DE2413791C2 - Process for the production of bent incandescent filaments and device for carrying out this process - Google Patents

Description

The invention relates to a method for producing bent filaments for electrical purposes Incandescent lamps in which an initially straight filament is bent around a mandrel and then annealed.

With many incandescent lamps, e.g. B. projection lamps or car lamps, in particular, are bent into a U-shape Incandescent filaments required. The filaments usually consist of tungsten wire and can be used as a single or double helix.

In the known processes for producing such curved incandescent filaments, the filament is first either wound on a core wire or a core wire in the straight coil pulled off the winding mandrel introduced (FR-PS 11 35 579). Together with the core wire, the filament is then inserted into the desired bent shape. In this case, however, the gradient of the individual turns of the incandescent filament is on the inside the bend is considerably smaller than on the outside, so that there is a risk that the distance between the individual turns becomes irregular from one another and that the turns even touch in part, which causes a short circuit at these points and the & 5 Filament burns out. To avoid these disadvantages, it is already known to use the straight helix Core wire to be inserted with lugs to ensure the smallest possible winding spacing to provide the curved helix (OE-PS 2 17 567). This core wire is then etched by pickling, i.e. Dissolving in acid, removed again.

Furthermore, there is a method for producing incandescent filaments known in which the tungsten wire is wound on a core wire and to achieve a uniform Helical pitch at the same time an auxiliary wire is wound, which is between the individual Lays threads of the helix and whose thickness corresponds to the desired pitch. After bending and annealing the filament, the core wire and the auxiliary wire are then pickled away. These procedures are cumbersome and time-consuming and require at least one core wire that is later on chemical Paths must be removed.

The invention is based on the object of a method for producing bent incandescent filaments to be specified in the case of a core-free straight turn! assumed and a curved helix practical is obtained without a slope error. Core-free helix has so far been deformed in a kind of spinning process, however, significant slope errors occurred.

In a method of the type mentioned at the outset, the object is achieved in that according to the invention the core-free straight helix grasped at its ends and with its front end around the corresponding to the Helical bending speed is guided around its axis rotating mandrel, while the rear Helix end is tracked in a straight line in the direction of the original helix axis.

Since the bending mandrel and the front end of the helix move at the same angular speed rotates, there is practically no relative movement between the coil to be bent and the mandrel and thus no friction, so that the individual turns are evenly spaced from one another remains in place even though there is no core wire in the helix.

While in the known method provided with a core wire bent coils after The bending process can be removed from the bending device and annealed in a separate annealing furnace, takes place in the method according to the invention, the annealing of the bent coil immediately after Bending process on the bending device. This results in a further simplification and reduction in price of the whole Manufacturing process.

It should also be mentioned that the method according to the invention can be used with any type of incandescent filament, regardless of whether the helix ends run in the direction of the helix axis or at an angle to the helix axis.

The invention also relates to a device for carrying out the method described. This Device is characterized in that two pliers for gripping the ends of the coreless straight Helix are provided so that the helical front pliers can be guided on a circular path around a mandrel is arranged that these pliers and the mandrel rotatable about its axis at the same angular speed are driven according to the helix bending speed, and that the rear end of the helix gripping pliers arranged in the longitudinal direction of the original straight helix axis so that they can be tracked and is driven accordingly.

So that the annealing of the bent coil can take place on the bending device, the two pliers are expediently designed as contact pliers.

In order to prevent the heated ones from sticking during the annealing process To avoid the helix on the bending mandrel, it is preferably made of a non-metallic material, in particular made of ceramic.

The invention will now be described in greater detail using an exemplary embodiment shown in the drawing explained.

The figure shows the most important parts of a device according to the invention in a schematic representation, the initial state of the device with the incandescent filament still straight and the final state is shown with the U-shaped bent filament with solid lines.

With 1 and 2, two insulated pliers are referred to, which grasp the initially straight helix 3 at its ends 4 and 5. The axis of the straight helix is denoted by XX. The pliers 2 is together with a ceramic mandrel 6, for. B. from AI2O3, rotatable about an axis 7 according to the arrow Pi by both parts z. B. are arranged on a not shown, rotatable about the axis 7 common disc, namely the mandrel 6 in its center of rotation and the pliers 2 in its edge region. When the disk is rotated, the pliers 2 take the front end 5 of the helix 3 with it and guide it around the mandrel 6, which is forcibly driven in accordance with the helix bending speed. During the bending process, the trailing pliers 1 with the rear end 4 Jer incandescent filament 3 are tracked in a straight line in the direction of the original filament axis XX according to the arrow P2. After the bending process, the pliers 1 and 2 and the incandescent filament 3 have assumed the positions shown with solid lines.

Then, by applying an electrical voltage to the contact tongs I and 2, the bent Coil 3 is heated and annealed under a protective gas atmosphere, whereby it anneals stress-free. As a result, and because the dome 6 is forced to run along with the front pliers 2 During the actual bending process, a bent, tension-free helix 3 has arisen, which is practical has no slope errors.

1 sheet of drawings

Claims (5)

Patent claims: 1. A method for the production of bent filaments for electric incandescent lamps, in which an initially straight filament is bent around a mandrel and then annealed, characterized in that the core-free straight filament (3) is detected at its ends (4, 5) and with its front end (5) is guided around the mandrel (6) rotating around its axis according to the helix bending speed, while the rear helix end (4) is tracked in a straight line in the direction of the original helix axis (XX). 2. The method according to claim 1, characterized in that that the annealing of the bent coil (3) immediately after the bending process on the bending device (1,2,3) takes place. 3. Device for performing the method according to claims 1 and 2, characterized in that two tongs (1, 2) for gripping the ends (4, 5) of the coreless straight helix (3) are provided, that the helical-guiding front pliers ( 2) is arranged on a circular path around a mandrel (6) so that these pliers and the mandrel rotatable about its axis are driven at the same angular speed corresponding to the helical bending speed, and that the pliers (1) engaging the rear end of the helix in the longitudinal direction of the original straight line Helical axis (XX) is arranged so that it can be tracked and is driven accordingly. 4. Apparatus according to claim 3, characterized in that the two pliers as contact pliers (1,2) are formed. 5. Apparatus according to claim 4, characterized in that the mandrel (6) consists of a non-metallic Material, preferably made of ceramic. 40