CHAIN SAW GUIDE BAR

Abstract: Chain saw guide bar for vehicle-born chain saws, assembled from one middle plate (15) and two side plates (16) by laser welding and including channels for supplying liquids to nozzles (17, 19) on one or both side plates, where the channels run between the middle plate and a side plate and are made leakproof by continuous laser welds (20) joining only the middle plate with that side plate, and where other laser welds (11) join all three plates and are made as short welds with interruptions (12).

Description: CHAIN SAW GUIDE BAR Background It is previously known to make chain saw guide bars with internal channels for liquids such as lubricant, fungicide or marking dyes, especially guide bars for tree harvesters. With traditional methods for assembly of guide bars by spot-welding of one middle plate with two side plates, channels can be made as grooves in the side plates or either side of the middle plate, but a common problem has been to keep the liquids from leaking between neighbouring channels. One solution of this problem has been to decrease the distance between spot welds, but this restricts the possibility of having independent channel patterns on both sides or crossing channels, as would be required for a reversible guide bar. Another solution is to use small diameter tubes inserted in the channels during manufacture or later, as in patents US 5,050,303 or US 5,143,131. Such designs require much effort in assembly and maintenance, however. It is also known from the patent US 4,641 ,432 to substitute for rows of spot welds a continuous laser weld penetrating and joining the three plates. Although such welds are leakproof, they restrict the possibility of having independent channel patterns even more than small distance spot welds would, and have the added disadvantage that a crack at any point in the weld can easily spread along the whole weld when the guide bar is bent, since a continuous weld may have large built-in stresses and is more brittle than the rest ofthe plates. The present invention concerns a guide bar joined by new configurations of laser welds, allowing leakproof independent channel patterns with more channels, and reducing the risk of spreading cracks. Description A chain saw guide bar according to the invention comprises two side plates (16) and one middle plate (15), shown before assembly in figure 2. The assembly is made with laser welds as shown in figure 1. The invention can be utilized for guide bars with various numbers and routing of liquid channels, and the figures show one preferred CONFIRMATION embodiment. Along both edges and possibly around the nose of the guide bar there is a groove (14) to guide a saw chain. The welds can serve two purposes, joining the plates with sufficient strength, and blocking leakage of liquid between channels. Welds with the purpose of joining are a weld along the edge (11) of the guide bar and a number of welds at the clamping end (13). To get a symmetric weld joining all three plates, a high laser power is used, or laser beams from both sides. To avoid high internal stresses and to reduce the risk of spreading cracks, the weld along the edge (11) consists of numerous short welds with unwelded interruptions (12). If a crack occurs in one ofthe short welds, the crack will not readily spread to the neighbouring short welds, since cracks propagate mainly through brittle material in the heat affected zone ofthe weld, and since there are no internal stresses in the interruptions. The welds at the clamping end (13) are short enough not to need interruption, but may have it. Inside of the edge weld (11) there is at least along the leading edge while cutting a channel for fungicide with a multitude of nozzles (17). The many nozzles ensure that the liquid pressure in this channel is low, and there is no requirement that the edge weld (11) should be leakproof for high pressure. Making the edge weld (11) with interruptions is thus no limitation. If the guide bar is reversible, this holds for both edges. Some minor leakage of fungicide into the chain groove (14) might also be tolerated, as the fungicide must anyway be sprayed from the nozzles (17) into the cutting area ofthe saw chain without harm to the chain. The channel for fungicide runs between the middle plate and the side plate with the nozzles, and may be made as grooves in either plate, or partly as cutouts (18) in the middle plate. Channels for marking dyes supply dye to one active nozzle (19) per channel, producing colour code marks on the timber pieces to indicate tree species, size and quality. Since there is only one nozzle per channel the pressure may be high, and for interpretation of the code it is very important that the dyes from different channels do not mix. A distinct dye mark is achieved by using the thickness of two plates for a nozzle, and locating the dye channel between the middle plate and the opposite side plate of where the dye emerges. The dye channels should thus be enclosed on all sides by leakproof laser welds (20) and be made as grooves (21) in the side plate. The nozzles (19) should preferably also be encircled by welds. The leakproof welds (20) should be made from one side only, joining the middle plate to one side plate, to allow independent channel patterns in the two side plates with several narrow channels crossing those on the other side. Single sided welds with shallow penetration will have less internal and bending stresses, and much less heat affected zone. For clear non-overlapping dye marking, the dye nozzles (19) from different channels should preferably be located in a row along the longitudinal axis ofthe guide bar. The risk of disturbing the code by motion ofthe timber is then minimized. Normally, liquids are sprayed downward onto the stump when felling a tree, and towards the measured and classified lower cut-off part ofthe tree when cutting to length even if the tree is then held horizontally. The liquids are usually supplied from the upper side ofthe guide bar opposite to the nozzles through supply holes at the clamping end, if the bar holder is prepared for liquid supply, or from the lower side as the nozzles through a special clamping plate with hose connections, if the holder is not so prepared. The figures show the first mentioned alternative, but it is also possible within the scope ofthe invention to have supply holes on the same side as the corresponding nozzles. Likewise, the bars can be reversible with nozzles on both sides, or non-reversible with nozzles on one side..

Claims: Claims 1. Chain saw guide bar assembled from two side plates (16) and one middle plate (15) by laser welding and including channels for supplying liquids from supply holes at the clamping end ofthe guide bar to nozzles (17,19) on one or both side plates, the channels being located between the middle plate and a side plate as grooves in either plate, characterized by some laser welds (20) delimiting liquid channels to avoid leakage, said laser welds joining the middle plate with one side plate only. 2. Chain saw guide bar according to claim 1 , characterized by some laser welds (1 1 ) joining all three plates and made as numerous short weld portions with interruptions (12). 3. Chain saw guide bar according to claim 1 , characterized by the channels made as grooves (21) in plates. 4. Chain saw guide bar according to claim 1 or 3, characterized by some channels having a single nozzle (19) to spray liquid on a sawn wood surface, said channels being enclosed by continuous laser welds (20) joining the middle plate with one side plate. 5. Chain saw guide bar according to claim 4, characterized by at least one channel having a multitude of nozzles (17), said channel being separated from channels having a single nozzle (19) by a continuous laser weld (20) joining the middle plate with a side plate. 6. Chain saw guide bar according to claim 4, characterized by nozzles (19) of channels having a single nozzle on the same side plate being all located in a straight line.

Inventors: LEINI ARVO, LOEFGREN PER-OLOF, PETTERSSON KARL-OLOF, LEINI, ARVO, LOEFGREN, PER-OLOF, PETTERSSON, KARL-OLOF
Applicants: SANDVIK AB, SANDVIK AKTIEBOLAG
Application year: 1996
Main classification: B27B17
IPC codes: A01G23, B27B17