US2236363A - Sheet feeding machine - Google Patents

Description

March 1941- H. T. BACKHOUSE 2,236,363

SHEET FEEDING MACHINE Filed March 50, 1939 2 Sheets-Sheet 1 Weaker Jud/7'00 a/f We a/rer Or/ve INVENTOR. v 6.155045 r iwzv'aslvo fine/(Haas:

ATTORNEYS Patented Mar. 25, 1941 PATENT OFFICE I SHEET FEEDINGMAC'HINE Headley Townsend Backhouse, London,- England Application thi ned, 1939, Serial No. 265,007

I In Great Britain April 1, 1938 7 Claims.

The invention comprises improvements in or relating to sheet-feeding machines and is 'concemed with stream feeders of the kind (hereinafter referred to as the kind described) in which sheets of paper or the like are separated and partly forwarded from the top of a stack by means operating to grip and lift the sheets at or near (1. e. within the rear half of the sheets) the rear edges thereof and in which the sheets are then removed (e. g. to a printing machine), by conveyor elements engaging the'front edge of the sheets, in the form of a continuous stream of partly underlapping sheets. a stream feeder of this kind'is described in U. S. Patent No. 2,108,702 and the present invention is particularly suitable for application to stream feeders as described in that patent.

In machines of the kind described the position of the rear edge of each sheet as it is lifted from the stack and forwarded towards the conveyor is accurately determined by the separating and forwarding means engaging the sheet at or near the rear edge. The exact position of the front edge of the sheet is, on the other hand, indeterminate because the sheets, as they are lifted from the stack, sag or, if an air blast is used under the sheets to assist separation, billow by varying amounts. It is, however, the front edge of the sheet which is taken first by the conveyor and which determines the position of the sheet on the conveyor in relation to the preceding and succeeding sheets and the difficulty therefore arises that the sheet may be misplaced on the conveyor in spite of the fact that the position of its rear edge is accurately controlled. It is an object of the present invention to provide a machine of the kind described in which this difficulty is largely reduced or overcome.

The invention consists in a machine of the kind described having a suction or equivalent gripper arranged to grip the underside of each sheet at or near the front edge after the sheet has been separated from the stack and in which the sheet is tautened from front to rear by relative movement away from one another in the direction of feeding and while gripping the sheet of the suction or equivalent gripper aforesaid and the means gripping the rear of the sheet, the potential movement being in excess of that required to tauten a sheet with normal amount of sag in order to be able to tauten sheets with abnormal sag and the machine being so constructed and arranged that when the sheet is taut the relative movement aforesaid ceases or One example of the suction or equivalent gripper slips on. the sheet without disturbing the accurate positioning of the sheet by the means gripping the rear of the sheet.

The relative movement of the suction or equivalent gripper engaging the front of the sheet and the means gripping the rear of the sheet may be effected by movement of the rear gripping means in the backwards direction or by moving the front gripper in the forwarding direction while maintaining the rear gripping means stationary. It is, however, preferred to effect the relative movement while both gripping means are moving in the forwarding direction, the front gripping means moving faster than the rear gripping means.

In the preferred form of the invention the front gripper also acts during the preliminary separation of the uppermost sheet as a front gauge or stop preventing creeping forward of the top sheets.

The front gripper, when it is a suction device, may be in the form of a tube extending transversely of the stack and having suction orifices in its upper surface or it may be constituted by one or more suckerslocated close to the front of the stack and, when there are two or more suckers, spaced apart across the stack.

In one form of the invention parts of the suction device or other gripper adjacent opposite side edges of the stack are arranged for relative movement, while gripping a sheet, in a direction transverse to the feeding direction to tauten the front edge of the sheet.

35 Four specific embodiments of the invention will now be described by way of example and with reference to the accompanying diagrammatic drawings in which:

Figures 1 to 5 show five successive positions in the cycle of operations of the front gripper in one embodiment;

Figure 6 is a section illustrating a second embodiment;

Figure 7 is a perspective view of the suction device employed in the embodiment shown in Figure 6;

Figure 8 is a side view partly in section illustrating a third embodiment;

Figure 9 is a section illustrating a fourth embodiment, and

Fig. 10 is a timing diagram showing the relative functioning of the front and rear suckers and the blowers with respect to the forms of the invention illustrated in Figs. 1 to 7 inclusive.

Like references indicate like parts in the several figures of the drawings.

In each example the sheets are separated and forwarded from their rear edges by means of suckers operating over the top of the stack in combination with an air blast directed underneath the rear edge of each uppermost sheet in turn, the arrangement being similar to that .described in U. S. Patent No. 2,108,702.

In the first example, which is illustrated in Figures 1 to 5,'the suction device consists of a tube I having a cross-section in the form of a right-angled triangle. The tube extends transversely of the stack 2 with one of its shorter sides 3 substantially vertical and the other shorter side 4 substantially horizontal. The horizontal side 4 is provided at intervals along the length of the tube with orifices to which suction may be applied through the tube.

During the operation of the machine the tube is given the following cycle of movements, for example by means of cams, for each sheet separated. At the beginning of the cycle the tube is located with its vertical face in contact with the front of the stack and with its horizontal face at a slightly higher level than the top of the stack so that the tube acts as a front gauge or stop. The tube remains in this position (which is shown in Figure 1) during the initial separation of the rear edge of the uppermost sheet. As soon as the rear edge has been separated, the tube drops vertically until its upper surface is substantially level with the top of the stack as shown in Figure 2. The front'edge 5 of the separated sheet is fed over the tube by means of the forwarding suckers 20 and air blast nozzles 2| at the rear of the stack to the position shown in Figure 3 and the tube then returns to its initial position engaging, and if necessary lifting, the front edge of the sheet in doing so, this position being shown in Figure 4. Suction is then applied to the tube causing it to grip the underface of the front edge of the sheet and the tube is moved in the forwarding direction towards conveyor rollers 6 located a short distance in front of the stack. The tube moves in the forwarding direction at a greater speed than the forwarding suckers at the rear of the sheet thereby tending to stretch or tauten the sheet from front to rear. The tube is of metal and the suction orifices are so proportioned and the suction is of such a strength that as soon as the sheet has been tautened the extra resistance of its front edge to forwarding causes the sheet to slip on the metal tube without moving the rear of the sheet in relation to the rear forwarding suckers. The tube is moved in the forwarding direction until the front edge of the sheet is presented to the conveyor rollers and engaged by them (as shown in Figure 5) when the suction is released and the tube returned to the initial position, thereby completing the cycle. Throughout the whole of the movements of the tube its axis remains substantially horizontal.

In the second example, shown in Figures 6 and 7, the suction device is constituted by a plurality of metal suckers I, say three, spaced apart across the front edge of the stack and each in the form of a short vertical tube of rectangular crosssection extending tangentially from a horizontal suction tube 8. The cycle of movements of the suckers to tauten and forward the sheets is similar to that of the triangular tube des r b d above, but in this embodimentihe movements are eifected by vertical and rotational movements of the horizontal suction tube. At the commencement of the cycle the rectangular sectioned sucker tubes lie vertically against the front of the stack with their ends 9, which constitute the suckers, extending above the top of the stack to form front stops as shown in Figure 6. As soon as the separation of the rear of the uppermost sheet has been effected the suction tube drops to the position shown in dotted lines in the figure carrying with it the suckers until the suckers are level with the top of the stack and the tube remains in that position until the front edge of the separated sheet has been forwarded over the suckers. The suction tube then rises vertically to engage the suckers with the underface of the sheet and as soon as engagement has been effected is rotated about its axis to move the suckers in the forwarding direction and to feed the front edge 5 of the sheet to the conveyor roller 6. To ensure that the suckers may have sufficient movement in the forwarding direction to present the sheet properly to the conveyor rollers, the lower conveyor roller is provided with circumferential grooves I0 into which the sucker tubes are received. As soon as the sheet has been engaged by the conveyor rollers, the suction is released and the horizontal suction tube rotated in the reverse direction to return the suckers to their initial position.

In Fig. 10 I have illustrated in a timing diagram the relative movements of the front and rear suckers and of the air blast nozzles, as well as the timing of the suction in the suckers and the .ir blast in the air blast nozzles. The diaram applies only to the two forms of the invention thus far described. The arrows indicate that during the periods so marked movement is up or down. The words "up and down indicate that during the periods to which they are applied the part in question remains up or down, as the case may be. The speed of the suckers in moving forward and backward is not indicated on the diagram, but as previously stated the forward travel of the front suckers is faster than that of the rear suckers, with the result that they separate relatively, as indicated by the fact that the distance a in Fla. 4 is increased to 11+ in Fig. 5.

In the third example shown in Figure 8, the suction device is in the form of a cylindrical suction tube II on which a closely fitting outer tube I2 is mounted, the outer tube being rotatable on the suction tube and having a succession of apertures i3 which, when the tube is turned successively register with corresponding apertures II (which may be slots or holes) on the upper surface of the inner suction tube. The tubes lie horizontally against the front edge of the stack and at the beginning of the cycle with their upper surface slightly above the level of the top of the stack as shown in Figure 8. In the operation of the device the outer tube I2 is rotated intermittently or continuously in the direction such that its upper surface moves in the feeding direction of the sheets and suction is applied through the apertures in the inner tube to each aperture ii in the outer tube as it moves into register with an aperture N in the inner tube. As the front edge of each sheet is fed forwardly by the rear forwarding suckers, it is engaged by the rotating outer tube and ripped and released by the apertures as suction is applied to them as they move into and out of register with the apertures in the inner tube. The forward rotation of the outer tube feeds the sheet at a greater rate than the forwarding suckers move the rear edge of the sheet thereby tending to stretch or tauten the sheet, but, as in the previous examples, the grip of the roller on the sheets is insufficient, to cause the sheets to slip in relation to the rear grippers. The roller in this example has an up and down movement similar to that of the tube in the first example but it does not movebodily 7 towards and away from the conveyor rollers.

According to the fourth example, shown in Figure 9, the lower conveyor roller 6 is provided with one or more circumferential grooves 15 and a suction tube It is provided for each groove extending between the rollers and received within the groove. The suction tube is supported from a horizontal tube I! located in front of the conveyor rollers and is formed at its rear-end with a. horizontal sucker mouth l8. The sucker mouth is moved, by movement of the tube in the groove of the conveyor roller, in the forwarding andreturn directions only.

When the front edge of the uppermost sheet has been forwarded from the top of the stack it is engaged on its underface by the sucker mouth l8 .and is drawn forwardly towards the conveyor rollers at a greater speed than the rear of the sheet is forwarded, thereby stretching or tautening the sheet. As in the previous embodiments the sucker mouth is arranged to slip on the sheet when it has been tautened but in this case the sucker is arranged to draw the sheet, while slipping on it, between the conveyor rollers. The sucker mouth then releases the sheet and is returned underneath the sheet to its initial position close to the front of the stack. In this embodiment the suction device does not act as a front stop and it is preferred, therefore, to employ the usual form of pivoted front stop IS in addition to the sucker.

It is to be understood that in each of the above embodiments the suction devices may be so modified that they grip the sheet adjacent to its opposite side edges and while gripping the sheet they may be moved away from one another transverse to the feeding direction to tauten the front edge of the sheet in addition to their movement to tauten the sheet from front to rear as described above.

In each of the examples described above the tautening of the sheet from front to rear is effected by movement of the front suction gripper at a speed greater than that of the rear suction gripper, the front gripper slipping on the sheet when it has been tautened. It is however, within the scope of the invention to arrange the machine in such manner that after suflicient relative movement of the front and rear grippers has taken place to tauten any sheet likely to be found in practice (with the necessary slip for sheets which have not the maximum amount of sag) the rear gripper releases the sheet which v is then carried forward by. the frontgripper pers remain stationary) and the rear grippers then release the sheet and return to their initial position to grip the next sheet and to carry out their second cycle. The completion of the forwarding of the sheet to the conveyor is effected by the front grippers which move forwards to present the sheet to the conveyor during the time that the back grippers are engaging and lifting the next sheet.

Further, in each of the above examples the front gripper has been arranged to slip on the sheet when a sheetwith normal sag has been tautened. It is however within the invention so to arrange the machine that as soon as the sheet has been tautened relative movement between the front and rear grippers ceases. This may, for example, be effected by providing. a resilient connection between the front gripper and its operating means so arranged that the additional resistance to movement experienced by the gripper when the sheet is taut causes the connection to give. Alternatively the operating means for the front gripper may consist of a cam arranged to eflect the'rearward movement of the gripper positively by engagement with a follower and against the action of a spring which tends to maintain the follower in contact with the roller. The forward movement of the gripper is effected by the spring which is only strong enough to tauten the sheets so that as soon as the sheets are taut the follower leaves the cam and further relative movement of the rippers ceases.

It is further to be understood that it is an important advantage of the mechanism herein described that any lack of parallelism between, the front and back edges of the sheets due to sag or the like is removed by the tautening of the sheets from front to rear,.thereby ensuring that the sheets are taken by the conveyor in the cor rect angular relationship, and that the relative slip between the sheets and the front grippers contributes largely to this result since different amounts of slip may take place at opposite sides of the sheets and, consequently, the opposite sides may be tautened until each side reaches the desired degree of tautness.

I claim:

1. In a machine for feeding sheets from the top of a pile, rear sucker means adapted to grip the uppermost sheet and move forward therewith, forward sucker means arranged in front of the pile adapted to grip the surface of the advanced sheet and move forwardly more rapidly than the rear sucker means, the grip of the rear sucker means being strong enough relatively to prevent slippage between the sheet and said rear sucker means.

2. In a machine for feeding sheets from the top of a pile, rear sucker means adapted to grip the uppermost sheet, raise it and move it forward, forward sucker means arranged in front of the pile adapted to move upwardly, grip the lower surface of the advanced sheet and move forwardly more rapidly than the rear sucker means, the grip of the rear sucker means being stronger than that of the forward sucker means in order that slippage may occur between the sheet and the forward sucker means after the sheet has been tautened.

3. In a machine for feeding sheets from a pile, feed rollers adapted to receive sheets from the top of the pile and move them forward, sucker means at the rear of the pile for gripping and raising the uppermost sheet and advancing it in the direction of feed, air blast means for raising the forward portion of the gripped sheet from the pile; forward sucker means located in front of the pile adapted to grip the under surface of the raised and advanced sheet and to mov forward at a speed in excess of the forward speed of the rear sucker means, the sheet forwarding effect of said forward sucker means being weaker than the sheet forwarding effect of said rear sucker means whereby the sheet is tautened while control of the position of the sheet is maintained by said rear sucker means, said forward sucker means continuing its forwarding impulse until the sheet is in the grip of said feed rollers.

4. In a machine for feeding sheets from a pile, feed rollers adapted to receive sheets from the top of the pile and move them forward, sucker means at the rear of the pile for gripping and raising the uppermost sheet and advancing it in the direction of feed, air blast means for raising the forward portion of the gripped sheet from the pile, pile gauging means at the front of the pile, the said pile gauging means being hollow and constituting a suction conduit having openings at its upper edge, the pile gauging means being adapted to grip the under surface of the raised and advanced sheet, to move forwardly at a speed in excess of the forward movement of said rear sucker means, and to exert a forwarding effect on the sheet weaker than that of the rear sucker means thereon, whereby the forward edge of the uppermost sheet is held against movement by said pile gauging means until the blast raises the sheet above the level of the pile and whereby the sheet is tautened after it is gripped by the pile gauging means, said pile gauging means continuing its forward impulse until the sheet is in the grip of said rollers.

5. In a machine of the class described, pile gauging means having a flat rear surface for engagement with a pile and being hollow in order to serve as a suction conduit, said hollow gauging means having suction openings at its upper end, and said gauging means being arranged and actuated to permit the uppermost sheet to advance somewhat beyond the forward end of the pile after which the gauging means grips the under surface of said advanced sheet and carries it forward away from the pile.

6. In a machine of the class described, pile gauging means having a flat rear surface for engagement with a pile and being hollow in order to serve as a suction conduit, said hollow gauging means having suction openings at its upper end and having movement up and down and forward and backward, said gauging means when lowered permitting the uppermost sheet to advance somewhat beyond the forward end of the pile after which suction is exerted to cause the gauging means to grip the under surface of the advanced sheet and whereby the forward movement of the gauging means carries the sheet forward for feeding purposes.

7. In a machine of the class described, pile gauging means having a flat rear surface for engagement with the pile and having an upper surface normally standing somewhat above the level of the pile, said gauging means being hollow in order to serve as a suction conduit and having suction openings in its upper surface, said gauging means moving down to substantially the level of the pile for permitting the uppermost sheet to be advanced over the gauging means, and then moving upwardly to grip the under surface of the sheet by suction and forwardly to further advance the sheet, and then with it suction broken moving backwardly to its normal position against the pile.

HEADLEY TOWNSEND BACKHOUSE.

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