Patent Description:
Conventionally, a pallet conveying device in which, in a production line, a pallet for loading a work is mounted on a pallet rail and the pallet is conveyed to each of processing stations by circulating an endless belt to which the pallet is anchored has been proposed (see <CIT>).

In the above-described pallet conveying device, a so-called synchronous belt on which protrusions and recesses extending in the width direction are provided alternately in the longitudinal direction in a consecutive manner is used as the endless belt. The pallet is formed with protrusions and recesses that can engage with the protrusions and recesses of the endless belt, and the protrusions and recesses of the pallet are engaged with the protrusions and recesses of the endless belt in a state in which the pallet is mounted on a pallet rail.

In the above-described pallet conveying device, the pallet is conveyed by circulating the endless belt to which the pallet is anchored. When circulation of the endless belt is stopped, the conveyance of the pallet is also stopped. Therefore, for example, by stopping the circulation of the endless belt in a state in which the pallet faces the processing station, the work loaded on the pallet can be subjected to processing at the respective processing stations.

In the above-described pallet conveying device, the synchronous belt is used as the endless belt. Because the endless belt needs to be circulated along the pallet rail, the endless belt has a flexibility. Thus, even if the protrusions and recesses of the pallet are engaged with the protrusions and recesses of the endless belt, gaps required for the circulation are formed therebetween. Therefore, in the above-described pallet conveying device, even if the position of the endless belt in the circulation can be controlled accurately, the position of the pallet anchored to the endless belt will be deviated by an amount corresponding to the gaps.

If such a deviation is caused between the endless belt and the pallet, it becomes difficult to cause the pallet to face the processing station accurately even if the circulation of the endless belt is accurately controlled. Thus, the conventional pallet conveying device is provided with a pallet-movement locking mechanism for allowing the pallet to face the processing station accurately. The general pallet-movement locking mechanism includes those provided with an anchoring hole formed in each pallet so as to face each of the processing stations and a fixing cylinder provided on each of the processing stations.

The fixing cylinder is a fluid pressure cylinder that is configured such that a pin inserted into the anchoring hole can be moved in and out. The pin is inserted into the anchoring hole by extending the fixing cylinder, and thereby, the pallet is allowed to face the processing station accurately and the movement of the pallet is prohibited in this state. By pulling out the pin from the anchoring hole by contracting the fixing cylinder, it becomes possible to move the pallet subsequently. <CIT> discloses a device according to the preamble of claim <NUM> and proposes to accurately position a workpiece in various areas of a conveying track by installing a belt-like driving member on two vertical directional guide lanes of a conveying direction and forming a crossing directional guide lane of a propelling device. A table plate is fixed on a housing part, a traveling member is supported on a height guideway through a guide roller, a side guideway is formed of a side guide surface of two reversing rollers, and a guide passage is formed together with the side guide surface of the traveling member. Since a rack is inserted into this area, a driving member meshes with the tooth part to constitute a feed device so as to perform feeding operation of the traveling member.

However, in the pallet-movement locking mechanism using the fluid pressure cylinder, in order to allow the pallet to face the processing station, the fluid pressure cylinder is extended to insert the pin into the anchoring hole after the circulation of the endless belt is stopped. In addition, the pallet that has been subjected to the processing needs to be moved after pulling the pin out from an anchoring hole by contracting the fluid pressure cylinder.

Thus, the time required for the extension or the contraction of the fluid pressure cylinder and the confirmation time required for a sensor to detect completion of the extension or the contraction are required in addition to the time required to convey the pallet, and therefore, it is conceivable that the time required for the conveyance of the pallet is increased.

In addition, in a case in which the pallet is stopped multiple times at narrow pitches, it is required to provide a plurality of fluid pressure cylinders at the narrow pitches. However, due to a mutual interference between the fluid pressure cylinders, it is not possible to arrange the fluid pressure cylinders at the pitches smaller than the external size of the fluid pressure cylinder. This means that it is not possible to stop the pallet multiple times at the pitches smaller than the external size of the fluid pressure cylinder. In other words, the pitches of the positions for stopping the pallet are limited.

An object of the present invention is to achieve accurate positioning of the pallet by eliminating gaps between protrusions and recesses of an endless belt and protrusions and recesses of a pallet.

The object is achieved with a pallet conveying device according to claim <NUM>.

The object is also achieved with a conveyed-pallet retaining method according to claim <NUM>.

In the following, a pallet conveying device <NUM> according to an embodiment of the present invention will be described with reference to <FIG>.

In the respective figures, mutually orthogonal three axes X, Y, and Z are set. The configuration of the pallet conveying device <NUM> will be described by stating that the X axis extends in the substantially horizontal transverse direction, the Y axis extends in the substantially horizontal front-rear direction, and the Z axis extends in the vertical direction. The pallet conveying device <NUM> in this embodiment illustrates a device that is provided in a production line for stators of electric motors, such as motors, etc. As shown in <FIG>, in the production line in this embodiment, three processing stations <NUM> to <NUM> are arranged linearly along the X axis direction at predetermined intervals.

The each of the processing stations <NUM> to <NUM> has a box shape and contains a machine tool (not shown) installed therein. The machine tools in the respective processing stations <NUM> to <NUM> automatically produce the stators (not shown) by performing various processing, such as an insertion of an insulating member, a swaging of a lead wire of a coil of various phase, an welding, and so forth, in a certain order, to a work (not shown) that is conveyed by the pallet conveying device <NUM>. The pallet conveying device <NUM> is provided with a pallet rail <NUM> that links a standby position and the plurality of processing stations <NUM> to <NUM>, which are arranged so as to be distributed along the line, and a pallet <NUM> mounted on the pallet rail <NUM>.

The plurality of processing stations <NUM> to <NUM> are arranged linearly along the X axis direction, and a standby table <NUM> serving as the standby position is arranged on the extension line thereof. The plurality of processing stations <NUM> to <NUM> respectively have platforms 11a to 13a on which the pallet rail <NUM> is fixed. The standby table <NUM> is provided with a top plate 14a on which the pallet rail <NUM> is fixed.

As shown in <FIG>, the pallet rail <NUM> in this embodiment is provided with a support plate <NUM> with a cross-section having a rectangular shape elongated in the Z axis direction and a commercially available linear-motion guide rail <NUM> that is fixed to an upper edge of the support plate <NUM> by screws. An attachment plate <NUM> is welded to a lower end of the support plate <NUM>. The attachment plate <NUM> is directly fixed to the platforms 11a to 13a of the respective processing stations <NUM> to <NUM> and the top plate 14a of the standby table <NUM> by screws (in <FIG>, the attachment plate <NUM> is fixed to the platform 13a of the third processing station <NUM>).

In other words, as shown in <FIG>, the pallet rail <NUM> is fixed to the platforms 11a to 13a of the respective processing stations <NUM> to <NUM> and the top plate 14a by the screws. With such a configuration, the pallet rail <NUM> is fixed so as to link the standby position above the standby table <NUM> and the plurality of processing stations <NUM> to <NUM>.

As shown in <FIG>, the pallet <NUM> has linear motion blocks 21a that catch the pallet rail <NUM>, a base 21b that is fixed to the linear motion blocks 21a by screws, and anchoring members <NUM> that are provided under the base 21b. The linear motion blocks 21a are configured so be movable on the pallet rail <NUM>.

The linear motion block 21a is commercially available as a pair with the linear-motion guide rail <NUM> of the pallet rail <NUM>. As shown in <FIG>, two linear motion blocks 21a are provided under the base 21b so as to be separated from each other in the X axis direction. By using the linear motion blocks 21a, it is possible to reduce resistance caused for the movement of the pallet <NUM> on the pallet rail <NUM> while prohibiting the movement thereof in the width direction (in the Y axis direction). With such a configuration, the pallet <NUM> is movably mounted on the pallet rail <NUM>.

A work supporting tool (not shown) for loading the work is further mounted on the base 21b of the pallet <NUM>. The pallet <NUM> is capable of holding the work with the work supporting tool. Details of the anchoring members <NUM> will be described later.

As shown in <FIG>, the pallet conveying device <NUM> is provided with pallet convey means <NUM> that conveys the pallet <NUM> along the pallet rail <NUM> between the standby position above the standby table <NUM> at which the pallet <NUM> is to be mounted and the plurality of processing stations <NUM> to <NUM> that are provided at positions away from the standby position. In this embodiment, the pallet convey means <NUM> is provided with an endless belt <NUM> that is provided so as to be able to circulate along the pallet rail <NUM>.

On both ends of the pallet rail <NUM> in the longitudinal direction, a first pulley <NUM> and a second pulley <NUM>, over which the endless belt <NUM> is suspended, are respectively provided. The first pulley <NUM> and the second pulley <NUM> in this embodiment are the same pulleys with the same shape and size. The pallet convey means <NUM> is further provided with a first actuator that rotationally drives the first pulley <NUM> and a second actuator that rotationally drives the second pulley <NUM>.

In this embodiment, a case in which both of the first pulley <NUM> and the second pulley <NUM> are rotated is shown. In the following, the second pulley <NUM> shown in <FIG> will be described as a representative. The second pulley <NUM> is provided with a pulley main body portion 24a around which the endless belt <NUM> is suspended and flanges 24b and 24c that are provided on both sides of the pulley main body portion 24a and that hold the endless belt <NUM> from the both sides in the width direction.

As shown in <FIG>, the first actuator and the second actuator are electrically driven servomotors that respectively rotate the first pulley <NUM> and the second pulley <NUM>. A first servomotor <NUM> serving as the first actuator, in which the first pulley <NUM> is attached to a rotating shaft, is attached to the first processing station <NUM>, and a second servomotor <NUM> serving as the second actuator, in which the second pulley <NUM> is attached to a rotating shaft 29a, is attached to the standby table <NUM>.

Because the first servomotor <NUM> and the second servomotor <NUM> have the same attachment configurations, the configuration for attaching the second servomotor <NUM> to the standby table <NUM> will be described as a representative. As shown in <FIG> and <FIG>, the support plate <NUM> of the pallet rail <NUM> is attached to the standby table <NUM>, and the second servomotor <NUM> is attached to an end portion of the support plate <NUM> such that the rotating shaft 29a is aligned with the Y axis direction. The second pulley <NUM> is attached to the rotating shaft 29a of the second servomotor <NUM> extending in the Y axis direction.

The endless belt <NUM> is a so-called synchronous belt. As shown in detail in <FIG>, on the endless belt <NUM>, protrusions and recesses 27a and 27b extending in the width direction are formed alternately in the longitudinal direction in a consecutive manner. The anchoring members <NUM> of the pallet <NUM> are formed with protrusions and recesses 26a and 26b that can engage with the protrusions and recesses 27a and 27b. In other words, the protrusions and recesses 26a and 26b are mesh teeth that mesh with the protrusions and recesses 27a and 27b of the endless belt <NUM>.

As shown in <FIG>, idle pulleys <NUM> are respectively provided on both end portions of the pallet rail <NUM>. With such a configuration, on the upper region side of the pallet rail <NUM> where the pallet <NUM> is to be mounted, the endless belt <NUM> is provided such that the protrusions and recesses 27a and 27b face the outer side. On the upper region side of the pallet rail <NUM>, which is the side where the pallet <NUM> is to be mounted, the idle pulleys <NUM> are respectively provided on the both sides of the pallet rail <NUM> in the longitudinal direction of the support plate <NUM>. The idle pulleys <NUM> guide the endless belt <NUM> to the end portion of the pallet rail <NUM> in the longitudinal direction so as to extend along the pallet rail <NUM>, and support the endless belt <NUM>.

On the both end portions of the pallet rail <NUM>, suspending pulleys <NUM> are respectively provided on the lower side of the first pulley <NUM> and the second pulley <NUM> such that the first pulley <NUM> and the second pulley <NUM> are respectively located between the suspending pulley <NUM> and the idle pulley <NUM>. The suspending pulleys <NUM> press, together with the idle pulleys <NUM>, the endless belt <NUM> towards the first pulley <NUM> and the second pulley <NUM> from the inner side of the pallet rail <NUM> in the longitudinal direction such that the endless belt <NUM> is suspended around the first pulley <NUM> and the second pulley <NUM>.

A detailed description will be given with reference to the configuration on the second pulley <NUM> side. As shown in <FIG>, the endless belt <NUM> is suspended around an outer circumference of the second pulley <NUM>. The outer circumference of the second pulley <NUM> is formed with protrusions and recesses 24d and 24e, which are capable of engaging with the protrusions and recesses 27a and 27b of the endless belt <NUM>, in the circumferential direction in a consecutive manner. The suspending pulleys <NUM> press, together with the idle pulleys <NUM>, the endless belt <NUM> towards the second pulley <NUM> from the inner side of the pallet rail <NUM> in the longitudinal direction. With such a configuration, the endless belt <NUM> is suspended around the second pulley <NUM>.

The suspending pulleys <NUM> are respectively provided on the both sides of the pallet rail <NUM> in the longitudinal direction of the support plate <NUM> via position adjusting mechanisms <NUM>. As shown in <FIG> and <FIG>, each of the position adjusting mechanisms <NUM> is provided with small rails 35a that are provided so as to extend in the longitudinal direction of the support plate <NUM>, a pivotably supporting stage 35b that is provided on the small rails 35a so as to be movable, a support stage 35c that is attached to the support plate <NUM>, and a screw member 35d that is provided on the support stage 35c so as to move the pivotably supporting stage 35b along the small rails 35a.

The suspending pulley <NUM> is pivotably supported by the pivotably supporting stage 35b of the position adjusting mechanism <NUM>. By adjusting the position of the pivotably supporting stage 35b in the longitudinal direction of the support plate <NUM> by moving the pivotably supporting stage 35b by the screw member 35d, it is possible to adjust the position of the suspending pulley <NUM> in the longitudinal direction of the pallet rail <NUM>.

By moving the suspending pulleys <NUM> provided on the both ends of the pallet rail <NUM> so as to be separated away from each other, it is possible to apply tension on the endless belt <NUM> that is suspended over the suspending pulleys <NUM>. As the tension is applied to the endless belt <NUM>, the endless belt <NUM> extending between the suspending pulley <NUM> and the idle pulley <NUM> are respectively pressed against the first pulley <NUM> and the second pulley <NUM>. Thus, the protrusions and recesses 27a and 27b are caused to engage with the protrusions and recesses of the first pulley <NUM> and the second pulley <NUM> without forming a gap therebetween. Therefore, by rotating the first pulley <NUM> and the second pulley <NUM>, it is possible to cause the endless belt <NUM> to circulate without deviation.

Reference sign <NUM> in <FIG> shows a belt receiver <NUM> that is provided on the support plate <NUM> in the vicinity of the idle pulley <NUM>. The belt receiver <NUM> is provided so as to extend in parallel with an upper region side belt 27c (the upper region side belt 27c of the endless belt <NUM>) that is suspended over the two idle pulleys <NUM>. When the upper region side belt 27c is deflected at the vicinity of the idle pulleys <NUM>, the belt receiver <NUM> comes into contact with the upper region side belt 27c to suppress further deflection and/or vibration.

As shown in <FIG>, the first pulley <NUM> is provided on the first processing station <NUM>, and the second pulley <NUM> is provided on the standby table <NUM>. The endless belt <NUM> that is suspended and tensioned around the first pulley <NUM> and the second pulley <NUM> is provided so as to link the standby position and the first processing station <NUM> at the most distant from the standby position along the pallet rail <NUM>.

The first servomotor <NUM> and the second servomotor <NUM> that respectively rotate the first pulley <NUM> and the second pulley <NUM> are respectively connected to control outputs from a controller <NUM>. The controller <NUM> is configured so as to perform a synchronous control of the first servomotor <NUM> and the second servomotor <NUM>. As the first servomotor <NUM> and the second servomotor <NUM> are driven by the synchronous control performed on the basis of instructions from the controller <NUM>, the first pulley <NUM> and the second pulley <NUM> are also rotated together with the rotating shafts of the first servomotor <NUM> and the second servomotor <NUM>. When the first pulley <NUM> and the second pulley <NUM> are rotationally driven in a state in which the endless belt <NUM> is tensioned, the endless belt <NUM> that is suspended by extending in the longitudinal direction of the pallet rail <NUM> is circulated.

The endless belt <NUM> is provided such that the protrusions and recesses 27a and 27b face outer side. Thus, as shown in <FIG>, the upper region side belt 27c of the endless belt <NUM> extends along the pallet rail <NUM> in a state in which the protrusions and recesses 27a and 27b face upward. Lower surfaces of the anchoring members <NUM> that are provided under the base 21b are formed with the protrusions and recesses 26a and 26b that engage with the protrusions and recesses 27a and 27b.

In other words, as the pallet <NUM> is mounted on the pallet rail <NUM> and the anchoring members <NUM> are placed from above over the upper region side belt 27c that is provided along the pallet rail <NUM>, the protrusions and recesses 27a and 27b formed on the endless belt <NUM> are caused to engage with the protrusions and recesses 26a and 26b of the anchoring members <NUM>.

Once the protrusions and recesses 26a and 26b of the pallet <NUM> engage with the protrusions and recesses 27a and 27b of the endless belt <NUM>, the movement of the pallet <NUM> in the longitudinal direction independent of the endless belt <NUM> is prohibited. With such a configuration, the pallet <NUM> is anchored to the endless belt <NUM>. As described-above, the pallet <NUM> mounted on the pallet rail <NUM> can be anchored by the endless belt <NUM> serving as the synchronous belt.

As the endless belt <NUM> to which the pallet <NUM> is anchored is circulated, the pallet <NUM> is moved along the pallet rail <NUM> together with the endless belt <NUM>. Thus, the pallet <NUM> can be conveyed, together with the work (not shown) loaded on the pallet <NUM>, along the pallet rail <NUM> along which the endless belt <NUM> extends.

Belt supporting devices <NUM> are provided on the support plate <NUM>. The belt supporting devices <NUM> prevent disengagement between the protrusions and recesses 27a and 27b of the endless belt <NUM> and the protrusions and recesses 26a and 26b of the anchoring members <NUM> that may be caused when the endless belt <NUM> is deflected and separated from the anchoring members <NUM>.

As shown in <FIG>, and according to the invention, each of the belt supporting devices <NUM> has: carrying tools <NUM> on which the upper region side belt 27c engaged with the anchoring members <NUM> is carried so as to be movable in the longitudinal direction; and coil springs <NUM>, each serving as biasing means, that bias the carrying tools <NUM> such that the protrusions and recesses 27a and 27b of the upper region side belt 27c carried on the carrying tools <NUM> are pressed against the protrusions and recesses 26a and 26b of the anchoring members <NUM>.

As shown in <FIG> and <FIG>, and according to the invention, the carrying tools <NUM> are located under the upper region side belt 27c and each has: a bottom plate <NUM> that extends in the longitudinal direction of the upper region side belt 27c; a pair of side walls <NUM> and <NUM> that are provided on both sides of the bottom plate <NUM> so as to be erected upright and so as to sandwich the upper region side belt 27c from both sides in the width direction; and a plurality of rollers <NUM> that are provided between the pair of side walls <NUM> and <NUM>.

As shown in <FIG>, the lengths L of the bottom plate <NUM> and the pair of side walls <NUM> and <NUM> in the longitudinal direction of the upper region side belt 27c are set so as to be substantially equal to or slightly smaller than the length S of the base 21b in the longitudinal direction of the pallet rail <NUM>. As shown in <FIG>, stepped portions 43b, into which both sides of the endless belt <NUM> respectively fall, are respectively formed on upper edges of the pair of side walls <NUM> and <NUM>.

As shown in <FIG> and <FIG>, in this embodiment, the four rollers <NUM> are respectively provided between the pair of side walls <NUM> and <NUM> so as to be aligned in the extending direction of the endless belt <NUM> and so as to be rotatable. The upper region side belt 27c side edges of which respectively enter the stepped portions 43b in between the pair of side walls <NUM> and <NUM> comes into contact with the four rollers <NUM>. As the four rollers <NUM> are rotated, it is possible to circulate the endless belt <NUM> without resistance. As shown in an enlarged view in <FIG>, inclined surfaces 43a that guide the endless belt <NUM> between the pair of side walls <NUM> and <NUM> are respectively formed on both sides of the pair of side walls <NUM> and <NUM> in the longitudinal direction.

The coil springs <NUM> bias the carrying tool <NUM> such that the protrusions and recesses 27a and 27b of the upper region side belt 27c carried by the carrying tool <NUM> are pressed against the protrusions and recesses 26a and 26b of the anchoring members <NUM>. Housings <NUM> are attached to the support plate <NUM> of the pallet rail <NUM>. Each of the housings <NUM> supports a plurality of carrying tools <NUM> (two carrying tools <NUM> in this embodiment). Supporting shafts <NUM> penetrate through the housing <NUM> in the vertical direction. The supporting shafts <NUM> are provided so as to be movable in the shaft direction.

The carrying tool <NUM> is attached to upper ends of the supporting shafts <NUM>. In this embodiment, a single carrying tool <NUM> is supported by two supporting shafts <NUM>. As shown in <FIG>, the housing <NUM> supporting the two carrying tools <NUM> is provided with the four supporting shafts <NUM> at predetermined intervals in the longitudinal direction of the housing <NUM>. Two carrying tools <NUM> are separately and independently attached on the upper ends of the four supporting shafts <NUM>. Reference signs <NUM> show slide bushes <NUM> that are provided in the housing <NUM> to support the supporting shafts <NUM> so as to be movable in the shaft direction.

The coil springs <NUM> are respectively interposed at the supporting shafts <NUM> between the carrying tools <NUM> and the housing <NUM> in a compressed state. An extending force exerted by the coil springs <NUM> acts in the direction in which the carrying tools <NUM> are separated away from the housing <NUM>. In a state in which the pallet <NUM> faces the carrying tool <NUM>, the upper region side belt 27c carried by the carrying tool <NUM> is pressed against the anchoring member <NUM>. In this embodiment, the biasing force exerted by the coil spring <NUM> is set to be from <NUM> to <NUM> N.

As in the carrying tools <NUM> shown on both sides in <FIG>, in a state in which the pallet <NUM> is not facing the carrying tool <NUM>, the supporting shafts <NUM> move upward in the Z axis direction by the biasing force exerted by the coil springs <NUM>. However, ring members <NUM> are respectively attached to lower parts of the supporting shafts <NUM> penetrating through the housing <NUM>. As the supporting shafts <NUM> move upward together with the carrying tool <NUM> and the ring members <NUM> come into contact with a lower surface of the housing <NUM>, a further upward movement of the supporting shafts <NUM> is prohibited. In other words, the ring members <NUM> limit a movable range R of the carrying tool <NUM>.

The movable range R of the carrying tool <NUM> in this embodiment, in other words, a lifted amount of the carrying tool <NUM> from the position of the carrying tool <NUM> in a state in which the upper region side belt 27c carried by the carrying tool <NUM> is pressed against the anchoring members <NUM> of the pallet <NUM> to the position of the carrying tool <NUM> in a state in which the pallet <NUM> is not present is less than the height h of the protrusions and recesses 27a and 27b of the endless belt <NUM>. In addition, as shown in the enlarged view in <FIG>, the depth F of the stepped portions 43b formed in the upper edges of the pair of side walls <NUM> and <NUM> is larger than the movable range R of the carrying tools <NUM> and smaller than the thickness D of the endless belt <NUM> (<FIG>).

The belt supporting devices <NUM> having the carrying tools <NUM> and the coil springs <NUM> as described above are provided at least at positions where the pallet <NUM> needs to be stopped by stopping the conveyance of the pallet <NUM>.

In this embodiment, the pallet conveying device <NUM> is provided so as to link the respective processing stations <NUM> to <NUM>. The machine tool in each of the processing stations <NUM> to <NUM> performs various processing on the work conveyed by the pallet conveying device <NUM>. Thus, the conveyance of the pallet <NUM> on which the work is loaded needs to be stopped in a state in which the pallet <NUM> is facing each of the processing stations <NUM> to <NUM> until the processing performed by the machine tool in each of the processing stations <NUM> to <NUM> is finished. Therefore, the belt supporting devices <NUM> are provided at least at the positions opposing to the respective processing stations <NUM> to <NUM>.

However, as shown in <FIG>, the plurality of carrying tools <NUM> are provided on the support plate <NUM> of the pallet rail <NUM> in the longitudinal direction in a continuous manner. In other words, in this embodiment, a plurality of housings <NUM> that support the carrying tools <NUM> are also provided in a continuous manner such that the carrying tools <NUM> are provided continuously over the entire length of the pallet rail <NUM>, which links the standby position and the plurality of processing stations <NUM> to <NUM>.

A belt rail <NUM> is attached via a plurality of attachment members <NUM> under the housings <NUM> on the support plate <NUM>. The plurality of attachment members <NUM> are provided at predetermined intervals in the longitudinal direction of the belt rail <NUM>. The belt rail <NUM> supports a lower region side belt 27d, extending between the suspending pulleys <NUM>, of the endless belt <NUM> that is suspended around the first pulley <NUM> and the second pulley <NUM> at its both ends. With such a configuration, the deflection of the lower region side belt 27d is suppressed. As shown in <FIG>, the belt rail <NUM> is a long object having a flat plate 56a receiving the lower region side belt 27d and flanges 56b that are respectively erected upright on both sides of the flat plate 56a.

Next, a conveyed-pallet retaining method using the pallet conveying device <NUM> will be described.

The conveyed-pallet retaining method of this embodiment includes: a step of mounting the pallet <NUM> on the pallet rail <NUM>, a step of conveying the pallet <NUM> by circulating the endless belt <NUM> in a state in which the protrusions and recesses 26a and 26b formed on the pallet <NUM> are engaged with the protrusions and recesses 27a and 27b of the endless belt <NUM> extending along the pallet rail <NUM>, and a step of retaining the pallet <NUM> at a desired position by stopping the circulation of the endless belt <NUM>.

Furthermore, in this embodiment, when the pallet <NUM> is retained at a desired position by stopping the circulation of the endless belt <NUM>, the protrusions and recesses 27a and 27b of the endless belt <NUM> are pressed against the protrusions and recesses 26a and 26b of the pallet <NUM>.

In this embodiment, the pallet <NUM> is conveyed between the standby position and the plurality of processing stations <NUM> to <NUM>. The work (not shown) to be processed is loaded on the pallet <NUM>. The loading of the work onto the pallet <NUM> is performed in a state in which the pallet <NUM> is mounted on the pallet rail <NUM> at the standby position or performed by mounting the pallet <NUM>, on which the work has been loaded in advance, on the pallet rail <NUM> at the standby position.

After the pallet <NUM> is mounted on the pallet rail <NUM>, the anchoring members <NUM> of the pallet <NUM> that are provided under the base 21b are placed from above over the upper region side belt 27c provided along the pallet rail <NUM>. By doing so, the protrusions and recesses 27a and 27b of the endless belt <NUM> engage with the protrusions and recesses 26a and 26b of the anchoring members <NUM>.

Once the protrusions and recesses 26a and 26b of the pallet <NUM> engage with the protrusions and recesses 27a and 27b of the endless belt <NUM>, the movement of the pallet <NUM> in the longitudinal direction independent of the endless belt <NUM> is prohibited. Thus, by circulating the endless belt <NUM>, it is possible to convey the pallet <NUM>.

The circulation of the endless belt <NUM> is performed by rotating the first pulley <NUM> and the second pulley <NUM> shown in <FIG>. The rotation of the first pulley <NUM> and the second pulley <NUM> is performed by synchronously driving the first servomotor <NUM> and the second servomotor <NUM> for rotationally driving the first pulley <NUM> and the second pulley <NUM> in accordance with the instructions from the controller <NUM>. As the first pulley <NUM> and the second pulley <NUM> are both rotated in the same direction and at the same speed, and as the endless belt <NUM> that is suspended around the first pulley <NUM> and the second pulley <NUM> is circulated, the pallet <NUM> anchored to the endless belt <NUM> is conveyed along the pallet rail <NUM>.

In this embodiment, as the pallet <NUM> is conveyed from the standby position, the pallet <NUM> faces the third processing station <NUM> first. At a stage where the pallet <NUM> faces the third processing station <NUM>, the first servomotor <NUM> and the second servomotor <NUM> are halted to stop the circulation of the endless belt <NUM>. By doing so, the pallet <NUM> anchored to the endless belt <NUM> is maintained at a state in which the pallet <NUM> faces the third processing station <NUM> and the pallet <NUM> is retained or made stationary at that position. Then, the machine tool (not shown) in the third processing station <NUM> is operated to perform a predetermined processing to the work loaded on the pallet <NUM>.

After the processing is finished at the third processing station <NUM>, the first servomotor <NUM> and the second servomotor <NUM> are again subjected to the synchronous control to rotate the first pulley <NUM> and the second pulley <NUM> at the same time, in the same direction, and at the same speed. By doing so, the endless belt <NUM> is circulated and the pallet <NUM> is conveyed again.

As described above, by causing the pallet <NUM> to face the respective processing stations <NUM> to <NUM> sequentially, the work is subjected to the processing. Finally, at the stage in which the pallet <NUM> faces the first processing station <NUM> at the most distant from the standby position, the first servomotor <NUM> and the second servomotor <NUM> are halted to stop the circulation of the endless belt <NUM>. By doing so, the pallet <NUM> anchored to the endless belt <NUM> is maintained at a state in which the pallet <NUM> faces the first processing station <NUM> at the most distant from the standby position and the pallet <NUM> is retained or made stationary at that position. The work loaded on the pallet <NUM> is then subjected to the processing at the first processing station <NUM>, thereby finishing a series of processing at the respective processing stations <NUM> to <NUM>.

After the processing is finished at each of the processing stations <NUM> to <NUM>, the pallet <NUM> facing the first processing station <NUM> is moved in the opposite direction and returned to the standby position. The backward movement of the pallet <NUM> is performed by circulating the endless belt <NUM> in the reverse direction. The endless belt <NUM> is circulated in the reverse direction by reversing the rotating directions of the first servomotor <NUM> and the second servomotor <NUM> and rotating the first pulley <NUM> and the second pulley <NUM> in the reverse direction in a synchronous manner.

As described above, by circulating the endless belt <NUM> in the reverse direction, it is possible to return the pallet <NUM> anchored to the endless belt <NUM> to the standby position. Once the pallet <NUM> is returned to the standby position, the first servomotor <NUM> and the second servomotor <NUM> are halted to stop the circulation of the endless belt <NUM>. By doing so, a state in which the pallet <NUM> anchored to the endless belt <NUM> is retained at the standby position of the pallet rail <NUM> is maintained.

At the standby position of the pallet rail <NUM>, the work loaded on the pallet <NUM> is exchanged or the pallet <NUM> on which the processed work is loaded is removed and new pallet <NUM> on which another work is loaded is mounted on the pallet rail <NUM>. Then, the pallet <NUM> is conveyed again to each of the processing stations <NUM> to <NUM>, and the processing is performed on the other work at the respective processing stations <NUM> to <NUM>.

As described above, in this embodiment, the pallet <NUM> engaged with the endless belt <NUM> is conveyed or retained at a predetermined position by rotating the first pulley <NUM> and the second pulley <NUM> in a synchronous manner to circulate the endless belt <NUM> or to stop the circulation of the endless belt <NUM> as required.

Especially, in this embodiment, as shown in <FIG>, the endless belt <NUM> is suspended by the idle pulleys <NUM> and the suspending pulleys <NUM> such that the endless belt <NUM> is pressed against the first pulley <NUM> and the second pulley <NUM> from the inside in the longitudinal direction of the pallet rail <NUM>. Therefore, it is possible to apply tension to the endless belt <NUM>. Thus, the protrusions and recesses 27a and 27b of the endless belt <NUM> are engaged with the protrusions and recesses 24d and 24e of the first pulley <NUM> and the second pulley <NUM> (see <FIG>) so as not to form any gaps therebetween. With such a configuration, it is possible to directly convert the rotational motion of the first pulley <NUM> and the second pulley <NUM> to the circulating motion of the endless belt <NUM> accurately.

The first pulley <NUM> and the second pulley <NUM> are driven by the synchronous control according to the instructions from the controller <NUM> by using the first servomotor <NUM> and the second servomotor <NUM> as the first actuator and the second actuator for rotationally driving the first pulley <NUM> and the second pulley <NUM>. Thus, the endless belt <NUM> is pulled by a first pulley (the first pulley <NUM>) being rotated and pushed towards the first pulley (the first pulley <NUM>) by a second pulley (the second pulley <NUM>). In addition, the endless belt <NUM> is pushed by the first pulley (the first pulley <NUM>) being rotated and pulled by the second pulley (the second pulley <NUM>). With such a configuration, compared with a case in which only a single pulley is rotated, it is possible to suppress the deflection, elongation, and so forth of the endless belt <NUM>. Thus, it is possible to avoid occurrence of variation in circulation speed of the endless belt <NUM>. By avoiding the occurrence of the variation in the circulation speed, it is possible to circulate the endless belt <NUM> accurately and to increase the accuracy of the conveyance of the pallet <NUM> anchored to the endless belt <NUM>.

For the relationship between the endless belt <NUM> and the pallet <NUM>, as shown in <FIG>, the synchronous belt is used as the endless belt <NUM>, and the protrusions and recesses 26a and 26b of the pallet <NUM> are engaged with the protrusions and recesses 27a and 27b. However, a gap is formed therebetween. Therefore, even if the position of the endless belt <NUM> during the circulation can be controlled accurately, the position of the pallet <NUM> anchored to the endless belt <NUM> is deviated by an amount corresponding to the gap.

In contrast, the belt supporting devices <NUM> are provided on the support plate <NUM> of the pallet rail <NUM>. The belt supporting devices <NUM> are provided at least at locations where the pallet <NUM> needs to be stopped at a predetermined position, in other words, at the locations where the belt supporting devices <NUM> respectively face the processing stations <NUM> to <NUM>. Thus, by causing the pallet <NUM> to face each of the processing stations <NUM> to <NUM> by stopping the circulation of the endless belt <NUM>, the pallet <NUM> also faces each of the belt supporting devices <NUM> at the same time.

As the pallet <NUM> is stopped and faces the belt supporting device <NUM>, the coil springs <NUM> of the belt supporting device <NUM> bias the carrying tool <NUM> such that the protrusions and recesses 27a and 27b of the upper region side belt 27c carried by the carrying tool <NUM> are pressed against the protrusions and recesses 26a and 26b of the anchoring members <NUM>. Therefore, the gap between the protrusions and recesses 27a and 27b of the endless belt <NUM> and the protrusions and recesses 26a and 26b of the anchoring members <NUM> under mutual engagement is squeezed and eliminated by the biasing force. Thus, the position of the pallet <NUM> relative to the endless belt <NUM> is maintained at the accurate position.

In this embodiment, the protrusions and recesses 27a and 27b are pressed against the protrusions and recesses 26a and 26b by the carrying tool <NUM> that is provided at a retaining position of the pallet <NUM> in advance and that movably carries the endless belt <NUM>. Thus, it is possible to prevent the endless belt <NUM> from being damaged when the protrusions and recesses 27a and 27b are pressed against the protrusions and recesses 26a and 26b. In addition, because the biasing force exerted by the coil springs <NUM> per unit area of the carrying tools <NUM> is from <NUM> to <NUM> N, it is possible to reliably squeeze the gap between the protrusions and recesses 27a and 27b of the endless belt <NUM> and the protrusions and recesses 26a and 26b of the pallet <NUM> without using excessive biasing means.

As described above, in this embodiment, by eliminating the gap between the protrusions and recesses 27a and 27b and the protrusions and recesses 26a and 26b, the pallet <NUM> is allowed to be retained at the accurate position. Thus, the pallet-movement locking mechanism that has been required for accurate positioning of the pallet in the conventional technique is no longer required. Therefore, the time required for the extension or the contraction of the fluid pressure cylinder and the confirmation time required for a sensor to detect completion of the extension or the contraction need not be required for the conventional pallet-movement locking mechanism.

In this embodiment, when the circulation of the endless belt <NUM> is stopped, it is possible to readily start the processing in the respective processing stations <NUM> to <NUM>. After the processing is finished, the circulation of the endless belt <NUM> is started readily, thereby conveying the pallet <NUM> readily. Thus, compared with the case in which the conventional pallet-movement locking mechanism is used, time required for the operation and confirmation is no longer required, and so, it is possible to perform the conveyance of the pallet <NUM> without delay.

In addition, because the pallet-movement locking mechanism that has been required in the conventional pallet conveying device is no longer required, the limitation to the pitch of the positions for stopping the pallet, which had been caused by the provision of the pallet-movement locking mechanism, is also eliminated. Thus, it is also possible to perform retaining of the pallet <NUM> at narrow pitches for multiple times. In other words, it is possible to retain the pallet <NUM> accurately even at relatively small pitches.

In a case in which the conventional pallet-movement locking mechanism is not provided, if the work loaded on the pallet <NUM> is processed after the pallet <NUM> is retained, an external force applied to the work during the processing may act as the biasing force in the direction in which the pallet <NUM> is moved.

In contrast, the circulation of the endless belt <NUM> in the pallet conveying device <NUM> is performed by rotationally driving the first pulley <NUM> by the first actuator and by rotationally driving the second pulley <NUM> by the second actuator, which is controlled in a synchronous manner with the first actuator. The stopping of the circulation of the endless belt <NUM> is also performed by actively stopping the rotation of the first pulley <NUM> and the second pulley <NUM> by both of the first actuator and the second actuator.

In such a case, the biasing force applied to the pallet <NUM> via the work during the processing of the work is converted as a force that rotates the first pulley <NUM> and the second pulley <NUM> on the both sides of the endless belt <NUM>, which is suspended around the first pulley <NUM> and the second pulley <NUM>, in the conveying direction. By using actuators capable of coping with such a force as the first actuator and the second actuator, it is possible to surely maintain a state in which the pallet <NUM> is retained at the accurate position even under the external force being applied to the work.

In this embodiment, as the first actuator and the second actuator for rotationally driving the first pulley <NUM> and the second pulley <NUM>, electrically driven servomotors capable of changing the rotation speed and rotation torque of the first pulley <NUM> and the second pulley <NUM> are used. Thus, it is possible to circulate the endless belt <NUM> accurately, and when the endless belt <NUM> is stopped, the stopped state can be maintained surely even if a tension is applied to the endless belt <NUM>. Thus, it is possible to maintain the retained state of the pallet <NUM> anchored to the endless belt <NUM> with reliability.

In this embodiment, the plurality of carrying tools <NUM> are provided along the longitudinal direction of the pallet rail <NUM> in a continuous manner. Thus, the carrying tools <NUM> are provided at other locations than the locations opposing to the respective processing stations <NUM> to <NUM>. With such a configuration, even in a case in which the positions of the processing stations <NUM> to <NUM> are changed or in which a new processing station is added, there is no need to additionally provide the belt supporting devices <NUM> in accordance with the change in the positions or the added processing station. Thus, the degree of freedom for providing the processing station or changing the positions is increased.

The movable range R of the carrying tools <NUM> is limited so as to be smaller than the height h of the protrusions and recesses 27a and 27b of the endless belt <NUM>. Thus, when the pallet <NUM> is moved from the carrying tool <NUM> to the adjacent carrying tool <NUM>, the upper region side belt 27c is prevented from being disengaged from the adjacent carrying tool <NUM>. Therefore, the endless belt <NUM> can be circulated stably, and so, it is possible to convey and retain the pallet <NUM> anchored to the endless belt <NUM> in a stable manner.

As described above, the pallet conveying device <NUM> is provided with: the pallet rail <NUM> configured to mount the pallet <NUM> in a manner movable in the longitudinal direction; the endless belt <NUM> provided along the pallet rail <NUM> so as to be able to be circulated, the endless belt <NUM> being provided with the protrusions and recesses 27a and 27b extending in the width direction, and the protrusions and recesses 27a and 27b being provided alternately in the longitudinal direction in a consecutive manner; the protrusions and recesses 26a and 26b formed on the pallet <NUM> so as to be able to engage with the protrusions and recesses 27a and 27b of the endless belt <NUM>; and the belt supporting device <NUM> provided on the pallet rail <NUM>, the belt supporting device <NUM> being configured to support the endless belt <NUM> such that the protrusions and recesses 27a and 27b of the endless belt <NUM> engage with the protrusions and recesses 26a and 26b of the pallet <NUM> in a state in which the pallet <NUM> is mounted on the pallet rail <NUM>.

The belt supporting device <NUM> has: the carrying tool <NUM> configured to carry the endless belt <NUM> in a movable manner; and the coil springs <NUM> serving as the biasing means configured to bias the carrying tool <NUM> such that the protrusions and recesses 27a and 27b of the endless belt <NUM> carried by the carrying tool <NUM> are pressed against the protrusions and recesses 26a and 26b of the pallet <NUM>.

It is preferable that the length of the carrying tool <NUM> in the longitudinal direction of the pallet rail <NUM> be limited so as to be equal to or smaller than the length of the pallet <NUM>, and the plurality of carrying tools <NUM> be provided in the longitudinal direction of the pallet rail <NUM> in a continuous manner.

It is preferable that the movable range R of the carrying tool <NUM> by the biasing means be limited so as to be smaller than the height of the protrusions and recesses 27a and 27b of the endless belt <NUM>. It is preferable that the biasing force exerted by the biasing means to bias the carrying tools <NUM> be from <NUM> to <NUM> N.

The conveyed-pallet retaining method includes: a step of mounting the pallet <NUM> on the pallet rail <NUM>; a step of engaging the protrusions and recesses 26a and 26b formed on the pallet <NUM> with the protrusions and recesses 27a and 27b of the endless belt <NUM> extending along the pallet rail <NUM>; a step of conveying the pallet <NUM> by circulating the endless belt <NUM>; and a step of retaining the pallet <NUM> by stopping the circulation of the endless belt <NUM>.

When the pallet <NUM> is retained by stopping the circulation of the endless belt <NUM>, the protrusions and recesses 27a and 27b of the endless belt <NUM> are pressed against the protrusions and recesses 26a and 26b of the pallet <NUM>.

It is preferable that the protrusions and recesses 27a and 27b of the endless belt <NUM> be pressed against the protrusions and recesses 26a and 26b of the pallet <NUM> by the carrying tool <NUM>, the carrying tool <NUM> being provided at the retaining position of the pallet <NUM> in advance, and the carrying tool <NUM> being configured to carry the endless belt <NUM> in a movable manner.

With the pallet conveying device <NUM> and the conveyed-pallet retaining method according to this embodiment, when the pallet <NUM> is retained at a desired position by stopping the circulation of the endless belt <NUM>, the protrusions and recesses 27a and 27b of the endless belt <NUM> are pressed against the protrusions and recesses 26a and 26b of the pallet <NUM> by the belt supporting devices <NUM>. Thus, the gap between the protrusions and recesses 27a and 27b of the endless belt <NUM> and the protrusions and recesses 26a and 26b of the pallet <NUM> under mutual engagement is squeezed and eliminated. Therefore, it is possible to maintain the pallet <NUM> at the accurate position with respect to the endless belt <NUM>.

By accurately controlling the circulation and the stopping of the endless belt <NUM>, it is possible to accurately retain the pallet <NUM> at the desired position without using the pallet-movement locking mechanism, which has been required in the conventional technique. In addition, it is possible to maintain a state in which the pallet <NUM> is retained at the desired position with reliability.

In addition, because the pallet-movement locking mechanism, which has been required in the conventional technique, is no longer required, the limitation to the pitch of the positions for stopping the pallet, which had been caused by the provision of the pallet-movement locking mechanism, is eliminated. Thus, in this embodiment, it may be possible to accurately stop the pallet <NUM> even at relatively small pitches.

Although the embodiment of the present invention has been described in the above, the above-mentioned embodiment merely illustrates a part of application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above-described embodiment.

In the above-described embodiment, a description has been given of a case in which the first servomotor <NUM> and the second servomotor <NUM> serving as the first actuator and the second actuator are controlled synchronously to rotate the first pulley <NUM> and the second pulley <NUM> at the same time, in the same direction, and at the same speed. However, as long as no variation is caused in the circulation speed of the endless belt <NUM>, the endless belt <NUM> may be circulated by rotating either one of the first pulley <NUM> and the second pulley <NUM>.

In the above-described embodiment, a description has been given of a case in which a single pallet <NUM> is mounted on the pallet rail <NUM> and the pallet <NUM> is conveyed in a reciprocating manner. However, the plurality of pallets <NUM> may be mounted on the pallet rail <NUM>. In this case, other circulation rail than the pallet rail <NUM> may be used to circulate the plurality of pallets <NUM>.

In the above-described embodiment, a description has been given of a case in which the first actuator and the second actuator are the electrically driven servomotors. However, as long as the first pulley <NUM> and the second pulley <NUM> can be rotated, the fluid pressure cylinder or a fluid pressure motor may be used as the first actuator and the second actuator.

In the above-described embodiment, a description has been given of a case in which the lengths L of the carrying tools <NUM> are limited so as to be the same as or so as to be equal to or smaller than the length S of the pallet <NUM>, and the plurality of carrying tools <NUM> are provided in the longitudinal direction of the pallet rail <NUM> in a continuous manner. However, it suffices that the carrying tools <NUM> are provided at locations where the pallet <NUM> needs to be retained after the conveyance has been stopped, and the carrying tools <NUM> may not necessarily be provided at other locations.

In the above-described embodiment, the length L of the carrying tool <NUM> is limited so as to the same as or equal to or smaller than the length S of the pallet <NUM>. However, as long as the location where the pallet <NUM> needs to be retained is included, the carrying tool <NUM> having the length L exceeding the length S of the pallet <NUM> may be used. For example, it may be possible to employ a structure in which the carrying tool <NUM> having a length that extends over the entire length of the pallet rail <NUM> is used, and the protrusions and recesses 27a and 27b of the endless belt <NUM> carried by the carrying tool <NUM> are pressed against the protrusions and recesses 26a and 26b of the pallet <NUM> mounted on the pallet rail <NUM> by the biasing means.

Claim 1:
A pallet conveying device (<NUM>) comprising:
a pallet rail (<NUM>) configured to mount a pallet (<NUM>) in a manner movable in a longitudinal direction;
an endless belt (<NUM>) provided along the pallet rail (<NUM>) so as to be able to be circulated, the endless belt (<NUM>) being provided with protrusions (27b) and recesses (27a) extending in a width direction, and the protrusions (27b) and recesses (27a) being provided alternately in the longitudinal direction in a consecutive manner; and
a plurality of belt supporting devices (<NUM>) provided on the pallet rail (<NUM>), each of the belt supporting devices (<NUM>) being configured to support the endless belt (<NUM>) such that the protrusions (27b) and
recesses (27a) of the endless belt (<NUM>) engage with anchoring members (<NUM>) of the pallet (<NUM>) formed with protrusions (26b) and recesses (26a)
in a state in which the pallet (<NUM>) is mounted on the pallet rail (<NUM>), characterized in that
each of the belt supporting devices (<NUM>) has:
carrying tools (<NUM>) on which the upper region side belt (27c) of the endless belt (<NUM>) engaged with the anchoring members (<NUM>) is carried so as to be movable in the longitudinal direction; and
coil springs (<NUM>), each serving as biasing means, that bias the carrying tools (<NUM>) such that the protrusions (27b) and recesses (27a) of the upper region side belt (27c) carried on the carrying tools (<NUM>) are pressed against the protrusions (26b) and recesses (26a) of the anchoring members (<NUM>), and
the carrying tools (<NUM>) are located under the upper region side belt (27c) and each has:
a bottom plate (<NUM>) that extends in the longitudinal direction of the upper region side belt (27c);
a pair of side walls (<NUM>, <NUM>) that are provided on both sides of the bottom plate (<NUM>) so as to be erected upright and so as to sandwich the upper region side belt (27c) from both sides in the width direction; and
a plurality of rollers (<NUM>) that are provided between the pair of side walls (<NUM>, <NUM>).