Hand power tool with a multi-part, manually operable quick-actio

Details Hand power tool with a multi-part, manually operable quick-actio Hand power tool with a multi-part, manually operable quick-actio

1991-05-24

1992-11-10

Parker, Roscoe V.

Abrasive tool making process, material, or composition

With carbohydrate or reaction product thereof

83666, 83698, B24B 4500

Patent

active

051613344

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention concerns a hand power tool with a multi-part, manually operable quick-action chuck for disc shaped tools. These hand power tools are mainly grinding machines. Such a machine is known with a quick-action chuck in accordance with the PCT application DE 87/00577. In the known machine, the disc shaped tools are held on one side against a shoulder of a drive spindle, and on the other side, they are subject to loading from a pressure plate of a chuck. The pressure plate concentrically embraces a threaded part which is axially secured in its position and arranged so that it can be rotated. A hand screw part embraces the pressure plate like a sleeve and, with the pressure plate, forms an annulus in which at least one rolling contact bearing and a drive which couples the hand screw part, the threaded part, and the pressure plate. During screw fixing and tightening of the chuck, the pressure plate is pressed axially against the tool, and the tool is thus pressed against the shoulder on the spindle side. Automatic tightening of the chuck occurs as the hand power tool is switched on. The drive facilitates a transmission with torque increase on tightening. The torque increase will also be effective during slackening of the chuck, by turning the hand screw part, whereby the friction contact between the pressure plate and the tool is cancelled. As soon as this friction contact ceases, the chuck as a whole can be loosened.
A disadvantage of the known hand power tool is a relatively high and uncontrollable chucking power between the pressure plate and the tool due to the automatic chucking during operation of this machine. A further disadvantage is the complicated design of the chuck which is susceptible to faults. Vibrations and dust, in particular, degrade the efficiency of the drive.


SUMMARY OF THE INVENTION

According to the invention, in a hand power tool of the above described type, the chuck has a rolling planetary drive, particularly a recirculating ball drive. This drive couples the hand screw part and the threaded part and the pressure plate.
The following advantages result for the hand power tool of this invention. Following a tool change without any ancillary tools with subsequent operation of the hand power tool, the chucking forces acting on the tool are defined and limited by the recirculating ball drive which acts like a friction clutch. The drive of the chuck is insensitive to dust and vibrations and can be easily cleaned even in its assembled state. It is further possible to retrofit the chuck of the hand power tool which is the subject of this invention, to other existing hand power tools with disc shaped tools, without any particular modification being required.
In one embodiment of the invention, at least one of the rolling contact bearings and spring means, advantageously a spring disc, forms a drive element, which couples the pressure plate, the threaded part and the hand screw part. The rolling contact bearing advantageously has rolling bodies and the rolling bodies are coupled with the threaded part so as to provide transmission of movement. There is a frictional connection between the threaded part and a rolling contact bearing, and also between the rolling bodies of the bearing and the pressure plate. The threaded part is fitted with a retaining ring in the area which is concentrically embraced by the pressure plate. The annulus is sealed in a friction contact by sealing rings placed in grooves, advantageously one in the threaded part and one in the pressure plate.
Advantageously, there are two rolling contact bearings in the chuck, one of which is an axial ball bearing resting against the pressure plate. This axial ball bearing runs on a front face of the disc spring. The other rolling contact bearing is an axial roller bearing resting against a threaded part, which axial roller bearing runs on another front face of the disc spring.
In another embodiment of the invention there are two disc springs provided. One of the disc springs is formed as a one-p

REFERENCES:
patent: 4955744 (1990-09-01), Barth et al.

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