US2522550A

US2522550A - Gas hammer speed control

Info

Publication number: US2522550A
Application number: US717147A
Authority: US
Inventors: Carl S Weyandt
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-12-19
Filing date: 1946-12-19
Publication date: 1950-09-19
Anticipated expiration: 1967-09-19

Description

Sept. 19, 1950 c, s, w D 2,522,550

GAS HAMMER SPEED CONTROL Filed Dec. 19, 1946 INVHVTOR.

Cm Mm/mr Patented Sept. 19, 1950 UNITED STATES FATENT OFFICE 4 Claims.

This invention relates generall to the control of the operation of an internal combustion percussion tool and more particularly to a manual control of the speed of th timing piston of an internal combustion percussion tool to regulate the frequency of reciprocation of the working piston and prevent the timing piston from racing away from the operation of the working piston.

In internal combustion percussion tools employing a captive timing piston and a slave working piston, there is very little load on the crankshaft of the timing piston as its only function is to control the operation of the tool to generate and ignite the spark and valve the ports for the admission of fuel to the combustion chamber where the energy is transferred to the working piston for the purpose of producing useful work. Thus the speed of operation of the working piston may be regulated by the control of the speed of the timing piston. The extreme light load on the timing piston permits it to frequently speed up and thereby get out of step with the operation of the working piston causing the latter to cease operation and prevent it from delivering useful work. When the working piston gets out of step with the timing piston it fails to operate on successive explosions making the tool useless as a percussive tool.

Different types of speed devices have been employed for controlling, checking or otherwise retarding the excessive speed of the captive piston in percussive tools of this character. Some methods of producing this result is by the use of a spark cutout or throttle control. However such modes necessitate the operation of the captive piston until its friction causes it to redues in speed sufficiently to reconnect the spark or resupply the fuel and cause the tool to again function as a percussive tool. This mode of control is undesirable because it takes too long for the timing piston to reduce its speed.

Another mode of controlling the speed of the captive piston is the provision of a centrifugal governor arranged to actuate an air vane in the carburetor to check the input flow or" fuel to the engine. This reduces the speed of the captive piston by lowering the supply of fuel. However it also reduces the power input to the working piston thereby operating the tool inefficiently making an undesirable speed control.

Another mode of controlling the speed of the captive piston is by the use of a speed governor arranged to apply a centrifugal brake on the crankshaft of the captive piston. This mode requires expenditure of energy in the form of friction, and the brake mechanism is not only subjected to wear but is very sensitive and requires frequent adjustment making it disadvantageous for this use.

Another mode of controlling the speed of the captive engine is by the use of means correlated with the speed of the captive piston arranged to control the flow of exhaust gases from the internal combustion chamber to thereby regulate the speed of the operation of the tool. This mode of control produces a contaminated mixture of fuel in the combustion chamber causing a reduction of power in the tool making it undesirable as a control.

Each individual internal combustion tool has its own particular speed characteristics due to differences in friction, valve locations within manufacturing tolerances, humidity and variations in fuel for the most efiicient operation in obtaining the greatest power output. Such automatic controls functioning independently of control by th operator will not produce the most efiicient operation of the tool.

The principal object of this invention is the provision of a device providing a manual control of the speed of the captive piston which is simplified in design and which does not have the disadvantages of the automatic controls.

Another object is the provision of a manual speed control for an internal combustion percussion tool which permits the operator to exact full load operation from the tool as required at various working speeds.

Another object is the provision of a manual speed control for an internal combustion percussion tool that permits operation of the tool without decreasing the number of power strokes or the energy delivered to the percussion piston at any desired working speed.

Another object is the provision of a simple and economical manual speed control for an internal combustion percussion tool which does Fig. 1 is a sectional view of an internal combustion percussion tool having a manual fingertip speed control applied thereto.

Fig. 2 is a sectional view of the manual combustion percussion tool taken on the line 22 of Fig. 1.

The present invention provides a manually operated control of the speed of the timing piston of an internal combustion percussion hand tool. This hand tool is operated from the vertical to the horizontal position and may be employed as a hammer, a drill, a ballast tamper, a concrete buster or for performing similar useful work. This hand tool is completely self-contained as it does not require the use of a supplementary apparatus in its operation.

Referring to the drawing, the internal combustive percussive tool comprises a cylinder at having a timing piston II and the percussion working piston !2 arranged to operate therein. lhe timing piston I I is operatively connected with the balanced crankshaft i3 by means of the connecting rod M. One end of the crankshaft i3 is provided with a covered starting pulley I5 and the other end carries a flywheel IE having fan blades for the purpose of supplying a stream of air to cool the internal combustion tool. A crankcase head I! is attached to the upper end of the cylinder H] and is adapted to carry the aligned crankshaft bearings and other stationary parts of the gas hammer, such as the bracket l8 on which is mounted a handle [9 with the fuel throttle lever together with the housing 2| which encloses the flywheel Hi, the fuel tank 8, and the carburetor 9. All of these parts are secured to the crankcase l1 and the cylinder H) and provides a relatively small and compact and unitary tool.

A tool holding member 22 is bolted to the lower end of the cylinder I!) by means of the four tie bolts 23 which are fastened at their upper ends through the bracket l8 and which extend the full length of the crankcase head I1 and cylinder [0. The tool holding member 22 is bored to receive the working piston guide 24 which extends into and fits the bore of the differential chamber 25 of the cylinder H3, and is provided with a flange clamped between the end of the cylinder and tool holding member as shown in Fig. 1.

The percussive working piston l2 has a depending stem 26 with a striking portion extending through the guide 24 and is arranged to strike the top of the tool 2'! which is slidably supported within predetermined limits in the bore of the tool holding member 22 and is re tained by the spring latching member 28.

The percussive working piston I2 is a differential piston and the combustion or smaller end of this piston controls the port leading from the combustion chamber 30 through the valve control passageway 3! to the chamber 25 at the other end of the working piston for supplying products of combustion under pressure which are effective against the larger end of the working piston !2 for returning the same. The valve 32 in the passageway 31 is actuated by means of the reach rod 29 pivotally connected to the handle throttle lever 20 mounted on the handle I9, which throttle also controls the operation of the carburetor in supplying fuel to the engine.

The flywheel i6 is hollow and encloses a magneto and braker points for the purpose of'supplying the ignition of the internal combustion tool. These points are not shown but the braker arm cam is shown on the crankshaft at 33. The fan blades 34 are attached to the outer face of the flywheel I5 adjacent its perimeter and they form a vortex which is disposed adjacent the screened opening 35 in the housing 2! that surrounds the fan and tapers downwardly to around the lower end of the cylinder ll] partially covering the same, causing the air stream generated by the fan to flow transversely around the cylinder H3 between the cooling fins.

A brake pulley 36 is an integral part of the starting pulley l5 and lies between this pulley and the crank head housing IT. The brake pulley 35 consists of a rim section 53 connected by spokes 54 to the hub 55 of the starting pulley i5. As shown in Fig. 2 the rim 53 is in section and the upper part of the pulley is shown in elevation as indicated at 56. This pulley is slightly larger in diameter than the starting pulley and is provided with a perimetral surface functioning as a friction brake surface. The brake band lining 31 comprises the strap member 38 secured at one end to the bolt 40 which is adjustably fastened to the bracket it by the nuts ii and as. The lining 31 is secured to the band 3.8 by the usual rivet members 43. The other end of the band 38 is provided with a cylindrical socket member M which is slotted in the center as indicated at 5 for the purpose of receiving the stem portionfi of the manual control member ll. The lower end of the stem 456 is secured to the cross member 48 pivotally carried in the cylindrical socket member M. The upper end of the stem iii projects into an opening in the underside of the handle l9 and is provided with an offset bracket member 50, the outer end 5| of which is turned outwardly and arranged to engage on the bottom of the tubular handle member l 9 thus limiting the downward movement of the control member d1. The offset portion of the bracket member 59 is provided with a finger engaging 'surface 52 directly below the throttle lever 20.

The brake band 38 is adjusted by the nuts 4! and 42 to provide clearance for the pulley 36 when the stop 5! is at its lowermost position as shown in Fig. 2'. Any slight upward pressure on the finger engaging surface 52 causes the brake band to be contracted on the brake pulley 36 effecting a friction brake on the surface of the brake pulley. A slight application of this brake band is immediately effective to reduce the speed of the shaft i 3 thereby reducing the speed of the captive timing piston H. The application of the brake band on the pulley is such that it tends to draw the brake band into frictional engagement when brake pressure is applied thereto.

During operation of the internal combustion percussion tool the operator in supporting the tool by the tubular handle if! can feel when a change in load on the tool causes the captive timing piston to increase its speed, and immediately check the speed of the timing piston and thus maintain the same output of the working piston regardless of the change in load on the tool. In fact the operator can anticipate changes in load by watching the work of the tool, and with a slight application of the brake reduce the speed of the timing piston before it has had a change to race away from the operation of the working piston.

By manually controlling the operation of the internal combustion percussive tool in this manner maximum output may be obtained from the tool at all times irrespective of the change in load. This improved operation is not obtainable by any of the other modes of controlling the speed of the captive timing piston and represents the most important feature of this invention. By the use of this manual brake control, an operator is enabled to obtain maximum work per unit of time which is impossible by the use of any automatic control. This also represents a very important object of this invention.

An important object of this invention is the provision of a speed control for an internal combustion percussion tool which permits the operator to instantly regulate the striking power of the blow of the tool between zero and a maximum power output and also permits him to stop the tool instantly and independently of the throttle. This control of the power output of the tool cannot be obtained to the same extent by other modes of controlling the speed of the hammer. It is exceedingly important to provide instant power control over a percussion tool of this character as it increases its utility and permits the operator to work with greater efficiency.

The operator may constantly apply a predetermined load on the timing piston through the brake to operate the percussion working piston at any desired working speed and exact maximum power output on each power stroke of the working piston. Thus the operator has complete control over the independently operating working piston by controlling the speed of the timing piston and thereby controlling the timing of combustion in the combustion chamber. When supporting the tool during operation, the operator can grip the throttle with the handle [9 to maintain the throttle fully open and at the same time apply the brake with his index finger to control the timing of combustion. Very little energy is necessary to apply the brake and the tool may be readily stopped by increasing the pressure by the index finger.

This application is a continuation in part of application Serial No. 496,709 filed July 30, 1943 for Internal Combustion Percussion Tool, now Patent Number 2,433,007.

I claim:

1. In an internal combustion percussion tool, the combination of a casing having a combustion chamber, a timing piston reciprocable in said I combustion chamber to control the combustion of fuel therein, a percussion working piston reciprocable in the combustion chamber and driven in a working direction by the combustion of fuel and returned by exhaust gas, a crankshaft cari ried by the casing and operated by the timing piston, a throttle carried by the casing for regulating the supply of fuel to the combustion chamber, and manually operated brake means positioned to be actuated simultaneously with the throttle for applying a load on the crankshaft to control the speed of the timing piston and regulate the frequency of reciprocation of the working piston.

2. In an internal combustion percussion tool, the combination of a casing having a combustion chamber, a timing piston reciprocable in said combustion chamber to control the combustion of fuel therein, a percussion working piston reciprocable in the combustion chamber and driven in a working direction by the combustion of fuel and returned by exhaust gas, a crankshaft carried by the casing and operated by the timing piston, a brake pulley secured to said crankshaft, a brake band arranged to be contracted on said pulley, and a finger engaging surface attached to said brake band for applying a load on the crankshaft to control the speed of the timing piston independently of the combustion of fuel and regulate the frequency of reciprocation of the working piston.

3. In an internal combustion percussion tool, the combination of a casing having a guide handle and a combustion chamber, a timing piston reciprocable in said combustion chamber to supply and ignite the fuel and control the exhaust of the products of combustion from the combustion chamber, a percussion working piston reciprocable in the combustion chamber and driven in a working direction by the combustion of fuel and returned by exhaust gas, a throttle pivoted on the guide handle for regulating the flow of fuel supply, a crankshaft carried by the casing and operated by the timing piston, brake means on said crankshaft, and a finger control carried by the guide handle and positioned to be actuated simultaneously with the throttle for applying a load through the brake on the crankshaft to control the speed of the timing piston and regulate the frequency of reciprocation of the working piston without decreasing the power of combustion.

4. In a percussion tool, the combination of an internal combustion engine having a timing piston operating to control the combustion of fuel therein and a percussion working piston driven in a working direction by the combustion of fuel and returned by the pressure of exhaust gas, and manually operated brake means effective to control the speed of the timing piston independently of its operation and the amount of fuel supplied to the combustion chamber to regulate the frequency of operation of the working piston.

CARL S. WEYANDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,490,850 Porsche Apr. 15, 1924 1,920,765 Rasch Aug. 1, 1933 2,433,007 Weyandt Dec. 23, 1947