Manual sanding machine tool

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.

BACKGROUND OF THE INVENTION

The present invention concerns a manual grinding tool.

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.

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.

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.

The same disadvantages also apply for the abrasive sheet clamping system according to U.S. Pat. No. 3,540,161.

SUMMARY OF THE INVENTION

The manual grinding tool according to the present invention 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Due to the fact that the clamping lever is approximately 60 mm long and the active jaw has a lever length of approximately 20 mm, a convenient, secure clamping of the abrasive sheet is possible.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a manual grinding tool10(orbital sander) with a housing12that has a handle on the outside and an electric motor on the inside (not shown). An abrasive sheet carrier14is located at the bottom of housing12, which said abrasive sheet carrier, driven by a motor, is capable of being set into oscillating motion relative to housing12and, as a result, can remove material from a work piece (not shown) via sanding with an abrasive sheet16secured tightly below on its working surface15. The grinding dust that is created is capable of being blown out and/or suctioned up from the front side121toward the rear side122of manual grinding tool10via suction connecting piece120. Abrasive sheet16rests with its back side against the underside of abrasive sheet carrier14.

A clamping means designed as a two-armed clamping lever20with a swivel axis24is positioned in the front on the top side13of abrasive sheet carrier14. Above swivel axis24, clamping lever20is a swing arm and, below said swivel axis, it is a clamping jaw22. It rests with its outer contour27bent in the shape of a saber against locking face23of top side13of abrasive sheet carrier14. Swivel axis24of clamping lever20is located on a bracket28on the top side of abrasive sheet carrier14.

A tension spring26bears between the top side of swing arm21and an abutment (not shown) in housing12, which said tension spring can also be configured as a leg spring; it tries to pivot clamping lever20in the clockwise direction, whereby it presses clamping jaw22against locking face23and thereby clamps abrasive sheet end19in place.

In the upper region, swing arm21has a single, projecting knee serving as push button211. By means of this, swing arm21is capable of being moved downward using a finger, whereby tension spring26is loaded. Clamping jaw22then lifts away from locking face23, and the gap between outer contour27and locking face23opens so wide that abrasive sheet end19is released and can be removed.

The distance between swivel axis24of clamping lever20and locking face23is smaller than the distance between swivel axis24and the radially outermost point of outer contour27, so that, in the position with spring preload via spring26, clamping jaw22bears against locking face23on the top side13of abrasive sheet carrier14. As a result, the clamping force on abrasive sheet16increases in proportion to the forces that try to release abrasive sheet16against the direction of insertion.

Tension spring26is preloaded to such a low extent that, when outer contour27of clamping jaw22is tapped even slightly, abrasive sheet16displaces 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.

Clamping jaw22is composed at least partially of elastic, rubber-like material with a high coefficient of friction that limits relative motion between abrasive sheet16and clamping jaw22.

As viewed on the right, a clamping-tightening device configured as tongs34is located on the rear side122of abrasive sheet carrier14. It is composed of a clamping lever35with curved active clamping jaw36and a handle39that is a two-armed lever which is pivotable around a swivel axis40. Active clamping jaw36is composed of elastic material, e.g., spring steel. Also capable of being pivoted around swivel axis40is a clamping lever37that forms passive clamping jaw38and bears against the inner contour of active clamping jaw36when abrasive sheet16is tightened. The other abrasive sheet end17, which is diametrically opposed to abrasive sheet end19, is inserted and retained between passive clamping jaw38and active clamping jaw36.

When tongs34with retained sandpaper end17are pivoted around swivel axis40in the counterclockwise direction, its distance from the other sandpaper end19increases. As a result, abrasive sheet16is tightened and pulled taut against the underside of abrasive sheet carrier14. The tightening of abrasive sheet16is apparent in rear lower edge118of cushion that is pressed round in shape.

When tongs34are in the clamped position, clamping lever35assumes an end position in which handle39is snapped into locking groove49in the rear and/or lateral latching hook. By pressing latching hook48backward with the thumb and/or by pivoting handle39out of locking groove49against spring50, clamping lever35is released; it can pivot back into its open position with spring preload via spring42. Following said clamping lever, passive clamping jaw38—acted upon by a further compression spring44—moves into its own end position. Clamping lever35, under spring preload, continues to pivot past this point until its contact surface51bears against the top side47of passive clamping jaw38. In this stop position, tongs34are wide open, and the distance between active clamping jaw36and passive clamping jaw38is so great that sandpaper end17—indicated with the dashed line—can be inserted into tongs34quasi blindly.

Compression spring44, which applies preload to passive clamping jaws38, determines and/or limits the clamping force between active clamping jaw36and passive clamping jaw38.

If clamping lever35is released from its clamped position by releasing latching hook48and is pivoted around axis40in the clockwise direction to replace the abrasive sheet, the distance between the clamping points of sandpaper ends17,19becomes shorter once more, thereby releasing tension from abrasive sheet16, allowing it to be easily removed.

FIG. 2shows a spacial depiction of a further exemplary embodiment of abrasive sheet carrier114and manual grinding tool10according toFIG. 1as a top view diagonally from the front. A clamping lever200is located on front side121, as viewed on the right, which said clamping lever essentially corresponds to that inFIG. 1, although it has a separate actuating button2110that is supported in an abutment600in a manner that allows it to pivot around an axis of rotation610and bears elastically against the housing (not shown) via a compression spring (not shown).

When button2110is actuated in the direction of arrow333, the part of button2110located above axis610moves toward the housing. The part located below axis610pivots outwardly, whereby it bears against the top part of clamping lever200. When button2110is actuated, said clamping lever is pivoted outwardly in the clockwise direction, so that clamping jaw220lifts away from locking surface230and an abrasive sheet end clamped therebetween can be removed, because clamping force is no longer applied.

To enhance understanding ofFIG. 2, reference is made to the parts inFIG. 1having the same function and configuration. The first numeral in the reference numbers inFIG. 1is duplicated and placed in front of the reference numbers of the equally-acting parts inFIG. 2to distinguish them from yet match them to the reference numbers inFIG. 1.

As viewed on the left, abrasive sheet carrier114has tongs334on its rear side122, which said tongs essentially correspond to the tongs34explained in reference toFIG. 1, but the details of which have a different configuration. A clamping lever335for pivoting tongs334is located on only one side of abrasive sheet carrier114, and it is supported on this side at a stop445in a springy, latching manner.

Tongs334are 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 lever200on the diametrically opposed side of abrasive sheet carrier114.

FIG. 3shows the details of abrasive sheet carrier114according toFIG. 2at an angle from the rear underside, whereby the configuration of active clamping jaw336in interaction with passive clamping jaw338is 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 lever200, 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 carrier114is minimized. The parts of clamping lever200explained hereinabove with regard forFIGS. 1 and 2are clearly visible and will not be explained again here.

The procedure for installing an abrasive sheet16in manual grinding tool10according toFIG. 1will be explained hereinbelow: Manual grinding tool10with opened tongs334is held with one hand. Using the other hand, first abrasive sheet end19is inserted at clamping lever20on the front side of manual grinding tool10by pressing against outer contour27of clamping lever22. A gap opens between clamping jaw22and locking surface23, into which said gap abrasive sheet enters without clamping lever20having 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 lever20must be pivoted in the release direction to pull it back out.

When abrasive sheet16is slid slightly forward, abrasive sheet end19is inserted between clamping jaw22and locking face23so 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 end19tightly and securely to its abrasive sheet carrier14on the front side of manual grinding tool10.

Subsequently, second abrasive sheet end17is inserted and locked in opened tongs34located on the rear side of abrasive sheet carrier14. Abrasive sheet16is thereby stretched tightly. Since the clamping point of tongs1334moves along a circuit around swivel axis410away from the front side of manual grinding tool10, abrasive sheet16is held tightly against abrasive sheet carrier140and can therefore be used with high efficiency for sanding.

To remove abrasive sheet16from manual grinding tool10, clamping lever20is moved by pressing button211—as horizontal extension of swing arm21—together with said button around swivel axis24. Clamping jaw22, with its outer contour27, lifts away from abrasive sheet16and locking face23in such a manner that abrasive sheet16can easily be pulled out of the widening gap.

FIG. 4shows a top view of abrasive sheet carrier14of a manual grinding tool100with a further embodiment of abrasive sheet-clamping device340,500according to the invention.

The front side of abrasive sheet carrier14is seen on the right, whereby a pivoting lever500is shown on its top side, which said pivoting lever, with its clamping jaw510, presses an abrasive sheet end155of an abrasive sheet150downward toward the top side of abrasive sheet carrier14and retains it there. Pivoting lever500is capable of being pivoted against the spring force of a leg spring (not shown) in the release direction, as indicated by directional arrow560; when the end position is reached, abrasive strip end155can be pulled out under clamping jaw510. If pivoting lever500is pivoted via its handle520—as shown on the left—in the direction of arrow550, abrasive sheet end155is clamped tightly. Since pivoting lever500follows sandpaper end155, when said sandpaper is pulled outwardly, the abrasive sheet is clamped increasingly more tightly.

Abrasive sheet end155—shown on the left—is clamped tightly at the rear side of manual grinding tool1000between a clamping jaw340that is composed of an active jaw360and a passive jaw380. Active clamping jaw360is formed by a wire bracket370. Said wire bracket370is bent nearly in the shape of a semicircle—starting at swivel axis400and extending toward the left, as seen in the drawing—whereby it forms the crossbar-shaped active clamping jaw360from 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 carrier14at a distance from it and transitions—on the other side, with mirror symmetry to the bent region of wire bracket370—into an identically semicircularly bent second region that bears with its rear region on the top side of abrasive sheet carrier14.

Spring bracket370transitions from its region bent in the shape of a “c” at its two symmetrical contact surfaces on the top side of abrasive sheet carrier14, both of which said spring brackets are bent nearly perpendicularly outwardly parallel to the top surface of abrasive sheet carrier14into one axle stub410each, each axle stub forming—together with one groove430each between two projections440designed in the manner of abutments—a rocker pivot around swivel axis400.

Adjacent to axle stub410, each wire bracket370transitions outwardly into a 90° bend. On the front side—as shown in the drawing—it extends parallel to longitudinal axis370of handheld oscillating sander10and forms a clamping lever350with a handle390. On the rear side—as shown in the figure—it forms a damping piece355. With clamping tongs340in the clamped position, said damping piece bears against the top side of abrasive sheet carrier14such that relative motion does not occur between wire bracket370and abrasive sheet carrier14when oscillating sander10is operated. As a result, vibrations and disturbing noises are prevented when oscillating sander10is operated.

In the clamped position, clamping lever350is capable of being hung in latching hook450in an over-latching manner. The crossbar-shaped region of active clamping jaw360thereby bears against an elastic contact surface420—which has particularly good grip—of passive clamping jaw380, said contact surface being composed of plastic.

Contact surface420of passive clamping jaw380is formed by a rubbery strip part that is secured on the outer end of passive clamping jaw380configured as surface spring. Passive clamping jaw360extends parallel to the surface of abrasive sheet carrier14and is fixed thereto by the fact that it is clamped tightly under the foot-like end of oscillation body160.

Since passive clamping jaw380is configured as surface spring, it does not need any special means, e.g., a joint, to define swivel axis400.

As shown on the right, i.e., on the front side, abrasive sheet carrier14carries an abrasive sheet clamping system that corresponds in principle to that according toFIG. 1. The only difference is that pivoting lever500is preloaded in its clamping position by a leg spring (not shown) instead of by a tension spring.

FIG. 5shows a schematic depiction of active clamping jaw360as an element bent out of a single wire part. It is easy to see how clamping lever350, after the first right-angled bend, transitions into first axle stub410, and, from there via the second right-angled bend, it transitions into first semicircular wire bracket370, from there, via the third right-angled bend, it transitions into the actual, crossbar-shaped active clamping jaw360, from there, via the fourth right-angled bend, it transitions into the second, semicircular wire bracket370, from there, via the fifth right-angled bend, it transitions into the second axle stub410, and from there, via the final right-angled bend, it transitions into extension355serving as oscillating damper, which clamps against top side140of abrasive sheet carrier14with preload.

FIG. 6shows a further variant for oscillation damping of second wire bracket370that is elastically clampable in the clamped position between two elastic damping jaws655, so that vibrations and noises are therefore suppressed. Damping jaws650are located on the top side of abrasive sheet carrier14.

FIG. 7shows a further variant for vibration damping of second wire bracket370via a leaf spring660which bears outwardly on its arched circumference. Via its preload, wire bracket370and/or axle stub410are held against abrasive sheet carrier410and vibrations are suppressed.

FIG. 8shows a fourth variant for oscillation damping of second wire bracket370using a damping rubber member670positioned around the outer axle stub410, against the diagonally positioned angular surface671of which wire bracket370bears in the clamped position, and the oscillations of which are suppressed.

FIG. 9shows a further exemplary embodiment of a passive clamping jaw700alone, which is not composed of a surface spring380as inFIG. 4, but rather of a U-shaped spring wire piece. Between its U-legs710, passive clamping jaw700has a connecting piece720on its curvature with a contact body740made of rubber or plastic that forms a contact surface730for abrasive sheet end to rest against and for active clamping jaw360to engage with (FIG. 4). To dampen oscillations, passive clamping jaw700has a crossbar-shaped connecting body750composed of plastic or rubber, the connecting body being penetrated by U-legs710.

Ends760of U-legs710bent inwardly in the shape of a circle form screw eyelets that are gripped over by screws or the foot-shaped lower parts of oscillation body160and are thereby securable to abrasive sheet carrier14.

FIG. 11is nearly identical toFIG. 1and shows a manual grinding tool10(oscillating sander) with a housing12that includes a handle on the outside and an electric motor on the inside (not shown). An abrasive sheet carrier14is located at the bottom of housing12, which, driven by a motor, is capable of being set into oscillating motion relative to housing12and, as a result, can remove material from a work piece (not shown) via sanding with an abrasive sheet16secured tightly underneath on its working surface15. The grinding dust that is created is capable of being blown out and/or suctioned up from the front side121toward the rear side122of manual grinding tool10via suction connecting piece120. Abrasive sheet16rests with its back side against the underside of abrasive sheet carrier14.

A clamping means designed as a two-armed clamping lever20with a swivel axis24is positioned in the front on top side13of abrasive sheet carrier14.

Reference is made to the description ofFIG. 1regarding the remaining details of clamping lever20.

As viewed on the right, a clamping-tensioning device configured as tongs34is located on the rear side122of abrasive sheet carrier14, the clamping-tensioning device deviating from that according toFIG. 1in that it is composed of parts of wire and/or spring steel sheet having intrinsic spring action. It is composed of a clamping lever35with active clamping jaw36having mutiple bends and/or curves, the active clamping jaw conforming in principle to that according toFIG. 5, but with a slightly altered contour of the curved region. It has a handle39which forms a two-armed lever which is pivotable around a swivel axis40—which is secured in simple fashion using a screw510—formed by a groove (not shown) on top side13of abrasive sheet carrier14. Active clamping jaw36is composed of bent spring steel wire. A clamping lever370made of corrugated spring sheet bearing against the inner contour of active clamping jaw36when abrasive sheet16is clamped is also pivotable around the geometric extension of pivot axis40, the clamping lever forming passive clamping jaw38. The other abrasive sheet end17that is diametrically opposed to first abrasive sheet end19is inserted and retained between passive clamping jaw38and active clamping jaw36.

When tongs34with retained sandpaper end17are pivoted around swivel axis40in the counterclockwise direction, the distance between sandpaper ends17,19relative to each other increases. As a result, abrasive sheet16is tightened and pulled tightly against the underside of abrasive sheet carrier14. The tightening of abrasive sheet16becomes noticeable via the rear lower edge118of cushion18that is pressed round in shape.

When tongs34are in the clamped position, springy clamping lever35assumes an end position in which handle39is snapped into locking groove49of lateral latching hook48. By pressing clamping lever35toward housing12, said handle comes out of locking groove49and can thereby pivot freely back into its open position. Passive clamping jaw38, which springs back into its own position, thereby acts on said handle and carries it along into the “opened” position. Clamping lever35is capable of being pivoted further by hand to an end position forming a wide opening slit500(FIG. 2) between active clamping jaw36and passive clamping jaw38. In this end position, tongs34are opened wide and the distance between active clamping jaw36and passive clamping jaw38is so great that sandpaper end17—indicated with the dashed line—can be inserted into tongs34quasi blindly and in a self-locating manner without it having to be bent further upward out of the plane of working surface15.

The surface spring370, which self-tensions passive clamping jaw38, 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 jaw36and passive clamping jaw38in the clamped state, whereby, when surface spring270is short in design, a very strong clamping force is achieved, accompanied by a good hinged joint function.

If, to replace the abrasive sheet, clamping lever35is released from its clamped position by unlatching it from latching hook48and is pivoted around axis40in the clockwise direction, the distance between the clamping points of sandpaper ends17,19becomes shorter once more, whereby abrasive sheet16, relieved of tension, is simultaneously capable of being easily removed from opening slit500.

FIG. 12shows the horizontally situated tongs34with manual grinding tool10according toFIG. 11opened with loosely inserted sandpaper end17. By pivoting clamping lever35in the counterclockwise direction, active clamping jaw36moves closer to passive clamping jaw38and thereby carries sandpaper end17along due to its high friction on the rubber lining—indicated by the bold line—in the direction toward passive clamping jaw38and clamps it tightly thereto. When active clamping jaw36is pivoted further, it carries passive clamping jaw with clamped sandpaper end17along on its pivot path, thereby tightening abrasive sheet16and holding it tightly in the tightened position as a result of clamping lever35which is latched in latching hook48. The desired clamped position of abrasive sheet16is therefore created.

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.