SAW CHAIN WITH HARD COATING

CHAINE DE SCIE CHARGEE EN DUR

English Abstract

A B S T R A C T
A cutting tool, such as a saw chain in a power
chain saw, is subject to great wear. The cutting link
according to the invention, however, can be coated by a layer
of yellow titanium nitride or another nitride, carbide or
boride of a transition metal which makes a surface hardness
of at least 2000 HV and thus the life of such a chain is
multiplied compared to prior known and used coatings, such
as chromium.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A saw chain for power chain saws including at least one
portion having links each with a cutting edge created between a
steep front part thereof and a gradually inclined back part
wherein one of said parts is hard coated by means of sputtering
with a layer of yellow titanium nitride carbide TiNxC1-x,
wherein x is between 0 and 1, and parts of said link which are
not hard coated are coated by a layer of chromium.
2. A saw chain as claimed in claim 1, wherein the surface
hardness of parts coated by a layer of yellow titanium nitride
carbide exceeds 2000 HV.
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Description

The present i.nventi.on relates to saw chains of power
cha.in saws including linl<s of several Icincls, such ax drivi.ng
links and cutti.ng links.
It is above all the cutting linl< of the lirlks in
a saw chai.n that is subject to wear and requi.res sharpening
at certain intervals to make the chain work satisfactorily.
A dull chain causes ~n excessive amount of heating of the
wood, which thus beco~es discolored in the saw cut. Further-
more, a worn chain impli.es a risk of acci.dent as it may easily
break and hurt the operator. It is therefore important to
find a material, and a shal~e ~or the cutting link, wilich
keeps it sharp for ~ long peri.od of ti.rne. It i.s known to use
chrome chain links, wi.th the hard chrome coatin~ being a good
stiffening of the cuCtlng e~e of the li.nk. It has been
found, however, that the cutti.n~ speecl as wel.l. as the working
life of the link,wilL increase hy the a~pli.caci.on of a
coating of a harcler surf~ce m~teri.al than those hi.therto used.
Lately, cutti.ng tools have appeared which are
coated by compositi.ons wi.thi.n the ternary system Ti.-C-N,
substantia11y TiNXCl x ( ~ 1) which do not need to be
stoichiometric. An example thercof is the yellow titanium
nitride~hich mulciplies the li'fe of the tools. The coating
procedure vari.es an(3 incLudes reacti.ve evaporation and sput-
tering processes and con~binations oE reactive evaporation
and sputterir;g under Cile names of "reactive iOIl plating" and
"sputter ion plati.ng". 13y che reactive evaporati.on the
titani.u~ metal is bro-l~ht into ~ns ~hase and sfte^ a reaction
with a nitrogenous and/or c~rbonaceous ~as to condense as
titanium carbonitride or titanium nitrlde or carbide on the

object to be coated. sy direct sputteriny, b~7 inert gas.ion
bombing of the coating material~ a cathocle si~uttering takes
place and the sputterecl ma~erial conclenses as a surface layer
on the object to be coated. Reside titanium,transition
metals in generaL, together with boron, carbon and nitrogen
create a group of very hard materials which in principle are
applied as coatin~s l~y processes of the above type of sput-
tering and reactive ion plating. ixamples of such coatings
~re CrC, Ti~Ta-C, W-C, ~C (6% C-~), 7r Ti.-N anci Ti-B. The
procedures imply a saving of material, ancl quite new coating
materials can be used due to the flexibility oE the methods.
They are completely cLean and have no influence c~n personnel
or environment, and can also be effected by a sm,lll. number
of personnel.
The present invention has, as an object, to
improve the properties of the cutking link
for a higher cuttin~ speed, less frLction and heat dissipa~
tion in the saw CUt, less demancl Eor sharpening of the links,
and a longer liEe of che chaLn by the use of a coating o
20 yellow tit~umnitride or horide, carbide or nitride of a
transition metal. Besi~le these improved propert i25, the risk
of chain breakag~ and hence the risk of acciclents, wiLl be
reduced. All these anci other advantages,as set for~h here--
after,will appear when the chain is ~abricate(l in accordance
~5 with the Lnventic)n has the properties stated herein.
An embodimellt of a saw chain according to the
invention is shown in the soLe Eigure of the drawLng~ which
shows links of such a chain in s ide elevation.

~f~
For the driving oE the saw chain 10 around fl saw
guide bar periphery all driving links ll are provLded w:ith
proJections 12 which at the inner end of the guide bar mesh
wlth tee~h on a chain sprocket wheel, and are intended to
be guided in a gui.ding track 13 between longitudinal side
plates of the saw guide bar~ Between each pair of driving
links in the chain is a side link 14 which has points of
support 15 against the edges of the said gu:ide bar plates.
The driving links on each side of the cutting link 16 are
include~ in a combination of a side link 17 and the cutting
link which also have points of support a~ainst ~he said si.de
plates.
When the saw chain moves in a saw cut, the cuttin~
links cu~ the wood and endeavor to swivel around thei.r
forward points of support as every one o~ them lies behind
(after) the cutting edge whieh then tend~s to cut deeper in
the wood. In practice the swivel movement upwards of the
cutting link ifi limited by a shoulder attachment 18 located
at the forward end of the link. The differenee in levels
bet~een the cutting edge and this attachment is the maxlmum
cu~ting depth of the cutting l:ink.
Before the chain is assembled~ each one of the
links is coated. The usual chrome plating can be used e.g.
on side links and driving links. The cutting link can have
two diferent coatings, in which the top surface (or back)
19 and sometimes also the front of the cutting edge 20, which
is shown by dashed lines in the Figure, ~re coated by titan-
iumnitride or another hard material of the above type by
means oE a method, as for example~ mentioned in the introduc-
~ion, and the side surfaces and the attachment can bechromed.
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^ ~
The embodiment, as describe~ above, is an e~ample
of how to practice the present invent:ion. Some modifications
of the material and the method are within the scope of the
invention, as defined in the following claims.
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