Speaker grille

Abstract: A plurality of dummy bores with bottoms (21) are disposed in the vicinity of through holes (11) defining speaker sound emanating apertures. Each dummy bores (21) have a bottom shaped like a cone or pyramid (23) such that outer light rays (31) becoming incident through the dummy bores (21) are irregularly reflected from the bottom to emerge therefrom as decreased in intensity. With the above arrangement, the through holes (11) and dummy bores (21) may appear less differently from each other. Thus provided is a speaker grille of excellent design.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a speaker grille for use in cabinets constituting display units of television receivers, desktop personal computers and the like, or constituting audio systems. Prior Art Speaker grilles are designed to protect speaker diaphragms. Additionally, an importance is attached to the design of the grilles. Prior art speaker grilles generally include a plurality of through holes in the surface thereof which define sound emanating apertures for releasing air in front of the speaker out of the apparatus (out of the cabinet) and a plurality of dummy bores, or impenetrable holes, are formed around these through holes, as disclosed in US Pat. No.4,919,227, for example, according to which the preambles of claims 1, 3 and 6 have been delimited. The dummy bores are provided in the light of the design of the apparatus and have flat surface at the bottom thereof. The aforementioned through holes normally have a small inner diameter, such as 3 mm or less in a circular hole, in consideration of the design and protection of the speaker. The speaker grilles used in the cabinets of the television receivers or the like are generally formed from a resin material. The aforesaid through holes and dummy bores are required to have an appearance indistinguishable from each other such that the grille may feature good design with the integrity of appearance. Unfortunately, with the conventional arrangement of the speaker grilles, the difference in appearance between the through holes and dummy bores is relatively obvious, allowing the holes to be distinguished from the bores. The following fact is responsible for such obvious difference. That is, when outer light rays are admitted to the through holes from the front side of the speaker grille (as seen from a listener), the outer rays penetrate the through holes, making the through holes appear dark. In contrast, the outer rays becoming incident on the dummy holes are reflected from the flat bottom surface at the point end thereof so that the listener may recognize the color tone of the speaker grille itself. To reduce reflection of the outer rays becoming incident on the dummy bores, a depth of the impenetrable bores may be increased. An increased depth of the dummy bores means an increased depth of the through holes. Accordingly, when through holes of a small diameter and greater depth are formed from a resin material, a mold requires thin long pins which have lower strength and are more liable to break. Additionally, the resin material shrinks to capture the pins during the process of molding, resulting in difficulty to release the pins from molded pieces. This forms the cause of defective molding. Hence, an implicit increase in the length of the mold pins is not allowed. DISCLOSURE OF THE INVENTION In view of the foregoing, it is the object of the present invention to provide a speaker grille formed from a resin material by molding, wherein the through holes (sound emanating apertures) and dummy bores (impenetrable holes with bottoms) are indistinguishable from each other in appearance and which allows to eliminate difficulties in the process of resin molding said speaker grille. For achieving the above object , the present invention is characterized in that the bottom of the dummy bores at the point end thereof has any one of the forms including concave, convex and combination of concave and convex, instead of a flat surface, such that the light rays are irregularly reflected from the bottom surface. With this arrangement, the outer rays admitted to the dummy bores are irregularly reflected from the bottom surface thereof to be dispersed and reduced in intensity when emerging therefrom. Accordingly, the dummy bores appear dark similarly to the through holes. This makes it difficult to distinguish the through holes from the dummy bores by appearance, whereby the speaker grille of good design is provided. This arrangement also allows the through holes to have a small depth so as to eliminate the need for the use of thin long mold pins. Thus, a stable molding process of short cycle is realized. Needless to say, freedom of design is increased. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a television receiver employing a speaker grille according to an embodiment of the invention; FIG.2 is a sectional view of a principal portion of the above speaker grille; FIG.3 is a sectional view of dummy bores in the above speaker grille; FIG.4 shows sectional views of dummy bores of other embodiments hereof. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGs.1 through 3, an embodiment of the invention will be described hereinbelow. In FIG.1, Reference Character 1 denotes a pair of speaker grilles which are disposed at opposite sides of the face of a cathode-ray tube 3 of a television receiver 2. The speaker grilles 1 constitute a portion of a cabinet 4 of the television receiver 2. Each speaker grille 1 comprises a cylinder member 6 for guiding air in front of a speaker 5 and a panel 7 disposed at the front side of the cylinder member 6. The panel 7 is formed with a plurality of through holes 11 defining speaker sound emanating apertures for releasing air from the cabinet 4, the air being guided from the front side of the speaker 5 by the cylinder member 6, and a plurality of dummy bores 21 with bottoms which are disposed around the through holes 11. The speaker grilles 1 are formed from a resin material. The dummy bores 21, as shown in FIGs.2 and 3, each have a cylindrical interior wall 22 and a conical bottom surface 23 (conical concave) at the point end thereof. The impenetrable dummy bore 21 has a hole diameter 'a' of 3 mm or less, a depth 'b' of 0.5 mm or more, and a conical apex angle 'c' of 150° or more. Description will now be given on the behavior of the outer rays (straight light rays) becoming incident straight on the dummy bore 21 parallel to the interior wall 22 thereof. Outer rays 31 becoming incident straight on the dummy bore 21 (impenetrable hole) impinge against the conical surface 23 at the point end thereof to be reflected at angles determined by the conical apex angle 'c', and then to be irregularly reflected from the depthwise interior wall 22 of the dummy bore 21. As a result, reflected light rays finally emerging from the dummy bore 21 are dispersed to be decreased in intensity. Consequently, the dummy bores 21 appear dark in the depth thereof, thus appearing less differently from the through holes 11. As described above, it is possible without using mold pins of a greater length that even a dummy bore having a small hole diameter of 3 mm or less be made to differ less from the through hole 11. Thus, there can be attained a speaker grille 1 of excellent design. Additionally, the through holes 11 may have a smaller depth to eliminate the need for use of thin long mold pins so that the speaker grilles may be molded in a stable process of a short cycle. Needless to say, the freedom of design is also increased. Incidentally, in the case of a greater hole diameter 'a', the mold pins have a greater diameter which allows for increase in the depth 'b'. If the apex angle 'c' is greater than 150°, the conical surface approximates to a flat plane so that the light rays irregularly reflected therefrom are decreased. Other modes of the dummy bore 21 according to the invention are shown in FIG.4. The bottom surface of the dummy bore 21 may be in the form of a semispherical concave as shown in FIG.4(A), a concave combining a conical surface 23 and a semisphere as shown in FIG.4(B), a concave of a truncated pyramid as shown in FIG.4(C), a slanted plane 24 having a tilt angle '' of 15° or more as shown in FIG.4(D), a spherical convex 25 as shown in FIG.4(E), or a concavo-convex surface 26 in a form of a matrix of pyramid-like projections as shown in FIG.4(F). Similarly to the aforementioned embodiment, these dummy bores 21 also accomplish decreased difference in appearance from the through holes 11, and thus are realized speaker sound emanating apertures of excellent design. It is obvious to those skilled in the art that the bottom of the dummy bores 21 may be in any form that causes straight incident rays to be reflected irregularly, such as concave, convex, combination of concave and convex, slanted plane or the like. Similarly, the dummy bore may be practiced in any form as seen from the top, which includes, additionally to circle, polygons including triangle, rectangular and the like; ellipse; oblong circle and the like. While a preferred embodiment has been described, variation thereto will occur to those skilled in the art within the scope of the present inventive concepts which are defined by the following claims.

Claims: A speaker grille (1) formed from a resin material by molding, comprising through holes (11) defining speaker sound emanating apertures and a plurality of dummy bores (21) with bottoms, said dummy bores (21) being disposed in the vicinity of the through holes (11), characterized in that the bottoms of said dummy bores (21) have any one of the following forms: concave, convex and a combination of concave and convex. A speaker grille (1) as set forth in Claim 1, wherein the dummy bores (21) with bottoms are in either form of a circle of 3 mm or less in diameter or a polygon having a side of 3 mm or less, and are 0.5 mm or more in depth. A speaker grille (1) formed from a resin material by molding, comprising through holes (11) defining speaker sound emanating apertures and a plurality of dummy bores (21) with bottoms, said dummy bores (21) being disposed in the vicinity of the through holes (11), characterized in that the bottoms of said dummy bores (21) have at least one of the following forms: cone/pyramid, truncated cone/pyramid, semisphere and a combination of truncated cone/pyramid and semisphere. A speaker grille (1) as set forth in Claim 3, wherein the dummy bores (21) with bottoms are in either form of a circle of 3 mm or less in diameter or a polygon having a side of 3 mm or less, and are 0.5 mm or more in depth. A speaker grille (1) as set forth in Claim 3, wherein the bottom shaped like a cone or pyramid has an apex angle of 150° or less. A speaker grille (1) formed from a resin material by molding, comprising through holes (11) defining speaker sound emanating apertures and a plurality of dummy bores (21) with bottoms, said dummy bores (21) being disposed in the vicinity of the through holes (11), characterized in that the bottoms of said dummy bores (21) are in the form of a slanted planer (24). A speaker grille (1) as set forth in Claim 6, wherein the dummy bores (21) with bottoms are in either form of a circle of 3 mm or less in diameter or a polygon having a side of 3 mm or less, and are 0.5 mm or more in depth. A speaker grille (1) as set forth in Claim 6, wherein the slanted plane (24) has a tilt angle of 15° or more.

Inventors: SHIKATA NAOHIRO, SHIMIZU KAORU, SHIOTA TOMIO, SHIKATA, NAOHIRO, SHIMIZU, KAORU, SHIOTA, TOMIO, Shikata, Naohiro, Matsushita Elec. Ind. Co., Ltd., Shimizu, Kaoru, Matsushita Elec. Ind. Co., Ltd., Shiota, Tomio, Matsushita Elec. Ind. Co., Ltd.
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1996
Main classification: H04R1
IPC codes: H04N5, H04R1