Abstract:
An abrading machine braking system for use in braking a wheeled abrading machine having a rotating abrading tool used in abrading a surface. The abrading machine braking system uses two braking wheels that engage the surface of the wheels of the abrading machine and the braking wheels are fixed to the respective ends of a brake axle that is in turn coupled to a brake cylinder assembly. The brake cylinder assembly contains a plurality of steel discs that are keyed to a lengthwise slot in the brake axle so that the discs rotate with the axial. A plastic braking disc is located adjacent to one of the steel discs within the brake cylinder assembly and provides a braking force that is transmitted to the two brake wheels through the brake axle. A brake release handle is used to bring the braking wheels into contact with the wheels on the abrading machine and to remove them from contact with the abrading machine wheels.

Description:
BACKGROUND OF THE INVENTION 
   Wheel mounted abrading apparatus are in widespread use for flat or substantially flat surfaces such as various concrete and asphalt including floors, pavement and the like. Typically such abrading apparatus will use a rotating drum that has an outer surface containing various types of cutting or abrading elements. The abrading apparatus is mounted on wheels to make it mobile and so that it can be readily moved over the surface that is to be abraded. Unfortunately, when the rotating abrading tool or the like engages the surface that is to be abraded large frictional forces are created that provide a propulsion force to the wheel mounted abrading apparatus that tends to move the abrading apparatus away from the intended area that is to be abraded. This propulsion force can vary considerably depending upon the type of surface being abraded, the condition of the surface and the depth that the surface is to be abraded. 
   These propulsion forces can have undesirable consequences. As a result of these forces the surface can fail to be abraded as desired. The abrading apparatus may not have its cutting or abrading elements in contact with the surface being worked on for a sufficient time due to the propulsion forces to enable sufficient abrading of the surface or the surface can be abraded in a nonuniform manner. The operator of the wheel mounted abrading apparatus can manually grip the handles of the abrading apparatus to attempt to overcome the friction generated propulsion forces, but this may not be entirely satisfactory in achieving a satisfactory abraded surface. At the very least, such manual restraining action by the operator of the abrading apparatus can be very tiring. 
   Consequently, a braking system is needed that can counteract the undesired friction generated propulsion forces when they occur. Since friction generated propulsion forces can vary greatly due to different abrading tool surfaces and due to the material that is being abraded, it is highly desirable that any braking system be adjustable so that it can provide a range of braking forces. It is also highly desirable that the braking system be easily activated and deactivated by the operator of the wheel mounted abrading apparatus without interfering with the normal operation of the wheel mounted abrading apparatus. 
   The braking system for a wheel mounted abrading machine of this invention provides these benefits. This braking system invention provides a braking force that counteracts the friction generated propulsion forces and the braking system is readily adjustable to provide a wide range of braking forces. Moreover, the braking system is readily engaged and disengaged by the operator through the use of one hand while maintaining manual control of the wheel mounted abrading apparatus. This braking system invention also has provisions for the operator of the wheel mounted abrading apparatus through proper adjustments to apply a wide range of braking forces. This braking system invention has the added advantage that it can be used to retrofit existing wheel mounted abrading apparatus as well as being built into new wheel mounted abrading apparatus. This is possible since the abrading machine braking system invention applies its braking forces to the outer surfaces of the wheels or tires of the wheeled abrading machine or apparatus. 
   SUMMARY OF THE INVENTION 
   This invention relates to apparatus for controlling the speed or movement of wheeled surface abrading machines and more particularly to a braking system associated with the wheels of the surface abrading machine. 
   It is a primary object of the invention to provide a braking system for a wheeled surface abrading machine that effectively controls the speed of the wheeled surface abrading machine along the surface that is being abraded. 
   It is also an object of the invention to provide a braking system for a wheeled surface abrading machine that is easily used by the operator of the wheeled surface abrading machine. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that exerts an effective braking force on the wheels of the surface abrading machine. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is adjustable to provide various braking forces. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is readily adjustable by the operator of the wheeled surface abrading machine. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is easy to activate. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is easy to disengage. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that applies a braking force to the outer periphery of the wheels of the abrading machine. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is very effective. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is very reliable. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is easy to maintain. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that requires very little maintenance. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that has few moving parts. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is easy to repair. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that uses easily replaceable parts that are subject to wear. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that is uses inexpensive replaceable parts that are subject to wear. 
   It is an object of the invention to provide a braking system for a wheeled surface abrading machine that can be used to retrofit existing wheeled surface abrading machines. 
   These and other objects of the invention will be apparent from the following description of the abrading machine braking system for use in braking a wheeled abrading machine having a rotating cutter or other abrading element used in abrading a surface that includes two braking wheels that engage the surface of the wheels of the abrading machine with the braking wheels being fixed to the respective ends of a brake axle that is in turn coupled to a brake cylinder assembly. The brake cylinder assembly contains steel discs that are keyed to a lengthwise slot in the brake axle so that the discs rotate with the axle. A plastic braking disc is located adjacent to one of the steel discs within the brake cylinder assembly and provides a braking force that is transmitted to the two brake wheels through the brake axle. The abrading machine braking system includes a control rod that is used by the operator to manually bring the braking wheels into contact with the wheels on the abrading machine and to remove them from contact with the abrading machine wheels. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be hereinafter more fully described with reference to the accompanying drawings in which: 
       FIG. 1  is a perspective view of a portion of a wheeled surface abrading machine with the braking system invention with portions broken away; 
       FIG. 2  is an enlarged end view of a portion of the braking system illustrated in  FIG. 1  taken substantially in the direction of the line  2 — 2  with portions thereof broken away; 
       FIG. 3  is a sectional view of the structure illustrated in  FIG. 2  taken substantially in the direction of the line  3 — 3  thereof with certain components not shown in section; 
       FIG. 4  is a sectional view of the structure illustrated in  FIG. 3  taken in the direction of the line  4 — 4  thereof; 
       FIG. 5  is a sectional view of the structure illustrated in  FIG. 3  taken in the direction of the line  5 — 5  thereof; and 
       FIG. 6  is a sectional view of the structure illustrated in  FIG. 3  taken in the direction of the line  6 — 6  thereof. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIG. 1 , a portion of a conventional wheeled surface abrading machine is illustrated and is designated generally by the number  10 . The abrading machine  10  has a main housing  12  that contains rotatable abrading apparatus  14  that has a conventional rotating abrading element  15  that is abrading the surface  16 . This abrading action of the rotating abrading element  15  results in a forward force indicated by the arrow F being exerted on the abrading machine  10  that tends to propel the wheeled surface abrading machine  10  forward in the direction of the arrow F in an undesired manner. A generally rectangular wheel mount  18  extends rearward from the main housing  12  and two identical wheels  20  and  22  are rotatably mounted in a conventional manner on each side of the rear portion  24  of the wheel mount  18 . Two spaced apart control arms  26  and  28  are connected to the main housing  12  on each side of the wheel mount  18 . The wheeled surface abrading machine  10  and its various components that have been mentioned are conventional. 
   The braking system invention for a wheeled surface abrading machine is illustrated in  FIG. 1  and is designated generally by the number  30 . The braking system  30  comprises a generally rectangular shaped brake mounting plate  32  that has two upward extending end portions  34  and  36 . The inner portions of the upward extending end portions  34  and  36  are pivotally connected to the lower portions  42  and  44  of the respective control arms  26  and  28  by the respective conventional bolts  46  and  48  that extend through holes in the lower portions  42  and  44  of the control arms  26  and  28 . The bolts  46  and  48  are secured in place by conventional lock nuts or the like. 
   The braking system  30  also includes a brake assembly designated generally by the number  58  that is mounted on the upper surface  59  of the brake mounting plate  32 . The brake assembly  58  includes a brake cylinder assembly  60 , a brake adjusting mechanism  62 , a brake cylinder shaft  64 , and two cylindrical brake wheels  66  and  68  are non-rotatably mounted on the ends of the brake cylinder shaft  64  by the roll pins  65  or the like. The brake assembly  58  also includes two identical conventional shaft bearing assemblies  70  and  72  that are located on the respective upward extending portions  34  and  36  of the mounting plate  32  for rotatably mounting the brake cylinder shaft  64 . The bearing assemblies  70  and  72  are connected to the end portions  34  and  36  through conventional fasteners such as bolts  74  or the like. The brake cylinder assembly  60  is secured to a brake cylinder mounting plate  76  by welding or the like and the brake cylinder mounting plate  76  is in turn connected to the brake mounting plate  32  by the four conventional threaded mounting bolts  78 . 
   The details of the brake cylinder assembly  60 , the brake adjusting mechanism  62 , and the brake cylinder shaft  64  are best illustrated in  FIGS. 2 through 6 . As best illustrated in  FIGS. 2 and 3 , the brake cylinder assembly  60  comprises a hollow cylindrical brake cylinder tube  80  that is closed at one end portion  82  by a brake cylinder end cap  84  that has an enlarged cylindrical portion  86  that is located outside of the end portion  82  of the brake cylinder tube  80  and a smaller cylindrical portion  88  that fits within the end portion  82  of the brake cylinder tube  80 . The brake cylinder end cap  84  has a circular cross section hole  90  extending through it that is sized and shaped to rotatably receive a portion of the brake cylinder shaft  64 . In the preferred embodiment, the brake cylinder end cap  84 , the brake cylinder tube  80 , and the brake cylinder mounting plate  76  are welded together prior to the assembly of the braking system invention  30 . The other end portion  92  of the brake cylinder tube  80  is closed by another brake cylinder end cap  94  that has a circular cross section cylindrical portion  96  that is sized and shaped to freely slide within the end portion  92  of the brake cylinder tube  80 . This brake cylinder end cap  94  has an enlarged cylindrical portion  98  at its outer end. The end cap  94  has a centrally located circular cross section hole  100  extending through it that is sized and shaped to receive a portion of the brake cylinder shaft  64 . 
   As best illustrated in  FIGS. 3 through 6 , alternating steel discs  102  and plastic nylon discs  104  are located inside the brake cylinder tube  80  between the brake cylinder end caps  84  and  94  and a steel disc  103  is also located between the the brake cylinder end caps  84  and  94  near the end cap  94 . As illustrated in  FIG. 4 , the steel discs  102  are circular shaped and have a centrally located hole  106  that is sized and shaped to accept the adjacent portion  112  of the brake cylinder shaft  64 . The steel disc  102  also has a generally rectangular shaped projection  108  that extends into the circular shaped hole  106 . This projection  108  is sized and shaped to fit into an elongated channel or key seat  110  that runs lengthwise in the brake cylinder shaft  64  for the portion  112  of the cylinder shaft  64  that is to fit inside the brake cylinder tube  80  plus the portion  114  that extends to one end of the brake cylinder shaft  64 . In view of the projection  108  and the corresponding adjacent channel  110 , the steel disc  102  rotates with the brake cylinder shaft  64  within the brake cylinder tube  80 . 
   As illustrated in  FIG. 6 , the steel disc  103  is identical to the steel disc  102  illustrated in  FIG. 4  except that the projection  108  is omitted with the disc  103 . Since the disc  103  is identical to the disc  102  except for the omitted projection  108 , the hole  105  in the disc  103  is also the same size as the hole  106  in the disc  102 . Since the projection  108  is omitted, the steel disc  103  is not forced to rotate as the brake cylinder shaft  64  rotates as is the case with the other steel discs  102  that have the projection  108 . 
   As illustrated in  FIG. 5 , the plastic disc  104  also has a centrally located circular shaped hole  118  that is sized and shaped to accept a portion of the brake cylinder shaft  64 . However, there is no projection extending into this hole  118  as there is with the steel disc  102  and the projection  108 . Consequently, the plastic disc  104  is not forced to rotate with the brake cylinder shaft  64 . 
   As illustrated in  FIG. 3 , a coil compression spring  120  is located around the portion  112  of the brake cylinder shaft  64  within the brake cylinder tube  80  between the cylindrical portion  96  of the end cap  94  and the adjacent steel disc  103 . This spring  120  puts pressure on the disc  103  and the alternating steel discs  102  and the plastic discs  104 . As illustrated in  FIG. 3 , the brake cylinder shaft  64  has a right hand threaded portion  122  that is located adjacent to the end cap  94 . The brake adjusting mechanism  62  comprises the threaded portion  122  of the brake cylinder shaft  64  and a jam nut  123  that is threaded on a portion of the threaded portion  122  and the jam nut  123  is located immediately adjacent to the enlarged portion  98  of the end cap  94 . In view of this arrangement, when the jam nut  123  is turned in a clockwise direction it presses against the enlarged portion  98  of the end cap  94  and this in turn exerts a force on the spring  120  that in turn puts pressure, represented by the arrow and the letter P, on the steel disc  103  and the alternating steel discs  102  and plastic discs  104 . 
   As a result of this pressure P, the outer surface  125  of the plastic disc  104  that is located adjacent to the inner surface  127  of the brake cylinder end cap  84  is pressed against the inner surface  127  of the brake cylinder and cap  84  and is in frictional engagement with the inner surface  127 . Also, as a result of this pressure P, the opposite surface  129  of the same plastic disc  104  is in frictional contact with the adjacent surface  131  of the adjacently located steel disc  102 . As indicated previously, the steel discs  102  have projections  108  that fit into the adjacent channel  110  in the brake cylinder shaft  64  and hence the steel discs  102  rotate with the brake cylinder shaft  64 . In view of this arrangement, the plastic disc  104  with its surfaces  125  and  129  that are in frictional engagement with the respective surfaces  127  and  131  create a frictional braking force that tends to resist the rotation of the steel disc  104  with the surface  131  and the associated rotation of the connected brake cylinder shaft  64 . As illustrated in  FIG. 1 , when the brake wheels  66  and  68  that are non-rotatably fixed to the brake cylinder shaft  64  by the pins  65  are in contact with the respective wheels  20  and  22  this frictional braking force is transmitted to wheels  20  and  22  to resist movement of the wheeled surface abrading machine  10  due to the rotating abrading element  15  and its contact with the surface  16  that is being abraded. 
   The force BF illustrated in  FIG. 1  that the wheels  66  and  68  exert on the wheels  20  and  22  can be increased or decreased by the operator by adjusting the jam nut  123  illustrated in  FIG. 3 . This jam nut  123  can be appropriately turned or adjusted to compensate for variations in the force F caused by variations in the surface  16  and different abrading tools  15 . The jam nut  123  can also be adjusted by the operator to compensate for wear on the plastic disc  103  surfaces  125  and  129  or the adjacent steel disc  104  or when new metal and plastic discs  102 ,  103  and  104  are installed. 
   The plastic discs  104  that do not have the outer surface  125  located adjacent to the inner surface  127  of the brake cylinder end cap  84  are not subject to wear during the braking process and hence these plastic discs  104  can be used for spares for the plastic discs  104  that has its outer surface  125  located in contact with the inner surface  127  of the brake cylinder end cap  84  when it wears out. When this occurs, one of the plastic discs  104  that has not been subject to wear can be switched with the worn out plastic disc  104 . This is accomplished by removing the jam nut  123 , the brake cylinder end cap  94 , the spring  120 , plus the adjacent brake wheel  68  and the associated bearing assembly  72  in a conventional manner. Then, one of the plastic discs  104  that have not been subject to wear is switched with the worn out plastic disc  104  and the parts are reassembled in reverse order. To accomplish this, the discs  103 ,  102  and  104  are slipped off of the end of the brake cylinder shaft that had the brake wheel on it. This is made possible since the diameter of the respective holes  105 ,  106  and  118  in the steel disc  103 , the steel discs  102  and the plastic discs  104  are slightly larger then the diameter of the threaded portion  122  of the brake cylinder shaft  64  and this permits the discs  103 ,  102  and  104  to be slipped over the threaded portion  122  of the brake cylinder shaft  64  once the jam nut is removed from the shaft  64 . 
   As illustrated in  FIG. 1 , the brake wheels  66  and  68  are usually pressed into engagement with the respective surface abrading machine wheels  20  and  22  as a result of the pressure exerting means comprising the adjusting bolt  130  with its head and washer  132  and the threaded portion  134  with a portion that is threaded into the threaded hole  136  in the wheel mount  18 . The pressure exerting means also includes a compression coil spring  138  that is located around a portion of the threaded portion  134  of the adjusting bolt  130  and the lower end of the compression spring  138  is in contact with the brake mounting plate  32  and forces it in a downward direction that results in the brake wheels  66  and  68  being pressed against the wheels  20  and  22 . The distance D of the axis of rotation of the brake wheels  66  and  68  and the axis of rotation of the wheels  20  and  22  of the abrading machine  10  can be adjusted by turning the adjusting bolt  130  clockwise to narrow the distance and counter clockwise to increase the distance D. This adjusting bolt  130  permits compensation for a number of factors including wear of the abrading machine wheels  20  and  22  or the brake wheels  66  and  68 . 
   As illustrated in  FIG. 1 , a brake release mechanism is provided that is designated generally by the number  142 . This brake release mechanism  142  comprises a brake release handle  144  and a brake retaining bracket  146 . The brake retaining bracket  146  comprises an L shaped cross section member with a flat substantially vertically oriented side  148  that fits up against the inside surface  150  of the upper portion  152  of the control arm  28  and is attached to the inside surface  150  by conventional means such as by self tapping bolts or the like that are not shown. The brake retaining bracket  146  also has the flat substantially horizontally located brake handle retaining plate  154  that has a substantially circular shaped hole  156  that is sized and shape to permit the passage of the upper portion of a brake release handle  144  that comprises basically an elongated rod. The brake release handle  144  has a manual gripping handle portion  162  that extends towards the rear of the abrading machine  10  and is located to be within easy reach of the hand of the operator of the abrading machine  10 . A thin slot  164  is located in the brake handle retaining plate  154  and this slot  164  intersects the hole  156  in the brake handle retaining plate  154 . The slot  164  is sized and shaped to receive a reduced diameter portion  166  located on the upper portion  168  of the brake handle  144 . 
   The lower end portion of the brake handle  144  is rotatably mounted in a conventional manner on a shaft  172  that projects from the adjacent portion  36  of the mounting plate  32  by an enlarged loop  174  located on the lower end of the brake handle  144  that surrounds a portion of the shaft  172 . In view of this arrangement, when the manual handle portion  162  of the brake handle  144  is pulled upward by the operator this causes the connected mounting plate  32  to pivot upward which also causes the brake wheels  66  and  68  to be pulled away from the wheels  20  and  22  of the abrading machine  10  and as a consequence, no braking force BF is applied to the wheels  20  and  22 . The operator can lock the brake handle  144  in this upward position by pulling rearward or toward the rear of the abrading machine  10  on the manual handle portion  162  to cause the reduced diameter portion  166  located on the upper portion  168  of the brake handle  144  to slide into the slot  164  in the brake handle retaining plate  154  of the brake retaining bracket  146 . This prevents the handle  144  from moving downward until the operator pushes forward on the manual handle portion  162  to cause the reduced diameter portion  166  to be removed from the slot  164  since while the reduced diameter portion  166  is in the slot  164  the larger portion of the brake handle  144  located adjacent to the the reduced diameter portion  166  contacts the upper surface  173  of the brake handle retaining plate  154  and prevents downward movement of the brake handle  144 . 
   Also as indicated in  FIG. 1 , the braking system for a wheeled surface abrading machine  30  has means for rapidly replacing or repairing the main parts for the braking system  30  that are subject to wear comprising the indentations  180  and  182  in the respective end portions  34  and  36  of the mounting plate  32 . These indentations  180  and  182  permit the easy removal of the brake assembly  58  including the brake cylinder assembly  60  and associated brake cylinder mounting plate  76 , the brake adjusting mechanism  62 , the brake cylinder shaft  64  and the brake wheels  66  and  68  as well as the bearing assemblies  70  and  72  from the brake mounting plate  32  without disassembling these parts by merely removing the bolts  74  and  78 . Then the plastic disc  104  or discs  104  in the brake cylinder assembly  60  that has or have been subject to wear can easily be replaced as can the bearing assemblies  70  and  72 , or any other parts associated with the brake cylinder assembly  60 , or if desired, the complete brake assembly  58  can be replaced with or without new bearing assemblies  70  and  72 . This feature allows the surface abrading machine to be in full operation to the maximum extent possible since repair and parts replacement time is minimized. 
   The braking system invention for a wheeled surface abrading machine  30  is manufactured from conventional readily available materials known in the art. The braking system for a wheeled surface abrading machine  30  is also manufactured using standard cutting, drilling and welding equipment that is well known in the art using standard construction techniques. The braking system invention for a wheeled surface abrading machine  30  may be manufactured as part of a wheeled surface abrading machine  10  at the time the wheeled surface abrading machine  10  is manufactured or the braking system for a wheeled surface abrading machine  30  may be used to retrofit an existing wheeled surface abrading machine  10 . 
   In order to retrofit an existing wheeled surface abrading machine  10 , suitable holes are drilled in the in the lower portions  42  and  44  of the control arms  26  and  28  for the bolts  46  and  48 . Then, the upward extending end portions  34  and  36  of the mounting plate  32  and all the structure of the braking system  30  connected to the the mounting plate  32  is pivotally connected to the lower portions  42  and  44  of the control arms  26  and  28  of the existing wheeled surface abrading machine  10  by the bolts  46  and  48 . A suitable threaded hole  136  is formed in the wheel mount  18  and the threaded portion  134  of an adjusting bolt  130  is inserted into the hole  136  after a compression coil spring  138  is located around the adjusting bolt  130 . The brake retaining bracket  146  is also secured to the inside upper surface  150  of the upper portion  152  of the control arm  28  in the previously indicated manner. Then the brake release handle  144  is passed through the hole  156  in the brake handle retaining plate  154  and its lower end enlarged loop  174  is suitably located around a portion of the shaft  172  that projects from the portion  36  of the mounting plate  32 . This completes the retrofit of the existing wheeled surface abrading machine  10  with the braking system for a wheeled surface abrading machine  30 . 
   In order to use the braking system invention for a wheeled surface abrading machine  30 , the wheeled surface abrading machine  10  is operated by the operator in a conventional manner. However, when undue or excessive forward forces F are encountered due to the action of the rotating abrading element  15  with the surface  16  being abraded, the braking system for a wheeled surface abrading machine invention  30  is put into operation. This is accomplished by the operator manually grabbing the manual gripping handle portion  162  of the brake release handle  144  and pushing forward toward the front of the wheeled surface abrading machine  10 . This causes the reduced diameter portion  166  in the upper portion  168  of the brake handle  144  to move forward in the slot  164  of the flat surface brake handle retaining plate  154  of the bracket  146  until the reduced diameter portion  166  reaches the hole  156 . When the reduced diameter portion  166  reaches the hole  156 , the reduced diameter portion  166  is free of the slot  164  and the brake handle  144  is free to move up or down in the hole  156  since the handle  144  is no longer restrained by the surface  173  adjacent to slot  164  in the brake handle retaining plate  154  of the bracket  146 . The handle  144  then moves downward or toward the bottom of the surface abrading machine  10  since it is connected to the brake mounting plate  32  that is biased downward or toward the bottom of the abrading machine  10  by the compression spring  138 . When the brake mounting plate  32  moves downward, it results in the brake wheels  66  and  68  being pressed against the wheels  20  and  22  where they apply a braking force BF. 
   When a braking force BF is no longer required, the operator manually grabs the manual gripping handle portion  162  of the brake release handle  144  and pulls it in an upward direction until the reduced diameter portion  166  of the brake release handle  144  is located opposite the slot  164  in the bracket  146 . Then, the operator pulls the manual gripping handle portion  162  toward the rear of the abrading machine  10  to cause the reduced diameter portion  166  to enter the slot  164 . This results in the brake release handle  144  being locked in place in the slot  164  and this locks the brake mounting plate and the connected brake wheels  66  and  68  in place away from the wheels  20  and  22  of the surface abrading machine  10  so that no braking force BF is applied to the wheels  20  and  22 . The operator repeats this process each time the undesired forward forces F are encountered. 
   Although the invention has been described in considerable detail with reference to a certain preferred embodiment, it will be understood that variations or modifications may be made within the spirit and scope of the invention as defined in the appended claims.