According to the International Patent Classification (IPC) the subject of the invention has been marked and classified by basic classification symbols : A 63 C 17/02 which refers to roller-skates with two pairs of wheels, A 63 C 17/22 referring to the roller-skate wheels, and A 4313 5/02 referring to the skiing and similar footwear.

Technical Problem The teclmical problem wished to be solved by the subject invention consists of the following : how to design roller-skates/sneakers with two pairs of separable wheels which would be alternately adjustable for walking or roller- skating, practical, safe and easy to maneuver, light and comfortable for feet and for walking or roller-skating, simple to manufacture, easy to put on, assemble, maintain and handle, while the roller-skates would be noiseless, safe, steady, durable, financially viable, ergonomic, aesthetically perfect and meet strict standards the footwear and sports equipment must satisfy.

Background Art In non-patent and patent literature numeral solutions of classic roller- skates have been described. The term roller-skates most generally refers to the so-called maneuverable roller-skates with four wheels, distributed two by two in line, born by a specially-designed carrier adjusted for fixed or separable fixing onto the footwear of a user. Deficiencies of all these solutions are that primarily, while skating, all four wheels normally have to be positioned in the ground plane, i. e. surface, while the user's feet are forced to adjust to the position taken by the truck of the wheels, this position being constantly changeable and dependant upon the configuration of the ground. This, however, for the purpose of safe roller-skating, requires a maximally even surface, what restricts the use of these roller-skates. Apart from that, more wheels increase the frictional resistance of rolling, decreasing the motion speed, while making it difficult to maneuver the change of direction. These deficiencies have been largely tried to be overcome in roller-skates with distribution of two or more wheels put in line one behind another, born in the middle of the sole plate of a roller-skate, kno. wn as"In Line Skate"roller-skates. The applications for roller-skates of this type that can be found in the available fund of the local patent documentation are P- 1500/76, P-849/77, P-1343/81, P-2666/82, P-586/85, P-429/86, P-2027/88.

However, within the known solutions for roller-skates of the said type, with two pairs of mutually parallel wheels in line, the roller-skates that are known are the ones consisting of a sole plate bearing wheels with means of fixing them onto the common footwear.

The also-known roller-skates have been described in the patent document AT-PS 2 04 456 in which, between two front links and two back links, there are wheels, and between them is a network of links movable in longitudinal direction of the shoe axle.

Further, there are roller-skates known in which the wheels can be fixed in order to enable walking on them. The defect of this known solution is that even with the fixed wheels walking is hardly possible, or can be achieved with great difficulty.

Also known are the roller-skates from patent documents DE-PS 4 88 743 and FR-PS 4 64 879 in which the rollers are not put into the sole, but are movable by a side meshanism on shoes, so that they san be turned in front or behind the shoes. The deficiency in this known solution is that the length of shoes is thus insreased to a great extent. Further deficiency is that such roller- skates can be used only for roller-skating, while if used for walking, they are rather unsuitable because of their length.

One of the known solutions for roller-skates is presented in patent document YU PS 35 960 in which the roller-skates are designed for alternate walking and roller skating, with at least one front and one back roller put on the adjustable born double lever link inside the shoe sole. The double lever link, in the position for roller-skating, can be adjusted outside the sole level and is kept in the locked position by the locking device, while in the position for walking it is kept in the in the plane parallel to the sole plane. In the longitudinal axis of the sole two double lever links adjustable around the axles affixed in the sole are put, the free end of which is designed with chamfer interacting with a cylindrical shear pin for locking, put in the sole opening.

In yet another known solution of roller-skates presented in Yugoslav patent application P-1630/88 entitled"Sports Device"several solutions are presented. The solution concretely regarding the sports device as a device for rolling or skating, consisting of a base plate with support elements on it (two or three pairs of rollers or blades), arranged by adjacent oscillatory axles, with the help of which the sports device rests on the surface it moves on. However, the deficiecy of this solution is that the device is made more in the shape of a skateboard, i. e. sleigh, and less in the shape of roller-skates.

When sneakers as sportsshoes are in question, a known solution has been presented in the Yugoslav patent application P-124/80 entitled"Sports shoe with a zip"in which the band made of elastic fabric is inserted between the zip and the tongue of a sports-shoe in its middle. The zip is fixed to the elastic fabric bands, sown to the edges of the upper part of a sports-shoe. The outer tip is fixed to one end of the zip for easier zipping up, the edges of the upper part being aligned by pulling of the tip. The deficiency of this solution is that these ports shoes are used solely for walking and are not suitable for any other use.

Disclosure of the Invention This invention relates to roller-skates/sneakers with two pairs of separable wheels, consisting of sneakers, which are zipped up, special insoles and two front and two back wheels separably fixed in the insole. In the lower front part- the sole, and the back part-the heel of the sneakers, between the outsole and the insole the front light insert and back light insert are put. What represents the essence of the novelty is that in the insole, on its lower side, there are firmly arranged bushings for fixing the wheels. The insole, which is tub-shaped, is made with a relatively even sole and two almost vertical lateral sides, the lateral sides being interconnected by the elastic band for fixing. From the lower side of the sole in the insole, and on its front and back end, bushes with a screw thread into which the wheels are fixed with screws are fixed. The wheel consists of two disc plates, between which there is a middle plate, and roller bearing. The plates, which are arranged on the roller bearing, are fixed on the screw and secured from falling off by a bushing and a safety device. The axes of the back pair of wheels are coaxial, while the axes of the front pair of wheels are moved one to the other for value a. The sneaker consists of the upper part and the inner layer with the tongue, while the upper part and the layer are most favourably made of fabric or any other elastic material.

The aim of this invention is to present roller-skates/sneakers with two pairs of separable wheels which would be alternately adjustable for walking or roller-skating, practical, safe and easy to maneuver, steady, simple to manufacture and wear, noiseless, durable, aesthetically perfect.

The invention roller-skates/sneakers-with two pairs of separable wheels according to this patent invention has numerous advantages, some of which are as follows: simple structure safe, steady, easy to maneuver noiseless practical for roller-skating comfortable to wear the sneakers can also be used for walking simple to manufacture easy and simple to put on, assemble, maintain and handle, durable ergonometric with numerous different types of sneakers aesthetically perfect, aerodynamic satisfy strict standards for footwear and sports devices practically of unlimited duration suitable for serial production financially viable with relatively low production cost.

Brief Description of Drawings For the purpose of easier understanding of the invention, as for presenting how the easiest embodiment can be achieved in practice, the applicant refers to the attached drawings in which Figure 1 represents the roller-skates/sneakers with two pairs of separable wheels, according to this invention, in axonometric view, Figure 2 represents the roller-skate of Figure 1 in side view, Figure 3 represents the roller-skate of Figure 1 in the above view, Figure 4 represents the roller-skate of Figure 1 in the front view, Figure 5 represents the schematic elements of the sneaker of Figure 1 in axonometric view, Figure 6 represents the sneaker of Figure 5 in the side view and partial section, Figure 7 represents the support structure-the sneaker insert of Figure 5 in axonometric view, Figure 8 represents the wheel of a roller-skate of Figure 1 in its vertical cut.

Detailed Description of the Invention The roller-skates 1, according to this invention and Figures 1 through 6, basically consist of sneakers 2 (for the purpose of rationality only the left one is shown), insole 8, and two pairs of wheels 3, distributed two by two in line.

The sneaker, Figures 5 and 6, consists of three basic parts: upper side 5, made of fabric or any other elastic, i. e. soft material, insole 8, and inner layer 6.

The sneaker 2, which could be of any suitable and wanted model/shape, is made of artificial, or the combination of artificial and natural materials. Within the sneaker 2 the insole 8 is put as a support firm structure, preferably made of composite materials. For the protection of user's feet, the inner layer 6 with the tongue 6'is made of fabric or any other suitable material. In the lower front part - sole, and the back part-the heel of the sneakers 2, more precisely between the outsole 5'and the insole 8, the front light insert 11 and back air insert 12 are put.

There are pressed bulges in the inserts 11, 12, the bulges being achieved from the lower part of the insole 8. In these bulges bushings 10,10'are arranged while casting, into which bushings the wheels 3 are fixed. By this manner of construction the reduction of shock is achieved, i. e. amortisation of vertical forces while roller-skating.

From the upper part on the sneaker 2, to the front edges of the upper part 5, and above the tongue 6', there is an affixed zip 7 with a tip for pulling. The zip 7 enables the sneaker to be zipped up fast and easy upon being put on, as well as increases its durability and improvement of strain distribution. The sneaker 2 has been chosen as footwear for the roller-skate because it, with its elastic and bendable means, absorbs longitudinal components of strain, so the effect of those on the zip 7 is decreased, what prevents the effect of widening which could cause the unwanted unzipping. The zipping could certainly be replaced by any other known manners such as lacing, buckling, use of Velcro strap, and alike.

The insole 8, Figure 7, which is made of composite materials, is tub- shaped with relatively even sole and two relatively vertical sides. These sides serve for the purpose of security and side protection of ankles and they are interconnected by elastic band 9 for fixing. From the lower side of the sole, in the bulges on the front and on the back end of the insole 8, there are bushings 10, 10'with a screw thread for assembling the screws 4 of wheels 3.

The wheel 3, Figure 8, consists of two disk plates 13, between which the middle plate 14 made of silicon rubber is put. The plates 13,14 are put and fixed on the screw 4 over the rolling bearing 15, and altogether they are secured from falling off by the bushing 16 and safety device 17. The middle plate 14 made of silicon rubber in roller-skating makes the wheels and roller-skating itself noiseless. The wheels 3 are fixed through the screws 4 in the screw threads of the integrated bushings 10,10'of the insole 8. The axes of the back pair of wheels 3, Figure 3, are coaxial, while the axes of the front pair of wheels are moved one to another for value a, i. e., the wheel from the inner side of he sneaker, at thumb's place, is moved forward for value a as regards the wheels from the outer side.

The manner of functioning is simple and is obviously derived from the former description and drawings, so there is no need to describe it in detail separately. By fixing the assembly of the wheels 3 by the screws 4 in the bushings 10,10'of the insole 8, the sneakers 2 can be put on and fixed on feet by zipping the zip 7.

Industrial and Other Applicability of the Invention The manner of application comes obviously from the previously said, i. e. for the commercial use of this invention no special knowledge, directions for use, or experience is needed in order to apply it successfully. Only the knowledge of an average artisan in the field is needed and sufficient to successfully apply the invention, based on the description. All functional and ecological characteristics of the means have been successfully checked by the author.

Also, any improvements in design or changes in geometrical shapes that would be in the scope of the presented device and for the purpose of its functional improvement are deemed covered by this application.