CA1087730A - Spring loaded pickup arm for video disc playback - Google Patents

Spring loaded pickup arm for video disc playback

Info

Publication number
CA1087730A
CA1087730A CA260,452A CA260452A CA1087730A CA 1087730 A CA1087730 A CA 1087730A CA 260452 A CA260452 A CA 260452A CA 1087730 A CA1087730 A CA 1087730A
Authority
CA
Canada
Prior art keywords
stylus
spring
carriage
arm
track
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA260,452A
Other languages
French (fr)
Inventor
Anil R. Dholakia
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB37848/75A external-priority patent/GB1552763A/en
Application filed by RCA Corp filed Critical RCA Corp
Application granted granted Critical
Publication of CA1087730A publication Critical patent/CA1087730A/en
Expired legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B3/00Recording by mechanical cutting, deforming or pressing, e.g. of grooves or pits; Reproducing by mechanical sensing; Record carriers therefor
    • G11B3/02Arrangements of heads
    • G11B3/10Arranging, supporting, or driving of heads or of transducers relatively to record carriers
    • G11B3/12Supporting in balanced, counterbalanced or loaded operative position during transducing, e.g. loading in direction of traverse
    • G11B3/20Supporting in balanced, counterbalanced or loaded operative position during transducing, e.g. loading in direction of traverse by elastic means, e.g. spring
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B3/00Recording by mechanical cutting, deforming or pressing, e.g. of grooves or pits; Reproducing by mechanical sensing; Record carriers therefor
    • G11B3/44Styli, e.g. sapphire, diamond
    • G11B3/46Constructions or forms ; Dispositions or mountings, e.g. attachment of point to shank

Landscapes

  • Moving Of Heads (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Feeding And Guiding Record Carriers (AREA)
  • Moving Of The Head To Find And Align With The Track (AREA)

Abstract

Abstract of the Disclosure A video disc player for playing back prerecorded signals from a spirally-grooved and rotatable record includes a carriage mounted for lateral motion relative to a base plate of the player in correlation with lateral motion of a groove-riding stylus during playback. A stylus arm supported at one end within the carriage carries a stylus at the free end thereof. One end of a leaf spring for urging the stylus into the record groove is secured to the stylus. The second end of the leaf spring is mounted within the carriage above the stylus. The leaf spring provides stylus tracking pressure, properly locates the free end of the stylus arm relative to the carriage, establishes electrical connection between an electrode on the stylus and signal processing circuitry of the player.

Description

1~J87730 ~ RCA 69,355 1 The invention relates to a spring loaded stylus apparatus for a video disc player.
A video disc system of the type described in the U.S. Patent No. 3,842,194, generally utiliz~ records having groove densities of the order of four to eight thousand groove convolutions per inch. A typical video record of this type may have a g'roove convolution spacing of the order of 3.5 microns. The fragile walls of relatively narrow record grooves cannot be dependably relied upon to pull a stylus arm unit, around the compliant member, across the entire recorded surface of the record. Also, in video disc systems of the type described in abovesaid patent, it is desirable for accurate reproduction of the prerecorded signals that the stylus electrode maintain a substantially constant atti-tude in the record groove during playback. Therefore, alateral feed drive mechanism is provided for traversing a carriage supporting the stylus arm unit in proper time relationship with the lateral motion of the stylus due to the spiral groove so as to continuously maintain the longi-tudinal axis of the stylus arm substantially tangential to the spiral groove at the point of stylus/groove engagement during playback. The U.S. Patent No. 3,870,835, issued on March 11, 1975 to Frederick R. Stave, illustrates such a lateral feed drive mechanism.
The stylus needs a certain tracking force to assure proper tracking and seating of the stylus in the record groove during playback. Typically, all the tracking force comes from the weight of the stylus arm unit, and the tracking is, essentially, mass controlled along the record groove and up-and-down on any defect in the record groove.
-2-10~7730 RCA 69,355 1 In accordance with the principles of the present invention, a stylus arm unit having a mass lower than that required for desirable tracking force is provided, and a spring connected between the stylus and the carriage provides the desired tracking force. It has been found that such an arrangement substantially reduces signal drop-outs during playbac7c, because the leaf spring causes the stylus to quickly return to the record groove when the stylus is launched in space by a defect in the record groove.
In addition to providing stylus tracking force, the stylus spring may serve to properly locate the free end of the stylus arm relative to the carriage, and to establish electrical connection between an electrode on the stylus and signal processing circuit of the player.
Different systems have been heretofore tried to provide spring loading. Many of these systems employ a coil spring stretched between the stylus arm and a supporting structure. These systems, however, have proved unsatisfac-tory because they tend to bend the stylus arm setting up undesired oscillations therein and causing mistracking of the stylus. The problem is particularly acute where the stylus arm unit is extremely fragile and lightweight and where the tracking speed is relatively high. The apparatus of the present invention overcomes aforesaid problems.
In the accompanying drawings:

FIGURE l is a video disc player incorporating aspring loaded stylus apparatus embodying the present invention;

FIGURE 2 is a perspective view of a cartridge in which the spring loaded stylus apparatus of FIGURE l is 10~7730 RCA 69,355 1 housed:

FIGURE 3 is a perspective view of a stylus arm unit to which the spring loaded stylus of FIGURES 1 and 2 is secured;
5FIGURE 4 iS a side view of the stylus arm unit showing the spring loaded stylus apparatus;
FIGURE 5 is a front view of the stylus arm unit of FIGURES 3 and 4; and FIGURE 6 is a side view of a portion of another embodiment of the spring loaded stylus apparatus of the present invention.
In FIGURE 1, numeral 10 indicates a video disc player of the general type shown in U.S. Patent No. 3,B42,194 (Clemens). A record 11 is rotatably mounted for playback on a turntable 12 secured to a motorboard 13 of the player. A

carriage 14 is mounted for lateral motion relative to the motorboard 13 in correlation with lateral motion of a stylus 15 riding in a spiral groove disposed on the surface of the disc record 11 during playback.
A stylus arm unit 16 is housed in a cartridqe 17.
The cartridge 17 is received in a compartment 18 provided in the carriage 14. FIGURE 2 shows a perspective view of the cartridge 17.

As can be seen from FIGURE 3, the stylus arm unit 16 comprises a stylus arm 19 formed with an aluminum tube (e.g., 0.024 inch outer diameter and 0.002 inch thickness) with a plastic stylus holder 20 glued at one end of the stylus arm and a compliant member 21 inserted molded at the other end of the stylus arm. The compliant member 21 3o exhibits high compliance to low fre~uency motion of the 1~)87730 RCA 69,355 1 stylus arm 19 (e.g., due to record warpage, eccentricity, etc.). The stylus holder 20 has lower compliance than the compliant member 21, but exhibits relatively high compliance to high frequency motion of the stylus arm 19 (e.g., due to "orange peel" type record surface).
The compliant member 21 is in substantially unstressed condition when it is aligned with the stylus arm 19. A connector plate 22 is glued to the compliant member 21 in a manner that establishes 94 angle therebetween. The plastic stylus holder 20 contains a slot 23 in which the stylus 15 is glued in place. A small projection 24 is molded at the top of the plastic stylus holder 20 to engage with an abutment to relieve the stylus 15 from a locked groove.
The U.S. Patent 4,049,280, of M. A. Leedom, entitled, "PICKUP CARTRIDGE", issued September 20, 1977.
illustrates such a locked groove relief arrangement.
The stylus arm unit 16 is suspended in the cart-ridge 17 by an elastic diaphragm 25 as shown in FIGURES 1 and 2. A U-shaped spring 26 releasably clamps the stylus arm 19 in a retracted position in the cartridge 17 during storage and handling of the cartridge (i.e., while the cart-ridge is outside the compartment 18). The retracted position provides a location for the stylus 15 withdrawn within the confines of the cartridge 17 remote from an opening in the bottom wall of the cartridge through which the stylus may protrude ~e.g., during playbac~).
A support member 27 of an armstretcher apparatus 28 engages the connector plate 22 during containment of the cartridge 17 in the compartment 18. The armstretcher 28 is slidably mounted in the compartment 18 for movement between B

1~87730 RCA 69,355 1 a withdrawn position when a lid 29 of the carriage 14 is open to an advanced position when the carriage lid is closed in response to the motion of the carriage lid. The support member 27 enters the interior of the cartridge 17 through an opening 30 in the cartridge to eng~ge the connector plate 22 when the armstretcher 28 is advanced. The U.S. Patent No. 3,/11,641 illustrates such an armstretcher apparatus.
A spring defeat lever 31, secured to the carriage lid 29, enters the interior of the cartridge 17 through an opening 32 in the cartridge to defeat the clamping spring 26 during containment of the cartridge in the compartment 18 upon closure of the carriage lid.
; The cartridge 17 further includes a leaf spring 33, in the form of a ribbon, for urging the stylus 15 in the record groove to establish stylus tracking pressure during playback as shown in FIGURE 1. The first end of the leaf spring 33 is secured to the stylus 15 as shown in FIGURES 1,
3, and 4. The second end of the leaf spring 33 is secured to a flat 34 on a portion of a ball 35 as shown in FIGURES
1, 4, and 5. The ball 35 is friction loaded into a socket 36 provided in the cartridge 17 so that the flat portion protrudes from the socket. The cartridge 17 has an access opening 37 in communication with the socket 36 for inserting a tool into a hex-s~aped hole 38 provided in the ball 35 for the purpose of adjustment of the stylus. Such adjustment may, for example, serve to center the stylus arm 19 in the cartridge 17 or to vary the stylus/record tracking pressure.
After such adjustment at the factory, the ball 35 may be firmly glued in place.
The stylus adjusting apparatus is of the type 1~77~ RCA 69,355 1~
1 described in a U.S. Patent~4,030,123 of B. K. Taylor, et al., entitled, "STYLUS ADJUSTMENT APPARATUS
FOR A VIDEO DISC PLAYER", issued June 14, 1977.
The second end of the leaf spring 33 is located so that the stylus arm 19 is normally aligned with the compliant member 21. As previously indicated, the compliant member 21 is in substantially unstressed condition when it is aligned with the stylus arm 19. Alignment of the compliant member 21 with the stylus arm 19 is advantageous because it prevents formation of a "set" in the compliant member which may inter-fere with the ability of the stylus 15 to tra~k the record groove.
FIGURE 6 is a side view of a portion of another embodiment of the spring loaded stylus apparatus in which the leaf spring 33 is bowed in a direction opposite that shown in t~e embodiment of FIGURES 1-5.
Where the stylus 15 incorporates an electrode for detecting signal variations in the spiral groove in the record 11 during playback, the leaf spring may be made of conductive material to provide an electrical connection between the stylus electrode and the signal processing circuitry 40 (FIGURE 1) of the video disc player 10~ In that case, the first end of the leaf spring 33 is secured to the stylus 15 in a manner that establishes electrical connec-tion between the leaf spring and the stylus electrode. The signal processing circuitry 40 has an input terminal 41 which contacts the second end of the leaf spring 33 during contain-ment of the cartridge 17 in the compartment 18 to establish the abovementioned electrical connection.
The cartridge may be of the type described in the RCA 69,355 1 U.S. Patent 4,049,280, of M. A. Leedom, entitled "PICKUP CARTRIDGE", issued September 20, 1977.

Claims (6)

WHAT WE CLAIM IS:
1. Apparatus in a system for playing back prerecorded signals from a spiral track of a record rotatably mounted on a turntable by a track riding stylus secured to one end of a stylus arm; and including a base plate;
said apparatus comprising:
a carriage mounted for lateral motion relative to said base plate in correlation with lateral motion of said groove-riding stylus;
means for supporting the end of said stylus arm remote from said one end within said carriages a spring for urging said stylus into engagement with said record track during playback; said spring having a first end and a second end; said first end of said spring being secured to said stylus; and means for securing said second end of said spring within said carriage for movement therewith.
2. An apparatus as defined in Claim 1 wherein said spring comprises a leaf spring disposed in a bowed con figuration.

3. Apparatus as defined in Claim 1, comprising:
a compliant member securing the other end of said stylus arm within said carriage;
Claim 3 continued--means for causing lateral motion of said carriage during playback in correlation with said lateral motion of said track-riding stylus so that said stylus arm is maintained substantially tangen-tial to said track at the point of the stylus/track engagement;
and said means securing said second end of said spring within said carriage above said stylus so that said stylus arm is normally aligned with said compliant member.
4. Apparatus as defined in Claim l or 3, including a signal processing circuit having an input terminal located within said carriage; said spring being made of conductive material; said second end of said spring being connected to said input terminal: said stylus having an electrode; said securing of said first end of spring to said stylus effect-ing an electrical connection between said first end and said electrode to establish as electrical path between said stylus electrode and said signal processing circuit via said spring.
5. A pickup cartridge for transducing information from the spiral track of a grooved disc record comprising:
a housing having a bottom adapted to be supported adjacent said disc record;
a stylus arm assembly including:
a substantially straight and elongated stylus arm;
Claim 5 continued--a compliant member for supporting one end of said stylus arm within said housing and closely adjacent to, said housing bottom;
a stylus holder for securing a track-engaging stylus to the other end of said stylus arm;
said compliant member exhibiting relatively high compliance to low frequency motion of said stylus arm;
said stylus holder having a lower compliance than said compliant member, but said stylus holder exhibiting relatively high compliance to high frequency motion of said stylus arm; and the mass of said stylus arm assembly being insufficient to provide the desired tracking force as a function of gravity to track said disc record; and a spring connected between said stylus and said housing to provide the desired tracking force.
6. A pickup cartridge as defined in Claim 5 wherein said stylus includes a conductive electrode for detecting signals recorded on said disc record; wherein said spring being conductive; wherein said connector between said spring and said stylus serves to establish an electrical path from said stylus electrode via said conductive spring.
CA260,452A 1975-09-15 1976-09-02 Spring loaded pickup arm for video disc playback Expired CA1087730A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB37848-75 1975-09-15
GB37848/75A GB1552763A (en) 1975-09-15 1975-09-15 Spring load stylus record playback apparatus
US667,307 1976-03-16
US05/667,307 US4077050A (en) 1975-09-15 1976-03-16 Video disc player employing a spring loaded stylus apparatus

Publications (1)

Publication Number Publication Date
CA1087730A true CA1087730A (en) 1980-10-14

Family

ID=26263606

Family Applications (1)

Application Number Title Priority Date Filing Date
CA260,452A Expired CA1087730A (en) 1975-09-15 1976-09-02 Spring loaded pickup arm for video disc playback

Country Status (11)

Country Link
JP (1) JPS5237004A (en)
AT (1) AT356918B (en)
CA (1) CA1087730A (en)
CH (1) CH608906A5 (en)
DE (1) DE2641560C2 (en)
DK (1) DK141796B (en)
ES (1) ES451541A1 (en)
FR (1) FR2324090A1 (en)
IT (1) IT1068498B (en)
NL (1) NL7610194A (en)
NZ (1) NZ182050A (en)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE409252B (en) * 1975-09-18 1979-08-06 Rca Corp SIGNAL PICKUP CARTRIDGE
DE2641296C2 (en) * 1975-09-18 1984-05-10 Rca Corp., New York, N.Y. Device for scanning spirally recorded information with a spring-loaded scanning arm
DE2641297C2 (en) * 1975-09-18 1984-01-26 RCA Corp., 10020 New York, N.Y. Device in an optical disc player for releasably securing the scanning arm
JPS5252319A (en) * 1975-09-18 1977-04-27 Rca Corp Video disk reproducer
US4337536A (en) * 1980-02-04 1982-06-29 Rca Corporation Flylead for a video disc stylus cartridge
JPS5932043Y2 (en) * 1980-11-21 1984-09-08 日本ビクター株式会社 Signal pickup device in playback equipment
US4404669A (en) * 1982-01-20 1983-09-13 Rca Corporation Stylus assembly
GB2120446A (en) * 1982-04-08 1983-11-30 Rca Corp Holding apparatus for a disc record signal pickup stylus

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2643886A (en) * 1948-09-25 1953-06-30 Alexander E Di Ghilini Arm for recording and reproducing apparatus
GB1460912A (en) * 1973-03-26 1977-01-06 Rca Corp Spring loaded stylus arm pivot
US3870835A (en) * 1973-04-16 1975-03-11 Rca Corp Stylus control apparatus for a video disc record player
US3873783A (en) * 1974-03-28 1975-03-25 Rca Corp Universal stylus arm pivot coupling
US3917903A (en) * 1974-11-12 1975-11-04 Rca Corp Detachable pickup arm magnetic coupling

Also Published As

Publication number Publication date
NZ182050A (en) 1979-10-25
FR2324090B1 (en) 1982-07-02
NL7610194A (en) 1977-03-17
JPS5237004A (en) 1977-03-22
FR2324090A1 (en) 1977-04-08
DE2641560C2 (en) 1984-05-17
DK141796C (en) 1980-11-03
ES451541A1 (en) 1977-12-01
DK141796B (en) 1980-06-16
DE2641560A1 (en) 1977-04-14
JPS5737921B2 (en) 1982-08-12
IT1068498B (en) 1985-03-21
AT356918B (en) 1980-06-10
ATA677776A (en) 1979-10-15
CH608906A5 (en) 1979-01-31
DK413876A (en) 1977-03-16

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