Abstract:
A releasable coupling includes a male coupling portion having a frustoconical male plug portion, and a female coupling portion having a frustoconical female socket portion. The male and female coupling portions are locked together and unlocked by a bidirectional rotatable cam ring which drives one or more balls between the male and female coupling portions.

Description:
GOVERNMENT RIGHTS 
     This invention was made with government support under contracts 1 R41 NS050141-01 and 3 R41 NS050141-0151 awarded by The National Institutes of Health (NIH). The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to couplings having male and female portions for interconnecting subassemblies, and relates in particular to a precision coupling for axially and radially securing a specimen holder to a positioning assembly for mounting a specimen, such as a laboratory rodent, in an imaging machine such as an X-ray, CAT, MRI or PET machine. 
     2. Description of Prior Developments 
     Medical researchers and doctors need to study various anatomical features using different types of imaging devices such as X-ray machines, computerized axial tomography (CAT or CT) scanning machines, MRI machines and photon emission tomography (PET) machines. In order to produce images with the most detail and clarity, individual images from the various types of imaging devices are combined using sophisticated software to produce composite images. 
     In order to produce optimum composite images, the specimen being imaged must be accurately located within the field of view of each machine. This requires that the specimen be imaged in one machine, removed from that machine and properly located and set up in one or more additional imaging machines for additional imagining. This process can be time consuming and labor intensive. 
     What is needed is a method and apparatus for quickly, easily, accurately and repeatably positioning a specimen within the field of view of the same imaging machine and/or a series of different imaging machines over a period of time. A particular need exists for a convenient way to connect and disconnect a specimen holder to and from a modular receiver or positioning receiver system on one imaging machine and then connect and disconnect the same specimen holder to and from a different imaging machine without any complicated set up procedures. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed to provide an interconnection between a spacing and positioning system adapted to be connected to an imaging machine and a specimen holder which is adapted to hold and accurately position a specimen for repeatable placement in the same or different imaging machines. 
     The coupling includes male and female frustoconical plug and socket members. The frustoconical interconnection, coupling and resulting alignment provide both radial centering and positioning as well as axial registration and positioning along precision machined frustoconical surfaces. The male and female members or portions are axially and radially cammed into position by a rotatable cam ring acting on a circumferentially-spaced series of balls, such as ball bearings. 
     The cam ring can be manually-actuated or driven by an external power source. A manually-actuated screw or cam can also be used for such centering as well as an axially-actuated air cylinder and plunger. In any case, an axial and radial force is applied to the interface between the conical surfaces of the plug and socket members to register a positioning receiver system with the animal holder for accurate, repeatable positioning of a specimen within the field of view of an imaging machine. Nominally, a male cone portion is provided on an animal holder system, and a female cone portion is provided on the spacer assembly or positioning receiver system, however, this can be switched around if desired. 
     The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the Drawings: 
         FIG. 1  is a perspective view of an animal management system provided with a coupling assembly constructed in accordance with the present invention and shown in a decoupled or separated position; 
         FIG. 2  is a perspective view of  FIG. 1  shown in a coupled position; 
         FIG. 3  is an enlarged perspective view of the cam ring shown in  FIG. 1 ; 
         FIG. 4  is an enlarged perspective view of the coupling assembly of  FIGS. 1 and 2 , shown in a decoupled position and with the interconnection panel removed from the male coupling portion for clarity; 
         FIG. 5  is an exploded perspective view of the female coupling portion of  FIG. 4 ; 
         FIG. 6  is a perspective view in axial cross section of the male and female portions of the coupling assembly of  FIG. 1  in a fully engaged position; and 
         FIG. 7  is a perspective exploded view of the entire coupling assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in conjunction with the drawings, beginning with  FIG. 1  which shows an animal management system or specimen positioning system  10  including a coupling assembly constructed in accordance with a first embodiment of the invention. The positioning system  10  is adapted for use in an MRI positioning assembly such as disclosed in US patent application publication number US 2005/0027190A1, filed Aug. 10, 2001, under application Ser. No. 10/631,226, and which is incorporated herein by reference in its entirety. 
     While the specimen positioning assembly in U.S. 2005/0027190 , now U.S. Pat. No. 7,414,403, provides for a unitary specimen positioning assembly, the present invention provides for an equivalent modular, easily decoupled multicomponent positioning system. That is, the positioning system  10  of the present invention includes a detachable modular specimen holder or animal holding system  12  which is quickly and easily removably and selectively mountable on a positioning receiver assembly  14 . In U.S. 2005/0027190, now U.S. Pat. No. 7,414,403, the animal holding system and positioning receiver assembly are not readily detachable. 
     A modular coupling  16 , which embodies the present invention, is provided between the animal holding system  12  and the positioning receiver assembly  14  for accurately and repeatably coupling the animal holding system  12  to the positioning receiver assembly  14  to form system  10 , such as disclosed in U.S. patent application Ser. No.11/346,850, filed Feb. 3, 2006, titled “SPECIMEN POSITION SYSTEM FOR IMAGING MACHINES”. Coupling  16  includes a male coupling portion  18  mounted on an outer end of the animal holding system  12  and a female coupling portion  20  mounted on an inner end of the positioning receiver assembly  14 . If desired, the male and female portions  18 ,  20  of coupling  16  can be reversed, as long as all other compatible systems  10  are similarly adapted. 
     As can be appreciated from  FIGS. 1 and 2 , once the male coupling portion  18  is inserted within the female coupling portion  20 , a male keying member  22  projecting from a predetermined circumferential or clockwise position (such as 12 o&#39;clock) on the male coupling portion  18  is inserted and guided into a complementary axially-extending keying slot  24  formed in a predetermined circumferential or clockwise position (such as 12 o&#39;clock) in the female coupling portion  20 . This keying feature circumferentially aligns the animal holding system  12  with the positioning receiver assembly  14 . This clockwise alignment ensures proper, accurate and repeatable placement of a specimen held within the animal holding system  12  within a known axial plane within the field of view of an imaging machine. 
     As discussed in more detail below, once the male coupling portion  18  is almost fully inserted within the female coupling portion  20 , a cam ring or cam driver  26  with circumferentially-extending cam ramps  27  ( FIG. 3 ) mounted within the female coupling portion  20 , can be rotated by a cam lever or cam finger grip tab  28 . The cam ring acts as a cam driver to radially compress a circumferentially-spaced series of cams such as balls  29  loosely held within the female coupling portion  20 . This camming action on cam balls  29  axially wedges and locks a radially stepped registration surface  25  ( FIG. 4 ) on the male coupling portion  18  into a tight axial abutment against a front radial registration surface  31  on the front face of the female coupling portion  20 . At the same time, a frustoconical male plug portion  30  on the male coupling member  18  is pulled into and tightly seated and centered within a complimentary frustoconical female socket portion  32  formed within the female coupling portion  20 . 
     This conical nesting accurately and securely coaxially centers the male coupling portion  18  within the female coupling portion  20  and thereby coaxially aligns the animal holding system  12  with the positioning receiver assembly  14 . At the same time, the tight axial abutment between the male and female coupling portions  18 ,  20  along registration surfaces  25 ,  31  accurately axially locates and registers the animal holding system  12  with respect to the positioning receiver assembly  14 . 
     In order to release and separate the male coupling portion  18  from the female coupling portion  20 , an operator need only rotate or push the cam tab  28  in an opposite direction to that of the locking direction. The animal holding system  12  can then be easily removed and placed in another positioning receiver assembly  14  in a different type of imaging machine. 
     As further shown in  FIGS. 1 and 7 , the animal holding system  12  further includes an interconnection on panel  34  which includes ports  36  for the passage of fluids such as anesthesia gasses, and electrical connectors  38  for the connection of sensors located within animal holding chamber  39 . The fluid ports  36  and electrical connectors  38  communicate with aligned bores or passages  41  ( FIG. 4 ) formed through the male coupling portion  18 . Panel  34  can be connected to the male coupling portion  18  with axially-extending plastic screws, and as seen in  FIGS. 6 and 7 , each of the ports  36  is formed in a panel wall extending over a central bore through the coupling portions  18 ,  20 . 
     An optional electrical lead and fluid tube support tray  40  ( FIGS. 1 and 7 ) is fixed to the outer face  42  of the male coupling portion  18 , such as with plastic screws which thread into bores  44  ( FIG. 4 ) in outer face  42 . Tray  40  is removed from  FIG. 4  for clarity. Wires and tubes supported on tray  40  pass through the coaxially-aligned central through bores or passages in the male and female coupling portions  18  and  20 . Tray  40  receives and supports the electrical wires and fluid tubes (not shown) exiting the outer end of the male coupling portion  18 . As seen in  FIGS. 6 and 7 , the fluid ports  36  are smaller than the through bores in the male and female coupling portions  18 ,  20 . 
     As further shown in  FIG. 4 , the male coupling portion  18  further includes a cylindrical locking and alignment collar  50  extending axially from the smaller diameter outer or front end of the frustoconical male plug portion  30 . A cylindrical radial step  52  ( FIGS. 4 and 6 ) on the collar  50  is formed for receiving the cylindrical ball retainer sleeve  54  ( FIG. 5 ) extending from the rear portion of annular front socket member  56 . 
     Radial step  52  leads forwardly or outwardly into an annular locking groove  60  formed in collar  50 . Groove  60  is axially bounded by a rear wall  62  and a ramped or chamfered front wall  64 . Front wall  64  includes a small radial face  66  ( FIG. 4 ) adjacent the bottom of floor  68  of groove  60 . As discussed below, groove  60  coacts with balls  29  to produce a positive snap-type locking action between the male and female coupling portions  18  and  20 . 
     Turning now to  FIG. 5 , it is seen that the balls  29  are held within stepped radial bores  72  formed in the ball retainer sleeve  54 . A small step in the form of a small radial constriction at the bottom of each bore  72  prevents the balls  29  from passing completely through each bore. While four balls  29  spaced ninety degrees apart around sleeve  54  are shown in  FIG. 5 , any suitable number of balls may be used. Balls  29  may be formed of hard plastic, ceramic or glass. Nonferrous metals may also be used for balls  29 . Advantageously, all components of the coupling  16  are formed of nonferrous plastic materials so as to be suitable for use in MRI type imaging machines. 
     Once the balls  29  are loosely seated in bores  72 , the cam ring  26  is placed over the balls  29  and coaxially around the ball retainer sleeve  54 . A cup-shaped socket member  78  ( FIG. 5 ) is then placed over the cam ring  26  and tightly fixed to the front socket member  56  with plastic screws  80 . 
     The rear socket member  78  includes a rear annular wall  82  and a cylindrical front wall  84 . The front wall  84  has an open slot  86  for receiving and guiding the finger grip tab  28 . Mounting recesses  88  are formed in the rear wall  82  for receiving brackets  90  ( FIG. 1 ), to which the positioning receiver assembly  14  is attached. 
     As can be seen in  FIG. 6 , when the male coupling portion  18  is inserted into the female coupling portion  20 , the balls  29  are aligned over groove  60 . In order to lock the male and female coupling portions securely together, the cam ring  26  is rotated so as to gradually radially drive the balls  29  against the ramped or chamfered front wall  64  of the male coupling portion  18 . 
     As the cam ring is rotated, the cam ramps  27  force the balls  29  further radially inwardly against wall  64 . This creates an axial wedging force against wall  64  which axially pulls the male coupling portion  18  into the female coupling portion  20 . The coupling members  18  and  20  are closely dimensioned such that when the balls  29  clear the lower or radially inner end of wall  64 , the radial registration surfaces  25  and  31  are tightly axially abutted against one another. At this point, the balls  29  snap down with a quick positive action along radial face  66  ( FIG. 4 ) of groove  60  and securely seat against the floor  68  of groove  60 . 
     At this point, the coupling  16  is locked together, with frustoconical surfaces  30  and  32  tightly wedged together to produce an accurate coaxial alignment between the male and female coupling portions  18  and  20 . In  FIG. 6 , alignment pin or male keying member  22  is removed for clarity, but its mounting bore  92  is shown. Each component of the coupling assembly  16  is shown in exploded view in  FIG. 7 . As seen in  FIGS. 1 and 2 , the animal holding system  12  and animal holding chamber  39  are cantilevered from the coupling  16 . 
     There has been disclosed heretofore the best embodiment of the invention presently contemplated. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.