Abstract:
A pump suitable for use in a portable domestic is also disclosed. The steam cleaner has a housing accommodating a releasable water tank. The pump transfers water from the tank to a boiler for generating steam. In use, steam exits a nozzle for cleaning etc.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 0620857.3 filed in Great Britain on 20 Oct. 2006. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a pump and in particular to a pump suitably for use in a portable steam cleaner, especially for domestic use and to a pump suitable for use therewith. 
         [0004]    2. Description of Prior Art 
         [0005]    Steam cleaning appliances are well known, including small portable appliances used for general cleaning, de-greasing and sterilizing. They generally have a steam generator in the form of a heater or boiler supplied with water from an enclosed water tank by a small solenoid pump. While this is satisfactory for a basic appliance, there are inherent disadvantages resulting from this design. The solenoid pump either operates at one speed or requires complex electronic circuitry to change the frequency of the incoming power supply to operate at a different speed as the speed of a solenoid pump is linked to the frequency of the driving power. With only a single speed, the supply of water to the boiler and thus the steam generator is not controllable. The steamer first heats up the boiler and then water is added at a constant rate into the boiler which lowers the temperature of the boiler, reducing the temperature of the steam produced. During delivery along the outlet tube from the boiler, the steam has a tendency to cool down and condenses, the cooler the boiler the faster the steam condenses. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the invention to overcome or at least reduce these problems. 
         [0007]    Accordingly, in one aspect thereof, the present invention provides a peristaltic pump for moving a liquid, comprising: a motor having a motor shaft; a pump housing, including a pump body, forming a pump chamber, the pump housing being fixed to the motor; the pump chamber accommodating a number of rollers having an integral gear in mesh with a cog fixed to the motor shaft for rotation therewith; a first gear carrier having a number of axles on which the rollers are rotatably mounted respectively for maintaining a fixed spatial relationship between the rollers; and a resiliently collapsible tube, passing through the pump chamber and arranged to be compressed against a wall of the pump chamber by at least one roller at all times as the rollers rotate within the pump chamber. 
         [0008]    Preferably, the first gear carrier is rotatably mounted to the motor shaft. 
         [0009]    Preferably, the first gear carrier is rotatably mounted to the motor shaft by way of a bearing. 
         [0010]    Preferably, the first gear carrier is mounted to the distal end of the motor shaft. 
         [0011]    Preferably, a second gear carrier is fitted to the distal end of the axles. 
         [0012]    Preferably, the second gear carrier is journalled on the motor shaft. 
         [0013]    Preferably, the rollers have a cylindrical portion and a gear portion wherein the cylindrical portion has a smaller diameter than the gear portion. 
         [0014]    Preferably, the pump housing is formed by a first part which connects directly to a housing of the motor and a second part. 
         [0015]    Preferably, the second part of the pump housing is formed by two parts, an pump body having a cavity forming a peripheral wall of the pump chamber and an upper part with the upper part and the first part forming upper and lower caps for the pump body and closing axial ends of the pump chamber for the pump chamber. 
         [0016]    Preferably, the upper and lower caps are connected to the pump body by snap fit connectors. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0018]      FIG. 1  is a schematic sectional side view of a preferred portable steam cleaner; 
           [0019]      FIG. 2  illustrates a variable speed motor driven pump, being a preferred pump for the steamer of  FIG. 1 ; 
           [0020]      FIG. 3  is an exploded view of the pump of  FIG. 2 ; 
           [0021]      FIG. 4  is a partial sectional view of the pump of  FIG. 2 ; 
           [0022]      FIG. 5  is a perspective view of a pump body, being a part of the pump of  FIG. 2 ; 
           [0023]      FIG. 6  is a perspective view of a first gear carrier, being a part of the pump of  FIG. 2 ; 
           [0024]      FIG. 7  is a perspective view of an upper cap, being a part of the pump of  FIG. 2 : and 
           [0025]      FIG. 8  is a perspective view of an alternative pump for the steamer of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    The schematic illustration of  FIG. 1  shows a portable steam cleaner  10 , of the handheld pistol type. The cleaner  10  is a self-contained unit having a housing  11  accommodating a boiler  12 , a tank  13  for water, and a motor driven pump  14  for feeding water from the tank  13  to the boiler  12 . Boiler  12  has a heater arranged to heat water received in a chamber of the boiler to turn the water into steam. Steam is passed from the boiler  12  to a nozzle or outlet  15 , via a steam pathway  16 . The heater may have one or more heating elements and optionally, the elements are able to be selectively turned on to vary the heating capacity and heating time of the boiler. A selector switch may be operated by a user or the elements may be automatically switched by a temperature sensor means, such as a thermostat. Optionally, the speed of the motor is variable to match the heating of the boiler. 
         [0027]    A switch  17  for turning the cleaner on or off may be provided with several positions to select a desired heating or operational mode, such as OFF, LOW, MEDIUM, HIGH. Alternatively, not shown, separate switches could be employed for power and heater settings. 
         [0028]    The tank  13  is shown as being fully enclosed within the housing  11  but could be partially enclosed or even mounted externally of the housing. Water is transferred to the boiler  12  through passageways or tubes  18 . Optionally, a filter  19  to remove debris or particulate matter in the water may be fitted to the water delivery lines or passageways  18 . 
         [0029]    The pump  14  is a motor driven pump, which draws water from the tank  13  through the filter  19 , if fitted, to supply the boiler  12 . The motor of the pump is, preferably, a permanent magnet direct current (PMDC) motor, optionally a high voltage direct current motor running on rectified mains supply. Alternatively, the motor may be connected in series with a heating element to lower the motor operating voltage. 
         [0030]    Optionally, the motor speed is variable, to vary the flow rate of water to the boiler. This speed variation is relatively simple for a PMDC motor, as the speed is dependent on supply voltage. Thus a rudimentary control system may be to add additional resistance to the motor circuitry, such as by adding extra heating elements in series with the motor to further reduce the supply voltage, and thus to the motor speed. 
         [0031]    Alternately, the motor may be supplied with its own supply voltage through a separate controller. Thumb wheel switch  20  shown mounted along a handle portion  21  of the housing  11  for easy access by user, may control the output of the controller to the motor to vary the motor speed. This arrangement can be used for other types of motors, including a universal type motor or a brushless DC motor. Optionally and preferred, the motor may be supplied with a low voltage DC power derived from the main supply and supplied to the motor via a variable resistor operated by rotation of the thumb wheel switch  20  to vary the resistance of the motor circuit, thus varying the speed of the motor. Alternatively, a standard simple motor speed controller may be used. 
         [0032]    Mains power is applied to the cleaner via a power cord, here symbolically referred to by reference numeral  22 . 
         [0033]    The preferred pump is shown in  FIG. 2 . The pump  14  has a pump portion  24 , driven by a variable speed motor, such as a PMDC motor  25 . In the preferred embodiment, the pump portion  24  is a peristaltic pump. 
         [0034]      FIG. 3  shows the pump  14  exploded, while  FIG. 4  shows the pump  14  partially sectioned. Starting from the bottom of the pump  14  as shown in  FIG. 3 , the motor  25  is shown with a motor shaft  26  extending upwardly. The motor has a deep drawn metal housing  27  having an upper closed end  28  having a boss  29  formed therein for receiving a bearing (not shown) in which the motor shaft  26  is journalled (rotatably mounted). The lower end of the motor housing  27  is open and is closed by an end bracket  30  supporting a second bearing for the shaft  26 . 
         [0035]    A pump housing  32  is fixed to the upper closed end  28  of the motor housing  27 . A lower cap  33  of the pump housing  32  is held by two screws  34  which are screwed into threaded holes  35  in the upper end  28  of the motor housing  27 . The shaft  26  extends through a hole  36  in the lower cap  33 . 
         [0036]    A first gear carrier  37  is fitted to the shaft  26 , by way of a first gear bearing  38 . First gear carrier  37  is shown enlarged and from a lower angle in  FIG. 6 , which reveals a central cavity  39  forming a recess for receiving the first gear bearing  38 . The first gear carrier has three holes  40  equidistantly circumferentially spaced in which three axles  41  are fitted, as a press fit. A pinion  42  is pressed onto the shaft  26  and locates adjacent an upper surface of the first gear carrier  37 . Each axle  41  rotatably supports a respective roller  43 . Each roller  43  has a cylindrical roller portion  44  and a lower gear portion  45 , the gear portion  45  having a greater radial extent than the roller portion  44 . The gear portion  45  of each roller  43  is in mesh with the pinion  42 . Thus as the motor shaft  26  turns, the pinion  42  turns, driving each roller  43 . 
         [0037]    A second gear carrier  46  is fitted to the upper end of the axles  41  above the rollers  43  to support keep the upper ends of the axles  41  in fixed spaced relationship. The second gear carrier  46  also has a second gear bearing  47  for rotatably supporting the second gear carrier  46  on the shaft  26 . 
         [0038]    A further bearing  48  supports the distal end of the shaft  26  in a cavity  49  of an upper cap  50  of the pump housing  32 . Between the upper cap  50  and the lower cap  33  is a pump body  51 . The pump body  51  has an inner cavity  52 , which accommodates the rollers  43  and a tube  53  of resilient flexible material is located extending circumferentially along a significant portion of the inner surface of the cavity  52 , in this example, approximately 270°. The pump body  51  and the rollers  43  are arranged such that the tube  53  is compressed at points between the rollers  43  and the wall  54  of the cavity  52 . 
         [0039]    The tube  53  is formed with or is connected to connectors  55  forming the inlet and outlet. Which connector is the inlet depends on the direction of rotation of the rollers  43 . 
         [0040]    The pump body  51  is connected to the upper and lower caps  50 ,  33 , by snap lock connections indicated generally by reference numeral  56  for easy assembly and disassembly. Disassembly allows a tube to be replaced easily. The snap lock connections  56  preferably, as shown in this example, comprised flexible fingers  57  formed on the caps  33 ,  50  which extend over and lock onto stops  58  formed on the pump body  51 . The tube  53  extends along a generally curved or arcuate portion of the inner surface of the wall  54  of the pump body  51 . The tube  53  is held in place by passing through slots  59  in the wall  54 , allowing the tube  53  or preferably the connectors  55  at the ends of the tube  53  to extend out of the pump body  51  to connect with other tubes or hoses. 
         [0041]    Preferably, the connectors  55  have a flange  60  which locates in a groove  61  extending transversely of the slot  59  for capturing the connector  55  within the slot  59 . The open top of each slot  59  is closed by a slot projection  62  on the upper cap  50  which also has a corresponding recess  63  for receiving a part of the flange  61  of the connector  55 , as shown in  FIG. 7 . 
         [0042]    Preferably, the connectors  55  are separate items which are pressed into the ends of the tube  53  and the ends of the tube are clamped to the connectors  55  via the slots  59  and the slot projections  62  on the upper cap  50 . 
         [0043]    As shown more clearly in  FIG. 4 , the inner surface of the wall  54  of the pump body  51  is stepped allowing the gear portion  45  of the rollers  43  to extend outwardly under the step  64 . The stepped portion forms the wall which contacts the tube  53 . Blind apertures  65  may be formed in the wall  54  of the pump body, adjacent to the tube contact portion. A short arcuate portion  66  may be provided between the slots  59  in the wall  54  to support the rollers  43  where there is no tube, to reduce the radial stress on the motor shaft  26 . 
         [0044]    Lips  67  on the upper and lower caps align the caps  33 ,  50  with the pump body  51 , and thus the pump housing  32  with the motor  25 . As may be appreciated, the pump housing comprises the pump body and the upper and lower caps. Optionally, shaft  26  may have one or more steps to ease assembly, especially the fitting of the pinion  42 . 
         [0045]    In use, as the rollers are driven by the motor the rollers roll along the tube causing the tube to be compressed in an ever advancing sequence. The compression of the tube causes localised sealing of the tube or spot seals forming sealed compartments between successive compression points, and as the rollers roll along the tube, the sealed compartments, and their contents are progressively moved along the tube from inlet to outlet. 
         [0046]    The last compression point forms an open ended compartment until the next roller in sequence contacts and compressors the tube to form a new “last” compression point and seals the chamber in front, while forming a new open chamber at the inlet. At the outlet, as a roller breaks contact with the tube, the first compartment in the sequence opens up pushing its contents out through the outlet. 
         [0047]    The use of a variable speed motor driven pump for providing the flow of water from the tank to the boiler in a portable steam cleaner allows a user to vary the amount of steam being generated or used for a particular application at the user&#39;s choice. The peristaltic pump described provides a very useful motor driven pump for use in such an application. 
         [0048]      FIG. 8  illustrates an alternative pump  14  for use with the steamer. In this embodiment the pump  24  has a the pump portion  24  in the form of a gear pump, driven by a permanent magnet direct current (PMDC) motor  25 . As such the motor is a variable speed motor and the pump output depends on the speed of the motor. Alternatively, the motor could be a brushless DC motor or any other suitable variable speed motor. The brushless motor has an advantage of longer life due to the absence of brushes but the cost of the controller which replaces the brushes adds to the total cost of the motor. This is often a barrier to using a brushless motor but in this case the cost may be acceptable as there is a need for a controller to vary the speed of the motor which can be handled by the brushless motor controller. 
         [0049]    The embodiments described above, are given by way of examples only and various modifications will be apparent to persons skilled in the art without departing from the spirit of the invention as defined by the appended claims.