Patent Publication Number: US-2010126320-A1

Title: Vacuum based part separation

Description:
TECHNICAL FIELD 
     This invention relates to systems and methods for separating cut parts from a surrounding skeleton. 
     BACKGROUND 
     When an array of parts is cut from, for example, a sheet of material, e.g., using a laser cutting device, one separates the cut parts from the surrounding “skeleton,” i.e., the scrap sheet material that surrounds the cut parts. This separation can be done manually, which is labor intensive and slow. 
     SUMMARY 
     The systems and methods disclosed herein provide a simple and cost-effective way of separating cut parts from a skeleton. One can then transfer the cut parts to a desired location. 
     In one aspect, the invention features a part separation device for separating cut parts from a surrounding skeleton, the device including: a frame defining a vacuum passageway; attached to the frame, an array of suction devices, each suction device being movable between a normal self-sealed position, a pick-up position, and a release position; and, attached to the frame, at least one skeleton holder being configured to apply a release force to the skeleton thereby moving any suction devices in contact with the skeleton from the pick-up position to the release position, thereby releasing the skeleton from the suction devices. 
     Some implementations include one or more of the following features. Each suction device comprises a member defining a vacuum passage terminating in a suction opening, and at least one spring element configured to bias the member. The suction devices are configured so that, in the pick-up position, the vacuum passage of the member is in flow connection with the vacuum passageway of the frame. The release force acts in a direction opposite to a direction of a suction force of the suction devices. Each of the suction devices comprises a check valve that is movable between a closed position, corresponding to the self-sealed position of the suction device, and an open position. Each of the suction devices comprises a vent configured to allow a small amount of leakage past the check valve when the check valve is in the closed position. Each suction device further comprises a housing, the housing surrounding the member and forming a vacuum chamber between the member and the housing, the vacuum chamber being connected to the suction opening of the member. The spring element comprises a first spring acting between the member and the mount and a second spring acting between the housing and the mount. The member comprises an actuating extension for contacting a work piece to be attached to the suction cup. Each suction device is configured so that the member is movable by the first spring into a release position when a release force is applied to the housing. Each skeleton holder includes an outer housing and an extendable member, telescopically disposed within the housing, the extendable member being configured to apply the release force. The device further comprises a workpiece support configured to support the skeleton. The device further comprises a translation stage configured to move the frame relative to the workpiece support. 
     In another aspect, the invention features a method for separating a cut piece from a skeleton of a workpiece, the method comprising: supporting the workpiece on a workpiece support; vacuum attaching a first suction device to the cut piece and a second suction device to the skeleton, the suction devices being mounted on a frame; moving the frame away from the workpiece support to pull the cut piece from the skeleton; and, holding the skeleton down against the workpiece support to release the second suction device and separate the cut piece from the skeleton. 
     Some implementations include one or more of the following features. The method further comprises applying a blow out pressure to the first suction device to release the cut part from the first suction device. Holding the skeleton down comprises actuating a skeleton holder that is mounted on the frame. Actuating the skeleton holder comprises extending an extendable portion of the skeleton holder to maintain contact between the skeleton holder and the skeleton as the frame is moved away from the workpiece support. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view, taken from below, of a part separation device. 
         FIG. 2  is a side view of a skeleton holder and of a first and a second suction devices, shown in a starting position for a skeleton part. 
         FIG. 3  is a side view of the skeleton holder and the suction devices of  FIG. 2 , shown in an evacuation position. 
         FIG. 4  is a side view of the skeleton holder and the suction devices of  FIG. 3 , shown in a holding position. 
         FIG. 5  is a side view of the skeleton holder and the suction devices of  FIG. 4 , the first suction device being in a release position. 
         FIG. 6  is a side cross-sectional view of a first embodiment of the suction device, shown in an evacuation position. 
         FIG. 7  is a side cross-sectional view of the first embodiment, shown in a holding position. 
         FIG. 8  is a side cross-sectional view of the first embodiment, shown in a self-sealed position. 
         FIG. 9  is a side cross-sectional view of a second embodiment of a releasable suction device, shown in an initial position. 
         FIG. 10  is a side cross-sectional view of the second embodiment, shown in an evacuation position. 
         FIG. 11  is a side cross-sectional view of the second embodiment, shown in a holding position. 
     
    
    
     DETAILED DESCRIPTION 
     The part separation devices described herein allow cut parts to be automatically separated from a surrounding skeleton. A part separation device includes a frame on which suction devices are mounted. The suction devices grip the cut parts and skeleton by vacuum. Skeleton holders, which are also mounted to the frame, hold the skeleton down and thereby allow the suction devices to pull the cut parts from the skeleton. 
     As will be discussed in detail below, the suction devices are designed to automatically release an attached element (skeleton or cut part) under certain conditions. Thus, any suction devices that have gripped the skeleton can release it while the cut parts continue to be attached to the remaining suction devices. 
     Referring to  FIG. 1 , a part separation device  10  includes a frame  12  that is made up of a few, widely spaced frame members  14 , extending in a first direction, and many closely spaced, vacuum members  16  disposed generally perpendicular to the frame members  14 . A plurality of releasable suction devices  20 , the structure of which will be described in detail below, are mounted on the vacuum members  16 . A pair of a skeleton holder  18  and a suction device  20  is indicated in  FIG. 1  in detail A. In the example shown in  FIG. 1 , the suction devices are distributed as a closely spaced array. Skeleton holders  18 , e.g., solenoids, are mounted on at least some of the frame members  14 , for example, at or near the corners, as shown. During a pick up process, the suction devices  20  will attach to cut pieces and to the skeleton as will be discussed in further detail below. The skeleton holder  18  holds the skeleton down, allowing the suction devices to pull up on the cut parts and separate them from the skeleton. 
     As mentioned above, at some positions suction devices may also attach to the skeleton. To detach a suction device from the skeleton, the skeleton holders  18  hold the skeleton down on the underlying support, e.g., a pallet. The skeleton holder  18  is positioned such that it can apply a holding force to the skeleton when detaching the skeleton from the suction device. For example, by extending its length, the skeleton holder  18  holds the skeleton down as the frame  12  is lifted to pull up on the cut parts. Thus the skeleton holders apply a force to the skeleton and—via the skeleton—to those suction devices  20  attached to the skeleton. The force moves the suction devices to an operating state in which the vacuum is broken, as will be discussed below. 
     The part separation devices will now be described in further detail with reference to the drawings. We describe first the general concept of the disclosed suction devices, with reference to schematic drawings ( FIGS. 2-6 ), and then two exemplary implementations (shown in  FIGS. 6-8  and  9 - 11 ). 
     The operation of the part separation device is illustrated schematically in  FIGS. 2-6 . The part separation device is configured to selectively separate cut parts  21  from a remaining skeleton  22 . The operation is described based on a schematic skeleton holder  24  and two schematic suction devices  26 A and  26 B. The skeleton holder  24  and the suction device  26 A are positioned above the skeleton  22  whereas the suction device  26 B is positioned above the cut piece  21 . 
       FIG. 2  also shows a vacuum member  16 , on which the skeleton holder  24  and the suction device  26  are mounted. The vacuum member  16  includes a vacuum passage way  23 , which is, for example, connected to a vacuum pump such that a vacuum pressure prevails within the vacuum passage way  23 . The vacuum passage way  23  thereby represents a vacuum reservoir for the suction device  26 . 
     Each of the suction devices  26 A and  26 B includes a mount  28  that is mounted to the vacuum member  16  and that provides a ventilation opening  30 . Each suction device  26 A and  26 B further includes a pin  32  that is movable within an opening of the mount  28 . The movement is constrained by a spring element, e.g., a spring that is interacting between the mount  28  and the pin  32 . The pin  32  provides a vacuum passage  34 , e.g. a hole shaped in a t-form that connects first openings  36  with a suction opening  38 . The pin  32  also includes a check valve  39  as shown. The check valve may include, for example, a valve element, such as a ball, which is pulled upward by the vacuum against a seat. 
     In  FIG. 2 , the vacuum member  16  is mounted to a translation stage  40  of the part separation device. The translation stage  40  is connected to a control unit  42 . Thus, moving the translation stage  40  up or down varies the distance between a base plate  44  (and thus the skeleton  22  and cut piece  21 ) and the suction devices  26 A and  26 B (specifically, the suction opening  38 ). This movement also varies the distance between the skeleton holder  24  and the base plate  44 . The control unit is further connected with the skeleton holder  24  to control, for example, how far part  46  extends from a body part  48  of the skeleton holder  24 . 
     In  FIG. 2 , the suction devices  26 A and  26 B are in an initial operating position, in which the pins  32  are positioned such that the vacuum passage way  23  is in flow connection with the first openings  36 . The check valve is in an open position. However, at this point in the process the vacuum source is off. In this example, the initial position is an equilibrium position of the spring element. 
     When the translation stage  40  reduces the distance between the pins  32  and the base plate  44 , the pins  32  will contact the cut part  21  and the remaining skeleton  22  ( FIG. 3 ). The check valves are configured such that if the first opening  36  is in fluid communication with the vacuum passage way  23  and the suction opening  38  is sealed by a cut part  21  (or the skeleton  22 ), the check valve remains open. Then, the cut part  21  (or the skeleton  22 ) is attached to the pin  32  via the vacuum passage  34 . An exemplary evacuation position is shown in  FIG. 3 . If the suction opening  38  is sealed by the skeleton  22  or the cut piece  21 , the skeleton  22  or the cut piece  21  will be vacuum attached to the suction device  26 A. In general, in the evacuation position, the vacuum passage is connected to the vacuum passage way  23  of the vacuum member  16 , thereby connecting the suction opening  38  with a vacuum pressure reservoir. 
     Lifting the vacuum member  16  away from the base plate  44 , while maintaining suction, will cause the cut part to be lifted from the base plate  44 . This raised position is shown in  FIG. 4 . 
     During the lifting, the skeleton holder  46  is holding the skeleton  22  down, and thus the skeleton  22  is not lifted even though it is attached to the suction device  26 A. Instead, the pin  32  moves within the mount  28  and vacuum member  16 , breaking the vacuum connection between vacuum passage  36  of suction device  26 A and the vacuum passageway  23 . 
     To enable the skeleton  22  to be released from the suction device  26 A, the pins  32  are movable with respect to the mount  28  between the evacuation position and a releasing position ( FIG. 4 ). When initiating the release of the skeleton, translation stage  40  moves up and part  46  extends further out of the body part  48 . The part  46  moves further out so that it continues to contact skeleton  22  and applies a force to the skeleton. This force holds the skeleton down while the pin  32  of the suction device  26 A moves along the mount  28  until the first openings  36  are aligned with the ventilation openings  30  (see  FIG. 4 ). Due to venting through these openings, the vacuum within the vacuum passage  34  breaks and the skeleton  22  is released from being attached to the suction opening  38  ( FIG. 5 ). Meanwhile, the suction device  26 B remains attached to the cut piece  21  because the cut piece  21  is not connected to the skeleton  22  and thus is not held down by the skeleton holder  24 . 
     As soon as the skeleton  22  is released, there is no force acting on the pin  32  of the suction device  26 A and the spring element causes a movement of the pin  32  of suction device  26 A back into the initial position. At this point there is a fluid connection between openings  36  and passageway  23 , and as a result the check valve  39  seals the vacuum passage  34 . As shown in  FIGS. 4 and 5  and discussed above, the vacuum attachment of the cut piece  21  is not affected by the release mechanism. Thus, the suction devices are selectively released or maintained in engagement in order to separate cut piece  21  from the skeleton. 
     In  FIGS. 6-8 , a single-spring suction device  50  is shown in different operating states. Suction device  50  is an example of a preferred type of suction device that can be used in the part separation device  10  described above. The single-spring suction device  50  includes a mount unit, a pin  54 , a suction cup  56 , and a spring  58 . The mount unit includes a mount housing  60  and a ring plate  62 . Together with the base ring  62 , the mount housing  60  is screwed to a vacuum member  16 ′. Between the mount housing  60  and the ring plate  62 , ventilation channels  64  connect the inside of the mount unit with the surrounding atmosphere. 
     The pin  54  is made of a solid, vacuum tight material. To an end of the pin  54  (herein the “lower end”), the suction cup  56  is vacuum tight attached. Within the pin  54 , two intersecting holes  66  penetrate the pin  54  radially, thereby providing a flow connection to a central vacuum channel  68 . The vacuum channel  68  is closed at the end opposite to the suction cup (herein the “upper end”) and is in fluid communication with a suction volume  70  defined between the suction cup  56  and an element  71 . At the lower end, the vacuum channel  68  is machined so as to incorporate a check valve in which a sealing ball  72  is positioned. 
     As shown in  FIG. 6  an upper valve ring  73  is inserted into the vacuum channel. The ball  72  is blocked from leaving the vacuum channel at the lower end by a stop ring  74 . The stop ring  74  also holds a filter disc  175  to keep dirt and debris out of the vacuum system. 
     The pin  54  is movable along an axis of the suction device  50 . The movement of the pin  54  is constrained by the spring  58 , which surrounds a center part of the pin  54 . An upper end of the spring acts on a flange  75  of the pin  54  while the lower end of the spring  58  acts on a seat  76  of the mount housing  60 . The movement of the pin  54  is further limited in one direction by the flange  75  touching the base ring  62 , and in the opposite direction by a step  78  of the outer surface of the pin  54  touching the seat  76  of the mount housing  60 . 
     Within the range of possible pin positions, the intersecting holes  66  can move into flow connection with a vacuum passage way  23 ′ that is formed within the vacuum member  16 ′ (evacuation position). In some embodiments, the evacuation position can coincide with the flange  75  touching the base ring  62 . This position can be the same initial position which the pin  54  adopts due to the force of the spring  58 . 
     If the intersecting holes  66  are aligned with the vacuum passage way  23 ′ and no element  71  (cut part or skeleton) seals the suction volume  70 , the check valve will be activated by the air sucked into the vacuum channel  68 , thereby self-sealing the vacuum system of the part separation device as shown in  FIG. 8 . The self-sealing can also occur if, for example, the suction cup  56  covers a laser cut line such that the suction volume  70  cannot be sealed and evacuated. 
     In some cases, the intersecting holes  66  are aligned with the vacuum passage way  23 ′ and the suction cup  56  only partially seals against the element  71  (marginal sealing conditions). In these cases, the check valve will be deactivated by the air of suction volume  70  being sucked through a tiny hole  79  into the vacuum channel  68 . This reduces the pressure difference between the vacuum channel  68  and the suction volume  70  and the sealing ball  72  is released to position in which it does not seal against the ring  73 . Then, the vacuum system of the part separation device is in direct flow connection with the suction volume  70  and the element  71  is vacuum attached to the pin  54 . 
     Suction devices that are in the evacuation position can be unsealed by breaking the vacuum in the vacuum passageway  23 ′, e.g., by blowing compressed air through the vacuum passageway  23 ′. Such a blow-out cycle allows attached parts to be released quickly and, for example, dropped at a predefined position. 
     Suction devices to which the skeleton is attached can be unsealed using the skeleton holder  46 , shown in  FIG. 4  and discussed above. Skeleton holder  46  applies a force to the skeleton which compresses spring  58 , aligning holes  66  with channel  68 , and thereby moving the pin  54  into the release position. 
     The suction device described above performs well even under problematic sealing conditions, e.g., when the part to which the suction device is to be sealed is tipped or uneven. 
     In  FIGS. 9-11 , an actuating-pin suction device  100  (an alternative type of suction device) is shown in different operating states. The actuating-pin suction device  100  includes a pin  104  with an actuating pin extension  106 , a suction cup  108 , a first spring  110 , and a second spring  112 . 
     The suction device  100  also includes an inner housing  114 , an outer housing  116 , and a ring plate  118 . Together with the ring plate  118 , the outer housing  116  is mounted on a vacuum member  16 ″. Between the outer housing  116  and the ring plate  118 , ventilation channels  120  connect the inside of the mount unit  114  with surrounding atmosphere. 
     Constrained by the first spring  110 , the pin  104  is movable within the inner housing  114  and, constrained by the second spring  112 , the inner housing  114  is movable within the outer housing  116 . 
     The pin  104  provides a channel system  122  between a first set of openings  124  and a second set of openings  126 . The first set of openings  124  can be moved into fluid communication with a vacuum passage way  23 ″ or with the ventilation channels  120 . The second set of openings is in flow connection with a vacuum chamber  128  that is formed between the pin  104  and the inner housing  114 . A suction volume  130  is defined by the suction cup  122  and an attached element  134 , as shown in  FIG. 10 .  FIG. 10  also shows that the vacuum chamber  128  can be in flow communication with the suction volume  130  through an opening  136  in the inner housing  114 . 
     During operation of the suction device  100 , the pin  104  and the inner housing  114  are movable between an initial position, shown in  FIG. 9 , and an evacuation position, shown in  FIG. 10 , in which the element  134  (cut part or skeleton) is attached to the suction cup  108 . In order to break the vacuum and release the skeleton, the first set of openings  124  is positioned to overlap with the ventilation channels  120  or a volume  140  that is created when the inner housing  114  is moved away from the ring plate  118  ( FIG. 11 ). The volume  140  is in fluid communication with the ventilation channels  120 . The openings  124  are drawn downward into this position when the suction device is pulled downward by the holding force applied by the skeleton holders. 
     In  FIG. 9 , the suction device  100  is shown in an initial position, in which the first spring  110  positions the pin  104  with respect to the inner housing  114  and the second spring  112  positions the inner housing  114  with respect to the outer housing  116 . In the initial position, the vacuum passage way  23 ″ of the vacuum member  16 ″ is sealed by the pin  104 . Additionally, the suction volume  130  is sealed from the vacuum chamber  128 , as discussed above. 
     When the actuating pin  106  moves upward within the inner housing  114  ( FIG. 10 ), e.g., when the pin  106  is pushed against a surface of the element  134 , compressing spring  110 , openings  124  move into communication with the volume  140  ( FIG. 11 ). 
     The evacuation of a volume of the suction device  100  is initiated as soon as the first set of openings  124  is aligned with the vacuum passageway  23 ″. The evacuatable volume includes the channel system  122 , the vacuum chamber  128 , the opening  136 , and the suction volume  130 . In the operating state shown  FIG. 10 , the evacuatable volume has a lower pressure than the surrounding atmosphere and the element  134  is vacuum attached to the suction cup  108 . 
       FIG. 11  shows a position of the suction device  100  in which the spring  110  has moved to an uncompressed state and the pin  104  is being pushed downward. In the case shown in  FIG. 11 , the element  134  is part of the skeleton, and the suction device will move to the position shown in  FIG. 11 , and beyond it, to a release position (not shown) due to the force applied by the skeleton holder  46  ( FIG. 4 ), as discussed above. 
     The movement of inner housing  114  is biased by the force of the spring  112 . As soon as the first set of openings  124  aligns with volume  140 , the volume fills with atmospheric air and the vacuum attachment breaks, thereby releasing the element  134  and allowing the spring  112  to move the inner housing  114 , the suction cup  108 , and the pin  104  back to the initial position. 
     Other embodiments are within the scope of the following claims.