Patent Publication Number: US-RE38479-E

Title: Positive pressure automatic swimming pool cleaning system

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus powered from the pressure side of a pump for cleaning a water pool, e.g., swimming pool. 
     BACKGROUND OF THE INVENTION 
     The prior art is replete with different types of automatic swimming pool cleaners. They include water surface cleaning devices which typically float at the water surface and skin floating debris therefrom. The prior art also shows pool wall surface cleaning devices which typically rest at the pool bottom and can be moved along the wall (which term should be understood to include bottom and side portions) for wall cleaning, as by vacuuming and/or sweeping. Some prior art assemblies include both water surface cleaning and wall surface cleaning components tethered together. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method and apparatus driven by a positive pressure water source for cleaning the interior surface of a pool containment wall and the upper surface of a water pool contained therein. 
     Apparatus in accordance with the invention includes: (1) an essentially rigid unitary structure, i.e., a cleaner body, capable of being immersed in a water pool and (2) a level control subsystem for selectively moving the body to a position either (1) proximate to the surface of the water pool for water surface cleaning or (2) proximate to the interior surface of the containment wall for wall surface cleaning. 
     The invention can be embodied in a cleaner body having a weight/buoyancy characteristic to cause it to normally rest either (1) proximate to the pool bottom adjacent to the wall surface (i.e., heavier-than-water) or (2) proximate to the water surface (i.e., lighter-than-water). With the heavier-than-water body, the level control subsystem in an active state produces a vertical force component for lifting the body to proximate to the water surface for operation in a water surface cleaning mode. With the lighter-than-water body, the level control subsystem in an active state produces a vertical force component for causing the body to descend to the wall surface for operation in the wall surface cleaning mode. 
     A level control subsystem in accordance with the invention can produce a desired vertical force component using one or more of various techniques, e.g., by discharging an appropriately directed water outflow from the body, by modifying the body&#39;s weight/buoyancy characteristic, and by orienting hydrodynamic surfaces or adjusting the pitch of the body. 
     Embodiments of the invention preferably also include a propulsion subsystem for producing a nominally horizontal (relative to the body) force component for moving the body along (1) a path adjacent to the water surface when the body is in the water surface cleaning mode and (2) a path adjacent to the wall surface when the body is in the wall surface cleaning mode. When in the water surface cleaning mode, debris is collected from the water surface, e.g., by skimming either with or without a weir. When in the wall surface cleaning mode, debris is collected from the wall surface, e.g., by suction. 
     Embodiments of the invention are configured to be hydraulically powered, from the positive pressure side of an external hydraulic pump typically driven by an electric motor. This pump can comprise a normally available water circulation pump used alone or in combination with a supplemental booster pump. Proximal and distal ends of a flexible supply hose are respectively coupled to the pump and cleaner body for producing a water supply flow to the body for powering the aforementioned subsystems. The hose is preferably configured with portions having a specific gravity&gt;0.1 so that it typically lies at the bottom of the pool close to the wall surface with the hose distal end being pulled along by the movement of the body. 
     In preferred embodiments of the invention, the water supply flow from the pump is distributed by one or more control elements (e.g., valves) to, directly or indirectly, create water flows for producing vertical and horizontal force components for affecting level control and propulsion. A preferred propulsion subsystem is operable in either a normal state to produce a force component for moving the body in a first direction, e.g., forward, or a redirection (e.g.,backup) state to produce force components acting to move the body in a second direction, e.g., lateral and/or rearwardly. Water surface cleaning and wall surface cleaning preferably occur during the normal propulsion state. The redirection propulsion state assists the body in freeing itself from obstructions. 
     In a preferred heavier-than-water embodiment, a water distribution subsystem carried by the cleaner body selectively discharges water flows via the following outlets: 
     1. forward thrust jet 
     2. redirection or rearward (“backup”) thrust jet 
     3. forward thrust/lift jet 
     4. vacuum jet pump nozzle 
     5. skimmer jets 
     6. debris retention jets 
     7. sweep hose 
     8. front chamber fill 
     The water flows discharged from these outlets produce force components which primarily determine the motion and orientation of the body. However, the actual motion and orientation at any instant in time is determined by the net effect of all forces acting on the body. Additional forces which effect the motion and orientation are attributable, inter alia, to the following: 
     a. the weight and buoyancy characteristics of the body itself 
     b. the hydrodynamic effects resulting from the relative movement between the water and body 
     c. the reaction forces attributable to sweep hose action 
     d. the drag forces attributable to the supply hose, debris container, etc. 
     e. the contact forces of cleaner body parts against the wall surface and other obstruction surfaces 
     A preferred cleaner body in accordance with the invention is comprised of a chassis supported on a front wheel and first and second rear wheels. The wheels are mounted for rotation around horizontally oriented axles. The chassis is preferably configured with a nose portion proximate to the front wheel and front shoulders extending rearwardly therefrom. The shoulders taper outwardly from the nose portion to facilitate deflection off obstructions and to minimize drag as the body moves forwardly through the water. Side rails extending rearwardly from the outer ends of the shoulders preferably taper inwardly toward a tail portion to facilitate movement of the body past obstruction surfaces, particularly in the water surface cleaning mode. 
     The body is preferably configured so that, when at rest on a horizontal portion of the wall surface, it exhibits a nose-down, tail-up attitude. One or more hydrodynamic surfaces, e.g., a wing or deck surface, is formed on the body to create a vertical force component for maintaining this attitude as the body moves through the water along a wall surface in the wall surface cleaning mode. This attitude facilitates hold down of the traction wheels against the wall surface and properly orients a vacuum inlet opening relative to the wall surface. When in the water surface cleaning mode, a hydrodynamic surface preferably rises above the water surface thereby reducing the aforementioned vertical force component and allowing the body to assume a more horizontally oriented attitude in the water surface cleaning mode. This attitude facilitates movement along the water surface and/or facilitates skimming water from the surface into a debris container. 
     A preferred cleaner body in accordance with the invention is configured with a hollow front fin extending above the water surface when the body is operating in the water surface cleaning mode. The fin has an interior chamber which can be water filled to provide a downward weight to help stabilize the operating level of the body near the water surface. In the wall surface cleaning mode, the water filled fin has negligible effect when the body is submerged but when the body climbs above the water surface, the weight of the filled fin creates a vertical downward force tending to cause the body to turn and re-enter the water. 
     A preferred cleaner body in accordance with the invention carries a water permeable debris container. In the water surface cleaning mode, water skimmed from the surface flows through the debris container which removes and collects debris therefrom. In the wall surface cleaning mode, water from adjacent to the wall surface is drawn into the vacuum inlet opening and directed through the debris container which removes and collects debris from the wall surface. 
     The debris container, in one embodiment, comprises a main bag formed of mesh material extending from a first frame. The first frame is configured to be removably mounted on the chassis and defines an open mouth for accepting (1) surface water flowing over a skim deck when in the water surface cleaning mode and (2) outflow from a vacuum path discharge opening when in the wall surface cleaning mode. In accordance with a significant feature of a preferred embodiment, the debris container may also include a second water permeable bag interposed between the vacuum path discharge opening and the aforementioned main bag. The second or inner bag is preferably formed of a finer mesh than the main bag and functions to trap silt and other fine material. The inner bag is preferably formed by a length of mesh material rolled into an essentially cylindrical form closed at one end and secured on the other end to a second frame configured for mounting adjacent to said vacuum path discharge opening. The edges of the mesh material are overlapped to retain fine debris in the inner bag. 
     The debris container, in another embodiment, comprises a main bag formed of mesh material containing one or more sheets or flaps configured to readily permit water borne debris to flow therepast into the bag but prevent such debris from moving past the sheets in the opposite direction. More specifically, first and second sheets of flexible mesh material are mounted in the bag such that one edge of the first sheet lies proximate to one edge of the second sheet. When the body is moving in its forward direction, pool water flowing into the bag acts to separate the sheet edges to enable debris to move past the edges into the bag. When the body is moving in a direction other than forward, e.g., rearward or laterally, water flow through the bag toward the mouth of the bag acts to close the sheet edges to prevent debris from leaving the bag. 
     The operating modes of the level control subsystem (i.e., (1) water surface and (2) wall surface) are preferably switched automatically in response to the occurrence of a particular event, such as (1) the expiration of a time interval, (2) the cycling of the external pump, or (3) a state change of the propulsion subsystem (i.e., (1) normal forward and (2) backup rearward). The operating states of the propulsion subsystem (i.e., (1) normal forward and (2) backup rearward) are preferably switched automatically in response to the occurrence of a particular event such as the expiration of a time interval and/or the interruption of body motion. 
     In a first disclosed embodiment (e.g., FIGS. 2,  3 ) using a heavier-than-water body, the level control subsystem in an active state produces a water outflow from the body in a direction having a vertical component sufficient to lift the body to the water surface for water surface cleaning. 
     In a second heavier-than-water embodiment (e.g., FIG.  17 ), the body is configured with at least one chamber which is selectively evacuated by an on-board water driven pump when the body is at the water surface to enable outside air to be pulled into the chamber to increase the body&#39;s buoyancy and stability. 
     In a third heavier-than-water embodiment (e.g., FIG.  18 ), a body chamber contains an air bag coupled to an on-board air reservoir. When in a quiescent state, the chamber is water filled and the air bag is collapsed. In order to lift the body to the water surface, an on-board water driven pump pulls water out of the chamber enabling the air bag to expand to thus increase the body&#39;s buoyancy and allow it to float to the water surface. 
     In a fourth embodiment (e.g. FIG.  19 ), the body is configured with at least one chamber which contains a bag filled with air when in its quiescent state. The contained air volume is sufficient to float the body to the water surface. In order to sink the body to the wall surface, the level control subsystem in its active state supplies pressurized water to fill the chamber and collapse the bag, pushing the contained air under pressure into an air reservoir. 
     Preferably all of the embodiments include a level override control for enabling a user to selectively place the level valve in either the wall surface cleaning mode or the water surface cleaning mode. 
     Although multiple specific embodiments of cleaner bodies and level and propulsion control subsystems in accordance with the invention are described herein, it should be recognized that many alternative implementations can be configured in accordance with the invention to satisfy particular operational or cost objectives. For example only, selected features from two or more embodiments may be readily combined to configure a further embodiment. 
     Among the more significant features is the inclusion of a motion sensor mechanism (e.g., FIGS. 21,  22 ) to sense when the rate of forward motion of the cleaner body diminishes below a certain threshold. This can occur, for example, when the body gets trapped behind an obstruction. By sensing the motion decrease, a redirection state can be initiated to move the body laterally and/or rearwardly to free it of the obstruction. This motion sensing feature has potential application in various types of pool cleaners regardless of whether they operate at both the water surface and wall surface. In accordance with a preferred embodiment, the motion sensor operates in conjunction with a periodic control device which alternately defines first and second conditions. Redirection is initiated when two conditions occur concurrently; i.e., the period control device defining the second condition and the motion sensor indicating that forward motion has diminished below the threshold. 
     In accordance with another significant feature, redirection is preferably accomplished by discharging the output of a jet pump (e.g., FIG. 22) in a direction substantially laterally with respect to the body. 
     In accordance with a further useful feature, a presdure indicator carried by the body is preferably coupled to the water distribute system to indicate to a user whether the pressure magnitude being delivered to the body is within an acceptable operating range. 
     In accordance with a still further feature (e.g., FIGS. 29,  32 ), a pitch control subsystem is carried by the body to selectively orient the body&#39;s pitch to either (1) nose (i.e., front) up/tail (i.e., rear) down or (2) nose down/tail up. By selectively orienting the pitch of the body and providing forward propulsion, as from a single jet, the body can be driven either up to the water surface or down to the wall surface. The pitch control subsystem can be implemented by shifting weight and/or buoyancy between the front and rear of the body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically depicts a positive pressure driven cleaner in accordance with the invention in a water pool operating respectively in (1) a water surface cleaning mode (dashed line) and (2) a wall surface cleaning mode (solid line); 
     FIG. 2 schematically depicts a side view of a first cleaner body in accordance with the invention showing multiple water flow outlets which are selectively activated to enable the cleaner to operate in the water surface or wall surface cleaning mode and forward or backup state; 
     FIG. 3 is a functional block diagram depicting water flow distribution in the embodiment of FIG. 2; 
     FIG. 4 is a rear isometric view, partially broken away, of a preferred cleaner body in accordance with the invention; 
     FIG. 5 is a sectional view taken substantially along the plane  5 — 5  of FIG. 4; 
     FIG. 6 is a bottom plan view of the cleaner body of FIG. 4; 
     FIG. 7 is an exploded isometric view of the cleaner body of FIG. 4 showing the primary parts including the chassis, the water flow distributor, and the upper frame; 
     FIG. 8 is a sectional view of the front fin taken substantially along the plane  8 — 8  of FIG. 4; 
     FIG. 9 is a side view similar to FIG. 2 particularly showing the water flow outlets active during the wall surface cleaning mode; 
     FIG. 10 is a side view similar to FIG. 2 particularly showing the water flow outlets active during the water surface cleaning mode; 
     FIG. 11 is a side view similar to FIG. 2 particularly showing the water flow outlets active during the backup state; 
     FIG. 12A is a schematic representation of a preferred implementation of the water flow distributor of FIG.  3  and FIG. 12B comprises a sectional view through the direction controller of FIG. 12A; 
     FIG. 13 is a schematic representation of a preferred implementation of the water flow distributor of FIG. 3 including a motion sensor; 
     FIG. 14 is a side view of a preferred debris container inner bag; 
     FIG. 15 is a sectional view taken substantially along the plane  15 — 15  of FIG. 14 showing how the overlapped edges of the inner debris container bag are overlapped; 
     FIG. 16 is a sectional view taken substantially along the plane  16 — 16  of FIG. 5 showing how the inner bag of FIGS. 14,  15  is mounted to the cleaner body chassis; 
     FIGS. 17A,  17 B and  17 C depict a second heavier-than-water embodiment of the invention respectively schematically showing a side view, an isometric view, and a functional block diagram; 
     FIGS. 18A,  18 B and  18 C depict a third heavier-than-water embodiment of the invention respectively schematically showing a side view, an isometric view, and a functional block diagram; 
     FIGS. 19A,  19 B, and  19 C depict a fourth lighter-than-water embodiment of the invention respectively schematically showing a side view, an isometric view, and a functional block diagram; 
     FIG. 20 is a schematic representation of a water flow distributor implementation alternative to FIG. 12A; 
     FIG. 21 is a schematic representation of a water flow distributor implementation alternative to FIG. 13; 
     FIG. 22A is a functional block diagram of a water flow distribution subsystem alternative to that shown in FIG. 3 for use with the cleaner body of FIG. 2, FIG. 22B shows the orientation of the redirection jet pump discharge relative to the body, and FIG. 22C schematically depicts how the body typically reacts during the redirection state; 
     FIG. 23A is a schematically representation of a preferred implementation of the distributed subsystem of FIG.  22  and FIG. 23B is an enlarged view of a portion of FIG. 23A showing the relationship between the motion sensor paddle and the main relief port. 
     FIGS. 24A,  24 B,  24 C depict different positions of the valve subassembly of FIG. 23A for the backup state, the forward state/water surface mode, and the forward state/wall surface mode, respectively; 
     FIGS. 25,  26 ,  27  show a cross-section through a preferred control assembly for different respective positions of the manual override disk; 
     FIG. 28 is a timing chart describing the operation of the controller assembly of FIG. 23; 
     FIG. 29 is a functional block diagram similar to FIG. 18C but modified particularly to introduce a weight shift subsystem for controlling the pitch of the cleaner body; 
     FIGS. 30 and 31 respectively depict the body pitch in (1) a nose down/tail up orientation and (2) a nose up/tail down orientation; 
     FIG. 32 is a functional block diagram similar to FIG. 29 but showing a buoyancy shift subsystem for controlling body pitch; 
     FIG. 33 is an isometric view of a preferred debris bag showing sheets in the bag for permitting debris inflow but blocking debris outflow; 
     FIG. 34A is a schematic side representation of the debris bag showing its interior sheets open to permit debris entry; 
     FIG. 34B is a schematic sectional representation taken along line  34 B— 34 B of FIG. 34A; and 
     FIG. 34C is a view identical to FIG. 24B but showing the sheet edges closed to block debris outflow. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIG. 1, the present invention is directed to a method and apparatus for cleaning a water pool  1  contained in an open vessel  2  defined by a containment wall  3  having bottom  4  and side  5  portions. Embodiments of the invention utilize a unitary structure or body  6  configured for immersion in the water pool  1  for selective operation proximate to the water surface  7  in a water surface cleaning mode or proximate to the interior wall surface  8  in a wall surface cleaning mode. 
     The unitary body  6  preferably comprises an essentially rigid structure having a hydrodynamically contoured exterior surface for efficient travel through the water. Although the body  6  can be variously configured in accordance with the invention, it is intended that it be relatively compact in size, preferably fitting within a two foot cube envelope. FIG. 1 depicts a heavier-than-water body  6  which in its quiescent or rest state typically sinks to a position (represented in solid line) proximate to the bottom of the pool  1 . For operation in the water surface cleaning mode, a vertical force is produced to lift the body  6  to proximate to the water surface  7  (represented in dash line). Alternatively, body  6  can be configured to be lighter-than-water such that in its quiescent or rest state, it floats proximate to the water surface  7 . For operation in the wall surface cleaning mode, a vertical force is produced to cause the lighter-than-water body to descend to the pool bottom. In either case, the vertical force is produced as a consequence of a positive pressure water flow supplied via flexible hose  9  from an electrically driven motor and hydraulic pump assembly  10 . The assembly  10  defines a pressure side outlet  11  preferably coupled via a pressure/flow regulator  12 A and quick disconnect coupling  12 B to the flexible hose  9 . The hose  9  is preferably formed of multiple sections coupled in tandem by hose nuts and swivels  13 . Further, the hose is preferably configured with appropriately placed floats  14  and distributed weight so that a significant portion of its length normally rests on the bottom of wall surface  8 . 
     As represented in FIG. 1, the body  6  generally comprises a top portion or frame  6 T and a bottom portion or chassis  6 B, spaced in a nominally vertical direction. The body also generally defines a front or nose portion  6 F and a rear or tail portion  6 R spaced in a nominally horizontal direction. The body is supported on a traction means such as wheels  15  which are mounted for engaging the wall surface  8  when operating in the wall surface cleaning mode. 
     Embodiments of the invention are based, in part, on a recognition of the following considerations: 
     1. Inasmuch as most debris initially floats on the water surface, prior to sinking to the wall surface, the overall cleaning task can be optimized by cleaning the water surface to remove debris before it sinks. 
     2. A water surface cleaner capable of floating or otherwise traveling to the same place that debris floats to can capture debris more effectively than a fixed position skimmer. 
     3. The water surface can be cleaned by skimming with or without a weir, by a water entrainment device, or by scooping up debris as the cleaner body moves across the water surface. The debris can be collected in a water permeable container. 
     4. A single essentially rigid unitary structure or body can be used to selectively operate proximate to the water surface in a water surface cleaning mode and proximate to the wall surface in a wall surface cleaning mode. 
     5. The level of the cleaner body in the water pool, i.e., proximate to the water surface or proximate to the wall surface, can be controlled by a level control subsystem capable of selectively defining either a water surface mode or a wall surface mode. The mode defined by the subsystem can be selected via a user control, e.g., a manual switch or valve, or via an event sensor responsive to an event such as the expiration of a time interval. 
     6. The movement of the body in the water pool can be controlled by a propulsion subsystem, preferably operable to selectively propel the body in either a forward or rearward direction. The direction is preferably selected via an event sensor which responds to an event such as the expiration of a time interval or an interruption of the body&#39;s motion. 
     7. A cleaning subsystem can be operated in either a water surface cleaning mode (e.g., skimming) or a wall surface cleaning mode (e.g., vacuum or sweeping). 
     8. The aforementioned subsystems can be powered by a positive pressure water flow supplied preferably by an electrically driven hydraulic pump. 
     As will be explained in greater detail hereinafter, in typical operation, the body  6  alternately operates in (1) a water surface cleaning mode to capture floating debris and (2) a wall surface cleaning mode in which it travels along bottom and side wall portions to clean debris from the wall surface  8 . The body  6  preferably tows a flexible hose  16  configured to be whipped by a water outflow from a nozzle at its free end to sweep against the wall surface  8 . 
     Four exemplary embodiments of the invention will be described hereinafter. The first three of these embodiments will be assumed to have a weight/buoyancy characteristic to cause it to normally rest proximate to the bottom of pool  1  adjacent to the wall surface  8  (i.e., heavier-than-water). The fourth embodiment (FIGS. 19A,  19 B,  19 C) will be assumed to have a characteristic to cause it to rest (i.e., float) proximate to the water surface  7  (i.e., lighter-than-water). 
     With a heavier-than-water embodiment, an on-board level control subsystem in an active state produces a vertical force component for lifting the body to proximate to the water surface  7  for operation in a water surface cleaning mode. With a lighter-than-water embodiments, the level control subsystem in an active state produces a vertical force component for causing the body to descend to the wall surface  8  for operation in the wall surface cleaning mode. 
     FIRST EMBODIMENT (FIGS.  2 - 16 ) 
     Attention is now directed to FIG. 2 which schematically depicts a first embodiment comprised of a unitary body  100  having a positive pressure water supply inlet  101  and multiple water outlets which are variously used by the body  100  in its different modes and states. The particular outlets active during particular modes and states are represented in FIGS. 9,  10  and  11  which schematically respectively represent (1) wall surface cleaning mode, (2) water surface cleaning mode, and (3) backup state. 
     With reference to FIG. 2, the following water outlets are depicted: 
       102 —Forward Thrust Jet; provides forward propulsion and a downward force in the wall surface cleaning mode (FIG. 9) to assist in holding the traction wheels against the wall surface  8 ; 
       104 —Rearward (“backup”) Thrust Jet; provides backward propulsion and rotation of the body around a vertical axis when in the backup state (FIG.  11 ); 
       106 —Forward Thrust/Lift Jet; provides thrust to lift the cleaner body to the water surface and to hold it there and propel it forwardly when operating in the water surface cleaning mode (FIG.  10 ); 
       108 —Vacuum Jet Pump Nozzle; produces a high velocity jet to create a suction at the vacuum inlet opening  109  to pull in water and debris from the adjacent wall surface  8  in the wall surface cleaning mode (FIG.  9 ); 
       110 —Skimmer Jets; provide a flow of surface water and debris into a debris container  111  when operating in the water surface cleaning mode (FIG.  10 ); 
       112 —Debris Retention Jets; provides a flow of water toward the mouth of the debris container  111  to keep debris from escaping when operating in the backup state (FIG.  11 ); 
       114 —Sweep Hose; discharges a water flow through hose  115  to cause it to whip and sweep against wall surface  8 ; 
       116 —Front Chamber Fill; provides water to fill a chamber interior to hollow front fin  117  for creating a downward force on the front of body  100  when operating in the water surface cleaning mode (FIG.  10 ). 
     Attention is now directed to FIG. 3 which schematically depicts how positive pressure water supplied to inlet  101  from pump  10  is distributed to the various outlets of the body  100  of FIG.  2 . The pump  10  is typically controlled by an optional timer  120  to periodically supply positive pressure water via supply hose  9  to inlet  101 . The supplied water is then variously distributed as shown in FIG. 3 to the several outlets depending upon the defined mode and state. 
     More particularly, water supplied to inlet  101  is directed to an optional timing assembly  122  (to be discussed in detail in connection with FIG. 12) which operates a level controller  124  and a direction controller  126 . The direction controller  126  controls a direction valve  128  to place it either in a normal forward state or a backup rearward state. When in the backup state, water from supply inlet  101  is directed via valve supply inlet  130  to rearward outlet  132  for discharge through the aforementioned Rearward Thrust Jet  104  and Debris Retention Jets  112 . When in the forward state, water from supply inlet  101  is directed through outlet  134  to supply inlet  136  of level valve  138 . 
     Level valve  138  is controlled by controller  124  capable of defining either a wall surface cleaning mode or a water surface cleaning mode. When in the wall surface cleaning mode, water flow to supply port  136  is discharged via outlet  140  to Vacuum Jet Pump Nozzle  108  and Forward Thrust Jet  102 . When the level control valve  138  is in the water surface leaning mode, water flow supplied to port  136  is directed via outlet port  142  to Forward Thrust/Lift Jet  106  and to Skimmer Jets  110 . 
     Note also in FIG. 3 that an override control  146  is provided for enabling a user to selectively place the level valve  138  in either the wall surface cleaning mode or the water surface cleaning mode. Also note that positive pressure water delivered to supply inlet  101  is preferably also distributed via an adjustable flow control device  150  and the aforementioned Sweep Hose outlet  114  to sweep hose  115 . Additionally, note that the positive pressure water supplied to inlet  101  is preferably also directed to Fill outlet  116  for filling a chamber interior to hollow front fin  117  to be discussed in detail in connection with FIG.  8 . 
     The system of FIG. 3 can be implemented and operated in many different manners, but it will be assumed for purposes of explanation that the level valve  138  is caused to be in the water surface cleaning mode and about fifty percent of the time and the wall surface cleaning mode about fifty percent of the time. This scenario can be implemented by, for example, responding to a particular event such as the cycling of external pump  10  or by the expiration of a time interval defined by timing assembly  122 . The timing assembly  122  will typically, via direction controller  126 , place the direction valve  128  in its normal forward state a majority of the time and will periodically switch it to its backup state. For example, in typical operation the direction valve  128  will remain in its forward state for between one and one half to five minutes and then be switched to its backup state for between five to thirty seconds, before returning to the forward state. In a typical swimming pool situation this manner of operation will minimize the possibility of the cleaner body becoming trapped behind an obstruction for an extended period of time. In certain pool environments, where obstructions are more likely to be encountered, it may be desirable to more promptly initiate the backup state once the forward motion of the body has diminished below a threshold rate. Accordingly, the distribution system of FIG. 3 is preferably equipped with an optional motion sensor  152  which is configured to recognize a diminished forward motion of the body to cause the direction valve  128  to switch to its backup state. An exemplary implementation of the water flow distribution system of FIG. 3 will be described hereinafter in connection with FIG.  12 . An exemplary implementation of the water distribution system of FIG. 3 including the motion sensor  152  will be described hereinafter with reference to FIG.  13 . 
     Attention is now directed to FIGS. 4-8 showing a structural implementation of the first body embodiment  100  which is essentially comprised of upper and lower molded sections  154 T and  154 B. The lower section or chassis  154 B is formed of a concave floor member  160  having side rails extending around its periphery. More particularly, note left and right shoulder side rails  162 L, 162 R which diverge rearwardly from a chassis nose portion  164 . Side rails  166 L,  166 R extend rearwardly from the shoulder rails  162 L,  162 R converging toward the rear or tail end  168  of the chassis  154 B. The chassis is supported on three traction wheels  170  mounted for free rotation around horizontally oriented parallel axes. More particularly, the wheels  170  are comprised of a front center wheel  170 F, mounted proximate to the chassis nose portion  164 , and rear left and rear right wheels  170 RL and  170 RR. The wheels typically carry tires  171  which provide circumferential surfaces preferably having a sufficiently high coefficient of friction to normally guide the body along a path essentially parallel to its longitudinal axis. However, front wheel  170 F preferably has a somewhat lower coefficient of friction than wheels  170 RL and  170 RR to facilitate turning. 
     The chassis preferably carries a plurality of horizontally oriented guide wheels  176  mounted around the perimeter of the chassis for free rotation around vertical axes to facilitate movement of the body past wall and other obstruction surfaces. 
     As can best be seen in FIGS. 2,  6  and  7 , the chassis  154 B defines an inclined vertical passageway  180  which extends upwardly from a vacuum inlet opening  109  on the underside of the chassis (see FIG.  6 ). The passageway  180  is inclined rearwardly from the opening  109  extending to a vacuum discharge opening  182  proximate to the tail end  168  of the chassis  154 B. The aforementioned Vacuum Jet Pump Nozzle  108  is mounted within the passageway  180  proximate to the opening  109  and oriented to discharge a high velocity stream upwardly and rearwardly along the passageway  180 , as represented in FIG.  2 . This high velocity stream creates a suction at the vacuum opening  109  which draws water and debris from adjacent the wall surface  8  into the passageway  180  for discharge at the opening  182 . The vertical component of the stream assists in producing a hold down force when the unit is operating in the wall surface cleaning mode acting to urge the wheels  170  against the wall surface  8 . 
     The body  100  upper portion or frame  154 T defines a perimeter essentially matching that of the chassis  154 B. The frame is comprised of a deck  200  having upstanding side walls  202 L and  202 R extending therefrom. Each of the walls  202  defines an interior volume containing material  203  (FIG.  5 ), e.g., solid foam, selected to provide a weight/buoyancy characteristic to facilitate the body&#39;s assuming a desired orientation in the wall and water surface cleaning modes and in transition therebetween. The frame  154 T also defines the aforementioned front fin  117  which is centrally mounted on deck  200  proximate to the forward or nose portion. The fin  117  is shaped with a rounded front surface  208  and with side surfaces  210 L and  210 R converging toward a rear edge  212 . Aforementioned Skimmer Jets  110  and Debris Retention Jets  112  are mounted proximate to the rear edge  212 . The Jets  110  are comprised of three rearwardly directed outlets including a center outlet  110 C and left and right outlets  110 L and  110 R. The outlet  110 C is directed essentially along the center line of the body  100  whereas the Jets  110 L and  110 R diverge or fan out slightly from the center line. All of the Jets  110  are preferably oriented slightly downwardly with respect to deck  200  (see FIG. 10) to produce a vertical lift force component when active. The Debris Retention Jets  112  are also comprised of three outlets including a center outlet  112 C and left and right outlets  112 L and  112 R. Outlets  112 L,  112 R also diverge in an essentially fan pattern similar to the Skimmer Jets  110 . However, whereas the Skimmer Jets  110  are oriented slightly downwardly, the Debris Retention Jets  112  are oriented slightly upwardly (see FIG. 11) directed toward a rear debris entrance opening  218 . 
     More particularly, the side walls  202 L,  202 R respectively define inner surfaces  220 L,  220 R which converge rearwardly to guide water moving past fin  117  toward the rear debris opening  218  which is framed by rear cross member  227 , deck  200 , and the side wall surfaces  220 L,  220 R. A slot  228  is formed around opening  218  for removably accommodating an open frame member  230 . The frame member  230  has the aforementioned debris container  111 , preferably comprising a bag formed of flexible mesh material  231 , secured thereto so that water flow through opening  218  will flow into the container  111 . 
     A front cross member  240  extends between the walls  202 L and  202 R, preferably supported by the fin  117  proximate to the rear edge  212 . The cross member  240  defines rearwardly inclined hydrodynamic surfaces  242  (see FIG. 2) which, together with deck surface  200 , act to produce a downward force on the body as the body moves forward in the wall surface cleaning mode. This force assists in maintaining the traction wheels  170  against the wall surface  8  to properly position the vacuum inlet opening  109  in close proximity to the wall surface  8  (see FIG.  9 ). 
     The vacuum passageway  180  extends from vacuum inlet opening  109  and terminates at vacuum discharge opening  182  in close proximity to the upper surface of deck  200 . Thus, water drawn from the wall surface  8  through the vacuum passageway  180  will exit at the discharge opening  182  and be directed rearwardly through opening  218  and into the aforementioned debris container  111 . In order to assure relatively unobstructed water flow through debris container  111 , it is formed of a relatively coarse mesh material  231  sufficient to trap small pieces of leaves, for example, but insufficient to trap finer debris such as silt. In order to trap such finer material which sometimes accumulates on the wall surface  8 , a second or auxiliary debris container  250  is provided for mounting adjacent the vacuum discharge opening  182  (FIG.  7 ). The details of a preferred implementation of container  250  will be discussed in connection with FIGS. 14-16. However, at this juncture, it is to be noted that the container  250  comprises a bag formed of mesh material  253  (preferably having a finer mesh than that of bag  111 ) closed at an upper end  254  (FIG.  14 ). The bag  250  lower end  255  defines an open mouth extending around frame member  256  which is configured to be mounted in the vacuum discharge opening  182  so that the bag  250  extends rearwardly, into the main debris container bag  111 , as represented in FIG.  4 . 
     Attention is now specifically directed to FIGS. 5 and 7 which generally depict a “plumbing” subassembly  260  for implementing the water distribution system schematically represented in FIG.  3 . It will be recalled from FIG. 3 that positive pressure water is supplied via supply inlet  101  and then distributed to the various outlets  102 ,  104 , 106 , 108 , 110 ,  112 , 114 , and  116 , all of which can be seen in FIG.  7 . The plumbing subassembly  260  is mounted between the body chassis  154 B and the body frame  154 T. More specifically, the chassis floor member  160  is concaved and defines a recess for accommodating the plumbing subassembly  260  which is retained to the chassis by bracket  270 . Although the plumbing subassembly  260  contains the various elements of the distribution system shown in FIG. 3, including the timing assembly  122 , the direction controller  126 , the direction valve  128 , the level controller  124 , and the level valve  138 , they are not visible in FIG. 7 but will be discussed hereinafter in connection with FIG.  12 . 
     FIG. 8 shows a cross-section of front fin  117  and depicts interior chamber  262  having awater inklet  263  in its bottom wall  264 . The inlet  263  is coupled to aforementioned Front Chamber Filled outlet  116 . Overflow tubes  265  are mounted in chamber  262  having entrances  266  positioned to establish the height of the water volume in the chamber. The tubes  265  are open at their lower ends  267  to permit overflow water to exit from the chamber  262 . 
     Attention is now directed to FIGS. 9,  10  and  11  which respectively depict operation in the wall surface cleaning mode (forward state), the water surface cleaning mode (forward state), and the backup state (either mode). In each of FIGS. 9,  10 , and  11 , a water discharge stream is represented as exiting from the outlets active during that mode and/or state. The primary force components acting on the body are also represented in FIGS. 9-11. 
     FIG. 9 shows the body  100  in the wall surface cleaning mode with its wheel  170  engaged against a horizontally oriented portion of wall surface  8 . In this situation, note that the body assumes a nose down, tail up attitude, being oriented at an approximately 11° angle with respect to the horizontal. This attitude facilitates the development of appropriate vertical forces as the body moves forwardly through the water pool to hold the wheels against the wall surface  8 . More particularly, when operating in the wall surface cleaning mode, water is discharged from the Forward Thrust Jet  102  and the Vacuum Jet pump Nozzle  108 . Note that with the attitude depicted in FIG. 9, both of these outflows are directed to develop nominal vertical force components in the direction to press the wheels  170  against the wall surface  8 . Additionally, both of these outflows provide nominally horizontal thrust components acting to propel the body in a forward direction, i.e., to the left as depicted in FIG.  9 . This forward motion of the body through the water in turn develops vertical force components, e.g.,  270 , attributable to relative motion of the water acting against the various hydrodynamics surfaces, particularly surfaces  200  and  242 . The motion of the body  100  through the water in the wall surface cleaning mode will be somewhat randomized by the totality of forces acting on the body including the drag force of the supply hose  9  and debris container  111 , as well as the reaction forces produced by the whipping of the sweep hose  15 . The precise path followed by the body  100  will additionally be largely affected by the contours of the containment wall surfaces acting against the traction wheels  170 . As the body  100  moves along the wall surface, different ones of the forces will dominate at different times to cause the body to deviate from an essentially straight line travel path defined by the traction wheels  170 . This deviation is an intended consequence of the overall design of the apparatus and serves to randomize the motion of the body along the wall surface to clean the entire wall surface including bottom and side portions. To achieve optimum path travel for the contours of a particular containment wall, various ones of the thrust jets, e.g., Forward Thrust Jet  102 , are preferably mounted so that they can be adjustably directed, e.g., via a ball and socket configuration  274  (FIG.  7 ). Additionally, front wheel  170 F preferably exhibits a lower coefficient of friction than the other wheels  170  to facilitate turning from a single line path. 
     Attention is now directed to FIG. 10 which depicts the body  100  operating in the water surface cleaning mode adjacent to the water surface  7 . Note that in the water surface cleaning mode, Forward Thrust/Lift Jet  106  and Skimmer Jets  110  discharge water with a downward component to produce a vertical lift force to overcome the weight of the unit and maintain the body with an essentially horizontal attitude adjacent the water surface  7 . Note that in the water surface cleaning mode (FIG.  10 ), deck surface  200  is essentially parallel to the water surface  7  and the hydrodynamic surface  242  is above the water surface. Thus, neither surface produces the vertical downward force component in the water surface cleaning mode that it does in the wall surface cleaning mode of FIG.  9 . Also, note that the water filled front fin  117  is at least partially lifted out of the water in FIG. 10 so that its weight contributes a vertical downward force component. The path of travel along the water surface taken by the body  100  will be primarily determined by the direction of discharge of the Forward Thrust/Lift Jet  106  and Skimmer Jets  110 . Additionally, of course, it will be affected by the totality of other forces acting on the body including the drag forces attributable to the supply hose  9  and debris bag  111 , the reaction forces produced by the whipping of the sweep hose  115 , and the contact with wall and other obstruction surfaces. 
     Attention is now directed to FIG. 11 which depicts the active water outflows during the backup state which, it will be recalled, is defined by the direction valve  128  (FIG.  3 ). In the backup state, water is discharged from the Debris Retention Jets  112  and the Rearward Thrust Jet  104 . It will be recalled from FIG. 6 that the Thrust Jet  104  is displaced from the center line of the body  100  so that in providing rearward thrust, the body will tend to rotate around a vertical axis and thus be able to work its way around obstructions. The Debris Retention Jets  112  discharge through opening  218  into the bag  111  and thus prevent debris from coming out of the bag when the body is moving rearward as represented in FIG.  11 . 
     Although the embodiment described in FIGS. 2-11 has been assumed to use a heavier-than-water body, which uses water outflows to thrust it to the water surface, it should be understood that it could alternatively use a lighter-than-water body with the water outflows being directed to thrust the body down to the wall surface. 
     Attention is now directed to FIG. 12A which schematically represents a preferred implementation  300  of the water distribution system depicted in FIG.  3 . The implementation  300  is basically comprised of: 
     a. Direction valve  128  implemented by valve assembly  304 ; 
     b. Level valve  138  implemented by a valve assembly  306 ; 
     c. Direction controller  126  implemented by controller assembly  308 ; 
     d. Level controller  124  implemented by controller assembly  310 ; and 
     e. Timing assembly  122  implemented by nozzle  312 , turbine  314 , timing gear train  316 , and reduction gear train  318 . 
     For clarity of explanation, it will be assumed that the implementation  300  is designed to cause the body  100  to operate in accordance with the following exemplary schedule: 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                   
                 PROPULSION 
                   
               
               
                 CLEANING MODE 
                 DURATION 
                 STATE 
                 DURATION 
               
               
                   
               
             
            
               
                 WATER SURFACE 
                 30 Min. 
                 FORWARD 
                 90 Sec. 
               
               
                   
                   
                 BACKUP 
                  7 Sec. 
               
               
                 WALL SURFACE 
                 30 Min. 
                 FORWARD 
                 90 Sec. 
               
               
                   
                   
                 BACKUP 
                  7 Sec. 
               
               
                   
               
            
           
         
       
     
     Direction valve assembly  304  comprises a cylindrical valve body  330 D having a first end  331 D defining a supply inlet  332 D and a sealed second end  333 D. Forward outlet  334 D and rearward outlet  336 D open through side wall  337 D (respectively corresponding to outlets  134  and  132  in FIG.  3 ). The inlet  332 D communicates with either outlet  334 D or  336 D depending upon the position of valve element  338 D. Valve elements  338 D is carried by rod  340 D secured to piston  342 D. A spring  346 D contained within the valve body  330 D normally pushed piston  342 D toward the end  331 D of the valve body to seat outlet  334 D and communicate inlet  332 D with outlet  336 D. The valve body  330 D also defines a control post  350 D which opens through side wall  337 D between fixed partition  352 D and piston  342 D. Positive pressure water supplied to control port  350 D acts to move piston  342 D toward end  333 D against spring  346 D, thus causing valve element  338 D to seal rearward outlet  336 D and open forward outlet  334 D. 
     Direction valve control port  350 D is controlled by the output  364 D of the direction controller assembly  308 . The direction controller assembly  308  is preferably comprised of a cylindrical controller body  360 D having a circumferential wall defining an inlet  362 D and an outlet  364 D. Additionally, body  360 D defines an end wall  366 D having an exhaust port  368 D formed therein. A disk shaped valve element  370 D is mounted on shaft  372 D for rotation within the controller body as depicted in FIG.  12 B. During a portion of its rotation, the valve element  370 D seals exhaust port  368 D enabling positive pressure water supplied to controller inlet  362 D to be transferred via outlet  364 D to direction valve control port  350 D. During the remaining portion of its rotation, exhaust port  368 D is open, and positive pressure water from inlet  362 D is exhausted through port  368 D so that no significant pressure is applied to control port  350 D. Positive pressure water is supplied to inlet  362 D from tubing  380  coupled to direction valve body outlet  382 D which communicates directly with supply inlet  332 D. 
     In the implementation of FIG. 12, the direction valve assembly  304  inlet  332 D is connected to the aforementioned positive pressure supply inlet  101  shown in FIG.  3 . The direction valve assembly  304  forward outlet  334 D is connected to the inlet  332 L of level valve assembly  306 . Level valve assembly  306  is implemented essentially identical to direction valve assembly  304  and defines outlets  334 L and  336 L which respectively correspond to the water surface cleaning outlet  142  and the wall surface cleaning outlet  140  of FIG.  3 . 
     The positive pressure water from outlet  382 D is also delivered to turbine nozzle  312  and, via tubing  384 , to the inlet  362 L of the level controller assembly  310 . The outlet  364 L of the level controller assembly  310  is connected to the control port  350 L of the level valve assembly  306 . Level controller assembly  310  is implemented essentially identical to direction controller assembly  308 . 
     Nozzle  312  is positioned to turn turbine  314  which rotates drive shaft  386  of timing gear train  316  which drives both output gear  388  and output drive shaft  390 . Gear  388  forms part of a train to rotate the direction controller valve element  370 D. Shaft  390  forms part of a train to rotate the level controller valve element  370 L. More specifically, shaft  390  drives reduction gear train  318  to rotate the level controller valve element  370 L at a slow rate, e.g., once per hour, to alternately define thirty minute intervals for the water surface and wall surface cleaning modes. 
     Gear  388  drives the direction controller valve element  370 D via a clutch mechanism  392  depicted in FIG.  12 A. The clutch mechanism  392  normally disengages gear  388  from direction controller shaft  372 D but periodically (e.g., fifteen seconds during each ninety second interval) engages to rotate the shaft  372 D and direction controller valve element  370 D. The clutch mechanism  392  is implemented via a throw-out gear  393  carried by swing arm  394 . A tension spring  395  normally acts on swing arm  394  to disengage gears  393  and  388 . However, gear  388  carries cam  396  which, once per cycle, forces cam follower  397  to pivot swing arm  394  so as to engage gears  393  and  388 . Gear  393  is coupled via gear  398  to gear  399  which is mounted to rotate direction controller shaft  372 D. 
     In the operation of the apparatus of FIG. 12A, assume initially that the apparatus is in its quiescent state with direction valve assembly  304  rearward outlet  366 D open and forward outlet  334 D closed and with level valve assembly  306  wall surface cleaning outlet  336 L open and water surface cleaning outlet  334 L closed. When positive pressure water is supplied via inlet  101  to inlet  332 D of direction valve assembly  304 , it will be directed via tubing  380  to inlet  362 D of direction controller assembly  308 . Positive pressure water will also be supplied to nozzle  312  to drive turbine  314 . As a consequence, gear train  316  and reduction gear train  318  will rotate the level controller valve element  370 L to periodically seal exhaust port  368 L and periodically pressurize control port  350 L of level valve assembly  306 . When pressurized, it will move the piston of assembly  306  against spring  364 L to open water surface cleaning outlet  334 L. When control port  350 L is not pressurized, wall surface cleaning port  366 L will be open. Thus, the level valve assembly  306  will alternately open outlets  334 L and  336 L depending upon the position of the disk valve member  370 L of the level controller assembly  310 . In the assumed implementation, the water and wall surface cleaning modes will be alternatively defined for approximately equal periods of about thirty minutes each. 
     The direction valve assembly  304  similarly will open forward outlet  334 D when its control port  350 D is pressurized. When control port  350 D is not pressurized, then the rearward outlet  336 D will be open. Water pressure delivered to control port  350 D is determined by the position of disk valve element  370 D within direction controller  308 . In the assumed implementation, the direction controller  308  defines the forward propulsion state for approximately ninety seconds and then switches the direction valve assembly  304  to the backup propulsion state for approximately seven seconds. 
     From the foregoing explanation of FIG. 12A, it should be understood that the spring  395  normally acts to disengage gears  393  and  388  so that direction controller valve element  370 D is not driven. However, cam  396  periodically raises cam follower  397  to engage gears  393  and  388  to rotate the valve element  370 D to switch direction valve  304  to its backup state. Attention is now directed to FIG. 13 which illustrates an alternative water distribution implementation which incorporates a motion sensor ( 152  in FIG. 3) for the purpose of sensing when the forward motion of the body  100  has diminished below a certain threshold. This may occur, for example, when the body  100  gets trapped behind an obstruction, such as the entrance of a built-in skimmer. In such an instance, it is desirable to promptly switch the direction valve  128  to the back-up state. Whereas in FIG. 12A, spring  395  operates to normally disengage gears  393  and  388 , in the embodiment of FIG. 13, spring  402  is connected to swing arm  404  to normally engage gear  406  and output drive gear  408 . A motion sensor in the form of paddle  412  is structurally connected to the swing arm  404 . The paddle  412  is mounted so that when the body  100  is moving through the water in a forward direction ( 413 ), the relative water flow will act to pivot the paddle in a clockwise direction (as viewed in FIG. 13) to overcome the action of spring  402  to disengage gears  406  and  408 . So long as the body keeps moving in a forward direction above a threshold rate, the paddle  412  will overcome the spring  402  to disengage gears  406 , 408  and the direction controller shaft  372  will not rotate. However, when the forward motion of the body diminishes to below the threshold rate, the paddle  412  no longer overcomes the force of spring  402  and the shaft  372  is caused to rotate to switch the direction valve  304  to the backup state. 
     Notwithstanding the foregoing, even if the forward motion of the body is maintained, it is nevertheless desirable to periodically switch the direction valve  304  to its backup state. For this purpose, gear  408  carries a cam  414  which periodically lifts cam follower  415  to force engagement of gears  406  and  408 . 
     As noted, it has been assumed that the embodiments of FIGS. 12A and 13 define substantially equal intervals for the water surface cleaning mode and the wall surface cleaning mode. The relative split between the mode is, of course, determined by the configuration of level controller valve element  370 L. As depicted, valve element  370 L defines an arc of about 180° and thus, during each full rotation of valve element  370 L, it will open and close exhaust port  368  for essentially equal intervals. If desired, the valve element could be configured to define an arc either greater or less than 180° to extend one of the cleaning mode intervals relative to the other cleaning mode interval. For example, in order to extend the water surface cleaning interval, the exhaust port  368 L must remain closed for a greater portion of the valve element rotation, meaning that the valve element  370 L should extend through an arc greater than 180°. 
     It is sometimes desirable to enable a user to maintain the apparatus in either the water surface cleaning mode or the wall surface cleaning mode for an extended period. For this purpose, the piston rod  340 L of valve assembly  306  can be configured so that it extends through the closed end of the level control valve body  330 L. The free end of rod  340 L is connected to a U-shaped bracket  416  (FIG. 13) having legs  416 A and  416 B. Bracket  416  moves with the piston rod  340 L between the two positions respectively represented in solid and dash line in FIG. 13. A user operable control knob  417  is provided for selectively rotating shaft  418 , carrying a perpendicular arm  419 , between the three positions shown in FIG. 13 to selectively (1) bear against bracket leg  416 A to hold piston rod  340 L in its left-most position defining the wall surface cleaning mode, (2) bear against the bracket leg  416 B to hold piston rod  340 L in its right-most position defining the water surface cleaning mode, or (3) move clear of the bracket legs to allow the bracket  416  to move without interference. The control knob  417  is preferably provided with a ball  420  which can be urged by spring  421  into a fixed recess to selectively detent the knob in any of the three positions. 
     Attention is now directed to FIGS. 14-16 which illustrate the inner debris container  250  in greater detail. The container  250  is formed of fine mesh material  253  rolled into an essentially cylindrical form with edge  422 A overlapping edge  422 B. The material  253  is sewn or otherwise sealed to close end  254 . The second bag end  255  is secured to frame member  256  so that the position of the access opening defined by overlapping edges  422 A,  422 B is keyed to the frame member  256 . More particularly, frame member  256  defines projecting key  424  which is configured to be received in keyway  426  adjacent vacuum discharge opening  182  to orient the overlapping edges  422 A,  422 B upwardly. This orientation allows silt to be collected in the bag  250  without tending to bear against and leak out from between the edges. However, this configuration still allows a user to readily remove the frame  256  from the discharge opening  182  and spread the edges  422 A, 422 B to empty debris from bag. Short pull tables  430 , 432  are preferably provided to facilitate spreading the edges. 
     SECOND EMBODIMENT (FIGS.  17 A,  17 B,  17 C) 
     In the first embodiment depicted in FIGS. 2-16, the heavier-than-water body  100  is lifted to and maintained at the water surface by a vertical force produced primarily by water outflow from the body (e.g., outlets  106 ,  110 ) in a direction having a vertical component. 
     In the second heavier-than-water embodiment  500  depicted in FIGS. 17A-17C, the vertical force to maintain the body at the water surface is produced in part by selectively modifying the weight/buoyancy characteristic of the body  502 . The body  502  is configured similarly to body  100  but differs primarily in the following respects: 
     1—Front fin  517  is provided with an air hole  518 , preferably near its upper edge  520 , opening into interior chamber  522 . 
     2—Side walls  526 L,  526 R respectively define interior chambers  528 L,  528 R. 
     3—Awater powered jet pump  530  is provided for selectively pulling water out of, and air into, chambers  522 ,  528 L,  528 R. Jet pump  530  is supplied by positive pressure water via inlet  532  to create a suction at port  534  and a discharge at outlet  536 . 
     4—Tubing  540  extends from suction port  534  to drain ports  542 L,  542 R in the bottom panel of chambers  528 L,  528 R. Tubing  544  extends from the top of chambers  528 L,  528 R to drain port  546  in the bottom panel of front chamber  522 . 
     5—Skimmer jets  110  can be deleted. 
     In the wall surface cleaning mode, the body  502  (FIGS. 17A-15 17 C) will operate essentially the same as the body  100  (FIGS.  2 - 16 ). However, in the water surface cleaning mode, the level valve  550  (FIG. 17C) will supply positive pressure water to inlet  532  of pump  530  to draw water from chambers  522 ,  528 L  528 R, via tubing  540 ,  544 , while the body is concurrently lifted by water outflow from Forward Thrust/Lift Jet  554 . After the body rises sufficiently to place air hole  518  above the water surface, pump  530  will pull air in via hole  518  to fill chambers  522 ,  528 L,  528 R. By replacing the water in chambers  522 ,  528 L,  528 R with air, the weight/buoyancy characteristic of the body  502  is modified to first elevate and then stabilize body  502  proximate to the water surface with the deck  560  just below the water surface for effective skimming action. When level valve  550  next switches to the wall surface cleaning mode, positive pressure water flow to pump inlet  532  terminates, allowing pool water to backflow into jet pump  530  to fill the chambers  522 ,  528 L,  528 R with water, and force air out through hole  518 , thus causing the body  500  to descend to the wall surface bottom. 
     The Skimmer Jets  110  of the first embodiment may be deleted from the embodiment  500 . The outer water outlets (i.e., Forward Thrust Jet  564 , Rearward (backup) Thrust Jet  568 , Debris Retention Jet  570 , and Vacuum Jet Pump Nozzle  572 ) perform essentially the same in body  502  as in previously described body  100 . 
     THIRD EMBODIMENT (FIGS.  18 A,  18 B,  18 C) 
     Attention is now directed to FIGS. 18A-18C which illustrate a third embodiment  600  comprising a heavier-than-water body  602 . As will be seen, the embodiment  600  differs from the first embodiment depicted in FIGS. 2-16 in that the vertical force required to lift the body  602  to the water surface and maintain it at the water surface is produced primarily by selectively modifying the weight/buoyancy characteristic of the body  602  rather than directly by a water outflow. The body  602  is configured similarly to body  100  but differs primarily in the following respects: 
     1—Sidewalls  620 L,  620 R respectively define air holes  624 L,  624 R near their upper surfaces which open into central interior chambers  626 L,  626 R, The chambers  626 L,  626 R respectively define drain ports  628 L,  628 R opening through bottom panel  629 . 
     2—A water powered jet pump  632  is provided having a supply inlet  634 , a suction port  635 , and a discharge outlet  636 . The suction port  653  is coupled to drain ports  628 L,  628 R. When positive pressure water is supplied to pump inlet  634  from level valve  638  (FIG. 18C) in the water surface cleaning mode, a suction is created at port  635  to draw water out of chambers  626 L,  626 R. When valve  638  switches to the wall surface cleaning mode, the positive pressure supply to inlet  634  terminates and pool water flows backwards through pump  632  to fill central chambers  626 L,  626 R via drain ports  628 L,  628 R. 
     3—Front fin  640  defines a front interior chamber  642  having a drain port  644  in bottom panel  645 . 
     4—A water powered jet pump  648  is provided having a supply inlet  650 , a suction port  651  and a discharge outlet  652 . When positive pressure water is supplied to jet pump  648  from level valve  638  (FIG. 18C) in the water surface cleaning mode, a suction is created at port  651  to draw water out of chamber  642 . When the supply to inlet  650  terminates, pool water flows backwards through pump  648  to fill front chamber  642  via drain port  644 . 
     5—Rear interior chambers  660 L,  660 R are respectively formed rearwardly of central chambers  626 L,  626 R by partition wall  662 . The chambers  660 L,  660 R open via ports  664 L,  644 R and tubing  666  to a flaccid bag  668  physically contained within front chamber  642 . The chambers  660 L,  660 R are filled with air at atmospheric pressure (prior to installation) via a removable plug  670 . 
     6—Skimmer Jets  110  and Forward Thrust Lift Jet  106  of the first embodiment can be deleted from the embodiment  600  of FIGS. 18A-18C. Note in FIG. 18C that the Thrust Jet  672  is supplied from the forward outlet  674  of the direction valve  676  rather than from the level valve  638 . 
     When operating in the wall surface cleaning mode, the front chamber  642  and central chambers  626 L,  626 R will be filled with water, primarily via backflow through pumps  648 ,  632 , and flaccid bag  668  will be collapsed by the water in chamber  642 . When operation is switched to the water surface cleaning mode by level valve  638 , jet pump  648  pumps water out of front chamber  642  to permit bag  668  to inflate with air supplied from rear chambers  660 L,  660 R. This action fills chamber  642  with air (at a pressure less than atmospheric) enabling the body  602  to float to the water surface and lift air holes  624 L,  624 R above the water surface. With the holes  624 L,  624 R above the water surface, jet pump  632  evacuates water from central chambers  626 L,  626 R and fills them with air thereby providing additional buoyancy to elevate and stabilize the body  602  and position the deck  678  at just below the water surface for effective skimming action. 
     When valve  638  switches back to the wall surface cleaning mode, the positive pressure water supply to pump inlets  634  and  650  terminates allowing pool water to backflow through jet pumps  632 ,  648  into central chambers  626 L,  626 R and front chamber  642 . As a consequence, bag  668  collapses forcing its interior air back into rear chambers  660 L,  660 R while the air in central chambers  626 L,  626 R flows out of air holes  624 L,  624 R as pool water fills the central chambers. As a consequence, the body  602  will descend to the wall surface bottom. 
     The Skimmer Jets  110  and Forward Thrust/Lift Jet  106  of the first embodiment may be deleted from the embodiment  600 . The other water outlets (i.e., Forward Thrust Jet, Rearward (backup) Thrust Jet and Vacuum Jet Pump Nozzle) perform essentially the same in body  602  as in previously described body  100 . Note that the Thrust Jet  672 , because of its placement at the forward outlet  674  of direction valve  676  (FIG.  18 C), operates to provide forward propulsion in both cleaning modes. 
     FOURTH EMBODIMENT (FIGS.  19 A,  19 B,  19 C) 
     Attention is now directed to FIGS. 19A-19C which illustrate a fourth embodiment  700  comprising a body  702 . Whereas the first three embodiments thus far described were referred to as being heavier-than-water inasmuch as they sink in a quiescent or rest state and are lifted to the water surface in an active state, the body  702  can be considered as being lighter-than-water inasmuch as it floats in its quiescent state and is caused to descend in an active state. As will be described hereinafter, the body  702  is caused to descend in the wall surface cleaning mode primarily by selectively modifying its weight/buoyancy characteristic. The body  702  is configured similarly to body  100  but differs primarily in the following respects: 
     1—Sidewalls  720 L defines a rear interior chamber  726 L and a central chamber  728 L. Similarly sidewall  720 R defines rear and central chambers  726 R,  728 R. 
     2—Front fin  740  defines a front interior chamber  742 . 
     3—Central chambers  728 L,  728 R and front fin chamber  742  respectively contain flaccid bags  744 L,  744 R, and  746 . 
     4—An air tube  748  is provided opening into rear chambers  726 L,  726 R at  750 L,  750 R and into flaccid bags  744 L,  744 R and  746  at  752 L,  752 R and  754 . The rear chambers  726 L,  726 R and flaccid bags  744 L,  744 R and  746  are filled with air at atmospheric pressure (prior to installation) via removable plugs  760 . 
     5—A tube  764  is provided to selectively supply positive pressure water to central chambers  728 L,  728 R via outlets  766 L,  766 R and to front fin chambers  742  via outlet  768 . 
     6—Skimmer Jets  110  and Forward Thrust Lift Jet  106  of the first embodiment can be detected from the embodiment  700  of FIGS. 19A-19C. 
     In operation in the water surface cleaning mode, rear chambers  726 L,  726 R and flaccid bags  744 L,  744 R and  746  will all be filled with air at atmospheric pressure to produce a net buoyancy which floats the body at the water surface. When operation is switched to the wall surface cleaning mode by valve  770  (FIG.  19 C), this will supply pressurized water via water fill tube  764  to outlets  766 L,  766 R and  768 . This action will collapse flaccid bags  744 L,  744 R, and  746  and force the air therein via air tube  748 , into rear chambers  726 L,  726 R at a pressure above atmospheric. 
     When valve  770  (FIG. 19C) switches back to the water surface cleaning mode, the positive water pressure supplied to tube  764  is terminated, permitting the compressed air in rear chambers  726 L,  726 R to expand to fill bags  744 L,  744 R and  746  thus modifying the weight/buoyancy characteristic of the body to enable it to float to the water surface. 
     The water outlets (i.e., Rearward (backup) Thrust Jet, and Vacuum Jet Pump Nozzle) perform essentially the same in body  702  as in previously described body  100 . However, the Forward Thrust Jet  772  is supplied directly from the forward outlet  774  (FIG. 19C) of the direction valve  776  (FIG. 19C) so that it operates in both cleaning modes to provide forward propulsion. 
     The water distribution systems of FIGS. 17C,  18 C, and  19 C can each be implemented substantially as shown in FIGS. 12A or  13 . Attention is now directed to FIGS. 20 and 21 which respectively depict implementations alternative to those shown in FIGS. 12 and 13. 
     More particularly, FIG. 20 illustrates a water distribution system implementation  800  basically comprised: 
     a. Direction valve assembly  802   
     b. Level valve assembly  804   
     c. Direction controller  806   
     d. Level controller  808   
     e. Level controller timing assembly  810  primarily comprised of nozzle  812 , turbine  814 , timing gear train  816 , output shaft  818 , and timing disk  820 . 
     f. Direction controller timing assembly  830  primarily comprised of nozzle  832 , turbine  834 , timing gear train  836 , output shaft  838 , and timing disk  840 . 
     The direction valve assembly  802  and level valve assembly  804  can be substantially identical to the corresponding elements discussed in conjunction with FIG.  12 A. More particularly, direction valve assembly  802  is comprised of a cylindrical body  850  defining a supply inlet  852 , a forward outlet  854 , a rearward outlet  856 , a control port  858 , and a pressurized water outlet  860 . Spring  862  biases valve element  864  to the backup state, i.e., with forward outlet  854  closed and rearward outlet  856  open. When positive water pressure is supplied to control port  858 , valve element  864  moves downwardly to define the forward state, i.e., with forward outlet  854  open and rearward outlet  856  closed. 
     Level valve assembly  804  is similarly comprised of a cylindrical body  870  which defines a supply inlet  872 , a wall surface outlet  874 , a water surface outlet  876 , and a control port  878 . Spring  880  biases valve element  882  to the water surface cleaning mode, i.e., with wall surface outlet  874  closed and water surface outlet  876  open. When positive water pressure is supplied to control port  878 , valve element  882  is moved to define the wall surface mode with water surface outlet  876  closed and wall surface outlet  874  open. 
     Direction controller  806  and level controller  808  are substantially identical to the corresponding elements discussed in conjunction with FIG.  12 A. Direction controller  806  is comprised of a cylindrical body  888  having a peripheral wall  890  and an end wall  892 . The peripheral wall  890  defines an inlet  894  and an outlet  896 . The end wall  892  defines an exhaust port  898 . A disk shaped valve element  900  is mounted on the aforementioned output shaft  838  for rotation in the body  888 . During a portion of its rotation, valve element  900  seals exhaust port  898  enabling positive pressure applied to inlet  894  to be transferred via outlet  896  and tube  902  to direction valve control port  858 . During the remaining portion of its rotation, exhaust port  898  is open and positive pressure water from inlet  894  is exhausted through port  898  so that no significant pressure is applied to control port  858 . Positive pressure water is supplied to inlet  894  via tubing  906  coupled to pressurized water outlet  860 . 
     Level controller  808  also comprises a cylindrical body  908  having a peripheral wall  910  and an end wall  912 . The peripheral wall  910  defines an inlet  914  and an outlet  916 . The end wall defines an exhaust port  918 . A disk shaped valve element  920  is mounted on aforementioned output shaft  818  for rotation in the level controller body  908 . During a portion of its rotation, valve element  920  seals exhaust port  918  enabling positive pressure applied to inlet  914  to be transferred via outlet  916  to level valve control port  878 . During the remaining portion of its rotation, exhaust port  918  is open and positive pressure water from inlet  914  is exhausted through port  918  so that no significant pressure is applied to control port  878 . Positive pressure water is supplied to inlet  910  via aforementioned tubing  906 . 
     Tubing  906  also supplies positive pressure water to nozzles  812  and  832  to respectively rotate turbines  814  and  834 . Turbine  814  is mounted on shaft  924  and drives gear train  816  to drive output shaft  818 . Additionally, gear train  816  drives timing disk  820 . Similarly, turbine  834  drives shaft  930  which via gear train  836  drives output shaft  838 . Gear train  836  additionally drives timing disk  840 . 
     As can be seen in FIG. 20, timing disks  820  and  840  are mounted side by side in the same plane. A latch bar  950  mounted for hinged movement around pin  952  between a latched and unlatched position extends across the faces of disks  820  and  840 . Spring  954  normally urges latch bar  950  toward the latched position proximate to the faces of disks  820  and  840 . Disk  820  carries one or more lifter cams  960  on its face. Lifter cam  960  preferably has a ramp at its leading edge  962  configured to engage latch element  964  to lift latch  950  to its unlatched position as the disk  820  rotates in the direction of arrow  966 . 
     Disk  840  carries one or more stop elements  970  on its face, each configured to engage latch element  964  to stall rotation of disk  840  and output shaft  838  in its forward state when latch bar  950  is in its latched position. Stop element  970  is oriented relative to valve element  900  such that its engagement against latch element  964  acts to maintain direction controller  806  and direction valve  802  in the forward state. Periodically, when lifter cam  960  on disk  820  lifts latch bar  950  to its unlatched position, stop element  970  moves past latch element  964  enabling disk  840  and valve element  900  to rotate through substantially 360° passing through the backup or rearward state and returning to the forward state. At some point in its cycle, stop member  970  again engages latch element  964  thus stalling direction controller  806  in the forward state. 
     Thus, to summarize the operation of FIG. 20, rotation of the turbine  814  drives the gear train  816  to cause the level controller  808  to alternately define the wall surface and water surface cleaning modes. As the gear train  816  rotates, lifter cam  960  periodically lifts latch bar  950  to its unlatched position enabling stop element  970  of disk  840  (driven by turbine  834 ) to move past latch element  964  to cycle through the backup state. Although FIG. 20 depicts a single fixedly positioned lifter cam  960  and a single fixedly positioned stop element  970  on the face of disks  820  and  840  respectively, it is pointed out that a more complex and detailed timing pattern could be achieved if desired by utilizing multiple lifter cams and/or stop elements, and/or mounting them so that their respective positions on the disks can be varied. 
     Attention is now directed to FIG. 21 which illustrates a water distribution system  972  similar to that depicted in FIG. 20 but modified to sense when the forward motion of the cleaner body diminishes below a certain threshold. This can occur, for example, when the body gets trapped by an obstruction, such as the entrance to a built-in pool skimmer. In such an instance, it is generally desirable to promptly cycle the direction controller  806  to the backup state in order to free the cleaner body. To introduce this capability, the system of FIG. 21 differs from FIG. 20 in that the latch. bar  950  is no longer spring urged to the latched position. Rather, a paddle  974  is mounted at the free end of latch bar  950  and oriented such that forward motion of the cleaner body through the water pivots bar  950  around pin  952  toward the disks  820 ,  840 , i.e., the latched position. As long as the forward motion of the cleaner body remains above a certain threshold sufficient to press the latch element  964  with sufficient force to prevent movement of stop element  970  past latch element  964 , direction controller  806  will remain in its forward state (except for periodic interruption by lifter cam  960 , e.g., once every five minutes). If, however, the forward motion of the cleaner body diminishes below the threshold, the ramped leading edge of stop element  970 , will lift bar  950  and move past latch element  964  as disk  840  and output shaft  838  are allowed to turn. If disk  840  carries only a single stop element  970 , this action immediately initiates the valve element  900  cycle through the backup state and then to the forward state. FIG. 21, however, depicts multiple spaced stop elements  970   1 ,  970   2 ,  970   3  which function to essentially introduce a time delay in the forward state before the valve element  900  cycle is launched. Thus, if in the interval after the first stop element  970   1  passes latch element  964 , and prior to a subsequent stop element, i.e.,  970   2  or  970   3  passing latch element  964 , the cleaner body frees itself and resumes its forward motion, then the initiation of the subsequent stop element will engage latch element  964  to stall output shaft  838  movement and defer rotation of valve element  900  to the backup state. 
     Attention is now directed to FIG. 22A which schematically depicts a preferred arrangement, alternative to FIG. 3, for distributing positive pressure water supplied to inlet  101 A to the various outlets of the body  100  of FIG. 2, depending upon the defined mode and state. 
     More particularly, water supplied to inlet  101 A passes through in-line filter  101 B and is directed via inlet  121 A to an optional timing assembly  122 A (to be discussed in detail in connection with FIG. 23) which operates a state/mode controller  124 A. The controller  124 A controls a state/mode valve  128 A to place it either in a redirection (e.g., backup) state, or in a forward state defining a water surface mode or a wall surface mode. When in the redirection state, water from supply inlet  101 A is directed via valve supply inlet  130 A to outlet  132 A for discharge through the debris jets  112 A and redirection nozzle  104 A. Nozzle  104 A and open tube  104 B from a jet pump  104 C which increases the effectiveness of the discharge from nozzle  104 A. That is, nozzle  104 A discharges into the throat of tube  104 B to pull or entrain additional pool water into the tube so that discharge orifice  104 D delivers an outflow of greater mass at lower velocity as compared to the discharge from nozzle  104 A. Note (FIG. 22B) that the tube  104 B preferably bends toward the nose of the body to discharge an outflow having a significant lateral component, i.e., substantially perpendicular to the longitudinal front-to-rear direction of the body. The effect of the outflow is to redirect the body, that is extricate from obstructions, as is generally represented in FIG. 22C which first shows the body in solid line and then succeeding positions in phantom line. When the redirection state expires, controller  124 A will switch to the forward state to resume body forward motion. 
     When in the forward state/wall surface mode, water from supply inlet  101 A is directed through outlet  134 A to the vacuum jet pump nozzle  108 A and the forward thrust jet  102 A. When in the forward state/water surface mode, water from supply inlet  101 A is directed through outlet  142 A to the thrust lift jet  106 A and the skimmer jets  110 k. 
     Note also in FIG. 22A that an override control  146 A is provided for enabling a user to selectively place the valve  128 A, via controller  124 A, in either the wall surface cleaning mode or the water surface cleaning mode. Also note that the positive pressure water delivered to supply inlet  101  A is preferably also distributed via an adjustable flow control device  150 A and the aforementioned sweep hose outlet  114 A to sweep hose  115 A. Additionally, note that the positive pressure water supplied to inlet  101 A is preferably also directed to fill outlet  116 A for filling a chamber interior to the hollow front fin previously discussed in connection with FIG.  8 . It is also pointed out that the body preferably carries a pressure indicator  101 C comprised of a housing containing a diaphragm  101 D carrying an indicator pin  101 E. The diaphragm and housing together define a chamber  101 F which is coupled to the water distribution system (FIG. 22A) just downstream from in-line filter  101 B. The pressure in chamber  101 F bears against diaphragm  101 D to establish the position of indicator pin  101 E relative to an index marker  101 G. This relative positioning indicates to a user whether or not the magnitude of the supplied positive pressure is within the appropriate operating range for the unit. 
     The system of FIG. 22A can be implemented and operated in many different manners, but it will be assumed for purposes of explanation that the valve  128 A is caused to be in the water surface cleaning mode about fifty percent of the time and the wall surface cleaning mode about fifty percent of the time. As was mentioned in conjunction with the description of FIG. 3, this scenario can be implemented by, for example, responding to a particular event such as the cycling of an external pump, or by the expiration of a time interval. The valve  128 A switches from the forward state to the backup state in response to the expiration of a time interval and/or a reduction of forward body motion. Reduced forward body motion can be detected by an optional motion sensor  152 A configured to recognize diminished forward motion below a certain threshold to cause valve  128 A to switch to its backup state. A preferred implementation of the water flow distribution system of FIG. 22A is depicted in FIGS. 23-28, described hereinafter. 
     Attention is now directed to FIG. 23A which illustrates a preferred implementation  300 A of the water distribution system depicted in FIG.  22 A. The implementation  300 A is basically comprised of: 
     a. Valve assembly  1002  (implementing state/mode valve  128 A of FIG. 22A) comprising valve body  1004 , state actuator  1006  and mode actuator  1008 ; and 
     b. Controller assembly  1010  (implementing sate/mode controller  124 A, motion sensor  152 A, timing assembly  122 A and override control  146 A of FIG. 22A) comprising turbine  1012 , gear box  1014 , housing  1015  defining interior chamber  1016 , state disk  1018 , mode disk  1020 , motion sensor paddle  1022 , and override disk  1024 . 
     FIGS. 24A,  24 B,  24 C schematically depict the various operational states and modes of the valve assembly  1002 ; i.e., the backup state (FIG.  24 A), the forward state/water surface mode (FIG.  24 B), and the forward state/wall surface mode (FIG.  24 C). The valve body  1004  defines an inlet chamber  1030  and three outlet chambers  1032 ,  1034 ,  1036 . Ports  1040 ,  1042 ,  1044  respectively couple inlet chamber  1030  to outlet chambers  1032 ,  1034 ,  1036 . Valve elements  1050  and  1052 , respectively controlled by actuators  1006  and  1008 , operate to selectively couple the inlet chamber  1030  to only one outlet chamber at a time. 
     Inlet chamber  1030  defines an inlet port  1054  which is supplied with high pressure water via supply inlet  130 A. Outlet chamber  1032  defines an outlet port  1056  which is coupled to the aforementioned rearward thrust jet  104 A and debris retention jets  112 A. Outlet chamber  1034  defines outlet ports  1058  and  1060  which are respectively coupled to the aforementioned thrust lift jet  106 A and skimmer jets  110 A. Outlet chamber  1036  defines the outlet ports  1062  and  1064  which are respectively coupled to the aforementioned forward thrust jet  102 A and vacuum jet pump nozzle  108 A. 
     The actuators  1006  and  1008  comprise conventional hydraulic cylinders and are controlled by the selective application of a positive control pressure to their respective control ports  1066  and  1068 . The absence of a positive pressure applied to state actuator control port  1066  is represented by the terms {overscore (Ps)} and allows state actuator spring  1067  to position valve element  1050  to close port  1042 . The presence of a positive pressure applied to port  1066  is represented by the terms Ps and causes state actuator  1006  to move valve element  1050  to the left to close port  1040 . Similarly, with respect to mode actuator  1008 , a positive pressure applied to control port  1068  is represented by the term Pm which moves valve element  1052  to the left to close port  1042 . The absence of a positive pressure applied to control port  1068 , represented by the term {overscore (Pm)}, allows mode actuator spring  1069  to move valve element  1052  to the right to close port  1044 . 
     The following table I summarizes the various operational conditions for the valve assembly  1002  which are depicted in FIGS. 24A,  24 B, 24 C: 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 STATE 
                 MODE 
                   
                   
               
               
                 CONT. 
                 CONT. 
               
               
                 PRESS. 
                 PRESS. 
                 STATE/MODE 
                 FIG. 
               
               
                   
               
             
            
               
                 {overscore (Ps)} (default) 
                 (default) 
                 BACKUP 
                 24A 
               
               
                 Ps 
                 {overscore (Pm)} 
                 FORWARD/WATER SURFACE 
                 24B 
               
               
                 Ps 
                 Pm 
                 FORWARD/WALL SURFACE 
                 24C 
               
               
                   
               
            
           
         
       
     
     The controller assembly  1010  functions to selectively apply positive pressure to actuator control ports  1066  and  1068 , via tubes  1070  and  1072  in accordance with various operating conditions to be discussed hereinafter with reference to FIGS. 23A,  23 B and  25 - 28 . 
     Initially note that the controller assembly housing  1015  defines the following external ports communicating with interior chamber  1016 : 
     a. inlet supply port  1080  which receives high pressure water via tube  1082  to fill interior chamber  1016 ; 
     b. main relief port  1084 , which is either open or closed dependent on the action of state disk  1018  and motion sensor paddle  1022  to either relieve or maintain pressure in the chamber  1016 ; 
     c. supplemental relief port  1086  which is normally closed to maintain pressure in chamber  1016  but which opens once per cycle of the state disk  1018  to relieve pressure in the chamber; 
     d. outlet state port  1088  which transfers the pressure in chamber  1016  to state actuator control port  1066  (i.e., either Ps or {overscore (Ps)}); 
     e. outlet mode port  1090  which is either open or closed dependent on the action of mode disk  1020  and override disk  1024 ; when open, port  1090  transfers the pressure in chamber  1016  to mode actuator control port  1068  (i.e., either Pm or {overscore (Pm)}). 
     The state disk  1018  is mounted on shaft  1100  which is continuously rotated by turbine  1012 , via gearing (not shown) in gear box  1014 , driven by a waterflowdelivered by nozzle  1102  from the high pressure supply  130 A. The state disk  1018  defines a plurality of openings  1104  extending therethrough arranged along an outer annular track. The disk  1018  is mounted on shaft  1100  in interior chamber  1016  adjacent to the entrance aperture A 1  to main relief port  1084 . When the disk  1018  aligns an opening  1104  with aperture A 1 , aperture A 1  is said to be open and its open condition is represented by the term A 1 . When no disk opening  1104  is aligned with aperture A 1 , the aperture is said to be closed and its condition is represented by the term {overscore (A 1 )}. 
     The exit aperture A 2  of main relief port  1084  is open or closed by the action of paddle  1022 . The paddle is mounted to pivot on pin  1108  such that when the cleaner body  100  is moving forward, in either the water surface or wall surface modes, the paddle tail  1110  will close the aperture A 2 . When forward motion falls below a certain threshold, the exit aperture will open attributable to water pressure within chamber  1016 . These open and closed conditions of exit aperture A 2 , respectively represented by the terms A 2  and {overscore (A 2 )}, are depicted in FIG.  23 B. 
     Inasmuch as the entrance aperture A 1  and exit aperture A 2  are arranged in series, the relief port  1084  will be open to relieve pressure in chamber  1016  and at outlet state port  1088  when apertures A 1  AND A 2  are open (which can be expressed in logic notation as (A 1 *A 2 ). Relief port  1084  is closed when either aperture A 1  OR A 2  is closed; i.e., A 1 +A 2 . 
     State disk  1018  defines an inner annular track shown as containing a single opening  1112  placed to align with supplemental relief port  1086  once per state disk cycle. When aligned, the entrance aperture A 0  to port  1086  is open, expressed as A 0 , and when misaligned, the aperture is closed, expressed as {overscore (A0)}. 
     Thus, the pressure available at outlet state port  1088  for application to state actuator control port  1066  can be summarized in logic notation as: 
     
       
         {overscore (Ps)}=(A 1 *A 2 )+A 0   
       
     
     
       
         Ps=({overscore (A1)}+{overscore (A2)})+{overscore (A0)} 
       
     
     It will be recalled from table I that when the state control pressure is {overscore (Ps)}, the valve assembly  1002  defines the default backup state. When the control pressure has a value of Ps, the forward state is defined which for a mode control pressure value of Pm will be the water surface mode and for value {overscore (Pm)} will be the wall surface mode. 
     In typical operation, the cleaner body will stay in the forward state for a full cycle of state disk  1018 . It will be switched to the backup state once per cycle when opening  1112  moves into alignment with supplemental relief port  1086 . Throughout the remainder of the state disk cycle, if the forward motion of the body is sufficient to cause the paddle tail  1110  to close aperture A 2 , the periodic opening of aperture A 1  (attributable to movement of disk openings  1104  therepast) will have no effect. If the body&#39;s forward motion falls below a certain threshold allowing paddle tail  1110  to swing away and open aperture A 2 , then when a disk opening  1104  moves into alignment with aperture A 1 , the backup state will be initiated. It is parenthetically pointed out that the openings  1104  are preferably comprised of different length openings (long and short) alternately arranged along the annular track. In typical situations, a short backup state interval (initiated by a short opening  1104 ) will suffice to extricate the cleaner body from an obstruction which interrupted its forward motion. The longer openings  1104  are provided to create longer backup state intervals which may occasionally be desired for more significant obstructions. 
     In the forward state, the pressure at the outlet mode port  1090 , i.e., either Pm or {overscore (Pm)}, is determined by the rotational position of mode disk  1020  and override disk  1024  relative to the entrance to port  1090 . The override disk  1024  is mounted immediately adjacent to the entrance  1115  to port  1090  on shaft  1116  whose rotational position is intended to be set by a user, e.g., by a handle  1117 . The override disk  1024  is configured so it can define three distinct user selectable conditions relative to the port entrance  1115 ; namely, 
     a. Condition A 4  in which entrance  1115  is open regardless of the position of mode disk  1020  (FIG.  27 ); 
     b. Condition {overscore (A4)} in which entrance  1115  is closed regardless of the position of mode disk  1020  (FIG.  26 ); and 
     c. Condition A 4  in which entrance  1115  is either open or closed dependent on position of mode disk  1020  (FIG.  27 ). In this position, the override disk is essentially disabled and the system operates automatically. 
     In order to function in the aforedescribed manner, the override disk  1024  is configured with first and second arcuate portions of different radii; i.e., a small radius portion  1120  and a large radius portion  1122 . When the large radius portion  1122  is adjacent port entrance  1115 , as represented in FIG. 26, condition {overscore (A4)} is defined in which the port  1090  is blocked from chamber  1016 . Thus, for condition {overscore (A4)}, the mode control pressure valve is low {overscore (Pm)}. However, the portion  1122  includes an opening  1124  situated so that it can be aligned with port entrance  1115 . When aligned (condition A 4  as represented in FIG.  25 ), the override disk is essentially disabled and port  1090  will either be open or closed dependent on the position of mode disk  1020 . FIG. 27 depicts the third condition A 4  when the small radius portion  1120  of override disk  1024  is proximate to the port entrance  1115 . This position establishes an open path to the chamber  1016  regardless of the orientation of mode disk  1020 . 
     The mode disk  1020  is mounted on and is rotated by shaft  1128  which is continually driven by turbine  1012  via gearing (not shown) in gear box  1014 . The mode disk  1020  is configured with first and second arcuate portions of different radii; i.e., a small radius portion  1130  and a large radius portion  1132 . The mode disk  1020  is mounted immediately adjacent to the override disk  1024 . When the override disk is in the position represented in FIG. 25, the orientation of mode disk  1020  determines whether the output mode port  1090  opens to chamber  1016 . Port  1090  will be open to chamber  1016  when mode disk portion  1130  is proximate to opening  1124  in override disk  1024 . When mode disk  1020  rotates to move portion  1132  proximate to opening  124 , the mode disk will cover and close the opening. The open and closed conditions are respectively defined by the terms A 3  and {overscore (A3)}. 
     The following table  11  summarizes the aforementioned terms and in logic notation sets forth the respective conditions for producing the mode control pressure value Pm or {overscore (Pm)}. 
     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                 VARIABLES 
                 OPEN 
                 CLOSED 
                 DISABLE 
               
               
                   
               
               
                 (1) State Disk Aperture 
                 A1 
                 {overscore (A1)} 
                   
               
               
                 (2) Motion Sensor Aperture 
                 A2 
                 {overscore (A2)} 
               
               
                 (3) Mode Disk Aperture 
                 A3 
                 {overscore (A3)} 
               
               
                 (4) Override Disk Aperture 
                 A4 
                 {overscore (A4)} 
                 A4 
               
               
                 (5) Periodic Backup Aperture 
                 A0 
                 {overscore (A0)} 
               
            
           
           
               
               
               
            
               
                   
                 STATE 
                   
               
               
                   
                 BACKUP 
                 {overscore (Ps)} = (A1*A2) + A0 
               
               
                   
                 FORWARD 
                 Ps = ({overscore (A1)} + {overscore (A2)})*{overscore (A0)} 
               
               
                   
                 MODE 
               
               
                   
                 WATER SURFACE 
                 {overscore (Pm)} = [({overscore (A1)} + {overscore (A2)})*{overscore (A0)}]*[({overscore (A3)}*A4) + {overscore (A4)}] 
               
               
                   
                 WALL SURFACE 
                 Pm = [({overscore (A1)} + {overscore (A2)})*{overscore (A0)}]*[(A3*A4) + A4] 
               
               
                   
                   
               
            
           
         
       
     
     When the mode control pressure drops from high Pm to low {overscore (Pm)}, the mode actuator spring  1069  forces the actuator piston to the right requiring the displacement of water from port  1068  back through tube  1072 . To permit this reverse flow through tube  1072 , drainage paths are defined by the override disk  1024  and the mode disk  1132  as shown in FIGS. 25 and 26. More particularly, FIG. 25 shows a drainage path  1133  through port  1090 , override disk opening  1024 , one of the multiple radial trenches  1134  in mode disk  1020 , override disk opening  1135 , annular recess  1136  and out through housing drainage port  1137 . 
     In FIG. 26, the drainage path  1138  is via radial trench  1139  and then through annular recess  1136  and housing drainage port  1137 . 
     Reference is now directed to FIG. 28 which depicts a timing chart describing the operation of the controller assembly  1010  for an exemplary situation. 
     It will be assumed that the state disk  1018  completes a full cycle in about three minutes and the mode disk  1020  completes a full cycle in about twelve minutes. It will also be assumed that the water surface mode and wall surface mode have substantially equal durations; i.e., that the mode disk arcuate portions  1130  and  1132  subtend equal angles. It should be understood that these assumed quantities can be readily modified by a change in gearing and/or disk geometry. It should also be understood that although sharp edge transitions have been shown for the sake of simplicity in FIG. 28, in actuality all transitions would have a discernable slope. 
     Line (a) of FIG. 28 represents aforementioned aperture A 0  which is opened once per state disk cycle at  1140  as a consequence of opening  1112  aligning with relief port  1086 . 
     Line (b) represents aforementioned aperture A1 which opens periodically as state disk openings  1104  align with the entrance to main relief port  1084 . Note that line (b) represents long openings  1104  at  1142  and short openings at  1144 . 
     Line (c) represents the functioning of aperture A 2  for an assumed action of the motion sensor paddle  1022 . When the cleaner body forward motion exceeds a threshold rate, paddle  1022  closes aperture A 2  (as at  1146 ) and when the body encounters an obstruction to drop the rate of forward motion below the threshold, aperture A 2  opens (as at  1148 ). 
     Line (d) represents aperture A 3  which is closed at  1150  when the mode disk large arcuate portion  1132  blocks port entrance  1115 . When the mode disk rotates to bring the small arcuate portion  1130  proximate to the port entrance, aperture A 3  opens at  1152 . 
     Line (e) represents the functioning of aperture A 4  for an assumed action of the override disk  1024 . The values {overscore (A4)} A 4 , and A 4  are represented at  1158 ,  1160 , and  1162 , respectively. 
     Line (f) represents the pressure applied to state control port  1066  attributable to the conditions represented in lines (a) through (e). It will be recalled that pressure values {overscore (Ps)} and Ps respectively produce the backup and forward states. Line (f) shows the pressure at Ps  1164  because the aforementioned equation Ps=({overscore (A1)}+{overscore (A2)})*{overscore (A0)} is satisfied. The pressure drops to Ps at  1166  to initiate the backup state because aperture A 1  and A 2  are both open (lines (b) and (c)) at  1144  and  1148  thus satisfying the equation {overscore (Ps)}=(A 1 *A 2 )+A 0 . 
     Line (g) represents the pressure applied to mode control port  1068  attributable to the conditions represented in lines (a) through (e). Note that the pressure value is {overscore (Pm)} (water surface mode) at  1170  because the aperture A 3  is closed (i.e. value {overscore (A3)}) at  1150  in line (d). The pressure value is show as changing to Pm (wall surface mode), at  1172  attributable to the override disk (line (e)) being switched to value A 4  at  1160 . With the override disk disabled (i.e., A 4 ) at  1162 , the value of aperture A 3  at  1152 , causes the mode port pressure to have a value of Pm (wall surface mode) at  1174 . The mode port pressure is shown as switching to {overscore (Pm)} at  1176  when the override disk (line (e)) is switched to A 4 . 
     Attention is now directed to FIG. 29 which depicts a functional block diagram similar to FIG. 18C but modified to incorporate various enhancements including in-line filter  1200  and pressure indicator  1206 , which are identified to the corresponding elements discussed in conjunction with FIG.  22 A. Most significantly, however, FIG. 29 incorporates a pitch control subsystem  1210  which is used to selectively orient the body  6  either (1) nose (i.e., front) up/tail (i.e., rear) down, as represented in FIG. 31, or (2) nose down/tail up as represented in FIG.  30 . 
     The pitch control subsystem  1210  includes a tube  1212  defining an elongate interior volume  1214 . The tube defines end fittings  1216  and  1218  respectively coupling opposite ends of the elongate volume  1214  to the outlet ports  1220  and  1222  of level valve  1224 . 
     The tube  1212  contains a weighted member  1226  bearing ring seals  1228 . The member  1226  is configured to slide in the elongate volume  1214  from one end to the other with the ring seals  1220  engaging and sealing against the tube interior wall surface. The tube  1212  is mounted on the body  6  extending in the longitudinal direction from front to rear as depicted in FIGS. 30,  31 . 
     Fitting  1216  is coupled to level valve outlet port  1220  which supplies a positive pressure when the water surface cleaning mode is defined by level valve  1224 . As a result, weighted member  1226  is forced along tube  1212  toward the rear of body  6  to orient body  6  as shown in FIG. 31 in the nose up pitch orientation. 
     Fitting  1218  is coupled to level valve outlet port  1222  which supplies a positive pressure when the wall surface cleaning mode is defined to force weighted member  1226  toward the front of body  6  to orient body  6  as shown in FIG. 30 in the nose down pitch orientation. 
     FIG. 29 depicts a single nozzle  1230  used to provide propulsion thrust when direction valve  1232  defines the forward state. The thrust provided by nozzle  1230  will drive the body  6  either to the water surface or wall surface depending on the body&#39;s pitch and will then propel it along the selected surface. 
     FIG. 32 depicts a functional block diagram identical to FIG. 29 except that it uses buoyancy shift pitch control rather than the weight shift pitch control used in FIG.  29 . More particularly, FIG. 32 shows a buoyancy shift pitch control subsystem  1240  comprised of chambers  1242  and  1244  respectively containing flaccid bags  1246  and  1248 . An air tube  1250  couples the bags  1246  and  1248  which together contain sufficient air to fully distend one of the bags. 
     The chambers  1242  and  1244  are respectively coupled to the water surface cleaning port  1254  and the wall surface cleaning port  1256 . When port  1254  supplies a positive pressure to chamber  1242 , it acts to squeeze the air out of bag  1246  and transfer it to bag  1248  housed in chamber  1244  located at the front of body  6 . This increases the buoyancy of the body front end and consequently orients the body nose up. On the one hand, when port  1256  supplies a positive pressure, this squeezes air out of bag  1248  and transfers it via tube  1250  to bag  1246 . This increases the relative buoyancy of the body rear end to place it in a nose down pitch. 
     Attention is now directed to FIG. 33 which depicts an enhanced debris bag  1280  formed of a flexible water permeable, preferably mesh, material. The bag defines an entrance opening  1282  for passing water borne debris into the bag when operating in the forward state at either the wall surface or water surface. In order to block debris from exiting the bag when in the redirection or backup state, one or more flexible baffle sheets is mounted in the bag proximate to the bag opening  1282 . 
     More particularly, FIGS. 33 and 33A show first and second baffle sheets  1284  and  1286 , each depicted as being substantially rectangular. Sheet  1284  defines upstream edge  1290  and downstream edge  1292 . Sheet  1268  defines upstream edge  1294  and downstream edge  1296 . Upstream edges  1290  and  1294  are secured along their lengths to bag  1280  adjacent to opening  1282 . The corners of downstream edges  1292  and  1296  are secured to the bag sides as  1298  and  1300 . 
     In the forward state, water and debris flows into the bag from opening  1282 , between sheets  1284  and  1286  and acts to separate the downstream edges  1292  and  1296  as shown in FIG. 34B, allowing debris to move therepast. When the redirection state is defined to move the body laterally and/or rearwardly through the water, water may tend to move through the bag toward the opening  1282 . This action causes the edges  1292  and  1294  to close, i.e, move adjacent to one another to effectively block debris from exiting from the bag opening  1282 . 
     From the foregoing, it should be appreciated that a method and apparatus has been disclosed herein responsive to a positive pressure water source for cleaning the interior surface of a pool containment wall and the upper surface of a water pool contained therein. Apparatus in accordance with the invention includes an essentially unitary cleaner body and a level control subsystem for selectively moving the body to a position either proximate to the surface of the water pool for water surface cleaning or proximate to the interior surface of the containment wall for wall surface cleaning. 
     The invention can be embodied in a cleaner body having a weight/buoyancy characteristic to cause it to normally rest either (1) proximate to the pool bottom adjacent to the wall surface (i.e., heavier-than-water) or (2) proximate to the water surface (i.e., lighter-than-water). With the heavier-than-water body, the level control subsystem in an active state produces a vertical force component for lifting the body to proximate to the water surface for operation in a water surface cleaning mode. With the lighter-than-water body, the level control subsystem in an active state produces a vertical force component for causing the body to descend to the wall surface for operation in the wall surface cleaning mode. The level control subsystem can produce the desired vertical force component by any of several different mechanisms used alone or in combination; e.g., by discharging an appropriately directed water outflow from the body, by modifying the body&#39;s weight/buoyancy characteristic, or by orienting a hydrodynamic surface. 
     Although the present invention has been described in detail with reference only to a few specific embodiments, those of ordinary skill in the art will readily appreciate that various modifications can be made without departing from the spirit and scope of the invention.