Claims:CLAIMS
We claim:
1. A hydraulic drum brake (1000) for a motor vehicle comprising:
• a brake plate (102),
• an automatic brake adjuster body (110) attached to said hydraulic drum brake (1000),
• a pair of brake shoe (100 and 104),
• an adjuster bracket (128) and an adjuster wheel (106),
• an adjuster spring (122),
• a pawl arrangement (124) and
• a leaf spring (126)
• portion A, B and C
wherein said automatic brake adjuster body (110) is a hollow shaft or hollow tube having portions A, B with varying diameter cross section (ØY and ØX respectively).
2. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said automatic brake adjuster body (110) has a lower diameter section (ØX) in part B and a higher diameter section (ØY) in part A.
3. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said automatic brake adjuster body (110) has said lower diameter section (ØX) in part B towards said adjuster spring (122) side and said higher diameter section (ØY) in part A towards the head portion (114).
4. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said automatic brake adjuster body (110) is formed by tube swaging process.
5. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said leaf spring (126) is affixed on said automatic brake adjuster body (110) by at least one blind rivet (134).
6. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, a guide (130) is provided in said leaf spring (126) and slot (140) on said adjuster body automatic brake adjuster body (110) on said higher diameter section (ØY) side of said automatic brake adjuster body (110), to prevent anti-rotation of said leaf spring (126).
7. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said automatic brake adjustor (110) body is formed by tube swaging process to form different diameter cross sections (ØX and ØY).
8. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said automatic brake adjustor (110) body is machined with machined part (138) at said part B with lower diameter section (ØX) end so as to result in proper resting on said adjuster bracket (128).
9. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said head portion (114) of said automatic brake adjuster body (110) is trimmed for effective assembly with said brake shoe (104) to form trimmed part of adjuster head (144).
10. The hydraulic drum brake (1000) for a motor vehicle as claimed in claim 1 wherein, said automatic brake adjustor (110) body comprises a hole (142) formed by piercing to accommodate spring.

, Description:FIELD OF INVENTION
The present invention relates to a hydraulic drum brake with an automatic brake shoe adjuster body in motor vehicle. More specifically the present invention deals with auto adjuster mechanism for a hydraulic drum brake in three or four wheeled motor vehicle.

BACKGROUND OF INVENTION
A vehicle brake adjuster for a hydraulic drum brake in motor vehicles are being used for the periodic adjustments and thereby to ensure that in rest position the shoes of the brake are found at a predetermined and essentially constant distance from the facing drum wall. This action thereby facilitates the constant travel of the brake shoes, also following partial wear thereof over time. The simple mechanism it follows is the expansion of shoes for the engagement in the drum on application of vehicle brake.
When, due to wear, the brake shoes become thinner and their stroke against the walls of the drum tends to increase beyond a certain predetermined threshold, the adjuster automatically adjusts the rest position of the shoes, reaching a more extended rest position as a function of the achieved state of wear.
Some forms of adjuster are being actuated as a result of operation of the brakes by the fluid pressure means and others as a result of operation of the brakes by the mechanical means. There had been various developments in the field of automatic brake adjuster for drum brakes.
In the prior art 2445/CHE/2008, the drum brake adjuster is formed by metal forging process and the left side and right side has different mirror image structures. The drawback of this invention is that the shape formed has high dead weight, long machining cycle time and also assembling process becomes difficult due to separate right and left side adjuster body construction.
In another prior art 555/CHE/2009, the material for the adjuster is being changed so as to increase the braking efficiency. Even then the assembly process complexity remains same and the weight of the component doesn’t get reduced.
Hence, in light of the various limitations in the prior art there is a requirement of a brake adjuster for a motor vehicle which is inexpensive and easy to manufacture.
Thus the first objective of the present invention is to provide an automatic brake adjuster which is less expensive to produce.
Second objective of the present invention is to provide a brake auto adjuster which has variable diameter hollow tube or a hollow shaft.
The third objective of the invention is to produce brake auto adjuster body which is same for left side and right side and the adjuster body can just be mirrored for the placement in the left side to right side and vice versa.
The fourth objective of the invention is to produce brake auto adjuster with a high dimensional accuracy and less material wastage.
Fifth objection of the invention is to manufacture an automatic brake adjuster which can be easily manufactured.
Sixth or the final objective of the invention is to provide a guide for the leaf spring in the auto adjuster so as to prevent anti-rotation.
BRIEF DESCRIPTION OF THE INVENTION
In order to achieve the above objects, the present invention provides an automatic brake adjuster body which has a variable diameter cross section hollow tube, formed by swaging process. To cater the ease of manufacturability and assembly process, this invention is developed so that there is no requirement of separate left side and right side hollow tube production, and the adjuster tube formed can be assembled on either side depending on placement direction of leaf spring. A smaller diameter hollow tube is processed and made into larger diameter cross section with the help of swaging process so as to be able to accommodate the flattened end of the adjuster body. Similarly, a higher diameter hollow tube can also be taken and processed to a smaller diameter part and a higher diameter part.
The smaller diameter side of the hollow tube is being machined to generate flat face, for the proper adjuster bracket resting and the other flattened end is being trimmed so as to get smooth fitting and required shape for assembly on brake panel. The adjuster body where the leaf spring is attached has a leaf spring guide so as to prevent anti rotation.
Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.

BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects of the invention will become apparent by consideration of the accompanying drawings and their description stated below, which are merely illustrative of a preferred embodiment of the invention and do not limit in any way the nature and scope of the invention.
Figure 1 illustrates the internal view of the motor vehicle hydraulic drum brake including an automatic brake adjuster body in accordance with the present invention.
Figure 2a illustrates the perspective view of the automatic brake adjuster body as that available in the prior art.
Figure 2b illustrates the perspective view of the automatic brake adjuster body in accordance with the present invention.
Figure 3a illustrates the expanded view of the automatic brake adjuster body as that available in the prior art.
Figure 3b illustrates the expanded view of the automatic brake adjuster body in accordance with the present invention.
Figure 4 illustrates the automatic brake adjuster body in its assembled state in accordance with the present invention.
Figure 5a illustrates the brake adjuster body (110) which is to be used in the left side of wheel drum of the concerned vehicle.
Figure 5b illustrates the brake adjuster body (110) which is to be used in the right side of wheel drum of the concerned vehicle.
DETAILED DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
The Figure 1 shows the internal view of a hydraulic drum brake (1000), used in a motor vehicle, with brake plate (102) and having a pair of brake shoes (100, 104) which at the lower end reach against a fixed abutment (120) and at their upper ends are forced apart by a hydraulic wheel cylinder (108). The brake shoes (100, 102) are kept in contact with the fixed abutment (120) by a lower return spring (118) and in contact with the wheel cylinder (108) by an upper return spring (112). The automatic brake adjuster body (110) (110) is fitted inside the hydraulic drum brake (1000) has adjuster wheel (106) on one side and flattened head portion (114) at the other end.
Figure 2a depicts the perspective view of automatic brake adjuster body (110A) as available in the prior art in drum brake of a motor vehicle. The said automatic brake adjuster body (110A) of constant diameter cross section (ØY’) is the one formed by hot forging and machining work. One end of the automatic brake adjuster body (110A) is attached to the brake shoe (100) by the help of adjuster spring (122A) and at the other end to another brake shoe (104) by adjuster head portion (114A). The adjuster screw (132A) is fitted inside the automatic adjuster body (110A) and the adjuster wheel (106A) is engaged by a pawl (124A) to the leaf spring (126A). The adjuster bracket (128A) maintains the separation between the automatic brake adjuster body (110) body and the leaf spring (126A). Again the leaf spring is attached to the automatic brake adjuster body (110) body by rivets (136).
In the Figure 2b the perspective view of automatic brake adjuster body (110), which is of tube type and formed by swaging process, is depicted in accordance with the present invention. The automatic brake adjuster body (110) has three portions A, B and C wherein the portion A has diameter Y (ØY) which is higher as compared to part B which has lower diameter X (ØX). Part C is the transition phase between part A and B. The lower diameter side (ØX) of the adjuster body is machined with machined part (138) and is made so as to accommodate the adjuster screw (132). The diameter is then increased (ØY) so that the other end which is the head portion (114) can be flattened and thereby trimmed effectively. The adjuster screw (132) is fitted inside the automatic adjuster body (110A) on its lower diameter section (ØX) and the adjuster wheel (106) is engaged by a pawl (124) to the leaf spring (126). The adjuster bracket (128) maintains the separation between the automatic brake adjuster body (110) body and the leaf spring (126). Again the leaf spring is attached to the automatic brake adjuster body (110) body by at least one blind rivet (134). The leaf spring (126) is also provided with a guide (130) which fits in the slot (140) and helps prevent anti rotation of said leaf spring (126).
The Figure 3a and 3b depicts the expanded view of the automatic brake adjuster in accordance with the already existing prior art (110A) and as that of the present invention (110). The one in the Figure 3b is formed by tube swaging process and thereby has different diameter sections (ØX and ØY), whereas in the prior art 3a the component is formed by hot forging, and is of a constant diameter cross section (ØY’). Instead of two rivets (136) as that in the automatic adjuster body (110A) as in the prior art, the present automatic brake adjuster body (110) has one blind rivet (134) to attach the leaf spring (126) to the adjuster body.
The Figure 4 shows the assembled position of the automatic brake adjuster body (110) body in the hydraulic drum brake (1000). This clearly depicts that the head portion (114) of the automatic brake adjuster body (110) body is trimmed in a way so that it can well fit with the brake shoe (104) in the hydraulic drum brake (1000). The leaf spring (126) is riveted to the automatic brake adjuster body (110) body by a blind rivet (134) and also is provided with a guide (130) for anti-rotation which fits in a slot (140). The process of formation of the adjuster body (110) incorporates swaging a hollow tube or hollow shaft of uniform diameter and converting it to two different diameters (ØX and ØY). Thereafter for the head portion (114), the hollow shaft is flattened and then trimmed in the head portion to give the shape for proper fitting. Shaving is followed after trimming of the head portion (114) so that the irregular and the excess metal parts are trimmed off and trimmed end of adjuster head (144) is formed. Lastly, a suitable hole (142) or a slot is formed by piercing to provide guide for the spring.
The Figure 5a and 5b shows the brake adjuster body (110) which is to be used in the left side and the right side of the wheel drum of the concerned vehicle. Both the wheel drum sides have brake adjuster body (110) which are structurally same and are mirror image of each other.
The technical advancements offered by the present disclosure include:
• The present invention results in variable diameter brake auto adjuster which is produced effortlessly by swaging process and with less time for production.
• The auto adjuster body is formed in a way such that right side and left side can use the same hollow tube, thus resulting in ease of assembling.
• The manufacturing process used results in ease of mass scale production and also better dimensional accuracy.
• Anti-rotation of the leaf spring is prevented by the introduction of a guide for the leaf spring on the adjuster body.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

LIST OF REFERENCE NUMERAL

100, 104-Brake Shoe
102- Brake Plate
106, 106A- Adjuster Wheel
108- Wheel Cylinder
110, 110A - Automatic Brake Adjuster body
112, 118- Return Spring
114, 114A- Head Portion
116-Brake Lever
120- Fixed Abutment
122, 122A- Adjuster Spring
124, 124A- Pawl
126, 126A- Leaf Spring
128, 128A- Adjuster Bracket
130- Guide
132, 132A- Adjuster Screw
134- Blind Rivet
136- Rivet
138-Machined Part
140-Slot
142, 142A-Hole
144-Trimmed part of Adjuster Head
200, 200A- Expanded View of Automatic Brake Adjuster body
1000-HydraulicDrum Brake
ØX- Lower Diameter section
ØY- Higher Diameter section
ØY’-Constant Diameter Cross Section