Patent Application
20170268644
1. Technical Field
The present invention relates to ball screws and more particularly to a dustproof device for a ball screw.
2. Description of Related Art
When a ball screw is in operation, the rolling contact between the screw rod, the nut, and the balls causes abrasion and hence the generation of debris, or dust. If the debris remaining in the gap between the screw rod and the nut is not removed, the precision of transmission and the smoothness of operation of the ball screw will be compromised, and the service life of the ball screw will be shortened as a result.
U.S. Pat. No. 5,231,888 discloses sucking internally generated debris with a suction device, and yet the suction device adds to the complexity of the entire structure and to the installation cost. Japanese Patent No. 4967809 uses a magnet to increase the closeness between the lip of a dustproof device and a screw rod, but debris tends to be attracted into and subsequently accumulate in the spiral groove of the screw rod. That is to say, the magnet, though contributing to an enhanced sealing effect, indirectly increases the operating resistance of the whole structure.
The primary objective of the present invention is to provide a dustproof device applicable to a ball screw and featuring structural simplicity, a good sealing effect, and effectiveness in removing the debris between the nut and the screw rod of a ball screw so as to extend the service life of the ball screw.
To achieve the above objective, the first dustproof device provided by the present invention includes an annular body and an elastic valve plate. The annular body is provided at one end of a nut and is penetrated by a screw rod. The annular body has an inner annular surface provided with a dustproof lip abutting against the periphery of the screw rod. The annular body further has an outer annular surface provided with at least one debris exit. One end of the debris exit is in communication with a spiral passage formed between the nut and the screw rod. The elastic valve plate is connected to the annular body and is located at the opposite end of the debris exit of the annular body.
When subjected to the pressure of a fluid, the elastic valve plate opens the debris exit, allowing debris to flow out with the fluid through the debris exit. Once the pressure of the fluid is removed, the elastic valve plate closes the debris exit thanks to the elastic restoring force of the elastic valve plate itself.
The second dustproof device provided by the present invention has a debris exit on the side facing away from the nut, and the debris exit is in communication with the spiral passage via at least one pore. When a fluid reaches the dustproof device via the spiral passage, the pressure of the fluid pushes the pore open so that debris can flow out of the debris exit through the pore along with the fluid. As soon as the pressure of the fluid is removed, the pore restores its original diameter or shape.
Referring to
The annular body 20 has two corresponding positioning flanges 21 on its outer annular surface and two corresponding dustproof lips 22 on its inner annular surface. To assemble, the screw rod 12 is inserted through the annular body 20 until the positioning flanges 21 are engaged in the positioning groove 144 in the inner periphery of the nut 14. After assembly, the dustproof lips 22 of the annular body 20 abut against the periphery of the screw rod 12 to produce a sealing effect, preventing foreign matters from entering the gap between the screw rod 12 and the nut 14. In addition, three debris exits 23 are arranged at an equal spacing along the outer annular surface of the annular body 20. Each debris exit 23 has an end which, after assembly, faces the nut 14 and is in communication with the spiral passage 16.
Each elastic valve plate 30 is provided at one debris exit 23 of the annular body 20, or more particularly at the end of the debris exit 23 that faces away from the nut 14. In this embodiment, the inner periphery of the nut 14 has three valve plate grooves 146 adjacent to the positioning groove 144. After assembly, the elastic valve plates 30, each having an end connected to the outer annular surface of the annular body 20, are located in the valve plate grooves 146 of the nut 14 respectively and seal the debris exits 23 respectively.
According to the above, a fluid (e.g., grease) injected into the nut 14 can carry debris along the spiral passage 16 to the debris exits 23, where the fluid applies an outward pushing force to the elastic valve plates 30. The pressure of the fluid pushes open the elastic valve plates 30 and hence the debris exits 23, as shown in
Referring to
It is worth mentioning that the elastic valve plates are not essential to the dustproof device. Referring to
According to the above, the dustproof device of the present invention not only provides a good sealing effect, but also features a simpler structure and can discharge the debris in the gap between the screw rod and the nut of a ball screw more effectively than its prior art counterparts to extend the service life of the ball screw.
