HUB DEVICE Technical field The present invention concerns a hub device for a pair of saw blades comprising a first blade, which is adapted to rotate about an axis of rotation in a first direction, and a second blade, which is adapted to rotate about the same axis of rotation in a second direction oppsite to said first direction, wherein both blades have a blade body and cutting units, such as saw teeth or diamond clad segments, arranged along the periphery of blade body and adapted to run close to and in parallel with each other, and wherein the hub device comprises a first blade adapter having a support surface for that side of the first blade facing away from the second blade and dog means for rotating the first blade, and a second blade adapter having a support surface for that side of the second blade facing away from the first blade.

State of the art Hub devices of the type mentioned above are well known and besides the hub for the saw blades they also comprise driving shafts and cogwheels connected to these for driving the saw blades.

Drawbacks of the state of the art In the known hub devices both saw blades are floa- tingly mounted, i. e. only the outer sides of their stem blades supports themselves against parts of the hub devi- ces, while their inner sides do not have contact with any such parts. In practice this can cause the saw blades to start vibrating or start deviating from the desired saw cut. In the worst case this can lead to the peripheries of the saw blades beginning to creep apart, which quickly leads to a blade or machine brakedown.

The object of the invention Against this background the object of the present invention is to provide a hub device of the type men- tioned by way of introduction, said hub device obviating the problems with the state of the art.

Summary of the invention According to the invention this is achieved by means of a hub device of the type mentioned by way of introduc- tion, wherein the second blade adapter has screw holes cut in its support surface, into which screws are screw- able for locking the second blade onto the second blade adapter.

By locking the second blade with the adjoining sup- port surface by means of screws a blade stationary rela- tive to the hub device is created, the blade being dis- inclined to deviate from its contemplated working posi- tion. This means that the risk of vibrations is reduced drastically and that it becomes considerably easier to perform straight cuts by means of the pair of saw blades, because the stationary second blade guides the coopera- ting saw blade, which is floatingly mounted in a known fashion. Additionally the safe guiding of the blades lessens considerably the tendency of their peripheries creeping apart when biased.

According to the preferred embodiment of the hub device according to the invention the second blade adap- ter in relation to a driving unit for driving the hub device is provided for the outer one of the two blades.

The advantage with this solution is that it renders it possible from a factory delivering the second saw blade assembled with the adherent second blade adapter, thereby excluding bad assembly and thus the risk of blade or machine breakdown.

Brief description of the drawing A preferred embodiment of the invention is described in more detail below with reference to the attached drawing, wherein: Fig. 1 is a diagrammatic cross-sectional view show- ing two saw blades and a second blade adapter; and Fig. 2 is a longitudinal sectional view showing a hub device without any saw blades.

Description of the preferred embodiment In Fig. 1 are shown a first, inner saw blade 1 and a second, outer saw blade 2, said blades being adapted to cooperate with each other by rotating close to each other in opposite directions as shown. The blades 12 each com- prises a central blade body 3,4, which is made of steel sheet and has a rim of saw teeth 5,6 along its peri- phery. The blade bodies 3,4 are bent in such a way that they in use by means of spacer means 7 meet only in a peripheral part of the blade bodies 3,4, while they inside of this peripheral part together form a gap 8, which is exagerated heavily in the figure in order to illustrate the bending in a better way. Even outside said peripheral part there is a gap 9, but this one is much narrower and furthermore it is formed between the saw teeth 5,6 of the blades.

The second, outer blade 2 is assembled with a second blade adapter 10, which on its face facing the blade has a circular protrusion 11 for cooperating with a corres- ponding cut out 12 in the blade body 4 of the blade. Fur- thermore the blade adapter 10 has two diametrically opposite screw holes 13,14, which are provided in an even supporting portion 15 around said protrusion 11. The screw holes 13,14 correspond to countersunk holes which are formed in the blade body 4 of the blade and through which screws 16,17 with countersunk heads extend for cooperating with the screw holes 13,14 in the blade adapter 10 and fixing the blade 2 thereon.

In Fig. 2 the second blade adapter 10 is shown to- gether with remaining parts of a hub device 18 (for the sake of clarity the saw blades are not shown in this figure). As can be seen the second blade adapter 10 is stationary mounted on an inner shaft 19, which is mounted inside an outer shaft 20 driven by a motor (not shown) with the aid of a cogwheel 21 also mounted stationary on the inner shaft. On the outer shaft 20 a first inner blade adapter 22 is fixedly mounted. It is also driven by said motor with the aid a cogwheel 23. This is inverted in respect of the cogwheel 21 mentioned above, which leads to that it and thereby the first blade adapter 22 are rotated in a direction opposite the rotational direc- tion of the second blade adapter 10.

The first blade adapter 22 also has a circular pro- trusion 24. It is however adapted to engage with a corresponding cut out in the stem blade of the first blade. Furthermore the blade adapter 22 has two diame- trically opposed spigots 25,26, which protrude from an even supporting portion 27 around said protrusion 24. The spigots 25,26 correspond to holes that are formed in the blade body of the blade in order to floatingly fix the blade onto the first blade adapter 22 in cooperation with the spigots 25,26.

It is obvious that the embodiment of the hub device 18 described above can be varied in different ways within the scope of the claims. It is consequently possible to use the hub device 18 for other saw blades than the ones described above, to mount the second blade adapter 10 innermost and to fix the second blade with another kind of screw than the one described.