[0001] This invention relates to a pressure switch for controlling air conditioning systems
and the like.
[0002] In an air conditioning system, control means must be provided for activating and
deactivating the compressor, operating the fan and effecting auxiliary actions.
[0003] All these actions are required to be effected when the conditioning fluid pressure
reaches and/or exceeds predetermined values.
[0004] For example, Italian patent application MI93A000836 describes a pressure sensor device
controlling an air conditioning system or the like on three levels.
[0005] In the device illustrated in this patent application, the functions required of the
air conditioning system are implemented by the action of small stems acting on diaphragms
which pass from a convex configuration to a concave configuration, hence interacting
with a respective switch.
[0006] In this manner an electrical circuit is opened/closed, followed by the activation/deactivation
of the apparatus connected to it. In this device three pressure levels, say low, medium
and high, are concerned.
[0007] There is however a currently very strong requirement for the use of a fourth pressure
level in operating and controlling the air conditioning system, for example for safety
operations or for intermediate loading arrangements, etc.
[0008] However because of the development philosophy of traditional pressure switches, adding
a further pressure level creates considerable problems. In this respect, if the inventive
concept of the said patent application is followed, adding a new pressure level is
equivalent to providing the three-level device with an arrangement of elements which
is a simple repeat of arrangements which individually act on a single level.
[0009] This simple provision of new elements obviously results in increased overall dimensions,
increased weight and a proportionally increased cost. In addition, as the number of
mechanical elements increases, the pressure switch assembly becomes more articulated
and difficult, whereas its reliability decreases (being inversely proportional to
the number of said pieces).
[0010] An object of the present invention is to provide a pressure switch device which obviates
said problems of the state of the art. A further object is to provide a device which
is reliable, is of small overall size, and comprises the smallest possible number
of mechanical elements or pieces.
[0011] This object is achieved according to the present invention by a four-level regulator
for fluid-operated air conditioning systems, comprising a casing containing a first,
a second and a third electrical switch which are positioned in parallel within said
casing and act on respective electrical circuits, said switches including respective
fixed contacts and respective movable contacts, each of these including a push-rod
slidable between a withdrawn rest position and an advanced position for causing the
respective movable contact to move by the action of a respective substantially cap-shaped
elastic member, said substantially cap-shaped elastic members being definable between
an inwardly-turned rest configuration and an outwardly-turned configuration, the casing
also containing auxiliary return elements for facilitating the snap return of said
cap-shaped elastic members, between the fluid and the switches there being provided
an elastically deformable sealed retention diaphragm, said regulator being characterised
in that one of said elastic members and the push-rod connected to it are holed, said
casing containing a further fourth switch with a respective fixed contact and movable
contact acting on a relative electrical circuit, said fourth switch including a push-rod
inserted through said one of said elastic members and through said push-rod connected
to it, and operated by a fourth substantially cap-shaped elastic member definable
between an inwardly-turned rest configuration and an outwardly-turned configuration.
[0012] Advantageously said cap-shaped elastic members consist of metal discs of different
thicknesses, with a central part projecting from the remaining contour of the disc,
they being stacked to offer different resistances to axial force.
[0013] A series of important advantages derive from the aforesaid characteristics, including
the following:
- reduced axial and longitudinal dimension of the regulator;
- the form of the switches ensures minimum mounting tolerances, making it possible to
dispense with additional final setting operations;
- the constituent elastic elements of the movable contacts, formed from superposed thin
metal pieces, ensure considerable contact pressure with the switch closed and a considerable
return force on opening;
- the shape of the casing provides considerable electric wiring flexibility by cable
or connector exits of various types, without this involving alterations or structural
modifications to the regulator.
[0014] Further characteristics and advantages of the present invention will be more apparent
from the description thereof given hereinafter by way of non-limiting example with
reference to the accompanying figures.
Figure 1 is a perspective view of a four-level pressure regulator according to the
present invention;
Figure 2 is an exploded view of the regulator of Figure 1;
Figure 3 is an exploded view of a detail of the regulator of Figure 2;
Figure 4 is an exploded view of a second detail of Figure 2; and
Figure 5 is a detail of an elastic member inserted into a regulator according to the
present invention.
[0015] In Figure 1 the reference numeral 10 indicates a four-level regulator according to
the present invention. It consists of a threaded connector 21, a cap 22 and electric
cables 23 leaving the cap 22 and connected to apparatus (for example a compressor
or a fan), not shown.
[0016] Figure 2 shows the regulator 10 of Figure 1, in exploded view. At the bottom there
is the threaded connector 21, which is mounted on a conditioning fluid line of the
air conditioning system. The regulator is made to operate by the pressure in said
line. In contact with said connector 21 there is a seal gasket 24 on which a diaphragm
25 of high-strength elastic material rests. This material is advantageously kapton,
the flexibility, elasticity, mechanical strength and lightness of which make it excellent
for use. On the diaphragm there rest three groups of discs 26, 27 and 28 respectively,
acting as elastic members. Elastic members of different elasticity are obtained by
varying the size, thickness and number of the relative discs. From the figure it can
be seen that the two elastic members 26 and 27 are composed of two discs each, whereas
the member 28 is composed of three discs. Above the group of three discs 28 there
is a holed rigid spacer 29, on which there bears a holed disc 30 acting as the further
fourth elastic member.
[0017] Each of the first three elastic members 26, 27 and 28 interacts with a respective
push-rod 31, 32 and 33; the push-rod 33 is inserted through the hole in the spacer
29 and disc 30. On the disc 30 there acts a push-rod 34 of substantially different
shape from that of the other stem-like push-rods. In this respect, it comprises two
lateral flanges of lesser height but greater radial dimension than the other push-rods,
and is holed in the centre to allow insertion of the underlying push-rod 33. The said
push-rods act as operating elements for the movable contacts of the electrical circuits
to be opened or closed. The said groups of discs are housed in suitable circular seats
provided in a disc support 35. Above this latter there is a second support 36 containing
the movable contacts (in the form of blades fixed at one end), which are made to close
or open by the said push-rods.
[0018] The regulator is completed by a cap 22, which when assembly is complete covers and
seals all the aforesaid elements.
[0019] Figure 3 is an exploded view showing the unit comprising two axially aligned elastic
members already described with reference to Figure 2. In Figure 3 the movable contact
on which the push-rods 33 and 34 act is shown in greater detail. Specifically, the
contact is in the form of a thin blade 41 pivoted at one end 40 and caused to move
by the push-rod 34, in order to open or close a first electrical circuit. Straddling
the blade 41 there is a bridge 43. The blade 41 comprises a U-shaped cut defining
a part 44 (positioned in correspondence with the bridge 43) which is moved by the
push-rod 33. This interaction between the push-rod 33, the part 44 of the blade 41
and the bridge 43 results in the opening/closure of a second electrical circuit. The
elements indicated by the reference numerals 40 to 44 are all contained in the support
36, which on the opposite side to these houses a cut-out circuit 37.
[0020] Figure 4 further illustrates the structure of the support 36, and shows all the elements
involved in achieving electrical contact by the movement of said push-rods. Specifically,
the push-rods 31 and 32 act on the blades 43 and 45 respectively, which are fixed
at one end by rivets 47 and 48. The mechanism of action of the push-rod 33 has already
been described.
[0021] Auxiliary return means, not shown for simplicity, are provided for returning the
elements from their working position to their rest position.
[0022] The principle of operation of the regulator is as follows.
[0023] The elastic members 26, 27, 28 and 30 are formed with different levels of elasticity,
so that the devices to which they are connected are made to operate when different
pressure thresholds or values are attained. In this respect, when in the rest state
the constituent discs of the elastic members are in an inwardly-turned convex configuration
with the convex part facing the kapton diaphragm 25 and in contact with it. The fluid
enters the regulator through the threaded connector 21 and acts on the diaphragm 25.
The fluid pressure deforms the diaphragm, which however on its opposite side encounters
strong resistance by the series of discs of inwardly-turned convex configuration.
On exceeding predetermined pressure thresholds the discs pass from an inwardly-turned
convex configuration with that part emerging from the disc contour facing the diaphragm,
to an outwardly-turned concave configuration in which the concavity faces the diaphragm.
The pressure at which this configuration change occurs is determined essentially by
the elasticity of the relative elastic member.
[0024] This configuration change results in an induced movement of the push-rods 31, 32,
33 and 34 connected to the elastic members, which by way of respective rivets then
open or close electrical circuits. The relative electrical commands are then transferred
via the cables 23 leaving the regulator.
[0025] It is of particular interest to describe the operation of the elastic members 28
and 30, which are aligned according to the invention. Of these the more elastic is
the member 30 because it is composed of only one disc, having a lower resistance than
the group of three discs forming the member 28.
[0026] As the fluid pressure increases, the diaphragm 25 exerts an increasing force on the
member 28. This does not change its configuration from outwardly-turned to inwardly-turned
because a pressure sufficient for this has not yet been attained. The force is hence
transmitted practically unaltered to the spacer 29 which, being in intimate contact
with the disc 30, causes the configuration of the disc 30 to snap from outwardly-turned
to inwardly-turned when the fluid pressure reaches a first predetermined level. The
disc 30 then urges the push-rod 34 to act on the blade 41 so that it makes contact
with the relative rivet 42.
[0027] Only at a higher pressure level does the configuration of the elastic member 28 also
snap-change, causing the push-rod 33 to move and hence act on the blade 41 at its
cut part 44, which hence makes contact with the bridge 43.
[0028] The operation of the other two elastic members 26 and 27 is totally analogous. When
the pressure reaches suitable levels, the diaphragm 25 transfers to the discs, which
form said elastic members, a force sufficient to change their configuration from outwardly-turned
convex to inwardly-turned concave. This change results in movement of the relative
push-rods 31 and 32 and operation of the relative electrical contacts. This entire
mechanism is clearly shown in Figure 5, from which the outwardly-turned convex configuration
of the elastic member 26 can be seen. These movements are opposed by auxiliary return
means which, when the fluid pressure again falls below the respective critical values,
return the elastic members to their outwardly-turned convex rest configuration. These
auxiliary return means, which in Figure 5 are shown for example as a thin plate 51,
can generally consist of thin plate elements, flat springs acting on said movable
contacts, helical springs, linear springs etc.
1. A four-level regulator for fluid-operated air conditioning systems, comprising a casing
containing a first, a second and a third electrical switch which are positioned in
parallel within said casing and act on respective electrical circuits, said switches
including respective fixed contacts and respective movable contacts, each of these
including a push-rod slidable between a withdrawn rest position and an advanced position
for causing the respective movable contact to move by the action of a respective substantially
cap-shaped elastic member, said substantially cap-shaped elastic members being definable
between an inwardly-turned rest configuration and an outwardly-turned configuration,
the casing also containing auxiliary return elements for facilitating the snap return
of said cap-shaped elastic members, between the fluid and the switches there being
provided an elastically deformable sealed retention diaphragm, said regulator being
characterised in that one of said elastic members and the push-rod connected to it
are holed, said casing containing a further fourth switch with a respective fixed
contact and movable contact acting on a relative electrical circuit, said fourth switch
including a push-rod inserted through said one of said elastic members and through
said push-rod connected to it, and operated by a fourth substantially cap-shaped elastic
member definable between an inwardly-turned rest configuration and an outwardly-turned
configuration.
2. A four-level regulator as claimed in claim 1, characterised in that said cap-shaped
elastic members consist of metal discs.
3. A four-level regulator as claimed in claim 2, characterised in that said cap-shaped
elastic members have different elasticities.
4. A four-level regulator as claimed in claim 1, characterised in that said auxiliary
elastic return means consist of flat springs acting on said movable contacts.