Patent Publication Number: US-2004056127-A1

Title: Shredder for sheet material having an improved feeding mechanism

Description:
BACKGROUND TO THE INVENTION  
       [0001] This invention relates to improvements in feeding mechanisms. In particular, this invention relates to improvements in feeding mechanisms for sheet materials, such as paper, which are fed into a device, such as a shredder, for processing therein. These mechanisms are described hereinafter in relation to paper, but it will of course be appreciated that they could be used with many different types of sheet material.  
       DESCRIPTION OF THE PRIOR ART  
       [0002] Typically, in shredders, cutting discs are provided which themselves intermesh. Since these are mounted on rollers which rotate in opposite directions, they provide a nip into which paper can be fed, and draw paper through the shredder without the need for any further feeding mechanism. There are shredders, however, which operate on a different principle, for example the shredder described in pending U.K. Patent Application Serial No. 0210599.7, in which sheet material is shredded using rectilinear punches.  
       [0003] Typically feed rollers are used in such shredders to feed the paper into the shredding mechanism. The rollers are situated just before the shredding mechanism in the feed path of the paper, but, even so, when the edge of the paper leaves the rollers there is a small amount of paper left above the shredding mechanism which is not fed through. This problem can be minimized by siting the feed rollers as close as possible to the shredding mechanism, and by using gravity to assist the feed of the last part of the paper, but these solutions are not wholly satisfactory.  
       [0004] There is, therefore, a need for a continuous feed mechanism which can feed an entire piece of paper through such mechanisms.  
       SUMMARY OF THE INVENTION  
       [0005] According to this invention there is provided a shredder for sheet material comprising a shredding mechanism and an air feeding mechanism.  
       [0006] Use of an air feeding mechanism enables the sheet material to be fed completely through the shredding mechanism. The mechanism also has advantages in that the sheet material tends to stretch or crinkle less than when using a conventional mechanism. The air feeding mechanism also draws dust generated by the shredding process through the shredder where it is less likely to present a health hazard.  
       [0007] Preferably the air feeding mechanism comprises a suction means, which conveniently comprises a vacuum pump. Conveniently the pressure generated by the suction means is greater than 0.5 bar, preferably greater than 1 bar.  
       [0008] Conveniently an air flow path extends through the shredding mechanism, the suction means being preferably disposed after the shredding mechanism in the air flow path.  
       [0009] Preferably the air feeding mechanism comprises a collection means for collecting shredded particles, which conveniently comprises a permeable bag. Conveniently the collection means, or a further collection means, is also suitable for collecting dust generated during the shredding process.  
       [0010] Preferably the air feeding mechanism comprises a plurality of intermediate chambers disposed in the air flow path after the shredding mechanism and before the collection means.  
       [0011] Preferably the shredder further comprises feed rollers, which are conveniently located in the air flow path before the shredding mechanism. These assist the initial feeding of the sheet material. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012] An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing in which:  
     [0013]FIG. 1 shows schematically a section view of one embodiment of a shredder according to this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0014] The shredder  10  comprises a shredding mechanism  12 , an air feeding mechanism  14  and infeed rollers  16 . In this embodiment the shredding mechanism comprises a plurality of punch members  18  positioned in die members  20 . The mechanism is generally as described in pending U.K. Patent Application Serial No. 0210599.7, and only the feeding mechanisms will be described further herein.  
     [0015] Air feeding mechanism  14  comprises a vacuum pump  22  which is connected by tubes  24  to a collection chamber  26  which contains a paper bag  28  which functions as a collection bag for shredded particles. Tubes  30  connect the collection chamber to two smaller chambers, manifolds  32 ,  34 . Each manifold  32 ,  34  is arranged at the outlets of aperture channels  36 ,  38 , which receive punch members  18  when in their advanced position.  
     [0016] The air flow path through the machine will now be described. Air is drawn as shown by arrows X through a feed channel  40  in the die members  20 , which also acts as an inlet for paper  39  being fed to the shredding mechanism  14 . From the feed channel  40 , when the punch members  18  are in their retracted position, as shown in FIG. 1, air flows through the aperture channels  36 ,  38  to the manifolds  32 ,  34 . These manifolds  32 ,  34  provide a convenient way of connecting the many aperture channels  36 ,  38  in the die members  20 . Air flows from the manifolds  32 ,  34  to the paper bag  28  in the collection chamber  26 , and through the paper bag  28  to the vacuum pump  22 .  
     [0017] When the punch members  18  are in their advanced position they extend past the feed channel  40  into the aperture channels  36 ,  38  and substantially prevent air flow through the air feeding mechanism  14 .  
     [0018] To operate the shredder  10  a plurality of paper sheets  39  is fed into the shredding mechanism through infeed rollers  16 . These rollers  16  provide the initial feed, transporting the leading edge of the paper to the feed channel  40 . Once in the feed channel  40  the paper is subjected to a degree of suction pressure, and the high velocity of air in the infeed channel  40  draws the paper along the air path. The velocity of the air increases as the number of sheets of paper increases since this makes the infeed channel  40  narrower and thus the effectiveness of the air feeding mechanism  40  is retained despite the larger load.  
     [0019] When the paper reaches the shredding mechanism  14  it is shredded, generally as described in U.K. Patent Application Serial No. 0210599.7. A plurality of small paper particles  42  is thereby generated, which are carried along the air flow path through the aperture channels  36 ,  38 , the manifolds  32 ,  34  and the tubes  30  to the collection chamber  26 . These then collect in the paper bag  28 . Once full the paper bag  28  may be easily emptied, and the shredded particles  42  disposed of.  
     [0020] The suction generated by the air feeding mechanism  14  draws the paper through the shredder  10  and acts as a convenient way of collecting shredded particles  42 . The air feeding mechanism can, as shown in the embodiment above, be supplemented by infeed rollers  16 , but can also function as the sole feeding mechanism. Unlike infeed rollers the air feeding mechanism does not tend to crinkle or stretch the paper, but provides a smooth and effective feed.  
     [0021] Although described above in relation to a shredder it will be apparent that the air feeding mechanism outlined herein could be used in other devices, for example a printer, where sheet material must be fed past a processing head.  
     [0022] In the present specification “comprises” means “includes or consists of” and “comprising” means “including or consisting of”.  
     [0023] The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof.