WO1998037615B1

WO1998037615B1 - Apparatus for producing linear motion

Info

Publication number: WO1998037615B1
Application number: PCT/GB1998/000495
Authority: WO
Filing date: 1998-02-20
Publication date: 1998-10-01

Abstract

An electromagnetic apparatus for producing a linearly-acting force, consisting of two hollow members one of which is arranged to move axially within the other, and means associated with the hollow members for producing axially-alternating magnetic fields which interact to produce the said axially-directed force.

Claims

12

AMENDED CLAIMS

[received by the International Bureau on 13 August 1998 (13.08.98); original claims 1-15 replaced by new claims 1-16 (4 pages)]

) An electromagnetic apparatus for producing a controlled axially-directed force characterised in that there is included at least two tubular members (101 , 105) adapted to slide telescopically one within the other, a plurality of annular coils (103) affixed to at least a portion of the axial length of one of the tubular members (101 , 105), means (111) for generating circumferential electric

currents in the annular coils, means (108) for producing a multiple of radially- directed magnetic fluxes, the polarity of which alternates along at least a portion of the other tubular member, (101 ,105), the current-generating means

(111 ) including means for varying the magnitudes and directions of the electric currents in the coils (103) and/or the strengths and polarities of the magnetic fluxes, so as to cause the orthogonal electric currents and magnetic fluxes to interact and to provide a controlled mutually-orthogonal (axial) force tending to cause relative motion between the tubular members (101 , 105).

2) An apparatus for producing electromagneticaliy an axial force comprising two cup-shaped members (301 ,302) one fitted within the other and adapted to

allow relative motion therebetween, a plurality of annular coils (308) affixed to

at least a part of the length of one of the cup-shaped members (301 , 302), means (310) for producing a radially-directed magnetic flux the polarity of

which alternates along at least a part of the other of the cup-shaped members (301 , 302), the axial dimensions of the coils (308) having an exact relationship

with the axial dimensions of the components of the means for producing the

radially-directed magnetic flux and means (311 ) for generating the

circumferential electric currents in the coils (308) so as to produce an axial 13 force tending to cause relative motion between the cup-shaped members (301 ,

302).

3) An apparatus according to claim 1 or claim 2 characterised in that the inner

tubular member (105, 301 ) carries an array of permanent magnets (108, 310)

and the outer tubular element (101 , 302) carries an assembly of coils, (103,

308) through which the electric currents are passed by the controlling means

(111 ) to provide the said resultant axial force.

4) An apparatus according to claim 1 or claim 2 characterised in that the outer

tubular member (101 , 302) carries an array of permanent magnets and the

inner tubular element (105, 301 ) carries an assembly of coils through which

the electric currents are passed by the controlling means (111 ) to provide the

said resultant axial force.

5) An apparatus according to any preceding claim characterised in that the

means for producing a multiple of radially-directed magnetic fluxes comprises

an array of axially-magnetised elements with like poles facing and

ferromagnetic polepieces interposed

6) An apparatus according to any preceding claim characterised in that the

circumferential coils (103, 304) are arranged to be connected as a multi-phase

motor winding and the axial dimensions of the coils (103, 304) have an exact

relationship with the axial dimensions of the array of permanent magnets or

other means for producing the radially-oriented magnetic fluxes

7) An apparatus according to claim 1 or claim 2, characterised in that the radially-

directed magnetic flux is generated by the action of electric currents flowing in

annular coils (202) associated with one of the sliding members (101 , 105, 301 ,

302) and that there is included a member (201) associated with the other 14

sliding member (101 , 105, 301 , 302) such that eddy currents induced therein

by the electric currents flowing in the coils (202) interact with the magnetic flux

pattern produced by the currents flowing in the coils (202) so as to produce

the axial force

8) An apparatus according to any preceding claim, characterised in that there is

included at least one bearing and seal (109, 110), (311 , 312) between the

inner surface of the outer tubular member (101 , 309) and the outer surface of

the inner tubular member (105, 301) so as to prevent the access of harmful

environmental components to those parts of the device where relative motion

occurs.

9) An apparatus according to any preceding claim characterised in that each of

the tubular members (101 ,105) is fitted with a sealable attachment flange or

screw element (102,106) by means of which, in combination with the seal

(109) and the fabric of the structure to which they are attached, the tubular

members may together form a fluid container having a variable volume.

10) An apparatus according to any preceding claim, characterised in that the

means (111 , 311 ) for varying the circumferential currents is a multi-phase

power supply or electronic drive unit, the frequencies, phases and amplitudes

of the outputs from which can be varied to alter the resultant axial thrust

between the tubular members.

11 ) An apparatus according to claims 8 or 9, characterised in that there is

included means (109, 312) for producing a fluid-tight seal to the external

surface of the inner member at the position where the inner member (105,

301) protrudes from the outer member (101 , 302). 12) An apparatus according to claim 11 , characterised in that the space (307)

enclosed between the members (101 , 105), (301 , 302) contains a fluid at a

pressure different from that of the fluid external to the assembly, thereby to

generate an axial force on the sealed outer ends (102, 106), (305, 306) of the

two members (301 , 302).

13) An apparatus according to claim 11 or claim 12, characterised in that the

enclosed space within the members (101 , 105), (301 , 302) is connected to an

external fluid reservoir.

14) An apparatus according to any preceding claim characterised in that the

means (103, 308) for producing the circumferential electric currents

comprises a plurality of modules each comprising an annular coil, (401 ), an

external spacer (403) made of a ferromagnetic material and having the same

axial length as the coils (401 ), and a ring (402) made of a ferromagnetic

material having the same internal diameter as the coil (401 ) and the same

external diameter as the spacer (403), the rings (402) and coils (401 ) being so

shaped axially as to present a constant reluctance to the radially-directed

magnetic flux pattern produced by the magnetic field pattern generating means

(108).

15) An apparatus according to claim 14 characterised in that each coil (401 ) ring

(402) spacer (403) module is skewed or is displaced back and forth over one

complete rotation a distance equal to the axial length of a coil (401 ).

16) An apparatus according to claims 14 or 15 characterised in that each ring

(402) is integral with a spacer (403), so that the associated coil (401 ) rests in

a hollowed space within the integral part.