GB2085986A

GB2085986A - Disc brake

Info

Publication number: GB2085986A
Application number: GB8127793A
Authority: GB
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co OHG
Priority date: 1980-10-24
Filing date: 1981-09-15
Publication date: 1982-05-06
Also published as: IT8124622A0; FR2492928A1; DE3040185A1; GB2085986B; IT1139653B

Abstract

A spot-type disc brake comprises two rotating drive devices (e.g., as shown, spindle devices 11a, 11b or cam- type drives) which are arranged on one side of the brake disc (24) in the circumferential direction of the latter and work in opposite directions. The devices 11a, 11b act in parallel on only one brake shoe and are applied to move synchronously by means of respective swivelling levers 12a, 12b which are adapted to be spread apart by virtue of a pneumatic piston- cylinder arrangement 13, 14. As shown, the levers 12a, 12b are connected by joints 32, 33 to front faces 20 of cylinder 16; pistons 15 connected by a piston rod 19 are respectively situated in cylinders 16. Supply of air to cylinders 16 via (a) socket(s) 35 moves cylinders in opposite directions to move the levers 12a, 12b. Other illustrated embodiments involve a single piston- cylinder, and various modifications of the spindle devices and the mounting of the piston-cylinder arrangement are disclosed. <IMAGE>

Description

SPECIFICATION Disc brake This invention relates to a spot-type disc brake of the kind comprising two actuating devices with a rotating drive arranged on one side of the brake disc in series in the circumferential direction of the disc and working in opposite directions, these actuating devices acting in a parallel direction on only one brake shoe and being adapted to be acted upon by another actuating device via the respective swivelling lever, such that they always move synchronously in a brake-applying or a brake-releasing direction. The actuating devices to be taken into consideration in the first place are those with spindles. The use of front cam-type drives is also envisaged.

In a known embodiment of a spot-type disc brake of this kind (DE-OS 23 64 050), on application of the brake, the swivelling levers attached to the spindle-actuating devices move towards each other. The actuation is effected by a Bowden-cable. This known embodiment is disadvantageous in that the swivelling levers must be at a sufficient distance away from each other, so as not to collide on the actuation of the brakes, particularly in the case of worn-out brake pads, and thus hinder braking. To avoid this disadvantage spindle-actuating devices running in the same direction have already been used (GB--PS 14 92 784), but here a special actuating rod operating the two spindle-actuating devices jointly and synchronizing both movements is required. A pneumatic actuation would call for a complicated mechanism to operate it.

Furthermore, a spot-type disc brake (US-PS 4 089 393) is already known which features a carrier plate slidable towards the brake disc by means of two eccentric levers pivotable in opposite directions. For the actuation of the two spreader levers a pneumatic piston-cylinder arrangement may be interposed between the levers. This known spot-type disc brake needs considerable construction space, particularly in an axial direction, owing to the fact that the spreader levers protrude axially from the brake caliper and not radially as is the case with a spot-type disc brake provided with spindle-actuating devices.

All the known spot-type disc brakes of this type are floating-caliper brakes, where the actuation mechanism is only intended for one side of the brake disc. The use of two actuation devices aims at uniformly transmitting the brake actuation forces on the brake shoes, without the need for heavy and solid pressure plates.

Thus, the present invention aims at providing a spot-type disc brake of the type initially referred to, wherein a failure of the brakes due to collisiori of the spreader levers is not to be feared and the actuation devices can be housed in a space-saving and compact way.

According to the invention in its broadest aspect, a spot-type disc brake of the kind referred to is characterized in that the two spindleactuating devices can be operated in brakeapplying direction by spreading the swivelling levers through an interposed pneumatic pistoncylinder arrangement.

By virtue of this arrangement, a collision of the brake levers on actuation of the brakes is avoided, despite the use of spindle-actuating devices allowing for a compact design, because the two swivelling levers move away from each other during braking. As the swivelling levers extend radially from the spindle-actuating devices, practically no additional construction space is needed in an axial direction, thanks to the arrangement of the actuating device.

It is especially advantageous if, in the inoperative condition of the brake, the swivelling levers extend from the opposite circumferential areas of the spindle-actuating devices in a substantially tangential direction with respect to the latter and radially outwards. In this embodiment, the pneumatic actuation devices can be located in a particularly compact way, in order to obtain a good effect.

An especially simple embodiment is characterized by the fact that a cylinder or a piston installed therein is connected to the swivelling levers, the piston and the cylinder being exclusively attached to the two swivelling levers with which they are pivotally jointed.

An initial practical implementation of this embodiment is characterized by the fact that the cylinder is interposed between the two swivelling levers, the cylinder being pivotally connected with the one swivelling lever, and a piston rod of the piston is pivotally jointed with the other swivelling lever.

If the need for a radial arrangement of the cylinder arises, the arrangement should be such that the two swivelling levers are pivotally jointed by a cranked lever mechanism, on the toggle joint of which a piston rod of the piston acts substantially perpendicularly with respect to the extension of the cranked lever mechanism.

A further advantageous embodiment is developed in such a way that, in the inoperative condition of the brake, the cylinder extends outside the space between the swivelling levers and substantially perpendicularly to the swivelling levers and in their swivelling direction, the swivelling levers turned towards the cylinder being pivotally jointed with the front face out of which protrudes the piston rod, whereas the swivelling lever turned away from the cylinder is pivotally connected with the piston rod itself. Hereby, in the inoperative condition of the brake, the swivelling levers should lie as close to each other as possible and preferably substantially parallel. Thus, an important part of the radial space existing outside the spindle actuating devices is used for the housing of the pneumatic actuating device.

Nevertheless, a simple cylinder containing a piston suffices for the operation. In this embodiment also the cylinder and the piston are attached to the swivelling levers solely via the piston rod.

A further preferred embodiment is characterized by the fact that, on the opposite sides of the swivelling levers, there are located cylinders containing pistons connected to one another by a piston rod, the front faces of the cylinders through which the piston rod passes being respectively pivotally jointed with one of the swivelling levers.

Despite the fact that there are two cylinders and two pistons in this embodiment, they are arranged completely symmetrically to both swivelling levers and are connected to each other by the piston rod.

Above all, this embodiment is very stable in construction because the centre of gravity of the two cylinders is exactly at the point where the cylinders and the swivelling levers are pivotally connected to one another. Also, with this embodiment, when the brake is not applied, the swivelling levers lie close to each other and preferably substantially parallel to each other.

It is also an advantage if the brake, constructed according to the invention, is installed above the axis of rotation of the brake disc in order to avoid the effects of gravitational force in the direction of actuation. Moreover, at this point of installation the substantially vertically directed bouncing movements of the wheel can be absorbed in a better way.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an axially-directed inner view of a spot-type disc brake according to the invention, Figure 2 is a partial section of a top view of the embodiment described in Figure 1, Figure 3 is a diagrammatic illustration of the function of the brake, as described in Figure 1 and Figure 2, Figure 4 is a functional view, analogous to that of Figure 3, of a further embodiment, Figure 5 is a functional view of a further embodiment and Figure 6 is a functional view of a still further embodiment of the spot-type disc brake constructed according to the invention.

According to Figures 1 and 2, a floating caliper 22 is axially movably held ona brake carrier 21 at each of the points 23. As shown in Figure 2, the floating caliper 22 inwardly embraces the brake disc 24 fastened to the vehicle axle 38 and carries a brake shoe 25 on the arm 39 interposed between the wheel plate 27 and the brake disc 24. The wheel rim adjacent to the wheel plate 27 is indicated by the reference numeral 26.

Two spindle-actuating devices 11 a,11 b are arranged above each other in the floating caliper 22 on the side of the brake disc 24 opposite to the outer brake shoe 25.

Each spindle-actuating device 11 a,11 b features an actuating nut 28 rotatable by means of a swivelling lever 12a, 12b and a spindle 29 in engagement therewith via a ball-bearing thread and acting upon the inner brake shoe 30. The actuating nut 28 abuts against the floating caliper by means of a thrust bearing 31. The swivelling levers 12a, 12b could also be connected to the spindle 29, in which case the actuating nut 28 would also come into contact with the brake shoe 30. Suitable spindle actuating devices have been described in the DE-OS 29 46 850, 29 46 851, 29 46 852 and 29 46 853.

According to Figures 1 and 2, when the brake is not applied, the swivelling levers 12a,12b branch off in a tangential direction with respect to the circumferential areas of the spindle actuating devices 11 a, 11 b, lying opposite to each other, and vertically to the connecting line 40 between the axes 41 of the devices 11 a, 11 b. As illustrated in Figure 1, they lie substantially closely parallel to each other and substantially on a plane parallel to the brake disc 24.The ends of the swivelling levers I 2a, 1 2b are situated approximately in the peripheral zone of the brake disc 24, where they are affixed by means of joints 32, 33 to the front faces 20 of two coaxial piston-cylinder arrangements 13, 14, the axis 42 of which runs tangentially with respect to the brake disc 24 and to the swivelling levers in an off-position. The rotation axis of the joints 32, 33 stands perpendicularly to the plane of the disc and intersects the axis 42.

According to Figures 1 to 3, each pistoncylinder arrangements 1 3, 14 consists of a cylinder 16 containing a piston 1 5. The cylinders 16 are located outside the space 43 between the two swivelling levers 12a, 12b and lie, together with the front faces 20 of the piston-rod exits, opposite to each other. The two pistons 1 5 are connected to each other by a piston rod 19 which protrudes centrally out of the front faces 20. The joints 32, 33 are conveniently located on both sides of the piston rod 19 and are engaged with forked ends of the swivelling levers 12a, 12b.

According to Figure 3, return springs 34 are respectively interposed between the two pistons 1 5 and the front faces 20 of the cylinders 1 6.

These springs prestress each of the piston-cylinder arrangements 1 3, 14, thus allowing them to assume the brakes-off position that can be seen in Figures 1 and 3.

The piston-cylinder arrangements 13, 14 are substantially attached to the swivelling levers 12a, 12b. Extra devices can however be provided for connecting the piston-cylinder arrangements with the brake caliper and for absorbing shocks. It is thus, for instance, possible to provide for the additional attachment to the cylinders of crank levers located near the free ends of the cylinders, the crank levers having the same length as and lying parallel to the swivelling levers, so that they may be able to follow the movements of the cylinders during operation without producing clamping forces.

The piston rod 1 9 is hollow in construction and has a pressure supply socket 35 mounted centrally between the two joints 32, 33 of the swivelling levers 12a, 12b. Hereby one single pressure port is provided for the two cylinders 1 6 which effects merely a slight radial movement when the brake is applied. In this case the use of a relatively long flexible connecting line becomes redundant.

The method of operation of the spot-type disc brake described is as follows: In Figures 1 to 3 the brakes-off position of the spindle-actuating devices 11 a, 11 b is indicated by thick lines.

Thanks to the reaction forces transmitted by the piston rod 19, the two cylinders 16 move in opposite directions on the entry of air pressure into the cylinders 1 6 through the supply sockets 35, whereby the swivelling levers 12a, 12b are moved respectively in the opposite direction.

These swivel motions are transmitted onto the spindle-actuating devices 11 a,11 b due to the torsion-preventing coupling of the swivelling levers 12a, 12b with the spindle nuts 28, thus clamping the brake shoes 25, 30 to the brake disc 24. The fully expanded condition of the swivelling levers 12a, 12b is indicated in Figure 3 by chaindots. This condition of the swivelling levers corresponds with the maximum braking position.

Since the two cylinders 1 6 are merely interconnected by the piston rod 19 and are, moreover, attached nowhere else to each other except by the joints 32, 33, the latter can easily follow the curved broken line indicating the path of the joints 32, 33 shown in Figure 3.

Upon removal of the pressure from the supply sockets 35, the return springs 34 force the cylinders 1 6 back to their initial position corresponding to the brakes-off position.

According to Figure 4, only one cylinder 16 is pivotally connected to the swivelling lever 1 2a by means of a joint 32 provided in the centre of its front face 20. Here again the axis of the joint runs in an axial direction, i.e. it is perpendicular to the plane of the brake disc 24. With this embodiment the piston rod 19 of the piston 15 placed inside the cylinder 1 6 protrudes through an opening made in the front face 20 close to the joint 32 and extends to the end of the lower swivelling lever 12b, where it is connected to the swivelling lever 1 2b by means of a joint 33. Also the axis of said joint 33 is perpendicular to the brake disc 24; in other words, it runs parallel to the axes of the spindle actuating devices 11 a, 11 b.

When pneumatic pressure is exerted at the supply socket 35, the piston 1 5 and the cylinder 1 6 are displaced relative to each other, whereby both swivelling levers 12a, 12b move to the positions indicated by the chain-dots and the spindle-actuating devices 11 a,11 b clamp the brake shoes 25, 30 to the brake disc 24. Hereby the joints 32, 33 carry out the movement indicated by the broken line, which can only be effected over the joints 32, 33 due to the attachment of the piston-cylinder arrangement 13.

In the embodiment illustrated in Figure 5, the swivelling levers 12a,12b have a wider circumferential distance from one another which is sufficient to accommodate a piston-cylinder arrangement 13 therein. The cylinder is linked to swivelling lever 1 2a via joint 32 and the piston rod to swivelling lever 1 2b via joint 33.

The introduction of air pressure through the supply socket 35 causes displacement of the piston 15 inside the cylinder 16, whereby the two swivelling levers 12a. 12b are forced apart again and a braking action is initiated.

Upon release of the brake, a tension spring located directly between the swivelling levers 12a, 1 2b returns the swivelling levers 12a, 12b to their original position.

Figure 6 illustrates an embodiment in which the ends of the swivelling levers 12a, 12b are connected to each other by means of a cranked lever mechanism 17 jointed at reference numeral 36, 37. The toggle joint of the bent lever mechanism 18 is connected to the piston rod 19 of a piston 1 5 slidably located in the cylinder 1 6.

Contrary to the axes of the embodiments described above, the axis of the cylinder 1 6 of the embodiment according to Figure 6 extends in a radial direction.

In this embodiment, the cylinder 1 6 is not suspended freely between the swivelling levers 12a, 12b, but is rather firmly fixed to the floating caliper 22.

When pressure is admitted into the cylinder 16 through 35, the piston 1 5 slides in the direction of the spindle actuating devices 11 a,11 b, thereby pushing the cranked lever mechanism via the toggle joint 1 8 until it is fully stretched out. Thus the two swivelling levers 12a, 12b are set apart against the impact of the return spring. A stop 44 prevents the cranked lever mechanism 1 7 from reaching the dead centre. This is the only way the return springs 34 can force back the piston 1 5 to its original position when the air pressure is removed.

Claims

1. Spot-type disc brake of the kind comprising two actuating devices with a rotating drive arranged on one side of the brake disc in series and in the circumferential direction of the disc and working in opposite directions, these actuating devices acting in a parallel direction on only one brake shoe and being applied by means of another actuating device via the respective swivelling lever, such that they always move synchronously in a brakes-applying or brakes-releasing direction, characterized by the fact that the two spindleactuating devices (11 a, 11 b) are operable in brakes-applying direction through the spreading of the swivelling levers (1 2a, 1 2b) by means of an interposed pneumatic piston-cylinder arrangement (13, 14).

2. Spot-type disc brake as claimed in claim 1, characterized by the fact that, in the inoperative condition of the brake, the swivelling levers (12a, 12b) extend from the opposite circumferential areas of the spindle-actuating devices (11 a, 11 b) in a substantially tangential direction with respect to the latter and radially outwards.

3. Spot-type disc brake as claimed in claim 1 or claim 2, characterized by the fact that a cylinder (16), or a piston (15) installed therein is connected to the swivelling levers (1 2a, 1 2b) the piston and the cylinder being exclusively attached to the two swivelling levers with which they are pivotally jointed.

4. Spot-type disc brake as claimed in claim 3, characterized by the fact that the cylinder (1 6) is interposed between the two swivelling levers (1 2a, 1 2b) and that the cylinder (16) is pivotally connected with the one swivelling lever (1 2a) and a piston rod (1 9) of the piston (1 5) is pivotally jointed with the other swivelling lever (12b).

5. Spot-type disc brake as claimed in claim 3, characterized by the fact that the two swivelling levers (1 2a, 1 2b) are pivotally jointed by a cranked lever mechanism (17), on the toggle joint (18) of which a piston rod (19) of the piston (15) acts substantially perpendicularly with respect to the extension of the cranked lever mechanism (17).

6. Spot-type disc brake as claimed in claim 3, characterized by the fact that in the inoperative condition of the brake, the cylinder (16) extends outside the space between the swivelling levers (1 2a, 1 2b) and substantially perpendicularly to the swivelling levers (12a, 12b) and in their swivelling direction, the swivelling lever (1 2a) turned towards the cylinder (16) being pivotally jointed with the front face (20), out of which protrudes the piston rod (19), whereas the swivelling lever (12b) turned away from the cylinder (16) is pivotally connected with the piston rod (19) itself.

7. Spot-type disc brake as claimed in claim 1 or 2, characterized by the fact that on the opposite sides of the swivelling levers (1 2a, 1 2b) there are located cylinders (16) containing pistons (15) connected to one another by a piston rod (19), the front faces (20) of the cylinders through which the piston rod (19) passes being respectively pivotally jointed with one of the swivelling levers (12a, 12b).

8. Spot-type disc brake as claimed in claim 6 or 7, characterized by the fact that, when the brake is not applied the swivelling levers (1 2a, 1 2b) lie close and preferably substantially parallel to each other.

9. Spot-type disc brake as claimed in claim 7 or 8, characterized by the fact that the piston rod (19) is designed as a connecting line for the pressure fluid supply.

10. Spot-type disc brake substantially as described with reference to the accompanying drawings.