Diaphragm carburetor

• US 6,234,456 B1
• Filed: 07/23/1999
• Issued: 05/22/2001
• Est. Priority Date: 07/25/1998
• Status: Expired due to Fees

• Current Assignee: Andreas STIHL AG & Company KG (Stihl Holding AG & Company KG)
• Original Assignee: Andreas STIHL AG & Company KG (Stihl Holding AG & Company KG)
• Inventors: Gerhardy, Reinhard
• Primary Examiner(s): Chiesa, Richard L.
• Application Number:
  US09/360,105
• Time in Patent Office: 669 Days
• Field of Search: 261/34.1, 261/37, 261/35, 261/54, 261/64.1, 261/69.1, 261/69.2, 261/71, 261/DIG.23, 261/DIG.24, 261/DIG.38, 261/DIG.39, 261/DIG.68, 261/DIG.83, 261/DIG.84
• US Class Current: 261/35
• CPC Class Codes: F02M 1/02 the means to facilitate starting or idling being chokes for enriching fuel-air mixture automatic chokes F02M1/08
• CPC Class Codes: F02M 17/04 having fuel inlet valve controlled by diaphragm
• CPC Class Codes: F02M 7/12 Other installations, with moving parts, for influencing fuel/air ratio, e.g. having valves F02M7/24 takes precedence
• CPC Class Codes: Y10S 261/68 Diaphragm-controlled inlet valve

Abstract

A diaphragm carburetor for an internal combustion engine has a carburetor housing having an intake channel with a venturi section. A plate valve is positioned in the intake channel. A fuel outlet valve is mounted in the venturi section. A fuel-filled control chamber is provided and delimited at one side by a diaphragm. A fuel supply channel is connected to the control chamber. A supply valve is mounted in the fuel supply channel and actuated by the diaphragm. A first fuel channel connects the control chamber and the fuel outlet valve. At least one fixed main throttle is mounted in the first fuel channel for fixedly determining a fuel flow cross-section to the fuel outlet valve. A lever is provided for actuating the valve plate. An adjustable stop cooperates with the lever. The flow cross-section of the intake air is adjusted by the stop to a desired air/fuel ratio and is changeable, in a limited range, in a direction of increasing the flow cross-section.

Claims

1. A diaphragm carburetor for an internal combustion engine, said carburetor comprising:

a carburetor housing (3) having an intake channel (4) with a venturi section (6);

a plate valve (7, 8) positioned in said intake channel (4);

a fuel outlet valve (19) mounted in said venturi section (6);

a fuel-filled control chamber (15);

a diaphragm (16) delimiting one side of said control chamber (15);

a fuel supply channel (13) connected to said control chamber (15);

a supply valve (14) mounted in said fuel supply channel (13) and actuated by said diaphragm (16);

a first fuel channel (18) connected to said control chamber (15) and said fuel outlet valve (19);

at least one main throttle (20) mounted in said first fuel channel (18) having a fixed fuel flow cross-section;

at least one fixed throttle (25) mounted in a second fuel channel (21) for providing a constant fuel flow to said at least one main throttle (20);

a lever (29, 34) actuating said plate valve (7, 8);

an adjustable stop (30, 35) cooperating with said lever (29, 34), wherein a flow cross-section of the intake air is adjusted by said stop (30, 35) to a desired rich mixture limit and is changeable, in a limited range, in a direction of increasing the flow cross-section.

2. A carburetor according to claim 1, wherein said lever (29, 34) is connected to a shaft (7′

, 8′

) of said plate valve (7, 8).

3. A carburetor according to claim 2, wherein said lever (29, 34) is riveted to said shaft (7′

, 8′

).

4. A carburetor according to claim 1, wherein said stop (30, 35) is continuously adjustable, wherein said lever (29, 34) has a free end, and wherein a stroke limitation of said lever (29, 34) is realized when said free end (29′

, 34′

) contacts said stop (30, 35).

5. A carburetor according to claim 1, wherein said plate valve is a throttle valve (8) positioned downstream of said venturi section.

6. A carburetor according to claim 1, wherein said plate valve is a choke valve (7) positioned upstream of said venturi section (6).

7. A carburetor according to claim 1, wherein said stop (30, 35) is an adjusting screw (31, 36) threaded into a threaded bore (33, 37) of said carburetor housing (3).

8. A carburetor according to claim 7, wherein a rotation of said adjusting screw (31, 36) between a first end position, defining a minimal flow cross-section of the intake air, and a second end position, defining a maximum flow cross-section of the intake air, is approximately 270°

.

9. A carburetor according to claim 7, wherein a direction of rotation of said adjusting screw (31, 36) is such that turning in a clockwise direction causes a reduction of the flow-cross-section of the intake air.

10. A carburetor according to claim 1, wherein an adjusting range of said plate valve (7, 8) is from 85% to 100% of a flow cross-section of said intake channel (4).