PRIOR ART A flexible bar is known in an apparatus for different exercises located in the center of a spring to that bar ends are pressed together only by overcoming spring force.

To produce a variable force by which bar ends are pressed, a flexible rubber disk is wound around bar center. (DE 19620945).

A weight is known to be used with equipment for weightlifting exercises of the bar type, the plate being connected in such a way as to rotate during the exercise, this rotation being locked by a lever connected with the weight so that it rotates with the latter and located so that it is in contact with the outer foremost part of human hand moving during the exercise. The weight has projecting and concave parts on its front and rear surfaces to allow the subsequent weights put one next to the other to clutch so that all weights rotate together without the lever entering all weights. (US 4880229).

A weight exceptionally easy for use is known for exercises made by people, consisting of a disk of a mass sufficient to cause a resistance, when people move during the exercise and having at least one internal diameter with a central axis allowing to fit the disk on an equipment, the disk having a first and a second sides usually opposite one another and located radially on the central axis having a first and a second ends representing circles, an outer peripheral surface projecting between the first and second ends mentioned above of the first and the second sides mentioned above and at least one groove in the disk open towards the side of this outer peripheral surface the central axis of this groove crossing the internal central diameter, the groove being sufficiently large.

(US 5853355) A disk of great strength for weight-lifting is known, made of granulated vulcanized rubber from scrap. (KRAIBURG DE) The disadvantage of this disk is that it should be very thick in order to achieve the effect desired which makes the use of many disks of different weight for training very difficult.

A method of manufacture of disks to be used in weightlifting is known where at the bottom of a mould consisting of a lower part and a cover is laid a sticking layer of raw rubber and a vulcanizing agent, then a mixture heated in advance and consisting of granulated vulcanized rubber made of scrap and a binding agent composed of raw rubber and a vulcanizing agent is added, the disk is molded by vulcanizing the mould by heating under pressure, thus obtaining at high temperature, a cohesion between the mixture heated and the sticking layer and molding a disk body as shaped by mould surfaces, and finally the molded disk is cooled. (technology of KRAIBURG GUMM DEV GmbH) A disadvantage of this method is the impossibility of making a disk of high specific weight, high density and high strength parameters at the same time, therefore it is impossible to manufacture many disks of different weight, diameter and thickness.

SUMMARY OF THE INVENTION The purpose of this method is to manufacture a flexible disk for training equipment of high specific weight, great durability, high density and illimited possibilities of combination of weights, diameters, height, color, marking and to work out a method of its manufacture in which normal plastic rubber material is used as a raw material to obtain products of low cost.

The invention consists in the manufacture of a flexible disk for training equipment containing granulated vulcanized rubber from scrap, an elastomer base, fillers, softeners, additives and vulcanizing agents included in a rubber mixture to be molded all of them in the following quantities by weight: 50-80% of rubber, 20-30% of chalk, 5-30% of carbon black. 0-10% of oil. 0-40% of barite, 1-6% of zinc oxide, 0.1-0. 8% of stearic acid, 3-18% of granulated vulcanized rubber from scrap, 0.1-0. 9% of anti-oxydants, 0.1-0. 9 % of accelerator of sulphide type, 0.3-1% of accelarator of guanidine type, 1-3% of sulphur.

In a second version of the invention a plastifier is used a filler in the rubber mixture to be molded.

In a third version of the invention the rubber mixture to be molded contains dyes.

In a fourth version of the invention the flexible disk for training equipment is manufactured with an outer decorative layer representing a colored flexible film and an inner basic layer on an elastomer base.

The invention includes also a method of manufacture of a flexible disk for training equipment according to which granulated vulcanized rubber from scrap is mixed with the other ingredients of the rubber mixture to be molded containing an elastomer base, fillers, softeners, additives and vulcanizing agents in an open or closed rubber mixer. The rubber mixture thus obtained passes through a roll mill and a cooler until producing a smooth sheet of 5-lOmm thickness. The sheets are placed on heating tables where they are cut to obtain blanks or strips of precisely determined weight and size, then the blanks cut are put in the mould which has additional insert or inserts and is detachably fixed to an upper and a lower platens of a multi-platen hydraulic press. After the blank cut is put into the mould the latter is closed by closing the upper and lower platens of the hydraulic press and is vulcanized at a temperature of 150-170 C for 20-75 minutes, when a net is formed and a product subject to finishing is obtained. This product is taken out of the mould, it is cut along its internal and external diameters, then a metal insert is introduced in its internal diameter on a stand. Next an elastic dye forming an elastic film is laid on the flexible disk shaped in this way, and the colored flexible disks are then dried at atmospheric conditions for 1 to 6 hours and finally marked.

The flexible disk is shaped by introducing an additional insert in the mould consisting of limiting upper and lower plates, a lower molding plate, an upper molding plate, an intermediate molding plate, a core and fixing screws. The additional insert is to be placed on the limiting lower plate and the molding lower plate with its core connected by means of the fixing screws, then the intermediate plate is fixed on the additional insert and the lower molding plate. The rough blank made of the rubber mixture is placed in the area of the intermediate molding plate after which the mould is closed by pressing the upper and lower plates one to another so that it is possible to start vulcanizing.

In a second version of the invention the flexible disk is shaped after introducing in the mould two additional inserts on the lower limiting plate and the lower molding plate and the upper limiting plate and the upper molding plate respectively both having an upper and lower cores.

The advantages of this invention are as follows: The flexible disk manufactured according to the invention has very high operational parameters of reliability, functionality, wear resistance and specific weight, and the method of its manufacture allows to achieve a high economic efficiency due to the low cost of the materials and the technological process used.

By combining the basic substances used in the rubber mixture to be molded it is possible to ensure the high specific weight, the compression strength and the high durability of the flexible disk by reducing its thickness in addition, i. e. it is possible to manufacture disks of relative large surface along the diameter which facilitates the fitting of disks on the training equipment and causes a relatively uniform distribution of the weight on it and consequently a smaller torque with respect to the axis of the equipment, and as a result of all that its use is easier and the safety of the trained competitors is greater.

The composition of the rubber mixture on an elastomer base of which the flexible disks are to be molded allows to make blanks of well-determined weight and sizes corresponding to the pre-determined weight of the disk and to control their high relative density.

Due to the technological possibility of coloring and the use of an additional insert in the structure of the flexible disk mould which enables to make a relief layer technologically, the flexible disk becomes a carrier of additional information.

Depending on the requirements of the relevant user, the disk surface can be engraved in different ways with a view to marking different data and colored in a specific color. Thus it is possible to make combinations of disks of different colors and weights assembled depending on the requirements of the user and on the equipment available to the latter.

Disk molding is simplified, and it is carried out in an anti-isocyanide medium free from poisonous binding ingredients harmful to the workers employed in their manufacture.

The method of manufacture of flexible disks according to the invention ensures a high compaction of the mixture to be molded and allows to manufacture disks of different sizes and thicknesses depending on the weight specified in advance.

The expenses for raw materials and energy use in the manufacture of flexible disks are considerably smaller compared to those related to the manufacture of similar disks from granulated vulcanized rubber from scrap and binder.

THE DRAWINGS An example of manufacture of a mould for flexible disks, a working drawing of a flexible disk and an additional insert, all of them explaining the character of the invention are shown in the figures attached, as follows : Fig. 1-Partial view of a flexible disk for training equipment; Fig. 2-Cross-section of a flexible disk for training equipment ; Fig. 3-Cross-section of a mould for flexible disk with a blank to be vulcanized; Fig. 1-View of an additional insert for engraving intended to be built in the mould.

DETAILED DESCRIPTION The composition of the rubber mixture for molding flexible disks for training equipment can be illustrated with the following examples: EXAMPLE 1 The mixture to be molded is composed of : Rubber-50 kg; Chalk-130 kg; Carbon black-40 kg: Oil-10 kg; Barite-35 kg ; Zinc oxide-5 kg ; Stearic acid-0.9 kg; Vulcanized granulated rubber from scrap-8kg ; Anti-oxydants-0. 8 kg; BMTS accelerator-lkg ; DPG accelerator-0.9 kg; Sulphur-2kg.

EXAMPLE 2 The mixture to be molded is composed of : Rubber-100 kg; Chalk-100 kg; Carbon black-50 kg: Oil-10 kg; Barite-35 kg ; Zinc oxide-3 kg; Stearic acid-0.9 kg; Vulcanized granulated rubber from scrap-kg ; Anti-oxydants-0.8 kg; BMTS accelerator-1.3 kg; DPG accelerator-0.7 kg; Sulphur-2kg.

The flexible disks for training equipment are manufactured from the mixtures specified in Examples 1 and 2 which are obtained after mixing their ingredients in an open or a closed rubber mixer. Then the mixture to be molded is run through a roll mill and a cooler until obtaining a smooth sheet of a 5-10mm thickness. These sheets are laid on heating tables where they are cut into blanks or strips of precisely determined sizes and weights. The blanks are put thereafter in the mould A (fig. 3) which has an additional insert B (fig. 4) and is fixed detachably to the upper and the lower platens of a multi- platen hydraulic press. After the blank is inserted in the mould, the latter is closed by closing the upper and the lower platens of the hydraulic press. Further the mould is submitted to vulcanization at a temperature of 150-170C for 20-75 minutes, when a net is formed in the rubber mixture, and a product to be submitted to finishing is obtained. This product is taken out of the mould, cut along its external and internal diameters, and a metal insert is forced into its internal diameter on a stand. The flexible disk thus obtained is then coated with a resilient paint forming a flexible film on it. The flexible disk painted are left to dry at atmospheric conditions for 1-6 hours and then they are marked.

The molding of the flexible disk C (fig. 1 and fig. 2) is carried out by introducing the additional insert B in the mould A consisting of upper and lower limiting plates 1, lower molding plate 2, upper molding plate 3, intermediate molding plate 4, core 5 and fixing screws 6. The additional insert B is placed on the lower limiting plate 1 and the lower molding plate 2 with the built-in core 5 connected one with another by means of the fixing screws 6, then the intermediate molding plate 4 is fixed to the additional insert B and the lower molding plate 2. The blank 7 made of the rubber mixture is placed on the intermediate molding plate 4. The mould thus loaded is closed by closing the upper and the lower platens of the hydraulic press to which it is fastened in order to start vulcanizing.

In a second version of manufacture of the flexible disk the latter is molded by introducing two additional inserts on the lower limiting plate and the lower molding plate and the upper limiting plate and the upper molding plate respectively having an upper and lower cores. In this way it is possible to engrave elements on both radially opposed walls of the flexible disk at the same time.

The examples shown above are not limitative to the scope of the invention.

USE OF THE INVENTION The flexible disks for training equipments, subject of this invention, are used in sports and training centers, where the sets can be combined by including in them disks of different weight, diameter, height and minimum thickness which is an advantage from economic point of view, since it is possible to make multi-colored combinations of different disks of different parameters for equipping different apparatuses at relatively low expenses, because the relative weights of the rubber mixture and the ready parts are controlled and a finishing is carried out by additional coloring.