US2117132A - Releasable permanent magnet holding device - Google Patents

Description

M. BAERMANN, JR

May -1 0, 1 938.

' RELBASABLE PERMANENT MAGNET HOLDING DEVICE Filed July 22, 1935 [III] BY 4. iflM ATTORNEY Patented May 10, 1938 RELEASABLE PATENT OFFICE PERMANENT MAGNET HOLD- ING DEVICE Max Baermann, Jr., Cologne, Germany Application July 22,

In Germany Thainvention relates to a releasable permanent magnet holding device particularly for electric lamps which will adhere in any position to objects made of ferro magnetic materials.

It is known to provide electromagnets in the foot of an electric lamp but the use of such electromagnets has in practice many disadvantages. Direct current is necessary for their excitation, and that, unless D. C. mains are available, must be taken from a battery. When there are D. C. mains they commonly have so high a voltage that a magnet lamp supplied directly from them is dangerous to use.

Where there is an A. 0. supply this danger may be avoided by transforming down the voltage; but then a rectifier is necessary for supplying the electromagnet. So that in both cases complex apparatus liable to go out of order is necessary for the operation of a magnet lamp.

A further disadvantage of the known arrangement is that if the current fails, or falls oil on account of faulty contact, defect in the rectifier, or failure of the supply, the lamp no longer adheres, and unless the lamp is otherwise sufllciently supported it falls.

These disadvantages are avoided in the present invention by the use of permanent magnets of so high a coercive force .as to ensure adherence of the device to a support. A suitable material for such permanent magnets is an alloy having a coercive force of more than 240 and preferably more than 300 Oerst'edt.

To give the support and holder maximum utility a further feature of the invention contemplates the combination of magnets and pole shoes in the shape of a horseshoe magnet so that two similar flat poles, preferably of prismatic cross section, stand opposite one another, each terminating in two similar projections bounded on their ends by a plurality of mutually inclined planes. This form of pole shoe has in the middle of its contact surface a notch broadening outward while the outer edges are bevelled oil. Such a shape of pole face in combination with the horseshoe form is of great importance as regards the adherent power since two separate magnet poles will almost always be able to seat themselves simultaneously upon an object of whatever form it may be. Other forms of magnet, for instance, the iron clad magnet in which a central pole is surrounded by an annular pole, do not always enable both poles to contact with an object, moreparticularly if the latter has a curved airface. But the horseshoe form with projections bounded by slanting surfaces will suit almost 1935, Serial No. 32,878

July 23, 1934 any profile sufllciently to ensure the But a support or holder fitted with such strong I magnets could only be lifted from an object by the use of great force. A further feature of the 5 invention therefore contemplates the provision of a short circuiting device for the magnetic flux which facilitates the removal of the holder from an object to which it has been adherent. The magnetic short circuit is preferably in the immediate neighbourhood of the pole pieces for experiments have shown that with such strong magnets a short circuit is not always effective enough if applied only to the rear part of the magnet pole.

In accordance with the invention the two pole shoes are of U form with limbs of different length and are arranged on the two sides of the magnet with their shorter limbs applied to the magnet and the longer limbs forming the pole pieces, and the short-circuiting plate is arranged at the curve of the pole shoes. In this construction of the magnet limb a short-circuiting plate may be arranged on the rear side of the pole pieces without impairing the short circuiting action. The production of this form of holder is simple, cheap and easy.

An electric lamp may be attached to the holder'in any suitable fashion as, for example, by means of a wing nut. But the holder may be employed not only for supporting electric lamps but also as a support or hanger for any objects whatever. Where considerable strength is needed the invention provides a flat plate in which several separate permanent magnets are arranged one beside the other with their unlike poles opposite. To remove such a plate from an object to which it-is adherent, or to remove objects from the plate, the poles of the separate magnets must be short-circuited.

Such short-circuiting may be effected by movement to and fro of a short-circuiting armature at the rear of each magnet, preferably so that the several armatures move in succession and not simultaneously to lessen the power needed. For this purpose the armatures are preferably connected with cams upon a common shaft so ar-. ranged that when a particular position is reached all the armatures are freed and applied to the poles of the magnets. Such an arrangement is especially of advantage for magnets carried in a plate andhaving U-shaped pole shoes since the short-circuiting armatures may without detriment to the short-circuiting efl'ect be applied to the rear faces of the pole ends.

ill

Instead of effecting the short-circuiting by means of separate armatures it may be eflected by a leaf spring which in the short-circuiting position contacts with all poles and is pressed away from thempl ya cam or the like separating from them one after the other owing to its elasticity.

The accompanying drawings show examples of construction of the invention. 1 I

Figure 1 is a vertical longitudinal section through a holder with U -shaped pole shoes.

Figure 2 is a detail end view showing the form or the pole pieces of Figure 1.

Figure 3 is a vertical section through e-plate with inset magnets and with armatures actuated by a cam shaft.

Figure l is a view" at right angles to 3 section on the line E f-IV of Figure u e 5 is a vertical. section through a oset magne Winch the separate maghe shcrt-circuited by a leaf spring.

"""gure 6 is a plan of the plate.

the construction of holder shown in Figure 1 two iii-shaped pole pieces [3 with limbs of unequal length are secured by their shorter limbs M to the bar magnet l5 by means of a bolt l6, while the longer limbs l1 form the pole pieces. Each pole shoe l3 terminates in two projections l l bounded by inclined surfaces so that between the projections there is a notch broadening outward, while the outer edges of the projections are bevelled. This form of projection enables the device to contact sufficiently not only with concave and'jcpnvex surfaces but also with profiles of almost any form. The short-circuiting plate I9 is applied to the flattened bends l8 oi the pole shoes l3. When the holder is required to adhere to an object of magnetic material this plate is turned by meansoi the bolt 28 attached to itand so lifted from the pole shoes by the action of a pin it upon the curved surface oi the guide bush 22. A thumb piece 23 serves for turning the bolt to. The guide bush 22, the bolt 2e and a casing 2t surrounding the whole device are made oi non-magnetic material such as brass. On the pole piece side the device is protected irorn ingress of iron particles and dirt by a plate 25 oi non-magnetic material such as brass.

When large surface is required to which ar .tioles are to adhere or when greatstrength is necessary as, for instance, in chucks, a number oi adherent devices 2? may be mounted in a plate it or non-emagnetic material such as brass, their pole shoesloeing oi the form shown in Flg== are l. The several armatures 28 are actuated by cams 30 upon a. common shaft 29, the cams being of such form that on turning the shaft the armatures are lifted in succession from the magnets and in an end position are all applied to the magnets. Figures 3 and 4 illustrating this mechanism are of a diagrammatic character, but those skilledin the art will readily understand how to shape the cams with the necessary dwell to cause the armatures to be applied in succession, each armature then remaining-in engagement however until all are engaged. Alternatively, as shown in Figure 5, short-circuiting may be eflooted by a spring 3i which in the short-circuiting position contacts with all the magnets. Here again the figure is diagrammatic and in practice the spring 6 might need to be made thicker at any rate in the parts forming the actual armatures, to c y the pressed dot i '1; cam causes to eparate from the several in succession.

F. claim:

1. releasable permanent magnet hold ng device comprising a permanent magnet, iii-shaped pole shoes having limbs of unequal length, the shorter limbs being applied to the ends of said magnet, a short-circuiting armature, and means for bridging said armature across the bends oi the pole shoes and removing it therefrom.

2. A releasable permanent magnet holding device comprising a non-magnetic plate, a plurality of permanent magnets mounted in said plate, an armature for each magnet movable with respect to said plate into and out of short circuiting position relatively to its magnet, a shaft, and cam means thereon co-operating with the said armatures upon rotation of the shaft to remove them successively from their magnets.

3. A releasable permanent magnet holding device comprising a non-magnetic plate, a plurality of permanent magnets mounted in said plate with their poles in one a spring secured to said plate and lying along the line of poles, and means for pressing ,the end of said spring away from said poles so that said spring separates from the several poles in succession.

l. A releasable permanent magnet holding device comprising a permanent magnet, U shaped pole shoes having limbs of unequal length, the shorter limbs being applied to the ends of said magnet, a'siiort circuiting armature, and means including a rotatable shaft and a cam for bridging said armature across the bend of the pole shoes and removing it therefrom;

MAZQ-BAERMABW, Jim.

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