US3474362A

US3474362A - Detented presettable tuner,particularly for uhf television

Info

Publication number: US3474362A
Application number: US705385A
Authority: US
Inventors: John T Harten
Original assignee: Arris Technology Inc
Current assignee: Arris Technology Inc
Priority date: 1968-02-14
Filing date: 1968-02-14
Publication date: 1969-10-21
Anticipated expiration: 1986-10-21

Description

' Oct. 21, 1969 J. T. HARTEN 3,474,362

DETENTED PRESETTABLE TUNER, PARTICULARLY FOR UHF TELEVISION Filed Feb. 14, 1968 2 Sheets-Sheet l ATTORNEYS 2 l a M. M N M m4 R II: a 2 on rm; IIIIQ m V T H m 1 h h m F Y w B r m W wflqjdj azg ll EEEEFW U Oct. 21, 1969 J. T. HARTEN 3,474,362

DETENTED PRESETTABLE TUNER, PARTICULARLY FOR UHF TELEVISION Filed Feb. 14, 1968 2 Sheets-Sheet 2 FIGS f6 SC i 22 42 a FIG? e 68 i l '[g 74 i it H! u I 1" WI! l 11 l I mm 1 l 24/ J INVENTOR 40 50/ JOHN T. HARTEN ATTORNEYS United States Patent O 3,474,362 DETENTED PRESETTABLE TUNER, PARTICU- LARLY FOR UHF TELEVISION John T. Harten, Longmeadow, Mass., assignor to General Instrument Corporation, Newark, N.J., a corporation of Delaware Filed Feb. 14, 1968, Ser. No. 705,385 Int. Cl. H033 /02 US. Cl. 334-51 17 Claims ABSTRACT OF THE DISCLOSURE A detented presettable tuner of the variable capacitance type is provided, particularly for UHF television. There is a fixed chassis with a rotor shaft carrying rotor plates, and a tiltable cradle carrying stator plates, the cradle being mounted in the chassis for limited oscillation about the rotor shaft. A detent wheel is coupled to the rotor shaft for rotation therewith, and also a memory drum which has adjustable screw projections for fine tuning or channel selection at each detented position. A linkage responsive to and moved by the adjustable screws extends to the tiltable cradle. There is a selector shaft with r duction gearing to the rotor shaft, because the latter turns only about 180, whereas the selector shaft turns a full revolution, and the detent wheel and the memory drum are mounted on the selector shaft rather than the rotor shaft. A hollow shaft concentric with the selector shaft is geared to the selected adjustable screws to adjust the same. This gearing is normally disengaged, but a slip friction clutch driven by the hollow shaft brings the disengaged gearing into mesh when making a channel selection. The detent wheel and the reduction gearing are preferably mounted at the rear end of the chassis, and the memory drum and the preset mechanism including the slip friction clutch are conveniently mounted at the forward end of the chassis. The memory drum has sloping contour cams between the adjustable screws to ease the transition from one screw to the next, and a bellows type dashpot prevents rapid oscillation of the cradle when the memory drum is rotated.

BACKGROUND OF THE INVENTION There are seventy channels in the UHF band. These are covered by continuous tuning, typically a tuner of the gang capacitor type. However, it is desirable to provide channel selection with a step-by-stepor detent action as is done in the VHF band. It is not feasible or even desirable to detent all seventy channels, because in practice only a much smaller number of more widely spaced channels are available in any one geographical area.

It therefore has already been suggested to subdivide the UHF band into groups of channels, say twelve or twenty-four groups; to provide detent action for the selection of the group; and a presettable fine tuning action for the selection of the available channel in each group. This may be done by detenting the rotor shaft for the selection of the groups, and slightly tilting the stator of the gang capacitor for the selection of the desired channel in each group. The general object of the present invention is to improve such a tuner.

SUMMARY OF THE INVENTION The detented presettable tuner is of the variable capacitance type. A fixed chassis has a rotor shaft carrying rotor plates, and a tiltable cradle carrying stator plates, the cradle being mounted in the chassis for limited oscillation about the rotor shaft. A detent wheel is coupled to the rotor shaft for rotation therewith. A memory drum also is coupled to the rotor shaft and has adjustable pro- "ice jections for the fine tuning, there being one projection for each detented position. A linkage is provided which is responsive to and is moved by the adjustable projections of the memory drum, and which extends to the tiltable cradle so that the selected projection tilts the cradle according to the adjustment of the projection. A selector shaft with reduction gearing turns the rotor shaft, because the latter turns only about Whereas the selector shaft may turn a full revolution, and in preferred form both the detent wheel and the memory drum are mounted on the selector shaft rather than the rotor shaft. For UHF tuning the detent wheel is for groups of channels, and the memory drum is for selection of a particular channel in the group.

There is also a hollow shaft concentric with the selector shaft, and gearing between the hollow shaft and that one of the adjustable projections which is at the selected detent position. This gearing is normally disengaged, but a slip friction clutch driven by the hollow shaft brings the disengaged gearing into mesh for tilting the cradle when initially making a channel selection. Thereafter there is no need to use the hollow shaft and gearing, unless it be desired to change the selected channel, or to improve the accuracy of the fine tuning.

The adjustable projections are preferably radial screws carried by the memory drum, and a gear nut is provided for each screw to adjust the amount of its radial projection from the drum. The detent wheel and the reduction gearing are mounted on the selector shaft at the rear end of the chassis, which shaft may be extended for connection to a motor drive if the tuner is to be remotely controlled. The memory drum and its preset mechanism including the slip friction clutch and gearing are conveniently mounted on the selector shaft at the forward end of the chassis. The memory drum preferably has sloping contour cams between the projecting screws, in order to ease the transition from one screw to the next. A bellows type dashpot is connected to the cradle to prevent rapid oscillation of the cradle when the memory drum is rotated.

The foregoing and additional features are described in the following detailed specification, which is accompanied by drawings in which:

FIG. 1 is an elevation of a tuner embodying features of the invention;

FIG. 2 is a transverse section taken approximately on the line 22 of FIG. 1, and includes a flexible electrical cable connection which has been omitted in the other figures of the drawing;

FIG. 3 is a fragmentary view like FIG. 2, but showing the cradle tilted toward the right, relative to its position in FIG. 2;

FIG. 4 is an end elevation looking toward the rear of the tuner;

FIG. 5 is a bottom view of the tuner, with a part of the cradle wall broken away to show rotor and stator plates;

FIG. 6 is a fragmentary tranverse section taken approximately on the line 6-6 of FIG. 5;

FIG. 7 shows a part of the friction clutch of the preset mechanism;

FIG. 8 is a fragmentary view drawn to enlarged scale, and explanatory of the adjustable screws of the memory drum; and

FIG. 9 shows a fragment of a resilient tension device for the gear nuts of FIG. 8.

Referring to the drawings, the illustrated tuner comprises a fixed chassis generally designated 12 carrying a rotor shaft 14 with rotor plates 16 (FIGS. 5 and 6). There is also a tiltable cradle 18 which carries stator plates 20, these being insulatedly and fixedly mounted in the cradle 18. The parts of the tuner within the cradle 18 need not be described in greater detail because they may be conventional. The cradle is capable of a limited oscillation about the axis of the rotor shaft 14, as shown by the change from 'FIG. 2 to FIG. 3.

Because the rotor turns through only about one-half revolution the tuner preferably has a selector shaft 22 which is geared to the rotor shaft 14 by means of reduction gearing indicated at 24, 26. This provides approximately a two to one ratio, so that the selector shaft 22 turns through a full revolution. A detent wheel 28 is mounted on the selector shaft 22, and a cooperating precision detent 30 bears against the detent wheel 28 for selecting the desired rotor positions accurately. In the present case there are twelve such positions, but a different number, say eighteen positions or twenty-four positions, may be provided.

With twelve detent positions as shown, there are six channels in each group. Two detent positions, say the end two positions, would require tuning over only five channels. The range of vernier or fine tuning adjustment, suggested by the arrow 120 in FIG. 6, is made sufficient to cover at least the six channels, and preferably covers seven or eight channels. Overlapping is beneficial in making it possible to preset for two channels which are somewhat more closely spaced than anticipated and which fall in one group. With twenty-four detent positions, each position must cover at least three channels. Two positions, say the end two, would need to cover only two chanels. In this case the fine tuning range is easily and preferably made to cover say five channels instead of three, thus providing a desirable overlap at each end in all of the detent positions.

A memory drum 32 also is mounted on the selector shaft 22 and has adjustable projections 34 for fine tuning, there being one such projection for each detented position of the detent wheel. A linkage, generally designated 36, is responsive to and moved by the adjustable projections 34 and extends to the cradle 18 so that the selected projection 34 tilts the cradle 18 to a fine tuning position which is determined by the adjustment of the projection. The memory drum 32 is axially separated from the detent wheel 28, and has sloping contour earns 38 which ease the transition from one projection 34 to the next.

The projections 34 are adjusted by relative rotation of parts having mating screw threads. More specifically, in this case the parts 34 are non-rotatable radial screws carried by the memory drum, and there is a gear nut 40 for each screw to adjust its radial projection from the drum. A hollow shaft 42 is concentric with the selector 22, and operates gearing leading to the gear nut 40 of the selected screw 34 which corresponds to the detent position. A part of the gear train is normally disengaged, as will be seen in FIG. 5 by the retracted position of the gear 44, and the hollow shaft 42 turns a slip friction clutch indicated generally at 46 (FIG. 5) which drives a part 48 to bring the disengaged gearing into mesh for tilting the cradle 18.

The shaft 60 normally moves to the disengaged position shown in FIG. 5, and a light spring wire 61 (FIGS. 1 and 5) may be positioned against the outer end of the shaft 60 to insure its disengagement.

Referring now to FIG. 8, the drum 32 has radial slots 50 which are non-circular in cross section, and in which the screws 34 are disposed. In the present case the slots 50 are square in cross section, and the screws 34 have four flats which fit in the slot 50 to prevent rotation. The gear nut 40 has gear teeth around its periphery, and is internally threaded to mesh with the thread of the screw 34, this thread being on the four rounded corners of the screw, and being interrupted by the four flats. For convenience the screw may be referred to as a square screw, meaning that the shank fits non-rotatably in a square slot, and yet the screw action is retained in relation to the gear nut 40.

The memory drum may be constructed in varied ways,

but in the present case it is made of two parts, one being a diecast drum with the radial slots 50 (FIG. 7) open on one face, and the open face being closed by a flat circular cover plate 52. 0t its opposite face the diecast drum is thickened enough to protect the gear nuts 40, these being received in tangentially directed slots 54. In FIG. 8 a part of the cover plate 52 has been broken away. FIGS. 2 and 3 show how the teeth of the gear nuts are exposed through tangentially directed slots in the cover plate 52. The contour cams 38 are diecast integrally with the drum, and extend from the outer end of one radial slot to that of the next radial slot.

Referring now to FIG. 5, the hollow shaft 42 turns a bevel gear 56 meshing with a bevel gear 58 on shaft 60, one end of which is carried in a bearing 62, and the other end of which is carried in a horizontally slotted bearing 64, so that shaft 60 may swing from the outer position shown in FIG. 5, to an inner position in which gear 44 engages the adjacent gear nut 40 of the memory drum.

For this purpose the friction clutch 46 has a bent resilient washer 66 or other such friction means bearing against a driven member 48. Referring to FIG. 7, the hub or driven portion of member 48 has upwardly and downwardly projecting arms 68. Reverting to FIGS. 1 and 5, these arms 68 rest against a fixed bracket 70 forming a part of the fixed chassis 12. It will be evident that if the shaft 60 is turned in either direction its initial movement will cause either the upper or lower arm 68 to bear against the bracket 70 and so by reaction to move the outer end of shaft 60 rearward, as shown by the arrow at 72 in FIG. 5, thus bringing the gear 44 into mesh with the adjacent gear nut 40 of the memory drum. Continued rotation of the hollow shaft 42 rotates the gear nut, and so alters the projection of the screw 34, thereby tilting the cradle of the tuner for channel selection in the detented group of UHF channels.

Inasmuch as the cradle has only a limited range of oscillation, it is desirable to protect the mechanism against abuse should the hollow shaft 42 be turned forcibly when the cradle can no longer move. For this purpose a gear in the gear train, specifically gear 44 in this case, is frictionally driven, and for that purpose it is held between frictional drive members including a resilient washer shown at 45 in FIG. 5. Excessive turning of hollow shaft 42 results merely in slippage at the gear 44.

To provide friction to maintain the preset adjustment of the screw, and also to avoid lost motion or backlash, each of the tangential slots 54 (FIG. 8) is preferably provided with resilient fingers or other such tension device 74 which bears frictionally against the gear nut 40, and which nearly fills the clearance space in the slot 54.

In the present case each slot receives a bifurcated spring having arms 74 (FIG. 9), which straddle the screw 34 as shown in FIG. 8. These pairs of arms may be formed integrally and bent forward from an arcuate plate 75, which is secured against the back face of the diecast memory drum, as by means of screws, or studs which are integral with the casting. One of the holes for the screws is indicated at 77 in FIG. 8. It is convenient to subdivide the plate into say four sections, and in the present case each section has spring fingers to bear against three gear nuts. When the detent mechanism provides twenty-four positions, each arcuate plate section 75 of the tension device would have six pairs of spring fingers to take care of six gear nuts. However, I have also used a separate small back plate for each pair of spring fingers 74, on a drum with twenty-four square screws and detent positions. It will be understood that the tangential slots 54 which receive the gear nuts pass entirely through the diecast drum, thus opening the way for reception of the spring fingers 74 from the rear of the drum. The screws which hold the arcuate plates 75 against the drum have been omitted in FIGS. 1 and 5.

The detent wheel 28 is made of hardened steel, and its periphery is so contoured as to minimize pressure during its movement against the detent. The detent is of the precision type employing a hardened steel ball 30 (FIG. 4) of precise size carried in a precision hole in bracket 31 and moved by an upright lever 76, the lower end of which is pivotally secured in a bracket 78, and the upper end of which is pulled toward the left as viewed in FIG. 4, by means of a pull spring 80, the left end of which is anchored on a stud 82 fixedly secured to the chassis 12. Detent mechanisms are known, but the main requirement here is for great accuracy, in order to accurately position the rotor shaft 1-4 for reference points from which the fine tuning is accomplished.

The gear 26 is preferably of the anti-backlash type, that is, it comprises two parts 26 and 26' (FIG. 5), one of which is fixedly secured to the rotor shaft, as by means of its hub 84, and the other of which is rotatably displaced by a pair of compression springs 86 (FIGS. 1 and 4) received in diametrically opposed slots. Such gears are well known, and are sometimes referred to as scissor gears. The arrangement eliminates backlash between the teeth of

gear

24 and 26.

The rotor shaft 14 is carried in bearings designed for accuracy and low torque. There are four bearings in all, two of which mount the rotor shaft 14 in the cradle 18, and the other two of which mount the cradle assembly in the fixed chassis 12. As viewed in FIG. 5, the right or rear end of shaft 14 is carried in a ring of bearing balls 88. The chassis 12 acts as the stationary part of this bearing. There is a similar ring of bearing balls, not shown in section, but housed at 89, between the shaft 14 and the cradle 18. At its forward end the shaft 14 bears against and is carried by a single ball which in turn bears against a nest of say three balls, which are carried by a threaded stud 91 which is axially adjustable for thrust, and the position of which may be locked by means of a nut 93. This ball bearing arrangement is already used in variable gang capacitors, and may be conventional except that in this case the nut 93 is formed on the outside with a cup 95 which carries a nest of balls receiving a conical stud carried by an axially adjustable threaded plug 97, the adjustment of which may be locked by means of a lock nut 94. The purpose of the bearing arrangement is to provide precision combined with low friction, so that channel selection may be made with minimum torque.

The linkage for tilting the cradle 18 comprises a main generally upright lever 96 (FIG. 2), which has a hardened steel, generally cylindrical stud 98 pressed into a bushing at the lower end of the lever. This stud is acted on by the screws 34 of the drum 32. The stud 9 8 is small enough in diameter to fit between the contour cams 38 when the adjustment of the screw 34 is a relatively retracted one. The lever 96 has a flanged pivot pin 102 welded thereon, and a fixed mount 100 receives the pin 102, providing a long bearing pivot.

The upper end of lever 96 carries a short link 104 one end of which is bifurcated to receive the upper end of lever 96, these being joined by a pivot 106. The other end of link 104 is connected by a pin 108 to the cradle 18, the connection being made rigid by an enlargement indicated at 110 in FIG. 1. The cradle is biased in one direction by means of a pull spring, best shown at 112 in FIG. 1. The lower end of this spring is secured to the fixed chassis 12 as shown in FIGS. 1 and 2. The stud 98 then is resiliently urged toward the adjustable screws 34. This spring action eliminates clearance or backlash in the linkage between the memory drum 32 and the cradle 18.

The main electrical cable leading from the tuner to the rest of the apparatus (e.g. a television receiver) is shown at 114 in FIG. 2. It extends upward, but is bent downward as shown at 116, and is held by a bracket 118. The bend of the cable is so directed that it adds to the effect of the biasing spring 112, and urges the cradle counterclockwise as viewed in FIG. 2.

As so far described a rapid rotation of the selector shaft 22 would cause a rapid vibration or chattering of the mechanism, the cradle 18 tending to move in and out for each step of the drum. This may be avoided by the provision of dashpot means generally designated in FIGS. 1, 2 and 3. In the specific form here shown, there is an axially compressible rubber bellows 132 connected at one end 134 to the tiltable cradle, while the other end 136 is fixed. The end 134 may be a plastic element which is secured to the forward end of a strap 138, which is secured to the cradle as indicated by the screws 140 in FIG. 1. The end 136 may also comprise plastic elements which pass through and are secured to the upper end of a bracket 142, the lower end of which is secured to the stationary chassis as indicated by the screw 144 in FIG. 2. One end, in this case the end 136, has a constricted aperture such that air flows through it slowly. In consequence when the cradle is tilted and compresses the bellows, the stud '98 of the linkage 36 being in its outer position, as shown in FIG. 3, it tends to remain in that position, and does not move back between the successive steps of the memory drum until the drum is stopped at the selected position. The cradle and linkage then move to proper position as determined by the adjustment of the square screw for that detented position.

If the tuner is to be used under remote control, the motor drive is most conveniently attached to the rear end of shaft 22, which may be extended somewhat compared to the present showing in FIG. 1. This constitutes one advantage in locating the detent wheel 28 at the rear end of the chassis. Another advantage is that by locating both the reduction gearing and the detent mechanism at the rear end of the chassis, the forward end of the chassis is cleared to receive the memory drum and the preset mechanism, as here shown.

It is believed that the construction and operation of my improved detented presettable tuner, as well as the advantages thereof, will be understood from the foregoing detailed description. It will also be understood that while I have shown and described the tuner in a preferred form, changes may be made without departing from the scope of the invention.

I claim:

1. A detented presettable tuner of the variable gang capacitance type, said tuner comprising a fixed chassis, a rotor shaft carrying rotor plates, a tiltable cradle carrying stator plates, said cradle being mounted in said chassis for limited oscillation about the axis of the rotor shaft, a detent wheel rotatable with said rotor shaft, a cooperating detent bearing against said detent wheel for selecting rotor positions, a memory drum having adjustable projections for fine tuning, there being one projection for each detented position, and linkage responsive to and moved by said adjustable projections and extending to the tiltable cradle, whereby the selected projection tilts the cradle to a fine tuning position which is determined by the adjustment of the projection, said memory drum being axially separated from said detent wheel and having sloping contour cams between said fine tuning projections to ease the transition from one projection to the next.

2. A tuner as defined in claim 1, in which the rotor is designed for motion through about a half revolution, and in which there is a selector shaft and reduction gearing between the selector shaft and the rotor shaft so that the selector shaft turns through a full revolution, and in which the detent wheel and the memory drum are mounted on the selector shaft.

3. A tuner as defined in claim 2, in which the adjustable projections are adjusted by relative rotation of parts having mating screw threads, and in which there is a hollow shaft concentric with the selector shaft, and gearing between said hollow shaft and that one of the adjustable projections which is at the selected detent position, and in which a part of the gearing is normally disengaged, and in which the hollow shaft turns a slip friction clutch driving a part which brings the disengaged gearing into mesh for cradle tilt at the selected detented position of the tuner.

4. A tuner as defined in claim 3, in which the adjustable projections are radial screws carried by the memory drum, means to prevent rotation of the screws, and one of said parts comprises a gear nut for each screw to move the same to adjust its radial projection from the drum, the aforementioned gearing terminating at the Selected gear nut for rotation of the same.

5. A tuner as defined in claim 4, in which the drum has radial slots which are non-circular in cross section, and in which the radial screws are disposed in said slots and said means to prevent rotation comprises flats to prevent rotation thereof in said slots, and in which each screw is received in a corresponding gear nut which is rotatable to adjust the screw radially of the drum, said gear nuts being received in tangential slots to expose the gear teeth for engagement with a driving gear forming a part of the fine tuning mechanism.

6. A tuner as defined in claim 5, in which the detent wheel and the reduction gearing are mounted at the rear end of the chassis, and in which the memory drum and the preset mechanism including the slip friction clutch and gearing for preset tuning are mounted at the forward end of the chassis.

7. A tuner as defined in claim 6, in which there is slip friction means engaging one of the gears in the gearing between the hollow shaft and the gear nut in order to afford slippage if the hollow shaft is rotated beyond the limit of movement of the cradle.

8. A tuner as defined in claim 7, in which a bellows having a constricted air passage is connected at one end to the tiltable cradle while the other end is fixed, in order to provide a dashpot action such that the cradle will not oscillate with every contour cam of the memory drum when the said drum is rapidly rotated.

9. A detented presettable tuner of the variable gang capacitance type, said tuner comprising a fixed chassis, a rotor shaft carrying rotor plates, a tiltable cradle carrying stator plates, said cradle being mounted in said chassis for limited oscillation about the axis of the rotor shaft, a detent wheel coupled to said rotor shaft for rotation therewith, a cooperating detent bearing against said detent wheel for selecting rotor positions, a memory drum coupled to said rotor shaft and having adjustable projections for fine tuning, there being one projection for each detented position, linkage responsive to and moved by said adjustable projections and extending to the tiltable cradle, whereby the selected projection tilts the cradle to a fine tuning position which is determined by the adjustment of the projection, a selector shaft and reduction gearing be tween the selector shaft and the rotor shaft, a hollow shaft concentric with the selector shaft, gearing between said hollow shaft and that one of the adjustable projections which is at the selected detent position, means to cause said gearing to normally be disengaged, and a slip friction clutch driven by said hollow shaft and moving a part which brings the disengaged gearing into mesh for cradle tilt at the selected detented position of the tuner.

10. A tuner as defined in claim 9, in which the rotor is designed for motion through 180, and in which the selec tor shaft turns a full revolution, and in which the detent wheel and the drum are mounted on the selector shaft.

11. A tuner as defined in claim 9, in which the adjustable projections are radial screws carried by the memory drum, means to prevent rotation of the screws, and a gear nut for each screw to move the same to adjust its radial projection from the drum, the aforesaid cradle tilt shaft and gearing terminating at the selected gear nut for rotation of the same.

12. A tuner as defined in claim 11, in which the drum has radial slots which are non-circular in cross section, and in which the radial screws are disposed in said slots and have flats to prevent rotation thereof in said slots, and in which each screw is received in a gear nut which is rotatable to adjust the screw radially of the drum, said gear nuts being received in tangential slots to expose the gear teeth for engagement with a driving gear forming a part of the fine tuning mechanism.

13. A tuner as defined in claim 9, in which there is slip friction means engaging one of the gears in the gearing between the hollow shaft and the adjustable projection in order to afford slippage if the hollow shaft is rotated beyond the limit of movement of the cradle.

14. A tuner as defined in claim 9, in which a bellows having a constricted air passage is connected at one end to the tiltable cradle while the other end is fixed to provide a dashpot action such that the cradle will not oscillate with every projection of the memory drum when the said drum is rapidly rotated.

15. A tuner as defined in claim 1, in which a bellows having a constructed air passage is connected at one end to the tiltable cradle while the other end is fixed to pro- 'vide a dashpot action such that the cradle will not oscillate with every projection of the memory drum when the said drum is rapidly rotated.

16. A tuner as defined in claim 9, in which the detent wheel and the reduction gearing are mounted at the rear end of the chassis, and in which the memory drum and the preset mechanism including the slip friction clutch and the gearing engageable with the adjustable projections are mounted at the forward end of the chassis.

17. A tuner as defined in claim 9, in which the drum has contour projections between the adjustable projections in order to ease the transition from projection to projection despite differences in the radial position of the successive projections.

References Cited UNITED STATES PATENTS 6/1965 Mentzer 74-10 9/1966 Leedom 7410.4l

MILTON KAUFMAN, Primary Examiner