JP7548500B2 - Towing dolly - Google Patents

Description

This invention generally belongs to the technical field of towing carts, which are used to transport parts or cargo to required locations (destinations) in factories, logistics centers, airports, etc. by connecting multiple carts to a leading motorized transport vehicle.

Generally, when moving parts or cargo to a required location in a factory, logistics center, airport, etc., a towing cart is used by connecting multiple cars to a leading powered transport vehicle for transporting them. The more cars that are connected, the more they can be transported at one time, which is desirable from the standpoint of rationality and efficiency. However, as the number of cars connected increases, problems with the inner wheel difference that arise when turning paths, etc. become more pronounced, and this is an issue that needs to be resolved.
In other words, there is a demand for a towing bogie with small inside wheel difference so that it can follow as closely as possible the path of the leading towing bogie, and therefore the path of the leading powered transport vehicle, even when the number of vehicles connected to the bogie is increased.

For example, Patent Document 1 discloses a steering device for a towed cart in which, as described in the claims for the utility model registration and in Figure 3 etc., front, rear, left and right caster wheels 4a, 4b and 5a, 5b are arranged at equal left and right distribution positions with respect to the center line P of the cart body 3, the pivot levers 12 of the front caster wheels 4a, 4b are directed rearwardly to the rear of the pivot shaft 14, and a link 10 connected to this lever 12 is connected to a left and right equal distribution position near the center line on the rear side of the swing vertical shaft 9 of the cart towing member 7, and the pivot levers 13 of the rear caster wheels 5a, 5b are extended diagonally forward on the outside of the wheel with respect to the pivot shaft 14, and a link 11 connected to this lever 13 is connected to a left and right equal distribution position near the center line on the rear side of the front link connection points 10a, 10b of the cart towing member 7 so as to cross each other.
The steering device of the towed trolley described in Patent Document 1 has the following effect: "By arranging the pairs of front and rear caster wheels on the left and right sides in a distributed manner relative to the center line midway between the left and right sides of the trolley body, even if the caster wheels are rotated for steering, the ground support point of the caster wheel only moves parallel to the trolley body by a slight offset amount of the caster wheel, and the left and right stability of the towed trolley is almost unchanged from when it is towed in a straight line, so that the cargo can be moved safely" (for details, see the section on the effects of the invention in the specification).

Patent Document 2 discloses a vehicle that follows the wheel tracks of a towing vehicle in front, as described in the utility model claims and Figures 1 to 4, in which wheels 3, 3' are arranged at two points 1, 1', and connecting rods 4, 4' are arranged at points 2, 2' equidistant from an intersection 0 on the perpendicular bisector between the two points 1, 1', and are attached to a frame rod 5 to form a vehicle.
A vehicle that follows the wheel tracks of the towing vehicle described in Patent Document 2 has the following effect, as shown in Figure 4, "when towing around a curve in passage 8, as the leading vehicle changes course to follow the curve, the front and rear of the vehicle move in opposite directions to tow the trailing vehicle. The connecting rods of each vehicle move in the direction of the arrows shown in Figure 4 while being towed, and by following the wheel tracks 9 of the leading vehicle, the vehicle can easily traverse the curve" (see the middle of page 3 of the specification).

Patent Document 3 discloses a trolley comprising, as described in the claims and Figure 1 etc., a trolley base (a frame 10 constituting the trolley base), first to fourth steerable wheels 21, 22, 23, 24 supporting the vicinity of the four corners of the trolley base, respectively, and a non-steerable fifth wheel 80 supporting the central part of the trolley base, the fifth wheel 80 being made of a pneumatic tire and having a fixed running direction in a straight line.
The bogie in Patent Document 3 has the following effect: "A central wheel 80 is provided as a fixed wheel supporting the center of the bottom surface of the bogie (bogie base), so that, as shown in FIG. 1, the right front wheel 21 and the right rear wheel 23 turn in opposite directions depending on the towing direction, and the left front wheel 22 and the left rear wheel 24 turn in opposite directions, thereby suppressing the occurrence of an inner wheel difference when the bogie 100 turns" (for details, see paragraph [0039] of the specification).

Utility Model Registration No. 3037640 Publication No. 51-25334 JP 2007-30882 A

The steering device for the towed bogie in Patent Document 1 had the problem that it used a four-wheel steering system with a large number of parts, and the mechanism was complex, resulting in high manufacturing costs and maintenance fees.
In addition, when the towing vehicle is coupled and towed, when the towing vehicle turns from a straight line or turns and returns to a straight line, the front and rear wheels are steered in coordination, so that when the front wheels follow the towing direction, the rear wheels also follow immediately, which is a configuration similar to a so-called 4WS drive system. Therefore, the rear wheels are displaced before the ideal movement path, so there is a problem that when coupled, the towing vehicle cannot follow the movement path of the leading towing vehicle (leading powered transport vehicle).

A vehicle that follows the wheel tracks of the towing vehicle in Patent Document 2 has a smaller number of parts, but the towing bogies are rotatably connected to each other by connecting rods 4, 4' that protrude from the vehicle base, so there is a problem that the trailing bogie moves forward in a straight line due to inertia, and rotates around the connecting rods 4, 4' of the bogie as a fulcrum, causing it to start swerving (see Figure 11 of the present application).
In addition, since the rearmost cart is not supported by the following carts, if the center of gravity of the cargo is on the rear side of the cart base, the front wheels on the connecting rod 4 side will lift off the floor, causing a large difference in the inner wheels with the connecting rod 4 as the fulcrum, resulting in a problem of meandering (see Fig. 12 of the present application). Furthermore, when receiving cargo from each cart, each of the multiple connected carts will stop in a meandering state, which will cause a shift in the relative position to the cargo receiving location, making it difficult to receive the cargo (see Figs. 11 and 12 of the present application).

The bogie in Patent Document 3 has fewer parts, but like Patent Document 2, it has a configuration in which the connecting rod protrudes from the chassis, so there is an issue that the inertia of the following bogie causes the bogie to rotate around the connecting rod of the bogie as a fulcrum, causing it to start snaking. In addition, because the wheels at the four corners are free wheels, when the fifth fixed wheel 80 (90) in the center touches the ground, the bogie itself tends to rotate around the fifth fixed wheel, so there is an issue that the effects of inertia are easily felt.

Therefore, the object of the present invention is to provide a towing cart in which the guiding fixed casters attached to the towing bar become the front wheels of the towing cart, the guiding fixed casters prevent the towing cart from rotating (lateral swaying from side to side), the next towing cart follows the movement trajectory of the previous towing cart, and the inner wheel difference is small even when coupled.
Another object of the present invention is to provide a towing car which, when stopped, maintains an aligned row of towing carts without swaying from side to side, facilitating unloading operations.
Another object of the present invention is to provide a towing dolly which is economical, rational, easy to use and easy to handle by realizing a simple structure.

As a means for solving the above problems, the towing dolly according to the invention described in claim 1 comprises a towing bar 1 which, when the towing direction in which the dolly base 10 moves is set to the forward direction, protrudes forward from the front side of the dolly base 10 and has a base end 1a rotatably mounted on an axis 11;
A guided fixed caster 2 is provided on the underside of the towing bar 1 and configured so that a wheel axle 2a is located on the central axis of the shaft 11, and rolls in the axial direction of the towing bar 1;
The pair of left and right fixed casters 3L, 3R are located within the cart base 10, and a line F connecting the centers of the pair of left and right fixed casters 3L, 3R overlaps with a line from a turning center point O when towing a plurality of towing carts connected together, and the wheels 32 are oriented in a direction perpendicular to the line from the turning center point O;
A coupling part 4 that can be rotatably coupled to a towing bar 1 of a following towing dolly;
A swivel caster 5 is provided on the rear side of the carriage base 10,
This arrangement is characterized in that, when viewed in a plane, a front-to-rear line L connecting the center of the axis 11 located between the pair of fixed casters 3L, 3R and the center of the connecting part 4 intersects with a line F connecting the pair of fixed casters 3L, 3R at right angles, and the distance S between the axis 11 and the intersection G is equal to or less than the distance T between the intersection G and the connecting part 4.

The invention described in claim 2 is characterized in that, in the towing trolley described in claim 1, the towing bar 1 has a base end 1a formed in a T-shape in a plan view with a cross bar portion 6 extending in the left-right direction, the intersection portion of the T-shape in a plan view is rotatably mounted on the axis 11, and instead of the guiding fixed caster 2 that rolls in the axial direction of the towing bar 1, a plurality of guiding fixed casters 12 that roll in a direction parallel to the axial direction of the towing bar 1 are provided on the underside of the cross bar portion 6.

The invention described in claim 3 is characterized in that in the towing dolly described in claim 1 or 2, a weight member 7 is provided in the front direction of the dolly base 10.

The invention described in claim 4 is characterized in that in the towing dolly described in any one of claims 1 to 3, the pair of fixed casters 3L, 3R are constantly biased downward by a restoring elastic mechanism 8.

The invention described in claim 5 is characterized in that, in the towing trolley described in claim 1 , 3 or 4 , the towing bar 1 is provided with an eccentric hole 1d for changing the guiding fixed caster 2 into a swivel caster .

The invention described in claim 6 is characterized in that in the towing dolly described in any one of claims 1 to 5, the towing bar 1 is configured to be able to be lifted up.

The towing dolly according to the present invention has the following advantages.
(1) The guiding fixed casters attached to the towing bar that can rotate horizontally become the front wheels of the towing cart, and these guiding fixed casters prevent the towing cart from rotating (lateral swaying from side to side). The next towing cart follows the movement trajectory of the previous towing cart, and a towing cart with little inner wheel difference can be realized even when coupled.
When the vehicles are stopped, the aligned row of towing carriages is maintained without swinging from side to side, and a towing carriage that facilitates unloading can be realized.
By realizing a simple structure, it is possible to realize a towing dolly that is economical, rational, easy to use, and excellent in handling.
(2) When a weight is fixed to the front (front half) of the carriage base of the towing carriage and a pair of fixed casters on the left and right sides are provided with a restoring elastic mechanism, the effect of the weight maintains the ground contact state of the guide fixed casters more stably. In addition, the elastic force of the restoring elastic mechanism allows the ground contact pressure of the guide fixed casters to be always stable so that they are not affected by the unevenness of the floor or other conditions of the guide fixed casters. This makes it difficult for the towing carriage to rotate on its own axis, and even if the towing carriage is the last one, the guide fixed caster and the pair of fixed casters do not rise up and the ground contact pressure is secured, so that the towing carriages do not rotate on their own axis, and the line of connected towing carriages can be arranged in an orderly fashion without breaking the line, and there is no problem with unloading the cargo.
(3) In addition, according to the towing cart of the fourth embodiment, the towing cart can be changed into a general-purpose cart that is manually pushed by an operator.

FIG. 1A is a plan view (perspective view) showing a towing dolly according to the present invention, and FIG. FIG. 1C is an enlarged view of a main portion of FIG. FIG. 2 is a plan view (explanatory diagram) illustrating a state in which the towing dolly according to the present invention is towed. FIG. 5 is a plan view (explanatory diagram) showing the main part of FIG. 4 . FIG. 2 is a plan view showing a schematic diagram of a towing dolly according to another embodiment of the present invention; FIG. 1A is a plan view (perspective view) showing a different embodiment of a towing dolly according to the present invention, and FIG. FIG. 1A is a front view showing another embodiment of a towing dolly according to the present invention, and FIG. 1B is a perspective view showing a main portion of a towing bar used in FIG. FIG. 2 is a plan view showing a schematic diagram of a towing dolly according to another embodiment of the present invention; FIG. 2 is a plan view showing a schematic diagram of a towing dolly according to another embodiment of the present invention; FIG. 1 is an explanatory diagram showing a plan view of a towing dolly according to a conventional technique. FIG. 1 is an explanatory diagram showing a plan view of a towing dolly according to a conventional technique. FIG. 1 is an explanatory diagram showing a plan view of a towing dolly according to a conventional technique.

Next, an embodiment of the towing dolly according to the present invention will be described with reference to the drawings.

As shown in Figs. 1 and 2, when the towing direction in which the carriage base 10 moves is set as the forward direction, the towing carriage according to the present invention comprises a towing bar 1 which protrudes forward from the front side of the carriage base 10 and has a base end 1a rotatably mounted on a shaft 11;
A guided fixed caster 2 is provided on the underside of the towing bar 1 and configured so that a wheel axle 2a is located on the central axis of the shaft 11, and rolls in the axial direction of the towing bar 1;
The pair of left and right fixed casters 3L, 3R are located within the cart base 10, and a line F connecting the centers of the pair of left and right fixed casters 3L, 3R overlaps with a line from a turning center point O when towing a plurality of towing carts connected together, and the wheels 32 are oriented in a direction perpendicular to the line from the turning center point O;
A coupling part 4 that can be rotatably coupled to a towing bar 1 of a following towing dolly;
A swivel caster 5 is provided on the rear side of the carriage base 10,
In a plan view, a line L in the front-rear direction connecting the center of the shaft 11 located between the pair of fixed casters 3L, 3R and the center of the connecting part 4 intersects with a line F connecting the pair of fixed casters 3L, 3R at right angles, and the distance S between the shaft 11 and the intersection G is equal to or less than the distance T between the intersection G and the connecting part 4. This is because, if the distance S is long, the towing dolly will not be able to turn easily, so it is desirable to have the relationship S≦T.

The trolley base 10 is implemented as a rectangular plate material or a rectangular plate material attached to a frame, and casters such as the guided fixed casters 2 described below are attached to the underside.

The towing bar 1 is implemented as a long, thin plate-like member, with its base end 1a positioned in the center of the left and right front of the trolley base 10, and stacked with a sliding material 9 interposed between it and the trolley base 10 located above it.A connecting bolt (step bolt) 11 is screwed in a skewer-like manner from above the trolley base 10, so that the towing bar 1 can rotate horizontally around the connecting bolt 11 as an axis 11.
Incidentally, reference numeral 10a in FIG. 2 denotes a through hole formed in the bogie base 10 for passing the connecting bolt 11 therethrough, and reference numeral 1b denotes a screw hole formed in the towing bar 1 for screwing in the connecting bolt 11.

Furthermore, the guiding fixed caster 2 is attached to the lower end of the connecting bolt (shaft) 11. Specifically, the guiding fixed caster 2 is attached by screwing a U-shaped wheel support leg 21 opening downward to the lower surface of the base end 1a of the towing bar 1 and the lower end of the connecting bolt 11, and a wheel 22 is rotatably supported at the lower part of the wheel support leg 21 by a wheel axle (axle) 2a provided substantially horizontally between the sides of the wheel support leg 21 so as to roll in the axial direction of the towing bar 1, and is configured so that the wheel axle 2a is located concentrically with the connecting bolt 11, i.e., on the central axis of the connecting bolt 11.
Thus, in FIG. 1, the guiding fixed caster 2 rolls in the axial direction of the towing bar 1 when the towing bar 1 is in the center, rolls in the axial direction of the towing bar 1L when the towing bar 1L is swung to the left, and rolls in the axial direction of the towing bar 1R when the towing bar 1R is swung to the right, and so on, so that the guiding fixed caster 2 always rolls in the axial direction of the towing bar 1.
A connecting hole 1c is formed at the front axial tip of the towing bar 1 for connecting to another preceding towing bogie.

Next, as shown in Figure 3, the pair of fixed casters 3L, 3R are located within the trolley base 10, and a line F connecting the centers of the pair of left and right fixed casters 3L, 3R near the side of the trolley base 10 overlaps with a line from the rotation center point O when towing multiple connected towing trolleys, and the wheels 32 are configured to face in a direction perpendicular to the line from the rotation center point O.
Specifically, in this embodiment, the fixed casters 3L, 3R have a common configuration such as the same shape and size, so to explain the fixed caster 3L as an example, as shown in Figure 1B, a U-shaped wheel support leg 31 that opens downward is attached via a mounting plate 14 to the underside of the corresponding mounting portion of the trolley base 10, and a wheel 32 is supported at the bottom of the wheel support leg 31 by a wheel axle (axle) 3a that is arranged approximately horizontally between the sides of the wheel support leg 31 so as to be rotatable so as to roll in the direction in which the trolley base 10 travels.

Next, the connecting part 4 that can be rotatably connected to the towing bar 1 of the following towing bogie is implemented in this embodiment by forming a connecting hole 4 that penetrates in the plate thickness direction, and aligning the center with the connecting hole 1c of the towing bar 1 of the following towing bogie, and then passing a separately prepared pin through the connecting holes 4, 1c with the center aligned, to rotatably connect them. Note that the connecting means is not limited to this, and it can also be implemented by making one of the connecting holes 4, 1c a pin structure that fits into each other.

Next, the swivel caster 5 provided on the rear side of the dolly base 10 is provided to prevent the front of the dolly base 10 from floating up. In other words, when the luggage loaded on the dolly base 10 is biased backward, it acts like a seesaw around the pair of fixed casters 3L and 3R as a fulcrum, and is provided to prevent the front of the guiding fixed caster 2 and therefore the dolly base 10 (towing dolly) from floating up. If the guiding fixed caster 2 floats up, it may lose contact with the floor and impair reliable steering. Therefore, in this embodiment, the swivel caster 5 is provided in a pair in a symmetrical arrangement at the rear part of the dolly base 10, but is not limited to this. For example, one caster may be provided in the vicinity of the connecting portion 4, and the installation location and number of casters may be appropriately changed in design, provided that the float of the dolly base 10 is prevented.
Incidentally, as shown in FIG. 1B, the swivel caster 5 in this embodiment is implemented as an example only, with a U-shaped wheel support leg 51 that opens downward being rotatably attached via a mounting plate 15 to the underside of the mounting corresponding portion of the trolley base 10, and a wheel 52 is rotatably supported at the bottom of the wheel support leg 51 by a wheel axle (axle) 5a that is arranged approximately horizontally between the sides of the wheel support leg 51.

As can be seen from Figs. 3 and 4, the towing dolly according to the present invention is further arranged so that, in a plan view, a line L in the front-rear direction connecting the center of the shaft 11 located between the pair of fixed casters 3L, 3R and the center of the connecting part 4 intersects with a line F connecting the pair of fixed casters 3L, 3R at right angles, and the distance S between the shaft 11 and the intersection point G, which is equal to or smaller than the distance T between the intersection point G and the connecting part 4. With this configuration, the guiding fixed caster 2 becomes the front wheel of the towing dolly, and the guiding fixed caster 2 prevents the towing dolly from rotating (lateral shaking), and follows the movement trajectory of the leading towing dolly, realizing a towing dolly with as little inner wheel difference as possible even when coupled.

To explain more specifically, Fig. 3 shows a plan view of the running state when a plurality of towing dollies of the above configuration are connected to a leading powered transport vehicle (not shown) and towed along a curved road, and Fig. 4 shows the main parts. Incidentally, in Fig. 3, the symbol O indicates the turning center point, the symbol X indicates the moving trajectory line of the connection part between the towing bar 1 and the connection part 4, the symbol Y indicates the moving trajectory line of the axis 11 of the towing bar 1, and the symbol Z indicates the moving trajectory line of the intersection point G. As can be seen from Fig. 3, the three lines X, Y, and Z maintain the same distance from each other around the turning center O and maintain a good running state. It can also be seen that the wheels 32 are oriented in a direction perpendicular to the line from the turning center point O, specifically, the line connecting the turning center point O and the intersection point G.

Therefore, when multiple vehicles are coupled to the leading powered transport vehicle (not shown) shown in Figure 3 and towed around a curved road, the running state is as follows: for the front and rear towing dollies (for example, V and W in Figure 4), when the leading towing dolly (V) changes course around a curved road (see towing direction D), the towing bar 1 of the trailing towing dolly (W) rotates leftward about the axis 11 in accordance with the left direction towing of the leading towing dolly (V), and at the same time, the guiding fixed caster 2 of the trailing towing dolly (W) also rotates (turns) leftward to follow the leading towing dolly (V). In other words, when the direction of travel of the leading towing dolly (V) changes, the direction of the towing bar 1 and the guiding fixed caster 2 of the trailing towing dolly (W) change simultaneously to follow it. The guiding fixed casters 2 become the front wheels of the towing cart (W) and stop the towing cart (W) from rotating (on its own axis). Therefore, even when coupled with the pair of fixed casters 3L, 3R, the movement trajectory of the trailing towing cart (W) follows the movement trajectory of the leading towing cart (V), realizing a running state with little inner wheel difference even when coupled.

If the guiding fixed caster 2 were not present, there would be no front wheel (guiding fixed caster 2) to immediately follow the change in direction of the leading towing cart (V), and the trailing towing cart (W) would rotate due to the inertial force of the towing cart (W) as shown by the dashed line in Figure 10, and would exhibit a behavior that bulges outward, and would not follow the movement trajectory of the leading towing cart (V).
Of course, the behavior of a towing bogie consisting of multiple connected towing bogies, including the towing bogies V and W described above, exhibits very complex behavior based on the behavior described above; however, since the towing bogies (V, W) that follow each other roughly follow a similar movement trajectory, even if the number of towing bogies increases, towing operation with little inner wheel difference can be achieved, so that the preceding towing bogie and, ultimately, the leading powered transport vehicle's movement trajectory can be followed as closely as possible.

FIG. 5 shows a different embodiment of the towing dolly.
The towing dolly according to the second embodiment is different from the towing dolly according to the first embodiment in the configuration of the towing bar 1.
That is, the towing bar 1 according to the second embodiment has a base end 1a formed in a T-shape in plan view with a cross bar portion 6 extending in the left-right direction (extending in the left-right direction through the same axis as the shaft 11), and an intersection portion of the T-shape in plan view is rotatably provided on the shaft 11. Instead of the guiding fixed caster 2 that rolls in the axial direction of the towing bar 1, a plurality of guiding fixed casters 12 (two in total at both the left and right ends in the illustrated example) that roll in a direction parallel to the axial direction of the towing bar 1 are provided on the underside of the cross bar portion 6.
In the towing dolly according to the second embodiment, the strength and rigidity of the towing bar 1 is improved compared to the first embodiment, and the front side of the towing dolly is supported over a wide area, so that the towing dolly is more resistant to uneven loading of the load and has the effect of suppressing tire wear by reducing the load borne by each of the guide fixed casters 12. In addition, the weight of the front part of the towing dolly is increased, which contributes to preventing the front part of the dolly base 10 (towing dolly) from lifting up.
[Example 3]

FIG. 6 shows a different embodiment of the towing dolly.
The towing dolly according to the third embodiment is different from the towing dolly according to the first embodiment in the configuration of the pair of fixed casters 3L, 3R.
In this embodiment, the pair of fixed casters 3L, 3R according to the third embodiment are implemented with a common configuration, such as the same shape and size, so that the fixed caster 3L is taken as an example for explanation. As shown in Fig. 6B, a metal plate (weight material) 7 is provided in front of the mounting portion of the fixed caster 3L with a slight gap therebetween, and a leaf spring (recovery elastic mechanism) 8 of a length sufficient to reach the mounting portion of the fixed caster 3L is provided on the underside of the metal plate 7, so that the fixed caster 3L is constantly biased downward. The fixed caster 3L is implemented with a configuration in which a U-shaped wheel support leg 31 that opens downward is attached to the underside of one end of the leaf spring 8, and a wheel 32 is supported at the bottom of the wheel support leg 31 by a wheel axle (axle) 3a provided approximately horizontally between the sides of the wheel support leg 31 so as to be rotatable so as to roll in the traveling direction of the cart base 10.

In short, the towing dolly according to the third embodiment can more reliably maintain the guiding fixed caster 2 and the pair of fixed casters 3L, 3R in a good grounding state with respect to the floor, compared with the towing dolly according to the first embodiment. That is, the grounding state of the guiding fixed caster 2 is more stably maintained due to the weight effect of the metal plate 7. In addition, the elastic force of the elastic restoring mechanism 8 can always maintain the grounding pressure of the guiding fixed caster 2 stably so that it is not affected by the unevenness of the floor of the guiding fixed caster 2. Therefore, the towing dolly is unlikely to rotate on its own axis, and even if it is the last towing dolly, the guiding fixed caster 2 does not float up due to the seesaw principle and the grounding pressure is secured, so that the towing dolly does not rotate on its own axis, and the row of connected towing dollies is arranged in an orderly manner without breaking the formation, and there is no problem with unloading of the load.
In this embodiment, a leaf spring is used as the restoring elastic mechanism, but the invention is not limited to this and may be embodied using a coil spring.

FIG. 7 shows a different embodiment of the towing dolly.
The towing cart of this embodiment 4 is different from the towing cart of the above embodiment 1 in that the configuration of the towing bar 1 is modified so that the towing carts described in the above embodiments 1 to 3 can be converted into a general-purpose cart that can be pushed by hand by a single operator for use.
That is, the towing bar 1 according to the fourth embodiment is formed with an eccentric hole 1d for changing the guiding fixed caster 2 to a swivel caster in addition to the configuration of the first embodiment, and is implemented with a configuration that can be lifted up (compare Fig. 7A with Fig. 2). Meanwhile, the carriage base 10 is formed with a through hole 10b at a position corresponding to the eccentric hole 1d.

Therefore, when changing the model, the connecting bolt (shaft) 11 is removed from the carriage base 10, and the towing bar 1 and the guide fixed caster 2 are temporarily removed from the carriage base 10. Then, the towing bar 1 and the guide fixed caster 2 (wheel support leg 21) are fixed by screwing a screw into the shaft hole 1b. After that, the towing bar 1 and the carriage base 10 are aligned with the eccentric hole 1d and the through hole 10b, and are placed in a stacked state with the sliding material 9 interposed therebetween, and the connecting bolt (step bolt) 11 is screwed in a skewer-like manner from above the carriage base 10. Thus, the towing carriage according to Example 4 can be changed in design to change the shaft 11 of the towing bar 1 to an eccentric shaft 41 offset forward from the shaft 11, and the guide fixed caster 2 attached to the towing bar 1 can be changed to a swivel caster that rotates around the eccentric shaft 41.

The flip-up structure is, as shown in FIG. 7B, merely one example, implemented in such a way that the tow bar 1 is a two-part structure that can be connected by a connecting pin 18, and one of the front flip-up parts is provided with a support plate 19 that contacts the underside of the connecting pin 18 to keep the flip-up part horizontal, and the other part is provided with a wall part 1e against which the flip-up part abuts and keeps the abutted state.

Thus, the towing dolly of Example 4 can be changed from the towing dolly (see Examples 1 to 3) as shown in FIG. 7C to a general-purpose dolly as shown in FIG. 7D. The reference numeral 20 in the figure indicates a handle member.

FIG. 8 shows a different embodiment of the towing dolly.
The towing dolly according to this embodiment 5 is different from the towing dolly according to the above embodiment 1 in that each of the pair of fixed casters 3L, 3R is implemented as a two-wheel structure. By implementing the two-wheel structure, it is possible to reduce the load borne by each wheel, thereby reducing tire wear, and other economical effects.

FIG. 9 shows a different embodiment of the towing dolly.
The towing dolly according to the sixth embodiment differs from the towing dolly according to the third embodiment in that a pair of swivel casters 50 are provided as auxiliary wheels at the front of the towing dolly (compare Fig. 6A with Fig. 9). This provides wide support at the front of the towing dolly, making it more resistant to uneven loading of luggage and less likely to tip over.

Although the embodiments have been described above based on the drawings, it should be noted that the present invention is not limited to the illustrated examples, and includes the range of design modifications and application variations that are normally made by those skilled in the art as necessary, provided that the scope does not deviate from the technical concept of the present invention.

REFERENCE SIGNS LIST 1 towing bar 1a base end 1b shaft hole 1c connection hole 1d eccentric hole 2 guide fixed caster 2a wheel axle 21 wheel support leg 22 wheel 3L fixed caster 3R fixed caster 3a wheel axle 31 wheel support leg 32 wheel 4 connection portion (connection hole)
5 Caster 6 Horizontal bar 7 Weight member 8 Elastic mechanism for restoration 9 Sliding member 10 Cart base 11 Axle (connecting bolt)
12 Guide fixed caster 13 Step bolt 14 Mounting plate 15 Mounting plate 16 Towing bar 18 Connecting pin 19 Support plate 20 Handle member 41 Eccentric shaft CL On the left-right center line

Claims (6)

a towing bar that protrudes forward from a front side of the carriage base when a towing direction in which the carriage base moves is set as a forward direction and has a base end that is rotatably provided on an axis;
A guided fixed caster is provided on the underside of the tow bar and rolls in the axial direction of the tow bar, the wheel axle of which is located on the central axis of the axle ;
A pair of left and right fixed casters are located within the cart base, a line connecting the centers of the pair of left and right fixed casters overlaps with a line from a turning center point when towing a plurality of towing carts connected together, and the wheels are oriented in a direction perpendicular to the line from the turning center point;
A coupling part that can be rotatably coupled to a towing bar of a following towing dolly;
A swivel caster is provided on the rear side of the carriage base,
A towing cart characterized in that, in a plan view, a front-to-rear line connecting the center of the axle located between the pair of fixed casters and the center of the connecting part is arranged so that the distance between the axis and the intersection point formed perpendicular to the line connecting the pair of fixed casters is equal to or less than the distance between the intersection point and the connecting part. 2. The towing dolly according to claim 1, wherein the towing bar has a base end formed in a T-shape in plan view with a cross bar portion extending in the left-right direction, an intersection portion of the T-shape in plan view is rotatably provided on the axis , and a plurality of guiding fixed casters that roll in a direction parallel to the axial direction of the towing bar are provided on an underside of the cross bar portion instead of a guiding fixed caster that rolls in the axial direction of the towing bar. The towing dolly described in claim 1 or 2, characterized in that a weight is provided in the forward direction of the dolly base. The towing dolly described in any one of claims 1 to 3, characterized in that each of the pair of fixed casters is constantly biased downward by a restoring elastic mechanism. 5. A towing dolly according to claim 1, 3 or 4 , characterized in that the towing bar is provided with an eccentric hole for changing the guiding fixed caster into a swivel caster . The towing dolly described in any one of claims 1 to 5, characterized in that the towing bar is configured to be able to be lifted up.

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