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This is a continuation-in-part of application Ser. No. 29/117,980, filed Feb. 2, 2000, now pending. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to a trenching and edging device for digging trenches and for edging the soil for beds for flowers, shrubbery, mulch, etc. 
     Small trenching machines find application in those circumstances where it is necessary to dig a relatively narrow trench. This could be the case where cable TV is being buried to provide service to a residence or business, or could be when it is necessary to run a gas line, waterline, or other utility to a home or office. Further uses of such a trench could be for running irrigation line or what is known as radio or “invisible” fencing used to keep pets within a confined area, the pet then wearing a cooperating collar which is activated to shock the animal in the event the animal comes too close to the buried line. 
     Edging machines find use with landscapers and homeowners for defining a bed used for ornamental plantings, shrubbery, flowers, mulch, or the like and serve to form the defined edge of a bed to be created by cutting the soil to a depth, typically several inches, and then lifting the soil and moving it outwardly to form a mounded periphery for the bed. Generally, it is desirable that the turf adjacent the bed have a distinct, clean break between it and the bed. This provides for a clean definition of the bed which is desired for aesthetic and maintenance purposes. 
     Trenching machines and edging machines are known. For example, U.S. Pat. No. 4,939,854, issued to Boren, discloses a trencher having a digging depth adjustment configuration including a rotatable handle in order to accomplish such depth adjustment. U.S. Pat. No. 4,002,205, issued to Falk, and U.S. Pat. No. 5,226,248, issued to Pollard, both disclose bed edge forming machines for forming the edge of a bed. 
     U.S. Pat. No. 5,320,451, issued to Garvey, et al, discloses a tiller having a cable-laying attachment and also a provision for carrying a spool of cable, and a feed tube through which the cable is inserted into a trench. U.S. Pat. No. 5,009,270, issued to Vangsgard, discloses a sod-cutting machine having an adjustable depth adjustment, and U.S. Pat. Nos. 4,958,457, issued to Doskocil, and 4,979,573, issued to Williamson, both disclose devices using caster wheels for steering. The Doskocil device includes rear-mounted casters. 
     In view of the foregoing known devices, there still exists a need for a combination trenching and edging device which is designed to facilitate movement and steering of the device and which also can be used to dig at varying depths. 
     SUMMARY OF THE INVENTION 
     It is, therefore, the principal object of this invention to provide a combination trenching and edging system. 
     Another object of this invention is to provide an edging machine having readily variable digging depth adjustment capability. 
     Another object of this invention to provide a combination trenching and edging system having improved steerability during use. 
     Yet another object of the present invention is to provide an improved edging blade design. 
     Still another object of the present invention is to provide a edging blade which, during use, defines a groove in the soil for receiving conduit, tubing, wire, or the like. 
     Another object of the present invention is to provide an edging blade having self-sharpening cutting edges. 
     A further object of the present invention is to provide an edging blade which forces soil outwardly from the blade during use. 
     A still further object of the present invention is to provide a trenching machine and a method for digging a trench, laying conduit wire, cable or the like in the trench, and backfilling the trench after laying the wire or cable, all in a single pass. 
     Generally, the present invention includes a trenching and edging system which is portable, and operable by a single user. The present invention includes a soil bed edge-forming machine, having a frame and a motor and wheels connected to the frame. A digging blade is drivingly connected to the motor, and a digging depth adjustment member is connected to the digging blade, with the adjustment member being rotatable for allowing selective digging depth adjustment of the digging blade into the soil. 
     More specifically, the trenching and edging machine of the present invention includes steerable casters mounted on the rear of the machine which, together with a single front wheel, allow for a tight turning radius when using the machine, thereby facilitating maneuverability of the machine. The machine also includes a blade height adjustment which allows the trenching blade or edging blade height, and, accordingly, the digging depth, to be readily adjusted in substantially infinite variation between the raised and lowermost position. The machine is further capable of digging a trench, laying wire, cable, tubing, etc., and backfilling the trench in a single pass. 
     Another feature of the machine is a edging blade which includes spring steel digging fingers having carbide tips. As the edging blade is used, it forms a generally-perpendicular wall adjacent the edge of the bed and mounds the dirt towards the bed in an outwardly angled, tapered fashion, opposite the generally-perpendicular wall. At the base of the wall, adjacent the mounded dirt, a groove is formed which is generally below the elevation of the mounded dirt. This groove can be used for the laying of cable, herbicide, pesticide, and/or fertilizer lines, irrigation lines, radio or invisible fencing for pets, etc. 
     Moreover, the present machine includes a blade guard system which covers the trencher blade regardless of the digging depth of the trencher blade and which also covers the blade when the blade is in the fully raised state, such as would be the case when the machine is being transported. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing, as well as other objects of the present invention, will be further apparent from the following detailed description of the preferred embodiment of the invention, when taken together with the accompanying specification and the drawings, in which: 
     FIG. 1 is a perspective view of a trenching and edging system constructed in accordance with the present invention, illustrating the trenching and edging machine in use digging a trench; 
     FIG. 2 is a perspective view of the trenching and edging machine of the present invention. 
     FIG. 3 is a bottom perspective view of the trenching and edging machine constructed in accordance with the present invention; 
     FIG. 4 is a left side perspective view of the trenching and edging machine constructed in accordance with the present invention; 
     FIG. 5 is a partial perspective view of the blade drive configuration of the trenching and edging machine illustrated in FIGS. 1 through 4; 
     FIG. 6 is a partial perspective view taken along lines  6 — 6  of FIG. 5; 
     FIG. 7 is a perspective view of a bracket for the trenching and edging machine for carrying a blade for the machine; 
     FIG. 8 is a partial perspective view, with parts cut away, of the blade height adjustment configuration of the trenching and edging machine; 
     FIG. 9A is a partial side elevational view illustrating blade height adjustment configuration of the trenching and edging machine, illustrating a trenching blade in a raised position; 
     FIG. 9B is a partial side elevational view of the trenching and edging machine, illustrating the trenching blade in a lowered position; 
     FIG. 9C is a partial side elevational view illustrating the trenching and edging machine in the present invention simultaneously digging a trench, laying cable, wire, tubing, etc. and backfilling the trench; 
     FIG. 10 is a perspective view illustrating a hood for use in connection with the trenching machine for guiding and placing cable, wire, tubing, etc. within a trench; 
     FIGS. 11 through 13 are perspective views of an edging blade constructed in accordance with the present invention; and 
     FIG. 14 is a simplified view of a bed edge having a groove in the soil below the depth of the bed edge formed using the edging blade of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The accompanying drawings and the description which follows set forth this invention in its preferred embodiment. However, it is contemplated that persons generally familiar with earth working equipment will be able to apply the novel characteristics of the structures illustrated and described herein in other contexts by modification of certain details. Accordingly, the drawings and description are not to be taken as restrictive on the scope of this invention, but are to be understood as broad and general teachings. 
     Referring now to the drawings in detail, wherein like reference characters represent like elements or features throughout the various views, the trenching and edging system of the present invention is indicated generally in the figures by reference character  10 . 
     Turning to FIG. 1, the trenching and edging system  10  is shown in use as a trencher T. The user, or worker W is pulling the machine  10  rearwardly in order to form a trench  12  in the ground  14 . Machine  10  includes a frame, generally F, and a motor, generally M, connected to the frame F. Extending upwardly from frame F is a handle support arm  18 , to which a handle  20  is attached. Grips  22  are provided on the handle for grasping by worker W. 
     A drive lever  24  is pivotally connected to handle support  18 , the drive lever being pulled towards handle  20  by worker W when it is desired to engage the digging blade, generally B, which in FIG. 1 is shown as being a trenching blade  26 . The pulling of drive lever  24  by worker w causes a corresponding pulling of cable  28  which in turn engages a drive transmission, generally  30 , more clearly shown in FIGS. 2 and 5. 
     Also shown on FIG. 1 is a blade height/depth adjustment assembly, generally H, which will be discussed in more detail below. 
     Machine  10  includes shroud  32  and guard  34 , which are connected to frame F. Shroud  32  and guard  34  serve to cover trenching blade  26  during operation and during transport, primarily for safety purposes. Note that guard  24  is connected to frame F via a support bar  38 . A flexible guard  40  is attached to shroud  32  for deflecting rocks, dirt, or other underground buried objects which may be unearthed and thrown upwardly by trenching blade  26  during use. Flexible guard  40  could be constructed of rubber, plastic, or some other resilient material. 
     Attached to handle support  18  is a bracket  42  which supports a spool axle  44  for carrying a spool  48  of wire, conduit, cable, drip line, tubing, or the like when machine  10  is used for laying and burying same. The spool axle  44  includes a flange  52  on which spool  48  rests during use. Operation of machine  10  for burying such wire, cable, tubing, etc. will be discussed further below. 
     FIG. 2 illustrates the left side of machine  10  and the blade height adjustment configuration H in more detail. The mechanism H includes a crank arm  54  having a knob  56  rotatably connected to a threaded shaft or rod  58 . The shaft  58  extends through a tower  60  which includes a first collar  62  for receiving a pivotal link  64  and a second collar  66  for receiving a stationary link  68 . Collar  66  is configured for sliding movement relative to stationary link  68  when crank arm  54  is turned by knob  56  by the user. 
     As shown in more detail in FIGS. 6 through 9B, as crank arm  54  is turned, collar  66  moves upwardly or downwardly, depending on the direction of rotation of crank arm  54  with respect to stationary link  68 . This causes the upper end of pivotal link  64  to pivot with respect to collar  62  and the lower end  70  of pivotal link  64  to pull upon or push on a shaft  72 . Shaft  72  is connected to a bracket arrangement, generally  74 , which carries the transmission, or blade drive mechanism,  30  having digging blade B. Shaft  72  is carried in bosses  76 ,  78  which are fixedly connected to a bracket  80 . Bracket  80  includes an opening  82  for receipt of the drive shaft  84  of motor M, such opening also extending through a corresponding bracket  86  fixedly attached to frame F. Accordingly, rotation of crank arm  54  as shown in FIG. 8, advances threaded rod  58  upwardly or downwardly, which in turn causes pivotal link to pivot bracket arrangement  74 , thereby raising or lowering the digging blade B. 
     FIG. 7 illustrates bracket  80  in further detail, and bracket  80  includes boss  88  which carries a bushing  90  for drive shaft  84  (FIG. 5) for driving the digging blade. 
     FIG. 9A shows the digging blade B raised to its uppermost position. Note the position of pivotal link  64  and the upward incline of shroud  32 . FIG. 9B illustrates the blade in the lowered digging position, and note the relative position for the lower portion  70  of pivotal link  64  with respect to the bracket  80  which attaches stationary link  68  to frame F. 
     Returning to FIG. 2, machine  10  includes a single front wheel  92  and two rear wheels  94 ,  96  (FIG.  3 ). Rear wheels  94 ,  96  are caster wheels and freely pivot with respect to frame F. Curved support arms  98 ,  100 , connect the rear wheels to the frame F, and support arms  98 ,  100 , and include bosses  102  through which pivot axles  104  of wheels  94 ,  96  extend. 
     A downwardly extending flexible guard  106  is provided on the underside of frame F to further catch and minimize throw-back of objects onto worker W during use. Bracket arrangement  74 , discussed above, can be seen from another perspective in FIG. 2, and serves to shroud driven pulleys  108 ,  110 , which connect via two drive belts  112 ,  114 , to two drive pulleys  116 ,  118  (FIG. 5) connected to the output shaft  84  of motor M. It is noted here that motor M is shown as a gasoline-powered motor, and in a one preferred embodiment is a six (6) horsepower Briggs and Stratton Vanguard engine. An idler pulley  120  is also carried within bracket  80 , and will be discussed in further detail below. Shroud  32  attaches to a bracket  122  via bolt and nut combinations, generally  124 . 
     FIG. 3 is a view of the bottom of machine  10  and illustrates the construction of frame F and the attachment of support bar  38  to frame F. Support bar  38  carries guard  32 , which extends in front of trenching blade  26 . Trenching blade  26  includes outwardly extending digging fingers  128 , and trenching blade  26  is bolted to an axle  130  (FIG. 5) connected to drive pulleys  116 ,  118 . Note that rear wheel  96  is spaced outboard of trenching blade  26  in order to maintain the stability of machine  10  during use. 
     FIG. 4 illustrates crank arm  54  pivoted outwardly in a position for turning by knob  56 . A bracket  132  is provided with a retaining hole  134  for holding crank arm  54  and preventing it from rotating during use. This maintains the digging height of the blade once adjusted with crank arm  54 . 
     FIG. 4 also illustrates cable  136  extending downwardly from drive lever  24 . Cable  136  is connected to drive lever  24  via a pivotal connector  138 , and cable  136  passes beneath a guide roller  140 , which is attached to handle support arm  18 . 
     Cable  136  extends from guide roller  140 , as shown in FIG. 5, and terminates in a driving engagement member  142 , which includes and upstanding arm  144  and idler pulley  120 . A return spring  148  is also attached to arm  144 . Return spring  148  is attached at its other end to cable  136 . When drive lever  24  is pulled towards handle  20 , cable  136  is tightened. This pulling of the drive lever is performed against the tension force of return spring  148 , and the pulling of cable  136  causes member  142  to pivot, which in turn forces idler pulley downwardly against drive belts  112 ,  114 , thereby causing them to snuggly engage pulleys  108 ,  110 ,  116 ,  118 . This in turn causes the rotation of motor output shaft  84  to drive pulleys  116 ,  118 , to therefore drive the digging blade. Drive lever  24  acts as a “dead man” control, such that should worker W release drive lever  24 , idler pulley  120  retracts, thereby causing slack to be formed in drive belts  112 ,  114 , and the driving of digging blade B ceases. FIG. 5 illustrates idler pulley  146  in driving engagement with the drive belts. 
     FIGS. 9C and 10 illustrate use of machine  10  as a trenching, cable, tubing, wire, etc. laying, and backfill machine. This is one of the three major functions of the present invention. Use of machine  10  as a trenching machine has been discussed above. Trenches formed by such machine would be useful in laying sections of rigid pipe, for example, which are not flexible or of small enough diameter to be carried on a spool. However, where it is desired to lay cable, tubing, wire, etc. which is capable of being carried on a spool, then machine  10  can be used to dig a trench, lay such item and bury it all in a single pass. In this configuration machine  10  includes a hood  150  which attaches to frame F and which replaces shroud  32 . Hood  150  has a delivery chute  151  for returning soil which is being dug by trenching blade  26  back into the same trench. In the interim, however, an elongated member  152  such as pipe, cable, tubing, wire, drip line, pays out from spool  48  and is placed within the trench  12 . The elongated member  152  passes from spool  48  to an eyelet, or guide  154  carried on hood  150 . The elongated member then extends downwardly towards the trench, but first passes through a pivotal foot  160  which is pivotally connected to a front portion of hood  150  in a hinge-like configuration  161 . At the lowermost portion of foot  160 , a second guide  162  is carried through which the elongated member  152  passes. Foot  160  is allowed to pivot from side to side to accommodate for irregularities which may be found in the trench as the trench is dug. As the foot directs the elongated member to the lower portion of the trench, backfill soil  163  is simultaneously being delivered from the delivery chute  151  of hood  150  to backfill the trench, and, accordingly bury the elongated member  152 . 
     FIGS. 11 through 13 illustrate a bed edging blade  200  of the present invention. Machine  10  can be provided with the trenching blade  26 , as discussed above, or other suitable digging blades (not shown), or the landscaping bed edging blade  200 , thereby rendering machine  10  as capable of performing three functions, namely, (a) trenching; (b) trenching, laying, and backfilling; and (c) edging of beds. 
     Edging blade  200  is in overall shape generally similar to a pyramid or cone and includes a base plate  202 , and an end plate  204 . Base plate  202  is of a generally triangular shape, but includes three brace, or gusset, portions  206  which extend outwardly behind each of three base digging fingers  210 . Digging fingers  210  are preferably constructed of spring steel and preferably include at the ends thereof carbide cutting blades  212 . Digging fingers  210  are preferably welded to base plate  202 , which is in one preferred embodiment, made for mild steel. Base plate  202  includes a boss  214  which defines an axle opening  216  for receiving the drive axle  84  of drive pulleys  116 ,  118 . Extending upwardly from base plate  202  and terminating in end plate.  204  are three support members, or ribs, generally  220 , each of which are substantially equidistantly spaced apart from one another and acutely angled with respect to base plate  202 . These support members  220  are preferably constructed of steel and have an angled cross-section. Each support rib carries three digging fingers  222 . 
     Turning to FIG. 12, these digging fingers  222  are inwardly curved along their respective lengths. Each digging finger preferably includes a carbide tip or blade  212  at the end thereof. The leading edge  223  of each carbide tip is preferably substantially parallel to the support rib on which it is carried, as shown by arrows a. In other words, the angle of the leading edge of a digging finger with respect to base plate  202  is acute and is substantially the same acute angle as formed between the support rib  220  on which such digging finger  222  is carried and base plate  202 . 
     End plate  204  includes an opening  224  for allowing a socket wrench extension (not shown) to pass therethrough when edging blade  200  is attached to axle shaft  84  through use of a nut  226 . 
     The above-described construction of edging blade  200  provides certain advantages. First, as the edging blade is used, the outboard corner  230  (FIG. 11) of each digging finger  222  tends to hit the soil first during use and accordingly becomes worn down, such as shown in phantom in FIG.  11 . This ultimately causes a sharpening effect of the digging finger, and as wear of a tooth advances, continues to maintain the extreme ends of the digging fingers sharp. In essence, the digging fingers become generally self-sharpening. 
     Another advantage of the above construction is that because the digging fingers  222  are angled outwardly with respect to base plate  202 , i.e., the leading edge  223  of a digging finger  222  does not approach the soil precisely parallel to the soil surface. This causes the leading edge  223  to thus pierce, or shear, the soil incrementally as the lowermost portion of the finger first hits the soil and then the remainder of the leading edge  223  contacts the soil thereafter. This cutting action has been analogized to how scissors operate in that the entire cut to be made in a piece of paper, for example, by a pair of scissors, does not occur instantaneously, but instead the cut advances as the scissors are closed. This shearing action of digging fingers  222  is believed to provide a better digging action, as the digging fingers are less apt to “beat” or reverberate against the soil surface, since they do not approach the soil surface in a direct parallel relationship. The shearing action of the angled digging fingers  222  is also believed to improve use of the edging blade on hard soil, since a direct parallel approach of the digging fingers would likely cause more vibration and perhaps a “bouncing” of the digging fingers on such hard soil surface. 
     A further advantage of the leading edges of the digging fingers being angled outwardly with respect to the base plate  202 , is that such angling of the digging fingers causes an augering effect of the soil as the blade is used. This augering effect tends to propel the soil away from the base plate  202 , thereby building a desirable mound angled outwardly and tapered into the edge of the bed being worked. This also provides for a cleaner vertical wall, which is dug by base plate  202  and the base plate digging fingers  210 . The angled support ribs  222  tend to further provide an auguring effect, also forcing the soil upwardly on the bed mound. 
     Another significant feature of edging blade  200  is the fact that the base plate digging fingers  210  dig a groove  211  as shown in FIG. 14 extending below the base of the bed edge  213  being constructed. This groove allows for placement and receipt of drip line, which may be used to carry herbicide, fertilizer, pesticide, etc. around the perimeter of the bed. The groove could also be used to bury pet containment system wire, also known as invisible fencing. 
     By providing the three support ribs on edging blade  200 , the digging action of the blade  200  is staggered, as compared to prior art digging blades having two diametrically-opposed digging blade structures. This allows for a smoother operation and also staggers the cutting action of the blade, allowing for more continuous cutting action. This is expected to allow more digging capability for the same amount of horsepower motor as has been used in the past. 
     Further, with regards to the base plate digging fingers  210 , such fingers are effectively reinforced and supported along their length by the gussets  206  of base plate  202 . These gussets support the back side of each base plate digging finger, to thereby strengthen and prolong the life of such digging fingers. 
     The earth-working machine  10  of the present invention thus provides a versatile system for digging trenches, burying tubing, conduit, wire, etc., and also for forming edges of beds in the soil. As the machine is relatively small, and portable, it can be used in situations where bigger machines would not be appropriate, and also, because of its relatively small size, is less destructive on lawns, turf, etc., than would be certain larger machines. 
     Machine  10  is particularly maneuverable for equipment of its type. Another noteworthy feature is the position of the front wheel  92  with respect to the digging blade B, be it the trencher blade  26  or the edging blade  200 . As can be best seen from FIG. 9A, as the digging blade is pivoted in an arc from its lowermost position to its uppermost position, the center of rotation thereof remains close to the center of rotation of the front wheel, since the radius of the arc extends only slightly beyond front wheel  92 . In other words, whether the axis of rotation of the digging blade is above or below such axis of rotation, the digging blade can be in general vertical alignment with the axis of the front wheel, broadly speaking, and such positioning is sufficient to allow improved maneuverability of machine  10  during operation. Since the axis of rotation of the digging blade is close to that of the front wheel, through use of the steerable caster wheels, and because the front wheel is laterally spaced as closely as practical to the digging blade, relatively tight turns can be made with the machine  10  as it is pulled rearwardly during use. 
     Another feature of machine  10  is the safety aspect afforded by shroud  32  and guard  34 . Shroud  32  and guard  34  are configured to shield the digging blade not only when the digging blade is in its lowered, digging position, but also when it is in its raised, transport position. Furthermore, both shroud  32  and guard  34  can be used with either trenching blade  26  or edging blade  200 . 
     While preferred embodiments of the invention have been described using specific terms, such description is for present illustrative purposes only, and it is to be understood that changes and variations to such embodiments, including but not limited to the substitution of equivalent features or parts, and the reversal of various features thereof, may be practiced by those of ordinary skill in the art without departing from the spirit or scope of the following claims.

Summary:
A combination machine for trenching, for forming the edge of a bed, and for laying and burying tubing, cable, piping, and the like. The machine includes steerable caster wheels mounted on the rear of the machine which, together with a single front wheel, allow for a tight turning radius when using the machine. The machine also includes a blade height adjustment which allows for the trenching or edging blade depth to be readily adjusted in a substantially infinite variation. An edging blade is provided which when used with the machine forms a groove at the bed&#39;s edge for the laying of irrigation lines, or lines for herbicide, pesticide, and/or fertilizer for use in connection with the bed.