US3464500A

US3464500A - Percussion tool control means

Info

Publication number: US3464500A
Application number: US683578A
Authority: US
Inventors: Arthur W Wallace
Original assignee: Gardner Denver Inc
Current assignee: Gardner Denver Inc
Priority date: 1967-11-16
Filing date: 1967-11-16
Publication date: 1969-09-02
Anticipated expiration: 1986-09-02
Also published as: FR1572089A; JPS4839321B1

Description

Sept. 2, 1969 A. w. WALLACE PERCUSSION TOOL CONTROL MEANS 2 Sheets-Sheet 1 Filed NOV. 16, 1967 as 4 a4 so INVENTOR. ARTHUR M! WALLACE p 2, 1969 A. w. WALLACE 3,464,500

PERCUSSION TOOL CONTROL MEANS Filed Nov. 16, 1967 2 Sheets-Sheet 2 nits States ABSTRACT OF THE DISCLOSURE A motor control valve for percussion tools, such as rock drills, operable to idle or shut down the percussion motor when the tool shank is not in position to be struck by the reciprocating hammer of the motor. One embodiment consists of a pneumatic actuator for the motor control valve which receives a pressure signal via a hole cleaning tube which telescopically fits in the tool shank. When the tool shank moves out of hammer striking position the pressure signal, normally communicated through the hole cleaning tube, is interrupted thereby permitting the actuator to close the motor control valve to throttle the supply of motive air to the motor. Should the cleaning medium be liquid, a mechanical actuator is employed consisting of a hole cleaning tube having a motor valve element connected at one end and being connected to the tool shank for closing the motor valve when the shank moves out of hammer striking position.

Background of the invention Conventional pneumatic percussion tools such as rock drills commonly comprise a percussion motor having a cylinder and pneumatically reciprocated piston hammer disposed in the cylinder. A section of the working implement known as the shank is chucked in one end of the cylinder for limited axial movement and has one end designed to be struck by the piston hammer to transmit the percussive energy to the bit end of the working implement. Control of the motive fluid is usually accomplished by a manually operated throttle valve.

In applying the tool to the work, the shank is usually kept in striking position by continuously feeding the drill toward the work. However, often is the case when the feed rate is not suflicient to keep up with the drill penetration rate or a fault in the work material allows the shank to move forward out of piston hammer striking position. To prevent overtravel and impact of the piston hammer against the cylinder end Wall under the aforementioned circumstances, a protective pneumatic cushion chamber formed in the cylinder ahead of the piston hammer absorbs the kinetic energy of the hammer and serves as a rebound cushion to urge the hammer in the opposite direction.

One problem that results from utilizing the pneumatic cushion extensively is that the repeated compression of air trapped in the cushion chamber results in substantial temperature increase of the surrounding parts as they absorb the heat of compression from the trapped air. Also, a dangerous condition often results due to the presence of drill lubricating oil in the trapped air forming a combustible mixture susceptible to compression ignition. This unwanted combustion of the air-oil mixture in the hammer cushion is not only uncontrollable but almost invariably results in serious damage to the drill such as causing the hammer to seize in the cylinder, overheating and damage to other surrounding parts, and the creation of a hazardous condition to the drill operating personnel.

So rapidly does this phenomenon occur that a drill operating at or near full throttle will usually experience a heat-induced failure before the throttle can be closed atent Patented Sept. 2, 1969 even in the hands of a skilled operator. It is therefore particularly desirable to have automatic throttling control means immediately responsive to the shank being out of striking position to shut down or idle the drill percussion motor.

Another benefit of a control of the type described above is realized when pulling the drill steel from the hole. In the pulling operation the reverse feeding of the drill will also result in the shank moving out of hammer striking position. Automatic throttling of drill motive air will reduce total air consumption during that portio of the drilling cycle, and eliminate excessive vibration due to the reaction forces of the piston hammer cushion chamber as well as prevent the aforementioned overheating problem.

Summary of the invention The invention has as a principal object the provision of automatic control means for idling or shutting down a percussion tool of the type described in response to axial displacement of the tool shank from hammer striking position.

It is also an object of the invention to provide automatic means for idling the drill percussion motor during backing out or drill steel pulling operations.

A further object is the provision of automatic control means for idling or shutting down a drill percussion motor due to a failure of a cleaning fluid conduit seal or due to inadequate cleaning fluid pressure.

A still further object of the invention is the provision of automatic throttle control means to assure safe operation of the associated drill and prevent damage to the drill component parts resulting from compression ignition of the air-oil mixture comprising the percussion motor pneumatic cushion.

In one embodiment the throttling valve is actuated by a pneumatic piston responsive to the supply thereto of cleaning fluid through a double walled hole cleaning tube. The cleaning tube coacts with the shank to sense the position of said shank relative to the percussion hammer whereby cleaning fluid is supplied to the actuator.

An alternate embodiment utilizes the hole cleaning tube itself as a mechanical throttlin valve actuator. The drill steel shank frictionally engages the cleaning tube while the opposite end of the tube is attached directly to a throt tling valve located upstream of the percussion motor. Both the valve element and the cleaning tube moveably respond directly to changes in shank position.

The embodiments disclosed provide effective automatic control means which are simple and reliable in construction and operation.

The novel features as well as the objects and advantages of the invention will be well understood upon reading the following detailed description accompanied by the drawings, wherein like reference characters are used to designate similar parts.

Brief description of the drawings FIG. 1 is a longitudinal section of a typical independent rotation percussion rock drill assembly illustrating the preferred control components in position to admit motive air to the drill percussion motor.

FIG. 2 is a fragmentary longitudinal section of the assembly of FIG. 1 illustrating the drill steel shank out of striking position and the control conduit vented.

FIG. 3 is a fragmentary longitudinal section of the assembly of FIG. 1 with the control valve in a closed position in response to the condition of the shank as shown in FIG. 2.

FIG. 4 is a transverse section through the double walled cleaning fluid tube taken along the lines 4-4 of FIG. 2.

FIG. 5 is a transverse section taken along the lines '55 of FIG. 3 illustrating the control valve chest and various fluid passages therethrough.

FIG. 6 is a partial longitudinal section of a rock drill similar in many respects to the drill shown in FIG. 1 but illustrating a mechanically actuated version of the subject control means and is split along the axis 77 to show the two working positions of the control.

Description of the preferred embodiments Referring to FIGS. 1, 2 and 3 the illustrated drilling device is a percussion drill of the independent rotation type. In FIG. 1 the drill percussion motor is illustrated having a housing 10 with a cylinder bore 12 therethrough and a reciprocably disposed piston hammer 14. A distributing valve assembly 16 is operative to alternately supply motive air to

opposite sides

18 and 20 of the hammer 14 for a power stroke and return stroke, respectively. An exhaust port 22 in the cylinder housing 10 vents spent motive air to the atmosphere at the end of each hammer stroke. The hammer 14 has a stem 24 extending through a wear bushing 26 which in turn is housed in a cylinder sleeve 28. The hammer stem 24 also extends partially through a chuck driver 30 to the striking end 32 of the stem 24 which is shown in engagement with a cooperating striking surface 34 of a short section of drill steel known as the shank 36. The drill steel shank is retained for limited axial movement in a chuck 38 having internal splines 40 engaging complementary external splines 42 on the shank 36. The chuck 38 is rotatively drivable by the chuck driver 30 through mechanically engaging teeth, not shown, and the chuck 38 in turn rotates the shank 36. Drill steel rotation power is supplied by a pressure fluid motor and transmission generally designated by 44 through a drive shaft 46 to a second transmission of which the chuck 38 and driver 30 form a part, the driver 30 being supported on bearings 48 and also comprising a spur gear 50.

As previously mentioned, the shank 36 is mounted in the chuck 38 for limited axial movement so that percussive blows from the piston hammer 14 may be transmitted solely to the drill steel. The shank 36 is, however, retained in the drill by a cap 52 threadably attached to a chuck end housing 54 and is limited in its movement toward the piston hammer 14 by the splines 42 engaging a bushing 56 in the chuck driver 30. It will be noted that the splines 42 on the shank 36 and the stem 24 of the piston hammer are dimensioned such that the shank 36 may move longitudinally out of reach of the striking face 32 on the stem 24 before coming into contact with the cap 52. The hammer 14 is limited in its forward travel under the circumstances by a pneumatic cushion 58 formed by the cylinder bore 12 and the face 60. As the hammer 14 travels toward the face 60, the piston face 20 will close off supply ports for return stroke motive air, not shown. As the volume of the chamber 58 decreases a corresponding pressure increase will result, eventually reaching a value suflicient to halt the forward travel of the hammer 14 and return it toward the distributing valve 16 prior to commencement of another power stroke.

The shank 36 has a hollow interior 62 for conducting drill hole cleaning fluid such as compressed air or water through the drill steel to the hole for flushing drill cuttings during drilling operations. A slightly enlarged bore 64 in the shank 36 telescopically receives an elongated cleaning fluid tube member generally designated by 66 which eX- tends through the drill assembly to the rotation motor end housing 68 where it terminates with a tube head 70. The cleaning fluid tube 66 is retained in the drill assembly by a threaded nut 72 and packing 74. Cleaning fluid such as compressed air is introduced from a suitable source through a hose assembly 76.

Referring to the shank end of the cleaning fluid tube 66, a resilient sealing element 78 housed in the shank bore 64 sealingly engages the outer diameter of the tube 66 but is relatively slidable thereto and prevents leakage of cleaning fluid into the chuck end of the drill which is vented 4 through the chuck driver 30 at 80 and the chuck end hous ing 54 at 82.

The cleaning fluid tube 66 is of double walled construction having an interior passage 84 for the main flow of cleaning fluid, and an annular flow passage 86 formed by the inner tube 88 and outer tube 90. The annular flow passage 86 is sealed at the shank end by flaring the inner tube 88 tightly against the outer tube 90 by suitable means. The opposite end of the passage 86 is sealed by the tube head 70. Small radial ports 92 at the shank end of the tube 66 are located to allow cleaning fluid under pressure to communicate with the flow passage 86 (see FIG. 4) and to flow through the same toward the back end of the percussion motor housing 10 where ports 94 communicate with an actuator chamber 96 formed as part of a control valve chest 98, and a cover 100. As can be seen in FIG. 1 and FIG. 3 the control valve chest 98 is interposed between the motive air inlet port 102 and the percussion motor distributing valve 16. A valve spool 104 is connected to an actuator piston 106 reciprocably disposed in the chamber 96. A vent 108 keeps one side of the piston 106 at atmospheric pressure.

The position of the control valve spool 104 in FIG. 1 corresponds to normal operation of the percussion drill. In this condition the drill, mounted on a guide shell and feed assembly (not shown), would be fed toward the workface and the shank 36 would be maintained in blowreceiving relationship with the piston hammer 14. Cleaning fluid under pressure from the interior 84 of the tube 66 would also, by way of ports 92, flow through the annular passage 86 to the actuator chamber 96 causing the piston 106 to hold the valve spool 104 in the open position shown allowing full flow of motive air through the

passages

110 and 112 past the valve spool 104 and on to the distributing valve via

passages

114, 116 and 118 (see FIG. 5) to operate the percussion motor.

However, if the drill steel and shank 36 should strike a fault or voil in the drill workings or undergo a breakage of the drill steel, the shank 36 would be driven forward by the piston hammer 14 and remain out of striking relationship thus causing the cushion chamber 58 to absorb the kinetic energy of the piston hammer 14 during the power stroke by compressing the air trapped therein. This condition would also occur if the drill feed direction was reversed such as when pulling the drill steel out of the hole. Under normal power, the amount of energy imparted to the hammer is usually suflicient to cause extremely high compression ratios in the cushion chamber 58. The resulting temperature increase of the trapped air in the chamber 58 is often sufficient to cause ignition of the drill lubricating oil which is carried by the motive air.

The control valve operates to prevent this condition by substantially throttling the motive air supply to the distributing valve 16 in the following manner. As the shank 36 moves out of striking position the seal 78 slides along the tube 66 to the position shown in FIG. 2. In this position the compressed air cleaning fluid is cut off from the ports 92 and the actuator chamber 96 and annular flow passage 86 are vented to atmosphere through the hole 80 in the chuck driver 30 and the hole 82 in the chuck end housing 54.

A pressure surface on the valve spool 104, being somewhat irregular, allows motive fluid to act thereon to close the valve as shown in FIG. 3, thereby substantially throttling the supply of motive fluid to the percussion motor. Valve closing action is assisted by a coil spring 121 acting against the piston 106'.

A small amount of motive air can bypass the closed valve through the port 122 in the valve chest 98 thereby supplying the percussion motor with enough pressure fluid to idle the piston hammer 14 enough to vibrate the drill for pulling drill steel out of the drill hole but not imparting enough energy to result in high compression ratios in the cushion chamber 58. A suitable idling motive air flow rate is about percent of the full power flow rate.

Therefore, the control system described automatically responds to the shank 36 being out of hammer striking position and throttling of the drill under this condition is not dependent on the operation of the drill throttling valve, not shown, which usually is operable only by the drill operator.

As can be understood from the above description, the control valve would also close in the event of a failure of the tube seal '7 8, or insuflicient cleaning fluid pressure to keep the valve spool 184 in the open position. The resulting throttling down of the drill would signal the operator that one or both malfunctions had occurred.

FIG. 6 illustrates an alternate embodiment of the subject invention comprising a mechanical actuator in the form of a cleaning fluid tube 124 which is substantially frictionally retained by a tube sealing element 126 disposed in the bore 64 of the shank 36.

A valve disk 128 is aflixed to the opposite end of the tube 124 and telescopically receives a fixed section 130 of cleaning fluid tube in a bore 132 thereby forming a continuous closed conduit for communicating drill hole cleaning fluid to the shank 36. The fixed tube section 130 is retained in the end housing 68 in a manner similar to the embodiment of FIG. 1.

If the shank 36 moves out of blow receiving relationship with the piston hammer 14, as illustrated to the right of the axis 7-7 in FIG. 6, the tube 124 and valve disk 128 assembly will be pulled with the shank to the position shown. Additional biasing force to move the tube and valve disk assembly is provided by a coil spring 129 acting on the valve disk 128.

correspondingly, if the feed force on the drill steel is sufficient to move the shank 36 to the position shown to the left of the axis 77 in FIG. 6, the tube and valve disk assembly will be moved against the biasing force of the spring 129 due to the substantial frictional engagement of the tube 124 by the sealing element 126.

Should the sealing element 126 fail to provide suflicient gripping force on the tube 124 due to wear or other mal function the valve disk and tube assembly would still be operative since in moving to the position shown to the left of the axis 77 the shank 36 would engage the lower end of the tube 124 on the surface 131 formed as a shoulder by the reduced bore 62, to push the valve disk and tube assembly upward to the position shown.

A stepped sleeve 133 is disposed in the housing 10 between the distributing valve 16 and the motive air inlet port 102 and together with the valve disk 128 forms an annular flow passage with the valve disk 128 in the position shown to the left of the axis 77 in FIG. 6 which has a flow area bound by the disk circumference 134 and the wall 136 of the sleeve 133. With the valve disk 128 in the position shown to the right of the axis 77 in FIG. 6, corresponding to the shank 36 being out of blow-receiving relation with the piston hammer 14, a second annular flow passage is formed having an area bound by the disk circumference 134 and the stepped wall 138. This second flow area being substantially less than the first flow area restricts the flow of motive air to the distributing valve 16 when the tube 124 together with the valve disk 128 moves to the position corresponding to the shank being out of striking position.

The embodiment of FIG. 6 therefore performs the same function as the embodiment of FIGS. 1-5, that being to substantially idle the drill preventing overheating and ignition in the piston hammer cushion chamber and is particularly useful for drills using water or other liquid cleaning fluid mediums.

It will be apparent to those skilled in the art that the embodiments shown could be applied equally well to various designs of percussion drills, for example, those types using rifle bar type rotation mechanisms as opposed to the independent rotation type illustrated.

I claim:

1. In a percussion tool including:

a pressure fluid actuated percussion motor including a housing having a cylinder bore and a piston hammer reciprocably disposed therein.

pressure fluid supply means;

tool shank means disposed in one end of said housing and axially shiftable into and out of blow receiving relationship with said hammer, said shank means including a longitudinal bore therein; and

control valve means interposed between said pressure fluid supply and said percussion motor, said control valve including a pressure fluid actuator responsive to the supply and venting of pressure fluid therefrom to operate said control valve between a first position for providing flow of pressure fluid to said percussion motor and a second position for reducing flow of pressure fluid to said percussion motor, the improvement comprising:

a member disposed between said shank and said control valve and telescopically received in said bore in said shank, said member defining in part vent means and conduit means interconnecting said control valve actuator and said shank means for supplying pressure fluid to and venting pressure fluid from said actuator means in response to the axial shifting of said shank means; and

sealing means disposed in said bore of said shank means and sealingly engageable with said member whereby in response to the axial shifting of said shank means said sealing means interrupts the supply of pressure fluid to said conduit means.

2. The invention according to claim 1 wherein:

said member comprises a double walled tube having a first passage formed by the interior bore of an inner tube and a second passage formed by an annular space between said inner tube and an outer tube;

said first passage comprises means for supplying pressure fluid to said shank bore; and

said second passage comprises said conduit means interconnecting said shank means and said actuator means.

3. The invention according to claim 2 wherein:

said vent means comprises aperture means in said outer tube wall adjacent said telescopically receivable end of said member whereby in response to said shank means axially shifting into blow receiving relationship with said hammer, pressure fluid is supplied through said aperture means and said conduit means to said actuator means for moving said control valve to said first position and upon said shank means shifting out of blow receiving relationship with said hammer, said sealing means becomes interposed between said aperture means and said pressure fluid supply and said aperture means vents pressure fluid from said conduit and said actuator.

References Cited UNITED STATES PATENTS 897,958 9/1908 Boyer l7315 3,045,768 7/ 1962 Huffman 173-15 X 3,305,953 2/1967 Von Mehren et al. 173-15 X FOREIGN PATENTS 455,988 2/1928 Germany.

ERNEST R. PURSER, Primary Examiner U.S. Cl. X.R. 173--78