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Publication numberUS3865200 A
Publication typeGrant
Publication dateFeb 11, 1975
Filing dateNov 17, 1972
Priority dateNov 18, 1971
Also published asDE2157259B1, DE2157259C3
Publication numberUS 3865200 A, US 3865200A, US-A-3865200, US3865200 A, US3865200A
InventorsSchmidt Paul
Original AssigneeTracto Technik
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Burrowing apparatus
US 3865200 A
Abstract
A pneumatic burrowing apparatus comprising a tubular housing with a percussion tip mounted at the leading end of said housing and including a rearwardly directed portion extending interiorly of said housing, said tip being arranged for axial movement relative to said housing. A percussion piston is mounted for reciprocal motion within the housing and arranged to strike said percussion tip to impart a forwardly directed force thereto. Spring means mounted between the percussion tip and the housing are arranged to be compressed therebetween when the tip is driven forwardly by said percussion piston. A displacement cone mounted proximate the leading end of the housing moves forwardly with the housing during a burrowing operation but is loosely slidable relative to said housing when the housing is withdrawn from a burrowed opening.
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United States Patent Schmidt Feb. 11, 1975 [54] BURROWING APPARATUS 3,559.753 2/197! Meri etal. 173/139 X [75] inventor: Paul Schmidt, Saalhausen, Germany i I Primary E.\'ammerErnestR. Purser l l Asslgnee? Tracto'Techmk Paul Schmldt, Assistant ExuminerRichard E. Favreau Saalhausen' Germmy Attorney, Agent, or Firm-Toren, McGeady and 221 Filed: Nov. 17, 1972 s 21 Appl, No.: 307,573

ABSTRACT [30] F i A n i P i i D t 1 1 prneumatie brurrowing apparatus comprdisingha tIubZ- 18 97 I M57259 ar ousmg wit a percussion tip mounte att e ea NOV 1 1 German) ing end of said housing and mcludmg a rearwardly di- [57] Us Cl 175/19 73/99 173/133 rected portion extending interiorly of said housing, i 11/02 said tip being arranged for axial movement relative to [58] Pic. 73 94 said housing. A percussion piston is mounted for re- 91 ciprocal motion within the housing and arranged to strike said percussion tip to impart a forwardly di- [56} References cued rected force thereto. Spring means mounted between the percussion tip and the housing are arranged to be UNITED STATES PATENTS compressed therebetween when the tip is driven for- 955 899 4/l910 Proctor l73/l33 X wardly by Said percussion piston A displacement cone #931068 10/1933 f mounted proximate the leading end of the housing g X moves forwardly with the housing during a burrowing 5 H1960 g S 173/08 operation but is loosely slidable relative to said hous- 311371423 6/1964 ZinEiewi e z .II 173/91 x the housing is Withdrawn from burrowed 3,375,885 4/1968 Scott et al 175/94 X p 3,407 884 lO/l968 Zygmunt et al 173/91 3,465.834 9/1969 Southworth 1. 175/73 x 23 Claims 12 Drawing Figures ATEHTEU FEB 1 I 1975 SHEET 1 BF 6 TQE BURROWING APPARATUS The invention concerns a self-driven, pneumatic burrowing device, in particular for ground drilling, having a percussion tip and a percussion piston reciprocating in the housing. Such devices are also known under the designation ground rocket, percussion hammer or percussion drill and serve primarily to install supply lines, such as water pipes, electric or telephone lines under streets or sidewalks without requiring that the pavements or the sidewalks be broken open.

In known devices, the housing of the burrowing apparatus is subjected to very high loads, so that its life is normally at most 500 hours of operation. Moreover, the diameter of such devices is 135 mm and more, although in the practice 50 mm are usually sufficient as diameter for the bores. The large housing diameter entails high friction, which greatly reduces the advance of the device. Furthermore, there is greater danger of damage to the street pavement due to cross ripples, because the subsoil under streets, already compacted to a large extent, is also displaced upward against the pavement by the advance of the drill, so that the pavement rises slightly.

Other disadvantages of conventional driving drills reside in the high consumption of compressed air due to the large pressure surfaces, the danger of deviation from the desired drilling direction because of the large housing diameter, as well as the high production costs resulting from the fact that the interior of the housing is worked out of the solid material.

It is, therefore, the object of the invention to provide a burrowing apparatus which is free from the aforementioned disadvantages and in particular one which has a longer life than the conventional drills.

According to the invention, this is achieved in that the percussion tip is arranged in the housing of the driving drill and is displaceable in the axial direction thereof being supported on the housing in the working direction via a spring member. As a result not only is much less percussion energy required than in comparable conventional driving drills, but also the load on the housing is greatly reduced. This is attributed to the unique movement conditions effected in the driving drill according to the invention. Due to the displaceable arrangement and the elastic support of the percussion tip, the speed with which the percussion tip is moved after the impingement of the percussion piston is much greater, and that of the housing much smaller, than in conventional driving drills. Due to the improved advance, a smaller piston surface can be selected for admission with compressed air, and the housing diameter can be reduced considerably. The result of this is, besides a great reduction of the frictional resistance in the soil, an appreciable reduction of the production costs.

The present invention will be better understood by reference to the following detailed description of the preferred embodiments thereof, taken in connection with the accompanying drawing, in which:

FIG. 1 shows a longitudinal section through a driving drill according to the invention;

FIG. 2, is a detailed sectional view of another driving drill according to the invention;

FIGS. 3 to 6, are longitudinal sectional views showing equivalent details of a third driving drill according to the invention, in different operative positions, with a control device;

FIG. 7, is a perspective view of a mount for introducing the driving drills according to FIGS. 1-6 into the soil;

FIG. 8, is a sectional view of a driving drill according to the invention for opening up or widening an existing earth bore;

FIG. 9, shows a side elevation an aiming frame for aligning the driving drills;

FIG. 10, is a schematic view showing a driving drill according to the invention in tandem arrangement; and

FIGS. 11 and 12, are partial views showing in detail steering devices for a driving drill according to the invention.

According to FIG. 1, the housing 1 of a driving drill according to the invention consists of a honed commercial hydraulic tube, chromed for protection against corrosion and to reduce wear, having an outside diameter of between -95 mm, and provided at both ends with an internal thread. A bushing 2 is screwed into one end of housing I. In the center the bushing 2 has a collar 3 of the same diameter as housing 1, with the collar 3 being provided with bores 4 to enable engagement by a hook wrench for turning of the bushing 2. The bushing 2 includes external threads located axially rearwardly of the collar 3 configured to engage the internal thread of housing 1.

A threaded porof bushing 2 located axially forwardly of the collar 3 is configured to engage a housing front portion 5, which has the same diameter as the collar of bushing 2 and as the housing 1. On its side opposite the bushing 2, the portion 5 embraces by a collar 6 a pin 7 of a conical percussion tip 8, which again has the same outside diameter as collar 3 of bushing 2 and as the housing 1 and which embraces the housing portion 5 at an offset 9 with a collet 10.

Onto the free end of pin 7 a collar 11 is attached, for example, by screw threads or the like, which guides the percussion tip 8 in the housing front portion 5 and which has bores 12 extending axially rearwardly thereof to enable engagement by a socket wrench. Between collar 6 of the housing front portion 5 and collar ll of the pin 7, there is provided a compression spring 13 held in tension about the pin 7 by the collar 11. The adjustable initial tension of spring 13 assures that in the starting position shown the percussion tip 8 bears with its housing-side end face against collar 6 of the housing front portion 5. Direct contact is prevented, however, by an elastic disk 14 arranged between the percussion tip 8 and the housing front portion. All screwed parts are secured against detachment by locking plates.

In operation, by way of an intermediate piston 15 which in the starting position shown bears against pin 7 of the percussion tip 8, a pneumatically moved percussion piston 16 is caused to strike against pin 7 of percussion tip 8, so that the percussion tip lunges for ward from the housing front portion 5 into the soil. The intermediate piston 15 contributes to the crushing, for example of stones which cannot be pushed aside, by the vibrating percussion tip preceeding the housing, and for this purpose it is arranged in bushing 2 for displacement in axial direction and is supported in bushing 2 by a collar 17 on elastic buffers 18 arranged in the axial direction before and behind the collar. As the percussion tip 8 lunges forward. the housing 1 follows this movement under the pressure of spring 13 and of the elastic buffers 18. The buffers 18 are held in the bushing 2 by another collar 19 of bushing 2 and by a disk 20 secured in bushing 2 by a spring ring 30. The intermediate piston 15 forms a sub-assembly with bushing 2 and the elastic buffers 18, as does also the housing tip 5 with the percussion tip 8, collar 11 and plate springs 13. In operation, the condition of the spring member formed by the springs 13 is such that the amount of its compression, in what in the operating direction is the frontmost position of the percussion tip in the housing, is equal to or smaller than the maximum permissible amount.

The percussion piston 16 is guided in housing 1 by means of two guide rings 32, 33 arranged at an axial distance from each other on its shell 31 and is provided with slide rings 34 at the guide rings 32 and 33 to reduce the friction at housing 1. The guiding of the percussion piston 16 with the rings 32 and 33 insures sufficient freedom of movement for the percussion piston 16 even if housing 1 is twisted to a relatively high degree. Besides, the percussion piston 16 slides with its bored rear end, viewed in the direction of the percussion tip, sealing engaged on a control bushing 35, which is held with a collar 36 in an offset of the internal bore of the housing by a sleeve 37 screwed into the respective housing end and having a slightly larger diameter, in the portion protruding from housing 1, than the housing 1.

At the end away from the percussion piston 16, the control sleeve 35 has a connecting piece 38 designed as a flexible tube for connection to a compressed air line of a compressor (not shown). The compressed air coming from the compressor passes, in the operative state, through an internal bore 39 of the control sleeve 35 into the bored end of the percussion piston 16, so that the percussion piston is accelerated in the direction of the percussion tip 8. Owing to this, the percussion piston 16 moves in the housing 1 against the intermediate piston 15. The air present in housing 1 before the percussion piston 16in the direction of movement-escapes along the generated surface of the percussion piston. For'this purpose, the percussion piston 16 is provided between the guide rings 33 and 32 at the shell 31 with an external recess which at the front guide ring 33-in the direction of movement-is connected via an axial groove 40 with the housing cavity present between percussionpiston 16 and intermediate piston and via a bore 41 in shell 31 with a recess 42 at the outer circumference of the control sleeve 35 extending as an external opening. However, the connection with recess 42 in control sleeve 35 is interrupted by a suitable limitation of recess 42 or respectively a suitable arrangement of bore 41 in shell 31 of the percussion piston 16 approximately after one half of the distance traveled up to the intermediate piston, and the housing cavity lying before the percussion piston 16-in the direction of movement-is closed. Consequently, if the pressure of the compressed air supplied by the compressor continues to act at the bored end, there builds up in the housing cavity before the percussion piston 16 an air pressure which accelerates the percussion piston 16 in the opposite direction after impingement on the intermediate piston 15 and after transfer of the kinetic energy causing the advance of the percussion tip 8 and of the housing 1 to the intermediate piston 15. Simultaneously with the impingement of the percussion piston 16 on the intermediate piston 15, if the length of the control sleeve 35 is adequate, there results via the bore 41 in shell 31 of the percussion piston 16 a connection of the housing cavity lying between percussion piston 16 and intermediate piston 15 with the internal bore 39 of the control sleeve 35, and in addition to the admission in the bored end the percussion piston is pressurized at the other end with the compressed air coming from the compressor. As the area at the other endwhich in the working direction of the percussion tip 8 is the front end-is greater than the pressurized area at the rear end, the percussion piston 16 returns to its starting position under the differential pressure of both areas. Before it reaches its starting position, in which the percussion piston 16 bears against collar 36 on the control sleeve 35, there results again a connection of the housing cavity lying between the percussion piston 16 and the intermediate piston 15 with the recess 42 of the control sleeve 35 extending externally, so that the air pressure in this housing cavity decreases and the percussion piston 16 is decelerated by the pressure of the compressed air coming from the compressor now acting only in the bored percussion piston end. After reaching its starting position, the percussion piston 16 is again propelled forward without interruption for a new strike against the intermediate piston 15 at continued pressurization in the bored end and admission of air to the housing cavity lying before the other end.

The admission of air to the housing cavity via recess 39 in the control sleeve 35 occurs due to the fact that axially extending bores 43 are present in collar 36 of control sleeve 35 and housing 1 is open at what in the direction of the percussion tip 8 is the rear end, into which the bores 43 open, or respectively that it is provided with a protective tube 44 of plastic through which air can escape from housing 1 also when housing 1 is completely embedded in the soil, and which protectively embraces the compressed air line 38 leading to housing 1. The protective tube 44 is fastened to the housing 1 by a cutting ring screw connection. Specifically the cutting ring screw connection is composed of: a ring 45 which is located within the protective tube 44; a ring 46 which extends externally about the protective tube 44, is press-fitted with protective tube 44 into the internal bore of sleeve 37, and in so doing becomes clamped between sleeve 37 and in the outer side of pro tective tube 44; and a cap nut 47 screwed onto sleeve 37, to press the ring 46 with the protective tube 44 into sleeve 37. Alternatively, a simple clamping ring may be provided instead of the ring 46, i.e., the protective tube 44 may be drawn into sleeve 37 while being clamped between the ring 45 and the similarly clamping ring which may be additionally slit in the axial direction.

In the embodiment of the invention according to FIG. 2, the housing front portion 61 is screwed directly into the housing and comprises a percussion tip 62 in the form of a round chisel, which at the front end--taken in the working direction-is designed as a hollow chisel by an inward arch equal to the arch of a spherical surface. lntegrally formed at the other end of the tip 62 is a piston 66 and a pin 63. Pin 63 forms the strike surface for the respective percussion piston and is present, in the starting position shown, in the internal bore of a ring 64 which is attached, for example by screw threads or the like, with the housing front portion 61 into the housing 60. Ring 64 limits the movement of piston 66 against the working direction of the percussion tip 62. The movement in the working direction, during which the percussion tip 62 is guided on the one hand directly in the housing front portion 61 and on the other hand with piston 66 in the housing front portion 61, is limited by an offset 65 of the piston bore formed in the housing front portion 61 within which piston 66 is slidably movable. During this movement, the percussion tip 62 is supported on the housing front portion 61 by way of piston 66 and plate spring 67, which move the percussion tip 62 back into its starting position from its-in working direction in the housing front portion 61frontmost position after each percussion.

While in the example according to FIG. 1 the intermediate piston with its elastic suspension insures that the percussion tip 8 does not execute a movement inadmissible for the plate spring 13 despite a mass which is small in relation to the mass of the percussion piston 16, i.e. while in FIG. 1 the intermediate piston 15 prevents an inadmissible compression of the compression spring 13, an inadmissible compression of the plate spring 67 according to FIG. 2 is prevented by the offset 65.

Upon impingement of the percussion piston on pin 63 of the percussion tip 62, the latter, like the percussion tip 8 of FIG. 1, is driven forward out ofthe housing front portion 61, and via the plate spring 67 in the working direction of the percussion tip 62 a pressure is exerted on the housing front portion 61 and on the housing 60. At sufficient spring force of plate spring 67 this pressure is so strong that the housing 60 with its housing front portion 61 follows the percussion tip 62, just as under the pressure of plate spring 13 and of the elastic buffer 18 the housing 1 follows the percussion tip 8. Otherwise the friction in the soil, opposing a movement of the housing, and the housing movement possibly resulting from a previous return of the percussion piston to its starting position counter to the working direction of the percussion tip 62 will be overcome only with the impingement of the piston 66 on the offset 65 of the housing front portion. In any case, and in the same manner as the device of FIG. 1, a leading of percussion tip 62 relative to housing front portion 61 and to housing 60 in the form of a vibratory movement results, which improves the advance over conventional driving drills.

Furthermore, the advance according to FIG. 2 is further increased by a ring 68 placed on the housing front portion 61, whose diameter is larger than housing 60 and housing front portion 61. Ring 68 tapers in adaptation to the housing front portion 61 in the working direction of the percussion tip 62 and pushes the soil aside so that a bore is formed in the soil whose diameter is greater than the housing diameter, and that the friction of housing 60 with the soil is considerably reduced.

In order that ring 68 will not hinder a backward movement of housing 60, the seat of ring 68 on the housing front portion 61 is selected so that it detaches from the housing front portion 61 when, for example in the case of a bore hole extending in an undesired manner, the driving drill is to be positioned anew and the housing is, for this purpose, moved backward out of the soil by reversal of the respective percussion piston.

Further improvement of the advance is brought about by profile grooves which, extending crosswise to the longitudinal direction of the housing, largely prevent retraction of the housing 60 during the return stroke of the percussion in piston. In this connection, a sawtooth profile, such as that shown in FIG. 2 on the outer surface of housing 60 with teeth pointing backward in relation to the percussion tip, has proved particularly advantageous.

The reversal of the percussion piston for a backward movement occurs, according to FIGS. 3 to 6, in another driving drill according to the invention, by means of a cable line 69. Through the cable line 69 a sleeve 143 is moved.

The sleeve 143 cooperates with a control sleeve 135, a spring 136, and a ring 137. The control sleeve is designed as a tube which is mounted for sliding movement in the ring 137, fastened in the housing and provided with passage openings 101 for the air escaping from the housing. Ring 137 has a sleeve type prolongation 138, in which are present, at two different points, on a circular circumference, a number of radial bores for balls 139. In the operative position of the control sleeve 135 for backward running, shown in FIGS. 5 and 6, the balls 139 engage in two annular grooves 140 and 141 of the control sleeve 135. In the operative position for forward running shown in FIGS. 3 and 4, the balls engage in groove 141 and another annular groove 142 of the control sleeve. By the engagement of the balls 139 the control sleeve 135 is fixed in the respective operative position.

The result of the change of the control sleeve 135 from the operative position Forward Running to the operative position Backward Running is that the period during which the space-in the direction of the percussion tip-before the percussion piston is pressurized is substantially shortened, at constant time for a cycle of the percussion piston, whereas the period during which a pressure difference from bilateral admission with compressed air counter to the direction of the percussion tip acts on the percussion piston is lengthened accordingly. Thereby the movement of the percussion piston against the percussion tip is decelerated at an early time and possibly an impingement of the percussion piston on the percussion tip is prevented altogether and the movement of the percussion piston in the opposite direction is decelerated much less, so that the percussion piston impinges against ring 137 and imparts a backward movement to the housing.

The balls 139 are held in the fixed position by the spring-loaded sleeve 143 which slides in the housing of the driving drill. On actuating the cable line 69 to switch from backward running to forward running, sleeve I43 slides from the shown starting position with recesses 144 over the balls 139, which release the balls 139 to the extent that they can just slide out of the annular grooves 140 and 141 when the compressed air supply is interrupted and spring 136 pushes the control sleeve into the operative position for forward running. In the operative position for forward running, the fixing of the control sleeve 135 now occurs automatically after release of sleeve 143 by the return thereof into the starting position, in that sleeve 143 now pushes the balls 139 into the grooves 141 and 142 of the control sleeve 135. The switching of the driving drill from forward running to backward running requires another actuation of the cable line. Then, at suitable design of the spring 136 and with continued supply of compressed air, the control sleeve 135 moves back into the starting position shown in FIG. 6 under the compressed air pressure counter to the spring force.

A protective tube (not shown) may be selectively screwed to the housing end of the driving drill, the screw connection taking place on the sleeve with which ring 135 is clamped in the housing and which is provided with several grooves extending in axial direction and interrupting the screw thread for the protective tube. The grooves give the sleeve the effect of a screw tap, that is, by the grooves the protective tube can be screwed onto the sleeve without prepared thread and the sleeve cuts into the protective tube with its screw thread. Also a so-called wire grip can be used for the attachment of the protective tube. The protective tubecan moreover be provided with openings and be used for drainage if it remains in the soil.

Besides there is shown in FlGS. 3 to 5 a percussion tip 109 which, though being designed as a hollow chisel like the percussion tips according to FIG. 2 and being mounted displaceably and elastically in the housing, has a displacement cone 110 with a collet 111 which, like the collet of percussion tip 8 according to FIG. 1, cooperates with the housing tip. The displacement cone 110 is mounted on a conical intermediate piece of the percussion tip 109, and as the cone tapers in the working direction of the percussion tip 109, it is thereby firmly connected in the working direction with the percussion tip without additional aids, while being easily releasable counter to the working direction.

In FIG. 7, a mount 75 is shown, with which the driving drill according to the invention is introduced into the soil at the beginning of each drilling operation and brought into the starting position required for a desired earth drilling. The mount 75 has two jaws 76 and 77 adapted to the contour of the housing, which receive the housing of the driving drill between them and give the housing a position parallel to the longitudinal axis of the mount. The jaws 76 and 77 are fastened to the mount 75 for pivotal movement by means of parallel links 78 and 79, and at the area of contact with the housing they have a greater distance from the housing diameter when the parallel links 78 and 79 are in the vertical position or at right angles to the longitudinal axis of the mount. Due to the geometry of the parallel links 78 and 79, at each movement of the parallel links 78 and 79 out of their vertical position the jaws 76 and 77 move toward each other, i.e. they close. Conversely thejaws 76 and 77 open when their parallel links 78 and 79 are moved from an inclined position into the vertical. Due to an extension spring 80 articulated to one parallel link 79, the jaws 76 and 77 always strive to close. This tendency is countered when inserting the housing of a driving drill with a parallel link 79 prolonged in the form of a lever, i.e. the pivoting of the parallel links 78 and 79 by hand counter to the force of the extension spring 80, required for insertion of a housing, is facilitated by a prolongation of the parallel link 79 and pivoting of this parallel link 79. After insertion of the housing and release of the parallel link 79, the jaws 76 and 77 close around the housing automatically. At the same time, and with a suitable arrangement of the extension spring 80 or insertion of the housing, the jaws 76 and 77 and the parallel links 78 and 79 move oppositely to the working direction of the percussion tip belonging to the housing. After the driving drill has been set in operation, that is, after pressurization with compressed air, the percussion piston moves back and forth in the housing forces and forces equal in sum act on the housing in each axial direction of the housing. As a result of the clamping of the housing between the jaws 76 and 77 and their pivotal arrangement, the force acting on the housing in the working direction of the percussion tip leads, with adequate design of the extension spring 80, to a pivotal movement of the jaws 76 and 77 counter to the force of the extension spring 80. The jaws 76 and 77 then open, and the housing slides through between them by its residual energy. The force acting on the housing in the other axial direction, that is, in the pulling direction of the extension spring 80, leads instead to an intensified clamping between the jaws, which prevents movement. In this respect the jaws 76 and 77 form with the parallel links 78 and 79 a return barrier which, after suffieient anchoring ofthe mount in the ground, insures that the driving drill penetrates into the soil.

For anchoring in the ground, the mount 75 is connected with a bottom plate 88, which is anchored in the soil with bottom nails 81 before alignment of the mount 75. For its alignment the mount 75 is pivoted about a horizontal and a vertical axis. For this purpose mount 75 is connected with the bottom plate 88 via a cardan joint formed by a turntable 89 arranged for rotary movement on the bottom plate 88 and a pivotable suspension of mount 75 in lugs of turntable 89. After aligning, i.e. after pivoting about the vertical axis, turntable 89 can easily be fixed in its pivoted position with an adjusting screw 91. The same applies to the pivoting of the mount 75 in the lugs 90, i.e. to the pivoting of mount 75 about the horizontal axis. In this case the fixing is done with screws 92 designed as thumb screws, which also permit an extremely accurate pivoting about the horizontal axis. According to FIG. 7, when fixing mount 75 with the thumb screws 92, two thumb screws 92 arranged on both sides of the horizontal pivot axis cooperate, bracing mount 75 against the bottom plate 88.

The aligning itself is facilitated by a bubble level, a type of water level, and by a sight 82. The sight 82 includes a rod 83 at eye level which is inserted into the mount 75 perpendicular to the longitudinal axis thereof and carries at the upper end, on a cross beam 84, a rear sight 85 and a front sight 86 with sighting line parallel to the' longitudinal axis of the mount for sighting a reference point.

Besides, the housing ofthe driving drill rests in mount 75 in the jaws 76 and 77 and on a shell type support 87 arranged at a distance from the jaws 76 and 77. The support 87 not only improves the parallel position of the housing between the jaws 76 and 77, as it reduces the bending load of the jaws 76 to a negligibly small amount, but it also facilitates the insertion of the housing between the jaws 76 and 77 and the provision of a protective tube embracing the compressed air line to the housing and possibly the cable line.

FIG. 8 shows a driving drill according to FIGS. 3 to 5 converted for the boring open (widening) of an existing earth bore. According to FIG. 8, instead of the displacement cone a displacement cone is arranged on the percussion tip 109 and the housing of the driving drill is surrounded with an additional shell 121. At its tip the displacement cone 120 has a cylindrical piece of the same or a slightly smaller diameter than the existing earth bore. The outside diameter of the displacement cone 120 equals that of the shell 121 and determines the diameter of the earth bore during the wid' ening thereof.

Also'for the widening of an existing earth bore exact aligning of the driving drill is important. There are, however, difficulties in the use of a bubble level when the driving drill must be brought into a certain inclination. Such an inclination can easily be adjusted with an aiming frame 122 shown in FIG. 9. In addition to a sighting device consisting for example again of a front sight and rear sight, for the sighting of a certain target, the direction finding frame 122 has a plumb line 123 and is set for aligning, with feet 124 adapted to the housing of the driving drill, on the housing of the driving drill indicated in dash-dot lines in FIG. 9. By means of a plumb line 123 and a suitable scale, any position of the driving drill can then easily be determined.

This is possible also when the driving drill is connected in tandem arrangement according to FIG. 10 with a parallel lying guide body 125. After making a first earth bore, the guide body 125 is connected, for example by screwing, with the housing of the driving drill, which in FIG. 10 is marked 126, and is introduced into the existing bore with its front portion protruding relative to the percussion tip of the driving drill, to make a second earth bore, parallel to the first, at the same outside diameter as the housing of the driving drill. The driving drill having been set in operation, it drills a second bore parallel to the first, of the same diameter. The first bore suffers no adverse change due to the protrusion of the guide body 125 and its length from the driving drill, i.e. by the displacement work thereof.

For the steering of the driving drill there are provided lastly also wings 127 or 128 according to FIGS. 11 and 12. The wings 127 are disposed at any point of the housing of the driving drill lying diametrically opposite in pairs, are connected with the housing rigidly or articulatedly, and steer the driving drill according to its inclinationto the longitudinal axis of the housing automatically in a certain are through the soil, so that for example traversal beneath streets of low crown can also be accomplished with the driving drill at sufficient depth without any excavation of earth for positioning the driving drill. The wings 127 have a form tapering in the working direction of the driving drill and are connected with the housing of the driving drill either rigidly or articulatedly. The articulated connection permits the adjustment of the wing inclination to the longitudinal axis of the housing and hence a selection of the are on which the driving drill moves through the earth, or respectively it makes possible an adaptation to the nature of the ground to be traversed.

The articulated connection of the wings 127 includes a pin 129 fastened to the housing of the driving drill, on which is mounted for rotary movement a hub 130 which is welded, for example, to one end of the respective wing 127. In the other end of wing 127 is mounted a trunnion screw 131, which extends by its trunnion into one of several bores 132 arranged in the housing on a corresponding circular circumference around the pivot axis of the wing 127.

Instead of the wings 127 fastened to the housing of the driving drill, or in addition to the wings 127, there may be used for the steering of the driving drill a curved stiff protective tube 44a which, like the housing in FIG. 11, is shown in detail in FIG. 12 and is provided selectively with wings 128. The wings are preferably curved in the same amount as the protective tube and arranged lying opposite in pairs at the protective tube, parallel to the longitudinal axis thereof.

What is claimed:

l. Pneumatic burrowing apparatus particularly suitable for earth drilling comprising a tubular housing including a leading end adapted to act as the anterior of said apparatus during a burrowing operation, a percussion tip mounted in said housing at said leading end and including a rearwardly directed portion extending interiorly of said housing, said tip being arranged for axial movement relative to said housing, a percussion piston mounted for reciprocating motion within said housing and arranged to strike said percussion tip to impart a forwardly directed force thereto, pneumatic means including an energy source for imparting a striking force to said piston, spring means mounted between said percussion tip and said housing and arranged to be compressed therebetween upon relative movement of said tip forwardly of said housing, and a displacement cone mounted proximate said leading end for forward movement with said housing during a burrowing operation, said displacement cone being loosely slidable relative to said housing in a direction forwardly thereof.

2. Apparatus according to claim 1 including an adjustable stop member axially displaceable relative to said housing engaging said spring means for enabling adjustment of the spring force thereof.

3. Apparatus according to claim 1 including stop means engaging said percussion tip to limit movement of said tip relative to said housing.

4. Apparatus according to claim 1 wherein said displacement cone is mounted upon said percussion tip.

5. Apparatus according to claim 1 wherein said displacement cone is mounted upon a portion of said housing proximate said leading end.

6. Apparatus according to claim 1 including profile grooves arranged upon the outer surface of said tubular housing and extending transversely to the longitudinal direction of said housing.

7. Apparatus according to claim 1 including a protective tube attached to the rear end of said housing taken relative to the working direction of said percussion tip.

8. Apparatus according to claim 1 including a guide body attachable alongside of said tubular housing and extending generally parallel thereto.

9. Apparatus according to claim 1 including steering wings adjustably attachable to the exterior of said hous- 10. Apparatus according to claim 1 including a curved stiff protective tube attachable to said housing.

11. Apparatus according to claim 1 including an intermediate piston arranged in the line of action between said percussion piston and said percussion tip and being displaceable in the direction of movement thereof.

12. Apparatus according to claim 11 wherein said intermediate piston is resiliently mounted within said housing.

13. Apparatus according to claim 1 wherein said percussion tip is formed as a hollow chisel.

14. Apparatus according to claim 13 wherein said percussion tip is arched inwardly in the form of a spherical cap at the respective end face thereof extending toward the leading end of said apparatus in the working direction thereof.

15. Apparatus according to claim 13 wherein said percussion tip chisel comprises a circular cross sectional configuration. wherein said displacement cone is mounted upon said chisel and is arranged at a distance from said chisel tip which is a multiple of the diametral dimension of said chisel.

16. Apparatus according to claim 1 including a control sleeve mounted within said housing and having an internal bore designed as a compressed air inlet and being provided at its circumference with at least one air channel, said percussion piston being hollow at a rear end thereof taken in the working direction of said piston, said piston sliding by its hollow rear end in the space between said control sleeve and the inner wall of said housing and simultaneously forming a seal on said control sleeve and on the inner wall of said housing, there being provided in the hollow rear end of said percussion piston an opening which extends over at least one channel to the front end face of said percussion piston taken in the working direction thereof, said channel corresponding during the working stroke of said percussion piston with the channel in said control sleeve alone and during the return stroke of said combustion piston with the internal bore of said control sleeve alone.

17. Apparatus according to claim 16 wherein said control sleeve is displaceably arranged within said housing, with the displacement path of said control sleeve being limited by stop means, with a force exerted on said housing by said percussion piston in the working direction thereof being greater in one fixed position and smaller in another fixed position than the force ex- 12 erted on said housing in the opposite direction.

18. Apparatus according to claim 1 including a mounting assembly adapted to have said burrowing apparatus mounted therein for guiding said apparatus during a burrowing operation.

19. Apparatus according to claim 18 wherein said mounting device is provided with a return barrier consisting of two jaws held in a pair of spring loaded parallel links which are at the areas of contact with said housing in a vertical position of said parallel links arranged at a distance from each other which is greater than the outside diameter of said housing.

20. Apparatus according to claim 18 wherein said mounting device includes a bubble level enabling positioning of said mount at a desiredlocation.

21. Apparatus according to claim 18 wherein said mounting device includes an aiming frame with a plumb line device enabling positioning of said mount.

22. Apparatus according to claim 18 wherein said mounting device includes sighting means enabling desired orientation of said mount.

23. Apparatus according to claim 18 wherein said mounting device includes a bottom plate and a cardan joint interconnecting said mounting device with said bottom plate, said mounting device being adjustably positionable relative to said bottom plate to enable fixation thereof in the earth.

l =l l=

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Classifications
U.S. Classification175/19, 173/99, 173/133
International ClassificationE21B4/14, E21B4/00, E21B7/00, E21B7/26
Cooperative ClassificationE21B7/26, E21B4/145
European ClassificationE21B4/14B, E21B7/26