Clamp apparatus

A driving force transmission mechanism of a clamp apparatus includes first link arms, which are pivotally supported for rotation on ends of first and second piston rods, and second link arms, which connect other ends of the first link arms to respective ends on one end side of first and second clamp arms. Further, first rollers, which are provided on the one end of the first link arms, are guided in a horizontal direction along guide grooves of first guide members, and second rollers, which are provided on the other ends of the first link arms and the second link arms, are guided in a vertical direction along guide grooves of second guide members.

TECHNICAL FIELD

The present invention relates to a clamp apparatus for clamping a workpiece on an automated assembly line or the like.

BACKGROUND ART

Heretofore, for example, in an automated assembly line for automobiles, an assembly process has been carried out in which clamping is performed by a clamp apparatus under a condition in which pre-formed frames are positioned in an overlaid manner and the frames are welded together.

As one clamp apparatus of this type, for example, as disclosed in Japanese Patent No. 4950123, the clamp apparatus comprises a pair of clamp arms, the clamp arms being disposed on left and right sides and supported pivotally by pins, and an air cylinder that generates a driving force for rotating the clamp arms. By supplying a pressure fluid to the air cylinder, the driving force is transmitted to the clamp arms through a base connected to the end of a piston rod. By rotation of the clamp arms respectively through the pins, distal ends of the clamp arms are operated to open and close, to thereby grip a workpiece such as a frame or the like from left and right sides thereof.

SUMMARY OF INVENTION

However, with the aforementioned clamp apparatus, which is driven by an air cylinder as a drive unit thereof, in the event that a large clamping force is to be generated with respect to the workpiece, it is necessary for a large-scale air cylinder to be adopted, leading to an increase in the size of the apparatus. This also leads to an increase in the consumption amount of the pressure fluid needed to drive the air cylinder, accompanied by an increase in running costs for the clamp apparatus.

A general object of the present invention is to provide a clamp apparatus in which a desired clamping force can be obtained without increasing the size of the clamp apparatus, and which enables a reduction in running costs through achievement of energy savings.

The present invention is characterized by a clamp apparatus for rotating a pair of clamp arms and thereby clamping a workpiece between the clamp arms, comprising:

a body;

a drive unit disposed on the body and for displacing displaceable members along an axial direction under the supply of a pressure fluid;

the pair of clamp arms supported rotatably with respect to the body, the clamp arms being disposed in confronting relation to each other; and

a driving force transmission mechanism which connects ends of the displaceable members to ends of the clamp arms, and which transmits a driving force in the axial direction of the drive unit to the clamp arms for thereby rotating the clamp arms,

wherein the driving force transmission mechanism comprises a toggle link mechanism having first link arms supported rotatably on the displaceable members through first support members provided on ends of the first link arms, and second link arms, which connect second support members provided on other ends of the first link arms and ends of the clamp arms, and which are supported rotatably, respectively, with respect to the second support members and the ends of the clamp arms, and wherein the first support members are disposed for displacement in the axial direction, and the second support members are disposed for displacement in a perpendicular direction perpendicular to the direction of displacement of the first support members.

According to the present invention, the driving force transmission mechanism that makes up the clamp apparatus comprises a toggle link mechanism having the first link arms, which are supported rotatably on the displaceable members through first support members, and the second link arms, which interconnect second support members supported on other ends of the first link arms and ends of the clamp arms, and which are supported rotatably with respect to the second support members and the ends of the clamp arms. Further, the first support members are disposed for displacement in the axial direction together with the displaceable members, whereas the second support members are disposed for displacement in a direction perpendicular to the direction of displacement of the first support members.

In addition, by displacement of the displaceable members under a driving action of the drive unit, the driving force is transmitted to ends of the clamp arms through the first and second link arms, and when the workpiece is clamped upon rotation of the clamp arms, by operation of the first and second link arms that function as a toggle link mechanism, the driving force is boosted in power and then transmitted to the clamp arms.

Accordingly, even if the driving force output from the drive unit is small, by boosting and transmitting the driving force through operation of the driving force transmission mechanism that functions as a toggle link mechanism made up from the first and second link arms, a desired clamping force can be obtained without increasing the size and scale of the drive unit. In addition, since the amount of pressure fluid consumed in the drive unit can be suppressed, energy savings and a reduction in running costs can be realized.

DESCRIPTION OF EMBODIMENTS

As shown inFIGS. 1 through 5, a clamp apparatus10includes a body12, a pair of first and second clamp arms14,16, which are pivotally supported rotatably with respect to the body12, a drive unit18fixed to the body12, and a driving force transmission mechanism20that transmits a driving force of the drive unit18to the first and second clamp arms14,16.

The body12is constituted from a plate-shaped base22, which is arranged horizontally, and a pair of plate members24a,24b(seeFIG. 3), which are separated mutually by a predetermined distance, and are connected respectively to both opposite side surfaces of the base22. The plate members24a,24bare disposed perpendicularly with respect to the base22, and are formed with a predetermined height in an upward direction (the direction of the arrow A). Further, the base22is arranged, for example, on a floor surface or the like, and the clamp apparatus10is fixed in place by securing the base22using non-illustrated bolts or the like.

Further, on an upper part of the body12, a ceiling portion26is disposed, which is connected to ends of the pair of plate members24a,24b. The ceiling portion26is arranged perpendicularly with respect to the direction of extension (the direction of arrows A and B) of the plate members24a,24b, and is arranged substantially centrally in the widthwise direction (the direction of arrows C and D) in the body12. More specifically, the ceiling portion26is disposed substantially in parallel with the base22. On the ceiling portion26, receiving grooves28are formed respectively on side surfaces in confronting relation to the later-described first and second clamp arms14,16, and when a workpiece W is gripped by the clamp apparatus10, the workpiece W is arranged on the upper surface of the ceiling portion26.

The first and second clamp arms14,16are formed substantially in the same shape, and are arranged mutually and symmetrically about the drive unit18, and further are disposed between one of the plate members24aand the other of the plate members24b. Additionally, the first and second clamp arms14,16are supported rotatably on the body12through arm pins (support shafts)30, which are inserted through the first and second clamp arms14,16substantially centrally in the longitudinal direction thereof and which are supported by the pair of plate members24a,24b.

The first and second clamp arms14,16are L-shaped in cross-section, with bifurcated yoke portions32being formed on ends, i.e., one end side, thereof that are arranged on the side of the base22(in the direction of the arrow B), and gripping portions34for clamping the workpiece W being formed, respectively, on other ends, which are bent substantially perpendicularly with respect to the one end side.

Ends of later-described second link arms76a,76bare pivotally supported via link pins36on ends of the yoke portions32.

The gripping portions34are formed, for example, with substantially rectangular shapes in cross section, and mutually confronting gripping surfaces thereof are formed as vertical surfaces substantially parallel with the longitudinal direction of the first and second clamp arms14,16.

Further, the arm pins30are inserted in the first and second clamp arms14,16, respectively, through holes thereof at locations where the other end sides are bent with respect to the one end sides. Moreover, below the gripping portions34, positioning portions38are formed, respectively, which project with respect to the gripping surfaces of the gripping portions34. At a time of clamping when the first and second clamp arms14,16are made to approach each other and grip the workpiece W, the positioning portions38are brought into engagement, respectively, with the receiving grooves28of the ceiling portion26.

In the first and second clamp arms14,16, as shown inFIG. 1, a first distance L1 from the arm pin30to the center of the gripping region of the workpiece W on the gripping portion34, and a second distance L2 from the arm pin30to the link pin36are set such that the ratio between L1 and L2 is equal to a predetermined ratio (length ratio), and the second distance L2 is set to be greater than the first distance L1 (L1<L2).

The drive unit18is arranged between the pair of plate members24a,24b, and is disposed horizontally and separated a predetermined distance with respect to the base22. The drive unit18comprises a fluid pressure cylinder including a cylindrical cylinder tube (cylinder main body)40, a pair of first and second pistons (displaceable members)42,44disposed displaceably in the interior of the cylinder tube40, first and second piston rods (displaceable members)46,48, which are connected respectively to the first and second pistons42,44, and first and second rod covers50,52disposed on respective opposite ends of the cylinder tube40, and which displaceably support the first and second piston rods46,48, respectively.

Both end portions of the cylinder tube40are fixed to the plate member24bby fixing bolts56through attachment brackets54. In addition, first through third ports58,60,62, which penetrate in directions (the directions of arrows A and B) perpendicular to the axial direction of the cylinder tube40, are formed in a side surface of the cylinder tube40. Communication between the exterior and the interior of the cylinder tube40is enabled through the first through third ports58,60,62.

The first port (first port)58is disposed centrally in the axial direction (the direction of arrows C and D) of the cylinder tube40, the second port (second port)60is disposed in the vicinity of one end of the cylinder tube40on the side (in the direction of the arrow C) of the first clamp arm14, and the third port (second port)62is disposed in the vicinity of the other end of the cylinder tube40on the side (in the direction of the arrow D) of the second clamp arm16. More specifically, the first through third ports58,60,62are separated from each other mutually in the axial direction (the direction of arrows C and D) of the cylinder tube40.

In addition, tubes66, which are connected to a non-illustrated pressure fluid supply source, are connected to the first through third ports58,60,62through respective couplings64. Pressure fluid is supplied selectively either to the second and third ports60,62or to the first port58under a switching action of a non-illustrated switching device. The tubes66are connected to the second and third ports60,62so as to be capable of supplying pressure fluid simultaneously thereto.

The first and second pistons42,44are disk shaped, for example, with piston packings68being installed through annular grooves on the outer circumferential surfaces thereof. By sliding contact of the piston packings68with the inner wall surface of the cylinder tube40, leakage of pressure fluid between the cylinder tube40and the first and second pistons42,44is prevented.

Additionally, the first piston42is arranged on one end side (in the direction of the arrow C) from the center along the axial direction of the cylinder tube40, and the second piston44is arranged on the other end side (in the direction of the arrow D) from the center of the cylinder tube40. More specifically, the first piston42and the second piston44are disposed in parallel in the interior of the cylinder tube40, and are arranged at positions separated by the same distance respectively from the one end and the other end of the cylinder tube40.

Ends of the first and second piston rods46,48are inserted respectively through the centers of the first and second pistons42,44and are connected integrally to the first and second pistons42,44by crimping. Other ends of the first and second piston rods46,48are inserted through the first and second rod covers50,52and project respectively to the exterior from the one end and the other end of the cylinder tube40. Stated otherwise, the first piston rod46and the second piston rod48extend mutually in directions away from each other.

After insertion of the first and second rod covers50,52into the cylinder tube40, the first and second rod covers50,52are locked by locking rings70, which are placed in engagement with the inner circumferential surface of the cylinder tube40. By sliding contact of rod packings72, which are installed on inner circumferential surfaces of the first and second rod covers50,52, with outer circumferential surfaces of the first and second piston rods46,48, leakage of pressure fluid is prevented between the first and second piston rods46,48and the first and second rod covers50,52.

The driving force transmission mechanism20includes first link arms74a,74b, which are supported pivotally on other end portions of the first and second piston rods46,48, second link arms76a,76b, which connect the first link arms74a,74bto ends on one end side of the first and second clamp arms14,16, first rollers (rotating rollers)78that are supported pivotally on one end portions of the first link arms74a,74b, and second rollers (rotating rollers)80that are supported pivotally on other end portions of the first link arms74a,74band other end portions of the second link arms76a,76b.

The first link arms74a,74bare formed as plate-shaped members having a predetermined length in the longitudinal direction thereof. As shown inFIG. 3, one pair of the first link arms74aare provided on the first piston rod46side while one pair of the first link arms74bare provided on the second piston rod48side. The one end portions of the first link arms74a,74bare disposed in parallel, sandwiching the other end portions of the first and second piston rods46,48therebetween, and are supported rotatably through first roller pins (first support members)82.

Further, one pair of the first rollers78are disposed rotatably through the first roller pin82on outer sides of each pair of the first link arms74a,74b. The first rollers78are inserted in guide grooves (grooves)84aof a pair of first guide members (guide means)84, which are disposed respectively on inner wall surfaces of the pair of plate members24a,24b, and by movement of the first rollers78along the guide grooves84athat extend in parallel with the base22, the first rollers78are guided in substantially horizontal directions (the directions of arrows C and D). More specifically, the one end portions of the first link arms74a,74b, on which the first rollers78are pivotally supported, are displaced only in substantially horizontal directions under a guiding action of the first guide members84.

On the other hand, a second roller pin (second support member)86is disposed on the other end portions of each pair of the first link arms74a,74b, and one pair of the second rollers80are provided on outer sides of the other end portions of each pair of the first link arms74a,74b. Each pair of the second rollers80are supported rotatably by the second roller pin86, and the other end portion of each of the second link arms76a,76bis pivotally supported by the second roller pin86between the pair of the first link arms74a,74b.

The second rollers80are inserted in guide grooves (grooves)88aof a pair of second guide members (guide means)88, which are disposed respectively on inner wall surfaces of the pair of plate members24a,24b, and by movement of the second rollers80along the guide grooves88athat extend in vertical directions perpendicular to the base22, the second rollers80are guided in substantially vertical directions. More specifically, the other end portions of the first link arms74a,74b, and the second link arms76a,76b, on which the second rollers80are pivotally supported, are displaced only in substantially vertical directions (the directions of arrows A and B) under a guiding action of the second guide members88.

In this manner, the first link arms74a,74bconnect the other ends of the first and second piston rods46,48that constitute the drive unit18, to the other ends of the second link arms76a,76b. The first link arms74a,74bare supported rotatably with respect to the first and second piston rods46,48and the second link arms76a,76b, and transmit the driving force of the drive unit18to the second link arms76a,76b.

The second link arms76a,76b, in the same manner as the first link arms74a,74b, are formed as plate-shaped members having a predetermined length in the longitudinal direction thereof. The second link arms76a,76bare disposed rotatably in a state of being connected respectively to the first link arms74a,74bthrough the second roller pins86, which are pivotally supported on the other end portions thereof, and being connected respectively to the first and second clamp arms14,16through the link pins36, which are pivotally supported on the one end portions. In addition, the second link arms76a,76btransmit the driving force that was transmitted to the first link arms74a,74bonto the first and second clamp arms14,16to thereby rotate the first and second clamp arms14,16.

The clamp apparatus10according to the embodiment of the present invention is basically constructed as described above. Next, operations and advantages of the clamp apparatus10will be described. In the following description, the unclamped condition shown inFIG. 4, in which the gripping portions34of the first and second clamp arms14,16are separated mutually, will be referred to as an initial position.

In the initial position, pressure fluid is supplied to the interior of the cylinder tube40through the second and third ports60,62, whereby the first piston42and the second piston44are displaced by the pressure fluid in directions to mutually approach each other toward a center region of the cylinder-tube40.

A brief description will now be given concerning the workpiece W, which is gripped by the above-described clamp apparatus10.

For example, as shown inFIGS. 1 and 4, the workpiece W is made up from a first frame W1, which is U-shaped in cross section, and a second frame W2, which is U-shaped in cross section and is assembled together with the first frame W1to thereby constitute a vehicle frame.

The first frame W1is placed between the gripping portions34of the first and second clamp arms14,16with the opening thereof oriented downward (in the direction of the arrow B), whereas the second frame W2is mounted on the ceiling portion26with the opening thereof oriented upward (in the direction of the arrow A), and with the side walls thereof inclined such that the distance between the side walls gradually widens toward the side of the opening, and with the first frame W1being inserted in the interior of the second frame W2.

Stated otherwise, the second frame W2is arranged on an outer side with respect to the first frame W1, and the side walls of the second frame W2are inclined so as to widen toward the first and second clamp arms14,16.

In this state where the workpiece W is set in a predetermined position on the clamp apparatus10, first, under switching operation of the non-illustrated switching device, the pressure fluid that was supplied to the second and third ports60,62instead is supplied to the first port58. In this case, the second and third ports60,62are placed in a state of being open to atmosphere.

Accordingly, as shown inFIG. 1, by the pressure fluid that is introduced into the cylinder tube40, the first and second pistons42,44are pressed in directions to separate away from one another mutually, whereby the first and second piston rods46,48and the first rollers78are displaced respectively together with the first and second pistons42,44toward the first and second clamp arms14,16.

Along therewith, the one end portions of the first link arms74a,74bare pressed in directions to separate away from the drive unit18under a guiding action of the first rollers78, which are guided along the guide grooves84aof the first guide members84. The first link arms74a,74brotate about the first roller pins82, whereby the second rollers80, which are supported pivotally on other end sides thereof, move downward (in the direction of the arrow B) along the guide grooves88aof the second guide member88.

In addition, accompanying the downward movement of the second rollers80, the other end portions of the second link arms76a,76balso move downward (in the direction of the arrow B), whereby the second link arms76a,76b, via the link pins36, press the one end portions of the first and second clamp arms14,16in directions to separate mutually away from each other.

Consequently, the first and second clamp arms14,16are rotated mutually about the arm pins30in directions in which the gripping portions34approach one another, and the side walls of the second frame W2are pressed and deformed by the gripping portions34so as to approach each other mutually, whereby the side walls of the second frame W2abut against the side walls of the first frame W1, and the side walls of the first and second frames W1, W2become substantially parallel to each other. Thus, a clamped state in which clamping is completed is brought about (seeFIG. 1).

At this time, the positioning portions38are engaged respectively with the receiving grooves28of the body12, so that during clamping, the first and second clamp arms14,16are positioned at predetermined stop positions, and further rotation of the first and second clamp arms14,16is prohibited.

Further, at this time, as shown inFIG. 2, the first link arm74a(74b) is inclined at a first toggle angle θ1 toward the first clamp arm14(second clamp arm16) with respect to a vertical line S1passing through the center of the first roller pin82.

Owing thereto, the driving force output from the drive unit18is boosted in power and is transmitted to the second link arm76a(76b) as a thrust force T1, and since the second link arm76a(76b) is inclined at a second toggle angle θ2 toward the base22(in the direction of the arrow B) with respect to a horizontal line S2passing through the center of the second roller pin86, the thrust force T1is further boosted in power and is transmitted to the one end of the first clamp arm14(second clamp arm16) as a thrust force T2.

More specifically, the first link arms74a,74band the second link arms76a,76bfunction as a toggle link mechanism, which is capable of boosting the driving force from the drive unit18and transmitting the power-boosted driving force to the first and second clamp arms14,16. In addition, the driving force output from the drive unit18can be boosted in power by the first link arms74a,74band the second link arms76a,76bthat make up the driving force transmission mechanism20.

Further, as shown inFIG. 1, each of the first and second clamp arms14,16is formed such that the length (second distance L2) from the arm pin30toward the one end side thereof is longer than the length (first distance L1) from the arm pin30toward the other end side thereof. Therefore, when the workpiece W is clamped by the first and second clamp arms14,16, the driving force transmitted from the driving force transmission mechanism20is boosted in power by the length ratio (L2/L1) between the first distance L1 and the second distance L2, whereby the workpiece W can be gripped with the thus-increased clamping force.

More specifically, since the driving force output from the drive unit18is boosted by the first link arms74a,74band the second link arms76a,76bof the driving force transmission mechanism20, together with enabling the workpiece W to be clamped by further boosting the power and through rotation of the first and second clamp arms14,16, it is unnecessary for a large scale drive unit18to be provided in order to obtain a predetermined clamping force, and substantially the same clamping force can be obtained by a small scale drive unit18.

In addition, in a condition in which the first and second frames W1, W2are clamped by the first and second clamp arms14,16, the side walls of the first and second frames W1, W2are welded to each other by a non-illustrating welding apparatus, for example.

On the other hand, in the event that the clamped state shown inFIG. 1of the workpiece W by the first and second clamp arms14,16is to be released, under switching operation of the non-illustrated switching device, the pressure fluid that was supplied to the first port58of the drive unit18is once again supplied to the second and third ports60,62. Moreover, in this case, the pressure fluid is supplied such that the amount of pressure fluid supplied with respect to the second and third ports60,62is the same, and the first port58is placed in a state of being open to atmosphere.

Consequently, under a pressing action of the pressure fluid, the first and second pistons42,44are displaced in directions to approach each other, whereupon the first and second piston rods46,48and the first rollers78are displaced integrally therewith. In addition, accompanying displacement of the first rollers78, the one end portions of the first link arms74a,74bare displaced toward the drive unit18, whereas the second rollers80disposed on the other end portions thereof are moved upwardly under a guiding action of the second guide members88. Along therewith, the second link arms76a,76bare rotated, and then the one end portions of the first and second clamp arms14,16are pulled so as to approach one another mutually, whereby the first and second clamp arms14,16are rotated about the arm pins30in directions to cause the gripping portions34to separate away from each other. Thus, as shown inFIG. 4, an unclamped state is brought about in which clamping of the workpiece W is released.

In the foregoing manner, according to the present embodiment, in the clamp apparatus10equipped with the drive unit18having the pair of first and second pistons42,44, the driving force, which is output upon displacement of the first and second pistons42,44, is transmitted to the first and second clamp arms14,16, respectively, through the driving force transmission mechanism20. Thus, when the workpiece W is clamped, owing to the fact that the first link arms74a,74bare inclined at the first toggle angle θ1 toward the first and second clamp arms14,16with respect to vertical lines S1passing through the center of the first roller pins82, and the fact that the second link arms76a,76bare inclined at the second toggle angle θ2 toward the base22with respect to horizontal lines S2passing through the center of the second roller pins86, the driving force is boosted in power respectively by the first link arms74a,74band the second link arms76a,76b, whereby the thus-increased driving force can be transmitted to the one end portions of the first and second clamp arms14,16.

As a result, even though the driving force output by the drive unit18may be small, the driving force can be boosted in power by using the two toggle link mechanisms constituted from the first link arms74a,74band the second link arms76a,76b. Owing thereto, the workpiece W can be clamped at a desired clamping force by the first and second clamp arms14,16and, for example, even in the case that a large clamping force is required, such a large clamping force can be provided by a drive unit18(fluid pressure cylinder) that produces a small output. Thus, it is unnecessary for the clamp apparatus to be increased in scale, and since the amount of pressure fluid consumed in the drive unit18can be suppressed, energy savings and a reduction in running costs can be realized.

Further, concerning the first and second clamp arms14,16, the length (second distance L2) from the arm pin30to the one end side thereof connected to the link pin36is set to be longer than the length (first distance L1) from the arm pin30to the gripping portion34on the other end side thereof. Therefore, the driving force is further boosted in power by the length ratio (L2/L1), and the workpiece W can be clamped with the thus-increased clamping force upon rotation of the first and second clamp arms14,16. As a result, compared to a case of boosting power only with the driving force transmission mechanism20(toggle link mechanism) made up from the aforementioned first link arms74a,74band the second link arms76a,76b, a desired clamping force can be obtained using an even smaller drive unit18, and together therewith, the clamp apparatus10can be made even smaller in scale, with even greater energy savings, and a further reduction in running costs can be realized.

Furthermore, for example, by connecting respective speed control valves to the tubes66, which are connected with respect to the second and third ports60,62of the cylinder tube40that constitutes the drive unit18, when the workpiece W is clamped by supplying pressure fluid to the first port58, the discharge amount of the pressure fluid discharged from the second port60can be made different from the discharge amount of the pressure fluid discharged from the third port62, and thus, the rotational speed of the first clamp arm14and the rotational speed of the second clamp arm16can be changed.

For example, if the amount of pressure fluid discharged from the second port60is large, whereas the amount of pressure fluid discharged from the third port62is small, then the rotational speed of the first clamp arm14can be made faster, and the rotational speed of the second clamp arm16can be delayed or made slower with respect to the rotational speed of the first clamp arm14. Owing thereto, the gripping portion34of only the first clamp arm14is brought into abutment first against the workpiece W in order to position the workpiece W, and thereafter, the gripping portion34of the second clamp arm16is later brought into abutment against the workpiece W to clamp the workpiece W between the first and second clamp arms14,16. Consequently, in the clamp apparatus10, the workpiece W can be clamped reliably at a predetermined position without the need of performing a positioning operation of the workpiece W separately, and therefore, efficiency of clamping operation can be improved.

The clamp apparatus according to the present invention is not limited to the above embodiment. Various changes and modifications may be made to the embodiment without departing from the scope of the invention as set forth in the appended claims.