US1997070A - Internal combustion tool - Google Patents

Description

April 9, 1935.

J. A. MOULD INTERNAL COMBUSTION TOOL Filed July 11, 1931 INVENTOR MMUMMQ A'ITORNEYS 5 UNITED STATES PATENT OFFICE INTERNAL COMBUSTION TOOL James A. Mould, Milwaukee, Wis., assigner to Gas Tool Patents Corporation, Chicago, lll., a corporation of Delaware 1 Application July 11, 1931, serial No. 550,180

5 Claims.

'I'his invention relates to improvements in internal combustion tools. The present application is a companion to applications led July 11, 1931 by me, respectively bearing Serial Numbers 550,188 and 550,187 and-entitled respectively Internal combustion hammers and Internal combustion engines. 'This application is also a con-- tinuation in part of my application Serial No. 227,656. n1ed October 21, 1927 and entitled Internal combustion hammers.

Internal combustion hammers as previously constructed have been subject to rather frequent y breakage ofthe compression spring which supports the piston andimpels it during the compression stroke. Ordinarily, such breakage is overcome by reducing the temper of the spring, but in a tool of this character the power and effectiveness of the tool were found to be materially decreased by reduction in spring temper to the point that the tool became virtually inoperative without overcoming the problems of breakage. Experiments with various styles, types and sizes of springs have disclosed the fact that no spring known to spring manufacturers was capable of withstanding the successive vibratory shocks of the tool without crystallization while at the same time maintaining an operative spring load for the proper actuation of the piston. One. of the most important features of the present invention consists in the provision of a spring assembly by vmeans of which crystallization and breakage may be avoided in a spring subject to compression under the conditions of heat and shock existing in an internal combustion tool of this type.

It has further been found that the gauge and temper of the spring wire employed in the tool are critical. It hastaken years of experimentation to ascertain and reconcile the various factors involved in this problem and to provide an internal combustion tool with springs which will function satisfactorily over long periods of time and without breakage.

In the drawing:

Figure 1 is a vertical axial section through a device embodying this invention.

Figure 2 is a view in elevation illustrating in separated positions the component parts of the composite spring used in accordance with this invention.

Like parts are identified by the same reference characters throughout the several views.

In the particular device illustrated, the cylinder 3 has a jacket 4 provided with ns at 5 for heat radiation. The cylinder has an integral head shouldered at 6 to limit the upward movement of the piston 1. Above thelimit of piston movement is a spark plug 8 for igniting the charge.

The piston 1 carries a hammer 9 arranged to impact an anvil I0 guided for limited axial reciprocation in a bottom closure member II connected with the cylinder. Through the closure member II is applied a tool guide I2 adapted to receive any desired tool such as the drill shank I3 which extends into the socket I4 in anvil I Il to receive impact therefrom.

The sub-piston compression space includes th lower end of cylinder 3 and the upper end of closure member II into which leads charge admission port I5 from the charge forming device I I-more fully described in the companion applications above referred to. Transfer of the charge from the sub-piston compression space to the combustion chamber is effected under the control of piston 1 through passages |60 in the piston itself, and a cavity I1 in the wall of the cylinder. The device operates on the two cycle principle, the burned gases escaping through exhaust manifold I8 in the extreme lower position of the piston.

Ignition is controlled directly from the side of piston skirt and co-acting with a cam follower 20 carrying a timer contact 2| which moves to and from engagement with a spring mounted relatively xed timer contact 22.

`Since no crank shaft is employed, it is necessary to provide for spring return of the piston on its compression stroke. The present invention relates particularly-to the means for thus effecting piston return.

The piston spring'proper is shown at 25. It is a low pitch spring, preferably a gauge No. 7 W. 8: M. The gauge is rather critical and should be confined between W. & M. gauges 5 and 9 inclusive Anything beyond this range of sizes has been found inadequate of the device.

The temper of spring 25 is very critical. Long experience of spring manufacturers has Rockwell C Scleroscope scale degree average of Brinell cone kilomodels C and D numbers gram load scleroscopes As above noted, the ordinary remedy for spring breakage is to reduce the temper. In this particular instance, however, it has been found that the only satisfactory tempers for'the piston spring 25 are those ranging from Rockwell 46 to Rockwell 52 with a decided preference for tempers between Rockwell 48 and 50. A spring of-No. 7 W. & M. gauge and Rockwell 48 to 50 temper, 8% inches long and of the low pitch indicated in the drawing will, in the first few hours of use, take a permarient set at approximately 811g inches under an initial load, during use, of approximately 35 lbs. and an extreme load of approximately 117 lbs. After this initial set the spring will operate the piston over long periods of time without injury, breakage, or furtherchange of form.

In practice, the piston spring 25 is preferably supported on, a much heavier spring 26 which maintains the spring loading of spring. 25 and functions irf;l an important manner to absorb /shocks to which the apparatus is subject in operation and which might otherwise crystallize the piston spring 25. The gauge and temper of the supporting and shock absorbing spring 26 is not critical. It has been found satisfactory to use No. 4 W. & M. gauge and the customary 42 to 44 Rockwell hardness temper. The length of this spring in practice is l-- inches before it is subjected to pressure in the device.

It will be noted that the piston spring is guided about the hammer 9 while the supporting spring. 26 is guided about a boss on the upper end of anvil I0. In order to eliminate the necessity of any intermediate spring seat, and to prevent the coils of the two springs from interwinding, I prefer to wind the springs in opposite directions.

A supporting spring 26 maintains the piston normally at the top of the cylinder. The device is set in motion by supplying its timer with ignition current and its sub-piston compression space with a combustible charge, and by thus displacing the piston downwardly by means of the plunger mounted in the top of the cylinder. In the downward movement of the piston the piston spring 25 is compressed, and when the plunger is sharply released the piston is spring pressed t'oward its original position to compress the charge in the combustion chamber and control the operation of the timer for ignition.

Upon ignition of the charge in the combustion chamber, its sudden expansion drives the piston down by fluid pressure, thereby compressing a fresh charge for delivery to the combustion chamber and also subjecting spring 25 to pressure until its several coils are in substantial contact. At approximately this time the hammer carried by the piston will strike the anvil with a sharp percussion which would rapidly crystallize the piston spring but for the fact that said spring is supported resiliently on spring 26. Since the entirefspring system is under pressure in all piston positions, spring 26 will tend to expand sulficiently to take up any loss in the length of the spring system which may be occasionedby the shrinkage or set of spring 25.

I claim: 1. In an internal combustion tool, the combination with a cylinder, means for introducing and igniting a charge therein, a piston reciprocable in the cylinder, a hammer carried by the piston, and an anvil in the path of the hammer, of a spring system acting on the piston in a direction to return it from the anvil, said system including relatively longer and shorter springs, the longer spring having a temper of Rockwell 46 to 52 inclusive and a gauge ofI W. & M. 5 to 9 inclusive, and the shorter spring having `a lower temper and a larger gauge than the longer spring.

2. In an internal combustion tool, the combination with a cylinder, means for introducing and' igniting a charge therein, apiston reciprocable in the cylinder, a hammer carried by the piston, and an anvil in the path of the hammer, of a piston return spring subject to percussion shock upon engagement of the hammer with the anvil and provided with a resilient mounting, said piston spring comprising a relatively long spring having a temper in excess of Rockwell hardness 46 and a gauge less than 5, and said mounting comprising a relatively shorter spring of heavier gauge and lower temper.

y 3. The combination with a heavy part movable to and from engagement with a stop whereby to be subject to percussion, of a spring. sustaining the load of said part and urging said part from said stop, means for intermittently applying abruptly to said part a pressure wholly in excess of that of said spring and opposed thereto, whereby invariably to cause the-sharp striking of said stop by said part, and a yieldable mounting for said spring interposed between said stop and spring, said mounting being yieldable only to pressures of surge and impact in excess of those required for the support of said part, whereby to cushion said spring from the crystallizing effect of impact of said part upon said stop.

4. In a device of the character described, the combination' with a cylinder, a piston, a hammer connected with said piston and an anvil, of a compression spring acting upon said hammer and piston in opposition to the movement thereof toward said anvil, said spring being of adequate strength to store a portion of the energy developed in such movement, and a secondary spring adapted to act through the first in opposition to such movement and so constructed as to be stronger than said first mentioned spring, whereby to provide a resilient mounting adapted to absorb shock resulting from the'blow of said hammer on said anvil.

5. In a device of the character described, the

combination with a cylinder, a reciprocable piston therein, a hammer connected with said piston and an anvil in the path of said hammer, of spring means conned between said anvil and piston and comprising a relatively long spring of adequate strength to receive a portion of the energy developed by piston movement toward said anvil and to return said piston from said anvil,

series therewith between said piston and said anvil, whereby to be adapted to absorb shock to said first mentioned spring, said spring being oppositely wound whereby each provides a seattor the other. 1 JAMES A. MOULD.

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