EP0609943B1

EP0609943B1 - Anti-implosion band for a cathode ray tube

Info

Publication number: EP0609943B1
Application number: EP19940200209
Authority: EP
Inventors: Frank Cornelis Vijlbrief
Original assignee: Koninklijke Philips Electronics NV; Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 1993-02-03
Filing date: 1994-01-28
Publication date: 1997-05-14
Anticipated expiration: 2014-01-28
Also published as: EP0609943A1

Description

The invention relates to an anti-implosion band for a cathode ray tube, having suspension elements which are secured to said anti-implosion band and which are provided with suspension apertures, the anti-implosion band having a first and a second edge.
Cathode ray tubes are used in, inter alia, television receivers, computer monitors and the like.
A cathode ray tube comprises an evacuated envelope having, in general, a cone portion and a display window portion, the latter portion having a raised edge.
To preclude that a cathode ray tube implodes, the tube is customarily provided with an anti-implosion band. In particular, for example metal bands are used which are provided around the envelope in a heated state and, after cooling, surround the envelope, in general the raised edge of the display window, under a mechanical stress. The anti-implosion band is provided with suspension elements. These elements have suspension apertures. By means of said suspension apertures the cathode ray tube is mounted in a cabinet.
An anti-implosion band of the type mentioned in the opening paragraph is known from European Patent Application EP-A-421537. A cathode ray tube comprising such an anti-implosion band is also disclosed in said Application. The known anti-implosion band is made in such a manner that anti-implosion bands can be stacked. For this purpose, the suspension elements are extended in a direction transverse to the anti-implosion band and, viewed in a direction transverse to the plane of the anti-implosion band, project relative to the anti-implosion band. In practice, however, the suspension elements of the known anti-implosion band have the disadvantage that the suspension apertures are susceptible to damage.
It is an object of the invention to provide an anti-implosion band of the type mentioned in the opening paragraph, in which the above drawback is at least largely overcome in a simple manner.
To this end, an anti-implosion band of the type described in the opening paragraph is characterized in that each suspension element comprises a portion which extends transversely to the outside of the anti-implosion band said portion having a suspension aperture and each suspension element further comprising at least one projection which extends transversely to said portion, said projections extending parallel to the outer surface of the anti-implosion band and well beyond the first edge of the anti-implosion band, and in that, viewed in projection on a plane through an edge of the anti-implosion band, the second edge of the anti-implosion band falls within said projections and the suspension apertures fall outside said projections.
The anti-implosion band in accordance with the invention has at least one projection for each of the suspension elements, said projections extending upwards or downwards relative to the anti-implosion band, the opposite edge of the anti-implosion band, viewed in a projection on the plane of the anti-implosion band, falling within said projections. By virtue thereof, the anti-implosion bands can be stacked. Viewed in projection, the suspension apertures for suspending the cathode ray tube in a cabinet fall outside the projections. Such a construction can be used for every known anti-implosion band and does not require a redesign of the anti-implosion band. In comparison with the known anti-implosion band, the risk that the suspension apertures or the portion of the suspension element in which the suspension aperture is formed are damaged during the stacking of the anti-implosion bands is reduced. In the construction known from EP-A-421 537 there is a substantial risk that during stacking or transport of the anti-implosion bands the edge of an anti-implosion band causes damage to the suspension elements or suspension aperture of the anti-implosion band on top of which this anti-implosion band is stacked. Damage to the suspension apertures or the relevant portion of the suspension element may cause problems during the mounting of the cathode ray tube in the cabinet, resulting in rejects or delay.
If the anti-implosion band is substantially rectangular, preferably, the suspension element comprises, with respect to the diagonal through the relevant corner, two projections on either side of the corner and, preferably, the suspension element is solidly constructed.
By using eight projections, two on each corner on either side of the corner, the anti-implosion bands can be stacked in a simple manner. The suspension element can be solidly constructed in a simple manner. Rotation of an anti-implosion band relative to an overlying or underlying anti-implosion band may cause the stack as a whole, which consults of a plurality of anti-implosion bands, to assume a helical shape. This has the following disadvantages: the stack takes up more space than it does when no rotation occurs and the stack is more stable, i.e. it is less likely to fall over or move.
These and other aspects of the invention will be explained in greater detail by means of an exemplary embodiment and with reference to the companying drawing, in which

Fig. 1 is a diagrammatic perspective view of a cathode ray tube in accordance with the invention;
Figs. 2A up to and including 2F are different perspective views of a corner of a clamping band having a suspension element;
Fig. 3 shows corners of clamping bands stacked on top of each other;
Fig. 4 shows an anti-implosion band.
Fig. 5 shows a further example of a cathode ray tube in accordance with the invention.

Fig. 1 is a perspective view of a cathode ray tube having an evacuated envelope. This envelope comprises a display window 1, a cone-shaped portion 2 and a neck portion 3. In the neck there is accommodated an electron gun (not shown). The display window has a raised edge. An anti-implosion band 4 is clamped around said raised edge. This band will hereinafter also be referred to as clamping band 4. Suspension elements 5 are provided on the corners of the clamping band 4. Figs. 2A up to and including 2F are different perspective views of a corner of a clamping band 4 having a suspension element 5. Said suspension element comprises a first portion 6 which is secured to the clamping band 4, a second portion 7 having a suspension aperture 8, which portion extends transversely to the clamping band and, in this example, substantially parallel to the plane of the clamping band. The suspension element 5 further comprises projections 9 which extend on one side of the clamping band. Figs. 2A and 2D are views transversely to the diagonal of the clamping band. Fig. 2B is a view transversely to the second portion 7 with the suspension aperture 8. Fig. 2C is a view transversely to the first portion 6. Figs. 2E and 2F are perspective views of the corner of the clamping band and the suspension element. Fig. 2B shows that, viewed in projection on the plane of the anti-implosion band, the edge 10 of the anti-implosion band located opposite the projections falls within the projections 9. The projection 9 exhibits a small outward bend. By virtue of this bend an anti-implosion band can more easily be stacked on the preceding anti-implosion band. Preferably, portion 7 extends between the edges 10 and 11 of the anti-implosion band. Then the portions 7 do not project upwards or downwards relative to the anti-implosion band. Consequently, the risk of these portions becoming damaged during stacking is reduced as compared to a construction in which portions 7 and 8 do project upwards or downwards relative to the anti-implosion band. The projections do not affect the clamping action of the band. The bands can be readily stacked on top of each other. Fig. 3 shows a detail of a stack of anti-implosion bands. In this example, the corners of the anti-implosion bands are shown. It is clearly visible how the corners of the anti-implosion bands are stacked on top of each other. The projections are means for aligning anti-implosion bands with each other during stacking. Unlike the aligning means of known anti-implosion bands, these aligning means do not comprise suspension eyelets. Thus, the risk that the suspension eyelets are damaged is reduced.
Fig. 4 shows an anti-implosion band 4. Said anti-implosion band is approximately rectangularly shaped and centred around an axis 12. The plane of the anti-implosion band extends transversely to said centring axis. The diagonal of the anti-implosion band is formed by a line through two oppositely located corners. It will be clear that "extending in an upward or downward direction relative to the anti-implosion band" is to be understood to mean within the scope of the invention that in a horizontal position of the anti-implosion band, for example as diagrammatically shown in Figure 4, the projections extend in an upward direction relative to the anti-implosion band or if the anti-implosion band is inverted the projections extend in a downward direction relative to the anti-implosion band.
Preferably, the suspension element comprises, with respect to the diagonal through the relevant corner, two projections on either side of the second portion and, preferably, the suspension element is solidly constructed.
The use of eight projections, two on each corner on either side of the second portion, enables the anti-implosion bands to be stacked in a simple manner and the risk that a clamping band is rotated relative to an underlying or overlying clamping band is small. The suspension element can be solidly constructed in a simple manner. Rotation of an anti-implosion band relative to an overlying or underlying anti-implosion band may cause the stack as a whole, which consists of a plurality of anti-implosion bands, to assume a helical shape. This has the following disadvantages: the stack takes up more space than it does when no rotation occurs and the stack is less stable, i.e. it is more likely to fall over or move.
The invention is not limited to the above examples. The anti-implosion band shown is a so-called shrinkage band, i.e. a band which is provided around the envelope in a heated state and, after cooling, surrounds the envelope, in this example the raised edge of the display window, under a mechanical stress. In further examples, the anti-implosion band can be clamped around the envelope by tightening it. In the examples the fixing elements are secured to the outside of the anti-implosion band. The examples show suspension apertures 8. The specific shape of the suspension apertures is not important for a proper understanding of the invention. Said suspension apertures may be in the form of round holes as shown in the examples, or half-open holes or they may even consist of only an edge on which a clamping element which is for example present in the cabinet can be mounted.
Figure 5 shows a further example of a cathode ray tube having an anti-implosion band. In this example the projections are oriented towards the side of the cathode ray tube where the electron gun is situated.

Claims

An anti-implosion band (4) for a cathode ray tube, having suspension elements (5) which are secured to said anti-implosion band (4) and which are provided with suspension apertures (8), the anti-implosion band having a first (11) and a second edge (10), characterized in that each suspension element (5) comprises a portion (7) which extends transversely to the outside of the anti-implosion band (4) said portion (7) having a suspension aperture (8) and each suspension element (5) further comprising at least one projection (9) which extends transversely to said portion (7), said projections (9) extending parallel to the outer surface of the anti-implosion band and well beyond the first edge (11) of the anti-implosion band, and in that, viewed in projection on a plane through an edge of the anti-implosion band, the second edge (10) of the anti-implosion band (4) falls within said projections (9) and the suspension apertures (8) fall outside said projections (9).
An anti-implosion band as claimed in Claim 1, which is substantially rectangular, characterized in that the suspension element comprises, with respect to the diagonal through the relevant corner, two projections on either side of the corner.
An anti-implosion band as claimed in Claim 1 or 2, characterized in that the suspension element is solidly constructed.
A cathode ray tube having an anti-implosion band as claimed in Claim 1, 2 or 3.