Abstract:
This invention includes a latch member for a latch assembly, suitable for a removable battery package. The latch member accommodates attachment to a latch coupler of an electronic device. A resilient, springy-metal, deflectable latch member is provided. The latch member includes arms for coupling with a latch coupler, a locking arm for adhering to a plastic housing, and spring arms that cause a torsion element to twist when force is applied to the arms. The torsion element is at least twice as long as it is wide, and provides reliable return force despite a short travel length of the arms. The latch member is suitable for battery packages in which space is a premium.

Description:
BACKGROUND 
     1. Technical Field 
     This invention relates generally to latch devices, and more particularly, latch devices for removable battery packages for portable electronic products. 
     2. Background Art 
     Portable electronic devices, such as two-way radios, telephones, electronic games and personal data assistants for example, often have removable battery packages for supplying power. In many such configurations, a removable battery package is secured to a host electronic device by a latch system. The latch system ordinarily includes a portion situated on the battery package, and a portion situated on the host device. These portions then mate together to secure the battery package to the host device. 
     In one prior art approach, the latch system includes a catch on the battery package that engages a movable latch member on the host device. A user removes the battery package from the host device by pushing on the movable latch member to disengage the latch member from the catch. One problem with this approach is the cost of repair when the movable latch member on the host device is defective or is otherwise damaged. The host device must often be disassembled to replace the movable latch member, which can result in substantial expense. 
     Additionally, although the primary function of latch assemblies is to retain the battery to the electronic device, battery latches are typically required to perform multiple tasks as well. For example, the latch is used to ensure a snug, rattle-free fit between the battery and the electronic equipment. Furthermore, the latch often carries the burden of providing drop protection for the entire battery assembly. The difficulty associated with latch design optimization is compounded by often-competing design requirements. For example, while the latch should be designed to provide a snug fit between the battery assembly and the equipment housing (i.e., preventing disengagement when the product is dropped), the user must be able to engage and disengage the battery housing with minimal effort. 
     Manufacturers of portable electronic equipment are constantly trying to improve latch designs to meet these aforementioned requirements, often under cost and manufacturing constraints. For example, commonly assigned U.S. Pat. Nos. 5,607,792, issued to Garcia et al., and U.S. Pat. No. 5,895,729, issued to Phelps, III et al., each describe removable battery packages that incorporate reliable and efficient button latch assemblies for portable electronic devices. These patents are incorporated herein by reference for all purposes. Still, not withstanding these patents, design constraints—like space restrictions—within the battery pack sometimes preclude the use of these reliable latches. It would be therefore be desirable to have a similar type of latch mechanism that is as reliable and can be used in design environments where space is a premium. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an illustration of a commonly assigned, prior art latch assembly. 
     FIG. 2 is an illustration of a commonly assigned, prior art latch assembly. 
     FIG. 3 is an illustration of a springy-metal latch member in accordance with the invention. 
     FIG. 4 is an illustration of an exemplary battery housing for accommodating a springy-metal latch apparatus in member with the invention. 
     FIG. 5 is an exploded view of a latch member in accordance with the invention just prior to insertion into a battery housing. 
     FIG. 6 is an exploded view of a button prior to insertion into a battery housing in accordance with the invention. 
     FIG. 7 is an assembled battery housing in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” 
     Referring now to FIG. 1, illustrated therein is a commonly assigned, prior art latch assembly. FIG. 2 is a fragmentary, exploded, perspective view of the battery package  120 . The battery latch assembly  200  constitutes the portion of the battery latch system on the battery package. The battery latch assembly  200  is formed from a portion of a battery housing member  230 , a portion of a second battery housing member or battery cover  250 , a latch member  260 , and a button  270 . 
     The battery housing member  230  is preferably formed from plastic in a single piece mold construction. The battery housing member  230  has a latch mount portion  232  in the form of a recess or cavity in the battery housing member  230 . The latch mount portion  232  is defined by a plurality of sidewalls  241 ,  242 , and  243 , that form the surfaces of the latch mount portion  232 . Projections  245  extend from at least one surface  243  to define a narrow or restricted access latch member mount channel. The latch mount portion  232  further includes a raised portion or projection  235  extending within the cavity that forms a retention member or stop for the latch member  260 . Thus, the projections  245  form mount guides for mounting the latch member  260 , and the raised portion  235  serves to secure the latch member  260 . 
     The latch member  260  is a resilient cantilever structure preferably formed from stamped sheet metal. In one preferred embodiment, the latch member  260  includes two resilient cantilever arms  262 ,  264  connected by a bridge member  265 . Each cantilever arm  262 ,  264  has a latch portion, or catch  266 ,  268 . Preferably, the catch is a slot extending through an end portion of the cantilever arm. 
     The button  270  is preferably formed from molded plastic. The button  270  has finger grip portion  275  formed on a platform  271 . A mount base  273  extends from beneath the platform to form a groove  274  between the platform  271  and the mount base  273 . A protrusion  272  extends from the mount base  273  to form a stop or locking feature for the latch assembly. 
     The battery cover  250  is preferably formed from molded plastic. The battery cover  250  attaches to the battery housing member  230  to form an enclosure. The battery cover  250  has an overhanging wall portion  252  extending over the latch mount portion  232  of the battery housing member  230 . The battery cover  250  has a button hole  255  for accommodating the button  270 . The button hole  255  is preferably sufficiently large to allow the finger grip portion  275  of the button  270  to have a lateral range of movement within the button hole. The battery cover  250  also has a passage  251  extending therethrough that provides access to the latch member  260 . A notch  253 , formed along a surface defining the passage  251 , accommodates the protrusion  272  of the button to support the locking and unlocking feature of the latch assembly. 
     Referring now to FIG. 2, illustrated therein is another commonly owned, prior art latch assembly solution. The battery housing portions are identical to those recited in accordance with FIG.  1 . The difference between FIG.  1  and FIG. 2 lies in the cantilever arms  62 ,  64  of FIG.  2 . Here, the cantilever arms are bent away from the plane of the bridge member  265  to create a pre-loaded spring force against the button  271 . 
     From both FIGS. 1 and 2, it will be noted that the spring force exerted against the buttons is delivered by the cantilever motion of the arms. For example, again referencing FIG. 2, the bridge member  265  is held in a fixedly rigid position by the latch mount portion  232  of the battery housing  230 . This fixed relationship allows the latch mount portion  232  to hold the bridge member  265  steady while the button  271  exerts force on the cantilever arms  62 ,  64 . In effect, the latch mount portion  232  acts as a fulcrum for the cantilever arms  62 ,  64  to work against. This type of scheme works well when the housing  230  allows enough room for molding a plurality of sidewalls  241 ,  242 , and  243 , projections  245 , and a raised portion  235 , all of which are part in parcel of the latch mount portion  232 . 
     As electronic devices have gotten smaller and smaller, however, designers have less and less room in which to include features like a latch mount portion. This invention thus resolves this issue by offering an improvement over the prior art in that no latch mount portion is required. 
     Referring now to FIG. 3, illustrated therein is an improved springy-metal latch member  300  in accordance with the invention. The latch member  300  is a resilient structure preferably formed from stamped, springy, sheet metal. Like the prior art, the latch member  300  includes a bridge member and two arms  302  for receiving a button. 
     The bridge member  301  includes a pair of integral locking tabs  303  disposed angularly above the plane of the bridge member  301 . Each locking tab  303  includes a v-shaped notch  304  that is used to hold the latch member  300  in a battery housing. The v-shaped notch  304  performs the dual function of keying the latch (i.e., instructing an assembler as to which way to insert the latch member into a battery housing). It will be clear to those of ordinary skill in the art that it is not necessary for the notch to be v-shaped, as other notch shapes will work equally well. 
     The arms  302  are angled upwards to provide a preloaded force, and latch portions or catches  306  extend through an end portion of each respective arm  302 . A button may be inserted between the arms  302 . Once received, the button is locked in place between first and second pairs of tabs  305  extending inwardly from the arms  306 . 
     The improvement of the latch member  300  lies in the actuation of the arms  302 . Whereas the prior art relied upon a latch mount portion to act as a fulcrum for cantilever arms, the present invention employs curved spring arms  307  that provide a return force for the button. When the spring arms  307  rest against a battery housing, they form rigid members relative to the bridge member. The bridge member  301  has been designed to include a torsion element  308  that twists when force is applied to the arms  302 . Rather than actuating a purely cantilever motion, the latch member  300  uses torsion to provide return force. This allows the latch member  300  to operate in design environments where space does not allow a full-blown latch mount portion. 
     To provide the proper torsion, the bridge member  300  must be properly designed to provide torsion elements  308  that are capable of twisting without breaking or deforming. The length of the torsion element  308 —length being defined as the distance between the spring arm  307  and the arm  302 —must be at least a certain proportion to the width  309  of torsion member  308 . Experiments and finite element analysis have shown that this ratio must be at least 2:1. In other words, the length of the torsion element  308  must be at least twice the width. In one preferred embodiment, experiments yielded reliable performance at a ratio of 4:1. This ratio provided reliable spring force across thousands of cycles with no cracking, breaking or deformation. 
     Referring now to FIG. 4, illustrated therein is an exemplary housing  400  in which the latch member may operate. As can be seen from the figure, the depth of the upper housing  405  is too shallow to accommodate a latch mount portion. In its stead resides a series of small notches  401 ,  403 , and  404  that simply guide the latch member into the housing. These notches,  401 ,  403 , and  404  assist the technician in aligning the latch member at assembly. 
     Apertures  404  are present in the upper housing  401  for receiving the v-shaped notches of the locking tabs of the latch members. Additionally, a thin, flat stabilization plane  406  is provided to accommodate the spring arm of the latch. Optional end slots  407  may also be included to provide additional support to the torsion elements. 
     The invention offers numerous advantages over the prior art. The spring fingers, which help facilitate the twisting of the torsion elements, also work to eliminate “play” within the housing. They provide a solid button-latch feel, with no looseness or wobble. Further, the torsion-action of the latch member allows the latch member to operate in design environments where space is at a premium. The torsion element provides a high force even though the travel distance of the arms may be relatively short. 
     Referring now to FIG. 4, illustrate therein is an exploded view of the latch member  300  just prior to insertion in to a battery housing  400 . A notch  310  on the bridge member  301  mates with a guide post  408  in the battery housing  400  to ensure proper alignment. The spring arm  307  will rest upon the stabilization plane  406  after insertion. The notch  304  on the locking arm  303  interfaces with the aperture  404  once the latch member  300  is seated in the battery housing  400 . 
     Referring now to FIG. 6, a button  600  may then interface with the arms  302  of the latch member. When the button is first inserted, the arms  302  travel away from the outer portion  409  of the housing. The button then slips into the button hole  410 . Both the ledge  601  on the button  600 , which interfaces with the button hole  401 , and the button itself interfacing with the tabs (element  305  of FIG. 3) ensure that the button will not dislodge from the housing. FIG. 7 illustrates the assembled battery housing. 
     While the preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims. For example, while one preferred embodiment recites the latch member being employed in a battery pack, other two-piece device requiring attachment may also employ the latch member.