Abstract:
The present invention relates to a protector for a loudspeaker cone. The loudspeaker protector ( 25 ) comprises: a sheet of flexible material ( 26 ), the sheet being bounded by an edge ( 28 ); one or more mounting points ( 36 ) on the sheet ( 26 ), each mounting point ( 36 ) being adapted to receive a fixing member ( 38 ) through the sheet ( 26 ) and being positioned in a peripheral region ( 56 ) of the sheet ( 26 ); and one or more lines of weakness ( 50 ) in the sheet, the sheet ( 26 ) being thereby adapted to tear or break preferentially along the lines of weakness ( 50 ); in which the lines of weakness ( 50 ) separate the peripheral region ( 56 ) at each mounting point ( 36 ) from a central area ( 52 ) of the sheet ( 26 ), so that the central area ( 52 ) of the sheet may be torn from the peripheral regions ( 56 ) after the mounting points ( 36 ) have been held down by said fixing members ( 38 ).

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a protector for a loudspeaker cone. 
     2. Related Art 
     Loudspeaker cones are relatively fragile and easily damaged. A paper loudspeaker cone can be torn, punctured or creased by a single contact with a person&#39;s fingers or other object. Once a loudspeaker has been installed in a cabinet or other enclosure, it will be protected by its surrounds, including a mesh or grille through which sound is emitted by the loudspeaker. 
     In order to prevent accidental damage to loudspeakers between the point of manufacture and installation in an enclosure, it is known to provide a rigid moulded plastic grille that is permanently affixed to a frame surrounding the cone. This is an effective form of protection. Such rigid grilles have also been used to electrically insulate a metal loudspeaker frame from metal mounting screws passingthrough the frame. Disadvantages of such a rigid protective grille are that this is relatively expensive to manufacture, even in high volume, and the grille itself inevitably reflects and absorbs some of the sound emitted by the loudspeaker. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to address the problems cited above, and provide a protector for a loudspeaker cone when addresses these issues. 
     Accordingly, the invention provides a loudspeaker protector, comprising: a sheet of flexible material, the sheet being bounded by an edge; one or more mounting points on the sheet, each mounting point being adapted to receive a fixing member through the sheet and being positioned in a peripheral region of the sheet; and one or more lines of weakness in the sheet, the sheet being thereby adapted to tear or break preferentially along the lines of weakness; in which the lines of weakness separate the peripheral region at each mounting point from a central area of the sheet, so that the central area of the sheet may be torn from the peripheral region(s) after the or each mounting point has been held down by said fixing member(s). 
     Also according to the invention, there is provided a loudspeaker, comprising a frame, one or more mounting features by which the loudspeaker may be secured to an external object, a loudspeaker cone, and a loudspeaker protector, in which the cone is supported peripherally by the frame, the mounting features are provided on the frame beyond the periphery of the cone, the loudspeaker protector is affixed to the frame to protect the cone supported within the frame, and the loudspeaker protector has one or more mounting points in alignment with the mounting features of the frame, wherein the loudspeaker protector comprises: a sheet of flexible material, the sheet being bounded by an edge; one or more mounting points on the sheet, each mounting point being adapted to receive a fixing member through the sheet and being positioned in a peripheral region of the sheet; one or more lines weakness in the sheet, the sheet being whereby adapted to tear or break preferentially along the lines of weakness; in which the lines of weakness separate the peripheral region at each mounting point from a central area of the sheet, so that the central area of the sheet may be torn from the peripheral region(s) after the or each mounting point has been held down by said fixing member(s). 
     The mounting point in the loudspeaker protector is preferably an aperture, slit, dimple or other such feature formed or cut in the sheet material. If the mounting point is a hole through the sheet, then the sheet may include a sleeve that extends transversely away from the sheet around said hole. 
     Often, the loudspeaker frame will be a metallic frame. The mounting features of the frame can then be formed in the metal of the frame. The mounting points of the loudspeaker protector may then serve to insulate electrically the frame from the fixing members. In a preferred embodiment of the invention, each of the mounting features is an aperture in the frame, and the loudspeaker protector has a sleeve that extends into the aperture to insulate electrically the frame from the fixing member, which may be a metallic screw, bolt, press-fit stud or rivet. 
     The invention also provides a method of installing a loudspeaker in an enclosure using at least one fixing member, when the loudspeaker is according to the invention, wherein the method comprises the steps of: 
     a) placing the loudspeaker in the enclosure; 
     b) using the fixing member(s) to secure the loudspeaker within the enclosure; and then 
     c) pulling the loudspeaker protector from the loudspeaker to tear the loudspeaker protector along the lines of weakness in order to remove the central portion of the loudspeaker protector from the loudspeaker, while leaving the loudspeaker protector mounting points held to the loudspeaker at the fixing member(s). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a plan view of a prior art loudspeaker protector; 
     FIG. 2 is a plan view of a loudspeaker protector affixed to a loudspeaker, according to the invention; 
     FIG. 3 is a plan view of the loudspeaker of FIG. 2, with the loudspeaker protector removed, showing a loudspeaker cone supported by a metallic loudspeaker frame; 
     FIG. 4 is a plan view of the loudspeaker frame of FIG. 4; 
     FIG. 5 is a cross-sectional view through the loudspeaker and loudspeaker protector, taken through line V—V of FIG. 2; and 
     FIGS. 6,  7  and  8  are views of the internal surfaces of a car door, before, during and after installation of a loudspeaker with the loudspeaker protector of FIG.  2 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a prior art loudspeaker protector  1 , formed in a rigid moulded plastic material with a continuous oval rim  2  inside of which are a large number of perforations  4 . The perforations  4  are circular and closely packed so that these form a grille through which sound emitted by a loudspeaker may pass. 
     With reference now also to FIGS. 3 to  6  the loudspeaker protector  1  in use is permanently affixed to a conventional loudspeaker  30  by applying glue (not shown) between the rim  2  of the loudspeaker protector  1  and a similarly shaped rim  39  of a pressed steel loudspeaker frame  40 . Most of this glue is applied between matching flanges  12 , 14  of the loudspeaker protector  1  and loudspeaker frame  40 , in areas surrounding four matching holes  6 , 8  in each of the rim  2  of the loudspeaker protector  1  and rim  39  of the loudspeaker frame  40 . The holes  6 , 8  align so that a mounting screw or bolt  38  can be passed through each of the aligned pairs of holes  6 , 8  and into corresponding threaded bores  47  in an enclosure  75 , such as a recess in a metallic motor vehicle door  80 , to mount and secure the loudspeaker  30  to the enclosure  75 . 
     The loudspeaker protector  1  serves another purpose in this automotive application, by providing electrical insulation between the loudspeaker frame  30  and the four metal screws or bolts  38  used to secure the loudspeaker  30  to the metallic enclosure  75 . This insulation is ensured by a cylindrical sleeve  16  that inserts fully into the loudspeaker frame clearance holes  8  when the loudspeaker protector  1  is affixed to the loudspeaker  30 . This electrical insulation is important because it prevents electrical current from flowing from the metallic loudspeaker frame  40  to the metallic chassis of the circle through the connecting screw on at  38 , in the event that an electrical fault develops within the loudspeaker  30 . Because of this need for, electrical insulation, the loudspeaker protector  1  must be permanently affixed to the loudspeaker frame  40 . This does provide the benefit that physical protection is always provided to delicate components of the loudspeaker, in particular a loudspeaker cone  20 , a inner loudspeaker cone  22 , and a flexible surround  24  around the cone  20 . Usually, the loudspeaker cone  20  and inner loudspeaker cone  24  will be made from paper. However, the grille  4  does impair somewhat the sound quality of the speaker  30 . In order to minimize this impairment, the loudspeaker protector  1  is moulded from a relatively expensive plastic material sold under the trade mark Noryl, which is a PPE-PS blend. This has high strength, and is suitable for use with adhesives that can affix this permanently to the metal loudspeaker frame  40 . 
     Even in high volume production, the cost of the prior art loudspeaker protector  1  is about US$ 0.20 to US$ 0.25. This is a significant additional cost to the manufacturing cost of the loudspeaker  30 . 
     FIG. 2 shows a loudspeaker protector  25  according to the invention, when affixed to the loudspeaker  30  of FIG.  3 . The loudspeaker protector  25  comprises a sheet of flexible material  26 , which is preferably 250 μm thick film, for example polyester film (PET) or polyether sulphone (PES), which has been cut and moulded into shape. The loudspeaker protector  25  has an edge  28  that generally conforms to the peripheral outline  29  of the loudspeaker  30 , with the exception of a tab  32  that extends outwards from a rim area  34  of the protector  25 . 
     The loudspeaker protector  25  has four mounting points in the form of clearance holes  36  in the rim  34 . When the protector  25  is affixed to the loudspeaker  30 , these four clearance holes  36  align with the four holes  8  in the metallic frame  40  of the loudspeaker  30 . 
     FIG. 5 shows a cross-sectional view through the loudspeakers protector  25  when affixed to the loudspeaker  30  by means of an adhesive  37  in the vicinity of the loudspeaker protector clearance holes  36 . Also shown, is the metallic screw or bolt  38  passing through the hole  36  in the protector  25  and the matching clearance hole  8  in the loudspeaker metallic frame  40 . 
     The loudspeaker protector  25  has a cylindrical sleeve  42  that extends through the frame clearance hole  8  so that the metallic screw  38  cannot contact the metallic frame  40 . A compressible hemispheric button  44 , for example made from a foam-like material or an elastomeric material, is also provided on an undersurface  54  of the flange  14  of the loudspeaker frame  40  to provide vibration isolation and electrical insulation between the frame  40  and a metallic support surface  46  to which the loudspeaker  30  is secured by the four screws or bolts  38 . 
     As indicated by FIGS. 5 and 6, the loudspeaker  30  with loudspeaker protector  25  is first assembled to the supporting surface  46  with the loudspeaker protector  25  still protecting the loudspeaker cone  20 . The loudspeaker protector  25  has semicircular perforations  50  that extend around each of the mounting points  36  of the protector  25 , terminating at a peripheral edge  28  of the protector. The perforations therefore separate a central portion  52  of the protector  25  from four small portions  56  of sheet material  26  that extend around each of the four clearance holes  36 . 
     The perforations  50  form a line of weakness in the loudspeaker protector  25  so that a person may grip the projecting tab  32  and lift the protector  25  away from the loudspeaker  30  to cause the protector  25  to tear along each of the four perforations  50 , and thereby remove the loudspeaker protector central portion  52  from the loudspeaker  30 . The loudspeaker protector  25  is substantially removed from the loudspeaker  30 , except for the four small portions  56  that remain adhered by the adhesive  37  and secured by the bolt  38  to the peripheral flanges  14  in the loudspeaker frame  40 . The cylindrical insulating sleeves  42  therefore remain in place between the metallic screw  38  and loudspeaker frame  40 . 
     As can be seen from FIG. 2, the pull-tab extends from a rim or peripheral region  34  of the sheet material forming the loudspeaker protector  52 , but in such a way that this pull-tab  32  does not extend beyond rectangular bounds  60  defined by the long and short axes  62 , 64  of the oval loudspeaker cone  20 . This arrangement facilitates packaging of the assembled loudspeaker  30  and protector  25 , e.g. inside a matching rectangular cardboard shipping box (not shown). The pull-tab  32  therefore extends in a direction that lies between the major axis  62  and minor axis  64  of the oval loudspeaker  30 . 
     The central area  52  of the loudspeaker protector  25  is provided with a series of parallel corrugations  66  which have a rectangular channel cross-section as shown in FIG.  5 . The corrugations  66  extend in a direction transverse to a pull direction  68  of the pull-tab  32 . The corrugations  66  therefore permit the central area  52  to curl and roll in the pull direction  68  as the pull-tab  32  is used to remove the central area  52  of the loudspeaker protector  25  from the loudspeaker  30 . The corrugations  66  therefore provide stiffening in a direction normal to the plane of FIG. 2, while still permitting easy removal of the central area  52  of the protector  25  after the loudspeaker  30  has been installed in its enclosure  75 . 
     In order to help ensure that the central area  52  is removed after installation of the loudspeaker  30 , it is preferable if the loudspeaker central area  52  has a color noticeably different from that of the loudspeaker cone  20 . Usually, loudspeaker cones  20  are black, and so at least a portion of the central area  52  should be colored with a color other than black. Similarly, because the areas  56  of the loudspeaker protector  25  are left in place after removal of the central area  52 , it is preferable if these peripheral regions  56  of the loudspeaker protector  25  are colored black. 
     In order to provide the maximum protection, the central area  52  of the loudspeaker protector  25  is domed by a step  70  that rises from the peripheral rim  34  of the protector  25 . This provides a clearance gap  72  between the rubber isolating ring  24  connecting the loudspeaker cone  20  to the loudspeaker frame  40 . 
     The loudspeaker protector  25  according to the invention is relatively cheap to manufacture in large volumes. Because the protector  25  is temporary, it does not need to be designed to let sound from the loudspeaker pass through the protector with minimum disturbance. There is also no need to design the protector  25  so that this does not rattle or vibrate when the loudspeaker is operational. The material of the loudspeaker protector  25  may also be recyclable, thereby providing additional cost savings and reduced environmental impact. A loudspeaker protector according to the invention wherefore provides an economical solution to the problem of how to provide protection to the fragile parts of a loudspeaker between the manufacture of the loudspeaker and installation in an enclosure. 
     It is to be recognized that various alterations, modifications, and/or additions may be introduced into the constructions and arrangements of parts described above without departing from the spirit or scope of the present invention, as defined by the appended claims.