US2333419A - Gas hammer - Google Patents

Description

C. E. FITCH Nov. 2, 1943.

GAS HAMMER Filed OCT.. 8, 1940 s sheets-sheet@ NOV. 2, 1943. Q EI FlTCH 2,333,419

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ATTORNEY Nov. 2, 1943. c. E. FITCH 2,333,419

CTAS HAMMER Filed oct. e, 1940 s sheets-sheet s ATTO R N EY Nov. 2, 1943. c. E. FITCH 2,333,419

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Patenten lOV. A, 139s) GAS HAMMER Clifford E. Fitch, Cleveland, Ohio, assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application October 8, 1940, Serial No. 360,279

(Cl. l237) Claims.

This invention relates generally to percussive tools in which the motive power is derived from an integrally formed internal combustion engine, and more particularly to a tool of this type in which the driving piston is returned through its compression stroke by the momentum oi a fly wheel and crank shaft operatively connected to the driving piston.

Tools of the class to which this invention relates further embody a magneto and are portable, selfcontained units operable independently of any remote power source, and so are particularly adapted to the work of tie tamping and similar operations. It is intended, by the present invention, to produce a generally new tool of this class having an improved construction in several respects.

One object of the invention is to provide a supporting framework which will enable relatively light metals to be used in its construction and simplify the task of assembly.

Another object of the invention is to permit the crankcase chamber to be filled with oil as a lubricant for crank bearings.

Another object of the invention is to use the fly wheel of the fly wheel magneto as a fan to direct a stream of cooling air against the engine cylinder, without permitting the hot exhaust gases to pass through the magneto.

Still another object of the invention is to simplify starting of the engine when initiating operation of the tool. In carrying out this object there is provided an actuating assembly including a cable wound on a pulley wheel and adapted when pulled in an unwinding direction to operate the actuating assembly.

Other objects and structural details of the invention will be apparent from the following description when read in conjunction with the accompanying drawings, wherein:

Fig. l is a view, in elevation, of the tool of the present invention, shown adapted for tie tamping operations;

Fig. 2 is a View of the tool, in longitudinal section, taken along the line 2-2 of Fig. l;

Fig. 3 is a view, in longitudinal section, of the upper portion of the tool, this view being enlarged with respect to Fig. 2;

Fig. 4 is a detail View, in side elevation, oi the stator plate and associated parts of the magneto, as viewed looking in the direction indicated by the arrows 4-4 in Fig. 3;

Fig. 5 is a cross sectional View, taken along the irregular line 5-5 of Fig. 3, showing the starting mechanism of the tool, some parts being broken away to disclose details of construction; and

Figs. 6 to 9 inclusive are partly diagrammatic views showing the relative positions assumed by the driving piston, the crank mechanism and the hammer assembly at four different points in one cycle of operation, the parts being shown as viewed looking in the same direction as in Fig. 1.

As shown in Fig. l, the tool of the invention is a portable, unitary structure which may be manipulated by one or two men by means of properly disposed handles I0 and II. For purposes of description, the tool may be considered as divided into a plurality of cooperating sections or parts including an upper portion I5, a downwardly extending barrel I6 and a barrel extension II. Extension I'I supports a working implement I8 which, in the present instance, is a tamping bar. Referring also to Fig. 2, the inner end of the bar I8 projects into the barrel I6 in position to receive blows of percussion from a hammer piston I9. The piston I9 forms part of a free piston type hammer assembly and moves within a cylindrical cage 2I slidably mounted within the barrel I 6. The cage 2I is directly connected by means of a rod 22 to the driving piston 23 of the internal combustion engine and reciprocates with the driving piston to effect movement of the hammer piston I9.

The lower portion of the tool, including the hammer assembly and chuck parts supporting the tamping bar, is of conventional design and will be only brieily described. The adjacent ends of the barrel I6 and barrel extension I'I have a telescoping connection and are secured together byv bolts 24. A bushing 25 in the lower end of extension II and a bushing 26 in the barrel I6 near its lower end serve as guides and supports for the shank of bar I8. A collar 2'I on the bar is movable between the lower end of the bushing 26 and a rubber buffer 28 atop bushing 25 to limit longitudinal movement of the tamping bar. The bar i3 is pressed into engagement with the work during operation of the tool and is driven outwardly by repeated blows of percussion delivered upon its inner end by the hammer piston I9.

The cylindrical cage 2I is provided at its ends with annular enlargements or shoulders 29 and 3l which engage the inner wall of barrel I 6 and guide the cage in its reciprocating movement. Barrel I 6 is preferably closed from atmosphere to exclude dust. The mid-portion of the cage 2| is of reduced diameter to provide an arcuate space between the cage and the barrel I6. The reduced portion is formed with a series of openings 32. As shown in Figs. 2 and 8, passage 30 establishes continuous communication between the top and bottom of cage 2l to minimize pressure fluctuations at the ends of barrel I6. Passage 38 is out of communication with the openings 32 and the reduced intermediate part of the cage.

The piston I9 has a striking portion or stem extending through the lower end of the cage 2| in axial alignment with the tamping bar I8. The head of the piston has a sliding t with the inner wall of cage 2| and forms upper and lower compression chambers 33 and 34 within the cage adjacent the respective upper and lower ends thereof. According to the well-known manner of operation of this type hammer assembly, the piston I9 is driven from end to end of the Cylindrical cage by air compressed within the chambers 33 and 34 by relative movement of the cage. During the downward or power stroke of the cage 2 I, the air in chamber 33 is compressed and during the latter part of the stroke effects a rapidly accelerating downward movement of the piston I9. During the upward or return stroke of the cage, the hammer piston is returned in a similar manner by air compressed within the chamber 34. Upward movement of the piston is initiated by its rebound from the tamping bar I 8.

The connecting rod 22 is in the form of a Scotch yoke. It is connected to the cage 2| by means of a wrist pin 35 which is passed through aligned holes in the upper end of the cage and in the lower end of the connecting rod. The pin 35 also passes through a block 36 closing the upper end of the cage 2|. The block 36 is made preferably of aluminum and is pressed into position within the cage. Under the heat of operation the aluminum block 36 expands more rapidly than the steel cage 2| and so maintains its tight f1tting position. By reason of this arrangement, the thrust of the wrist pin is transferred direct to the cage and the pin does not tend to pull the aluminum head out of the cage. The upper end of connecting rod 22 extends into the driving piston 23 and is attached thereto by means of a cross pin 31.

The movement of the hammer assembly during one cycle of operation may be better understood through study of the several position views, Figs. 6-9 inclusive. These figures show a cylindrical cage 2|a having a series of longitudinal slots 40 in its mid-portion instead of the columnar perforations 32 of the cage shown in Fig. 2. The slots 40 and perforations 32 are merely alternative construction forms since the mode of operation of the hammer assembly is the same irrespective of the manner in which air is admitted to the interior of the cage. In Fig. 6 the cage 2 Ia is shown in its uppermost position just prior to the start of the downward stroke. During the initial downward movement of the assembly, the hammer piston I9, due to its inertia, moves at a slower instantaneous speed than the cage 2|a. Until the speed of the piston I9 equals that of the cage the size of air chamber, or pocket, 33 decreases as will be apparent from a comparison of Figs. 6 and 7. During the latter part of the downward stroke, the compressed air in chamber 33 expands, causing the hammer piston to move at a greater speed than the cage 2Ia. In Fig. 8 the piston I9 has delivered an impact to bar I8 and rebounded slightly, while in Fig. 9, the assembly is shown moving through its return stroke.

The upper portion I of the tool contains the mooofxn:

internal combustion engine and controls therefor including the starting mechanism and fly wheel magneto. In the illustrative embodiment, the engine is of the two-cycle type. The principal supporting elements for the engine are a pair of cast frame pieces 38 and 39 joined together to form a unitary supporting assembly. The adjacent ends of the pieces 38 and 39 are shaped as complementary engaging face, forming between them, a crankcase chamber 4| through which the connecting rod 22 passes. The driving piston 23 moves within a cylinder 42 secured to the frame pieces 38 and 39 directly above the crankcase chamber 4|. Referring also to Figs. 6 to 9 inclusive, it will be seen that the piston 23 divides the interior of the cylinder 42 into upper and lower chambers 43 and 44 which may be identied respectively as the combustion and pre-compression chambers. A mixture of gasoline and air is introduced into the combustion chamber 43 through a passage 45 (Figs. 6 to 9) in the cylinder 42 while burned gases within the cylinder may escape through an exhaust port 46. The passage 45 communicates with a supply passage 41, formed betweenjthe supporting elements 38 and 39. The flow of' gasoline and air into the passage 41 is controlled by a carburetor 48 (see also' Fig. 1) supported by the elements 38 and 39v at the lower end of the supply passage. 'I'he carburetor 48 has a passageway including a set of ports 49 for directing air to the passage 41,a'nd a restricted passageway 5| which deliversfgasoline to the supply passage. Both carburetor passageways are controlled by a pressure responsive valve 52, yieldingly held in closed position by a spring 53. When the pressure within passage 41 drops suihciently to permit atmospheric pressure to overcome the spring 53, valve 52 is forced inwardly to open position and air and gasoline is drawn into the engine supply passages. In order that the quantity of fuel admitted to the engine may be varied an adjustable metering valve 55 is provided in the carburetor. The inner end of valve 55 extends within the passageway 5| and controls the rate of ow therethrough in accordance with the position of adjustment of the valve. The carburetor passageway 5| communicates in a manner not shown herein with a gasoline storage tank 54 (Fig. 2) formed in the supporting element 38.

Supply passage 41 communicates also with the pre-compression chamber 44. The passage 45 is controlled by the piston 23 and is open only in the lowermost position of the piston (Fig. 8). In the operation of the engine an explosive charge, previously introduced into combustion chamber 43, is ignited by a spark plug 56, extending into the upper end of cylinder 42. The piston 23 is thereby driven downward through its power stroke, and, near the end of its downward movement, uncovers exhaust port 46. Immediately after the opening of exhaust port 46, the piston 23 uncovers passage 45 and a fresh mixture of gasoline and air flows into the chamber 43. The fresh mixture is directed upwards by a curved dei'lecting surface 51 on the head of piston 23 and forces the burned gases downward and out the exhaust port. When in the lowermost position of Fig. 8, the piston 23 cuts off communication between the pre-compression chamber 44 and the supply passage 41. At the start of the upward or return stroke of the piston (initiated in a manner later to be described) the passage 45 and exhaust port 46 are closed and communication between chamber 44 and supply passage 41 is re-established. As the piston 23 continues its upward movementl the pre-compression chamber 44 expands in size and the pressure within the chamber and passage 41 is thereby caused to drop. As shown in Fig. 9 at some point -in the upward movement of the piston the pressure in passage 41 becomes suiciently low to cause unseating of the valve 52 and admit air and fuel through the carburetor 48. The fresh gases flow through the passage 41 to the pre-compression chamber 44 and passage 45 but are prevented from entering the combustion chamber 43 at this time. While a new charge is drawn into the supply passages, the one previously admitted to the chamber 43 is compressed and, as the piston 23 reaches the uppermost position of Fig. 6, is ignited. The resulting downward movement of the piston 23 again reduces the size of the precompression chamber 44 and the gases within the chamber are compressed and forced out into the supply passages 41 and 45. When the passage 45 is opened, at the end of the power stroke, the charge compressed within the supply passages flows into the combustion chamber and the operations described above repeated to continue operation of the engine. The engine thus completes a cycle of operation in one reciprocating movement of the piston 23; each descent of the piston being a power stroke occasioned by an explosion in the combustion chamber 43.

For effecting return movement of the piston 23 and thereby of the hammer assembly comprising elements I9 and 2|, there is provided a crank mechanism including a crank shaft 58 (Figs. 2 and 3). The shaft 58 is rotatably supported in ball bearing assemblies 6I and 62 which are positioned respectively in element 39 Iand a housing 59, the latter being secured to the frame piece 39. The left hand endof the shaft 58 (as viewed in Fig. 3) extends into the crank case chamber 4| and has formed integrally therewith, a crank arm 63. The arm 63 has an outwardly projecting stud 64 extending into a rectangular slot 65 in the connecting rod 22. As shown in Figs. 6 to 9 the slot 85 is an elongated horizontally disposed opening formed in a shouldered portion 66 of the connecting rod. A slide block 51 is supported within the slot 65 and is adapted to receive the stud 64. By reason of this connection the rod 22 and the crank shaft 58 are constrained to move in unison and operation of either element eifects a simultaneous operation of the other. Their relationship as driven and driving elements is interchangeable. In considering the operation of the crank mechanism it will be observed that in Fig. 7 the connection rod 22 is moving downward through its power stroke and that the crank arm 63 is being positively driven in a clockwise direction, with the stud 64 occupying a position near the right hand end of the slot 65. As the power stroke continues the crank assembly is rotated a further distance, causing the stud 54 and slide block 61 to move leftward in slot 65, and at the end of the downward stroke the parts take the position shown in Fig. 8. At this point in the cycle the positive drive is transferred from the piston 23 to the crank shaft 53 which continues to rotate with suflicient momentum to carry the connection rod 22 and associated parts upward through their return stroke. The work of the return movement is performed chiey by a y wheel 68 (Figs. 2 and 3) keyed to the shaft 5B. On the power stroke of the piston 23 suflicient kinetic energy is stored in the iiy wheel 6B to continue the rotation through the downward stroke.

'Ihe crank arm B3 is formed in addition to the portion carrying stud 64, with an oppositely extending portion 69 which is generally fan-shaped and carries a weight 1| near its outer edge. The crank arm 63 is thus counterbalanced and additional momentum is thereby imparted to the crank assembly during a portion of its rotary movement. At the start of the return stroke slide block 81 moves leftward from the center of the slot 65 and at approximately the middle of the return stroke reaches the extreme leftward position of Fig. 9. As the crank shaft 58 continues to turn, the piston 23 is lifted to its uppermost or Fig. 6 position, as the slide block 61 is shifted rightward in slot 65.

In order that the crankcase chamber 4l may be filled with oil, to lubricate the bearings in the crank assembly, suitable oil seals are placed at points where seepage from the chamber might take place. As shown in Fig. 3, these seals include separate sets of packing rings 12 and 'I3 which encircle the rod 22 and are supported between the elements 38 and 39 at respective points above and below the chamber 4I. The motion of rod 22 is conned to a straight line, thereby enabling the seal to be effective. A third seal 14 surrounds the shaft 58 and is positioned within the element 39 to the rear, or to the right as viewed in Fig. 3, of the bearing 6l.

The ignition system of the tool includes a flywheel magneto mechanism for generating an electric current, which current is supplied to the spark plug 58 under the control of suitable timing or circuit breaking mechanism. The iiy wheel magneto and circuit breaker are combined in a unitary structure which in itself is old and well known. The unit is enclosed by the adjacent ends of the supporting element 39 and housing 59 (Fig. 3) and includes among its elements, the iiy wheel 63 rotatable with shaft 58. The periphery of the ily wheel 68 extends inward to form a rim 'I5 in which a magnet 16 is fixed. The remaining elements of the magneto are mounted on a stator plate 'l1 secured to the supporting element 39 Within the recessed outer face thereof. Referring also to Fig. 4 these stationary elements comprise a coil T8, a condenser 'I9 and a pair of contact elements 8l and 82 within the circuit leading to spark plug 56. The element 8l is carried by a rocker arm 83 (Fig. 4) which may be moved in a clockwise direction to separate the elements 8| and 82 and so open, or break, the circuit. Movement of the arm 83 is controlled by a cam 84 keyed to the shaft 58. The cam 84 cooperates with a follower stud on the arm 83 and is so formed as to hold the arm normally in disabled position and to permit the engagement of contact points 8l and 82 only during a predetermined portion of each cycle of operation. The manner in which the magneto functions to produce an electric current is too well known to require a detailed description here. It may merely be said that in the present construction the magnet 1G acts as the rotor which sets up magnetic lines of force as it revolves around the stationary coil 18.

Operation of the tool is initiated by means effective to rotate the crank shaft 58, and thereby to actuate the magneto mechanism and the driving piston 23. As shown in Fig. 3, the right hand end of the shaft 58 extends through and beyond the housing 59 and has a plate 85 screwed thereon. Referring also to Fig. 5 it will be seen that the element 85 is constructed as a threearmed holder plate, each arm of the plate being formed with a bent over ear 86 for the support of a pivot pin 81. Loosely mounted on each pivot pin 81 is a pawl 88 having a rearwardly extending portion 88a engageable with the ear 86 to limit outward movement of the pawl. The pawls 88 are adapted for cooperation with the teeth of a ratchet wheel 89 formed integrally with a stub shaft or actuating element 9| (Fig. 3). As shown in Fig. 3, the stub shaft 9| is axially aligned with the crank shaft 58 and has its inner end recessed to receive the reduced outer end of the crank shaft. The ratchet wheel 89 encircles the hub of holder plate 85 and lies in the same vertical plane as the pawls 88. The right hand end of the stub shaft 9| is journaled in the hub 92 of a cover 93 which is secured to the housing 59, and encloses all of the parts lying outside the housing. The stub shaft 9| and crank shaft 58 are thus mounted for independent rotation but may be connected through the ratchet wheel 89 and pawl holder 85 for operation as a unit. As shown in Fig. 5, in the normal rest position of the tool, at least one of the pawls 88 is permitted to drop by gravity into engagement with the teeth of wheel 89, the parts being so arranged that clockwise movement of the ratchet wheel effects a simultaneous clockwise movement of the pawl holder 85, while counterclockwise movement of the ratchet wheel may be accomplished independently of the pawl holder. With the machine at rest, therefore, if the stub shaft 9| is caused to rotate in a clockwise direction (Fig. 5) the crank shaft 58 will be driven in a similar direction, through elements 85 and 89, to effect reciprocation of the driving piston 23 and thereby initiate operation of the engine. When the engine has started, the speed of rotation of the crank shaft 58 quickly surpasses that of stub shaft 9| and the pawls 88 are drawn out of engagement with the ratchet wheel 89 by centrifugal force.

To facilitate actuation of the stub shaft 9| there is secured thereto a disc 94 which acts as the hub of a pulley wheel 95 to which it is riveted. The pulley Wheel 95 has a cable 96 wound around its outer periphery and, as shown in Fig. 5, the free outer end of the cable is passed through an opening 91 in the cover 93. Outside the cover, the cable 96 is fastened to a handle 98 having a tapered shank 98a extensible into the opening 91 to limit inward movement of the cable. The inner end of the cable 96 is fixed to the pulley Wheel 95, so that when the handle 98 is manually grasped and pulled outward the unwinding cable drives the assembly comprising pulley wheel 95 and stub shaft 9| in a clockwise direction. Rewinding of the cable upon the pulley wheel is accomplished automatically by a spring means which tensions the wheel in a counter-clockwise, or winding, direction. This means resides in a coil spring 99 (Figs. 3 and 5) mounted within the pulley Wheel 95. The inner end of spring 99 is secured to the stationary hub 92, of cover 93, while the outer end of the spring engages a stud |0| mounted within the wheel 95 and movable therewith. Movement of the pulley wheel in an un- Winding, or clockwise direction, as viewed in Fig. 5, serves to tension the spring 99. When the handle 98 is released after being pulled outward to start the engine, the spring 99 is permitted to expand from its tensioned condition and, in so doing, acts on the stud |0| to return the pulley Wheel 95 and cable 9B to their normal positions of Fig. 5.

A simple and effective means for cooling the engine cylinder 42 is also provided in the tool. As shown in Figs. 1, 2 and 3, the upper end of the cylinder 42 is enclosed by a hood |02 which serves as a shield and as a deilector for directing a cooling current of air around the cylinder. The hood |02 is secured to the housing 59 and the open lower end thereof fits over a correspondingly shaped opening |03 in the periphery of the housing The outer face of housing 59 has a series of openings |04 (one shown) spaced around the bearing 62, and these openings, in cooperation with a set of ports |05 in the cover 93 communicate the interior of the housing with the atmosphere. An unrestricted air passage from the rear of the tool to the hood |02 is thus established. In order that a steady current of air may be maintained along this passage, the rear face of the fly wheel 68 is provided with a circumferential row of fan blades |06. It will be noted .ijf that in the present cooling system, the currentofk air generated by the fan blades |06 is drawn into the housing 59 and discharged therefrom without passing through the magneto. Possible damage to the magneto, resulting from the flow of hot gases of combustion therethrough, is avoided.

What is claimed is:

1. A portable, self-contained percussive tool comprising an internal combustion engine including a cylinder, a hammer barrel axially aligned with said cylinder, supporting means for said cylinder and barrel comprising a pair of frame pieces interposed between said elements and having complementary engaging faces forming a crank case chamber and a fuel supply passage separate from said crank case chamber and communicating with said cylinder, a fly wheel magneto mechanism supported within one of said frame pieces and operated by said engine to supply current thereto, and a fuel storage tank embodied in the other of said frame pieces, said fly wheel magneto and said fuel tank being positioned on opposite sides of said crank case chamber and disposed about a common longitudinal axis, at right angles to the longitudinal axis of said cylinder and said barrel.

2. In a percussive tool, the combination of an internal combustion engine including a cylinder, a hammer barrel axially aligned with said cylinder, supporting means for said cylinder and barrel comprising a housing interposed between said elements and having oppositely disposed faces for engagement with said cylinder and said hammer barrel, a fly Wheel magneto mechanism supported within said housing and operated by said engine to supply current thereto, a fan integral with the rotor of said fly wheel magneto for setting up a current of air, and means for directing such current of air through said housing to the outer surface of said cylinder Without causing it to pass through said magneto,

3. In a percussive tool, the combination With an internal combustion engine having a cylinder and a driving piston therein, a hammer assembly, and a connection rod between said driving piston and said hammer assembly, of a rotatable crank shaft operatively connected to said connection rod, a ily Wheel magneto for supplying current to said engine, the rotor of said magneto being driven by said crank shaft, a fan integrally formed with the rotor of said fly wheel magneto for setting up a current of air, and an air conducting passageway leading from said fan to the outer surface of the cylinder of said internal combustion engine, said passageway by-passing said magneto to prevent a forced flow of air therethrough.

4. A portable self-contained percussive tool, comprising an internal combustion engine including a cylinder, a hammer barrel axially aligned With said cylinder, a piston in said cylinder dening combustion and pre-compression chambers in the upper and lower ends thereof, a hammer assembly in said hammer barrel, a connection rod in the form of a Scotch yoke between said piston and said hammer assembly, supporting means for said cylinder and barrel comprising an intermediate housing forming a crankcase chamber through which said connection rod passes, means sealing said chamber from communication with said cylinder and said barrel, a fuel supply passage within said intermediate housing communicating with said combustion and pre-compression chambers in said cylinder, a shaft supported by said housing at right angles to said connection rod and having a crank arm Within said crankcase chamber operatively engaged with said Scotch yoke, and a fly Wheel magneto operated by said shaft to supply current to said engine.

5. In a percussive tool, the combination of an internal combustion engine including a cylinder,

a hammer barrel longitudinally spaced from said cylinder, movable elements in said cylinder and said hammer barrel, a connection between said elements, supporting means for said cylinder and barrel comprising an intermediate housing forming a crankcase chamber through which said connection means passes, a shaft supported by said housing at right angles to the longitudinal axis of said cylinder, one end of said shaft extending into said crankcase chamber and having a crank arm operatively engaged with said connection means and the other end of said shaft lying outside said housing, a rotor on the outer end of said shaft functioning as part of a fly-wheel magneto supplying current to the engine, a ian integral with said rotor, an auxiliary housing enclosing said fan and having an inlet through which air is drawn by said fan and an outlet through Which air may be discharged, said outlet being arranged to direct the air away from said magneto and said inlet and outlet being so positioned that the air stream forced through said auxiliary housing by-passes said magneto, and an air conduit mounting on said auxiliary housing in a position of registry With said outlet and extending as a hood around said cylinder.

CLIFFORD E. FITCH.

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