DEVICE FOR CARRYING FINISHING ON A BALL THREAD DRIVE

Description

FIELD

[0001] The present invention relates to field of manufacturing technology.DEFINITION

[0002] Shank portion - The expression "shank portion" used in the present disclosure refers to, but is not limited to, a stem or a shaft of an implement such as a ball screw or a nail or a pin.BACKGROUND

[0003] A ball screw is a mechanical linear actuator that converts rotational motion into linear motion with little friction. Conventionally, a ball screw includes a threaded shaft which provides a helical raceway for balls and functions as a precision screw. Ball screws are generally used in steering systems for automobiles and for motion transmission in machine tools.

[0004] During manufacturing, it is required that ball screws be machined with a super finishing operation after heat treatment. Conventional methods of performing a finishing operation on ball screws include manual / semi-automatic processes which are far from reliable because of the human intervention involved. An example of performing a finishing operation on ball screws includes polishing the ball screw manually using various abrasives, precision machining, grinding methods, and the like. While the conventional manual polishing has the limitation of less reliability and less accuracy, the precision machining or grinding methods are expensive and do not necessarily meet the surface finish requirements, especially Tp (Plateau Ratios) that is critical for maintaining a lubricating film on the surface.

[0005] There exists prior arts that teach conventional methods for finishing threads of a ball screw.

[0006] DE102011055661A1 teaches a device for producing outer ball screw on a workpiece. The device comprises a pair of grinding wheels arranged in such a way that the ball screw is formed in a single operation. However, DE102011055661A1 does not teach a feature that helps in finishing the threads of the ball screw.

[0007] WO2006008258 discloses a grinding wheel for producing external or internal ball threads on workpieces. The grinding wheel is equipped with a grinding element whose outer contour corresponds to a thread of the ball screw to be manufactured. Each element is provided with two stages, wherein one stage is used for pre-machining the workpiece and the other stage is used for finishing the workpiece. However, usage of the grinding wheel is time consuming and expensive as only a single thread can be manufactured and finished at a given instant of time.

[0008] JP2000198063A teaches a device for lapping thread groove of a nut. A threaded rod-shaped lap rod having a diameter smaller than a groove bottom diameter of a thread groove is inserted into the thread groove. A processing pressure applied between the nut and the lap rod allows lapping by rotating the lap rod. Then again, the device of JP2000198063A is used for lapping each ball screw thread individually, thereby increasing the cost and effort of manufacturing the ball screw.

[0009] JP2002103195 teaches a groove machining device which is configured to finish a groove. The device includes a tip face having a shape of a cross section of the groove. A lapping tape is supplied between the groove to be finished and the tip face. The lapping tape is pressed against the groove and the lapping process is performed. According to the teaching of JP2002103195, only one thread can be finished at one time, thereby making the process expensive.

[0010] US2586848 describes a belt sanding apparatus comprising a rotatably mounted disc for use in backing up or supporting sheet abrasives at the point where the workpiece being abraded contacts the abrasive coated side of the abrasive sheet during an abrading operation. US2586848 does not however teach finishing of ball screw threads.

[0011] US2015056893 teaches a method for polishing a ball screw by means of a polishing tape which is provided on a press roller. The press roller has to be moved over each thread, individually, to enable its finishing.

[0012] Accordingly, there exists a need to provide an assembly for performing a super finishing operation on ball screws which overcomes the abovementioned drawbacks.OBJECTS

[0013] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows: An object of the present invention is to provide an assembly comprising an apparatus for performing a super finishing operation on a ball screw surface with superior speed, reliability, and efficiency.

[0014] Another object of the present invention is to provide an assembly comprising an apparatus for performing a super finishing operation on a ball screw, which is simple and cost effective.

[0015] Other objects and advantages of the present invention will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.SUMMARY

[0016] The present invention envisages an assembly comprising an apparatus for performing a finishing operation on the threads of a ball screw. The invention is set out in the appended set of claims, wherein the apparatus comprises a holder for holding the ball screw. The apparatus further comprises a replaceable finishing tool having threads complementary to the threads of the ball screw, and a drive mechanism for rotating the holder to facilitate angular displacement of the ball screw relative to the threads of the replaceable finishing tool to perform a finishing operation on the threads of the screw.

[0017] As defined in appended claim 1, the assembly further includes an abrasive belt received within the finishing tool such that the abrasive belt forms an interface between the section of threads of the finishing tool and the threads of the ball screw, wherein the angular displacement of the ball screw within the finishing tool facilitates a finishing operation of the ball screw via the finishing tool and the abrasive belt. In an embodiment, the abrasive belt is a non-woven abrasive belt.

[0018] As defined in appended claims 3 and 4, the assembly further includes a housing configured to hold the finishing tool. In an embodiment, the finishing tool and the housing are separate components which are assembled together. In another embodiment, the housing and the finishing tool are manufactured as an integral component.BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

[0019] An assembly comprising an apparatus for performing a finishing operation on a ball screw of the present disclosure will now be described with the help of the accompanying drawing, in which: Fig. 1A illustrates a schematic view of the apparatus for performing a finishing operation on a ball screw, in accordance with an embodiment of the present disclosure; Fig. 1B illustrates isometric view of the assembly comprising the apparatus for performing a finishing operation on a ball screw, in accordance with an embodiment of the present disclosure; Fig. 2 illustrates an isometric view of a finishing tool used in the apparatus of Fig. 1A; and Fig. 3 illustrates a motion of a ball screw and its arrangement during a super finishing operation performed using the apparatus of Fig. 1A. LIST OF REFERENCE NUMERALS

[0020] 10 - Finishing tool 10A - Tooling portion 20 - Abrasive belt 30 - Housing 40 - Ball screw 40A - Threads 40B - Shank portion 42 - Holder 44 - Drive mechanism 100 - Ball screw superfinishing apparatus 1000 - Assembly comprising ball screw apparatus and abrasive belt. DETAILED DESCRIPTION

[0021] At the manufacturing stage of a ball screw, it is required that the ball screw be machined with a super finishing operation after the heat treatment. The conventional methods of performing a finishing operation on the ball screws include manual / semi-automatic processes which are far from reliable because of the human intervention involved. An example of performing a finishing operation on the ball screws includes polishing the ball screw manually using various abrasives, precision machining, grinding methods, and the like. While the conventional manual polishing has the limitation of less reliability and less accuracy, the precision machining or grinding methods are expensive and do not necessarily meet the surface finish requirements, especially Tp (Plateau Ratios) critical for maintaining a lubricating film on the surface.

[0022] To overcome the aforementioned drawbacks, the present disclosure envisages an assembly comprising an apparatus for performing a finishing operation on a ball screw which does not rely on human intervention by a human operator. Also, the assembly disclosed in the present disclosure does not involve the use of expensive components like precision machines or grinding machines.

[0023] The apparatus of the present disclosure is hereinafter described with reference to Fig. 1A through Fig. 3. Fig. 1B illustrates isometric view of an assembly comprising an apparatus 100 for performing a finishing operation on a ball screw 40, in accordance with an embodiment of the present disclosure. Fig. 2 illustrates an isometric view of a finishing tool 10 used in the apparatus 100. Fig. 3 illustrates a motion of the ball screw 40 and its arrangement during a super finishing operation performed using the assembly 1000.

[0024] The present invention envisages an assembly 1000 comprising an apparatus 100 for performing a finishing operation on threads 40A on a ball screw 40. The apparatus 100 comprises a holder 42 for holding the ball screw 40, a replaceable finishing tool 10 having a section of threads 10B complementary to the threads 40A of the ball screw 40, and a drive mechanism 44 for rotating the holder 42 to facilitate angular displacement of the ball screw 40 relative to the section of threads 10B of the replaceable finishing tool 10 to perform a finishing operation on the threads 40A of the ball screw 40.

[0025] According to the present invention, the assembly 1000 further comprises an abrasive belt 20 that is received within the finishing tool 10 such that the abrasive belt 20 forms an interface between the section of threads of the finishing tool 10 and the threads of the ball screw 40, wherein an angular displacement of the ball screw 40 within the finishing tool 10 facilitates the finishing / super-finishing operation of the ball screw 40 via the finishing tool 10 and the abrasive belt 20. In an embodiment, the abrasive belt 20 is a non-woven abrasive belt.

[0026] In an embodiment, the assembly 1000 further comprises a housing 30 wherein the finishing tool 10 supported within the housing 30. In an embodiment, the housing 30 and the finishing tool 10 are separate components which are assembled together by means of fasteners or rib-slot arrangements. In another embodiment, the housing 30 and the finishing tool 10 are manufactured as an integral component.

[0027] The finishing tool 10 has a tooling portion 10A defined by an inner periphery of a circular slot configured on the finishing tool 10. The tooling portion 10A is provided with the section of threads 10B complementary with the thread formations configured on the ball screw 40. The abrasive belt 20 is received within the tooling portion 10A such that the abrasive belt 20 forms the interface between the tooling portion 10A and the ball screw 40, wherein a rotation of the ball screw 40 within the tooling portion 10A facilitates the finishing / superfinishing operation of the ball screw 40 via the tooling portion 10A and the abrasive belt 20.

[0028] Referring to Fig. 1A through Fig. 3, there is shown the apparatus 100 which is described in more detail hereinafter. The apparatus 100 comprises the finishing tool 10 which is a screw based contact tool and the unwoven abrasive belt 20. The finishing tool 10 is configured within the housing 30. The housing 30 holds the finishing tool 10 firmly therein. In an embodiment, the housing 30 and the finishing tool 10 are manufactured as an integral unit.

[0029] The finishing tool 10 is a specially made screw type tool which helps follow the ball screw 40 profile. In an embodiment, the finishing tool 10 includes a section of inward threads 10B configured thereon that correspond to the threads and grooves of the ball screw 40 to be super-finished. Specifically, the section of inward threads 10B facilitate the holding of the ball screw 40 therein during the super finishing operation being performed on the ball screw 40.

[0030] In an operative configuration, the ball screw 40 is rotated by the holder 42 that is coupled with a drive mechanism 44. In an embodiment, the holder 42 is a head stock of a lathe machine which is given a rotary drive, as seen in Fig. 3. In another embodiment, the holder 42 is configured on a motor that is the drive mechanism 44. The rotation of the ball screw 40 causes engagement of the ball screw 40, the unwoven abrasive belt 20, and the finishing tool 10 by applying pressure on the apparatus 100. The engagement and rotation of the ball screw 40 with the tooling portion 10A gives a traversing motion to the finishing tool 10. The ball screw 40 is angularly displaced clockwise and counterclockwise alternately, in an operative configuration of the finishing tool 10 to give forward and reverse strokes to the finishing tool 10. TECHNICAL ADVANCEMENTS

[0031] The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an assembly comprising an apparatus for performing super finishing operation on a ball screw, which: operates with superior speed, reliability, and efficiency; and is simple and cost effective.

Claims

1. An assembly (1000) comprising: i. an apparatus (100) for performing finishing operation on the threads (40A) on a ball screw (40), said apparatus (100) comprising: - a holder (42) for holding said ball screw (40), and being characterized by - a replaceable finishing tool (10) having a tooling portion (10A) defining a section of threads (10B) complementary to said threads (40A) of said ball screw (40); and - a drive mechanism (44) for angularly displacing said holder (42) to facilitate the angular displacement of said ball screw (40) relative to said section of threads (10B) of said replaceable finishing tool (10) to perform a finishing operation on said threads (40A) of said ball screw (40); and ii. an abrasive belt (20) configured to be received within said finishing tool (10) such that, when said abrasive belt (20) is received within said finishing tool (10), it forms an interface between said section of threads (10B) of said finishing tool (10) and the threads (40A) of said ball screw (40), such that the angular displacement of said ball screw (40) relative to said section of threads (10B) of said finishing tool (10) facilitates a finishing operation of the threads (40A) of said ball screw (40) via said finishing tool (10) and said abrasive belt (20).

2. The assembly (1000) as claimed in claim 1, wherein said abrasive belt (20) is a non-woven abrasive belt.

3. The assembly (1000) as claimed in claim 1, which includes a housing (30) configured to hold said finishing tool (10).

4. The assembly (1000) as claimed in claim 3, wherein said finishing tool (10) and said housing (30) are separate components which are assembled together.

5. The assembly (1000) as claimed in claim 3, wherein said housing (30) and said finishing tool (10) are manufactured as an integral component.

6. The assembly (1000) as claimed in claim 1, wherein said drive mechanism (44) is configured to facilitate the alternate clockwise and counterclockwise angular displacement of the ball screw (40) within the tooling portion (10A), to give the finishing tool (10) a traversing reciprocal motion in forward and reverse strokes to perform the finishing operation on the threads (40A) of the ball screw (40).