US1382821A - Power-hammer - Google Patents

Description

'0. B. COATES.

POWER HAMMER.

APPLICATION FILED FEB. 6, 1920.

Patented J 11116 28, 192 1.

- 3 SHEETS-SHEET I C. B. COATES.

POWER HAMMER.

APPLICATION FILED FEB-5,1920.

C. B. COATES.

POWER HAMMER.

APPLICATION FILED FEB.G,1920A 1,882,821 Patented June 28, 1921 I 3 SHEETS-SHEET 3.

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UNITED STATES PATENT OFFICE.

CHARLES B. COATES, OF CHICAGO, ILLINOIS, 'ASSIGNOR TO CHICAGO PNEUMATIC TOOL COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW JERSEY.

POWER-HAMMER.

Specification of Letters Patent.

Patented June 28, 1921,

Application filed .Febrnary 6, 1920. Serial No. 356,601.

T 0 all whom it may concern:

Be it known that 1, CHARLES B. CoA'rEs, a citizen of the United States, residing at Chicago, in the county of Cook and, State of Illinois, have invented certain new 'and'useful Improvements in Power-Hammers, of which the following is a specification.

My invention relates to percussive power hammers operated preferably, though not necessarily, by an electric motor as the prime mover and adapted to hammer purposes, such as chipping, drilling, riveting or the tamping of broken stone or.similar ballast by means of a chisel, drill, rivet set, tamper bar, or the like, to one end of which the striking member such as the hammer piston of the power hammer imparts its blow. The Ol)]8(3t of my invention is to provide a simple, efiicient and reliable machine of this type, characterized more particularly by the employment of a compression chamber through which high pressure air is intermittently introduced or in which it is produced by a compression piston directly reciprocated by the electric or other type of'motor, in combination with means whereby such high pressure air is discharged against a hammer piston operating in a cylinder or barrel, such air being so discharged when it is at its maximum pressure and after the hammer piston has start ed on its downward movement to strike the blow, thereby causing such hammer piston to deliver quick and powerful blows upon the inner end of the shank of the working tool inserted into the front end of the barrel.

Other features of advantage and utility in my power hammer will be apparent from the description hereinafter given.

In the drawings Figure 1 is a central sectional elevation of my power hammer: Fig. 2 a section on the line 22 of Fig. 1; Figs. 3 and 4 horizontal sections on the lines 3* and 4;4: respectively of Fig. 1: Figs. 5, (l and. 7 sectional elevations of the compression cylinder and hammer cylinder and their pistons, showing the moving parts in different positions during a cycle of operation; Figs. 8, 9, 10 and 11 sectional elevations of a moditied form of construction and illustrating the position of the compression piston and hammer piston in different relative positions during a cycle of operation; and Fig. 12 a detailed view of a modified form of construct on more particularly of the compression piston.

My hammer is a power hammer operated preferably by a prime mover located in the hammer structure itself and while any suitable motor may be employed as such prime mover, I prefer an electric motor because it is the most convenient and compact and also the most desirable because electric current which is avallable everywhere can be supplied thereto at any distance through cables,

My invention will therefore be described in connection with an electric motor located in the hammer structure itself as the prime moverwithout intention of limitation thereto. Moreover, I prefer to employ in my hammer a reciprocating compression piston as the means for producing the high pressure air intermittently required for the operation of my hammer. but it will be understood that my invention in its broader aspect is not to be limited to this particular ty )e of means for producing such pressure.

eferring to the particular embodiment of my invention as illustrated in Figs. 1 to 7 the power hammer comprises the motor structure and casing therefor at the upper or rearward end thereof to which is-attached a gear case and also a compression and hammcr casing and a cylinder or barrel. To the casing there is also attached a suitable handle or grip for handling and operating the hammer.

Referring to the details of construction as shown particularly in Fig. 1. the motor frame or casing 1 which is of s lble size and shape contains a suitable electric motor 2. This motor has an armature shaft 3 hearing in the end plate 4 clamped against one .cnd oi' the casing 1 and formed at its outer end as a pinion 5 which meshes with a gear (3 secured to the crank shaft T. This crank shaft operates within a gcar case formed by the platc -l and an outer parallel plate 8 and has its hearings in said plates. This crank is also provided with a countcrl)alance i).

The handle 10 which is here of a shape to receive the grip of the hand of the operator and to be thereby handled and directed in the work is secured in suitable manner to the motor casing and to the gear casing. This handle contains the electric motor switch indicated generally at 11 and is provided with a button 12 for convenient operation of the switch.

To the motor casing and gear casing is secured in suitable manner as by means of the bolts 13 a casing 14 containing two chambers 15 and 16 arranged side by side or in parallel planes. The chamber 15 is the compression chamber and within it operates the compression piston 17 which is directly connected. to the crank shaft 7 by means of the connecting rod 18 whereby the piston 17 is reciprocated by the electric motor. This compression chamber is provided with a lateral air inlet port 19 through which atmospheric air is admitted when the piston 17 has moved upwardly to a position to clear and uncover such port. The air compressed by this piston is discharged through a bottom discharge port 20 entering into the other chamber as now to be explained.

Within the chamber 16 there is secured in suitable manner as by screw threading thereinto the hammer cylinder or barrel 21. The upper or rearward end of this cylinder enters a considerable distance into the casing 14 and the piston chamber of this cylinder 21 may therefore be said to overlap the compression chamber 15. At a point coincident with the wide discharge port 20 the threads of the chamber 16 and of the cylinder 21 are cut away to thereby form an annular groove 22 which communicates with the piston chamber 23 of the cylinder 21 by means of a seriesof radial ports 24.

Within the piston chamber there reciprocates a hammer piston 25 which is adapted'on its forward stroke to strike the shank of the working tool 26 which is inserted in the front end of the hammer cylinder and on its rearward or upward stroke to pass upwardly beyond the line of ports 24 and into a cushioning space formed therebeyond in the rearward end of the piston chamber. By preference means are provided for supplying high compression air on the top or rear end of the piston when it is in this cushioning space. If desired the piston could have a loose fit in the piston chamber above the line of ports 24 but I prefer to employ the means as shown in Fig. 1. These means consist of a small port 27 leading upwardly from one of the ports 24 longitudinally through the wall of the hammer cylinder and into the extreme rear end of the piston chamber. By preference this end of the chamber is counterbored as indicated at 28 in order to provide for the unrestricted flow of the compressed air from this passage27.

The hammer cylinder 21 is provided at a point intermediate its length with an exhaust port 29 preferably closed by a suitable check valve 30 which is here a at valve in the form of a spring secured to the hammer cylinder by the screw 31. The hammer'cylinder is also provided near its lower end with a permanently open exhaust port 32.

Describing a cycle of operation and beginning with the hammer parts in their rear position as shown in Fig. 5 at which time the crank to which the rod 18 is connected is in its uppermost position, it will be noted that at this time the compression piston 17 is also in its uppermost position and with its lower face above the inlet port 19 whereby the compression cylinder below the piston is permitted to be filled with air at atmospheric pressure. At this time the hammer piston 25 is near the upper end of its piston chamber and its body covers and closes the ports 24.

As the compression piston 17 descends the air below is compressed to a high degree. During this compression stroke of the piston 17, a verysmall amount of air has passed through the small passage 27 and initiated the return movement of the hammerpiston on its power stroke. The upper or rear end of the hammer piston reaches the port or ports 24 at approximately the instant of maximum compression in the compression chamber as shown in Fig. 1. At this instant the entire charge of this high pressure air is admitted through the series of ports 24 against the upper end of the hammer piston, causing it to be driven downwardly or forwardly against the tool shank with great force and delivering an effective, snappy, and powerful blow.

Fig. 6 shows the crank pin of the crank shaft advanced slightly beyond the lower- ,most point after it has passed the lower crank position and started 011 its upward stroke. The hammer piston is shown with out an arrow in order to indicate that it is now in a neutral position and the interval between the crank positions shown in Figs. 1 and 6 represent approximately the crank angle or interval during which the blow is struck.

The compression cylinder 15 is of very much larger diameter than the hammer piston chamber 23 and relative strokes of the compression piston and the hammer piston aresuch that the displacement of the compression piston is much greater than the displacement of the hammer piston. This results in a considerable terminal pressure acting on the upper end of the hammer piston when the blow is struck. This excess pressure above atmospheric pressure raises the check valve 30 and the air in the compression 'chamber and the hammer piston chamber above the upper end of the hammer piston, is reduced to atmospheric pressure, after which the check valve closes.

Fig. 7 shows the crank at an angle of 90 degrees on its upward stroke anddue to the rarefication of the air below the comdue to the considerable vacuum created in both of their chambers.

As the upper end of the hammer piston passes the ports 24 on its upward movement, there is some compression above it due to the air being unable to leak out rapidly enough through the passage 27. Thisresults in the cushioning of the hammer piston at the upper end of its stroke. s

It is obvious that the compression piston being actuated positively by the crank shaft and the hammer piston belng controlled on its upward stroke by vacuum created by the upward movement of the compression piston, the hammer piston willlag somewhat in its movement behind the compression piston and the hammer piston will be stopped in its upward movement at approximately the point shown in Fig. 5. It will be noted that the hammer piston acts as a valve to close the discharge port or ports of the compression chamber until practically full compression is attained and that it does not receive the charge of this high compression air until it is actually moving downward on its power stroke.

As shown in Fig. 1 the center of the grip of the handle 10 is in line with the center line indicated by the broken line 33-33 which passes through the center 'of the power cylinder and working tool and also approximatelythrough the center of gravity of the complete hammer which is a distinct advantage inasmuch as it provides a perfectly balanced tool while being handled and also applied to the work.

In Figs. 8 to 11 I have shown a modified form of construction in which the compression chamber and hammer piston chamber insteadof being placed in parallel are arranged concentrically and with the compression piston provided with a central bore to act as a continuation of the hammer piston chamber. As shown the hammer cylinder 34 has formed integral therewith at its upper end a compression cylinder 35 forming therewithin the compression chamber 36. The cylinder 34 has a piston chamber 37 within which reciprocates the piston 38. The compression piston 39 is provided with .a central bore 40 which is in line with the bore or chamber 37 and into which the piston on its upward movement passes. The chamber or space 40 may therefore be said to constitute a part or a continuation of the piston chamber 37 and to overlap the compression chamber 36 in the same general sense as in the construction previously described. The mode of operation is substantially the same as above described in connection with the other form of construction with the exception that in this modified form a leakage of air is provided at 41 be tween the piston and the chamber 40 for the admission of a small quantity of compressed air from the chamber 36, in order to initiate the downward moyement of the piston after it has entered the chamber or pocket 40 which acts as a cushioning chamber.

In Fig. 12 I have shown another modified form of construction which is similar to that illustrated'in Figs. 8 to 11 with the exception that the pressure against the rear end of the. piston to initiate its return is not provided by the compression chamber 36 but by separate means consisting of a reciprocating piston 42 which is connected by means of the rod 43 with the crank shaft of the motor and is adapted to reciprocate in a central bore 44 of the compression piston 45. The mechanism is so timed that after the piston- 46 has entered the bore 44 the piston 42 will move downwardly toward the piston 46 and compress the air in the space between these two pistons with the result that the piston 46 will be initiated in its movement on its downward or power stroke. In this construction the piston 45 is connected to the crank shaft by means of a pair of arallel rods 47.

claim:

1. In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating with the piston chamber, means for intermittently compressing the air in such compression chamber to a high or working pressure, said two chambers having communicating ports, one being always open to supply compressed air to initiate the movement of the piston on its power stroke and the other being intermittently open so as to cause a discharge of high pressure air against the hammer piston after it has started on its power stroke.

2. In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating. with the piston chamber, said piston being adapted to close such communication on its return stroke, means for supplyinga restricted amount of compressed air from said chamber against the piston toinitiate its movement on its power stroke, and means for intermittently compressing the air in such compression chamber to a high or working pressure which is admitted against one end of the piston after it has moved on its power stroke to a position to open such communication.

3. In a power hammer, the combination of a cylinder having a piston chamber, a hammer/piston reciprocable in such chamber, a compression chamber communicating with the piston chamber, means for intermittently compressing the air in such compression chamber to a high or working pres sure, said two chambers being connected so as to cause a discharge of high pressure airpression chamber, to a high or working'pressure, said two chambers having a connecting port intermediate the length of the piston chamber so as to cause a sudden discharge of high pressure air against the piston to provide the energy for its power stroke, means providing a pocket to receive the piston after its extreme rearward stroke, and means for admitting air under pressure from the compression chamber to the pocket behind the-piston to initiate its return movement.

5, In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a com ression chamber communicating with the plston chamber, and a compressing piston for intermittently compressing the air in such compression chamber to a high or working pressure, said compression chamher being longer than the stroke of its piston to provide'at one end a space for the high pressure and said hammer piston being arranged to govern the communication between the two chambers, closing the same during the time of such compression and opening the same at the time of such high compression to cause the air pressure to act upon the piston on its power stroke.

6. In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating with the plston chamber, a power operated piston reciprocating in such compression chamber,- such latter chamber having an inlet air port governed by such power piston and bein adapted to discharge the compressed a1r through a discharge port communicating with thepiston chamber, said hammer piston being arranged to govern such discharge port which is located at the extreme end of the co ression chamber and through which the compressed air is discharged after stroke.-

7. In a power hammer, the combination of a cylinder having a piston chamber, a piston reciprocable therein, a second cylinder having a compression chamber communicating with the piston chamber and overlapping the same, that portion of the piston chamber which overlaps the compression chamber acting as a pocket to receive the piston on its rearward stroke, and means for compressing the air in the compression chamber, said piston governing the communication between the two chambers and acting to admit the compressed air against its rearward end for the power stroke of such piston.

8. In a power hammer, the combination of a cylinder having a piston chamber, a piston reciprocable therein, a second cylinder having a compression chamber communicating with the piston chamber and overlapping the same, that portion of the piston chamber which overlaps the compression chamber acting as a pocket to receive the piston on its rearward stroke, and means for compressing the air in the compression chamber, said piston governing the communication between the two chambers and acting to admit the compressed air against its rearward end for the power stroke of such piston, said two chambers being arranged in parallel planes and having a lateral communicating passage for the compressed air.

9. In a power hammer, the combination of a cylinder having a piston chamber, a piston reciprocable therein, a second cylinder having a compression chamber communicating with the iston chamber and overlapping the same, t iat portion of the piston chamber which overlaps the compression chamber acting as a pocket to receive the piston on its rearward stroke, and means for compressing the air in the compression chambpr, said piston governing the communication between the two chambers and acting to admit. the compressed air against its rearward end for the power stroke of such piston and means for admitting a small quantity of the compressed air from the compression chamher to said pocket and behind the piston.

I 10. In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating with the piston chamber, and means for intermittently compressing the air in such compression chamber to a high or working pressure, the said piston being arranged to govern the communication between the two chambers, closing the same during the time of such compression and opening the same at the time of such high compression to cause the air pressure to act upon the piston on its power stroke, said piston chamber the hammer piston has started on its power having intermediate its length an exhaust port controlled by said piston.

11. In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating with the piston chamber, and means for intermittently compressing the air in such compression chamber to a high or working pressure, the said piston being arranged to govern the communication between the two chambers, closing the same during the time of such compression and opening the same at the time of such-high compression to cause the air pressure to act upon the piston on its power stroke, said piston chamber having intermediate its length a check-valve governed exhaust port controlled by said piston.

12.111 a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating with the piston chamber, and means for intermittently compressing the air in such compression chamber to a high or working pressure, the said piston being arranged to govern the communication between the two chambers, closing the same during the time of such compression and opening the same at the time of such high compression to cause the air pressure to act upon the piston on its power stroke, said piston chamber having intermediate its length an exhaust port which is uncovered by the rearward end of the piston on its power stroke.

13. In a power hammer, the combination of a cylinder having a piston chamber, a hammer piston reciprocable in such chamber, a compression chamber communicating with the piston chamber, and means for intermittently compressing compression chamber to a high or working pressure, the said piston being arranged to govern the communication between the two chambers, closing the same during the time of such compression and opening the same at the time of such high compression to cause the air pressure to act upon the piston on its power stroke, said piston chamber. having intermediate its length an exhaust port controlled by said piston, and an always 0 en exhaust port at the front end of-the piston chamber.

CHARLES B. COATES.

the air in such

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