TITLE

MONO-COMPONENT SHOE FOR USE IN A HEAVY COMMERCIAL VEHICLE BRAKE MANUFACTURING METHOD

FIELD OF THE INVENTION

This invention generally relates to a method for the manufacture of the brake mechanism and particularly relates to a method for the manufacture of brake shoes for a commercial vehicle application. More particularly this invention is for the manufacture of a mono-component shoe for use in a heavy commercial vehicle brake.

BACKGROUND OF THE INVENTION

A brake shoe is the part of a braking system which carries the brake lining in the S cam brakes used on commercial automobiles. It is a curved metal block that presses against and arrests the rotation of a wheel through brake drum. The brake shoe assembly is also vital to augment rib strength and to transmit force from S cam mechanism to hold the brake.

S cam actuated brake shoes have been produced commercially for many years and consists of two shoe webs, one shoe rim and a shoe lining. The shoe web and shoe rim are produced from sheet metal parts of different sheet thickness manufactured by stamping process using a press tool. The shoe lining is an arched non metallic molded part made out of asbestos or non asbestos material.

The heavy commercial vehicle brake shoe carries the metal rim and the two metal webs, the webs are welded onto the rim perpendicular to rim face, maintaining definite gap between webs. It also carries the asbestos brake lining, which is riveted to the metal shoe. When the brake is applied, the shoe moves and presses the lining against the inside of the rotating drum. The friction between lining and drum provides the braking effect.

During the conventional commercial vehicle brake shoe manufacturing process, the arch shaped web is crafted from a steel strip width slightly more than the width of the component and blanked out using press machine. The tonnage of press is determined based on the profile and thickness required for the shoe web, with the usual thickness of the shoe web being twice that of the shoe rim thickness. Around 50% of the input material goes as wastage or scrap.

During the conventional heavy commercial vehicle brake shoe manufacturing process, the rim is crafted from a steel strip formed from a coiled sheet material that is then blanked out using a press machine. The tonnage of press is determined based on the profile and thickness required for the shoe rim, with the usual thickness of the shoe rim being half that of the shoe web thickness. The blanking process involves hot rolled steel strip being fed into the progressive blanking die and being blanked out into the required shape by punching process. Around 15% of the input material goes as wastage or scrap.

To achieve proper flatness, the webs are being planished using a high tonnage hydraulic press machine whereas to achieve true radius the rims are radius formed using a high tonnage Knuckle joint mechanical press. The web & rim after their individual manufactures are joined together by metal inert gas (MIG) welding using a special purpose semi automatic machine. Through this process the shoe rim is joined to the two shoe webs. Further stages in the heavy commercial vehicle brake shoe manufacturing process, include shoe truing, broaching at the roller and fulcrum ends, induction flame hardening at the roller and fulcrum ends and painting. The lining is riveted on the outer profile of the shoe rim to form an S cam commercial vehicle brake shoe. Rim to webs are also joined by using cold riveting method in this case the rims will carry punched out slots to receive the projected metal in the webs throughout the periphery, the projected metal will get inserted in the rim slots, pressed intact initially and secured by cold riveting process.

The above mentioned conventional blanking operation and MIG welding operation method for the manufacture of brake shoe web and rim and for joining them as part of the final brake shoe assembly, is being widely used by the present auto ancillaries and spare parts industries which are engaged in the manufacture of heavy commercial vehicle brake shoe.

However the concerns voiced in this conventional method are many. Firstly the use of inert gas such as argon & carbon dioxide in the MIG welding operation are harmful to the environment. MIG welders are also often exposed to dangerous gases and particular matter. MIG welding further produces smoke containing particles of various types of oxides, and the size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger and operators are always working in hot zone and the metal shoe is very hot after welding and requires forced air cooling or waiting time is additionally needed. Additionally, carbon dioxide and ozone gases can prove dangerous if ventilation is inadequate. Furthermore, the use of compressed gases in MIG welding poses an explosion and risk at the workplace.

Further the conventional commercial vehicle brake shoe manufacturing operation results in a tremendous EB power constraint during power cut situation which is a disadvantage to the manufacturer. Again, the percentage of waste that is obtained while conventionally manufacturing the heavy commercial vehicle brake shoe is high as explained earlier.

Therefore is it the need of the hour in the industry to develop a heavy commercial vehicle brake shoe and manufacturing method that is able to overcome the above difficulties with much superior quality, is environmental friendly and reduces the scraps produced during the manufacturing process.

Some of the prior art in this field reveal diverse techniques deals with various kinds of manufacturing methods for brake shoe assemblies:

Indian Patent No. 197268 discloses a composition brake shoe for use on a railway freight vehicle for reconditioning a wheel tread surface of such railway freight vehicle during a normal braking application on such vehicle, said composition brake shoe comprising: (a) a brake surface having a predetermined configuration and a predetermined surface area; (b) a first friction type composition material having a predetermined shape and at least initially extending entirely over said predetermined surface area of said brake surface of said composition brake shoe; and (c) a second friction type composition material formed as a discrete insert, having a predetermined shape, and molded into said first friction type composition material, said second friction type composition material initially being completely embedded within said first friction type composition material, one surface of said discrete insert being disposed facing said surface area of said brake surface of said composition brake shoe, said one surface of said discrete insert being incrementally exposed as said first friction type composition material is eroded away due to frictional engagement with such wheel tread surface during normal braking operations, said second friction type composition material exhibiting greater abrasive properties than said first friction type composition material, said second friction type composition material consists essentially of a ceramic grinding material, said first friction type composition material extending entirely over said surface area of said brake surface of said composition brake shoe after said second friction type composition material formed as said discrete insert has been worn away due to frictional engagement with such wheel tread surface during normal braking operations.

Patent No. 198244 describes a brake shoe for an internal shoe drum has an arcuate platform carrying a lining of friction material on its outer face. A web extends perpendicularly from the inner face of the platform and provides a shoe tip intended to be supported on an angled surface of the brake abutment. This shoe tip has a pair of differently directed surface portions.

Patent No. 216768 claims a brake shoe assembly for a vehicle comprising: a brake lining having a predetermined thickness which gradually wears away and increases in temperature during a vehicle braking application; a housing positioned to wear away and increase in temperature concurrently with said brake lining; and a thermally sensitive switching element encapsulated in said housing for directing power from a power source to a remote indicator in response to the temperature of said housing exceeding a predetermined temperature threshold.

Patent No. 221669 describes an improved brake shoe assembly having a cylindrically curved brake shoe platform defining a portion of a cylinder, an inner supporting surface and an outer supporting surface and a brake friction material matrix disposed on the outer supporting surface of the brake shoe platform, the brake friction material matrix defining a friction surface, wherein the improvement is characterized by: a plurality of extensions projecting from said brake shoe platform outer supporting surface through said brake friction material to said friction surface, and wherein each of said plurality of extensions terminates above said friction surface.

Patent No. 221778 claims a brake shoe assembly for a drum brake, the brake shoe assembly being a single-piece construction and including a brake shoe of generally circular form having two separate and opposed ends, and defining a pair of friction lining mounting sections disposed on opposite sides of the brake shoe. The friction lining mounting sections have a T-shaped cross-sectional form defining an arcuate, radially outer platform for mounting a friction lining and a radially inwardly extending web. The brake shoe including hinge means between the lining mounting sections, facilitating pivoting movement of the lining mounting sections, to alter the separation between the brake ends between a brake operative condition in which in use, the friction lining engages a braking surface of a drum to which the brake shoe assembly is fitted, and a brake inoperative condition in which there is no such engagement. The brake shoe assembling further includes a backing plate depending from the brake shoe in the region of the hinge means for mounting the brake shoe to a brake shoe assembly support.

Patent No. 240978 claims a brake shoe assembly for a vehicle comprising: a brake lining having a predetermined thickness for gradually wearing away as the brake shoe assembly brakes the vehicle; and a sensor having a pair of spaced electrical conductors and an electrical resistance for indicating said thickness of said brake lining located across said pair of spaced conductors, said pair of spaced conductors being cohered to a substrate; said sensor positioned to wear away concurrently with said brake lining thereby continuously changing said electrical resistance to an infinite number of values across said pair of spaced conductors.

However none of the existing prior art discloses any manufacturing method of a mono component heavy commercial vehicle brake shoe. The present invention attains this objective and provides a method for manufacturing a mono component brake shoe for a heavy commercial vehicle brake assembly having a completely integrated rim and web in the brake shoe. The conventional blanking of rim, web and welding operation of the rim to web is done away with.

The present invention minimizes the wastage of sheet material since it is formed as a single component brake shoe, thereby removing the need for welding of various parts or any other connectors such as by fasteners or welds. The brake shoe according to the present invention is thus environmental friendly. As the assembly has a single piece construction, the sliding or vibrations of component parts relative to other component parts is greatly reduced. Moreover, the limited number of components of the brake shoe assembly provide for easier installation and maintenance. The lesser number of parts and the elimination of stages of operation in manufacturing make the present invention an ideal model for lean manufacturing method.

The blanking and drawing process of the single piece sheet in the present invention focuses on increasing the quality and life of the brake shoe and resultantly minimizing wear and tear due to the absence of multiple parts welded together. The manufacturing process of the present invention further ensures that maximum percentage of input raw material is converted into product output and the brake shoe assembly is produced in a single piece form. Hence the present invention provides a cost effective method of manufacturing a heavy commercial vehicle brake shoe where the percentage of waste is very minimal, welding operation is totally eliminated and throughput time is reduced drastically. The present invention provides a mono component heavy commercial vehicle brake shoe that does not require the separate joining of the rim onto the brake shoe and web, thus increasing the strength of the brake shoe.

Further it will be apparent to those skilled in the art that the objects of this invention have been achieved by providing a mono component shoe for use in a heavy commercial vehicle brake manufacturing method which is unique in nature unlike existing manufacturing methods for brake shoes. Various changes may be made in and without departing from the concept of the invention. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing and modifying other methods and structures for carrying out the same purpose of the present invention. Further, features of some stages disclosed in this application may be employed with features of other stages. Therefore, the scope of the invention is to be determined by the terminology of the following claims and the legal equivalents thereof.

OBJECTIVES OF THE INVENTION:

This invention may be summarized, at least in part, with reference to its objects.

The foremost object of the present invention is to present a novel manufacturing method for producing a single unit brake shoe assembly combining together the brake shoe rim and web as a single component.

Another object of the present invention is to provide a cost-effective manufacturing method for producing a single unit brake shoe assembly whereby the number of stages in the entire production process is reduced.

Another object of the present invention is to eliminate the joining by the welding operation in the brake shoe manufacturing process using high tension electrical power or cold riveting operation using special purpose equipment.

Another object of the present invention is to reduce the percentage of scrap from the direct input materials during rim and web manufacturing process.

Another object of the present invention is to increase the strength of the brake shoe due to the manufacturing of the brake shoe as a single unit.

Another object of the present invention is to lessen the wear and tear from the friction and heat generated during brake shoe usage by providing the brake shoe being as a single unit.

Another object of the present invention is to facilitate easy handling of the raw material.

Yet another object of the present invention is maximum utility of the raw material and save input.

A further object of the present invention is to increase the inventory turn ratio by reduce the through put time. Hence this process is thus making the present invention highly suitable as a lean manufacturing method to enable just- in-time manufacturing to the buyers.

Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.

SUMMARY OF THE INVENTION

The present invention embodies a mono component shoe for a heavy commercial vehicle brake manufacturing method that eliminates the various steps of separate web stamping operation, separate web planishing operation, separate rim stamping operation, separate rim radius forming operation, MIG welding of the web and rim and shoe truing operation to achieve shoe radius.

DESCRIPTION OF THE DRAWINGS

The advantages and features of the present invention will be more readily apparent by persons skilled in the art when considered in reference to the following description and when taken in conjunction with the accompanying drawings listed below Figure 1 is a comparative flow chart illustrating the manufacturing process of the present invention in comparison to the conventional manufacturing method.

Figure 2 is a perspective diagram of the present invention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of particular applications of the invention and their requirements. The present invention can be configured as follows:
The present invention manufacturing process was derived after the trial of various

manufacturing types to produce a mono component brake shoe. As the first step towards the manufacture of a mono component brake shoe, a double T forming operation, including inputting a blank metal sheet, U forming, reverse forming and T forming was performed. However the resultant brake shoe had openings that were found at the extreme ends of the brake shoe and wrinkles at the middle of the brake shoe. Therefore this double T forming operation was dropped. Subsequently a radial forming operation consisting of the steps of shearing, first draw, reverse draw, trimming and piercing, radial forming, crushing, and web cropping and piercing was performed. However this radial forming operation was dropped due to the complicated tool design and high tool development cost. Thirdly a rolling operation consisting of the steps of shearing, first draw, reverse draw, trimming and piercing, rolling, crushing, and web cropping and piercing was performed. However this rolling operation was dropped since the rolled component did not have a true radius, excess spring back was observed and heavy tonnage was required for the roll forming slide. Fourthly a radial draw operation was tried consisting of the steps of inputting a blank metal sheet,, first draw, reverse draw, crushing, and wire cutting and machining. This radial form operation was able to deliver the basic form of the present invention. There was no gap at the rear side, no wrinkles or material gathering and consistency in drawing.

In a preferred embodiment of the present invention, to produce the required form of brake shoe assembly, the development length based on radius of the web and rim is measured.

In a preferred embodiment of the present invention, as shown in Figure 1, the first step of producing a mono component brake shoe is shearing (1). The shearing process (1) produces the metal sheet of the requisite dimensions as is required for the drawing process.

In a preferred embodiment of the present invention, as shown in Figure 1, the second and third steps of producing a mono component brake shoe is the draw operation (2)(3). Using a customized heavy press tool, first two draw stages are carried out using conventional presses like mechanical or hydraulic presses. The said press contains top and bottom tool assemblies clamped to the machine bed. Individual sheets of steel are fed into the press by loading them in the locator provided in the die holder assembly.

During the first draw (2), when the operator initiates the press, the top assembly descends on the sheet and the basic shoe form (13) consisting of two webs (10) (11) and a rim (12) is formed using the descending force of the press. During the second draw (3), when the operator initiates the press, the top assembly descends on the basic shoe form (13) consisting of two webs (10) (11) and a rim (12) and the form is refined.

In a preferred embodiment of the present invention, as shown in Figure 1, the fourth step of producing a mono component brake shoe is crushing (4). A customized heavy press tool is used for crushing operation using a straight sided column press machine. The said press contains top and bottom tool assemblies clamped to the machine bed. The brake shoe form (13) is placed on the lower press such that the two crests between the three grooves on the brake shoe (13) are crush-formed into two webs (10) (11) during the descent of the crushing top tool on the lower press.

In a preferred embodiment of the present invention, as shown in Figure 1, the fifth step of producing a mono component brake shoe is notching (5). During the notching operation, the metal brake shoe (13) has an outside scrap edge removed (14) by the use of multiple shear blades that are set at right angles to each other.

In a preferred embodiment of the present invention, as shown in Figure 1, the further steps of producing a mono component brake shoe are trimming (6), rivet hole piercing (7), cropping and piercing (8) and spot welding (9). The two webs (10) (11) of the brake shoe (13) undergo an end cropping operation (6) at all the four corners trimmed (15). The trimmed part of the brake shoe (13) is fed into a mechanical press and cropped and punched with a press tool (8). The punched part is resistance welded at both ends of the shoe assembly (13) in a standard spot welding machine (9) for creating the final brake shoe assembly for heavy commercial vehicles consisting of a single sheet crafted into the two webs and rim. The slight channels (16) behind each web (10)(11), which is formed when the metal of each crest between two indents is folded inside during the draw and crushing process, provides ventilation to and cools the brake shoe (13), thus reducing the heat produced during braking operation.

Additionally, the brake shoe assembly (13) may require certain treatments for corrosion and wear resistance and for strengthening purposes, such as suitable heat treatments or surface hardening.

The wastage scrap out of the forming stage in the present invention is nil. The wastage scrap out of the end cropping, forming, crushing, gimp forming and trimming, piercing the holes in the innovative process and method is also minimal. This is in contrast to the substantial wastage skeleton scrap that is generated during the conventional process of producing separate brake shoe webs and rims and welding them together.

To sight an example the costs of producing a conventional commercial vehicle brake shoe consisting of separate and welded together webs and a rim is Rs. 166.30 per piece. The costs of producing a conventional commercial vehicle mono component brake shoe as per the present invention is Rs. 143.80 (Approx.) The cost reduction per brake shoe production as per the present manufacturing method is almost 14%. Each brake assembly requires two such shoes and each vehicle requires eight shoes.

Throughput time can be drastically reduced in mono component brake shoe manufacturing method as per the present invention. Further dependency on electric power for MIG welding can be eliminated. There is also no need for the separate procurement of materials and separate manufacturing process for brake shoe web and brake shoe rim. Thus there is no need of storage areas in company factory for brake shoe web and rim for conversion into the final brake shoe product. The present invention thus produces a mono component brake shoe with lesser number of parts that is cost effective and highly capable of withstanding wear and tear. Since the MIG welding stage is avoided, the present invention is environmentally friendly. The present invention is thus ideally suited for Lean Manufacturing Method.

While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.

It will be apparent to those skilled in the art that the objects of this invention have been achieved by providing the above invention. However various changes may be made in the structure of the invention without departing from the concept of the invention. Therefore, the scope of the invention is to be determined by the terminology of the following claims and the legal equivalents thereof.

CLAIMS:

What is claimed is:

1. A mono-component shoe, for use in a heavy commercial vehicle brake manufacturing method comprising of the stages of shearing (1), first draw (2), second draw (3), crushing (4), notching (5), trimming (6), rivet hole piercing (7), cropping and piercing (8) and spot welding (9), characterized in that said method uses a single metal sheet to produce a mono component brake shoe (13) with two webs (10) (11)and rim (12) without the separate MIG welding of said two webs (10)(11) onto said rim (12).

2. The manufacturing method as claimed in Claim 1 wherein a single metal sheet roll undergoes shearing operation (1) to produce said single metal sheet with preferable dimensions based on the size and shape to the intended design.

3. The manufacturing method as claimed in Claim 1 wherein said single metal sheet is fed into a press of a customized heavy weight hydraulic or mechanical press tool by loading them in a locator provided in a die holder assembly between a top tool assembly and a bottom tool assembly clamped to said press tool machine bed.

4. The manufacturing method as claimed in Claim 1 wherein during the first draw operation (2), when the operator initiates said press tool, said top tool assembly descends on said single metal sheet and a basic brake shoe form consisting of two webs (10)(11) and a rim (12) is formed using the descending force of said press and during the second draw (3), when the operator initiates said press tool, said top tool assembly descends on said basic brake shoe form and a refined brake shoe form (13) consisting of two web (10)(11) and a rim (12) is obtained.

5. The manufacturing method as claimed in Claim 1 wherein said refined brake shoe form (13) undergoes crushing operation (4) with a customized heavy weight hydraulic or mechanical press crushing tool with a top tool assembly and a bottom tool assembly clamped to said press crushing tool machine bed.

6. The manufacturing method as claimed in Claim 1 wherein said refined brake shoe form (13) is placed on aid bottom tool assembly such that two crests (webs) between the three grooves on said refined brake shoe form (13) are crush formed into two webs (10)(11) during the crushing descent of said top tool assembly on said lower tool assembly to form a brake shoe (13).

7. The manufacturing method as claimed in Claim 1 wherein said brake shoe (13) has slight channels (16) behind each said web (10)(11), which is formed when the metal of each crest between two indents is folded inside during the draw (2)(3) and crushing process (4).

8. The manufacturing method as claimed in Claim 1 wherein said brake shoe undergoes notching operation (5) and has an outside scrap edge (14) removed by the use of multiple shear blades that are set at right angles to each other, undergoes trimming operation (6) and said two webs (10)(11) are trimmed at the end of all the four corners (15), is fed into a mechanical press and cropped and punched (8) with a press tool and undergoes rivet hole piercing (7) and the punched part of said brake shoe (13) is resistance welded (9) at both ends of a brake shoe assy with a spot welding machine to create said mono component shoe (13).

9. The manufacturing method as claimed in Claim 1 wherein said mono component shoe (13) single unit cost of production is approximately 14% cheaper to the present method of manufacturing apart from input material saving.

10. The manufacturing method as claimed in Claim 1 wherein said method eliminates individual conventional manufacturing stages of web stamping, rim stamping, rim radius forming, joining of both web and rim using welding and shoe truing.