Pallet transport device and pallet transport method

Abstract

To reduce the number of required pallets by changing a pitch of the pallets.SOLUTION: A pallet conveyance device comprises: a circulation belt 20 which is arranged so as to extend in a conveyance path and be able to circulate; drive means 30 which makes the circulation belt circulate to convey a pallet 11 mounted on the belt; and stop means 40 which stops conveyance of the pallet. The circulation belt comprises: a free flow belt 21 which can stop conveyance of the pallet 11 by the stop means; and a conveyor belt 26 which is provided continuously with the free flow belt 21. The drive means 30 is configured to make the circulation speed of the conveyor belt 26 different from the circulation speed of the free flow belt 21. The plurality of free flow belts 21 are provided via the conveyor belt 26. The stop means 40 is provided at both of a processing spot for stopping conveyance of the pallet 11 and a stand-by spot for temporarily stopping the pallet 11 in the vicinity of the processing spot.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a pallet conveying device and a pallet conveying method for conveying a pallet on which a workpiece is mounted together with the workpiece.

Background Art

[0002] Conventionally, in a manufacturing line, a free-flow conveyor is provided so as to connect a plurality of machine tools, and a pallet on which a workpiece is mounted is mounted on the free-flow conveyor and conveyed, and a predetermined processing is performed on the workpiece mounted on the pallet conveyed to the machine tool at the conveyance destination.

[0003] And, as a device for conveying such a pallet on which a workpiece is mounted, it has been proposed to provide a pallet feed pawl-fixed pitch feed conveyor that is arranged parallel to the free-flow conveyor on which the pallet is mounted, is driven by a servo mechanism, and is transferred in the same direction as the free-flow conveyor (see, for example, Patent Document 1).

[0004] In such a pallet conveying device, by increasing or decreasing the feed speed of the fixed pitch feed conveyor, even when the speed of the free-flow conveyor is increased, the impact of the pallet and parts at the time of stopping can be eliminated, and a boundless state can be realized is said.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, since the pallet transport device that transports the pallet loaded with the workpiece along with the workpiece is generally installed to connect to a machine tool that performs a predetermined processing on the workpiece, when the pallet faces the machine tool, the transport of the pallet carrying the workpiece is stopped or its transport speed is significantly reduced in order to process the workpiece.

[0007] On the other hand, although multiple pallets for loading workpieces are provided and transported sequentially, in the conventional pallet transport system described above, which is equipped with a fixed-pitch feed conveyor, the spacing between pallets remains constant. As a result, pallets are also loaded onto the free-flow conveyor that spans between machine tools during workpiece processing, which increases the number of pallets required and also results in the inconvenience of extending the time between processing at one machine tool and processing at the next.

[0008] The object of the present invention is to provide a pallet conveying device and a pallet conveying method that can reduce the number of pallets required by changing the pitch of the pallets being conveyed. [Means for solving the problem]

[0009] The present invention is an improvement on a pallet conveying device comprising a circulating belt that extends along a conveying path and is circulating so as to carry pallets, a driving means for circulating the circulating belt and conveying the pallets carried on the circulating belt, and a stopping means for stopping the conveyance of pallets regardless of the circulation of the circulating belt.

[0010] Its distinctive configuration includes a circulating belt which comprises a free-flow belt capable of stopping the transport of pallets by a stopping mechanism, and a transport belt provided continuously with the free-flow belt, and the driving mechanism is configured to make the circulation speed of the transport belt and the circulation speed of the free-flow belt different.

[0011] In this case, it is preferable that multiple free-flow belts are provided via a conveyor belt, and if a pair of support plates that sandwich the pallet from both sides in the width direction are provided along the conveyor path, stopping means can be provided between the pair of support plates at both a processing point where the conveyance of the pallet is stopped and a waiting point near the processing point where the pallet is temporarily stopped.

[0012] Furthermore, the drive mechanism preferably comprises a first motor for circulating the free-flow belt and a second motor provided separately from the first motor for circulating the conveyor belt. When the conveyor belt has alternating and continuous grooves extending in the width direction, it is preferable to form grooves on the pallet that can engage with the grooves when mounted on the conveyor belt, and it is even more preferable to provide a retaining member to prevent the pallet mounted on the conveyor belt from lifting off the conveyor belt.

[0013] On the other hand, another aspect of the present invention is a pallet transport method that transports pallets using the above-mentioned pallet transport device.

[0014] Its distinctive feature lies in its ability to increase the circulation speed of the conveyor belt compared to that of the free-flow belt, thereby increasing the transport speed of pallets loaded onto the conveyor belt compared to that of pallets loaded onto the free-flow belt.

[0015] When using a conveyor belt in which irregularities extending in the width direction are formed alternately and continuously in the longitudinal direction, it is preferable to convey the pallets mounted on the circulating conveyor belt by engaging the irregularities with those irregularities. [Effects of the Invention]

[0016] In the pallet conveying device and pallet conveying method of the present invention, by making the circulation speed of the conveyor belt and the circulation speed of the free-flow belt different, the conveying speed of pallets mounted on the conveyor belt is made faster than the conveying speed of pallets mounted on the free-flow belt, thereby increasing the distance between a pallet that has been transferred from the free-flow belt to the conveyor belt and the next pallet remaining on the free-flow belt.

[0017] Therefore, by transferring the pallet carrying the workpiece processed by the upstream processing machine from the free-flow belt to the conveyor belt, the pallet can be relatively quickly conveyed to the processing location by the downstream processing machine. As a result, it becomes possible to reduce the number of pallets required when continuously processing a plurality of workpieces, and at the same time, the time between processing in one processing machine and processing in the next processing machine can be shortened compared to the conventional method of conveying pallets at a constant pitch.

[0018] In particular, if concavities and convexities are formed on the conveyor belt and mating concavities and convexities that can engage with the concavities and convexities are formed on the pallet, the movement of the pallet independent of the conveyor belt is prohibited. Therefore, even if the circulation speed of the conveyor belt is increased, the pallet can be reliably conveyed at the same speed.

Brief Description of the Drawings

[0019] [Figure 1] It is a top view showing the pallet conveying device according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view taken along line A-A of FIG. 1. [Figure 3] It is a cross-sectional view taken along line B-B of FIG. 1. [Figure 4] It is a cross-sectional view taken along line C-C of FIG. 1. [Figure 5] It is a top view showing a state in which a pallet is mounted on the free-flow belt and confronted with the first processing machine in the pallet conveying device. [Figure 6] It is a front view corresponding to FIG. 5 showing a state in which the pallet is confronted with the first processing machine. [Figure 7] It is a top view showing a state in which after the pallet is confronted with the first processing machine, the pallet is further mounted on the free-flow belt and stopped at a standby location. [Figure 8] It is a front view corresponding to FIG. 7 showing a state in which the pallet is stopped at both the processing location and the standby location. [Figure 9]It is a top view showing the state where the pallet moves from the end of the free-flow belt to the conveyor belt. [Figure 10] It is a front view corresponding to FIG. 9 showing the state where the pallet moves from the end of the free-flow belt to the conveyor belt. [Figure 11] It is a top view showing the state where the pallet moves from the end of the conveyor belt to the free-flow belt. [Figure 12] It is a front view corresponding to FIG. 11 showing the state where the pallet moves from the end of the conveyor belt to the free-flow belt. [Figure 13] It is a top view showing the state where the pallet is stopped at both the processing location and the standby location of the next machine tool. [Figure 14] It is a front view corresponding to FIG. 13 showing the state where the pallet is stopped at both the processing location and the standby location of the next machine tool.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] Next, the best mode for carrying out the present invention will be described based on the drawings.

[0021] In FIGS. 1 to 4, a pallet conveying device 10 according to the present invention is shown. In each figure, three axes X, Y, and Z orthogonal to each other are set, where the X-axis extends in a substantially horizontal lateral direction, the Y-axis extends in a substantially horizontal front-rear direction, and the Z-axis extends in a vertical direction, and the configuration of the pallet conveying device 10 will be described.

[0022] As shown in FIGS. 1 and 2, the pallet conveying device 10 in the present invention includes a circulation belt 20 provided so as to be extendable and circulatable in a conveying path and carrying the pallet 11, a driving means 30 for circulating the circulation belt 20 and conveying the pallet 11 mounted on the circulation belt 20, and a stopping means 40 for stopping the conveyance of the pallet 11 regardless of the circulation of the circulation belt 20.

[0023] In other words, the present invention is a pallet transport device 10 used in a case where a pallet 11 loaded with workpieces (not shown) is transported on a circulating belt 20, and the transport of the pallet 11 is stopped by a stopping means 40 in front of machine tools 1 and 2 (Figure 1) provided along the transport path, and the machine tools 1 and 2 process the workpieces (not shown) loaded on the pallet 11.

[0024] Although Figure 1 shows a case where two machine tools 1 and 2 are installed on one side of the pallet transport device 10 of the present invention, this is just one example, and the number of machine tools 1 and 2 will vary depending on the workpiece that needs to be processed, and the number of pallets 11 will be increased or decreased as appropriate according to the number of machine tools 1 and 2.

[0025] In this embodiment, a frame 9 is provided extending to connect multiple machine tools 1 and 2, and on the frame 9, a pair of support plates 16 are fixed parallel to each other at a predetermined distance in the width direction (Y direction) along the transport path (X direction) of the pallet 11.

[0026] Furthermore, the circulation belt 20 in the pallet transport device 10 is provided on each of the opposing sides of the pair of support plates 16 so as to support both sides of the pallet 11 in the width direction, and the pallet 11 is configured to be mounted on this pair of circulation belts 20.

[0027] As shown in the enlarged view of Figure 2, the pallet 11 in this embodiment comprises a base 12 that is rectangular in shape when viewed from above and is supported on both sides by a circulation belt, a mounting device 13 provided on the upper surface of the base 12 for mounting workpieces (not shown) to be processed by machine tools 1 and 2, and a contact material 14 provided on the lower surface of the base 12 that is in direct contact with the circulation belt 20.

[0028] Here, the shape of the mounting device 13 varies depending on the type of workpiece to be transported, and multiple pallets 11 equipped with this mounting device 13 are prepared in order to transport multiple workpieces in succession. For this reason, an example is shown in which the base 12 of the pallet 11 is provided with a cushioning material 15 located at the rear in the transport direction, which abuts against the front edge of the subsequent pallet 11.

[0029] As shown in Figures 3 and 4, with the circulation belt 20 supporting both sides of the pallet 11 in the width direction, the pair of support plates 16 are configured to sandwich the pallet 11 from the width direction with a predetermined gap between them, thereby preventing displacement in the width direction without hindering the movement of the pallet 11 in the transport direction.

[0030] Returning to Figures 1 and 2, the characteristic configuration of the present invention is that the circulation belt 20 comprises a free-flow belt 21 capable of stopping the transport of the pallet 11 by the stopping means 40, and a transport belt 26 provided continuously with the free-flow belt 21 and without the stopping means 40, and the driving means 30 makes the circulation speed of the transport belt 26 and the circulation speed of the free-flow belt 21 different.

[0031] Specifically, the free-flow belt 21, which is the circulation belt 20, is installed in a location facing the machine tools 1 and 2 and is configured to stop the transport of the pallet 11 by the stopping means 40, while the transport belt 26, which is installed continuously with the free-flow belt 21, is installed in a location where it is not necessary to stop the transport of the pallet 11.

[0032] Since the circulation belts 20 provided on opposing parts of a pair of parallel support plates 16, 16 are arranged in a symmetrical structure, to explain using the circulation belt 20 provided on one support plate 16 as a representative example, as shown in Figure 2, on the opposing side of the support plate 16, there are driven pulleys 22, 27 around which the free-flow belt 21 and the conveyor belt 26 are routed, in a part where the free-flow belt 21 is provided facing the machine tools 1, 2, and in a part where the conveyor belt 26 is provided without facing the machine tools.

[0033] The free-flow belt 21 and the conveyor belt 26 surround the driven pulleys 22 and 27, and are wrapped around the support plate 16 on opposite sides of each other such that their upper edges are continuous in the horizontal direction.

[0034] Furthermore, drive shafts 23a and 28a are installed and pivotally supported on the portion of the pair of support plates 16 where the free-flow belt 21 is provided and the portion where the conveyor belt 26 is provided, respectively. On the opposing sides of the pair of support plates 16, drive pulleys 23 and 28 of the same shape and size are attached to the drive shafts 23a and 28a, respectively.

[0035] The frame 9 is separately equipped with first and second motors 31 and 36, which serve as driving means 30 for circulating the free-flow belt 21 and the conveyor belt 26, and the rotating shafts 31a and 36a of these motors are connected to drive shafts 23a and 28a, respectively (Figures 3 and 4).

[0036] The drive pulleys 23 and 28 are provided on the opposite side of the support plate 16, on the same plane as the other driven pulleys 22 and 27, respectively. Near the drive pulleys 23 and 28, a pair of deflection pulleys 24 and 29 are pivotally supported on the support plate 16, respectively, to deflect the free-flow belt 21 and the conveyor belt 26, which constitute the circulating belt 20, so that they are routed around the drive pulleys 23 and 28.

[0037] Furthermore, support members 17 are attached to the support plate 16 to support the continuous upper edges of the free-flow belt 21 and the conveyor belt 26 that surround the driven pulleys 22 and 27, and to prevent them from slackening. The support members 17 are provided by being screwed to the support plate 16, and these support members 17 accommodate the upper edges of the free-flow belt 21 and the conveyor belt 26, forming grooves 17a (Figure 4) that prevent them from moving in the width direction.

[0038] Then, when the first and second motors 31 and 36 are driven by a command from a controller (not shown), the drive pulleys 23 and 28 on opposite sides of the pair of support plates 16 rotate simultaneously, and the circulating belt 20, consisting of a free-flow belt 21 and a conveyor belt 26 located on opposite sides of the support plates 16, is wrapped around these drive pulleys 23 and 28 and circulates in the same direction, surrounding the driven pulleys 22 and 27.

[0039] Figures 1 and 2 show a case where multiple free-flow belts 21 are provided via a conveyor belt 26. Specifically, the pallet conveying device 10 in the figures includes an upstream free-flow belt 21 provided facing the upstream machine tool 1, a conveyor belt 26 continuous with the free-flow belt 21, and a downstream free-flow belt 21 provided facing the downstream machine tool 2, which is continuous with the conveyor belt 26.

[0040] As a result, the conveyor belt 26 is interposed between the free-flow belts 21, which are provided opposite the machine tools 1 and 2, and the conveyor belt 26 is provided to connect the free-flow belts 21.

[0041] Then, by driving the first and second motors 31 and 36, which are the drive means 30, the free-flow belt 21 and conveyor belt 26, which are the circulation belt 20 on which the pallets 11 are mounted, are circulated, and the pallets 11 move while mounted on the free-flow belt 21 and conveyor belt 26. The pallets 11 that have moved on the upstream free-flow belt 21 move from its end to the conveyor belt 26 and are mounted there, and move further, and then move from its end to the downstream free-flow belt 21 and are mounted there, and are transported further.

[0042] Here, the free-flow belts 21 that support both sides of the pallet 11 in the width direction are configured such that the outer surface on which the pallet 11 is mounted is flat, allowing the pallet 11 mounted on that outer surface to slide. Between the pair of free-flow belts 21 that support both sides of the pallet 11 in the width direction, there is a stopping means 40 that prevents the movement of the pallet 11 regardless of the circulation of the free-flow belts 21, which are the circulation belts 20, and stops the transport of the pallet 11 by causing the pallet 11 to slide on the outer surface of the free-flow belts 21.

[0043] The stopping means 40 in the figure is a fluid pressure cylinder with its main body 40a attached to the frame 9, with its retractable rod 40b pointing upward, as shown in Figure 3. The fluid pressure cylinder 40, which is the stopping means, is configured such that when the retractable rod 40b protrudes upward from the main body 40a, as shown by the solid line, the retractable rod 40b comes into contact with the leading edge of the pallet 11 that is moving on the circulating free flow belt 21, causing the pallet 11 to slide on the outer surface of the free flow belt 21 regardless of the circulation of the free flow belt 21, thereby stopping the transport of the pallet 11. Furthermore, as shown by the dashed line, when the retractable rod 40b is retracted into the main body 40a, the movement of the pallet 11 on the circulating free flow belt 21 is permitted.

[0044] As shown in Figures 1 and 2, the flow-resistant cylinder 40, which is the stopping means, is provided in both the upstream free-flow belt 21 and the downstream free-flow belt 21, and is installed at both the processing location where the machine tool 1, 2 (Figure 1) stops the transport of the pallet 11 on which the workpiece to be processed is loaded, and at the waiting location where the pallet 11 heading toward the processing location is temporarily stopped near the upstream side of the processing location.

[0045] On the other hand, the conveyor belt 26, which is provided to connect the upstream free-flow belt 21 and the downstream free-flow belt 21 in the middle of the two, is a so-called toothed belt 26, as shown in the enlarged view of Figure 2, in which irregularities 26a and 26b extending in the width direction are formed alternately in the longitudinal direction on the outer surface which is the mounting surface of the pallet 11.

[0046] Furthermore, the contact material 14 provided on the base 12 of the pallet 11 has protrusions 14a and 14b that can engage with the protrusions 26a and 26b of the circulating belt. Specifically, the protrusions 14a and 14b of the contact material 14 are configured to be the same shape and size in cross-section so that they can engage with the protrusions 26a and 26b of the conveyor belt 26. When the pallet 11 is placed on the conveyor belt 26 and the contact material 14 overlaps with the conveyor belt 26, the protrusions 14a and 14b formed on the contact material 14 engage with the protrusions 26a and 26b formed on the conveyor belt 26, thereby preventing the pallet 11 from moving in the X-axis direction independently of the conveyor belt 26.

[0047] Furthermore, in order to maintain the engagement between the pallet 11 and the conveyor belt 26, a retaining member 18 is provided to prevent the pallet 11 from lifting off the conveyor belt 26. The retaining member 18 in the figure is a flat plate attached to the upper surface of a pair of support plates 16 that sandwich the pallet 11 from both sides in the width direction, and is configured to prevent the pallet 11 from lifting off the conveyor belt 26 by covering the sides of the base 12 on the pallet 11 from above and making contact with it.

[0048] Next, the pallet transport method according to the present invention using the above-described pallet transport device will be explained.

[0049] The pallet transport method in the present invention is a pallet transport method that uses the above-mentioned pallet transport device 10 to move a plurality of pallets 11 on which workpieces for processing are mounted, wherein the pallets 11 are mounted on a circulation belt 20, and the circulation belt 20 is circulated in that state to transport the pallets 11 mounted on the circulation belt 20.

[0050] In this pallet transport device 10, the circulating belt 20 includes a free-flow belt 21 and a transport belt 26 that is continuously connected to the free-flow belt 21. By circulating both belts in the same direction and loading pallets 11 onto the circulating belt 20, the loaded pallets 11 are transported in the same direction.

[0051] The circulation of this circulation belt 20 is carried out by the drive means 30, which drives the first and second motors 31 and 36, which are the drive means, to simultaneously rotate the drive pulleys 23 and 28 on opposing sides of the pair of support plates 16, causing the free flow belt 21 and the conveyor belt 26, which are the circulation belt 20 that are wrapped around these drive pulleys 23 and 28 and are continuous on the opposing sides of the support plates 16, to circulate in the same direction.

[0052] The explanation will describe a case in which a pallet 11 loaded with a workpiece (not shown) is transported on a circulating belt 20, and the transport of the pallet 11 is stopped by a stopping means 40 in front of machine tools 1 and 2 (Figure 1) located along the transport path, and the machine tools 1 and 2 process the workpiece (not shown) loaded on the pallet 11.

[0053] Then, the workpieces (not shown) are placed on the mounting device 13 on the pallet 11, and the pallet 11 with the workpieces is placed on the upstream end of the circulation belt 20, that is, on the upstream end of the upstream free flow belt 21, as shown by the dashed lines in Figures 5 and 6.

[0054] The pallet 11, mounted on the upstream side of the free-flow belt 21, is moved downstream along with its upper edge due to the contact resistance with the upper edge moving downstream of the circulating free-flow belt 21. When it reaches the front of the machine tool 1, which is positioned opposite the free-flow belt 21 on the upstream side, the transport of the pallet 11 is stopped by the stopping means 40.

[0055] Specifically, as shown in Figure 6, the flow-resistant cylinder 40, which is a stopping means installed at the processing location where the upstream machine tool 1 stops the transport of the pallet 11 in order to process the workpiece, has its retractable rod 40b protruding upward from the main body 40a, while the flow-resistant cylinder 40, which is a stopping means installed at the waiting location upstream of the processing location, has its retractable rod 40b retracted into the main body 40a.

[0056] In this state, when the pallet 11 is placed on the upstream end of the circulating free-flow belt 21, the pallet 11 moving downstream passes through the waiting area and, upon reaching the processing area, comes into contact with the retractable rod 40b of the flow-pressure resistant cylinder 40, which is a stopping means provided at the processing area. As a result, regardless of the circulation of the free-flow belt 21, the pallet 11 slides on the outer surface of the free-flow belt 21, preventing it from moving any further downstream, and thus stopping its transport.

[0057] In this manner, the stopping means 40 stops the transport of the pallet 11, but the circulation speed of the free-flow belt 21 is set so that the workpiece (not shown) does not bounce up, shift, or fly out of the pallet 11 during this stop. While the movement of the pallet 11 is stopped at the processing location by the stopping means 40, the upstream machine tool 1 processes the workpiece (not shown) loaded on the pallet 11 whose movement has been stopped.

[0058] In this embodiment, a stopping means 40 is also provided at a waiting area upstream of the processing area. As shown in Figures 7 and 8, when the aforementioned pallet 11 reaches the processing area, the retractable rod 40b of the flow-resistant cylinder 40, which is a stopping means provided at the waiting area, is extended upward from the main body 40a. This allows the next pallet 11, which is loaded with another workpiece (not shown), to be placed at the upstream end of the free-flow belt 21 during processing of the workpiece loaded on that pallet 11, and the next pallet 11 loaded with that other workpiece can be stopped at a waiting area near the processing area.

[0059] Once the machining of the workpiece mounted on the pallet 11 at the machining site is completed by the machine tool 1, the pallet 11 carrying the workpiece is transported downstream. This transport is initiated by retracting the extension / retraction rod 40b of the flow-resistant cylinder 40, which is a stopping means, into the main body 40a, thereby eliminating the contact between the extension / retraction rod 40b and the pallet 11.

[0060] As a result, due to the friction between the circulating free-flow belt 21 and the pallet 11, the pallet 11 moves downstream along with the upper edge of the free-flow belt 21 as it circulates and moves downstream.

[0061] Furthermore, if a pallet 11 is also stopped at a waiting area upstream of the processing area, as shown in Figures 9 and 10, the stopping means 40 at the processing area is released, and at the same time, the stopping means 40 at the waiting area is released. Specifically, the retractable rod 40b of the flow-resistant cylinder 40, which is the stopping means at the waiting area, is retracted into the main body 40a. As a result, the pallet 11 at the waiting area moves to the processing area, and the stopping means 40 at the processing area prevents further transport, allowing the processing at the upstream machine tool 1 to start immediately.

[0062] When the stopping condition caused by the stopping means 40 is resolved, the pallet 11 carrying the workpiece that has been processed moves downstream from the processing area. When the moving pallet 11 reaches the downstream end of the free flow belt 21, the pallet 11 transfers onto the conveyor belt 26, which is provided to be continuous with the free flow belt 21 and circulates.

[0063] When the pallet 11 is transferred onto the conveyor belt 26, the contact material 14 on the pallet 11 overlaps with the conveyor belt 26. As shown in the enlarged view of Figure 10, the irregularities 14a and 14b formed on the contact material 14 engage with the irregularities 26a and 26b formed on the conveyor belt 26, preventing the pallet 11 from moving in the X-axis direction independently of the conveyor belt 26. Consequently, the pallet 11 is transported downstream at a speed equal to the circulation speed of the conveyor belt 26.

[0064] When the pallet 11, which is mounted on the conveyor belt 26 and moving downstream, reaches the downstream end of the conveyor belt 26, as shown in Figures 11 and 12, the pallet 11 will then move onto the downstream free-flow belt 21, which is provided to circulate continuously with the conveyor belt 26.

[0065] Then, due to the circulation of the downstream free-flow belt 21, the pallet 11 moving further downstream will come into contact with the downstream machine tool 2, which is provided in conjunction with the downstream free-flow belt 21, as shown in Figures 13 and 14, and the transport of the pallet 11 will be stopped again for processing by the downstream machine tool 2.

[0066] The stopping of the pallet 11's transport on the downstream free-flow belt 21 is performed by a stopping means 40 located opposite the downstream free-flow belt 21. The specific operation is the same as that of the upstream free-flow belt 21 described above, so a repeated explanation will be omitted. With the transport stopped, the downstream machine tool 2 performs machining on the workpiece loaded on the pallet 11 while the pallet 11 is stopped from moving.

[0067] Furthermore, since the free-flow belt 21 downstream is also provided with a stopping mechanism 40 at a waiting area upstream of the processing area, when the machine tool 2 is processing at the downstream processing area, the pallet 11 loaded with the next workpiece can be transported further and stopped at the waiting area.

[0068] Once the machining by the downstream machine tool 2 is complete, the pallet 11 is transported downstream again along with the workpiece. This transport is initiated by retracting the extension / retraction rod 40b of the flow-pressure resistant cylinder 40, which is the stopping means, into the main body 40a, thereby releasing the stop. Then, due to the friction between the circulating free-flow belt 21 and the pallet 11, the pallet 11 moves downstream again and is recovered from the downstream end of the free-flow belt 21 along with the workpiece machined by the machine tool 2.

[0069] In this case, if a pallet 11 is also stopped at a waiting area upstream of the processing area, when the stopping means 40 at the processing area is released and the stopping means 40 at the waiting area is released at the same time, the pallet 11 at the waiting area moves to the processing area, and the stopping means 40 at the processing area prevents further transport, allowing the processing at the downstream machine tool 2 to start immediately.

[0070] Furthermore, a distinctive feature of the present invention is that the circulation speed of the conveyor belt 26, which is the circulation belt 20, is increased compared to the circulation speed of the free-flow belt 21, thereby making the conveying speed of the pallet 11 mounted on the conveyor belt 26 faster than the conveying speed of the pallet 11 mounted on the free-flow belt 21.

[0071] In this embodiment, the drive means 30 includes a first motor 31 that circulates the free-flow belt 21 and a second motor 36 that circulates the conveyor belt 26. By controlling the first and second motors 31 and 36 to drive at different rotational speeds based on commands from a controller (not shown), the circulation speed of the conveyor belt 26 can be increased relatively easily.

[0072] As described above, in the pallet transport device 10 of the present invention, which is provided to connect machine tools 1 and 2 that perform predetermined processing on a workpiece and transports a pallet 11 together with the workpiece, when the pallet 11 faces multiple machine tools 1 and 2, the transport of the pallet 11 carrying the workpiece is stopped by the stopping means 40, thereby allowing each machine tool 1 and 2 to process the workpiece.

[0073] Here, the pallets 11 on which the workpieces are loaded are sequentially placed on the free-flow belt 21 and transported, but the circulation speed is set so that the workpieces do not bounce, shift, or fly out of the pallets 11 when the pallets 11 are stopped. For this reason, there is a limit to how much the circulation speed of the free-flow belt 21 can be increased to increase the transport speed of the pallets 11.

[0074] However, in this invention, where the circulation speed of the conveyor belt 26 constituting the circulation belt 20 is increased compared to the circulation speed of the free-flow belt 21 facing the machine tools 1 and 2, the spacing between the multiple pallets 11 that are sequentially loaded onto the free-flow belt 21 expands as each pallet 11 is loaded onto the conveyor belt 26, so it is not always constant.

[0075] In other words, the pallet 11, which is loaded with a workpiece that has been processed by the upstream machine tool 1, is placed on the circulating free-flow belt 21 and transported downstream, and from the downstream end of the free-flow belt 21, the pallet 11 is transferred to the conveyor belt 26. By making the transport speed of the pallet 11 on the conveyor belt 26 faster than the transport speed of the pallet 11 loaded on the free-flow belt 21, the distance between the pallet 11 and the next pallet 11 loaded on the free-flow belt 21 is significantly increased.

[0076] Then, from the downstream end of the conveyor belt 26, the pallet 11 moves onto the slower-moving free-flow belt 21 downstream, and faces the downstream machine tool 2 which is provided in conjunction with that downstream free-flow belt 21.

[0077] Therefore, the time that the pallets 11 are loaded onto the conveyor belt 26, which is stretched to connect the upstream free-flow belt 21 and the downstream free-flow belt 21, is shortened, making it possible to transport the pallets 11 carrying the workpieces processed by the upstream machine tool 1 to the processing location of the downstream machine tool 2 relatively quickly. This makes it possible to reduce the number of pallets 11 required when processing multiple workpieces continuously. At the same time, it is also possible to shorten the time between processing at one machine tool 1 and processing at the next machine tool 2 compared to the conventional method in which the pallets 11 are transported at a constant pitch.

[0078] In particular, as shown in the enlarged views of Figures 10 and 12, when the pallet 11 is mounted on the conveyor belt 26, the irregularities 14a and 14b formed on the contact material 14 engage with the irregularities 26a and 26b formed on the conveyor belt 26. This prevents the pallet 11 from moving in the X-axis direction independently of the conveyor belt 26. Therefore, even if the circulation speed of the conveyor belt 26 is significantly increased, the pallet 11 can be reliably transported at an equal speed.

[0079] Furthermore, in this embodiment, a retaining member 18 is provided to prevent the pallet 11 mounted on the conveyor belt 26 from lifting off the conveyor belt 26. As a result, the engagement between the conveyor belt 26 and the pallet 11 is reliably maintained, and even when the conveyor belt 26 is circulated at a high speed, displacement of the pallet 11 relative to the conveyor belt 26 is prevented. Consequently, even if the circulation speed of the conveyor belt 26 is significantly increased, it becomes possible to reliably transport the pallet 11 at high speed at that high circulation speed.

[0080] In this way, it is possible to increase the conveying speed by the conveyor belt 26, so even in layouts where the distance between each machine tool 1 and 2 is relatively long, for example, the pallet 11 can be conveyed quickly.

[0081] Furthermore, if the processing times for multiple machine tools 1 and 2 are roughly the same, then by transporting the pallet 11 carrying the workpiece that has been processed by the upstream machine tool 1 to a waiting area near the downstream machine tool 2 for a time equal to the processing time when the transport of the pallet 11 is stopped in front of the machine tools 1 and 2, the number of pallets 11 required between those machine tools 1 and 2 will be reduced to one, and the number of surplus pallets 11 can be significantly reduced.

[0082] In the above-described embodiment, contact materials 14 were provided on both sides of the lower part of the base 12, and the contact materials 14 were made to come into contact with the free-flow belt 21 and the conveyor belt 26 that constitute the circulation belt 20. However, as long as the pallet 11 can slide against the free-flow belt 21, the base 12 may be made to come into direct contact with the free-flow belt 21 and the conveyor belt 26 without providing contact materials 14.

[0083] Furthermore, although the above-described embodiment described the case in which a fluid pressure cylinder is used as the stopping means 40, these are merely examples, and other actuators such as servo motors may be used as the stopping means 40, as long as the transport of the pallet 11 can be stopped regardless of the circulation of the free flow belt 21.

[0084] Furthermore, although the stopping means 40 stops the transport of the pallet 11, a buffering means may be provided to flexibly stop the pallet 11 so that workpieces (not shown) do not bounce or fly out of the pallet 11 when it stops.

[0085] Furthermore, the above-described embodiment described a pallet transport device 10 that connects two machine tools 1 and 2, comprising an upstream free-flow belt 21, a transport belt 26 continuous with the free-flow belt 21, and a downstream free-flow belt 21 continuous with the transport belt 26. However, although not shown, the pallet transport device 10 may also connect three or more machine tools. In this way, even if the number of processing steps increases due to the increase in the number of machine tools, by adding multiple free-flow belts 21 facing each machine tool via the transport belt 26, it is possible to change the pitch of the pallets on which the workpieces are mounted and reduce the number of pallets required, thereby achieving the objective of the present invention. [Explanation of Symbols]

[0086] 10 Pallet transport device 11 Palettes 14a,14b Uneven surface 16 Support plate 18 Retaining member 20 Circulation belt 21 Free Flow Belt 26 Conveyor belt 26a,26b unevenness 30 Driving means 31 First Motor 36 Second motor 40. Flow-resistant pressure cylinder (stopping mechanism)

Claims

1. A conveying device that conveys multiple pallets (11) along a conveying path, The pallet (11) is capable of mounting a workpiece to be processed by a machine tool, and the surface to be processed (14a, 14b) is formed alternately and continuously in the longitudinal direction along the transport path of the pallet (11). A free-flow belt (21) is positioned opposite the machine tool and transports the pallet (11) on which the workpiece is mounted by circulation. A stopping means (40) that brings the retractable rod (40b) into contact with the pallet (11) and causes the pallet (11) to slide on the outer surface of the free flow belt (21) regardless of the circulation of the free flow belt (21), thereby stopping the transport of the pallet (11), A conveyor belt (26) is positioned in a location without the machine tool, continuously arranged with the free-flow belt (21), and mounted on the pallet (11). The conveyor belt (26) has interlocking protrusions (26a, 26b) that engage with the interlocking protrusions (14a, 14b) of the pallet (11), which are alternately and continuously formed in the longitudinal direction along the conveying path of the pallet (11). A driving means (30) that circulates the conveyor belt (26) and the free-flow belt (21) in the same direction, Equipped with, In the free-flow belt (21), while the transport of the pallet (11) is stopped by the stopping means (40), the workpiece placed on the pallet (11) is processed by the machine tool. The drive means (30) is configured to increase the circulation speed of the conveyor belt (26), which is located in a part of the machine tool area that is continuous with the free-flow belt (21), to a higher speed than the circulation speed of the free-flow belt (21). A pallet transport device characterized by the following features.

2. The pallet conveying device according to claim 1, wherein a plurality of the free-flow belts (21) are provided via the conveying belts (26).

3. A pair of support plates (16, 16) that sandwich the pallet (11) from both sides in the width direction are provided along the transport path, The stopping means (40) is provided between the pair of support plates (16, 16) at both a processing location for stopping the transport of the pallet (11) and a waiting location near the processing location for temporarily stopping the pallet (11). The pallet transport device according to claim 1 or 2.

4. The pallet conveying device according to any one of claims 1 to 3, wherein the driving means (30) comprises a first motor (31) for circulating the free flow belt (21) and a second motor (36) provided separately from the first motor (31) for circulating the conveying belt (26).

5. A retaining member (18) is provided to prevent the pallet (11) mounted on the conveyor belt (26) from lifting off the conveyor belt (26). A pallet transport device according to any one of claims 1 to 3.

6. A pallet transport method for transporting a pallet (11) using a pallet transport device (10) according to any one of claims 1 to 5, The circulation speed of the conveyor belt (26) is increased compared to the circulation speed of the free-flow belt (21), thereby increasing the conveying speed of the pallets (11) mounted on the conveyor belt (26) to be faster than the conveying speed of the pallets (11) mounted on the free-flow belt (21). A pallet transport method characterized by the following.

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