Convertible pump system
This application is a continuation-in-part of co-pending application Ser. No. 108,606, filed Oct. 15, 1987, now abandoned. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     A pump system according to the present invention finds significant utility as a fluid pressure source for directing fluid under pressure through a &#34;jetting&#34; line; e.g., a hose or equivalent flexible conduit operative to clear blockages in fluid-conducting lines of the types commonly found in industrial environments; e.g., sewage lines, water lines, grease lines and the like. A typical jetter line has an outlet nozzle designed to pressurize the blockage while using part of the fluid pressure to advance the jetting line as the blockage deteriorates. Because lines requiring blockage removal are often sinous in parts, it is found that variations in fluid output or pulses from the pump pressurizing the jetting line is extremely helpful in causing the jetting line to accommodate all but the sharpest bends and curves. Accordingly, it is a principal object of the invention to provide a convertible pump system; that is, a pump system whose output is adjustably convertible between maximum output and a lesser output, and to achieve the conversion by simple and expedient means so that the pump is under control of the user at all times. A feature is the adaptability of the conversion system to existing pumps, thus effecting cost savings in manufacture, use and maintenance. 
     Further features, objects and advantages will appear as a preferred embodiment of the invention is developed in the ensuing description and accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a representative pump in maximum output mode. 
     FIG. 2 is a similar view showing the pump in reduced output mode. 
     FIG. 3 is a graphic illustration of the output vs. revolutions characteristic of the FIG. 1 system. 
     FIG. 4 is a similar illustration as respects the FIG. 2 system. 
     FIG. 5 is a similar illustration showing the results when the relief valve pulsates in response to a part-open, part-closed condition of the control valve. 
     FIG. 6 is a reduced-scale view showing a typical jetter line connected to the pump output. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     FIGS. 1 and 2 illustrate the pump relatively simply and thus omit refinements that could obviously be included in commercial versions. Basically, the pump comprising a casing or housing (10) having an inlet side (12) and an outlet or discharge side (14). In the jetting environment for which the pump is especially adapted, the inlet is designed for connection to a source of water (not shown), preferably heated, at typical city water pressure. A valve (16) is disposed in the inlet for manual control. The pump housing is formed interiorly with a crankcase (18) which contains driving means for a plurality of pumping elements, here a pair of pistons (20) and (22) diametrically opposed at opposite sides of the axis of a crankshaft (24), here representative of the driving means which may be powered by any suitable source, such as an electric motor, internal-combustion engine, etc. (not shown). 
     The upper piston operates in conjunction with a chamber (26) which branches at (28) and (30), respectively, to the inlet and outlet (12) and (14). Typical check valves (32) and (34) control the entrance and discharge of fluid to and from the chamber as the piston reciprocates, the valve (32) opening to admit fluid while the valve (34) is closed and vice versa. The lower piston operates with a lower chamber (36) which has inlet and outlet check valves (38) and (40) respectively associated with the branches (28) and (30). 
     From the description thus far, and without more, the pump is a multi-piston (two) type with the pistons taking in from the inlet (12) via (28) and discharging through the branch (30) and outlet (14) as the pistons reciprocate and the check valves (32), (34), (38) and (40) alternately open and close, thus furnishing maximum pulsing output to whatever line is connected to the outlet or high-pressure side (14) of the pump. 
     In order to reduce the output of the pump, as by converting it from a two-piston pump to a one-piston pump, a converter means is provided, here in the form of a converter or dump line or passage (42) that leads from the upper piston chamber (26) to the inlet side of the pump and controlled manually by a suitable adjustable or variable valve (44). When the valve (44) is closed, the dump line is of course blocked and two-piston operation results. When the valve (44) is opened, the dump line is also open and any fluid taken into the chamber (26) by the piston (20) through the intake check valve (32) is pumped out or dumped to the line (42) and not out through the check valve (34) to the pressure or outlet branch (30). As best seen in FIGS. 3 and 4, the pump delivers (pulses) on every half revolution as a two-piston pump (FIG. 3) and on only every other half-revolution as a one-piston pump (FIG. 4). 
     FIG. 6 shows schematically the association of the output of the pump with a jetter line (48) which has at its terminal or remote end a jetter head (50) of typical design operative to jet fluid rearwardly (arrows 52) so as to advance the line in order to enable it to clear blocked passages, etc. Adjustment of the valve (44) between its open and closed positions creates the results depicted in FIGS. 3 and 4, respectively. Intermediate results, for example as shown in FIG. 5, occur according to whether and to what extent a relief valve (54) opens and closes, which develops pulsating flow characteristics in the jetter line, which, being stretchable within limits, advances. The operator can observe the jetter line as to vibration and can control the metering effect of the valve (44), causing the relief valve (54) to &#34;hammer&#34; between open and closed positions. For example, assuming a pump delivery of 2.25 GPM at 1000 psi and a jet head flow of 1.75 GPM at 1000 psi: when the valve (44) is closed, a flow of 0.50 GPM will keep the relief valve open. When the valve (44) is metered upon for an estimated flow of 0.40 GPM, the excess of 0.10 GPM has to flow through the relief valve. This small flow rate causes the relief valve to hammer and thus the jetter hose to vibrate, increasing its &#34;activity&#34; so far as concerns its jetting function. 
     The variable and on-off feature via the valve (44) is important in breaking up various kinds of blockages. For example, in a frozen water line, with limited hot water available, operation at reduced capacity reduces water consumption and thus prolongs the length of time that the water will stay in the hot-to-warm range. Also, the spaced intervals or pulses in the one-piston mode enable manual manipulation of the jetting line or hose for easier travel through bends, curves, etc. The simple construction makes for a light-weight design, leading to economy and portability, especially when the unit must be carried up and down stairs, ladders, etc. 
     Features and advantages not specifically pointed out here will occur to those versed in the art, as will many modifications in the preferred embodiment disclosed, all without departure from the spirit and scope of the invention.