GB2090353A - Mechanically actuated disc brake with sliding saddle wear adjustment - Google Patents

Abstract

In one shank 5 of the saddle 1 an actuating shaft 7 is rotatably mounted which has a radially projecting collar 9 with balls 11 inserted between collar 9 and a bearing ring 13 to convert the rotary movement of the actuating shaft into an axial movement of a thrust bolt 15 acting on brake lining carrier 2. A readjustment device is provided which comprises a readjustment ring 29 which is arranged coaxially to the thrust bolt 15 and is connected for interaction with the shaft 7 in such a way that, when an angle of rotation, corresponding to a defined lining wear, of the shaft 7 is exceeded, the readjustment ring 29 is rotated. During the release of the brake, the readjustment ring 29 takes along a readjustment nut 14 which is coupled thereto and is screwed onto the thrust bolt 15. The actuating shaft 7 to secure it against axial displacement, is supported, on that side of the collar 9 which is opposite the balls, via a journal bearing 27 on the sliding saddle 1. The bearing ring 13 is axially displaceable relative to the brake saddle 1, but it is secured against rotation and is supported on the readjustment nut 14. The readjustment ring 29 is rotatably mounted on the nut 14 and is coupled to a control device which consists of a groove and of a stud 31 engaging in the groove 30 to effect rotation of the readjustment ring 29, when shaft 7 is rotated. A number of embodiments are illustrated and described. <IMAGE>

Description

SPECIFICATION Mechanically actuated disc brake with sliding saddle The invention relates to a mechanically actuated disc brake having a sliding saddle which is mounted for displacement transversely to the brake disc and embraces the brake disc with its two shanks each provided with a brake lining carrier with a brake lining, and an actuating shaft which is rotatably mounted in one shank and, at its end terminating as a bush, has a radially projecting collar provided on one of its sides, with helical races which are to receive balls and correspond to helical races in a bearing ring and serve to convert the rotary movement of the actuating shaft into an axial movement of a thrust bolt acting on one of the brake lining carriers, and a readjustment device comprising a readjustment ring which is arranged coaxiallyto the thrust bolt and is connected for interaction with the actuating shaft in such a way that, when a pivoting angle, corresponding to a defined wear of the lining, of the actuating shaft is exceeded, the readjustment ring is rotated and, on return into its starting position during the release of the brake, also rotates a re- adjustment nut which is coupled thereto and is screwed onto the thrust bolt and is thus brought into the flux of force from the actuating shaft to the thrust bolt.

In a known disc brake of this type (German Offenlegungsschrift 2,647,353) the actuating shaft passes through the bearing ring supported on the sliding saddle, so that the actuating shaft itself is axially displaced on rotation. Due to the direct end face contact with the readjustment nut, the actuating shaft transmits the axial displacement movement to the thrust bolt The readjustment nut is designed virtually in the form of a disc, and corrugated springs which are located to the two sides thereof and have the shape of annular discs and which each have a firm support relative to the sliding saddle, enclose the readjustment nut between them.On one of its end faces, provided with helical toothing in the form of saw teeth, the readjustment ring coupled to the actuating shaft is in contact with corresponding helical toothing.

This known design suffers from substantial disadvantages. On the one hand, with regard to construction, the axial displaceability of the actuating shaft must be taken into account by providing an elastic sealing cover between the pivot lever seated on the actuating shaft and the brake saddle, which sealing cover can absorb both the pivot movements of the lever and the approach of the lever to the brake saddle. In a functional respect, the fact should be criticised that the frictional resistance of the actuating shaft, which is still low at the beginning of the pivot movement, relative to the readjustment nut in contact therewith is intended to make possible a relative rotation between the shaft and the readjustment nut The consequence of this is a relatively uncontrolled, excessive retention of the readjustment ring relative to the readjustment nut.During the braking stroke, an additional rotation as the consequence of an excessive pivoting angle of the actuating shaft in the case of wear of the brake lining is superimposed on this relative rotation. When the brake is released, the readjustment nut is intended to move the thrust bolt forward for a certain length. Because of the dependence on the frictional conditions, however, this length cannot be accurately predetermined.

It is the object of the invention to provide a disc brake of the type initially set out, which is distinguished by especially accurate readjustment in spite of simple design, easy running and small space requirement.

The disc brake according to the invention, in which the stated object is achieved, is characterised in that the actuating shaft, to secure it against axial dis placement, is supported, on that side of the collar which is opposite the helical races, via a journal bearing on the sliding saddle, that the bearing ring is axially displaceable relative to the brake saddle but is secured against rotation and is supported on the readjustment nut shaped in the form of a bush, and that the readjustment ring is rotatably mounted on the readjustment nut and is coupled to a control device which consists of a groove and of a stud engaging in the groove and effects rotation of the readjustment ring when the actuating shaft is rotated or, as a resultthereof,the bearing ring is axially displaced.

The invention is thus based on the realisation that exactly predetermined working conditions of the brake can be achieved when provision is made for the actuating shaft to be axially undisplaceable and when it is ensured at the same time that the bearing ring can be displaced axially in order to take along the thrust bolt via the readjustment nut in contact with the bearing ring, but that the bearing ring nevertheless cannot execute a rotation which would impair exact actuation of the brake. The invention is also based on the realisation that the play between the stud and the groove determines the pivot angle, within which a readjustment is not yet initiated, and that the readjustment point can accordingly be predetermined accurately in time.

In a further development of the disc brake according to the invention, it has been found to be particularly advantageous when the readjustment ring, under the effect of a spring axially acting thereon, with a surface of approximately conical shape bears against an annular edge of the readjustment nut. The use of such a frictional cone has the advantage of infinite readjustment.

The groove of the control device can run parallel to the axis of the actuating shaft and it can be located either in the actuating shaft or in the readjustment ring. In this case, the stud must be fixed either to the readjustment ring or the actuating shaft.

The groove of the control device can, however, also run obliquely to the axis of the actuating shaft and can be located either in the sliding saddle or in the adjustment ring. In this case, the stud must be fixed either to the readjustment ring or to the sliding saddle.

When the brake linings have to be renewed, or when the basic setting of the brake must be altered, it is necessary to rotate the readjustment nut inde pendently of the actuating shaft Since the readjustment device is located within the sliding saddle, however, it is accessible only after removal of the actuating shaft.

An advantageous further embodiment of the invention therefore provides for the readjustment device to be located outside the sliding saddle. The result of this constructional measure is that the readjustment device is accessible from the outside for adjustment purposes, without time-consuming dismantling work.

Forthe same purpose, it is envisaged in an alternative embodiment of the invention that the readjustment nut is joined, secure against rotation, to an extension piece which passes coaxiallythrough the actuating shaft, and that a readjustment bush coupled to the readjustment ring is connected via a slip clutch to the extension piece.

Since the readjustment bush is coupled to the readjustment ring which in turn is connected for interaction with the actuating shaft, a rotation of the actuating shaft, in normal operation of such a sliding saddle disc brake, entails a rotation of the readjust- ment nut If required, however, the readjustment nut can be rotated from the outside, independently of the actuating shaft, by rotating i Extension piece with a suitable tool sothatthe retaining force exerted by the slip clutch is overcome and the extension piece is rotated relative to the readjustment bush.

Further details, advantages and features of the invention can be seen from the description which follows and from the drawing, to which reference is explicitly made with respect to the disclosure of all the details not described in the text and in which: Figure 1 shows a section parallel to the axis, through the sliding saddle disc brake according to the invention, according to a first embodiment, Figure 2 shows a cross-section through the brake of Figure 1 along the line ll-ll in Figure 1, Figure 3 shows a diagrammatic plan view of a detail of the brake, in the direction of the arrow Ill in Figure 7, Figure 4 shows a longitudinal section through a second embodiment of the sliding saddle disc brake according to the invention, Figure 5 shows a detail of the brake according to Figure 4 in the region of the arrow V in Figure 4, on an enlarged scale, Figure 6 shows a section, parallel to the axis, through a third embodiment of the sliding saddle disc brake according to the invention, Figure 7 shows a view in the direction of the arrow VII in Figure 1, showing a readjustment ring, Figure 8 shows a view in the direction ofthe arrow Vlll in Figure 1, showing a counter-nut, Figure 9 shows a section parallel to the axis, through a fourth embodiment of the sliding saddle disc brake according to the invention, and Figure 10 shows a cross-section along the line X-X in Figure 9.

As can be seen from the drawing, the sliding saddle Iso brake illustrated comprises a sliding saddle 9 which embraces the brake disc 6, indicated in dots and dashes, with its tw5) shanks 4 and 5. The two shanks are each provided with a brake lining carrier 2 which carries a brake lining 3 facing the brake disc 6. An actuating shaft 7 is mounted, rotatable via a lever 8, in the shank 5 of the sliding saddle 1. This actuating shaft 7 terminates as a bush-shaped end with a radially projecting collar 9. On its side facing away from the leverS, this collar 9 is provided with at least two, preferably three, helical races 10 which are to receive balls 11 which, on the other side, run in corresponding helical races 12 on a bearing ring 13.

The mutually corresponding helical races 10 and 12 are arranged relative to one another on the collar 9 and bearing ring 13 respectively in such a way that a rotation of the actuating shaft 7 is converted into an axial movement of the bearing ring 13 and a readjustment nut 14. A thrust bolt 15, the end face of which bears against a part 16 holding the brake lining carrier 2, is screwed into this readjustment nut 14. To transmit axial forces from the bearing ring 13 to the bush-shaped readjustment nut 14, the latter is provided with a radially projecting shoulder 17 on which the bearing ring is supported.To enable the bearing ring 13 to be axially displaced under the action of the actuating shaft 7, without participating in the rotation of the shaft 7, a securing device against rotation is provided in the form of a guide groove 18 which is parallel to the axis and in which engages a guide pin 19 which passes radially through the sliding saddle 1. This guide pin 19 is formed by thr end, projecting from the end face, of a screw bolt 20 which is screwed into a threaded bore of the sliding saddle 1. For 5implicity, this screw bolt is drawn in a position in which its axis is in the vertical section plans f the sliding saddle.In reality, however, the screw bolt 20 with the guide pin 19 is in a position which is angularly displaced relative to the plane of the drawing.

In orderto prevent the thrust bolt '8 5 from rotating with the readjustment nut 14, the thrust bolt 15 is provided, in the region of its head bearing against the part 16, with a recess 21 in which a nose 22 of the part 16 engages.

It can be seen from Figure 1 that a sheet metal ring 23 which is subject to the action of a helical spring 24 bears against the front end of the readjustment nut 14. The free end of this spring is supported via a ring 25 on a shoulder of the sliding saddle 1. A ring sleeve 26 which consists of an elastic plastic and extends between the sliding saddle 1 and the thrust bolt 15, protects the actuating mechanism againstthe penetration of foreign bodies, dirt and moisture.

On the rear side of the collar 9, facing away from the helical races 10, a journal bearing 27 is provided, by means of which the actuating shaft 7 is supported on the sliding saddle 1, specifically via an annular disc 28 which bears against a shoulder of the sliding saddle 1.

As can be seen from Figure 1, a readjustment ring 29 is rotatably mounted on that end of the readjustment nut 14 which faces away from the shoulder 17.

This readjustment ring 29 has a groove 30 in an arrangement parallel to the axis. A stud 31 which is joined to the actuating shaft 7 and has a diameter which is smaller by the play "L"than the width of the groove, engages in this groove 30. At the outer end of the readjustment nut 14, a securing ring 32 is provided which serves to support a corrugated dise 33 which exerts a spring force on the readjustment ring 29. Under the action of the corrugated disc 33, a helical toothing 34 in the form of saw teeth on the end face of the readjustment ring 29 is held in a corresponding helical toothing 35 which is provided on a shoulder of the readjustment nut 14.

The disc brake described operates as follows: When the actuating shaft 7 is rotated via the lever 8, tEhe balls 11 on the helical races 1 O or 12 cover a rolling distance, which causes the bearing ring 13to move towards the brake disc 6. In doing so, the bearing ring takes along, over the shoulder 17, the read justment nut 14 and the thrust bolt 15 5 which is screwed into the latter and which, via the part 16, causes the brake lining 3 seated on the brake lining carrier 2 to come into contact with the brake disc 6.

Due to the reaction force, the sliding saddle 1 is axially displaced towards the right, relative to the brake disc 6, until finally the brake lining carrier 2, located on the shank 4, with its brake lining 3 also comes into contact with .Ine brake discS.

During this actuation of the brake, the force of the spring 24 must be overcome, which tends to return all the parts again into the starting position, when the brake is released.

During the r station of the actuating shaft 7, its col- lar 9 is supported via the journal bearing 27 on the sliding saddle 1. When the actuating shaft7 is pivoted, tho stud 31 moves in the groove 30 of the readjustment ring 29, corresponding to the play "L" illustrated in Figure 2. When the wear of the brake linings exceeds a predetermined degree, a correspondingly greater pivot angle of the actuating shaft7 is then necessary for applying the brake. Accordingly, the stud 31 then comes into contact with the other end of the groove 30 and the readjustment ring 29 is thus taken along so that the latter is rotated relative to The readjustment nut 14.When the rotary movement of the readjussment ring 29 relative to the readjustment nut 14 exceeds the width of one tooth of the helical toothing 34, 35, one tooth of the helical toothing is skipped. When the parts move back after the end of the braking step, the actuating shaft7 takes along the readjustment nut 14, via the stud 31 and the readjustment ring 29 with the helical toothing 34, 35 which is then in engagement so that the thrust bolt 15 is screwed out of the readjustment nut 14 in the direction of the brake disc 6, to an extent corresponding to the wear of the lining. In this way, compensation for the wear of the lining is ensured by an automatic readjustment.

With respect to the basic construction, the second embodiment in Figure 4 is identical to the embodiment according to Figure 1. Identical components are therefore marked with identical reference symbols.

Essentially, this embodiment differs from that according to Figure 1 in that the groove 30a has the form of a helical groove which, additionally, is shown in Figure 4 in a position offset by 90 . In this case, the stud 31 a engaging in this helical groove 30a is arranged in a fixed position in the sliding sad dle 1.

In this embodiment also, the bearing ring 13 is provided with a guide groove 18 in which engages a guide pin 19 which passes radially through the sliding saddle. This guide pin is of cylindrical shape and is provided with flattenings 36 in the region of the guide groove. At the rear end, the guide pin 19 has a radial shoulder 37 which, in conjunction with a corresponding recess in the associated bore of the sliding saddle, determines the extent to which the pin projects from the bore. The section of the bore, receiving the guide pin 119,is adjoined byea larger section, provided With a thread, for receiving a hexagon socket bolt 38 which dixies the guide pin.To align the fiattenings 36 of the guide pin 19 relative to the guide groove 18, a retaining pin 39 is provided in the region of the recess of the bore in the sliding saddle, a slot 40 being associated with the retaining pin in the region of the radial shoulder 37 of the guide pin.

As can be seen from Figure 4, in this embodiment, the stud 31 a which engages in the groove 30a trmeå as a helical groove is located on the outer end of the guide pin 19, passing through the guide groove 18 of the bearing ring 13, in such a way that it projects from the guide pin.

In the embodiment according to Figure 4, the readjustment ring 29 is also subject to the spring action of a corrugated disc 33. As can be seen especially clearly from Figure 5, the readjustment ring 29 is supported in this case with a surface of approximately conical shape on an annular edge 42 of the readjustment nut 14.

In the embodiment according to Figure 4, a radially projecting strip 43 which engages in a guide groove 44 of the brake saddle 1 is joined to the thrust piece 15, in order to secure the latter against rotation.

In the second embodiment described above, rotation of the actuating shaft 7 also causes, via the balls 11 and the helical races associated wh"h them, the bearing ring 13 to be axially displaced, the adjacent readjustment nut 14 and the thrust bolt 15 scrnwed into the latter being taken along. As soon as a predetermined angle of rotation of the actuating shaft7 is exceeded, the stud 31 a comes into contact with the opposite edge of the helical groove 30a, due to the axial displacement of the readjustment ring 29, so that further pivoting of the actuating shaft 7 rotates the readjustment ring 29, with a corresponding additional axial displacement of the latter. With this rotation, a relative movement of the conical surface 41 of the readjustment ring 29 with respect to the annular edge 42 of the readjustment nut 14 takes place, because the flange of the bearing ring 13 is supported on the readjustment nut 14, so that the latter cannot rotate. When the individual brake elements are returned into the starting position under the action of the spring 24, when the brake jaws are relieved, the readjustment nut 14 is taken along by the readjustment ring 29, during the pivoting back, underthe action of the stud 31a engaging in its groove 30a. Since the thrust bolt 15 is secured against rotation by the strip 43 engaging in the guide groove 44, it is screwed out, during this relative rotation of the readjustment nut 14 with respect to the thrust bolt 15, in order to compensate for the wear of the brake linings.

Of course, the helical toothing 34,35 used in the first embodiment according to Figure 1 can also be used in this embodiment in place of the conical surface 41 with the annular edge 42.

In the third embodiment shown in Figures 6,7 and 8, the thrust bolt 15 5 screwed into the readjustment nut 14 bears with its end face against a piston 121 which holds the brake lining carrier 2. The guide pin 19, used for securing the bearing ring 13 against rotation, passes through a groove 122 which is formed in the piston 121 and is parallel to the axis.

A ring sleeve 126 of an elastic plastic, which extends between the sliding saddle 1 and the thrust bolt 15, protects the actuating mechanism against the penetration of foreign bodies, dirt and moisture.

On the rear side of the collar 9, facing away from the helical races 10, a journal bearing 127 is provided, via which the actuating shaft7 is supported on a ring disc 128 which bears against a flange 142 fixed to the sliding saddle 1 by means of four bolts 143.

The readjustment nut 14 is joined, secure against rotation, to an extension piece 141 by means of a pin 124 and is thus in functional engagement with the readjustment device.

A readjustment bush 144 is screwed firmly onto the extension piece 141 and is secured against loosening by a counter-nut 125. To make the connection absolutely secure, the connection piece 141 has a slot 137 in which an indentation 138, which can be seen in Figure 8, is provided by deformation of a cylindrical part projecting from the counter-nut 125.

By means of a compression spring 123, the complete readjustment device 144, 141, 124, 14 is brought into contact with the shoulder 17 on the bearing ring 13 and the spreader device 9, 11, 13 is thus held on the ball guides 10,12 without play. The journal bearing 127 is set for freedom from play by means of a setting nut 139 which is screwed onto the actuating shaft and is rotatably supported on the flange 142 by means of a thrust plate 140.

As can be seen from Figure 6, a readjustment ring 129 is rotatably mounted on that end of the readjustment device 144, 141, 124, 14 which faces away from the shoulder 17. As Figure 7 shows, this readjustment ring 129 has two four-cornered studs 131 which engage in axial grooves 130 in the actuating shaft 7, the studs 131 having a thickness which is smaller than the width of the axial grooves 130 by the free clearance L.

Between the counter-nut 125 and the readjustment ring 129, a compression spring 133 is provided, under the action of which the readjustment ring 129, by means of a helical toothing 134 in the form of saw teeth on the end face, is held in contact with corres ponding helical toothing 135 on the readjustment bush 14.

The control part located next to the actuating lever 8 is protected by a special seal 132 of an elastic plastic against the penetration of foreign bodies and moisture.

The disc brake described operates as follows: When the actuating shaft7 is rotated by means of the lever 8, the balls 11 on the helical races 10 or 12 cover a rolling distance which has the result that the bearing ring 30 moves towards the brake disc 6. In doing so, the bearing ring takes along, over the shoulder 17, the readjustment nut 14 and the thrust bolt 15 which is screwed into the latter and which, via the piston 121, causes the brake lining 3 seated on the brake lining carrier 2 to come into contact with the brake disc 6. Due to the reaction force, the sliding saddle 1 is axially displaced towards the right, relative to the brake disc 6, until finally the brake lining carrier 2 located on the shank4, with its brake lining 3 comes into contact with the brake disc 6.

During the rotation of the actuating shaft 7, its collar 9 is supported via the journal bearing 127 and the ring disc 128 on the flange 142 of the sliding saddle 1. When the actuating shaft 7 is pivoted, the groove 130 of the latter moves relative to the stud 131 of the readjustment ring 129, corresponding to the play L illustrated in Figure 7. When the wear of the brake linings exceeds a predetermined degree, a correspondingly greater angle of rotation of the actuating shaft 7 is then necessary for applying the brake.

Accordingly, the stud 131 then comes into contact with the other end of the groove 130 and the readjustment ring 129 is thus taken along so that the latter moves relative to the readjustment bush 144.

When the rotary movement of the readjustment ring 129 relative to the readjustment bush 144 exceeds a length corresponding to the width of one tooth of the helical toothing 34, 13C, one tooth ePF thehelical toothing is skipped. When the parts move back after the end of the braking step, the actuating shaft 7 takes along the stud 131 of the readjustment ring 129, which stud then takes along the readjustment bush 144viathe helicaltoothings 134,135 which are then in engagement. Since the readjustment bush 144 is joined, secure against rotation, to the extension piece 141, the latter and hence also the readjustment nut 14 are likewise rotated.This has the consequence that the thrust bolt 15 is screwed out of the readjustment nut 14 in the direction of.the brake disc 6, to an extent corresponding to the wear of the lining. In this way, a compensation of the wear of the brake linings is ensured by automatic readjustment.

The dismantling process which becomes necessary in the case of renewal of the brake linings and a new basic setting, is very simple. Initially, the special seal 132 is taken off, and the helical toothing 134,135 is then taken apart. This is done by displacing the readjustment ring 129 towards the compression spring 133, by hand or by means of a tool suitable for the purpose. By placing a spanner on the hexagon of the counter-nut 125, the thrust bolt 15 and the piston 121 can now be brought into the starting position by meansofthe readjustment device 144,141,124,14.

In the fourth embodiment shown in Figures 9 and 10, the readjustment nut 14 is likewise joined, secure against rotation, to an extension piece 141. A readjustment ring 229 which is supported via a corru gated spring 233 on the readjustment nut 14 is mounted rotatably on the extension piece 141. The readjustment ring 229 has an axial groove 230 in which engages a stud 231 which projects radially inwards from the actuating shaft 7. As can be seen from Figure 10, the stud 231 has a diameter which is smaller than the width of the axial groove 230 by the free clearance Loathe L oi: the brake.

With interposition of a tolerance ring 245, a readjustment bush 244 is slipped over the extension piece 141 and is secured against ioosening by a securing ring 246. Helical toothing 234 in the form of saw teeth on the end face of the readjustment ring 229 is, under the action of the corrugated spring 233, held in engagement with a helical toothing 235 on the facing end of the readjustment bush 244.

A counter-nut 125 is screwed onto the front end of the extension piece 141. A helical spring 123 is supported on a disc 248 bearing against a nut 125 and on a constriction 249 of the actuating shaft 7. By means of This compression spring 123, the complete readjustment device 224,299,114 is brought into contact with the shoulder 17 of the readjustment nut 14 on the bearing ring 13, and the spreader device 9, 11, 13 on the ball guides 10, 12 is thus kept freefom play.

A closure bolt 232 is screwed into the front end of the actuating shaft7 in order to protect the read justnient device against the penetration of dirt or water.

In principle, the sliding saddle disc brake shown in Figures 9 and 10 operates in the same way as the third embodiment described above. When the actuating shaft 7 is rotated via the lever 8, its stud 231 moves relative to the groove 230 of the readjustment ring 229, corresponding to the free clearance Shown in Figure 10. When the wear of the brake linings exceeds a predetermined degree, a correspondingly greater angle of rotation of the actuating shaft 7 is then necessary for applying the brake. Accordingly, the stud 231 then comes into contact with the other end of the groove 230 and the readjustment ring 229 is thus taken along so that the latter moves relative to the readjustment bush 244.

When the rotation of the readjustment ring 229 relative to the readjustment bush 244 exceeds the width of one tooth of the helical toothing 234,235, one tooth of the helical toothing is skipped. When the parts move back after the end of the braking step, the actuating shaft 7 with the stud 231 takes along the readjustment ring 229 which, via the helical toothings 234,235 which are then in engagement, takes along the readjustment bush 244. Since the readjustment bush 244 is frictionally connected via the tolerance ring 245 to the extension piece 141, the latter and hence also the readjustment nut 14 are likewise rotated. This has the consequence that the thrust bolt 15 is screwed out of the readjustment nut 14, in the direction of the brake disc 6, to an extent corresponding to the wear of the lining. In this way, the wear of the lining is automatically compensated.

The dismantling process which becomes necessary in the case of renewal of the brake linings and a new'basic setting, is extremely simple. Initially, the closure bolt 232 is taken off and a socket spanner is then placed onto the counter-nut 125 in order to rotate the extension piece 141 and hence the readjustment nut 14. In doing so, the thrust bolt 15 is screwed out of the readjustment nut 14 or into the latter, depending on the direction of rotation of the counter-nut 125. In fact the readjustment bush 244 is in engagement, via the helical toothings 234, 235, with the readjustment ring 229 which is joined, secure against rotation, to the actuating shaft 7 via the stud 231. Consequently, the readjustment bush 244 cannot be rotated independently of the actuating shaft 7. However, the setting process is not impeded by this circumstance, since the static friction of the tolerance ring 245 can readily be overcome by the torque exerted by the socket spanner on the counter-nut 125.

Claims (24)

1. Mechanically actuated disc brake having a sliding saddle which is mounted for displacement transverselyto the brake disc and embraces the brake disc with its two shanks each provided with a brake lining carrier with a brake lining, an actuating shaft which is rotatably mounted in one shank and, at its end terminating as a bush, has a radially projecting collar provided, on one of its sides, with helical races which are to receive balls and correspond to helical races in a bearing ring and serve to convert the rotary movement of the actuating shaft into an axial movement of a thrust bolt acting on one of the brake lining carriers, and a readjustment device comprising a readjustment ring which is arranged coaxially to the thrust bolt and is connected for interaction with the actuating shaft in such a way that, when a pivoting angle, corresponding to a defined wear of the lining, of the actuating shaft is exceeded, the readjustment ring is rotated and, on returning into its starting position during the release of the brake, also rotates a readjustment nut which is coupled thereto and is screwed onto the thrust bolt and is thus brought into the flux of force from the actuating shaft to the thrust bolt, characterised in that the actuating shaft (7), to secure it against axial displacement, is supported, on that side of the collar (9) which is opposite the helical races (10,12), via a journal bearing (27; 127) on the sliding saddle (1), that the bearing ring (13) is axially displaceable relative to the brake saddle (1) but is secured against rotation and is supported on the readjustment nut (14) shaped in the form of a bush, and that the readjustment ring (29; 129; 229) is rotatably mounted on the readjustment nut (14) and is coupled to a control device which consists of a groove (30; 30a; 130; 230) and of a stud (31; 31a; 131; 231) engaging in the groove and effects rotation of the readjustment ring (29; 129; 229) when the actuating shaft (7) is rotated or, as a result thereof, the bearing ring (13) is axially displaced.

2. Disc brake according to Claim 1, characterised in that the groove (30; 130; 230) of the control device runs parallel to the axis of the actuating shaft (7) and is located either in the actuating shaft or in the readjustment ring (29; 229), and that the stud (31; 131; 231) is fixed either to the readjustment ring (129) or to the actuating shaft (7).

3. Disc brake according to Claim 1, characterised in that the groove (30a) of the control device runs obliquely to the axis of the actuating shaft (7) and is located either in the sliding saddle (1) or in the readjustment ring (29), and that the stud (31 a) is fixed either to the adjustment ring (29) or to the sliding saddle (1).

4. Disc brake according to Claim 1, characterised in that the readjustment ring (29), under the effect of a compression spring (33) axially acting thereon, with a surface (41) of approxirnately conical shape bears against an annular edge (42) of the readjustment nut (14).

5. Disc brake according to Claim 1, characterised in that the readjustment ring (29), under the effect of a compression spring (33) axially acting thereon, with a helical toothing (34) in the form of saw teeth on the end face, bears against an end face, having a corresponding helical toothing (35), of the readjustment nut (14).

6. Disc brake according to Claim 1, characterised in that the bearing ring (13) is supported on a radially projecting shoulder (17) of the readjustment nut (14), and that, to secure it against rotation, a guide groove (18) parallel to the axis is provided, in which engages a guide pin (19) which passes radially through the sliding saddle (1).

7. Dise brake according to Claim 3, characterised in that the pin (31a) which protrudes into the helical groove (30a) projects from the ou4-er end of the guide pin (19) which passes through. .: 5dc- groove (18) ofthe bearing ring (13).

8. Disc brake according to Claim 6 or7, characterised in that the guide pin (19) is of cylindrical shape and is provided with flattenings (36) in the region of the guide groove (18).

9. Disc brake according to one of Claims 6 to 8, characterised in that the guide pin (19) is provided, on the rear end, with a radial shoulder (37) which, in conjunction with a corresponding recess of the associated bore in the sliding saddle, determines the extent to which the stud (31) projects from the bore.

10. Disc brake according to Claim 9, character ised in that the section of the bore, which receives the guide pin (19), is adjoined by an outer section provided with a thread, for receiving a hexagon socket bolt (38) which fixes the guide pin.

11. Disc brake according to Claim 8 and 10, characterised in that, in order to align the flattenings (36) of the guide pin (19) relative to the guide groove (18), a retaining pin (39) is provided in the region of the recess of the bore in the sliding saddle, a slot (40) being associated with the retaining pin in the region of the radial shoulder (37) of the guide pin (19).

12. Disc brake according to one of Claims 1 to 11, characterised in that the thrust bolt (15) is provided with a radially projecting strip (43) which engages in a guide groove (44) of the sliding saddle (1).

13. Disc brake according to Claim 1, characterised in that the readjustment device (144, 141,24, 14) is located outside the sliding saddle (1).

14. Disc brake according to Claim 13, characterised inthatthe readjustment nut (14) is joined, secure against rotation, to an extension piece (141) which passes coaxially through the actuating shaft (7) and, at its free end protruding from the actuating shaft, is joined, secure against rotation, to a readjustment bush (144).

15. Disc brake according to Claim 14, characterised in that the readjustment ring (129), under the effect of a compression spring (133) axially acting thereon, with a helical toothing (134) in the form of saw teeth on the end face bears against an end face, having a corresponding helical toothing (135), of the readjustment bush (144).

16. Disc brake according to Claim 15, characterised in that the free end of the extension piece (141) is provided with an external thread onto which the readjustment bush (144) and a counter nut (125) are screwed, the compression spring (133) being supported on the readjustment ring (129) and on the counter-nut (125).

17. Disc brake according to Claim 15, characterised in that, in the end face of its free end, the extension piece (141) is provided with a slot (137) in which engages a locking deformation (138) made on a projecting cylindrical part of the counter-nut (125).

18. Disc brake according to one of Claims 14to 16, characterised in that a cup-shaped sealing sleeve (132) which encloses the free end of the extension piece (141) is slipped over the actuating shaft (7).

19. Disc brake according to Claim 1, characterised in that the readjustment nut (14) is joined, secure against rotation, to an extension piece (141) which passes coaxially through the actuating shaft (7), and that a readjustment bush (244) coupled to the readjustment ring (229) is connected via a slip clutch (245) to the extension piece (141).

20. Disc brake according to Claim 19, character- ised in that the readjustment bush (2443 is slipped onto the extension piece (141), with iai;srposition or a tolerance ring '245).

21. Disc bra4e according to Claim 20 character ised in that the readjuement ring (229), under sr the effect of a compression spring (233) axially acting thereon, with a helical toothing (234) in the form of saw teeth on the end face bears against an end face, having a corresponding helical toothing (235), of the readjustment bush (244).

22. Disc brake according to Claim 21, characterised in that the free end of the extension piece (141) is provided with an outer thread onto which a counter-nut (125) is screwed.

23. Disc brake according to one of Claims 19 to 22, characterised in that a closure bolt (232) is screwed into the free end of the actuating shaft (7).

24. Disc brakes according to Claim 1, substantially as herein described with reference to and as illustrated in the accompanying drawings.