Method and apparatus for forming valve cores

A first locator engages lands defining a first groove in a valve core to position that first groove accurately relative to a first pair of notch forming tools. The first pair of notch forming tools then engage axially extending edges of lands defining that first groove to form metering notches. The first locator and first pair of notch forming tools are disengaged from the valve core. Then, a second locator engages lands defining a second groove to accurately position the valve core relative to a second pair of notch forming tools. The second pair of notch forming tools engage the valve core to form metering notches in the edges of lands defining the second groove. The second locator and second set of notch forming tools are retracted from engagement with the valve core. Thus, the metering notches are precisely and independently formed relative to each land.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved method and apparatus 
for shaping the edges of flow control lands of a valve core, and more 
specifically to a method and apparatus for forming fluid flow metering 
notches in the lands of a valve core. 
Power steering control valves of the type disclosed in U.S. Pat. Nos. 
3,709,099 and 3,921,669 have a valve core which is rotatable relative to a 
valve sleeve. The valve core has axially extending lands with axially 
extending grooves between the lands. The lands and grooves in the valve 
core cooperate with passages in the sleeve to direct fluid flow to and 
from a power steering motor. Metering notches have been formed in the 
edges of the lands in the valve core to provide a metered flow of fluid 
under pressure through the valve. The metering notches provide a variation 
in the flow area through the valve to provide the desired power assist 
characteristics. 
The metering notches must be accurately formed relative to the lands. Even 
slight inaccuracies in forming the metering notches relative to a land 
results in a different response of the power steering motor upon actuation 
in one direction than the response which is obtained upon actuation in the 
other direction. 
Prior art methods and apparatus for forming metering notches in valve cores 
are disclosed in U.S. Pat. Nos. 4,100,785 and 4,103,407 and in German Pat. 
No. 3,137,367. Typically, the valve core is positioned by a locator, and 
then the metering notches are simultaneously formed in the edges of a 
plurality of lands of the valve core by a plurality of tools which are 
simultaneously brought into engagement with the edges of the lands. Due to 
manufacturing tolerances, one or more of the lands may be slightly 
displaced from their intended position relative to other lands. Thus, the 
metering notch formed on one side of a displaced land may be slightly 
wider than the intended width of the metering notch, while the metering 
notch on the other side of the land may be slightly narrower than its 
intended width. Due to the difference in the configuration of the metering 
notches on opposite sides of the land, the response of the power steering 
motor to rotation of the valve core in opposite directions will be 
somewhat different. In high pressure hydraulic fluid flow control, small 
differences in flow area can produce large differences in result. Hence, 
extreme accuracy in forming flow control edges is critical. 
SUMMARY OF THE PRESENT INVENTION 
The present invention provides a new and improved method and apparatus for 
manufacturing a valve core with precisely located and formed metering 
notches. In practicing the invention, a first locator engages surfaces of 
lands on opposite sides of one of a plurality of grooves formed in the 
valve core to position that groove and lands relative to a first set of 
notch forming tools. Metering notches are then formed in only the edges of 
the lands on opposite sides of that groove. Since the surfaces of only the 
lands in which the metering notches are to be formed is engaged by the 
locator to position the valve core, a slight inaccuracy in the location of 
the lands relative to other lands does not result in inaccurate formation 
of the metering notches in the land edges. 
Once the metering notches have been formed in the edges of at least one of 
the lands, the first locator is disengaged from the land surfaces defining 
the groove. A second locator is then moved into engagement with land 
surfaces defining the next groove to position the next land relative to a 
second set of notch forming tools. Once the next land has been positioned 
relative to the second set of notch forming tools, the metering notches 
are formed in the edges of the next land. Thus, any inaccuracy in the 
location of the next lands or groove relative to the other lands or 
grooves does not result in inaccuracy in the configuration of the notches 
in the land edges defining the next groove.

DESCRIPTION OF ONE SPECIFIC PREFERRED EMBODIMENT OF THE INVENTION 
The present inventon relates to the manufacture of a valve and particularly 
to the formation of notches in the edge of a land of a valve core which 
rotates within a valve sleeve. Valves made in accordance with the 
invention may have many uses and may be of different constructions. The 
valve described herein is a valve for use in a hydraulic power steering 
mechanism. 
The valve includes a valve core 20 (FIG. 1) received in a valve sleeve 22 
(FIG. 2). The valve core 20 (FIG. 1) has a generally cylindrical body 24 
having an input end portion 26 and a distal end portion 28. The input end 
portion is connectable with a shaft (not shown) fixed to the steering 
wheel of the vehicle. The distal end portion 28 has a pair of drive keys 
32 for connection with a worm shaft (not shown) of a power steering gear, 
as is known. 
The cylindrical body 24 of the valve core 20 has a plurality of lands 36 on 
its outer surface defining a plurality of axially extending grooves 38. 
FIG. 2 illustrates the valve core 20 and sleeve 22 cooperating in a 
neutral position in an open center power steering valve. In this neutral 
position, pressurized fluid is delivered from a pump through inlets 46 
into grooves 38a and 38b. The fluid is then directed over the lands 36 
through ports 48 and 50 which communicate with respective chambers in a 
power steering motor. The fluid is then directed from ports 48 and 50 
through the grooves 38 into outlets 51 which are connected with a fluid 
reservoir. 
Upon rotation of the valve core 20 relative to the sleeve 22 fluid pressure 
is increased in respective power steering motor chambers. For example, if 
the valve core 20 is rotated counterclockwise, as viewed in FIG. 2, ports 
48 are further exposed to inlets 46 while being further restricted from 
the outlets 51. Simultaneously, ports 50 are further restricted from inlet 
46 while further exposed to outlets 51. Thus, the power steering chamber 
connected with ports 48 is further pressurized to actuate a power steering 
motor in one direction. It will be obvious that rotating the valve core 20 
clockwise, as viewed in FIG. 2, functions to similarly pressurize the 
chamber connected with ports 50 to actuate the power steering motor in 
another direction. 
Metering notches 54 are selectively provided in some of the axially 
extending edges 56 of the lands 36. The metering notches 54 provide a 
gradual and controlled variation of the fluid flow area at one edge 56 of 
a land 36 upon rotation of the valve core 20, as is known. 
In accordance with the present invention, the metering notches 54 are 
simultaneously formed in both edges 56 of one land 36 after that one 
groove defined by the lands has been accurately positioned relative to 
forming tools. Thus, a first groove 38a (FIG. 5) is accurately positioned 
by a first locator 62 relative to a first set of forming tools 64. The 
metering notches 54 are formed in the first two lands 36 and then the 
locator 62 and forming tools 64 are disengaged from the valve core 20. 
Then, the second groove 36b is accurately positioned by a second locator 
72 relative to a second set of forming tools 74. The metering notches 54 
are then formed in the second lands 36 by the second set of forming tools 
74 while the first locator 62 is not engaged with the valve core 20. 
The valve core 20 produced in accordance with the present invention has the 
advantage that each groove 38a and 38b is separately positioned before 
the metering notches 54 are formed in the lands defining such groove. 
Therefore, any misalignment of the grooves 38 with respect to each other 
due to manufacturing tolerance stack-up does not affect the accuracy of 
location of the metering notches 54 relative to a particular land. For 
example, if one groove 38 is circumferentially offset somewhat relative to 
other grooves, the metering notches 54 are nonetheless accurately formed 
in the lands defining both of the grooves. 
The apparatus embodying the present invention engages the surfaces of a 
first set of lands 36 defining a first groove 38a to position the first 
set of lands and then forms metering notches 54 in the edges 56 of that 
first set of lands. The apparatus then disengages the first set of lands. 
The apparatus then engages the surfaces of a second set of lands 36 
defining a second groove 38b and forms metering notches 54 in the edges 56 
of the second set of lands 36. 
The apparatus of the present invention includes a fixture 82 (FIG. 3) with 
six hydraulic cylinders 84 attached. Each hydraulic cylinder 84 is 
actuated by a fluid circuit 86. FIG. 3 illustrates the fluid circuits 86 
schematically on the left side of the apparatus and has eliminated them 
from the right side of the apparatus for simplicity. It will be obvious 
that similar fluid circuits are also used on the right side of the 
apparatus in FIG. 3. A programmable controller 88 operates to control the 
solenoids 90 of the fluid circuits 86 for timing the sequence as to when 
each hydraulic cylinder 84 is actuated. 
Each of the hydraulic cylinders 84 is of the single-acting piston type, as 
is known. The hydraulic cylinder 84 is spring biased to the normally 
retracted position illustrated in FIG. 5. Fluid is directed to the 
hydraulic cylinder 84 (FIG. 3) by the control valve 92 of the fluid 
circuit 86. The control valve 92 normally vents the hydraulic cylinder 84 
to the reservoir 94. Fluid is selectively delivered from a supply pump 96 
through the control valve 92 to the hydraulic cylinder 84 when the 
solenoid 90 receives an actuating signal from the programmable controller 
88. Although FIG. 3 illustrates three separate reservoirs 94 and pumps 96, 
it will be obvious that one pump and one reservoir could be fluidly 
connected with all of the cylinders 84. Each solenoid 90 is electrically 
connected to the programmable controller 88 by wires 102, 104 or 106. 
Wires 103, 105 and 107 are electrically connected to solenoids (not shown) 
on the right side of the apparatus in a similar manner. 
The fixture 82 (FIG. 4) includes a base plate 112 with a circular opening 
114 to allow the distal end portion 28 of the valve core 20 to extend 
through the base plate. The base plate 112 has a resting surface 116 for 
the drive keys 32 to engage to support the valve core 20 and prevent the 
valve core 20 from further downward axial movement relative to the fixture 
82. 
The fixture 82 also includes an upper portion 120 attached to the base 
plate 112. The upper portion 120 has a circular opening 122 for the valve 
core 20 to axially extend through. The upper portion 120 also has a pair 
of slots 124 (FIG. 3) extending therethrough, so that the drive keys 32 do 
not contact the upper portion 120 as the valve core 20 is longitudinally 
extended through the opening 122. The slots 124 also serve to rough 
position the valve core 20 so that the grooves 38a and 38b are 
approximately in a desired position relative to the locators 62 and 72 
(FIG. 5). The circular openings 114 and 122 (FIG. 4) are slightly larger 
than the outside diameter of the valve core 20. This allows a gap or 
clearance 126 (FIG. 3), to exist so that the valve core 20 can easily be 
passed through the circular openings 114 and 122. 
The apparatus has a first locating assembly 132 (FIG. 5), which includes 
the first locator 62, for engaging the surfaces defining a first groove 
38a. A first set of coining punches 134 includes a pair of forming tools 
64 for forming metering notches 54 in opposite edges of a first set of 
lands 36. 
The apparatus also has a second locating assembly 142, which includes the 
second locator 72, for engaging the surfaces defining a second groove 38b. 
A second set of coining punches 144 includes a pair of forming tools 74 
for forming the metering notches 54 in the edges of the second set of 
lands 36. 
The valve core 20 (FIG. 3) is telescopically inserted through the opening 
122 in the fixture 82. The drive keys 32 (FIG. 4) engage the resting 
surface 116 of the base plate 112 to prevent any further downward axial 
movement of the valve core 20. The gap 126 (FIG. 3) permits the valve core 
20 to move slightly in a rotational and linearly transverse direction 
relative to the valve core axis. 
The first locating assembly 132 is actuated by a signal from the 
programmable controller 88 to extend inwardly towards the mounted valve 
core 20. The solenoid 90 associated with the first locating assembly 132 
receives the signal from the programmable controller 88 through wire 104 
(shown broken for simplicity). The solenoid 90 changes the position of the 
control valve 92 to direct pressure from the pump 96 to the hydraulic 
cylinder 84a through hydraulic line 146. Hydraulic pressure exerts a force 
on the piston in the cylinder 84a, as is known, to extend the locator tool 
62 from its retracted position of FIG. 5 to engage the mounted valve core 
20, as illustrated in FIG. 6. The first locator 62 is shaped similar to 
the groove 38a configuration. 
As the first locator 62 is extended, locator surfaces 152 (FIG. 7) engage 
the groove sides 154. This causes the valve core 20 to rotate in either 
direction 156 in order to be properly positioned relative to the first set 
of forming tools 64 (FIG. 5). A clearance gap 158 exists between the 
bottom surface of the groove 38a and the leading edge 159 of the first 
locator 62. This assures that the locator surfaces 152 contact only the 
groove sides 154. Extending the first locator 62 to engage the valve core 
20, forces the cylindrical body 24 and lands 36 of the valve core to 
contact the circular openings 114 and 122 (FIG. 4) of the fixture 82 
opposite the first locator. This solidly holds the valve core 20 in the 
desired position for coining the metering notches 54. 
The first locator 62 has a pair of recesses 162 (FIG. 8) to prevent contact 
with the first set of forming tools 64 upon their extension to engage the 
valve core 20. The recesses 162 also prevent displaced material 166 from 
engaging the first locator 62 during formation of the metering notch 54. 
This assures that the displaced material 166 does not reposition the valve 
core 20 during formation of the metering notch 54. 
Once the groove 38a is located accurately relative to the first set of 
forming tools 64, metering notches are formed in the groove sides 154 
where they intersect the lands 36. The hydraulic cylinders 84b (FIG. 3) 
are operated simultaneously to move the punches from a retracted position, 
as seen in FIG. 5, to the extended position illustrated in FIG. 6. As the 
first set of forming tools 64 extend, the nose or leading edge of the 
forming tools engages the land 36 adjacent to the groove 38a. The nose of 
the forming tool pushes metal of the land inwardly to form the metering 
notch 54 in the lands 36. The first set of forming tools 64 are adjusted 
to stop, as is known in the art, at a predetermined depth. 
Once the first set of forming tools 64 have formed the metering notches 54 
to their predetermined depth, the first set of coining punches 134 are 
activated by the programmable controller 88 to move from their extended 
position back to the retracted position illustrated in FIG. 5. Next, the 
programmable controller 88 signals the first locating assembly 132 to move 
from its extended position, engaging the valve core 20, back to the 
retracted position illustrated in FIG. 5. 
During the formation of the metering notches 54, only the first locator 62 
engages the valve core 20. The second locator 72 remains in its retracted 
position as illustrated in FIG. 6. Therefore, the valve core 20 was 
accurately positioned in order to form the metering notches 54 only in the 
lands 36 defining first groove 38a. 
After metering notches 54 are formed and the first locator 62 and the first 
set of coining tools 64 are retracted, the apparatus is ready to form 
metering notches in the lands 36 defining the second groove 38b. The 
second locating assembly 142 (FIG. 5) is then actuated to extend from the 
retracted position illustrated in FIG. 5, to the extended position 
illustrated in FIG. 9. The second locator 72 engages sides of the second 
groove 38b as described above for the first locator 62 engaging the first 
groove 38a. The valve core 20 can move slightly to accurately locate the 
sides of the second groove 38b relative to a second set of forming tools 
74. 
The second set of coining punches 144 is then signaled to extend by the 
programmable controller 88. The second set of forming tools 74 then engage 
the valve core to form metering notches 54 similar to the manner described 
above for the first groove 38a. At this time, the first locator 62 and the 
first set of forming tools 64 are in their retracted position out of 
engagment with the valve core 20. 
The programmable controller 88 signals the second set of coining punches 
144 to retract from engagement with the valve core 20. The programmable 
controller then signals the first locating assembly 142 to move to the 
retracted position illustrated in FIG. 5. The valve core 20 is then 
removed from the fixture 82.