US2056305A - Radio receiver - Google Patents

Description

Oct. 6, 193 6. A, THOMAS 2,056,305

RADIO RECEIVER Original Filed Oct. 29, 1931 3 Sheets-Sheet l 1936- A. A. THOMAS 2,056,305

RADIO RECEIVER Original Filed Oct. 29, 1931 3 Sheets-Sheet 2 -4 INVENTOR zwwmh Oct. 6, 1936. A HOMA 2,056,305

RADIO RECEIVER Original Filed Oct. 29, 1931 3 Sheets-Sheet 5 Patented Oct. 6, 1936 UNITED STATES PATENT OFFICE RADIO RECEIVER of Delaware Application October 29, 1931, Serial No. 571,736 Renewed March 6, 1936 3 Claims.

My invention is for a radioreceiver housed in a shallow inexpensive cabinet adapted to be hung on a Wall like a picture or set in a recess in the Wall. A receiver of this kind is especially useful in city apartments where rooms are small and have scarcely enough floor space to hold the necessary furniture. I

The problem of limited floor space in the small homes of city dwellers has occupied the attention of radio manufacturers, and so we have recently had the so-called shelf or table models and the tall columnar models in the shape of grandfather clocks. But even the latter require floor space and are furthermore expensive on account of the necessary cabinet Work and the enclosed clock. As for the midget sets, they require another piece of furniture to support them, such as a desk, a shelf, or mantel, and these may not always be on hand or may be filled with other things. A further objection to the midget sets is the close crowding of the parts into very small space, so that disturbing electric interactions are liable to occur, not to mention the difiiculty of getting at the parts when necessary.

I have solved the problem in a different way: by constructing a radio receiver that can be hung on a wall in any convenient position. Every room, no matter how small or cluttered with furniture, has plenty of free wall space, so there is no dimculty in placing my new type of wall receiver in such a room. Another practical advantage of my receiver lies in the low cost of the shallow cabinet in which the parts are mounted. The sides of the cabinet are so narrow as to require no fancy finish or ornamentation, and only the front panel need be of attractive appearance. Furthermore, the constituent parts of the receiver are supported on shelves without being crowded and are thus fully exposed for easy access when the door of the cabinet is opened.

The novel features and utility of my invention will be fully understood from a description of the accompanying drawings, in which Fig. 1 is a small perspective view of my new wall receiver;

Fig. 2 is a front View of the open cabinet on a larger scale;

Fig. 3 is a vertical section on the bro-ken line 3-3 of Fig. 2;

Fig. 4 is a sectional plan view on line 44 of Fig.

Fig. 5 shows an enlarged vertical section on line 5-5 of Fig.2, the central portion of the cabinet being broken away for lack-of space;

Fig. 6 is a fragmentary sectional view of the volume-control mechanism;

Fig. 7 represents an enlarged view of a portion of the cone speaker construction;

Fig. 8 is a fragmentary view showing the 5 mounting of a radio tube on a shelf in the cabinet;

Fig. 9 is a vertical section of the left end of the cabinet to show one form of latch device for the front panel; 10

Fig. 10 is a fragmentary view, partly in section, of a modification in which the rotary tuning knob is axially adjustable to volume-controlling position;

Fig. 11 is a section on line l|ll of Fig. l0;

Fig. 12 is a section on line |2l2 of Fig. 11;

Fig. 13 shows an enlarged section through the combined tuning and volume-controlling knob of Fig. 10;

Fig. 14 is a section on line l4l4 of Fig. 11;

Fig. 15 shows how the vacuum tubes may be supported in a horizontal position; and

Fig. 16 illustrates a modified driving connection between the tuning shaft and a knob projecting from the bottom of the cabinet.

The outer cabinet C is a shallow casing, usually of wood or other insulating material, comprising a back wall It, narrow side pieces 2 and 13, a bottom or base plate 54, a top section l5, and a front panel or door [6, which is hinged at l! or otherwise movably connected to the cabinet. The depth of the cabinet need not be more than five inches and may even be less; the width as a rule will be about eighteen or twenty inches, and the total height about thirty inches. I give these figures merely by way of example and not in a restricted sense. The panel It may be covered with tapestry or a painted canvas, or it may carry a mirror, particularly if the cabinet is to behung over a mantel. The top section I5 is here shown as an ornamental dome-like extension which forms a chamber [.8 for housing a cone loudspeaker indicated as a whole by L. The structural details of the loudspeaker will be described later on. A partition I!) preferably separates the sound chamber l8 from the rectangular main compartment 20 in which the other constituent parts of the receiver are mounted. In the present instance, the compartment 20 contains a pair of shelves 2| and 22 50 secured to the back wall In by brackets 23 or in any other practical way. These shelves may be strips of wood, bakelite, or other insulating material.

The upper shelf 2| supports all the vacuum 55 tubes 24 required by the particular type of receiver circuits employed, these tubes being preferably arranged in a single row for easy access. It may be assumed that the large left-hand tube 24' is a rectifier tube, while the others are the usual detector and amplifier tubes, as will be understood without further explanation. The contact pins 25 of the vacuum tubes pass through openings in shelf 2i into pressure engagement with spring contacts 25 secured to the underside of the shelf (see Fig. 8). The tight frictional fit of contact pins 25 in the shelf holds the tubes firmly in place. In Fig. 2 the tubes 25-24 are supported in vertical position, and in Fig. 15 they are mounted horizontally on a vertical base 27 attached to the back wall 55. A horizontal shelf 28 projecting from base 27 or the back wall l8 holds the tubes against accidental displacement. If the receiver has so many tubes that they can not all be mounted on the shelf in a single row, some of the tubes may be arranged in a second row, as indicated at 25a. in Fig. 3.

' The lower shelf 22 is this instance supports all operative parts of the receiver other than the vacuum tubes and tuning condensers. In Fig. 2 I have indicated by way of example a power pack 29 and three transformers 35 covered by a common metal shield 3!. There will, of course, be other electrical devices, depending upon the kind or type of circuits usedsuch as b-y-pass condensers, resistances, regenerative coils and other requisite parts with which every radio engineer is familiar. A suitable volume-controlling unit indicated as a whole by V may also be mounted on shelf 22 for operation by a rotary hand knob 32 projecting from the front panel [5. The structural details and operating connections of this volume-control unit will be described in due course. It is evident that the tubes 2 i2'2da can be mounted on the lower shelf 22, and the electrical parts 29, 30, etc., transferred to shelf 2! The space between the lower shelf 22 and the bottom plate Hi of the cabinet contains the necessary tuning condensers K of the usual type and number. By way of example I have shown four sets of condenser plates in two gangs mounted on a pair of vertical rotary shafts 33, which are supported in a U-shaped bracket 34 attached to the back wall H! by screws 55 or otherwise. Although I have shown only two condenser gangs and two supporting shafts 33, it is obvious that as many more condensers and shafts may be added as are necessary for the particular type of receiver housed within the cabinet. The supporting bracket 5 which may conveniently be a single casting of aluminum, has a pair of vertically aligned bearings 55 and 3? (see Figs. 5 and 10) for supporting a rotary shaft 33. This shaft carries a pair of spaced bevel gears 3955 and a pair of pulleys M52, which may be a single pulley with a double groove. The condenser shafts 33 are provided with pulleys 43 and &4 (see Fig. 2) which are connected to the driving pulleys 4i and AZ'respectively by belts 65 and 46. Instead of using belts or pulleys for connecting the driving shaft 38 with the tuning shafts 33, I may use any other practical form of transmission means.

The front door or panel l5 of the radio cabinet carries a rotary knob i'l which operates a bevel pinion 48 arranged in mesh with the bevel gear 40 on the vertical driving shaft 38. The gear reduction between parts 58 and may be about 1:4. A simple way to connect the parts 41 and 4a is to secure them to the oppos te en of a rotary pin or stud 49 journalled in a suitable bearing member 55, which is mounted on the inner wall of the hinged door 16, as clearly shown in Fig. 5. The meshing bevel gears 48 and 48 are readily separable and engageable to permit closing and opening of door IS. The gear teeth may be slightly rounded at the outer edges, so that the pinion =38 slides easily into mesh with gear 45' when the door !6 is closed. If we assume that the tuning shafts 33 change the capacity of the condensers from minimum to maximum in half a revolution, the operating knob 4'! will require several turns to cover the full tuning range.

Referring to Fig. 5, the bracket 3 has a top bearing 5! adapted to support a rotary pin or stud 52, which carries a bevel gear 53 arranged in permanent mesh with the bevel gear 39 on shaft 38. On the outer end of pin 52 is mounted a dial plate 55, which has suitable notations thereon to indicate the various broadcasting stations in the usual way. The station indications on the dial 54 are visible through an opening 55 in the front panel is. The gears 39 and 53 are in a 1:1 ratio, because it is assumed that the frequency or wave length indications on dial 54 extend over an arc or 180 degrees. It should be noted that the rotary dial 54 is in permanent relation to the condenser shafts 33, and this relation is not disturbed by the separation of gears and 40 when the door it is opened. Nor does it matter if somebody should idly spin the knob il when the door is open, because it is only when the pinion 53 is in mesh with the bevel gear 48 that the tuning shafts 33 and dial 54 are operated in synchronism. V

A small electric light bulb 56 may be mounted on shelf 22 behind the dial 554 to illuminate the notations appearing thereon. If the dial 54 is opaque, the light from lamp 56 is thrown by a small reflector 51 into the narrow space 5'! for illuminating the front of the dial. The reflector 51 is preferably mounted on the back of panel I 5, so that the lamp 555 is fully accessible when the panel is swung open. If desired, however, the reflector 57 may be attached to shelf 22 in any convenient way. Instead of a movable dial plate 55 and a fixed pointer 58, I may use the equivalent reverse arrangement consisting of a movable pointer and a fixed dial. It should be noted that the tuning condensers and station indicator, to-- gether with their driving connections, are all carried by the brackett and thus constitute a unitary structure which can be assembled on the work bench and placed in the cabinet as a single piece of apparatus.

The loudspeaker L comprises a cone diaphragm 59 which need be not more than five or six inches in diameter and may be less than four inches deep. The concave side of diaphragm 59 faces a round opening 6!! in the cabinet for emission of sound waves generated by the diaphragm. The opening 55 is covered by an ornamental grille or other perforated member 5|, which is removably held in place by any practical means. The mouth of diaphragm 59 terminates in a flat annular flange 62 adapted to be engaged by a clamping ring 63, which is secured by screws 64 or otherwise to the surrounding framework 65 of the cabinet. The flange 62 of the diaphragm may be cemented or otherwise secured to the clamping ring 63. The latter carries a cross-arm 56 to which the field magnet of the electromagnetic driving unit is secured. The parts '63 and 66 may be a single casting of duralumin which is light, strong and non-magnetic. The cross-arm 66 has a circular enlargement :61 at the center .for supporting the circular base 68 of the field magnet indicatedas a whole by M. Screws or other .fastening members 69 hold the magnet M :rigidlyto the cross-arm 66.

A magnetic shell 18 is attached to the .base plate 68 by screws H or otherwise, so that the two parts are held in intimate magnetic contact as if they were a single :member. The base of shell '10 has approximately'the same'diameter as the disk 68, but the polar end 10 of the shell is contracted to form a. narrow annular airgap 12 with a central cylindrical pole piece '13 :projecting rearwardly from the base 68 of the :magnet. .The

parts 88 and 13 may be a single-casting, or'secured together as separate pieces. If '13 is the :north pole of the magnet, the surrounding annular pole piece 210 will be the south pole, and vice versa.

The magnet M may be eithera permanent magnet or an electromagnet. In the latter .case the magnet is of material having highmagnetic permeability, and a field coil 14 is mounted on the central 'pole piece 13. The coil is, of course, :positioned before the shell 18 is attached to the base member 68.

The cone diaphragm 59. which may be made of stiff paper, celluloid, impregnated cloth, or even thin sheet metal, carries a light non-magnetic shell 15 for supporting a speech coil 16. The rear end 11 of diaphragm 59 may be closedand consist of a flat disk to which the flat flange '18 of the .coil form 15 is secured by cementing or otherwise. To prevent lateral displacement of the speech coil 16 in the annularairgap 12, I place a thin stretched band [9 of rubber or like material over the end of pole piece 13 for engaging the coil form 15 and thereby holding it :in concentric relation to the pole piece during the axial vibrations of the coil. This'construction is clearly shown in Fig. 7, which is grossly exaggerated for clearness. By mounting the magnet M within the conical space formed by the front face of the diaphragm, it is vpossible to accommodate the entire loudspeaker mechanism in the shallow chamber l8, which is not much deeper than the axial length of the cone diaphragm itself. This is apparent from Figs. 3 and 5.

Attention is called to the fact that the :parts of the loudspeaker may be assembled into a unitary structure before the latter .is attached to the cabinet by the screws 64. To remove the loudspeaker from the cabinet (as for inspection or repair), it is only necessary to take off the cover BI and loosen the screws 64. Should it be found in any particular instance that thechamber 18 produces undesirable resonance due to sound waves generated back of the diaphragm, it is only necessary to line the chamber with felt, soft rubbenor other sound-absorbing material 80. This acoustic insulationof the loudspeaker from the rest of the cabinet also tends to eliminate vibration of the vacuum tubes .24 during the operation of the loudspeaker. If necessary ordesirable, the acoustic chamber l8 may have openings 8! for the escape of sound from the back side of the diaphragm.

Referring toFig. 6, the volume-controlling device V comprises an insulating base plate-82 fixed in vertical position on shelf 22, and this plate has an integral circular projection 83 which sup ports a resistance coil 84 wound on an'insulating ring 85. Astud or pin 85.journalled in the supporting plate 82 carries at its frontenda toothed clutch member 87 and a contact arm 88 arranged to wipe over the resistance coil 84. The contact .arm Z88 :may convenientlyibe attached to an insulatingscollar89 on shaft 86. The knob 32 'isat- 'tached'tothe'outertend of a rotary pin :90 mounted'on the front door -18 and carrying at its inner end a toothed clutch member 9!, which is arzrangedtomesh'with the adjacent clutch member 8'l1when the door :is fully closed. Fig. 6 shows the door 15 slightly opened, so that the clutch members 81 and SI are disconnected. During the final 'closing'movement of the door, the pointed :or bevelled teeth of clutch members 81 and 9| automatically interlock, whereby the knob 32 is operatively connected to the rotary contact arm 88. Itis assumed that the resistance 84 is so conrn'ectedzin circuit that, when the knob '32 is turned one way (usually clockwise), the volume is increased, while reverse rotation of the knob cuts .thevolume down. The clutch members 81 and 9| are :so arranged as to meshsimultaneously with the meshing of gears '40 :and 48 when the door I6 is fully closed.

.It is probably most convenient to have the tuning knob 4'! on the front door l-B of the cabzinet, as :above described. This arrangment of the tuning knob also permits the cabinet to be set-inn .recess in the wall, so that the front of the cabinet is substantially flush with the outer "face of the wall. When the cabinet is hung on the wall like a picture, the tuning knob may .projectfrom the bottom of the cabinet, as shown in Fig. '16, where theknob 4-?" is attached to the lower :en'd'of .avertical shaft '92 journalled in a bearing .93. The latter may conveniently be made an integral part of the U-shaped support- :ing bracket .34 perviously described. The upper end of the -rotary shaft 92 carries a small gear wheel :or pinion 94, which is permanently in mesh .witha larger gear wheel 95 on the driving'shaft 38. In this instance there is noneed of separating the meshing gears 94 and 95, because the opening of door f6 does not disturb them. The mounting :of the tuning knob 41 below the cabinet makes it practically invisible and leaves the front door I 8 an unbroken surface, except for the smallknob 32 .and the dial opening 55. Even the knob .32 can be :removed from the front panel i6by placing the volume-controlling device V at the bottom -:of the cabinet so that the knob would project beneath the cabinet like the tuning knob 4.7 :in Fig. 16.

Instead of using two separate knobs H (or 41) and 32, one for tuning and the other for controlling theloudspeaker volume, I provide a novel construction in which .a single knob performs the triple function of tuning, controlling the volume, and turning the-electric power on and off. Refcrri'ngato Figs. 10-13, the front door I 6 carries on the outside a bearing member .96 for supporting ashaft 91, which is capable :of rotaryand axial movements. The innerend of shaft-9'! carries a gear wheel '98 in addition to the bevel pinion 48 which nneshes with the driving gear 40 on shaft 38, as :previously explained. A knob 99 is connected to the outer end of shaft 9.! for rotating thelatter and also pulling it out 'orpushing it in. When the knob 99 is fully pushed in, as shown in full lines "in Fig. 10, the bevel pinion 48 is in mesh with the bevel gear 40 on shaft 38. When the 'knobis pulled out to the dotted position 99' inJFig. :10, ithepinion 48 disengages the gear wheel fi-and the gear wheel'SB on shaft Q'I-isshifted to position 98 for-a purpose that will presently become clear. Any suitable means may be employed to hold the shaft :91 "in either of its two axial ipositions. .In Fig. 13 the shaft 91 has a pair of spaced annular grooves I09 and HH adapted toreceive a ball I 92 which is pressed into the grooves by an expanding coil spring I93 housed in the bearing member 96. An adjustable screw Hi4 permits regulating the tension of spring i533, so that the ball I92 presents just the right amount of friction to lock the shaft 91 releasably in either of its two axial positions. The grooves I99 and E are so placed that, when the knob 99 is pushed in, the ball Hi2 projects into groove IIJIJ, as shown in Fig. 13. When the knob 99 is pulled out, the second groove I0! comes into alignment with the retaining ball I92.

Referring to Figs. 11 and 12, it will be seen that the front door I6 supports a rotary gears ring 595 which surrounds a circular resistance coil I99 wound on an insulating core I91. An arcshaped strip or plate 898 is attached to the inner face of door It by screws I99, and this plate has a pair of integral hooks or fingers H9 which extend along the inner face of the annular core I91 and then project laterally over the same. Small screws or pins I I2 connect the core I9? to the fingers H3, whereby the rheostat coil I96 is firmly held in place against the inner wall of door IE. The. outer ends of fingers IIB extend over the gear ring 595, whereby the latter is retained against axial displacement. The gear ring H35 and core ID! are preferably made of insulating material like fiber or bakelite. A pin or stud I I3, mounted in door I6 centrally of gear ring I95 and resistance coil I99, carries a rotary contact arm 554 which is preferably a spring finger attached to an insulating washer or bearing sleeve H5. The inner end of pin I53 carries a metal nut or collar H9, and a metallic washer II! is interposed between the end nut H6 and the hub of arm H4. The outer end of pin H3 is formed with (or has attached thereto) ahead II? which fits in a recess H8 ofthe supporting door E9; A spring washer M9 located in recess H8 tends to push the pin head ill outward, whereby the rotary arm H4 is maintained in good electrical contact with thepin IE3.

A conductor I29 is connected at one end to the metal pin H3 in recess II8, and the other end of this conductor is attached to a binding post I2I secured to the inside of door I6. One end of the rheostat coil 593 is connected to a conductor I22, which leads to a binding post I23. The conductors I29 and I22 are housed in grooves I24 cut in the inner face of the door, so that the conductors will not interfere with the mounting of coil I99 and the movements of gear ring I95. The free end of the spring contact arm H4 rests in a radial slot I25 in gear ring E95, whereby the rotation of the latter in either direction carries the contact arm' along. The spring arm H4 is so shaped that it remains in firm pressure engagement with the resistance element 596 during the rotary movements of the actuating gear I95. A radial extension 29 on gear ring I95 engages a pair of fixed stops l2! and I28. The angular distance between these stops is such as to confine the rotation of gear ring I95 to the maximum and. minimum of loudspeaker volume. It may be assumed that the volome is loudest when the extension I99 engages the stop I28, so that the volume increases when the knob 99 is turned clockwise, as viewed from the front of the cabinet. 'The circuit wires attached to binding posts I H and i 23 are sufiiciently loose to permit opening of the door. Another way to connect the binding posts I2I-and I23 in circuit is to mount a pair of fixed terminals in the cabinet in such position that they abut against the binding posts when the door I 9' is fully closed. This separable engagement of the binding posts with the fixed terminals permits opening of the door without the need of loose wires.

It is clear from Fig. 10 that, as long as the .knob 99 remains pushed in, the bevel gear 48 is in mesh with gear 49 to operate the tuning shaft, but the gear 98 on shaft 97 is out of mesh with the gear ring 595, so that'the rheostat arm I 94 is not actuated during the tuning operation. After the'desired station has been tuned in by rotation of knob 99, the operator pulls out the knob, thereby disconnecting the pinion 48 from the tuning shaft 33 and coupling the gear 98 to the gear ring 695. If now the pulled-out knob 99 is rotated, the contact arm 5 I4 moves over the resistance element I96 and changes the volume to higher or lower degree, depending upon the direction in which the knob is turned. When the knob 99 while in pulled-out position is turned counterclockwise until the extension I 26 strikes the fixed stop I27, a switch arm I29 is moved away from its associated contact I39 and the electric power for the receiver is cut off. The switch arm E29 isshown in the form of a spring finger having a hump I29 arranged in the path of the extension 523 on gear ring I95. The normal tension of spring finger I29 holds it in pressure engagement with the stationary contact I39, so that the spring finger automatically moves to closing position when the extension 526 moves away from stop I27. The end of extension I29 is preferably bevelled or pointed, so that the switch arm I29 is not opened until just before the extension strikes the stop, I2l. The operator therefore knows that, when he turns the knob 99 counterclockwise as far as it will go, the power switch is open and remains in that condition until the knob is turned clockwise; The inward pressure of the opened spring arm I29 against the radial lug I26 tends to hold the gear ring I95 and all connected parts against accidental movement.

A pair of conducting strips or stifi wires I3I and I32 are connected to switch members I29 and I39, respectively, and extend downward along the inner face of door I6, as shown in Figs. 11 and 14. The lower ends of conductors I3I and I32 are bent laterally to form horizontal projections 33 adapted to engage insulated contacts I34 and I 35 mounted on the bottom plate I4 of the radio cabinet. The lateral extensions I33 of conductors l3l-I32 are separable from the stationary contacts I34 and I35 to permit opening of the front door I 6. When the door is closed, the lateral extensions 33 automatically slide into engagement with contacts I34 and I35, which may be in the form of spring fingers to assure a firm pressure engagement with the extensions I33. 'It is assumed that the main current leads of a storage battery or a house-lighting system are connected to the terminals I34 and I35. Another practical advantage of disconnecting the movable switch members I29 and 539 from the stationary terminals I 34 and I 35 lies in the fact that the opening of door I6 automatically cuts off the power, even if the switch arm I29 should be closed. A person thus knows that, when he opens the door IE to inspect the inside mechanism, all circuits are open and there is no danger of getting an electric shock. If the receiver is to be tested while the door I9 is open, it is only necessary to connect the terminals I34 and I35 temporarily by a piece of wire, or a movable contact arm which may be mounted on one of the terminals.

The door I6 is preferably latched in closed position to assure the meshing of gear members 4I 48 and clutch members 8I9I. A practical form of concealed latch device is shown in Figs. 2, 4 and 9. The door I6 carries near its left end a pair of fingers I 36 arranged to be engaged by latches I3? which are pivoted at I38 to the end panel I2. A vertically slidable bar I39 is pivotally connected to both latches I 3! and carries at its lower end a push-button I40, which projects through an opening in the bottom of the cabinet. A contracting coil spring I4I is connected at one end to rod I 33 and at the other end to a fixed pin I42, whereby the latches I3'I are normally held in locking engagement with the fingers I36, as will be clear from Fig. 9. When a person pushes the button I40 up, the rod I 39 lifts the latches I31 to releasing position, and the door I6 free to be opened. A fixed stop I43 arranged near the upper latch I37 holds both latches in substantially horizontal position when the door is opened, so that the subsequent closing of the door automatically causes the bevelled ends of latches I37 to ride over the fingers I36 into locking engagement therewith.

It is desirable to provide a continuous circulation of air through the chamber 20 to carry 01? the heat necessarily developed by the operation of the transformers and the vacuum tubes. For this purpose the bottom I4 of the cabinet has air holes I44 and at the top of the chamber are air holes I45 cut in the end panels I2 and I3. If necessary, the shelves 2| and 22 may also have air holes, but as a rule that will not be necessary, because the front ends of the shelves are sufficiently spaced from the closed door I6 to permit free circulation of cooling air through the entire chamber.

Although I have shown and described certain specific constructions, I want it understood that my invention is not limited to any details set forth, unless expressly included in the claims. Changes and modifications will probably occur to those skilled in the art in manufacturing my invention for commercial use, without departing from the scope of the appended claims. Further, it is not necessary that all the various novel features of my invention shall be embodied in a single device, for it is possible to use some features without others. When I speak of a wall in the claims I do not necessarily mean the wall of a room, but I include broadly any wall-like or upright support to which the cabinet may be hung or otherwise attached.

I claim as my invention:

1. A radio receiver cabinet having a front panel movable to open position, a hand-operable rotary spindle carried by said front panel and mounted for axial movement to either of two positions, a rotary tuning shaft in said cabinet, a volumecontrol device in said cabinet, means for establishing a separable driving connection between said spindle and said tuning shaft when the spindle is in one of its axial positions, whereby said panel is free to be moved to open position, and other means for establishing a separable driving connection between said spindle and said Volume-control device, only one of said driving connections being operative at one time.

2. A radio receiver cabinet having a rotary tuning shaft, a rotary volume-controlling member, a hand-operated shaft having rotary and axial movements, means for preventing lateral movement of said shaft, means for connecting said hand-operated shaft in one of its axial positions to said tuning shaft, means for connecting said hand-operated shaft in its other axial position to said volume-controlling member, a normally closed switch having a movable contact, and a rotary part operated by rotation of said shaft in volume-controlling position to move said contact to circuit-breaking position.

3. A radio receiver cabinet having a movable panel, a volume-control device mounted on said panel, a rotary knob also mounted on said panel for operating said device, a power switch mounted on said panel, rotary means operated by the rotation of said knob for opening said switch and holding it open as long as said knob remains in a certain radial position, a pair of terminals mounted on said panel and electrically connected to said switch, a second pair of terminals mounted in the cabinet independently of said panel, and means whereby the terminals on the panel automatically move into circuit-closing engagement with the terminals in the cabinet, said engagement being separable to permit opening of the panel.

ADOLPH A. THOMAS.

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