Patent Publication Number: US-10329782-B1

Title: Isolator overtravel protection for walk-behind floor scraper

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to machines for stripping floor coverings from a floor, and more specifically improvements to protect from damage the elastomeric shock mounts employed on walk-behind floor stripping machines to reduce vibration while permitting orbital movement of the machine&#39;s cutting blade. 
     II. Related Art 
     In 1979, U.S. Pat. No. 4,162,809 was awarded on a motorized carpet and tile stripping machine that comprised a box-like housing mounted on a pair of wheels disposed near the rear of the housing and a cutting blade projecting outwardly from the front of the housing. The blade was adapted to engage the floor beneath a floor covering that had been adhesively bonded to the floor. The housing supported an electric motor having an output shaft that was coupled to the machine&#39;s cutting head by means of an eccentric drive shaft. Thus, the motor caused the cutting head to move in an orbital or elliptical pattern. An elongated handle was affixed to the upper deck of the housing and sloped rearward and upward terminating in handle grips. Machines made in accordance this patent proved to be effective in operation. However, such machines required a high degree of manual effort. The machines also vibrated excessively making the machines very difficult to control. 
     The problem of control was solved by the invention described and claimed in U.S. Pat. No. 4,626,033. This patent discloses a motion-retainer bar assembly between the machine&#39;s frame and cutting head&#39;s drive bar to modify the degree of eccentricity between the drive bar and the shaft of the electric drive motor. While the inclusion of this retainer bar made it easier to control the machine, vibration continued to be excessive. Also, while the machine adequately separated the floor covering from the floor, considerable adhesive residue remained on the floor. 
     An important invention to reduce vibration was disclosed in U.S. Pat. No. 4,963,224. This patent discloses a pair of OILITE® sleeve bearings and a pair of guide rods. These were employed to constrain the motion of the cutting head to reciprocatory, back-and-forth movement parallel to the path of travel of the machine. This invention reduced machine vibration and prolonged the useful life of the machine and minimized its meantime to repair. However, there was no improvement seen in the ability of the machine to remove adhesive residue from the floor following the stripping of the floor covering from the floor. 
     Yet another improvement was made which allowed the machine to do a better job removing adhesive residue from the floor. Specifically, U.S. Pat. No. 6,135,566 discloses a design which significantly increases the downward force of the machine&#39;s cutting blade against the floor by drastically increasing the overall weight of the machine thereby improving the ability of the machine to remove adhesive residue. This additional weight, however, made it much more difficult for the operator to push the machine. The invention of U.S. Pat. No. 6,135,566 also solved this problem by providing a drive system for the machine in which the same motor used to drive the cutting blade also drives the machine&#39;s wheels, making the machine self-propelled and reducing the work effort required by the operator. 
     The foregoing describes the state of the art as it has existed over the last 20 years. Applicants&#39; assignee has had significant commercial success selling machines based upon the inventions referenced above. However, one nagging issue remains with such machines. Specifically, the cutting head is mounted to the underside of the machine and driven by the eccentric. During normal operation, the sleeve bearings (also known as isolators) function well to permit oscillatory movement of the cutting blade relative to the machine while at the same time dampening vibration to an acceptable level. However, from time to time during a floor covering removal operation, obstacles are encountered. All too often, machine operators abuse and misuse the machine when they encounter obstacles. Some operators push on the machine to try to plow through the obstacle. Others try to use the machine like a pry bar in an effort to remove the obstacle. These action exert too much or the wrong kind of force on the cutting head, often beyond the load-carrying capacity of the isolators. Long term and repetitive excess stretching of the isolators through such action leads to tears and ultimate failure. 
     As described in U.S. Pat. No. 6,135,566, the isolators (resilient elastomeric shock-mount members) are constructed by injection molding the elastomeric member onto a steel mounting plate having drilled and tapped holes formed therein. The isolators are susceptible to failure when either of the plates separate from the elastomeric member or the elastomeric member fractures or tears. For the last 17 years, there has been no solution to this problem other than to instruct the machine operators not to push the machine through obstacles, not to run into walls or other obstacles, and not to use the machine to pry obstacles from the floor. Machine operators often ignore these instructions leading to failure of the isolators. 
     SUMMARY OF THE INVENTION 
     The present invention represents an improvement to machines of the type described above which protects the isolators from damage in the event the machine operator encounters an obstacle and does not proceed as instructed. Specifically, the present invention provides for a walk-behind floor stripping machine an assembly comprising a main body plate and a cutting head adapted for oscillatory movement of the cutting head relative to the main body plate. The cutting head is affixed to the bottom surface of the main body plate via a plurality of isolators, each isolator comprising a top plate and a bottom plate held in spaced apart relation by an elastomeric overmold member. The assembly also includes a plurality of stops. In certain embodiments of the present invention, each of these stops has a body portion comprising a base, a neck extending from the base, and a removable flange, such as a washer, adapted to be attached to the end of the neck opposite the body portion. The body portion is affixed to either the main body plate or the cutting head. The neck is adapted to extend through an opening in the other of the main body plate and the cutting head such that the stop generally resides between the main body plate and the cutting head. The flange is then attached to the neck to complete the assembly. The base and the flange are each broader than the opening through which the neck extends. As such, the base, the neck, and the flange of the stop cooperate with surfaces surrounding the opening to permit oscillatory motion of the cutting head assembly and, at the same time, limit flex and shear movement of the cutting head that could be damaging to the isolators. 
     The invention contemplates various improvements be made to the design of the isolators and the way they are mounted. In one embodiment, each isolator includes threaded openings in the top and bottom plate. These openings are adapted to receive the threaded shaft of a bolt. During assembly, one of the bolts is passed through an opening in the main body plate to secure the isolator to the main body plate and the other bolt is passed through an opening in the cutting head to join the isolator to the cutting head. In another embodiment, one of the bolts is positioned so that the head of the bolt is positioned between the two plates of the isolator and the shaft of the bolt extends through an opening in one of the two plates. The head of this bolt is encapsulated during the overmold step used to create the elastomeric overmold member. Still another improvement concerns pockets formed in the main body plate, the cutting head assembly, or both. Each of these pockets is adapted to receive an end of an isolator to provide further structural stability not only to preserve the integrity of the isolator, but also to help retain the elastic overmold member of the isolator in position relative to the plate of the isolator located in the pocket in the event the isolator begins to fail. 
     The stop may also have features beyond those described above. For example, the body portion of the stop may include opposing flattened sides to permit the body portion to be gripped during installation by a wrench or set of pliers. The stop typically includes a threaded channel that extends longitudinally the entire length of the stop. Alternatively, there can be a separate threaded recess at each end of the stop. In either case, the threaded channel (or the pair of threaded recesses) receives a pair of bolts. One of the bolts of the pair of bolts is adapted to couple the stop to either the main body plate (or the cutting head) and the other pair of bolts is adapted to couple the flange (or washer) to the stop. 
     The aforesaid features of the stop allow the cutting head and isolators to perform their intended function during normal operation. However, if the force on the cutting blade held by the cutting head becomes too great, the stop and flange will engage to prevent over-torqueing of the elastomeric portion of the isolator and thus prevent damage to the isolator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which like numerals in the several views refer to corresponding parts. 
         FIG. 1  is a perspective view of the floor covering stripping machine shown in U.S. Pat. No. 6,135,566 representing the state of the prior art; 
         FIG. 2  is an exploded view of the machine of  FIG. 1  showing the construction thereof which, again, is representative of the prior art; 
         FIG. 3  is a cross-sectional view of an improved isolator; 
         FIG. 4  is a perspective view of a hardened stop; 
         FIG. 5  is a side view of the stop of  FIG. 4  with the internal structures shown in dashed lines; 
         FIG. 6  is an exploded perspective view of an assembly including a base plate, a cutting head, a plurality of isolators and a plurality of hardened stops made in accordance with the present invention; 
         FIG. 7  is a cross-sectional view of the assembly of  FIG. 6 ; 
         FIG. 8  is a more detailed cross-sectional view of the portion of  FIG. 7  labeled “A”. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top” and “bottom” as well as derivatives thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “connected”, “connecting”, “attached”, “attaching”, “join” and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece, unless expressively described otherwise. 
       FIGS. 1 and 2  are reproduced from U.S. Pat. No. 6,135,566 granted to Martin L. Anderson and now owned by National Flooring Equipment, Inc. This patent, in its entirety, is incorporated by reference.  FIG. 1  shows the exterior of a walk-behind, self-propelled floor stripping machine  10 . The machine  10  includes a main body plate  12 . Mounted on top of the main body plate  12  is an electric motor  18  that drives the wheels  14  and simultaneously oscillates the cutting head  28  which holds a floor-engaging cutting blade  16 . To advantageously increase the weight of the blade, a front weight member  24  bolts to the main body plate  12 . Likewise, heavy steel side plates  20  and  22  bolt to the housing (not shown). The housing contains the elements that impart motion from the motor  19  to both the wheels  14  and the cutting head  28 . Extending upward and rearward of the housing is a handle  38  used by an operator to control the machine. 
       FIG. 2  shows the various components of the machine in exploded view. These are all described in detail in U.S. Pat. No. 6,135,566 and this entire description will not be repeated here. Of specific interest, however, is the manner in which the cutting head  28  is mounted beneath and to the main body plate  12 . 
     Specifically, a pair of L-shaped slide rods  146  and  148  project upwardly and rearwardly from the top of the cutting head  28 . Mounted to the bottom of the main body plate  12  are a pair of elastomeric shock-mount members  138  (only one of which is shown). The elastomeric members are injection molded onto steel mounting plates  140 . Each of the elastomeric members  138  has a longitudinally extending bore  144  containing a self-lubricating seal bearing adapted to receive the L-shaped slide rods  146 / 148  which reciprocate within the bearings as the motor  18  drives the concentric shaft  132  to oscillate the blade  16 . 
       FIGS. 3-8  show a novel alternative arrangement for attaching a cutting head  260  to a main body plate  240 . The arrangement shown in  FIGS. 3-8  incorporates cylindrical isolators  200  to isolate and dampen vibration and stops  220  to prevent damage to the isolators  200  due to excessive forces applied to the cutting head member. 
       FIG. 3  shows, in cross-section, one of the isolators  200 . As shown, each isolator  200  includes a metal top plate  202 . The metal top plate  202  includes a central threaded orifice  204 . Isolator  200  also includes a metal bottom plate  206  having a central orifice  208 . Isolator  200  further includes a bolt  210  having a head  212  positioned between plates  202  and  206  and a threaded shaft  214  extending through the central orifice  208  of the bottom plate  206 . Finally, the isolator  200  includes an elastomeric rubber or rubber-like material  216  over-molding the plates  202 ,  206  and the head  212  of bolt  210 . 
       FIGS. 4 and 5  illustrate one of the stops  220 . The stop has a body portion  222  with a round base  224  and a side wall  226  having opposing flattened portions  228 . Projecting from the body portion  222  is an elongate neck  230 . Neck  230  has a smaller diameter than the diameter of base  224  of the body portion  222 . 
     Extending longitudinally through the stop  220  and open to the top of the body portion  222  and the bottom of the neck  230  is a threaded channel  232 . The threads may extend the entire length of channel  232  or the threads may only be present in the top and bottom sections of the channel  232 . Alternatively, the body portion  222  and the neck  230  can be provided with central threaded recesses, one extending inwardly from the top of body portion  222  and the other extending inwardly from the bottom of neck  230 . 
       FIGS. 6-8  illustrate how a plurality of isolators  200  and a plurality of stops  220  are employed in combination with nuts, bolts and washers to join a main body plate  240  and a cutting head member  260  together. In the embodiment of  FIG. 6 , seven isolators  200  are employed, only five of which are shown. Two stops  220  are also employed. 
     As illustrated in  FIGS. 7 and 8 , the bottom of the main body plate  240  is provided with separate receiver pocket  242  for each isolator  200 . The receiver pocket  242  is slightly larger in diameter than the top of the isolator  200  such that the receiver pocket  242  is adapted to receive the top of an isolator  200  and limit lateral movement of the isolator  200 . Extending through the main body plate  240  at the center of each pocket  242  is a passageway so that the threaded shaft of a bolt  244  can pass through the main body plate  240  and be inserted into the threaded orifice  204  of the top plate  202  of the isolator  200  to couple the isolator  200  to the main body plate  240 . 
     After all the isolators  200  are coupled to the main body plate  240 , the stops  220  are coupled to the main body plate in a similar fashion. Specifically, the main body plate  240  also has holes  246  adapted to receive the threaded shaft  250  of a bolt  248 . The top of the body portion  222  of a stop  220  is aligned with a hole  246  and the end of shaft  250  is then passed through the hole  246  and into the threaded channel  232  to couple the stop  220  to the main body plate  240 . A wrench or pliers can grip the opposing flattened portions  228  of the stop  220  to assist in tightening the stop  220  relative to the main body plate  240  and bolt  248 . 
     As best illustrated in  FIG. 6 , the cutting head  260  has three different sets of holes. Holes  262  are adapted to receive the threaded shafts  214  extending from the bottom of the isolators  200 . Holes  264  are adapted to receive the necks  230  of the stops  220 . The holes  264  are larger in diameter than the necks  230 , but smaller in diameter than the base  224  of the body  222 . Holes  266  receive bolts  267  used to couple bearing  265  to the cutting head  260 . Hole  267  receives an eccentric shaft such as  132  (see  FIG. 2 ) that cooperates with the motor  18  and is joined to bearing  265  to impart oscillatory motion to the cutting head  260 . 
     After all the isolators  200  and stops  220  have coupled to the main body plate  240 , the threaded shaft  214  of each isolator  200  and the neck  230  of each stop  220  is passed through the above-described holes  262 / 264  of the cutting head  260 . Nuts  215  are then coupled to each of the threaded shafts  214  of each isolator. Also, a bolt  249  is passed through a flange (e.g., washer)  270  which is tightened to the bottom end of the neck  230  by mating the threaded shaft of bolt  249  with the threads of channel  232  located in the region of the neck  230 . The neck  230  is longer than the thickness of the cutting head member  260 . As such, the cutting head member  260  is loosely sandwiched between the flange  270  and the base  224  of the body  222  of stop  220 . Likewise, because the neck is narrower than the diameter of the holes  264 , some back and forth play is permitted. 
     Further assembly of the machine is completed generally as described in U.S. Pat. No. 6,135,566 with the assembly of the main body plate  240 , the cutting head  260 , the isolators  200  and stops  220  replacing the assembly of main plate  12 , cutting head member  28  and shock mount members  138 . Operation of the machine  10  is also much the same from an operator standpoint with several clear advantages. Some of these advantages are described below. 
     First, with the design shown in U.S. Pat. No. 6,135,566, excessive forces on the cutting head would, over time, cause the metal plate of the isolator to separate from the elastomeric member, essentially rendering the machine inoperable. With the present design, the stops  220  and washers  270  associated therewith engage and prevent further movement of the cutting head before similar damage to the isolators  200  can occur. More specifically, the stops  220  and washers  270  permit oscillatory motion of the cutting head, but limit excessive flex and shear movement that damage the isolators. 
     Second, the side walls of the pockets  242  limit side-to-side movement of the elastomeric member  216  relative to a plate  202  of the isolator  200  further reducing the risk of damage to the isolator  200 . 
     Third, the stops  220  protect the isolators  200  from too great a force being applied to the cutting head  260 . The stops  220  also protect the bearing  265 , the eccentric shaft and other elements used to transfer motion from the motor to the cutting head  260 . 
     Various modifications can, of course, be made considering the disclosure provided without deviating from the present invention. Thus, the disclosure is intended to be exemplary rather than limiting.