Magnet Assembly for a Linear Electromechanical Machine
A magnetic assembly for a linear electromechanical machine, the assembly comprising an annular support centered on an axis of reciprocation of the machine. A magnet assembly is attached to the annular support. The magnet assembly comprises at least one annular part which is substantially magnetic. The annular part has at least one non-conductive portion in a substantially radial plane and extending at least half of the way through the wall of the annulus.
1 . A magnetic assembly for a linear electromechanical machine, the assembly comprising an annular support centred on an axis of reciprocation of the machine, a magnet assembly attached to the annular support, the magnet assembly comprising at least one annular part which is substantially magnetic and is centred on the axis of reciprocation, wherein the at least one annular part has at least one non-conductive portion in a substantially radial plane and extending at least half of the way through the wall of the annulus.
2 . An assembly according to claim 1 , wherein the non-conductive portion is a slit.
3 . An assembly according to claim 1 , wherein the non-conductive portion is a solid non-conductive material.
4 . An assembly according to claim 3 , wherein the non-conductive portion is integrally formed with the annular part.
5 . An assembly according to claim 3 , wherein the non-conductive portion is a component inserted into a slot in the annular part.
6 . An assembly according to any one of the preceding claims, wherein the annular support is a drum arranged, in use, to reciprocate along the axis of reciprocation.
7 . An assembly according to any one of claims 1 to 5 , the assembly being a stator, wherein the annular support is fixed with respect to a reciprocated component.
8 . An assembly according to any one of the preceding claims, wherein the non-conductive portion extends from an axially facing face of the magnet.
9 . An assembly according to any one of claims 1 to 7 , wherein the non-conductive portion extends from a radially facing face of the magnet.
10 . An assembly according to any one of the preceding claims comprising two non-conductive portions, each extending from opposite faces of the magnet.
11 . An assembly according to any one of the preceding claims, wherein the or each non-conductive portion extends across at least 75% of the part.
12 . An assembly according to claim 11 , wherein the or each non-conductive portion extends across substantially 90% of the part.
13 . An assembly according to claim 2 , wherein the slit extends fully across the part.
14 . An assembly according to any one of claims 3 to 5 , wherein the or each non-conductive portion extends fully across the part.
15 . A method of forming an annular magnet using an annular mould having a central axis and a plurality of feed nozzles, the nozzles being arranged in a circle about the central axis and corresponding to the annular mould and being movable in the direction of the central axis, at least one nozzle containing powdered non-conductive material and the remaining nozzles containing powdered magnetic material, the method comprising lowering the nozzles into the mould, dispensing powdered material into the mould, raising the nozzles as the material is dispensed to fill the mould, removing the nozzles, compacting and heating the powdered material to form a single ring, and exposing the material to a magnetic field to create magnetic poles.
16 . A method according to claim 15 , wherein the material is exposed to a magnetic field before the material is compacted and heated.
17 . A method according to claim 15 or claim 16 , wherein the material is exposed to a magnetic field after the material is compacted and heated.