The object of the invention is a method for the manufacture of a rechargeable, flexible electric battery. Further, the object of the invention is also an electric battery manufactured using the method. In the electric battery of the invention there occurs both a primary and secondary chemical reaction.

Prior art

In a conventional circuit board there is provided at least on the one surface of the circuit board substrate a laminated metal foil covering the whole surface. A conventional way to manufacture such a circuit board of a laminate is to use the etching method, in which the conductive metal remaining on the circuit board is protected for the duration of etching with a material enduring etching and patterned in accordance with the layout to be manufactured. The metal remaining unprotected is removed using a chemical engraving process. The metal foil can be, for example, copper laminate.

So-called printable electronics can be used in the manufacture of electric circuit entities. In the manufacturing method the printing plate or ink material in the printing plate touches and grips to the material functioning as bed. An electrically insu- lating material is used as the bed, on top of which the desired circuit entities are produced by printing. Electrically functional materials, liquid or powdery, are available for the manufacture of electrically conductive, insulating, semiconducting and optical circuit elements. In addition to the printing of the material, also different films, which may be insulants or conductive can be glued to the structure. In flexible circuit board structures either a polyimide-based film (PI) or polyester- based film (PET) or polyether sulphone film (PES) is generally used as the ductile substrate. The polyimide film withstands temperatures of over 300°C. Some poly- imide trademarks are Kapton®, Apical® and Upilex®. Polyester-based films withstand temperatures of approximately 100°C. Examples of polyester-based trade- marks are Mylar® and Melinex®.

The roll-to-roll manufacturing method is used in the manufacture of flexible circuit boards, in which method film-type circuit board material is processed as long bands, which have been roiled onto coils. The roll-to-roll manufacturing technique is well suited to be used in case of large manufacturing batches.

Also different batteries and accumulators have been manufactured onto flexible circuit board films. The main part of batteries printed onto circuit board films is based on zinc (Zn) or manganese oxide (MnOa) materials or lithium-based structures.

Electric batteries based on zinc or manganese oxide materials have been manufactured using the roll-to-roll manufacturing method. However, a problem with the manufacture of such electric batteries are both the printability characteristics of the materials used in them and the allocation of the separating layer or film needed between the electrodes of the battery. Because of these problems, it has not been possible to get the yield of electric batteries produced using the roll-to-roll manufacturing method to a satisfactory level.

Probable applications of a flexible electric battery are self-adhesive labels or other elastic applications of printed electronics, to which the recharging of installed galvanic batteries is difficult to execute.

Conventionally the battery solutions implemented with the technique described above are usually disposable (primary cell). In certain applications, they have been used to replace individual button-cell batteries. The nickel-iron accumulator (NiFe) once patented by Edison was used in vehicles until the 1970's, but nowadays it is mainly used as energy storage for solar panels. Edison's accumulator has a nickel(lll) hydroxide cathode (Ni(OH) ₂ ) and an iron oxide anode (Fe ₃ 0 ₄ ). Potassium hydroxide (KOH) can be used as electrolyte. An Edison-type accumulator has a short charging time, which is well suited for electric cars. However, the accumulators are of a very big size in relation to the charge that can be charged to them.

When the charge of an Edison-type electric battery has discharged, the battery is usually removed from the object of use, if it is a disposable device entity, to which the battery is attached. Because the Edison-type electric battery runs down fairly quickly, the in many ways superior electric battery technology cannot be used without a recharge possibility. Probable applications of flexible electric batteries are self-adhesive labels or other elastic applications of printed electronics, the galvanic recharge of which is difficult to execute also in the Edison accumulator.

Objectives of the invention It is an objective of the invention to present a rechargeable, flexible electric battery, super-capacitor or accumulator executable with printing technology.

The objectives of the invention are achieved with a battery, accumulator or super- capacitor, which is manufactured with the roll-to-roll technology by making use of different materials suitable for the printing of an iron-nickel accumulator. In con- nection with the manufacture of the material layers for an electric battery or super- capacitor, a spiral double-acting coil is also manufactured around the battery, by means of which the battery can be charged wirelessly. The coil is made either in connection with the cathode or anode layer in the same process step.

It is an advantage of the invention that the flexible electric battery or super- capacitor can be recharged innumerable times. If the application is, for example, a self-adhesive label, it will not become useless after the charge of the electric battery or super-capacitor has discharged, because it is rechargeable with a wireless charging device.

It is a further advantage of the invention that a coil can be provided around the electric battery or super-capacitor, which can be used in the wireless recharging process of the electric battery or super-capacitor.

In addition it is an advantage of the invention that the coil prepared around the electric battery or super-capacitor can also be used as NFC antenna (Near Field Communication) for the identification of different devices using RFID technology (Radio Frequency Identification) and data transfer for very short distances, at most of a few centimetres, on a narrow data transfer band. The NFC device can function both as a reader device and identifier.

It is a further advantage of the invention that the insulating net separating the cathode and anode of the electric battery from each other can be printed reliably onto the cathode material by using printing technology.

It is a further advantage of the invention that the materials for the electric battery are recyclable. In addition it is an advantage of the invention that the electric battery has a very long service life (20 - 50 years).

It is a further advantage of the invention that the electric battery has a good endurance of overcharge. It is a further advantage of the invention that the electric battery withstands complete discharge.

It is a further advantage of the invention that the electric battery withstands freezing.

It is a further advantage of the invention that the electric battery is hermetic. It is yet a further advantage of the invention that the materials for the electric battery are basic materials easily available.

It is characteristic of a flexible electric battery of the invention manufactured with a roll-to-roll manufacturing equipment that also a spiral coil is made around the electric battery of the same flexible metal film as the second one of the electric battery electrodes, the electric battery being arranged to be charged wirelessly and/or to be connected to a wireless data transfer system by using the said coil.

It is characteristic of the roll-to-roll manufacturing method of a flexible electric battery of the invention that a spiral coil is manufactured by etching around the electric battery of the same metal foil as the metal foil supporting the cathode electrode or anode electrode of the electric battery, the electric battery being chargeable wirelessly and/or connectable to a wireless data transfer system by using the said coil.

Some advantageous embodiments of the invention are presented in the dependent claims. The basic idea of the invention is as follows: An electric battery or super-capacitor of the invention is manufactured using roll-to-roll technology. In the electric battery of the invention both primary and secondary reactions occur as a chemical reaction.

In connection with the manufacturing process of the cathode, anode and neces- sary insulating layers of the electric battery, also a double-acting coil is prepared in connection with the electric battery, the coil being used both in the wireless re- charging of the electric battery of the invention and the management of the data transfer needs of the electronic component connected to the electric battery. Advantageously on the side facing the outer surface of the cathode or anode of the electric battery there may be a material layer of high permeability, such as a ferrite layer, which is used for shaping the electro-magnetic field generated in wireless charging or data transfer of the object of use, to which the electric battery of the invention has been mounted.

Also in case of a super-capacitor its electrodes and insulating materials are grown advantageously by printing onto a suitable material film using the roll-to-roll print- ing technology.

The manufacture of an electric battery of the invention will next be explained in detail. The manufacturing steps used in the manufacture of a super-capacitor have not been illustrated separately. In connection with the specification of the electric battery reference is made to the enclosed drawings, in which Figures 1 a - 1 g are exemplary illustrations of a flexible electric battery of the invention according to manufacturing steps, observed in the direction of the cathode and the cross-sections of these;

Figure 2 is an exemplary flowchart of the main manufacturing steps of the cathode of the electric battery of the invention; and Figure 3 is an exemplary flowchart of the main manufacturing steps of the anode of the electric battery of the invention and the final assembly steps of the electric battery.

The embodiments in the next specification are only exemplary and one skilled in the art may execute the basic inventional idea also in some other way than the one depicted in the specification. Although reference may be made to an embodiment or embodiments in several places of the specification, this does not mean that the reference would only be applied to one depicted embodiment or that the depicted feature would only be usable in one depicted embodiment. Individual features of two or more embodiments may be combined and thus achieve new em- bodiments of the invention.

Figures 1a - 1g are exemplary illustrations of the manufacture of a flexible electric battery 10 of the invention using the roll-to-roll manufacturing process. The materials used in the electric battery 10 of the invention make possible the primary and secondary chemical reactions needed in the discharge and recharge of an electric charge. During the manufacture of an electric battery the semi-finished cathode and anode products are driven several times through the devices in the manufacturing line. The various material layers shown in Figures 1 a - 1 g can be a result of one or more processing transactions of the same material in the roll-to-roll equipment.

The manufacture of an electric battery according to the first embodiment of the invention is explained in Figures 1 a - 1 g. In this advantageous embodiment the cathode of an electric battery, such as an accumulator or super-capacitor, and the coil surrounding it have been made by etching from a copper foil of Cu/PET laminate (Figure 1 a).

In a second advantageous embodiment of the invention the coil in connection with the electric battery has been manufactured to the connection of the anode from a metal plate used in the manufacture of the anode. However, the invention is not restricted to a solution based on Cu/PET foil, but the manufacture of the electric battery according to the second embodiment of the invention and the antenna connectable to it can alternatively be made by originally using pure copper foil as follows. In this manufacturing method there is no need for separate work phases for connecting to each other the components of two sepa- rate conductive layers of a flexible circuit board, on which the electric battery of the invention, such as an accumulator or super-capacitor is located, through the insulating layer by using electrically conductive vias.

The electric vias possibly needed are manufactured onto the first surface of the copper foil acting as the bed for the electric battery by printing insulating and con- ductive layers. The first surface of the copper foil is part of the outer surface of the electric battery of the invention facing the cathode. The layers printed onto the first surface are patterned to suit the purpose of use. The first patterned layer to be printed onto the first surface of the copper foil is an insulation layer. The insulation layer is left with openings at the electrical vias to be manufactured. In the next pro- cessing steps, one or several conductive, semi-conductive or insulating material layers can be printed onto the patterned first insulation layer so that the desired circuit entity can be provided onto the side of the outer surface of the cathode of the electric battery. The necessary electrical vias are advantageously implemented by pressing conductive material into the openings patterned to the first insulation layer. The conductive material pressed to the openings achieves an electrical contact from the printed conductive layer to the copper foil acting as bed for the cathode. Several layers of patterned insulating and conductive layers can be superimposed.

When all material layers to be provided onto the first surface of the copper foil have been printed, the side of the cathode of the electric battery made by printing is advantageously attached to an appropriate support film. The support film can contain openings, through which an electrical connection can be made either to the metal foil or conductive layer of the electric battery.

After this the copper cathode of the electric battery of the invention and the coil around the electric battery are patterned onto the other still unprocessed side of the copper foil advantageously by etching. After the etching of the cathode and coil, material layers according to Figures 1 a - 1 g can advantageously be printed onto the cathode electrode of the electric battery and the coil made by etching to prepare the cathode of the electric battery 10 and the insulating net insulating the cathode from the anode.

It is an advantage of the electric battery according to the second embodiment that it is possible to make the contact of the cathode either above and/or below the copper foil belonging to the cathode. In addition the connection of the connecting points of the cathode, anode and coil to an outer electrical circuit can be made by printing the conductors from the connecting points to the outer electrical circuit.

In Figure 1a there is illustrated the manufacture of a cathode of an electric battery according to the first embodiment of the invention by etching from Cu/PET lami- nate. Both the cathode electrode 1 10 of the electric battery and the surrounding coil have been etched from a copper foil of Cu/PET laminate.

In Figure 1 a the cathode electrode of the electric battery 10 and the exemplary coil 120 are shown both from above and as a cross-section in the direction A-B. For the sake of clarification of Figures 1 a - 1 g and for facilitating the specification the thicknesses of the material layers of the cross-section A-B are shown in an exemplary way in all Figures so that they can be easily distinguished from each other.

The thickness of the copper foil of the Cu/PET laminate used is advantageously approximately 18 μιη. The thickness of the PET film is approximately 50 μιη. An exemplary cathode electrode 1 10 is in Figure 1 a shown principally in the form of a rectangle. In Figure 1 a the cathode electrode 1 10 also has a downwards extending projection 1 10a, from which the cathode of the finished electric battery 10 can be electrically connected to an outer electrical circuit (not shown in Figures 1 a - 1g). It is obvious for one skilled in the art that the geometric shape of the cathode electrode 1 10 can deviate from the example depicted in Figure 1 a.

The exemplary coil 120 in Figure 1 a has two laps. The coupling points of the coil are marked with references 121 and 122. The coil 120 is connectable to an external electric circuit arrangement from the coupling points. However, the coil struc- ture 20 of the invention is not restricted to the shown geometrical shape or the depicted two laps, but the shape of the coil can be chosen to suit the application and, depending on the application, the coil may also have several laps.

In Figure 1b there is illustrated a cathode electrode after one or several insulating layers 101 have been printed on top of the laps of the coil 120 and the edge areas of the copper cathode electrode 1 10. No insulating material has been printed on top of the coupling area 110a of the cathode electrode or the coupling points 121 and 122 of the coil. The insulating material used endures the alkaline electrolyte solution used.

This above-mentioned cathode electrode 1 10 of the electric battery remaining un- insulated is next coated electrolytically with a nickel layer 1 1 1 , the thickness of which is advantageously about 4 pm. Also the coupling area 1 10a of the cathode and the coupling points 121 and 122 of the coil are advantageously coated with nickel (references 1 1 1 a, 121 a and 122b).

In Figure 1c there is shown the cathode electrode of the electric battery 10 of the invention after the material layer 1 12 consisting advantageously of nickel(lll) hydroxide (Ni(OH) ₂ and carbon has been printed onto the area of the cathode electrode with the nickel coating 1 11. Instead of carbon, also other conductive materials enduring an alkaline solution may be used in connection with the nickel(lll) hydroxide. No nickel(lll) hydroxide is dispensed on top of the nickel-plated coupling area 1 1 1 a of the cathode electrode and the nickel-plated coupling points 121 and 122 of the coil. In an advantageous embodiment they are coated with gold so that the joint to be made to them would be as reliable as possible. In an advantageous embodiment of the invention an electrolytic solution is dispensed onto the nickel-plated surface 11 1 of the cathode electrode so that the water in the solution reacts with nickel and generates a nickel(lll) oxide layer to the cathode. In Figure 1d there is illustrated the cathode of the electric battery 10 of the invention after two insulating layers 113 and 1 13a and 1 13b different from each other have been printed onto the cathode electrode. The insulating layers 1 13a and 1 13b on the outer edges of the cathode electrode are solid insulant. At the actual cathode electrode 110 a gridded structure 1 13 of the insulant has been printed on- to the nickel(lll) hydroxide layer 1 12, which in the electric battery of the invention functions as the element separating the cathode and anode.

The height of the separating net 113 to be provided is determined by the number of successive printing times used in the manufacture of the net. The insulant for the separating net 1 13 has been chosen so that it does not dissolve or break in the electrolytic solution used in the electric battery.

No insulating material has been printed onto the coupling area 1 1 1 a of the cathode electrode 1 10 or the coupling points 121 a and 122a of the coil at this processing step.

Figure 1e illustrates an adhesive layer 1 14, which in the cross-sectional view comprises the sections 1 14a and 1 14b, printed on the outer edges of the cathode electrode. No adhesive layer has been printed onto the coupling area 110a of the cathode electrode or the coupling points 121 a and 122a of the coil in this processing step.

After the printing of the adhesive layer the semi-finished cathode 1 of the battery 10 of the invention is ready to be joined with the semi-finished anode. in Figure 1f there are illustrated some advantageous embodiments of the semifinished anode of the electric battery 10 of the invention. The anode electrode 160 is prepared advantageously by printing a mixture of iron oxide (Fe ₃ 04) and carbon onto the support film 150. Instead of carbon also other conductive materials with- standing an alkaline solution can be used in connection with iron oxide. The support film can be a PET film, metal coated PET film or iron film. An exemplary anode electrode 160 is depicted mainly in the form of a rectangle in Figure 1f. The anode electrode 160 in Figure 1f also has a downwards extending projection 160a, from which the anode of a finished electric battery 10 can be electrically connected to an external electric circuit (not shown in Figures 1 a - 1 g). It is obvious for one skilled in the art that the geometric shape of the anode electrode 160 can deviate from the example in Figure 1 f.

Openings are prepared to the support film 150 and 170 of the anode advanta- geously by etching to the places, which become opposed with the coupling area 1 10a of the cathode and the coupling points 121 and 122 of the coil.

Cross-sectional views in Figure 1 f present two advantageous alternatives for the support film structure of the anode (options C and D).

In the alternative C the metal foil 170 has been laminated onto the outer surface of the PET film acting as the support film.

In the alternative D the support film has advantageously three layers. Between the PET film 150 against the anode electrode and the metal foil 170 forming the outermost layer there is the layer 190 of ferromagnetic material, for example fer- rite, on a material layer of approximately 300 μιη. This ferromagnetic layer 190 is used for forming the magnetic flux originated by or applied to the coil 120 so that the recharging of the electric battery 10 is made more effective. When the coil is used in data transfer utilizing the ferromagnetic material layer 190, this material layer 190 affects the data transfer direction used both in transmission and reception. In Figure 1 g there is shown how the electric battery 10 of the invention is assembled from the semi-finished cathode 1 and semi-finished anode 2.

Before the semi-finished anode 2 is connected to the semi-finished cathode 1 , potassium hydroxide (KOH) 180 is advantageously printed on the insulation net 1 13 of the cathode electrode. When the electrolyte 180 has been dispensed onto the cathode electrode, the anode according to Figure 1 f is pressed onto the cathode. The cathode and anode are glued to each other by the adhesive layer 1 14.

Also other metals can be used as electrodes for the electric battery and also some other alkaline solution can be used as electrolyte, but in this case the voltage and charging capacity of the electric battery to be prepared change. After the semi-finished cathode 1 and the semi-finished anode 2 have been glued together, the result is a prepared electric battery 10, which is hermetically closed by two metal films both from the side of the cathode and anode. The electric couplings of the electric battery 10 of the invention can advantageously be made using crimped joints extending through the structure. The reference 16 illustrates the crimp joint perforating the coupling area 111 a of the cathode. The reference 17 illustrates the crimp joint perforating the coupling area 160a of the anode. The references 18 and 19 illustrate the crimp joints perforating the coupling points 121 a and 122a of the coil 120. With the connectors 16 and 17 the electric battery can be coupled both with the control circuit in connection with the coil 120 and the electronic circuit supplied by the electronic battery. Through the connectors 18 and 19 the coil 120 can be coupled both with the charging circuit of the electric battery and NFC electronics. The coil 120 of the invention can thus advantageously be used both in the charging of the electric battery and as data transfer equipment for the electronic circuit connected to the electric battery.

In the manufacturing method of the invention described above a flexible electric battery or super-capacitor can be produced either onto a Cu/PET laminate or pure copper foil using the roll-to-roll technology. With the manufacturing method of the invention it is possible to achieve a rechargeable electric battery or super- capacitor, the thickness of which is approximately 0.1 - 0.2 mm. The manufacturing method of the invention can be used for the cost-effective manufacture of rechargeable electric batteries and super-capacitors for various RFID and NFC cir- cuit applications.

Figure 2 is an exemplary flowchart of the main steps for the method for manufacturing the cathode electrode of an advantageous embodiment of the electric battery of the invention shown in Figures 1 a - 1 e. In connection with the explanation of the flowchart in Figure 2 the reference numbers presented more closely in Fig- ures 1 a - 1 g are used as clarifying reference numbers.

The actual manufacturing steps for the cathode of the rechargeable flexible electric battery 10 are preceded by step 20. In step 20 either a Cu/PET laminate or pure metal foil 1 10 is ready in the roll-to-roll manufacturing equipment, the metal foil advantageously being a copper foil with no separate support film attached. Later in the specification the manufacturing process of the cathode electrode is depicted by using the Cu/PET laminate.

In step 21 a copper electrode 1 10 and coil 120 with its coupling points 1 10a, 121 and 122 are manufactured by etching onto the Cu/PET laminate. In step 22 the edge areas of the cathode electrode of the electric battery 10 under manufacture are coated with insulation 101 at one or several printing rounds. The number of printing rounds can be used for determining the thickness of the insulating layer to be generated. The actual cathode electrode, coupling point 1 10a of the cathode electrode and coupling points 121 and 122 of the coil 120 are not coated with the insulation 101 .

In step 23 the uninsulated copper foil 1 10 of the cathode electrode and the coupling points 1 10a, 121 and 122 are coated advantageously electrolytically with a nickel layer 1 1 1 , 1 1 1 a, 121 a and 122a of approximately 4 μιη at one or several manufacturing times.

In step 24 a nickel(lll) hydroxide layer 1 12 is printed onto the nickel-plated cathode electrode at one or several printing times.

Step 25 comprises advantageously several printing times with an insulation paste. One or several uniform insulating layers 1 13a and 1 13b are printed onto the edges of the cathode electrode. So many insulating layers are printed that a sufficient volume is generated at the actual cathode electrode for the electrolyte to be used.

Additionally in step 25 an insulating net 1 13 of insulating material is printed onto the nickel(lll) hydroxide layer 1 12 printed in step 24. In a manner described above insulating paste is printed all the way to the edges of the cathode electrode, but in the active area of the battery the insulating layer is advantageously netlike. The thickness of the insulating net 1 13 is determined by how many printing times are used for the manufacture of the net. The material of the insulating net 1 13 does not dissolve or crack to pieces because of the electrolyte 1 18 to be added in the later manufacturing steps. in step 25 the first printing time of the insulating paste is advantageously uniform on the edges 1 13a and 1 13b and netlike 1 13 in the middle. During the next printing times the insulating layers 1 13a and 1 13b still have uniform edges, but in the areas of the insulating net 1 13 they are only points, which attach to the knot points of the insulating net 1 13 manufactured during the first printing time. Thus the insu- lating points can be made to attach to certain places of the insulating net so that more volume is achieved for the electrolyte used, when the insulating net 1 13 is in its entirety printed advantageously only one time.

Thus the electric battery 10 of the invention does not need a conventionally needed separate separator film, paper or other porous film, which cannot be added printing-technically, but which has to be added between the cathode electrode and anode electrode.

After the printing times of step 25 have been carried out, an adhesive layer 1 14 is printed at one or several printing times in step 26. The semi-finished cathode 1 of the electric battery 10 is ready for final assembly after the printing time of the adhesive layer.

Figure 3 illustrates an exemplary flowchart of the main steps of the method for the manufacture of an anode electrode of a first embodiment of the electric battery of the invention and the main steps of the final assembly of the electric battery 10. The actual manufacturing steps of the anode of the rechargeable flexible electric battery 10 are preceded by step 30. In step 30 the roll-to-roll manufacturing equipment has ready either the metal/PET support film 150 or 170 or met- al/ferrite/PET support film 150, 190, 170.

In step 31 a material layer 160 comprising iron oxide and carbon is printed onto the support film used so that the geometrical shape and size of the printed layer correspond to the geometrical shape and size of the cathode. Also the coupling area 160a of the anode is formed of the same material mixture.

After the step 31 the semi-finished anode 2 can be connected to the semi-finished cathode 1. The final assembly of the electric battery of the invention is initiated in step 41 , in which the electrolyte 180 used is dispensed into the cavities formed by the insulating net 1 13 in the semi-finished cathode 1. The electrolyte 180 is advantageously potassium hydroxide (KOH). The electrolyte 180 is also dispensed onto the cathode advantageously as one work step of the roll-to-roll manufacturing process. After the electrolyte has been dispensed into the semi-finished cathode 1 , the semi-finished anode 2 is connected to it in step 42 so that the anode electrode 160 consisting of iron oxide and carbon presses against the insulating net 1 13 on the cathode, filled with electrolyte. The adhesive layer 1 14 encircling the outer edges of the semi-finished cathode 1 presses simultaneously against the PET film 150, which has been left pure and which is located on the outer edges of the semifinished anode 2, thus closing the outer edges of the battery 10 hermetically. When the semi-finished cathode 1 and the semi-finished anode 2 have been attached to each other, a hermetically closed electric battery 10 has been achieved, in which the outer surfaces of both the cathode and anode are protected by the metal films 1 10 and 170. In step 43 electrical connectors 16, 17, 18 and 19 are connected to the manufactured electric battery. The electrical connections can advantageously be implemented by crimped joints through the edge area of the electric battery, to which the coupling points 1 11 a, 121 a, 122a and 160a have been made during the manufacturing process described. When using crimped joints, holes have been manu- factured at the place of the connectors 16, 18 and 19 before the implementation of the crimp joint, for example, during the manufacture of the semi-finished anode 2.

It is obvious for one skilled in the art that the manufacturing process according to the first embodiment of the invention shown in the flowcharts in Figures 2 and 3 can be modified so that the coil included in the electric battery of the invention is provided in connection with the anode of the battery. Also the printing of the insulating net 1 13 can be made onto the anode electrode 160 instead of the cathode electrode.

Some embodiments of a rechargeable and flexible electric battery according to the invention and the manufacturing method of these have been described above. The invention is not restricted to the described solutions, but the inventional idea may be applied in several ways within the limits set by the patent claims.