Self-propelled percussion unit for driving cemetery markers and method of using same

#This invention relates generally to a method and apparatus for reducing the cost of maintaining a cemetery and, more particularly, to a self-propelled percussion unit, and method of using same, especially adapted for driving previously installed cemetery markers into the ground so that grass can be cut with a mower running over the cemetery markers with the mower blade operating at a normal cutting height.

#In recent years, the cost in maintaining cemeteries has increased dramatically to the point where cemetery maintenance is a real problem. Where cemetery markers were installed projecting above the ground, a self-propelled mower cannot pass over the raised marker when the mower blade is operating in a normal cutting position. The cost to hand trim markers is becoming prohibitive, and mowing costs are substantial if a mower must maneuver around protruding markers. The problem has become so severe that a large number of cemeteries no longer permit a marker to be installed projecting above the ground where it will interfere with a self-propelled mower. Although grass immediately around a grave marker can be controlled by grass killers and the like, this is expensive and still requires that the mower negotiate around the raised markers. The increase in maintenance cost caused by the raised markers has in some cases been sufficient to justify cemetery workers digging up markers and their foundations, deepening the excavation and then reinstalling the foundation and the marker flush with the ground. This manual operation is time consuming and expensive, and the cost to manually relocate the marker flush with the ground can easily be on the order of $10 to $20 per marker. This cost is almost prohibitive with large older cemeteries having literally thousands of raised cemetery markers.

#The principal object of the present invention is to reduce the cost in maintaining cemeteries that presently have cemetery markers projecting above the ground sufficiently to interfere with a self-propelled mower passing over the marker while it is cutting grass.

#Other objects, features and advantages of the present invention wil become apparent in connection with the following description, the appended claims and the accompanying drawings in which:

#FIG. 1 is a front view of a self-propelled percussion unit for driving cemetery markers into the ground according to the present invention;

#FIG. 2 is a side elevational view of the front portion of the self-propelled unit shown in FIG. 1;

#Referring more particularly to the drawings, a hammer 10 is carried on the lower end of a heavy weight 12 that is vertically reciprocally mounted on a hammer tower 14 that is carried for transverse positioning on a frame 16 mounted on the front of a self-propelled wheeled tractor 18. Except for minor modification of the hammer 10, per se, and the hydraulic control, the arrangement and construction of the weight 12, tower 14, frame 16 and tractor 18 may be substantially identical to that described and disclosed in U.S. Pat. No. 3,172,483, granted March 9, 1965, which patent is hereby incorporated by reference thereto. Self-propelled percussion units of this general type are well known for a multiplicity of uses, for example, tamping fills, cutting and breaking pavement, driving posts and pilings, and the like, and are available from several manufacturers including the Arrow Manufacturing Company of Denver, Colorado, to which the aforementioned U.S. Pat. No. 3,172,483 was assigned. Such prior art percussion units include a hydraulic system (not shown) which, under the control of the operator, controls a hydraulic cylinder 22 (via hydraulic hoses 24) which in turn raises weight 12 via a pulley arrangement 28 and cable 26 that is connected to the top of weight 12. When the operator initially energizes cylinder 22, cable 26 is retracted to move weight 12 upwardly on opposed ways 30 to a raised position, generally anywhere from an inch or so up to several feet, for example, 8 feet. At this point, the hydraulic system automatically releases weight 12 so that it falls freely to develop a high impact force at hammer 10. Typically, weight 12 might be 1000 pounds.

#In conventional percussion units, the controls of the hydraulic systems are arranged such that, once the operator initiates the operation, the cylinder will be cycled repeatedly until the operator deactivates the control. According to one aspect of the present invention, the hydraulic control is modified so that the weight 12 and hammer 10 are raised and dropped only once each time the operator actuates the control, as by control handle 32. This is a very simple modification that can be accomplished by by-passing the automatic sequencing valve. Aside from this minor modification and the modification of the hammer as will be described, the above described percussion unit may be otherwise substantially identical to the aforementioned commercially available units. As set forth in greater detail in the aforementioned U.S. Pat. No. 3,172,483, the horizontal position of the vertical hammer tower 14 can be adjusted transversely of the vehicle by suitable means (not shown) on frame 16, and the tower can also be pivoted sideways on a first horizontal axis or forwardly and rearwardly on another horizontal axis so that the direction of the impact provided by hammer 10 can be selected.

#According to the present invention, the commercially available percussion unit is modified by adding an impact transmitting member 34 that can be raised and lowered independently of hammer 10 and can be positioned below hammer 10 on top of a cemetery grave marker 36. More particularly, the member 34 comprises a generally rectangular frame 38 having a pair of side or end plates 40, front and rear plates 42, 43 and top plate 44. The plates are securely welded together to form a downwardly opening cavity 46 in which wood timbers 48 are mounted so as to fill the cavity and project below plates 40, 42, 43 and form a flat, lower cushion surface 50 for engaging directly against marker 36. The frame 38 and particularly the top plate 44 must be rigid, strong and hard to withstand repeated severe impact forces from hammer 10. In one embodiment of the present invention, top plate 44 was a 2-inch thick steel plate, 26 inches in depth (in a direction longitudinally of the wheeled tractor 18) and 22 inches wide (in a direction transversely of the tractor 18). Plates 40, 42, 43 are formed of 1-inch thick steel plate, 4 inches tall so that the cavity 46 can accommodate two 8 .times. 10 .times. 24 wood timbers of generally rectangular cross section with the upper surface of the timbers bottomed against the lower surface of top plate 44. Although the timbers can be maintained in the cavity by making them slightly oversized and driving them in place, preferably they are held in place on the frame 38 by a pair of bolts 52 that extend transversely through the timbers and the side plates 40. Although various types of wood timbers could be used, it has been found that elm timbers operate very effectively since, although very soft in comparison to steel, elm is a relatively hard wood that will withstand repeated impact against the marker without splitting and splintering.