Patent Description:
A sliding nozzle device for use in a ladle or a tundish is composed using two or three refractory plates, each of which is attached to a respective one of two or three plate-receiving metal frames. When these plates reach the end of their life due to wear damage, it is necessary to open the sliding nozzle device to take out the old plates from respective ones of the plate-receiving metal frames, and replace the old plates with new ones. This replacement operation imposes a heavy burden on an operator, because it has to be performed under high temperature, and the weight of the plate, particularly heavy ones, is close to <NUM>.

Therefore, in recent years, it has been studied to perform the plate replacement operation using a robot arm. For example, one of the present inventors disclosed, in the below-mentioned Patent Document <NUM>, a plate holding apparatus capable of holding a plate in a state in which it is attached to a balancer or a robot arm. In a case where this plate holding apparatus is attached to a robot arm to perform the plate replacement operation, it is desired, from a viewpoint of further reducing the burden on an operator, etc., to also perform, by the robot arm, operation of selectively opening and closing an openable-closable component of the sliding nozzle device, such as a slide metal frame in which a sliding plate is received, a slide metal frame holding unit for holding the slide metal frame, or a spring box for applying a surface pressure.

Meanwhile, in an iron foundry, the sliding nozzle device is attached to the bottom of a molten steel pot such as a ladle or a tundish. Thus, when detaching a used plate, the plate assembled to the sliding nozzle device has to be detached from the side of the bottom of the molten steel pot in a state in which the molten steel pot is laid down. In this case, the molten steel pot is laid down by manipulating a crane. However, since the crane is manually manipulated, the laid-down position of the molten steel pot will vary by, e.g., several centimeters, each time.

Thus, in order to allow the aforementioned opening-closing operation for the openable-closable component of the sliding nozzle device to be performed under position control of the robot arm, the position of the sliding nozzle device has to be accurately measured each time. In recent years, measurement of the position of an object during use of the robot arm has been commonly performed, using of a technique of acquiring an image of the object by a camera, and subjecting the acquired image to image processing, thereby correcting positional coordinates of the object. However, with regard to the sliding nozzle device, it has been found that, in the image processing, there is a problem that a measurement accuracy in a front-rear direction (distance) becomes poor, although measurement accuracies in an up-down direction and in a right-left direction are at a practical level.

This is because the image is acquired during a drop in temperature of the sliding nozzle device just after being used at high temperature, so that the size of an image-acquisition reference area of the sliding nozzle device varies each image-acquisition due to thermal expansion, thereby an error in positional coordinates, particularly, in the front-rear direction (distance) is more likely to arise. Further, if undulation, flaw, adhesion of foreign substances or the like occurs in the image-acquisition reference area during use of the sliding nozzle device, it also becomes a factor causing an error in the image processing.

If a measurement error arises in the distance between the sliding nozzle device and the robot arm, the opening-closing operation for the openable-closable component of the sliding nozzle device is likely to become unable to be properly performed. For example, if the slide metal frame becomes unable to be opened to a given position, a problem will arise that, when taking out a plate by the robot arm in the next step, the slide metal frame is pushed and displaced, and thereby the plate becomes unable to be gripped by the robot arm. On the other hand, if the slide metal frame is not completely closed, a problem will arise that a surface pressure becomes unable to be applied in the next step.

As above, it has been found that, since the sliding nozzle device is used under a very severe condition that it receives radiation heat of molten steel having a temperature of <NUM> or more, while holding the plates through which the high-temperature molten steel passes, and is exposed to splash of the molten steel, and dust, the conventional position measurement technique has a problem of poor measurement accuracy in distance. Patent Document <NUM> relates to an assembly robot for assembling a workpiece into an object and its control method. Patent Document <NUM> relates to a plate holding device.

A problem to be solved by the present invention is to provide an opening-closing apparatus capable of selectively opening and closing an openable-closable component of a sliding nozzle device to respective given positions in a reliable manner.

The scope of the present invention is defined by independent claim <NUM>, and further embodiments of the invention are specified in dependent claims <NUM> and <NUM>.

The present invention makes it possible to selectively open and close the openable-closable component of the sliding nozzle device to respective given positions in a reliable manner.

An opening-closing apparatus <NUM> according to one embodiment of the present invention comprises: a hand tip part <NUM>; a plate holding device <NUM> detachably holding the hand tip part <NUM>; and a force sensor <NUM> disposed on the side opposite to the hand tip part <NUM> with respect to the plate holding device <NUM>, as shown in <FIG>, wherein the opening-closing apparatus <NUM> is formed by mounting an assembly of these components to a robot arm <NUM>, for example, as shown in <FIG>.

As shown in <FIG>, the hand tip part <NUM> comprises: a ring <NUM> serving as an engagement portion; a retainer rod <NUM> holding the ring <NUM>; and a base plate <NUM> having a central region to which the retainer rod <NUM> is fixed. The base plate <NUM> is composed of a rectangular-shaped metal plate, and provided with two protrusions <NUM> on a surface thereof opposite to the ring <NUM>.

The plate holding device <NUM> is composed using the plate holding device disclosed in the Patent Document <NUM>, and capable of detachably holding not only the hand tip part <NUM> of the opening-closing apparatus <NUM> according to this embodiment, but also a plate of a sliding nozzle device.

As shown in <FIG>, the force sensor <NUM> is assembled to the plate holding device <NUM> as the plate holding device disclosed in the Patent Document <NUM>, on the side opposite to a pressing portion <NUM> with respect to a parallel gripper (parallel hand) <NUM> serving as a widening and narrowing means. More specifically, the plate holding device <NUM> comprises: a parallel gripper <NUM> serving as a widening and narrowing means; a pair of (two) holding portions <NUM> each attached to a respective one of parallel claws <NUM> of the parallel gripper <NUM>; and a pressing portion <NUM> provided in front of a gripper body <NUM> of the parallel gripper <NUM>, and the force sensor <NUM> is provided on the side opposite to the pressing portion <NUM> with respect to the parallel gripper <NUM>. Further, each of the holding portions <NUM> has a respective one of two engagement grooves <NUM> formed at opposed positions to extend along respective distal edges of the holding portions <NUM>.

It should be noted here that the widening and narrowing means is not limited to the parallel gripper <NUM>. For example, a parallel chuck may be used. Alternatively, it may be composed using a hydraulic cylinder, an air cylinder or the like. Further, the widening and narrowing means is not necessarily limited to the configuration in which the pair of holding portions <NUM> are selectively widened and narrowed while maintaining a parallel relationship therebetween. For example, it may be configured such that a distance between the distal edges of the pair of holding portions <NUM> are selectively widened and narrowed by swinging movements of the pair of holding portions <NUM> about respective base ends (intersection point) thereof.

As shown in <FIG>, this plate holding device <NUM> is configured to hold four corners of the base plate <NUM> of the hand tip part <NUM> by the holding portions <NUM>, and simultaneously bring the pressing portion <NUM> into contact with the protrusions <NUM> of the base plate <NUM>, thereby making it possible to reliably the hand tip part <NUM> without wobbling.

The pressing portion <NUM> comprises seven bolts <NUM>, a support plate <NUM> having seven through-holes, seven coil springs <NUM>, and a base plate <NUM>, wherein each of the bolts is disposed to penetrate through a respective one of the through-holes of the support plate <NUM> and a respective one of the coil springs <NUM>, and fixed to the base plate <NUM>. The base plate <NUM> is attached to the gripper body <NUM> of the parallel gripper <NUM>. The pressing portion <NUM> further comprises a pressing plate <NUM> fixed to the support plate <NUM>, i.e., integrated with the support plate <NUM>, with a gap therebetween. Thus, the pressing plate <NUM> can be moved toward the base plate <NUM> while compressing the coil springs <NUM>. Here, a certain gap may be provided between each of the through-holes of the support plate <NUM> and a corresponding one of the bolts <NUM>. In this case, the pressing plate <NUM> can be moved even when it is in a tilted state. The pressing plate <NUM> is set at a position where the coil springs <NUM> are compressed when the base plate <NUM> of the hand tip part <NUM> is held by the holding portions <NUM> (engagement grooves <NUM>). Therefore, the base plate <NUM> of the hand tip part <NUM> held by the holding portions <NUM> is pressed against a region of an inner wall surface of each of the engagement grooves <NUM> on the far side with respect to the pressing portion <NUM>.

The force sensor <NUM> is attached to a flange <NUM> on the side opposite to the pressing portion <NUM> with respect to the gripper body <NUM> of the parallel gripper <NUM> by bolts. That is, the force sensor <NUM> is a sensor configured to detect a force received from the hand tip part <NUM> by the holding portions <NUM> and/or the pressing portion <NUM>. Such a force sensor to detect a force is also referred to as "haptic sensor", and a type of haptic sensor commonly used in robot arms or the like may be employed. In this embodiment, a six-axis force sensor is used as the force sensor <NUM>.

Next, with reference to <FIG>, the overall configuration and the usage state of the opening-closing apparatus according to this embodiment will be described. It should be noted that, in <FIG> and the after-mentioned <FIG>, the plate holding device <NUM> integrated with the force censor <NUM> is shown in an appropriately simplified form.

In <FIG>, a ladle <NUM> just after completion of casting is laid down on a ladle support <NUM> installed on a floor <NUM>. A sliding nozzle device <NUM> is attached to the bottom <NUM> of this ladle, and, in the posture illustrated in <FIG>, a sliding direction of a sliding plate thereof is approximately aligned with a vertical direction.

Abase end of the robot arm <NUM> is fixed to a robot arm mount <NUM> installed on the floor <NUM>, and a flange of the force sensor <NUM> integrated with the plate holding device <NUM> is mounted to a distal end of the robot arm <NUM> by bolts. Further, the hand tip part <NUM> is held by the plate holding device <NUM>. Here, the force sensor <NUM> and the distal end of the robot arm <NUM> are connected in series, such that central axes thereof are aligned with each other. It should be understood that the force sensor <NUM> may be separated from the plate holding device <NUM> and provided on the side of (integrated with) the robot arm <NUM>. In this case, the force sensor <NUM> and the distal end of the robot arm <NUM> are also connected in series, such that the central axes thereof are aligned with each other.

In this embodiment, the robot arm <NUM> is a <NUM>-axis vertical articulated robot arm, and capable of freely changing the posture and position of the hand tip part <NUM> mounted to the distal end thereof.

A three-dimensional sensor <NUM> comprising a camera 16a and a laser irradiator 16b is attached around the distal end of the robot arm <NUM>. An image acquired by the camera 16a is input to an image processing device, and, in the image processing device, three-dimensional positional coordinates are corrected by an image processing process. The resulting coordinate information is input to a control unit <NUM>, so that the robot arm <NUM> is moved to move the plate holding device <NUM> to an openable-closable component of the sliding nozzle device <NUM>. On the other hand, information detected by the force sensor <NUM> is continuously input in the control unit <NUM>. Then, based on the information from the force sensor <NUM>, etc., the control unit <NUM> controls movement of the hand tip part <NUM> via the robot arm <NUM>.

Next, with reference to <FIG>, a method of, after completion of casting, opening a slide metal frame holding unit <NUM> as one openable-closable component of the sliding nozzle device <NUM> attached to the bottom <NUM> of the ladle <NUM> will be described.

First of all, in <FIG>, while the slide metal frame holding unit <NUM> of the sliding nozzle device <NUM> is irradiated with laser light from the laser irradiator 16b, an image of the slide metal frame holding unit <NUM> is acquired by the camera 16a and subjected to image processing, thereby computing a misalignment of the slide metal frame holding unit <NUM> with respect to a reference position and correcting three-dimensional positional coordinates of the slide metal frame holding unit <NUM>. The corrected three-dimensional positional coordinates of the slide metal frame holding unit <NUM> is input to the control unit <NUM> (see <FIG>; with regard to the control unit <NUM> in the following description, also see <FIG>), so that the robot arm <NUM> is operated to move the hand tip part <NUM> mounted to the robot arm <NUM>, to a position illustrated in <FIG>.

In this embodiment, the slide metal frame holding unit <NUM> comprises an engagement rod <NUM> serving as a to-be-engaged portion for engagement with the hand tip part. The ring <NUM> of the hand tip part can be engaged with the engagement rod <NUM> in a state in which the ring <NUM> is freely fitted around the engagement rod <NUM> with a gap therebetween.

That is, the above position illustrated in <FIG> means a state in which the ring <NUM> of the hand tip part <NUM> is engaged with the engagement rod <NUM> of the slide metal frame holding unit <NUM>. As above, the engagement rod <NUM> and the ring <NUM> are engaged with each other in the state in which the ring <NUM> is freely fitted around the engagement rod <NUM> with a gap therebetween in a horizontal direction. Thus, even when a certain amount of error arises in the three-dimensional positional coordinates of the slide metal frame holding unit <NUM>, the engagement between the engagement rod <NUM> and the ring <NUM> can be achieved. In this embodiment, the outer diameter of the engagement rod <NUM> is set to <NUM>, and the inner diameter of the ring <NUM> is set to <NUM>, so that a gap to be formed therebetween in a horizontal direction is <NUM> on one side thereof. This gap may be determined depending on measurement accuracy of a position measurement device such as the aforementioned three-dimensional sensor <NUM>. For example, it may be set in the range of <NUM> to <NUM> on one side thereof.

From the state illustrated in <FIG>, the control unit <NUM> operates to controllably operate the robot arm <NUM> so as to start moving the hand tip part <NUM> in a direction causing the slide metal frame holding unit <NUM> to be opened. In this process, the hand tip part <NUM> receives a force in a tensile direction, and this force is detected by the force sensor <NUM>. In this embodiment, the tensile force is detected as a negative value. Further, in this embodiment, if the absolute value of the tensile force is less than a given threshold, the hand tip part <NUM> is moved to open the slide metal frame holding unit <NUM>.

Here, since the sliding nozzle device is used to control the flow rate of molten steel in a high-temperature environment, there can arise a situation where, due to seizure of the openable-closable component such as the slide metal frame holding unit <NUM> or adherence of molten steel and slag to the openable-closable component, a large force needs to or it becomes difficult to open the openable-closable component. In this situation, if the robot arm <NUM> is forcedly driven, the hand tip part, the plate holding device <NUM> or the robot arm <NUM> itself is likely to be damaged. In order to prevent such a damage, the hand tip part <NUM> is moved, if the absolute value of the force detected by the force sensor <NUM> is less than the given threshold.

With a view to detecting that the ring <NUM> of the hand tip part <NUM> fails to be engaged with the engagement rod <NUM> of the slide metal frame holding unit <NUM>, a lower limit of the absolute value of a force to be detected by the force sensor <NUM> may be set. Specifically, when the absolute value of the force detected by the force sensor <NUM> during the movement of the hand tip part <NUM> is less than a give value (the above lower limit), it may be determined that the ring <NUM> of the hand tip part <NUM> fails to be engaged with the engagement rod <NUM> of the slide metal frame holding unit <NUM>. In view of this, it can be said that, in this embodiment, the movement of the hand tip part <NUM> is performed if the absolute value of the force detected by the force sensor <NUM> falls within a given range (of the lower limit to the given threshold).

In the course of opening the slide metal frame holding unit <NUM>, it takes the state illustrated in <FIG>, and, when the slide metal frame holding unit <NUM> is fully opened, it reaches the state illustrated in <FIG>. The state illustrated in <FIG> is a state in which the slide metal frame holding unit <NUM> cannot be opened any more, and the absolute value of the force detected by the force sensor <NUM> reaches the given threshold. In the present invention, when the absolute value of the force detected by the force sensor <NUM> reaches the given threshold, the movement of the hand tip part <NUM> is stopped.

Here, although the three-dimensional positional coordinates of the slide metal frame holding unit <NUM> is measured by the three-dimensional sensor <NUM>, an error is likely to arise in the positional coordinates for the aforementioned reason. Thus, if the robot arm <NUM> is driven under position control, the above error causes a situation where the slide metal frame holding unit <NUM> cannot be opened to a desired position, which leads to the occurrence of a problem in an operation of detaching a plate by the robot arm <NUM> in the next step. On the other hand, if hand tip part <NUM> is further moved in the open direction despite the slide metal frame holding unit <NUM> has already been opened to the desired position, the hand tip part, the plate holding device <NUM> or the robot arm <NUM> is likely to be damaged. In order to prevent these problems, when the absolute value of the force detected by the force sensor <NUM> reaches the given threshold, the movement of the hand tip part <NUM> is stopped.

The slide metal frame holding unit <NUM> is located on each of both sides of a slide metal frame <NUM>. In this embodiment, the two slide metal frame holding units <NUM> are coupled together via a link, i.e., has a mechanism configured such that, when one of the slide metal frame holding units <NUM> is opened or closed, the other slide metal frame holding units <NUM> is also opened or closed in an interlocking manner.

Next, an operation of closing the slide metal frame holding unit <NUM> will be described. This operation is a reverse process with respect to the operation of opening the slide metal frame holding unit <NUM>, and thus the description will be started from the state illustrated in <FIG>.

In <FIG>, based on the three-dimensional positional coordinates of the slide metal frame holding unit <NUM> from the control unit <NUM>, the robot arm <NUM> is controllably operated to move the hand tip part <NUM> and engage the ring <NUM> of the hand tip part <NUM> with the engagement rod <NUM> of the slide metal frame holding unit <NUM>.

Subsequently, the hand tip part <NUM> is moved in a direction causing the slide metal frame holding unit <NUM> to be closed. In this process, the hand tip part <NUM> receives a force in a tensile direction, and this force is detected by the force sensor <NUM>. In this embodiment, the tensile force is detected as a negative value, as mentioned above. Further, in this embodiment, if the absolute value of the tensile force is equal to or less than a given threshold, the hand tip part <NUM> is moved to close the slide metal frame holding unit <NUM>. In the course of closing the slide metal frame holding unit <NUM>, it takes the state illustrated in <FIG>, and, when the slide metal frame holding unit <NUM> is fully closed, it reaches the state illustrated in <FIG>. The state illustrated in <FIG> is a state in which the slide metal frame holding unit <NUM> cannot be closed any more, and the absolute value of the force detected by the force sensor <NUM> reaches the given threshold. In this embodiment, when the absolute value of the force detected by the force sensor <NUM> reaches the given threshold, the movement of the hand tip part <NUM> is stopped.

Claim 1:
An opening-closing apparatus (<NUM>) for selectively opening and closing an openable-closable component of a sliding nozzle device (<NUM>), comprising:
a hand tip part (<NUM>) comprising an engagement portion, wherein the engagement portion is configured to be engaged with the openable-closable component of the sliding nozzle device (<NUM>) in a state in which the engagement portion is freely fitted around a portion of the openable-closable component with a gap therebetween in a horizontal direction;
a force sensor (<NUM>) configured to detect a force received by the hand tip part (<NUM>);
a robot arm (<NUM>) to which the hand tip part (<NUM>) and the force sensor (<NUM>) are mounted; and
a control unit (<NUM>) configured to control operation of the robot arm (<NUM>),
wherein the control unit (<NUM>) is configured to operate the robot arm (<NUM>) so as to: move the hand tip part (<NUM>) toward the openable-closable component of the sliding nozzle device (<NUM>) and engage the hand tip part (<NUM>) with the openable-closable component of the sliding nozzle device (<NUM>); then move the hand tip part (<NUM>) to move the openable-closable component, if an absolute value of the force detected by the force sensor (<NUM>) is less than a given threshold; and stop the movement of the hand tip part (<NUM>), when the absolute value of the force detected by the force sensor (<NUM>) reaches the given threshold,
wherein the engagement portion is a ring (<NUM>) at the hand tip part (<NUM>) configured to engage with an engagement rod (<NUM>) at the openable-closable component of the sliding nozzle device (<NUM>), or wherein the engagement portion is a rod at the hand tip part (<NUM>) configured to engage with an engagement ring at the openable-closable component of the sliding nozzle device (<NUM>).