Abstract:
A surface cleaning head for cleaning a surface is provided that includes a housing that has a cleaning chamber surrounded by a peripheral wall and open at the bottom, and in which a cleaning nozzle is mounted on a spray arm and is freely rotatable about a rotational axis, and a jet pump for suctioning off cleaning fluid applied to a surface, the jet pump having a pump inlet channel connected to a combining channel via a mixing chamber, and a motive nozzle upstream from the combining channel. To improve the surface cleaning head, the pump inlet channel is oriented radially with respect to the spray arm and connected to the peripheral wall of the cleaning chamber, the diameter of the combining channel is 14 to 18 mm, and the distance between the motive nozzle and the combining channel is at least 10 mm.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of international application number PCT/EP2011/053778, filed on Mar. 14, 2011, which claims priority to German Appl. No. 10 2010 003 079.1, filed on Mar. 19, 2010, both of which are incorporated herein by reference in their entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a surface cleaning head for cleaning a surface, comprising a housing that has a cleaning chamber which is surrounded by a peripheral wall and open at the bottom, and in which at least one cleaning nozzle is mounted on a spray arm so as to be freely rotatable about an axis of rotation for applying cleaning fluid to the surface to be cleaned, and comprising a jet pump for suctioning off cleaning fluid that is applied to the surface, the jet pump having a pump inlet channel that is in flow connection with the cleaning chamber and is connected to a combining channel via a mixing chamber, a motive nozzle for forming a suction flow being situated upstream from the combining channel. 
         [0003]    The invention further relates to a surface cleaning arrangement having a surface cleaning head and an outlet line. 
         [0004]    This type of surface cleaning head is known from U.S. Pat. No. 4,895,179. A spray lance of a high-pressure cleaning appliance may be connected to the surface cleaning head so that the cleaning nozzle situated on the spray arm may be supplied with pressurized cleaning fluid by the high-pressure cleaning appliance. The cleaning fluid may be sprayed onto the surface to be cleaned by means of the cleaning nozzle. The nozzle thus experiences a recoil, thereby setting the spray arm in rotation about the axis of rotation. At least two diametrically opposite spray arms, each carrying a cleaning nozzle, are usually used, whereby the nozzles may be simultaneously acted on by pressurized cleaning fluid. 
         [0005]    In addition to the cleaning nozzles, the known surface cleaning head has a jet pump which operates according to the principle of a Venturi pump. The jet pump is situated above the housing, and is in flow connection with the cleaning chamber via a connecting line leading alongside the cleaning chamber. The jet pump includes a pump inlet channel which is connected to a mixing chamber, and a combining channel downstream from the mixing chamber. Upstream from the combining channel, a motive nozzle is in alignment with the combining channel, and may be acted on by pressurized cleaning fluid so that a suction flow forms in the mixing chamber and the combining channel. A diffuser is connected to the combining channel. An outlet line may be connected to the diffuser. The suction flow generated by the motive nozzle allows the fluid that is applied to the surface to be cleaned, together with removed dirt, to be suctioned off and discharged via the outlet line. 
         [0006]    For operating the surface cleaning head known from U.S. Pat. No. 4,895,179, the surface cleaning head is supplied with cleaning fluid under a pressure of at least 207 bar at a delivery rate of at least 1,620 liters per hour. Due to the high pressure of the cleaning fluid and the high delivery rate, a suction flow may be formed by means of the jet pump which is strong enough to effectively suction off the cleaning fluid that is applied to the surface to be cleaned. 
         [0007]    Surface cleaning heads having at least one rotating cleaning nozzle which may be supplied with pressurized cleaning fluid and which have a jet pump for suctioning off the cleaning fluid that is applied to the surface are also known from DE 100 66 009 B4 and DE 103 13 396 B4. In these surface cleaning heads as well, the cleaning fluid is supplied to the motive nozzle under high pressure and at a high delivery rate. 
         [0008]    It is an object of the present invention to improve a surface cleaning head of the generic kind in such a way that the pressure and the delivery rate of the cleaning fluid may be reduced without significant losses of suction force of the suction pump. 
       SUMMARY OF THE INVENTION 
       [0009]    For a surface cleaning head of the type stated at the outset, this object is achieved according to the invention in that the longitudinal axis of the pump inlet channel is oriented radially with respect to the axis of rotation of the at least one spray arm, and the pump inlet channel is connected to the peripheral wall of the cleaning chamber, the diameter of the combining channel being 14 mm to 18 mm, and the distance between the motive nozzle and the combining channel being at least 10 mm 
         [0010]    In the surface cleaning head according to the invention, the pump inlet channel is connected to the cleaning chamber along a longitudinal axis that is aligned in the radial direction. The pump inlet channel is connected to the combining channel via the mixing chamber, and the motive nozzle is situated upstream from the combining channel. Thus, the mixing chamber as well as the motive nozzle are situated at a short distance from the cleaning chamber, and thus also at a short distance from the surface to be cleaned. As a result, an effective suction flow is formed in the cleaning chamber, with the aid of which the surface to be cleaned may be suctioned, and the pressure of the cleaning fluid supplied to the motive nozzle may be selected to be lower than for the surface cleaning head known from U.S. Pat. No. 4,895,179. For example, the pressure of the cleaning fluid supplied to the motive nozzle may be less than 150 bar, and the delivery rate may be less than 800 liters per hour, in particular less than 600 liters per hour. 
         [0011]    A further increase in the effectiveness of the surface cleaning head is achieved according to the invention in that the diameter of the combining channel is 14 mm to 18 mm For smaller combining channel diameters, although a considerable delivery pressure is formed at the outlet of the combining channel, the transmission of air through the combining channel is relatively low. For large diameters, a high air transmission rate is obtained, but only a relatively low delivery pressure then results at the outlet of the combining channel, so that there is a risk that the cleaning fluid may no longer be reliably transported up to the free end of an outlet line via which the fluid conveyed by the jet pump is discharged. In combination with a distance of at least 10 mm, in particular a distance of at least 15 mm, between the motive nozzle and the combining channel, for a combining channel diameter of 14 mm to 18 mm, a considerable suction flow may be generated not only in the region of the pump inlet channel, but also in the region of an outlet line, in particular a discharge hose, situated downstream from the combining channel. This has the advantage that the cleaning fluid suctioned off from the surface to be cleaned may be discharged via the outlet line even in case the outlet line has a certain upward oblique inclination with respect to the horizontal. This provides the user with the option, for example, of cleaning a terrace, the outlet line extending along an ascending floor area or surmounting a small garden wall, for example. The surface to be cleaned may thus be effectively suctioned, and the sucked away cleaning fluid may be placed under a considerable delivery pressure by the jet pump so that it may be discharged in a reliable manner 
         [0012]    In an advantageous embodiment of the invention, the distance between the motive nozzle and the combining channel is at most 60 mm. 
         [0013]    In particular a distance of 40 mm between the motive nozzle and the combining channel has proven to be particularly advantageous in order to generate a particularly effective suction flow for suctioning the surface to be cleaned and to place the sucked-up fluid under a considerable delivery pressure at the lowest possible pressure of the cleaning fluid that is supplied to the motive nozzle, and at the lowest possible delivery rate of the cleaning fluid, so that the sucked-up fluid may be discharged in a reliable manner. 
         [0014]    The distance between the motive nozzle and the combining channel is preferably 1.3 to 4.3 times the diameter of the combining channel For providing an effective suction flow, it is advantageous for the distance between the motive nozzle and the combining channel to be at least 1.3 times the diameter of the combining channel. Thus, the motive nozzle should not be situated directly at the inlet of the combining channel On the other hand, the distance between the motive nozzle and the inlet of the combining channel should also preferably not be greater than 4.3 times the diameter of the combining channel, since otherwise the suction flow is impaired. 
         [0015]    The length of the combining channel is preferably at least 10 mm. In particular, a length of 20 mm has proven to be advantageous for increasing the effectiveness of the jet pump. 
         [0016]    It is advantageous if a diffuser is connected to the combining channel and has an opening angle of 4° to 12°, in particular an opening angle of 8°. The diffuser forms a line portion which is connected to the combining channel and continuously widens. The achievable suction flow may be improved in this way. 
         [0017]    The combining channel and the diffuser advantageously have a combined length of at least 30 mm. 
         [0018]    The ratio of the diameter of the combining channel to the combined length of the combining channel and the diffuser is advantageously 0.13 to 0.25. 
         [0019]    In a preferred embodiment of the invention, the motive nozzle is formed as a cone jet nozzle, the opening angle of the cone jet being 15° to 40°. The opening angle of the cone jet is advantageously 20° to 25°. 
         [0020]    In a particularly preferred embodiment of the invention, the housing has an outer wall which surrounds the peripheral wall of the cleaning chamber, the pump inlet channel being mounted on the peripheral wall and on the outer wall. In particular, it may be provided that the pump inlet channel protrudes through the outer wall to the outside. Thus, the pump inlet channel extends, at least partially, inside the housing, namely, in the region between the peripheral wall of the cleaning chamber and the outer wall of the housing. The installation space of the surface cleaning head may thus be kept relatively low. The pump inlet channel may protrude beyond the housing to the outside at its end region that faces away from the cleaning chamber. This increases the stability not only of the pump inlet channel, but also of the portions of the outer wall and of the peripheral wall connected to the pump inlet channel Thus, the pump inlet channel not only has the function of establishing a flow connection between the cleaning chamber and the mixing chamber of the jet pump, but also forms a mechanical reinforcing element which increases the mechanical stability of the surface cleaning head. 
         [0021]    At least three support elements are advantageously situated in the region between the peripheral wall of the cleaning chamber and the outer wall of the housing for supporting the surface cleaning head on the surface to be cleaned. The support elements may be provided, for example, in the form of rollers or casters, with the aid of which the surface cleaning head may be moved along the surface to be cleaned. 
         [0022]    The peripheral wall of the cleaning chamber preferably has a circular cylindrical shape, and in top view, the outer wall of the housing preferably has a triangular shape with rounded corner regions, one support element being situated in each corner region. The support elements are thus overlapped by the housing, and the surface cleaning head has a very compact design overall. 
         [0023]    It is advantageous if a pump outlet channel which defines the mixing chamber and the combining channel, and optionally also the diffuser, is mounted at the end of the pump inlet channel that faces away from the peripheral wall of the cleaning chamber. The pump outlet channel is preferably aligned coaxially with the pump inlet channel 
         [0024]    It is advantageous for the housing of the surface cleaning head, the pump inlet channel, and the pump outlet channel to be integrally joined to one another. The housing, pump inlet channel, and pump outlet channel are preferably formed as an integral molded plastics part. The manufacturing and assembly costs of the surface cleaning head may thus be kept low. 
         [0025]    In an advantageous embodiment, the assembly of the surface cleaning head is simplified in that the motive nozzle is mounted on a nozzle mounting which is insertable into the pump inlet channel and mechanically connectable to the pump inlet channel The nozzle mounting is preferably latchable to the pump inlet channel. In a first assembly step, the motive nozzle may be fixed to the nozzle mounting, and the nozzle mounting together with the motive nozzle fixed thereto may be subsequently inserted into the pump inlet channel and mechanically connected thereto. 
         [0026]    In an advantageous embodiment of the invention, the nozzle mounting is connected, via a second line portion extending above the at least one spray arm within the cleaning chamber, to a first line portion which passes through a top wall of the cleaning chamber. The motive nozzle which is fixed to the nozzle mounting may be supplied with pressurized cleaning fluid via the line portions. In such a configuration, the surface cleaning head is characterized by a particularly compact design. 
         [0027]    It is advantageous if the surface cleaning head has a distributor unit which is connected to the at least one cleaning nozzle via a first branch line, and to the motive nozzle via a second branch line, a supply line being pivotably mounted on the distributor unit. The spray lance of a high-pressure cleaning appliance, for example, may be connected to the supply line. The distributor unit may be supplied with pressurized cleaning fluid via the spray lance and the supply line. The distributor unit is connected to the at least one cleaning nozzle via the first branch line so that the surface to be cleaned may be sprayed with cleaning fluid, and is connected to the motive nozzle via the second branch line so that the motive nozzle may be acted on by pressurized cleaning fluid to form a suction flow. As mentioned above, the second branch line may have a first line portion which passes through the top wall of the cleaning chamber, and a second line portion which is connected to the first line portion and extends within the housing to the nozzle mounting of the motive nozzle. 
         [0028]    The motive nozzle advantageously extends into the mixing chamber. 
         [0029]    It is advantageous if the mixing chamber tapers conically in the direction of the combining channel. The mixing chamber preferably has the shape of a truncated cone, and extends from the pump inlet channel to the combining channel. The cone angle of the mixing chamber is preferably 20° to 50°, in particular 25° to 35°. A cone angle of 30° is particularly advantageous. 
         [0030]    The combining channel is advantageously cylindrical. 
         [0031]    The pump inlet channel likewise preferably has a conical taper; i.e., the flow cross-section of the pump inlet channel is reduced in the direction of the mixing chamber. 
         [0032]    The pump inlet channel preferably has a wedge-shaped design. 
         [0033]    In an advantageous embodiment, the pump inlet channel has two side walls oriented at an angle to one another. The side walls are preferably oriented at an angle of 90° to one another. 
         [0034]    A connecting device for connecting to the outlet line is advantageously situated downstream from the combining channel. In particular, it may be provided that the pump outlet channel is releasably connectable to the outlet line via the connecting device. 
         [0035]    It is advantageous if a coupling device having a connection diameter of 28 mm to 40 mm and which is connected to the outlet line is connectable to the connecting device. Pressure losses during discharge of the sucked-up fluid may thus be kept low, while a considerable flow velocity may still be formed. The outlet line and the coupling device may preferably engage with one another. For example, the outlet line may engage with or be fitted onto a tubular coupling element of the coupling device. 
         [0036]    The invention further relates to a surface cleaning arrangement for cleaning a surface, comprising a surface cleaning head which is preferably formed as described above, and comprising an outlet line which is connected to the surface cleaning head, the surface cleaning head including a housing having a cleaning chamber which is surrounded by a peripheral wall and open at the bottom, in the cleaning chamber at least one cleaning nozzle being mounted on a spray arm so as to be freely rotatable about an axis of rotation for applying cleaning fluid to the surface to be cleaned, and the surface cleaning head for suctioning off cleaning fluid that is applied to the surface including a jet pump having a pump inlet channel that is in flow connection with the cleaning chamber and is connected to a combining channel via a mixing chamber, a motive nozzle for forming a suction flow being situated upstream from the combining channel, and the outlet line being connected to the surface cleaning head downstream from the combining channel. To be able to reduce the pressure and the delivery rate of the cleaning fluid that is supplied to the surface cleaning arrangement without impairing the suction force of the jet pump, the longitudinal axis of the pump inlet channel is oriented radially with respect to the axis of rotation of the at least one spray arm, and the pump inlet channel is connected to the peripheral wall of the cleaning chamber, and the diameter of the combining channel is one-third to two-thirds the internal diameter of the outlet line. 
         [0037]    As a result of the radial orientation of the pump inlet channel which is directly connected the peripheral wall of the cleaning chamber, and due to the selection of the diameters of the combining channel and the outlet line in a ratio of one-third to two-thirds, effective suctioning of the surface that is sprayed with cleaning fluid and effective discharge of the sucked-up fluid and the removed dirt may be achieved at a reduced pressure and decreased delivery rate of the cleaning fluid that is supplied to the surface cleaning head. In particular, an internal diameter of the outlet line of 28 mm to 40 mm is advantageous. 
         [0038]    The following description of a preferred embodiment of the invention serves for explanation in greater detail in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1  shows a schematic top view of a surface cleaning arrangement, having a surface cleaning head to which an outlet line is connected; 
           [0040]      FIG. 2  shows a sectional view of the surface cleaning head along the line  2 - 2  in  FIG. 1 ; 
           [0041]      FIG. 3  shows a sectional view of the surface cleaning head along the line  3 - 3  in  FIG. 1 ; and 
           [0042]      FIG. 4  shows a sectional view of the surface cleaning head along the line  4 - 4  in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    The drawing schematically illustrates a surface cleaning arrangement  5  according to the invention having a surface cleaning head  10  according to the invention. The surface cleaning head  10  has a hood-like housing  12 , which in the top view has a substantially triangular shape with rounded corners. The housing  12  includes a top wall  14 , the outer edge of which is connected to an outer wall  16 . A circular cylindrical peripheral wall  18  which surrounds a cleaning chamber  20  projects downwardly from the top wall  14  at a distance from the outer wall  16 . In the region between the outer wall  16  and the peripheral wall  18 , support elements in the form of support wheels  22 ,  23 , and  24  are respectively associated with each corner region of the housing  12 , by means of which the surface cleaning head  10  can be supported on a surface to be cleaned, and the surface cleaning head  10  can be moved along the surface to be cleaned. 
         [0044]    A circumferential splash guard and sealing element in the form of a bristle strip  26  is situated at the free edge of the peripheral wall  18 , by means of which the cleaning chamber  20  can be sealed off with respect to the surface to be cleaned, and the escape of spray water from the cleaning chamber  20  may be prevented. 
         [0045]    Situated above the top wall  14  is a distributor unit  28  that has a distributor line  29 , the longitudinal axis  30  of which is oriented perpendicularly with respect to the cylinder axis  31  that is defined by the cylindrical peripheral wall  18 . 
         [0046]    The distributor unit  28  forms a bearing element on which a supply line  33  is mounted so as to be pivotable about the longitudinal axis  30  of the distributor line  29 . At its free end that faces away from the housing  12 , the supply line  33  carries a connecting element  34  to which, for example, a spray lance of a high-pressure cleaning appliance, which is known per se and therefore not illustrated in the drawing, may be connected. 
         [0047]    The supply line  33  opens into the distributor line  29 , which is connected to a first branch line  36  that is aligned coaxially with the cylinder axis  31  and extends into the cleaning chamber  20 , and at its free end, carries two diametrically opposite spray arms  37 ,  38 . The two spray arms  37  and  38  each carry a cleaning nozzle  39  and  40 , respectively, at their free end. A surface to be cleaned in the region enclosed by the bristle strip  26  may be sprayed with cleaning fluid by means of the cleaning nozzles  39  and  40 . The cleaning nozzles  39  and  40  generate an obliquely downwardly directed liquid jet of a cleaning fluid, which, upon exiting from the cleaning nozzles  39 ,  40 , exerts a torque on the spray arms  37 ,  38 , thus setting them in rotation about the cylinder axis  31 . 
         [0048]    The distributor line  29  is in flow connection with a jet pump  45  via a second branch line  43 . The jet pump includes a motive nozzle  46  which is fixed to a nozzle mounting  48 . The nozzle mounting  48  is inserted into a pump inlet channel  50  and is mechanically connected thereto. In the illustrated embodiment, the nozzle mounting  48  is latched to the pump inlet channel  50 . The pump inlet channel  50  extends from a lateral opening  52  in the peripheral wall  18  and through the outer wall  16 , along a longitudinal axis  53  oriented radially with respect to the cylinder axis  31 ; i.e., the pump inlet channel  50  protrudes outwardly beyond the housing  12 . This is apparent in particular from  FIG. 4 . A pump outlet channel  55 , which is aligned coaxially with the pump inlet channel  50  and carries a connecting device at its free end, is integrally connected to the pump inlet channel  50 . The connecting device includes an annular space  61  which encloses the pump outlet channel  55  at its free end region and is externally delimited by a sleeve  62 . The sleeve  62  is integrally joined to the pump outlet channel via a radially outwardly protruding shoulder  63 . A coupling device  57  is connected to the connecting device. The coupling device  57  includes a coupling flange  58  having a central connection opening  59 . A first socket piece  60  extends into the annular space  61  and is releasably connected to the sleeve  62 , for example via a bayonet connection. On the side facing away from the first socket piece  60 , a second socket piece  64  is molded onto the coupling flange  58 , coaxially with the longitudinal axis  53 . The second socket piece  64  forms a tubular coupling element into which an outlet line in the form of a flexible discharge hose  76  is inserted. The discharge hose  76  is non-detachably joined to the coupling device  57  by means of an adhesive, and together with the coupling device  57  may be separated from the pump outlet channel  55 , and as necessary, connected to same. The internal diameter of the discharge hose  76  is advantageously identical to the diameter of the connection opening  59 , and is preferably 28 mm to 40 mm. 
         [0049]    The flow cross-section of the pump inlet channel  50  decreases in the region between the lateral opening  52  and the pump outlet channel  55 . For this purpose, the pump inlet channel has two side walls  78 ,  79  which are oriented obliquely, namely, at an angle of 90°, relative to one another, as is apparent from  FIG. 4 . 
         [0050]    Within the pump outlet channel  55 , the pump inlet channel  50  is connected to a mixing chamber  65 , which has a frustoconical configuration and tapers conically in the direction facing away from the pump inlet channel  50  at a cone angle of 30°. In the pump outlet channel  55 , the mixing chamber  65  is connected to a cylindrical combining channel  67  having a diameter of 14 mm to 18 mm and a length of 40 mm. The distance between the motive nozzle  46  and the combining channel  67  is at least 10 mm, in particular at least 15 mm, and at most 60 mm. In the illustrated exemplary embodiment, the distance is 40 mm. Within the pump outlet channel  55 , in the direction facing away from the pump inlet channel  50 , the combining channel  67  is connected to a diffuser  69 , which expands conically in the direction facing away from the pump inlet channel  50 ; in the illustrated embodiment, the cone angle of the diffuser  69  is 8°. In its end region, the diffuser  69  is enclosed by the annular space  61 , into which the first socket piece  60  of the coupling device  57  extends. The connection opening  59  adjoins at the end of the diffuser. 
         [0051]    As previously mentioned, the motive nozzle  46  is mounted on the nozzle mounting  48 . The motive nozzle  46  is in alignment with the combining channel  67 , and at its free end extends into the mixing chamber  65 . The flow connection between the motive nozzle  46  and the distributor line  29  is established via the second branch line  43 . The second branch line has a first line portion  71  which starts at the distributor line  29  and passes through the top wall  14  of the housing  12  at a distance from the first branch line  36 . Within the cleaning chamber  20 , above the spray arms  37 ,  38 , the first line portion  71  is connected to a second line portion  72  of the second branch line  43 , on the free end of which the nozzle mounting  48  together with the motive nozzle  46  is mounted. The motive nozzle  46  is configured as a cone jet nozzle; i.e., it emits a liquid jet, shaped as a cone jet, which is directed toward the combining channel  67 . In the illustrated embodiment, the opening angle of the cone jet is approximately 22°. 
         [0052]    As mentioned above, the connection diameter of the coupling device  57 , i.e., the diameter of the connection opening  59 , as well as the internal diameter of the discharge hose  76 , is 28 mm to 40 mm The ratio of the diameter of the combining channel  67  to the connection diameter of the coupling device  57 , and thus to the internal diameter of the discharge hose  76 , is one-third to two-thirds. 
         [0053]    The liquid jet emitted by the motive nozzle  46  strikes the combining channel  67 , and according to the known Venturi principle, generates a suction flow which is directed into the pump inlet channel  50  and the pump outlet channel  55  connected thereto. By means of the suction flow, cleaning fluid which has been applied to the surface to be cleaned together with removed dirt may be picked up from the surface and discharged via the discharge hose  76 . The discharge hose  76  is releasably connected to the pump outlet channel  55 . Within the discharge hose  76 , a liquid flow which is directed in the direction facing away from the surface cleaning head  10  forms under the action of the motive nozzle  46 . Sucked-up cleaning fluid flows through the discharge hose  76 , even when the hose has a certain upward inclination. Due to the radial orientation of the pump inlet channel  50  which is connected to the peripheral wall  18  and of the pump outlet channel  55  that is connected to the inlet channel, and due to the diameter of the combining channel  67  and the connection diameter of the coupling device  57 , as well as the selected distances between the motive nozzle  46  and the combining channel  67 , there is little risk of fluid in the discharge hose  76  flowing back to the surface cleaning head  10 . 
         [0054]    The surface cleaning head  10  is also characterized by high mechanical stability. The cleaning nozzles  39 ,  40 , the same as the motive nozzle  46 , are situated within the housing  12 , and the second line portion  72  of the second branch line  43  also extends inside the housing  12  and is thus protected from mechanical damage. The pump inlet channel  50  is fixed both to the peripheral wall  18  and to the outer wall  16 , forming a stable anchor for the pump outlet channel  55 . The housing  12  together with the peripheral wall  18  and the outer wall  16 , in combination with the pump inlet channel  50  and the pump outlet channel  55 , forms an integral molded plastics part which has high mechanical stability and is manufacturable at low cost. The nozzle mounting  48  may be inserted into the pump inlet channel  50  through the lateral opening  52  in the peripheral wall  18  and latched thereto after the motive nozzle  46  has been fixed to the nozzle mounting  48  beforehand