A solenoid plunger (36) is disposed for reciprocation in a plunger pocket that is formed by the stationary parts of a solenoid-type actuator (10). A flexible diaphragm (22) closes the plunger pocket's open mouth and is deformed by movement of a plunger (36) between an open position, in which it is displaced from a valve seat (20), and a closed position, in which it is seated on the valve seat and thereby prevents flow from a valve inlet (16) to a valve outlet (18). The diaphragm thereby isolates the plunger from the fluid thereby being controlled, but a separate, incompressible fluid fills the chamber in which the plunger reciprocates. A through-plunger passage (44, 56) provides a low-flow-resistance path for the incompressible fluid to flow into and out of the portion (52) of the plunger chamber behind the plunger as the plunger moves. This reduces actuation time and thus the energy required for an actuation. The chamber in which the plunger reciprocates is formed by elements (22, 26, 32, and 34) through which the incompressible fluid can diffuse only very slowly, so the actuator can be long-lived even if it small in size.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns solenoid-type actuators and in particular actuators of the type whose armatures are disposed in fixed-volume sealed chambers.

2. Background Information

Electromagnetically operated valves ordinarily employ solenoid-type actuators. An armature, often referred to as a “plunger” in valve-type applications, is so disposed in a guide as to allow it to reciprocate. The plunger includes ferromagnetic material that forms part of the path taken by magnetic flux that results when current flows in a solenoid coil. The magnetic path's reluctance varies with plunger position. In accordance with well-known magnetic principles, therefore, the flow of solenoid current results in a magnetic force that tends to urge the plunger in one or the other direction.

In an increasingly large number of valve installations, the power employed to drive the solenoid coil comes from batteries. This makes constraints on power dissipation severe in many instances. In the case of battery-powered automatic toilet flushers, for instance, battery life is expected to be three years or more. A great deal of effort has therefore been devoted to minimizing the energy expended in any given valve actuation.

One result of such efforts is the use of an incompressible fluid to fill plunger-isolating chambers. It is desirable in many applications for the plunger to be isolated from the fluid that the solenoid-operated valve controls. A common approach to achieving the result is to enclose the plunger in a chamber whose closure at one end is provided by a flexible diaphragm. The diaphragm acts as the valve member, i.e., the member that is seated in the valve seat to close the valve and that is withdrawn from the valve seat to open it. Typically in response to the force of a bias spring, the plunger moves to an extended position, in which it deforms the diaphragm into the shape that causes it to seal the valve seat. Typically in response to magnetic force resulting from solenoid-current flow, the plunger is withdrawn against the spring force to allow the valve to open.

To enhance energy savings, a permanent magnet is often used to retain the plunger in the position opposite the one in which the bias spring holds it. To allow the valve to assume the latter (typically valve-closed) position, the solenoid is driven in such a direction as to counter the permanent magnet's magnetic field and thus allow the spring force to close the valve. An actuator that thus requires power only to change state but not to remain in either state is known as a latching actuator.

Independently of whether the sealed-solenoid-chamber actuator is of the latching type, though, further energy savings can be achieved by filling the closed plunger chamber with an incompressible fluid. To appreciate the advantage that an incompressible-fluid-filled chamber affords, consider the valve operation in which a plunger is moving the diaphragm into its seated position in response to a bias spring's force. The fluid that the valve controls is usually under pressure, and that pressure will prevail over the diaphragm's outside face. If the plunger chamber, which is on the other side of the diaphragm, is simply filled with, say, air at ambient pressure, the bias spring will need to overcome the force that the controlled fluid's pressure exerts. If the plunger chamber is filled with an incompressible fluid such as water, on the other hand, the controlled fluid's pressure is transmitted to the incompressible fluid within the plunger chamber, and the force that it exerts on the diaphragm's outside face is canceled by the resultant force on its inside face. The spring therefore does not need to exert as much force as it otherwise would, and this means that the power expended in retracting the plunger against that spring is similarly less.

In short, combining the incompressible-fluid-filled plunger chamber with other energy-saving actuator features has lead to great economies in automatic-valve-actuation use.

SUMMARY OF THE INVENTION

But we have recognized that further energy savings can be achieved by adapting to isolated-plunger-chamber use a feature sometimes seen in actuators that do not isolate their plungers. Specifically, we employ various approaches to permitting the incompressible fluid to flow past the plunger with less flow resistance than reluctance-minimizing designs would ordinarily present.

In one approach, the actuator's stationary assembly includes a coil, as is conventional. As is also conventional, that assembly forms a pocket wall the defines an armature pocket having front and rear ends. As is typical in isolated-plunger arrangements, moreover, the armature pocket is closed except for a mouth at its front end, over which a flexible diaphragm is secured to form with the pocket wall a substantially fluid-tight armature chamber. And the armature is positioned as usual in the armature chamber to be guided by the pocket wall between forward and rear positions.

But we provide grooves in, or otherwise selectively relieve, the armature and/or pocket wall. Now, the armature contains the usual high-permeability material that forms part of a path for the magnetic flux that current flowing through the coil generates. For the coil current to result in the necessary magnetic force on the armature, that magnetic path's reluctance must vary between the armature's forward and rear positions. To achieve the greatest force for a given current flow, though, the path reluctance when the armature is in its lower-reluctance position should be as low as possible. This normally dictates a relatively small clearance between the armature and the pocket wall. But we have recognized that selectively relieving the armature and/or pocket wall can actually save energy in small actuators, even though it results in some reluctance increase. Specifically, we have recognized that the current increase necessitated by the increased reluctance is more than compensated for by the coil-drive-duration reduction that results from reduced resistance to the incompressible-fluid flow necessitated by plunger travel.

The clearance between the armature and the pocket wall will still be less than a maximum clearance value throughout a majority of the armature's periphery, but the armature and/or the pocket wall is relieved enough at least at one, relieved portion of the armature's periphery that the flow resistance is reduced significantly. Specifically, the flow resistance is less than half of what it would be if the relieved portion's clearance were no more than the maximum clearance in the remainder of the periphery.

In an alternative approach to employing the present invention's teachings, an armature that is similarly driven magnetically in an armature chamber forms an internal fluid-flow passage instead of, or in addition to, enhanced-clearance portions about its periphery. As the armature moves toward and away from the rear end of the armature pocket, the resultant incompressible-fluid flow occurs through that passage.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1depicts an actuator10threadedly secured to a pilot-valve body12. Together with the actuator10, the pilot-valve body12forms a pilot-valve chamber14. The pilot-valve body member12forms an inlet passage16by which fluid enters the pilot-valve chamber, and it also forms a pilot-valve outlet passage18by which fluid can leave the chamber when the pilot valve is open.

The pilot-valve body also forms an annular valve seat20past which fluid must flow to leave the pilot-valve chamber14through the outlet18. In the state thatFIG. 1illustrates, though, the actuator10's flexible diaphragm22is seated on the valve seat20and thereby prevents such flow: the pilot valve is closed. A washer24threadedly secured to the actuator10's front pole piece26traps the diaphragm22's outer end against that pole piece. The diaphragm thereby isolates a chamber28from the fluid in the pilot-valve chamber. An O-ring30similarly prevents the fluid in the pilot-valve chamber14from escaping between the actuator10and the pilot-valve body12.

The front pole piece26cooperates with a coil bobbin32and a rear pole piece34to form a rigid pocket wall that, together with the flexible diaphragm22, defines the chamber28in which the actuator10's plunger36can reciprocate. An actuator housing38crimp-fit over the front pole piece26holds the front pole piece and the bobbin together. It also holds a permanent magnet40against the rear pole piece34. (The drawings illustrate a latching version of the actuator, but the invention's techniques are also applicable to non-latching actuators, which typically would not include the permanent magnet.)

In the state thatFIG. 1depicts, a bias spring42extending into an axial recess44formed by the plunger36holds the diaphragm22in the seated position. Even though the pressure in the pilot-valve chamber14can be expected to be significant and therefore exert a considerable upward force on the diaphragm22, the spring14is designed to exert relatively little force. The spring can nonetheless keep the diaphragm seated, because the plunger chamber28is filled with an incompressible fluid, whose escape from the plunger chamber two O-rings46and48cooperate with the chamber-defining elements to prevent. As a consequence, the pilot-valve chamber14's pressure is transmitted into the plunger chamber28, and the resultant force balances the force that the pilot-valve chamber's pressure exerts.

To operate the pilot valve, current is driven through a coil50wound on the bobbin32. To open the pilot-valve, the current's direction is such that the resultant magnetic flux reinforces the flux from the permanent magnet40. The plunger36is (at least partially) made of high-magnetic-permeability material, as are the front and rear pole pieces26and34and the actuator housing38. The bobbin32is made of a low-magnetic-permeability plastic. The pole pieces, plunger, and housing therefore provide a path for most of the flux that the coil's current generates. From the clearance in the plunger chamber28's rear portion52between the plunger36and the rear pole piece34, it will be appreciated that this flux path's reluctance decreases as the plunger moves rearward and thereby reduces that clearance. So, when the direction of flux generated by coil-current flow is such as to reinforce the magnet40's flux, a resultant increased magnetic force will tend to drive the plunger36upward in FIG.1. Since the spring force is not very great, the power expended in driving enough coil current for this purpose can be small.

In the illustrated embodiment, if the annular protuberance that provides the valve seat20were removed, the diaphragm22would assume an unstressed shape, in which its bottom face is disposed slightly below the valve-seat position. So the diaphragm has a slight natural bias toward the illustrated, closed-pilot-valve position. But the diaphragm22forms a recess that receives an enlarged plunger head portion54, so the diaphragm22is secured to the plunger and rises with it. When the plunger36reaches the upward, valve-open position, the flux path's reluctance will have fallen enough that the force caused by the permanent magnet40's flux can hold the plunger36unaided in that position against the force of the bias spring42. The coil current can therefore be discontinued. In the illustrated, latching version of the actuator, therefore, power needs to be expended to drive the coil only until the plunger36initially assumes its rear, valve-open position. (In non-latching versions, the coil current must keep flowing to keep the valve open.)

Now, the amount of current needed to cause the necessary magnetic force depends, among other things, on the magnetic path's reluctance, so the actuator will typically be designed to minimize reluctance. As a consequence, the clearance between the plunger36and the pocket wall will ordinarily be made as small as possible. Particularly in the case of small actuators, though, we have recognized that minimizing path reluctance can actually result in unnecessary energy expenditure in an actuator that has an incompressuble-fluid-filled isolated plunger chamber. This is because the time required for the plunger to move from its forward position to its rear position will depend on what the resistance is to incompressible-fluid flow that must occur between the plunger chamber's rear portion52and other plunger-chamber portions as the plunger36moves. In theFIG. 1embodiment, therefore, we have reduced flow resistance by providing an internal passage, which includes the plunger's central recess44and a laterally extending bore56, for fluid flowing to and from the rear plunger-chamber portion62.

AlthoughFIG. 1does not make this apparent, some flow can also occur around the plunger36rather than through it, because there is some clearance between the plunger and the pocket wall. But the flow resistance of that path is many times the flow resistance of the path through the plunger. Without the through passage, the flow resistance of the path around the plunger would result in a much greater plunger travel time. So, although providing the through passage and particularly the lateral bore increases the flux path's reluctance and thus the current magnitude required for a given force, the energy expended for a single actuation is less than it would be in the absence of the through-plunger passage. Of course, the internal passage will not in all applications need to be as large as the drawing suggests, particularly if the chosen incompressible fluid is relatively inviscid. But the through-plunger path should offer less flow resistance than the paths around the plunger do.

A through-plunger passage is not the only way to obtain the desired reduction in flow resistance.FIG. 2is a cross section of an alternate embodiment36′ of the plunger. AlthoughFIG. 2illustrates plunger36′ as including the central recess44, that recess is not required for flow purposes. So it is not necessarily part of a passage that permits flow into and out of the plunger chamber's rear portion52; plunger36′ may not have a lateral bore corresponding to FIG.1's bore56, for example.

The arrangement ofFIG. 2nonetheless can afford the energy savings of theFIG. 1arrangement, because it forms grooves58in relieved portions of its periphery. AsFIG. 2shows, the clearance between the plunger36′ and the bobbin32is small throughout most of the periphery, and this tends to help keep the magnetic path's reluctance low. But the grooves provided in the relieved portions of the periphery reduce the flow resistance to a relatively small value. The grooves need not be as large as the drawing indicates, but they should reduce the flow resistance throughout the plunger's travel to less than half what it would be if the clearance in those relieved areas were equal to the maximum clearance in the remainder of the periphery. While the result is greater reluctance than would otherwise be the case, the reduction in flow resistance causes the energy expended per actuation to be small despite the greater required current.

In a further alternative, which the drawings do now show, the plunger itself has no grooves, but the pocket wall does. Of course, a further alternative would be to provide relieved areas in the pocket wall and the plunger both.

As was stated above, FIG.1's plunger chamber28is essentially fluid-tight: the diaphragm22prevents the controlled liquid from entering that chamber, and that chamber is sealed against any substantial leakage of the incompressible fluid from within it. We have recognized, though, that small actuators require additional fluid-retention measures. In this context, a small actuator is one in which the ratio of the incompressible-fluid volume to the plunger-chamber wall's surface area is less than 0.2 cm. For such actuators, diffusion through the chamber walls can become a significant problem. Over time, that diffusion will cause the chamber volume to decrease and result in the diaphragm's so puckering as to require excessive diaphragm strain for the actuator to reach a desired state. This can result in the actuator's becoming stuck or at least requiring excessive energy to change state.

We have therefore so chosen the incompressible fluid and the materials making up the diaphragm and pocket wall that the incompressible-fluid loss due to diffusion through the chamber wall is less than 2% per year. In the example, in which the ratio of volume to surface area is approximately 0.04 cm., we have achieved this by using a mixture of approximately 50% propylene glycol and 50% water as the incompressible fluid. The bobbin is made of polypropylene, the diaphragm and O-rings are made of EPDM rubber, and the pole pieces are made of 430F magnetic stainless steel. Other materials can be used instead, of course but they must be so chosen that the resultant rate of incompressible-fluid loss falls within the indicated limit, and we prefer that the incompressible fluid be at least 30% propylene glycol, with the remainder of the fluid substantially water.

FIG. 3illustrates the actuator in a pilot-valve application. As will be explained presently, the actuator operates a pilot valve, which triggers a control valve, which controls a toilet's flush valve. InFIG. 3, a toilet tank is evidenced only by its bottom wall60. That tank defines an interior chamber62containing water to be used to flush a toilet bowl (not shown). As will be explained in due course, water from chamber62flows to the toilet bowl through a conduit64sealed by an O-ring66to the tank's bottom wall.

A cap member68prevents the tank's water from entering the conduit64except through ports70that the conduit member64forms.

A flush-valve member72forms a recess in which an O-ring74is secured. In the position thatFIG. 3depicts, that O-ring seats on a flush-valve seat76and thereby prevents tank water that has entered the conduit member through ports70from flowing into the flush passage78that leads to the bowl.

A compression spring80biases the flush-valve member72away from the illustrated seating position, but pressure exerted downward on a piston head82that the flush-valve member72forms keeps the flush-valve member72seated. Specifically, the flush-conduit cap forms a cylinder84in which a piston portion86of the flush-valve member72can reciprocate. Line pressure delivered by a conduit88into the interior90of the flush-conduit cap68's neck portion92is communicated into the cylinder84's interior94, from which an O-ring seal95prevents escape around the flush valve's piston portion86. So it is the water-supply pressure that keeps the flush valve closed.

The flush-conduit cap68's neck portion92forms at its upper interior edge a control-valve seat96for a control-valve diaphragm98. The pilot-valve body12is threadedly secured to a receptacle100formed on a head portion of the flush-conduit cap68. The pilot-valve body12thus captures the control-valve diaphragm98between it and the cap68.

The pilot-valve member12forms a locating pin102that extends through an aperture in the control-valve diaphragm98. AsFIG. 1shows, the locating pin102forms a bleed groove104by which water in the cap neck's interior90can seep into a control-valve pressure chamber106. Because of this seepage, the pressure that prevails within the cap neck's interior90and thus within the flush-valve cylinder94also comes to prevail within the control-valve pressure chamber106. Moreover, that pressure prevails over a greater area of the control-valve diaphragm98's upper face than it does over that diaphragm's lower face, so it exerts a downward force tending to keep the control-valve diaphragm98seated.

To open the flush valve—i.e., to cause the flush-valve member72to lift off seat76—control circuitry not shown drives the actuator's coil50to open the pilot valve in the manner described above. This permits the pressure within the control-valve chamber106to be relieved through the pilot-valve inlet and outlet passages16and18. Water that thus leaves passage18can flow through a port107formed by a generally cylindrical housing108sealed to the pilot-valve body12by an O-ring109to protect the actuator10from the tank water. Because of the high resistance to flow through the bleed groove104, the resultant pressure loss in the control-valve chamber106is not immediately transmitted to the cap neck's interior90, so the net force on the control-valve diaphragm98is now upward and unseats it. As can best be seen inFIG. 1, the bottom surface of the pilot-valve member12provides a diaphragm stop that includes an annular diaphragm-stop ring110from which diaphragm-stop teeth111extend radially inward. This prevents the control-valve diaphragm98from being deformed excessively by the upward force exerted on it.

Once the control-valve diaphragm98has been unseated, fluid can flow from the cap neck's interior90over control-valve seat96and out control-valve ports112. This relieves the pressure within cylinder chamber94that had previously kept the flush-valve member72seated. The flush-valve spring80can therefore unseat the flush-valve member, and water flows from the tank interior62through flush-conduit ports70and the flush passage78into the toilet bowl.

As was mentioned above, the illustrated embodiment of the actuator is of the latching type, so it requires no current flow to cause it to remain in its open state. In versions that are not of the latching type, current needs to keep flowing if the valve is to remain open, and the valve can be closed by simply stopping current flow. To use the illustrated, latching-actuator-operated pilot valve to close the flush valve, though, current must be driven through the coil50in the reverse direction so that the resultant flux tends to cancel that of the permanent magnet and thereby allow the pilot valve's bias spring42to drive the plunger36into the forward, closed-valve position. In this position, fluid can no longer leave the control-valve chamber106. Flow through the bleed groove104therefore causes pressure within that chamber to build up slowly to the point at which the resultant force on the control-valve diaphragm98again seats that diaphragm. This closes the exit path from the cylinder interior94, so the supply pressure prevails there and drives the flush-valve member72to its seated position.

FIG. 4shows the actuator assembled onto a different pilot-valve body114. The actuator ofFIG. 4is essentially the same as the one of FIG.1and will therefore be referred to by the same reference numeral, but FIG.4's pilot-valve body114is considerably smaller than FIG.1's pilot-valve body12, and it is threadedly secured to the front pole piece26's interior threads instead of its external ones.FIG. 4shows the pilot valve in its open position, in which the diaphragm22is unseated from the pilot-valve seat116. As will be explained in connection withFIGS. 5A and 5B(together, “FIG.5”), this pilot valve is used to control a main flush valve for a non-tank-type flusher.

AsFIG. 5shows, the upper end of a flush conduit118forms a valve-chamber wall120. That wall forms a main valve chamber into whose interior122a supply-line conduit124introduces water from the building's water supply. With the pilot valve in the open state, whichFIG. 4depicts, the main, flush-valve diaphragm126would ordinarily be lifted from its seat128, butFIG. 5depicts that diaphragm in its seated state, in which it prevents flow from chamber122into the flush conduit118's flush passage130. In this state, a bleed passage132formed in the flush diaphragm126slowly admits water from the valve chamber122into a pressure chamber134. Diaphragm126and a pressure cap136form pressure chamber134. The pressure cap136is held against the upper edge of the chamber wall120by an upper housing138that a retaining ring140secures to the chamber wall120.

Ordinarily, the supply pressure thereby prevails within pressure chamber134and therefore holds the diaphragm126in the illustrated, closed position. The supply pressure ordinarily prevails there because a pressure-relief path that will now be described is usually kept closed by the actuator10.

The actuator10is threadedly secured in an actuator receptacle142formed by the pressure cap136. That receptacle forms a receptacle inlet passage144by which water can flow from the pressure chamber134, and it also forms an outlet passage146from which water can flow through the central passage148of the flush diaphragm126's positioning tube150to the flush passage130. Because of O-rings152and154, flow from the receptacle inlet passage144to the reciprocal outlet passage146can take place only by way of a path through pilot-valve inlet passages156, into the pilot-valve chamber158, around pilot-valve seat116, through pilot-valve outlet passage160, and through receptacle port162. For this to occur, the pilot-valve diaphragm22must be unseated. Since it usually is not, fluid cannot ordinarily escape from the pressure chamber134, so flow through the flush diaphragm126's bleed passage132can result in the pressure-chamber pressure that ordinarily keeps diaphragm126seated.

When the pilot valve assumes the open state theFIG. 4illustrates, though, the pressure in the pressure chamber134can be relieved too quickly for it to be replenished by flow through the bleed passage132, so the pressure in the flush-valve chamber122unseats the flush diaphragm126and allows flow from chamber122around flush-valve seat128and through the flush passage130to the toilet bowl.

Although the illustrated examples show the actuator only as being used in pilot valves, it can also be used in other valves and, indeed, in non-valve applications. By employing the present invention's teachings, the benefits of incompressible-fluid-filled isolated-plunger chambers can be maximized in small-actuator applications, where the constraints on energy usage are often most severe. It therefore constitutes a significant advance in the art.