A STRUCTURAL ELEMENT, A SET OF SUCH ELEMENTS AND A METHOD FOR PRODUCING IT

Abstract: A set of structural members comprise one or more rod-shaped element (25) comprising one or more co-axial metallic tubes (10, 18-20) which may serve as electrical conductors. One or more spaces (21-24) defined by the tube or tubes is/are filled with a compact solidified mass (17), such as plastic which may be injected into the tube or tubes by means of an injection moulding apparatus. The set may be used for simply providing a light and rigid structure, or it may be used for providing a highly flexible means of interconnecting a processor network of a number of members, the connection providing both power, data, light, gas and/or liquid.

Description: A STRUCTURAL ELEMENT , A SET OF SUCH ELEMENTS AND A METHOD FOR PROCUDING IT structure comprising such a set, and a method for producing the structural elements The present invention relates to a structural element of the type comprising at least 5 one elongated tubular metal body having inner walls defining at least one inner cavity. The relationship between bending strength and weight is much more favourable for a tubular body than for a solid rod-shaped body having the same cross-sectional size and shape. 0 The present invention provides a structural element of this type having a substantially improved bending strength. Thus, the present invention provides a structural element comprising at least one 5 elongated tubular metal body having inner walls defining at least one inner cavity, and a compact mass of a solidified material filling at least one such cavity. The compact mass may be of a material having a specific weight, which is substantially smaller than the specific weight of the metal. This means, that a 0 relatively thin-walled tubular body filled with such compact mass may obtain substantially the same bending strength as a corresponding solid metal member while the weight of the composite body comprising the metal tube and the solidified material may be substantially smaller than the weight of a corresponding solid metal body. 5 The tubular metal body may have any cross-sectional shape, such as circular or polygonal, and the tubular body may have a uniform cross-section along its total length, or the size and/or shape of the cross-section may vary along the length of the tubular body. 0 According to the invention the structural element may comprise at least two coextending, coaxial and radially spaced tubular bodies, and the cavity containing the compact mass may be defined between the inner wail of an outer tubular body and the outer wall of an inner tubular body. Thus, two or more cylindrical tubes may be arranged co-axially within each other and may be retained in their mutual positions by radial spacing means and/or the space or spaces defined between the tubes or tubular bodies. At least one and preferably all of the tubular bodies is/are made from electrically conductive material. When the compact mass is an electrically insulating material the radially spaced tubular bodies may perform a double function, namely as structural members and as electrical conductor. The tubular body may be made from any suitable metal, such as steel, aluminium or copper or any alloy of such metals. Preferably, however, the tubular body is made from stainless steel. The cavity or bore or all cavities defined within the structural element may be filled completely with the compact mass of solidified material. However, as another possibility the inner, central tubular body of said coaxial, coextending tubular body or bodies may define a longitudinally extending gas or liquid passage therein. The structural element may then function not only as a structural member, but also as gas or air conducting conduit. The compact mass may be an opaque material. However, in some cases the compact mass in at least one cavity may be a transparent material functioning as a light conducting material. The structural element may then function in the same manner as light conducting fibres. In order to allow the structural element according to the invention to be connected to another similar structural element or to any other object, the structural element according to the invention preferably comprises connecting means. The connecting means may, for example, comprise complementary male and female connecting means arranged at opposite ends of the structural member, respectively. As an example, the male and female connecting means may have a stepped configuration with radial steps corresponding to the radial spacing between tubular bodies. Thus, the aligned tubular bodies in a pair of interconnected structural elements may be in electrically conductive contact with each other and interconnected elements may then serve as electrical conductors. Alternatively or additionally, the connecting means may comprise threads formed on or connected to at least one end of the tubular body. In a preferred embodiment opposite ends of the element having mating inner and outer threads, respectively, formed thereon. As an example, outer threads may be formed in the outer surface of the tubular body at one end thereof, and inner threads may be formed in an inner surface of a sleeve, which is connected to an opposite end of the tubular body and which may receive an end portion of another similar structural element according to the invention and engage with outer threads formed thereon. The threads are preferably formed on complementary conical surfaces so that electrical contact may be obtained between the metallic tubular bodies of the interconnected elements. The electrical conductor and the surrounding tubular body may define a coaxial conductor. The compact mass may comprise any suitable material, which preferably has a specific weight substantially lower than that of the metal forming the tubular body. It is important that the mass completely fills out the cavity without any substantial inclusions of gas or air. Furthermore, the compact mass should preferably adhere to the inner walls of the tubular body such that the compact mass does not tend to be driven out from the tubular body when bending forces are applied to the structural element. The compact mass may, for example, comprise a thermoplastic material and/or a hardened glue. It is then possible to introduce the mass into the tubular body in a fluid or pasty condition and thereafter the mass may be hardened or solidified. The structural element according to the invention may further comprise at least one electrical conductor extending longitudinally through the inner of the tubular body and being electrically isolated from the tubular metal body, the conductor being embedded in the compact mass. In this case the inner cavity of the tubular body is defined between the outer surface of the electrical conductor and the inner surface of the tubular body. Such structural element may, for example, be used in electrical apparatuses, such as lamps and robots, and may at the same time serve not only as part of the supporting structure, but also as an electrical cable having one or more conductors. The structural element may comprise a first tubular conductor and a second preferably solid conductor extending within the first conductor and being electrically isolated therefrom so as to define a co-axial conductor within the tubular metal body. The invention also relates to a set of structural members for making a rod structure. In a first embodiment, said set comprising a plurality of structural elements as described above and pivot connecting members for pivotally interconnecting pairs of said structural elements. By means of such set it is possible to make structures of various kinds having pivotally interconnected parts. The connecting members may contain electrical conductors interconnecting the tubular metal bodies or other conductors of the interconnected structural elements. Thus, electric power may be supplied from a central power source to lamps, electric motors, actuators and other power consumers arranged in the structure via the conductors forming an integral part of the structural elements. The set of structural elements according to the invention may be used for making toys, robots, lamps etc. The first embodiment of the set of structural members may further comprise bearing connecting members for rotatably interconnecting pairs of said structural elements, and at least some of the pivot and/or bearing connecting members may include an electrically powered actuator, such as an electric motor. Thereby it is possible to build rather complicated structures adapted to special requirements from such set of structural members. Also, when structural members comprise electrical and/or optical conductors for transporting power, electrical pulses or light, the pivot connecting members preferably comprise means for transporting at least part of such power, electrical pulses or light from one structural element of the pair to the other. In a second embodiment, the set of structural members may be one wherein, or in addition, at least part of the connecting members comprise processing means communicating via electrical or optical conductors of the structural elements. At least part of the connecting members comprising processing means may comprise actuator means for performing a movement of an element, the actuator means of a structural element being controllable by the processor means of the structural element. In this manner, the structure now may comprise a network of distributed processors for use in a number of applications. One application may be that of a robot either for "serious" use or as a toy. An application of distributed processors for such use, which application is focussed on the typically limited power supply in battery powered units, may be seen in WO 98/45923. In that situation, at least part of the connecting members preferably comprise processing means comprising means for providing data for transmission to processing means of other structural elements, the data providing means being chosen from the group of data storages, sensors, or detectors. Such storages may be any standard data storages for use with processors and/or in computers. The data may be any type of data required for the individual processors to perform their intended operation. Sensors may be any sensors for use in e.g. robots, such as acceleration sensors, microphones, pressure sensors, strain sensors, light detectors, such as CCD's, temperature sensors, humidity sensors, movement sensors, velocity sensors, etc. In order for the structure to be able to move, the moving means are preferably adapted to perform a relative movement between two structural elements or between two connecting members. In that situation, the actual structure needs not merely be a stationary structure having the purpose of keeping the connecting members in contact, but the structure itself may perform the movement. This is especially possible due to the superior stiffness of the preferred structural elements. Alternatively or in addition to the two embodiments of the set of structural members, at least one of the connecting members may comprise means for generating a light beam and for transmitting the light beam into an optical conductor of at least one structural element, and wherein the at least one structural element is connected to a connecting member comprising means for receiving the light beam. Such transmitted light may be used for simple illumination and/or for data transport via the beam of light. Naturally, in any of the embodiments, the connecting members may be adapted to engage with any number of structural elements, such as 2, 3, 4 or more. Thus, such members may be l-shaped, T-shaped, Y-shaped, X-shaped, or star-shaped. Also, a manufacturer of sets of structural elements may choose to use different diameters, engaging means or the like in order to make his structural elements and connecting means incompatible with those of other manufacturers of such sets - independently on the internal structure of the elements and members and independently of the contents and operation of the members. Finally, as the structural elements may comprise a gas of liquid passage, the connecting members are preferably adapted to provide gas or liquid to a structural element or receive gas or liquid from one. In that manner, also gas or liquid may be transported through the structure via the structural elements. The present invention also relates to a method of producing a structural element, said method comprising introducing a material in a fluid or pasty condition into an inner cavity of a tubular metal body and solidifying the fluid or pasty material within the tubular body so as to form a compact mass of the material filling said cavity. The compact mass is preferably adhered to the inner walls of the tubular body. Therefore, the inner surface of the tubular body is preferably cleaned before introducing the fluid of pasty material therein and/or the inner surface of the tubular body is roughened so as to obtain a mechanical locking or a high friction between the inner surface of the tubular body and the solidified material. The material is advantageously introduced into an inner cavity or space defined between the inner wall of an outer tubular body and the outer walls of an inner, coaxial tubular body, whereby the structural element being produced may also serve as a tube or conduit for conducting air, gas, or liquid. The material may be a thermoplastic material, which is injected into the inner cavity of the tubular member in a heated condition. Such injection may take place under a high pressure, for example by using an injection moulding apparatus. Alternatively, the material may comprise two or more components, which are mixed immediately before injecting the mixture into the inner cavity of the tubular body, and which interact chemically so as to solidify the material. At least one longitudinally extending electrical conductor may be arranged within the cavity prior to introducing the fluid or pasty material therein, whereby the structural element produced may also function as an electric cable. The invention will now be further described with reference to the drawings, wherein Fig. 1 is a longitudinal sectional view of a first embodiment of the structural element according to the invention, Fig. 2 is a longitudinal sectional view of a second embodiment according to the invention, Fig. 3 shows in an enlarged scale one end of the element of Fig. 2, Fig. 4 is a perspective view of a pair of interconnected elements as that shown in Fig. 2 and a pair of different connecting links, Fig. 5 is an exploded perspective view of the pivot link shown in Fig. 4, Fig. 6 shows in an enlarged scale the connection between the rod element and the pivot link in Fig. 4, Fig. 7 and 8 are perspective views showing parts of structures, which may be made by means of a set of structural members according to the invention. The rod-shaped structural element shown in Fig.1 comprises a tube 10 made from metal, such as stainless steel. Outer threads 1 1 are formed at one end of the tube and a sleeve 1 2 fitting around and fastened to the opposite end of the tube extends axially from the opposite tube end. Inner threads 1 3 complementary to the outer threads 1 1 are formed on the inner surface of the sleeve 1 2. An electrical conductor 14 extending axially through the tube 10 has a projecting male part 1 5 at one end of the tube 10 and a female part or socket 1 6 extending into the inner space of the sleeve 1 2. The inner space or cavity of the tube 10 is completely filled with a solidified thermoplastic material 1 7 adhering to the inner surface of the tube wall so that the conductor 14 is embedded in the plastic material. Two or more rod-shaped structural elements of the type shown in Fig. 1 may be interconnected by screwing the outer threads 1 1 at one end of a first structural element into engagement with the inner threads 1 3 of a second similar structural element, whereby the male part 1 5 of the conductor 1 5 of the first structural element 8 is received in the female part 1 6 of the second structural element so as to establish electrical contact between the conductors 14 of the united elements. The thermoplastic material 1 7 may be heated and injected into the inner space of the tube 1 0 in its heated condition under a high pressure, for example by means of an injection moulding apparatus, whereby inclusions of air or gas in the plastic mass may be avoided. The bending resistance or bending strength of the structural element according to the invention is substantially increased compared to the bending resistance or bending strength of the metal tube 10, while the weight of the structural element according to the invention need not be much higher than the weight of the metal tube, because the specific weight of the plastic material is substantially smaller than the specific weight of the metal in the metal tube. The rod-shaped element shown in Figs. 2 and 3 comprises not only the outer tube 10, but also three further tubes 18, 1 9 and 20 arranged co-axially within the outer tube 10. Annular spaces 21 , 22, and 23 are defined between the tubes 1 0 and 1 8, 1 8 and 1 9, and 1 9 and 20, respectively. All of these spaces may be filled with a preferably electrically insulating mass or material 1 7. The mass or material 1 7 filling the spaces 21 , 22 or 23 need not be the same, but may be different and have different characteristics. As an example, the mass filling one of the spaces may be transparent and may serve as a light conductor for conducting light from a light source to a remote destination. The central space or bore 24 defined within the innermost tube 20 may also be filled with mass or material or may be unobstructed. In the latter case the bore 24 may be used as a conduit for directing a gas or liquid flow through a structure built by means of a set of structural members according to the invention. The lengths of the tubes 10 and 18-20 are different such that the tube end has a stepped configuration and the surface of each tube is exposed at the end of the tube. Fig. 4 shows a pair of rod-shaped elements 25 similar to the element shown in Figs. 1 and 2. These elements 25 are interconnected by a rotary connecting link 26 which may, for example, contain a bearing member allowing mutual rotation of the elements 25 around their longitudinal axis. One of the rod-shaped elements 25 is connected to a pivotal connecting link 27 allowing mutual pivotal movement of interconnected rod- shaped elements 25 around an axis extending at right angles to the longitudinal axis of the adjacent rod-shaped elements. As shown in Fig. 5, the pivotal connecting link 27 may comprise two co-operating parts, Figs. 5a and 5b, respectively, each having a substantially hemispherical housing part. The rim portions of these housing parts define a circular outer bead 30 and a complementary inner groove 31 , respectively. The housing parts are preferably made from plastic or a similar resilient material, so that the circular bead 30 may be pressed into engagement with the groove 30, whereby the link parts shown in Fig. 5 may perform a mutually rotational or pivotal movement. The link part shown in Fig. 5a includes a number of concentrically arranged, mutually electrically insulated circular conductors 32. The housing part comprises a protruding male stud member 33, which as shown in Fig. 4 may have a stepped configuration corresponding to that shown in Fig. 3. Each of the co-axial metallic tubes of the male stud member is electrically connected to a respective one of the circular conductors 32. Similarly, the link part shown in Fig. 5b includes a number of flaps 34 arranged in a pattern so as to engage with the corresponding circular conductors 32. The flaps 34 are in electrically conductive connection with corresponding co-axial metallic tubes incorporated in a female stud member 35. In the situation where the members are to also transmit light from one structural member to another, a light guide may be positioned in the centre of the elements 33 and 35, or a flap 34 and a circular conductor 32 may be replaced by circular light guides adapted to transmit light from one to the other. Naturally, these light guides are in optical contact with the light guides in the structural elements. Also, if the members are to also transmit gas or liquid, a guide therefor is provided in the centre of the members 33 and 35. In that situation, only the outer, circular light guide may be provided for additional optical "contact" . Fig. 6 shows a male stud member 33 and a female stud member 35, which may be interconnected such that opposite end surfaces of corresponding metallic tubes 18-20 come into electrical contact. Preferably, the engaging end surfaces of the tubes 1 8-20 are conical. 10 Rod-shaped structural elements 25, rotary connecting links 26, and pivotal connecting links 27 may be included in a set of structural members according to the invention. Such set may also comprise block-shaped connecting members 36 and 37 having bores for receiving the free ends of the rod-shaped elements 25 and connecting members 38 shaped so that the rod-shaped elements may be interconnected in almost any mutual angular position. Such set of structural members may be used for building robots, lamps and a wide range of other structures requiring supply of electrical power, gas, liquid, data and/or light. Such set of structural members is, of course, also excellent for use as a toy. Figs. 7 and 8 show examples of structures made from structural members. It should be understood, that the any of the connecting links may comprise an actuator, such as an electric motor, a light source and/or an electronic control device or any other electronic device. This actuator may either e.g. provide a sound or provide a movement of an element. This movement may be due to e.g. a rotation of a wheel connected to the connecting member, or the actuator may function between two structural members so as to e.g. alter an angle there between in order to enable the structure itself to move. Also, the members 36 or 37 may form part of a toy, such as a Lego® toy or a Knex® toy where the members are adapted to engage with standard Lego® or Knex® units and where the structural members form additional parts to the toy now providing interconnections as simple, stiff interconnections or interconnections also providing transport of power, data, light, gas, and/or liquid between members. This brings about a whole new type of toy or "apparatus" where distributed processors may be used. Such processors may be provided in all or some of the members 36 and 37, and they may communicate and be powered via the electrical and/or optical conductors in the elements 25. Also, the members 36 and 37 may comprise data generators, such as data storages or sensors or detectors providing data for the processors to take into account. 1 1 Such data may be visual data from e.g. a camera or CCD provided e.g. in a member 36 or 37 or as a separate unit providing data to a member 36 or 37. The data may also relate to a velocity, acceleration, and/or movement of the structure, or relate to the surroundings thereof, such as temperature, humidity, or to strain or force exerted on the structure. A toy may thus be made in the shape of e.g. a fire truck where water is transported through the structural elements from a reservoir to a fire hose, and wherein a siren may be comprised in one connecting member, light is provided at a central member and transported via structural members to the roof of the fire truck, and where e.g. the ladder of the truck is movable. The truck may be controlled by a single processor provided at one connecting member, the processor transmitting controlling signals to actuators, light generators, and other controllable parts via the structural elements, and the processor acting on data from e.g. a camera provided in another connecting member and feeding data therefrom to the processor via structural elements. Also, naturally, the fire truck may comprise any number of processors communicating via the structural elements for e.g. controlling different parts of the fire truck or for e.g. handling communication between the fire truck and a remote control handled by an operator. Naturally, this type of toy may be "upgraded" to a more "serious" robot now comprising a "skeleton" of rigid elements not merely performing the function of providing the structure but also that of providing communication, power, light, gas, and/or liquid from member to member in the structure. Thus, a structure comprising any type of processor or processing network and having any type of data generator or sensors/detectors may be made, and the enabling the processor(s) to act on the data and e.g. move or perform any other action, is simply a matter of programming. It should be understood that the material or mass 1 7 included in the spaces 21 -24 may serve as spacing members and/or electrical insulation. Therefore, in cases where the strength of the rod-shaped elements is not decisive, the mass or material introduced therein need not necessarily be compact, but may be more or less 1 2 compressible. Thus, the mass or material 1 7 may, for example, be foamed plastics material or may otherwise include air or gas-filled spaces.

Claims: 1 3 CLAIMS 1 . A structural element comprising an elongated tubular metal body having inner walls defining an inner cavity, and a compact mass of a solidified material filling said cavity. 2. A structural element according to claim 1 and comprising at least two coextending, coaxial and radially spaced tubular bodies, said at least one cavity containing the compact mass being defined between the inner wall of an outer tubular body and the outer wall of an inner tubular body. 3. A structural element according to claim 1 or 2, wherein at least one of the tubular bodies is made from electrically conductive material. 4. A structural element according to claim 3, wherein the tubular metal body is made from steel, aluminium, copper or any alloy thereof. 5. A structural element according to claim 4, wherein the tubular body is made from stainless steel. 6. A structural element according to any of the claims 2 - 5, wherein the inner, central tubular body of said coaxial, coextending tubular bodies defines a longitudinally extending gas or liquid passage therein. 7. A structural element according to any of the claims 1 - 6, wherein the compact mass in at least one cavity is a transparent material functioning as a light conducting material. 8. A structural element according to any of the claims 1 -7, further comprising connecting means formed on or connected to at least one end of the tubular body. 9. A structural element according to claim 8 comprising complementary male and female connecting means arranged at opposite ends of the structural member, respectively. 14 10. A structural element according to claim 9, wherein opposite ends of the element have mating inner and outer threads, respectively, formed thereon. 1 1 . A structural element according to any of the claims 1 -10, further comprising at least one electrical conductor in the form of a wire or rod extending longitudinally through the inner of one of the tubular bodies and being embedded in the compact mass, so as to be electrically isolated from the tubular metal body. 1 2. A structural element according to claim 1 1 , wherein the electrical conductor and the surrounding tubular body defines a coaxial conductor. 1 3. A structural element according to any of the claims 1 -1 2, wherein the compact mass comprises a thermoplastic material. 14. A structural element according to any of the claims 1 -1 3, wherein the compact mass comprises a hardened glue. 1 5. A set of structural members for making a rod structure, said set comprising a plurality of structural elements according to any of the claims 1 -14 and connecting members for interconnecting pairs of said structural elements. 1 6. A set of structural elements according to claim 1 5, wherein the connecting members are pivot connecting members for pivotally interconnecting pairs of said structural elements 1 7. A set of structural members according to claim 1 6 further comprising bearing connecting members for rotatably interconnecting pairs of said structural members. 18. A set of structural members according to claim 1 6, wherein at least two structural members comprise electrical and/or optical conductors for transporting power, electrical pulses or light, and wherein the pivot connecting members comprise means for transporting at least part of such power, electrical pulses or light from one structural element of the pair to the other. 1 5 1 9. A set of structural members according to claim 1 6, 1 7, or 18, wherein at least some of the pivot and/or bearing connecting members include an electrically powered actuator. 20. A set of structural members according to claim 1 9, wherein the actuator is an electric motor. 21 . A set of structural members according to any of claims 1 5-20, wherein at least part of the connecting members comprise processing means communicating via electrical or optical conductors of the structural elements. 22. A set of structural members according to claim 21 , wherein at least part of the connecting members comprising processing means comprise actuator means for performing a movement of an element, the actuator means of a structural element being controllable by the processor means of the structural element. 23. A set of structural members according to claim 21 , wherein at least part of the connecting members comprising processing means comprise means for providing data for transmission to processing means of other structural elements, the data providing means being chosen from the group of data storages, sensors, or detectors. 24. A set of structural members according to claim 22, wherein the moving means are adapted to perform a relative movement between two structural elements or between two connecting members. 25. A set of structural members according to any of claims 1 5-24, wherein at least a first connecting member comprises means for generating a light beam and for transmitting the light beam into an optical conductor of at least one structural element, and wherein the at least one structural element is connected to a second connecting member comprising means for receiving the light beam. 26. A set of structural members according to any of claims 1 5-25, wherein at least one structural element comprises a gas of liquid passage, and wherein at least one 1 6 connecting member is adapted to provide gas or liquid to the structural element, and wherein at least one connecting member is adapted to receive gas or liquid from the structural element. 5 27. A method of producing a structural element, said method comprising introducing a material in a fluid or pasty condition into a longitudinally extending inner cavity defined within a tubular metal body and solidifying the fluid or pasty material within the tubular body so as to form a compact mass of the material filling said cavity. 10 28. A method according to claim 27, wherein the material is introduced into an inner cavity or space defined between the inner wall of an outer tubular body and the outer walls of an inner, coaxial tubular body. 1 5 29. A method according to claim 27 or 28, wherein at least one longitudinally extending electrical conductor is arranged within the cavity prior to introducing the fluid or pasty material therein. 30. A method according to any of the claims 27-29, wherein the material is a 20 thermoplastic material, which is injected into the inner cavity of the tubular member in a heated condition. 31 . A method according to any of the claims 27-30, wherein the material comprises two or more components, which are mixed immediately before injecting the mixture 25 into the inner cavity of the tubular body, and which interact chemically so as to solidify the material. 32. A method according to any of the claims 27-31 , wherein the material is injected into the inner cavity by means of an injection moulding machine. 30

Inventors: REIPUR JOHN, REIPUR, JOHN
Applicants: REIPUR JOHN, REIPUR TECHNOLOGY A S, REIPUR TECHNOLOGY A/S, REIPUR, JOHN
Application year: 1999
Main classification: H01B7
IPC codes: A63H33, B29C45, F16L9, G02B6, H01B7, H01R24, H01R35