Abstract:
An assembly that engages a component to a computer system includes a cover adapted to retain the component and to be inserted within a chassis of the computer system. A slide movably coupled to the cover has a proximal position associated with inserting the cover into the chassis and a distal position associated with withdrawing the cover from the chassis. A detector coupled to a lock and to the slide detects movement of the slide to actuate the lock. The lock is coupled to the slide and to the detector, and blocks movement of the slide towards the distal point when the lock is in an engaged state.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mechanical and electrical apparatus for connecting and disconnecting components of a computer system. More particularly, the present invention relates to such connecting and disconnecting components while the computer system is operating. 
     2. Description of Related Art 
     Computer systems such as file servers and storage servers in computer networks are relied upon by large numbers of users. When a file server or storage server is out of operation, many people are inconvenienced. Thus, technology has been developed which supports maintenance and service of computer systems while they remain operational. One part of maintenance and service includes the replacement of components. So-called hot swap technology allows the replacement of components without turning off the power or resetting the computer system as a whole. 
     Typical hot swap technology employs resources for signaling the system and components in the system about an intention to remove or replace a component. Also, the technology includes routines that stabilize communications among the components, and manage the distribution of power to components during the exchange. 
     The exchange of components on computer systems for maintenance and repair requires human operators. Human operators are prone to misuse or abuse the mechanical and electrical resources associated with hot swap technology. For example, an operator may attempt to withdraw a component from a computer chassis without first executing hot swap electrical routines to prepare the component. Also, with components that require significant force for engagement and disengagement, human operators may damage delicate parts of system while applying the force for engagement or disengagement. 
     Therefore, is desirable to provide a mechanism that reduces the possibility of misuse or abuse by human operators of mechanisms for engaging and disengaging components, and mechanisms for managing the electrical hot swap processes. 
     SUMMARY OF THE INVENTION 
     The present invention provides a mechanism that prevents premature disengagement of components of the computer system, and reduces the mechanical force needed to be applied by operators for the engagement and disengagement of components. Thus, an operator expects to apply a relatively light force to remove or insert a component on the computer system. The light force applied minimizes the chance of mechanical damage to the system. Also, the mechanism is able to block attempted removal of a component if the electrical processes necessary for hot swap have yet to complete. The combination results in a substantially more reliable system, less prone to damage during the hot swap operation. 
     According one aspect of the invention, a module is provided for computer system. The computer system includes a chassis having one or more slots for accepting the module. Processing resources associated with removing and inserting modules during operation are included in the computer system. The module according to the present invention comprises a cover adapted to fit within the slot in the chassis. A system component, such as a controller circuit board, disk drive array, or other data-processing resource is mounted with the cover. A connector coupled to the component includes a plurality of connection elements adapted to mate with corresponding elements in the computer system on the chassis. Means for preventing mishandling, such as those described in more detail below, are included. Such means include mechanical and electrical components which provide leverage for engaging and disengaging the component, and which communicate with the host system to prepare for electrical disengagement and engagement of the component. Also, such means include a lock or other mechanism for preventing the mechanical disengagement of a component when the system has yet to electrically prepare for the disengagement. 
     According to one embodiment of the invention, a mechanism for providing leverage for engagement and disengagement of the component in the cover is included. The mechanism includes a slide mounted on the cover. A pivotal connection is provided near a distal end of the slide. The proximal end of the slide is adapted to extend outside the cover, and act as a handle for an operator. The lever system is coupled to and actuated by movement of the slide. The lever system provides for balanced engagement of the component with the connectors in the host system. 
     In one preferred embodiment, the slide is movable among an inserted position, at least one intermediate position and an extended position. The lever system translates movement of the slide in the direction from the intermediate position to the extended position into force causing disengagement of the connector, and translates movement of the slide in the direction from the extended position to the intermediate position into force for engagement of the connector. A portion of the motion from the inserted position toward the intermediate position provides a dead region, in which no force is translated from the slide through the lever system to tend to disengage the component. This dead region is utilized for sensing motion, to enable electronic lock to prevent further disengagement if the system has not prepared for it. 
     In another preferred embodiment a lock is included which prevents motion of the slide from being translated to disengagement force. The lock is coupled to the host system, and engages the slide when the host system has not finished preparing for the disengagement. In one preferred system, power is normally not applied to the lock. In this embodiment, the lock includes a mechanical stop which prevents motion until the operator applies an enabling act, such as depressing a spring loaded tongue element. When the enabling act is executed, power is applied to the lock. Unless the system signals that it is ready for disengagement, the lock prevents further disengagement action. 
     The lever system in a preferred embodiment comprises first and second lever arms coupled to a pivotal connection near the distal end of the slide. The first lever arm extends toward a first lateral edge of the cover. The first lever arm is coupled to a fulcrum near the first lateral edge. The opposite end of the lever arm is coupled to an engagement member adapted to engage with a mechanical stop on the chassis. The second lever arm extends to the second lateral edge of the cover. The second lever arm is coupled to a fulcrum near the second lateral edge. The opposite end of the second lever arm is coupled to a second engagement member. For balanced operation, the first and second lever arms are essentially the same length and apply substantially equal force in response to motion of the slide. The engagement member in this embodiment is connected near the lateral ends of the respective lever arm. The engagement member is biased via a spring to swing outward to engage a mechanical stop on the chassis. During engagement, the spring tends to force the engagement member to extend outside the cover and engage the mechanical stop. The lever arm acts to apply an engagement force against the mechanical stop. During disengagement, the lever arm acts to reverse the engagement force. Also first and second retraction arms are coupled respectively with the first and second lever arms. A retraction arm is coupled to the engagement member and to a pivotal connection on the slide, such as the same pivotal connection to which the lever arm is connected. The retraction arm acts in response to motion of the slide towards the retracted position to pull against the force of the spring and withdraw the engagement member inside the cover to allow removal of the component. 
     In yet another embodiment, the host system includes a graphical user interface or other interface allowing an operator to signal the system of an intention to remove a component. In response to the operator signal, the host system performs power management and communication management routines to prepare the system for a hot swap operation. Until the power and communication management routines have been completed, the lock associated with the component to be removed is set in a position to prevent removal. 
     The present invention provides mechanical and electrical components which improve the reliability of systems with hot swap capability, and make such operations more easily executed. 
     Further aspects and advantages of the present invention can be seen upon review of the figures, the detailed description, and the claims which follow. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a front view of a computer system employing the concepts of this invention. 
     FIG. 2 is a top view of a cover under this invention showing a slide in an inserted position. 
     FIG. 3 is a top view of the cover of FIG. 2 with the slide in the extended position. 
     FIG. 4 is a back view of the cover in FIG.  2 . 
     FIG. 5A is an isometric close-up of an interior portion of the cover showing a lock and the slide in a first stage. 
     FIG. 5B is an isometric close-up of the interior portion of the cover showing the lock and the slide in a second stage. 
     FIG. 5C is an isometric close-up of the interior portion of the cover showing the lock and the slide in a third stage. 
     FIG. 6A is an isometric close up of an interior portion of the cover showing an assembly of components for inserting the cover into a chassis, the assembly of components being in the first stage. 
     FIG. 6B is an isometric close up of an interior portion of the cover showing an assembly of components for inserting the cover into the chassis being in the second stage, the assembly of components being in the second stage. 
     FIG. 6C is an isometric close up of an interior portion of the cover showing an assembly of components for inserting the cover into the chassis being in the third stage, the assembly of components being in the third stage. 
     FIG. 7 is an isometric close-up of a pivot connection used with an embodiment of this invention. 
     FIG. 8 is a plan view of alternative embodiment of a module cover according to the present invention, the slide being in a fully inserted position. 
     FIG. 9 is a plan view of the embodiment of FIG. 8, the slide being in a first intermediate position. 
     FIG. 10 is a plan view of the embodiment of FIG. 8, the slide being in a second intermediate position. 
     FIG. 11 is a plan view of the embodiment of FIG. 8, the slide being in a fully withdrawn position. 
    
    
     DETAILED DESCRIPTION 
     A detailed description of embodiments of the present invention is provided with reference to the figures, in which FIG. 1 shows a computer system chassis  100  having a plurality of modules and a graphic user interface  160  according to the present invention. The computer system chassis  100  has a face  145  through which components are added to and communicate with the host processing system in the chassis  100 . The components are engaged to communicate with the host processor through a corresponding slot or opening in the face  145  of the chassis  100 . The data processing resources in a preferred system provide storage services for a network of computers. In such preferred system, the components include memory modules, such as large arrays of flash EPROMs or disk drives storing large amounts of information. In addition, network interface components are included supporting a network architecture to provide memory services to many users. The host system in the chassis  100  further includes processing resources associated with removing and inserting modules during operation of the host. 
     The components are mounted in covers that are removably mounted on the chassis  100  through the slots in the face  145 . Such components include controller circuit boards, disk drives, memory circuit boards and other devices having resources for communicating with the host system. In the simplified example shown in FIG. 1, modules  110 ,  115  and  120  are arranged vertically in the face  145 . The modules  110 ,  115  and  120  each include handles  111 ,  116 ,  121 , and respective covers as shown in more detail in FIG.  2 . The handles  111 ,  116 ,  121  are engaged with a mechanism on the respective cover for locking the component within the chassis  100  when the host system is operational. For applications having connectors with large numbers of I/O pins, a handle is coupled with a mechanism providing leverage for insertion force. 
     As represented schematically in FIG. 1, other modules  125 ,  130 ,  135  are shown in the face  145 . These modules are formed in alternative configurations, such as in a horizontal alignment relative to the chassis  100 . Such alternative modules may include disk drive arrays or other types of components designed for operation with the host system. In the example shown the additional modules  125 ,  130  and  135  include handles  126 ,  131  and  136  adapted for coupling with a locking mechanism and an assembly for translating motion of the handle into insertion and removal force for the component. 
     Also shown in FIG. 1 is a graphic user interface GUI  160 . The GUI  160  provides an interface for operator of the device. The interface is monitored by control processes in the host system for managing hot swap operations. Thus, the GUI includes a module select window having graphical buttons  161 ,  162  and  163  by which users are able to select modules and functions related to such modules for execution by the processes in the host system. Thus logic within the host system is coupled to the interface for managing the preparation of communication systems and power management resources for removal and insertion of components. In one embodiment, the GUI  160  also acts to signal the operator when the component is ready for removal, and the host system is no longer overriding the lock mechanism on the component. 
     The modules, such as module  110  of the system include a component mounted within a cover. The cover includes structure for securing a connector for connection of the component to the system communication structure, and a mechanism for engaging and disengaging the module with the system chassis. Also a mechanical lock is included with the cover which is engaged to prevent removal of the module unless the system has released the lock. FIGS. 2-7 illustrate one embodiment of the cover. FIGS. 8-11 illustrate an alternative embodiment of the cover. Both embodiments include means for engaging and disengaging the a module according to the present invention. The illustrated means constitute preferred embodiments of the present invention. Other mechanisms based on a lever system, and an engagement member coupled to the lever system are also suitable alternatives. Also, a lock mechanism is provided for preventing operation of the lever system under system control. 
     FIG. 2 illustrates one embodiment of a cover  200  according to the present invention. The cover  200  includes a front face  201  which includes a variety of structures (e.g.  202 ,  203 ) which provide openings for switches, connectors and indicators intended to be visible through the cover. The cover  200  includes a back face  204  against which an array  205  of connectors is mounted for establishing electrical communication with the host system bus. The cover includes a left side wall  206  and a right side wall  207 . The cover  200  includes a base plate on which guides  208  and  209  are mounted. A slide  210  is positioned between the guides  208  and  209 , and is moveable between an inserted position as illustrated in FIG. 2, an intermediate position, and a withdrawn position as illustrated in FIG.  3 . 
     A pivot  211  is mounted on the slide  210 . The pivot  211  is constructed using a riser secured to the slide  210  and extending upward from the plane of the drawing. The pivot  211  is adapted to receive a first lever arm  212  and a second lever arm  213 . The first lever arm  212  extends from the pivot  211  through a fulcrum  214  near the left side  206  of the cover. Opposite the fulcrum  214 , a second end  216  of the first lever arm  212  is connected to an engagement member  218 . The engagement member  218  includes a hook  220  adapted to engage a mechanical stop (not shown) on the chassis. In a similar fashion, the lever arm  213  extends through a fulcrum  215  on the right lateral side  207  of the cover. A second end  217  of the lever arm  213  is coupled to an engagement member  219 . The engagement member  219  includes a hook  221  adapted to engage a second mechanical stop (not shown) on the chassis. 
     Structural plates  250  and  251  secure the fulcrums  214  and  215  for the lever system. The lever system illustrated in FIG. 2 provides gain in force between 10 to 1 and 20 to 1. This gain is important for engagement of covers and components that include large arrays of connectors  205 , such as hundreds of connectors, which require engagement force on the orders of tens to hundreds of pounds. Other lever systems are suitable for use as well. Also in some systems which require less engagement force, the mechanical gain is not as important. 
     The use of the first and a second lever arms  212 ,  213  provides for essentially balanced operation of the engagement members  218 ,  219 . 
     Although not shown in FIGS. 2 and 3, the first lever arm  212  and second lever arm  213  have elongated openings near the pivot  211  which allow for sliding engagement with the pivot  211 . 
     As can be seen, operation of the slide  210  causes the lever arms  212  and  213  to rotate on the respective fulcrums  214 ,  215 . In the inserted position as shown in FIG. 2, the engagement members  218  and  219  are pulled toward the front face  201  of the cover under an engagement force caused by the lever action. As the slide  210  is withdrawn from the cover, the engagement members  218  and  219  are pushed away from the front face  201 , allowing disengagement of the hooks  220 ,  221  from a chassis. 
     Retraction arms  222  on the left side and  223  on the right side are also coupled to the pivot  211 . These retraction arms could be coupled to other pivot points associated with the slide  210  if desired. The retraction arm  222  is coupled to a spring  224  which tends to pull the lateral end  226  of the retraction arm  222  toward the back face  204  of the cover. The lateral end  226  of the retraction arm  222  is coupled to the engagement member  218  at a pivot  228 . The spring  224  through this connection tends to rotate the engagement member  218  in a counter-clockwise direction out of the side  206  of the cover in order to engage the chassis. 
     The retraction arm  223  extends to the right side engagement member  219 , and is coupled to a spring  225  at a lateral end  227 . Also, the lateral end  227  is connected to a pivot  229  on the engagement member  219 . The action of the spring  225 , connected in this manner, tends to drive the engagement member  219  in a clockwise direction out the side  207  of the cover. 
     The system shown in FIG. 2 also includes a lock mechanism  260  generally coupled with the slide  210 . The lock mechanism includes a pawl  261  mounted on a pivot  262  coupled to the slide  210 . A spring  263  tends to cause the pawl  261  to rotate in a counter-clockwise direction. A mechanical stop  264  is mounted on the cover  200  adjacent the slide  210 . The rail  209  includes an angular surface  265  against which the pawl  261  tends to rotate as the slide  210  is withdrawn. A solenoid  266  is mounted above the pawl  261 . The solenoid  266  includes a pin not shown which is normally in a withdrawn position. When the pin is withdrawn, the pawl will rotate outward and engage the mechanical stop  264  to prevent withdrawal of the slide  210 . If the solenoid  266  is engaged, the pin will extend downward, and prevent the pawl  261  from rotating outward to engage the stop  264 . Thus, when the pin is extended, the slide  210  will be freely withdrawn past the lock mechanism, and allow disengagement action of the lever arms and retraction arms as described above. Otherwise, the lock will act to prevent disengagement of the cover until the pin on the solenoid  266  is extended. 
     The lock also includes a spring loaded tongue element  267 , or other element requiring an operator action to begin the withdrawal process. A switch  268  is coupled with the tongue element  267 . The tongue element  267  includes a ridge  269  which tends to engage a bar on the cover, or the chassis, and prevent motion of the slide  210 . When an operator the presses the tongue element  267 , the ridge  269  is lowered below the bar on the cover and the switch  268  is engaged. The switch  268  enables the solenoid  266 . A signal provided by the host system controls the solenoid  266  so that it remains in the withdrawn position unless the system is ready for withdrawal of the component on the cover. If the system is ready for withdrawal, the solenoid  266  extends the pin downward and allows withdrawal of the slide  210 . 
     As the slide  210  is withdrawn from the fully inserted position as shown in FIG. 2 to the intermediate position at which the pawl  261  engages the mechanical stop  264 , there is essentially no disengagement force applied to the engagement members  218 ,  219  because of the sliding engagement of the lever arms  212 ,  213  with the pivot  211 , and the relatively small distance traversed by the slide. Furthermore, because little force is needed to cause motion of the slide, the operator will not tend to pull too hard and damage the system. The motion from the fully inserted position to the intermediate position allows for detection of the attempted withdrawal of the component, and prevention of that withdrawal if the system has not prepared for it. 
     FIG. 3 illustrates the cover and lever assembly of FIG. 2 with the slide  210  in the withdrawn position. In this position, the lever arms  212 ,  213  pivot around the respective fulcrums  214 ,  215  and cause the engagement members  218 ,  219  to be pushed away from the front face  201  to release the engagement force. The retraction arms  222 ,  223  are extended to the end of the slots  270 ,  271  at the ends near the pivot  211 . This pulls against the springs  224 ,  225  and causes the engagement member  218  to rotate in a clockwise direction, and the engagement member  219  to rotate in a counter-clockwise direction, withdrawing engagement members away from the chassis, and allowing the cover  200  to be removed from the chassis. 
     As a module is inserted, the action of the retraction arms  222  and  223  tends to allow the engagement members  218 ,  219  to rotate outward and engage the chassis. The action of the lever arms  212 , 213  applies engagement force against the chassis to secure the connectors  205  with corresponding connectors in the chassis. 
     FIG. 4 is a view of the back end  204  of the cover  200  showing a component connector  420  used to couple a memory module with the computer system  100 . The component connector  420  is mounted on the cover  200 , or alternatively formed for example on a circuit board in the cover, as an extension of the mounted component. The cover  200  provides a back panel  410  through which the component connector  420  extends to engage with the corresponding mating connector (not shown) of the computer system  100 . The component connector  420  may have either male or female connector elements. The individual pins are not shown in FIG. 4, to avoid crowding in the drawing. 
     In one example, the component comprises a memory module including a large pin connector, such as ones suitable for employment with arrays of FLASH EPROM modules that store many gigabytes of information. FIG. 4 illustrates an embodiment incorporating a large male or female pin connector on the cover  200 , where the pins/holes are arranged in clusters  421 , including four or more rows of pins. The large pin connector  420  may include over 1500 pins/holes and several ground and power contacts which engage a mating connector within the chassis. For large pin connectors such as one illustrated by FIG. 4, a force greater than 200 pounds may be necessary to engage the memory module with the computer system  100 . 
     Multiple guide pins  430  are also incorporated into the component connector  420 , or in the back panel  410 , to guide the component connector into engagement with the mating connector of the chassis. In this example, three guide pins  430  are spaced horizontally to extend from the back end  204  of the cover  200 . The guide pins may be positioned on either the back panel  410  or on an interface surface of the component connector. The guide pins  430  align the component connector  420  with respect to the slot or opening of the chassis when an insertion force is applied to the cover  200 . In particular, large pin connectors used with the component connector  420  benefit from guide pins  430  because the guide pins more readily ensure alignment between the memory module and the computer system when the insertion force is applied to the component connector. 
     FIGS. 5A-5C provide a close-up illustration of the lock mechanisms  260  on the slide  210 . First with reference to FIG. 5A, the slide  210  is in a fully inserted position. The tongue element  267  tends by its spring action to lift away from the slide  210 . A ridge  535  engages a bar  516  on the front face of the cover and prevents withdrawal of the slide. The pawl  261  is shown in a position such that the solenoid  266  may engage a pin  555  with the pawl  261  by extending downward. A stop  530  positions the pawl  261  in the manner shown to let the pin extend past the top surface of the pawl so that a side  532  of the pawl will ride along the pin. If the pin is not extended, then the side  532  of the pawl will ride adjacent the guide member  209  in the region  265  as described before. 
     The proximal end  506  of the slide  210  is formed to provide a handle for the operator. The mechanical stop  264  is reinforced with structural members  544  and  534 . 
     The tongue element  267  is secured to the slide  210  by elements  522  which may be screws, welded joints or other structural connectors. The tongue element has a region  520  which is normally inside the wall  516 . The ridge  535  is formed in the region  520 . Also, a switch contact  524  is formed on the tongue element  267  in the region  520 . The switch contact  524  is adapted to contact a switch  268  mounted on the bar  516  on the cover. When the contact  524  is spaced away from the switch  268 , the system enables the solenoid  266  as mentioned before. 
     FIG. 5B illustrates the lock  260  with the pawl  261  engaged at the mechanical stop  264 . Skis occurs if the pin  555 , shown in FIG. 5A is withdrawn from the solenoid to  266 , allowing the surface  532  of the pawl  261  to ride along the wall in region  545  of the guide  209 . In order to reach this position, the tongue element  267  must be depressed, causing the ridge  535  to slip under the bar  516 , and the contact  524  to lose contact with the switch  268 . 
     FIG. 5C illustrates the lock mechanism  260  in substantially the same position as that of FIG. 5B, except that the solenoid  266  is engaged to prevent the pawl  261  from engaging the mechanical stop. Thus, the slide is in a position to be withdrawn from the cover. It can be seen in FIG. 5C that the pin  555  of the solenoid  266  is extended downward, and the surface  532  of the pawl rides on the pin  555  to prevent engagement with the mechanical stop  264 . 
     The lock mechanism shown in FIGS. 5A-5C is characterized by a solenoid  266  which has a normally extended pin  555 . In this manner, when the power is off for the system, the pin is extended, and the slide may be withdrawn. Thus, a lock which allows withdrawal of the system when power is off is an advantageous aspect of the invention. 
     Other configurations of locks can be utilized, including solenoid having normally withdrawn pins, other electromagnetically actuated components, or other electromechanical configurations which allow for system control of the lock during hot swap operations. 
     FIGS. 6A-6C illustrate the engagement member  218  in engaged and disengaged positions. As can be seen in FIG. 6A, the lever arm  212  is secured through a fulcrum  214  to the engagement member  218  at pivot  216 . The fulcrum  214  is secured to the cover by structure  250 . The retraction arm  222  is secured to the engagement member  218  at pivot  655 . The spring  224  is coupled between the retraction arm  222  and the cover. As shown in the drawing, the engagement member has a hook region  220  which is engaged with a mechanical structure  610  on the chassis. Structure  610  includes a surface  612  within a cut out area  615 , against which the hook  220  applies engagement force. The head  650  of the engagement member  218  fits within the cut out area  615  of the member  610 . This member is engaged along the left side  206  of the cover in the example shown. In FIG. 6B, the lever arm  212  has been moved to the intermediate position against the stop on the tongue member. In this illustration can be seen that the head  650  of the engagement member  218  remains within the cut out area  615 , and little or no disengagement force is applied. In FIG. 6C the lever arm  212  is moved toward the fully retracted position, releasing the head  650  of the engagement member  218 , so that the hook  220  does not engage the member  612 . The retraction arm  222  pulls against spring  224  to withdraw the head  650  from the member  610  allowing reaction of the component. 
     The engagement member and lever system illustrated can be replaced with a variety of other mechanisms, including mechanically operated and magnetically operated engagement devices. The present system allows for significant leverage action to apply insertion force for large connector components, using smooth, easy action withdrawing and inserting the slide. 
     FIG. 7 illustrates the pivot  211  on the slide  210 , and the manner in which the lever arms  212  and  213  and the retraction arms  222  and  223  are engaged with the pivot  211 . In FIG. 7, the slide is in the withdrawn position, such that the distal end of the slide is adjacent the solenoid  266 . The retraction arms  223  and  222  include slots  710 . When the slide  210  is in the withdrawn position as shown in FIG. 7, with the distal end of the slide near the solenoid  266 , the pivot  211  engages the ends of the slots  710 , and applies force to withdraw the engagement member inside the cover as described above. 
     The lever arms  212  and  213  also include slots which couple with the pivot  211 . The slots allow for the linear slide to drive arcuate motion of the lever arms, and for movement of the slide from the fully inserted position to the intermediate position without applying significant lever force to the engagement members. 
     FIGS. 8,  9 ,  10 , and  11  illustrate an alternative configuration of the lever assembly and mechanical lock for a module cover  800  according to the present invention, adapted for systems which require lower engagement and disengagement forces than are developed using the configuration of FIGS. 2 and 3. The cover  800  includes a front wall  801  and a back wall  802 . A left side wall  803  and a right side wall  804  are formed on the cover  800 . The chassis includes mechanical stop structures  805  and  806  on the left and right sides, respectively, of the slot in the chassis which receives the cover  800 . 
     The mechanism includes a slide structure  810  which has a left extending arm  811  and a right extending arm  812 . The left end of the left extending arm  811  includes a guide surface  813  which is adapted to slide along a receiving surface  815  on the left side wall  803 . The end of the right extending arm includes a guide surface  814  which is adapted to slide along a receiving surface  816  on the right side wall  804 . Also, the slide  810  is secured by a riser  820  within a slot  821 . The slot  821  establishes the maximum inserted position and the maximum withdrawn position of the slide  810 . Although not shown in the drawing, a spring loaded switch, like the tongue assembly  267  of FIGS. 2 and 3, and in FIGS. 5A-5C, is mounted by fasteners at the fastener receiving holes  822  on the slide. A mechanical lock including a pawl  823  is also mounted on the slide  810  in the manner discussed above with respect to FIGS. 5A-5C. The pawl  823  is adapted to strike a stop member  824  on the cover  800  unless a solenoid pin is extended to drive the pawl to a position which avoids contact with the stop  824 , as described above. This structure is placed in a different location on the slide  810  than the similar structure describes above with respect to FIGS. 5A-5C. The mechanical lock can be positioned at any convenient location on the slide as suits the need of the particular embodiment, and adopt a variety of mechanical and electromechanical structures. 
     The slide includes a handle structure  850  at the proximal end of the slide. 
     The distal end of the slide  850  is adapted to extend long enough to hold the pawl  823  and improve structural integrity during sliding from inserted to withdrawn positions of the slide  810 . 
     The assembly includes a left lever arm  830  and a right lever arm  831 . The left lever arm  830  is coupled to a fulcrum  832 . The right lever arm  831  is coupled with fulcrum  833 . The lever arms  830 ,  831  include respective inside curved surfaces  834  and  835 . Likewise, the lever arms  830 ,  831  include respective outside curved surfaces  836  and  837 . In the inside curved surfaces  834  and  835  are adapted to engage with pivot  838  and bar  840  on the left, and a pivot  839  and bar  841  on the right. The outside curved surfaces  836  and  837  are adapted to engage with pivots  842  and  843  on the left and right sides respectively. The left lever arm  830  includes an engagement end  844  adapted to apply engagement force against the stop  805  in the chassis. The right lever arm  831  includes an engagement end  845  adapted to fit with the stop  806  in the chassis. 
     Operation of the lever assembly can be understood with respect to FIGS. 9,  10 , and  11 , which use the same reference numbers as FIG.  8 . As can be seen in FIG. 8, the inside curved surfaces  834 ,  835  of the lever arms  830 ,  831  contact outside surfaces of the bars  840  and  841  which are parallel to the direction of motion of the slide. The outside curved surfaces  836  and  837  of the left and right lever arms contact pivots  842  and  843  respectively. The engagement ends  844  and  845  of the lever arms  830  and  831  apply force against the stops  805  and  806 , which force tends to hold the mechanism in the chassis. 
     In FIG. 9, the slide  810  is shown withdrawn to an intermediate position. Between the position of FIG.  8  and the position of FIG. 9, there is no cover movement. The inside surfaces  834  and  835  of the lever arms ride against the bars  840  and  841  until the position indicated in FIG.  9 . The engagement ends  844  and  845  continue to apply engagement force against the stops  805  and  806  respectively. 
     FIG. 10 illustrates a position in which the slide  810  is near a fully withdrawn position. As the slide moves from the position of FIG. 9 to the position of FIG. 10, the inside surfaces of the lever arms  830 ,  831  rotate about the pivots  838  and  839 . The pivots  842  and  843  engage the outside surfaces  836  and  837 . As the lever arms move through the position of FIG. 10, they apply leverage to overcome the connector resistance and cause the engagement ends  844  and  845  to apply disengagement force against the stops  805  and  806 . 
     FIG. 11 illustrates the slide  810  in the fully withdrawn position. This position, the riser  820  is against the distal end of the slot  821  on the slide  810 . The lever arms  830  and  831  rotate so that the engagement ends  844  and  845  are withdrawn relative to the cover  800 , allowing removal of the cover from the chassis without resistance from the stops  805  and  806 . The outside curved surfaces  836  and  837  rotate on the pivots  842  and  843  during the final lever transition. 
     As the component is inserted, the lever system goes through low leverage transition between positions of FIG.  11  and FIG. 10, and begins to apply higher leverage after the position of FIG.  10 . In the transition from the position of FIG. 10 to the position of FIG. 9, the lever system overcomes the connector resistance. In the position of FIG. 9, the component is fully engaged. As the slide is inserted from the position of FIG. 9 to the position of FIG. 8, there is no component movement. 
     In the region of movement of the slide between the inserted position of FIG.  8  and the intermediate position of FIG. 9, there is essentially no movement of the engagement ends  844  and  845  of the lever arms. The detector mechanism described above operates to detect attempted removal of the component in this region of no movement. This allows the electromechanical lock to engage if the system is not prepared for removal of the component, or to allow removal if the system is prepared. 
     Computer systems incorporating principles of this invention provide several advantages. In particular, the invention provides an assembly that allows for modules engaged with a computer system to be safely and easily hot-swapped. For example, the cover  200 ,  800  under this system may only be removed when the logic of the computer system confirms that the module is ready to be disengaged from the system. Moreover, the cover  200 ,  800  may include safeguards that prevent damage to the lock, module, or computer system by users who suddenly apply significant forces to prematurely disengage the module. In addition, the cover may include a leveraged translational mechanism including a combination of levers, retraction arms and engagement members which allow for easy engagement and disengagement of the module from the computer system. In an embodiment of the invention, the translational mechanism may leverage a force applied to a slide  210 ,  810  of the cover  200 ,  800  to allow users to easily insert and engage modules requiring significant insertion forces. 
     Two separate issues with regard to hot swapping modules in computer systems include: 
     1. Plugging or unplugging cards requires the system bus be “stopped” or noise could cause data or program corruption. 
     2. Data in the card could be lost if a card were removed without giving the system time to store the data. 
     To prevent unexpected extraction of a card, a mechanical and electrical lock using a solenoid in one example is used. The solenoid is used to lock the lever mechanism on each board module. The solenoid is energized by the module power supply thus preventing the energized module from being removed. In order to reduce energy consumption a switch on the release latch turns on the solenoid only when moved, i.e., when someone is trying to remove the module. A short pin on the bus connector can be polled to ensure the card release latch. Removal of a card is done using the front panel display management interface or the management interface remotely. The LEDs on the boards not ready to be removed can flash amber while the LED on board that is ready to be extracted is unlit. Note that the bus will continue to operate until a user squeezes the release latch to the card. This operates a switch in the latch that alerts the system the card is being unplugged. Bus activity is suspended. 
     The embodiments shown are advantageous for reasons including: 
     1. The solenoid is powered from the onboard DC/DC power supply in the module. 
     2. Non-operating (de-energized) boards may be removed at any time. 
     3. A switch on the release latch alerts the system when a board is being unplugged. 
     4. To save power and reduce heat the solenoid only operates when the release latch is squeezed. 
     5. No force is applied to the solenoid when the module is locked and a user attempts to remove the module. 
     6. Only a small force is applied to the solenoid when the system is unlocked. This allows the use of a very small solenoid. 
     The foregoing description of preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.