Indicator follower mechanism for measuring apparatus

Claim 1

MEASURING APPARATUS HAVING AN INDICATOR MOVEABLE IN ACCORDANCE WITH THE RESPONSE OF THE APPARATUS, AN INDICATOR FOLLOWER MOVEABLE ALONG THE PATH OF MOVEMENT OF THE INDICATOR, MEANS INDICATING WHEN THE INDICATOR FOLLOWER IS ALIGNED WITH THE INDICATOR, MEANS TO DENOTE THE POSITION OF THE INDICATOR FOLLOWER WHEN IT IS ALIGNED WITH THE INDICATOR, A REVERSIBLE ELECTRIC MOTOR AUTOMATICIALLY TO ADJUST THE INDICATOR FOLLOWER ALONG THE PATH OF MOVEMENT OF THE INDICATOR TO A POSITION OF ALIGNMENT THEREWITH, AND CONTROL MEANS FOR SAID POWER MEANS, SAID CONTROL MEANS INCLUDING MEANS WHICH ENERGIZES THE POWER MEANS TO DRIVE THE INDICATOR FOLLOWER IN SUCH DIRECTION AS TO RESTORE ALIGNMENT OF THE INDICATOR FOLLOWER AND THE INDICATOR UPON MOVEMENT OF THE LATTER FROM A POSITION OF ALIGNMENT WITH THE INDICATOR AND WHICH DEENERGIZES THE POWER MEANS WHEN THE INDICATOR FOLLOWER REGAINS ALIGNMENT WITH THE INDICATOR, THE CONTROL MEANS COMPRISING A MASK FORMING AT LEAST A PART OF THE INDICATOR, A SOURCE OF LIGHT RAYS ON ONE SIDE OF THE MASK, TWO IDENTICAL PHOTOELECTRIC CELLS SENSITIVE TO SAID RAYS ON THE OTHER SIDE OF THE MASK, SAID CELLS BEING SPACED ALONG THE PATH OF MOVEMENT OF THE INDICATOR, SAID SOURCE OF RAYS AND THE CELLS BEING MOUNTED ON THE INDICATOR FOLLOWER FOR MOVEMENT THEREWITH, THE LIGHT SOURCE, CELLS, AND MASK BEING SO CONSTRUCTED AND ARRANGED THAT WHEN THE INDICATOR FOLLOWER IS ALIGNED WITH THE INDICATOR BOTH CELLS RECEIVE EQUAL AMOUNTS OF RAYS FROM THE LIGHT SOURCE AND THAT WHEN THE INDICATOR FOLLOWER IS OUT OF ALIGNMENT WITH THE INDICATOR THE CELLS RECEIVE UNEQUAL AMOUNT OF RAYS FROM THE LIGHT SOURCE, AND A CONTROL CIRCUIT OF THE BRIDGE TYPE INTERPOSED BETWEEN THE CELLS AND THE MOTOR AND FUNCTIONING TO DRIVE THE MOTOR IN THE PROPER DIRECTION TO RESTORE THE INDICATOR FOLLOWER TO A POSITION OF ALIGNMENT WITH THE INDICATOR.