Spindle Clamp For Tool Holder

Abstract

A machine tool clamping device for releasably holding a tool holder having a tapered shank and a knob protruding from the tapered shank, the clamping device having: a spindle, rotatable about an axis, and having a tapered socket at a lower end thereof and an axial passage, the tapered socket being complementary in shape to the shank of a tool holder. Clamping members are pinned to the spindle and extend into the axial passage, the clamping members being pivotal between a clamped position in which the clamping members clamp the tool holder knob, and an unclamped position in which the clamping members release the tool holder knob. A drawbar is slidable within the spindle axial passage between the clamping members, the drawbar having a surface that acts to pivot the clamping members between the clamped and unclamped positions depending on the position of the drawbar within the axial passage. A spring is arranged between the drawbar and the spindle to bias the drawbar to the clamped position.

Claims

1. A machine tool clamping device for releasably holding a tool holder having a tapered shank and a knob protruding from the tapered shank, the clamping device comprising: a spindle, rotatable about an axis, and having a tapered socket at a lower end thereof and an axial passage, the tapered socket being complementary in shape to the shank of a tool holder; clamping members pinned to the spindle and extending into the axial passage, the clamping members being pivotal between a clamped position in which the clamping members clamp the tool holder knob, and an unclamped position in which the clamping members release the tool holder knob; and a drawbar slidable within the spindle axial passage between the clamping members, the drawbar having a surface that acts to pivot the clamping members between the clamped and unclamped positions depending on the position of the drawbar within the axial passage.

2. The clamping device according to claim 1, further comprising a spring arranged between the drawbar and the spindle to bias the drawbar to the clamped position.

3. The clamping device according to claim 1, wherein the clamping members are arranged spaced apart at 180 degrees about the spindle axis, each of the clamping members having a lower end that includes a hook portion having a radially inwardly extending member for clamping the tool holder knob.

4. The clamping device according to claim 1, wherein the clamping members are curved outwardly from top ends to bottom ends.

5. The clamping device according to claim 1, wherein the clamping members are curved in a semicircular shape.

6. A machine tool clamping arrangement, for holding a tool holder onto a hollow spindle, for tool holder having a head, the hollow spindle having an axial shaft passage; clamping members that are pinned to the hollow spindle and are located at least partially inside the hollow spindle to pivot between a clamped and unclamped orientation, the clamping members being outwardly curved and being pinned by pins at central locations of the clamping members to the hollow spindle, wherein upper portions of the clamping members are arranged to be spread apart by a taper on a draw bar as it is raised, causing lower portions of the clamping members to pinch together to be positionable beneath the head of the tool holder.

7. The machine tool arrangement of claim 6, wherein the hollow spindle has windows through a sidewall of the hollow spindle, and the pins that pin the clamping members to the hollow spindle are each fit in a radial direction into a respective window by way of pin-receiving slots formed in the hollow spindle on opposing sides of each window.

8. The machine tool arrangement of claim 6, wherein a spring is fit between the hollow spindle and a drawbar to create a clamping force on the clamping members via movement of the drawbar to lock the tool holder to the spindle.

9. The machine tool arrangement of claim 6, wherein the drawbar has a ring fixed on an upper portion thereof and the hollow spindle has a ring fixed on the spindle and spaced apart from the drawbar ring, and the spring is arranged between the two rings, surrounding the drawbar and urging the drawbar to cause a tapered end of the drawbar to spread the top ends of the clamping members and pinch the bottom ends of the clamping members toward each other to urge the tool holder tightly into the spindle.

10. The machine tool arrangement of claim 9, wherein the spring comprises a stack of spring washers.

11. The machine tool arrangement of claim 6, wherein the tool holder has a head, and the clamping members provide a positive locking of the tool holder to the spindle as the upper portions of the clamping members are braced against the drawbar to prevent any movement, and the lower portions are braced under and against the head of the tool holder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a vertical section illustrating a clamping device according to the present invention; and

[0019] FIG. 2 is a fragmentary sectional view taken generally along line 2-2 of FIG. 1, with some portions removed for clarity.

DETAILED DESCRIPTION

[0020] While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an io exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

[0021] An exemplary embodiment of a clamping device provides a hollow cylindrical spindle 10 having a tapered socket 16 formed on one end thereof which holds a tapered shank tool holder 20. The tool holder holds a tool, such as a bit 21. The spindle 10 is driven in rotation by a motor M, which drives the tool holder 20 and the tool 21 to do work on a workpiece.

[0022] The spindle 10 has an axial passage 22 open to the tapered socket 16. The spindle 10 is supported for rotation by upper and lower annular bearings 30 and 32. The upper bearing 30 includes a stationary annular race 30a, a rotating annular race 30b zo and a plurality of ball bearings 30c between the races 30a, 30b. The lower bearing 32 includes a stationary annular race 32a, a rotating annular race 32b and a plurality of ball bearings 32c between the races 32a, 32b.The tapered shank tool holder 20 has a tapered shank 36 which is complementary to the tapered socket 16, and a knob 38 which protrudes from the tapered end thereof. Furthermore, the spindle 10 has two keys 40, 42 which fit into two key channels 44, 46 on the tapered shank tool holder 20. The keys are formed on the perimeter edge of the opening in tapered socket 16.

[0023] A drawbar 50 is arranged slidable vertically within the passage 22 of the spindle 10. The drawbar 50 is surrounded by a spring 52 may comprise a stack of Belleville spring washers 54. Other types of springs, such as a coil spring, are encompassed by the present invention. A ring 60 that is fixed to the spindle 10 supports the spring which urges against a ring 66 fixed to the drawbar 50, thus urging the drawbar 50 upward with io respect to the spindle 10. The drawbar 50 has a tapered bottom region 70.

[0024] Two clamping members 74, 76 are located within windows 77, 78 formed through the side wall of the spindle 10. The clamping members 74, 76 are pivoted at pins 80, 82 at central areas thereof to the spindle 10 in the windows 77, 78, to pivot or rotate about horizontal axes. Upper end portions 74a, 76a of each clamp element face the drawbar 50 and are in sliding contact with the drawbar. The clamping members 74, 76 are curved with lower end portions 74b, 76b extending inward to underlie the knob 38 of the tool holder 20 when in the clamped orientation.

[0025] A cylinder 108 is provided above the spindle 10. The draw bar 50 has a top end 109 extending above the spindle 10 and below the cylinder 108. The cylinder 108 includes a piston 110 slidable therein. The cylinder 108 receives hydraulic or pneumatic fluid P under pressure into a chamber 111 to move the piston 110 downward against the top end 109 of the drawbar 50 to force the drawbar 50 downward with respect to the spindle 10 against the urging of the spring 52.

[0026] When the drawbar 50 is moved downward against the urging of the spring 52, lowest portions 112, 114 of the drawbar 50 contact and force apart the lower end portions 74b, 76b of the clamping members as the clamping members 74, 76 pivot about the pins 80, 82. At the same time, the upper end portions 74a, 76a move inwardly as the clamping members 74, 76 pivot about the pins 80, 82 as the taper of the drawbar region 70 narrows. As the lower end portions 74b, 76b of the clamping members separate, the knob 38 escapes the grasp of the clamping members 74, 76, and the tool holder 20 disengages from the spindle 10.

[0027] Although two clamping members are shown arranged at U.S. Pat. No. 180 degrees across a center axis of the drawbar, three clamping members arranged at U.S. Pat. No. 120 degrees spacing around the center axis of the drawbar. Other numbers of clamping members could also be used.

[0028] The clamping members 74, 76 are advantageously curved to reduce internal stress on the clamping members 74, 76 under clamping pressure.

[0029] FIG. 2 shows in section the clamping members 74, 76 being diametrically opposed across the spindle 10. During assembly, the pins 80, 82 that pivotally mount the clamping members 74, 76 can be fitted into the windows by way of radial slots 124, 126, 134, 136 extending from an outside of the spindle 10 inwardly to the position of mounting of the pins 80, 82. The pins 80, 82 can be fixed into the slots 124, 126, 134, zo 136 by plugs or by welding, or other known means. Alternately, the pins can be pushed through tangential bores 138, 142 to be also pushed through the clamping members 74, 76, prepositioned in the windows 77, 78.

[0030] The clamping members 74,76 provide a positive locking of the tool holder to the spindle as the upper portions 74a, 76a of the clamping members are braced against the drawbar to prevent any movement, and the lower portions 74b, 76b are braced under and against the knob 38 of the tool holder. The reaction forces on the clamping members are taken up by the pins 80, 82.

[0031] Although the spring 52 is shown to create a clamping force on the clamping members to lock the tool holder to the spindle, it is also possible that instead of a spring, pneumatic or hydraulic pressure could be used against a piston to create the clamping force on the clamping members to lock the tool holder to the spindle. Alternately, a solenoid created force or a magnetic force could be used to create the clamping force on the clamping members to lock the tool holder to the spindle. Due to the positive locking of the clamping members, a reduced clamping force would be needed to mechanically lock the tool holder to the spindle.

[0032] From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.