US3734214A - Head for horizontal boring - Google Patents

Abstract

A head for an auger for horizontal earth boring has four point support which assists in keeping the hole round and in line. The boring head, attached to the working end of an auger shaft has two opposed boring arms formed with tooth holding sockets for replaceable digging teeth and also for a pilot bit. To the rear of the arms is an expansion tooth head having opposed arms intermediate the boring head arms. These arms carry on their outer ends holders for expansion teeth which pivot outward when the auger is rotated in one direction and inward when the auger is reversed. The expansion teeth and outermost boring head teeth are 90* apart and hence the head is supported so that its tendency to bore a hole which is elliptic toward the bottom is overcome. Further, adjustment is provided for the maximum extent of outward pivotting of the expansion tooth holder for different casing wall thicknesses.

Description

United States Patent 1191 Benetti et al.

1 1 May 22,1973

[54] HEAD FOR HORIZONTAL BORING Primary Examiner-Joseph H. McGlynn [75] Inventors: John G. Benetti, Cupertino; Walter Assstam 'f"" Favrea" L. Sturgeon, Los Altos, both of Attorney"juhan Caplan Calif. [57] ABSTRACT [73] Ass1gnee: Pengo Corporation, Sunnyvale,

C lif, A head for an auger for horizontal earth boring has four point support which assists in keeping the hole [22] Flledi Sept 1971 round and in line. The boring head, attached to the [21] Appl. No.: 183,326 working end of an auger shaft has two opposed boring arms formed with tooth holding sockets for replacea- 52 US. Cl. ..17s/3s4 175/171 175/62 ble digging teeth and a PM the 299/86 the arms is an expansion tooth head having opposed 51 1m. (:1. ..E2lb 9/00 aims intermediate the Ming head aimsarms 58 Field of Search ..175/384, 292, 342, carry their outer ends hiiideis expansion teeth 175/382, 383, 299/61 80 which pivot outward when the auger is rotated in one direction and inward when the auger is reversed. The [55] R f r it d expansion teeth and outermost boring head teeth are 90 apart and hence the head is supported so that its UNITED STATES PATENTS tendency to bore a hole which is elliptic toward the 2,990,896 7/1961 Kandle ..17s/171 bottom is Overcom- Further, adjustment is Provided 1,848,192 3/1932 Newman ....175/384 for the maximum extent of outward pivotting of the 1,173,500 2/1916 Frank ....175/384 expansion tooth holder for different casing wall 2,783,974 3 1957 Veasman ..175/384 thicknesses, 3,508,622 4/1970 Benetti et al. ..l75/384 X 4 Claims, 4 Drawing Figures PAIENTEU M22 1975 I John INVENTOR G. Bene HZ HEAD FOR HORIZONTAL BORING This invention relates to a new and improved head for horizontal earth boring. More particularly, the invention relates to a head which has essentially two parts one displaced approximately 90 relative to the axis of rotation of the head from the other. The forward portion has conventional earth boring teeth which dig out the largest area of the hole being bored. Rearwardly, the head has a second part having expansion holders with teeth to dig out the perimeter of the holes thereby cutting clearance for the casing. The expansion holder has expansion teeth which are pivotally mounted thereon, so that when the head is rotated in normal cutting direction the expansion holder and the teeth carried thereby pivot outwardly to dig out the perimeter of the hole, but when the direction of rotation is reversed, the holders pivot inwardly to permit retraction of the head within the casing after excavation is completed.

Accordingly, a principal purpose of the present invention is to provide a self-expanding, self-retracting clearance cutter, or expansion cutter, which is adjustable in the extent of expansion thereof.

Another and very important feature of the invention is the fact that the expansion tooth holders are displaced approximately 90 from the cutting tooth holders and this provides four point contact of the head with the ground being excavated. The four point contact results in more true alignment of the hole being dug and also a more precise diameter. One of the problems of existing expansion head augers is that elliptic holes are cut because the expansion tooth holders are mounted on the same arms as the cutting tooth holders. Mounting expansion holders displaced relative to the cutting holders in accordance with the present invention keeps the auger on center and maintains a more accurate grade. The four point expansion more adequately supports the weight of the head on the sidewalls of the hole being excavated and thus helps to overcome the tendency for the auger to deviate downwardly from a straight line.

Anotherfeature of the invention is the provision of convenient means for adjusting the amount of outward expansion of the expansion teeth to accommodate different outside diameters of casing and also to compensate for wear of the teeth with the passage of time.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a schematic, side elevational view showing a head in accordance with the present invention and a portion of an auger to which it is attached engaged in horizontal boring.

FIG. 2 is an end elevation of the structure of FIG. 1.

FIG. 3 is a fragmentary plan view of the arm on which the expansion holder is mounted partially broken away to reveal internal construction and also to conserve space.

FIG. 4 is a fragmentary, side elevational view of a portion of FIG. 3.

The present invention is intended for use on an auger such as conventional auger 11 which has a central shaft 12 about which is disposed one or more helical flights 13. On the working end of shaft 12 is a head 14 which may be formed with a hub 16 attached to the end of the shaft 12. In the accompanying drawings a pilot bit 17 is attached to the forward end of hub 16, and said bit may have removable bit teeth 18 in accordance with U. S. Pat. No. 3,426,860 or may be otherwise constructed.

Extending radially, displaced 180 from each other, are digging arms 19 and attached thereto on either side of the head are castings 21 held in place by means of bolts 22 and having a plurality of sockets 23 for the purpose of securing removable digging teeth 24. The position, number and shape of teeth 24 is subject to considerable variation. Various means may be used to hold the teeth 24 in place, such as the means shown in U. S. Pat. No. 2,968,880.

Immediately rearward of arms 19 are front and rear expansion arms 26, 27. Arms 26, 27 are parallel to each other and angularly displaced relative to arms 19 by (see FIG. 2). Arms 26, 27 are preferably spaced apart in the direction of the axis of shaft 12 a short distance by spacer 28 at the center. Additional spacers 29 are positioned between the outer ends of the arms 26, 27. As best shown in FIG. 3, the outer spacers 29 are semicircular in shape and at least one end 31 is radially disposed. Between each end of arms 26, 27 is an expansion holder 32 having a set screw 33 extending through projection 35 and bearing against end 31. Jam nut 34 holds the set screw 33 in the required position of adjustment. Holder 32 pivots about pivot pin 36 which passes through the arms 26, 27 and is held thereby. The outer end of holder 32 is provided with a socket 37 to receive an expansion tooth 38. Again, the shape and manner of holding tooth 38 is subject to variation, but a preferred shape and means is disclosed in U.S. Pat. No. 2,968,880.

The head 14 is intended for use in horizontal boring. In such use, the shaft 12 is rotated and moved axially by means of a machine (not shown) which also forces behind the head 14 a casing 41 which is very slightly less than the size of the hole being dug and which supports the walls of the hole against cavitation and also supports the weight of the earth above the hole and any structures thereon against collapse. In use of the device, the shaft 12 is rotated so that the head 14 turns in clockwise direction as viewed in FIG. 2. The pilot bit 17 tends to maintain the direction of the hole being dug in a straight line. The arms 19 are preferably slightly smaller than the internal diameter of casing 41 and dig out the earth as the head advances. The earth is then conveyed to the opposite end of the auger by the flight 13, all as well understood in the earth digging art. When the auger is turning in digging direction, the outer ends of the teeth 38 encounter the wall of the hole being dug and tend to pivot the holder 32 outwardly i.e., counter-clockwise as viewed in FIG. 2 about pivots 36. The extent of their outward pivoting is adjusted by means of set screw 33 which bears against end 31. Preferably, the teeth 38 dig a hole which is just slightly larger than the outside diameter of casing 41 so that the casing may be driven behind the head as cutting continues. When the excavation is completed, the shaft 12 is turned in an opposite direction and this causes the holder 32 to pivot inwardly thus permitting the head to be withdrawn within the casing 41 and removed.

Although the pilot bit 17 and the rigidity of shaft 12 tend to keep the hole being excavated by the head 14 in a straight line, nevertheless there is a tendency for the direction of the hole to drift downwardly under the influence of gravity and this is augmented when hard structures such as rocks are encountered which give a downward thrust. In the types of expansion heads which have hitherto been used, the expansion tooth holders are mounted on the outer ends of arms 19 and do not satisfactorily overcome the tendency toward downward deviation. Another effect of downward deviation of the auger head is the tendency to dig a hole which is non-circular, that is, which is deeper at the bottom than elsewhere around the perimeter and this may cause a subsidance of the ground surface above the hole being dug. It is one of the features of the present invention, as best shown in FIG. 2, that there are four points 42 at which the head 14 is supported by the wall of the hole being dug. These are, respectively, the two points at which the outermost teeth 24 engage the wall of the hole being dug and the two points at which the teeth 38 engage said wall. The four point suspension is much more effective than two point suspension in overcoming the deviation heretofore mentioned.

What is claimed is:

1. An earth auger head having an axis of rotation comprising a shaft, a plurality of first arms each carrying a plurality of first tooth holders, first teeth in said first tooth holders, said first teeth positioned to bore earth at the end of a hole substantially transverse to said axis of rotation, a plurality of second arms spaced rearwardly of said first arms and disposed substantially midway between said first arms, said second arms comprising diametrically disposed, parallel, thin, narrow front and rear expansion arms, each said expansion arm transverse to said axis and spaced relative to each other along said axis, said first and second arms fixed to said shaft, an expansion holder mounting means on the outer end. of each said second arm disposed between said front and rear expansion arms, a pair of spacers between said front and rear expansion arms spacing said expansion arms apart, an expansion holder pivotally mounted in each said mounting means about a second axis parallel to said axis of rotation, a second tooth in each said expansion holder pivoting about said second axis between a retracted position inside the perimeter of the hole bored by said first teeth and an extended position outside said perimeter, said second teeth positioned to dig the outside of said hole when in extended position, said second teeth when in extended position being substantially midway between the two adjacent outermost first teeth when viewed in a direction parallel to said axis of rotation, said expansion holders pivoting to extended position when said head is rotated in one direction of rotation and to retracted position in reverse direction of rotation of said head.

2. A boring head according to claim 1 in which one saidspacer is located adjacent the outer end of said second arm and is formed with an abutment and each said holder has a set screw engaging said abutment to limit the outward extension of the second tooth held in said holder.

3. An earth auger head according to claim 1 which further comprises a first abutment on each said second arm and a second abutment on each said expansion holder, said abutments coming into contact with each other to limit outward pivotal movement of said holder as said head is turned about its axis of rotation in first direction to limit the outside diameter of the hole being bored. 7

4. A boring head according to claim 3 in which one said abutment is adjustable in position to adjust the size of said outside diameter.

Claims (4)

1. An earth auger head having an axis of rotation comprising a shaft, a plurality of first arms each carrying a plurality of first tooth holders, first teeth in said first tooth holders, said first teeth positioned to bore earth at the end of a hole substantially transverse to said axis of rotation, a plurality of second arms spaced rearwardly of said first arms and disposed substantially midway between said first arms, said second arms comprising diametrically disposed, parallel, thin, narrow front and rear expansion arms, each said expansion arm transverse to said axis and spaced relative to each other along said axis, said first and second arms fixed to said shaft, an expansion holder mounting means on the outer end of each said second arm disposed between said front and rear expansion arms, a pair of spacers between said front and rear expansion arms spacing said expansion arms apart, an expansion holder pivotally mounted in each said mounting means about a second axis parallel to said axis of rotation, a second tooth in each said expansion holder pivoting about said second axis between a retracted position inside the perimeter of the hole bored by said first teeth and an extended position outside said perimeter, said second teeth positioned to dig the outside of said hole when in extended position, said second teeth when in extended position being substantially midway between the two adjacent outermost first teeth when viewed in a direction parallel to said axis of rotation, said expansion holders pivoting to extended position when said head is rotated in one direction of rotation and to retracted position in reverse direction of rotation of said head.

2. A boring head according to claim 1 in which one said spacer is located adjacent the outer end of said second arm and is formed with an abutment and each said holder has a set screw engaging said abutment to limit the outward extension of the second tooth held in said holder.

3. An earth auger head according to claim 1 which further comprises a first abutment on each said second arm and a second abutment on each said expansion holder, said abutments coming into contact with each other to limit outward pivotal movement of said holder as said head is turned about its axis of rotation in first direction to limit the outside diameter of the hole being bored.

4. A boring head according to claim 3 in which one said abutment is adjustable in position to adjust the size of said outside diameter.

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