CA1133130A - Video disc player - Google Patents

Abstract

ABSTRACT

A video disc player assembly is described employ-ing a fixed base member with a pair of fixed rails, and a movable carriage member employing a pair of linear bearing assemblies in engagement with said rails. A capstan and pulley assembly provides a means for moving the carriage member over the rails in the base member. A motor and spindle are mounted an the carriage for rotary driving of the video disc. A centering means is provided to accur-ately center the disc about the spindle, and a stabilization plate is provided adjacent and parallel to the rotating disc.

Description

3~3 ~

~/L~O 5C ?b~lER
TECHNICAL F_IELD
mis invention relates to an improved video disc playerJ and in particular to a video disc player having an improv~d mechanical structure for moving the carriage member a~d centering the disc about the spindle.
BRIE_ SUMMARY OF THE INVE~TION
Th 5 is a brief summary o~ the video disc player unlt. A ~unction o~ the video dlsc player unl~ is to pro~
10 vide a support means ~or the video di~c or information carrier. ~he in~orma~ion carrier is adapted to be rotated about ~ts central axis at a relatively high speed. Dis-pos~d upon the information carrier are a series of bumps and lands successively arranged forming an in~orma~ion track, The arrangements of bumps and lands are indicative o~ & video encoded ~M carrler. An alternative embodlment might have an arrangement o~ bump~ and lands indicativ~ Or another ~orm o~ encoding, such as digltal encodlng. The support means providing restraint ~or the informatlon - 20 carrier is accuratel~ de~ined with respect to the plane of an ob~ective lens and impar~s a crltical degree of parallelism to khe plane of the objective lens. The ob~ectlve lens cooperates with a collimated light source and optlcal elements, such as mirrors and lens, in ~ormlng a read beam, and the read beam ls utilizable ln recovery o~ ~n~ormation stored on the information carrier by the arrangement of bumps and lands, which arrangement is ln-dicative o~ a video encoded frequency modulated carrier.
; me v~deo dl~c is mounted for rotation on a ~, :, ,. , ~ ' ' ~ ' ` ' ' ~3L33~3~

carriage, and the carriage is mounted for reciprocal motion with respect to the support means on a locator rail and a support ~ollower rall. The carriage includes a locator bearing assembly and a support follower bear~ng assembly which engage the locator and follower rails, respectively, and a resiliently mounted rolling ratainer is a~sociated with each bearing assembly to maintaln engage-ment between the bearing and rail. The locakor rall co-operates with the locator bearing assembly to provide allgnment means such that only one rail need be aligned ln a plane parallel to a plane defined by the center line of the spindle and extended radially to the center line o~ the ob~eckive lens. The support follower rail provides a working surface for the support follower bearing assem-15 bly such that the support follower bearing assembly pro-vides only a means of support without impark-lng any angular direction which would be in confllct with the alignment prescribed by the locator bearing assembly.
Although the video disc player unit is provided 20 With both a locator bearing assembly and a support follower bearing assembly~ alternative embodiments need not be so equlpped; for instance a lathe requirlng accurate align-ment of a particular item of kooLing would only require the utilization of the locator bearing assembly and its a~soclated form of support means.
The support means as described herein and coupled with the locator bearing a~sembly and the ~upport ~ollower bearing assembly cooperate to provide a critical degree of' translational accuracy and a frictionless means of accom-plishing this translational accuracy.
A stabillzation plate is mounted on the carriageand provides stabilization means to the video disc such thak the video disc is isolated from vibrations and com-pensated for inherent unflatness developed ln the disc during manufacture. The stabilization means as employed in the preferred embodlment determines the vertlcal dis-tance between the rotating video disc member and the skabilization plate. The vertical distance is accomplished by the restrlction of the air exit point located adJacent ~133~L30 to the ~pindle and motor assembly and the stabilizatlon plate.
The increased vertical distance between the video disc member and the stabilization plate provides a higher degree of latitude in vldeo disc speci~ications. Prior art vldeo discs would contact or scrape the stabilization plate or other components of the video dlsc player unit.
The increased vertical dlstance thus allows a disc of greater un~latness to be utilized on the pre~erred embodi-ment o~ the video disc player unit.
~ he carriage assembly employs a clamp assemblyproviding clamping means to the video disc adapted about its central aperture to be rotated at a high rotational speed. This clamping means cooperates with the spindle assembly and a centering device disposed thereon to firmly retain the vldeo disc member about its central aperture upon the spindle assembly and allowing a clamping means which provide~ ~or a high degree of user convenience. This clampin-g means or a version thereof would be utilizable in any device wherein a means o~ ~irm restraint but allowing a high degree of user convenience would be required.
me carriage assembly also employs a centering devlce which cooperates with the clamp assembly and pro-vides centering means to compensate for variations in the radial size o~ the central aperture o~ the video disc member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is an elevational vlew wlth a port~on o~
the external houslng removed to illustrate the video disc player unit;
FIG~ 2 is a bottom plan view of the carriage and the carriage support plate;
FIG. 3 is an elevational view o~ the basic mechan-ical portion o~ the video disc player unit taken generally along the line 1-1 o~ FIG. l;
FIG. 4 is an enlarged elevational view partly in section of the spindle and motor assembly taken gener-ally along the line 3-3 o~ FIG. 3~
FIG. 5 is an enlarged fragmentary, elevational ~33L3~ `

~iew o~ the locator bearing assembly indicated in FIG. l;
FIG. 6 is an enlarged, fragmentaryJ elevational view of the support follower bearing assembly indicated in FIG. l;
FIG. 7 is a ~urther enlarged9 partly sectional view o~ the support follower bearing as it zppears in FI~o 6;
FIG. 8 is a partly sectional view taken gener-ally along the line 8-8 o~ FIG. 7;
FIG. 9 is an elevational view with the llnear bearlng partly broken away taken on the line 9-9 of FIG.
7;
FIG. 10 is a fragmentary bottom plan view of the sprlng loaded rolling retalner; and FIG. 11 is a fragmentary elevational view of the loaded rolling retainer.
DETAI~ED DESCRIPTION OF THE I~ENTION
Referring to FIG. 1, which is a dlagram of a video disc player unit 1, utilizable in the playback of an 20 ln~ormation carrier 2, adapted to be rotated about its center at a relatively high speed. The lnformation carrier is a substantially planar substrate having a first surface 3 and a second surface 4 and provlded with a central aperture (not shown). Disposed between the ~lrst 25 surface 3 and the second surface 4 are a series of bumps and lands~ the bumps being primarily light defracting and the land areas being primarily light re~lective. The alternately de~racting and re~lecting bump~ and lands are indicative of a modulated FM carrier, the bumps and lands belng arranged in such a manner as to ~orm a spiral having a predetermined pitch. The informaklon carrier 2 will henceforth be referred to as a video dlsc for ease o~
description.
- The video disc player unit 1 comprises a spindle and motor assembly 5 for impart~ng rotation tothe video disc 2 about its central axis and provided with a clamp assembly 6 for retaining said vldeo disc 2 about the central axis o~ the spindle and motor assembly 5 and par-allel to a stationary platform hence fbrth referred to as ~3~L~

a stabillzatlon plate 7.
The video disc player unit l includes a means of accurately translaking the spindle and motor assembly 5 and the attached video disc 2 radially beneath an optical brldge 8 provided with a light source and optical path (not shown). The position of the optical bridge 8 is maintained vertically above the rotating video disc 2 by means of a number of optical bridge support posts 9 and ~irmly restrained at point of contact lO by means of a threaded device ll, such as a screw, ~hich screw 1~ main-tai~ed in a threaded aperture located in the optical bridge support post 9 which aperture is not shown in FIG.
1, to the carriage support plate 12. The optical brldge support post 9 passing vertically through an upper plate 13 hence~orth known as a protective dust shield, and pro-vided with an aperture (not shown) allowing the transla-tion of the spindle and motor assembly 5 and attached disc

2 throughout their range o.~ linear translation.
The accurate translation o~ ~he spindle and motor assembly 5 and the attached video disc 2, radially with respect to the video disc 2 ~eneath the optical bridge 8, is provided by a carriage 14 having a locator bearing assembly 15 and a support ~ollower beari~g assembly 16 allowing an accurate linear translation of the spindle and motor assembly 5 and the attached video disc 2, and a restraining ~orce is supplied by a resillently attached rolllng retainer 17. The means of resillent attachment is accomplished by a nu~ber of springs and grommets which wlll be discussed in detail in FI~. ll. Said rssil1ently attached rolling retainer 17 3upplies a downward force to the locator ~aring assembly 15 and the support follower bearlng assembly 16.
The translational motion imparted to the carriage 14 is supplied by a carriage drive capstan (not shown) and directed to the carriage 14 by means of a carriage drive cable 18. The carriage drlve cable 18 is directed circum~
ferentially about a carriage drive pulley 19 by means of a carriage drive cable guide 20. The carriage drive pulley l9 supplies a carriage position potentiometer 21 L~L3a.~3~

with a motive force dlrectly relatable to the location of the carriage 14. The carriage position potentiometer renders a direct current voltage proportional to the posi-tion of the carrlage 14 at any given moment.
The carriage support plate 12 is supplie~d with a number of structural support ribs 22 utillzed to strengthen the carriage support plate 12, the carriage support plate 12 also havIng stiffening ribs 23 located in the area of the locator bearing assembly 153 and the support ~ollower bearing assembly 16 where structural integrity has the highest degr@e o~ significance.
The carriage support plate 12 having an upper pl~ne 24 and a lower plane 25 securely conjoined by means o~ a connecting angle 26 which cooperates with the upper plane 27 o~ the carriage 14, and the lower ~ane 28 of the carriage 14 which are interconnected by means of a connec~
ing angle 29 to form a more compact video disc player unit 1. Also indlcated by FIG. 1 at the arrows 29A and 29B are two substantially parallel surfaces, which surfaces cooperate to maintain the points of contact of the linear bearing which will be described in detail in FIG. 5.
The carriage support p:late 12 forms a secure attachment to the base 30 by means of a carriage support post 31 through a shock mountin~ dead rubber grommet 32 and is restr~ined by a threaded device, such as a stud (not shown). The carriage support plate 12 cooperates wlth the carriage support post 31 to form a rigid support for the carriage.
^ In order to contain the rotating disc 2 and the collimated light source (not shown), to the area o~ the vldeo disc player unit 1, the unit is Bupplied wlth two side covers 33 and a cover 34 which is ~irmly attached through a hinge 35 allowing access to the mechanical portion of the video disc player unit 1. The cover 34 is supplled with a mechanical stop 36 whlch attaches to the front cover 37 of the video disc player unit 1.
Now referring to FIG. 2 which indicatcs a bottom plan view of the carriage support plate 12, and the car-riage 14, and their relationship.

~33 FIG. 2 shows the protective dust cover 13 and its aperture 38 allowing ~or the translation of the carriage 14 throughout lts range of travel.
The translation o~ the carriage 14 1s achieved by means of the carriage drive capstan 39 at which point the carriage drive cable 18 is wound circumferentially about the carriage drive capstan sha~t 40. The path of the c&rriage drive cable 18 is prescribed by a number of carriage drive cable guides 20.
It can be seen by a person skilled in the art, that as the carriage drive capstan 39 and its associated carriage drive capstan shaft 40 are rotated, the carriage drive cable 18 will be wound or ~nwound circum~erentially about the carriage drive capstan shaft 40, in a direct relationship with the direction of rotation of the car-rlage drive capstan sha~t 40, thus imparting a motive ~orce to the carriage ~ through the carriage drive cable 18 and its associated points of attachment 43 and 44 to the c~rriage 14. The cooperation o~ carriage drive capstan 39, the carriage drive cable 18 and the carriage drive -cable guides 20, form the carriage drive~ utilizable as means of imparting linear motion to the carriage.
The carriage drive cab:Le 18 having a device 413 such as a spring, which device supplies tension and dampen-ing to said carriage drive cable 18, and having attachmentto ~aid carrlage drive 18 at the point 42. The carriage drive cable 18 having a means of attachment to the car-riage 14 at. the points o~ attachment 43 and 44, said points of attachment 43 and 44 being accomplished by the

3 means of a ~hreaded device 459 such as a screw. The threaded device 45 is restrained in its position by means o~ a threaded aperture (not shown) Continuing with FlG. 2, it can be seen that the stabilization plate 7 is sup~lied with a numbsr o~ struc-tural ribs 46 greatl~ enhancing the structural integritywithout appreciably increasing the mass of said stabillza-tion plate 7. The stabilization plate 7 is rigidl~
attached to the carriage 14 by means o~ a number o~ adjust-able retaining screws 47. Due to this rigid attachment~

~33~3~

the stabilizat-lon plate 7 is directed to move in con~unc-tion with the carriage 14. The maintaining of a low mass stabilization plate allows for faster forward and re~erse speeds that might be utilized in a re~ect or search mode.
The low mass carriage and stabilization plate assembly allow for the use o~ a lower energy capstan drive for said carriage drive, since the low mass assembly is incapable of s~orlng as much inertia as an assembly utilizing a solid stabilization plate.
The advantages of utilizing a belt type drive system having a capstan drive ~orming the motive force are such that the capstan drive allows for precise servo control of the carriage 14 speed. This s~stem also elim-inates problems with qscillations and irregularities in 15 carrLage speed due to the cooperation of the capstan and dampening spring in isolating said carriage 14 from these forms of irregularities.
It can be seen from FIG. 2 that the carriage 14 - is supplied with an aperture 48 which provides a placement point for the spindle znd motor assembl~J 5. This aperture 48 cooperates with the dual planes 27 and 28 of the car-riage 14 and the dual planes 24 and 25 of the carriage support plate 12 to provide a means of lowering vertically the spindle and motor assembly which is the limiting factor 25 in reducing the vertical size of the video disc player unit 1. The cooperation of the carriage 14, the stabilization plate ~ and the spindle and motor assembly 5 ~orm the carriage assembly~ utilizable in the support, rotation and translatlon of the video disc 2.
Continuing with FIG. 2~ it can be seen t'nat the resiliently mounted rolling retainer 17 is provided with a groo~e 49 allowing for a predetermined area of travel.
Also visible in FIG~ 2 is a threaded aperture 50 which provides a restraining point for a threaded device 35 such as a stud (not shown).
Also shown in FIG. 2 is a limit switch 48a which will be further discussed in FIG. 3.
Now referring to FIG. 3, indicated by the arrow 51 is the range of travel allowed tne carriage 1'~. This ~33~3~

g .
travel is mechanically l-lmlted b~ the limit switch 48a and a limit switch 52; these limit switches 48a and 52 collectively operate to define the furthermost boundaries of the carriage travel, and provide a positive means o~
sareguarding the video disc player unit 1 from unnecessary damage due to operator error or a mechanical malfunction.
Continuing with FIG. 3, it can be seen that the optical bridge ~ is provided with an optical bridge shield 53 which optical bridge shield 53 fully encloses the optical bridge 8. This is provided for safety reasons as the collimated light source 55, such as a laserg is required to have such shielding to el~minate the occurrence of pre-ventible injuries to the user.
The optical bridge 8 is formed by the optical bridge base 54 and attachment of the associated optical bridge components, such as mirrors 56 and 57 which direct the collimated light reflected from the surface 3 of the video disc 2 in order to recover information stored thereon.
The optical bridge ~ is also prGv~ided with a lens driver assembl~ 58 which lens driver assembly focuses the read beam generated by the collimated light source 55 such that the read beam is maintained in critlcal focus on the bumps and lands disposed upon the video disc 2 and in a manner such that the lens driver assembl~ will main-tain said critical focus throughout any vertical excursionsthe video disc may undergo due to its own imperfections.
Continuing with FIG. 3~ it can be seen that the lower plane 25 of the carriage support plate 12 ~orms a bend 59 thus directing the c~rriage support plate 12 ver-3 tically to form an upright 60, said upright ~0 directingthe carriage support plate 12 towards its upper plane 24 via an elbow 61. Disposed upon the upper plane 24 of the carriage support plate 12 is a threaded aperture 62 which cooperates with a threaded device 63, such as a screw, to restrain the protective dust shield 13 in ~ts required pos-ltion.
Still referring to FIG. 3, it can be seen that the threaded aperture 50 cooperates with a threaded device 64, such as a stud, and passing through an aperture 65 ~L33~

provided in the carriage support plate post 31 to form the restraining member of the carriage support plate post 31.
Continuing with FIG. 3, it can be seen that the stabilization plate 7 is provided with a number of threaded apertures 67 which apertures 67 cooperate with a number o~
ad~ustable retaining screws 47 to provide an ad~ustable means of restraint such that the stabilizatlon plate con-~orms to a critical perpendicularity to the central axis 59 o~ the spindle and motor assembly 5 and havlng a number of threaded locking means 68, such as nuts, which nuts cooperate with the adJustablè retaining screws 47 to insure sald critical perpendicularity to the central axis of the splndle and motor assembl~ 5.
Still referrlng to FIG. 3, it can be seen that a tachometer disc 70 is shown securely attached to the spindle and motor assembly 5. Said tachometer disc 70 is utilizable in generating an electrlcal signal indicative of the spindle speed at any given moment. Said electrical 2Q signal provides an accurate representation to servo means such that the servo means will maintain the spindle speed within a critical limit of a desired speed of rotatlon.
- Now referring to FIG. 4, a detailed diagram of the spindle and motor assembly 5~ the clamp as~embly 6 and the stabil~zation plate 7 is provided. Further, a novel centering means for use with the video disc player 1 and spindle and motor assembly 5 is illustrated and described.
FIG. 4 shows a motor 71 which motor i5 utilize-able for lmparting a rotational mot~on to a video disc 2~
3 said rnotor retained in its locakion by means of a threaded devlce 73, such as a screw, which screw cooperates with a threaded aperture 75 and passes through an aperture 75 provided in a motor mount 72. Said motor rnount 72 is vibrationally isolated from the remainder of the spindle 35 assembly by means o~ a dead rubber mount 74. Said motor 71 is a panca~e type and is commercially available.
The spindle 77 is securely connected to the motor 71 by rneans of a threaded device 78, such as a nut, which nut cooperates with a threaded lower portion 79 of the ~33:~3iD

splndle 77, said threaded lo~er por~ion 79 ~s~ng t~ugh an apertured spacer 80~ such as a washer.
The spindle 77 1s provided wlth a .means accurately locating said spindle about its central axis 69, said means also providing a high degree o~ nearly ~rlctionless rota-tion. This is accomplished by the implementation of the lower bearing 81 and the upper bearing 82. The lower bearing 81 is retained by a means, such as a press fit~
in a recess 83. The upper bearing 82 is also retained by 10 a means) such as a pre3s ~it, in a recess 84. The lower bearing 81 is further provided with a thrust washer 85, said thrust washer 85 limiting the amount of vertical motion o~ the spindle 77.
Continuing with FIG. 4, the spindle 77 is provlded 15 w~th a video disc support ring 86 which video disc support ring is arranged about the central axis 69 of the spindle 77 and having an upper plane 87 arranged in a critical perpendlcularly to the central axis 69 and directly adja-cent to the plane of the second surface 4 of the video 20 disc 2. Said video disc support ring 86 having a lower pl~ne 88 in intimate contact w~th an upper plane 89 o~
the upper bearing 82, and provided with a l~p 90 for the positioning of a compresslon spring 91.
Still looklng at ~IG. 4~ it can be seen that the 25 splndle 77 is provided with a centering device 92 which centering device is arranged in critical perpendicularity to the central axis 69 of the splndle 77~ ~aid centering dev$ce 92 being of a substantially conical shape and resi~
in~ in a recess 93 ~ormed b~ the vertical connectlon 30 upr~ght 94 of the video disc support ring 86, sald center-lng device having a ~irst posltion 95 and a second poRition 96. The centering device 92 cooperate~ with the central aperture 97 of the video disc 2 and the clamp assembly 6 in providing an accurate means of locating said video disc 35 2 about the central axis 69 of the spindle 77.
In order to place a video dlsc 2 on a video disc player unit 1 the clamp assembly is removed ~rom the 3plndle 77. This will be descrlbed in detail further on.
The video dlsc 2 is placed on the spindle and motor 3 ~ ~ 3~D
-~2-assembly 5 such that the second surface 4 of the video disc 2 contacts the upper plane 87 of the video disc support ring 8v. The central aperture 97 of the vldeo disc 2 contacts the centering device 92 at a point 100.
The centering device 92 at this point is residing in its first position 95, sald first po~ition being described as the centering device's upper vertical limit of travel as defined by a retaining device 98, such as a snap rlng, a~
it resides ln a groove 99 about the central axis 69 of the 10 spindle 77. The centering device 92 receives an upward pressure ~rom the compression spring 91 which malntains it vertlcally against the retaining device 98. The coope~
ation between the conical shape o~ the centering device ~ ~ 92 and the upward pressure of the compression spring 91 : 15 allow a wide variation in radial size of the central aper-ture 97 of the video disc 2, without substantially degrad-ing the centering device's ability to accurately locate the video disc 2 about the central axis 69 of the spindle 77. As the clamp assembly 6 is replaced on the spindle 20 77, the clamp assembl~ 6 engages the video disc 2, and wlth the clamp as~embly in its restrained position~ the - vldeo disc 2 is firmly held between the video disc sup-port ring 86 and the clamp assembly 6, allowin~ the video disc 2 to rest at a point of contact on the conical sur--25 face of the centering device 92 individually defined ~y the radial size o~ the central aperture 97 of the video disc 2.
Continuing with Figure 4, the clamp assembly 6 will now be described in detail. The clamp assembly 6 is 3 provlded with a main clamplng portion 103 being prlmarily cyllndrical in ~hape and having a conical base 104 and provided ~ith a flange 105 disposed upon it3 uppermost region. The main clamplng portion 103 provides the re-straint for the video disc 2 when cooperating with the 35 video disc support ring 86 and the centering device 92.
The remainder o~ the clamp assembly 6 is provided to allow ease of o~eratlon yet insuring a secure restraint of both the clamp assembly 6 and the video disc 2. The clamp ,Jassembl~ 6 is provided with a release button 106 which is ~33~3~

utilizable in the removal of the clamp assembly 6 from the spindle 77. The release button 106 is provided wit'n a lip 109 and the main clamping portlon 103 is provided with a ledge 110, said lip 109 and said ledge 110 cooperate to form a cylindrical recess wherein resides a compression spring 111, said compression spring 111 retalning the release button 106 to its upperrnost limit of travel. The relea~e button 106 is provided with a threaded aperture arran~ed about the central axis 69 of the spindle 77 and not shown in Figure 4. Said threaded aperture in the release button 106 cooperates with a threaded device, such as a screw to form a mechanical stop ~or a plunger 113.
The plunger is provlded with a compression spring 114, said compression spring residing on a ledge 115 formed on the plunger 113 and supplying a downward force to the plunger 113.
To secure the clamp assembly 6 to the spindle 77, a number o~ steel balls 107 are received in an equal number of apertures 108 on the release button 106, and the balls engage an annular groove 120 in the spindle. By this arrangement, and as illustrated in FIG. ~ the release button 106 is secured to the spindle 77, and the main clamping portion 103 o~ the clamp aqsembly is urged lnto clamping engagement with the disc 2 by the compression spring 111.
To remove the clamp a~sembly 6 from the spindle 77, two fingers are placed under the flange 105, and the release button 106 is depressed with the thumb. Thls action pull~ the main clamping portion 103 upwardly) 30 bringing a widened inside diameter portion 116 o~ the main portion 103 ad~acent the steel balls 107, thereby permitting the balls to move radially outwardly out o~
the annular groove 120. In this position, the clamp assembly 6 can be axially withdrawn from the spindle 77, 35 and as the clamp assembly is so withdrawn, the plunger 113 moves downwardly within the release button 106 until an outer surface 112 o~ the plunger 113 engages the balls 107 and retains them within the clamp assembly while it is disengaged ~rom the spindle.

3L~L3313~D

Illustrated in FIGS. 5 and 6 is a novel locator and follower bearing arrangement for controlling the linear translation of the carriage 14 with respect to carriage support 12. ~ow referring to Figure 5 which is an enlarged sectional view of the locator bearing assembly, the loca-tor bearing assembl~ is formed by the cooperation of the lower plane 28~ the connection angle 29, the upper plane 27, and a diverging angle 135, and their relative disposi-~`~ tion on the carriage 14. The connecting angle 29 and the dlverging angle 135 form a truncated a~sembly to which isattached a linear bearing 122. The bearing 122 has a - point of contact to a truncated rail 125 having an upper sur~ace 127 and a lower surface 126 which attaches to the carriage support plate 12 by means of a threaded device (not shown). The truncated rail 125 has two side connect-ing pieces 128 and l29 and two working surfaces 123 and 124. The diverging angle 135 has a second linear bearing 134 attached by means of a threaded device 133, such as a ~ screw, cooperating with a second threaded aperture 130.
- 20 The locator bearing assembly is maintained in in~imate contact with the truncated rail 125 by means of the resil-ientl~ ~ounted rolling retainer 17. The locator bearing assembly provides an accurate means of frictionless trans lation for the carriage 14 throughout its travel.
- 25 Now referrlng to Flgure 6 which is an enlarged sectional view of the locator follower bearlng assembly.
The locator follower bearing is arranged upon the carriage 14 by means of a connecting angle 29 cooperating with the upper plane ~7 of the carriage 14. Attached to the upper 30 portion of the carriage 14 is a linear bearing 136 re-strained in this position by the cooperation of a threaded aperture 137 and a threaded device 138, such as a screw, passing through an aperture 139 in a llnear bearing 136.
The linear bearing 136 has a point of contact on the work-ing sur~ace of a substantially square rail 144 having aworking surface 140, a s~de connecting surface 141 and a second side connecting surface 142. Tlle support follower rail 144 is restrained in its position through its surface 143 b~J means of a number of threaded devices, such as ` ~ ~ 3 3 screws~ not shown in Figure 6. The support follower bearing supplies support to the carriage 14 dlrectly opposing the locator bearing assembly such that both sides of the carriage 1~ are supported equally. The support follower bearing assembly provides the required support without lmparting an angular direction to the plane o~ translation of the carriage as defined by the locator bearing assembly.
In order to provide for smooth, relatively fric-tionless translation of the carriage 14 along the locator and follower rails, the linear bearings 122~ 134 and 136 o~ novel construction are provided. It will be appreciated that the linear bearings 122, 134 and 136 are o~^~similar construction, and accordingly, one of these bearings will be described in detail with reference to Figure 7, which is a cross-sectional view through the support follower bearlng 136. From this view~ a number of steel balls 145 are indicated hav-lng a point of contact at the point 147 and the point 148, the point 147 forming a contact with the working surface 140 o~ the support ~ollower rail and the p~nt 148 having a point of contact with a steel shoe 149. The steel ball 145 can be seen residing in a recess 146, hence~orth re~erred to as the oval track. The steel balls 145 are retained within the linear bearing by a cover plate 150, the cover plate 150 being retained b~r a tab 151.
Now re~erring to Figure 8 which shows the steel shoe 149 residing in the slot 152 and having a point of contact with t~e carriage at the po~nt 153; ind~cated at the points 148 are the polnts o~ contact with the steel shoe o~ the balls 145. Indicated at the points 147 are the points of contact of the steel balls with the working surface 140 of the support ~ollower rail 144. Indicated at 154 can be seen a radius on the opposite side of the steel shoe 149 from the s~eel balls 145. ~hls radius allows the linear bearing to be sel~-aligning. This marks one improvement over the normal linear bearings available today, in that this linear bearing is capable o~ main-taining a critlcally accurate translation despite irregu-larities in working surfaces provided for the linear 3 3 ~ 3 bearing.
Now referring to Figure 9 showing an elevational view o the linear bearing p2rtially cut away to show the relat-Lonship of the parts~ indicated at 145 are the steel balls residing in the oval track 14~. ~he cover 150 has been cut away to show the path of the oval track 146. The tab 151 is still indicated. The steel shoe 149 is indi-cated ln the slot 152.
Now referring to Figure 10 showing the resiliently mounted rolling retainer from a bottom plan view. A shafk i5 lndicated at the point 153 which retains a roller 154 by means of a retaining device, such as a snap rlng. The shaft 153 passes through a truck 156 where it is restrained by a r0tain device~ such as snap ring 157. A threaded device such as a screw is indicated at 158 and a rubber bu~hing 159 is retained by the screw 158.
Now referring to Figure 11 which is an elevation-al view of the res~liently mounted rolling retainer 17, the roller is indicated at 154, said roller being maln-; 20 talned by the sl~aft 153 and restrained by the snap ring 155. The truck 156 supplies a mounting platform for the roller and is provided wlth an aperture (not shown), through wh~ch a threaded device 158, such as a screw, passes vertically towards the carriage 14 where it cooper-ates with a threaded aperture 160 to restrain the resili-ently mounted rolling retainer 17. The threaded device 158 passes through a spring lol, which spring 161 supplies a downward force to the carriage 14. The spring 161 and the rubber bushing cooperate to provide the resilient attachment o~ the rolling retainer 17. This resiliently mounted rolling retainer allows for a high degree of re-straint and provldes for reliable self-alignment of the locator bearing assembly and the support follower bearing assembly without impairing their ~rictionless translation.
Another novel ~eature of the present inventio~
resides in a method and means by which the rotating disc 2 is stabilized. More specifically~ referring again to Figure 4, it can be seen that the stabilization plate 7 is provlded with an upright 204, this upright 204 is provided '~:
, 3J~3 with the aperture 75 wherein the threaded devlce 73 is retained. The upright 204 cooperates with the motor mount 72 forming a cavity 205, the cavity 205 employing an aper-ture (not shown) provided for lngress of air to the cavity 205. The cavity serves as a storage means for a volume of air, whlch volume of air is provided as a ready supply such that a portion of this volume of air is available at an annular air exit point 201. The air supplied at the air exit point 201 i9 employed in a region 203 which is formed 10 by interaction of the stabilization plate 7 and the second surface 4 o~ the video disc 2. The video disc 2 and the ~tabilization plate 7 are arranged about the central axis 69 of the spindle 77 and maintain a critical perpendicu-larity to the central axis 69 of the spindle 77.
The use of a stabilization plate is well known in prior art. However, it has been determined experimentally that the vertical distance between the stabilizatlon plate 7 and the second surface 4 of the video disc 2 is of a critical nature such that the interaction of the stabili-20 zatlon plate 7, and the video disc 2 will cooperate to provide a degree of stability to the video disc 2 not normally inherent ln the video disc. It has been deter-mined that a vldeo d~sc can have a nature such that it is substantially unflat. This unflatness is generated 25 at the time of the manufacture of the video disc and is lndividually variable video disc to video disc. This unflatness ls detrimental to the optimum operation of the video disc player unit in that ~n unflat video dlsc will scrape or in other ways, contact the surface of the 30 stabilization plate or other components of the vldeo disc player unit when the disc is rotated about the central axis of the spindle. An obvious means of rectifying this problem is to extend vertically the distance between the video disc 2 and the stabilization plate 7. However, it 35 was determined that the cooperation between the stabili-zation plate and the video disc no longer existed, and the dampening effect provided by the reglon 203 of alr between the lower surface 4 o~ the video disc 2 and the stabiliza-tion plate 7 acted in a manner such that it no longer 3~1 3 dampened the oscillations to which the video disc 2 is prone. Through experimentation~ the air exit point 201 and lts available areas were identifled as cooperating with other factors~ well known to a person skilled in the art~ such that the available area of the air exit point was contributing to this lack of dampening of the oscilla-tions to whlch the video disc is prone. It was further determined by llmiting the available area to a mathe-matically ascertainable amount that this detrimental effect could be eliminated. The area of the air exit polnt 201 in the present embodiment is approximately 6 tenths of a square centimeter. This effectively eliminates the problem by allowing an extended vertical distance between the stabilization plate and the video disc such khat an unflat video disc no longer scrapes or contacts the stabiliza-tion plate or other components in the video disc player unit upon imparting rotatlon to the video disc.
While the inventlon has been particularly shown and described with reference to a preferred e~bodiment and alterations thereto, it would be understcod by those skllled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the inventlon.

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Claims (4)

1. A method of stabilizing a disc in a video disc player of the type which includes a video disc mounted for rotation on a support ring fixed to a rotating spindle, a fixed stabilization plate spaced from and generally parallel to said rotating disc and having a central open-ing for receiving said rotating support ring and forming an annular air inlet through which air is permitted to enter a space between said plate and said disc, said method of stabilizing said disc comprising the step of: restrict-ing said annular air inlet between said support ring and said stabilization plate.

2. The method of stabilizing a video disc as claimed in Claim 1 wherein said annular air inlet is restricted to an area of about 0.6 square centimeters.

3. A video disc support assembly comprising: a motor and spindle means means rotationally driving a video disc in a predetermined plane, said spindle means having a central axis positioned perpendicular to said plane; a video disc support means positioned about said central axis and having a generally flat annular surface lying in a plane parallel to said predetermined plane and arranged to abut one side of said disc; and a fixed stabilization plate mounted about said spindle and having a generally flat surface arranged parallel to and spaced from said one side of said disc forming an air space between said plate and said disc, said plate including a central aper-ture sized to closely surround said video disc support means, forming a relatively small air inlet between said support means and said stabilization plate through which air can flow into said air space, thereby restricting said flow of air and stabilizing said rotating disc.

4. The video disc support assembly as claimed in Claim 3 wherein the area of said air inlet is restric-ted to about 0.6 square centimeters.