The current invention relates to magnetic assembly means having a everlasting magnet as a supply of magnetic potential producing meeting forces. More specifically, the invention pertains to assembly technique of this kind appropriate to be used in chemically aggressive environments with out there being any attainable detrimental influence on the assembly forces
Such meeting means may, for example, be utilized in odontology for sustaining dental prostheses in place. DESCRIPTION OF THE PRIOR Art
U.S. Pat. No. 4,431,419 discloses retaining means for dental prostheses having a cap inflexible with the dental prosthesis and having a housing of a ferromagnetic material with a everlasting magnet housed therein. This housing varieties part of a magnetic circuit which is closed, when the prosthesis is in place, by a ferromagnetic counterpiece anchored in the denture. The housing is hermetically sealed by a masking layer which protects the magnet from the salivary setting.
On this earlier system the protecting layer is of a plastics materials, extra specifically acrylic resin which covers one of many faces of the magnet and which is sealed to the interior periphery of the wall of the casing.
When the cap and the counterpiece are assembled, this overlaying layer is interposed between the magnet and the counterpiece, thereby offering a flux gap, i.e. a excessive reluctance passage in relation to the circulation of flux developed by the permanent magnet. An meeting force is thus achieved which is far smaller than the power which the magnet might develop within the absence of the flux gap.
Another drawback of this earlier association resides in the truth that a considerable part of the magnetic flux circulates alongside the leakage path by way of areas of the mouth within the neighborhood of the prosthesis which could possibly be harmful to the wearer thereof, causing dentists to be reluctant to make use of such prostheses for their patients
French patent application No. 86.06805 dated May 9, 1986 offers an preliminary resolution to the problems associated with the meeting technique of U.S. Pat. No. To read more info in regards to Big Power Neodymium Magnet On Sale review the web-page. 4,431,419 in that it proposes the alternative of the protecting layer of plastics material by a overlaying layer formed from a really thin pellet product of a everlasting magnetic materials.
However, while this answer does provide an enchancment in respect of the magnetic facet, since it succeeds in lowering the dimensions of the flux hole, however, it creates manufacturing and sealing issues since the pellet needs to be welded to the casing or mounted between the edge of the peripheral wall of the casing and the magnet itself. Moreover, it’s difficult to supply a thin pellet of this kind. Brief DESCRIPTION OF THE INVENTION
It’s an object of the invention to offer permanent magnetic assembly means combining good safety for the magnet with maximum efficiency of magnetic attraction, rendering it significantly appropriate to be used in odontology.
It is thus an object of the invention to supply magnetic assembly means for the meeting of two objects, the first of which has a magnetized capsule and the second a counterpiece of a ferromagnetic material, mentioned capsule comprising, on the one hand, a casing of a ferromagnetic material during which a everlasting magnet is housed and which forms part of a magnetic circuit for the flux of the magnet, the circuit being closed by mentioned counterpiece when the 2 objects are assembled and, alternatively, a cover for hermetically sealing stated casing, whereby mentioned cover is of a ferromagnetic materials and the bottom and the wall of the casing are linked to one another by a thin peripheral partition constituting a saturable zone and defining a boundary at the bottom of mentioned wall of a peripheral polar piece which kinds, with said counterpiece and mentioned bottom, a path of weak reluctance for the flux of said magnet.
In consequence of those features, the magnetic circuit conveying the flux of the everlasting magnet is closed by way of the underside of the casing, the counterpiece and the lateral wall of the casing, with out interposition of a flux hole, because the underside and the peripheral base of this lateral wall can relaxation instantly on the counterpiece. The traces of magnetic drive developed by the everlasting magnet are thus nearly completely utilized.
Complete tightness is guaranteed on the interface of the capsule and the counterpiece since the bottom, the intermediate partition and the lateral wall are formed in a single piece. It is then relatively simple to provide a tight closure on the cover facet via welding for instance, the cover and the casing each being fabricated from ferromagnetic material. Moreover, the part of the casing opposite the counterpiece can simply be lodged in the thing which receives the capsule to make sure even higher tightness. That is notably the case in the applying of the means for the retention of dental prostheses wherein the capsule might be moulded throughout the structure of the prosthesis with only the outer face on the counterpiece aspect of the capsule being uncovered. Brief DESCRIPTION OF THE DRAWINGS
The invention shall be better understood from a research of the next description give for example of the embodiment of the invention:
Within the hooked up drawings, given solely for purposes of illustration:
FIG. 1 shows an overall sectional view of a magnetic meeting means in keeping with the invention as used for retaining a dental prosthesis;
FIG. 2 is a sectional view on a larger scale of the assembly technique of the invention;
FIG. Three is a diagram of the strains of flux developed by the magnet in the magnetic meeting means.
FIG. Four is a common view of a dental equipment also in keeping with the invention. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
Whilst the next description is specifically related to the application of the invention to odontology it is clear that the magnetic assembly technique of the invention may be advantageously employed in all instances where it is important to provide good bonding between two objects with minimal area occupied by the assembling means and providing efficient protection for the magnet in the environmental medium.
FIG. 1 shows a magnetic assembly means the capsule 1 of which is mounted in the first object O1, namely a dental prosthesis, the counterpiece 2 of which is anchored within the second object O2, on this case the foundation of a tooth.
The counterpiece or implant 2 is formed by a shank 3 (FIG. 2) designed to be cemented in standard method into the radicular channel of the basis of the tooth, this shank being surmounted by a cover four tailored to the shape of the gingival mucosa. This cover could also be circular.
The capsule 1 includes a casing 5 made of ferromagnetic materials corresponding to an alloy of the ferro-nickel type having excessive saturation induction. The material sold under the Trade Mark “Permanom” by Vacuum Schmelz of Hanau, Federal Republic of Germany is appropriate. The outer form of the casing 5 could be apart from cylindrical, notably within the case of an software differing from that envisaged herein.
The casing 5 has a bottom 6, a peripheral partition 7 enclosing this bottom and an outer wall 8, the base 8a of which is partially indented by a circular groove 9 opening in direction of the operational surface 10 of the capsule (the decrease floor of the capsule within the position proven in the figures). The depth of this groove determines the thickness of the partition 7 and to a considerable extent the magnetic behaviour of the meeting.
The underside 6 is hollowed out to kind a housing 11 for the decrease part of the permanent magnet 12, the north and south poles of which are situated on the two opposing surfaces, it being understood that the magnet can be placed in an reverse position to that proven. The flux developed by this magnet is thus oriented alongside the X–X axis of the assembly means. The magnet 12 is ideally made of an alloy having a excessive vitality product, resembling for example samarium-cobalt.
A cover 13 of ferromagnetic materials is fitted in the top of the casing 5. It’s mounted in place with the help of a peripheral welding band 14 obtained, for example, by laser welding. To prevent this band from projecting past the higher face of the capsule 1, the outer wall eight is provided with a raised annular edge 15.
The outer cylindrical surface of the wall 8 is supplied with two annular grooves 16 to permit the capsule 1 to be anchored in the body of the dental prosthesis.
FIG. Three shows a diagram of the lines of pressure of the magnetic subject generated within the capsule 1. The slender passage formed by the peripheral partition 7 is so dimensioned that it is saturated as a way to constitute a zone of very excessive magnetic reluctance. The traces of power are thus concentrated by means of the base 8a of the peripheral wall of the casing where they create a excessive engaging power. This base thus forms a peripheral polar piece.
These strains of drive move into the cover 4 and return to the bottom 6 without passing by means of a flux gap capable of making any substantial magnetic reluctance. To scale back this reluctance at the flux hole to a negligible worth the contact faces are preferably rigorously polished.
From the other facet of the magnet the traces of pressure circulate by the cover thirteen and from there into the outer wall 8 additionally with out encountering a flux gap, the cover 13 being tailored with precision to the diameter of the opening of the casing 5.
It has been present in apply that a casing of an outer diameter of the order of 4.5 mm, of a top of 2.00 mm, provided with a samarium-cobalt magnet of a diameter within the region of three mm and a top of about 1 mm can have a partition thirteen the thickness of which is between 0.05 and 0.1 mm relying on the forces of attraction to be achieved. It is obvious that completely different dimensions of the meeting means are potential both within the framework of the foregoing utility and in other purposes of the invention.
Reverting to FIG. 1 it is obvious that, as in contrast with the prior art proposals, the assembly means for dental prostheses of the invention has a capsule 1 which is positioned in inverted condition, i.e. with a backside which is utilized to the cover of the implant. On its reverse face this capsule is in direct contact with the plastics supplies of which the dental prosthesis is composed. There outcomes excellent tightness of the capsule and effective protection for the magnet against assault by the salivary medium. The magnet thus retains all its magnetic properties regardless of the duration of use of the prosthesis.