Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Reexamination Certificate
1998-12-21
2001-06-05
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
C074S116000, C101S147000, C101S247000, C101S352080
Reexamination Certificate
active
06240795
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a cam-controlled power differential gear for a sheet acceleration system, which is formed of a pregripper having an acceleration course determinable by a control cam driven at a single speed.
In sheet-fed rotary printing presses, it is customary for a sheet oriented on a feeding table to be gripped by a sheet acceleration system formed as a pregripper, and accelerated up to processing speed. After transferring the sheet to a sheet transport drum, the pregripper is decelerated down to a standstill and then is reaccelerated in the direction of the feeding table, with a subsequent deceleration down to a standstill at the feeding table. Because of the cyclical motion of the sheet acceleration system over a machine cycle, forces of inertia are generated which create torques acting upon the control cam; these torques are superimposed upon the torques operative in the drive system and thus cause torque fluctuations which, in the final analysis, cause registration errors and doubling or double impressions, respectively, which consequently lead to defective quality or a rejection of the printed products. The torque fluctuations also cause increased wear of the printing press.
From the published German Patent Document DE 41 09 824 A1, a cam-controlled power differential gear has become known heretofore which minimizes the aforedescribed problems. To that end, four compensating masses are provided, offset from one another by 90°, which engage with a common compensating cam. Rollers respectively assigned to one compensating mass pass per period, i.e., one reciprocating pivoting motion of the pregripper, through two identical motion segments without a resting phase at a sheet transfer location on the feeding table. The length of the resting phase is in fact determined solely by the reversal point of the pregripper on the feeding table. This very severely restricts the free choice of a pregripper motion principle.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a cam-controlled power differential gear for a sheet acceleration system wherein the principle of motion for the pregripper is freely selectable.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a cam-controlled power differential gear transmission for a sheet acceleration system, which is formed of a pregripper having an acceleration course determinable by a control cam driven at a single speed, comprises two compensating masses pivotably supported diametrically opposite one another, and respective control cams assigned to the compensating masses, respectively, for controlling the pivoting motion thereof.
In accordance with another feature of the invention, the control cams for controlling the pivoting motion of the compensating masses are disposed on a common axis, and the differential gear transmission includes another control cam for generating a pivoting motion of the pregripper, the other control cam being disposed on an axis parallel to the common axis.
In accordance with a further feature of the invention, the control cams for controlling the pivoting motion of the compensating masses and another control cam for generating a rocking motion of the pregripper are disposed on a common axis.
In accordance with an added feature of the invention, one of the control cams is an inner control cam, and the other of the control cams is an outer control cam.
In accordance with an additional feature of the invention, the control cams for controlling the pivoting motion of the compensating masses are fixed to a machine frame, and the other control cam for generating a pivoting motion of the pregripper is disposed in a rotatably drivable manner.
In accordance with yet another feature of the invention, the pregripper has a resting phase on a feeding table amounting to a machine angle &phgr;=approximately 60°.
In accordance with yet an added feature of the invention, the compensating masses are able to execute a pivoting motion even during the resting phase.
In accordance with a concomitant feature of the invention, the power differential gear transmission includes control rollers, respectively, assigned to the control cams, each of the control rollers having a roller lever, and each roller lever having an abutment for bracing against a compression spring.
An advantage of the invention is that by the free choice of the principle of motion of the pregrippers, the resting phase upon sheet transfer from the feeding table can be given such a length that a calm sheet transfer is possible.
If an angle of approximately 60° is provided, the resting phase of the pregripper on the feeding table is very long, thus assuring a calm sheet transfer.
Pivotally supported compensating masses are provided at locations diametrically opposite one another. This provision achieves good balancing of the power differential gear transmission.
A compression spring provided between control rollers for the pivoting motion of the compensating masses improves the contact of the control rollers with the various control cams to which they are assigned.
In the second exemplary embodiment, provision is made for the control cam effecting the oscillating motion of the pregripper to be disposed on a common axis of the control cams effecting the pivoting motion of the compensating masses.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a cam-controlled power differential gear for a sheet acceleration system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein:
REFERENCES:
patent: 3888129 (1975-06-01), Velan et al.
patent: 4416198 (1983-11-01), Rasenberger
patent: 4583728 (1986-04-01), Mathes
patent: 4854236 (1989-08-01), Thünker et al.
patent: 5544546 (1996-08-01), Döpke
patent: 4109824A1 (1991-10-01), None
patent: 19532856A1 (1997-03-01), None
Fenstermacher David
Greenberg Laurence A.
Heidelberger Druckmaschinen Aktiengesellschaft
Lerner Hebert L.
Stemer Werner H.
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