Saw-blade fixation device

Abstract: The invention relates to a device for fixing a saw-blade (3) provided with an opening (4) to a carrier (1) which is connected to a drive device to make a reciprocating movement, wherein the device comprises: a wall (2) extending in the direction of movement which is suitable for contact with a side of the saw-blade (3); a fixation body (10) which is rotatable opposite the wall (2) around a shaft (9) extending perpendicularly of the direction of movement and parallel to the wall (2) and which is provided with a protrusion (12) which is movable into the opening (4) arranged in the saw-blade (3); and urging means (18) for urging the fixation body (10) to a fixation position wherein the protrusion (12) extends into the opening (4) arranged in the saw-blade (3). Fixation herein takes place because via the sphere (12) the saw-blade (3) generates a moment in clockwise direction relative to the shaft. This moment is counteracted by a moment that is generated by the friction between the actuating rod and the contact surface.

Description: The present invention relates to a device for fixing a saw-blade provided with an opening to a carrier which is connected to a drive device to make a reciprocating movement. Such devices are generally known. Such known devices are often applied for example in power jigsaws or so-called all-purpose saws. The connection between saw-blade and carrier in these fixation devices forming part of the prior art is mostly embodied in that an element presses the saw-blade against the carrier by means of a screw connection. Guide edges are usually arranged to determine the correct position of the saw-blade on the carrier. The use of a screw makes it necessary to emply a screwdriver or a socket head wrench to fix a saw-blade in the saw or to remove a saw-blade thereform. When using electrical hand tools the use of a screwdriver or the like is of course less desirable; there is the danger of this tool being misplaced and the use thereof is time-consuming. US-A-3,555,678 discloses a device for fixing a saw blade provided with an opening to a carrier which is connected to a drive device to make a reciprocating movement, and comprising a wall extending in the direction of movement and which is suitable for contact with a side of the saw blade; a fixation body located opposite the wall and being rotatable around a shaft extending perpendicularly of the direction of movement and parallel to the wall and which is provided with a protrusion which is movable into the opening in the saw blade; and urging means for urging the fixation body to a fixation position wherein the protrusion extends into the opening in the saw blade. Although this document discloses a fixation device with which the saw-blade is well fixed on a carrier capable of performing a reciprocating movement, and wherein no extra tool is necessary for fitting or removing the saw-blade, it has the drawback that this fixation device transfers the forces from the saw-blade to the carrier through the shaft, leading to rapid wear if used in a power saw. The aim of the invention is to avoid this drawback. This object is achieved in that the shaft is located such that the projection of it's axis onto the wall is within the opening in the saw blade in its fixed position, and that the protrusion is fit for pressing the saw blade against the wall. The friction provides in an at least partial transfer of the forces through friction. Other steps which improve the practical value of the fixing device are disclosed in the appended claims. The present invention will now be elucidated with reference to the included embodiments, in which: fig. 1 shows a perspective, partially broken away view of a fixation device according to the present invention; fig. 2 shows a cross sectional view of the fixation device depicted in fig. 1; fig. 3 is a side view of the fixation device shown in fig. 1; fig. 4 shows a cross section of a second embodiment of the fixation device shown in fig. 1; and fig. 5 shows a cross section of a variant of the embodiment shown in figures 1-3. Depicted in figures 1, 2 and 3 is a carrier 1 which is connected to a drive device (not shown in the drawing) which is constructed and connected to the carrier such that the carrier 1 can perform a reciprocating movement. The carrier 1 comprises a wall 2 against which a saw-blade 3 can be positioned. The saw-blade 3 is provided with an opening 4. Although it is recommended that a round opening be applied, this is in no way necessary; it is possible to use a differently shaped opening. A U-shaped bracket 5 is fixed to the carrier 1. The U-shaped bracket comprises two side pieces 6, 7 which are placed mutually opposite and which are connected by a back portion 8. Arranged in each of the side pieces 6,7 is an opening through which extends a shaft 9. The back portion can also be formed by the carrier 1. A fixation body 10 is fixed on the shaft. The fixation body has a prismatic form and is provided with a cavity 11 in which is situated a clamping body 12 embodied in the present embodiment as a sphere. The fixation body is further provided with a protrusion 13. In each of the side pieces 6, 7 is arranged a slot 14 and 15 respectively. An actuating rod 16 extends through the slots 14, 15. For fixation purposes sleeves 17 are clamped onto both ends of the actuating rod 16. The design of the slots 14, 15 is otherwise such that the actuating rod 16 is always enclosed by the fixation body 10 and the protrusion 13 thereof. A spring 18 wound from wire is further arranged. The spring extends from the end 19 which lies against the upper side piece 7 to the shaft 9, is wound approximately one and a half times therearound, then extends up against the actuating rod 16, is bent downward and again extends along the actuating rod 16 to the shaft 9, is again wound one and a half times therearound and finally ends against the lower side piece 6. The winding direction and the dimensions of the spring are selected such that the spring exerts a force on the actuating rod 16 such that this is urged in the slot towards the carrier 1. Instead of this spring construction it is of course possible to apply other spring configurations. The operation of this device will now be described. With the embodiment shown in figures 1, 2 and 3, in the position in which no saw-blade is enclosed the actuating rod 16 is urged by the spring 18 into contact with the contact surface 20 of the fixation body 10. Since the fixation body 10 can move freely, it is pushed aside. When a saw-blade is introduced, it will be pushed from the left-hand side between the sphere 12 and the carrier 1. To make insertion possible the actuating rod 16 is moved manually counter to the spring pressure, whereby the fixation body 10 with the sphere 12 can rotate freely and the saw-blade 3 can be inserted. The insertion movement is continued until the sphere 12 falls into the cavity 4. This can be felt via the saw-blade, whereafter the user can release the actuating lever 16 and this is urged by the spring pressure into contact with the contact surface 20. Fixation herein takes place because via the sphere 12 the saw-blade generates a moment in clockwise direction relative to the shaft 9. This moment is counteracted by a moment that is generated by the friction between the actuating rod 16 and the contact surface 20. Because the contact surface 20 and the path that the actuating rod 16 can traverse are for a large part parallel, the friction force is so great that it exceeds the moment generated by the saw-blade so that the device can withstand shocks endured by the saw-blade, for example when the saw jams. It is important here that the angle enclosed between the contact surface 20 and the path to be traversed by the actuating rod 16 is very small so that the friction force which is in any case a normal force forms for the greater part a transverse force on the path. This force is thus absorbed by the right-hand edge of the slots 14 and 15. Fixation thus takes place in the following manner. When the saw-blade 3 is subjected to forces which pull the saw-blade 3 out of the fixation device, the clamping body 12 is rotated together with the fixation body 10 by the saw-blade 3 such that the clamping body 12 presses the saw-blade 3 against the carrier 1. The clamping action is thus reinforced and it is impossible for the saw-blade to be moved outward. Conversely, if the saw-blade 3 is subjected to a force which pushes the saw-blade 3 inward, an attempt is then made to rotate the fixation body 10 toward the actuating rod 16. However, this is prevented by the friction force between the surfaces 20 in contact of the fixation body 10 and the actuating rod 16. As a result of the shapes and position of the slots 14, 15, the rod 16 can only move substantially parallel to the contact surface. Fixation thus also takes place in this direction. When the fixing mechanism must be released, the actuating rod 16 only has to be removed manually from the contact surface 20, which is easily done because, as stated, the friction force is a normal force, and the fixation body 11 is released. It is then easy to remove the saw-blade. In the above described embodiment a separate sphere is described which is freely rotatable in the fixation body 11. It is however also possible to fix a protrusion on the fixation body which assumes the function of the sphere. Such an embodiment is shown in fig. 4. Herein the fixation body 10, which takes a slightly more rounded form in this embodiment, is provided with a protrusion 21. The essential difference lies in the fact that the protrusion cannot rotate relative to the fixation body; this drawback can be minimized by a suitable design, choice of material and, perhaps, lubrication. This embodiment otherwise corresponds with the embodiment shown in figures 1, 2 and 3. Finally, fig. 5 shows an embodiment wherein the fixation of the saw-blade takes place automatically. For this purpose a lever 22 is arranged which is rotatably disposed relative to the U-shaped bracket 5 by means of a shaft 23. The bottom slot 14 is further provided with an extension 24 into which the actuating rod 16 can be moved. The lever 22 extends into the vicinity of the carrier 1, while the other side of the lever 22 extends over the extension 24. In the starting position the actuating rod 16 is in the extension 24 of the slot 14. The fixation body 10 is thus unlocked and the saw-blade can be inserted. When the saw-blade has been inserted far enough it touches the lever 22 which will rotate relative to the bracket 5 and which will press the actuating lever 16 out of the extension 24 into the slot 14, whereafter it is urged into the fixation position by means of spring pressure generated by the spring 18 and a situation is obtained which has already been described with reference to fig. 1-3. When the saw-blade is taken out, the lever 16 is moved manually into the recess 24, whereby the fixation body 10 is released, and the lever 22 is actuated whereby the saw-blade 3 is ejected. A spring is otherwise arranged which urges the lever 22 to the position in which the saw-blade is ejected.

Claims: Device for fixing a saw blade (3) provided with an opening (4) to a carrier (1) which is connected to a drive device to make a reciprocating movement, and comprising: a wall (2) extending in the direction of movement and which is suitable for contact with a side of the saw blade (3); a fixation body (10,12) located opposite the wall (2) and being rotatable around a shaft (9) extending perpendicularly of the direction of movement and parallel to the wall (2) and which is provided with a protrusion (12) which is movable into the opening (4) in the saw blade (3); and urging means (16,17,18,19) for urging the fixation body (10,12) to a fixation position wherein the protrusion (12) extends into the opening (4) in the saw blade (3), characterized in that the shaft (9) is located such that the projection of it's axis onto the wall (2) is within the opening (4) in the saw blade (3) in its fixed position, and that the protrusion is fit for pressing the saw blade (3) against the wall (2). Device as claimed in claim 1, characterized in that the protrusion (12) is at least partially spherical and that the dimension of the opening (4) arranged in the saw-blade (3) is smaller in the direction of movement than the diameter of the at least partially spherical protrusion (12). Device as claimed in claim 1 or 2, characterized in that the protrusion (12) forms part of a clamping body that is arranged at least partially in a cavity (11) present in the fixation body (10), and which is urged by means of spring pressure into the opening (4) arranged in the saw-blade (3). Device as claimed in claim 1 or 2, characterized in that the fixation body (10) is fixed onto a shaft (9) extending transversely of the direction of movement and parallel to the wall (2), which shaft (9) is bearing mounted in a U-shaped frame (5) which is attached with its rear side to the wall (2). Device as claimed in claim 4, characterized in that the urging means (16; 18, 19) are formed by an actuating body (16, 17) movable along a path (14, 15) in substantially tangential direction relative to the shaft (9), and that the path (14, 15) runs such that the actuating body (16, 17) touches the fixation body (10) when the latter is in the fixation position and the fixation body (10, 13) is subjected to a friction force from the actuating body (16, 17) such that forces exerted by the saw-blade (3) have no effect on the position of the fixation body (10, 13). Device as claimed in claim 5, characterized in that the actuating body (16, 17) is formed by a pin (16) which extends through slots (14, 15) arranged in each of the legs of the U-shaped frame (5), which slots (14, 15) extend substantially parallel to the contact surface (20) of the fixation body (21, 13). Device as claimed in claim 6, characterized in that the slots (14, 15) are curved and that the contact surface (20) of the fixation body (21) is curved, wherein both radii of curvature differ little. Device as claimed in claim 6 or 7, characterized in that an element (18, 19) is arranged which urges the pin (16, 17) to the position in which it touches the fixation body (10, 21). Device as claimed in claim 5, 6, 7 or 8, characterized in that the actuating member (16, 17) can assume a rest position lying outside the path (14, 15), and that a lever (22) is arranged which extends into the path of the saw-blade and which pushes the actuating member (16, 17) from its rest position into its path (14, 15) when the saw-blade (3) is pulled in.

Inventors: QUIRIJNEN ANTONIUS JACOBUS JOH, QUIRIJNEN, ANTONIUS JACOBUS JOHANNUS
Applicants: SKIL EUROP BV, SKIL EUROPE B.V.
Application year: 1993
Main classification: B23D51
IPC codes: B23D51