Abstract:
A manual grinding tool, in particular an oscillating sander ( 10 ), with a housing ( 12 ) and an abrasive sheet carrier ( 14 ), against the working surface ( 15 ) of which an installable abrasive sheet ( 16; 150 ) rests, whereby said abrasive sheet is installed using clamping means ( 20, 23; 360, 500 ) which clamp opposite abrasive sheet ends ( 17, 19; 155 ) to the abrasive sheet carrier ( 14 ), is made easier to operate and handle because it is lighterweight and more effective by the fact that the clamping means ( 20, 23; 350, 500 ), together with an abrasive sheet end ( 17; 155 ) clamped thereto, are capable of being moved away from the diametrically opposed abrasive sheet end ( 19; 155 ) which is also clamped thereto, so that said abrasive sheet is locked under tensile stress, whereby the clamping means are composed of resilient material.

Description:
BACKGROUND INFORMATION  
       [0001]     The present invention concerns a manual grinding tool according to the general class of claim  1 .  
         [0002]     An orbital sander with a sanding plate on which abrasive sheets are installed is made known in GB patent publication 23 22 582; the abrasive sheets are capable of resting with their back against the underside of the sanding plate and are clampable in place on their top side. The underside of the abrasive sheets, where sanding means are provided, faces downward/outwardly and, when the abrasive sheet carrier is mounted on a workpiece, it is usable for sanding.  
         [0003]     The operator must use both hands to clamp the abrasive sheets in place, and the hand power tool should be placed on a solid surface. Using one hand, one end of the abrasive sheet is inserted into a slit between an opened clamping jaw and the top side of the abrasive sheet carrier, and the clamping jaw is held open in the release position until the end of the abrasive sheet is inserted so that it closes via spring force when the clamping jaw is released. This is the clamped position in which the abrasive sheet end is fixed. The abrasive sheet is automatically tightened to a certain extent in that the rotatably mounted clamping jaw tries to roll away from the abrasive sheet end, thereby carrying it along, due to an inclined-plane contact surface on the top side of the abrasive sheet carrier.  
         [0004]     The same procedure is used with the other abrasive sheet end as is used with the first abrasive sheet end, whereby the clamping force and tightening force of the clamping means are limited.  
         [0005]     The same disadvantages also apply for the abrasive sheet clamping system according to U.S. Pat. No. 3,540,161.  
       ADVANTAGES OF THE INVENTION  
       [0006]     The manual grinding tool according to the present invention having the characterizing features of claim  1  has the advantage of particularly convenient, rapid clamping—combined with the abrasive sheet being stretched tight—using only one hand, with simplified manufacture of the clamping means at lower cost and significant weight reduction. This results in increased abrasive performance and greater overall efficiency of the manual grinding tool.  
         [0007]     Due to the fact that the first abrasive sheet end is capable of being inserted using just one hand into a self-opening slit and is automatically clampable there, and, subsequently, the second abrasive sheet end is insertable—also using just one hand—into the clamping device and is then capable of being stretched tight, to the tearing limit, the abrasive sheet is capable of being fixed quickly and safely against misuse between the two clamping points and the working surface of the abrasive sheet carrier in such a manner that it is stretched tightly and, during sanding, a relative motion between the abrasive sheet carrier and the abrasive sheet is largely prevented.  
         [0008]     Due to the fact that the slit which clamps the first abrasive sheet end is opened using a single, central, easily located operating button to release the abrasive sheet, the operating comfort of the manual grinding tool is particularly high.  
         [0009]     Due to the fact that one of the clamping means is configured as tongs, between the clamping jaws of which an abrasive sheet end is clampable, and due to the fact that the tongs—together with the clamped abrasive sheet end—are movable around a swivel axis and are lockable in an end position, secure clamping followed by stretching-tight of the abrasive sheet is attainable in a convenient and reliable manner using simple means.  
         [0010]     The tongs have the advantage that abrasive sheets of any thickness are clampable with maximum clamping force, because a long closing path enables all dimensional differences to be compensated for in a sensitive manner, whereby the clamping force attained is stronger than has been previously achieved. In addition, abrasive sheets having different lengths—within limits—can be installed on the hand power tool, because a long overhang can easily form between the open active clamping jaw—configured in the shape of a half ring or bracket—and the passive clamping jaw, and it can be comfortably accommodated there.  
         [0011]     Due to the fact that the passive clamping jaw is configured as corrugated spring sheet which is capable of being deformed around a bending region in the manner of a hinge, the one end of which is clamped to the housing in the manner of a transverse beam, and the free end of which has a friction lining, in particular rubber, the desired flat spring characteristic (a small force/travel ratio) with extremely short installation length of the passive clamping jaw is attainable in a space-saving fashion.  
         [0012]     Due to the fact that the passive clamping jaw—as viewed from the free end, from right to left—first extends upwardly as a sine wave followed by a semi-sine wave having a smaller amplitude, the corrugated spring sheet is reliably clampable with the desired spring force.  
         [0013]     Due to the fact that the active clamping jaw is part of a two-armed clamping lever, one of which said clamping levers serves as a handle which is detachably lockable in the clamped position in an over-latching manner, and due to the fact that the tongs, to this end, are pivotable around the swivel axis between two end positions that define the clamped and released positions, it is particularly easy to install an abrasive sheet.  
         [0014]     Due to the fact that the clamping lever can be pivoted into its holding position in an over-latching manner via an over-latching hook bent inwardly toward the housing in the manner of a barb, the tongs are lockable in a particularly comfortable and operationally-reliable manner by pressing the clamping lever perpendicularly and/or they are capable of being released in a failsafe manner by pressing them toward the housing in a self-locating manner.  
         [0015]     Due to the fact that, with the tongs in the clamped position, the active clamping jaw rests against the passive clamping jaw with a minimum clamping force achievable with spring means, the clamping force at the abrasive sheet end to be clamped is capable of being determined by selecting the appropriate elastic means.  
         [0016]     Due to the fact that the active clamping jaw is bent in the manner of a half ring and grips around the passive clamping jaw in such a manner that it rests against the outside of the passive clamping jaw to clamp the abrasive sheet and carries it along when pivoted into the clamped position, a user-friendly clamping-tightening mechanism with reduced risk of injury when replacing the abrasive sheet and/or working with the manual grinding tool is created, because protruding edges on the manual grinding tool are prevented. A defined spring load-deflection curve of the active clamping jaw is achieved via its bracket or arch-shaped configuration having a certain wire diameter, so that a maximum clamping force between the clamping jaws is established in the clamped position.  
         [0017]     Due to the fact that the passive clamping jaw has a full-length longitudinal notch to accept the active clamping jaw, the grip between the passive clamping jaw and sandpaper end is improved and the clamping force is strengthened further.  
         [0018]     Due to the fact that, in addition to the tongs for the one abrasive sheet end, clamping means for the other abrasive sheet end are provided, which said clamping means act in a manner such that they allow the abrasive sheet to enter in a preferred direction, but release in the reverse direction with special actuation, it is possible to clamp the abrasive sheet quickly using just one hand.  
         [0019]     In this case, one-hand operation means that, in fact, only one hand need be active to insert and fix the abrasive sheet. The other hand can be used alone to fix the hand power tool, e.g., to press it against a base.  
         [0020]     Due to the fact that the clamping jaws are composed of elastic, rubber-like material, the clamping servo effect becomes stronger as the clamping of the abrasive sheet increases. This servo effect is also strengthened by the fact that the outer contour of the clamping jaw is bent progressively with a small variation in pitch.  
         [0021]     Due to the fact that the clamping jaws are composed of sheet metal and/or wire and are provided with a rubber coating, they are easy-to-manufacture, lightweight and functionally reliable.  
         [0022]     Due to the fact that the clamping jaw and/or the active clamping jaw are insertable in a groove in the housing and are secured against coming out by means of a screw which extends partially over the groove, a high degree of functional safety of the tongs is achieved with little effort when the sandpaper is clamped.  
         [0023]     Due to the fact that the clamping jaw is positioned horizontally and the insertion slit must be opened wide—whereby it can even lie below the plane of the sanding plate—the abrasive sheet need not be angled upward or bent to be inserted into the slit; instead, it can be inserted in a self-locating, extremely convenient—“blindly”, even—very casual manner, and then stretched tight.  
         [0024]     Due to the fact that the clamping lever is approximately 60 mm long and the 2 active jaw has a lever length of approximately 20 mm, a convenient, secure clamping of the abrasive sheet is possible. 
     
    
     DRAWING  
       [0025]     Exemplary embodiments of the invention are described in greater detail in the subsequent description with reference to an associated drawing.  
         [0026]      FIG. 1  shows a side view of the manual grinding tool according to the invention with clamping device,  
         [0027]      FIG. 2  is a top view at an angle from above of the abrasive sheet carrier of a further embodiment of the manual grinding tool with clamping device,  
         [0028]      FIG. 3  is the underside view according to  FIG. 2 ,  
         [0029]      FIG. 4  is a further exemplary embodiment of the manual grinding tool according to the invention,  
         [0030]      FIG. 5  is a spacial representation of the active clamping jaw made of wire, shown alone,  
         [0031]      FIG. 6  is an active clamping jaw end, shown alone,  
         [0032]      FIG. 7  is an exemplary embodiment of the active clamping jaw end,  
         [0033]      FIG. 8  is another exemplary embodiment of the active clamping jaw end,  
         [0034]      FIG. 9  is an exemplary embodiment of a passive clamping jaw made of wire,  
         [0035]      FIG. 10  is a further exemplary embodiment of a clamping jaw made of spring wire and spring sheet, and  
         [0036]      FIG. 11  is the exemplary embodiment according to  FIG. 11  with opened clamping jaw. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0037]      FIG. 1  shows a manual grinding tool  10  (orbital sander) with a housing  12  that has a handle on the outside and an electric motor on the inside (not shown). An abrasive sheet carrier  14  is located at the bottom of housing  12 , which said abrasive sheet carrier, driven by a motor, is capable of being set into oscillating motion relative to housing  12  and, as a result, can remove material from a work piece (not shown) via sanding with an abrasive sheet  16  secured tightly below on its working surface  15 . The grinding dust that is created is capable of being blown out and/or suctioned up from the front side  121  toward the rear side  122  of manual grinding tool  10  via suction connecting piece  120 . Abrasive sheet  16  rests with its back side against the underside of abrasive sheet carrier  14 .  
         [0038]     A clamping means designed as a two-armed clamping lever  20  with a swivel axis  24  is positioned in the front on the top side  13  of abrasive sheet carrier  14 . Above swivel axis  24 , clamping lever  20  is a swing arm and, below said swivel axis, it is a clamping jaw  22 . It rests with its outer contour  27  bent in the shape of a saber against locking face  23  of top side  13  of abrasive sheet carrier  14 . Swivel axis  24  of clamping lever  20  is located on a bracket  28  on the top side of abrasive sheet carrier  14 .  
         [0039]     A tension spring  26  bears between the top side of swing arm  21  and an abutment (not shown) in housing  12 , which said tension spring can also be configured as a leg spring; it tries to pivot clamping lever  20  in the clockwise direction, whereby it presses clamping jaw  22  against locking face  23  and thereby clamps abrasive sheet end  19  in place.  
         [0040]     In the upper region, swing arm  21  has a single, projecting knee serving as push button  211 . By means of this, swing arm  21  is capable of being moved downward using a finger, whereby tension spring  26  is loaded. Clamping jaw  22  then lifts away from locking face  23 , and the gap between outer contour  27  and locking face  23  opens so wide that abrasive sheet end  19  is released and can be removed.  
         [0041]     The distance between swivel axis  24  of clamping lever  20  and locking face  23  is smaller than the distance between swivel axis  24  and the radially outermost point of outer contour  27 , so that, in the position with spring preload via spring  26 , clamping jaw  22  bears against locking face  23  on the top side  13  of abrasive sheet carrier  14 . As a result, the clamping force on abrasive sheet  16  increases in proportion to the forces that try to release abrasive sheet  16  against the direction of insertion.  
         [0042]     Tension spring  26  is preloaded to such a low extent that, when outer contour  27  of clamping jaw  22  is tapped even slightly, abrasive sheet  16  displaces said clamping jaw from the outside against the direction of tension, creates the gap by itself which is needed for insertion, and is easily inserted and pushed back with one hand.  
         [0043]     Clamping jaw  22  is composed at least partially of elastic, rubber-like material with a high coefficient of friction that limits relative motion between abrasive sheet  16  and clamping jaw  22 .  
         [0044]     As viewed on the right, a clamping-tightening device configured as tongs  34  is located on the rear side  122  of abrasive sheet carrier  14 . It is composed of a clamping lever  35  with curved active clamping jaw  36  and a handle  39  that is a two-armed lever which is pivotable around a swivel axis  40 . Active clamping jaw  36  is composed of elastic material, e.g., spring steel. Also capable of being pivoted around swivel axis  40  is a clamping lever  37  that forms passive clamping jaw  38  and bears against the inner contour of active clamping jaw  36  when abrasive sheet  16  is tightened. The other abrasive sheet end  17 , which is diametrically opposed to abrasive sheet end  19 , is inserted and retained between passive clamping jaw  38  and active clamping jaw  36 .  
         [0045]     When tongs  34  with retained sandpaper end  17  are pivoted around swivel axis  40  in the counterclockwise direction, its distance from the other sandpaper end  19  increases. As a result, abrasive sheet  16  is tightened and pulled taut against the underside of abrasive sheet carrier  14 . The tightening of abrasive sheet  16  is apparent in rear lower edge  118  of cushion that is pressed round in shape.  
         [0046]     When tongs  34  are in the clamped position, clamping lever  35  assumes an end position in which handle  39  is snapped into locking groove  49  in the rear and/or lateral latching hook. By pressing latching hook  48  backward with the thumb and/or by pivoting handle  39  out of locking groove  49  against spring  50 , clamping lever  35  is released; it can pivot back into its open position with spring preload via spring  42 . Following said clamping lever, passive clamping jaw  38 —acted upon by a further compression spring  44 —moves into its own end position. Clamping lever  35 , under spring preload, continues to pivot past this point until its contact surface  51  bears against the top side  47  of passive clamping jaw  38 . In this stop position, tongs  34  are wide open, and the distance between active clamping jaw  36  and passive clamping jaw  38  is so great that sandpaper end  17 —indicated with the dashed line—can be inserted into tongs  34  quasi blindly.  
         [0047]     Compression spring  44 , which applies preload to passive clamping jaws  38 , determines and/or limits the clamping force between active clamping jaw  36  and passive clamping jaw  38 .  
         [0048]     If clamping lever  35  is released from its clamped position by releasing latching hook  48  and is pivoted around axis  40  in the clockwise direction to replace the abrasive sheet, the distance between the clamping points of sandpaper ends  17 ,  19  becomes shorter once more, thereby releasing tension from abrasive sheet  16 , allowing it to be easily removed.  
         [0049]      FIG. 2  shows a spacial depiction of a further exemplary embodiment of abrasive sheet carrier  114  and manual grinding tool  10  according to  FIG. 1  as a top view diagonally from the front. A clamping lever  200  is located on front side  121 , as viewed on the right, which said clamping lever essentially corresponds to that in  FIG. 1 , although it has a separate actuating button  2110  that is supported in an abutment  600  in a manner that allows it to pivot around an axis of rotation  610  and bears elastically against the housing (not shown) via a compression spring (not shown).  
         [0050]     When button  2110  is actuated in the direction of arrow  333 , the part of button  2110  located above axis  610  moves toward the housing. The part located below axis  610  pivots outwardly, whereby it bears against the top part of clamping lever  200 . When button  2110  is actuated, said clamping lever is pivoted outwardly in the clockwise direction, so that clamping jaw  220  lifts away from locking surface  230  and an abrasive sheet end clamped therebetween can be removed, because clamping force is no longer applied.  
         [0051]     To enhance understanding of  FIG. 2 , reference is made to the parts in  FIG. 1  having the same function and configuration. The first numeral in the reference numbers in  FIG. 1  is duplicated and placed in front of the reference numbers of the equally-acting parts in  FIG. 2  to distinguish them from yet match them to the reference numbers in  FIG. 1 .  
         [0052]     As viewed on the left, abrasive sheet carrier  114  has tongs  334  on its rear side  122 , which said tongs essentially correspond to the tongs  34  explained in reference to  FIG. 1 , but the details of which have a different configuration. A clamping lever  335  for pivoting tongs  334  is located on only one side of abrasive sheet carrier  114 , and it is supported on this side at a stop  445  in a springy, latching manner.  
         [0053]     Tongs  334  are shown in the clamped state, in which their clamping pont and/or an abrasive sheet end (not shown) has been pivoted to the greatest possible distance away from clamping lever  200  on the diametrically opposed side of abrasive sheet carrier  114 .  
         [0054]      FIG. 3  shows the details of abrasive sheet carrier  114  according to  FIG. 2  at an angle from the rear underside, whereby the configuration of active clamping jaw  336  in interaction with passive clamping jaw  338  is clearly shown. In the clamped position shown, they bear against each other and can retain an abrasive sheet end (not shown) clamped between them pivoted away from clamping lever  200 , so that an associated abrasive sheet is capable of being stretched tightly such that movement of the abrasive sheet relative to the working surface of abrasive sheet carrier  114  is minimized. The parts of clamping lever  200  explained hereinabove with regard for  FIGS. 1 and 2  are clearly visible and will not be explained again here.  
         [0055]     The procedure for installing an abrasive sheet  16  in manual grinding tool  10  according to  FIG. 1  will be explained hereinbelow: Manual grinding tool  10  with opened tongs  334  is held with one hand. Using the other hand, first abrasive sheet end  19  is inserted at clamping lever  20  on the front side of manual grinding tool  10  by pressing against outer contour  27  of clamping lever  22 . A gap opens between clamping jaw  22  and locking surface  23 , into which said gap abrasive sheet enters without clamping lever  20  having to be actuated separately. Even a small inserted section of the abrasive sheet end is “automatically” prevented, via strong force, from coming back out, i.e., it is clamped, and clamping lever  20  must be pivoted in the release direction to pull it back out.  
         [0056]     When abrasive sheet  16  is slid slightly forward, abrasive sheet end  19  is inserted between clamping jaw  22  and locking face  23  so far that it extends past it by approximately 5 mm. As a result, a relatively small amount of effort is required to clamp first abrasive sheet end  19  tightly and securely to its abrasive sheet carrier  14  on the front side of manual grinding tool  10 .  
         [0057]     Subsequently, second abrasive sheet end  17  is inserted and locked in opened tongs  34  located on the rear side of abrasive sheet carrier  14 . Abrasive sheet  16  is thereby stretched tightly. Since the clamping point of tongs  1334  moves along a circuit around swivel axis  410  away from the front side of manual grinding tool  10 , abrasive sheet  16  is held tightly against abrasive sheet carrier  140  and can therefore be used with high efficiency for sanding.  
         [0058]     To remove abrasive sheet  16  from manual grinding tool  10 , clamping lever  20  is moved by pressing button  211 —as horizontal extension of swing arm  21 —together with said button around swivel axis  24 . Clamping jaw  22 , with its outer contour  27 , lifts away from abrasive sheet  16  and locking face  23  in such a manner that abrasive sheet  16  can easily be pulled out of the widening gap.  
         [0059]      FIG. 4  shows a top view of abrasive sheet carrier  14  of a manual grinding tool  100  with a further embodiment of abrasive sheet-clamping device  340 ,  500  according to the invention.  
         [0060]     The front side of abrasive sheet carrier  14  is seen on the right, whereby a pivoting lever  500  is shown on its top side, which said pivoting lever, with its clamping jaw  510 , presses an abrasive sheet end  155  of an abrasive sheet  150  downward toward the top side of abrasive sheet carrier  14  and retains it there. Pivoting lever  500  is capable of being pivoted against the spring force of a leg spring (not shown) in the release direction, as indicated by directional arrow  560 ; when the end position is reached, abrasive strip end  155  can be pulled out under clamping jaw  510 . If pivoting lever  500  is pivoted via its handle  520 —as shown on the left—in the direction of arrow  550 , abrasive sheet end  155  is clamped tightly. Since pivoting lever  500  follows sandpaper end  155 , when said sandpaper is pulled outwardly, the abrasive sheet is clamped increasingly more tightly.  
         [0061]     Abrasive sheet end  155 —shown on the left—is clamped tightly at the rear side of manual grinding tool  1000  between a clamping jaw  340  that is composed of an active jaw  360  and a passive jaw  380 . Active clamping jaw  360  is formed by a wire bracket  370 . Said wire bracket  370  is bent nearly in the shape of a semicircle—starting at swivel axis  400  and extending toward the left, as seen in the drawing—whereby it forms the crossbar-shaped active clamping jaw  360  from a radially inwardly bent region, bent at a right angle outwardly and/or axially. Said active clamping jaw extends parallel to the rear transverse edge of abrasive sheet carrier  14  at a distance from it and transitions—on the other side, with mirror symmetry to the bent region of wire bracket  370 —into an identically semicircularly bent second region that bears with its rear region on the top side of abrasive sheet carrier  14 .  
         [0062]     Spring bracket  370  transitions from its region bent in the shape of a “c” at its two symmetrical contact surfaces on the top side of abrasive sheet carrier  14 , both of which said spring brackets are bent nearly perpendicularly outwardly parallel to the top surface of abrasive sheet carrier  14  into one axle stub  410  each, each axle stub forming—together with one groove  430  each between two projections  440  designed in the manner of abutments—a rocker pivot around swivel axis  400 .  
         [0063]     Adjacent to axle stub  410 , each wire bracket  370  transitions outwardly into a 900 bend. On the front side—as shown in the drawing—it extends parallel to longitudinal axis  370  of handheld oscillating sander  10  and forms a clamping lever  350  with a handle  390 . On the rear side—as shown in the figure—it forms a damping piece  355 . With clamping tongs  340  in the clamped position, said damping piece bears against the top side of abrasive sheet carrier  14  such that relative motion does not occur between wire bracket  370  and abrasive sheet carrier  14  when oscillating sander  10  is operated. As a result, vibrations and disturbing noises are prevented when oscillating sander  10  is operated.  
         [0064]     In the clamped position, clamping lever  350  is capable of being hung in latching hook  450  in an over-latching manner. The crossbar-shaped region of active clamping jaw  360  thereby bears against an elastic contact surface  420 —which has particularly good grip—of passive clamping jaw  380 , said contact surface being composed of plastic.  
         [0065]     Contact surface  420  of passive clamping jaw  380  is formed by a rubbery strip part that is secured on the outer end of passive clamping jaw  380  configured as surface spring. Passive clamping jaw  360  extends parallel to the surface of abrasive sheet carrier  14  and is fixed thereto by the fact that it is clamped tightly under the foot-like end of oscillation body  160 .  
         [0066]     Since passive clamping jaw  380  is configured as surface spring, it does not need any special means, e.g., a joint, to define swivel axis  400 .  
         [0067]     As shown on the right, i.e., on the front side, abrasive sheet carrier  14  carries an abrasive sheet clamping system that corresponds in principle to that according to  FIG. 1 . The only difference is that pivoting lever  500  is preloaded in its clamping position by a leg spring (not shown) instead of by a tension spring.  
         [0068]      FIG. 5  shows a schematic depiction of active clamping jaw  360  as an element bent out of a single wire part. It is easy to see how clamping lever  350 , after the first right-angled bend, transitions into first axle stub  410 , and, from there via the second right-angled bend, it transitions into first semicircular wire bracket  370 , from there, via the third right-angled bend, it transitions into the actual, crossbar-shaped active clamping jaw  360 , from there, via the fourth right-angled bend, it transitions into the second, semicircular wire bracket  370 , from there, via the fifth right-angled bend, it transitions into the second axle stub  410 , and from there, via the final right-angled bend, it transitions into extension  355  serving as oscillating damper, which clamps against top side  140  of abrasive sheet carrier  14  with preload.  
         [0069]      FIG. 6  shows a further variant for oscillation damping of second wire bracket  370  that is elastically clampable in the clamped position between two elastic damping jaws  655 , so that vibrations and noises are therefore suppressed. Damping jaws  650  are located on the top side of abrasive sheet carrier  14 .  
         [0070]      FIG. 7  shows a further variant for vibration damping of second wire bracket  370  via a leaf spring  660  which bears outwardly on its arched circumference. Via its preload, wire bracket  370  and/or axle stub  410  are held against abrasive sheet carrier  410  and vibrations are suppressed.  
         [0071]      FIG. 8  shows a fourth variant for oscillation damping of second wire bracket  370  using a damping rubber member  670  positioned around the outer axle stub  410 , against the diagonally positioned angular surface  671  of which wire bracket  370  bears in the clamped position, and the oscillations of which are suppressed.  
         [0072]      FIG. 9  shows a further exemplary embodiment of a passive clamping jaw  700  alone, which is not composed of a surface spring  380  as in  FIG. 4 , but rather of a U-shaped spring wire piece. Between its U-legs  710 , passive clamping jaw  700  has a connecting piece  720  on its curvature with a contact body  740  made of rubber or plastic that forms a contact surface  730  for abrasive sheet end to rest against and for active clamping jaw  360  to engage with ( FIG. 4 ). To dampen oscillations, passive clamping jaw  700  has a crossbar-shaped connecting body  750  composed of plastic or rubber, the connecting body being penetrated by U-legs  710 .  
         [0073]     Ends  760  of U-legs  710  bent inwardly in the shape of a circle form screw eyelets that are gripped over by screws or the foot-shaped lower parts of oscillation body  160  and are thereby securable to abrasive sheet carrier  14 .  
         [0074]      FIG. 11  is nearly identical to  FIG. 1  and shows a manual grinding tool  10  (oscillating sander) with a housing  12  that includes a handle on the outside and an electric motor on the inside (not shown). An abrasive sheet carrier  14  is located at the bottom of housing  12 , which, driven by a motor, is capable of being set into oscillating motion relative to housing  12  and, as a result, can remove material from a work piece (not shown) via sanding with an abrasive sheet  16  secured tightly underneath on its working surface  15 . The grinding dust that is created is capable of being blown out and/or suctioned up from the front side  121  toward the rear side  122  of manual grinding tool  10  via suction connecting piece  120 . Abrasive sheet  16  rests with its back side against the underside of abrasive sheet carrier  14 .  
         [0075]     A clamping means designed as a two-armed clamping lever  20  with a swivel axis  24  is positioned in the front on top side  13  of abrasive sheet carrier  14 .  
         [0076]     Reference is made to the description of  FIG. 1  regarding the remaining details of clamping lever  20 .  
         [0077]     As viewed on the right, a clamping-tensioning device configured as tongs  34  is located on the rear side  122  of abrasive sheet carrier  14 , the clamping-tensioning device deviating from that according to  FIG. 1  in that it is composed of parts of wire and/or spring steel sheet having intrinsic spring action. It is composed of a clamping lever  35  with active clamping jaw  36  having mutiple bends and/or curves, the active clamping jaw conforming in principle to that according to  FIG. 5 , but with a slightly altered contour of the curved region. It has a handle  39  which forms a two-armed lever which is pivotable around a swivel axis  40 —which is secured in simple fashion using a screw  510 —formed by a groove (not shown) on top side  13  of abrasive sheet carrier  14 . Active clamping jaw  36  is composed of bent spring steel wire. A clamping lever  370  made of corrugated spring sheet bearing against the inner contour of active clamping jaw  36  when abrasive sheet  16  is clamped is also pivotable around the geometric extension of pivot axis  40 , the clamping lever forming passive clamping jaw  38 . The other abrasive sheet end  17  that is diametrically opposed to first abrasive sheet end  19  is inserted and retained between passive clamping jaw  38  and active clamping jaw  36 .  
         [0078]     When tongs  34  with retained sandpaper end  17  are pivoted around swivel axis  40  in the counterclockwise direction, the distance between sandpaper ends  17 ,  19  relative to each other increases. As a result, abrasive sheet  16  is tightened and pulled tightly against the underside of abrasive sheet carrier  14 . The tightening of abrasive sheet  16  becomes noticeable via the rear lower edge  118  of cushion  18  that is pressed round in shape.  
         [0079]     When tongs  34  are in the clamped position, springy clamping lever  35  assumes an end position in which handle  39  is snapped into locking groove  49  of lateral latching hook  48 . By pressing clamping lever  35  toward housing  12 , said handle comes out of locking groove  49  and can thereby pivot freely back into its open position. Passive clamping jaw  38 , which springs back into its own position, thereby acts on said handle and carries it along into the “opened” position. Clamping lever  35  is capable of being pivoted further by hand to an end position forming a wide opening slit  500  ( FIG. 2 ) between active clamping jaw  36  and passive clamping jaw  38 . In this end position, tongs  34  are opened wide and the distance between active clamping jaw  36  and passive clamping jaw  38  is so great that sandpaper end  17 —indicated with the dashed line—can be inserted into tongs  34  quasi blindly and in a self-locating manner without it having to be bent further upward out of the plane of working surface  15 .  
         [0080]     The surface spring  370 , which self-tensions passive clamping jaw  38 , having the form of a one-and-a-half sine wave with a small amplitude region toward the clamping point determines and/or limits the clamping force between active clamping jaw  36  and passive clamping jaw  38  in the clamped state, whereby, when surface spring  270  is short in design, a very strong clamping force is achieved, accompanied by a good hinged joint function.  
         [0081]     If, to replace the abrasive sheet, clamping lever  35  is released from its clamped position by unlatching it from latching hook  48  and is pivoted around axis  40  in the clockwise direction, the distance between the clamping points of sandpaper ends  17 ,  19  becomes shorter once more, whereby abrasive sheet  16 , relieved of tension, is simultaneously capable of being easily removed from opening slit  500 .  
         [0082]      FIG. 12  shows the horizontally situated tongs  34  with manual grinding tool  10  according to  FIG. 11  opened with loosely inserted sandpaper end  17 . By pivoting clamping lever  35  in the counterclockwise direction, active clamping jaw  36  moves closer to passive clamping jaw  38  and thereby carries sandpaper end  17  along due to its high friction on the rubber lining—indicated by the bold line—in the direction toward passive clamping jaw  38  and clamps it tightly thereto. When active clamping jaw  36  is pivoted further, it carries passive clamping jaw with clamped sandpaper end  17  along on its pivot path, thereby tightening abrasive sheet  16  and holding it tightly in the tightened position as a result of clamping lever  35  which is latched in latching hook  48 . The desired clamped position of abrasive sheet  16  is therefore created.  
         [0083]     The means of attaining the object of the invention, according to the invention, are not limited to the arrangement of a self-clamping lever system on the side diametrically opposed to the tongs; instead, a conventional clamping lever system with spring preload can also be provided.