WO2023144645A1

WO2023144645A1 - Apparatus for performing superfinishing operation on threads of a ball screw

Info

Publication number: WO2023144645A1
Application number: PCT/IB2023/050302
Authority: WO
Inventors: Milind Kelkar; Venkatesh Kulkarni
Original assignee: Grind Master Machines Private Limited
Priority date: 2022-01-27
Filing date: 2023-01-13
Publication date: 2023-08-03
Also published as: DE112023000018T5; AU2023203285A1

Abstract

The present disclosure relates to the field of superfinishing technology. In particular, the present disclosure relates to an apparatus (100) for performing finishing operation on a ball screw (40). The apparatus (100) comprises a holder (42) for holding the ball screw (40), a replaceable finishing tool (10) defining 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 threads (10B) of the replaceable finishing tool (10) to perform a finishing operation on the threads (40A) of the ball screw (40).The apparatus disclosed in the present disclosure can be used for performing super-finishing operations on a ball screw or any other kind of a screw.

Description

APPARATUS FOR PERFORMING SUPERFINISHING OPERATION ON THREADS OF A BALL SCREW

THIS APPLICATION IS A PATENT OF ADDITION TO INDIAN PATENT APPLICATION NO. 201621020178 FILED ON JUNE 13^th , 2016.

FIELD

The present disclosure relates to field of superfinishing technology. Particularly to a field of super finishing operation on threads of a ball screw.

DEFINITION

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

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.

During manufacturing, it is required that ball screws be machined with super finishing operations after heat treatment. Conventional methods of performing finishing operations 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 (bearing ratio) that is critical for maintaining a lubricating film on the surface.

Accordingly, there exists a need to provide an apparatus for performing super finishing operations on threads of a ball screws which overcomes the abovementioned drawbacks. OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

An object of the present disclosure is to provide an apparatus for performing super finishing operation on threads of a ball screw surface with superior speed, reliability, and efficiency.

Another object of the present disclosure is to provide an apparatus for performing super finishing operation on threads of a ball screw, which is simple and cost effective.

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

SUMMARY

The present disclosure envisages an apparatus for performing super finishing operation on threads of a ball screw. The ball screw having helical raceway for a plurality of balls. The apparatus comprises a holder for holding the ball screw, 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.

The apparatus further includes a slit film backed abrasives received within the finishing tool. The slit film backed abrasives forms an interface between the finishing tool and the ball screw. The angular displacement of the ball screw within the finishing tool facilitates finishing operation of the ball screw via the finishing tool and the slit film backed abrasives. Further hight (B) of individual slits of the slit film backed abrasives is dependent on the ball screw circumference at its pitch diameter and width (A) of the individual slits is dependent on the circumference of the ball.

In an embodiment hight, (B) of individual slits is selected from the group ranging from one third to one half of the ball screw circumference at its pitch diameter.

In another embodiment, width (A) of the individual slits is selected from the group ranging from one third to one half of the circumference of the ball. In yet another embodiment, the apparatus further includes a housing configured to hold the finishing tool.

In yet another embodiment, the finishing tool and the housing are separate components which are assembled together.

In yet another embodiment, the housing and the finishing tool are manufactured as an integral component.

In yet another embodiment, film backed abrasive is slit into multiple parts according to the dimensions of threads of the ball screw.

In yet another embodiment, the ball screw is rotated clockwise and counter clockwise alternately to provide forward and reverse strokes to the tool.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

An apparatus for performing super finishing operation on threads of 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 super finishing operation on threads of a ball screw, in accordance with an embodiment of the present disclosure;

Fig. IB illustrates isometric view of the apparatus for performing super finishing operation on threads of 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. 1 A;

Fig. 3 illustrates a motion of a ball screw and its arrangement during a super finishing operation performed using the apparatus of figure 1 ; and

Fig. 4 illustrates slit film backed abrasives in accordance with an embodiment of the present disclosure.

LIST OF REFERENCE NUMERALS

100 - Apparatus for performing super finishing operation on threads of a ball screw 10 - Finishing tool

10A - Tooling portion

10B- Threaded portion on the tool

20 - Slit film backed abrasives

30 - Housing

40 - Ball screw

40A - Threads

40B - Shank portion

42 - Holder

44 - Drive mechanism

202 - Specific Gap between two slits

A- width of the individual film backed abrasives of slit film abrasives

B- Height of the cut portion of the slit film abrasives

DETAILED DESCRIPTION

Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.

Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises”, “comprising”, “including” and “having” are open-ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof.

When an element is referred to as being “mounted on”, “engaged to”, “connected to” or “coupled to” another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.

The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

Terms such as “bottom”, “inner”, “outer”, “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.

The present description envisages an apparatus 100 for performing super finishing operation on threads of a ball screw (also referred to as ball screw super finishing apparatus 100).

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 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 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 (bearing ratio) critical for maintaining lubricating film on the surface. To overcome the aforementioned drawbacks, the present disclosure envisages an apparatus for performing super finishing operation on a ball screw which does not rely on human intervention by human operator. Also, the apparatus disclosed in the present disclosure does not involve the use of expensive components like precision machines or grinding machines.

The apparatus 100 of the present disclosure is hereinafter described with reference to Fig. 1A through Fig. 3. Fig. IB illustrates an isometric view of the apparatus 100 for performing super finishing operation on threads of 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 apparatus.

The present disclosure envisages an apparatus 100 for performing super finishing operation on threads 40A of a ball screw 40. The ball screw (40) having helical raceway for a plurality of balls (not shown in figure). 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 threads 10B of the replaceable finishing tool 10 to perform a super finishing operation on the threads 40A of the ball screw 40.

In an embodiment, the apparatus further comprises a slit film backed abrasives 20 that is received within the finishing tool 10 such that the slit film backed abrasives 20 forms an interface between the finishing tool 10 and the ball screw 40. Angular displacement of the ball screw 40 within the finishing tool 10 facilitates the finishing/superfinishing operation of the ball screw 40 via the finishing tool 10 and the slit film backed abrasives 20.

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

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 formations 10B complementary with the threads 40A configured on the ball screw 40. The slit film backed abrasives 20 is received within the tooling portion 10A such that the slit film backed abrasives 20 forms the interface between the tooling portion 10A and the ball screw 40. Angular rotation of the ball screw 40 within the tooling portion 10A facilitates the finishing/super-finishing operation of the ball screw 40 via the tooling portion 10A and the slit film backed abrasives 20.

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 screwbased contact tool and the slit film backed abrasives 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.

The finishing tool 10 is a specially made in the form of screw type tool which helps follow the ball screw 40 profile. In a preferred 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 super finishing operation.

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 tool 10 is displaced such that the tool engages the ball screw, and the ball screw is rotated on its longitudinal axis. The finishing operation is carried out by engagement of the ball screw 40, the slit film backed abrasives 20, and the finishing tool 10 by applying pressure on the tool 10. The engagement and rotation of the ball screw 40 with the tooling portion 10A gives a traversing motion to the tool 10. The ball screw 40 is rotated clockwise and counter clockwise alternately to give forward and reverse strokes to the tool 10.

The slit film backed abrasives 20 is flexible and can reach into to the intricate parts of the ball screw groove. Further, hight (B) of individual slits of the slit film backed abrasives is dependent on the ball screw circumference at its pitch diameter and width (A) of the individual slits is dependent on the ball circumference.

In an embodiment hight (B) of individual slits is selected from the group ranging from one third to one half of the ball screw circumference at its pitch diameter and width (A) of the individual slits is selected from the group ranging from one third to one half of the circumference of the ball.

In an embodiment a specific gap (height wise) (202) between two slits is provided to maintain the strength of the slit film backed abrasives 20.

TECHNICAL ADVANCEMENTS

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of as apparatus comprising an apparatus for performing super finishing operation on a ball screw, which:

• provides flexibility in superfinishing the intricate parts of the ball screw

• operates with superior speed, reliability, and efficiency; and

• is simple and cost effective.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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.

Claims

CLAIMS:

1. An apparatus (100) for performing super finishing operation on threads (40 A) of a ball screw (40), the ball screw having helical raceway for a plurality of balls, said apparatus (100) comprising:

- a holder (42) for holding said ball screw (40);

- a replaceable finishing tool (10) having a section of threads (10B) complementary to said threads (40 A) of said ball screw (40);

- a drive mechanism (44) for rotating said holder (42) to facilitate 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 (40 A) of said screw (40); and

- a slit film backed abrasives (20) configured to be received within said finishing tool (10) such that the slit film backed abrasives (20) forms an interface between said finishing tool (10) and said ball screw (40), angular displacement of said ball screw (40) within said finishing tool (10) facilitates finishing operation of said ball screw (40) via said finishing tool (10), wherein hight (B) of individual slits of the slit film backed abrasives is dependent on the ball screw circumference at its pitch diameter and width (A) of the individual slits is dependent on the circumference of the ball.

2. The apparatus (100) as claimed in claim 1, wherein hight (B) of individual slits is selected from the group ranging from one third to one half of the ball screw circumference at its pitch diameter.

3. The apparatus (100) as claimed in claim 1, wherein width (A) of the individual slits is selected from the group ranging from one third to one half of the circumference of the ball.

4. The apparatus (100) as claimed in claim 1, which includes a housing (30) configured to hold said finishing tool (10). The apparatus (100) as claimed in claim 2, wherein said finishing tool (10) and said housing (30) are separate components which are assembled together. The apparatus (100) as claimed in claim 1, wherein said film backed abrasive (20) is slit into multiple parts according to the dimensions of said threads (40A) of said ball screw (40). The apparatus (100) as claimed in claim 1, includes a drive mechanism (44) to facilitate the rotation of said ball screw (40) with the tooling portion (10A) giving a traversing motion to the tool (10), wherein the ball screw (40) is rotated clockwise and counter clockwise alternately to provide forward and reverse strokes to the tool