TWO-STAGE EJECTOR

Abstract

This two-stage ejector comprises a body (16) including: a compressed air intake (E); a compressed air injection nozzle (17) placed downstream of the air intake; a central duct (18); and an outlet mixer (19).

The injection nozzle (17), the central duct (18) and the outlet mixer (19) are disposed along an axis (X-X′) of the ejector so that the ends of the axial duct are respectively spaced apart from the nozzle and from the mixer so as to form a first and a second suction zone (23, 25) that communicates with a single common air suction chamber (21).

Claims

1. Two-stage ejector produced as a single piece, characterised in that it comprises a body (16) including: a compressed air intake (E); a compressed air injection nozzle (17) placed downstream of the air intake; a central duct (18); and an outlet mixer (19), the injection nozzle (17), the central duct (18) and the outlet mixer (19) being disposed along an axis (X-X′) of the ejector so that the ends of the axial duct are respectively spaced apart from the nozzle and from the mixer so as to form a first and a second suction zone (23, 25) that communicates with a single common air suction chamber (21).

2. Ejector according to claim 1, wherein the suction chamber communicates with a suction duct (20) intended to be connected to a suction air volume and that extends perpendicular to the axis of the ejector.

3. Ejector according to claim 1, wherein the air injection nozzle comprises a cylindrical supply duct comprising a narrowing section (26) and an expansion chamber (27) placed downstream of the narrowing section.

4. Ejector according to claim 1, wherein the central duct (18) is cylindrical.

5. Ejector according to claim 4, wherein the central duct comprises an intake (22) having an inner peripheral surface with convex axial section and converging in the direction of the compressed air flow.

6. Ejector according to claim 4, wherein the central duct comprises an air outlet (24) having an outer peripheral surface with bevelled axial section.

7. Ejector according to claim 1, wherein the outlet mixer (19) has a diameter increasing in the direction of the air flow.

8. Ejector according to claim 1, wherein the central duct (18) is attached to the body by at least one support (28).

9. Ejector according to claim 1, wherein the diameter of the central duct is between the outlet diameter of the injection nozzle (17) and the intake diameter of the mixer (19) and the length of the central tube is between one and ten times the inside diameter thereof.

10. Ejector according to claim 9, wherein the diameter of a narrowing section of the air injection nozzle is the smallest diameter of the passage sections of the fluid along the general axis (X-X′) of the ejector and the diameter of the outlet of the injection nozzle is between the diameter of the narrowing section and the inside diameter of the upstream end of the central duct.

11. Vacuum lifting device (100) comprising a lifting tube (104), a two-stage ejector (15) according to claim 1, a valve (109) supplying said ejector (15) and controlling the lifting tube (104).

Description

[0041] Other aims, features and advantages of the invention will become apparent upon reading the following description given only by way of non-limiting example, and made with reference to the appended drawings wherein:

[0042] FIGS. 1 and 2, already mentioned, illustrate respectively the structure of a single-stage ejector and of a multi-stage ejector according to the prior art;

[0043] FIG. 3 illustrates the structure of a two-stage ejector in accordance with the invention; and

[0044] FIG. 4 illustrates the relative performances of a single-stage ejector, of a multi-stage ejector and of a two-stage ejector in accordance with the invention, in terms of suction flow rate and of vacuum level, these three ejectors having the same consumption of compressed air at identical supply pressure.

[0045] FIG. 5 illustrates the structure of a lifting device in accordance with the invention.

[0046] FIG. 3 shows a two-stage ejector in accordance with the invention, designated by the general numerical reference 15.

[0047] This ejector 15 comprises a body 16, produced as a single part, comprising an intake E equipped with a thread and intended to be connected to a compressed air supply source, for example at a pressure in the order of 5 bars conventionally used in industrial environments, and a gas outlet S.

[0048] Inside, the body 16 comprises a compressed air injection nozzle 17, disposed downstream of the intake E, a central duct 18 and an outlet mixer 19.

[0049] The nozzle 17, the central duct 18 and the outlet mixer 19 are successively placed between the intake E and the outlet S along the general axis X-X′ of the ejector.

[0050] Moreover, the body 16 includes a suction duct 20 provided with an internal thread for connecting the ejector 15 to the inner volume to be sucked of a suction pad (not shown).

[0051] The suction duct 20 extends perpendicular to the axis X-X′ and is located opposite the median portion of the central duct. It delimits with this and the inner wall of the body a single common suction chamber 21 for the two stages of the ejector 15.

[0052] As can be seen, the nozzle 17 is spaced apart from the upstream end 22 of the central duct so as to form an expansion zone 23 for the first stage.

[0053] Moreover, the downstream end 24 of the central duct 18 is spaced apart from the outlet mixer 19 so as to form an expansion zone 25 for the second stage.

[0054] The expansion chambers 23 and 25 constitute suction zones that communicate with the common suction chamber 21.

[0055] The suction nozzle 17 includes a cylindrical supply duct comprising a narrowing section 26 and an expansion chamber 27 located downstream of the narrowing section 26.

[0056] The inner peripheral surface of the upstream end 22 of the central duct 18 is converging and includes a longitudinal section of convex shape so as to guide the compressed gas mixed with the suction gas towards the inside of the duct.

[0057] On the downstream side, the outer peripheral surface of the downstream outlet 24 of the central duct 18 has a bevelled longitudinal section so as to channel the suction gas into the expansion zone.

[0058] Moreover, the outlet mixer 19 has a globally cylindrical shape but has an inside diameter increasing in the direction of the outlet S in order to facilitate the ejection of the air flow towards the outside in subsonic flow.

[0059] As previously indicated, the assembly of the ejector is produced as a single part. The central duct 18 is connected to the body 16 by one or more supports 28, here two in number, integrally formed with the body.

[0060] Advantageously, the diameter of the central duct is between the outlet diameter of the expansion chamber 27 and the intake diameter of the mixer 19.

[0061] The length of this central tube is advantageously between one and ten times the inside diameter thereof.

[0062] As regards the injection nozzle 17, the diameter of the narrowing section 26 is the smallest diameter of the passage sections of the fluid along the general axis X-X′ of the ejector.

[0063] The diameter of the outlet of the injection nozzle 17 is for its part advantageously between the diameter of the narrowing section 26 and the inside diameter of the upstream end 22 of the central duct 18.

[0064] By way of non-limiting example, the ejector may have the following characteristic dimensions: [0065] outlet diameter of the injection nozzle: 4 mm [0066] narrowing section diameter of the nozzle: 3 mm [0067] diameter of the central duct: 8 mm [0068] length of the central duct: 35 mm [0069] intake diameter of the downstream mixer: 10.5 mm

[0070] FIG. 4 illustrates the performances of the two-stage ejector that has just been described.

[0071] In this figure, the curve A corresponds to a single-stage ejector according to the prior art, the curve B corresponds to a conventional multi-stage ejector and the curve C corresponds to a two-stage ejector in accordance with the invention. These three ejectors have the same compressed air consumption at identical supply pressure.

[0072] The results appearing in FIG. 4 are obtained for a supply pressure in the order of 5 bars.

[0073] As can be seen, the ejector according to the invention makes it possible to obtain a vacuum level of 50%, similar to the vacuum level obtained by means of a single-stage ejector.

[0074] Conversely, it makes it possible to obtain a more than doubled suction flow rate in relation to a single-stage model, and this with a structure devoid of moveable parts.

[0075] FIG. 5 illustrates the structure of a lifting device 100 in accordance with the invention.

[0076] The lifting device 100 is capable of handling, inclining, lifting a wide range of loads.

[0077] For this, it comprises a lifting tube 104, of length L proportional to the pressure contained in said tube.

[0078] More specifically, it is the negative pressure in the lifting tube 104 that makes it possible to grip an object 108 via a suction pad 107.

[0079] It should be noted that when no object is gripped, the presence of a lower check valve 106 makes it possible to maintain a sufficient negative pressure at the lifting tube 104.

[0080] The lifting device 100 further comprises a valve 109, controlled by an operator, and capable of supplying the two-stage ejector 15 with the compressed air coming from the intake E. This makes it possible, by the high suction flow rate of the two-stage ejector 15, to rapidly empty the lifting tube 104, which gives the system a good dynamic reactivity.

[0081] In other terms, the lifting device 100 makes it possible to lift a load without time limit while generating less noise.

[0082] In addition, this configuration of the lifting device 100 makes it possible, if the two-stage ejector 15 is located inside a vacuum chamber, to significantly reduce the frictions of the air.

[0083] The performances of the system are therefore improved.