A latch for retaining moving parts on an enclosure service module (ESM) is provided. This latch comprises a retaining groove in the latch that holds a self-clinching standoff fastener attached to the ESM. A return spring is contained within a molded cavity in the latch, and an alignment groove in the latch is placed at one end of the return spring. The alignment groove guides an alignment pin on the ESM into a secure position, and the return spring applies pressure against the pin while the pin is in the alignment groove.

BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention is directed toward an apparatus for securing insertion/extraction levers on modular computer components. 
     2. Description of the Related Art 
     Controller modules and drive trays are modular computer components that are usually connected together in a customer-specified configuration to produce storage systems. Controller modules function as the interface between a host system and the drive tray array. The drive trays use enclosure service modules (ESMs) as the interconnection to the drives contained within a drive tray. The ESMs also perform diagnostic monitor functions for the drive array. 
     ESM may take the form of customer replaceable units (CRUs), which make up subsystems within a storage system. This provides the customer with more freedom and direct control over the configuration and maintenance of the subsystems. The CRUs contain insertion/extraction levers that are used to install and remove CRUs from a storage system chassis. When these levers are not being used for insertion or extraction, they must be kept firmly folded and retained in place with a latch. 
     Current approaches to this problem have not been successful. Previous designs were either not substantial or durable enough to do the job, functioned poorly due to their complex nature, or interfered with other structures and features on the face of the Customer Replaceable Unit (CRU). One such unit used a long lever arm that prevented an acceptable label set from being added to the face of the CRU. One unit used a pivoting metal structure that required many components and made it necessary for the user to manipulate the latch with unnatural combinations of rotating and pulling motions. Several designs used perforations through the face of the CRU that allowed the escape of radiated electrical noise. However, none of these previous designs was able to meet the necessary requirements. 
     Therefore, it would be desirable to have a mechanism for securing the insertion/extraction levers of a CRU that is durable, does not interfere with the structures of the CRU, and is not overly complex. 
     SUMMARY OF THE INVENTION 
     The present invention provides a latch for retaining moving parts on an enclosure service module (ESM). This latch comprises a retaining groove in the latch that holds a self-clinching standoff fastener attached to the ESM. A return spring is contained within a molded cavity in the latch, and an alignment groove in the latch is placed at one end of the return spring. The alignment groove guides an alignment pin on the ESM into a secure position, and the return spring applies pressure against the pin while the pin is in the alignment groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  depicts a front view pictorial diagram illustrating a Customer Replaceable Unit (CRU) with a CRU latch in accordance with the present invention; 
         FIG. 2  depicts a perspective view pictorial diagram illustrating a CRU with an extended insertion/extraction lever in accordance with the present invention; 
         FIG. 3  depicts a front view pictorial diagram illustrating a CRU latch in accordance with the present invention; 
         FIG. 4  depicts a rear view pictorial diagram illustrating a CRU latch in accordance with the present invention; 
         FIG. 5  depicts a pictorial diagram illustrating the relationship between the latch and the mounting points on a CRU is depicted in accordance with the present invention; and 
         FIG. 6  depicts a front view pictorial diagram illustrating the latch attached to the CRU in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The description of the preferred embodiment of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention the practical application to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 
     With reference now to the figures and in particular with reference to  FIG. 1 , a front view pictorial diagram illustrating a Customer Replaceable Unit (CRU) with a CRU latch is depicted in accordance with the present invention. The CRU  100  is depicted with its insertion/extraction levers  101  and  102  folded in and locked in place by the latch  110 . The latch  110  keeps the levers  101  and  102  locked in this folded position while the CRU  100  is installed in a storage system, or when the CRU  100  is not in use and is being stored. 
     Referring now to  FIG. 2 , a perspective view pictorial diagram illustrating CRU  100  with an extended insertion/extraction lever  101  is depicted in accordance with the present invention. When the CRU  100  has to be installed or extracted from a storage unit, the levers  101  and  102  are extended and used as handles by service personnel to move the CRU  100  into and out of position. Although the latch  110  is pictured attached to the CRU  100  in  FIG. 2  for purposes of illustration, it would normally be removed when the lever  101  is unfolded. 
     Referring to  FIG. 3 , a front view pictorial diagram illustrating a CRU latch is depicted in accordance with the present invention. The latch  300  is molded from an engineering plastic resin such as Acrylonitrile Butadiene Styrene (ABS) or Lexan or an alloy of both. As can be seen, the front surface is textured and contoured to provide a non-slip grip and to be easy to use. The latch  300  is also designed for visual and functional clarity. The latch  300  uses integral guidance and requires no perforations of the CRU wall upon which is mounted, which maintains a barrier to radiated emissions that would otherwise emanate from such openings. 
     Referring to  FIG. 4 , a rear view pictorial diagram illustrating a CRU latch is depicted in accordance with the present invention. The present invention is easy to use and has a compact design using a return spring and a pressed-in pin on the CRU for guidance. The return spring  301  is trapped within the body of the latch  300 . An alignment track  302  molded into the latch  300  beneath the return spring  301  functions as a track for the pin pressed into the metal body of the CRU (as described below). 
     Referring to  FIG. 5 , a pictorial diagram illustrating the relationship between the latch and the mounting points on a CRU is depicted in accordance with the present invention. Installation of the latch  300  on the CRU  500  is simple. The alignment pin  501  on the CRU  500  is guided into the alignment track  302  below the return spring  301 . The alignment pin  501  also does “double duty” by compressing the return spring  301 , resulting in a very crisp and positive feeling latch operation. When not actuated, the latch return spring  301  is essentially unloaded, except for the retention force that it exerts against the latch cavity. Because the alignment track  302  for the press-in alignment pin  501  is located beneath the return spring  301 , this takes advantage of the difference between the depth of that cavity and the overall molded height of the latch  300 . This design conserves space in that it does not require separate areas to be devoted to both functions, which is a significant improvement over previous designs. 
     The latch  300  is retained to the CRU  500  via another piece of pressed-in hardware that fits into a retaining groove  303  in the latch  300 . This retaining hardware is, e.g., a PEM self-clinching standoff fastener  502 . The plastic latch  300  is sized and designed to be retained by a single screw driven into the self-clinching fastener  502 . The extended length of retaining groove  303  provides relief around the screw head and near the top of the self-clinching fastener  502 , which allows for motion while not retaining the latch  300  too tightly. 
       FIG. 6  depicts a front view of the latch  300  attached to the CRU  500 . This view clearly illustrates how the self-clinching fastener  502  retains the latch  300 , while still having the relief space described above. 
     An alternate embodiment of the present invention uses a plastic spring that is integral with the latch body. One end of the spring is attached internally to the latch. The other end captures the alignment pin on the CRU. This accordion-pleated spring compresses on actuation and then restores itself to its unactuated position via forces stored in the plastic spring. The nature of such springs suggests that an alternate material would be more appropriate for such a design. This type of spring is best made with tough materials such as nylons and polypropylene. There may also be a tendency for engineering plastics such as ABS or Lexan to crack under repeated loading. This integral spring is designed to completely surround the alignment pin and fully capture it, which results in forced positional consistency. The interference of the periphery of the spring and sides of the cavity provides the alignment. Spring radii are designed to be generous and to thus limit build-up stresses during operation. 
     The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.