Robotically actuated tool changer and method for changing tools

Abstract

A tool change system for replacing a dross removal tool mounted in a tool holder attached to an industrial robot and a method thereof. The tool change system includes a tool holder, a tool having a tool shaft with a plurality of connection elements spaced along the tool shaft, and a tool holder for storing the tool when not connected to the tool holder. A robot wrist end having the attached tool holder can engage the first connection element of the tool and exert an axial force and a rotational force on the tool shaft. The tool holder holding the tool can withstand the axial force and the rotational force, allowing the clamps in the tool holder to open and engage the second connection element to clamp the tool.

Description

TECHNICAL FIELD

[0001] The present invention relates to an industrial robot for removing dross and scum from a molten metal bath in a hot dip galvanizing line. In addition, the present invention relates to a tool change system for changing tools connected to a robot and a method thereof. BACKGROUND

[0002] After manufacturing steel and iron products, hot dip galvanizing is often performed to make the products more corrosion resistant and to improve durability, lifetime, versatility, stability or even aesthetics. A "clean" preheated product, such as a sheet, strip or plate, is placed in or passed through a molten metal electroplating bath comprising zinc, zinc alloy or any other suitable metal or metal alloy to provide a coating for the iron or steel.

[0003] Due to the reaction between the iron or steel and the molten metal or metal alloy, dross, slag and scum, hereinafter referred to as dross, is formed on the liquid surface of the bath. These impurities can severely affect the surface quality of the galvanized product, and therefore it is necessary to remove these impurities from the bath. This is usually done manually by an operator under very heavy and high-risk conditions.

[0004] The task of removing dross can also be performed by an industrial robot having a dross removal tool extending from a robot arm. Some robots use one tool only for removing dross, but this results in a relatively low efficiency. Therefore, robots have been developed with a change device that allows automatic change of the tool attached to the robot arm.

[0005] Patent application no. CN 109423588 A (Wei et al.) describes an example of a robot capable of automatically selecting a dross or scum removal tool. A tool change system for connecting and holding various tools is attached to the robot arm and is pneumatically driven under the control of a solenoid valve. A drawback of this robot is that a pneumatic circuit is needed to perform the clamping action, which results in a relatively complex design and reduces the robustness of use. Systems that make a bayonet type joint by axially aligning a chuck with the shaft of the tool and making axial and torsional movements to engage the chuck and the tool are also known. However, this type of connection is sensitive to the accuracy of the alignment and the presence of any debris on the end of the tool shaft.

[0006] It is desirable to provide a tool change system for a dross removal robot that has a less complex design and a higher robustness. In particular, the tool change system should be operable under conditions that are typically dominant in such environments, where dross, slag and other types of dirt can be trapped on the tool, making automatic engagement complex. SUMMARY

[0007] Thus, according to a first aspect of the present invention, there is provided an industrial robot for removing dross and scum from a molten metal electroplating bath in a hot dip galvanizing line. The robot comprises a robot body, a robot arm having a shoulder end connected to the robot body and a free wrist end, and a tool holder connected to the wrist end. The term "tool holder" refers here to a non-actuated, passive mechanism. The tool holder is configured to pick up, mount and put down a dross removal tool having a tool shaft and a plurality of connection elements extending outwardly from said tool shaft and spaced along said tool shaft. According to embodiments, the tool holder has a first jaw engaging a first connection element and a second jaw engaging a second connection element, whereby one of the jaws is displaceable relative to the other to engage and disengage the connection elements by movement of the robot arm, the displacement being effected by a series of forces exerted on the tool shaft of the tool by the counter force provided by the robot arm against the tool holder.

[0008] The displacement of one of the jaws relative to the other opens and closes the tool holder. One advantage of the tool holder is that the relative displacement of the jaws and the switching between tools can be driven and controlled entirely by the robot itself. This makes the gripping very robust and requires little or no maintenance on the tool holder. In the heavy-duty working environment of the robot, parts of external actuators or connections between the robot and external actuators can be prone to damage. The tool holder according to the invention does not require additional media, wires or other elements for controlling the pick-up, gripping and release of the tools. The tool holder is also relatively inexpensive to manufacture and has low maintenance costs.

[0009] The use of connection elements spaced along the tool shaft allows the tool holder to overcome large axial and rotational forces. In this context, rotational forces are intended to mean rotations about an axis perpendicular to the tool shaft, i.e. resulting in a bending moment in the shaft. Rotational forces coinciding with the axis of the shaft will be referred to as torsional forces.

[0010] In addition, the use of connection elements extending outwardly from the shaft makes the system very insensitive to debris. Parts of dross or other dirt on the tool shaft will not impede the connection, since the connection is established through the connection elements and not directly on the surface of the tool shaft itself. It will of course be understood that debris can also attach itself to the connection elements. However, the relevant dimensions of the connection elements can typically be smaller than the relevant dimensions of the shaft. Any dirt attaching itself to the connection elements will be more easily moved by the interaction with the jaws of the holder. In particular, for the same connection force exerted by the robot wrist end and the tool holder when making the connection, a greater pressure will be encountered on the surface of the smaller connection elements than on a larger diameter shaft.

[0011] It will be appreciated that the rotational force transmitted from the clamp to the tool during connection and use will depend on the critical dimension between the clamping surfaces. For a clamp according to the application having jaws engaging with the connection elements, this will be determined primarily by the distance between the connection elements. This should be at least greater than the width or diameter of the tool shaft. In embodiments, the first and second connection elements are spaced apart at a distance of at least three times the width of the tool shaft, preferably at a distance of about five times or more the width of the tool shaft. The spacing of the connection elements along the tool shaft results in a connection capable of withstanding a sufficiently large rotational force.

[0012] In embodiments, the tool shaft further has so-called holding elements spaced apart along the tool shaft. The holding elements are arranged to engage with the tool holder, thereby allowing the tool holder to withstand the axial and rotational forces exerted by the tool clamp. The connection of the tool shaft at multiple locations along the tool shaft allows the tool holder to overcome the axial and rotational forces exerted by the tool clamp while keeping the tool shaft in a fixed position. Preferably, the holding elements are also spaced apart along the tool shaft at a distance corresponding to the distance applicable to the connection elements. It will be appreciated that the force exerted to the connection elements will largely correspond to the force that the holding elements need to overcome.

[0013] In embodiments, the connection elements and the holding elements can coincide. In other words, the same elements or parts of the same elements can be used to engage the respective jaws of the clamp and also to engage the tool holder. Alternatively, the holding elements and the connection elements can be different and can be located at different positions along the tool shaft. The skilled person will appreciate the various structures that can be used as connection elements and holding elements, including plates, pins, flanges, hooks, barbs, etc.

[0014] In a preferred embodiment, pins are used, the pins extending from the shaft a sufficient distance to allow engagement by the jaws without the jaws being in direct contact with the shaft. Round pins are preferred, the diameter of the round pins being smaller than the width or transverse dimension of the shaft. The pins can be smaller than half the width of the shaft, or even smaller than one third of the width of the shaft. The jaws are preferably provided with recesses corresponding in shape to the shape of the connection elements. In the case of pins, the jaws can have slots of similar diameter to the pins, which can fall into the slots.

[0015] The first and second connection elements can be provided by a pair of upper pins and a pair of intermediate pins, and the holding elements can be provided by a pair of intermediate pins and a pair of lower pins. Thus, the intermediate pins or parts thereof serve both as connection elements for connecting the tool to the tool clamp and as holding elements for connecting the tool to the tool holder. This allows a compact design of the tool holder, in which the distance along the tool shaft for connecting the tool to the tool clamp and the tool holder is optimally used. Preferably, the distance between the upper pins and the intermediate pins and the distance between the intermediate pins and the lower pins are the same. The compactness allows the selection of tools having a relatively short tool shaft.

[0016] In this case, it can be desirable to arrange the jaws of the tool clamp to engage the pin with a width that is larger than the width of the tool holder engagement. The tool holder can be arranged to engage the pin with a width that is slightly wider than the width of the shaft. The jaws of the clamp can be arranged to engage the pin with a width that is slightly wider than the width of the tool holder. In this way, the clamp can fit around the tool holder during picking up and putting down of the tool. It should be understood that the reverse can also be true in case the tool holder fits around the clamp.

[0017] In an embodiment, the jaws of the tool clamp are biased towards each other by a spring element, wherein the first jaw is arranged to engage the first connection element when the spring is unloaded, and wherein the spring element is configured to allow the jaws to open when a force is exerted on the tool shaft, thereby providing space for the second jaw to engage the second connection element. The term "spring element" is used herein to refer to any type of spring or resilient element that biases the jaws in a direction towards each other. The jaws can only be opened when a sufficiently large force is exerted on the spring element. The jaws and the spring element contribute to a connection between the tool clamp and the tool that is rigid and has no slack.

[0018] In an embodiment, the tool clamp further comprises a blocking element that is movable between a first position in which the blocking element prevents the tool clamp from disengaging, and a second position in which the blocking element does not prevent the tool clamp from disengaging. The blocking element thus prevents the tool from disengaging accidentally. Preferably, the blocking element prevents the jaws from opening, thereby avoiding that only the spring element acts to keep the jaws closed. The blocking element can for example prevent the second connection element from leaving the second jaw by preventing axial movement of the second connection element, which can result in a force being exerted against the spring element.

[0019] In another embodiment, the blocking element is biased towards the first position. This allows the blocking element to passively lock the tool, since in the neutral position in which no external force is exerted, the blocking element prevents the tool mounted in the tool clamp from disengaging. The blocking element contributes to a connection between the tool clamp and the tool that is rigid and has minimal slack. Preferably, the blocking element is arranged to move to the second position by engaging against a portion of the tool holder. This movement can be part of a movement initiated by the robot arm, such that the blocking element is pressed against the tool holder with a force that is sufficient to overcome the bias of the blocking element.

[0020] In embodiments, the robot uses rotational and translational movements of the wrist end to control picking up and putting down the tool. Rotational and translational movements are also necessary for successful dross removal. In preferred embodiments, no additional wrist end degrees of freedom are needed at the wrist end in addition to the ones needed for dross removal. This makes the tool holder flexible for use with existing robots. In embodiments, the rotational and translational movements take place in a single plane. By rotating the tool holder onto the tool shaft, no sliding movement of the tool holder along the tool shaft surface is needed. In dirty environments, sliding of a surface can become difficult once the surface is contaminated with debris.

[0021] In embodiments, the first jaw is a pivotable upper jaw that is displaceable relative to a second, fixed lower jaw by pressing the tool down into the tool holder. This is convenient because the robot can easily apply pressure to the top surface of the tool shaft or to the upper surface of a connecting element extending from the tool shaft.

[0022] In embodiments, the tool holder comprises one or more centering members that contact the tool shaft around the contact surface. The centering members are arranged to provide lateral stability to the tool during the dross removal action. In preferred embodiments, the centering members contact the tool shaft over at least 50% of the circumference of the circumferential surface of the tool shaft and over less than 10% of the distance between the first pair of connecting elements along the tool shaft. The limited contact surface between the tool holder and the tool shaft prevents problems with connecting the tool once the contact surface has become dirty in the working environment.

[0023] According to yet another aspect of the invention, and according to the advantages and effects described above, a tool holder for use with an industrial dross removal robot is provided. In preferred embodiments, the tool holder comprises a conventional connector for attaching the tool holder to the wrist end of the industrial robot.

[0024] According to yet another aspect of the invention, and according to the advantages and effects described above, a tool holder for use with an industrial robot and a tool holder as described above is provided. The tool holder is configured to withstand the forces exerted by the industrial robot and the tool holder when engaging and disengaging the tool.

[0025] According to yet another aspect of the invention, and according to the advantages and effects described above, a dross tool for use with the robot, the tool holder and the tool holder described above is provided. The dross tool has a tool shaft configured to engage with the tool holder and the tool holder, and further has a property that facilitates the dross removal process. In embodiments, the tool can have different properties such as a sieve, a basket, a rake or a net. In addition, the tool can have different sizes or shaft lengths. The skilled person will understand when to use which tool.

[0026] According to another aspect of the application, a tool changer system is provided, comprising: a tool gripper configured to be connected to an end of a wrist of an industrial robot; a tool for removing dross and scum from a molten metal bath in a hot dip galvanizing line, the tool having a tool shaft and a plurality of connection elements extending outwardly from the tool shaft and spaced apart along the tool shaft by a distance greater than a width of the tool shaft; and a tool holder configured to be mounted in a tool docking station. The tool gripper has a first jaw and a second jaw configured to engage a first connection element and a second connection element, respectively, whereby at least one of the jaws is displaceable relative to the other to open and close the gripper, thereby engaging and disengaging the connection elements by movement of the tool gripper, thereby exerting a force on the tool shaft against a counter force provided by the tool holder.

[0027] The tool changer system can be used in combination with a conventional industrial robot. The tool gripper is easily attached to the end of the wrist of the industrial robot, and the tool changer mechanism relies only on actuation of the robot itself and the interaction between the tool gripper, the tool and the tool holder. No external actuation is required, which makes the tool changer system easy to use flexibly in combination with an already operating robot. In particular, although the application has been described in the context of a dross removal robot, the tool changer can also be implemented for changing similar tools, in particular tool changers used in challenging environments where debris accumulated on the shaft of the tool makes tool changing difficult.

[0028] In embodiments, the tool holder comprises a pair of side walls. The tool shaft is supported between the side walls with at least 1 mm of space between the outer surface of the tool shaft and the side walls. Preferably, the space between the outer surface of the tool shaft and the side walls is between 1 mm and 3 mm. This space provides some slack in the position of the tool shaft relative to the tool holder, which allows the system to deal with accumulation of debris, such as dross, slag, zinc spatters, dust or other types of dirt. Even if the debris crusts on the tool and / or the tool holder, the tool gripper can still place the tool in the tool holder. In particular, the tool can be moved away from a central position due to debris accumulated on one side of the shaft. As will be appreciated by the skilled person, the lateral engagement of the gripper with the tool described here is operable even when the tool shaft is not in the center of the holder.

[0029] The space between the tool shaft and the side walls also allows the tool holder to hold tools with different tool shaft diameters. In addition, the tool gripper can be configured to receive tools with different tool shaft sizes. In particular, within the range that the connection elements are still located in the same respective positions, the tool gripper can engage them regardless of the size or position of the shaft.

[0030] According to another aspect of the invention, and according to the advantages and effects described above, there is provided a method for picking up a dross removal tool from a tool holder in a tool docking station by an industrial robot. The industrial robot has a tool gripper attached to a wrist end of a robot arm, and the tool has a tool shaft with a plurality of connection elements extending outwardly from the tool shaft and spaced along the tool shaft. The method comprises the steps of engaging a first jaw of the tool gripper with a first connection element of the tool, exerting a series of forces on the tool shaft through a connection between the first jaw and the first connection element to open the tool gripper by increasing a distance between the first jaw and a second jaw of the tool gripper, wherein the tool holder is configured to provide a resistance to the series of forces, controlling the robot wrist end to engage the second jaw of the tool gripper with a second connection element, and controlling the robot wrist end to extract the tool from the tool gripper and lock the tool in the tool gripper.

[0031] A particular feature of the invention is to allow the tool to be exchanged mainly with lateral movement of the tool gripper towards the shaft of the tool in order to engage the shaft. This is in clear contrast to arrangements where a chuck or gripper is moved axially onto the shaft. Thus, according to embodiments, there is provided a tool exchange system comprising a passive tool gripper configured to be connected to a wrist end of an industrial robot, a tool having a tool shaft and a plurality of connection elements extending outwardly from the tool shaft and spaced along the tool shaft at a distance greater than a width of the tool shaft, and a tool holder, wherein the tool holder is arranged to pick up and put down the tool from the tool holder by action of the robot arm to move the tool holder in a mainly lateral direction relative to the tool shaft. Forces in an axial direction can be exerted on the connection elements to open and close the gripper. This lateral engagement avoids the need for alignment and axial movement of the gripper onto one end of the shaft, which requires higher precision and is more susceptible to the presence of debris on the shaft.

[0032] Advantageously, the robot can pick up the tool using only the motion of the robot itself, interacting with the tool and the tool holder. The tool gripper itself is a passive device. Once the tool is mounted in the tool gripper, a rigid connection with little slack is provided, which is strong enough to perform the dross removal action without accidentally falling off the tool. BRIEF DESCRIPTION OF DRAWINGS

[0033] Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which corresponding reference symbols indicate corresponding parts. In the drawings, like reference numerals indicate like parts. Multiple instances of an element can each be individually referred to as the element appended with a separate letter to the reference numeral. For example, two instances of a particular element "20" can be referred to as "20a" and "20b". The reference numeral can be used without the appended letter (e.g. "20") to generally refer to an unspecified instance or all instances of that element, whereas the reference numeral can include the appended letter (e.g. "20a") to refer to a particular instance of that element.

[0034] Figure 1 A perspective view of an embodiment of an industrial robot for removing dross from a zinc bath is shown schematically.

[0035] Figure 2 A front view of an embodiment of a dross removal tool is shown schematically.

[0036] Figure 3A A perspective view of an embodiment of a tool clamp is shown.

[0037] Figure 3B A perspective view of an embodiment of a tool clamp is shown. Figure 3C A partial cutaway perspective view of an embodiment of a tool clamp is shown.

[0038] Figure 3C A front view of an embodiment of a tool clamp is shown. Figure 3A A front view of an embodiment of a tool clamp is shown.

[0039] Figure 4 A tool docking station for use in conjunction with the tool clamp of Figure 3 is shown.

[0040] Figure 5 A to F show stages in a method of picking up a tool using the tool clamp of Figure 3. Figure 5

[0041] A to E show stages in a method of putting down a tool using the tool clamp of Figure 3. Figure 6 Figure 6 The drawings are for illustrative purposes only and are not intended to limit the scope or protection of the claims. DETAILED DESCRIPTION

[0042] The following is a description of certain embodiments of the invention given by way of example only and with reference to the accompanying drawings.

[0043]

[0044] Figure 1 ​​A perspective view of an industrial robot 1 is schematically shown for removing dross 5 from a zinc bath 9 in a continuous hot dip galvanizing line. Steel sheets (not shown) are guided through the zinc bath 9 which results in the formation of dross 5 on the surface of the zinc bath 9. The robot 1 is located at one side of the zinc bath 9 to remove dross 5 from the surface. Other devices as part of the hot dip galvanizing line can be located at the same side, or any other side, of the zinc bath 9. If desired, multiple dross removal robots 1 can be provided around the same zinc bath 9.

[0045] The robot 1 has a robot body 11 fixed to a base plate 3, and a robot arm 12 extending from a shoulder 15 of the robot body 11. The robot arm 12 has an upper arm 13 and a lower arm 14, and terminates in a wrist end 16. At the wrist end 16, a dross removal tool 4a is connected by a tool holder 2. The robot 1 can control the movement of the dross removal tool 4a. The dross 5 can be removed by dipping the tool 4a into the zinc bath 9 and performing a scooping movement just below the liquid surface. Subsequently, the robot 1 can lift the dross removal tool 4a and turn sideways to deposit the scooped material in a container 6.

[0046] Various tools 4a, 4b, 4c can be used to remove the dross 5. The robot 1 has a first tool 4a installed, but can automatically exchange the first tool 4a for another suitable tool 4b, 4c stored in a tool docking station 7. The tools 4 are held in tool holders 71 in the docking station 7. To put down the first dross removal tool 4a and pick up a second dross removal tool 4b, 4c, the robot 1 is turned around its own vertical axis so that the wrist end 16 of the robot 1 faces the docking station 7. Subsequently, the robot 1 performs a precise movement to put down the first tool 4a into an empty holder in the docking station 7, and to select a second tool 4b from another holder 71 in the docking station 7.

[0047] To achieve all these movements, the robot wrist end 16 is provided with at least five degrees of freedom. The first three degrees of freedom allow the wrist end 16 to perform translational movements in three-dimensional space. The fourth degree of freedom is for rotational movement around the normal axis z of the robot itself, to e.g. face the tool docking station 7 instead of the zinc bath 9. The fifth degree of freedom is a pitch movement around a transverse axis Y perpendicular to the normal axis z. In this embodiment, the pitch movement is needed to pick up or put down a tool 4 from the docking station 7. It will be appreciated that the robot 1 can have additional degrees of freedom, and that not all degrees of freedom are necessary in a particular embodiment.

[0048] Figure 2An embodiment of a dross removal tool 4 connectable to the robot 1 is schematically shown. The dross removal tool 4 has a cylindrical tool shaft 41 having a diameter of about 3 cm and a length of 1 m. In other embodiments, the tool shaft can also have another diameter, for example 4 cm or a diameter between about 2 cm and 5 cm. From one end of the tool shaft 41 extends a dross removal attribute 45. Alternative embodiments can have other attributes 45, for example a rake, a spatula, a sieve, a basket or a net. Preferably, the tool has both a surface capable of carrying removed dross and openings in the surface to release excess liquid back into the zinc bath 9. The person skilled in the art will understand the type of tool suitable for the dross removal process. It will also be understood that not all tools are used for scooping or sieving liquid, but for example also for stirring the liquid. In addition, different embodiments of the tool 4 can not only have different attributes 45, but also tool shafts 41 of different lengths.

[0049] A plurality of connection elements protrude from the tool shaft 41 and are arranged to connect the tool shaft 41 to the tool holder 2 of the robot 1. These connection elements can be subdivided into upper pins 43 and middle pins 42. In addition, a plurality of holding elements protrude from the tool shaft 41, which are arranged to connect the tool shaft 41 to the tool holder 71 in the docking station 7. The holding elements can be subdivided into lower pins 44 and middle pins 42.

[0050] The upper pins 43 are arranged close to the top end of the tool shaft 41. The middle pins 42 are at a distance of about 6 times the diameter of the tool shaft 41 from the upper pins 43. The middle pins 42 are spaced apart from the lower pins 44 at the same distance of about 6 times the diameter of the tool shaft 41.

[0051] Figure 3 shows an embodiment of the tool holder 2. Figure 3A To figure B shows a perspective view, elements Figure 3C A front view is shown. In Figure 3B For the sake of clarity, a plurality of components on one of the two symmetrical sides of the tool holder 2 are omitted.

[0052] The tool holder 2 has a connection plate 21 for connecting the tool holder 2 to the robot wrist end 16 (schematically shown in Figure 3A ). The connection plate 21 is connected to a frame 22 extending along a central axis C, which is defined as the axis along which the tool shaft 41 extends when mounted in the tool holder 2.

[0053] A plurality of centering members 23a, 23b are connected to the frame 22 and are spaced apart at different locations along the central axis C. The centering members 23 guide the tool shaft 41 and prevent any movement of the tool shaft 41 in a direction other than along the central axis C, or a radially outward unloading movement through the opening 26 between the two side walls which extend from the frame 22 on opposite sides of the central axis C. As such, the centering members 23 also prevent any rotation of the tool 4 other than rotation about the central axis C. In embodiments, the centering members 23 can be configured to provide guidance to respective tool shafts of a plurality of tools each having a different tool shaft diameter.

[0054] The side walls have an upper side wall portion 48 and a lower side wall portion 24. The lower side wall portion 24 includes a lower bearing seat 25 which is configured to receive the intermediate pin 42 extending from the tool shaft 41. The intermediate pin 42 is supported by the lower bearing seat 25 when the tool 4 is mounted in the tool clamp 2.

[0055] The upper side wall portion 48 is protected by a housing 27. The opening 26 between the side walls extends between two portions of the housing 27. The opening 26 extends in a direction parallel to the central axis C and is wide enough to allow the tool shaft 41 to enter laterally through the opening 26.

[0056] Figure 3B It is shown that the tool clamp 2 also has an upper bearing structure 29. The upper bearing structure 29 has two side bars 31 located on opposite sides of the central axis C, and a hinge 28 rotatably connected to the upper side wall portion 48. Each of the side bars 31 has an upper bearing seat 30 on its lower edge. These upper bearing seats 30 are arranged to receive the upper pin 43 extending from the tool shaft 41.

[0057] Two tension springs 32, one of which is shown, are located on opposite sides of the central axis C. The tension springs 32 are arranged to bias the upper bearing structure 29 to rotate about the hinge 28. A first end (not shown) of each tension spring 32 is connected to the lower side wall portion 24. A second end 34 of each tension spring 32 is connected to the upper bearing structure 29. As such, the upper bearing structure 29 can act as one jaw of the tool clamp 2. A second jaw of the tool clamp is provided by the lower side wall portion 24.

[0058] The tool holder 2 also comprises two cams 35 which guide the action of picking up and putting down the tool 4. In addition, the cams 35 provide a blocking mechanism when the tool 4 is installed. Each of the cams 35 has a tip 36 and a blocking portion 37. The cams 35 are connected to each other to rotate together about the transverse axis y and are biased by a torsion spring 38. The torsion spring 38 is connected to the frame 22 and biases the cams 35 towards a neutral position. In the shown view, the cams 35 are in the neutral position in which the blocking portions 37 are positioned above the exit path of the middle pin 42. In this way, the blocking portions 37 block the middle pin 42 from disengaging from the lower bearing seat 25.

[0059] Figure 3C A front view of the tool holder 2 is shown in which a tool shaft 41 of an installed tool is visible. The cams 35 are thin and each of the cams 35 is located in a narrow space between the tool shaft 41 and the lower side wall portion 24. The middle pin 42 has a larger diameter close to the tool shaft 41 and a smaller diameter towards the end. At the smallest diameter, the middle pin 42 engages with the lower bearing seat 25 in the lower side wall portion 24. This leaves space between the tool shaft 41 and the side wall portions 24, 48 for a portion of the tool holder 71 to engage with the middle pin 42. This portion of the tool holder 71 is also aligned with the cams 35.

[0060] In Figures 3A to 3C a position in which the tool 4 is installed in the frame 22. The connection of the tool 4 to the tool holder 2 is rigid. The clamping mechanism is provided by the lower bearing seat 25, the upper bearing structure 29 and the tension spring 32. In the unloaded position of the tension spring 32, the tool shaft 41 is prevented from moving along the central axis C. Only when the spring 32 is stretched, the tool holder is opened. The tool holder also partially prevents displacement in a direction perpendicular to the tool shaft 41.

[0061] In addition, the blocking portions 37 of the cams 35 prevent the middle pin 42 from disengaging from the lower bearing seat 25 and the centering member 23 prevents the tool shaft 41 from moving in the transverse direction. Due to the tool holder 2 supporting the tool 4 at different positions spaced along the tool shaft 41, rotation is also prevented.

[0062] Figure 4 An embodiment of a docking station 7 is shown which is suitable for use with the tool holder 2 of Figures 3A to 3C The docking station 7 has three tool holders 71 for receiving tools 4. Each of the tool holders 71 is symmetrically shaped and has a side wall 73 on each side of the central axis C. Here, the central axis C is again defined as the axis in the direction of the tool shaft 41 of the tool 4 when installed in the tool holder 71.

[0063] Each of the side walls 73 has a top wing 75 with a top seat 72 and a lower wing 76 with a lower seat 74. The top seat 72 is configured to accommodate the middle pin 42 of the tool 4, while the lower seat 74 is arranged to accommodate the lower pin 44 of the tool 4.

[0064] The side walls 73 and the wings 75, 76 are relatively thin and arranged with only a slight spacing from the tool shaft 41. Preferably, the space between the outer surface of the tool shaft 41 and the side walls 73 is between 5% and 10% of the diameter of the tool shaft 41. This spacing allows the system to handle some accumulation of debris on the tool 4 and the tool holder 71 without preventing or hindering the placement of the tool 4 in the tool holder 71. In this embodiment, the spacing between the tool shaft 41 and the tool holder side walls 73 is approximately 2 mm to 2.5 mm.

[0065] The spacing is small enough to allow the tool clamp 2 to be placed on the top wing 75 of the tool holder 71, which means that the tool clamp 2 accommodates the top wing 75 inside the housing 27 and in the space between the lower side wall portion 24 and the tool shaft 41, as described above in relation to Figure 3C The double installation position, i.e. the tool 4 is installed in both the tool clamp 2 and the tool holder 71, the top wing 75 is thus positioned between the tool shaft 41 and the lower side wall portion 24 of the tool clamp 2. In this double installation position, the thicker part of the middle pin 42 is supported by the top seat 72 of the top wing 75, and the thinner part of the middle pin 42 is supported by the lower support seat 25 of the tool clamp 2. The tool clamp 2 and the tool holder 71 are further aligned to allow the cam tip 36 to contact the edge 77 of the side wall 73 when picking up or putting down the tool.

[0066] Figure 5 A to Figure 5 F illustrates a method for picking up a tool 4 from a tool holder 71 in the docking station 7. The different steps are illustrated in a side view of the tool clamp 2 and the tool holder 71. For the sake of clarity, continuous lines are also used for parts of the components that are not visible in the side view.

[0067] Figure 5 A illustrates the starting position of the tool clamp 2 for picking up a tool 4. The central axis C of the tool clamp 2 is tilted relative to the main axis of the tool shaft 41. The robot 1 controls the movement of the tool clamp 2 in the slightly tilted state to approach the tool holder 71 laterally. The robot wrist end 16 moves the tool clamp 2 through the X-Z plane without rotating the tool clamp 2 until the upper support bar 29 comes into contact with the tool shaft 41. The sliding movement through the X-Z plane is continued until the upper pin 43 is engaged in the upper support seat 30.

[0068] Figure 5B shows this position. The formed connection allows the upper support structure 29 to pivot around the upper pin 43. After this connection is made, the robot wrist end 16 is rotated in the X-Z plane around the transverse axis Y while simultaneously pressing the tool 4 down into the tool holder 71. By supporting the tool shaft 41 in the top seat 72 and the lower seat 74 of the tool holder 71, the tool 4 is prevented from rotating in the X-Z plane. The resistance provided by the tool holder 71 allows the spring 32 to extend. Rotation is continued until the cam tip 36 contacts the edge 77 of the side wall 73 of the tool holder 71 Figure 5 C).

[0069] Rotation is then continued while the cam tip 36 remains in contact with the edge 77 of the side wall 73. The resistance provided by the edge 77 pushes the cam 35 inwards while the robot 1 continues to push the rotation. This resistance is sufficient to counteract the bias of the torsion spring 38 connected to the cam 35. The cam 35 rotates and the blocking portion 37 is moved out of the way to clear the path for the intermediate pin 42 in the lower support seat 25. At the same time, rotation continues and the top wing 75, including the top seat 72, is accommodated between the frame side wall 24 of the tool clamp 2 and the tool shaft 41.

[0070] Once the central axis C of the tool clamp 2 is aligned with the main axis of the tool shaft 41, rotation is automatically stopped. The lower support seat 25 of the frame 22 has now moved to a position below the intermediate pin 42 Figure 5 D).

[0071] The robot 1 then pulls the tool clamp 2 upwards along the central axis in a straight upwards direction Figure 5 E). The stretched spring 32 is unloaded and the intermediate pin 42 is automatically accommodated in the lower support seat 25. The tool 4 is now locked in the tool clamp 2 between the clamps formed by the stretched spring 32, the lower support seat 25 and the upper support structure 29.

[0072] The robot 1 can then move the tool clamp 2 away from the tool holder 71. When the tool clamp 2 is removed, the torsion spring 38 forces the cam 35 to automatically move back to their neutral position where the blocking portion 37 of the cam 35 is located above the lower support seat 25 Figure 5 F). The path for uncoupling the intermediate pin 42 is now blocked.

[0073] The entire process of picking up and installing a tool is driven by the motion of the robot itself and no external forces, energy or media are required to establish the lock other than the reaction forces due to the interaction between the robot 1 and the docking station 7. This has several advantages. For example, it makes the tool clamp 2 robust and relatively inexpensive. No external actuators are required to pick up the tool other than the robot itself.

[0074] The connection is made by rotation, in which the tool holder and the tool holder are in contact with each other only at a limited number of contact areas. Advantageously, the engagement of the tool does not require the surfaces of the tool holder and the surfaces of the tool to slide over each other. In the heavy work environment in which the sludge removal robot works, the surfaces are easily soiled or damaged, which can cause problems with the smooth sliding of two parallel surfaces. The tool holder according to the invention is free of this problem.

[0075] The method for picking up is thus robust and the precision required for picking up the tool is relatively low. Although the position of the tool shaft in the tool holder can not be precise, the tool holder is still able to pick up the tool from the tool holder. The robot can operate the tool holder with a very high precision of approximately a few tenths of a millimeter. Once the first jaw has engaged the first connection element, forces are exerted on the tool shaft of the tool that overcome the counter forces provided by the tool holder. These forces determine the position of the tool shaft in the tool holder, which is required for the engagement of the connection elements with the tool holder.

[0076] Figure 6 A to Figure 6 E shows the method for placing the tool 4 into the tool holder 71 of the docking station. Figure 6 A shows the starting position of the tool holder 2 for unloading the tool 4. The central axis C of the tool holder 2 is parallel to the central axis of the tool holder 71. The robot 1 controls the movement of the tool holder 2 to approach the tool holder 71 without rotating the tool holder.

[0077] Figure 6 B shows that the tool holder 2 first comes into contact with the tool holder 71 by the cam tip 36. The middle pin 42 and the lower pin 44 are located at a higher vertical height than the top seat 72 and the lower seat 74 of the tool holder 71, respectively. The cam tip 36 needs to be aligned with the edge 77 of the side wall 73.

[0078] After the first contact between the tool holder 2 and the tool holder 71, the movement is continued and the cam 35 is pushed inward into the housing 27 of the tool holder 2 between the upper wall portion 48 and the tool shaft 41. The movement is continued until the lower bearing seat 25 and the middle pin 42 are aligned with the central axis of the tool holder 71. The cam 35 is now fully retracted and the blocking portion 37 has moved away from the lower bearing seat 25.

[0079] The tool holder 2 is then moved downwardly so that the middle pin 42 is accommodated in the top seat 72 of the tool holder 71 and the lower pin 44 is located in the lower seat 74 of the tool holder 71.

[0080] Figure 6C shows the tool 4 in this double mounted position. To disengage the tool clamp 2, the robot 1 rotates the wrist end 16 while pushing the tool shaft 41 down in the top seat 72 and the lower seat 74 of the tool holder 71. The resistance provided by the tool holder 71 causes the tension spring 32 to extend, thereby opening the clamp formed by the lower support seat 25 and the upper support structure 29. Once the spring has extended enough, the tool clamp 2 can be removed from the tool holder 71 Figure 6 D).

[0081] While moving the tool clamp 2 away from the tool holder 71, the torsion spring 38 forces the cams 35 back to their neutral position. Then, the robot 1 with the tool clamp 2 is ready to pick up another tool 4 Figure 6 E).

[0082] The present application can be implemented in other specific forms without departing from the spirit or essential characteristics thereof. The described implementations are to be considered in all respects only as illustrative and not restrictive. The scope of the application is, therefore, indicated by the appended claims, rather than by the description preceding them. What is claimed is:

Claims

1. An industrial robot for removing dross and scum from a molten metal coating bath in a hot dip galvanizing line, the robot comprising: - a robot body; - a robot arm having a shoulder end and a wrist end, the shoulder end being connected to the robot body; and - a tool gripper connected to the wrist end and configured to pick up, mount and put down a dross removal tool, the dross removal tool being receivable in a tool holder of a tool docking station, the dross removal tool having a tool shaft and a plurality of connection elements extending outwardly from the tool shaft and being spaced along the tool shaft by a distance greater than a width of the tool shaft, wherein the tool gripper has a first jaw and a second jaw, the first jaw engaging a first connection element, the second jaw engaging a second connection element, one of the first jaw and the second jaw being a pivotable jaw, and wherein the other of the first jaw and the second jaw is a fixed jaw, wherein the pivotable jaw is displaceable relative to the fixed jaw to engage and disengage the connection elements by movement of the robot arm, wherein the first jaw and the second jaw are biased towards each other by a spring element, wherein the first jaw is arranged to engage the first connection element when the spring element is unloaded, and wherein the spring element is configured to allow the first jaw and the second jaw to open when a force is exerted on the tool shaft, thereby providing space for the second jaw to engage the second connection element, the displacement of the pivotable jaw being effected by the robot arm exerting a series of forces on the tool shaft of the dross removal tool overcoming a reaction force provided by the tool holder. the first connection element and the second connection element are spaced apart by a distance of at least three times the width of the tool shaft.

2. The robot of claim 1, wherein, the tool shaft has holding elements spaced along the tool shaft, the holding elements being arranged to engage the tool holder, thereby allowing the tool holder to take up forces exerted by the tool gripper.

3. The robot of claim 1 or 2, wherein, the first connection element and the second connection element each comprise a pair of upper pins and a pair of intermediate pins, and the pair of intermediate pins and a pair of lower pins form the holding elements.

4. The robot of claim 3, wherein, the tool gripper further comprises a blocking element displaceable between a first position in which the blocking element prevents the tool gripper from disengaging from the connection elements and a second position in which the blocking element does not prevent the tool gripper from disengaging.

5. The robot of claim 1 or 2, wherein, the blocking element is biased towards the first position.

6. The robot of claim 5, wherein, the blocking element is arranged to be displaced to the second position by engagement against a portion of the tool holder.

7. The robot of claim 5, wherein, the forces required to engage and disengage the connection elements are effected by rotational and translational movement of the wrist end in a plane aligned with the tool shaft.

8. The robot of claim 1 or 2, wherein, the first jaw is a pivotable upper jaw displaceable relative to the second jaw, the second jaw being a fixed lower jaw, by pressing the dross removal tool down into the tool holder.

9. The robot of claim 1 or 2, wherein, ​ 10. The robot of claim 1 or 2, wherein, The tool clamp comprises one or more centering members contacting the tool shaft along a contact area.

11. A tool holder, wherein, The tool clamp is connected to a wrist end of a robot arm and is configured to pick up, mount and put down a dross removal tool, which is accommodatable in a tool holder of a tool docking station, the dross removal tool having a tool shaft and a plurality of connection elements extending outwardly from the tool shaft and spaced apart along the tool shaft by a distance greater than a width of the tool shaft, wherein the tool clamp has a first jaw engaging a first connection element and a second jaw engaging a second connection element, one of the first jaw and the second jaw being a pivotable jaw and wherein the other of the first jaw and the second jaw is a fixed jaw, wherein the pivotable jaw is displaceable relative to the fixed jaw to engage and disengage the connection elements by movement of the robot arm, wherein the first jaw and the second jaw are biased towards each other by a spring element, wherein the first jaw is arranged to engage the first connection element when the spring element is unloaded, and wherein the spring element is configured to allow the first jaw and the second jaw to open when a force is exerted on the tool shaft, thereby providing space for the second jaw to engage the second connection element, the displacement of the pivotable jaw being performed by the robot arm exerting a series of forces on the tool shaft of the dross removal tool overcoming a counter force provided by the tool holder.

12. A tool holder in which a dross removal tool can be accommodated, the tool holder and the dross removal tool being used with a robot and a tool clamp, wherein, The tool clamp is connected to a wrist end of a robot arm of the robot and is configured to pick up, mount and put down the dross removal tool, the dross removal tool having a tool shaft and a plurality of connection elements extending outwardly from the tool shaft and spaced apart along the tool shaft by a distance greater than a width of the tool shaft, wherein the tool clamp has a first jaw engaging a first connection element and a second jaw engaging a second connection element, one of the first jaw and the second jaw being a pivotable jaw and wherein the other of the first jaw and the second jaw is a fixed jaw, wherein the pivotable jaw is displaceable relative to the fixed jaw to engage and disengage the connection elements by movement of the robot arm, wherein the first jaw and the second jaw are biased towards each other by a spring element, wherein the first jaw is arranged to engage the first connection element when the spring element is unloaded, and wherein the spring element is configured to allow the first jaw and the second jaw to open when a force is exerted on the tool shaft, thereby providing space for the second jaw to engage the second connection element, the displacement of the pivotable jaw is performed by the robot arm exerting a series of forces on the tool shaft against a counter force provided by the tool holder, and the tool holder is configured to withstand the forces exerted by the robot and the tool clamp when engaging and disengaging the dross removal tool, wherein the tool holder comprises a pair of side walls, a top seat and a lower seat, the tool shaft being supported in the top seat and the lower seat.

13. The tool holder of claim 12, wherein, There is at least 1 mm of space between the outer surface of the tool shaft and the side walls.

14. A tool change system comprising: - a tool clamp configured to be connected to a wrist end of an industrial robot; - a tool for removing dross and scum from a molten metal coating bath in a hot dip galvanizing line, the tool having a tool shaft and a plurality of connection elements extending outwardly from the tool shaft and spaced apart along the tool shaft by a distance greater than the width of the tool shaft; and - a tool holder configured to be mounted at a tool docking station; wherein the tool clamp has a first jaw configured to engage a first connection element and a second jaw configured to engage a second connection element, one of the first jaw and the second jaw being a pivotable jaw and the other of the first jaw and the second jaw being a fixed jaw, wherein the pivotable jaw is displaceable relative to the fixed jaw to engage and disengage the connection elements by movement of the robot arm, wherein the first jaw and the second jaw are biased towards each other by a spring element, wherein the first jaw is arranged to engage the first connection element when the spring element is unloaded, and wherein the spring element is configured to allow the first jaw and the second jaw to open when a force is exerted on the tool shaft, thereby providing space for the second jaw to engage the second connection element, the displacement of the pivotable jaw is performed by the robot arm exerting a force on the tool shaft against a counter force provided by the tool holder.

15. The tool changer system of claim 14, wherein, The tool holder comprises a pair of side walls, and wherein the tool shaft is supported between the pair of side walls, and there is at least 1 mm of space between the outer surface of the tool shaft and the side walls.

16. A method of picking up a dross removal tool from a tool holder in a tool docking station with an industrial robot, the industrial robot having a tool gripper attached to a wrist end of a robot arm, and the dross removal tool having a tool shaft with a plurality of connecting elements extending outwardly from the tool shaft and spaced apart along the tool shaft, wherein, The tool clamp comprises a pivotable first jaw, a fixed second jaw, and a spring element biasing the first jaw and the second jaw, wherein the method comprises the steps of: - engaging the first jaw of the tool clamp with a first connection element of the dross removal tool when the spring element is unloaded; - exerting a force on the tool shaft against a counter force provided by the tool holder to displace the pivotable jaw. - by the connection between the first jaw and the first connection element, exerting a series of forces on the tool shaft to tension the spring element and open the tool clamp by increasing the distance between the first jaw and the second jaw of the tool clamp, wherein the tool holder is configured to provide resistance to the series of forces; - controlling the robot wrist end to engage the second jaw of the tool clamp with the second connection element; and - controlling the robot wrist end to extract the dross removal tool from the tool holder and to lock the dross removal tool in the tool clamp.

Images