Abstract:
An abrasive disc which may be attached to a holder having a suction device associated therewith. The disc includes a body of soft, resilient material and abrasive layers on both sides. Apertures, openings, and orifices in the abrasive layers and in the edge of the body allow air and particles to be drawn into internal passages in the body of the disc and flow out of the body to the suction device in the holder. The apertures also facilitate attachment of the abrasive disc to the holder.

Description:
BACKGROUND AND OBJECTS 
     1. Field of the Invention 
     The present invention relates to an abrasive disc which may be readily fixed on a holder. The disc is stabilized on the holder by means of pins projecting from the holder, and these pins also allow for easy removal of the disc from the holder. The abrasive disc is provided with apertures for sucking air up and grinding particles by means of a suction device. 
     2. Description of the Prior Art 
     Abrasive discs with apertures for sucking up air and grinding particles are expensive to produce, since the passages extending within said discs substantially complicate the process of manufacturing. Consequently, the discs are provided only with few passages, said discs are permanently secured on a holder and the grinding paper is exchanged in regular intervals. The grinding paper is fastened with a pressure sensitive glue, but the paper is easily unglued because of grinding particles becoming wedged in under the paper during operation. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a grinding device of the abovementioned type, which is inexpensive to produce despite a plurality of passages, which permits a stable fixing of grinding paper or the like, which permits easy mounting on the holder, stable fixing on said holder and quick demounting from the holder, and which allows for two opposed sides of the same to be used for grinding. 
     SUMMARY OF THE INVENTION 
     The foregoing difficulties in the prior art are overcome and the foregoing objects are achieved by providing an abrasive disc including a body of soft, resilient material having oppositely facing sides and an edge therebetween, a first abrasive layer and a first set of grooves on one side of the body, the abrasive layer extending across the grooves, a first set of openings in the edge, a first set of apertures in the first abrasive layer, the openings and apertures being connected with the grooves, whereby, in operation, air and particles may be drawn into openings and apertures, through the grooves and toward a suction device associated with the holder for the disc. According to more detailed aspects of the invention, there may be a second abrasive layer having a set of apertures on the other side of the disc, and second sets of openings and grooves. Either of the sets of apertures may be used in fastening the disc to its holder. In this regard, portions of the abrasive layer immediately adjacent the apertures are inwardly foldable in response to engagement with pins extending from the holder. These portions will abrasively engage the pins to secure the abrasive disc to the holder. 
    
    
     DRAWINGS 
     The invention will be further described below with reference to the accompanying drawings in which; 
     FIG. 1 shows the abrasive disc according to the invention from underneath and partly in section; 
     FIG. 2 is a section through the abrasive disc arranged on a holder; 
     FIG. 3 is a section through a portion of the abrasive disc before it is mounted on the holder and finally; 
     FIG. 4 is a section through said portion of the abrasive disc after its mounting on the holder. 
    
    
     DESCRIPTION 
     The abrasive disc 1, which is to be described in more detail hereinafter, is designed to be arranged on a driven holder 2 and cooperate with a suction device (not shown). In FIG. 2, the holder 2 is in the form of a plate with projecting pins 3. The plate is supported by a ring 4 connected thereto, and is rotated and oscillated by means of a drive shaft 5 via an eccentric body 6 and a ball bearing 7. A housing 8 is placed above the plate of the holder 2, said housing having a connection piece 9 for connection to the suction device. When the abrasive disc 1 securedly securedly pressed on the plate 2, passages in the abrasive disc are communicating with the suction device via holes 10 in the plate 2, via the interior of the housing 8 and via the connection piece 9. 
     According to the invention, the abrasive disc 1 may easily be pressed on and attached to the holder 2 with any one of its opposed sides against the holder. After the pressing the abrasive disc 1 shall be fixedly secured on the holder and easy removable from the same, e.g. for being turned and pressed onto the holder with the abrasive for the grinding directed against the holder. Further, the abrasive disc must provide a stable securing of the abrasive, the abrasive disc shall be inexpensive to produce so that it may be thrown away after wearing out the abrasive and the abrasive disc must provide effective grinding particle collecting properties. 
     In order to accomplish this, the abrasive disc 1 according to the invention comprises a body 12 of a soft, resilient material, preferably expanded material, such as styrene. On two opposed sides 12a, 12b, an abrasive layer 11a, 11b is attached by, for example, glueing on each side respectively. The layers have greater density than the body 12. The opposed sides 12a, 12b of the body 12 are provided with grooves 14a, 14b. These grooves are covered by the abrasive layers respectively and to define passages which open against an edge 12c extending between the sides 12a, 12b of the body. Grooves 14a and 14b also open against the sides of the abrasive layers by means of apertures 15, 16 in said layers respectively and are connected to the suction device. The grooves 14a or 14b are placed beside each other at a distance somewhat exceeding the width of the grooves. This means that there are at least 32 air intakes provided in the preferred embodiment in the drawings. 
     If the pins 3 are sufficiently pointed (pointed pins not shown) they may be forced through the abrasive layers 11a, 11b, respectively and forced into the soft, resilient material of the body 12. Thus, the edges around every hole made by the pins 3 in the abrasive layers are bent inwardly so that the abrasive grains on each abrasive layer 11a, 11b engage the pins respectively. Consequently, displacement of the abrasive disc 1 on the pins 3 is effectively prevented, i.e. the abrasive is fixedly secured on the holder 2 during rotation and oscillation thereof. If desired, the abrasive disc is easily removable for turning or replacement with another disc, e.g. a disc having another size on the abrasive grains of the abrasive layer. 
     In order to provide a similar secure mounting of the abrasive disc 1 on the holder 2 and also to prevent disturbance of the air flowing in the disc, the body 12 is provided with holes 13 corresponding to the pins 3. The grooves 14a, 14b are connected to these holes 13 i.e. air flows streaming through the grooves must also pass through the holes 13. The pins 3 extend independently of the direction from which they are inserted in the holes 13 of the body 12, down through said holes 13 at least partially and preferably totally blocking the grooves 14a or 14b (14b in FIG. 2) under the abrasive layer 11a or 11b (11b in FIG. 2) lying closest to the holder 2 while leaving open the grooves 14a or 14b (14a in FIG. 2) under the abrasive layer 11a or 11b (11a in FIG. 2) turned away from the holder 2. Thus, the pattern of the air flow will be as follows see FIG. 2), Air is sucked in through apertures of the grooves 14a and openings in the edge 12c, passes the apertures 15, and through these taking up grinding particles, passes the annular channel 17a of two annular channels 17a, 17b extending in the opposed sides of the body 12, passes bores 18 and thereby (and/or when passing the annular channel 17a) passing orifices 19a in the abrasive layer 11a and through these orifices 19a taking up grinding particles. The air flow thereafter passess through the bores 18, without disturbance from air entering through the grooves 14b. The air also flows via orifices 119a in the abrasive layer 11b to the holes 10 in the holder 2 and, via these holes 10, to the interior of the housing 8 and the connection piece 9 to the suction device. 
     In order to ensure substantial adherence between the abrasive disc 1 and the holder 2, the apertures 15, 16 in the abrasive layers 11a, 11b may be considerably less in size than the holes 13 beyond said apertures 15, 16. This means that the portions 11c, 11d overlapping the holes 13 in the body 12 are folded into the holes 13 when the pins 3 are forced in through said holes (see FIGS. 3 and 4). 
     Accordingly the abrasive grains on the portions 11d (and when the disc is turned, the abrasive grains on the portions 11c) will define a friction lining in the holes 13 for the pins 3. 
     To eliminate the risk that the holes in the abrasive disc do not communicate with the holder 2, said holder may be provided with a ring 20 (e.g. of a rubber material) of which the inner edge 20a lies outside the orifices 19a, 19b (19b in FIG. 2) in the abrasive layers 11a, 11b (11b in FIG. 2). This insures that a slit is formed between the disc 1 and the holder 2, through which slit air may flow obliquely, if necessary. 
     In order to create, for example three rows of grinding particle intakes (15, 16, 19a in FIG. 1) in each abrasive layer, the pins 3 may be arranged in two rows, whereby the pins 3 in one row are laterally displaced in relation to the pins 3 in the other row. 
     When describing the preferred embodiment, certain alternatives have been referred to. However, it is possible to define other sub-assemblies not mentioned here but within the scope of the present invention. For example the pins 3 may be hollow and define percolation passages.