Patent Publication Number: US-9420931-B2

Title: Surface treating machine

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a machine for treating work surfaces such as floors formed of carpet, tile, wood and other materials. The most efficient and effective surface treatments employ a vibration, “scrubbing”, motion to loosen materials on the work surface. On floors and other work surfaces, a machine typically uses a cleaning towel, “pad”, in combination with a solvent, including water or steam, and/or a cleaning agent. When the cleaning towel scrubs the floor and becomes dirty, the towel is replaced with a clean one. 
     In U.S. Patent publication 20070107150 A1 having inventor Yale Smith and published May 17, 2007, a Carpet Cleaning Apparatus And Method With Vibration, Heat, And Cleaning Agent is described. In that patent publication, a combination of vibratory motion, controllable heat, and cleaning agents are used. The apparatus includes a base cleaning plate, heating elements with electrical connections, and means for moving the cleaning plate to produce a scrubbing motion. 
     Important attributes of surface treating machines are cleaning effectiveness, ease of use, convenience, stability, light weight, low machine wear, long life and ease of maintenance. These attributes are import for machines used by professionals in heavy duty environments or used by other consumers in home or other light duty environments. 
     Cleaning effectiveness requires that machines include a small oscillation that creates a local vibration in a cleaning plate to impart a “scrubbing” movement to the surface being treated. For cleaning floors, the local vibration is preferably in a range of several millimeters. Cleaning effectiveness and convenience requires that the shape of the cleaning plate be rectangular so as to be readily used along straight edges and easily moved into rectangular corners. In order to satisfy these attributes, machines with round bottom plates are undesirable. 
     Ease of use and convenience require stability, appropriate size and weight and ease of operator control. Designs that position the motor and drive assembly high above the cleaning plate are undesirable since such configurations tend to accentuate vertical instability. Vertical instability results in unwanted oscillation of the cleaning plate up and down in a mode that is in and out of the plane of the work surface. The plane of the work surface is referred to as the floor surface plane or the XY-plane. Vertical instability is distinguished from horizontal oscillations providing local vibration to impart a “scrubbing” movement to the cleaning plate. The horizontal oscillations are parallel to the plane of the work surface, that is, parallel to the XY-plane. Vertical instability is additionally undesirable because it uses excessive amounts of energy, reduces the energy efficiency of the machine and causes increased wear on the motor, the dive shafts, the drivers and the drive bushings. The increased wear increases maintenance and decreases the life of the machine. User fatigue is dramatic when unwanted vertical oscillations occur. 
     High energy efficiency is an important attribute. For machines powered by an AC electrical service through an AC-to-DC converter or powered by a battery, the size and cost of the motor is a function of the energy requirements needed to drive the transmission and the cleaning plate. For DC motors, the energy requirements are important for the motor and for the AC-to DC converter used to convert the AC electrical service to DC. The more energy efficient the machines, the smaller and less expensive are the AC-to-DC converters, batteries and motors required to power the machines. 
     Another factor in cleaning effectiveness is determined by the material of the machine in contact with the floor material. Brushes are not absorbent and therefore are inefficient in removing solid and liquid matter from a floor. For existing machines that use a towel, the towels are typically synthetic and do not absorb and hold solid and liquid matter from a floor. For towels that are primarily cotton, they have the disadvantage of not scrubbing well and also have high friction with the floor surface resulting in low energy efficiency. 
     In light of the above background, it is desirable to have improved surface treatment machines for treating carpets, tiles, wood and other surface materials. 
     SUMMARY 
     The present invention is a machine for treating a surface lying in an XY-plane comprising a body, a body plate attached to the body, a drive assembly attached to the body and a cleaning plate assembly. The drive assembly includes a motor having a motor drive shaft and a transmission having offset drivers driven by the motor drive shaft. The cleaning plate assembly has an eccentric drive member engaging the offset drivers to drive the cleaning plate assembly in an oscillating pattern parallel to the XY-plane and relative to the body plate. 
     In embodiments, the motor drive shaft extends in a direction normal to the XY-plane, and the transmission connects from the motor drive shaft to the eccentric drive member of the cleaning plate assembly with belts and gears. 
     In embodiments, the motor drive shaft extends in a direction parallel to the XY-plane, and the transmission connects from the motor drive shaft to the eccentric drive member of the cleaning plate assembly. 
     In embodiments, the present invention is a machine for treating a surface lying in an XY-plane comprising a body, a body plate attached to the body, a drive assembly attached to the body, a cleaning plate assembly and one or more ball bearings positioned between the body plate and the cleaning plate for separating the body plate and the cleaning plate. The drive assembly includes a motor having a motor drive shaft and a transmission having offset drivers driven by the motor drive shaft. The cleaning plate assembly has an eccentric drive member engaging the offset drivers to drive the cleaning plate assembly in an oscillating pattern parallel to the XY-plane and relative to the body plate. 
     In embodiments, the body plate and the cleaning plate each have pockets near edges for receiving the ball bearings whereby the ball bearings roll in the pockets during movement of the cleaning plate in the oscillating pattern. In embodiments, the pockets have side walls and the side walls lined with soft material for suppressing noise when the ball bearings roll in the pockets during movement of the cleaning plate. In embodiments, one or more of the pockets is lined with a compressible soft material whereby the ball bearings are maintained in contact with both the body plate and the cleaning plate. In embodiments, the offset drivers each have a driver offset measured from a center axis of the respective offset driver drive shaft whereby the cleaning plate assembly is constrained to move in a treatment region bounded by approximately +/− the driver offset where the driver offset is typically between 4 and 10 mm. 
     In embodiments, the present invention is a machine for treating a surface lying in an XY-plane comprising a body, a body plate attached to the body, a drive assembly attached to the body, a cleaning plate assembly and one or more ball bearings positioned between the body plate and the cleaning plate for separating the body plate and the cleaning plate. The cleaning plate assembly has a convex shape for driving the machine in a forward direction. The drive assembly includes a motor having a motor drive shaft and a transmission having offset drivers driven by the motor drive shaft. The cleaning plate assembly has an eccentric drive member engaging the offset drivers to drive the cleaning plate assembly in an oscillating pattern parallel to the XY-plane and relative to the body plate. In embodiments, the cleaning plate and an eccentric drive member are engaged by force toward the center of the eccentric drive member to draw the cleaning plate into the convex shape. 
     The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a side view of one embodiment of a surface treating machine on a surface to be treated. 
         FIG. 2  depicts an isometric view of the surface treating machine of  FIG. 1 . 
         FIG. 3  depicts a front view with further details of one embodiment of the drivers and the cleaning plate assembly of the machine of  FIG. 1 . 
         FIG. 4  depicts a side view of the drivers and the cleaning plate assembly of  FIG. 3 . 
         FIG. 5  depicts a front view of the motor and support for the surface treating machine of  FIG. 1  and  FIG. 2 . 
         FIG. 6  depicts a top view of the motor and support of  FIG. 5 . 
         FIG. 7  depicts a perspective view of the motor and support of  FIG. 5 . 
         FIG. 8  depicts a front view of the gears, pulleys and belts that form a part of one embodiment of the transmission for the surface treating machine of  FIG. 1  and  FIG. 2 . 
         FIG. 9  depicts a top view of the gears, pulleys and belts of  FIG. 8 . 
         FIG. 10  depicts a top view of the pulleys and belts that form a part of an embodiment of the transmission of  FIG. 3 . 
         FIG. 11  depicts a front view of the pulleys and belts of  FIG. 10 . 
         FIG. 12  depicts a top view of the pulleys and belts that form a part of another embodiment of the transmission of  FIG. 3 . 
         FIG. 13  depicts a front view of the pulleys and belts of  FIG. 13 . 
         FIG. 14  depicts an isometric view of the transmission of  FIG. 12 . 
         FIG. 15  depicts an isometric view of the reversing belt in the transmission in  FIG. 14 . 
         FIG. 16  depicts four different positions of the cleaning plate when the offset drivers are rotating in opposite directions. 
         FIG. 17  depicts a top view of the four different positions of the cleaning plate when the offset drivers are rotating in opposite directions as shown in  FIG. 16 . 
         FIG. 18  depicts four different positions of the cleaning plate when the offset drivers are rotating in the same directions. 
         FIG. 19  depicts a top view of the four different positions of the cleaning plate when the offset drivers are rotating in the same direction as shown in  FIG. 18 . 
         FIG. 20  depicts a front view of the cleaning plate assembly and the body plate of  FIG. 3 . 
         FIG. 21  depicts a bottom view of the body plate of  FIG. 20  along the section line  20 - 20 ′ of  FIG. 20 . 
         FIG. 22  depicts an end view of the body plate of  FIG. 21 . 
         FIG. 23  depicts a top view of the cleaning plate of  FIG. 20  along the section line  23 - 23 ′ of  FIG. 20 . 
         FIG. 24  depicts an end view of the cleaning plate of  FIG. 23 . 
         FIG. 25  depicts a top view of the top portion of the offset driver member that forms part of the drive assembly of  FIG. 20 . 
         FIG. 26  depicts a top view of the bottom portion of the offset driver member that forms part of the drive assembly of  FIG. 20 . 
         FIG. 27  depicts a front view of the top and bottom portions of the offset driver member that forms part of the drive assembly of  FIG. 20 . 
         FIG. 28  depicts a front view of the offset driver member extending through the fixed body plate and attached to the cleaning plate. 
         FIG. 29  depicts the fixed body plate adjacent the cleaning plate and held offset from the cleaning plate by rolling bearings. 
         FIG. 30  depicts an expanded view of a portion of  FIG. 29  with the fixed body plate adjacent the cleaning plate and held offset from the cleaning plate by one rolling ball bearing. 
         FIG. 31  depicts the view of  FIG. 30  with the fixed body plate adjacent the cleaning plate and held offset from the cleaning plate by one rolling bearing rolled in one direction. 
         FIG. 32  depicts the expanded view of  FIG. 30  with the fixed body plate adjacent the cleaning plate and held offset from the cleaning plate by one rolling bearing rolled in a direction opposite of the direction of  FIG. 31 . 
         FIG. 33  depicts an expanded view of  FIG. 30  showing details of the lining of the pockets for the rolling bearing. 
         FIG. 34  depicts the alternate embodiment of an expanded view of  FIG. 30  showing details of the lining of the pockets for the rolling bearing in an expanded state. 
         FIG. 35  depicts the alternate embodiment of an expanded view of  FIG. 30  showing details of the lining of the pockets for the rolling bearing in a compressed state. 
         FIG. 36  depicts a view of the cleaning plate over a cleaning pad. 
         FIG. 37  depicts a simplified representation of the geometry of the cleaning plate. 
         FIG. 38  depicts a graphical representation of the forces being created by the cleaning plate and the torque on the drive assembly. 
         FIG. 39  depicts a cleaning pad affixed to the cleaning plate with fasteners. 
         FIG. 40  depicts a perspective view of a portion of the cleaning pad of  FIG. 40 . 
         FIG. 41  depicts a bottom view of the cleaning plate and the attachment pads. 
         FIG. 42  depicts a top view of the pulleys and belts that form another embodiment for offset drivers. 
         FIG. 43  depicts a top view of the pulleys and belts that form still another embodiment for offset drivers. 
         FIG. 44  depicts a front view of an embodiment of the cleaning plate assembly and the body plate like that of  FIG. 20 . 
         FIG. 45  depicts an exploded front view of an embodiment of the cleaning plate assembly and the body plate of  FIG. 46 . 
         FIG. 46  depicts an assembled front view of an embodiment of the cleaning plate assembly and the body plate of  FIG. 47 . 
         FIG. 47  depicts a top view of an embodiment of the cleaning plate assembly and eccentric drive member of  FIG. 48 . 
         FIG. 48  depicts a diagram for explaining the forward drive of the geometry of the cleaning plate assembly and eccentric drive member of  FIG. 47 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a surface treating machine  1  includes a body  9 , a drive assembly  10  and a cleaning plate assembly  12 . A body plate  16  is rigidly attached to the body  9 . The cleaning plate assembly  12  is driven by the drive assembly  10  for cleaning or polishing the floor surface lying in a floor plane denominated as the XY-plane. The cleaning plate assembly  12  includes a cleaning plate  12 - 1  and a cleaning pad  12 - 2 . In some embodiments, the machine  1  includes a skirt  8  attached as part of the body  9  and superimposed over the cleaning plate assembly  12 . 
     In  FIG. 1 , the machine  1  includes a handle assembly  15  affixed to the body  9  for enabling a user to guide machine  1  over a floor surface lying in the XY-plane. The handle assembly  15  has a length extending from the body  9  at a variable angle with the XY-plane. One or more compartments  17  are attached to or the handle assembly  15 . The compartments include, for example, one or more fluid compartments  17 - 1  for storing water, cleaners or other solutions and one or more electrical compartments for housing an AC-to-DC converter  17 - 2  or a battery  17 - 3 . The handle assembly may include items not explicitly shown such as an AC power cord, a power plug for operation with an AC-to-DC converter, an electrical control line and an ON/OFF switch. The handle assembly  15  is rotationally attached to body  9  and adjusts to acute angles with the cleaning surface when in use for cleaning. The handle assembly  15  includes a latch for latching the handle assembly  15  in the vertical position for transport and storage of the machine  1  when not in operation. 
     The drive assembly  10  has a drive assembly height dimension, H, measured from the XY-plane. The cleaning plate assembly  12  typically has a length and a width lying in the XY-plane of the floor surface. The smaller one of the length and the width dimensions, or the only dimension if the length and width are equal, of the cleaning plate assembly  12  is the minimum treatment dimension, M_D. In order to provide stability for the machine  1 , the height dimension, H, typically is less than one half of the minimum treatment dimension, M_D. A low drive assembly height dimension is important in minimizing or preventing unwanted vertical instability. Vertical instability results in unwanted oscillation of the cleaning plate up and down in a mode that is in and out of the XY-plane of the work surface. Such unwanted oscillations are a complex function of the floor surface material and movements of the machine during operation as well as the design of the machine. For normal and intended operation, the machine is operating with oscillations in the XY-plane of the floor surface. When the machine is moved from location to location on a floor by a machine operator, some forces out of the XY-plane inherently result. If the drive assembly  10  height dimension, H, is too high, these forces out of the XY-plane tend to accumulate in intensity reaching a resonant vibration frequency identified as vertical instability. Such vertical instability can be difficult to control by an operator and is wasteful of energy. In some embodiments, the vertical instability is minimized or eliminated by having the drive assembly height dimension, H, less than one half of the minimum treatment dimension, M_D. 
     In  FIG. 2 , an isometric view of the surface treating machine  1  of  FIG. 1  is shown. The surface treating machine  1  includes a body  9  with a handle assembly  15 . The handle assembly  15  is shown latched in the upright position. The cleaning plate assembly  12  is driven by the body  9  in an oscillating pattern. 
     In  FIG. 3 , a front view with further details of one embodiment of the drive assembly  10 , the body plate  16  and the cleaning plate assembly  12  of  FIG. 1  is shown. The drive assembly  10  includes a motor  30  and a transmission  20 . The transmission  20  includes a first transmission assembly part  20 - 1  and a second transmission assembly part  20 - 2 . The first transmission assembly part  20 - 1  connects to the second transmission assembly part  20 - 2  through a motor drive shaft  21 , a first drive shaft  21 - 1 , and a second drive shaft  21 - 2  and a third drive shaft  21 - 3 . In the second transmission assembly part  20 - 2 , a base  31  supports the motor  30  and the first drive shaft  21 - 1 , the second drive shaft  21 - 2  and the third drive shaft  21 - 3 . 
     The first drive shaft  21 - 1  is supported by first bearings  26 - 1  and  27 - 1  in the base  31  which connects to a first offset driver  22 - 1 . A first bushing  23 - 1  engages the first offset driver  22 - 1 . The second drive shaft  21 - 2  is supported by second bearings  26 - 2  and  27 - 2  in the base  31  which connects to a second offset driver  22 - 2 . A second bushing  23 - 2  engages the second offset driver  22 - 2 . The first bushing  23 - 1  and the second bushing  23 - 2  are mounted in the eccentric drive member  29 . The first offset driver  22 - 1  and the second offset driver  22 - 2  rotate in first bushing  23 - 1  and the second bushing  23 - 2 , respectively. Because the first offset driver  22 - 1  and the second offset driver  22 - 2  have offsets from the center lines of drive shafts  21 - 1  and  21 - 2 , the eccentric drive member  29  oscillates within an opening in the body plate  16 . In some embodiments, a drive shaft  21 - 3  is supported by bearings  41 - 1  and  42 - 1  in the base  31 . 
     The transmission first assembly part  20 - 1  operates to transfer the rotational motion of the drive shaft  21  to the drive shafts  21 - 1  and  21 - 2  and thereby to the offset drivers  22 - 1  and  22 - 2 . The offset drivers  22 - 1  and  22 - 2  drive the cleaning plate assembly  12  in a vibrating motion in the XY-plane by a ±OFFSET_D. The offset driver  22 - 1  has an OFFSET_ 1  offset from the center axis of the drive shaft  21 - 1  by the offset OFFSET_ 1  that is equal to OFFSET_D. The offset driver  22 - 2  has an OFFSET_ 2  offset from the center axis of the drive shaft  21 - 2  by the offset OFFSET_ 2  that is equal to OFFSET_D. The offset drivers  22 - 1  and  22 - 2  each have a driver offset, equal to OFFSET_D, measured from a center axis of the respective offset driver drive shaft whereby the cleaning plate assembly  12  is constrained to move in a treatment region bounded by approximately +/− the driver offset. 
     In  FIG. 3 , the motor drive shaft  21  and portions of the transmission  20  are located with the motor drive shaft  21  extending in the +Z-axis direction, a direction away from and normal to the XY-plane. The transmission  20  connects from the motor drive shaft  21  around the motor  30  to the bushings  23 - 1  and  23 - 2  in the eccentric drive member  29 . The positioning of portions of the transmission  20  above the motor  30  and away from the XY-plane of the floor surface is desirable in that it enables ready and easy access for repair or other servicing and keeps those portions of the transmission  20  away from the potentially wet or dirty cleaning environment of the floor surface at the XY-plane. 
     In  FIG. 3 , the motor  30  in one embodiment is a pancake shaped printed motor that is compact in size, high in output torque, high in energy efficiency, 75%-85%, high in reliability and low in noise using rare earth magnets and operable in voltages from 12 volts to 48 volts. Such motors are sold, for example, by Golden Motors of Shanghai, China. The DC motors have a higher starting torque than AC motors. The low DC voltages provide good user safety and are battery capable. In one embodiment described, the motor  30  has a no-load operation at 3200 RPM which is reduced by the transmission to 2000 RPM. In another embodiment, the motor  30  has a no-load operation at 2880 RPM which is reduced by the transmission to 1800 RPM. 
     In  FIG. 4 , a side view of the drive assembly  10 , the body plate  16  and the cleaning plate assembly  12  of  FIG. 3  are shown. The drive assembly  10  includes a motor  30  and a transmission  20 . The base  31  supports the motor  30  and the transmission  20 . The transmission  20  includes a first transmission assembly part  20 - 1  and a second transmission assembly part  20 - 2 . In  FIG. 4 , the first transmission assembly part  20 - 1  connects to the second transmission assembly part  20 - 2  through a motor drive shaft  21  and a second drive shaft  21 - 2 . In the second transmission assembly part  20 - 2 , a base  31  supports the motor  30  and the second drive shaft  21 - 2 . The second drive shaft  21 - 2  is supported by second bearings  26 - 2  and  27 - 2  and connects to the second offset driver  22 - 2 . A second bushing  23 - 2  in the eccentric drive member  29  engages the second offset driver  22 - 2 . The transmission  20  operates to transfer the rotational motion of the drive shaft  21  to the drive shaft  21 - 2  and thereby to the offset driver  22 - 2 . The offset driver  22 - 2  drives the cleaning plate assembly  12  with a vibrating motion. 
     In  FIG. 5 , a front view is shown of the motor  30  and the support base  31  supporting the motor  30  for the surface treating machine  1  of  FIG. 1  and  FIG. 2 . The support base  31  has openings  28 - 1 ,  28 - 2  and  28 - 3  for bearings. The support base  31  is rigidly attached to a handle assembly mount  15 - 1 . The handle assembly mount  15 - 1  includes rigid end brackets  15 - 2  rigidly attached to base  31  and includes handle mount  15 - 3  that is rotatably attached to the rigid end brackets  15 - 2 . The handle mount  15 - 3  engages the handle  15  of  FIG. 1  and  FIG. 2 . 
     In  FIG. 6 , a top view of the motor  30  and support base  31  of the drive assembly  10  of  FIG. 3  is shown with the axis of drive shaft  21  of drive motor  30  extending in the Z-axis direction away from the XY-plane and normal to the drawing page. The base  31  has holes  28 - 1 ,  28 - 2  and  28 - 3  for receiving the transmission shafts,  21 - 1 ,  21 - 2  and  21 - 3 , see  FIG. 3 , and bearings,  26 - 1  and  27 - 1 ;  26 - 2  and  27 - 2 ; and  41 - 1  and  42 - 1 , see  FIG. 3 . The support base  31  is rigidly attached to a handle assembly mount  15 - 1 . The handle assembly mount  15 - 1  includes rigid end brackets  15 - 2  rigidly attached to base  31  and includes handle mount  15 - 3  that is rotatably attached to the rigid end brackets  15 - 2 . The handle mount  15 - 3  engages the handle  15  of  FIG. 1  and  FIG. 2 . 
     In  FIG. 7 , a perspective view is shown of the motor  30  and support base  31  of  FIG. 6  without the handle assembly mount  15 - 1 . The base  31  has holes  28 - 1 ,  28 - 2  and  28 - 3  for receiving the transmission shafts,  21 - 1 ,  21 - 2  and  21 - 3 , see  FIG. 3 , and bearings,  26 - 1  and  27 - 1 ;  26 - 2  and  27 - 2 ; and  41 - 1  and  42 - 1 , see  FIG. 3 . 
     In  FIG. 8 , a front view with further details of one embodiment of the drive assembly  10 , the body plate  16  and the cleaning plate assembly  12  of  FIG. 1  is shown. The drive assembly  10  includes a motor  30  and a transmission  20 . The transmission  20  includes a first transmission assembly part  20 - 1  and a second transmission assembly part  20 - 2 . The first transmission assembly part  20 - 1  connects to the second transmission assembly part  20 - 2  through a motor drive shaft  21 , a first drive shaft  21 - 1 , and a second drive shaft  21 - 2  and a third drive shaft  21 - 3 . In the second transmission assembly part  20 - 2 , a base  31  supports the motor  30  and the first drive shaft  21 - 1 , the second drive shaft  21 - 2  and the third drive shaft  21 - 3 . 
     The first drive shaft  21 - 1  is supported by first bearings  26 - 1  and  27 - 1  in the base  31  which connects to a first offset driver  22 - 1 . A first bushing  23 - 1  in the eccentric drive member  29  engages the first offset driver  22 - 1 . The second drive shaft  21 - 2  is supported by second bearings  26 - 2  and  27 - 2  in the base  31  which connects to a second offset driver  22 - 2 . A second bushing  23 - 2  in eccentric driver  29  engages the second offset driver  22 - 2 . The third drive shaft  21 - 3  is supported by third bearings  41 - 1  and  42 - 1  in the base  31 . 
     The transmission first assembly  20 - 1  operates to transfer the rotational motion of the drive shaft  21  to the drive shafts  21 - 1  and  21 - 2  and thereby to the offset drivers  22 - 1  and  22 - 2 . The transmission assembly  20 - 1  in one embodiment includes motor pulley  24  connected to the motor drive shaft  21 , a first pulley  24 - 1  connected to a first drive shaft  21 - 1  and a second pulley  24 - 2  connected to the second drive shaft  21 - 2 . A third pulley  24 - 3  is connected to the drive shaft  21 - 3 . A gear  37 - 1  connects to the drive shaft  21 - 3 . A gear  37 - 2  connects to the drive shaft  21 - 3 . The gear  37 - 1  engages and in operation rotates the gear  37 - 2 . 
     The pulleys  24 ,  24 - 1 ,  24 - 2  and  24 - 3  together with the gears  37 - 1  and  37 - 2 , as part of the transmission  20 , operate to transfer the rotational motion of the drive shaft  21  from motor  30  to the drive shafts  21 - 1  and  21 - 2 . The motor pulley  24  is driven in the clockwise direction and drives pulley  24 - 1  and drive shaft  21 - 1  in the clockwise direction through belt  36 - 2 . The pulley  24 - 2 , attached to drive shaft  21 - 1 , is driven in the clockwise direction and drives pulley  24 - 3  and gear  37 - 1  attached to drive shaft  21 - 3  in the clockwise direction through belt  36 - 1 . The gear  37 - 1  attached to drive shaft  21 - 3  and driven in the clockwise direction engages gear  37 - 2  and turns gear  37 - 2  and drive shaft  21 - 2  in the counterclockwise direction. The pulleys  24 - 2  and  24 - 3  are of the same diameter and design so that the drive shafts  21 - 1  and  21 - 3  turn in the same direction and at the same speed. The gear  37 - 1  and the gear  37 - 2  are of the same diameter and design so that the drive shafts  21 - 3  and  21 - 2  turn at the same speed but rotate in opposite directions. Because the first offset driver  22 - 1  and the second offset driver  22 - 2  have offsets from the center lines of drive shafts  21 - 1  and  21 - 2 , the eccentric drive member  29  oscillates within an opening in the body plate  16 . 
     In  FIG. 9 , a bottom view is shown of the transmission first assembly  20 - 1  of  FIG. 8  taken along the section line  9 - 9 ′ in  FIG. 8 . The transmission first assembly  20 - 1  operates to transfer the rotational motion of the drive shaft  21  to the drive shafts  21 - 1  and  21 - 2 . The transmission assembly  20 - 1  includes motor pulley  24  connected to the motor drive shaft  21 , a first pulley  24 - 1 , not shown in  FIG. 9 , see  FIG. 8 , connected to a first drive shaft  21 - 1  and a second pulley  24 - 2  connected to the first drive shaft  21 - 1 . A third pulley  24 - 3  is connected to the drive shaft  21 - 3 . A gear  37 - 1  also connects to the drive shaft  21 - 3 . A gear  37 - 2  connects to the drive shaft  21 - 3 . The gear  37 - 1  engages the gear  37 - 2 . The pulleys  24 - 2  and  24 - 3  are of the same diameter and design so that the drive shafts  21 - 1  and  21 - 3  turn in the same direction and at the same speed. The gear  37 - 1  and the gear  37 - 2  are of the same diameter and design so that the drive shafts  21 - 3  and  21 - 2  turn at the same speeds but in the opposite directions. 
     In  FIG. 10 , a top view is shown of the pulleys  24 ,  24 - 1 ,  26 - 1  (not shown) and  26 - 2  and belts  36 - 1  and  36 - 2  that form a part of another embodiment of the transmission first assembly  20 - 1  of  FIG. 3 . The transmission first assembly  20 - 1  operates to transfer the rotational motion of the drive shaft  21  to the drive shafts  21 - 1  and  21 - 2 . The transmission assembly  20 - 1  includes motor pulley  24  connected to the motor drive shaft  21 , a first pulley  24 - 1  connected to a first drive shaft  21 - 1  and a pulley  24 ′- 3  connected to the second drive shaft  21 - 2 . The pulley  24 - 2  (not shown) is below the pulley  24 - 1 . The belt  36 - 2  connects between the pulley  24  and the pulley  24 - 1 . The belt  36 - 1  connects between the pulley  24 - 2  (not shown) and the pulley  24 ′- 3 . The transmission first assembly  20 - 1  operates so that the drive shafts  21 - 3  and  21 - 2  turn at the same speed and in the same direction. 
     In  FIG. 11 , a front view is shown of the pulleys and belts of  FIG. 10 . The transmission assembly  20 - 1  includes motor pulley  24  connected to the motor drive shaft  21  and a first pulley  24 - 1  connected to a first drive shaft  21 - 1 . A pulley  24 - 2  connects to the first drive shaft  21 - 1  and a pulley  24 ′- 3  connects to the second drive shaft  21 - 2 . The belt  36 - 2  connects between the pulley  24  and the pulley  24 - 1 . The belt  36 - 1  connects between the pulley  24 - 2  and the pulley  24 ′- 3 . The transmission first assembly  20 - 1  operates so that the drive shafts  21 - 1  and  21 - 2  turn at the same speed and in the same direction. 
     In  FIG. 12 , a top view is shown of the pulleys  24 ,  24 - 1 ,  26 - 1  (not shown) and  26 - 2  and the belts  36 - 1  and  36 - 2  that form a part of another embodiment of the transmission first assembly  20 - 1  of  FIG. 3 . The transmission first assembly  20 - 1  operates to transfer the rotational motion of the drive shaft  21  to the drive shafts  21 - 1  and  21 - 2 . The transmission assembly  20 - 1  includes motor pulley  24  connected to the motor drive shaft  21 , a first pulley  24 - 1  connected to a first drive shaft  21 - 1  and a pulley  24 ′- 3  connected to the second drive shaft  21 - 2 . The pulley  24 - 2  (not shown) is below the pulley  24 - 1  and first drive shaft  21 - 1 . The belt  36 - 2  connects between the pulley  24  and the pulley  24 - 1 . The belt  36 - 1  connects between the pulley  24 - 2  (not shown) and the pulley  24 ′- 3 . The belt  36 - 1  is twisted so that the transmission first assembly  20 - 1  operates with the drive shafts  21 - 3  and  21 - 2  turning at the same speed and in opposite directions. 
     In  FIG. 13 , a front view is shown of the pulleys and belts of  FIG. 12 . The transmission assembly  20 - 1  includes motor pulley  24  connected to the motor drive shaft  21  and a first pulley  24 - 1  connected to a first drive shaft  21 - 1 . A pulley  24 - 2  connects to the first drive shaft  21 - 1  and a pulley  24 ′- 3  connects to the second drive shaft  21 - 2 . The belt  36 - 2  connects between the pulley  24  and the pulley  24 - 1 . The belt  36 - 1  connects between the pulley  24 - 2  and the pulley  24 ′- 3  and is twisted so that the drive shafts  21 - 3  and  21 - 2  turn at the same speed and in opposite directions. 
     In  FIG. 14 , an isometric view of the transmission of  FIG. 12  is shown. The transmission assembly  20 - 1  includes motor pulley  24  connected to the motor drive shaft  21  and a first pulley  24 - 1  connected to a first drive shaft  21 - 1 . The belt  36 - 2  connects between the pulley  24  and the pulley  24 - 1 . A pulley  24 - 2  connects to the first drive shaft  21 - 1  and a pulley  24 ′- 3  connects to the second drive shaft  21 - 2 . The belt  36 - 1  connects between the pulley  24 - 2  and the pulley  24 ′- 3  and is twisted so that the drive shafts  21 - 1  and  21 - 2  turn at the same speed and in opposite directions. The belt  36 - 1  is separated at the crossover location between the pulleys  26 - 1  and  26 - 2  by the belt separator  36 - 3 . The belt separator  36 - 3  is made of metal, plastic or other smooth material that does not cause excessive wear of the belt  36 - 1 . 
     In  FIG. 15 , an isometric view is shown of the reversing belt  36 - 1  and the belt spacer  36 - 2  in the transmission in  FIG. 14 . 
     In  FIG. 16 , shifted top views of four different positions are shown of the cleaning plate  12 - 1  according to the  FIG. 8  and  FIG. 12  transmissions. The four different positions are designated  95 - 1 ,  95 - 2 ,  95 - 3  and  95 - 4 . In  FIG. 16 , the offset drivers  22 - 1  and  22 - 1  are rotating in opposite directions. With the offset driver of  FIG. 16 , the drive shafts  21 - 1  and  21 - 2  remain aligned. In embodiments such as  FIG. 16  with the counter rotation of the offset drivers  22 - 1  and  22 - 2 , the cleaning action is particularly suitable for hard surfaces such as wood floors and rugs with short piles and loops. A 2 millimeter offset has been found suitable for a machine having a minimum treatment dimension, M_D, of 7 inches. 
     In  FIG. 17  a non-shifted top view of the four different positions of  FIG. 16  are shown for the cleaning plate  12 - 1 . According to  FIG. 17 , the  FIG. 8  and  FIG. 12  transmissions drive through the four different typical positions designated  95 - 1 ,  95 - 2 ,  95 - 3  and  95 - 4 . 
     In  FIG. 18 , top views of four different positions are shown of the cleaning plate  12 - 1  using the  FIG. 10  transmission. The four different positions are designated  96 - 1 ,  96 - 2 ,  96 - 3  and  96 - 4 . In  FIG. 18 , the offset drivers  22 - 1  and  22 - 1  are rotating in the same direction. With the offset driver of  FIG. 10 , the drive shafts  21 - 1  and  21 - 2  remain aligned. In the embodiments such as  FIG. 10 , with the same direction rotation of the offset drivers  22 - 1  and  22 - 2 , the cleaning action is particularly suitable for soft surfaces such as rugs with deep piles and loops. A 4 millimeter offset has been found suitable for a machine having a minimum treatment dimension, M_D, of 7 inches. For hard surfaces such as wood floors and rugs with short piles and loops, a 2 millimeter offset has been found suitable for a machine having a minimum treatment dimension, M_D, of 7 inches. In general, the first offset and the second offset are in a range from approximately 2 millimeters to 4 millimeters. However, the range of off-sets can be larger for machines having different treatment dimensions. 
     In  FIG. 19  a non-shifted top view of the four different positions of  FIG. 18  are shown for the cleaning plate using the  FIG. 10  transmission. The four different positions are designated  96 - 1 ,  96 - 2 ,  96 - 3  and  96 - 4 . 
     In  FIG. 20 , a front view of an embodiment of the cleaning plate assembly  12  and the body plate  16  of  FIG. 3  is shown. The transmission  20  of  FIG. 3  operates to transfer the rotational motion of the drive shaft  21  to the drive shafts  21 - 1  and  21 - 2  of  FIG. 20  and thereby to the offset drivers  22 - 1  and  22 - 2  and the eccentric drive member  29 . The eccentric drive member  29  is rigidly attached to and/or is formed as part of cleaning plate  12 - 1 . The offset drivers  22 - 1  and  22 - 2  and the eccentric drive member  29  drive the cleaning plate  12 - 1  and cleaning pad  12 - 2  in a vibrating motion in the XY-plane by ±OFFSET_D, See  FIG. 3 . A first bushing  23 - 1  in the eccentric drive member  29  engages the first offset driver  22 - 1 . A second bushing  23 - 2  in eccentric driver  29  engages the second offset driver  22 - 2 . The eccentric drive member  29  extends through an opening in the rigid body plate  16 . 
     In  FIG. 21 , a bottom view of the body plate  16  of  FIG. 20  is shown taken along the section line  20 - 20 ′ of  FIG. 20 . The body plate  16  has pockets  81 , including pockets  81 - 1 ,  81 - 2 , . . . ,  81 - 6 , for receiving ball bearings. The body plate  16  includes an opening  93  for receiving the eccentric drive member  29 . The opening  93  is larger than the size of the offset driver member  29  which is shown by a broken line in  FIG. 21  with clearance offset  25  surrounding the broken line. The clearance offset permits the eccentric drive member  29  to vibrate within the opening  93  without contacting the body plate  16 . 
     In  FIG. 22 , an end view of the body plate  16  of  FIG. 21  is shown taken along section line  22 - 22 ′ of  FIG. 21 . The body plate  16  includes the deep recesses  81 - 3  and  81 - 6  for holding ball bearings, like ball bearing  91  shown as typical, in recess  81 - 3 . 
     In  FIG. 23 , a top view of the cleaning plate  12 - 1  of  FIG. 20  is shown taken in the direction of the section line  23 - 23 ′ of  FIG. 20 . The cleaning plate  12 - 1  includes a recess region  29 ′ for receiving and attaching to the offset driver member  29  of  FIG. 20 . The vibrating cleaning plate  12 - 1  has pockets  82 , including pockets  82 - 1 ,  82 - 2 , . . . ,  82 - 6 , for receiving ball bearings which are in the pockets  81 - 1 ,  81 - 2 , . . . ,  81 - 6 , respectively, of body plate  16  in  FIG. 21 . 
     In  FIG. 24 , an end view of the cleaning plate  12 - 1  of  FIG. 23  is shown taken along section line  24 - 24 ′ of  FIG. 23 . The cleaning plate  12 - 1  includes the shallow recesses  82 - 3  and  82 - 6  for engaging ball bearings like ball bearing  91  in  FIG. 22 . The shallow recesses  82 - 3  and  82 - 6  are juxtaposed the deep recesses  81 - 3  and  81 - 6  when the body plate  16  is juxtaposed the cleaning plate  12 - 1 . The ball bearings, like ball bearing  91 , are seated in the deep recesses  81 - 3  and  81 - 6  and contact the shallow recesses  82 - 3  and  82 - 6 . The diameters of the ball bearings are greater than the combined depths of the shallow recesses  82 - 3  and  82 - 6  and the deep recesses  81 - 3  and  81 - 6  so that the ball bearings hold the body plate  16  apart from the cleaning plate  12 - 1 . 
     In  FIG. 25 , a top view of the top portion  29 - 1  of the offset driver member  29 , the offset guide that forms part of the drive assembly  10  of  FIG. 20  is shown. The top portion  29 - 1  includes bearing openings  23 A- 1  and  23 A- 2  for receiving the offset drivers  22 - 1  and  22 - 2 . 
     In  FIG. 26 , a top view of the bottom portion of the offset driver member that forms part of the drive assembly of  FIG. 20  is shown. The bottom portion  29 - 2  includes bearing openings  23 B- 1  and  23 B- 2  for receiving the offset drivers  22 - 1  and  22 - 2 . 
     In  FIG. 27 , a front view of the top portion  29 - 1  and the bottom portion  29 - 2  of the offset driver member  29  are positioned together to form offset driver member  29 . 
     In  FIG. 28 , a front view is shown of the offset driver member  29  extending through the fixed body plate  16  and is attached to the cleaning plate  12 - 1 . The clearance distance  25  is between the body plate  16  and the offset driver member  29 . 
     In  FIG. 29 , the fixed body plate  16  is adjacent the cleaning plate  12 - 1  and is held offset from the cleaning plate  12 - 1  by rolling bearings, particularly ball bearings  91 - 3  and  91 - 6 , shown as typical. The ball bearing  91 - 3  rolls in recess  81 - 3  in body plate  16  and in recess  82 - 3  in cleaning plate  12 - 1 . The ball bearing  91 - 6  rolls in recess  81 - 6  in body plate  16  and in recess  82 - 6  in cleaning plate  12 - 1 . 
     In  FIG. 30 , an expanded view is shown of a portion of  FIG. 29  with the fixed body plate  16  adjacent the cleaning plate  12 - 1  and held offset from the cleaning plate  12 - 1  by one rolling bearing, ball bearing  91 . Ball bearing  91  is typical of ball bearings  91 - 3  and  91 - 6  of  FIG. 29 . Ball bearing  91  has a diameter, D b , large enough to maintain a gap of dimension C to separate body plate  16  and the cleaning plate  12 - 1 . The diameter, D b , equals a height, H b , which is sufficient to maintain the gap C when the ball bearing is within the pockets  81  and  82 . The diameter, D C , of the pockets  81  and  82  is substantially greater than the diameter, D b , to enable the cleaning plate  12 - 1  to oscillate in the XY plane relative to the fixed body plate  16  in the manner described in connection with  FIG. 16  through  FIG. 19 . 
     In  FIG. 31 , the expanded view of  FIG. 30  is shown with the fixed body plate  16  adjacent the cleaning plate  12 - 1  and held offset from the cleaning plate  12 - 1  by ball bearing  91 . The cleaning plate  12 - 1  has moved the maximum amount in one direction along the Y-axis. The ball bearing  91  has sufficient room in the pockets  81  and  82  to allow the movement of the cleaning plate  12 - 1  since the diameter of the cavity, D C , is large enough to permit such movement. 
     In  FIG. 32 , the expanded view of  FIG. 30  is shown with the fixed body plate  16  adjacent the cleaning plate  12 - 1  and held offset from the cleaning plate  12 - 1  by ball bearing  91 . The cleaning plate  12 - 1  has moved the maximum amount in a direction along the Y-axis opposite the movement direction in  FIG. 31 . The ball bearing  91  has sufficient room in the pockets  81  and  82  to allow the movement of the cleaning plate  12 - 1  since the diameter of the cavity, D C , is large enough to permit such movement. 
     In  FIG. 33 , an expanded view of  FIG. 30  shows details of the wall linings  97 ,  98  and  99  of the pockets  81  and  82  for the rolling ball bearing  91 . The wall linings  97 ,  98  and  99  are made of soft materials and prevent the ball bearing  91  from bouncing or banging and hence prevent loud noises. The soft materials suppress noise when the ball bearings, such as typical ball bearing  91 , roll in the pockets, such as typical pockets  81  and  82 , during movement of the cleaning plate  12 - 1 . 
     In  FIG. 34 , an expanded view is shown of one embodiment of a lining  99  region depicted in circle B in  FIG. 33 . In the  FIG. 34  embodiment, the lining  99  is elastic in nature and is in the expanded state with a thickness, S 1 , filling all the space between the ball bearing  91  and the wall of the body plate  16 . 
     In  FIG. 35 , the embodiment of  FIG. 34  is shown is in the compressed state with a thickness, S 2 , filling all the space between the ball bearing  91  and the wall of the body plate  16 . The thickness, S 2 , is less than the thickness, S 1 . The difference between thickness, S 2 , and the thickness, S 1 , results from slight movements in the cleaning plate  12 - 1  caused by oscillations during operation. 
     In  FIG. 33 ,  FIGS. 34 and 35 , the cavity  81  is typical of one or more of the pockets lined with a compressible soft material  99 - 1  whereby the ball bearings, such as typical ball bearing  91 , are maintained in contact with both the body plate  16  and the cleaning plate  12 - 1 . 
     In  FIG. 21  through  FIG. 35 , it is apparent that the body plate  16  and the cleaning plate  12 - 1  each have pockets  81  and  82  for receiving the ball bearings whereby the ball bearings roll in the pockets during movement of the cleaning plate  12 - 1  in the oscillating pattern. It is further apparent that the body plate  16  and the cleaning plate  12 - 1  are rectangular in shape having longer sides and shorter sides. While rectangular is preferred in some embodiments, the body plate  16  and the cleaning plate  12 - 1  can have any convenient shape. Regardless of shape, two or more of the ball bearings are positioned near edges of the cleaning plate. In a rectangular embodiment, at least two of the ball bearings are positioned along one of the longer sides. 
     In  FIG. 36 , a view is shown of the cleaning plate  12 - 1  over a cleaning pad  12 - 2 . The locations are shown of the motor drive shaft  21 , the first drive shaft  21 - 1 , the second drive shaft  21 - 2  and the third drive shaft  21 - 3 . The drive shaft  21 - 1 , by way of example, has a bending force applied by the cleaning plate  12 - 1 . Those portions of the cleaning plate  12 - 1  that are farthest from shaft  21 - 1  operate with a longer moment arm and hence apply greater bending torque against the drive shaft. By way of example a moment arm, MA, is shown from drive shaft  21 - 1  to the far corner of cleaning plate  12 - 2 . 
     In  FIG. 37 , a graphical representation is shown of a force diagram representing cleaning plate  12 - 1  and the torque applied to a drive shaft in the drive assembly. The drive shaft torque, T S , is equal to the force, F, applied by the plate times the moment arm, MA. The greater the moment arm, MA, the greater the torque. The greater the force, F, the greater the torque. Torque against a drive shaft is undesirable since it tends to cause wear that shortens the life of the machine and tends to cause vibrations that make use of the machine uncomfortable. The addition of ball bearings described in connection with  FIG. 21  through  FIG. 35  substantially shortens the moment arms and hence substantially improves the life of the machines while improving the comfort of using the machines. 
     In  FIG. 38 , a graph of torque, T, versus force, F, is shown. When the ball bearings described in connection with  FIG. 21  through  FIG. 35  are not employed, the torque increases directly as a function of the force as shown by the solid line. However, when the ball bearings described in connection with  FIG. 21  through  FIG. 35  are employed, the torque increases to a low value and does not increase more as a function of increasing force as shown by the broken line. 
     In  FIG. 39 , a front view is shown of the cleaning plate  12 - 1  and the cleaning pad  12 - 2 . The pad  12 - 2  is attached to the cleaning plate  12 - 1  by hook-and-loop fasteners where the hooks  53 , including hooks  53 -A, are attached to the cleaning plate  12 - 1  and the “loops”, including loops  53 ′-A, are part of the pad  12 - 2 . 
     In  FIG. 40 , a perspective view is shown of a cutaway section A of the cleaning pad  12 - 2  of  FIG. 39 . The hook-and-loop fastener  53 -A and  53 ′-A are typical of the hook-and-loop fasteners of  FIG. 39 . The loop portion  53 ′-A is fulfilled by the cover  62  that surrounds the cotton center  61 . In addition to providing the “loop” function of the hook-and-loop fastening, the cover  62  is more abrasive then the cotton core  61 . The more abrasive cover  62  functions when cleaning to dislodge more stubborn stains and particles. By way of contrast, the cotton center  61  is more absorbent and tends to absorb stains and particles dislodged by the abrasive cover  62  and by any liquid applied, such as water or cleaning solution. 
     In  FIG. 41 , a bottom view is shown of the cleaning plate  12 - 1  and the attachment pads  53 . The attachment pads  53 - 1 ,  53 - 2 , . . . ,  53 - 11  perform the “hook” function of the hook-and-loop fastening as described in connection with  FIG. 40 . 
     In  FIG. 42 , a top view is shown of the pulleys  124 - 1 ,  124 - 2 ,  126 - 1  and  126 - 2  and belts  136 - 1  and  136 - 2  that form another embodiment of a transmission for connecting to offset drivers. The pulleys  124 - 1  and  124 - 2  are mounted on the motor drive shaft  21  which extends from either side of motor  30 . The pulleys  124 - 1  and  124 - 2  rotate in the XZ-plane. The pulleys  126 - 1  and  126 - 2  are mounted on the drive shafts  21 - 1  and  21 - 2 , respectively, and drive the eccentric drives. The pulleys  126 - 1  and  126 - 2  rotate in the XY-plane. The belt  136 - 1  connects between pulley  124 - 1  and pulley  126 - 1  and is twisted clockwise for turning pulley  126 - 1  and drive shaft  21 - 1  clockwise. The belt  136 - 2  connects between pulley  124 - 2  and pulley  126 - 2  and is twisted counter-clockwise for turning pulley  126 - 2  and drive shaft  21 - 2  counter-clockwise. 
     In  FIG. 43 , a top view is shown of the pulleys  224 - 1 ,  224 - 2 ,  126 - 1  and  126 - 2  and belts  236 - 1  and  236 - 2  that form another embodiment of a transmission for connecting to offset drivers. The pulleys  224 - 1  and  224 - 2  are mounted on the motor drive shaft  21  which extends only on one side of motor  30 . The pulleys  224 - 1  and  224 - 2  rotate in the XZ-plane. The pulleys  126 - 1  and  126 - 2  are mounted on the drive shafts  21 - 1  and  21 - 2 , respectively, and drive the eccentric drives. The pulleys  126 - 1  and  126 - 2  rotate in the XY-plane. The belt  236 - 1  connects between pulley  224 - 1  and pulley  126 - 1  and is twisted clockwise for turning pulley  126 - 1  and drive shaft  21 - 1  clockwise. The belt  236 - 2  connects between pulley  224 - 2  and pulley  126 - 2  and is twisted counter-clockwise for turning pulley  126 - 2  and drive shaft  21 - 2  counter-clockwise. 
     In  FIG. 44 , a front view of an embodiment of the cleaning plate assembly  12  and the body plate  16  like that of  FIG. 20  is shown. The transmission  20  operates to transfer rotational motion to the drive shafts  21 - 1  and  21 - 2  and to the eccentric drive member  29 . The eccentric drive member  29  is rigidly attached to cleaning plate  12 - 1 . The eccentric drive member  29  drives the cleaning plate  12 - 1  and attached cleaning pad  12 - 2  in a vibrating motion in the XY-plane by ±OFFSET_D, See  FIG. 3 . The body plate  16  is rigidly attached to the base  31 . The cleaning plate  12 - 1  and attached cleaning pad  12 - 2  move with an oscillation in the XY-plane relative to the body plate  16 . The ball bearings  91 , including ball bearings  91 - 1  and  91 - 3 , keep the cleaning plate  12  separated from the body plate  16 . 
     In  FIG. 45 , an exploded front view of an embodiment of the cleaning plate assembly  12  and the body plate  16  of  FIG. 44  is shown. The eccentric drive member  29  is rigidly attached to cleaning plate  12 - 1 . The eccentric drive member  29  drives the cleaning plate  12 - 1  and attached cleaning pad  12 - 2  in a vibrating motion in the XY-plane by ±OFFSET_D, See  FIG. 3 . The eccentric drive member  29  attachment to cleaning plate  12 - 1  is accomplished using bolts  130  including bolts  130 - 1 ,  130 - 2 ,  130 - 3  and  130 - 4 . The bolts  130  are oriented to engage the threaded holes  131 , including holes  131 - 1 ,  131 - 2 ,  131 - 3  and  131 - 4 , in the cleaning plate  12 - 1  when the cleaning plate  12 - 1  is brought in close proximity to the eccentric drive member  29 . As the bolts  130  are screwed into the threaded holes  131 , the ball bearings  91 - 1  and  91 - 2  are compressed between the cleaning plate  12 - 1  and the eccentric drive member  29 . The ball bearings  91 - 1  and  91 - 3  keep the cleaning plate  12  separated from the body plate  16 . The cleaning plate  12 - 1  while generally rigid in nature, still tends to bend slightly under the force of the tightening bolts  130 . The bending draws the cleaning plate closer to and in contact with the eccentric drive member  29  in the center region while the ball bearings  91  prevent the bending around the edges. The shape of the bending is concave when viewed looking in the Z-axis direction at the bottom of the cleaning pad  12 - 2 . 
     In  FIG. 46 , an assembled front view of an embodiment of the cleaning plate assembly  12  and the body plate  16  of  FIG. 45  is shown. The eccentric drive member  29  is rigidly attached to cleaning plate  12 - 1  by the bolts  130 , including bolts  130 - 1 ,  130 - 2 ,  130 - 3  and  130 - 4 . The bolts  130  are fully tightened. The concave arc of the cleaning plate  12 - 1  and cleaning pad  12 - 2  is shown by the RISE dimension measured from the reference line near the center to the bottom of the cleaning pad  12 - 2 . At the edges near the ball bearings  91 , including ball bearings  91 - 1  and  91 - 3 , the cleaning pad  12 - 2  is in contact with the reference line and hence the concave shape of the cleaning plate  12 - 1  and cleaning pad  12 - 2  is formed. 
     In  FIG. 47 , a top view is shown of an embodiment of the cleaning plate assembly  12  and eccentric drive member  29  of  FIG. 46 . The base  31  and the handle assembly  15 - 1  are shown with broken lines to show the orientation. The orientation in the FORWARD direction is indicated by the arrow. The eccentric drive member  29  is rigidly attached to cleaning plate  12 - 1  by the bolts  130 , including bolts  130 - 1 ,  130 - 2 ,  130 - 3 ,  130 - 4 ,  130 - 5  and  130 - 6 . The bolts  130  are fully tightened and the concave arc of the cleaning plate  12 - 1  and cleaning pad  12 - 2  as shown in  FIG. 48  is shown schematically in  FIG. 49  as the arrow  140 . The entire cleaning plate assembly  12  has the concave shape as further represented by arrow  141 . In operation as described in connection with  FIG. 16  and  FIG. 17 , the entire cleaning plate assembly  12  has an oscillator motion. The vibrating cleaning plate  12 - 1  includes pockets  82 - 1 ,  82 - 2 , . . . ,  82 - 6  for receiving ball bearings which are in the pockets  81 - 1 ,  81 - 2 , . . . ,  81 - 6 , respectively, of body plate  16 , see  FIG. 21  and  FIG. 23 . The ball bearings in the pockets  82 - 1  and  82 - 4  have a generally oval-shaped counter-clockwise rotation and the ball bearings in the pockets  82 - 3  and  82 - 6  have a generally oval-shaped clockwise rotation. Similarly, areas of the cleaning pads in the vicinity of the pockets  82 - 1  and  82 - 4  in the vicinity of the pockets  82 - 3  and  82 - 6  have generally the same counter-clockwise and clockwise rotations, respectively. The typical cleaning pad locations  112 - 1  and  112 - 4  in the vicinity of the pockets  82 - 1  and  82 - 4  have counter-clockwise rotations and the typical cleaning pad locations  112 - 3  and  112 - 6  in the vicinity of the pockets  82 - 3  and  82 - 6  have clockwise rotations. The cleaning pad locations  112 - 1  and  112 - 4  and the cleaning pad locations  112 - 3  and  112 - 6  are selected as typical since the entire cleaning pad  12 - 2  is a continuum of many such small locations. 
     In  FIG. 48 , a diagram is shown for explaining the forward drive of the geometry of the cleaning plate assembly  12  and eccentric drive member  29  of  FIG. 47 . The clockwise rotation of the cleaning pad locations  112 - 1  and  112 - 4  is depicted as having two parts, a solid part farthest away from the center of the concave shape and a broken-line part closer to center, C, of the concave shape. Because of the concave shape, the solid part tends to be pushed harder toward the floor or other surface being treated than the broken-line part. Accordingly, the forward force, F 1 , for the counter-clockwise oscillation  112 - 1  is greater than backward force, B 1 . The net force in the forward direction for the oscillation  112 - 1  is the difference, F 1 −B 1 . In a similar manner, the forward force, F 4 , for the counter-clockwise oscillation  112 - 4  is greater than backward force, B 4 . The net force in the forward direction for the counter-clockwise oscillation  112 - 4  is the difference, F 4 −B 4 . In a similar manner, the forward force, F 3 , for the clockwise oscillation  112 - 3  is greater than backward force, B 3 . The net force in the forward direction for the clockwise oscillation  112 - 3  is the difference, F 3 −B 3 . In a similar manner, the forward force, F 6 , for the clockwise oscillation  112 - 6  is greater than backward force, B 6 . The net force in the forward direction for the clockwise oscillation  112 - 6  is the difference, F 6 −B 6 . 
     When all the net forces as described in connection with  FIG. 48  are summed, the result is a positive FORWARD drive force that helps propel the machine  1  of  FIG. 1  and  FIG. 2  forward rendering the machine easier to use. If the direction of rotation of the motor is reversed, then the driving direction is reversed to backward. 
     When a user is pushing the machine  1  of  FIG. 1  and  FIG. 2  in the forward direction, the resulting force on the handle  15 , attached as shown in  FIG. 47 , exerts an increased force at the rear of the cleaning plate  12 - 1 . This increased force tends to increase the forces of the F 1  and F 3  type and hence increase the FORWARD drive. Similarly, when a user is pulling the machine  1  of  FIG. 1  and  FIG. 2  in the backward direction, the resulting force on the handle  15 , attached as shown in  FIG. 47 , exerts a decreased force at the rear of the cleaning plate  12 - 1  thereby reducing the FORWARD drive and making it easier to pull the machine backward. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention.