A device at high speed spindles

Abstract: A device at spindles, e.g. machine tool spindles for high rotational speeds, which spindles radially outside their rotational axis (R) are equipped with separate elements attached thereto, such as driving and positioning shoulder and counter-weight, whereby said separate elements (4, 5) are secured to the spindle (1) by locking pins (9) arranged to extend through bores (7, 8) arranged at an angle to the rotational axis (R), and adapted during rotation to give the locking pins a component force caused by the centrifugal force, in a direction causing the elements (4, 5) to be wedged, and the locking pins to be pressed into the bores.

Description: The present invention refers to a device at spindles, e.g. machine tool spindles for high rotational speeds, which spindles are equipped with separate elements attached thereto, such as driving and positioning shoulder and counter-weight. A device of this kind is known for example from DE-U-8027894. Such separate elements traditionally have been fitted to the spindle nose, by means of screws engaging into axial, threaded bottom holes in the radial flange of the standardized spindle nose. At the extremely quick-running spindles - up to 20000 rpm and even more - which today occur for some machine tool applications, the high rotational speeds result in centrifugal loads acting on the driving and positioning shoulder and on the counter-weight positioned diametrically opposed thereto, which will be so big, that the screw joints, due to high bending and shearing stresses, will burst during operation, whereby the shoulder and the counter-weight might come loose, and, due to the very high peripheral speed, be thrown away at very high speed, which might lead to serious injuries to personnel and damages to material. The purpose of the present invention is to provide a device at high speed spindles according to the preamble, by means of which the problems related above are solved with a maintained standardized spindle nose, by means of the features defined in the characterizing part of claim 1. Hereinafter the invention will be further described with reference to an embodiment shown in the accompanying drawing. Fig. 1 shows in an end view a spindle nose of a machine tool spindle with driving and positioning shoulder and counter-weight attached thereto in accordance with the invention. Fig. 2 is a cross-section along line II-II in Fig. 1. In Fig. 1 is shown in an end-view a spindle nose 1 of a machine tool spindle with cone 2 an a radial flange 3, situated outside this, and to which is attached a driving and positioning shoulder 4, and a counter-weight 5 positioned diametrically opposed thereto. The shoulder 4 as well as the counter-weight 5 are both in conventional manner fitted to the flange 3 by means of an axially arranged screw 6. Beside that, the shoulder 4 as well as at the counter-weight 5 have provided thereto - in the embodiment shown - two further bores 7, 8 each provided in the flange 3. As can be seen in the cross-section through the spindle nose 1 along line II-II, shown in Fig. 2, wherein the spindle nose is shown only partially, these further bores 7, 8 do not extend axially but under an angle relative to the rotational axis R of the spindle. These bores thus extend from positions at a distance from the rotational axis R of the spindle at the free side of the flange to positions at a bigger distance from the rotational axis R at the rear side of the flange. Each of the bores 7, 8 preferably incorporates a first through portion 7a, 8a, having a smaller diameter, and which opens at the rear side of the flange, and continues in a larger diameter portion 7b, 8b arranged coaxially thereto and opening at the front side of the flange, i.e. on the flange side provided with the cone opening. In each of these larger bore portions 7b, 8b is provided a locking pin 9, which is received, preferably under press fit, in the bigger bore portion 7b and 8b, resp., but which has a bigger diameter than the smaller bore portion 7a and 8a resp., opening at the rear side of the flange. By securing the shoulder 4 and the counter-weight 5 to the spindle nose in this manner, the pins 9 - at the very quick rotation of the spindle - due to the centrifugal force, will urge shoulder and counter-weight by wedge action harder against their grooves in the spindle nose, and at the same time the locking pins also will be more firmly pressed into their drilled holes 7b and 8b, resp., due to centrifugal force. Due to this extra locking effect, which increases with higher running speed of the spindle, it is efficiently prevented that elements attached to the flange of the spindle might come loose and be thrown away. By letting the bores 7, 8 extend right through the flange 2, it is obtained in a simple manner a possibility to dismantle the pins 9 which have been inserted in these bores and which after rotation have been heavily driven thereinto, by driving them out the with a mandrel or a similar tool, which is inserted in the bore straight through the bore portion 7a, 8a with smaller diameter. The invention is not limited to the embodiment shown in the drawing and described in connection thereto but modifications are possible within the scope of the accompanying claims.

Claims: A device at spindles, e.g. machine tool spindles for high rotational speeds, which spindles radially outside their rotational axis (R) are equipped with separate elements attached thereto, such as driving and positioning shoulder and counter-weight, characterized therein, that said separate elements (4, 5) are secured to the spindle (1) by locking pins (9) arranged to extend through bores (7, 8) arranged at an angle to the rotational axis (R), and adapted during rotation to give the locking pins a component force caused by the centrifugal force, in a direction causing the elements (4, 5) to be wedged, and the locking pins to be pressed into the bores. A device as claimed in claim 1, characterized therein, that the locking pins (9) are provided with fit in the different bores (7, 8). A device as claimed in claim 1 or 2, characterized therein, that said bores (7, 8) are provided in a radial flange (3) on the spindle (1). A device as claimed in claim 3, characterized therein, that the bores (4, 5) extend through the flange (3) and at the portion situated farthest from the rotational axis (R) has a bore portion (7a, 8a) of smaller diameter than the locking pin (9) and the portion of the bore (7b, 8b) wherein the locking pin fits with press fit. A device as claimed in anyone of the preceding claims, characterized therein, that the elements (4, 5) are secured to the spindle, besides by the locking pins (9) also by means of screw joints (6) provided in conventional manner.

Inventors: GOETHBERG SVEN, WENDEBERG HANS, GOETHBERG, SVEN, WENDEBERG, HANS, Göthberg, Sven
Applicants: SKF AB, AKTIEBOLAGET SKF
Application year: 1995
Main classification: B23C5
IPC codes: B23B31, B23Q3, B23B19