Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
1998-08-18
2001-02-13
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C271S082000, C101S409000
Reexamination Certificate
active
06186499
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a sheet gripper in a sheet-fed rotary printing press, wherein a spring applies a holding force between gripper fingers and a gripper pad of the sheet gripper.
A sheet gripper of this general type has become known heretofore from U.S. Pat. No. 4,947,748 wherein there is shown and described a sheet gripper element or finger cooperating with a gripper pad. The gripper element is pivotally supported by a gripper housing therefor on a likewise pivotable shaft. In the immediate vicinity of the gripper element, a counteracting stop is secured to the shaft and is operatively connected to the gripper housing by a compression spring. The compression spring is disposed in prestressed condition between the gripper housing and the counteracting stop, so that when the gripper element meets the gripper stop, the full force of the prestressed compression spring comes into effect.
An impact resulting from this encounter can cause the gripper element to spring back from the gripper pad when processing speeds are high, thereby impairing a true-register holding or retention of the sheet that is to be transported. Furthermore, the cylinder carrying the sheet gripper is excited to vibrate.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a sheet gripper in a rotary printing press wherein excitation of vibrations is minimized.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a sheet gripper in a sheet-fed rotary printing press, having a pivotally supported gripper shaft, whereon a gripper element cooperatable with a gripper pad is pivotally disposed and a clamping element is fixedly disposed, comprising a spring element for placing the gripper element and the clamping element into operative contact, the spring element being formed as a leaf spring.
In accordance with another feature of the invention, the sheet gripper includes a fixed fastener disposed at one end of the leaf spring.
In accordance with a further feature of the invention, the sheet gripper includes a gripper housing for the gripper element, the other end of the leaf spring located distal from the fixed fastener being connected to the gripper housing.
In accordance with another feature of the invention, the sheet gripper includes an adjusting device for adjusting a spaced distance between the gripper element and the gripper pad, the adjusting device being disposed between the other end of the leaf spring and the gripper housing.
In accordance with an added feature of the invention, the clamping element is formed with a contact surface engageable by the leaf spring.
In accordance with an additional feature of the invention, the leaf spring is disposable so as to rest uniformly, with prestressing, on the contact surface.
In accordance with yet another feature of the invention, the contact surface is flat, and the leaf spring is curved and rests uniformly with prestressing on the flat contact surface.
In accordance with yet a further feature of the invention, the contact surface has a concave curvature, and the leaf spring has a rectilinear form.
In accordance with yet an added feature of the invention, the curvature extends in a direction from a fastening location at one end of the leaf spring to the other end of the leaf spring located distal from the one end thereof.
In accordance with still another feature of the invention, the curvature of the contact surface corresponds to a bending line assumed by a beam fixedly fastened at one end thereof, when a load distributed over the length of the beam is applied thereto.
In accordance with still a further feature of the invention, the contact surface is formed by a plurality of rails.
In accordance with still an added feature of the invention, the rails are disposed in parallel.
In accordance with still an additional feature of the invention, the sheet gripper includes a compression spring disposed between an abutment of the gripper housing and an abutment of the clamping element.
In accordance with another feature of the invention, the compression spring is slightly prestressed for eliminating bearing play between the gripper housing and the gripper shaft.
In accordance with a concomitant feature of the invention, the gripper element is disposed in a cylinder gap formed in a sheet-transport cylinder of the sheet-fed rotary printing press.
An advantage of the invention is, in particular, that both upon closing and opening of the gripper element, the intensity of impacts and shocks, which occur, for example, when, upon closing, the gripper element meets the gripper pad or, upon opening, a counterpart stop strikes an abutment of the gripper element, is minimized.
In an advantageous feature, the leaf spring according to the invention is provided with a fixed fastener at one end thereof, thereby, in conjunction with a defined contact surface, producing a degressive spring characteristic curve.
A contact surface for the relaxing leaf spring has a concave curvature. The curvature is designed so that the leaf spring rests uniformly thereon with prestressing. Under load, the leaf spring gradually lifts away from the curved contact face, so that the leaf spring has a nonlinear degressive spring characteristic curve, which makes for a gentler closing and opening of the gripper element.
In a preferred embodiment, the curvature takes the form of a bending line that a beam fixedly fastened at one end thereof assumes upon being loaded with a load distributed over the length thereof. As a result of this provision, the leaf spring, when relieved, presses gently against the contact surface until the leaf spring finally reaches a position of repose, wherein a uniform force is established between the leaf spring and the contact surface.
To minimize soiling between the contact surface and the leaf spring, the contact surface is formed of a plurality of narrow rails, spaced apart from one another, which are preferably disposed parallel to one another.
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 sheet gripper in a sheet-fed rotary printing press, 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.
REFERENCES:
patent: 4716828 (1988-01-01), Hartung et al.
patent: 4719854 (1988-01-01), Ruger et al.
patent: 4947748 (1990-08-01), Hiltwein et al.
patent: 5128726 (1992-07-01), Cassano et al.
patent: 5199757 (1993-04-01), Simeth
patent: 5390600 (1995-02-01), Thunker
patent: 5542657 (1996-08-01), Kemmerer et al.
patent: 356 241 (1922-07-01), None
patent: 670 298 (1939-01-01), None
patent: 1 761 308 (1971-05-01), None
Greenberg Laurence A.
Heidelberger Druckmaschinen Aktiengesellschaft
Lerner Herbert L.
Skaggs H. Grant
Stemer Werner H.
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