Abstract:
An improved temperature control and drip valve assembly which provides for a positive control of the amount of water introduced into the steam chamber of a steam iron in relation to the temperature setting of the steam iron. A self-cleaning capability is provided for flushing the steam chamber and its steam vents.

Description:
FIELD OF THE INVENTION 
     This invention relates to a temperature control and drip valve assembly for a steam iron. This invention is primarily concerned with household steam irons but aspects of the invention may be useful in other applications. 
     BACKGROUND OF THE INVENTION 
     Steam is created in a steam chamber of a steam iron by passing water through a drip valve onto the heated soleplate of the iron. Because different temperatures are required for satisfactory pressing of different fabrics, steam irons are provided with thermostats for adjusting the heat output of the heating element that heats the soleplate. A steam iron is incapable of producing steam at lower temperature levels and can produce increasing amounts of steam as the temperature levels increase. Because there is a correlation between the temperature of the soleplate and the amount of water which should be introduced into the steam chamber to produce steam satisfactory for ironing which is neither superheated and dry or unduly wet, steam irons are provided with mechanisms for varying the amount of water introduced into the steam chamber in accordance with the temperature settings of the heating element. These mechanisms also ensure that water will not be introduced into the steam chamber if the soleplate is insufficiently hot to produce steam. There is an ever-present need to provide improved assemblies for controlling the amount of steam produced, if any, relative to the temperature setting of the heating element. 
     SUMMARY OF THE INVENTION 
     This invention provides an improved temperature control and drip valve assembly for a steam iron. 
     An object of this invention is to provide an improved temperature control and drip valve assembly which provides for a positive control of the amount of water introduced into the steam chamber of a steam iron in relation to the temperature setting of the steam iron. 
     A temperature control in accordance with this invention includes a rotatable temperature control knob, a rotatable drive member connected to said knob for rotation therewith, and a thermostat having a rotatable temperature adjusting shaft connected to the drive member for rotation therewith. Rotation of the control knob can thereby be used to control the temperature generated by the heating element. 
     Further in accordance with this invention, the control knob has a vertical shaft having a downwardly-facing shoulder and the drive member has an upwardly facing shoulder confronting the downwardly-facing shoulder. The shoulders have complementary cam surfaces engaged by a cam follower which is integral with a vertically movable valve stem which has a lower end that cooperates with a valve seal to control the amount of water permitted to drip from a water reservoir into the steam chamber. Accordingly, rotary movements of the control knob to control the temperature generated by the heating element are also transmitted to vertical movements of the valve stem. 
     Further in accordance with this invention, a self-cleaning capability is provided for flushing the steam chamber and its steam vents by fully opening the valve port so that the steam chamber can be filled with water from the water reservoir. To this end, the control knob is vertically movable relative to said drive member through a limited distance which is sufficient to fully open the valve port, as will be described further below. 
     Other objects and advantages will become apparent from the following description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a steam iron made in accordance with this invention. 
     FIG. 2 is an exploded isometric view of the iron of FIG.  1 . 
     FIG. 3 is an exploded isometric view of parts of a temperature control and drip valve assembly and including parts of a spray and steam pump assembly which forms part of the iron of FIG.  1 . 
     FIGS. 4 and 5 are fragmentary elevational views illustrating the operation of a cam and a cam follower in controlling the vertical location of the valve stem. 
     FIGS. 6 and 7 are fragmentary cross-sectional views of the valve seal and the valve stem to illustrate the operation of the valve. 
     FIG. 8 is a fragmentary cross-sectional view of the lower portion of the valve stem taken along line  8 — 8  of FIG.  6 . 
     FIG. 9 is fragmentary view, partly in cross section, showing the raising of the cam follower for self-cleaning purposes. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS. 1 and 2, the present invention is illustrated in connection with a household steam iron, generally designated  10 , having a soleplate  12  with a steam chamber  14 , covered by a base cover  16  which supports a handle  18 . Handle  18  has a lower portion  20  which confines a water reservoir  21  and an upper portion  22  which receives an electronic control module  24  and which is covered by a top cover  26 . The handle upper portion  22  and the top cover  26  constitute a handgrip. In addition, the iron  10  includes a rear cover  28 , temperature control knob  30  for setting a thermostat  32  mounted on the soleplate  12 , and a drip valve assembly including a drip valve stem  34  for dripping controlled quantities of water into the steam chamber  14  through a drip valve seal  35 . As well known, the water dripped into the steam chamber  14  is heated by an electrical heating element in the soleplate  12 , vaporizes and forms steam which exits from the soleplate  12  through plural steam vents (not shown). The heating element and the electronic controls are connected to house current by means of a power cord connected to the rear cover  28 . The particular iron  10  shown in the drawings also has a pair of manually-operable pistons  36  and  38 , respectively used to spray water forwardly of the iron through a nozzle  40  and to create a burst of steam by pumping water by way of a thermoplastic tube connection  42  into the steam chamber  14 . 
     The water reservoir  21  has a forwardly projecting, concave front face  44  and a water conduit  46  extending from the front face  44  into the hollow interior of the reservoir  21 . A fill port assembly, generally designated  48 , is used to enable one to pour water into the water reservoir  21  and also to cover the water conduit  46  during normal use of the iron to prevent contaminants from entering into the reservoir  21 . 
     With reference to FIG. 3, the temperature control knob  30  is mounted for rotation on a bearing  50  formed at the front end of the top cover  26  and has plural hooks  52  which extend into engagement with openings in a hollow control knob shaft  54  that is normally located below the bearing  50 . The knob  30  has an “off” or “0” mark which, when the knob  30  is rotated to a position in which the thermostat  32  prevents energization of the heating element  15 , is aligned with an indicator  56  on the top cover  26 . The proper orientation of the knob  30  is assured by means of a depending rod  58  that must be aligned with an opening  60  in the upper sidewall of the knob shaft  30 . The lower end of the knob shaft  54  extends into the hollow upper end of a rotatable drive member  62  and is connected to the knob shaft  54  for rotation therewith. The drive member  62  is rotatably mounted on the water reservoir  21  by hooks  62 A (FIG.  2 ). The drive member  62  in turn is connected by a metal connecting member  64  to an adjusting shaft forming part of the thermostat  32  in order to adjust the thermostat  32  to the desired heat level. 
     Relative rotation between the knob shaft  54  and the drive member  62  is prevented by the engagement between ribs  66  inside the hollow interior of the drive member  62  and a complimentary surface of the knob shaft  54 . The drive member  62  is connected to the knob shaft  54  by a pair of hook arms  65  (only one of which is shown in FIG. 3) that engage beneath a pair of diametrically opposed tabs  67  inside the upper end of the drive member  62  (again only one tab being shown in FIG.  3 ). This construction allows for the knob  30  and its shaft  54  to be raised relative to the drive member  62  for self-cleaning purposes, as will be described below. 
     The knob shaft  54  has a downwardly-facing shoulder  70  and the drive member  62  has an upwardly-facing shoulder  72  confronting the downwardly-facing shoulder  70 . The shoulders  70  and  72  have complementary cam surfaces which control the vertical height of the valve stem  34  as will now be described. 
     With reference to FIGS. 6,  7  and  8 , the valve stem  34  is molded in one piece and has a lower end which comprises a cylindrical body of a size to close the port in the valve seal  35  and a downwardly-extending notch or recess  74  of increasing dimension. As is apparent, the valve stem  34 , when lowered as shown in FIG. 6, fully closes the port in the valve seal  35  and opens the port by increasing degrees when the valve stem  34  is raised. The upper end of the valve stem  34  comprises an integral cam follower  76  that extends into the space between the shoulders  70  and  72 , an integral pair of arms  78  that engage the outer surface of the drive member  62  to prevent the valve stem  34  from rotating, and an integral triangular rear portion  80  that engages between the cylinder portions of the pump housing  81  so that the head of the valve stem  34  is always held in a position in which the cam follower  76  extends between the shoulders  70  and  72 . 
     FIGS. 4 and 5 show how rotation of the temperature control knob shaft  54  controls the height of the valve stem cam follower  76 . As shown in FIG. 4, there is a substantial length of the shoulders  70  and  72  which have no contour which would raise or lower the valve stem  34 . This is because the seal port is not opened until the temperature setting is sufficiently high to create steam. FIG. 5 shows a condition in which the valve stem follower  76  is raised to cause the valve stem  34  to be raised to create the condition shown in FIG. 7 in which water is dripped from the water reservoir  21  into the steam chamber. 
     A valve stem seal  82  is shown in FIG.  3 . This bears against the top portion of the water reservoir  21  through which the valve stem  34  extends. A U-shaped clamp  84  on the pump housing  81  holds the seal  82  in sealing relation to the water reservoir  21 . 
     In most positions of the temperature control knob  30 , the knob shaft  54  is prevented from being raised into the bearing  50  at the front of the top cover  26  by means of stop members  86  in the bearing  50  that engage a flange  88  on the outside of the knob shaft  54 . However, when the temperature control knob  30  is set to the “0” position, gaps  90  in the flange  88  are aligned with the stop members  86  so that the knob  30  can be elevated as shown in FIG.  9 . At the “0” position of the knob shaft  54 , a finger  92  on the knob shaft  54  engages under the cam follower  76 , so that the raising of the temperature control knob is accompanied by the raising of the valve stem  34 , and a corresponding full opening of the seal port. This operation can be used for self-cleaning of the soleplate as mentioned above. 
     Although the presently preferred embodiment of this invention has been described, it will be understood that within the purview of the invention various changes may be made within the scope of the following claims.