ROTATABLE MEMBER FOR A VEHICLE DISC BRAKE OF THE LIQUID COOLED TYPE

Abstract: A rotatable member for a brake of the liquid cooled type comprises a disc (2) provided on opposite sides with annular braking faces (3, 4). The disc incorporates a plurality of angularly spaced liquid supply slots (12) which extend through the material of the disc and radially outwards from a position inwardly of the inner peripheral edges of the braking faces (3, 4). A portion (13) at the inner end of each slot (12) is of a circumferential length greater than the remainder of the slot (12). The member may comprise a braking member for the brake, or it may be separate from the brake and act as a pump member in the form of a turbo disc.

Description: This invention relates to a rotatable member for a brake of the liquid cooled type according to the preamble of claim 1. The invention is also concerned with vehicle disc brakes of the liquid-cooled type, of the kind in which at least one rotatable friction braking member slidably keyed to a shaft to be braked is rotatable in a housing containing a cooling liquid for cooling the braking member, and actuating means is provided for urging the braking member into engagement with a relatively stationary braking surface to apply the brake. Brakes of that kind are commonly used in tractors or the like vehicles, and the cooling liquid usually comprises oil from the gearbox. In order to minimise parasitic drag, particularly when the oil is cool, and conserve consequent power, it is usual for the oil in the gearbox to be maintained substantially at the minimum level only necessary to provide adequate lubrication. This, in turn, creates the problem that such a minimum level represents a volume of oil which is normally inadequate to achieve a degree of cooling of the braking member necessary to sustain a minimum wear life for the lining. In our GB-A-2 141 193 we have disclosed a disc brake of the kind set forth in which the braking member carries a lining of friction material, and the lining of friction material is separated into inner and outer annular rings by a single annular groove, substantially coaxially with the axis of rotation of the rotatable friction braking member, said groove acting as a reservoir for cooling liquid, throttling means are provided for throttling the flow of liquid across the braking faces of the rings, and reservoir supply flow grooves are provided in the inner ring to replenish the cooling liquid of the annular groove. In some of the specific constructions disclosed in GB-A-2 141 193, the reservoir supply grooves comprise slots which pass through the material of the braking member and the lining and are parallel-sided and elongate radially, the slots extending radially outwards from a position inwardly of the inner edge of the inner ring. We are also aware of GB 2 087 998 which discloses a liquid cooled disc brake having a friction disc with a friction lining provided with spiral groove patterns, outwardly widening wedge grooves provided extending for the full radial depth of the friction lining, and circular reservoir holes provided adjacent the wedge grooves just radially inside of the inner edge of the friction lining. In use the circular reservoir holes of the friction disc line up axially with slots provided in stators of the disc brake and part of the areas of the slots in the stators and reservoir holes in the friction discs are superimposed to allow cooling liquid to flow into the circular reservoir holes and via a narrow throttling neck into the narrow inner end of the wedge grooves. Flow of cooling liquid to the friction lining is throttled by the narrow neck joining the reservoir holes to the outwardly widening wedge grooves. According to a first aspect of the invention a rotatable member for a brake of the liquid-cooled type comprises a rotatable disc having an inner peripheral edge and an outer peripheral edge and an annular braking surface adapted for engagement with a stationary braking surface of a brake to which the member is to fitted, and the disc incorporates a plurality of angularly spaced liquid supply grooves in the form of slots which extend through the material of the disc and radially outwards from a position inwardly of the inner peripheral edge, characterised in that the slots comprise radial arm portions and circumferential arm portions extending substantially perpendicularly to the radial arm portions, the radial arm portions extending outwards from the circumferential arm portions which are disposed at a position inwards of the inner peripheral edge of the annular braking surface of the member, the circumferential width of the circumferential arm portions being greater than that of the radial arm portions. Such a rotatable member is well suited for use in a liquid cooled disc brake having a minimal oil level. The disc may be provided on opposite sides with annular braking surfaces, each having an inner peripheral edge and an outer peripheral edge. Increasing the circumferential length of the circumferential arm portion of each slot increases liquid "pick-up", thereby enhancing the distribution of liquid to the braking surfaces. Each slot may be of substantially L-shaped outline, or Tee-shaped outline, with the foot of the L, or the head of the Tee constituting the circumferential arm portion. Preferably the braking member is also combined in an assembly with a plurality of angularly spaced baffles with extend axially from at least one face of the braking member and preferably correspond in number to the number of slots provided in the member, the baffles overlie the circumferential arm portions of the slots but terminate short of the inner peripheral edge of the respective braking surface. The baffles may be disposed adjacent to the trailing edges of the slots for a normal forward direction of rotation of the members in order to improve the direction of cooling liquid into the slots. When the slots are of L-shaped outline, the circumferential arm portions extend circumferentially relatively away from baffles. Consequently the baffles are arranged within a reservoir for cooling liquid which is defined between the braking member and an annular wall and to which liquid is supplied from a sump by suitable means, such as by gravity or a pumped supply. When the rotatable member comprises a rotatable pump member for circulating liquid through a brake of the liquid-cooled type the disc is also provided with an arrangement of liquid-flow grooves constructed and arranged according to the amount of liquid to be carried. For example, the disc may have wider artery grooves feeding smaller capilliary grooves, and/or smaller capilliary grooves leading into larger vein grooves which then expel oil from the disc. Preferably the disc comprises an annular metal core provided on opposite sides with linings of friction or other similar material, the slots extend through the material of the core and through the linings, and the liquid flow grooves are provided only in the linings. This has the advantage that the pump member may also be utilised to act as a braking member in a disc brake of the liquid-cooled type. Conveniently, however, the pump member may be separate from and outside the braking members or stack in a brake of the liquid-cooled type. This enables us to increase the diameter beyond that of the friction members which, in turn, allows greater peripheral speeds, large annular volume, and much lower oil feed level, for example from below the normal level of liquid in the sump of an axle. In such a construction the pump member is driven from the shaft to be braked and on which it is slidably mounted. In other constructions the pump member may be installed in other positions, for example at the entrance to the differential driving the axle to be braked, or between the differential and the or each axle or half shaft. A second aspect of the invention comprises a disc brake incorporating a rotatable member in accordance with the first aspect of the invention. Some embodiments of our invention are illustrated in the occupying drawings in which: Figure 1 is an end view of a friction braking member for a brake of the liquid-cooled multi-plate type; Figure 2 is a section on the line 2-2 of Figure 1; Figure 3 is a view similar to Figure 1 of another friction member; Figure 4 is a section on the line 4-4 of Figure 3; Figure 5 is a section on the line 5-5 of Figure 3; Figure 6 is a view similar to Figure 1 illustrating a portion of a rotatable disc for a brake of the liquid-cooled multi-plate type; Figure 7 is a section through a brake of the multi-plate type embodying the disc of Figure 6 as a pump member; Figure 8 shows the incorporation of the disc of Figure 6 at the entrance to a differential; and Figure 9 shows the incorporation of spaced discs in an axle. The friction braking member illustrated in Figures 1 and 2 of the accompanying drawings is suitable for use as a rotatable braking member in a multi-plate disc brake of the liquid-cooled type, such as that disclosed in our GB-A-2 141 193, with the braking member mounted for sliding axial movement on a rotatable shaft 1 which extend axially through the housing of the brake. The housing also defines a sump for liquid for cooling the braking surfaces of the brake, specifically the engaging faces between the rotatable friction braking members, and the relatively stationary components. The friction braking member comprises a metal disc 2 of annular outline which is slidably splined on the shaft 1. The disc 2 is provided on opposite sides with annular linings 3 of friction material which are superimposed and of which the outer peripheral edges coincide with the outer peripheral edge of the disc. A wall 4 of dish-shaped outline comprises oppositely directed inner and outer annular flanges 5, 6 which are interconnected by a circumferentially extending rim 7. The inner flange 5 is of greater radial length than the outer flange 6, and the outer flange 6 is secured to the disc with its outer peripheral edge disposed inwardly of the inner peripheral edge of the lining 3. A reservoir 10 for liquid defined between the wall 4 and the disc 2 is adapted to be supplied with liquid at a level 11 in the sump in the housing. The braking member is provided with a plurality of angularly spaced slots 12, each of generally Tee-shaped outline, and through which liquid is fed from the reservoir 10 and to the outer faces of the friction linings 3 which constitute braking faces. Specifically each slot has an inner portion 13 comprising the head of the Tee which extends circumferentially in opposite direction from a central stem 14 which, in turn, extends radially towards the peripheral edge of the member. The heads 13 of all the slots 12 lie on a pitch circle. The slots 12 extend between opposite sides of the member, passing through both the material of the disc 2, and the material of the friction linings 3. Innermost portions of the heads 13 project into the reservoir 10 to enable liquid to be fed by centrifugal force from the reservoir 10, and onto the braking faces. To enhance the pick-up and retention of liquid within the slots 12, the reservoir 10 is divided interiorly into a plurality of angularly spaced chambers, each of generally segmental outline, by means of angularly spaced radial baffles 15 corresponding in number to the number of slots 12 provided. The baffles 15 extend from the outer edge of the reservoir 10, thereby overlapping the innermost portions of the heads 13, substantially to the inner edge of the flange 5, and each baffle 15 is located at the trailing end of each respective slot 12, for a given normal forward direction of disc rotation. The baffles 15 act to direct the cooling liquid into the respective slots 12. As in the constructions described in GB-A- 2 141 193, the outer faces of the linings 3 are provided with liquid-flow grooves 16 to facilitate the transfer of liquid across the braking faces. In the member illustrated in Figures 3-5, the baffles 15 are extended radially inwardly of the inner peripheral edge of the flange 5 and are inclined with respect to the wall 4 and the disc 2 itself so that the disc acts as an impeller to help fill the reservoir 10. The slots 12 are of L-shaped outline with their feet 19 projecting circumferentially relatively away from the baffles 15 which are again located at the trailing ends of the slots 12. The wall 4 and the baffles 15 are constructed from metal pressings 20, 21. The pressing 21 is generally flat with flaps 23 bent up from it, and the pressing 20, which comprises the wall 4, is of generally dish-shaped outline with the free ends of the flaps 23 engaging the inner face of the wall 4. The pressings 20 and 21 are attached to the disc by any suitable means, for example by welding, the use of tags, or by bonding. The braking member of Figures 3-5 is otherwise the same as that of Figures 1 and 2, and corresponding reference numerals have been applied to corresponding parts. The rotatable member 39 illustrated in Figure 6 of the drawings is similar to that of Figure 1 and may be used as a braking member in a multi-plate disc brake of the liquid-cooled type as described above. In this construction the slots 12 again extend through the material of the metal disc 2 and both annular linings 3 are formed with patterns of liquid-flow grooves 30 to facilitate the transfer of liquid across the outer faces of the linings. As illustrated, each pattern of flow grooves comprise an artery groove 31 which leads from the outer end of a stem 14 of a slot 12, and feeds smaller capilliary grooves 32 which are generally radial and terminate at the edge of the respective lining 3. In addition, a single capilliary groove 33 extends radially outwards from the outer end of the stem 14 itself. The heads 13 of adjacent slots 12 are also interconnected by capilliary grooves 34 which, in turn, lead into larger vein grooves 35, again terminating at the edge of the member. The rotatable member illustrated in Figure 6 may also be embodied in a brake of the multi-plate liquid-cooled type in a position which is separate from, and spaced from the braking member, or stack. In such a construction, the member acts as a turbo disc or pump member. As illustrated in Figure 7 the member 39 is spaced axially in a housing 40 from the brake stack 41 and is slidably mounted on a shaft or axle 42 adapted to be braked. The diameter of the member 39 is greater than that of the braking members of the stack of which one is illustrated at 43. This increases the peripheral speed in comparison with that of the braking members, enabling a larger volume of liquid to be pumped from a much lower liquid or oil level in a sump as shown at 44. The turbo-disc 39 may be installed as shown in Figure 8 at the entrance to an axle differential 50 to pump liquid to each of two liquid-cooled brakes 51, 52, each adapted to brake one respective axle or half shaft 53, 54. In another construction shown in Figure 9, a turbo disc is associated with each brake 51, 52.

Claims: 1. A rotatable member for a brake of the liquid-cooled type comprises a rotatable disc (2) having an inner peripheral edge and an outer peripheral edge and an annular braking surface (3) adapted for engagement with a relatively stationary braking surface of a brake to which the member is to be fitted, and the disc incorporates a plurality of angularly spaced liquid supply grooves (12) in the form of slots which extend through the material of the disc and radially outwards from a position inwardly of the inner peripheral edge, characterised in that the slots comprise radial arm portions (14) and circumferential arm portions (13; 19) extending substantially perpendicularly to the radial arm portions (14), the radial arm portions extending outwards from the circumferential arm portion (13; 19) which are disposed at a position inwards of the inner peripheral edge of the annular braking surface (3) of the member, the circumferential width of the circumferential arm portions being greater than that of the radial arm portions. 2. A member according to claim 1, characterised in that the member comprises a rotatable friction member for a disc brake of the liquid-cooled type with the disc (2) provided on opposite sides with annular braking surfaces (3), each having an inner peripheral edge and an outer peripheral edge. 3. A member according to claim 1 and claim 2, characterised in that each slot (12) is substantially L-shaped outline, and the foot (19) of the L constitutes the circumferential arm portion. 4. A member according to claim 1 or claim 2, characterised in that each slot (12) is substantially of Tee outline with the head (13) of the Tee constituting the circumferential arm portion. 5. A member according to any of claims 2-4, characterised in that the braking member is also combined in an assembly with a plurality of angularly spaced baffles (15) which extend axially from at least one face of the braking member the baffles overlie the circumferential arm portions (13) of the slots but terminate short of the inner peripheral edge of the respective braking surface. 6. A member according to claim 5, characterised in that the baffles (15) correspond in number to the number of slots (12) provided in the member. 7. A member according to claim 5 or claim 6, characterised in that the baffles (15) are disposed adjacent to the trailing edges of the slots (12) for a normal forward direction of rotation of the members in order to improve the direction of cooling liquid into the slots. 8. A member according to claim 7, characterised in that the circumferential arm portions (13) of the slots (12) of L-shaped outline extend circumferentially relatively away from the baffles (15). 9. A member according to any of claims 5-8, characterised in that the baffles (15) are arranged within a reservoir for cooling liquid which is defined between the braking member and an annular wall (4) and to which liquid is adapted to be supplied from a sump by suitable means, such as by gravity or a pumped supply. 10. A member according to claim 1, characterised in that the rotatable member comprises a rotatable pump member for circulating liquid through a brake of the liquid-cooled type and the disc (2) is also provided with an arrangement of liquid-flow grooves (31, 32, 34, 35) constructed and arranged according to the amount of liquid to be carried. 11. A member according to Claim 10, characterised in that the disc (2) has wider artery grooves (31) feeding smaller arterial capilliary grooves (32), and/or smaller veinous capilliary grooves (34) leading into larger vein grooves (35). 12. A member according to any preceding claims, characterised in that the disc (2) comprises an annular metal core provided on opposite sides with linings (3) of friction or other similar material, the slots (12) extend through the material of the core and through the linings, and liquid flow grooves (31, 32, 34, 35) are provided only in the linings. 13. A member according to claim 1, characterised in that the annular braking surface (3) is defined on one planar face of the member and a reservoir for cooling liquid (10) is secured to the other, opposite, planar face of said braking member at a position radially inside the inner peripheral edge of the friction lining (3), and the circumferential arm portion (13; 19) of the slot is disposed at least partially within the area of the reservoir (10) and provides a fluid pathway from the reservoir secured to said other planar face of the member to the radial arm portion (14) of the slot and thereby to the braking surface provided on said one planar face of the braking member. 14. A disc brake comprising a housing defining a relatively stationary braking surface, a shaft to be braked, and a rotatable member in accordance with any of claims 1 to 13.

Inventors: CAMPBELL, ROY, GREEN, ANDREW PETER, PRICE, ANTHONY GEORGE
Applicants: LUCAS INDUSTRIES PUBLIC LIMITED COMPANY
Application year: 1988
Main classification: F16D65
IPC codes: F16D65, F16D69