Ball plunger for use in a hydraulic lash adjuster and method of making same

Abstract

A cold-formed ball plunger blank is provided for use in manufacturing a finished ball plunger used in a hydraulic lash adjuster that includes a check valve assembly having a check ball and a retainer. The ball plunger blank includes a cup-shaped member that extends from a first end to a second end along a longitudinal axis. The cup-shaped member includes a ball portion adjacent the first end of the member and a body portion adjacent the second end of the member. The body portion has a cavity disposed therein, a counterbore extending from the second end of the body towards the first end of the member, and a shoulder that separates the cavity from the counterbore and at least partially closes the cavity. The shoulder defines a ball seat surface configured to receive the check ball and a retainer receiving surface configured to receive the retainer, wherein the ball seat surface and the retainer receiving surface are to sized to the final dimensions of the finished ball plunger. A method of cold-forming a ball plunger blank including providing a slug having first and second ends, backward extruding the slug at its first end to form a cavity that is defined by a wall, forming a generally ball-shaped outer surface at the second end of the slug to final dimensions, and upsetting at least a portion of the wall to form a shoulder that at least partially closes the cavity and defines a ball seat surface to its final dimensions.

1 . A cold-formed ball plunger blank used to manufacture a finished ball plunger for use in a hydraulic lash adjuster including a check valve assembly having a check ball and a retainer, the ball plunger blank comprising:
 a cup-shaped member that extends from a first end to a second end along a longitudinal axis, the cup-shaped member including:
 a ball portion adjacent the first end of the member; and 
 a body portion adjacent the second end of the member, the body portion having a cavity disposed therein, a counterbore extending from the second end of the body towards the first end of the member, and a shoulder that separates the cavity from the counterbore and at least partially closes the cavity, 
 the shoulder defining a ball seat surface configured to receive the check ball and a retainer receiving surface configured to receive the retainer, 
 wherein the ball seat surface and the retainer receiving surface are to sized to the final dimensions of the finished ball plunger. 
   
   
   
       2 . The ball plunger blank of  claim 1 , wherein the ball portion includes a generally ball-shaped outer surface sized to the final dimensions of the finished ball plunger. 
   
   
       3 . The ball plunger blank of  claim 1 , wherein the generally hemispherical outer surface of the ball portion includes a dimple that extends along the longitudinal axis of the member. 
   
   
       4 . The ball plunger blank of  claim 1 , wherein the ball seat surface includes a rounded annular surface. 
   
   
       5 . The ball plunger blank of  claim 1 , wherein the retainer receiving surface includes a flat annular surface that is oriented substantially perpendicular to the longitudinal axis of the member. 
   
   
       6 . The ball plunger blank of  claim 1 , wherein the cavity includes a first bore adjacent the first end and a second bore adjacent the second end, the second bore having a larger inner diameter than the first bore. 
   
   
       7 . A unitary ball plunger for use in a hydraulic lash adjuster that includes a check valve assembly having a check ball and a retainer, the ball plunger comprising:
 a generally tubular member that extends from a first end to a second end along a longitudinal axis, the tubular member including:   a ball portion adjacent the first end of the member, the ball portion including a generally ball-shaped surface that is cold-formed to its final dimensions and a hole that is generally coaxial with the tubular member;   a body portion adjacent the second end of the tubular member, the body portion having a bore disposed therein that communicates with the hole in the ball portion, a counterbore extending from the second end of the body towards the first end of the tubular member, and a shoulder provided between the bore and the counterbore that at least partially closes the bore, the shoulder defining a ball seat surface configured to receive the check ball and a retainer receiving surface configured to receive the retainer, wherein the ball seat surface and the retainer receiving surface are both cold formed to their respective final dimensions; and   a stem portion that separates the ball portion from the body portion.   
   
   
       8 . The ball plunger of  claim 7 , wherein the body portion includes an annular groove positioned closer to the second end of the member than the first end of the member. 
   
   
       9 . The ball plunger of  claim 8 , wherein the body portion includes a hole that is located within the groove in the body portion, that is oriented generally perpendicular to the longitudinal axis of the tubular member, and that communicates with the bore. 
   
   
       10 . The ball plunger of  claim 7 , wherein the ball seat surface includes a rounded annular surface. 
   
   
       11 . The ball plunger of  claim 7 , wherein the retainer receiving surface includes a flat annular surface that oriented substantially perpendicular to the longitudinal axis of the tubular member. 
   
   
       12 . The ball plunger of  claim 7 , wherein the cavity includes a first bore adjacent the first end and a second bore adjacent the second end, the second bore having a larger inner diameter than the first bore. 
   
   
       13 . A method of cold-forming a ball plunger blank comprising the steps of:
 providing a slug having first and second ends;   backward extruding the slug at its first end to form a cavity that is defined by a wall;   forming a generally ball-shaped outer surface at the second end of the slug to final dimensions; and   upsetting at least a portion of the wall to form a shoulder that at least partially closes the cavity and defines a ball seat surface to final dimensions.   
   
   
       14 . The method of  claim 13 , wherein the providing step includes shearing wire to a desired length to form the slug. 
   
   
       15 . The method of  claim 13 , further comprising the step of squaring the first and second ends of the slug before the backward extruding step. 
   
   
       16 . The method of  claim 13 , further comprising the step of forming a first indentation in the first end of the slug and a second indentation in the second end of the slug before the backward extruding step. 
   
   
       17 . The method of  claim 13 , further comprising the step of forming a dimple in the ball-shaped outer surface. 
   
   
       18 . A method of cold-forming a ball plunger blank using a cold-forming machine having a cutoff station and five forming stations, the method comprising the steps of:
 at the cutoff station, shearing wire to a desired length to form a slug having first and second ends;   at the first forming station, squaring the first and second ends of the slug and forming an indentation in the first end of the slug;   at the second forming station, backward extruding the slug at its first end to form a first bore that is defined by a tubular wall and forming a generally ball-shaped surface to near final dimensions;   at the third forming station, backward extruding the slug through its first end to form a second bore in the slug having a smaller diameter than the first bore;   at the fourth forming station, upsetting at least a portion of the tubular wall to form a shoulder that at least partially closes the first bore and defines a ball seat surface to near final dimensions; and   at the fifth forming station, coining the shoulder to form the ball seat surface to final dimensions.   
   
   
       19 . A method of manufacturing a finished ball plunger for use in a lash adjuster assembly, the method comprising the steps of:
 cold-forming a ball plunger blank having a longitudinal axis to near net shape including the steps of:
 providing a slug having first and second ends; 
 backward extruding the slug at its first end to form a body portion having a cavity disposed therein that is defined by a wall, 
 forming a ball portion adjacent the second end of the slug, the ball portion including a generally ball-shaped surface sized to its final dimensions, and 
 upsetting at least a portion of the wall to form a shoulder that at least partially closes the cavity and defines a ball seat surface sized to its final dimensions; and 
   machining the ball plunger blank to complete the finished ball plunger.   
   
   
       20 . The method of  claim 19 , wherein the machining step includes:
 cutting an annular groove in the ball plunger blank to form a stem portion between the ball portion and the body portion;   cutting an annular groove in the body portion of the ball plunger blank;   drilling a hole in the ball portion of the ball plunger blank that is generally coaxial with the longitudinal axis of the ball plunger blank and communicates with the cavity; and   drilling a hole in the body portion of the ball plunger blank that is located within the groove in the body portion, that is oriented generally perpendicular to the longitudinal axis of the ball plunger blank, and that communicates with the cavity.