Patent Application
20060244204
1. Field of the Invention
The invention relates to a-sheet brake for a press and has braking elements diverging in the sheet running direction in order to tauten the printing material sheets transversely.
In published, non-prosecuted German patent application DE 39 39 212 A1, a sheet brake is described whose braking elements are formed as suction rings. The suction rings are aligned divergently, that is to say obliquely outward opposite to one other from the center of the machine, so that the printing material sheet is pulled obliquely outward on both sides by the suction rings and is tautened transversely with respect to the sheet running direction. However, the effectiveness of this transverse tautening still requires improvement.
Further prior art is contained in published, non-prosecuted patent applications DE 44 35 988 A1 and DE 196 20 938 A1, corresponding to U.S. Pat. No. 6,056,287.
It is accordingly an object of the invention to provide a sheet brake for a press which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which provides more effective transverse tautening.
The sheet brake for a press according to the invention, has braking elements diverging in the sheet running direction in order to tauten the printing material sheets transversely. The braking elements are driven so as to circulate at a nonuniform speed.
In the sheet brake according to the invention, the braking elements revolve at a nonuniform speed with a uniform printing or machine speed of the press. In this case, the braking elements in sheet contact with the incoming printing material sheets are periodically accelerated and retarded again. The speed profile of the speed of circulation of the sheet brake resulting from this guarantees a particularly high efficiency of the transverse tautening. This is because trials have resulted in the surprising effect that the transverse sheet tautening effected by the divergent oblique alignment of the braking elements is boosted noticeably by the dynamic cyclic operation of the sheet brake.
In one development, the braking elements are mounted in two braking modules and the sheet brake contains only these two braking modules, that is to say no further braking module.
According to a further development, the braking elements are constructed as endless bands or belts.
In a further development, the sheet brake or its motor has a control link to a control device, which controls the nonuniform speed in accordance with a specific speed profile.
Apart from the sheet brake according to the invention, the invention also includes a press equipped therewith and a control method for the speed control of the sheet brake.
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 brake for a 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.
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.
Referring now to the figures of the drawing in detail and first, particularly, to
Each braking module 9, 10 has at least one braking element 14, 15 which circulates about two geometric axes 12, 13 and which, at least in some sections, is aligned obliquely with respect to the sheet running direction 7. With respect to
In the example shown, each braking element 9, 10 has two round belts guided in parallel as the braking elements 14, 15, the braking runs of the round belts that make contact with the printing material sheets 6 during braking and transverse tautening being sections of the braking elements 14, 15 aligned obliquely with respect to the sheet running direction 7. In the region of its braking run, each braking element 14 of the first braking module 9 is inclined with respect to the left-hand sheet side edge at an angle of inclination to be measured relative to the sheet running direction and amounting to a few degrees. In the region of its braking run, each braking element 15 of the second braking module 10 is aligned with respect to the right-hand sheet side by an angle of inclination which is just as large but has the opposite sign. Consequently, the braking elements 14, 15 diverge and effect the transverse tautening of the printing material sheet 6 via a frictional connection.
The braking modules 9, 10 in each case contain a suction opening 16 to which vacuum can be applied in order to attract the printing material sheet 6 onto the braking elements 14, 15 by suction.
At curve point A, the printing material sheet 6 is attracted by the suction openings 16 and, consequently, brought into contact with the braking elements 14, 15 which, at this time, are circulating at the maximum brake speed VB/max, which is lower than the maximum sheet speed vS/max or could be equal to the maximum sheet speed vS/max. The curve point A designates what is known as the jumping time, at which the printing material sheet 6 jumps onto the sheet brake 4.
At the curve point B, the grippers of the gripper bar 5 open, so that the printing material sheet 6 is braked by friction by the sheet brake 4 between the curve point B and the curve point C. The sheet brake 4 advantageously already tautens the printing material sheet 6 in the time interval between the curve points A and B, that is to say while the printing material sheet 6 is still held firmly at its leading edge by the gripper bar 5 and is transported in the sheet running direction 7.
At the curve point C, the sheet speed vS is exactly as high as the maximum brake speed vB/max. Between the curve points A and C there is a sliding phase 17 of the printing material sheet 6, in which the latter slides on the braking elements 14, 15 with slippage in the sheet running direction 7. From the curve point C as far as the curve point D, the braking elements 14, 15 and the printing material sheet 6 lying on the latter move at a uniform, common speed vS=VB, which corresponds to the maximum brake speed VB/max.
From the curve point E as far as the curve point F, the braking elements 14, 15 together with the printing material sheet 6 move with a uniform, common speed vS=VB, which corresponds to the minimum brake speed vB/min.
From the curve point D as far as the curve point E, a reduction in the brake speed vB takes place (braking phase), so that the braking elements 14, 15 and the printing material sheet 6 are retarded together.
Between the curve point C and the curve point F, there is what is known as an adhesion phase 18, in which there is no speed difference in the sheet running direction 7 between the braking bands 14, 15 and the printing material sheet 6 and adhesive friction is virtually present. In the adhesion phase 18, the lateral stretching (transverse tautening) of the printing material sheet 6 also takes place as a result of the braking elements 14, 15 pulling the printing material sheet 6 apart laterally from inside to outside in the process.
At the curve point F, the printing material sheet 6 leaves the sheet brake 4 and, at the curve point G, comes to rest on the delivery stack 8. Between the curve points F and G there is what is known as the free flight phase 19 of the printing material sheet 6, in which the latter sinks down onto the delivery stack 8.
From the curve point E as far as the curve point L, the sheet brake 4 runs at the minimum brake speed vB/min, the curve point H designating the end of the clock cycle of the preceding printing material sheet and the start of the clock cycle of the following printing material sheet 6.
The clock cycles of the dynamically driven sheet brake 4 are synchronized with what is known as the machine angle (rotary angular position) and the machine speed of the press by an electronic control device 20 (see
From the curve point L as far as the curve point M, which is chronologically before the curve point A and in which the sheet brake 4 has reached the maximum brake speed vB/max again, the brake speed vB is increased (acceleration phase).
From the curve point M as far as the curve point D, the sheet brake 4 maintains its maximum brake speed vB/max.
The graph illustrated in
The control device 20 drives a motor 21 driving the circulating movement of the sheet brake 4 (see
The advantage with the speed profile in
In order to limit the jolt occurring within the movement of the sheet, a speed profile according to
This application claims the priority, under 35 U.S.C. ยง119, of German application DE 10 2005 020 251.9, filed Apr. 28, 2005; the prior application is herewith incorporated by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 020 251.9 | Apr 2005 | DE | national |
