JP6155120B2 - Casters and wheelchairs - Google Patents

Description

  The present invention relates to a caster structure.

  Casters are often provided for moving and changing the direction of structures (whether with or without a power mechanism) that carry people and objects such as trolleys and wheelchairs. At this time, when there is a step in the movement route, it is known that it is difficult to get over the step if the height of the step becomes a certain level or more with respect to the size of the wheel. Patent Document 1 discloses a caster in which auxiliary wheels are provided on both sides of a main wheel in order to improve a step-over ability.

JP 2004-237970 A

  In the invention described in Patent Document 1, as a premise, only the case of entering from the front with respect to the step is assumed. However, when actually using a cart or a wheelchair, it is not always possible to enter the step from the front due to restrictions on the moving space. Alternatively, there is a case where the operator enters the step step obliquely due to an operation mistake. The inventor has obtained the knowledge that, when entering from an angle with respect to the step, the caster is more difficult to get over than entering from the front even if the step is the same height. Also, if you attempt to get over the step in such a situation, the posture of the carriage, wheelchair, etc. may become unstable.

The above situation will be specifically described with reference to FIG. FIG. 17 is a schematic view of the behavior of a conventional single-wheel caster when viewed obliquely from the upper side with respect to a level difference of a predetermined height or more. FIG. 17A shows the state in which the structure to which the caster 600 is attached enters the step so that the angle between the traveling direction K of the caster 600 and the edge step S of the step is θ (vertical direction). ). Elements other than the wheels of the caster 600 are omitted. The rotation axis of the caster wheel is Oz, and the pivot axis of the caster 600 is Cz.
First, the caster 600 contacts the step S in FIG. If the height of the step with respect to the caster 600 is greater than or equal to a predetermined level, the caster 600 cannot get over the step S. Specifically, when approaching from the front, the height that can be overcome is about 60% of the radius of the wheel, but as the approach angle becomes acute, the height that can be overcome decreases and the entrance angle becomes 30%. It becomes about 40% of the radius of the wheel at a degree. Therefore, even if the level difference can be overcome when entering from the front, it may not be possible to get over from an angle.

  Due to the force received from the step S, a rotational force (turning force) about the direction perpendicular to the running surface (ground) is generated on the caster 600 around the turning axis C. As shown in FIG. Starts rotating (turning) on the spot. Since the frictional resistance received from the ground against the turning motion is smaller than the frictional resistance that tries to get over the step, the turning motion does not stop and the direction of the caster 600 is different from the step S as shown in FIGS. The casters 600 rotate until they become parallel. In this state, the force that the caster 600 tries to overcome the step S does not work, and the failure to overcome is determined.

  It is an object of the present invention to improve the caster's ability to climb over when entering the step at an angle.

In one aspect, the present invention provides a frame, a mounting portion that is provided on the frame and that connects the frame to a structure so that the frame can be pivoted about a mounting shaft, and a first that is mounted on the frame. And two second wheels that are attached to the frame and are arranged on both sides of the first wheel and are smaller than the first wheel, respectively, and the first wheel and the second wheel When the distance between the wheel d, the turning radius of the first wheel and phi, d <meets the phi, the first radius of the wheel R, alpha constant (0 <α <90 ° ) , A caster that satisfies d <φcosα and 2R−φ <d * tanα is provided.

  The caster having the structure according to the present invention has a high step-over ability with respect to an approach from an oblique direction.

The external view of the wheelchair 10 with which the caster 100 was attached. The perspective view of the caster 100. FIG. The side view of the caster 100. FIG. The front view of the caster 100. FIG. The top view of the caster 100. FIG. The figure showing the structure of the flame | frame 110 and the connection part 120. FIG. (A) is the schematic diagram which looked at the caster 100 from upper direction. (B) is the schematic diagram which looked at the caster 100 from the horizontal direction. The schematic diagram which looked at a mode that caster 100 approached to a level difference from the upper part (the 1). Schematic view of caster 100 entering from the top (step 2) Schematic view of caster 100 entering from the top (step 3) Schematic view of caster 100 entering from above the step (No. 4) The schematic diagram which looked at the state which the caster 100 gets over a level | step difference from the side (the 1). The schematic diagram which looked at the state which the caster 100 gets over a level | step difference from the side (the 2). The schematic diagram which looked at the state which the caster 100 gets over a level | step difference from the side (the 3). The schematic diagram which looked at the state which the caster 100 gets over a level | step difference from the side (the 4). The schematic diagram which looked at the state which the caster 100 gets over a level | step difference from the side (the 5). (A)-(h) is the schematic diagram which looked at the behavior when the conventional caster approached diagonally with respect to the level | step difference from the upper direction.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an external view of a wheelchair 10 to which a caster 100 is attached. The wheelchair 10 is an electric wheelchair having a seat surface 11, a backrest 12, a footrest 13, an armrest 14, an operation unit 15, a caster 100, and a rear wheel 200. In addition to the wheelchair 10, a motor, a battery, a shaft, and the like that are driven to rotate the rear wheel 200 and change the direction of the rear wheel 200 (that is, the direction of the wheelchair 10) according to the operation content of the operation unit 15. And a drive mechanism (not shown). The caster 100 functions as a front wheel. The caster 100 is attached to the support 190.

The detailed structure of the caster 100 will be described with reference to FIGS.
FIG. 2 shows the appearance of the caster 100. Z is a vertical direction, and the X and Y planes are planes (ground) perpendicular to Z. Normally, when the wheelchair 10 travels in an + X direction on an ideal flat surface without an obstacle, the direction of the caster 100 is the + X direction.
The caster 100 is roughly composed of a frame 110, a connecting portion 120, a main wheel 130, and an auxiliary wheel 140. The connection part 120 includes an attachment member 124, a damper 123, and a nut 122, and is attached to the frame 110 via the nut 122. The damper 123 is an elastic body including an elastic material such as rubber and a spring, and deforms a force (impact or load) from the Z direction received from the vertical with respect to the caster 100 by unevenness of the running surface. Absorb. The nut 122 is a component of a hinge mechanism (not shown) that rotatably connects the connecting portion 120 and the frame 110. Along with the deformation of the damper 123, the frame 110 rotates with respect to the connection portion 120 about the rotation axis C4. The damper 123 and the hinge mechanism may be omitted. In this case, the connection part 120 and the frame 110 are connected in a state where their relative positions are fixed.

  An attachment member 124 is attached to the connection portion 120. The attachment member 124 has a round bar shape, and a screw for fitting into the support 190 is cut on the surface thereof. As a method for fixing the attachment member 124 to the support 190, a known connection mechanism other than screws may be employed. The center of the attachment member 124 is the turning axis C3, and the caster 100 can be rotated (turned) 360 ° around the turning axis C3 while being attached to the wheelchair 10.

  The frame 110 is a plate-shaped member made of a pair of metal members. The frame 110 fixes the main wheel 130 and the two auxiliary wheels 140. The frame 110 has a hole 111 for weight reduction. The frame 110 is provided with three mounting holes 112 for mounting the main wheel 130. By selecting the position of the hole to be used, the positions of the main wheel 130 and the auxiliary wheel 140 with respect to the frame 110 can be changed. Instead of providing a plurality of holes, a slit through which the bolt shaft passes may be provided so that the fixing position can be adjusted. FIG. 2 shows an example in which the main wheel 130 is fixed at the lowest position using a nut 115.

The main wheel 130 has a central structure such as a flat plate and spokes and a flexible material such as rubber provided on the outside thereof, and is fixed to the frame 110 via a nut 115 so as to be rotatable about the rotation axis C1. In addition, the structure of the main wheel 130 is not restricted to this, What is necessary is just to have a function as a wheel rotated centering around the rotating shaft C1.
One auxiliary wheel 140 is provided on each side of the main wheel 130, and is fixed to the frame 110 via a bolt 144 so as to be rotatable about the rotation axis C2. In this example, the wheel diameter of the main wheel 130 is larger than that of the auxiliary wheel 140. The auxiliary wheel 140 need not be the same as the main wheel 130 in terms of structure and material. In short, the auxiliary wheel 140 only needs to have a function as a wheel that rotates about the rotation axis C2.
In addition, about the thickness of the main wheel 130 and the auxiliary wheel 140, the example shown in FIGS. 2-5 is only an example.

  The positional relationship between the main wheel 130 and the auxiliary wheel 140 (relationship between the rotation axis, the central axis, and the turning axis) will be described with reference to FIGS. FIG. 3 is a side view of the caster 100. As shown in the figure, the turning axis C3 does not necessarily coincide with the rotation axis C2, but may coincide. The auxiliary wheel 140 is vertically above the main wheel 130. That is, when the wheelchair 10 is traveling normally (when traveling on a flat ground), the main wheel 130 contacts the ground, and the auxiliary wheel 140 does not contact the traveling surface. Thereby, the rolling resistance of the caster 100 can be reduced.

4 is a front view of the caster 100, and FIG. In the ZY plane, the central axis Q1 coincides with the turning axis C3. The central axis Q1 is parallel to the central axis Q2 and the central axis Q3. The distances from the turning axis C3 to the central axis Q1 and the central axis Q2 are equal. The rotation axis C1 and the rotation axis C2 are parallel. The rotation axis C1 and the rotation axis C2 do not necessarily coincide with each other, but may coincide with each other. The center axis Q1 and the rotation axis C1 are orthogonal.
be able to.

  FIG. 6 shows the structure of the frame 110 and the connecting portion 120 with the main wheel 130 and the auxiliary wheel 140 removed. The frame 110 is provided with three mounting holes 113 for mounting the auxiliary wheel 140. Thereby, the position of the auxiliary wheel 140 with respect to the frame 110 can be adjusted. The number of holes is not limited to the example shown in the figure. In short, in a preferred embodiment, the frame 110 is provided with at least one of a hole for determining the mounting position of the first wheel and a hole for determining the mounting position of the second wheel.

The positional relationship between the main wheel 130 and the auxiliary wheel 140 will be described in more detail with reference to FIG. In the drawing, main points and axes related to the arrangement of the main wheel 130 and the auxiliary wheel 140 are depicted, and other elements are appropriately discarded.
FIG. 7A is a schematic view of the caster 100 viewed from above in order to explain the positional relationship between the main wheel 130 and the auxiliary wheel 140 in a plane (XY plane) perpendicular to the turning axis C3. A circle drawn with the turning center P and the radius φ is a turning trajectory (referred to as a turning circle) of the main wheel 130. The distance between the main wheel 130 and each auxiliary wheel 140 is d, the distance from the turning center P to the tip of the auxiliary wheel 140 is L1, and each of the line segment E1E2 and the line segment EP is β. Also, the approach angle of the caster 100 with respect to the step S is defined as an approach angle α. At this time, at least the following conditions are satisfied.
d <φ (1)
This is synonymous with at least a part of the auxiliary wheel 140 being located in the turning circle. This embodiment is characterized in that d depends on φ. When d is set large so that the auxiliary wheel 140 goes out of the turning circle, the one auxiliary wheel 140 comes into contact with the step S when entering obliquely, and the caster 100 starts a turning motion, whereby the other auxiliary wheel 140 is turned. Is in contact with the step S, the force for getting over the step S by the two auxiliary wheels 140 is not efficiently generated.

In a preferred embodiment, in addition to the above conditions, the following conditions are satisfied.
2R−φ <d * tanβ (0 ° <β <90 °) (2) and d <φcosβ (3)
In the case of the approach angle α = β, when the caster 100 enters the step S, one auxiliary wheel 140 (the left auxiliary wheel 140 in the figure) first contacts the step S, and this contact is triggered. In addition, the caster 100 is synonymous with the condition that the main wheel 130 does not contact the step S and the other auxiliary wheel 140 contacts the step during the turning motion.

In a preferred embodiment, in addition to the above conditions, the following conditions are satisfied.
20 ° ≦ β ≦ 30 ° (4)
As a result of experiments, the inventor has found that the step overcoming ability depends on β (in other words, the distance d), and that the overcoming ability is highest when β (d) is in the above range.

Even when β is in a range other than the above (4) and satisfies the following conditions, a considerable improvement in overcoming ability was recognized.
15 ° ≦ β ≦ 45 ° (5)
Further, even when β is in a range other than the above (5) and satisfies the following conditions, an improvement in the overcoming ability was recognized to some extent.
10 ° ≦ β ≦ 60 ° (6)
It was found by the same experiment that if β is made too large (that is, d is made too small), the caster 100 cannot successfully shift from the turning motion to the motion for overcoming the step S. Note that reducing β means an increase in the size of the caster 100 as a whole, and therefore, β = 30 ° is suitable as a condition for achieving both compactness and step-over performance.

FIG. 7B is a schematic view of the caster 100 viewed from the lateral direction. Hereinafter, the positional relationship between the main wheel 130 and the auxiliary wheel 140 in a plane (ZX plane) perpendicular to the rotation axis will be described. The radius (rotation radius) of the main wheel 130 is R, the rotation radius of the auxiliary wheel 140 is r, and the distance between the rotation center of the main wheel 130 and the auxiliary wheel 140 is L2. Further, a point below the point where two circles intersect in the ZX plane is defined as Tx.
At this time, the following conditions are satisfied.
r> R / 3 (7)
L2> Rr (8)
Formula (8) is a condition for at least a part of the auxiliary wheel 140 to be outside the turning circle (that is, there is a possibility that the auxiliary wheel 140 may contact the step S before the main wheel 130). .

  In Expression (7), if the height from G to Tx is 40% of R, the position higher by 0.6 * r from Tx is located higher than the position higher by 0.6 * R from G. This is derived from the condition (0.4R + 0.6r> 0.6R). Here, the numbers 0.4 and 0.6 generally indicate that the height of the step that can be overcome when entering from the front (approach angle 90 °) is about 60% of the radius of the wheel, When the approach angle is 30 °, the height of the step that can be overcome is considered to be about 40% of the radius of the wheel.

That is, as shown in the figure, in the case of the step S having a height H, when entering from the front, the two auxiliary wheels 140 first come into contact with the step S, and at this time, the substantial height of the step over which the auxiliary wheel 140 gets over. Is smaller than 0.6r, the auxiliary wheel 140 can get over the step S. When the auxiliary wheel 140 has overcome the step S, the main wheel 130 comes into contact with the step S next time. At this time, the substantial height of the step that the main wheel 130 should get over is 0.4R (<0.6R), so the main wheel 130 can get over the step S. As a result, the caster 100 gets over the step S as a whole.
On the other hand, when entering from the front, if the step S is lower than 0.4R, only the main wheel 130 contacts R. Since 0.4R <0.6R, the auxiliary wheel 140 can get over the step S without any problem. In addition, in the case of a step having the same height, the auxiliary wheel 140 can get over the step S as described above even if it enters from an angle of about 30 °.

  Hereinafter, the behavior of the caster 100 when the caster 100 enters the step S at the approach angle α when the step height H is 0.4R or more will be described with reference to FIGS. As described above, under this condition, with a conventional caster (for example, a caster in which the auxiliary wheel 140 is not attached to the caster 100 shown in FIG. 7), the turning motion starts, and it cannot be overcome regardless of the approach angle. . On the other hand, with the caster 100, it is possible to get over even if it is an oblique approach. This will be described in detail below.

FIGS. 8 to 11 show that the caster 100 shown in FIG. 7 enters obliquely and cannot step over the step as it is, and the time from the start of the turning motion to the start of the jumping motion is shown. It is shown in series. In the following example, for the sake of convenience, the approach angle α = β = 30 °.
First, as shown in FIG. 8, the tip of one auxiliary wheel 140 contacts at W <b> 1 of the step S. Then, the auxiliary wheel 140 generates a rotational force due to the force received from the edge of the step S, and a force that tries to get over the step S works. At the same time, the auxiliary wheel 140 starts a turning motion by the force received from the edge of the step S. Here, since the step S is not so low that it can be overcome as it is, as shown in FIGS. 9 and 10, the caster 100 starts a turning motion with W1 as a fulcrum.

And as shown in FIG. 11, the other auxiliary wheel 140 contacts in W2. At this time, the caster 100 faces the step S. At this time, the rotational force (force over the step) is higher than the turning force acting on the auxiliary wheel 140. As a result, the turning motion of the caster 100 is finished, and the two auxiliary wheels 140 are rotated by the frictional force with the step S and start to climb the edge of the step S. Thus, the caster 100 shifts from the turning movement to the movement over the step S.
If the distance to the tips W1 and W2 of the auxiliary wheels 140 with respect to the turning axis is too small (the distance between the auxiliary wheel 140 and the main wheel is too small; β is too large), the caster 100 is adjusted to the step S. In contrast, the turning force cannot be sufficiently canceled, and the turning motion that supports W2 starts this time, and the probability of failing to get over increases.

  12 to 16 are diagrams showing the time series from the time when the caster 100 faces the step S to the time when the ride over the step S with the height H is completed. A point where the main wheel 130 contacts G at a point Tg on the outer periphery and contacts the edge of the step S on the outer periphery of the auxiliary wheel 140 is represented by a contact point T0. The auxiliary wheel 140 generates a rotational force due to the frictional force at the contact point T0, and the auxiliary wheel 140 starts to get over the step S as the auxiliary wheel 140 rotates. Then, the main wheel 130 (that is, the entire caster 100) floats from G, and the contact point on the outer periphery of the auxiliary wheel 140 shifts to T1 as shown in FIG. As the auxiliary wheel 140 further rotates, the contact point on the outer periphery of the auxiliary wheel 140 shifts to Tx as shown in FIG. In this state, over the step S for the auxiliary wheel 140 is completed.

  Thereafter, the main wheel 130 comes into contact with the edge of the step S. That is, the main wheel 130 is rotated by the frictional force received from the edge of the step S, so that the main wheel 130 starts to get over. Specifically, the contact point on the outer periphery of the main wheel 130 with the step S shifts from Tx to T1 as shown in FIG. Furthermore, as shown in FIG. 16, the contact point on the outer periphery of the main wheel 130 shifts to T3 as the main wheel 130 rotates. As a result, the ride over the step S for the main wheel 130 is completed, and the ride over the step S is completed for the caster 100 as a whole.

As described above, according to the present embodiment, the auxiliary wheel 140 is provided at a position corresponding to the turning radius and the turning center of the main wheel 130, so that the step is higher than the conventional step and is entered from an oblique direction. You can even get over.
The reason why the angle of entry is 30 ° is that it is difficult to actually enter the step at an acute angle of more than 30 degrees. Of course, the structure of the caster 100 described above exhibits a higher step-over capability than conventional ones even when the caster 100 enters at another approach angle. Further, the “step” does not mean only an obstacle having a surface perpendicular to the traveling surface. In short, a “step” is a height gap that exists between two smooth running surfaces.

<Modification>
The above embodiment can be modified as appropriate. Hereinafter, the viewpoint when performing the modification will be exemplified.
The wheelchair 10 need not be four wheels. For example, the caster 100 may be a three-wheeled wheelchair that uses only one auxiliary wheel 140 as a front wheel. Alternatively, it may be a six-wheeled wheelchair provided with two rear wheels 200 and a total of four auxiliary wheels 140 in front of and behind the two rear wheels 200. Moreover, the wheelchair 10 does not need to be electric.
The subject to which the caster 100 is attached may be, for example, a general carriage for carrying luggage other than a wheelchair. In short, an object can be placed and moved while changing its direction, and its application is not limited.

DESCRIPTION OF SYMBOLS 10 ... Wheelchair, 11 ... Seat surface, 13 ... Footrest, 12 ... Backrest, 14 ... Armrest, 15 ... Operation part, 100 ... Caster, 200 ... Rear Rings, 190 ... posts, 110 ... frames, 111 ... holes, 112 ... mounting holes, 113 ... mounting holes, 190 ... posts, 140 ... main wheels, 130 ... Auxiliary wheel, C1, C2 ... Rotating shaft, 123 ... Damper, 120 ... Mounting part, 124 ... Mounting member, 122 ... Nut, 115 ... Nut, 144 ... · Bolts, 141 ... nuts, C3 ... swiveling axis, C4 ... rotating shaft, S ... step, α ... entry angle, φ ... turning radius, H ... step height, T0: contact point, R, r ... turning radius, P ... turning center, Q1, Q, Q3 ... central axis

Claims (6)

Frame,
An attachment portion provided on the frame and connected to the structure so that the frame can be pivoted about an attachment axis;
A first wheel attached to the frame;
Two second wheels attached to the frame and disposed on opposite sides of the first wheel, respectively, smaller than the first wheel;
With
When the distance between the first wheel and the second wheel is d and the turning radius of the first wheel is φ, the following formula d <φ (1)
Meet the,
When the radius of the first wheel is R and α is a constant (0 <α <90 °),
The following formula
d <φcosα (2)
2R-φ <d * tanα (3)
Meet,
Casters. Assuming that the distance from the turning center to the tip in the traveling direction of each second wheel in a plane perpendicular to the mounting shaft is L1, the following equation
d / L1 = cos α (20 ° ≦ α ≦ 30 °) (4)
The caster according to claim 1, wherein: If the distance from the turning center to the tip in the traveling direction of each second wheel is L1 in the plane of the mounting axis, the following formula
d / L1 = cos α (15 ° ≦ α ≦ 45 °) (5)
The caster according to claim 1, wherein: The radius of the second wheel is r, and the distance between the rotation center of the first wheel and the rotation center of the second wheel in a plane perpendicular to the rotation axis of the first wheel is L2. Then, the following formula r> R / 3 (6)
L2> R−r (7)
The caster according to claim 1, wherein: The frame is provided with a plurality of holes for determining the mounting position of the first wheel and at least one of the holes for determining the mounting position of the second wheel. The caster according to any one of claims 1 to 4 . A wheelchair using the caster according to any one of claims 1 to 5 as a front wheel.

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