US 2560559 A
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July 17, 1951 H; c. DEARBORN 2,560,559
GASOLINE OPERATED PNEUMATIC TO0L 4 Sheets-Sheet 1 Filed Dec. 10, 1945 July 17, 1951 H. c. DEARBORN 2,560,559
GASOLINE OPERATED PNEUMATIC TOOL Filed Dec. 10, 1945 4 Sheets-Sheet 2 Henry 0. Dem-born July 17, 1951 H. c. DEARBORN 2,560,559
GASOLINE OPERATED PNEUMATIC TOOL Filed Dec. 10, 1945 4 ;Q'Sheet-s-Sheet 5 gwue/wto'b Henry C. Dearborn July 17, 1951 H. c. DEARBORN 0,
GASOLINE OPERATED PNEUMATIC TOOL Filed Dec. 10, 1945 4 Sheets-Sheet 4 awue/rvkw Henry 02 Dearbarn Patented July 17, 1951 UNI-"TED. sr s TENT OFFICE (Granted under the act of March 3,1883, as
' amended April 30, 1928; 370 Q. G. 757) 3 Claims.
This invention-pertains to improvements in a gasoline operated pneumatic tool and especially to a, device designed as a hammer, vibrator, or pavement breaker. V
Ordinarily pneumatic tools are operated bycompressed air suplied by a compressor operated by a high horsepower engine.
An object of this invention is to provide a small, low-horsepower combustion enginaicapable of supplying the necessary combustion fuel mixture to a combustion chamber in the pneumatic tool.
Another object of this invention is to provide a pneumatic tool which is compact, light in weight, and is easily portable.
Details of the invention are described in connection with the following drawings'in which:
Fig. 1 is a diagrammatic showing of the assembly;
Fig. 2 is a longitudinal cross section of the engine;
Fig. 3 is asection pneumatic tool; i
Fig. 3a is an intermediate section of the pneu matic tool; and
Fig. 3b is the lower section oi the pneumatic tool.
"The device as shown consistsof a small two stroke cycl gasoline engine 5!! which supplies compressed combustible fuel 'to -a combustion chamber in the pneumatic tool 53. Although the engine isshown as a separate unit, it would be practical to mount the small engine directly on the pneumatic tool to become an integralpart thereof.
Details of the engine design are shown in 2. Crankshaft It! has two throws one of which is connected by means of connecting rod iii! to piston I98 in cylinder Hi3. Cylinder 198 is the power cylinder. The other throw of crankshaft i0! is connected by means of connecting rod iii to piston H! in cylinder H53. Cylinder ill} is the compression cylinder and compresses the combustion fuel for the combustion chamber of the pneumatic tool.
It will be observed that pistons use and H I travel towards each other simultaneously and in so doing cause crankcase compression in the crankcase. The gas so compressed has been drawn into the crankcase through the carburetor 40 and through poppet valve H6. When the pistons reach the bottom of th stroke, piston I09 uncovers exhaust port Hi5, and then uncovers intake port I22. This is conventional two stroke engine design. Piston H l uncovers intake port of the cylinder head in the 523 only. On the return stroke a low pressure condition is set up in the crankcase which then draws in a new charge of combustible fuel. Piston Hill advances towards spark plug t2 and into firing position while piston H-l forces its compressed charge through valve lI.-2 into manifold Crankshaft 16! carries flywheel 62 which is provided with groove H33 adapted to "receive a rope starter. Flywheel M22 provided with fan blades 84 and W3 on itscircumference. These blades provide a cooling flow-of air over the oylinders. Mounted on the underside of the flywheel are permanent magnets :1 BE and lil i which are carried past field coils l fl l to provide low tension current for a purpose later described.
Compressed fuel in'engine manifold E E5 is conducted through hose 3-5 to a manifold M on the pneumatic tool. Passage of this-gas is controlled by poppet valve .31! which can be opened or closed by the operator .upon moving grip lever 52, inasmuch as lever 92 is connected by link 38 and lever 32 to operate valve 38. Upon opening of valve 3d, gas, under pressure passes into the cylinder head manifold of the pneumatic .tool and, being under pressure, opens valve M. Valve M3 is normally held in closed position by lever 22 which is lifted by spring 28.
Compressed fuel is thus conducted to combusti'on chamber 34. Piston i chamber 3 3 is held against compression by means of long coil spring I.
Passageway 29 in the tool cylinder head con-j ducts the gas to a diaphragm switch It. When a predetermined pressure is reached diaphragm i5 is distorted to provide an electrical connection across posts It and 11. Electrical energy supplied by the engine magneto is fed through a three cable conduit 9 through line D to energize magnets 2!. This results in a lifting action on lever 22 to cause valve M to seat. The same connection causes a flow of current through wire A to energize a relay which makes a circuit with a high tension coil thereby producing a spark producing current which is conducted by high tension line l9 to spark plug 23. The spark thus produced ignites the charge in combustion chamber 34 causing piston l to strike anvil 26.
Relatively low pressure. in this manifold will cause valve i l to open.
'3 The force of the blow on the anvil is transmitted to tool bit 25. This bit is removable and interchangeable to permit the use of various types of tools and is retained by retainer spring 24.
Piston I at the bottom of its stroke uncovers ports 21A and 213 in cylinder 2. These ports permit the escape of burned fuel. Pressure being thus relieved in the combustion chamber results in automatic opening of valve M to permit an inflow of fresh gas which is compressed by the returning piston propelled by spring 1.
As previously stated, escaping gas after combustion is ejected through ports 21A and 27B and in flowing through these ports is conducted through openings in the handle support assemblies 28 and 29. The flow of exhaust gas through ports 21A and 2113 will set up a flow of air, which will cool the fins on cylinder 2.
Since it is standard practice to mix lubricating oil with the fuel in a two stroke cycle engine, adequate lubrication will be provided by the fuel.
The engine is built as small as practical for the obvious purpose of obtaining maximum weight reduction. The speed of the engine must be adequate to provide the desired fiow of combustible mixture. Thus, if the engine has only one third the displacement of the hammer it would be 'necessary to run the engine at 3000 R. P. M.s to provide 1000 hammer blows per minute.
It will be apparent that the assembly may be modified by substituting a four stroke cycle engine to pump the combustible fuel or there may be a unit to pump only air with means provided to inject fuel. may be of any desired conventional design.
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
Having described my invention, I claim:
1. In a pneumatic tool providing a tool bit, the combination of a head for said tool bit, a combustion chamber, a piston engageable with said head reciprocable in said chamber, an exhaust port uncovered by said piston at one end of its stroke, a spring for returning said piston to operative position, a manifold connected to said chamber by a port, a solenoid operated valve located in said port, ignition means in said chamber, a switch responsive to pressure in said chamber for simultaneous operation of said solenoid and said ignition means by an electrical current, a second port opening into said manifold, and a separate compressor for fuel connected to said second port by flexible conduit, said compressor comprising one cylinder of a two cylinder two cycle internal combustion engine having one carburetor for supplying fuel to the cylinder used as a compressor and to the other or driving cylinder and having a by-pass conduit connecting said flexible conduit with said crankcase with a pressure responsive valve in said by-pass, where- The body of the pneumatic tool by said compressor supplies the tool with a fuelair mixture at a constant pressure.
2. A tool comprising a combustion chamber, a piston slidable in said combustion chamber adapted to impart striking force to a tool bit, valve means opening into said combustion chamber for admitting a fuel charge, an exhaust port opening into said combustion chamber, a constant pressure compressor consisting of two cylinders mounted on and opening into a crankcase, a piston in each cylinder operative together on one crankshaft in said crankcase, a carburetor adapted to admit a fuel charge to said crankcase, passages connecting said crankcase with a port in the lower end of each of said cylinders for the conduction of fuel charges thereto, said ports being uncoverable by said pistons at their down-stroke position, a conduit connecting the first of said cylinders with said valve means on said combustion chamber, a pressure relief valve connecting said conduit with said crankcase, a second exhaust port on the second of said cylinders, and ignition means for the second of said cylinders and said combustion chamber.
3. A constant pressure compressor for supplying a fuel-air mixture to a portable explosively operated tool at a constant pressure comprising two cylinders mounted on and opening into a crankcase, a piston in each cylinder operative to gether on one crankshaft in said crankcase, a carburetor adapted to admit a fuel charge to said crankcase, passages connecting said crankcase with a port in the lower end of each of said cylinders for the conduction of fuel charges thereto, said ports being uncoverable by said pistons at their down-stroke position, a flexible conduit connecting the first of said cylinders with the inlet of the tool, a by-pass connecting said crankcase with said conduit, a pressure responsive valve in said by-pass, an exhaust port on the second of said cylinders, and ignition means for the second of said cylinders.
HENRY C. DEARBORN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 865,889 Harford Sept. 10, 1907 890,546 Wittmann June 9, 1908 1,008,863 Reuter Nov. 14, 1911 1,033,503 White 'July 23, 1912 1,088,761 Anderson Mar. 3, 1914 1,598,476 Cribier Aug. 31, 1926 1,934,935 Luxmore Nov. 14, 1933 2,394,904 Fowler Feb. 12, 1946 2,402,920 Seibold June 25, 1946 2,403,398 Reggio July 2, 1946 FOREIGN PATENTS Number Country Date 255,519 Great Britain July 21, 1926