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This application is the U.S. national phase of International Application No. PCT/US2005/030675 filed on Aug. 29, 2005 and published in English on Mar. 9, 2006 as International Publication No. WO 2006/026553, which application claims the benefit of South African Provisional application No. 2004/6888 entitled “Automatic Pool Cleaner” filed on Aug. 30, 2004 and claims the benefit of U.S. Provisional Application No. 60/615,523 entitled “Automatic Swimming Pool Cleaners and Associated Hoses” filed on Oct. 1, 2004 and claims the benefit of U.S. Provisional Patent Application No. 60/645,883 entitled “Automatic Swimming Pool Cleaners and Associated Hoses” filed on Jan. 21, 2005, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This INVENTION relates to automatic pool cleaners, more specifically to automatic pool cleaners of the suction kind, also referred to as the “pull” kind. It relates to a method of operating such a pool cleaner; to a hose and to a hose section for such a pool cleaner; and to an automatic pool cleaner of the suction kind. 
     BACKGROUND OF THE INVENTION 
     Although the Applicant does not wish to be bound by theory, it is believed that a brief, simplified explanation of the mechanism causing a pool cleaner head to move along a surface will assist a reader&#39;s understanding of the invention. 
     A suction kind, automatic pool cleaner includes a pool cleaner head having a suction pad interfacing with a substrate or surface to be cleaned, and a resilient hose interconnecting an inlet through the pad with a suction inlet of a pump for pumping pool water via a suction area at the interface of the pad and the surface to be cleaned, and via the hose to the pump. In the pool cleaner head, downstream of the suction pad inlet and upstream of the hose, there is provided a flow interruption mechanism for cyclically interrupting the flow, fully or partially. Water flowing along the hose has momentum due to mass and flow speed. Thus, when the flow is interrupted, an area of negative pressure is created in the hose and, because of the cyclic nature of the flow interruption, the negative pressure occurrences are presented as negative pressure pulses. At the occurrence of each negative pressure pulse, over pressure externally of the hose causes contraction and thus a shortening of the hose and thus a corresponding, jerking, displacement of the pool cleaner head. Simultaneously with the interruption of flow, suction between the suction pad and the surface being cleaned is temporarily interrupted, thus facilitating displacement. When flow is resumed, the negative pressure pulse is cancelled, pressures are equalized and the hose extends again, while auction between the pad and the surface is reinstated thus preventing or hindering the head from being displaced. 
     SUMMARY OF THE INVENTION 
     In, accordance with a first aspect of this invention, there is provided a method of operating an automatic pool cleaner of the suction kind including causing a hose of the pool cleaner cyclically to contract and to expand by cyclically, intermittently, interrupting flow of water through a pool cleaner head, the method including intensifying said contraction and expansion in an upstream, compliant portion of the hose adjacent the pool cleaner head and attenuating said contraction and expansion in a remaining, downstream, less compliant, portion (e.g. an element  24  of  FIG. 1 ) of the hose downstream of said upstream compliant portion. 
     The Applicant believes that said intensifying contraction/expansion in said compliant portion of the hose (which can also be described as concentrating shortening/lengthening of the hose during negative pressure pulses proximate the head) enhances movement of the head. It is believed that such shortening of the hose, which causes jerking displacement of the head as explained above, when it takes place proximate the head, is more effective than a comparable shortening taking place more evenly over the length of the hose. The Applicant has observed both ends of the compliant portion being drawn together during negative pressure pulses and that a significant enhancement in movement of the head takes place, compared to a comparable installation but with a conventional hose. Movement enhancement is expected to be between about 10% and about 30%. In an initial test, axial movement of an upstream end of the compliant portion, acting against a constant load or mass showed an improvement of slightly more than 20% compared to a conventional hose. 
     Frequently, the hose is a composite hose provided by several, individually replaceable, sections. The method may thus include selecting a section incorporating said upstream, compliant portion from a plurality of sections having similar but non-identical compliant portions. The compliant portions may differ in respect of compliance or resilience. The section may be empirical by trying different compliant sections to find an appropriate one. The selection may be on the basis of selecting a compliant portion having a compliance to render a ratio of the compliances of said upstream compliant portion and said downstream less compliant portion an optimum. 
     In accordance with a second aspect of this invention, there is provided a method of operating an automatic pool cleaner of the suction kind, including reducing a frequency of flow interruptions in a head thereof, by rendering a portion of a hose thereof, proximate the head, more compliant than a remaining portion of the hose downstream of said portion proximate the hose. 
     The frequency may be reduced by between about 2% and about 15%. In an initial test, a reduction of about 5% was achieved compared to hoses not having such a more compliant portion. 
     In accordance with a third aspect of this invention, there is provided a method of operating an automatic pool cleaner of the suction kind, including reducing an intensity or amplitude of negative pressure pulses by rendering a hose of the pool cleaner more responsive in longitudinal contraction to negative pressure pulses by rendering a portion of a hose of the pool cleaner, proximate a head of the pool cleaner, longitudinally more compliant than a remaining portion of the hose. 
     The Applicant expects that this will increase an average flow rate of water through the head, by between about 2% and about 15%. In an initial test, an increase in average flow of about 5% was observed. 
     The method in accordance with any one of aspects one to three may include protecting said compliant portion of the hose against scuffing or abrasion in use, by means of radially outwardly projecting flanges proud of a general outer periphery. The flanges may be in the form of windings of a continuous helix or spiral along the length of said compliant portion. 
     In accordance with a fourth aspect there is provided a hose for an automatic pool cleaner of the suction kind, which hose has an upstream connector at an upstream end for connection to a pool cleaner head, and a downstream connector at a downstream end for connection to piping leading to a pump, the hose having, proximate the upstream connector, a compliant portion which is more compliant or less resilient than a remaining portion of the hose proximate the downstream connector. 
     When the hose is a composite hose comprising a plurality of hose sections, the compliant portion may be incorporated in a compliant hose section proximate the upstream connector. Conveniently, said compliant hose section may comprise said compliant portion and connectors fast with the compliant portion. 
     In accordance with a fifth aspect, there is provided a compliant hose section for a hose of an automatic pool cleaner of the suction kind, which compliant hose section includes a compliant portion providing at least a portion of the compliant hose, section, the compliant portion being compliant in longitudinal direction and in bending, the compliant portion comprising a generally longitudinally extending resilient element and a hose wall. 
     The compliant hose section may include the compliant portion and opposed connectors fast with the compliant portion for connecting the compliant section to other components of a pool cleaner. Advantageously, the wall of the hose section may incorporate said resilient element in the form of a spiral, the wall further including a sleeve of flexible material extending along the spiral. 
     The resilient element may be of metal. Instead, the resilient element may be of a synthetic polymeric material. 
     In one embodiment, the sleeve may be in the form of a moulding of synthetic polymeric material which is highly compliant, the sleeve including a helical formation providing an outward convex ridge formation and an opposing inward concave groove formation, the resilient element being seated under radial compression, internally, within the groove formation. 
     Advantageously, the sleeve may include a protecting outer formation for protecting it against scuffing or abrasion, the outer protecting formation standing proud of a general outer periphery of the compliant hose section. The outer formation may be in the form of outwardly projecting spiral or helical ribbing, Advantageously it may be integral with and an outward extension of said outward, convex ridge formation. 
     The compliant portion may have a length, when in relaxed condition, of between 0.1 and 0.5 meter (approx. 3.9-19.7″), preferably between 0.15 and 0.3 meter (approx. 5.9-11.8″), most preferably between 0.2 and 0.25 meter (approx. 7.9-9.8″). 
     In accordance with a sixth aspect, there is provided an automatic pool cleaner of the suction kind which includes a pool cleaner head, and a generally resilient hose in accordance with the second aspect, for connecting the pool cleaner head to a suction end of a pump. 
     When the hose is a composite hose comprising a plurality of hose sections, one of them may be a hose section in accordance with the fifth aspect. 
     Further in accordance with the sixth aspect, there is provided an automatic pool cleaner of the suction kind comprising 
     an automatic pool cleaner head; 
     a first hose section; and 
     a second hose section having a first end detachably connected to the automatic pool cleaner head and a second end detachably connected to the first hose section, the second hose section being (i) more compliant than the first hose section and (ii) more contractable than the first hose section when in use. 
     The second hose section (i) may have an inner diameter and may comprise a longitudinally extending resilient element having a diameter greater than the Inner diameter. The second hose section is a compliant hose section in accordance with this invention. 
     Additionally disclosed is a positive locking mechanism for two hose sections. Included as part of the mechanism are two protrusions spaced circumferentially about the exterior of a first hose section at or adjacent an end of the section. Also included are two curved channels spaced circumferentially about the exterior of a second hose section, commencing at an end of the section. Incorporated into each channel is a restriction narrowing its width. 
     In use, each protrusion of a first hose section is inserted into a corresponding channel of a second hose section. Rotating either hose section causes the protrusions to travel within the channels until they contact the restrictions. Thereafter, manual force may be applied to push the protrusions beyond the restrictions, temporarily separating slightly the boundaries of the channels to permit continued travel of the protrusions. As the protrusions push past the restrictions, the boundaries return to their original positions, trapping the protrusions within the channels and providing a positive latching of two hose sections. 
     Disconnecting the hose sections may proceed simply by rotating either hose section in the opposite direction. Again, manual force may be applied to push the protrusions back through the restrictions, allowing them to travel back through the remainder of the channels to the end of the second section. Once the protrusions reach the ends of the channels, the first and second hose sections will separate. 
     Detailed as well is an alternate locking mechanism for sections of hose. Unlike the previously-discussed mechanism, this alternate one requires no twisting of either section to effectuate locking. Instead, one section may simply be pushed onto the other, with clips extending from one section engaging recesses in the other section. (Thumb) tabs forming parts of the clips may be used to release them from the recesses if the hose sections must be separated. 
     Also optionally included in versions of this mechanism may be pliable material underlying the tabs and to which the tabs are directly or indirectly connected. Depressing the tabs deforms the pliable material, permitting the clips to disengage the recesses. When the tabs are not depressed, the pliable material typically will return to its normal (undeformed) state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is now described by way of examples with reference to the accompanying diagrammatic drawings. In the drawings 
         FIG. 1  shows, in section, a pool and a pod cleaner installation in accordance with the invention operating in the pool; 
         FIG. 2  shows, to a larger scale, fragmentarily, a first embodiment of a hose section forming part of the pool cleaner installation of  FIG. 1 ; 
         FIG. 3  shows, to yet a larger scale, fragmentarily, in section, the hose section of  FIG. 2 ; 
         FIGS. 4 to 6  show, in respect of a second embodiment, respectively a three dimensional side view, an axial section, and a three dimensional view in section; 
         FIGS. 7-10  illustrate an exemplary locking mechanism for two hose sections, with the figures collectively displaying a sequence of positions of protrusions of the mechanism within corresponding channels; 
         FIGS. 11-13  detail an alternate exemplary locking mechanism for two hose sections, with  FIG. 11  providing a cross-sectional view of portions of coupled hose sections. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the drawings, more specifically to  FIG. 1 , a pool is indicated generally by reference numeral  10 . It comprises a wall  12  bounding sides and a floor of the pool and containing a body  14  of water. A pool cleaner  16  is operative in the pool  10  to clean the wall  12 . 
     The pool cleaner  16  is of the suction kind, comprising a pool cleaner head  18  having a suction pad  19  interfacing with the wall  12 . A hose assembly  20  communicates an area immediately below the suction pad  19  with a pump, which is not shown, for pumping water via said interface between the suction pad  19  and the wall  12  via the pool cleaner head  18  and the hose assembly  20  to a filter arrangement. 
     In accordance with the invention, and with reference more specifically also to  FIGS. 2 and 3 , the hose assembly  20  comprises a hose section  22 , proximate the pool cleaner head  18 , which has special characteristics in accordance with this invention. 
     The hose section  22  comprises a body or wall  26  and connectors  28  and  30  at opposite ends of the body  26 , The body  26  is formed of a spiral element  32  and a sleeve of flexible synthetic polymeric material  34  extending along the spiral element  32 . 
     The sleeve forms a conduit for conducting water. It is highly compliant, both longitudinally and in bending. The spiral element too is of low resilience longitudinally and in bending, yet is resistant to collapsing radially under external pressure to render the hose section resistant to radial collapsing during internal negative pressure pulses. 
     In one embodiment, the spiral element  32  is sandwiched between two layers forming the sleeve  34 . The spiral element  32  is secured directly to the connectors  28 ,  30 , and in other embodiments may be secured via the sleeve  34  to the connectors  28 ,  30 . The spiral element  32  need not necessarily be sandwiched between two layers, however. Instead, other embodiments of the sleeve of the hose section  22  may employ only a single layer of polymeric material  34  or, regardless of the number of layers of material  34 , may position the spiral element  32  so that it is not sandwiched between layers. 
     The spiral element  32  is of predetermined resilience, selected in respect of resilience characteristics of the material, the cross section (for example diameter) of the element, the diameter of the body or wall  26 , the pitch of the loops of the spiral element  32  and the like. The spiral element  32  may be of metal or metal alloy which is resistant, or which has been treated to be resistant, to corrosion in pool water, especially bearing in mind the sometimes hostile characteristics of pool water. In other embodiments, the spiral element  32  may be of synthetic polymeric material. It is preferred that the spiral element  32  is of a relatively lightweight metal or metal alloy. 
     The resilience of the spiral element  32  imparts resilience in longitudinal direction to the hose section  22  such that the hose section  22 , when in operation as part of the pool cleaner  16 , contracts during negative pressure pulses to a contracted length of between about one fifth and about one half, advantageously between about one quarter and about two fifths, preferably to about one third of its length when relaxed. It is to be appreciated that operating characteristics for pool cleaners differ, and that operating characteristics for identical pool cleaners in differing pool cleaning installations also differ. Thus, it is envisaged that routine empiric experimentation will be conducted to produce, for a specific pool cleaner, a range of such hose sections covering a variety of operating conditions brought about by a corresponding variety of possible pool cleaner installations. When commissioning a pool cleaner installation, empiric selection of an appropriate hose section to suite the specific installation will be conducted. Selection may be from a plurality of similar hose sections which are non-identical, incorporating progressive changes in resilience. 
     It is a further object of the invention to provide the hose section  22  such that it has a very small resistance against bending, thus facilitating bending of the hose assembly in the region of the hose section  22  thus to facilitate deviations from a straight line of the pool cleaner head, for example when it has to negotiate bends, corners, and the like. This is achieved in embodiments as disclosed by having the sleeve of a highly compliant material and construction and by rendering the compliant portion or section resistant to radial collapse during negative pressure pulses internally of the portion or section by means of the resilience spiral element, yet by not unduly increasing the resilience in longitudinal direction or in bending due to the presence of the resilient spiral element. By nature of its construction, the resilient spiral element has low resilience (i.e. high compliance) longitudinally and in bending, yet is highly resistant against radial collapse or crushing. 
     Yet a further advantage which the Applicant believes is achieved in accordance with this invention, is that the low resistance to bending of the hose section  22  proximate the pool cleaner head  18  will lessen the tendency of the pool cleaner head  18  to follow the specific arrangement at any time of the hose assembly  20 , and thus to render the pool cleaner head  18  more responsive to external factors other than that caused by the hose assembly  20  to deviate from a straight line. 
     As disclosed above, by intensifying or concentrating contraction/expansion of the hose by means of the compliant portion proximate the head, the movement of the head is significantly enhanced or increased. 
     With reference to  FIGS. 4 ,  5  and  6  a further embodiment of a hose section in accordance with the invention is generally indicated by reference numeral  122 . The hose section  122  is very compliant such that, in comparison to a conventional hose, it has a higher compliance. 
     The hose section  122  is in many respects similar to the hose section  22  of  FIGS. 1 to 3 , and it generally has the same advantages. Thus, it is not again described in detail, but reference will be made merely to differences. Also, like reference numerals are used to, indicate like components or features. 
     The hose section  122  includes a hose body  126  and connectors  128 ,  130  at ends thereof to allow connection of the hose section  122  into a hose for a pool cleaner of the suction kind. The hose section  122  includes a sleeve  134  and a resilient element  132 . 
     The sleeve  134  is in the form of a moulding od synthetic polymeric material having high compliance. It is in the form of a spiral or helix having, intermittently, a radially outer, convex ridge formation  136  and an outer concave valley formation extending between adjacent loops of the ridge formation and indicated by reference numeral  138  . Internally, the convex ridge formation is presented as inner, concave seat formation within which the spiral resilient element  132  is seated. 
     The sleeve  134  and the resilient element  132  are manufactured separately. During assembly, a trailing end of the resilient element  132  is held fast while a leading end is rotationally strained in the direction of the helix and is screwingly pulled through the passage along the sleeve  134 . Such straining of the resilient element decreases its diameter, thus allowing it easily to be led into position within the sleeve  134 . When it is released, the natural resilience of the resilient element distends it to abut the sleeve  134  internally, and by appropriate manipulation, the windings or loops of the spiral element  132  are seated within the inner, concave seat formation  136 . It is to be appreciated that a relaxed diameter of the resilient element  132  is at least slightly more than a nominal diameter of the seat formation  136  such that the resilient element  132  is under compression when in position within the sleeve  134 . 
     It is to be appreciated that the diameter of the resilient element  132  is larger than the inner periphery of the sleeve  134  as presented by the outwardly concave, inwardly convex valley formation  138  spanning between adjacent ridge windings. 
     By way of development, integrally moulded with the ridge formations  136 , an outer spiral rib formation  140  is integral therewith to protect the sleeve  134  against abrasion, scuffing and the like. 
     In addition to the advantages mentioned above, the Applicant has found that the frequency of flow interruptions in the pool cleaner head is reduced, while the flow of water through the head increases, indicating an increased efficiency. Furthermore, the intensity or level of the negative pressure pulses is reduced which, together with the reduced frequency of interruptions, is conducive to longevity and durability. 
     Illustrated in  FIGS. 7-10  are portions of respective first and second hose sections  204  and  208 . Sections  204  and  208  may form part of hose assembly  20  of the invention and preferably (although not necessarily) connect ultimately to a suction-kind pool cleaner  16 . Additionally, sections  204  and  208  may be formed similar to either of hose sections  22  or  122  if desired. However, sections  204  and  208  need not be so formed, and indeed may be conventional in many respects. 
     Detailed especially in  FIG. 7  are ends  212  and  216  of respective sections  204  and  208 . End  212 , nominally designated a “male” connector or cuff, is designed to be fitted into the nominally “female” cuff of end  216 . Typically, each section  204  and  208  will have both a male cuff and a female cuff, with the male cuff located at one end of the section and the female cuff located at the other end of the section. Sections  204  and  208  need not necessarily be configured in this manner, however. 
     End  212  preferably has a portion that is cylindrical in shape, with one or more protrusions  220  extending from its exterior surface  222 . In at least one embodiment of section  204 , two protrusions  220  are spaced one hundred eighty degrees along the circumference of end  212 . Protrusions  220  advantageously may have circular cross-section, although other shapes may be employed instead. 
     End  216  likewise has a portion that is cylindrical in shape, with diameter slightly larger than that of the cylindrical portion of end  212 . End  216  thus may receive end  212  as part of the connection process. End  216  also includes one or more channels  224 , with the number of channels  224  beneficially equaling the number of protrusions  220  so as to provide a one-to-one correspondence therebetween. Such correspondence need not necessarily exist, however, although typically the number of protrusions  220  would not exceed the number of channels  224 . 
     As shown in  FIGS. 7-10 , each channel  224  commences at edge  228  of end  216  and preferably is curved: Channels  224  have maximum width slightly greater than the diameter of the cross-section of protrusions  220  so as to allow protrusions to travel within them. Channels  224  also each include one or more restrictions  232 , which decrease the width to a value slightly less than the diameter of the cross-section of protrusions  220 . 
     By curving channels  224 , fitting of end  212  into end  216  and rotation of protrusions  220  within the channels  224  may occur simultaneously. In essence, once protrusions  220  are aligned with entrances to channels  224  (see  FIG. 8 ), fitting end  212  into end  216  will cause the protrusions  220  to enter the channels  224 . Boundaries of channels  224  will guide travel of protrusions  220  (see  FIG. 9 ), resulting in one of sections  204  and  208  rotating relative to the other until protrusions  220  contact restrictions  232 . 
     Because restrictions  232  decrease the width of channels  224  to less than the diameter of protrusions  220 , the protrusions  220  cannot naturally travel beyond the restrictions  232  within the channels  224 . However, section  208  may be formed of plastics or other material with some resiliency, so that manual or other force may be employed to compel slight separation of restrictions  232  to allow protrusions  220  to pass thereby. When the force no longer is applied, restrictions  232  will rebound to their normal positions, trapping protrusions  220  within channels  224  (see  FIG. 10 ). 
     Protrusions  220  and channels  224  thus provide a positive locking system for, principally, hoses used in connection with suction-kind automatic swimming pool cleaners. The locking system requires no additional parts, as existing male and female cuffs themselves positively connect together. When no suction pressure is applied to the hose, sections  204  and  208  nevertheless may remain interlocked, reducing the likelihood of their separating when handled by consumers. Moreover, if the swimming pool cleaner head, for example, is configured with either protrusions  220  or channels  224 , a terminal hose section of the invention may connect, and positively lock, to the head too. 
     Depicted in  FIGS. 11-13  are portions of respective first and second hose sections  304  and  308 . Sections  304  and  308 , like sections  204  and  208 , may form part of hose assembly  20  of the invention. They too preferably, but not necessarily, connect ultimately to a suction-kind pool cleaner  16 . Likewise, sections  204  and  208  may be formed similar to either of hose sections  22  or  122 , although such forming is not necessary. 
       FIG. 11  illustrates coupling of sections  304  and  308 . Shown in  FIG. 11  is end  312  of section  304 , which in use may abut (or be fitted into or have fitted into it) end  316  of section  308 . Many sections  304  and  308  will include both an end configured like end  312  and, opposite that end, an end configured like end  316 . Any section  304  or  308  need not necessarily be created in this manner, however. 
     Each of ends  312  and  316  preferably has a cylindrical portion. Extending beyond this portion of end  316  may be one or more clips  320 . Clips  320  typically are elongated, with each comprising a (thumb) tab  324  at one end and a protrusion  328  at the other. 
     Incorporated into end  312  are one or more recesses  332 . Recesses  332  are adapted in use to receive protrusions  328 , locking an end  312  to an end  316 . In some embodiments of sections  304  and  308 , clips  320  may be made generally immobile, so that protrusions  328  remain in recesses  332  by a friction fit. 
     Preferably, however, portions of clips  320  containing protrusions  328  are movable toward and away from exterior surface  336  of section  304 . Moving these portions away from exterior surface  336  disengages protrusions  328  from recesses  332 . By contrast, moving protrusions  328  toward exterior surface  336  permits the protrusions  328  to engage recesses  332 . 
     Movement of a clip  320  may be effected using its tab  324 . Underlying tab  324  beneficially may be pliable material  340  able to compress, or at least deform, when subjected to external forces. Thus, depressing tab  324  causes it to travel into the area initially filled by material  340 , forcing the remainder of clip  320  (including the portion containing protrusion  328 ) to move away from exterior surface  336 . Because material  340  tends to return to its initial position when not subjected to these forces, releasing tab  324  causes clip  320  to travel to the position shown in  FIGS. 11-13 , in which protrusions have seated in recesses  328 . 
     Shown in  FIG. 11  are two clips  320  and two corresponding recesses  328 , each clip  320  spaced one hundred eighty degrees from the other about the circumference of its corresponding section  308 , and each recess  328  spaced similarly about the circumference of its associated section  304 . More or fewer clips  320  and recesses  328  may be provided if necessary or desired, and the number of clips  320  and recesses  328  on coupled sections need not always correspond. Nevertheless, preferably at least two clips  320  and recesses  328  are included on any section  304  or  308  containing such clips and recesses, with each clip  320  engaging a single recess  328 . 
     The foregoing is provided for purposes of illustrating, explaining, and describing exemplary embodiments and certain benefits of the present invention. Modifications and adaptations to the illustrated and described embodiments will be apparent to those skilled in the relevant art and may be made without departing from the scope or spirit of the invention.

Summary:
Automatic pool cleaners and associated hoses are detailed. Hoses may contract and expand in use and include sections of differing compliancies. Such contractions and expansions may be intensified in more compliant portions and attenuated in less compliant portions. Also discussed are positive locking mechanisms for adjacent hose sections.