CUTTING LINK FOR A SAW CHAIN

Abstract: Cutting link for a saw chain comprising an inner mainly flat link section (1) that is provided with two apertures (2) by means of which the cutting link is fixed to two adjoining links in the saw chain via axle journals, and a cutting member (3) that is arranged protruding from the flat link section (1). The cutting member (3) shows an upper section (3.1) that extends mainly perpendicular to the flat link section (1) and shows a cutter (3.2) at its front edge, and an open rear gavel (3.3) at its rear edge in the direction of motion of the saw chain. The rear gable (3.3) of the cutting member (3) inclines forward in the direction of motion of the saw chain at an angle of c2 = 50-80 DEG to the longitudinal direction (L) of the flat link section (1). The cutting member (3) shows a mainly U-shaped cross section, the opening betweens the shanks being directed sideways on the link section (1).

Description: CUTTING LINK FOR A SAW CHAIN TECHNICAL FIELD The present invention relates to a cutting link for a saw chain comprising an inner, preferably flat link section that is provided with two apertures by which the cutting link is connected to two adjoining links in the saw chain via axle journals, and a cutting member that is arranged protruding from the flat link section. The cutting member shows an upper section that extends mainly perpendicular to the flat link section and shows a cutter at its front edge, and a rear gavel at its rear edge in the direction of motion of the saw chain. The invention is not limited to cutting links showing an inner flat link section as this also may show other shapes. BACKGROUND TECHNICS Known cutting links are developed with regard to different kinds of sawing. The main difference is in the link being intended for cutting across the wood grain, which gives long chips, or for cleavage along the grain, which gives short powder-like chips. It turned out that the transportation of chips from the cutting links above all in crosscutting is of very high importance in order to be able to increase the cutting speed e.g. in timber cutting. An improvement of the transportation or evacuating of chips from the cutting links gives a distinct reduction of cutting time, that is, an increased production of timber-cutting. A saw chain intended for crosscutting is described in the German patent application DE 2 254 647 and a saw chain intended for cleavage is described in the German patent application DE 1 453 151. Still another saw chain intended for crosscutting is described in the United States patent application US 2 652 076. In that saw chain the respective cutting link shows a cutting member with an U-shaped cross-section, the aperture between the shanks of the U-shape being directed sideways on the link section. The cutting member also shows an open rear gable with the cutting member seen in the direction of motion of the saw chain. That type of saw chain has been in use during long times and has shown being acceptable for the cutting speeds and feedings that have been sufficient until the end of the eighties. The known saw chain however does not come up to the demands of today for cutting speed as it not admits a sufficiently free discharge of chips through the open rear gable of the cutting member. The object of the present invention therefor is to improve the discharge of chips from the cutting member and thereby attain a higher cutting speed. DESCRIPTION OF THE INVENTION A distinct improvement of the transportation of chips from the cutting links has been attained with a cutting link that like known cutting links comprises an inner flat link section that is provided with two apertures by means of which the cutting link is fixed to two adjoining links in the saw chain via axle journals, and a cutting member that is arranged protruding from the flat link section. The cutting member shows an upper section with a preferably U-shaped cross-section, the aperture between the shanks being directed sideways in relation to the link section. The upper section extends mainly perpendicular to the flat link section and shows a cutter at its front edge and an open rear gavel at its rear edge in relation to the direction of motion of the saw chain. In a preferred embodiment of the cutting link according to the invention the rear gable of the cutting member inclines forward in the direction of motion of the saw chain an angle of c2 = 50-80° to the longitudinal direction of the flat link section, preferably an angle of c2 = 50° to the longitudinal direction of the link section. The open rear gable of the cutting member is formed naturally as the cutting member shows a U-shaped cross-section, which also is known from existing cutting links. The surprising increase of the sawing speed that is made possible by the present invention seems to lie in the fact that the cutting member on the cutting link shows a relatively seen shorter outer shank, seen in the direction of motion of the saw chain which leads to a reduced braking of motion of the chips that have to pass between the shanks of the cutting member. Thus the discharge of chips from the cutting member is made easier. It is actually thinkable to make the outer shank generally shorter in the direction of motion than similar shanks on known cutting links and showing a straight rear gable and otherwise unchanged dimensions of the cutting link and attain that increased sawing speed. That possibility, however, is limited by the strength of the material in the cutting links as its base gets too short and may burst why an inclining or a concave rounded rear gable according to the invention is to prefer. In order to improve the sawing result even more the round grinding of the cutter of today may be replaced by a hexagonal or octagonal grinding. Further alterations of the geometry of the cutting link, which also make a higher sawing speed possible are evident from the description to the drawings below. By the altered geometry a faster sawing in otherwise equal sawing conditions is obtained but also a great reduction of cracks in the end-grain timber in cutting of tree trunks, which also conduces to increase the economical profit in e.g. timber-cutting. Further features and characteristics concerning the present invention are evident from the description to the drawings subsequently and from the claims. DESCRIPTION TO THE DRAWINGS The invention is described below as an example of an embodiment in connection with the enclosed drawings . Figure 1 shows a cutting link seen from one side. Figure 2 shows the cutting link according to figure 1 seen from the right . Figure 3 shows the cutting link according to figure 1 seen from above. The cutting link that is shown in the figures comprises a flat link section 1 that is provided with two apertures 2 with which the cutting link is fixed to two adjoining drive links in the saw chain by means of riveted axle journals, not shown in the figures. An opposite link is fixed on the opposite side of the drive links on the same axle journals. The drive links show drive members in-turned towards a driving wheel whereas the respective cutting link shows a cutting member 3 out- turned from the saw chain. A so-called raker clearance head 4 protrudes in the plane of the link section 1 in front of the cutting member 3. The cutting member 3 shows a mainly U-shaped cross-section, the aperture between the shanks being directed aside in relation to the flat link section 1 and the plane through the saw bar along which the saw chain runs. The outer shank 3.1 of the cutting member 3 thereby extends mainly in a plane perpendicular to the flat link section 1. The cutting member 3 shows in addition to that a cutter 3.2 at its front edge in the direction of motion and a rear gable 3.3 at its back edge in that direction of motion. In figure 1 and 3 the outline of the rear section of a known cutting link is drawn dash-dotted whereas the cutting link according to the invention is drawn with continuous lines. The longitudinal direction and the direction of motion of the cutting link are marked with an arrow L in figure 1 and 3. In the following the saw bar is meant to be in a vertical plane. The cutter 3.2 in known links has an inclination al = 85° but in the example according to the invention an inclination a2 = 70-85°, preferably a2 = 78 o towards the horizontal plane through the longitudinal direction L. The cutter 3.2 has along the shank 3.1 the same inclination b = 60° towards the vertical plane through the longitudinal direction L in as well known links as in the example according to the invention, but may differ as well . The rear gable 3.3 of the cutting member 3 has in known links an inclination cl = 87°-90° but in the example according to the invention an inclination c2 = 50-80°, preferably c2 = 50° towards the horizontal plane through the longitudinal direction L. The rear gable 3.3 of the cutting member 3 has along the shanks 3.1 in known links an inclination dl = 90° but in the example according to the invention an inclination d2 = 70-90°, preferably d2 = 70° towards the vertical plane through the longitudinal direction L. The outer shank 3.1 of the cutting member 3 inclines backward from the cutter with an approximate rake angle e = 5° in the example according to the invention but may differ as well. The bottom of the cutting member 3 between the shanks inclines backward from the cutter 3.2 towards the plane through the flat link section 1 with an approximate rake angle f = 4° in the example according to the invention but may differ as well. The outer shank 3.1 of the cutting member 3 shows a length 11 that in the example according to the invention is about 2/3 of the length 12 at the base of the cutting member 3 at the flat link section 1. All in all the above mentioned geometry implies that the outer shank 3.1 of the cutting member 3 shows the shape of a parallel trapezium with the base 11 and an opposite top 13, the length of which is determined by the angles of inclination b and d2 respectively of the sides. The outer surface that the outer shank 3.1 of the cutting member 3 shows is accordingly considerably smaller than in known saw chains and gives accordingly less friction to the cut chips which passs easier through the open rear gable .

Claims: CLAIMS 1. Cutting link for a saw chain comprising an inner, mainly flat link section (1) that is provided with two apertures (2) by which the cutting link is connected with two adjoining links in the saw chain via axle journals and a cutting member (3) that is arranged protruding from the flat link section (1) with a mainly U-shaped cross-section, the aperture between the shanks being directed sideways on the link section (1) , the cutting member (3) showing an outer shank (3.1) provided with a cutter (3.2) at its front edge and an open rear gable (3.3) at its rear edge seen in the direction of motion of the saw chain, characterized in that the outer shank (3.1) of the cutting member (3) shows a length in the direction of motion of the saw chain that is smaller than the disposable space of length that its base has at the connection of the base with the flat link section (1) • 2. Cutting link according to claim 1, characterised in that the length of the outer shank (3.1) consists of 2/3 of the disposable space of length at the base of the cutting member (3) . 3. Cutting link according to claim 1 or 2 , characterised in that the rear gable (3.3) of the cutting member (3) inclines forward in the direction of motion of the saw chain an angle of c2 = 50-80° to the longitudinal direction (L) of the flat link section (1) . 4. Cutting link according to claim 3, characterised in that the rear gable (3.3) of the cutting member (3) inclines an angle of c2 = 50° to the longitudinal direction (L) of the link section (1) . 5. Cutting link according to any of the claims 1-4, characterised in that the outer section of the back edge of the shank (3.1) inclines forward in the direction of motion of the saw chain an angle d2 = 70-90° towards the plane through the flat link section (1) . 6. Cutting link according to claim 5, characterised in that the outer section of the back edge of the shank (3.1) inclines an angle d2 = 70° towards the plane through the flat link section (1) . 7. Cutting link according to any of the claims 1-6, characterised in that the cutter (3.2) inclines forward in the direction of motion of the saw chain an angle a2 = 70-85° towards a plane in the longitudinal direction (L) of the saw chain that extends perpendicular towards the plane through the flat link section (1) . 8. Cutting link according to claim 7, characterised in that the cutter (3.2) inclines an angle a2 = 78° towards the longitudinal direction (L) of flat link section (1) . 9. Cutting link according to any of the claims 1-8, characterised in that the cutter (3.2) inclines forward to the direction of motion of the saw chain an angle b = 60° . 10. Cutting link according to any of the claims 1-9, characterised in that the outer shank (3.1) of the cutting member inclines backwards in relation to the direction of motion of the saw chain in a rake angle e = 5°.

Inventors: GUSTAVSSON ROLF, GUSTAVSSON, ROLF
Applicants: GUSTAVSSON ROLF, GUSTAVSSON, ROLF
Application year: 1999
Main classification: B27B33
IPC codes: B27B33