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BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to tools and appliances used in the roofing trade. More particularly, the present invention comprises a powered shingle removing machine, which is pushed across a shingled roof, and which uses a powered, oscillating blade mechanism to lift and remove previously installed shingles. 
   2. Description of the Related Art 
   Most gabled roofs utilize wood sheathing overlaid with tarpaper, with lapped shingles forming the outermost cover. Various types of shingles are used, from glass fiber and other composites to older felt and tar composite material. While the tar-based shingle has been known for much longer than more modern materials and is not so durable as many modern shingle materials, it is often still the most cost-effective type of shingle for a roof, depending upon the environment and other factors. 
   Any shingle, regardless of type, will eventually deteriorate due to exposure to ultraviolet from the sun, moisture from precipitation, etc. While it is common to install a second layer of new shingles over a single existing layer, eventually the older shingles must be removed for replacement. This is a physically demanding task when performed by hand without the use of power machinery. Generally, various scraping tools, such as modified flat shovels, are used to wedge between the shingles and the underlying tarpaper or sheathing, with the edge of the shovel shearing or pulling the roofing nails which held the shingles in place. The physical effort involved, particularly when performed on a sloping roof, is extremely taxing. 
   Accordingly, various powered machines have been developed in the past to perform the task of removing shingles from roofs. Such machines typically include an electric motor or internal combustion engine that drives a mechanism, which, in turn, lifts and peels shingles from the roof surface. An example of such a machine is found in German Patent No. 4,221,672, published on Jan. 5, 1994. The device includes a wheel on a lateral axis, with the wheel having an eccentric pin extending therefrom. The pin engages a single, forwardly extending lever, with a fixed pin or axle extending laterally through a slot in the lever to restrain movement of the lever. A single, relatively narrow comb extends from the forward end of the lever. 
   None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a shingle removing machine solving the aforementioned problems is desired. 
   SUMMARY OF THE INVENTION 
   The shingle removing machine includes a frame having a power plant (internal combustion engine, electric, hydraulic, or pneumatic motor, etc.) with a handle and controls extending therefrom. The power plant drives a lateral axle, which in turn has a drive arm wheel at each end thereof. Each wheel has an eccentric pin, with a blade drive arm extending forwardly from each eccentric. The blade drive arms are interconnected at their forward ends, and drive a pair of relatively wide shingle removal blades. The forward ends of the blade drive arms include rollers, which rest upon sloped ramps extending from the forward end of the frame. Rotation of the blade arm drive wheels results in forward and rearward reciprocation of the drive arms and blades, with the rollers and ramps causing the blades to lift and lower during each cycle to lift and separate the shingles from the underlying surface. The shingle removing machine may be disassembled easily in the field for repair or replacement of components as required. 
   These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental, perspective view of a shingle removing machine according to the present invention, showing its operation in the removal of shingles from a roof. 
       FIG. 2  is a right side elevation view of the shingle removing machine of the present invention, showing further details thereof. 
       FIGS. 3A ,  3 B,  3 C and  3 D are a sequential series of right side elevation views of the shingle removing machine of the present invention showing the position of the blade drive arms and blades during the rotation of the blade drive arm wheels. 
       FIG. 4  is an exploded perspective view of the blade drive arm axle, wheels, and blade drive arm assembly of the shingle removing machine of the present invention, showing the various components and their relationships. 
   

   Similar reference characters denote corresponding features consistently throughout the attached drawings. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The present invention comprises a powered machine for removing conventional lapped shingles from a roof. A blade assembly is oscillated forwardly and rearwardly to drive between the shingles and the underlying roofing paper or sheathing, with the geometry of the mechanism also lifting the shingles slightly when the blades have been driven to their forwardmost position. 
     FIG. 1  of the drawings provides an environmental perspective view of the shingle removing machine  10  in use removing shingles S from a roof R. The machine  10  includes a frame  12  having opposite forward and rearward ends, respectively  14  and  16 , and a width  18 . The frame  12  may be formed of any suitable materials, e.g., steel tubing, which has been welded to form the frame assembly  12 . This provides an extremely strong and rigid, but relatively light structure to support the various components of the machine and to provide the required durability to withstand the forces involved during operation of the device. A deflector or guard (not shown, in order to show the underlying structure and components) may be installed over at least the forward portion of the frame in order to keep loosened shingles from falling into the frame and moving components. 
   Left and right support wheels, respectively  20  and  22 , extend from the frame  12  generally adjacent the rearward portion thereof, and serve to support most of the weight of the machine. A handlebar assembly  24  extends from the rearward end  16  of the frame  12 , enabling an operator to control and maneuver the machine. The handlebar assembly  24  preferably includes suitable controls  26  (shown in  FIG. 2 ) for the prime mover  28  (e.g., internal combustion engine, as shown, or alternatively an electric, hydraulic, or pneumatic motor, etc.). 
     FIG. 4  provides an exploded perspective view of the forward portion of the frame  12  and the drive or actuating mechanism for the shingle removing machine. The engine or motor  28  drives a rotary driveshaft  30  within a tubular housing, with the driveshaft  30  extending directly from the engine or motor  28  and conventionally geared to rotate a drive arm axle  32  disposed laterally across the frame  12 . It will be understood that the power train used to translate rotary motion of the engine or motor shaft into rotation of the drive arm axle  32  is not critical, and any power train or coupling system known in the art may be used to translate rotation of the motor shaft into rotation of the drive arm axle  32 . An internal combustion engine and drive system, such as that used in a conventional garden tiller, may be readily adapted for use with the present machine  10 . The drive arm axle  32  has a left end  34   a  and opposite right end  34   b , with a left and a right blade drive arm wheel, respectively  36   a  and  36   b , secured to the two drive arm axle ends  34   a  and  34   b . It should be understood that these blade drive arm wheels  36   a  and  36   b  are sufficiently high in the frame  12  that they do not contact the underlying surface, i.e., they do not provide any propulsion for the machine  10  per se. Rather, they serve to actuate the blade mechanism disposed at the front end  14  of the frame  12 . 
   Left and right blade drive arms, respectively  38   a  and  38   b , attach to their respective blade arm drive wheels  36   a  and  36   b  by means of eccentric pins  40   a  and  40   b  which extend laterally from their respective drive wheels. The two blade drive arms  38   a  and  38   b  extend forwardly from their attachment to their drive wheels  36   a  and  36   b  and provide the driving linkage for a pair of shingle removal blades, as discussed further below. Each blade drive arm  38   a ,  38   b  has a forward end, respectively  42   a  and  42   b , with a laterally disposed blade mount tube, respectively  44   a  and  44   b , extending inwardly (i.e., toward one another in the completed assembly) from the forward ends  42   a ,  42   b  of the two blade drive arms  38   a ,  38   b.    
   Each blade mount tube  44   a  and  44   b  includes a blade mount plate, respectively  46   a  and  46   b , extending generally forwardly therefrom. The blade mount plates  46   a ,  46   b  provide for the removable and replaceable attachment of left and right shingle removal blades, respectively  48   a  and  48   b , by means of conventional threaded fasteners or other suitable attachment means. The shingle removal blades  48   a ,  48   b  extend forwardly from the blade mount plates  46   a ,  46   b  and comprise the forwardmost extremity of the machine  10 . The blades  48   a ,  48   b  are preferably conventional; such blades are readily available commercially to facilitate replacement when required. It will be noted in  FIG. 1  of the drawings that the two blades  48   a  and  48   b  combine to span essentially the entire width  18  of the machine  10  in the completed assembly. 
   The two blade drive arms  38   a ,  38   b  with their blade mount tubes  44   a ,  44   b  and blade mount plates  46   a ,  46   b  are preferably provided as two separate left and right hand components, in order to facilitate removal and replacement of components in the field. The forward ends  42   a ,  42   b  of the two drive arms are secured to one another by an interconnecting shaft  50  which passes concentrically through the two hollow blade mount tubes  44   a  and  44   b . A central roller bearing  52  is installed on the lateral interconnecting shaft  50  before assembling the two blade mount tubes  44   a  and  44   b  on the shaft  50 , with a left and a right hand roller bearing, respectively  52   a  and  52   b , being installed on the shaft  50  outboard of the respective blade mount tubes  44   a  and  44   b  after they have been installed on the shaft  50 . 
   The forward end  14  of the frame  12  includes a low, flat plate  54  extending thereacross, which connects the to longitudinal forward frame members together. The plate  54  also serves as a support for the forward ends of the blade drive arms  38   a ,  38   b  and their various attachments described further above. The plate  54  includes a series of roller support ramps, comprising a central ramp  56  and left and right ramps  56   a  and  56   b . The roller bearings  52  through  52   b  ride on their respective ramps  56  through  56   b , with the ramps imparting some vertical motion to the blades  48   a ,  48   b  as they are reciprocated forwardly and rearwardly by the blade drive arms  38   a  and  38   b  and drive mechanism. 
     FIGS. 3A through 3D  illustrate the relative motion of the shingle removal blades during the operation of the machine  10 . While  FIGS. 3A through 3B  illustrate the operation of the machine  10  only from the right side, it will be understood that the two blade arm drive wheels  36   a  and  36   b  rotate in unison with one another and that the two blade drive arms  38   a ,  38   b  are immovably affixed relative to one another. Thus, the explanation of the operation of the right side components as shown in  FIGS. 3A through 3D  will be seen to cover the simultaneous operation of the components of the opposite side of the machine as well. 
   In  FIG. 3A , the right side blade arm drive wheel  36   b  is rotated to position the eccentric pin  40   b  at the top of the drive wheel, thus positioning the attachment end of the blade drive arm  38   b  at the same point. The uppermost portion of the wheel  36   b  is moving primarily in a forward direction as the wheel rotates clockwise (as seen from the right side in  FIGS. 3A through 3D ), thus driving the blade drive arm  38   b  and blade  48   b  in a predominately forward direction, as shown by the forward movement arrow F in  FIG. 3A . The forwardly and downwardly sloped ramps, e.g., ramp  52   b  in  FIG. 3A , allow the blade  48   b  (and its attached counterpart) to lower to the level of the underlying surface as it is being thrust forward, thus passing between the overlying shingles and the underlying surface to separate the shingles from the underlying surface. 
   As the blade arm drive wheel  36   b  rotates another ninety degrees, the eccentric pin  40   b  and attachment end of the blade drive arm  38   b  will rotate to the forwardmost portion of the wheel  36   b , as shown in  FIG. 3B . This portion of the wheel is moving primarily downwardly, with very little forward or rearward motion imparted to the blade drive arm  38   b  at this point. Rather, the attachment end of the blade drive arm at the eccentric pin  40   b  is moving primarily downward. This results in a slight upward movement of the shingle removal blade  48   b  due to its rotation about the fulcrum of the roller bearing  52   b , as indicated by the upward movement arrow U in  FIG. 3B , thus lifting the shingles after being driven forwardly beneath them, as shown in  FIG. 3A  and described further above. 
   In  FIG. 3C , the blade arm drive wheel  36   b  has rotated another ninety degrees, to position the eccentric pin  40   b  at the bottom of the wheel, where its movement is predominately to the rear in the clockwise rotation of the drive wheel  36   b . This draws the blade arm  38   b , and its attached shingle removal blade  48   b , rearwardly, as indicated by the rearward or backward arrow B in  FIG. 3C , allowing the machine  10  to be advanced by the operator. At the same time, the blade  48   b  remains in a relatively elevated position due to the relatively low position of the eccentric pin  40   b  and attachment end of the blade drive arm, thus holding the shingles clear of the underlying surface during this portion of the operational cycle. 
     FIG. 3D  illustrates the position of the drive components when the drive wheel  36   b  has rotated 270 degrees clockwise from its initial position of  FIG. 3A . In  FIG. 3D , the eccentric pin  40   b  is positioned at the rearward or trailing side of the blade arm drive wheel, thus drawing the blade drive arm  38   b  to its rearwardmost position and raising the rearward end of the blade drive arm. This draws the roller bearings, e.g., right hand bearing  52   b , rearwardly and upwardly along their corresponding ramps, e.g., ramp  56   b , thus lifting the shingle removal blade  56   b  to continue to hold any shingles clear of the underlying surface. However, the primary component of motion of the eccentric pin  40   b  and attachment end of the drive arm  38   b  is upward at this point, thus resulting in a slight downward motion of the blade  48   b  (as shown by the downward arrow D in  FIG. 3D ) before it is thrust forwardly again as the cycle continues. This allows the operator to push the machine  10  forward, sliding the front plate forward to the attachment point of the shingles. As the drive wheel  36   b  continues to rotate back to the position shown in  FIG. 3A , the blade drive arm  38   b  and shingle removal blade  48   b  are driven forwardly and slightly downwardly to penetrate beneath the next area of attached shingles, thus repeating the cycle. 
   In conclusion, the shingle removing machine greatly facilitates the removal of shingles from a roof. The geometry of the drive arm actuation oscillates and reciprocates the shingle removing blades in an efficient pattern, wedging beneath and then lifting the shingles clear of the underlying roof structure. The structure of the present machine greatly simplifies maintenance of the device, enabling the operator of the machine to replace the shingle removal blades, and other moving components, quickly and easily. Accordingly, the present shingle removing machine will prove to be a valuable addition to the tools and equipment inventory of the professional roofing contractor and others who have occasion to perform such work. 
   It is to be understood that the present invention is not limited to the embodiment described above, but encompasses any and all embodiments within the scope of the following claims.

Summary:
The shingle removing machine includes a frame supporting a power source, which, in turn, drives a lateral axle with a wheel at each end thereof, with each wheel having an eccentric pin driving a blade drive arm. Separate wheels support the frame. Each blade drive arm extends forwardly and has a relatively wide shingle removal blade at its forward end. The blades extend substantially the width of the machine. The forward ends of the blade drive arms are interconnected and include rollers riding on sloped ramps on the forward end of the frame. Rotation of the blade arm drive wheels reciprocates the blade drive arms forwardly and rearwardly, with the blades also lifting and lowering during the cycle as the forward ends of the arms ride up and down the ramps. The blade drive arm assembly may be quickly and easily disassembled for maintenance and repair in the field.