US2828405A

US2828405A - Low voltage heating circuit

Info

Publication number: US2828405A
Application number: US403687A
Authority: US
Inventors: Lowell D Morrison
Original assignee: Ideal Industries Inc
Current assignee: Ideal Industries Inc
Priority date: 1954-01-13
Filing date: 1954-01-13
Publication date: 1958-03-25
Anticipated expiration: 1975-03-25

Description

March 25, 1958 D. MORRISON 2,323,405

LOW VOLTAGE HEATING CIRCUIT Filed Jan. 13. 1954 a; 172M??? far 5y J ar/rr & Cartier v Jim/7205.5

United States Patent lndiistries,.lnc. Sycamore; 111;,2aacorporation ofv Deiaware:

kp'plicationlanuary 1a; 1954', Serial .No. 403,687

l'Claim. Cl. 219-40 My invention resides in the field of apparatus for heating metal pieces. to. a predetermined temperature range so that they can besoldered, fused, or otherwise suitably, secured together by the application of'heat.

More specifically, my invention relates to an electricaldevice for heating aluminum tubing, or the like; so that it can be maintained between two predeterminedtemperatures within a selected temperature rangefor a predetermined period of time so that the aluminum tubing will soak or heat' for a selected period in the desired temperature range.

A primary object of my invention is an electrical heating device generally of the above-described character for bringing. aluminum tubing: upto a: predeterminedtemperature range, and maintaining it within that temperature. range for a predeterminedperiod of time.

Anothcr.object isanelectrical heating device of 'the above-described character which requires very littletsupervision, by the. operator once the aluminum tubing has been clamped in position and the device turned on by the operator.

Another object is an electrical heating device of the above-described character which will very accurately maintain aluminum tubing 01' similar pieces between an upper and lower temperature which describes the temperature range, and will oscillate the temperature of the aluminum tubing back and forth between these two limits for a predetermined period of time.

Other objects will appear from time to time in the ensuing specification and drawing in which a schematic wiring diagram with various associated parts of my invention is diagrammatically illustrated.

In the drawing, a conventional source of line current is provided at 10, it being understood that this current is the usual 115 volts A. C. The current is carried to the invention through a pair of conventional leads 12 and 14. A manually operable switch 16 is provided in the line 14, but it could be in either lead. A step-down transformer 18 is connected in parallel with the line current through a pair of leads 20 and 22.

The high side of a main step-down transformer 24 is connected to the line 12 through a lead 26. The high side of this transformer 24 is provided with a plurality of taps 28, each of which is connected to the pair of

tap switches

30 and 32 through an appropriate number of leads. For purposes of illustration, tap switch 32 will be referred to as the high temperature tap switch, while tap switch 30 will be referred to as the low temperature tap switch. The switch selector arm of each tap switch is connected to a pair of

contacts

34 and 36 through

appropriate leads

38 and 40.

Contacts

34 and 36 are associated with another pair of contacts 41 and 42 respectively, each of which may be connected to the line 12 through lamp indicators 44 (for contact 41) and 46 (for contact 42).

The low side of the main step-down transformer 24 is connected to the ends of an appropriate clamping 7. 2,828,405 Patented Mar. 25,-. 1.958

ice

mechanism, indicated. generally at 48,. through a pair of appropriatev leads 50' and5'2.v The clamping mechanism.48.can beofanyconventionalshape or configuraa tion and its ends. are designed. to releasably' clamp a workpiece W. The clampingmechanism48 may have a pair of pivoted clamping elements spring-biased to-. ward'each'other withelectrodes54. and 56 on its ends so. as to rigidly clamp. a. workpiece W between them.- With a workpiece positioned between the two electrodes, the circuit for the lowside-ofithemain step-down transformer. will be completed.

A toroidal coil 58 may surround the" lead 50 and is connected to an appropriate meter. 60'through a pair of leads. 62 and 64. The. meter 60 is appropriately graduated so that the amount of current is readily reflected and observable.

The low side ofthe step-down transformer 18' is con! nected in series with arelay coil 66 and by appropriate leads 68 and 70 to a thermostat 72- positioned on the workpiece W adjacent the. electrodes. 54 and 56. The core 74 on the relay. coil 66 carries a pair of. contacts 76 and 78 which engagev

contacts

34 and 41, or 36 and 421 Itshould be. understood that the core 74 of this relay canbe spring-biased into one. position and moved into. the other position when the relay 66 is. energized.

If. desired, a timing mechanism and. switch 77 can be put in one of main line lads- 12. or 14 so that the unit will automatically. be deenergiied after a selected period of time. 7

The a use, operation. and function. ofmy invention are as follows:

To connect two aluminum pieces together, the heating period used is dependent upon the material used to connect the two workpieces. In my specific case, I use a thermo-setting plastic which involves a curing process. This plastic sets after a certain period of time and any additional heat applied to such a connection will only burn the plastic. My unit has a main circuit and a secondary circuit jointed together by a step-down transformer 24. A pair of branch circuits form a part of the main circuit and connect a plurality of taps on the high side of the transformer to the source of electric power. The taps are connected to two tap switches which complete the branch circuits. An auxiliary circuit controlled by the thermostat 72 includes the relay 66 and the relay selects one of the branch circuits.

Sections of aluminum tubing or the like in the form of workpieces W to be secured together are positioned between the

electrodes

54 and 56. The thermostat element 72 is positioned on the workpieces W directly adjacent the electrodes so that it will reflect the temperature of the joint. The operator then positions the manually settable tap switches 30 and 32 at selected positions to establish the desired upper and lower temperature limits of the temperature range and closes the manually operable switch 16. The thermostat 72 is normally open and the relay 66 is not energized. Contacts 76 and 78 are spring-biased into engagement with the contacts 36 and 42 so that the current passing through the step-down transformer 24 is controlled by the high temperature tap switch 32. As soon as the temperature of the workpiece W reaches the selected high temperature value, the thermostat 72 closes and energizes relay 66 drawing the contacts 76 and 78 into engagement with

contacts

34 and 41. This closes the low temperature tap switch circuit, and the stepdown transformer 24 is then on the low temperature heat for the

electrodes

54 and 56. The temperature of the workpiece W will then gradually cool until in a short period of time the thermostat 72 will open again and deenergize the relay 66. This reverses the contacts and the high temperature tap switch 32 is in use again.

The

lamps

44 and 46 are in parallel with the two tap switch circuits so that the operatorcan quickly tell whether the unit is on low or high hea The coil 58 with its meter 60 reflects whether the unit in general is operating satisfactorily. Its primary function is to reflect whether or not proper contact has been made between the

electrodes

54 and 56 and the workpiece W.

It should be understood that the tap switches 30 and 32 are manually settable so that the upper and lower temperature limits are adjustable. Each of the tap switches are shown as individually adjustable but they could be suitably connected together so that they would be adjusted together while being disposed at a fixed angle with respect to each other.

While I have shown and described. the preferred form of my device, it should be understood that many alterations, modifications and changes can be made without departing from the inventions fundamental theme. For example, I have described the device as being used primarily for welding, soldering, or joining together aluminum tubing; however, it should be understood that the device can be used to heat any type of workpieces when the operator desires to hold the workpiece in a temperature range between upper and lower temperature limits for a predetermined period of time. The current used in the line 10 could also be any voltage. I have stated that the thermostat 72 is normally open; however, this could be reversed with the contacts 76 and 78 being spring-biased intoengagement with the

contacts

34 and 41. I, therefore, wish that my invention be unrestricted except as by the appended claim.

I claim:

In a device for electrically heating aluminum tubing workpieces and the like, a main circuit adapted to be connected to a source of electric power, a secondary circuit with a pair of electrodes adapted to engage the aluminum tubing workpieces to be heated, a step-down transformer between themain and secondary circuits with its low side in the secondary circuit, the main circuit including a pair of parallel branch circuits, each completing the main circuit between the high side of l the transformer and the source of electric power, two

sets of control switches in the branch circuits, the high side of the step-down transformer having a plurality of taps, each of the branch circuits including a manually adjustable tap switch connected to the taps, the tap switches being 'in parallel, each having contacts connected to all of the taps, auxiliary circuit connected to and energizable by the main circuit by an auxiliary step-down transformer, the auxiliary circuit including a temperature responsive switch responsive to the temperature of the aluminum tubing workpieces for opening and closing the'auxiliary circuit, and a relay in the auxiliary circuit controlling the sets of control switches for closing one set of control switches when the tem perature responsive switch is closed, thereby. closing the auxiliary circuit, to energize one branch circuit and for closing. the other set of control switches when the temperature responsive switch is open, thereby opening the auxiliary circuit, .to energize the other branch circuit.

References Cited in the file of this patent