Abstract:
Operation of a system for injecting a predetermined amount of a secondary fluid into a primary fluid stream. The system uses a liquid additive injection pump driven by a fluid powered motor that is driven by the primary fluid stream and can be selectively suspended by an on/off switch mechanism. The fluid powered motor includes a housing enclosing a differential pressure piston assembly having a piston movable within housing between upstroke and down stroke positions; a valve mechanism establishing a differential pressure within the housing to produce movement of the piston; an over-center mechanism coupled to the valve mechanism to toggle the valve mechanism between open and closed positions; and an actuating shall coupled to the over-center mechanism.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a liquid additive injection pump powered by a fluid motor driven by a primary fluid stream to which the liquid additive is to be injected. More specifically, the present invention relates to a mechanism to selectively suspend injection of the liquid additive. 
     BACKGROUND OF THE INVENTION 
     Fluid powered motors driving an additive injection pump connected to a source of fluid additives are typically installed in a line containing primary fluid under pressure. The primary fluid produces reciprocating movement of a piston assembly within a housing of the fluid motor. The fluid motor in turn reciprocates a piston within a cylinder of the additive injection pump to draw a quantity of secondary fluid into the primary fluid. Such devices have been applied to add medication to drinking water for poultry and livestock, treat water with additives, add fertilizer concentrate to irrigation water, or add lubricant or cleaning agents to water. In liquid additive injection pumps, such as that shown in U.S. Pat. No. 4,558,715, reciprocating movement of the piston assembly is produced by a valve mechanism operable to establish a differential pressure. Specifically, opening and closing of the valve mechanism synchronized to the upstroke and down stroke positions of the piston assembly produces a pressure differential that moves the piston through its reciprocating cycle. Opening and closing of the valve mechanism is synchronized to the piston assembly by an over-center mechanism, which is actuated coincident with the piston assembly reaching the ends of its upstroke and down stroke positions. The over-center mechanism is spring-biased and serves to toggle the valve mechanism open and closed when an actuating shaft carried by the piston assembly engages stops that define the ends of its upstroke and down stroke excursions. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system to inject a secondary fluid into a primary fluid. The system includes a fluid powered motor driven by a primary fluid stream. The fluid motor in turn drives a liquid additive injection pump to meter a secondary fluid. The fluid powered motor is provided with an on/off switch to suspend injection of the secondary fluid into the primary fluid by suspending operation of the fluid powered motor. In a system wherein the fluid powered motor has a reciprocating piston assembly movable in response to a differential pressure established by toggling of a valve mechanism, the position of an actuating shaft serving as a triggering stop for an over-center mechanism can be selectively offset by an on/off switch mechanism such that the piston assembly reaches the end of its upstroke excursion prior to the valve mechanism being toggled. Without the valve mechanism being toggled, reciprocating movement of the piston assembly is suspended because a differential pressure to move the piston in the down stroke excursion cannot be established. As a consequence, the liquid additive injection pump is not driven and injection of the secondary fluid is suspended. 
     The on/off switch mechanism may be provided as an extension of the actuating shaft. Further, the on/off switch mechanism may include a cam mechanism to axially displace the actuating shaft into an offset position. The cam mechanism may include a handle for ease of manipulation by an operator. The handle may be provided in a manner so as to assume first and second positions corresponding to the “on” and “off” positions of the switch mechanism by being thrown from side-to-side through a 180 degree arc. A visual indicator of the condition of the on/off switch mechanism may also be provided. Such a visual indication may be provided by indicia, such as a color, disposed on a portion of the actuating shaft that protrudes through the surface of the housing when the shaft is displaced into the offset position. 
     The on/off switch mechanism may comprise a sleeve disposed on the top of the fluid motor housing and an insert axially movable relative to the sleeve. A handle actuated cam mechanism is coupled to the insert to move the insert relative to the sleeve such that the insert is displaced to assume a retracted position when the switch mechanism is in the “off” position and a fully inserted position when the switch mechanism is in the “on” position. The insert is coupled to the actuator shaft such that when the insert is retracted relative to the sleeve the actuator shaft is moved to the offset position and the reciprocating piston reaches the end of its upstroke excursion without an engagement of a stop on the actuating shaft that triggers the over-center mechanism to toggle the valve mechanism. As a consequence, reciprocating movement of the piston is arrested. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cut-away illustration of a fluid motor powered liquid additive injection pump provided with an on/off switch to suspend reciprocating movement of the piston assembly of the fluid powered motor; 
         FIG. 2  is a vertical cross-section illustration of the fluid powered motor portion of the liquid additive injection pump of  FIG. 1  wherein the on/off switch mechanism is in the “on” position and there is normal operation of the reciprocating piston assembly of the fluid powered motor to the end of its upstroke excursion, which results in the valve mechanism being toggled by the over-center mechanism; 
         FIG. 3  is a vertical cross-section illustration of the fluid motor portion of the liquid additive injection pump of  FIG. 1  wherein the on/off switch mechanism is in the “off” position and normal operation of the reciprocating piston assembly of the fluid motor is suspended; 
         FIG. 4  is an illustration of the on/off switch mechanism mounted atop a fluid powered motor driven liquid additive injection pump and showing the visual indicia that the switch mechanism is in the “off” position; and 
         FIG. 5  is a vertical cross-section illustration of the fluid powered motor portion of the liquid additive injection pump of  FIG. 1  wherein the on/off switch mechanism is in the “on” position and there is normal operation of the reciprocating piston assembly of the fluid motor to the end of the down stroke excursion. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a fluid powered motor  10  is shown. A housing  12 , including cover  12 A and lower body  12 B, which are connected by clamp  12 C and O-ring  12 D, encloses the fluid powered motor components. An inlet conduit  14  provides for acceptance of a primary fluid stream and outlet conduit  16  discharges the primary fluid stream. The outlet conduit  16  includes an adapter  16 A and gasket  16 C held with a nut  16 B to an outlet port  17  in lower body  12 B. Coupled to fluid powered motor  10  is liquid additive injection pump  18 . An inlet conduit having a fitting  20  provides for acceptance of a liquid additive. The liquid additive is drawn into pump  18  from an additive reservoir (not shown) and injected into the primary fluid stream. Metering of the liquid additive is adjustable by ratio adjustment sleeve  22  and locking pin  22 A. Liquid additive injection pump  18  includes a dosage piston  23 , which is movable within inner cylinder  25 A and outer cylinder  25 B by connecting piston rod  27 . The fluid powered motor  10  is coupled to the connecting piston rod  27  to drive the liquid additive injection pump. 
     The internal components of the fluid powered motor  10  within housing  12  include a piston assembly  24 . A valve mechanism  26  is carried on piston assembly  24  and includes poppet valves  26 A- 26 D. An actuator shaft  28  extends through piston assembly  24  and is coupled to an over-center mechanism (not shown) that actuates valve mechanism  26 . Opening and closing of valve mechanism  26  at the upstroke and down stroke positions of the piston creates a differential pressure within housing  12  effective to produce reciprocating movement of piston assembly  24 . The internal components of fluid powered motor  10  constitute what is termed a “differential pressure reciprocating piston assembly”. 
     At the top of housing  12  is on/off switch mechanism  32 . A sleeve  34  extends from the top of housing  12 . An insert  36  (not shown) is axially movable relative to sleeve  34  by actuation of a cam mechanism  38  using handle  40 . The handle rotates through an arc of 180 degrees as it is thrown from side-to-side between the “on” and “off” positions of the switch mechanism  32 . The switch mechanism  32  is shown in the “on” position in FIG.  1 . In the “on” position of the switch mechanism, the insert  36  is fully inside sleeve  34 . The insert  36  is coupled to actuator shaft  26  to establish the vertical position of the shaft relative to the housing cover  12 A. 
     Referring next to  FIG. 2 , fluid powered motor  10  is shown in a cross-sectional view that includes the over-center mechanism  42 , which is not in view in FIG.  1 . Also illustrated in  FIG. 2  is the coupling of actuator shaft  28  to insert  36 . In the illustrated embodiment, the actuator shaft  28  and the insert  36  are integrally formed as a single unit. Further, as shown, a cap  44  sits atop insert  36 . When the switch mechanism is in the “off” position, protrusion of the actuator shaft  28  from the housing cover  12 A provides visual indicia of the condition of the switch mechanism as being “off.” The portion of actuator shaft  28  that protrudes from housing cover  12 A may be colored, such as in red, to assist in providing the visual indicia of the condition of the switch mechanism. 
     As seen in  FIG. 2 , actuator shaft  28  includes a circumferential shoulder  46 , which is aligned to be engaged by collar extension  48  on piston assembly  24 . As will be appreciated, when piston assembly  24  moves in the upstroke excursion, inner collar extension  48  will engage shoulder  46 . Upon collar extension  48  engaging shoulder  46 , valve mechanism  26  is moved to the closed position and the over-center mechanism  42  is triggered to toggle into a position that maintains closure of the valve mechanism. Upon closure of the valve mechanism, a differential pressure is created that causes the piston assembly to begin moving in the down stroke excursion portion of its reciprocating cycle. In the position of actuator shaft  28  shown in  FIG. 2 , the range of movement of the piston assembly to the end of its upstroke permits the over-center mechanism to fully toggle. As will also be appreciated, the over-center mechanism forms a bi-stable device that establishes the valve mechanism alternately in open and closed positions. With the actuator shaft  28  in the position shown in  FIG. 2 , normal operation providing reciprocating movement of the piston assembly  24  can continue. 
     In  FIG. 3 , the handle of the on/off switch mechanism  32  has been moved to the “off” position. As seen, the insert  36  and the attached actuator shaft  28  are displaced to the offset position. As will be appreciated, when piston assembly  24  moves in the upstroke excursion, inner collar extension  48  cannot engage shoulder  46  because the outer collar extension  50  will engage the top of housing cover  12 A ahead of time. As a consequence, valve mechanism  26  will not close to create the differential pressure within housing  12  that is necessary to move piston assembly  24  in the down stroke excursion portion of its reciprocating cycle. Also, although over-center mechanism  42  will be partially moved, as seen in  FIG. 3 , it will not fully toggle. With the actuator shaft  28  is the position shown in  FIG. 3 , normal reciprocating movement operation of the piston assembly  24  will not continue and liquid additive will no longer be injected into the primary fluid stream. Upon movement of handle  40  to the “on” position, however, the inner collar extension  48  will engage shoulder  46  on actuator shaft  28 . The valve mechanism will close and the over-center mechanism will complete toggling. The necessary differential pressure required for reciprocating movement of piston assembly  24  will be re-established within housing  12  and normal operation will resume. 
       FIG. 4  provides an illustration of a fluid motor powered liquid additive injection pump provided with an on/off switch mechanism in accordance with the present invention. As shown, the switch mechanism is mounted atop the housing of the fluid powered motor. In the close-up details also shown in  FIG. 4 , the switch mechanism is shown in the “on” and “off” positions. Further shown in  FIG. 4  is that when the switch mechanism is in the “off” position the insert  36  at the upper end of the actuator shaft  28  protrudes from the housing. Moreover, a visual indication in the form of a color (i.e., red) is provided on the insert to signify the “off” condition of the switch mechanism to the user/operator. When the switch mechanism is in the “on” position, the insert does not protrude from the housing and the color indicator is not visible. 
       FIG. 5  shows the down stroke position of the piston assembly  24  when the on/off switch mechanism  32  is in the “on” position. As will be noted, the valve mechanism  26  has the poppet valves closed in the seated position. Also, the over-center mechanism  42  is in the opposite bi-stable condition to that shown in FIG.  2 . 
     Although a specific embodiment of the invention has been set forth herein for purposes of explanation and illustration. It is to be understood, however, that various alterations, substitutions, and modifications may be made to the embodiment described herein without departing from the spirit and scope of the invention as set forth in the appended claims.