GB2173232A - Percussive action machine for making holes in the ground - Google Patents

Abstract

A percussive action machine comprises a housing (1) which accommodates a hammer (2) movably arranged to define inside the housing (1) a forward stroke chamber (6) and a return stroke chamber (5). The machine is provided with an air-distributor (3) fashioned as a sleeve (11) having passages (15, 16). The machine is further provided with a means for alternately communicating the chamber (5) with the chamber (6) and with the outside, this means having the form of at least one bore (20) arranged inside the hammer (2) in line with its axis. Communicating with this bore (20) is a tubular control valve (18) extending through the forward stroke chamber (6) and having in its wall at least one hole (21) wherethrough the chamber (5) alternately communicates with the chamber (6) and with the outside. <IMAGE>

Description

SPECIFICATION Percussive Action Machine for Making Holes in the Ground This invention relates to air-operated percussive action machines used in civil engineering and mining, and more particularly to machines to making holes in the ground.

The invention can find a most beneficial application in devices intended for making horizontal, inclined and vertical holes in the ground being compacated during trenchless laying of underground communication lines under highways, earth embankments and other structures.

The machine according to the invention can also be used for driving piles, down-the-hole soil compacting, as well as for forcing tubes and other structural elements in the ground.

The essence of the present invention resides in that in a percussive action machine for making holes in the ground comprising a cylindrical housing accommodating a reciprocable hammer defining inside the housing a forward stroke chamber continuously communicating with an air-feeding line and a return stroke chamber communicating alternately with the forward stroke chamber and with the outside through a conduit means provided in the hammer which includes an air-distributor fashioned as a sleeve having holes and secured in the housing, and a tubular control valve movably arranged relative to the sleeve to be capable of opening and closing the holes in the sleeve, and a locking means for moving the tubular control valve and fixing it in two extreme positions in one of which the return stroke chamber communicates with the outside through the conduit means provided in the hammer and through the airdistributor, in the other extreme position the return stroke chamber communicating with the forward stroke chamber, according to the invention, the forward stroke chamber is defined between end faces of the sleeve and hammer, whereas the conduit means has the form of at least one bore provided in the hammer in line with its axis, this bore communicating with the tubular control valve extending through the forward stroke chamber and having in its wall at least one hole wherethrough the return stroke chamber communicates alternately with the forward stroke chamber and with the outside.

Such a construction of the percussive action machine make it possible to extend its service life by virtue of the absence in parts subjected to impact loads of elements susceptible to stress concentrations, such as transverse holes and sudden variations in the configuration of the hammer. This also enables to substantially increase the impact power developed by the hammer (and consequently make the machine more efficient) through elongating the stroke of the hammer, since during the travel of the hammer toward the reduction in the volume of the return stroke chamber the latter continuously communicates with the outside through the conduit means in the hammer and air-distributor, whereby no counterpressure exerting a braking effect on the hammer is produced.

Preferably the sleeve has a projecting tubular portion the wall of which is provided with holes, whereas a free end thereof is received by the bore of the hammer and it has slidably arranged thereon the tubular control valve of the air-distributor so that in its extreme position it acts to alternately close the holes of the tubular portion of the sleeve wherethrough the return stroke chamber communicates alternately with the forward stroke chamber and with the outside.

This arrangement enables to prevent the action of the forces of friction on the tubular control valve caused by the hammer, these forces of friction otherwise tending to displace the tubular control valve from a position which it assumes thanks to the action of the locking means of the hammer.

Therefore, the machine operates more reliably (thanks to a more stable working cycle), which is especially important for percussive action machines with elongated hammer strokes.

Advisably, the tubular control valve is provided with a spring means ensuring its compression to the sleeve subsequent to the acceleration of the hammer during its return stroke.

This arrangement renders the machine more fail-safe through a reliable fixation of the tubular control valve in its extreme position (when the return stroke chamber communicates with the outside through the conduit means and airdistributor) by the spring means, thus preventing accidental displacements of the control valve relative to the sleeve under the action of impact and vibration loads exerted on the housing of the machine, and makes the machine shorter in length through minimizing the travel of the tubular control valve relative to the sleeve. Such an arrangement is especially advantageous for machines in which the deceleration travel of the hammer is comparable with the travel length of its acceleration during the return stroke.

Alternatively, the tubular control valve has the form of two relatively movable and coaxially cooperating tubes, the wall of at least one of these tubes having holes closable by the other tube, through which holes the return stroke chamber alternately communicates with the forward stroke chamber and with the outside.

Such an arrangement of the tubular control valve provides a more economical cycle in which a more efficient use can be made of the power of the compressed air source (compressor unit) thanks to utilizing the energy of compressed airfor producing a useful work; this arrangement being especially preferable in machines of a relatively large (over 200 mm) outer diameter.

Advisably, the tubular control valve has the form of two parallel tubes, the walls of each of these tubes having at least one hole so that in its extreme positions the sleeve closes the hole of one of the tubes wherethrough the return stroke chamber communicates with the forward stroke chamber and the hole of the other tube wherethrough the return stroke chamber communicates with the outside.

Owing to the fact that each of the parallel tubes has only one mounting surface (viz., outer surface), less stringent tolerances are required during the manufacture of mating parts.

The invention will now be described in greater detail with reference to various preferred embodiments thereof taken in conjunction with the accompanying drawings, in which: Fig. lisa longitudinal sectional view of a percussive action machine for making holes in the ground showing a hammer during its return stroke; Fig. 2 is a longitudinal sectional view of the percussive action machine showing the hammer at the point of delivering an impact; Fig. 3 is a sectional view of the percussive action machine during its reverse percussive action;; Fig. 4 is a longitudinal schematic sectional view of an alternative embodiment of the proposed percussive action machine in which the sleeve of an air-distributor has a projecting tubular portion a free end of which is received buy a bore of the hammer and it has mounted thereon a tubular control valve of the air-distributor; Fig. 5 is a longitudinal sectional view of an alternative embodiment of the percussive action machine according to the invention in which the tubular control valve is provided with a spring means, the hammer being shown while terminating its forward stroke; Fig. 6 is a schematic illustration of yet another embodiment of the proposed percussive action machine in which the tubular control valve of the air-distributor has a blind end;; Fig. 7 is a longitudinal sectional view of one more alternative embodiment of the percussive action machine in which the tubular control valve has the form of a two parallel tubes, the hammer being shown while terminating its return stroke; Fig. 8 is a longitudinal sectional view of the preferred embodiment of the percussive action machine in which the tubular control valve has the form of two parallel tubes, the hammer being shown while terminating its forward stroke; and Fig. 9 is a longitudinal sectional view of yet another preferred embodiment of the percussive action machine in which the tubular control valve has the form of two coaxial tubes, the hammer being shownwhileterminating its forward stroke.

A percussive action machine for mating holes in the ground (Fig. 1) comprises a cylindrical housing 1, a hammer 2, and an air-distributor3 communicating with an air-feeding line 4. The hammer 2 and the air-distributor 3 divide the interior of the housing 1 into three chambers, particularly a return stroke chamber 5, a forward stroke chamber 6 occupying a space between an end face 7 of the hammer 2 and an end face 8 of the air-distributor3, and a discharge chamber 9 continuously communicating with the outside through a passage 10.

The distributor 3 includes a sleeve 11 engaged by a thread 12 in a nut 13 (Fig. 1) secured in the housing 1 through a resilient element 14 (to compensate for manufacturing inaccuracies of the mating elements), this resilient element 14 having an inlet hole 15 communicable with the air-feeding line 4 and a discharge hole 16 one end of which terminates in a recess made in the sleeve 11, whereas the other end communicates with the outside, and a tubular control valve 18 extending through the forward stroke chamber 6 and serving to open and close the hole 16 during its travel relative to the sleeve 11.

The aforedescribed embodiment of the percussive action machine according to the invention in which thanks to the arrangement of the return stroke chamber 5 outside of the hammer 2 the latter has a substantially uniform configuration, whereas air conduit means are fashioned as passages extending in parallel with the longitudinal centerline of the hammer (impact pulse action line), makes it possible to increase the service life of the machine by virtue of obviating stress concentrations in the parts thereof acted upon by impact loads.

With reference to Fig. 4, another modification of the percussive action machine according to the invention includes a sleeve 22 serving the same purpose as the sleeve 11 in the embodiment represented in Fig. 1. This sleeve 22 has an annular slot 23 in which the control valve 18 is received and a projecting tubular portion 24 the free end of which is disposed inside a bore 20 of the hammer 2; its wall having a hole 25 which, upon registration with a hole 21 of the tubular control valve 18, communicates with the forward stroke chamber 6, as well as a hole 26 which communicates through the discharge passage 16 with the outside upon registration with the hole 21 of the tubular control valve 18.Therewith, the tubular control valve 18 is not subjected to friction forces from the hammer 2, and therefore it is necessary that the forces of friction acting on the tubular control valve 18 from the tubular portion 24 of the sleeve 22 could overcome or be greater than the weight force of the valve 18 (this being a prerequisite for reliable operation of the proposed machine when drilling substantially vertical holes).

In an alternative modification of the percussive action machine according to the invention represented in Fig. 5 the tubular control valve 18 is provided with a spring means 27 to force the valve 18 toward the sleeve 11 subsequent to acceleration of the hammer 2 (viz., travel art a distance L1) during the return stroke and during part of the travel of the hammer 2 in the forward stroke. The length of travel of the tubular control valve 18 between its extreme positions with such an arrangement of the machine is minimal to depend only on the size of its hole 21 (as seen best in Fig. 5, the length L2 of travel of the tubular control valve 18 approximates the length of the hole 21 of the tubular control valve 18 as measured along the longitudinal centerline of the machine).

By virture of the fact that fixing the tubular control valve 18 in one of its extreme positions is ensured by the spring means 27 rather than the force of friction, it is possible to considerably reduce the forces of friction between the tubular control valve 18 and sleeve 11 and thereby reduce friction heat release to result in a longer life and trouble-free operation of the machine.

According to the embodiment of the percussive action machine illustrated in Fig. 6, the tubular control valve has the form of a blind-end tube 28, the control valve and the sleeve 11 being of substantially shorter axial length, since at the extreme position of the tubular control valve 18 corresponding to the termination of the forward stroke of the hammer it is not required that the wall of the tubular control valve 18 should close the recess 17 in the sleeve 11, as is indispensable in the modification of the percussive action machine with reference to Fig. 1.

Referring now to Fig. 7, there is shown an alternative embodiment of the percussive action machine according to the invention in the housing 1 of which there is rigidly secured a sleeve 29 intended for a purpose essentially similar two the sleeve 11 of the modification illustrated in Fig. 1. The control valve 18 has the form of two parallel movably arranged tubes 30 and 31. Each of these tubes is controlled by its own means for locking in the hammer 2; the tube 3Oby the inner shoulders of a recess 32, and the tube 31-by the inner shoulders of a recess 33.

The bore in the hammer 2 has the form of parallel passages 34 and 35 communicable with the return stroke chamber 5. The locking means are fashioned so that the travel length of the tube 30 in the hammer 2 is shorter than the travel length of the tube 31 in the hammer 2 by a value L4. Hole 36 are provided in the wall of the tube 30, the wall of the tube 31 being provided with hole 37.

The end of the tube 30 on which the hole 36 is provided is received by a hole 38 of the sleeve 29, whereas the end of the tube 41 with a hole 37 is disposed in a hole 39 of the sleeve 29.

Thanks to such a construction, the tubular control valve 18 can assume throughout the length L4 of the reverse stroke of the hammer 2 an intermediate position (viz., one when the hole 36 is already closed, while the hole 37 is not yet open) at which the reverse stroke chamber 5 is isolated from the forward stroke chamber 6 and from the outside, whereby the hammer 2 tends to accelerate in the travel length L4 thanks to the energy produced by expansion of compressed air occupying the return stroke chamber 5.

Such an arrangement of the proposed percussive action machine ensures a more economical working cycle during which useful work is done both by the energy of compressed air expended for the prolonged inlet to the reverse stroke chamber 5 (the distance L3 of the hammer stroke as seen best in Fig.

8) and the energy of expansion of compressed air in the return stroke chamber 5 to result in that the power of the compressed air source is utilized to its full potential.

Fig. 9 is an illustration of another preferred embodiment of the percussive action machine according to the invention. The housing 1 of the machine has rigidly affixed thereto the sleeve 29 serving the same purpose as the sleeve 11 in the embodiment represented in Fig. 1. A hole 39 of the sleeve 29 receives an end of the tubular control valve 18 having the form of two coaxial tubes 40 and 41. The tube 40 received by the hole 39 is provided with a hole 42 communicating with the discharge passage 16, and a hole 43 wherethrough the return stroke chamber 5 communicutes with the forward stroke chamber 6. Each of these tubes is controlled by its own means for locking in the hammer 2, particularly, the tube 40 has inner shoulders of a recess 49 for this purpose, while the tube 41 has shoulders of a recess 45.These locking means are arranged so that the length L6 of travel of the tube 41 in the hammer 2 is shorterthan the length L6 of travel of the tube 40 by a value L7. The tube 41 is adapted to open and close the hole 43 of the tube 40.

The percussive action machine for drilling holes in the ground according to the present invention operates in the following manner (Fig. 1).

Compressed air is fed through the inlet hole 15 to the forward stroke chamber 6 for the hammer 2 to start its travel forward, while the return stroke chamber 5 continuously communicates with the outside through the bore 20, tubular control valve 18 (held in place by the forces of friction from the sleeve 11 during the forward stroke of the hammer), the hole 21, recess 17 and discharge passage 16. At the end of the forward stroke the hammer2 acts to move by the inner shoulder of the recess 19 the tubular control valve 18 forward (Fig. 2) and deliver an impact on the housing 1 thereby driving it into the ground. In the forward position of the tubular control valve 18 the compressed air flows from the forward stroke chamber 6 through the hole 21 and bore 20 to the reverse stroke chamber 5, whereby the hammer starts its backward motion.For a length of its backward stroke the hammer 2 moves at a uniform acceleration rate, the tubular control valve resting in place. Thereafter, the hammer 2 acts to shift by the inner shoulder of the recess the control valve 18 to the rear position, whereby the hole 21 registers with the recess 17forthe airto escape from the return stroke chamber 5. This initiates a uniformly decelerated travel backwards of the hammer 2 together with the control valve 18 thanks to the kinetic energy acquired thereby at the portion of the stroke terminated by the complete stop of the hammer and the control valve 18 in the rearmost position (Fig. 1).

In order to reverse the percussive action of the proposed machine, it is necessary to axially displace the sleeve 11 (Fig. 3). The percussive action reversal means is fashioned in this particular case a threadingly engageable pair including the sleeve 11 and nut 13. By imparting rotation to the sleeve 11 it is possible to set it to the frontmost or rearmost positions corresponding to the forward or backward percussive action of the machine, respectively.

Compressed air is admitted to the return stroke chamber 5 earlier during the backward percussive action of the machine than during the forward percussive action for the hammer 2 to be stopped by the compressed air occupying this chamber short of delivering an impact on the housing. Conversely, escape of the air occurs with a delay, and therefore during its reverse stroke the hammer 2 strikes on the housing 1. Under the action of such strikes the machine moves backwards along the hole already made.

For machines in which the deceleration travel of the hammer in its reverse stroke is comparable with the length L1 of its travel for acceleration, a more preferable embodiment is one represented in Fig. 5.

This modification of the percussive action machine operates in a similar manner during the forward stroke of the hammer and during the length L, of acceleration thereof for the return stroke.

Subsequent to the hammer 2 travelling through the length L1 during the return stroke, it acts to move the tubular control valve 18 the distance L2to its extreme position by the inner shoulder of the recess 19 through the spring means 27, whereby the hole 21 registers and communicates with the recess 17 for the air to escape from the return stroke chamber 5. The hammer 2 then decelerates and the control valve 18 is immobile, whereas the spring means 27 is compressed to lock the control valve 18 in its extreme position.

The tubular control valve 18 is maintained in the thus locked state by the force of compression of the spring means 27 during the forward stroke of the hammer 2 at a portion of its accelerated travel equal in length to the length of decelerated travel of the hammer during its return stroke.

For percussive action machines consuming the amount of air for their operation comparable with the rate of compressed air production fed by a compressed air source it is advisable to make use of the modification with reference to Figs. 7 and 9.

The embodiment of the percussive action machine shown in Fig. 7 operates as follows.

Compressed air is admitted through the inlet passage 15 to the forward stroke chamber 6. The hammer 2 responds moving forward; the return stroke chamber 5 continuously communicating through the bore 20, tube 31 (remaining immobile during the travel of the hammer), hole 37 and discharge passage 16 with the outside.

At the end of the forward stroke the hammer 2 acts to displace the tube 30 by the inner shoulders of the recesses 32 and 33 forward and delivers an impact on the housing 1 forthe machine to be driven into the ground. In the forward position of the tubes 30 and 31 the hole 37 of the tube 31 is closed by the walls of the bore 39, whereas the hole 36 of the tube 30 opens for the compressed air to flow therethrough and through the interior of the tube 30 and passage 35 of the hammer 2 to the return stroke chamber 5. Because the surface area of the hammer 2 on the side of the return stroke chamber 5 is greater than its surface area on the side of the forward stroke chamber 6, the hammer 2 starts its backward travel. The initial portion or length L3 (Fig.

8) of the return stroke travel of the hammer 2 is accompanied by continuous inlet of compressed air to the return stroke chamber at a pressure substantially equalling the feed-line pressure, whereas the subsequent length L4 (Fig. 8) is travelled due to the expansion of the compressed air occupying the reverse stroke chamber 5. At the end of its return stroke the hammer 2 moves the tubes 40 and 41 backward for the return stroke chamber 5 to communicate with the outside through the hole 37, whereby air escapes from the return stroke chamber 5 and the forward stroke of the hammer 2 is initiated.

In the modification of the above construction compressed air is admitted to the reverse stroke chamber 5 through the tube 30 and discharged through the tube 31. This ensures that throughout the length of the forward stroke of the hammer 2 the return stroke chamber 5 communicates with the atmosphere (viz., via the tube 31), whereas the return stroke of the hammer 2 can be viewed as having three stages: initial-accompanied by a continuous admission of compressed air to the return stroke chamberS; intermediate-- accompanied by adiabatic expansion of compressed air in the return stroke chamber 5; and final-when the return stroke chamber 5 communicates with the outside.

Such an arrangement of the percussive action machine makes it possible to admit compressed air to the return stroke chamber 5 and discharge it therefrom via different tubes capable of independent movement. During the forward stroke of the hammer no counterpressure is produced to exert a braking action on the hammer and the return stroke is more economical, that is the compressor power is used more efficiently. As a result, at the same power consumed by the compressor, other conditions being equal, this embodiment is advantageous in that energy losses associated with the need for the hammer to overcome a counterpressure in the return stroke chamber 5 are prevented and in that the kinetic energy of compressed air is used more effectively, whereby the percussive action machine of this modification is more economical in operation and features a greater impact power.

The modification of the percussive action machine illustrated in Fig. 9 operates in the following manner.

Compressed air is admitted through the inlet passage 15 to the forward stroke chamber 6 wherefrom it is conveyed through the hole 43, interior of the tubes 40 and 41 and bore 20 to the return stroke chamber 5. Because the surface area of the hammer 2 on the side of the chamber 5 is greater then the surface area thereof on the side of the chamberS, the hammer 2 starts its travel backwards. The first portion or length L5 of the return stroke of the hammer is accompanied by continuous admission of compressed air to the return stroke chamber 5 under a pressure substantially equal to the pressure in the air-feeding line.

Subsequent to travelling through the length L the hammer 2 acts to displace the tube 41 by the inner shoulders of the recess 45 relative to the tube 40, the latter closing the hole 43 and separating the return stroke chamber 5 from the forward stroke chamber 6. During a subsequent travel of the hammer 2 (a length of its stroke equal to the length L7) the tube 41 is displaced together with the hammer 2 relative to the tube 40 which remains immobile, the movement of the hammer occurring thanks to the energy of expansion of compressed air admitted to the return stroke chamber 5 at the length L5 of travel of the hammer 2.After the hammer 2 travels through the length L6 (from the start of its return stroke), it acts to move the tube 40 rearwards by the inner shoulders of its recess 44 until the hole 42 registers with the recess 17 of the discharge passage 16. Therewith, the return stroke chamber 5 communicates with the outside through the bore 20, interiors of the tubes 40 and 41, hole 42 and discharge passage 16. Air is discharged from the return stroke chamber 5 and the forward stroke of the hammer 2 is initiated during which the return stroke chamber 5 continuously communicates with the outside through the bore 20, tubes 40 and 41, bore 2, recess 17 and discharge passage 16.

At the end of the forward stroke the hammer 2 acts to simultaneously move the tubes 40 and 41 by the inner shoulders of the recesses 44 and 45 so that the hole 42 becomes closed by the walls of the bore 39 of the sleeve 29, while the hole 43 opens, whereby the hammer 2 delivers an impact on the housing 1 to drive it into the ground. The aforedescribed cycle is thereafter recommenced.

As compared with the prior art constructions, the propsed percussive action machine for driving holes in the ground ensures a reduction in stresses exerted on the elements of the machine by impact loads, as well as prevents the development of a counterpressure in the return stroke chamber imparting a braking action on the hammer during its forward stroke.

These advantages makethe machine lOto 15% more reliable in operation and provide an infinite increase (within the limits of one outer diameter of the machine) in the impact power through a more extensive hammer stroke.

Claims (6)

1. A percussive action machine for making holes in the ground comprising a cylindrical housing accommodating a reciprocating hammer provided with an air-distributor in the form of a sleeve having holes therein, the sleeve being secured in the housing and having a tubular control valve movably arranged relative to the sleeve, the hammer forming inside the housing a forward stroke chamber continuously.communicating with an air-feeding line, and a return stroke chamber defined between the ends of the sleeve and hammer and alternately communicating with the forward stroke chamber and with the outside through a conduit means in the hammer in the form of at least one bore arranged in the hammer in line with its axis, the tubular control valve communicating with this bore to pass through the forward stroke chamber and having in its wall at least one hole wherethrough the return stroke chamber communicates alternately with the forward stroke chamber and with the outside.

2. A percussive action machine as claimed in claim 1 in which the sleeve has a projecting tubular portion the wall of which is provided with holes, a free end thereof being received by the bore of the hammer, the tubular control valve of the airdistributor being slidably arranged thereon so that in its extreme positions it acts to alternately close the holes in the tubular portion of the sleeve wherethrough the return stroke chamber alternately communicates with the forward stroke chamber and with the outside.

3. A percussive action machine as claimed in claim 1 in which the tubular control valve is provided with a spring means ensuring its compression to the sleeve subsequent to the acceleration of the hammer during its reverse stroke.

4. A percussive action machine as defined in any of the claims 1 to 3 in which the tubular control valve has the form of two parallel tubes with the walls of each of these tubes having at least one hole so that in its extreme positions the sleeve alternately closes the hole of one of the tubes wherethrough the return stroke chamber communicates with the forward stroke chamber and the hole of the other of these tubes wherethrough the return stroke chamber communicates with the outside.

5. A percussive action machine as claimed in any of the claims 1 to 3 in which said tubular control valve has the form of two coaxially cooperating tubes capable of movement relative to each other, the wall of at least one of these tubes having holes closable by the other of these tubes wherethrough the return stroke chamber alternately communicates with the forward stroke chamber and with the outside.

6. A percussive action machine as claimed in any of the preceding claims substantially as described in the description and represented in the drawings.