This application claims priority of German patent application no. 10 2010 007 081.5, filed Feb. 6, 2010, the entire content of which is incorporated herein by reference.
The invention relates to a guide bar for the saw chain of a motor-driven chain saw which includes an elongated bar base body made of solid material.
U.S. Pat. No. 4,794,696 discloses a solid-material guide bar whose base body has openings for weight reduction. These openings are closed by cover plates which lie flush on the corresponding flat sides of the guide bar base body. In order to ensure sufficient stability, the cover plates must be precisely adapted to, inserted in, and fixed to the countersinks of the openings. This involves high production costs.
It is an object of the invention to develop a guide bar of solid material with weight recesses in such a manner that a simple and precise production with high stiffness of the guide bar is ensured.
The guide bar of the invention is for a saw chain of a motor driven chain saw. The guide bar includes: an elongated bar base body of solid material having a first end and a second end; a direction reversal section for the saw chain and the direction reversal section being arranged at the first end of the bar base body; a mounting section for fixating the guide bar and the mounting section being arranged at the second end; the bar base body defining an edge and having a flat side; a guide groove formed in the edge of the bar base body and being configured to guide the saw chain; a weight recess formed in the flat side of the bar base body and extending essentially along the bar base body between the mounting section and the reversal section; a cover plate for closing the weight recess; and, the weight recess having a longitudinal rib arranged therein for supporting the cover plate and the longitudinal rib extending in the longitudinal direction of the bar base body.
According to an embodiment of the invention, the weight recess opens to only one flat side of the guide bar base body, so that processing is required only on one side of the base body of the bar. The weight recess extends between the mounting section of the guide bar and the reversal section of the guide bar. A longitudinal rib, which supports a cover plate, is arranged in the weight recess. In this way, the cover plate is supported transversely to the longitudinal direction of the guide bar thereby ensuring high dimensional stability.
The longitudinal rib extends from one end of the weight recess to the other end of the weight recess and partitions the weight recess into component recesses. Thus, a plurality of recesses, which extend over the length of the guide bar base body, lie next to each other transversely to the longitudinal direction of the guide bar base body. This increases the connection stiffness of the weight-reduced guide bar of solid material.
The cover plate lies flush in a plane with the flat side of the guide bar base body. For this purpose, the cover plate is set in a countersink of the weight recess. The cover plate lies in the countersink in such a manner that its edge forms a gap with the peripheral edge of the weight recess. A connecting seam fixing the cover plate to the guide bar base body is accommodated in this gap. Preferably, this is done via a weld seam, in particular a bifocal laser weld seam. In this welding process two laser welding beams which are at a distance to each other are directed at the material and the edges (peripheral edge of the weight recess and the edge of the cover plate) are liquified so that the gap fills. Such a welding device is disclosed in DE 20 2004 017 854 U1.
In a further embodiment of the invention, the recess is ventilated, preferably through an intermittent weld seam.
The material of the cover plate is preferably hardened and tempered steel which preferably has the same or a higher carbon content than the guide bar base body. Expediently, the material of the cover plate has a degree of hardness of 20 to 58 HRC; a carbon content of 0.25% to 1% is advantageous. The material is especially 50CrMo4.
The invention will now be described with reference to the drawings wherein:
The guide bar 1 shown in
At the other end 7 of the guide bar base body 3, a mounting section 8 is formed, which, in the shown embodiment, is provided as one piece with the guide bar base body 3.
The guide bar base body 3 has a guide groove 10 (
The guide bar base body 3 is of solid material such as hardened and tempered steel, thus consisting of a one-part component. 50CrMo4 is preferably used as a material. This leads to a rigid and strong guide bar 1 which is provided with a weight recess 11 in order to reduce weight. The weight recess 11 essentially extends along the guide bar base body 3 between the mounting section 8 and the reversal section 5 over more than half the length of the guide bar base body 3. In the shown embodiment, the weight recess 11 essentially extends from the mounting section 8 to the reversal section 5.
The weight recess 11 is closed by a cover plate 12 which, as shown in
The weight recess 11 is a trough-like recess with a rectangular cross section and is open only toward one flat side 13 of the guide bar base body 3. In order to support the cover plate 12 over its width, at least one longitudinal rib 14 is provided in the weight recess 11. In the shown embodiment, two longitudinal ribs (14, 15) are provided in the weight recess 11. The two ribs (14, 15) essentially extend over the entire length of the weight recess 11 in the longitudinal direction 19 of the guide bar 1; thus, the weight recess is divided into a plurality of component recesses (16, 17, 18) extending in the longitudinal direction of the guide bar base body 3, so that a plurality of component recesses lie adjacent to each other transversely to the longitudinal direction of the guide bar base body 3. In the shown embodiment, three component recesses (16, 17, 18) are adjacent to each other.
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The edge 28 of the cover plate 12 is located in the countersink 22 of the guide bar base body 3 at a distance S from the peripheral edge 26 of the weight recess 11, so that there results a peripheral gap 27 between the edge 28 of the cover plate 12 and the peripheral edge 26 of the countersink 22. The supporting surface 29 of the cover plate 12 in the countersink 22 is larger transversely to the longitudinal direction 19 of the guide bar base body 3 than the width S of the gap 27, so that complete covering of the component recesses 16, 17 and 18 is invariably ensured independently of the position of the cover plate 12 in the countersink 22. The hollow spaces created by the weight recess 11 are ventilated; this can be provided by ventilating openings 30 or by a partially interrupted connecting seam 31 by which the cover plate 12 is fixed in the countersink 22 of the guide bar base body 3. The ventilation is preferably closed upon completion of the guide bar 1, for example, by a plug or the like.
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The guide bar base body 3 is a high-quality hardened and tempered steel, preferably 50CrMo4. The cover plate 12 is made of steel having a degree of hardness of 20 to 58 HRC Rockwell hardness number; the material preferably has a carbon content in the range of 0.25% to 1%. In a further embodiment of the invention, the cover plate 12 is made of hardened and tempered steel which, according to the invention, has a higher carbon content than the guide bar base body 3. In particular, the cover plate 12 consists of a hardened and tempered steel 50CrMo4. It can be practical to design the cover plate of the same material as the guide bar base body.
It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
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10 2010 007 081.5 | Feb 2010 | DE | national |