GB1600562A

GB1600562A - Video disc player

Info

Publication number: GB1600562A
Application number: GB4610/78A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1977-02-09
Filing date: 1978-02-06
Publication date: 1981-10-21
Also published as: CA1110763A; ES233778U; BR7800704A; AT355828B; IT7820037A0; DE2803823A1; DE2803823C2; BE863728A; NL7701332A; IT1093642B; ES233778Y; FR2380613B1; SE419483B; FR2380613A1; DK53778A; ATA78878A; DD134156A5; AU3303778A; ZA776204B; SE7801326L

Description

(54) VIDEO DISC PLAYER (71) We, N.V, PHILIPS' GLOEILAMPEN FABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, The Netherlands do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a video disc player for playing-back optically readable video discs, comprising: a housing; a cover which is pivotable on the housing between a fully opened position and a fully closed playing position and which in the playing position is arranged to cover a video disc positioned on the player; latching means for latching the cover in its playing position, which latching means comprise a spring-loaded movable catch and a latch which is secured to the cover and in the playing position thereof extends into the housing through an opening therein and which comprises a latching cam which cooperates with the catch in the playing position of the cover, and a safety stop; unlatching means for releasing the latched cover from its playing position for movement towards an unlatched position in which the cover is free to be moved into the fully opened position, which unlatching means comprise a manual actuating member, an unlatching member on which the catch is movably mounted and which is movable between a rest position and an unlatching position by means of the manual actuating member, and unlatching spring means for resiliently urging the cover from its playing position towards said unlatched position, the unlatching member being movable from its rest position to its unlatching position by actuation of the manual actuating member and, when so moved, displacing the catch relative to the latch so that the catch is disengaged from the latching cam and moved into a position in which the cover can be moved by the unlatching spring means into a safety position which is situated between the playing position and the unlatched position, in which safety position the safety stop abuts the catch under the action of the unlatching spring means, and the unlatching member being operable, when returning from its unlatching position to its rest position, to displace the catch relative to the latch so that the catch is disengeged from the safety stop to permit the cover to be moved to its unlatched position by the unlatching spring means; a main motor; a drive spindle driven by the main motor for rotating a video disc; an electric supply source for powering the main motor; a main motor switch controlled by the latch for switching-on and switching-off the supply of an electric supply current to the main motor, switching-on being effected druing movement of the cover from its unlatched position to its playing position and switching-off being effected during movement of the cover from its playing position to its safety mechainsm which imposes a controlled delay on retrun movement of the unlatching member from its unlatching position to its rest position to allow the speed of rotation of the drive spindle to fall below a predetermined value.

Such a video disc player has already been described in our prior dise patent specification no.

1 538 488. In this video disc player the latch on the cover is constructed to actuate the main motor switch to switch on the main motor when the cover is latched in the fully closed position. In practice it is impossible to make the instant at which the catch exactly reaches the level on the latching cam at which the cover becomes latched, and thus cannot be opened without actuation of the unlatching means, exactly coincide with the instant at which the main motor is switched on. Consequently, this earlier video disc player is constructed so that the main motor switch is actuated just before the catch latches the cover in the fully closed position. However, as a result of this an incorrect operation of the video disc player is possible, which may lead to an unsafe situation.

This is because a user may lower the cover far enough for the main motor to be switched on but not far enough for the cover to be latched, and subsequently open the cover again. During playing a video disc is generally driven at a speed of 1800 revolutions per minute (mains frequency 60 Hz) or 1500 revolutions per minute (mains frequency 50 Hz). In the earlier video disc player the video disc is braked by automatic braking means provided for this purpose if the cover is re-opened in the above circumstances. However, it is considered undesirable for braking to be effected whilst the cover is open. The reason for this is that when the cover is open the video disc is not pressed onto the drive spindle by a disc-loading means, as is the case when the cover is closed, but lies freely on the drive spindle. When the drive spindle is braked abruptly by the automatic braking means it is not unlikely that the video, disc, which may still rotate rapidly, will be flung off the drive spindle. Also in video disc players which are not provided with an automatic braking means, the high speed may result in the video disc being flung off the drive spindle.

According to the present invention, in a video disc player having the construction set out in the opening paragraph of this specification, the latch comprises an additional latching cam which, when the unlatching member is in its rest position, co-operates with the catch at an intermediate position in the movement of the cover from the unlatched position to the playing position, which intermediate position is reached before supply of current to the main motor is switched on, and an additional safety stop which, during movement of the cover from said intermediate position to the playing position, is cooperable with the catch to prevent the unlatching member being moved from its rest position when the cover has not yet reached its playing position but has reached a position but has reached a position in which the supply of current to the main motor is switched on.

An embodiment of the invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a video disc player according to an embodiment of the invention with the cover open, Figure 2 is a perspective view of a number of parts of the video disc player of Figure 1, including a latch which is connected to the cover of the player and unlatching means and safety means, and Figure 3 is a front elevation of the latch and, in cross-section a catch.

The video disc player shown in Figure 1 is of the type in which optical information on a video disc is read by reflection with the aid of a laser beam. The player comprises a housing 1 on which a cover 2 is mounted which is hingeable about an axis 50. On the player a video disc 3 is shown positioned for playing. During playing the disc 3 is covered by the closed cover 2. In this closed playing position the cover is latched by latching means to be discussed hereinafter, unlatching being possible by means of a manual actuating member consisting of an unlatching button 4 and forming part of unlatching means to be discussed hereinafter. In the housing a motor 5 is mounted (see Figure 2) for rotoring the video disc. This motor, hereinafter to be referred to as "the main motor", is coupled with a drive spindle 6 for a rotary support on which the video disc is supported during playing. The housing 1 also accommodates a radiation source in the form of a laser 7, which is schematically shown in Figures 1 and 2 and which may, for example, consist of a heliumneon laser. In Figure 2 the beam of radiation produced by the laser is designated 8.

During unlatching the unlatching means yet to be discussed co-operate with a number of safety means (see Figure 2). These safety means comprise the following: a) Switching means in the form of a switch 9, provided with a plurality of switching contacts, not shown, for switching-on and sff a power supply source, not shown, for the main motor 5. The electrical connections between an electric power supply source and the switch 9 and the main motor 5 are omitted from Figure 2 for the sake of clarity. By the actuation of the switch 9, which is provided with a pushbutton 10, the power supply to the main motor is switched on or off.

b) Automatic braking means for braking and stopping the drive spindle 6. In the embodiment of Figure 2 these means comprise a brake lever 11 which is pivotably connected at 43 to the housing, a brake disc 12 on the drive spindle, and a brake band 13 which is provided with a brake lining 14 and which at one end 15 is anchored to the housing and at its other end 16 is connected to the brake lever 11. As will be explained subsequently when the operation of the various safety means is described, the brake band 13 co-operates with a part of the circumference of the brake disc 12 when the cover 2 is open, but leaves the disc 12 completely free in the playing position of the cover.

The braking means also include a tension spring 17, which at one end is connected to the brake lever 11 and at the other end is rigidly connected to the housing via a pin 18. This spring urges the brake lever continuously towards the braking position, c) Switching means for extinguishing the radiation source, which switching means comprise at least one switching contact on the switch 9. The electrical connections to the laser are not shown.

d) Shielding means which enter the radiation path of the radiation beam 8 for shielding this radiation beam before it can emerge from the housing 1. In the embodiment of Figure 2 these shielding means comprise a shielding lever 19 which is hingeably connected to the housing, and a vane 20 which is connected to the lever 19. This vane is situated in the radiation path of the radiation beam 8 is the shielding position of the shilding lever 19 so as to mask the beam, but in the playing position of the cover allows this beam to pass freely through an opening 21 formed in the vane. Furthermore, the shielding means include a tension spring 31 which continuously urges the shielding lever 19 in a direction towards a downwardly bent lug 22 on the brake lever 11. Thus, the brake lever 11 and the shielding lever 19 are continuously in contact with each other and co-operate with each other.

The brake lever 11 also co operates with the cover 2 of the video disc player in a manner yet to be discussed.

The video disc player of Figure 1 is provided with the directing means 23 for directing a read beam at the information tracks of the video disc 3. These directing means comprise an objective which belongs to a focussing device, which objective is provided with a number of optical elements for focussing the light beam onto the information track and with means for receiving the reflected light beam. A suitable focussing device is described in our prior patent specification no. 1 536 203. This focussing device is mounted on a carriage underneath the deck 44 of the video disc player, which carriage is radially movable relative to the drive spindle 6. This carriage is not shown in the drawing and can be driven by means of an electric auxiliary motor, not shown. In order to prevent the video disc player from being damaged during removal of a video disc, further safety means are provided, viz., interrupting means, comprising at least one switching contact on the switch 9, for preventing an electric current from being applied to the said auxiliary motor.

Furthermore, for preventing the focussing device and in particular the objective from being damaged, there are provided interrupting means, also comprising at least one switching contact on the switch 9, for preventing an electric current from being applied to the objective motor.

Both the auxiliary motor of the carriage and the objective motor are motors which are energized via a servo system. Consequently, they are included in a control circuit. The auxiliary motor is included in a control circuit for the radial tracking of the spiral track on a video disc and the objective motor in a control circuit for following the axial movements of the disc with the objective. When the video disc is removed this results in the said control circuits continuously receiving an error signal, as a result of which the auxiliary motor will move the carriage into one of its extreme positions, whilst the objective motor will set the objective to its highest position. Thus, the objective may be damaged, for example, during the placing of the next disc to be played on the rotary support. It is also undesirable for the carriage to be continuously kept in the extreme position, because the motor would then constantly receive a voltage of maximum value in the stationary condition.

The latching and unlatching means will now be discussed.

The latching means comprise a latch 24 which is connected to the cover 2 and the shape of which is most clearly shown in Figures 2 and 3. It has a bevelled free end 25, an oblique cam surface 26 at one side which co-operates with the brake lever 11, a latching cam 45, a safety stop 41, an additional latching cam 46 and an additional safety stop 47. As can be seen in Figure 2, each of the latching cams 45 and 46 projects from the front of the latch 24 and has an oblique cam surface at the front which extends forwards and upwards and terminates at a shoulder at the upper side of the cam. In the closed, playing position of the cover the brake lever 11 is pressed against the cam surface 26 under the influence of the tension spring 17 and is thus held out of the braking position. In the playing position of the cover the latch projects into the housing through an opening 49 therein and the free end 25 of the latch co-operates with a leaf spring 27. This spring is connected to the housing 1 and continuously bears against the free end 25 of the latch in the playing position of the cover. Also connected to the leaf spring 27 is a hooked member 28. When the cover is open, i.e. in the situation shown in Figure 2, the hooked member 28 blocks movement of the brake 11 away from the braking position. The latching means furthermore comprise a catch in the form of a pin 29 which is movable axially against the force of a compression spring 30.

The unlatching means comprise the unlatching button 4, which can manually be moved to the left by the user in order to unlatch the cover 2. The button 4 co-operates with a pin 32 which is mounted on an unlatching slide 33 which also carries the catch 29.

On the unlatching slide is fixed a bracket 34 to which one end of a tension spring 39 is attached which at its other end is connected to a pin 40 on the housing 1 and which continuously loads the bracket 34. The unlatching slide 33 is thus continuously pulled to the right in Figure 2 by the tension spring 39. During unlatching the force of this spring must consequently be overcome by means of the button 4.

When the cover 2 is open the various co-operating parts are in the positions shown in Figure 2. At a given instant during the downward movement of the cover 2 the end 25 of the latch 24 comes into contact with the leaf spring 27. The cover is now in what will be referred to as its "unlatched position". In this position the end of the catch 29 which faces the latch 24 bears against a flat front surface 42 of the latch In Figure 3 the path 51 of the end of the catch 29 on the latch 24 when the cover 2 is moved from its unlatched position to its latched playing position and is subsequently unlatched again is indicated by means of a broken line and arrows. In the unlatched position of the cover the end of the catch is in a position relative to the latch which in Figure 3 is designated I. By further closing the cover against the force of the leaf spring 27, to an intermediate position II, the catch 29 is brought into engagement with the upper side of the additional latching cam 46. Once arrived in this intermediate position the cover can no longer be opened, not even by the actuation of the unlatching button 4, because the additional safety stop 47, in conjunction with the catch 29 prevents the latching slide 33 from being moved to the left.

Owing to the downward movement of the leaf spring 27, the hook-shaped member 28 has been moved downwards and can no longer prevent the brake lever 11 from being rotated. This rotation is effected by pressing the cover 2 downwards from its intermediate position II into the playing position III against the resistance of the leaf spring 27. This brings the catch 29 into engagement with the upper side of the latching cam 45 so that the cover is latched in the playing position. At the same time the side cam surface 26 moves the brake lever 11 so that the brake band 14 is disengeged from the brake disc 12 and the main motor is switched on by the main switch 9. Moreover, servo-circuits for the previously mentioned auxiliary motor and objective motor are switched on, the shielding lever 19 is actuated and the laser 7 is ignited. An unsafe manipulation of the cover and also of the manual actuating member 4 is precluded because the additional latching cam 46 and the additional safety stop 47 prevent the catch from following a path on the latch 24 other than that indicated in Figure 3 by the broken line 51. Hence, the cover can be unlatched only after complete latching.

The cover is released from the latched position III by manually moving the button 4 to the left. As a result the unlatching slide 33 is also moved to the left, so that the end of the catch 29 slides off the top of the latching cam 45 and comes on a flat front surface 48 of the latch 24. The leaf spring 27 presses the cover 2 upwards. However, the safety stop 41 now prevents the cover 2 from being opened further, because in the left-hand position of the unlatching slide 33 the catch 29 butts against the stop 41. The cover is now in its safety position, designated IV in Figure 3. A safety mechanism is provided which comprises a plunger 35 which is connected to the bracket 34 and forms part of a damping device 36 comprising a cylinder 37 filled with grease, the plunger 35 and a fixing bracket 38. The damping device 36 imposes a controlled delay on return movement of the unlatching slide 33 to the right upon release of the button 4. Only when the unlatching slide 33 has been slid back completely to the right can the cover 2 be opened fully again. The initial .displacement of the cover 2 immediately after the actuation of the unlatching button 4, which initial displacement is equal to the distance between the upper sides of the latching cam 45 and safety stop 41, is sufficient to ensure that the brake lever 11 no longer co-operates with the side cam surface 26 of the latch 24. Thus, immediately after the actuation of the unlatching button 4 the tension spring 17 can rotate the brake lever about its hinge pin 43. As a result of this rotation the end 16 of the brake band 13 is moved over such a distance that the brake lining 14 comes into contact with the brake disc 12. During the movement of the brake lever 11, the button 10 of the switch 9 has also been moved outwards so that the main motor 5 is switched off, the laser beam 8 is extinguished and the auxiliary motor which drives the carriage of the focussing device, as well as the objective motor of the focussing device, are switched off. At the same time the lug 22 on the brake lever rotates the shielding lever 19 about its hinge pin 44 so that a closed portion of the vane 20 enters into the path of the laser beam 8 to prevent the beam emerging from the objective while the cover is open and there is no video disc on the player.

Reference is made to the specification of our co-pending patent application no 1 600 561, which describes a video disc player having a safety mechanism which ensures that the cover of the player cannot be opened until the speed of the motor which drives the video disc has been reduced to a safe value.

WHAT WE CLAIM IS: 1. A video disc player for playing-back optically readable video discs, comprising: a housing; a cover which is pivotable on the housing between a fully opened position and a fully closed playing position and which in the playing position is arranged to cover a video disc positioned on the player; latching means for latching the cover in its playing position, which latching means comprise a spring-loaded movable catch and a latch which is secured to the cover and in the playing position thereof extends into the housing through an opening therein and which comprises a latching cam which co-operates with the catch in the playing position of the cover, and a safety stop; unlatching means for releasing the latched cover from its playing position for movement towards an unlatched position in which the cover is free to be moved into the fully opened position, which unlatching means comprise a manual actuating member, an unlatching member on which the catch is movably mounted and which is movable between a rest position and an unlatching position by means of the manual actuating member, and unlatching spring means for resiliently urging the cover from its playing position towards said unlatched position, the unlatching member being movable from its rest position to its unlatching position by actuation of the manual actuating member and, when so moved, displacing the catch relative to the latch so that the catch is disengaged from the latching cam and moved into a position in which the cover can be moved by the unlatching spring means into a safety position which is situated between the playing position and the unlatched position, in which safety position the stop abuts the catch under the action of the unlatching spring means, and the unlatching member being operable, when returning from its unlatching position to its rest position, to displace the catch relative to the latch is disengaged

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. even by the actuation of the unlatching button 4, because the additional safety stop 47, in conjunction with the catch 29 prevents the latching slide 33 from being moved to the left. Owing to the downward movement of the leaf spring 27, the hook-shaped member 28 has been moved downwards and can no longer prevent the brake lever 11 from being rotated. This rotation is effected by pressing the cover 2 downwards from its intermediate position II into the playing position III against the resistance of the leaf spring 27. This brings the catch 29 into engagement with the upper side of the latching cam 45 so that the cover is latched in the playing position. At the same time the side cam surface 26 moves the brake lever 11 so that the brake band 14 is disengeged from the brake disc 12 and the main motor is switched on by the main switch 9. Moreover, servo-circuits for the previously mentioned auxiliary motor and objective motor are switched on, the shielding lever 19 is actuated and the laser 7 is ignited. An unsafe manipulation of the cover and also of the manual actuating member 4 is precluded because the additional latching cam 46 and the additional safety stop 47 prevent the catch from following a path on the latch 24 other than that indicated in Figure 3 by the broken line 51. Hence, the cover can be unlatched only after complete latching. The cover is released from the latched position III by manually moving the button 4 to the left. As a result the unlatching slide 33 is also moved to the left, so that the end of the catch 29 slides off the top of the latching cam 45 and comes on a flat front surface 48 of the latch 24. The leaf spring 27 presses the cover 2 upwards. However, the safety stop 41 now prevents the cover 2 from being opened further, because in the left-hand position of the unlatching slide 33 the catch 29 butts against the stop 41. The cover is now in its safety position, designated IV in Figure 3. A safety mechanism is provided which comprises a plunger 35 which is connected to the bracket 34 and forms part of a damping device 36 comprising a cylinder 37 filled with grease, the plunger 35 and a fixing bracket 38. The damping device 36 imposes a controlled delay on return movement of the unlatching slide 33 to the right upon release of the button 4. Only when the unlatching slide 33 has been slid back completely to the right can the cover 2 be opened fully again. The initial .displacement of the cover 2 immediately after the actuation of the unlatching button 4, which initial displacement is equal to the distance between the upper sides of the latching cam 45 and safety stop 41, is sufficient to ensure that the brake lever 11 no longer co-operates with the side cam surface 26 of the latch 24. Thus, immediately after the actuation of the unlatching button 4 the tension spring 17 can rotate the brake lever about its hinge pin 43. As a result of this rotation the end 16 of the brake band 13 is moved over such a distance that the brake lining 14 comes into contact with the brake disc 12. During the movement of the brake lever 11, the button 10 of the switch 9 has also been moved outwards so that the main motor 5 is switched off, the laser beam 8 is extinguished and the auxiliary motor which drives the carriage of the focussing device, as well as the objective motor of the focussing device, are switched off. At the same time the lug 22 on the brake lever rotates the shielding lever 19 about its hinge pin 44 so that a closed portion of the vane 20 enters into the path of the laser beam 8 to prevent the beam emerging from the objective while the cover is open and there is no video disc on the player. Reference is made to the specification of our co-pending patent application no 1 600 561, which describes a video disc player having a safety mechanism which ensures that the cover of the player cannot be opened until the speed of the motor which drives the video disc has been reduced to a safe value. WHAT WE CLAIM IS:

1. A video disc player for playing-back optically readable video discs, comprising: a housing; a cover which is pivotable on the housing between a fully opened position and a fully closed playing position and which in the playing position is arranged to cover a video disc positioned on the player; latching means for latching the cover in its playing position, which latching means comprise a spring-loaded movable catch and a latch which is secured to the cover and in the playing position thereof extends into the housing through an opening therein and which comprises a latching cam which co-operates with the catch in the playing position of the cover, and a safety stop; unlatching means for releasing the latched cover from its playing position for movement towards an unlatched position in which the cover is free to be moved into the fully opened position, which unlatching means comprise a manual actuating member, an unlatching member on which the catch is movably mounted and which is movable between a rest position and an unlatching position by means of the manual actuating member, and unlatching spring means for resiliently urging the cover from its playing position towards said unlatched position, the unlatching member being movable from its rest position to its unlatching position by actuation of the manual actuating member and, when so moved, displacing the catch relative to the latch so that the catch is disengaged from the latching cam and moved into a position in which the cover can be moved by the unlatching spring means into a safety position which is situated between the playing position and the unlatched position, in which safety position the stop abuts the catch under the action of the unlatching spring means, and the unlatching member being operable, when returning from its unlatching position to its rest position, to displace the catch relative to the latch is disengaged

from the safety stop to permit the cover to be moved by the unlatching spring means into its unlatched position; a main motor; a drive spindle driven by the main motor for rotating a video disc; an electric supply source for powering the main motor; a main motor switch controlled by the latch for switching-on and switching-off the supply of an electric supply current to the main motor, siwtching-on being effected furing movement of the cover from its unlatched position to its playing position and switching-off being effected furing movement of the cover from its playing position to its safety position; and a safety mechanism which imposes a controlled delay on return movement of the unlatching member from its unlatching position to its rest position to allow the speed of rotation of the drive spindle to fall below a predetermined value; wherein the latch comprises an additional latching cam which, when the unlatching member is in its rest position, cooperates with the catch at an intermediate position in the movement of the cover from the unlatched position to the playing position, which intermediate position is reached before the supply of current to the main motor is switched on, and an additional safety stop which, during movement of the cover from said intermediate position to the playing position, is cooperable with the catch to prevent the unlatching member being moved from its rest position to its unlatching position when the cover has not yet reached its playing position but has reached a position in which the supply of current to the main motor is switched on.

2. A video disc player substantially as herein described with reference to the accompanying drawings.