Technical Field

The present invention relates to a start-up unit for electric motors of compressors or the like.

Background Art

With particular reference to electric motors used for compressors or like machines, the use is known of a start-up unit connected to the electric motor and suitable for allowing the correct start-up and operation of the electric motor itself.

The start-up units of known type generally comprise a run condenser and a startup condenser connected together in parallel.

The start-up units of known type also comprise a relay of the electromechanical type connected to the start-up condenser and calibrated specifically according to the type of electric motor.

In particular, the electromechanical relay is suitable for connecting the start-up condenser in parallel to the run condenser during the starting phase of the electric motor of the compressor and is suitable for disconnecting the start-up condenser at the end of such starting phase.

The start-up units of known type can also comprise a containment box inside which the run condenser, the start-up condenser and the electromechanical relay are fixed.

The three component parts are electrically connected the one to the other, inside the box, by means of suitable wiring cables.

The start-up units of known type have however a number of drawbacks.

In particular, during the fitting and the installation of the start-up unit, the startup condenser, the run condenser and the electromechanical relay must be suitably arranged and fixed inside the containment box and, afterwards, must be electrically connected together.

This necessarily requires a fitting and installation operation which is not simple and which is time consuming.

Furthermore, the dimensions of the two condensers and of the electromechanical relay, as well as the need to have enough room inside the box to make the necessary connections, results in a far from negligible overall dimension of the start-up unit.

Description of the Invention

The main aim of the present invention is to provide a start-up unit for electric motors of compressors or the like which allows to make the fitting and installation operations easier.

Another object of the present invention is to provide a start-up unit for electric motors of compressors or the like which has small overall dimensions.

Another object of the present invention is to provide a start-up unit for electric motors of compressors or the like which allows to reduce the risk of fire in case of a fault affecting the condensers.

Another object of the present invention is to provide a start-up unit for electric motors of compressors or the like which allows to overcome the mentioned drawbacks of the state of the art in the ambit of a simple, rational, easy and effective to use as well as low cost solution.

The above objects are achieved by the present start-up unit for electric motors of compressors or the like, comprising at least a run condenser which can be connected to at least an electric motor of a compressor or the like, at least a start-up condenser connected in parallel to said run condenser and at least a switch device connected to said start-up condenser and suitable for connecting said start-up condenser during a starting phase of said electric motor and for disconnecting said start-up condenser at the end of said starting phase of the electric motor, characterized by the fact that it comprises:

- at least a container for housing said run condenser and said start-up condenser;

- first electric connection means made on said container and connected to said run condenser and to said start-up condenser;

- at least a protection element associated with said container in correspondence to said first electric connection means and having said switch device;

- second electric connection means made on said protection element, connected to said first electric connection means and to said switch device and connectable to said electric motor.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more evident from the description of a preferred, but not sole, embodiment of a startup unit for electric motors of compressors or the like, illustrated purely as an example but not limited to the annexed drawings in which:

Figure 1 is an axonometric view of the start-up unit according to the invention; Figure 2 is an exploded view of the start-up unit according to the invention; Figure 3 is a partial section view of the start-up unit according to the invention; Figure 4 is an axonometric view which shows schematically the electric connections between the first and second electric connection means of the startup unit according to the invention;

Figure 5 is a general electric diagram of the start-up unit according to the invention.

Embodiments of the Invention

With particular reference to such figures, globally indicated by 1 is a start-up unit for electric motors used in compressors or the like.

The start-up unit 1, in particular, can be connected to an electric motor M of a compressor of conventional type and is suitable for allowing the correct start up and operation of the electric motor itself.

The start-up unit 1 comprises a run condenser 2 which can be connected to the electric motor M of the compressor and a start-up condenser 3 connected in parallel to the run condenser 2.

The start-up unit 1 also comprises a switch device 4 connected to the start-up condenser 3 and suitable for connecting the start-up condenser 3 during a starting phase of the electric motor M and for disconnecting the start-up condenser 3 at the end of the starting phase of the electric motor M.

In point of fact, during the starting phase of the electric motor M the switch device 4 is closed and connects the start-up condenser 3 in parallel to the run condenser 2.

At the end of the starting phase of the electric motor M, the switch device 4 is opened and disconnects the start-up condenser 3, leaving only the run condenser 2 connected to the electric motor M.

Advantageously, the start-up unit 1 comprises a single container 5 for housing the run condenser 2 and the start-up condenser 3.

In particular, the container 5 has first electric connection means, indicated altogether in the illustrations by the reference 6, connected to the run condenser 2 and to the start-up condenser 3.

The start-up unit 1 also comprises a protection element 7 associated with the container 5 in correspondence to the first electric connection means 6.

Advantageously, the protection element 7 has the switch device 4 and is also provided with the second electric connection means, indicated altogether in the illustrations by the reference 8.

The second electric connection means 8, in particular, are connected to the switch device 4, to the first electric connection means 6, and therefore to the run condenser 2 and to the start-up condenser 3, and can be connected to the electric motor M.

Usefully, as shown in detail below, the presence of a single container 5 of the run condenser 2 and of the start-up condenser 3, having first electric connection means 6, together with the presence of a protection element 7 with integrated inside it the switch device 4 and having second electric connection means 8 which can be connected to the first electric connection means 6, allows simplifying the fitting and installation operations of the start-up unit 1 and reducing the overall dimensions of the start-up unit itself.

Advantageously, the switch device 4 used in the start-up unit 1 and integrated inside the protection element 7 is made up of an electronically-controlled relay or of an electronic device having the same function.

The use of the electronically-controlled relay 4, instead of an electromechanical type relay as normally occurs in the state of the art, allows using the same relay for start-up units 1 for electric motors with different technical specifications, thus in fact limiting the relay versions to be used.

With particular but not sole reference to the embodiment of the start-up unit 1 shown in the illustrations, the container 5 comprises an external wrapping 9 made of metal material, preferably aluminium.

Usefully, the metal external wrapping 9 is hermetically closed and allows reducing the risk of fire in case of a fault affecting one of the condensers 2 and 3.

Preferably, the external wrapping 9 is substantially cylindrical and is provided at one extremity with an opening 10 for the introduction and electrical connection of the run condenser 2 and of the start-up condenser 3 during the assembly of the start-up unit 1.

The container 5 also comprises a cover 11 fixed to the external wrapping 9 in correspondence to the opening 10, for the hermetic closing of the opening itself. Preferably, the cover 1 1 is fixed to the edge of the opening 10 by seaming.

Different shapes and connections of the external wrapping 9 and of the cover 1 1 cannot however be ruled out.

Usefully, the container 5 comprises an internal wrapping 12 made of electrically insulating material .

Preferably, the internal wrapping 12 has a cylinder shape and is inserted substantially to measure inside the external wrapping 9.

Preferably, the run condenser 2 and the start-up condenser 3 have a cylinder shape, are housed in the internal wrapping 12 with the start-up condenser 3 arranged below with respect to the run condenser 2 and are immersed in a resin gel or liquid with excellent dielectric qualities suitable for mechanically and electrically protecting the condensers themselves.

An insulating element 13, substantially disk-shaped, is placed between the run condenser 2 and the cover 11, to ensure this is correctly fastened.

Usefully, the first electric connection means 6 are made in correspondence to the cover 11 of the container 5.

In particular, the first electric connection means comprise:

a first electric connector 14 electrically connected to the run condenser 2 by means of a first connection cable 15;

- a second electric connector 16 electrically connected to the start-up condenser 3 by means of a second connection cable 17;

a third common electric connector 18 electrically connected to both the run condenser 2 and the start-up condenser 3 by means of a third connection cable 19.

With particular reference to the embodiment of the start-up unit 1 shown in the illustrations, the insulating element has a first, a second and a third hole 20, 21, 22 to allow the first, second and third connection cable 15, 17 and 19 respectively to pass through from the run condenser 2 and from the start-up condenser 3 towards the first, second and third electric connector 14, 16 and 18. As shown in the illustrations, the protection element 7 is preferably made up of a cap with a substantially cup shape which, once fastened to the container 5, covers and protects the first electric connection means 6 and encloses inside it the electric connections with the second electric connection means 8.

Usefully, interlocking means are provided between the cap 7 and the extremity 23 of the container 5 having the first electric connection means 6.

In particular, such interlocking means comprise a protrusion 24 extending along the entire perimeter of the extremity 23 and which, once the start-up unit 1 has been fitted, is engaged inside a suitable groove 25 made on the inner surface of the cap 7, in the proximity of the edge of the opening of the cap itself and along the entire perimeter of such edge.

In particular, the protrusion 24 is made up of the edge of the cover 11 fixed to the external wrapping 9.

Advantageously, the second electric connection means 8 comprise a plurality of electric terminals 26, 27, 28 and 29 made in correspondence to an inner surface

30 of the cap 7 facing towards the first electric connection means 6.

In particular, with reference to the embodiment of the start-up unit 1 shown in the illustrations, each of the electric terminals 26, 27, 28 and 29 is made up of a respective connector of the so-called "faston" type with one or more blades depending on the number of necessary connections.

The use cannot however be ruled out of electric terminals of different type.

In particular, as shown in the figures 4 and 5, the second electric connection means comprise:

a first electric terminal 26, having two blades;

a second electric terminal 27, having just one blade; a third electric terminal 28, having four blades;

a fourth electric terminal 29, having three blades.

The first electric terminal 26 is connected to the first electric connector 14 on the container 5 by means of a cable 31 and can be connected to a first input 32 of the electric motor M by means of a cable 33.

The second electric terminal 27 is connected to the second electric connector 16 on the container 5 by means of a cable 34.

The third electric terminal 28 is connected to the third electric connector 18 on the container 5 by means of a cable 35 and can be connected to a second input 36 of the electric motor M by means of a cable 37, to a power supply line by means of a cable 38 and, if necessary, to a cooling fan V of the compressor by means of a cable 39.

The fourth electric terminal 29 is connected to the electronically controlled relay 4, to pilot its opening and closing, and can be connected to a third input 40 of the electric motor M by means of a cable 41, to the supply line by means of a cable 42 and, if necessary, to the cooling fan V by means of a cable 43.

Advantageously, the electronically controlled relay 4 is connected between the first electric terminal 26 and the second electric terminal 27 and is suitable for connecting the first electric terminal 26 to the second electric terminal 27 during the starting phase of the electric motor M and for disconnecting the first electric terminal 26 from the second electric terminal 27 at the end of said starting phase of the electric motor M.

Usefully, a discharge resistance of the start-up condenser 3, not shown in the illustrations, is fitted directly in the electric circuit inside the protection element, between the second electric terminal 27 and the third electric terminal 28.

Usefully, the cap 7 comprises two U bolts 44 for tightening the cables which go to the electric motor M, to the cooling fan V and to the power supply line.

Usefully, the earth terminal can be obtained directly on the metal external wrapping 9 of the container 5, in correspondence to the fastening tang 45 arranged on the bottom of the container 5 and used to fasten the run condenser 2 and the start-up condenser 3.

Usefully, the start-up unit 1 comprises means for interrupting the electric connection between the run condenser 2 and/or the start-up condenser 3 and the first electric connection means 6, suitable for intervening in case of a fault in the condensers themselves.

In particular, such interruption means comprise a fold 46 of the side wall of the external wrapping 9, which extends along the entire perimeter in the proximity of the extremity 23.

The interruption means also comprise at least one thin section 47 present on at least one of the electric connection cables 15, 17 and 19, preferably on the third connection cable 19 which connects the third electric connector 18 to the run condenser 2 and to the start-up condenser 3.

In case of a fault of the run condenser 2 and/or of the start-up condenser 3, a gas develops inside the container due to the decomposition of the film making up the condensers themselves.

The increase in gas inside the container 5 leads, consequently, to an increase in pressure inside the container itself.

This results in turn in the stretching of the fold 46, with consequent moving away of the extremity 23 from the rest of the external wrapping 9 and traction of the third connection cable 19 until the breakage of the thin section 47.

The interruption of the electric connection with the run condenser 2 and with the start-up condenser 3 thus allows avoiding the further development of gas and the explosion of the start-up unit 1.

It has in practice been ascertained how the described invention achieves the proposed objects.

In particular, the fact is underlined that the presence of a single container of the run condenser and of the start-up condenser, having first electric connection means, together with the presence of a protection cap with integrated inside it the electronically controlled relay and having second electric connection means connectable to the first electric connection means, permits simplifying the fitting and installation operations of the start-up unit and reducing the overall dimensions of the start-up unit itself.

Furthermore, the presence of a single metal external wrapping, together with the presence of interruption means of the electric connection of the condensers, allow reducing the risk of explosion in case of a condenser fault.

Furthermore, the use of an electronically controlled relay, instead of an electromechanical type relay as commonly occurs in the state of the art, allows using the same relay for start-up units for electric motors with different technical specifications, thus in fact limiting the relay versions to be used.