Patent Publication Number: US-5893524-A

Title: Paper shredder

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a paper shredder, particularly a small paper shredder. The paper shredder includes a shell-like lower housing part which includes the cutting rollers with their bearing plates at the end faces and the stripping elements, and an upper housing part which is provided with a material inlet slot and can be placed on the lower housing part. 
     2. Description of the Related Art 
     Small paper shredding apparatus of the above-described type are known, for example, from DE 40 08 654 A1 and include a two-part injection-molded housing of synthetic material in which, in addition, the usually web-shaped stripping elements including the cutting roller bearings are integrated in the housing during injection molding. Although this apparatus can be easily assembled, there is the disadvantage that these known apparatus do not run smoothly and are loud during operation because all drive and work noises are transmitted as vibrations to the housing which additionally acts as an amplifying sound board. 
     SUMMARY OF THE INVENTION 
     Therefore, it is the primary object of the present invention to provide a small paper shredder which is extremely simple to assemble, which produces extremely little structure-borne noise radiation and runs very smoothly. 
     In accordance with the present invention, the bearing plate on the drive side for the cutting rollers simultaneously forms the single-piece bottom of an also shell-like gear housing which can be closed by means of a cover. The entire cutting mechanism including gear housing, cutting rollers and stripping elements is mounted in the area of the bearing plates on the end faces through vibration-damping elements in the lower housing part. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing: 
     FIG. 1 is a schematic top view of the lower part of an open paper shredder housing; and 
     FIG. 2 is a cross-sectional view, on a larger scale, taken along sectional line A--A of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A paper shredder according to the present invention, particularly a small paper shredder, is composed in its basic construction of a shell-like lower housing part 2 which includes the cutting rollers 4, 4a and 5, 5a together with their bearing plates 3 and 8 at the end faces, the corresponding stripping elements 6 and 7 as well as the outlet gap SA for the cut material, and an upper housing part 1 provided with an inlet gap MZ for the material to be cut, wherein the upper housing part 1 can be placed on the lower housing part 2. 
     The essential feature for meeting the above-described object in such a paper shredding apparatus is the fact that, according to the present invention, the bearing plate 3 on the drive side for the cutting rollers 4, 5 simultaneously forms a single-piece bottom 3a of an also shell-like gear housing 3, 3a, 3b which can be closed by means of a cover 3c, and that the entire cutting mechanism including gear housing 3, cutting rollers 4, 5 and stripping elements 6, 7 is mounted in the area of the bearing plates 3 and 8 on the end faces through vibration-damping elements 9 in the lower part 2 of the housing. 
     As a result of the two principal features according to the present invention, the entire cutting mechanism unit has a high inherent stability and manufacturing accuracy, and, due to the vibration-damping acoustic uncoupling from the housing, the cutting mechanism unit practically has no structure-borne sound radiation and, thus, the unit operates extremely smoothly and quietly. 
     In accordance with another further development of the present invention, the cutting rollers 4, 4a and 5, 5a and their comb-like stripping ledges 6, 7 are connected to the two bearing plates 3 and 8 on the end faces in a positively locking and/or frictionally locking manner by insertion in appropriate recesses; consequently, the apparatus is constructed in such a way that it is extremely simple to assembly and maintain; in addition, individual structural groups can be prefabricated and assembled later. 
     In accordance with another feature according to the present invention which is important with respect to the operation of the cutting mechanism, the stripping ledges 6, 7 are of a synthetic slide bearing material and rest on the cutting edges 4, 5 while being in close contact with the cores 4a and 5a of the cutting rollers, and the free ends 4b and 5b of the stripping elements 6 and 7 on the roller cores 4a and 5b are constructed nose-shaped with pointed ends. This produces the necessary stability of the comb-like stripping elements. 
     In order to prevent paper from reaching the gap between the cutting mechanism and the upper housing part 1 when material is inserted into the apparatus and particularly when the rollers rotate backwardly, another feature of the present invention provides that the surfaces 6a and 7a of the stripping ledges 6 and 7 have over their entire lengths transverse webs 11 arranged at a distance opposite each other, and the upper housing part 1 has corresponding recesses 12, wherein the transverse webs 11 engage in the recesses 12 without contacting the recesses 12, so that they are acoustically uncoupled from each other. 
     In accordance with another important feature of the cutting mechanism, the bottom sides 6b and 7b of the stripping ledges 6 and 7 each have a longitudinal web 6c and 7c which engages in corresponding recesses 13a of the longitudinal housing girders 13 at the bottom, wherein the girders 13 are located in the open bottom area 2c of the lower housing part 2 and include guide surfaces 13b which extend from the cutting rollers 4, 5 obliquely toward the bottom. On the one hand, this configuration prevents dust and cutting material particles from being clogged in the housing area; in addition, since small units of this type generally do not have an automatic switch-off when the collecting container is filled, cut material is prevented from penetrating into the cutting mechanism from below when the receiving container SB is full; this effect is further reinforced by means of an obstacle-like step 13c at the bottom side of the longitudinal girders 13 and the protruding configurations of the corners or edges K of the stripping ledges 6 and 7 in the area of the cut material outlet gap SA. Moreover, these longitudinal edges K of the stripping ledges 6 and 7 are located, in relation to the center axis M of the cutting rollers, at a distance s 1  below the center axes M which is greater than the dimension a between the center axes M and the upper surfaces 6a and 7a of the stripping elements. 
     The paper shredding apparatus according to the present invention is operationally completed by an on/off switch 14 together with a switching vane 14a which projects into the material inlet gap MZ and serves for the automatic start-up of the cutting mechanism when material is inserted. 
     The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.