Abstract:
A micro push-button assembly includes a pin which has a head, a shoulder, a neck and a chamfer at the distal end. Other elements include a spring, a washer, and a seal. This unitized push-button assembly has two opposing ends each with distinct functionalities. One end of the assembly includes means extending above the head for press-in captivation with an exterior button while the other end has means for press in captivation with a support member such as a wrist watch chassis. The assembly is provided to the watch manufacturer as a pre-assembled unit with the spring and seal already set onto the operating pin. The final press-fit assembly can be accomplished by hand.

Description:
RELATED APPLICATIONS 
       [0001]    This is a non-provisional patent application which is related to provisional patent application Ser. No. 62/127,511 entitled, “Micro Push-Button Assembly” filed Mar. 3, 2015 priority from which is hereby claimed. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a push-button assembly used in personal electronic devices such as wrist watches. More particularly, the invention relates to an assembly that connects a push-button to the chassis of the electronic device for actuating electrical switches or controlling other components within the electronic device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Very small push-buttons are used on wrist watches to control time setting and other functions of the watch. Currently, electronic watch manufacturers use a series of loose components assembled during the construction of the watch to secure the button to the watch chassis. The button assembly must seal the inside of the device and allow for actuation of an interior button through a more ergonomic exterior button. The loose components of prior art button assemblies include a grooved pin, a C-clip, a spring, a seal and a washer. The C-clip, which affixes the button assembly to the watch chassis, must be installed by hand from the side of the pin inside the watch in a very tight space. Performing this assembly task is difficult and time-consuming Therefore it would be desirable to provide a pre-assembled push-button assembly, which can be easily affixed to the watch and which voids the need to hand assemble many loose components. 
       SUMMARY OF THE INVENTION 
       [0004]    The push-button assembly in accordance with preferred embodiments of the invention is provided to the manufacturer as a pre-assembled unit with a spring and seal already assembled on an operating pin. The pin assembly includes a pin having a head, a shoulder, a neck and a chamfer at the distal end. The pin assembly also includes a spring, a washer, and a seal. This unitized pin assembly has two opposing ends each with distinct functionalities. One end of the pin includes means extending above the head for press-in captivation with an exterior button while the other end has means for press-in captivation with a watch chassis. Because the elements of the assembly can be fitted together in one direction, machine assembly rather than hand assembly is possible. Furthermore, this unitized, pre-assembly of parts makes the final assembly at the manufacturing site relatively easier, quicker and cheaper than the prior art. 
         [0005]    In preferred embodiments, the operating pin comprises, in order from top to bottom beginning immediately below a head, a shoulder, a shank having a narrowed neck portion, and a flange with a chamfer at a bottom distal end of the shank. A coil spring surrounds the shank neck portion and is operative between the flange above it and a seal below it, which captivates the spring to the pin. The pin reciprocates within a central bore of the seal, which has means on its exterior for attaching the pin to a support member. The seal is preferably elastomeric and has an exterior undercut. A washer may be interposed between the head of the pin and the seal. Button attachment means extends upwardly from the top of the head of the pin and is knurled so that it attaches the pin to a button receiving hole by simple manual press-fit. A support member such as a wrist watch chassis includes a receiving hole with a collar that engages the seal undercut to attach the push-button assembly to the watch chassis also by manual press fit. In one preferred embodiment, the button has a pair of laterally disposed guide fingers that engage and translate within apertures in the support member. 
         [0006]    In another preferred embodiment, the pin assembly further includes a button pre-assembled to the pin of the assembly described above. In this embodiment, the assembly can also be attached to the watch chassis by a simple manual press fit. 
         [0007]    The invention has many differences from the push-button devices of the prior art. Other differences and advantages will follow from the foregoing explanation and the following drawings and description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an assembly view of a push-button assembly in accordance with preferred embodiment with the components shown in cross-section along with a watch button and chassis; 
           [0009]      FIG. 2  is a side elevation of an assembled push-button assembly of  FIG. 1 ; and, 
           [0010]      FIGS. 3 a  and 3 b    are cross-sectional, assembled views of a push-button assembly connecting a watch button to a watch chassis showing the button in extended and depressed positions, respectively, in accordance with an embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]    A push-button assembly in accordance with a preferred embodiment of the invention is shown in  FIGS. 1-3  and is designated generally by reference numeral  10 . Referring to  FIG. 1 , the push-button assembly  10  generally comprises an operating pin  13 , a spring  23 , a washer  25 , and a seal  27 . In a preferred embodiment, the push-button assembly  10  is used, and described hereinafter, to connect a push button  11  to the chassis  29  of a watch. 
         [0012]    Referring to  FIG. 1 , the operating pin  13  has an upper knurled portion  15  and a head  17 , which are constructed and arranged to connect with a bore  16  in a watch button  11 . Preferably, the pin  13  is affixed to the button  11  by force fitting the knurled portion into an interior, textured receiving hole  16  in the button  11 . In other embodiments, the pin  13  could be affixed using other known fastening techniques including adhesives. 
         [0013]    Proceeding axially from the head  17 , the pin  13  also includes a shoulder  12  having a diameter smaller than the diameter of the head  17 , a shank neck  19  having a diameter smaller than the shoulder  12 , and a flange  21  having a diameter intermediate the diameters of the shoulder  12  and neck portion  19 . Preferably, the flange  21  has a chamfer  20  at the bottom most distal end. Preferably, the head  17  has the largest diameter on the pin  13  and includes a bottom surface  17 a that contacts one end of the compression spring  23 . 
         [0014]    The shoulder  12  preferably has a diameter slightly smaller than the inner diameter of the coil spring so that the coil spring  23  is centered on the pin when the spring  23  is mounted on and envelopes (wraps around) the shoulder  12 . The shank neck  19  is bounded above by the shoulder  12  and below by the flange  21 . 
         [0015]    The compression spring  23  is mounted over the shank neck  19  and shoulder  12  of the pin  13 . One end of the compression spring  23  abuts the bottom surface  17   a  of the head  17  and the other end of the spring  23  abuts a flat washer  25 , which has an outer diameter greater than the diameter of the spring  23 . The inner diameter of the washer is greater than the diameter of the flange  21  so that the washer  25  can be installed over the shank neck  19 . The washer  25  provides a stop at the bottom end of the spring  23 . Thus, the spring  23  is captivated between the head  17  and the washer  25 . 
         [0016]    A seal  27  is installed over the flange  21 . In this preferred embodiment, the seal  27  has a flat head  22 , an axial bore with a beveled mouth  24 , an undercut  26  and a tapered, frustoconical end  28 . Preferably, the seal  27  is composed of elastomeric material. The bore has an interior size and shape that compliments the exterior size and shape of the flange  21  so that the seal can be installed over and fit snugly on the flange  21 . The head  22  of the seal supports the washer  25  from below. The washer  25  can be a separate component as shown or could be incorporated into the seal  27  as a single piece. The chamfer  20  allows the seal to be easily installed on the flange in the assembly process described below. 
         [0017]    In this embodiment, the push-button assembly  10  is assembled by first placing the spring  23  over the neck portion  19 , around the shoulder  12 , and up against the bottom surface  17   a  of the pin head  17 . The washer  25  is then placed against the free end of the spring  23 . Lastly, the seal  27  is installed over the flange  21  with the head abutting the underside of the washer  25  to prevent the washer from being pushed back off. The chamfer  20  on the end of the pin and an internal bevel around the mouth  24  of the seal  27  allow the seal to easily stretch over the flange  21 . In preferred embodiments, the seal  27  is made of rubber or a similar material with good lubricity and elasticity. The central bore of the seal  27  mates resiliently with the neck  19  of the pin to provide a snug fit. 
         [0018]    In another preferred embodiment of the invention, the push-button assembly  110  includes a button  11  that is pre-assembled to the top of the pin  13  but otherwise has the same construction as the assembly  10  described above. In this embodiment, the push-button assembly  110  is assembled by first attaching the button  11  to the top of the pin  13 . The pin head  17  provides a positive stop that seats the pin  13  against the bottom face of the button  11 . The pin 13  is preferably press fit into the button  11 . The remainder of the assembly  110  is then assembled in the same manner as the assembly  10  described above. 
         [0019]    The seal  27  also functions to attach the assembly to a watch chassis  29 . To achieve this function, the seal  27  has the flat head  22 , the beveled mouth  24 , the undercut  26 , and the tapered, frustoconical end  28 . In a preferred embodiment, the watch chassis  29  has a hole  30  into which the push-bottom assembly  10  or  110  connects. The hole  30  includes an inner, relatively-thin collar  31 , which reduces the diameter of the hole  30  in that region. The push-button assembly  10  or  110  is connected to the chassis by simply pressing the assembly into the chassis hole  30 . By doing so, the seal  27  is compressed into the collar  31  and pressed down to a point where the seal undercut  26  snaps around the collar  31 . This structure resiliently clinches the assembly  10  or  110  to the watch chassis  29 . The flat shape of the seal around the bottom of the undercut prevents the assembly from easily pulling back over the collar  31  and out of the chassis  29 . 
         [0020]    A fully-assembled push-button assembly  10  is shown in  FIG. 2  in isolation without a button llor watch chassis  29  affixed thereto. The push-button assembly  10 , and likewise push-button assembly  110 , consists of unitized, joined components, which can be handled separately without additional components and which can be utilized as a universal sub-component that can be applied to numerous different button and support structure combinations. 
         [0021]    The components of  FIG. 1  are shown fully assembled in  FIGS. 3 a  and 3 b   . The push-button assembly  10  or  110  is shown in operation when attached to a watch chassis  29  as it is pushed and released. It will be appreciated by those of skill in the art that the various dimensions of the components are selected so that the action of the button  11  is compatible with the features of the watch chassis. For example, the bottom face of the button  11  should contact the chassis  29  when or just before the pin reaches its maximum point of extension. In this embodiment, a button  11  is shown having guide fingers  10   a  and  10   b  that are laterally disposed on opposite sides of the operating pin. The guide fingers  10   a,    10   b  slideably engage corresponding apertures in the chassis and provide lateral and torsional support to the button  11  during its movement. 
         [0022]    The embodiments of the invention described above provide a simplified, ergonomic button assembly that can be easily applied to a space-constricted chassis. Preferred embodiments of the invention are particularly suited for electronic watches. 
         [0023]    The foregoing description of preferred embodiments is to be considered illustrative only of the principles and possible embodiments of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. Accordingly, suitable modifications and equivalents may be resorted to, all falling within the scope of the invention which shall be determined only by the following claims and their legal equivalents.