VALVE BLOCK ASSEMBLIES

Abstract: A valve block assembly having internal delivery channels and a common outlet channel is provided with two delivery valve surfaces with access to the common channel. The common channel comprises easily cleaned linear sections 26, 126 running alternately from one surface to the other, and connecting surface grooves 25, 125 at the valve sites. Diaphragm valves 19, 20, 21 are provided with relief grooves 4a to accommodate deformation of the diaphragm 5. The V-like cross-section of the connecting grooves 25, 125 of the common channel and the conical shape of the nearby outlet 24a of a delivery channel 24 assure that the valve may be opened by only a small actuating force. Reservoirs 10 feeding the delivery channels 24 have an inert atmosphere controlled by pressurizing and venting channels 22, 23 in the valve block 16, 116. Exposure of plastic tubing to oxygen is kept to a minimum. The assembly is particularly adapted for use in a protein sequencer to supply reactants without cross-contamination or oxidative decomposition.

Description: Field of the Invention This invention relates to a valve block assembly of the kind having multiple inlets and a single outlet. Such assemblies find particular application in protein sequencers. Background of the Invention Wittman-Liebold, US Patent 4008736, describes a valve arrangement in which a common conduit is formed in the valve block. All delivery valve sites lie on the same surface and are connected by zig-zagging portions of the conduit. While this type of common conduit may be cleaned by flushing, it cannot be cleaned easily with a wire. It is also difficult to machine. Graffunder, US Patent 4168724, replaced the slider valves of the Wittman patent with diaphragm valves. These valves are closed by fluid pressure in an actuator chamber adjacent to the diaphragm, and opened by evacuating the chamber. The zigzag sections of the common conduit intersect at the surface of the valve block. All delivery valve sites lie on the same surface. This apparatus has several disadvantages. First, it is necessary to provide vacuum and high pressure sources. Second, the diaphragm has a tendency to cold flow into the common conduit at the point of intersection, requiring that it be moved a greater distance in order to open the valve. This in turn places greater demands on the evacuation system, and increases the wear and tear on the diaphragm. Hunkapiller, US - A - 4558845, replaces the zigzag sections of Wittman-Liebold with straight sections which are easier to clean and to machine. However, each valve site is placed on a separate block, and the common conduit is alternatively a channel in a block and tubing exposed to the atmosphere. Hunkapiller also replaced Wittmann's actuation mechanism with a plunger that is spring-biased to a closed position. A solenoid device is used to draw the plunger to an open position. Since Hunkapiller retains the narrow access port of the previously described apparatus, his valve is likewise subject to the problem of membrane "cold flow". Summary of the invention According to the present invention there is provided a valve block assembly comprising a valve block having a valve surface for receiving a diaphragm valve, and a delivery channel connectable to an external reservoir, characterised in that the valve block has at least two valve surfaces each of which has at least one valve site adapted to receive a diaphragm valve, and in that there is provided a common outlet channel connectable to a reservoir and comprising at least two linear sections, each section having an inlet end at a valve site on one valve surface, each valve site including a connecting groove in said common channel connecting the outlet end of one section to the inlet end of an adjacent section, each delivery channel having an outlet at a valve site but spaced from said groove, said diaphragm valve being adapted to control fluid communication between said groove and said delivery channel outlet without affecting fluid communication along said common channel. Thus the invention is directed to a valve block assembly which eliminates undesirable features of prior devices. It has several noteworthy aspects. The only exposed tubing leads from the gas regulators to the block assembly and from the valve block assembly to the receiving vessel (reaction chamber). This reduces the exposure of sensitive chemicals to oxygen diffusing through the walls of exposed tubing or leaking in where the tubes are joined to other structures. In protein sequencers, delivery rates are low, so a particular reactant may be exposed to diffusing oxygen for hours before moving to the reaction chamber. Much of the pressurizing and venting conduits for maintaining an inert atmosphere of appropriate pressure in the reservoirs is in the form of channels within the block. That part which is tubing is, with the aforestated exceptions, disposed within the controlled atmosphere of the reservoirs themselves. In contrast, prior apparatus make heavy use of tubing, which is vulnerable to atmospheric attack. See Wittman, US Patent 3959307; Hood US Patent 4252769. The common outlet conduit is composed of surface grooves at the valve sites and linear connecting sections which are open to the surface at both ends. Thus, each section may be easily cleaned by passing a wire through the section. Also, these linear sections are easier to form than the zigzag sections of prior devices. The grooves are less readily blocked by cold flowing of the diaphragm of the valve than is the narrow port of the prior devices. If the side walls of the grooves diverge as they approach the surface, only a slight movement of the diaphragm away from the groove is needed to open fluid communication between the groove and the delivery port at each valve site. The exit hole of the adjacent delivery channel preferably has a conical or frusto-conical shape for similar reasons. Since only a slight separation of the valve diaphragm is needed, vacuum is not essential to valve operation. Since each valve has its own diaphragm, the diaphragm may be selected of a material which is appropriate for containing the contents of the corresponding reservoir, and the diaphragm itself may be kept small. The solenoid-holding block preferably has a two-tier design that reduces compressive forces on the valve block. The upper tier holds the solenoid and the lower tier presses against the membrane. Compressive forces are mainly absorbed by the membrane rather than by the valve block. The lower tier also provides the plunger guide hole. The lower tier compresses the periphery of the diaphragm, so that, absent other forces, the center would bulge into the plunger guide hole. The plunger is spring-biased to compress the center of the diaphragm. When the plunger is withdrawn by the solenoid, the center of the diaphragm springs back to the bulging position. The lower tier of the solenoid-holding block preferably has a relief groove into which the membrane may "cold-flow". Without this feature, the membrane may "cold-flow" into the plunger hole, the delivery channel and the common channel, thereby impairing the operation of the valve. Other advantages of the present valve block design will be apparent from the following description, claims, and drawings. Brief description of the drawing Figure 1 shows an isometric view of a first embodiment of a valve block assembly; Figure 2 is a sectional view across the valve block assembly; Figure 3 (a), (b) and (c) are a series of views of the valve block as seen from the front, underneath and the rear side respectively; Figure 4 is an isometric view of the interior of the valve block assembly, illustrating the various channels; Figure 5 is a view of the valve means with the relief groove, as compared to a view of a prior art valve without such a groove; Figure 6 (a), (b) and (c) are a side and two end views respectively of the present valve means, shown below a prior art valve means respectively in open and closed positions; and Figure 7 is a plan and side view of a second embodiment of a valve block assembly. Detailed description of the invention In the first preferred embodiment, a valve block 16 has two delivery valve surfaces, best seen in Figure 3 (b). At least one valve site is provided on each surface. The valve block provides a plurality of inlets and a common outlet. At each valve site is an inlet or delivery channel 24 and an access to the common channel running to common outlet 18. The access is in the form of a groove 25 on the valve surface. The common outlet channel connects each valve site to a valve site on the other valve surface. Linear channel sections 26 connect the groove 25 of one valve site to the groove of the next valve site on the other surface. Since channel sections 26 are linear, and are open to both valve surfaces, they may be cleared of any obstruction by running a fine wire through the section. Moreover, these sections do not present the problem of a dead volume interior to the valve block. As seen in Figure 1, fluid reservoirs 10 may be connected to the valve block 16. These supply fluids in the form of gases and liquids by tubing 11 and 13, respectively, to delivery channels 24, as shown in Figure 2. Each delivery (feeder) channel communicates with one valve site at output end 24a. This output end 24a is spaced apart from the open groove 25. A diaphragm valve 19, 20 and 21 is disposed at each valve site. When a delivery valve 19 is closed as shown in Figure 2, a diaphragm or membrane 5 is pressed against output end 24a and open groove 25, so fluid cannot pass out of the delivery channel 24 and into the common channel 26. However, the diaphragm merely covers and does not plus the groove, so fluid already in the common channel but upstream of the valve may flow through the groove and on downstream. Opening delivery valve 19 allows pressurized fluid from channel 24 to leak into groove 25. Preferably, the groove has a "V-shaped" or "rounded V-shaped" cross-section, so that only a small movement of the diaphragm is needed to permit this flow. Referring to Figures 1 and 2, a solenoid-holding block 4 is internally threaded to accept a standard solenoid 1. The solenoid comprises a plunger 3 biased by a spring 2 against the membrane 5. The unusual two-tiered design of each block 4 allows the block to be secured directly to an aluminium cradle 15 surface with screws through the upper tier. The lower cylindrical tier extends inside the aluminium cradle 15 to make the seal at the valve block 16 surface by pressing against the captive diaphragm 5. This design also ensures precise alignment of the solenoid plunger 3 over the channel entry/exit holes 25, 24 in the valve block 16 because the cylindrical lower tier can be made perfectly concentric with a guide hole 4b in the block 4. Another advantage of this two-tiered design is that the solenoid-holding block 4 never comes into direct contact with the valve block 16 material . This is very important because valve blocks are made from chemically resistant thermoplastics which all cold-flow when subjected to mechanical stress. A design which puts any part of a solenoid-holding block directly on the plastic can change the mechanical properties of the valve, especially if the plastic material is heated or exposed to chemicals which even mildly attack it. In the present design, the only thing under compression in this critical area is the diaphragm 5, so negligible mechanical stress is placed on the valve block material 16. A controlled amount of compressive force can be applied to this diaphragm 5 by machining the solenoid-holding block 4 lower tier to the appropriate length. For example, if the membrane 5 is 0.5mm (0.020 in) thick and the lower tier extends to within 0.38mm (0.015 in) of the valve block 16 surface, 0.13mm (0.005 in) compression is applied when the solenoid-holding block 4 is secured into position. A relief groove or recess 4a in the lower tier surface accommodate diaphragm material 5 which would otherwise cold-flow into the plunger guide hole 4b. If too much material flows into the plunger guide hole 4b, it will overcome the force from the plunger spring 2 and jam the plunger 3 upwards, (as can be seen in the prior art view of Figure 5) preventing the valve from working. While this recess is preferably in the form of an annular groove, it may take other forms which provide a relief volume into which the stressed diaphragm may flow. A controlled amount of deformation is desirable since excess material within the plunger guide hole 4b acts as a spring and helps the diaphragm 5 lift. The relief groove 4a, while not essential, is preferred because it prevents overcompression of this material. The ideal balance is calculated by adjusting the parameters of membrane compression and relief groove 4a internal volume for a given guide hile 4b diameter. The self-assisting action of the membrane is one key element in reliable valve operation. The entire solenoid-holding block 4 is designed to take advantage of this self-assisting action. Previous zero-dead-volume designs have required either a vacuum/pressure or vacuum/spring membrane actuation for reliable operation. The present design takes advantage of the energy stored in the compressed membrane to help lift it from the sealing surface. This is extremely important since it allows one to do away with awkward and expensive vacuum systems to "assist" the valves. In addition, it makes for a much less complicated solenoid/plunger arrangement since it does not have to be vacuum-tight. Also, all channels at or terminating at the valve block 16 sealing surfaces are countersunk, as shown at 27 in Figure 3(c) or Figure 4, so that a conical or V-shaped depression is formed at the surface. This allows a good seal and ensures that cold flow of the diaphragm 5 into the valve channel openings will form complementary conical V-shaped protrusions which will move out of the channel easily when the valve is actuated. Without the conical or V-shaped countersink 27, the diaphragm 5 will cold-flow in a cylindrical shape and effectively plug the channel. This cylindrical plug must lift entirely out of the channel before fluid can flow because the internal surfaces of the valve channel and the membrane plug cannot separate. The conical or V-shape formed by the present design will allow fluid to flow as soon as the diaphragm 5 moves because the two surfaces will instantly separate (see Figure 6). The tubings 11 and 13 in the reservoirs 10 are exposed only to a controlled atmosphere. When pressure valves 21 are opened, inert gas enters the valve block 16 at inlets 8 and 9 and is directed through channels 22 (Figure 3) into a tubing 12 of reservoirs 10. Excess gases are vented through channels 23 in vent valve block 16, when vent valves 20 are opened. The gases to be vented, which may be noxious, are routed via internal conduit 30 (Figure 2) in a sealed chamber 31, forming part of a vent manifold 6, 14, to one or more vents and removed via lug connection 7, 17 (Figure 1) from the apparatus. Inert 0-rings 28 on the bottom of valve block 16 provide a gas-tight-seal where the reservoirs 10 are screwed into inert bottle caps 29 of the lower aluminium cradle 15 of the block 16 (See Figure 2). While, preferably, a single inert atmosphere is supplied to all reservoirs, it is possible to provide different reservoirs with different gases. Also, it is possible to eliminate tubing 12 and permit the channels 22 to communicate directly with reservoirs 10. Numerous modifications will be apparent to those of ordinary skill in the art. The tube leading from the gas regulators may be made of nonporous metal. The tubing running from the valve block assembly to the reaction chamber may be eliminated by mounting the reaction chamber on the valve block assembly. (A detached reaction chamber is, however, easier to heat.) In another embodiment, shown in Figure 7, (in which similar references are increased by 100) a valve body 116 provides more than two valve surfaces. As shown, the valve body is octagonal, with each of the eight sides providing a valve site (only two diaphragm valves 120 being shown). The common channel comprises a series of linear intervalve sections 126, each section running from one side to an adjacent side. It terminates in a section 118 running from the final valve site to the center, where an axial outlet channel 130 is located. At each valve site, one may provide connecting grooves 125 as taught above, or provided intervalve sections which intersect at the valve surface as taught by Hunkapiller, US Patent 4558845, referred to above. In another modification (not shown), the common channel of the valve block is provided with a common inlet "upstream" of the feeder channels. This inlet may be helpful in a number of respects. First, it can be used to introduce a fluid which will clean or dry the common channel. Second, the common outlet of one valve block could be connected to the common inlet of another. If desired, this inlet may be valved.

Claims: A valve block assembly comprising a valve block having a valve surface for receiving a diaphragm valve, and a delivery channel connectable to an external reservoir, characterised in that the valve block (16) has at least two valve surfaces each of which has at least one valve site adapted to receive a diaphragm valve (19, 20, 21), and in that there is provided a common outlet channel connectable to a reservoir, and comprising at least two linear sections (26), each section having an inlet end at a valve site on one valve surface and an outlet end at a valve site on another valve surface, each valve site including a connecting groove (25) in said common channel connecting the outlet end of one section (26) to the inlet end of an adjacent section (26), each delivery channel (24) having an outlet (24a) at a valve site but spaced from said groove (25), said diaphragm valve being adapted to control fluid communication between said groove and said delivery channel outlet (24a) without affecting fluid communication along said common channel. An assembly according to claim 1, characterised in that the groove (25) has side walls (27), said side walls diverging as they approach the valve surface, whereby the opening of the valve is facilitated. An assembly according to claim 1 or claim 2, further characterised in that a diaphragm valve means (14) is disposed at each valve site. An assembly according to any preceding claim, characterised in that the valve block (16) provides channels (23, 22) for venting and pressurizing the reservoirs. An assembly according to claim 3 or claim 4, characterised in that the valve means comprises a diaphragm (5) capable of sealing said connecting groove from said delivery end, means (3) for urging said diaphragm into a sealing position, means having a recess (4a) into which said diaphragm may flow if the diaphragm deforms in the sealed position, and means (1) for urging said diaphragm out of a sealing position. An assembly according to claim 5, characterised in that the diaphragm (5) is biased to a sealing position. An assembly according to any preceding claim, characterised in that said common channel is provided with a common inlet upstream of said reservoirs and a common outlet (18) downstream thereof. An assembly according to any of claims 2 to 7, characterised in that the outlet (24a) of the delivery channel (24) is conical (27) or frusto-conical in shape. An assembly according to any one of claims 1 to 8, characterised in that the common outlet of one valve block assembly is connected to the common inlet of another such valve block assembly.

Inventors: CARTIER, PAUL KELSO III, FARNSWORTH, VINCENT ROBERT
Applicants: PORTON INSTRUMENTS, INC.
Application year: 1987
Main classification: B01J4
IPC codes: C40B40, F16K7, B01J19, C40B60