Gear cutting – milling – or planing – Milling – Cutter spindle or spindle support
Patent
1991-10-18
1992-09-15
Bilinsky, Z. R.
Gear cutting, milling, or planing
Milling
Cutter spindle or spindle support
279131, 408240, B23B 3114
Patent
active
051471655
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a centrifugal spindle and more particularly to the control of collets to grip the shank of tools of different sizes.
In a typical spindle, the shaft has a collet for gripping tools which can be opened and closed by means of a signal.
A typical method of operation of these known spindles is to utilize disc springs built into the shaft and a pneumatic ram system to compress the springs when required to open the collet. When the air supply to the ram system is released, the ram withdraws and the disc springs draw the collet into the shaft, firmly clamping the tool shank in position. These known spindles have the disadvantage that the pneumatic system is somewhat cumbersome.
An aim of the present invention is to overcome the above mentioned disadvantage and provide an improved and simplified control of the collet to grip the shank of the tools.
According to the present invention there is provided a centrifugal spindle comprising a hollow shaft having a collet at one end for gripping a tool shank and a centrifugal loading means housed within the hollow shaft, wherein the loading means comprises two coaxial pistons spaced from each other and linked by flexible connecting members, one piston being secured axially to the hollow shaft while the other piston is secured to the collet so that rotation of the shaft causes the flexible connecting members to move radially outwards under centrifugal force to draw the piston and collet into the hollow shaft gripping the tool shank.
In a preferred construction of the centrifugal spindle, weights are connected to the flexible members intermediate their ends.
Preferably, there are two flexible connecting members with two intermediate weights.
Conveniently, the flexible connecting members have a flat cross-section and the weights have a curved surface, the connecting members being formed integral with the pistons and weights.
An embodiment of a centrifugal spindle and collet according to the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is an axial cross-section of a centrifugal spindle;
FIG. 2 is a side elevation of the centrifugal loading means;
FIG. 3 is a plan view of the loading means shown in FIG. 2, and
FIG. 4 is a cross-section taken along the line 4--4 of FIG. 3.
The centrifugal spindle comprises a hollow shaft 1 fitted with a collet 2 fixed to a centrifugal loading means generally indicated at 3. This loading means comprises two coaxial pistons 4 and 5 linked together by flexible members 6. Intermediate bob weights 7 are formed integrally with the members 6 and the pistons 4 and 5.
One piston 4 is secured axially to one end of the hollow shaft 1 by a screw-threaded bolt 8 which passes through an annular member 9 engaging a shoulder 10 of the shaft and is screwed into the end of the piston 4. Annular member 9 is secured by suitable means to the hollow shaft 1. The other piston 5 is connected axially with the collet 2 by a screw-threaded pin 11, the ends of which screw into the collet 2 and piston 5, respectively.
As can be seen in the cross-section in FIG. 4, the flexible members 6 have a flat cross-section and are integrally formed with the pistons 4 and 5 and bob weights 7 which have a curved outer surface which conforms to the inner diameter of the hollow shaft.
In operation, when the centrifugal spindle is rotated about its longitudinal axis, centrifugal force F1 acts upon both the flexible members 6 and bob weights 7. This force F1, causes both the flexible members 6 and the bob weights 7 to move radially outwards. The geometric form of the flexible members 6 is such that the radial forces generated by the bob weights 7 are greatly amplified in the axial direction. The axial force F2 so generated draws the collet 2 into the shaft 1, thus providing the desired grip on the tool shank 12.
The problem with a centrifugal collet is that the radial forces generated increase with the square of the speed and, if one is to achieve an adequate clamping force at relatively low
REFERENCES:
patent: 1990525 (1935-02-01), Chancellor
patent: 2686682 (1954-08-01), Csaki
patent: 3625528 (1971-12-01), Sage
Bilinsky Z. R.
Federal Mogul Westwind Air Bearings Ltd.
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