US1841351A - Power hammer - Google Patents

Description

Jan. 12, 1932.

W. F. TROTTER POWER HAMMER Filed March 16 1929 :5 Sheets-Sheet 1 a; 4 i I 1% l'l q 64 W lwnonueu Jan. 12, 1932; w. F. TROTTER POWER HAMMER 3 Sheets-Sheet 2 Filed March 16, 1929 I77 Md ATTORNEY,

Jan. 12, 1932. w. F. TROTTER POWER HAMMER Filed March 16, 1929 3 Sheets-Sheet 3 INVENTOR WATTORNEY Patented Jan. 12, 1 932 UNITED STATES PATENT OFFICE WALTER F. TROTTER, OF CINCINNATI, OHIO, ASSIGNOR TO THE OHIO ELECTRIC HAM- MER CORPORATION, A. CORPORATION OF OHIO POWER HAMMER Application filed March 16, 1929. Serial No. 347,668.

This invention relates to power driven improper placement of the anvil or tool head hammers or drills for breaking pavement and with resultant badly timed impact, the objecconcrete surfacing or drilling the same by tive here being a uniform deceleration or localized impact and intermittent rotation of cushioning to a complete stop and retraction 5 the tool, and is particularly directed to an without detriment to the mechanism or shock 5 improved mechanism for converting rotary to the operator, smoothing out the driver motion into reciprocatory motion for imaction' by merging and checking the recoil pacting the, tool, and to a mechanism for rapmovement in the retraction actuation of the idly and accurately intermitting rotation of ram.

the tool for alternate rotation and impact. Another object is to provide in this type 60 The'motion converting mechanism is in of ram actuating device a yieldability of; the form of a driven cam device having two Contact between the ram and the actuating cam surfaces, the cam reciprocating a ram or means. driver by alternateengagement with the re Another object is to provide an improved spective cam faces, and thecam surfacesmade mounting for the ram or driver for hig .yieldable under impact or ram engagement. velocity reciprocation. One cam face is formed with a portion of -An intermittent motion device is provided sharp curve for initially imparting a high and inserted in conjunction with the forevelocity impulse to the ram, directing it togoing device for intermittent rotation of a 0 ward an anvil or head end of the tool, and drill impacted by the ram, and this device is the other cam face is so cleared in the adjaincorporated as a part of a worm and worm rent portion that there will be no engagegear transmission inserted between the cam ment of the ram with the first cam surface to driving shaft and the drill. interfere with the sudden impact. There- The provision is made, to accomplish this fore, as induced by this cam impulse, the result, of a worm havingathread of varying 75 ram moves of its own momentum against the pitch, by means of which a part'revolution tool anvil andimpartsaheavy impact thereto. of the Worm advances the worm Wheel one The ram and tool anvil are so related that the tooth. The present invention utilizes the impact comes during the free movement of remainder of a particular thread convolution the ram. If the tool is not in position as as the idling period for the worm gear. This 30 might occur, due to the rapid hammering, oris accomplished by terminating the rise or the fact that the tool was not held firmly pitch of theth'read upon a part revolution, against the work, theram is decelerated by and continuing the remainder in a plane at 3! engagement with auniformly curved portion right angles to the axis of the worm and 0 of the first cam, this portion straightening therefore with no p tch. The part of the out into a horizontal, and uniformly curving thread having no pitch merely passes bel'n a reverse direction to slowly retract-the tween the teeth of the worm gear wlthout ram for the next succeeding blow. rotating effect until the ad o1ning convolu- 4 It is therefore an object of this invention to tion is'engaged. As long as a lead or use provide a device for reciprocating the ram of a particular convolution of the worm or driver of the machine for impacting a tool, thread is sufficlent to advance the worm gear which device initially sharply and uniformly a least one ooth,'the rem in er of he conaccelerates the ram in downward movement volution may be straight or even of negative andthereafter releases the same, permitting pitch, the latter being of utility when oscillas 9 it to strike the tool head or anvil under the tion of a gear is desired. 5

influence of its own momentum. It is, therefore, another object of this in- It is another objectto provide for eflicient vention to provide intermittent rotary modeceleration of the actuated ram moving untion by means of a continuously meshing o der the normal, high, necessary velocity parworm and worm gear. Um ticularly when there is a failure of impact or It is further-provided that the teeth of the worm gear are straight out in part "and diagonally cut in part so that the workingsurfaces of said teeth are smoothly engageable either by the pitch portion of the worm thread or by the straight portion thereof.

Another object of this invention is to efficiently synchronize the action of the drill impacting device and the intermittent 'rotative motion device to insure intermittent impact and rotation of the tool.

Further objects and advantages will be more fully set forth in the description of the accompanying drawings, in which:

Figure l is a perspective view of'a concussion or drilling apparatus embodying the features of the present invention.

Figure 2 is a central sectional view taken longitudinally of the apparatus.

Figure 3 is a transverse sectional view taken on line 33, Figure 2, illustrating the fan for cooling the motor.

Figure 4 is a sectional view taken on line 44, Figure 2, illustrating the guided mounting of the ram in the frame. Figure 5 is a sectional view taken on line 5-5, Figure 2, showing the relatiqn of thecam to the ram.

Figure 6 is 'a transverse sectional view taken on line 66, Figure 2, illustrating the transmission for intermittently rotating the anvil from the cam shaft.

- Figure 7 is an enlarged side elevation of the cam removed from the machine.

Figure 8 is a diagrammatic or developed view illustrating. the cam layout and relation of the respective cam surfaces.

Figure 9 isan enlarged detail view of the worm' and worm gear used for imparting intermittent rotation to the anvil.

Figure 10 is a side elevation of Figure 9.

Figure 11 isa diagrammatic view or development of the thread of the Worm.

The apparatus embodying the features of the present invention is shown in the nature of a portable electrically driven concussion or drilling device. It embodies, in general, a power source as an electric motor mounted in the upper endthereof, the motor driving a cam shaft through an appropriate speed reduction gearing, and the cam shaft extending longitudinally of the normally vertically extending body of the apparatus and j ournalled in the respective ends thereof.

The concussion device primarily comprises a doublefaced cam having the advantages previously outlined, and the cam in operative engagement with a guided ram. or driver, this ram or driver being disposed "for reciprocal motion longitudinally of the body of the device. Below the ram and in alignment therewith an anvil is disposed in the frame.

.In the case of the drill, the anvil is mounted for rotation and is rotated by means of a gearing-arrangement from the cam shaft, the anvil being in slide connection With its rotabreaking tool being used a conveniently manipulated attachment device is used for afiixing the tool to the frame relative to the anvil.

Referring to the drawings, the frame of thedevice is made up of a motor casing 15, a driver and operating means casing 16, and an anvil transmission casing 17, these casings secured together in vertical relation. Handles indicated at 15 are provided on the casing, one at the top and one extending laterally therefrom. A rotor or armature 18 isvertically journalled in the motor casing and has its shaft 19 1 extending downwardly through a lower bearing 20 and a pinion gear 21 secured on the extending end. A hearing plate 22 is secured between the upper or motor casing and the intermediate or ram casing, this plate having the bearing 20 secured therein journalling the lower end of the motor shaft and also a bearing 23 journalling the upper end of a cam shaft 24. The cam shaft 24 extends longitudinally within the intermediate casing and isjournalled in the lower or anvil transmission casing.

A fan 25 is secured on the motor shaft between thebody of the motor and the bearing plate, the air circulation being through apertures 26 in the lower portion of the side walls of the motor casing and apertures 26 in the top wall thereof. -A gear 27 is keyed to the cam shaft and is in mesh with the pinion 21 of the motor. a

- The driver cam 28 is keyed to the shaft intermediate the shaft length, being maintained against longitudinal displacement by means of a collar29 engaging lts lower hub and holding it against a spacer sleeve 30 fixed to the shaft 24 between its upper hub and the gear 27. The cam is sectional, the sections 31, 32, thereof each having peripheral flanges oppositely disposed, the surfaces of the flanges being the ram actuating and controlling mediums as hereinafter described. The cams are yieldingly spaced apart by means of a coil spring 33 under compression seated in deepconcentric grooves 34 in the opposing faces of the sections. The co-related peripheral flanges of the cams pass between a pair of rollers 35-35 mounted on the vertically reciprocably mounted ram 36.

V The ram is vertically guided between pairs of ball bearing rollers 37, a pair ateach side thereof, these ball bearing rollers engaging in grooves 38 longitudinally formed in the side walls of the ram and being journalled in the side walls of the casing. The journalling of the ball bearing rollers is by means of headed studs 39 passing through the side wall of the casing and rigidly held in position by means of nuts 40, there being an intermediate shoulder 41 on the shank of each stud engaging the inner side of bushings fixed in the casing wall and preventing clamping of the inner ring of the ball bearing rollers, this loose mounting of the inner bearing ring permitting greater freedom of motion of the ram. The ram is floatingly guided for reciprocal motion in these ball bearing connections for reducing the friction and allowing the ram to move with a maximum of freedom, and when released from the influence of the cam moves under its own momentum for impact with the tool.

An anvil or impact transmitting bar and spindle 42 is mounted in alignment with the ram and has its upper end positioned for impact by the ram. The anvil has a hexagon shaped upper end 43 for rotative connection with a sleeve 44 rotatively j ournalled in bearings 45 secured in the transmission casing. The anvil extends through a downwardly disposed boss 46 of the casing and has a chuck 47 formed on its lower end.

A retainer sleeve 48 is screw-threaded onto the lower end of the boss and has an inwardly extending abutment flange 49 at its lower end. An annular shoulder 50 is formed on the chuck portion of the anvil and is adapted to engage the inwardly turned flange, this inwardly turned flange 49 being spaced away from the lower end ofthe boss, and the annular shoulder of the anvil engaging therewith prevents the anvil from dropping from the device. The spacing of the inner flange from the end of the boss 46 is suflicient to permit the unhampe'red movement of the.

anvil under the impacts of the concussion device. i

A drill 51 is socketed in the chuck in the 4 conventional manner and engagement of the ram at the beginning of a cycle. The cam' moving to the left, as viewed from the ram side, presents a sharply curved lower cam surface 52 which engages the lower roller of the ram and imparts downward movement to the ram.

If the anvil is properly positioned, the impact of the ram with the tool causes the ram to dwell in the position of impact where the slowly rising surface 53 of the upper cam comes smoothly into engagement with the upper roller of the ram and retracts the driver for the succeeding blow.

It will be apparent from Figure 8, that after the ram has departed from engagementwith the lower cam, the distance between the upper and lower cam surfaces decreases materially so that there is considerable clearance for the ram to move in, prior to engagement of the upper or return cam surface 53 with the upper roller.

1t frequently happens that the anvil is not in exact position to receive the impact or concussion, this occurring when there is chattering of thetool or when the tool is not held firmly against the work. For this reason, the upper cam surface is provided with a portion 54 adjacent the point of departure 55 on the lower cam which is designed to engage the upper roller of the ram, this portion 54 being of uniform cury e to a horizontal to slowly andsmoothly decelerate the ram in its downward direction in the event of failureof impact. This decelerating surface smooths out into a horizontal and then rises to represent the previously described slow rising surface 53 for retracting the ram. The ends of the developed view represent the beginning of.

the cycle, being taken at a coincidental line on the cam.

The throwing cam 32 has its throwing face shaped to give theram a uniformly accelerated motion downwardly. or in a direction to impact with the tool which continues while the ram is in contact with the throwing face. After leaving the throwing face of the cam 32 the ram is free to continue for a limited distance under the influence of its own momentum. It is during this period the impact with the tool or anvil takes place. If the weight relation between the ram and tool is correct, the ram comes practically to rest and remains so until contact is made between the ram and the upper or returning cam. The surface 54 of the upper cam 31 from the point or end of the throwing face of the throwing cam 32 continues to recede and with the rotation of the cam provides for the free motion of the ram for impact with the tool and comes to rest before again acted upon by the cam or the upper cam 31. The receding portion of the upper cam also serves to give the ram a uniformnegative acceleration or gradually retards the downward motion of the ram if the tool is not in position to stop or receive the impact. This action continues with the rotationof the cam until the ram is brought to rest by non-ram moving portion of the upper cam, whereupon the surface of the upper cam ascends to move the ram in an opposite direction.

The two cams. aresplined upon the shaft with the spring under tension interposed between the cams pressing each cam inthe direction in which the cam throws or moves the ram. Each cam, therefore, is capable of yielding motion or automatic adjustment to relieve it of sudden shocks interposed thereon when coming into engagement with the ram either at a point at which one of the cams decelerates the motion of the ram or counter acts the motion of the ram. The cams can thus be made separately facilitating in their manufacture. The cams are loosely keyed upon the shaft with their cam faces outwardly and stops placed on the shaft, spaced a distance apart slightly greater than the combined length of the cams along the shaft. The spring interposed between two cams serves to cushion the cams.

intermittent motion is imparted to the rotatively mounted sleeve 44, which is in rotative connection with the anvil, by means of a cross shaft 64 journalled in'the side walls of the frame. A worm 65 is pinned to the cam shaft 24 at its lower end, this worm beingin engagement with a worm wheel 66 keyed to the cross shaft. At the other end of the cross shaft 64 a worm 67 is keyed thereto and properly spaced thereon by means of spacer sleeves 68 for meshing with a worm wheel 69 keyed to the anvil sleeve 44. 1

It is the particular formation of these last mentioned .worm and worm' gear elements which provides the intermittent motion. The

Worm of this combination is shown as of a.

single thread formation. The pitch. of the worm is variedand half of a convolution thereof is devoted to a gear turning pitch and the other half is a straight thread for idling of the worm wheel. I

Regarding a given thread, as shown in the developed view Figures 9 and 11, the thread has a pitch for one-half convolution as at 70, and then is straightened out to a plane at right angles to the axis of the worm for a half convolution as at 71 where it joins the next pitch or rise portion. By utilizing half a convolution of thethread spiral for the lead, the worm wheel is advanced-one tooth and the remainder of the revolution is devoted to a dwell. i 4

Due to the fact of the use of a worm of this nature the thread presented to the worm gear is at varying angles, that is to say, at the angle of the desired pitch or at right angles to the axis of the worm. The teeth of the worm wheel are therefore cut or milled see F i re 10) parallel with the axis thereof as and also aim. tangent as at 73, the'angle of tangent corres onding to the pitch of the worm thread. T is provides teethedges always in substantial driving engagement with the thread of the worm.

Another variation of the lead, which may be used, is of the ensuing nature. If the driving lead or pitch of each convolution is of greater length than is necessary for advanc- ,ing the worm wheel one tooth, the excess advance of the worm wheel over the one tooth, requirement could be reversed by giving the remainder of the convolution a reverse or negative lead equal to the excess.

It can be seen that by this arrangement the motion of the worm wheel could be made forward and stationary for each revolution or convolutionfof the worm, or it could be made forward and backward, or it could be made forward, stationary and backward, provided, however, in all instances the restriction of having an advance. of the 'worm wheel one tooth. The excess beyond that could be varied in any manner as aforesaid.

By properly positioning the cam on the cam shaft and relating the transmission thereto, the impact is given to the anvil While the straight portions of the worm are in mesh so that the rotative dwell comes when the impact is being delivered. This synchronizatibn is highly desirable for a drill since the turning of the drill at the moment of impact would unduly wear or break off the sharpened edges thereof.

Having described my invention, I claim:

1. In a tool of the class described, a ram floatingly supported for reciprocal motions for impact with a cutting tool, and a pair of cams splined.upon an axis and rotatable as a unit, one for moving the ram in one direction and the other in a reverse direction, said cams each-yieldable in a direction counter to the direction in which it moves the ram.

2. In a tool of the class described, a ram, floatinglyrs upported for reciprocal motions for impact with a cutting tool, a pair of cams rotatable as a unit, one for moving the ram in one direction and the other in a reverse direction, and means for yieldingly urging said cams in opposite directions axially, said means taking up the shocks when the cams respectively become effective upon the ram with the reversal of strokes. f

In witness whereof, I hereunto subscribe my name. r

" WALTER F. TROTTER.

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