GB2533680A

GB2533680A - Interconnecting mechanism for choke in rotary-valve carburetor

Info

Publication number: GB2533680A
Application number: GB1518071.4A
Authority: GB
Inventors: Shen Wei; Liu Kai; Dai Wei-Ming; Pei Yong
Original assignee: Jiangsu Sumec Hardware and Tools Co Ltd
Current assignee: Jiangsu Sumec Hardware and Tools Co Ltd
Priority date: 2014-12-22
Filing date: 2015-10-13
Publication date: 2016-06-29
Anticipated expiration: 2035-10-13
Also published as: GB2533680B; CN104533663A; DE102015116744B4; CN104533663B; GB201518071D0; DE102015116744A1

Abstract

An interconnecting mechanism of a choke in a rotary-valve carburettor 11. The rotary valve 13 has an arm 12 which is radially formed with a first boss (A). A gear wheel 7 is engaged with one side of a gear rack 5 which has an inclined plane on a bottom thereof near the rotary valve arm, and the inclined plane is provided with a hooked step (B) for engaging with the rotary valve arm boss (A). The gear wheel has a second boss (C) near the choke 10, and the choke has a third boss (D) that corresponds to the second boss. The second boss and the third boss are interlocked to interconnect the gear wheel and the choke. The mechanism simplifies the structure of control lever and simplifies operation of cold start. During cold start, there is no need to separately control the choke and the rotary valve in terms of opening. and after warming up, there is no need to manually open the choke.

Description

INTERCONNECTING MECHANISM FOR CHOKE IN ROTARY-VALVE CARBURETOR

TECHNICAL FIELD

[0001] The present invention relates to an interconnecting mechanism for a choke in a rotary-valve carburetor, and belongs to the technical field of mechanical structure.

DESCRIPTION OF RELATED ART

[0002] A rotary-valve carburetor adjusts intake of combustible mix gas by rotating its rotary valve to control both the throttle and the main gauging hole in terms of opening.

Such a carburetor is extensively used in engine-driven gardening device such as gasoline mowers, brush cutters and branch shears. Compared to butterfly valve carburetors that are equally popular, a rotary-valve carburetor provides better fuel atomization and is structurally simpler. The simple structure is favorable to quality control of gasoline engine products. However, the existing rotary-valve carburetors also have some inherent shortcomings as compared to butterfly valve carburetors.

[0003] For ensuring successful start of engines in low-temperature conditions and simplifying operation to be best possibility, a butterfly valve carburetor usually has its choke and its throttle connected by an interconnecting mechanism. The interconnecting mechanism has two functions: 1) when the choke is closed, the interconnecting mechanism makes the throttle have a certain size of opening, so as to get enough air intake and combustible mix gas concentration for the engine to start at low temperature; and 2) after the engine is started and gets warm, interconnecting mechanism can makes the choke open automatically when the throttle is operated.

[0004] Due to its structure, a butterfly valve carburetor has its choke shaft and throttle shaft adjacent and parallel to each other, and this is an advantage hard to get in a rotary-valve carburetor.

[0005] Presently, the commercially available rotary-valve carburetors adopt three approaches to better low-temperature start: 1. Providing a completely independent choke mechanism on the air filter connected to the carburetor, wherein opening and closing of the choke fully depend on manual operation; 2. Providing a mechanism on the carburetor for making the rotatory valve rise in the axial direction, wherein the mechanism and the rotatory valve interconnect each other, in which the mechanism is to be activated by manually pressing a button associated therewith before low-temperature cold start in order to rise the needle valve for a certain level for increased oil supply quantity, and after the engine is started and gets warm, the control lever is operated to rotate the carburetor's rotatory valve and the mechanism returns to its initial position; and 3. Providing a choke on the air filter connected to the carburetor, wherein the choke and the rotary valve are connected via an interconnecting mechanism, so that when the control lever is operated to move the carburetor's rotary valve, the interconnecting mechanism trigger the choke to open, in which the motion of the choke does not lead to the motion of the rotary valve.

[0006] In the first scheme, the choke is independent. For ensuring that the carburetor provides enough oil supply quantity when the choke is closed, an additional throttlehalf-open button has often to be provided on the control lever to better control the opening of the rotary valve. As to the second scheme that involves no use of a choke, the oil supply during idling is increased by using the rotary valve to achieve positional change of the needle valve. At the same time, for maintaining proper rotational speed of the engine during idling, the initial opening of the rotary valve has to be limited. Thus, when the ambient temperature is low, even if the concentration of the mix gas is increased, air intake can never be effectively increased, leaving the cold start operation less effective. While the third scheme does achieve interconnection between the rotary valve and the choke, in case of cold start, an additional throttle-half-open button on the control lever is also required for controlling the opening of the rotary valve.

[0007] None of the aforementioned schemes can achieve motional interconnecting between the choke and throttle like that seen in the butterfly valve carburetor. The first and third schemes require controlling the positions of the choke and of the rotary valve separately, so the operation is complex. While the second scheme is easy to perform, it is relatively ineffective in cold start.

SUMMARY OF THE INVENTION

[0008] Objective: for overcoming the shortcomings of the prior art, the present invention provides an interconnecting mechanism for a choke in a rotary-valve carburetor, which realizes interconnected control form the choke to the rotary valve.

The design simplifies the structure of control lever and simplifies operation of cold start. During cold start, there is no need to separately control the choke and the rotary valve in terms of opening, and after warming up, there is no need to manually open the choke. All the main components are received in the air filter without making significant structural change to the carburetor, and the exterior of the carburetor can remains unchanged.

[0009] Technical scheme: for addressing the technical problems as mentioned above, the present invention implements the following technical scheme: an interconnecting mechanism for a choke in a rotary-valve carburetor, the interconnecting mechanism comprising an air filter casing, a gear rack, a gear wheel, the choke, the carburetor, a rotary valve arm, and a carburetor rotary valve, the carburetor including a carburetor rotary valve, the rotary valve arm being affixed to the carburetor rotary valve; the interconnecting mechanism being characterized in: the rotary valve arm being radially formed with a first boss; the gear wheel being engaged with one side of the gear rack; the gear rack having an inclined plane on a bottom thereof near the rotary valve arm, and the inclined plane being provided with a hooked step for engaging with the first boss of the rotary valve arm; the gear wheel having a second boss near the choke, and the choke having a third boss that is configured to match the second boss, wherein the second boss and the third boss are interlocked to interconnect the gear wheel and the choke in terms of motion.

[0010] The interconnecting mechanism is characterized in that: the choke is provided with a rotatory shaft that passes through a through hole formed on the air filter casing and is inserted into a center hole of the gear wheel, in which a torsion spring is mounted around the rotatory shaft for returning the choke and has one end fixed in the air filter casing and an opposite end connected to the choke.

[0011] The interconnecting mechanism is characterized in that: the gear rack is provided with a compression spring for returning the gear rack.

[0012] The interconnecting mechanism is characterized in that: the gear wheel is equipped with a lever that is operatable to drive the gear wheel to rotate; [0013] The interconnecting mechanism is characterized in that: the gear wheel is made from material that includes POM (Polyoxymethylene) or the gear rack is atop provided with a handle that is operatable to drive the gear rack to move downward.

[0014] As a preferred scheme, the interconnecting mechanism is characterized in that: the rotary valve arm is provided with a fixed throttle-cable support that has a rotary centerline parallel to a rotary centerline of the rotary valve arm and has a flat upper surface [0015] The interconnecting mechanism is characterized in further comprising a gear wheel cover that is fixedly connected to the air filter casing and is provided with a downward-facing boss, wherein the boss has a bottom facing the upper surface of the fixed throttle-cable support and the boss of the gear wheel cover restricts upward displacement of the carburetor rotatory valve by restricting displacement of the fixed throttle-cable support.

[0016] As a preferred scheme, the interconnecting mechanism is characterized in that: the gear wheel cover is fixedly connected to the air filter casing by means of a fastening bolt.

[0017] As a preferred scheme, the interconnecting mechanism is characterized in further comprising a retaining ring that is arranged between the rotatory shaft of the choke and the gear wheel.

[0018] Beneficial effects: the disclosed interconnecting mechanism realizes interconnected control from the choke to the rotary valve. With the interconnecting mechanism, while the choke is closed, the rotary valve is driven to rotate for a small angle. After the choke is closed, in response to an opposite control force applied to the lever or the handle or due to the counterforce of the spring itself, the carburetor's rotary valve moves upward, so as to drive the valve pin to move upward. When the upper surface of the fixed throttle-cable support on the rotary valve arm contacts the bottom of the boss of the gear wheel cover, the carburetor's rotary valve stops moving. This process contributes to increased air intake of the rotary valve and the increased oil supply quantity of the needle valve, thereby facilitating cold start. Upon completion of cold start, by operating the lever to make the throttle cable drive the rotary valve to rotate, the choke opens. The design simplifies the structure of control lever and simplifies operation of cold start. During cold start, there is no need to separately control the choke and the rotary valve in terms of opening, and after warming up, there is no need to manually open the choke. All the main components are received in the air filter without making significant structural change to the carburetor, and the exterior of the carburetor can remains unchanged.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a perspective view of a first embodiment of the present invention; FIG. 2 is an exploded view of the first embodiment of the present invention; FIG. 3 is a perspective view of the gear wheel and the choke assembled together according to the present invention; FIG. 4a and FIG. 4b show initial and returned states of the first embodiment of the present invention; FIG. 5a and FIG. 5b show initial and returned states of the first embodiment of the present invention; FIG. 6a and FIG. 6b depict the first embodiment of the present invention wherein the choke is closed; FIG. 6c illustrates the relation between the carburetor rotary valve and the rotary valve arm as well as the proportional relation between the valve pin and the main gauging hole; FIG. 7a is a perspective view of a second embodiment of the present invention; FIG. 7b is an exploded view of the second embodiment of the present invention; FIG.8a is an exploded view of the third embodiment of present invention; FIG.8b and Sc show initial and returned states of the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be further explained with reference to some particular embodiments.

[0021] Embodiment 1: As shown in FIG. 1 through FIG. 6, an interconnecting mechanism for a choke of a rotary-valve carburetor comprises an air filter casing 8, a gear rack 5, a gear wheel 7, a choke 10, a carburetor 11, a rotary valve arm 12, and a carburetor rotary valve 13. The carburetor 11 includes the carburetor rotary valve 13 to which the rotary valve arm 12 is attached. The rotary valve arm 12 is radially formed with a first boss A. The gear wheel 7 is engaged with one side of the gear rack 5. The gear rack 5 has an inclined plane on a bottom thereof near the rotary valve arm 12, and the inclined plane is provided with a hooked step B for engaging with the first boss A of the rotary valve arm 12. The gear wheel 7 has a second boss C near the choke 10, and the choke 10 has a third boss D that is configured to match the second boss C. The second boss C and the third boss D are interlocked to interconnect the gear wheel 7 and the choke 10 in terms of motion.

[0022] The choke 10 is provided with a rotatory shaft that passes through a through hole formed on the air filter casing and is inserted into a center hole of the gear wheel 7. A torsion spring 9 is mounted around the rotatory shaft for returning the choke and has one end fixed in the air filter casing and an opposite end connected to the choke. The gear rack 5 is provided with a compression spring 4 for returning the gear rack. The compression spring 4 is firmly pressed by a compression spring stop 3. The gear wheel 7 is equipped with a lever 15 that is operatable to drive the gear wheel 7 to rotate.

[0023] The rotary valve arm is provided with a fixed throttle-cable support 17 that has a rotary centerline parallel to a rotary centerline of the rotary valve arm 12 and has a flat upper surface E. [0024] The interconnecting mechanism further has a gear wheel cover that is fixedly connected to the air filter casing. The gear wheel cover 2 is provided with a downward-facing boss. The boss has a bottom F facing the upper surface E of the fixed throttle-cable support 17. The boss of the gear wheel cover restricts upward displacement of the carburetor rotatory valve 13 by restricting displacement of the fixed throttle-cable support 17.

[0025] As a preferred scheme, the interconnecting mechanism is characterized in that: the gear wheel cover 2 is fixedly connected to the air filter casing 8 by means of fastening bolts 1.

[0026] Further, as a preferred scheme, the disclosed interconnecting mechanism also comprises a retaining ring 6 that is arranged between the rotatory shaft of the choke 10 and the gear wheel 7.

[0027] Embodiment 2: as shown in FIG. 7a and FIG. 7b, instead of the lever 15 on the gear wheel 7 as described in Embodiment 1, a handle 16 is attached to the top of the gear rack 5 for driving the gear rack 5 to move downward. The handle 16 is exposed outside the air filter casing 8, so that an operator can use the handle 16 to operate the choke 10 and the carburetor rotary valve 13.

[0028] Embodiment 3: as shown in FIG. 8a to FIG. Sc, there is no compression spring 4 on the gear rack 5 and the height can be reduce. The gear wheel 7 is made from material that includes POM to provide the elasticity. There is a cut 71 on the gear wheel 7 near the hooked step B of the gear rack 5.

[0029] The present invention uses a specially designed rotary valve arm to replace the existing one conventionally seen in rotary-valve carburetors. The disclosed rotary valve arm 12 is novel for have radially a first boss A for transmitting displacement.

[0030] An air filter box having an air filter that is configured to work with the foregoing carburetor assembly comprises an air filter casing 8 that is level with the plane in which the air inlet of the carburetor 11 is located, and is fixed to the heat-insulating seat of the cylinder by means of mounting bolts. In the air filter casing, there are a transmission composed of a gear wheel 7 and a gear rack 5, a rotatable choke 10, a rotatory shaft passing through the center hole of the gear wheel. The rotation of the gear wheel 7 can be transmitted to the choke 10 via the connecting structure between the gear wheel 7 and the choke 10 (i.e. the second boss C and the third boss D). The gear wheel or the gear rack can drive the choke to close. Also comprised are at least one torsion spring 9 that makes the choke peripherally return, and an optional compression spring 4 acting in an axial direction of the gear rack 5 to help the choke to return. The gear rack 5 has an inclined plane whose terminal is formed with a hooked step B. The inclined plane helps to ensure that when the choke is open, the inclined plane and the rotary valve arm 12 are separated by a certain interval. The gear rack moves downward and the inclined plane pushes the rotary valve arm to rotate. When the gear rack move downward to the extent that the hooked step B is lower than the bottom of the first boss A, the gear rack 5 and the rotary valve arm 12 interlock each other. The carburetor rotary valve 13 opens with a small angle. Another function of the return spring (i.e. the compression spring 4 or the torsion spring 9) is that when the external force from the operator stops, the gear rack 5 returns upward and drives the rotary valve arm 12 to make the carburetor rotary valve 13 axially rise for a predetermined distance. This enlarges the nozzle of the carburetor, and in turn increases the oil supply quantity of the carburetor. Upon completion of the engine's cold start, the operator operates the throttle cable to drive the rotary valve arm to rotate, thereby dismissing the interlock between the gear rack 5 and the rotary valve arm 12. The choke then automatically opens. Throughout the above-mentioned process, the gear wheel 7, the gear rack 5, the choke 10, the rotary valve arm 12, and the carburetor rotary valve 13 remain interconnected in terms of motion.

[0031] The present invention works as follows: When the lever of the gear wheel 7 is moved clockwise as indicated in the drawing, the rotatory motion is converted to the linear motion of the gear rack 5 in the axial direction of the carburetor rotary valve 13. Alternatively, the handle 16 on the gear rack 5 is directly pushed downward, so that the inclined plane at the end of the gear rack 5 contacts the first boss A of the rotary valve arm 12, and the rotary valve arm 12 is pushed to rotate. When the gear rack 5 moves to its bottommost, the hooked step on the plane B of the gear rack 5 comes to interlock with the bottom of the first boss A of the rotary valve arm 12, as shown in FIG. 5a. As the gear wheel 7 rotates, the second boss C on the lever of the gear wheel 7 pushes the third boss D on the choke 10, so as to close the choke 10, as shown in FIG. 5b. This increases the vacuum at the carburetor's throat during start.

[0032] After the gear rack 5 and the rotary valve arm 12 interlock with each other, once the external force exerted on the rotary valve arm 12 is eliminated, the counterforce from the compression spring 4 and from the torsion spring 9 makes the rotary valve arm 12 axially move upward, in turn driving the valve pin 14 to move upward. When the upper surface E of the fixed throttle-cable support 17 on the rotary valve arm contacts the lower surface F of the boss on the gear wheel cover, the carburetor rotary valve stops moving, as shown in FIG. 6a and FIG. 6b. This enlarges the opening of the gauging hole G of the main nozzle 18, as shown in FIG. 6c, and in turn increases the oil supply quantity of the carburetor. When the upper surface E of the fixed throttle-cable support 17 on the rotary valve arm 12 contacts the lower surface F of the boss on the gear wheel cover 2, the needle valve 14 rises to the preset altitude, so as to ensure the concentration of the mix gas is high enough for the clod start of the engine.

[0033] Upon completion of the clod start of the engine, the rotary valve arm 12 is pulled via the throttle cable, so the first boss A of the rotary valve arm 12 disengages from the hooked step B on the inclined plane of the gear rack 5. Then the gear rack 5 is returned to its initial position by the compression spring 4, and this in turn drives the gear wheel 7 to return. At the same time, the torsion spring 9 makes the choke 10 to return to its initial position.

[0034] The present invention has been described with reference to the preferred embodiments and it is understood that the embodiments are not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present invention should be encompassed by the appended claims.

Claims

CLAIMS: 1. An interconnecting mechanism for a choke in a rotary-valve carburetor, the interconnecting mechanism comprising an air filter casing, a gear rack, a gear wheel, the choke, the carburetor, a rotary valve arm, and a carburetor rotary valve, the carburetor including a carburetor rotary valve, the rotary valve arm being affixed to the carburetor rotary valve; the interconnecting mechanism being characterized in: the rotary valve arm being radially formed with a first boss; the gear wheel being engaged with one side of the gear rack; the gear rack having an inclined plane on a bottom thereof near the rotary valve arm, and the inclined plane being provided with a hooked step for engaging with the first boss of the rotary valve arm; the gear wheel having a second boss near the choke, and the choke having a third boss that is configured to match the second boss, wherein the second boss and the third boss are interlocked to interconnect the gear wheel and the choke in terms of motion.
2. The interconnecting mechanism of claim 1, being characterized in that: the choke is provided with a rotatory shaft that passes through a through hole formed on the air filter casing and is inserted into a center hole of the gear wheel, in which a torsion spring is mounted around the rotatory shaft for returning the choke and has one end fixed in the air filter casing and an opposite end connected to the choke.
3. The interconnecting mechanism of claim 1, being characterized in that: the gear rack is provided with a compression spring for returning the gear rack.
4. The interconnecting mechanism of claim 1, being characterized in that: the gear wheel is equipped with a lever that is operatable to drive the gear wheel to rotate.
5. The interconnecting mechanism of claim 1, being characterized in that: the gear rack is atop provided with a handle that is operatable to drive the gear rack to move downward.
6. The interconnecting mechanism of claim 2, being characterized in that: the rotary valve arm is provided with a fixed throttle-cable support that has a rotary centerline parallel to a rotary centerline of the rotary valve arm and has a flat upper surface.
7. The interconnecting mechanism of claim 6, being characterized in further comprising a gear wheel cover that is fixedly connected to the air filter casing and is provided with a downward-facing boss, wherein the boss has a bottom facing the upper surface of the fixed throttle-cable support and the boss of the gear wheel cover restricts upward displacement of the carburetor rotatory valve by restricting displacement of the fixed throttle-cable support.
8. The interconnecting mechanism of claim 7, being characterized in that: the gear wheel cover is fixedly connected to the air filter casing by means of a fastening bolt.
9. The interconnecting mechanism of claim 7, being characterized in further comprising a retaining ring that is arranged between the rotatory shaft of the choke and the gear wheel.
10. The interconnecting mechanism of claim 1, being characterized in that: the gear wheel is made from material that includes POM.