US3785248A

US3785248A - Rock drill

Info

Publication number: US3785248A
Application number: US00092028A
Authority: US
Inventors: E Bailey
Original assignee: Individual
Current assignee: Sullivan Machinery Co
Priority date: 1970-11-23
Filing date: 1970-11-23
Publication date: 1974-01-15
Anticipated expiration: 1991-01-15

Abstract

A rock drill and more particularly an independent rotation rock drill assembly having an improved method and apparatus for initiating reciprocable movement of the piston thereof.

Description

United States Patent [191 Bailey Jan. 15, 1974 1 ROCK DRILL [76] Inventor: Edward A. Bailey, RFD N0. 2, Box

37, Newport, NH. 03773 [22] Filed: Nov. 23, 1970 [21] Appl. No.: 92,028

[52] US. Cl. 91/6, 91/232 [51] Int. Cl. F0lb 25/00, F011 21/02 [58] Field of Search 91/6, 224, 232, 239;

[56] References Cited UNITED STATES PATENTS 3,279,326 10/1966 Harvey et a1. 91/224 2,999,482 9/1961 7 3,038,449 6/1962 Murphy, Jr. et a1. 91/6 3,596,560 8/1971 Butterworth 91/6 1,940,143 12/1933 Overly 91/232 3,118,348 l/1964 Kline 91/232 1,662,576 3/1928 .leschke 91/239 FOREIGN PATENTS OR APPLICATIONS 972,080 10/1964 England 91/6 941,041 3/1956 Germany 91/6 Primary Examiner-Martin P. Schwadron Assistant Examiner-A. M. Zupcic V AttorneyE. Wallace Breisch [57] ABSTRACT A rock drill and more particularly an independent r0- tation rock drill assembly having an improved method and apparatus for initiating reciprocable movement of the piston thereof.

5 Claims, 2 Drawing Figures ROCK DRILL Some rock drills presently in use are classified as independent rotation" rock drills which have a separate air motor carried thereby for imparting rotation to a striking bar through suitable gearing. Independent rotation rock drills provide for reciprocable movement of the piston head therewithin in a variety of manners, for example, the more or less conventional kicker port valve types or the valveless cycle type employing a plurality of passageways for channeling air under pressure to respective piston impart and retract passageways. An example of the latter mentioned valveless cycle independent rock drills is found and illustrated in U.S. Pat. Application Ser. No. 59,290, filed July 29, 1970, and assigned to the same assignee as is this invention now U.S. Pat. No. 3,666,024.

With such rock drills as described hereinabove problems often arise in the initial starting phase thereof for under circumstances known to those skilled in the art the piston head has a tendency at times to freeze when pressurized air is initially supplied thereto. The

freeze of the piston head can best be viewed as a condition wherein the pressures in the impact and retract chambers are virtually equal or the pressure differential therebetween is too small to initiate the cyclic movement of the piston. The tendency of the piston to freeze occurs most frequently when the rock drill is in a substantially horizontal position, however, freezing of the piston can occur in any position of the rock drill.

By means of the present invention which includes a connection from a fluid pressure line, other than the main fluid pressure line for supplying air under pressure for the reciprocable movement of the piston head, directly to either the impact or retraction passageways, the hereinabove mentioned problem of piston freeze is substantially overcome.

These and other objects and advantages of the present invention will become more readily apparent from a reading of the following description and drawings in which:

FIG. 1 is a portion of a central longitudinal vertical section through a rock drill embodying the principles of the present invention and showing the piston in an intermediate cyclic position thereof; and

FIG. 2 is a plan view of a portion of a rock drill viewed on lines 2-2 of FIG. 1.

An elongated and pneumatically powered rock drill embodying the principles of this invention and of a type shown and described in U.S. Pat. Application Ser. No. 59,290, filed July 29, 1970, and assigned to the same assignee as is this invention now U.S. Pat. No. 3,666,024 comprises an elongated annular motor cylinder 12 which axially receives a stepped cylindrical piston l4 therewithin for delivering impact loads to a suitable striking bar 16 which is suitably adapted to carry a drill steel (not shown). The motor cylinder 12 is disposed intermediate a rear back or casing head 18 and a front or forward yoke 20. Cylinder l2, piston 14, casing head 18 and yoke 20 are generally coaxial with respect to a longitudinal axis X-X of rock drill 10.

A plurality of circumferentially spaced exhaust portals 22 extend radially through cylinder 12 intermediate the axial ends thereof. An elongated annular motor cylinder lining 24, having an outer diameter thereof substantially equal to the inner diameter of cylinder 12, is axially received within the interior of cylinder 12 and oriented such that the axial ends thereof are in approximate transverse alignment with respective axial ends of cylinder 12. Liner 24 additionally has a plurality of circumferentially spaced exhaust portals 26 which extend radially therethrough intermediate the axial ends thereof and when liner 24 is received and aligned within cylinder 12, portals 26 are in open communication with respective portals 22 of cylinder 12. The above described alignment of liner 24 within cylinder 12 is retained in any suitable manner, for example, a plurality of radially inwardly extending set screws 28 which engagingly communicate between liner 24 and cylinder 12.

Liner 24 is of stepped cylindrical longitudinal cross section which has a constant outer diameter and includes a rear portion 30 and an increased inner diameter forward portion 32. An annular interior shoulder 34 is formed where

portions

30 and 32 meet intermediate the axial ends of liner 24. A stepped cylindrical buffer ring 36 which includesa rearward portion 38 having an outer diameter thereof substantially equal to the inner diameter of liner portion 32 is coaxially received within portion 32 such that the rearwardmost end thereof engages shoulder 34 and the forwardmost end thereof is transversely aligned with a forwardmost end of portion 32. A forward portion 40 of buffer ring 36 has an outer diameter thereof less than the outer diameter of portion 38 and extends axially and forwardly from the forwardmost end thereof.

An exterior shoulder 42 is formed at the intersection of

portions

38 and 40. The annular forward yoke 20 includes a flange 44 at the rearward end thereof which has an inner diameter thereof substantially equal to the outer diameter of buffer ring portion 36 and as such, flange 44, engages shoulder 42 and the forward ends of cylinder 12 and liner 24 thereby retaining buffer ring 36, cylinder 12 and liner 24 in the above described relative positions.

A disc shaped rearward supporting ring 46 having an outer diameter thereof shown as equal to the outer diameter of motor cylinder 12 is coaxially disposed intermediate the rearward end of cylinder 12 and the forward end of casing head 18. With support ring 46 positioned as described above, the travel of piston head 14 is limited to that distance between the forwardmost end of ring 46 and the rearwardmost end of buffer ring 36.

Piston 14 comprises a rear portion 50 having an outer diameter thereof substantially equal to the inner diameter of the rear portion 30 of liner 2-4 and an elongated reduced diameter stem 52 which extends coaxially forwardly from piston portion 50. Piston 14 is slidably received within liner 24 and upon such reception the stem 52 thereof is slidably received within a coaxial through bore 54 which extends longitudinally through buffer ring 36. Stem 52 has a plurality of circumferentially aligned and spaced, outwardly open grooves 56 spaced about the outer periphery and intermediate the axial ends thereof. As shown grooves 56 have a generally rectangular cross section with the long sides thereof extending generally parallel to the longitudinal axis X-X of rock drill 10.

A pneumatic fluid pressure source (not shown) provides a supply of pneumatic pressure fluid, such as air, to rock drill 10. To retract the piston 14 from the down stroke or impact position thereof, that is the position wherein head 14 is in engagement with the rear end of striking bar 16, pressurized air flows: from the source; through a conduit 57; through a passageway 58 in casing head 18 communicating between the rearward and forward ends thereof; through a plurality of bores 60 which are circumferentially spaced about ring 46 and inwardly spaced from the outer periphery thereof and open into an outwardly open groove 62 in a forward end portion of ring 46; through groove 62; and through a plurality of passageways 64 which communicate between groove 62 and respective ones of a plurality of liner passageways 66. Liner passageways 66 are shown as radially outwardly open circumferentially spaced grooves which extend axially along the outer periphery of liner 24 generally parallel to axis XX. The forward ends of passageways 66 terminate intermediate the axial ends of the forward portion 32 of liner 24. The pressurized air flows through passageway 66 and into respective passageways 68. Passageways 68 extend radially inwardly from the forward ends of respective passageway 66 and open into a passageway 70 in buffer ring 36 communicating between the inner and outer periphery thereof. The pressurized air flows; through passageway 66; through passageways 68; through passageway 70 and into the grooves 56 about the outer periphery of stem 52.

Spaced axially forwardly from passageway 70, a passageway 72 in buffer ring 36 also communicates between the inner and outer periphery thereof. When piston head 14 is in the down stroke or impact position discussed hereinabove,

passageways

70 and 72 register with grooves 56 adjacent the rearward and forward ends thereof respectively. The pressurized air from passageway 70 flows: through grooves 56; through passageway 72; and through a plurality of radially extending passageways 74 in liner 24 communicating between the inner periphery thereof and the forward end of respective ones of a plurality of liner passageways 76. Liner passageways 76 are shown as radially outwardly open circumferentially spaced grooves which extend axially along the outer periphery of liner 24 generally parallel to axis X--X. The rearward ends of passageways 76 terminate axially intermediate the forward axial end of rear portion 30 of linear 24 and exhaust portals 26.

A plurality of radially inwardly extending passageways 78 in liner 24 communicate between respective liner passageways 76 adjacent the rearward ends thereof, and the inner periphery of liner 24. With piston 14 in the downstroke or impact position passageway 78 opens into a retracting chamber 80 which is defined by and comprises that area between the inside diameter of liner 24 and the outside diameter of stem 52 axially intermediate rear piston portion 50 and the rearward end of buffer ring 36. Pressurized air flows from linear passageway 76; through passageways 78 and into retracting chamber 80 whereat such pressurized air reacts against the forward annular surface of piston head portion 50, and accordingly, urges the piston l4 axially rearwardly to the upstroke position thereof.

During the initial portion of the upstroke travel of piston head 14 an impact chamber 82, which is defined by and comprises that area of the inner periphery of liner 24 axially intermediate the rearward end of piston 14 and the forward end of supporting ring 46, is in open communication with the aligned exhaust portals 22 and 26 and as such the pressure within area 82 during such initial upstroke travel is substantially atmospheric. The term substantially atmospheric is used herein for portals 22 and 26 exhaust into an encompassing muffler assembly 84 and a slight back pressure somewhat higher than atmospheric will exist within muffler assembly 84. Assembly 84 is opened to atmosphere at portals 86 spaced about the periphery thereof. The air within impact chamber 82 will exhaust through portals 22 and 26 for the portion of the upstroke travel of piston 14 which maintains open communication between portals 22 and 26 and chamber 82.

FIG. 1 illustrates the operation of the impact motor when piston 14 is in a position intermediate the upstroke and downstroke position thereof. In the intermediate piston head position, stem grooves 56 are no longer in communication with passageway 72 and, as such, the flow of pressurized air therethrough and eventually into retracting chamber is discontinued. The open communication between impact chamber 82 and portals 22 and 26 is also discontinued by the outer periphery of piston portion 50 registering radially adjacent to portals 26. Chamber 80 and the passageways leading thereto comprise a substantially isolated system and accordingly the pressurized air within chamber 80 begins to expand and as such continues to apply pressure to the forward annular surface of piston head portion 50 thereby maintaining the rearward or upstroke movement thereof. Upon such continued upstroke the air within chamber 82, which chamber 82 also comprises a substantially isolated system, compresses and offers a resistance to the upstroke movement ofthe pis' ton head 14. The expansion of the air within chamber 80 coupled with the upstroke momentum imparted to piston head 14 when passageway 72 was still in communication with the fluid pressure source, will provide an upstroke force to piston 14 greater than the resistance presented by the compression of air within chamber 82, thereby forcing piston 14 to the upstroke position thereof. The resistance offered by the compression of air within chamber 82 provides an instantaneous rebound force to aid in the downstroke travel of piston 14 as hereinafter described.

In the upstroke or retracted position of piston head 14 passageway 70 is in open communication with grooves 56 adjacent the forward ends thereof. A passageway 88 in buffer ring 36 which is spaced axially rearwardly of passageway 70 communicates between the inner and outer periphery of ring 36. When piston 14 is in the upstroke position passageway 88 is in open communication with grooves 56 adjacent the rearward ends thereof.

To move the piston 14 from the retracted or upstroke position thereof into impact engagement with the striking bar 16, pressurized air flows: through passageway 70; and grooves 56; through passageway 88; and through a plurality of passageways 90 in liner 24 which communicate between passageway 88 and respective ones of a plurality of liner passageways 92 adjacent the forward ends of passageways 92. Linear passageways 92 as shown comprise radially outwardly open circumferentially spaced grooves which extend axially along the outer periphery of liner 24 generally parallel to axis urges X.

A plurality of radially extending passageways 94 in liner 24 communicate between respective liner passageways 92, adjacent the rearward ends thereof and axially intermediate the forward end of supporting ring 46 and exhaust portals 26, and the inner periphery of liner 24. With piston head 14 in the upstroke position passageways 94 are in open communication with the impact chamber 82. Pressurized air flows through passageways 92; and through passageway 94 into impact chamber 82 whereat such pressurized air reacts against the rearward surface of piston portion 50 and, accordingly, urges piston 14 forwardly into impact with striking bar 16.

During the initial portion of the downstroke travel of piston 14 the retract chamber 80 is in open communication with aligned exhaust portals 22 and 26 and as such the pressure within chamber 80 during such initial downstroke travel is substantially atmospheric. The air within retracting chamber 80 will exhaust through portals 22 and 26 for the portion of the downstroke travel of piston 14 which maintains open communication between portals 22 and 26 and chamber 80.

When piston 14 is in an intermediate position during the downstroke cycle thereof, grooves 56 are no longer in communication with passageway 90 and, as such, the flow of pressurized air therethrough and eventually into impact chamber 82 is discontinued. The open communication between retracting chamber 80 and portals 22 and 26 is also discontinued by the outer periphery of piston head portion 50 registering radially adjacent portals 26. The pressurized air within chamber 82 begins to expand, and, as such, continues to apply pressure to the forward annular surface of piston head portion 50 thereby maintaining the forward or downstroke movement thereof. Upon such continued downstroke movement the air within chamber 80 compresses and offers a resistance to the downstroke movement of the piston 14. The expansion of the air within chamber 82 coupled with the downstroke momentum imparted to piston 14 when passageway 90 was still in communication with the fluid pressure source will provide a downstroke force to piston 14 greater than the resistance presented by the compression of air within chamber 80, thereby forcing piston 14 into the full downstroke position thereof, that is, into impact with striking bar 16. The resistance offered by the compression of air within chamber 80 eventually decreases the force with which piston 14 strikes striking bar 16, however, the pressure within chamber 80 offers an instantaneous rebound force to aid in the upstroke travel of piston 14 as hereinbefore described.

Striking bar 16 is rotated by a pneumatically operable independent motor 100. The output from motor 100 is delivered to striking bar 16 in any suitable manner, for example, as shown and illustrated in the above mentioned U.S. application Ser. No. 59,290 now U.S. Pat. No. 3,666,024. Motor 100 is suitably supported in any suitable manner and as shown in FIG. 2 is positioned within a forward radially outwardly expanded portion of muffler assembly 84. Air under pressure flows from a source (not shown) and through a rotation motor conduit 101 which communicates between the source and motor 100. Conduit 101 is independent from impact conduit 57 and pressurized air is selectively and respectively supplied to each of such con-,

piston 14 greater than the resistance present by the compression of air within chamber 82, thereby forcing piston 14 to the upstroke position thereof. Likewise, when piston 14 is in the intermediate position of the downstroke travel thereof, the expansion of air within chamber 82 coupled with the downstroke momentum imparted to piston 14 when passageway was still in communication with the fluid pressure source will provide a downstroke force to piston 14 greater than the resistance presented by the compression of air within chamber 80, thereby forcing piston 14 into the full downstroke position thereof, that is, into impact with striking bar 16. It was additionally noted that the resistance offered by the compression of air within respective chambers offers an instantaneous rebound force to aid in the cyclic travel of the piston 14. While the hereinabove setforth cyclic operation of piston 14 is generally true, experience has found that the piston 14 has a tendency at times to freeze when pressurized air is initially supplied thereto. The freeze of the piston can best be viewed as a condition wherein the pressure within the impact chamber 82 is virtually equal to the pressure within the retract chamber 80 or the pressure differential between such chambers is too small to initiate cyclic movement of the piston 14. The tendency of the piston 14 to freeze occurs most frequently when the rock drill 10 is in a substantially horizontal position, however, freezing of the piston can occur in any position of the rock drill 10. The freezing will generally occur when the piston 14 is in a position intermediate the upstroke and downstroke position thereof. In such an intermediate position stem grooves 56 are not in communication with either

passageway

72 or 88 and hence the flow of pressurized air into either the impact or retraction chambers is discontinued and also the open communication between the portals 22 and 26 and a respective one of the

chambers

80 and 82 is discontinued by the outer periphery at piston head portion 50 registering radially adjacent portals 26. As previously mentioned the passing of the piston 14 through the intermediate cyclic position would have no effect on the cyclic movement thereof because of the momentum imparted thereto when a respective chamber was in communication with the pressurized source coupled with the expansion of the pressurized air within such a chamber; however, when initially starting the impact motor the momentum imparted to the traveling piston is somewhat less because the rebound force which aids the travel of the piston 14 is not initially present in the system. Thus, the piston 14 travels to the intermediate position and freezes. Other factors affecting the start up of the cyclic movement of the piston 14 include cold and non-circulating lubricant, impurities within the lubrication system, and the like.

By means of the start-up bolster assembly 104 of the present invention the hereinabove mentioned problem of piston head freeze during start up operations is substantially eliminated. As shown start-up bolster assembly 104 comprises a conduit 106 having one end thereof in communication with rotation motor conduit 101 and the other end thereof in communication with a choke assembly 108. A radial bore extends through cylinder 12 and'opensinto a liner passageway 76. A radially inwardly extending portion of choke assembly 108 is suitably captively received within bore 110. Choke assembly 108 is constructed such that a predetermined measured amount of pressurized air passes therethrough.

With a start-up bolster assembly 104 as described hereinabove a flow of pressurized air to the impact motor is initiated and, if freeze up of piston 14 occurs, pressurized air is supplied to the independent motor 100 through conduit 101. A small amount of such pressurized air then flows through assembly 104 into passageway 76, through passageway 78 and into retracting chamber 80 thereby providing a sufficient pressure differential between chambers 80 and 81 to initiate the cyclic movement of piston 14. It is to be noted that the quantity of air flowing through choke assembly 108 is not sufficient to register any measurable decrease in the efficiency of the operation of rock drill 10. Also, in the event it is desired to use the rotation motor 100 without activating the piston 14, the quantity of air flowing through choke assembly 108 is not sufficient to initiate movement of the piston 14 if no other source of pressurized air is flowing to the impact motor. Likewise, if it is desired to operate the impact motor without operating the rotation motor 100, the amount of air flowing through the choke assembly 108 will have no effect on the standstill condition of motor 100.

Inasmuch as the invention herein resides in the method and apparatus for initiating reciprocable movement of the piston 14, various modifications can be made to the preferred embodiment described hereinabove without departing from the scope of the invention, for example: bolster assembly 104 can communicate with groove 92 rather than groove 76 and hence the impact chamber 82 will receive additional pressure rather than the retracting chamber 80 as described hereinabove; the bolster assembly 104 can communicate directly with either the impact chamber 82 or the retracting chamber 80; a separate line from the fluid pressure source can be provided for the bolster assembly 104 rather than tapping off conduit 101; a pilot operable check valve can be provided for selective operation of bolster assembly 104; bolster assembly 104 can be used with rock drills of a type other than the rock drill described hereinabove; and the like.

The scope of the invention is defined by the claims set forth hereinafter.

What is claimed is:

1. A rock drill of a type having an elongated body with a chamber extending longitudinally therein, a hammer piston comprising a head portion and a stem portion reciprocable within said chamber through impacting, neutral and retracting positions for percussively actuating a striking bar upon movement of said piston within said chamber, with said neutral position being axially intermediate said impacting and retracting positions and end portions of said chamber being piston impacting and retracting chamber portions, respectively, piston passageway means in said piston in communication with respective ones of said chamber portions upon movement of said head portion of said piston into a respective chamber portion, the improvement comprising: first passageway means in said body being in communication with said piston passageway means during at least a major portion of said piston movement and adapted to be connected to a first fluid pressure source; and second passageway means in said body being in communication with only one of said chamber portions during said piston movement and adapted to be connected to a second fluid pressure source to provide initiation of reciprocation of said piston when said piston is in said neutral position.

2. A rock drill as specified in claim 1 wherein said second passageway means provides pressure fluid to said selected one of said piston chamber portions at a pressure less than the pressure of the pressure fluid supplied to said chamber by said first passageway means.

3. A rock drill as specified in claim 1 wherein said second fluid passageway means comprises a conduit having one end thereof in communication with said second fluid pressure source, and a valve assembly in said conduit adjacent the other end thereof.

4. A method of initiating cyclic movement of the hammer piston within the piston chamber of a rock drill wherein said piston reciprocates through impacting, neutral and retracting positions and has passageways communicating alternately with respective end portions of said chamber during such cyclic movement comprising the steps of: supplying pressure fluid to one end portion of said piston chamber to provide initiation of reciprocation of said piston when said piston is in said neutral position; supplying pressure fluid to said end portions of said piston chamber to maintain such cyclic movement; and said first mentioned supplying being from a source of such pressure fluid independent of the source of said second mentioned supplying.

5. A method as specified in claim 4 wherein said first and second mentioned supplying take place substantially simultaneously.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 785 248 Dated January 15 1974 Inventor(s) Edward A. Bailey It is certified that error appears in the aboveeidentified patent andthat said Letters Patent are hereby corrected as shown below:

Claim rock drill as specified in claim 1 wherein said first and second fluid pressure sources are supplied from a common supply means and each of said sources are independently controlled.

Claim 7, A method as specified in claim 4- wherein said sources .of pressure fluid are supplied from'a common supply means and each of said sources are inde endently controlled.

On the cover sheet below "Abstract", "5 Claims" should read 7 Claims Signed and sealed this 23rd day of April 1971+.

(SEAL) Attest:

EDWARD I'I.FLETCIIEII,JR. G. MARSHALL DAi-IN Attesting Officer Commissioner of Patents