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Publication numberUS2672847 A
Publication typeGrant
Publication dateMar 23, 1954
Filing dateJun 10, 1950
Priority dateJun 10, 1950
Publication numberUS 2672847 A, US 2672847A, US-A-2672847, US2672847 A, US2672847A
InventorsBergmann Carl A
Original AssigneeLe Roi Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Reciprocable hydraulic impact motor
US 2672847 A
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Description  (OCR text may contain errors)

March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 $heetsSheet 1 INVENTOR. wee/22$ MW March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 Sheets-Shem 2 19 f TOE/Vi $451 March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 Sheets-Sheet 3 March 23, 1954 c. A. BERGMANN 2,672,847



Patented Mar. 23, 1954 RECIPROCABLE HYDRAULIC IIWPACT MOTOR Carl A. Bergmann, Milwaukee, Wis., assignor, by

mesne assignments, to Le Roi Company, a corporation of Delaware Application June 10, 1950, Serial No. 167,335

4 Claims.

My present invention relates in general to improvements in hydraulic machines, and relates more particularly to various improvements in the construction and operation of hydraulically actuated reciprocable impact motors of the type covered generally by my Patent No. 2,512,763, granted June 27, 1950.

In my prior patent above identified, I have shown an improved hydraulically actuated portable impact motor embodying a differential piston reciprocable by liquid underlpressure with the aid of a balanced valve which is rotatable to automatically alternately admit pressure liquid to the opposed piston faces, and a resilient or pneumatic cushion for storing energy delivered by the piston while travelling in one direction and for returning the stored power to the piston so as to deliver powerful impact blows when moving in the opposite direction. The rotation of the automatic valve of this prior impact machine was effected by an auxiliary rotary hydraulic motor driven by liquid under pressure from the same source which supplied actuating liquid to the piston of the main motor; and the timing of the valve and of the pneumatic cushion was such that pressure liquid was admitted to the smaller face of the differential piston and was released from the opposite larger face thereof precisely when the cushion attained its maximum power or energy storing position.

While this prior impact assemblage was highly successful and superior to previous hydraulic hammers in operation, the portable unit was relatively bulky and cumbersome to manipulate and the construction of the hammer employing a double acting piston and the location of the rotary automatic control valve made it rather difiicult to insure accurate timing and also introduced complications in production and assembly of parts. Thentoo, since these portable impact units are utilized under widely varying temperature conditions which may detrimentally affect accurate timing and functioning of the control valve, the previous device did not make adequate provision for automatically compensating for such temperature variations in the actuating iquid which travels in a closed circuit, and more than one hammer could not be effectively operated from the same liquid supply source. In addition to these objections and deficiencies, the prior impact motors could not be readily actuated to deliver either light or heavy blows at the will of the operator, and since oil is ordinarily employed in these hammers no positive provision was made for utilizing escaping oil to best advantage and for preventing messy conditions.

It is therefore a primary object of the present invention to provide various improvements in the construction and operation of such reciprocable hydraulic impact motors whereby the structure is materially simplified and the functioning thereof is vastly improved.

Another important object of this invention is to provide an improved portable hydraulically actuated impact unit comprising a reciprocable power piston and an automatically functioning valve for controlling the delivery of liquid to and from the piston, wherein the control valve is formed and disposed to produce impact blows of maximum intensity and with minimum vibration of the unit.

A further important object of the invention is to provide a light but powerful reciprocable impact motor comprising relatively few simple, and compact and durable parts which may be quickly and conveniently assembled or dismantled, and which function automatically with utmost precision and dependability.

Still another object of my invention is to provide an improved hydraulic impact assemblage in which the temperature of the power trans mitting liquid may be effectively automatically controlled to insure uniform speed and most efficient operation of the system, and which is readily operable to deliver either light or heavy blows or impacts of any desired intensity.

An additional object of the present invention is to provide an improved oil actuated impact motor wherein leakage liquid is prevented from messing the exterior of the unit, and may be utilized to lubricate various parts of the equipment.

Another object of my present invention is to provide an improved portable hydraulically actuated powerful impact tooland system, which is simpler and less expensive than that shown in my prior patent, and in which several hammers may be effectively operated from a common closed fluid supply circuit.

These and other objects and advantages of the present invention will be apparent from the following description.

A clear conception of the several features involved in my present improvement, and of the construction and operation of a typical portable hydro-pneumatic hammer embodying the invention, may be had by referring to the drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

I Fig. 1 is a longitudinal central section through one of the improved. reciprocable hydraulic impact motors and its resilient pneumatic cushioning device, showing the difierential piston and the cushioning plunger in impact delivery position in solid lines and the latter in its opposite extreme. 99$?! g9 ,3' 'q-?! .193%

Fig. 2 a side elevation of the portable power unit shown in Fig. 1 looking toward one of the air filters for the pneumatic cushioning device;

Fig. 3 is an enlarged transverse section through the rotary automatic liquid flow central valve of the unit, taken along the line 3-3 of Fig. i and showing the valve in piston up-stroke position;

Fig. 4 is a similarly enlarged transverse section through the rotary automatic liquid flow control valve, also taken along the line 3.73 of Fig. l but showing the valve in piston, downstroke or impact delivery position; v Fig. 5 is a likewise enlarged transverse section through the recipro'cable power unit taken along the line 55 of Fig. 1;-

Fig. 6 is a somewhat more enlarged transverse section through the thermostatic control device for the valve impelling rotary. motor of the im: proved impact assemblage, taken along the line 6-5 of Fig. 1 and showing the automatic temperature actuated motor speed control;

Fig. '7 is an enlarged central vertical section through the manually actuated liquid flow regu lating valve of the type. shown in Fig. l, but showing this valve set for delivery oflight blows;

Fig. 8 is a likewise. enlarged central vertical section through a modified type of manually 3.0? tuated liquid flow regulating valve, likewise show,- ing the sameset for. light blows; and

Fig. 9. is a partially exploded diagram showing a typical liquid supplyand; circulating system for actuating and controlling the. liquid flow.

The gist of my present invention is the provie sion of a compact but powerfulv hY-dI'QnPHGUIH8tiC hammer having an impact deliver-y piston cooperating withv a pneumatic blow: augmenting cushion and provided with difierential opposite faces the smaller ofwhich is. constantly exposed to. pressure liquidv from. a closed; circulatqry system while the largeris alternately exposable to fresh pressure. liquid from the supply.- system together with pressure liquid from the smaller face during impactstrokesand toexhaust, during the. return strokes, and: a simple constan tating automatically functioning valve. disposed coaxia v f the power piston. for controllin the now. of" liquid to andfrom. the. piston, races; so; as o produ impa t. blows. or maximu n n ty without introducing excessive vibration the liquid circulating system. the invention has been s cw b way or illustration as. bein adrantaec uslr appl cable. to. a. univcr a umovable portable hammer. employing. oil as; the acma i g quid: and. havin the control va u onerable by a rotary hydraulic motor. it; iSgILOtr the nt nt-ta h i b un cqcssar lr res ctthe utili y oi the mprov d f atures; a i is a so. colem: plated that specific descriptive terms employed e e n e iv n they r ad t. nossib nte p tat c c cntwitnthe disclosure.

Referring to. the drawi gs, the. typical portable hydro-pneumatic. hammer shown therein oomprisesinv general a compositeelongated-main casing consisting of: alincd, andcoaxial; sections- H), H, l2, I3, I54? firmly. but detachablyinter-connected by. bolts [Sanctcompression springs t6; a hydraulic power piston l'l reciprocable within a or .8 fame n a. whale: sl eve '9; metered centrally within thev casing section H and having a large impact or upper face and a smaller annular retracting or lower face 2i surrounding its piston rod 22; a single automatic annular rotary liquid flow control valve 23 journalled in the casing section I I in axial alignment with the b e, 8 nd b n s an l r tatab by a tary hydraulic motor 24 housed within the casing section [0; a manually operable flow regulating valve 25 slidably confined within a housing 2Q secured to the casing section II and being operable by means of a lever 21 and an arm 28 pivotally associated with one of the hammer manipulating handles 29 which are formed integral with the casing section [0; a pneumatic cushioning plunger 30 slidably confined within a bore termed the casing section l2 and being flexibly secured to the main piston rod 22; an impact transmitting plug 3| slidably confined within a central bore formed in the casing section l3-,and projecting. into. the path of travel of the plunger 30 and an impact. tool or implement, 3-2 detachably and slidably confined Within the casing section l4 in alinement with the pl L The upper casing section I0 is formed as, a cap snugly embracing the upper portion of; thecylinder section II and likewise, embracing a partition 33 which segregates the automatic control valve 23 from its propellin motor 24. The single annular valve 23. is adapted o c ns ant r tated at high speed by the rotor ofqthe hydraulic motor 24 through a shaft. 34- journalled in the partition 33, and the valve. 2.3 1815. a. pair of diametrically opposed radial ports 35 which are inwardly in open communication with the larger upper face 20- of the power piston I], and this valve must be. totally balanced at all times. The control valve23 is rotatable. within a stationary bushing 36 secured to the casing section II and having therein two accurately formed sets of opposed passages, 38 of which the passages 31 are. of less circumferential width than the passages 38. and the. former communicate with high pressure liquid conduits 38 while the latter;- like.- wise communicate with the low pressure conduits 40, seeEigs. 1, 3'and4.

In. order to effectively.- balance the pressures acting upon the valve 23-, the opposite end surfaces of this. valve are constantly; connected to the valve ,interior and to the upper piston displacement chamber through openings 43, as shown in Fig. l. The cylinder sleeve I 9 is fixedly secured to the casing section H. and in orderto prevent. dangerously; high pressures in the upper cylinder chamber, thev upperextremity of the sleeve t9; isprovided; with cut-outs which communicate with the high pressure conduits 39 past spring pressed; ball relief-- valves. 42; as shown in Fig. 5.

hiquid underpressure. is; normallyadmitted to the. valve driving motor 24, from the high pressure conduits; 31% through a. duct 45; and spent liquid is: exhausted: from, the rotor of the motor 21 through. aduct 4.6; and in order to maintain the speed of; the auxiiiarymotorrotor constant it is. necessary to retaintheflow of propelling liquid sutlicient to; maintain the. desired speed. Since 0 2 rir ie iebly t l m as t actuatin liquid. this. oil out and fiowmore readily when warm; when cold... and the temperature of the. liquid delivered to the motor 24 maytherefore be. utilized toregulate thespeed ofthe motor rotor-either. atthemotor'itself; or atsome other e aliw he, i uid. r ula i g systems sirated: n: E is end- 1a ne d valve 41 is disposed in thehigh pressure inlet duct 45' on the motor 24, and the needle valve 41 is movable in one direction by a bellows 48 surrounded by fluid which is expansible when heated to close the needle, and is positively movable in the opposite direction by a helical compression spring 49 to open the needle, more or less. When the oil is warm less liquid will pass through the motor 24 than when cold, but the bellows 48 and spring will automatically compensate for variations in temperature or fluency of the oil so as to maintain substantially constant speed of revolution of the automatic valve 23.

This speed of rotation of the automatic valve 23 may also be controlled by maintaining constant viscosity of the oil in a closed system with the aid of mechanism such as illustrated in Fig. 9 and without utilizing a bellows and spring actuated needle valve 41 in the unit itself. In this modified system, a constant pressure variable delivery pump 50 is driven by an internal combustion engine 5| having an oil cooler 52 associated therewith, and the pump 50 has an intake line 53 communicable with asupply reservoir 54 provided with an inlet pipe 55 and also has a flexible discharge line 56 connected to the high pressure conduits 39 of the hydraulic hammer unit. The exhaust pipe 51 of the engine 5| has two branches 58, 59 one of which passes through the oil 60 within the reservoir 54 and the other of which leads to the atmosphere, and the flow of hot exhaust gases through these branches 58, 59 is controllable by a flap valve 6|. The reservoir inlet pipe 55 also has two branches 62, 63 one of which passes through the cooler 52 and the other of which is flexible and communicates with the exhaust conduits 40 of the portable impact unit, and the flow of liquid through these return branches 62, 63 is controllable by another flap valve 64. The flap valves BI, 54 are movable by a thermostat 65 which is activated by a bulb 56 disposed within the oil 60 in the reservoir 54 in a manner to be specifically explained later on.

The manual regulating valve may be either of two types, and as shown in Figs. 1 and 7, the housing 25 of the manually operable flow shutoff and regulating valve 25 may be secured directly to the side of the casing section II through an opening in the section II], and the valve 25 which is located in the high pressure conduit 39 is of the reciprocating piston type and is totally balanced by virtue of the fact that its opposite ends are connected to the low pressure conduit 43 while its medial portion is recessed to provide annular opposed faces exposable to the high pressure conduit 39 only when the valve is opened. As previously indicated, the regulating valve 25 is adapted to be opened more or less by means of the lever 2! and arm 28, but this valve 25 is constantly urged toward closed position relative to both the pressure and exhaust lines by a spring 68 coacting with its end remote from the valve stem 5%. The lever 21 is swingably suspended from the casing section It! by a pivot it and has a slot cooperable with a pin 1| so as to limit the swinging motion thereof, and the arm is is swingably suspended within one of the handles 29 by another pivot 12 and coacts with the valve stem 59 and with a horn 13 formed integral with the lever 21. The handles 29 may also be provided with suitable gripping coverings l4 and one of these handles serves to protest the adjacent regulating valve assembly. The flow regulating valve 25' of Fig. 8 is different from that shown in Fig. 7, since it connects the conduits 39; 4D with each other when the hammer is 6 inactive, and this permits free circulation of the oil 60.

When operating these portable hammer units it is frequently desirable for the operator to regulate the intensity of the blows delivered to the tool 32 and to be able to deliver light blows when performing certain types of work where normal heavy blows might be destructive. In order to permit such operation the valve 25 or 25' is provided with a chamfer 15 which enables the operator to gradually increase the intensity of the impacts when starting, or to maintain light blow intensity by merely holding the lever 21 down to a limited extent. Such operation will cause the chamfer I5 to throttle the flow of liquid delivered to the piston I! to any desired extent thus resulting in blows of variable intensity.

The piston rod 22 is guided for reciprocation in a sleeve bearing 11 confined within the lower end of the casing section I! in axial alinement with the cylinder sleeve I9, and this bearing 11 is lubricated by leakage oil from the upper cylinder chamber. An annular groove 1'! in the bearing H communicates with one or more low pressure passages 38 through a duct 18, see Fig. 1, and serves to return the leakage oil. Thus, only a small amount of leakage oil is passed for the lubrication of the pneumatic cylinder and other moving parts. The pneumatic plunger 30 which is slidably confined within a bore of the casing section 12, is flexibly connected to the lower extremity of the piston rod 22 by means of a universal joint 19, and this plunger 30 is cooperable with air inlet and exhaust ports to confine and compress air in a cushioning chamber 8| formed between the casing section H and the plunger within the upper portion of the section l2 whenever the plunger rises. The ports iii! are communicable with the ambient atmosphere through a pair of air filters 82 removably confined within pockets formed in the casing section l2 by perforated plates 83 swingably secured to the section l2 and which are held in closed position by spring retainers 84. The casing section is within which the motion transmitting plug 3| is slidably confined, has lubricant conducting passages 85' formed therein and cooperating with similar passages in the section i2 for conducting leakage oil 60 from the bearing TI to the plug 3| and implement 32 without permitting such oil to escape to the exterior of the main casing body, and the tool or implement 32 may be det-achably secured to the lowermost casing section I4 by means of a spring pressed latch 85, as illustrated. in Fig. 1.

When the improved hydro-pneumatic impact units have been properly constructed and assembled as shown and described, they may be utilized either singly or in multiple in connection with systems utilizing either constantly or intermittently operable pumps or other sources of supply wherein the oil is circulated either con stantly or at will. If the hammer units are associated with system embodying a constant pressure variable delivery pump 5!] as in Fig. 9,

the type of regulating valve 25 shown in Figs. 1, 7 and 9 should be utilized, and with this type of valve 25 the flow of oil 50 through th flexible pipes 56, 63 will be interrupted when the corresponding unit is not in use and the lever 21! thereof is released. However, if a constant liquid delivery is utilized, a modified flow regulating valve of the type shown in Fig. 8 should be employed, and this valve 25 will permit free circulation of the oil Bl] through the supply and discharge pipes 56, 63ofeachhammer unitwhen. inactive andthe lever 21 thereof is released.

Ineither case,.when the lever 21 of a portable hammer is depressed, liquid under high pressure willbe admitted to the conduits 39 of the corresponding unitand will revolve the rotor of the motor 24' thereby constantly rotating the balanced automatic; control valve 23 and at high speed, and liquid under high pressure is always admitted to the lower smaller face 2-! of the differential. power piston 11 as soon as the valve 25 or 25 is opened. Whenever the rotary control valve. 23 reaches the position shownin Fig. 3 with the ports communicating with. the larger or wider passages 38 and. with the low pressure conduits 40, then thelarger piston face 20 will be exposed. to. exhaust and the high. pressure liquid. constantly acting upon the smaller piston face 2| will move the piston I1 and the air compression plunger 30 upwardly to cause the, latter to. confine and, compress air within the cushioning chamber 81 At the instant when the piston I1 and plunger 30 reach the upper end of their upstroke, the automatic valve 2:3 will have advanced toward the position shown in Fig. 4 so as-to connect the upper piston face 20 with the high pressure conduits 539 and with the; upper piston, displacement chamber through the ports 35. and smaller passages 3i; whereupon the high pressure liquid will cooperate with the pneumatic energy. stored within the chamber 8 I-, to cause the plunger 30 to deliver a sharp impact blow to the implement 32 through the plug. 3!.

This cycle, of. operations will be rapidly repeated during, continued rotation of the valve 23,. and the liquid Eli-will flow constantly in the same direction through. the; conduits 39, 4E as long as the regulating valve 25 is held in open position; and by properly manipulating the valve 25- as above described the hammer unit may be caused to delivereither light or heavy blows to the-tool 3 2. If the automatic speed control for the auxiliary v-alve driving motor 24 shown in Figs; 11 and 6 is utilized, the: fluid coacting with the bellows 48 will. adjustv the needle valve 41 in: accordancewi-th variations in the temperature of theoil Gil-flowing through the motor 24 so as to'maintain the motor speed substantially constant, and this speed regulating device may be utilized in conjunction with any type of liquid circulation but does not necessarily affect the viscosityor fluency of the oilby heating or cooling the same.

However, the speed of the hammers may also be regulated by maintaining constant viscosity of the actuating liquid and, by utilizingv a system such as shown: Fig. 9 whereby the oil: may be either. heated or cooled to suit. In this automaticviscosity control.system,.the constant pressure.- variable delivery pump 50 may simultaneously operate onev or more impact units past regulating, valves 25, and the flap valves El, 64 willbe automatically adjustedby the thermostat 65 to cause. more. or. less. cooling or heating of the liquid. Whenthe 011,611, in. the power system is hot and. highly fluent, the; valve 6] will. be positioned as shownin solid lines to cause the hot engine exhaust gases to escape directly to the atmosphere through. the branch pipe 59", and the other valve 63 will be positioned as shown in dotand-dash. lines. to. cause, the oil. returning, from the-impact unit. to,. travel.- through; the. cooler 52 and. to; become fluent; Iii-the. b11160, too cold. anctnot. sufficiently. flu ntr trie'gvawe 5 I will 8. be positioned as-shown in dot-and-dash lines and the other valve 63 will be positioned as' shown in solid lines, thereby causing the cooler 5'2 to be out out and. the exhaust from the engine 5| to travel through the branch pipe 58, thus heatingthe liquid and increasing its fluency. This improved system therefore functions toautomatically' control the viscosity of the oil so as to'maintain constant speedof the motor 23, thus providing great flexibility in operation of the" hammers and effective functioning thereof in hot and cold regions.

From the foregoing detailed description of the construction and operation of my improved reciprocabl'e impact motor and system, it should be apparent that I have" in fact provided a hydro-pneumatic hammer unit which is simple, compact and durable in construction, and which is moreover highly efficient in use and flexible in its adaptations. The unit embodies onlya single simple automatic valve 23' and a single simple manual flow' regulating valve 25 in order to actuate the same so as to produce impacts of desired intensity desirable for performing various classes of work, and by locating the'motor 24', valve 23, piston l1, plunger 30 and plugti in axial alinement within axially separable and al'ined casing sections, all of these parts may be quickly and conveniently assembled or dismantled for inspection. The annular valve 23 and its confining bushing 36- may be accurately machined so as to opera-tewith utmost precision in producing maximum blows; and by causing the oil 6'5) to constantly flow in the same direction through each' portable unit, vibration is reduced to a minimum and annoyance to the operators is minimized.

The speed of the motor 24 can be selected or set manually with the aid of the needle valve 41, and is maintained by the thermostat 65. This reduces the manipulators effort to a minimum. The use of the valve 25' permits any desired numbers of the individual units to be operated bya single constant pressure, variable delivery pump,

while valve25" is preferably used in conjunction with constant delivery pumps f'orunits requiring only one hammer. The present improved unitsare therefore entirely automaticin operation except for the actuation of the starting and stopping'lever 21; and may be effectively operated in extremelyhot or coldweather; All valves are'not only accurately timed but are also automatically balanced, and'escaping oil is also utilized to advantage-for lubrication purposes. The improved portableunits may'be manufactured at moderate cost in various sizes for diverse uses, and are capable of delivering powerful impacts considering their compactness;

It should be understood that it is, not desired to limit this invention to the exact details of construction or to theprecisemode of operation of the typical hydraulic impact units herein shown and described, for various. modifications within. the. scope of the appended claims may occur. topersons skilled inthe art;

I claim:

1'. In a hydraulicallyactuatedxreciproeablaimr pact motor, a casingqhaving a bore; a piston reciprocablewithin said bore and having opposed facesex-posable to'liquid under pressure, a rotary valve associatedwith-saidcasing and being automaticallyoperableito-admit said liquid to saidpiston faces, arotary. motor. operable. by the pres.- sure, .liquidtor actuatesaid valve; and. a thermastatoperablaby; variations inithetemperature. of

9 said liquid admitted to the piston through said valve for automatically varying the speed of rotation of the valve by regulating the speed of said motor.

2. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having differential opposed faces exposable to liquid under pressure, a valve associated with said casing and being automatically rotatable about the axis of said piston to admit said pressure liquid to the opposed piston faces and from the smaller to the larger face, a rotary motor operable by said liquid to rotate said valve, and a thermostat operable by variations in the temperature of said liquid for passing through said valve for automatically regulating the speed of said motor in accordance with variations in the viscosity of the liquid.

3. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and. having differential opposed faces the smaller of which is constantly exposed and the larger of which is alternately exposable to liquid under pressure, a rotary'valve associated with said casing and being automatically rotatable about the piston axis to admit said liquid to the opposed piston faces, a rotary motor operable by said pressure liquid to rotate said valve, a thermostat operable by variations in temperature of the liquid passing through said valve for maintaining uniform selected speed of said motor and reciprocation of the piston, and means for manually regulating the flow of liquid to said automatic valve to vary the selected speed of movement and the intensity f" of the impacts delivered by said piston.

4. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having opposed faces one of which is alternately exposable to liquid under pressure and to exhaust while the other is constantly exposable to said pressure liquid, a rotary valve associated with said casing beyond one end of said piston and being rotatable to admit liquid under pressure to both of said faces and to alternately exhaust said one face, a rotary motor operable by said pressure liquid to constantly rotate said valve, and a thermostatically controlled valve confined within said casing and being operable by variations in the temperature of the liquid admitted to said piston past said rotary valve to automatically vary the speed of rotation of said motor.


References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 320,293 Saunders June 16, 1885 660,434 Herzler et a1. Oct. 23, 1900 1,087,799 Massey et a1 Feb. 17, 1914 1,104,946 Wilhelm July 28, 1914 1,558,221 Bayles et al. Oct. 20, 1925 2,166,940 Conradson July 25, 1939 2,512,763 Bergmann June 27, 1950 FOREIGN PATENTS Number Country Date 501,146 Great Britain Aug. 26, 1938.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2876742 *Oct 13, 1955Mar 10, 1959Eva R LemertVariable speed fluid pressure actuated impact device
US2896916 *Oct 2, 1956Jul 28, 1959Benight Raymond FDrilling equipment
US2942850 *Jul 23, 1957Jun 28, 1960Mckee CompanyMultiple drill
US3339644 *Apr 1, 1965Sep 5, 1967Racine Hydraulics & MachineryHydraulic hammer
US3792740 *Apr 5, 1972Feb 19, 1974Cooley WHydraulic powered hammer
US4324275 *Jan 7, 1980Apr 13, 1982Ward John DRetrofitting methods and retrofitted hydraulic drives
US4373874 *Jul 6, 1981Feb 15, 1983Albert PhillipsFluid actuated pump system
U.S. Classification91/40, 173/212, 91/419, 92/134, 91/335, 173/127, 91/417.00R, 173/169
International ClassificationB25D9/00, B25D9/12
Cooperative ClassificationB25D9/12
European ClassificationB25D9/12