[invention Title]

GAUGE-CHANGEABLE WHEELSET FOR RAILWAY VEHICLE

[Technical Field] The present invention relates , in general , to gauge- adjustable wheelsets for railway vehicles and, more particularly, to a gauge-adjustable wheelset for a railway vehicle which automatically changes a gauge thereof such that the railway vehicle is able to travel between two kinds of railways having different gauges , and which includes : an axle, having a sliding part and a cap mounting part ; a wheel fitted over the sliding part of the axle so as to be movable in a left or right direction; a support cap securely fitted over the cap mounting part of the axle; a locking block rotatably fitted over the support cap, so that left or right movement of the wheel is controlled by rotation of the locking block; a flange coupled to the right end of the support cap to control a locking or unlocking operation of the locking block; a spring holder coupled to the left end of the support cap; and a compression spring provided between the flange and the spring holder, thus reducing the number of elements and the manufacturing costs , being easily mounted to a bogie thanks to structural features thereof , and having an advantage of saving energy thanks to reduced rotational

inertia .

Furthermore, according to another embodiment of the present invention, the present invention relates to a gauge- adjustable wheelset for a railway vehicle which simply realizes a gauge-adjustable system and has a structure such that elements thereof are easily assembled and disassembled.

As well, according to a further embodiment of the present invention, the present invention relates to gauge- adjustable wheelsets for railway vehicles and, more particularly, to a gauge-adjustable wheelset for a railway vehicle which automatically changes the distance between opposite wheels such that the railway vehicle is able to travel on railways having different gauges, and which prevents locking elements from being contaminated by water, dust or filth, thus ensuring the smooth operation and superior performance of the wheelset .

[Background Art]

Background information pertaining to gauge-adjustable wheelsets for railway vehicles according to the present invention is presented below.

Since the latter half of the 1960 ' s, countries using nonstandard-gauge rails or countries that border on the countries using nonstandard-gauge rails, such as Spain

(where 1435mm gauge rails are used along with 1668mm gauge rails) , Germany (where 1435mm gauge rails are used) , Japan

(where 1067mm gauge rails are used along with 1435mm gauge rails) , Russia (where 1520mm gauge rails are used) , Poland

(where 1435mm gauge rails are used) , France (where 1435mm gauge rails are used) , etc . , have been interested in the development of gauge-adjustable trains that are able to adjust their gauges while traveling .

Among these countries, Spain first began studies on gauge-adjustable systems and put them to practical use . When constructing railways at first, due to the geographical features of Spain, located southwest of France, Spain adopted broad-gauge rails (1, 668mm) for the purpose of preventing the invasion of neighboring countries, and, subsequently, Spain continued to use broad- gauge rails . However, the management of the broad-gauge rails causes several problems that result from the difference in gauge between broad-gauge rails and standard-gauge rails

(1, 435mm) , which have been used in newly-established sections and in neighboring countries . These problems interfere with uninterrupted travel and the carriage of goods . From that time until this day, various ideas for solving the problems have been proposed and studies and developments for putting the ideas into practical use have been conducted. Meanwhile, in the case of Korea, the south-north transcontinental railway project is underway, so that

interest in solutions to overcome the difference in gauge between the south-north railway, which uses standard-gauge rails, and a Russian railway, which uses broad-gauge rails at a border therebetween has increased. Transhipment, bogie-changing and a gauge-adjustable bogie are representative examples of solutions that have been under consideration.

Furthermore, in Korea, investigation into efficient management of a dual gauge system has been conducted, and several gauge-adjustable systems , which were developed in

Spain, Germany, Russia, Poland and Japan, have been introduced.

Among conventional gauge-adjustable wheelsets , which are techniques for dual gauge systems, Poland Patent No . PL181969 (1997) is shown in FIGS . 1 and 2 , and European

Patent No . EP0873930 (1998) is shown in FIGS . 3 and 4.

As shown in FIG. 2, a gauge-adjustable wheelset disclosed in Poland Patent No . PL181969 (1997) includes a locking unit, in which elastic rod-shaped elements 2 , each having a predetermined length, are disposed around an axle at regular angular intervals and serve to control lateral movement of a wheel . Typically, twenty to thirty rod-shaped elements 2 are used.

However, in this gauge-adjustable wheelset, the rod- shaped elements 2 must be repeatedly bent for gauge conversion, so that a problem of fatigue of the rod-shaped

elements 2 occurs . As well, because the locking unit consists of twenty or more elements 2 , there is a problem in that high costs are incurred in order to maintain and repair them. Meanwhile, as shown in FIG. 4, in a gauge-adjustable wheelset disclosed in European Patent No . EP0873930 (1998) , three pairs of locking levers 3 are used as a locking unit, and a compression spring is disposed in a circumferential direction. However, in this gauge-adjustable wheelset, the locking levers 3 protrude from the axle to relatively high heights in a direction perpendicular to the axle, that is, outwards with respect to the axle, and, when a locking or releasing process is executed, the locking levers 3 protrude further outwards with respect to the axle . Therefore, this gauge-adjustable wheelset is problematic in that the overall volume of the locking unit is increased, and the structure is complex.

Furthermore, the conventional gauge-adjustable wheelset has a structure such that an outer cylindrical body, serving as a cover, pushes the locking levers to realize locking motion of the locking levers . Therefore, the outer cylindrical body made of metal should be relatively thick in order to ensure the strength thereof . The outer cylindrical body serves to protect interior elements .

However, this gauge-adjustable wheelset is problematic in that, when it is desired to inspect the locking unit and other elements for maintenance and repair of the gauge-adjustable wheelset, the wheelset must be completely disassembled.

[Disclosure] [Technical Problem]

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a gauge-adjustable wheelset for a railway vehicle which automatically changes a gauge thereof such that the railway vehicle is able to travel between two kinds of railways having different gauges, and which includes : an axle, having a sliding part and a cap mounting part; a wheel fitted over the sliding part of the axle so as to be movable in a left or right direction; a support cap securely fitted over the cap mounting part of the axle; a locking block rotatably fitted over the support cap, so that left or right movement of the wheel is controlled by circumferential rotation of the locking block; a flange coupled to a right end of the support cap to control a locking or unlocking operation of the locking block; a spring holder coupled to a left end of the support cap; and a compression spring provided between the flange and the

spring holder, thus reducing the number of elements and the manufacturing costs, being easily mounted to a bogie thanks to structural features thereof, and having an advantage of saving energy thanks to reduced rotational inertia. Another object of the present invention is to provide a gauge-adjustable wheelset for a railway vehicle in which the spring holder has a removable mounting structure such that a process of assembling or disassembling the elements including the locking block, the flange, the support cap, the compression spring and the spring holder can be easily executed, and which has a structure such that, even if a relatively large force is applied between the wheels and the rails, the wheels can continue to rotate together with the axle . A further object of the present invention is to provide a gauge-adjustable wheelset which makes it possible for a railway vehicle to travel two kinds of railways having different gauges and prevents locking operation related elements and the junction between the wheel and the axle from being contaminated by water or dust, and which has a structure such that inspection of the elements, for example, ascertainment of whether an element is damaged, can be easily conducted without completely disassembling the elements . Yet another object of the present invention is to provide a gauge-adjustable wheelset which makes it possible

to reduce the effort and cost required for maintenance and repair, increase reliability, and ensure stable transportation in the operation of a railway vehicle that travels on two kinds of railways having different gauges .

[Technical Solution]

In order to accomplish the above objects, the present invention provides a gauge-adjustable wheelset for a railway vehicle that automatically changes a gauge thereof such that the railway vehicle travels between two kinds of railways having different gauges . The gauge-adjustable wheelset comprises : an axle, with a sliding part and a cap mounting part provided on the axle; a wheel fitted over the sliding part of the axle so as to be movable in a leftward or rightward direction; a support cap securely fitted over the cap mounting part of the axle; a locking block rotatably fitted over the support cap, so that left or right movement of the wheel is controlled by circumferential rotation of the locking block; a flange coupled to a right end of the support cap to control a locking or unlocking operation of the locking block; a spring holder coupled to a left end of the support cap; and a compression spring provided between the flange and the spring holder.

The wheel may include : an extension part that integrally extends towards a medial portion of the axle;

and a plurality of locking pieces provided on a circumferential outer surface of the extension part . Each of the locking pieces may have a plurality of locking notches therein. The support cap may include: a stopper provided on a right end of the support cap and supporting the flange; a locking key extending from a left surface of the stopper and preventing the flange from rotating in a circumferential direction of the axle; a plurality of extension parts provided on a left end of the support cap and coupled to the spring holder; and a plurality of guide slots defined between the extension parts, so that the locking pieces of the wheel are inserted into respective guide slots such that the wheel is integrally rotated along with the axle .

The flange may include : a disk plate provided on a right end of the flange and being brought into contact with a release rail such that the flange is moved leftward or rightward; a key notch, into which the locking key provided on the support cap is inserted; a locking blade inserted into a blade slot formed in the locking block, so that the locking block is locked to or rotated by the locking blade; and a spring receiving part, by which the compression spring is held. The locking blade of the flange may include : a horizontal part extending in a horizontal direction; and an

inclined part angled from the horizontal part .

The locking block may include : a blade slot formed in a right end of the locking block, so that a locking blade provided on the flange is inserted into and moved in the blade slot; a plurality of locking protrusions provided on a left end of the locking block, so that, when the wheelset is in a locked state, the locking protrusions are inserted into related locking notches of the wheel ; and a plurality of insertion notches formed around respective locking protrusions, so that locking pieces of the wheel are inserted into respective insertion notches in a locked or unlocked state .

The blade slot of the locking block may include : a horizontal slot part and an inclined slot part which correspond to a horizontal part and an inclined part provided in the locking blade of the flange .

The spring holder may include : a support plate contacting a left end of the compression spring, so that a compression force of the compression spring is applied to the support plate; a spring receiving part provided on an outer edge of a surface of the support plate to prevent the compression spring from moving; a cap fastening part provided on a circumferential inner edge of the support plate and fastened to the extension parts of the support cap,- and a plurality of locking piece receiving notches formed in the support plate around the cap fastening part,

so that each of the locking pieces of the wheel is inserted into each of the locking piece receiving notches so as to be movable leftward or rightward.

In another aspect, a gauge-adjustable wheelset for a railway vehicle according to another embodiment of the present invention automatically changes a gauge thereof such that the railway vehicle travels between two kinds of railways having different gauges . The gauge-adjustable wheelset comprises : an axle, with a sliding part and a cap mounting part provided on each of opposite ends of the axle; a wheel, with a through hole formed in the wheel so that the axle is inserted into the through hole, an extension part protruding from a predetermined portion adjacent to a circumferential edge of the through hole, and a plurality of locking pieces provided on a circumferential outer surface of the extension part; a support cap securely fitted over the cap mounting part of the axle; a locking block rotatably fitted over the support cap, so that a path along which the wheel is moved in an axial direction is controlled by circumferential rotation of the locking block; a flange to rotate the locking block in a direction using a release rail and to rotate the locking block in an opposite direction using a compression spring; and a spring holder screwed to the support cap . The support cap may include : a coupling body fitted over an outer surface of the cap mounting part of the axle;

a plurality of locking keys protruding from a circumferential outer surface of the coupling body and preventing the flange from rotating in a circumferential direction of the axle,- a stopper provided on a first end of the coupling body and supporting the flange; a plurality of extension parts provided on a second end of the support cap and coupled to the spring holder; and a plurality of guide slots defined between the adjacent extension parts, so that the locking pieces of the wheel are inserted into the respective guide slots such that the wheel is integrally rotated along with the axle .

The spring holder may include : a support plate having a disk shape, with a through hole formed at a central position through the support plate so that the axle is inserted into the through hole; a spring receiving part protruding from an outer edge of a first surface of the support plate; a plurality of coupling parts protruding from a second surface of the support plate at predetermined positions adjacent to a circumferential edge of the through hole, the coupling parts being coupled to the support cap; and a plurality of guide slots formed between adjacent coupling parts, so that the locking pieces of the wheel move along respective guide slots .

Furthermore, a plurality of movable slots may be formed in the extension part of the wheel such that ends of locking bolts are movable in the respective movable slots,

a screw hole may be formed in each of the extension parts of the support cap, and a coupling hole may be formed in each of the coupling parts of the spring holder, so that the locking bolts are tightened into the coupling holes and the screw holes, which are respectively formed in the coupling parts of the spring holder and in the extension parts of the support cap, and the end of each locking bolt is movably inserted into each of the movable slots, which are formed in the extension part of the wheel . The coupling parts of the spring holder may comprise three coupling parts .

The flange may include : a disk plate supporting the compression spring and being brought into contact with the release rail ; a spring receiving part protruding from a surface of the disk plate in a cylindrical shape and preventing the compression spring from moving; a plurality of extension parts extending from predetermined positions on a circumferential edge of a through hole, into which the support cap is inserted; a locking blade protruding from each of the extension parts, so that the locking blades move along respective blade slots, formed in the locking block, thus guiding rotation of the locking block; and a plurality of key notches formed between the adjacent extension parts and guiding movement of locking keys of the support cap .

The locking block may include : a blade slot, along

which each locking blade of the flange is moved; a plurality of locking protrusions to engage with related locking notches of the wheel, thus supporting the wheel; and a plurality of insertion notches, in which respective locking pieces of the wheel are placed and moved.

In a further aspect, a gauge-adjustable wheelset for a railway vehicle according to a further embodiment of the present invention comprises : an external cover provided around an axle outside a wheel; and an internal cover, having a cylindrical shape, coupled at a first end thereof to an inner surface of the wheel and coupled at a second end thereof to a flange .

The gauge-adjustable wheelset may further comprise an air vent hole formed through the wheel such that air circulates between an external space defined by the external cover and an internal space defined by the internal cover.

The external cover may include : an external cover plate fitted over the axle; and an external cover pipe coupled at a first end thereof to the external cover plate and coupled at a second end thereof to an outer surface of the wheel using a bolt coupling unit .

The gauge-adjustable wheelset may further comprise an external assistant ring to press the second end of the external cover pipe .

The external cover pipe may comprise a bellows pipe .

The flange may be provided with an extension part that extends towards the wheel, and the second end of the internal cover may be coupled to the extension part of the flange using a bolt coupling unit . The gauge-adjustable wheelset may further comprise an internal assistant ring to press the second end of the internal cover.

The internal cover may have a bellows shape .

[Advantageous Effects] As described above, in the present invention, a gauge-adjustable wheelset for railway vehicles has a structure such that a process of locking or unlocking the position of a wheel can be executed using a single locking block, thus reducing the number of elements . Unlike conventional techniques, the elements are integrally operated in conjunction with each other without using a coupling means such as a bolt . In addition, thanks to special features of each element, the structural strength thereof is increased, so that the maintenance and repair thereof are easy, thus reducing maintenance and repair costs .

Furthermore, in the gauge-adjustable wheelset of the present invention, the volume in a direction perpendicular to the axle is markedly reduced, so that the present invention can be easily mounted to a bogie, compared to the

conventional techniques . As well, because the present invention has a structure capable of reducing rotational inertia, there is an advantage of saving energy.

Meanwhile, in a gauge-adjustable wheelset according to another embodiment of the present invention, a spring holder is coupled both to the wheel and to an end of a support cap using bolts, pins or keys but not using a force-fitting or welding method. Therefore, when it is desired to replace a flange, a spring or a locking block, which constitutes the gauge-adjustable wheelset, with a new one, a process of disassembling the spring holder from the support cap and reassembling it therewith is easily executed, thus reducing expense and effort required to maintain and repair the wheelset . Furthermore, in this embodiment, locking pieces of the wheel are reliably supported in guide slots defined by a plurality of coupling parts, which extend from an edge of a through hole of the spring holder. Hence, even if a relatively large force is applied between the wheel and the rail, because the guide slots are not deformed, the wheel can still be integrally rotated along with the axle .

In a gauge-adjustable wheelset according to a further embodiment of the present invention, an external cover and an internal cover are respectively provided outside and inside the wheel . When the railway vehicle changes the gauge, as well as when it travels on one kind of railway,

the junction between the wheel and the axle and the locking operation related elements are prevented from being contaminated by water or dust . In addition, junctions between the gauge-conversion related elements and other elements are prevented from being contaminated, thus preventing corrosion of the elements, an increase in friction, and malfunction of locking blades .

Furthermore, in this embodiment, when it is desired to inspect the locking operation related element, for example, to ascertain whether there is a damaged element, because the wheelset is opened merely by pushing and folding the internal cover to one side, the inspection of the elements can be easily conducted without completely disassembling the elements . As well, in the operation of a railway vehicle that travels on two kinds of railways having different gauges, the present invention makes it possible to reduce effort and expense required for maintenance and repair, increase reliability, and ensure stable transportation.

[Description of Drawings]

FIG. 1 is a sectional view of a gauge-adjustable wheelset according to a first conventional technique;

FIG. 2 is an exploded perspective view showing the gauge-adjustable wheelset according to the first conventional technique;

FIG. 3 is a sectional view of a gauge-adjustable wheelset according to a second conventional technique;

FIG. 4 is views showing the operation of the gauge- adjustable wheelset according to the second conventional technique;

FIG. 5 is an exploded perspective view of a gauge- adjustable wheelset for railway vehicles, according to a first embodiment of the present invention;

FIG. 6 is detailed views showing a wheel used in the gauge-adjustable wheelset according to the present invention;

FIG. 7 is detailed views showing a support cap used in the gauge-adjustable wheelset according to the present invention; FIG. 8 is detailed views showing a flange used in the gauge-adjustable wheelset according to the present invention;

FIG. 9 is detailed views showing a locking block used in the gauge-adjustable wheelset according to the present invention;

FIG. 10 is detailed views showing a spring holder used in the gauge-adjustable wheelset according to the present invention;

FIG. 11 is views showing a process of assembling the gauge-adjustable wheelset according to the present invention;

FIG. 12 is a plan view and a sectional view showing a railway gauge conversion system, on which the operation of the gauge-adjustable wheelset of the present invention is conducted; FIG. 13 is views showing the operation of the gauge- adjustable wheelset according to the present invention;

FIG. 14 is views showing the coupling between the flange and the locking block of the gauge-adjustable wheelset according to the present invention; FIG. 15 is views showing the coupling between the wheel and the locking block of the gauge-adjustable wheelset according to the present invention;

FIG. 16 is a perspective view of an assembled gauge- adjustable wheelset for railway vehicles, according to a second embodiment of the present invention;

FIG. 17 is a detailed view showing a wheel of the gauge-adjustable wheelset of FIG. 16 ;

FIG. 18 is a detailed view showing a support cap of the gauge-adjustable wheelset of FIG. 16 ; FIG. 19 is a detailed view showing a flange of the gauge-adjustable wheelset of FIG. 16 ;

FIG. 20 is a detailed view showing a locking block of the gauge-adjustable wheelset of FIG. 16 ;

FIG. 21 is detailed views showing a spring holder of the gauge-adjustable wheelset of FIG. 16;

FIG. 22 is views showing a process of assembling the

gauge-adjustable wheelset of FIG. 16 ;

FIG. 23 is a view of a gauge-adjustable wheelset for railway vehicles in which covers are provided, according to a third embodiment of the present invention; FIG. 24 is a view showing the gauge-adjustable wheelset of FIG. 23 from which the covers have been removed;

FIG. 25 is a sectional view showing the operation of the gauge-adjustable wheelset of FIG. 23 on a broad-gauge railway;

FIG. 26 is a sectional view showing the operation of the gauge-adjustable wheelset of FIG. 23 on a standard- gauge railway;

FIG. 27 is an enlarged view of a circled portion A of the gauge-adjustable wheelset of FIG. 25 ; and

FIG. 28 is an enlarged view of a circled portion B of the gauge-adjustable wheelset of FIG. 25.

[Best Mode]

Hereinafter, a gauge-adjustable wheelset for railway vehicles according to the present invention will be described in detail with reference to the attached FIGS . 5 through 15.

First, a railway gauge conversion system for application of the gauge-adjustable wheelset of the present invention will be explained herein below with reference to

the related drawing.

FIG. 12 is a plan view (a) and a sectional view (b) showing the railway gauge conversion system, on which the gauge-adjustable wheelset of the present invention is operated. In this drawing, the construction of a railway for application of the present invention is shown.

As shown in FIG. 12 , standard-gauge rails 10 , broad- gauge rails 20 , guide rails 30 , gauge conversion rails 40 and release rails 50 are required for operation of the gauge-adjustable wheelset of the present invention. The gauge conversion rails 40 are provided between the standard-gauge rails 10 and the broad-gauge rail 20. The gauge conversion rails 40 serve to guide conversion of the gauge . The guide rails 30 serve to prevent wheels 200 from becoming derailed during the gauge conversion and guide a gradual change of the gauge . The release rails 50 have a parallel section and narrowing/widening sections, and guide lateral movement of flanges 400 for realizing the gauge conversion. Hereinafter, the construction of the gauge-adjustable wheelset according to a first embodiment of the present invention, which travels on the railway gauge conversion system, will be explained in detail . In the gauge- adjustable wheelset of the present invention, the left and right sides of an axle 100 are symmetrical, therefore, for ease of description, the present invention will be

explained with reference to the left side of the axle 100.

As shown in FIG. 5 , a sliding part 110, on which the wheel 200 moves in a lateral direction, and a cap mounting part 120 are provided on each end of the axle 100. Furthermore, as shown in FIG. 6 , the wheel 200 includes an extension part 210 , which is integrally- provided around an axle hole and extends a predetermined length towards the medial portion of the axle . FIG. 6 (a) is a perspective view of the wheel 200. FIG. 6 (b) is a front view of the wheel 200. FIG. 6 (c) is a side view of the wheel 200.

As shown in FIGS . 6 (a) and 6 (b) , a plurality of locking pieces 220 , each of which protrudes in a radial direction, is provided around the extension part 210. Locking notches 221, each having a shape corresponding to the shape of each locking protrusion 520 of a locking block 500 , are formed under a lower surface of each locking piece 220.

It is preferable that three locking pieces 220 be provided in consideration of the diameter of the axle 100, as shown in FIG. 6 (b) . The number of locking notches 221 formed in each locking piece may change according to the gauge change circumstances, but, in the present invention, in consideration of manufacturing and operating conditions , two locking notches 221 are formed in each locking piece, such that the gauge can be converted between the standard-

gauge rails 10 and the broad-gauge rails 20.

Meanwhile, a support cap 300 is fitted over the cap mounting part 120 of the axle 100 by force-fitting or welding . FIG. 7 (a) is a perspective view of the support cap 300. FIG. 7 (b) is a front view of the support cap 300. FIG. 7 (c) is a side view of the support cap 300. The support cap 300 includes a stopper 310 , locking keys 320 , extension parts 330 , and guide slots 340.

In detail, as shown in FIG. 7 (a) , the stopper 310 , which is provided on the right end of the support cap 300 , serves to prevent the flange 400 from being excessively moved towards the medial portion of the axle by a compression spring 600 during gauge conversion or while the railway vehicle is traveling . Furthermore, as shown in FIGS . 7 (a) and 7 (c) , each locking key 320 extends to the left from a surface of the stopper 310 and is inserted into each key notch 420 of the flange 400 , so that the flange 400 is integrally rotated along with the axle 100 and is prevented from idling with respect to a circumferential direction of the axle .

Meanwhile, as shown in FIG. 7 (a) , the extension parts 330 are provided on a left end of the support cap and are coupled to respective cap fastening parts 730 of a spring holder 700. The guide slots 340 are formed between the extension parts 330, and the locking pieces 220 of the wheel 200 are inserted into the guide slots 340 so as to be

movable in left and right directions .

The guide slots 340 execute a role such that rotating force is applied to the locking notches 221 of the wheel 200 and, thus, the wheel 200 is integrally rotated along with the axle 100 even in an unlocked state of the locking block 500 when the locking protrusions 520 of the locking block 500 have been removed from the locking notches 221 of the wheel 200.

FIG. 8 (a) is a perspective view of the flange 400. FIG. 8 (b) is a front view of the flange 400. FIG. 8 (c) is a side view of the flange 400.

As shown in FIG. 8, the flange 400 is coupled to the right end of the support cap 300 and serves to control locking of the locking block 500. The flange 400 includes a disk plate 410 , the key notches 420, locking blades 430 , and a spring receiving part 440.

In detail, the disk plate 410 contacts the release rail 50 during gauge conversion, thus moving the flange 400 left or right . When the distance between the release rails 50 is increased, the flange 400 is moved to the left against the elastic force of the compression spring 600. When the distance between the release rails 50 is reduced, the flange 400 is moved to the right while the elastic force of the compression spring 600 is applied to the disk plate 410.

As shown in FIG. 8 (b) , the key notches 420 are fitted

over the respective locking keys 320 of the support cap 300 described above, thus making it possible for the flange 400 to integrally rotate along with the axle 400 , and preventing the flange 400 from idling with respect to a circumferential direction of the axle 400.

Meanwhile, the locking blades 430 are inserted into blade slots 510 of the locking block 500 and move in a lateral direction, thus locking or rotating the locking block 500. As shown in FIGS . 8 (a) and 8 (c) , to correspond to the shape of the blade slot 510 of the locking block 500 , each locking blade 430 has a structure, in which a horizontal part 431 extends in a lateral direction and an inclined part 432 is angled upwards from the horizontal part 431. Furthermore, the compression spring 600 is fitted over the spring receiving part 440. The compression spring 600 is repeatedly compressed and extended between the spring receiving part 440 and a spring receiving part 720 of the spring holder 700. FIG. 9 is a detailed view of the locking block 500. In detail, FIG. 9 (a) is a perspective view of the locking block 500. FIG. 9 (b) is a front view of the locking block 500. FIG. 9 (c) is a side view of the locking block 500.

The locking block 500 has a diameter larger than that of the support cap 300. The locking block 500 is fitted over the support cap 300 so as to be rotatable in a

circumferential direction. The locking block 500 includes the blade slots 510 , the locking protrusions 520 and insertion notches 530.

In detail, referring to FIG. 9 (a) , each blade slot 510 has a horizontal slot part 511 and an inclined slot part 512 , so that each locking blade 430 of the flange 400 is inserted into the blade slot 510 and moves in a lateral direction. The operational relationship between the locking blades 430 and the blade slots 510 will be explained later herein.

When the gauge-adjustable wheelset is in a locked state, the locking protrusions 520 engage with the respective locking notches 221 of the wheel 200. When it is in an unlocked state, the locking protrusions 520 are removed from the respective locking notches 221. The operational relationship between the locking protrusions 520 and the locking notches 221 will be also described later herein.

As shown in FIGS . 9 (a) and 9 (b) , each insertion notch 530 is formed around each locking protrusion 520 and provides a space in which each locking piece 220 is inserted and moved to the left and right when in an unlocked state . This will be also described in detail in an explanation of a gauge conversion process . Meanwhile, as shown in FIG. 10 , the spring holder 700 serves to restrict movement of the compression spring 600

in a leftward direction. FIG. 10 (a) is a perspective view of the spring holder 700. FIG. 10 (b) is a front view of the spring holder 700. FIG. 10 (c) is a side view of the spring holder 700. As shown in the drawings, the spring holder 700 includes a support plate 710, the spring receiving part 720 , the cap fastening parts 730 and the locking piece receiving notches 740.

The support plate 710 contacts a left end of the compression spring 600 and receives compression force therefrom. The spring receiving part 720 is provided along an outside edge of the support plate 710 and prevents the compression spring 600 from moving in an undesired direction.

The locking piece receiving notches 740 are formed in the inner edge of the support plate 710. The locking pieces 220 of the wheel 200 are inserted into the respective locking piece receiving notches 740 , so that the left or right movement of the locking pieces 220 is guided by the locking piece receiving notches 740. The cap fastening parts 730 are fitted over and fixed to the respective extension parts 330 of the support cap 300 , which is securely fastened to the axle 100 , therefore the spring holder 700 also cannot be moved in a horizontal direction.

Hereinafter, a process of assembling the gauge- adjustable wheelset for railway vehicles according to the present invention will be described with reference to the

drawings .

As shown in FIG. 11, to assemble the gauge-adjustable wheelset, the support cap 300 is first fitted over the axle

100. Here, the support cap 300 is coupled to the axle 100 by force-fitting or welding, such that they are integrated with each other (FIG. 11 (b) ) .

Subsequently, the flange 400 is fitted over the support cap 300 (FIG. 11 (c) ) , and the locking block 500 is fitted over the support cap 300 , such that the locking blades 430 of the flange 400 are inserted into the respective blade slots 510 of the locking block 500 (FIG.

IKd) ) .

Thereafter, the compression spring 600 is fitted over the locking block 500 , but, in these drawings, the process of assembling the compression spring 600 is not shown in order to clearly show the coupling relationship between the flange 400 and the locking block 500.

After the compression spring 600 is fitted, the spring holder 700 is assembled (FIG. 11 (e) ) . Lastly, the wheel 200 is coupled to the axle 100 , such that the locking pieces 220 thereof correctly engage with the locking protrusions 520 of the locking block 500 , thus completing the process of assembling the gauge-adjustable wheelset of the present invention (FIG. 11 (f) ) . The sequence of the gauge conversion process of the gauge-adjustable wheelset of the present invention, having

the above-mentioned construction and assembly process, will be described herein below with reference to FIGS . 12 , 13 , 14 and 15. Here, a process of gauge conversion from broad- gauge rails 20 to standard-gauge rails 10 will be described.

(1) when traveling on the broad-gauge rails 20 (phase D

While the railway vehicle travels on the broad-gauge rails 20 , gauge conversion is not conducted. Also, in this state, the lower surface of the horizontal part 431 and the upper surface of the inclined part 432 of each locking blade 430 of the flange 400 are respectively held by upper and lower surfaces of the horizontal slot part 511 of each blade slot 510 of the locking block 500 , so that the locking block 500 and the flange 400 integrally rotate along with the axle 100, and each locking protrusion 520 of the locking block 500 maintains a state of being inserted into one locking notch 221 of each locking piece 220 of the wheel 200 (see, FIGS . 13 (a) , 14 (a) and 15 (a) ) . (2) when entering the widening section of the release rails 50 (phase 2)

The railway vehicle still travels on the broad-gauge rails 20, but the gauge of the release rails 50 widens . Therefore, due to the shape of the release rails 50, the flange 400 is moved towards the end of the axle 100 against the elastic force of the compression spring 600 (see FIG.

13 (b) ) .

At this time, the inclined part 432 of the locking blade 430 of the flange 400 moves to the left and thus pushes the lower surface of the inclined slot part 512 of the locking block 500. Then, the locking block 500 rotates due to the structural shape thereof (see, FIG. 14 (b) ) .

At that time, the locking protrusion 520 of the locking block 500 is removed from the locking notch 221 of the wheel 200 by the rotation of the locking block 500 , so that the wheel 200 enters a state such that it is movable in a leftward or rightward direction (see, FIG. 15 (b) ) .

(3) when traveling on the gauge conversion rails 40 (phase 3)

As the gauge is reduced in the state such that the wheel 200 is movable in a leftward or rightward direction, the wheel 200 is moved along the rail towards the medial portion of the axle . At this time, the wheel 200 moves slowly due to the structural shape of the gauge conversion rail 40 and the guide rail 30 (see FIGS . 13 (c) and 15 (c) ) . (4) a process of entering the standard-gauge rails 10 (phase 4)

In an early stage of standard-gauge rail entry, in which the railway vehicle enters the standard-gauge rails

10 after the axial movement of the wheel 200 has completed by passing through the gauge conversion rails 40, because the gauge of the release rails 50 is still constant, the

compression spring 600 between the standard-gauge rail 10 and the release rail 50 maintains a state of being compressed and stores a restoring force.

Thereafter, as the gauge of the release rails 50 is reduced, the flange 400 is moved both by the structural shape of the release rail 50 and by the elastic force of the compression spring 600 in an axial direction. In detail, when the inclined part 432 of the locking blade 430 of the flange 400 is moved in a rightward direction, the locking block 500 is rotated and returned to the original position thereof, and the inclined part 432 of the locking blade 430 enters a state of being held by the upper and lower surfaces of the horizontal slot part 511 of the blade slot 510 , that is, a locked state (see, FIGS . 13 (d) and 14 (a) ) .

Simultaneously, as the locking block 500 is rotated, the locking protrusion 520 of the locking block 500 is inserted into the other locking notch 221 of the locking piece 220 of the wheel 200 (see, FIG. 15 (d) ) . The railway vehicle is freed from the restriction of the release rails 50 and travels normally along the standard-gauge rails 10 , thus completing the gauge conversion of the gauge- adjustable wheelset of the present invention.

Meanwhile, the operational principle of the gauge- adjustable wheelset of the present invention, when the railway vehicle moves onto broad-gauge rails 20 from

standard-gauge rails 10 , is the same as that when the railway vehicle moves onto standard-gauge rails 10 from broad-gauge rails 20.

Furthermore, as described above, the gauge-adjustable wheelset of the present invention has the three locking pieces 220 of the wheel 200 , the three locking protrusions 520 of the locking block 500, and the three locking blades 430 of the flange 400. Thanks to this structure, kinetic stability is ensured, and even if some element is damaged, the entire system can operate normally.

Meanwhile, as shown in FIG. 16, a gauge-adjustable wheelset for railway vehicles according to a second embodiment of the present invention includes an axle 100 , which is provided with a sliding part 110 and a cap mounting part 120 , and a wheel 200 , which has therein a through hole, into which the axle 100 is inserted, an extension part 210 , which protrudes from a surface of the wheel around the through hole, and at least one locking piece 220, which is provided on the circumferential outer surface of the extension part 210. The gauge-adjustable wheelset further includes a support cap 300 , which is fitted over the cap mounting part 120 of the axle 100 , and a locking block 500 , which is fitted over the support cap 300 and controls the path along which the wheel 200 moves using the circumferential rotation thereof . The gauge- adjustable wheelset further includes a flange 400. When

pushing force of the release rail 50 is applied to the flange 400, the flange 400 rotates the locking block 500 in one direction. When the restoring force of the compression spring 600 is applied to the flange 400, the flange 400 rotates the locking block 500 in the opposite direction. The gauge-adjustable wheelset further includes a spring holder 700, which is coupled to the support cap 300.

In the wheel 200, as shown in FIG. 17, the extension part 210 is integrally provided on the wheel around the through hole and extends a predetermined length towards the medial portion of the axle. Movable slots 211 are formed on a sidewall of the extension part 210 at positions corresponding both to bolt holes 360 formed through an extension part 330 of the support cap 300 and to coupling holes 745 formed through a coupling part 735 of the spring holder 700 , so that an end of a locking bolt 760 , which is fastened both into a corresponding coupling hole 745 and into a corresponding bolt hole 360 , is movably inserted into a corresponding movable slot 211. The locking piece 220, which protrudes in a radial direction, is provided on the circumferential outer surface of the extension part 210. Locking notches 221 are formed in the surface of the locking piece 220, so that each locking protrusion 520 of the locking block 500 is locked to one locking notch 221 of the locking piece 220. It is preferable that an appropriate number of locking pieces 220 be provided such that the

wheel 200 is stably and integrally rotated along with the axle 100 by the locking pieces 220 that slide in guide slots 340 and 750 which are respectively formed in the support cap 300 and the spring holder 700. For example, in this embodiment, three locking pieces 220 are provided. Preferably, the number of locking notches 221 in each locking piece 220 is in proportion to the number of different gauges of rails .

In other words, if the railway vehicle travels on two kinds of rails having different gauges, two locking notches 221 are formed in each locking piece . If the railway vehicle travels on three kinds of rails having different gauges, three locking notches 221 are formed in each locking piece . As shown in FIG. 18, the support cap 300 is fitted over the cap mounting part 120 of the axle 100 by force- fitting or welding . The support cap 300 has a cylindrical shape and includes a coupling body 350 , which is fastened to the cap mounting part 120 , a stopper 310 , which protrudes from a circumferential outer surface of a first end of the coupling body 350, the extension parts 330, which longitudinally extend from a second end of the coupling body 350 , and locking keys 320 , which protrude from the circumferential outer surface of the coupling body 350. The bolt holes 360, which correspond to the coupling holes 745 of the coupling part 735 of the spring holder

700, are formed in the respective extension parts 330.

The stopper 310 serves to prevent the flange 400 from being removed from the position thereof . The locking keys 320 are inserted into key notches 420 formed in the flange 400 , so that, when the flange 400 is moved by the release rail 50 in one direction or moved by the restoring force of the compression spring 600 in the opposite direction, the locking keys 320 guide the movement of the flange 400. Furthermore, the locking keys 320 make it possible for the flange 400 to integrally rotate along with the axle 100. The extension parts 330 guide the locking pieces 220 of the wheel 200 , such that the locking pieces 220 slide between the guide slots 340 formed between the extension parts 330. Furthermore, the extension parts 330 are in close contact with the locking pieces 220, which slide therebetween, thus making it possible for the wheel 220 to integrally rotate along with the axle 100. The locking bolts 760 are tightened both into the coupling holes 745 of the spring holder 700 and into the bolt holes 360 of the extension parts 330 , so that the coupling part 735 of the spring holder 700 is securely coupled to the support cap 300.

As shown in FIG. 19, the flange 400 is fitted over the first end of the support cap 300 and is supported by the stopper 310 of the support cap 300. The flange 400 prevents the compression spring 600 from being removed, and is moved in an axial direction by the operation of both the

release rail 50 and the compression spring 600 , thus guiding the locking block 500 such that the locking block 500 rotates during gauge conversion. The flange 400 includes a disk plate 410 which supports the compression spring 600 , a spring receiving part 440 which has a cylindrical shape and protrudes from a surface of the disk plate 410 , and extension parts 450 which extend from the surface of the disk plate 410 around an inside edge of a through hole, which is formed through the disk plate 410 , and into which the locking cap 300 is inserted. The flange 400 further includes locking blades 430 which protrude from respective extension parts 450 and are inserted into respective blade slots 510 formed in the locking block 500, so that the locking blades 430 move in the respective blade slots 510 and thus guide rotation of the locking block 500. The flange 400 further includes the key notch 420 which is formed between adjacent extension parts 450 and guides movement of each locking key 320 of the support cap 300.

The locking block 500 has a diameter larger than that of the support cap 300 and is fitted over the support cap 300 so as to be rotatable in a circumferential direction of the axle . As shown in FIG. 20, the locking block 500 has therein the blade slots 510 , into which the locking blades 430 of the flange 400 are inserted. The locking block 500 includes the locking protrusions 520 which are provided at predetermined positions so that the locking protrusions 520

are locked to the locking notches 221 of the wheel 200 to hold and support the wheel 200, and insertion notches 530, in which the respective locking pieces 220 of the wheel 200 are inserted and moved. Each blade slot 510 has a horizontal slot part 511 and an inclined slot part 512 which correspond to the shape of each locking blade 430 of the flange 400 such that they are operated in conjunction with each other . In detail, when the locking blades 430 are inserted into the inclined slot parts 512 , the locking block 500 is rotated by the surfaces of the inclined slot parts 512 in one direction. When the locking blades 430 are removed from the inclined slot parts 512 , the locking block 500 is rotated in the opposite direction. As shown in FIG. 21, the spring holder 700 serves both to prevent the compression spring 600 from being removed and to securely couple the wheel 200 to the axle 100. FIG. 21 (a) is a first side perspective view of the spring holder 700. FIG. 21 (b) is a second side perspective view of the spring holder 700.

The spring holder 700 has a disk shape . A through hole, into which the extension part 330 of the support cap 300 is inserted, is formed at a central position through the spring holder 700. The spring holder 700 includes a support plate 710 which supports the compression spring 600 , a spring receiving part 720 which extends from the

outside edge of a first surface of the support plate 710, and a plurality of coupling parts 735 which protrude from a second surface of the support plate 710 around the inside edge of the through hole . A guide slot 750 is formed between adjacent coupling parts 735, so that each locking piece 220 of the wheel 200 is movably inserted into the guide slot 750.

Furthermore, the coupling hole 745 is formed through each coupling part 735 at a position corresponding both to each of the movable slots 211, which are formed through the extension part 210 of the wheel 200 , and to the bolt hole 360 , which is formed through each of the extension parts 330 of the support cap 300. The coupling parts 735 of the spring holder 700 are fastened to the extension parts 330 of the support cap 300 using the locking bolts 760, which are tightened both into the coupling holes 745 and into the bolt holes 360 of the support cap 300.

After the support cap 300 has been fitted over the axle 100 and the flange 400, the locking block 500 and the compression spring 600 are fitted over the support cap 300. Thereafter, the spring holder 700 , having the above- mentioned construction, is fitted over the second end of the support cap 300. Subsequently, the extension parts 330 of the support cap 300 and the coupling parts 735 of the spring holder 700 are securely coupled to each other using the locking bolts 760. Here, each locking bolt 760 is

constructed such that the end thereof is movable in each movable slot 211 formed through the extension part 210 of the wheel 200.

Meanwhile, FIG. 22 illustrates a process of assembling the gauge-adjustable wheelset of the present invention. FIG. 22 (a) shows a state in which the support cap 300 is assembled with the axle 100 by force-fitting or welding, the flange 400 is fitted over the support cap 300, the locking block 500 is fitted over the support cap 300 such that the locking blades 430 of the flange 400 are inserted into the respective blade slots 510 of the locking block 500 , and the compression spring 600 is subsequently fitted over the locking block 500.

FIG. 22 (b) shows a process of tightening each locking bolt 760 into each coupling hole of the spring holder 700 after the spring holder 700 has been fitted over the extension part 330 of the support cap 300. FIG. 22 (c) shows the spring holder 700 fastened to the extension parts 330 of the support cap 300 by the locking bolts 760, which are tightened both into the coupling holes 745 of the coupling part 735 and into the bolt holes 360 of the support cap 300.

Not shown in the drawings, the wheel 200 is thereafter fitted over the sliding part 110 of the axle 100. The extension part 210 of the wheel 200 is inserted into a gap defined between the sliding part 110 and the

extension part 330 of the support cap 300. Each locking piece 220 is inserted both into each guide slot 750 of the spring holder 700 and into each guide slot 340 of the support cap 300. Furthermore, each locking piece 220 is inserted into each insertion notch 530 of the locking block 500 , and each locking protrusion 520 is locked into one locking notch 221 of each locking piece 220, thereby the wheel 200 is fastened to the axle 100. At this time, the wheel 200 is mounted to the axle 100 after the locking bolts 760 have been slightly loosened, such that the end of each locking bolt 760 is received into each movable slot 211 formed in the extension part 210 of the wheel 200. After the wheel 200 is disposed at a correct position, the locking bolts 760 are tightened. The gauge-adjustable wheelset of the present invention having the above-mentioned construction is operated in conjunction with the railway gauge conversion system. As shown in FIGS . 12 (a) and 12 (b) , the railway gauge conversion system is provided in a gauge conversion section which connects two kinds of rails having different gauges, such as standard-gauge rails 10 and broad-gauge rails 20 , to each other. The railway gauge conversion system includes gauge conversion rails 40 , which induce a gradual change of the gauge, guide rails 30 , which are provided on opposite sides of each gauge conversion rail 40 to prevent each wheel 200 from becoming derailed, and

release rails 50 , which are provided between the gauge conversion rails 40 to operate the gauge-adjustable wheelset .

The operational relationship between the gauge- adjustable wheelset according to the second embodiment of the present invention and the railway gauge conversion system provided on the ground will be described in detail herein below.

The locking blades 430 of the flange 400 are held by the horizontal slot part 511 of the blade slots 510 formed in the locking block 500, so that the locking block 500 is integrally rotated along with both the flange 400 and the axle 100 , and each locking protrusion 520 of the locking block 500 maintains a state of being locked to one locking notch 221 of each locking piece 220 of the wheel 200 (phase

D •

Thereafter, when the flange 400 is pushed by the release rail 50 and thus moved towards the wheel 200 against the elastic force of the compression spring 600 , the inclined part 432 of the locking blade 430 of the flange 400 pushes the inclined slot part 512 of the blade slot 510 of the locking block 500 , thereby the locking block 500 is rotated. At this time, the locking notches 221 of the wheel 200 are disengaged from the locking protrusions 520 of the locking block 500, so that the wheel 200 enters a state of being movable in a lateral direction

(phase 2) .

Subsequently, the wheel 200 is moved towards the medial portion of the axle by reduction in the gauge of the rails (phase 3) . Thereafter, when the railway vehicle moves onto the standard-gauge rails 10 after having passed through the gauge conversion rails 40, the gauge of the release rails 50 is reduced. Thereby, the flange 400 is moved towards the medial portion of the axle by the restoring force of the compression spring 600. Then, the locking block 500 is rotated and returned to the original position thereof, so that the other locking notch 221 of each locking piece 220 is locked to each locking protrusion 520 of the locking block 500, and the railway vehicle travels normally along the standard-gauge rails 10 (phase 4) .

In the gauge-adjustable wheelset according to the second embodiment of the present invention, the spring holder 700 is fastened to the extension parts 330 of the support cap 300 using the locking bolts 760 but not using a force-fitting or welding process . Therefore, when it is desired to replace the flange 400 , the compression spring 600 , the locking block 500, the support cap 300 or the spring holder 700 with a new one, the processes of disassembling the spring holder 700 from the support cap 300 and reassembling it therewith can be easily executed.

Furthermore, in the gauge-adjustable wheelset

according to the second embodiment of the present invention, the locking pieces 220 of the wheel 200 are securely supported by the guide slots 750 defined between the coupling parts 735, which extend from the inner edge of the through hole formed at the center of the spring holder 700. Accordingly, even if a relatively great force is applied to the wheel 200 by the rails, because the guide slots 750 do not become structurally deformed, the wheel 200 can stably rotate along with the axle 100. FIGS . 23 through 28 show a gauge-adjustable wheelset for railway vehicles, according to a third embodiment of the present invention. The gauge-adjustable wheelset according to the third embodiment of the present invention has a structure such that it can travel on standard-gauge rails 10 , broad-gauge rails 20 and narrow-gauge rails and is protected from the surroundings .

As shown in FIG. 23 , the gauge-adjustable wheelset according to the third embodiment includes an external cover 800, which is provided on the outer surface of a wheel 200 and around the axle 100, and an internal cover 820 , which is coupled at a first end thereof to the inner surface of the wheel 200 and coupled at a second end thereof to a flange 400.

Here, as explained in the gauge-adjustable wheelset according to the second embodiment, the flange 400 of the third embodiment controls the rotation of a locking block

500 , which allows the wheel 200 to move in a lateral direction when the locking block 500 is rotated in a circumferential direction of the axle, thus guiding gauge conversion when the railway vehicle enters a gauge conversion section of the rails . Furthermore, after the gauge conversion has been completed, the flange 400 limits the rotation of the locking block 500 , such that the railway vehicle can travel stably.

In the gauge-adjustable wheelset according to the third embodiment, a plurality of air vent holes 830a and 830b is formed through the wheel 200, such that an external space 880 defined by the external cover 800 communicates with an internal space 890 defined by the internal cover 820. The external cover 800 includes an external cover plate 815 and an external cover pipe 810. The external cover plate 815 has a circular plate shape, with an insertion hole formed at the central position through the external cover plate 815, so that the external cover 800 is fitted over the axle 100 through the insertion hole . The external cover pipe 810 is coupled at a first end thereof to the outer edge of the external cover plate 815 by pressing and coupled at a second end thereof to the outer surface of the wheel 200 using bolt coupling units 870. The first end of the external cover pipe 810 and the outer edge of the external cover plate 815 are overlapped with each

other and, thereafter, bent and treated through a pressing process, thus ensuring airtightness .

Here, the external cover plate 815 may be fastened to the axle using a coupling means such as a bolt . As shown in Fig. 27 , each bolt coupling unit 870 includes a bolt, which is inserted into a bolt hole formed through the wheel 200, and a nut, which is screwed to an external threaded part formed on the end of the bolt . As the nut and bolt are tightened, the second end of the external cover pipe 810 is pressed on the wheel 200 , so that the external cover 800 is airtightIy coupled to the wheel 200. Furthermore, the bolt coupling units 870 press and fasten the first end of the internal cover 820 to the wheel 200 , such that the internal cover 820 is airtightly coupled to the wheel 200. Here, first inside assistant rings 850 are further provided such that the first end of the internal cover 820 is evenly pressed onto the wheel 200.

The external cover 800 further includes external assistant rings 840 which serve to press the second end of the external cover pipe 810 onto the wheel 200. The external assistant rings 840 evenly press the second end of the external cover pipe 810 when the bolt coupling units 870 are tightened, thus ensuring airtightness between the external cover pipe 810 and the outer surface of the wheel 200.

Preferably, as shown in FIGS . 25 and 26, the external cover pipe 810 comprises a bellows pipe, such that, even though the volumes of the external space 880 and the internal space 890 change while the railway vehicle executes gauge conversion, the external cover 800 and the internal cover 820 are prevented from damage . Furthermore, the external cover pipe 810 may be an elastic body to respond to changes in volume of the external and internal spaces 880 and 890. As well, it is also preferable that the internal cover 820 comprise a bellows pipe . The internal cover 820 may also be an elastic body to respond to changes in volume of the external and internal spaces 880 and 890.

As shown in FIG. 28, the flange 400 includes an extension part 860 , which extends a predetermined length towards the wheel 200 , so that the second end of the internal cover 820 is coupled to the extension part 860 of the flange 400 through bolt coupling units 875.

Furthermore, second inside assistant rings 855 are provided on the internal cover 820 to press the second end of the internal cover 820 onto the flange 400. That is, when the bolt coupling units 875 are tightened, the second inside assistant rings 855 evenly press the edge of the second end of the internal cover 820 onto the extension part 860 of the flange 400, thus ensuring airtightness between the internal cover 820 and the extension part 860

of the flange 400.

While the railway vehicle travels between the broad- gauge rails 20 and the standard-gauge rails 10, the wheel 200 is moved in a lateral direction corresponding to gauge conversion, therefore the volumes of the external space 880 and the internal space 890 change . Here, as shown in FIGS . 25 and 26 , the air vent holes 830a and 830b provide passages that allow air to move therethrough between the external space 880 and the internal space 890, thus preventing the external cover 800 or the internal cover 820 from being damaged by changes in volume of the external space 880 or the internal space 890.

As such, the gauge-adjustable wheelset according to the third embodiment of the present invention includes the external cover 800, which is provided on the outer surface of the wheel 200, and the internal cover 820 , which is provided on the inner surface of the wheel 200 , thereby reliably protecting the elements of the gauge-adjustable wheelset from the surroundings without affecting the parts thereof .

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims .

[industrial Applicability]

As described above, the present invention provides a gauge-adjustable wheelset for a railway vehicle which automatically changes a gauge thereof such that the railway vehicle is able to travel between two kinds of railways having different gauges, and which includes : an axle, having a sliding part and a cap mounting part ; a wheel fitted over the sliding part of the axle so as to be movable in a left or right direction; a support cap securely fitted over the cap mounting part of the axle; a locking block rotatably fitted over the support cap, so that left and right movement of the wheel is controlled by circumferential rotation of the locking block; a flange coupled to a right end of the support cap to control a locking and unlocking operation of the locking block; a spring holder coupled to a left end of the support cap; and a compression spring provided between the flange and the spring holder, thus reducing the number of elements and the manufacturing costs, being easily mounted to a bogie thanks to structural features thereof, and having an advantage of saving energy thanks to reduced rotational inertia .

Furthermore, according to another embodiment of the present invention, the present invention provides a gauge- adjustable wheelset for a railway vehicle which simply realizes a gauge-adjustable system and has a structure such

that elements thereof are easily assembled or disassembled.

As well, according to a further embodiment of the present invention, the present invention provides gauge- adjustable wheelsets for railway vehicles and, more particularly, provides a gauge-adjustable wheelset for a railway vehicle which automatically changes the distance between opposite wheels such that the railway vehicle is able to travel on railways having different gauges, and which prevents locking elements from being contaminated by water, dust or filth, thus ensuring the smooth operation and superior performance of the wheelset .