US1973630A - Switch - Google Patents

Description

Sept. 11, 1934. M. .1. JOHNSON SWITCH Filed Oct. 18, 1932 lab Ho Patented Sept. 11, 1934 UNITED STATES PATENT OFFICE to The Lewis Enlin C mpany, Naugatuck, Conn., a corporation of Connecticut Application October 18, 1932, Serial No. 638,292

4 Claim.

This invention relates to switches particularly of the type adapted for use with currents of low voltage.

In certain phases of the electrical arts, as for 5 instance when it is desired to measure temperatures or other conditions by means of thermocouples, the contact-resistance is a factor and it is essential that it be reduced to a minimum. For instance, in the example mentioned where the current source is a thermocouple the contact resistance must be substantially nil in order for the instrument properly to indicate the temperature.

Accordingly it is an object of this invention to provide a switch having very low contact resistance.

Again referring to the example given, where the source of current is a thermocouple, it is frequently desired to have a single indicating instrument which may be connected to one after the other of the thermocouples, and frequently as in the case of airplanes testing to a large number of points when it is desired to determine the temperature.

' An object of this invention is to provide a rotary switch which will permit an indicating instrument to be connected to the thermocouples one after the other with a minimum of current leakage, both as between the leads coming from the thermocouples and the leads coming from the indicating instrument, and yet permit a large number of thermocouples to be controlled by the single switch.

A feature of the present invention is the provision of a rotary switch in which the contact arm is given a definite step-by-step movement, so that there is no danger of the arm engaging two contacts at the same time which would result in the danger of short-circuiting, or, in giving an improper reading to an indicating device if the switch is electrically connected for such a purpose.

Another feature of the present invention is the provision of a rotary switch structure which may be used equally well as one-way single make and break switch, or, as a two-way double make and break switch. To this end, there is provided a main working mechanism which, if used singly, is particularly adapted for series operation and, when used doubly, one superposed upon the other, is particularly adapted for two-way operation.

It is another object of the present invention to provide a rotary switch especially adapted for use in quickly and alternatively connecting a plurality of testing devices such as thermocouples with a plurality of indicating devices in one form, and to provide a related device adapted to quickly and alternatively connect a plurality of test devices to a single indicating device by the mere expedient of turning a single actuator step-by-step into various stations.

A feature of the present invention is the provision of a plurality of superposed thin switch arms with fingers for engaging the contacts rather than a single comparatively heavy arm, which improve electrical connection between the contacts. In one form, these arms are supported at a point remote from the switch actuating shaft in such manner that a substantially equal amount of pressure is applied by the switch arms to both a main contact near the center of switch and the secondary contacts which are located a considerable distance from the center.

Another feature of the present invention is the provision of a bearing which serves the double purpose of journaling the actuator shaft and forming a main contact.

, A further feature is the provision of a built up switch unit which may be assembled upon an end cap of the switch casing and quickly assembled to the casing by merely sliding it into place. This unit is also arranged to align and support a large number of current conducting 85. wires.

Other features and advantages will appear hereinafter.

In the drawin Figure 1 is a front view of the rotary switch of the present invention.

Fig. 2 is a sectional view taken axially through the center of the switch, on the line 2-2, Fig. 1.

Fig. 3 is a cross-sectional view taken on the line 3-3, Fig. 2.

Fig. 4 is a similar cross-sectional view taken on the line 44, Fig. 2.

Fig. 5 is a cross-sectional view taken on line 5-5, Fig. 2, and shows the structure for insuring a step-by-step movement.

Fig. 6 shows the switch of the present invention connected in parallel with a plurality of test devices and a single indicating device.

Fig. 7 is an axial sectional view similar to Fig. 2, but shows the one-way form.

Fig. 8 is a plan view of the one-way form of switch connected with a plurality of test devices and a plurality of indicating devices.

Because the switch of the present invention will find its greatest use-or application in a twoway form (double make and break) as shown in Figs. 2, 3, 4 and 6 in particular, this form will be described first, although it should be understood that parts thereof are equally advantali geous in the one-wayform described hereinafter.

The two-way switch 12 comprises a cylindrical casing 13 having screw receiving ears 14-for attachment to an instrument board or the like, and is enclosed with a dial plate 15 on the front and with a cap 16 at the back. The dial plate is held upon the casing with small screws 17 and the cap is held in place with screws 18 passing through the casing and entering suitably threaded holes in an extension 19 portion of the cap which fits within the casing.

According to the present invention the cap also serves as a mount for a lower switch unit 20 and an upper switch unit 21 in that form of the invention shown in.Figs. 2 to 6 inclusive and for the switch unit 22 in that form of the invention shown in Figs. 7 and 8.

. The lower switch unit 20 comprises a plate 23 of insulating material provided with a hole near the center adapted to receive a bearing 24 which may be either forced in place or held in place by a nut 30 drawing the bearing into the plate until a flange 25 thereon is drawn firmly into engagement with the plate. The bearing is provided with a hole 26 in which ashaft 27 is supported for rotation.

. The main bearing, in this form of the invention, also serves as a main contact and for this purpose a lead 28 and a terminal washer 29 are connected to the shank of the bearing where they are held in place with the nut 30 when the latter is tightened.

The plate 23 also forms an insulating support for a plurality of secondary contacts 31 which are preferably circularly arranged relative to the axis of the bearing 24 and the shaft 27. These contacts are provided with a head portion and a shank extending through suitable holes with a nut 32 on the under side to draw and hold them in place. Feed wires 33 are then connected to the individual contacts through the medium of a second nut 32 on each threaded shank, or by spot soldering as shown in Fig. 2. Only one or two representative wires 33 are shown connected to the contacts 31, but in regular use a wire would be connected to each contact. This has been done so that other details in the drawing may be shown more completely- Current is passed from the individual secondary contacts 31, one at a time, to the main contact 24 through a yielding switch arm 34 carried by the shaft 27. Downturned fingers 35 and 36 on the arm engage with the contacts 24 and 31 respectively. In order to insure good electrical connection and transmission of current the arm 34 is preferably made of several pieces 34', (four as shown) superposed upon each other, and with the end fingers 35 and 36 on eachslightly beyond the ends of the next lower piece and with succeeding fingers of slightly greater length than the thickness of the material so that each piece is capable of a maximum flexing action and so that each finger is sure to connect with the contacts.

This connection and flexing action is further improved according to the present invention by the provision of a switch arm carrier 37 of insulation connected to the shaft with a pin 38 and arranged to support the arm pieces 34' at a point remote from the axis of the shaft 27 and near the center of the arm 34 so that all of the fingers 35 and 36 engage the contacts 24 and 31 with substantially equal pressure. Accordingly, the carrier 37 is provided with an abutment 38a oflset relative to the axis of the shaft, and a screw 39 is passed through the arms 34' and into a suitable threaded hole to secure thearms to the oflset abutment 38a. on the carrier. Insulation of the arm 34 from the shaft 27 is effected by the carrier 37 which is made of insulation, and by a sleeve 40 of insulation on the shaft 27 which prevents a U shaped portion 41 (see Fig. 3) of the arms from engaging the shaft.

It is customary to provide a single flat switch arm in rotary switches, and when this is provided it is necessary to have it made of thick material. Such an arm does not have much resiliency and consequently there is the danger of both insuflicient and excess pressure on the contacts which would cause, respectively, incomplete electrical connection and special effort in operating the switch. However, with the present invention the several thin arms 34' may be drawn yieldingly toward the contacts a considerable extent so that there is never any danger of insuflicient conduction and will yield easily for high contacts and thereby not impede operation of the switch. Also the downturned fingers 35 and 36 tend to cut into the top of the contacts and thereby remove corrosion and insure good electrical connection at all times.

The shaft 27 and associated switch arm 34 may be rotatably maintained in the desired axial position with the desired degree of pressure on the contacts by passing any suitable collar or a collar 42 portion of an index plate 45 onto the shaft until it engages with the lower end of the bearing 24 where it is fastened in position on the shaft with a screw 43 after the contact arm 34 is located for the proper amount of pressure upon the contacts 24 and 31. Although this type of connection serves to keep the fingers on the switch; arm in goodengagement with the contacts there is no snap action from contact to contact, which is desirable in some instances.

In its preferred embodiment the present in= vention provides a structure 44 for effecting a snap action between the contacts 31, one after the other, so that there is a quick make and break electrically and a definite step by step movement of the switch arm, and so that the fingers 36 on the switch arm 34 will engage with only one contact 31 at a time. The present preferred arrangement for accomplishing this comprises a combined collar 42, and the index plate 45 connected to the lower end of the shaft 27 with a set screw 46 and having a plurality of equally spaced and radially arranged indexing notches 47 in which a spring plunger. 48 is adapted to work. The spring plunger comprises a sleeve 49 having a threaded connection 50 with the plate 23 and having a bore in which a plunger pin 51 is supported for axial movement and yieldingly urged toward the index notches 47 by a spring 52 which is held in the bore by a screw 53. The index plate is located on the shaft so that the plunger 51 is in one of the notches 47 when the switch arm 34 is centered upon a contact 31 so that as a user begins to rotate the shaft 27 the angular walls of the notches 47 tend to restrain rotation until the end of the plunger reaches the top of the plate. Thereafter, a quick snap action of the plate 45 and switch arm 34 to the next succeeding sta- 1193 is accomplished as the end of the plunger rides over one of the intermediate flats 54 between thenotches. The plunger 51 snaps into the next succeeding notch so that there is a positive step-by-step action, and a quick make and break electrical connection between the contacts. I

The upper switch unit 21 is similar to the lower switch unit 20 in many respects, for it comprises a plate 23', hearing and main contact 24 and a plurality of secondary contacts 31'. However, another lead 55 is connected to the main contact and a plurality of other leads 56 are connected to the secondary contacts. Also, a slightly longer shaft 27a is Journaled in the bearing. A small carrier 57 is connected to this shaft with a pin 58 and like the carrier 37 it supports an arm 34a preferably made from a plurality of arm pieces on an abutment 59 with a screw 39 offset from the axis of the shaft so that fingers 35' and 36 thereon engage the contacts 31' and 24' with substantially equal pressure.

The switch arms 34a on the upper switch unit 21 are like the arms 34 on the lower switch unit 20 insulated from the shaft 27a by the carrier block 57 which is made of insulating material and engagement of the arms with the shaft is prevented by a sleeve 40 of insulating material. After the contact arms are assembled to the carrier 57 the shaft 27a is passed through the bearing 24 and moved toward the contacts until fingers 35' and 36' engage their respective contacts with the desired degree of pressure where they are held in place by a space sleeve 60 engaging'the bottom of the bearing 24' when a clutch collar 61 is fastened on the shaft with a screw 62.

The lower and upper switch units 20 and 21 are supported one upon the other and supported on the end cap 16 for rigidity and to prevent turning. This assembly is effected by passing the main lead wires 28 and 55' through suitable apertures 63 and 64 in the plate 23 and apertures 65 and 66 in the cap 16; and by passing the secondary lead wires 56 of the upper switch unit 21 through apertures 67 in the plate 23 of the lower switch unit and through apertures 68 of the end cap while the secondary leads 33 of the lower switch unit 20 are passed through a set of apertures 69 in the end cap. If preferred, the wire clearance passages 63, 64 and 67 may, in order to facilitate assembly, be in the form of notches on the periphery such as the one or two representative notches 70 shdwn in Fig. 3. However, location and rigidity of the leads is better insured by threading them through the holes as described hereinbefore.

After the leads are so threaded through their respective apertures the upper and lower switch units 20 and 21 are connected through the medium of a clutch connection 71 comprising a plurality of pins 72 on the collar 61 extending into suitable holes 73 provided therefor in the carrier 37 of the lower switch unit. This clutch connection insures conjoint rotation of the shafts 27 and 270.. A substantially close fit is provided by this clutch so that the spring plunger 51 and indexing devices 44 of the lower switch unit ,effects a conjoint snap movement and quick make and break electrical action of the upper switch unit 21.

The dial plate 15 may be fastened in place with the screws 17 either before or after the switch units 20 and 21 and end cap 16 are connected to the casing for the upper end of the shaft 27a passes through a hole 72 therein, after which an insulating sleeve 73v is placed on the shaft so that there will be no short circuit between the plate and the shaft and then a handle or actuator knob 74 is passed onto a reduced section of the shaft where it is held in place with a holding screw 75. A pointer 76 is connected to the actuator knob which points in the direction of the station numerals 77.

A plurality of standards 80 are connected to the plate 23' of the upper switch unit with screws 81 to properly space and support the upper unit relative to the lower unit, and completed by a threaded shank portion 82 of lower standards 83 passing through the plate 23 of the lower switch unit to enter threaded holes 84. Connection of the two united switch units to the end cap 16 is then accomplished by passing flat head screws 85 through the end cap and tightening them in the threaded holes 86 of the lower standards 83. This structure is such that all of the assembly work may be done extraneously of the case 13, may be added to the case easily in final assembly,'and may be taken from the case very conveniently for repairing or alteration in the wiring.

This duplex form of switch 12 is especially advantageous where it is desired to have a two way or double make and break switch action and is especially advantageous for use in connecting a plurality of the thermocouples 78 or other similar test devices to a single indicating device 79 as shown schematically in Fig. 6. The indicating device has the two leads 28 and 55 extending to the main contacts 24 and 24' respectively and each thermocouple 78 has the wires 33 and 56 extending to the secondary contacts 31 and 31' on the lower and upper switch units 20 and 21 respectively. This arrangement is such that current from a thermocouple 78 passes through the leads 33 and 56 to associated secondary contacts 31 and 31' on the lower and upper switch units, thence through switch arms 34 and 34a to main contacts 24 and 24 and thereafter through the leads 28 and 55 to the indicating device 79, for a reading. As the knob 74 and associated switch arms are moved into successive stations individual thermocouples 78 are connected electrically to the one indicating device.

From the above it will be seen that the present invention provides a switch for the wire of each pair of leads from the thermocouples which are connected respectively to contacts on widely separated insulated plates and that the leads from the indicating instrument are also respectively connected to contacts on these widely separated plates. Hence when the switch handle 74 is turned an individual pair of leads from a single thermocouple and no other leads from any thermocouple is connected to the pair of leads from the indicating instrument. In this way the use of common return wires or other expedients heretofore employed and their disadvantages are avoided.

In Fig. 7 there is shown a modified form of the present invention embracing many of the novel features already described in detail in a one-way or series operation switch 22 which is capable of only a single make and break in the electrical circuit. This form of switch like the lower and upper switch units 20 and 21 comprises the plate 23 supporting a plurality of alternate contacts 31a. and 31b and a bearing 24 for a shaft 87 near the center. In this form.

of the invention the bearing is notutilized as a.

main contact and may for economy be dispensed with by journalling the shaft directly in the insulating plate 23; however, to reduce wear and to improve operation of the switch it is deemed desirable now to provide the metal bearing.

In this form, however, the shaft 87 supports a carrier 88 of insulation, which extends a substantially equal amount on both sides of the shaft to provide a double support for a switch arm 89. The latter in its preferred form extends in substantially a straight line across the axis of the shaft 87 and at its outer ends is provided with turned down 'fingers 90 and 91. The arm at its center is provided with a hole sufficiently large to clear the shaft at all times and is connected to both sides of the carrier with screws 92. This arm 88 similarly to the arm 34 in Figs. 2, 3, and 4 is preferably made of a plurality of thin arm pieces 89 each superposed arm piece being slightly longer and integral fingers of each being of greater height than the next lower one. Thus, each of the arm pieces is capable of individual flexing and the fingers on each are capable of fully' engaging the contacts.

The switch arm may be yieldingly held in engagement with the contacts 31a and 311) by moving them toward the contacts until the desired degree of pressure is obtained and then tightening the collar 42 to the lower end of the shaft with the set screw 43. It is preferred, however, to also use the index plate 45 and the spring plunger 48 in the plate 23 at 50 so that a snap movement and a quick make and break action occurs. The carrier 88 and switch arms thereon are connected to the shaft with a pin 93 so that they cannot shift vertically and to insure their rotation with the shaft.

This form of the present invention is especially adapted for the use in electrically closing a plurality of lines 94, each line including a thermocouple 95 and an associated indicating device 96, with a wire 97 extending from one pole of the thermocouple directly to the indicating device, another wire 98 extending from the indicating device to the contact 31a on the 'switch, while yet another wire 99 extends from the other pole of the thermocouple to an associated contact 31b on the switch. Thus, it will be seen that with this form of switch the circularly arranged contacts contain sets of associated input and output contacts 31a and 31b which are preferably diagonally opposite each other across the axis of the shaft 87, and that fastened to the end cap with flat head screws 102. This assembly is then placed within a short casing 103 and held in place with screws 18. A dial plate 150. is connected to the casing with screws 17. In this form, however, the

switch is provided with only half as many working stations if the plate 23 with twenty eight contacts 31a and-31b is used. For example,

if the ends and 91 of the switch arm 89 are diagonally opposite,- the end 91 will engage with the contact underlying the numeral 28 Fig. 1 when the end 90 movesin a clockwise direction to a contact underlying the numeral 14. Thus, the dial 15a in this form contains the run of numerals 1 to 14 only. Assembly is completed by moving an insulating sleeve 104 onto the shaft 87 and connecting a handle or actuator knob 74 to the shaft in the same manner as shown in Fig. 2.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

Having thus described the invention, what is claimed as new and for which it is desired to obtain Letters Patent, is:-

1. In a rotary switch, a metallic enclosing casing; a stationary plate of insulation in said casing and secured thereto; a metal bearing in said plate and forming a main contact; a shaft extending into said casing and journaled in said bearing; a plurality of secondary contacts on said plate; a switch arm adapted to engage with and pass current from said main bearing contact to said secondary contacts; a handle and pointer on the shaft exteriorly of the casing; and an arm on said shaft within the easing adapted to support the switch arm at a point remote from the'axis of the shaft and substantially midway the length of the switch arm, so that the switch arm engages the main contact and secondary contacts with equal pressure, the switch arm being bifurcated to straddle the shaft and engage the opposite portion of the main contact.

2. In a rotary switch, the combination of a plate of insulation carrying a main contact and secondary contacts and having a shaft journaled in said plate carrying a switch arm adapted to bridge the gap between said main contact and said secondary contact; another plate of insulation carrying a main contact and secondary contacts and having a shaft journaled therein carrying a switch arm adapted to bridge the gap between said main contact and said secondary contacts; means for supporting one of said plates upon the other and in spaced parallel relation; and a connection joining the shaft in the one plate with the shaft of the other plate for conjoint rotation, said connection permitting longitudinal shifting of one shaft relative to the other and including a nonmetallic member to insulate one shaft from the other.

3. In a rotary switch, the combination of a plate of insulation carrying a main contact and secondary contacts and having a shaft journaled in said plate carrying a switch arm adapted to bridge the gap between said main contact and said secondary contact; another plate of insulation carrying a main contact and secondary contacts and having a shaft journaled therein carrying a switch arm adapted to bridge the gap between said main contact and said secondary contacts; means for supporting one of said plates upon the other and in spaced parallel relation; and a connection joining the shaft in the one plate with the shaft of the other plate for conjoint rotation, said connection permitting longitudinal shifting of one shaft relative to the other and including a nonmetallic member to insulate one shaft from the other, one of said shafts having an operating handle and the other having a detent plate :01- holding the shafts in predetermined adable with the latter and the back plate of the casing; main .and secondary contacts and a switch arm carried by said second-named insulating plate; and guide apertures in said firstnamed plate of insulation through which lead wires extending through the back plate of the casing to the secondary contacts on the secondnamed plate of insulation may pass and be held in spaced relation and out of engagement with the secondary contacts on the first-named plate of insulation.

MANFRED J. JOHNSON.

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