US2233113A - Radio receiving apparatus - Google Patents

Description

Feb. 25, 1941. a n- JR 2,233,113

RADIO RECEIVING APPARATUS Filed Aug. 25, 1958 3 Sheets-Sheet 1 5 77 INVENTOR q 7 BYRoM J, SMU'H C/iu z.

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ATTORNEY Feb. 25, 1941. a J n- JR 2,233,113

RADIO RECEIVING APPARATUS INVENTOR BYRoM J. SMITH @Z/Qw' ATTORNEY Feb. 25, 1941. SMITH, JR 2,233,113

RADIO RECEIVING APPARATUS Filed Aug. 25, 1938 :s sheets-sheet s INVENTOR BYROM J. SUITH BY Gi A flQA/ ATTORNEY Patented Feb. 25, 1941 UNITED STATES PATENT OFFICE RADIO RECEIVING APPARATUS Byrom J. Smith, Jr., Indianapolis, Ind., assignor to Fairbanks, Morse & (30., Chicago, 111., a. corporation oi Illinois My invention relates to radio receiving apparatus, and more particularly to improvements in switching means for the control of motor driven tuning mechanisms used in connection with radio receivers.

The principal purpose of my invention is to provide improved switch means of pre-selector type for controlling the operation of an electric motor that serves to drive, or effect the adjustment of variable condensers or other tuning media, whereby the receiver may be quickly and accurately tuned to the signal frequency of any one of a number of predetermined transmitting stations by the actuation of a selector switch,

5 which, if desired, may be located remote from the receiver.

An object of my invention is attained in the provision of an improved control unit for the motor that drives the tuning condensers, comprising a bank of individually adjustable commutator elements which are rotated by the driving motor in unison with said condensers. The motor is adapted to be circuited with, and controlled by, any selected one of these commutators,

each of which is identified with a desired transmitting station by effecting an angular adjustment thereof relative to the bank of tuning condensers. An important object of the present invention is directed to the provision of a switch unit of this character which is compact, requiring but small mounting space, and wherein the individual commutators are adapted to be pre-set by a simple adjusting operation that can be readily and quickly accomplished by the user.

These and other objects and advantages will more readily appear from the following detailed description of a preferred exemplary embodiment of the invention, and from the accompanying drawings, Fig. 1, of which is a side sectional view through the chassis of a radio receiving unit, showing a preferred arrangement of the tuning condensers, driving motor, and preselector motor control organization; Fig. 2 is an enlarged side sectional View of the motor control organization;

Figs. 3 and 4 are sectional views taken at lines 33 and 4-4, respectively, of Fig. 2; Fig. 5 is a quarter-sectional side view of paired contact discs; Fig. 6 is an exploded view of an adjustable commutator element, these members comprising parts of the motor control organization; Fig. 7 is a plan view of a key or locking element used for eifecting an adjustment of the commutator elements, and Fig. 8 is a skeleton view showing, diagrammatically, the wiring arrangement of the 55 control organization.

Referring now by characters of reference to the drawings, in Fig. 1 numeral I0 denotes a horizontal shelf or the equivalent in the chassis casing of a radio receiver, the front and rear walls of which casing are indicated at H and [2, respectively. Mounted forwardly on shelf [0 is a bank of tuning condensers l3, of conven tional type, having a common control shaft I 4. Suitably keyed to the condenser shaft near its forward end is a gear l5 that meshes with a pinion IS on a countershaft H. A sheave l8 on shaft I1 is operatively connected by a suitable belt or cord l9 to a power shaft 20 that extends parallel to shafts l4 and IT. The forward end of shaft 20 projects through the front panel 2| of the receiver cabinet and carries a manipulating knob 22 which may be used when it is desired to tune the receiver by hand and, as will hereinafter appear, to effect an adjustment of the station selecting means. A reversible electric motor 23 of suitable type and construction, 0011- nected to shaft 20 at its rear end through gear 24 and pinion 25, provides power for effecting socalled automatic tuning of the receiver. It will be noted that the power transmission means operatively connecting condenser shaft l4 and motor 23, namely the belt drive l9 and the gear sets l5-l6 and 2425, are of speed reducing character so that motor 23 functions to drive the condenser shaft at a relatively low speed.

A control unit for motor 23, embodying the essential features of the present invention, is indicated generally at 30. This unit comprises a frame having opposite end plates 3| and 32 of generally rectangular shape (see Fig. 3), secured together in the formation of a rigid structure by means of tie rods 33. The top, bottom and sides of the frame structure are substantially open so that the interior functioning members of the unit are easily accessible. If desired, a suitable removable casing or enclosure (not shown) for the unit may be provided. The end plates 3|, 32 have in-turned feet 34 for securement as by screws 35 to the shelf I0. A rotatable shaft 36 extends centrally through the frame and has its ends journalled in the end plates 3|, 32. The control unit is preferably positioned in the chassis structure so that the shaft 36 is disposed in axial alignment with the condenser shaft I4, enabling direct interconnection of these shafts by a simple coupling member. A prefered type of coupling, appearing in Fig. 1 is sufiiciently flexible as to permit of limited mis-alignment of the shafts l4 and 36, yet maintains them in constant phase relationship at all times. -As will be hereinafter more readily understood, it is necessary to the proper operation of the control unit to have the two shafts rotate conjointly and .without angular displacement of one relative to in Fig. 5, and a unitary, adjustable contact ring which is made up of the parts illustrated in Fig. 6. The number of commutator assemblies provided may be varied to suit the manufacturer, and will depend upon the number of transmitting stations desired to be preselected for so-called push button or automatic tuning. Thus, a control unit embodying eight of the adjustable commutator assemblies, to be hereinafter described in detail, enables the user to tune in any one of eight preselected transmitting stations merely by actuating a switch identified with the desired station. This number will, in most instances, be sufficient to meet the requirements of the average user. By virtue of the improved arrangement herein set forth the manufacturer may readily vary the scope of the control unit by in creasing or diminishing the number of commutator assemblies, and these are constructed to permit of compact relative disposition so as to minimize the size of the unit.

Describing now the contact members shown separately in Fig. 5, numeral 4| denotes a thin disc of resilient metal having a central opening 42 for the reception of shaft 38. In assembly, disc 4| is intended to be in electrical communication with shaft 38, and to insure positive contact between these members disc opening 42 is made slightly smaller than the shaft, short radial slots in the disc permitting the adjacent metal to yield sufliciently to accommodate and tightly embrace the shaft when the disc is forced thereon. The marginal portion of disc 4| is bent angularly as indicated at 43, so as to effect peripheral contact with the side face of a contact ring 44. Disc 4| is provided with openings 45, disposed diametrically on opposite sides of its center for the reception of rods 48 and short insulating sleeves 41 which preclude electrical communication between the disc and said rods.

A second contact disc 48, similar in shape and contour to disc 4| is provided with an insulating hub portion 49, preferably molded thereto, the hub 49 serving to preclude electrical communication between disc 48 and shaft 38, and also serving as a bearing for the adjustable commutator ring, hereinafter described. In assembly disc 48 is intended to be electrically connected to rods 48, and for effectuating this purpose the disc 48 is provided with suitably disposed openings 50 for the rods, the adjacent disc metal engaging the rods in the same manner that discs 4| engage shaft 38, previously described. The marginal portion of disc 48 is bent for peripheral contact with the confronting side face of contact ring 5|. Rods 48 are secured at 52 to a contact disc 53 which is fixedly mounted on shaft 38 through the agency of a hub portion 54 that serves to insulate disc 53 from the shaft. It will now appear that, in

assembly, disc 53 is electrically connected to each of the discs 48 by means of rods 48, and shaft 38 is electrically connected'to each of the discs 4|, the two circuits being completely insulated from each other. All of the contact discs 4|, 48 and 53 are locked against relative rotation by rods 48, and the entire assembly thus far described is locked to the shaft by means of a key 55, the component parts being held together between a shoulder 58 on the shaft and an end plate 81 which may be press-fitted on the shaft, or secured thereto in any other desired manner.

The adjustable members of the commutator assemblies embody the parts best appearing in Fig. 6, and each includes the contact rings 44 and 5| and an intermediate insulating body portion 58. The rings 44 and 8| are identical and each is characterized by an outer peripheral edge 59 that extends slightly less than half the circumference of the ring, or through an angle of approximately 178 degrees, such edge extending radially beyond the complemental edge 88. A shoulder 8| is formed at one side of the ring where the edges 59 and 88 meet, and diametrically opposite the shoulder 8| there is formed a marginal recess 82, the purpose of which will hereinafter appear. In assembly the rings 44 and 5| are arranged in coaxial, spaced-apart relation, with their so-called high margins 58 disposed at opposite sides of the composite structure, the recesses 82 being in registration and the shoulders 8| being separated by an opening or gap 83 (Fig. 4), approximately one degree in circumferential extent. The body por tion 58 preferably consists of an insulating plastic, such as Bakelite, die-cast in place between the rings 44 and 5| and serves to unify the assembly and to insulate the rings from each other. As will be seen from Fig. 6, the body member 58 has rim portions 84 that overlie the reduced marginal edges 88 of the rings, and an inner flange or hearing part 85. A marginal recess 88 registering with the ring recesses 82 is formed in the body member 58. Each of the ring assemblies previously described is mounted on one of the hub members 48, and is closely fitted thereto so that a relatively tight juncture occurs at the mating surfaces 81 and 88, respectively, of each hub member 41 and its associated ring assembly. The connection between these parts should be sufficiently tight to prevent unintended slippage therebetween, since under normal operation the contact ring should turn with the shaft 38 as though it were integral therewith, yet not so tight as to preclude angular adjustment of the ring relative to the hub member, accomplished in the manner hereinafter explained.

Each of the commutator assemblies is provided with a resilient contact finger or brush 10, an additional finger ll of similar type being provided for contact with disc 53. These contact fingers extend transversely of shaft 38 from an elongated insulating base 12 that bridges the frame plates 3|, 32, the fingers being provided with U-shaped contact terminals 13 that engage the peripheral margins of the adjustable ring assemblies and disc 53 at points vertically below shaft 38. The opposite ends of the contact fingers are provided with suitable terminal fittings for connection with lead wires.

A channel-shaped bar 15 overlying the shaft assembly extends between and has its opposite ends secured to the frame plates 3|--32. This bar is provided with a series of paired slots 18, one pair for each commutator assembly, the slots of each pair being in alignment with a vertical diameter aaaaus through its associated commutator. The bar 15 serves to support and position a commutator adjusting tool 11, shown in Fig. 7, the shank portion 18 of which is adapted to be inserted into and extended through a selected pair of slots 16 for engagement with a commutator ring assembly at the marginal recess 66, as shown in Fig. 3. As a means for directing the tool shank 18 to the lower slot after it has been inserted into the upper slot, each pair thereof is provided with a spring guide finger 19.

Describing now the manner in which the control unit is electrically connected to the motor 23, and with special reference to Flig. 8 it will be noted that the contact rings are circuited with disc 53 through rods 46 and conductors 4 8, the latter in reality being constituted by the contact discs bearing the same designation. Also, the contact 36 through conrings 4-4 are circuited with shaft ductors 4| the equivalent of the contact discs similarly designated. The motor 23 may be of any suitable reversible type, for simplicity shown as having a winding 80 connected at one end to shaft 36 through a conductor 81, the equivalent of a ground connection. The opposite end of winding '0 is connected by a conductor 82, to contact spring 1! v that engages disc 53. Winding 60 has a centerterminal 83 which is connected to one 01' a pair of power supply lines 84. The other power line is connected to the common terminal wire 86 of a group of single-pole selector switches 86 whose opposite terminals are connected, individually and respectively, to the contact brushes 10 by lead wires 81. The selector switches 86 are preferably provided with mechanical means (not shown), that operate to prevent more than one thereof from being closed at a particular time. A switch unit of this character is well known in the art and in effect, is the equivalent of a multi-throw switch. The selector switches 86 may be mounted on the control panel of the radio receiver, or, if desired, may be separated therefrom wtih connections made through a suitable multiple wire cable, .thus providing for remote control of the instrument.

To pre-set a commutator ring of the pro-selector unit 30 so that actuation of the particular switch 86 circuited with that ring will cause the receiver to become tuned to a desired transmitting station, the following procedure is used. The tool 11 is inserted through the appropriate pair of slots 16 and the 30 is turned as by manual knob 22, to bring the recess 66 of the selected commutator ring into registration to enable the tool shank to enter the said recess. Thus, the commutator ring becomes locked in such position, shown in Fig. 3, that its associated brush 10 bears upon the insulating materiol in the gap 63, being out of electrical contact with both of the ring elements 44 and 5|. Now, with the receiving apparatus conditioned for operation, knob 22 is manipulated to tune the instrument to the signal frequency of the desired sending station. Since the selected commutator ring is temporarily looked as previously described, it cannot turn with the tuning condenser and other rotatable parts of the unit 3|. Accordingly, the selected commutator ring is given a definite angular setting with respect to that position of the condenser which tunes in the desired transmitting station. The tool 11 may now be removed and used in the described manner for effecting thesetting of the other commutator rings.

The described apparatus functions in the following manner to tune in desired stations. Re-

, instantaneously entire rotor assembly of unit fer-ring to Fig. 7, wherein letters are attached to the reference numerals of corresponding parts to distinguish the several commutator circuits from each other, assume that a station identified with the selector switch 88a is desired. Such switch is closed to complete the electric circuit through conductor 81a,.oontact brush 10a, commutator ring element Ma, contact disc a, rods 46, disc 53, brush 1|, right hand portion of the motor winding 80, and back to the power supply lines '84. Motor 23, thusly energized, turns the rotor assemblies of the condenser and control unit in a clockwise direction until the circuit becomes broken by reason of the contact end of brush 10a. riding oil of the ring element Ma at the gap 680. The commutator ring will then be in its pre-set position, corresponding to a position of the condenser rotor that eflects accurate tuning of the desired station identified with selector switch 860. Because of its relatively low speed and low inertia, the compound rotor organization stops almost when the circuit is broken at gap 66a, but should the brush ride over this gap and contact with ring element a, motor 23 will become reenergized in a reverse direction, being circuited through ring element 44a, contact disc a, shaft 36, ground connection 8!, and the left hand portion of the motor winding 80. However, by properly proportioning the size of the gaps 63a, etc., and the contact ends of brushes 16a, no so-called hunting will occur.

The control unit herein described is adapted for use with condensers of prevalent type which have a tuning range of approximately 180 degrees. When the commutator rings are properly pre-set, their marginal, or locking slots 66 will remain at all times in the uppermost hemi-circle and cannot become engaged by the brushes 10.

From the foregoing description it will appear when one of the selector switches '86 is closed, the motor 23 operates under the control of the communtator ring associ ated with that particular switch until the selected station is tuned 1n.

Having described my invention with reference to a single presently preferred embodiment thereof, it will be understood that various changes may be effected without departing from the spirit and full intendment of the invention which is defined by .the appended claims.

I claim:

1. A preselector switching mechanism of the character described, comprising a frame, a shaft journalled in said frame, a plurality of commutator assemblies, each including an insulating hub fixed to said shaft, 8. pair of relatively insulated, axially spaced conductor discs, a commutator ring mounted for angular adjustment on said hub between said discs, said ring including a pair of contact segments separated by an insulating gap, each of said conductor discs bearing laterally on one of said contact segments, means electrically interconnecting one conductor disc of each switch assembly, means electrically interconnecting the remaining conductor discs, a plurality of brushes mounted on said frame, each coacting with one of said commutator rings to make electrical contact with the commutator segments individually and adapted to break such contact at said insulating gap, and means for temporarily locking each commutator ring to the frame to facilitate adjustment of the angular setting thereof relative to said shaft.

2. A preselective control device of the character described, comprising a rotatable metal shaft, a

plurality of commutator assemblies, each including an insulating hub fixed to said shaft, a commutator ring frictionally retained on said hub, adapted for angular adjustment relative thereto, and comprising a pair of relatively insulated conducting segments, a pair of conducting discs flanking said commutator ring, each bearing laterally on one of said segments, one of said paired discs being mounted on said hub and in- 10 sulated thereby from the shaft, and the other of said paired discs directly engaging said shaft; a conducting rod extending through aligned apertures in said discs, means connecting said rod to the hub-mounted discs, means insulating said rod from the shaft-engaging discs, 9. contact ring and brush assembly communicating with said rod, and an individual brush for each commutator ring, adapted alternately to engage the segments thereof.

BYROM J. SMITH, JR.

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