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CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of U.S. patent application Ser. No. 10/821,488 filed Apr. 9, 2004 now U.S. Pat. No. 7,097,391. 
    
    
     TECHNICAL FIELD 
     This invention relates to pneumatically transported carriers, and particularly to fluid type carriers for carrying medical samples and other hazardous materials. 
     BACKGROUND OF THE INVENTION 
     The transportation of items through pneumatic tubes is well known. Recently, a need has arisen to transport medical samples and other hazardous material within such carriers. For safety purposes, it has been desirable to seal the interior of the carrier from the outside in the event that a sample spills or leaks within the carrier. Examples of such designs are illustrated in U.S. Pat. No. 5,636,947 to Valerino Sr. et al and U.S. Pat. No. 5,655,677 to Fratello et al. 
     Typically, such designs use some type of a seal which is compressed when the carrier is closed to provide isolation. Normally, a latch of some type is used to hold the carrier in the closed position. However, a latch can be caught by sharp corners in a pneumatic tube, or sprung by sudden impacts or violent motion within the tube. If the latch opens, the seal of the carrier is jeopardized. A need exists for a design which preserves the integrity of the seal during the rough handling that such carriers often experience. Other critical applications for latches also exist, such as on luggage transported by airplane, etc, where the luggage is subject to severe handling, and the unintentional opening of a latch can lead to loss of the contents, etc. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, a carrier is provided which has a first half and a second half hinged together to permit the first and second halves to move between an open position and a closed position. At least one main latch is movable between a latched position and an unlatched position to hold the first and second halves in the closed position when the latch is in the latched position. The main latch includes a stationary portion secured to the first half, with the stationary portion defining a guide. A movable portion is mounted to the stationary portion for sliding motion between a first limit and a second limit. A cam is mounted on the second half. The movable portion engages the cam to move the first and second halves into the closed position as the movable portion is moved toward the first limit. A resilient safety latch is mounted on the stationary portion to engage the movable portion when the first and second halves are in the closed position to secure the latch in the latched position. The safety latch also has a knob forming a finger contact portion to allow the safety latch to be moved away from the movable portion to release the main latch. 
     In accordance with another aspect of the present invention, the movable portion has an aperture to receive a portion of the safety latch when the main latch is in the latched position. The safety latch can be molded integrally with the stationary portion. The cam can be integrally molded in the second half. Two main latches can be provided, with a cam integrally molded in each half so that the first and second halves can be identical. 
     In accordance with another aspect of the present invention, the carrier can include a wear band, the wear band including a seal material and a flexible backing strip. The first and second halves include a channel to slidably receive the backing strip to secure the wear band on the first and second halves. 
     In accordance with another aspect of the present invention, the first and second halves are formed of anti-microbial material. 
     In accordance with another aspect of the present invention, the carrier includes an ergonomic design. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the accompanying Drawings, in which: 
         FIG. 1  is a perspective view of a carrier incorporating a first embodiment of the present invention in the closed position; 
         FIG. 2  is a perspective view of a carrier incorporating a first embodiment of the present invention in the open position; 
         FIG. 3  is an exploded view of the main latch on the carrier; and 
         FIG. 4  is a cross sectional view illustrating the wear band. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the accompanying drawings, wherein like or corresponding parts are designated by the same reference numerals, there is illustrated a carrier  10  of the type used to carry items therein in a pneumatic tube system. The carrier  10  can carry medical samples, letters, objects, and the like. The carrier  10  includes a first half  12  and a second half  14 . The first half has first hinge elements  16  while the second half has second hinge elements  18  which, along with a hinge pin  20 , form a hinge  22 , as seen in  FIG. 2 , to allow the halves of the carrier  10  to be moved between an open position, seen in  FIG. 2 , to insert or remove the item to be carried, and the closed position, seen in  FIG. 1 , ready for transportation through a pneumatic tube. 
     As best seen in  FIG. 2 , the first half  12  has a continuous peripheral groove  24  formed in edge surface  26  which receives an O-ring (not shown). The second half  14  has a continuous raised ridge  30  which, when the carrier  10  is in the closed position, as seen in  FIG. 1 , is compressed against the O-ring to form a continuous seal to isolate the interior  32  of the carrier from exterior the carrier. Alternatively, both halves can have a groove  24 , with the O-ring sealing between the grooves when the carrier  10  is in the closed position, allowing the first and second halves  12  and  14  to be identical. Thus, the carrier can safely carry hazardous materials, such as medical and biological fluid samples. Designs of this general type are disclosed in U.S. Pat. Nos. 5,636,947 and 5,655,677, the disclosures of which are hereby incorporated by reference in their entirety herein. 
     To hold the carrier  10  in the closed position, two main latches  34  and  36  are employed. As best seen in  FIG. 3 , each main latch includes a base  38  secured to one of the halves  14  and  16 , preferably by screws threaded into threaded inserts  48  molded into the halves  14  and  16 . The base  38  includes a portion forming slide  120  which extends the length of the base  38 , and a safety latch  70 . The safety latch  70  is cantilevered from the remainder of the base  38  by forming the base  38  with opening  122  surrounding three sides of the safety latch  70 , leaving only one side integral with the remainder of the base  38 . This allows the safety latch  70  to be deflected relative the rest of the base  38  as will be described hereinafter. The safety latch  70  includes a raised knob  124  at the free end of the safety latch  70 . 
     A slidable catch  42  is secured to the base  38  so that the catch  42  can slide the length of the base  38  along the slide  120 . A cam  126  is molded into the halves  12  and  14  immediately opposite the position of base  38  on the mating half. When the halves  12  and  14  are in the closed position, catch  42  can be slid along slide  120  from the open position  130  at the outer end of the slide to engage the cam  126  on the mating half. As the catch  42  continues to be slid along slide  120 , the catch  42  will travel along the curved surface  128  of the cam  126  to draw the halves into ever tighter engagement. As catch  42  is slid from the open position  130 , the catch  42  slides over the knob  124  on the safety latch  70 , causing the safety latch  70  to deflect underneath the catch  42  and permit the catch  42  to move along the slide  120 . As the catch  42  moves into the latched position, the knob  124  is aligned with aperture  134  in the catch  42  and the safety latch  70  rebounds, with the knob  124  popping up into the aperture  134  to hold the catch  42  in the latched position. The knob  124  and safety latch  70  will lock the catch  42  in the latched position until an operator depresses the knob  124  out of the aperture, allowing the catch  42  to then be slid to the unlatched position. It is very unlikely the knob  124  will be depressed inadvertently as it lies below the level of the upturned ends  136  of the catch  42 , as seen in  FIG. 3 . Also, the main latches  34  and  36  do not have elements that pop up or pivot outwardly as they become unlatched, avoiding the possibility of these elements being sheared off or otherwise damaged as the carrier is used. 
     As is well understood, the main latch  34  or  36  can be moved from a latched position, where the catch  42  tightly engages the cam  126  to hold the carrier  10  in the closed position, to an unlatched position, permitting the catch  42  to be disengaged from the cam  126  to allow the carrier  10  to be opened. As can be seen, the halves  12  and  14  can be mirror images of each other, with one end of each half having a cam  126  and the other end mounting base  38 , allowing a single mold to be used to make both halves. 
     Preferably, the first and second halves  12  and  14 , base  38 , catch  42  and safety latch  70  are molded and formed of polycarbonate, ABS, nylon, such a PA66 or PA6 nylon, or any suitable engineered plastic. Alternatively, the base  38 , catch  42  and safety latch  70  can be formed of a flexible metal, such as steel. 
     Another advantage of the carrier  10  is the wear bands  80 . Wear bands  80  reduce damage to the carrier as the carrier is driven through the pneumatic tubes and also provides a seal between the carrier and the inner walls of the tubes to reduce air leakage past the carrier that would reduce the driving force of the pressurized air behind the carrier. As can be appreciated, these wear bands are subject to considerable abuse and require frequent replacement. 
     Wear bands  80  are designed to simplify and shorten the replacement process. A channel  82  is secured at each end of halves  12  and  14 . Channel  82  includes upturned edges  84  as seen in  FIG. 4 . The wear bands  80  are formed of a flexible contact material  86  and a backing  88  having edges  90 . The contact material  86  can be carpeting or fabric material as used in a Velcro system. The backing  88  is sufficiently rigid to be slid into a channel  82  from one end of the channel  82 , until the backing  88  completely fills the channel  82 , with the edges  90  of the backing  88  engaging the edges  84  of the channel. The channel  82  can be separate from the halves  12  and  14  and attached to the halves by any suitable technique, such a gluing, riveting, etc. or the channel  82  can be actually molded into the halves  12  and  14  and thus be integral therewith. 
     The hinge elements  16  and  18  prevent the backing  88  from entering or exiting the channel  82  from the hinge side of the halves  12  and  14  so that the wear bands  80  can only be removed or installed from the other side of the halves. When the carrier  10  is in the closed position, the wear bands  80  on the mating halves also move into mating relationship, preventing the wear bands  80  from sliding out of the channels  82  during use. When a wear band  80  must be replaced, it is necessary only to open the carrier and slide the wear band  80  to be replaced from its channel  82 . The new wear band  80  is installed by simply sliding the new band  80  into the channel  82 . 
     The carrier  10  is made easier to grasp and manipulate by forming recesses  92  at each end of the carrier. Seven are shown at each end in the Figures. Also, ribs  94  can be formed at the ends of the carrier and slots  96  on the sides of the carrier to allow the carrier  10  to be more readily grasped. 
     The carrier  10  can be color coded to facilitate use. For example, if carriers  10  are used in a hospital, carriers used in the emergency room can be red, carriers used in the X-ray department can be green, carriers used in billing can be blue, carriers used in the maternity ward can be purple, etc. With color coding, it will be immediately apparent where the carrier is coming from or going to. 
     Another advantage of the carrier  10  is the use of an anti-microbial material, such as anti-microbial plastics, to form the first and second halves  12  and  14 . Anti-microbial plastics can be formed by molding into the plastic particles of glass containing anti-microbial metal ions such as silver (Ag). Such treated glass is sold by Ishizuka Glass Co., Ltd. of Nagoya, Japan. An anti-microbial material can be used in any style of carrier, such as a carrier that is not leak resistant. For example, anti-microbial material can be used in all hospital and bank carrier products. 
     While the main latches  34  and  36  are described above in use with a carrier  10 , the latches can be used in many other applications. For example, main latches  34  and  36  can be used as the latches on a suitcase or briefcase. Both suitcases and briefcases are often subject to abuse, particularly if placed in the cargo hold of an aircraft. Also, materials carried in such cases, for example important business documents in a briefcase, may be so sensitive and valuable as to justify the added security in using main latches  34  and  36  to prevent an unintentional opening of the case. Other uses of latches  34  and  36  can be on equipment cases, ballot boxes, drawers, etc. 
     Although several embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions of parts and elements without departing from the spirit and scope of the invention.

Summary:
A fluid-tight carrier ( 10 ) is disclosed which has main latches ( 34  and  36 ). Each main latch has a safety latch ( 70 ) which secures the main latches within the latched position until an operator deflects the safety latch ( 70 ) away from the slidable catch ( 42 ) to permit the main latch to be moved to the unlatched position. This prevents inadvertent opening of the carrier due to impact on the carrier. The carrier can be formed of anti-microbial material, have removable wear strips and includes an ergonomic design.