Back to results
US 3,962,665 AGranted
Thermally actuated liquid level sensor
AssigneeIdeal Corporation
InventorsEdward Wojcik, Ricardo Limeres
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeIdeal Corporation
InventorsEdward Wojcik, Ricardo Limeres
Estimating the term…
An electro-thermally activated liquid level sensor that functions reliably under widely varying conditions of ambient temperature and supply voltage makes use of an elongate bimetal element cantilevered at one end thereof in a heat conductive wall adapted to be contacted by the liquid and heated by an electrical resistance element, e.g. by a resistance wire wound about the bimetal element and grounded through it, so that the free end of the bimetal element will close cntacts for a signalling circuit when liquid is not contacting said wall and will open the contracts in response to the loss of heat through the fixed end when liquid is contacting said wall. The bimetal element is composed of oppositely oriented bimetal strip segments fixed one to an end of the other and proportioned with the windings of the resistance wire, so that the switching action of the free end is not voltage-dependent; i.e., it will persist in the absence of a heat sink at said wall irrespective of variations of current flow through the resistance element.
A liquid level sensor comprising a heat-conductive wall adapted to be contacted by a body of liquid, an elongate bimetal element protruding from said wall, said element having one end thereof fixed in thermally conductive relation to said wall and having its other end disposed away from said wall, contact means operable by said other end to open or close a signalling circuit, and electrical resistance means disposed along said bimetal element and connectible with a source of electrical current for heating said element, said bimetal element while being heated by said resistance means having either of two distinct postures in which, respectively, its said other end holds said contact means in either circuit opening or circuit closing position, said bimetal element and said heating means constituting means operative at any voltage of said current, absent heat loss from said element as to a body of liquid contacting said wall, to hold said other end substantially on the same line relative to said fixed end so as to maintain one of said postures, and operative during such heat loss to displace said other end laterally into the other of said postures.
A liquid level sensor comprising a heat-conductive wall having a probe portion thereof protruding outwardly therefrom to be contacted by a body of liquid and forming a recess on its inner side, an elongate bimetal element having one end thereof fixed in said recess in thermally conductive relation to said probe portion and having its other end disposed away from said wall, said bimetal element comprising a first substantially straight segment of bimetal strip material extending from said fixed end and a second substantially straight segment of said material joined to an end of said first segment and extending therefrom to said other end, the respective metals of said segments being oppositely oriented so that said segments will bow in opposite directions when heated, a movable contact fixed to said other end of said element, a relatively fixed contact engageable by said movable contact and connected with a terminal connectible with a signalling circuit, an electrical resistance wire wound about and electrically insulated from a major part of the length of said bimetal element, one end of said wire being connected with a terminal for connection with a source of current and the other end of said wire being connected to said element near said other end of said element, said element and said wall upon grounding of said wall providing a path to ground for current passed through said wire, the respective lengths of said segments and the respective windings of said wire about them being such that at any voltage of said current, absent heat loss from said element as to a body of liquid contacting said probe portion, said other end of said element will be held in a posture closing said contacts, yet during such heat loss said element will deform to hold said movable contact away from said fixed contact.
Dependencies are inferred from the claim text.