Disc brake piston retraction tool with backing plate expansion structure

A disc brake piston retraction tool is provided. When the tool is applied to a large-scale disc brake, it is necessary to increase the width in the left-to-right direction of the working surface of a pressure plate of the tool. A plate expansion unit is coupled to the outer surface of the pressure plate. When a locking unit is inserted in a coupling hole of the pressure plate, a steel ball is retracted. After the steel ball passes through the coupling hole, a compression spring rebounds to produce a positioning effect. The backing plate can be easily and quickly mounted to the outer surface of the pressure plate to increase the width of the working surface of the pressure plate. The locking device allows the steel ball to be retracted to exit the coupling hole.

FIELD OF THE INVENTION

The invention relates to a disc brake piston retraction tool with a backing plate expansion structure, which can increase the width in the left-to-right direction of the working surface of a pressure plate of the tool. The tool can be applied to a single-cylinder or dual-cylinder piston brake.

BACKGROUND OF THE INVENTION

In general, auto mechanics responsible for repairing disc brakes and replacing brake pads may use various press machine tools. For these press machine tools, one difficulty is the need for professional mechanical use capabilities to achieve the retraction of one or more pistons associated with the caliper housing. Therefore, for brake repair and brake pad replacement, there is a need to operate an easy-to-use tool for retraction of one or more pistons.

There is a conventional art about a disc brake piston retractor tool. The tool is placed in the inner space of the caliper housing. Through the reciprocating operation of the reversible ratchet wrench, the first pressure plate and the second pressure plate are unidirectionally driven to gradually move outwardly toward the extended position. The first pressure plate abuts against the fixed wall of the caliper housing as a support, and the second pressure plate is used to push the protruding piston back to the initial position in the cylinder associated with the caliper housing. In the aforementioned conventional art, the spacer bar of the reversible ratchet wrench assembly is simply pulled back and forth to push the piston back into the cylinder. However, the above-mentioned conventional tool is applied to a single-cylinder piston caliper housing. Due to the matching of the operating space or the restrictive conditions of the piston position of the housing, if it is applied to a large double-cylinder piston caliper housing, it is difficult for the pistons to be retracted synchronously because of the insufficient width of the left and right working surfaces of the first and second pressure plates. Using tools of different specifications may solve this problem. But, this increases the cost to purchase tools.

SUMMARY OF THE INVENTION

The primary object of the invention is to provide a disc brake piston retraction tool with a backing plate expansion structure, comprising a reversible ratchet wrench that can be pulled and operated back and forth for a force output end of the reversible ratchet wrench to be selectively switched so as to drive a pair of pressure plates to expand away from each other or retract toward each other. The pressure plates each have at least two coupling holes. A plate expansion unit is coupled to an outer surface of each of the pressure plates via the coupling holes. The plate expansion unit includes a backing plate. The backing plate has a width in a left-to-right direction greater than that of the corresponding pressure plate. The backing plate has at least two fixing holes corresponding to the coupling holes. A locking device is fixedly connected to each of the two fixing holes. The locking device includes a plug, a compression spring, a steel ball, and a sleeve.

Preferably, the plug includes a plug body. One end of the plug body has a fixing post that is coupled and fixed to a corresponding one of the fixing holes. A surface of the plug body is radially formed with a receiving hole.

Preferably, the compression spring is installed in the receiving hole.

Preferably, the steel ball is in contact with one end of the compression spring and installed in the receiving hole. The steel ball is biased by the compression spring.

Preferably, the sleeve is tightly fitted and fixed on the surface the plug body. The sleeve has a restricting hole that is slightly smaller in diameter than the receiving hole so that part of the steel ball extends out of the restricting hole.

When the tool is applied to a large-scale disc brake, it is necessary to increase the width in the left-to-right direction of the working surface of the pressure plate. The plate expansion unit is coupled to the outer surface of each of the pressure plates. When the locking unit is inserted in the coupling hole, the steel ball is retracted. After the steel ball passes through the coupling hole, the compression spring rebounds to produce a positioning effect. The backing plate can be easily and quickly mounted to the outer surface of the pressure plate to increase the width in the left-to-right direction of the working surface of the pressure plate. The locking device allows the steel ball to be retracted to exit the coupling hole, so that the plate expansion unit can be easily removed from the outer surface of the corresponding pressure plate. The original working mode of the pair of pressure plates can be recovered quickly. The tool provided by the invention can be applied to a single-cylinder or dual-cylinder piston brake.

Preferably, the backing plate has a working surface. One end of the fixing hole, facing the working surface, is formed with a flared conical hole portion. The plug is made of a low-hardness metal material. A nail hole is formed in a center of an end face of the fixing post. The fixing post is placed in the fixing hole. A high-hardness nail is struck into the nail hole by pressing. The end face of the fixing post is enlarged and deformed in the conical hole portion, so that the plug is fixedly connected to the fixing hole. Besides, the nail is flush with the working surface of the backing plate.

Preferably, the receiving hole of the plug is a circular hole passing through the plug body. The sleeve is fitted on the surface of the plug body to restrict the compression spring from exiting the receiving hole. The compression spring is stopped in the receiving hole by the sleeve, so that the steel ball is pushed by the compression spring to protrude from the restricting hole.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS.1to7, a disc brake piston retraction tool10of the invention is shown and comprises a reversible ratchet wrench11that can be pulled and operated back and forth. Through a switching member12, a force output end13of the reversible ratchet wrench11is selectively switched to drive a pair of pressure plates14to expand away from each other or retract toward each other. The pressure plates14of the tool10each have at least two coupling holes140. A plate expansion unit20is coupled to the outer surface of each of the pressure plates14via the coupling holes140. The plate expansion unit20includes a backing plate21. The backing plate21has a width in a left-to-right direction greater than that of the corresponding pressure plate14. The backing plate21has at least two fixing holes22corresponding to the coupling holes140. A locking device30is fixedly connected to each of the two fixing holes22. The locking device30includes a plug31, a compression spring32, a steel ball33, and a sleeve34.

The plug31includes a cylindrical plug body310. One end of the plug body310has a cylindrical fixing post311that is coupled and fixed to the corresponding fixing hole22. The surface of the plug body310is radially formed with a receiving hole312.

The compression spring32is installed in the receiving hole312.

The steel ball33is in contact with one end of the compression spring32and installed in the receiving hole312. The steel ball33is biased by the compression spring32.

The sleeve34is a cap-shaped sleeve, which is tightly fitted and fixed on the surface of the plug body310. The sleeve34has a circular restricting hole340that is slightly smaller in diameter than the receiving hole312, so that part of the steel ball33extends out of the restricting hole340.

When the tool10is applied to a large-scale disc brake (such as a double-cylinder piston brake), it is necessary to increase the width in the left-to-right direction of the working surface of the pressure plate14. As shown inFIG.5, FIG.6andFIG.7specifically, the plate expansion unit20is coupled to the outer surface of each of the pressure plates14. When the locking unit30is inserted in the coupling hole140, the steel ball33is retracted (referring to the compression of the compression spring32). After the steel ball33passes through the coupling hole140, the compression spring32rebounds to produce a positioning effect. The backing plate21can be easily and quickly mounted to the outer surface of the pressure plate14to increase the width in the left-to-right direction of the working surface of the pressure plate14. The locking device30allows the steel ball33to be retracted (the compression of the compression spring32) to exit the coupling hole140(equivalent to the reverse action inFIG.5), so that the plate expansion unit20can be easily removed from the outer surface of the corresponding pressure plate14. As shown inFIG.1specifically, the original working mode of the pair of pressure plates14can be recovered quickly. The tool provided by the invention can be applied to a single-cylinder or dual-cylinder piston brake.

According to the above embodiment, as shown inFIG.2,FIG.3andFIG.4specifically, the backing plate21has a working surface210. One end of the fixing hole22, facing the working surface210, is formed with a flared conical hole portion220. The plug31is made of a low-hardness metal material (such as aluminum, iron). A nail hole313is formed in the center of the end face of the fixing post311. The fixing post311is placed in the fixing hole22, and a high-hardness nail40(such as a steel nail) is struck into the nail hole313by pressing (using a hydraulic press machine). The end face of the fixing post311is enlarged and deformed in the conical hole portion220, so that the plug31is fixedly connected to the fixing hole22. Besides, the nail40is flush with the working surface of the backing plate21.

According to the above embodiment, as shown inFIG.2andFIG.4specifically, the receiving hole312of the plug31is a circular hole passing through the plug body310. The sleeve34is fitted on the surface of the plug body310to restrict the compression spring32from exiting the receiving hole312. The compression spring32is stopped in the receiving hole312by the sleeve34, so that the steel ball33is pushed by the compression spring32to protrude from the restricting hole340.