WO2007122578A1

WO2007122578A1 - Displacement compressor/aspirator for medical use with simplified assembly and assembly method

Info

Publication number: WO2007122578A1
Application number: PCT/IB2007/051467
Authority: WO
Inventors: Massimiliano Azzi
Original assignee: Massimiliano Azzi
Priority date: 2006-04-20
Filing date: 2007-04-20
Publication date: 2007-11-01
Also published as: ITVI20060119A1

Abstract

A displacement compressor/aspirator with simplified assembly, particularly for use in aerosol therapy and/or drainage of biological fluids, comprises a piston (17) held in a cylinder (20), a motor (10) operably coupled to the piston (17), a protective casing (2) for housing the motor (10), the cylinder (20) and the piston (17), a head (28) having an inlet conduit (29) and an outlet conduit (31). The casing (2) has an upper half-shell (5) and a lower half-shell (4) rigidly connected by first screw fastener members or the like (6). The cylinder (20) is integrally joined to the lower half-shell (4) of the casing (2) and is formed of one piece with the lower half-shell (4) or is rigidly joined thereto by second screw fastener means or the like (6'). The first (6) and second (6') fastener means are designed to be inserted from the exterior of one of the half-shells (4, 5) thereby simplifying operations and reducing assembly times.

Description

DISPLACEMENT COMPRESSOR/ASPIRATOR FOR MEDICAL USE WITH SIMPLIFIED ASSEMBLY AND ASSEMBLY METHOD

Field of the invention

The present invention is generally applicable to the field of apparatus for compressing and sucking fluids of any type, either at gas or liquid state, and particularly relates to a compressor/aspirator with simplified assembly.

In a preferred but non exclusive embodiment, the apparatus of the invention is designed for medical use and may be advantageously employed for aerosol therapy and/or drainage of fluids.

In a second aspect, the invention provides a method for simplified assembly of a displacement compressor/aspirator as mentioned above.

Background of the invention

Compressors/aspirators for aerosol therapy are well-known and available which essentially have a casing, normally formed of plastic, containing a compressor/aspirator unit driven by an electric motor, and having respective conduits for air intake and compressed air delivery to outside.

Compressed air is blown into a Venturi tube within a flask designed to collect the medicament to be nebulized and connected to a mask or mouthpiece for a user.

Prior art apparatus as briefly described above may be also used as aspirator devices for suction or drainage of fluids, such as air, water, oil, milk, serum, mucus or others, such as for tracheotomized patients. In both cases, the compressor/aspirator unit may be of various types, such as rotary, Roots or peristaltic, reciprocating diaphragm or cylinder-piston displacement types.

A preferred embodiment of the invention particularly provides a compressor/aspirator that uses a reciprocating displacement compressor/aspirator unit of the cylinder-piston type.

In such prior art apparatus the motor is typically mounted to the piston, cylinder and head to form a compressor unit, whereupon the assembled unit is placed in the casing and connected thereto by tubes. For simplified assembly, certain manufacturers have omitted the tubes and extended the intake and delivery conduits on the head of the compressor unit to lead them out of the casing.

US-B-6,318,360 discloses an aerosol therapy apparatus, whose casing has a lower half-shell and an upper half-shell, and in which the head on the compressor/aspirator unit is extended out of the casing. Nevertheless, in this prior art apparatus the compressor unit has to be assembled separately and its installation in the casing requires relatively complex and laborious operations.

Summary of the invention

A major object of the present invention is to further improve prior art apparatus, by providing a displacement compressor/aspirator of the cylinder-piston type, having a simplified construction and facilitated assembly and thereby providing advantages in terms of cost effectiveness.

A particular object is to provide a displacement compressor/aspirator that requires a small number of components and assembly steps, thereby minimizing the assembly time. A further object is to reduce the complexity and number of connection members between the various parts.

These and other objects, as better explained hereafter, are fulfilled by a displacement compressor/aspirator for medical use with simplified assembly, particularly for aerosol therapy and/or drainage of fluids, as defined in claim 1 , which comprises a piston located in a cylinder, a motor operably coupled to said piston for promoting its reciprocating motion, a protective casing for housing said motor, said cylinder and said piston, a head associated to said cylinder and having an inlet conduit and an outlet conduit for the fluid to be sucked in or compressed respectively, wherein said casing has an upper half-shell and a lower half-shell designed to be rigidly mutually coupled by first screw or similar fastener members, said cylinder being integrally joined to said lower half-shell of said casing.

Conveniently, the cylinder has a substantially flat bottom wall with a substantially cylindrical side wall extending therefrom, said cylinder being formed of one piece with said lower half-shell.

Preferably, the bottom wall of said cylinder coincides with a substantially flat portion of the bottom wall of said lower half-shell.

As an alternative, the cylinder is a separate attached element and its bottom wall is rigidly joined to said lower half-shell by said second screw or similar fastener members.

Thanks to this configuration, the cylinder need no longer be mounted to the motor in a prior assembly, and the piston simply has to be mounted in the cylinder, which latter becomes integral with the lower half-shell.

Also, conveniently the head is associated to the bottom wall from the exterior of said lower half-shell at the substantially flat bottom wall of said cylinder by second screw fastener members or the like. Furthermore, said first and said second screw fastener means or the like are designed to be inserted from the exterior of one of said half-shells, e.g. the lower one, to simplify the assembly process and reducing assembly times.

In a second aspect, the invention provides a method for assembling the compressor/aspirator, as defined in claim 19.

Advantageous embodiments of the invention are defined in accordance with the independent claims.

Brief description of drawings

Further features and advantages of the invention will be more apparent from the detailed description of a preferred, non-exclusive embodiment of the compressor/aspirator structure according to the invention, which is described by way of as a non-limiting example with the help of the annexed drawings, in which:

FIG. 1 is a partly fragmented side view of a displacement compressor/aspirator structure according to the invention;

FIG. 2 is a side view of the assembly of Fig. 1 with the upper part being removed for better visibility of inside parts;

FIG. 3 is a partly broken away front view of the structure of FIG. 1 , as taken along a plane Ill-Ill;

FIG. 4 is a partly sectioned side view of the structure of Fig. 3, as taken along the plane IV-IV; FIG. 5 is a top view of the structure of Fig. 2;

FIG. 6 is a bottom view of the structure of Fig. 2;

FIG. 7 is a partly exploded bottom perspective view of the structure of Fig.

1 ;

FIG. 8 is a perspective view of the compressor/aspirator of the invention, in which the upper half-shell 5 is separate from the lower half-shell 4;

FIG. 9 is a perspective view of the lower half-shell 4, in which the motor is removed; FIG. 10 is a perspective view of the lower half-shell 4 wherein the head 28 and the valves 26, 27 have been separated and an enlargement of the bearing area 50 is also provided.

Detailed description of a preferred embodiment

Referring to the above figures, a compressor/aspirator of the invention, overall designated by numeral 1 , may be employed as a portable apparatus for compression/suction of fluids in general.

In a preferred, non exclusive embodiment, the apparatus may be designed for aerosol therapy, in which case it will be provided in combination with a flexible tube T for connection to a nebulizer flask, which is not shown and is not part of the present invention.

Alternatively, the displacement compressor/aspirator according to the invention may be used for sucking in liquids such as water, oils, blood, serum, mucus and others, e.g. for tracheotomized persons.

The compressor/aspirator 1 essentially comprises a casing 2, typically formed of molded plastic or die-cast aluminum, within which a motor/compressor unit 3 is housed.

Advantageously, the casing has a lower half-shell 4 and an upper half-shell which are designed to be connected by first fastener members, preferably screws or threaded pins 6 or the like.

The lower half-shell 4 has a bottom wall 7 joined to side walls 8. Hollow columns 39, 39', 39", 39'" extend from the bottom wall 7 for the passage of the screws 6 which engage in corresponding seats formed on the inner surface of the upper half-shell 5. The terms lower and upper as used herein to define the half-shells 4, 5 are intended with particular reference to the configuration as shown in the annexed figures. Nevertheless, it will be understood that other arrangements for the half- shells 4 and 5 will be possible, e.g. right half-shell and left half-shell, without departure from the scope of the invention.

One of the two half-shells 4, 5 may be configured independently of the other to provide aesthetic variants, without the need to modify the other half-shell and the relevant mold. For instance, the upper half-shell 5 which, in the particular embodiment of the figure is the only visible part, as it almost wholly covers the lower half-shell 4, may be provided in any desired form, such as a toy-like form, and be formed of any material, possibly transparent. Light may be further provided inside the compressor/aspirator. Also, the half-shells may also be of different materials and color, to provide a pleasant aesthetic effect. A plurality of interchangeable upper half-shells 5 may be further provided, for connection with the same lower half-shell 4.

The motor/compressor unit 3 includes a conventional electric motor 10, having a cooling fan 11 fitted to a motor shaft 12 and with an armature connected by wires 13 to an external power line through a switch 14.

For the two half-shells 4, 5 to be joined together, latch prongs 35, 35', 35", ... are provided on the inner wall of the upper half-shell 5 for engagement with the edge 36 of the wall of the lower half-shell 4. These prongs 35, 35', 35", ... allow the upper half-shell 5 and the motor 10 to be spaced apart, thereby promoting heat dissipation. A path is thus created between the rear slits 37 and the air space between the inner wall of the upper half-shell 5 and the edge 36 of the lower half- shell 4, which allows free air flow therethrough.

The prongs 35, 35', 35",... further provide a strong and reliable structure. The configuration of the coupling grooves 38, 38', 38", ... further facilitates assembly thereby greatly accelerating it. The two half-shells 4, 5 may be joined together by means of special columns 39, 39', 39", 39'" and 40, 40', 40", 40'" extending from the two half-shells. Particularly, in the configuration with the two half-shells 4, 5 formed from different materials, the columns may have such a size as to impart maximized strength to the assembly, although less expensive materials or materials whose aesthetic value is higher than mechanical strength may be also employed. For example, if the upper half- shell 5 is formed of a weaker material than the lower half-shell 4, the lower columns 39, 39', 39", 39'" may be considerably longer than the upper columns 40, 40", 40", 40'".

Furthermore, the lower columns 39, 39', 39", 39'" may be located very close to the motor, thereby forming a highly sturdy, rigid cell which effectively holds the motor in place and damps vibrations. Thus, any motion of the motor relative to the lower half-shell 4 is reduced, and malfunctioning is prevented.

Supports 41 , 41' and 42, 42' may be provided in the upper and lower half-shells 4, 5 for holding the motor 10 in position. Also, in order to minimize vibrations of the latter, the supports 41 , 41' and 42, 42' may be equipped with elastic shock absorbers 43, 43' and 44, 440', preferably made of rubber.

This configuration has a vibration damping effect and effectively withstands horizontal stresses without imparting excessive motion to the motor, which would affect compression and performances of the pump. On the other hand, damped motion of the motor allows discharge of the overpressures caused by the asymmetry of the effort required of the motor by piston pumps. This provides higher performances using lower power motors.

Use of elastic shock absorbers 43, 43' and 44, 44' with an accurate selection of the shapes and materials employed, allows control of motor displacements in the cell, such selection influencing vibrational behavior and performances. The rubber of the elastic shock absorbers 43, 43' and 44, 44' may have a hardness in a range from 30 to 80 Shore A. Practical tests have shown that the best compromise of performances, stability, vibrations and noise is obtained with a hardness of 50 Shore.

A recess 45 may be formed in the bottom wall 7 of the lower part of the half-shell 4, for the power cord to be wound and contained therein when not in use.

In a preferred non exclusive configuration, as shown in the annexed figures, an eccentric 15 having a pivot or roller 16 may be mounted to the motor shaft 12, to function as a cam or crank.

The compressor/aspirator may be of the reciprocating displacement type and include a piston 17 having an elongate portion 18 whose upper end is connected to the eccentric 15 and a mushroom-shaped expanded portion 19 slideably held within an approximately cup-shaped cylinder 20, having a substantially flat bottom wall 21 and a substantially cylindrical side wall 22.

Suitably, the expanded portion 19 of the piston 17 will be equipped with a sealing element 23, such as a gasket, for providing a sealing action as the element slides against the side wall 22 of the cylinder 20.

In an alternative embodiment, not shown, the motor 10 may be of the linear type, with its shaft connected to or forming part of the piston 17, at the elongate portion 18 thereof.

Preferably, in this particular configuration, the sealing element 23 may be a diaphragm fixed to the bottom of the expanded portion 19 of the piston 17 and to the bottom wall 21 of the cylinder 20.

According to the invention, the cylinder 20 is integrally joined to the lower half-shell 4 of the casing 2. In a first embodiment, the cylinder 20 is integrally formed of one piece with the lower half-shell 4. Particularly, the bottom wall 21 of the cylinder 20 coincides with a substantially flat portion of the bottom wall 7 of said lower half-shell 4.

In a second embodiment, not shown, the cylinder 20, which also has a substantially flat bottom wall 21 and a substantially cylindrical side wall 22, instead of being formed integrally is attached, i.e. separately formed from a plastic or metal material, possibly different from the material of the casing 2 and later joined thereto using second screw fastener members or the like, which may be different from or identical to the former.

In both cases, two openings are formed in the bottom wall 21 of the cylinder 20, i.e. an outlet 24 and an inlet 25 respectively, both having respective valves 26, 27 for allowing one-way fluid flow.

Advantageously, a head 28 is associated to the cylinder 20.

The head 28 may be a prismatic block with an outlet conduit 31 and an inlet conduit 29 extending therethrough. The outlet conduit 31 is in fluidic communication with the outlet 24 of the cylinder 20 and may have a spout 30 for connection of a supply tube T of an aerosol therapy flask. The inlet conduit 29 is in fluidic communication with the inlet 25 of the cylinder 20.

Advantageously, the valves 26, 27 are external to the lower half-shell 4 and held between the bottom wall 7 of the latter and the head 28.

The head block also has a filtering chamber 34 with a removable sealing plug having a hole for fitting a filter 33 therein.

Alternatively, the functions of the intake 25 and escape 24 openings may be inverted to provide aspirator operation. The head 28 has compensation chambers 46, 47 for reducing the noise of the compressor/aspirator and optimizing performances while reducing air turbulence.

Suitably, the head block 28 may be accommodated in a receptacle 28' in the outer face of the lower half-shell 4 and attached thereto by second fastener members, i.e. screws or threaded pins 6', possibly coinciding with the screw members 6. The particular configuration of the head 28 and the special housing 28' formed in the lower half-shell 4 ensure secure fixation and reliable seal using 2 screw fasteners only. The bearing areas 49, 50 of the valves 26, 26 have been appropriately sized to allow accurate opening control thereon, and thence to reduce stresses, prevent deformation and accurately adjusting the opening and reducing noise.

It will be appreciated that only one of the half-shells 4, 5, preferably the lower half- shell 4, will be designed for insertion of the first and second fastener members 6, 6' from the exterior thereof, to facilitate assembly.

Advantageously, the material that forms the lower half-shell 4 is a filled polyamide, preferably Glass Sphere Filled Nylon PA66. Thus, the cylinder 20 may be formed integrally with the lower half-shell 4 without the need of lining the cylinder with a different material to impart smoothness thereto. Indeed, this material combines high mechanical performance, even under thermal stress, and excellent smoothness of the cylinder 20 which is required for proper operation of the whole compressor/aspirator 1. The sphere filler provides a higher surface polish and increases the smoothness of the cylinder 20, the sphere filler also has a uniform shrinkage and therefore dramatically reduces anomalies. Polyamide generally provides good aesthetic results. However, it shall be understood that any other polyamide filling material may be used, without departure from the scope of protection as defined in the annexed claims.

In a preferred, non exclusive embodiment of the invention, a special receptacle may be provided on the back of the lower half-shell 4, for a board integrating a switch and/or an X-socket and/or a fuse or else, not shown due to its being known per se. Furthermore, the back wall of the lower half-shell 4 may incorporate an additional compartment for a board, preferably slideably inserted therein, which integrates the desired electric parts to be held in position by the upper half-shell mounted thereon. The board may be also not siideably inserted but constructed to be held within the wall and allow access to the switch, the socket or anything else through holes.

In a further preferred non exclusive embodiment, the various electric parts may be integrated on the motor, either individually (fuse, switch, etc.), or together (such as in a presoldered board), thereby eliminating their respective assembly times. This solution may be implemented by making changes to the plastic parts of the motor, through the provision of extension flanges, or in other manners.

In a preferred non exclusive embodiment, the motor 10 may include at least one fuse, and a corresponding fuse holder.

The assembly method comprises the steps of accommodating the motor 10 in the protective casing 2 and mounting the head 28 on the casing 2. The casing 2 has such a construction as to comprise at least one upper half-shell 5, a lower half- shell 4 and a cylinder 20. The latter is formed in view of being integrally joined to the lower half-shell 4 of the casing 2. Furthermore, the upper 5 and lower half- shells are coupled together by suitable screw fastener members or the like 6, inserted from the exterior of one of the half-shells.

The above configuration and assembly method avoid the need of multiple assemblies, testing of semifinished products and production of a large number of components. All the details may be previously formed and mounted to the casing 2, which is closed by inserting the screws from one side, thereby involving a minimized number of steps, which may be also carried out automatically, e.g. using assembly robots. Thanks to the concentration of all the functional parts of the compressor/aspirator in the lower half-shell 4 further provides a reduction of assembly times and costs.

The visible structure of the preferred non exclusive embodiment illustrated herein allows the whole apparatus to be assembled with no need for internal hook-like arrangements, which require special tools, until final closure.

In view of the foregoing, it clearly appears that the invention fulfills the intended objects and specifically to provide a displacement compressor/aspirator having simplified structure and assembly.

Furthermore, the possibility of mounting the head 28 from the outside, affords a simpler and safer maintenance. Most of the typical operations on this type of compressors, such as replacement of valves or the head due to tube fitting failures, may be carried out without opening the device and without risking contact with live parts, especially during testing.

The compressor/aspirator of this invention is susceptible of a number of modifications and changes, within the inventive concept disclosed in the appended claims. All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departure from the scope of the invention.

While the compressor/aspirator and its assembly method have been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Claims

1. A compressor/aspirator with simplified assembly, particularly for medical use, aerosol therapy and/or drainage of fluids, comprising: - a piston (17), housed in a cylinder (20);

- a motor (10), operably coupled to said piston (17) for promoting its reciprocating motion;

- a protective casing (2) for housing said motor (10), said cylinder (20) and said piston (17); - a head (28) associated to said cylinder (20) and having an inlet conduit

(29) and an outlet conduit (31 ) for the fluid to be sucked in or compressed respectively; wherein said casing (2) comprises at least one upper half-shell (5) and one lower half-shell (4), to be mutually connected together by first screw or similar fastener members (6), said cylinder (20) being integrally joined to one of said half- shells (4, 5), said head (28) being mounted externally to said casing (2).

2. Compressor/aspirator as claimed in claim 1, characterized in that said cylinder (20) has a substantially flat bottom wall (21) with a substantially cylindrical side wall (22) extending therefrom, said cylinder (20) being formed of one piece with said lower half-shell (4).

3. Compressor/aspirator as claimed in claim 2, characterized in that said bottom wall (21) of said cylinder (20) is formed of a substantially flat portion of the bottom wall (7) of said lower half-shell (4).

4. Compressor/aspirator as claimed in claim 1, characterized in that said cylinder (20) has a substantially flat bottom wall (21) with a substantially cylindrical side wall (22) extending therefrom, said bottom wall (21) being rigidly joined to said lower half-shell (4) by said second screw or similar fastener members (6').

5. Compressor/aspirator as claimed in any preceding claim, characterized in that said head (28) is associated to said bottom wall (7) of said lower half-shell (4) by second screw or similar fastener members (6').

6. Compressor/aspirator as claimed in any preceding claim, characterized in that said head (28) is held in a seat (28') on the outer surface of said lower half-shell (4) at the substantially flat outer bottom wall of said cylinder (20).

7. Compressor/aspirator as claimed in claim 5, characterized in that said head (28) has respective one-way valves (26, 27) at said inlet and outlet conduits (29, 31) externally to said lower half-shell (4).

8. Compressor/aspirator as claimed in any preceding claim, characterized in that said lower wall (21 ) of said cylinder (20) has at least one pair of air inlet and outlet openings (24, 25) in line with said inlet conduit (29) and outlet conduit (31) of said head (28).

9. Compressor/aspirator as claimed in claim 1 , characterized in that a plurality of hollow cylindrical columns (39, 39', 39", 39'") extend from said bottom wall (7) of said lower half-shell (4) for insertion and accommodation therein of said first (6) and second (6¹) screw or similar fastener members.

10. Compressor/aspirator as claimed in claim 9, characterized in that said upper half-shell has a plurality of mating columns (40, 40', 40", 40'") corresponding to the columns (39, 39', 39", 39'") that extend from the lower half-shell, said lower columns (39, 39', 39", 39'") being considerably longer than the upper columns (40, 40', 40", 40"').

11. Compressor/aspirator as claimed in claim 10, characterized in that said lower columns (39, 39', 39", 39'") are located in the proximity of the motor (10) to restrain vibration thereof during operation.

12. Compressor/aspirator as claimed in any preceding claim, characterized in that said first and said second screw or similar fastener means (6, 6') are designed to be inserted from the exterior of one of said half-shells (4, 5), to simplify the assembly process and reducing assembly times.

13. Compressor/aspirator as claimed in claim 12, characterized in that said one of said half-shells is said lower half-shell (4).

14. Compressor/aspirator as claimed in any preceding claim, characterized in that said piston (17) has an elongate end portion (18) associated to said motor (10) and an expanded end portion (19) which is equipped with a sealing element (23) for providing a sealing action against the inner surface of said cylinder (20).

15. Compressor/aspirator as claimed in claim 14, characterized in that said motor (10) is of the linear type, with a shaft connected to said elongate portion (18) of said piston (17). said elongate end portion (18) is designed to be connected to eccentric means (15, 16) associated to said motor (10).

16. Compressor/aspirator as claimed in claim 14, characterized in that said motor (10) is of the linear type, with a shaft connected to said elongate portion (18) of said piston (17).

17. Compressor/aspirator as claimed in claim 1 , characterized in that said lower and upper half-shells (4, 5) have a modular inner configuration for accommodating a standard compressor/aspirator and a customized outer configuration.

18. Compressor/aspirator as claimed in claim 16, characterized in that said lower half-shell (4) is formed from a material selected from the group composed of filled polyamides and polyacetal resin.

19. Compressor/aspirator as claimed in claim 18, characterized in that said material used for forming said lower half-shell (4) is a Nylon 66.

20. Compressor/aspirator as claimed in claim 19, characterized in that said material used for forming said lower half-shell (4) is a glass sphere filled polyamide.

21. Compressor/aspirator as claimed in any preceding claim, characterized in that said lower half-shell (4) is formed from a material other than that of said upper half-shell (5).

22. Compressor/aspirator as claimed in any preceding claim, characterized in that said lower half-shell (4) has a color other than that of said upper half-shell (5).

23. Compressor/aspirator as claimed in any preceding claim, characterized in that said upper and lower half-shells (4, 5) have supports (41 , 41', 42, 42') for holding the motor (10) in the operating position.

24. Compressor/aspirator as claimed in claim 23, characterized in that said supports (41 , 41', 42, 42') comprise elastic shock absorbers (43, 43' and 44, 44') to minimize motor vibration (10).

25. Compressor/aspirator as claimed in claim 24, characterized in that said elastic shock absorbers (43, 43' and 44, 44') are formed of a rubber having a hardness from 30 to 80 Shore A, and preferably of about 50 Shore.

26. Compressor/aspirator as claimed in any preceding claim, characterized in that the bottom wall (7) of the lower half-shell (4) includes a recess (45), for the power cord of the compressor/aspirator to be wound and contained therein when not in use.

27. Compressor/aspirator as claimed in any preceding claim, characterized in that the head (28) has compensation chambers (46, 47) for reducing the noise of the compressor/aspirator and optimizing performances while reducing air turbulence.

28. Compressor/aspirator as claimed in any preceding claim, characterized in that said upper half-shell (5) has latch prongs (35, 35', 35", ...) for connection thereof with the lower half-shell (4).

29. Compressor/aspirator as claimed in claim 28, characterized in that said latch prongs (35, 35', 35", ...) are large enough to space the upper half-shell (5) from the lower half-shell (4), to define an air space therebetween.

30. Compressor/aspirator as claimed in claim 29, characterized in that said upper half-shell (5) have a plurality of rear slits (37) for defining a path with said air space, which enhances cooling air circulation.

31. Compressor/aspirator as claimed in any preceding claim, characterized in that said lower half-shell (4) has a compartment for a board that integrates all the electric parts of said compressor/aspirator.

32. Compressor/aspirator as claimed in any preceding claim, characterized in that said upper half-shell (5) has a sufficient surface area to cover the whole side wall of the lower half-shell (4).

33. Compressor/aspirator as claimed in any preceding claim, characterized in that said motor (10) has at least one fuse with a corresponding fuse holder.

34. A method for simplified assembly of a displacement compressor/aspirator as claimed in any preceding claim, comprising the steps of:

- providing a motor (10) and a piston (17);

- providing a protective casing (2) having a cylinder (20) and composed of at least one upper half-shell (5) and one lower half-shell (4);

- providing a head (28) designed to be associated to said cylinder (20) and having an inlet conduit (29) and an outlet conduit (31) for the fluid to be sucked in or compressed respectively;

- accommodating said motor (10) in said casing (2); wherein said cylinder (20) is integrally joined to one of said half-shells (4, 5) of said casing (2), said half-shells (4, 5) being mutually connected by suitable screw or similar fastener members (6) inserted from the exterior of only one of them, and wherein said head (28) is mounted to the exterior of said casing (2) to simplify assembly and maintenance processes.

35. Method as claimed in claim 34, wherein said one of said half-shells (4, 5) is said lower half-shell (4).

36. Method as claimed in claim 34, wherein said head (28) is mounted to said lower half-shell (4) in a complementarily shaped receptacle (28') formed in the outer face thereof.