Technical field

Information

  • Patent Grant
  • 6349488
  • Patent Number
    6,349,488
  • Date Filed
    Friday, November 12, 1999
    25 years ago
  • Date Issued
    Tuesday, February 26, 2002
    22 years ago
  • Inventors
  • Examiners
    • Batson; Victor
    Agents
    • Stratton Ballew PLLC
Abstract
A trencher mountable on a vehicle such as a tractor, includes a substantially horizontal hollow stationary member positioned substantially perpendicular to the direction of travel of the vehicle, an extension member which is slidably receivable within the stationary member and a member for extending and retracting the extension member with respect to the stationary member. The trencher further includes a swiveling member pivotably attached to one end of the extension member with the swiveling member being horizontally pivotable with respect to the extension member. The trencher further includes a trenching head attached to the other end of the swiveling member, the trenching head including a trenching wheel and a device for pivotably raising and lowering the trenching head with respect to the swiveling member, and a frame for mounting the trencher to the vehicle.
Description




TECHNICAL FIELD




The invention relates to the field of digging implements. More specifically, the invention provides an apparatus and method for digging narrow trenches.




BACKGROUND OF THE INVENTION




In the field of irrigation system installation, as well as in other fields, it is often necessary to provide shallow, narrow trenches in which to bury irrigation pipes and the like. The formation of the trenches is usually achieved using a trencher. The trencher is a device which cuts into the soil to leave a narrow trench of desired depth. The trencher may either be a complete implement including motivation means, or it may be an implement which is attachable to the power take-off (PTO) or hydraulics system of a powered implement such as a tractor, backhoe or loader. Generally, the trencher is substantially centered behind the motivation means, creating a trench that is parallel to the direction of travel.




Until recently, the commonly known and commercially available trenchers met the needs of those irrigation system installers who installed irrigation systems in orchards. When it was necessary to install or replace irrigation lines, the installer simply drove the trencher between the trees—either along the defined planting rows, or perpendicular to them—to make trenches where necessary. However, relatively recently evolved cultural practices in orchards, especially apple orchards, have rendered trenchers only partially useful in digging trenches for orchard irrigation lines. Specifically, many orchardists have begun replacing older trees with new varieties which grow closer to the ground, and require trellising for optimal production. The trellising and the trees themselves make it impossible for a conventional trencher to pass between trees perpendicular to the planting rows. Therefore, any additional or replacement irrigation lines in an established trellised orchard require that the trench be dug by hand. A similar problem exists in vineyards, where grape plants are planted too close together to allow the passage of a conventional trencher or tractor.




SUMMARY OF INVENTION




The present invention provides a trencher which is mountable on a vehicle such as a tractor. The trencher includes a hollow stationary member, and an extension member which is slidably receivable within the stationary member. A means is provided for extending and retracting the extension member with respect to the stationary member. The trencher further includes a swiveling member pivotably attached to one end of the extension member, and a trenching head attached to the end of the swiveling member. The swiveling member is securable in a position parallel to the extension member. A means is provided for raising and lowering the trenching head with respect to the swiveling member. The trencher is mounted to the vehicle with a mounting frame.




In an embodiment of the invention, the means for raising and lowering the trenching head is a hydraulic actuator.




In an additional embodiment of the invention, the means for extending and retracting the extending member is a hydraulic actuator.




In a further embodiment of the invention, the swiveling member is alternatively securable in a perpendicular position relative to the extension member.




In an additional embodiment of the invention, the swiveling member is securable in a stored position.




In yet a further embodiment of the invention, the trencher includes a cradle for receiving the trenching head in a stored position.




In an additional embodiment, the trenching head includes a body; a motor having a motor shaft; a motor compartment within the body for receiving the motor; a first sprocket affixed to the motor shaft positioned outside the motor compartment; a wheel shaft for being received within the trenching wheel; a second sprocket affixed to the wheel shaft; and a drive chain operatively engaged between the first sprocket and the second sprocket.




In an embodiment, the trenching head includes a protective case affixed to the body for enclosing the motor shaft, drive chain, and sprockets.




In an embodiment, the trencher includes a first deflector and a second deflector. The first deflector directs dirt and debris away from a newly cut trench, positioned over the trenching head. The first deflector includes a first plate and a second plate. Each plate has an upper edge, and the upper edges meet to form an apex over the trenching wheel. The second deflector is positioned over the trenching head, opposite the first deflector, and is for directing dirt and debris tossed up by the trenching wheel onto the first deflector.




In another embodiment, the first plate and the second plate of the first deflector are made of sheet steel and heavy rubberized fabric. The rubberized fabric is positioned adjacent to the trenching wheel.




In another embodiment, the motor for turning the trenching wheel is a hydraulic motor.




In an additional embodiment, a dolly wheel is attached to the body of the trenching head for supporting the trenching head while in use in a “float” mode.











BRIEF DESCRIPTION OF DRAWINGS





FIG. 1

is a perspective view of a trencher of the present invention, showing the trencher in a parallel, extended position;





FIG. 2

is a perspective view of a trencher of the present invention, showing the trencher in a parallel, retracted position;





FIG. 3

is a perspective view of a trencher of the present invention, showing the trencher in a perpendicular position;





FIG. 4

is a rear elevation view of a trencher of the present invention, showing the trencher in a parallel, retracted position;





FIG. 5

is a top plan view of a trencher of the present invention, showing the trencher in a parallel, retracted position;





FIG. 6

is a top plan view of a trencher of the present invention, showing the trencher in a parallel, extended position;





FIG. 7

is a rear elevation view of a trencher of the present invention, showing the trencher in an extended, operating position;





FIG. 8

is a top plan view of a trencher of the present invention, showing the trencher in a retracted perpendicular operating position;





FIG. 9

is a side elevation view of a trencher of the present invention, showing the trencher in a retracted perpendicular operating position;





FIG. 10

is a top plan view of a trencher of the present invention, showing the trencher in a retracted, semi-stored position;





FIG. 11

is a rear elevation view of a trencher of the present invention, showing the trencher in a retracted, stored position;





FIG. 12

is a side elevation view of a trencher of the present invention, showing the trencher in a retracted, stored position;





FIG. 13

is a side elevation view of a trencher of the present invention, showing the trencher in a retracted, stored position;





FIG. 14

is a partial top plan view of a trencher of the present invention, showing the trencher head; and





FIG. 15

is a partial side elevation view of a trencher of the present invention, showing the trencher head.











DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS




The trencher


10


of the present invention is shown in

FIGS. 1-15

. In general, the trencher comprises an arm


12


, a trenching head


14


, a mounting frame


16


and a cradle


18


for securing the trenching head in a stored position when not in use.

FIGS. 1 through 13

show a preferred embodiment of the trencher attached to a tractor, although the trencher may be used with any vehicle capable of supporting and moving the trencher, and providing power thereto, as will be discussed in greater detail below.




The arm


12


of the trencher


10


includes a horizontal stationary member


20


, and an extension member


22


which is slidably received within the stationary member. In an alternative preferred embodiment, the extension member includes two or more telescoping sections (not shown). The extension member


22


of the arm


12


has a first end


24


and a second end


26


. The extension member first end is received within the stationary member. In a preferred embodiment of the invention, the stationary member is provided with a plurality of rollers


28


positioned along its length to aid the sliding movement of the extension member therein.




A means for extending and retracting the extension member is provided by the invention. In a preferred embodiment, a first hydraulic actuator


30


having a first end


32


and a second end


34


is provided for extending and retracting the extension member


22


of the arm


12


relative to the stationary member


20


. The first end of the first hydraulic actuator is pivotally joined to the stationary member at a first pivot connector


36


, and the second end of the first hydraulic actuator is similarly pivotally joined to the extension member at a second pivot connector


38


. A hydraulic actuator made by Applied Industrial Technology (part no. 22411) has been used successfully. In addition to a hydraulic actuator, the use of other extending and retracting means is also contemplated.




The arm


12


further comprises a swiveling member


40


having a first end


42


and a second end


44


. The second end


26


of the extension member


22


and the first end of the swiveling member are joined by a first hinge


46


. The first hinge has a vertical axis, allowing the swiveling member to move on a horizontal plane.




The trenching head


14


of the trencher


10


is joined by a second hinge


48


to the second end


44


of the swiveling member


40


. The second hinge has a horizontal axis, permitting the trenching head to be tilted in an upward and downward direction with respect to the swiveling member. A means for raising and lowering the trenching head is provided by the invention. In a preferred embodiment, a second hydraulic actuator


50


, having a first end


52


and a second end


54


, is pivotally joined at its first end to a third pivot connector


56


. The second hydraulic actuator is pivotally joined at its second end to a fourth pivot connector


58


. A hydraulic actuator made by Applied Industrial Technology (part no. 2060 B) has been used successfully. In addition to a hydraulic actuator, the use of other means for raising and lowering the trenching head is also contemplated.




The trenching head


14


is shown in detail in

FIGS. 14 and 15

. The trenching head includes a body


60


having a motor compartment


62


therein for receiving a motor


64


. In a preferred embodiment, the motor is a hydraulic motor. A hydraulic motor made by Applied Industrial Technology (part no. 104-1004) has been used successfully. As shown in

FIGS. 1

,


2


,


3


,


5


,


6


,


8


, and


10


, a motor compartment cover


66


is provided for enclosing the motor compartment to protect the motor from dirt, rocks and other debris. The motor compartment cover is removably secured on the motor compartment using screws or other fastening means. The motor


64


has a motor shaft


68


which extends through the body


60


to receive a first sprocket


70


.




The trenching head


14


further comprises a trenching wheel


72


. The trenching wheel has a plurality of teeth


74


attached thereto for breaking up and lifting soil. In a preferred embodiment, the teeth are removably attachable to the trenching wheel. This allows broken or damaged teeth to be quickly and easily removed and repaired or replaced, without having to replace the entire trenching wheel. Digging teeth manufactured by Ditch Witch (part nos. 133-925 and 133-924) have been used successfully.




The digging wheel rotates about a horizontal wheel shaft


76


. Preferably, the wheel shaft is hexagonal in cross section, and removably receivable in the trenching wheel. A hex shaft manufactured by Ditch Witch (part no. 145-244) has been used successfully for the wheel shaft. In this preferred embodiment, the trenching wheel is held in position on the wheel shaft with a hex bearing. Hex bearings manufactured by Ditch Witch (part no. 125-620) have been used successfully. The wheel shaft is fitted with a second sprocket


78


. A drive chain


80


is operatively engaged on the first sprocket


70


and the second sprocket. Also preferably, the first and second sprockets and the drive chain are enclosed in a protective case


82


as shown in

FIGS. 1 through 8

and


10


, to prevent debris from fouling the sprockets, drive chain, and cooperating parts. Lubrication of the chain and sprockets is accomplished through a capped port


84


provided in the protective case. Sprockets made by Applied Industrial Technology (part nos. 100BS10X1 and 10010016) have been used successfully for the first and second sprockets.




In a preferred embodiment, the trenching head


14


includes a first deflector


86


for deflecting debris away from a newly cut trench, and away from the wheel shaft


76


, as detailed in

FIGS. 14 and 15

. The first deflector has a first sloped panel


88


with an upper edge


90


, a lower edge


92


, a leading edge


94


, and a trailing edge


96


; and a second sloped panel


98


with an upper edge


100


, a lower edge


102


, a leading edge


104


, and a trailing edge


106


. The upper edges of the panels meet to form an apex


108


, except where a gap between the panels is left for the trenching wheel


72


to protrude. Preferably, the sloped panels are fabricated of sheet steel and heavy rubberized fabric, with the rubberized fabric making up the part of the sloped panels adjacent to the trenching wheel. The rubberized fabric is slightly elastic, and thus minimizes jams caused by rocks becoming wedged between the trenching wheel and the sloped panels. The lower edges of the panels extend laterally beyond the body


60


of the trenching head


14


. The leading edges of the panels extend forwardly, beyond the end of the trenching head, and the trailing edges extend in the opposite direction to cover the wheel shaft within the body of the trenching head. In a preferred embodiment, the first deflector further comprises a lip


110


which extends perpendicularly from the leading edges of the panels. The first deflector is affixed to the body of the trenching head with a pair of mounting brackets


112


, and extends upwardly and outwardly therefrom.




A second deflector


114


is affixed to the body


60


of the trenching head


14


opposite the first deflector. The second deflector forms a canopy over a portion of the trenching wheel


72


, and serves to direct dirt and debris onto the first deflector


86


.




According to the invention, power for the hydraulic actuators


30


and


50


and the motor


64


is provided by a hydraulic power source, including one or more pumps, on the vehicle to which the trencher


10


is mounted. A first hydraulic line


116


is provided from the hydraulic power source to the first hydraulic actuator


30


; a second hydraulic line


118


is provided from the hydraulic power source to the second hydraulic actuator


50


; a third hydraulic line


120


and a fourth hydraulic line


122


are provided from the hydraulic power source to the motor


64


. To provide added power to the trenching wheel, the motor may be served by a hydraulic pump separate from the pump serving the hydraulic actuators. Conventional hydraulic valves are utilized to control power to the actuators and motor.




The trencher


10


of the present invention is mounted on a vehicle such as a tractor. In use, the tractor advances in a direction x. The trencher is adapted to dig a trench which follows direction x. Additionally, the trencher is adapted to dig a trench in direction y, where x and y are perpendicular. Thus, the trencher of the present invention can be used in a situation where trenches are required in both direction x and direction y. For example, a low-trellised apple orchard is planted in rows. A tractor can travel along the planting rows, but it cannot travel between the trees, in a direction perpendicular to the planting rows, because the branches and trellising are too close to the ground to permit passage. The trencher of the present invention would be useful in this example, because it can dig a trench along the planting row, in direction x, and then, with a simple adjustment to the trencher, be used to dig trenches in direction y, between the trees of the planting row.




To use the trencher


10


of the present invention to dig a trench in direction x, the trencher is secured in a first configuration X, as shown in

FIGS. 3

,


8


and


9


. In this configuration, the swiveling member


40


is parallel to direction x, and perpendicular to the extension member


22


. In a preferred embodiment, a retaining bar


130


having a first end


132


and a second end


134


is provided for securing the swiveling member in configuration X. Both the first end and the second end of the retaining bar have a hole for receiving a bolt or a peg. The second end


26


of extension member


22


includes a horizontal first tab


126


with a hole therethrough. Similarly, the first end


42


of the swiveling member


40


includes a horizontal second tab


128


with a hole therethough. In use, the hole in the first end of the retaining bar is aligned with the hole in the first tab, and a peg or bolt is inserted into the holes. Likewise, the hole in the second end of the retaining bar is aligned with the hole in the second tab, and a peg or bolt is inserted into the holes to secure the retaining bars in place.




In configuration X, the trencher


10


is operated by activating the hydraulic power supply to extend the first hydraulic actuator


30


from the retracted position shown in

FIG. 8

, if necessary, to reach the desired starting point. When the arm is extended to the desired length, the trenching head


14


is lowered to the soil by activating the hydraulic power supply to extend the second hydraulic actuator


50


, causing the trenching head to pivot in a downward direction on the second hinge


48


. In order to begin the trenching operation, the hydraulic power supply is activated to provide power to the motor


64


, which turns motor shaft


68


. As the motor shaft turns, first sprocket


70


also turns, engaging drive chain


80


. The drive chain turns the second sprocket


78


, which in turn rotates the trenching wheel


72


. As the trenching wheel rotates, the teeth


74


cut a trench in the soil. The trenching head


14


can be lowered to the desired depth once the trenching wheel begins to turn. As the trenching wheel


72


and teeth


74


cut a trench in the soil, dirt and debris are tossed upward into the trenching head, and sprayed out and deflected by the second deflector


114


to land on the first deflector


86


. The first deflector directs the dirt and debris away from the trenching wheel, and causes it to fall away outside the newly cut trench.




With the trenching wheel


72


still turning, the vehicle is advanced, thereby causing the trencher


10


to dig a trench in direction x, parallel to the direction of travel of the vehicle. When the trench is complete, the motor


64


is stopped and the second hydraulic actuator


50


is then retracted, thus raising the trenching head


14


above the ground.




In

FIGS. 1

,


2


,


4


,


5


,


6


, and


7


, the trencher


10


is shown in configuration Y. In this configuration, the swiveling member


40


is parallel to direction y, and parallel to the extension member


22


. In use, the trencher is locked in configuration Y aligning the hole in the horizontal first tab


126


the hole in the horizontal second tab


128


, and inserting a peg or bolt


124


therein.




In configuration Y, the trencher


10


is operated by activating the hydraulic power supply to extend the first hydraulic actuator


30


from the retracted position shown in

FIGS. 2

,


4


and


5


, and thus extend extension member


22


from its position inside stationary member


20


. The length of the arm


12


is thereby increased to reach a beginning digging point, as shown in

FIGS. 1 and 6

. When the arm is extended to the desired length, the trenching head


14


is lowered to the soil by activating the hydraulic power supply to extend the second hydraulic actuator


50


, causing the trenching head to pivot in a downward direction on the second hinge


48


. In order to begin the trenching operation, the hydraulic power supply is activated to provide power to the motor


64


, which turns motor shaft


68


. As the motor shaft turns, first sprocket


70


also turns, engaging drive chain


80


. The drive chain turns the second sprocket


78


, which in turn rotates the trenching wheel


72


in a forward direction d. As the trenching wheel rotates, the teeth


74


cut a trench in the soil. The trenching head


14


can be lowered to the desired depth once the trenching wheel begins to turn. As the trenching wheel and teeth cut a trench in the soil, dirt and debris are tossed upward into the trenching head, where they are deflected by the second deflector


114


to land on the first deflector


86


. The first deflector directs the dirt and debris away from the trenching wheel, and causes it to fall away, outside the newly cut trench.




With the trenching wheel


72


still turning, the first hydraulic actuator


30


is slowly retracted, thus sliding the extension member


22


into the stationary member


20


. In this way, the arm


12


is shortened, and the trencher


10


is returned to the retracted position, as shown in

FIGS. 2

,


4


and


5


. The motor


64


is then stopped, and the second hydraulic actuator


50


is retracted, thus raising the trenching head


14


above the ground. With the trencher in this position, the vehicle can be advanced to the next position where a trench in direction y is required.




The trencher


10


of the present invention can be secured in a stored position on the vehicle to which it is mounted, as shown in

FIGS. 9-12

. In the stored position, the swiveling member


40


is folded on the first hinge


46


so that it is adjacent to and nearly parallel with the stationary member


20


. The body


60


of the trenching head


14


is received in the cradle


18


. The cradle comprises one or more horizontal cradle arms


136


, each having a top edge


138


. In a preferred embodiment, the cradle arm includes at least two horizontal arms. A notch


140


cut in the top edge of the cradle arm receives the body


60


of the trenching head. The stored position is useful while the vehicle is being moved and the trencher is not in use. The stored position is also useful when the vehicle is parked.




In a preferred embodiment of the invention, the trenching head


14


may be optionally fitted with a dolly wheel


142


attached to the body


60


on the side opposite the protective case


82


, as shown in FIG.


9


. The dolly wheel is suspended from a dolly wheel bracket


144


, which bolts to the body of the trenching head. When the trencher is used in configuration X, it may be desirable to allow the trenching head


14


to “float,” to accommodate the contours of the ground. This is easily accomplished using hydraulic controls commonly available. The dolly wheel allows the trenching head to “float” while preventing it from sinking too deep in the soil. The dolly wheel swivels slightly to follow the path of the vehicle.




In compliance with the statutes, the invention has been described in language more or less specific as to structural features and process steps. While this invention is susceptible to embodiment in different forms, the specification illustrates preferred embodiments of the invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and the disclosure is not intended to limit the invention to the particular embodiments described. Those with ordinary skill in the art will appreciate that other embodiments and variations of the invention are possible, which employ the same inventive concepts as described above. Therefore, the invention is not to be limited except by the following claims, as appropriately interpreted in accordance with the doctrine of equivalents.



Claims
  • 1. A trencher mountable to a vehicle, the trencher comprising:a substantially horizontal hollow stationary member, the stationary member positioned substantially perpendicular to the direction of travel of the vehicle; an extension member sized to be slidably received within the stationary member, the extension member having a first end and a second end, the first end being received within the stationary member; a means for extending and retracting the extension member with respect to the stationary member; a swiveling member having a first end and a second end, the first end of the swiveling member pivotably attached to the second end of the extension member, the swiveling member horizontally pivotable with respect to the extension member, and the swiveling member being securable in a position parallel to the extension member; a trenching head pivotably attached to the second end of the swiveling member, the trenching head including a trenching wheel and a means for turning the trenching wheel; a means for pivotably raising and lowering the trenching head with respect to the swiveling member; and a mounting frame for mounting the trencher to the vehicle.
  • 2. The trencher of claim 1, wherein the means for lowering and raising the trenching head is a hydraulic actuator.
  • 3. The trencher of claim 1, wherein the means for extending and retracting the extension member is a hydraulic actuator.
  • 4. The trencher of claim 1, wherein the swiveling member is securable in a perpendicular position relative to the extension member.
  • 5. The trencher of claim 1, wherein the swiveling member is securable in a stored position.
  • 6. The trencher of claim 1, further comprising a cradle for receiving the trenching head in a stored position.
  • 7. The trencher of claim 1, wherein the trenching head further comprises:a body; a motor, said motor having a motor shaft; a motor compartment within the body for receiving the motor; a first sprocket affixed to the motor shaft, said sprocket positioned outside the motor compartment; a wheel shaft for being received within the trenching wheel; a second sprocket affixed to the wheel shaft; and a drive chain operatively engaged between said first sprocket and said second sprocket.
  • 8. The trencher of claim 7, wherein the trenching head further includes a protective case affixed to the body for enclosing the motor shaft, drive chain, and sprockets.
  • 9. The trencher of claim 7, further comprising:a first deflector for directing dirt and debris away from a newly cut trench, the first deflector positioned over the trenching head, and the first deflector comprising a first plate and a second plate, each plate having an upper edge, the upper edges of the plates meeting to form an apex over the trenching wheel; and a second deflector positioned over the trenching head opposite the first deflector, the second deflector for directing dirt and debris tossed up by the trenching wheel onto the first deflector.
  • 10. The trencher of claim 9, wherein the first plate and the second plate are made of sheet steel and heavy rubberized fabric, the rubberized fabric being positioned adjacent to the trenching wheel.
  • 11. The trencher of claim 7, wherein the motor is a hydraulic motor.
  • 12. The trencher of claim 7, further comprising a dolly wheel attached to the body of the trenching head.
  • 13. A trencher mountable to a vehicle, the trencher comprising:a hollow stationary member; an extension member sized to be slidably received within the stationary member, the extension member having a first end and a second end, the first end being received within the stationary member; a means for extending and retracting the extension member with respect to the stationary member; a swiveling member having a first end and a second end, the first end of the swiveling member pivotably attached to the second end of the extension member, the swiveling member being securable in a position parallel to the extension member; a trenching head pivotably attached to the second end of the swiveling member, the trenching head including a trenching wheel and a means for turning the trenching wheel, and the trenching head further comprising: a body; a motor, said motor having a motor shaft; a motor compartment within the body for receiving the motor; a first sprocket affixed to the motor shaft, said sprocket positioned outside the motor compartment; a wheel shaft for being received within the trenching wheel; a second sprocket affixed to the wheel shaft; and a drive chain operatively engaged between said first sprocket and said second sprocket; a means for raising and lowering the trenching head; and a mounting frame for mounting the trencher to the vehicle.
  • 14. The trencher of claim 13, wherein the trenching head further includes a protective case affixed to the body for enclosing the motor shaft, drive chain, and sprockets.
  • 15. The trencher of claim 13, further comprising:a first deflector for directing dirt and debris away from a newly cut trench, the first deflector positioned over the trenching head, and the first deflector comprising a first plate and a second plate, each plate having an upper edge, the upper edges of the plates meeting to form an apex over the trenching wheel; and a second deflector positioned over the trenching head opposite the first deflector, the second deflector for directing dirt and debris tossed up by the trenching wheel onto the first deflector.
  • 16. The trencher of claim 15, wherein the first plate and the second plate are made of sheet steel and heavy rubberized fabric, the rubberized fabric being positioned adjacent to the trenching wheel.
  • 17. The trencher of claim 13, wherein the motor is a hydraulic motor.
  • 18. The trencher of claim 13, further comprising a dolly wheel attached to the body of the trenching head.
US Referenced Citations (33)
Number Name Date Kind
2568959 Illies Sep 1951 A
2883067 Davis Apr 1959 A
2969601 McMaster Jan 1961 A
3387891 Simms et al. Jun 1968 A
3419976 Reising Jan 1969 A
3514038 McQuinn May 1970 A
3683522 Rousseau et al. Aug 1972 A
3834049 Bond Sep 1974 A
3896570 McMurray Jul 1975 A
4010900 Flix et al. Mar 1977 A
4034875 Pugh et al. Jul 1977 A
4044952 Williams et al. Aug 1977 A
4119154 Miller Oct 1978 A
4252274 Kubacak Feb 1981 A
4459767 Cartner Jul 1984 A
4475604 Albertson et al. Oct 1984 A
4523684 Baisden Jun 1985 A
4542940 Marten Sep 1985 A
4612715 Cartner Sep 1986 A
4709736 Bellars Dec 1987 A
4727691 Kubacak Mar 1988 A
4787324 DeWitt et al. Nov 1988 A
4808026 Clarke, Jr. et al. Feb 1989 A
4832412 Bertrand May 1989 A
4942682 McDowell Jul 1990 A
5027534 Sackett Jul 1991 A
5135287 Karnes Aug 1992 A
5212897 Jefferson May 1993 A
5245769 Wammock Sep 1993 A
5247743 Holloway et al. Sep 1993 A
5645179 Mohar Jul 1997 A
5864970 Maddock et al. Feb 1999 A
6125943 Valois Oct 2000 A