Turning – Lathe – Having hollow cutter head
Patent
1991-11-20
1993-05-04
Bilinsky, Z. R.
Turning
Lathe
Having hollow cutter head
82 73, B23B 512
Patent
active
052071367
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a rotary head machining unit holding at least two pivoting tools for machining a non-rotating part centered on the axis of rotation of the head, comprising:
a frame to which are attached a rotor comprising the rotary head and a spindle integral with it, the rotor having an axial conduit and being connected with rotary drive means;
axial means for guiding said part, said means being attached with bearings to the spindle or the rotary head;
means for maintaining and axially displacing the part;
at least two tool supports attached to the rotary head so as to pivot around respective axles parallel to the axis of rotation, each support having a transversely disposed control lever;
and means for controlling pivoting which cooperate with said levers and comprise at least one rotary control element which is movable in axial translation within the rotor and is attached to a translation device, and pairs of contact means disposed on each control lever, respectively, and on the corresponding rotary control element, each pair of contact means comprising a guiding surface and a support surface in contact with the guiding surface in a position which varies as a function of translation of the rotary control element.
Rotary heads for pivoting tools have long been used for screw cutting. They are able to machine metal parts in the form of a long wire traversing the rotor axially. Units of this type presently on the market generally have two or three tools, certain ones being independently controlled. To avoid problems of centrifugal acceleration resulting from head rotation, the tool supports pivot around respective axles which are eccentric in relation to the axis of rotation.
In such a unit the means for controlling pivoting of the tool supports play an essential role in machine performance with respect to precision and work speed. In one known system, pivoting of the tool holder is controlled by a rotary element with a conical surface upon which the control lever of the corresponding support rests. This element is integral with a sliding ring displaced by means of a translation mechanism. The lever is held in place on the conical surface by the effects of centrifugal acceleration acting on a counterweight, so that there is no play in the transmission.
This control system has certain disadvantages. Since the axis of the conical surface is relatively far from the pivoting axis of the corresponding tool support, the relationship of transmission between axial movement of the conical surface and radial tool displacement is linear for only the very smallest displacements. This precludes any usefulness for finishing fairly large diameter parts without a compensating device. Imprecise finishing results, even if numerical control is used. Furthermore, to control several tools independently, several concentric slidable sockets are needed, each having a cone-shaped portion activating the corresponding lever. This leads to very complex mechanics requiring great precision. In addition, the conical surfaces must be located on open segments spread out along the rotor periphery, thereby making the unit very susceptible to centrifugal force. This mechanical complexity, the resulting cumbersomeness and the effect of centrifugal force prevent very high rotation speeds, and thus high work speed. Finally, it is practically impossible to increase the number of tools beyond three without increasing the complexity and dimensions of the rotor, which would result in further reductions in performance.
European Patent Application No. 12 154 describes a rotary head holding a pair of opposing tools, each having a pivoting support backed by a spring and held by a radially adjustable slide block. The position of the slide blocks is controlled by axial displacement of a cover with a conical interior surface upon which the slide blocks rest. This control mechanism, located relatively far from the axis of rotation, is large and heavy, and does not allow for separate control of each tool. U.S. Pat. Nos. 3,866,495 and 3,817,1
REFERENCES:
patent: 1646758 (1927-10-01), Matthews
patent: 3528327 (1970-09-01), Lindemann
patent: 3817130 (1974-06-01), Goeke
patent: 3866495 (1975-02-01), Goeke
Evard Daniel
Piguet Pierre-Louis
Rossetti Hubert
Bilinsky Z. R.
Esco S.A.
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