Abstract:
A damper for loudspeaker is constituted by mounting tubular knitted tinsel cords through an adhesive agent of acrylic emulsions having a tackiness onto one surface of a corrugated damper body. The damper is thereby rendered easily manufacturable and highly flexible enough for restraining any breaking of the tinsel cords and improving the reliability.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates to dampers used as a constituting member of loudspeakers employed in various acoustic devices and equipments or, more specifically, to a damper for loudspeakers which is called as a conductive damper with tinsel cords mounted on a surface thereof, and to a method for manufacturing such damper.  
         DESCRIPTION OF RELATED ART  
         [0002]    Generally, voice coils of the loudspeaker are supported by a frame through the damper for vibration, and lead wires of the voice coils are connected through the tinsel cords to input terminals of the loudspeaker. Since the tinsel cords are generally disposed in a space between a diaphragm and the damper, there has been a problem that the tinsel cords are caused to move rockingly during the operation of the loudspeaker so as to hit the diaphragm or damper and generate an abnormal noise and so on, and this tendency has been increased to be more remarkable as the loud speaker is developed to be more minimized and thinner in the dimensions.  
           [0003]    In order to solve this problem, there has been suggested a damper in which the tinsel cords are made integral with the damper by means of an adhesion or a sewing-up, as has been disclosed in, for example, Japanese Patent Laid-Open Publications Nos. 10-336788 and 2000-41296, in the former of which the tinsel cords employed are of thin and plain woven ones held onto one surface of the damper body by means of heat fusion of a strip-shaped polyurethane member, while in the latter of which a tubular-knitted tinsel cord stronger and less damageable than the plain-woven one upon heat compression is used as bonded with polyurethane layer interposed. It has been also possible to bond the tinsel cords onto the damper body with an adhesive agent of silicones employed.  
           [0004]    However, in the case where such plain-woven tinsel cord is used as has been disclosed in the former Publication 10-336788, there has been a problem that, upon being soldered, a very small thickness of the wire causes the solder to leach out and the soldering has been made complicated. While in the case of such tubular knitted tinsel cords as employed in the latter Publication 2000-41296 the soldering is not caused to become so complicated, the manufacturing has been complicated, including the case of the former Publication 10-336788, due to that the polyurethane member is required to be peeled off at a portion inside the tinsel cords disposed adjacent to an inner aperture of the damper body. Yet, as the tinsel cord has no extensibility, it cannot be bonded along the wave of corrugations of the damper body so that there arises a risk of causing the solder foil to be flawed and damaged with any excessive force applied forcibly for matching with the corrugations, an exclusive-use molding dies are required, and there has been a problem that the manufacture as a whole has been complicated.  
           [0005]    Further, in the case of the mounting of the tinsel cords with the adhesive agent of silicones employed, there has been another problem that the adhesive agent soaks into stitches of the cords so as to cause a risk of breaking the cords as hardened with the soaked agent cured, so as to lower the reliability, and to disturb required displacement of the damper. Since the tinsel cords are secured to the surface of the damper as made integral therewith, further, it has been unable to closely bond the tinsel cords to the damper body along the corrugations from the inner end to the outer end thereof, and there has been a risk of damaging the cords due to that the tinsel cords are shortened so as to be unable to move following the vibration of the damper body but to apply an excessive tension to the tinsel cords.  
         TECHNICAL FIELD  
         [0006]    It is an object of the present invention to overcome the foregoing problems in the prior art; to provide a damper for the loudspeakers which is made easier to manufacture, high in the flexibility to be assured in free operation as the damper, and improved in the reliability with damage of the tinsel cords restrained; and to provide a method for manufacturing such damper.  
           [0007]    According to the present invention, the above object can be established by means of provision of a damper for the loudspeakers in which tubular knitted tinsel cords are bonded to one surface of a body of the damper provided with corrugations through an adhesive agent of acrylic emulsions having a tackiness interposed. 
       
    
    
       [0008]    Other objects and advantages of the present invention shall become clear as the following description of embodiments of the invention advances with reference to accompanying drawings showing the respective embodiments.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view of the damper in an embodiment of the present invention;  
         [0010]    [0010]FIG. 2 is a fragmentary sectioned view as magnified of the damper in FIG. 1;  
         [0011]    [0011]FIGS. 3 a  to  3   f  are explanatory views for manufacturing steps of the damper in an embodiment according to the present invention; and  
         [0012]    [0012]FIGS. 4 a  and  4   b  are explanatory views for hook means in a molding die employed in the manufacturing steps of the method according to the present invention. 
     
    
       [0013]    While the present invention shall now be described in the followings with reference to the embodiments shown in the accompanying drawings, it should be appreciated that the intention is not to limit the invention only to the embodiments shown but rather to include all alterations, modifications and equivalent arrangements possible within the scope of appended claims.  
       DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0014]    Referring to FIG. 1, there is shown a damper for loudspeakers in an embodiment according to the present invention, in which the damper  10  comprises a body  11  formed in a ring shape having a plurality of corrugations  12  of concentric circles. A pair of tubular knitted tinsel cords  13  are provided as bonded in strip shape on one surface  11   a  of the damper body  11  to lie along the shape of the corrugations  12 , with a layer of adhesive agent  14  interposed, from outer peripheral edge  11   b  to inner peripheral edge  11   c.  Outer ends of these tubular knitted tinsel cords  13  extend outward and are provided at tip ends with soldered parts  15 . As has been well known, these soldered parts  15  are connected to relay terminals (not shown) of the loudspeaker. Inner ends of the wires are also provided with soldered parts  16  which are connected to lead wires (not shown) of voice coils on a coil bobbin, as also well known. The damper body  11  is provided at outer periphery with a positioning notch  17  for use upon bonding of the tubular knitted tinsel cord  13  employed in this case is formed by winding copper foils of a copper wire rolled to be less than ¼ of the generant diameter less than 0.10 mm around meta-series alamid fibers of single or twin woven center thread of 40 count into a tinsel, and assembling 4 to 16 tinsels into a cord at a weaving pitch of 20±5/turn, so as to be of a structure less damageable upon being subjected to the heat under pressure. With such assembling of the wires at a coarse weaving pitch, the tubular woven tinsel cord  13  is made to be less breakable upon being worked under pressure but readily crushable to be easily flattened, so that the adhesion properties between molding die gap and the damper body upon molding can be improved and the configure of the corrugations  12  can be stabilized so as not to impair inherent properties of the damper body  11 . Further, since the tubular knitted tinsel cords  13  employed are small in the thickness, the cords  13  are improved in the bending properties with respect to the vibration, so as to be also improved in the durability.  
         [0015]    In addition to such bendability because of the special structure of the tinsel cords  13  tubular woven, the cords  13  and damper body  11  are coupled in flexible manner through the adhesive agent  14  having the tackiness, whereby the damper body  11  is further improved in the freedom of motion, with the effect of preventing the breakage of the tinsel cords  13  also improved.  
         [0016]    In FIG. 2, there is shown the structure in which the tubular knitted tinsel cords  13  are coupled through the adhesive agent  14  onto the damper body  11 . In assembling this structure, the adhesive agent  14  having the tackiness is applied in a strip shape from the inner peripheral edge to the outer peripheral edge on the one surface  11   a  of the body  11 , and the tubular knitted tinsel cords  13  are placed over the strip of the agent  14  to be bonded to the damper body  11 . Even when the adhesive agent  14  strikes through the tubular knitted tinsel cords  13 , the agent  14  can maintain its tackiness so that the tubular knitted tinsel cords  13  can be kept not to be hardened by the adhesive agent. For this adhesive agent  14 , a product named BOND 7 (by SUMITOMO-3M) of an adhesive agent of acrylic emulsions can be effectively used. This adhesive agent  14  does not lower its adhesivity even after being dried, so as to be of viscoelastic type which maintaining the tackiness.  
         [0017]    When the damper  10  operates with the voice coils for the vibration of the diaphragm, therefore, the adhesive agent  14  does not disturb the operation but rather acts as a cushion for the tubular knitted tinsel cords  13 , so as to improve the freedom of the operation of the damper  10  in cooperation with the excellent bendability of the tubular knitted tinsel cords  13 , without any influence on the dynamic properties of the diaphragm eventually, while preventing the tubular knitted tinsel cords  13  from being broken.  
         [0018]    [0018]FIGS. 3 a  to  3   f  show respective steps of bonding the tubular knitted tinsel cords  13  onto the damper  10 , wherein manufacturing steps of the body  11  of the damper  10  are of known art generally adopted and detailed description thereof shall be omitted here.  
         [0019]    First, as shown in FIG. 3 a,  the damper body  11  is provided with a notch  17  as a positioning guide, at an outer peripheral part used as an adhering margin to a frame or the like part of the loudspeaker. For the shape of this notch  17 , any proper one of square and round bottomed U-shape and an arcuate shape can be adopted. The notch  17  is used as a positioning mark at a bonding step of the tubular knitted tinsel cords  13  with respect to the damper body  11 , in the intention of improving the positioning precision and the workability. Then, as shown in FIG. 3 b,  the damper body  11  is disposed at a predetermined position on a working station by means of the notch  17 . At the position where the damper body  11  is disposed, a projection or the like (not shown) fittable in the notch  17  is provided, and the positioning may be made by engaging the notch  17  to the projection upon the disposition of the body. The adhesive agent  14  is then applied to predetermined zones on the one surface  11   a  of the body  11  by means of a biaxial coating robot  20 . A proper amount of the adhesive agent  14  can be applied uniformly onto the corrugations  12  therealong, without being applied excessively to fill up grooves in the corrugations. While the biaxial coating robot  20  has been referred to as means for applying the adhesive agent  14 , the invention is not limited thereto but any other proper means may be employed.  
         [0020]    The damper body  11  coated with the adhesive agent  14  at two zones substantially parallel with each other as shown in FIG. 3 c  is left to stand for a predetermined period to dry the agent.  
         [0021]    As shown in FIG. 3 d,  the tubular knitted tinsel cord  13  cut into a predetermined length at every disposition and having soldered parts  15  at both ends is placed on a combining molding die  21  as folded back at the central portion hung around a center hook  21   a  of the die  21  to lie substantially in parallel. The combining molding die  21  comprises a base die  21 A including a damper mounting part  22   a  having the center hook  21   a,  and a pressure mold  21 B disposed on the base die  21 A, the damper body  11  is mounted on the damper mounting part  22   a  configured substantially the same as the damper body  11 , with the one surface  11   a  faced to the mounting part  22   a  and with the notch  17  positioned between the parallel folded back portions of the tinsel cord  13 , and the body  11  is pressed against the cord  13  by means of the pressure mold  21 B. At this pressing step, no heat is applied, and it is possible to restrain the adhesive agent  14  from being fused to adhere to the die  21 A so as to contaminate therearound.  
         [0022]    Then the damper body  11  to which the folded-back tinsel cord  13  is bonded, as shown in FIG. 3 e,  is released from the die  21 , soldered parts  16  are provided to the tinsel cord  13  at positions along the inner peripheral edge of the body  11 , and an excess central folded-back portion  16   a  of the cord outside the soldered parts  16  is cut off. In cutting the excess portion  16   a,  as shown in FIG. 3 f,  certain extent of the portion out of the soldered parts  16  may be left or the portion may be completely removed.  
         [0023]    [0023]FIG. 4 a  shows another embodiment of the center hook  21   a  of the molding die  21 A, in which the tubular knitted tinsel cord  13  is hung around outer periphery of a disk-shaped part  21   c  having a short columnar part  21   b,  and the disk-shaped part  21   c  has an outer configuration fittable into the aperture  18  of the damper body  11  (FIG. 1). FIG. 4 b  shows a further embodiment of the hook, in which a columnar part has in outer periphery thereof a guide groove  21   d  for hanging therein the tubular knitted tinsel cord  13 , so that the cord can be prevented from being deviated.