CA3031875A1 - Transportation system - Google Patents

Abstract

A transportation system including one or more transportation assemblies. The transportation assembly includes a body, two or more sets of first wheels, and two or more sets of second wheels. The first wheels are mounted to the body and include first wheel treads configured for engaging a pair of first rails spaced apart by a first distance. The first rails are positioned at one or more first grades. The second wheels are also mounted to the body, and include second wheel treads that are configured for engaging a pair of second rails that are spaced apart by a second distance that is larger than the first distance. The second rails are positioned at one or more grades that are steeper than the first grade.

Description

TRANSPORTATION SYSTEM
FIELD OF THE INVENTION
[0001] The present invention is a transportation system.
BACKGROUND OF THE INVENTION

[0002] In the conventional configuration of railroad equipment (i.e., steel treads engaging standard rails), the gradient is limited by the ability of a prime mover (i.e., a locomotive) to push or pull the load-carrying cars. The weight of the locomotive enhances traction, but as the gradient increases, the tractive effort available to move payload decreases. As is well known in the art, increasing the gradient will ultimately reach a point where the locomotive is unable to move the loaded cars up grade.

[0003] Steel wheel treads on standard rails offer maximum operating efficiency, due to minimum rolling resistance. The shape of the standard rail has been optimized for use with steel wheel treads.

[0004] One conventional solution has been to use softer treads, to increase the gradient that the loaded cars can be moved over. Because of the increase in friction, there are some disadvantages, e.g., increased costs due to increased wear on the softer wheels, and decreased overall efficiency. In any event, even with softer wheel treads, there is a significant reduction in load haulage capacity as the steepness of the track increases.

[0005] The constraints to which conventional railroad equipment are subject tend to have significant consequences, i.e., they may result in significant costs. For example, a tunnel boring machine engages ground at a front end thereof to produce muck (broken ground) that is removed from the back end of the tunnel boring machine by any suitable method. As is well known in the art, the muck may be loaded at a back end of the tunnel boring machine into muck cars, typically, relatively small-capacity rail-mounted cars. The muck cars are included in a muck train.

[0006] In this arrangement, the maximum grade at which the muck train can operate may limit the grade of the tunnel that is excavated by the tunnel boring machine.
This constrains the tunnel design, and in certain contexts (e.g., when constructing penstocks at a hydroelectric power plant), such constraints may result in significantly greater expense overall.
SUMMARY OF THE INVENTION

[0007] There is a need for a transportation system that overcomes or mitigates one or more of the defects or disadvantages of the prior art. Such defects or disadvantages are not necessarily included in those listed above.

[0008] In its broad aspect, the transportation system includes one or more transportation assemblies. Each transportation assembly includes a body and two or more sets of first wheels mounted to the body and respectively having first wheel treads configured for engaging a pair of first rails spaced apart by a first distance, the first rails being positioned at one or more first grades, and at least two sets of second wheels mounted to the body and respectively having second wheel treads configured for engaging a pair of second rails spaced apart by a second distance that is larger than the first distance. The second rails are positioned at one or more second grades that are steeper than the first grade.
BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention will be better understood with reference to the attached drawings, in which:

[0010] Fig. 1A is an embodiment of a transportation system of the invention including an embodiment of a transportation assembly of the invention and an embodiment of a rail assembly of the invention;

[0011] Fig. 1B is a schematic illustration of another embodiment of the rail assembly of the invention, on which the transportation assembly of Fig. 1A is positionable, drawn at a smaller scale;

[0012] Fig. 1C is a portion of the rail assembly of Fig. 1B, drawn at a larger scale;

[0013] Fig. 1D is another portion of the rail assembly of Fig. 1B;

[0014] Fig. 1E is an isometric view of an embodiment of a car included in the transportation assembly of the invention;

[0015] Fig. 2A is an isometric view of embodiments of sets of first and second wheels positioned on first rails of the rail assembly, drawn at a larger scale;

[0016] Fig. 2B is an isometric view of the wheelsets of Fig. 2A prior to engagement of the second wheels with transition portions of second rails of the rail assembly;

[0017] Fig. 2C is an isometric view of the wheelsets of Figs. 2A and 2B
in which the second wheels are positioned on the transition portions;

[0018] Fig. 2D is an isometric view of the wheelsets of Figs. 2A-2C
positioned on straight portions of the second rails;

[0019] Fig. 3A is a side view of the wheelsets of Figs. 2A-2D positioned on the first rails;

[0020] Fig. 3B is a side view of the wheelsets of Figs. 2A-2D prior to engagement of the second wheels with transition portions of second rails of the rail assembly;

[0021] Fig. 3C is a side view of the wheelsets of Figs. 2A-2D in which the second wheels are positioned on the transition portions;

[0022] Fig. 3D is a side view of the wheelsets of Figs. 2A-2D in which the second wheels are engaged with the straight portions;

[0023] Fig. 4A is a front view of the wheelsets of Figs. 2A-2D in which the first wheels are engaged with the first rails;

[0024] Fig. 4B is a front view of the wheelsets of Figs. 2A-2D in which the first wheels are engaged with the first rails, and the wheelsets are in the transition zone;

[0025] Fig. 4C is a front view of the wheel sets of Figs. 2A-2D in which the second wheels are engaged with the transition portions of the second rails, and the wheelsets are in the transition zone;

[0026] Fig. 4D is a front view of the wheel sets of Figs. 2A-2D in which the second wheels are engaged with the straight portions of the second rails;

[0027] Fig. 5A is a side view of an embodiment of the transportation assembly that includes an embodiment of an arrestor module, drawn at a larger scale;

[0028] Fig. 5B is a cross-section of the arrestor module of Fig. 5A, taken along section C-C;

[0029] Fig. 5C is a cross-section of a portion of the arrestor module of Figs. 5A and 5B
showing brake shoes of the arrestor module in a disengaged condition, drawn at a larger scale;

[0030] Fig. 5D is the cross-section of Fig. 5C in which the brake shoes are shown in an engaged condition;

[0031] Fig. 6A is a front view of the wheelset of Figs. 2A-2D, drawn at a smaller scale;
and

[0032] Fig. 6B is a side view of the wheelset of Fig. 6A.
DETAILED DESCRIPTION

[0033] In the attached drawings, like reference numerals designate corresponding elements throughout. Reference is made to Figs. 1A-4D and 6A-6B to describe an embodiment of a transportation system 20 of the invention. In one embodiment, the transportation system 20 preferably includes one or more transportation assemblies 22 (Fig. 1A). It is preferred that each of the transportation assemblies 22 includes a body 24 and two or more sets 26 of first wheels 28 mounted to the body 24 and configured for engaging a pair of first rails 30 spaced apart by a first distance "D1". As will be described, the first rails 30 preferably are positioned at at least one first grade "G1". Preferably, the transportation assembly 22 also includes two or more sets 32 of second wheels 34 mounted to the body 24 and respectively comprising second wheel treads 36 (Fig. 2A) configured for engaging a pair of second rails 38 spaced apart by a second distance "D2" that is larger than the first distance "D111. As will also be discussed further below, it is preferred that the second rails 38 are positioned at at least one second grade "G2" that is steeper than the first grade "G1".

[0034] As will be described, in one embodiment, each of the transportation assemblies 22 preferably includes a motor "M", so that the load in the transportation assembly 22 improves the traction thereof.

[0035] The first and second rails 30, 38 are included in an embodiment of a rail assembly 39 of the invention. As will be described, the first rails 30 preferably are conventional. As illustrated in Fig. 1B, in one embodiment, the rail assembly 39 preferably includes a lower set of first rails (located at a lower elevation) and an upper set of first rails (located at a higher elevation), identified in Figs. 1B-1D by reference characters 30A, 30B for clarity of illustration. Those skilled in the art would appreciate that the arrangement schematically illustrated in Fig. 1B may be used where the transportation assembly 22 (not shown in Figs. 1B-1D) is used to move material from a lower level (i.e., at which the first rails 30A are located) to an upper level (i.e., at which the second rails are located), and vice versa.

[0036] Those skilled in the art would also appreciate that, depending on the circumstances, the rail assembly 39 may, alternatively, include only the first rails 30A and the second rails 38, or the first rails 30B and the second rails 38.

[0037] As can be seen, e.g., in Fig. 1B, the first grade "Gl" is relatively flat. Those skilled in the art would be aware that, in general, the first grade "Gl" may vary between 0% and approximately 10% or more. The second grade "G2" preferably is much steeper than the maximum of the first grade "Gi". It is believed that the second grade "G2" may be up to approximately 30% or more and may be safely climbed by the transportation assembly 22 of the invention.

[0038] It will be understood that the transportation assembly 22 may move up the first and second grades "Gl" and "G2" in the direction indicated by arrow "A", in Fig.
1B and may move downwardly on the first and second grades "G1" and "G2" in the direction indicated by arrow "B"
in Fig. 1B.

[0039] It will also be understood that the transportation system 20 preferably includes the transportation assembly 22 and the rail assembly 39. The rail assembly 39 preferably includes the first rails 30, and the second rails 38.

[0040] It is preferred that the first rails 30 are conventional steel rails, and the second rails 38 are not, as will be described.

[0041] As can be seen in Figs. 1C and 1D, the first rails 30 and the second rails 38 preferably overlap laterally in a transition zone "Z". For clarity of illustration, the transition zone "Z" is shown in Figs. 1C and 1D as including transition sub-zones "ii" and "Z2".

[0042] It has been found that, for a smooth transition of the transportation assembly 22 from the first rails 30 to the second rails 38, a part "C" of the second rails 38 in the transition sub-zone "Z2" preferably is located at substantially the same grade as the first rails 30, i.e., at grade "Gi". For clarity of illustration, a line "J" that is parallel to grade "Gi"
is included in Fig. 1C.

[0043] In Figs. 1C and 1D, the vertical distance between a top running surface "Si" of the first rails 30 and a top running surface "S2" of the portion of the second rails 38 that is in the transition sub-zone "Z2" is identified by the reference character "Hi" for convenience. It will be understood that the distance "Hi" is exaggerated in Figs. 1C and 1D for clarity of illustration.

[0044] In one embodiment, a portion "K" of the first rails 30 that is located in the transition region "Z" gradually diverges downwardly from the grade "Gi". It has been found that this downward trajectory provides for a more smooth transition of the transportation assembly 22 from the first rails 30 to the second rails 38, when the transportation assembly 22 is travelling in the direction indicated by arrow "A". For clarity of illustration, the vertical distance between the top surface of the first rail 30 at the end of the portion "K" and the surface "S2" proximal to the second rail 38 is identified by reference character "H2" in Figs. 1C and 1D.

[0045] It has also been found that the grade "G2" preferably is determined in order to permit the transportation assembly 22 to be substantially aligned, grade-wise, for the change in gradient, i.e., from "Gi" to "G2", and from "G2" to "Gi". Depending on the circumstances, "G2" may include more than one grade, which may be based on one or more radii.

[0046] As can be seen in Figs. 4B and 4C, in one embodiment the second rails 38 preferably are positioned further apart from each other than are the first rails 30, i.e., "D2" is larger than "Di". Those skilled in the art would appreciate that, in an alternative embodiment, the second rails 38 may be positioned more closely to each other than the first rails 30, i.e., distance "D2"
may alternatively be less than distance "Di". As illustrated in Figs. 2A-2D, the first rails 30 and the second rails 38 overlap laterally only in the transition zone "Z" (Fig.
1B) in which the grade at which the transportation assembly 22 is positioned changes from the first grade "Gi" to the second grade "G2", and vice versa, depending on the transportation assembly's direction of travel.

[0047] It will also be understood that, for convenience, only one of the first rails and only one of the second rails will be described in detail, as the other rail in each case is substantially the same.

[0048] The second rails 38 preferably include portions 40 thereof that are positioned at the second grade "G2". As noted above, the second grade "G2" may include a number of grades.
For instance, as can be seen in Figs. 1C and 1D, it is preferred that the part "C" of the second rails 38 is a relatively small part of the portion 40 of the second (augmented) rail. The upper, or running, surfaces "S1" and "S2" of the first rails 30 and of the portions 40 of the second rail respectively define the first and second grades "G1" and "G2".

[0049] As can be seen in Figs. 1C, 1D, and 2A, in one embodiment, the second rails 38 preferably include transition portions 42 thereof that are formed to enable the transportation assembly 22 to move relatively smoothly between the first rails 30 and the portions 40 of the second rails 38. Those skilled in the art would appreciate that the transition portions 42 may have any suitable configuration. For example, as illustrated in Fig. 1B, in one embodiment, the transition portion 42 has an upper surface 44 thereof that is substantially straight.

[0050] The transition portion 42 extends between a first end 46, at which the upper surface 44 is proximal to the running surface "S1" of the first rail 30, and a second end 48, at which the upper surface 44 is proximal to the running surface "S2" of the second rail 38 (Fig. 2B). As illustrated in Fig. 1B, it is believed that the transition portion 42 may be relatively short.

[0051] As can be seen in Figs. 50 and 5D, in one embodiment, the second rail 38 preferably includes a web portion 70 that supports an inner upper flange 72 and an outer upper flange 74. In Figs. 2A-2D, it can also be seen that, in the transition portion 42 of the second rail 38, the inner upper flange 72 has been removed. As will be described, this is believed to facilitate the movement of the transportation assembly 22 between the first rail 30 and the straight portion 40 of the second rail 38.

[0052] Also, part of the outer upper flange 74 is removed, to provide a chamfered portion 75 of the outer upper flange 74, to facilitate movement of the unit up the inclined surface 42.

[0053] It can be seen in Fig. 1C that the downwardly-bent portion "K" of the first rail 30 causes the second wheels 34 to engage the inclined surfaces 42 as the transportation assembly 22 moves in the direction indicated by arrow "A".

[0054] Preferably, in the transition zone "Z", the sets 32 of the second wheels 34 engage the second rails 38 and the sets 26 of the first wheels 28 engage the first rails 30 (Figs. 2A-3D), although not necessarily simultaneously. As will be described, in the transition zone "Z", the engagement of the first wheels 28 with the first rails 30 and the engagement of the second wheels 34 with the second rails 38 may be sequential. If the engagement is sequential, then the order in which the wheels engage the respective rails depends on the direction in which the assembly 22 is moving.

[0055] As can be seen in Fig. 3A, the first wheel 28 preferably includes a first wheel tread 50 that engages the upper surface "Si" of the first rail 30.

[0056] The manner in which the first wheel treads 50 of the first wheels 28 initially engage the upper surface "Si" of the first rail 30 before the second wheel treads 36 of the second wheels 34 engage the surface 44 of the transition portion 42 can be seen in Figs. 3A
and 3B, in which the first and second wheels 28, 34 are moving in the direction indicated by arrow "A".

[0057] In Fig. 3B, the first and second wheels 30, 34 are entering the transition zone "Z".
At that point, the first wheel treads 50 of the first wheels 28 are still engaging, and supported by, the upper surface "Si" of the first rails 30.

[0058] As can be seen in Figs. 3B and 3C, the upper surface 44 of the transition portion 42 may define a substantially straight incline, ending at the upper surface "S2" of the straight portion 40 of the second rail 38.

[0059] Preferably, the transition portion 42 is formed so that the second wheel tread surface 36 engages the upper surface 44 near the second end 48 of the transition portion 42. At that point, illustrated in Fig. 3C, the first wheel tread surface 46 may still be engaged with the upper surface "Si" of the first rail 30.

[0060] As can also be seen in Figs. 3C and 3D, forward movement of the transportation assembly 22 (i.e., in the direction indicated by arrow "A" in Figs. 3C and 3D) causes the entire transportation assembly 22 to be raised due to the engagement of the second wheel tread surface 36 with the upper surface 44 at the upper end 48 of the transition portion 42, and with the upper surface "S2". Due to such engagement, the first wheel tread 50 is raised above the first surface "Si" by a vertical distance "V" (Fig. 3D).

..

[0061] As noted above, in one embodiment, the first rail 30 preferably includes the portion "K" thereof, which is generally convex, relative to the second rail 38, and which is also positioned below the second rail 38. When the transportation assembly 22 is moving in the direction indicated by arrow "A", the first wheels 28 follow the first rails 30 until the first wheels 28 are lifted upwardly, off the first rails 30, due to the engagement of the second wheels 34 with the inclined surfaces 42 of the second rails 38.

[0062] Similarly, when the transportation assembly 22 is travelling in the direction indicated by arrow "B", the first wheels 28 engage the portion "K" of the first rail 30 when the second wheels 34 have travelled sufficiently far along the portion 42 to cause the first wheels 28 to engage the portion "K".

[0063] As can be seen, e.g., in Figs. 4A, 6A, and 6B, in one embodiment, it is preferred that pairs of the first wheels 28 and pairs of the second wheels 34 are respectively positioned coaxially in a wheelset 52. It will be understood that the transportation assembly 22 may include one or more drive modules 54, to which one or more muck car modules 56 may be attached (Fig.
1A). Each of the modules 54, 56 preferably includes at least two of the wheelsets 52.

[0064] As will be described below, in one embodiment, the muck car modules 56 may include motors respectively, and the drive modules may not be needed.

[0065] An axis "X" about which each of the first and second wheels 28, 34 rotates is schematically illustrated in Figs. 4B, 4C, and 6A.

[0066] From the foregoing, it can be seen that the transportation assembly 22 may be hauling a payload uphill, and/or downhill. These are discussed separately.
Down Grade Haulage

[0067] In this scenario, an empty train moves up grade, and payload is moved downgrade.

[0068] The drive is sized to manage the empty train's tractive effort needs up the grade.

[0069] The system can support haulage on standard rail on gradients up to 10%, extending gradeability to 30% on augmented rail (the second rails 38).

[0070] The system can be battery powered with the regeneration available in controlling the loaded train downgrade offsetting the energy required to move the empty train up grade.

[0071] In one embodiment, a compound wheel with a size reduction between the standard rail wheel (larger) and augmented rail wheel (smaller), both fixed to a common axle, preferably provides increased tractive effort. Halving the wheel diameter on the augmented rail would double the train's gradeability between the standard rail and augmented rail sections.

[0072] In applications where the gradient differential between the standard rail and augmented rail sections exceeds a factor of 2.5, a gear reduction preferably is added between the rail wheel and the softer augmented tire to balance the loading on the drive.

[0073] A transportation assembly 122 that includes at least one main gearbox 180 and at least one planetary gearbox 182 is illustrated in Fig. 1E. The transportation assembly 122 preferably also includes at least one motor "M" (Fig. 1E). As can be seen in Fig. 1E, in one embodiment, the first wheels 128 preferably are mounted to an axle 184 and driven through the main gearbox 180, and the second wheels 134 preferably are mounted to rotate about other, non-co-axial axes. The second wheels 134 preferably are driven through the planetary gearbox 182.
It will be understood that the motor "M" transmits power to the axle 184 via the main gearbox 180, and the rotating axle 184 in turn transmits power to the second wheels 134 via the planetary gearbox 182. It will be understood that the transportation assembly 122 has a larger capacity (e.g., larger than the transportation assembly that is illustrated in Fig.
1A), and the transportation assembly 122 is for use in an up-grade haulage system, in which the transportation assemblies 122 are loaded when hauling up grade.

[0074] As will be described, tractive effort in the loaded condition can be augmented with mechanical axle braking with an arrestor module added to the system to positively secure the train on the augmented rail.

[0075] Those skilled in the art would appreciate that the transportation assembly 22 is required to have the capacity to back up grade when fully loaded, but such performance only needs to be marginal, as this is an emergency condition and it is acceptable that the drive can only sustain loaded up grade performance for a minimum amount of time.
Up Grade Haulage

[0076] In this scenario, a loaded train is moved up grade.

[0077] System supports haulage on standard rail up to a 10% grade extended to 30% on augmented rail (second rails 38).

, ..

[0078] The drive is sized to manage the loaded train's tractive effort needs up the grade.

[0079] The power source preferably is via a trolley feed, or diesel-electric, as the regeneration available in controlling the empty train down grade is minimal compared to the energy requirements to move the loaded train upgrade.

[0080] As will be described, an arrestor module is added to the system to positively secure the train when an augmented track system is utilized.

[0081] In these circumstances, a gear reduction between the softer tire 34 and rail wheel 28 (Fig. 1E) is required to allow a common drive to effectively service both applications.

[0082] Utilizing a planetary bogie configuration with a second softer tire located at each rail wheel provides a compact assembly with an increased load capacity per axle for larger capacity haulages (Fig. 1E).

[0083] As the speed differential between the two rail systems increases, it may be necessary to introduce a clutch (not shown), which allows the rail wheels to free-wheel during the train's operation on the augmented section 38. The free-wheeling reduces wheel face wear and smoothens the transition between the two trackage systems.

[0084] Completely supporting the load being carried with driven wheels proportionately increases the available traction as the load on the wheels increases. Grade capability (gradeability) is not impacted by fluctuations in the gross weight of the transportation assembly, unlike a conventional train configuration.

[0085] In use, when the transportation assembly 22 is travelling in the direction indicated by arrow "A", when one of the wheelsets 52 first enters the transition zone "Z", the first wheel treads 50 of the first wheels 24 are engaging the surfaces "Si" of the first rails 30. As the wheelset 52 progresses further into the transition zone "Z", the second wheel treads 36 engage the surfaces "S2" of the second rails 38. After this occurs, the entire wheelset 52 is lifted upwardly due to the grade of the upper surface 44 of the transition portion 42.

[0086] When the wheelset 52 progresses past the second end 48 of the transition portion 42, the second wheel treads 36 are engaging the surfaces "S2" of the second rails 38.

..

[0087] In another embodiment, the second wheel treads 36 preferably include a high-friction material, e.g., rubber. This material is advantageous because, due to its use, the second wheels 34 are unlikely to slip on the second surface "S2" of the second rails 38. Because the second rails 38, the surfaces "S2" of which are intended to be engaged by the second wheel treads 36, are generally located at relatively steep grades, including the high-friction material on the second wheel treads 36 has the advantage of enhancing the ability of the transportation assembly 22 to travel on the steeply inclined second rails 38.

[0088] Those skilled in the art would appreciate that the high-friction material has the disadvantage that it is more susceptible to wear than the steel of the first wheel treads 50.

[0089] Due to the relative steepness of the second grade "G2" at which the second rails 38 are positioned, in one embodiment, it is preferred that one or more arrestor modules 60 are attached to the transportation assembly 22 (Fig. 5A). It will be understood that the arrestor module 60 provides an emergency brake function. Those skilled in the art would appreciate that the first and second wheels would also be braked during operation by braking systems (not shown) that are controlled by an operator.

[0090] It will also be understood that the straight portion 40 of the second rail 38 of Fig.
5A is illustrated at a substantially flat grade solely to simplify the drawing. Those skilled in the art would appreciate that the straight portion 40 may be positioned at any suitable grade "G211 .

[0091] Preferably, the arrestor module 60 includes an arrestor module body 61 and one or more sets of brake shoes 64 (Fig 5B) mounted to the arrestor module body 61. As will be described, the brake shoes 64 preferably are movable between a disengaged condition (Fig. 5C), in which the brake shoes 64 are disengaged with the second rails 38, and an engaged condition (Fig. 5D), in which the brake shoes 64 are engaged with the second rails 38, to hold the transportation assembly 22 stationary relative to the second rails 38.

[0092] It is also preferred that the arrestor module 60 includes idler wheels 65 (Figs. 5B-5D) that are mounted to the arrestor module body 61, to support the arrestor module body 61 when the brake shoes 64 are disengaged from the second rails 38. The idler wheels 65 also guide the arrestor module 60 up or down the transition portion 42. The idler wheels 65 thread onto the second or first rails (as the case may be) at speed.

[0093] It is also preferred that the arrestor module 60 additionally includes an actuator (not shown) operatively connected with the brake shoes 64, for controlling engagement of the brake shoes 64 with the second rails 38.

[0094] As can be seen in Fig. 5A, the arrestor module body 61 preferably is connected with the body 24 of the transportation assembly 22. It is preferred that the arrestor module body 61 is connected with the body 24 of the transportation assembly 22 by a linkage (not shown) that holds the arrestor body module 61 relatively rigidly relative to the body 24 front to back. However, subject to the foregoing, it is also preferred that the arrestor module body 61 be somewhat movable vertically relative to the body 24, and also that some side-to-side movement of the arrestor module body 61 relative to the body 24. Such side-to-side movement may be needed, e.g., to enable the transportation assembly 22 and the arrestor module 60 to negotiate curves in the railway.

[0095] In one embodiment, the brake shoes in the arrestor module 60 preferably includes one or more upper brake shoes 64u, and one or more lower brake shoes 64L
(Figs. 5C, 5D). In Fig. 5C, the upper and lower brake shoes 64, 64L are shown as being disengaged from upper and lower surfaces 66, 68 of the flange 70 of the second rail 38 (Fig. 5C). In Fig. 5D, the upper and lower brake shoes 64u, 64L are illustrated in the engaged condition. It will be understood that the upper and lower brake shoes 64u, 64L remain disengaged from the surfaces 66, 68 respectively until the brake shoe 64u is moved to its engaged condition.

[0096] To engage the inner upper flange 72, the brake shoe 64u is moved downwardly by a suitable means (e.g., preferably a suitable spring) (not shown) upon actuation, i.e., it is moved in the direction indicated by arrow "E' in Fig. 5D. Preferably, upon engagement of the upper brake shoe 64u with the upper surface 66 of the flange 70, the spring continues to urge the upper brake shoe 64u downwardly, to press the upper brake shoe 64u against the upper surface 66 with force.

[0097] It is also preferred that the shoes 64u, 64L are released by a suitable mechanism (e.g., hydraulic, pneumatic, electric) (not shown). The brake subassembly is biased to engagement of the brake shoes with the flange 70, i.e., upon a power failure or an emergency stop button being depressed, the brake shoes are urged against the upper flange by the springs.

[0098] The downward movement of the upper brake shoe 64u, and its engagement with the inner upper flange 72, causes upward movement of the arrestor module body 61 and the idler wheel 65, so that the idler wheel 65 is disengaged from the outer upper flange 74 when the upper brake shoe 64u engages the inner upper flange 72. The direction of such upward movement is indicated by arrow "F" in Fig. 5D, i.e., the upward movement of the arrestor module body 61 is in a direction opposite to the downward direction indicated by arrow "E".

[0099] In use, when the transportation assembly 22 moves from the first rails 30 into the transition zone "Z", the brake shoes 64 are not required to be positioned above and below the upper inner flange 70 because, as noted above, the upper inner flange 70 has been removed from the transition portion 42 of the second rails 38. Instead, the upper and lower brake shoes 64u, 641 are positioned above and below the brake shoes 64 respectively at the commencement of the straight portion 40 of the second rails 38.

[0100] As noted above, the arrestor module 60 is intended to provide an emergency braking function, i.e., to prevent the transportation assembly 22 from moving downwardly on the straight portion 40 of the second rails 38 in an uncontrolled way, e.g., in abnormal circumstances that would compromise otherwise workable traction on the gradient.

[0101] Those skilled in the art would appreciate that the invention may be used in a number of applications other than tunnelling, e.g., surface mining, and also underground mining.

[0102] It will also be appreciated by those skilled in the art that the invention can take many forms, and that such forms are within the scope of the invention as claimed. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims (6)

l claim:

1. A transportation system comprising at least one transportation assembly comprising:
a body;
at least two sets of first wheels mounted to the body and respectively comprising first wheel treads configured for engaging a pair of first rails spaced apart by a first distance, the first rails being positioned at at least one first grade; and at least two sets of second wheels mounted to the body and respectively comprising second wheel treads configured for engaging a pair of second rails spaced apart by a second distance that is larger than the first distance, the second rails being positioned at at least one second grade that is steeper than said at least one first grade.

2. The transportation system according to claim 1 in which the second rails comprise a transition portion in which said at least two sets of second wheels engage the second rails and said at least two sets of first wheels engage the first rails.

3. The transportation system according to claim 1 in which said at least two sets of first wheels and said at least two sets of second wheels are respectively positioned coaxially.

4. The transportation system according to claim 1 in which said at least one transportation assembly additionally comprises at least one arrestor module mounted to the body, said at least one arrestor module comprising at least one set of brake shoes movable between a disengaged condition, in which the brake shoes are disengaged with the second rails, and an engaged condition, in which the brake shoes are engaged with the second rails, to hold the transportation assembly stationary relative to the second rails.

5. The transportation system according to claim 4 in which said at least one arrestor module additionally comprises an actuator operatively connected with the brake shoes, for controlling engagement of the brake shoes with the second rails.

6. A transportation assembly comprising:
a body, in which a load having a weight is receivable;

a plurality of wheels mounted to the body, the wheels being formed to engage at least one running surface; and at least one motor connected to the wheels, for driving each of the wheels, whereby the weight of the load urges the wheels against said at least one running surface.