BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of a conventional dust-proof structure for a ball screw disclosed by U.S. Pat. No. 6,571,653 B1;
FIG. 2 is a cross sectional view of a conventional dust-proof structure for a ball screw disclosed by U.S. Pat. No. 6,178,839 B1;
FIG. 3 is a plan view of a dust-proof structure for a ball screw in accordance with the present invention;
FIG. 4 is an illustrative view of showing the force analysis of the dust-proof structure for a ball screw in accordance with the present invention;
FIG. 5 is an exploded view of a dust-proof structure for a ball screw in accordance with a first embodiment of the present invention;
FIG. 6 is an illustrative view of a dust-proof structure for a ball screw in accordance with a second embodiment of the present invention;
FIG. 7 is an illustrative view of a dust-proof structure for a ball screw in accordance with a third embodiment of the present invention; and
FIG. 8 is an illustrative view of a dust-proof structure for a ball screw in accordance with a fourth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be more clear from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention.
Referring to FIG. 3, a dust-proof structure for a ball screw in accordance with the present invention is shown and comprises: a wiper 1, a wiping piece 2 and a fastening device 5.
The wiper 1 is a C-shaped structure defined with a gap 3 for accommodation of the wiping piece 2. A bevel surface 11 is formed at either end of the wiper 1 and located at either side of the gap 3. The wiping piece 2 is also provided at either side thereof with a bevel surface 21 for mating with the bevel surfaces 11 of the gap 3, so that the wiper 1 and the wiping piece 2 come into contact with each other via the bevel surfaces.
Referring to FIG. 4, which is an illustrative view of showing the force analysis of the dust-proof structure for a ball screw in accordance with the present invention. Since the dust-proof structure uses the bevel surfaces to contact the wiper, when the external force to be applied is Fc, the resultant pushing force of the wiping piece 2 toward the screw shaft is only Fc*sin a. Furthermore, when the angle a is no greater than 10°, the resultant pushing force of the wiping piece 2 toward the screw shaft is only approximately 0.15 Fc. Therefore, the wiping piece 2 will abut against the surface of the screw shaft with a very light force, so that the degree to which the wiping piece 2 abuts against the surface of the screw shaft is controllable. Therefore, it not only has the dust proof effect, but also can prevent the occurrence of the excessively great friction.
Please refer to FIG. 5 for a better understanding of the present invention. The wiper 1 is a C-shaped structure defined with the gap 3 for accommodation of the wiping piece 2. The wiper 1 together with the wiping piece 2 are inserted in the groove 91 of the nut 9, and then a bolt 5 is used to shrink the gap 3 by tightening the wiper 1 from both sides, so as to make the wiping piece 2 abut closely against the surface of the screw shaft, thus effectively solving the problem of dust invasion and high friction drag.
FIG. 6 shows a dust-proof structure for a ball screw in accordance with a second embodiment of the present invention, in which, a pair of protruding pieces 12 is formed at both abutting ends of the wiper 1 and located at both sides of the gap 3. A fastening device 4 is positioned on the protruding pieces 12 to shrink the gap 3 by applying a radial force to the wiper 1, thus making the wiping piece 2 abut closely against the surface of the screw shaft.
The interacting force between the bevel surfaces of the wiping piece 2 and the wiper 1 pushes the wiping piece 2 toward the surface of the screw shaft, thus effectively solving the problem of dust invasion and high friction drag.
The abovementioned interacting force and the radial force is produced by screwing the bolt 5 through the protruding pieces 12 into a nut 6.
FIG. 7 shows a dust-proof structure for a ball screw in accordance with a third embodiment of the present invention. In addition to being tightened by the fastening device 4, the wiper 1 can also be closed by inserting an elastic piece 7 into the blind holes 13 formed in the surface of the wiper 1.
FIG. 8 shows a dust-proof structure for a ball screw in accordance with a fourth embodiment of the present invention, wherein the wiper 1 is tightened by screwing the bolt 5 through a spring 8 and the protruding pieces 12 and into a nut 6.
The user can make an adjustment progressively according to the wear of the wiping piece 2, and then fasten the wiper 1 by using the bolt 5 and the nut 6.
The adjustment should be made progressively because: the wiping piece 2 remains abutting closely against the surface of the bolt 5 for a certain period of time after installation, but as time goes by, the wear of the wiping piece 2 increases and the bolt 5 becomes loose, the wiping piece 2 will not be in contact with the surface of the screw shaft again. At this moment, the spring 8 on the bolt 5 can be used to adjust the wiping piece 2 and make it abut closely against the surface of the screw shaft again. The advantages of this design are that only the wiping piece 2 comes into contact with the surface of the screw shaft, on the other hand, the spring 8 allows the wiping piece 2 to keep abutting against the surface of the screw shaft, and the dust-proof function will not be affected by the wear of the wiping piece and the loose of the bolt 5.
To summarize, the dust-proof structure for a ball screw in accordance with the present invention is a C-shaped structure defined with a gap for accommodation of the wiping piece, and formed at either side of the gap is a bevel surface. The wiping piece is also formed at both sides thereof with a bevel surface for mating with the bevel surface of the gap, so that the wiper and the wiping piece are maintained into contact via the bevel surfaces. Moreover, a fastening device is provided at the outer edge of the gap to shrink the gap by applying a radial force to the wiper, thus making the wiping piece abut closely against the surface of the screw shaft.
Therefore, the interacting force between the bevel surfaces of the wiping piece and the wiper pushes the wiping piece toward the surface of the screw shaft, thus effectively solving the problem of dust invasion and high friction drag.
While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.
Patent Application
20080092678
