Abstract:
A collapsible bilge pump includes outer and inner cylinders telescopable between retracted and extended posiions. A piston is movable up and down within the inner cylinder. Check valves in the bottom of the outer cylinder and in the piston permit the pump to take in water at the bottom end of the pump and discharge it from the top end. The collapsible pump is easily stowed, and its short stroke, limited to the length of the inner cylinder, is substantaially easier to perform.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    My related and copending Provisional Applicaton No. 61/459,755 was filed on Dec. 20, 2010. That filing date is claimed for this application. 
     
    
     BACKGROUND INFORMATION 
       [0002]    This invention is a collapsible, manually operated, bilge pump. The pump collapses to approximately 60% of its full operating length for stowage, and extends to full length for use. 
         [0003]    Manually operated bilge pumps are commonly used for water removal from kayaks and other small water craft. A bilge pump is a prudent safety device for small boats. Kayakers in particular use them for water removal after a capsize. 
         [0004]    Commonly used bilge pumps include a cylinder with a piston, piston rod, and handle movable relative to it. The cylinder body includes suitably valved intake and discharge ports, and a foam float. Such pumps are typically about 2.5″ diameter and 20″ high. A pump of that size will lift water from the bottom of the hull and expel it over the cockpit rim of a kayak or gunwales of a canoe. A substantially shorter pump will not perform well. Other pump types, such as foot-operated, are available but their popularity in small craft and, particularly in kayaks, is limited. 
         [0005]    One problem with typical prior art bilge pumps is the size of the pump and the difficulty of stowing it in the boat when not in use. In a kayak, the pump must be readily accessible, not stowed in forward or aft compartments, and storing it in the cockpit is difficult because of limited space. The most common solution for kayakers is to secure the bilge pump on the deck under bungee lines. However, this is also problematic as bungee layouts on decks often do not provide secure attachment and pumps can be lost at sea due to natural boat movements or washed off the deck by waves. If it is secured on the back deck, it may be difficult to reach by a seated kayaker, and the pump&#39;s presence there can interfere with common rescue techniques such as the cowboy reentry, the paddle float rescue, and numerous assisted rescues. If secured on the fore deck, the pump can interfere with paddle strokes, particularly sweep strokes used to turn the vessel. A bilge pump secured on the fore deck may also preclude use of this area for other items the kayaker needs to be visible and readily accessable, such as navigation charts, tide tables, and the like. 
         [0006]    My collapsible design greatly alleviates the storage problem experienced by small boat operators and kayakers. A 20″ extended pump can be collapsed to 12.5″. And a kayaker can find space for my pump, either inside the cockpit behind the seat back, or hung under the fore deck, or attached to the hull between and below the legs. 
         [0007]    Another benefit of my invention is the surprisingly improved ergonomics of its operation. A manual bilge pump is a two-stroke device. The upward stroke pulls water into a the cylinder below the piston while water above the piston is lifted and expelled through the discharge port. Then, the downward stroke transfers water from below the piston to above the piston. This water is then expelled on the next upward stroke. In a typical pump, stroke length is determined by the length of the piston rod which is a few inches less then the overall length (or height) of the pump. The volume of water lifted on the upward stroke is the area of the cylinder&#39;s internal cross-section times the stroke length. One commonly available pump has a stroke length of 13″ and stroke volume of about 27 cubic inches. This is about a pound of water being lifted by the operator on each upward stroke. The operator also has to work against internal friction of the device. With a kayaker in a seated position and pumping out his cockpit, the stroke involves arm movement from approximately chest height to head height. This motion is derived from smaller arm and shoulder muscles, such as triceps and deltoids which tire easily. In these conditions, stroke frequency is relatively low. 
         [0008]    Compared with the prior art, my collapsible pump has a stroke that is only half as long, the “work zone” where operator effort is applied is lower and more conveniently located in front of the chest, and each pump stroke lifts only half as much weight of water. In these conditions, strokes are easier, and it becomes natural to stroke at a rate more than double the stroke rate for a conventional pump. The net result is that my invention pumps faster than a conventional bilge pump with seemingly less input effort. 
       SUMMARY OF THE INVENTION 
       [0009]    The collapsible bilge pump of this invention includes outer and inner cylinders telescopable between retracted and extended positions. A piston is movable up and down within the inner cylinder. Check valves in the bottom of the outer cylinder and in the piston permit water intake at the bottom end of the pump and discharge from the top end. The collapsible pump is easily stowed, and its short stroke, limited to the length of the inner cylinder, is substantially easier to perform. 
     
    
     
       DRAWINGS 
         [0010]    In the accompanying drawings: 
           [0011]      FIGS. 1A ,  1 B are elevation and sectional views of my pump in its collapsed state. 
           [0012]      FIGS. 2A ,  2 B show the pump, and an enlarged detail, in its extended state. 
           [0013]      FIGS. 3A ,  3 B,  3 C show the pump, and enlarged details, operating in an upward stroke. 
           [0014]      FIGS. 4A ,  4 B,  4 C show the pump, and enlarged details, operating in a downward stroke. 
           [0015]      FIG. 5  is an enlarged sectional detail of an alternate configuration. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0016]      FIGS. 1A ,  1 B are elevation and sectional views of my pump  10  in its collapsed state. An inner cylinder  11  is nested within an outer cylinder  12 . The top end of the outer cylinder  12  is necked down to a diameter matching the outside diameter of the inner cylinder  11 . The bottom end of the inner cylinder  11  is flared outward to a diameter matching the inside diameter of the outer cylinder  12 . The flaring and necking are over a relatively short dimension, for example 20 mm, and at a relatively small angle, for example 2 degrees. These cylinders and their conical portions may be produced by secondary forming of extruded tubes, or by injection molding, or by other known methods. 
         [0017]    The bottom end of the outer cylinder  12  includes a fluid inlet check valve  13 . The inlet valve  13  includes passages  14  for water intake into the pump intake chamber  15 . The passages  14  also act as coarse filters to prevent large debris from entering the pump. The inlet valve  13  includes a top planar valve seat  19 . The annular bottom edge of the outer cylinder  12  abuts the valve seat  19 . 
         [0018]    An inlet valve flap  18  is a flexible membrane of elastomeric material such as viton or neoprene. The inlet valve  13  is a check valve. In operation, piston upstroke draws water into the pump inlet chamber  15  (below the piston) with the valve flap  18  flexed upward. At the end of the upstroke, the valve flap  18  lies back over the valve seat  19  to hold that water in the inlet chamber  15 . 
         [0019]    A nozzle housing  30  on the top of the inner cylinder  11  includes a bearing through which a pump shaft  20  is movable up and down, and a discharge port  17  to expel water in a generally horizontal direction. Shaft  20  is of a rust-proof material such as stainless steel, brass, or plastic. The shaft  20  includes a handle  21  on its upper end. Its lower end is shouldered and threaded. A lift check valve  22  includes an axial bore to fit onto the shaft  20  and is secured to the lower end of the shaft by a nut  23 . The lift check valve  22  includes a lower body with water passages  24  through it. The lower body is shouldered to a diameter slightly smaller than the inside diameter of the inner cylinder  11  allowing it to slide loosely within the inner cylinder  11 . The shoulder of the lower body forms a seat for a lift check valve membrane  26 . 
         [0020]    The lift check valve membrane  26  is a thin flexible membrane with a circular perimeter and an axial hole. The membrane  26  is mounted on the valve housing  22  by stretching it over a flange in the axial portion of the diaphragm valve housing. The lift check valve  22  is constrained in this location between the housing shoulder and flange. The diaphragm valve membrane is typically 0.5 mm thick, and its diameter is slightly less than the inside diameter of the inner cylinder  11 . 
         [0021]    The pump shaft  20 , lift check valve  22 , valve membrane  26 , and nut  23  together form the piston subassembly. 
         [0022]    A flotation collar  35  of a durable foam material fits snugly over the outer cylinder  12  and extends along its length. The flotation collar  35  is thick enough to float the entire pump. As an example, the flotation collar of  FIG. 1  is about 2.5″ diameter and volume about 14.9 cubic inches. 
         [0023]      FIG. 2  shows the pump in the extended position. Detail A shows the necking of the outer cylinder  12  mating with the flare of the inner cylinder  11  to form a water tight seal. Interference between the two conical sections creates a wedge lock. The desired angle of the mating conic sections produces a lock sufficient to resist normal pumping forces, though not sufficient to resist a sharp axial shock or a twisting push. If the angle is too large, the inner and outer cylinders may not lock. If the angle is too small, one or both cylinders could fracture from stress, or lock too tightly. Because the pumping operation requires two hands, one to hold the pump and one to operate the piston, the holding hand can resist the downward force of pumping action and minimize the tendency of the cylinders to unlock. 
         [0024]      FIG. 3  shows the extended pump with the piston moving upward. Upward motion of the piston creates a slight vacuum pressure under the piston, causing the diaphragm valve to seal against the seat area of the diaphragm valve housing, and the inlet valve  2  to flex off its seat on the inlet valve housing. If the lower end of the pump is immersed in water, water will flow into the chamber intake below the piston, and water above the piston will be expelled through the nozzle  17 . 
         [0025]      FIG. 4  shows the piston in downward motion. Positive pressure is now created in the chamber below the piston, closing the inlet valve against its seat and stopping flow in the lower end of the pump. The positive pressure below the piston opens the lift check valve  22  upward, allowing water to flow into the upper pump chamber. This action transfers water from the lower inlet chamber to the upper discharge chamber for discharge (on the following upstroke) through the nozzle  17 . 
         [0026]    While the preferred embodiment utilizes interference of flared and necked sections of the inner and outer cylinders respectively to limit extension, and to lock the cylinders in position, other arrangements might instead be employed. One example is shown in  FIG. 5  in which extension limitation and locking are accomplished with threaded sections of inner and outer cylinders. Another arrangement might include tabs on the inner cylinder and slots in the outer cylinder to limit extension and lock the cylinders in the extended position. 
         [0027]    In the following claims, any terms indicative of orientation (e.g. upper, lower; top, bottom; horizontal, vertical) are meant only to correspond with the illustrations and to facilitate an understanding of the claimed invention. Such terms are not intended as positive limitations. 
         [0028]    The foregoing description, including any dimensions, of a preferred embodiment is illustrative. The concept and scope of the invention are not limited by such details but only by the following claims.