GB2028941A

GB2028941A - Disc Brake with Automatic Wear Compensating Arrangement

Info

Publication number: GB2028941A
Application number: GB7928906A
Authority: GB
Original assignee: Maschinenfabrik Stromag GmbH
Current assignee: Maschinenfabrik Stromag GmbH
Priority date: 1978-09-02
Filing date: 1979-08-20
Publication date: 1980-03-12
Also published as: FR2434963A1; GB2028941B; IT7925399A0; DE2838423C2; SE437707B; SE7906767L; FR2434963B3; IT1165294B; DE2838423A1

Abstract

The brake comprises a pressure plate 6 arranged to urge brake lining 7 against a disc 10 to be braked by means of springs 8, the brake being released by moving a retraction bolt 4; in order to maintain the release stroke of bolt 4 substantially constant, regardless of the wear of the brake, release movement is transmitted to the bolt 4 by a clamping lever 14 which defines together with a fixed part 24 a wedge-shaped space into which can be drawn an actuating means 30 by means of an electromagnet 23. Upon electromagnet actuation the means 30 is moved to jam the clamping lever 14 upon bolt 4, whereas upon brake actuation upon de-energization of electromagnet 23 the lever 14 is free to be urged against the actuating means 30 by means of a spring 11; and the lever 14 is then slidable on bolt 4 to give automatic new compensation. The actuating means 30 compress rollers 15, 17. In the embodiment of Figures 3, 4 two brake linings (31, 32) are provided and a stirrup spring 34 replaces the compression spring 11 of Figures 1 and 2. <IMAGE>

Description

SPECIFICATION Disc Brake with Automatic Wear Compensating Arrangement This invention concerns a disc brake with an automatic wear compensating arrangement in which the brake linings are spring urged against brake discs via pressure plates and are releasable via retraction bolts which are connected with the pressure plates and which are axially adjustable independently of the brake wear by way of an adjustable abutment located on the end of the bolt remote from the pressure plates and acted upon by the retraction force.

Disc brakes of this kind are known (DE-OS 2418225). The wear dependent adjustment is in this case achieved by way of threaded sleeves screwed on the retraction bolts, which are provided with a kind of free wheel coupling which is subjected to a rotary shifting movement via connecting rods during each release operation, in order to effect an axial adjustment of the retraction bolts by way of the sleeves. If the wear is greater than an axial shift which can be effected by a free wheel rotation which passes a rest position provided by the free wheel coupling, then the retraction bolts and the pressure plates are adjusted according to the corresponding rest position. Disc brakes of this kind however require for their construction and assembly a relatively great expenditure, and a fine adjustment which is less than the increment of the free wheel is not possible.

It has proved that especially with disc brakes for crane drives sometimes adjustment arrangements which operate stepwise in the manner described are not sufficient.

A variety of further proposals for wear compensation have been made, which are especially provided plate couplings (Antriebstechnik 12(1973) No. 12, S. 362, page 368), and a retraction arrangement is also known for disc brakes (DE-OS 2657332), in which via the clamping effect of an extending spring disc continuous automatic wear compensation can be achieved. These constructions however require additional arrangements for the changing of the brake linings.

It is accordingly an object of the present invention to provide a disc brake of the kind initially referred to, in which a continual wear adjustment is possible without requiring an expensive construction.

In accordance with the invention the adjustable abutment is a clamping member which is slidable on the retraction bolt and is acted upon by the force of a spring in the direction of the pressure plate, and which comprises an engagement flank for an actuating means which transmits the retraction and clamping force. By means of this arrangement there is provided a simple mechanically operated wear compensating arrangement, which is functionally simple and therefore reliable, but always gives the security of a trouble free adjustment. The clamping member may comprise a clamping lever with an inclined ramp for an actuating member which is preferably shiftable in a direction perpendicular to the retraction bolt. It is however also possible to provide clamping parts which are acted upon axially, for example with clamping arrangements operating in the manner of a free wheel.

The clamping lever can in accordance with a simple embodiment engage loosely on the retraction bolt by way of a bore, which facilitates sliding on the retraction bolt, so that when acted upon by the spring the clamping lever is positioned with its bore concentric to the retraction bolt and is easily slidable upon the latter. In order to release the brake, the actuating means engages upon the clamping lever and applies thereto a rotary moment in relation to the axis of the retraction bolt, so that the clamping lever becomes clamped onto the retraction bolt by means of its bore and achieves through the movement of the actuating means the retraction of the retraction bolt and thereby the release of the coupling.

A very simple and effective arrangement is achieved when the inclined ramp forms a wedgeshaped gap with a supporting flank on a guide plate which is fixed with respect to the housing and serves for the support of the retraction bolt, the actuating means being arranged to be drawn into the wedge-shaped gap by means of a drive mechanism. This arrangement enables a relatively large axial force to be transmitted to the retraction bolt without it being necessary for the forces to be transmitted transversely thereto for the operation of the actuating member to become too great. It is indeed known, in the case of disc brakes, to provide a wedge gap between a fixed bearing surface and a bearing flank connected with the retraction member, as a force transmitting element (Trade publication on Mechanical Brakes on Electric Motors of the firm E.Bauer, Esslingen), an automatic wear adjustment is in this case however not provided; furthermore an adjusting screw must be correspondingly manually actuated.

It has proved that the arrangement in accordance with the invention, especially in the case of embodiments with such a wedge-shaped gap, is advantageous when an electromagnet is provided as the driving means, and the armature thereof is connected with the actuating member in the wedge-shaped gap by way of links. The direction of movement of the armature can thereby be arranged at right angles to the axis of the retraction bolt, so that it thereby also provides the advantage of a compact and space saving construction in which the axial extent of the retraction bolt does not need to be increased due to the adjustment arrangement.

The clamping lever may advantageously be acted upon by a compression spring which is arranged at the end of the retraction bolt and is correspondingly fastened on the retraction bolt.

This arrangement is likewise very space saving and enables the pushing action upon the clamping lever for the adjustment operation to be concentric with the axis of the retraction bolt.

It is however possible to use a blade spring which is fixed to the housing and presses with its free end upon the margin of the locating bore of the clamping lever. In order to achieve as symmetrical a ioading of the clamping lever as possible the blade spring may be bent at its free end and the locating bore of the clamping bolt may be bifurcated. Instead of a blade spring it is possible to provide a U-shaped torsion spring, of which a stirrup part is arranged on the clamping lever and of which the ends are fixed. Also this arrangement enables the necessary adjustment, so that in both cases there are provided springs which exert a constant return spring force throughout the range of the possible wear compensation and the correspondingly required spring movement.

Finally, it is advantageous and possible, to guide the retraction bolt slidably in the guide plate by way of a low-friction slide bearing or by way of a roller bearing, which enables easy actuation, even when the retraction force is applied eccentrically of the retraction bolt. Constructional advantages are also achieved when the pressure plate is urged against the brake lining noncentrally by means of plate springs which are arranged between the guide plate and the pressure plate. Thereby additional space for the arrangement of the pressure springs is superfluous.

The invention is explained further in the description set out below and is illustrated in the drawing, in which: Figure 1 is a diagrammatic section through an embodiment of disc brake in accordance with the invention, along the line I-I of Figure 2, Figure 2 is a view in the direction of the arrow 2 of Figure 1 with the clamping lever removed, Figure 3 is a part section through another embodiment of a disc brake in accordance with the invention, and Figure 4 is a partial view of the disc brake of Figure 3 in the direction of the arrow IV.

Referring to Figures 1 and 2, there is provided in a housing 1 for a disc brake a guide plate 2 which is provided with a central boss 3 for guiding a retraction bolt 4. The retraction bolt 4 is located in a corresponding bore of the boss 3, which is provided respectively at its forward and rearward ends with slide guides 5 for the retraction bolt 4, which facilitate sliding of the retraction bolt. It would however also be possible, instead of the slide guides 5 to provide corresponding roller bearings. Also mounting with articulated linkages or with blades and sockets are possible.

The retraction bolt 4 is on one side fixed to a pressure plate 6, which in the illustrated position engages on a brake lining 7 and is pressed against this brake lining through the action of a plurality of plate springs 8 which are arranged between the guide plate 2 and pressure plate 6 and located in a corresponding recess 9 of the pressure plate.

The brake lining 7 presses against a disc 10 which in a manner not further illustrated is connected with a drive to be braked.

On the side remote from the pressure plate 6 a compression spring 11 is arranged on the retraction bolt 4 and is retained with the aid of a ring 12 fixed at the end of the retraction bolt 4.

This compression spring presses on the bearing region 1 3 of a clamping lever 14, which in the illustrated position is pressed by means of a compression spring 11 against a roller 1 5 which runs in a correspondingly recessed guideway 16 on the clamping lever 14. As shown in Figure 2, the roller 1 5 is bounded by two outer rollers 1 7 which are supported together with the roller 1 5 upon a common shaft 18 and are held in spaced relation to one another by means of intermediate rings 19. Two outer links 20 also engage on the shaft 1 8 and are linked by way of a connecting bolt 21 to an armature 22 of an electromagnet 23. This electromagnet 23 is arranged in the space below the retraction bolt 4.An additional axial space is therefore unnecessary.

The two lateral rollers 17, which in common with the roller 1 5 are arranged on the shaft 18, one, as shown in Figures 1 and 2, on supporting flanks 24 which are fixed with respect to the guide plate 2 and are also connected to the boss 3 by way of stiffening webs 25. The supporting flanks 24 are arranged on projections 26 above the stiffening ribs 25.

The supporting flanks 24 are arranged at right angles to the axis 27 of the retraction bolt 4 in the illustrated example. The guideway 1 6 for the roller 1 5 forms an inclined ramp 28, which forms with reference to a plane perpendicular to the axis 27 of the retraction bolt 4 an angle of approximately 100. Thus there is formed between the supporting flanks 24 and the inclined ramp 28 a wedge-shaped space which is restricted in the downward direction.

The manner of operation of the disc brake is as follows: In the operating position shown in Figures 1 and 2 the pressure plate 6 is urged against the brake linings 7 under the action of the pressure springs 8. The drive, not shown, which in particular may be a crane drive, is therefore braked. For the release of the brake the electromagnet 23 is energised and pulls the armature 26 downwards. Thus by way of the links 20 the rollers 15 and 1 7 are drawn into the wedge space between the supporting flanks 24 and the inclined ramp 28. The clamping lever 14 thereby exerts a retraction force upon the retraction bolt 4 against the action of the spring 11 and in dependence upon the correspondingly selected stroke of movement of the electromagnet 23 the brake is thereby released, so that the pressure plate 6 with or without the brake lining-in accordance with the type of construction-is shifted away from the disc which is to be braked. Thus a precisely defined release movement can be obtained, which determines the time necessary for the following braking operation.During this retraction operation the bore 29 of the clamping lever 14 clamps itself upon the retraction bolt 4, When braking is required, the energisation of the electromagnet 23 is terminated, and the stressed plate springs 8 which are essentially stronger than the compression spring 11 again press the pressure plate 6 against the brake lining 7, whereby the rollers 1 5 and 17 which cooperate with the actuating member 30 for the release of the brake are forced outwardly in the wedge space between the supporting flanks 24 and the inclined ramp 28. It is additionally naturally possible, also to provide an additional return spring for the armature 22.If the angle of the wedge space and the material of the rollers 1 5 and 17 and the supporting flank 24 and the inclined ramp 28 are correspondingly selected however, sticking of the mechanism can in any case be prevented, so that the return position can also be achieved through the action of the plate springs 8. If wear occurs during the braking operation, then the retraction bolt 4 is returned to the left by a correspondingly greater amount than in the previous braking operation. If the clamping lever were fixed to the retraction bolt a corresponding play would occur between the rollers 1 5 and 1 7 and the cooperating bearing flanks of the wedge space.Since the clamping lever 14 is easily slidable on the retraction bolt 4 however and subject to the action of the spring 11, during a shifting of the retraction bolt 4 to the left, i.e. during the braking operation, it is independent of the shifting movement of the retraction bolt and is driven under the action of the spring 11 so that the inclined ramp 29 rests constantly against the roller 1 5 and remains in this position independently of the movement of the retraction bolt 4. The latter therefore becomes shifted somewhat more to the left than during the preceding release and braking operation owing to the occurrence of wear, so that during renewed release of the brake the same operating conditions exist as previously, so that the same release path and thereby the same release time can be maintained.

By means of this arrangement there is therefore provided an automatic wear compensating arrangement, which can be very space saving and very simply constructed, but which is very reliable. The clamping lever 14 is in each case forced back to lie against the actuating means 30, namely the cooperating roller 15, and clamps itself onto the retraction bolt 4 as soon as the actuating member is drawn into the wedge space. It therefore becomes immediately rigid with the retraction bolt 4 when the release operation is initiated and is in other respects maintained independent of the retraction bolt 4.

Thus a continual compensation of the brake lining wear at any given time can be achieved.

The basic construction of the embodimentshown in Figures 3 and 4 corresponds to that of Figures 1 and 2 with the difference that in Figures 3 and 4 a two face spring actuated brake is provided, having two brake linings 31 and 32 which are arranged on an inwardly toothed disc 33 which is shiftable upon the shaft to be braked, which is only diagrammatically illustrated. A further difference exists in the type of return spring which is incorporated, which in this case is not arranged on the retraction bolt 4. The return spring 34 is formed as a stirrup spring, of which free ends 35 are fixed in position on the likewise fixed part 25a of the housing which comprises the fixed supporting ramps 24. The return spring 34 is formed symmetrically and comprises on both sides of the stirrup part 36 spiral spring portions 37 which provide for the spring action. Also with this embodiment a continual and automatic wear compensation can be achieved.

Claims

1. A disc brake with an automatic wear compensation arrangement, including a pressure plate arranged to urge a brake lining against a brake disc, a retraction bolt connected to the pressure plate and an abutment member slidably mounted on the shank of the retraction bolt and having an abutment face for engagement by an actuating means for the transmission of retraction force to the retraction bolt, the arrangement being such that upon the application of a retraction force to said abutment face the abutment member becomes clamped to the retraction bolt for the transmission of movement thereto, whereas, when the actuating means is in an idle condition the abutment member is free to be moved relatively to the retraction bolt in a direction towards the pressure plate under the force of a correspondingly located return spring.

2. A disc brake as claimed in Claim 1, wherein the said abutment member comprises a clamping lever and the abutment surface thereof comprises an inclined ramp.

3. A disc brake according to Claim 1 or 2, in which the said abutment member is provided with a bore by way of which it loosely engages the retraction bolt.

4. A disc brake according to Claim 2 or Claim 3 as appended thereto, wherein the said ramp surface defines with respect to a supporting surface which is fixed with respect to a fixed bearing for supporting the retraction bolt, a wedge-shaped slot into which the said actuating member is arranged to be drawn by means of an actuating mechanism.

5. A disc brake as claimed in Claim 4, in which the angle of the said wedge-shaped slot is so determined in accordance with the materials of the members defining the slot and the said actuating member, and the force to be applied thereto during release of the brake, that jamming of the mechanism is prevented.

6. A disc brake according to Claim 4 or 5, in which the said actuating mechanism comprises an electromagnet of which the armature is linked to the said actuating member.

7. A disc brake as claimed in Claim 6, in which the direction of movement of the said armature is at right angles to the axis of the said retraction bolt.

8. A disc brake as claimed in any one of Claims 1 to 7, in which the said abutment member is spring loaded by means of a compression spring arranged at the end of the said retraction bolt.

9. A disc brake according to any one of Claims 1 to 8, in which the said abutment member is spring loaded by means of a blade spring which is fixedly mounted and the free end of which engages upon the abutment member in the region of the retraction boit.

10. A disc brake as claimed in Claim 9, in which the said blade spring is bent at its free end, and in which the abutment member comprises a bifurcated bearing aperture.

11. A disc brake as claimed in any one of Claims 1 to 10, in which the said abutment member is spring loaded by means of a U-shaped torsion spring.

12. A disc brake as claimed in Claim 11, in which the free ends of the said return spring are fixed and in which a central stirrup part connected to said free ends by way of lateral coil spring portions is arranged to engage upon the said abutment member.

13. A disc brake according to any one of Claims 1 to 12, in which the said retraction bolt is axially slidably guided in low-friction slide bearings or a roller bearing.

14. A disc brake as claimed in any one of Claims 1 to 13, in which the said pressure plate is arranged to be pressed against the brake lining by way of non-centrally located plate springs.

15. A disc brake as claimed in Claim 14, in which the said plate springs are located between the pressure plate and a plate member containing a guideway for the said retraction bolt.

1 6. A disc brake substantially as described herein with reference to Figs. 1 and 2 of the accompanying drawings.

1 7. A disc brake substantially as described herein with reference to Figs. 3 and 4 of the accompanying drawings.

18. The features as herein described, or their equivalents, in any novel selection.