US2547224A - Pneumatic hammer - Google Patents

Description

April 3, 1951 w. E. M GUIRE 2,547,224

PNEUMATIC HAMMER Filed Aug. 30, 1946 INVENTOR. William llMacGwir A my's.

Patented Apr. 3, 19 51 PNEUMATIC HALIMER William E. MacGuire, Louisville, Ky., assignor to Frank B. Yingling, Hamilton, Ohio Application August 30, 1946, Serial No. 694,091

Claims. (01. 121-13) The present invention relates to pneumatic tools such as pneumatic hammers or the like, and

has for an object the provision of a pneumatic percussion too1 which is simple in construction and relatively inexpensive of manufacture.

Another object of the invention is to provide a tool of the class described in which a sphere, preferably of hardened steel, operates in a cylindrical bore as a combined, power piston, impact member and control. 1

A still further object of the invention is to provide in a pneumatic tool a sphere shaped piston operating in a cylindrical bore with a tolerance for clearance such that during reciprocation of the ball during operation there is maintained at all times a film-like cushion of pressure air in lieu of oil lubricant.

A further object of the invention is to provide a device of this kind which is rapid in operation and does not become heated during prolonged use and in which there is no discernible wear on the operating parts.

A still further object of the invention is to provide a pneumatic tool of triggerless construction which automatically begins and ceases operation as it is pressed'to and removed from the work at hand, thereby relieving the operator of the task and care of operating a trigger.

Another important object of the invention is to provide a tool of the class described which requires a minimum of maintenance and repair service even under conditions of common neglect.

These and other important objects are objects are obtained by the means described herein and exemplified in the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional view through a pneumatic hammer embodying the invention.

Fig. 2 is a view taken on line 22 of Fig. 1.

Fig. 3 is across-sectional view taken on line 3--3 of Fig. 1.

Fig. 4 is a plan view of the rubber retainer (removed) and forming a detail of Fig. 2.

Fig. 5 is a plan view of a modified form of retainer for use in lieu of the device of Fig. 4.

Pneumatic hammers generally, and particularly the smaller types of pneumatic hammers have heretofore been attended by certain disadvantages in that they are frequently out of service and subject to expensive repair shop services. Furthermore, such hammers have not, been adaptable to long continued operation since they become hot and have to be laid aside for cooling in order to avoid costly repairs or ruination of thedevice. The lubrication of previousl known pneumatic hammers has always presented a critical problem because of the danger of premature breakdown and expensive repairs.

The device omits the usual auxiliary piston operating control valve. The ball piston receives propelling air force in a direct flow from the supply line during operation.

All of the objectionable features of heretofore known and used pneumatic hammers are overcome by devices embodying the invention.

As exemplified in the drawings the device of the invention comprises a suitably shaped body or casting I!) having a handle portion II and an integral body 12 which together form' a pistol shaped device that is easy to manipulate. Other shapes of handles may be used, especially in larger devices.

Extending longitudinally rearwardly into the body I2 from the forward end thereof is a main cylindrical bore l3 which is interiorly threaded at M at the front end. The bore I3 terminates in a dished or tapered end wall l5 at the rear which corresponds in shape to the end of a drill.

valve bushing 20 is seated in the rear end of chamber l8 and is provided with diametrically opposed holes 2l2l which are aligned to communicate with and form a continuation of the supply passage ll. Holes 2l2l are normally closed by a sliding cylindrical air valve 22 reciprocably mounted in said bushing 20. The

valve 22 base. circumferentialgroove 23 which may be brought into registry with holes 2l-2l to place that part of passage ll in the handle I l in communication with the inlet passage l5 to the rear end of the main cylindrical bore It. The forward end of valve 22 is developed into a stem 24 which extends through the center of chamber [8 and terminates behind a threaded end plug 25 which closes the forward end of said chamber. i

For convenience in construction a tubular steel casing 26 is pressed into bore l3 to a seating position against the tapered end wall 15 thereof, and this casing has a finished (smooth) cylindrical bore 21 wherein a spherical piston and impact member 28 operates freely. The sphere or ball 28 may be a hardened steel ball purchaseable in the open market in the desired size, for example, one inch (1") in diameter. The bore and ball are true as nearly as may be within commercial limits.

At this point it is to be noted that an initially true sphere within a true cylindrical bore of greater diameter than the sphere will afford practically a single near point of contact only between the sphere and the surrounding surface of the bore. In practice, the device of the invention may have a tolerance of about .0015 provided between a one inch (1) ball 28 and the inner surface of bore 2?, so that when the parts are at rest there is little more than a theoretical single point of contact between the bodies.

The ball piston 28 is yieldably urged to the rear end of bore 2! by alcoiled push spring 29 which is housed in bore 2?. A tool receiving socket member 3% is slidably entered into bore 221' of casing 25 and has at its rear end an extended portion 3i of reduced diameter which is surrounded by spring 25. The spring 29 abuts shoulder 32 on the socket member 35. The forward end of member til has an annular flange 33 which fits in the main bore it, this flange having a hardened projection or trigger arm 34 integral therewith and extending radially through a guide slot 35 which is cut through the common wall portion 3% between bores 13 and it, said slot extending from the front end of threads i i to the forward end of tubular casing 25. A hollow end cap 3? has a threaded nipple 38 which is screw threaded into, threads H at the forward end of bore i3 and this end cap positively limits the outward movement of tool socket 36. An axial bore 39 through the end cap 31 is formed of suitable diameter to freely pass the shoulder 4d formed at a distance from the end 4! of a tool such as a rivet set 52. The end 4! of the tool d2 which passes through the tool socket 35 is thus centered in the bore 2? and subject to impact by the ball 28.

In order to avoid accidentally dropping tool 82 out of the tool socket 3%] there is provided, an annular rubber retainerfifi which seats, in an an,- nular counterbore 44 in the end, cap. The, retainer ring 53 has an inwardly extending flange of lesser thickness radially slit at intervals to form flexible teeth 45 which may be forcibly flexed toward the rear or front by the passage of the tool shoulder 43* into or out of the axial bore 39. (See also Fig. 4.)

As an alternate arrangement a coil spring formed suitably to ring shape 43% (see Fig. 5) may be used in lieu of retainer 43.

In valve chamber H) a coil spring 48 surrounds the stem 2 and abuts the end of bushing. 28: at one end while the forward end presses against a shoulder ll integral with the stem and abut.- ting the trigger piece 34, said trigger piece having a perforation therein to freely pass the projecting end of valve stem 2i.

From the foregoing it will be apparent that valve 22 normally closes air supply passage i? and that in order to energize the device it is necessary that a tool such as 42 be operatively mounted as shown in Fig. l and pressure applied to the tool sufficient to move tool socket 156 rearwardly, thus compressing spring 46 under the trigger piece 34 and also exerting some slight compression on spring 29. When this pressure has served to move annular groove 23 to registry with holes 2I-2I, air entering passage 11 from an exterior source (as hereinafter described) passes directly into inlet it and moves the ball piston 23 against the resistance of spring 29.

An exhaust port 48 is drilled through tubular casing 25 and the common wall 38 so that as ball' piston 28 passes the exhaust port 48, the pressure is exhausted into chamber i8 which is in turn opened to the atmosphere through a vent 49. The built up pressure is thus momentarily reduced and relieved at approximately the instant when the ball 28 strikes the rear end of tool 4i whereupon the rebound of the ball and the release of the compression of spring 29 return the ball piston toward the rear wall I5.

' It should be noted, however, that this return movement is quite rapid and that the flow of inlet pressure air has not been cut off so that the ball tends to compress the incoming air and thus cushions the ball against actual contact with rear wall [5 on the return stroke during operation. The actual travel of the ball, except in starting and stopping of the hammer, is thus shortened but very rapid and the reciprocation continues uninterruptedly so long as valve 22- is held in an open position by pressing the work end of tool d2 against the work.

Should the tool slip from the work, the reciprocation and impact ceases instantly because the spring instantly shuts on the air pressure supply at the holes 2l2l.

In the present embodiment there is provided an exteriorly disposed, adjustable air valve 50 with a threaded nipple 5| screwed into the bottom end of the handle II. The member 58 has an angularly related nipple 52 for the attachment of a conventional air pressure hose (not shown). Angularly related bores 53 and 54 are controlled by a threaded needle valve 55, the end of the needle valve projecting exteriorly as a flattened pin 56 and extending through a similarly shaped elongated aperture 57 in an exteriorly knurled hollow thimble 5B. A Washer 59 riveted to, the end of flattened stem serves to retain a spring 58 beneath it for pressing the bottom of the thimble toward the flattened end bl of the boss 62 from the center of which the threaded valve 55-55 extends. Surrounding said valve 55-56 a series of drilled holes or sockets63 are spaced apart at to each other, and theseholes selectively receive a pin 65 which projects from. the bottom face of thimble 58. The air pressure supply to the device is thus easily and positively regulated, as desired without the use of any tools whatsoever, by merely pulling out on the thimble against the resistance of spring 55 to unseat pin 64 from one of the holes 63 while turning the thimble for adjusting the threaded valve 55.

By the arrangement shown, the regulator valve 50 may be quickly detached from the hammer II if desired while the valve remains connected with the. air hose (not shown) t will be understood that the hammer of the invention, as herein exemplified, is completely automatic and requires no, manually operable finger or valve to start and stop operation other than the pressure of the inserted toolv upon the work. This is particularly desirable for riveting and certain other operations particularly. because;

. the operator can position the end of tool 42 exactly as desired upon the work without; energizing the ball. The combined resistance of springs 29' and 6 are overcome by pressing the body H toward the work after the tool 42 has been positioned, a pressure of ten (10) to fifteen (.159

pounds being required ordinarily in order to open valve 22 and admit operating; pressure through inlet port H5 at the rear of bore 21.

It has been found that with the tool pressed against the Work sufficiently to open valve 22, the

incoming pressure at 90gpounds per square inch,

for example, is effective on half the circumference" of ball 28 and drives it forward against the resistance of spring 29 which is thus loaded, but not completelycompressed at the moment piston 28 strikes the end 4! of the tool. The combined impact rebound force and the pressure of spring 29 which is exerted upon the ball valve begins to drive the ball rearwardly during the initial returnalso the loading pressure of spring 29 is greatly reduced whereupon the built up pressure behind the ball again drives it rapidly forward on the next impact stroke.

As has been previously noted the ball 28 has an actual clearance which allows a film of pressure air to surround the ball on all sides during operation so that oil lubricators in the hammer, as well as in the pressure supply line (not shown), are done away with completely. The ball having the previously mentioned clearance within the cylindrical bore is apparently at all times centered within the bore and. pressing toward the hollow interior of the spring coil 29. The ball, however, is free to turn and the impact point on the ball is more or less constantly changing. There is a notable absence of any discernible traces of wear on the ball or the cylindrical surface of the bore 21 despite the absence 'of any introduced lubricant. c

It will be understood that the tolerance between the ball and the cylinder may be quite close and that it would normally be somewhat greater for a larger ball piston operating in a bore of greater diameter than that exemplified hereinbefore. This variation in clearance tolerance follows generally the practice of increasing the tolerances as the diameters are increased.

In practice it has been found that the limits of reciprocation of the ball piston 28 will be found on opposite sides of the exhaust port 48 as established by the factors of the spring pressure, the built up air cushioning pressure and the resultant rebound from the impact of the ball piston on the tool.

The hammer as described makes it impossible to operate the piston on the tool unless the latter is pressed against the work. The hazard to bystanders from tools accidentally discharged from pneumatic hammers of this kind is completely eliminated. 7

It will be understood that various modifications may be made in the structural details and the means for controlling the admission of pressure air to the device, all within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In apneumatic hammer the combination of a body having a cylindrical bore, a spherical piston freely reciprocable in the bore, a tool receiving socket mounted for limited reciprocation in the forward end of said bore, a coil spring within the bo-reand having its opposite ends abutting said tool receiving socket and said spherical pisto'n respectively, a trigger piece integral with the socket, the body having an air inlet passage communicating with the rear end of the cylindrical bore, and a self-closing valve controlling the air inlet passage and yieldably moved to open position by the trigger piece as the socket is moved into the cylindrical bore against the yielding resistance of the spring.

2. In a pneumatictool the combination of a body member having a cylindrical piston-receiving bore and a valve-receiving'bore in parallelism therewith separated by a common wall portion, said wall portion having an exhaust port opening therethrough intermediate its ends and further having a slot adjacent its forward end, a tool receiving member reciprocable in the forward end of the bore and having a trigger piece extending through said slot in the common wall and into the saidvalve-receiving bore, the body member further having an air supply passageway extending from the exterior thereof and thence transversely through the valve-receiving bore and terminating at the rear end of the piston-receiving bore, a slide valvein the valve- 7 receiving bore controlling said pressure supply passage and having a shouldered stem member engaging the trigger piece, a spring urging said stem and trigger .piece forwardly for yieldably retaining. the valve in closed position, a spherical piston'in the cylindrical bore, a coil spring in said bore abutting the toolreceiving member and the spherical piston, a hollow end cap secured on the body coaxially of the cylindrical bore and provided with an internal annular groove concentric. with the axial bore, and a centrally apertured deformable tool retainer seated in said groove in said end cap.

3. In a pneumatic hammer the combination of a body having a longitudinal cylindrical bore, a spherical piston reciprocable in said bore, a movable tool-receiving member in said bore, a compression spring in the bore between said piston and said tool-receiving member, a tool in said member with an end disposed operatively in the path of the piston and means actuated by said tool-receiving member for automatically controlling an operating pressure supply to the bore behind the piston.

4. In a pneumatic hammer the combination of a body having a longitudinal bore, a'piston reciprocable in said bore, a tool receiver having limited movement longitudinally in the forward end of the bore, a coil spring interposed between said tool receiver and said piston, a self closing valve for controlling a compressed air supply to the rear end of the bore, and means on the tool receiver for opening the valve as said receiver is moved into the bore against the resistance of said spring.

5. In a pneumatic hammer the combination of a body having a longitudinal bore, a piston reciprocable in said bore, a longitudinally open tool receiver mounted for limited axial movement at the forward end of the bore, a coil spring in the bore yieldably urging said piston and said receiver to opposite ends of the bore,'and a spring closed valve for controlling a compressed air supply to the rear end of the bore and actuable to open position by the tool receiver as said receiver is moved rearwardly in the bore.

WILLIAM E. MAcGUIRE.

(References on following page) REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Moore "-1 Aug 31, 1897 Keller Sept; 30, 1902 Dunlap Apr. 28, 1908 Boyer Sept. 8, 1908 Townsend May 27, 1913 Lewis Nov. 17, 19-14 Wade June 1, 1.926

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