Abstract:
The cutting cylinder of a rotary cutting machine has at least one radial needle for retaining waste projecting radially from its surface. A waste ejector has a rectilinear part parallel to the generatrix of the said cylinder and traversed by at least one slot coinciding with the trajectory of said radial needle for the passage thereof. A support has a first part secured to the frame of the rotary cutting machine, a second part secured to said ejector and connected to the first part by a guide defining a transverse trajectory relative to the edge of said ejector and intersecting said cylinder. An adjustment device moves the said second part along the transverse trajectory and an elastic connection exerts a prestressing of the second part on the adjustment device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a system for adjusting the position between a waste ejector and a cutting cylinder for material in strip form in a rotary cutting machine, cylinder comprising at least one radial needle for retaining waste and projecting radially from its surface, ejector having a rectilinear part parallel to the generatrix of the cylinder and traversed by at least one slot coinciding with the trajectory of radial needle for the passage thereof. 
     2. Description of Related Art 
     When the cardboard waste is separated from a strip during its cutting for the manufacture of folding boxes in particular, on rotary cutting machines, it is essential that the waste should be ejected controllably to prevent it causing any jamming. To this end, one of the two cutting cylinders between which the strip of cardboard is cut comprises radial needles between the cutting fillets, which needles penetrate the waste during a cutting operation and separate it from the strip, entraining it with the cylinder, while the strip moves away from the cylinder following a horizontal trajectory. 
     This waste must then be extracted from radial needles during rotation of the cylinder in order to free radial needles and enable them to penetrate other waste during their next passage in the cutting zone of the cardboard strip. To this end, ejectors are provided in the form of fixed combs with edges parallel to the cylinder generatrix, cut out so that they can very closely approach the trajectory of the cutting fillets of the cylinder while allowing the radial needles projecting beyond the apices of said cutting fillets to pass. The edges of the ejectors can thus be inserted between the apices of the cutting fillets and the waste and extract the waste from the radial needles when the latter move away from the ejectors following the rotation of the cylinder. 
     The edges of these combs must be positioned with high precision with respect to the cylinder. If too large a spacing is left between the apices of the cutting fillets and the edges of the combs, there is a risk that the cardboard waste will pass between the comb and the fillet. This may initially result in a deformation of the comb and may also break the radial needle and hence a fillet. The damage increases generally with rotation of the cylinder, until the machine stops. If, on the other hand, the distance is too small, there is a risk that the comb will come into collision with a cutting fillet and also cause damage successively until stoppage of the machine. 
     Since the comb is subjected to impacts whenever it meets waste, and in view of the very small tolerances allowed for its positioning, it not only has to be positioned with very high accuracy but must also be prevented from vibrating, since otherwise the said two risks can occur more or less simultaneously on different combs. 
     To guarantee reliable operation of a waste ejector of the type referred to, it must satisfy an extremely strict specification. The positioning of the comb must be possible with a tolerance of not more than ±0.02 mm. Its rigidity may not allow a movement in excess of 5 μm, even in response to impacts. The comb must not undergo any torsion irrespective of the axis considered. 
     To be able to satisfy the above positioning accuracy, there must be an adjustment system. Conventional adjustment systems assume the existence of a guide for each adjustment axis. Consequently, the movable element must be locked on the guide once it has reached the required position,-and this implies a displacement with respect to the desired position, induced by the locking. It is therefore necessary to proceed by repetition and this repetition method which is more or less carried out at random involves the risk that the final precision accepted will be only approximate, together with the danger that implies. 
     The use of cross-guides with locking, which is well known in machine tools, would give a solution which is considered expensive in the area of folding box manufacture and hence economically unacceptable. Finally, it is difficult to have access to means for adjustment along the different axes on one and the same surface of the component requiring adjustment, so that the adjustment operation is rendered difficult. 
     The object of this invention is to obviate the above disadvantages at least partly. 
     BRIEF SUMMARY OF TEE INVENTION 
     To this end, the invention relates to a system for adjusting the position between a waste ejector and a cylinder for cutting material in strip form in a rotary cutting machine. 
     The system according to the invention has few components and is compact and economic. Its design, in which the prestressed strips connecting the two parts of the support act as a guide without any play, results in an adjustment which does not depend on any hysteresis effect and which has an excellent resolution. The system has a very good rigidity both static and dynamic in the three axes, including the axis along which the adjustment is made. Its static and dynamic torsion rigidity is high along the three axes. The adjustment components of the system have orientations directed towards the exterior of the machine which are easily accessible. The adjustment and dismantling can be effected by means of one and the same key, simplifying to the maximum the various interventions required on the machine. 
     Other features and advantages will be apparent from the following description of one embodiment of this system which is illustrated diagrammatically and by way of example in the accompanying drawing wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation of two cutting cylinders which are deliberately shown out of scale in order to explain the underlying problem. 
     FIG. 2 is an enlarged-scale partial side view of a cutting cylinder as shown in FIG. 1 with the embodiment of the ejection system according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The cutting cylinders  1 ,  2  shown in FIG. 1 constitute a cutting unit of a rotary cutting machine which may comprise a plurality of units side by side. Rotary cutting machines of this kind are generally used to cut cardboard into strip for the purpose of the manufacture of folding boxes. 
     These cutting cylinders  1 ,  2 , which in this example are of the type cutting by shearing, more usually designated as rotary pressure cut or RP cylinders, comprise on their respective surfaces a network of cutting fillets  3 ,  4 ,  5 ,  6  respectively. This invention could also be applied to the case of cutting cylinders operating by compression and generally denoted by the logo CRC. A strip of cardboard  7  moves horizontally in the direction of the arrow F between said cutting cylinders  1 ,  2  and is cut when two cutting fillets  3 ,  4  of these two respective cylinders  1 ,  2  are in the relative position shown in FIG.  1 . 
     The cardboard waste produced during the cutting operation must be ejected controllably in order to prevent it from causing jamming. To this end, one of the two cutting cylinders  1 ,  2 , preferably the lower cylinder  2 , is provided with radial needles  8  which project radially outside a circle  9  corresponding to the trajectory described by the apices of the cutting fillets  4 - 6  around the axis of rotation of the cylinder  2 . The radial needles are appropriately positioned on the surface of the cylinder  2  at places where cutting of the cardboard strip  7  produces waste  10 . Thus these radial needles pierce the strip of cardboard  7  simultaneously with the cutting of waste  10  so that when the cardboard strip  7  continues its horizontal trajectory in the direction of the arrow F the waste  10  is driven in a circular trajectory around the cylinder  2  in the direction of the arrow F 1  and is thus separated from the cardboard strip  7 . 
     Obviously it is essential to proper operation of the cutting machine that the waste  10  should be detached from the radial needle  8  so that the latter can extract waste on each revolution of the cutting cylinder  2 . This extraction of the waste  10  for its controlled ejection is produced by means of an ejector in the form of a comb which must be capable of insertion between the fillet  6  and the waste  10 . 
     FIG. 2 illustrates a comb  11  of this kind, showing a portion of the lower cutting cylinder  2  and a radial needle  8  on which waste  10  has been stuck. The comb  11  comprises a slot  11   a  directed perpendicularly to its front edge  11   b  which is parallel to the generatrix of the cylinder  2 . This slot  11   a  is disposed on the circular trajectory described by the radial needle  8  around the axis of rotation of the cutting cylinder  2 , to allow passage of the radial needle  8  so that the front edge  11   b  of the comb  11  can very closely approach the trajectory  9  of the apex of the cutting fillets  4 - 6 , so that it can engage between trajectory  9  and the waste  10 . 
     Said comb  11  is positioned and fixed on a support  12  by fixing screws  13 . Said support  12  is in turn fixed to the frame (not shown) of the cutting machine by means of a rail or guide cross-member  14  engaging a support flange  15  formed on the support  12 , so that the latter can be fixed on the cross-member  14  by screws  16 . If the support  12  is moved along the guide cross-member  14 , the slot  11   a  of the comb  11  can be made to coincide with the circular trajectory of the radial needle  8 . 
     The support  12  comprises two parts, one  12   a  secured to the support flange  15 , the other  12   b  connected to the comb  11 . These two parts are interconnected by two parallel flexure strips  12   c . The respective planes of these flexure strips  12   c  are substantially tangential to two circles concentric to the cutting cylinder  2 , so that the part  12   b  can move within the limit of elastic deformation of the strips  12   c  in the direction of the double arrow F 2 . Consequently, the parallel strips  12   c  form as it were a deformable parallelogram so that they can primarily have a guide role, defining a displacement of the comb  11  along a trajectory perpendicular to the edge  11   b  of said comb  11 , which intersects the cylinder in such manner that the distance between the edge  11   b  of the comb  11  and the cylinder  2  can be modified. These strips  12   c  thus act as a return means within the limit of their elastic deformation, the function of which will be apparent hereinafter. 
     The part  12   b  of the support  12  has a screwthread  17 , the axis of which is perpendicular to the planes of flexure strips  12   c . A tapped and screwthreaded bushing  18  terminating in a collar  18   a  at one end is introduced into an opening in the fixed part  12   a  of the support  12  formed coaxially to the screwthread  17 . Bushing  18  is held by its collar  18   a  and projects into a space  19  formed between the fixed part  12   a  and the movable part  12   b  of the support  12 . A nut  20  is engaged over the screwthreaded part of the bushing  18  in order to fix it to the fixed part  12   a.    
     The internal tapping of the bushing  18  and the internal tapping  17  of the movable part  12   b  have different respective pitches. In the example described, the pitch of the tapping  17  is greater than that of the bushing  18 . An adjustment screw  21  has two successive screwthreaded sections, an end section  21   a  engaged in the tapping  17  of the movable part  12 c and a section  21   b  engaged in the tapping of bush  18 . Since the pitch of the tapping  17  is greater than that of the bush  18 , when the adjustment screw  21  is screwed it pulls the movable part  12   b  against the fixed part  12   a  of the support  12 , causing the strips  12   c  to flex, so that the edge  11   b  of the comb  11  is moved away from the trajectory  9  of the edges of the cutting fillets  4 - 6 . 
     By arranging for the flexure strips  12   c  always to operate from the same side of their neutral position, the problem of taking up the play between the threads of the screwthreads and those of the tappings does not arise, since the strips constantly exert thereon a prestressing always extending in the same direction. 
     The force exerted by the impacts produced on the meeting between a comb  11  and waste  10 , has no influence on the adjustment system. In fact, the main component of this force occurs in a direction substantially parallel to the strips  12   c  and has no appreciable influence likely to produce micromovements by taking up the play between the screwthreads and tapping of the adjustment system  17 ,  18 ,  21 . 
     By way of example, the difference in the pitches of the screwthreads  21   a ,  21   b  of the adjustment screw  21  produces a displacement of 0.25 mm between the movable part  12   b  and the fixed part  12   a , for each revolution of the adjustment screw  21 , corresponding to 0.7 μm for a 1 degree rotation. It is a simple matter to dimension the strips  12   c  so as to obtain an adjustment travel of the order of 0.5 mm without plastic deformation. In one embodiment of the adjustment system according to the invention, the strips  12   c  have a thickness of 5 mm, a length of 28 mm and a width of 42 mm, corresponding to the width of the support  12 . It is interesting to note that the length of the parallel strips  12   c  is substantially equal to their width, and this gives excellent resistance to torsion. 
     Of course a number of supports  12  can be positioned along the cross-member  14  depending on the respective positions and the number of waste items to be removed on each revolution of the cutting cylinder  2 , each of said supports  12  bearing a comb  11  whose slot  11   a  coincides with a circular trajectory of a radial needle  8 . A plate  22  extending over the entire length of the cutting cylinders  1 ,  2  covers the support assembly  12 . It is situated in extension of the top surface of the comb  11 . It enables the adjustment systems to be protected while facilitating the flow of the waste  10 , preventing the same from sticking, for example, to the slot  19 . 
     The adjustment of the position of the comb  11  in its two axes of movement is obtained by means of two screws  16 ,  21  which are accessible on the same surface of the support  12  oriented parallel to the cylinder  2  and hence easily accessible. A single key enables these adjustments to be carried out, and the same applies to the removal of the support  12  or replacement of the comb  11 .