|Publication number||US3749446 A|
|Publication date||Jul 31, 1973|
|Filing date||Aug 25, 1971|
|Priority date||Aug 25, 1971|
|Publication number||US 3749446 A, US 3749446A, US-A-3749446, US3749446 A, US3749446A|
|Original Assignee||Doty J|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (5), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
[451 July 31, 1973 United States Patent 1 Doty Primary Examiner-Ernest R. Purser An0meyForrest .l. Lilly i 1 TRENCHING MACHINE Inventor: John T. Doty, 2238 E. 21st St., Long Beach, Calif. 90810 Aug. 25, 1971  ABSTRACT A trenching machine having a vertically swinging boom pivotally mounting a weighted trenching  Filed:
 Appl.No.: 174,705
stick with for selectively swinging the boom vertically and the trenc lower trenching teeth and operating means 3mm mmk m t stick horizontally relative to the boom to excav trench and releasing the boom and trenching stic drop freely from an elevated posi U .mm
material encountered in the trenc trenching stick has telescoping members interconnected by energy absorbing means which isolate from the boom the shock forces produced by the impact of the stick with the ground and cushion relative rebound  References Cited UNITED STATES PATENTS movement of the members following impact. The boom is raised and released to drop by a winch including a a dead end anchored to the machine by a ring which yields to permit braking of the winch thout danger of parting or a v r I 1 1 spilling the cable.
9 Claims, 3 Drawing Figures 78 to Hoist winch drum to Drug winch drum PATENTEBJULB 1 I975 to Hoist winch drum to Drug winch drum John T. Dofy,
ATTORNEY TRENCHING MACHINE BACKGROUND OF THE INVENTION 1. Field This invention relates generally to earth working machines and more particularly to an improved trenching machine.
2. Prior Art A trenching machine is an earth working machine for excavating trenches in the ground to receive pipe, electric cables, and the like. A variety of such trenching machines have been devised. Most, if not all, of these existing machines suffer from the disadvantage of being incapable of trenching in or through hard materials, such as various types of earth formations, rocks, and the like. As a consequence, when such hard materials are encountered, it is necessary to employ auxiliary equipment to break up the material, which is both time consuming and costly.
BRIEF SUMMARY OF THE INVENTION The present invention provides an improved trenching machine which is uniquely constructed to excavate trenches in both relatively soft and relatively hard materials. Accordingly, when a hard material is encountered in a trenching operation, the latter may continue uninterrupted without the need to employ auxiliary equipment to break up the hard material.
To this end, the trenching machine has a boom pivotally mounted at its inner end on a vehicle, such as a self-propelled crawler and pivotally mounting at its outer end a weighted trenching device commonly referred to as a trenching stick. Projecting longitudinally from the lower end of this trenching stick are trenching teeth. Operating means, such as hoist and drag winches including cables extending between winch drums on the vehicle and the upper and lower ends of the trenching stick, are provided for raising and lowering the boom and trenching stick and swinging the stick on its pivotal connection to the boom to excavate a trench. The winches may also be operated to release the boom and trenching stick to drop freely from an elevated position for fragmenting hard material.
According to one important feature of the invention, the trenching stick is uniquely constructed to isolate from the boom and other machine parts the shock forces produced by impact of the stick with the ground, thus to avoid damage to the boom and other parts. To this end, the trenching stick is constructed in two telescoping sections interconnected by energy absorbing springs. When the boom and trenching stick are dropped to fragment hard material, the energy absorbing springs yield following impact of the trenching stick with the material to absorb the kinetic energy of the descending boom and upper stick section. The energy absorbing springs also cushion rebound of the trenching stick sections to their normal extended relation following impact.
The hoist winch of the trenching machine is equipped with a brake which the operator applies to brake the winch drum following impact of the trenching stick, with the ground. If the brake is applied too soon, the descending boom and trenching stick may be retarded by the winch cable prior to impact with a sufficient force to part the cable. On the other hand, if the brake is applied too late, the cable may spill from the winch drum, in which case the cable must be properly rewound on the drum.
According to an additional feature of the invention, the hoist cable has a dead end which is anchored to the machine by a spring which yields to avoid both parting and spilling of the cable.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a trenching machine according to the invention;
FIG. 2 is an enlarged side elevation of the trenching stick of the machine; and
FIG. 3 is an enlarged section taken on line 33 in FIG. 2.
DESCRIPTION OF A PREFERRED EMBODIMENT The trenching machine 10 of the invention illustrated in the drawings has a vehicle 12, such as a crawler, mounting a rotary platform 14 which turns on a normally generally vertical axis. Pivotally mounted at its inner end on the platform 14, to swing vertically on a normally generally horizontal axis 16, is a boom 18. A trenching stick 20 is pivotally mounted on the outer end of the boom 18 to swing on a pivot axis 22 parallel to the inner boom axis 16. Operating means 24 are provided for selectively swinging the boom 18 vertically and swinging the trenching stick 20 horizontally relative to the boom to excavate a trench and for releasing the boom and stick to drop freely from an elevated position to fragment hard material. 7
' The trenching stick 20 has a telescoping construction and includes upper and lower telescoping sections 30, 32. The upper section 30 has upper and lower tubular members 34, 36 with abutting flanges 38 which are bolted together to join the members into a rigid unit. A reinforcing rib 40 is welded to the front side of the upper tubular member 34. Welded to the rear side of the upper tubular member 34 adjacent its lower end is a tongue 42 which is attached by a pivot 44 to the outer end of the boom 18.
The lower trenching stick section 32 has an upper tubular member 46 rigidly joined at its lower end to a relatively massive lower member 48, referred to as a billet. The upper tubular member 46 slides within the lower tubular member 36 of the upper trenching stick 7 section 30. Welded or otherwise rigidly joined to opposite sides of the tubular members 36, 46 are brackets 50. Compression springs 52 are mounted between and seat at their ends against these brackets to yieldablyresist relative telescoping movement of the trenching stick sections 30, 32. The spring brackets 50 mount spring retainers 54 which engage within the ends of the springs 52 to locate the springs laterally relative to the brackets.
Springs 52 yieldably urge the trenching stick sections 30, 32 to extended positions. Extending slidably through the spring brackets 50 and centrally through the springs 52 are tie bolts 56 having upper and lower shoulders 58. Between the upper spring brackets 50 and tie bolt shoulders 58 are compression springs 60 which surround the bolts and seat against the brackets and shoulders. Tie bolts 56 and springs 60 limit relative extension movement of the members 30, 32 and cooperate with the springs 52 to normally retain the members in their partially extended positions of FIG. 1. As will be explained presently, the springs 52, 60 together constitute an energy absorbing means 62 which serves to isolate from the boom 18 and other machine parts the shock force produced by impact of the trenching stick 20 with hard material to be fractured and to cushion relative rebound extension movement of the stick sections 30, 32 following impact.
At the lower end of the trenching stick 20 are longitudinally projecting trenching teeth 64. These teeth are rigidly joined to a base plate 66 which, in turn, is firmly attached to the lower end of the billet 48.
The operating means 24 of the trenching machine includes a hoist winch 68 and a drag winch 70 on the vehicle platform 14. The vehicle 12 is propelled and the winches 68, 70 powered by an engine 72 on the vehicle. Winches 68, 70 include drums 74, 76. Attached at one end to the hoist drum 74 is a hoist cable 78. This cable extends from the hoist drum upwardly to and around a pulley 80 on an upstanding frame 82 fixed to the platform 14, then outwardly to and around a pulley 84 on the upper end of the trenching stick 20, then back to and around a second pulley 86 on the frame 82, and finally outwardly to and around a second pulley 88 on the upper end of the stick. The outer end of the hoist cable 78, referred to as its dead end, is attached to a bolt 90 which extends centrally through a spring 92 within the upper trenching stick member 34. The upper end of this spring seats against a plate 94 which is fixed within the upper stick'member and through which the bolt 90 slidably extends. The lower end of the spring seats against a shoulder 96 on the lower end of the bolt.
Fixed at one end to the drag winch drum 76 is a drag cable 98. This drag cable extends from the drum over a pulley 100 on the inner end of the boom 18, then outwardly to and around a pulley 102 attached by a pivotcd link 104 to the rear side of the billet 48, then back to and around a second pulley 106 on the inner end of the boom, and finally back to the link 104 to which the cable is attached by a cable socket 108.
In normal trenching operation of the trenching machine, the hoist and drag winches 68, 70 are operated to raise and lower the boom 18 and swing the trenching stick 20 horizontally relative to the boom to excavate a trench. More specifically, this trenching operation involves periodically swinging the lower end of the stick forwardly relative to the boom, lowering the boom to engage the trenching teeth 64 with the ground, drawing the lower end of the stick toward the vehicle 12 to drag the teeth rearwardly along the ground, and then elevating the boom and repeating the procedure until the trench has been excavated to the desired depth. The machine is then advanced to a new section of ground and the entire operation repeated.
When rock or other hard material is encountered which must be first fragmented or broken up before trenching can continue, the hoist and drag winches 68, 70 are operated to elevate the boom 18 and trenching stick 20 with the latter in a generally vertical attitude over the hard material and then release the boom and stick to drop freely into impact with the material. The kinetic energy of the descending boom and stick, and particularly the billet 48, drives the trenching teeth 64 into the material to break up the latter. This procedure is repeated until the hard material is sufficiently fragmented to permit resumption of normal trenching operation.
As noted earlier, the energy absorbing means 62 serves the twofold function of isolating from the boom 18 the shock forces produced by impact of the trenching stick 20 with hard material being fragmented and cushioning rebound movement of the trenching stick sections 30, 32 following impact. Thus, each time the trenching stick is released to drop into impact with hard material, the stick sections 30, 32 descend in unison until the lower end of the stick impacts the material. The lower stick section 32 is then suddenly arrested. The upper stick section 30 and boom 18, on the other hand, continue to descend with resultant relative telescoping movement of the stick sections and compression of the springs 52. Compression of these springs gradually absorbs the kinetic energy of the descending boom and upper stick section to arrest the same without any severe shock loading of the boom or other machine parts. Immediately after impact, the compression springs 52 reexpand to return the stick sections 30, 32 to their normal extended positions in a relatively high speed rebound motion. Springs 60 cushion this rebound of the sections to prevent severe shock loading of the tie bolts 56 and spring brackets 50.
Included in the hoist and drag winch controls are brakes for the winch drums 74, 76. During fragmenting operation of the machine, the hoist winch brake is applied at the end of each downward stroke of the trenching stick. If this brake is applied too soon, i.e., before impact of the stick with the ground, a tension load is applied to the hoist cable 78 which tends to part the cable. On the other hand, if the brake is applied too late, i.e., after impact, continued rotation of the hoist drum 74 because of its momentum will tend to spill cable from the drum, requiring the cable to be properly rewound on the drum.
The hoist cable spring 92 is provided to prevent such parting and spilling of the hoist cable 78. Thus, if the hoist winch brake is applied too soon, the spring yields to avoid excessive tension in the hoist cable. On the other hand, if the brake is applied too late, the spring, which is normally partially compressed, even during free fall of the trenching stick 20 due to the drag of the hoist cable, expands upon impact to take up any slack in the hoist cable to prevent spilling of the cable. If desired, the dead end of the hoist cable may be anchored to the vehicle platform 14 through the cable spring 92.
1. A trenching machine, comprising:
a vehicle; I
a boom pivotally mounted at its inner end on said vehicle to swing vertically on a normally generally vertical pivot axis;
a weighted trenching stick at the outer end of said boom including an elongated upper member pivotally mounted on the outer end of the boom to swing on a transverse pivot axis below the upper end of the stick and parallel to said inner boom axis, a lower toothed trenching member movable lengthwise of the upper member, and resilient energy absorbing means acting between said members to yieldably resist longitudinal movement of said lower member relative to said upper member;
operating means for selectively swinging said boom vertically and swinging said trenching stick relative to the boom to excavate a trench, and releasing said boom and stick to drop freely from an elevated position to fragment hard material encountered in the trenching operation, said operating means comprising winch means for raising and lowering said boom and elevating and then releasing said boom to drop freely, said winch means including a powered winch drum on said vehicle, a cable attached at one end to said drum and extending between said drum and the outer ends of said boom to raise and lower the boom upon winding of the cable on and unreeling of the cable from the drum, and a spring in said cable to permit dropping and braking of the boom without parting of the cable or spilling of the cable from the drum.
2. A trenching machine according to claim 1, wherein said cable spring is anchored to and carried by said trenching stick.
3. A trenching machine according to claim 1, wherein said cable extends in a number of runs around pulleys on said vehicle and the outer end of said boom to reduce the load on said cable spring.
4. A trenching machine according to claim 1, wherein said cable is connected to the upper end of said trenching stick, whereby said winch means may be operated to swing the lower end of said trenching stick away from said vehicle, and
said operating means comprises a second winch means including a second powered winch drum on said vehicle and a second cable attached at one end to said second drum and extending between said lattcr drum and the lower end of said stick, whereby said second winch means may be operated to swing the lower end of said trenching stick toward said vehicle.
5. A trenching machine according to claim 4, wherein said trenching stick members comprise telescoping members;
said energy absorbing means comprise springs for resisting relative telescoping movement of said members to cushion impact of said lower member with hard material to be fractured and springs for resisting relative extension movement of said members to cushion relative rebound movement of the members under the force of said first mentioned springs following impact, and
said lower trenching stick member comprises a relatively massive billet and projecting teeth on the lower end of the billet.
6. A trenching machine according to claim 5, wherein said cable spring is contained within the upper end of said trenching stick and is anchored to said upper stick member.
7. A trenching machine, comprising:
a boom pivotally mounted at its inner end on said vehicle to swing vertically on a normally generally vertical pivot axis;
a weighted trenching stick pivotally mounted on the outer end of said boom to swing on a transverse pivot axis of the stick parallel to said inner boom axis and having projecting trenching teeth at the lower end of the stick; and
operating means for selectively raising and lowering said boom and swinging said trenching stick on its pivotal connection to said boom to excavate a trench, and releasing said boom and stick to drop freely from an elevated position to fracture hard material encountered in the trenching operation, said operating means comprising a winch means to raise, lower and release said boom to drop freely including a powered winch drum on said vehicle, a cable attached at one end to said drum and extending between said drum and the outer end of the boom, and a spring anchored at one end to said machine and attached at its other end to the other end of said cable to permit braking of said boom at the end of its drop without parting of the cable or spilling of the cable from said drum.
8. A trenching machine according to claim 7,
wherein said spring is carried by said trenching stick.
9. A trenching machine according to claim 8, wherein said spring is contained within the upper end of said trenching stick and is anchored to the upper stick member.
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|U.S. Classification||299/37.3, 173/87, 175/299|