Vapor pressure pump

A vapor pressure pump for delivering a liquid into a system operating at a higher pressure or located at a higher level by action of a vapor pressure produced from a portion of the liquid to be delivered. The pump comprises a closed reservoir for liquid, which includes an unidirectional liquid inlet, an unidirectional liquid outlet, a vapor exhaust valve adapted to balance the pressure between the unidirectional liquid inlet and the reservoir during its filling. The pump also comprises a vapor generator for producing vapor inside the reservoir at a pressure sufficient to force out the liquid contained therein through the liquid outlet, and a control device for operating the vapor generator only when the liquid fed by the liquid inlet has reached a predetermined level in the reservoir. According to the invention, the vapor generator comprises an evaporation chamber in vapor communication with the closed reservoir, and a device responsive to the control device for sampling a portion of the liquid contained in the reservoir when the liquid in the reservoir has reached the predetermined value, and for supplying the sampled liquid into the evaporation chamber. The vapor generator also comprises a heating system for evaporating the sampled liquid supplied into the evaporation chamber to produce the pressure vapor required to force the liquid out of the reservoir.

BACKGROUND OF THE INVENTION 
The present invention relates to a vapor pressure pump for delivering a 
liquid into a system operating at a higher pressure or located at a higher 
level by action of a vapor pressure produced from a portion of the liquid 
to be delivered. 
Many types of vapor pressure pumps have been developed in this particular 
field. The pressure pumps known and commercialized under the names of 
"acid egg" or "pulsometer" are examples thereof. 
Every pump of this particular type comprises a closed reservoir fed with a 
liquid under the effect of gravity via an inlet valve. The pump is useful 
for discharging the liquid in another reservoir having an internal 
pressure higher than the one of the first reservoir, or being placed above 
it. When a predetermined level of liquid is reached in the pump, a vapor 
or gas pressure higher than the pressure to force back, is injected or 
produced into the reservoir. As a result, the liquid is expelled into an 
outlet pipe through an exhaust valve. 
Injection or production of a gas or vapor pressure in the reservoir may be 
carried out in two different manners. In the former one, vapor pressure is 
generated and stocked in a distinct reservoir. When the predetermined 
level of liquid is reached, an electrical, pneumatic or mechanical 
mechanism actuates the opening of a flood-gate connecting the vapor 
reservoir to the pump. In the latter one, a float-operated heat source is 
disposed inside the reservoir to evaporate a portion of the liquid 
contained therein and raise the vapor pressure at a value sufficient to 
expel the liquid as soon as the level of the liquid inside the reservoir 
has reached the predetermined level. Such a "thermodynamic" pump is 
described by way of example in U.S. Pat. No. 4,227,489 to Regamey, for use 
in a boiler and heat exchanger system. 
BRIEF SUMMARY OF THE INVENTION 
The present invention proposes a vapor pressure pump of the above-mentioned 
type, which pump distinguishes over the known prior art in that it 
comprises improved means for ensuring cyclic functioning of the pump, 
control of the heat source and generation of vapor. 
More particularly, the invention proposes a vapor pressure pump in which 
vapor is generated from a small portion of the liquid to be pumped, which 
portion is sampled from the reservoir only when a predetermined level is 
reached by the liquid in said reservoir. In order to generate vapor, the 
sampled liquid is discharged on a surface heated to cause flash 
evaporation of the liquid. This evaporation creates a sudden rise of 
pressure that holds as long as necessary to expel the liquid contained in 
the reservoir. 
The portion of the liquid used for the generation of vapor is sampled only 
when the reservoir of the pump is full. The remaining portion of the 
liquid to be pumped is never in contact with the hot surface, thus 
minimizing the energetic comsumption by the pump. 
DETAILED DESCRIPTION OF THE INVENTION 
The vapor pressure pump according to the invention which is used for 
delivering a liquid into a system operating at a higher pressure or 
located at a higher level by action of a vapor pressure produced from a 
portion of said liquid to be delivered, basically comprises: 
a closed reservoir for liquid, which reservoir comprises an unidirectional 
liquid inlet, an unidirectional liquid outlet, and a vapor exhaust valve 
adapted to balance the pressure between the unidirectional liquid inlet 
and the reservoir during its filling; 
means for producing vapor inside that reservoir at a pressure sufficient to 
force out the liquid contained in it through the liquid outlet, and 
control means for operating the vapor producing means only when the liquid 
fed by the liquid inlet has reached a predetermined level in the 
reservoir. 
The vapor pressure pump is advantageously characterized in that its vapor 
producing means comprises: 
an evaporation chamber in vapor communication with the closed reservoir; 
means responsive to the control means for sampling a portion of the liquid 
contained in the reservoir when the liquid in the reservoir has reached 
the predetermined value, and for supplying this sampled liquid into the 
evaporation chamber; and 
heating means for evaporating the sampled liquid supplied into the 
evaporation chamber to produce the vapor pressure required to force the 
liquid out of the reservoir. 
As aforesaid, the pump according to the invention is utilized for 
delivering a liquid into a system operating at a higher pressure or 
located at a higher level by action of a vapor pressure produced from a 
portion of the liquid to be delivered. 
More particularly, the pump according to the subject invention may be 
utilized in a solar heating system or a heat recovery system such as 
described in U.S. patent application Ser. No. 506,542 filed on June 21, 
1983 in the name of the same Applicant. 
According to a preferred embodiment of the invention, the evaporation 
chamber is located inside the closed reservoir. Furthermore, the control 
means comprises a float and the sampling means comprises a first obturator 
operated by this float for intermittently opening a liquid discharge 
aperture provided between the reservoir and the evaporation chamber. This 
aperture is sized and positioned to let the required portion of liquid 
flow by gravity from the reservoir to the evaporation chamber to produce 
the necesssary vapor pressure. 
The closed reservoir must be provided with a vapor exhaust valve adapted to 
balance the pressure between the unidirectional liquid inlet and the 
reservoir during filling thereof. The vapor exhaust valve includes an 
aperture and a second obturator which is actuated in counteraction to the 
actuation of the liquid discharge aperture by the operation of the float. 
The first and second obturators are preferably provided at the ends of a 
vertically extending stem passing through the float. This stem has such a 
length that the closure of the aperture of the vapor exhaust valve by the 
second obturator occurs simultaneously with the opening of the discharge 
aperture by the first obturator, and vice versa. These first and second 
obturators consist of seat-engaging surfaces. 
Advantageously, the evaporation chamber is defined between the inner wall 
of the closed reservoir and the outer wall of another reservoir located 
inside the closed reservoir in coaxial position with respect thereto. 
The upper part of the other reservoir is open so as to facilitate the 
gravity outflow of liquid in it. The other reservoir may be supported by a 
few contacting points at the bottom of the closed reservoir. 
Moreover, the liquid discharge aperture is provided at the bottom of the 
other reservoir whereby the accumulated condensed liquid may escape and 
fill up the volume between the walls of the coaxial reservoirs. 
The closed reservoir may be made of a heat-conductive material such as 
metal, while the other reservoir is made of a heat-insulating material, to 
reduce thermal exchanges between the hot wall of the closed reservoir and 
the wall of the other reservoir. This arrangement allows an effective 
functioning of the pump without heat loss during the heating of the liquid 
to be pumped. 
The float may be made of a heat-insulating material for thermally 
insulating the liquid surface in the other reservoir. 
The heating means of the pump may consist of a continuously operating 
heating sleeve extending all around the outer wall of the closed 
reservoir. This heating sleeve may be controlled by a thermostat. The said 
closed reservoir is therefore constantly maintained at a temperature 
sufficiently high to cause flash evaporation of the liquid discharged 
between the outer wall of the other reservoir and the inner wall of the 
closed reservoir. 
The pump has no moving parts, except for the valves and float. 
Thermal efficiency is a very important feature in solar heating systems or 
heat recovery systems at low temperature. The existing pumps do not take 
into account that a good functioning of the pump is achieved only when the 
heat transfer vapor condensation is reduced to the minimum. It is thus 
further necessary to reduce the surface of liquid by means of an 
insulating float as well as the thermal conductivity of the wall of said 
other reservoir. If these conditions are not met, the vapor condensation 
generated on the surface of liquid which is cooler, and on the reservoir 
surface, would delay the rising of pressure inside the pump until the 
internal medium, including the liquid to be pumped, is elevated at the 
saturation temperature corresponding to the pumping pressure. As a result, 
the cycle duration would be unduly prolonged and the energy required for 
pumping would be increased. 
In order to obtain the vapor necessary to create the pressure inside the 
reservoir when filled up, a small portion of the liquid contained in the 
other reservoir is brought to escape therefrom and to come into contact 
with the hot internal wall of the closed reservoir so as to suddenly 
vaporize. To this end, the bottom of the other reservoir may be provided 
with a small aperture which is kept closed by means of a first obturator 
as long as the latter is not raised by the float when it reaches the upper 
extremity of the reservoir. When the obturator is raised by the float, the 
liquid is discharged through the aperture and flows out by gravity on the 
hot wall where it is instantaneously vaporized. The obturator remains in 
an upward position as long as the float does not lower it when it has 
reached the lower part of the reservoir. The liquid escapes from the other 
reservoir as long as it is enclosed therein thus causing maintenance of 
pressure sufficient to expel the liquid from the reservoir in the outlet 
pipe through the liquid exhaust valve. 
As aforesaid, for obtaining at a given time the vapor necessary to create 
the pressure inside the pump, the existing systems have resort either to 
the injection of a vapor under pressure contained in another reservoir, or 
to the opening of a heat feeding circuit immersed in the liquid to be 
pumped or in a portion of said liquid. The first system is unfavourable 
since the permanent maintenance of a vapor or gas reservoir at a desired 
pressure is necessary. The second system cannot be actuated unless the 
power of the heat source so utilized is sufficient to overcome the 
lowering of the pressure caused by the vapor condensation on the cool 
walls of the reservoir and on the open liquid surface as well as being 
sufficient to create and maintain the pressure required for expelling the 
liquid. Since no vaporization must take place in the reservoir before all 
the liquid has penetrated it, in fact any premature elevation of pressure 
would prevent its inlet, the starting of the heat source must wait for the 
almost filling up of the pump. This operation is generally actuated by 
means of a float, which at a certain predetermined level, switches on the 
heat source, thus creating delays or necessitating a higher power heat 
source. 
In the pump according to the subject invention, the heat source preferably 
works out continuously to maintain, by means of a thermostat, the 
temperature of the closed reservoir lower than a maximum value for 
preventing overheat. Its functioning is only indirectly related to that of 
the pump. In accordance with the invention, vapor is generated only at a 
given time when the reservoir of the pump is full; the production of vapor 
is obtained instantaneously without waiting for the temperature 
equilibrium, and the elevation of pressure in the closed reservoir of the 
pump is achieved instantaneously to maintain in a closed position the 
vapor exhaust valve and the inlet liquid valve. 
The upward and downward motion of the obturators is simple and tolerances 
of manufacture and positioning are easy to achieve. It further ensures a 
self-regulating mechanism without any external intervention. This 
utilization of a closed metallic reservoir having a high thermal capacity 
promotes the maintenance of vaporization, thus of pressure, neither 
suffering the drawbacks of a lowering of temperature, nor having resort to 
a heat source with a high power. 
The power required for working out such a pump is reduced to the minimum, 
so that it becomes an important factor when the pump is connected to a 
solar energy or thermal waste products recovery system at low temperature. 
According to another preferred embodiment of the invention, the pump may be 
provided with other liquid control mechanisms having the same effect. Use 
can be made, for example, of a self-priming siphon positioned inside the 
closed reservoir in such a manner that it becomes operative when the level 
of the liquid in said reservoir has reached its predetermined value. 
The siphon has the same function as the aperture of the bottom of said 
other reservoir, i.e. it allows the sampled liquid to be vaporized and it 
ensures the draining of said liquid as long as said other reservoir is not 
empty. 
The float keeps its function of thermal insulator of the liquid surface in 
the reservoir as well as its function of actuating mechanism of the 
obturator of the vapor exhaust valve. Said valve operates in counteraction 
to the actuation of the siphon by means of the obturator operated by the 
float. Said obturator is provided at one end of a vertically extending 
stem passing through the float. This obturator consists of a seat-engaging 
surface. 
As for the first embodiment, the evaporation chamber is advantageously 
defined between the inner wall of the closed reservoir and the outer wall 
of another reservoir located inside the closed reservoir in coaxial 
position with respect thereto. 
The other components of this pump are similar to those defined above for 
the first form of embodiment of the subject invention. 
An improved functioning of the pump according to the subject invention is 
achieved when the following conditions are met: 
(1) The hot surface is at such an elevated temperature and has such a high 
thermal inertia that the evaporated liquid produces and maintains the 
pressure necessary for discharging the liquid. 
(2) The surfaces in contact with the liquid to be pumped have a low thermal 
conductivity to avoid any further condensation of vapor on walls cooled by 
the said liquid, and any elevation of temperature; if this characteristic 
is not satisfied, a lowering of pressure inside the pump as well as a 
needless reheat of the liquid may occur. 
(3) The quantity and flow of the sampled liquid are sufficient to generate 
and maintain a pressure corresponding to the height of the column or 
pressure to overcome, during all the emptying of the pump. 
(4) The surface of liquid in contact with vapor is reduced to the minimum 
and insulated for avoiding any further condensation of vapor. 
(5) The means for sampling the liquid to be vaporized, for opening and 
closing the valves and the vapor exhaust valve are passive, i.e. subjected 
to the rise of the level of liquid as well as to the internal pressure of 
the pump without interference of any external electrical or mechanical 
control elements.

BRIEF DESCRIPTION OF THE DRAWINGS 
The pump shown in FIG. 1, comprises a tightly closed reservoir (1) and 
another reservoir (2) located inside the closed reservoir (1) in coaxial 
position with respect thereto. 
The reservoir (2) is slightly separated from the reservoir (1) to define 
between their walls a small available space called an evaporation chamber 
(3). The closed reservoir (1) is made of a heat-conductive material and is 
heated by means of an external heat source (4). The other reservoir (2), 
which is made of an insulating material, is completely open on top and has 
a small aperture (5) at the bottom. An insulating float (14) is enclosed 
with the other reservoir (2). 
The pump also comprises a condensed liquid inlet pipe (6), a vapor exhaust 
valve (7) for balancing the pressure between the pump and the remaining 
part of the system, and a liquid exhaust pipe (8). 
The functioning steps of this pump will now be described. 
When the reservoir (2) is empty and the pressures are balanced, the liquid 
to be pumped is discharged by gravity in the reservoir (2) through pipe 
(6) via the oneway valve (9) lowered by means of the pressure of the 
column of liquid in said pipe (6). In order to avoid that the liquid 
discharged in reservoir (2) enters evaporation chamber (3) and comes into 
contact with the hot wall of the closed reservoir (1), a first obturator 
(10) closes the aperture (5) at the bottom of the reservoir (2). This 
first obturator (10) is operated by the float (14). Said first obturator 
(10) is mechanically interconnected to a second obturator (12) which is a 
component of vapor exhaust valve (7), each obturator being provided at the 
ends of a rigid stem (11). Said stem (11) has such a length that the 
closure of the aperture of the vapor exhaust valve (7) by the second 
obturator (12) occurs simultaneously with the opening of the discharge 
aperture (5) by the first obturator (10), and vice versa. The vapor 
exhaust valve (7) is connected to a vapor exhaust pipe (13) through which 
vapor may escape when the valve (7) is opened. Such an opening allows one 
to balance the pressure inside the closed reservoir (1) with the pressure 
over the liquid to be delivered by gravity into the reservoir (2) through 
the inlet pipe (6). As the reservoir (2) is filled up, the float (14) made 
of insulating material, which initially was leaning against the base of 
the first obturator (10), raises. When it reaches the base of the second 
obturator (12), it lifts it to close the aperture of the vapor exhaust 
valve (7). As a result, the aperture (5) at the bottom of the reservoir 
(2) is freed, which enables the discharge of liquid in the evaporation 
chamber (3). 
The outer wall of the closed reservoir (1) being maintained hot by means of 
the continuously operating heating sleeve (4) extending all around it, 
when in contact therewith, the liquid which escapes through the aperture 
(5) instantaneously evaporates so as to create a sudden elevation of 
pressure into the pump. The inlet valve (9) therefore closes and the 
liquid exhaust valve (15) opens to expel the liquid accumulated in the 
reservoir (2) through pipe (8). As the liquid level lowers, the pressure 
kept elevated by the discharge of the liquid through the aperture (5) 
maintains closed the aperture of the vapor exhaust valve (7). When the 
reservoir (2) is empty, the weight of the float (14) leans against the 
lower obturator (10) which closes the aperture (5) at the bottom and which 
forces the upper obturator (12), held in position by the internal 
pressure, to free the aperture of the vapor exhaust valve (7). The 
pressure being balanced between a given system and the pump, the valve (9) 
opens again to let the liquid fill up the reservoir (2). The cycle 
therefore repeats itself. 
According to another embodiment of the invention shown in FIG. 2, the 
discharge of liquid in the evaporation chamber (3) is carried out by means 
of a self-priming siphon (16), positioned inside the other reservoir (2) 
in such a manner that it becomes operative when the level of the liquid in 
said reservoir (2) has reached its predetermined value. Said siphon (16) 
has the same function as the aperture (5) (cf. FIG. 1) at the bottom of 
the other reservoir (2). 
As for the first embodiment, the float (14) actuates the mechanism of the 
obturator (12) of the vapor exhaust valve (7). Said valve (7) operates in 
counteraction to the actuation of the siphon (16). The obturator (12) is 
provided at one end of a vertically extending stem (11) passing through 
the float (14). 
In FIG. 3, a thermostat is shown associated with the heating sleeve 
surrounding reservoir 1. Condensate is collected in the heat exchanger 
which is equipped with heating coils.