Ball screw with a circulating assembly

A ball screw with a circulating assembly is disclosed. The circulating assembly of the ball screw is divided into a first circulating block and a second circulating block and can be assembled on the ball screw in such a method that the first and the second circulating blocks are assembled separately, so that the circulating assembly is applicable to the screw shaft whose helical groove doesn't extend to the shoulder portion thereof. In addition, the circulating assembly is limited in terms of an angle, and the relation between the first circulating block and the second circulating block is especially limited, so that the ball screw is applicable to the nuts with smaller outer diameter. Hence, the ball screw can be applied to both the nuts with smaller diameter and the screw shafts whose helical groove doesn't extend to the shoulder portion thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ball screw, and more particularly to a ball screw with a circulating assembly.

2. Description of the Prior Art

Referring toFIG. 1showing a first conventional ball screw with a circulating element, the circulating element11is axially installed into an end surface of the nut12and includes a nail portion111. The nail portion111protrudes from the circulating element11and into the outer helical groove131of the screw shaft13for connecting the outer helical groove131of the screw shaft13to the circulating element11. The circulating element11can guide the balls14into the circulating hole (not shown) in the nut12to allow the balls14between the screw shaft13and the nut12to circulate endlessly and eliminate the impact caused by the circulation of the balls14. However, since the outer helical groove131of the screw shaft13and the nail portion111of the circulating element11are fitted in a concave-convex manner, so that one end of the outer helical groove131of the screw shaft13must be open. In other words, the outer helical groove131of the screw shaft13must extend to the shoulder portion of the screw shaft13, thus reducing the service life of the ball screw.

Referring toFIG. 2showing a second conventional ball screw with circulating assembly, the circulating assembly is of the sectional type, namely it consists of an inner circulating block16and an outer circulating block17so that it can be applied to the screw shaft18whose helical groove doesn't extend to the shoulder portion thereof. However, since the top surface171and the bottom surface172of the outer circulating block17are both planar and parallel to each other without any angle therebetween, such a structure must cooperate with a nut19with a larger outer diameter and is thus not applicable to the nuts of special specifications, especially the nuts by European industrial standards, such as the nuts by Deutsche industry norm.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a ball screw with a circulating assembly which can be applied to both the nuts with smaller outer diameter and the screw shaft whose helical groove doesn't extend to the shoulder portion thereof.

Hence, to achieve the above objective, a ball screw with a circulating assembly in accordance with the present invention comprises a screw shaft, a nut and a circulating assembly. The screw shaft includes an axis and an outer helical groove in an outer surface thereof around the axis of the screw shaft. The nut is mounted on the screw shaft along the axis of the screw shaft and includes an inner helical groove in an inner surface thereof around the axis of the screw shaft. The inner helical groove cooperates with the outer helical groove to define a loaded path for receiving a plurality of balls. The nut further includes a circulating hole in communication with the inner helical groove, and a recess which is formed in an end surface thereof along the axis of the screw shaft. The recess includes a bottom surface and a side surface which the circulating hole penetrates.

The circulating assembly is disposed in the recess of the nut along the axis of the screw shaft and divided into a first circulating block and a second circulating block along the axis of the screw shaft. The first circulating block includes a top surface, and a first dividing surface opposite the top surface. The second circulating block includes a second dividing surface which is planar and abuts against the first dividing surface, and a bottom surface which is planar and abuts against the bottom surface of the recess. Between the bottom surface of the second circulating block and the second dividing surface of the second circulating block is defined, an angle. A maximum distance between the first dividing surface and the top surface of the first circulating block is denoted as HC1 while a maximum distance between the second dividing surface and the bottom surface of the second circulating block is denoted as HC2, and they satisfying the relation: HC2>HC1.

By such arrangements, since the circulating assembly of the present invention is divided into the first circulating block and the second circulating block, it can be assembled on the ball screw in such a method that the first circulating block which has a nail portion which is prone to causing interference is placed between the screw shaft and the nut first, and then the second circulating block is assembled on the nut in the axial direction of the nut. Hence, the ball screw of the present invention can be applied to the screw shaft whose outer helical groove shaft doesn't extend to the shoulder portion thereof.

Furthermore, the present invention is further limited in the circulating assembly having an angular design, and the HC1 and HC2 are further limited to satisfying the relation: HC2>HC1, hence, the present invention can be applied to the nuts with smaller outer diameter, satisfying the requirements of the new or old forms of nuts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS. 3-7, a ball screw with a circulating assembly in accordance with a preferred embodiment of the present invention is illustrated and comprises: a screw shaft20, a nut30, and a circulating assembly.

The screw shaft20includes an axis21and an outer helical groove22in an outer surface thereof around the axis21. Both ends of the outer helical groove22can be closed (which means that the helical groove22of the screw shaft20doesn't extend to the shoulder portion of the screw shaft20) or open (which means that the helical groove22of the screw shaft20extends to the shoulder portion of the screw shaft20). In the present embodiment, both ends of the helical groove22are closed.

The nut30is mounted on the screw shaft20along the axis21and includes an inner helical groove31in an inner surface thereof around the axis21. The inner helical groove31cooperates with the outer helical groove22to define a loaded path for receiving a plurality of halls91. The nut30further includes a circulating hole32in communication with the inner helical groove31, and a recess33formed in an end surface thereof along the axis21and located correspondingly to the outer helical groove22and the circulating hole32. The recess33includes a bottom surface331opposite the outer helical groove22and a side surface332which the circulating hole32penetrates.

The circulating assembly is disposed in the recess33of the nut30along the axis21and divided into a first circulating block40and a second circulating block50along the axis21, in other words, the circulating assembly is divided into the first circulating block40and the second circulating block50from an abutting surface thereof (a surface of the circulating assembly which abuts against the side surface332of the recess33) to an end surface thereof (a surface of the circulating assembly opposite to the abutting surface).

The first circulating block40includes a top surface41, and a first dividing surface42opposite the top surface41. The second circulating block50includes a second dividing surface51which is planar and abuts against the first dividing surface42, and a bottom surface52which is planar and abuts against the bottom surface331of the recess13. Between the bottom surface and the second dividing surface51is defined an angle A ranging from 18 to 25 degrees. The maximum distance between the first dividing surface42and the top surface41is denoted as HC1 while the maximum distance between the second dividing surface51and the bottom surface52is denoted as HC2, and they satisfy the relation: HC2>HC1.

In addition, the bottom surface52of the second circulating block50abuts against the bottom surface331of the recess33, and between the second dividing surface51and the bottom surface52is formed a second abutting surface53abutting against the side surface332of the recess33. Between the first dividing surface42and the top surface41of the first circulating block40is formed a first abutting surface43which is located on the same plane as the second abutting surface53. The first abutting surface43cooperates with the second abutting surface53to define the abutting surface of the circulating assembly. The first circulating block40includes a first end surface44opposite the first abutting surface43while the second circulating block50includes a second end surface54which is opposite the second abutting surface53and located on the same plane as the first end surface44. The first end surface44cooperates with the second end surface54to define the end surface of the circulating assembly.

Furthermore, the first circulating block40is formed with a positioning portion45protruding from the first dividing surface42, and the second circulating block50is farmed with a positioning concave55recessed in the second dividing surface51toward the bottom surface52for engagement with the positioning portion45. The positioning portion45and the positioning concave55can be configured as desired, and in the present embodiment, the positioning portion45and the positioning concave55are, for example, a dovetail block and a dovetail groove.

Moreover, the first circulating block40further includes a first curved surface48connected between the top surface41and the first dividing surface42, a first circulating channel46recessed into the first dividing surface42toward the top surface41, and a nail portion47disposed in the helical groove22of the screw shaft20and located on the first curved surface48. The second circulating block50further includes a second curved surface599with the same curvature as the first curved surface, a second circulating channel56recessed in the second dividing surface51toward the bottom surface52. The first circulating channel46cooperates with the second circulating channel56to define a circulating channel92in communication with the circulating hole32and the loaded path, and a circular outer profile of the circular circulating channel92is connected to the bottom surface52of the second circulating block50.

Additionally, the bottom surface331of the recess33includes a threaded groove3311, and the second circulating block50further includes a protruding ear58. The protruding ear58includes a locking hole581in alignment with the threaded groove3311of the nut. A screw59is screwed into the threaded groove3311by cooperating with the locking hole581of the protruding ear58.

The aforementioned is the summary of the positional and structural relationship of the respective components of the preferred embodiment in accordance with the present invention.

For a better understanding of the present invention, its operation and function, reference should be made to the following description:

The present invention is applicable to the screw shaft whose helical groove doesn't extend to the shoulder portion thereof.

Referring toFIG. 8, in assembly, the nut30is mounted on the screw shaft20first, and next, the first circulating block40will be deflected slightly in the radial direction of the nut30for preventing the nail portion47from interfering with the screw shaft20and then placed into the recess33of the nut30. Referring toFIG. 9, when the first abutting surface43of the first circulating block40abuts against the side surface332of the recess33, the first circulating block40will be deflected in the radial direction of the nut30an angle to make the nail portion47be disposed inside the outer helical groove22of the screw shaft20. After that, as shown inFIG. 10, the second circulating block50will be placed in the recess33of the nut30in the axial direction of the nut30and combined to the first circulating block40by engaging the positioning concave55of the second circulating block50with the positioning portion45of the first circulating block40. Finally, the screw59is inserted through the locking hole581in the protruding ear58of the second circulating block50and screwed with the nut30, so that the circulating assembly can be stably located in the recess33of the nut30. With the above assembling method, the present invention can avoid interference with the thread of the screw shaft and can be applied to the screw shaft20whose helical groove doesn't extend to the shoulder portion thereof, thus widening the application range of the ball screw.

2. The present invention is applicable to nuts with smaller outer diameter:

The present invention specially aims at the angle design of the circulating assembly, in other words, the angle A between the bottom surface52of the second circulating block50and the second dividing surface51is limited between 18 degrees and 25 degrees, and the first and the second circulating blocks40,50are limited in height, in other words, the HC1 of the first circulating block40and the HC2 of the second circulating block50satisfy the relation: HC2>HC1, by such arrangements, the present invention is applicable to the nuts with the smaller outer diameter, especially to the nuts by European industrial standards, such as the nuts by Deutsche industry norm.