Metal tools and implements – making – Blank or process – Saws
Patent
1994-09-09
1995-09-12
Watts, Douglas D.
Metal tools and implements, making
Blank or process
Saws
30383, 164 80, 164 98, B23D 6300, B23K 3102, B27B 1702
Patent
active
054489296
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
It is previously known from the patents U.S. Pat. Nos. 3,416,578 and 4,768,289 to coat a severely loaded edge with some hard and wear-resistant metal layer at the nose of such chainsaws that do not have a nose sprocket. This applies to chainsaws used to cut minerals, or to cut wood where mineral grains may be lodged in the bark or stirred from the ground. Traditionally the edge has been coated with cobalt alloys, such as known by the trademark "Stellite", applied by gas welding. These have a very high surface tension when molten, and will not run off or sag until they have solidified. The weld metal will form a thick rounded bead along the edge, and much of the deposited metal will have to be ground off to form a smooth running face for the saw chain.
Cobalt alloys are relatively expensive, and not very resistant to acidic wood. Nickel alloys with equal or better resistance and lower cost are known, but can not be used in the same way since they have too low surface tension when molten. They might be applied through flame or plasma spraying, where a finely powderized alloy is introduced in a stream of hot gas and transferred as molten droplets to the surface of a cold work piece. This method will also consume more material than will ultimately stay on the guide bar and requires much work to grind away the excess.
Hardfacing alloys can also be applied according to the patent U.S. Pat. No. 5,144,867 by inserting one end of a guide bar blank in a mold filled with powderized alloy, heating the mold and the blank to the melting point of the alloy to let the alloy form a wear resisting layer on the blank, and finally milling or grinding a chain groove through the layer. According to that patent, the grinding work on the edges and on the outside of the guide bar is reduced.
OBJECTS AND SUMMARY
The present invention concerns a method for applying hard wear-resistant layers, which also reduces the need for grinding of the groove, and which creates less environmental problems than other alloy powder methods. This is important, since dust from nickel as well as cobalt alloys are allergenic and injurious to health.
An object of the invention is to provide the edges of the nose part of a guide bar with a hard wear-resistant layer, one edge at a time when the chain groove is already made, and the chain groove is blocked during the process by a plate extending from a mold.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a lateral view of a guide bar blank (10) prepared for hardfacing and a mold (15),
FIG. 2 is a cross section through the mold and the nose part of the guide bar when assembled prior to the melting of the alloy,
FIG. 3 is a corresponding section through an alternative form of the invention, and
FIG. 4 a lateral view of the nose part of a guide bar after hardfacing but before final grinding.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The guide bar blank (10) preferably comprises three spot-welded thin plates and or of one solid thicker plate is provided with a chain groove along its sides (17) and around the nose (12). The groove is formed either by making the middle plate of the three thin plates narrower than the outer plates, or by grinding or milling a groove in the edge of the thicker plate. The bottom (18) of the groove runs continuously from one side around the nose to the other side. Along the sides (17) the edges are located at a greater distance from the bottom (18) than they are at the nose (12). Where the sides (17) meet the nose (12) it is advantageous to make the edge with a locally raised portion (11) even further from the bottom (18).
The hardfacing layer is shaped against a mold (15) from which extends a plate (14) with a thickness matching the width of the chain groove, and with a contour matching the groove bottom at the nose. At the mold the plate (14) borders to a wall (19) with the same curvature as the nose of the completed guide bar. If the sides are made with raised portions (11) the wall (19) should have matching diversions (20) at its ends. Suitable materials
REFERENCES:
patent: 2962812 (1960-12-01), Gommel
patent: 3241228 (1966-03-01), Rayniak et al.
patent: 3416578 (1968-12-01), Irgens
patent: 3744363 (1973-07-01), Espana et al.
patent: 3858321 (1975-01-01), Conaty
patent: 3987543 (1976-10-01), Ratz et al.
patent: 4742861 (1988-05-01), Shoher et al.
patent: 4768289 (1988-09-01), Apfel et al.
patent: 5144867 (1992-09-01), Yajima et al.
Sandvik AB
Watts Douglas D.
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