US2609813A - Gas hammer - Google Patents

Description

` mwa/w A Sept. 9, 1952 S. B. MAURER ET AL GAS HAMMER Original Filed Aug. l5, 1946 2 SHEETS- SHEET l INVENTORS .SPENCER B, MAUREI? ,sA/eLacAT/M HOWARD ,0. ,SBE/w Sept. 9, 1952 S. B. MAURER ET AL GAS HAMMER original Filed Aug. 15, 194e 2 SHEETS-SHEET 2 A INVENTORS .SPENCER B. MAURER ATTORNEY Patented Sept. 9, 1,952

2,609,813 GAS HAD/[MER Spencer B. Maurer and Howard PrEbert, Cleve` land, Ohio, assignors to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Original application August 15, 1946, `Serial No. 690,654. Divided and this application July 8, 1949, Serial No. 103,662

9 Claims. 1

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 improvements to a tool of this type in which the driving piston is returned through its `compression stroke by the momentum of a ily-wheel and' crankshaft operatively connected to the driving piston. A tool of the class to which this invention :relates is illustrative by a gas hammer for which :a Patent No. 2,333,419, was issued `to Clifford E. Fitch on November 2, 1943.

In the illustrative embodiment oi the present invention, a tie tamper is driven by a gasoline powered single cylinder, two cycle, air-cooled .i

engine designed to impart `rapid downward blows to the tamping bar which is `mounted vertically in the lower end of 'the tool. The engine -is mounted directly atop `a .cast aluminum housing which is the main` body of the tool land. to which are secured a gasoline supply tank, a carburetor, air cooling .appara-tus, hammer piston barrel, and manipulative handles. The location of these handles in line with `and just above the center of gravity yoi' the tool assembly i insures a proper balance for easy handling of the device. The tool is operated by one man who grasps the two handles near the top where most of the weight is :concentrated Aand directs the tool by placing the spade `of the 'tamping bar in position and allowing the toolI to -dri-ve the stone ballast under the -ties as desired. The operator then lifts the `tool to another spot to` repeat the operation, the tool continuing -to operate during the transfer movement. Thus the tool operates continuously without any loss .of time.

An object of the invention is tor ,provide a novel arrangement of the :tamping bar in relation yto the driving elements which will be highly` `effective in operation. y

A further object is to improve the structural arrangement of the striking piston, .the` piston cage, and the piston barrel so that these members will operate more eiciently in `combination with each other and as a means Aof transmitting power from the main crankshaft 4to the tamping bar.

Other objects of the invention ,are to provide a tamping bar arrangement in a percussive tool having the above-objects in mind, which is simple in construction, has a minimum number of parts, easy to assemble and take apart, compact and eiiicient in operation.

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

Fig. 1 is a View, in perspective, oi the tool of the present invention, .shown adapted for the tamping operations, with the starter handle `in the lowered position;

Fig. -2 is a longitudinal Sectional view 4taken generally along the line 2-2 o-f Fig. 1, the. lower part of the tool being Shownin elevation;

Fig, 3 is `an enlarged `1cngiti1dina-l sectional view taken generally .along line. `3--3 of Fig. l, showing the striking hammer and cage lowered or foremost position Ain Contact :with the Working implement Fig. 4 isa cross-section as indicatedfby the arrows 4fil-4 in Fig'- 3;

Fig. 5 is a strobotac `chart .0f the hammer? -Dosi-tion shown in relation to the Vacuum, open por-t, and pressure regions of the striking cage at progressive angular positions of A,the crank.

As shown -n Figg. l, `the tool of the invention is a portable, unitary structure which may be manipulated by one or two `men by means of properly and conveniently `disposed handles 1 3 and t4. For purposes of description, the tool may be considered as divided into a phiraliiy of cooperating sections or parts including an rupper portion l5, a downwardly extending barrel I6, and a barrel extension or nose `Il. Extension or nose -ll supports a work-ing implement la which, in the presen-t instance, is `a tamping bar. Referring also to Fig. 3, the inner end of the bar .l-8 projects into the `barrel l6- in `position ,to receive blows ,of percussion `from a hammer piston i9. T-he piston i9 `forms part of a fr ee piston type hammer assemblyand moveswithin a cylindrical 4cage 20 slidably mounted within `the barrel |16. The cage 20 is reciprocated by power `transmission*means connected to the driving 4lpiston 2| ,of the internal combustion engine,` Fig. V2. The transmission means, yhereinafter -rnore ,fully described-f, comprises :an engine `cranlshaft 22 driven by the piston 2l, a main crankshaft 23 actuated by the eng-ine crankshaft ,2,2 through pinion and gear `meansand-a connecting'rod 24 between the main `cranks-riait 2.3 and the .cage 2,0. The reciprocating `action of cage `il] `imparts `repetitive hammering action to the :hammer `pis- `ton :i9 `as yLieren-latter described.

The ,bar i8, maintained in operative .position Within-the barrel iand oaifnfslnose Il, is pressed into `engagement with the .work -by the .operator during 4operation of the tool and is driven Youtwardly by repetitive blowsoi percussion delivered upon its .inner end by the hammer piston t9, The adjacent-ends .of `the barrel LG and `the barrel nose Il are provided with flanges 1.5 and 26 respectively which are secured together ,by bolt .means 2.1. `As best shown Lin Fis. aldea-1b.- ing` sleeve 2 8 to maintainwjthetamping 'bar iii in `alignment with the. barrel .and nose `is .disnosed within the outer end of .the 'barrellnose il and fis provided jat itsinner ,end with a' `ilange 29 which seats upon an Vinwardly projecting shoulder '3,0 `of the nose jl Sleeve 28 ismmade in two pieces Ahaving complementary recesses forming ahexagonal opening for thebar I8. vThe The latter ring abuts a retainer ring 33 'A which is seated in fixed positionY between the upper end of the nose I1' and shoulder 34 adjacent the flange 25 on the lower end of the barrel I6. Abutting the inner end of the retainer ring 33 is an upper snubber ring 3,5 which is maintight closure for a chamber or air pocket 51 which -v lies above hammer piston I9. verselyvbored to receive the Vwrist pin 55 and is The head is trans- Vprovided at its upper end with a square recess tained in such abutting position by aV preloaded compression spring 36 extending between the ring 35 and an internal annular hangs 3i upon the barrel I5. The resistance of the spring is such as to maintain ring 35 in abutting relationship with retainer ring 33 and thereby to maintain the tamping bar in predetermined position under the weight of the tool as positioned for normal operations. The lower snubber ring 32 is formed with an internal annular seat i3 and the upper snubber ring 35 is provided with an internal annular seat 39, said seats being arranged in opposition to form with the intervening retainer ring 33 a chamber 4I within which a collar or fiange 42 on the tamping bar i9 reciprocates. The tamping bar is driven downwardly or outwardly by the blow of the hammer piston I9, the collar 42 sometimes striking the seat 38 of the lower snubber ring 32 which yields with the preloaded compression spring 3l. Ii the tamper bar I8 is held off the ground with the machine in operation the spring 3i reacts to force the bar upwardly after each blow, driving it against the seat 39 of the upper snubber ring 35 where its force is absorbed by said ring as yieldingly reinforced by the preloaded compression spring 36. The upper snubber ring 35 is formed with an upwardly projecting cylindrical flange 43 which, in conjunction with the sleeve I5, maintains the tamping bar in axial alignment with the hammer piston I3.

The tamping bar is driven in its working operations by blows percussively imparted vby the striking or hammer piston I9 which is slidingly mounted in cage 29, Fig. 3. which is made from seamless steel tubing, is provided at its ends with annular enlargements or shoulders 44 and 45 which slidingly engage the inner wall of barrel l5. The mid-portion of the cage 25 is of reduced external diameter to provide an annular spaceV 46 between the cage and the barrel, and said portion of reduced diameter is formed with a series of circumferentially spaced ports or openings 41 to cooperate with a groove 48 in the piston I9 as hereinafter more fully described. The shoulders i4 and d5 are formed with circumferentially-arranged longitudinal recesses 49 which serve to connect the annular space 46 respectively with chamber 52 of the main crankshaft andk barrel chamber 53, Figs. 3 and 4. Continuous communication is thus established between the top and bottomA of the cage to minimize pressure fluctuations. The chambers 52 and 53 may be vented by exhaust ports 52 and 53' or alternatively may be enclosed from the atmosphere and maintained at any suitable pressure. In any event, the pressure fluctuations in chambers 52 and 53 are slight, due to the equalizing effect of recesses 43 which transfer air fromone chamber to the other and thereby inhibit compression in either chamber as a result of the movements of cage 29 and piston I9. Cage 20 is connected to the connecting rod 24 by means of a pivot pin 55 which is passed through aligned holes in the upper end of the Cylindrical cage 2o,

to receive the lower end of the connecting rod. The cage head ES'has a downwardly protruding portion 55 which `lls up a considerable part of the air pocket 5l. Reciprocating movement is impartedto the cage 29 by the connecting rod 24, and rist'ransmitted through the air pocket 5l to the striking piston I9, as will shortly appear.

The striking or hammer piston I9 has a sliding nt with the inner wall of the cage 20 and is formed with a lower face 5B which'functions as a hammer surface to strike the upper face of the tamping bar I8. The piston `I9 is formed with a cup shaped recess 59. in its upper portion and with'circumferential groove 48 approximately midway its length. Grooveii is connected to recess 53 by radial ports Si), so that upon the registration of ports lil with'groove `4i'the interior of the cage 20 is connected to atmosphere through recess 59, ports 5U, groove 48, ports41, space d3, recesses 49, chambers 52 Iand' 53, and exhaust ports 52v and 53'. Recess 591is shaped to loosely receive the protruding portion of cage head 56, andforms a continuation of the pocket 5i. VUpon downward movement of the cage 20, air is compressed Within such pocket 51 forcing the piston I9-downwardly to strike the V'tamping bar i5. At this point the circumferential ports Il? in the cage are brought into registration with the groove 48 in the piston, and the compressed air in the pocket is set free.Y The cage 20 thereupon moves upwardly during the ports 4'I out of registration with the groove 48 and a partial vacuum or area of low pressure 'is created in the cage pocket 5l. This will cause the piston to follow the vcage upwardly until theports and groove are again in registration. The momentum of the hammer piston I9 carries'it upwardly for a short time after the cage has started downwardly, thereby forming a compressed air cushion which prevents the han'im'erV 'piston from striking the cage. As the cage continues downwardly, the compressed air Aforces the piston downwardly to begin anew'cycle'.

Reference is made to the chart, shown as Fig. 5, :for a graphic explanation of the movement ci the cage 29 and hammer piston I9 in relation to the angle or the main crankshaft 23. In operation, the cage 29, whose position relative to the barrel E6 is depicted by Vfour solid lines,

' reciprocates through a two inch stroke, being driven by the crankshaft at approximately 1400 revolutions (or reciprocationslper minute. The piston I9, represented by broken lines, operates inside the cage and its movement is ailected by the cage only through the air pressure inthe chamber or pocket 5l above the piston I9. When the machine is standing up resting on the bar IS with the cage 20 at Vthe bottoni of its stroke and the piston I9 down on the bar, the port holes 4l in the cageregister withY the groove i5 in the piston. When the cage rises, theports in the piston are closed and a partialfvacuum is created in the closed chamber 51.7between the piston and cage head. This creates a net upward force on the piston causing it ,to rise after the cage. This accelerating force continues to increase until the piston attains a'higher velocity than that of the cage whichwoccurs under 5. normal operation somewhere around 280 but under starting conditions may occur later. Then the accelerating force begins to decrease although the upward velocity of the piston continues toA increase until the piston Aand cage ports again line up and atmospheric pressure is restored to the air chamber 51 and 59. This occurs at about 330 under normal operation, and at top dead center the piston ports again close off as the piston rides into the pressure pocket or upper portion of the cage. The upward velocity of the piston is then reduced as its energy is absorbed by the air being compressed in the pressure pocket 51. At about 60 past T. D. C. the piston has lost its upward motion and starts downward. Since the cage is movingdownward at a now increasing rate (due to the crank angle) the piston and cage continue to move relative to each other building up a still higher air pressure in the air pocket 51 as some of the kinetic energy of the rotating parts is converted andl stored in the compressed air. At about 90 past T. D. C. the piston has attained the same velocity as the cage (maximum cage velocity occurring at this point), and peak air pressure has been attained. From this point to 155 the piston I9 is accelerated above cage speed as the energy stored in the air is returned to the piston in the form of increased downward velocity. At this point, 155 past T. D. C., the ports are again opening and the piston has attained its maximum downward velocity. The piston then strikes the bar I8 at about 170 crank angle just as the Vacuum pocket 51 is again about to close.

The exact point at which the bar I8 is struck depends upon the relative location of the bar to the rest of the machine. If no downward force is applied to the machine by the operator, the machine will tend to rise until the bar collar 42 is down close to the snubber ring 32 as illustrated diagrammatically in Fig. 5. The piston having struck the bar transfers a large portion of its energy to the bar and rebounds upward with a low velocity as shown on the chart. The upward velocity of the cage exceeds that of the piston at` about 200 past T. D. C. and the piston rides into the vacuum pocket 51 and starts a new cycle. Any loss of air from the pressure pocket through leakage around the piston I9 is made up when the cage and piston ports line up again allowing atmospheric air to enter. This tends to maintain constant conditions from one cycle to the next and insures uniform operation.

Compared with a prior commercial structure, which is shown in Fitch Patent 2,333,419, the primary advantages of the present type cage and piston arise from the removal of the bottom pressure pocket and the change in character of the top pocket. The volume of the top pocket has been increased so that more air is available to be compressed. This means that a lower peak pressure will be attained in absorbing the upward energy of the piston and returning it in a downward direction. The length of the piston stroke while in the pressure pocket will as a result also be increased so `that the lower average pressure will impart the same energy to the piston. This reduction in peak pressure means reduced forces on all rotating parts and less vibration of the whole machine. The protruding portion 56 of the aluminum cage head 56 is designed to` fit down inside the hollow portion of the piston It when the piston is near the top of the'pressure pocket. This is necessary so that the nal volume of` the air chamber at peak'pressure 61 will be small enough to prevent` the piston from actually touching the cage head.

The removal of the bottompressure pocket of the old design eliminatd the possibilty of the piston riding into this pocket atfull striking velocity if snubber failure should allow thebar to drop below normal level. This happened quitefrequently on the old machine whenthe rubber snubbers failed causing breakage cfV magneto parts, crankcase housings, crankshafts and other fairly rugged parts of themachi'ne. In the new machine a vacuum pocket on` top ef the piston has replaced the lower pressure pocket andas a result if snubber failure should occur the pis-ton will ride right through the-vacuum pocket and thus it drops out of engagement with the cage ports and ceases to operate until-the bar has been restored to its proper position. This happens when the piston port groove li-B `drops below the bottom of the cage. It is impossible for the pist0n to come completely out of the cage.

The peak force that can be `exerted on the piston or cage by the vacuum pocket 51- is not large, since little is required tovraise the piston. on the up stroke of the cage during normal operation. W hen the piston does drop out ofthe cage vacuum pocket it ceases to strike the bar It andthe motor speeds up thus advising the operator that something is wrong and at the same time preventing further operation which might harm other parts of the machine.

Still comparing the present invention fwith its predecessor, both the cage and the piston` are simpler in design and much cheaper to manufacture. Several difficult precision grinding operations have been eliminated and the total lathe time considerably reduced. The great reduction in weight of the reciprocatingY parts has reduced the inertia forces which contribute to vibration of the entire machine. The elimination of the scotch yoke and substitution of the light weight cage and connecting rod was an important improvement along this line.

The machine is further protected from shock loading by the two preloaded snubber springs 35 and 3| which limit the upward and downward motion of the bar by absorbing the energy from the bar in either direction at relatively low peak forces. Approximately ofbar shake is provided before the bar collar 42 contacts either spring. In normal tamping operations, with the operator applying a slight downward pressure on the machine, the bar collar is about 1/8" away from the ring 32 on the lower snubber spring si, and since the bar travel per blow is muchless than this, the bar collar does not contact either ring 32 or ring 35. However, when the machine is being lifted, the lower snubber spring 3l absorbs the full energy of downward motion of the. bar and returns the bar upwards at a reduced velocity due to energy having been lost in friction chiefly between the bar and the two hexagonal bushings 43 and 28 which guide it. The function of the upper snubber spring 35 is to absorb the energy of the upward motionor the bar I8 and return it in a downward direction. The `bar may oscillate back and forth several times before theV energy is dissipated and the next blowis struck.

The upper portion l5 of the `tool contains the internal combustion engine and :controls therefor, including the starting mechanism and flywheel magneto. In the illustrative embodiment the engine is of the two-cycle type. The principal supporting element for, the engine is a frame piece or crank case Bl, to which isbolted a cover the frame piece and cover being made of Y identified asthe combustion chamber and the pre-compression chamber. A mixture of gasoline and air is introduced into the combustion chamber 66 through a port El in the cylinder 64 while burned gases resulting from the explosion within the cylinder will escape through an exhaust port EB. The port 6'! communicates with a transfer passage 69 formed in the cylinder head. rThe flow of gasoline and air into the precompression chamber S2 is controlled by a carburetor, not shown.

Transfer passage 69 communicates also with the precompression chamber 62 by a port l!) in the piston, whenever port 7G registers with a complementary cylinder port. The port l is controlled by the piston v2| and is open only in the lowermost operative position of the piston, as in Fig. 7. In the operation of the engine an explosive charge, previously introduced into the combustion chamber 66 is ignited by a spark plug ma mounted in the cylinder head |35 and extending into chamber 66. The piston 2i is thereby driven downward through its power stroke, and near the end of its downward movement uncovers exhaust port B8. Shortly after the opening of such port, the piston 2| uncovers port El' and a pre-compressed mixture of gasoline and air flows into the combustion chamber El?. The mixture is directed upwards by deflecting surface 14 on the head of the piston 2| and forces the burned gases downward and out of the exhaust port 68. Near the start of the upward or return stroke of the piston the port 61 and exhaust port S8 are closed. As the piston 2| continues its upward movement the precompression chamber 62 expands in size and draws a fresh mixture of air and gas from the carburetor. The fresh gases are prevented from entering the combustion chamber 66 at this time. While a new charge is thus drawn into the precompression chamber t2, the one previously admitted to the chamber 66 is compressed and, as the piston reaches its uppermost position, is ignited and explodes. The downward movement of the piston resulting from the explosion again reduces the size of the precompression chamber |52 and the gases within the chamber are first compressed and later transferred through the supply passages` E9 to the upper chamber 65. The engine thus completes a cycle of operation in two strokes or one reciprocation of the piston; each descent of the piston being a power stroke occasioned by an explosion in the combustion chamber.

The left hand end of the engine crankshaft extends into the crankcase chamber 62 and has keyed thereto, a crank arm 19. Arm 19 has an outwardly projecting stud 8| extending into the connecting rod 63 and is also formed with a counterweight `|33.

For effecting return motion of the piston 2 and thereby of the piston hammer assembly, a iiywheel 84 is mounted upon the outer end of the engine crankshaft. The kinetic energy stored in the ily-wheel 84 on the power stroke of the piston 2|, in conjunction with the counterweight 83, is

sufcient to continue the rotation'of the crankshaft 22 and to transmit through the crank arm l and connecting rod 53 force for the return stroke of the piston 2|. The connection between the rod 63 and the crankshaft 22 is such that they are constrained to move in unison, and operation of Veither element effects a simultaneous operation of the other. Their relationship as driven and driving elements is mutual and reversible.

The ignition system of the tool includes a ilywheel magneto mechanism S2 for generating an electric current which is supplied through a cable to the spark plug 70a and is adapted to supply interrupted current under the control of suitable timing or circuit breaking mechanism. The ilywheel magnet mechanism is mounted upon the right hand end of the crankshaft 22, and retained against longitudinal movement alongrthe shaft by a suitable nut E@ and washer dI.

The engine crankshaft 22 drives the main crankshaft 23 by means of pinion 93 on the engine crankshaft and the gear wheel S63 which is integral with the main crankshaft. Main crankshaft 2S is rotatably mounted inthe frame 6i by needle bearings Se and ball thrust bearings 5l, and is provided at its forward portion with splines which form a pinion S8 to cooperate with the toothed clutch ring 99 on shaft |07. The inner face of gear 'wheel @Il is provided with a stud which projects into the terminal portion |63 of the cage connecting rod 2d. Connecting rod 2t is connected at its lower end to the cage 2 by pin 55. It thus may be seen that the reciprocal motion of the engine or driving piston 2| is transmitted through the connecting rod 63 and the crankshaft arm 'i9 to impart rotary motion to the engine crankshaft 22 and that in operation the engine crankshaft 22 drives the main crankshaft 23. Crankshaft 23, through the cage connecting rod 24, acts as a reciprocating driver for the cage 20.

The starter shaft |67 is mounted in the frame el, its end portions being supported by needle bearings HS and |59 which are carried respectively by the frame t! and the starter cover |2I.

In the illustrative embodiment the total gear ratio from the starter shaft lill to the engine crankshaft 22 is 11.4 to 1. Thus a quarter turn of the starter shaft will turn the engine over approximateiy three times. A rapid downward thrust of the starter handle i3 through its normal ten inch stroke (approximately one-quarter turn of starter shaft) will produce more than three full revolutions of the engine at a fairly high speed.

The gear ratio between the engine crankshaft 22 and the main crankshaft 23 is about 2.85 to 1. The advantages or using a high speed motor with gear reduction are more power per cubic inch of motor, more cooling air with a smaller fan, better magneto operation (hotter spark) and smoother operation due to larger number of smaller motor impulses and accentuated ily-wheel effect of the rather heavy magnete rotor.

. When the tool is not in operation the starter handle Itis maintained in locked position against one side ofthe tool by the latching mechanism ISA-l. When the tool is in operation, the starter handle is clear of the latching mechanism, as in Fig. 1. Latching mechanism |36 comprises a stud |35 screwed into the frame 6|, a latchV |35 which is pivotally mounted on the outer end of the stud and 1s provided with a handle |31, a helical spring |38 mounted upon the stud to urge the latch outward, -a `nut |39 preventing'outward movement of thelatch, anda cotterpin |40 to secure the nut onV the stud |235. The spring is formed with "anextendin-g terminal IAM which is in pressing It is not `necessary for the operator to transfer his grip from? the-'starting handle after starting the machine since this handle is also used for manipulata ing `the unit. 'Tolunlock thelatch, it is merely necessary forl'theoperator by manipulative pressure to-li't the latch in a clockwise direction, slightly beyond the horizontal position and move thestarterhandle'lS outwardly in a clockwise dii reotion to the position shown in Fig. l. He then by a quick thrustoi the starter handle can sta-rt `the-motorl The air cooling system has been provided for the toolandser'ves not `only to cool the engine vbut to "keepother" parts yof the tool at a tempervatuiuthat is comfortable forthe operator. rlhe rearl face of {theffly-wheel 84 is provided with a oircumferentialI rowfof fan blades |54 which drive a steady current of air as indicated by the arrows upwardlyand `into the space beneath and within vthe aluminum hood |55. Air is supplied through The hood, which is the screened passage L55. secured to the frame Bti, extends completely over the engine and is formed with a downwardly `turned shi-rtA |51- which extends below the exhaust manifold 1153. This extension ofthe hood below fthe exhaust port forms an important feature of `the invention?. The exhaustrgas is driven from the piston chamber 't5 at high speed tending to create a low pressure area in the confined space within the adjacenthoed and thereby implements the fans in the circulation of the air cooling supply. To facilitate such `circulation the exhaust deflector |58 is` shaped with a tapered throat as in the case of a fjetpump.

The exhaust deector |58 may be removed whenever it is desired to scrape carbon from the exhaust port E38.` To thisV end the deilector is attached to the cylinder head 65 by means of screws 69 which are readily accessible through holes |S| in the hood't.

The illustrative machine will operate for over three 'hours without refilling the gas tank, and no Alubroation..other than oil mixed with the gasoline is required. The entire machine is lubricated by the oil mixed with the gasoline in the ratioof about 16. to 1. A portion of this oil is diverted from the engine crankcase 62 and sprayed into the main crankcase 52 in a fine mist where it thoroughly lubricates all parts and gradually drains down through the machine running out along the bar t8. This continual oil iiow has a purging eiect as it tends to wash out any dirt that may get into the machine. The starter ing-a further camming action upwardly until the .cross-bar Ffinally-#clears the latch. The handle 'fis thus'quiicklylocked intoa position which is' inoperativefior starting purposes but operative in a fthe-sense or enabling the manipulation of the umachine during tamping operations.

parts are also wel-1 lubricated byoil seeping into the starter compartment ofthe housing through the needle bearing 96 which supports the main crankshaft between the two compartments.

The leakage of` oilffrom the engine crankcase through the shieldedball bearing 11 to the main crankcase occurs during each precompression stroke of the engine when the pressure in the engine' crankcase exceeds that in the main. crankcase 52. Lubrication of the engine parts is not impaired and the quantity of oil lost as smoke through the engine exhaust |58 is reduced.

This application is a division of applicants,

parent application -Serial No. 690,654, filed August 15,l 1946, which issued as Patent No. 2,533,437, on December 12, 1950. Additionalv divisions of the same parent application are as follows: Serial No. 175,742, led July 2.5, 1950, contains claims" to a combined engine and tool; Serial No. 176,984, led August 1, 1950, contains claims to a cooling system for an internal oomhustion engine; and Serial N o. 248,076, led September 19, 1951, contains claims for an. engine starter mechanism.

l What is claimed is:

1. In a percussive tool, a housing, a barrel member mounted thereon, a hammer assembly including a floating hammer member adapted to reciprocate within the barrel, a working implement arranged within the barrel and having a collar thereon, said implement being adapted to transmit intermittent blows of the floating hammer member, a retainer ring mounted in the barrel and extending into the interior thereof adjacent the implement collar, an inner snubber ring formed with a shoulder adapted to seat the collar, an outer snubber ring formed with a shoulder adapted for seating the collar and disposed opposite the inner snubber ring shoulder, the retainer ring serving to space the two opposite snubber ring shoulders apart a greater distance than the thickness of the collar, to provide a space wherein the collar may float snub-free, and spring means within the barrel adapted to maintain the snubber rings in contact with the retainer ring when the tool is at rest, the outer snubber ring and associated spring means being adapted to absorb the shock` of the collar at a predetermined point upon its outward movement in response to a blow of the floating hammer and the inner snubber ring and associated spring being. adapted toabsorb the shock of the collar at a predetermined point upon its reaction from the outer spring thereby to intermittently position the working implement at a predetermined point for the reception of intermittent hammer blows.

2. A hammerassembly comprising containing means,l a hollow member slidable therein having an intermediate portion in spaced relation to the containing means and formed with 'connecting meansleading from the intermediate space` to atmosphere and with separate connecting means from the intermediate space to the interior of the member, a iioating hammer slidable within the hollow member and adapted to form with the hollow member an air-tight chamber, said hammer being provided with means including a passageway adapted to connect the chamber to the space between the containing means and the hollow member, the foregoing elements being so arranged that uponmovement of the hollow member one direction a region of low pressure will be formed adapted to cause the iioating hammer to trail the hollow member and upon movement of the hollow member in the other direction a having connecting means to the interior of the cylinder and to atmosphere; a oating hammer member within the cylindrical member forming therewith 'an air-tight chamber and having means therethrough adapted to cooperate with the foregoing connecting means to form an air connection between said space and said chamber, said hammer being adapted to trail the cylindrical member upon the formation of a region of low pressure by the movement of the member in one direction and being adapted to move in the other direction to impart a hammer blow under pressure created by the cylindrical member in moving in the other direction; percussion means disposed within the tubular member and adapted to be actuated by intermittent blows of the harnmer means; preloaded compression spring means to maintain the percussion means in predetermined position; and precompression spring means initially spaced from the percussion means and operative to yieldingly limit the movement of the percussion means in response to the blows of the hammerrmember.

4. In a percussive tool, a hammer assembly comprising a hollow cylinder provided with shoulders at its opposite ends with an internally projecting head and with a mural port between the shoulders; a piston hammer member reciprocable therein formed with a recess opposite the cylinder head and with a peripheral groove connected to the recess by at least one passage, said cylinder and hammer piston being adapted to form anair-tight enclosed chamber therebetween; and a containing member adapted to slidably enclose the cylinder to form a cylindrical space therebetween, said members being so arranged that the cylinder upon movement in one direction will create a region of low pressure in the chamber thereby to lcause the hammer piston to trail the cylinder and upon movement in the other direction will create a region of high compression to drive the hammer piston in the opposite direction, the regions of low and high pressure being opened to atmosphere by the registration of the piston passageway with the mural port of the cylinder.

5. In a percussive tool of the class wherein the Vstriking implement is driven by repetitive blows from a reciprocating free hammer piston, in combination, containing means, a tubular member spaced therefrom and having longitudinally recessed shoulders at its opposite endsl and at least one port intermediate the shoulders, said Shoulders providing Yslidable means for the tubular member within the containing means and the longitudinal recesses forming access to atmosphere for the space between the containing means and the tubular member, a oating hammer piston lslidably mounted Within the tubular member and formed with a recess in its upper portion, a groove in its periphery, and at least one passage connecting the groove and the recess, and a head member associated with the tubular member adapted in conjunction with the hammer piston and tubular member to form a completely enclosedchamber therebetween, said elements being so arranged that the tubular member with associ'- ated head upon movement in one direction will compress the air inthe chamber to drive the hammer piston in one direction and upon movement in the other direction will create a region of low pressure sufficient to cause the hammer piston totrail the tubular member.

6. In a percussive tool of the class wherein the striking implement is driven by repetitive blows from a reciprocating free hammer piston, in combination, a stationary containing member; a slidable member adapted to reciprocate within the containing member comprising a tubular central portion with at least one mural port, shoulders at the opposite ends of the tubular portion formed with recesses adapted to connect to atmosphere the space between the containing and slidable members, and a head member having a projection extending longitudinally into the tubular portion; and a floating hammer member reciprocable within the slidable member and having a recess adapted to form with the slidable member, including the internally projecting head, a completely enclosed air-tight chamber, said hammer member having a peripheral groove connected to its recess by at least one passageway; and the arrangement of the members being such that the port of the slidable member may be brought into registration with the peripheral groove of the hammer member thereby to connect the enclosed chamber at atmosphere.

7. In a percussive tool, a housing, a motive power device, an impact element actuable thereby in a predetermined path, a percussion to'ol po.R sitioned with one end in said path to be strucl; by the impact element, said tool having a shoulder element, a pair of co-axially aligned helical snubbing springs disposed on opposite sides of said shoulder element, and means for spacing the adjacent inner ends of the two springs to provide a minimum free floating space for the tool shoulder. Y

8. A' percussive tool, as in claim 7, including a `ioating end ring for the inner end of each spring, and a spacer to separate the two oating end rings to provide a free floating space for the tool shoulder. f

9. A percussive tool, as in claim 8, in which each floating end ring is provided With a shoulder to be engaged by the tool shoulder in the corresponding direction of movement of the tool.

SPENCER B. MAURER. HOWARD P. EBERT.

REFERENCES CITED The following references are ofY record inthe file of this patent:

UNITED STATES PATENTS Amtsberg et al Jan. 12, 1943

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