Device for regulating compressors or aspirators

BACKGROUND OF THE INVENTION

Specifically, though not exclusively, the invention is usefully applied in dental aspirating apparatus.

In the following description and in the accompanying figures reference is made to an aspirator (a suction or “vacuum” pump) but all of the description could also be applied to compressors.

Aspirators are much-used in dental aspiration plants where a depression has to be created in connection with suction tubes.

It is well-known that the coils of electric motors actuating the aspirators are subject to heating-up: this heating-up increases as the current supply absorbed by the motor increases, which in turn increases in line with the degree of depression required.

To limit this heating-up, a valve is usually provided, usually arranged in the aspiration conduit connecting the aspirator to the environment in which the depression is to be created. When the valve is opened it places the aspiration conduit (or the above-mentioned environment) in connection with the outside. This valve is opened when a predetermined pressure difference is reached between the outside environment and the inside environment, which corresponds to a predetermined electrical current which crosses the motor coils. In this way, without stopping the machine, excessive heating-up is avoided due to over-heating of the motor coils.

The problems encountered with compressors when the internal pressure increases are very similar.

The heat produced by aspirators is dispersed in the outside environment. For this reason the manufacturers always recommend that the machines be located in well-aired and cool places in order for the machine to perform optimally. Unfortunately, for reasons of space, aesthetic preference, or in order to avoid any irritation that might be caused by the admittedly low noise level of aspirators, these machines are often arranged in small and closed places, generally lacking in air; sometimes they are even kept away from the outside environment.

In these conditions, the heat dispersed by the aspirators causes considerable build-up of heat in the surrounding atmosphere, with a consequent heating of the aspirator to beyond realistic limits, causing deterioration in its performance or even faulty functioning and, in particularly grave cases, or in the absence of devices blocking the motor when it reaches dangerous temperatures, a fire hazard. All of the above can happen without the electric current in the coils reaching levels which correspond to a depression level warranting the interjection of the above-cited valve, which would reduce electric current absorption and thus reduce the heat produced by the machine.

If there is a thermal cut-off protection for the motor, a frequent case, the motor is shut down before the aspirator reaches its maximum potential. To prevent machine shut-down, or to reduce its occurrence to an absolute minimum, sometimes the manufacturers themselves calibrate the pressure-differential valves to more prudent levels, thus in effect lowering the potential of the machine and doing an injustice to those users who carefully follow the instructions provided with the machine and locate the aspirator in a correct ambience in order to allow plenty of ventilation.

The main aim of the present invention is to obviate the above-cited drawback in the prior art, by providing a device for regulation of compressors and aspirators which enables the machines to function at maximum potential when the conditions of the outside environment are optimal, but which reduces the machine's performance level when there is an imperfect surrounding environment.

A further aim of the invention is to prevent excessive heating-up of the machine without having to shut the machine down.

An advantage of the device is that it can be applied easily to existing machines. These aims and more besides are all attained by the invention as it is characterized in the claims that follow.

SUMMARY OF THE INVENTION

In a delivery conduit for a compressor or an aspiration conduit for an aspirator, which connects the compressor or the aspirator to a closed environment, a first valve is inserted, and opening and a closing of which is commanded by a temperature of an external environment. The valve is normally closed for external temperatures which are lower than a predetermined level and open, placing the conduit in communication with the outside environment, when the external temperature exceeds the predetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will better emerge from the detailed description that follows, of a preferred but nonexclusive embodiment of the invention, illustrated purely by way of example in the appended figures of the drawings, in which:

FIG. 1

is a diagram of either an aspirator or a compressor of the type of the invention;

FIG. 2

is a detail of

FIG. 1

, in section and in enlarged scale, relating to the valve of the device of the invention;

FIG. 3

is a view in the direction indicated by arrow A in FIG.

2

.

DESCRIPTION OF THE PREFERRED EMBODIMENTS.

With reference to the figures of the drawings,

1

denotes in its entirety an aspirator, constituted by a pump

1

a

and an electric motor

1

b

, from an aspiration conduit

2

originates and connects the aspirator to a closed environment

13

. The aspirator extracts air from the closed environment

13

through the conduit

2

as shown by arrow A in

FIG. 1. A

discharge conduit

2

a

is connected to the aspirator

15

for removing the air aspirated therefrom as shown by arrow B in FIG.

1

.

Leading out of the aspiration conduit

2

there is a cylindrical sleeve

5

, a first end

5

a

of which is connected to the aspiration conduit

2

and a second end of which

5

b

is connected to the outside environment. An annular seating

9

is afforded in the sleeve

5

, to which an obturator

7

, predisposed inside the sleeve

5

, is associated.

The obturator is normally in a closed position, i.e. pressed against the seating

9

, in which position the obturator

7

prevents passage of air through the sleeve

5

.

The obturator

7

is kept pressed against the seating

9

by an elastic element, in the illustrated embodiment a helix spring

8

, which is preloaded at a predetermined load, and is loaded against the opening of the obturator

7

. A chamber is afforded inside the obturator

7

, which chamber

10

is filled with a material having a high heat-dilation coefficient, for example a thermometric liquid. An end of a rod

11

projects from the chamber

10

, which rod

11

is slidable in an axial direction and another end of which is inserted in the chamber

10

, sunk in the thermometric liquid. The section of the exit hole of the rod

11

from the chamber

10

is completely occupied by the section of the rod

11

itself, in order to prevent any exiting of material from the chamber

10

. A striker element

12

, fixed with respect to the sleeve

5

, is constrained to the end of the rod

11

projecting from the chamber

10

. This striker element

12

, which in the figures is illustrated as a metal bar arranged diametrically and constrained to the ends of the external surface of the sleeve

5

, is arranged in such a way that it obstructs an externalwise sliding by the rod

11

. For this purpose the striker element

12

is arranged above the end of the rod

11

which exits from the chamber

10

.

The above-described device realises a first valve

4

and a second valve

6

which have a common seating and obturator, and therefore which both act in opening or closing the connection between the aspiration conduit

2

and the outside environment. The two valves are, however, differently controlled and are independent from each other, and are functionally different and distinct. The opening and closing of the first valve

4

is commanded by the temperature in the outside environment. When the outside temperature increases, the material contained in the chamber

10

dilates and pushes the rod

11

externalwise; the rod

11

then pushes against the striker element

12

and thus pushes the obturator

7

away from the seating

9

, opening the valve

4

and placing the aspiration conduit

2

in communication with the outside environment. The quantity of thermometric material, the section of the rod

11

and its initial distance from the striker element

12

are calculated in such a way as to cause an opening of the valve when the external temperature rises above a predetermined level, normally comprised between 45° C. and 55° C.

The opening and closing of the second valve

6

is commanded by the difference between the closed environment

3

and the outside environment. When this difference, to which a precise absorption of electric current corresponds, and therefore a precise coil temperature, overcomes the load on the spring

8

, the obturator

7

distances from the seating

9

and opens the valve, setting the aspiration conduit

2

in communication with the outside environment. This functioning of the valve

6

, activated by a motor coil temperature of between 90° C. and 120° C., is similar to the functioning of known valves mounted on aspirators of known type.

When, in any one of the above-described ways, the connection between the aspiration conduit

2

and the outside environment is opened, the absorption of electric current by the aspirator motor is drastically reduced, as is the performance of the motor (which the user will notice in the guise of a fault), and the production of heat by the motor. The reduction of heat by the machine and/or an intervention by the user, i.e. making more cool air available to the machine in order to reduce the outside temperature in the surrounding atmosphere, cause the valves to close and bring the machine back into conditions of normal operation, without having to shut the machine down. The above-described device behaves as a normal, known-type overpressure valve for the current absorbed by the motor when the temperature is within normal parameters, while it becomes an added protection cutoff when the temperature limits are exceeded.

If the device is applied not on an aspirator but on a compressor, the 15 conformation of the device will be slightly different as air delivered to closed environment

13

will move in a direction opposite to that of arrows A and B as shown by arrows C and D. The device will be located on the delivery conduit, the obturator will open externalwise and the rod will move in an opposite direction against an internal striker element; but its functioning will be altogether similar to what is described above.