JPH038307B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a wheel-type vehicle that runs on its own while applying tension between a pair of opposing tracks, such as a pair of opposing ropes. Regarding traveling equipment.

[Prior Art] When transporting objects using a track, there are two possible methods: moving the track, or keeping the track fixed and moving a device on the track.

Conventional examples of the former include elevators, ropeways, lifts, cranes, etc., and examples of the latter include monorails, trolleys, railways, etc., and suspended self-propelled devices that utilize the frictional force between ropes and wheels. be able to.

[Problems to be solved by the invention] The various conventional transport devices and traveling devices described above have the following problems:
As is well known, they are used selectively depending on the distance traveled and other various conditions, but with the exception of the last-mentioned suspended self-propelled device that uses the frictional force between the rope and wheels. In either case, it is extremely difficult or impossible to transport or move objects within a narrow and curved space. In addition, track facilities generally tend to be large-scale, and changing routes is extremely troublesome and may even be impossible due to restrictions such as locational conditions.

On the other hand, the above-mentioned suspended self-propelled device has a considerable advantage in terms of freedom in choosing routes, but if swinging while traveling is unavoidable or if the rope is tilted, it will be greatly affected by gravity, making traveling difficult. It has disadvantages in other senses, such as being difficult.

Furthermore, each of the above-mentioned conventional devices has considerable limitations in the facility conditions of the track itself and the running posture of the traveling device, and for example, in a device that is premised on the use of a pair of tracks, such as a railway track, this is not the case. The tolerance range for the inclination of the plane containing a pair of tracks and the variation in the spacing between the tracks is quite narrow, and on the other hand, there is a device that uses a single track that does not require consideration at least about the mutual installation conditions of the tracks, i.e. Even in the monorails, ropeways, lifts, and suspended traveling devices mentioned above, the posture of the traveling device that straddles or is suspended from the track is to a certain extent with respect to one predetermined direction (generally the vertical direction). The vehicle is only allowed to tilt within the range; for example, riding while lying on your side or upside down is absolutely not allowed.

However, at construction sites for various buildings and facilities,
Due to space constraints, it is often necessary to transport equipment, materials, etc. through intricate ramps and winding paths. Furthermore, in chemical plants and nuclear power plants, in order to prevent major accidents and ensure safe operation of the plant, it is now necessary to monitor and inspect the operating status of the plant while freely moving in three-dimensional space.

Robotizing these tasks is a great hope for the future, and especially in the nuclear industry, it is an essential requirement that goes beyond simple rationalization and labor savings.

As a result, the conventional traveling devices as described above cannot meet these future demands, no matter what type is used.

The present invention has been developed from this point of view, and is capable of running independently between a pair of tracks arranged opposite each other, and can well follow changes in the distance and attitude between the tracks. A traveling device that can travel while closely following the inclination and bending of the track even in a limited narrow space.To put it simply, it has a high degree of freedom in a wide range of areas, including design freedom, facility freedom, travel freedom, posture freedom, etc. Its main purpose is to provide traveling equipment.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following features:
An inter-track running device for running independently between the pair of tracks; a pair of car frames each holding a pair of wheels separately through joints; and one of the pair of car frames on the distal end side. a pair of arms that hold the two arms; a joint means that allows each of the vehicle frames to tilt relative to the axis within a plane that includes the axis of the arms; and a joint means that connects adjacent ends of the pair of arms to each other; extensible urging means for urging the arms of the vehicle to move away from each other in opposite directions on the same axis; intersection angle detection means for detecting each intersection angle between the axis and each of the vehicle frames held by each of the arms; At least one of the pair of wheels held on each of the vehicle frames is a driving wheel, and a drive means for driving the wheel; By applying both wheels of the vehicle frame to the other track, each wheel is placed in a steered state where the direction is guided by each track via joints provided on the vehicle frame; The biasing force of the biasing means generates a thrusting tension on the pair of tracks, and the thrusting tension is used as a self-sustaining force of the device; Based on each intersection angle detected by the intersection angle detection means, Provided is a track-to-track running device characterized in that the wheel driving force generated by each wheel is controlled variably in a complementary manner to obtain the device self-propelling power while maintaining the device self-sustaining power.

[Operation] The inter-track running device configured as described above can be operated as follows.

When this device is positioned between a suitable pair of tracks, such as a pair of ropes stretched at intervals, and each wheel of each car frame is applied from the inside to the corresponding track, the pair of arms holding the car frame will Due to the biasing force applied to the arm, a tension force is generated between the pair of tracks through the vehicle frame and the wheels, and this tension force causes the device to become self-supporting as a whole.

In this state, if at least one of the pair of wheels attached to each vehicle frame is used as a driving wheel and driven by the drive means, the entire device starts moving forward or backward along the pair of tracks.

Furthermore, the pair of arms can extend and contract toward and away from each other while receiving a biasing force.
Moreover, since each vehicle frame can be tilted in a plane that includes the axis of each arm using joints, even if the distance between a pair of tracks varies within a certain range depending on the location under the current driving condition, each The vehicle frame is tilted with respect to the axis of each arm so as to follow the corresponding trajectory at that time, and each arm also expands and contracts appropriately, allowing the device to continue traveling while remaining independent.

However, if each driving wheel, one on each car frame, could only be driven with the same driving force or rotational speed, the tilt of each car frame and each arm would become extremely large, causing the device to collapse, causing a pair of As a result of the arms fully extending in the direction away from each other, it is also conceivable that the tension between the tracks, that is, the self-sustaining force of the device, is lost.

Therefore, in order to prevent this, this device is provided with an intersection angle detection device, which detects each intersection angle between each vehicle frame and the axis of the arm, that is, each inclination angle between each arm and the corresponding vehicle frame. Based on these differences, the driving force applied to each driving wheel by the driving means is variably controlled in a complementary manner to prevent posture collapse. There are several concrete ways to perform complementary driving force variable control, but the most basic method is to slightly reduce the driving wheels of the vehicle frame on the side with the larger inclination angle, and to greatly increase the driving wheels of the car frame on the side with the smaller inclination angle. Drive. In this way, the inclinations of each vehicle frame and each corresponding arm are always controlled so that they are substantially the same, and therefore the posture of the apparatus can be suppressed to fluctuations within a substantially constant range.

Since this device uses the above-mentioned running principle, it can run following the curved or twisted surface including the pair of tracks. In particular, even if the bending is greater than a certain degree, each wheel is held to the corresponding vehicle frame via a joint, so by appropriately setting the rotation angle range and mechanical viscosity of the joint, it is possible to guide the wheel to the corresponding trajectory. The vehicle can be automatically steered easily, and can therefore follow such large bends well.
Furthermore, depending on the location, the arm can be rotated around its axis according to the torsion of the orbital surface, allowing it to take a passing posture such as lying down on its side or upside down.

In addition, it is sufficient that the pair of tracks to be engaged by this device is constructed with a tension that does not significantly expand the gap when receiving the pushing tension applied from this traveling device. There are no major facility requirements, but rather sufficient flexibility can be achieved, and the design and workability of track facilities can be greatly improved.

The track material and track form are also essentially arbitrary.
It can be made of various materials and have various shapes, such as a metal or non-metallic rope, T-shape, H-shape, channel shape, or angle shape. Therefore, the wheels can be of any suitable shape, such as one that straddles the track or one that fits into the groove of the track.

Furthermore, if a conductive material such as a suitable metal is used for the pair of tracks, the pair of tracks can be used as a power supply line for driving various electrical systems of this device or as a signal line for exchanging various signals. You can also do that.

[Embodiment] FIG. 1 shows a schematic configuration of a basic embodiment of the traveling device of the present invention.

The traveling device 10 as a whole has a pair of arms 1, 1.
These arms are arranged on the same axis and their adjacent ends are connected to each end of the biasing means 9. The biasing means 9 is schematically shown in the figure as a mechanical spring by phantom lines, and the biasing means 9 biases the pair of arms 1, 1 away from each other as shown by arrows F. They can also shrink toward each other while being pushed.

This biasing means 9 is housed, for example, in the main body 4, and the main body 4 can also have a carrier part (not shown) for supporting the object to be conveyed by the device 10, and the internal parts will be described later. It can also contain electrical circuit systems and the like that control each operation of this device.

Each vehicle frame 2, 2 is held at the tip of each arm 1, 1 via joints 7, 7. In this case, each vehicle frame is held by each arm at approximately its center position, and the joints 7, 7 are held in at least one plane including the common axis of both arms, for example, the plane of FIG. Each vehicle frame can be tilted as shown by angles θa and θb.

However, it is preferable that the device as a whole be designed to be tiltable only within that one plane. The reason for this will be understood from the operation of this embodiment described later, but for this purpose, the joint 7 can be, for example, a pivot joint that rotates only around one axis orthogonal to the axis of the arm. .

In this embodiment, a joint 8 is provided along the length of at least one arm to allow rotation around the arm axis. However, as has been omitted in the above-mentioned summary structure, this is a desirable component in the embodiment, and one of the vehicle frame 2 and the main body 4, which are opposed to each other via the joint 8, It allows relative rotational deviation between the vehicle frames 2 and 2 about the arm axis, and performs the function described later.

Each vehicle frame 2 has a U-shape, for example, and has wheels 3a and 3b at the tips of both legs of the U-shape, respectively. Each wheel is of course rotatable, and its axis of rotation is perpendicular to the plane of the paper in FIG.

Further, each wheel is held on each vehicle frame by a respective joint 6, and the direction of the wheel can be changed by this joint 6. Accordingly, in accordance with the illustrated embodiment, this joint 6 is a joint in a U-shaped vehicle frame whose rotation axis is the leg axis of the U-shaped leg.
However, since the car frames 2, 2 are not limited to the U-shape, generally speaking, this joint 6 rotates the entire wheel around an axis perpendicular to the wheel axis, or at least an axis parallel to this. can be rotated,
It only needs to be a joint that can change the direction of the wheel.

At least one of the pair of wheels 3a, 3b held on each car frame, for example, the two wheels 3a, 3b on the upper right side and the lower left side in the figure, is connected to a drive device 5, 5 provided in each corresponding car frame. Rotationally driven by. Therefore, the other wheels 3a and 3b of each vehicle frame serve as idlers or follower wheels.

In addition, each wheel has a pair of target trajectories Wa,
The form is adapted depending on the shape of Wb.
For example, in this embodiment, if ropes are used as tracks, each wheel has a groove on its circumferential surface that allows it to straddle the ropes Wa, Wb. This is well illustrated in the embodiments of FIGS. 3-5, which show more specific embodiments.

Further, although not shown, this device has means for detecting the inclination angle between each arm and the corresponding vehicle frame, that is, the intersection angles θa and θb between the vehicle frame and the axis related to the arm, and the difference between the detected intersection angles is Based on this, the driving forces of both driving wheels 3a and 3b are controlled in a cooperative and complementary manner, for example, in the manner described later. As this intersection angle detection means, any known appropriate rotation angle detection means such as a potentiometer can be employed. Also, if it is necessary to direct each intersection angle θa and θb for reasons of electronic control, which will be described later,
For example, in the figure, the direction in which each intersection angle is indicated by an arrow may be set as positive.

For convenience, the following explanation will be based on the assumption that the trajectories Wa and Wb are a pair of ropes strung at an appropriate distance as mentioned above.This device operates within the space defined between the pair of ropes. Insert and use.

That is, when the entire device 10 having the above structure is positioned within the pair of ropes Wa, Wb, the urging force generated by the urging means 9 in the main body 4 causes the arms 1, 1 to
The wheels 3a, 3b of the vehicle frames 2, 2 extend away from each other and are held at both ends of each wheel;
Fit a and 3b to each corresponding rope,
Even in this state, the biasing means 9 biases each wheel against the corresponding rope from the inside to the outside, so that when viewed from the main body 4, both ropes Wa and Wb The tension is applied from the inside, and the urging force or tension acts as a self-sustaining force for the device, and the device as a whole becomes self-supporting between the pair of ropes.

Under this condition, if each drive device 5 drives the corresponding driving wheels 3a, 3a, the device self-propelling power can be obtained. Of course, the driving direction of both driving wheels is, for example, the first
In the figure, it is determined depending on whether the device as a whole moves in the direction indicated by arrow Tf or in the opposite direction indicated by arrow Tb.

As shown in FIG. 2, which schematically shows the progress state between positions Q1 and Q7, this device 10 can be used even if the distance between the pair of ropes Wa and Wb varies depending on the location. Even if the rope undulates independently, while changing the intersecting angles θa and θb between each arm 1 and each vehicle frame 2, the tension force generated by the biasing means 9 and the reaction force from the rope can be adjusted. It is possible to travel between these trajectories while expanding and contracting the distance between the tips of both arms so as to maintain balance.

However, if the driving wheels 3a, 3a are always driven only with the same driving force or rotation speed, the positions of the pair of vehicle frames in the traveling direction may shift significantly back and forth along the rope, and both arms 1, 1 There may be cases where the tension force generated by the biasing means becomes ineffective due to, for example, being fully extended.

Therefore, in the present invention, as described above, the intersection angles θa and θb representing the degree of inclination between each arm and each vehicle frame are detected, and the driving wheels 3a and 3a are controlled in a cooperative and complementary manner according to the difference. do.

Of course, the control mode is not uniquely determined, and several methods can be considered, but as one basic control mode, for example, the intersection angle θa,
After detecting θb, they are compared, and the driving wheel 3a with the smaller value is rotated to a greater extent than the other driving wheel.

For example, if θa<θb in FIG. 2, the driving wheel 3a applied to the upper rope Wa is driven at a higher rotational speed than the driving wheel on the lower rope Wb side.

In this way, the arm shaft connecting the centers of both vehicle frames will be
Since the entire device moves while being positioned perpendicular to the line connecting the centers of the tracks, the overall posture of the device does not collapse to the extent that it loses its tension.

Furthermore, when both intersection angles θa and θb have the same value, the posture of the apparatus is sufficiently stable, so it is sufficient to rotate both driving wheels with the same energy.

In addition, as schematically shown in FIG. 1, for example, when a mechanical spring is used, the biasing means 9 is compressed in response to the reaction force received from the rope, thereby accumulating a large biasing force inside. However, it may be provided with appropriate feedback control means so as to always produce the same poking tension as possible. Such control becomes particularly simple when using electromagnetic, hydraulic or pneumatic biasing means. However, of course, feedback control such as making the biasing force variable in accordance with the compressive force is an example matter that may be performed as necessary.

Although FIG. 2 shows a case where the ropes or tracks are arranged on the same plane, it is clear that the device 10 can run stably even when this plane is bent or twisted. This can be clearly seen by holding both edges of the sheet of paper shown in Figure 2 and actually bending it, or by holding both corners and twisting it.

In addition, even if such bending of the plane containing the pair of tracks becomes greater than a certain degree, and the direction in which the rope extends differs greatly at the position of the pair of wheels of each vehicle frame, this case is omitted in Figure 2. However, as shown in FIG. 1, since each wheel is supported by a joint 6 so as to be able to change direction, it is automatically steered by a rope, so that it can follow such bending well.

Furthermore, in this embodiment, since the rotary joint 8 is disposed on one arm, even if the pair of ropes Wa and Wb have a spatially twisted relationship in some parts, each vehicle frame will be able to move around each corresponding rope at that time. Accordingly, the device 1 of this embodiment can face the required direction independently.
0 can travel even between pairs of tracks that are partially twisted.

FIGS. 3 to 5 show the embodiment shown in FIG. 1 in more detail.

When the vehicle frame 2 is U-shaped, the wheels 3a,
The joint 6 for bringing the arm 3b into a steered state by a rope and the rotary joint 8 disposed on one arm 1 can be easily constructed using, for example, an existing thrust bearing or the like.

Further, the joint 7 that allows the vehicle frame 2 to rotate or tilt only in one plane with respect to each arm 1 can be easily configured as a pivot joint using an existing radial bearing or the like. .

The intersection angle detecting devices P1, P1 can be configured with various existing potentiometers that convert the inclination of the arm and the vehicle frame into a rotation angle of the gear 11 and detect the rotation angle, for example.

The drive device 5 for each driving wheel 3a, 3a may include a power source such as a conventional electric motor M, and the drive energy of the power source may be transferred using a belt, gear, or other suitable drive train 51 using known and existing technology. What is necessary is to transmit it to the driving wheels 3a.

Although not shown in the drawings, for example, in the main body 4, there is provided information for each driving wheel in order to perform the above-mentioned device posture stability control according to the difference between the intersection angles θa and θb detected by the intersection angle detection devices P1 and P1. It has a built-in circuit device that complementarily varies the rotational speed of the motor.

It is also preferable to provide a rotation amount detector P2 in order to know the total traveling distance of the device, etc. In that case, the meter itself may be a known and existing suitable one, and it can be installed, for example, on the power transmission train 51.
What is necessary is to engage the input rotating shaft with the input rotating shaft. Furthermore,
In order to detect the central position between the pair of ropes at any given time, for example, a device for detecting the amount of expansion and contraction of each arm may be incorporated into the main body 4.

By incorporating the rotation amount detector P2 and the center position detecting means, it is possible to determine an unknown trajectory on an appropriate coordinate system simply by running the device. Therefore, it is also possible to expect applications such as, for example, temporarily assembling a pair of tracks in a complicated space that is difficult to measure, and running the present device on this to learn the overall shape of the space.

By the way, in the embodiments so far, the device of the present invention has been explained as a single device, but according to the present invention, it is also possible to assemble a multiple device, that is, a traveling device in which several devices are connected.

FIG. 6 shows a case where two units are connected as an example of such a case, and the same reference numerals as in FIGS. 1 to 5 indicate the same or corresponding components as in the previous embodiment.

A pair of traveling devices 10, 10, which may have substantially the same configuration as the first embodiment, are connected by a joint 18, and the joint 18 is connected to a telescoping device 19 that is extendable and retractable, and detects the telescoping length L of this device. It has a device (not shown) to do so.

The joint 18 and the main body parts 4, 4 of each device are connected by pivot joints 17, 17, and a rotation joint 16 is also provided in the joint 18.

Further, this point is different from the traveling device 10 of the first embodiment described above.
Unlike, the pair of arms 1, 1 are both equipped with rotary joints 8, 8.

This arrangement of each joint is intended to eliminate the mutual influence of the postures between the devices 10 and 10, but the joint
8 and each device 10 are connected, for example, by a universal joint, just as in the first embodiment, only one joint 8 on the arm side of each device is sufficient, and as already mentioned, the orbits are mutually connected. If the torsion of the arm is not large enough to cause a problem, the joint 8 in the arm may be omitted.

Note that the joint 16 in the joint 18 may be provided at the joint on one side of the main body of the device.

This multiplexing device can be operated as follows.

Basically, the driving devices of both devices 10, 10 are driven so that the length L of the expansion/contraction device 19 in the joint 18 is always kept constant.

In other words, while the drive device of one traveling device 10 is the main one and drives its driving wheels as explained in the first embodiment, the drive device of the other traveling device 10 is the secondary one. The driving wheels are driven so that the length L of the telescoping device 19 is set to a predetermined value. For example, in FIG. 6, if the right traveling device 10 is assumed to be driven to the right, the length L of the telescopic device 19 in the joint 18 is increased, so that the left traveling device 10 is driven to the right. Shrink this.

Conversely, when the right side device 10 is driven to the left or the left side device 10 is driven to the right, the length L of the telescoping device 19 in the joint 18 is shortened, so that the length of the driven side is shortened. The traveling device 10 attempts to move away from the main drive side and return its length L to within a predetermined range.

From the above mechanism, it can be seen that the embodiment shown in Figure 6 can be further developed to connect multiple units in series, but in any case, if the above-mentioned connection method and travel control mode are adopted, multiple units of the traveling device of the present invention can be connected in series. Even when the platforms are connected, no unreasonable force is generated, and the entire system feels as smooth as if it were running alone.

Furthermore, when materials are transported by multiple units connected in parallel, it is convenient to provide the carrier section for the materials at the joint 18, since the positional fluctuation is minimized.

In addition, when three or more traveling devices are connected, some of the traveling devices may not have driving wheels.

As detailed above, since the device of the present invention has a simple structure, those skilled in the art can make various design changes. For example, as mentioned above, the biasing means 9 is not limited to a mechanical spring, but can be configured using electromagnetic force, hydraulic pressure, pneumatic pressure, etc., and the biasing force is inversely proportional to the amount of compression deviation. It is possible to use both a type with a control system that generates a biasing force that is as constant as possible regardless of the amount of compression deflection.

In addition, the joints 6 provided on each car frame to make each wheel steered are generally not spread over a wide range even if the rope has a fairly large curvature, that is, draws a fairly small arc, depending on the length of the car frame. Since there is no need to allow rotation, depending on the case, it may be sufficient to provide some flexibility around the axis, and therefore, it can be simply constructed using a spring or the like. This also applies to the other rotary joints 8 and 16.

Furthermore, as seen in the above embodiment, if the structure around the pair of vehicle frames is configured symmetrically,
Compared to the case where a dedicated vehicle frame structure is adopted for the lower side, this is greatly advantageous in terms of design, manufacturing, and cost. However, of course, this is not limiting, and therefore, depending on the case, it is not always necessary to connect each arm at the center of each vehicle frame.

As for the driving wheels, the wheels 3a and 3b at both ends of each vehicle frame
It is also possible to drive both as driving wheels. Increasing the number of driving wheels increases the frictional force between the wheels and the track, which can generate greater traction force. In addition, when the wheels 3a and 3b at both ends of each vehicle frame are driven as driving wheels, they are generally controlled by the same control signal, but if each wheel is provided with a dedicated drive device 5, 5, both wheels can be driven. It can be rotated asynchronously and there are no conflicts. If a working gear device is used, one drive device 5 can simultaneously drive two wheels at both ends of the vehicle frame without stress.

As for the track, as mentioned above, it is not limited to rope, but if it is made of electrically conductive material such as rigid rope, there is a pair of tracks, so it can be used as a power supply line or signal transmission line. You can also do it.

For example, the wheels or each car frame and the main body are electrically insulated, while at least one wheel of each car frame is electrically connected to the track, and then an appropriate route is established from the electrically connected wheels. It is also possible to take out the current applied to the track and use this to operate the drive device 5 and various control circuits.

In the same way, various control signals can be sent to the drive device by, for example, adopting various appropriate modulation methods, or conversely, information such as inter-orbit center position information can be picked up from the device via the orbit. You can also do it.

[Effects of the Invention] According to the present invention, a device is provided that can run autonomously on a pair of tracks that have to vary considerably in distance, are curved, inclined, or are twisted overall. be able to.

Therefore, it is possible to obtain a device that can freely run in a narrow and complicatedly curved space, which was previously thought to be difficult for a self-propelled vehicle.

Therefore, this device can be used extremely effectively for transporting various equipment and materials necessary for various tasks such as monitoring, inspection, maintenance, and repair at construction sites and various plants. It can also be used for

Furthermore, its configuration is relatively simple, and in that sense it is sufficiently practical.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a basic embodiment of the inter-track running device of the present invention, Fig. 2 is an explanatory diagram of an example of the running state of the device shown in Fig. 1, Figs. 3, 4, and 5. 6 are a side view, a front view, and a plan view of an embodiment in which the first illustrated device is more specific, respectively, and FIG. 6 is a schematic configuration diagram of an embodiment in which two devices are connected. In the figure, 1 is an arm, 2 is a car frame, 3a, 3b are wheels,
4 is a main body, 5 is a drive device, 6, 8, 16 are rotary joints, 7, 17 are pivot joints, 9 is a biasing means,
10 is the main traveling device as a whole.

Claims (1)

[Scope of Claims] 1. An inter-track running device located between a pair of tracks spaced apart and for running independently between the pair of tracks; a pair of car frames held apart from each other; a pair of arms holding one of the pair of car frames on the distal end side; tilting each of the car frames with respect to the axis within a plane including the axis of the arms; an extensible urging means that connects adjacent ends of the pair of arms and urges the pair of arms to move away from each other in opposite directions on the same axis; Intersection angle detection means for detecting each intersection angle with each of the vehicle frames held by each arm; A drive means for driving at least one of the pair of wheels held by each of the vehicle frames as a driving wheel; By applying both wheels of one of the pair of car frames to one of the pair of tracks, and applying both wheels of the other car frame to the other track, each wheel is connected to each track via a joint provided on the car frame. In addition to being in a steered state in which the direction is guided; in the steered state, a pushing force of the biasing means is used to generate a pushing tension force on the pair of tracks, and the pushing tension force is used as a self-sustaining force of the device. On the other hand; Based on each intersection angle detected by the intersection angle detection means, the wheel driving force generated by each of the pair of drive means is variably controlled in a complementary manner to obtain a device self-propelling force that maintains the device self-sustaining force. An inter-track running device characterized by: