EP1697088B1 - Quick clamping device and control method - Google Patents

Abstract

The device has a cylinder (1) with a body (10) fixed operatively to a tool. The cylinder has a rod (11) movable with respect to the body, and a clamp (2) articulated around a swiveling axis (X) on the rod and selectively driven by the rod. The clamp (2) moves between a tightening position and a relaxation position. The rod extends along a translation axis which passes between guide units and support units. An independent claim is also included for a process of controlling a device for clamping a part.

Description

The invention relates generally to techniques relating to mechanical machining.

More specifically, the invention relates, according to a first aspect, to a device for clamping a workpiece on a tool, comprising a jack and a flange, the jack being selectively actuated by a pressurized fluid and comprising itself a body fixed in operation to the tool and a rod movable relative to the body, and the flange being hinged about a pivot axis on the rod and selectively driven by the rod, this flange struggling on a determined race between a position clamping and releasing position, and rotated on at least part of its stroke.

Clamping devices are well known in mechanical engineering.

In their oldest and most rudimentary embodiment, these devices use screw jacks operating in the manner of a vice, these devices having the defect today unacceptable to require a very important actuation time.

In the newer clamping devices, which use hydraulic or pneumatic cylinders, the flange is approximated to the workpiece to be clamped and applied to it by simple rotation of this flange about its pivot axis.

Although they can be operated quickly, these devices themselves, however, have several defects.

In particular, the rotation of the flange may have the effect of sliding the workpiece to be clamped or deformed.

Given the relatively large distance between its axis of rotation and its support on the part to be clamped, the flange itself can buckle, which causes unacceptable inaccuracy of clamping.

In addition, the importance of the torque resistant to tightening forces to over-size the known devices of this type.

In this context, the main purpose of the invention is to provide a compact, fast, retractable, powerful clamping device, and moreover free from the aforementioned defects.

For this purpose, the device of the invention, moreover in conformity with the generic definition given in the preamble above, is essentially characterized by it further comprises guiding members and bearing elements, in that the guiding members comprise a guiding member fixed relative to the body and a movable guiding member connected to the flange, these guiding members. fixed and movable cooperating to drive the flange in a rotational movement about the pivot axis at least at the end of its stroke towards its release position and in a translational movement at least at the end of its stroke to its position in that the support elements comprise a fixed support element relative to the body and a movable support element connected to the flange, these fixed and movable support elements cooperating selectively, at least on the end of the stroke of the flange to its clamping position, to afford each other, away from the guide members, a sliding contact parallel to the translational movement of the flange and allowing a bridging of the flange on the piece to ser rer.

Preferably, the rod extends along a translation axis which passes between the guide members and the support elements, this arrangement allowing a balancing of the forces resistant to clamping and a very effective self-locking of the flange.

The movable guide member is for example constituted by a cam formed of two grooves hollowed symmetrically in the flange on either side of a median plane of the flange and the rod, transverse to the pivot axis.

Each groove advantageously has a path whose first and second ends are respectively relatively distant and relatively close to the pivot axis, this path approaching continuously the pivot axis from its first end to its second end, and comprising a portion straight pathway terminating at the first end and a curved path portion adjacent to the straight path portion and terminating at the second end.

Thanks to this arrangement, the flange is retractable completely automatically.

The fixed guide member may then be constituted by a pair of pins or rollers attached to the cylinder body and respectively engaged in the grooves forming the cam.

The movable support element is for example constituted by a bearing heel carried by the flange and extending symmetrically on either side of a median plane of the flange and the rod, transverse to the axis pivoting, the fixed support element then itself being constituted by a bearing surface of the cylinder body, on which the bearing heel bears symmetrically with respect to said median plane.

In a preferred embodiment of the invention, the jack is a double-acting jack, for example hydraulic, comprising first and second chambers separated by a piston integral with the rod, the flange being driven from its release position to its clamping position by admission of fluid under pressure into the first chamber of the jack, and being driven from its position clamping to its release position by admission of fluid under pressure in the second chamber of the cylinder.

In the case where the rod leaves the cylinder on the side of its first chamber, the fixed guide member and the fixed support member may be carried by a portion of the cylinder body which is shaped as a yoke, the flange being guided in its median plane between two parallel faces vis-à-vis this part forming a screed.

On the other hand, in the case where the rod leaves the cylinder on the side of its second chamber, the flange is for example shaped as a yoke and encloses the body of the jack which guides it in its median plane.

In both cases, each pin or roller is advantageously located above a plane transverse to the rod containing the pivot axis, in a direction corresponding to the movement that the rod makes to drive the flange to its release position .

A perfect retraction of the flange can be obtained by providing that the flange rotates at least equal to 90 degrees between its clamping position and its release position.

The invention also relates, according to a second of its aspects, to a control method of the device previously described, this method being characterized in that it comprises an operation consisting of measuring the pressure of the actuating fluid admitted into this device and check the position of the flange and / or the clamping force by checking the value of the measured pressure.

• les figures 1 et 2 sont deux vues en perspective d'un dispositif de serrage conforme à un premier mode de réalisation de l'invention et dont la bride est en position de serrage;
• la figure 3 est une vue en perspective d'un dispositif de serrage conforme à un second mode de réalisation de l'invention et dont la bride est en position de serrage;
• la figure 4 est une vue en coupe partielle du dispositif illustré aux figures 1 et 2 mais dont la bride est en position de relâchement, la coupe étant réalisée suivant un plan parallèle au plan médian de ce dispositif;
• la figure 5 est une vue en coupe du dispositif illustré aux figures 1 et 2, réalisée suivant le plan médian de ce dispositif;
• la figure 6 est une vue en coupe du dispositif illustré aux figures 1 et 2 et complété par une embase formant à la fois distributeur de fluide et support d'intégration du dispositif dans l'outillage, la coupe étant réalisée suivant le plan médian de ce dispositif;
• la figure 7 est une vue de dessus du dispositif illustré aux figures 1 et 2;
• la figure 8 est une vue latérale partielle du dispositif illustré aux figures 1 et 2;
• la figure 9 est une vue latérale du dispositif illustré à la figure 3;
• la figure 10 est une vue de face du dispositif illustré à la figure 3;
• la figure 11 est une vue latérale du dispositif illustré à la figure 3 mais dont la bride est en position de relâchement; et
• la figure 12 est une vue en coupe du dispositif illustré à la figure 3, réalisée suivant le plan médian de ce dispositif.

Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which:

• Figures 1 and 2 are two perspective views of a clamping device according to a first embodiment of the invention and the flange is in the clamping position;
• Figure 3 is a perspective view of a clamping device according to a second embodiment of the invention and whose flange is in the clamping position;
• FIG. 4 is a partial sectional view of the device illustrated in FIGS. 1 and 2 but whose flange is in the release position, the section being carried out along a plane parallel to the median plane of this device;
• Figure 5 is a sectional view of the device shown in Figures 1 and 2, made along the median plane of this device;
• FIG. 6 is a sectional view of the device illustrated in FIGS. 1 and 2 and completed by a base forming both a fluid distributor and an integration support for the device in the tooling, the section being made along the median plane of this device; device;
• Figure 7 is a top view of the device shown in Figures 1 and 2;
• Figure 8 is a partial side view of the device shown in Figures 1 and 2;
• Figure 9 is a side view of the device shown in Figure 3;
• Figure 10 is a front view of the device shown in Figure 3;
• Figure 11 is a side view of the device shown in Figure 3 but the flange is in the release position; and
• Figure 12 is a sectional view of the device shown in Figure 3, made along the median plane of this device.

As previously announced, the invention relates to a device for clamping a workpiece P on a tool for machining thereof, this device essentially comprising a jack 1 and a clamp 2.

The jack 1 is for example constituted by a double-acting hydraulic jack and comprises a body 10 fixed in operation to the tool itself placed in a machining center, and a rod 11 movable relative to the body 10 of this jack .

The body 10 of the jack has a bore inside which a piston 12, integral with the rod 11, defines two chambers 101 and 102 of variable and complementary volumes, opening on the outside by means of respective ports 101p and 102p each of which can be connected to a high pressure hydraulic source while the other is connected to a low pressure reservoir.

The flange 2, which is articulated on the rod 11 about a pivot axis X, is driven at will by the rod 11, itself driven by the piston 12.

The flange 2 thus struggles, on a determined stroke, between a clamping position illustrated in particular in FIGS. 1 to 3, and a release position, illustrated in Figure 4 for the first embodiment, and in Figure 11 for the second embodiment.

Under these conditions, the flange 2 is driven from its release position to its clamping position by admission of fluid under pressure in the first chamber 101 of the cylinder 1, and is driven from its clamping position to its release position by admission of fluid under pressure in the second chamber 102 of this cylinder 1.

The device of the invention derives most of its advantages from the fact that it comprises guide members 3 and bearing elements 4, the guide members 3 themselves comprising a guide member 31 fixed with respect to the body 10 and a movable guide member 32 connected to the flange 2, and the support elements 4 comprising, in the same way, a support member 41 fixed relative to the body 10 and a movable support member 42 connected at the flange 2.

The fixed and movable guide members, 31 and 32, cooperate to drive the flange 2 in a rotational movement about the pivot axis X at least at the end of the stroke of this flange towards its release position, and for driving the flange 2 in a translation movement at least at the end of the stroke of this flange to its clamping position.

On their side, the fixed and mobile support elements, 41 and 42, cooperate, at least at the end of the stroke of the flange 2 towards its clamping position, to afford each other, at a distance from the guide members 3 , a sliding contact parallel to the translational movement of the flange 2 and allowing a bracing of the flange 2 on the part to be clamped P.

According to another important characteristic of the invention, the rod 11 preferably extends along a translation axis Z which passes between the guide members 3 and the support elements 4.

In each of the two embodiments illustrated, the movable guide member 32 is constituted by a cam formed of two grooves, such as 32a, hollowed symmetrically in the flange 2 on either side of a median plane M of the device , this median plane M being transverse to the pivot axis X and constituting a plane of symmetry for the flange 2 and for the rod 11.

In addition to the groove 32a, the flange 2 thus has a groove 32b which, although not visible in the figures, is deduced from the groove 32a by symmetry with respect to the plane M.

Each of the grooves 32a and 32b has a path that is continuously approaching the pivot axis X from the first end 321 of this path to its second end 322.

As shown in FIGS. 4, 9, and 11, this path includes a straight path portion 320r terminating at the first end 321 and a curved path portion 320c adjacent to the straight path portion 320r and terminating at the end. second end 322.

The fixed guide member 31 is constituted by a pair of pins or rollers, such as 31a, fixed to the body 10 of the cylinder 1 and respectively engaged in the grooves forming the cam.

In addition to the stud or the roller 31a engaged in the groove 32a, the body 10 thus has a stud or a roller 31b engaged in the groove 32b and which, although not visible in the figures, is deduced from the stud or roller 31a by symmetry by ratio to the median plane M.

As shown in Figures 4 and 11, each pin or roller such as 31a is located above a plane T which is transverse to the rod 11 and which contains the pivot axis X, when following a direction that corresponds to the movement made by the rod 11 to drive the flange 2 to its release position.

The movable support element 42 is constituted by a bearing heel which is carried by the flange 2 and which extends symmetrically on either side of the median plane M of the device.

The fixed support element 41 is constituted by an external bearing surface of the body 10 of the cylinder 1, on which the support heel 42 bears symmetrically with respect to the same median plane M.

In the first embodiment of the invention, illustrated in FIGS. 1, 2 and 4 to 8, the rod 11 leaves the jack 1 on the side of its first chamber 101.

In this case, the fixed guide member 31 and the fixed support member 41 are advantageously carried by a portion 100 of the body 10 of the jack which is shaped as a yoke, and the flange 2 is then guided in its median plane M between two parallel faces vis-a-vis, 100a and 100b, belonging to this portion 100 forming a screed.

This embodiment allows a large rotation of the flange 2 between its clamping position and its release position, typically a rotation of amplitude equal to or greater than 90 degrees.

In addition, as shown in FIG. 6, the jack 1 can in this case be mounted in a base 5 fixed to the tool, forming a fluid distributor, and therefore itself comprising two fluid inlet-outlet ports 101q. and 102q respectively corresponding to the ports 101p and 102p of the jack 1.

In the second embodiment of the invention, illustrated in FIGS. 3 and 9 to 12, the rod 11 leaves the jack 1 on the side of its second chamber 102.

In this case, it is preferably the flange 2 which is shaped as a yoke, this flange then enclosing the body 10 of the cylinder 1, which guides it in its median plane M.

In order to optimally control the actuation of the device previously described, it is recommended to measure the pressure of the operating fluid admitted in this device, so that it is then possible to control the position of the flange and / or the clamping force by checking the value of the measured pressure.

In particular, it is therefore possible to provide that the measured pressure reaches or exceeds a determined minimum threshold, typically to prevent the clamping force from being insufficient, or to provide that the measured pressure remains below a maximum threshold determined for example to prevent the clamping force from damaging the workpiece.

Given the compressibility of the air, this method has the additional advantage of allowing a very fine adjustment of the clamping force in the case where the actuating fluid is constituted by compressed air.

Claims (13)

1. Device for clamping a workpiece (P) to a tool, comprising a ram (1) and an arm (2), the ram (1) being selectively actuated by a pressurized fluid and itself comprising a body (10) fixed when in use to the tool and a rod (11) that is movable relative to the body (10), and the arm (2) being hinged to the rod (11) about a pivot axis (X) and selectively driven by the rod (11), which arm (2) executes a defined stroke between a clamping position and a release position and undergoes a rotation for at least a part of its stroke; which device is characterized in that it also includes guide members (3) and bearing elements (4), in that the guide members (3) comprise a guide member (31) that is fixed with respect to the body (10) and a movable guide member (32) that is connected to the arm (2), said fixed and movable guide members (31, 32) acting together to drive the arm (2) through a rotational movement about the pivot axis (X) at least at the end of its stroke towards its release position and through a translational movement at least at the end of its stroke towards its clamping position, and in that the bearing elements (4) comprise a bearing element (41) that is fixed with respect to the body (10) and a movable bearing element (42) that is connected to the arm (2), which fixed and movable bearing elements (41, 42) act together selectively, at least at the end of the stroke of the arm (2) towards its clamping position, to offer each other, at a distance from the guide members (3), a sliding contact parallel to the translational movement of the arm (2), allowing the arm (2) to apply pressure to the workpiece to be clamped (P).
2. Clamping device according to Claim 1, characterized in that the rod (11) extends along an axis of translation (Z) as it passes between the guide members (3) and the bearing elements (4).
3. Clamping device according to Claim 1 or 2, characterized in that the movable guide member (32) consists of a cam formed by two slots (32a, 32b) formed symmetrically in the arm (2) on either side of a mid-plane (M) of the arm and of the rod, lying transversely to the pivot axis (X).
4. Clamping device according to any one of the preceding claims combined with Claim 3, characterized in that each slot (32a, 32b) defines a path whose first and second ends (321, 322) are respectively relatively distant from and relatively close to the pivot axis (X), this path continually approaching the pivot axis (X) from its first end (321) to its second end (322), and comprising a straight path portion (320r) ending at the first end (321) and a curved path portion (320c) adjacent to the straight path portion (320r) and ending at the second end (322).
5. Clamping device according to any one of the preceding claims combined with Claim 3, characterized in that the fixed guide member (31) consists of two nipples or rollers (31a, 31b) fixed to the body (10) of the ram (1), each engaged in its respective cam slot (32a, 32b).
6. Clamping device according to any one of the preceding claims, characterized in that the movable bearing element (42) consists of a bearing projection (42) on the arm (2) and extends symmetrically either side of a mid-plane (M) of the arm and of the rod, transversely to the pivot axis (X), and in that the fixed bearing element (41) consists of a bearing surface (41) of the body (10) of the ram (1), on which surface the bearing projection (42) bears symmetrically about said mid-plane (M).
7. Clamping device according to any one of the preceding claims, characterized in that the ram (1) is a double-acting ram comprising first and second chambers (101, 102) separated by a piston (12) mounted on the rod (11), the arm (2) being driven from its release position to its clamping position by the admission of pressurized fluid into the first chamber (101) of the ram (1), and being driven from its clamping position to its release position by the admission of pressurized fluid into the second chamber (102) of the ram (1).
8. Clamping device according to Claim 7, characterized in that the ram (1) is a hydraulic ram.
9. Clamping device according to either of Claims 7 and 8, characterized in that the rod (11) passes out of the ram (1) through its first chamber (101) and in that the fixed guide member (31) and the fixed bearing element (41) are supported by a yoke-shaped part (100) of the ram body (10), the arm (2) being guided in its mid-plane (M) between two opposing parallel faces (100a, 100b) of this yoke part (100).
10. Clamping device according to either of Claims 7 and 8, characterized in that the rod (11) passes out of the ram (1) through its second chamber (102) and in that the arm (2) is yoke-shaped and grasps the body (10) of the ram (1), which guides it in its mid-plane (M).
11. Clamping device according to any one of the preceding claims combined with Claim 5, characterized in that each nipple or roller (31a, 31b) is situated above a plane (T) lying transversely to the rod (11) containing the pivot axis (X), in a direction corresponding to the movement described by the rod (11) in driving the arm (2) towards its release position.
12. Clamping device according to any one of the preceding claims, characterized in that the arm (2) describes a rotation of at least 90 degrees between its clamping position and its release position.
13. Method of controlling the device according to any one of the preceding claims, characterized in that it comprises an operation of measuring the pressure of the actuating fluid admitted into this device and monitoring the position of the arm and/or the clamping force by ascertaining the value of the measured pressure.

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