Immersion heater for aquariums

Claim 2

In a safety heating device for upright immersion in liquid filled aquariums: a housing including an axially extending heat transmitting tube with imperforate side walls and in imperforate end wall forming a chamber sealed except at its upper end and having linearly heat expansible, heat conducting liquid therein; an electrical circuit; an electrically operated heater connected in said circuit and extending axially in said tube and being substantially immersed in said liquid; an actuator assembly closing the top of said tube and having an axially and linearly movable plunger operatively associated with said liquid to be reactive to thermal expansion of the liquid while the liquid is in a liquid state for axial movement relative to said tube; a switch connected in said circuit with said heater comprising first and second electrical contacts; means supporting said plunger so as to be spaced from the surface of the liquid by an air space having a volume less than about ten percent of the liquid volume and said plunger being responsive to the thermal expansion of the liquid via said air space as a damping medium to activate and deactivate the switch contacts with expansion and contraction of said liquid to control the temperature of said liquid via energization and deenergization of said heater and maintain a constant liquid temperature.

Claim 3

The device of claim 1 wherein an expansible and contractible resilient bellows diaphragm is connected in sealing relation between said housing and plunger to support the plunger and, if necessary, aid in returning it to initial position when the liquid contracts.

Claim 4

The device of claim 2 wherein said plunger includes an axially extending stem of reduced diameter having a curvilinear end surface; and said switch also incorporates spreadable contact bars for carrying said contacts, axially disposed to be contacted and spread by said stem.

Claim 5

The device of claim 3 wherein said plunger has a groove for receiving a beaded end of said diaphragm and the opposite end of the diaphragm also has a bead, the said opposite end being retained by a frame part fixed to said housing.

Claim 6

The device of claim 4 wherein said frame part comprises a diaphragm surrounding guide for the stem having an end wall with an axial guide opening through which said stem extends.

Claim 7

The device of claim 1 as set forth wherein the position of at least one of said contacts is adjusted by a linearly adjustable member carried by said housing; and indicia for adjusting the latter member, which relate to the linear expansion of the liquid in which the heater is immersed, are provided.

Claim 8

The device as set forth in claim 1 wherein the actuator assembly includes a fixed plug having an opening and said plunger is received for axial movement in said opening, said plunger extending axially upwardly beyond said plug in all operating positions thereof; and an axially extending tubular bellows diaphragm surrounding said plunger and sealably mounted to said plunger at its upper end, and fixed to said plug to seal off said tube at its lower end, said diaphragm functioning to support the plunger and, if necessary, assist in returning it to initial position when the liquid contracts.

Claim 9

The device as set forth in claim 7 wherein said housing includes a diaphragm surrounding guide having an end wall with an axial guide opening through which said plunger extends.

Claim 10

The device as set forth in claim 1 wherein said first and second contacts comprise spreadable contact bars axially disposed to be spread by said plunger.

Claim 11

The device as set forth in claim 9 wherein said bars are mounted on a linearly adjustable member which cooperates with indicia for gauging the extent of its adjustment.

Claim 12

The device as set forth in claim 9 wherein said plunger includes an axially extending upper stem of reduced diameter having a curvilinear end surface for engaging and spreading said bars.

Claim 13

The device as set forth in claim 9 wherein said bars comprise leaf spring resilient members with outwardly flared ends preloaded to normally dispose the contacts in engagement.

Claim 14

The device as set forth in claim 1 wherein a high temperature safety bi-metallic thermostat in operative contact with said liquid is additionally serially connected in said circuit to energize and deenergize said heater.

Claim 15

The device as set forth in claim 13 wherein said thermostat is immersed in said liquid and set to operate when the liquid is at a considerably higher temperature than that which will break said contacts.

Claim 16

The device as set forth in claim 1 wherein a mechanism is provided in the portion of the tube occupied by the heater to help overcome the convection current effect in the liquid.

Claim 17

The device as set forth in claim 15 wherein the mechanism comprises a particulate bed of heat retentive material provided only in the lower end of tube.

Claim 18

The device as set forth in claim 15 wherein said heater comprises an electrically non-conductive heating element core having resistance heater coils disposed thereon, and said mechanism includes a greater concentration of coils at the lower end of said core.

Claim 19

The device as set forth in claim 15 wherein said mechanism includes alternatively staggered, axially spaced, laterally extending baffles which laterally bridge the tube except for perimetral passages between the baffles and tube.

Claim 20

The device as set forth in claim 1 wherein at least one of said contacts is mounted on an axially adjustable member operated by an adjusting screw, with a knob thereon disposed outside the upper end of the housing; and a removable cover is provided on said housing over said knob.

Claim 21

In a safety heating device for upright immersion in liquid filled aquariums: a housing including an axially extending heat transmitting tube with imperforate side walls and an imperforate end wall forming a chamber sealed except at its upper end and having linearly heat expansible, heat conducting liquid therein; an electrical circuit; an electrically operated heater connected in said circuit and extending axially in said tube and immersed in said liquid, an actuator assembly closing the top of said tube and including means operatively associated with said liquid to be reactive to thermal expansion of the liquid while the liquid is in a liquid state, said reactive means including a plunger movable axially linearly, responsive to temperature change in the liquid, to various positions dependent on the temperature of said liquid; a diaphragm surrounding the plunger and connected at one end to the plunger and at the other end to the housing to support the plunger; a normally closed switch, connected in said circuit with said heater, comprising normally electrically connected first and second electrical contacts positioned to be electrically disconnected with axial upward movement of said plunger to deactivate the switch with expansion of said liquid and control the temperature of said liquid via deenergization and energization, of said heater.

Claim 22

In a safety heating device for upright immersion in liquid filled aquariums: a housing including an axially extending heat transmitting tube with imperforate side walls and an imperforate end wall forming a chamber sealed except at its upper end and having linearly heat expansible, heat conducting liquid therein; an electrical circuit; an electrically operated heater connected in said circuit and extending axially in said tube and immersed in said liquid, an actuator assembly closing the top of said tube and including means operatively associated with said liquid to be reactive to thermal expansion of the liquid while the liquid is in a liquid state, said reactive means including a plunger movable axially linearly, responsive to temperature change in the liquid, to various positions dependent on the temperature of said liquid; a diaphragm surrounding the plunger and connected at one end to the plunger and at the other end to the housing to support the plunger; a normally closed switch, connected in said circuit with said heater, comprising normally electrically connected first and second electrical contacts positioned to be electrically disconnected with axial upward movement of said plunger to deactivate the switch with expansion of said liquid and control the temperature of said liquid via deenergization and energization, of said heater.

Claim 23

The device of claim 20 wherein a bi-metallic safety thermostat device, serially connected in said circuit, is at least partly immersed in said fluid.

Claim 24

The device as set forth in claim 20 wherein said diaphragm normally holds the plunger at a spaced distance above the lower end of the plug to provide an air space of predetermined volume between the lower end of the plunger and the normal upper level of liquid when the liquid is at operating temperature.

Claim 25

The device as set forth in claim 20 wherein said diaphragm is an expansible and contractible resilient bellows member functioning to seal the tube and position the plunger.