Patent Document

TECHNICAL FIELD 
     The present invention relates in general to pneumatic valves and, more particularly, to pneumatic safety valves for preventing a pneumatic hose from flailing dangerously in the event that the hose ruptures or in the event that a pneumatic tool accidentally decouples from the hose. 
     BACKGROUND OF THE INVENTION 
     Pneumatic equipment is often used in various fields of industry, particularly in the areas of mining and resource extraction. Typically, pneumatically driven equipment is supplied with compressed air from a pneumatic pump via a long pneumatic hose. Occasionally, a pneumatic tool may accidentally decouple from the pneumatic hose or the hole itself may rupture. Air rushing through the open end of the hose can cause the hose to whip and flail violently, thus posing a serious danger to operators and other personnel working near the rupture point who can be seriously physically injured by the flailing pneumatic hose. 
     A hose rupture valve located upstream of the rupture point acts to prevent the flailing of the ruptured hose by stopping, or at least greatly slowing, the outflow of air. To date, however, hose rupture valves have been both expensive to purchase and cumbersome to operate. Several prior-art hose rupture valves required the pressure source to be shut down and the pneumatic fluid bled away before the hose could be reconnected or repaired so that normal operations can resume. Other prior-art hose rupture valves, while permitting a limited flow of fluid through the valve after the rupture of the hose, were very complicated to build and thus expensive to purchase. 
     Applicant&#39;s earlier U.S. Pat. No. 5,004,010 entitled HOSE RUPTURE VALVE, which issued to Wilfred Huet on Apr. 2, 1991, disclosed a hose rupture valve for preventing excessive and dangerous flow of fluid through a high pressure hose when the hose is ruptured or the pneumatic tool connected thereto is accidentally decoupled downstream of the valve. The hose rupture valve included a housing containing a cylinder having a pivotally mounted “vane” (i.e. a pivotally mounted flap). During normal operation, the vane would be held open by a spring. If the hose downstream of the valve were ruptured or accidentally decoupled from the pneumatic tool, the pressure within the cylinder would suddenly decrease relative to the pressure within the housing, causing the vane to pivot into a closed position to prevent the excessive flow of fluid through the outlet port of the valve. Although this hose rupture valve functioned very well, further improvements to the design, particularly to simplify manufacturability, would be highly desirable. 
     SUMMARY OF THE INVENTION 
     An object of this invention to provide a new and improved pneumatic safety valve which is simple and inexpensive to manufacture. Accordingly, the present invention provides a pneumatic safety valve having inlet and outlet ports for connection to a high-pressure air hose and to pneumatic equipment, respectively, or alternatively to another section of hose. The pneumatic equipment can include any pneumatically driven tool such as, for example, rock drilling tools and chipping hammers used in the mining industry, or, again by way of example only, rivet guns or pneumatic wrenches used in manufacturing industries. 
     The pneumatic safety valve has an internal air conduit in fluid communication with the inlet and outlet ports. The air conduit cooperates with a pivotal flap that selectively closes to prevent a sudden discharge of air in the event of a hose rupture or an accidental decoupling of the pneumatic tool from the hose. By containing the highly pressurized air and preventing the air from rapid discharge, the valve prevents the air hose from flailing or whipping violently, thus eliminating the physical dangers to operators and other personnel in the vicinity of the rupture. 
     The flap is biased in an open position, for example using a spring, to allow pressurized airflow through the valve during normal operations. In the event that the hose ruptures or that the tool decouples from the hose, the sudden pressure differential (between the outlet and the air inside the valve) overcomes the resistance of the spring and forces the flap to shut, thus precluding the hose from flailing or whipping violently. 
     Subsequent to a rupture or a decoupling, the valve automatically equilibrates pressure over a period of time since the flap does not hermetically seal the orifice of the air conduit in the valve, thus permitting pressurized air to bleed out of the valve. Once the pressure equalization has been achieved, (and once the user has shut off pressure source) the hose can be repaired or the tool can be reconnected. Once pressure in the valve has been re-equilibrated, the spring-biased flap will return to its open position to once again permit air to flow through the valve. 
     Accordingly, one aspect of the present invention provides a pneumatic safety valve for protecting a user of high-pressure pneumatic equipment from a rupture in a high-pressure air hose or from an accidental decoupling of the air hose from the pneumatic equipment. The valve comprises a tubular housing having an inlet port and means for coupling the inlet port to the air hose. The valve also comprises a tubular insert having an outlet port and means for coupling the outlet port to the pneumatic equipment, the tubular insert having threads for engaging complementary threads on the housing for securing the insert to the housing such that a portion of the tubular insert extends into an interior of the housing to define an air conduit between the interior of the housing and the outlet port. The valve further comprises a flap pivotally mounted at an orifice of the conduit, the flap being pivotally movable between an open position for admitting high-pressure air from the housing into the conduit and a closed position for preventing the high-pressure air from flowing into the conduit, the flap moving into the closed position when air pressure downstream of the outlet port suddenly decreases below the pressure inside the housing. The valve further comprises biasing means for biasing the flap into an open position allowing high-pressure air to flow through the outlet port to thus power the pneumatic equipment. 
     Another aspect of the present invention provides a method of safely operating pneumatic equipment driven by high-pressure air supplied through a high-pressure hose. The method comprises steps of coupling a high-pressure hose to a high-pressure air source and coupling the hose to the safety valve described in the foregoing paragraph for protecting a user of the pneumatic equipment from a rupture in the hose or from an accidental decoupling of the hose from the pneumatic equipment. The method also includes steps of coupling the pneumatic equipment to the outlet port of the safety valve and opening the high-pressure air source to pressurize the hose to power the pneumatic equipment. 
     Yet another aspect of the present invention provides a pneumatic safety valve comprising a housing having an inlet port and means for coupling the inlet port to the air hose, and an insert having an outlet port and means for coupling the outlet port to the pneumatic equipment, the insert having threads for engaging complementary threads on the housing for securing the insert to the housing such that a portion of the insert extends into an interior of the housing to define an air conduit between the interior of the housing and the outlet port. The valve includes a flap pivotally mounted at an orifice of the conduit and movable between an open position for admitting high-pressure air from the housing into the conduit and a closed position for preventing the high-pressure air from flowing into the conduit when air pressure downstream of the outlet port suddenly decreases below the pressure inside the housing. The valve also includes a spring for urging the flap into an open position to enable high-pressure air to flow through the valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
         FIG. 1  is a side cross-sectional view of a pneumatic safety valve in accordance with an embodiment of the present invention; 
         FIG. 2  is an isometric perspective view of the valve of  FIG. 1  shown with the tubular insert detached from the tubular housing and with the flap in the closed position; 
         FIG. 3  is an exploded view of the tubular insert and flap assembly; and 
         FIG. 4  is a partially schematic side elevation view of the valve of  FIG. 1  in use wherein the inlet port is coupled to an air compressor via a high-pressure hose and the outlet port is coupled for another hose to pneumatic equipment. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a pneumatic safety valve, generally designated by reference numeral  10 , in accordance with a preferred embodiment of the present invention. In the preferred embodiment, as illustrated in  FIG. 1 , the valve  10  includes a tubular housing  20  and a tubular insert  30 . Although the housing  20  and the insert  30  need not be tubular, a tubular housing and a tubular insert are preferred because pressure vessels having circular cross-sections are known to provide optimal pressure containment. The housing and insert can be made of cast steel. 
     As shown in  FIG. 1 , the pneumatic safety valve  10  is assembled by securing the tubular insert  30  to the tubular housing  20  to define a passageway for airflow from an inlet port  22  on the tubular housing  20  to an outlet port  32  on the tubular insert  30 . In the preferred embodiment shown in  FIG. 1 , the tubular housing  20  has a set of internal threads  24  which engage (or mesh with) a complementary set of external threads  34  formed on the tubular insert  30 . The tubular insert  30  is thus threaded (or screwed) into the tubular housing  20  such that a portion of the tubular insert extends into a cavity (or bore) of the tubular housing. In the preferred embodiment shown in  FIG. 1 , the tubular insert is partially inserted into the tubular housing until a head or “cap”  36  (i.e. a disc-like flange on the insert) abuts the annular end  26  of the tubular housing. An annular groove in the cap  36  receives an O-ring  37  to ensure an airtight, hermetic seal between the cap and the annular end  26  of the tubular housing. 
     As shown in  FIG. 1 , the inlet port  22  of tubular housing  20  includes a means for coupling the housing to a high-pressure hose. Similarly, the outlet port  32  of the tubular insert  30  also includes a means for coupling the insert to pneumatic equipment. Preferably, the means for coupling the housing to the hose includes internal threads and the means for coupling the insert to the pneumatic equipment also includes internal threads. These “pipe threads” can be made in different sizes and with different threads to connect to industry-standard hose connectors or custom made to couple to specific pneumatic fittings. In other words, as shown in  FIG. 1 , the inlet port and the outlet port each includes an internally threaded annular extension  29 ,  39  protruding from the housing for receiving respectively externally threaded connectors of the air hose and pneumatic equipment. Thus, in operation, air flows into the housing through the inlet port  22  and exits the valve through the outlet port  32 . The direction of predominant air flow is shown by the arrows in  FIG. 1 . 
     In the preferred embodiment shown in  FIG. 1 , a portion  40  of the tubular insert that extends into an interior of the housing  20  define an air conduit  42  between the interior of the housing and the outlet port  32 . 
     As shown in  FIG. 1 , the valve  10  has a flap  50  pivotally mounted at an orifice  44  of the conduit  42 , the flap being pivotally movable between an open position (as shown in  FIG. 1 ) for admitting high-pressure air from the housing into the conduit and a closed position (shown in  FIG. 2 ) for preventing the high-pressure air from flowing into the conduit. The flap  50  moves into the closed position when air pressure downstream of the outlet port suddenly decreases below the pressure inside the housing. 
     As shown in  FIG. 1 , the valve  10  has a biasing means for biasing the flap  50  into an open position allowing high-pressure air to flow through the outlet port to thus power the pneumatic equipment. The biasing means preferably includes a spring  60  anchored at one end to a mounting point  62  within the valve (e.g. a hole in the insert or a hook or notch on the outer surface of the insert) and connected at the other end to the flap  50 . The conduit of the insert is dimensioned to provide sufficient clearance for the spring  60  when the tubular insert  30  is partially inserted into the tubular housing  20 . If the spring  60  were ever to fail, the flap  50  would still close to prevent the dangerous flailing of the air hose. Thus, the spring-loaded flap provides a fail-safe mechanism for ensuring that the air hose does not whip violently in the event of a decoupling or a rupture. After a rupture or decoupling, the pressure will equilibrate and a new spring can be reattached (as part of the refurbishment of the valve). 
     In a variant, the spring could be a torsional spring mounted perpendicularly to the axis of the conduit. In another variant, instead of a spring, the biasing means may be provided by a combination of rotational friction and gravity which would hold a hanging flap (upside down) in an open position. 
     The valve preferably further includes a means for stopping the flap  50  at a predetermined angle from a longitudinal axis of the conduit  42 . The stopping means can be an integral extension  70  of the flap shaped to bear against an outside side wall of the conduit when the flap swings open to the predetermined angle, such as was disclosed in Applicant&#39;s U.S. Pat. No. 5,004,010. 
     In the preferred embodiment shown in  FIG. 1 , the flap  50  is a solid member having an elliptical shape. The flap  50  preferably has a flat surface  52  for closing against the orifice to block air from entering the orifice. In another embodiment, the flap can have a small aperture for equilibrating pressure in the event that the flap closes shut, such as was disclosed in Applicant&#39;s U.S. Pat. No. 5,004,010 although Applicant has subsequently discovered that this aperture is unnecessary to equilibrate pressure provided that the flap does not hermetically seal against the orifice of the conduit. In the event that the flap closes off the orifice, the valve gradually automatically equilibrates pressure since the surface of the flap does not hermetically seal the orifice of the air conduit, thus permitting pressurized air to bleed out of the valve. Operation of the valve will be discussed in greater detail below. 
     In the preferred embodiment, as shown in  FIG. 1  and  FIG. 2 , the conduit  42  is truncated at an acute angle (e.g. about 45 degrees relative to a longitudinal axis of the conduit) to form an elliptical orifice. Accordingly, the flap  50  should have a correspondingly elliptical shape to fully cover the elliptical orifice when the flap  50  is in the closed position. 
     As shown in  FIGS. 1 and 2 , the flap  50  preferably includes a bracket  54  which supports the flat surface  52  and which is pivotally mounted about a pivot (the construction of which will be elaborated below). The spring  60  is disposed within a gap  64  between an inside wall  66  of the housing and an outside wall  68  of the insert. Preferably, the spring is anchored at one end to the mounting point  62  and connected at the other end to an attachment point on the integral extension  70  the flap  50 . In the preferred embodiment, the spring  60  is anchored in tension between the mounting point  62  and the flap  50  so that the spring urges the flap toward the open position until the stopping means (the integral extension  70 ) bears against an outer surface of the conduit (i.e. the outside wall of the insert  68 ). 
     As shown in  FIG. 2 , on an outer surface of the valve there is preferably a visual marker (such as an arrow  25  or other indicator) enabling the user to properly orient the valve to thereby ensure that the inlet port is coupled to the air hose while the outlet port is coupled to the pneumatic equipment (as the valve must be oriented in the correct direction for it to operate). 
     As shown in  FIG. 3 , a transverse bore  72  is formed in the integral extension  70  of the flap. This transverse bore  72  is dimensioned to loosely receive a cotter pin  58  so that the flap can rotate freely around the cotter pin when the latter is inserted through the bore. Each end of the cotter pin  58  is constrained within a respective hole  56  formed in each of two parallel extension arms  55  that extend outwardly beyond the orifice of the insert. In other words, as shown in  FIG. 3 , the arms  55  of the insert hold the cotter pin transversely to the axis of the conduit. In that orientation, the cotter pin  58  serves as a shaft about which the flap  50  can pivot. 
       FIG. 4  shows the pneumatic safety valve  10  in use with a high-pressure air hose  80  and pneumatically-driven equipment  90 . The inlet port  22  of the pneumatic safety valve  10  is coupled to the a fitting  84  on the end of the high-pressure hose  80 . The air hose  80  is connected, in this example, to an air compressor  82  (although this could be any high-pressure air source). The outlet port  32  of the valve is coupled to the pneumatic equipment  90  or to another section of hose  86  having an end fitting  88 , which is typically a threaded connector designed to connect to the pipe threads  38  at the outlet port. Tests performed with this pneumatic safety valve have demonstrated a capacity to withstand at least 2000 psi. 
     Once the air source  82  and the equipment  90  are turned on, high-pressure air can flow in an unobstructed manner through the open airway of the valve  10  because the flap  50  outside the air conduit is biased into the open position. It is important to note that since pressure builds up relatively slowly inside the valve when the air source is turned on, the flap is not forced shut, i.e. the minor pressure differential between the upstream and downstream sides of the flap is too small to overcome the spring force. 
     However, in the event of a hose rupture or an accidental decoupling of the pneumatic tool from the hose, the pivotal flap  50  shuts to prevent a sudden discharge of air. By containing the highly pressurized air and preventing the air from rapid discharge, the valve prevents the air hose from flailing or whipping violently, thus eliminating the physical dangers to operators and other personnel in the vicinity of the rupture. 
     Subsequent to a rupture or a decoupling, the valve automatically equilibrates pressure over a period of time since the flap does not hermetically seal the orifice of the air conduit in the valve, thus permitting pressurized air to bleed out of the valve. Once pressure has equalized, repairs can be made and/or the equipment/hose can be reconnected. Once pressure in the valve has been re-equilibrated, the spring-biased flap will return to its open position to once again permit air to flow through the valve. 
     Another aspect of this invention provides a method of safely operating pneumatic equipment driven by high-pressure air supplied through a high-pressure hose. The method includes steps of coupling a high-pressure hose to a high-pressure air source (such as air compressor) and coupling the hose to an inlet port  22  of the safety valve  10  in order to protect a user of the pneumatic equipment from a rupture in the hose or from an accidental decoupling of the hose from the pneumatic equipment. The method also includes steps of coupling the pneumatic equipment (such as pneumatic jack hammer and its local hose) to the outlet port  32  of the safety valve  10  and opening the high-pressure air source to pressurize the hose to power the pneumatic equipment. By way of example only, other types of pneumatic equipment include rock drilling tools, chipping hammers, rivet guns or pneumatic wrenches. 
     It is obvious for those skilled in the art that as the technology develops the basic idea of the invention can be implemented in various ways. The invention and the embodiments thereof are thus not restricted to the examples described above, but they may vary within the scope of the claims.

Technology Category: 4