US2871835A - Power operated hammers - Google Patents

Description

Feb. 3, 1959 H. L. HOCKEL ET AL 2,871,835

POWER OPERATED HAMMERS Filed July 2', 1956 Q Kw o a In A 1 W: H F 4 In .II: y 6 3 M 59%8 ire States Patent iii Patented Feb. 3, 1959 POWER OPERATED HAMMERS Hans Ludwig Hockel, Mannheim-Feudenheim, and Ernest Ueckert, Mannheim, Germany, assignors to Knorr-Bremse G. m. b. H., Munich, Germany Application July 2, 1956, Serial No. 595,562 Claims priority, application Germany July 2, 1955 Claims. (Cl. 123-7) This invention relates to hammers adapted to be operated by internal combustion engines comprising free pistons and wherein the combustible mixture is introduced and the piston returned by compressed air. Such hammers operate on a two-stroke cycle with applied ignition in the vicinity of the top dead centre. Situated in the upper part of the working cylinder is a valve which controls the compressed air for the return movement (upward movement) of the piston and a valve for controlling the supply of the combustible mixture. These valves are brought into their open and closed or venting positions by the pressure difference between the pressure in the combustion chamber and the pressure of the compressed air supplied from the exterior or the force of a spring. The movements take place suddenly, producing considerable acceleration and retardation forces which, in the case of hitherto known constructions, often led to the valves being broken. In order to supply fuel, compressed air is admitted to a pressure-resistant closed fuel container, the fuel being forced out by the excess pressure in the fuel container through a nozzle opening which is arranged at a point in the air supply circuit at which a reduced pressure prevails as the result of a local increase in speed.

In known constructions of carburetters for hammers operated by internal combustion engines, the fuel outlet point is situated in the region of the outer limit of the upper part of the cylinder anclis connected to the mixture inlet valve by angled ducts which include variations in cross-section. This arrangement has considerable disadvantages since for example some of the fuel droplets are precipitated on the bends or angles, and cross-see tional variations, thus giving rise to reduced power and ignition failures.

It is an object of the invention to provide a construc- I tion wherein the possibility of breakage of the valves will e eliminated or greatly reduced.

According to the present invention a valve for hammers op erated by internal combustion engines and comprising a :ree piston movable in a working cylinder, the said valve having a head or sealing portion facing the combus' tion chamber and a hollow cylindrical stem is characterised in that the stem is grooved or recessed to re ceive a disc-shaped support member of larger overall diamjeter than said stem, the arrangement being such that as the head or sealing portion is moved away from its seating said support member will act as an abutment cooperating with a portion of the casing.

With such an arrangement the tensile stresses produced in the valve stem upon impingement on the seat surface are reduced as much as possible and are taken up by as, large a cross-section as possible, which likewise serves to transmit the forces which are produced when a support member strikes up against its matching surface on the casing.

A further object of the invention is to obviate the aforesaid disadvantages of known carburetters.

This problem is solved according to the invention in that the air inlet passage and the fuel nozzle are arranged co-axially with mixture inlet valve, which is fashioned as a hollow body open at the nozzle side, the spacing between the open end of the valve and the end of the air passage being the smallest possible permitted by wear and reconditioning of the valve seat. The air passage and the nozzle form an annular gap which is situated concentrically with respect to the common longitudinal axis and into which one or more fuel outlet ports open transversely to the said axis.

By this arrangement the result is achieved that the fuel which is sprayed out of the nozzle is carried by the current of air only into the space in the mixture inlet valve, so that fuel which, owing to the intermittent method of operation of a hammer and the interruption of the air flow upon closure of the mixture inlet valve, may fall out of the air current, merely tends to be deposited in the hollowvspace in the mixture inlet valve. During operation it is not possible for deposition to occur, since the high temperature in the bottom of the mixture inlet valve causes immediate evaporation.

According to the invention this effect is further promoted by the position of the mixture outlet holes at that end of the mixture inlet valve which is near the combustion chamber.

In order that the invention may be clearly understood and readily carried into effect the same will now be more fully described with reference to the accompanying drawings, wherein:

Fig. l is a longitudinal sectional view through two valves showing the method of arrangement,

Fig. 2 is a plan view of the abutment disc,

Fig. 3 is a sectional view through the control valve at the point where the abutment disc is arranged.

In Fig. l, i denotes a control valve which is arranged in the upper part of a cylinder 2, the latter being closed by a member 3. The valve 1 is formed at diametrically opposed points with grooves 4, as is clearly illustrated in Fig. 3, said grooves being adapted to accommodate an abutment disc 5. The disc 5 is formed with a slot (Fig. 2) which permits of lateral insertion of said disc into the grooves 4 the arrangement being such that once in position the disc will be prevented from undesired displacement transversely to the longitudinal axis of the valve by virtue of the provision of a spring 6 which bears, at one end, on the disc 5 and, at its other end, against a closure screw 7 to urge the valve 1 to the illustrated position where disc 5 engages the upper part 2 of the cylinder. 7

The control valve 1 operates in the following manner:

Compressed air under a pressure of approximately 2-3 kg./cm. is introduced in a manner which is not illustrated in the drawings into an annular space 8.

In the illustrated position, the control valve 1 establishes a communication with an annular space 9 which is connected by way of a passage it) to the space at the underside of a free piston 11. The upward travel of the piston produces in the combustion chamber 12 an in creased pressure which presses the control valve 1, arranged with a sealing fit in the upper part 2 of the cylinder, in opposition to the force of the spring 6, until artists the scaling face 13- bears against the upper part 2 of the I cylinder.

In this position the annular space 9 communicates with a space 14- which is vented in to the open air. The underside of the piston 11 is thereby relieved of pressure, so that no unnecessary resistance is opposed to the increase in pressure in the combustion chamber 12 which is produced simultaneously with the initiation of combustion, and which drives the piston downwards to strike against the tool (not shown). In its lower position, the piston frees the exhaust slots (which are also not shown). The drop in pressure in the cylinder which is caused thereby enables the spring 6 to return the valve again into the illustrated position. This movement is arrested by the abutment disc 5.

In the right-hand half of Fig. l, 15 denotes a iixturc inlet valve which is also arranged with a tight fit in the upper part 2 of the cylinder. it is held in the illustrated closure position by a spring 16, which bears against an abutment disc 1'7 and against the upper part 2 of the cylinder. The upper side of the mixture inlet valve 15' is subjected to load by the pressure of compressed air which flows into the space 18 through a Venturi orfunnel shaped passage 19, such air coming from a chamber 20, and entraining fuel from the nozzle 21.

In the upper part 2 of the cylinder and in the memher 3, the fuel nozzle 21, the passage 19 and the mixture inlet valve 15 are axially aligned. The fuel nozzle 21 is pressed by a compression spring 26, which bears against a closure screw 27, against a projection 28 of the member 3.

The mixture inlet valve 15 has a head or sealing portion 22 which is adapted under the influence of the compression spring 16 to bear with a fluid-tight fit against a correspondingly shaped face formed on the upper part 2 of the cylinder. In the open position of the mixture inlet valve, the disc 17 serves as a stroke limiting means. The construction of the disc 17 corresponds to that of the disc 5.

The mixture inlet valve 15 operates in the following manner:

When it is desired to operate the hammer, the fuel container is subjected to excess pressure in a manner which is not illustrated in the drawings. The fuel passes from the fuel container by way of a conduit which is not shown in the drawings, into a chamber 29 and thence into the inner space of the fuel nozzle 21. Situated approximately at the point where the air passage is narrowest, is the fuel outlet aperture 3th Compressed air passes into the space 21 simultaneously with the admission of air to the fuel container. When during the downward travel of the piston 11, the pressure in the combustion chamber 12 has dropped so far that the pressure in the chamber 18 is capable of overcoming the first-mentioned pressure and also the force of the spring 16, the mixture inlet valve 15 is pushed downwards until the disc 17 bears against the upper part 2 of the cylinder so that combustible mixture can flow from the space 18 into the cylinder and can scavenge the residual combustion gases towards the exhaust slots. When the valve 15 is opened, a strong current of air is produced in the annular cross-section 31, which causes a drop in pres-- sure at this point so that fuel will issue from the aperture 3d. The mixture passes from the passage 19 into a space 32 in the valve 15 and thence through a transverse aperture 33 past the valve face 22 into the com bustion chamber 3.2, where it is ignited by a sparking plug which is not shown in the drawings. When, during the upward travel of the piston 11, the pressure in the combustion chamber 12 increases until it is capable, together with the force of the spring 16 of overcoming the effect of tie air pressure prevailing in the space It the mixture inlet valve 15 is again pushed upwards until the head portion 22 thereof bears with a fluid-tight elfect against the upper part 2 of the cylinder.

In more detail, it is important that the annular gap 31 is disposed concentrically relatively to the parts 21, 19 and 15, in order that even with the fuel outlet aperture 30 positioned at one side, the whole of the mixture passes into the space 32. The provision of a conical inlet 34 to said space 32 facilitates this effect. A shalloW depression 35 below the apertures 33 seems to have an advantageous influence on evaporation of fuel, since any accumulations of fuel are fed to the hottest part of the mixture inlet valve 15. The stem 23 of the valve 1 and the stem 24 of the valve 15 are hollow and are given the largest possible diameters in order to reduce the stresses caused in the cross-section of the stems by accelerations and retardations. At the same time, this construction increases the surface which serves to takevup surface pressure.

We claim:

1. In a hammer operated by an internal combustion engine having a cylinder with a piston moveable freely therein; the combination of a casing at the top of the cylinder and having a guide bore opening into the cylinder with a sealing face formed at said opening, said casing further having a first increased diameter cylindrical space co-axial with said guide bore and with an annular shoulder being defined at the bottom of said first space and a second cylindrical base co-axial with and disposed between said first cylindrical space and said guide bore, said second cylindrical space having a diameter intermediate the diameter of said first space and the outer diameter of said guide bore, a valve including a hollow cylindrical stern slidable in said guide bore and a head at the lower end of said stem having a sealing lip to engage upwardly against said sealing face with the inner diameter of said sealing li and the outer diameter of said stem being nearly equal, said stem having a recess therein adjacent the upper end thereof. and a disc member having a slot opening at one side thereof and being received in said recess, said disc member having a diameter greater than said outer diameter of the stern and less than the diameter of said first cylindrical space, said disc member being disposed in said base to engage said shoulder and thereby limit the longitudinal movement of said valve in the direction displac ing said sealing lip away from said sealing face, the axial distance between said shoulder and said sealing face being smaller than the axial distance between said disc member and said sealing lip, said disc member being furthermore provided with a cylindrical projecion at the side thereof facing toward said second cylindrical space and a helical spring disposed in said second cylindrical space engaging, at one end, against said disc member around said projection and, at its other end, against the bottom of said second cylindrical space.

2. In a hammer operated by an internal combustion engine having a cylinder with a piston movable freely therein; the combination as in claim 1, wh ein said casing has means therein defining a Venturi-snaped air passage therein coaxial with said valve, and a. (re! nozzle within said air passage, said hollow cylindrical stem -i." the valve opening axially at the end thereof facing towa i' said air passage, said open end of the hollow stem 'cni n spaced only a small distance from the adjacent endl oi" said air passage.

3. In a hammer operated by an internal combustion engine having a cylinder with a piston movable frccly therein; the combination as in claim wherein siud nozzle has at least one transverse fuel outle ort opera ing into an annular space defined between said nozzle and said air passage.

4. In a hammer operated by an internal combustion engine having a cylinder with a piston movable freely therein; the combination as in claim. 3, wherein said valve has ports extending transversely to the longitudinal axis of the valve adjacent the end of the latter remote from .Wwvi M 14 44v 4 ,7 1

said nozzle and opening from the interior of said hollow stem in the vicinity of said sealing lip of said head,

5. In a hammer operated by an internal combustion engine having a cylinder with a piston movable freely therein; the combination as in claim 4, wherein said interior of the hollow stem has a shallow depression at the end thereof adjacent said head, said depression extending belowsaid transverse ports of the valve.

References Cited in the file of this patent UNITED STATES PATENTS 1,193,738 Thomas Aug. 8, 1916

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