Abstract:
The disclosure addresses a relief valve suitable for use in systems for delivering relatively viscous fluids. The described relief valve includes a housing and a valve mechanism moveable relative to an opening into the housing to allow or prevent flow from a flow path adjacent the relief valve into and through the housing. The relief valve is configured to minimize, and in many examples, essentially eliminate, a cavity between the housing opening and the adjacent flow path. Elimination of this cavity offers significant advantages as it minimizes or eliminates a location for pumped materials to accumulate and/or cure, which can lead to impairment or disabling of the relief valve operation.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/890,229, entitled “ZERO CAVITY RELIEF VALVE,” filed on Oct. 12, 2013, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present invention relates generally to pumping and spraying systems and, more particularly, to pressure relief valves suitable for use in such pumping and spraying systems. 
         [0003]    Peristaltic pumps, piston pumps and double-diaphragm pumps are commonly used to pump highly viscous materials. The pumps transport and inject under pressure various materials ranging from fluid slurries to heavy sanded grouts, such as cement slurries, sanded cement mixes, bentonite mixes (with or without sand), repair mortars, high strength non-shrink grouts and self-leveling products. Common characteristics of these materials are that they are often fluid or semi-fluid, have a relatively high specific gravity and are often granular in composition (all these types of materials are referenced herein as a “fluid” or as “fluids”). Generally, such highly viscous materials can be considered to be materials that would be resistant to pouring from a pail. When the material is moving freely out of the pump and through hoses, the material generally maintains its integrity. However, under pressure the materials tend to settle out of suspension and agglomerate within the hose and the discharge portion of the pump. When this occurs, the pressure within the entire discharge system can increase to the maximum pump capacity. 
         [0004]    In order to clear the agglomerated material, an operator will customarily actuate a manually operated pressure relief valve to relieve system pressure so the hoses can safely be disconnected and cleaned. Unfortunately, due to the geometry of these types of valves, typically lever-actuated butterfly or ball valves, there is usually a considerable distance between the flow line and the actual valve mechanism that forms a dead space. The dead space can become plugged with the agglomerated material rendering the valve inoperable. In some circumstances the material can cure or harden, or otherwise generally solidify, within the dead space rendering the valve useless and frequently necessitating its replacement. A ball-type relief valve has been designed to reduce dead space, as is described in U.S. Pat. No. 7,644,904. 
       SUMMARY 
       [0005]    A relief valve comprises a housing and a valve member moveable relative to an opening into the housing to allow or prevent flow from a flow path adjacent the relief valve into and through the housing. The relief valve is configured to minimize, and in many examples, essentially eliminate, a cavity between the housing opening and the adjacent flow path. In some example configurations, the relief valve includes a cap which couples to the housing. In many examples, the moveable valve member is longitudinally moveable, such as in the form of a plunger configured to reciprocate within the housing. In one such example configuration, the housing extends between an inlet end and an outlet end, and includes a valve seat disposed proximate the inlet end, and a port disposed between the inlet end and the outlet end. The cap is connected to the housing at or near the outlet end. In some embodiments, the plunger extends through the cap and into the housing to the inlet end to selectively engage the valve seat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a schematic of a pumping and spraying system in which the minimum cavity relief valve of the present invention may be used. 
           [0007]      FIG. 2  is a cross-sectional view of a prior art relief valve having a dead space between the flow line and the relief valve mechanism. 
           [0008]      FIG. 3  is a cross-sectional view of a minimum cavity relief valve of the present invention in which the relief valve mechanism is positioned in close proximity to the flow line. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    In this description, references to “one embodiment” or “an embodiment,” or to “one example” or “an example” in this description are not intended necessarily to refer to the same embodiment or example; however, neither are such embodiments mutually exclusive, unless so stated or as will be readily apparent to those of ordinary skill in the art having the benefit of this disclosure. Thus, a variety of combinations and/or integrations of the embodiments and examples described herein may be included, as well as further embodiments and examples as defined within the scope of all claims based on this disclosure, as well as all legal equivalents of such claims. 
         [0010]      FIG. 1  is a schematic of pumping and spraying system  10  in which a minimum cavity relief valve  12  in accordance with the present invention may be used. System  10  includes container  14 , pump  16  and spray mechanism  18 . Container  14  comprises a hopper or some similar vessel into which a material for pumping and spraying is loaded. The material may comprise mortar, grout or any of the aforementioned materials. Container  14  feeds the material into an inlet of pump  16  through feed line  20 . Pump  16  may comprise any suitable pump as is known in the art for pumping highly viscous materials. In various embodiments, pump  16  may comprise a peristaltic pump, a piston pump or a diaphragm pump. Pump  16  pumps the material to spray mechanism  18  through high pressure flow line  22 , which comprises sections  22 A and  22 B. Spray mechanism  18  may be manually operated to discharge pressurized material at a desired location. In various embodiments, spray mechanism  18  may comprise any suitable mechanism for dispersing or otherwise placing the material as required for the specific application at hand, for example, e.g., a nozzle, spray gun or spray wand. In order to facilitate depressurizing of system  10 , such as for shut-down and cleaning of system  10 , high pressure flow line  22  is provided with relief valve  12 . In the present example, relief valve  12  is provided in a T-fitting that couples a relief line  24  with sections  22 A and  22 B of flow line  22 . Relief line  24  may feed back into container  14 . The relief valve  12  may be constructed in accordance with any of the configurations discussed later herein. 
         [0011]      FIG. 2  is a cross-sectional view of a prior art relief valve  30  having dead space (“DS”) between flow line  32  and relief valve mechanism  34 . Relief valve mechanism  34  comprises ball  36 , which is rotated by lever  38 . Housing  40  for ball  36  is spaced from flow line  32  by an extension member  42 . As such, extension member  42  forms an elongated channel that can become fouled and plugged with material from within flow line  32 . This fouling material can impair or prevent operation of the relief valve when ball  36  is rotated when it is desired to allow material to flow in and through housing  40 . The relief valve described with reference to  FIG. 2  operates in a substantially similar fashion as the prior art valve described in U.S. Pat. No. 7,644,904, except as to placement of the ball as described in that patent. 
         [0012]    In order to reduce dead space within the T-fitting of the type depicted in  FIG. 2 , it is desirable that the valve mechanism of relief valve be positioned as close as possible to flow line  22 . The minimum cavity relief valve of the present invention eliminates dead space DS by positioning the inlet to the relief valve mechanism in “close proximity” to the flow line. As used herein, the term “close proximity” is used to define a relationship in which relief valve closure mechanism (for example the valve seat that is engaged by a valve member to close flow within the valve) is sufficiently close to the primary flow path through flow line  22  as to eliminate a gap in which material from flow line  22  can accumulate in a sufficient volume as to impair the function of the relief valve. It is preferred that any gap between the valve seat and the nominal dimension of the flow path will be less than +/− 0.15 inch. In view of the objective that the new relief valve configuration eliminates any cavity adjacent the relief valve cavity sufficient to accumulate a potentially problematic volume of material, the relief valve may also be termed a “zero cavity relief valve.” 
         [0013]      FIG. 3  is a cross-sectional view of minimum cavity relief valve  100  of the present invention in an example mounting for use, in which a relief valve seat  126  configured to be selectively engaged by a valve head  118  (on a valve actuation mechanism  102 ) is positioned in close proximity to flow line  104 . In the depicted example, minimum cavity relief valve  100  comprises housing  106  (including a valve seat  126 ), a cap  108 , a valve mechanism (here in the form of a plunger  110  having a valve head  118 ), a lever  112 , a seal assembly  114 , and an O-ring  116 . 
         [0014]    In the depicted example, relief valve  100  is connected to flow line  104  through a “T” fitting  120 . In some embodiments, relief valve  100  will be configured to engage and be retained by a conventional industry standard, “off-the-shelf,” T-fitting, as opposed to, for example, a special function T-fitting configured specifically for housing the relief valve. Use of such special function T-fittings may in some cases complicate assembly and/or maintenance of the systems incorporating such fittings. By way of example only, for some systems that can benefit from use of the relief valve assemblies as described herein, female branch NPT fittings in accordance SAE standard SAE J514, are recognized as industry standard fillings; as are fittings further in accordance with SAE standards SAE 140427, SAE 140438, and SAE 140424. Additional recognized standards may be applicable to T-fittings for various applications, as will be apparent to persons skilled in the art. 
         [0015]    As noted relative to  FIG. 1 , in many applications for relief valve  100 , flow line  104  is a high pressure line that extends from a pump outlet to a sprayer, and includes sections  104 A and  104 B. T-fitting  120  connects sections  104 A and  104 B with relief valve  100 . As such, T-fitting  120  forms a portion of flow line  104 . Conduit portion  122  of T-fitting  120  may be connected to sections  104 A and  104 B in any suitable manner, such as through a threaded connection, to define a portion of the primary flow path  130 . Neck  124  of T-fitting  120  defines an aperture  136  forming a relief branch of flow line  104 , and extends from conduit portion  122  to couple with housing  106  of relief valve  100 . 
         [0016]    Thus, housing  106  is configured to place the valve seat  126 , which defines an inlet to housing  106 , immediately adjacent the primary flow path  130  through flow line  104 . In one preferred example, housing  106  is configured to place the lowermost end of the housing, at which valve seat  126  is located, within +/− 0.15 inch of the adjacent surfaces  132 ,  134  defining primary flow path  130  immediately adjacent aperture  136  within neck  124 , in which relief valve  102  is mounted. 
         [0017]    Housing  106  may be connected to neck  124  by any suitable manner, such as through a threaded connection, as shown at  138 , or a metallurgical connection (welding or brazing). A releasable connection, such as threaded coupling  138 , is preferred for many applications. Housing  106  extends between an inlet end, at which valve seat  126  is disposed, and a second end. In the depicted embodiment, the second end is coupled with a cap  108 , which accommodates a portion of longitudinally movable valve mechanism  102 . Housing  106  includes an outlet port  128  between the inlet and second ends. Outlet port  128  may be coupled to an appropriate fitting to facilitate attachment to a return line (as indicated at  24  in the system drawing of  FIG. 1 ). Cap  108  is threaded to housing  106  and an O-ring  116  is positioned between cap  108  and housing  106  to form a seal therebetween. 
         [0018]    In the depicted example, the valve mechanism  102 , in the form of plunger  110 , extends through and mechanically engages cap  108 . As shown, plunger  110  is threaded into cap  108  at a threaded engagement  140 , such that a first end extends to selectively engage valve seat  126  at valve head  118 , and a second end extends out of housing  106  and through cap  108 . Thus, the second end of plunger  110  facilitates control of the position of plunger  110  (and thus control of the valve opening or closing) from outside of the housing  106 . Seal  114  is positioned around plunger  110  to prevent material within relief valve  100  from bypassing plunger  110 , and exiting from cap  108 . In one embodiment, seal  114  comprises one or more U-cup seals disposed within a counter bore  142  around a bore  136  for plunger  110 . 
         [0019]    A lever  112  is connected to the second end of plunger  110  to provide a mechanical advantage in rotating plunger  110  in the threaded engagement with cap  108  to cause longitudinal movement of valve head  118  relative to housing  106 . In one embodiment, lever  112  is inserted into a through-bore in plunger  110 . As plunger  110  is rotated, valve head  118  translates longitudinally relative to valve seat  126 . Valve head  118  and valve seat  126  are shaped to mate with each other in a closed state to form a seal that prevents material from within conduit portion  122  from entering housing  106 . In an open state, material flows into housing  106  and exits at port  128  to relieve pressure in the pumping and spraying system. 
         [0020]    In other configurations, the relief valve will not include a separate cap, and the valve member will directly engage housing  106 . Such engagement may again be through a threaded coupling, as discussed relative to the depicted example. In other examples, the valve mechanism such that only a portion rotates relative to the housing (to achieve the longitudinal translation), while another part, such as the valve seat, will be restrained from rotating, and will move only longitudinally. 
         [0021]    Relief valves relieve pressure from the pumping and spraying system if the system becomes blocked, or “packs out” material. Thus, without proper functioning of a relief valve, the whole system may become inoperable. Typically, relief valves are only flushed when they are actually operated or opened. If the relief valve is not flushed after each use, as is often the case when an operator does not remember to do so, it will become fouled and plugged and cannot be used the next time the system is operated. 
         [0022]    Minimum cavity relief valve  100  prevents materials from agglomerating and/or curing within the pressure relief valve itself, thereby eliminating or substantially reducing the operability of the relief valve. Valve seat  126  is positioned in close proximity to conduit portion  122  to substantially eliminate any dead spaces between the primary flow path  130  of conduit portion  122  and valve seat  126 . Thus, in selected embodiments, housing  106  is configured such that it extends through neck  124  to support valve seat  126  adjacent conduit portion  122 . As such, there is no space for a problematic volume of material to remain in neck  124  below valve seat  126  when valve mechanism  102  is in a closed state. 
         [0023]    While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.