GB1592889A

GB1592889A - Centring and adjusting device for motor vehicle internal shoe brakes

Info

Publication number: GB1592889A
Application number: GB5231777A
Authority: GB
Original assignee: Deutsche Perrot Bremse GmbH
Current assignee: Deutsche Perrot Bremse GmbH
Priority date: 1977-01-31
Filing date: 1977-12-15
Publication date: 1981-07-08
Also published as: FR2393195A1; AT374898B; ATA877677A; DE2703891A1; IT1089591B; FR2393195B1

Description

(54) CENTRING AND ADJUSTING DEVICE FOR MOTOR VEHICLE INTERNAL SHOE BRAKES (71) We, DEUTSCHE PERROT BREMSE GMBH., of 6800 Mannheim 71, Friedrichsfeld, West Germany, a Body Corporate organized under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a centring and adjusting device for motor vehicle internal shoe brakes, and brakes incorporating such devices.

In a known such device (German Patent 1148 892) wherein the supporting housing is of closed construction to protect against soil ing, a centring spring acts on a disc connected to a sleeve which by rotation adjusts the spacing between the shoes The disc is fixed to the sleeve to rotate therewith and has a projection which engages in a detaining recess of a ring forming part of the closed supporting housing. A slidable anchor pin of which the sleeve forms part is mounted to be capable of displacement in the central bore of the said ring but is centred within it by the centring spring. After manual adjustment involving rotation of a toothed disc also arranged on the adjusting sleeve, the retaining projection of the first-mentioned disc jumps into the next retaining recess of the ring so that the sleeve is held at the desired increment of rota tion, and adjusting screws within it with their respectively right-hand and left-hand screw threads are screwed into or out of the adjust ing sleeve by the desired axial amount to adjust the spacing of the brake shoes.

However, it has been found that if the vehicle is braked while moving in reverse the slidable anchor pin is shifted in such a manner relative to the supporting housing that the re taining projection of the second disc can be moved clear away of the retaining recess of the ring and consequently there is no longer any security against rotation (though rotation is resisted by the frictional contact of the screwthread of the adjusting screw in the adjusting sleeve). Therefore in certain cases it is possible for a slight rotational movement to take place when there are oscillations and vibrations coming from the vehicle and from the road surface. If as a result of this projection instead of being in register with the previous detaining recess is in register with an unrecessed portion of the ring there will be a general axial displacement of the brake shoe system towards the disc. A compensating adjustment may follow, which would mean that the operating travel available would no longer be sufficient for applying the brake shoes against the brake drum.

With that construction also, if there is a careless adjustment the retaining projection of the disc can abut on to the elevation between two retaining recesses of the ring, so that the situation described hereinbefore can occur.

The invention has as its object to provide a centring and adjusting device which eliminates the aforesaid disadvantages of the stated device, and at the same time to simplify it, so that the adjusting sleeve should always be satisfactorily retained against un desired turning movements both in forward travel and also when travelling in reverse.

According to the invention we provide a centring and adjusting device for the shoes a motor vehicle internal shoe brake wherein a slidable anchor pin is axially displaceable relative to a supporting housing and includes a rotatable element rotatable for screw threadedly adjusting the axial length of the slidable anchor pin, a centring spring biasing the slidable anchor pin to an axially centralised position relative to the housing, a toothed wheel on the rotatable element an.d constrained to rotate together with it, and a retaining spring for retaining the toothed wheel against undesired rotation, the retaining spring including a portion held in position by the centring spring and a portion extending parallel to the axis of the slidable anchor pin and engaging with the toothed wheel. Preferably, the centring spring acts in respectively opposite directions on respective shoulders extending transversely relatively to the axis of the rotatable element the shoulders being respectively part of sleeve members one at each end of the rotatable element, the sleeve members being respectively coupled to the rotatable element to transmit the said actions of the centring spring to it, and the portion of the retaining spring held by the centring spring being sandwiched between one end of the latter and one of said shoulders.

Then in the preferred direction of travel, namely forward travel, the slidable anchor pin slides through in such a manner relatively to the supporting housing that the retaining spring takes part in the displacement movement of the slidable anchor pin i.e. the rotatable element with the toothed wheel which is arranged thereon and is held in the locking position by the retaining spring. On travelling in reverse and therefore with displacement of the slidable anchor pin in the opposite direction, the toothed wheel is shifted relatively to the end of the retaining spring which is in retaining engagement therewith and which extends approximately parallel to the axis of the rotatable element but, given proper design, without the retaining connection being discontinued at any point of time.

It has been found very advantageous having regard to making the end of the plate spring which is in retaining engagement with the toothed disc particularly resistant to abrasion, to give the said end an approximately Vshaped cross-section. A cross-section of this kind is also advantageous from the point of view that in the case of subsequent adjustment it allows temporary release of the retaining engagement situation.

Particularly simple assembly is provided if that end of the plate spring which is acted upon by the centring spring comprises a central hole with a hole generally conforming to the external diameter of the rotatable element. It has been found very advantageous if that end of the plate spring which comprises the hole is provided with a bent out portion which engages flat with the rotatable element and thus can be used for securing the desired position in the assembled state.

An arrangement of the centring and adjusting device which is particularly simple from the production point of view is obtained if under the pressure of one end of the centring spring the plate spring bears on a radial flange, forming one shoulder of one of the sleeve members which surrounds the rotatable element coaxially and with it extends through one hole in the housing, the other end of the sleeve member abutting against the toothed disc.

According to a further feature it is advantageous if the other end of the centring spring acts directly on a radial flange, forming the shoulder of a second one of the sleeve members which also surrounds the rotatable element coaxially and extends with it through the other hole in the housing, the free end of the said sleeve member abutting on a securing ring sunk into a groove in the adjusting nut.

A completely shielded mounting of the slidable anchor pin within the supporting housing is necessary only if it were necessary to anticipate relatively heavy soiling.

With the device according to the present invention, which is used in vehicles wherein there is not so much danger of soiling, it has been found very advantageous in order to keep manufacture as simple as possible in order to save as much cost as possible, to make the housing of U-shaped construction and to provide two collinear holes receiving the slidable anchor pin in the two legs of the housing.

This device according to a further feature is advantageously characterised by such an arrangement of the plate spring relatively to the supporting housing that a slot which is provided at one end of the plate spring and which separates two tongues extends parallel to one leg of the supporting housing.

A particular embodiment of the invention is shown by way of example in the accompanying drawings wherein: Figure 1 shows a longitudinal section through the device and Figures 2 and 3 show a front view and plan view respectively of a retaining spring used in the device shown in Figure 1.

The centring and adjusting device indudes a supporting housing 1 which is capable of being mounted (in a manner not shown) on the brake cover plate by means of a hexagon bolt, and also a slidable anchor pin 2 including a rotatable element in the form of an adjusting sleeve 4 mounted to be capable of rotation in sleeves 3,3', and which is in effect a double nut having an internal surface screw threadedly engaged with adjusting screws 5,6 which have oppositely directed threads. An adjusting wheel in the form of a toothed disc 7 is pressed securely onto one end of the adjusting sleeve 4. The supporting housing 1 is U-shaped so that the sleeves 3,3' with their radial flange 8,8' can bear on the mutually closer edges of respective holes receiving them in the legs 9,9' of the supporting housing 1, under the action of a centring spring 10 surrounding the adjusting sleeve 4 in the region between the two legs 9,9'. The sleeve 3 abuts with one end against the toothed disc 7, so that its flange 8 forms a shoulder which extends transversely relatively to the axis of the adjusting sleeve 4, through which shoulder one end of the centring spring 10 acts on the aajusting sleeve 4 to urge it in one direction (leftwards as seen in Figure 1). The sleeve 3' bears with its free end against a securing ring 11 which is sunk in a groove of the adjusting sleeve 4, so that the flange 8' forms a further shoulder which extends transversely relatively to the axis of the adjusting sleeve and by means of which the centring spring 10 at its other end acts directly on the adjusting sleeve 4 to urge it in the other direction. Between the one end of the centring spring 10 and the flange 8 of the sleeve 3 there is interposed one end of a retaining spring in the form of a spring plate 12, secured in position by the action of the spring force of the centring spring, the bentover other end 12' of the said spring 12 extending approximately parallel to the axis of the adjusting sleeve 4, being in retaining engagement with the toothed disc 7. The portion of this end of the plate which actually cooperates with the toothed disc 7 for retaining the latter against rotation has a substantially V-shaped cross-section, and has appreciable axial length such that within the expected range of displacement of the slidable anchor pin, it will at all times remain in engagement with the periphery of the disc.

In order to ensure a satisfactory position of the spring plate 12 in the assembled state, that end of the spring plate 12 which is acted upon by the centring spring 10 has a hole 13 the diameter of which corresponds to the external diameter of the adjusting sleeve 4. The hole 13 is punched out in such a manner that there is formed a slight bent-out region 14 at the lower edge of the hole, extending out of the plane of the plate spring, this bent-out region forming a flat which avoids cutting into the adjusting nut 4 during operation. It also has further bent-over portions 15 which in the assembled position of the spring plate 12, by abutment on the supporting housing 1, prevent rotation of the spring plate 12 about the axis of the adjusting sleeve 4.

The centring and adjusting device just described operates as follows: If adjustment by hand is desired, rotation of the adjusting sleeve is carried out by means of the toothed disc 7. The end 12' of the spring plate 12 which is in retaining engagement with the toothed disc 7 can yield briefly for such adjustment, but otherwise remains always in engagement with the teeth of the toothed disc 7 even if the slidable anchor pin is displaced, whether in forward travel or reverse travel.

For example, if the adjusting sleeve 4 is displaced together with the adjusting screws 5,6 and the toothed disc 7 towards the right in Figure 1 the sleeve 3 carries the spring plate 12 along also, by means of its flange 8. The centring spring 10 which was compressed in this displacement then urges the slidable anchor pin back into the illustrated initial position.

In the event of displacement of the slide lock towards the left in Figure 1, the sleeve 3 and the spring plate 12 remain in the illustrated position. The toothed disc 7 however can move towards the left together with the adjusting nut 4. In spite of this relative movement of the toothed disc 7 and the plate spring 12, retaining engagement is maintained between the elongate notch in the end portion 12' and the selected recess in the disc.

WHAT WE CLAIM IS: 1. A centring and adjusting device for the shoes of a motor vehicle internal shoe brake wherein a slidable anchor pin is axially displaceable relative to a supporting housing and includes a rotatable element rotatable for screwthreadedly adjusting the axial length of the slidable anchor pin, a centring spring biasing the slidable anchor pin to an axially centralised position relative to the housing, a toothed wheel on the rotatable element and constrained to rotate together with it, and a retaining spring for retaining the toothed wheel against undesired rotation, the retaining spring including a portion held in position by the centring spring and a portion extending parallel to the axis of the slidable anchor pin and engaging with the toothed wheel.

2. Device according to Claim 1 wherein the centring spring acts in respectively opposite directions on respective shoulders extending transversely relatively to the axis of the rotable element, the shoulders being respectively part of sleeve members one at each end of the rotatable element, the sleeve members being respectively coupled to the rotatable element to transmit the said actions of the centring spring to it, and the portion of the retaining spring held by the centring spring being sandwiched between one end of the latter and one of said shoulders.

3. Device according to Claim 2 wherein the end portion of the retaining spring which is under the pressure action of one end of the centring spring bears against a radial flange forming one shoulder of the slidable anchor pin of one of the sleeves, which abuts with its other end against the toothed wheel, and which passes with the rotatable element through an aperture in the supporting housing.

4. Device according to Claim 3 wherein the other end of the centring spring bears directly against a radial shoulder, forming the other shoulder of the slidable anchor pin, of the second of the sleeves which with its free end abuts on a securing ring sunk in a groove of the rotatable element, and which passes with the rotatable element through an aperture in the supporting housing.

5. Device according to Claim 4 wherein the supporting housing is U-shaped and the two holes which receive the slidable anchor pin are arranged collinearly in the two legs of the supporting housing.

6. Device according to any one of the preceding claims wherein the end of the retaining spring which is in retaining engagement with the toothed wheel has a substantially V-shaped cross-section elongate ridge.

7. Device according to any one of the preceding claims wherein the retaining spring is a plate spring whose end portion acted upon by the centring spring includes a hole with an outline which corresponds generally to the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. centring spring 10 and the flange 8 of the sleeve 3 there is interposed one end of a retaining spring in the form of a spring plate 12, secured in position by the action of the spring force of the centring spring, the bentover other end 12' of the said spring 12 extending approximately parallel to the axis of the adjusting sleeve 4, being in retaining engagement with the toothed disc 7. The portion of this end of the plate which actually cooperates with the toothed disc 7 for retaining the latter against rotation has a substantially V-shaped cross-section, and has appreciable axial length such that within the expected range of displacement of the slidable anchor pin, it will at all times remain in engagement with the periphery of the disc. In order to ensure a satisfactory position of the spring plate 12 in the assembled state, that end of the spring plate 12 which is acted upon by the centring spring 10 has a hole 13 the diameter of which corresponds to the external diameter of the adjusting sleeve 4. The hole 13 is punched out in such a manner that there is formed a slight bent-out region 14 at the lower edge of the hole, extending out of the plane of the plate spring, this bent-out region forming a flat which avoids cutting into the adjusting nut 4 during operation. It also has further bent-over portions 15 which in the assembled position of the spring plate 12, by abutment on the supporting housing 1, prevent rotation of the spring plate 12 about the axis of the adjusting sleeve 4. The centring and adjusting device just described operates as follows: If adjustment by hand is desired, rotation of the adjusting sleeve is carried out by means of the toothed disc 7. The end 12' of the spring plate 12 which is in retaining engagement with the toothed disc 7 can yield briefly for such adjustment, but otherwise remains always in engagement with the teeth of the toothed disc 7 even if the slidable anchor pin is displaced, whether in forward travel or reverse travel. For example, if the adjusting sleeve 4 is displaced together with the adjusting screws 5,6 and the toothed disc 7 towards the right in Figure 1 the sleeve 3 carries the spring plate 12 along also, by means of its flange 8. The centring spring 10 which was compressed in this displacement then urges the slidable anchor pin back into the illustrated initial position. In the event of displacement of the slide lock towards the left in Figure 1, the sleeve 3 and the spring plate 12 remain in the illustrated position. The toothed disc 7 however can move towards the left together with the adjusting nut 4. In spite of this relative movement of the toothed disc 7 and the plate spring 12, retaining engagement is maintained between the elongate notch in the end portion 12' and the selected recess in the disc. WHAT WE CLAIM IS:

1. A centring and adjusting device for the shoes of a motor vehicle internal shoe brake wherein a slidable anchor pin is axially displaceable relative to a supporting housing and includes a rotatable element rotatable for screwthreadedly adjusting the axial length of the slidable anchor pin, a centring spring biasing the slidable anchor pin to an axially centralised position relative to the housing, a toothed wheel on the rotatable element and constrained to rotate together with it, and a retaining spring for retaining the toothed wheel against undesired rotation, the retaining spring including a portion held in position by the centring spring and a portion extending parallel to the axis of the slidable anchor pin and engaging with the toothed wheel.

external diameter of the rotatable element, around which that end portion is positioned with the element passing through the hole.

8. Device according to claim 7 wherein one region of the edge of the hole is formed by a bent-out portion which is for flat engagement with the outer surface of the rotatable element.

9. Device according to any one of the preceding claims wherein the end portion of the retaining spring engaged by the centring spring includes also abutment means for abutment against the supporting housing to prevent rotation of the retaining spring.

10. Centring and adjusting device for a motor vehicle internal shoe brake substantially as herein described with reference to and as illustrated in the accompanying drawings.

11. An internal shoe brake assembly for a motor vehicle incorporating a centring and adjusting device according to any one of the preceding claims.