US2810550A

US2810550A - Earth boring machine

Info

Publication number: US2810550A
Application number: US279724A
Authority: US
Inventors: Cohen Mark Isidore; Gully Ronald James
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-04-01
Filing date: 1952-04-01
Publication date: 1957-10-22
Anticipated expiration: 1974-10-22

Description

Oct? 22, 1957 M l. COHEN ET EARTH'BORING mcnms' 5 Shets-Sheet 1 Filed April 1', 1952 N VEN TORS "HR/Q LS/HOBE COHEN 6ND Kan/Aw JAMES cuLp/ ,g-rTy5 Oct. 22, 1957 M. I. COHEN ETA L ,3 0,

EARTH BORING MACHINE Filed April 1, 1952 5 Sheets-Sheet 2 Q m vz/vrogs N MHEK 100195 COHEN AND RONALD JAMES GULLY meeflm gwda A TTOTclVEYS M. l. COHEN ETAI. 2,810,550

EARTH BORING MACHINE Filed April 1, 1952 5 Shets-Sheet'fi MARK 15/0025 COHEN cm RONALD JAMES GULLY ATT" oak/Eva Oct. 22, 1957 Filed April 1, 1952 M. I. COHEN ETAL EARTH BORING MACHINE 5 Sheets-Sheet 4 Lyn /'/v vsN-roes RONALD JAMES GULLV fi BNEYS Mme/c 5 0012: 0011mm United States Patent p EARTH BORING MACHINE Mark Isidore Cohen, Elwood, near Melbourne, Victoria, and Ronald James Gully, Maidstone, near Melbourne, Victoria, Australia Application April 1, 1952, Serial No. 279,724

9 Claims. (Cl. 25522) This invention relates to an improved earth boring machine of the type generally referred to as a post hole digger, and it refers particularly to a hydraulica1lyoperated machine for boring holes, in the earth, in any type of soil which is relatively rock-free.

In hydraulically-operated post hole diggers as hitherto made it has been known to provide a boring bar, usually of rectangular section, attached to a vertically reciproeating piston, the rectangular bar passing through rectangular glands housed in the piston cylinder. In such an arrangement it is technically not possible in practiceespecially owing to wear of the parts which occurs in use-to prevent soil and grit from being carried by the boring bar into the interior of the oil-filled cylinder wherein the piston is located. As a result there is caused excessive wear of the piston and/ or the cylinder, as well as of the pumps and valves, and there is consequently caused leakage of oil due to that ingress of grit and soil. Moreover, in previously known constructions of post hole diggers the boring member has been attached directly to the piston and, therefore, it has been required to pass through the cylinder wherein the piston is mounted. As a result it has been necessary to restrict the cross-sectional size of the boring bar to the limits defined by the area of the cylinder.

The principal object of this invention is to provide a construction of hydraulically-operated post hole digger in which all the oil-operated components of the machine will be sealed against the ingress of grit and soil, so that wear of the parts will be greatly reduced. A further object is to devise a construction of apparatus of the type specified, in which the strength of the boring member of the machine may be increased. Another object is to provide, in a post hole digger, means whereby air may be introduced to the bottom portion of a hole bored by the use of the apparatus so as to facilitate the withdrawal of the auger, and earth carried thereby, from the hole. A dependent object is to devise a construction of air passageway or conduit, for an air bleed to the bottom portion of an auger, which will be of simple character and adapted to be readily incorporated in an earth boring machine. A still further object is to provide a construction of earth borer having simple yet efficient means whereby an anger may be disengaged from an obstruction in the earth. And yet another object of the invention is to provide a post hole digger that will be of extremely sturdy design and construction, relatively economical to manufacture, and efiicient in operation.

The invention devised with these and other objects in view consists, broadly, of a post hole digger having a cylinder,-means for driving the cylinder rotationally about its central longitudinal axis, a piston mounted in the cylinder, means for supplying fluid under pressure as desired to either one side or the other of the piston so as to move the cylinder linearly in either one direction or the opposite direction, and means for attaching a boring member to the cylinder, the piston being so Patented Oct. 22, 1957 mounted that ingress of dust, grit and other foreign matter to the interior of the cylinder will be prevented.

The boring member consists of or includes an auger and a feature of the invention resides in the provision of' means for introducing, to the lower end portion of the auger, a supply of air so as to assist in the removal of the auger from the earth. This may be done by means of a liner tube leading to an air bleed hole at the bottom of the cylinder or by means of an air supply pipe fastened to the outside of the cylinder. In the latter case the air supply pipe may also act as a spline member for the transmission of rotary motion to the cylinder.

It is also a feature to mount the auger at the lower end of the cylinder in such a manner that in the event of the auger jamming, and the forward drive being broken, then by a reversal of the drive to the apparatus the auger may be removed from the hole by a screwing action.

Furthermore, the rotary drive to the cylinder is through pivotally adjustable drive means and the cylinder is so mounted that it may be tilted forwardly and backwardly, and also sideways, so that even though the machine may be set at an inclination-as on the side of a hill--the post holes may still be formed vertically. There is also provided an air breather in the tank which contains the hydraulic fluid required for the operation of the apparatus.

In order that the invention, and the advantages thereof, may be readily understood and the invention may be conveniently put into practical form we shall now describe one particular construction of apparatus made according to the invention and also two modifications thereof. These constructions are illustrated in and by .the accompanying drawings, wherein:

Fig. 1 is a view in side elevation showing the post hole digger, made according to the invention, mounted at the rear of a transport vehicle;

Fig. 1A depicts, in side elevation, the reservoir tank for the hydraulic fluid which is employed to raise and lower the auger, and for altering the inclination of the auger;

Fig. 2 shows the complete apparatus, in plan view;

Fig. 3 is a view of the apparatus in rear elevation;

Fig. 4 shows a vertical cross-section through the driving apparatus, that is to say the devices for raising and lowering the auger and for driving it rotationally, the arrows depicting the direction of flow of hydraulic fluid when the auger is being lowered and the dotted arrows illustrating the flow of air to the auger;

Fig. 5 illustrates, in vertical cross-section, the prepared construction of the auger and the means for connecting it to the lower end of the cylinder so as to provide for a supply of air to the lower end portion of the auger when the anger is being withdrawn from the ground;

Fig. 6 is a vertical cross-section taken on the line and in the direction indicated by the arrows 6-6 of Fig. 5.

Fig. 7 is a horizontal cross-section taken on the line and in the direction indicated by the arrows '7-7 of Fig. 4;

Fig. 8 shows, in vertical cross-section, a modification of the air supply to the interior of the auger; and

Fig. 9 illustrates, in vertical cross-section a modified arrangement of the cylinder and piston, with the hydraulic feed thereto.

The pipes for the hydraulic system are shown in Fig. 2 only, for purposes of clarity; and Figs. 4-9, inclusive are shown on larger scale than Figs. 1, 2 and 3.

As illustrated in the drawings the earth boring ap paratus is mounted upon the rear end part of a transport vehicle 11 which also carries a suitable source of powersuch as an electric motor or an internal combustion engine 12. Two bearing blocks 13 and frame members 14 are also securely mounted on the vehicle 11, and the yoke 15 which carries the main portion of the earth boring apparatus is supported by a shaft 16 journaled in the bearing blocks 13. The yoke '15 is thus mounted so as to enable it to be tilted about a longitudinal axis.

At the rear or outer end of the yoke '15 are two bearings 17 wherein are pivotally mounted two trunnions or pintles 18 fastened to the opposite sides of a gear housing 19. Also secured to this gear housing on its upper side, is an outer tubular housing 20, and an internally splined guideway 21 is rotatably mounted within said gear housing. A crown wheel 22 is fastened .to said guideway-- suitable bearings being provided to support the crown wheel in positionand said crown wheel is driven by a pinion gear wheel 23 fastened to the inner end of a driving shaft 24 which is journaled in bearings mounted within the pin'tle 18 at one side of the gear housing 19. A tube 25' having a number of substantially circular sp-line members 26 secured to-its outer surface, is slidably fitted within the splined guideway 21-50 as to be longitudinally slidable within the outer tubular housing 20, and the lower end of said tube 25 projects downwardly through the lower side of the gear housing 19.

A plug member 27 is fastened to the lower-end of the tube 25. The member has a-central boss 28 on its inner, or upper, face, and on its outer faceis a larger boss '29 to which the auger 30 is fastened. The rotary drives are such that when the'pinion 23 is rotated the crown wheel 22 will be driven, and a drive will be imparted through the internally splined guideway 21 to the splined tube 25, and thence to the auger 30.

Mounted within the splined tube 25 is an inner tube or cylinder 31 having a plate 32 at its upper end. The plate 32, cylinder 31 and splined tube 25 are securely fastened together so that the cylinder 31 will move with the tube 25, and vice versa. At the lower end of the cylinder 31 is a closure plug 33 having in its under surface a recess 34 wherein the boss 28 on the inner surface of the plug member 27 is engaged-the cylinder 31 being thus held coaxial with the splined tube 25. A tubular piston rod 35 having at its lower end a suitable pistonhead 36 is so mounted that it fits slidably within the cylinder 31, passing through the plate 32, and a central pipe or tube 37 is fitted within the tubular piston rod 35 so as to project downwardly through the piston head 36 and into the lower end portion of the cylinder. A suitable gland 38 is provided on the plate 32 at the upper end of the cylinder 31, fitting about the piston rod 35 so that leakage of oil between said cylinder 31 and the tubular piston rod 35 will be prevented or at least largely reduced.

The upper end portion of the tubular piston rod 35 is firmly secured within an end closure 39 at the upper end of the outer tubular housing 20, so that the piston 35 is held in fixed position relative to that-outer housing. The upper end portion of the tube 37 projects through and is secured to the closure plate 40 at th upper end of the piston rod 35. Suitable oil pipe lines 41 and 42 are connected to the upper end portion of the tubular piston rod 35 and to the upper end portion of the central pipe or tube 37, respectively.

The piston head 36 consists of a sleeve member 43 which is fastened to the lower end of the piston rod 35 and to the lower end portion of the central tube 37, a piston head member 44 rotatably mounted on said sleeve 43, glands 45 fitted about said member44, and opposed roller or

ball races

46 and 47 at the opposite ends of the member 44. The upper hall race 46 is located between .a shoulder on the sleeve member 43 and said member 44 and the lower part of the cage of the lower ball race 47 is non-rotatable on the sleeve member 43, The piston head member 44 can, therefore, turn rotationally with the cylinder 31. V g

If hydraulic fluid under pressurebe introduced to the through the pipe 42 then the direction of flow will be as indicated by the arrows in Fig. 4, the hydraulic fluid flowing down the central tube 37 and into the lower portion of the cylinder 31. There will thus be exerted a downward pressure upon the cylinder and an upward pressure upon the piston head 36. The piston head being fixed, the cylinder 31 will, therefore, be moved downwardly. The hydraulic fluid in the upper portion of the cylinder 31 is permitted to escape by flowing through holes 48 provided near the 'lower end of the piston rod 35-a short distance above the piston head 36-the hydraulic fluid flowing into the :piston rod 35 and then upwardly so as to pass into the pipe 41. And if the direction of flow of the hydraulic fluid be reversed then the cy inder 31 Will be moved upwardly.

Near the upper end of the outer housing 20 there is secured an air inlet pipe 49 by means of which air is admitted to the interior of the housing 20. Openings 50 are formed through the upper end portion of the splined tube 25 so as to enable air to flow freely from the housing 20 into-the space between the inner wall of the tube 25 and the outer surface of the cylinder 31. Air passageways 51 are provided in the plug member 27 and an axial passageway 52 is formed in the auger 30, thereby permitting air to how downwardly through said auger.

The mounting of the auger is illustrated in Fig. 5,

interior of the cylinder 31 v as follows:

The auger 30 is screwed on to the boss 29 at the lower end of the member 25 and a shear pin 83 is fitted tightly in registering horizontal holes formed through the auger 30. That is to say, if the normaldirection of rota- .fitted within .the said hole so as to tion of the auger 30' be clockwise (or right hand) then the threads on the boss 29 and, inside the top of the auger will be left-handed. And if the auger be so made that its normal direction of rotation be anti-clockwise (or left-hand) then the screw threads will be right-handed. Consequently, if the auger encounter an obstruction such as would cause overloading of components of the apparatus the shear pin 83 will break and the boss 29 at the lower end of the member 25 will be unscrewed from the auger. Then, by reversing the direction of the drive the boss .29 may be screwed back into the open upper endof the auger 30 and the auger disengaged from the obstruction by a-screwing action.

The centering bit 84 at the lower end of the auger 30 is made as a separatepart which is fastened to the main portion of the auger by a transverse pin 85. This pin is fitted through opposed holes near the lower end of the auger 30 and it passes through a slot 86 in a neck portion of the centering bit 84. That neck portion fits neatly but slidably within the lower end portion of the auger '30, the lower end of said auger being charnfered inwardly at 87 and the centering bit 84' being shaped accordingly so that when the centering 'bit 84 is pressed upwardly its 'chamfered shoulder will press firmly upon the chamfered edge 87, a suitable liquid seal being provided .to seal the-lower end of the auger 30 against entry of dirt and grit. The neck portion of the centering bit 84 has an upward extension 88 formed with a hole extending downwardly into the slot 86. This hole is screw threaded at its upper end, to receive a bolt 89 having a lock nut. thereon. A helical compression spring 90 is press upon the pin 85. This spring 90 acts to hold the upper portion of the centering bit -84 vertically retracted into the auger 30. Air passageways 91 are provided in the neck position of the centering bit so as to enable the free flow of air downwardly therethrough to an appropriate postion ad- 'jacent the chamfered edge 87 at the lower end of the auger.

During the boring action of the auger 30 the centering bit 84 presses upwardly upon the chamfered edge 87 but when, upon completion of a boring operation, the auger 30 is drawn upwardly for a short distance the centering bit remains stationary particularly in heavy soil thereby providing a circumferential opening between the chamfered edge 87 and the chamfered shoulder of the bit 84. Thelower or outlet ends of the passageways 91 will then be in registration with that opening so as to permit the free flow of air into the lower end of the hole bored in the earth. The movement of the centering bit 84 relative to the auger 30 is limited by the pin 85 engaging the top of the slot 86.

By reason of this arrangement air may flow through the pipe 49 into the housing 20 and splined tube 25, thence through the

passageways

51 and 52, and out through the circumferential opening between the chamfered edge 87 and the shoulder 84. When the auger bit 30 is to be withdrawn from a formed hole in the earth the air introduced to the lower portion of that hole will relieve any reduction in pressure which may result from the upward movement of the auger and thereby facilitate the removal of the auger from said hole.

The drives to the pinion 23 and the means for moving the gear housing 19, and the apparatus supported thereby, in a pivotal manner are of somewhat conventional character. For convenience, a brief description is now given.

A gear box 55 is carried by the yoke 15 and in this gear box is mounted the gears driving the shaft 24, and also bearings for a shaft 56, which is connected through a universal to one end of an extensible transmission member 57. This member 57 consists of two parts, one of which is slidably fitted into the other in such manner that there is a driving connection between them. The other end of the extensible member 57 is connected through a universal to the output shaft 58 of the engine 12. As the shaft 24 is co-axial with the pintles or trunnions 18 supporting the gear box 19 and the auger-operating apparatus, and as the transmission member 57 is extensible, and that member is connected to the shafts 56 and 58 through universal joints, the gear housing 19 and the apparatus carried thereby may be moved pivotally relative to the yoke 15 without the rotary drives being affected. And the yoke 15 may be moved pivotally on its shaft 16 without affecting the drives to the crown wheel 22 by reason of the provision of the extensible transmission member 57'.

Mounted on the frame members 14 are the devices for moving the gear housing 19 angularly and the drives for moving the yoke 15 pivotally.

A member 59 is mounted on the shaft 16 so that it will move with said shaft, and pairs of

links

60 and 61 are pivotally mounted on said member 59, said links being connected by stays 62. Two links 63 are connected to the outer housing and to the upper ends of the links 61, the links 63 being angled at their front ends and interconnected by a cross-bar 64. A hydraulic ram 65 is mounted at the upper ends of the links 60 and the piston of said ram is connected to the cross-bar 64. The parts are so arranged that when the piston of the ram 65 is moved outwardly the outer housing 20 will be tilted rearwardly in the direction of the arrow A in Fig. 1.

The devices for moving the yoke 15, and the apparatus carried thereby, pivotally about the shaft 16 consist of a hydraulic ram 66 which is pivotally mounted on the transport vehicle 11 and having its piston connected to a crank arm 67 secured to the yoke shaft 16.

It will be apparent that if the hydraulic ram 66 be operated then the yoke 15, the apparatus carried thereby and also the member 59 which supportsthe links, 60,61,

62 and 63 and the ram 65 will be moved pivotally about the shaft 16 as fulcrum. V

The arrangement of the several sets of hydraulic pipes and the controls for operating the apparatus are. shown diagrammatically in Fig. 2. .The pipes 68, 69 which are connected to the hydraulic ram 65 are also connected to a control member 70, the pipes 71, 72 from the hydraulic ram 66 are connected to a control member 73 and the pipes 41, 42-from the tubular, piston'rod 35 and the central tube respectively are connected to a control member 74. The three control members are interconnected by inlet and return headers which have

hydraulic pipes

75 and 76, respectively, connected to them. Suitable relief valves are provided. The pipe 75 is connected to a pump 77 driven from the engine 12 and a short pipe 78 leads from the pump 77 to a hydraulic fluid reservoir or tank 79. The return pipe 76 is connected directly to the tank 79.

There is also provided a gear shift lever 80 bymeans of which the rotational drives to the pinion 23 andcrown wheel 22 may be controlled.

- An important, though simple, feature of the invention isillustrated infFigs. 1A and 2. This feature consists of the provision of means for maintaining atmospheric pressure on top of the oil in the tank 79, when the tank is tilted owing to the machine resting upon uneven and/or sloping ground. For this purpose we provide several tubes 81 secured to the underside of the top of the tank 79 and extending from the several corners of the tank to the filler neck 82. This filler neck extends a' substantial dis tance upwardly from the top of the tank 79, and the ends of the tubes 81 are located only a short distance below the top of the filler neck 82. Consequently, the tank 79 may be tilted to any reasonable position and when so tilted one or more of the breather tubes 81 will conduct air to the highest portion of the tank 79 so as to maintain atmospheric pressure above the level of oil in the tank.

Fig. 8 illustrates a modified construction of air supply line leading to the passageways 51 in the plug 27. Instead of the air being admitted to the interior of the outer housing 20, and thence to the interior of the tube 25, there are provided one or more hollow tubes 92 on the outer side of the tube 25. These tubes 92 may also act as splines 26 or they may be provided as independent air supply lines fitting slidably in appropriately shaped recesses in the member 21. Each of the tubes 92 is closed at its lower end and a short distance above said'lower end there is an outlet opening communicating with a passageway 51A- in the plug member 27 so that air is permitted to flow from the tubes 92 into the passageways. The remainder of the construction is substantially the same as that already described.

Referring now to the modified construction illustrated in Fig. 9, there is provided an outer housing 20 fastened to the gear housing 19 as previously described. Fastened to the upper end of the outer housing 20 is a closure member 39, and securely fastened to that member 39 is a cylinder tube 93 which is located within the housing 20 so as to be co-axial therewith. Also secured to the upper end of the housing is an oil supply tube 37A which fits coaxially through the housing and the cylinder tubethe oil supply tube 37A extending downwardly through the cylinder tube 93 to within a short distance of the bottom of said cylinder tube.

Slidably fitted in the driving member 21 is an externally splined tube 25A adapted to have the auger bit 30 detachably fastened to its lower end in the manner as previously described. This splined tube can extend up wardly into the outer housing 20, fitting between the inner wall of that housing and the outer wall of the cylinder tube 93 which is fixedly mounted within the housing 20. Within the'splined tube 25A, near the lower end thereof, is fastened the lower half of thrust ball or roller race .94

and :the upper :part. of :that hearing is fastened to the lower end of a tubular piston rod 95,,a member 96 being provided :to'. hold. together the two parts of. the race 94. The lower end of the tubular piston rod'95 is closed, the piston rod being of such diameter internally that -it fits. about the oil supply tube 37A and of such external diameter that it fits freely within the fixed-cylinder tube 93.

A piston head '97 is fastened to the upper end of the piston rod 95, said-piston head-97 having a suitable gland 98 to prevent leakage of 'oil pastthe oil supply tube 37A and a gland99 to prevent leakageofi oil past the wall of the cylinder tube '93. A short distance below the piston head 97 openings lttllaareprovided in the wall of the tubular piston -rod95. At the bottom end of the-cylindter tube 93 there is fastened a member 101 having "a suitable gland 102 fitting about the piston rod 95 in such manner that leakages of fluid .past the gland are --substantially :prevented. Also fitted to the closure;39at-tlie top oftheouter housing 20 is a second oil supply tube 41 which communicates directly with the upperendof the cylinder tube 93 supplying hydraulic fluid to the interior of said cylinder tube 'above the piston head 97.

It is robe-noted that'in this construction theouter hous- 'ing 20, cylinder tube 93 and central tube 37A are stationary parts and the splined tube 25A and tubular piston rod 95 are movable relative to saidstationary parts.

' The arrangement of the parts is such that hydraulic fluid supplied through the central tube 37 A will flow downwardly through that tube andout the lower end thereof into the interior of the tubular'piston rod 95. The fluid canthen flowthrough the openings 100 into the stationary cylinder tube 93. The hydraulic fluid will then exert pressure between the member 101 and the underside of the piston head 97. As .the member 101 is held in fixed position the upward pressure on the underside of the piston head will operate in such a manner as to cause the piston head 97, as well as the tubular piston rod 95, the thrust bearing 94, and the splined tube 25A to rise relative to the cylinder tube 93. Hydraulic fluid above the piston head 97 can flow freely through the return pipe 41.

7 If the direction of flow of hydraulic fluid be reversed then the fluid will flow through the pipe 41into the upper 'end portion of the cylinder tube 93 and will force the piston head 97, tubular piston rod 95, and splined tube 25A downwardly relative to the cylinder tube 93. The hydraulic fluid within the lower portion of the cylinder tube will then be forced to flow through the openings 100 into the tubular piston rod and thence through the open lower end of the central tube 37A so as to be exhausted through said tube.

The rotary motion imparted by thepinion gear wheel 23 acting through the crown gear wheel 22 and the member 21 will-cause to be rotated the splined tube 25A, and the auger 30mounted at its lower end, but will not cause the tubular piston rod 95 to rotate. Consequently, the

glands

98, 99 and 102 are exposed to axial reciprocating movement only, and not to rotational action. The air supply system previously describedin either of its formsmay be readily incorporated with this construction of apparatus, as may be the other features described above. As shown in Fig. 9, air holes 51X may provide for passage of the air to the auger.

What wedo claim is:

1. In a post hole digger the combination of a driving member mounted for rotational motion comprising a hollow cylindrical tube, a single crown wheel surrounding and firmly joined to said tube, said tube containing vertical splined guideways on its inner surface, a driven member-of tubularshape having spline members on its outersurface mounted slidably within said driving member and operatively connected thereto so that the driven member adapted to rotate when the drivingmember is rotated, threaded means for mounting at one end ot the driven member an anger having thereon aheliea'l fiight, a piston mounted in the driven member, means for supplying fluid under pressure selectively to either side of the piston, means for sealing the end of the driven member adjacent to the auger against ingress of foreign matter to its interior, the driven member being adapted to move linearly in one direction when .fluid under pressure is supplied to one side of the piston and to move linearly in the opposite direction when fluid under pressure is supplied to the other side of the piston, and means contained within said driven member for supplying air from the upper-end to the lower end of said drivenmem her, an anger atone end of the driven member, means for supplying air from the lower end of said driven member to the upper end-of the auger, and an air passage in the anger, the outlet of the air passage being located below the lower end 'of the auger flight.

2. In a post hole digger the combination of a driving member mounted for rotational motion comprising a hollow cylindrical tube, a single crown wheel surrounding and firmly joined to said tube, said tube containing vertical splined guideways on its inner surface, a driven member #oftubular shape having spline members on its outer surface mounted slidably within said driving member and operatively connected thereto so that the driven member is adapted to rotate when the drivingmember is rotated, threaded means for mounting an auger at one end of the driven member, a'piston mounted in the driven member, means for supplying fluid under pressure selectively to either side of the piston, means for sealing the end of the driven member'adjacent to the auger against ingress of foreign matter to its interior, the driven memher being adapted to move linearly in'one direction when fluid under pressure is supplied to one side of the piston and to move linearly in the opposite direction when fluid under pressure is supplied to the other side of the piston, and means contained within said driven member for supplying air from the upper end to the lower end of said driven member, an anger provided with screw threads engaged with screw threads formed at the lower end of said driven member, and a shear pin extending through the lower end of said driven member and the upper end of said auger, the screw threads of the driven member and of the auger being firmly engaged to prevent longitudinal movement and being opposite in hand to the normal operative direction of rotation of the auger.

3. In a post hole digger, a driving member mounted for rotational motion comprising a hollow cylindrical tube, a single crown wheel surrounding and firmly joined to said tube, said tube containing vertical splined guideways on its inner surface, a driven member of tubular shape having spline members on its outer surface mounted slidably within said driving member and operatively connected thereto, the driven member being adapted to rotate when the driving member is rotated and the driven member being adapted to have an auger threadedly fastened to one end of said driven member, a cylinder within the driven member, a piston 'head within the cylinder, a piston rod connected to the piston head, means for supplying hydraulic fluid under pressure to one end portion of the cylinder, means for supplying hydraulic fluid under pressure to the opposite end portion of the cylinder, the driven member being adapted to move linearly in one direction when hydraulic fluid under pressure is fed into one. end portion of the cylinder and to move linearly in the opposite direction when hydraulic fluid under pressure is. fed into the other opposite end portion of the cylinder, and passageways contained within said driven member for supplying air from the upper end to the lower end of said driven member, an auger connected to the driven member, said auger having an air passage from its upper end which is in communication with the lower end of -the air passageway of-the driven member to an outlet below the lower end of the auger flight, and a valve in the air passage, said valve being adapted to seal the outlet of the air passage against ingress of dirt and grit.

4. In a post hole digger, a driving member mounted for rotational motion comprising a hollow cylindrical tube, a single crown wheel surrounding and firmly joined to said tube, said tube containing vertical splined guideways on its inner surface, a driven member of tubular shape having spline members on its outer surface mounted slidably within said driving member and operatively connected thereto, the driven member being adapted to rotate when the driving member is rotated and the driven member being adapted to have an auger threadedly fastened to one end of said driven member, a cylinder within the driven member, a piston head within the cylinder, a piston rod connected to the piston head, means for supplying hydraulic fluid under pressure to one end portion of the cylinder, means for supplying hydraulic fluid under pressure to the opposite end portion of the cylinder, the driven member being adapted to move linearly in one direction when hydraulic fluid under pressure is fed into one end portion of the cylinder and to move linearly in the opposite direction when hydraulic fluid under pressure is fed into the other opposite end portion of the cylinder, and passageways contained within said driven member for supplying air from the upper end to the lower end of said driven member, an air inlet opening at the upper end of said driven member, said cylinder within said driven member being spaced from the inner surface of said driven member so as to provide an air passageway from the top of the driven member to the lower end thereof.

5. In a post hole digger, a driving member mounted for rotational motion comprising a hollow cylindrical tube, a single crown wheel surrounding and firmly joined to said tube, said tube containing vertical splined guideways on its inner surface, a driven member of tubular shape having spline members on its outer surface mounted slidably within said driving member and operatively connected thereto, the driven member being adapted to retate when the driving member is rotated and the driven member being adapted to have an auger threadedly fastened to one end of said driven member, a cylinder within the driven member, a piston head within the cylinder, a piston rod connected to the piston head, means for supplying hydraulic fluid under pressure to one end portion of the cylinder, means for supplying hydraulic fluid under pressure to the opposite end portion of the cylinder, the driven member being adapted to move linearly in one direction when hydraulic fluid under pressure is fed into one end portion of the cylinder and to move linearly in the opposite direction when hydraulic fluid under pressure is fed into the other opposite end portion of the cylinder, and passageways contained within said driven member for supplying air from the upper end to the lower end of said driven member, at least one air passageway member being secured to the outer surface of the driven member to constitute a spline for making a driving connection between the driving and driven members.

6. In a post hole digger, the combination of a driving member mounted for rotational motion about a generally vertical axis, a tubular driven member extending generally vertically through said driving member and axially slidably keyed thereto for rotation therewith and for axial reciprocation with respect thereto, said driven member being adapted to mount an auger at the lower end thereof, a piston and cylinder assemblage, of which one of the piston and cylinder elements is axially fixedly mounted and the other is rigidly connected to said driven member for axial reciprocation of the latter under the influence of fluid under pressure acting alternately on opposite sides of said piston element, a packing between said piston and cylinder elements, bearing means between said driven member and said assemblage effective to permit rotational motion of said driven member by said driving member without corresponding relative rotational motion of said piston and cylinder elements and said packing therebetween, an auger mounted on the lower end of said driven member, and a passageway contained within said driven member for supplying air from the upper end to the lower end of said driven member.

7. The post hole digger of claim 6 wherein said piston has a piston rod connected to said driven member through said bearing means, and wherein said driven member laterally encloses said piston rod to protect the latter from dirt handled by an auger secured to the lower end of said driven member.

8. The post hole digger of claim 6 wherein said piston has a piston rod on which said piston is journalled by said bearing means, and wherein said driven member is a part of said cylinder whereby rotational motion of said driven member and cylinder imparts corresponding rotational motion to said piston and said packing.

9. In a post hole digger, the combination of a driving member mounted for rotational motion about a generally vertical axis, a driven member extending generally vertically through said driving member and axially slidably keyed thereto for rotation therewith and for axial reciprocation with respect thereto, an anger having a helical flight therearound, said auger being threadedly engaged with the lower end of said driven member, the threads of said auger and of said driven member being of hand opposite to that of the flight, and complementary key means holding said auger and said driven member against relative rotation whereby torque is transmitted by said driven member to said auger for digging a hole as said driven member and auger are moved downwardly and rotated, said threads being effective, upon failure of said key means, to permit continued rotational motion of said driven member without corresponding rotational motion of said auger and to enable positive withdrawal of said auger from a hole by reverse rotational motion of said driven member.

References Cited in the file of this patent UNITED STATES PATENTS 168,454 Coman Oct. 5, 1875 1,811,002 Dodds June 23, 1931 2,192,192 Johansen Mar. 5, 1940 2,320,612 Kandle Jan. 1, 1943 2,415,572 Jaques Feb. 11, 1947 2,565,547 Collins Aug. 28, 1951 2,598,203 Acker May 27, 1952 FOREIGN PATENTS 144,262 Australia Nov. 19, 1951