Electro-mechanically switched permanent magnet holding device

Claim 2

An electro-mechanically switched permanent magnet holding device comprising a permanent magnet disposed between a pair of pole members which provide a first and a second magnetic circuit respectively through a load and a keeper end of the device, a control winding disposed about one of the pole members for switching the permanent magnet flux between said first and second magnetic circuits, a keeper plate disposed on the pole faces at the keeper end of the device and movable a distance therefrom limited by a stop portion of a nonmagnetic safety member, spacing means which extend from the keeper plate to the load end of the device for a distance which is equal to the length of the pole members plus the maximum air gap to be encountered in normal use at the load end of the device, and means for passing a current pulse through the control winding in either direction.

Claim 3

An electro-mechanically switched permanent magnet holding device as claimed in claim 1, wherein the spacing means comprises spacer rods which slidably extend through bores in the pole members.

Claim 4

An electro-mechanically switched permanent magnet holding device as claimed in claim 1, wherein the keeper plate is provided with a cover which surrounds the upper periphery of the magnet and pole members, and wherein sealing means are located between the cover and the said upper periphery so as to prevent dirt from entering the space between the keeper plate and the upper faces of the pole members.

Claim 5

An electro-mechanically switched permanent magnet holding device as claimed in claim 1, comprising one or more pairs of permanent magnets, each permanent magnet being disposed between a pair of pole members, said control winding being disposed about central pole-members which are disposed between the two magnets of a pair of magnets.

Claim 6

An electro-mechanically switched permanent magnet holding device as claimed in claim 1, wherein the means for passing a current pulse through the control winding include a non-magnetic control rod which retractably extends from the load end of the device so as to abut against the load, the control rod being adapted to operate a switch which controls a current pulse to the control winding when the space between the keeper plate and the load is just greater than said distance by which the spacing means extend from the keeper plate.

Claim 7

An electro-mechanically switched permanent magnet holding device as claimed in claim 1 wherein said maximum air gap is approximately 0.9 millimeters.

Claim 8

A magnetic lift device for transporting a magnetic load comprising, a permanent magnet, a pair of pole members with the permanent magnet disposed between said pole members so as to provide a first and a second magnetic circuit through a load end and a keeper end, respectively, of said device, a control winding magnetically coupled to at least one of said magnetic circuits for controlling the attractive force at said load and keeper ends of the device in response to a current pulse applied thereto, a non-magnetic safety member secured to said device at the keeper end and having a stop portion, a keeper plate disposed at the keeper end of the device adjacent one pair of faces of the pole members and displaceable therefrom until engaged by the stop portion of said safety member, means for selectively applying a current pulse to the control winding, and spacer means coupled to the keeper plate and extending therefrom to the load end of the device, the length of said spacer means being equal to the length of the pole members plus a predetermined length equal to the maximum expected air gap at the load end of the device in normal operation.

Claim 9

A magnetic lift device for transporting a magnetic load comprising, a permanent magnet, a pair of pole members with the permanent magnet disposed between said pole members so as to provide a first and a second magnetic circuit through a load end and a keeper end, respectively, of said device, a control winding magnetically coupled to at least one of said magnetic circuits for controlling the attractive force at said load and keeper ends of the device in response to a current pulse applied thereto, a non-magnetic safety member secured to said device at the keeper end and having a stop portion, a keeper plate disposed at the keeper end of the device adjacent one pair of faces of the pole members and displaceable therefrom until engaged by the stop portion of said safety member, means for selectively applying a current pulse to the control winding, and spacer means coupled to the keeper plate and extending therefrom to the load end of the device, the length of said spacer means being equal to the length of the pole members plus a predetermined length equal to the maximum expected air gap at the load end of the device in normal operation.

Claim 10

A lift device as claimed in claim 7 wherein the spacer means comprises a rod slidably extending through a bore in a pole number with one end secured to the keeper plate and the other end freely movable to contact a load member at the load end and retractable therefrom when the keeper plate is moved in a direction away from the load end of the device.

Claim 11

A lift device as claimed in claim 8 wherein said current pulse applying means comprises a switch secured to the keeper plate and a non-magnetic control rod retractably extending from the load end of the device so as to contact a load when in place, said control rod extending to the keeper plate so as to operate said switch at a predetermined separation between the keeper plate and the load.