Blocking valve for refrigeration or air conditioning systems

Blocking valve for refrigeration or air conditioning systems, of the type which includes: a hermetic compressor driven by an electric motor, a condenser, an evaporator, a capillary tube between the condenser and the evaporator, and a blocking valve between the condenser and the capillary tube. The blocking valve has a housing (42) defining an inside chamber with inlet and outlet passage in fluid communication with the condenser (31) and, respectively, with the capillary tube (32). A magnetic slide (41) installed in the chamber can be displaced between an opening position and a closure position of the valve. Electromagnetic elements (46, 47) assembled in the housing (42) are selectively and automatically energized during a period of time sufficient to cause the displacement of the slide (41) from one operating position to another in accordance with an operating condition of the system, the slide (41) being retained in its operating positions by action of non-electromagnetic forces.

BACKGROUND OF THE INVENTION 
This invention refers to refrigeration or air conditioning systems which 
use capillary tubes as a control element and, more specifically, to a 
blocking valve for these systems. 
Refrigeration and air conditioning systems essentially consist of a 
compressor, a condenser, a capillary tube and an evaporator. 
In these systems, when the evaporator temperature reaches a predetermined 
value and the compressor is switched off, there occurs the migration of 
the heated fluid from the condenser side (the high pressure side) to the 
evaporator (low pressure side). This migration of the refrigerant to the 
evaporator at each stop of the compressor causes a loss of the cooling 
capacity in the system (approximately 6% in systems which use 
reciprocating compressors and 12% in systems which use rotary 
compressors), since the refrigerant, besides heating the evaporator, must 
be compressed once again at each new start of the compressor, when the 
normal operation cycle of the system is reestablished, that is, when the 
pressure and temperature levels are reestablished in each unit of the 
system. 
A first known solution to solve this problem involves the use of a solenoid 
valve, installed between the condensor and the capillary tube. In this 
type of system, the valve is energized simultaneously with the stop of the 
compressor (rotary compressor), preventing the refrigerant from flowing 
from the condenser to the evaporator. 
One problem of this solution is that the valve remains energized during the 
stop of the refrigeration system, and consequently, during the stop of the 
compressor, consuming during that time a considerable amount of energy. 
Another known solution is described in the patent document GB 2121942 A. 
This system includes a one-way valve (26) installed between the suction 
side (21a) of a compressor (21) and the evaporator (25) to prevent the 
refrigerant flow from the side of the suction to the evaporator. A 
pressure responsive type valve (37) is installed between the condenser and 
the evaporator (25) to prevent the flow of the fluid from the condenser 
(22) to the evaporator (25) during the stop of the compressor (21). A 
connection tube (34) is connected between the valve (37) and the suction 
side (21a) of the compressor (21) to transmit the pressure from the 
suction side to the valve. The closure of the valve (37) is controlled by 
the suction pressure from the compressor (21). When the compressor (21) 
suction pressure becomes higher than a given predetermined value, it acts 
on the valve (37) preventing the passage of the refrigerant fluid from the 
condenser to the evaporator. 
This solution has the inconvenience that it can only be applied to 
refrigeration systems which use rotary compressors, since this valve (37) 
is controlled by the pressure of the refrigerant gas which returns through 
the suction line during compressor (21) stops. 
This return of the refrigerant gas through the suction line after the 
compressor stops, occurs due to the constructive characteristics of the 
rotary compressors. In this type of compressor, the refrigerant gas, 
discharged at a high pressure into the housing, leaks through the 
mechanical assembly to the suction side, which effect is used to activate 
the valve (37). 
In reciprocating compressors, this effect of the refrigerant gas leakage 
through the mechanical assembly to the suction line does not occur, thus 
making impossible the use of this type of valve in systems using 
reciprocating compressors. Another inconvenience of this solution is the 
number of welds to be performed in the tubing due to the requirement of at 
least one additional tube (34) in the refrigeration circuit. This tube 
(34) is required for measuring the pressure of the suction line (21a). 
OBJECTS OF THE INVENTION 
The objective of this invention is to provide a blocking valve for 
refrigeration and air conditioning systems which may be applied both in 
systems which use rotary compressors and in systems using reciprocating 
compressors. 
A further objective of this invention is to provide a blocking valve for 
refrigeration and air conditioning systems which have a low power 
consumption. 
Still another objective of this invention is to provide a blocking valve 
for refrigeration air conditioning systems, which does not require the 
installation of additional tubes in the mentioned systems, thus reducing 
the number of welding operations to a minimum. 
BRIEF DESCRIPTION OF THE INVENTION 
The above objectives are obtained with a blocking valve to be installed in 
refrigeration or air conditioning systems, of a type having a hermetic 
compressor driven by an electric motor; a condenser and an evaporator, 
connected, respectively, at the compressor discharge and suction sides. 
There also is a capillary tube type control element installed between the 
condenser and the evaporator; and a blocking valve between the condenser 
and the capillary tube. 
According to this invention, the blocking valve comprises a housing 
defining an internal chamber with an inlet passage in fluid communication 
with the condenser and outlet passage in fluid communication with the 
evaporator. A magnetic slide is assembled inside the chamber, in a way 
that it can be displaced between a non-operative position, maintaining 
open the inlet and outlet passage and an operative position, sealing the 
outlet opening. Electromagnetic elements assembled to the housing are 
selectively and automatically energized, preferably by the electric motor 
circuit, for a period sufficient to cause the displacement of the magnetic 
slide valve from one operational position to another according to the 
energization of the compressor electric motor. The retention of the 
magnetic valve slide in its inoperative and operative positions is 
accomplished by the action of non-electromagnetic forces acting on the 
magnetic slide at least during the maintenance of same in the respective 
inoperative or operative position. 
In a preferred form of the invention, the housing in which the magnetic 
slide is lodged has two tubular parts assembled concentrically. The 
internal tubular part is of a non-magnetic material and is externally 
provided with opening and closing coils. The external tubular part is of a 
ferromagnetic material and is externally assembled over the opening and 
closing coils which are fastened to the mentioned inner tubular part of 
the housing. 
In this preferred form of invention, the opening coil is connected in 
series with the electric motor start winding. Consequently, the valve 
opening occurs simultaneously with the start of the motor, in which moment 
the opening coil is energized and the magnetic slide displaced to the 
opening position. The retention of the slide in this position occurs by 
the action of its own weight. The valve must, therefore, in this 
embodiment, be installed in a vertical position. 
The closing coil is connected in parallel with the motor terminals (main 
winding) at the same time the motor is switched off. The closing of the 
valve consequently occurs simultaneously with the disconnection of the 
motor, when it acts as generator during its deceleration, causing an 
electric current to circulate through the closing coil, which displaces 
the magnetic slide to the closing position. The retention of the slide in 
this position is accomplished by the difference of pressure between the 
high and low pressure sides of the system. 
The so constructed blocking valve presents a very reduced power consumption 
as, contrary to the conventional solution (solenoid valve), it does not 
remain energized during the standstill period of the system, but is only 
energized at the times the compressor stops and starts, which represents a 
fraction of a second. 
Besides, in the above described configuration, the current consumption of 
the power supply system occurs only in the moment of the valve opening, 
whilst its closing is made at the expense of the power generated by the 
motor at the moment it is switched off and, therefore, without any 
consumption of current from the power supply. 
Another advantage of the blocking valve is that it does not require the 
installation of additional tubings in the system, thus making unnecessary 
additional welding operations, which bring about more costs with tests and 
control. 
Another advantage is that this valve is electrically driven, thus acting 
independently of the pressures of the system. This is why it can be 
applied in systems which use both rotary and alternative compressors.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in FIG. 1, the refrigeration system has a hermetic compressor 30, 
a condenser 31, a capillary tube 32 and a evaporator 33. In systems using 
rotary compressors a one-way valve 34 (check valve) is usually installed 
between the compressor 30 and the evaporator 33. The function of this 
valve is to prevent the passage of the heated refrigerant gas from the 
housing of the compressor 30 to the evaporator 33 in moments of stoppage, 
of the system. 
In order to avoid the passage of the refrigerant gas from the condenser 31 
to the evaporator 33 through the capillary tube 32, during the compressor 
stoppage periods, the system uses a blocking valve 40 installed, in the 
example shown in the illustration, between the condenser 31 and the 
capillary tube 32. 
As shown in FIGS. 2 and 3, the blocking valve 40 has a magnetic slide 41 
which is moving inside the housing 42. The housing 42 is formed by an 
inner round tubular part 42a and an outside round tubular part 42b, 
concentrically assembled. As shown in the illustration, the inner tubular 
parts 42a is externally provided with opening 46 and closing 47 coils for 
producing an electromagnetic field. The outside tubular part 42b is 
assembled over the opening 46 and closing 47 coils, radially fastened to 
the inner tubular part 42a by means of an intermediate ring 48 and a pair 
of end disks 42a by means of an intermediate ring 48 and a pair of end 
disks 49a and 49b, these latter defining, together with the inner tubular 
part 42a, a chamber in the inside of which slide 41 shifts. 
One aspect regarding the construction of the housing 42 is that the inner 
tubular part 42a must be of a non-magnetic material, whilst the outside 
tubular part 42b, the ring 48 and the disks 49a and 49b must be of 
magnetic material in order that the electromagnetic fields from coils 46, 
47 acts on the slide 41 of valve 40 (see the flow lines represented in 
FIG. 2). The housing 42 is connected to the condenser 31 (the high 
pressure side of the system) by means of the holes 43 in the disk 49b and 
to the evaporator 33 (low pressure side of the system) by means of the end 
44 of the capillary tube 32. 
The magnetic slide 41 is provided with a sealing surface 45, which in its 
closing position is seated on end 44 of the capillary tube 32, closing the 
passage of the refrigerant to the evaporator 33. As shown in FIG. 3, the 
magnetic slide 41 has a preferably square cross section with chamfered 
edges, so that the slide 41 may shift freely between its two positions 
without compressing the refrigerant fluid inside the chamber. Other 
polygonal forms of the section may be adopted in the construction of the 
slide 41. 
The valve is operated by means of the circuits shown in FIGS. 4, 5 and 6. 
According to what is shown in FIG. 4, the electric circuit for operation of 
the blocking valve 40, is made up, in the illustrated preferred form, the 
blocking valve, by closing coil 47 and opening coil 46 and a two-way 
switch 50, connected to the electric circuit of the motor, which has a 
start winding 51, starting device 52, main winding 53 and operates from a 
power source 54. The electric circuit of the motor normally includes a 
starting capacitor 55 connected in series with the starting winding 51. 
The two-way switch 50 is normally operated by the system thermostat. 
The blocking valve opening takes place at the moment the motor starts when 
the starting switch 52 permits the temporary circulation of the current 
through the blocking valve opening coil 46, which is connected in series 
with the start winding 51 of the motor. By the temporary energizing of the 
opening coil 46, slide 41 is displaced to the position shown in FIG. 2, 
i.e. with its sealing end 45 separated from the refrigerant fluid outlet 
opening or end 44 of the capillary tube 32 which leads to the evaporator 
33. When deenergizing the start winding of the motor and, consequently, 
the opening coil 46, the slide 41 remains in its non-operative or valve 
opening position due to the action of its own weight, as the valve is 
assembled so as to have its inside chamber arranged at least approximately 
in a vertical manner. It should be, however, understood that the slide 41 
can be kept in its inoperative position by the pressure balance at the 
inlet and outlet openings of the chamber, supported by the provision of 
any mechanical device able to exert a slight elastic force on the slide, 
so as to force it lightly and constantly into the inoperative position. 
The closure of the blocking valve 40 occurs at the moment the motor is 
switched off, when the two-way switch 50 shifts from position A to 
position B, connecting in parallel the closure coil 47 of the valve 40 
with the main winding 53 of the motor, when the latter is still in 
deceleration movement. During this deceleration period, the motor acts as 
a power generator, imposing the temporary circulation of a current through 
the blocking valve closure coil 47 generated by the main winding 53. This 
causes the displacement of the slide 41 by magnetic attraction up to the 
closure position. 
One of the alternative forms of the electric circuit required to operate 
the blocking valve 40, is shown in FIG. 5. In this circuit, the closure 
coil 47 is connected in series with a temporizing device 56 of the PTC 
(positive temperature coefficient) type. 
The opening of the blocking valve 40 occurs in the same way as the one 
previously described with basis on the circuit of FIG. 4. 
The closure of the blocking valve 40 in this alternative circuit form takes 
place after the disconnection of the motor, when the two-way switch 57 
shifts from position A to position B, connecting the power source 54 to 
the closure circuit. 
When connected to the power source 54, the closure coil 47 is energized 
displacing the slide 41 to the closure position. The temporizing device 
56, which in this case is a PTC element, makes that the circulation of the 
current increase through the closure coil 47 temporary, limiting after a 
certain time the current value to a rather lower value that the initial 
one. 
One variation of this temporizing device 56 is shown in FIG. 6. This 
circuit has a diode 60 connected in series with a capacitor 61 and with a 
discharge resistor 62, the capacitor 61 and the discharge resistor being 
connected in parallel. 
With the deenergizing of the closure coil 47, after the complete stop of 
the motor according to the configuration of FIG. 4 or after the period 
established by the temporizer 56 according to the embodiments of FIGS. 5 
and 6, slide 41 remains in its operative position of valve closure by 
action of the pressure differential existing between the high and low 
pressure sides of the system. The opening of fluid outlet 44 from the 
valve chamber is dimensioned so as to warranty the application of a 
closing force on the slide 41 which is greater than the sum of all forces 
acting on the slide in the sense to separate it from the closure position 
in the condition of the deenergized opening coil 46. 
It should further be understood that the opening and closing 
electromagnetic forces which act on the slide are dimensioned to provide 
the safe displacing of the slide to its respective operating positions and 
further that the activation period of these forces are dimensioned to 
permit that the conditions of pressure in the system are reached, which 
are particular to each of the two operating conditions of same, 
represented by "compressor operating" and "compressor at standstill".