Revolving doors

Claim 1

A revolving door comprising at least one upright door element arranged in outwardly extending disposition about an upright axis of revolution, motor means being provided together with control means operable to position the door at a first rotational disposition from which, when the door is turned in one direction by a user pushing against said door element, power assistance is given to the door to effect rotation thereof wherein said control means includes first means responsive, upon movement of the door from said first rotational disposition in said one direction, to cause operation of said motor means to effect said power assistance for a predetermined time, limit means being provided to cause the door to then come to rest at said first rotational disposition, in the absence of continued pushing by said user, after movement of the door under action of said motor means, wherein said control means further includes second means responsive to positioning of said door at a second rotational disposition, advanced in said one direction from said first rotational disposition, to initiate operation of said limit means, wherein said motor means includes a split phase capacitor start induction motor and said first means includes a timing circuit and a first switch operable upon said movement of the door from said first rotational disposition to initiate operation of said timing circuit, said timing circuit operating to then apply electrical current from an electric supply to one winding of said motor to cause said operation thereof for said predetermined period, wherein said second means includes a second switch operated upon positioning of said door at said second rotational disposition, to operate said limit means, said limit means comprising said motor, said second means operating in response to operation of said second switch means to apply said supply to said one winding of said motor and a unidirectional current from said supply to the other winding thereof whereby said motor operates at low speed and acts as a brake, wherein said first and second switches are arranged to be operated by a cam which is rotated by the door during use thereof, and wherein said first and second switches have operating arms which extend towards and are resiliantly biased towards the cam periphery and the cam has a portion extending over most of its periphery, which portion is of constant radius, and a single outward lobe, the free ends of the arms being positioned such that at said first rotational disposition the lobe is positioned therebetween so that neither arm is moved substantially radially outwardly from rest positions thereof and neither switch is operated, said cam outwardly pressing the arm of the first switch during said turning of the door in said one direction from said first rotational disposition to momentarily operate the said first switch and outwardly pressing the arm of the second switch towards the end of a full revolution of the door to operate the second switch, the speed of said motor when acting as said brake being such as to normally prevent the door and cam from moving in said one direction under its own acquired momentum so far past the location at which the second switch becomes inoperative as to initiate operation of said first switch, unless the door is so moved by a user.