Patent Publication Number: US-2012027509-A1

Title: Retention system

Description:
BACKGROUND 
     The present invention relates to a retention system and more particularly to a retention system suitable for use in hydraulic flow systems. 
     Hydraulic units are used in a variety of applications, including refrigeration systems. Most units consist of a housing with one or more bores in which valves or other components are installed to control the performance of the assembly and control pressure and flow within assembly passageways. The valves need a retention device to hold them in place. The most common types of retention for these devices are threaded sleeves or spools which need to be torqued into place. Due to thermal and vibrational forces acting on flow systems, especially those in the aerospace industry, threaded closures run the risk of becoming loose and backing out. Therefore, secondary retention methods are required to accompany the threaded closures. Some common secondary retention devices used are lock-wire (wire is mechanically attached to the threaded member and locked to another place), locking pellets and locking inserts. While these conventional methods work, they require adequate spatial envelope to fit within a system. In addition, they also place additional constraints on how the system may be set up, as well as adding weight to the system. 
     SUMMARY 
     A system to retain a sleeve within a housing includes a sleeve, a spring loaded retaining pin which can be moved to be fully within the sleeve, a locking pin to hold the retaining pin within the sleeve when the sleeve is being set into or withdrawn from the housing, and an annular recess in the housing to receive the retaining pin when the sleeve is set in the housing, the locking pin is removed and the retaining pin is pushed outward by the spring. The sleeve is retained within the housing when the spring pushes the retaining pin outward so that the retaining pin engages the annular recess in the housing. 
     A method of retaining a sleeve within a housing includes inserting a first spring loaded retaining pin into a first blind hole within a sleeve; moving the first retaining pin so that the spring is compressed and the first retaining pin is totally inside the sleeve by engaging a part of the first retaining pin with a tool going though a first slot in communication with at least part of the first blind hole; and inserting a first locking pin into a first locking hole which intersects with the first blind hole so that the first locking pin holds the first retaining pin within the sleeve, compressing the springs. It further includes inserting the sleeve into the housing and removing the locking pin to allow the first retaining pin to engage an annular recess in the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an exploded view of the retention device of the current invention. 
         FIG. 1B  is a perspective view of the retention device of the current invention being inserted into a housing. 
         FIG. 2A  shows an end view of an embodiment of a retention device according to the current invention set in a housing. 
         FIG. 2B  shows a cross sectional view of the retention device of  FIG. 2A  along line  2 B- 2 B. 
         FIG. 2C  shows a cross section view of the retention device of  FIG. 2B  along the line  2 C- 2 C. 
         FIG. 3A  shows a perspective view of an embodiment of the retention device of the current invention in a housing, and with a tool compressing a retaining pin within the sleeve to enable removal of the sleeve from the housing. 
         FIG. 3B  shows a cross sectional view of an embodiment of the retention device of the current invention with the pins compressed into the sleeve and held there by locking pins. 
         FIG. 4  shows a cross-sectional view of a section of a flow system which uses an embodiment of the retaining device of the current invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is an exploded view of the retention system of the current invention.  FIG. 1B  is a perspective view of the retention system of the current invention being inserted into a housing.  FIGS. 1A-1B  include retention system  10  with valve sleeve  12  (which includes front face  14 ; flange  16 ; first blind hole  18  with slot  20  and locking hole  22 , and second blind hole  24  with slot  26  and locking hole  28 ), first retaining pin  30  (with head  32 , neck  34 , shoulder  36  and stem  38 ) with spring  40 , and second retaining pin  42  (with head  44 , neck  46 , shoulder  48  and stem  50 ) with spring  52 , first locking pin  54 , second locking pin  56 , O-ring  58  and housing  60  with an annular recess  62  (see  FIGS. 2B-2C ). 
     Valve sleeve  12  includes first blind hole  18  and second blind hole  24  in flange  16 , extending into flange  16  and parallel with front face  14 . Slot  20  is in communication with at least part of first blind hole  18 , and first locking hole  22  intersects with first blind hole  18 . Slot  26  is in communication with at least part of second blind hole  24 , and second locking hole  28  intersects with second blind hole  24 . First blind hole  18  holds first retaining pin  30  and spring  40 . Second blind hole  24  holds second retaining pin  42  and spring  52 . Spring  40  connects to stem  38  of first retaining pin  30  and pushes retaining pin  30  outward from blind hole  18 . Spring  52  connects to stem  50  of second retaining pin  42  and pushes second retaining pin  42  outward from second blind hole  24 . Blind holes  18 ,  24  are of sufficient length so that each respective spring can compress and heads  32 ,  44  of retaining pins  30 ,  42  can fit entirely within flange  16  of valve sleeve  12 . Retaining pins  30 ,  42  can be made of a metallic material such as steel or aluminum or a plastic, depending on requirements of the system. 
       FIG. 1B  shows a perspective view of the retention device of the current invention being inserted into a housing. Retaining pins  30 ,  42  are compressing springs  40 ,  52  so that retaining pins  30 ,  42  are sitting completely inside flange  16  of valve sleeve  12 . First locking pin  54  is inserted into first locking hole  22  to hold head  32  of first retaining pin  30  within sleeve  12 , and second locking pin  56  is inserted into second locking hole  28  to hold head  44  of second retaining pin  42  within sleeve  12 . This enables sleeve  12  to easily slide into housing  60 . Locking pins  54 ,  56  each have a portion that is not inside of locking holes  22 ,  28  when inserted. This portion which “sticks out” provides an portion of each locking pin to easily grip and pull on when removal of locking pins  54 ,  56  is desired (when springs  40 ,  52  no longer need to be compressed due to sleeve  12  being set within housing  60 ). 
       FIG. 2A  shows an end view of an embodiment of a retention system according to the current invention set in a housing.  FIG. 2B  shows a cross sectional view of the retention system of  FIG. 2A  along line  2 B- 2 B.  FIG. 2C  shows a cross section view of the retention system of  FIG. 2B  along the line  2 C- 2 C.  FIGS. 2A-2C  include valve sleeve  12  (which includes front face  14 ; flange  16 ; first blind hole  18  with first slot  20  and first locking hole  22 , and second blind hole  24  with second slot  26  and second locking hole  28 ), first retaining pin  30  (with head  32 , neck  34 , shoulder  36  and stem  38 ) with spring  40 , and second retaining pin  42  (with head  44 , neck  46 , shoulder  48  and stem  50 ) with spring  52 , first locking pin  54 , second locking pin  56 , O-ring  58  and housing  60  with annular recess  62 . 
     As mentioned in relation to  FIGS. 1A-1B , valve sleeve  12  is retained within housing  60  through retention system  10 . Retaining pin  30  and spring  40  sit in first blind hole  18 . Spring  40  contacts stem  38  of retaining pin  30  to push retaining pin  30  outward towards housing  60 . When spring  40  pushes retaining pin  30  outwards, head  32  of retaining pin  30  engages recess  62  in housing  60 . Second retaining pin  42  sits in second blind hole  24  and is pushed outward by spring  52  (in contact with stem  50  of retaining pin  42 ) so that head  44  of retaining pin  42  engages recess  62  in housing  60 . 
     Blind holes  18 ,  24  are strategically placed in sleeve  12  at positions so that retaining pins  30 ,  42  can sit totally within flange  16  of sleeve  12  for installation or removal of sleeve  12  from housing  60 , and so that when sleeve  12  is set in housing  60 , pins  30  and  42  can act together to retain sleeve  12  in place within housing  60 . This retention is attained by retaining pins  30 ,  42  being pushed outwards by springs  40 ,  52  so that heads  32 ,  44  engage annular recess  62  in housing  60 . 
     Through the use of spring loaded pins which can retract to fit entirely within blind holes in a sleeve, the retention system of the current invention can securely hold a valve sleeve in place within a housing without the need for secondary retention systems which may take up additional space, weight, block some flow within the system and/or add other constraints to the system. In past systems, threaded closures were often used to retain valve sleeves and spools within housings. Because many flow systems are subject to thermal and vibrational forces, especially those in the aerospace industry, the threaded closures ran the risk of becoming loose and backing out. Therefore, secondary retention methods were required. These included such things as lock-wire, where wire is mechanically attached to the sleeve and locked to another place. Other methods of secondary retention used are lock pellets or locking inserts which may impede flow. The current invention retains a sleeve within a housing without the need for a secondary retention system and the additional constraints added by the secondary retention system which the torqued retention systems require. 
       FIG. 3A  shows a perspective view of an embodiment of the retention system of the current invention in a housing, and with a tool, such as an ice pick, compressing a retaining pin within the sleeve to enable removal of the sleeve from the housing.  FIG. 3B  shows a cross sectional view of an embodiment of the retention system of the current invention with the pins compressed into the sleeve and held there by locking pins.  FIGS. 3A-3B  include valve sleeve  12  with front face  14 , flange  16 , first blind hole  18  with first slot  20  and first locking hole  22 , and second blind hole  24  with second slot  26  and second locking hole  28 ; first retaining pin  30  (with head  32 , neck  34 , shoulder  36  and stem  38 ) with spring  40 ; and second retaining pin  42  (with head  44 , neck  46 , shoulder  48  and stem  50 ) with spring  52 ; first locking pin  54 ; second locking pin  56 ; housing  60  with recess  62 ; and tool  66 . 
     Tool  66  goes into slot  20 , engages neck  34  of retaining pin  30 , and moves pin  30  further into blind hole  18 . This movement of pin  30  compresses spring  40  and moves head  32  of pin  30  within flange  16  of sleeve  12 . Once head  32  of pin  30  is within flange  16  of sleeve  12 , first locking pin  54  can be inserted into locking hole  28  (which intersects with blind hole  18 ). Tool  66  can then be removed from slot  20 , and locking pin  54  (in locking hole  28 ) blocks head  32  of spring  30  from moving outwards towards housing, and therefore keeps spring  40  compressed and pin  30  entirely within sleeve  12 . The same procedure can be used to compress spring  52  and retain pin  42  within blind hole  24  using locking pin  42 . 
     As seen in  FIGS. 3A-3B , sleeve  12  with retention system can easily be set in or removed from within housing  60 . This can be done by using tool  66 , which may be any suitable tool (e.g., an awl, an ice pick, etc.), to engage the neck of the retaining pin, and move the pin further into the blind hole in the sleeve so that the head of the pin is within the sleeve, compressing the spring which is in contact with the pin stem. The pin can be held in that position by inserting a locking pin into the locking hole. Because the locking hole intersects the blind hole, the locking pin contacts the head of the pin keeping the pin within the sleeve and the spring compressed to easily set in or remove the sleeve from a housing. This design enables the sleeve and retention device to be inserted, removed and reused, as nothing is damaged through use of a tool to engage the neck of the pin, move it inwards and use of an easily removable locking pin to prevent the retaining pin from moving outward during setting in or removal of the sleeve from the housing. 
       FIG. 4  shows a cross-sectional view of a section of a flow system which uses an embodiment of the retaining system of the current invention, and includes pipe fitting  68  with inner diameter D 1 ; valve sleeve  12  with flange  16 , flow channels  70 ,  72  and outer diameter D 2 ; O-ring  58 ; housing  60  with annular recess  62  and arrows indicating fluid flow F. 
     Pipe fitting  68  is welded into housing  60  to bring pipe fitting  68  and sleeve  12  into fluid flow communication. Sleeve  12  is retained within housing  60  by heads  32 ,  44  of pins  30 ,  42  being pushed outward (by springs  40 ,  52  acting on pins  30 ,  42 , see  FIGS. 2B-2C ) to engage recess  62 . 
     As can be seen in  FIG. 4 , outer diameter D 2  of sleeve  12  is smaller than inner diameter D 1  of pipe fitting  68 . By using spring loaded pins  30 ,  42  which fit into blind holes  18 ,  24  within housing  60 , sleeve  12  is able to be retained in this system despite the outer diameter D 2  of sleeve  12  being smaller than inner diameter D 1  of pipe fitting  68 . The current invention retains sleeve within a housing even in “stepped bore” situations as demonstrated in  FIG. 4 , while eliminating the need to use secondary retention system (as needed in past systems) which can impede some flow and add weight to the system. 
     In summary, the retention system described herein is a simple and small means to retain flow controlling assemblies within a housing through the use of blind holes with springs, retaining pins and an annular recess in the housing which also allows easy insertion and removal of the sleeve from the housing. The easy insertion and removal comes from the retaining pins and springs sitting in the blind holes, and the retaining pins being able to be moved completely into the blind hole by a tool engaging the retaining pin neck through a slot in communication with at least a part of the blind hole, and the retaining pin being able to be retained in that position with an easily removable locking pin inserted a locking hole, allowing the sleeve with retention system to be easily inserted, removed and reused. This design can reduce or eliminate the need for additional closures and retention means, and add more flexibility into design of the overall system. The smaller size also reduces the weight of the system, resulting in economic benefits. 
     While the invention has been discussed mostly in relation to including two spring loaded retaining pins, it can include only one spring loaded retaining pin or three or more spring-loaded retaining pins to hold the valve sleeve in place depending on the requirements of the system. The spring-loaded retaining pins can also have a different configuration than those shown in  FIGS. 1A-4 , as long as they are able to sit fully within the valve sleeve for installation and removal and be pushed outward into holes in the housing when the sleeve is set within the housing. Generally, if three spring-loaded retaining pins are used, they would be similar to what is shown in  FIGS. 1A-3B , only the three spring-loaded retaining pins would be equally spaced throughout the sleeve, sitting about 120 degrees apart. If four pins were used, they would sit about 90 degrees apart and generally be equally spaced. 
     While the invention has been discussed mostly in relation to setting a valve sleeve within a housing, it could also be used to retain a closure, a static spool or other mechanisms in place within a housing, a bore or another structure in which they sit. It is intended mainly for unidirectional flow systems, but can withstand reduced loading in bi-directional flow systems. The system may be used as part of a hydraulic flow system in an aerospace application. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.