GB2097951A

GB2097951A - Video projection apparatus

Info

Publication number: GB2097951A
Application number: GB8211101A
Authority: GB
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1981-05-01
Filing date: 1982-04-16
Publication date: 1982-11-10
Also published as: KR880004550Y1; GB2097951B; CA1194352A; JPS57176780U; FR2505117A1; DE3216211A1; NL8201817A; KR830004369U; JPS6141345Y2; FR2505117B1

Abstract

A video projection apparatus comprises a housing-like chassis 1 accommodating projection lenses 2, cathode-ray tubes 3, and at the front a reflecting mirror 5. With this apparatus, the reflecting mirror 5 can be moved to an advanced position for projection of light from the cathode- ray tubes 3 by reflection from mirror 5 onto a screen 51, and a withdrawn position accommodated in a front portion of the chassis 1, by driving a pair of extension-contraction mechanisms 9. <IMAGE>

Description

SPECIFICATION Video projection apparatus This invention relates to video projection apparatus for projecting onto a screen light emitted from cathode-ray tubes.

According to the present invention there is provided a video projection apparatus comprising: a housing-like chassis accommodating projection lenses and cathode-ray tubes and provided at the front with a reflecting mirror; a drive source; first and second drive sections driven as a pair by said drive source; a pair of extension-contraction mechanisms disposed in parallel between said respective drive sections and said reflecting mirror and driven for extension and contraction by the driving force of said drive sections; and a coupling shaft disposed between the rear ends of said cathode-ray tubes and the rear end of the chassis and coupling said drive sections to each other; said pair of extension-contraction mechanisms being driven for extension and contraction in synchronism with each other by said coupling shaft driven by the driving force of said drive sections.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an embodiment of video projection apparatus according to the invention; Figure 2 is an enlarged side view, partly broken away, of drive sections and extension-contraction mechanisms; Figure 3 is a sectional view, partly omitted, showing the coupling of individual drive sections to a coupling shaft; Figure 4 is a fragmentary sectional view showing extensible pipes with a third extensible pipe extended; Figure 5 is a longitudinal sectional view of a drive section prior to operation of an operating lever; and Figure 6 is a longitudinal sectional view of the drive section after operation of the operating lever.

As shown in Figure 1, the video projection apparatus comprises a housing-like chassis 1 accommodating a plurality of projection lenses 2 and corresponding cathode-ray tubes 3. A reflecting mirror 5 is provided at the front 4 of the chassis 1.

Inside the chassis 1 are provided a drive motor 6 as a drive source, first and second drive sections 7 and 8 driven as a pair by the drive motor 6, extension-contraction mechanisms 9 and 10 driven as a pair for extension and contraction by the respective drive sections 7 and 8, and a coupling shaft 11 provided between the rear ends 3a of the individual cathode-ray tubes 3 and the rear end 1 a of the chassis, and coupling the drive sections 7 and 8. The extension-contraction mechanisms 9 and 10 are driven in synchronism for extension and contraction by the coupling shaft 11 driven by the drive sections 7 and 8.

A drive shaft 12 of the drive motor 6, as shown in Figures 2 and 3, has an integral worm gear 14 rotatably disposed inside an outer casing 13 covering the drive section 7. The worm gear 14 is in mesh with a worm wheel 1 5. A disc-like clutch plate 1 6 is provided on the same shaft as the worm wheel 1 5. The clutch plate 1 6 is secured to a drive shaft 1 7. The drive shaft 1 7 is rotatably supported inside the outer casing 13. Between the clutch plates 1 6 and the worm wheel 1 5 there is provided an overload prevention mechanism 18 which serves to prevent an overload state from occurring when a load in excess of a predetermined value is applied.In this embodiment, at the time of normal driving, contact plates 1 8a and 1 8b respectively provided on the clutch plate 1 6 and the worm wheel 1 5 are in contact. When a load in excess of a predetermined value is applied to the worm wheel 15, the plates 1 8a and 1 8b are separated, whereby the drive motor 6 is disconnected.

A small gear 1 9 is provided integrally with the drive shaft 17, and a gear section 1 9a of the small gear 19 is in mesh with a gear section 20a of a large gear 20. The large gear 20 is rotatably supported by a shaft 21 secured to the outer casing 13.

On the side of the chassis 1 opposite to the first drive section 7, the second drive section 8 driven by the drive motor 6 is secured to the chassis 1. The second drive section 8 has the same construction as the first drive section 7 except that the worm gear 14 driven for rotation by the drive motor 6, the worm wheel 15, the overload prevention mechanism 18 and the clutch plate 1 6 are not provided. More particularly, a drive shaft 23 rotatably supported inside an outer casing 22 of the second drive section 8 is provided with an integral small gear 24, and a gear section 24a of the small gear 24 is in mesh with a gear section 25a of a large gear 25. The large gear 25 is rotatably supported on a shaft 26 secured to the outer casing 22.

The pair of extension-contraction mechanisms 9 and 10 provided in parallel between the first and second drive sections 7 and 8 on the one hand and the reflecting mirror 5 on the other hand each comprise first, second and third extensible pipes 27, 28 and 29 consisting of respective large, middle and small cylinders in this embodiment. Of the extensible pipes 27, 28 and 29, a driving strip 30 extends through the second and third extensible pipes 28 and 29 such that it can be driven for running through the second and third extensible pipes 28 and 29 with the rotation of the large gear 20 for each of the drive sections 7 and 8.

The tip of the third extensible pipe 29 is coupled to a reflector cover 5a covering the reflecting mirror 5 via a hinge mechanism to be described later. The extensible pipe 29 has a stem as a cylindrical section 29a, in which a cylindrical bush 31 is fitted and secured thereto as shown in Figure 2. A coupling member 32 for integrally coupling the end 30a of the aforementioned driving strip 30 and the extensible pipe 29 is provided inside the bush 31.

The second extensible pipe 28, the diameter 12 of which is slightly greater than the diameter l, of the third extensible pipe 29, has a tip cylindrical section 28a, and an annular stop member 34 is fitted in and secured to the cylindrical section 28a of the second extensible pipe 28 such that it is urged in the direction of an arrow X in Figure 2 by a push ring 33 fitted on the outer periphery of an intermediate portion of the third extensible pipe 29. The second extensible pipe 28 has a stem as a cylindrical section 28b, in which is securely fitted a disc-like bush 36 having an insertion hole 35 through which the driving strip 30 is inserted.

The first extensible pipe 27, which has a diameter 13 slightly greater than the diameter 12 of the second extensible pipe 28, has a tip portion as a cylindrical section 27a, in which is securedly fitted an annular stop member 38 urged in the direction of the arrow X in Figure 2 by a push ring 37 fitted on the outer periphery of an intermediate portion of the second extensible pipe 28. The first extensible pipe 27 has a stem as a cylindrical section 27b, in which a cylindrical member 40 having a lead opening 39 through which the driving strip 30 of the first drive section 7 is led out is secured by a set screw 41 to the cylindrical section 27b. A guide member 42 for guiding the driving strip 30 is provided inside the lead opening 39.

The driving strip 30 has a sufficient length to extend the extensible pipes 27, 28 and 29 to a desired position. An insertion hole 30b in which the gear section 20a of the large gear 20 is provided in the longitudinal direction of the driving strip 30 such that its diametrical dimension corresponds to the gear section 20a.

The driving strip 30 is driven along a strip path 43 formed arcuately as part of the outer periphery of the large gear 20, and Its other end can be withdrawn along a guide 45 provided on an upright portion 44 of the chassis 1 up to the neighbourhood of the upper end of the chassis 1.

The extension-contraction mechanism 10 which has the same construction as the extension-contraction mechanism 9 is provided between the second drive section 8 and the reflecting mirror 5.

The opposite ends 11 a and 11 b of the coupling shaft 11 for coupling the pair of drive sections 7 and 8, as shown in Figure 3, are provided with respective integral sleeves 46 and 47. One end 1 a of the coupling shaft 11 is fitted in and secured by means of a screw 48 to a through hole 46a of the sleeve 46, and the other end 11 b of the coupling shaft 11 is fitted in the through hole 47a of the other sleeve 47, with the two being secured to each other by a nut 49.

The operation of the embodiment will now be described. The operation will first be described in connection with the case of forwardly projecting the reflecting mirror 5 from the front 4 of the chassis 1.

First, the drive motor 6 is driven, for example under remote control. The rotational driving force of the drive motor 6 is transmitted by the rotational drive shaft 12, the worm gear 1 4 integral with the drive shaft 12, the worm wheel 15 in mesh with the worm gbar 14, the overload prevention mechanism 18, the clutch plate 16, a recess 1 6a formed on one side of the clutch plate 16, the small gear 19 in mesh with the recess 1 6a and the large gear 20 in mesh with the small gear 1 9 in that order to cause rotation of the large gear 20 at a predetermined speed. With the rotation of the large gear 20 thus caused, the driving strip 30 which is in mesh with the gear section 20a of the large gear 20 is led off through the lead opening 39 of the first drive section 7.

Meanwhile, the rotational driving force transmitted from the small gear 19 is transmitted through the drive shaft 17 to which the small gear 19 is secured, the sleeve 46, the coupling shaft 11 and the sleeve 47 in that order to the drive shaft 23 of the second drive section 8. Since this rotational driving force is transmitted through the small gear 24 integral with the drive shaft 23 and the large gear 25 in mesh with the small gear 24, the large gear 25 is rotated at the same speed as the large gear 20 in the first drive section 7. Thus, the other driving strip 30 which is in mesh with the gear section 25a of the large gear 25 is led off from a lead opening (not shown) of the second drive section8 in synchronism with the driving strip 30.

As the pair of driving strips 30 are led off through the respective lead openings 39 in synchronism to one another, the third extensible pipes 29, to which the tips 30a of the driving strips 30 are secured by the coupling members 32, are pushed out forward along the inner peripheral surfaces of the second extensible pipes 28. The third extensible pipe 29 is pushed out until the push ring 33 fitted on the outer periphery of the pipe 29 is brought into contact with the stop member 34 secured to the tip of the second extensible pipe 28 as shown in Figure 4.

Consequently, the stop member 34 is pushed, so that the second extensible pipe 28 is pushed forwards along the inner periphery of the first extensible pipe 27. The second extensible pipe 28 is pushed out along the inner periphery of the first extensible pipe 27 until the push ring 37 fitted on the outer periphery of the pipe 28 engages with the stop member 38 secured to the tip of the first extensible pipe 27. Thus, the reflector cover 5a, having the reflecting mirror 5 accommodated in the opening 4a formed at the front 4 of the chassis 1 such as to cover the front of the projection lenses 2, is forwardly projected by the pair of extension-contraction mechanisms 9 and 10 as shown in Figure 1. During this movement, hinge mechanisms 50 provided between the reflector cover 5a and the tips of the third extension pipes 29 function to correct the mounting position of the reflecting mirror 5 such as to satisfy the light projection optical system, in which light emitted from the cathode-ray tubes 3 is projected onto a screen 51 through the projection lenses 2, and the mounting position of the reflecting mirror is fixed by stop sections provided in the neighbourhood of the hinge mechanisms 50. Thus, the reflecting mirror 5 is held stationary at a position satisfying the light projection optical system.

Now, the operation of moving the reflecting mirror 5 from the position shown in Figure 1 into an accommodated position as shown by dashed lines in the figure will be described.

In this case, the drive motor 6 is driven in the opposite direction to that in the previous operation. The rotational driving force of the drive motor 6 is thus transmitted through the rotational drive shaft 12, the worm gear 14 integral with the drive shaft 12, the worm wheel 1 5 in mesh with the worm gear 14, the worm wheel 15 in mesh with the worm gear 14, the overload prevention mechanism 18, the clutch plate 15, the small gear 19 in mesh with the recesses 1 6a formed on one side of the clutch plate 1 6 and the large gear 20 in mesh with the small gear 19 in that order to cause rotation of the large gear 20 at a predetermined speed.With the rotation of the large gear 20 the driving strip 30 in mesh with the gear section 20a of the large gear 20 tends to move towards the upper end of the chassis 1 through the lead opening 39 of the first drive section 7, an opening 52 along the guide 45.

The rotational driving force transmitted from the drive motor 6 to the small gear 1 9 is also transmitted through the drive shaft 1 7 secured to the small gear 19, the sleeve 46, the coupling shaft 11 and the sleeve 47 to the drive shaft 23 of the second drive section 8. Since this rotational driving force is further transmitted through the small gear 24 integral with the drive shaft 23 and the large gear 25 in mesh with the drive shaft 23, the large gear 25 is rotated in synchronism with and at the same speed as the large gear 20 in the first drive section 7 mentioned above. Thus, the other driving strip 30 in mesh with the gear section 25a of the large gear 25 is pulled through an opening (not shown) of the second drive section 8 in synchronism with the first-mentioned driving strip 30.

As the pair of driving strips 30 are pulled through the respective openings 52 in synchronism with each other, the third extensible pipes 29, to which the tips of the driving strips are secured via the coupling members 32, are pushed into the stem of the second extensible pipes 28 along the inner periphery thereof. The third extensible pipe 29 is retracted until the lower end 31 a of the bush 31 fitted in the stem of the pipe 29 strikes the upper end 53a of a bush 53 secured to the stem of the second extensible pipe 28. Consequently, the bush 53 moves, and the second extensible pipe 28 is retracted to the stem of the first extensible pipe 29 along the inner periphery thereof until it is stopped at a position in the neighbourhood of the lead openings 39 of the drive sections 7 and 8.Thus, the reflector cover 5a having the reflecting mirror 5 is accommodated in the opening 4a formed at the front 4 of the chassis 1 by the pair of extensioncontraction mechanisms 9 and 10 as shown by the dashed lines in Figure 1.

When the reflector cover 5a is retracted into the opening 4a, the lower edge of the cover 5a is brought into contact with the bottom 1 b of the chassis 1, and its upper edge opposite the lower edge is turned about the hinge mechanisms 50 towards the chassis 1. Thus, the reflector cover 5a is accommodated in the opening 4a such as to cover the front portions of the projection lenses 2.

While the above description has been concerned with the case where the reflecting mirror 5 is automatically moved forwardly from the front 4 of the chassis 1 and also in the converse direction towards the front 4 of the chassis 1 by the driving force of the drive motor 6, the same operation can be effected manually as will be described hereinafter with reference to Figures 5 and 6.

An operating lever 55 which is rotatably mounted on the outer casing 13 of the first drive section 7 via a pivotal pin 54 is rotated in the clockwise direction in Figure 5. As a result, one end 57b of an urging rod 57, the other end 57a of which is mounted on the operating lever 55 via a pin 56, projects in the leftward direction in Figure 5 from an insertion hole 58 formed in the outer casing 1 3. Thus, a manual plate 59 secured to the end 57b of the urging rod 57 and the small gear 19, in which the manual plate 59 is mounted, are both moved in the longitudinal direction of the drive shaft 17. Consequently, a recess 1 9b formed on the outer periphery of the small gear 19 is detached from a projection 1 6b formed on one side of the clutch plate 1 6.Thus, the small gear 1 9 and the clutch plate 1 6 are separated from each other, and by rotating the manual plate 59 in a predetermined direction in this state, the drive shaft 17, the small gear 1 9 and the large gear 16 can be rotated manually to operate the reflecting mirror 5 in a predetermined direction via the pair of extension-contraction mechanisms 9 and 10.

Thus, the embodiment of video projection apparatus comprises projection lenses and cathode-ray tubes disposed inside a housing-like chassis, and a reflecting mirror mounted at the front of the chassis. It also comprises a drive source, first and second drive sections driven as a pair by the drive source, a pair of extensioncontraction mechanisms disposed in parallel between the respective drive sections and the reflecting mirror and driven for extension and contraction by the driving force of the drive sections and a coupling shaft disposed between the rear ends of the cathode-ray tubes and the rear end of the chassis and coupling the drive sections to each other. When the pair of extension-contraction mechanisms are driven for extension and contraction in synchronism with each other by the coupling shaft driven by the driving forces of the drive sections, the reflecting mirror can be automatically projected to a predetermined position and withdrawn into the chassis, using a very simple construction.

Because the pair of extension-contraction mechanisms are driven for extension and contraction in synchronism with each other, it is possible to move the reflecting mirror while maintaining the correct attitude satisfying the video optical system.

Moreover, since the coupling shaft is provided between the rear end of the cathode-ray tubes and the rear end of the chassis, there is no need to provide any particular space for its disposition, and this contributes to the size reduction of the entire apparatus.

Claims

1. A video projection apparatus comprising: a housing-like chassis accommodating projection lenses and cathode-ray tubes and provided at the front with a reflecting mirror; a drive source; first and second drive sections driven as a pair by said drive source; a pair of extension-contraction mechanisms disposed in parallel between said respective drive sections and said reflecting mirror and driven for extension and contraction by the driving force of said drive sections; and a coupling shaft disposed between the rear ends of said cathode-ray tubes and the rear end of the chassis and coupling said drive sections to each other; said pair of extension-contraction mechanisms being driven for extension and contraction in synchronism with each other by said coupling shaft driven by the driving force of said drive sections.

2. A video projection apparatus according to claim 1 wherein said first and second drive sections are disposed inside said chassis adjacent to the rear end thereof and adjacent to the opposite sides thereof.

3. A video projection apparatus according to claim 1 wherein said pair of extension-contraction mechanisms each include a plurality of cylindrical extensible pipes having different diameters and a driving strip extending through said extensible pipes and driven for extension and contraction in the longitudinal direction of said extensible pipes.

4. A video projection apparatus according to claim 3 wherein said driving strip is a long flexible bar with teeth or holes for meshing with a pinion or worm gear of each said driving section.

5. A video projection apparatus substantially as hereinbefore described with reference to the accompanying drawings.