Abstract:
A hand-operated machine tool includes a movable lever having a cutting portion and a driving portion, a stroke drive comprising a rotating stroke eccentric driven about a rotation axis, the stroke drive operable with the driving portion to reciprocate the cutting portion between end positions, a cam carrier comprising an adjusting cam disposed between the stroke eccentric and the driving portion and operable to move together therewith, the adjusting cam comprising a pitched portion, and a retaining stop configured to engage the cam carrier and move between a released position and an active position. When the retaining stop is moved to the released position, the cam carrier engages and drives the stroke eccentric. When the retaining stop is moved to the active position, the cam carrier disengages the stroke eccentric, thereby adjusting the end positions of the movable lever.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of PCT application PCT/EP 2004/007460, filed on Jul. 8, 2004, which claims priority to European Patent Application No. 03 017 222.5, filed on Jul. 30, 2003. The priority applications are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     This description relates to a hand-operated machine tools for machining workpieces, such as slitting shears for metal sheets and the like.  
       BACKGROUND  
       [0003]     German Application No. DE 298 04 012 U1 discloses a slitting shear with a two-armed cutting lever. This is pivotable about a cutting-lever axis, and an eccentric of a mechanical tool drive acts on one lever arm. On the other lever arm, the cutting lever is provided with blades for machining sheet metal. Two of these blades extend as longitudinal blades in the feed direction of the known slitting shear. A third blade extends as a transverse blade in the transverse direction of the longitudinal blades. Complementary counterblades on the tool housing are associated with the longitudinal blades and the transverse blade of the cutting lever. The cutting-lever axis is vertically adjustable. Depending upon the height of the cutting-lever axis, either only the longitudinal blades of the cutting lever pass the associated counterblades on the tool housing or, in addition to the longitudinal blades, the transverse blade of the cutting lever also passes the associated counterblade on the housing. When a metal sheet is cut, in the first-mentioned case a continuous metal strip is cut away as the slitting shear moves in the feed direction. If, owing to corresponding adjustment of the cutting-lever axis, the transverse blade of the cutting lever also passes the associated counterblade, the metal strip, which has previously been cut away, is clipped off.  
         [0004]     To adjust the height of the cutting-lever axis and, therefore, to adjust the movement end positions of the bladed cutting-lever arm, the known slitting shear utilizes a threaded adjusting drive, which is manually actuated by the machine operator by means of a hand crank.  
       SUMMARY  
       [0005]     According to one aspect, a hand-operated machine tool includes a movable lever having a cutting portion and a driving portion, a stroke drive comprising a rotating stroke eccentric driven about a rotation axis, the stroke drive operable with the driving portion to reciprocate the cutting portion between end positions, a cam carrier comprising an adjusting cam disposed between the stroke eccentric and the driving portion and operable to move together therewith, the adjusting cam comprising a pitched portion, and a retaining stop configured to engage the cam carrier and move between a released position and an active position. Upon movement of the retaining stop to the released position, the cam carrier engages and drives the stroke eccentric, and upon movement of the retaining stop to the active position, the cam carrier disengages the stroke eccentric, thereby adjusting the end positions of the movable lever.  
         [0006]     According to another aspect, a hand-operated machine tool includes an electric motor, a fixed cutter comprising a fixed longitudinal blade surface and a fixed transverse blade surface, and a movable cutter positionable a distance from the fixed cutter along a stroke length and comprising a movable longitudinal blade surface and a movable transverse blade surface, the movable cutter operably connected to the electric motor for reciprocation. The stroke length is adjustable to selectively engage the fixed transverse blade surface and the movable transverse blade surface and completely cut a material positioned between the fixed and movable blades.  
         [0007]     In some embodiments, the machine tool also includes a stroke length control having a first operation state wherein only the fixed longitudinal and movable longitudinal blade surfaces pass each other and also having a second operation state wherein both the fixed longitudinal and movable longitudinal blade surfaces pass each other and the fixed transverse and movable transverse blade surfaces pass each other.  
         [0008]     In some embodiments, the stroke length control includes a stroke drive including a rotating stroke eccentric driven about a rotation axis, the stroke drive operable to reciprocate the movable cutter. The stroke length control can be manually actuated by an operator.  
         [0009]     In some embodiments, the machine tool includes a cam carrier comprising an adjusting cam disposed between the stroke eccentric and the driving portion and operable to move together therewith, the adjusting cam comprising a pitched portion and a retaining stop configured to engage the cam carrier and move between a released position and an active position. Upon movement of the retaining stop to the released position, the cam carrier engages and drives the stroke eccentric, and upon movement of the retaining stop to the active position, the cam carrier disengages the stroke eccentric, thereby adjusting the end positions of the movable lever.  
         [0010]     In various embodiments, the movement executed by the tool-side driving member in the stroke direction is converted into a working movement of the machining tool, the position of the tool-side driving member in the stroke direction determines the position of the machining tool in the direction of its working movement. The aforementioned position of the tool-side driving member and thus also the aforementioned position of the machining tool is variable by the cam carrier, specifically by the adjusting cam provided on it. Owing to the pitch of the adjusting cam, the position of the tool-side driving member changes with the movement of the adjusting cam into the space between the stroke eccentric and the tool-side driving member. According to one embodiment, this movement is produced by means of the rotating stroke eccentric and therefore without the machine operator having to carry out a corresponding adjusting movement. Before movement of the adjusting cam into the space between the stroke eccentric and the tool-side driving member, retaining stop is released provided for the cam carrier. At most, the operator has to release the retaining stop for the cam carrier. The machine operator can therefore substantially concentrate on advantageous alignment and guiding of the hand-operated tool throughout the entire process of machining the workpiece. Correspondingly high-quality machining results can be achieved with the hand-operated tool.  
         [0011]     In some embodiments, the cam carrier is directly connected to the stroke eccentric to ensure that the cam carrier is driven by the stroke eccentric in a functionally reliable manner.  
         [0012]     In some embodiments, the retaining stop for the cam carrier is released via the cam carrier itself. Accordingly, in the interests of a structurally simple and small tool drive, a part which is functionally necessary for adjustment of the movement end positions is itself used for releasing the retaining stop.  
         [0013]     In some embodiments the stroke eccentric has a plurality of functions. On the one hand, it serves to drive the machining tool. Furthermore, it drives the cam carrier for adjusting the movement end position of the machining tool. Lastly, the stroke eccentric at least makes a contribution towards releasing the retaining stop for the cam carrier, thereby first enabling the cam carrier to be driven.  
         [0014]     In some embodiments a deflection device for the cam carrier effects the release of the retaining stop provided for the cam carrier and the movement of the adjusting cam into the space between the stroke eccentric and the tool-side driving member.  
         [0015]     In some embodiments, the pitch of the adjusting cam on the cam carrier is selected so that the height of the cam carrier between the stroke eccentric and the tool-side driving member adopts its starting value again after at least two deflections of the cam carrier. Consequently, the starting conditions are produced again after at least two adjusting processes. After the adjusting device has been activated at least twice, the movement end position of the machining tool again corresponds to the initial movement end position. The described embodiments can be applied to a slitting shears implementation. Initially, the movement end position of the bladed arm of the cutting lever can be set so that only the longitudinal blades of the cutting lever co-operate with the longitudinal counterblades on the machine housing and thereby cut away a continuous metal strip. By adjusting the cam carrier or the adjusting cam one or more times, a movement end position for the cutting tool can then be defined in which the transverse blade of the cutting tool clips off the metal strip, which has previously been cut away, in co-operation with the associated counterblade on the housing. After one or more further adjustments, the starting state is then produced in which a continuous metal strip is cut away again.  
         [0016]     In some embodiments, the hand-operated tool includes a deflection device for the cam carrier, by means of which deflection device the cam carrier is deflectable so that it is accessible for subsequent deflection. Should the machine operator adjust the movement end position of the machining tool and if at least one subsequent deflection is automatically effected, the machine operator can limit himself to triggering the adjustment process on the basis of the above inventive features. The operator only has to ensure one deflection of the cam carrier. The following deflection or deflections of the cam carrier can then be carried out without the operator having to take any action in this respect.  
         [0017]     According to various embodiments, the deflection of the cam carrier can take place in different ways. The hand-operable machine tool can include a catching device to block the cam carrier moving with the stroke eccentric and the tool-side driving member, preferably in a positive-locking manner. In the case of one embodiment of the invention, it is to be actuated manually by the operator.  
         [0018]     In some embodiments, the rotating stroke eccentric forms part of the deflection device and co-operates as such with the catching device for deflection of the cam carrier.  
         [0019]     In some embodiments, the hand-operated tool includes structurally simple means for ensuring defined movement of the cam carrier during its adjustment. The stroke eccentric itself serves as a guide for the cam carrier.  
         [0020]     In some embodiments, the machine tool comprising at least one catching device comprising a plurality of positive-locking recesses formed by tooth spaces in teeth circumferentially arranged around the cam carrier. The plurality of tooth spaces ensures that the positive-locking projection of the catching device can be brought into engagement with a tooth space at any time and, as a result, the catching device can be activated.  
         [0021]     In some embodiments, a retaining stop is provided which, during continuous operation of the hand-operated tool, ensures that the machine setting for the movement end positions of the machining tool is effectively secured. In spite of this, the retaining stop for adjusting the movement end positions is releasable in a simple manner.  
         [0022]     In a particular compact embodiments, the thrust member of the retaining stop for the cam carrier can be formed by the tool-side driving member.  
         [0023]     In some embodiments, the hand-operated tool is configured for slitting metal sheets, for example, which can be set in a simple and operator-friendly manner, to a continuous operating state for cutting away a continuous material strip or to an operating state in which the previously produced material strip is clipped off. The tool according to this embodiment can be applied to hand-operated machine tools of a wide variety of types.  
         [0024]     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0025]      FIG. 1  shows an electric, hand-operated slitting shear for machining sheet metal, having a cutting tool with adjustable movement end positions;  
         [0026]      FIG. 2  shows the hand-operated slitting shear according to  FIG. 1  in use on a metal sheet;  
         [0027]      FIG. 3  shows an exploded view of the tool drive of the hand-operated slitting shear according to  FIGS. 1 and 2 , inter alia with a two-part cam carrier with an adjusting cam and external teeth;  
         [0028]      FIGS. 4A-4D  show different views of the part of the cam carrier, according to  FIG. 3 , provided with the adjusting cam;  
         [0029]      FIGS. 5A-5C  show different views of the part of the cam carrier, according to  FIG. 3 , provided with the external teeth;  
         [0030]      FIGS. 6A-6C  and  7 A- 7 C each show three individual views illustrating the method of operation of the hand-operated slitting shear according to FIGS.  1  to  5 C for cutting away a metal strip;  
         [0031]      FIGS. 8A-8C  and  9 A- 9 C each show three individual views illustrating the method of operation of the hand-operated slitting shear according to FIGS.  1  to  7 C for clipping off a metal strip which has previously been cut away;  
         [0032]      FIGS. 10A-10C  show highly schematic individual views of the conditions in the region of the cam carrier according to FIGS.  3  to  5 C during the process of cutting away a metal strip; and  
         [0033]      FIGS. 11A-11D  show highly schematic individual views of the conditions in the region of the cam carrier according to FIGS.  3  to  5 C during the process of clipping off a metal strip which has previously been cut away.  
     
    
       [0034]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0035]     As shown in  FIG. 1 , a hand-operated slitting shear  1  has a multipart machine housing  2 . A high-performance electric motor with a motor shaft extending in the longitudinal direction of the hand-operated slitting shear  1  is accommodated in a rear housing part  3 . A front housing part  4  of the machine housing  2  holds the transmission for the hand-operated slitting shear  1  and mounts a cutting lever  5  by means of a cutting-lever swivel pin  6 . The cutting lever  5  is movable about the cutting-lever swivel pin  6  in the direction of a double arrow  7  and, if necessary, can be removed with little effort.  
         [0036]     The movement end positions of the cutting lever  5  are adjustable. An adjusting device  8  with an actuating means  9 , shown in  FIG. 1 , is provided for this purpose. The actuating means  9  is arranged in the vicinity of an on/off switch  10  of the hand-operated slitting shear  1 . Like the on/off switch  10 , the actuating means  9  of the adjusting device  8  can also be manually reached by the machine operator holding and guiding the hand-operated slitting shear  1  without the operator having to change his grip on the hand-operated slitting shear  1  for this purpose.  
         [0037]      FIG. 2  shows the hand-operated slitting shear  1  in the process of slitting a metal sheet  11 . As the hand-operated slitting shear  1  advances, a metal strip  12  is cut away and issues from an opening provided for this purpose in the machine housing  2 . In order to avoid obstructions while the metal sheet  11  is being machined and also to avoid scratches on the surface of the metal sheet and/or to avoid injury to the machine operator caused by an excessively long metal strip  12 , this has to be clipped off from time to time. The structural measures provided for this purpose on the hand-operated slitting shear  1  will be explained in detail herein below.  
         [0038]     As shown in  FIG. 3 , the actuating means  9  for adjusting the movement end positions of the cutting lever  5  comprises a lever arrangement  13 . The lever arrangement  13  has an operator-side lever  15  which is pivotable about a first lever axis  14 . The lever  15  is provided with a push button  16  at one end and articulated on a tool-side lever  17  at its other end. The tool-side lever  17  is pivotable about a second lever axis  18  and is articulated on a first control member  20  by means of a pivot pin  19  at its end remote from the operator-side lever  15 . The pivot pin  19  is guided in slots  21  of a holder  22  for the lever arrangement  13  in the direction of a double arrow  23 .  
         [0039]     The first control member  20  is movable with the pivot pin  19  in the direction of the double arrow  23 . On its underside remote from the pivot pin  19 , the first control member  20  has a tooth-shaped projection  24 .  
         [0040]     The cutting lever  5  has a driving arm  25  acting as a tool-side driving member and, on the opposite side of the cutting-lever swivel pin  6 , a cutting arm  26 . The latter forms the cutting tool of the hand-operated slitting shear  1  and is provided for this purpose with two longitudinal blades  27  extending in the feed direction of the hand-operated slitting shear  1  and with a transverse blade  28  which connects the longitudinal blades  27  to one another at the free end of the cutting arm  26 . On the front housing part  4 , two complementary longitudinal counterblades  29  are associated with the longitudinal blades  27  of the cutting arm  26 . A transverse counterblade  30  is provided on the front housing part  4  of the machine housing  2  as a counterpart to the transverse blade  28 .  
         [0041]     The underside of the driving arm  25  of the cutting lever  5  is acted upon by a strong helical spring  32  via a thrust piece  31 . The helical spring  32  is supported on the front housing part  4  of the machine housing  2  via an abutment  33  fixed to the housing.  
         [0042]     The pivoting movement of the cutting lever  5 , which is necessary to cut the workpiece, is generated by means of a stroke drive. In addition to the electric motor, which is not shown in  FIG. 3 , the stroke drive comprises a stroke eccentric  34  rotatably mounted on journals  35 ,  36 . The journals  35 ,  36  define a rotation axis  37  of the stroke eccentric  34 , about which the stroke eccentric  34  rotates. The driving arm  25  of the cutting lever  5  is moved downwards in a stroke direction by means of the rotating stroke eccentric  34 . This movement of the driving arm  25  takes place against a restoring force which is exerted by the helical spring  32  and which, after each downwards stroke of the driving arm  25 , generates an upwards stroke in the stroke direction.  
         [0043]     In the mounted state, the stroke eccentric  34  is held within a two-part cam carrier  38  between the journals  35 ,  36 . An adjusting cam  40  is formed on a first part  39  of the cam carrier  38  and has a roughening  41  on its outer surface in order to increase friction.  
         [0044]     The first part  39  of the cam carrier  38 , provided with the adjusting cam  40 , is shown in detail in the individual views in  FIGS. 4A-4D . Accordingly, the adjusting cam  40  has a depression  42  adjoined on one side by a substantially linear cam part  44 , seen in a circumferential direction  43 . The pitch of the linear cam part  44  is relatively great. A substantially coil-shaped cam part  45  with a relatively small pitch extends on the side of the depression  42  opposite the linear cam part  44 .  
         [0045]     A radially narrowed, sleeve-type axial portion  46  adjoins the axial portion—provided with the adjusting cam  40 —of the first part  39  of the cam carrier  38 . The axial portion  46  carries a second part  47  ( FIG. 3 ) of the cam carrier  38 . The second part  47  of the cam carrier  38  is fixedly connected to the first part  39 . As an alternative to the illustrated two-part arrangement of the cam carrier  38 , a one-piece formation would also be possible.  
         [0046]     The second part  47  of the cam carrier  38  is shown in detail in  FIGS. 5A-5C . It has an axial portion  49 , provided with knurling-type outer teeth  48 , and a smooth-walled axial portion  50 . The knurling-type teeth  48  on the axial portion  49  has a tooth space  51 , and the smooth-walled axial portion  50  has a wedge-shaped recess  52 .  
         [0047]     The cam carrier  38  with its parts  39 ,  47  is part of the adjusting device  8  ( FIGS. 11A-11D ) for adjusting the movement end positions of the cutting lever  5 . A second control member  53  with a projection  54  and a detent  55  are shown in  FIG. 3  as further components of the adjusting device  8 . The detent  55  is guided on a rear wall  56  of the front housing part  4  in the direction of the double arrow  23 . In addition, the rear wall  56  mounts the journal  36  of the stroke eccentric  34  by means of a bearing eye  57 .  
         [0048]     The method of operation of the hand-operated slitting shear  1  will be explained in detail with the aid of  FIGS. 6A  to  9 C and with reference to  FIGS. 10A-10C  and  11 A- 11 D.  
         [0049]      FIGS. 6A-6C  and  7 A- 7 C show the hand-operated slitting shear  1  during a normal cutting operation, i.e. in the operating state in which the cutting lever  5  cuts a continuous metal strip  12  from the metal sheet  11 .  FIGS. 8A-8C  and  9 A- 9 C show the conditions for clipping off the metal strip  12  which has previously been cut away.  
         [0050]     In  FIGS. 6A-6C , the driving arm  25  of the cutting lever  5  is in its upper end position during a normal cutting operation. Therefore, the cutting arm  26  of the cutting lever  5  is in its lower end position in  FIGS. 6A-6C  during a normal cutting operation. In contrast,  FIGS. 7A-7C  show the driving arm  25  of the cutting lever  5  in its lower end position and the cutting arm  26  of the cutting lever  5  in its upper end position during a normal cutting operation.  
         [0051]     The cutting lever  5  is moved in a reciprocating manner between the upper and the lower end positions in a stroke direction  58  by means of the stroke eccentric  34 . In the stroke direction  58 , the stroke eccentric  34  and the driving arm  25  of the cutting lever  5  are supported against one another via the cam carrier  38 , specifically via the adjusting cam  40 . As shown in the  FIGS. 6C and 7C , the adjusting cam  40  of the cam carrier  38  rests against the driving arm  25  of the cutting lever  5  in the region of the depression  42 .  
         [0052]     The cam carrier  38  moves together with the driving arm  25  of the cutting lever  5 . In spite of the “unround” path of movement of the stroke eccentric  34 , the point of support of the cam carrier  38  on the driving arm  25  does not change its position on the driving arm  25  during the movement of the cam carrier  38 . This is achieved on the one hand by the detent  55 , which engages in the wedge-shaped recess  52  in the cam carrier  38 . In addition, the helical spring  32  exerts a quantitatively great perpendicular force on the cam carrier  38  via the thrust piece  31  and the driving arm  25  of the cutting lever  5 . A great frictional force holding the cam carrier  38  on the driving arm  25  results from this perpendicular force, not least owing to the roughening  41  on the surface of the adjusting cam  40 . Accordingly, the detent  55  and the spring-loaded driving arm  25  form a retaining stop for the cam carrier  38 . Furthermore, there is a positive connection between the driving arm  25  of the cutting lever S and the depression  42  in the adjusting cam  40 . Moreover, the friction between the inner wall of the cam carrier  38  and the stroke eccentric  34  is substantially reduced by means of a needle bearing  60 , which can be seen in  FIGS. 6A  to  9 C.  
         [0053]     All in all, driving of the cam carrier  38  by the stroke eccentric  34 , with rotation of the cam carrier  38  into the space between the eccentric disc  34  and the driving arm  25 , is prevented. A path of movement  61 , which is described by the knurling-type teeth  48  on the cam carrier  38  during a normal cutting operation and associated stroke movements, is shown in the middle sectional views in  FIGS. 6A-6C ,  7 A- 7 C,  8 A- 8 C,  9 A- 9 C. The conditions resulting in the region in which the cam carrier  38  is supported on the driving arm  25  during a normal cutting operation are highly schematically shown in  FIGS. 10A-10C .  
         [0054]     As shown in  FIGS. 7A-7C , there is an upper movement end position or a top dead centre position for the cutting arm  26  of the cutting lever  5 , in which position only the longitudinal blades  27  on the cutting arm  26  and the longitudinal counterblades  29  on the machine housing  2 , but not the transverse blade  28  on the cutting arm  26  and the transverse counterblade  30  on the housing, co-operate with one another.  
         [0055]     If, starting from the operating state of the hand-operated slitting shear  1  as shown in  FIGS. 6A-6C  and  7 A- 7 C, the metal strip  12  produced during this operating state is to be clipped off, the push button  16  of the adjusting device  8  has to be depressed into the position shown in  FIGS. 8A-8C  and  9 A- 9 C by the operator of the hand-operated slitting shear  1 . This movement of the push button  16  effects displacement of the first control member  20  downwards in the figures via the lever arrangement  13 . In the same direction as the first control member  20 , the detent  55  is displaced against the action of a spring force. As a result, the detent  55  moves out of the wedge-shaped recess  52  in the smooth-walled axial portion  50  of the cam carrier  38 . The cam carrier  38  initially retains its position relative to the driving arm  25  of the cutting lever  5  despite the release of the detent  55 . The reason for this is the friction acting between the cam carrier  38  and the spring-loaded driving arm  25  of the cutting lever  5 .  
         [0056]     During its upwards movement with the stroke eccentric  34  and the driving arm  25 , the knurling-type teeth  48  of the cam carrier  38  then comes into engagement with the now lowered tooth-shaped projection  24  on the first control member  20  (see also  FIG. 11B ). The first control member  20  now acts as a catching device for the cam carrier  38 , which moves together with the stroke eccentric  34  and the driving arm  25 , and blocks the cam carrier  38  on its outer surface. The cam carrier  38  is subsequently deflected by the rotating eccentric disc  34  about the point at which it is blocked by the first control member  20 . This deflection is achieved with overcoming the friction acting between the driving arm  25  of the cutting lever  5  and the cam carrier  38 , specifically the adjusting cam  40 . Consequently, the retaining stop formed for the cam carrier  38  by the driving arm  25  is released by the stroke eccentric  34 .  
         [0057]     As a result of the deflection, the adjusting cam  40  moves counter to a direction of rotation  59  of the stroke eccentric  34  in a movement direction  62  into the space between the eccentric disc  34  and the driving arm  25  of the cutting lever  5  (see also  FIG. 11C ). Owing to the pitch of the adjusting cam  40 , the height of the cam carrier  38  between the stroke eccentric  34  and the driving arm  25  increases as the adjusting cam  40  moves between these two parts (see also  FIG. 11D ).  
         [0058]     After the deflection of the cam carrier  38  as a result of the engagement of the first control member  20  in the knurling-type teeth  48 , the cam carrier  38  is supported on the driving arm  25  of the cutting lever  5  in a position in which, after the first control member  20 , the projection  54  of the second control member  23  now also engages in the knurling-type teeth  48  on the cam carrier  38 . Previously, the knurling-type teeth  48  was still circumferentially aligned so that it came to lie with the tooth space  51  at the level of the projection  54  of the second control member  53  on passing the second control member  53  during the executed strokes, as a result of which the projection  54  could not engage in the knurling-type teeth  48 . The second control member  53  is not shown in  FIGS. 11A-11D  in order to simplify the drawing.  
         [0059]     The second control member  53  also forms a catching device for the cam carrier  38  and, as such, also blocks the cam carrier  38  on its outer surface. This blocking also leads to deflection of the cam carrier  38  by the action of the rotating stroke eccentric  34  and, associated therewith, to continued movement of the adjusting cam  40  in its direction of movement  62 .  
         [0060]     If, during the upwards stroke of the cam carrier  38  that follows the downwards stroke after the first engagement of the first control member  20  in the knurling-type teeth  48 , the first control member  20  is still in its lowered position, the first control member  20  causes further deflection of the cam carrier  38  and therefore further movement of the adjusting cam  40  into the space between the stroke eccentric  34  and the driving arm  25  of the cutting lever  5 .  
         [0061]     If the operator of the hand-operated slitting shear  1  releases the push button  16  immediately after the first engagement of the first control member  20  in the knurling-type teeth  48 , the first control member  20  automatically moves back into its starting position. This return movement of the first control member  20  is effected by a restoring spring provided for this purpose on the lever arrangement  13 . In this case, after the first and then also only engagement of the first control member  20  in the knurling-type teeth  48 , further deflection of the cam carrier  38  is brought about solely by the second control member  53 .  
         [0062]     In both cases, the adjusting cam  40  moves further and further into the space between the stroke eccentric  34  and the driving arm  25  of the cutting lever  5 . Associated with this is a continuous increase in the height of the cam carrier  38  between the stroke eccentric  34  and the driving arm  25 . This in turn results in downwards displacement of the top and bottom dead centre position of the driving arm  25  of the cutting lever  5 . This goes hand in hand with displacement, in the opposite direction, of the top and bottom dead centre position of the cutting arm  26  on the cutting lever  5 . Consequently, the cutting arm  26  of the cutting lever  5  moves back and forth between the end positions shown in  FIGS. 8A-8C  and  9 A- 9 C. In its upper movement end position shown in  FIGS. 9A-9C , the transverse blade  28  on the cutting arm  26  co-operates with the transverse counterblade  30  on the machine housing  2 . As a result, the previously produced metal strip  12  is clipped off. An increase in the number of catching devices for the cam carrier  38  would result in faster adjustment of the movement end positions.  
         [0063]     The right-hand sectional view in  FIGS. 8A-8C  shows the cam carrier  38  before its first deflection by the first control member  20 . In  FIGS. 9A-9C , the cam carrier  38  is shown in the position associated with the maximum end position displacement of the cutting lever  5 . Further deflection of the cam carrier  38 , starting from the conditions shown in  FIGS. 9A-9C , transfers the cam carrier  38  to its starting position before the start of the adjustment of the movement end positions. In this starting position, the tooth space  51  in the knurling-type teeth  48  on the cam carrier  38  then again lies opposite the projection  54  on passing the projection  54  of the second control member  53 . Further deflection of the cam carrier  38  by the second control member  53  is therefore not possible. If, furthermore, the first control member  20  is also transferred to its retracted starting position, the hand-operated slitting shear  1  can again work in a normal cutting operation and again cut away a continuous metal strip  12 .  
         [0064]     The transfer of the cam carrier  38  from a position according to  FIGS. 9A-9C  to the starting position according to  FIGS. 6A-6C  and  7 A- 7 C is assisted by the helical spring  32  and the shape of the adjusting cam  40 . The helical spring  32  exerts a force on the adjusting cam  40  via the driving arm  25 . This force acts upon the linear cam part  44  of the adjusting cam  40  of the cam carrier  38  and thereby produces displacement of the cam carrier  38  in spite of the friction between the adjusting cam  40  and the driving arm  25 , the linear cam part  44 , according to  FIGS. 9A-9C , lying relatively steeply.  
         [0065]     The detent  55  moves back into its locking position on the smooth-walled axial portion  50  of the cam carrier  38  after complete rotation of the cam carrier  38  under the effect of the restoring force acting upon it and then engages again in the wedge-shaped recess  52  in the cam carrier  38 .  
         [0066]     A number of embodiments of have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.