Lubricatable ball spline device

The disclosure relates to a driving device of a processing machine, more particularly to a lubricatable ball spline device.

A ball spline device, as disclosed in U.S. Pat. No. 5,809,838, includes a screw shaft, a ball nut sleeved on the screw shaft, a first ball unit fitted between the screw shaft and the ball nut, a rolling bearing sleeved on the ball nut, and a second ball unit disposed between the ball nut and the rolling bearing. The rolling bearing has a first oil supplying hole formed in an outer race thereof. The ball nut has an inner peripheral surface, an outer peripheral surface, and a plurality of second oil supplying holes communicating with the first oil supplying hole through an annular gap. When lubricant oil is introduced into the ball spline device via the first oil supplying hole, the lubricant oil must fill up the annular gap before the lubricant oil can flow through the second supplying holes to a space between the screw shaft and the ball nut, thereby resulting in excessive oil and poor lubrication efficiency. Further, this type of ball spline device cannot produce a good lubricating effect for the first and second ball units.

Another ball spline device, as disclosed in Taiwanese Patent Publication No. 1444542, includes a screw shaft, a ball nut sleeved on an outer portion of the screw shaft, a first rolling ball unit disposed between the screw shaft and the ball nut, a bearing outer ring sleeved on the ball nut, and a second rolling ball unit disposed between the bearing outer ring and the ball nut. The ball nut has two spaced-apart protruding portions, an annular oil channel disposed between the protruding portions, and a plurality of oil holes extending radially through an inner peripheral face from the annular oil channel. The bearing outer ring has an oil supplying hole communicating with the annular oil channel. Although the provision of the protruding portions can prevent excessive lubrication of the lubricant oil on the second rolling ball unit, because the protruding portions are spaced apart from each other, the second rolling ball unit is not sufficiently lubricated.

Therefore, an object of the present disclosure is to provide a lubricatable ball spline device that is capable of overcoming at least one of the drawbacks of the prior art.

Accordingly, a lubricatable ball spline device of this disclosure includes a ball spline shaft, a ball nut, a linear bearing unit, a bearing ring, an oil path accessory and an annular bearing unit. The ball spline shaft extends along an axis, and has a shaft outer peripheral surface, and a plurality of spaced-apart pairs of first ball-rolling grooves formed in the shaft outer peripheral surface and extending axially along a length of the ball spline shaft. The ball nut is slidably sleeved on the ball spline shaft and has a nut inner peripheral surface opposite to the shaft outer peripheral surface, a nut outer peripheral surface opposite to the nut inner peripheral surface, a plurality of oil guide holes extending through the nut inner and outer peripheral surfaces, a plurality of pairs of second ball-rolling grooves formed in the nut inner peripheral surface and respectively opposite to the pairs of first ball-rolling grooves, at least one annular third ball-rolling groove formed in the nut outer peripheral surface and surrounding the axis, and a communication channel formed in the nut outer peripheral surface and communicating with the at least one third ball-rolling groove.

The linear bearing unit is mounted between the shaft outer peripheral surface and the nut inner peripheral surface to permit the ball nut to move slidably relative to the ball spline shaft. The linear bearing unit has a first ball retainer, and a plurality of sets of first balls mounted in the first ball retainer. Each set of the first balls is disposed between one pair of the first ball-rolling grooves and a corresponding opposed pair of the second ball-rolling grooves. The bearing ring is rotatably sleeved on the ball nut and has a bearing ring inner peripheral surface opposite to the nut outer peripheral surface, a bearing ring outer peripheral surface opposite to the bearing ring inner peripheral surface, an oil supplying hole extending through the bearing ring inner and outer peripheral surfaces, and at least one annular fourth ball-rolling groove formed in the bearing ring inner peripheral surface and surrounding the axis. The at least one fourth ball-rolling groove is opposite to the at least one third ball-rolling groove.

The oil path accessory includes a positioning portion disposed between the bearing ring inner peripheral surface and the nut outer peripheral surface, and an oil passage corresponding in position to the oil supplying hole. The positioning portion has an oil storage space with an opening facing the nut outer peripheral surface and communicating with the oil passage. The oil supplying hole, the oil passage, the oil storage space and any one of the oil guide holes cooperatively form a continuous oil path extending from the bearing ring outer peripheral surface to the nut inner peripheral surface. The annular bearing unit is mounted between the nut outer peripheral surface and the bearing ring inner peripheral surface to permit the bearing ring to rotate relative to the ball nut. The annular bearing unit has a second ball retainer, and a plurality of second balls mounted in the second ball retainer. The second balls are disposed between the at least one third ball-rolling groove and the at least one fourth ball-rolling groove.

Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a fragmentary perspective view of a lubricatable ball spline device according to the embodiment of this disclosure;

FIG. 2 is an exploded perspective view of the embodiment;

FIG. 3 is a sectional view of the embodiment taken along line of FIG. 1 ; and

FIG. 4 is a sectional view of the embodiment taken along line IV-IV of FIG. 3 .

Referring to FIGS. 1 to 4 , a lubricatable ball spline device according to the embodiment of the present disclosure is shown to comprise a shaft 10 (which is configured in the illustrated embodiment to be a ball spline shaft), a ball nut 20 , a linear bearing unit 30 , a bearing ring 40 , an oil path accessory 50 and an annular bearing unit 60 .

The ball spline shaft 10 extends along an axis (L), and has a shaft outer peripheral surface 11 , and a plurality of pairs of first ball-rolling grooves 12 formed in the shaft outer peripheral surface 11 and extending axially along a length of the ball spline shaft 10 . As shown in FIG. 4 , the ball spline shaft 10 is provided with three pairs of first ball-rolling grooves 12 that surround the axis (L) and that are angularly spaced apart from each other by 120 degrees.

The ball nut 20 is sleeved on the ball spline shaft 10 and is slidable along the length thereof. The ball nut 20 has a nut inner peripheral surface 21 opposite to the shaft outer peripheral surface 11 , a nut outer peripheral surface 22 opposite to the nut inner peripheral surface 21 , a plurality of oil guide holes 23 extending through the inner and outer peripheral surfaces 21 , 22 , a plurality of pairs of second ball-rolling grooves 24 formed in the nut inner peripheral surface 21 and respectively opposite to the pairs of first ball-rolling grooves 12 , two annular third ball-rolling grooves 25 formed in the nut outer peripheral surface 22 and surrounding the axis (L), and a plurality of communication channels 26 formed in the nut outer peripheral surface 22 and parallel to the axis (L). The oil guide holes 23 are arranged in pairs. In this embodiment, the ball nut 20 is provided with three pairs of oil guide holes 23 that surround the axis (L) and that are angularly spaced apart from each other by 120 degrees. The oil guide holes 23 are disposed between the third ball-rolling grooves 25 . The third ball-rolling grooves 25 are axially spaced apart from each other. The communication channels 26 are disposed between and are communicated with the third ball-rolling grooves 25 . Each communication channel 26 is located between two oil guide holes 23 of each pair.

The linear bearing unit 30 is mounted between the shaft outer peripheral surface 11 and the nut inner peripheral surface 21 to permit the ball nut 20 to move slidably relative to the ball spline shaft 10 . The linear bearing unit 30 includes a first ball retainer 31 , and a plurality of sets of first balls 32 mounted in the first ball retainer 31 . Each set of the first balls 32 is disposed between one pair of the first ball-rolling grooves 12 and a corresponding opposed pair of the second ball-rolling grooves 24 .

The bearing ring 40 is rotatably sleeved on the ball nut 20 , and has a bearing ring inner peripheral surface 41 opposite to the nut outer peripheral surface 22 , a bearing ring outer peripheral surface 42 opposite to the bearing ring inner peripheral surface 41 , an oil supplying hole 43 extending through the bearing ring inner and outer peripheral surfaces 41 , 42 , and two annular fourth ball-rolling grooves 45 formed in the bearing ring inner peripheral surface 41 and surrounding the axis (L). The fourth ball-rolling grooves 45 are respectively opposite to the third ball-rolling grooves 25 .

The oil path accessory 50 includes a positioning portion 51 disposed between the bearing ring inner peripheral surface 41 and the nut outer peripheral surface 22 , and a connecting pipe 52 connected to the positioning portion 51 . The positioning portion 51 has an inverted U-shaped cross section, and includes an arcuate bight portion 511 abutting against the bearing ring inner peripheral surface 41 , two leg portions 512 extending downwardly and respectively from two opposite ends of the bight portion 511 and abutting against the nut outer peripheral surface 22 , and an oil storage space 513 cooperatively defined by the bight portion 511 and the leg portions 512 and having an opening facing the nut outer peripheral surface 22 . The connecting pipe 52 is disposed in the oil supplying hole 43 , and defines an oil passage 521 communicating with the oil storage space 513 through a hole 5111 in the bight portion 511 . The oil supplying hole 43 , the oil passage 521 and the oil storage space 513 and any one of the oil guide holes 23 cooperatively form a continuous oil path extending from the bearing ring outer peripheral surface 42 to the nut inner peripheral surface 21 . Further, as shown in FIG. 4 , two oil guide holes 23 of each pair are spaced apart by an angular distance smaller than an angular width of the oil storage space 513 relative to the axis (L). The positioning portion 51 of this embodiment is made of a low coefficient of friction or porous material, such as plastic or felt having a coefficient of friction of 0.2 to 0.3.

The annular bearing unit 60 is mounted between the nut outer peripheral surface 22 and the bearing ring inner peripheral surface 41 to permit the bearing ring 40 to smoothly rotate relative to the ball nut 20 , and includes a second ball retainer 61 , and two sets of second balls 62 mounted in the second ball retainer 61 . Each set of the second balls 62 is disposed between one of the third ball-rolling grooves 25 and the respective fourth ball-rolling groove 45 .

With reference to FIGS. 3 and 4 , when lubricant oil is introduced into the ball spline device of this disclosure through the oil supplying hole 43 , the lubricant oil (see the arrows shown in FIG. 4 ) will flow into the oil storage space 513 through the oil supplying hole 43 , the oil passage 521 and the hole 5111 in the bight portion 511 . When the oil path accessory 50 rotates along with the bearing ring 40 to a position above any one pair of the oil guide holes 23 , the lubricant oil can directly lubricate the linear bearing unit 30 disposed between the ball spline shaft 10 and the ball nut 20 through the continuous oil path to provide a smooth linear movement of the ball nut 20 relative to the ball spline shaft 10 . When the oil path accessory 50 is moved away from a position above any one pair of the oil guide holes 23 , the lubricant oil is stored in the oil storage space 513 , and will not conduct lubrication, so that excessive lubrication can be prevented.

Hence, in this disclosure, through the cooperation of the oil path accessory 50 and the oil guide holes 23 , a communication path of the continuous oil path can be increased, and an effect of storing the lubricant oil can be achieved, so that lubrication of the linear bearing unit 30 can be conducted and excessive lubrication of the linear bearing unit 30 can be prevented. Further, because the positioning portion 51 of this embodiment is made of a low frictional coefficient or porous material, wearing of the two leg portions 512 of the positioning portion 51 can be prevented during rotation of the bearing ring 40 relative to the ball nut 20 so as to ensure tight sealing of the continuous oil path.

Moreover, with the communication channels 26 communicating with the third ball-rolling grooves 25 , when the lubricant oil is introduced into the oil supplying hole 43 , and the oil path accessory 50 is moved to a position above any one of the communication channels 26 , the lubricant oil can flow uniformly to two opposite sides of the annular bearing unit 60 through the oil storage space 513 and the one of the communication channels 26 to lubricate the second balls 62 . Thus, a good lubricating effect is obtained.

Therefore, the object of this invention can indeed be achieved.

While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.