US2374873A - Radio control system and multiple circuit switch - Google Patents

Description

1945. E. F. MCDONALD. JR 2,374,873

RADIO CONTROL SYSTEM AND MULTIPLE CIRCUIT SWITCH.

Filed Aug. 13, 1941' 2 Sheets-Sheet 1 INVENTOR ATTORNEY$ May 1, 1945. 2,374,873

RADIO CONTROL SYSTEM AND MULTIPLE CIRCUIT SWITCH E. F. M DONALD. JR

Filed Aug. 13, 1941 2 Sheets-Sheet 2 ATTORNEYfi Patented May 1, 1945 RADIO CONTROL SYSTEM AND MULTIPLE CIRCUIT SWITCH Eugene F. McDonald, J12, Chicago, 111.

Original application April 25, 1941, Serial No. 390,406, new Patent No. 2,346,177, dated April 11, 1944. Divided and this application 13, 1941, Serial No. 406,677

8 @Claims.

The present invention relates to a control system for a radio set, and more particularly to an improved system by which certain functions of a radio receiving set, such as muting, tuning and control of the volume of sound emitted from the loud speaker of the set, may be controlled in a simpler and more expeditious manner.

The present invention is particularly useful in connection with radio receivers mounted in motor vehicles, although it has general application wherever it is desired to control a plurality of functions of a radio receiver. The conventional hand tuning or actuation by hand of station selcctors with conventional automobile radio receiver installation constitutes a serious hazard, as the drivers attention is distracted and serious accidents have frequently resulted. Furthermore, it is many times important to mute the radio receiver for short periods of time in order to be able to listen for warning bells at railroad crossings or for the sounds of approaching vehicles or trains. In addition, it is many times desired to change the volume of sound emitted from the loud speaker of the radio receiver, and in ac cordance with the present invention this function may be controlled by means in combination with the muting and tuning means without distracting the drivers attention.

In accordance with the present invention, muting of the radio receiver, the selection of the desired signal to be received, and control of sound volume from the receiver can be accomplished through a single member actuated, for example, by foot control with a special type of'switch mounted on the floor board of an automobile. This enables the control operations of the radio receiver, which ordinarily require close attention by the driver, to be carried out without requiring the driver to look at the radio set or remove either hand from the steering wheel.

Another aspect of the invention also provides a multiple circuit switch for controlling a plurality of circuits which embodies novel features of construction which permit manufacture of its parts from low cost readily formed materials, and which also facilitate assembly of the parts.

The embodiment of the switch selected for illustrating this aspect of the invention is designed so it may control two electrical circuits'by interrupting both circuits in its normal position and sequentially closing these circuits in a predetermined order as the switch operator is moved from its normal to its fully operated position. The point at which the first circuit has been closed and the second circuit is about to be closed August is indicated to the sense of touch of a person returns from its fully operated position to its normal position, the circuit last to be closed is openedfirst, the point where the second circuit has opened and the first circuit is about to be opened again being indicated to the sense of touch. Upon completion of movement of the switch operator to the normal position, both circuits are opened. This design also makes it possible for the first circuit to be closed and thereafter opened without disturbing the second circuit which remains open under such circumstances. This design also embodies a contact spring of great durability and a contact arrangement which is not affected by excessive operating pressures. And, moreover, this design readily lends itself to use in combination with a volume control or other type of rheostat operable by the operating member of the switch. It will be understood that a switch having the novel structural features to be disclosed herein may be designed to accommodate a variety of circuit controlling contact arrangements.

The primary. object of the present invention is to provide a novel control system for a radio receiving set.

Another object of the present invention is to to provide a novel control system for a radio remobile radio receiving set.

Another object of the invention is to provide a novel device for muting a radio receiver or selecting a desired signal, or performing both of these functions simultaneously.

Another object of the invention is to provide a novel device for muting a radio receiver, select ing a desired signal, or changing the volume of sound emitted by the loud speaken,

Astill further object of the present invention is to provide a novel switch having a plurality of operating functions which are indicated to the sense of touch of the person operating the switch.

Another object of the invention is to provide a novel switch for closing a plurality of circuits in sequence and maintainin each circuit change and restoring the circuits to their original condition in reverse order,

A further object of the invention is to provide a muting or tuning switch for radio apparatus controllable by the foot of a vehicle operator.

A still further object of the present invention is to obtain substantially complete shielding of the circuits of a remote tuning control device connected to a radio receiver to prevent these A still further object of the present invention is to provide a novel switch of the type subjected to heavy operating pressures in which a relatively light contact spring of great durability is employed and in which adjustment of the contact arrangement is not disturbed by employment of excessive operating pressures.

Other and more specific objects of the invention will become apparent as the following detailed description of a specific embodiment of the invention proceeds with reference to the accompanying drawings in which:

Figure l is an elevational view partly in section of a switch embodying the invention, the section being taken on line l-l of Figure 2.

Figure 2 is a view in plan of the switch of Figure 1.

Figure 3 is a view in plan of a portion of the switch of Figure 1.

Figure 4 is a diagrammatic representation of a system in which a switch of the invention may be used.

Figure 5 is an exploded view showing the parts partially sectioned on line |--l of Figure 2.

Figure 6 is an elevational view, partly in section, of a modification of the switch of Figure 1.

Figure 7 is a view in plan of a portion of the switch of Figure 6.

Figure 8 is a diagrammatic representation of a i system in which the switch of Figure 6 may be Referring to the drawings in detail and for the present to Figures 3 and 4 thereof, reference numeral l0 indicates tunable radio apparatus such as a radio receiver having a solenoid operated station selecting device indicated generally by,

reference character II. This device is shown diagrammatically as being located exteriorly of the receiver ID for the sake of convenience of illustration. The switch of this invention, to be described in detail hereinafter, is indicated by reference character l2 and is operatively connected to the device II by a shielded cable [4. The device ll comprises a shaft I1 operatively connected to a ratchet gear I8. The shaft l1 carries or is otherwise connected to a plurality of switches (not shown) which connect previously tuned sets of cooperating circuit elements in the tunable circuits of the receiver so as to obtain automatic tuning of a plurality of preset stations. The operative connection to the tuning switches within the receiver I0 is indicated by the shaft H and may be obtained by mounting the switches on this shaft as suggested above, or in any other suitable manner, such as by means of gears, belt drives, etc. It will be understood that any type of electrically operated tuning device may be operated by the switch l2. One type of such device is shown in Patent 2,216,671 granted to Eugene F. McDonald, Jr., and dated October 1, 1940. This patent may be referred to for further details of a system of radio control in which a switch of this invention may be used to obtain the advantages pointed out herein.

The electrical connections of the tuning and muting system will now be described briefly before proceeding to a detailed description of the switch II. The power supply may comprise a vehicle battery H which is connected to the receiver by way of a receiver power switch 2|. The receiver is provided with a speaker 23 operated by a voice coil 24 supplied by the output of the receiver and having one terminal connected to ground at 26. Conductor 21 of the cable I4 connects the other terminal of the voice coil 24 to a contact 28 of the switch l2. The switch I2 is preferably mounted on the floor boards of the vehicle in which the system is installed or. upon some part of the vehicle easily reached by the occupant thereof. The reciprocably movable contact 29 (Fig. 1) of the switch is electrically connected to the grounded base plate 45 through members 59, 66, 61, 11 and 37. The base plate 45 and hence the switch casin is connected to ground at 30 by way of the metallic sheath 3| of the cable I4. The point of connection to ground 30 is preferably some metallic part of the device the circuits of which are operated by the switch l2 and to which the cable [4 is connected. In Figure 4, the ground may be made directly to the external casing of the receiver Ill.

The switch I2 has another contact 33 (Fig. l connected to a solenoid 34 by way of a strip 53 and a conductor 36. The other terminal of the solenoid is connected to the ungrounded terminal of the battery 19 through the receiver power switch 2|. The operating button 31 serves as a switch operator to move the movable contact 28. Depressing the operating button 31 of the switch i2 causes contact 29 to engage contact 28 grounding conductor 21 to short circuit the voice coil of the speaker through ground. This serves to mute the speaker. A further depression of the operating button 31 of the switch completes the circuit through the solenoid from ground at 30 by way of the cable sheath 3!, the contacts 29, 28 and 33, the conductor 36 and the battery i l.

The solenoid 34 has a core 38 to which is pivotally connected, as at 39, a pawl 4i. A pawl spring 42 biases the pawl into engagement with the teeth on the ratchet wheel l8. circuit through the solenoid is completed, the core is retracted to rotate the ratchet l8 in the direction indicated. After the solenoid has rotated the ratchet to tune in a transmitting station, which occurs almost immediately, the switch button may be released and the solenoid core will be returned to its original position by means of a spring 44,

The switch l2, the parts of which are shown in section by Figure 1 of the drawings, and dissulating material 41 and 48 secured together also by rivets 5|. The previously described contact member 33 is secured on a protuberant portion When the 52 of the metallic strip 53 which is retained between the sheets 41 and 48. Ear 540n the strip 53 provides a terminal to which the conductor 36 may be integrally secured in a permanently conductive manner by soldering or welding. The contact 28 is secured on a resilient member such as a spiral spring 56 which is secured to the insulating sheet 41 by eyelets 51. The contact spring 56 of spiral form has an inherently long life in use. Since the spring 56 is free of abrupt bends, and since its resilience does not depend on its being bent at any one point between its ends, it i not subject to crystallization and breakage. An upturned portion 58 provides a terminal connection for integrally receiving the conductor 21 in good electrical contact.

The cup-shaped contact enclosing member 59 is apertured for connection to the base plate 45 by eyelet connections 6! or other suitable means. The eyelet connections shown possess the advantage of receiving bolts, screws or other connecting means for securing the switch l2 to the floor board or other part of the vehicle, and also, the switch may lie closely in contact with the vehicle floor board or other part. Notches 62 (Figure 2) are formed in the contact enclosing member 59 to accommodate the insulated conductors 21 and 36. A guide bushing 63 of insulating material is crimped to an aperture 64 located substantially concentrically with'respect to the contacts 28 and 33. The guide bushing 63 serves a three-fold purpose in that it provides an insulating abutment for the contact spring 56, serves as a guide for the contact 29 and positions a comparatively powerful contact biasing spring 66. The spring 66 presents two substantially flat ends, one of which rests on top of the member 59 and the other of which reacts aag'inst a disk or washer 61 which surrounds the reduced portion 68 of the circular body of the contact 29. The washer 61 is seated in the shoulder 69 of the contact 29. The disk 61 preferably has an outside diameter such that it fits slidably in the cylindrical housing 10 which has an inwardly turned flange 11 providing a restricted portion indicated by the reference character 12 which serves to limit outward movement of the washer 61 and thereby holds the spring 66 partly compressed. It will be seen from this that the movable contact 29 is guided for longitudinal movement without assistance from the aperture 13 in the housing 19. At the end of the housing opposite the flange H is an outwardly turned flange 14 by'means of which the housing is fastened by Welding or other suitable means to the top of the contact enclosure member 59. Above the washer 61 is a cylindrical sleeve 16. This sleeve i surrounded by another spring 11, which is lighter than the spring 66, and the whole is enclosed by the operating button 31 which is riveted onto the top of the contact 29 at 18. The operating button 31 overlaps the housing 10 to preventdirt and foreign matter from entering the switch body. In this manner the spring 11 is somewhat compressed under ordinary conditions. The aperture 13 in the housing 10 is large enough to accommodate the spring 11. Upon exertion of pressure on the operating button 31 to move the contact 29 toward circuit closing engagement with the contact 28, the spring 11 is compressed until the inner surface of the button 31 engages the top of the sleeve 16. At this time, the contact 29 is in full circuit closing engagement with the contact 28. This completes a circuit. In Figure 3, the circuit is completed from the speaker voice coil to ground in the manner explained above by grounding the conductor 21, thereby muting the speaker. At this point, the contact has not yet engaged the contact 33. Further movement of the operating button 31 must necessarily cause compression of the spring 66 since there is now a direct connection between the button 31, the sleeve 16 and the washer 61. The added resistance of the heavier spring 66 enables the operator to sense the'point at which the circuit of conductor 21 has been closed and the closing of the circuit of conductor 36 is about to occur. Upon additional movement of the contact 29, the contact 28. which is now grounded by the contact 29, engages the contact 33 to complete the circuit to be controlled which includes conductor 36. In Figure 3. this circuit is completed through the solenoid 34 and serves to change stations.

In operation of the switch, it will be noted that the alignment of the contacts 29, 28 and 33 by reason of their concentric arrangement, prevents damage or misalignment thereof by excessively heavy pressures exerted on the operating button 31. With the button 31 fully depressed, the thrust of contact 29 is taken by the contact 28 which is solidly in contact with the fixed contact 33. The spiral spring 56, therefore, is not called upon to resist any of the excess pressure which may be exerted on the operating button, but it is fully effective to maintain the concentric location of the contact 28. Any force tending to displace the contact 28 laterally i prevented by the resistance to bending of the springin the direction of its greatest dimension in cross section. Inthis respect, the spring may be regarded as a beam curved to spiral shape.

- Figure 5 of the drawing serves to show the simple nature of the switch parts and the ease with which they may be assembled. While the manner of assembling the parts of the switch I2 is believed to be apparent from the foregoing. a

suggested mode of assembly will be briefly described. The contact spring 56 is secured to insulating sheet 41, and this and insulating sheet 48 are assembled as a unit 46 together with the contact support 53 to which contact 33 has already been secured. This unit is fastened together and secured to the base by means of the rivets 5|.

The insulating guide bushing 63 may be formed into position over the aperture 64 in the contact enclosing member 59, following which the parts carried by the member 59 may be assembled to it by slipping the washer 61 over thereduced part 68 of the contact member 29 until it rests against the shoulder 69. The contact 29 with the washer 61 in place is inserted upwardly through the aperture 13 in the housing 10. The sleeve 16 and the spring 11 may then be slipped into place to surround the reduced contact portion 68. The operating button '31 is then riveted in plac as indicated by the reference character 18. The spring 66 may now be placed on the member 59 in a position determined by the bushing 63. The housing 10 may now'be secured to the contact enclosing member 59 by welding the flange 14 thereto. Assembly of the switch is completed by crimping the fastening means 6| on the base 45 to the contact enclosure 59 as shown in Figure 1.

Assembly of the switch I2 may be carried out in other ways to suit particular manufacturing methods and assembling machinery if used. The foregoing description of a suggested mode of assembl is illustrative only of the ease with which the switch of this invention may be assembled.

Figures 6 and 7 of the drawings disclose a modified multiple circuit controlling switch in accordance with the present invention. In this case, a combined circuit controlling switch 8|, which is a modification of the switch I2 of Figures 1 to 3 and 5, provides for reducing the volume of sound as well as for muting and tuning the receiver.

Figure 8 of the drawings discloses the modified system, and similar reference characters are used to designate the same elements as in Figures 3 and 4. The receiver I8. the station selecting device II and the accessory equipment for the receiver are substantially'like those illustrated in Figure 4 of the drawings. The combined multiple circuit controlling switch 8|, the parts of which are shown in section by Figure 6 of the drawings, is similar in structure to the switch I2 of Figures 1 to 3 and of the drawings, and is preferably mounted on the floor board of the vehicle inwhich the system is installed so as to be in a position for convenient operation by the foot of the driver of the vehicle, or it may be installed upon some part of the vehicle easily reached by another occupant thereof. The switch 8I is operatively connected to the device II by a shielded cable 82 which encloses the conductors 83 and 84. The conductors 83 and 84 correspond to the conductors 21 and 38 of Figures 3 and 4 of the drawings. The conductor 83 of the cable 82 connects the undergrounded terminal of the speaker voice coil 24 to the contact 85 of the switch I2. The conductor 84 is connected to one terminal of the solenoid 34 and to the contact 86 of the switch 8I. The other terminal of the solenoid, which is the same as the solenoid 34 of Figure 4, is connected to the ungrounded terminal of the battery I9 through the receiver power switch 2 I. The conductor 83 also provides a connection to the volume control section 81 of the circuit controlling switch 8I from the voice coil 24 of the speaker. The operating connection between the solenoid core 38 and the ratchet wheel I8, constituting parts of the device H, is the same as that shown in Figure 4 of the drawings.

The switch contact 85 is carried by a spiral spring member 88 and the contact 881s secured upon a contact supporting strip 89 (Fig. '7). IA wafer-like contact assembly 9 I, comprising sheets of insulating material 92 and 93, is secured to the base plat 94 of the switch by tubular rivets or other suitable fastening means 98. The rivets 98 also serve to secure the sheets 82and 93 together so as to retain the contact strip 89 in position between them. The contact strip 89 is provided with a protuberant portion 91, which is apertured as indicated by reference character 98. The previously mentioned contact 88 is secured on the protuberance 91. An ear 99 on the strip 89 provides a terminal to which the conductor 84 may be integrally secured in a permanently conductive member as by soldering or welding. The contact 85 is secured on the apertured portion I8I of the spiral spring member 88. The spiral spring member 88 is fastened to the insulating sheet 92 by suitable fastening means such as the eyelets I82. An upturned portion I83 of the spring 88 provides a terminal connection for integrally receiving the conductor 83 in good electrical contact.

The cup-shaped contact enclosing member I84 is adapted for connection to the base plate 94 by eyelet connections I86 or other suitable securing means A series of notches located in the,

same position as the notches 82 in Figure 2 of the drawings may be provided in the annular wall of the contact enclosing member I84 to accommodate the insulated conductors 83 and 84. The reciprocable and rotatable contact I81 is guided for longitudinal movement by a guide bushing I88 of insulating material which is crimped to an aperture located substantially concentrically with the apertures in the contact supporting members 88 and 89. The guide bushing I88 performs substantially the same functions as the bushing shown in Figures 1 and 5 of the drawings. A disk or washer I89 surrounds the reduced portion III of the circular body of the contact I81 and is seated on the shoulder II2. A spring II4 presents two substantially flat ends, one of which rests on the member I84, and the other rests against the washer I89. The washer I89 fits slidably in a cylindrical housing I I8 which has an inwardly turned flange II1 providing a restricted portion indicated at I I8. Outward movement of the washer I89 is limited by the restricted portion II8 to thereby hold the spring I I4 partly compressed. The housing II8 may be secured to the top of the contact enclosure member I84 by welding its outwardly turned flange II9 to the enclosure member. A cylindrical sleeve I2I surrounds the reduced portion III of the contact [81 and rests on the washer I88. This sleeve is surrounded by another spring I23 which is lighter than the spring H4. The aperture provided at the top of the housing [I6 is large enough to accommodate the spring I 23. button I24, comprising the cup-shaped member I25 and the annular member I21, is riveted onto the top of the contact member I81 as indicated by reference character I28. The annular member I21 is knurled or otherwise formed to provide a roughened surface as indicated by reference character I29, so that it may be rotated by the foot of the person desiring to control the volume of sound emitted by the loud speaker 23 of the radio receiver I8. The cup-shaped member I25 overlaps the housing II8 to prevent dirt and foreign matter from entering the switch. After the connection l28 is made the spring I23 is held in compression between the combined knob and button I24 and the washer I89. The portion of the contact I81 which provides the permanent connection I 28 is preferably square in cross section to fit a square aperture in the cap member I25, thereby to insure rotation of the contact I 81 when the combined operating knob and button is rotated. It will be understood that any irregular shape in cross section -may be given to the portion of the contact I81 which provides for the riveted connection for the purpose of insuring rotation of the contact I81 with the combined knob and button I24. The switch casing is connected to ground at I38 (Figures 7 and 8) by way of the metallic sheath I3I of the cable 82. The point of connection to ground I38 is, like the point 38 of Figure 4, preferably some metallic portion of the device to which the cable 82 is connected. In Figure 8 the ground connection may be nfade directly to the external casing of the receiver 18. The movable contact I81 of the switch 8I is electrically connected to the grounded base plate 94 through the members I84, II4, I89, I23 and I25.

The combined operating knob and button I24 is operated in the same manner as the operating button 31 of the switch I2 of Figure 1 to mute and tune the receiver. Upon exertion of pres- The combined operating knob and sure on the combined operating knob and button I24 to reciprocate the contact IIII toward circuit closing engagement with the contact 85, the top of the sleeve I2I is engaged by the inner surface of the combined knob and button following initial compression of the spring I23.

At this time the contact III! is in full circuit closing engagement with the contact 85, completing a circuit from the speaker voice coil to ground by grounding the conductor 83 and thereby muting the speaker. At this point in its movement, the contact I01 has not brought the contact 85 into circuit closing engagement with the contact 86. Further movement of the combined knob and operating button I24 causes the spring II4 to be compressed since there is now a direct connection between the knob and operating button I24, the sleeve I2 I and the washer I09. Because of the added resistance of the spring H4, the operator can sense the point at which the circuit of conductor 83 has been closed and the closing of the circuit of conductor 84 is about to occur. Additional movement of the contact III! will cause the contact 85, which is now grounded by the contact lGl, to engage the contact 86 to complete the circuit including the conductor 84.

The volume control section 81 of thecombined switch 3i includes a volume control rheostat I32 which. may be of any well known type, adjustable by rotating its operating shaft I33. The rheostat I32 is shown as being secured to a bracket I34 by means of a nut I36. The supporting means for 'the rheostat just described. is convenient since volume control rheostats are readily available which are of the panel mounted type shown,

employing the nut I36. However, it will be understood that any type of rheostat may be mounted in any desired manner on the switch 8| with its operating shaft projecting upwardly into the body of the switch as shown in Figure 6 of the drawings, or the combination of a switch and volume control may be eifected in other ways. To prevent ingress of foreign matter into the volume control section 81 and the contacts of the switch BI, a cover member I3! is provide which encloses the rheostat I32 and the lower end of the switch.

The operating shaft I33 of the rheostat is slotted or bifurcated as shown at I38 so as to provide an extensible driving connection with a pin at I39 projecting from side to side through a bore MI in the end of the contact IO'I. The extensible connection provided between the bifurcated end of the shaft I33 and the pin I39 permits the contact ID! to be moved longitudinally in the manner explained above to control the circuits of the conductors 83 and 84.

Rotating the combined knob and button I24 will adjust the amount of resistance included in the muting circuit, and hence will regulate the volume of sound emitted by the loud speaker. This is preferably to be accomplished by foot operation as explained above. The set may be muted at any time in the manner pointed out above irrespective of the angular position of the rheostat shaft I33.

The operation of the multiple circuit control system of Figure 8 will now be explained briefly. Muting and tuning is accomplished in the manner already pointed out in connection with the description of the structure of the combined switch 8|. The volum of sound emitted by the loud speaker 23 is controlled by varying the amount of resistance placed in shunt with the loud speaker voice coil 24. The usual volume control arrangement. inriinated hv reference character I40, ordinarily forming a part of the receiver, is operated in the normal manner to select a desired volume level, and the volume control rheostat I32 serves to reduce the volume below this level when desired. The volume control arrangement of Figure 8 of the drawings does not interfere with the use of the ordinary volume control, nor does it interfere with the automatic volume control usually supplied with present day receivers. Special shielding or insulation need not be provided for the conductor 83. The arrangement illustrated by Figure 8 of the drawings has the advantage that it does not require any conductors between the combined switch 8| and the receiver I8 in addition to those shown in Figure 4 of the drawings. It will be understood that the volume control section 81 of the switch 8| may be used to replace the regular volume control of the receiver it suitable precautions are taken to shield the leads between the receiver and the volume control so as to substantially eliminate the possibility of leakage and of picking up stray noises or stray cordance with this invention in which volume' control as well as mutin and tuning may be accomplished by the combined switch SI of Figures 6 and 7 of the drawings. In this figure similar reference characters are used to designate the same elements as are illustrated by Figure 4. The receiver M, the station selecting device I I and the accessory equipment for the receiver may be of any conventional type such as is illustrated in Figure 4 of the drawings. Suitable output terminals on the receiver I0 serve to energize the voice coil 24 of the loud speaker 23. The combined switch 8| a, which is similar to the switch 8I of Figuresfi and 8, is provided with a volume control potentiometer I44 which has one terminal of its resistor I46 connected to ground at any suitable point in or on the switch casing, or on the sheath I41 of the shielded cable I48. The remaining terminal of the resistor I46 is connected to the muting contact 86 of the switch 8 I a preferably by way of a conductor I49 connected to the conductor I5I. The conductor I5| corresponds in function to the conductor 83 of Figure 8 and is connected to one terminal of the voice coil 24 of the loud speaker, the other voice coil terminal being grounded. The conductor I52 connects to the solenoid 34 which performs the same function as the solenoid 34 of Figure 4 of the drawings. A contact I54, slidable on the resistor I46, is connected to the cathode I56 of an amplifier tube I5I in the radio receiver ID by way of a conductor I58. This tube I5'Iis preferably on of the audio amplifier tubes and may be the combined detector and amplifier tube used in most present day radio receivers. The volume control arrangement just described does not interfere with the use of the regular volume control I59, nor does it interfere withthe automatic volume control the cathode circuit of an audio amplifier tube. V

The phase relationship of the voltage applied to the amplifier tube cathode is such that a reduction in gain results. Since the signal voltage fed into the audio amplifier depends on the setting of the regular volume control I59 of the receiver, the auxiliary inverse, feed back volume control of Figure 9 gives a variation in audio output about a reference level established by the main volume control. The value of the resistor I46 is not critical and may, for standard receivers of present day design, be in the neighborhood of 500 ohms. The system of Figure 9 has the advantage of not requiring high impedance circuits externally of the receiver which would pick u undesirable noises or be affected by insulation leakage. The relatively low impedance circuit, including the resistor H6 and the slidin contact I54, have substantially no tendency to pick up extraneous signals or noises generated by the vehicl engine,

1 A plurality of switches, such as those shown in Figures 1 and 6, may be employed so that the receiver may be controlled from more than one point. The system of the present invention enables station changing, control of sound volume and muting of the radio set by a single footoperated control device without the operator having to look at the set, or dial, or remove his hands from the automobile controls. The system of the present invention is particularly applicable to the control of automobile radio sets and has been described in detail with respect to.operation from low voltage batteries. However, other type of radio sets, such as sets operated from alternating current or higher voltage direct current, may be operated from a remote point in accordance with the principles of the present invention. The invention has been illustrated in connection with an electrical type of automatic tuning wherein individual presettable condensers or inductances are employed, but is also applicable to other types of automatic tuning arrangement.

From the foregoing detailed description of the switch of this invention it will be seen that a low cost multiple circuit switch is provided, the parts of which may be readily manufactured from cheap materials and assembled by a few relatively simple operations.

It will also be seen that the switch of this invention may readily be adapted for controlling the volume of sound emitted by the loud speaker associated with a radio receiver.

This application is a division of my co-pending application Serial No, 390,406, filed April 25, 1941 now Patent No. 2,346,177 issued April 11, 1944.

While there is shown and described here an illustrative embodiment of the invention, the invention may be embodied in other forms, and therefore, the invention is not limited except as indicated by the terms and scope of the appended claims.

I claim:

1. In a switch, a base member, a fixed contact, a yieldable contact, an insulating support for said contacts comprising a pair of superimposed sheets of insulating material, said fixed contact being retained between said insulating sheets, said yieldable contact being secured to the top one of said insulating sheets, fastening means securing said sheets in contact retaining relationship and securing said assembled sheets, including said contacts, to said base member, a contact enclosing member, an insulating contact guide located in one wall of said member, a longitudinally movable contact slidable in said guide, a housing for such movable contact provided with an aperture through which said contact projects, said housing being secured to said contact enclosing member, resilient means in said housing for biasing said movable contact to contact opening position, a contact actuating member secured to said movable contact member, said actuating member having a portion overlapping said housing, and additional resilient means for biasing said movable contact to contact opening position housed within said overlapping portion of said operating member.

2. A switch comprising a switch body, a fixed contact, a first movable contact spaced from said fixed contact and movable into engagement with said fixed contact, a second movable contact spaced from said first movable contact and movable into engagement with said first movable contact and further movable to move said first movable contact into engagement with said fixed contact, means for securing all of said contacts to said switch body and insulating said contacts from each other, a first resilient means resisting movement of said second movable contact into engagement with said first movable contact a second resilient means resisting movement of said second movable contact after said second movable contact has engaged said first movable contact, said second resilient means having substantially greater resistance to movement of said second movable contact than said first resilient means.

3. A switch comprising a switch body, a fixed contact, a movable contact spaced from said fixed contact and movable into engagement with said fixed contact, a reciprocable contact spaced from said movable contact and movable into engagement with said movable contact and further movable to move said movable contact into engagement with said fixed contact, means for securing all of said contacts to said switch body and insulating said contacts from each other. a first compression spring surrounding said reciprocable contact and resisting movement of said reciprocable contact into engagement with said movable contact, a second compression spring surrounding said reciprocable contact and resisting further movement of said reciprocable contact after engagement with said movable contact, said second compression spring having substantially greater resistance to said movement of said reciprocable contact than said first compression spring.

4. A switch ,comprising a switch body, a fixed contact, a movable contact spaced from said fixed contact and movable into engagement with said fixed contact, a reciprocable contact spaced from said movable contact and movable into engagement with said movable contact and further movable to move said movable contact into engagement with said fixed contact, means for securing all of said contacts to said switch body and insulating said contacts from each other, a first compression spring surrounding said reciprocable contact and resisting movement of said reciprocable contact into engagement with said movable contact, stop means for limiting further compression of the first spring after engagement between said reciprocable contact and said movable contact, a second compression spring surrounding said reciprocable contact and resisting further movement of said reciprocable contact after'engagement with said movable contact, said second compression spring having substantially greater resistance to said movement of said reciprocable contact than said first compression spring.

5. A switch comprising a switch body, a stationary contact, a yieldable contact, means for securing said contacts to said switch body and insulating said contacts from each other, a reciprocable contact in alignment with said fixed and yieldable contacts and movable into engagement with said yieldable contact, said reciprocable contact being further movable to carry said yieldable contact into engagement with said stationary contact, a guide for said reciprocable contact carried by said body, a spring surrounding said reciprocable contact and having one end in reacting engagement with said body, a second spring surrounding said reciprocable contact and having one end in reacting engagement with the other end of said first spring and its other end in reacting engagement with said reciprocable contact to urge said reciprocable contact away from said yieldable contact, said first spring having substantially greater reaction than said second spring to provide for deformation of said second spring during movement of said reciprocable contact into engagement with said yieldable contact, and means limiting further deformation of said second spring after engagement of said reciprocable contact with said yieldable contact so as to provide for deformation of said first spring during said further movement of said reciprocable contact. I

6. A switch comprising a switch body, afixed contact, a resiliently mounted contact, means for supporting said contacts in said switch body and insulating said contacts from each other, a movable contact movable into engagement with said resiliently mounted contact and further movable to move said resiliently mounted contact into engagement with said fixed contact, means tor guiding said movable contact in said switch body, a compression spring for resisting movement of said movable contact into engagement with said resiliently mounted contact, a second compression spring in alignment with said first compression spring, for resisting said further movement of said movable contact, said second spring having substantially greater resistance to compression than said first spring, a movable means against which one end of said second spring is.

seated, said second spring having its opposite end seated against said. switch body, spring engaging means carried by said movable contact against which one end of said first spring is seated, the other end of said first spring being seated against said movable means, and means for limiting compression of said first spring after engagement of said movable contact and said resiliently mounted contact.

7. An electric switch comprising a stationary contact, a resiliently mounted contact movable into engagement with said stationary contact, a switch body enclosing said contacts, means for securing said contacts in said body and insulating said contacts from said body, said body having an aperture in alignment with said contacts, an elongated movable contact member having one end movable into said body throughsaid aperture into engagement with said yieldably mounted contact and'further movable to move said yieldably mounted contact into engagement with said stationary contact, a housing for said contact member secured to said body and having an aperture through which the other end or said contact member extends, an annular member or greater diameter than said last mentioned aperture positioned in said housing and slidable on said contact member, a first compression spring surrounding said contact member, said spring having one end reacting against said annular iii) member and its other end reacting against said body, an operating member secured to said other end of said movable contact member, a second compression spring surrounding said contact member, said second spring having one end reacting against said annular member and its other end reacting against said operating member, a sleeve within said second spring and slidable on said movable contact between said annular member and said operating member, said sleeve limiting the compression of said second spring, said first spring having substantially greater resistance to compression than said second spring to provide for compression of said second spring during said initial movement and compression of said second spring during said further movement of said contact member, said contact member having means for limiting sliding of said annular member on said contact member due to expansion of said second spring so as to retain said I contact member in said housing.

8. A switch comprising a fixed contact, a yieldable contact, a switch body enclosing said contacts, means for supporting said contacts in said body and insulating said contacts from each other, said body having an aperture in alignment with said fixed contact, said yieldable contact being positioned between said fixed contact and said aperture, a reciprocable contact having one end movable into said body through said aperture, a guide for said reciprocable contact secured in said aperture to maintain alignment of said reciprocable contact with said yieldable and fixed contacts during movement of said reciprocable contact, a housing for said reciprocable contact secured to said body and having an aperture in alignment with said first mentioned aperture through which the other end of said reciprocable contact projects, an annular member surrounding said reciprocable contact and slidably engaging said reciprocable contact and the internal perimeter or said housing, a first compression spring positioned in said housing and surrounding said reciprocable contact member, said spring having one end reacting against said annular member and its other end reacting against said body, said annular member being of greater diameter than said last mentioned aperture so that said housing provides a stop for said annular member to limit expansion 01 said spring, an operating member secured to said other end of said reciprocable contact, a second compression spring surrounding said reciprocable contact and having one end reacting against said annular member and its other end reacting against said operating member, said reciprocable contact having an offset portion upon which said annular member rests to limit expansion 01' said second spring, said first spring having substantially greater resistance to compression than said second spring to provide for compression of said second spring during movement or said reciprocable contact into engagement with said yieldable contact, and means to limit compression of said second spring to provide for compression of said first spring during further movement or said reciprocable contact for carrying said yielding contact into engagement with said fixed contact.

EUGENE F. MCDONALD, JR.

CERTIFICATE OF CORREC TI ON Patent No. 2,57h,875. y 191L5- EUGENE F MCDONALD JR It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, sec-- 0nd column, lines 29 and 50, strike out "to provide a novel control system for a radio remobile" and insert instead -provide a novel safety control eystem for an eutomobi1e--'; page 5, first column, line 58, for "aeginst" reed -against--; page-Li, firstcolumn, line 63, for "member as" read -menner as; and that the said Letters Patent shouldbe read with this correction therein thatthe same may conform to the record of the case in the Patent Office.

Signed and sealed this 7th day of August, A. D. 19115.

Leslie Frazer (Seal) Acting Commissioner of Patents.

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