Patent Application
20110278133
1. Field of the Invention
The present invention relates generally to a main shaft locking apparatus applicable for a power tool, according to which when the power tool is not provided with power supply, a main shaft of the power tool is prevented from being rotated by any external force and does not generate any noise.
2. The Prior Arts
A conventional power tools, e.g., a power drill, is typically driven by electric power, and can be classified into corded, cordless (chargeable) or a combination of both. Generally, the power tool not only can hold a drilling bit for drilling a hole, but also can hold a screwdriver bit to screw or unscrew a screw. Usually, the corded power tool is more powerful than the cordless power tool and is more suitable for heavy duty. However, when the power tool is used in places without any socket, the cordless power tool driven by a chargeable battery is the only option. Unfortunately, when the battery is running low and is unable to recharge, the cordless power tool is unable to operate. Similarly, a sudden power failure may instantly disable the corded power tool. When the power is not supplied normally, the power tool can be temporarily operated as a manual tool. For example, the power tool is used as a regular manual screwdriver.
A conventional power tool usually includes a motor having a driving shaft, a driving gear coupled with the driving shaft of the motor, a gear set engaged with the driving gear, a follower gear engaged with the gear set and a central shaft coupled with the follower gear. In such a way, when the power tool is temporarily operated as a manual screwdriver, the follower gear alternatively serves as a temporary driving gear. The torque generated thereby is transmitted by the gear set to the original driving gear which is coupled to the driving shaft of the motor. As such, the screwdriver bit runs idly, and the power tool cannot be used as a manual screwdriver.
Taiwan Patent Nos. 410,714 and 334,869 have proposed main shaft locking mechanisms as a solution with respect to the foregoing problems. However, the main shaft locking mechanisms employs a fixing ring, and a main shaft and a plurality of rollers or steel balls secured in an inner hole of the fixing ring. When the power is not supplied to the power tool and an external force is applied to drive the main shaft to rotate, the main shaft drives the rollers or the steel balls to interfere against the fixing ring, thereby locking up the main shaft. However, the mechanism requires the fixing ring to be machined with a very high precision, which makes concentricity between the main shaft and the fixing ring. Otherwise, an unsatisfactory concentricity between the main shaft and the fixing ring may adversely cause the force to be non-uniformly distributed onto the rollers or the steel balls, so as to impair the locking effect.
Taiwan Patent No. M363,979 has disclosed a main shaft locking device to overcome the aforementioned disadvantages. However, no matter the main shaft is rotated clockwise or counterclockwise; the device inevitably makes noise due to gaps defined between detent members and the polygonal main shaft. A user may feel uncertain because the existence of gaps during operation.
A primary objective of the present invention is to overcome disadvantages of conventional main shaft locking mechanism of a power tool, in which no matter the main shaft is rotated clockwise or counterclockwise, gaps defined between a fastening ring, detent pins and sides of the polygonal main shaft generate noise during operation and a user may feel uncertain.
One of characteristics of the present invention is that a main shaft locking apparatus having a plurality of detent pins is provided with an elastic retaining device having elastic portions. The detent pins are disposed in the elastic retaining device, and an output shaft passes through the elastic retaining device. The elastic portions of the elastic retaining device act on the detent pins, thereby eliminating gaps between a fastening ring and the output shaft. Therefore, no matter a power system drives the output shaft to rotate clockwise or counterclockwise or the output shaft actively rotates clockwise or counterclockwise, no noise is made due to the aforementioned gaps.
In order to achieve the objectives, a gapless main shaft locking apparatus according to the present invention includes a fastening ring, an elastic retaining device, a plurality of detent pins, a driving plate and an output shaft. The elastic retaining device has an inner space in which elastic portions and cylinder portions are disposed with a manner of being respectively arranged as a pair and aligned at correspondingly symmetrical positions along an axial direction of the inner space. The elastic retaining device is installed in the fastening ring. The detent pins are installed in the inner space of the elastic retaining device and each of the detent pins is respectively disposed between one of the elastic portions and one of the cylinder portions. The driving plate is connected to a power system and provided with a central hole. The periphery of the central hole includes a plurality of fan-shaped convex portions. A side surface of the driving plate has a plurality of concave slots circularly arranged for receiving the elastic retaining device. The output shaft is a polygonal shaft having a cross section in a regular polygonal shape. The polygonal shaft passes through the central hole of the driving plate, and each side of the polygonal shaft is respectively in contact with one of the detent pins. No matter the output shaft is rotated clockwise or counterclockwise, part of the detent pins can be immediately locked in the fastening ring through actions of the elastic portions, so the output shaft is unable to be rotated, and no noise is generated with the existence of gaps.
Compared to conventional mechanical designs, the present invention has advantages that the locking effect of the main shaft is not influenced by unsatisfactory concentricity, no noise is generated during operation and the user feels more certain to the operation.
The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which:
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Referring to
The fastening ring 1 has a through hole 10, and is installed inside the housing 6. The elastic retaining device 2 is disposed in the through hole 10 of the fastening ring 1, and the elastic retaining device 2 has an inner space 20. Elastic portions 22 and cylinder portions 24, respectively arranged as a pair and aligned at correspondingly symmetrical positions, are disposed on a side wall of the inner space 20 and along an axial direction of the inner space 20. Referring to
Referring to
After the aforementioned components are assembled, when the output shaft 5 actively rotates to drive a tool bit, such as a drill bit or a screwdriver bit, a motor of the power tool drives a reduction gear set to rotate, the reduction gear set drives the planetary gear set to rotate and the planetary gear set drives the driving plate 4 to rotate. As shown in
As shown in
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
