GB1592064A - Chucks - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO CHUCKS (71) We, HAN Ju CHO of 482-3 Sangdo-II dong, Kwanack-ku, Seoul, Korea and YOUNG KAB CHA of 4368 Shinkil-dong, Yeoung Deung Po-Ku, Seoul, Korea, both Korean citizens, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to chucks such as would be used, for example in drilling machines, to receive the shank of the cutting tool, for example a drill bit.

Hitherto, the shell of a chuck has been produced with a bevel gear on its inner face, and the shell must be of high strength to withstand the forces resulting from the insertion of the cutting tool. Also, repeated insertion and removal of cutting tools causes wear on the bevel gear with a consequent reduction in its working life. Also, jaws of conventional chucks are relatively long in comparison with the diameter of the shell, which tends to increase the force required to insert the cutting tool. The wear that can thereby be occasioned to the jaws needs only to be very small before the chuck does not properly grip the cutting tool. In addition to the above, conventional chucks tend to be complex to produce, the complexities, together with the high rate of wear that can be experienced, making such chucks relatively uneconomic.

According to the present invention, a chuck comprises a shell, a body within the shell having a projecting screw threaded stem, a guide bush mounted within and secured against rotation relative to the shell, the guide bush having a central bore within which a nut is located, with connection means between the bore and the nut to prevent relative rotary motion, but which allows relative linear movement therebetween, the nut being in screw threaded engagement with the screw threaded stem on the body, and the nut bearing axially against spring load jaw members mounted in the shell, with the jaw members bearing against the inside face of a frusto-conical end section of the shell.

Thus, relative rotation between the screw threaded stem on the body and the nut, urges the nut into or out of the bore in the guide bush. By drawing the nut into the bore, the chuck jaws can slide up the frusto-conical section and allow the springs to open the jaws to allow the insertion or removal of the cutting tool. By driving the nut out of the bore, the jaws are slid down the frustoconical section to close the jaws against the spring action and onto the shank of a cutting tool inserted between the open jaws. Thus a cutting tool can be placed into the chuck without the application of force. Once the tool is in place and gripped by the jaws, rotary motion imparted to the cutting tool by the drive shaft has the effect of urging the nut out of the bore of the guide bush to maintain the chuck jaws firmly locked on to the shank of the cutting tool.

One embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a sectional side elevation of a chuck according to the invention; Figure 2 corresponds to Figure 1, but shows a cutting tool in place; Figure 3 is a section on the line A-A of Figure 1; and Figure 4 is a section on the line B-B of Figure 1.

In the drawings, a chuck has a shell 1 within which is located a body 2 having a close sliding fit in the shell, the body being mounted on steel balls 3 lying in co-operating recesses in the body and on the inside face of the shell. A hole 4 is provided in the shell to allow the insertion of the steel balls after the body has been positioned in the shell. Below the body a guide bush 5 is provided, secured against relative rotation with respect to the shell such as by being a force fit therein. The guide bush 5 has a central bore 6 having diametrically opposed splines 7, which engage in co-operating recesses in a nut 8, with the nut 8 in engagement with a screw threaded stem 9 extending from the body 2 into the bore 6.

The free end of the nut 8 engages jaws 10 lying within a frusto-conical section 11 of the shell I, the jaws being split jaws with springs 12 to urge them to an open position, and having an outer periphery with a taper conforming to that of the frusto-conical section l l. The body 2 is provided with a recess 13 to receive a drive member 14.

By providing a left hand thread on the stem 9 and in the nut 8, holding the body 2 stationary (and thus the stem 9) clockwise rotation of the shell when viewed in the direction of arrow C causes clockwise rotation of the guide bush 5 and thus to draw the nut 8 up the stem into the bore 6 in the guide bush, thus allowing the jaws 10 to slide up the frusto-conical section 11 of the shell and when the springs 12 open the jaws to allow the insertion (or removal) of a drill bit 15.

Anticlockwise rotation of the shell, with the body stationary, has the opposite effect to close the jaws on to the drill bit. Alternatively, by holding the shell stationary and rotating the body anitclockwise, the nut is drawn up the stem to open the jaws, and clockwise rotation urges the nut down the stem to close the jaws on to the drill bit 15.

This has the effect that in use, the forces applied during a drilling operation are always such as to close the jaws on to the drill bit.

The invention, therefore provides a relatively simple chuck which eliminates the need for the shell to be formed with bevel gear on its inner surface, and allows the insertion and removal of a cutting tool without the need to apply force on the jaws, and yet in use applies a gripping action on the cutting tool which increases as the cutting forces increase, in a manner which minimizes wear on the chuck components.

WHAT WE CLAIM IS:-- 1. A chuck comprising a shell, a body within the shell having a projecting screw threaded stem, a guide bush mounted within and secured against rotation relative to the shell, the guide bush having a central bore within which a nut is located, with connection means between the bore and the nut to prevent relative rotary motion, but which allows relative linear movement therebetween, the nut being in screw threaded engagement with the screw threaded stem on the body and the nut bearing axially against spring load jaw members mounted in the shell, with the jaw members bearing against the inside face of a frusto-conical end section of the shell.

2. An chuck substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. shell I, the jaws being split jaws with springs 12 to urge them to an open position, and having an outer periphery with a taper conforming to that of the frusto-conical section l l. The body 2 is provided with a recess 13 to receive a drive member 14. By providing a left hand thread on the stem 9 and in the nut 8, holding the body 2 stationary (and thus the stem 9) clockwise rotation of the shell when viewed in the direction of arrow C causes clockwise rotation of the guide bush 5 and thus to draw the nut 8 up the stem into the bore 6 in the guide bush, thus allowing the jaws 10 to slide up the frusto-conical section 11 of the shell and when the springs 12 open the jaws to allow the insertion (or removal) of a drill bit 15. Anticlockwise rotation of the shell, with the body stationary, has the opposite effect to close the jaws on to the drill bit. Alternatively, by holding the shell stationary and rotating the body anitclockwise, the nut is drawn up the stem to open the jaws, and clockwise rotation urges the nut down the stem to close the jaws on to the drill bit 15. This has the effect that in use, the forces applied during a drilling operation are always such as to close the jaws on to the drill bit. The invention, therefore provides a relatively simple chuck which eliminates the need for the shell to be formed with bevel gear on its inner surface, and allows the insertion and removal of a cutting tool without the need to apply force on the jaws, and yet in use applies a gripping action on the cutting tool which increases as the cutting forces increase, in a manner which minimizes wear on the chuck components. WHAT WE CLAIM IS:--

1. A chuck comprising a shell, a body within the shell having a projecting screw threaded stem, a guide bush mounted within and secured against rotation relative to the shell, the guide bush having a central bore within which a nut is located, with connection means between the bore and the nut to prevent relative rotary motion, but which allows relative linear movement therebetween, the nut being in screw threaded engagement with the screw threaded stem on the body and the nut bearing axially against spring load jaw members mounted in the shell, with the jaw members bearing against the inside face of a frusto-conical end section of the shell.

2. An chuck substantially as hereinbefore described with reference to the accompanying drawings.