US2068713A - Control device - Google Patents

Description

Jan. 26, 1937. N. c. SCHELLENGER CONTROL DEVI CE 5 Sheets-Sheet 1 Filed Dec. 26, 1933 izz/anion Newton GScfzeZZerz Jan. 26, 1937. N. c. SCHELLENGER 2,063,713

CONTROL DEVICE Filed Dec. 26, 1955 3 Sheets-Sheet 2 s W [rzven to) 125 Nezuzfazz CScfieZZenge Jan. 26, 1937. c scHELLENGER 2,068,713

CONTROL DEVICE Filed Dec. 26, 1933 3 Sheets-Sheet 3 I fnventar. Newton C'ScizeZZenger. F7124- fig: z

Patented Jan. 26, 1937 UNITED STATES PATENT OFFICE Application December 26, 1933, Serial No. 703,917

6 Claims.

This invention relates to control devices and particularly to a switch adapted to be combined with a variable resistance device toform a combination unit adapted for use as volume control or tone control apparatus in electrical sound transmitting systems such as radio sets, public address systems, and the like.

More particularly, the invention relates to the switch portion of a combination unit including a variable resistance device having a resistance element and a contactor engaging the resistance element and movable thereover for varying the resistance of the circuit in which the variable resistance is connected and an improved switch of the slow break type arranged to be opened and closed by a predetermined movement of the contactor.

In control devices of the aforementioned type, particularly where the devices are to be employed in radio receivers, it is especially desirable that the switch be small, inexpensive to construct, certain in operation, capable of carrying relatively high currents, operable with a minimum of arcing, and without chattering, both when moved into closed position and when jarred or vibrated while in closed position. These numerous and exacting requirements arise from the compact design of radio receivers and severe usage to which they are subjected.

The switch, when employed as a power current switch, must be capable of carrying for a short time, a short-circuit current of many times, the normal current, and, when employed for example in an automobile radio receiver must be capable of carrying for a short time substantially the short circuit current of the storage battery which may amount to severel hundred amperes. Also, when employed in a portable receiver, the switch must be constructed so as to maintain good contact and operate satisfactorily even when subjected to jars and vibrations.

Where a switch is to be employed to control a circuit supplied with cycle alternating current, such as is commonly employed to supply the power for operating radio receivers, I have found that a switch of the slow break type, wherein the contacts are separated relatively slowly, is to be preferred over a switch of the quick-break type, wherein the contacts are separated relatively quickly. In the latter type of switch, although the contacts are separated quickly, they are not separated quickly enough to prevent the drawing of a long, destructive are between the contacts. This hot arc will continue in existence until the voltage decreases to zero to quench the are, hence, unless the arc is struck at a point of time on the voltage cycle only a very short period before the voltage value decreases to zero, the arc will be in existence sufliciently long to cause detrimental burning due to its comparatively great average length and corresponding large amount of heat developed.

Since the arc is sustained through a relatively great proportion of the half-cycle, the arc is drawn to a relatively great length due to the rapid separation of the contacts, and a substantial amount of heat is generated with the consequent burning and pitting of the contacts and the emanation of conductive gases and incandescent particles of metal, all of which eflects are detrimental to the life of the switch.

The present invention contemplates the design of a switch of the slow break type wherein the contacts are separated so slowly that, substantially irrespective of the portion of the voltage cycle at which separation of the contacts is initiated, the contacts are not separated a sumcient distance to produce an are which generates any considerable amount of heat, before the voltage decreases to a zero value to quench the arc; thereafter the contacts are separated, as will be seen, with no arc, the separation being suflicient to prevent re-striking of the arc before the voltage value again increases from zero to maximum. Since the arc is quenched prior to attaining any substantial length, no substantial amount of heat is generated and there is no appreciable burning of the contacts and substantially none of the destructive eflfects usually attendant upon the occurrence of an arc of long occurrence.

In a manually operated switch, and particularly in a switch ofthe type arranged to be operated by the movement of the contactor of a variable resistance device through a portion of its travel beyond that portion of its travel wherein it is active to vary the efiective resistance of the device, it is desirable that the completion of the opening or closing be signalled by a tactile and/or audible signal. An example of such a signal is the click accompanying the operation of the well-known snap switch. However, the snap switch is a quick break switch and, as pointed out in the foregoing, is not as satisfactory for many installations as a slow break switch. 5

The present invention provides a switch of the slow break type wherein the contacts are maintained in contact under a suflicient pressure to prevent chattering caused by jars or vibrations; wherein the contacts are separated without de- 5 structive arcing; wherein the contacts are brought together with a wiping blow and are separated with a wiping action to keep the surfaces clean and polished; and wherein the completion of the opening or closing of the switch is indicated by a positive signal.

One of the objects of the present invention is the provision of the switch portion of a combination variable resistance device and switch unit which is simple in construction, inexpensive to manufacture and efiicient in operation.

Another object of the invention is the provision of the switch portion of a combined variable resistance device and switch unit of the type wherein the switch is operated by the movement of the contactor of the variable resistance device through a predetermined portion oi its travel, in which unit the operation ofthe switch is accompanied by the minimum amount and intensity of arcing.

Another object of the invention is the provision in switch unit of the aforementioned type 01- a novel mechanism for transmitting movement from a variable resistance device to the switch contacts.

Another object of the invention is the provision'in a switch of the slow break type of an arrangement for producing a tactile and audible indication of thecompletion of the opening or closing of the switch.

Another object of the invention is the provision in a switch or a combined switch and variable resistance device unit of a housing arrangement wherein the terminal elements of the switch are completely surrounded and protected by the housing arrangement.

Other objects of the invention will appear from the following description taken in connection with the appended drawings, wherein:

Fig. 1 is a top plan view showing a combination variable resistance device and switch constructed according to the invention;

Fig. 2 is a side elevational view, showing the device shown in Fig. 1, with portions of the housing broken away to show the interior;

Fig. 3 is a bottom plan view showing that portion of the variable resistance device which carrice the switch, with the switch secured thereto;

Figs. 4, 5, and 8 are bottom plan views, showing the switch. with a portion of the actuator cut away to show the construction, the switch being shown in closed", "break" and open" positions. respectively;

Fig. '7 is an end elevational view showing the switch;

Figs. 8, 9, 10, and 11 are fragmentary sectional views showing constructional details of the switch and associated actuator;

Fig. 12 is an enlarged isometric view of the actuator:

Fig. 13 is an isometric view of the blank from which one of the contacts is formed;

Figs. 14 and 15 are bottom plan and end e1evational views, respectively, of the terminal housing member;

Figs. 16 and 1'7 are bottom plan views showing a modified form of switch, the switch being shown in .closed", and "open" positions, respectiv lr:

Figs. 18 and 19 are fragmentary bottom plan and longitudinal sectional views showing a portion of a switch having a modified construction of circuit completing member;

Hgs.20and2iareviewssimi1arto1 'igs.2and

and 3 showing a device having a modified form of actuator and switch;

Figs. 22, 23, and 24 are bottom plan views showing the switch of Fig. 20 and a portion of the actuating element, the switch being shown in "closed, dead center and open" positions, respectively;

Figs. 25 and 26 are fragmentary sectional views showing constructional details of the switch of Fig. 20;

Fig. 2'7 is an isometric view showing the blank from which the contact member is formed;

Fig. 28 is an isometric view showing a modified form of the gear portion of the actuator of Fig. 21; and

Fig. 29 is a reduced plan view showing the grounding connector.

Referring more in detail to the drawings, Fig. 1 shows a combined switch and variable resistance device unit, the variable resistance embodying constructional features disclosed and claimed in my copending applications Serial No. 672,955, filed May 26, 1933, and Serial No. 871,031, filed May 15, 1933.

The variable resistance device i comprises a base 2 of insulating material carrying a fiat carbonaceous resistance element 3, formed by depositing a conducting film on an insulating support, and connected at its ends to terminals 4, 5, secured to the base 2 and a threaded bushing 6 in which bushing 6 is journaled an operating shaft 1. On the operating shaft 1 is mounted an actuator arm 8 which carries an upstanding switch actuating pin 8 and a contact arm ill, the free end of which arm i engages a diskshaped contact element ll resting upon the resistance element 3. The contact arm III is electrically connected to a third terminal l2, where.- by, upon rotation of the shaft 1, the contact element ii is moved over the surface of the resistance element 3 to vary respectively the amount of resistance connected between each of the end terminals 4, and the central terminal I2. As will be understood, if the variable resistance device is to be employed as a simple variable resistance, instead of a voltage divider, connections will be made only to one end terminal and the center terminal.

A metallic cupped housing member I: is provided with integral ears l4. II, I8, I! which are bent over against the base 2 to secure the housing member ll thereto, thus constituting a closed housing for the variable resistance device I.

A switch It is housed in a housing member is (Figs. 4 to 6) of molded insulating material and having a recess 20 in which is disposed a pair of contact members 2|, 22 and the switch actuating or cam portion 23 of an actuator 24.

The contact member 2|, which is of general straight shape, and formed from a resilient metal having good electrical and thermal conductivity, such as phosphor-bronze alloy, has an end seated in a slot 25 in an end wall 26 of the housing member IS. The contact member is firmly positioned by the corner of a boss 21 extending from the end wall and an opposing projection 28, extending from a side wall 23 of the housing member is which corner and projection 23 grip the end of the contact member 21 and by the cam 23 and the end of the other contact member 22. The contact member 2i is formed with an inclined portion Ill providing a hump II, and with a contact .portion 32 bent to make an angle of substantially 135 with the principal portion of the contact member 2|.

The second contact member 22 is similarly seated in a slot 33 and gripped at the end by the other corner of the boss 21, a projection 34 and the cam 23, and is held thereby in substantial parallelism with the first contact member 2|, The second contact member 22 is likewise formed with an inclined portion 35 and hump 36 and, in addition, has a portion 31 extending substantially perpendicularly from the principal portion toward the contact portion 32 of the other contact member 2|, which contact portion 32 is engaged under pressure, when the switch is in closed position, by a contact portion 33 formed by bend ing out the end of the perpendicularly extend ing portion 31.

The corners of the boss 21 and the projections 28, 34 are so positioned relatively to their respective contact members 2|, 22 that the portions of the contact members 2|, 22 which extend into the housing l9 are forced toward one another. When the switch is in closed position, the contact portions 32, 38 engage under pressure which action, combined with the positioning of the ends of the contact members 2|, 22 by the boss 21 and the projections 23, 34, causes the contact members 2|, 22 to be firmly gripped in the housing l3. When the switch is in a position, such as shown in Figs. 5 or 6, wherein the contact members 2|, 22 do not have full pressure engagement, the cam 23 serves to position the ends of the contact members 2|, 22 to thus assist the boss 21 and projections 23, 34- in gripping the contact members 2|, 22.

The contact member 2| is formed from a blank similar to that shown in Fig. 13, which blank, as will be seen, has a portion 39 formed with a perforation 43 for connection to a conductor (as will hereinafter be described) and an open transverse slot 4| and a tapered portion 42 extending therefrom.

Referring to Fig. 11, the connection portion 33 of the contact member 2| extends through the slot 25 in the end wall 26 of the housing member I9 and the transversely slotted portion engages the slotted portion of the end wall 26 to secure the contact member 2| against longitudinal movement. The tapered portion 42 extends longitudinally of the housing l3 and is spaced therefrom by virtue of its tapered form, thereby being movable freely within the housing 23 without rubbing against the wall thereof. The other contact member 22 is formed from a blank similar to, but longer than, the blank 42 and has a portion 43 provided with a perforation 44 and a slot (not shown) the slot engaging the slotted portion of the end wall 26 of the housing'member ID; the tapered portion of this contact is also free from engagement with the walls of the housing member 9.

Rotatably mounted in the housing member in a position between the contact members 2|, 22 is the actuator 24, formed of molded insulating material. The actuator 24 has the shape shown in detail in Fig. 12 and comprises the switch actuating portion 23 formed as a cam, lying in the switch housing |9 (Fig. 4) and positioned to engage the contact members 2|, 22, and a gear portion 41 (Fig. 2), constituting the female gear element of an intermittent gear mechanism, which gear portion 41 lies in the variable resistance device housing l3 in the path of movement of the switch actuating pin 3 which pin 3 constitutes the male element of the intermittent motion mechanism.

As shown in Figs. 8, 9, 10, and 12, the actuator 24 is formed with a pair of trunnions 43, 43 pro- Jecting from its ends, one of which trunnions 43 is journaled in an integral .cup 53 formed in the bottom of the wall of the switch housing member l9, the trunnion 43 being journaled in a collar 5| formed in a tongue 52 struck from and offset from the end wall of the cupped housing member l3.

The cam portion 23 or the actuator 24 (Figs. 4 to 6) has two diametrically opposite toes 53, 54 positioned for cooperation with the contact members 2|, 22 respectively. The toe 53 does not engage its cooperating contact member 2| when the switch is in the closed position (Fig. 4), but the.

other toe 54 is arranged to bear against its contact member, in all positions of the switch, with sufficient force to prevent the actuator 24 from rattling in its bearings.

A stop element 55 formed integral with the housing member serves to halt the actuator 24 when the cam portion 23 lies angularly of the transverse axis of the housing member l3, in the position shown in Fig. 4. The stop element 55 also halts the actuator 24 when the latter is in the open position,- shown in Fig. 6, wherein the cam portion 23 lies substantially transversely of the housing I!) and the toes 53, 54 are in engagement with their corresponding contactmembers 2|, 22 and contact elements 32, 33 are spreadout of mutual engagement.

When the switch I3 is in the closed position, the contact portion 32 bears against the contact portion 38. The contact portions 32, 38 are pressed into engagement by the boss 21 and projections 28, 34, against the inherent spring pressure of the contact members 2|, 22 and the latter are so shaped and positioned that the force of each is applied along a line directed approximately at an angle of 45 to the line of application of the force exerted by the other contact member, whereby the pressure of one contact element against the other is much greater than the force exerted to move either contact element in the direction in which the cam moves it. This wedging of the contact elements provides a contact pressure sufliciently high that engagement of the contact elements is positive, the contact resistance is uniform, and the contact elements are so t ghtly pressed together that the vibrating of the switch mounting as will often occur in service, cannot cause chattering of the contact elements with the consequent arcing and burning of the contact elements.

When the switch is in closed position, the

perpendicular portion 31 of the contact member 22 is sprung at a greater than normal angle by engagement with the other contact member 2|. As the cam 23 is rotated about its pivot in a counter-clockwise direction (as viewed in Figs. 4 to 6) the toe 54 presses out upon the contact member 22 to move the principal portion thereof away from the other contact member 2|. As the rotation of the cam 23 is continued, the other toe 53'engages its cooperating contact member 2| and the contact members 2|. 2'! are spread apart. During the movement of the actuating member 24 and the simultaneous movement of both contact members 2|.. 22. the spring tension of the contact member 22 acts to move the perpendicular portion 31 in a direction to decrease the angle which the perpendicular portion 31 makes with the pr ncipal portion of the contact member 22. This action, combined with the separating movement of the contact members 2|,

22, causes the contact portion 33 to be drawn 7- along the surface of the other contact portion 52 to provide an extensive wiping action therebetween as will be seen by comparing the position of the contact portions 22, 55 shown in Fig. 4, with their position in Fig. 5. In Fig. 4 the contact elements 22, 55 are in closed position and in Fig. 5, they are at the end of the wiping movement and in the "break" position, Just prior to the separating movement. The extent of the wiping action is augmented by the movement of the contact portion 52 outwardly along a line lying at a small angle to the plane of the areas of contact of the contact elements 52, 25.

Upon further rotation of the cam 23, the contact members 2|, 22 are still further spread and the contact portions 42, ll separated and moved to the position shown in Fig. 6. As will be seen from Fig. 5, the last points of engagement are the heel portion of the contact portion 52 and the toe of the other contact portion 35 and hence any arcing which takes place occurs between these portions of the contact elements and not between the areas that are in contact when the switch is in the fully closed position.

The contact members 2|, 22 are formed with the inclined portions 25, 25 positioned for engagement by the toes 53, 54 when the arm 25 is in the open",position, shown in Fig. 6, wherein the contact members 2|, 22 are held out of engagement by the cam 24. The inclined portions 55, 55 provide the angular humps 3|, 55 on the contact members 2|, 22 whereby, when the switch is being thrown into the "open" position and the toes 55, 54 ride over these humps Ii, 25

and onto the inclined portions 20, 25 the tuming movement of the actuator 24 is accelerated by the spring action of the contact members 2| 22 in squeezing against the toes 53, 54, as the latter tend to ride down the inclined portions 35, 35. The acceleration is made positive at its beginning by the positioning of the humps ll, 25' for engagement by the toes 53, 54 simultaneously whereby a "dead center position is attained by the actuator 24 when the humps 3|, 35 are engaged by the toes 51, 54. As the cam 24 passes through the dead center position, the squeezing action of the contact members 2|, 22 upon the cam 22 rapidly rotates the cam 22 into a position transverse of the housing l9 (Fig. 6) wherein it lies up against the stop 55 and is held in position by the pressure of the contact members 2|, 22 to maintain the contact members 2 22 apart. On account of the lost motion in the intermittent gear mechanism, the cam moves into the open position freely and quickly after it passes the dead center position.

If, when the switch is in open position, as shown in Fig. 6, the cam 22 is rotated in a clockwise direction, the toes 53, 54 ride up on the inclined portions 35, 35, against a resistance to rotation of the cam offered by the necessity of the cam 25 spreading thecontact members 2|, 22 as it rides up the inclined surface. As the toes ll, 54 ride over the humps Si, 56, the cam passes through the dead center" position and thereafter, the resistance to rotation is suddenly released and the contacts spring rapidly into engagement. Because of the lost motion connection provided by the intermittent gear mechanism, the cam 22 is free to rotate independently of the movement of the pin 9 and hence the cam 28 is rotated to closed position very rapidly.

The action of the contact members 2i, 22

in closing is similar to, but the reverse of, the

action in opening. Since the contact members 2|, 22 are under considerable stress when spread apart, the release of the spreading force, causes slid along one another .into the positions shown in Fig. 6. This sliding or wiping action is in addition to and accompanies the sharp blow resulting from the rapid engagement of the contact portions 32, I5.

It will be seen that, upon the closing of the switch, the contact elements are brought into engagement with considerable force and, as they engage, the surfaces slide along each other through a distance approximately equal to the length of the area of contact. This combined blow and wiping action serves to thoroughly loosen and dislodge any loose foreign matter such as particles of burned contact material, scale, oxide, dirt, and the like, and the wiping action serves to brush such loosened material 03 the surfaces and to polish the latter.

The wedging action between the contact members prevents bouncing when the contact elements are brought into contact and, when the switch is in closed position, prevents separation of the contact elements due to jars or vibrations, hence no burning or welding of the contact elements can take place due to these causes. Such burning and welding is of very common occurrence in many switches and is highly destructive and it is of greatest importance to insure against such harmful effects as the consequent roughening of the contact surface accelerates these effects. The life of the switch is very materially reduced unless some provision, suchas for example in the present invention, is made to prevent these harmful effects.

The gear portion of the actuator 24, which extends into the variable resistance device housing l3, has a cut out portion or slot 56 forming two teeth 51, 58 and movably positioned to receive the switch actuating pin 9 when the arm 5 of the variable resistance device is in its initial position with the contactor near one of the end terminals 4 or 5. When the arm 5 is in its initial position, the switch I8 is in the open position. As the arm 8 is moved from the initial position, by the rotation of the shaft 1, the pin 9 moves in the slot 56 to engage the tooth 51 to rotate the actuator 24 which closes the switch i8 as described above. Upon continued movement of the arm 8, the pin 9 disengages from the slot 55 of the actuator 24 leaving the switch I8 in closed position. When the arm 8 is moved back toward the initial position, the pin 9 re-engages the actuator 24 and, as the arm moves into the initial position, bears against the tooth 55 to rotate the actuator 24 and open the switch l8.

During the first portion of the movement of the actuator 24 to open the switch i8, the toes 53, 54 (Figs. 4 to 6) ride on the contact members 2 22 against an increasing resistance to rotation offered by the spring action thereof. When the toes 53, 54 ride over the humps Ii, 36, this resistance to rotation is suddenly released and the rotation of the actuator 24 is assisted'instead .of being resisted as previously. Because of the intermittent gear connection between the variable resistance and the switch, the gear portion 41 is free to disengage from the pin 9 which it does under the influence oi the squeezing action of the contact elements 2|,'22 upon the cam 23. Thus, it the shaft 1 is being manually rotated to rotate the actuator 8 which moves the pin 9, a positive indication inthe nature of a jerk is felt by the operator as the dead center position is passed through and thus a tactile indication of the operation of the switch is provided. Such an indication is provided in an analogous manner by the inclined portions 30, 35 and humps v 3 I, 36 to signal the closing of the switch.

with considerable force and an audible click produced which click serves as an audible indication that the operation of the switch has been completed. Thus it will be understood that the signal provided to indicate the completion of the operation of the switch is both tactile and audible.

The switch housing member I9 has a pair of depending bosses or lugs 59, 6|] which project through perforations 6 I,,62 in the variable resistance device housing member I3 to locate the switch housing I9 thereon. Struck up from the housing member I3 are two integral ears 63, 64 which are bent over respectively against two integral inset steps 65, 66 formed on two sides of the housing member I9 and sloped upwardly away from the housing member I9 to secure the latter firmly on the variable resistance device housing I3. The steps 65, 66 are indented from the side of the housing member I9 to provide notches 61, 68 which provide additional locking of the housing I9 as well as additional strength of the portions 65 and 66. Interposed between the switch housing I9 and the variable resistance device housing I3 is a flat disk-shaped insulating member 69 having perforations (not shown) receiving the actuator 24, the ears 63, 64, the lugs 66, 6|, respectively, which insulating member 69 serves to insulate the contact members 2|, 22 from the variable resistance device housing I3.

When the switch housing I9 is held against the insulating member 69 by the bent over ears 63, 64, the contact members 2|, 22 are clamped at their end portions 39, 43 between the bottom wall of the switch housing I 9 and the insulating member 69 thus positively positioning the contact members 2|, 22 and preventing movement thereof in the slots 25, 33. The tapered portions do not engage either the housing I9 or the insulating member 69 and hence are free to move as above described.

The straight, perforated end portion 39 of the contact member 2| is projected from the switchhousing member I9 to constitute a terminal element for antinsulated conductor 18 constituting a portion of sthe circuit (not shown) in which the switch I8 is to begconnected. The bare end of the conducting portion 1| of the conductor 18 is projected through the perforation 48 in the end portion 39 and bent over against the latter, and a quantity of solder 12 locks the conducting portion 1| and the end portion 39 together and provides positive electrical connection therebetween. A second insulated conductor 13 having a bare end 14 is similarly connected to the end portion 43 of the other contact member 22 constituting a nal elements and the bare ends 1|, 14 of the con- , ductors 18, 13; the corners of the side walls of the housing 16 are formed with notches 11, 18 (Figs. 14 and 15) to accommodate the conductors 18, 13. Formed integrally with the terminal housing member 16 is a central partition 19 having a tongue 80 which enters a recess 8| (Figs. '1 and 8) formed in the end of the switch housing member I9 and a pair of bosses 82, 83 which extend through perforations (not shown) in the variable resistance device housing member I3 and the insulator 69. An car 84 struck up from the variable resistance device housing member I3 through the insulating plate 69 and bent over against an inclined flange or inset step 85 cooperates with the tongue 88 and the bosses 82, 83 to lock the terminal housing member 16 securely against the variable resistance housing member I3 and the switch housing member I9. This terminal housing member may, of course, be omitted if desired.

In Figs. 16 and 17 is shown a switch embodying certain of the inventive principles hereinbefore set forth but having the contact members shaped and arranged to provide a simultaneous double break in the circuit. Such an arrangement is often desirable in that the break is more positive than in a single break switch and arcing consequently even less than the slight arcing which takes place in the previously described switch. Such a switch may, in certain cases, be made more compact than the form described above.

In this modified form, the switch 86 comprises a recessed housing member 81 formed in general similarly to the housing of the first form of switch and a pair of generally parallel contact members 88, 89 formed like the contact member 2| of the first form and seated in slots 98, 9|, a boss 92 and projections 93, 94 holding the contact members 88, 89 in the housing 81 and tensioning them toward each other in a manner similar to that described in connection with the switch of Figs. 4-6. The contact members 88, 89 are provided with inclined portions 95, 96 and humps 91, 98 and the ends are oppositely bent at angles of approximately I35 relative to their respective body portions to form contact portions 99, I which, when the switch is in closed position, have pressure engagement respectively with contact elements IOI, I82 constituted by bent ends of a circuit-completing member I03.

The circuit-completing mmber I63 is triply bent to form two diverging return bends I04, I which bends are seated in suitably shaped open arcuate seats I06, I81 and-are held therein by a stud I89 upstanding from the floor of the housing 81; the stud I09 bears against the circuitcompleting member I83 intermediate the return bends I84, I05. The circuit-completing member seats I00, I01 and against the stud I00 by its own inherent spring pressure, it having been compressed when inserted and then permitted to expand to its normal position, thus causing the intermediate portion and the ends of the return bends I04, I05 to press against the coopc ating portions of the housing 01.

The contact portions 00, I00 of the contact members 00, 00 are so positioned that normally they would be closer together than the contact portions I0l, I02 oi the circuit-completing member I00 when the latter are in their free positions (as seen in Fig. 17). Thus, when the switch 00 is in the closed position shown in Fig. 16, the contact members 00, 00 force the ends of the circuit-completing member I03 closer together, thereby providing a relatively high pressure between the contact portions 00, I00, IOI, I02.

The return bends I04, I05 are free to move in their respective seats I00, I01 under the pressure exerted by the contact members 00, 00 and hence the free ends of the circuit-completing member I00 have a considerable unrestrained length and the contact portions I0l, I02 are movable through a considerable distance under the influence of the contact portions 99, I00. Such long movement of the contact portions IOI, I02 provides a very substantial wiping action between the contact portions 00, I00, IOI, I02 as the contact members 80, 00 are moved into or out of engagement with the circuit-completing member I00.

As the free ends of the circuit-completing member I00 extend at considerable angles to the free ends of the contact members 00, 00 respectively, the cooperation between these members is analogous to that explained in connection with the first form of switch. The members being mutually approachable at considerable angles, there is a very substantial Wedging action therebetween which provides a high contact pressure between the contact elements and in addition, there is a substantial travel of the contact portions relative to and in contact with one another which insures a satisfactory wiping of the contact surfaces.

Where it is desired to construct the switch 00 (Figs. 16 and 17) as a three pole switch, the citcult-completing member is formed as shown in Figs. 18 and 19. In this switch 0011, which is similar to the switch 80 shown in Figs. 16 and 17, except as hereinafter pointed out, a casing III has a pair of contact members H2, H0 provided with contact portions II4, II5 cooperating with contact portions H0, H1 formed in the free ends, a circuit-completing member IIO having return bends IIO, I20 seated in recesses I2I, I22 in the housing III. Formed integrally with the central portion of the circuit-completing member III and bent at a right angle thereto is a tongue I20 which extends through an open slot I24 in the end wall of the casing I I I and projects therefrom to constitute a terminal having a pertoration I25 for receiving a circuit conductor (not shown). When the switch housing I24 is clamped in place the tongue I20 is firmly held between the wall of the switch housing and the insulating plate.

In Figs. 20 to 27 is shown another embodiment of the invention, the inventive concept being applied to a switch of the double pole type, a variant form of actuator being shown for connecting the switch with the variable resistance device.

I00 is so formed that it is securely held in its The variable resistance device I20 is similar to that shown in Fig.1 and comprises a base I21, a cupped housing member I20secured thereto, a threaded mounting bushing I20 secured in the base I21 and journaling a shaft I00 on which shaft is mounted an actuator arm IOI carrying a switch actuating pin I02 positioned to move into engagement with an actuator I00.

The actuator I00 comprises a metallic gear I04 pivotally mounted on the inside of the housing member I20 by a hollow rivet I05 and has a pair of spaced downwardly offset teeth I00, I01 positioned to cooperate with the actuating pin I02 to constitute an intermittent gear mechanism, and a pair of opposed yokes I00, I30 having open slots I40, I. The open slots I40, I receive depending legs I42, I40 of a cam portion I44 of the actuator I00 which has a trunnion I45 journaled in an integral bearing I40 in the inside of the wall of a switch housing member I41 and another trunnion (not shown) journaled in the hollow rivet I05. The switch housing member I41 is secured to the variable resistance device housing I20 in a manner analogous to that previously described, as will appear from the drawings.

The side edges I48, I40 of the cam portion I44 of the actuator I03 cooperate respectively with contact members I50, I5I secured inthe switch housing I41. The movement of the cam I44 is halted by the legs I42, I43 striking against the ends of arcuate slots I52, I50 in the housing member I20 hence no stop element need be provided in the switch housing I41 as is required where the previously described actuator 24 is employed.

The switch housing member I41 is shown in Figs. 20-22 and comprises a molded insulating member having a recess I54 formed with a pair of open arcuate extensions I55, I50 providing spaced seats. Nested in the extension I55 is the contact member I50 having a return bend I51 shaped to fit the seat. The contact member I50 is formed from a blank similar to that shown in Fig. 27, the material being resilient and having good electrical and thermal conductivity such as phosphor-bronze alloy. The blank comprises an enlarged connection portion I50 having a perforation I50 and an open slot I00 therein and a reduced tail IOI having a pair of ears I02, I00 extending from the edge at points on both sides of the portion in which the return bend I51 is made.

The contact member I50 has its return bend I51 loosely seated in the recess I55, as stated above, and has the slotted connection portion I50 projecting through a slot I04 in the end wall I05 opposite the end wall in which the recesses I50, I50 are formed. The connection portion I50 is locked between the housing member I41 and an insulating-plate I00 (Fig. 25) interposed between the switch housing I41 and the variable resistance device housing I20. The ears I02, I00 near the return bend serve to space the edges of the reduced portion from the insulator I00. The step portion I01 on which the return bend rests spaces the spring from the switch casing to prevent portions 01 the spring that have greater movement from rubbing on the floor of the housing I41. The ears I02, I00 do not bear tightly enough against the insulator I00 to prevent movement of the return bend as a whole.

The other contact member I5I is formed in an identical manner and is seated in the seat I50 and held by a slot I00 in a position corresponding to, but opposite the position of the first contact member I50.

III

Projecting through a slot I69 formed in the end wall intermediate the first, slots I54, I88, is a short contact member I10, having a connection portion formed similarly to those of the long contact members I50, I5I and a short portion I1l wedged between a boss I55a, a projection I12 on the end wall and a stud I13 upstanding from the bottom wall of the housing I41, the short portion I1I terminating slightly beyond the stud I13 in a bent end- I14 constituting a contact portion.

The free end of the corresponding long contact member I50 has a bent end I15 constituting a contact portion positioned, when the switch is in the position shown in Fig. 22, to press with considerable force against the contact portion I14 formed on the short contact member I10.

A slot I15 similar to the slot I69 receives a second short contact member I11 and a suitably disposed projection I18 and the stud I13 secure the short contact member I11 in a manner corresponding to that in which the other contact element I10 is secured, a contact element I19 on this member cooperating with a contact element I 80 of the associated long contact member I5I.

The long contact members I50, I5I are so formed and disposed that the contact portions I15, I80 are movable in arcs in directions such that when the contact portions I15, I80 are moved into engagement with their corresponding contact elements I14, I19 there is a wedging engagement therebetween and considerable contact pressure is developed. The contact portions I15, I80 are spread more than normally when they engage their corresponding contact portions I14, I19 in the position of Fig. 22 so that, in this position, the return bends are under initial compression.

When the actuator I33 is swung to rotate the camportion I44, the edges I48, I49 bear against parallel portions of the long contact members I50, I5I to release the pressure which the contact portions I15, I80 exert upon their corresponding contact portions I14, I19 and during the initial portion of this movement the contact portions I15, I80 are pushed across the other contact portions I14, I 19 respectively to provide a substantial wiping action therebetween.

As the edges I48, I49 of the cam portion I44 ride onto inclined portions I8I, I82 formed by bends in the long contact members I50, I5I respectively, the cam portion I44 passes through a position (Fig. 23) which-is, in effect, a dead center position and thereafter, the movement of the actuator I33 is accelerated by the squeezing action exerted on the cam portion I44, the cam portion I44 being rapidly moved, without being under the control of the switch actuating pin I32, to a position wherein the legs I42, I43 of the cam portion I44 strike against the ends I52, I53 of the arcuate slots.

The gear portion of the actuator may be formed in an alternative manner as shown in Fig. 28 by punching a flat gear I83 from a sheet of insulating material which gear I83 has the general shape of the metallic gear portion I34 shown in Figs. 20, 21 and 25 with a cut out I84 cut therein to provide gear teeth I85, I86 for engagement by a switch actuating pin (similar to pin I32) and a pair of yoke portions I81, I88 adapted to receive the legs of a cam portion (similar to cam I 44).

Where it is desired to electro-magnetically and electrostatically shield the variable resistance device, as explained more in detail and claimed in connection with a snap switch and variable resistance device in my copending application Serial No. 675,377, filed June 12, 1933, an electrical grounding connection for the housing I3 is provided by-a thin connector I 3a. The connector I So surrounds the shaft and is clamped at' one end by the securing washer 6a, which locks the bushing in the housing. The other end of the connector I3a is clinched by the ear I4 thus electrically connecting the housing I3 to the bushing and through the bushing to the shaft which latter may be grounded. A similar connector I280. is shown in Fig. 20 in connection with the housing I28.

It will be seen from the foregoing that the switch in all forms shown and described above provides for aslow break", that is, the contact elements are separated relatively slowly. This switch is distinguishable from the well-known snap switch since in the present switch, the separating movement of the contact elements is under the control of the operator until after the circuit is broken whereas in the "snap switch the operator has no direct control over the movement of the contact elements, the separating movement being initiated only after the snapping mechanism has been energized and released and the operator has lost control over the operation of the switch.

It will further be seen that the invention is not to be limited to the employment of the switch with a variable resistance device but it may be employed with any other device having an actuatingmember for transient engagement with the gearportion'of the actuator, or the switch may be employed by itself and operated directly by providing an actuating mechanism adapted to transiently engage the actuator to rotate the latter.

I claim:

1. A switch comprising, a base, a plurality of spring contact members, means mounting said members on said base for mutual engagement, means including a cam rotatable into engagement with at least one of said contact members for controlling the movement of said contact members into and out of engagement, means for accelerating the movement of said cam and stop means for halting the movement of said cam, said accelerating means including an inclined surface on at least one said contact members and the stop being positioned for engagement by said cam during the engagement of said cam with said inclined surface.

2. A slow break switch comprising a plurality of contact elements, means for moving said contact elements apart including a cam engaging at least one of said elements, transiently engageable means for actuating said cam to selectively control the position of the movement thereof until said contacts have been separated and means constituted by at least one of said contact elements for continuing the movement of said cam after the disengagement of said transiently engaging means.

3. A slow break switch comprising a plurality of contact elements, means including a cam engaging at least one of said contact elements for moving them apart, a stop member lying in the path of said cam and means including at least one of said contact elements, said cam and said stop member for producing an audible click indicating the operation of the switch.

4. A slow break switch comprising a plurality of contact elements, means mounting said contact elements mutually in wedging pressure engagement, means including a cam for moving at least one of said contact elements slidably away from the other to open said switch and for controlling the closing thereof, operator means including a transiently engageable connection for actuating said cam and means on at least one of said contact elements for imparting an acceleration to said cam to move it independently of said operator means during a portion of the travel of said contact element.

5. A slow break switch comprising a pair of cooperating contact members, means mounting said contact members in mutual engagement, means including a cam engaging at least one 0! said contact members for eiiecting separation 01 said contact members, transiently engageable means for actuating said cam to controllably separate said contacts, means including at least one of said contact members and active upon the disengagement of said transiently engageable means tor imparting an acceleration to said cam and means aoesma for halting the movement of said cam prior to the normal end of its accelerated movement. I

6. A slow break switch comprising a pair of cooperating contact members means mounting said contact members in mutual pressure engagement, means including a cam bearing upon at least one of said contact members for separating said contact members to open said switch. transiently engageable means for actuating said cam, means including at least one of said contact members for imparting an acceleration to said cam when said transiently engageable means is disengaged, said contact members being positioned to engage with a mutual wiping blow prior to the normal end of said accelerated movement when said cam is actuated to close said switch.

NEWTON C. SCHELLENGER.

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