BACKGROUND
The present invention relates to double-diaphragm pumps and particularly to valves that direct the flow of pressurized air to air chambers of double-diaphragm pumps. Conventional double-diaphragm pumps include two diaphragms, one coupled to each end of a connecting rod. Pressurized air is alternately pumped into and evacuated from air chambers created between each of the diaphragms and an air cap associated with each diaphragm. As pressurized air is being pumped into the air chamber associated with one diaphragm, the air chamber associated with the other diaphragm is evacuated so that the diaphragms work together in a reciprocating motion to pump a fluid through the pump.
In conventional double-diaphragm pumps, a main valve (typically a spool valve) controls the filling and emptying of the air chambers. The spool valve typically moves back and forth along its axis, connecting and blocking various channels through the pump to control the flow of pressurized air. Typically, a pilot valve associated with the main valve is used to start the main valve moving in one direction or another. The pilot valve is used to help “kick” the main valve back and forth.
SUMMARY OF THE INVENTION
According to the present invention, a pump includes a spool valve that acts as its own pilot valve.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a pump according to the present invention including a spool valve having a spool positioned in a left-most position, thereby routing pressurized supply air to a right air chamber;
FIG. 2 is a schematic illustration of the pump of FIG. 1 with the spool in a center or intermediate position blocking the supply of pressurized air to the right air chamber and to a left air chamber;
FIG. 3 is a schematic illustration of the pump of FIG. 1 with the spool in a right-most position, thereby routing pressurized supply air to the left air chamber; and
FIG. 4 is a schematic illustration of the pump of FIG. 1 according to an alternative embodiment of the present invention.
DETAILED DESCRIPTION
Referring to FIG. 1, a pump 100 according to the present invention includes a spool valve or main valve 102 having a spool 104. The spool 104 has an exterior surface 105 and includes a left channel 106 and a right channel 108 formed through the spool 104. As the spool 104 slides within a valve housing 116, the channels 106 and 108 alternatingly direct supply air from a supply channel 110 to either of a left air chamber 112 or right air chamber 114. The spool 104 is housed within the valve housing 116 so that the exterior surface 105 of the spool is spaced from an interior surface 117 of the housing 116. The left air chamber 112 and the right air chamber 114 are associated with left and right diaphragms, respectively, (not shown) in a double-diaphragm pump arrangement, as will be readily known to those of ordinary skill in the art. As will also be readily known to those of ordinary skill in the art, the supply of air to one of the left and right air chambers 112, 114 causes the diaphragm associated with that air chamber to move to an extended or outward position pumping fluid out of an associated fluid chamber (not shown) on the opposite side of the diaphragm. At the same time, the opposite diaphragm moves to a withdrawn or inward position, drawing fluid into a fluid chamber (not shown) associated with it.
Referring to FIG. 1, the spool 104 is moved to a left-most position within the valve housing 116. The spool 104 is moved to the left-most position as the result of supply air from the supply channel 110 filling a supply chamber 118, thereby applying force to a supply face 120. As can be seen with reference to FIGS. 1–3, and as will become more apparent below, the volume of the supply chamber 118 changes depending on the position of the spool 104. However, in all cases, the supply chamber 118 is being supplied pressurized air from the supply channel 110 and, therefore, the supply face 120 always has a force on it which makes the spool 104 tend to move to the left.
With the spool 104 moved to its left-most position as shown in FIG. 1, a right spool port 122 of the spool 104 is in fluid communication with the supply chamber 118. This allows pressurized air to flow from the supply chamber 118 through the right spool port 122 and into the right channel 108. In this way, air flows along a pathway 124 expanding the right air chamber 114 and driving its associated diaphragm outward. Additionally, the pressurized air flowing into the right air chamber 114 provides a force, indicated by arrows 125, on a right end face 123 that, along with the force on the supply face 120, pushes the spool 104 to the left. (It should be noted that in FIG. 1, as well as FIGS. 2 and 3, the pressurized supply air is indicated by a dark dotted texture. Although it is pointed out above that the supply air flows along pathway 124 when the spool 104 is in its left-most position, the dark dotted texture indicates the spaces that are filled with pressurized supply air. Additionally, exhaust air (discussed below) is indicated by a lighter dotted texture in FIGS. 1–3.)
At the same time, with the spool 104 in its left-most position, a left spool port 126 is in fluid communication with a left exhaust chamber 128 that is connected through a left exhaust port 130 to a left exhaust channel 132. In this way, air is exhausted from the left air chamber 112 along a pathway 134 causing a left diaphragm associated with the left air chamber 112 to collapse inwardly. Additionally, as will be readily apparent to one of ordinary skill in the art, FIG. 4 illustrates an embodiment of the present invention wherein the right diaphragm 162 and left diaphragm 160 may be interconnected by a connecting rod 164. Therefore, the supply of pressurized air to the right air chamber 114 causing it to expand and drive its associated right diaphragm 162 outwardly will, through the connecting rod 164, pull the left diaphragm 160 inwardly.
When the left diaphragm moves to a certain extent inwardly, it begins pushing on the spool 104. The left diaphragm may push on the spool 104 through direct contact, or through some mechanical connection such as a pin, arm, tab, etc., as will be readily apparent to one of ordinary skill in the art. Eventually, the left diaphragm will move the spool 104 to an intermediate or center position, as shown in FIG. 2. Referring to FIG. 2, in the intermediate position, the right spool port 122 is blocked by a right seal 136, thereby cutting off the flow of pressurized supply air from the supply chamber 118 to the right air chamber 114. At the same time, a left seal 138 blocks the left spool port 126 so that it is no longer connected to the left exhaust chamber 128 and air is no longer exhausted from the left air chamber 112. With the spool 104 in its intermediate position, air is neither supplied to nor exhausted from either the left air chamber 112 or the right air chamber 114. However, the movement of the left diaphragm, discussed above, which moved the spool 104 to the intermediate position shown in FIG. 2, is sufficient to move the left spool port 126 just beyond the left seal 138, so that the left spool port 126 is in fluid communication with the supply chamber 118.
Referring to FIG. 3, with the left spool port 126 in fluid communication with the supply chamber 118, pressurized supply air from the supply channel 110 flows through a supply port 140 along a pathway 142 and into the left air chamber 112. The flow of supply air into the left air chamber 112 creates a force, indicated by arrows 143, on a left-end face 144 of the spool 104. Even though the supply air continues to provide a force on the supply face 120 that tends to move the spool 104 to the left as discussed above, the spool 104 nevertheless moves to the right because the force 143 applied to the left-end face 144 is greater than the force on the supply face 120. This is because the total surface area of the surfaces that comprise the left-end face 144 is greater than the total surface area of the supply face 120. As shown in FIG. 3, the surface area of the left-end face 144 is approximately twice the surface area of the supply face 120. However, other configurations where the surface area of the left-end face 144 is greater than the surface area of the supply face 120 may be used. Because of the differential in surface areas between the left-end face 144 and the supply face 120, the spool 104 moves from a position wherein the left spool port 126 is just right of the left seal 138 to its right-most position.
With the spool 104 positioned as shown in FIG. 3, pressurized supply air is supplied to the left air chamber 112 pushing outwardly the left diaphragm. At the same time, the right spool port 122 is in fluid communication with a right exhaust chamber 146 that is connected to a right exhaust channel 148. In this way, air from the right air chamber 114 flows along a pathway 150 exhausting the right air chamber 114. In a manner similar to that discussed above with regard to the left diaphragm, this causes the right diaphragm to collapse inwardly. Eventually, the right diaphragm contacts, either directly or indirectly, the right end of the spool 104 urging it to the left. The collapsing movement of the right diaphragm causes the spool 104 to move left and again assume the intermediate position shown in FIG. 2. In the position shown in FIG. 2, the supply of pressurized air through the left spool port 126 and the left channel 106 is cut off, thus removing the force on the left-end face 144. The force on the supply face 120 created by the pressurized air in the supply chamber 118 takes over in the absence of the force 143 on the left-end face 144. Therefore, the spool 104 tends to again move to the left once the collapsing right diaphragm has moved the spool 104 far enough over (to its trip point) so that the left seal 138 cuts off the flow of supply air through the left spool port 126. The force of the pressurized supply air on the supply face 120 moves the spool 104 to its left-most position as shown in FIG. 1, and the cycle discussed above starts over.
Although the invention has been described in detail with reference to certain described constructions, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.
Patent Grant
7025578
