Abstract:
A latch system employs momentum exchange impact damping. A latch is slicleably arranged within a housing so that the latch can slide between a latch position and a release position. A damper spring urges a damper against a wedge of the latch. When a mechanical impact urges said latch toward the release position, the latch wedge impacts the damper so as to exchange momentum from the latch to the damper so that the latch remains in the latch position.

Description:
BACKGROUND 
       [0001]    Latches can generally be actuated inadvertently. Such inadvertent latch actuation can result in undesired unlatching of a secured item. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a bottom view of a latch system. 
           [0003]      FIG. 2  is a side sectional view of the latch system of  FIG. 1 . 
           [0004]      FIG. 3  is a flow chart of a method according to which the latch system of  FIG. 1  responds to an impact and to a continuous force. 
           [0005]      FIGS. 4-11  are side sectional views of the latch system of  FIG. 1  at different stages of the method of  FIG. 3 . 
           [0006]      FIG. 12  is a rear perspective of an all-in-one computer including the latch system of  FIG. 1 . 
           [0007]      FIG. 13  is a rear perspective view of the computer of  FIG. 12  is a service position with a cover removed. 
           [0008]      FIG. 14  is a perspective view of a stand of the computer of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    All-in-one computers integrate computing components and a display into a single housing. Some all-in-one computers provide an access panel on the back (the side opposite the display) for servicing and upgrades (e.g., installing memory). The access panel may be covered by a hinged stand when the all-in-one computer is in a shipping position. 
         [0010]    For servicing, the all-in-one computer can be laid display-down on a surface. The stand can be pivoted to and latched in an open position to provide access to the access panel and, when the access panel is removed, to the interior of the all-in-one computer. If the latch inadvertently fails, the stand may collapse toward a closed position, potential injuring a hand or fingers of a user or technician working on the computer. 
         [0011]    A latch system AP 1 , shown in  FIGS. 1 and 2 , prevents a sudden unintended collapse of a hinged assembly without requiring detents that can fail due to wear and tear. Latch system AP 1  includes a latch mechanism  11  and a hinge  13 . Hinge  13  includes a strike plate  15 . Latch mechanism  11  includes a latch housing  19 , a latch  20 , a latch spring  21 , an impact damper  23 , and a damper spring  25 . Latch  20  includes a wedge  27 , an elongated shaft  29 , a damper stop  31 , and a spring stop  33 . Shaft  29  extends at least partially through damper  23 , and latch spring  21  extends at least partially through damper spring  25 . 
         [0012]    Operation of latch system. AP 1  is in accordance with a method ME 1 , flow-charted in  FIG. 3 . Method ME 1  begins at method segment M 1  with latch system AP 1  in latch position, which is the situation in  FIGS. 1 and 2 . In particular, latch  20  is urged forward to a latch position against a feature of latch housing  19 . Damper  23  is urged by damper spring  25  against the back of damper stop  31  of latch  20  so that impact damper  23  abuts latch  20 . 
         [0013]    From method segment M 1 , method ME 1  divides into an “impact” branch B 1 , and a “continuous-force” branch B 2 . At method segment M 12  of branch B 1 , strike plate  15  impacts latch wedge  27  so as to direct latch from its latch position toward a release position (in which latch spring  21  would compress). This impact is indicated by the transition between  FIG. 4  (in which strike plate  15  is moving toward latch wedge  27 ) and  FIG. 5  (in which strike plate  15  is contacting latch wedge  27 ). As a result of the impact, momentum is transferred to latch  20 . 
         [0014]    Instead of responding to this impact by moving toward a release position, latch  20  exchanges its momentum with abutting damper  23 , at method segment M 13 . This causes damper  23  to move in the release direction, compressing damper spring  25  at method segment M 14 , during which damper  23  separates from and no longer abuts latch  20  (as shown in  FIG. 6 ), which remains in its latch position. At method segment M 15 , damper spring  25  forces damper  23  back against latch stop  31  so that damper  23  again abuts latch  20 , as indicated in  FIG. 7 . Since latch  20  did not exit the latch position, strike plate  15  does not clear latch wedge  27 . In the context of a monitor stand, collapse is prevented. 
         [0015]    At method segment M 22  of branch B 2 , hinge  13  is moved under a user&#39;s control to a folding position, as indicated in  FIG. 8 . When strike plate  15  contacts latch  20 , latch stop  31  engages damper  23 , as indicated in  FIG. 9 . At method segment M 23 , further continuous force from the user causes latch  20  and damper  23  to move toward the release position together, as indicated in  FIG. 10 . At method segment M 24 , strike plate  15  is able to clear latch  20 , as indicated in  FIG. 11 . At method segment M 25 , damper spring  25  and latch spring  21  restore damper  23  and latch  21  to the latch position. 
         [0016]    Latch system AP 1  is used in the context of an all-in-one computer  50 , shown in  FIG. 12 . All-in-one computer  50  is shown having a body  51 , a stand  53 , and a service cover  55 . Cover  55  can be removed to expose computer internal components, e.g., for adding or replacing a memory module, as shown in  FIG. 13 . 
         [0017]    In  FIG. 13 , computer  50  is shown in a service position with stand  53  in a fully open position with respect to a hinge bracket  57 , which is attached flush to computer body  51 . Cover  55  has been removed from body  51  to provide access to internal components of computer  50 , e.g., so that memory modules can be added. A hinge cover  59  includes a release  61 , for releasing stand  53  from a fully open position. If stand  53  suddenly collapses toward a closed position (against body  51 ) and onto a user&#39;s hand (e.g., while the user is inserting a memory module), injury could result. Latch system AP 1  helps prevent such a collapse and associated injury. 
         [0018]    Stand  53  is shown in greater detail in  FIG. 14  with hinge cover  59  removed. Hinge springs  63  urge stand  53  to close. A locking mechanism is designed to prevent this closing until release  61  is activated. However, if the locking mechanism fails, latch mechanism  11  prevents stand  13  from suddenly closing. 
         [0019]    In the context of stand  53 , latch system AP 1  positively stops the stand when accidentally released from the fully open position. Unlike the conventional friction detent system, where the performance of the detent deteriorates with the wear of the detent features, the performance of latch system AP 1  does not change with repeated use. Latch system allows the user to switch the stand between service and shipping positions without any manual operation of the latch. Unlike the detent based stand system, latch system AP 1  operates with continuous force feedback and results in an enhanced user experience. Latch system AP 1  can be totally enclosed in a housing hidden from the user and is not subject to mishandling, confusion, or damage. 
         [0020]    While a conventional latch system can be designed to automatically lock and release the hinge during the normal user operation, it may not stop the accidentally released stand. The forces involved in normal user operation of the stand and the accidental release of the stand are very much different in nature. While the force applied to the stand by a user during a normal operation is static in nature, the forces resulting from an accidental release of the stand are dynamic in nature. The dynamic force of the closing stand can easily overcome the spring force of the latch if the latch is designed to move in either direction: release and lock. If a very stiff spring latch or a detent is used, it may be set to stop the accidentally released stand, but the user operation of such stand may involve a large force to overcome the spring or detent force, interfering with usability. If a deadbolt type latch is used, the action is in one way and may involve a user to manually release the latch. Latch system AP 1  combines a two-way sliding latch system and an impact-damper system so as to provide for stopping the accidentally released stand as well as to release it without additional means of manually controlling the latch. 
         [0021]    Latch system AP 1  can stop an accidentally closing stand before it reaches a point where a user&#39;s hand may be trapped between the closing stand and the chassis of the monitor. The engagement of the latch with the accidentally closing stand is accomplished by utilizing the dynamic response characteristics of the latch system to the impulse input. The response of the latch system to a static force input such as folding the stand automatically releases the latch from the locked position. A computer or monitor product that incorporates latch system AP 1  may omit conventional shipping detent mechanisms in the stand hinge; therefore, the folding and unfolding of the stand involves a minimum force; the operation of the stand is smooth with steady force feedback. 
         [0022]    Latch system AP 1  also provides audible feedback to the user when the unfolding stand reaches the closed service position. Latch system AP 1  includes three main functional assemblies, stand hinge, sliding latch mechanism, and impact damper assembly as shown in  FIG. 1 . Strike plate  15  is a part of the stand hinge system and rotates about the axis of the hinge shaft when the stand is operated. Strike plate  15  is a metal part formed with a curved surface and is located on the hinge so that it interfaces with a wedge profile of the sliding latch. 
         [0023]    The interaction between strike plate  15  and sliding latch  20  changes the direction of the force imparted by the closing stand to a direction that is parallel to the axis of the hinge. This change of direction of force also dissipates some of the impact energy through friction and reduces the linear momentum of the sliding latch, making it more manageable by the impact damper assembly. The strike plate may be formed from a part of the conventional hinge system by modifying it with a contoured surface. Or, it may be a separate metal part that is added to the conventional hinge axis. 
         [0024]    The spring constants of the return springs of the latch and the damper are determined so that the combined spring force can overcome the spring torque of the stand hinge spring so that the latch stays engaged in a closed position after the transient of the impact response. When the user opens the stand from the completely folded shipping position, the return spring automatically pushes the latch in the armed position and provides the user with the audible feedback that the stand is fully unfolded to the service position. 
         [0025]    When the speed of the closing stand is high as in the case where the open stand becomes accidentally released ( FIGS. 3-7 ), the interaction between stand, sliding latch, and impact damper is dynamic in nature. When the stand is accidentally released from the fully opened position, the potential energy stored in the hinge spring is converted into a kinetic energy. A part of this energy is imparted upon the sliding latch through the interaction between the strike plate and the wedge end of the sliding latch. This energy is transferred to the sliding latch and the linear momentum sets the latch in motion towards the impact damper. However, because the impact damper mass abuts the latch mass by the preloading return spring, the imparted linear momentum is transferred to the mass of the impact damper without moving the latch mass. 
         [0026]    The linear momentum sets the mass of the damper in motion away from the latch while the sliding latch stays in position so that the impact damper does not abut the latch. The rebounding damper mass counters any transient motion of the latch. Since the latch does not move enough distance, the strike plate of the stand cannot clear the latch and the stand stops at the latch position at the end of the impact transient. The combined force of the return springs on the sliding latch and the damper overcomes the spring torque of the hinge spring and the stand remained stable at the latch position after the transient. 
         [0027]    When the speed of the closing stand is low as in the case ( FIGS. 8-11 ) where the user tries to fold the stand beyond the safety latch position for storage or shipping, the interaction between the three bodies are static in nature. The impact damper is degenerated as a simple spring and the sliding latch and the damper mass move together as the user pushes the stand down to the shipping position. As the stand closes, the force applied to the stand by the user is amplified by the long moment of the arm of the stand and easily overcomes the return spring force. The strike plate clears the sliding latch and the stand reaches the fold position. 
         [0028]    Alternative latch systems can be used in various types of stands and in other contexts to provide ready intended motions while preventing sudden motions in response to impacts. Different dimensions of the latch and other components can be employed, as can different materials. These and other variations upon and modifications to the illustrated latch system are provided for by the following claims.