GB2246825A

GB2246825A - An automatic brake adjuster for simplex and duo-duplex brakes

Info

Publication number: GB2246825A
Application number: GB9115943A
Authority: GB
Inventors: Bernd Rupprecht
Original assignee: Deutsche Perrot Bremse GmbH
Current assignee: Deutsche Perrot Bremse GmbH
Priority date: 1990-08-01
Filing date: 1991-07-24
Publication date: 1992-02-12
Anticipated expiration: 2011-07-24
Also published as: IT1251103B; ITMI912052A0; DE4024455C2; GB2246825B; GB9115943D0; ITMI912052A1; BR9103281A; DE4024455A1

Abstract

An automatic brake adjuster includes first and second ends (10, 12) connected respectively to a screw (14) and an element (18); a nut (16); and a sleeve (32) coupled at one end to the nut via an arresting spring (44) and at the other end via a one-way drive (34) to a bush (26). On relative axial movement of the ends, the bush will be rotated via a pin and slot connection (28, 30). On brake release, the ends will be forced together against bias of spring (20), and, if brake wear has occurred, the bush will rotate the sleeve (32) and the sleeve will rotate the nut relative to the screw to effect adjustment. Resetting is achieved by manual rotation of the nut (16) relative to the sleeve, and spring-biassed pin (59) prevents rotation of the nut during brake application. <IMAGE>

Description

1 f I- AN AUTOMATIC ADJUSTING DEVICE FOR SIMPLEX AND DUO-DUPLEX BRAKES

This invention relates to an automatic adjusting device for simplex and duo-duplex brakes of the type comprising first and second connecting ends which are movable towards one another against the force of an intervening spring, with an adjusting screw connected to the first connecting end and an adjusting nut which engages said screw, the effective distance between the two connecting ends being adjustable by relative rotation of said screw and said nut, with a bush which is mounted between the connecting ends and is connected with the second_ connecting end so as to be rotated relative to the first connecting end upon axial movement of the second connecting end relative to the first connecting end, with an intermediate sleeve mounted on the exterior of the adjusting nut, and a one-way drive coupling provided between the bush and the intermediate sleeve whereby the bush is able freely to rotate in one direction when the connecting ends are moved apart, but upon rotation in the opposite direction picks up the intermediate sleeve when, after exceeding a path during the previous free rotation, which corresponds with a certain degree of play as predetermined by the one-way drive coupling, the connecting ends move closer to one another, and with an arresting device positioned between the intermediate sleeve and the adjusting nut to prevent relative rotation therebetween during the braking process yet permit such relative rotation when the adjusting nut is operated from the outside to reduce the distance between the connecting ends.

An adjusting device of this type is described in Austrian Patent Specification AT-PS 387 074. The arresting means of this known adjusting device is in the form of a tolerance ring, which is positioned between the intermediate sleeve and the adjusting nut and k SJL230791 2 provides respective static or adhesive friction between these elements.

When replacing the brake linings, it is necessary to reset the brake shoes by means of the adjusting device, so that the brake drum can be pulled off over the brake linings which are embedded therein. This resetting is achieved by operating a toothed gear, which is connected to the adjusting nut, by means of a suitable tool. The static or adhesive friction of the tolerance ring has to be overcome in this operation as the adjusting nut is turned in the locking direction of the one-way drive coupling, i.e. in opposition to the direction of adjustment. In practice, this has proved not to be fully satisfactory as the static or adhesive friction of tolerance rings of this type is subject to certain variations.

An object of the invention is to provide an improved arresting device, for an adjusting device of this type, which more readily permits resetting, and in a more reliable manner.

According to the invention, this object is achieved in that the arresting device is in the form of a spring element which is non-rotatably connected to the intermediate sleeve and is provided with means which arrestingly engage into corresponding recesses provided in the adjusting nut.

With this construction of arresting device the torque applied to the adjusting nut for resetting the adjusting device is precisely defined.

An exemplary embodiment of the invention is illustrated in the drawing and will be explained in more detail hereinafter. In the drawing:

1 i 1 i i 1 1 i 1 1 i i 1 1 i 1 1 SJL230791 3 Fig. 1 is a partially cross-sectional side view of the exemplary embodiment of an adjusting device in accordance with the invention; Fig. 2 is an end view of the intermediate sleeve, from the left hand end as viewed in Fig. 1; Fig. 3 is an enlarged plan view of a spring plate; and Fig. 4 is a side view of the spring plate shown in Fig. 3.

The automatic adjusting device illustrated in Fig. 1 has one connecting end 10 which can be attached, for example, to one brake shoe of a drum brake with two brake shoes, and another connecting end 12 which can be attached to a handbrake lever which is connected to the other brake shoe. A tension spring between the two brake shoes pulls them together and thereby determines the distance of the two brake shoes relative to the connecting ends of the adjusting device. When the brake is operated the brake shoes are spread apart to abut the brake drum and the adjusting device is consequently extended. If the extension of the adjusting device exceeds a certain amount, this is not completely reversed when the brake is released, i.e. the adjusting device is thereby extended. This means that the distance between the brake shoes and the brake drum is decreased, effectively achieving a brake adjustment.

The adjusting device shown in Fig. 1 is constructed in detail as follows:

An adjusting screw 14 is integrally connected to the first connecting end 10. An adjusting nut 16 is screwed onto the adjusting screw 14. An intermediate sleeve 32 is rotatably located over the adjusting nut 16 and extends to the second connecting end 12 which has an SJL230791 t 4 integral cylindrical protrusion 18 inserted in axially movable manner into the intermediate sleeve 32. A pressure spring 20 acts between a constriction of the intermediate sleeve 32 and the end of the protrusion 18 to urge the second connecting end 12 outwardly, away from the intermediate sleeve 32. To ensure that the protrusion 18 cannot slide out of the intermediate sleeve 32 when the device is not installed in operative position, a pin 22 is provided, which engages in a broad annular groove 24 provided on the protrusion 18. The annular groove 24 is of adequate extent in the longitudinal direction such that the axial displacement of the protrusion 18 required for the operation of the brake is not impeded.

The part of the protrusion 18 located outside the intermediate sleeve 32 is provided with a bush 26, which is a transfer means and which is rotatably mounted on the protrusion 18. A pin 28, mounted in the bush 26, extends inwardly therefrom and engages into a slot 30 in the protrusion 18 which is transverse relative to the longitudinal axis of the device. The pin 28 is retained against falling out of the bush 26 by means of an external ring 31. The end of the intermediate sleeve 32 is positioned adjacent the bush 26, and both are provided with a saw-toothing at their abutting ends, thereby establishing a one-way drive coupling 34. A pressure spring 36 presses the ring 31 against the bush 26, and thus the latter against the intermediate sleeve 32. An elastic collar 40 extends over the one-way drive coupling 34 in order to protect the arrangement from dirt and water.

At the opposite end of the intermediate sleeve 32 there is a protrusion 52 with lateral flattenings 54, as best seen in Fig. 2. This protrusion 52 serves to hold an arresting device, which is in the form of a specially shaped spring plate 44 (Figs. 3 and 4). The disc-like i I I i i j i j 1 i i 0? 1 i i i i f I i i SJL230791 spring plate 44 comprises two flexed spring areas 46 and an inner free space or aperture 48 bounded by abutment surfaces 50, in which respect the contour of the free space 48 and the contour of the sleeve protrusion 52 match each other so that the plate 44 fits snugly over the protrusion 52. As the abutment surfaces 50 of the spring areas 46 extend along the flattenings 54 of the intermediate sleeve 32, the spring plate 44, which is to serve as a coupling member, is non-rotatably mounted upon the latter.

The adjusting nut 16 has a flange 42, which is provided with external toothing, and with lateral recesses 58.

Arresting noses 56, which are formed into the ring of the spring plate 44 in opposing planar regions between the spring areas 46, engage into the said lateral recesses 58 of the flange 42 of the adjusting nut 16, and the spring areas 46 are held under tension between the sleeve 32 and the nut 16.

When the adjusting device, installed in its operative position in a brake, is tensioned by means of the brakeshoe retracting spring (not illustrated) all the adjusting or returning parts are under spring tension.

When the brake shoes are spread apart during operation of the brake, the protrusion 18 and with it the connecting end 12 are displaced axially outwards due to the force of the pressure spring 20. This axial displacement of the protrusion 18 is converted, due to the transverse slot connection 28, 30, into a rotary movement of the bush 26, serving as a transfer member, in the free-wheeling direction of the one-way drive coupling 34.

If the operating path, i.e. the axial displacement of the protrusion 18, is so small that no tooth of the saw SJL230791 6 toothing, which forms the one-way drive coupling 34, is jumped over, or if the play determined by the tooth gap of the coupling 34 is not exceeded, then the bush 26 will return to its initial position without taking along the intermediate sleeve 32 when the brake is released and the axial protrusion 18 moves back into the intermediate sleeve 32.

However, if the operating path of the brake is so long that the bush 26 jumps over one or more teeth in the free-wheeling direction of the oneway drive coupling 34, then the intermediate sleeve 32 is taken along upon release of the brake when the protrusion 18 moves back, due to the pulling force of the brake-shoe return spring (not illustrated), into the intermediate sleeve 32, and when, in consequence thereto the bush 26 rotates in the locking direction. Due to the non-rotatable connection of the intermediate sleeve 32 and the adjusting nut 16, as established by the spring plate 44, the adjusting nut 16 is turned relative to the adjusting screw 14 by a distance corresponding with the number of jumped teeth, so that the adjusting device is extended. The brake shoes will not return fully to their initial position, and the brake is adjusted.

If the bush 26, which is loaded by the pressure spring 36, jumps over one tooth or more in the free-wheeling direction of the one-way coupling 34 whilst the brake shoes are spread, it subjects the intermediate sleeve 32 to a torque via the friction of the saw teeth which are moved relative to each other. If this torque is larger than the thread friction between the adjusting nut 16 and the adjusting screw 14, there is a danger of the adjusting nut 16 being rotated in the releasing direction. Such unintentional turning of the adjusting nut 16 would probably also be assisted by vehicle vibrations during the braking process.

T 1 1 1 i i J 1 1 1 i i 1 SJL230791 7 In order to avoid this possibility, a pin 59 is fitted into a radial bore of the adjusting screw 14 and abuts against the inside thread of the adjusting nut 16 under the force of a pressure spring.

To reverse the adjusting path, for example after replacing the brake lining, it is necessary to move the adjusting nut 16 in the locking direction of the one-way drive coupling 34. If no special provisions are made this would mean that the protrusion 18 and with it the connecting end 12 would have to be turned, which is not possible in the assembled state. However, in the illustrated embodiment, the adjusting nut 16 can be moved without further ado into the locking position of the one-way drive coupling 34 for returning the adjusting path, because the portion of the one-way drive coupling 34 which is on the intermediate sleeve 32 is not fixedly connected to the adjusting nut 16, but is connected thereto via the spring plate 44, which can transfer a limited torque only. Consequently, only the spring force of the spring areas 46 has to be overcome for the adjusting nut 16 to be turned past the arresting noses 56 of the spring plate 44. For ease of resetting, the flange 42 of the adjusting nut 16 is provided with the aforementioned external toothing which is accessible via an aperture in the brake cover plate of the brake. An adjustment can therefore be made through this aperture by means of a screwdriver without having to remove the brake cover plate.

In summary, the spring plate 44, serving as an arresting means, transfers rotary movement for the adjusting process from the one-way drive coupling 34 to the adjusting nut 16. Also, by separating the flow of force between the adjusting members 16 and 32, it permits very simple turning of the adjusting nut 16 in the locking direction of the one-way drive coupling 34, when that is necessary upon resetting.

i j i SJL230791

Claims

8 1. An automatic adjusting device for simplex and duo-duplex brakes comprising first and second connecting ends which are movable towards one another against the force of an intervening spring, with an adjusting screw connected to the first connecting end and an adjusting nut which engages said screw, the effective distance between the two connecting ends being adjustable by relative rotation of said screw and said nut, with a bush which is mounted between the connecting ends and is connected with the second connecting end so as to be rotated relative to the first connecting end upon axial movement of the second connecting end relative to the first connecting end, with an intermediate sleeve mounted on the exterior of the adjusting nut, and a oneway drive coupling provided between the bush and the intermediate sleeve whereby the bush is able freely to rotate in one direction when the connecting ends are moved apart, but upon rotation in the opposite direction picks up the intermediate sleeve when, after exceeding a path during the previous free rotation, which corresponds with a certain degree of play as predetermined by the one-way drive coupling, the connecting ends move closer to one another, and with an arresting device positioned between the intermediate sleeve and the adjusting nut to prevent relative rotation therebetween during the braking process yet permit such relative rotation when the adjusting nut is operated from the outside to reduce the distance between the connecting ends, characterised in that the arresting device is in the form of a spring element which is nonrotatably connected to the intermediate sleeve and is provided with means which arrestingly engage into corresponding recesses provided in the adjusting nut.

-A i i i f i i i 1 i 1 1 i 1 1 i i i 1 SJL230791 9 2. An adjusting device as claimed in claim 1 wherein the spring element is in the form of a disc-like spring plate having an inner free area or aperture bounded by parallel abutment surfaces, two spring areas providing these abutment surfaces, and arresting noses or projections, disposed between the spring areas and engagable under spring bias into the recesses of the adjusting nut.

3. An adjusting device as claimed in claim 2 wherein the intermediate sleeve has a protruding portion formed with parallel flattened regions for the abutment of the abutment surfaces of the spring plate.

4. An adjusting device as claimed in claim 2 or 3 wherein the adjusting nut has a flange, and the recesses to accommodate the arresting noses of the spring plate are provided in the flange.

5. An adjusting device as claimed in claim 4 wherein the flange of the adjusting nut is provided with an outer toothing.

6. An adjusting device as claimed in any preceding claim wherein the intermediate sleeve has a tubular extension for receiving part of a cylindrical protrusion of the second connecting end.

7. An adjusting device as claimed in claim 6 wherein the bush is mounted on the cylindrical protrusion of the second connecting end so as to be both rotatable and axially displaceable thereon.

8. An adjusting device as claimed in any preceding claim wherein a pin is fitted in a radial bore of the adjusting screw and abuts under the force of a spring against the inside thread of the adjusting nut.

SJL230791 9. An automatic adjusting device for simplex and duo-duplex brakes substantially as hereinbefore described with reference to and as illustrated by the accompanying drawing.

Published 1992 at The Patent Office. Concept House. Cardiff Road. Newport. Gwent NP9 I RH. Further copies may be obtained froni Sales Branch. Unit 6. Nine Mile Point. Ownifelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mazy Cray. Kent- Z 1 1 1 1 i 7 I i 1 1 i i i i 1 1 i i i 1 I