Guide bar for a saw chain having a reduced-wear direction-reversing section

Abstract

A guide bar for a saw chain includes an elongate, flat base body made of a basic material. The base body extends along a longitudinal center axis and, in order to guide a saw chain, has a running surface formed on an outer periphery thereof and a guide groove formed in the outer periphery of the base body. The guide groove has a groove base. A direction-reversing section for the saw chain is provided at one end of the base body. The direction-reversing section includes at least one add-on component having a running surface made of more wear-resistant material than the basic material of the base body. The add-on component is secured to the base body of the guide bar by at least one weld seam. The weld seam extends between the add-on component and the base body and is located spatially beneath the groove base.

Claims

1. A guide bar for a saw chain, the guide bar defining a plane and a longitudinal center axis and comprising: an elongated, flat base body extending along said longitudinal center axis and having first and second outer flat sides; said base body having an outer periphery and having a guide track formed on said outer periphery for the saw chain; said guide track including a running surface and a guide groove having a groove base; a direction-reversing section for the saw chain configured on one end of said base body; said direction-reversing section being configured as an add-on component; said running surface, said guide groove of said base body and said groove base being continued in said add-on component so as to cause said running surface and said guide groove together with said groove base to continue in said add-on component; said base body being made of a first material and said add-on component being made of a second material having a wear resistance greater than said first material; said first and second flat sides having respective projections formed thereon in the region of said add-on component; said projections being configured to extend in the direction of said longitudinal center axis and overlap said add-on component; said add-on component having respective outer surfaces formed as support surfaces parallel to corresponding ones of said first and second flat sides of said base body and positioned in between said projections; said projections being in contact engagement with corresponding ones of said support surfaces so as to hold said add-on component therebetween; said add-on component being fixed to said base body by a first weld seam on an edge of said first outer flat side of said base body and a second weld seam on an edge of said second outer flat side of said base body; said first and second weld seams running between said add-on component and said base body and lying over their respective lengths (S) spatially below said groove base of the guide bar; and, at least one of said weld seams extending in depth perpendicularly to said first and second flat sides so as to cause one of said support surfaces of said add-on component to be welded with a corresponding one of said projections.

2. The guide bar of claim 1, wherein said base body and said add-on component conjointly define an overlapping region whereat said base body overlaps said add-on component and the corresponding weld seam is configured to delimit said overlapping region.

3. The guide bar of claim 1, wherein said add-on component has a position on said base body and is fixed form tight on said base body in said position.

4. The guide bar of claim 3, wherein said projections are configured to fix said add-on component in said position thereof on said base body.

5. The guide bar of claim 4, wherein at least one of said projections has a longitudinal edge; and, said weld seam extends along said longitudinal edge of said one projection over a segment of said length (S) thereof.

6. The guide bar of claim 1, wherein said add-on component has respective recessed regions for receiving corresponding ones of said projections thereon.

7. The guide bar of claim 6, wherein said projections are received in respective ones of said recessed regions without play.

8. The guide bar of claim 6, wherein said projections conjointly define a gap (a) therebetween and said add-on component has a thickness at said recessed regions thereof which is greater than said gap (a) so as to permit said add-on component to be clampingly held between said projections.

9. The guide bar of claim 1, wherein said wear resistant material of said add-on component is a sintered material.

10. The guide bar of claim 9, wherein said wear resistant material of said add-on component is a stellite.

11. The guide bar of claim 1, wherein said add-on component comprises two add-on component halves placed together to define said add-on component.

12. The guide bar of claim 11, wherein said two add-on component halves are identical parts.

13. The guide bar of claim 11, wherein said add-on component defines a partition plane; and, said first and second weld seams merge with each other at said partition plane.

14. The guide bar of claim 1, wherein each of said projections has a longitudinal edge which extends along said groove base.

15. The guide bar of claim 1, wherein each one of said weld seams lies spatially below said groove base in the longitudinal direction of said guide track over the entire length (S) of the weld seam; said one weld seam is at a distance (A) from said groove base measured in the plane of said guide bar; and, said distance (A) is less than three times the depth (T) of said guide groove.

16. The guide bar of claim 15, wherein said distance (A) is less than two times the depth (T) of said guide groove.

17. The guide bar of claim 1, wherein each one of said weld seams follows the course of said guide track so as to cause the distance between the weld seam and guide track at the tip of said guide bar to be at most twice as great as the distance between the weld seam and the guide track at the butt edge of the add-on component to the base body of said guide bar.

18. The guide bar of claim 17, wherein segments of each one of said weld seams are connected to each other via an arcuate segment of the weld seam; and, said arcuate segment has a maximum spacing to said guide track which is less than twice the depth (T) of said guide groove.

19. The guide bar of claim 17, wherein the distance of the weld seam to the guide track measured perpendicularly to the tip of the guide bar is less than thrice the depth (T) of said guide groove.

20. The guide bar of claim 1, wherein each of said weld seams, viewed in a direction toward said groove base, is arranged below said groove base so as to cause material stress in the region of said guide groove to be reduced.

21. The guide bar of claim 1, wherein said direction-reversing section is configured without a direction-reversing sprocket wheel.

22. The guide bar of claim 1, wherein each one of said weld seams extends in depth in the region of said add-on component to between said projections so as to cause a first one of said weld seams on said first outer flat side and a second one of said weld seams on said second outer flat side to touch each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with reference to the drawings wherein:

(2) FIG. 1 is a schematic side view of a motor-driven chain saw;

(3) FIG. 2 is a perspective view of a guide bar for a motor-driven chain saw according to FIG. 1;

(4) FIG. 3 is a side view of the guide bar according to FIG. 2;

(5) FIG. 4 is a plan view of the outer periphery of a longitudinal edge of the guide bar according to FIG. 3;

(6) FIG. 5 is an enlarged view of the detail V in FIG. 3;

(7) FIG. 6 is a section view taken along line VI-VI in FIG. 5;

(8) FIG. 7 is an enlarged partial view of the add-on component made of more wear-resistant material;

(9) FIG. 8 is a section view taken along line VIII-VIII in FIG. 5;

(10) FIG. 9 is a partial view of a further embodiment of the direction-reversing section of a guide bar having an add-on component;

(11) FIG. 10 is a section view taken along line X-X in FIG. 9;

(12) FIG. 11 shows a perspective view of a guide bar before the add-on component is attached to the base body;

(13) FIG. 12 shows a side elevation view corresponding to the perspective view of FIG. 11; and,

(14) FIG. 13 is a section view taken along line XIII-XIII of FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

(15) FIG. 1 schematically illustrates a motor-driven chain saw 1. Arranged in the housing 2 is a drive motor for driving a saw chain 4 that runs around a guide bar 3. The drive motor can be a combustion engine, an electric motor, a compressed air motor or similar motor. In the rear housing region, the motor-driven chain saw 1 has a rear handle 5, extending in the longitudinal direction of the housing 2. The handle 5 has operator-controlled elements 6. A bale handle 7 is provided in the front region of the housing 2. The bale handle straddles the housing 2 transversely to the longitudinal direction thereof. Arranged in front of the bale handle 7 is a hand guard 8 which, by pivoting, triggers a safety braking unit (not illustrated in more detail).

(16) The guide bar 3 extends from the front region of the housing 2 in the longitudinal direction of the motor-driven chain saw 1; at the rear clamping end 9 of the guide bar 3. The guide bar is secured in a clamped manner between a sprocket wheel cover 10 and the housing 2.

(17) In the exemplary embodiment shown, the guide bar 3 includes an elongate, flat base body 11. A direction-reversing section 13 for the saw chain 4 is formed at that end 12 of the base body 11 that is opposite the clamping end 9. The direction-reversing section 13 comprises an add-on component 14 which (at least in the region of its outer periphery, which forms a running surface 17 (FIG. 2) for the saw chain) is formed from a more wear-resistant material than the base body material of the base body 11.

(18) The base body 11 extends along a longitudinal center axis 15 in the longitudinal direction of the motor-driven chain saw 1. A running surface 17 is formed on the outer periphery 16 (FIG. 2) of the base body 11. A guide groove 18, which has a groove base 19 (FIG. 6, FIG. 10), is furthermore provided centrally in the outer periphery 16. The running surface 17 extends on both sides of the guide groove 18.

(19) The add-on component 14, which forms the direction-reversing section 13 at the front end 12 of the guide bar 3, is firmly connected to the base body 11 by at least one weld seam 20 (FIG. 5, FIG. 9), wherein (as FIGS. 5 and 9 show) the weld seam 20 extends between the add-on component 14 and the base body 11 of the guide bar 3, and is thus located at the front end 12 of the guide bar 3. Along a major part of its length S, the weld seam 20 extends spatially between the longitudinal center axis 15 of the guide bar 3 and the groove base 19 (FIGS. 5 and 9) of the guide groove 18. The weld seam 20 between the add-on component 14 and the base body 11 is thus located (perpendicularly to the open guide groove 18 or the groove base 19 in the viewing direction 40) beneath the groove base 19.

(20) As is illustrated schematically and in a greatly enlarged manner in FIGS. 5, 6 and 10, the weld seam 20 is located at a distance A from the groove base 19 of the guide groove 18 of preferably less than about twice the depth T of the guide groove 18, in particular less than half the depth T of the guide groove 18. The weld seam 20 is thus at a distance, measured in the plane of the guide bar 3, from the running surface 17 of the guide bar 3 of less than about three times the depth T of the guide groove 18, in particular less than twice the depth T of the guide groove 18; the distance of the weld seam 20 from the running surface 17 corresponds to the sum of the distances A plus T. In particular, the distance A of the weld seam 20 from the groove base 19 is in the range between 0.3 mm and 10 mm, preferably in a range from 0.5 mm to 5 mm, in particular about 0.77 mm. The depth T, measured from the running surface 17 to the groove base 19, of the guide groove 18 is in the range between 2 mm and 20 mm, preferably between 3 mm and 10 mm, in particular 5.05 mm.

(21) As FIGS. 2 and 3 show, the guide bar has, in the region of the clamping end 9, a greatest height H, measured transversely to the longitudinal center axis 15, that decreases continuously as far as the direction-reversing section 13 at the free end 12. Such a guide bar is also known as a carving bar.

(22) In the exemplary embodiment according to FIGS. 3 to 8, the add-on component 14 comprises two add-on component halves (14a, 14b) (FIG. 6), wherein the add-on component halves (14a, 14b) are preferably identical parts, that is, are formed in an identical manner.

(23) As can be seen in particular from FIG. 6, the guide groove 18 of the base body 11 continues in the add-on component 14. FIG. 6 shows that not only the guide groove 18 but furthermore also the groove base 19 of the guide groove 18 is formed in the add-on component 14.

(24) In the exemplary embodiment shown, the guide bar 3 is a built-up guide bar 3; its base body 11 comprises a center plate 30 which is covered by side plates 31. The outer sides of the side plates 31 furthermore form flat sides 32a and 32b of the base body 11 of the guide bar 3. One side plate 31 forms the first flat side 32a and the other side plate 31 forms the second flat side 32b. Alternatively, the guide bar 3 can also be formed from a solid material.

(25) Each side plate 31 has a finger-like extension in the form of a projection 33, wherein the projection 33, which is formed in a substantially flat manner, extends in the direction of the longitudinal center axis 15 and forms the end 12 of the base body 11. In the direction of the longitudinal center axis 15, the projection 33 engages in the add-on component 14 in order to fix the latter in its position on the base body 11. In this case, provision is made for the projection 33 to be held in an approximately play-free manner in the add-on component 14, while the abutment edges 35 located in the root region of the projection 33 have slight play (u) with respect to the edge 22 of the add-on component 14. This avoids static redundancy of the support of the add-on component 14 on the projection 33.

(26) In the exemplary embodiment according to FIGS. 2 to 8, the projection 33 of the base body 11 of the guide bar 3 engages over the add-on component 14; in other words, the projections 33 overlap the add-on component 14. In this case, provision is made for the weld seam 20 to be positioned such that it delimits the overlap region 34.

(27) The add-on component 14 is fixed in its position at the front end of the base body 11 preferably in a form-fitting manner, for which purpose it interacts in a suitable manner with the projections 33. Thus, a projection that extends in the direction of the longitudinal center axis 15 can be formed on the base body 11 of the guide bar 3 on each flat side (32a, 32b) in the region of the direction-reversing section 13, the projection 33 being received in a recessed region 23 of the add-on component 14. The recessed region 23 is formed in the outer side 21 of an add-on component 14a or 14b and receives the projection 33 substantially along its entire length that extends in the direction of the longitudinal center axis 15. Preferably, a projection 33 is received in the recessed region 23 largely without play to lie in contact engagement with support surface 23a as shown in FIG. 8. The recessed region 23 is advantageously deeper than the material thickness of the projection 33. The depth of the recessed region 23 is selected such that the outer side 21 of the add-on component 14 is located approximately in the same plane as the flat side 32a or 32b of the guide bar 3.

(28) In the exemplary embodiment, the add-on component is composed of two add-on component halves 14a and 14b which rest against one another in a partition plane 38; the projections 33 are in this case each located in a recessed region 23 of one add-on component half 14a and 14b, such that the add-on component halves 14a and 14b of the add-on component 14 are held between the projections 33. Preferably, the add-on component halves 14a and 14b of the add-on component 14 are dimensioned such that the material that remains in the region of the recessed regions 23 has a thickness (d) which corresponds approximately to the distance (a) between the projections 33 of the two side plates 31. Preferably, the thickness (d) is formed with a slight excess thickness such that the add-on component 14 composed of the add-on component halves 14a and 14b is held in a clamped manner between the projections 33. This can be advantageous in the preassembly of the guide bar.

(29) Once the add-on component halves (14a, 14b) of the add-on component 14 have been plugged onto the end 12 of the base body 11 of the guide rail 3, the add-on component 14 is fixed preferably by means of welding. Laser welding is particularly suitable for this purpose, wherein the weld seam 20 is configured such that it extends along the contour of the projection 33. The weld seam extends advantageously along a segment 24 of its length S along the longitudinal edges 36 and 37 of the projection 33. As illustrated in FIG. 5, the weld seam 20 extends along the two longitudinal edges 36 and 37 of the projection 33, wherein the segments 24 of the weld seam 20 are connected together at the longitudinal edges via an arc segment 25 of the weld seam 20. The arc segment 25 of the weld seam 20 corresponds to the shape of the free end of the projection 33. As FIG. 5 shows, the weld seam 20 extends over the entire edge of the projection 33. The edge of the projection 33 is formed by the longitudinal edges 36 and 37 and the arc segment 39, connecting the longitudinal edges 36 and 37, of the free end of the projection 33.

(30) As FIG. 5 shows, the weld seam 20 continues over a run-out segment 26 in the base body 11 of the guide bar 3. The length of the run-out segment 26 corresponds approximately to the length L, measured in the direction of the longitudinal center axis 15, of the projection 33.

(31) As can be seen from FIGS. 6 and 8, the projections engage on both flat sides (32a, 32b) of the base body 11 of the guide bar 3 into in each case one add-on component half (14a, 14b) of the add-on component 14 and fix the latter in position on the base body 11. The weld seam 20 is executed on each of the flat sides 32a and 32b of the guide bar 3, as the sectional illustration in FIG. 8 shows. In this case, a weld seam 20 passes to such a depth that the weld seam 20 on the one, first flat side 32a and the weld seam 20 on the other, second flat side 32b merge into one another or come into contact with one another in the region of the partition plane 38 of the add-on component 14. As a result, not only is each add-on component half (14a, 14b) of the add-on component 14 firmly connected to the respective side plate 31 of the base body 11, but the add-on component halves (14a, 14b) are also connected together cohesively in the region of their partition plane 38.

(32) In the exemplary embodiment according to FIGS. 9 and 10, the add-on component 14 consists of two add-on component halves 14a and 14b which are each connected individually to a side plate 31. An add-on component half 14a or 14b rests with its inner edge 41 against the longitudinal edges 36 and 37 and against the arc segment 39, connecting the longitudinal edges together, of the free end of the projection 33, preferably without play. The abutment edge 35 of the add-on component has in this caseas also illustrated in FIG. 5slight play (u) with respect to the edge 22 of the base body 11 of the guide bar 3, the edge extending on both sides of the projection 33 in the root region of the projection. As a result of the play (u), static redundancy of the add-on component 14 on the base body 11 of the guide bar 3 is avoided.

(33) FIG. 11 shows a perspective view of the guide bar before the add-on component (14a, 14b) is welded to the base body 11. FIG. 12 shows a side elevation view corresponding to the perspective view of FIG. 11 and FIG. 13 is a section view taken along line XIII-XIII of FIG. 12.

(34) As FIG. 10 shows, in the exemplary embodiment according to FIGS. 9 and 10, the center plate 30 projects in between the add-on component halves 14a and 14b of the add-on component 14. The edge 41 of an add-on component half 14a and 14b is thus located lower than the groove base 19 perpendicularly to the groove base 19 of the guide groove 18 in the viewing direction 40.

(35) The weld seam 20 is guided along the longitudinal edges 36 and 37 and along the arc segment 39, connecting the longitudinal edges, of the projection 33, wherein the run-out segments 26 of the weld seam 20 extend, in continuation of the longitudinal edges 36 and 37, into the base body 11 of the guide bar.

(36) Since the center plate 30 projects in between the add-on component halves 14a and 14b, the groove base 19 is located higherin the viewing direction 40 onto the groovethan the edge 41 of the add-on component; the weld seam 20 is thus located beneath the groove base 19.

(37) The weld seam 20 extends in the region between the edge 41 of the add-on component 14 and the side plates 31 of the base body 11 of the guide bar 3 and is thus located, along a majority of its lengthin the exemplary embodiment along its entire lengthbeneath the groove base 19 in the add-on component 14; in other words, the weld seam 20 is located, as seen in thepreferably perpendicularviewing direction 40 onto the groove base 19, beneath the groove base 19. The weld seams 20 executed on both flat sides 32a and 32b of the guide bar 3 in order to secure the add-on component halves 14a and 14b of the add-on component 14 are expediently produced by laser welding; the depth of the weld seam 20 can preferably be set such that the weld seams 20 applied to the opposite flat sides 32a and 32b of the guide bar 3 come into contact and/or are connected cohesively together at the depth.

(38) The add-on component 14 or 14, or the add-on component halves (14a, 14b, 14a, 14b) of an add-on component (14, 14), preferably consist of a sintered material, expediently of Stellite. A material known under the designation Stellite 12, which is based on a cobalt-base alloy with 29 percent by weight of chromium, 8 percent by weight of tungsten and 1.3 percent by weight of carbon, can be used as Stellite.

(39) The add-on component or its add-on component halves can also consist of different materials, it being essential that at least the running surface for the saw chain is formed from a wear-resistant material such as Stellite or the like.

(40) In the exemplary embodiments shown, the weld seam 20 is shown as a continuous weld seam; it may be expedient, rather than a continuous weld seam, to provide welding spots which are located in a row one after the other and form a dotted weld seam.

(41) In the exemplary embodiments shown, the projection 33 extending as an extension in the direction of the longitudinal center axis 15 is formed such thatstarting in the root region of the projectionit forms two longitudinal edges 36 and 37 which are substantially straight and run toward one another (FIG. 5). A longitudinal edge (36, 37) of a projection 33 forms, in continuation, an angle of about 5 to 15, in particular 10, with the longitudinal center axis 15. The continuations of the two longitudinal edges 36 and 37 thus enclose an angle of about 10 to 30, in particular an angle of 20. The two longitudinal edges 36 and 37 are connected together via an arc segment 39 of the free end of the projection 33. The arc segment 39 is a circular arc segment with a circumferential angle of less than 180, in particular 160.

(42) 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.