Sheet locating device
United States Patent Illingworth et al.  
 SHEET LOCATING DEVICE Inventors: Edward Albert Ernest lllingworth;  
 Eric Stone, both of lllford, England Ilford Limited, llford, Essex, England Filed: Nov. 6, 1973 Appl. N0.: 413,203  
 Assignee:  
 Foreign Application Priority Data Nov. 22, 1972 United Kingdom 53868/72 U.S. Cl. 83/17; 83/22; 83/35; 83/39; 83/251; 83/282; 83/418 Int. Cl 326d 7/02; B65h 9/00; B26d 9/00 Field of Search 83/17, 22, 35, 39, 251, 83/250, 255, 282, 404, 418  
 References Cited UNITED STATES PATENTS 3,112,665 12/1963 Hansel et al. 83/251 X Primary Examiner Frank T. Yost Attorney, Agent, or Firm-Wenderoth, Lind &amp; Ponack [5 7] ABSTRACT Method of performing a cross cutting operation on a travelling flexible web of material to form discrete sheets of material followed by an operation on the trailing edge of the thus formed severed sheet of material, which method comprises moving the leading edge of the web to a clamping station, clamping the leading edge of the web, cross cutting the web to form a severed sheet of the flexible web material, causing the middle of the severed sheet to bow in a predetermined curvature whilst maintaining the trailing edge of the sheet parallel to the position in which it was cross cut, thus causing the trailing edge of the sheet to move towards the leading edge of the sheet by a pre-determined distance and then performing the operation on the trailing edge of the severed sheet.  
 18 Claims, 3 Drawing Figures PATENTEnAPmsiis&#39; sum 10 3 sum 2 1g 3 PATENTEBAPR 1 5 I975 sumaqg&#39;g,  
 SHEET LOCATING DEVICE BACKGROUND OF THE INVENTION This invention relates to the severing of travelling web material into discrete sheets on which a further op eration is performed. In operations of this type often the web is severed by means of a cross-cutting operation and if any further operation is required to be performed on the thus formed trailing edge of the severed sheet, it is then required that the severed sheet be moved so as to remove its trailing edge from the means which performs the cross-cutting.  
 SUMMARY OF THE INVENTION It is an object of the present invention to provide such a method wherein the severed sheet is not required to be moved away from the cross-cutting station.  
  Therefore according to the present invention there is provided a method of performing a cross cutting operation on a travelling flexible web of material to form discrete sheets of material followed by an operation on the trailing edge of the thus formed severed sheet of material, which method comprises moving the leading edge of the web to a clamping station, clamping the leading edge of the web, cross cutting the web to form a severed sheet of the flexible web material, causing the middle of the severed sheet to bow in a pre-determined curvature whilst maintaining the trailing edge of the sheet parallel to the position in which it was cross cut, thus causing the trailing edge of the sheet to move towards the leading edge of the sheet by a predetermined distance and then performing the operation on the trailing edge of the severed sheet.  
  The middle of the severed sheet of flexible web material can be caused to bow by means of air pressure, by means of suction or by a mechanical means forcing the middle of the severed sheet into a spaced located on one side of the sheet.  
  However it is preferred that the middle of the severed sheet is caused to bow by making it conform to the shape of a block having a concave hollow therein (concave block). Most preferably the sheet is made to conform to the shape of the concave block by means of a convex block which is ofthe same curvature as the concave block and which forces the middle of the sheet into the middle of the concave shaped block. This may be aided either by air pressure directed from the convex block towards the concave block or by suction means in the concave block.  
  The convex block may have a flat shoulder member which clamps the severed sheet to a flat portion of the platform holding the free end flat and parallel to the position in which it was cross-cut after the convex block forces the middle of the severed sheet into the concave block. However in another embodiment a separate clamp is provided which clamps the severed sheet to a flat portion of the platform;  
  Most preferably both the concave and convex blocks are covered with protective material, e.g., looped nylon velvet. This serves to minimise any pressure effects on the sheet.  
  One use of the method of the present invention is in the production of round cornered photosensitive films which are cut from webs of photosensitive film material. Examples of such sheets of film material are X-ray films, it being desirable that X-ray films have round corners to prevent damage to the envelopes in which the films are to be placed.  
  Therefore according to another aspect of the present invention, there is provided a method of preparing round cornered photosensitive film sheets from a web of photosensitive film material, which method comprises moving the leading edge of the web to a clamping station, clamping the leading edge of the web, removing the corners of the leading edge of the web, crosscutting the web to form a severed sheet of film, causing the middle of the severed sheet to bow in a predetermined curvature, whilst maintaining the trailing edge of the severed sheet parallel to the position in which it was cross cut, thus causing the trailing edge of the sheet to move towards the leading edge of the sheet by a pre-determined amount and then removing the corners from the trailing edge of the severed sheet.  
  Preferably the four corners of the sheet of film are removed by a punching operation.  
  In this embodiment of the invention in particular it is preferred that the severed sheet is caused to bow in the middle by forcing it into a convave block by means of a convex block.  
  Preferably both the convex block and the concave block have shoulders thereon between which the film is clamped holding it flat and parallel to the position in which it was cross cut.  
  Most preferably in this embodiment of the invention both the convex and the concave blocks are covered with protective material, e.g., looped nylon velvet. This is a non-frillable material and serves to minimise pressure marks on the photosensitive sheet material.  
  In an operation wherein a web of photosensitive material is cut into discrete sheets, each of which have round corners, it would be possible to perform the cutting and round-cornering operations in one movement but such an operation would seriously damage the web and any coating thereon. However it is possible to remove the corners from the sheet using a punching operation wherein a length of the entire middle of the film web has to be punched out in order to remove the corners on the trailing edge of the sheet. But this is a considerable waste since the base itself is expensive and the coating thereon is also expensive. However by use of the method of a present invention the only film waste is the actual corners of the film which are removed.  
  According to yet another aspect of the present invention, there is provided an apparatus for cross cutting and roundcornering webs of flexible material into discrete sheets each of which have round corners, which apparatus comprises a platform over which a travelling web of material can be caused to move, a clamping means located on the platform for clamping the leading edge of the flexible web material, a web cross cutting means, a concave shaped block located either above or below the path of the web between the clamping means and the cross cutting means, and on the reverse side of the web from the concave block a convex block having the same curvature as the concave block and which is loated in register therewith and means to enable the convex block to locate in the concave block thereby causing a sheet of web therebetween to bow in a predetermined curvature, clamping means being provided which serve to clamp the severed film holding it flat and parallel to the position in which it is cut together with punching means for round-cornering each of the four corners of the severed sheet. Preferably both the concave and convex blocks are covered with protective material, e.g., looped nylon velvet. Preferably the apparatus also comprises a pair of driven nip rollers through which the web is traversed and which serve to move the web through the apparatus and also to apply a tension to the web.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 of the accompanying drawings is a diagrammatic view of an apparatus according to the present invention and by means of which the method of the present invention may be performed.  
  FIG. 2 of the accompanying drawings represents schematically the operative steps of the method of the present invention.  
  FIG. 3 is a view of a modified embodiment of the invention.  
 DETAILED DESCRIPTION OF THE INVENTION In the drawings on a web supporting platform 1 there is located a clamp 2 which acts to clamp the leading edge of a travelling web W as it is fed through the apparatus. Located on either side of the clamping means are two punches 3 and 4. On the other end of the platform is a guillotine 5 which serves to cross-cut a web. Located inwards from the guillotine 5 are two punches 6 and 7 for round-cornering the trailing edge of the sheet when formed. The punches 3, 4, 6 and 7 are connected to a superstructure which is located over the platform but which for simplicity is not shown in the drawing. Located beneath each punch is a die into which in operation the punch fits. These dies are labelled 3A, 4A, 6A and 7A. Located above each punch is a solenoid means which serve to actuate each punch. These solenoid means are labelled 3B, 4B, 6B and 7B. In the middle of the platform is a concave block 9 having a shoulder 10 and a block 11 which is convex on its under surface, located above concave block 9 in register therewith and which is of such a curvature that it fits into the concave block 9. Both the innersurface of concave block 9 and the outersurface of convex block 11 are covered with a protective covering of looped nylon velvet, as is the undersurface of the clamp 12 and the surfaces of the clamp 2 and the shoulder 10 over which the web W passes. A clamp 12 is located above a flat part of the platform 1 (this clampis connected to the superstructure of the device which is not shown). Also present on the platform are a mounted pair of nip rollers 13.  
  In operation the travelling flexible web W is fed through the guillotine 5 which is in the open position over the concave block 9 into the nip of the pair of nip rollers 13 and then through the clamping means 2. The travelling web W is indexed to travel so that its leading edge stops at the end of the&#39;clamping means 2. The web is then clamped in the clamping means 2. The punches 3 and 4 then act to round-corner the corners of the leading edge of the flexible web material. The guillotine 5 then acts to sever the web material forming a severed sheet of flexible material. The convex block 11 then moves down causing the flexible sheet to conform to the shape of the concave block 9, The sheet of flexible material thus is bowed to a pre-determined curvature,  
 while its trailing edge remains parallel to the position in which it was severed from the web, held in position between the clamp 12 and the shoulder 10. The act of bowing the flexible sheet causes its trailing edge to move towards its leading edge by a pre-determined amount. The punches 6 and 7 are then able to operate and remove the corners from the trailing edges of the sheet. The convex block 11 is then raised, the clamping means opened and the flexible sheet is traversed out of the apparatus by means of the nip rollers 13 which are then caused to operate.  
  In FIG. 1 a clamp 12 is shown which is located above the shoulder 10. In another embodiment of the apparatus, as shown in FIG. 3, the clamping means employed is a flat shoulder 14 attached to the block 11 which is located over the shoulder 10.  
  In FIG. 2 the four drawings show the four main operative steps of the method.  
  The first drawing shows the step (a) of clamping the leading edge of the travelling flexible web W.  
  The second drawing shows the step (b) of crosscutting the travelling to form a discrete sheet.  
  The third drawing shows the step (c) of bowing the middle of the discrete sheet in a pre-determined curvature. The effect of this step is to move the trailing edge of the discrete sheet towards its leading edge by a predetermined distance L whilst maintaining this edge parallel to the position in which it was crosscut.  
  The fourth drawing shows the step (d) of performing an operation on the displaced trailing edge of the sheet. Optionally an operation may simultaneously by performed on the leading edge of the sheet.  
  Alternatively an operation on the leading edge of the sheet may be performed at any time after step (a) for example after step (a) and before step (b).  
 What is claim is:  
  1. A method of performing a cross cutting operation on a travelling flexible web of material to form discrete sheets of material followed by an operation on the trailing edge of the thus formed severed sheet of material, which method comprises moving the leading edge of the web to a clamping station, clamping the leading edge of the web, cross cutting the web to form a severed sheet of the flexible web material, causing the middle of the severed sheet to bow in a pre-determined curvature whilst maintaining the trailing edge of the sheet parallel to the position in which it was cross cut, thus causing the trailing edge of the sheet to move towards the leading edge of the sheet by a predetermined distance and then performing the operation on the trailing edge of the severed sheet.  
  2. A method according to claim 1 wherein the middle of the severed sheet of flexible web material is caused to bow by means of air pressure forcing the middle of the severed sheet into a space located on one side of the sheet.  
  3. A method according to claim I wherein the middle of the severed sheet is caused to bow by making it conform to the shape of a concave block.  
  4. A method according to claim 3 wherein the sheet is made to conform to the shape of a concave block by means of a convex block which is of the same curvature as the said&#39;concave block and which forces the middle of the sheet into the middle of the concave block.  
  5. A method according to claim 4 wherein the convex block has a flat shoulder member which clamps the severed sheet to a flat portion of the platform holding its free end flat and parallel to the position in which it was cross-cut after the convex blocks forces the middle of the severed sheet into the concave block.  
  6. A method according to claim 4 wherein a clamp clamps the severed sheet to a flat portion of the platform holding its free end flat and parallel in the position in which it was cross-cut, after the convex block forces the middle of the sheet into the concave blocks.  
  7. A method according to claim 4 wherein both the convex block and the concave block are covered with protective material.  
  8. A method according to claim 7 wherein the protective material is looped nylon velvet.  
  9. A method of preparing round-cornered photosensitive film sheets from a web of photosensitive film material, which method comprises moving the leading edge of the web to a clamping station, clamping the leading edge of the web, removing the corners of the leading edge of the web, cross-cutting the web to form a severed sheet of film, causing the middle of the severed sheet to bow in a predetermined curvature whilst maintaining the trailing edge of the severed sheet parallel to the position in which it was cross-cut, thus causing the trailing edge of the sheet to move towards the leading edge of the sheet by a pre-determined amount and then removing the corners from the trailing edge of the severed sheet.  
 10. A method according to claim 9 wherein the four corners of the sheet of film are removed by a punching 14. A method according to claim 1 wherein the middle of the severed sheet of flexible web material is caused to bow by means of suction forcing the middle of the severed sheet into a space located on one side of the sheet.  
  15. A method according to claim 1 wherein the middle of the severed sheet of flexible web material is caused to bow by a mechanical means forcing the middle of the severed sheet into a space located on one side of the sheet.  
  16. An apparatus for cross-cutting and roundcornering webs of flexible material into discrete sheets each of which have round corners, which apparatus comprises a platform over which a travelling web of material is caused to move, a clamping means located on the platform for clamping the leading edge of the flexible web material, a web cross cutting means, a concave shaped block located on one side of the path of the web between the said clamping means and the said cross cutting means, and on the reverse side of the web from the said concave block a convex block having the same curvature as the concave block and which is located in register with the said concave block, and means to enable the convex block to locate in the concave block thereby causing a sheet of web therebetween to bow in a pre-determined curvature, there being provided clamping means which, in operation, serve to clamp the film holding it flat and parallel to the position in which it is cut, together with punching means for round-cornering each of the four corners of the sheet.  
  17. Apparatus according to claim 16 wherein both the concave block and the convex block are covered with protective material.  
 18. Apparatus according to claim 16 which further comprises a pair of driven nip rollers.