Drill or milling head

Details Drill or milling head Drill or milling head

1999-08-24

2001-06-12

Briggs, William (Department: 3722)

Gear cutting, milling, or planing

Milling

With cutter holder

C279S050000, C279S074000, C279S134000, C408S240000

Reexamination Certificate

active

06244798

ABSTRACT:

BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a drill or milling head. In particular, this drill or milling head is suited for machines which serve to produce fine structures, such as printed circuit milling machines and engraving machines. For the purpose of changing the tool in similar types of drill or milling heads, it is known to provide a rod for actuating collet chucks which is extended through a hollow drive shaft of the motor or of the drill or milling head and engages with the collet chuck by means of gearing. In order to open the collet chuck, the actuating rod is pushed in the direction of the collet chuck, either manually by means of a hand-activated knob found above the motor or pneumatically, which causes the collet chuck to be turned, i.e. screwed, and thereby opened. However, for this the motor must first be turned off. When this is forgotten, the drill or milling head is damaged since then the actuation rod, which is not rotating, comes into contact with the collet chuck, which is rotating. Then, it can even happen that the collet chuck comes completely off the drill or milling head and thereby poses the danger of injury to people.
A drill or milling head with a rapid change mechanism is known German Patent Document from DE 34 34 699 C2. However, in this drill or milling head it also is disadvantageous that during the changing of a tool which is in place, there is at least a danger of damaging the drill or milling head if the motor accidentally was not previously switched off.
SUMMARY OF THE INVENTION
Therefore, it is the object of the invention to provide a similar type of drill or milling head, with which if one neglects to first switch off the motor when changing the tool, there is no damage to the drill or milling head and no possibility of the danger of injury, and thereby to simplify servicing and make it safer.
Invention as described hereinafter.
Since the force necessary for the axial displacement of the collet chuck is transmitted via a friction clutch, it is not possible upon opening for a collet chuck which is accidentally still turning to come into interlocking contact with a part which is not rotating. Rather, the force of axial displacement is transmitted to the collet chuck or the shaft, which is fixed to the collet chuck, using a frictional contact via the friction clutch.
Preferably, the friction clutch is comprised of an axial part which can be moved with respect to the shaft and a part which can be displaced axially and which is fixed to the shaft, where both the parts have surfaces which conform to each other and which come into contact upon actuation of the rapid change mechanism. There, it is provided that both parts are supported pressing against the force of one spring each on their tool side. Thus, it is assured that, when in a state of rest, there is a distance between both parts and that when they are put together, in the eventuality that the part which is fixed to the shaft is turning, only friction which doesn't cause damage to a drill or milling head will occur between the surfaces.
In accordance with a preferred embodiment of the invention, the part which can be moved with respect to the shaft is cylindrical and is located concentrically with respect to the shaft and has, on the end near the motor, a ring-shaped shoulder. The part which is fixed to the shaft is an annular seal with an encircling fitting strip. On the ring-shaped shoulder and the encircling fitting strip, the conforming surfaces are designed flat and vertical with respect to the shaft.
The rapid change mechanism can be actuated manually by means of a handle. There, it can also be provided that the handle can be locked in the position in which the collet chuck is open. This provides the advantage that the operator has both hands free for handling the drill or milling tool. In contrast, when the rapid change mechanism of the prior art is actuated manually, the actuation knob must remain pressed throughout the whole replacement process.
The handle can, for instance, be a lever which has a handle section and a functional section, which is located inside the housing of the drill or milling head. There, it is provided that this functional section of the lever forms an acute angle with a horizontal plane when in resting position and a right angle with the shaft when in an actuating position, and furthermore is adjacent on the side near the motor to a stationary surface of the drill or milling head and is adjacent on the side near the tool to the part which is moveable with respect to the shaft. When in the actuating position, the functional section of the lever has a larger maximal extension in the axial direction than in the resting position. Thus it is that when the lever is moved from its resting position to its actuating position, the part of the friction clutch which is moveable with respect to the shaft is pushed to the end of the drill or milling head which is near the tool, and the shaft or collet chuck is thereby pushed with it, as described in further detail below, in order to thus bring about the opening of the collet chuck.
The functional section of the lever is preferably ring-shaped and arranged concentrically with respect to the shaft. If the exterior diameter of the functional section is equal to the interior diameter of the housing and the exterior of the functional section is curved convexly, it can be that this is adjacent to the housing of the drill or milling head at every place along its total circumference, excluding the region where the handle section is located. In this way, the lever can only be moved in its angular placement with respect to the shaft and if necessary for locking can be turned slightly around the axial direction of the drill or milling head, but aside from this is stationary. The handle section extends through an opening in the housing.
The maximum extension of the functional section in the axial direction, which can change depending on its position, is preferably achieved in that on the functional section of the lever, on the same side as the tool, in the plane which is perpendicular to the longitudinal axis of the lever and in which the shaft lies when the lever is in actuating position, a cam is disposed on each side of the shaft and another cam is disposed on the same side as the motor, across from the handle section of the lever. The two cams on the tool side and the cam on the motor side are thus staggered at 90°. Therefore, the functional section, when in a horizontal position, i.e. in the actuating position, has a larger axial extension than in the tilted position of the resting position.
Upon movement of the lever from its resting position to its actuating position, the two cams on the tool side press against a stopping surface of the part which is moveable in the axial direction with respect to the shaft. This then pushes against the ring seal, which is affixed to the shaft. Through actuation of the lever, the shaft is thus pushed towards the tool-side end of the drill or milling head. Along with the shaft, the collet chuck is also displaced with respect to the clamping sleeve. As a result, the collet chuck opens, whose gripping arms lie, in the end section of the clamping sleeve, against an inner surface of the clamping sleeve which tapers conically up to the motor in an axial direction.
The rapid change mechanism can also be actuated pneumatically.
It can be provided that, in order to enable an easy separation of the motor and drill or milling head, a drive shaft of the motor and the shaft of the drill or milling head are connected to each other via a clutch. Preferably, the clutch involved is an elastic clutch, so that oscillations in the axial direction are absorbed.
If necessary, the drill or milling head can be connected to different motors very easily via a clutch plate. The result is a modular building method for a drill or milling head which constitutes a completely autonomous unit with a mechanism for quickly and safely changing the tool.


REFERENCES:
patent: 2370729 (1945-03-01), H

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