FR2550115A1 - Clamping device - Google Patents

Abstract

The present invention relates to a device for clamping a thin part to a support in a definitive manner. The device comprises a casing 1 to be fixed to a support 3, a clamping part 5 pivoting on a shaft 7 integral with the support and driven by a driving means such as a jack 16 by the intermediary of a rod 9 and a moving device 12 which slides on a bearing surface 13 of the casing. This moving device is connected to the driving means by a link 14, 19 which allows a certain play and transmits only compression or tensile forces coming from the driving means. Application to mechanical construction workshops, particularly in the automobile industry.

Description

 The present invention relates to a device for clamping, in a non-definitive manner, a thin piece on a support.

 More particularly, the invention is applicable to the clamping of a sheet on a forming support, in order to give this sheet a desired shape or position, for example that of an automobile body part obtained by a technique used in sheet metal work , such as cold forming, welding, drilling, etc ......

 Such a device must allow clamping with sufficient force to prevent any subsequent displacement of the part relative to its support, it must however allow rapid clamping and loosening. It must also be of low weight so that it can be easily moved at the end of a series of similar operations. It must also have a tightening stroke defined by precise limits, with a large force in the vicinity.

 On the other hand, it must have a high resistance to wear in the abrasive atmosphere of a workshop.

 The most common current devices include a housing that is fixed to the support using screws, a clamping piece movable by pivoting about a first axis fixed relative to the housing, this piece being in two parts, namely: part forming a connecting rod, mounted on the axis, and a part forming a clamping arm, which is fixed to the first by screwing or otherwise.

 The clamping piece is connected to the rod of a jack which is integral with the housing by a link which is articulated on the one hand on the clamping piece and, on the other hand, on the rod of the jack by parallel axes. to that of the clamping piece. The rectilinear movement of the cylinder rod is thus transformed into a circular arc movement of the end of the clamping arm and the force exerted on it depends on the relative position of the various axes of articulation, it is particularly high if the line joining the axes of the rod is close to a perpendicular to the rod of the jack, and if the line joining the articulation axis of the rod to the rod, to the axis of rotation of the rod; is roughly parallel to the cylinder rod. If this configuration is reached when the cylinder piston reaches the end of its stroke, the force exerted by the clamping arm is maximum near the end of its stroke. ci, which ensures effective clamping for sheets of a determined thickness while providing security in the event that a part of too small thickness is engaged, because it will not be clamped.

 On the contrary, if an abnormally strong piece of thickness is engaged, an alarm can be provided which warns the jack cylinder cannot go to the end of its travel.

 These commercial devices, however, have the disadvantage of a fairly long and difficult adjustment when changing the thickness of the parts to be treated, on the other hand they are of limited duration due to the appearance of games, in particular at the level of the cylinder.

 The object of the present invention is to provide a device whose settings can be changed more quickly when moving from one series of parts to another, while having an increased longevity.

The present invention therefore provides a device for exerting a workpiece clamping force on a support comprising
- a case that can be fixed on the support,
- a clamping piece movable by pivoting around a first axis fixed relative to the support,
- a link articulated at a point on the clamping piece by a second axis parallel to the first,
- a member movable in a rectilinear manner under the action of a motor means exerting on this member a push or a pull in the direction of movement of the movable member, this movable member being articulated on the link by means of a third axis parallel to the first for a bracing action, which has the particularity that the movable member is guided by a bearing surface integral with the housing, and in that this movable member is connected to the motor means by a connection allowing a certain play and essentially transmitting only pushing or pulling forces in the direction of movement of said movable member.

 The consequences of the design of the device according to the invention are that the reactions of the link in the direction perpendicular to the movement of the movable member are absorbed by a support surface which can be flat and produced with a treatment giving it a large resistance to bearing wear which has no other function. The parts of the bearing surface and of the movable member which are intended to come into contact with one another can be ground and specially treated for low friction and a high resistance to wear and deformation. .

 On the contrary, the drive means, which can be the rod of a jack, is no longer subjected to stresses in one direction only and can be treated accordingly, and in particular not be subjected to bending. 'a cylinder, the bore through which the rod exits the cylinder has improved wear resistance.

 In addition, the disassembly of the drive member is made much easier, since slight variations in alignment have no influence on the movement of the movable member, since the latter is guided otherwise.

 Preferably, the connection between the drive means and the movable member is ensured by direct contact between these two parts, or parts which are integral with each of them, when pressure stresses are transmitted to the movable member, then that this connection is ensured by intermediate pieces such as pins, which are movable in a practical housing in the drive means and the movable member, for return strokes, where the member is stressed in traction with weaker forces .

 Such an arrangement facilitates the disassembly of the motor means and its reassembly.

Preferably, means for adjusting the limits of the travel of the clamping piece are arranged at the point of contact between the movable member and the driving dean,
Thus, disassembly of the motor means allows easy adjustment of these limits.

 Preferably affixed, provision is made for the clamping part to be in two parts, one of which is articulated on the rod, and the other forming a clamping bar, is made integral with the first by means of a fluted shaft which extends the hinge pin connecting the clamping part to the shoemaker. It is thus possible to obtain a wide range of strokes of the clamping bar, their number corresponding to that of the grooves, and the intermediate strokes which can be easily obtained by means; the setting described above.

Other advantages and particularities of the invention will emerge from the description which follows, which relates to a practical example of embodiment, given without limitation and illustrated by the drawings, among which
Fig.l is a section of a device according to the invention, in the clamping position;
Fig.2 is a similar section of the device zêFe in partial release position;
Fig.3 is a partial section of the device 6 showing the position sensors.

 Fig.4 is a view similar to that of Figure 3 and illustrating an alternative embodiment.

 Figure 1 shows a device comprising a case 1 formed mainly of two side cheeks, on either side of the plane of the figure, connected by spacers.

 The shoemaker carries a flange 2 which is used for its attachment to the support 3 which carries the part to be clamped 4.

 A clamping arm 5 is fixed to a connecting rod 6 which is pivoted in the housing by means of an articulation shaft 7, the connection between the arm 5 and the connecting rod 8 is ensured by two flanges 8 located on either side of the plane of the figure. The assembly of the clamping arm 5, the connecting rod 6 and the flanges 6 constitutes the clamping piece.

The connecting rod 6 is articulated on the connecting rod 9,
it also consists of two flanges located on either side of the plane of the figure, by an axis 10, parallel to the shaft 8. The link 9 carries another axis ll, parallel to the previous one, which connects it to a yoke 12, which constitutes the movable member mentioned above.

 The yoke is designed to slide along a guide surface 13 provided on an internal face of the housing, and the plane of which is parallel to that of the axes indicated above. The yoke has a blind hole 14, parallel to the guide surface, and which is situated substantially in the axis of the rod 15 of a jack 16 which constitutes the driving member. The jack 16 is carried by the housing 1 thanks to an annular pin 17. On the rod 15 is screwed a "floating nut 18 capable of transmitting the forces from the jack to the yoke. This guide nut has a play in the blind hole 14, it is held there by pins 19 which are themselves held with play in tangential bores both to the floating nut and to the wall of the blind hole.

 The adjustment of the stroke of the yoke, and therefore that of the clamping arm is obtained in a simple way by acting on the screwing of the floating nut on the rod of the jack. This adjustment is maintained by a lock nut 20.

 The reference 21 represents a sheet metal or plastic cover which completes the housing to prevent the ingress of dust and which can be dismantled for checking or lubrication.

 Figure 2 shows the same elements as Figure 1, but in the partially open position. The flange 2, the support 3, the part to be clamped 4 and the clamping arm 5 have not been shown. The connecting rod has rotated approximately 700 from the open position. The total stroke of the cylinder corresponds to a rotation of well over 900 of the clamping piece.

The compartment of the two figures also shows that the link is, in the closed position, almost
right angle with the direction of movement of the yoke.

This means that a relatively large displacement of the yoke corresponds to a low rotation of the workpiece.
Tightening . The position of the latter can therefore be adjusted with great precision and great force can be exerted.

On the contrary, in the open position, the link is almost parallel to the direction of movement of the yoke, which allows rapid opening.

 The device that has just been described is likely to present a certain number of variants. The flanges 8 can be omitted, and in this case the connecting rod 6 has an extension which directly carries the clamping arm 5.

The cover 21 is then in two parts on each side of the extension of the connecting rod 5 and it is made of flexible material so as to accompany it in its movement. This arrangement provides greater robustness.

 If it is desired to increase the adjustment possibilities, for example when parts 4 of very different thicknesses have to be treated, provision is made for the shaft 7 which carries the connecting rod to have two grooved extensions on either side of the shoemaker , and that the flanges 8 have openings of shape corresponding to these grooved parts. It is thus easy to modify the position of the flanges and of the clamping arm 5 relative to the connecting rod 6. These modifications correspond to angles of defined value, which depend on the number of splines, and the fine adjustment is made by screwing the nut 18.

 This arrangement lends itself well to the addition of a manual tightening and locking handle. This handle is advantageously mounted on the shaft 7 with a large rotational safety clearance, for example 1600, to avoid back movements. One can, for example, provide that two drive pins arranged at 1800, on either side of the axis of the shaft 7 and integral with it, cooperate with two pins integral with the handle and located at the same distance from the axis.

 In another variant, the jack 16 is fixed to the case by means of a rotating flange, such that the jack can turn on its axis before it is locked. It is thus possible to arrange the supply lines in the most practical way depending on the space available.

 The flange 2 for fixing to the support can also be fixed to the housing, or rather to the flange which carries the jack, using a clamp which allows its orientation to be chosen. It is thus easier to clamp pieces of very different shapes on the same support, or to adapt to supports of different shape.

 Another advantage of the invention results from the fact that the guidance of the yoke allows improved precision in the detection of its position. In a particularly interesting embodiment, illustrated in FIG. 3, the part 22 of the housing which carries the sliding surface 13 is crossed by an elongated lumen 23 of length at least equal to the stroke of the yoke.

A drive finger 24, constituted by a coil spring or an elastic pin to compensate for any play; is carried by the yoke 12 and passes through the lumen 23 to drive a slider 25 located on the outer face of the part 22. This slider also has a lumen 26, of length slightly less than that of the stroke of the yoke. The slide 25 carries a plate 27 which bears alternately on two limit switches 28,29. A locking device constituted by a ball screw immobilizes the slide and prevents an undesired recoil of it in particular during the recoil of the chap, e,
According to a variant, the slide 25 does not have a light 26 but carries two fingers or pins which penetrate into the light 23 with a center distance less than the stroke of the jack which is necessary for the actuation of the limit switches 28,29 . These fingers or pins play the same role as the edges of the light
26. Figure 4 shows such fingers or pins, associated
with a centering finger 24 of a particular type.

 When the yoke 12 arrives in the closed position, on the left in FIG. 3, the finger 24 drives the slide 25 by acting at the end of the light 26. The plate 27 then actuates the corresponding limit switch 28. the yoke 12 moves back to go towards the open position, the finger 24 enters the slide 25 only when one arrives near the end of the race.

Thus, any anomaly corresponding to an imperfect tightening or an incomplete opening is signaled by the fact that the corresponding sensor is not actuated. This detection is made precise by the short distance between the yoke 12 and the slide 25.

When tightening with a manual approach, for example using a manual tightening and locking handle mounted on axis 7 as indicated above, and when the parts to be tightened are not very regular, it may happen, with the arrangement which has just been described, that the physical force is insufficient to tighten the device Up to actuate the travel detector 28. Such a drawback is avoided by using the embodiment described in FIG. 4
In this embodiment, the slide 25 does not have a light 26 but it carries a pin 40 which protrudes on its inner face, and a series of ball impressions 41, located on the same internal face, aligned from the pin 40 in the direction opposite to that of the advance of the yoke 12 during tightening. These impressions have an abrupt edge 42 on the side of the pin 30 and an edge with a lower slope 43 on the opposite side. The drive finger 24 is constituted by an eclipsable ball screw, comprising a ball 44 pushed by a spring of adjustable force. The ball 44 of the finger 24 is intended to penetrate into the imprints 41, while the side wall of the finger is intended to bear against the pin 40.

 The operation is as follows: during tightening, the yoke 12 is driven by the manual drive lever in the direction of its extreme left position in FIG. 4, it arrives in the vicinity thereof and stops before to reach it. The ball 44, housed in one of the indentations 41 entering during this movement the slide 25, which actuates the end-of-travel detector 28. This then emits a signal which authorizes the establishment of the pressure in the cylinder chamber to complete buttress and exert the desired force on the clamping arm 5.

 The yoke 12 then moves to the left but does not drive the slider 25, which is retained by the end-of-travel detector 28, and the ball 44 jumps from one footprint to another. In the final position, shown in FIG. 4, the ball 44 is in the last impression and the pulling finger 24 is practically in contact with the pin 44.

 In this position, the locking device 30, consisting of a ball screw whose imprint is only shown in Figures 3 and 4 is in action to prevent a return.

 The force of the ball screw is adjusted to allow actuation of the limit switch 28 without risk of damaging it.

 During the operation in the opposite direction, the ball 34 tends to drive the slide 25 to the left, but it is retained by the locking device 30, the force of which is chosen accordingly. The ball 44 therefore jumps from one imprint to another, which is facilitated by the gentle slope of the edges 43, and the drive finger 24 finally comes to reach a pin 45, similar to the pin 40. Thanks to this- ci, it entralne the slide 25 by overcoming the force of the locking device, and the plate 27 moves until actuating the detector 29 of end of return stroke.

 In a variant, the locking device 30 is omitted, and it is the resistance specific to the depression of the limit switch 29 which temporarily retains the slide 25.

Claims (13)

 1. Device for exerting a clamping force on a part (4) on a support (3) comprising:  -a shoemaker (1) that can be fixed on the support,  a clamping piece (5,6,8) movable by pivoting around a first axis (7) fixed relative to the support,  a movable member (12) which can move under the action of a motor means (16) following a rectilinear path in a plane perpendicular to the axis (7) of the clamping piece,  -a link (9) articulated on the clamping part (5,6,8) by a second axis (10) and on the movable member (12) by a third axis (ll), these two axes being parallel to the first , said link transforming the rectilinear movement of the movable member into a pivoting with ar-byutement of the clamping piece, characterized in that the movable member (12) is guided by a bearing surface (13) integral with the byttier , and in that this movable member is connected to the motor means by a link (14,18,19) allowing a certain play and essentially transmitting only thrust or traction forces in the direction of movement of said movable member.  2. Device according to claim 1, characterized in that the connection between the movable member and the drive means is ensured by an intermediate piece (18) integral with the drive means and which directly transmits the pressure forces to the movable member. , while it transmits the tensile forces to it via auxiliary parts such as pins (l9) movable with a relative clearance relative to the movable member and to the intermediate part.  3. Device according to claim 2, characterized in that the intermediate piece (18) carries adjustment means, such as a screw, to determine the limit of the travel of the clamping piece.  4. Device according to one of claims 1 to 3, characterized in that the clamping part comprises two parts connected by a splined shaft (7), which makes it possible to change its geometry by rotation of one of the parts relative to the splined tree.  5. Device according to one of claims 1 to 4, and in which the drive means is a jack (16) whose body is fixed to the shoemaker and the rod is connected to the movable member by said link allowing a certain play, characterized in that said jack (16) is detachably connected to the shoemaker (1) and to the movable member (12).  6. Device according to claim 5, characterized in that the means for connecting the jack (16) to the boot (1) make it possible to vary the position of the jack, before locking, by rotation about the axis of said jack.  7. Device according to claim 6, characterized in that the means allowing the fixing of the jack (16) on the casing (1) are also adjustable in position relative to the axis of the jack.  8. Device according to one of claims 1 to 7, and comprising sensors (28,29) sensitive to the fact that the movable member (12) reaches one of the ends of its travel, characterized in that the sensors are actuated by a slide (25) having an elongated opening (23) in which a drive finger (24) can move, integral with the movable member, and in that said finger (24) consists of a spring or elastic piece which compensates for any play.  9. Device according to one of claims 1 to 7, and comprising sensors (28,29) sensitive to the fact that the movable member reaches one of the ends of its travel, characterized in that the sensors are actuated by a slide ( 25) carrying drive fingers (40,45) between which can move a drive finger (24) secured to the movable member.  10. Device according to one of claims 8 or 9, characterized in that there is provided a locking device (30) which immobilizes the slide (25) when the movable member is in the working position and prevents unwanted recoil of the latter, in particular during the retraction of the movable member.  11. Device according to one of claims 8 to 10 characterized in that the drive finger (24) comprises a ball (44) pushed by a spring and capable of cooperating with a series of successive imprints (41) provided on the slide to drive the latter by manual displacement of the mobile body until actuating a sensor (28) which controls the actuation of the motor means.  12. Device according to claim ll, characterized in that said imprints provided on the slide have an edge (42) more abrupt on the side corresponding to the movement of the movable member towards the active position than on the opposite side (43).  13.Device according to one of claims xl to 12 characterized in that a manual tightening and blocking handle can cause the clamping part (5,6,8) with a Safety game to avoid back impact.