US2214800A

US2214800A - Percussive tool

Info

Publication number: US2214800A
Application number: US281814A
Authority: US
Inventors: Sr William A Smith
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1939-06-29
Filing date: 1939-06-29
Publication date: 1940-09-17
Anticipated expiration: 1957-09-17

Description

Sept. 17, 1940. w. A. SMITH, `sR '35,214,809`

. APERcUssIvE moor.

INVENTOR HIS ATTORNEY w. A. SMITH. 's

PERCUSS IVE TOOL Sept. 17, 1940.

Filed June 29, 1959 s sheets-sheet 3 HIS ATTORNEY.

Patented Sept. 17, 1940 lUNITED STATES PATENT OFFICE PERCUSSIVE TOOL Application June 29, 1939, Serial No. 281,814

GCIaims.

This invention relates to percussive tools, and more particularly to an internal combustion engine operated percussive tool of the type in which the working implement is capable of free reciprocatory movement with respect to the element actuating it.

One object of the invention is to construct a rugged, compact and powerful percussive tool that may be conveniently manipulated and guided with respect to the work and which will be capable of fulfilling all the requirements of a tool of this character in the various positions which it may occupy in practice.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings accompanying 'this specification and in which similar reference numerals refer to similar parts,

Figure 1 is a side elevation of lthe percussive tool constructed in accordance with the practice of the invention.

Figure 2 is an elevation, partly in section, of the percussive tool,

Figure 3 is a transverse view,in section, taken through Figure 1 on the line 3 3 showing more particularly the interior of the percussive element,

Figure 4 is a transverse view, in section, taken through Figure 3 on the line 4 4,

Figure 5 is a view similar to Figure 3 taken on the line 5 5 in Figure 1 and showing the interior of one of the power cylinders,

Figure 6 is a transverse fragmentary view, in section, taken through Figure 5 on the line 6 6, and

Figure '7 is a view takeny through Figure 6 on the line 1 1.

Referring more particularly to the drawings, 2U designates, in general, a percussive tool, and 2i a working implement which the percussive tool yis intended to actuate.

In the form of the invention illustrated the percussive tool comprises a crank casing 22 supporting upon its rearward end a fuel tank 23 and at its forward end a pair of depending

engine cylinders

24 and 25 and a percussive cylinder 26 arranged between the engine cylinders and axially of the percussive tool 20.

In accordance with the practice of the invention, the fuel tank, which may be rigidly secured to the crank casing 22 in any suitable manner, serves as a support for a handle 21 whereby the percussive tool may be guided. The fuel tank is accordingly provided with an internal rib 28 which extends entirely therethrough and has a bore 23 to accommodate a bolt 30 upon the ends of which are disposed grip members 3i.

At the upper end of the fueltank is a lling opening 32 normally sealed by a plug 33 and between the fuel tank and the crank casing 22 is a. pad or gasket 34 of nonconducting material, such -as asbestos, to prevent the transmission of heat from the power element to the fuel tank. Bushings 35, also of asbestos, encircle the rearward ends of the

cylinders

24 and 25 and seat in recesses 36 in the crank casing to minimize the flow of heat from the engine cylinders to the crank casing.

The interior of the crank casing 22 is divided into a plurality of crank chambers, three in the present instance designated 31, 38 vand 39, by walls 40 arranged at spaced points within the crank casing. 'I'he walls 40, together with the outer walls 4| of the crank casing, serve as supports for a crank shaft 42 which extends entirely through the crank casing and carries on one exposed end lugs 43 for interlocking engagelment with clutch members 44 of a crank 45 whereby the crank shaft may be rotated for start 25 ing the engine element of the tool.

The crank shaft has three

crank pins

46, 41 and 48 each carrying a connecting rod 49 of which two are connected to pistons 50 and 5I in the

cylinders

24 and 25 and the remaining rod is connected to a plunger 52 reciprocable in -a piston chamber 53 in the percussive cylinder 26. The power element of the tool operates on thetwo .cycle principle and each piston 50 and 5I is provided on its outer end or head with a baille 54 to cause the incoming fuel charge to swerve downwardly into the lower portions of the

cylinders

24 and 25 and thereby avoid undue loss of un-` burned fuel through the exhaust ports 55 in the engine cylinders.

The fuel charge is ignited in the cylinders 24 and by sparking plugs 56 suitably attached to the lower portions of the cylinders, and the sparking periods are controlled by a-timer 5I attached to an end of the crank shaft 42. 'I'he timer 51 may be connected, in a well known manner, to a coil 58 attached to the side of the percussive tool and having a cable 59 which may lead to a source of electrical supply, as for example a battery (not shown).

As a preferred arrangement each engine cylinder is provided With an individual fuel metering device arranged entirely within the casing of the percussive tool. These devices, of which only one is shown and designated 60, are arranged in the upper portion of the crank casing 22 directly between the i'uel tank 23 and the

adjacent crank chambers

31 and 38 wherewith they communicate through passages 6| in the crank casing.

Each metering device comprises a cylindrical member 62 which is disposed in al recess 63` in the crank casing and having a flange 64 at its upper end which is clamped between the gasket 34 and a shoulder 65 in the recess for holding the metering device xedly in position. In the central portion of the member 62 is a hub 66 which is joined to the body of the member 62 by ribs 61 cooperating with the body portion of the member and the hub to denne passages 6 8 through which the air constituent of .the fuel charge passes to the passage 6| and thus to the associated crank chamber. this purpose is conveyed to the passages 68 by channels 69 extending through columns 10 within the fuel tank 23, and in the rearward ends of the channels 69 are screen plugs 1| to prevent the entrance of abrasive matter into the channels 69.

'I'he air flow from the channel- 69 to the passage 6| is controlled by a poppet valve 12 which seats against the lower end surface 13 of the cylindrical member 62 and has an upwardly extending stem 14 slidable in the bore 15 in the hub 66. In the upper end of the stem 14 is an annular groove 16 to-receive a split collar 11 that seats into a depression 18 of a sleeve 19 disposed about the stem 14, and on the periphery of the sleeve 19 is a ange 80 that serves as a seat for a spring 8| seated upon the ribs 61 to normally press the valve 12 against the surface 13. A suitable space 62 exists between the upper end of the hub 66 and the sleeve 19 to permit of a limited degree of endwise movement of the valve for opening communication between the passages 68 and 6|. e

An additional function of the valve 12 is to controlcommunication between the passage 6| and the interior ofthe fuel tank 23. The cylindrical member 62 is accordingly provided with a plurality of channels 83 which extend from one end to the other of the cylindrical member and have their outlet openings lying within the compass of the valve 12 so that when the'valve is seated against the surface 13 the outlet ends of the channels 83 will be fully sealed thereby.

In order to prevent clogging of he channels 83 by such particles of foreign; atter as may be entrained in the fuel, said channels are preferably of considerably larger cross sectional area than the flow area necessary for thefuel requirements of the power element of the tool, and filler pins 84 are disposed in the channels 83 to cooperate with the walls thereof for dening restricted annular passages 85 through which fuel may ow to the passage 6|. 'Ihe pins 84 are suspended in the channels 83, having heads 86 that rest upon shoulders 81 at the upper ends of the channels 83.

As a preferred arrangement the fuel is introduced into intermediate portions of the channels 83 by passages 88 extending through the member 62 and the gasket 34 and opening into an annular supply chamber 89 on the lower end of the fuel tank 23. The supply chamber 89 is in open communication with the interior of the fuel tank through passages 90. Between the supply chamber 89 and the passages 88 is a screen 9| to prevent foreign matter from entering the channels 83 and the associated crank chamber where the fuel charge is thoroughly mixed and from whence it flows to the engine cylinders The air utilized for` through passages 92 leading from the crank chambers to points in the cylinders approximately in the same transverse plane as the exhaust ports 55.

- Although the percussive tool is provided, at various points, with insulating members adapted to prevent the transmission of heat from the engine cylinders to adjacent portions of the structure it has been found to be advantageous to provide means for causing the quick dissipation of the heat of combustion. To this end the percussive tool is provided with a blower or fan 93 for directing jets of air against the sides of the

cylinders

24 and 25. The fan sa is driven by the crank shaft 42 and is mounted upon a shaft 94 carrying a pinion 95 that meshes with a gear 96 keyed to a web 91 of the crank shaft.

'I'he fan is arranged in a chamber 98 in the side of the crank casing and a cover 99 for the chamber 98 supports an anti-friction bearing for an .end of the shaft 94. A similar bearing |0| is disposed in the crank casing adjacent the pinion 95 to support the opposite end of the shaft 94.

' In order to subject the fuel in the tank 23 to the cooling effect of the air impelled by the fan 93 and thus further reduce the chances of vaporization of fuel in the tank, the inlet 'passage |02 for the fan is formed along the side of the fuel tank and is of considerable width so that it extends along the major portion of such side. Owing to this arrangement the inner wall |03 of the passage, and which wall forms #bounding surface for the fuel tank, will be kep at a low temperature and thereby exert a coo ing effect upon the fuel.

The air discharged by the fan 93 passes into the chamber 98, th cev through a discharge port |04 in the cra casing and a nozzle v|05 having two diverging branches |06 which are positioned so as to direct the air against the sides of the

engine cylinders

24 and 25.

In addition to the cylinder 26 and the plunger 52 the percussive element comprises a hammer piston |01 reciprocable in the piston chamber |08 containing the plunger 52 for delivering blows to the working implement 2|, the shank of which extends into the front end of the piston chamber and carries a collar |09 for engagement with a steel retainer |||l carried by a front head attached vto the cylinder 26 for guiding the working implement. The hammer piston |01 is hollow having a cavity ||2 to receive a reduced extension |I3 of the plunger wherewith the hammer piston is in slidable and non-interlocking engagement.

The peripheral surface of the cavity ||2 serves as a guide for the extension I3 and the rearward end portion ||4 of the plunger is enlarged and in slidable engagement with the wall of the piston chamber. 'Ihe plunger y52 is thus guided by the walls of the piston chamber and of the cavity ||2. By reason of this construction an annular chamber I5 will exist around the plunger 52 between the enlargement ||4 thereof and' the rearward end surface- ||6 of the hammer piston.

The portion of the cavity |2 forwardly of the plunger 52 constitutes a pressure chamber ||1 in which air is alternately compressed to transmit the force of the plunger to the hammer piston on the power stroke of the plunger and expanded to a sub-atmospheric value on the return stroke 0I the plunger to cause the hammer piston |01 to be retracted to stroke.

In order to avoid the necessity'of maintaining a perfect seal between the peripheral surface of the plunger 62 and the cooperating surface of the hammer piston for the sake-of preventing a diminution of the air entrapped in the pressure chamber I I1 it is contemplated to effect an intermitten admisssion of atmospheric air into the pressure chamber ||1 to compensate for such air as may be forced from the cavity ||2 during the power stroke of the plunger of the hammer piston and during which time the air in the pressurel chamber ||1 will, of course, be materially compressed.

In the form of the invention illustrated, the air utilized for this purpose is derived from the crank chamber 39 which the air enters through a passage ||8 in a rib ||9 extending through the fuel tank and having a strainer plug |20 at its outer end to filter the air.

The crank chamber 33 is in direct communication with the interior of the plunger 52, and in the enlarged portion |I4 of said plunger are radial ports |2| which, in the extended position of the plunger, communicate with an annular groove |22 in the wall of the piston chamber to permit the passage of air from the cranlv: chamber into the annular chamber |I5.

Communication is aiforded between the annular chamber ||5 and the pressure chamber ||1 through channels in the periphery of the plunger and in the adjacent contacting surface of the hammer piston. 'I'he channels in the plunger are in the form of longitudinally extending grooves |23 of such length that their rearward ends will be exposed by the skirt of the hammer piston during the rearward stroke of the plunger and during which time the hammer piston will assume its most forwardly position with respect to the plunger. The grooves |23 preferably extend to points near the front or lower end of the plunger and are in constant communication with an annular groove |24 near the rearward end of the cavity ||2, and from the groove |24 extend grooves |25 forwardly along the wall of the cavity ||2 to a second annular groove I3 adjacent the pressure chamber I1.

Thus, in practice, when the plunger 52 starts forwardly on the working stroke its initial movement will take place relatively to the hammer piston and will cause the rearward ends of the grooves |23 to be covered by the adjacent portion of the skirt of the hammer piston. Air will then be entrapped in the pressure chamber ||1 and be compressed, since it serves as the medium through which the force of the plunger 52 is transmitted to the hammer piston. and when the plunger reaches the end of its working stroke the hammer piston will be projected forwardly against the working implement 2| to deliver its blow.

'Ihe forward movement of the hammer piston, relatively to the plunger 52, will cause the rearward ends of the grooves |23 to be uncovered by the hammer piston and air will then again be admitted into the pressure chamber ||1 through the grooves |23, |24 and |25. 'I'his admission of make-up air into the pressure chamber ||1 takes place during the interval in which the ports |2| are in registry with the groove |22.

Upon reversal of the plunger the ports |2| are drawn out of registry withthe groove |22 and the ensuing rearward movement of the plunger will create a sub-atmospheric pressure in the the starting position of the power chambers I5 and I1 and cause the hammer piston to follow the plunger rearwardly.

The front end of the piston chamber, below the hammer piston 01, is normally maintained in communication with the atmosphere so that atmospheric pressure will be constantly present forwardly of the hammer piston to impel it rearwardly in accordance with the rearward movement of the plunger 52. The air serving this function is, in the present instance, conveyed from the crank chamber 39 by a passage |26 in the crank casing 22 and the cylinder 26 and opening into the front end of the piston chamber |08.

Normally, the valve |21 occupies a position to prevent communication between the passage |26 and the groove |3| and is only positioned to admit air into the groove |3| and, therefore, into the pressure chamber ||1 whenever it is intended to avoid the delivery of blows against the working implement, as for example when shifting the percussive tool from one drilling site to another while the engine element is in operation. In such case the valve |21 is rotated to a position in which the port |30 is in communication with the uppermost portion of the passage |26. Air will then flow through these passages and through the groove |3I and the ports |32 into the front end of the cavity ||2 to maintain atmospheric pressure therein. The hammer piston |01 will then remain at'rest in the forward end of the piston chamber |06 and will be undisturbed by the movement of the plunger, since then the pressures in the forward end of the piston chamber and within the cavity I I2 will be the same.

Preferably, a port |33 is provided between the portion of the passage I 26 lying forwardly or below the valve |21 and the adjacent portion of the piston chamber |08 so that when the working implement is removed from the path of the hammer piston, and in consequence of which the hammer piston |01 will rest upon the forward Wall of the piston chamber |08, the ports |32 will register with the port |33 to maintain the chamber ||1 in communication with the atmosphere and thereby avoid a tendency, on the part of the hammer piston, to reciprocate while the percussive tool is running idle. l

In order to assure a plentiful supply of lubricant to the bearings of the crank shaft 42 an oil chamber |34 is formed in the upper surface of the crank casing 22 and suitable oil passages |35 lead from the oil chamber to the bearings of the crank shaft. 'I'he oil passages |35 all extend in of oil in the chamber |34 and said opening |36 is sealed by a plug |31.

I claim:

1. A percussive tool, comprising a casing having a piston chamber, a hammer piston in the piston chamber having a pressure chamber, and a plunger slidable in the' piston chamber and in the pressure chamber for actuating the hammer piston and cooperating with the hammer piston to create a sub-atmospheric pressure in the pressure chamber to cause the hammer piston to follow the plunger in one direction.

2. A percussive tool, comprising a casing having a piston chamber, a hammer piston in the piston chamber having a pressure chamber, a plunger slidable in the piston chamber and in the pressure chamber for actuating the hammer piston and cooperating with the hammer piston to create a sub-atmospheric pressure in the pressure chamber and thereby cause the hammer piston to follow the plunger in one direction, and means on the plunger and the hammer piston cooperating with each other to intermittently admit atmospheric air into the pressure chamber.

3. A percussive tool, comprising a casing having a piston chamber, a hammer piston in the piston chamber having a pressure chamber, a plunger slidable in the piston chamber and in the pressure chamber for actuating the hammer piston and cooperating with the hammer piston to create a sub-atmospheric pressure in the pressure chamber and thereby cause the hammer piston to follow the plunger in one direction, passages in the plunger to convey atmospheric air into the pressure chamber, and means on the'hammer piston to control the passages.

4. A percussive tool, comprising a casing having a piston chamber, a hammer piston in the piston chamber having a pressure chamber, a

plunger slidable in the piston chamber and in the pressure chamber for actuating the hammer piston and cooperating with the hammer piston to create a sub-atmospheric pressure in the pressure chamber and thereby cause the hammer piston to follow the plunger in one direction, passages in the cooperating surfaces of the plunger and the hammer piston to convey atmospheric air into the pressure chamber, and means on the hammer piston cooperating with the plunger to control the passages.

5. A percussive tool, comprising a casing havingA a piston chamber, a hammer piston in the piston chamber having a pressure chamber, a plunger slidable in the piston chamber and the pressure chamber for actuating the hammer piston and cooperating with the hammer piston to create a sub-atmospheric pressure in the pressure chamber to cause the hammer piston to follow the plunger during alternate strokes of the plunger, vand manually operable means for selectively introducing atmospheric air into the pressure chamber.

6. A percussive tool, comprising a casing having a piston chamber, a hammer piston in the piston chamber having a pressure chamber, a plunger slidable in the piston chamber and the pressure chamber and cooperating with the hammer piston to create a sub-atmospheric pressure in the pressure chamber to cause the hammer piston to follow the plunger during alternate strokes of the plunger, a passage in the casing to convey atmospheric air to the front end of the piston chamber, a passage in the hammer piston communicating with the pressure chamber, and a manually operable valve to selectively control communication between the passages.

WILLIAM A. SMITH, SR.