Abstract:
An arrangement and method of manufacture for providing a connection between one end of a control rod and a headed pin includes a hard plastic housing having a pin receiving cavity defined therein, the housing overmolded over the rod end and a soft elastomeric vibration isolator to hold the same together without assembly clearances or subjecting the vibration isolator to direct pressure from the pin to avoid excessive lash in the connection. Retention prongs are integrally molded and configured to engage the head of the pin when inserted in the cavity to be deflected to allow assembly and thereafter resist extraction, with the insertion forces much lower than the extraction force.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional applications Ser. No. 60/386,986, filed Jun. 7, 2002 and Ser. No. 60/400,082, filed Jul. 31, 2002. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention concerns rod end terminal connections commonly used to connect control rods to pins mounted to automobile transmission levers and the like to enable shifting of the transmission by the driver of the automobile. The pin is retained in a housing by a ball feature head on the pin snap fit to retention features on the housing. It has become standard practice to interpose a vibration isolator between the connected rod and pin to prevent vibrations from being felt by the driver when grasping a shifter or other member. See U.S. Pat. No. 4,581,953 for an example of such a connection.  
         [0003]     The vibration isolator is usually constructed of a soft compressible material and excessive lash can result if the isolator material is directly contacted by the pin.  
         [0004]     Such connections have been provided by assembling several parts together, and the necessary clearances for assembly also contribute to excessive lash at the connection.  
         [0005]     The cost of manufacturing such linkages typically is high due to the need to assemble several components, and the need to insure that proper assembly of the components has been accomplished.  
         [0006]     Another difficulty is encountered in designing the usually snap fit assembled pin and rod connection so that the force to assemble the connection must be low while the force resisting disconnection of the components must be much higher.  
         [0007]     It is the object of the present invention to provide an arrangement for providing a connection between a pin and control rod including a vibration isolator which minimizes lash between the connected components.  
         [0008]     It is a further object to provide such an arrangement which can be manufactured at low cost.  
         [0009]     It is yet another object to provide a snap fit pin-rod connection in which a desired greater separation force and lesser assembly force can be easily designed for.  
       SUMMARY OF THE INVENTION  
       [0010]     These and other objects which will become apparent upon a reading of the following specification and claims are achieved by an arrangement for establishing a rod end terminal connection having a vibration isolator of minimal thickness interposed between the rod and an overmolded minimally compressible hard plastic housing capturing the rod end and a vibration isolator interposed between the rod end and a pin receiving cavity defined by a hard plastic structure enclosed within the housing. Preferably the vibration isolator is itself overmolded onto the rod end, received in grooves in the rod and to be securely locked thereto. The hard plastic defined cavity is configured to receive the pin and a plurality of integral arcuate prongs are arranged about the inside of the cavity. The prongs are readily deflectable outwardly engagement of the head of the pin with sloping prong surfaces to accommodate insertion of the pin, but pin movement out is resisted by flat prong ends which requires application of a desired high extraction force to deflect the prongs and allow removal of the pin.  
         [0011]     The overmolding of the hard plastic housing eliminates assembly of separate parts as well as eliminating clearances and lash resulting from having separate parts. The housing opening has an overlying web blocking entrance of the pin into the cavity from the wrong side to insure insertion of the pin into the housing from the prior side. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a perspective view of an arrangement for establishing rod end head pin connection according to the invention.  
         [0013]      FIG. 2  is a plan view of the arrangement shown in  FIG. 1  with a fragmentary view of a rod end.  
         [0014]      FIG. 3  is a vertical sectional view taken through the rod end terminal connection shown in  FIG. 1 .  
         [0015]      FIG. 4  is a horizontal sectional view taken through the rod end terminal connection shown in  FIG. 1 .  
         [0016]      FIG. 5  is a fragmentary partially sectional perspective view from one side of the connection and mated pin shown in  FIGS. 1-4 .  
         [0017]      FIG. 6  is a fragmentary partially sectional endwise perspective view of the connection shown in  FIGS. 1-5 .  
         [0018]      FIG. 7  is a fragmentary plan view of a connection with a mating pin according to a second embodiment of the invention.  
         [0019]      FIG. 8  is a view of a vertical section through the connection shown in  FIG. 1 .  
         [0020]      FIG. 9  is a plan view of an assembled inner core piece and vibration isolator components included in the connection shown in  FIGS. 7 and 8 .  
         [0021]      FIG. 10  is a side elevational view of the assembled inner piece core and vibration isolator components shown in  FIG. 9 .  
         [0022]      FIG. 11  is a perspective view of the inner core and assembled isolator components shown in  FIGS. 9 and 10 .  
         [0023]      FIG. 12  is a perspective fragmentary view of the rod and terminal connection and mating pin shown in  FIGS. 7 and 8 . 
     
    
     DETAILED DESCRIPTION  
       [0024]     In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.  
         [0025]     Referring to the drawings, and particularly  FIGS. 1-6 , the present invention provides an arrangement for establishing a connection between a headed pin  10  and one end of a steel control rod  12 . Such connections are commonly used to couple a transmission control rod to an automotive transmission lever by a pin allowing relative rotation. Other control linkage systems for automotive and other applications widely use such connections which allow a changing angle of the control rod on the pin as it is advanced retracted.  
         [0026]     This connection includes a thin walled (approximately 1 mm thick) soft elastomeric vibration isolator  14  preferably molded in place onto the one end of the control rod  12 , with a recess  16  on the one end of the rod  12  keying the vibration isolator  14  to insure retention thereon. The recess  16  also forms an annular feature  17  in the vibration isolator. The vibration isolator  14  could also be separate molded and assembled onto the one end of the control rod  12  (a suitable material is Bayer Desmopan 453 polyester polyethylene based grade) Shore hardness scale 53D (ASTM D2240).  
         [0027]     A pin receiver housing  18  is molded over the vibration isolator  14  and projects in a lengthwise direction away from the one end of the rod  12  to offset a hard plastic structure defining a pin receiving cavity  20  extending in a normal direction from the longitudinal axis of the control rod  12 .  
         [0028]     A portion of the housing  18  is received into the annular recess  17  formed in the vibration isolator  14  to be positively keyed thereto for secure retention.  
         [0029]     The housing  18  is molded from a hard plastic such as Dow Vydyne R533 (Nylon 66% graphite filled (33%), Rockwell harness scale M95 (ASTM D785).  
         [0030]     A pair of pin retention features comprising arcuate prongs  22  are integrally formed on opposite sides of the cavity  20 . Each prong  22  includes an axially extending base wall  24  spaced inwardly from the inside of the housing  18  to create a space allowing a radially outward deflection thereof.  
         [0031]     A radially inward projecting lip portion  26  extends from the free end of the base wall  24 , having a sloping undersurface  28  and a flat end surface  30  at the top as viewed in the drawings.  
         [0032]     The lower end of the cavity  20  is open while a web  32  extends there across at the top to provide an orientation feature insuring correct assembly with the pin  10  able to be inserted only from below as seen in the drawings.  
         [0033]     The pin  10  has a spherical head  34  which when inserted into the cavity  20  deflects the prongs  22  radially outward facilitated by the sloping undersurface  28  of the prongs being cammed outwardly by the spherically curving head  34 . Integral ribs  23  limit outward deflection of the prongs  22 .  
         [0034]     After the head  34  is inserted sufficiently, the head  34  passes lips  26  of the prongs  22  allowing the prongs  22  to snap back to present the flat end face to the undersurface of the head  34 .  
         [0035]     A flange  38  on the pin  10  limits further insertion travel of the pin  34  by engaging the bottom  40  of the housing  18 .  
         [0036]     The insertion force required to install the pin  10  is much less than the force necessary to remove the pin  10  as a result of the sloping undersurface  28  and the flat end face  30 . By varying the thickness of the wall  24 , any particular insertion force maximum and extraction force minimum can be designed for to meet the application requirements. The wall  24  is placed in bending by the camming out of the prongs  22  as the ball head  34  is inserted.  
         [0037]     The manufacturing process involves molding the vibration isolator  14  to the one end of the rod  12 .  
         [0038]     The manufacturing steps are as follows:  
         [0039]     This subassembly is then placed in a mold and housing  18  is overmolded around the isolator-rod subassembly, the housing  18  having a portion located at one end of the rod  12  and formed with a socket opening with radially inwardly projecting engagement prongs for securing the pin. The housing  18  in being molded from a hard plastic material, a low installation force for installing the pin can be achieved compared with much higher extraction forces required to separate the housing  18  from the pin  10 .  
         [0040]     The specific manufacturing process steps are as follows:  
         [0041]     The vibration isolator  14  is installed around the end of the steel rod  12 . The groove  16  in the end of the rod  12  will match up to an inner ridge on the isolator. The vibration isolator  14  is molded around the end of the steel rod  12  with the groove and ridge matching.  
         [0042]     Once the vibration isolator  14  rod  12  subassembly is made, molding of the final terminal assembly takes place. The vibration isolator  14  rod  12  subassembly is placed in the mold into a predetermined position. No special position for orientation is needed. The prongs  22  and load feature of the housing  18  is then molded to create the final assembly. This molding process interlocks the vibration isolator  14  rod  12  subassembly with the newly molded housing  18 .  
         [0043]     This connection and method provides several advantages. The first is that the hard plastic housing  18  with engagement prongs  22  comprise a socket contacting the pin  10 , allowing the design of the prongs  22  to set the amount of installation and extraction force desired. By changing the prong design, i.e., the thickness of the wall, the amount of installation load required to secure the pin  10  can be reduced to meet any requirements and still maintain the required minimum extraction force.  
         [0044]     The second advantage is that by molding the housing  18  around the vibration isolator  14  and steel rod end, this will provide increased strength to the rod end assembly and ensure that the housing  18 , vibration isolator  14 , and steel rod  12  are securely assembled. This design will also interlock these components to eliminate any tolerance gaps between individual parts. Prior designs had the possibility for tolerance gaps between parts, which will cause free play in the system known as “lash”.  
         [0045]     The third advantage is that the vibration isolator  14  is wrapped around the steel rod  12  to avoid direct contact with the pin  10 . The vibration isolator  14  is molded with a small cross section wall to lower the thickness of material subject to compression. This will lower system lash and while still maintaining adequate vibration dampening capabilities.  
         [0046]     The fourth advantage is a reduction in manufacturing cost. By molding the housing  18  over the vibration isolator/steel rod subassembly there is a reduction in cost for manufacturing the connection.  
         [0047]     The fifth advantage is obtained by the addition of the orientation feature  36  to the housing  18 . By adding this feature integrally the housing  18  can only go onto the pin  10  in one direction. Previously this was done by installing a separate component, increasing the cost of manufacture.  
         [0048]     This design will make it easier to install on the vehicle, reduces cost, and reduces the number of parts in the assembly.  
         [0049]     The second embodiment is shown in  FIGS. 7-12 , in which a hard plastic housing  38  is directly molded to one end of the control rod  12 .  
         [0050]     The ring shaped vibration isolator  40  is assembled onto a generally cylindrical hard plastic core piece  42  separately molded. The housing  38  is molded over the vibration isolator  40 . Thus, the vibration isolator  40  does not directly contact the pin  10 .  
         [0051]     The core piece  42  has a central pin receiving cavity  46  formed with inwardly facing deflectable prongs  44  and orientation feature  48  as in the first described embodiment.  
         [0052]     A ridge  43  on the core piece  42  forms grooves  45  matching grooves  47  on the vibration isolator  40  on the core piece  42  and, together with a ridge  41  on the vibration isolator  40 , these ensure mutual retention to the overmolded housing  38 .  
         [0053]     The vibration isolator  40  is installed around the inner core piece  42 . The grooves  45  match up on both parts. The vibration isolator  42  is fully assembled around the inner core piece  42  and the grooves matched. Direction does not matter since the vibration isolator  42  is symmetrical and will go on either direction.  
         [0054]     The inner core piece subassembly is placed in the mold along with the groove end of the steel rod  12 . The inner core piece subassembly is installed on a special pin in the mold. This special pin correctly positions the inner core piece subassembly so that the load path feature of the inner core piece  42  is in an axial line with the steel rod  12 . This will insure that the contact prongs  44  will be positioned  90  degrees to the steel rod  12 .  
         [0055]     Once the inner core piece subassembly is in place, the steel rod  12  is placed in the mold. The rod  12  is positioned so that the rod end contacts the ridge  43  vibration isolator  40 . This will serve as a position stop for the steel rod  12 . This stop feature will make it easier for the operator to properly place the steel rod  12  for the final molding.  
         [0056]     Once the steel rod  12  and the inner core piece subassembly are correctly in place, the outer housing  38  is molded over these two other components. This molding process interlocks the inner core piece subassembly and the steel rod to form the final terminal rod assembly.