Technical Field

The invention is a power grid tube formed by a bundle of longitudinal parallel conductors at a selected distance, which are wound with a conductor of a selected pitch, where both conductors are connected at the crossing points by welding. The invention further relates to a method of manufacturing a power grid tube.

Background Art

Accurate and repeatable winding of the grid tube is a basic prerequisite for quality production of grid tubes. An inaccurate and unrepeatable technological process can lead to the production of scrap. In piece production, the entire technology is implemented manually. The operator winds the grids on a special mandrel and then manually rotates the mandrel and spot welds the spiral onto the grid. A mandrel with winding pins is used as standard. This mandrel is relatively difficult to produce, which brings with it considerable financial costs. Furthermore, the mandrel contains grooves for guiding the wires. It is technologically very difficult to produce these grooves. Adherence to the required dimensions and accuracy again entails considerable financial costs. First, the longitudinal wires are wound over pins. After winding all the longitudinal wires, the conductor helix is wound with a precisely defined pitch. The wires of the helix of the conductor are spot welded to the longitudinal wires, in the order of a thousand points. The resulting grid is secured from below with tantalum tape, which is again spot welded on all the longitudinal wires. Then the wound grid is removed from the mandrel and a special lid is welded onto it. The prior art in this field is described in particular in US7880375B2 or US3826948A. Disclosure of Invention

The essence of the invention is a power grid tube formed by a bundle of longitudinal parallel conductors at a selected distance, which are wrapped with a conductor at a selected pitch, where both conductors are connected by welding at crossing points. At one end the bundle of conductors is capped and at the opposite end the bundle of conductors is wrapped with tape, and at the point of contact of the cap and the tape with the conductors welds are formed.

It is advantageous if the parallel conductors are made of molybdenum and if the cap is made of tantalum, because of their suitable physical-chemical properties.

It is also advantageous if the pitch of the conductor is greater than 1°. Such a pitch guarantees a sufficiently dense network for the power tube conductor.

The invention also relates to a method of manufacturing a power grid tube, in which the mandrel fits the caps at both ends. The mandrel defines the dimensions of the manufactured power grid tube. Tensioning, or the controlled stretching of the wires in the longitudinal direction, i.e. in the axis of the winding mandrel, is realized by means of a clamping device and a braked wire spool. When tensioning in the transverse direction, when winding the longitudinal bundle of conductors with a transverse conductor at the selected pitch, the rotation of the mandrel and the braked coil is used to feed the wire into the mandrel space. The wire is spot welded to the longitudinal axis of the grid, i.e. to the wire of the longitudinal grid, and it is pulled and wound on the mandrel by rotation.

The caps are connected by a bundle of parallel conductors which are welded to the caps, after which the bundle of parallel conductors is wound with a conductor with which they are welded together at the crossovers. In the vicinity of one of the caps, the wires and the wrapping tape with which it is welded, the bundle of wires between the lid and the tape is broken and the finished grid is removed from the mandrel.

It is advantageous if the mandrel with the tube is cooled before removal by placing it in a cold environment, which guarantees easier removal of the power grid tube from the mandrel.

Description of drawings

In Fig. 1 and Fig. 2 is an isometric view of the power grid tube. Fig. 3 shows a view of the device for producing the power grid tube and the position of the mandrel. Fig. 4 is an isometric view of the mandrel.

Description of example embodiment

The grid of the power tube is formed by a bundle of longitudinal conductors V. The longitudinal conductors V are arranged in parallel at a selected distance. The longitudinal conductors V are wound with a conductor S at a selected pitch, where both conductors V and S are connected at the crossing points by spot welding. At one end, the conductor bundle V is provided with a cap 1, and at the opposite end, the conductor bundle V is wrapped with tape 2. The conductor in the form of the wires V consists of a molybdenum-based material. The wire has a diameter of approximately 0.28 mm. The cap 1. consists of a tantalum- based material. Spot welds are formed at the point of contact of cap 1 and tape 2 with conductors 1 and 2.

The mandrel T is provided with caps 1. at both ends. The mandrel T is fixed to the rotating motor by means of a coupling. On one side, the mandrel T is mounted in a conductive bearing L, which allows the transmission of electrical energy from the spot welding device B. The chuck travels by linear electric motor to the beginning of the mandrel T. The bundle of the parallel wires V is clamped in the chuck which tensions the bundle V to the right to the other end of the mandrel T. The wire of which the bundle of parallel wires V consists is unwound from the braked coil 3. The tension of the wire is approximately 50 N. The wire is guided in the axis of the mandrel T. The caps 1 are connected by a bundle of parallel wires V which is welded to the caps, after which the bundle of parallel conductors V is wrapped with a conductor S, with which they are welded together at an intersection. In the vicinity of one of the caps 1 the conductors V and S are wrapped with a tape 2 with which it is welded. Then the bundle of conductors V between the cap 1 and the tape 2 is broken and the finished grid is removed from the mandrel T.

Welding of the longitudinal conductor V takes place after unwinding the wire of which the conductor V consists. Then, the spot welding tip is moved by biaxial robot R to the point of overlap of the wire with the circumferential surface of the lid 1 on one side of the grid. The tip is pressed with a defined force, and when the required force is reached, spot welding occurs. The welding is repeated again with a tip shift of approximately 1 millimetre. There are two spot welds on one conductor V on one cap . Then the tip of the robot_R passes over the right cap 1 and performs the same welding procedure. Then the clamp tears the rest of the conductor V at the right cover 1. by moving it upwards. The conductor V is thermally affected at the spot welding, therefore tearing off the conductor V is possible and very effective. Then the clamp moves to the left side, clamps the conductor V and again by moving up tears the conductor V from the side of the left cap 1.. Next, the mandrel T is turned by a defined angle by means of a servomotor. The clamp still holds the wire V and moves it to the right again. The whole process is repeated until all the conductors V in the longitudinal axis are welded. In this exemplary embodiment, there are 90 wires that are angularly offset from each other by 4° with respect to the centre of rotation of the power grid tube.

The transverse welding of the conductor S in the form of a wire is conditioned by the welded longitudinal axis of the grid. For the quality of the welded grid, it is necessary to use a guide ring on the conductor straightening system S. The ring is placed on the mandrel T, or the welded axis, such that in this exemplary embodiment all 90 conductors in the bundle slide into the 90 grooves. To weld the conductor S, an unwinding device O is used, located behind the device perpendicular to the longitudinal axis of the mandrel T. Welding of the conductor_S begins by welding the wire on the cap 1 on the longitudinal axis of the grid, i.e. in the bundle of longitudinal parallel conductors V.

Then, by means of a servomotor, the mandrel T is rotated to the position of another conductor S, and by means of a linear motor, the conductor S consisting of a wire of helical pitch is moved, and this movement at the same time moves the straightening ring. Next, the wire is welded that crosses the longitudinal axis wire. This process is repeated until the entire grid is complete. Finally, a circumferentially overlapping plate is welded to the end of the grid to terminate the grid. The sheet is inserted manually and requires an operator during the welding process. Then the conductor S is cut off manually. When the tube grid is welded, the whole mechanism must be disassembled again to remove it. The rest of the conductor_S is cut off after welding and then the winding tip, guide ring, guide sleeve and then the whole winding mandrel T are removed. After disassembling the mandrel T and releasing the caps 1 of the grid, the grid cannot usually be removed from the mandrel T, its left part behind the end plate must first be cut off.

The mandrel T on which the grid is mounted is then cooled for several minutes in a freezer or in liquid nitrogen.

Industrial applicability

A power grid tube formed by a bundle of longitudinal parallel wires at a selected distance, which are wound with a wire at a selected pitch, where both wires are connected by welding at crossing points and its method of production can be applied especially in the production of triode and tetrode grids used mainly for laser cutting systems, dielectric or induction heating.