US 3881452 A
An improved chain saw and method of operating a chain saw in a cold, humid environment where ice may form in the carburetor of the chain saw engine is disclosed. An ice-inhibiting substance is mixed with the fuel and lubricating fluid and introduced into an interior portion of the carburetor in conjunction with the combustible mixture of fuel, lubricating fluid, and air during operation of the two-cycle internal combustion chain saw engine in order to inhibit the formation of ice therein. The ice inhibiting means may be premixed with the lubricating fluid.
Description (OCR text may contain errors)
ilmted States Patent 11 1 1111 3,881A52 Dilworth et al. 1 1 May 6, 1975 [54l METHOD AND APPARATUS FOR 3.067J38 12/1962 Johan ct ul. 44/58 X OPERATING AN ENG|NE DRWEN CHMN 3.230.057 1/1966 Sieker 44/58 SAW N AN ENVRONMENT WHERE CE :xggg IN THE CARBURETOR OF THE 3,498,280 3/1970 Zimmerer et ul. 123/122 R l v t J h L i D h S t M FOREIGN PATENTS OR APPLICATIONS n en ms: 0 n ews wor an a on1ca' 753,622 2/1967 Canudu 44/58 ,zlmmere" 423.510 2/1935 United Kingdom 123/1911 A both of Cahf. 1731 Assignee: McCulloch Corporation, Los Primary Examiner-Charles J. Myhre Angeles. Calif. Assistant Examiner-R. H. Lazarus  Filed: Jan. 22 973 $232215 Agent, or Firm-Burns, Doane, Swecker &
 Appl. No.: 325,346
 ABSTRACT U.S. Cl. An improved chain saw and method of perating a In. CL t chain aw in a Id environment wherg ice 1 Field Search 193 A may form in the carburetor of the chain saw engine is 44/53 disclosed. An ice-inhibiting substance is mixed with the fuel and lubricating fluid and introduced into an 1 Rem'mces cued interior portion of the carburetor in conjunction with UNITED STATES PATENTS the combustible mixture of fuel, lubricating fluid. and 2307526 9/1957 Foreman 44/53 X air during operation of the two-cycle internal combus- 2.843.463 7/1958 Gaston e1 n1 44 53 tion chain saw engine in order to inhibit the formation 2.844.448 7/1958 Heislcr ct a1 44/58 X of ice therein. The ice inhibiting means may be pre- 2,876,750 3/1959 Carr 123/1 A mixed with the lubricating fluid. 2,883,276 4/1959 Larsen i23/l A X 2.896.593 7/1959 Riemenschneider 123/1 A 1 Claim 3 Drawing Figures 1 METHOD AND APPARATUS FOR OPERATING AN ENGINE-DRIVEN CHAIN SAW IN AN ENVIRONMENT WHERE ICE MAY FORM IN THE CARBURETOR OF THE ENGINE BACKGROUND OF THE INVENTION This invention relates generally to a novel method and apparatus for operating a chain saw in a relatively cold environment. More particularly. this invention provides a chain saw including an ice inhibitor which substantially inhibits the formation of ice in the internal portion of a carburetor of the two-cycle engine of the chain saw to substantially prevent carburetor blockage during operation of the engine in cold. humid atmmospheric conditions.
Because of the substantial increase in the use of gasoline engines of the two-cycle type for chain saws by the general public and by the logging and lumber industry. satisfactory. trouble-free engine performance is extremely desirable in the operation of such engines. Two-cycle chain saw engines giving dependable performance can be manufactured in small sizes. making their use ideal forv service in remote regions of the world wherein large scale logging operations have begun to take place.
in the operation of gasoline engines of the two-cycle type. a lubricating oil-gasoline motor fuel mixture which not only functions as a fuel. but also provides lubricatin in a highly diluted form without the sump-type or crankcase lubrication system. is utilized. Many chain saw operators use special chain saw lubricating oil for this purpose. Moreover. manufacturers may provide chain saw lubricating oil in containerscorresponding to the volume of the fuel reservoir to facilitate mixing the proper ratio of gasoline and lubricant.
When internal combustion engines of the type noted are operated in cold (approximately 40F to sub freezing. temperatures). humid (approximately 50-100! relative humidity). weather. or in a cold humid environment immediately surrounding the cngine. a stalling problem may be encountered. it has generally been recognizcd that repeated engine stall- 2 over. the stalling of a chain saw engine in the mid: felling a tree may impose a serious safety hazard wl precise timing is critical to control of the fall.
A variety of methods and apparatus presently i for heating the carburetor of a chain saw engine to prove operation under relatively cold weather co tions. For example. a closed circuit. radiatomypc ings under such cold. humid conditionsmay be caused Y by a formation of ice in the carburetor. The accumulation of this ice produces a blockage in the carburetor. most generally in the vicinity of the throttle. and may seriously interfere with the production of a fuel-air mixture suitable for combustion in-the cylinder of the engine. it is known that gasoline evaporating in the carburetor has a sufficient refrigerating effect to condense and freeze the moisture present in air even in temperaturessomewhat above the freezing temperature. As a result. ice particles may deposit along the interiorof the carburetor. and as noted above. partially or completely block the air passage between the carburetor wall and the carburetor throttle valve with a resulting stalling. This stalling may be particularly pronounced when the chain saw engine is idling.
As noted above. the chain saw art has advanced to the state where many lumbering operations are conducted with internal combustion engine-operated. portable chain saws. M any of these logging operations take place in extremely cold or snowy climates. and excessive engine stalling as a result of ice formation in the carburetor may be a source of serious annoyance and expense with a resulting increased fuel consumption. inconvenience and delay of frequent restarting. Moretem. which has been found to be particularly effer for preheating the air which is passed to the carbur air inlet of the engine. is disclosed in a'U.S. Zimm et al. Pat. No. 3.498.280. in addition. a method ill". paratus for utilizing a stream of exhaust gas. whit generated by a chain saw engine. by directing stream. as a free flow. through air towards a PI lected location on 'a chain saw is disclosed in a Loop Pat. No. 3.678.973.
While these prior concepts are individually un and advantageous. there has remained a need for 1 tional techniques which would be operable to facil the operation of chain saws under cold weather Ct tions. Since compactness and simplicity have bec some of the primary characteristics of modern chain saws. it has become desirable. in coping icing tendencies. to provide a solution to such problems without engendering structural compl and added fabrication costs.
it is. therefore. a general object of the present it tion to provide a method and apparatus for inhil the formation-of .ice in the caiburetor of 'a two-l chain saw enginewhich minimizes or reduces the lems and limitations previously existing in the prio his a more particular object to provide a methl operation of a two-cycle chain saw engine whic eludes the use of an ice inhibitor'to substantially vent the formmation of ice inside a carburetor of a cycle chain saw engine.
it is also an object of the present invention to pr an engine for a chain saw and other devices whicl be operated in a cold. humid orsnowy environ without an external carburetor heating means to ll the formation of ice in the carburetor thereof.
Another object of the present invention is to pr a method of inhibiting the formation of ice in th buretor of a two cycle chain saw engine which or may be employed without requiring modification conventional chain saw structure.
An additional object of the present invention provide a method which minimizes trouble to a saw operator whereby an ice inhibitor may be ducedinside the carburetor of an engine for a saw or. say. a snowmobile during operation of ti gine bymeans of an additive premixed with the eating oil. for the engine. which ice inhibitor su tially prevents the formation of ice in the carbun an amount sufficient to induce stalling of the en A method and apparatus for inhibiting the for: of ice in a two-cycle chain saw engine accordin preferred embodiment of the present inventi tended to accomplish at least some of the foregoi jects includes a chain saw having a frame. a cut connected to the frame. a cutting chain trained i the outside of the cutter bar. and a two-cycle n eating piston internal combustion engine conne the frame for selectively driving the cutting cl will. of course. be appreciated that a rotary pis gine could be used in the practice of this lilVClillt internal combustion engine has a carburetor in an interior portion comprising an induction passage. :1 throttle valve. a venturi throat which is defined by a portion of the induction passage and the throttle valve. and a choke plate. An ice inhibiting means is mixed with the fuel and lubricating fluid and introduced into the interior portion of the carburetor in which ice may form in conjunction with the combustible mixture of fuel. lubricating fluid and air. That is to say. during the operation of the engine. the ice inhibiting means is carried through the carburetor with the combustible mixture. As the mixture passes through thecarburetor. ice is substantially prevented from forming within the interior of the carburetor. By introducing the ice inhibitor into the interior of the carburetor in such a manner to prevent the ice from forming. blockage of the carburetor from ice deposits is substantially prevented. An ice inhibiting means intended to accomplish at least some of the foregoing results may include. but is not limited to. hexylene glycol (i.e.. 4-methyI-2.4-pentanedioll.
Other objects and advantages of the present invention will become apparent with reference to the following detailed description of a preferred embodiment thereof in connection with the accompanying drawings. in which:
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partial sectional view of a chain saw according to the present invention:
FIG. 2 is a schematic sectional view of the carburetor of the chain saw of FIG. I wherein an ice inhibiting means has been introduced; and
FIG. 3 is a schematic sectional view of a carburetor in the prior art wherein deposits of ice have accumulated to block flow through the carburetor.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawings. wherein like refer ence characters have been applied to like parts throughout. in FIG. I there is illustrated a chain saw having a guide bar I2 supporting a cutter chain I4. A handle 16 provides a triggertype. throttle lever 18. A two-cycle. internal combustion engine 20 serves to impart power to the cutter chain I4 so as to cause the chain 14 to traverse or train around the periphery of the guide bar 12. A drive connection interposed between the engine and the cutter chain may include a conventional. pull-type starter. Alternatively. an electrical self-starting system (not shown) may be provided.
In any event. this structure is now well known in the chain saw art. It corresponds. in general. for example. to the basic structure described in a publicly available McCulloch Shop Manual associated with the Mac [-10 and 2-l0 chain saw manufactured by the McCulloch Corporation. Los Angeles. Calif.
The chain saw may further include a fuel tank 22. and an engine mounting bracket 24. The bracket may comprise an integral portion of a casting or may be a molded portion ofa fuel tank 25. An upper portion 26 of the chain saw 10 comprises an enclosure 28. The enclosure 28 provides a carburetor housing cavity 30. the lower end portions of which are defined by enclosure walls 34.
A conventional carburetor 36 is positioned in the cavity and is disposed in air flow transmitting communication with an inlet passage 38 in a now wellknown manner.
An upper portion 40 of the carburetor 36 contains a conventional opening 42 leading to an air transmitting or carburetor induction passage 44.
The carburetor 36 is secured to the engine 20 with the induction passage 44 connected to an engine inlet 56 which communicates with the crankcase of the engine 20. The upper portion of the cavity 30 may be closed by a preformed. foraminous air filter 46.
Turning now to FIG. 2. there is schematically depicted the carburetor 36 of the engine 20 illustrated in the chain saw I0 of FIG. I. The carburetor 36 includes a carburetor body 48. having an induction passage 44 therethrough which includes an air inlet portion 50 and a mixture outlet portion 52 with a venturi 54 interposed therebetween and connecting the passage portions 50.52. By having the diameter of the inlet portion 50 the same as that of the outlet portion 52. improved operation may be obtained.
The flow of fluid through the induction passage 44 is controlled by means of a throttle plate or valve of the butterfly type. which is mounted on a throttle shaft 62.
Means for providing a suitably rich mixture for cold starting and warm up is provided by a butterfly type of choke plate or valve 64 which is mounted on the shaft 66. Means are also provided by idle fuel jet 65 for sup plying fuel to the carburetor when the engine is idling. The choke valve 64 is disposed in the air inlet portion 50 of the induction passage 44 and may be of the same diameter as the throttle valve 60. Any suitable wellknown means may be used for rotating the choke valve shaft 66 so that the choke valve will be moved to a closed or open or intermediate position.
These components thus far described are now well known. There will now be described a unique concept for inhibiting the formation of ice in the carburetor. As noted above. carburetor icing has continued to be a problem in the operation of chain saws utilizing twocycle internal combustion engines where the chain saw is operated in a relatively cold and humid environment. When the chain saw I0 is operated in such a cold. humid environment without provision for anti-icing. ice 67 may accumulate within the interior portion of the carburetor and particularly may accumulate on the throttle plate 60 as shown in FIG. 3. Many icing problems occur when the throttle plate 60 is in or near the closed or idle position. Under these conditions. little. if any. fuel is discharged by the main jet (not shown) of the carburetor. During idling of the engine. ice formation may occur. above. below and in the small opening between the throttle plate 60 and the carburetor wall. In addition. any ice which does accumulate on the throttle plate when it is open tends to obstruct the idle air flow when the throttle is closed. Hence this accumulation may be sufficient to appreciably block the flow of combustible fuel mixture through the carburetor with a result in rough engine operation and stalling.
The present invention functions to inhibit ice formation in the internal portion of the carburetor I0 and thereby substantially prevents ice crystals from accumulating on the induction passage surfaces to form a blockage.
As shown in FIG. 3. in the absence of the ice inhibiting means of the present invention. ice will generally form on edges 68 of the throttle plate 60 and can spread progressively across the plate face 70. Simultaneously. ice may accumulate along the walls of the induction passage 44. especially while the engine is idling. when an increased fluid flow around the throttle may enhance the evaporation of gasoline and. hence. may produce an increased refrigerating effect. Without the use of anti-icing devices. ice formation may accumulate both on the throttle plate 60 and along the side walls of the carburetor in such a manner as to restrict the flow of combustible mixture. Such a restriction may result in engine stalling or rough operation. and the chain saw will often fail to perform until the blockage is removed.
While there is no intention to be bound by theoretical considerations. it appears that the ice inhibitor may lower the freezing point of water in the internal portions of the carburetor to a temperature below that which would ordinarily occur in the carburetor of a two-cycle chain saw engine operating in a cold. humid environment. In addition. or alternatively. the ice inhibitor may provide a film on the internal portions of the carburetor as it passes in contact therewith preventing an adhesion of ice crystals thereon. Regardless. a two-cycle chainsaw engine according to the present invention has a substantially lower tendency towards formation of ice within the interior portions of the carburetor and a correspondingly lessened tendency towards engine stalling under conditions in which ice may form.
While ice crystals may not be absolutely prevented from forming in the carburetor. the present invention prevents any ice crystals which may form from accumulating in a manner which will restrict the flow of fluid through the carburetor body. As indicated in FIG. 2. occasional ice particles 72 may still form in the induction passage 44. However. the effect of the ice inhibiting means is sufficient to prevent a blockage or to otherwise interfere with the operation of the chain saw. Normally. the small particles of ice which may form notwithstanding the presence of the ice inhibiting means simply pass into the crankcase of the engine where they are almost instantaneously vaporized because of the relatively high temperatures therein.
During operation of the engine. an ice inhibiting means is introduced into the carburetor by means of the fuel supply system. The ice inhibiting means is mixed with the fuel-lubricating oil mixture of the twocycle chain saw engine in an amount sufficient to in-' hibit the formation of ice within the carburetor of the engine without. however. appreciably adversely affecting the combustibility or volatility of the mixture to be ignited in the engine cylinder which amount. in the case of hexylene glycol as the ice inhibiting means. may be from about (M to 0.2 1 by .volume of the fuel. The ice inhibiting means preferably is premixed with the lubricating oil (which premix is thereafter mixed with gasoline to provide the combustible mixture which is exploded in the engine cylinder) to facilitate mixing the correct proportionof ice inhibiting means. The concentration of inhibitor in the oil may depend also upon the ratio of oil to gasoline recommended by the manufacturer of the lubricant. ln the case of hexylene glycol used with oil intended to be mixed in the proportions of 40:1 1 volume of oil to 40 volumes of gasoline). the concentration of inhibitor in the oil will range from about 4 to 8'4.
it will be appreciated that in utilizing the nov method and apparatus for inhibiting carburetor icing a chain saw engine according to the present inventio certain significant advantages are provided.
in particular. the present invention eliminates a "Cl for structurally complex heating apparatus to increa: the temperature of the carburetor walls or of the intai air to the carburetor as well as the need for an exteril heater or for pre operation modifications which to: increase the cost and complexity of the chain saw c gine. The ice inhibitor of the present invention may 1 used when weather or temperature conditions so r quire it and may otherwise not be used. Hence. the is provided a maximum of flexibility of operation wi a minimum of complexity and cost.
Of further significance is the fact that the ice inhil tor may be introduced into the fuel system of a cha saw engine by means of the lubricating oil. This assur that the proper proportion of ice inhibitor is used to i hibit icing while. at the same time. there is an assuran that the fuel volatility is not interfered with. Such an a rangement permits improved operation of a chain s: in a cold environment. and. in commercial situatio such as logging operations. may substantially increa the efficiency of chain saw use.
Thus. it is apparent that there has been provided. accordance with the invention. a method and apparal for inhibiting icing in the carburetor of a two-cyl chain saw engine that substantially satisfies the obje and advantages set forth above. Although the pres invention has been described in conjunction with a s cific embodiment it is evident that many alternativ modifications. and variations will be apparent to lht skilled in the art in light of the foregoing disclosure the invention. Accordingly. it is intended that all St alternatives. modifications. and variations which within the spirit and scope of the invention as deiir in the appended claims be embraced thereby.
What is claimed is:
l. A method for operating a chain saw in an envir ment where ice may be formed in a carburetor me thereof. and wherein said chain saw comprises:
a two-cycle. internal combustion. chain saw engi 45 a cutter chain drivenly engaged with said chain 1 engine;
reservoir means connected to said chain saw enr and operable to contain a combustible lubrica so oil-gasoline mixture for transmittal to a carbon means;
carburetor means for transmitting a volatile mix of air and said lubricating oil-gasoline mix therethrough for passage to a combustion chan of said chain saw engine; and
said carburetor means having an interior portior eluding aninduction passage;
said method comprising:
a. storing an ice inhibiting means with a lubric:
b. maintaining a ratio of said ice inhibiting meal said lubricating oil composition so as to ensure when said lubricating oil composition is added predetermined lubricating ratio to said gasoli ratio of ice inhibiting means to gasoline will 1 matically be provided which will substantially vent the formation of ice when said gasoli drawn through said induction passage with ai temperature of less than about 40F and having a relative humidity of greater than about 50%,
. concurrently mixing said lubricating oil composid. providing. in said reservoir means. said combustible lubricating oil-gasoline mixture containing an ice inhibiting means mixed therewith and operable to substantially prevent the formation of ice within said induction passage of said carburetor means during operation of said chain saw engine in an environment where ice may be formed in said carburetor means and where said mixture is drawn through said induction passage with air at a temperature of less than about 40F and having a relative humidity greater than about 50%:
. operating said chain saw engine to pass said combustible mixture through said carburetor means of said chain saw engine and thereby introduce said 8 ice inhibiting means into said induction passage of said chain saw engine to substantially inhibit a formation of ice therein and prevent an ice blockage in said induction passage when said chain saw engine is operated in an environment where ice may be formed in said carburetor means. and where said mixture is drawn through said induction pas- I sage with air at a temperature of less than about 40F and having a relative humidity greater than about 40%;
. said combustible lubricating oil-gasoline mixture.
containing said ice inhibiting means. being contained within said reservoir means during said operation of said chain saw while being subject to chain saw operation-induced vibration;
g. said volatile mixture of air and lubricating oilgasoline mixture being transmitted through said induetion passage of said chain saw engine carburetor means with said ice inhibiting means while said induction passage is subject to said chain saw operation-induced vibration; and
b. said volatile mixture of air lubricating oil-gasoline mixture. including said ice inhibiting means. being transmitted from said induction passage through a crank case of said chain saw engine prior to combustion of said volatile mixture in said combustion chamber of saidchain saw engine.
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