Electromagnet

Details Electromagnet Electromagnet

1999-02-08

2001-05-01

Barrera, Ray (Department: 2832)

Electricity: magnetically operated switches, magnets, and electr

Magnets and electromagnets

With magneto-mechanical motive device

C335S262000, C335S270000, C335S277000, C251S129150

Reexamination Certificate

active

06225886

ABSTRACT:

BACKGROUND TO THE INVENTION
The invention relates to an electromagnet, comprising a coil which can be supplied with current and which thus generates a magnetic field and moves an armature when supplied with current, and wherein the armature serves for controlling a valve or another element, the movement of the armature being damped by one or more damping elements.
Aforementioned electromagnets are widely used in the field of engineering. They serve, for example in textile machines, for a rapid weft insertion.
The above-described electromagnets also serve, however, for the control of gaseous and liquid media (in particular in liquid or hydraulic circuits), for example in a valve or as a control electromagnet or solenoid in applications where service life and time are critical.
Use in weaving machines or other textile machines, particularly, demands a high performance of electromagnets. The electromagnets are expected to achieve extremely high service-life requirements and switching frequencies. This results in considerable mechanical stresses on the electromagnet and the movably mounted elements.
German patent 31 32 396 describes an electromagnet which uses resilient elements as damping bodies which absorb the kinetic energy of the armature and thus avoid premature wear of the electromagnet.
In order to achieve the high clock frequencies, corresponding accelerations of the armature must be achieved. Particular importance is attached in this regard to the bearing of the armature, since an inaccurate bearing of the armature can lead to unequal stress on the damping elements, which then wear preferentially at these locations, and then jeopardizes the entire usability of the device.
Owing to the high frequencies, there is also considerable development of heat in the magnet coil. This leads, for reasons of design, to larger air gaps in order to allow constructionally for the thermal expansion of the components. However, on the other hand, this limits the effective magnet gaps and thus reduces the efficiency of the device.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is to improve electromagnets as described above in such a way that they have a longer average service life and a higher efficiency.
To achieve this object, the invention starts out from an electromagnet comprising a coil which can be supplied with current and which thus generates a magnetic field and moves an armature when supplied with current, and wherein the armature serves for controlling a valve or another element, the movement of the armature being damped by one or more damping elements. According to the invention, the armature runs on a plastic sliding surface, in particular a sliding film of plastic, such as a plastics film on which the armature slides. The use of a film is a clever way to solve the problem of the thermal expansion, since the inserted film undergoes little thermal coupling by virtue of the small degree of mechanical contact with the rest of the device and thus a smaller constructional air gap is necessary. It has also been found that the film bearing serves for a precise and low-wear bearing of the armature, whereby transverse forces or misalignments of the armature are optimally compensated for, leading to a comparatively uniform loading of the damping elements. As a result, unequal wear of the damping elements is avoided, thereby resulting in a high reliability and long service life of the electromagnet.
The film bearing has proved to be particularly wear-resistant. The thin-walled film means a saving of space without impairing the mechanical reliability or stability. Small and relatively accurately definable bearing gaps reduce the air-gap losses at the magnetic transition, thereby improving the magnetic properties of the magnet and thus also increasing the efficiency. There is also an advantage here in terms of the production of the device. In the known armature guides, the armature runs on the inner surface of a tube. This tube was produced, for example, by making a bore in a solid material. For armature guidance which is as precise as possible, it was necessary to make the bore in the tube as accurately as possible. This high outlay is saved by the proposal according to the invention. There are no longer any exacting requirements to be considered as regards the surface quality of the tube, since this task is taken on by the plastic running surface, in particular by the inserted film. The solution according to the invention thus leads to a lower-cost construction and a simpler assembly of the device.
Besides the use of a plastic film, it is also possible to allow the armature to slide on a suitably designed plastic surface. In this case, this surface takes on the task of the film.
A further advantage of the design according to the invention lies, in particular, in the possibility to compensate for dimensional tolerances during the production of the electromagnets by suitable variation of the thickness of the film. Hitherto, magnets which had too great a dimensional tolerance were automatically rejected, since the excessively large air gaps limited the performance or efficiency of this device and thus were no longer usable for certain applications. Since the movable armature slides on a plastic sliding surface, the thickness of this surface can be adapted so that optimal conditions exist. It is thus possible, by suitable selection of the film thickness, to compensate for dimensional tolerances during production, when testing the devices. This advantage also arises when the devices are being overhauled. If the device is worn, in particular at the movable parts, owing to the long lifetime, it is possible to overhaul and restore the device simply and at low cost by suitably exchanging these movable parts and the plastic sliding surface cooperating therewith, and where appropriate a thicker sliding surface. The advantages resulting therefrom in terms of reusability and recyclability of the costly devices are obvious.
Besides the use of a plastic film, there is provision, for example, in the known armature guide for the use of a bush fabricated from special plastic, on the inner surface of which the armature slides. A further variant which is possible is a plastic coating on the inner surface of the armature guide facing the armature.
The use of the plastic film enables the film to be dismounted more easily, in particular when the armature can be removed simply from the core. In the event of the film being worn, it can be easily be exchanged and the device rendered usable again.
In a preferred design of the invention, a modular construction of the electromagnet is provided in which, for the armature with the armature guide and the coil, there is provided in each case a separate assembly which are releasably connected to one another. Such a design results in a simpler and lower-cost construction and assembly of the electromagnet. It is also possible to perform simple maintenance of the electromagnet, since the appropriate assemblies can be exchanged as required. A releasable connection may be achieved, for example, by a suitable screwed or clamped connection. This results not only in an advantage in terms of the assembly and construction of the electromagnet, but an advantage is also achieved in terms of the operation of the device. By virtue of the separate design, a substantial thermal decoupling of the electromagnet or the coil on the one hand and the armature assembly on the other hand is achieved. Since thermal conduction takes place essentially through direct contact of these two assemblies, it is possible to reduce the thermal contact by dispensing with or reducing a direct connection, whereby the thermal problems in particular at the high frequencies described can be significantly diminished, leading to an increase in the reliability of the device. As an alternative to this, however, it is also possible to construct the device as a non-separable unit. In this case, for example, fixed, unreleasable connections are used. The assemblies to be connected to one another are in this

Affiliated with

Also associated with

Rating

Electromagnet does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Electromagnet, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electromagnet will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2531666