US3807509A

US3807509A - Advancement device for a horizontal earth boring machine

Info

Publication number: US3807509A
Application number: US00325884A
Authority: US
Inventors: M Linsay
Original assignee: Allied Steel and Tractor Products Inc
Current assignee: Allied Steel and Tractor Products Inc
Priority date: 1973-02-20
Filing date: 1973-02-20
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30
Also published as: DE2406671A1; JPS49126117A; CA991206A; ZA739433B; FR2218467B1; NL7402212A; IT1008247B; AU6415574A; GB1466351A; FR2218467A1

Abstract

A system for advancing and retracting rail mounted horizontal earth boring machinery. The system includes a walking beam structure slidably mounted to the chassis of the horizontal earth boring machinery. The walking beam is located underneath the horizontal earth boring machinery between the rails. The walking beam has pins which can be engaged with the rails supporting the horizontal earth boring machinery. The pins are actuated by a pivotally mounted rod which slidably engages a pin actuating linkage located on the walking beam. By slidably mounting the walking beam under the horizontal earth boring machinery and by controlling the engaging and disengaging of the pins associated with the walking beam by the slidably engaged rod, simple and inexpensive mechanical control of the earth boring machinery can be accomplished at a specific control position on the unit. Further, the overall length of the horizontal earth boring machinery is reduced by the placement of the walking beam under the chassis of the horizontal earth boring unit.

Description

United States Patent [191 Linsay Apr. 30, 1974 1 1 ADVANCEMENT DEVICE FOR A HORIZONTAL EARTH BORING MACHINE [75] Inventor: Michael Linsay, South Euclid, Ohio [73] Assignee: Allied Steel & Tractor Products,

' Incorporated, Cleveland, Ohio 22] Filed: Feb. 20, 1973 21 Appl. No.: 325,884

[52] US. Cl 173/152, 175/62, 254/29 [51] Int. Cl. E2lc 5/11 [58] Field of Search 173/152, 156; 175/62, 122;

Primary ExaminerErnest R. Purser Attorney, Agent, or FirmLyon & Lyon [5 7 ABSTRACT A system for advancing and retracting rail mounted 4 horizontal earth boring machinery. The system includes a walking beam structure slidably mounted to the chassis of the horizontal earth boring machinery. The Walking beam is located underneath the horizontal earth boring machinery between the rails. The walking beam has pins which can be engaged with the rails supporting the horizontal earth boring machinery. The pins are actuated by a pivotally mounted rod which slidably engages a pin actuating linkage located on the walking beam. By slidably mounting the walking beam under the horizontal earth boring machinery and by controlling the engaging and disengaging of the pins associated with the walking beam by the slidably engaged rod, simple and inexpensive mechanical control of the earth boring machinery can be accomplished at a specific control position on the unit. Further, the overall length of the horizontal earth boring machinery is reduced by the placement of the walking beam under the chassis of the horizontal earth boring unit.

9 Claims, 5 Drawing Figures PATENTEUAPRBO 191 3807509 SHEET 1 BF 2 i Z Az' 54 30/04 i! 73% This invention relates to horizontal earth boring machinery. More specifically, this invention is directed to improved means for controlling and mounting a walking beam for horizontal earth boring machinery.

Heavy-duty earth boring equipment has been developed for boring horizontal holes under a variety of barriers, such as roadways, where it is inconvenient or impossible to dig a trench traversing the barrier. Such equipment generally includes a rail mounted frame to which a power unit, a drive train and an auger are attached. A cylindrical casing pusher is often included near the back of the auger to force casing into the bore as the auger advances. The larger of these devices have also employed powered means for advancing and retracting the horizontal earth boring machinery along the rails during the operation of the unit. Walking beams have been employed in combination with rails to which the beams may be selectively engaged and disengaged. The walking beams act to anchor a hydraulic cylinder or other such power means which acts'from the anchoring point of the walking beam to push or pull the horizontal earth boring unit along the rails. The walking process is accomplished by first engaging the walking beam with the rails. A horizontal earth boring unit is then forced to advance by actuating a hydraulic cylinder anchored through the walking beam. After the horizontal earth boring unit has'advanced a predetermined distance, the walking beam is disengaged from the rails and brought forward to a next engagement with the rails. The process may then be repeated to create a walking type action to either advance or retract the boring unit.

The walking beam unit has generally been placed behind the horizontal earth boring machinery in the 'power driven units. A problem associated with the 'the dismounting of a single operator from the central control position to actuate the walking beam as the system is advanced or retracted. To avoid the requirement for either two operators or one operator controllng the equipment at a plurality of positions, hydralically operated control systems have been devised. These control systems have not met with resounding acceptance because of the added complexity of the machinery and the cost of incorporating such systems on the unit.

A second problem associated with the placement of the walking beam behind the earth boring unit is the resulting overall length of the unit. In operating boring machinery, it is necessary in many instances to dig a pit into which the machinery must be lowered to reach the elevation of the intended horizontal bore. This pit is often for the singular purpose of positioning the horizontal earth boring equipment and the cost of excavating such a pit must be considered as being part of the boring cost. As a result of this added cost, it is beneficial to make the earth boring units as'compact as possible. By extending the walking beamv out behind the unit, a larger pit is required. Also, when the operator is required to go back to the walking beam to actuate the locking mechanism, an even larger pit is necessary.

A compact power advancement system for horizontal earth boring machinery requiring a single operator who can, act to control the unit 'froma single station has been sought. Such a unit would most advantageously incorporate simple mechanical linkages for operating system for a horizontal earth boring unit which is com' pact, requires a single operator to operate the unit from one control position and incorporates simple, inexpensive mechanical control linkages. The walking beam of the present invention is positioned beneath, rather than behind, the horizontal earth boring unit chassis. By positioning the walking beam beneath the horizontal earth boring unit, the overall size of the unit is not influenced by the power advancement means whatsoever. Further, the central placement. of the walking beam makes it possible for a single operator to manipulate the locking mechanis m of thewalking beam from a central control station throughmechanical linkages.

A second object of the present invention is to provide a walking beam which is slidably mounted to the chassis of the horizontal earth boring unit. By slidably mounting the walking'beam tothejchassis rather than directly to the rails, the walking beam' will not interfere with the advantageous placement of the various components of the horizontal earth boring unit which would be necessary to avoid the path taken by the walking beam as it oscillates relative to theearth boring unit during the walking process. This central placement of the walking beam on. the chassis has most advantageously affected the overall size and complexity of the unit.

Another object of the present invention is to provide mechanical linkage betweenthe operator control station of the unit and the locking mechanisms of the centrally located walking beam. A .pivotally mounted rod is provided on the horizontal earth boring unit which slidably engages the locking mechanism of the walking beam. Because of this'sliding engagement,- the control linkage remains relatively uncomplicated and .at'the same time provides positive control as the walking mechanism oscillateswith respect to the control posi-- tion of the earth boring unit.

Thus, a power advancement system fora horizontal earth boring unit is disclosed which reduces the size of the overall unit, allows asingle operator to control the entire operation from a central control position and incorporates simple, inexpensive mechanical control linkages to operate the power advancement system. Further objects and advantages will become apparent from the discription herein.

FIG. 1 is a side view of the horizontal earth boring unit specifically illustrating the central control station.

FIG. 2 is a cross-sectional view taken alongline 2 2 of FIG. 1 which illustrates the locking mechanism in the locked position. a

FIG. 3 is a fragmentary cross-sectional view taken along line 2-2 of FIG. 1 illustrating the locking mechanism in its unlocked position.

FIG. 4. is a cross-sectional plan view taken along line 4-4 of FIG. 1 illustrating the locking mechanism, the locking mechanism controls and the walking beam.

FIG. 5 is across-sectional view taken along line 5-5 of FIG. 2 illustrating the walking beam as it is carried by the carriage of the horizontal earth boring unit.

Turning now to the drawings, FIG. 1 schematically illustrates the horizontal earth boring unit as basically comprising a power unit 10, a transmission unit 12, a casing pusher 14 and an auger 16. A chassis generally designated 18 provides a mounting base for the horizontal earth boring unit. Two parallel rails 20 having cross ties 22 support the chassis 18.

As shown in FIG. 2, the chassis generally designated 18 includes two

angle members

24 and 26 which extend from the back of the unit to the casing pusher l4 and ride on the bearing surfaces 28 of the rails 20. The

chassis members

24 and 26 have plates 30 fixed to the

chassis members

24 and 26 which extend outward in pairs. Pivoted arms 32 are positioned between the pairs I of plates 30 and are pivotally mounted thereon about pins34. Locking plates 36 are welded to the arms 32 to engage the rails 20 below the bearing surfaces 28. These locking assemblies are provided to-keep the horizontal earth boring machine on the rails when in operation.

A walking beam generally designated 38 in. FIGS. 4 and 5 is provided beneath the chassis 18 for advancing and retracting the horizontal earth boring unit along the rails 20. The walking beam 38 includes a cross member 40 extending across the width of the walking beam 38 at its forward end and two

skids

42 and 44 abutting the cross member 40 and extending rearward the length of the walking beam 38 forming its lower surface near the rails 20. Channel members 46 and 48 which run the length of the walking beam 38 form the sides of the walking beam 38. The channel members 46 and 48 are welded to the cross member 40 and the

skids

42 and 44 to form a single walking beam structure. A mounting plate 50 is positioned across the back of the unit between the channels 46 and 48. A supplemental brace 52 is attached to the cross member 40 of the walking beam 38. The supplemental brace 52 includes

plates

54 and 56 which extend rearward to the mounting plate 50. The supplemental brace 52 acts to support the mounting'plate 50 atits center to reduce the effect of bending moments on the mounting plate 50 which is otherwise only attached at its ends to the channelrnernbe'rs 46 and 48.

Spacers

58 and 60 are positioned on top of the channel members 46 and 48 respectively.

Means are provided for selectively engaging the walking beam with the rails 20. Selective engagement may be provided by

pins

62 and 64 slidably mounted to the walking beam 38. The

pins

62 and 64 are to extend laterally on the walking bean 38 into selective engagement with slots 66 provided through the rails 20 for this purpose. Reinforcing members 68 are provided at each slot 66 to prevent tearing of the rails under the high loads imposed during operation of the walking beam 38. The slots 66 are spaced periodically along the rails 20 to accommodate the advancing or retracting walking beam 38 as it first engages and then disengages therails in successive steps to advance the horizontal earth boring unit. The spacing of the slots 66 is deter- The

pins

62 and 64 are slidably mounted in foursided guide structures which guide the

pins

62 and 64 laterally into and out of engagement with the rails 20. A guide structure is provided for each pin. The guide structures extend ourward to the channel members 46 and 48 where pin holes 70 and 72 accommodate the

pins

62 and 64 as they extend outward to engage the slots 66. The forward side of each guide structure is formed by the back side of the mounting plate 50 which extends across the width of the walking beam 38. Horizontal

top plates

74 and 76 are positioned directly above the

pins

62 and 64 respectively and are welded to the mounting plate 50.

Horizontal bottom plates

78 and 80 are similarly attached to the mounting plate 50 and extend below

pins

62 and 64. The horizontal plates 74 through 80 are slightly wider than the width of the

pins

62 and 64 to allow unrestricted passage of the

pins

62 and 64 between the horizontal plates. Back

plates

82 and 84 are welded to the respective horizontal top and bottom plates in positions parallel to the mounting plate 50 and spaced therefrom by the width of the horizontal plates. The

pins

62 and 64 may be of any convenient cross-section. A preferred design to minimize wear and provide good shear strength includes a square cross-section which is reduced at its leading end to facilitate the insertion of the pin through the slots 66. The

pins

62 and 64 are of sufficient length to prevent binding within the four-sided guide structures. The pin length must be compromised to allow adequate space for the pin actuating means which is to be located between the

pins

62 and 64. The lengths of the pins must be determined from established engineering principles. These lengths are influenced by the width of the walking beam 38, the design of the actuating mechanism for locking the walking beam 38, and the mechanical advantage available to move the pins. Also to prevent binding of the pins, due to moment forces exerted thereon, the various plates 74 through 84 should preferably extend inward to points near the furthest retracted positions of the innermost ends of the

respective pins

62 and 64. However, it is preferred that the plates do not extend so far toward the center of the walking beam that they might interfere with the actuating mechanisms associated with the

pins

62 and 64.

An actuating means is provided to control the engagement and retraction of the locking pins 62 and 64. In the preferred embodiment, this locking means includes a control rod 86 which is pivotally mounted to the chassis 18 through bearing 88 and to the walking beam 38 on the mounting plate 50 through bearing 90. The bearing 90 mates with the control rod 86 in sliding engagement which allows the walking beam 38 to move longitudinally with respect to the control rod 86. A

pivot arm 92is slidably mounted on the control rod 86 adjacent the bearing 90. The pivot arm 92 is constrained to pivot with the control rod 86' at any point on the control rod 86 along the length of travel of the walking beam 38 with respect to the horizontal earth boring unit. The control rod 86 may be of any cross section which allows the pivot arm 92 to slide thereon I but prevents the pivot arm 92 from rotating on the'con mined by the operating stroke of the drive mechanisms 7 forcing the machinery along the rails 20.

trol arm 86. A square rod is employed in the preferred embodiment as the control rod 86. The pivot arm mates with the control rod 86 by means of a square hole centrally located in the pivot arm 92.. Sufficient tolerance is allowed between the square control rod 86 and the pivot arm 92 in order that the pivot arm 92 may freely slide along the control rod 86. However, the square hole in the pivot arm 92 should not be so large as to allow the square control rod 86 to rotate relative to the pivot arm 92.

The pivot arm 92 includes

slots

94 and 96 located at either end thereof.

Pins

98 and 100 are positioned through the pivot arm 92 and the

slots

94 and 96 to pivotally mount connecting

links

102 and 104.

Connecting links

102 and 104 are also pivotally mounted at their outward ends by means of pins 106 and 108 in yoke sections of the locking pins 62 and 64 located at the inner ends of the

pins

62 and 64. One horizontal upper guide plate 74 extends inward to a point near the center of the walking beam 38 to form a mounting base for a stop 110 which is positioned to interfere with the actuating mechanism of the

pins

62 and 64 to prevent excessive retraction thereof. FIGS. 2 and 3 illustrate the pin actuating mechanism having the pins in the engagement position and in the retracted position respectively. Spring means may be conventionally provided to bias the

pins

62 and 64 toward the locked position as shown in FIG. 2. If a spring means is employed for so biasing the

pins

62 and 64, the operator will not be required to operate the actuating means to re-engage the pins as they approach a new slot 66.

To operate the actuating means, an arm 112, as best shown in FIG. 4, is rigidly clamped to the control rod 86. Linkage 114 is pivotally mounted to the arm 112 at a point eccentrically located with respect to the control arm 86. The linkage 114 is pivotally mounted at its upper end to the walking beam control lever 1 16. Thus, as the walking beam control lever 116 is actuated, the control rod 86 is rotated. As the control rod 86 rotates, the locking pins 62 and 64 will engage or disengage from the rails 20 by means of the actuating mechanism centered about the control rod 86 between the

pins

62 and 64. By employing the control rod 86, the walking beam control lever 116 may be centrally located at the control station. The control rod 86 extends from a point where the control lever can be conveniently linked thereto through simple and inexpensive mechanical linkage to a point beyond the furthest backward point of travel of the walking beam 38. The use of this mechanical linkage enables the operator to control the walking beam 38 from the central control area of the horizontal earth boring machine and further allows the positioning of the walking beam underneath the horizontal earth boring unit rather than behind the unit. One purpose for locating the walking beam behind the unit in the more conventional systems is to allow easy access to the walking beam for mechanical control thereof. The present system is able to advantageously locate the walking beam beneath the unit without complicating the control mechanisms.

Means are provided for mounting thewalking beam 38 to the underside of the chassis 18. Such support means must be capable of keeping the walking beam 38 in alignment with respect to the rails 20 in order that the

pins

62 and 64 associated with the walking beam 38 will be capable of engaging the rails by lining up with the slots 66. Also, the support structure is preferably located under the chassis 18 so as not to interfere with the travel of the horizontal earth boring unit along the rails 20. One device for accomplishing this support function is provided by a support frame generally designated 118. The support frame 118 is fixed to a chassis member 120 by fasteners 122. The support frame 118 has a top section 124 which extends to the

angle members

124 and 126 of the chassis 18.

Vertical sections

126 and 128 then extend downward adjacent rails to a point just below the walking beam 38.

Flanges

130 and 132 extend inward from the vertical sections 126 and 128 a distance sufficient to support the

skids

42 and 44 of the walking beam 38. The support frame 1 18 runs underneath the chassis 18 from the back end of the

angle members

24 and 26 to the casing pusher 14. The channel members 46 and 48 in combination with the skids 43 and 44 and the

spacers

58 and 60 fit beand bind therein. The channel members 46 and 48 of the walking beam 38 are also positioned sufficiently close to the

vertical sections

126 and 128 of the support frame 118 so that the walking beam 38 cannot twist about a vertical axis and bind under the chassis 18. Slots 134 are provided along a' substantial portion of the

vertical sections

126 and 128 of the support frame 118 to allow unobstructed passage of the

pins

62 and 64 into engagement with the rails 20. Further, the slot 134 allows the horizontal earth boring unit to advance while the

pins

62 and 64 are locked within the slots 66.

By positioning the support frame 1 18 on the carriage 18, the walking beam 38 which is supported by the support frame 118 will not interfere with the movement of the horizontal earth boring unit. This is true even though the walking beam 38 is centrally mounted under the chassis 18. Conventional systems employ the rails 20 to mount the walking beam 38. Such a system would not be practical in this instancefThe method of mounting the walking beam 38 in the present invention therefore enables the placement of the walking beam 38 under the chassis 18.

To cause the walking beam 38 to move relative to the chassis 18 of the horizontal earth boring machinery, driving means are provided. Such means must be capable of selectively providing both tensile and compressive forces in order that the walking beam 38 can be 'moved in either direction relative to the horizontal earth boring unit. One device for accomplishing this function includes the use of one or more hydraulic cylinders 136 having a first end attached to the walking beam 38 and a second'end attachedto the chassis 18 of the horizontal earth boring unit. Two cylinders 136 are provided on the preferred embodiment. The rod ends 138 of the hydraulic cylinders 136 are coupled by means of pins 140 to bracketts 142 and 144 which are in turn fixed to the mounting plate of the walking beam 38. The mounting plate 50 is located between the bracketts 142 and 144 and the locking pins 62 and 64. This allows the force of the cylinders 136 acting through bracketts 142 and 144 to pass directly through the locking pins 62 and 64 into the rails 20. The cylin-- der ends 146 and 148 of the hydraulic cylinders 136 are likewise attached by means of pins 150 to bracketts 152 and 154. The bracketts are in turn mounted on the support member 156 of the chassis 18. The cylinders 136 are hydraulically coupled with a pump powered by the power unit 10. This hydraulic pump is most conveniently a variable volume pump which has the characteristic of going to zero output when the cylinders reach their minimum or maximum extensions. A pump control 158 is shown in FIG. 1. Also shown in FIG. 1 is clutch control 160 and the shift mechanism 162 for thetransmission 12.

Summarizing the operation of the horizontal earth boring machinery with specific attention paid to the advancement mechanisms, the horizontal earth boring unit is positioned on the tracks 20 and the walking beam 38 is locked into the tracks 20 with the cylinders 136 contracted. The cylinders 136 are then expanded by operating control lever 158 which activates the variable volume pump. As the cylinders 136 expand, they push the earth boring unit forward along the rails 20. When the cylinders have reached a maximum expanded position, the walking beam 38 is unlocked from the rails 20 by means of the walking beam control lever 116 which pivots the control rod 86 which in turn disengages the

pins

62 and 64 through the pivot arm 92. When the walking beam 38 is unlocked, the cylinders are caused to contract which pulls the walking beam 38 are then re-engaged with the rails 20 by repositioning the walking beam control lever 116. The process may thenbe repeated to advance the unit further.

Thus, an advancement system is disclosed which provides for a walking beam located beneath the chassis of the earth boring'unit. The system may be simply and inexpensively controlled through mechanical linkage at a control center conveniently near the transmission, clutch, and pump controls. While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein described. The invention,therefore, is not to be restricted except as necessary by the prior art and by the spirit of the appended claim.

I I claim:

l. A horizontal earth boring device comprising an earth boring unit;

a chassis for mounting said earth boring unit thereto;

a plurality of rails supporting said chassis; a walking beam; drive means for driving said walking beam relative to said chassis; locking means operably mounted on said walking beam for selectively engaging said rails; actuating means'operably linked to said locking means for actuating said locking means; and I support means fixed to said chassis for slidably supporting said walking beam. 2. The device of claim 1 wherein said walking beam is located under said chassis.

3. The device of claim 1 wherein said support means includes a top section mounted to said chassis; 7 two mutually parallel, vertical side sections,'said vertical side sections being spaced to fit about said walking beam to keep said walking beam aligned;

and.

two bottom sections extending inward from said two vertical sections and being parallel to said top section, said bottom sections supporting said walking beam and being spaced from said top section to fit forward to the next pair of slots 66. The

pins

62 and 64 about said walking beam to prevent tipping thereof.

4. The device of claim 3, wherein said support means is made from one sheet of material.

5. The device of claim 1 wherein said support means provides for free movement of said locking means relative to said support means when said locking means engages said rails.

6. The device of claim 1 wherein said actuating means includes a slidable coupling enabling said actuating means to accommodate relative movement of said walking beam and said chassis.

7. The device of claim 1 wherein said actuating means includes a rod pivotally mounted to said chassis;

control means linked to said rod for selectively pivoting said rod into a plurality of positions; and

means slidably engaging said rod, said engaging means being operably mounted on said walking beam to operate said locking means.

8. The device of claim 1 wherein said actuating means includes a rod pivotally mounted to said chassis, said rod having a non-circular cross section;

I control means linked to said rod for selectively pivoting said rod into a piurality of positions, said control means being operably mounted to move with said chassis; and

means slidably engaging said rod, said engaging means being operably mounted on said walking beam to operate said locking means and being constrained to pivot with said rod.

9. A horizontal earth boring device comprising an earth boring machine;

two rails supporting said earth boring machine;

a walking beam mounted under said earth boring machine; l

at least one hydraulic cylinder for driving said walking beam relative to said earth boring machine, said cylinder being mounted at a first end to said walking beam and at a second end to said earth boring machine;

locking means operably mounted on said walking beam for selectively engaging said rails;

actuating means operably linked to said locking means for actuating said locking means, said actuating means including a rod having a non-circular cross section and being pivotally mounted to said earth boring machine, control means mounted on said earth boring machine and being linked to said rod for selectively pivotting said rod into a plurality of positions, and means slidably engaging said rod and being constrained to'rotate therewith, said engaging means being operably mounted on said walking beam to operate said locking means; and

section supporting said walking beam.

Claims

1. A horizontal earth boring device comprising an earth boring unit; a chassis for mounting said earth boring unit thereto; a plurality of rails supporting said chassis; a walking beam; drive means for driving said walking beam relative to said chassis; locking means operably mounted on said walking beam for selectively engaging said rails; actuating means operably linked to said locking means for actuating said locking means; and support means fixed to said chassis for slidably supporting said walking beam.

2. The device of claim 1 wherein said walking beam is located under said chassis.

3. The device of claim 1 wherein said support means includes a top section mounted to said chassis; two mutually parallel, vertical side sections, said vertical side sections being spaced to fit about said walking beam to keep said walking beam aligned; and two bottom sections extending inward from said two vertical sections and being parallel to said top section, said bottom sections supporting said walking beam and being spaced from said top section to fit about said walking beam to prevent tipping thereof.

7. The device of claim 1 wherein said actuating means includes a rod pivotally mounted to said chassis; control means linked to said rod for selectively pivoting said rod into a plurality of positions; and means slidably engaging said rod, said engaging means being operably mounted on said walking beam to operate said locking means.

8. The device of claim 1 wherein said actuating means includes a rod pivotally mounted to said chassis, said rod having a non-circular cross section; control means linked to said rod for selectively pivoting said rod into a plurality of positions, said control means being operably mounted to move with said chassis; and means slidably engaging said rod, said engaging means being operably mounted on said walking beam to operate said locking means and being constrained to pivot with said rod.

9. A horizontal earth boring device comprising an earth boring machine; two rails supporting said earth boring machine; a walking beam mounted under said earth boring machine; at least one hydraulic cylinder for driving said walking beam relative to said earth boring machine, said cylinder being mounted at a first end to said walking beam and at a second end to said earth boring machine; locking means operably mounted on said walking beam for selectively engaging said rails; actuating means operably linked to said locking means for actuating said locking means, said actuating means including a rod having a non-circular cross section and being pivotally mounted to said earth boring machine, control means mounted on said earth boring machine and being linked to said rod for selectively pivotting said rod into a plurality of positions, and means slidably engaging said rod and being constrained to rotate therewith, said engaging means being operably mounted on said walking beam to operate said locking means; and support means fixed to said earth boring machine for slidably supporting said walking beam, said support means including a support structure having a top section mounted to said earth boring machine, two mutually parallel, vertical side sections having a slot therethrough to permit passage of said locking means relative to said support means, and two bottom sections extending inward from said two vertical sections parallel to said top section, said bottom section supporting said walking beam.