Abstract:
A hand-held endless belt abrading machine comprises a base portion and a main portion, which portion is rotatable relative to the base portion around an axis extending in a forward and rearward direction of the abrading machine. The main portion comprises an air motor having a rotational shaft extending in a direction transverse to the abrading machine and projecting from the left end of the air motor, so that an abrading endless belt assembly drivingly connected to the output shaft is positioned to the left relative to the motor and the base portion which is held by a hand of an operator. When a left-handed person uses the abrading machine, the main portion is turned 180° relative to the base portion to shift the abrading endless belt assembly to the right relative to the base portion, thereby enabling the operator to readily observe the abrading belt assembly in operation.

Description:
[0001]     This application claims priority under 35 U.S.C. §119 to Japanese Patent Application Nos. 2003-272050 filed Jul. 8, 2003 and 2003-417614 filed Dec. 16, 2003, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an abrading machine and, in particular, to an endless belt abrading machine wherein an endless belt is rotatably driven and brought into contact with a workpiece to be abraded.  
         [0004]     2. Description of the Related Art  
         [0005]     In a conventional endless belt abrading machine, when an operator wishes to abrade a workpiece, s/he holds the machine with either a left or right hand, and brings the belt of the machine into contact with a workpiece to be abraded. Conventional endless belt abrading machines are provided with an air motor having a rotation shaft extending in a direction transverse to the machine; and are also provided with a drive pulley, which is drivingly connected to a left end of the rotation shaft; with a driven pulley positioned forward of and spaced apart from the drive pulley; and with an endless belt which is engaged with and extends between the drive and driven pulleys. During operation, an operator generally holds the machine using his/her right hand. Operating the machine in this manner, it is relatively easy for the operator to observe a workpiece being abraded, since the endless belt is positioned to the left of the operator&#39;s right hand which is holding the machine. However, in a case that an operator is left-handed and uses his/her left hand to hold the machine at its rear end, it is difficult for the operator to observe a workpiece being abraded since the belt abrading the workpiece is positioned to the left of the operator&#39;s left hand which is holding the machine. Consequently, it is difficult for a left-handed person to effectively operate the machine.  
         [0006]     To solve the drawback of the conventional art, there has been proposed an endless belt abrading machine which is adapted to be used upside down, or to be used wherein a position of a holding portion of the machine is changed from a left to right side relative to an endless belt of the machine. (For example, refer to Japanese Patent Application No. 2002-220567). One of the features of the machine of the prior invention is that when the machine is operated with a holding portion being shifted from a right to a left side, a direction of the motor&#39;s rotation can be reversed, thus enabling the abrasion belt to be driven in the same direction as that in which an operator is facing. Consequently, sparks which are generated upon abrading a workpiece move in a direction away from the operator, thus enabling an abrasion operation to be easily and safely carried out.  
         [0007]     In the machine of the prior invention, a ring valve is mounted on an outer surface of the machine, and functions as a valve controller for starting and stopping rotation of the machine&#39;s air motor. To achieve this function, however, the ring valve must be manually moved in either a forward or rearward direction by an operator, which requires use of both of the operator&#39;s hands. Moreover, if it is desired to set a holding portion from a right to a left side in the machine of the prior invention, the entire machine must be turned upside down. Consequently, in a case, for example, where an indicator showing a degree of load is mounted on an outer surface of the machine, setting a holding portion of the machine from a right to a left side results in a drawback that the indicator is visually obscured.  
       SUMMARY OF THE INVENTION  
       [0008]     In view of the above-described drawbacks of the conventional art, an object of the present invention is to provide a hand-held endless belt abrading machine, which includes a main portion, and also a base portion, which portion is connected to a rear of the main portion. The main portion has an air motor which has an axis of rotation which acts in a direction transverse to the machine; a drive pulley which is drivingly connected to an output shaft, which extends in a lateral direction from one end of the air motor; a driven pulley which is positioned forward of and spaced apart from the driven pulley; and an endless belt which is engaged with and extends between the drive pulley and the driven pulley. In addition, the main portion is pivotable about an axis which extends longitudinally from the base portion between a first operational position, where the output shaft of the air motor is extended to the left, and a second operational position, where the output shaft is extended to the right. The base portion has a first air passageway, which is connected to a source of compressed air for supplying compressed air to the main portion to drive the air motor; a stop valve which is adapted to open and close the first air passageway; and a valve controller for operating the stop valve.  
         [0009]     In the abrading machine of the present invention, the endless abrading belt can be set to be on either a right side or a left side relative to the main portion of the machine. This is accomplished by simply rotating the main portion of the machine while keeping the base portion of the machine in a fixed position. Consequently, a stop valve controller mounted on the base portion remains in a fixed position relative to a position of the operator thus enabling an operator to readily operate the valve controller, while selectively positioning the abrasive endless belt at either the right or the left side, depending on a convenience of observation of an operator.  
         [0010]     The stop valve controller may be movable between a depressed position and a position in which it is not depressed, to thereby enable the stop valve to be opened and closed.  
         [0011]     The air motor may also have first and second openings to be selectively supplied with compressed air depending on whether it is desired to rotate the machine&#39;s air motor in either a forward or in a reverse direction. The main portion may also have a second air passageway including a common passage having an air inlet, which communicates with the first air passageway of the base portion, and first and second branched passage respectively extending to the first and second openings of the air motor.  
         [0012]     On an outer surface of the main portion of the machine, there may be provided a ring valve, which is movable between a first position and a second position. When the ring valve is located in the first position, the common passage is brought into communication with the first branched passage; and when the ring valve is located in the second position, the common passage is brought into communication with the second branched passage.  
         [0013]     The main portion of the machine may have a columnar portion extending in the forward and rearward direction and having a circular cross-section. The columnar portion is provided with the second air passageway. Specifically, the common passage extends from the air inlet to an air outlet opening at the outer surface of the columnar portion. The first branched passage extends from a first inlet/outlet opening formed in the outer circumferential surface at a position circumferentially spaced apart from the air outlet to the first opening of the air motor. The second branched passage extends from a second inlet/outlet opening formed in the same surface at a position circumferentially spaced apart from the air outlet and the first inlet/outlet opening to the second opening of the air motor.  
         [0014]     The ring valve may be mounted on the outer circumferential surface of the columnar portion and is rotatable between a first position where the air outlet is communicated with the first inlet/outlet opening and a second position where the air outlet is communicated with the second inlet/outlet opening.  
         [0015]     In accordance with another aspect of the present invention, there is provided a hand-held endless belt abrading machine comprising: a main portion including an air motor having a rotational shaft extending in a direction transverse to the abrading machine and projecting from one lateral end of the air motor, the air motor further having first and second openings and being adapted to be selectively supplied with compressed air through either the first opening or the second opening depending on whether it is desired to rotate the motor in a forward or rearward direction, a drive pulley drivingly connected to a tip end of the output shaft of the air motor, a driven pulley positioned forward of and spaced apart from the drive pulley, and an abrading endless belt engaged with and extending between the drive and driven pulleys; and a base portion connected to a rear of the main portion and including: an air inlet passage for supplying compressed air to the air motor, an air outlet passage for discharging air exhausted from the air motor to the outside of the machine, a stop valve for opening and closing the air inlet passage, the stop valve having an outer end projecting outside the base portion, and a lever for operating the stop valve, the lever being pivotably mounted on the base portion to move between an opening position where the stop valve opens the air inlet passage, and a closing position where the stop valve closes the air inlet passage.  
         [0016]     When the main portion is located in the first operational position, the air inlet passage of the base portion is communicated with the first opening, while the air outlet passage is simultaneously communicated with the second opening of the motor; and when the main portion is located in the second operational position, the air inlet passage is communicated with the second opening, while the air outlet passage is simultaneously communicated with the first opening. The main portion includes a sleeve mounted thereon so as to be movable in a longitudinal direction of the main portion between a rotation-prevention position, where the sleeve is engaged with the base portion to prevent the main portion from rotating relative to the base portion, and a rotation-enabling position where the sleeve is disengaged from the base portion to permit the main portion to rotate relative to the base portion.  
         [0017]     The main portion may include a rearward facing surface which faces the base portion and forms a right angle with an axis extending in the forward and rearward direction, and first and second air passages opening which are positioned to be diametrically opposite each other on a circle on the rearward facing surface centering around an axis extending in the forward and rearward direction through the base portion. The first and second air passages are communicated with the first opening and the second opening of the motor, respectively. The air inlet passage of the base portion may include a larger diameter portion and a smaller diameter portion, arranged in that order, from a front end thereof adjacent to the rearward facing surface of the main portion. The larger diameter portion is provided with a cylindrical seal movable in the forward and rearward direction, and with a coil spring which urges the cylindrical seal against the rearward facing surface. The cylindrical seal has a front end slidably and hermetically engageable with the rearward facing surface of the main portion. When the main portion is located in the first operational position, the cylindrical seal is communicated with the first air passage; and when the main portion is in the second operational position, the cylindrical seal is communicated with the second air passage.  
         [0018]     The lock sleeve may include a notch which is formed in a rear end periphery thereof such that, when the sleeve is located in the rotation-prevention position, the notch engages with a pin secured on an outer circumferential surface of the base portion to prevent the main portion from rotating relative to the base portion.  
         [0019]     The base portion may comprise an outer cylindrical portion and an inner cylindrical portion disposed in the outer cylindrical portion which extends in the forward and rearward direction of the machine. The inner cylindrical portion has a longitudinal hole which forms the air inlet passage. A space extending in a longitudinal direction of the inner and outer cylindrical portions is formed between an outer surface of the inner cylindrical portion and an inner surface of the outer cylindrical portion, the space functioning as the air outlet passage.  
         [0020]     The inner cylindrical portion of the base portion may have a forward end extending beyond a front end of the outer cylindrical portion of the base portion. The main portion may include a cylindrical joint, which extends rearward to hermetically receive the forward end of the base portion such that the base portion is rotatable about a longitudinal axis thereof while maintaining an air-tight state between the cylindrical joint and the forward end of the base portion, and a columnar portion which has the first and second air passages, and is positioned inside and extends rearward of the main portion member terminating at the rearward facing surface. An air outlet passage is formed between an inner surface of the cylindrical joint of the main portion and the outer surface of the columnar portion of the main portion, the air outlet passage extending from the air motor.  
         [0021]     The cylindrical joint of the main member has an inner surface provided with a pair of stop portions which are adapted to be engaged with the forward end of the cylindrical portion defining the air inlet passage to position the main portion at the first and second operational positions, respectively.  
         [0022]     The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is a sectional plan view of an endless belt abrading machine of the first embodiment of the present invention.  
         [0024]      FIG. 2   a  is a plan view of the endless belt abrading machine in a state where a belt is in its initial position.  
         [0025]      FIG. 2   b  is a left side view of  FIG. 2   a.    
         [0026]      FIG. 3   a  is a plan view of the endless belt abrading machine in a state where the belt is located at a side opposite to that shown in  FIG. 2   a.    
         [0027]      FIG. 3   b  is a right side view of  FIG. 3   a.    
         [0028]      FIG. 4  is a transverse sectional view of an air motor of the endless belt abrading machine showing the positional relation of the air passages to the air motor.  
         [0029]      FIG. 5   a  is a sectional view taken along line V-V of  FIG. 1  and  FIG. 4  wherein the ring valve is positioned such that the air motor rotates in its normal direction.  
         [0030]      FIG. 5   b  is a sectional view taken along line V-V of  FIG. 1  and  FIG. 4  wherein the ring valve is positioned such that the air motor rotates in a reverse direction.  
         [0031]      FIG. 6  is a sectional plan view of the endless belt abrading machine of another embodiment of the present invention.  
         [0032]      FIG. 7  is a sectional plan view of the endless belt abrading machine of the second embodiment of the present invention.  
         [0033]      FIG. 8   a  is a sectional view taken along line VIIIa-VIIIa of  FIG. 7 .  
         [0034]      FIG. 8   b  is a side view of a main portion of the machine showing a direction of rotation of the belt when a basic portion of the machine and the main portion have the relation shown in  FIG. 8   a.    
         [0035]      FIG. 9   a  is a sectional view taken along line VIIIa-VIIIa of  FIG. 7  showing a state where the basic portion of the machine has been rotated 180° relative to the main portion of the machine, as viewed from the position shown in  FIG. 8   a.    
         [0036]      FIG. 9   b  is a side view of the main portion of the machine showing a direction of rotation of the belt when the basic portion and the main portion of the machine have the relation shown in  FIG. 9   a.    
         [0037]      FIG. 10  is a sectional view similar to that shown in  FIG. 8   a , but where a lock sleeve has been moved forwards.  
         [0038]      FIG. 11  is a sectional view taken along line XI-XI of  FIG. 7 .  
         [0039]      FIG. 12  is a sectional view taken along line XII-XII of  FIG. 10 .  
         [0040]      FIG. 13  is a sectional view similar to that of  FIG. 12 , but shows a base portion of the machine rotated by 180° relative to its position shown in  FIG. 12 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0041]     An embodiment of the endless belt abrading machine according to the present invention will now be described below with reference to the accompanying drawings.  
         [0042]      FIG. 1  is a sectional plan view of the endless belt abrading machine of the present invention. To clearly illustrate the structure of the abrading machine of the present invention, in  FIG. 1 , a base portion of the abrading machine  24  (which will be described hereinafter) is shown in a position rotated by 90° relative to a usual position of the machine&#39;s main portion  22 , as viewed along the machine&#39;s longitudinal axis from left to right.  FIG. 2  is a plan view of the machine in which the machine&#39;s base portion  24  is shown in its usual operation.  FIG. 2   b  is a side view of the machine.  
         [0043]     The machine  10  has the main portion  22  and the base portion  24 . The main portion  22  includes: an air motor  12  having an axis of rotation which is transverse to the machine  10 ; a drive pulley  16  which is drivingly connected to an output shaft  14 , and which extends laterally from one end of the air motor; a driven pulley  18 , which is positioned forward of the drive pulley  16 ; and an endless belt  20  (shown in  FIG. 2   a ,  FIG. 2   b ), which is engaged with each of the drive and driven pulleys  16 ,  18 .  
         [0044]     The base portion  24  includes a first air passageway  32  connected to a hose  30  extending from a source of compressed air (a pump) for supplying compressed air to the main portion  22  to drive the air motor  12 , a valve  34  for opening or closing the first air passageway  32 , and a lever  36  pivotably fitted on a circumferential top area of the base portion  24 . The lever  36  is movable between a depressed position and a released position, so as to enable the valve  34  to open or close the first air passageway  32 . In the illustrated example, the first air passageway  32  has an axial portion, a radial portion and a slanting portion. The axial portion extends parallel to an axis of the base portion from a joint opening, which is located at a rear end of the base portion and is connected to the hose  30 . The radial portion extends radially from the front end of the axial portion. The slanting portion extends forward and radially inward from the radial portion. The stop valve  34  has a valve member (a ball)  34   a  set in the radial portion of the first air passageway  32 , and a spring  34   b  which urges the valve member  34   a  against a valve seat formed on the inner surface of the radial portion of the first air passageway  32 . The lever  36 , which is pivotable about a pivot pin  36   a , is retained in the released position, as shown in  FIG. 1 , by way of a lever retainer  42 , which is rotatable about a pivot pin  40  positioned forward of the pivot pin  36   a , and which is urged by a spring to engage with a lower surface of the lever  36 . The lever retainer  42  has an extending portion  42   a  extending upwards of the lever  36 . When the extending portion  42   a  of lever retainer  42  is moved downwards in a clockwise direction about the pivot pin  40  (against the action of the spring  34   b ), the lever retainer  42  is rotated clockwise, which enables the lever  36  to be moved downwards counterclockwise about the pivot pin lever  36   a . When the extending portion of lever retainer  42   a  is enabled to move upwards again, the lever retainer  42  and the lever  36  are sprung back into the position, as shown in  FIG. 1 , under the action of the spring  34   b . Further, there is provided a connecting rod  34   c  extending vertically between the underside of the lever  36  and the valve member  34   a . When the lever  36  is depressed or released, the connecting rod  34   c  acts on the valve member  34   a  to cause it to be either seated in or separated from the valve seat, and to thereby either open or close the stop valve  34 .  
         [0045]     Hereinafter, the main portion  22  will be described in more detail. The portion  22  is adapted to be rotated about a longitudinal axis of the base portion of the machine  24  to a first operational position, where the output shaft  14  of the motor extends to the left of the machine ( FIG. 1 ,  FIG. 2   a ), and can also be rotated to a second operational position, where the output shaft  14  extends to the right of the machine( FIG. 3   a ).  
         [0046]     The air motor  12  is a vane motor, as shown in  FIG. 4 , and has first and second openings  12   a ,  12   b ; and is selectively supplied with compressed air through either the first opening  12   a  or the second opening  12   b  to be caused to rotate in either a forward or reverse direction.  
         [0047]     As shown in  FIG. 4 , the main portion  22  includes a second air passageway  46  which has a fluid passage extending from an air inlet  44  connected with the slanting portion of the first air passageway  32  of the base portion  24  to the first or the second opening  12   a ,  12   b  of the air motor. There is further provided a ring valve  48 , which controls an air flow through the second air passageway  46  on an outer surface of the main portion  22 . The ring valve  48  is rotatable between a first and the second position. As will be described later, when the ring valve  48  is in the first position, the air inlet  44  of the second air passageway  32  is adapted to communicate with the first opening  12   a  of the air motor; and when the ring valve  48  is in the second position, the air inlet  44  of the second air passageway  32  is adapted to communicate with the second opening  12   b  of the air motor.  
         [0048]     More specifically, as shown in  FIGS. 4, 5   a  and  5   b , the main portion  22  includes a columnar portion  51  having a circular cross-section and defines the second air passageway  46 . The columnar portion  51  has a common passage  46   a  ( FIGS. 5   a  and  5   b ), a first branched passage  46   b  ( FIGS. 5   a  and  5   b ,  FIG. 4 ) and a second branched passage  46   c  ( FIGS. 5   a  and  5   b ,  FIG. 4 ). The common passage  46   a  extends from the air inlet  44  ( FIG. 1 ) to an air outlet  50  opening at an outer surface of the columnar portion  51 . The first branched passage  46   b  ( FIGS. 5   a  and  5   b ,  FIG. 4 ) extends from a first inlet/outlet opening  52  which is provided on the outer surface of the columnar portion  51  circumferentially spaced apart from the air outlet  50 , to the first opening  12   a  of the air motor. The second branched passage  46   c  ( FIGS. 5   a ,  FIG. 4 ) extends from a second inlet/outlet opening  54 , which is provided on the outer surface of the columnar portion  51  circumferentially and in symmetrical relation to the first inlet/outlet opening  52  about the air outlet  50 , to the second opening  12   b  of the air motor.  
         [0049]     The ring valve  48  is provided with arcuate recesses  58 ,  59 ,  60  on an inner surface thereof. When the ring valve  48  is in the first position ( FIG. 5   a ,  FIG. 4 ), the arcuate recess  58  connects the air outlet  50  and the first inlet/outlet opening  52  to allow flow to flow to the air motor; and the arcuate recess  59  connects the second inlet/outlet opening  54  to an exhaust passage  46   e  formed in the columnar portion to allow exhaust to flow from the air motor, under which condition the air motor rotates. When the ring valve  48  is in the second position ( FIG. 5   b ), the arcuate recess  58  connects the air outlet  50  and the second inlet/outlet opening  54  to allow air to flow to the air motor; the arcuate recess  60  connects the first inlet/outlet opening to the exhaust passage  46   d  in the columnar portion to allow exhaust from the air motor, under which condition the air motor rotates in a reverse direction.  
         [0050]     The driven pulley  18  is rotatably mounted on a distal end of a tension bar  62  in the same manner as in the abovementioned invention (Japanese Patent Application No. 2002-220567). The rear end portion of the tension bar is inserted into a cylindrical portion  64   a  which extends forward from a housing  64  of the air motor  12 , and is urged forward by a compression spring  66  provided in the cylindrical portion  64   a . In this way, tension is applied to the endless belt  20  which is engaged with both the driven pulley  18  and the drive pulley  16 . An annular groove  68  is formed on a peripheral surface of the tension bar  62 . When it is required to replace a belt, the tension bar  62  is inserted into the cylindrical portion  64   a  against the action of the compression spring  66 , which permits a spring  70  to engage in the annular groove  68  and to retain the tension bar  62 . After replacement of the belt, when the spring  70  is disengaged from the annular groove  68 , the tension bar is returned to its previous state under the action of the compression spring  66 . In  FIG. 2   b , the reference numeral  72  denotes a pulley. For the purpose of forming an abutting portion  20   a  on the endless belt  20  for a workpiece, the pulley  72  is engaged with the endless belt  20 . Also, the pulley  72  is supported by a bracket  74 , which is mounted on the tension bar  62  to project downwardly. The bracket  74  is detachable from the tension bar  62 . In a case where the main portion is reversed between the first position shown in  FIG. 2  and the second position shown in  FIG. 3  (upside down as seen in those figures.), the bracket  74  is detached from an initial position on tension bar  62  to be next attached at a longitudinal opposite position from the initial position on the tension bar  62  so that the pulley  72  supported by the bracket always remains set beneath the tension bar  62 . In  FIG. 1 , the numeral  78  denotes a cover which is detachably mounted on the cylindrical portion  64   a  by a screw  78   a.    
         [0051]     As stated, the main portion includes the housing  64  of the air motor, the columnar portion  51  fixed to the rear of the housing, the ring valve  48  rotatably mounted around the outer surface of the columnar portion, and the tension bar  62  mounted on and extending toward from the side of the housing  64  of the air motor, and is rotatable around the longitudinal axis of the cylindrical base portion. As is clearly shown in  FIG. 1  and in  FIG. 4 , the columnar portion  51  is fixedly connected to the housing  64  by a lock nut  81  threaded into the housing  64  of the air motor  12  through a washer  83 . A rear half of the columnar portion  51  is inserted into the cylindrical base portion  24  coaxially, and is held rotatably about the central axis of the base portion  24 . Further, the columnar portion  51  is provided with a through hole which extends from the rear end to the front end of the columnar portion. The rear and front ends of the through hole are blocked by blocking members  79 ,  80  which are threadably engaged thereinto, to form the second air passageway  46  between the blocking members. The blocking member  80  engaged with the rear end has a bolt-like form, and has a head portion  80   a , which is positioned in and engaged with the first air passageway  32  to prevent the columnar portion  51  from moving out of the main portion  24 . In  FIG. 4 , the reference numeral  82  denotes a hexagonal socket head cap screw. The screw  82  is threadingly engaged with a threaded bore formed radially through the base portion  24 , and is engaged in recess  51   a  formed on the outer surface of the columnar portion  51 , which results in prevention of the columnar portion  51 , and hence the main portion  22 , from rotating relative to the base portion  24 . The recesses  51   a,    51   a  are arranged in a pair, with each recess being provided on the columnar portion in diametrically opposed positions relative to one another. When the main portion is in the abovementioned first position (shown in  FIG. 2   a ) or in the second position (shown in  FIG. 3   a ), the screw  82  is engaged with a corresponding one of the recesses  51   a  to fix the main portion to the base portion. The numeral  84  denotes a through-hole provided in the ring valve  48  for insertion of an Allen key for turning the hexagonal socket head cap screw. Referring to  FIG. 6 , there is shown another embodiment of the present invention in which a ball  88  is used instead of the screw  82 . Specifically, in this embodiment, there is provided a bore  90  which extends radially in the columnar portion  51  of the main portion  22  and opens at the outer surface thereof. The ball  88  is set in the bore  90  and is urged radially outwardly by a spring  92  set in the bore  90 . Further, the ball  88  is engaged in recesses formed at a circumferentially predetermined position on an inner surface of the base portion  24  surrounding the columnar portion  51 , to prevent the columnar portion  51 , and hence the main portion  22 , form rotating relative to the base portion  24 . The recesses are arranged in a pair, with each recess being provided on the base portion  24  in diametrically opposed positions relative to one another. When the main portion is in the abovementioned first position (shown in  FIG. 6 ) or in the second position (the reversed position of the main portion shown in  FIG. 6  relative to the base portion), the ball  88  is engaged with a corresponding one of the recesses to fix the main portion to the base portion .  
         [0052]     Next, a second embodiment of the endless belt abrading machine according to the present invention will be described with reference to the accompanying drawings.  FIG. 7  is a sectional plan view of the endless belt abrading machine of the present invention.  FIG. 8  is a sectional view taken along line VIIIa-VIIIa of the  FIG. 7 .  
         [0053]     This endless belt abrading machine  110  has a main portion  116  and a base portion  118 . The main portion  116  includes an air motor  112  and an endless belt  114  driven by the air motor  112 . The base portion  118  is connected to a rear part of the main portion  116  in order to supply and exhaust compressed air for the air motor  112 .  
         [0054]     The air motor  112  is a vane-type motor and has a rotor  120  rotatable about an axis extending transversely of the machine  110 , a rotor chamber  122  for accommodating the rotor, and a rotor housing  128  including a first and a second air passage  124 ,  126  for supplying and exhausting compressed air to and from the rotor chamber  122 . In the illustrated example, the rotor housing  128  has a cylindrical liner portion  128 - 1  provided on the interior surface, and has first and second openings  124 - 1 ,  126 - 1  which respectively interconnect with the first and second air passage  124 ,  126 . The endless abrading belt  114  is engaged with the drive pulley  132 , which is drivingly connected to an output shaft  130  which extends laterally from one end of the air motor  112 ; with the driven pulley  136  being positioned forward of the drive pulley  132  by a tension bar  134 .  
         [0055]     The base portion  118  has a base portion member  140  which is rotatably connected with a rear portion of the rotor housing  128  of the air motor  112  about an axis extending forward and rearward. The base portion member  140  has an air inlet passage  142  and an air outlet passage  144 , and is rotatably mounted between the first position and the second position. In the first position ( FIG. 8   a ), the air inlet passage  142  is adapted to communicate with the first air passage  124  and the air outlet passage  144  is adapted to communicate with the second air passage  126 . In the second position ( FIG. 9   a ) where the base portion  118  has been turned 180° from the first position, the air inlet passage  142  is adapted to communicate with the second air passage  126 , and the air outlet passage  144  is adapted to communicate with the first air passage  124 . When the base portion member  140  is in the first position, as shown in  FIG. 8   a  and  FIG. 8   b , the rotor  120  and the belt  114  are turned counterclockwise, as indicated by the arrows in those figures. When the base portion member  140  is in the second position, as shown in  FIG. 9   a  and FIG.  9   b , the rotor  120  and the belt  114  are turned clockwise as indicated by arrows in those figures.  
         [0056]     On an outer periphery surface of the base portion member  140 , there are provided a lock sleeve  146 , which is movable only forward and rearward relative to the rotor housing  128 , and a coil spring  149  which urges the lock sleeve  146  rearward. The lock sleeve  146  is formed with a notch on a periphery of its rear end for fitting a pin  150  to be fixedly mounted to the base portion, and to be movable between a rotation-restraining position ( FIG. 7 ,  FIG. 8 ) and a rotation-enabling position ( FIG. 10 ). In the rotation-restraining position ( FIG. 7 ,  FIG. 8 ), the lock sleeve  146  fits the pin  150 , which prevents the base portion member  140  from turning relative to the rotor housing  128 . In the rotation-enabling position ( FIG. 10 ), the lock sleeve  146  is moved forward from where the lock sleeve is in the holding position and is released by the pin  150 , which allows the base portion member  140  to rotate relative to the rotor housing  128 . Further, there is provided a rod-like poppet valve  152  in the base portion member  140 , for closing and opening the air inlet passage  142 . The poppet valve  152  is urged by the coil spring  154  to a position for closing the air inlet passage  142  ( FIG. 8   a ) and an upper end thereof extends outside of the base portion member  140 . Further, there is provided a lever  156  in the base portion member  140 . The lever  156  is rotatably fitted on the base portion member  140  to be moved between an opening position (depressed position) where the lever  156  is adapted to depress the valve  152  to open the air inlet passage  142 , and a closing position (undepressed position) where the coil spring  154  allows the valve  152  to return to the position to close the air inlet passage  142 .  
         [0057]     The lever  156  with a lever pivot pin  160  is retained in a released position shown in  FIG. 8   a  by a lever retainer  164 , which is pivotably mounted on a pivot pin  162  positioned forward of the lever pivot pin  160 ; and the lever retainer is urged under the action of a spring to be engaged with an under surface of the lever  156 . The lever retainer  164  has an extending portion  166  which extends upward of the lever  156 . When the extending portion  166  of the lever retainer  166  is moved down clockwise about the pivot pin  162  (against the action of the spring), the lever retainer  164  is rotated clockwise, which enables the lever  156  to be moved down counterclockwise about the pivot pin of lever  160 . When the extending portion of lever retainer  166  is released, the lever retainer  164  and the lever  156  are sprung back into the position shown in  FIG. 8   a.    
         [0058]     As will be seen from  FIG. 11 , the base portion member  140  is generally cylindrically shaped, and has a cylindrical portion  170  which extends in the direction of the axis of the base portion member  140 . The cylindrical portion  170  has a bore which forms the air inlet passage  142 . An outer surface of the cylindrical portion  170  and an inner surface of the base portion member  140  defines a space which extends axially thereof, and which forms the air outlet passage  144 .  
         [0059]     The rotor housing  128  of the air motor  112  has a cylindrical joint  172  which extends rearward, and rotatably and hermetically receives a front end portion of the base portion member  140  about longitudinal axis. In the cylindrical joint  172 , there is formed a rearward facing surface  174  (forming a right angle with the longitudinal axis) facing a front end of the base portion member  140 . Both the first and the second openings  124 ,  126  extend from the rotor chamber to the rear end surface of the cylindrical joint  172 .  
         [0060]     The air inlet passage  142  of the base portion member  140  is provided with a larger diameter portion  180  and a smaller diameter portion  182 , in that order, from a front end thereof adjacent to the rearward facing surface  174  of the rotor housing  128 . In the larger diameter portion  180 , there are provided a cylindrical seal  184  movable in a forward and a rearward direction, and a coil spring which urges the cylindrical seal against the rearward facing surface  174 . A front end surface of the cylindrical seal  184  is hermetically and slidably engaged with the rearward facing surface  174  of the rotor housing  128 .  
         [0061]     Further, in the illustrated example, the cylindrical portion  170  forming the air inlet passage  142  projects beyond the front end surface of the base portion member  140 . The rearward facing surface  174  has a semi-circular form ( FIGS. 12, 13 ) delineating a path along which the front end of the cylindrical portion  170  is moved when the base portion is turned between the first and second positions relative to the main portion. The rearward facing surface  174  is defined by a rear end surface of a columnar potion  176  which axially extends inside the cylindrical joint  172 , and has a semi-circular cross section. The first air passage  124  and the second air passage  126  are formed to extend through the columnar portion  176  in a forward and rearward direction, and are arranged to open through the rearward facing surface at diametrically opposite positions on a circular area on the surface having a center, through which an axis for rotation of the base portion member  140  extends. Moreover, a second outlet passage is defined between an inner surface of the cylindrical joint  172  and an outer surface of the columnar portion  176 , and allows exhaust air to flow from the rotor chamber  122  to the air outlet passage  144  in the base portion member  140 . As shown in  FIG. 12  and  FIG. 13 , there are provided a pair of stop portion  188 ,  188  which are engaged with a distal end of the cylindrical portion  170  having the air inlet passage  142  to prevent excess rotation of the base portion member  140 , when the base portion member  140  is rotated to either the first position or the second position.  
         [0062]     In  FIG. 8   a  the numeral  190  denotes a pipe for communicating an air inlet (not shown) of the base portion member  140  to a pump. The numeral  192  is an installation sleeve for installing the lock sleeve  146  and the coil spring  149  on the base portion member  140 . The tension bar  134  shown in  FIG. 8   b  is provided with an idle roller  196  at its midpoint via a bracket  194 . The bracket  194  is adapted to be detached from one side of the tension bar  134  and to be transferred to another side (upper side) to enable the abrading belt to be adjusted in response to the positional change of the main portion  116  relative to the base portion member, as described above.  
         [0063]     The endless belt abrading machine  110  according to the second embodiment of the present invention has the arrangement described above. When an operator operates the machine  110  holding it with his/her right hand, the operator holds the base portion member  140  having the arrangement shown in  FIGS. 7, 8   a , such that the abrading belt  114  is located to the left side relative to the base portion member  140 , and accordingly is positioned forward and to the center of the operator. In a case where the base portion member  140  is set in the first position as shown in  FIG. 8   a , the belt is enabled to be turned in a counterclockwise direction, and in the second position as shown in  FIG. 9   a , the belt is enabled to be turned in a clockwise direction. In addition, when an operator operates the machine  110  with holding it with his/her left hand, the main portion  116  is turned through 180° relative to the base portion member from the position shown in  FIG. 7 , whereby the main portion  116  is located to the right side of the base portion member  140  held by operator&#39;s left hand forward and to the center of the operator. When the base portion member  140  is set to either the first position or the second position as desired by an operator, the belt is enabled to be turned in a desired direction.  
         [0064]     It should be noted that the present invention is not limited to the foregoing embodiments, and can be modified in a variety of ways without departing from the gist of the present invention.  
         [0065]     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.