Device for separating the lowermost sheet from a stack

Abstract

A device for separating a lowermost sheet from a stack, having a hopper for holding the stack and a pushing device arranged underneath the hopper and having a pushing element capable of being moved linearly back and forth, of which the pushing edge is movable relative to the bearing plane of the stack in the hopper, wherein the projection for positive conveying of this pushing edge changes with respect to the bearing plane.

Claims

1. A device for separating at least one lowermost sheet from a stack, comprising at least: a hopper having at least one table (7) forming a bearing plane (100) for holding sheets of a stack, a pushing device (1) arranged underneath the hopper having at last one slide (10) that is movable back and forth in a pushing direction (110), having at least one pushing element (14) arranged on the slide (10) and which has at least one pushing edge (14.1, 14.2), wherein the least one pushing edge (14.1, 14.2) has a projection with respect to the bearing plane (100) for positive conveying, wherein the at least one pushing element (14) of the at least one pushing device (1) is arranged rotatably about a rotation axis (140) in a holder of the at least one slide (10), wherein the rotation axis (140) is arranged essentially parallel to the pushing direction (110), and a retaining device (3) having at least one retaining element (30), which delimits the hopper in the pushing direction (110) and is arranged at a distance from the bearing plane (100) in such a way that the at least one retaining element (30) forms a gap with the bearing plane (100) through which at least one lowermost sheet of the stack can be guided, wherein the gap and thus the passage height are adjustable, wherein the at least one pushing edge (14.1, 14.2) of the at least one pushing element (14) is movable relative to the bearing plane (100) of the hopper, wherein the projection for positive conveying of the at least one pushing edge (14.1, 14.2) changes with respect to the bearing plane (100).

2. The device of claim 1 wherein the pushing element (14) has at least two pushing edges (14.1, 14.2) distributed about the rotation axis (140) in such a way that, in accordance with the rotary position of the pushing element (14) about the rotation axis (140), exactly one of the pushing edges (14.1, 14.2) of said element has a projection for positive conveying with respect to the bearing plane (100).

3. The device of claim 1 wherein the at least one pushing element (14) or in a holder thereof, includes at least one clamping element or detent element (16), which fixes the pushing element (14) in a predetermined rotary position.

4. The device of claim 3 comprising a first position-adjusting device (2) having at least one controllable drive (22), which is at least temporarily drive-connected to the at least one pushing element (14) in such a way that the at least one controllable drive (22) determines the predetermined rotary position of the respectively associated pushing element (14).

5. The device of claim 4, wherein the first position-adjusting device (2) comprises at least one separable clutch (17), wherein a first clutch half (17.1) is arranged on the at least one pushing element (14) in such a way that the first clutch half (17.1) is rigidly connected to the pushing element (14) as far as the rotation axis (140) is concerned and that this first clutch half (17.1) performs the pushing movement jointly with the pushing element (14), and that a second clutch half (17.2) of the separable clutch (17) is arranged on the frame of the pushing device (1) rotatably about the rotation axis (140) of the pushing element (14) in such a way that the second clutch half (17.2) does not move in the pushing direction.

6. The device of claim 5, comprising an arrangement of the second clutch half (17.2), which is stationary as far as the pushing movement is concerned, in such a way that the closing of the clutch (17) is brought about by a movement of the slide (10), in a direction opposite the pushing movement, into the starting position of its pushing movement and/or into a position situated beyond the pushing movement of the slide (10).

7. The device of claim 1, wherein the at least one pushing device (1) is movable in a position-adjusting direction (101) perpendicular to the pushing direction (110).

8. The device of claim 1, comprising: at least two pushing devices (1), wherein the at least two pushing devices (1) each have a separate drive (11) which is permanently drive-connected to the corresponding slide (10).

9. The device of claim 8, wherein the at least two pushing devices (1) are arranged perpendicularly to the common pushing direction (110) and spaced apart from one another over a width of the sheet to be separated in such a way that the pushing elements (14) of the at least two pushing devices (1) jointly catch the same sheet for positive conveying, in order to separate said same sheet jointly from the stack in the pushing direction (110).

10. The device of claim 8, wherein the separate drives (11) of the at least two pushing devices (1) are connected controllably and by means of data transmission lines (61) to a control (60) of the device.

11. The device of claim 8, wherein the at least two separate drives (11) each have a linear motor, wherein in each case the stator (11.2) of the linear motor is formed from permanent magnets and in each case the controllable rotor (11.1) is arranged on the slide (10).

12. The device of claim 8, comprising a sensor system (33) for detecting the angular position of the separated sheet with respect to the pushing direction (110), wherein said sensor system is arranged downstream of the at least one retaining element (30) and connected by means of at least one data transmission line (65) to the control (60) of the device.

13. An installation for cutting sheets from cardboard and/or pasteboard, having at least a first separation device (71) for separating a sheet from a stack, having at least one transport device (72) with at least one transport direction (201) for feeding the separated sheet into: a first cutter (73) arranged downstream of the first separation device (71) having at least one rotary cutter, said at least one rotary cutter comprising circular knives rotatable about a rotational axis for dividing the infed sheet into multiple sub-sheets, wherein the rotation axes of the circular knives forming the at least one rotary cutter are arranged essentially perpendicular to the first transport direction (201), a stacking device (74) arranged downstream of the first cutter (73) for forming an auxiliary stack from the sub-sheets, a device for separating of claim 1 arranged downstream of the stacking device (74) for separating a lowermost sheet from the auxiliary stack, wherein the pushing direction (110) of the device for separating of claim 1 runs perpendicular to the first transport direction (201), a second cutter (76) arranged downstream of the device for separating of claim 1 in the pushing direction (110), and a delivery (77) arranged downstream of the second cutter (76).

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following, the invention will be described using an exemplary embodiment and with reference to the figures, to which reference shall be made regarding all details not mentioned any further in the description. Shown are:

(2) FIG. 1 a device for separating a lowermost sheet, in a perspective view;

(3) FIG. 2 a section of a separation device, in a perspective view;

(4) FIG. 3 an installation for cutting pasteboard sheets, in a perspective view.

DETAILED DESCRIPTION

(5) As shown in FIG. 1, the device for separating a lowermost sheet from a stack comprises two similar pushing devices 1, which jointly separate one sheet in each case. The following explanations pertaining to one pushing device 1 apply equally to both pushing devices 1.

(6) The hopper for holding a sheet stack is located above the pushing devices 1. The not illustrated sheet stack rests on the table 7 formed from multiple parts. The horizontal bearing surface of this table 7 defines the bearing plane 100. The parts of the table 7 are each at a distance from one another perpendicularly to the pushing direction 110. These spaces provide the necessary clearance for the pushing device 1. The hopper can be enhanced by adding a not illustrated stack monitor.

(7) A retaining device 3, which delimits the hopper in the pushing direction 110, is provided above the bearing plane 100. This device comprises two retaining elements 30, which are held in a laterally displaceable manner by means of a linear guide 32 running perpendicularly to the pushing direction 110. Both retaining elements 30 are each mounted on the common guide rail by a holder 31. The holders 31 are each connected to a separate position-adjusting device. This position-adjusting device comprises a spindle drive 40 actuated by a controllable actuator 41.

(8) The retaining elements 30 are mounted at a distance from the bearing plane 100 such that a passage opening is formed between the retaining elements 30 and the bearing plane 100 for the sheets to be separated. This distance is adjustable to the thickness of the sheet to be separated by means of a not illustrated position-adjusting device of known type.

(9) A frame 5 made of one pair of cross members 50 and one pair of longitudinal members 51 holds the pushing devices 1. The latter are mounted in a width direction 101 perpendicular to the pushing direction 110 via linear guides 52. Respective controllable position-adjusting devices 6 with spindle drives 53 enable automatic format adjustment in a width direction 101 perpendicular to the pushing direction 110.

(10) The pushing device 1 has a slide 10, which is arranged movably back and forth in a pushing direction 110 by means of a linear guide 12. The slide 10 is driven controllably along this linear guide 12 by a linear servomotor 11. The rotor 11.1 of the linear servomotor 11 is mounted on the slide 10 itself and connected to a control 60 of the device by a data transmission line 61. The stator is made of permanent magnets 11.2. The use of a linear servomotor 11 enables the position of the slide 10 along the pushing direction 110 to be easily determined. Furthermore, different movement profiles can be defined for the slide 10 owing to the servo drive. These movement profiles can be adapted to the respective sheet lengths or include the movement to a park or setup position outside the movement range of the slide needed for the pushing, for example.

(11) The slide 10 bears a bearing bracket 13, in which the pushing element is mounted rotatably about an axis 140. The rotation axis 140 runs parallel to the pushing direction 110. The pushing element 14, which projects into a space or cutout of the hopper table 7, bears four pushing edges 14.1, 14.2 distributed uniformly about the rotation axis 140 for catching the lowermost sheet of the stack by its the back edge. Depending upon the rotary position of the pushing element 14, one of these pushing edges 14.1 points upwards and thus creates the projection with respect to the bearing plane 100 needed for the pushing. The respective projections of the individual pushing edges 14.1, 14.2 differ from one another such that the pushing element 14 can be incrementally adjusted to different sheet thicknesses by switching its operative pushing edge 14.1, 14.2.

(12) In order to fix the rotary position of the pushing element 14, an elastic pressure piece 16 is provided in the mounting bracket 13. With its spring-mounted ball, the pressure piece 16 engages in a depression of the pushing element 14 assigned to the corresponding pushing edge 14.1, 14.2. The pushing element 14 is thus secured against inadvertent turning and can also be switched as needed to another pushing edge 14.1, 14.2.

(13) A position-adjusting device 2 is provided for this adjustment of the pushing element 14. This device comprises a controllable positioning drive 22. The positioning drive 22 is connected to the control 60 of the device via a data transmission line 62. The drive connection to the pushing element 14 includes a separable clutch 17 consisting of two clutch halves 17.1, 17.2.

(14) A first clutch half 17.1 is rigidly and permanently connected to the pushing element 14 and is thus also subjected to the movement of the slide 10. A second clutch half 17.2 is rigidly and permanently connected to the positioning drive 22 of the position-adjusting device 2. As far as the pushing movement is concerned, the positioning drive 22 with the second clutch half 17.2 is mounted stationarily on the pushing device 1. The second clutch half 17.2 comprises a blade, which engages in the slot of the first clutch half 17.1, whereas the slide 10 is situated in its setup position along the pushing direction 110. By leaving this setup position, the clutch 17 is separated and the drive connection between the pushing element 14 and the positioning drive 22 is interrupted.

(15) The lower of the two pushing devices 1 shown in FIG. 1 has its slide 10 in a park or setup position, in which the clutch 17 is closed. The upper pushing device 1 on the other hand has its slide 10 in an essentially forward end position, in which the clutch 17 is open and a distinct distance between the two clutch halves 17.1, 17.2 is discernible.

(16) The device comprises two light barriers 33 arranged on the retaining device 3. These are connected to the control 60 of the device via data transmission lines 65. The light barriers 33 detect the leading and the trailing edge of the separated sheet in the pushing direction 110 downstream of the retaining elements 30. In the pushing direction 110 at the same height, they are spaced at a distance from one another in the width direction 101 in such a way that they serve to detect the angular position of the leading and the trailing edges of the sheets. This angle information makes it possible for the control 60 to correct a detected angle error immediately during the pushing-out by variable actuation of the linear servomotors 11.

(17) FIG. 3 shows such a separation device as a component of a cutting installation for pasteboard sheets. This installation comprises a multiplicity of different devices, which apart from the described separation device 75 are sufficiently known and therefore shall not be described in any further detail here.

(18) The installation comprises a first separation device 71 for separating an uppermost sheet from a stack. A first transport device 72 conveys the separated sheet in a first transport direction 201 to a subsequent first cutter 73. This first cutter 73 comprises multiple rotary cutters for separating the infed sheet into multiple sub-sheets parallel to one another. The sub-sheets are combined into auxiliary stacks in a subsequent first stacking device 74 in the first transport direction 201 and conveyed in a second transport direction 202 perpendicular to the first transport direction 201 into the hopper of the described separation device 75. The pushing direction 110 of the separation device 75 is identical to the second transport direction 202 of the installation. The re-separated (sub-)sheets are conveyed without changing direction through the downstream-disposed second cutter 76. The first cutter 73 and the second cutter 76 are similar and differ from each other essentially in the number and position of the respective longitudinal cuts. In the second transport direction 202, a second stacking device 77 connects to the second cutter 76, combines the cut sheets into stacks and feeds them to a delivery 78, from which these sheet stacks can be removed.