US3273870A

US3273870A - Carburetor

Info

Publication number: US3273870A
Application number: US424856A
Authority: US
Inventors: Johnson Dolores
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1965-01-11
Filing date: 1965-01-11
Publication date: 1966-09-20
Anticipated expiration: 1983-09-20

Description

P 1966 E. A. JOHNSON 3,273,870

CARBURETOR Filed Jan. 11, 1965 /Z/ I7 #9 F |G.4.

59 X A 1\\\\\ .2- NvEN R @7 6/ ELDON A.JOHNSON, DECEASED 32 BY DOLORES JOH N, A MINISTRATRIXI AGENT United States Patent 3,273,870 CARBURETOR Eldon A. Johnson, deceased, late of St. Louis County,

Mo., by Dolores Johnson, administratrix, St. Louis County, Mo., assignor to ACE Industries, Incorporated,

New York, N.Y., a corporation of New Jersey Filed .lan. 11, 1965, Ser. No. 424,856 Claims. (Cl. 261-41) This invention relates to carburetors, and more particularly to carburetors for small engines. The carburetors of this invention are suitable for engine driven devices including chain saws and other portable power tools.

Carburetors for small engines such as those used with power saws and other portable tools must be small to provide the desired portability and must also be sensitive or quickly responsive to the operating conditions of the engine. The tool and carburetor are frequently rnoved to various attitudes or positions and the carburetor is required to perform equally Well in all positions. Also, power saws and other portable tools are frequently left outside overnight in cold climates and the carburetor must function properly even though it is quite cold.

Among the various objects of this invention may be noted the provision of a novel carburetor for engines of the type described which has optimum operating characteristics under various temperature conditions; the provision of a novel carburetor, for engines of tools of the class described, which is sensitive and quickly responsive to changing engine operating requirements; and the provision of a novel carburetor for portable engine driven devices having improved cold starting performance. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

FIG. 1 is a side elevation of a carburetor of this invention, showing a portion of an engine to which it it attached;

FIG. 2 is a bottom view of the carburetor of FIG. 1;

FIG. 3 is an enlarged cross section taken on line 33 of FIG. 1;

FIG. 4 is an enlarged cross section taken on line 44 of FIG. 1;

FIG. 5 is a cross section view of the diaphragm assembly used in the carburetor of this invention; and

FIG. 6 is a fragmentary cross section through the idle cavity of the carburetor taken substantially parallel to the fuel and air mixture conduit.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to the drawings, a carburetor of this invention is indicated in its entirety by the reference numeral 1. The carburetor 1 has a body 3 connected at one end to the intake manifold portion of an engine 5. A fuel and air mixture conduit 7 in body 3 receives air and fuel and mixes them in the conduit, the mixture moving from the right to the left as shown in FIG. 1 into the intake manifold of the engine 5. Movement of fuel and air in the conduit 7 is governed by operating conditions in the intake manifold of the engine 5 as well as a manually operated throttle valve 13 rotatably mounted on a throttle shaft 15 journalled in the carburetor body 3.

A choke valve 9 is located in the upstream or inlet end of the fuel and air mixture conduit 7. Choke valve 9 is mounted on a choke shaft 11 which is journalled in the body 3 of the carburetor. Downstream from the choke valve 9 is the throttle valve 13. A venturi section 17 is formed in conduit 7 between the choke valve 9 and throttle valve 13.

A nipple 19 is mounted on body 3 for connection to a fuel line 20 from a source of fuel as a fuel tank T. The body 3 of the carburetor is formed with a cavity 21 of small volume or capacity which forms part of a fuel chamber 22 which receives fuel from nipple 19 through a passage 23. Passage 23 has a restricted opening or orifice 25 at its upper end as shown in FIG. 3 which is in communication with the nipple 19.

Positioned within the passage 23 is an inlet valve assembly indicated generally at 27. The valve assembly 27 comprises an annular valve seat 29 seated against a shoulider at the upper end of passage 23 adjacent the orifice 25. Seat 29 is held in place by an annular retainer 31 which is press-fitted in the upper end of the passage -23. Fuel from nipple 19 may pass through orifice 25, the annular seat 29 and retainer 31 into the passage 23.

A needle valve 33 has a tapered end 35 which engages the seat 29 to close the valve assembly against the passage of fuel. A tip 37 of the needle 33 passes through the hole or opening in the seat 29 and guides movement of the needle within the passage 33. The needle 33 has an annular flange or shoulder 39 spaced from the tapered portion 35.

An annular retainer 41 is pressfitted in the lower end of the passage 23 opposite from the seat 29. A coil compression spring 43 is positioned within passage 23 with its ends engaging the flange or shoulder 39 on the needle 33 and the retainer 41. The spring 43 reacts from retainer 41 against the flange 39 biasing end 35 of the needle 33 upwardly as viewed in FIG. 3 into sealing engagement with the seat 29. The lower end of the needle 33 has an annular peripheral groove 45 located beneath the retainer 41 adapted to receive an arm for moving the needle 33.

The needle 33 is skeletonized, that is, all excess metal has been removed from the needle to thereby reduce the Weight of the valve assembly and of the carburetor. Also, the valve assembly 27 utilizes the passageway 23 as the valve housing or body to thereby eliminate a separate sleeve frequently used in carburetor constructions, thus further reducing the overall weight of the valve assembly 27 and of the carburetor l.

A fuel chamber cover plate 47 is mounted at the bottom of the carburetor by screws 49 passing through edge portions of the plate and threaded in tapped holes in the body 3. Cover plate 47 has a hole 51 in the center thereof.

A diaphragm assembly shown generally at 53 in FIG. 5 comprises a molded diaphragm 55 made of a flexible fuel resistant material. The diaphragm 55 has a circular center hole 57. An annular corrugation or loop 59 is molded in the diaphragm 55 adjacent its periphery. This loop projects above the upper surface of the center portion of the diaphragm. Loop 59 is spaced radially outwardly from hole 57 and is generally concentric therewith.

An annular gasket 61 is adhesively bonded to the lower surface of the diaphragm 55 at its periphery outward of the loop 59. The gasket 61 is engaged by the rim of plate 47 in mounting the diaphragm assembly in the carburetor in the position illustrated in FIGS. 3 and 4. The flat edge portion of the diaphragm 55 between loop 59 and the periphery of the diaphragm engages a shoulder in the body 3 around the cavity 21 and thus forms a fuel tight seal between the periphery of the diaphragm 55 and the edge of the body cavity 21. Diaphragm 55 forms with cavity 21 a sensing fuel chamber 22.

A diaphragm backing plate 63 is adhesively bonded to the lower surface of the diaphragm 55, the periphery of the plate 63 being located approximately at the radially inner edge of the loop 69. At the center of plate 63 is an integrally formed button 65 which projects through the hole 57 in diaphragm 55 and above the upper surface of the center portion of diaphragm 55.

With the diaphragm assembly 53 mounted at the bottom of the body 3, the loop 59 projects upwardly and lies closely adjacent to the wall in body 3 defining the upper limit of the sensing chamber 21 as seen in FIGURES 3 and 4. The plate 63 at the bottom of the assembly is closely adjacent to an annular shoulder portion 67 (FIG. 4) of the cover 47 to limit the outward or downward flexure of the diaphragm assembly.

In some prior art carburetors for portable tools, the diaphragm assembly is made of relatively heavy parts and due to the fuel in the sensing chamber tends to collapse or sag outwardly after the apparatus has been used. This situation under very cold conditions and with the carburetor not in use causes the diaphragm to take a set in the sagged position, resulting in loss of sensitivity in the sensing chamber and resulting in slow starting of the associated engine. The close spacing of shoulder 67 from the diaphragm plate 63 limits sagging of the diaphragm under the weight of fuel in chamber 22. Also, formation of the diaphragm with loop 59 facilitates flexing of the diaphragm when cold, thereby making the carburetor of this invention more responsive to engine starting requirements under adverse conditions. In addition, flexing of the diaphragm 55 during normal operation is improved by formation of the loop 59 which is permanently molded in the diaphragm.

A pivot pin 69 is mounted in the body 3 extending across pump chamber 22. A valve operating lever or arm 71 is pivotally mounted on pin 69, the latter being received in a loop 73 of the arm. The latter has a struck-out tang or tangs 75 overlying the pin to hold the arm on the pin with the weight of the arm being carried by the pin.

The arm or lever 71 has a forked end 77 received in the groove 45 of the needle 33 and engageable with adjacent portions of the needle so that movement of the arm or lever 71, on counterclockwise pivoting thereof as shown in FIG. 3, moves the needle 33 down thereby to open the valve assembly 27 to the passage of fuel. The end 79 of arm 71 is in downward engagement with the button 65 of the diaphragm assembly 53 so that when the diaphragm assembly is flexed upward the button 65 engages the portion 79 of arm 71 to move the arm.

A fuel passage 81 connects a cavity 83 in the body 3 with the passage 23. A plug 34 separates cavity 83 and fuel chamber 21. A nozzle passage 85 connects cavity 83 with the venturi portion 17 of the mixture conduit 7.

An adjusting screw 93 is threaded in a hole 95 which opens into the cavity 83 substantially opposite from the passage 81. A tapered end 97 of the adjusting screw 93 is partially positionable in the passage 81. Screw 93 is adjusted relative to passage 81 to regulate the flow of fuel from the passage 81 to cavity 83.

An annular packing or gasket 99 fits tightly to and surrounds the shank portion of the adjusting screw 93 and is located in an annular groove 94 formed in the adjusting screws 93. Packing 99 prevents fuel leakage through hole 95 around the adjusting screw 93 and also prevents any unwanted turning of screw 93 during engine operation.

An idle cavity 105 (FIG. 6) in body 3 is in communication with the mixture conduit 7 through ports or open ings 107 and 108 located at opposite sides of throttle valve 13 when in its closed or idle position. The lower end of the idle cavity 105 is closed by a plug 109. The plug 109 fills a substantial portion of the cavity 105 to thereby reduce the volume of the cavity and thus avoid slopping of fuel in the idle cavity. During idling operation of the engine, air in the conduit 7 passes through the upstream hole or port 107, through the cavity 105, and is discharged through the port 108 downstream of the 4 throttle valve 11. By maintaining cavity 105 at a minimum volume, emulsification of fuel and air in the cavity 105 is prevented. As a result substantially solid fuel flows through the downstream port 108 sooner than carburetors having larger idle cavities.

Referring to FIGURE 4, a passage 111 has an orifice at its inner end in communication with the cavity 105. An adjusting screw 113 is threaded in passage 111 and has a tapered end 115 positionable in the small end of the passage 111 to control flow of fuel into the cavity 105. A fuel well 117 provides a conduit for delivery of fuel from the fuel chamber 21 to the passage 111 for transfer to the idle cavity 105.

An annular seal or packing 119 surrounds the adjusting screw 113 and an annular washer 121 abuts this packing or seal 119. A coil spring may be carried on the shank of screw 113 to compress washer 121 against packing 119 to form a tight seal.

Operation of the carburetor 1 is as follows:

Cranking of the engine 5 pumps air through the fuel and air mixture conduit 7. Flow of air past the main fuel nozzle with the throttle valve open provides a subatmospheric pressure at the mouth or outlet of the nozzle at the venturi 17 in the conduit 7. This low pressure at the mouth of the nozzle 85 is transferred through cavity 83, passage 81 and passage 23 to the pump chamber 21. The bottom of the diaphragm assembly is at atmospheric pressure due to the hole 51 in plate 74. As a result of this pressure differential, the diaphragm assembly 53 is moved upwardly in chamber 21. Upward movement of the diaphragm 55 moves the button 65 of the diaphragm backing plate 63 against the end portion 79 of the arm or lever 71 which pivots about the pin 69 to pull down the needle valve 33 from its seat 29. Fuel then enters the body through the nipple 19 and flows past seat 29 into the cavity or passage 23. Fuel is then delivered through the retainer 41 to the pump chamber 21 and is passed through the passage 81 into the cavity 83 for delivery through the nozzle 85 to the fuel and air mixture conduit 7.

As the fuel chamber 21 fills with fuel, the diaphragm 55 is forced downwardly toward plate 47 and spring 43 reacts against retainer 41 and flange 39 biasing the needle 33 against its seat 29. Thus fuel is delivered to the fuel chamber in response to fuel requirement in the engine transmitted through vacuum or pressure changes in the conduit 7 and engine 5. By making the fuel chamber 21 small, the apparatus is quickly responsive to changes in fuel requirements for the engine as sensed in the fuel and air mixture conduit 7.

When the throttle valve 13 is at its idle position as shown in FIGS. 1, 4 and 6, fuel passes from the fuel chamber 21 through the well 117 and passage 111 into the idle cavity 105. Air entering the upstream port 107 passes through the idle cavity and is discharged with fuel through the downstream port 108.

When the diaphragm 55 is cold and the engine is being started, the loop 59 aids in obtaining initial flexing or movement of the diaphragm assembly to open the valve assembly 27. Diaphragm loop 59 and plate 47 limit sagging of the diaphragm assembly toward plate 47 when the engine 5 is not operating, particularly when the saw or tool has been out in the cold for an extended period of time. The light weight of the diaphragm assembly (as compared with some prior art carburetors) further minimizes sagging of the diaphragm. The weight of the arm or lever 71 is carried by pivot pin 69, not by the diaphragm assembly as in some prior art carburetors, thereby further reducing the weight on the diaphragm assembly and the tendency of the assembly to sag downwardly.

The valve assembly 27 eliminates the usual outer sleeve frequently utilized with prior art carburetor constructions and also has a skeletonized needle 33 to further reduce the over-all weight of the carburetor.

Another advantage of the carburetor construction of this invention is that the diaphragm assembly 53 can be preassembled with the seal or gasket 61 adhered to the diaphragm 55 and with the diaphragm plate 63 bonded in place. The entire assembly is then easily mounted in the fuel chamber 21.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A carburetor comprising a body having a fuel and air mixture conduit, said body having, a fuel chamber and a fuel inlet passage extending to said fuel chamber, an inlet valve in said fuel passage, a diaphragm formed of flexible material extending across said chamber, said diaphragm having; a center hole and an annular preformed loop molded therein concentric with said hole, a plate secured to one surface of the diaphragm and having a button projecting through said hole in said diaphragm, valve operating means including an arm connected to said inlet valve and operable by said button for operation of said inlet valve in response to movement of said diaphragm to regulate delivery of fuel through said fuel passage to said chamber, said body having a fuel passageway formed between said fuel chamber and said fuel and air mixture conduit for transfer of fuel from said chamber to said mixture conduit, a gasket secured to said diaphragm at its margin, a cover plate clamped against the peripheral margin of said diaphragm and engaging said gasket outwardly of said loop to hold said diaphragm in position in said chamber, a portion of said cover plate constituting a stop engageable by said diaphragm plate to limit outward movement of said diaphragm plate and outward flexing of said diaphragm and, means adhesively bonding said diaphragm plate and said gasket to said diaphragm.

2. A carburetor as set forth in claim 1 having a pivot pin in said fuel chamber, and a tang struck from said arm mounting said arm on said pin with said pin carrying the weight of said arm.

3. A carburetor as set forth in claim 1 having an adjusting screw sealingly mounted in said body with a portion of the screw being located in said passageway between said fuel chamber and said fuel and air mixture conduit so that adjustment of said screw controls passage of fuel through the passageway.

4. A carburetor as set forth in claim 1 having a pin in said fuel chamber pivotally mounting said arm.

5. A carburetor as set forth in claim 1 wherein said passageway between said fuel chamber and said fuel and air conduit includes an idle cavity and two ports between said idle cavity and said conduit spaced axially along said conduit, said idle cavity having a relatively small volume.

References Cited by the Examiner UNITED STATES PATENTS 2,270,259 1/1942 Burke 92-102 X 2,645,062 7/1953 Senesky 92102 X 2,680,605 6/1954 Bracke. 2,733,902 2/1956 Phillips. 2,823,905 2/1958 Brown. 2,841,372 7/1958 Phillips. 2,984,465 5/1961 Hazzard. 3,133,129 5/1964 Phillips. 3,169,154 2/1965 Martin et al.

HARRY B. THORNTON, Primal Examiner.

RONALD R. WEAVER, Examiner.