Patent Grant
9352917
The invention relates to a method for removing a substantially planar work piece from the top of a stack of work pieces. It further relates to an apparatus for removing a substantially planar work piece from the top of a stack of work pieces.
In many applications, substantially planar work pieces, such as e.g. metal sheets, need to be removed one by one from a stack of work pieces. Corresponding methods and devices allowing for automatic removal and feeding e.g. to a processing station, are known. Often, these devices seize the top work piece from the stack by suitable grippers, e.g. magnetic elements or suction cups, and transport it to a desired location by moving the grippers together with the seized work piece.
One of the applications where corresponding devices are used is the processing of metal sheets in order to manufacture car body parts. Large-sized metal sheets are punched and shaped to obtain the desired geometry, in particular in a multi-stage press or press line. Prior to processing, a feeder seizes the top work piece of a stack and feeds it to the first processing station, which may be the head press but also stations for pre-processing such as de-greasing, cleaning, etc.
Removing the top sheet—and only the top sheet—from the stack is difficult: Often, neighboring sheets adhere to each other, e.g. because of coatings of the sheets (such as an oil film), which leads to sticking together of two or more sheets. However, if more than one sheet is seized and fed to the downstream process line, this may lead to severe damage up to destruction of a press tool. Current demands regarding processing speed make de-stacking even more challenging.
Several methods and devices for automatic destacking are known from the prior art. As an example, German patent No. 671 402 (Schuler) relates to an automatic apparatus for lifting and feeding strips to high speed presses, punching machines or similar. The strips are lifted from a stack and fed to a pincing feeder. A stop for the strip is arranged below the pincer neighboring the stack. Between the stop and the downstream edge of the stack, a lifting device is arranged for lifting the downstream end of the strip to the transport plane of the pincer. A suction device is arranged close to the upstream end of the stack. It is used for partially detaching the strip from the stack and may also be used for feeding the strip to the pincing feeder. Alternatively, there may be a separate feeding device for that purpose.
DE 33 12 459 A1 (Lewecke Maschinenbau) relates to a method for separating planar work pieces, such as flake boards, adhering to each other, when the topmost work piece is to be lifted by a suction gripper. For that purpose, pressurized air is directed into the gaps between adjacent workpieces. Furthermore, the separation process is supported by jerky accelerations and decelerations of the lifting movement.
DE 10 2005 062 713 A1 (Holzma Plattenaufteiltechnik) discloses a device for separating and removing a partial stack comprising at least one extended sheet from a remaining stack. The device includes an air nozzle which may be directed to the region of a separating plane below the lowest sheet of the partial stack. It may further include a separating element which may be introduced into a gap produced by the action of the air nozzle, in order to mechanically securing the gap and enlarging it, if required. In a further step, the partial stack is removed by means of a transport device comprising a transport bar and tongs.
Still, the known devices have drawbacks when removing extended and comparably heavy sheets, especially when a high throughput is required. The additional steps for improving the separation make the removal process more complicated and time-consuming.
It is the object of the invention to create a method and a device pertaining to the technical field initially mentioned, that allow for fast and reliable removal of substantially planar work pieces from the top of a stack.
The solution of the invention is specified by the features of claims 1 and 8. According to the invention, the method comprises the step of
Correspondingly, the device according to the invention comprises
It is to be noted that it is not required that the gripper lifts the work piece in such a way that it loses contact with the rest of the stack over its entire surface, but that lifting the work piece should be at least such that the separator element may be introduced in between the lifted work piece and the neighboring work piece. Furthermore, the possible movement of the gripper should have a vertical component allowing for lifting the gripped work piece in the way described before, it is not required that the gripper is movable along a (straight) vertical path. Similarly, the possible movement of the separator element should have a horizontal component allowing for introducing the separator element in between the two mentioned work pieces, it is not required that the separator element is movable along a (straight) horizontal path.
The invention allows for a pre-separation of the topmost work piece from the stack of work pieces, prior to actually removing the work piece by the transport device. The transport device grips the pre-separated work piece, which allows for seizing the work piece by the transport device in a much faster way than in cases where the work piece has to be separated in the context of being seized by the actual transport device. Pre-separation is largely independent from the activity of the transport device or downstream processing stations, with the only constraint that pre-separation has to be completed when the transport device approaches the work piece. Correspondingly, there is more time available for the entire separation process while at the same time the achievable speed of removing the work piece by the transport device is increased.
The gripper gripping the work piece on a top surface avoids the need for contacting the stack along its sides, which may require complicated controlling of the respective elements and may interfere with further elements of the system.
Accordingly, the invention allows at the same time for better reliability as well as for higher throughput of the removal process. In fact the method and apparatus according to the invention are particularly suited for the handling of metal sheets having sizes between 500×500 mm and 4500×2200 mm, at processing rates of 12/min or higher.
Preferably therefore, in the context of the inventive method, the steps of gripping and lifting the work piece and introducing the separator element are effected during removal and/or feeding of the preceding work piece by the transport device.
The inventive apparatus and method are particularly suitable for the removal of non-ferromagnetic metal sheets, such as aluminium sheets. These sheets tend to adhere to each other, at the same time most magnetic units will not be applicable for separating or even gripping the sheets.
Accordingly, a preferred embodiment of the inventive apparatus has a gripper comprising a suction system for gripping the top surface of the work piece. The suction system allows for gripping non-ferromagnetic metal sheets or other work pieces by just contacting their top surface. They are easy to implement and cost-efficient. Furthermore, the work pieces may be rapidly and easily released by switching off the vacuum applied to the suction system.
Instead of a suction system (or in addition thereto) elements based on other effects may be employed, such as magnetic grippers (for work pieces made from a ferro-magnetic material) or mechanical grippers (especially if the work pieces comprise suitable structures on their top surface, which allow for the application of mechanical grippers).
In a preferred embodiment, the separator element comprises an injector for feeding pressurized gas in between the lifted work piece and the neighboring work piece. Pressurized air is preferred as it is easily available.
The feeding of pressurized gas may support the separation of the neighboring work pieces, especially in regions where separation has not been accomplished by the actions of the gripper. It may also prohibit that the work pieces—once separated—adhere to each other again, especially during the seizure of the top work piece by the transport device.
Pressurized gas may be feed prior and during the introduction of the separator element in between the work pieces and/or after it has been fully introduced, i.e. reached its end position between the work pieces.
Preferably, the separator element comprises a separator panel and an injection nozzle arranged below the separator panel. The separator panel is formed in such a way that it guides gas ejected through the nozzle in between the lifted work piece and the neighboring work piece. This means that, generally, the mouth of the nozzle will be set back with respect to the front end of the separator panel. The separator panel being introduced in between the work pieces and having a generally flat form (the main surface of the panel being in particular parallel to the main surfaces of the work pieces of the stack) is well suited for guiding the gas stream. Depending on the work pieces to be separated, suitably directing the pressurized gas may be crucial for a reliable separation. Furthermore, additional guide elements may be dispensed of, the separator panel has a double function of mechanically supporting the lifted work piece and guiding the gas stream.
Alternatively, the injection nozzle may be arranged differently, e.g. at the front end of the separator element or above the separator element.
Preferably, the work piece is gripped in a region close to an edge of the work piece. Furthermore, the separator element is introduced in between the work pieces in this region. This allows for a simple construction of the apparatus, generates maximum separation forces along the respective edge and ensures that the separator element can be introduced in between the work pieces.
Accordingly, it is preferred to have a plurality of grippers and separator elements being arranged along a lateral edge of the work piece. The plurality of grippers and separator elements ensure that even large work pieces are reliably separated and kept separated in a large part thereof. Arranging the grippers and separator elements along a lateral edge keeps the back end and the front end of the stack free, which facilitates feeding and removal of work pieces to or from the stack, respectively. It is to be noted, that in the context of this preferred embodiment the invention requires to have grippers and separator elements only along one of the lateral edges, i.e. the opposing lateral edge is as well accessible, if required.
The plurality of grippers and separator elements may have separate drives, actuators, guides and controllers or may share some or all of these components.
Still, it is possible to have grippers acting on a region distant from any of the edges of the work piece. Grippers may also be arranged along a plurality of lateral and/or cross edges of the work piece.
Preferably, the gripper is removed after having introduced the separator element and prior to approach of the gripping elements of the transport device. Similarly, advantageously the work piece is gripped by the transport device when it is at least partially supported by the separator element.
The separation is upheld due to the separator element, therefore the gripper is not required anymore for that purpose. Removing the gripper exposes the entire top surface of the work piece, which means that substantially any available transport device may grip and remove the work piece, with maximum speed. Special solutions are not required.
Advantageously, the gripper and the separator element are arranged on the same unit. This allows for a simple construction and installation of the inventive apparatus. Furthermore, some of the required movements, such as a horizontal movement along a working direction, that are required for both the gripper and the separator element may be actuated by a common element.
In the context of that embodiment, it is preferred that the unit comprises a first carriage carrying the gripper, the first carriage being movable along a horizontal working direction and a second carriage carrying the separator element, the second carriage being movable along the working direction, whereas the movements of the two carriages are substantially independent from each other. Furthermore, the gripper is movable in a substantially vertical direction with respect to the first carriage. This allows for implementing all the required degrees of freedom in a simple, reliable and cost-efficient way.
Furthermore, it is advantageous to have a working direction that is perpendicular to a transport direction of the transport device. In that case, the unit is arranged sideways of the work pieces and the working direction runs perpendicular to the lateral edge facing the unit(s).
Alternatively, the gripper and the separator are separate entities with separate mountings and separate drives.
Other advantageous embodiments and combinations of features come out from the detailed description below and the totality of the claims.
The drawings used to explain the embodiments show:
In the figures, the same components are given the same reference symbols.
On one end, the guide rail 61 extends over the stack 10 such that work pieces seized by the transport mechanism 60 may be transported along the guide rail 61 in the transport direction 1 to a subsequent station, i.e. the first station of a multiple-stage press. For that purpose, the main carriage 62 is moved along the guide rail 61 until the cross-beams 65.1 . . . 65.6 carried by the main carriage 62 are positioned over the stack 10. This is the situation shown in
Transport devices 60 as shown in
In the situation shown in
The operation part 30 comprises a gripper carriage 31, which is movable relative to the base part 21, along the longitudinal extension of the device 20, i.e. perpendicular to the longitudinal edge of the stack. For that purpose, the gripper carriage 31 is supported on a first guide rail attached to a lateral panel 22 of the device 20 neighboring the support beam 70 of the machine frame. Linear movement of the gripper carriage 31 relative to the guide rail is actuated by a pneumatic cylinder 32 attached between the base part 21 and the rear end of the gripper carriage 31. A suction cup 33 is attached to a four-bar linkage 34 and actuated by a further pneumatic cylinder 35, the rear end of which being mounted to the gripper carriage 31, the front end of which controlling a control arm 34a of the four-bar linkage 34.
The operation part 30 further comprises a separator carriage 41, which is movable relative to the base part 21, along the longitudinal extension of the device 20, i.e. perpendicular to the longitudinal edge of the stack. For that purpose, the separator carriage 41 is supported on a second guide rail attached to the gripper carriage 31. Linear movement of the separator carriage 41 relative to the guide rail 36 is actuated by a pneumatic cylinder 42 attached between the base part 21 and the rear end of the separator carriage 41. A separator panel 43 is attached to the front end of the separator carriage 41. In cross-section, the separator panel has a central flat section and lateral sections including an inner region extending from the central section in an inclined direction as well as an outer region parallel to the central flat section of the separator panel 43. The width of the inner region of each lateral section decreases in the direction of the free end of the separator panel 43. Below the separator panel 43 an injection nozzle 44 is arranged at the front end of the separator carriage 41, along the middle axis of the separator panel 43 (see also
The further pneumatic cylinder 35 of the gripper carriage 31 is attached to a pneumatic line and the suction cup 33 is attached to a further pneumatic line, both via a first energy chain 51 linking the gripper carriage 31 to the base part 21. The injection nozzle 44 is supplied with pressurized air via the first energy chain 51 and a second energy chain 52 linking the gripper carriage 31 to the separator carriage 41.
The
In order to pre-separate the topmost work piece 11 from the stack 10, the gripper carriage 31 is moved to its foremost position by actuating the pneumatic cylinder 32. Next, the suction cup 33 is lowered by actuating the further pneumatic cylinder 35 until the upper surface of the topmost work piece is contacted. The resulting situation is shown in
Next, the suction cup 33 is lifted by means of the pneumatic cylinder 35. Along the corresponding edge, the topmost work piece 11 lifted as well, creating a clearance between the topmost lifted work piece 11 and the second work piece of the stack 10. Then, the separator carriage 41 is moved to its foremost position by actuating the pneumatic cylinder 42, where the front part of the separator panel 43 extends into the clearance between the topmost lifted work piece 11 and the second work piece. The corresponding situation is shown in
Next, air is injected into the clearance through the nozzle 44. Finally, the vacuum applied to the suction cup 33 is switched off. The topmost work piece 11 is deposited on the separator panel 43. Now, the gripper carriage 31 may be retracted to its back position, reaching the situation as shown in
Pre-separation happens in the time interval when the previous work piece has been fully removed from the stack of work pieces, prior to gripping and removing the next work piece by the transport device. Correspondingly, pre-separation will ease and speed up the removal of the work pieces without and additional time requirement.
The invention is not limited to the described embodiment. Various elements, in particular the mountings and actuators of the suction cup and the separator, may be embodied in other ways. Depending on the length of the work pieces to be removed, a single device or a smaller number of devices for pre-separating may suffice or more than nine devices are needed.
In summary, it is to be noted that the invention creates a method and a device for removing a substantially planar work piece from the top of a stack of work pieces, that allow for fast and reliable removal.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CH2012/000137 | 6/22/2012 | WO | 00 | 1/16/2015 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/188987 | 12/27/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4470589 | Singer | Sep 1984 | A |
| 5092578 | Bergmeier et al. | Mar 1992 | A |
| 5290023 | Sasaki et al. | Mar 1994 | A |
| 5542658 | Wirz et al. | Aug 1996 | A |
| 20060170146 | Kato | Aug 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 1809504 | Jul 2006 | CN |
| 1814528 | Aug 2006 | CN |
| 671 402 | Feb 1939 | DE |
| 31 36 544 | Mar 1983 | DE |
| 33 12 459 | Oct 1984 | DE |
| 10 2005 062 713 | Jul 2007 | DE |
| 0 173 613 | Mar 1986 | EP |
| 2653419 | Oct 2013 | EP |
| H04-22431 | Feb 1992 | JP |
| 04-094830 | Mar 1992 | JP |
| 11-232421 | Aug 1999 | JP |
| 2002-211776 | Jul 2002 | JP |
| 776974 | Jul 1980 | SU |
| Entry |
|---|
| Chinese Office Action dated Sep. 20, 2015 issued in corresponding Chinese Application No. 201280074151.0 with an English Translation. |
| Japanese Office Action dated Apr. 12, 2016 issued in corresponding JP Application No. 2015-517569 with an English translation. |
| Number | Date | Country | |
|---|---|---|---|
| 20150197404 A1 | Jul 2015 | US |
