Gripping clamp for a robotic arm comprising pads elastically stressed with respect to jaws and method for monitoring contamination by smear testing by means of such a clamp

Abstract

The invention relates to a gripping clamp (30), in particular suitable for monitoring contamination of a surface (112) by smear testing, which comprises: a clamp body (22); a mechanical interface (18) for connection to a modular effector (16) of a robotic arm (12); two jaws (24); a transmission mechanism (26) for connecting the jaws (24) to the clamp body (22) and converting commands of the mechanical interface (18) into movements of the jaws (24) between a mutually spaced configuration and a mutually closer configuration; two pads (32, 34) mounted on the jaws (24) via support mechanisms (38) configured to allow the pads (32, 34) to move with respect to the jaws (24) along paths parallel to each other, independently of the position of the jaws (24); and elastic return means (36) configured to urge each of the pads (32, 34) towards an end position on its path, on the same side. The pads (32, 34) respectively define gripping surfaces with a V-shaped cross section so as to allow a rod to be gripped between the surfaces.

Description

[0001] Description

[0002] Title: Gripper for robotic arm comprising pads subjected to elastic loads relative to jaws and method for contamination control by smearing using such a gripper

[0003] technical field

[0004] The present invention relates to the general field of gripping grippers intended for modular effectors of robotic arms.

[0005] It relates in particular to such a gripping device, adapted for monitoring contamination, for example by radioactive particles, of the outer surface of packages containing radioactive materials such as waste generated by nuclear power plants. It also relates to a method for monitoring surface contamination by smearing, using such a gripping device.

[0006] Prior art

[0007] The storage of nuclear waste is a major technical and environmental challenge.

[0008] Some of this waste is stored in containers housed in secure facilities within designated centers. For the most radioactive waste, this is generally temporary storage pending transfer to deep geological disposal sites. For waste with lower levels of radioactivity and shorter half-lives, it may be permanent storage.

[0009] These containers, generally called "packages" when they contain radioactive materials, must be regularly inspected to ensure they are in good condition. For this purpose, contamination checks of the outer surface of the packages are carried out using a technique called smear testing. This involves applying an absorbent material, such as felt, to the surface to be tested and moving the material across the surface. To guarantee the accuracy and reproducibility of these checks, the pressure applied to the absorbent material must be controlled. In some cases, standards are imposed for this purpose by state authorities. Since human access to the rooms or cells where the packages are stored is restricted, contamination checks are generally carried out using a dedicated industrial robot, remotely controlled or programmed for this task. Such a robot is usually complex and bulky.

[0010] In this context, the inventors set themselves the goal of being able to implement contamination controls using a remotely controlled or programmed robotic arm equipped with a modular effector.

[0011] In general, a robotic arm effector, often called a "terminal tool" or "terminal effector", is the part of the robotic arm that interacts directly with the environment.

[0012] A modular effector is an effector onto which different tools can be mounted depending on the intended use. Such a modular effector typically has a mechanical interface for tool changes, sometimes automated. Modular effectors often have a standardized mechanical interface, so tools from different manufacturers can be easily attached and detached.

[0013] Description of the invention

[0014] The objective stated above is achieved by the invention by means of a gripping clamp comprising:

[0015] - a clamp body;

[0016] - a mechanical interface to connect the gripper body to a modular effector of a robotic arm;

[0017] - two jaws;

[0018] - a transmission mechanism configured to connect the jaws to the gripper body and convert commands transmitted by the mechanical interface into jaw movements between a configuration of mutual spreading and a configuration of mutually closing the jaws, regardless of the jaw position; - two pads, arranged opposite each other, mounted respectively on the jaws by means of support mechanisms configured to allow movement of the pads relative to the jaws along trajectories parallel to each other; and

[0019] - elastic return means configured to stress each of the skates towards an extreme position on its trajectory, on the same side.

[0020] The gripper thus defined allows the grasping of tools between the pads and offers in particular possibilities of controlling a force applied by such a tool on an object by controlling the force applied to the pads by elastic means of return, as will appear more clearly in what follows.

[0021] In addition, the pads define V-shaped gripping surfaces to allow a rod to be gripped between said surfaces.

[0022] The gripping clamp is therefore particularly suited to gripping tools equipped with a gripping shank.

[0023] In preferred embodiments of the invention, a first of the skates comprises two teeth, each defining a part of the gripping surface of the first skate, and defining a notch between them, and a second of the skates comprises a tooth defining at least a part of the gripping surface of the second skate and arranged so as to fit between the two teeth of the first skate in the configuration of mutually approaching jaws.

[0024] Thus, the jaws can be brought closer together when there is no rod between the pads than when a rod, such as the gripping shank of a tool, is present between them. This characteristic can be used to confirm that such a rod has indeed been grasped by the gripper, as will become clearer later.

[0025] In preferred embodiments of the invention, at least one of the pads includes a stop arranged at one end of the gripping surface located on a side opposite said extreme position, in the configuration of the jaws coming together. Such a stop limits the insertion depth of the rod between the pads, in the direction opposite to the extreme position.

[0026] In preferred embodiments of the invention, the support mechanisms each include a ball guide rail.

[0027] In preferred embodiments of the invention, the support mechanisms are configured so that the movements of the skates along said trajectories are rectilinear translations.

[0028] In preferred embodiments of the invention, the elastic return means comprise, for each of the pads, a compression spring interposed between a support plate rigidly attached to the pad in question and a stop rigidly attached to the corresponding jaw.

[0029] In preferred embodiments of the invention, the support plate is arranged to come against the corresponding jaw and thus define said extreme position.

[0030] The invention also relates to a robotic device, comprising a robotic arm equipped with a modular end effector, and a grasping gripper of the type defined above, mounted on the modular end effector via its mechanical interface.

[0031] The invention also relates to a method for checking the contamination, particularly radioactive contamination, of an object's surface by smearing, using a robotic device of the type defined above, comprising steps consisting of:

[0032] - A) to provide a smear tool having, on one side, a smear surface, and on the opposite side, a gripping rod;

[0033] - B) with the jaws in their mutually separated configuration, maneuver the robotic device so as to bring the gripper into a position such that the gripping rod of the smear tool is positioned between the pads; then

[0034] - C) maneuver the robotic device so as to move the jaws to their mutually approaching configuration until the gripping rod of the smear tool is clamped between the pads; then - D) maneuver the robotic device so as to bring the smear surface into contact with the object surface and such that the elastic return means apply a force to the pads resulting in pressure of the smear surface on the object surface; then

[0035] - E) maneuver the robotic device so that the smear surface sweeps at least part of the object's surface; then

[0036] - F) move the smear surface away from the object; then

[0037] - G) analyze the surface of the smear in order to detect any possible contamination.

[0038] In preferred embodiments of the invention, step G is implemented by means of a radioactivity detector.

[0039] The invention also relates to a computer program product comprising code instructions for executing the steps of a process of the type defined above, when said program is executed on an electronic control unit.

[0040] Brief description of the drawings

[0041] The invention will be better understood, and other details, advantages, and features thereof will become apparent from the following description, given by way of non-limiting example and with reference to the accompanying drawings, in which:

[0042] [Fig. 1] is a schematic side view of a robotic device comprising a robotic arm equipped with a modular end effector on which is mounted a gripper of a known type;

[0043] [Fig. 2] is a schematic perspective view of a grasping gripper according to a preferred embodiment of the invention, mounted on a modular effector such as the modular effector of the robotic arm of Figure 1;

[0044] [Fig. 3] is a schematic exploded perspective view of the gripper of figure 2, without its body and transmission mechanism;

[0045] [Fig. 3A] is a larger scale view of part of Figure 3, showing a first pad of the gripper; [Fig. 3B] is a larger scale view of another part of Figure 3, showing a second pad of the gripper;

[0046] [Fig. 4] is a schematic perspective view, from the side, of the gripper of figure 2 (without its body and transmission mechanism), whose jaws are in a mutually spreading configuration;

[0047] [Fig. 5] is a view similar to figure 4, showing the jaws in a mutually approaching configuration;

[0048] [Fig. 6] is a schematic diagram illustrating an example of a context in which a contamination control process can be implemented according to an embodiment of the invention;

[0049] [Fig. 7] is a schematic perspective view, from the side, of the gripper of figure 2 (without its body and transmission mechanism) and of an object to be controlled, during the implementation of the process.

[0050] Throughout these figures, identical references may designate identical or analogous elements.

[0051] Detailed presentation of preferred embodiments

[0052] Figure 1 schematically illustrates a known type of robotic device 10, comprising a robotic arm 12 mounted on a drive unit 14 and having a modular end effector 16 at its end. The drive unit 14 is conventionally designed to supply the robotic arm 12 with power and transmit commands to it. The modular end effector 16 is provided with a connection interface 17 to which, for example, the mechanical interface 18 of a conventional type of gripper 20 is connected.

[0053] Such a gripper generally comprises a gripper body 22, the mechanical interface 18 by which the gripper body 22 is connected to the modular effector 16, as well as two jaws 24, and a transmission mechanism 26 configured to connect the jaws 24 to the gripper body 22. Such a transmission mechanism 26, which includes for example connecting rods arranged to define a deformable parallelogram, is generally configured to convert commands transmitted by the mechanical interface, for example in the form of movements of one or more transmission member(s) provided for this purpose, into movements of the jaws 24 between a configuration of mutual spacing of the jaws and a configuration of mutual approach of the jaws.

[0054] Figure 2 illustrates a grasping gripper 30 according to a preferred embodiment of the invention, intended to be able to be mounted on a robotic arm such as the arm 12 of Figure 1, in place of the grasping gripper 20.

[0055] The gripper 30 is similar to the gripper 20 described above in that it also comprises, in an analogous manner, a gripper body 22, a mechanical interface 18 by which the gripper body 22 is connected to the modular effector 16, as well as two jaws 24, and a transmission mechanism 26 configured to connect the jaws 24 to the gripper body 22. As explained above, the transmission mechanism 26 allows the conversion of commands transmitted by the mechanical interface into movements of the jaws 24 between a configuration of mutual spreading of the jaws and a configuration of mutual bringing them together.

[0056] The gripping clamp 30 is nevertheless distinguished from the clamp 20 by the characteristics which will now be described with constant reference to figure 2 and with reference to figures 3-5.

[0057] The gripping clamp 30 is provided with two pads 32, 34 as well as elastic return means 36.

[0058] The two pads 32, 34 are arranged opposite each other and are respectively mounted on the jaws 24 by means of corresponding support mechanisms 38 configured to allow movement of the pads 32, 34 relative to the jaws along respective trajectories parallel to each other, independently of the position of the jaws, as will become clearer in what follows.

[0059] For this purpose, each of the support mechanisms 38 includes, for example, a ball guide rail 40. Such a mechanism includes a carriage 42, a rail 44 engaged in a slide defined by the carriage, and balls (not visible in the figures) interposed between the rail 44 and the carriage 42 by being trapped in the slide. Such a mechanism conventionally allows precise, low-friction linear movement (which can be rectilinear or curvilinear) between the carriage 42 and the rail 44. In the preferred example shown, the carriage 42 of each of the support mechanisms 38 is rigidly fixed to the corresponding jaw 24, so that the rail 44 is movable relative to the jaw 24. The corresponding slide 32, 34 is rigidly fixed to the rail 44, for example on a surface of the rail opposite the carriage 42, so that the slide 32, 34 moves with the rail 44 relative to the carriage 42.Of course, other types of mechanisms can be used as support mechanisms 38, for example, flat slide mechanisms or roller guide rails.

[0060] Furthermore, the support mechanisms 38 are advantageously configured so that the movements of the carriages 32, 34 along the aforementioned trajectories are rectilinear translations. In this case, the rails 44 and the slides defined by the carriages 42 are thus rectilinear in shape. Although translations along curvilinear trajectories remain possible within the general framework of the invention, rectilinear translations offer the advantage of lower cost with regard to the guide rails.

[0061] The direction A of the trajectory of each of the pads 32 and 34 (or, in the case of a curvilinear trajectory, the plane of this trajectory) is preferably orthogonal to a direction of the movement of the jaws 24, at least when the latter reach their configuration of mutual approach (the direction of the movement of the jaws 24 may possibly vary in cases where the transmission mechanism drives the jaws 24 along respective curvilinear trajectories).

[0062] As regards the elastic return means 36, these are configured to move each of the pads 32, 34 towards an extreme position on its trajectory. The respective extreme positions of the pads 32, 34 are defined on the same side (relative to the trajectories and, in this case, relative to the jaws), for example, on the left side in the figures, and these extreme positions generally constitute distal extreme positions, with reference to the entire gripping gripper 30. For this purpose, the elastic return means 36 include, for example, for each of the pads, a compression spring 50 (or helical spring) interposed between a support plate 52 rigidly attached to the pad 32, 34 in question, and a stop 54 rigidly attached to the corresponding jaw. The stop 54 is arranged on the opposite side to the aforementioned extreme position, with respect to the support plate 52, in this case to the right of the support plate 52.Each compression spring 50 is, for example, mounted on a corresponding support bar 56 rigidly attached to the corresponding jaw 24. Furthermore, the support plate 52 has an opening 58 (Figure 3) through which the support bar 56 passes with clearance. The compression spring 50 thus rests against the periphery of the opening 58 (Figures 4 and 5).

[0063] The support plate 52 is advantageously arranged to abut against the corresponding jaw 24, thus defining the extreme position of the trajectory of the skate 32, 34. In Figures 2, 4, and 5, each of the skates 32, 34 is in its defined extreme position. Conversely, in Figure 3, the skate 32 visible at the bottom is in an opposite extreme position, generally constituting a proximal extreme position, for which the compression springs 50 are in a state of maximum compression.

[0064] Of course, other types of return means can be used, such as tension springs arranged between each jaw 24 and the plate 52.

[0065] In the illustrated example, each of the jaws 24 is formed of a beak 60 and a support plate 62. The beak 60 is for example similar to that found on some conventional gripping grippers such as the gripper 20 of figure 1, and thus has a general triangular shape with, along one side, two orifices for the articulation of the connecting rods of the transmission mechanism 26 (figure 2), and along another side, a heel 64 by which the beak 60 is fixed on one face of the support plate 62, while the corresponding carriage 42 is fixed on an opposite face of the plate. In addition, the corresponding support bar 56 is connected to an edge of the support plate 62. To limit the size of the gripping clamp 30, the support plates 62, and therefore the support bars 56, are oriented in an inclined direction relative to an output axis of the modular effector 16.The jaws 24 of the gripper 30 can thus be relatively close to the effector 16, without the support bars 56 interfering with the effector 16.

[0066] Figure 3 shows, in addition to the gripping gripper 30, a smear tool 70 intended to be used in combination with the robotic device 10 equipped with the gripper 30 in a particular application of the invention, as will become clearer in what follows.

[0067] Such a smear tool 70 comprises an absorbing element 72, such as a felt pad, and a support 74. This support 74 is formed of a disc 76, a distal face of which is covered by the absorbing element 72, and a gripping rod 78 extending outward from a proximal face of the disc 76 to allow the gripping of the smear tool 70. The felt pad defines, on its free surface (i.e. on the side opposite the disc 76), a smear surface 79, intended to collect particles on the surface of an object to be inspected.

[0068] The 32, 34 pads are advantageously suited for gripping rods such as the gripping rod 78.

[0069] To this end, the pads 32 and 34 define V-shaped gripping surfaces 80 and 82 respectively, enabling the gripping of such a rod between these surfaces. These gripping surfaces allow, in particular, the gripping of rods of different diameters and promote self-centering of the rods during gripping.

[0070] In the illustrated example, the first of the skates 32 has two teeth 84 and 86, each defining a portion of the gripping surface 80 of the first skate 32 (Figure 3A). These two teeth 84 and 86 define a notch 88 between them. It should therefore be understood that the gripping surface 80 is defined by each of the teeth 84 and 86 and is interrupted by the notch 88.

[0071] Furthermore, a second of the pads 34 has a tooth 90 defining at least part—and in this case, all—of the gripping surface 82 of the second pad 34 (Figure 3B). This tooth 90 is arranged so as to fit between the two teeth 84 and 86 of the first pad 32 in the configuration of mutual jaw contact (Figure 5). To this end, as shown in Figure 3B, the tooth 90 and a base 92 of the notch 88 have conjugate shapes allowing the tooth 90 to fit snugly against the base 92 in the configuration of mutual jaw contact. Similarly, teeth 84 and 86 have conjugate forms of regions 94 and 96 of the second skate 34 which adjoin tooth 90 of the latter, on either side of this tooth 90, so that teeth 84 and 86 can fit regions 94 and 96 in the configuration of mutual approach of the jaws.

[0072] Thus, the jaws 24 can be brought closer together in the absence of a rod between the pads 32 and 34 (as in Figure 5) than when a rod, such as the gripping rod 78, is present between the pads (as in Figure 7). This feature is advantageously used to confirm that such a rod has indeed been grasped by the gripper 30. In fact, the limiting position adopted by the jaws 24 in response to a clamping command, that is, a command tending to move the jaws into their mutually close position, directly indicates the presence or absence of a rod between the pads 32 and 34.

[0073] Finally, at least one of the pads 32, 34 advantageously includes a stop which, in the configuration of the jaws coming together, is arranged at one end of the gripping surface 80, 82 located on a side opposite to the extreme position. Such a stop limits the insertion depth of the rod between the pads 32 and 34, in the direction opposite to the extreme position.

[0074] In the illustrated example, each of the skates 32, 34 has such a stop. For this purpose, the first skate 32 has, for example, a lug 98 adjacent to one of the teeth 84 (located on the proximal side of the skate) and centered between two lateral edges of the skate 32 defined parallel to the aforementioned trajectory (Figure 3A), while the second skate 34 has, for example, a stop tooth 100 positioned at a distance from the tooth 90 of the second skate (Figure 3B), so that the tooth 84 of the first skate can fit between the tooth 90 and the stop tooth 100 of the second skate, in the configuration of mutual jaw proximity (Figure 5). The stop tooth 100 also has a recess 102 (Figure 3B) into which the lug 98 fits, in the configuration of mutual jaw proximity.

[0075] One particular, though not exhaustive, application for which the 30 gripping clamp was developed concerns the control of contamination, particularly radioactive, of an object's surface using the so-called smear test. This type of control is commonly referred to as "non-contamination testing".

[0076] Figure 6 illustrates very schematically the main elements involved in the implementation of a process for controlling the contamination of an object's surface by smearing, using the robotic device 10 equipped with the gripping clamp 30 described above.

[0077] In addition to the device 10, these elements include a smear tool, such as the smear tool 70 described above, an object 110 such as a radioactive waste container whose outer surface 112 is to be controlled, and an electronic control unit 120 which can be configured to implement a computer program including code instructions for carrying out the steps of the process.

[0078] The electronic control unit 120 can, alternatively, be operated by an operator, for example by means of a master arm configured so that the robotic arm 12 replicates the maneuvers of the master arm.

[0079] The robotic device 10, the object 110 to be controlled and the smear tool 70 are generally enclosed in a secure sealed room 130, without the possibility of access by an operator.

[0080] Such a process generally includes steps consisting of:

[0081] - A) make available the smear tool 70, the latter being for example placed on a tool holder provided for this purpose;

[0082] - B) with the jaws 24 in their mutually separated configuration, maneuver the robotic device 10 so as to bring the gripper 30 into a position such that the gripping rod 78 of the smear tool is positioned between the pads 32 and 34; then - C) maneuver the robotic device 10 so as to move the jaws 24 towards their mutually combined position until the gripping rod 78 of the smear tool is clamped between the pads 32 and 34, in this case between the gripping surfaces 80 and 82; then

[0083] - D) maneuver the robotic device 10 so as to bring the smear surface 79 into contact with the surface 112 of the object 110 and so that the elastic return means 36 apply a controlled force on the pads 32 and 34, resulting in pressure from the smear surface 79 on the surface 112 of the object; then

[0084] - E) maneuver the robotic device 10 so that the smear surface 79 sweeps at least part of the surface 112 of the object 110 (figure 7); then

[0085] - F) move the smear surface 79 away from the object 110; then

[0086] - G) analyze the surface of smear 79 in order to detect any possible contamination.

[0087] Step C is preferably implemented so that the gripping rod 78 is against the stop, which in this case is formed by the lug 98. The length of the rod 78 being known, the position of the rubbing surface 79 with respect to the pads 32 and 34 is thus fixed.

[0088] Furthermore, since the position and shape of the object 110 are also known, it follows that during step E, regardless of the position of the smear surface 79 on the surface 112 of the object 110, the position of the gripper 30, which is directly deduced from the posture of the robotic arm 12, provides information on the degree of retraction of the pads 32 and 34 relative to their extreme position and therefore on the degree of compression of the springs 50, from which is deduced the force applied on the pads 32 and 34 by the springs 50 and therefore the pressure applied by the smear surface 79 on the surface 112 of the object 110.

[0089] A simple position control of the robotic arm 12 thus allows control of the pressure applied by the smear surface 79 on the surface 112.

Claims

Demands 1. Gripper (30), comprising: - a clamp body (22); - a mechanical interface (18) for connecting the gripper body (22) to a modular effector (16) of a robotic arm (12); - two jaws (24); - a transmission mechanism (26) configured to connect the jaws (24) to the gripper body (22) and convert commands transmitted by the mechanical interface (18) into movements of the jaws (24) between a configuration of mutual separation of the jaws and a configuration of mutual retraction of the jaws; characterized in that it comprises: - two pads (32, 34), arranged opposite each other, and respectively mounted on the jaws (24) by means of support mechanisms (38) configured to allow movement of the pads (32, 34) relative to the jaws (24) along trajectories parallel to each other, independently of the position of the jaws (24); and - elastic return means (36) configured to stress each of the pads (32, 34) towards an extreme position on its trajectory, on the same side; wherein the pads (32, 34) respectively define gripping surfaces (80, 82) with a V-shaped cross-section so as to allow the gripping of a rod (78) between said surfaces.

2. Gripping clamp according to claim 1, wherein: - a first of the skates (32) has two teeth (84, 86) each defining a part of the gripping surface (80) of said first skate, and defining between them a notch (88); and - a second of the skates (34) has a tooth (90) defining at least part of the gripping surface (82) of said second skate, and arranged so as to fit between said two teeth (84, 86) of the first skate (32) in the configuration of mutual approach of the jaws (24).

3. Gripper according to claim 1 or 2, wherein at least one of the pads (32, 34) has a lug (98, 100) arranged at one end of the gripping surface (80, 82) located on a side opposite said extreme position, in the configuration of mutually approaching jaws (24), to limit the insertion depth of the rod (78) between the pads, in a direction opposite to the extreme position.

4. Gripping clamp according to any one of claims 1 to 3, wherein said support mechanisms (38) each comprise a ball guide rail (40).

5. Gripping clamp according to any one of claims 1 to 4, in which the support mechanisms (38) are configured so that the movements of the skates (32, 34) along said trajectories are rectilinear translations.

6. Gripping clamp according to any one of claims 1 to 5, in which the said elastic return means (36) comprise, for each of the pads (32, 34), a compression spring (50) interposed between a support plate (52) rigidly attached to the pad (32, 34) considered and a stop (54) rigidly attached to the corresponding jaw (24).

7. Gripping clamp according to claim 6, wherein said support plate (52) is arranged to come against the corresponding jaw (24) and thus define said extreme position.

8. Robotic device (10), comprising a robotic arm (12) provided with a modular end effector (16), and a grasping gripper (30) according to any one of claims 1 to 7, mounted on the modular end effector (16) via said mechanical interface (18). 16 9. A method for checking the contamination of a surface (112) of an object (110) by smearing, using a robotic device (10) according to claim 8, comprising steps consisting of: - A) to provide a smear tool (70) having, on one side, a smear surface (79), and on the opposite side, a gripping rod (78); - B) with the jaws (24) in their mutually separated configuration, maneuver the robotic device (10) so as to bring the gripper (30) into a position such that the gripping rod (78) of the smear tool (70) is positioned between the pads (32, 34); then - C) maneuver the robotic device (10) so as to move the jaws (24) towards their mutually approaching configuration until the gripping rod (78) of the smear tool (70) is clamped between the pads (32, 34); then - D) maneuver the robotic device (10) so as to bring the smear surface (79) into contact with the surface (112) of the object (110) and such that the elastic return means (36) apply a force on the pads (32, 34) resulting in pressure from the smear surface (79) on the surface (112) of the object; then - E) maneuver the robotic device (10) so that the smear surface (79) sweeps at least part of the surface (112) of the object; then - F) move the smear surface (79) away from the object (110); then - G) analyze the smear surface (79) in order to detect any possible contamination.

10. Method according to claim 9, wherein step G is carried out by means of a radioactivity detector.

11. Product computer program comprising code instructions for the execution of steps of a process according to claim 9 or 10, when said program is executed on an electronic control unit (120).

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