CA1234021A - Air-operated reversible percussive action machine - Google Patents

Abstract

AIR-OPERATED REVERSIBLE PERCUSSIVE ACTION MACHINE
Abstract An air-operated reversible action percussive machine comprises a housing in which there is disposed for recipro-cations a hammer, defining therewith a front working chamber and having a through radial passage. In the axial interior of the hammer on the side of its tail end there is provided a substantially cylindrical tube of stepped configuration which includes first and second steps of large and small diameters, respectively, these steps having radial passa-ges. The first step of the tube defines with the hammer a rear working chamber, and with the second step defines an annular cavity in which a spring-loaded sleeve capable of axial displacements is disposed. The outer diameter of the sleeve is substantially less than the inner diameter of the first step of the tube to form therebetween an annular passage. The machine is further provided with a means for pressure sealing the above annular cavity, and also a means for controlling the displacements of the sleeve.

Description

lZ3~)21 This invention relates generally to civil engineering and road construction machinery~ and more particularly to air-operated reversible percussive action machines.
The invention can find most advantageous application in machines for making holes in the ground, or in machine~
for driving into the ground steel tubes used as casings for underground communications.
Other possible applications of the proposed air-opera-ted reversible percussive action machine include driving tubular piles into the ground, deep-hole 90il compacting, and forcing small piles directly in the ground.
Wide use have found lately air-operated reversible percussive action machines, the provision for reversal being necessary for retracting the machine from holes or for disconnecting the machine from a tube subsequent to driving it into the ground.
An ever increasing application of air-operated rever-sible percussive action machines calls for improvements in terms of their reliability. During driving horizontal holes in length over 15-20 meters, or during driving vertical holes (such as for deep-hole soil compacting, pressing con-crete piles in the ground, etc.) when retracting the machi-ne from holes is complicated, the mechanism for reversing the percussive action must be especially reliable.
Of no less importance is to simplify the device struc-turally to improve its reliability, make it less complicat-~ 2 --~ 2 ~
ed and les~ expensive in fabrication, as well as to ensurea more prompt switchover of the machine to a rearward per-cussive action.
There is known a device (cf., West Gerr~n Patent No. 1,634,417) which includes a substantially hollow cylin-drical housingt a hammer accommodated inside the housing for axial reciprocations and delivering impacts on the housing by its front or rear portion, and a stepped tube threadingly connected to the housing through a flange ele-ment.
In order to reverse the percussive action of such a device, it is necessary to displace the stepped tube to a new position toward the tail end of the housing by rotating an air supply hose fi~edly attached to the stepped tube.
Inherent in the above device is its in~ufficient reli-ability due to that reversal is complicated or even impos-sible when driving vertical or elongated horizontal holes.
Also, the reversal of the percussive action of the above device requires a number of time-consuming operations affecting its efficiency, these operations including termi-nation of the supply of compressed air, disconnection of the air hose from the compression, and pulling the hose prior to rotating it.
There is also known another percussive action machine (cf., West German Patent No, 2,340,751) vvhich comprises a hollow cylindrical housing, a hammer reciprocating inside the housing and intended to deliver impacts on the housing lZ340~1 by its front or rear portion, and a tube of stepped confi-guration rigidly secured in grooves of the tail end of the housing through a locking means and connected to the hammer.
~ or reversing the percussive action of the aforementi-oned machine use is made, apart from a hose, of a fle~ible steel cable. By pulling the cable the action of the locking means i9 eliminated, and the stepped tube is moved to a new position, that is reversal is made possible by a simple li-near motion of the stepped tube instead of the rotational movement.
However, the hose must also be turned to bring the ætepped tube out of engagement with the grooves and put it in registration with other grooves in its rearmost position.
In consequence, the device described in West German Patent No. 2,340,751 suffers from essentially the same disadvanta-ges as those described here~ofore.
~ here is further known a percussive action machine (cf., We~t German Patent ~o. 2,105,229) which differs from the aforedescribed ones only by the construction of the stepped tube, the latter including an outer step having through radial passages and an inner step with similar through radial passages, the tube being secured coaxially with the housing to be capable of turning and displacing axially relative to the outer step.
A switchover to the reverse percussive action is done here by turning the inner step of the tube relative to the outer step by a multiple supply of compressed air to the machine )21 This device offers some sdvantage over those already described in that there is no need for rotating the hose.
However, the mschine is disadvantageous in that the multiple delivery of compressed air may bring some uncer-tai~ty as to whether the operator is aware of the machine function subsequent to every succesqive delivery of compres-sed air, or whether the machine will operate at all, since intermediate positions are possible apart from the forward and rearward percussive actions. Another disadvantage resi-des in that the machine is structurally overcomplicated and therefore difficult to manufacture.
A device which bears the closest resemblance to one to be proposed in the description that will follow is an air-operated reversible percussive action machine as taught in ~est German Patent No. 2,722,298. This machine comprises a housing, a hammer axially reciprocable inside the houqing and having in its tail portion an axial cavity open on one end and a through radial passage. The hammer defines with the housing a front working chamber. A stepped tube also accommodated inside the housing includes substantially cy-lindrical steps of large and small diameters with radial passages provided therein.
The large diameter step is disposed in said axial ca-vity of the hammer to define a rear working chamber, where-as the step of small diameter is secured by a flange in the tail portion of the housing. Installed with precision inside the stepped tube is a spring-loaded sleeve. An air 1~3~)2~

supply hose functions as a means for controlling the a~ial displacement of the spring-loaded sleeve. The forward per-cussive action of the machine is initiated when the ~leeve sssumes the frontmoRt position; reversal being accomplished by moving the sleeve to the extreme rear position.
In general, this device obviates the disadvantages inherent in theheret~fo~e described constructions of the prior art percussive action machines, since reversal i8 achieved by merely applyi~g tension to the hose, and the elements of the machine are at any time in a position to execute either the forward or the rearward actions.
~ Iowever, even this device is not without some draw-backs. For exa~.ple, the sliding action and pressure-sealing of the sleeve on the two of its cylindrical surfaces calls for precision fabrication of the ~ating surfaces due to which the machine is rather difficult to manufacture. It also lacks reliability because sliding of the sleeve along its two cylindrical surfaces may result in jamming, espe-cially when dirt adheres to such surfaces.
Also, the machine has a pressure-sealed interior con-sisting of three isolated sections defined by the spring-loaded sleeve and the stepped tube. This interior is made hermetic likewise due to the precision of the sliding sur-faces.
It is an object of this invention to improve the reli-ability of reversing the percussivé action of the machine.
Another object is to provide an air-operated revers-ible percussive action machine which would be easier to 1~3~

manufacture.
One more object of the invention is to structurallysimplify the machine.
These and other objects and attending advantages are attained by that in an air-operated reversible percussive action machine compri~ing a housing, a hammer disposed for reciprocations inside the housing and having in its tail portion an a~ial cavity open on the end thereof, and a through radial passage to define with the housing a front working chamber, a cylindrical tube of stepped configura-tion which includes first and second cylindrical steps of large and 3mall diameters, respectively, having through ra-dial passages, the first step of the tube being arranged in the cavity of the hammer to form a rear working chamber, the second step of the tube being rigidly attached in the tail end of the housing by means of a flange J a spring-loaded sleeve in9talled inæide the stepped tube for a~ial displacements therein and provided with a means for control-ling ~uch displacements, this sleeve forming with the tube an annular cavity, and g means for pressure-sealing this cavity, characterized in that the first and second steps of the tube are arranged coaxially, the spring-loadeldsleeve being disposed on the second step of the tube inside its first ætep, the outer diameter of this sleeve being sub-stsntially less than the inner diameter of the first step of the tube to define an annular passage therebetween.
The proposed construction of the machine obviates 4a~21 sliding of the sleeve on the fir~t cylindrical step of the tube, which prevents it~ jamming during displacement. Such a construction does not call for precision during finishing the outer surface of the sleeve and the surface of the first step of large diameter embracing the sleeve.
~ his in turn considerably simplifies the ~achine struc-turally and makes it easier to fabricate. The provision of the annular passsge between the sleeve and the first step of the tube prevents jamming of the sleeve during its dis-placements, which improves the overall reliability of the machine.
Other objects and attending advantages will become more fully apparent from a more detailed description of va-rious preferred embodiments there that follows taken in conjunction with the accompanying drawings, in which:
~ ig. 1 is a longitudinal sectional view of an air-ope-rated reversible percussive action machine according to the invention in which the mutual position of the elements thereof corre~ponds to a forward percussive action of the machine;
Fig. 2 shows position of the elements for a reverse action of the machine according to the invention; and Fig. 3 is a longitudinal sectional view of an alterna-tive embodiment of the proposed machine.
An air-operated reverslble percussive action machine comprises a housing 1 and a hammer 2 accommodated for reci-procations inside the housing 1. In its tail end the hammer 12;34~)Zl

2 has an axial cavity and a through passage 3. The hammer 2 defines with the housing 1 a front working chamber 4, ~ he housing 1 also accon~odates a substantially cylin-drical tube 5 of stepped configuration having two cylindri-cal steps 6 and 7 of large and small diameter, respective-ly; these steps being arranged coaxially one relative to the other. The tube 5 i~ rigidly secured on the tail por-tion of the housing 1 by means of a flange 8 af~i~ed to the step 7. The step 6 has a through radial passage 9, whereas the step 7 has a through radial passage 10 and an axial passage 11. The step 6 is disposed inside the a~ial cavity of the hammer 2 to define therewith a rear working chamber 12. Disposed between the steps 6 and 7 of the tube 5 is an annular cavity 13 in which on the step 7 there is arranged for a~ial reciprocations a cylindrical sleeve 14 having an outer diameter substantially less than the inner diameter of the step 6 for preventing contact between the sleeve 14 and the inner cylindrical surface of the step 6.
Interposed between the sleeve 14 and the step 6 i8 an annu-lar passage 15. ~ounted on the step 7 of the tube 5 is a spring 16 one end of which bears on the flange 8 and the other end on the end face of the sleeve 14. A means for pressure - sealing the cavity 13 is provided in the form of an elastic sealing element 17 arranged on the end face of the sleeve 14, and a seat 18 in the inner portion of tke step 6. The displacements of the sleeve 14 is controlled by a steel cable 19 (Figs. 1 and 2), or by a tube 20 (Fig.
_ 9 _

3) one end of which is connected to an air delivery hose 21, whereas the other end is connected to the sleeve 14 by means of a pin 22 secured in the passage 10 and capable of a~ial displacement relative to the step 7.
Provided between the flange 8 and the hammer 2 in the housing 1 is an interior 23 communicable via holes 24 made in the flange 8 with the atmosphere.
The proposed machine operates in the following manner.
(a) The forward percussive action of the machine.
Normal position of the sleeve 14, that is extreme re-lative to the head end of the device, is maintained by the spring 16 (Fig. 1). This position of the sleeve 14 corres-ponds to the forward percussive action of the machine. The initial position of the hammer in the housing 1 ma~ be ar-bitrary. The cable 19 is free of tension. Prior to opera-tion the machine is connected to a compressor (not shown~.
By using the hose 21, the machine is orientated in a re-quired direction and pressed against the soil to be driven into by the forward, somewhat sharpened, portion by using a special starting device or by ~ simple lever.
Thereafter, the compressor outlet valve is opened for the compressed air to flow along the hose 21, and a~ial passage 11 of the tube 5 to the rear working chamber 12.
The compressed air acts to shift the hammer 2 until it stops against the end face of the head portion of the hous-ing 1 and open the radial passage 3 of the hammer 2 as shown in Fig. 1. The compressed air then enters the front 1~34{);~1 working chamber 4. Because the working surface area of the hammer 2 on the ~ide of the chamber 4 is greater than on the side of the chamber 12, then at equal pressures in these two chambers 4 and 12 a force applied to the hammer 2 on the side of the chamber 4 is greater than the force act-ing on the side of the chamber 12. Under the action of the resultant force the hammer 2 is caused to move toward the flange 8 (to the right - hand side as shown in Fig. 1).
Subsequent to blocking the radial passage 3 by the cy-lindrical step 6, that is after terminating the delivery of compressed air to the chamber 4, the hammer 2 continues its travel under the action of the pressure o~ expanding air in the chamber 4. Upon registration of the radial pPssage 3 of the hammer 2 with the radial passage 9 of the step 6, the air is conveyed from the chamber 4 through the passages 3 and 9 to the cavity 13, and thereafter to the interior 23 to escape through the holes 24 of the flange 8 to the atmosphere.
Because there is no preæsure in the chamber 4, while the chamber 12 is Gontinuously exposed to the pressure of compressed air, the hammer 2 travels toward the head end of the housing 1 (to the left-hand side as shown in Fig.1) to deliver an impact on its inner end face.
At the moment of the impact the chamber 4 is filled with compressed air in the manner described heretofore, and the cycle is recommenced.
~ he action of impacts on the housing 1 makes the ma-chine to penetrate the ground (when making a hole), or todrive into the ground a steel pipe for which purpose the machine is connected coa~ially to this pipe.
(b) The rearward action of the machine.
~ uch a reversal is normally needed to return the ma-chine from the hole previously made thereby.
In order to switch the machine over to a rearward per~
cussive action, it i9 necessary, without terminating the supply of compressed air, to apply a tension force to the cable 19 (Figs.-1 and 2) and, by overcoming the compression force of the spring 16, to move the sleeve 14 to its rear-most position; in other words, to move it from the position shown in Fig. 1 to the position illustrated in Fig. 2.
In this latter position the elastic sealing element 17 is brought into intimate contact with the seat 18 to thereby pressure-seal the annular cavity 13. This causes the radial passage 10 of the cylindrical step 7 to open and change the functions of the radial passage 9 of the step 6 and ~nnular cavity 13; particularly, they are dis-connected from the system of discharge passages to be brought into engagement with the system of passQges supply-ing compressed air to the working chamber 4.
In the mutual position of the elements of the propos-ed machine illustrated in Fig. 2 compressed from the com-pressor is conveyed along the hose 21 and a~ial passage 11 to the rear working chamber 12, and through the radial pas9age 10 to the annular cavity 13. The pressure of com-lZ34~);21 pressed air in the annular cavity 13 acts to press the~leeve 14 with the sealing element 17 against the seat 18 of the step 7 to be held in this position thus overcoming the compression force of the spring 16.
Under the action of the pressure of compressed air in the chamber 12 the hammer 2 initiates its travel toward the ends face of the head end of the housing 1. ~hen the radial passage 3 of the hammer 2 is brought in registration with the radial passage g of the step 6, compressed air is caus-ed to flow from the annular cavity 13 to the chamber 4.
This decelerates the movement of the hammer 2 and make~ it stop at a certain distance from the flange 8 of the housing 1. ' .
When the chamber 4 is filled with compressed air, the hammer 2 travels toward the flange 8 to deliver an impact thereon. At the moment of the impact compressed air is caused to flow from the chamber 4 through the radial pas-sage 3 of the hammer 2 to enter the interior 23, as seen best in ~ig. 2, and to thereafter escape to the atmosphere through the holes 24 of the flange 8.
Subsequent to delivering an impact on the flange 8, the hammer 2 is acted upon by the pressure of air in the ch~mber 12 to start its travel toward the head end of the housing 1 for the cycle to be reGommenced in the aforede~-cribed fashion.
~ eliable reversal of the percussive action of the pro-posed machine is ensured when the following conditions are iZ3402i complied with:
(1) P1 ~ Pr; (2) Pa ~ P2 + Pr' where P1 i~ the preliminary compression force of the spring 16;
P2 is the final compression force of the spring 16;
Pr is the force of resistance (friction) to the move-ment of the hose 21 during the forward percussive action of the machine (Fig. 3); and Pa is the force produced by the pressure of compress-ed air in the annular cavity 13 acting to force the sleeve 14 toward theseat 18.
A switchover of the action of the proposed machine to reverse may be done both prior to starting and during ope-ration in the forward percussive action mode without termi-nating the supply of compressed air to the machine.
During rearward percussive action of the machine the annular-cavity 13 is continuously under the pressure of compressed air, which guarantees continuous blocking of the annular cavity 13 by the sleeve 14 snd, consequently, a stable position of the sleeve 14 in engagement with the seat 18.
Opening of the annular cavity 13, i.e. communication with the atmosphere, is possible only when the supply of compressed air is terminated, which allows to displace the sleeve 14 to a position shown in Fig. 1 by means of the spring 16.

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An air-operated reversible percussive action machine comprising:
a housing;
a hammer disposed inside said housing to be capable of axial reciprocations;
said hammer having an axial cavity open on one end thereof, and a through radial passage;
a front working chamber defined by said housing and said hammer;
a cylindrical tube of stepped configuration including disposed coaxially a first step of large diameter and a second step of small diameter, these steps having through radial passages;
said first step of said tube being disposed in said axial cavity of said hammer;
a rear working chamber disposed between said first step of said tube and said hammer;
a flange arranged in the tail end of said housing and rigidly connected to said second step of said tube;
an annular cavity between said steps of said tube;
a spring-loaded cylindrical sleeve mounted on said se-cond step of said tube in said annular cavity and capable of axial reciprocations;
outer diameter of said sleeve being substantially less than the inner diameter of said first step of said tube;

an annular passage between said sleeve and said first step of the tube;
a means for pressure-sealing said annular cavity;
and a means for controlling the displacements of said sleeve.

2. An air-operated reversible percussive action machine comprising:
a housing;
a hammer accommodated inside said housing and capable of axial reciprocations, said hammer striking blows on a front inner end of said housing when opera-ting in a forward percussive action operational mode and striking blows on a tail inner end of said housing when operating in a rearward percussive action opera-tional mode, and said hammer having an axial cavity open on a first end facing said tail inner end of said housing and a through radial passage facing said tail inner end, said hammer defining with said housing a front working chamber near said front inner end of said housing;
a cylindrical tube coaxially accommodated in said housing near said hammer and having a stepped configura-tion wherein a first step has a larger diameter than a second step, said first step having a through radial passage and located within said axial cavity of said hammer in a manner forming a rear working chamber with said hammer and said second step having a through radial opening within said annular cavity and said radial open-ing being in an opened position when the machine is operat-ed in said rearward percussive action mode and being in a closed position when the machine is operated in said forward percussive action mode, said first and second steps of said cylindrical tube forming an annular cavity between them;

a means for pressure-sealing said annular cavity;
a means for controlling displacements of said spring-loaded cylindrical sleeve, said means having a traction member located outside the reversible percussive action machine; and a flange mounted on said second step of said cylindrical tube and connecting said cylindrical tube to said tail end in said housing.

3. An air-operated reversible percussive action machine according to claim 2, wherein said means for controlling said displacements of said spring-loaded sleeve comprises a tube disposed inside said second step of said cylindrical stepped tube; and a pin connecting said spring-loaded sleeve to said cylindrical stepped tube, said pin located in said through radial opening of said second step of said cylindrical tube and axially movable within the percussive action machine.