Linear motor with air-lift bearing unloading

Claim 2

A positioning device comprising: a stationary portion. a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coils; said armature further including a mass of magnetically attractive material, whereby a static attractive force exists between at least some of said plurality of permanent magnets and said mass of magnetically attractive material; at least first and second cooperating bearing means for supporting said movable portion against said static attractive force; said first cooperating bearing means being a contact-type bearing means; and said second cooperating bearing means being of a type having a fluid forced between facing surfaces for supporting a first portion, but less than all, of said static attractive force, whereby said second cooperating bearing means is effective for supporting a remainder, less than all, of said static attractive force at all times during operation of said positioning device.

Claim 3

A positioning device according to claim 1 wherein said second cooperating bearing means is an air bearing.

Claim 4

A positioning device according to claim 2 wherein said second cooperating bearing means includes means for controlling a magnitude of said first portion.

Claim 5

A positioning device according to claim 3 wherein said means for controlling a magnitude includes an air pressure regulator effective for controlling a pressure of air forced between said facing surfaces.

Claim 6

A positioning device comprising: a stationary portion; a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coil means for applying a static load to said movable portion; at least first and second cooperating bearing means for supporting said movable aportion against said static load; said first cooperating bearing means being a contact-type bearing means; said second cooperating bearing means being of a type having a fluid forced between facing surfaces for supporting a portion, but less than all, of said static load, whereby said second cooperating bearing means is effective for supporting a remainder, less than all, of said static load; said first and second cooperating bearing means being further effective for supporting a load added to said static load; means for determining a magnitude of a remainder of said load and said static load borne by said first cooperating bearing means; and means for controlling a flow of said fluid forced between said facing surfaces to a value effective for maintaining said remainder substantially constant under changes in said load.

Claim 7

A positioning device comprising: a stationary portion; a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coil means for applying a static load to said movable portion; at least first and second cooperating bearing means for supporting said movable aportion against said static load; said first cooperating bearing means being a contact-type bearing means; said second cooperating bearing means being of a type having a fluid forced between facing surfaces for supporting a portion, but less than all, of said static load, whereby said second cooperating bearing means is effective for supporting a remainder, less than all, of said static load; said first and second cooperating bearing means being further effective for supporting a load added to said static load; means for determining a magnitude of a remainder of said load and said static load borne by said first cooperating bearing means; and means for controlling a flow of said fluid forced between said facing surfaces to a value effective for maintaining said remainder substantially constant under changes in said load.

Claim 8

A positioning device according to claim 5 wherein said means for determining includes means for measuring said remainder.

Claim 9

A positioning device according to claim 6 wherein said means for measuring includes a load cell.

Claim 10

A positioning device according to claim 6 wherein said means for controlling a pressure of air includes a lift control responsive at least to a measurement of said remainder.

Claim 11

A positioning device according to claim 5 wherein said means for determining includes means for predicting said remainder.

Claim 12

A positioning device according to claim 1 wherein said stationary portion is affixed to a machine bed.

Claim 13

A positioning device according to claim 1 wherein: said stationary portion is affixed in a slot in a bed of a machine; and said movable portion is disposed in said slot facing said stationary portion.

Claim 14

A positioning device according to claim 11 wherein said movable portion is connected to a load by a load bar extending from said slot.

Claim 15

A positioning device according to claim 12, further comprising at least one means for sealing said slot against entry of dirt into said slot whereby said positioning device operates in a clean environment.

Claim 16

A positioning device according to claim 13 wherein said at least one sealing means includes: a first flexible seal affixed along a first edge of said slot; a second flexible seal affixed along a second edge of said slot and forming a line of sealing contact with said first flexible seal; said load bar deforming at least one of said first and second flexible seals for passing therepast; and at least one of said first and second flexible seals forming a sealing contact with said load bar.

Claim 17

A positioning device according to claim 1 wherein said first cooperating bearing means includes a sliding bearing.

Claim 18

A positioning device according to claim 1 wherein said first cooperating bearing means includes a rolling bearing.

Claim 19

A positioning device comprising: a stationary portion; a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coils; said armature further including a mass of magnetically attractive material, whereby a static attractive force exists between at least some of said plurality of permanent magnets and said mass of magnetically attractive material; means for affixing a load to said movable portion; at least spaced-apart first and second bearing means for supporting said movable portion against said static attractive force and said load; said first and second spaced-apart bearing means bearing first and second load portions, respectively, made up of said magnetic attractive force and said load; said first bearings means including a first fluid-type bearing and a first contact-type bearing; said first fluid-type bearing including first means for supporting a first portion, but less than all of said first load portion; said first contact-type bearing supporting a first remainder, but less than all, of said first load portion at all times during operation of said positioning device; said second bearing means including a second fluid-type bearing and a second contact-type bearing; said second fluid-type bearing including second means for supporting a second portion, but less than all, of said second load portion; and said second contact-type bearing supporting a second remainder, but less than all, of said second load portion at all times during operation of said positioning device.

Claim 20

A positioning device comprising: a stationary portion; a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coils; said armature further including a mass of magnetically attractive material, whereby a static attractive force exists between at least some of said plurality of permanent magnets and said mass of magnetically attractive material; means for affixing a load to said movable portion; at least spaced-apart first and second bearing means for supporting said movable portion against said static attractive force and said load; said first and second spaced-apart bearing means bearing first and second load portions, respectively, made up of said magnetic attractive force and said load; said first bearings means including a first fluid-type bearing and a first contact-type bearing; said first fluid-type bearing including first means for supporting a first portion, but less than all of said first load portion; said first contact-type bearing supporting a first remainder, but less than all, of said first load portion at all times during operation of said positioning device; said second bearing means including a second fluid-type bearing and a second contact-type bearing; said second fluid-type bearing including second means for supporting a second portion, but less than all, of said second load portion; and said second contact-type bearing supporting a second remainder, but less than all, of said second load portion at all times during operation of said positioning device.

Claim 21

A positioning device according to claim 17 wherein said first and second means for supporting including at least one pressure regulator for regulating a pressure of said fluid applied between facing surfaces.

Claim 22

A positioning device comprising: a stationary portion; a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of magnets; means for applying a static load to said movable portion; means for affixing a load to said movable portion; at least spaced-apart first and second bearing means for supporting said movable portion against said static load and said load; said first and second spaced-apart bearing means bearing first and second load portions, respectively, made up of said static load and said load; said first bearing means including a first fluid-type bearing and a first contact-type bearing; said first fluid-type bearing including first means for supporting a first portion, but less than all, of said first load portion; said first contact-type bearing including means for supporting a first remainder, but less than all of said first load portion; said second bearing means including a second fluid-type bearing and a second contact-type bearing; said second fluid-type bearing including second means for supporting a second portion, but less than all of said second load portion; said second contact-type bearing supporting a second remainder, but less than all of said second load portion; said first means for supporting includes a first pressure-control device for controlling said first portion of said first load portion; said second means for supporting includes a second pressure-control device for controlling said second portion of said second load portion; means for determining said first and second remainders; and means for controlling independently said first and second pressure-control devices to maintain said first and second remainders substantially constant.

Claim 23

A positioning device comprising: a stationary portion; a movable portion; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of magnets; means for applying a static load to said movable portion; means for affixing a load to said movable portion; at least spaced-apart first and second bearing means for supporting said movable portion against said static load and said load; said first and second spaced-apart bearing means bearing first and second load portions, respectively, made up of said static load and said load; said first bearing means including a first fluid-type bearing and a first contact-type bearing; said first fluid-type bearing including first means for supporting a first portion, but less than all, of said first load portion; said first contact-type bearing including means for supporting a first remainder, but less than all of said first load portion; said second bearing means including a second fluid-type bearing and a second contact-type bearing; said second fluid-type bearing including second means for supporting a second portion, but less than all of said second load portion; said second contact-type bearing supporting a second remainder, but less than all of said second load portion; said first means for supporting includes a first pressure-control device for controlling said first portion of said first load portion; said second means for supporting includes a second pressure-control device for controlling said second portion of said second load portion; means for determining said first and second remainders; and means for controlling independently said first and second pressure-control devices to maintain said first and second remainders substantially constant.

Claim 24

A machine tool comprising: a bed; a slot in said bed; a stationary portion affixed in said slot; a movable portion in said slot; means extending from said slot for connecting said movable portion to a load external to said slot; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coils; said armature further including a mass of magnetically attractive material, whereby a static attractive force exists between at least some of said plurality of permanent magnets and said mass of magnetically attractive material; at least first and second spaced-apart bearing means for supporting said movable portion against said static attractive force and said load; said first and second spaced-apart bearing means bearing first and second load portions, respectively, made up of said magnetic attractive force and said load; said first bearing means including a first fluid-type bearing and a first contact-type bearing; said first fluid-type bearing including first means for supporting a first portion, but less than all, of said first load portion; said first contact-type bearing supporting a first remainder, but less than all, of said first load portion; said second bearing means including a second fluid-type bearing and a second contact-type bearing; said second fluid-type bearing including second means for supporting a second portion, but less than all, of said second load portion; said second contact-type bearing supporting a second remainder, but less than all, of said second load portion; said first means for supporting includes a first pressure-control device for controlling said first portion of said first load portion; said second means for supporting includes a second pressure-control device for controlling said second portion of said second load portion; means for determining said first and second remainders; and means for controlling independently said first and second pressure-control devices to maintain said first and second remainders substantially constant.

Claim 25

A machine tool comprising: a bed; a slot in said bed; a stationary portion affixed in said slot; a movable portion in said slot; means extending from said slot for connecting said movable portion to a load external to said slot; one of said stationary portion and said movable portion including a plurality of permanent magnets affixed upon a surface thereof; the other of said stationary portion and said movable portion including an armature affixed facing said plurality of permanent magnets; said armature including a plurality of armature coils; said armature further including a mass of magnetically attractive material, whereby a static attractive force exists between at least some of said plurality of permanent magnets and said mass of magnetically attractive material; at least first and second spaced-apart bearing means for supporting said movable portion against said static attractive force and said load; said first and second spaced-apart bearing means bearing first and second load portions, respectively, made up of said magnetic attractive force and said load; said first bearing means including a first fluid-type bearing and a first contact-type bearing; said first fluid-type bearing including first means for supporting a first portion, but less than all, of said first load portion; said first contact-type bearing supporting a first remainder, but less than all, of said first load portion; said second bearing means including a second fluid-type bearing and a second contact-type bearing; said second fluid-type bearing including second means for supporting a second portion, but less than all, of said second load portion; said second contact-type bearing supporting a second remainder, but less than all, of said second load portion; said first means for supporting includes a first pressure-control device for controlling said first portion of said first load portion; said second means for supporting includes a second pressure-control device for controlling said second portion of said second load portion; means for determining said first and second remainders; and means for controlling independently said first and second pressure-control devices to maintain said first and second remainders substantially constant.

Claim 26

A machine tool according to claim 20 wherein said means for determining includes at least first and second means for measuring said first and second remainders.

Claim 27

A machine tool according to claim 21 wherein said first and second means for measuring includes at least first and second load cells.

Claim 28

A machine tool according to claim 20 wherein said means for determining includes means for predicting said first and second remainders.