Platform lifting device and transport vehicle equipped with platform lifting device

Abstract

To provide a platform lifting device and a transport vehicle equipped with a platform lifting device that offer a high degree of design flexibility while enabling the lifting and lowering of heavy objects. [Solution] A cargo bed lifting device 4 raises and lowers a cargo bed 13 supported by a link mechanism 12 by swinging a link mechanism 12 by moving a cylinder rod 24 in a drive means 11, and is equipped with a biasing means 26 that applies a biasing force to the link mechanism 12 to swing in the upright direction.

Description

Technical Field

[0005] , , , , , ,

[0001] The present invention relates to a load lifting device capable of lifting and lowering an article and a transport vehicle equipped with the load lifting device.

[0002] In recent years, for the improvement of business efficiency and productivity, automation has been progressing for various operations performed in facilities such as factories and logistics warehouses. For example, automated transport equipment may be installed in a logistics warehouse. The transport equipment shown in Patent Document 1 includes a storage shelf standing on the floor with a plurality of storage lines vertically and horizontally, a traveling vehicle that moves articles in the storage shelf, and an in-storage lifter and an out-storage lifter.

[0003] In transport equipment, articles are often placed on a common pallet and stored. When being shipped out, the pallet transported to the out-storage lifter needs to be further transported to the next location, for example, to a section where packing work is performed in the case of logistics. Although a transport vehicle different from the traveling vehicle can be used for the movement from this out-storage lifter to the next section, a lifting function is required to load and unload the pallet between the placement table in the next section.

[0004] For example, the transport vehicle having a lifting function described in Patent Document 2 includes a pantograph-type load lifting device on the upper part of the traveling body main body. A hydraulic or electric cylinder is connected to the pantograph, and the pantograph is swung by the forward and backward movement of the cylinder rod, and the load supported on the upper part of the pantograph is lifted and lowered.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a cargo bed lifting device like the one described in Patent Document 2, when raising the cargo bed from a lowered position, the lowered pantograph arm is pushed by the cylinder rod. The more the angle of the pantograph arm is reclined, such as in the lowered position, the greater the ratio of the vertical movement distance of the upper end of the pantograph arm to the rotational distance of the pantograph arm when the pantograph arm is raised, i.e., the distance the cargo bed is raised. In other words, in the initial lowered position where the pantograph arm is completely lowered, a larger load is placed on the cylinder compared to later positions. This leads to a problem where the cylinder has to be enlarged to raise the pantograph arm in this initial lowered position, resulting in a low degree of design freedom for the cargo bed lifting device.

[0007] This invention was made in view of these problems, and aims to provide a platform lifting device and a transport vehicle equipped with a platform lifting device that allow for the lifting and lowering of heavy objects while offering a high degree of design flexibility. [Means for solving the problem]

[0008] To solve the above problems, the cargo bed lifting device of the present invention is A cargo bed lifting device that raises and lowers a cargo bed supported by a link mechanism by swinging a link mechanism by moving a cylinder rod in the drive mechanism, The device is characterized by having a biasing means that provides a biasing force to the link mechanism to cause it to swing in the upright direction. This feature allows the link mechanism to be raised with a greater force than the driving force of the drive mechanism by applying a biasing force from the biasing means to the link mechanism. This enables the lifting and lowering of heavy objects without increasing the size of the drive mechanism, thus increasing the design flexibility of the cargo platform lifting device.

[0009] The biasing means is characterized by applying a biasing force to the link mechanism to cause it to swing in the upright direction only within a predetermined swing range on the side of the link mechanism in its initial tilted position. This feature allows for miniaturization of the biasing mechanism and increases the design flexibility of the loading platform lifting device by applying a biasing force only in the initial tilting position, where the link mechanism is completely tilted, which places a particularly heavy load on the driving mechanism.

[0010] The aforementioned link mechanism is configured such that pantograph arms, formed by pivotally connecting intersecting arms, are arranged opposite each other on the left and right sides, and the lower ends of these pantograph arms are connected to each other on the left and right sides by a connecting member. The drive means is such that the cylinder rod moves back and forth parallel to the direction of movement of the connecting member, which moves horizontally in conjunction with the swinging of the pantograph arm. The biasing means is characterized by being positioned on the opposite side of the cylinder rod, with the connecting member in between. This feature allows for effective use of the space between the left and right pantograph arms that constitute the link mechanism by arranging the driving means and the biasing means opposite each other with a connecting member in between.

[0011] The biasing means is characterized in that it stores energy only within a predetermined swing range on the initial tilted position of the pantograph arm, by the swinging of the pantograph arm in the tilting direction. This feature allows for energy storage to occur only in the initial tilted position where the pantograph arm is fully lowered. This eliminates the need for continuous driving force from the drive mechanism for energy storage, thus preventing the drive mechanism from becoming larger.

[0012] One end of a rod member is pivotally attached to the connecting member, and the other end of the rod member is inserted through a guide hole formed in the frame to which the pantograph arm is attached. The biasing means is characterized by being a coil spring inserted through the rod member. According to this feature, the rod member is guided into the guide hole, allowing the coil spring, which is the biasing means, to be precisely compressed and extended in the axial direction, thereby efficiently applying biasing force.

[0013] To solve the above problems, the transport vehicle equipped with the cargo bed lifting device of the present invention is A transport vehicle equipped with a cargo bed lifting device that raises and lowers a cargo bed supported by a link mechanism by swinging a link mechanism by moving a cylinder rod in the drive mechanism, The device is characterized by having a biasing means that provides a biasing force to the link mechanism to cause it to swing in the upright direction. This feature allows the link mechanism to be raised with a greater force than the driving force of the drive mechanism by applying a biasing force from the biasing means to the link mechanism. This enables the lifting and lowering of heavy objects without increasing the size of the drive mechanism, thus increasing the design flexibility of the cargo platform lifting device.

[0014] The biasing means is characterized by applying a biasing force to the link mechanism to cause it to swing in the upright direction only within a predetermined swing range on the side of the link mechanism in its initial tilted position. This feature allows for miniaturization of the biasing mechanism and increases the design flexibility of the loading platform lifting device by applying a biasing force only in the initial tilting position, where the link mechanism is completely tilted, which places a particularly heavy load on the driving mechanism.

[0015] The aforementioned link mechanism is configured such that pantograph arms, formed by pivotally connecting intersecting arms, are arranged opposite each other on the left and right sides, and the lower ends of these pantograph arms are connected to each other on the left and right sides by a connecting member. The drive means is such that the cylinder rod moves back and forth parallel to the direction of movement of the connecting member, which moves horizontally in conjunction with the swinging of the pantograph arm. The biasing means is characterized by being positioned on the opposite side of the cylinder rod, with the connecting member in between. This feature allows for effective use of the space between the left and right pantograph arms that constitute the link mechanism by arranging the driving means and the biasing means opposite each other with a connecting member in between.

[0016] The biasing means is characterized in that it is energized only within a predetermined swing range on the initial posture side of the collapse of the panta arm by the swing of the panta arm in the collapsing direction. According to this feature, by enabling energization only on the initial posture side of the collapse where the panta arm is in a fully collapsed state, it is possible to prevent the need for a continuous driving force of the driving means for energization and prevent enlargement of the driving means.

[0017] One end of the rod member is pivotally attached to the connecting member, and the other end of the rod member is inserted into a guide hole formed in a frame body to which the panta arm is attached. The biasing means is a coil spring inserted through the rod member. According to this feature, the rod member is guided by the guide hole, so that the coil spring as the biasing means is accurately compressed and extended in the axial direction, and the biasing force can be efficiently applied.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view showing the entire conveying facility in which a carrier equipped with a loading platform lifting device in an embodiment of the present invention is used. [Figure 2] It is a perspective view showing a carrier with the loading platform located at the lowest position. [Figure 3] It is a perspective view showing a carrier with the loading platform located at the lowest position. [Figure 4] It is a side sectional view showing a carrier with the loading platform located at the lowest position. [Figure 5] It is a sectional view taken along the line A-A of FIG. 4. [Figure 6] It is a perspective view showing the loading receiving platform on the warehousing side. [Figure 7] It is a side sectional view of the carrier in a state where the natural length of the coil spring is equal to the separation dimension between the receiving member and the rod portion of the frame body. [Figure 8] It is a side sectional view showing a carrier with the loading platform located at the highest position. [Figure 9] It is a sectional view taken along the line A-A of FIG. 8. [Modes for carrying out the invention]

[0019] The embodiments for implementing the cargo bed lifting device and the transport vehicle equipped with the cargo bed lifting device according to the present invention will be described below based on examples. [Examples]

[0020] A transport vehicle equipped with a platform lifting device according to the embodiment will be described with reference to Figures 1 to 9. For the sake of explanation, the upper right of Figure 2 will be considered the front of the transport vehicle, and the lower left of Figure 2 will be considered the rear of the transport vehicle.

[0021] A transport platform equipped with a platform lifting device is used in factories, warehouses, logistics centers, etc., to transport goods by traveling on the floor. In this embodiment, the transport vehicle can load and unload pallets 9 of the same specifications on which goods 3 are placed, as well as individual pallets 9, and transport them. (Hereafter, goods 3 and pallets 9 may be referred to simply as "goods.")

[0022] As shown in Figure 1, the transport equipment S comprises a storage shelf 102 erected on the floor with multiple storage lines 102a, 102a, ... on the top, bottom, left, and right; a shelf vehicle 101 for moving pallets 9 within the storage shelf 102; an inbound lifter 123A and an outbound lifter 123B; an inbound receiving platform 126A and an outbound receiving platform 126B; a lateral movement passage 127; and a transport vehicle 1.

[0023] Although not described in detail here, the shelf vehicle 101 travels along the storage line 102a and lateral passage 27 of the storage shelf 102, lifting the stored goods 3 along with their pallets 9, and can transport goods between the receiving lifter 123A and the outbound lifter 123B and any point on the storage line 102a.

[0024] The loading lifter 123A and the loading lifter 123B are mainly composed of a plurality of masts 122 erected on the floor, a lifting platform 124 supported by these masts 122 so as to be movable in the vertical direction, and a lifting drive unit (not shown) that moves the lifting platform 124 in the vertical direction.

[0025] The lifting platform 124 is equipped with a transfer device (not shown), which moves the pallet 9 horizontally and allows the pallet 9 to be transferred between the lifting platform 124 and the receiving platform 126A and the receiving platform 126B, respectively.

[0026] As shown in Figures 2 to 5, the transport vehicle 1 has a vehicle body 2 that can travel on the floor and a cargo bed lifting device 4 that is positioned above the vehicle body 2. In Figure 2, the cargo bed 13 is in its lowest position, and in Figure 3, the cargo bed 13 is in its highest position. The vehicle body 2 has a vehicle body housing 20, a plurality of wheels 30, 31 attached to the vehicle body housing 20, and a drive motor for driving the drive wheels 31 which is built into the vehicle body housing 20 (not shown here), a sensor device, a storage battery, an MPU, a communication unit, etc.

[0027] The MPU is a computing unit that controls the driving motion of the vehicle body 2, the operation of the cargo bed lifting device 4, and determines the driving path. The drive motor for driving and the drive means 11 of the cargo bed lifting device 4 are powered by the battery. The communication unit is a wireless communication means for communicating with base stations and operating terminals, and can receive command signals from base stations and operating terminals, and transmit data stored in the memory unit.

[0028] Furthermore, the vehicle body 2 is equipped with a front sensor (not shown) capable of detecting the presence or absence of objects in front and a back sensor (not shown) capable of detecting the presence or absence of objects behind. The front sensor and back sensor are laser scanners capable of detecting objects over a wide range in the horizontal direction. The drive motor is also equipped with a rotary encoder (not shown) as an acquisition means for detecting rotational speed and acquiring position information.

[0029] The MPU rotates the drive motors based on command signals, and the drive wheels, driven by these motors, roll across the floor surface, causing the vehicle to move. By controlling the rotation direction and speed of the drive motors provided for each drive wheel, the transport vehicle 1 is capable of moving in a straight line in the forward and backward directions and turning.

[0030] Information about the necessary tasks is transmitted to the transport vehicle 1 from the base station or operating terminal. Upon receiving the task information, the MPU of the transport vehicle 1 takes into account its own position information and orientation information to create the optimal travel route to the outbound receiving platform 126B (or inbound receiving platform 126A), and the optimal travel route from the outbound receiving platform 126B (or inbound receiving platform 126A) to a designated transport destination not shown in Figure 1, and autonomously travels along these routes.

[0031] When the transport vehicle 1 arrives at the outbound loading platform 126B (or inbound loading platform 126A), the MPU of the transport vehicle 1 reads a two-dimensional code placed on the floor using a reader (not shown) installed on the underside of the vehicle body. The two-dimensional code stores position information and phase information of the outbound loading platform 126B (or inbound loading platform 126A), and the MPU of the transport vehicle 1 makes fine adjustments based on this information to achieve the correct position and phase relative to the outbound loading platform 126B (or inbound loading platform 126A).

[0032] The MPU operates the platform lifting device 4 after determining that the transport vehicle 1 has moved to the correct position and phase relative to the outbound loading platform 126B (or inbound loading platform 126A). Figure 6 shows the inbound loading platform 126A. Since the inbound loading platform 126A and the outbound loading platform 126B have the same structure, the structure of the inbound loading platform 126A will be described here, and the description of the outbound loading platform 126B will be omitted.

[0033] As shown in Figure 6, the receiving platform 126A is configured with a frame 126c that is open in one direction and has a roughly U-shape in plan view, and guide pieces 126d formed at each of the four corners of the frame 126c. The guide pieces 126d have orthogonal inclined surfaces that widen upwards, so as to guide the four corners of the pallet 9. The MPU performs the operation of unloading the pallet 9 from the receiving platform 126B if it is for the receiving platform 126B, and loading the pallet 9 onto the receiving platform 126A if it is for the receiving platform 126A.

[0034] Furthermore, while the transport vehicle 1 avoids stationary obstacles in its direction of travel using front and rear sensors, multiple transport vehicles 1 can operate simultaneously within the facility. Therefore, there is a risk that the travel paths of the autonomous transport vehicles 1 may overlap, intersect, etc. (hereinafter simply referred to as "intersections"). If the distance between the transport vehicles 1 whose travel paths intersect is sufficiently large, there is no risk of collision. Therefore, each transport vehicle 1 monitors the distance between them using its respective MPU, and performs collision avoidance processing as appropriate only when it is determined that there is a risk of collision.

[0035] As shown in Figures 2 to 5, the cargo bed lifting device 4 of the transport vehicle 1 comprises a frame 10, a link mechanism 12, a cargo bed 13 supported at the upper end of the link mechanism 12, and a drive means 11 for swinging the link mechanism 12. The aforementioned storage battery and MPU are also included in the cargo bed lifting device 4.

[0036] The link mechanism 12 is constructed by arranging pantograph arms 14, 14 opposite each other on the left and right sides, and connecting the lower ends of the pair of pantograph arms with a connecting member 17. Hereafter, since the pair of opposing pantograph arms 14 have the same configuration, one pantograph arm 14 will be described, and the description of the structure of the other pantograph arm 14 will be omitted.

[0037] In this embodiment, the pantograph arm 14 is formed by two intersecting arms 15A and 15B that intersect approximately in the center of their longitudinal direction and are pivotally connected by a shaft portion 16. Of the two arms 15A and 15B that make up the pantograph arm 14, one arm 15A is inclined so that its lower end is located at the rear of the transport vehicle 1 and its upper end is located at the front of the transport vehicle 1, while the other arm 15B is inclined so that its lower end is located at the front of the transport vehicle 1 and its upper end is located at the rear of the transport vehicle 1. Furthermore, the upper ends of the two arms 15A and 15B that make up the pantograph arm 14 are pivotally connected to the loading platform 13, spaced apart in the front-rear direction.

[0038] The lower end of one of the arms 15A and 15B that make up the pantograph arm 14 is pivotally attached to the left and right opposing side rods 10a of a frame 10, which is roughly rectangular in plan view, built into and supported by the body housing 20 of the car body 2. In addition, a round rod-shaped connecting member 17 is attached to the lower end of one of the arms 15A that make up the pantograph arm 14, and the lower ends of the left and right opposing arms 15A, 15A are connected to each other.

[0039] Furthermore, both longitudinal ends of this connecting member 17 are positioned to pass through the lower ends of the opposing left and right arms 15A, 15A outwards, and rollers 18 are pivotally attached to both ends of these arms 15A, 15A so as to be able to roll back and forth. More specifically, a rail 100a with upper and lower guide surfaces is formed on the inside of the opposing left and right side rods 10a that constitute the frame 10, and the aforementioned rollers 18 are positioned between the upper and lower guide surfaces of the rail 100a.

[0040] The connecting member 17 has a round bar shape with a roughly circular cross-section, and a pair of receiving members 19 are attached to the center of its longitudinal direction, spaced apart on the left and right. The receiving members 19 are roughly cylindrical and are loosely fitted to the connecting member 17 so as to be rotatable in the circumferential direction and movable in the longitudinal direction.

[0041] The tip of the cylinder rod 24 of the electric actuator 21, which constitutes the driving means 11, is connected to the front part of the receiving member 19, sandwiching the connecting member 17, so that it can swing up and down.

[0042] The drive mechanism 11 consists of a pair of left and right electric actuators 21, 21 that can operate independently of each other, and includes a hollow cylindrical cylinder 22, a cylinder rod 24 that can move back and forth relative to the cylinder 22, and a motor 23.

[0043] The electric actuator 21 is a known type, and houses an axially extending ball screw (not shown) that is rotated by a motor 23. A nut (not shown) is fixed to the cylinder rod 24, which is screwed onto the ball screw in a way that restricts its rotation. When the motor 23 rotates the ball screw, the nut is screwed along the ball screw, causing the cylinder rod 24 to move forward and backward. In other words, since the ball screw and nut on the cylinder rod 24 are always screwed together, the forward and backward movement of the cylinder rod 24 is restricted when the rotation of the motor 23 stops. Thus, the electric actuator 21 has a locking mechanism in the unpowered state. Furthermore, the left and right electric actuators 21, 21 operate synchronously.

[0044] As shown in Figures 4 and 5, one longitudinal end of a rod member 25, which constitutes the guide means, is fixed to the rear side of the receiving member 19 opposite to the cylinder rod 24. The free end of the rod member 25 is inserted through a guide hole 10c formed in the rear rod portion 10b that constitutes the frame 10.

[0045] Furthermore, a coil spring 26, which is a biasing means, is inserted through the rod member 25 between the receiving member 19 on the rod member 25 and the rod portion 10b of the frame 10. The coil spring 26 is a compression spring, and its natural length is shorter than the front-to-back dimension between the receiving member 19 and the rod portion 10b of the frame 10 when the link mechanism 12 is in its most upright position, that is, when the loading platform 13 is in its highest position (see Figure 8).

[0046] Next, the lifting and lowering operation of the cargo bed lifting device 4 of the transport vehicle 1 will be explained using Figures 4 to 9. During the lowering operation, the pair of left and right motors 23, 23 are driven to extend the cylinder rods 24, 24, and the tips of the cylinder rods 24, 24 push the connecting member 17 backward via the receiving members 19, 19 to which it is connected. As a result, the lower end of one of the arms 15A, 15A that make up the left and right pantograph arms 14, 14 to which the connecting member 17 is connected is pushed backward, that is, in a direction away from the lower end of the other arm 15B, 15B, and as a result the pantograph arms 14, 14 swing in the tilting direction, the cargo bed 13 is lowered.

[0047] Furthermore, since the link mechanism 12 is configured to stabilize in a tilted position in its natural state due to the weight and self-weight of the loading platform 13, the cylinder rods 24, 24 constantly support the weight of the loading platform 13 and the tilting load on the arms 15A, 15B via the connecting member 17, and if there are items placed on the loading platform 13, their weight is also supported via the connecting member 17. In other words, when the loading platform 13 is lowered, the motors 23, 23 that extend the cylinder rods 24, 24 are used as the driving force, and the weight of the loading platform 13, the tilting load on the arms 15A, 15B, and, if there are items placed on the loading platform 13, their weight pushes the connecting member 17 backward, thereby reliably compressing the coil spring 26 against the biasing force.

[0048] As described above, the coil spring 26 has a natural length shorter than the front-to-back dimension between the receiving member 19 and the rod portion 10b of the frame 10 when the loading platform 13 is in its highest position. Therefore, as shown in Figure 7, as the loading platform is lowered, the front-to-back dimension between the receiving member 19 and the rod portion 10b of the frame 10 shortens to become equal to the natural length of the coil spring 26, causing both ends of the coil spring 26 in the longitudinal direction to come into contact with the receiving member 19 and the rod portion 10b of the frame 10, respectively.

[0049] Furthermore, the coil spring 26 is compressed and energized by the swinging of the link mechanism 12 in the tilting direction only within a predetermined range from the state in which both longitudinal ends are in contact with the receiving member 19 and the rod portion 10b of the frame 10 to the initial tilting position (see Figure 4).

[0050] As described above, since the electric actuator 21 has a locking mechanism, the link mechanism 12 can maintain its initial tilting position, in other words, the compressed state (energy-stored state) of the coil spring 26 is maintained.

[0051] Conversely, during the upward movement, from the initial lowered position of the pantograph arm shown in Figure 4, the motors 23, 23 are driven to move the cylinder rods 24, 24 backward, and the tips of the cylinder rods 24, 24 pull the connecting member 17 via the receiving member 19 to which they are connected. As a result, the lower end of one arm 15A, 15A, which constitutes the left and right pantograph arms 14, 14 to which the connecting member 17 is connected, is pulled forward, that is, in a direction closer to the lower end of the other arm 15B, 15B, and as a result the pantograph arms 14, 14 swing in the direction of standing upright, the cargo bed 13 is raised. The link mechanism 12 is maintained in the upright position by the locking mechanism of the electric actuator 21.

[0052] From the initial lowered position of the pantograph arm 14 shown in Figure 4, after the point when the loading platform 13 has risen to the natural length of the coil spring 26, and the front-to-back dimension between the receiving member 19 and the rod portion 10b of the frame 10 has increased (see Figure 7), both longitudinal ends of the coil spring 26 are separated from the receiving member 19 and the rod portion 10b of the frame 10.

[0053] In other words, the biasing force of the coil spring 26 functions to press the lower end of one of the arms 15A, 15A in the upright direction of the link mechanism 12 only within a predetermined range from the initial lowered position of the pantograph arm 14 until both longitudinal ends are separated from the receiving member 19 and the rod portion 10b of the frame 10. In other words, within this predetermined range, the biasing force of the coil spring 26 is supplementarily applied to the driving force of the motors 23, 23 as the driving means 11 that moves the cylinder rods 24, 24 backward, allowing the link mechanism 12 to be raised with a greater force than the driving force of the driving means 11. Therefore, it is possible to raise and lower heavy objects without increasing the size of the driving means 11, and the design freedom of the cargo bed lifting device 4 can be increased. In addition, the negative impact on the drivability of the vehicle body 2 due to the increased size of the driving means 11 is minimized.

[0054] After the longitudinal ends of the coil spring 26 are separated from the receiving member 19 and the rod portion 10b of the frame 10, the loading platform 13 is raised to the required height solely by the driving force of the driving means 11 (see Figures 8 and 9).

[0055] In this way, by simply installing a coil spring 26 that provides a biasing force in the upright direction of the link mechanism 12, the lifting operation of the cargo bed 13 can be assisted, especially in the initial tilted position where the link mechanism 12, which places a large load on the drive means 11, is completely tilted down. This allows for the lifting of items of sufficient weight with a simple configuration. Furthermore, by using a lightweight coil spring 26, there is no impact on the drivability of the vehicle body 2.

[0056] Furthermore, the drive mechanism 11 is composed of a pair of left and right electric actuators 21, 21 that operate synchronously. This allows the driving force required to raise and lower the cargo bed 13 to be distributed, thereby reducing the dimensions of the drive mechanism 11, especially its height. Similarly, the coil springs 26 that constitute the biasing mechanism are arranged in pairs on the left and right, facing each other in the direction of parallel movement of the connecting member, which allows for a reduction in the diameter of each coil.

[0057] As described above, by reducing the height dimensions of the drive mechanism 11 and the coil spring 26, a large upper space above the part of the vehicle body 20 that controls the driving function can be secured, and the link mechanism 12 is contained within this upper space of the vehicle body 20 in the initial tilted position (see Figures 2 and 4) and is not exposed to the outside.

[0058] Furthermore, the drive mechanism 11 has cylinder rods 24, 24 that move parallel to a connecting member 17 that connects the lower ends of the pantograph arms constituting the link mechanism 12, and the biasing means, a coil spring 26, is positioned on the opposite side of the connecting member 17 from the cylinder rods 24, 24. With this arrangement, the drive mechanism 11 and the coil spring 26 are positioned horizontally opposite each other with the connecting member 17 in between, and the amount of upward protrusion of the drive mechanism 11 and the coil spring 26 can always be kept small from the initial tilted position (see Figure 4) to the fully upright position (see Figure 8). Specifically, both the drive mechanism 11 and the coil spring 26 are always located below the shaft portion 16 of the pantograph arm 14, which effectively prevents wiring necessary for the movement of the vehicle body 2, the lifting and lowering operation of the cargo bed lifting device 4, and detection by sensors from interfering with the swinging operation of the pantograph arm 14.

[0059] Furthermore, the coil spring 26 stores energy only within a predetermined range of oscillation on the initial tilting side of the pantograph arm 14, due to the oscillation of the pantograph arm 14 in the tilting direction. Therefore, continuous driving force from the drive means 11 is not required for energy storage, and the size of the drive means 11 can be prevented from being increased.

[0060] Furthermore, one end of the rod member 25 is pivotally attached to the connecting member 17, and the free end of the rod member 25 is inserted through a guide hole 10c formed in the frame 10, and a coil spring 26 is inserted through the rod member 25. As a result, the rod member 25 is guided through the guide hole 10c, so that the coil spring 26 is accurately compressed and extended in the direction of movement of the connecting member 17, enabling efficient energy storage and biasing force application.

[0061] Furthermore, by employing a link mechanism 12 using the pantograph arm 14, the lifting length of the loading platform 13 is longer than the stroke length of the cylinder rod 24 from the initial tilted position to the fully upright position, which sufficiently prevents interference between the guide piece 126d of the loading platform 126A or the loading platform 126B on the receiving side and the pallet 9, enabling reliable loading and unloading.

[0062] Furthermore, in the above embodiment, the coil spring 26 was described as having a natural length shorter than the front-to-back dimension between the receiving member 19 and the rod portion 10b of the frame 10 when the link mechanism 12 is in its most upright position, that is, when the loading platform 13 is in its highest position (see Figure 8). However, the invention is not limited to this configuration, and for example, the coil spring 26 may be configured to always be in contact with the receiving member 19 and the rod portion 10b of the frame 10, that is, the natural length of the coil spring 26 may be greater than or equal to the front-to-back dimension between the receiving member 19 and the rod portion 10b of the frame 10 when the loading platform 13 is in its highest position.

[0063] Although embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to these embodiments, and any changes or additions that do not depart from the spirit of the present invention are also included.

[0064] For example, the cargo bed lifting device 4 is not limited to being installed on top of a drivable vehicle body 2, but may also be used as a standalone unit.

[0065] Furthermore, the link mechanism constituting the cargo bed lifting device 4 is not limited to a configuration using a pantograph arm 14, but may also be a parallel link structure, for example.

[0066] Furthermore, the biasing means that provides a biasing force to cause the link mechanism 12 to swing in the upright direction is not limited to the coil spring 26 which is a compression spring, but may also be a tension spring or a gas spring, for example.

[0067] Furthermore, the drive means 11 is not limited to a configuration using an electric actuator 21 with a locking mechanism; for example, a fluid pressure cylinder operated by hydraulics or pneumatics may be used, and the locking mechanism may be a lock pin or the like operated by another drive source. [Explanation of Symbols]

[0068] 1. Transport vehicle 2 car bodies 3 Products (goods) 4. Cargo bed lifting device 9 Pallets (goods) 10 Frame 10b Rod 10c Guide hole 11 Driving means 12 Link mechanism 13. Cargo bed 14 Pantograph Arms 15A, 15B tonearm 16. Shaft section 17 Connecting member 18 Laura 19 Receiving member 20 Vehicle body 20 Vehicle body 21 Electric Actuator 22 volts 23 Motor 24 Cylinder rod 25 Coil Springs 25 Rod members 26 Coil Springs 31 Drive wheels 100a rail 101 Vehicles on shelves 102a Storage Line 102 Storage shelves 122 Mast 123A Inbound lifter 123B Exit Lifter 124 Elevator 126A Loading platform on the receiving side 126B Outbound loading platform 126c frame 126d Guide piece S Conveying equipment

Claims

1. A cargo bed lifting device that raises and lowers a cargo bed supported by a link mechanism by swinging a link mechanism by moving a cylinder rod in the drive mechanism, A loading platform lifting device characterized by comprising a biasing means for applying a biasing force to the link mechanism to cause it to swing in the upright direction.

2. The loading platform lifting device according to claim 1, characterized in that the biasing means applies a biasing force to the link mechanism to cause it to swing in the upright direction only within a predetermined swing range on the side of the link mechanism in its initial tilted position.

3. The aforementioned link mechanism is configured such that pantograph arms, formed by pivotally connecting intersecting arms, are arranged opposite each other on the left and right sides, and the lower ends of these pantograph arms are connected to each other on the left and right sides by a connecting member. The drive means is such that the cylinder rod moves back and forth parallel to the direction of movement of the connecting member, which moves horizontally in conjunction with the swinging of the pantograph arm. The loading platform lifting device according to claim 1, characterized in that the biasing means is arranged on the opposite side of the cylinder rod, with the connecting member in between.

4. The cargo bed lifting device according to claim 3, characterized in that the biasing means is energized only within a predetermined swing range on the initial tilted position side of the pantograph arm by the swinging of the pantograph arm in the tilting direction.

5. One end of a rod member is pivotally attached to the connecting member, and the other end of the rod member is inserted through a guide hole formed in the frame to which the pantograph arm is attached. The loading platform lifting device according to claim 4, characterized in that the biasing means is a coil spring inserted through the rod member.

6. A transport vehicle equipped with a cargo bed lifting device that raises and lowers a cargo bed supported by a link mechanism by swinging a link mechanism by moving a cylinder rod in the drive mechanism, A transport vehicle equipped with a platform lifting device, characterized by having a biasing means that applies a biasing force to the link mechanism to cause it to swing in an upright direction.

7. The transport vehicle equipped with a platform lifting device according to claim 6, characterized in that the biasing means applies a biasing force to the link mechanism to cause it to swing in the upright direction only within a predetermined swing range on the side of the link mechanism in its initial tilted position.

8. The aforementioned link mechanism is configured such that pantograph arms, formed by pivotally connecting intersecting arms, are arranged opposite each other on the left and right sides, and the lower ends of these pantograph arms are connected to each other on the left and right sides by a connecting member. The drive means is such that the cylinder rod moves back and forth parallel to the direction of movement of the connecting member, which moves horizontally in conjunction with the swinging of the pantograph arm. A transport vehicle equipped with a platform lifting device according to claim 6, characterized in that the biasing means is arranged on the opposite side of the cylinder rod, with the connecting member in between.

9. A transport vehicle equipped with a cargo bed lifting device according to claim 8, characterized in that the biasing means stores energy only within a predetermined swing range on the initial tilting position side of the pantograph arm by the swinging of the pantograph arm in the tilting direction.

10. One end of a rod member is pivotally attached to the connecting member, and the other end of the rod member is inserted through a guide hole formed in the frame to which the pantograph arm is attached. A transport vehicle equipped with a platform lifting device according to claim 9, characterized in that the biasing means is a coil spring inserted through the rod member.

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