GB2231630A

GB2231630A - Brake drum for motor vehicles

Info

Publication number: GB2231630A
Application number: GB9005063A
Authority: GB
Inventors: Bernd Rupprecht
Original assignee: Deutsche Perrot Bremse GmbH
Current assignee: Deutsche Perrot Bremse GmbH
Priority date: 1989-03-20
Filing date: 1990-03-07
Publication date: 1990-11-21
Also published as: GB9005063D0; FR2644535A1; IT1239360B; SE9000777L; SE9000777D0; IT9019611A0; NL9000591A; IT9019611A1; DE3909067A1

Description

t:3 I- e-;3 (D 1 Brake Drum for Motor Vehicles This invention relates to a

brake drum for motor vehicles, comprising a brake carrier mounted on an axle stub, an expanding-wedge device bolted to the brake carrier and a diaphragm cylinder co-acting with the expanding-wedge device, which cylinder has a guide tube for mounting the latter.

Brake drums of this type are described in German Patent Specifications DEOS 25 50 855, DE-PS 29 13 127 and DE-OS 31 31 423. In these known brake drums, the expanding-wedge device includes a housing neck, part of which forms a fitting collar. The end region of the housing neck remote from the expanding-wedge device is provided with an inner thread into which the guide tube of the diaphragm cylinder is screwed. However, this assembly of component groups - brake carrier, expandingwedge device, diaphragm cylinder -, which is known in the state of the art, causes considerable productionand finishing effort which has proved to be disadvantageous.

According to the wishes of customers, and based on location of the fitted brake in the vehicle, the individual brake carriers have holes provided on circular courses of different diameters, and different hole spacings and fitment sizes. Therefore, the wishes 2 of the customers have to be taken into consideration as early as during the manufacture of the cast brake carrier and during the finishing work, which is why brake carriers have to be manufactured in many varied forms.

Futhermore, the manufacturers of motor vehicles use diaphragm cylinders from different manufacturers which results in different dimensions of the threaded connections for screwing the diaphragm cylinder or its guide tube into the housing of the expanding-wedge device. Consequently, the cast housing of the expanding-wedge device has to be manufactured and finished in a plurality of housing shapes - either according to the embodiment of the brake carrier or according to the threaded connection for the diaphragm cylinder.

Apart from the given reasons, the plurality of housing embodiments is also dictated by the fitting position of the expanding-wedge-device housing on the brake carrier whilst taking into account the application angle cc, the angle formed by the diaphragm-cylinder axis and the brake axis, which is dependent on the available fitting space of the brake at the vehicle axle stub.

With respect'thereto, the following possibilities for influencing the application angle can be realised:

3 straight brake carrier with an expanding-wedge housing with angled housing neck, brake carrier angled in the accommodation area of the expanding-wedge housing with straight expanding-wedge housing, or both component groups at one application angle.

The application angle ocand the construction of the brake carrier with the expanding-wedge housing mounted thereon also determine the accommodation size of the brake in the fitted position in the vehicle. This size is measured from the abutment surface of.the brake carrier at the axle stub to the centre axis of the pressure members of the expanding- wedge device which engage the brake-shoe bridges.

In practice, a large accommodation measurement results on the one hand in increased space requirements of the brake, and on the other hand in increased tensioning within the brake in the event of high brake moments occurring.

To overcome this disadvantage, it is already known (DE-PS 30 01 476) to construct the brake carrier and the expanding-wedge housing as a one piece cast. However, this solution is still not fully satisfactory as the one piece cast is rather complicated which makes its production and finishing very difficult. Furthermore, the one piece cast embodiment cannot be 4 chosen of a cast quality which on the one hand permits inductive hardening at the brake-shoe-support angle (in simplex brakes), and on the other hand possesses such slide properties as required for the piston bores in the area of the expanding-wedge housing. Therefore, elaborate finishing work is required. Furthermore, the one piece embodiment makes future repair work complicated and elaborate as, for example, repair work at the expanding-wedge device requires removal of the entire brake, or damage to one part of it requires the exchange of the entire brake carrier including expand ng-wedge device. This has proved to be uneconomic.

It is an object of the invention to further develop the brake drum of the mentioned type so that the disadvantages in the prior art can be overcome namely by achieving a reduction in the assortment of different expandingwedge housing shapes, and by meeting all demands made on an individual brake type.

This object is achieved according to the invention in that the guide tube of the diaphragm cylinder is attached to the brake carrier by means of a screw connection, and the through-opening in the brake carrier is coaxial to the axis of the diaphragm cylinder.

By these constructive measures, assorted expanding-wedge housing shapes can be dispensed with so that every brake carrier can be fitted with a uniform housing shape during production or in the event of repair work.

According to the invention, the guide tube of the diaphragm cylinder can be directly or indirectly connected to the brake carrier.

Direct connection can advantageously be accomplished by the throughopening of the brake carrier having, in its end region opposite the expanding-wedge device, a threaded bore and the guide tube of the diaphragm cylinder being provided with a respective outside thread for threadedly engaging therewith.

Indirect connection can be accomplished by the guide tube of the diaphragm cylinder being fitted into a through-opening of a flange which is screwed to the brake carrier, the through-openings of the brake carrier and the flange being coaxial.

In the case of indirect mounting of the guide tube to the brake carrier in the aforesaid way that at least some of the screw bolts used to fix the flange should extend through respective through-openings of the brake carrier and be screwed into threaded bores of 6 expanding-wedge device.

Two particularly advantageous forms of embodiment of the invention are illustrated in the drawings and described more in detail below. They show, in Fig. 1: a front view of a simplex brake drum for motor vehicles, with the brake drum received; Fig. 2: a cross section along the line II-II in Fig.

1; Fig. 3: a cross section along the line III-III in Fig. 1; Fig. 4: an enlarged section, similar to Fig. 2, through a modified embodiment; and Fig. 5: A top view of the flange used in the embodiment according to Fig. 4.

The brake carrier 1 shown in Figs. 1 and 2 has a central insert opening 2 and a pattern of holes 4 arranged therearound on a circular course. These holes 4 serve for mounting the brake carrier 1 to a (not illustrated) axle stub.

Opposite to each other in the brake carrier 1 there are a first section 5, which serves to accommodate an expanding-wedge device 6 on the inside of the brake and a guide tube 7 of the diaphragm cylinder 8 on the outside, and a second section 9, which serves as an t 7 angular support 10 for brake shoes 11, 12. Furthermore, the brake carrier 1 has at its outer periphery devices 13,14 for holding and guiding the brake shoes 11, 12.

The first section 5 of the brake carrier 1 includes several throughopenings 15 which are congruent with threaded bores 16 of the expandingwedge device 6 by means of screwbolts 17, the brake carrier 1 is provided in its section 5 with a further through-opening 18 including a downward step or recess 19 into which engages a fitting collar 20 of the expandingwedge device 6 and centres same. Between a shoulder 21 of the step or recess 19 of the brake carrier 1 and the facing side 22 of the fitting collar 20 of the expanding-wedge device 6 is a sealing ring 23. in a section at the outside of the brake, the through-opening 18 of the brake carrier 1 is extended into the form of a threaded bore 24. Into this threaded bore 24 is screwed the guide tube 7 of the diaphragm cylinder 8.

In order to obtain the required application angle cr, the through-opening 18 as well as all the abovementioned components serving for mounting the diaphragm cylinder 8 and the expanding-wedge device 6 in a straight brake carrier-1 are tilted with respect to the brake axis. A further possibility for influencing the application angle m lies in an angled section 5 with respect to the plane of the brake carrier 1, or a 1 8 combination of the two variants. In each case the through-opening 18 in the brake carrier 1 is coaxial with the axis of the diaphragm cylinder 8.

Fig. 4 shows a further, very simple possibility for mounting the diaphragm cylinder 8 onto the section 5 at the outside of the brake carrier 1. The crosssectional view chosen in Fig. 4 does not show the possible fitting and centering of the expanding-wedge device 6 via the fitting collar 20 and the step or recess 19 in the brake carrier 1 as in Fig. 2.

Deviating from the aforedescribed embodiment, no threaded connection between the guide tube 7 of the diaphragm cylinder 8 and the brake carrier 1 is provided in the embodiment of Figs. 4 and 5. To achieve connection, a flange 25 is attached to the end of the guide tube 7. This flange 25 has a centrally orientated through-opening 26 which is.axially aligned with the through-opening 18 of the brake carrier 1 as well as with the opening in the fitting collar 20 of the expanding-wedge device. Further openings 27 of the flange 25 enable its mounting to the section 5 of the brake carrier 1. The brake carrier 1 has four throughopenings 15 as in the first embodiment, as well as two additional threaded bores 28. Two of the throughopenings 15'are arranged on a step 29 near the outer periphery of the brake carrier 1 and are shorter than Z 9 the outer other two through-openings 15.

In this case, the expandingwedge device 6 is mounted directly by means of two screwbolts 17 through the step 29, as well as by two further screwbolts 30, which simultaneously connect the flange 25 to the brake carrier 1. Two further screw-bolts 31 aid direct mounting of the flange 25 onto the brake carrier 1 by way of two threaded bores 28. In this respect, the screwbolts 30 and 31 extend through respective throughopenings 32, 33 of the flange 25.

The possibilities for influencing the application angle ocare the same as with the first embodiment.

It will be readily appreciated by a person skilled in the art that the basic idea of the invention can also be applied to a duplex brake drum, in which case, the section 9 can be arranged like the aforedescribed section 5 so as to accommodate a further expanding-wedge device.

Claims

CLAIMS:

1. A brake drum for motor vehicles, comprising a brake carrier mounted on an axle stub, an expandingwedge device bolted to the brake carrier, and a diaphragm cylinder co-acting with the expanding-wedge device, which cylinder has a guide tube for mounting the latter, characterised in that the guide tube of the diaphragm cylinder is mounted to the brake carrier, and the through-opening in the brake carrier is coaxial to the axis of the diaphragm cylinder.

2. A brake drum as claimed in claim 1, characterised in that the throughopening of the brake carrier has, in its end region opposite the expanding-wedge device, a threaded bore, and the guide tube of the diaphragm cylinder is provided with a respective outside thread for threadedly engaging therewith.

3. A brake drum as claimed in claim 1, characterised in that the guide tube of the diaphragm cylinder is fitted into a through-opening of a flange which is bolted to the brake carrier, the through-openings of the brake carrier and the flange being coaxial.

4. A brake drum as claimed in claim 3, characterised in that at least some of the bolts used to fix the flange extend through respective through-openings of the Z brake carrier and are screwed into threaded bores of the expanding-wedge device.

5. A brake drum as claimed in any preceding claim characterised in that the expanding-wedge device has a collar which fits into the main throughopening of the brake carrier.

6. A brake drum for motor vehicles substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3, or Figs. 4 and 5, of the accompanying drawings Flublished1990 at ThePatcra Office. State House. 66 71 High Holborn. Londor.WC1R4TP Furthercopies maybe obtained from The Patent Office. Salles Branch. St Mary Cray. Orpington, Kent BR5 3RD. Printed by Multiplex techmques ltd. St Mary Cray, Kent, Con. 1187