GB2129076A - Self brake assembly - Google Patents

Abstract

The brake assembly comprises an input shaft (22) which operates to drive a gear pump (96) for circulating oil over interposed brake discs (136) and plates (140), the oil being operative to move a piston (142) to bring discs and plates into braking relationship upon speed increase of the input shaft in one direction of rotation only to a certain point to provide self-governing speed regulation. The piston (142) is also acted upon by coaxially arranged helical compression springs (146, 147) to apply the brake but the biasing force of these springs may be overcome by control hydraulic fluid applied to a chamber (154), which is overridden during the regulation. In the opposite direction of rotation the brake is not applied. <IMAGE>

Description

SPECIFICATION Brake unit The present invention relates generally to brake units and more particularly to brake units of the oil shear type having internal oil pump means operative selectively to circulate oil in response to rotation of the brake unit in a preselected direction.

Various types of brake units are used in conjunction with well drilling rigs such as those used in construction of oil and gas wells. In one manner of drilling oil and gas wells, a length or stand of pipe is connected to a drill bit which is then rotated thereby drilling deeper into the ground. As the well progresses, it is necessary to install a casing which usually consists of stands of larger diameter pipe connected together which operate to guide the drilling apparatus, support surrounding ground formations, seal the sides of the opening as well as other various purposes. The drilling apparatus generally comprises a drawworks assembly which includes a cable drum, driving apparatus for rotatably driving the cable drum, a main brake and a secondary brake often referred to as a mode absorber.The drawworks performs various functions including raising and lowering the drilling pipe and bit for bit replacement, and connection of additional stands of drill pipe as well as to control drilling pressure.

Also, the drawworks may be used to assist in installation of the casing as well as replacement thereof should the casing become worn due to extended drilling operations. The main brake is commonly intimately associated with the cable drum of the drawworks operating to stop and hold the drilling apparatus, pipe stands or the like at any desired position whereas the mode absorber operates in the nature of a governor to limit lowering speeds. The mode absorber may be in the form of a water brake which utilizes the resistance of a turbine rotating through a fluid for example. While the mode absorber does reduce the rate of acceleration thereby increasing the available response time for an operator to effect corrective measures, it will constitute a significant drag during raising operations unless disconnected from the drawworks.If the mode absorber is allowed to remain connected to the drawworks, power consumption may be significantly increased as well as operating speeds reduced due to this drag. Thus, it is generally necessary to disconnect the mode absorber during raising. Not only does the disconnecting procedure require loss of valuable operating time but also the disconnection of the mode absorber eliminates the added safety factor due to the increased response time provided thereby within which the operator may actuate the brake should a power failure be encountered. Futher, such absorbers constitute an additional piece of equipment requiring maintenance as well as additional controls to adjust the resistance for varying lowering speeds.

In our copending patent application No. 8029571, serial No. 2059525, from which the present application is divided and which has substantially the same disclosure as the present application, we claim a brake unit comprising: a housing; an input shaft rotatably journaled within said housing; a plurality of brake discs mounted on said input shaft and rotatable therewith; a plurality of brake plates interposed between said brake discs and non-rotatably mounted within said housing; actuating means for moving said brake plates and said brake discs into and out of braking relationship thereby to impede rotation of said input shaft; and a fluid pump driven by said input shaft and operative to supply fluid through primary fluid passage means to circulate across said brake plates and discs to cool and lubricate same, said pump also being operative upon rotation of the input shaft in one direction to generate a fluid pressure to assist operation of said actuating means to move said brake discs and plates into braking relationship, a secondary passage being provided operative to supply fluid to said pump in response to rotation of said input shaft in a direction opposite said one direction whereby drag due to pumping action of said pump is reduced, a fluid outlet chamber surrounding said brake discs and plates and receiving fluid flow from said brake plates and discs during rotation of said input shaft in said one direction and supplying fluid to said secondary passage in response to said opposite direction of rotation, said secondary passage including a secondary inlet connected to said outlet chamber and a secondary outlet connected to said primary passage means, said secondary passage being operative to by-pass said brake discs and plates.

According to the present invention there is provided a self-brake assembly of the oil shear type having automatic speed governing means comprising: a housing; an input shaft rotatably journaled within said housing; a plurality of brake discs axially movably mounted on said input shaft and rotatable therewith; a plurality of brake plates non-rotatably axially movably mounted within said housing and interposed between said brake discs; clamping means for axially moving said brake discs and said brake plates into braking relationship; control means for releasing said clamping means whereby said input shaft is allowed to rotate; and means responsive to rotation of said input shaft to override said control means and cause said clamping means to move said brake discs and said brake plates into braking relationship.

The present invention will become further apparent from the following description of a preferred embodiment taken in conjunction with the accompanying drawings, wherein: Figure 1 is an elevational view of a drilling rig having drawworks apparatus for raising and lowering stands of pipe to which a brake unit in accordance with the present invention is operatively connected; Figure 2 is a side elevational view of a brake unit embodying the present invention; Figure 3 is a front elevational view of the brake unit; Figure 4 is a fragmentary longitudinal crosssectional view of the upper portion of the brake unit, the section being taken substantially along the line 4-4 of Figure 2; Figure 5 is a fragmentary transverse crosssectional view taken along line 5-5 of Figure 4; Figure 6 is a fragmentary transverse crosssectional view taken along line 6-6 of Figure 4; and Figure 7 is an elevational view of the brake unit of Figure 2 shown in operative relationship with associated primary and secondary fluid reservoirs.

Referring now to the drawings and in particular to Figure 1, there is illustrated a brake unit 10 in operative relationship with a drilling rig assembly 12. Drilling rig assembly 12 may be of any conventional design such as those commonly utilized in oil and gas well constructions and will generally include a derrick 14, a conventional drawworks assembly having cables 1 8 leading to derrick 14 and cooperable with blocks supported thereon for raising and lowering tooling, drill bits, or other equipment out of and into the well, and associated drive means 20 for driving the drawworks assembly. Drive means 20 may conventionally be of any type suitable for use in the particular locality of drilling such as an electric motor, gas or diesel engine or even steam engine if desired.In any event, an input shaft 22 of brake unit 10 will be operatively connected to the drawworks assembly either via drive means 20 or directly to the drawworks shaft 21 as illustrated so as to control rotation thereof during operation as is described in greater detail below.

Referring now to Figures 2 through 4, the construction of brake unit 10 will be described in detail. As shown, brake unit 10 comprises a housing 24 of generally cylindrical cross-section having a pair of longitudinally spaced end plates 26 and 28 secured to opposite ends thereof by a plurality of suitable fasteners such as bolts 30 so as to define a cavity 31 therebetween. Housing 24 also has a plurality of depending mounting feet or flange portions 32 provided with suitable openings 34 therein so as to enable the brake unit to be secured to a work platform or other suitable foundation or supporting surface.

As best seen with reference to Figure 4, end plate 26 has an opening 36 provided therein through which input shaft 22 extends into cavity 31. Similarly, end plate 28 also has an opening 38 within which the terminal end 40 of input shaft 22 is received. Input shaft 22 is provided with a pair of axially spaced annular grooves 42 and 44 adjacent opposite ends thereof within which are fitted dust seals 46 and 48 respectively so as to effectively seal shaft 22 within respective openings 36 and 38. Additional annular grooves 50, 52, and 54, 56 are disposed on shaft 22 interiorly from respective grooves 46 and 48 and are all adapted to receive suitable oil seals 57.

Preferably, dust seals 46 and 48 as well as oil seals 50, 52, 54 and 56 will be in the form of piston rings.

An interiorly disposed portion 58 of input shaft 22 is provided with at least one and preferably two circumferentially spaced axially extending slots or keyways 60 and 62 which are adapted to receive elongated keys 64 and 66.

A generally cylindrically shaped gear and brake disc carrier 68 is fixedly secured to portion 58 of input shaft 22 and has an axially extending radially outwardly spaced flange portion 70 designed to engage a bushing 72 mounted within end plate 26 so as to rotatably support the driven end portion 74 of input shaft 22. Bushing 72 is secured to end plate 26 by suitable fastening means in the form of radially inwardly extending bushing screws 76.

Immediately adjacent and axially outwardly of bushing 72, end plate 26 is provided with an annular labyrinth comprising a plurality of grooves 78 provided in end plate 26 and surrounding flange portion 70 in close proximity thereto so as to control or limit oil leakage through bushing 72 into area 73 surrounding input shaft 22. Gear and brake disc carrier 68 will preferably be shrink fitted to input shaft 22 with keys 64 and 66 being operative to prevent relative rotation therebetween.

Gear and brake disc carrier 68 has an enlarged diameter splined center portion 82 upon which an annular or ring gear 84 having a correspondingly splined center bore is supported for rotation therewith. Gear 84 is supported upon gear carrier 68 in such a manner as to enable relative axial movement therebetween, gear 84 being axially restrained between axially spaced opposed wall portions 86 and 88 of housing 24.

As best seen in Figure 5, housing 24 is provided with three circumferentially spaced interconnected chambers 90, 92 and 94 disposed radially outward from gear 84. Center chamber 92 has a gear pump 96 rotatably supported upon a fixed shaft 98. Opposite end portions of shaft 98 are received within openings 100 and 102 provided in wall portions 86 and 88 respectively.

A bushing 103 is secured to gear pump 96 by a plurality of screws 104 extending radially inward from the circumference thereof. In order to prevent screws 104 from backing out during operation, a dowel 105 is installed in an axially extending passage 106 in a position so as to overlie the radial outer portion of screws 1 04.

Dowel 105 may be retained within passage 106 in any suitable manner such as by a plug 108. In order to supply lubricant to bushing 103, shaft 98 is provided with an axially extending passage 109 opening into space 110 and having a radially extending passage 112 communicating with the inner end thereof. As shown, radial passage 11 2 is positioned so as to be approximately aligned with the axial center of bushing 103. Shaft 98 is also provided with an oil seal 11 3 disposed within groove 115 provided on the outer or left end thereof as seen in Figure 4 which operates to prevent oil leakage therefrom.

Preferably both bushings 72 and 103 will be circumferentially segmented with slight clearances being provided between each of the segments so as to allow for thermal expansion thereof during operation of the brake unit.

As best seen with reference to Figures 2 and 3, chamber 90 is provided with an outwardly opening fluid inlet connection 114 adapted to have a fluid conduit connected thereto so as to supply fluid to chamber 90. Chamber 90 then acts as a supply reservoir supplying such fluid to gear pump 96 which is driven by counterclockwise rotation to input shaft 22 via gear 84 and is operative to pump such fluid under pressure into the next circumferentially spaced adjacent chamber 94.

An enlarged diameter generally cylindrical center portion 116 of gear and brake disc carrier member 68 is provided with a plurality of circumferentially spaced axially extending relatively shallow slots 122 which operate to provide axial oil passages for conducting lubricant to the brake discs and plates. A second plurality of circumferentially spaced axially extending slots 124 are also provided on portion 11 6 interposed between slots 122, each of which is adapted to receive an axially extending elongated gib 126.

Gibs 126 are of an irregular shape generally as shown in Figure 6 having a base portion 128 which is received in slot 124, a circumferentially narrowed neck portion 130 extending generally radially outward therefrom and oppositely circumferentially outwardly extending arcuate shaped upper portions 1 32. Each of gibs 126 are preferably secured to portion 11 6 of gear carrier 68 by a plurality of axially spaced fasteners 134 threadedly engaging openings provided in the bottom portions of slots 124. Extending between and adapted to be retained by respective gibs 126 are a plurality of radially outwardly extending brake discs 136 which are axially movable therealong and rotatable with input shaft 22.Gibs 126 and brake discs 136 may be of the type disclosed in copending patent application No. 39268/78. Alternatively, if desired brake discs 136 may be in the form of continuous annular rings as opposed to circumferentially segmented discs as shown.

Center portion 11 6 of gear carrier 68 also has an axially extending flange portion 164 extending to the right as viewed in Figure 4 which engages a bushing 166 secured in a recess 168 provided in end wall 28 so as to thereby rotatably support terminal end portion 40 of input shaft 22. Bushing 1 66 is preferably circumferentially segmented so as to allow for thermal expansion thereof and each of the segments are secured in recess 1 68 by a suitable threaded fastener 1 70. Another labyrinth comprising a plurality of grooves 1 72 is also provided being disposed axially outwardly from bushing 1 66 which serves to control the amount of lubricating oil leakage therefrom into area 1 74 surrounding input shaft 22.

A brake plate support member 138 is fixedly secured to housing 24 and projects axially inward into cavity 31 in radially outwardly spaced relationship to brake discs 136. A plurality of brake plates 140 are axially movably mounted on member 1 38 and project radially inward therefrom, the same being interposed between respective brake discs 1 36. Brake plate support member 138 is also provided with a plurality of radially extending spaced restricted openings 1 62 which operate to allow oil supplied to the brake plates and discs to flow radially outward therefrom during a lowering operation into area 110.

Center portion 11 6 of gear carrier 68 is also provided with a plurality of axially extending spaced bores 1 76 having one end opening into area 1 74 and the other end opening into area 73.

Bores 1 76 serve to place area 73 in fluid communication with area 1 74 so as to equalize the pressure therebetween and allow oil accumulating within area 73 to drain into area 1 74. End wall 1 78 is provided with an opening 1 80 to which a fluid conduit may be connected to return oil from areas 73 and 1 74 to a remote main reservoir or tank. Also, a relatively small quantity of oil will leak past seals 57 provided on opposite end portions of input shaft 22 thereby lubricating same and will accumulate in respective areas 182 and 1 84 provided adjacent to and surrounding terminal end portion 40 and driven end portion 74 of input shaft 22 respectively.To prevent excessive accumulation and loss of oil in areas 182 and 184, openings 1 86 and 188 respectively are provided to which fluid conduits may be connected to direct this leakage oil to a remote secondary reservoir or scavenger tank.

Actuating means are provided for selectively axially moving brake discs 136 and plates 140 into and out of braking relationship which include an axially movable piston assembly 142 having a brake plate engaging surface 144. Resilient biasing means in the form of a plurality of pairs of coaxially arranged helical compression springs 146,147 are provided extending between surface 148 of piston 142 and recessed seating surfaces 1 50 of housing 24. Thus there are provided first and second pluralities of springs, each of the springs of the first plurality of springs being disposed concentrically within an associated one of the springs of the second plurality of springs.

Springs 146 and 1 47 are operative to cause piston 142 to exert a clamping force on brake discs 1 36 and plates 140 between surface 144 and an axially spaced opposed surface portion 1 52 of housing 24. A control pressure chamber 1 54 is also provided which acts as control means for the actuating means by receiving pressurized control hydraulic fluid through passage 1 56 in housing 24 which fluid operates to exert a first force to move piston 142 axially to the right as seen in Figure 4 overcoming the biasing force of springs 146 and 147 thereby releasing the clamping force. Pressure chamber 1 54 is sealed by axially spaced fluid seals 1 58 and 160 provided on piston assembly 142.

As shown in Figure 7, brake unit 10 has inlet 114 and outlet 1 94 connected to a primary lubricant reservoir or tank 212 via conduits 214 and 216 respectively. As brake unit 10 is designed for cyclic and reversing operation, it is desirable to maintain cavity 31 in a lubricant flooded condition so as to prevent cavitation or pounding of gear pump 96. This may be easily accomplished by merely positioning tank 212 so as to place the oil level 217 therein above the top of brake unit 1 0.

Another return conduit 21 8 is also connected to tank 212 extending from opening 180 of brake unit 10 and operative to return lubricant accumulating within areas 73 and 1 74 thereof.

A secondary tank 220 is also provided having fluid conduits 222 and 224 extending from openings 1 86 and 1 88 respectively connected thereto which operate to drain lubricant from areas 1 82 and 1 84 respectively. A float switch 226 is provided in tank 220 which controls a pump 228 so as to return lubricant accumulating within tank 220 to primary tank 212 via conduit 230.Preferably, tank 220 will be positioned relative to brake unit 10 so as to enable gravity draining of lubricant from areas 182 and 1 84. As only a relatively small amount of lubricant is anticipated to accumulate in areas 1 82 and 1 84 of brake unit 10, it is believed preferable to employ a cyclically operating system utilizing a level responsive pump means; however, if desired a continuously operating relatively low capacity pump could be utilized in place thereof.

The operation of brake unit 10 will now be described in conjunction with the operation of a drilling rig although it should be noted that the present invention may find application in conjunction with other varied apparatus.

As illustrated, brake unit 10 is constructed for rotation of input shaft 22 in a counterclockwise direction as indicated by arrow 1 90 during a lowering operation. In order to initiate a lowering operation, it is first necessary to release the braking force generated by the clamping action exerted by piston assembly 142 on interposed brake discs 136 and plates 140 due to springs 146 and 147. This is accomplished by admitting hydraulic fluid under controlled pressure through passage 1 56 into chamber 1 54 thereby causing piston assembly 142 to move axially to the right as viewed in Figure 4 reducing the clamping pressure and allowing gravitational forces acting on the equipment to be lowered to impart counterclockwise rotation to input shaft 22.This counterclockwise rotation of input shaft 22 and associated gear carrier 68 and gear 84 will operate to cause a clockwise rotation of gear pump 96 which will operate to pump oil under pressure from inlet 114 and chamber 90 through pumping chamber 92 into chamber 94. Wall portion 86 of chamber 94 is provided with an arcuate shaped slot 191 which piaces chamber 94 in fluid communication with area 1 92 adjacent gear carrier 68. Oil will thus be applied under pressure to provide lubrication to splines 82 and therethrough to bushing 72 and a controlled leakage amount through labyrinth 78 to seals 57.

The majority of this pressurized oil will be forced from area 192 through axially extending slots 122 and thence radially outwardly between interposed brake discs 136 and brake plates 140 thereby providing a continuous film between these opposed surfaces as well as serving to lubricate and cool same. This oil will then flow into area 110 via passages 1 62 provided in brake plate support member 138. Both the number and size of passages 162 will be selected relative to the volume of oil flow so as to generate a substantial pressure drop thereacross. Thus, during a lowering operation area 1 92 will experience a relatively high pressure substantially above that experienced by area 110.This pressure differential will, of course, be dependent upon the speed of rotation of input shaft 22 and associated gear pump 96.

A portion of the oil flowing into area 110 will be diverted to axially extending passage 109 and radially extending passage 11 2 so as to lubricate bushing 103 of gear pump 96. The remaining oil will accumulate in the lower portion of cavity 31 and be returned to a remote reservoir or supply tank via a return opening 194 provided in a lower sidewall portion of housing 24.

As best seen in Figure 4, and as described above, the braking force generated by piston 142 is released by the application of a controlled hydraulic pressure to chamber 154 so as to overcome the biasing action of springs 146, 147.

However, as the rotational speed of input shaft 22 increases, gear pump 96 will attempt to increase the oil flow through the brake unit which increased oil flow will be resisted by the controlled orifice passages 1 62 thereby resulting in an increased pressure within areas 1 92 and 1 96. As shown, piston 142 has a surface area 198 within another area or chamber 200 which is axially opposed to surface area 202 thereof disposed within chamber 1 54. Therefore as chamber 200 is in relatively unrestricted fluid communication with area 196, any increased fluid pressure therein will be exerted on surface 198 of piston 142.Thus, as the speed of rotation of input shaft 22 increases, pressure within area 1 96 and correspondingly within area 200 will increase to the point where the pressure differential between surfaces 202 and 1 98 will cause piston 142 to move axially to the left as illustrated thereby applying a braking force so as to decrease the rotational speed of shaft 22. As the speed decreases, the pressure within areas 1 96 and 200 will also decrease until a constant speed is achieved. Thus, the brake unit of the present invention provides internal selfgoverning speed regulation. This represents an important safety feature of the present invention in that should a sudden increase in lowering speed be encountered such as may occur should a drill break through into an underground cavern, a power failure during a raising operation or the like, the increased speed of rotation of gear pump 96 will increase the pressurization of the oil being circulated which increased oil pressure will overcome the control pressure exerted on piston assembly 142 so as to create a clamping force on brake discs 1 36 and plates 140 thereby preventing complete loss of control and possible equipment damage.

During a raising operation, input shaft 22 will be caused to rotate in a clockwise direction thereby imparting counterclockwise rotation to gear pump 96 causing the pumping action thereof to reverse or pump oil from chamber 94 to chamber 90.

As it is desirable to conduct the raising operations at as high a speed as possible within safe operating limits, restricted passage 1 62 will not be sufficient to allow enough oil flow therethrough to prevent starvation of gear pump 96. Further, in order to minimize the power required to effect raising of the drill stands, it is desirable to provide a free flowing of lubricant to gear pump 96 so as to reduce drag resulting therefrom. Accordingly, housing 24 is provided with an opening 204 communicating with area 110 to which a fluid conduit 206 is connected.

Fluid conduit 206 extends through a check valve 208 to another opening 210 provided in end plate 28 which opens into area 196 of brake unit 1 6.

Thus, as area 110 is maintained in an oil flooded condition due to the head pressure generated by the elevation of main supply tank oil level relative to the elevation of the brake unit, oil will be caused to flow through conduit 206, check valve 208 and into area 196. Thence, oil will be drawn through slots 122 into area 192, chamber 94 and through gear pump 96 being returned to the main supply tank via inlet chamber 90. Thus, starvation of gear pump 96 will effectively be prevented thereby eliminating the possibility of cavitation or pounding occurring. Further, this reduced drag feature eliminates the need for disconnecting the brake unit in order to achieve rapid raising of equipment from the drill hole with a minimum of power consumption.Thus, as the brake is continuously connected, it remains in standby condition providing an added safety factor should be a power failure or other raising equipment fault occur.

It should be noted that check valve 208 is designed to allow oil flow from area 110 to area 1 96 but prevent oil flow from 1 96 to area 110 thereby assuring pressurization of area 1 96 during lowering operations.

As previously mentioned, bushings 72 and 1 66 along with labyrinth grooves 78 and 1 72 operate to at least partially seal cavity 31 of brake unit 1 6.

However, due to the relatively high pressure as well as the need to provide lubrication to bushings 72 and 166, some oil leakage will occur.

Accordingly, areas 72 and 174 will both be subjected to some pressurized oil flow which oil is returned to the main tank via passages 176 and fluid conduit 218 connected to opening 180.

Additionally, some oil leakage will occur past seals 57 at each end of shaft 22 into respective areas 182 and 1 84 to which fluid conduits 222 and 224 are connected which operate to drain fluid therefrom. However, the oil presence within areas 1 82 and 184 will be at or very near atmospheric pressure and because the oil level in tank 212 is above the level of areas 1 82 and 184 it is not possible to return this oil directly to the main tank due to the head produced thereby. Accordingly, fluid conduits 222 and 224 drain lubricant to secondary tank 220 thereby raising float switch 226 to a level sufficient to actuate pump 228.

Pump 228 will then operate to return the oil from tank 220 to tank 212 via conduit 230 thereby reducing the oil level in tank 220 until float switch 226 de-actuates pump 228.

While brake unit 10 has been illustrated as constructed with input shaft 22 designed to rotate in a counterclockwise direction during lowering operations, this may be easily modified for clockwise rotation during lowering by moving inlet connection 11 4 to communicate with chamber 94 and moving slot 1 91 to the corresponding location in communication with chamber 90. The operation and oil circulation pattern within brake unit 10 will otherwise be substantially identical to that described above.

Claims (9)

1. A self-brake assembly of the oil shear type having automatic speed governing means comprising: a housing; an input shaft rotatably journaled within said housing; a plurality of brake discs axially movably mounted on said input shaft and rotatable therewith; a plurality of brake plates nonrotatably axially movably mounted within said housing and interposed between said brake discs; clamping means for axially moving said brake discs and said brake plates into braking relationship; control means for releasing said clamping means whereby said input shaft is allowed to rotate; and means responsive to rotation of said input shaft to override said control means and cause said clamping means to move said brake discs and said brake plates into braking relationship.

2. A brake assembly as claimed in claim 1, wherein said rotation responsive means comprises fluid pumping means driven by said input shaft and operative to generate a fluid pressure, the magnitude of said pressure varying directly with the speed of rotation of said input shaft and passage means within said housing for conducting said fluid pressure to said clamping means.

3. A brake assembly as claimed in claim 2, wherein said fluid pumping means also operates to circulate fluid across said brake discs and plates.

4. A brake assembly as claimed in claim 1,2 or 3, wherein said clamping means includes biasing means for urging said brake discs and plates into braking relationship.

5. A brake assembly as claimed in claim 4, wherein said clamping means comprises a piston member movably disposed within said housing and having a surface engageable with one of said brake discs and plates and another surface communicating with said fluid pressure.

6. A brake assembly as claimed in claim 5, wherein said biasing means comprises a plurality of springs extending between said piston member and said housing.

7. A brake assembly as claimed in claim 6, wherein said biasing means comprises first and second pluralities of springs, each of the springs of said first plurality of springs being disposed concentrically within an associated one of the springs of said second plurality of springs.

8. A brake assembly as claimed in claim 2, wherein said pumping means is a gear pump drivingly engaging said input shaft,

9. A brake assembly as claimed in claim 8, wherein a gear is provided adjacent one end of said input shaft and drivingly engages said gear pump.

9. A brake assembly as claimed in claim 8, wherein a gear is provided adjacent one end of said input shaft and drivingly engages said gear pump.

10. A brake assembly as claimed in claim 9, wherein said gear is a ring gear axially movably mounted on said input shaft.

11. A brake assembly as claimed in claim 10, wherein said input shaft includes a gear and brake disc carrier secured thereto, said ring gear being mounted on said carrier adjacent one end thereof and said brake discs being axially movably secured thereto.

12. A brake assembly as claimed in claim 11, further comprising bearings within said housing supportingly engaging opposite end portions of said carrier, said bearings rotatably supporting said input shaft, and labyrinth seals provided between said carrier and said housing immediately axially outwardly of each of said bearings, said bearings and said labyrinth seals cooperating to limit axially outwardly directed fluid flow.

13. A brake assembly as claimed in claim 12, wherein each of said bearings comprises a plurality of circumferentially extending and spaced segments.

14. A brake assembly as claimed in any one of claims 8 to 13, wherein said gear pump comprises a gear rotatably supported upon a shaft secured within said housing and includes bearing means secured to the pump gear.

15. A brake assembly as claimed in claim 14, wherein said bearing means are secured to said pump gear by a plurality of threaded fasteners.

1 6. A brake assembly as claimed in claim 15, further comprising dowel means overlying outer ends of said threaded fasteners, said dowel means being operative to prevent backing out of said fasteners during operation of said brake assembly.

17. A brake assembly as claimed in claim 1 5 or 16, wherein said bearing means coinprises a plurality of circumferentially extending spaced bushing members.

New claims or amendments to claims filed on 23-12-83.

Superseded claims 1-9.

New or amended claims:

1. A self-brake assembly comprising a housing; an input shaft rotatably journaled within said housing; a plurality of brake discs axially movably mounted on said input shaft and rotatable therewith; a plurality of brake plates nonrotatably axially movably mounted within said housing and interposed between said brake discs, the brake discs and plates being adapted to have fluid circulated thereacross during use of the brake assembly; clamping means actuable axially to force said brake discs and said brake plates into braking relationship; means for releasing said clamping means whereby said input shaft is allowed to rotate; and fluid pressure generating means responsive to rotation of said input shaft in one direction of rotation only to supply pressure fluid which at a predetermined speed of rotation will override said releasing means to actuate said clamping means to move said brake discs and said brake plates into braking relationship, said fluid pressure generating means being so arranged that upon rotation of said input shaft in the opposite direction of rotation the fluid pressure generating means does not cause actuation of the clamping means.

2. A brake assembly as claimed in claim 1, wherein said fluid pressure generating means comprises a fluid pump driven by the input shaft and operative to generate a fluid pressure the magnitude of which varies directly with the speed of rotation of said input shaft, fluid communication being provided from the pump to the clamping means.

3. A brake assembly as claimed in claim 2, wherein said pump is also operative to circulate fluid across said brake discs and plates.

4. A brake assembly as claimed in claim 2 or 3, wherein said clamping means includes biasing means for urging said brake discs and plates into braking relationship.

5. A brake assembly as claimed in claim 4, wherein said clamping means comprises a piston member movably disposed within said housing and having a surface engageable with one of said brake discs and plates and another surface exposed to pressure fluid from the fluid pressure generating means.

6. A brake assembly as claimed in claim 5, wherein said biasing means comprises a plurality of springs extending between said piston member and said housing.

7. A brake assembly as claimed in claim 6, wherein said biasing means comprises first and second pluralities of springs, each of the springs of said first plurality of springs being disposed concentrically within an associated one of the springs of said second plurality of springs.

8. A brake assembly as claimed in any one of claims 2 to 7, wherein said fluid pump is a gear pump drivingly engaged by said input shaft.