
Filing date: 1986-03-20
Publication date: 1987-09-23
Also published as: EP0238336A1; GB8606993D0

Description

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GB 2 188 108 A

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SPECIFICATION

Gas compressor assemblies

5 This invention relatestoagascompressorassembly incorporating a clutch on the drive shaft thereof.

In the published Specification No. 2,147,371 A of a United Kingdom Patent Application there is described a clutch driven air compressor assembly, 10 the clutch being disposed between an engine and a piston and cylinder compressor, is spring loaded into the engaged condition and can be disengaged by the application of fluid pressure to an annular chamber containing a non-rotary annularpiston 15 which acts on the rotating clutch assembly to release it. It is necessary in such an assembly not only to provide a hardened facing on the annular piston but also precise machining is necessaryforthe positioning of locating means providing a high 20 degree of accuracy of location to prevent undesired take up snatch.

The present invention seeks to reduce the aforementioned shortcomings by providing a piston of which some rotation is permissible. 25 According to the present invention there is provided an air compressor assembly including a housing having a rotatable compressor shaft a rotatable input shaft in line therewith and a multiplate spring applied clutch via which the 30 compressor shaft is drivable by the input shaft, a fluid pressure operable annular release piston having inner and outer seals sealingly moveable in an annular pressure chamber which when pressurised acts on the rotating clutch assembly to 35 releasethe drive wherein said piston comprises a element moulded of resilient seal material on a rigid annularformerto provide integral inner and outer seals.

Preferably annular compression and tension 40 springs are provided to act on the outer and inner seals respectively to urge them against respective cylindrical walls of the chamber.

In orderthatthe invention may be more clearly understood and readily carried into affect the sample 45 will be further described by way of example with reference to the accompanying drawings.

Figure 1 illustrates a sectional view of a single cylinder compressor assembly in accordance with one embodiment of the invention and,

50 Figure2 illustrates an enlarged part-sectional view of a release piston employed in the compressor of Figure 1.

Referring to Figure 1 the compressor has a cast metal housing in the form of a combined crankcase 55 and cylinder denoted by reference 1 the cylinder being provided with a valve plate 2 containing the necessary valves co-operating with a cylinder head 3 with suitable inlet and output ports the details of which are of no consequence in relation to the 60 present invention and may be of a suitable construction. The compressor is provided with a piston 4 and a connecting rod 5 for effecting reciprocation of the piston 4 in the bore 6 of the cylinder by virtue of rotation of a crankshaft 7 the free 65 end of which runs in an oil pressure-lubricated bush

8 in an end plate 9 on one end of the crankcase. The other end of the crankcase is provided with a generally cylindrical integrally cast extension 10 which houses a clutch assembly via which the 70 crankshaft is driven by a rotatable input shaft portion 11 which runs in a ball bearing 12 captive in a further end plate 13 on this end of the housing. The outer end of the shaft 11 is provided with a key-way 14 and suitablefixingmeansfor mounting a gearwheel for 75 engagement with a geartrain of an internal combustion engine for driving the compressor. The input shaft 11 is integral with an input part 15 of a multi-plate clutch this input part being coaxial with and embraced by an output part 16 of the clutch, the 80 output part being carried on a spline 17 on the crankshaft of the compressor. The output part of the clutch comprises a hub portion 18 which is directly splined at 17 and co-operable therewith and the outer clutch plates 19 of the clutch there is an outer 85 cage 19 which is urged into a clutch engaged position bya pairofannulardiscsprings 20. The clutch assembly is retained together by an internal circlip 21 located in the cage member 19for reacting the force of the disc springs 20 and pneumatically 90 operable annular clutch release piston 22 is provided engageable with the cage 19 through a p.v.c. thrust element 23 in a sense to compress the springs 20 and release the clutch. Piston 22 is movable in an annular pressure chamber 28 and will be described in greater 95 detail below with reference to the enlarged sectional view in Figure 2.

The main bearing of the compressor on the drive side is provided by a substantial ball race 24 and the inward end of the input shaft and clutch input 100 member 15 is carried on a bearing 25 within a recess in the input part 15fixing means for retaining the bearing on the crankshaft being provided by a suitable nut 26. These bearings and the crank pin of the crankshaft are lubricated from the end plate 9 via 105 oil ways (not shown) in the crankshaft.

Considering now the manner of putting together the compressor assembly the compressor including the crankshaft, connecting rod and piston are first assembled together with the necessary valve and 110 cylinder head components. On the other hand, the output member 16 of the clutch assembly is assembled as a separate unit with plates properly aligned following which the pneumatic release piston 22 is placed in position, the clutch assembly 115 comprising the inner and outer plates and the disc spring 20 (retained together by virtue of the circlip 21) is placed onto the spline 17 on the crankshaft followed by the bearing 25andthefixing means including the locking nut 26. Thereafterthe input part 120 15 ofthe clutch integral with the shaft 11 already assembled into the bearing 12 in the end cover 13 are introduced into the assembly lining up the shaft form with the internal projections ofthe clutch plates and inserting the necessary fixing bolts (not shown) for 125 the plate 13.

Referring to Figure 2 ofthe drawings the annular piston 22 of Figure 1 typically comprises a mild steel former 41 around which a one-piece moulding of suitable flexible synthetic material is formed as 130 shown. This moulding provides a relatively thin

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GB2 188 108 A

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intermediate piston enclosing portion 42, respective inner and outer resilient locating or centralising shoulders 43 and 44 and annular inner and outer seal portions 45 and 46. The moulding is shaped with respective inner recesses 47 and 48 in the vicinity of the seal portion 45 and 46 to receive respective tension and compression springs 49 and 50. Spring 49 is such as to urge the smaller diameter seal portion 45 inwardly against the inner cylindrical wall ofthe pressure chamber 28 and spring 50 is such as to urge the larger diameter seal portion against the outer cylindrical wall ofthe pressure chamber 28. The thrust element 23 is attached to the outer surface ofthe portion 42 as shown.

In operation ofthe assembly, in the absence of a suitable compressed air signal in the control passage 27 from a governor or control valve, the clutch assembly will be in the engaged condition and therefore full drive torque will be applied on the 20 input shaft 11 through the clutch assembly to the crankshaft ofthe compressorforcharging compressed air storage reservoirs. Upon attainment of a first predetermined compressed air pressure in the reservoirs, the governor orcontrol valve will 25 provide a pressure signal via the passage 27 to the release piston 22 which will thereby be urged leftwards to compress the disc springs 20 and quickly release the clutch. The compressorthen stops until the controlling pressure signal in passage 30 27 is again removed to re-engage the clutch. During the released condition ofthe clutch, there is a tendencyfor rotation ofthe piston 22 in pressure chamber 28 and the material of which the piston is moulded is chosen to allow for this to occur, it being 35 remembered thatthe clutch operates "wet" in the presence of lubricating oil from the compressor bearings. When the pressure in the storage reservoirs falls again below a second relatively lower pressure value the signal pressure at port 27 is 40 rapidly removed whereby the clutch re-engagesto reinstate the charging mode.

4. An aircompressor substantially as described herein with reference to Figure 1 and Figure 2 ofthe accompanying drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd, 8/87, D8991685.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.

Claims

45 1. An aircompressorassembly including a housing having a rotatablecompressorshaft,a rotatable input shaft in linetherewithanda multiplate spring applied clutch via which the compressor shaft is driveable by the input shaft, a 50 fluid pressure operable annular release piston having innerand outer sealssealinglyaxially moveable in parallel cylindrical walls of an annular pressure chamber which when pressurised act on the rotating clutch assembly to release the drive 55 wherein said piston comprises an element moulded of resilient seal material on a rigid annularsupport member and integrally providing said innerand outerseals.
2. An air compressor assembly as claimed in

60 claim 1 wherein said seal material extends across the outerface of said support member.
3. An aircompressor assembly as claimed in claim 1 or2 said support member carrying a thrust elementengageable in clutch releasing mannerwith

65 said clutch.