Patent Application
20150260267
1. Field of the Invention
The present invention relates to linear actuator technology and more particularly, to an improved structure of rotor module with anti-jam function for use in a linear actuator
2. Description of the Related Art
In contrast to the circular motion of a motor, a linear actuator uses a motor to provide linear motion, and therefore, linear actuators are widely used in all kinds of machine tools and large machinery. A typical linear actuator converts rotary motion of a motor rotor into linear displacement via a screw rod that is threaded into an inner thread in the motor rotor. However, if a conventional linear actuator bears a load or vibrations occurred in the surrounding areas during operation, the inner thread of the motor rotor can be not accurately meshed with the screw rod, causing the screw rod to get jammed and further making the linear actuator to lose its original function.
The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide an anti--jam structure for linear actuator, which prevent the screw rod of the linear actuator from being jammed during rotation.
To achieve this and other objects of the present invention, an anti-jam structure in accordance with the present invention is used in a linear actuator and adapted for rotating a screw rod, comprising a screw nut, a cover member and a magnet holder. The screw nut comprises a screw rod passage extending through two opposite ends thereof and defining an internal thread segment and a threadless segment, and at least one elongated slot longitudinally extended from one end thereof corresponding to the threadless segment and disposed in communication between the screw rod passage and the atmosphere. The cover member is mounted on the screw not to block the elongated slot. The magnet holder defines therein an accommodation chamber that accommodates the screw nut and the cover member.
Thus, during operation of the linear actuator, the at least one elongated slot allows the screw nut to be elastically compressed, preventing the screw rod from being jammed due to bearing of a load or high vibrations.
Preferably, the screw nut and the cover member are mounted in the accommodation chamber of the magnet holder by insert molding.
Preferably, the screw nut comprises an annular groove extending around the periphery thereof for enabling the cover member to be mounted on the outside wall of the screw nut.
Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure.
Referring to
Referring to
The cover member 12 is made from an elastic material and can be mounted around the outside wall of the screw nut 11 to block the elongated slot 114. In this embodiment, the cover member 12 is C-shaped, comprising a planar base portion 121, two opposing end portions 122, and a through hole 123 located at the center of the planar base portion 121. for the passing of the screw rod 40. The planar base portion 121 has two opposite ends thereof respectively connected to the end portions 122. Each end portion 122 has one end thereof connected to a respective one end of the planar base portion 121 and an opposite end thereof bent inwardly to form a hook portion 124. Thus, when the cover member 12 is attached to the outside wall of the screw nut 11 in the axial direction of the screw rod passage 111, the hook portions 124 can be hooked in the annular groove 115 and the end portions 122 can block the elongated slot 114.
The magnet holder 13 has an accommodation chamber 131 defined therein and adapted for accommodating the screw not 11 and the cover member 12 and for allowing the screw rod 40 to pass therethrough. In this embodiment, after the screw nut 11 and the cover member 12 are assembled, they are fixedly mounted in the accommodation chamber 131 of the magnet holder 13 by insert molding. Because the two end portions 122 of the cover member 12 have already blocked the elongated slot 114 prior to the insert molding, and therefore the applied molten plastic will not flow into the elongated slot 114, ensuring the elongated slot 114 can actually be effective. Further, because the elongated slot 114 has a certain length and its major part is disposed corresponding to the threadless segment 113, the elongated slot 114 provides sufficient space for enabling the screw nut 11 to be elastically compressed in case the screw rod 40 and the internal thread segment 112 are incorrectly meshed, preventing the screw rod 40 and the screw nut 11 from being stuck with each other.
After understanding the structural details of the anti-jam structure 10 of the linear actuator 1, the other component parts of the linear actuator 1 are introduced hereinafter with reference to
The stator module 20 comprises a casing 21, a front cover 22 and a back cover 23. The front cover 22 and the back cover 23 are mountable in the casing 21. Further, a rotor mount 25 is set between the front cover 22 and the back cover 23 at the center. The front cover 22 and the back cover 23 each providing a mounting portion 24 for the winding of one respective coil of wire 26. In order to prevent the coil of wire 26 from being exposed to the outside and to increase the magnetic field strength, the casing 21 has an inner magnetic yoke 27 and an outer magnetic yoke 28 respectively mounted at the inner and outer perimeters thereof corresponding to the mounting portion 24 of each of the front cover 22 and the back cover 23.
Further, the magnetic holder 13 has a first axle bearing 31, an annular magnet 32 and a second bearing 33 mounted on the periphery thereof in a proper order from top to bottom. When assembled, the screw nut 11, the cover member 12, the magnet holder 13, the first axle bearing 31, the annular magnet 32 and the second axle bearing 33 constitute a rotor module 30. This rotor module 30 is mounted at the rotor mount 25.
The screw rod 40 has its one end, namely the front end connected to an external bar 41 with a lock pin 42. The periphery of the other end, namely, the rear end, of the screw rod 40 provides an outer thread 43. Thus, the rear end of screw rod 40 is threadable into the internal thread segment 112 of the screw nut 11. The screw rod 40 further comprises a pinhole 44 transversely disposed at a middle part thereof adjacent to the outer thread 43 for the mounting of a locating pin 45 to prohibit the screw rod 40 from rotation during the operation of the linear actuator 1.
When the coil of wire 26 at the back cover 23 of the stator module 20 is electrically conducted, the coil of wire 26 induces a magnetic field to drive the rotor module 30 to rotate, thereby rotating screw nut 11. At this time, the screw rod 40 has already threaded into the internal thread segment 112 of the screw nut 11 and the locating pin 45 has already mounted in the screw rod 40, therefore, during rotation of the screw nut 11, the screw rod 40 is caused to move linearly forward (or backward) subject to the rotation of the rotor module 30.
During linear displacement of the screw rod 40, the elongated slot 114 of the screw nut 11 enables the screw nut 11 to be flexibly compressed, assuring accurate mesh between the screw rod 40 and the internal thread segment 112 and preventing the screw rod 40 and the internal thread segment 112 from being stuck with each other. Therefore, even the screw rod 40 carries a load or the linear actuator 1 works under a vibration environment, the linear actuator 1 will not get stuck. Further, it is to be noted that the number of the elongated slot can be more than one, achieving the same effect of the present invention.
Although a particular embodiment of the invention as been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.
