U.S. patent number 3,678,973 [Application Number 05/110,043] was granted by the patent office on 1972-07-25 for method and apparatus for heating carburetor air and flushing an air filter in a chain saw.
This patent grant is currently assigned to McCulloch Corporation. Invention is credited to Wendell Harold Loop.
United States Patent |
3,678,973 |
Loop |
July 25, 1972 |
METHOD AND APPARATUS FOR HEATING CARBURETOR AIR AND FLUSHING AN AIR
FILTER IN A CHAIN SAW
Abstract
A method and apparatus for preheating air passing to the
carburetor of a chain saw engine and concurrently flushing a
carburetor air filter. A method and apparatus for utilizing a
stream of exhaust gas, generated by a chain saw engine, by
directing said stream, as a free flow, through air toward a
preselected location on a chain saw.
Inventors: |
Loop; Wendell Harold
(Prineville, OR) |
Assignee: |
McCulloch Corporation (Los
Angeles, CA)
|
Family
ID: |
22330928 |
Appl.
No.: |
05/110,043 |
Filed: |
January 27, 1971 |
Current U.S.
Class: |
30/123.4; 30/381;
55/385.1; 83/13; 123/556; 123/568.11 |
Current CPC
Class: |
F02M
26/17 (20160201); B27B 17/00 (20130101); F02M
35/08 (20130101); F02B 63/02 (20130101); Y10T
83/04 (20150401) |
Current International
Class: |
B27B
17/00 (20060101); F02M 25/07 (20060101); F02M
35/02 (20060101); F02M 35/08 (20060101); B27b
017/02 (); F02m 031/04 () |
Field of
Search: |
;143/32R
;123/122R,119A,122D |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schran; Donald R.
Claims
I claim:
1. A method of operating a chain saw comprising:
operating a chain saw with an internal combustion engine;
forming a stream of at least a portion of exhaust gas generated by
said engine;
directing said stream of exhaust gas
into a throat means defined by a portion of said chain saw:
passing a portion of said exhaust gas from said stream through
filter means and into a carburetor air inlet means of said internal
combustion engine; and
passing another portion of said exhaust gas from said stream, as a
flushing flow, into generally surface flushing cooperation with a
portion of said filter means.
2. A method of operating a chain saw as described in claim 1:
wherein said throat means functions substantially as venturi throat
means; and
wherein said stream of exhaust gas, directed into said throat
means, entrains ambient air therewith.
3. A method of operating a chain saw as described in claim 1:
wherein said flushing flow of exhaust gas, subsequent to passing in
generally flushing cooperation with said filter means, is directed
generally toward a hand grasped portion of said chain saw.
4. A method of operating a chain saw as described in claim 1:
wherein said stream of exhaust gas, while being directed into said
throat means, is substantially isolated from a cutter chain of said
chain saw by the imposition of barrier means between said throat
means and said cutter chain; and
wherein said flushing flow of exhaust gas, while being directed to
exit from said chain saw, is substantially isolated from said
throat means by the imposition of barrier means between said throat
means and said exiting flow of exhaust gas.
5. A method of operating a chain saw comprising:
operating a chain saw with an internal combustion engine;
passing at least a portion of the exhaust gas generated by said
internal combustion engine through spark arrestor means;
extracting a portion of exhaust gas from said spark arrestor means
and forming a jet stream of exhaust gas issuing from said spark
arrestor means;
directing said stream of exhaust gas
generally rearwardly of a cutting chain of said chain saw, and
into venturi throat means defined by a housing portion of said
chain saw;
providing barrier means interposed generally longitudinally between
said venturi throat means and said cutter chain;
entraining ambient air with said jet stream of exhaust gas as said
exhaust gases pass into said venturi throat means;
passing a portion of said exhaust gas and entrained ambient air
from said venturi throat means
through filter means, and
into a carburetor air inlet of said internal combustion engine;
passing another portion of said exhaust gas and entrained air, as a
flushing flow, from said venturi throat means into generally
surface flushing cooperation with an exterior portion of said
filter means disposed in communication with ambient air;
directing an exiting flow of said flushing flow of exhaust gas and
entrained air rearwardly away from said chain saw, generally toward
a hand-grasped portion of said chain saw; and providing barrier
means between said exiting flow of said flushing flow and the said
venturi throat means.
6. A method of utilizing a stream of exhaust gas, generated by a
chain saw engine including a carburetor induction passage, to treat
a portion of said chain saw, said method comprising:
generating exhaust gas in a working chamber of a chain saw internal
combustion engine;
passing at least a portion of said exhaust gas into stream defining
conduit means;
directing exhaust gas through said conduit means and causing said
exhaust gas to exit from said conduit means as a generally
unconfined stream directed generally toward a preselected location
on said chain saw;
said preselected location comprising passage means communicating
with, and operable to transmit air to, said carburetor induction
passage of said chain saw engine; and
said exhaust gas stream exiting from said conduit means as a
generally unconfined, warmed gas flow and, in passing through said
passage means, entraining and warming a flow of fresh air flowing
to said carburetor induction passage.
7. A method as described in claim 6 wherein:
said directed stream of exhaust gas
flushes at least a portion of said preselected location.
8. Apparatus for operating a chain saw, said apparatus
comprising:
an internal combustion engine;
means operable to form a stream of at least a portion of exhaust
gas generated by said engine;
throat means defined by a portion of said chain saw;
carburetor means including air inlet means;
air filter means operable to filter air passing to said air inlet
means;
means operable to direct said stream of exhaust gas into
said throat means defined by a portion of said chain saw;
means operable to pass a portion of said exhaust gas from said
stream through said filter means and into said carburetor air inlet
means; and
means operable to pass another portion of said exhaust gas from
said stream, as a flushing flow, into generally surface flushing
cooperation with a portion of said filter means.
9. An apparatus for operating a chain saw as described in claim
8:
wherein said throat means is operable to function substantially as
venturi throat means; and
wherein said throat means is operable to cause said stream of
exhaust gas to entrain ambient air therewith.
10. An apparatus for operating a chain saw as described in claim 8
including:
means for directing said flushing flow of exhaust gas, subsequent
to its passing in generally flushing cooperation with said filter
means, generally toward a hand grasped portion of said chain
saw.
11. An apparatus for operating a chain saw as described in claim 8
including:
first barrier means interposed generally between said throat means
and a cutter chain of said chain saw;
exiting means operable to direct said flushing flow out of said
chain saw and away from a cutter chain thereof; and
second barrier means interposed between said throat means and said
exiting means.
12. Apparatus for operating a chain saw, said apparatus
comprising:
an internal combustion engine;
a cutter chain drivenly engaged with said engine;
spark arrestor means;
means operable to pass at least a portion of exhaust gas generated
by said internal combustion engine through said spark arrestor
means;
means for extracting a portion of exhaust gas from said spark
arrestor means and forming a jet stream of exhaust gas issuing from
said spark arrestor means;
venturi throat means defined by a portion of said chain saw;
carburetor means including air inlet means;
air filter means operable to filter air passing to said air inlet
means;
means for directing said stream of exhaust gas
generally rearwardly of said cutting chain, and
into said venturi throat means defined;
barrier means interposed generally longitudinally between said
venturi throat means and said cutter chain;
said venturi throat means being operable to cause the entraining of
ambient air by said jet stream of exhaust gas as said exhaust gases
pass into said venturi throat means;
means for passing a portion of said exhaust gas and entrained
ambient air from said venturi throat means
through said filter means, and
into said carburetor air inlet;
means for passing another portion of said exhaust gas and entrained
air, as a flushing flow, from said venturi throat means into
generally surface flushing cooperation with an exterior portion of
said filter means disposed in communication with ambient air;
a hand graspable portion of said chain saw;
means for directing an exiting flow of said flushing flow of
exhaust gas and entrained air rearwardly away from said chain saw,
generally toward said hand-graspable portion of said chain saw;
and
barrier means interposed generally between said exiting flow of
said flushing flow and the said venturi throat means.
13. Apparatus for utilizing a stream of exhaust gas, generated by a
chain saw engine including a carburetor induction passage, to treat
a portion of said chain saw, said apparatus comprising:
stream defining conduit means;
means for passing at least a portion of chain saw engine generated
exhaust gas into said stream defining conduit means; and
means for causing exhaust gas to exit from said conduit means as a
generally unconfined stream directed generally toward a preselected
location on said chain saw;
said preselected location comprising
passage means communicating with, and operable to transmit air to,
said carburetor induction passage of said chain saw engine; and
said passage means being operable to receive said exhaust gas
stream, which exits from said conduit means as a generally
unconfined, warmed gas flow, with said warmed gas flow passing
through said passage means and entraining therewith and warming a
flow of fresh air flowing to said carburetor induction passage.
14. Apparatus as described in claim 13 including:
means operable to cause said directed stream of exhaust gas to
flush at least a portion of said preselected location.
Description
GENERAL BACKGROUND, OBJECTS AND SUMMARY OF INVENTION
For several years it has been recognized that a chain saw could be
operated more effectively under cold weather conditions by
providing it with a mechanism for preheating the air which is
passed to the carburetor air inlet of the saw.
A "closed" circuit, radiator-type system which has been found to be
particularly effective for this purpose is disclosed in a U.S.
Zimmerer et al. Pat. No. 3,498,280.
The Zimmerer et al. system is characterized by a circulation path
which serves to direct exhaust gas from a spark arrestor or muffler
to a carburetor air, heating radiator and from the radiator back to
the spark arrestor or muffler.
In the sense that Zimmerer et al. proposes a confined flow of
exhaust fluid between a spark arrestor or muffler and a radiator,
the Zimmerer et al. concept may be characterized as entailing a
"closed" system.
Other practitioners in the chain saw art concerned with cold
weather operation have proposed "open" systems. For example, it has
been proposed to utilize the fan of a chain saw engine to blow air
around the chain saw engine cylinder, and across an air filter
through which air must pass enroute to the air intake of the chain
saw engine carburetor. This arrangement enables fan circulated air
to be heated as it flows in heat absorbing contact with the
cylinder and exhaust muffler or spark arrestor. In thus being
heated, the circulated air enters the chain saw carburetor in a
condition more amenable to supporting combustion.
While these prior concepts are individually unique and
advantageous, there has remained a need for additional techniques
which would be operable to facilitate the operation of chain saws
under cold weather conditions.
It is believed that it would be particularly beneficial to utilize
the advantages of the structural simplicity which characterizes
"open," hot gas circulating systems while effectively utilizing the
open flow to both heat carburetor intake air and flush a carburetor
air filter.
It is also believed that it would be desirable to utilize a heated
flow of gas to, at least to some extent, provide a flow of warmed
air in the vicinity of a chain saw hand grip so as to improve
operator comfort.
It is also believed that it would be desirable to utilize a
confined flow of exhaust, generated by a chain saw engine, as a
heating device of particular effectiveness, while causing the flow
of exhaust gas to entrain with it at least some ambient air so as
to concurrently transmit to a carburetor air inlet combustible air
and a substantial amount of heat.
In accomplishing at least some of the foregoing objectives there is
presented, through this invention, a method of operating a chain
saw where a stream of at least a portion of exhaust gas generated
by a chain saw engine is formed. This stream of exhaust gas is
directed into throat means defined by a portion of the chain saw. A
portion of the exhaust gas is passed from this stream through
filter means, and then into a carburetor air inlet of the chain saw
engine. Another portion of the exhaust gas from this stream
functions as a flushing flow and is passed in generally surface
flushing cooperation with a portion of the filter means.
In the context of this basic method approach, a second
independently significant aspect of the invention involves a
technique where the throat means functions as a venturi throat. In
this manner, the exhaust gas passing through the throat means
entrains fresh ambient air for transmittal to the carburetor air
inlet.
Still in the context of the basic method above described, a third
aspect of the invention involves the directing of a portion of the
flushing flow, as it exits from the chain saw, generally toward a
hand gripped portion of the chain saw so as to provide at least
some warming effect in relation to an operator's hand.
Still in the context of the basic method above described, a fourth
aspect of the invention involves the utilization of barriers so as
to tend to isolate the above described throat means from a chain
saw cutter chain. In this manner the heated gas passing through the
throat means tends to be isolated from cuttings generated by the
cutter chain during operation of the chain saw. In this fourth
independent aspect of the invention, another barrier means is
provided between the exiting flow of exhaust gas and the throat
means so as to affirmatively tend to prevent a recycling of exhaust
gas, which has completed its flushing action, back into the throat
means.
Still other independently significant aspects of this invention
involve unique combinations of apparatus means which
synergistically interact to implement the foregoing method
steps.
DRAWINGS
In describing the invention, reference will be made to a preferred
embodiment shown in the appended drawing. In this connection, it
will be understood that the drawings and following "Description of
the Preferred Embodiment" reflect a preferred embodiment only and
are not restrictive in relation to the scope of the invention.
IN THE DRAWINGS
FIG. 1 provides a fragmentary, partially sectioned, vertical
elevational view of a representative chain saw which is provided
with the carburetor air heating and carburetor air filter flushing
features of the present invention;
FIG. 2 provides a fragmentary, perspective view of a portion of the
FIG. 1 chain saw illustrating, in "exploded" format, various
components of a spark arrestor and exhaust stream generating
mechanism;
FIG. 3 provides a fragmentary, partially sectioned, transverse view
of cylinder exhaust passage, spark arrestor, and exhaust stream
generating means of the FIG. 2 assembly; and
FIG. 4 provides an external, side elevational view of the FIG. 1
chain saw.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the invention as illustrated in FIGS.
1-4 comprises an operating structure through which certain
objectives of the apparatus have been achieved.
In describing this preferred embodiment, reference will first be
made to the overall chain saw structure, following which detailed
aspects of the carburetor air heating and carburetor air filter
flushing aspects of the invention will be described.
OVERALL CHAIN SAW STRUCTURE
As shown in FIG. 1, chain saw 1 comprises an engine 2. Engine 2
includes a cylinder head 2a and a cylindrical cylinder wall 2b.
Cylinder wall 2b contains a piston (not shown) which reciprocates
longitudinally of the chain saw, i.e., generally along the axis
X.
The piston contained within the cylinder 2 is connected by
conventional chain saw drive means 3 to a cutter chain 4. Cutter
chain 4 is conventionally supported upon a guide bar 5, a portion
only of which is shown in FIG. 1.
Chain saw 1 additionally includes a transverse handle 6 and a
longitudinally extending handle 7.
An upper portion 7a of handle 7 supports a conventional throttle
trigger 8.
In a manner, now well understood in the art, an operator may grasp
handle 7a, for example with his right hand. With the index finger
of the right hand, the operator may manipulate the throttle trigger
8. Concurrently, the operator may grip and support the chain saw
handle 6 with his left hand.
Chain saw 1 may be provided with a variety of auxiliary mechanisms
intended to facilitate and improve the overall operation of the saw
1. For example, an oiler actuating button 9 is schematically shown
in FIG. 1 as being positioned in operating proximity to the
operator's hand which manipulates the throttle 8.
The upper portion of chain saw 1 comprises housing means defining a
fuel tank 10 and an enclosure 11. As shown in FIG. 1, enclosure 11
provides a carburetor housing cavity 12, the lower end portions of
which are defined by enclosure wall means 11a and 11b. Side walls
of enclosure 11 are defined by longitudinally extending wall means
which interconnect rear and front wall means 11a and 11b in a
conventional manner, similar, for example, to the arrangement
described in the aforesaid Zimmerer et al. U.S. Pat. No.
3,498,280.
A conventional carburetor 13 is positioned in cavity 12 and is
disposed in air flow transmitting communication with inlet passage
means of cylinder means 2, in a now well known manner.
The upper portion 13a of carburetor 13 contains a conventional
opening leading to an air transmitting or carburetor induction
passage.
The upper portion of cavity 12 is closed by a preformed, foraminous
air filter 14.
A cover 15 is detachably secured to housing means 16 of chain saw
1. This detachable securing of cover 15 is implemented by a
threaded stud 17 which projects upwardly from, and supported upon,
a bracket 18. Bracket 18, as shown in FIG. 1, may be supported by
the body of carburetor 13. A threaded female fastener 19,
journalled in an upper portion of cover 15, serves to threadably
engage stud 17 in relation to the chain saw wall means 16.
As is generally described, for example, in the aforesaid Zimmerer
et al. U.S. Pat. No. 3,498,280, upwardly facing ledge means 16a,
provided by wall means 16, encircles cavity 12 and provide
peripheral support for lower edge means 15a of cover 15. Ledge
means 16a may generally encircle wall means 11 to insure that cover
15 fully houses cavity 12 and filter 14 when seated on ledge means
16a.
In a manner generally described in United States Zimmerer et al.
U.S. Pat. No. 3,498,280, cover means 15 may be provided with rim
means which engage the sides and forward peripheries of the filter
means 14 so as to press these portions of the filter means firmly
against filter seat means, i.e., upper edge or rim means 11c of
wall means 11.
Such a filter securing and cover mounting arrangement is utilized,
for example, on a model CP 125 chain saw manufactured by and
available from McCulloch Corporation, 6101 West Century Boulevard,
Los Angeles, Calif. 90045.
As is also shown in FIG. 1, a resilient, gasket-like washer 20 may
be interposed between the lower portion of fastener 19 and the
upper surface of filter 14, with gasket 20 encircling stud 17. With
this arrangement, when fastener 19 is threadably engaged with stud
17, it will press gasket 20 against filter 14 so as to secure the
filter 14 against the mounting bracket 18 and thus provide
intermediate stabilization for the filter 14.
Peripheral stabilization for the filter 14 will be provided by the
aforesaid ledge means 11c and the filter side and forward edge
engaging portions of cover 15, which engage lower and upper
portions, respectively, of filter 14.
FIG. 1 illustrates the manner in which portion 16b of wall means 16
and portion 11a of wall means 11 cooperate to define a generally
upwardly converging and downwardly opening mouth 21a of venturi
throat means 21. Venturi throat means 21 extends upwardly through
the assembly shown in FIG. 1, and passes through a restricted
throat zone 21b disposed intermediate the filter 14 and a portion
15a of the cover 15. Venturi throat means 21 generally enlarges in
zone 21c, i.e., in a zone disposed generally between portion 14b of
filter 14 and portion 15b of cover 15.
As is apparent from reference to FIG. 1, filter portion 14a
generally overlies the air inlet providing, upper portion 13a of
carburetor 13.
The rearward portion of cover 15 is provided with rearwardly
directed opening means 22. Such opening means 22 may comprise, as
shown in FIG. 4, a series of laterally displaced openings 23,
separated by generally vertically extending web means 24.
A spark arrestor and/or muffler 25 is mounted on the right side of
the cylinder wall 2 by viewing the chain saw 1 so as to look
forward from the handle 7 toward the cutter chain 4. An exhaust
stream defining conduit 26 is connected with spark arrestor 25 and
communicates through transverse passage means 27 with the interior
of spark arrestor 25.
Spark arrestor 25 is also mounted in communicating relation with an
exhaust passage 2c of cylinder 2. Thus, exhaust gas will be
transmitted through passage 2c from the interior of cylinder 2 into
the spark arrestor 25. At least a portion of this exhaust gas will
then pass through passage means 27 into stream defining conduit
26.
Conduit 26, as shown in FIGS. 2 and 3, is curved upwardly and
rearwardly away from opening 27 and is also inclined inwardly
toward venturi throat means 21.
As will be apparent from reference to FIGS. 2 and 3, an outlet end
28 of conduit means 26 will direct a generally jet stream-like
configuration of exhaust gas from conduit means 26 into venturi
throat means 21.
As is shown in FIGS. 2 and 3, venturi throat means 21 may be
elongate in a direction extending laterally of the longitudinal
median plane of the chain saw 1. Throat means 21 may be divided
along its length into a series of vertically extending openings 29,
separated by generally vertical wall means or web means 30.
With this arrangement, the stream of exhaust gas issuing from the
conduit means opening 28 will probably enter a plurality of
segmental openings 29 of venturi throat means 21.
With the overall structure of the chain saw having been described,
it now becomes appropriate to consider, in some detail, those
aspects of the invention which are directed to the utilization of
the stream of exhaust gas issuing from conduit means 26 for the
purposes of heating carburetor inlet air, flushing the upper
surface of filter means 14, and at least to some extent providing a
flow of heated air issuing through opening means 22 in the vicinity
of an operator's hand grip portion 7a.
Structure and Mode of Operation of Carburetor Air Inlet Heater and
Filter Flusher
With the arrangement shown in FIGS. 1, 3 and 4, operation of the
chain saw engine causes exhaust gas to pass from the exhaust port
means 2c of cylinder 2 and enter an interior cavity 31 of spark
arrestor 25 through a spark arrestor inlet passage defining means
32. Exhaust gas passes from an inner portion 31a of cavity 31,
through a foraminous spark arresting screen 33, and into an outer
cavity portion 31b. Some of the exhaust gas leaves cavity portion
31b through louvers 34, some of which are shown in FIGS. 2 and
3.
Another, extracted portion of the exhaust gas enters conduit 26
through conduit inlet passage means 27.
As shown in FIG. 3, the end extremity of conduit 26 adjacent
passage means 27 is plugged by plug means 35. The other end 28 of
the conduit means 26 is open and provides an exit for a stream of
exhaust gas.
Thus, the portion of exhaust gas extracted from cavity 31, via
conduit means 26, issues from conduit means outlet 28 as a jet
stream, schematically depicted in FIG. 1 by flow line 36.
This stream of gas 36 is directed generally rearwardly of the
cutting chain 4, and inwardly of saw 1 toward throat means 21, so
as to pass upwardly into the venturi throat means 21.
A generally intermediate portion of chain saw 1, including wall
means 11a, operably provides first barrier means interposed
generally longitudinally between the venturi throat means and the
cutter chain 4. This barrier means, generally depicted by reference
numeral 37, includes engine mounting wall means and operates to
tend to prevent or impede cuttings, generated by operation of the
chain 4, from being carried directly into the throat means 21.
Because of the venturi nature of throat means 21, the jet-like
stream 36 will entrain ambient fresh air with the exhaust gas of
the stream 36 and carry such fresh air into the venturi throat
means 21.
A portion of stream 36, generally depicted by reference numeral 38,
in the restricted or relatively high pressure portion of throat
21b, will flow through the filter means or filter web 14 and into
the carburetor air inlet end 13a. Thus, this diversion of
carburetor feeding air 38 occurs in the relatively narrow portion
21b of the venturi throat means, i.e., the portion downstream of
the relatively wide mouth portion 21a of the venturi throat
means.
Another portion of the flow of exhaust gas and entrained air,
generally depicted by flow direction 39, passes generally
longitudinally over the exterior surface of filter means 14. This
exterior surface is disposed in communication with ambient air.
The flushing flow 39 of exhaust gas and entrained air serves to
maintain the exterior surface of the filter means 14 in a
relatively clean condition, free of excessive accumulations of
cutting operation generated, wood cuttings.
The flow of fluid in the throat portion 21c will be reversed, due
to closed throat end 21d, as generally depicted by flow direction
40. This reversal in flow will cause some exhaust gas and entrained
air to flow rearwardly out of the chain saw, through passage means
22. This rearward flow of gas will be directed generally toward the
hand of the operator which is gripping the hand grip portion 7a. In
this manner, a flow of at least partially warmed air will be
directed toward the operator'hand so as to tend, at least to some
extent, to improved operator comfort.
The exiting air flow 40 will carry with it at least some of any
cuttings which may have accumulated in the throat 21. It will here
be recognized that the flushing action of stream portion 39 will
have made such accumulated cuttings amenable to removal from the
cavity throat 21 by operation of the exiting flow 40, i.e., the
exiting flow of the prior flushing flow 39.
In order to tend to ensure that the exiting flow 40 is not recycled
back into the venturi throat means 21, a cover provided wall means
15c functions as second barrier means interposed between the
exiting zone 22 and the entry zone or throat 21.
Having described the basic mode of operation of the heating and
flushing aspects of the chain saw system, it now becomes
appropriate to consider certain detailed aspects of the spark
arrestor and the conduit mechanism which provides the diverting
flow of exhaust gas for heating and flushing purposes.
Spark Arrestor and Conduit Mechanism
Components of the spark arrestor and flow diverting mechanism have
previously been described in connection with FIG. 3, and will now
be described in greater detail in connection with FIGS. 2 and
3.
Spark arrestor 25 is fabricated from two shell-like or cup-like
halves 41 and 42. Shell half 41 may be secured to the base wall of
cylinder means 2 by conventional threaded fasteners (not shown)
which pass through a flange portion 43 of inlet passage defining
means 32 into the body of the cylinder side wall 2b.
In the arrangement shown in FIG. 3, the base wall 44 of shell half
41 is supported, at least in part, on cylinder cooling ribs 45.
Base wall 44 may also be secured by threaded fastening means 46 to
boss portion (not shown) of cylinder wall means 2b.
Passage defining means 32 may be secured to the shell half 41 of
spark arrestor 25 by web means 47. As shown in FIG. 3, web means 47
comprises an integral but extended portion of the left-most wall
32a of passage defining means 32. Web means 47 may be secured at
its upper and lower ends to the interior of shell 41 by
spot-welded, tab means 48.
The foraminous or perforate disc 33, of outwardly directed, concave
configuration, is provided with openings 49 and is supported on a
lip portion 50 of shell half 41 as generally shown in FIG. 3. As is
also shown in FIG. 3, outer shell half 42 is provided with a rim 51
which engages the outermost rim portion 52 of perforate disc 33 as
to provide a sandwiched assembly of components 41, 33 and 42.
A conventional, circumferentially constrictable, clamp means 53
serves to grippingly engage the sandwiched rim means 51, 52 and 50
so as to secure the components 42, 33 and 41 in the assembled
relation depicted in FIG. 3.
With the components disposed in this assembled relation, exhaust
gas passing into the cavity 31 will be obliged to pass through the
openings 49 of perforate disc means 33 before reaching the louvers
34 or the conduit means inlet 27. Exhaust gas, in passing through
the perforations 49 of disc 33, will tend to cause sparks to be
extinguished or to be prevented from flowing out of the spark
arrestor 25.
As an additional safety device, a heat shield and outflow baffle
plate 54 may be secured, by brazing or welding, to the outer
cup-like member 42. As shown in FIG. 3, heat shield and baffle
means 54 is disposed in outwardly spaced relation relative to the
louvers 34, recognizing, of course, that louvers disposed
immediately behind the baffle means 53 are not illustrated in FIG.
2.
Conduit means 26 is secured by brazing or welding to component 42
of the spark arrestor so as to cause an inwardly facing transverse
aperture 27a of conduit means 26 to be aligned with an outwardly
facing aperture 27b of component 42. With the apertures 27a and 27b
thus aligned, and conduit means 26 oriented as above-described, the
conduit means 26 may be permanently connected, as by brazing or
welding, to the exterior of the component 42.
SUMMARY OF MAJOR ADVANTAGES AND SCOPE OF INVENTION
In large part, the significant advantages of the invention reside
in an effective concept for supplying a flow of heated fluid to the
vicinity of a carburetor air filter to perform both air heating and
filter flushing functions.
Significantly, this dual function action is accomplished without
requiring significant modification of the basic chain saw
structure. Primarily, all that is involved is the addition of a
simple diversion conduit which is uniquely placed and oriented so
as to generate a stream of exhaust gas operable to concurrently
perform intake air heating and air filter cleaning functions.
It is also noteworthy that residual heat in the gas, passed across
the filter, is directed back towards an operator's hand so as to
enable such residual heat to perform a hand warming function.
The effective placement of barrier means relative to the gas intake
throat, the gas exit, and the cutting chain, minimize tendencies
for cuttings to be circulated or recirculated into the vicinity of
the air filter.
As will be apparent, other configurations and arrangements may be
employed for conveying a flow of exhaust fluid to the vicinity of
the air filter means 14.
For example, in certain situations it is contemplated that exhaust
gas may be transmitted directly upwardly out of a muffler and/or
spark arrestor so as to flow transversely across the air filter 14
rather than longitudinally of the air filter as described in
connection with the preferred embodiment.
It is also contemplated that the diverted flow of exhaust fluid may
be transmitted toward the air filter in the form of a flattened or
broad stream instead of in the form of a rod-like stream issuing
from a flow diverting conduit. Desirably, such a flattened stream
of exhaust fluid would be directed so as to cause the flattened
stream to flow generally contiguously with the exterior surface of
the air filter so as to achieve optimum flushing action.
Those familiar with the chain saw art and this disclosure may well
recognize additions, deletions, substitutions or other
modifications which could be effected in order to accomplish some
or all of the objectives of this invention.
However, it will be recognized that the overall scope of invention
is set forth in the appended claims.
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