Abstract:
The current invention relates generally to a valve recession measuring tool and method for using the same. The valve recession measurement is based upon a measured height of a surface on a portion of the valve relative to a reference plane. The invention operates without requiring the removal of any of the valve rocker arms.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit under Title 35, United States Code, § 119(e) of U.S. Provisional Application Ser. No. 60/848,747 filed Oct. 2, 2006. 

   BACKGROUND 
   Tools for measuring the height of a valve relative to a reference plane or surface are sometimes used to determine how far a valve has recessed into a cylinder head. The amount of recession may be an indication of cylinder head life, so that the cylinder head can be replaced before a damaging failure occurs. 
   Such tools may be referred to as valve height measuring tools or valve recession measuring tools. Typically, an initial measurement will be taken to determine the relative distance between a point on the valve in the cylinder head and another surface. For a number of valve head configurations, known existing tools require that the cylinder head cover and valve rocker arms be removed to expose the valves and to expose a surface of the cylinder head upon which the tool may be placed. Measurements will be taken at periodic intervals, and the difference between the measurements represents valve recession. Each time a measurement is taken, the cylinder head covers and the valve rocker arm assemblies must be removed. In addition to the time required to remove the rocker arms, time must be spent readjusting the rocker arms, which occurs each time the rocker arms are removed and replaced. 
   SUMMARY 
   A valve height measuring tool, which may also be referred to as a valve recession measuring tool, has a center hub defining a reference plane. A measuring assembly, which includes a measuring device, is rotatably mounted to the center hub and will measure the height of valves in a cylinder head relative to the reference plane. The measuring device may be rotated relative to the hub and move along the reference plane from one valve to the next valve until a measurement for all valves in the cylinder head is taken. 
   The valve height measuring tool has a bushing rotatable relative to the center hub, and to the reference plane defined thereon. The bushing is disposed in a cylindrical well defined in the center hub. The measuring device is preferably connected to the bushing and is rotatable therewith. A stem is connected to the center hub in a bottom thereof. 
   Valve recession is determined by measuring valve height or valve distance relative to the reference plane at periodic intervals, and calculating the height change which corresponds to the valve recession in the cylinder head. Prior to taking any measurements, the cylinder head cover is removed and the valve height measuring tool is placed in the measuring position on the cylinder head. The valve height measuring tool is a self-positioning tool, in that it will fit on the cylinder head only in the measuring position. The measuring device will contact the reference plane, and is “zeroed” on the reference plane. The reference plane has cutouts through which the valves extend. The measuring device is moved to engage the valve on a surface thereof, for example, on a valve spring retainer surface, and the height, or distance is measured. Because the reference plane is a constant, measurements can be taken relative to the same surface with accuracy. Measurements are taken at periodic intervals and a comparison of the measured distances discloses the valve recession. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 —Is an exploded perspective view of the hub, bushing and stem of the valve recession measuring tool. 
     FIG.  2 —Is a top view of an embodiment of the hub. 
     FIG.  3 —Is a view from line  3 - 3  of  FIG. 2 . 
     FIG.  4 —Is a side view of the hub. 
     FIG.  5 —Is a side view of a stem of the valve recession measuring tool. 
     FIG.  6 —Is a side view of a rotatable bushing. 
     FIG.  7 —Is a top view of a rotatable bushing. 
     FIG.  8 —Is a perspective view of the valve recession measuring tool. 
     FIG.  9 —Is a cross-sectional view of the hub, the bushing and the stem of the valve recession measuring tool. 
     FIG.  10 —Is a top view of a cylinder head with the cover removed, rocker arms still connected, and the valve recession measuring tool in place. 
     FIG.  11 —Is a view from line  11 - 11  of  FIG. 10 . 
     FIG.  12 —Is a section view showing a valve extending through a cylinder head. 
     FIG.  13 —Is an example of a prior art tool used to determine valve recession. 
     FIG.  14 —Shows the prior art tool measuring valve height. 
   

   DETAILED DESCRIPTION 
     FIGS. 13 and 14  depict an example of a prior art measuring platform  5  which requires removal of the rocker assemblies associated with valves in a cylinder head prior to measuring a height of a valve relative to the platform. Repetitive measurements are taken to determine a height change which corresponds to valve recession in the cylinder head but the cylinder head cover, along with the rocker arm assemblies must be removed any time a measurement is taken. 
   Valve recession measuring tool  10 , which may also be referred to as a valve height measuring tool  10 , will measure valve height relative to a reference plane without the necessity of removing the valve rocker assemblies associated therewith. Valve recession in a cylinder head, which is a parameter that may be utilized to predict cylinder head life, can thus be determined without removing rocker arm assemblies. 
   Valve recession measuring tool  10  comprises hub  15 , bushing  20 , and stem  25 . Bushing  20  is rotatable relative to hub  15 , and stem  25  is connected to hub  15 , and may be, for example, threaded to hub  15 . A measuring assembly  30  is connected to bushing  20 . Valve recession tool  10  is shown in a measuring position in  FIGS. 10 and 11  on a cylinder head  32 , with the cylinder head cover removed. Cylinder head  32  is of a type that might be used, for example, in a 6, 12 or 16 cylinder engine, that would require 6, 12 or 16 cylinder heads. Each cylinder head  32  in the described embodiment has four valves  34  with a valve head  35 , which is shown in  FIG. 12 . Valve head  35  may have a plurality of portions, for example,  35   a ,  35   b  and  35   c , each of which has a slightly different angle from vertical at the outer surface thereof. A valve seat  37  is fixed in cylinder head  32 , and may be pressed into cylinder head  32 . Seat  37  may be machined to match the angles on valve head  35 . Each valve  34  comprises a valve stem  36  extending from valve head  35  and has a valve end  38 . A valve spring  40  is disposed about valve stem  36 , and a valve spring retainer  42  is fixed to valve stem  36  to hold valve spring  40  in place. Valve spring retainer  42  has a valve spring retainer surface  44 . A split lock ring, or split bushing  43  is disposed about valve stem  36  and has a ridge  45  thereon that extends into a groove  47  on valve stem  36 . Valve spring retainer  42  fits around the tapered outer surface of split bushing  43 , and the force applied by valve spring  40  uses split bushing  43  to close around valve stem  36  and valve spring retainer  42  is held in place by split bushing  43 . 
   Cylinder head  32  includes rocker arm assemblies  46 . Each rocker arm assembly  46  has a pair of rocker arms  48 , each of which in operation will normally be in contact with its corresponding valve end  38 . Cylinder head  32  also includes a spark plug  49  in a spark plug well. When cylinder head  32  is operating in an engine, valve  34  will move so that valve head  35  reciprocates out of contact and back into contact with valve seat  37 . Valve head  35  will repetitively engage and disengage valve seat  37 , and will do so with sufficient force such that over time valve seat  37  will wear, causing valve recession into valve seat  37 . 
   Referring back to  FIGS. 1 ,  2 , and  3 , hub  15  has a top surface  50  and a bottom surface  52 . When measuring tool  10  is in its measuring position, bottom surface  52  will engage a cylinder head surface  54 . Hub  15  defines a cylindrical inner well  56  with diameter  58 . Cylindrical inner well  56  extends from top surface  50  downwardly a portion of the way through thickness  60  of hub  15  which is defined by top and bottom surfaces  50  and  52  thereof. Inner well  56  has bottom  62 . An opening  64 , which is preferably a threaded opening  64 , extends from bottom  62  of cylindrical well  56  to bottom surface  52  of hub  15 . 
   A semi-circular, or U-shaped groove  66  defined in hub  15  defines upper and lower rims  68  and  70 , respectively, with a space  72  extending therebetween. Center hub  15  has a periphery  74 , that may be a circular periphery  74 , with arcuate cutouts  76  therein. A center line  78  bisects hub  15  when it is placed in its measuring position, which may be referred to as a 0° and 180° position when measuring tool  10  is mounted on cylinder head  32 . As will be explained in more detail, hub  15  is an automatically positioning or self-positioning hub, since it can only be placed in the 0° or 180° position, which is the proper measuring position. 
   Hub  15  defines a reference plane or reference surface  80 , which may be, for example, a recessed ledge at the periphery  74  of hub  15 . Reference plane  80  is not continuous, and is interrupted by cutouts  76 . Reference plane  80  establishes a reference surface for taking measurements, and provides for accurately taking repeatable, consistent measurements of valve height relative thereto. 
   Referring to  FIG. 1 , stem  25  has first or upper end  82  and second or lower end  84 . Stem  25  is threaded at the upper end  82  thereof for threaded connection to hub  15  at threaded opening  64 . Stem  25  has central opening  86 , and is adapted to circumscribe spark plug  49  in cylinder head  32 . 
   Bushing  20  has a bushing outer surface  90  with outer diameter  92 . A shoulder  94  has upper and lower surfaces  95  and  96  and extends radially outwardly from diameter  92 . A mounting point opening  98 , which is a threaded opening  98 , may be defined in top surface  95  of shoulder  94 . Measuring assembly  30  is connected, for example, by threading to bushing  20  at mounting point  98 . Bushing  20  has central opening  100  with first and second diameters  102  and  104 , wherein diameter  104  is smaller than diameter  102 . When valve height measuring tool  10  is assembled, bushing  20  is slidably disposed in cylindrical inner well  56  of hub  15 , and is rotatable relative to hub  15 . Measuring assembly  30 , which is attached to bushing  20 , is likewise rotatable relative to hub  15 , and to reference plane  80 . 
   Referring now to  FIG. 8 , measuring assembly  30  comprises a mounting rod  110 , universal mounting clamp  112 , support arm  114  and measuring device  116 . Mounting rod  110  is preferably affixed to bushing  20  by threading into mounting opening  98  to connect measuring device  116  to bushing  20 . Universal clamp  112  tightens around mounting rod  110  to leave a desired length of mounting rod  110  below universal clamp  112 . Support arm  114  is slidably disposed through universal clamp  112  and tightened into place. Support arm  114  is affixed to, and may be integrally affixed to measuring device  116 . Variations of the combination of mounting rod  110 , support arm  114  and universal clamp  112  may be used. Measuring device  116  may be any device capable of measuring a differential distance between two surfaces. The embodiment shown depicts a back plunger indicator. 
   The method of operation of valve recession measuring tool  10  comprises removing a cylinder head cover (not shown) to expose the valves  34 . Valve recession measuring tool  10  may be used with any number of cylinder head types, but is particularly useful with cylinder heads used in the VHP family of Waukesha engines. As depicted in  FIGS. 10 and 11 , cylinder head  32  has four valves  34 . Rocker arm assemblies  46  are left in place, and measuring tool  10  is placed in its measuring position. Measuring tool  10  can only be placed in a proper measuring position, the 0° or 180° position, and therefore self positions, or automatically positions. Any spark plug wire is removed and spark plug  49 , and any extension, will extend through central opening  86  in stem  25 , and opening  100  in bushing  20 . If desired, measuring tool  10  can be used without stem  25 . 
   Bottom surface  52  of hub  15  will engage cylinder head surface  54  when measuring tool  10  is in place in its measuring position, so that reference plane  80  will be a constant. Bushing  20  is placed in inner well  56 , and is rotatable relative to hub  15  and to reference plane  80 . Mounting rod  110  is threaded to bushing  20 , and universal clamp  112  is tightened thereon so that a tip end  118  of measuring device  116  will contact reference plane  80 . Measuring device  116  may have an extender  120 , so that tip  118  is on extender  120 . Measuring device  116  may be positioned so that extender  120  is generally upright, or may be angled, but in either case, will be “zeroed” on reference plane  80 . In other words, tip end  118  will be placed into contact with reference plane  80 , and the readout on the measuring device  116  will be set to zero. 
   Bushing  20  is rotated relative to reference plane  80 , and when tip  118  reaches a cutout  76 , it is moved to engage a surface on valve  34 , and determine a height, or distance relative to the reference plane  80 . The distance will be readable from the gauge or back plunger indicator  116 . The surface may be, for example, a valve spring retainer surface  44 . Preferably, the surface on which the measurement is taken is higher or above reference plane  80  on hub  15  as viewed in  FIG. 11 . Bushing  20 , along with measuring assembly  30 , is rotated relative to the hub so that in the embodiment shown, a measurement is taken with respect to each valve  34 , and in the example shown on valve spring retainer surface  44  of each valve  34 .  FIG. 10  shows in phantom lines measuring device  116  rotated and positioned to measure valve height for the three valves  34  other than the valve  34  over which the measuring device is placed in  FIG. 10 . 
   The initial measurement is preferably taken on a cylinder head  32  in an engine that has been operated for a short period of time, for example, two to three days. The first measurement is a base measurement. Each valve  34  can be identified, for example, as an intake or an exhaust valve and can be identified by which side of the center line  78  the valve  34  is on for purposes of record-keeping. Other record-keeping variations are likewise possible. 
   The cylinder head cover may be replaced after initial measurements are taken, and the engine operated for a period of time. At scheduled intervals, for example, sixty to ninety days or at scheduled shut-downs, measurements are taken and compared with the prior measurement. The difference between measurements will constitute the amount of valve recession  122  (see  FIG. 12 ) into valve seat  37 . Valve recession is an indicator that may be utilized for determining and predicting cylinder head life and a corresponding engine life. For example, a valve recession of 0.075 to 0.100 may constitute sufficient recession such that the cylinder head should be replaced. Such numbers are exemplary and the values may differ depending upon the cylinder head. The amount of valve recession is an indicator of when the cylinder may fail, and allows maintenance and/or replacement to be scheduled prior to the predicted failure of the cylinder, which if it occurs can be a catastrophic event. Generally, all of the cylinder heads in an engine will be replaced at once. Cylinder heads in an engine may be replaced once or twice but generally after cylinder heads have been replaced two times, the entire engine may be replaced or rebuilt. 
   As described herein, valve recession measuring tool  10  can accurately and repetitively measure valve height, and specifically the height or distance from a reference plane to a point on the valve. Measurements are taken, and valve recession is determined without removing rocker arm assemblies  46 . Because rocker arm assemblies  46  are not removed, valuable time is saved. With prior art devices, such as the platform  5 , rocker arm assemblies must be removed so the legs of the platform engage a cylinder head surface. For example, prior art tool  5  has platform surface  130  with legs  132  extending downwardly therefrom. Platform surface  130  is placed over valves  34  and legs  132  will engage a cylinder head  32 . A measuring device  136  will rest upon platform surface  130 , and extend through a slot  138  to engage an end of valve stem  36 . Rocker arm assemblies and the cylinder head cover are then replaced. The process takes several hours during which the engine could be operating and personnel can be engaged in other tasks. 
   Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as those inherent therein. While preferred embodiments of the present invention have been illustrated for the purpose of the present disclosure, changes in the arrangement and construction of parts and the performance of steps can be made by those skilled in the art, which changes are encompassed within the scope and spirit of the present invention as defined by the appended claims.