Abstract:
A Push To Connect (PTC) fitting cartridge for connecting to a pneumatic device, such as, an air brake or a height control valve, the PTC fitting cartridge including at least one protrusion positioned on an outer surface of the PTC fitting cartridge, which is provided to interact with an undercut positioned on an inner surface of a port. The undercut interacts with the protrusion to substantially eliminate stress on the surrounding material to reduce the chance of fraction thereof.

Description:
CROSS REFERENCE 
       [0001]    The present application is a divisional of pending U.S. patent application Ser. No. 11/484,448, filed on Jul. 11, 2006, the content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a Push To Connect (PTC) fitting cartridge used in a pneumatic device, and more specifically to a high strength plastic PTC cartridge attached to a housing of a pneumatic device, the system substantially eliminating stress on the housing due to the PTC cartridge. 
       BACKGROUND OF THE INVENTION 
       [0003]    Pneumatic devices, such as, air brakes and height control valves, such as are used on heavy equipment, have been in use for many years. Pneumatic devices typically utilize a number of pneumatic lines, which must be connected and interconnected to the various devices. The pneumatic device typically comprises a housing to which a number of components may be connected. The housing is provided with a number of openings for receiving various connections and component connections. 
         [0004]    Numerous types of connectors may be connected to the housing and may include, for example, threaded connectors, friction connectors and so forth. Push To Connect (PTC) fittings may also be used with various types of housing configurations. PTC fittings present a number of distinct advantages over other types of connectors. For instance, it is a relatively simple matter to connect pneumatic tubing with a PTC fitting as one simply needs to push the connector into a port, where the connector is retained by an interference fit. 
         [0005]    Typically, PTC fittings are provided manufactured of a relatively hard plastic. The plastic is typically a highly engineered grade, having high strength characteristics. This means that the plastic material will have relatively little “give” as very high strength characteristics are advantageous for critical applications, such as, vehicle braking and vehicle ride height control. 
         [0006]    The pneumatic device housing may also be provided with a highly engineered grade plastic port for receiving the plastic connector. In addition, various portions of the housing may comprise a highly engineered grade plastic with relatively high strength characteristics. Interference fit connectors, such as a PTC fitting, introduce stress to the surrounding material as the introduced stress between the connector and the port, maintains the connection. 
         [0007]    However, a problem arises in particular with vehicle air brake and vehicle control valve applications, in part, due to the required relatively high strength characteristics of the PTC fitting. The press fit induces “hoop” stress in the port and subsequently the housing, which often results in fracturing in the surrounding material. Any fracturing of the surrounding material can result in loosening of the connection and/or catastrophic failure of the braking and/or height control system. Any failure of vehicle safety systems is unacceptable. 
         [0008]    Therefore, what is desired is a PTC fitting manufactured of a highly engineered grade plastic having high strength characteristics for use in a vehicle air brake and/or height control system that substantially eliminates fracturing in the surrounding material due to introduced stress. 
         [0009]    It is still further desired to provide highly reliable vehicle air brake and/or height control system that uses a PTC fitting manufactured of a highly engineered grade plastic having high strength characteristics that is received in a port of the pneumatic device. 
       SUMMARY OF THE INVENTION 
       [0010]    These and other objectives are achieved in one advantageous embodiment, by the provision of a PTC fitting cartridge manufactured of a highly engineered grade plastic having high strength characteristics used in a vehicle air brake and/or height control system, which when advanced into a component, interconnects with an undercut provided in the surrounding material to substantially eliminate any “hoop” stress to avoid any fracturing of the surrounding material. 
         [0011]    In this manner, rather that utilize the standard interference fitting, the PTC fitting cartridge of the present invention uses a snap fit for retention in the air brake housing or the height control valve housing. The highly engineered grade plastic PTC fitting cartridge will initially deflect radially inward upon advancement into the connector. The exterior of the PTC connector is provided with at least one protrusion that upon advancement of the protrusion past the undercut re-expands radially outward to interact with the undercut. In this manner, any “hoop” stress that may initially be experienced by the surrounding material upon advancement of the PTC fitting cartridge into the port, is only temporary because the PTC fitting cartridge is allowed to re-expand to its normal shape past the undercut. 
         [0012]    As the protrusion(s) interacts with the undercut forming an interlock between the PTC fitting cartridge and the port, the PTC fitting cartridge is securely maintained or locked into the port. Therefore, the convenience of using a PTC fitting cartridge manufactured of a highly engineered grade plastic having high strength characteristics may be used in connection with a vehicle brake housing or a height control valve housing, while still not compromising the integrity of the pneumatic vehicle system. 
         [0013]    It is contemplated that the PTC fitting cartridge may further be provided with means for removing the PTC fitting cartridge from the port. This may include, for example, means for disengaging the protrusion(s) from the undercut, such as deflection of the protrusion(s) radially inwardly so that the PTC fitting cartridge may be withdrawn from the port. For example, the PTC fitting cartridge may be provided with a shoulder on either side of the PTC fitting cartridge to which inward pressure may be applied to deflect the protrusion(s) inwardly. In this manner, the PTC fitting cartridge may then be unlocked from the port and then withdrawn from the housing. 
         [0014]    In one advantageous embodiment, a pneumatic device assembly is provided, comprising a housing for the pneumatic device, where the housing has a port located therein. The pneumatic device assembly further comprises a push to connect fitting cartridge receivable in the port, where the push to connect fitting cartridge comprises plastic and includes at least one protrusion located on an outer surface thereof. The pneumatic device assembly is provided such that the port has an undercut located on an inner surface thereof for receiving the protrusion to create an interlock between the push to connect fitting cartridge and the housing, and the pneumatic device is selected from the group consisting of: a pneumatic brake and a pneumatic height control valve. 
         [0015]    In another advantageous embodiment, a method for connecting a push to connect fitting cartridge to a pneumatic brake or a pneumatic height control valve is provided, comprising the steps of positioning a protrusion on an outer surface of a plastic push to connect fitting cartridge, and positioning a port in a housing of the pneumatic brake or a pneumatic height control valve for receiving the plastic push to connect fitting cartridge therein. The method further comprises the steps of forming an undercut in an inner surface of the port, inserting the plastic push to connect fitting cartridge into the port, and forming an interlock between the push to connect fitting cartridge and the port through the interaction of the protrusion with the undercut. 
         [0016]    In still another advantageous embodiment, a pneumatic device assembly is provided, comprising a housing for the pneumatic device, where the housing having a port located therein, and the port has an inner surface with a cross section diameter of (d 2 ). The port also includes an undercut located on the inner surface, with the undercut having a cross section diameter of (d 4 ), where diameter (d 2 ) is smaller than diameter (d 4 ). The pneumatic device assembly further comprises a push to connect fitting cartridge receivable in the port, where the push to connect fitting cartridge comprises plastic and includes at least one protrusion located on an outer surface thereof. The pneumatic device assembly is provided such that the protrusion, upon advancement of the push to connect fitting cartridge into the port, interacts with the undercut to form an interlock, and the pneumatic device is selected from the group consisting of: a pneumatic brake and a pneumatic height control valve. 
         [0017]    Other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings and accompanying detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an illustration of a PTC cartridge to be inserted into a housing of a pneumatic device. 
           [0019]      FIG. 2  is an illustration of the PTC cartridge according to  FIG. 1  inserted into the housing of the pneumatic device. 
           [0020]      FIG. 3  is an enlarged view of the connection between the PTC connector and the component. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views. 
         [0022]      FIGS. 1 and 2  illustrate a pneumatic device assembly  10 , in which a Push To Connect (PTC) fitting cartridge  12  is illustrated. As seen in  FIG. 1 , PTC cartridge  12  is insertable into port  14  of pneumatic device  16 , which may include, for example, a pneumatic brake and a pneumatic height control valve. 
         [0023]    The PTC cartridge  12  is provided having a generally cylindrical diameter, but may, be provided with virtually any type of cross-section. PTC cartridge  12  is illustrated in  FIG. 1  generally having a cross-section diameter (d). 
         [0024]    PTC cartridge  12  is further illustrated in  FIG. 1  having a cartridge shoulder  28 , which is defined having a cross-section diameter (d 1 ). As can be seen in  FIG. 1 , cartridge shoulder  28  extends out beyond outer surface  26  of the PTC cartridge  12 , such that, diameter (d 1 ) is larger than diameter (d). 
         [0025]    PTC cartridge  12  is further illustrated having a tube  18  connection, which is illustrated in  FIGS. 1 and 2 . Tube  18  may couple to PTC cartridge  12  by means of a tube cavity  20 , which extends from a distal end  22  of PTC cartridge  12 . Tube cavity  20  is provided for receiving pneumatic tube  18  therein, the tube  18  coupled to the port  14  via the PTC cartridge  12 . Tube  18  is provided such that, pressurized air may be selectively introduced and/or exhausted from the pneumatic device  16  via the tube  18 . 
         [0026]    Referring now to port  14  of pneumatic device  16 , port  14  is provided having a generally cylindrical diameter and is provided with an inner surface  24  that is designed to receive outer surface  26  of the PTC cartridge  12  in relatively close fit. The inner surface  24  of port  14  is illustrated having a cross-section diameter (d 2 ). 
         [0027]    In this manner, it is a relatively simple matter to insert PTC cartridge  12  into port  14  to couple tube  18  to pneumatic device  16  as is illustrated in  FIG. 2 . 
         [0028]    Port  14  is further provided with a port shoulder  30 , which is designed to abut cartridge shoulder  28  of PTC cartridge  12  as shown. As can be seen, port shoulder  30  is provided with a beveled section  32  to simplify the insertion of PTC cartridge  12 . 
         [0029]    Port shoulder  30  is provided such that, when PTC cartridge  12  is inserted therein, PTC cartridge  12  is steadied and securely maintained therein. Cartridge shoulder  28  is also provided as a stop for PTC cartridge  12  when cartridge shoulder  28  abuts up against port shoulder  30 . As can be seen, the cross-section diameter (d 1 ) of cartridge shoulder  28  is larger than the cross-section diameter (d 2 ) of the inner surface  24  of port  14 . 
         [0030]    As seen in  FIG. 2 , tube  18  may be inserted in to tube cavity  20  via tube cavity opening  34 . Tube cavity opening  34  is indicated as having an opening with a cross-section diameter (d 3 ), while tube cavity is shown having a cross-section diameter (d 4 ), where diameter (d 3 ) is larger than diameter (d 4 ). In this manner, tube  18  encounters a beveled edge at tube cavity opening  34  to facilitate insertion of tube  18  in cavity opening  34 . 
         [0031]    Referring now to  FIG. 3 , an enlarged view of a section of  FIG. 2  is illustrated, which shows PTC cartridge  12  inserted in port  14 , and more particularly, the interaction of PTC cartridge  12  with the inner surface  24  of port  14 . 
         [0032]    As shown in  FIG. 3 , outer surface  26  of the PTC cartridge  12  is provided with protrusion(s)  36 , which in this embodiment are provided as teeth to engage with inner surface  24 . Also illustrated in  FIG. 3  is undercut  38 , which is situated on inner surface  24  of port  14 . Undercut  38  is provided to engage with protrusion(s)  36  such that, upon advancement of PTC cartridge  12  into port  14 , a snap fit occurs and an interlock is developed. For example, the cross-section diameter (d) of PTC cartridge  12  is provided slightly larger than the cross-section diameter (d 2 ) of the inner surface  24 . Therefore, advancement of PTC cartridge  12  into port  14  will generate “hoop” stress on the surrounding material as the protrusion(s)  36  are slightly deflected radially inward. However, as the protrusion(s)  36  advance past undercut  38 , the protrusion(s)  36  is then able to expand radially outward again thereby reliving any “hoop” stress temporarily encountered by port  14 . 
         [0033]    It may also be seen from  FIG. 3 , that an O-ring  40  is provided in a channel  42 , which is positioned between the inner surface  24  and the PTC cartridge  12 . In this manner an air-tight seal may be created between PTC cartridge  12  and port  14 . It is contemplated that O-ring  40  may comprise any type of material as desired for the application, but typically will comprise a pliable elastic material, such as, for example, rubber. 
         [0034]    It can be seen from  FIG. 3  that the interlock created between PTC cartridge  12  and port  14  creates a highly secure connection, which will not easily be interrupted. This is very advantageous as the coupling will not loosen or disconnect due to, for example, vibration. 
         [0035]    It may however, become necessary to disconnect PTC cartridge  12  for servicing, replacement, etc. As an interlock has been created between PTC cartridge  12  and port  14 , simply applying withdrawing pressure may not detach the PTC cartridge  12  from port  14 . Accordingly, detaching means are provided in the form of cartridge shoulder  28 , which may be deflected radially inward to as to disengage protrusion(s)  36  from undercut  38 . In this manner, PTC cartridge  12  may then be easily withdrawn from port  14 . 
         [0036]    In this manner, a highly engineered grade plastic PTC fitting cartridge may effectively be used for connection of air tubes or conduits to an air brake or height control valve. Therefore, the present system allows for the speed and convenience of PTC fittings to be taken advantage of, while at the same time, any stress encountered by the surrounding material is substantially eliminated to avoid fracture of the surrounding material. 
         [0037]    Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.