US3818399A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Permanent magnet devices
Assignee: James Neill Holdings Ltd
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Filing: 1973-01-24
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Granted: 1974-06-18
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Expires: 1993-01-24
Abstract
Abstract A permanent magnet device comprising at least two pairs of aligned plate-like polepieces of ferromagnetic material such as mild steel, and at least two permanent magnets in upper and lower rows magnetised in opposite directions through their thickness, associated with and lying between the pairs of polepieces, at least one of the magnets being capable of movement relative to at least one other and relative to the pairs of polepieces from a first position where the magnets and the polepieces co-operate to provide a maximum external magnetic field strength (the ON position) to a position where the external magnetic field is reduced to substantially zero (the OFF position).
Inventors
- 👤 A Edwards
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:52
CPC Classifications
B; B23; B23Q; B23Q3/00; B23Q3/15; B23Q3/154; B23Q3/1546
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
106 words
A permanent magnet device comprising at least two pairs of aligned plate-like polepieces of ferromagnetic material such as mild steel, and at least two permanet magnets in upper and lower rows magnetised in opposite directions through their thickness, associated with and lying between the pairs of polepieces, at least one of the magnets being capable of movement relative to the other and relative to the pairs of polepieces from a first position where the magnets and the polepieces co-coperate to provide a maximum external magnetic field strength an on position, to a position where the external magnetic field is reduced to substantially zero an off position.
Claim 2
Dependent Claim
106 words
A permanent magnet device comprising at least two pairs of aligned plate-like polepieces of ferromagnetic material such as mild steel, and at least two permanet magnets in upper and lower rows magnetised in opposite directions through their thickness, associated with and lying between the pairs of polepieces, at least one of the magnets being capable of movement relative to the other and relative to the pairs of polepieces from a first position where the magnets and the polepieces co-coperate to provide a maximum external magnetic field strength an on position, to a position where the external magnetic field is reduced to substantially zero an off position.
Claim 3
Dependent Claim
41 words
A permanent magnet device as in claim 1, wherein the relative movement is such that the magnets can be moved to a third position where an external magnetic field is produced opposite in direction to that provided by the first position.
Claim 4
Dependent Claim
32 words
A permanet magnet device as in claim 1, wherein the magnets are of slab form and magnetised through the thicknesses of the slabs such that opposite polar faces are of opposite polarity.
Claim 5
Dependent Claim
29 words
A permanent magnet device as in claim 1, wherein corresponding polar faces of the magnet associated with adjacent pairs of polepieces in the on position are of opposite polarity.
Claim 6
Dependent Claim
35 words
A permanent magnet device as in claim 1, wherein the upper and lower magnets are moved, relatively to each other by sliding between the polepieces until each bridges the gap between the pairs of polepieces.
Claim 7
Dependent Claim
68 words
A permanent magnet device as in claim 1, wherein adjacent pairs of polepieces are provided with at least one magnet permanently held between one pair of polepieces and a second magnet magnetised through its thickness in the reverse direction movable from a position between the other pair of polepieces, the ON position, to a position where both magnets are associated with one pair of polepieces, the OFF position.
Claim 8
Dependent Claim
50 words
A permanent magnet device as in claim 1, wherein the magnetic attractions between each polar surface of each magnet and the neighbouring polepieces are substantially equal to one another but of opposite direction, whereby there is substantial balancing of the magnetIc forces acting on the polar faces of the magnets.
Claim 9
Dependent Claim
15 words
A permanent magnet device as in claim 1, wherein the device is a work-holding device.
Claim 10
Dependent Claim
49 words
A permanent magnet device as in claim 8, wherein the magnets and the polepieces are so proportioned that the polar surface area of permanent magnet in contact with a polepiece is greater than the area of the same polepiece in contact with any ferromagnetic article held by the device.
Claim 11
Dependent Claim
31 words
A permanent magnet device as in claim 1, wherein the movable magnets are mechanically supported to hold the magnets in their positions between the polepieces and to move them as required.
Claim 12
Dependent Claim
25 words
A permanent magnet device as in claim 10, wherein the movable magnets are positioned in appropriately shaped holes in a support bar of non-magnetic material.
Claim 13
Dependent Claim
27 words
A permanent magnet device as in claim 11, wherein the bar is moved longitudinally between the polepieces and as it moves it carries the magnets with it.
Claim 14
Dependent Claim
16 words
A permanent magnet device as in claim 1, wherein all the movable magnets are moved simultaneously.
Claim 15
Dependent Claim
35 words
A permanent magnet device as in claim 1, wherein some of the movable magnets are movable separately from the remainder of the movable magnets whereby the device can be switched on and off in sections.
Claim 16
Dependent Claim
23 words
A permanent magnet device as in claim 1, wherein for maximum utilisation of the magnets their width substantially equals that of the polepieces.
Claim 17
Dependent Claim
32 words
A permanent magnet device as in claim 1, wherein the magnets are produced from high coercivity ferrite material, when thin magnets may be employed with a consequent narrow spacing of the polepieces.
Claim 18
Dependent Claim
80 words
A permanent magnet device as in claim 8, comprising a base plate of non-magnetic material, side plates and end plates of ferromagnetic material, the base plate having a series of rectangular recesses running longitudinally of the base plate into each of which is secured a number of spaced polepieces, the longitudinal gaps between adjacent rows of polepieces being loaded with upper and lower rows of magnets, the gaps between the upper faces of the polepieces being filled with non-magnetic material.
Claim 19
Dependent Claim
52 words
A permanent magnet device as in claim 17, wherein the movable magnets are located in support bars provided with recesses in which the magnets are a close fit, and the ends of the support bars extend to operating means for simultaneous movement of the upper and lower support bars in opposite directions.
Claim 20
Dependent Claim
43 words
A permanent magnet device as in claim 18, wherein the operating means is a pin passing through a vertical slot in each support bar, each pin being located in and secured to rotatable plates, to one of which is secured an operating handle.
Claim 21
Dependent Claim
26 words
A permanent magnet device as in claim 19, wherein the length of the slot is dictated by the degree of movement required of the support bar.
Claim 22
Dependent Claim
43 words
A permanent magnet device as in claim 17, wherein the spacing between adjacent polepieces in the transverse direction is maintained by rods bridging the side plates on which distance pieces are provided, the distance pieces lying in the longitudinal gaps between the polepieces.
Claim 23
Dependent Claim
94 words
A permanent magnet device as in claim 8, comprising a base plate of non-magnetic material, side plates and end plates of ferromagnetic material, the inside faces of the side plates being provided with spaced location pegs to locate transversely disposed packs of polepieces in alternation with magnets whereby adjacent packs provide the longitudinal rows of polepieces and lower fixed magnets, the gaps between the polepieces above the fixed magnets being loaded with the upper rows of magnets, and the gaps between the polepieces above the upper rows of magnets being filled with non-magnetic material.
Claim 24
Dependent Claim
46 words
A permanent magnet device as in claim 22, wherein the movable magnets are located in support bars provided with recesses in which the magnets are a close fit, the ends of the support bars extending to operating means whereby the support bars can be moved simultaneously.
Claim 25
Dependent Claim
59 words
A permanent magnet device As in claim 23, wherein the operating means is a rack and pinion, the racks being formed on one edge of the support bars and engaged by the pinion passing across the support bars, the pinion extending to epicyclic gearing to which is secured an operating handle whereby all the supporting bars are moved simultaneously.
Claim 26
Dependent Claim
28 words
A permanent magnet device as in claim 1, wherein additional polepieces and associated magnets are disposed transversely adjacent said two permanent magnets, transversely adjacent magnets being oppositely magnetised.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-17 | 1977-12-17 | 1978-06-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-17 | 1981-12-17 | 1982-06-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-17 | 1985-12-17 | 1986-06-18 | $7700.00 | Window Closed / Lapsed |