Solenoid operated valve and dashpot assembly

A dashpot assembly has a movable cylindrical element mounted within a housing. The movable element has a chamber with a first opening for restricting flow of fluid into the chamber and a second opening for permitting rapid flow of fluid out of the chamber. An enlarged head is disposed inside the chamber and is coupled to a poppet with a spring coupled between the poppet and the movable element. When the poppet moves in a direction away from the movable element, the enlarged head closes the second opening and pulls the element. Fluid then flows into the chamber only through the restricted first opening, thereby damping the rate of movement of the poppet. When the poppet moves in a direction toward the movable element, the enlarged head opens the second opening and the spring is effective to move the element in the same direction; fluid flows unrestricted through the second opening, thereby permitting an undamped movement of the poppet.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
This invention relates generally to dashpot assemblies and more 
specifically to dashpot assemblies used for damping the movement of 
poppets. 
B. Background Art 
A problem common to solenoid actuated poppet valves is obtaining proper 
response to the pressure actuating force to produce the desired control of 
fluid. Too slow or too fast movement responsive to the applied pressure 
may result in uncontrolled oscillation, chatter, and generally 
unacceptable performance. More particularly, poppet valves provide quick 
opening and closing times but produce rapid fluid changes, which in turn 
produce abrupt displacement of a mass or load downstream of the valve 
seat. This abrupt displacement may cause damage to the mass being 
displaced. 
In some applications it is desirable to damp the opening of a valve orifice 
but permit its rapid closing. As shown, for example, in U.S. Pat. No. 
4,202,250, a dashpot assembly controls the movement of a normally closed 
poppet. When actuated to open, the dashpot is effective to damp the 
opening of the valve orifice by damping the movement of the poppet. 
However, when actuated to close, the dashpot permits rapid closing of the 
orifice. 
In some applications the reverse may be desirable. That is, it may be 
desirable to damp the closing of an orifice but permit its rapid opening. 
As an example, in an agricultural combine having a heavy header and 
springy tires, a normally open poppet is actuated to a closed state to 
start raising the header, but is actuated to the normally open state to 
stop raising the header. Accordingly, the starting movement of the header 
must be damped to prevent start shock. On the other hand, once the header 
reaches to desired height, overshoot must be prevented by rapidly stopping 
the raising. 
Therefore, an object of this invention is to provide a dashpot assembly for 
damping the movement of a poppet during its actuation to the closed state, 
but to provide an undamped movement during its actuation back to its open 
state. 
SUMMARY OF THE INVENTION 
A valve system having a raise and a lower two stage valve assembly with the 
raise assembly including a raise pilot and a raise second stage. The lower 
assembly includes a lower pilot and a lower second stage. The raise and 
lower second stage poppets each have an outer contour to provide a 
predetermined flow area. 
A dashpot assembly is provided for the lower second stage poppet and 
comprises an element mounted in a fluid-filled housing for movement in 
each of two opposite directions. The movable element has formed in it 
first and second openings through at least one of which fluid must flow to 
permit movement of the movable element in either of the opposite 
directions within the housing. The first opening permits through it only a 
restricted flow of fluid and the second opening permits through it a 
relatively large and rapid flow of fluid. There is further provided means 
for closing the second opening and for following movements of the poppet. 
Upon movement of the poppet in a first direction the closing means also 
(a) causes the movable element to follow movements of the poppet by moving 
in one of said opposite directions in the housing and (b) closes the 
second opening to permit restricted fluid flow only through the first 
opening in the movable element. In this manner, the movement of the 
movable element and the poppet is damped. Upon movement of the poppet in a 
second direction the closing means is effective to open the second opening 
to permit rapid fluid flow through the second opening and thereby to 
permit relatively undamped movement of the movable element and poppet.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1, 2A and 2B, there is shown a dashpot assembly 80 
for controlling the movement of a poppet 110. Dashpot assembly 80 
comprises cylindrical element 94 slidably mounted within a housing 90. 
Poppet 110, it will be understood, is a conventional poppet which can be 
actuated to close or open an orifice 111 of a fluid circuit (not shown). 
When moving in a direction away from movable element 94, poppet 110 tends 
to close the orifice; when moving in a direction toward movable element 
94, the poppet tends to open the orifice. As will be explained in detail, 
dashpot assembly 80 is effective to damp the rate of movement of poppet 
110, when the poppet is moving to the left in a direction away from 
movable element 94; dashpot assembly 80, however, permits an undamped 
movement of poppet 110, when the poppet is moving to the right in a 
direction toward movable element 94. 
More particularly, housing 90 comprises an elongated member having at one 
end a decreased outer diameter externally threaded extension 130 which is 
adapted to be threaded into a complementary internally threaded port of a 
fluid circuit (not shown). 
Housing 90 has inner bore 116 formed in two sections. A first of the 
sections defines a decreased inner diameter tubular chamber 116b disposed 
adjacent poppet 110. Chamber 116b opens into an increased inner diameter 
tubular chamber 116a which is remote from the poppet. A radially directed 
inner wall 118 connects the inner walls of chambers 116a, b. Movable 
element 94 defines a first section 94b of decreased outer diameter which 
is movably received within chamber 116a. A second section 94a has an 
increased outer diameter which is movably received within chamber 116a. 
Section 94a of element 94 has an inner tubular chamber 104a remote from 
poppet 110 which decreases in inner diameter to form a tubular chamber 
104b for section 94b. An inner radial wall 114 connects the inner walls of 
chambers 104a and 104b and defines an opening between the chambers. The 
other ends of both chambers are also open. 
A connecting rod 100 has threads 120 at one end which threadedly engage 
poppet 110. The other end of rod 110 extends through chamber 104b and 
terminates in an enlarged head 106 disposed within chamber 104a. The outer 
diameter of rod 100 and the inner diameter of chamber 104b are selected so 
that fluid may easily flow through the channel formed between rod 100 and 
chamber 104b so long as head 106 is positioned away from wall 114 as 
illustrated in FIG. 2A. Head 106 has a substantially larger outer diameter 
than the diameter of channel 104b. Inner surface 106a of head 106 facing 
wall 114 is flat thereby to provide a sealing surface when surface 106a 
engages wall 114 as shown in FIG. 2B. Accordingly, when poppet 110 moves 
to the left, surface 106a of head 106 engages wall 114 thereby pulling 
element 94 to the left toward poppet 110 and closing the opening into 
chamber 104b. 
Section 94a has a radially extended restricted opening 102 which couples 
chamber 104a and chamber 116a. A conventional O-ring 88 is provided within 
an outer groove of element 94a to sealingly engage the inner wall of 
chamber 116a. Seal 88 is disposed between restricted orifice 102 and the 
end of element 94 remote from poppet 110. Accordingly, when element 94 is 
driven to the left by head 106, fluid flows from the chamber formed 
between element 94 and wall 118 solely through restricted opening 102 and 
into chamber 104a. In this manner, opening 102 provides a metered flow of 
fluid into chamber 104a when element 94 is moved to the left with chamber 
104b closed. 
It will now be understood that when poppet 110 moves in a direction away 
from movable element 94, enlarged head 106 engages wall 114 and covers the 
opening into chamber 104b and then pulls element 94 to the left. In this 
manner, three important functions are provided by head 106. The first 
function is the engaging of inner wall 114, the second is the closing of 
chamber 104b and the third is the moving of element 94. 
A spring 96 is disposed around rod 100 and between section 94b and poppet 
110. Specifically, spring 96 has its right-hand end received within a 
recess formed in section 94b and its left-hand end disposed within an 
extended recess within poppet 110. When poppet 110 moves to the right 
toward element 94, spring 96 is effective to push element 94 to the right 
toward end cap 82. 
The right-hand end of housing 90 is sealed by an end cap 82 threadedly 
engaged within the housing and engaging a sealing O-ring 84. In order to 
adjust the extreme right-hand movement of element 94 away from poppet 110, 
there are provided shims 86 disposed on the inner wall of end cap 82. The 
shims are held in place on the inner wall by the fluid (action of 
adhesion). It will be understood that the left travel of element 94 in a 
direction towards poppet 110 is determined by wall 118. Further, the 
length of section 94b is selected to provide a stabilized axial guide for 
rod 100 as it moves within chamber 104b. 
In considering in detail the operation of dashpot assembly 80, FIG. 2A 
shows movable element 94 in its rightward most position. It will be 
understood that in this position poppet 110 is in its valve open position. 
In conventional manner, upon actuation of poppet 110 toward its closed 
position by the fluid circuit the poppet begins its movement in a 
direction to the left away from movable element 94. Accordingly, enlarged 
head 106 moves by way of connecting rod 100 to engage inside wall 114 and 
close chamber 104b. As poppet 110 continues moving to the left, head 106 
begins to move element 94 to the left. Since the only opening to chamber 
104a from the fluid circuit and chamber 116 is through restricted opening 
102, fluid from chamber 116 is metered through this opening into chamber 
104a. Thus, the movement of element 94 in a direction toward inside wall 
118 is damped by the rate of fluid flow through restricted opening 102. 
Consequently, poppet 110 is also damped in its valve closing movement in a 
direction to the left. Damping continues until poppet 110 is fully seated 
in the position shown in FIG. 2B. 
Upon actuation of poppet 110 toward its normally open position by the fluid 
circuit, the poppet begins its movement to the right toward movable 
element 94 starting from the position shown in FIG. 2B. Accordingly, 
enlarged head 106 moves to uncover the opening into chamber 104b. As 
poppet 110 continues moving to the right, spring 96 is compressed and 
begins to exert a sufficient force to move element 94 in a direction away 
from inside wall 118 and away from poppet 110. As element 94 moves, fluid 
inside chamber 104a begins to easily flow through chamber 104b into the 
fluid circuit. Accordingly, element 94 moves in an undamped manner until 
poppet 110 stops or until element 94 is stopped by shims 86 as shown in 
FIG. 2A. Thus, poppet 110 moves to the right only against spring force 
without damping by element 94. In this manner poppet 110 and dashpot 
assembly 80 are recocked for succeeding operations. 
It will be noted that when poppet 110 begins its travel from the valve 
fully open position shown in FIG. 2A in a direction away from movable 
element 94, damping does not begin until after enlarged head 106 has 
engaged inside wall 114 and closed chamber 104b. In the example shown in 
FIG. 2A, head 106 is positioned approximately 1/16 inch away from inside 
wall 114, and thus poppet 110 will move 1/16 inch without any damping. The 
reason for this initial undamped movement of poppet 110 will be explained 
later. Such 1/16 inch positioning may be varied by adjusting the biasing 
of spring 96. Specifically, when poppet 110 moves to the right, the amount 
of compression of spring 96 may be adjusted to vary the travel of the 
poppet before the spring exerts sufficient force to move element 94. After 
the predetermined amount of compression has been reached, spring 96 begins 
to move element 94 in the same direction. In this example, the amount of 
compression has been predetermined to permit head 106 to be 1/16 inch from 
inside wall 114 during poppet reset. 
In summary, after an initial undamped movement of poppet 110, head 106 
engages inside wall 114 and closes chamber 104b. Subsequently, poppet 110 
is damped in its travel until it is fully seated in and closes orifice 
111. When actuated to its normally open position, poppet 110 is permitted 
to move in an undamped manner until it is returned to its normal position. 
The poppet and dashpot are recocked automatically for succeeding 
operations. 
It will be understood that dashpot assembly 80 is effective in its 
operation with any shape or type of poppet assembly. Thus, the above 
operation is effective with a valve assembly such as that described in 
Ser. No. 842,264 and U.S. Pat. No. 3,980,002, which are incorporated 
herein by reference. 
To better understand the advantages of the present invention, its operation 
in conjunction with a valve system used for positioning control of a heavy 
header load in an agricultural combine will now be described. Referring to 
FIGS. 3-6, there is shown an automatic positioning control valve system 10 
for hydraulically moving load 35, a header for a combine, through a 
predetermined distance. Valve system 10 includes a two stage raise valve 
assembly having first stage solenoid operated pilot valve 24 and second 
stage 26. In addition, valve system 10 includes a two stage valve assembly 
for lowering the load comprising first stage solenoid operated pilot valve 
20 and second stage 22. Pilot valve 20 is shown as a normally closed 
solenoid operated valve and is described in detail, for example, in U.S. 
Pat. No. 3,737,141 which is incorporated herein by reference. Pilot valve 
24 is shown as a normally open solenoid operated valve and is described in 
detail, for example, in U.S. Pat. No. 3,765,644, incorporated herein by 
reference. Second stage 26, as shown in FIG. 4 comprises poppet 26a 
controlled by dashpot assembly 80, of FIG. 1. Second stage 22, as shown in 
FIG. 5, includes poppet 22a controlled by dashpot assembly 62. 
In the quiescent or idle state, as shown in FIG. 6, raise pilot 24 and 
lower pilot 20 are deenergized and are in their illustrated normally open 
and normally closed states, respectively. Accordingly, second stage valves 
26 and 22 are respectively open and closed. Pressure is maintained across 
flow divider 30 at a predetermined value, such as approximately 50 psi, 
and applied to pilot line 15a. With large orifice 24a open, pressure in 
line 14 is maintained at a very low value and thus second stage 26 is 
maintained with poppet 26a fully open. Specifically, poppet 26a has a stub 
or blunt nose end 26f which is shown in FIG. 4 to the right of second 
stage orifice 26b by about 1/16 inch, for example, to provide a 
substantially large opening in the idle state. 
If it is necessary to raise header 35 to avoid an obstacle, immediate 
response is available. Specifically, when valve 24 is electrically 
actuated from the open to the closed state, the 50 psi back pressure on 
pump 11 is immediately available and provides an instantaneous initial 
response through lines 15a, 14 and 14a to the pilot of valve 26. As a 
result of the availability of the 50 psi at line 15a, poppet nose end 26f 
begins its undamped but short travel toward orifice 26b, as already 
mentioned, and there is an initial rapid pressure rise. The unloading of 
pump 11 continues until nose end 26f travels to a point about even with 
the right side of orifice 26b. The undamped travel of poppet 26a is 
stopped as a result of head 106 engaging the inside wall of element 94, as 
already mentioned. Thus, poppet 26a travels rapidly for 1/16 inch 
distance, for example, to the left without restriction. At that time, the 
pressure increases to a static load or pressure balance and check valve 58 
opens with fluid under pressure being applied to cylinder 31. 
The purpose for the initial short but rapid travel to the left by poppet 
26a is to minimize "dead time". It will be understood that "dead time" is 
defined as the time from actuation of pilot 24 until the time of pressure 
balance when fluid is first applied under pressure to cylinder 31. Since 
movement of header 35 does not occur until the end of this dead time, it 
is an advantage that dead time be substantially short. 
After pump 11 becomes loaded at the balance pressure, poppet 26a goes 
through a major portion of the stroke where the stroke is controlled by 
the damping of dashpot assembly 80. The manner in which dashpot assembly 
80 damps poppet 26a has already been described. During this time, the 
start raise shock is effectively minimized as a result of this damping. In 
addition, during this time, the start raise shock is minimized as a result 
of the parabolic contour of section 26e which provides a constant 
acceleration pressure between section 26d and orifice 26b, as described in 
detail in U.S. Pat. Nos. 3,980,022 and 4,202,250 which are incorporated 
herein by reference. When poppet 26a reaches its fully closed position, 
pump 11 remains loaded and the balance pressure continues to raise header 
35. 
Thus, with pilot 24 energized and second stage 26 closed, pressure is 
applied to cylinder 31 by way of check valve 58 to raise header 35. At the 
time the header arrives at a desired position, the raise function is 
terminated by deenergizing pilot valve 24 which is returned to its 
normally open state. Since orifice 24a is of substantially large area, it 
allows a rapid flow of fluid from line 14a through the poppet and then to 
tank 25. As a result, poppet 26a opens rapidly, since dashpot assembly 80 
does not damp any poppet movement to the right, as already described. The 
rapid opening of orifice 26b causes the speedy unloading of pump 11, 
thereby to quickly stop the raising of header 35. 
In summary, the advantage of the raise section having dashpot assembly 80 
is an initial rapid increase in pressure to balance pressure during a 
relatively small value of dead time. As soon as the pressure balance is 
achieved, check valve 58 opens and thereafter there is a controlled 
closing of poppet 26a and substantially linear flow rate change for 
minimized start raise shock. In this manner, there is a controlled 
transition from the unload phase to the load phase and as soon as pressure 
balance is achieved, the shock is controlled. The raise is stopped much 
faster than the start to prevent overshoot of the header. All this is 
achieved with the dashpot assembly 80 since it (1) permits an initial 
undamped poppet movement to the left, followed by a damped movement for 
the major portion of the stroke, and (2) permits an undamped movement to 
the right when poppet 26a is returned to its normally open state. 
Referring now to FIGS. 4 and 5, valve 30 comprises spool 30a which engages 
at its lower portion spring 30b and has intermediate openings which 
communicate with central chamber 30d and with line 18 which is coupled to 
the secondary functions. Chamber 30d has at its lower end restricted 
orifice 30e and at its upper end orifice 34. An upper end cap 30f engages 
the upper end of spool 30a. Under normal circumstances with no hydraulic 
power required in line 18 or any loading by the raise circuit, fluid flow 
from pump 11 and inlet 17 causes spring 30b to become compressed and fluid 
flows into groove 30c and then to bypass line 16. With spring 30b properly 
selected, the pressure at inlet 17 is maintained at approximately 50 psi. 
When there is demand for pressure from line 18, fluid flows from inlet 17 
through orifice 34 into central chamber 30d and then through orifice 30e 
to the lower end of the spool. Thus, spool 30a moves upwardly as a 
function of the priority system pressure on line 18. By maintaining the 
drop across orifice 34, there is provided a constant flow to the secondary 
functions with flow divider 30 effectively operating as two sources of 
pressure that can be independently pressurized. 
In the manner previously described, load 35 is raised during the time of 
energization of the solenoid of valve 24. Upon deenergization of this 
solenoid, the idle or quiescent state is resumed and pump 11 is again 
unloaded. In the idle state, pilot valve 20 is closed and high pressure 
oil freely passes through restriction 50 and line 52 so that full pressure 
from cylinder 31 is available in chamber 23 to the right of poppet 22a, as 
shown in FIG. 5. In this manner, second stage lower valve 22 is maintained 
in the illustrated closed position. 
Upon energization of the solenoid of pilot valve 20, there is provided flow 
through the orifice thereof and by way of pilot line 57 to tank 25. In 
this manner, there is established a flow across orifice 50. Accordingly, 
the pressure in chamber 23 is decreased and the system pressure in line 54 
is effective to move poppet 22a away from orifice 22b and allow fluid to 
flow from cylinder 31 through line 54, line 25c and then to tank 25. 
The rate of opening of poppet 22a is dampened by dashpot assembly 62 which 
operates in the following manner. When poppet 22a moves to the right away 
from orifice 22b, the right hand face 22c thereof pushes against the left 
hand face of dashpot cylinder 62b. Dashpot cylinder 62b is spring biased 
by spring 68 secured at its right hand end to adjustable plunger 64. 
Assembly 62 has a chamber 66 within which fluid is compressed. Fluid is 
released from chamber 66 by way of a flow restriction 60a, into chamber 
23. As that fluid is released, poppet 22a is thus restricted in the speed 
it opens or moves to the right away from orifice 22b. Accordingly, dashpot 
assembly 62 is effective to restrict and dampen the opening of poppet 22a 
thereby to dampen the lowering of header 35. 
It will be understood that there is no restriction on the closing of poppet 
22a since as poppet 22a moves to the left, it is free to separate from 
dashpot cylinder 62b. When these elements separate, fluid is allowed to 
freely flow from chamber 23 through unrestricted conduit 62a into chamber 
66. In this manner, spring 68 is effective to reset dashpot assembly 62 
for the next open command to lower header 35. 
It will now be understood that the opening of poppet 22a and the resultant 
lowering of header 35 is dampened by means of dashpot assembly 62. During 
this time, the start lower shock is effectively minimized as a result of 
the damping of the dashpot. Additionally, the parabolic contour of 
sections 22e-g provides a substantially linear flow rate change between 
the sections and orifice 22b. 
When poppet 22a reaches its fully open position, header 35 continues to 
lower until poppet 20 is deenergized. At that time, poppet 20 returns to 
its normally closed state and poppet 22a unrestricted by damping assembly 
62 rapidly closes to prevent undershoot of header 35. 
It will further be understood that both poppets 22a and 26a each have 
substantially parabolic contours 22e-g and 26d, respectively, each having 
an outer, smooth, imperforate and continuous surface. Further, orifices 
15, 24a, 20a and 50 may be considered fixed flow restricting orifices 
having precalculated and nonvariable dimensions. For poppet 22a which is 
always disposed within orifice 22b, the dimensions of parabolic contour 
22e-g, second stage orifice 22b and orifices 20a and 50 are chosen in 
predetermined relations for providing the substantially linear flow rate 
change, particularly with respect to opening of the valve as previously 
described. In this manner, there is provided a constant acceleration in 
lowering of header 35. With respect to poppet 26a, the dimensions of 
contour 26e, orifice 26b and orifices 15 and 24a are chosen in a 
predetermined relation for providing the substantially linear flow rate 
change from the time of pressure balance until poppet 26a closes. In this 
manner, there is a constant acceleration in raising header 35.