US1867428A - Heater circuit and control - Google Patents

Description

July 12, 1932.

Filed April 2. 1950 2 Sheets-Sheet 1 INVENTOR FRED G.VON HOORN July 12, 1932. F. G. VoN HOORN v 1,867,428

HEATER CIRCUIT ANDA CONTROL v Filed April 2, 1950 2 Sheets-Sheet a Fly-3:7- Y 4/ I 5/ W, z/ {Z 7% i Z v 3 V T 67 q Z; T 7,2" l d9 70 E a 7/ 53 INVENTOR FRED c. vo- HOORN' WYA Wy 'v i225: ailorizeys 45 A {7 B 45? I I Patented July 12-," 1932 G. VON HOORN, 0F BRIDGEPCRT, CONNECTICUT, ASSIGNOR T0 TEE BRYANT ELEC- TRIO COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPCBATION OF CONNECTICUT HEATER CIRCUIT AND CONTRCL Application filed April 2, 1936. Serial No. M1317.

This invention has to do with the control of electrical heating elements and with a system including a two-part resistance unit and a switch suitably connected to establish circuits for giving high, medium and low degrees of heating selectively, whether the current is obtained from a two-wire feed line or from a three-wire line having a neutral Wire. The three-wire line may be either'a direct current line of the Edison type, an alternating current single phase line, or two phase lines and the neutral of an alternating current, three phase, four wire system. A single switch is provided, and with any of these types of feed and without change in the arrangement of the contacts or in the connections from the switch to the heater unit, the three degrees of heating and an open circuit condition are obtained at will by putting the switch in its different positions.

In the drawings:

Figures 1, 2, 3 and 4 are diagrams of the connections established between a supply line and a two-part resistance by the different blades of a switch in its-high, medium, low and cit positions respectively.

Figure 5 is a diagrammatic view of a transformer feeding a single phase, three-wire line.

. Figure 6 is a similar View representing either a generator or the secondary winding of a so called star transformer feeding a three phase, four-wire line.

Figures 7 and 8 are views in elevation from opposite sides of a switch arranged to embody the invention.

Figure 9 is a plan View of the base of the same switch, only the fixed contacts being in place.

The resistance unit has an intermediate connection point giving two parts or resist ances A, B which are put in circuit in diilerent ways to give difierent degrees of heating, the common use being in an electric range. The range as generally built and sold has a switch and "feed line busesor other feed line connection means as parts of its structure, in addition to the resistance unit, so

that it need only be connected with the feed wires to be operated.

In some districts the current is supplied by a three-wire line of which one wire is at neutral potential. This may be an Edison threewire directcurrent system or the analogous alternating current line from a single phase source, (see Fig. 5) the neutral 11 of which is obtained by tappingin at the mid-point 10 of the secondary winding of the transformer. In other supply systems, three wires, including a neutral wire, are used at any one point but they are three of the four wires of a three phase line leading from a generator or from the secondary winding of a star or Y transformer (Figure 6). In that case the neutral wire 12 is connected to the neutral point 13 of the transformer and each of the other three wires 14, 15, 16 is connected to a phase winding. The yoltage between any two phase lines, e. g. 15, 16, is not the same as that between a phase line and the neutral wire 12 but is of the order of 1.7

times as great' When the neutral and two phase lines are used as a three wire supply at a particular point, there is a similarity to the single phase three wire system but not an identity with it since in the latter the voltage difference across the outside lines is twice the voltage across one outside line and the neutral line 11, whereas in the four wire, three phase system, that is not the case. Finally, there is the common two-wire system, either with direct or alternating cur-' rent, which is used in many cases as the supply for electric ranges. 1

The switch andtheconnections described below are such that an electric range made in accordance with them may be used, without change in the switch or in the connections be tween the resistance, the switch and the line terminals, regardless of which of the types of feed described above is used, the only change in any other part of the range being the addition or removal or" a connection between two of the feed line terminals to change from a three-wire feed to a two-wire or vice versa. Such ranges therefore may be used in dif ferent localities were the power systems are difi'erent. The switch, which is the part requiring the most processing, may be the same for all ranges and being thus standardized may be manufactured with greater economy.

The switch shown here is of the three blade type and in its mechanical construction may be of any known suitable type giving a rotation of the three blades in unison in successive steps or quarterturns.

The upper blade or commutator 20 of the switch has three arms of equal length and at the level at which it turns are two fixed contacts 21, 22 at adjacent quarter points about the base. The middle blade 30 has three blades also, one of which, 31, is longer than the other two, 32, 33 which are at right angles to it. Considered with reference to angular position, this blade has its arm 31 on the side opposite from that arm of the upper blade which is at right angles to the other two. There are three fixed contacts at the middle level, including two, 34, 35, at adjacent quan ter points opposite the quarter points at which the upper fixed contacts are located, these two being long enough to engage either a long or a short arm of the middle blade 30. The third, fixed contact 36 at this level is beneath the upper contact 21 or, in other words, is at the same quarter point and is a short Contact, that is to say, it can be engaged by the long arm 31 but not by the short arms 32, 33. The. lower blade 40 has two arms 41, 42 which are in line on a diameter of the blade and parallel to the two arms of each of the other blades that are in line with each other. Co-acting with these arms 41, 42 are two diametrically opposite fixed contacts 43, 44 both long enough to be engaged by either arm of the blade. The contact 43 is at the same quarter point as the middle contact 35, and the other lower contact 44 is beneath the upper contact 22.

The upper blade controls some of theconnections between one end 45 of the resistance unit and one feed wire terminal while the lower blade controls altogether the connections between the other end 46 of the resistance and a second terminal. Themiddleblade has the control of the connection between the intermediate point 47 of the resistance and a third terminal in addition to controlling the part ofthe connections, between the said one end of the resistance and the corresponding feed wire terminal, that are not controlled by the upper blade. "It will be noted from the description following that the middle blade acts to close a connection from the one terminal to the one end of the resistance 45 only when the upper blade is in an open position and when the middle blade itself is not acting to-close a connection from "the intermediate point 47 of the resistance to the third ter- B by the line 50 while the other upper con- V tact 22 is connected to the bus C by the line 51. The conductor 52 connects the contact 36 of the middle deck with the line 50, hence with the same end 45 of the resistance B, and the middle contact 34 is connected with the intermediate point 47 of the resistance A by the line 53, the connection to the bus D being from the contact 35 by way of the line 54. One

lower contact 43 is in connection with the outare mutually insulated and are spaced to turn at the levels of the fixed contacts. The latter are mounted on the switch base 62 around the well 63 in which the switch movement, including the escapement for giving a snap action, is mounted.

The wall of the base is cut away at certain points to form ledges at the desired three levels. A low ledge64 supports a strap 65 which extends out fromthe ledge and is bent downwardly, and which carries the lower fixed contact 44 at one end and a binding post 66 at the other end. The binding post scrveseither to connect directly to the feed line (as shown in Fig. 9) or, where a panel of buses is used, to a leader forming the connection 56 to the bus E as described above and as illustrated in Figures 1 to 4. A ledge 67 at a higher level provides support for a binding post 68 connected directly with the contact 34 at the middle level and serving as a load terminal, being intended for the connection 53 leading to the intermediate point" 47 of the resistance. Between these two ledgesand on the top of the'base wall is secured a binding post 69 which has a curved extension 70 to the quarter point at one side of it where the extension positions the contact 22, formed by its end, at the level of the upper deck, directly above the contact 44.

This binding post 69 is for, either the line 51 7 leading to the bus C or a feed line wire itself.

On the other side of the base isa low ledge 71 on which is a binding post 72 integral with the lower contact 43, this binding post providing a terminal for the line 55 connectmiddle deck supports a binding post 74 that is directly connectedyby a curved extension 75 to the middle contact 35 thus located above the lower contact 43. Either the line 54 from the bus D or the feed wire D itself is connected to this binding post 7 4 which may be referred to as a mid-connection as it is the point of connection between the switch and the feed line that is the neutral in the three memes I wire supply. On the same ledge 73 is a bind ,shown in Figure 5, the busD is connected to the neutral wire and the buses C and E to the outside wires. In that case, the positions of the switch blades and the difi'erent connections thereby brought about are as shown in Figures 1, 2, 3 and 4 respectively for high, mediumand low heating and for the open circuit condition. For the high degree, the two resistances are across the outside wires, the lower blade 4 0 connecting one outside wire to the outside end of the resistance A nection with the intermediate point of the resistance but that is not a material factor with either an Edison or a single phase threewire supply since the neutral is not relied upon to determine the current flowing in each resistance. In the next position of the switch, that is, with the blades advanced one quarter turn clockwise, the resistanceA is cut out by the lower blade 40 and the resistanceB is put across the outside line and the neutral by reason of the connections from bus C to bus D through the upper blade to the resistance and thence through the middle blade. This is for medium heating.

Another turn of the blades gives the connections for low heating, putting the two resistances in series across one outside line and the neutral line. The lower blade connects the outside feed line E to the outer end of the resistance A while, the middle blade connects the outer end of the resistance B with the neutral line by way of the lines 50, 52, 53 and bus D.

' A further. turn of the blades opens all ofthe connections to the resistance unit. It is to be noted that in this off position, all of the blades are disconnected from the live contacts 22, 35 and 44, thus giving a complete three-pole break, a condition that is very desirable.

When the current is received from a threewire supply consisting of two phase lines and a neutral forming part'of a three phase four-wire system, no changes whatsoever are made in the switch or in the connections from the switch to the resistance. The neutral feed wire 13' is connected with the bus D and the two phase wires (e. g. 14, 15 in Figure 6) are connect-ed respectively with the buses C and E. When the switch blades are turned, the same connections are established, putting both resistances across the outside lines with a connection from the neutral line to the intermediate point for high heating, one resistance alone across one outside line and the neutral for medium heat, and both resistances in series across the other outside line and the neutral for the low degree of heating. As in the case of an Edison three-wire feed or a single phase three-wire feed, this arrangement gives a balanced load. 7 I

The connection from the neutral tothe intermediate point in the high heat position becomes important when the three Wires of a three phase, four-wire supply are used. That connection is the one established, by the middle blade 30 in the position for high heat, from the neutral bus D to the intermediate point 47 of the resistance. As said above, the voltage across two phase wires is not twice the voltage between one phasewire and the neutral as in the Edison and the single phase three-wire systems, With the intermediate point at the potential of the neutral wire, however, the voltage across each resistance is the phase voltage so that the effect given is the same as having twice that voltage across the two resistances in sefrom the-switch to the resistances and to the buses, but provision is made to adapt the buses to the two feed wires. A short strap, indicated by the dotted line F in Figure 1, is added to connect the buses C and E. Then one feed wire is connected to either of'these buses and the other feed wireis connected to the bus D that serves as the neutral in the three-wire feed. That isiequivalent to connecting the upper contact 22 to the lower contact 44. and feeding both from one supply wire or to connecting one side of the two-wire line to both terminals C, E.

The three degrees of heating are obtained in the same three positions of the switch blades. In the position shown in Figure 1, the two resistances are put in parallel across its the-mains because the intermediate point is dle blade and the lines 52 and 50 between the switch and the resistance.

As set forth ab0ve,.it is possible to con- 'nect the feed wires to buses forming part of the heater installation and to connect the switch contacts 22, 35 and 44 with these buses. Instead of using buses, the binding posts on the switch itself may be used as the connection pointsfor the feed Wires. If desired other expedients may be adopted as there are many available- The words feed wire terminals are used here to designate generally the means for effecting the juncture between the switch contacts and the feed wires, with no intent to put a limitation on the way the connection is brought about. For no other reason than to give it a name for more convenient reference, the feed wire terminal that is at the neutral when a threev wire feed is employed and that is at the potential of one side of a two-wire line when that is used, is referred to as the mid-terminal. In adapting the system to a twowire feed, the connection F between feed wire terminals may be of any sort suitable for establishing the potential of one side of the two-wire line at the two terminals; or one of the two wires may be branched and connected with both terminals. The changeover may, if desired, be made by changes in the switch designed to connect the two contacts 22 and 44 or their equivalents but that is not necessary.

I have used the term feeder in the appended claims with the intent that that term of the resistance to one feeder, a second blade arid contacts controlling connections from another feeder to the midpoint and to the other end of the resistance, and closing a connection to the midpoint in two consecutive on positions and to said other end in a third.on position, the first blade 'being open in the second of'said consecutive on positions, together with a third blade controlling connections from said other end of the resistance to a third feeder, and closing a connection in said two consecutive on positions and opening it in the third on position, said switch having a spindle to which said blades are connected and by which position, a second blade connecting the neutral wire only with the mid-point of the resistance in the high and medium positions and only with the said one end of the resistance in the low position, and a third blade connecting the other outside wire only with the other end of the resistance in the high and low positions and not connecting them in the medium position said switch having a spindle to which said blades are connected and bydvhich they are rotatable simultaneously.

3. A switch having three circuit closing positions for giving high, medium and low degrees of heating when controlling flow of current in a two part resistance from a two- W1I'8 feed line, the said switch having one blade connecting one side of the feed line to one end of the resistance in the high and medium positions and not connecting them in the low position, a second blade conmeeting the other side of the line only with the mid-point of the resistance in the high and medium positions and only with the said one end of the resistance in the low position, and a third blade connecting the said one side of the line with the other end of the resistance in the high and low positions and not connecting them in the medium position said switch having a spindle to which said blades are connected and1 by which they are rotatable simultaneous y.

In'testimony whereof I have signed my name to this specification.

FRED G. VON HOORN.

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