Turning – Process of turning
Patent
1983-09-16
1986-08-26
Husar, Francis S.
Turning
Process of turning
409200, B23C 306, B23C 518
Patent
active
046075500
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a crankshaft turning machine operating on the dual cam, or double eccentric, principle, in which a cutterhead is carried in an internal cam and the latter is carried in an external cam rotatable in a casing, and both cams being adjustable as to their mutual position.
It is known in turning machines operating on the dual cam, or double eccentric, system, when machining the crankpins of crankshafts to perform the machining of the cheeks by a plunge cut. The plunge cut operation starts out from a concentric position of the gyro cutterhead with respect to the workpiece axis, i.e., from a position from which the gyro cutterhead can move to each crankpin to machine it.
During the plunge cut operation, the gyro cutterhead revolves in the conventional manner. Its center moves on a circular path of less than 360.degree.. The magnitude of the rotatory movement or of the turning angle depends on the diameter of the crankpin. In this process, most of the machining of the crankshaft cheeks is comleted.
As soon as the crankpin diameter is reached, i.e., the present turning angle has been covered, the shift is made to circular feed, and then the crankpin is machined down to the specified diameter. The plunge-cutting operation is controlled by the internal cam; during the plunge cutting operation the external cam is locked up.
After the crankpin diameter is reached, the internal cam is coupled with the external cam in order to perform the circular feed in which the center of the gyro cutterhead moves around the crankpin being machined.
In order to achieve a coupling between the inside and the outside cam at the end of the plunge cutting operation, after the crankpin diameter has been arrived at, it is known to interrupt the movement of the internal cam and couple the two cams together. In this changeover, a reduction of the rotatory speed of the internal cam takes place or the internal cam is stopped, so that a position of the gyro cutterhead results in which the forces occurring become very low. Furthermore, as a result of the feed-stopped phase, more than one of the cutting edges of the gyro cutterhead pass over the cutting point. This again causes a flatting of the crankpin. Such flatting makes it necessary to provide for a larger oversize on the crankpin so as to make it possible to correct any flats in the next circular feed.
It is the object of the invention to design the machine of the kind mentioned above such as to avoid the formation of flats upon the changeover from the plunge cut to the circular feed.
This object is achieved in accordance with the invention by having the transition from the plunge cut to the circular cutting operation take place without a phase in which the feed is stopped.
Due to the fact that no feed-stopped phase takes place in the transition from the plunge cutting operation, no abrupt force variations occur. Also a plurality of the cutters of the cutterhead do not pass over a cutting point. Thus, flatting is prevented, and time is saved.
The avoidance of the feed-stopped phase can be achieved in a variety of ways. It depends on which of the two cams is driven, or on whether both cams are driven.
If, for example, the internal cam is driven, the external cam can be coupled to the internal cam after the end of the plunge cut, without the occurrence of any phase in which the internal cam is stopped. If the shafts driving the two cams are concentric, this can be accomplished by providing on the shaft driving the internal cam an axially displaceable coupling sleeve having a pin projecting parallel to the shaft axis, which can be coupled with a driver mounted on the shaft driving the external cam. The disk-like driver can have a ramp surface forming a recess and terminating in an abutment. In the coupling operation, the pin of the coupling sleeve runs on this ramp surface until it engages the abutment and drives the external cam through the driver. It is desirable that the abutment be prolonged by a bore into which the pin of the coupling bushing snaps.
In this kind of c
REFERENCES:
patent: 4276794 (1981-07-01), Berbalk
patent: 4423991 (1984-01-01), Derr
Husar Francis S.
Kearns Jerry
Oerlikon-Boehringer GmbH
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