Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
2001-11-23
2004-05-11
Lavinder, Jack (Department: 3683)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C074S424820, C277S354000
Reexamination Certificate
active
06732599
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wiper ring to be mounted to an end portion of a nut of a ball screw and also relates to a ball screw provided with such wiper ring.
Japanese Utility Model Laid-open Publication No. HEI 6-6795 disclosed such a wiper ring, in which one end side portion or entire portion of a wiper ring is divided into a plurality of segments or blocks in a circumferential direction thereof, and each of the segments is pressed towards radially center side by means of spring to thereby improve tightness between an inner peripheral portion of the wiper ring and a screw shaft disposed inside therein.
In such known art, in the structure in which only the one end side portion of the wiper ring is divided into a plurality of segments or blocks, there is usually formed a cutout portion, called “bias-cut”, at one portion of the wiper ring in its circumferential direction for separating the same. However, in an arrangement in which such wiper ring is mounted to a screw shaft, the bias-cut portion is widened (opened) and the inner peripheral portion of the wiper ring is deformed unwillingly in form of non-circular shape, and for this reason, at a portion opposite to the bias-cut forming portion of the wiper ring, the segment is closely contacted to the screw shaft. However, on the side of the bias-cut forming portion, the tightness of the segment to the screw shaft is made worse. As a result, sealing performance of the ball screw may be made different at various portions, thus being inconvenient.
On the other hand, the case where the entire portion of the wiper ring is divided into a plurality of segments or blocks will cause the following defective.
In such structure, when a gap is formed between adjacent two segments in the circumferential direction thereof, the gap may be widened when the segments are shifted. In such occasion, foreign material or like may easily invade and lubricant may easily leak through the widened gap. On the contrary, when the segments are contacted to each other in order to eliminate such gap, the movement of the respective segment towards the radially central portion of the segment due to such mutual contacting will be limited, which results in degradation of tightness between the segments and the screw shaft and deterioration of the sealing performance. Furthermore, in a case where any foreign material is clogged between the segment and the screw shaft, the segment is displaced towards the radially outer peripheral side against the force of the spring pressing the segment, and hence, the inner peripheral portion of the segment is separated from the screw shaft, thus deteriorating the sealing performance and hence being defective.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a wiper ring and a ball screw provided with the wiper ring, by which sealing performance of a screw shaft with respect to segments of the wiper ring can be enhanced.
The above and other objects can be achieved according to the present invention by providing, in one aspect, a wiper ring to be applied to a screw unit having a shaft member comprising:
a plurality of segments each constituted as independent element having a seal portion to be contacted to the shaft member;
support shafts extending in an axial direction of the shaft member so as to correspond to the segments, respectively, the segments being arranged in a circumferential direction of the shaft member to be rotatable about the support shafts, the support shafts being connected to each other through support members so as to limit relative movement of the respective support shafts; and
a spring member for urging the segments arranged circumferential direction of the shaft member so as to be directed towards radially central side of the shaft member.
According to the wiper ring of this aspect, the respective segments are deformed in their attitudes so as to closely contact the shaft member such as screw shaft of the ball screw unit while being pressed towards the central side of the screw member by means of spring and rotating about the support shafts such as pins. Accordingly, the respective segments can be well contacted to the shaft member, and the improved sealing performance can be realized at any circumferential position.
Further, the support shafts of the respective segments are mutually connected to thereby limit or restrict the relative movement of the support shafts, so that the movement of the segments in the circumferential and radial directions can be properly limited. Therefore, the biting of foreign material in a widened gap between the segments in the circumferential direction can be prevented, the leakage of lubricant can be also prevented, and the degradation of the sealing performance due to the movement of the segments in the radially outer peripheral direction can be further prevented.
Further, in the present invention, the state, that the support shafts as rotational centers of the respective segments are connected to each other, means that the support shafts are connected to each other through members different from the segments or through the segments themselves to thereby restrict the relative movement therebetween. The support shafts may be constituted independently from the segment, or segment itself is utilized as support shaft.
In a preferred embodiment of this aspect, the support member is a support ring formed as a member independent from the segments and the support shafts are connected to each other through the support ring.
In this example, the respective segments are supported by the support ring to be rotatable about the support shafts such as pins. The support ring may be separated at one portion in its circumferential direction, and in such case, since the cut portion corresponding to the bias-cut in the conventional structure of the wiper ring is formed on the support ring, the wiper ring can be entirely deformed and the segments can be surely urged against the shaft member by the spring member.
Furthermore, according to this aspect, (N−2) segments in the plural segments (N: total number thereof are formed with the support shafts and hole portions for receiving the support shafts in an arrangement shifted in the circumferential direction of the shaft member, either one of remaining two (2) segments is provided with the support shaft and another one of the remaining two segments being formed with the hole portion, the segments being connected to each other by fitting the support shafts to the hole portions of the adjacent two segments in the circumferential direction in a manner that the remaining two segments are unconnected.
According to this example, the respective adjacent segments can be supported to be rotatable about the support shafts and the respective support shafts can be connected through the segments. Therefore, no connection is made between two segments, so that the cut (separated) portion, corresponding to the conventional bias-cut, is formed and the wiper ring can be entirely deformed. Thus, the segments can be surely urged against the shaft member by the spring member.
Furthermore, it may be possible that each of the segments comprises a segment body having the seal portion and a support plate arranged in a manner shifted in the circumferential direction with respect to the segment body, either one of the support plate and the segment body is formed with the support shaft and another one thereof is formed with the hole portion.
In this example, since the support plate extends behind a slit formed between the segment bodies, so that the inside and outside portions of the wiper ring are not communicated through the slit, and hence, the invasion of foreign material can be prevented as well as leakage of the lubricant.
In another aspect of the present invention, there is also provided a wiper ring to be applied to a screw unit having a shaft member comprising:
a support ring;
a plurality of segments each hav
Iida Katsuya
Michioka Hidekazu
Nishide Tetsuhiro
King Bradley
Lavinder Jack
THK Co. Ltd.
Westerman Hattori Daniels & Adrian LLP
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