Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-01-11
2002-11-05
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C428S034100, C428S034700, C428S035700, C428S035800, C428S036400, C428S036800, C428S423100, C428S425800, C524S430000, C524S432000, C524S433000, C524S434000, C524S435000, C524S436000, C524S437000, C524S438000, C524S440000, C524S441000, C524S589000, C524S590000
Reexamination Certificate
active
06476113
ABSTRACT:
TECHNICAL FIELD
The present invention relates to elastomers containing a filler or plurality of fillers that can be magnetically aligned in such a way that products formed by such elastomers present a useful magnetic field in a similar manner to a permanent or electro magnet. These magnetically-filled elastomers can be thermo-plastically formed, thermoformed, or formed as a result of a thermosetting reaction. The present invention also relates to methods for aligning the magnetic fillers in these elastomers. An embodiment of the present invention particularly relates to the provision of magnetically-filled polyurethane elastomers. Furthermore, the present invention relates to the employment of elastomers and, more particularly, magnetically-filled elastomers in vibration dampening devices.
BACKGROUND ART
It is well known that particles of certain pure metals, namely iron, cobalt, and nickel, can be treated in such a way that their magnetic moments or domains become aligned and said particles then behave as magnets, that is, they acquire a magnetic field within which magnetic materials may be influenced as to their energy content and potential. The strength of the field increases according to the percentage of the domains present and those aligned. The field can be further increased by the addition of other metals or their oxides to form magnetic alloys, as, for example, by the addition of barium, boron, cobalt, copper, iron, neodymium, nickel, promethium, samarium, and strontium, and alloys thereof. Trialloys, such as neodymium-iron-boron, can also be formed to further increase the field strength.
Another group of suitable magnetic materials consists of ferrites, as, for example, lodestone. These include the oxides of iron to which small quantities of transition metal oxides such as cobalt or nickel have been added. These are known as spinel ferrites and have the general formula M(OFe
2
O
3
) where M is a divalent transition ion. Another form of ferrite is iron oxide to which the oxides of the reactive metals strontium or barium have been alloyed. Ferrites are particularly useful because they are easily reduced to a powder and can be reformed to suitable shapes by compaction or as a component of a plastic or ceramic compound. However, the present invention is not restricted to the use of magnetic material in the form of lodestone or oxides of iron, although these are often preferred because of cost, coercivity, achievable field strength, and ease of reconstitution or molding. Alternatives include, but are not restricted to, the primary magnetic elements as discussed above, namely, cobalt, iron, nickel and alloys that include barium, boron, cobalt, copper, iron, neodymium, nickel, promethium, samarium, strontium, and alloys thereof. Examples of suitable alloys are cobalt-samarium and neodymium-iron-boron.
Advantageously, such magnetic material can be machined into special shapes or reduced to a free-flowing powder, sometimes as fine as 600 mesh, and reconstituted by introducing a binder, sintering under pressure, or by introducing the powder as a component of a compound that at some stage becomes liquid and subsequently solidifies. Such carriers can range from glass to wax in natural conversion processes and from ceramics to plastics in synthetic systems. Other suitable matrices for carrying such magnetic material include natural and synthetic woven and non-woven materials, flexible plastic, and various forms of foam and rubber. In the prior art, such carriers produce substantially rigid magnets. In the present invention, it has been found that magnetic fillers may be incorporated into thermoplastic and thermosetting elastomers to provide physically soft elastomer-based magnets that produce a useful magnetic field.
It has also been found that the field strength of such elastomer-based magnets is a function of the coercivity of the magnetic filler and its packing density. The packing density has been found to be dependent on the particle shape of the filler, its surface texture, and the nature or melt viscosity of the carrier elastomer. Consequently, it is one object of this invention to mold components that exhibit the maximum possible field strength commensurate with the packing density of the magnetic filler. Methods for aligning the magnetic filler within the elastomeric matrix in order to increase the packing density and resultant magnetic field are also disclosed.
Additionally, lightweight filler materials may be employed in the present invention. It has been found that reinforcing lightweight filler materials may be advantageously employed in the compositions of the present invention because they perform the dual function of reducing the overall density and improving the mechanical strength of the composite.
When magnetic material is incorporated into a typical rubber matrix, the resultant product's hardness is generally about 60 on the Shore A scale. In the prior art, plastic- and rubber-based magnets have been made flexible by casting in them in very thin cross-section, in which case, however, the field strength is usually impractically low. To overcome this low field strength, the magnetic sheet is often rolled to form a round or square section tube, resulting in an almost total loss of cross-sectional flexibility while retaining such longitudinal flexibility as to make them useful for gaskets, including domestic appliances such as refrigerators where curvature is gentle and sharp bends are catered for by mitre jointing.
It has been found that magnets of higher strength, that is of thicker cross-section, are capable of attracting the hemoglobin content of erythrocytes present in blood plasma. Such magnets may be strategically placed in medical devices to attract erythrocytes to various parts of the body to increase the oxygen supply to that point. In use, these magnets are embedded in or attached to rubber, plastic, cloth or other materials to hold them in place.
It should be appreciated that, in the prior art, these magnets are necessarily small in diameter, comparatively large in cross-section, and of a hardness at least measurable at about 50 on the Shore A scale. Such magnets must be cushioned if they are placed near to soft tissue, and any barrier between the field source and such soft tissue will reduce the effective field strength of the magnet. Thus, in one embodiment of the present invention, soft, energy dissipating, polyurethane elastomer compositions containing magnetic material are provided for comfortable employment in medical devices for the purpose of attracting the hemoglobin present in blood plasma. These polyurethane elastomer compositions can be worn next to soft tissue without interfering with the comfort or well being of the wearer as they are capable of deflecting easily but with a limited degree of permanent compression and with a predetermined recovery rate similar to that of the soft tissue with which they are going to closely function. A preferred elastomeric composition useful for such devices is an additional embodiment of the present invention.
The thermosetting and thermoplastic elastomeric compositions of the present invention have also been found to be useful in vibration dampening systems. More specifically, it has been found that visco-elastic polymers derived from elastomers of the present invention can advantageously be employed in vibration dampening devices.
In an embodiment of the present invention, a simple vibration dampening device having upper and lower constraining components that are influenced by at least one separating layer of a magnetically charged elastomer is provided. Preferably, the elastomer is a visco-elastomer as discussed hereinabove. However, it has been discovered that the elastomer need not be magnetically-filled to be useful in the vibration dampening systems of the present invention although such elastomers are preferred.
The introduction of a magnetically active substance into the elastomer presents an additional facet to the control of dampening devices in that the magnetically active component of t
Niland Patrick D.
Remington Products Company
Renner Kenner Greive Bobak Taylor & Weber
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