Steam iron with pressure equalization apparatus

A steam iron has a water storage tank, an evaporation chamber to provide steam for ironing, and a drip valve for regulating the flow of water from the tank into the evaporation chamber. A pressure chamber in the tank is connected to the evaporation chamber via a pressure equalization passage. The pressure chamber is also connected to receive water from the tank via a non-return valve and is connected to feed water to said evaporation chamber via said drip valve.

BACKGROUND OF THE INVENTION 
The invention relates to a steam iron having a water storage tank, an 
evaporation chamber to provide steam for ironing, and a drip valve for 
regulating the flow of water from the tank into the evaporation chamber. 
Steam irons of this type have long been known. They may be used either as 
dry irons or as steam irons, as desired. For steam ironing, a metered 
quantity of water is fed from the tank into the evaporation chamber 
provided in the soleplate of the iron via the drip valve. As the 
hydrostatic pressure of the column of water in the water storage tank 
bearing on the valve is reduced, the quantity of steam produced in the 
evaporation chamber and escaping through the soleplate falls sharply over 
a certain period of time. In addition, during the steam ironing operation, 
pressure is built up in the evaporation chamber which affects the quantity 
of water flowing out of the drip valve. In order to equalize the pressure 
different in the chamber and in the interior of the tank, it has been 
proposed that the tank and the evaporation chamber be connected to each 
other by a pressure equalization tube (DE-AS 19 31 847). With this type of 
pressure equalization, steam flows out of the evaporation chamber through 
the pressure equalization tube into the upper part of the water storage 
tank during steam ironing. The steam is at a temperature of about 
100.degree. Celsius. Consequently, the upper part of the steam iron, 
particularly the handle, is heated to such an extent that the handling of 
the steam iron is greatly affected and the number of materials from which 
the handle can be manufactured is reduced considerably. 
In order for the pressure equalization to operate satisfactorily, the tank 
in known steam irons must be tightly sealed during steam ironing so as to 
prevent pressure equalization with the atmosphere. A leaky sealing 
mechanism or a fill opening which is not quite closed will cancel out the 
effect of pressure equalization entirely. 
SUMMARY OF THE INVENTION 
According to the invention there is provided a steam iron including a water 
storage tank, an evaporation chamber to provide steam for ironing, a drip 
valve for regulating the flow of water from the tank into the pressure 
chamber connected to the evaporation chamber for pressure equalization 
therewith, the pressure chamber being connected to receive water from the 
tank via a non-return valve and being connected to feed water to said 
evaporation chamber via said drip valve. 
Thus during steam ironing the same pressure conditions prevail in the 
pressure chamber at the inlet end of the drip valve and in the evaporation 
chamber at the outlet end of the valve, while only the pressure chamber, 
rather than the water storage tank as a whole, is pressurized and heated 
by being connected to the evaporation chamber. It is, therefore, possible 
to avoid excessive heating of the upper part of the iron, particularly the 
handle, and furthermore the interior of the tank may be connected directly 
to atmosphere. 
In a preferred embodiment the pressure chamber is connected to the 
evaporation chamber via a pressure equalization passage and to the 
interior of the water storage tank via a non-return valve. The interior of 
the water storage tank is connected to atmosphere. As a result, during 
steam ironing, only the pressure chamber is heated by the steam. 
Consequently, only the water inside the pressure chamber reaches a 
temperature of about 100.degree. C., while the water in the water storage 
tank is heated only to about 60.degree. C. The water storage tank, the 
handle area and the cover of the tank thus remain cool. As a result, less 
expensive thermoplastics may be used to construct the steam iron. The 
water storage tank need not be made of metal but may be made from a 
thermoplastic synthetic material. Moreover, an even ironing temperature is 
obtained over the entire soleplate, since the water supplied to the 
evaporation chamber from the pressure chamber is already at a temperature 
of about 100.degree. C. Consequently, less heat of evaporation is taken 
from the soleplate at the drip point. Since the pressure equalization 
takes place only between the pressure chamber and the evaporation chamber, 
there is no need for any additional sealing mechanism for closing the fill 
opening of the water storage tank. During steam ironing, with the drip 
valve open, water is conveyed from the pressure chamber into the 
evaporation chamber and here converted from a liquid into steam. As a 
result of the pressure equalization, overpressure prevails within the 
pressure chamber, to keep the non-return valve closed against the 
hydrostatic pressure of the column of water in the tank. If the pressure 
chamber is empty, the overpressure in the pressure chamber falls briefly. 
As a result, water is able to flow from the water storage tank into the 
pressure chamber via the non-return valve and the pressure chamber is 
refilled from the water storage tank. This process is repeated until 
either the drip valve is closed or the water storage tank is empty. A flap 
secured at one end is fully adequate as a non-return valve. 
Preferably a valve rod is provided for actuating the drip valve from 
outside the water storage tank. 
Preferably a pressure equalization passage connects the pressure chamber 
and the evaporation chamber, and another non-return valve is provided 
between the pressure equalization passage and the pressure chamber. This 
prevents water from flowing out of the pressure chamber through the 
pressure equalization passage and the evaporation chamber when the iron is 
in an inclined position.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The partial view of the steam iron shown in the drawing shows part of a 
soleplate 16, an evaporation chamber 18 and a heating element 15. The 
evaporation chamber 18 is sealed off by a cover 14. A water storage tank 1 
is arranged above the evaporation chamber 18. The tank 1 is connected to 
the evaporation chamber 18 via a short feed pipe 13. Inside the water 
storage tank 1 is a pressure chamber 7 which is connected to the 
evaporation chamber 18 via a pressure equalization passage or tube 11. 
Water is supplied from the tank 1 to the pressure chamber 7 through a 
non-return valve 8. The non-return valve 8 consists of a flap which is 
secured at one end, as at 9, to a housing 5 of the pressure chamber 7. In 
use, water is conveyed from the pressure chamber 7 through a drip valve 12 
into the evaporation chamber 18. An actuating knob 2 is connected to a 
valve rod 3 which is connected to a valve needle 6, and by operating the 
knob 2 so as to move the rod 3 in the direction of the arrow, the flow of 
water through the drip valve 12 is regulated. The valve rod 3 is sealingly 
guided in the housing 5 of the pressure chamber 7. Between the pressure 
equalization tube 11 and the pressure chamber 7 there is another 
non-return valve 4, so that even when the iron is held in an inclined 
position it is impossible for water to flow out of the pressure chamber 7 
via the tube 11 and into the evaporation chamber 18. 
The water storage tank 1 is filled through the fill opening 10. The 
pressure chamber 7 is also filled through the non-return valve 8. The 
element 15 can then be switched on and, for steam ironing, the drip valve 
12 is opened. Water flows through the drip valve 12 from the pressure 
chamber 7 into the evaporation chamber 18 where it is evaporated. Due to 
the pressure equalization tube 11, the pressure now built up here also 
prevails in the pressure chamber 7 and the non-return valve 8 is closed. 
The pressure chamber 7 remains closed until all the water contained in the 
pressure chamber 7 has been conveyed into the evaporation chamber 18 and 
as a result the overpressure in the pressure chamber 7 has fallen. Water 
then flows again into the pressure chamber 7 out of the water storage tank 
1 which communicates with the atmosphere. This process is repeated until 
the drip valve 12 is closed or the tank 1 is empty. Due to the preferred 
construction of the pressure chamber 7 the water flows evenly out of the 
chamber 7 into the evaporation chamber 18. 
Modifications to the specific embodiment of the steam iron and to any broad 
aspects thereof referred to or suggested herein may be apparent to those 
skilled in the art and the disclosure hereof is extended to encompass any 
such modifications.