Patent Publication Number: US-2011072945-A1

Title: Cutting unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY 
     This is a continuation in part of application Ser. No. 10/797,024, filed Mar. 11, 2004, priority to which is claimed under 35 U.S.C. §120, the disclosure of which is incorporated herein by reference. This application is based upon application number 04 009 250.4, filed Apr. 20, 2004 in the European Patent Office, the disclosure of which is incorporated herein by reference and priority to which is claimed under 35 U.S.C. §119. 
    
    
     FIELD OF THE INVENTION 
     The invention concerns a cutting unit for trimming sheet material such as paper, films or the like, having a planar bed for supporting the sheet material, which bed is equipped on one side with a guillotine cutting device that has a pivotably mounted knife arm having a blade held thereon and a counterknife held in stationary fashion on the bed. 
     BACKGROUND OF THE INVENTION 
     Cutting units of the aforesaid kind are provided in particular for office use. They serve to trim paper sheet material, usually of DIN A4 format and smaller, at most DIN A3 format. The cutting units have a guillotine cutting device on one longitudinal side. A guillotine cutting device of this kind has a knife arm, mounted pivotably about a horizontal axis at one corner of the bed, on which a cutting knife, projecting on the lower side, is attached. It corresponds to a counterknife secured on the bed. Arranged at the free end of the knife arm is a handle with which the knife arm can be pivoted down from an upwardly pivoted position, with the consequence that a sheet material projecting beyond the counterknife is trimmed. Such cutting units have been used in offices for decades in essentially the same configuration. 
     Sheet material can be cut relatively well with such cutting units if the sheet material projects not inconsiderably beyond the counterknife, since otherwise the risk exists that the excess length will be pushed downward by the blade and not trimmed cleanly. A sheet stack comprising several sheets can also be cut simultaneously, provided the sheet stack&#39;s height is not too great. 
     Difficulties are encountered in producing a smooth cut edge if, in particular, there is only a small excess length beyond the counterknife. With guillotine cutting devices the risk also exists that the bearing assembly of the knife arm may acquire play over time, so that in order to produce a smooth cut it is necessary to press the knife arm with considerable pressure against the counterknife. Since this condition of the cutting unit is not detectable, unsatisfactory cutting results are obtained. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to configure a cutting unit of the kind cited initially in such a way that good cutting results are obtained even under difficult conditions. 
     According to the present invention, this object is achieved in that there is provided, preferably on a different side of the bed, a rotary cutting device that has a knife carriage displaceable on a guide bar and a circular knife rotatably mounted therein. The basic idea of the invention is thus to make available a cutting unit having two different kinds of cutting device, the one cutting device having strengths in the area in which the other cutting device works less well. Whereas the guillotine cutting device is suitable in particular for trimming sheet stacks, the rotary cutting device according to the present invention is characterized by a clean cut even with minimal excess lengths or when cutting off margins. It can therefore be used particularly effectively for trimming the margins of photographic prints or the like. The cutting unit according to the present invention is thus substantially more versatile to use, and takes up no more space than known cutting units of the species. 
     In a development of the invention, provision is made for the guillotine and rotary cutting devices to be arranged so that they have cutting directions extending in parallel fashion. This creates the possibility of trimming sheet material on both sides simultaneously and in absolutely parallel fashion, in which context the spacing could be dimensioned in accordance with a specific standard format. There can also be provided, between the guillotine and rotary cutting devices, a stop bar that extends parallel to the cutting directions and is displaceably guided transversely to the cutting directions. 
     The circular knife advantageously has a rotation axis parallel to the bed. The circular knife should be in contact, or at least be pressable, with its blade against a counterknife bar that can be made, for example, of plastic. 
     According to a further feature of the invention, provision is made for the guide bar to be raisable from a lower cutting position into an upper initial position, and lowerable from the latter back into the cutting position; and for the gap between bed and guide bar to be inaccessible from the ends of the guide bar. The idea underlying this is to effect the vertical movement of the circular knife not by way of the knife carriage but by means of the guide bar, by first raising the guide bar in order to slide the sheet stock through and then lowering it into the cutting position in which the circular knife rests on the bed. This makes handling of the cutting operation substantially simpler, and results in clean cuts. It is particularly important in this context that the gap between guide bar and bed be inaccessible from the ends of the guide bar, i.e. be covered there, so that it is not possible for the operator&#39;s fingers to enter the gap in that region and get caught as the guide bar is lowered. 
     In a further embodiment of the invention, it is proposed that the guide bar be guided in vertically displaceable fashion in the region of its ends so that it can be raised and lowered parallel to the bed, preferably by no more than 20 mm, preferably approx. 12 mm. As an alternative to this, however, provision can also be made for the guide bar to be mounted pivotably about a horizontal axis in the region of one end, specifically through an angle of at most 10°, preferably 4 to 5°. In order for the gap between bed and guide bar to be inaccessible at the two ends of the guide bar, those ends should overlap the bed. It is understood that in the context of a pivotably mounted guide bar, this overlap is necessary only at the latter&#39;s free end and not in the region of the pivot bearing, since the pivot bearing itself already constitutes a barrier to access to the gap between bed and guide bar. If an overlap is provided, this can be done by way of a downwardly projecting protective tab overlapping the bed. To ensure good lateral guidance of the guide bar in this region, the protective tab should fit into a matching slot in the bed. 
     The guide bar can be suspended in such a way that without actuation, it assumes the cutting position in which the circular knife rests on the bed. The guide bar can be raised manually in order to slide the sheet material through the gap between guide bar and bed. As an alternative to this, however, the possibility also exists that without actuation, the guide bar is held in the initial position by means of a spring. This facilitates sliding of the sheet material through the gap, but requires that the guide bar be pushed down for the cutting operation. A clean cut is obtained with this embodiment as well, however, since the guide bar can be pushed down with one hand and the knife carriage displaced with the other hand; this is much simpler in terms of handling than with known rotary cutting devices, in which the knife carriage must be pushed down and simultaneously displaced. 
     Provision is further made according to the invention for the guide bar to be retainable in the cutting position at its vertically movable end(s) with an immobilization device or devices. The guide bar is thereby immobilized for the cutting operation and cannot move by itself, and need not be pushed down during the cutting operation if a spring is working against it. This simplifies operation of the cutting unit. 
     The or each immobilization device is preferably embodied as a snap device into which the guide bar automatically and disengageably snaps upon movement into the cutting position, so that immobilization of the guide bar in the cutting position is not associated with additional actions. All that is necessary for the disengagement operation after the cutting operation is an actuation of the snap device in order to disengage it. The snap device can have for that purpose an actuation slider that is mounted at an appropriate location. 
     In a further embodiment of the invention, it is proposed that the bed have a region having a flexible edge, preferably a cutting bed made of an elastomeric material, and that the guide bar with the knife carriage be associated movably with the cutting unit. The user thus has the ability to arrange and use the rotary cutting device differently within the region of the elastic cutting bed. The guide bar should, in this context, protrude above a support plate that is placeable on the cutting bed. The support plate is preferably made of a transparent plastic, and lines can be provided that extend parallel to the guide bar and permit alignment of the guide bar. 
     The invention further provides that the guillotine cutting device is exchangeable for the rotary cutting device and vice versa. The bed can, in this fashion, be equipped alternately with the cutting device that is especially suitable for that particular cutting operation. If, for example, a sheet material made up of several plies of paper or film is to be trimmed, the guillotine cutting device is joined to the bed. If individual photographs or the like are to be trimmed, the guillotine cutting device is replaced with the rotary cutting device, since it is particularly suitable therefor. The advantage of exchangeability as compared with a fixed arrangement of both cutting devices is the fact that the one cutting device does not interfere with placement of the sheet material when trimming with the other cutting device. This also makes it possible to keep the bed relatively short in the direction transverse to the longitudinal axis of the respective cutting device, and thus to make the cutting unit compact and thus also easy to transport. 
     Releasable joining between the bed and the respective cutting device can be accomplished in various ways. For example, the bed on the one hand and the guillotine cutting machine and rotary cutting machine on the other hand can comprise complementary holding elements with which either the guillotine cutting device or the rotary cutting device can be attached on one side of the bed. The holding elements should comprise detent devices that enable simple attachment and at the same time ensure that the respective cutting device is attached in the correct position. The detent devices can be embodied in such a way that they are self-locking upon attachment of the cutting device, but require a disengagement actuation upon removal. This ensures that the cutting device in question cannot release itself from the detent position. 
     Lastly, provision is made according to the invention for the bed to comprise an additional bed that can be pulled out and retracted transversely to the longitudinal axis of the guillotine or rotary cutting device. The bed can thereby be made substantially longer for trimming larger formats. For smaller formats and for transporting the cutting unit, the additional bed can be retracted into the main bed so that the cutting unit requires only a small amount of space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is illustrated in more detail, with reference to exemplary embodiments, in the drawings, in which: 
         FIG. 1  is an oblique view of the cutting unit according to the present invention; 
         FIG. 2  is a side view of the rotary cutting device of the cutting unit according to  FIG. 1 ; 
         FIG. 3  is a cross section through the cutting unit according to  FIGS. 1 and 2  in the region of the rotary cutting device; 
         FIG. 4  is an oblique view of a further exemplary embodiment of the cutting unit according to the present invention, before the cutting operation; 
         FIG. 5  is the oblique view according to  FIG. 4 , after the cutting operation; 
         FIG. 6  is an oblique view of a third embodiment of a cutting unit, restricted to the corner region having the free end of the guide bar; 
         FIG. 7  is an oblique view of a fourth exemplary embodiment of the cutting unit according to the present invention, with the rotary cutting device placed movably with respect to it; 
         FIG. 8  is the oblique view according to  FIG. 6  with the rotary cutting device placed on the cutting unit; 
         FIG. 9  is an oblique view of a fifth exemplary embodiment of the cutting unit according to the present invention, with replaceable guillotine and rotary cutting devices; and 
         FIG. 10  is a cross section through the cutting unit according to  FIG. 9 , with the guillotine cutting device in place. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Cutting unit  1  depicted in  FIG. 1  comprises a frame plate  2 , substantially rectangular in plan, whose horizontal upper side forms a bed  3  for sheet material to be trimmed. A guillotine cutting device  4  is arranged on the upper (in this view) longitudinal side, and a rotary cutting device  5  on the lower (in this view) longitudinal side. 
     Guillotine cutting device  4  comprises a knife arm  6  that is mounted pivotably, in a bearing  7 , about a horizontal axis extending transversely to the longitudinal side there. Knife arm  6  is equipped on its lower side, substantially over its entire length, with a cutting knife that is concealed in this view. Configured at the free end of knife arm  6  is a handle  8  with which knife arm  6  can be pivoted upward and downward. In the position shown, knife arm  6  is located in the lower terminal position. 
     The cutting knife of knife arm  6  corresponds to a counterknife  9  that is recessed flush into bed  3 . Joined to knife arm  6  is a protective apparatus  10  that covers the cutting knife when knife arm  6  is raised, and thus offers protection for the operator. 
     Rotary cutting device  5  comprises a guide bar  11  that extends at a distance from bed  3  between two holding blocks  12 ,  13 , parallel to the cutting edge and cutting direction of guillotine cutting device  4 . A knife carriage  14  is guided on guide bar  11  displaceably in the direction of the longitudinal axis of guide bar  11 , and can be slid manually back and forth. 
     As shown in particular by  FIGS. 2 and 3 , a circular knife  15  is mounted rotatably on knife carriage  14 , specifically about a horizontal axis  16  that extends transversely to the longitudinal axis of guide bar  11 . Circular knife  15  projects downward beyond knife carriage  14  and makes contact against a counterknife bar  17  that is recessed into bed  3  and extends parallel to guide bar  11 . In the example according to  FIGS. 2 and 3 , circular knife  15  is presently traveling over a sheet of paper  18  and cutting off its excess length  19  by displacement of knife carriage  14 . 
     Extending between guillotine cutting device  4  and rotary cutting device  5 , parallel to them, is a stop bar  20  against which sheet material can be aligned. Stop bar  20  encompasses at the end a guide bar  21 , and is guided thereon in transversely displaceable fashion. Guide bar  21  extends at right angles to the cutting directions of guillotine cutting device  4  and rotary cutting device  5 . 
     Cutting unit  31  depicted in  FIGS. 4 and 5  comprises a frame plate  32 , substantially rectangular in plan, whose horizontal upper side forms a bed  33  for sheet material to be trimmed. Located in the region of the front (in this view) longitudinal side of frame plate  32  is a rotary cutting device  34 . The guillotine cutting device additionally present in the embodiment according to  FIGS. 1 through 3  is not depicted here in further detail. 
     Rotary cutting device  34  comprises a guide bar  35  that extends, at a distance from bed  33 , parallel to the longitudinal side of frame plate  32 . A knife carriage  36  is guided, displaceably in the direction of the longitudinal axis of guide bar  35 , on guide bar  35 . It surrounds guide bar  35  in U-shaped fashion and has on the upper side an attachment  37  with which knife carriage  36  can be slid manually back and forth. Knife carriage  36  has, on the front (in this view) side, a bearing shaft  38  which extends horizontally and transversely with respect to the longitudinal axis of guide bar  35 , and on which a circular knife  39  is mounted in freely rotatable fashion. Attached on bed  33  below circular knife  39  is a support surface  40  that is made of an elastomeric material. It extends over the entire movement range of circular knife  39 . 
     Guide bar  35  is joined pivotably, at the end located remotely in the views, to frame plate  32  via a pivot bearing  41 . The pivot axis extends horizontally and transversely to the longitudinal axis of guide bar  35 . Access to the gap between guide bar  35  and bed  33  is blocked by pivot bearing  41  in the region of this end of guide bar  35 . At the other end, guide bar  35  comprises a downwardly directed protective tab  42 . The latter fits into a guide groove  43  that is shaped into the short longitudinal side of frame plate  32  in such a way that protective tab  42  is enclosed on both sides and laterally guided. 
     In  FIG. 4 , guide bar  35  is located in an upwardly pivoted initial position, so that circular knife  39  is raised away from support surface  40  and a sheet material  44  to be trimmed can be slid without impediment through the gap between guide bar  35  and bed  33 . In this position, guide bar  35  is held by a spring arranged close to pivot bearing  41 , knife carriage  36  being located adjacent to pivot bearing  41 . In this position, the lower end of protective tab  42  is still located in guide groove  43  so that the gap between guide bar  35  and bed  33  is inaccessible from this end as well. 
     For the cutting operation, guide bar  35  is pivoted downward against the spring and then assumes the position depicted in  FIG. 5 , in which it extends substantially parallel to bed  33 . In that context, circular knife  39  comes into contact against support surface  40 . Knife carriage  36  is then displaced out of the position shown in  FIG. 4  in the direction of the free end of guide bar  35  with slight pressure on support surface  40 , in which context circular knife  39  performs a rotary movement and simultaneously cuts sheet material  44 . Trimmed sheet material portion  45  resting on bed  33 , and cut-off sheet material portion  46 , remain behind. 
     Cutting unit  47  depicted in  FIG. 6  differs from cutting unit  31  only in the configuration of the region at the free end of guide bar  35 ; for identical or functionally identical parts, therefore, the reference numbers already used for  FIGS. 4 and 5  are adopted for the description of this embodiment of cutting unit  47 , and reference is made to the previous description. Only the differences will be presented below. 
     Instead of protective tab  42 , guide bar  35  has at its free end a superimposed terminating block  48  that is enclosed on both sides by a guide block  49  embodied as a horizontal U and is thereby guided transversely to its longitudinal axis. Shaped into the end surface of terminating block  48  is a recess (not depicted in detail here) into which fits a catch guided in guide block  49 . The catch is joined rigidly to an actuation slider  50  that is guided displaceably in the directions of double arrow A, actuation slider  50  being tensioned by a spring in the direction toward terminating block  48 . 
     In the depiction shown, guide bar  35  is located in the (lower) cutting position and is held in that position by the catch, so that the cutting operation can be performed with no need to push guide bar  35  down. After the cutting operation, actuation slider  50  is displaced to the left, i.e. away from terminating block  48 , so that the catch moves out of the recess in the end surface of terminating block  48  and guide bar  35  is released. The latter then pivots automatically, because of the action of the spring, into the upper initial position. For another cutting operation, guide bar  35  is once again pivoted toward bed  33 . When the cutting position is reached, the catch snaps into the recess in terminating block  48  and thus once again retains guide bar  35 . 
     Cutting unit  51  depicted in  FIGS. 7 and 8  likewise comprises a frame plate  52 , substantially rectangular in cross section, whose horizontal upper side forms a bed  53  for sheet material to be trimmed. A guillotine cutting device  54  is provided on an upper (in this view) longitudinal side, and a rotary cutting device  55  in the region of the lower (in this view) longitudinal side. 
     Guillotine cutting device  54  comprises a knife arm  56  that is mounted pivotably, in a bearing  57 , about a horizontal axis extending transversely to the longitudinal side there. Knife arm  56  is equipped on its lower side, substantially over its entire length, with a cutting knife that is concealed in this view. Configured at the free end of knife arm  56  is a handle  58  with which knife arm  56  can be pivoted upward and downward. In the position shown, knife arm  56  is located in the lower terminal position. 
     The cutting knife of knife arm  56  corresponds to a counterknife, also not visible here, that is recessed flush into bed  53 . Joined to knife arm  56  is a protective apparatus  59  that covers the cutting knife when the knife arm is raised, and thus offers protection for the operator. 
     Rotary cutting device  55  comprises a guide bar  60  on which a knife carriage  61  is guided displaceably in the direction of the longitudinal axis of guide bar  60 . It can be slid manually back and forth. A circular knife (not depicted here in detail) is mounted rotatably on knife carriage  61 , specifically about a horizontal axis that extends transversely to the longitudinal axis of guide bar  60 . The circular knife projects downward beyond knife carriage  61 . Guide bar  60  is attached on a support plate  62 . Support plate  62 , and guide bar  60  with knife carriage  61 , are movable parts that can be placed at the very bottom onto bed  53  with support plate  62 , as is apparent from  FIG. 2 . 
     Also belonging to rotary cutting device  55  is a cutting bed  63  that, for use, can be inserted into a recess  64  in bed  53 , as is likewise apparent from  FIG. 2 . Cutting bed  63 , made of an elastomer, terminates flush with the upper surface of bed  53 . Cutting bed  63  acts as a counterknife for the circular knife. 
     In order for rotary cutting device  55  to be used, the unit comprising guide bar  60 , knife carriage  61 , support plate  62 , and cutting bed  63  is placed in the position shown in  FIG. 8 . The unit comprising guide bar  60 , knife carriage  61 , and support plate  62  on cutting bed  63  can be displaced by hand to allow the cut to be performed at the intended point on the sheet material. 
     Extending between guillotine cutting device  54  and rotary cutting device  55 , parallel to them, is a stop bar  65  against which sheet material can be aligned. Stop bar  65  encompasses at the end a guide bar  66 , and is guided thereon in transversely displaceable fashion. Guide bar  66  extends at right angles to the cutting directions of guillotine cutting device  54  and rotary cutting device  55 . 
     Cutting unit  71  depicted in  FIGS. 9 and 10  comprises a frame plate  72 , substantially rectangular in plan, whose horizontal upper side constitutes a bed  73  for sheet material to be trimmed. Bed  73  is supplemented with an additional bed  74  that is depicted in  FIG. 9  in the pulled-out state. It is intended, when larger sheet material is being trimmed, to make available a larger bed for the sheet material. For trimming smaller formats and for transporting cutting unit  71 , additional bed  74  is slid into a slot below bed  73 . Bed  73  itself can thus, as illustrated, be relatively narrow. 
     A guillotine cutting device  75  and a rotary cutting device  76  are associated with bed  73 . They are embodied as parts separate from bed  73  that can be alternately joined to bed  73  in a manner described in detail below. Guillotine cutting device  75  comprises a knife arm  77  that is supported in a bearing  78 , pivotably about a horizontal axis, in a bearing block  79 . Knife arm  77  is equipped on its underside, substantially over its entire length, with a cutting knife  80 . Configured at the free end of knife arm  77  is a handle  81  with which knife arm  77  can be pivoted upward and downward. Joined to knife arm  77  is a protective apparatus  82  that covers cutting knife  80  when knife arm  77  is raised, and thus offers protection for the operator. 
     Bearing block  79  is joined rigidly, via a bridge support  83  extending parallel to knife arm  77 , to a retainer  84  arranged close to handle  81 . A detent device (not depicted here in detail), which prevents pivoting of knife arm  77  with respect to bridge support  82  while guillotine cutting device  75  is being handled, can be provided between retainer  84  and knife arm  77 . 
     Rotary cutting device  76  comprises a guide bar  85  on which a knife carriage  86  is guided displaceably in the direction of the longitudinal axis of guide bar  85 . It can be slid manually back and forth. A circular knife (here concealed by a knife housing  87 ) is mounted on knife carriage  71  rotatably about a horizontal axis extending transversely to the longitudinal axis of guide bar  85 . The circular knife projects downward beyond knife housing  87 . As in the exemplary embodiment according to  FIGS. 4 and 6 , guide bar  85  is mounted on a bearing block  88  pivotably about an axis extending parallel to the knife axis. At the other end, guide bar  85  fits into a terminating block  78  [sic: ? 89 ] that is identical in design to terminating block  48  of cutting unit  47  depicted in  FIG. 6 , to the description of which reference is made. Bearing block  88  and terminating block  89  are connected via a longitudinal support  90  whose upper side comprises a cutting bed  91  for the circular knife. 
     Frame plate  72  has an end surface  93  that is provided for the attachment of either guillotine cutting device  75  or rotary cutting device  76 . Mounted on end surface  93  are two hook-shaped holding elements  94 ,  95  that, with end surface  93 , form grooves open at the top. Guillotine cutting device  75  and rotary cutting device  76  comprise retaining bars, complementary thereto, that fit into the grooves upon attachment of guillotine cutting device  75  or rotary cutting device  76 . For that purpose, guillotine cutting device  75  or rotary cutting device  76  is placed against end surface  93  from above, and then lowered. 
     End surface  93  is set back at its ends so that recesses  96 ,  97  are formed there in frame plate  72 . Bearing block  79  and retainer  84  of guillotine cutting device  75 , on the one hand, and bearing block  88  and terminating block  89  of rotary cutting device  76 , on the other hand, fit into recesses  96 ,  97 . They each project in such a way that they fit into recesses  96 ,  97  when guillotine cutting device  75  or rotary cutting device  76  is in contact against end surface  93  and fitted into holding elements  94 ,  96 . 
     Detent flanges  98 ,  99  protrude upward in recesses  96 ,  97 . Detent flanges  98 ,  99  are fastened to frame plate  92  and are spaced laterally and frontally away from the walls of frame plate  72 . At their upper ends, detent flanges  98 ,  99  form detent lugs  100 ,  101 . 
       FIG. 10  is a section through cutting unit  71  in plane A-A of  FIG. 9 , showing guillotine cutting device  75  placed onto frame plate  72 . Bearing block  79  comprises a slot  102 , open at the bottom and top, that is delimited by a retaining strip  103  that is mounted on bearing block  79  and rests against the walls of recesses  97 . Retaining strip  103  is overlapped at the top by detent lug  101  of detent flange  99 , so that bearing block  79  is securely retained in recess  97  by detent flange  99 . A corresponding configuration is provided in retainer  84  in terms of recess  96  and detent flange  98  therein, so that guillotine cutting device  75  is securely and nondisplaceably retained there as well. It is understood that bearing block  88  and terminating block  89  of rotary cutting device  76  are embodied in identical fashion on the side facing toward frame plate  72 , so that rotary cutting device  76  is retained in the same fashion when exchanged with guillotine cutting device  75 . 
     Insertion of retaining strip  103  into the gap between detent flange  99  and the oppositely located wall of recess  97  is accomplished by vertically downward motion from above. In this context, detent flange  99  is bent away from the oppositely located wall of recess  97  until detent lug  101  snaps over retaining strip  103 . To remove guillotine cutting device  75  from frame plate  72 , detent flanges  98  are bent away manually until retaining strips  103  can slide past detent lugs  100 ,  101 , and guillotine cutting device  75  can thus be moved vertically upward and removed from frame plate  72 . Rotary cutting device  76  can then be placed onto frame plate  72  from above, snap-locking with detent flanges  98 ,  99 .