JPS6212410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a pair of brake shoes carrying a friction lining that engages a rotating drum and mounted on a torque plate; an operating cam disposed therebetween; and a cam supporting the cam and rotatably supported on the torque plate about a fixed axis so as to widen the distance between adjacent ends of the pair of brake shoes. In particular, the automatic clearance adjustment device includes a housing mounted on and fixed to the torque plate, and a pair of thrust assemblies. each thrust assembly acts between the cam and the adjacent end of one of the brake shoes, and each thrust assembly operates to compensate for wear of the friction lining of one of the brake shoes. comprising first and second members threaded together for relative rotation to increase the effective length of the assembly, the first member being restrained from rotation relative to an adjacent end of the brake shoe; The second member has gear teeth, and the automatic clearance adjuster is configured to rotate both thrust assemblies in the same manner at the same time to increase the effective length of both thrust assemblies by the same amount. A type of automatic clearance adjustment comprising a drive mechanism constantly meshing with the gear teeth of the two members and a rotation device for rotating at least one of the second members when adjustment is required to compensate for wear of the brake lining. Regarding equipment.

Automatic clearance adjustment devices of the type described in British Patent Specification No. 1,431,023 and corresponding US Pat. No. 3,891,068 are known. In this known arrangement, each thrust assembly is in direct rocking engagement at each end with the cam and the respective shoe end, and the entirety of each thrust assembly is controlled by the mutual rotation of the first and second members mentioned above. It moves angularly as it moves.

In this known automatic clearance adjustment device, there is no need to damage the threads, bend the thrust assembly, and create a frictional force of sufficient magnitude to prevent rotation of the second member relative to the first member. , have experienced difficulties in constructing thrust assemblies with sufficient strength to withstand brake braking and adjustment forces. Furthermore, angular motion of the thrust assembly complicates the apparatus for rotating the single second member, and such angular motion also creates significant inertial forces that must be absorbed by the cam and shoe ends. Therefore, an inherent vibration tendency occurs. Furthermore,
The first and second members of each thrust assembly are difficult to seal against ingress of dirt or other foreign matter without a complex sealing structure or by locating the thrust assembly in a sealed housing. It is.

The invention provides an automatic clearance adjustment device of the type described above, in which the pivoting device is connected via a one-way drive clutch to a fixed member of the brake, and the second
In an automatic clearance adjustment device comprising a pinion that engages directly or indirectly with said gear teeth of said member, said thrust assembly each being connected to said one of said housings.
A strut is inserted between the cam and each of the second members, the cam being slidably guided in the axial direction through the pair of holes, and the cam is connected to the thrust assembly via the strut to rotate the camshaft. The cam and the second member are each formed with a partially spherical recess, and both ends of the support column are inserted into the recess. It is characterized by rocking engagement.

Angular movement of the thrust members is thus eliminated, and the thrust assemblies further reduce or nearly eliminate bending loads and frictional forces that prevent rotation between the first and second members of each thrust assembly. significantly reduces the occurrence of

Preferably, in each thrust assembly, the first member includes a nut and the second member is rotatable within the bore and guided for axial sliding therein.

When attached to a shutter drum brake, an integral strut is inserted between each second member and the cam, and both ends of the strut are pivotally engaged in complementary recesses with hemispherical outlines in the second member and the cam. . The struts can be of relatively light construction, thereby minimizing the inertia of the swinging parts.

Therefore, the angularly moving portion is of constant axial length and the characteristics of the adjustment device remain constant regardless of the effective length of the thrust assembly.

Screws can be easily protected against the ingress of dirt or other foreign objects. For example, a simple boot can be provided between each nut and the housing, with the part of the second member projecting through the nut being housed in a cover carried by the nut.

An embodiment of an inner shovel drum brake incorporating an automatic clearance adjustment device according to the invention is shown in the accompanying drawings.

In the inner shoe drum brake shown in FIGS. 1 to 4, a pair of arcuate brake shoes 1, 2 each having spaced apart radial webs 3, 4 are made of a cast plate or forged piece. It is provided on the torque plate 5. Each shoe 1, 2 carries a friction lining 6 which engages a rotating drum (not shown).

The actuator assembly 7 is located between one pair of adjacent shoe ends, and the other pair of shoe ends are in contact with a fixed receiving surface 8 in the form of a fixed block. As shown, both the housing 9 and the fixed receiving surface 8 of the actuator assembly 7 include portions of the torque plate 5. A circular dirt shielding body 10 is provided on the surface of the torque plate 5 opposite to the shoes 1 and 2.

Actuator assembly 7 includes a cam 11 carried on or integral with a camshaft 12 rotatably journalled in a shaft 13 in a bore 14 in torque plate 5 parallel to the axis of the brake. The cam 11 has opposing hemispherical recesses 14,15 in which the hemispherical ends of a pair of struts or dollies 16,17 are received, the outer ends of the struts being adjacent to the thrust assemblies 18,19. Complementary semicircular recess 20,2 at the end
1 and acts on the adjacent shoe ends via thrust assemblies 18,19.

When the shaft 12 is rotated to apply the brake, the struts 16 and 17 are pressed in opposite directions,
The pillars 16 and 17 also move angularly, and the ends are in the recesses 14 and 1.
It swings at 5, 20, 21. The brake functions as a one-leading, one-trailing, shed-drum type brake in both directions of drum rotation.

Each thrust assembly 18, 19 forms part of an automatic clearance adjuster to maintain brake clearance at a substantially constant value. Each thrust assembly 18, 19 includes a nut 22 that engages the respective shoe end and a threaded projection 23 that is threaded through the nut 22. Each nut has a protrusion 24 housed between the webs 3, 4 of its respective shoe 1, 2 to prevent rotation of the nut. Each threaded protrusion 23 has a cylindrical piston portion 25 which is slidably guided within a bore 26 of the housing 9.
, the bore 26 is tangential to the axis of the brake, and the piston part 25 is connected to the web 3 at its free end.
4 and has an integrally reduced diameter threaded stem 27 which is threaded through the nut 22.
Recesses 20 and 21 are provided at the inner end of the piston portion 25. Each projecting stem 27 has a closure cup 28 of metal or plastic material carried on the nut 22.
Concertainer type sealed boot 29
is connected between the nut 22 and the proximal end of the hole 26.

The crown wheel type pinion 30 is the camshaft 1
It is rotatably provided coaxially with the cam 11 in the enlarged portion of the hole 14 opposite to the cam 11 . The enlarged portion of the hole 14 is closed by a plug 32 which is held in place by a circlip 33. Spring 34 is plug 3
2 and the crown wheel 30, pressing the crown wheel 30 into engagement with the gear teeth 35 on the inner end of the piston portion 25, such that rotation of one of the protrusions 23 causes a corresponding rotation of the other protrusion 23. achieved with. Therefore, if one of the protrusions 23 is rotated to increase the effective length of one thrust assembly 18, the effective length of the other assembly 19 will likewise increase.

Rotation of the protrusion of the thrust assembly is achieved by a pinion 36 rotatably supported in a hole 37 provided in the housing 9 parallel to the axis of the brake, and the pinion 36 is connected to a one-way drive clutch (not shown). It is connected to the fixed member via.

Normally, the return spring assembly 38 moves the shoes 1, 2 into a retracted position where the protrusion 23 is pressed inside its hole 26 until the camshaft 12 contacts a rotation stop (not shown) in an air cylinder that rotates it. Press.

When applying the brake, the lugs 23 are pressed outward and the teeth 35 on the lugs 23 of the thrust member 18 engage the pinion 36, causing it to rotate when the brake braking movement is excessive. When the shoes 1 and 2 are retracted by the operating effect of the spring assembly 38, the pinion 36 is prevented from rotating by the clutch, and the inward movement in the longitudinal direction of the protrusion 23 meshed with the pinion 36 is caused by the rotation of the pinion 36.
The effective length of the thrust assembly 18 is increased with rotation of the thrust assembly 18. As mentioned above, crown wheel 3
Since rotation of one protrusion 23 is accompanied by the same rotation of the other protrusion 23, the effective lengths of both thrust assemblies increase simultaneously and by the same amount.

In a variant, the crown wheel 30 coaxial with the cam 11 is replaced by a toothed wheel carried by the inner end of the radial shaft.

Furthermore, rather than meshing with one of the protrusions, the pinion 36 can mesh with a crown wheel 30 or a toothed wheel of the construction described in the previous section. In such a construction, the pinion 36 rotates when adjustment is required to provide rotation of the two protrusions 23.

By providing the hole 26 substantially tangentially to the axis of the brake, the line of action of the protrusion 23 on the shoe end substantially coincides with the axis of the thrust assemblies 18, 19, so that the thrust assemblies 18, 19 are substantially compressed. It receives only force and hardly any bending load.

The abutment surface formed between the shoe end and the nut 22 is configured to allow the shoe end to slide along the nut as the lining 6 wears.

If necessary, the adjusting device of the invention can be returned to the initial adjusting position by rotating the pinion 36 without first having to remove the drum.

In the brake shown in FIGS. 5 to 10, a shaft 40 is rotatably supported in a hole 41 of an end cap 42 which closes the end of the enlarged portion of the hole 14 opposite the shaft 12. has been done. The bore 41 is perpendicular to the main longitudinal axis of the bore 14, but radially spaced from the axis of the bore 14 itself. Both ends of the shaft 40 protruding from both ends of the hole 41 include pinions 43 that constantly mesh with gear teeth 45 on the inner end of the piston portion 25, so that rotation of one of the protrusions 23 causes a corresponding rotation of the other protrusion 23. It is becoming more and more accompanied by movement. Therefore, by increasing the effective length of one thrust assembly 18,
To compensate for the wear of the friction lining 6, the protrusion 2
3 causes an equivalent increase in the effective length of the other assembly 19.

Rotation of the protrusion of the thrust assembly 18 is achieved by a pinion 46 rotatably supported in a hole 47 provided in the housing 9 in a position parallel to the axis of the brake. The adjusting device 49 is connected to the fixed member via a one-way drive clutch 48. Adjustment device 49 is shown in British Patent Specification No. 1419254.

Normally, the return spring 38 moves the shoes 1 and 2 to the protrusion 23.
is pushed into the hole 26 in the retracted position,
Press until the shaft 12 contacts a rotation stop (not shown) in the air cylinder that rotates it.

During braking, the protrusion 23 is pushed outward, causing the protrusion 23 of the thrust assembly 18 and the pinion 4 to be pressed outward.
The arrangement of the teeth 45 on the upper part 3 is such that the convex element 23 is prevented from rotating, and the shaft 40 rotates when normal braking is performed. Similarly, when releasing the brake, the shaft 40 pivots in the opposite direction.

When braking is excessive, the engagement of the teeth 45 of the protrusion 23 of the pinion 46 causes the pinion 46 to rotate against the force of the clutch 48. Show 1,
When the pinion 2 is retracted by the action of the spring 38, the rotation of the pinion 46 is suppressed by the clutch 48, and the convex element 23 engaged with the pinion 46 moves inward in the longitudinal direction, causing the convex element 23 to rotate. Thrust assembly 1
Increase the effective length of 8. As mentioned above, axis 4
0 and pinion 43, one convex element 2
3 is accompanied by an equivalent rotation of the other protrusion, whereby the effective lengths of both thrust assemblies are simultaneously increased by the same amount.

When the brake is first assembled, any back clearance between the teeth 45 on the protrusion 23 and the teeth on the pinion 43 will be absorbed during the first few brake applications.

The adjustment device 49 can be returned to the initial adjustment position by means of a manual operating member 51, which can be used without first having to remove the drum.

The construction and operation of the brakes in FIGS. 5 to 10 are otherwise the same as those in FIGS. 1 to 4, and corresponding parts have been given corresponding numbers.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of a brake including a clearance adjustment device according to the present invention, with the drum omitted for clarity; FIG. 2 is a cross-sectional view of the main parts of the brake; and FIG. 3 is a cross-sectional view of the adjustment device. 4 is a sectional view taken along line 4--4 in FIG. 3, FIG. 5 is a plan view showing the other brakes with the drum omitted for clarity, and FIG. Figure 5 is a cross-sectional view of the main parts of the brake, Figure 7 is a rear view of the foreign object shield used in the brake shown in Figure 5, and Figure 8 is a cross-sectional view taken along line 8--8 in Figure 7. , FIG. 9 is an enlarged sectional view taken along the center line of the shoe of the adjusting device, and FIG. 10 is a sectional view taken along the line 10--10 of FIG. 1, 2: brake shoe, 6: friction lining, 7: actuator assembly, 9: housing, 11: cam, 12: camshaft, 18, 19: thrust assembly, 22: first screw member (nut),
23: Second screw member (convex), 26: Hole, 30:
Crown wheel type pinion, 34: Spring, 3
5: Gear tooth, 40: Horizontal shaft, 41: Horizontal hole, 42:
Housing, 43: Pinion, 45: Gear tooth.

Claims (1)

[Scope of Claims] 1. A pair of brake shoes carrying a friction lining that engages a rotating drum and mounted on a torque plate, and a brake shoe disposed between respective adjacent ends of the pair of brake shoes. and a cam shaft that supports the cam and is rotatably supported on the torque plate about a fixed axis so as to widen the distance between adjacent ends of the pair of brake shoes. An automatic clearance adjustment device for a one-leading/one-trailing type vehicle shutter drum brake, the automatic clearance adjustment device comprising a housing mounted on the torque plate and fixed to the torque plate, and a pair of housings. thrust assemblies, each thrust assembly acting between the cam and the adjacent end of one of the brake shoes, each thrust assembly reducing wear of the friction lining of one of the brake shoes. comprising first and second members rotatably threaded relative to each other to compensate and increase the effective length of the thrust assembly, said first member being relative to an adjacent end of said brake shoe; rotation is inhibited, the second member has gear teeth, and the automatic gap adjustment device includes:
Wear of the brake lining and a drive mechanism that constantly meshes with the gear teeth of both second members to rotate both thrust assemblies simultaneously and in the same manner to increase the effective length of both thrust assemblies by the same amount. a rotation device for rotating at least one of the second members when adjustment is required for compensation;
In the automatic clearance adjusting device, the rotating device comprises a pinion connected to a fixed member of the brake via a one-way drive clutch and meshing directly or indirectly with the gear teeth of the second member, The solid bodies 18 and 19 are respectively connected to the housing 9
axially slidably guided through a pair of holes 26 of the
Supports 16 and 17 are interposed between the cam 11 and each of the second members 23, and the cam 11 is connected to the thrust assemblies 18 and 19 via the supports in response to rotation of the camshaft 12. Both brake shoes 1,
The cam 11 and the second member 23 are respectively formed with partially spherical recesses 20, 21; 14, 15,
An automatic gap adjustment device characterized in that both ends of the pillars 16 and 17 are swingably engaged in the recess. 2. Adjustment device according to claim 1, characterized in that said first member (22) of said thrust assembly comprises a nut and said second member (23) is rotatable within said hole (26). 3. The drive mechanism includes a pinion 30 in the form of a crown wheel rotatably supported in the housing 9, a spring 34 biasing the pinion into constant engagement with the gear teeth 35 of both second members 23; Claim 1 characterized in that
Adjustment device of paragraph 2 or paragraph 2. 4. The drive mechanism includes a pair of interconnected pinions 43 rotatable about an axis perpendicular to the axis of rotation of the cam 11, each pinion 43
The adjusting device according to claim 1 or 2, characterized in that the gear teeth 45 of one of the second members 23 are always engaged with the gear teeth 45 of the second member 23. 5 The pair of pinions 43 are connected to the housing 4
5. The adjusting device according to claim 4, wherein the adjusting device is fixed to both ends of a shaft 40 which is rotatably supported in a hole 41 of FIG.