Abstract:
A movable gripper unit including a housing and a first gripper arm and a second gripper arm for gripping a printed product. The first and second gripper arms are slidingly supported with respect to the housing. The housing is movable along a track. Also disclosed is a method of gripping a printed product including gripping a printed product in a gripper unit and moving the printed product with respect to the gripper unit while the printed product remains gripped.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to printing presses and more particularly to a device and method for transporting printed products. 
     2. Background Information 
     Web printing presses print a continuous web of material, such as paper. The continuous web then is cut in a cutting unit so as to form book blocks. These book blocks can be sections of a newspaper, for example. In order to transport or process the book blocks, for example to perform a trimming operation, it is often desirable to firmly grip the book using grippers which are moveable along a track. 
     U.S. Pat. No. 5,727,783 purports to disclose an apparatus for the delivery of sheets of printed products. A plurality of grippers move along a track at a certain pitch and hold the printed products. The printed products however are fixed with relation to their respective gripper, and must be transferred to a deceleration device to be decelerated. This transfer can cause damage to the printed products. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide for a device and method for gripping and transporting printed products whereby the printed products may move relative to the grippers. An additional or alternative object of the present invention is to reduce potential damage to printed products. 
     The present invention provides a gripper unit including a housing, and a first gripper arm and a second gripper arm for gripping a printed product, the first and second gripper arms slidingly with respect to the housing. The housing is movable along a track. 
     Since the first and second gripper arms may slide with respect to the housing, the speed of the printed product held by the gripper arms may be varied with respect to the track velocity. This speed variation may occur even while the printed product is firmly held by the gripper arms. 
     The first gripper arm preferably is attached to a first bar, and the second gripper arm to a second bar. Each bar is attached at each end to a slidable carriage, slidable in a slot formed in a side of the housing, which preferably is of an inverted U-shape. The first bar preferably is fixed to with respect to the carriages at its end, and the second bar preferably can rotate so as to move the second gripper arm to grasp a printed product against the rotationally-fixed first gripper arm. 
     The rotatable second bar preferably is spring-loaded with respect to the carriages at its end, so that the second gripper arm is forced into an open position. 
     An actuating lever attached to the rotatable second bar and one of the carriages can move the second bar against the spring force so that the second gripper arm grasps the printed product. Moreover, a cam can lock over center so as to hold the lever in a closed position. A latch can then lock the lever in the closed position, so that the second bar cannot rotate back to the open position. 
     Once the latch is unlatched, the product can be released, since the spring-loading of the second bar forces the second gripper arm to an open position. 
     A cam may also be provided, and connected to a V-shaped hinge having two arms. One arm is connected to the side of the housing and another arm to the slidable carriage. A cam follower acting on the cam can flatten the V-shaped hinge, so as to move the slidable carriage in the slot with respect to the housing. The hinge may lock over center. Each side of the gripper unit preferably has a cam/hinge arrangement. 
     The present invention also provides a gripping device including a track and a plurality of gripper units running in the track, each gripper unit including a housing, and a first gripper arm and a second gripper arm for gripping a printed product, the first and second gripper arms slidingly supported within the housing. 
     The gripping device may further include a chain drive for driving the gripper units, preferably at a constant speed. A cam follower may be provided to slide the gripper arms of each gripper unit with respect to the housing, so as to change the velocity of the printed products while the products remain gripped. The cam follower may interact with a cam connected to a slidable carriage supporting the gripper arms within the housing. 
     The present invention also provides a method of gripping a printed product including gripping a printed product in a gripper unit and moving the printed product with respect to the gripper unit while the printed product remains gripped. The printed products preferably are gripped by two gripper arms and then slid within a slot in a housing during the moving step. Advantageously, a cam interaction can be used to effect the sliding motion. 
     Preferably, a second of the gripper arms is rotatable and the method includes locking the second arm in a closed position with a latch and releasing the latch to release the product. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two preferred embodiments of the present invention are described below by reference to the following drawings, in which: 
     FIG. 1 shows a first side of a gripper unit of a first embodiment of the present invention in an open position running along a track; 
     FIG. 2 shows a first side of the gripper unit of FIG. 1 with the gripper arms advanced with respect to the housing; 
     FIG. 3 shows a first side of the gripper unit of FIG. 1 with the gripper arms locked closed; 
     FIG. 4 shows a perspective view of the gripper units as shown in FIG. 2; 
     FIG. 5 shows a second side of the gripper unit as shown in FIG. 3; 
     FIG. 6 shows a second side of the gripper unit with the gripper arms slid to the rear of the gripper unit housing; 
     FIG. 7 shows the gripper unit as in FIG. 6, but with the gripper arms sprung open; 
     FIG. 8 shows schematically the second gripper arm and bar of the gripper unit of the first embodiment; 
     FIG. 9 shows a side view of a second embodiment of a gripper unit according to the present invention; 
     FIG. 10 shows a perspective view of the rear and side of the second embodiment; 
     FIG. 11 shows a top perspective view of the gripper unit of FIG.  9 : 
     FIG. 12 shows a front side perspective view of the gripper unit of FIG. 9; 
     FIG. 13 shows the gripper units of the second embodiment in a track; and 
     FIG. 14 also shows the gripper units of the second embodiment in a track. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a gripper unit  1  running on a track or path  2 , for example through a constant-speed chain. Gripper unit  1  includes a housing  3  having a first side  10  and a second side  110  (shown in FIG.  4 ). Housing  3  thus may be of an inverted U-shape for example. First side  10  has a slot  12  in which a carriage  14  can slide back and forth. Gripper unit  1  includes a first gripper arm  20  and a second gripper arm  30  for gripping a printed product  5 . First gripper arm  20  is fixed with respect to carriage  14 , for example by being attached to a bar  22 , which connects fixedly to another carriage in a slot on the second side of housing  3 . 
     Second gripper arm  30  is attached fixedly to a bar  32 , which is rotatable within carriage  14 . Second gripper arm  30  is spring-loaded with respect to carriage  14  to rotate in the direction of arrow  34 , so that second gripper arm  30  is forced to an open position as shown. An actuating lever  36  is fixedly attached to bar  32 . One arm  42  of a V-shaped hinge  40  is rotatably attached to bar  32 , and rotatably attached to a second arm  44  of hinge  40  by a pin  45 . The second arm is rotatably attached to the housing  3  by a pin  48 . A cam  46  is attached fixedly to arm  42 . 
     Cam  46  can be acted upon by a cam follower  50 , so as to forced hinge  40  to open, thereby sliding carriage  14  forward in slot  12 . FIG. 2 shows the carriage  14  being slid forward in slot  12  in the direction of arrow  6 . As actuating lever  36  interacts with actuating pin  37 , lever  36  is forced in the direction of arrow  35 , i.e. against the spring force represented by arrow  34  in FIG.  1 . Actuating arm  36 , which is fixedly attached to bar  32 , thus causes bar  32  to rotate counterclockwise. 
     Since second gripper arm  30  is fixedly attached to bar  32 , second gripper arm  30  rotates downwardly as indicated by arrow  39 . 
     As shown in FIG. 3, cam follower  50  has forced cam  46  downwardly, so that hinge  40  locks over center line  60 . Carriage  14  is moved to a forwardmost position in slot  12 . An end of carriage  14  may be inward of slot  12  and extend beyond the housing  3 , however carriage  14  may not move more forwardly owing to step  15  (see also FIG. 2) which interacts with the end of slot  12 . 
     In the position shown in FIG. 3, lever  36  has moved counterclockwise so that bar  32  and gripper arm  30  have rotated to grip printed product  5 . 
     FIG. 4 shows a perspective view of the gripper unit  1  as shown in FIG.  3 . Housing  3  includes first side  10 , second side  110  and a top side  11 , which can run on track  2 , shown schematically. Second side  110  has a slot  112  in which a carriage can slide. Also near second side  110  of gripper unit  1  is a cam  146  supported on a V-shaped shaped hinge  140  having a first arm  142  and a second arm  144 . 
     FIG. 5 shows the side of gripper unit  1  opposite the side shown in FIG.  3 . Second hinge  140  is locked over center by a second cam follower  150  acting on cam  146 . Arm  144  of hinge  140  is rotatably connected to a pin  148  and to a pin  145 . Arm  142  of hinge  140  is connected to pin  145  and to bar  32 . A carriage  114  is slid forward in slot  112  by the action of cam  146 , which is forced downwardly by cam follower  150 . 
     A latch  136  is attached rotatably by a pin  137  to carriage  114 , so as to be act clockwise about pin  137 . This clockwise force can be effected for example using a spring, or alternately can occur simply from the center of gravity of latch  136  always being located behind pin  137 . As actuating lever  36  was moved in direction  133  to rotate bar  32  as described with respect to FIG. 3 above, latch  136  locks bar  32  by interacting with a step  132  at a second end of bar  32 . Latch  136  thus prevents bar  32  from rotating counterclockwise as shown in FIG. 5, i.e. to prevent second gripper arm  30  from opening. 
     Gripper unit  1  thus may travel along track  2  with printed product  5  gripped, preferably at a constant speed. To change the velocity of the printed product along track  2 , cam followers can act on cams  46  and  146  to slide carriages  14  and  114  with respect to the housing  3 , which may travel at constant velocity. Thus the gripper arms may slide back and forth as determined by the cam follower shape. This ability to change velocity without varying the housing velocity has several advantages, including eliminating or reducing the need to have a separate deceleration device to decelerate the printed products. 
     To release the gripped printed product or signature, the cams are forced to an uppermost position by their respective cam followers. As shown in FIG. 6, cam follower  150  forces cam  146  upwardly so that latch  136  almost contacts pin  148 . Printed product  5  is still gripped. In FIG. 7 cam  146  has been forced higher, so that latch  136  interacts with pin  148  to rotate and release bar  32  and step  132 . Since bar  32  is spring-loaded in direction  134 , bar  32  rotates, as do lever  36  and second gripper arm  30 , as shown by arrow  135 . 
     Printed product  5  thus is no longer gripped and may be deposited, for example, on a conveyor belt, or transferred to another gripping device. 
     FIG. 8 shows schematically a possible configuration for the bar  32 , actuating lever  36  and second gripper arm  30 , all of which are fixedly connected to one another. The lever may be acted upon by actuating pin  37  to rotate the lever  36  in the direction of arrow  180 , which operated counter to a spring force indicated by arrows  181  and  182 . Bar  32  may have two slots  183  and  184  into which leaf springs, for example, can be fit to provide the spring force. The other ends of the leaf springs can be attached to the housing  3  (see FIG.  4 ). The step  132  on bar  32  is also shown. 
     FIG. 9 shows a side view of a second embodiment of the present invention including a gripper unit  200 . Gripper unit  200  includes a housing  203  having attached prongs  204  and  205  (FIG.  11 ). Housing  203  has two roller surfaces  223  and  224 , on which a roller  208  and a roller  213  (FIG. 12) can move, respectively. 
     As shown in FIGS. 13 and 14, gripper units  200  move in a track  201 , the housing  203  being attached at the top for example to a chain running in track  201 . 
     As shown in FIGS. 9,  10 ,  11  and  12 , gripper unit  200  includes a first gripper arm  220  and a second gripper arm  230  for gripping a printed product. First gripper arm  220  is supported by rollers  206 , which can roll along prongs  204 ,  205 , so that gripper arm  220  slides with respect to housing  203 . 
     Second gripper arm  230  is rotatably connected to arm  220  at pivot  212 . A Bellevue spring washer arrangement  210 , shown schematically, keeps arm  230  open when the arm  220  is in a rear position (to the left in FIG.  9 ). The other end of the spring is attached to an arm  209  connected to roller  208  at one end and to a pin  212  at the other end. The spring  210  actually can be located to the inside of arm  230 , but is shown at the outside for clarity purposes. 
     Arm  230  is rotatably supported with respect to arm  220  about pin  212 , which is also connected to one end of an arm  214 . The other end of arm  214  is connected by a pivot  232  to a lever  242 , which is rotatable about a rod  245  rotatably supported in housing  203 . The lever  242  has at one end a cam follower  246  which can be activated by a cam  250 . 
     The second embodiment operates as follows: as cam  250  pushes cam follower  246  downwardly, roller  213  supported at an end of arm  214  is moved upwardly along roller surface  224  in a direction indicated by arrow  215 . Pin  212  at the same time is pulled forward through arm  214  in a general direction  216  which causes gripper arms  220  and  230  to slide forward, so that rollers  206  roll forward on prongs  204 ,  205 . Arm  209  is also pulled forward by pin  212  so that roller  208  rolls along roller surface  223  and moves downwardly as shown in FIG.  9 . The tension in spring  210  thus reduces and arm  230  moves downwardly to grip a printed product between arms  220  and  230 . The roller  213  can lock in the gripped position, as roller  213  can rest above a curved position in surface  224 . To release the product, a cam can be provided to move cam follower  246  upwardly and roller  213  downwardly. 
     The second embodiment may be preferable to the first embodiment, in that no latches are required and rolling produces the sliding so that friction is reduced. 
     The term “gripper arm” as used herein can include any structure used to grip a printed product and not just the bent sheets shown in the figures. The term “housing” as used herein can include any structural unit including a frame or bars, and need not “house” any elements. The term“carriage” as used herein is defined broadly as a movable element. The term “sliding” as used herein is defined as a smooth relative motion between two elements and can include a rolling arrangement. 
     U.S. Pat. No. 5,727,783 is hereby incorporated by reference herein.