Assembly of anti-implosion bands, anti-implosion band for such an assembly and display tube comprising such an anti-implosion band

Abstract: An assembly of at least two detachably superposed anti-­ implosion bands 14, 24. Each anti-implosion band 14, 24 comprises suspension elements 15, 25 projecting from the anti-implosion band 14, 24. The suspension elements 25 of the anti-implosion band 24 surround the anti-implosion band 14 with clearance. As a result hereof, anti-­ implosion bands can be stacked in a simple manner to form an assembly, and the anti-implosion bands can be detached in a simple manner.

Description: The invention relates to an assembly of at least two detachably superposed annular anti-implosion bands. The invention also relates to an anti-implosion band for such an assembly. The invention further relates to a display tube comprising such an anti-implosion band. A display tube which generally comprises an evacuated envelope having a substantially rectangular display window can be used in black and white, colour and projection television, apparatuses for displaying digits and letters (Data Graphic Display) and in other apparatuses in which a display tube is used. To preclude that the display tube implodes, the envelope is customarily provided with an anti-implosion band. In particular, annular metal bands are used which are provided around the display window in a heated state and, after cooling, surround the display window under a mechanical stress. In general, the anti-implosion bands are manufactured separately from the envelope in large numbers and have to be stored and/or transported before they can be provided around the envelope. In practice however, it appears, that storing and/or transporting anti-implosion bands can sometimes lead to deformation of said bands. Deformation of an anti-implosion band is undesirable because it may give rise to problems during the provision of the anti-implosion band around the display tube and, in some cases, it may even lead to fracture of the envelope during the cooling of the anti-implosion band. It is an object of the invention, inter alia , to at least largely preclude the deformation of the anti-implosion bands during storage and transport. According to the invention, this object is achieved by constructing the anti-implosion bands in a manner such that an assembly of at least two detachably superposed substantially identical annular anti-implosion bands is characterized in that the assembly is substantially rectangular and the central axes of the annular anti-implosion bands substantially coincide, each of the anti-implosion bands having a substantially rectangular shape and an inner and an outer surface which each extend substantially parallel to the central axis of the respective anti-implosion band , suspension elements being secured to said outer surface and projecting from the anti-implosion band in a direction substantially parallel to the central axis of the respective anti-implosion band, and at least a part of the outer surface of at least one of the anti-implosion bands being loosely surrounded by the projecting parts of the suspension elements of the other anti-implosion band. The invention is based on the insight that the suspension elements can be advantageously used to facilitate the stacking of anti-implosion bands to form an assembly. This insight is not described in the state of the art in which storage and/or transport of the anti-implosion bands is carried out by stacking them. Since the known anti-implosion bands do not have projecting suspension elements, said bands can move relative to each other and may sometimes even be in a clamping engagement which causes deformation of the anti-implosion bands and, in addition, detaching two clamping anti-implosion bands is labour-intensive and may lead to deformations. By virtue of the fact that the suspension elements of the one anti-implosion band of the assembly according to the invention partly loosely surround the outer surface of the other anti-implosion band, it is possible on the one hand to stack the anti-implosion bands in a simple manner without the bands being in a clamping engagement and, on the other hand, to limit the displacement relative to each other in a direction parallel to an annular surface. As a result hereof, the assembly remains stable during transport and deformations of the anti-implosion bands as a result of vibrations and shocks are at least largely precluded. A preferred embodiment of an assembly according to the invention is characterized in that the section of each anti-implosion band is provided with a profile transversely to the annular surface, and in that the width of the contact surface between the ends of the superposed anti-implosion bands is at least equal to half the thickness of an anti-implosion band. By virtue of this construction, an assembly of at least two profiled anti-implosion bands is found to be stable. In order to ensure that the movement of the anti-implosion bands relative to each other is limited, preferably, the distance over which the suspension element projects from the anti-implosion band is at least 20% of the width of the anti-implosion band. Moreover, taking the assembly apart does not require much force because the anti-implosion bands are not stacked in a clamping manner. An anti-implosion band for an assembly according to the invention permits stacking and unstacking to be carried out in a simple operation which can be mechanized and offers a satisfactory implosion-protection to the display tube. In certain types of display tubes the anti-implosion band is provided with a coating to preclude undesirable light reflections at the anti-implosion band. To ensure that this coating is not damaged during the stacking and transport of the anti-implosion bands, a preferred embodiment of an anti-implosion band according to the invention is characterized in that the suspension elements are L-shaped and the width of the anti-implosion band is smaller than the length of the part of each suspension element which extends substantially transversely to the annular surface of the anti-implosion band. In practice, a L-shaped suspension element can be secured to the outer surface in a simple manner, for example, by welding a part of the suspension element to the outer surface. The part which extends transversely to the part secured to the outer surface can be used to suspend the display tube in a cabinet. By selecting the width of the anti-implosion band to be smaller than the part of the suspension element which extends transversely to the annular surface, it is precluded that during the stacking of two anti-implosion bands to form an assembly, two anti-implosion bands lie against each other in an undesirable manner, as a result of which damage to a coating applied to said bands is limited to a sufficient degree. A preferred embodiment of an anti-implosion band according to the invention is characterized in that the suspension elements are secured to the corners of the anti-implosion band. In this manner it is precluded that in an assembly the said anti-implosion band and an anti-implosion band provided thereon rotate relative to each other in an undesirable manner. The suspension elements secured in the corners limit the directions of movement of the anti-implosion bands. A display tube comprising an anti-implosion band according to the invention exhibits a satisfactory implosion safety. These and other aspects of the invention will be described and explained by means of exemplary embodiments and with reference to the accompanying drawing, in which Fig. 1 is a diagrammatic elevational perspective view of a display tube Fig. 2 is a diagrammatic sectional view of a first embodiment of an assembly of two anti-implosion bands according to the invention, Fig. 3 is a diagrammatic sectional view of a second embodiment of an assembly according to the invention, Fig. 4 is a diagrammatic sectional view of a third embodiment of an assembly of two anti-implosion bands according to the invention, Fig. 5 is a diagrammatic perspective view of an embodiment of an anti-implosion band according to the invention, Fig. 6 is a diagrammatic sectional view of a further embodiment of an assembly according to the invention, and Figs. 7a, 7b and 7c are diagrammatic cross-sectional views of profiled anti-implosion bands which can be used in the framework of the invention. Fig. 1 is an elevational view of a display tube comprising an evacuated glass envelope containing a substantially rectangular display window 1, a conical enveloping portion 2 and a neck portion 3. A substantially rectangular anti-implosion band 4 is provided around the display window 1, said band substantially reducing the risk of implosion of the envelope as a result of external forces (for example when the display tube is dropped) or the risk of spontaneous implosion. In particular a metal band having a shape which is substantially equal to the shape of the outer surface of the display window 1, but with a slightly smaller circumference, is used for the anti-implosion band. The metal band is heated until its circumference is larger than that of the display window and, subsequently, it is provided around said display window. The band is then left to cool, as a result of which the band surrounds the display window under a mechanical stress. The metal band may be profiled as well as flat. To suspend the display tube in a cabinet, the anti-implosion band 4 is provided with suspension elements 5 which can be connected to cooperating elements in the cabinet. An anti-implosion band according to the invention, which is provided with suspension elements will be described in more detail with reference to the Figs. 2 up to and including 6. In general, anti-implosion bands and envelopes of display tubes are manufactured separately. Before the anti-implosion bands are provided on the envelope they have to be stored and/or transported. The storage and/or transport can be carried out in a simple manner by stacking the anti-implosion bands according to the invention in cooperation with the suspension elements to form an assembly. Fig. 2 is a diagrammatic sectional view of an assembly of two substantially identical anti-implosion bands 14, 24 which each comprise a number of suspension elements 15, 25. It will be obvious that the assembly may comprise more than two anti-implosion bands and that the invention is not limited to the example described herein. Each anti-implosion band 14, 24 is substantially rectangular and defines an annular surface 16, 26 and a central axis 17, 27. In the substantially rectangular assembly the central axes 17 and 27 substantially coincide. The anti-implosion bands 14, 24 each have an inner surface 18, 28 and an outer surface 19, 29, which surfaces extend substantially parallel to the central axis 17, 27 of the respective anti-implosion band. The suspension elements 15, 25 are secured to the anti-implosion bands 14, 24 at the location of the outer surfaces 19, 29. The suspension elements 15, 25 each project from the respective anti-implosion band 14, 24 in a direction . In this preferred embodiment, all suspension elements of one anti-implosion band project in the same direction. As a result hereof, the suspension elements 25 of the anti-implosion band 24 surround the outer surface 19 of the anti-implosion band 14. To preclude that the anti-implosion band 14 becomes jammed between the suspension elements 25, said elements 25 must surround the band 14 with clearance. This can be attained, for example, by providing each suspension element 15, 25 with a sufficiently large bend 13, 23. The mutual position of the anti-implosion bands 14, 24 in the assembly remains substantially equal, inter alia during transport of the assembly, amongst others because the suspension elements 25 limit the movement of the band 14 in a direction parallel to the annular surface 26. For this purpose, the suspension elements project from the anti-implosion band, preferably, over a distance of at least 20% of the width of the band. Consequently, deformations of the anti-implosion bands caused by said bands being jammed during transport substantially no longer occur. In addition, the removal of an anti-implosion band from the assembly can be carried out in a simple manner because the anti-implosion bands in the assembly are stacked loosely relative to each other. Moreover, the anti-implosion bands in the assembly are of a relatively small volume because the suspension elements of the one anti-implosion band partly overlap the other anti-implosion band. Fig. 3 is a diagrammatic view of an alternative embodiment of an assembly of two anti-implosion bands 14, 24 according to the invention, in which the suspension elements 15, 15′, 25, 25′ are L-shaped. The suspension elements 15, 25 and 15′, 25′ are provided with apertures 12, 22 for suspending the display tube in a cabinet. In this embodiment, the width b of an anti-implosion band 24 is larger than the length 1 of the part of the suspension element 25 which extends substantially transversely to the annular surface of the anti-implosion band 24 ( b > 1 ). For example, the length 1 of the part of the suspension element is 10 mm, the width b of the anti-implosion band is 20 mm and the thickness d of the band is 1.2 mm. The distance u over which the suspension element projects from the bandp is, for example, 3 mm. In the present example the corner 29 of each suspension element of the anti-implosion band 24 is rounded to ensure that the other anti-implosion band 14 of the assembly can be arranged between the suspension elements in a simple manner. Preferably, the width b of the anti-implosion band 24 is smaller than the length l of the part of the suspension element 25 which extends transversely to the annular surface ( b < l ), as shown in the diagrammatic sectional view of Fig. 4. By virtue of this construction an aperture 30 is formed between the two anti-implosion bands 14 and 24, so that said anti-implosion bands 14, 24 do not lie against each other. This is particularly advantageous with anti-implosion bands comprising, for example, an anti-reflection coating. Since the anti-implosion bands do not lie against each other, this coating remains substantially undamaged. For example, the length l of the part of the suspension element is 21 mm, the width b of the anti-implosion band is 20 mm and the distance u is 3 mm, so that the space between the two anti-implosion bands is 1 mm. The suspension elements may be provided, for example, in the centres of the sides of the anti-implosion band, but advantageously they are secured to the corners of the anti-implosion band 34, as shown in the diagrammatic perspective view of Fig. 5. when the suspension elements 35 are secured to the corners of the anti-implosion band 34 it is precluded that in an assembly another anti-implosion band rotates undesirably relative to the anti-implosion band 34, which could cause a clamping engagement of the bands. In the above-described exemplary embodiments, the anti-implosion bands are manufactured from flat metal bands. However, the invention can be applied just as advantageously when anti-implosion bands manufactured from profiled metal bands are used, as diagrammatically shown in Fig. 6. The anti-implosion bands 14′ and 24′ are provided with a profile in the form of a bend and have a uniform thickness d′, viewed width wise. To obtain a stable assembly, the profile in the form of a bend is such that the width W of the contact surface 40 between the two anti-implosion bands 14′ and 24′ is at least equal to half the thickness of the band d′. when the contact surface 40 is smaller there is a risk that during stacking the anti-implosion band 14′ is arranged obliquely in the anti-implosion band 24′, which could lead to an undesirable engagement. Other embodiments of profiled metal bands which can be used in the framework of the invention are shown in the diagrammatic and cross-sectional views of Figs. 7a, 7b and 7c. In Fig. 7a and Fig. 7b suspension elements are shown. By way of example, the invention is described by means of a display tube having a glass, conical enveloping part. To those skilled in the art it will be obvious that the invention is not limited thereto, and that the invention applies just as well to a display tube having a box-shaped enveloping part which may be manufactured from metal. Further, the invention is not limited to the constructions of the suspension elements described herein, and to those skilled in the art it is obvious that the suspension elements may be of many different types as long as the projecting parts of the suspension elements of an anti-implosion band in an assembly with another anti-implosion band surround the latter with clearance.

Claims: An assembly of at least two detachably superposed substantially identical annular anti-implosion bands (14,24; 14′,24′), which assembly is substantially rectangular and in which the central axes (17,27) of the annular anti-implosion bands substantially coincide, each of the anti-implosion bands having a substantially rectangular shape and an inner (18,28) and an outer surface (19,29) which each extend substantially parallel to the central axis (17,27) of the respective anti-implosion bands, suspension elements (15, 25) being secured to said outer surface (19,29) and projecting each from the anti-implosion band (14,24) in a direction substantially parallel to the central axis (17,27) of the respective anti-implosion band, at least a part of the outer surface (19) of at least one of the anti-implosion bands (14) being loosely surrounded by the projecting parts of the suspension elements (25) of the other anti-implosion bands (24). An assembly as claimed in claim 1, characterized in that the section of each anti-implosion band is provided with a profile extending substantially parallel to the central axis of respective anti-implosion band, and in that the width (W) of the contact surface (40) between the ends of the superposed anti-implosion bands is at least equal to half the thickness (d′) of an anti-implosion band. An anti-implosion band suitable for being stacked having a substantially rectangular shape and an inner (18,28) and an outer surface (19,29) which each extend substantially parallel to the central axis (17,27) of the anti-implosion band, suspension elements (15, 25) being secured to said outer surface (19,29) and projecting each from the anti-implosion band in a direction substantially parallel to the central axis of the anti-implosion band, the suspension elements being such that, when stacking two anti-implosion bands, at least a part of the outer surface (19) of one of the anti-implosion bands (14) is loosely surrounded by the projecting parts of the suspension elements (25) of the other anti-implosion bands (24). An anti-implosion band as claimed in claim 3, characterized in that the suspension elements are L-shaped and the width (b) of the anti-implosion band is smaller than the length (l) of the part of each suspension element which extends substantially parallel to the central axis of the anti-implosion band. An anti-implosion band as claimed in claim 3 and 4, characterized in that the distance (u) over which the suspension element projects from the anti-implosion band is at least 20% of the width of the anti-implosion band. An anti-implosion band as claimed in claim 3, 4 or 5, characterized in that the suspension elements are secured to the corners of the anti-implosion band.

Inventors: BONGENAAR HENDRIK, HESSELS FRANCISCUS ANTONIUS JO, BONGENAAR, HENDRIK, HESSELS, FRANCISCUS ANTONIUS JOHANNES
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1990
Main classification: H01J29
IPC codes: H01J29