Patent Publication Number: US-6668693-B2

Title: Mechanism for paper towel dispensers

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a mechanism for paper towel dispensers, and particularly to a mechanism suitable for cutting and distributing sheets of paper or of another material after taking them from a roll. The present invention also relates to a paper towel dispenser comprising said mechanism. 
     EP 871390 discloses a mechanism for paper towel dispensers comprising a cutting device having at least one movable blade arranged inside a cylinder, which drags the sheet of paper taken from a roll. However, said known mechanism involves a considerable manufacture and maintenance complexity, as well as a non-efficient functioning of the cutting device, with risk of jamming of the mechanism itself. 
     BRIEF SUMMARY OF THE INVENTION 
     Object of the present invention is therefore to provide a mechanism which is free from said drawbacks. Said object is achieved by a mechanism, the main features of which are specified in the first claim and other features are specified in the following claims. 
     By virtue of the particular rotational-translational drive system which it is provided with, the cutting device of the mechanism according to the present invention has a precise and fluent movement of the blades outwards from the cylinder. 
     Further, thanks to the pair of mutually engaged toothed wheels and to the guides of the supporting structure, said movement of the blades is perfectly synchronized with that one of the cylinder, so as to avoid the mechanism jamming. 
     According to a particular aspect of the invention, the translatory movement of the member transmitting the rotation to the movable blades is caused by a pair of relieves made inside the supporting structure of the cylinder, so as to obtain a precision of movement without complex and/or expensive guides. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     Further advantages and features of the mechanism according to the present invention will appear to those skilled in the art from the following detailed and non-limiting description of one embodiment thereof with reference to the accompanying drawings, wherein: 
     FIG. 1 shows a left side view of the mechanism according to said embodiment; 
     FIG. 2 shows a right side view of the mechanism of FIG. 1; 
     FIG. 3 shows a front view of the mechanism of FIG. 1; 
     FIG. 4 shows a side cross-sectioned view of the mechanism of FIG. 3 taken along plane IV—IV; 
     FIG. 5 shows a side cross-sectioned view of the mechanism of FIG. 3 taken along plane V—V; 
     FIG. 6 shows a side cross-sectioned view of the mechanism of FIG. 3 taken along plane VI—VI; and 
     FIG. 7 shows a side cross-sectioned view of the mechanism of FIG. 3 taken along plane VII—VII. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1 to  3 , it is seen that the mechanism according to said embodiment of the invention comprises in a known way a supporting structure formed of a pair of side walls  1 ,  2  mutually connected by means of at least one profiled transverse bar  3  acting as a lower guide. This supporting structure can be mounted inside a housing (not shown in the figure). The upper portion of side walls  1 ,  2 , is provided with a pair of semi-cylindrical seats  4 ,  5  wherein the ends of a tube  6  can rotate, around which at least one sheet of paper or other material is wound so as to form a roll  7 . The end portion  8  of this sheet passes around a cylinder  9  parallel to tube  6  and protrudes under transverse bar  3 , so that it can be pulled by a user in the direction indicated by arrows  10 . End portion  8  of the sheet is guided around cylinder  9  by an idle cylinder  11  parallel thereto. Cylinder  9  can be rotated between side walls  1 ,  2  by manually pulling end portion  8  of the sheet or by rotating a round handle  12  which is arranged outside side wall  2 . This round handle is fixed to one external end of a pair of hubs  13  which are fixed in a coaxial way to the lateral surfaces of cylinder  9  and which cross walls  1 ,  2 . The rotation of cylinder  9 , which occurs in the direction indicated by arrows  14 , is opposed for a half-turn and then pushed for the other half-turn by a tension spring  15  fixed between side wall  1  and a disk  16  which is partially toothed with oblique teeth. This disk is fastened to the external end of a hub  13  of cylinder  9  and is arranged outside wall  1 . After performing one turn around its axis, disk  16  is blocked by a spike  17  hinged to wall  1  so as to oppose the contrary rotation thereof. By this ratchet gear, cylinder  9  can be easily rotated of one turn at a time when end portion  8  of the sheet is pulled or handle  12  is rotated. 
     With reference also to FIGS. 4 and 5, there is shown that one hub  13  of cylinder  9  can rotate coaxially inside a cylindrical toothed wheel  18 , having internal or external teeth, which is fixed to the internal surface of wall  2  and is engaged with another cylindrical toothed wheel  19  having the same number of teeth or a whole submultiple thereof. The toothed wheel  19  can slide along the internal surface of wall  2  and is arranged at one end of a rod  20  which longitudinally crosses cylinder  9  and can slide therein. The other end of rod  20  is provided with a skid  21  which can slide along the internal surface of wall  1 . 
     The internal surface of side wall  1  is suitably provided with at least one relief  22  which acts as a guide and has a gradually varying thickness, so that skid  21 , by sliding along this wall in the sense indicated by arrows  23 , shifts rod  20  horizontally inside cylinder  9  towards side wall  2 . Particularly, relief  22  extends itself for about one quarter of a circumference coaxially with the longitudinal axis of cylinder  9 . Even the internal surface of side wall  2  is suitably provided with at least one relief  24  which acts as a guide and has a gradually varying thickness, so that the toothed wheel  19 , by sliding along this wall in the sense indicated by arrows  23 , shifts rod  20  horizontally inside cylinder  9  towards side wall  1 . Also relief  24  extends itself for about one quarter of a circumference coaxially with the longitudinal axis of cylinder  9 , but in the preceding quadrant of that of relief  22  in the sense of arrows  23 . Therefore, by means of relieves  22  and  24  it is possible to slide horizontally rod  20  and toothed wheel  19  with an alternated motion synchronized with the rotary motion of the cylinder itself. A pin  25  is fastened to the lateral surface of the toothed wheel  19  turned towards cylinder  9 . 
     Referring also to FIG. 6, it is seen that a shaft  26  is arranged coaxially around rod  20  and can rotate parallely to the longitudinal axis of cylinder  9  in a set of eccentric round seats  27  made in disks arranged inside the cylinder itself. One or more movable blades  28 , preferably curved and provided with triangular points, are fixed to shaft  26 . Through suitable openings made in the cylindrical surface of cylinder  9 , these blades can protrude outwards. This is achieved by rotating shaft  26  around its axis against the force exerted by a tension spring  29  arranged inside cylinder  9 . 
     With reference also to FIG. 7, it is seen that the end of shaft  26  turned towards wall  2  is provided with a pin  30  protruding from a side wall of cylinder  9  through an opening  31  which extends for about one quarter of a circumference coaxially with the longitudinal axis of shaft  26 . 
     During the use, the end portion  8  of the sheet wound around roll  7 , when a user pulls it, proceeds in the direction of arrows  10 , thus rotating cylinder  9  in the direction of arrows  14 . During the rotation of cylinder  9 , toothed wheel  19  rotates around its axis and horizontally shifts along the latter towards side wall  1 . When toothed wheel  19  is positioned along relief  24 , pin  25  abuts against pin  30 , thus dragging it therewith. By this measure, shaft  26  rotates for about a quarter of a circumference, thereby extending out of cylinder  9  blades  28 , which cut the end portion  8  of roll  7 . 
     When toothed wheel  19  is over relief  24 , skid  21  slides along relief  22  and shifts rod  20  towards side wall  2 , thus separating pin  25  of toothed wheel  19  from pin  30  of shaft  26 . By this measure, shaft  26  is made free and rotated backwards by spring  29  which withdraws inside cylinder  9  blades  28 , so that these cannot hit idle cylinder  11  during the rotation of cylinder  9 . A new sheet end portion  8  is dragged under profiled bar  3  by final movement of cylinder  9  due to spring  15 , so that the mechanism according to the present invention can be used again in the above described way.