The subject invention relates to a pump for inflating rafts and similar inflatable devices, and in particular to such a pump which can provide either a large volume of air per stroke for initially filling the inflatable device, or a smaller volume of air per stroke for topping off a substantially filled inflatable device when its internal pressure has increased.
Many inflatable devices have to be filled or have air added to them at a remote location where only a hand-operated pump is available. Many inflatables, such as river rafts, contain a large volume of air. In order to fill them in a reasonable time with a hand pump the pump needs to deliver a relatively large volume of air with each stroke. However, as the raft approaches full inflation pressure, which is around 3 PSI, it becomes very difficult to operate a large volume hand pump. Thus, it is common to rely first on a high volume pump to initially fill the raft in the first instance, and then rely on a second lower volume pump which is easier to operate at higher pressures to top off the raft from time to time as required. This requires carrying two pumps in the raft. While two-stage pumps which serve both needs are available, they either are too large or cumbersome to carry on a-raft, or they have a pumping mechanism which is unreliable when exposed to water and sand, which a pump carried on a raft ultimately would be. Thus, the need remains for a single hand-operated pump, of a size that can be carried on a raft, having a simple dependable pumping mechanism which is not affected by sand and water that can provide both high volume of air to fill an empty or nearly empty raft and still be easy to operate as the raft becomes full and the pressure increases.
This is accomplished in the subject invention by providing a pump having a first chamber with a first piston and a second chamber with a second piston. A plunger is attached to the first piston and a locking mechanism causes activation of the plunger to move the first piston in the first chamber without moving the second piston in the second chamber when the plunger is first rotated in a first direction to a first position, and causes activation of the plunger to move the second piston in the second chamber without moving the first piston in the first chamber when the plunger is first rotated in a second direction to a second position.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
Referring now to
Slidably located concentrically in the outer tube is an inner tube 20 which has an outside diameter which is slightly less than the diameter of the opening 18 in the first cap 16. Located at one end of the inner tube 20 is a second piston 24 which moves in the second chamber 22 when the inner tube 20 is moved in and out of the pump. Located at the other end of the inner tube 20 is a second cap 26 which has a central opening 28 located in it,
Slidably located concentrically in the inner tube 20 is a plunger 32. The plunger 32 has an outer diameter which is slightly less than the opening 28 in the second cap 26. Located at one end of the plunger 32 is a first piston 34 which moves in the first chamber 30 when the plunger is moved in and out of the pump. Located at the other end of the plunger is a handle 36. A first centering ring 102 is located in the second cap 26. The first centering ring has an inner diameter which slidably receives the plunger 32 and keeps the plunger 32 centered in the inner tube 20.
Located in the end cap 12 at the outlet end of the second chamber 22 is a second check valve 38. The second check valve 38 allows air to be forced out of the second chamber 22 into the outlet 14 when the second piston is moved toward the outlet and prevents air from being drawn back into the second chamber when the second piston is moved away from the outlet. Located in the second piston 24 is a first check valve 40. The first check valve allows air to be forced out of the first chamber 30 into the outlet 14 when the first piston is moved toward the outlet 14 and prevents air from being drawn into the first chamber 30 when the first piston is moved away from the outlet 14.
Referring now to
The second piston 24 includes a thin planar annular pressure ring 50 which has an outer diameter which is slightly less than the inner diameter of the outer tube 10. Located slightly in front of the pressure ring 50 is a thin planar annular relief ring 52 which is similar to the pressure ring 50 except that it has a series of discontinuities 54 located around its periphery. A shelf 58 extends around the periphery of the second piston between the pressure ring 50 and the relief ring 52. A second O-ring 56 rests on the shelf 58. The second O-ring 58 is made from a material that is similar to the material used for the first O-ring 48. The relief ring 52 is separated from its associated pressure ring 50 by an amount that is greater than the diameter of the second O-ring 56, and the diameter of the second O-ring 56 is such that it allows the second piston to move in the second chamber 22 and yet provides an airtight seal between them. In operation when the second piston 24 is moved inwardly into the second chamber 22, the second O-ring 56 is urged against the pressure ring 50 and a seal is created,
Both pistons are operated by grasping the handle 36 at the end of the plunger 32 and pulling it repeatedly outward from the pump and back inwardly into the pump. The desired piston is selected through a locking mechanism. The locking mechanism allows movement of the plunger to move the first piston 34 in the first chamber 30 without moving the second piston 24 in the second chamber 22 when the handle 36, and plunger 32, are first rotated in a first direction to a first position. However, when the handle 36, and plunger 32, are rotated in a second direction to a second position movement of the plunger 36 moves the second piston 24 in the second chamber 22 without moving the first piston 34 in the first chamber 30. The locking mechanism 62 also prevents movement of the plunger altogether when rotated to a third position which is intermediate the first and second position.
The locking mechanism includes a first lock which locks the second cap 26 to the first cap 16 when the second cap is rotated in a first direction A to a first position relative to the first cap,
The locking mechanism 62 also includes a second lock which locks the handle 36, and thus the plunger 32, to the second cap 26 when the handle is rotated in a second direction B to a second position relative to the second cap 26,
In operation by rotating the handle in the first direction A, the first lock is engaged and the second lock is disengaged. In this position movement of the handle causes movement of the first piston 34 in the first chamber 30 without moving the second piston 24 in the second chamber 22. When the handle 36 is rotated in the opposite or second direction B, the first lock is disengaged and the second lock is engaged. In this position movement of the handle causes movement of the second piston 24 in the second chamber 22 without movement of the first piston in the first chamber. Thus, the pump can either create a high volume of air to fill a raft, or create a lower volume of air in order to accommodate the higher pressure when topping off the raft. Air is drawn into the first chamber when the first piston is pulled away from the pump through the space between the plunger and the second cap, and air is pulled into the second chamber when the second piston is pulled outwardly in the pump through the gap between the inner cylinder and the first cap.
While most raft inflation fittings have built-in check valves, the check valves 34 and 38 prevent air from passing between the first and second chambers when the pump is being used.
The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.