SHEET PROCESSING MACHINE

Abstract

A sheet processing machine comprises a receiving area (38) for collecting a sheet pile and a device (36) for determining the height of the sheet pile. The device (36) comprises a manually displaceable first sensor element arranged at a first side (48) of the receiving area (38), and an automatically displaceable second sensor element (50) arranged at an opposite side (52) of the receiving area (38) such that the first and second sensor elements (50) are arranged opposite each other along a width direction of the receiving area (38). The first sensor element and the second sensor element (50) are displaceable along a length direction of the sheet receiving area (38), wherein the first sensor element is one of a light emitting source and a light receiving sensor (56) and the second sensor element (50) is the other one of a light emitting source and a light receiving sensor (56). The light emitting source and the light receiving sensor (56) form a light barrier (58) along the width direction when facing each other.

Claims

1. A sheet processing machine comprising: a receiving area for collecting a sheet pile; and a device for determining a height of the sheet pile, the device comprising a manually displaceable first sensor element arranged at a first side of the receiving area, and an automatically displaceable second sensor element arranged at an opposite side of the receiving area such that the first and second sensor elements are arranged opposite each other along a width direction of the receiving area, and the first sensor element and the second sensor element being displaceable along a length direction of the sheet receiving area, wherein the first sensor element is one of a light emitting source and a light receiving sensor and the second sensor element is the other one of the light emitting source and the light receiving sensor, the light emitting source and the light receiving sensor forming a light barrier along the width direction when facing each other.

2. The sheet processing machine according to claim 1, wherein the first sensor element and the second sensor element are mounted on a first rail and a second rail, respectively.

3. The sheet processing machine according to claim 2, wherein the first sensor element is mounted by a slotted guide slider in a slotted guide of the first rail.

4. The sheet processing machine according to claim 1, the second sensor element being displaceable by means of a motor of the second sensor element, especially an actuator of the second sensor element.

5. The sheet processing machine according to claim 1, the device comprising a control unit connected to the first sensor element and to the second sensor element, the control unit being adapted to receive a sensor signal from the light receiving sensor and to control a movement of the second sensor element.

6. The sheet processing machine according to claim 5, the control unit being adapted to move the second sensor element along the length direction to a working position, wherein in the working position the sensor signal is non-zero, preferably wherein in the working position the sensor signal is maximum.

7. The sheet processing machine according to claim 6, the control unit being adapted to move the second sensor element to the working position each time the first sensor element has been moved.

8. The sheet processing machine according to claim 1, wherein the first sensor element is arranged at an operator side of the sheet processing machine and the second sensor element is arranged at an opposite operator side of the sheet processing machine.

9. The sheet processing machine according to claim 1, wherein the receiving area is part of a blank separation station of the sheet processing machine and the sheet pile is a pile of blanks.

Description

[0033] Further advantages and features will become apparent from the following description of the invention and from the appended figures which show a non-limiting exemplary embodiment of the invention and in which:

[0034] FIG. 1 schematically shows a sheet processing machine according to the invention;

[0035] FIG. 2 shows a perspective view of a device for determining the height of a sheet pile of the sheet processing machine of FIG. 1; and

[0036] FIG. 3 shows a partial side view of the device of FIG. 2.

[0037] FIG. 1 schematically shows a sheet processing machine 10 making it possible to cut blanks 11 from a succession of sheets 12. These blanks 11 are usually intended to be subsequently folded and bonded to form packaging boxes.

[0038] However, the sheets 12 might generally be made of e.g. paper, cardboard, foil, a composite material thereof or any other material routinely used in the packaging industry.

[0039] The sheet processing machine 10 comprises a series of processing stations that are juxtaposed but interdependent one another in order to form a unitary assembly. The processing machine 10 includes a loading station 14 followed by a cutting station 16 (also usually named punching station) comprising for example a die or platen press 18 where the sheets 12 are transformed by cutting, a waste removal station 20 wherein most of the waste parts are stripped, a blank separation station 22 (also usually named reception station) for separation of the blanks 11 (or blanking operation) by means of a blanking tool 23 and an evacuation station 24 for removing the residual waste sheets of the punched sheets 12.

[0040] The number and nature of the processing stations may vary depending on the nature and the complexity of the converting operations to be carried out on the sheets 12.

[0041] The sheet processing machine 10 also has a transfer mechanism 26, which in the shown embodiment is a conveyor, to make it possible to individually move each sheet 12 from an outlet of the loading station 14 to the evacuation station 24.

[0042] The conveyor uses a series of gripper bars 28 that are mounted so as to be moveable by means of two loops of chains 30 one placed laterally on each side of the sheet processing machine 10. Each loop of chains 30 travels around a loop which allows the gripper bars 28 to follow a trajectory passing successively by the cutting station 16, the waste removal station 20, the blank separation station 22 and the evacuation station 24.

[0043] Each gripper bar 28 travels on an outward path in a substantially horizontal plane of passage between a driven wheel 32 and an idler wheel 34, and then a return path in the top portion of the sheet processing machine 10. Once returned to the driven wheel 32, each gripper bar 28 is then able to grip a new sheet 12 at a front edge of the sheet 12.

[0044] In FIG. 1, each processing station is illustrated in the form of two rectangles symbolizing respectively its top portion and its bottom portion that are positioned on each side of the plane of movement of the sheets 12.

[0045] In FIG. 1, a transverse (or lateral), longitudinal and vertical direction are indicated by the orthogonal spatial system (T, L, V).

[0046] The terms upstream and downstream are defined with reference to the direction of movement of sheets 12 in a handling direction as illustrated by the arrow D in FIG. 1.

[0047] The sheet processing machine 10 further comprises a device 36 for determining the height of a sheet pile in a receiving area 38 of the blank separation station 22. Accordingly, the sheet pile is a pile of blanks 11 in the shown embodiment.

[0048] The device 36 is connected to a control unit 40, e.g. by an Ethernet connection, the control unit 40 being adapted for controlling the device 36. However, the device 36 could also be connected to the control unit 40 by any means which provides a sufficiently fast exchange of signals between the device 36 and the control unit 40. E.g., the connection can also be established wireless, e.g. by Wi-Fi. The control unit 40 further comprises a storage module 42.

[0049] The sheet processing machine 10 further comprises a human-machine-interface 44 which in the shown embodiment is a touch-sensitive display.

[0050] By the human-machine-interface 44, a (not shown) operator can control the operation of the sheet processing machine 10. Further, information about the current status of the sheet processing machine 10 can be displayed on the human-machine-interface 44 to inform the operator.

[0051] In FIG. 2, a perspective view of the device 36 is shown.

[0052] The device 36 comprises a first sensor element 46 arranged at a first side 48 of the receiving area 38 and a second sensor element 50 arranged at an opposite side 52 of the receiving area 38 such that the first sensor element 46 and the second sensor element 50 are opposite each other along a width direction of the receiving area 38 which in the shown embodiment corresponds to the transverse direction T (see FIG. 1).

[0053] The first sensor element 46 comprises a light emitting source 54 and the second sensor element 50 comprises a light receiving sensor 56.

[0054] In principle, the light emitting source 54 and the light receiving sensor 56 could also be swapped, i.e. the first sensor element 46 could also comprise the light receiving sensor 56 and the second sensor element 50 could comprise the light emitting source 54.

[0055] When the light emitting source 54 and the light receiving sensor 56 are facing each other as shown in FIG. 2, a light barrier 58 is formed between the light emitting source 54 and the light receiving sensor 56. Accordingly, any interruption of the light barrier 58 can be registered based on the sensor signal of the light receiving sensor 56.

[0056] The first sensor element 46 is mounted to a first rail 60 and the second sensor element 50 is mounted to a second rail 62, wherein the first rail 60 and the second rail 62 are parallel to each other and to a length direction of the receiving area 38 which is perpendicular to the width direction of the receiving area 38 and which in the shown embodiment corresponds to the longitudinal direction L.

[0057] The first rail 60 and the second rail 62 are mounted to a first frame 64 and a second frame 66, respectively. The first frame 64 and the second frame 66 are connected to the blank separation station 22. Accordingly, the device 36 is suited to be retrofittable to existing sheet processing machines 10.

[0058] In principle, the first frame 64 and the second frame 66 could also be parts of the blanking separation station 22 instead of being parts of the device 36.

[0059] FIG. 3 shows a side view of selected parts of the device 36 of FIG. 2.

[0060] From FIG. 3 it becomes apparent that the first sensor element 46 is mounted by a slotted guide slider 68 in a slotted guide 70 of the first rail 60. Accordingly, the first sensor element 46, and therefore the light emitting source 54 (see FIG. 2) are displaceable along the length direction of the receiving area 38 as indicated by the double-arrow P.sub.1 shown in FIG. 3.

[0061] More specifically, the first sensor element 46 is manually displaceable along the length direction of the receiving area 38 by the operator, i.e. the first side 48 of the receiving area 38 is arranged at an operator side of the sheet processing machine 10 which can be easily accessed by the operator.

[0062] The second sensor element 50 comprises an actuator 72, rendering the second sensor element 50 automatically displaceable along the length direction of the receiving area 38 as indicated by the double-arrow P.sub.2 in FIG. 3.

[0063] The opposite side 52 of the receiving area 38 is arranged at an opposite operator side of the sheet processing machine 10 which cannot be easily accessed by the operator.

[0064] In the following, the mode of action of the sheet processing machine 10 in regard to the device 36 will be discussed in more detail.

[0065] For preparing the sheet processing machine 10 for a sheet processing job, the operator sets the sheet processing machine in a set-up mode via the human-machine-interface 44. This change in operation mode is registered by the control unit 40. In principle, the device 36 could also be used analogously without entering a specific set-up mode.

[0066] Next, the operator manually displaces the first sensor element 46 along the length direction of the receiving area 38 by shifting the slotted guide slider 68 along the slotted guide 70 to a target position.

[0067] The target position is chosen such that, during operation of the sheet processing machine 10, when blanks 11 are collected in a pile of blanks 11 in the receiving area 38 up to a target height, at least a part of the uppermost blank 11 of the pile of blanks 11 is at the same position along the length direction of the receiving area 38 as the light emitting source 54 of the first sensor element 46.

[0068] With other words, if the blanks 11 in the pile of blanks 11 do not extend over essentially the complete length direction of the receiving area 38, the first sensor element 46 is placed by the operator at a position in which the blanks 11 will be present.

[0069] The control unit 40, which is connected to the first sensor element 46 and to the second sensor element 50, registers that the first sensor element 46 has been moved and starts to automatically displace the second sensor element 50 along the second rail 62 by controlling the actuator 72 for finding a working position of the second sensor element 50.

[0070] To determine the working position, the light receiving sensor 56 transmits its sensor signal at every position along the second rail 62 to which the second sensor element 50 has been moved by the control unit 40.

[0071] The control unit 40 stores the received sensor signals together with the associated position along the second rail 62 in the storage module 42.

[0072] When the light emitting source 54 and the light receiving sensor 56 are facing each other, the light barrier 58 is formed (see FIG. 2), resulting in a non-zero sensor signal from the light receiving sensor 56. The better the alignment of the light emitting source 54 and the light receiving sensor 56, the higher the resulting sensor signal will be, i.e. the maximum sensor signal is indicative for the best alignment between the light emitting source 54 and the light receiving sensor 56.

[0073] Therefore, the working position is determined by the control unit 40 by identifying the position of the second sensor element 50 along the second rail 62 at which the received associated sensor signal has been maximum. Therefore, the second sensor element 50 is moved to this position along the second rail 62.

[0074] Afterwards, the control unit 40 transmits a message to the human-machine-interface 44 to inform the operator that the device 36 has been properly set up and the light barrier 58 has been successfully formed.

[0075] Therefore, the operator can change the sheet processing machine 10 from the set-up mode to an operation mode in which the sheets 12 are processed to form blanks 11 which stack to a pile of blanks 11 in the receiving area 38.

[0076] During the operation of the sheet processing machine 10, the first and second sensor elements (46, 50) work in an intermittent fashion: when the sheet processing machine ejects a blank, the sensor elements are temporarily disabled for the time the blank needs to cross the light barrier. The remaining time, the light receiving sensor 56 is receiving constantly or at least once per pre-determined time unit, for example once per 50 ms, transmits the current sensor signal to the control unit 40. Advantageously, the light receiving sensor comprises several sensor cells disposed one above the other to precisely determine the height of the uppermost blank 11.

[0077] As soon as the pile of blanks 11 reaches a height at which the uppermost blank 11 is at the same height as the light barrier 58, the light barrier 58 will become interrupted and the sensor signal of the light receiving sensor 56 will drop, especially drop to a value of zero or at least to a value corresponding to the noise level of the light receiving sensor 56.

[0078] This change of the sensor signal is registered by the control unit 40. The control unit 40 is adapted to transmit a message to the human-machine-interface 44 that the height of the pile of blanks 11 has reached the height of the light barrier of the device 36.

[0079] Preferably, this height corresponds to a target number of blanks 11 such that the operator can stop the operation of the sheet processing machine 10 and remove the produced blanks 11 from the blank separation station 22.

[0080] In principle, the control unit 40 can also be adapted to automatically stop the operation of the sheet processing machine, once the light barrier 58 becomes interrupted.

[0081] For the next sheet processing job, the operator can again enter the set-up mode and manually adjust the position of the first sensor element 46, if necessary, and repeat the above described process.

[0082] In the embodiment described above, the device 36 for determining the height of the sheet piles is used to detect when a pile of sheets 12, more specifically a pile of blanks 11, is piled up which essentially corresponds to determine at which point in time during operation of the sheet processing machine 10 a certain number of blanks 11 have been produced.

[0083] However, the device 36 could also be used analogously to detect when a pile of sheet 12 becomes torn down, i.e. to detect when so many sheets 12 have been removed from the pile of sheets 12 that the height of the sheet pile is lower than the height of the light barrier 58.

[0084] The sheet processing machine according to the invention provides an especially simple to operate and cheap possibility for checking the height of a sheet pile. Further, the operation of the sheet processing machine can be easily adjusted to a wide variety of sizes and/or shapes of the sheets.