Claims
- 1. A sheet transfer apparatus for a rotary printing machine capable of successive printing selectively on one or both sides of a sheet, comprising a transfer cylinder mounted between the side walls of said machine for rotation about its central axis and being provided adjacent the surface thereof with a fixed transverse bar and with a rotatable shaft spaced therefrom, gripping means secured to said shaft in opposition to said bar, said bar and said gripping means adapted to receive the edge of a sheet therebetween, and means for selectively actuating said shaft to cause said gripping means to engage said transverse bar and hold said sheets during rotation of said cylinder, comprising a fixed centering ring mounted between said transfer cylinder and one side wall coaxially with the axis of rotation of said transfer cylinder, said centering ring having a pair of circular segments secured to opposed peripheral faces of said centering ring adjacent each other, said segments having radially extending circular cam surfaces, roller means carried at one end of said shaft adjacent said centering ring for engaging the cam surfaces of each of said circular segments, means for biasing said roller means to engage with said cam surfaces, said engagement causing said gripping means to be activated into engagement with said transverse bar, the first of said segments being fixed with respect to said centering ring and the second of said segments being circumferentially adjustable with respect to said first of said segments to vary the length of engagement of said rollers with said cams whereby the point at which said grippers are free from engagement with said transverse bar is adjustable relative to the degree of rotation of said transfer cylinder.
- 2. A sheet transfer cylinder according to claim 1, wherein a pinion is rotatably mounted on said one side wall, said second circular segment is provided with a toothed portion, and said pinion is adapted to engage with said toothed portion to provide said circumferential adjustment of said second segment, said toothed portion being provided with adjustable stop means for limitation of the travel of said second circular segment.
- 3. A sheet transfer cylinder according to claim 2, wherein a scale and pointer are mounted on said toothed portion and said one side wall to provide indicia for regulation of the degree of circumferential adjustment of said second segment.
- 4. A sheet transfer cylinder according to claim 1, wherein said one end of said shaft is provided with a lever and said lever mounts a pair of said rollers.
Priority Claims (1)
| Number |
Date |
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| 5389-71 |
Jul 1971 |
CS |
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BACKGROUND OF INVENTION
This is a continuation of application Ser. No. 273,356, filed July 20, 1972.
The present invention relates to rotating printing machines and in particular to sheet transfer cylinders therefor, by which a paper sheet is seized on the cylinder, and turned over for printing on two sides.
A present technique for transferring paper sheets from one multicolor printing unit to the following printing unit is to use chains in which are mounted carrier rods provided with pairs of gripper members which seize the sheet. This mechanism for transferring sheets is simple and inexpensive, but it does not guarantee accurate registration for printing. A further disadvantage is the development of excessive noise at high printing speeds. When paper sheets are transferred by means of the chains and associated grippers it has been found necessary to utilize additional mechanisms in order to turn the sheets. Sheet transfer drums are frequently used for the transfer of the paper sheets to be printed. Such an arrangement provides satisfactory registration of the sheets even at high printing speeds. The transfer of the paper sheets by means of such transfer drums also enables the turning of the sheets for printing on both sides during a single passage through the printing machine. With this arrangement one of the sheet transfer drums or cylinders generally has a diameter twice the size of the other transfer cylinder, enabling a relative adjustment of the gripper sets on the respective transfer cylinders so that the grippers of one transfer cylinder delivers the paper sheet with its trailing edge into the grippers of the adjacent transfer cylinder.
It has heretofore been known to construct transfer cylinders with grippers which seize the leading edge of the paper sheet and to thereafter transfer the sheet with suction elements which are arranged on the surface of the cylinder adjacent to seize the trailing edge of the sheet. After such elements suck the paper sheet, the trailing edge of the sheet can be seized by the grippers of the following printing unit whereby the sheet is simultaneously transferred and turned so as to be ready for printing on the following unit.
The known mechanisms which enable conversion of the sheet transfer so that cylinder printing can be effected on either one or both sides are very complicated and expensive to produce. Due to the complexity of these mechanisms their accuracy in holding the paper sheet aligned during transfer is reduced and failure often occurs. The adjustment of such mechanisms by means of auxiliary control cams is time consuming, complicated, and the productivity of the printing machine is reduced.
Accordingly, an object of the present invention is the provision of a sheet transfer cylinder having a sheet gripper mechanism which can readily be adjusted for printing of the paper sheet on either one or both sides.
Another object of the invention is the provision of a sheet transfer cylinder having a gripping mechanism which is of relatively simple construction and performs reliably.
These objects, others and the advantages of the present invention will be seen from the following disclosure.
According to the present invention there is provided a sheet transfer cylinder for a rotary printing machine, having a cylinder on which is mounted a mechanism for gripping the sheets to be transferred and for turning the sheets. The cylinder is adapted to be rotatably mounted in side walls of the machine. One of the side walls is provided with a fixed centering ring coaxial with the axis of the transfer cylinder. The centering ring has a pair of circular segments secured to opposed peripheral faces thereof, the first of the segments being circumferentially adjustable with respect to the centering ring and the second of the segments being non-adjustable with respect to the centering ring. The sheet transfer is provided adjacent the surface thereof with a rotatable shaft adapted to carry the sheet gripping means secured rigidly thereto, and roller means carried at one end of the shaft adapted to engage with the outer surfaces of the first and second circular segments respectively. Rotation of the transfer cylinder results in movement of the rollers and actuation of the gripping means.
The mechanism of this invention requires only a simple manipulation to convert the printing machine from a capability for printing one side of the paper sheet to a capability for printing on both sides of the sheet, or vice-versa. While adjusting the machine, the suction elements are simultaneously adjusted in such a way that the distance between the suction elements and the grippers remain unchanged.
The invention is more fully described, by way of example, in the following description in which reference to the accompanying drawings is made.
US Referenced Citations (5)
Continuations (1)
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Number |
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273356 |
Jul 1972 |
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Patent Grant
3944218
