US 3151687 A
Description (OCR text may contain errors)
Oct. 6, 1964 SHUICHIRO SATO ETAL 3,151,687
DRIVING HEAD WITH PLURAL. IMPACT MOTORS 6 Sheets-Sheet 1 Filed May 23, 1960 F g. lb
6 INVENTORS HU/C 0 o B mo IVAKAO/(A 7275/6 Arman 6 Fig.
Oct. 6, 1964 SHUICHIRO SATO ETAL DRIVING HEAD WITH PLURAL IMPACT MOTORS 6 Sheets-Sheet 2 Filed May 23, 1960 INVENTORS SH u/oj 1964 SHUICHIRO SATO ETAL 3,
DRIVING HEAD WITH PLURAL IMPACT MOTORS Filed May 23, 1960 V 6 Sheets-Sheet 3 Fig. 5
INV EN TORS 5/10/0090 54 7'0 dmo Mme/m 2&4 M
Oct. 6, 1964 SHUICHIRO SATO ETAL 3,151,637
DRIVING HEAD WITH PLURAL IMPACT MOTQRS Filed May 25, 1960 6 Sheets-Sheet 4 Fig. 9 Fig. IO
INVENTORS (Sill/ICIfI/PO 541-0 d/Ra Mm! am 73m? Arm/W Oct. 6, 1964 SHUICHIRO SATO ETAL 3,151,687
DRIVING HEAD WITH PLURAL IMPACT MOTORS 6 Sheets-Sheet 5 Filed May 23, 19 0 Fig.
i ollalaludl Fig.
INVENTORS 5l/U/d/l/fio 54 B dma Mil/401m 3% 52 7/750? Ame/vs? Oct. 6, 1964 SHUICHIRO SATO ETAL 3,151,687
DRIVING HEAD WITH PLURAL IMPACT MOTORS 6 Sheets-Sheet 6 Filed May 23, 1960 Fig. IB
INVENTOK9 a "Mm A SMWA w E Z, W7 4MB United States 3,152,687 DRE n s; HEAD WETH PLUPAL IMPACT MGTGRS Shuichlro Sato and Jiro Nalraoka, Tolryo, Japan, assignors to Nippon Sharyo Seize Kaisiia, Ltd, Atsuta-hu, Nagoya-shi, Japan, a company of Eapan Filed May 23, 196i er. No. 31,148 Qlairns priority, appiication Japan, May 25, 1959, 34/ 15,719 7 Claims. (Ci. 175-421) This invention relates to an apparatus for digging deep holes in the soil, and in particular to an apparatus for digging deep holes for inserting piles therein.
In recent years, the larger the scale of buildings becomes, the longer the foundation piles are required. Very frequently, piles of 30 meters long must be inserted in the soil. In order to insert long foundation piles in the soil, it is generally considered advantageous to dig holes in advance and then place concrete columns therein. However, the method actually practiced consists in driving into the soil cas ng tubes of the length, approximately equal to that of the holes to be dug, pulling out said driven casing tubes to form the required holes on their precise position.
The experience shows that the maximum depth of the holes dug in accordance with the above-mentioned method is aproxirnately meters. It is extremely difdcult to dig deeper holes, due to the following reasons:
Since a casing tube is driven into the soil by hitting the upper end thereof, the longer such casing tube is, the more the driving energy applied to the upper end is absorbed and damped by the elasticity of the casing tube itself, before said energy is transmitted to the lower end thereof, whereby the digging force acting efiectively on the lower end of the tube decreases considerably. Also, the driving force applied to the upper end of the casing tube must be restricted for fear that the casing tube would break or collapse after it reaches a certain depth due to the lateral pressure and surface friction on the exterior of the casing tube.
Furthermore, in case high frequency vibration is given to the upper end of the casing tube for decreasing skin friction applied to the sides thereof due to soil pressure, the vibration energy, just as the above driving energy, is damped before it is transmitted to the lower end of the casing tube, so that no eifective vibration can be imparted thereto.
For such reasons, no high operation efiiciency can be expected from the hitherto practiced methods.
The defects of such methods are considered due to hitting the casing tubes from the upper end thereof and driving the same down into the soil.
The object of the present invention is to eliminate such defects. According to the present invention, the driving force is applied to the casing tubes at the lower part thereof, near the driving end of the casing tubes, instead of hitting at the upper end, said driving force being effectively utilized, with the least loss, for driving down the casing tubes, thereby providing the method for digging holes of the desired depth, without resorting to casing tubes of a great length.
In order to accomplish the above object, the invention is characterized in that a driving unit of a compartively small length containing a driving device therein is used, said driving unit being driven down by means of said driving device; a hollow tube, hereinafter referred to as follower, is coupled to said driving unit when the upper end of the latter almost reaches the soil surface so that a further operation of driving down the driving unit can be made; a second follower is coupled to the above first follower when the upper end of the latter almost reaches the soil surface; thereafter, the same process is repeated by coupling the third, fourth followers in succession whereby the driving unit is driven down deeper and deeper; and when the desired depth is attained, the driving operation of the driving unit is stopped, and the driving unit and the followers are pulled out, whereby the required holes are formed.
The invention is hereinafter explained with reference to the attached drawings which illustrate the mode of the present invention and certain embodiments of the driving units and other accessory devices for use in the present invention. It must be noted, however, that such embodiments are illustrated by way of examples, not limiting the scope of the invention.
In the drawings,
PEG. 1a shows a longitudinal sectional view of an embodiment of the driving unit for digging deep holes in accordance with the method of the present invention,
FIG. 1b a sectional view of the lower part of another embodiment of the driving unit,
FIG. 2 shows the bottom plan view of the driving unit shown in PEG. la or lb,
FIG. 3 shows the self-propelling device provided with a tower and a machinery compartment, said tower for holding the driving unit shown in FIG. la or lb, for applying thrust to the driving unit and the followers towards the soil and for lifting the same from the soil,
FIG. 4 shows a sectional view of the yoke for applying thrust to the driving unit towards the soil, provided in the device shown in FIG. 3,
PEG. 5 shows a plan view of the guide for driving unit, provided in the device shown in PEG. 3,
FIG. 6 shows the sectional View at line A-A of FIG. 5,
FIG. 7 shows the mode of connecting a follower to the driving unit underground,
PEG. 8 shows a longitudinal sectional view of the semicylindrical member of the follower,
FIG. 9 shows a plan view of the tubular follower formed by putting together two semicylindrical members,
FIG. 10 shows the mode of connecting two semicylindrical members vertically adjoining,
PEG. 11 shows another embodiment of the follower,
FIG. 12 shows the end plan view of the follower shown in FIG. 11,
FIG. 13 shows the sectional view of the connecting parts of adjoining two followers shown in FIG. 11,
FIG. 14 shows the ring formed connector for the followers shown in PEG. 11,
FIG. 15a shows the mode of connecting followers in succession to the driving unit which is being driven into the soil,
PEG. 15b shows the mode of pulling out from the soil the driving unit which has been driven to the desired depth, and
FIG. shows the state of the hole after the driving unit and the followers were pulled out.
In PEG. la, the driving unit is made of material having a high strength, such as cast steel. The body or head 31% is so shaped as to have a high rigidity to be driven into the soil, the inside thereof being hollow. At the lower part of the body or head 15 a pneumatic hammer unit it is provided, and the surface or shoulder 1421 of the body or head it is hit with the ram 111 of the hammer ii. The pneumatic hammer 11 is of well known mechanism enclosed in the housing 111a seated on a shoulder 9 in the bore 8 of the body 10. 112 shows a piston rod, 113- a piston, and 114 a valve means respectively, which structure is old and well known in the pneumatic hammer art and is not shown. A valve gear structure of this character is illustrated in United States Patent 2,637,304, issued May 5, 1953. One or more vibrator hammers 12 engaging the upper end of the cast steel body 113.
' driving point. p the driving point 167, a'rubber sleeve lisprovided,
U are fixed in the body 1 1. Similarly as shown in FIG. 1a
7 each of the well known pneumatic vibrators, each of which is in the form of the vibrator hammer 12 has a piston 121 which makes a rapid reciprocating movement inside of its cylinder mounted on the top of the housing 111a of the air hammer '11. The hammering force of the vibrators 12 is smaller than that of the pneumatic hammer 11, but its vibration frequency is higher. At the upper part of the body or head 10, an extracting hammer 13 is the same character as that of the vibratory hammer 12 although smaller and is mounted on the tops of the cylinders of the vibratory hammers 12, the upper end of the housing of the hammer 13 isrseated on a shoulder 13a in the cap 14 which is secured within the bore 8 of the body 19 and has the annular shoulder 13b The ram 131 is made to hit the inner surface 141 of the cap 14. The cap 14- and the body 19 are coupled rigidly together and made water-tight. A plurality of Water jet nozzles 102 are provided at suitable positions on thetlower end of the body or headltt). These nozzles are supplied from'the water header passage 103, supplied with water by a passage passing through the wall of the body 10, the wall of the hammer 11, and a connecting line passing through the space provided between the body or head 18' andt-he hammer 11, and a line passing through the space provided near to the'vibrator hammer 12 and the extracting hammer 13 contained within a cylindrical housing mounted between the vibrating hammers 12 and the cap 14, and being led upwards, and connected to the hose 155 through an opening provided on the cap 14. The
'inlets of hammers 11, 12 and 13 are respectively connected to the air supply hoses 151,152 and 153 and the outlets thereof are'jointly connected to the common exhaust hose 154. The parts where such hose groups pass through the cap 14 are also made strictly water-tight. This is due to the fact that the operation must be very cover 17 is provided on the body or head 10 for the purpose of protecting the rubber sleeve 16. The water outlet passages from the header 103a are provided on the driving point 197, similarly to the embodiment shown in FIG. 10. Since water supply 163a is made by the flexible rubber hose 10317 from the body, no trouble is caused to the water passage due to the reciprocation of the driving point 197; 7
Similarly to the embodiment shown in FIG. 1b, the groove 105a and the groove 106 are provided respectively on the outer surface of the driving point 107 and around the body or head 10.
frequently made with the driving unit beneath the level of'underground water. Around the cap 14, an annular groove 142 for coupling followers is provided, and a plurality of hooks 143 for suspending the whole body of the driving unit are provided nearer to the center of the cap than the groove 142. On the cone surface at the bottom of the body or head 10, several shallow grooves 1115, are provided radially. Such grooves, extended to the side of the body or head 113 and the cap 14, form upright grooves 166. The purposes for providing such grooves are to wash the sludge away with water jetted from the hole102 and to guide and maintain the driving direction of the driving unit. The total length of the driving unit is made as small as possible, to provide a compact unit that can be readily guided while driving downwardly through the soil can be kept within the limits practically allowable. t Another embodiment of driving unit is shown in FIG.
' 1b. In FIG. 1b, a section of the lower part, namely the driving point of the driving unit is'illustrated. The difference in the embodiments shown in EEG. 1a and in FIG. 1b consists in that, in the latter, the body or head 10 r is not built as one unit, but the movable driving point 1117 is provided in the axial direction to the body 19'. A cylinretaining pins-109a fixed to the body prevent the driving A plurality of axial guiding grooves 1419 are pointlti? from being disengaged. The ram 111 of the t hammer 11 hits the top surface. or. shoulder 1111 of the Between'the cylindrical guide'1ti3 and said rubb'er sleeve preventing underground'water from permeating through to the cylindrical sliding surface and to the hammer, without, however, impeding the move- In the embodiment of FIG. 1b, the ratio of the mass of the independent driving point 107' to the mass of the ram 111 becomes considerably smaller than in the case of FIG. 10, thereby increasing the force given to the soil by the driving point 107. This is extremely advan tag'eous in that the force given by the hammer is much more effectively utilized;
"the device shown in FIG. 3 suspends and guides the driving unit 1 at the desired position, adjusts its driving direction through the guide 6 and applies downward pressure to'it. The tower 2 is fixed to the machinery compartment 4 which is mounted and can be swung on the selfpropelling device 3, such as a crawler. The tower 2 is fixed on' the base 21. For fixing the'base 21 on the ground, the jack 211 and the sleeper 212 attached to the 7 base itself are used. The driving unit 1' is hung by means of the sheave 22 and the hoist rope 5. The abovementioned air and Water hose groups are connected to the air source and the water pump (not shown) in the machinery compartment or on the ground, through the sheave 23, and can follow the driving unit to the desired depth in the soil. On the tower 2, one or more sets of guide 6 for the driving unit 1 are provided, which finely adjusts the position of the driving unit. The guide 6 is movably mounted so that the driving unit and the followers can be engaged or disengaged at will.. On the upper end of the driving unit 1, the thrust yoke 7 is provided, which has a hole 71 at its center for passing through the hoist rope 5 and hose group 15, and has rope shackles 72 at its two ends. To the rope shackle 72, the wire ropes 73 are connected, which are led to the machinery compartment 4 through the sheaves 213 on the base 21. By pulling the rope 73, a downward thrust force is given to the yoke 7. As shown in FIG. 4, the
62, arms 63 and 64 are connected by the pins 621, and
said arms 63 and 64 are connected together by the pin 631, thereby forming Ta supporting frame which is not deformable on its own plane. To the frame 62 and the arm 63,, the adjusting screws 622 and 632 are respectively provided, and to each end of the screws 6-22 and 632, the shoe 65, which'supports the driving unit 1 and is freely rotatable with respect to the respective screw, is
connected. By using such supporting device, the position and .thedirection of the driving unit 1 canbe adjusted freely within a certain limit with'respect' to the tower 2, and by providing 'two sets of such guide 6 on the upper and lower parts respectively of the tower 2, the direction of center line of the driving unit 1 can be adjusted precisely. Setting and unsetting of the driving unit 1 I can be made, alter removing the. pin 631 and opening the farms '53 and 64. V I i When the pneumatic hammer 11 ismade to operate, the hoist rope 5 is loosened, and the thrust rope 73 is pulled in, the driving unit 1 starts to drive'into the soil due to the hitting force. of the hammer 11 and the thrust- L9 force or" the thrust yoke 7. The thrust force of the yoke 7 is limited by the weight of the machinery compartment 4, the self-propelling device 3 and the tower 2. If necessary, such limitation can be compensated by a dead weight which may be put on the base 21. In case the soil is comparatively hard, it can be crushed mainly by the hitting force of the hammer 1-1. But, in case the soil is sandy and the driving unit cannot be driven solely by the hitting force of the hammer, high frequency vibration can be given to the driving unit with the vibrator 12,
whereby it can drive into the soil without difficulty. Such high frequency vibration has the effect of decreasing the skin friction caused by the soil pressure which is applied to the side of the driving unit. Therefore, by operating the hammer 11 and the vibrator 12 simultaneously, the hitting force of the hammer 11 is not decreased by said skin friction, whereby the hitting energy can efiectively be utilized with the least loss. Similarly to the well known method, pressure water, and/or pressure air are led through the hole 102 for removing the sludge to make the operation easier.
Now, when the greater part of the body of the driving unit 1 is driven in the soil, as shown in FIG. 7, the guide 6 is opened as above-mentioned, the thrust yoke 7 is elevated, and then the semicylindrical follower members 8, made of steel plate, are joined together into cylindrical form and connected to the upper end of the driving unit 1. As shown in FIG. 8, the member 8 has its total length almost equal to that of the driving unit 1, has its diameter slightly smaller than that of the driving unit 8 for the purpose of decreasing the skin friction, has at its lower end a flange 81 to be engaged to the groove 142 which is provided at the upper end of the driving unit 1, and has at its uper end the groove 82 which has the same shape as that of the groove 142. At the joint of the two semicylindrical members, are provided a pair of flanges 83 which have respectively holes 831. By clamping the flanges 83 with the bolts 832 through said holes 831, a cylindrical follower is formed, as shown in FIG. 9. The driving unit 1 and the follower 8 are connected together at the groove 142 and the flange 8. The above connecting operation is not obstructed by the presence of the hoist rope 5 and the hose group 15, as is clear from FIG. 7. The upper bolt 832 can easily be inserted in the hole 831. To make it easier for the lower bolt 832 to be inserted, an extra hole 833 is provided on the cylindrical member 8.
On the semicylindrical members 8, small holes 84 of the size not permitting earth and sand to intrude therethrough are made in large numbers. Thanks to such holes, underground water and also water fed for the operational reasons which are outside of the cylindrical follower can enter thereinto, whereby the water pressures inside and outside of the follower are equalized. When the follower 3 is connected to the driving unit 1, the guide 6 is closed, the thrust yoke 7 is put on the top of the follower, and then the driving unit is driven in the soil in the same way as above-mentioned. And, as shown in FIG. 15a, when the first follower 8 is almost driven in the soil, the second follower 8' is connected to the first follower in the same way as above-mentioned, as shown in FIG. 10. Thereafter, similar operations are repeated until the desired depth is attained.
Another embodiment of the follower, shown in FIG. 11, is different from that shown in FIGS. 7-10 in that the follower is not formed by connecting two semicylindrical members, but is formed initially as cylindrical, and has therein, as its integral elements, water pipes, pressure air pipes and exhaust pipes.
In FIG. 11, 85 is a steel plate cylinder having Small holes 84a similarly to the steel plate 8 in FIGS. 7 and 8, and has annular; flanges 851 at its two ends. FIG. 12 shows one end of the follower 85. An exhaust pipe 861 is provided in its center. An air pipe 862 for the main hammer and the vibrator hammer is provided at the inside of said exhaust pipe 861, and a Water pipe 863 at the outside thereof. Such pipes are held in their respective position by the stay bars 864. A plurality of aligning knocks 352 are provided on the annular flange for keeping the positions of air pipe and water pipe when the follower is to be connected with a succeeding follower.
As shown in FIG. ll, rubber joints 865, 8% and 857 are provided, which, by jamming themselves together, contribute to make a tight connection of pipes when a follower is joined with the driving unit or with the preceding follower.
The two follower ends are joined together, as in FIG. 13. As is clear from the figure, a ring formed connector 89 is engaged in the grooves of the respective annular flange 851, which assures a positive connection of the two followers.
In FIG. 14, the ring formed connector 89 is shown disassembled. It is composed of a pair of semicircular rings @141 and 8915, having a recess 892 at their joining parts, and is connected with a bolt nut 893 which is so designed that the heads thereof do not project out of the circle formed by followers. The said recess 892 is placed between the flanges 851.
When the driving unit 1 reaches the required depth, the action of the driving hammer 11 is made to stop. In the embodiment shown in FIGS. 7-10, the extracting hammer 13 is made to operate for giving the driving unit 1 upward impacts, while the hoisting force is being applied to the driving unit 1 by means of the hoist rope 5. By doing so, the driving unit and the followers are gradually extracted upwards by the same principle as in the well known pile extraction method. In the embodiment shown in FIGS. lll4, the upward extraction force can be imparted to the driving unit I through the followers themselves, instead of by the rope 5. Therefore, the extraction force is stronger and a higher efiiciency can be expected than in the embodiment shown in FIGS. 7-10. Furthermore, no retractable hose group shown in FIG. 7 is needed, and the hoses coming from the air source and the water pump need not be fed beyond the length of one follower unit. Such are extremely advantageous because both the structure and the operation can be simplified.
The structure of the upper end of the driving unit 1 and the lower surface of thrust yoke 7 are similar to that of the connecting parts of the followers shown in FIGS. 11-14, and the yoke 7 is extracted upwards by a means such as wire ropes.
In the case of extraction, as in the case of driving downwards, the vibrator 12 is made to operate, if necessary, for decreasing the skin friction. When the extracting operation is made, a negative pressure is created under the driving unit which obstructs the extracting operation. Also, there is a fear that the hole may cave in by a violent flowing in of underground water. FIG. 1512 shows the sheathing method for keeping such danger away by compensating for said negative pressure and preventing said caving in. Namely, from the jet nozzle 102, sheathing material 9, such as slurry, is supplied, and the extracting operation is made while filling up the hole with such sheathing material. Thereafter, by removing the followers in the order reverse to that of driving into the soil, the holes for laying piles or for other purposes are completed as shown in FIG. 150. The piles can be constructed either by pressing the precast pile units in the holes or by pouring concrete thereinto.
In the practice of the present invention, the completed holes can be utilized for sand piles and compaction piles. And, if necessary, the driving unit and the followers, covered with casings, may be driven into the soil, and after completion of driving operation, the driving unit and the followers may be pulled up, leaving said casings underground, whereby the completed hole is sheathed with casings.
By the method of the present invention, the hitting force is produced always at the lower end of the driving unit,
and therefore, the hitting energy can 'most effectively be utilized. It is known that the soil pressure horizontally applied to the driving unit and the followers is largest in the neighbourhood of said lower end, due to the fact that the driving unit drives into the soil by pushing the soil aside, and is not so large at the places where the driving unit already passed through and the followers were inserted. For this reason, the followers do not require thick walls to resist the soil pressure. Furthermore, the vibration energy given to the lower end of the driving unit tends to decrease upwards. This makes no harm to the operation, because the vibration energy is needed for decreasing the skin friction which is applied to the driving unit and to its neighbourhood. In other words, the vibration energy may be smallbecause the mass of the object to be vibrated is also smfll. As the driving unit used for the method of the present invention is of steel, its driving force can be made far larger than in the case of pile points used in the hitherto practised button pile method.
It can be said, accordingly, that, by applying the same amount of hitting energy, a larger and more effective soildriving force can be obtained at-the end of the driving unit and the operation efficiency can be made higher than by the hitherto practiced method. 7
It is another advantage that the straight driving direction of the train of followers underground can be maintained and an individual follower does not buckle for the reason that said train is tracted by the driving unit lowest situated, the effect of thrust applied by the thrust yoke being negligible, and therefore holes or" a high slenderness ratio, not realized by the well known method, can be completed.
It is a further advantage that an inclined hole may be made by tilting the tower and'the base.
Furthermore, the tower may be of a size much smaller than the total length of the hole. The machinery also can be of a small size and of a light weight. The machinery can be moved easily by the self-propelling device, making it possible to shorten considerably the time spent for the installation, withdrawal and transportation of the whole device. gives a high stability during operation, and is safe against a strong wind. Such are other advantages of the invention.
Lastly, a most important advantage is that the impact noise scarcely reaches the ground surface, because hitting is performed deep underground; By the hitherto practised method, it was experienced that the operational hours must be shortened considerably due to impact noise, especially in cities and towns. Such difliculty may be eliminated by the method of the present invention.
We claim: I 1 l. A hole driving unit consisting of adrill head, a body extending upwardly from said drill head, a reciprocating hammer carried by. the body and'striking said drill head downward blows to force said drill head into the ground and form a hole, and a vibratory hammer means mounted in said body to vibrate the same at a hi er frequency thansaid reciprocating hammer to reduce the resistance between the unit and the ground, a bore having a shoulder v above'said drillhead, a housing for said reciprocating hammer mounted on said shoulder in said body and perto the upper end of said body and clamping the housing.
of said extracting hammer against said vibratory hammer means and said reciprocating hammer housing to hold the said extracting hammer to strike said cap A low tower is easy to be transported,"
' engage their respective shoulder, means mounted between V "same in operativerelation to each other and permitting 2 A, hole driving unit consisting of a hollow body'arranged at its upper end for attachment to a tubular column, a drill head closing the bottom of said body and having a driving point on its under side and an anvil on its top side, shoulder meansin the lower end of said hollow body, a reciprocating hammer having a housing engaging said shoulder means and having a downwardly V umn, a drill head closing the bottom of said body and having a driving point on its under side and an anvil on its top side, shoulder means in the lower end of said hollow body, a reciprocating hammer having a housing engaging said shoulder means and having a downwardly extending ram to strike said anvil on said drill head to force the headpoint into the ground and form a hole, a cap closing the upper end of said hollow body, and vibratory hammer means mounted in an independent unitary housing held between said reciprocating hammer housing and said cap member.
4. A hole driving unit consisting of a hollow'body arranged at its upper end for attachment to a tubular column, a drill head closing the bottom of said body, and 7 having a driving point on its under side and an anvil on its top side, shoulder means in the lower end of said hollow body, a reciprocating hammer having a housing engaging said shoulder means and having a downwardly extending ram to strike said anvil on said drill head to force the headpoint into the ground and form a hole, a cap closing the upper end of said hollow body and having an anvil and a cap shoulder means on its inner under side,
a second reciprocating hammer havinga housing engag ing said cap shoulder means and having an upwardly extending ram to strike said cap anvil, and means extending between said housings to hold them against said shoulder means.
5. The hole driving unit of claim 4 wherein said last mentioned means is a plurality of. self-contained independent vibratory hammers having'their unitary housings disposed in spaced relation between said housings to vibrate said-body and the column attached thereto vertically and at a higher frequency than either of said reciprocating hammers to reduce the skin resistance of said driving unit relative to the ground.
6. A hole driving unit consisting of a hollow body having a chamber with upper and lower shoulders and closed by a cap at its upper end and arranged for attachment to a tubular column, a drill head closing the bottom of said body, means attaching said drill head to said body for limited relative movement therewith, an anvil on the inner underside of said cap, an anvil on the inner top side of said head, opposed upper and lower reciprocating hammers each having a housing mounted in said chamber to the housings of said" hammers to hold them on said shoulders, a ram for said upper hammer operable to engage said cap anvil, a ram' for said lower hammer oper able to engage said anvil on said drill head.
7. The hole driving unit of claim 6 which also includes a plurality of vertically operative self-contained hammers having their independent housings mounted between the housingsio f saidreciprocating hammers to suppl y an axial annular high frequency vibratory motion, to said driving unit to reduce the ground resistance. g
H (References on following page) References Cieal in the file of this patent UNITED STATES PATENTS Marsden July 29, 1884 Drain Sept. 28, 1897 Ferguson Mar. 16, 1909 Clark Oct. 10, 1911 Noble Feb. 2, 1915 Schumacher May 15, 1917 Stone Nov. 15, 1927 10 Pierce July 3, 1928 B1umentha1 May 9, 1933 Greenlee Aug. 31, 1937 Steuerman Oct. 17, 1944 Huffman et a1 June 28, 1960 Degen Sept. 6, 1960 FOREIGN PATENTS Great Britain Jan. 26, 1905