WO2000007749A1

WO2000007749A1 - Method for joining metal tubes to the casing of refrigeration compressors

Info

Publication number: WO2000007749A1
Application number: PCT/EP1999/004320
Authority: WO
Inventors: Jose Sarro Alonso
Original assignee: Zanussi Elettromeccanica S.P.A.
Priority date: 1998-08-04
Filing date: 1999-06-22
Publication date: 2000-02-17
Also published as: ITPN980058A1; IT1305519B1

Abstract

Method for joining a metal tube (1) to the casing (3) of a refrigeration compressor, in which said tube (1), that is previously subject to an operation that brings about a relief ring on the cylindrical surface of its portion that remains on the outside of the casing, is first inserted in an opening in said casing, while said relief ring is then electro-welded onto the corresponding outer surface of the casing and said terminal portion is flanged towards the wall of the inner annular surface of the casing so that the annular edge of said terminal portion is sealed by heading against said inner annular surface. Preferably, said terminal portion is flanged by means of a tool provided with at least a centering tip surrounded by an annular cup.

Description

METHOD FOR JOINING METAL TUBES TO THE CASING OF

REFRIGERATION COMPRESSORS

DESCRIPTION

The present invention lefeis to an improved method for coupling metal tubes with the mteπoi of a casing that is made itself of metal material, it further relates to a casing made with such a method

It is largely known m the ail that in lefngeiation appliances, m particular for household application, the electiic compressor used for the refngei nt medium is enclosed in a metal casing which is connected to the reftigeiatmg cncuit thiough some metal delivery and suction tubes that are generally coupled by some biazmg piocess in an an -tight mannei , le heimetically, with the mteiioi of said casing

It is further a largely known fact that such a coupling must be able to meet a numbei of definite lobustness, stiength and tightness lequiiements even aftei undergoing a certain defoimahon

These tubes, in fact, aie pievailmgly, and accoiding to specific needs and requirements, made of eithei copper-clad iron oi coppei , and during the assembly of the lefngeiatmg cncuit they may be subject to bending and, theiefoie, forced away with lespect to then oiiginal attachment position Since they aie made of metal, and aie theiefoie mheiently πgid oi neaily ngid, the sh m that is imparted to them is tiansmitted almost totally to the tube-to-casmg coupling portion, which must theiefoie be earned out by using a paiticulai caie and taking

-ι- a number of appiopnate measures in view of ensuring the required strength, lobustness and tightness thereof

To such a purpose, p or-art techniques call foi a welding or brazing operation to be earned out for each tube-to-casmg coupling This method, however, has a mam drawback in that it is certainly expensive and involves quality standards that are not yet fully assured owing to the inherent weakness of the welding/brazing operation that owing to its having to be earned out on the extenoi of the casmg, affects only a limited, final portion of the tube and the corresponding opposite portion of the casmg

In oidei to do away with such a problem, a commonly known practice is to insert a steel washei around the metal tube and lock it m position on said tube by means of furnace brazing Subsequently, upon the insertion of the tube in the lespective opening in the casmg, said washer is welded on to the annular portion of the casmg circumscribing said opening, piefeiably by means of a lesistance welding process

Such a method enables m fact an impioved mechanical strength to be obtained in coiiespondence of the insertion section of the tube m the casing with lespect to sti esses that may possibly be imparted to the tube itself

A lathei similai solution consists in obtaining such an external element also thiough the piovision in addition to said washei or even as a leplacement theieof, of an external annulai beading of the tube having an outside diametei that is appiopi lately mci eased with lespect to the outside diametei of the tube itself, and then welding said beading on to the casing as descπbed above m connection with the washei

Howevei even this solution although more unexpensive and effective is not capable of I emovmg oi 1 educing a certain weakness of the coupling of the tube with the mteiioi of the casing m the case of excessive sti esses put on it in paiticulai flexui al sti esses imparted to oi acting on the tube It would therefore be desirable, and it is actually a main purpose of the present mvenhon, to provide a method for couplmg the metal tubes of a refrigerating circuit to the hermetically sealed metal casing enclosing the compressor, which is not only effectively capable of combining a high mechanical lobustness and a high resistance against leakages due to tightness defects, but is also adapted to be automated and, therefore, to enable a sensible reduction m costs to be obtained

This aim is reached m the method that is described below by way of non-limiting example with refei ence to the accompanying drawmgs, m which

- Figure 1 is a symbolic perspective external view of a compiessor casmg provided with some inlet/outlet tubes,

- Figui e 2 is a cross-sectional view of a type of tool that can be used to cany out the method according to the piesent invention,

- Figure 3 is a cross-sectional view of the above cited type of tool along with the cross-sectional view of a tube and the casing m the insertion zone of said tube in the casing,

Figuie 4 is a cross-sectional view of the phase m which the tube is welded on to the casing fiom the outside

- Figuie 5 is a cross-sectional view of the end portion of a tube adapted to be coupled with a coi i espondmg opening m the casing accoidmg to the piesent invention,

- Figure 6 is a cross-sectional view of the portion of casing wall comprising an opening pi ovided foi couplmg with a 1 espective tube

The basic idea behind the piesent invention is descnbed below Refemng to Figuie 5 it can be noticed that the tube 1 is processed, near its end portion due to be inserted m the opening 2 of the casing 3, in view of providmg it with a bulge extending ovei an entire section and taking the form of a relief rmg 4

The piocess carried out m order to obtain said relief ring can be performed according to a number of methods that are generally known m the art In the following description, anyway, one of said processes adapted to produce said relief nng will be generally indicated with the term of "expansion"

Refei ring now to Figui e 4 it can be noticed that the tube 1 , aftei said expansion operation is inserted m the opening provided in the casing 3 m such a manner as to ensure that the teirmnal portion 5 of said tube is pushed well into the internal volume 6 of the casmg 3

Subsequently said tube 1 is electio-welded with said lelief nng 4 on to the outer surface of the casing 3 by means of a first electrode 7 placed on the exterior of the casing, orthogonally thereto, in contact with the external zone of said annular lelief, while a second electiode 6 provided inside the casing is placed m contact with the annulai internal zone of the same casing aiound said opening

A sealed couplmg of the tube with a i espective opening m the casing 3 is bi ought about in this way It is howevei fully appaient that such an opeiation falls cleaily short of ensunng an adequate stiength of the coupling m the case of stresses m particular flexui al ones that may be imparted to the external portion of the tube

In oi dei to theiefoie impiove said mechanical stiength of the coupling, said teimmal portion 5 of the tube 1 is caused to undeigo a beading opeiation from mside as lllustiated in Figures 2 and 3 showing a tool 9 pi ovided with a centeimg tip 10 suiiounded by an annulai cup 11 this tool is opeiated from mside against said teirmnal portion 5 of the tube m such a mannei that the lattei is caulked oi flanged to foim a cuil-like folding 12 against the innei wall of the casing so as to enable a second sealed junction of the tube with the casing to be obtained in correspondence of the pressure and contact zone between said curl-like folding 12 and the corresponding inner annular surface 13 of the casmg around said opening 2.

This circumstance, further to obviously improving the sealing, le. air-tightness characteristics of the so obtained coupling, enhances also the strength thereof against the strains it may be exposed to owing to stresses, in particular of a flexural kind, being imparted to the tube, since it can be clearly inferred from the illustration in Figure 3 that the terminal portion of the tube is actually embedded and clamped in the opening 2 across the whole thickness of the casing, ie. owing to the welding on the outside and said caulking or flanging on the inside.

An advantageous improvement of the invention can be seen to be illustrated in Figures 3 and 6, in which it can be noticed that the annulai' portion of outer surface of the casmg 3, against which said relief ring 4 is then welded, is processed, preferably by coining, so as to impress in the same surface portion an appropriate annular recess 15 capable of at least partially accomodating said relief ring 4 before welding.

Said coimng operation increases the contact surface between said relief ring 4 and the surface of said casing 3, with the result of a further improvement in the tightness and the mechanical strength of the joint.

It will be appreciated that the description and illustrations set forth above with reference to the accompanying drawings have been given merely as a non-limitmg exemplification of the invention, and that any of a number of further variants and modifications can therefore be devised and introduced without departing from the scope of the present invention.

-_)-

Claims

CLAMS

1 Method for joining a metal tube (1) to an outei casmg (3) of a hermetically sealed compressor, m which a terminal portion (5) of said tube is first of all inserted in an appiopnate opening (2) pi ovided m said casing, and before being so inserted m said opening said tube is caused to undergo an expanding opeiation adapted to bnng about a lelief nng (4) on the cylmdncal suiface of its portion that lemams on the outside of the casing, m which said lelief nng (4) is subsequently electro-welded onto the coriespondmg outer surface of the casmg that surrounds annularly the insertion mouth of the I espective opening, said welding bemg can led out by means of a fiist electrode (7) placed on the extenoi of the casmg, orthogonally thereto and m contact with the outei zone of said annular relief, and a second electrode (8) placed mside the casing in contact with the innei annular zone of the same casing suiiounding said opening characterized in that after said welding, said teimmal portion is caulked oi flanged towaids the wall of the innei annulai surface (13) of the casing so as to cause the annular border of said teimmal portion to undeigo a cuil-like folding (12) that seals against said inner annulai suiface (13)

2 Method accoidmg to claim 1 characterized m that said teimmal portion (5) is caulked oi flanged by means of a tool (9) that is pi ovided with at least a centei ing tip ( 10) sui I ounded by an annulai cup (11)

3 Outei casing foi electiic compiessois m particulai foi use m household-type l efngei atoi s compnsing at least a pluiality of metal tubes adapted to transfer the refrigerant medium from the interior of the compressor to the external refrigerating circuit and vice-versa, in which each tube enters the mte╧Çor of said casing (3) through a respective appropriate opening (2), characterized in that the terminal portion (5) of said tubes is fully inserted m the respective opemng (2) so as to come out directly inside the casing while passmg fully through the whole thickness of the wall of the casing.

4. Outer casing according to claim 3, characterized in that the terminal portion (5) of said metal tubes, as inserted m the respective inlet opemng, is provided on the mside with a backwai'd caulking or curl-like foldmg (1 ) of an annular form that abuts against the inner annular surface (13) of said casmg that surrounds said opening.

5. Outer casing according to claim 4, characterized in that said tubes are provided, on the outside of the casing, with a relief ring (4) protrudmg from the surface of the tube and adhering (welded) against the outer surface of the casing.

6. Outer casing according to claim 5, characterized in that said outer surface of the casing surrounding the respective opening is provided with an annular recess (15), and that said relief ring (4) is at least partially accomodated in said i espective annular lecess.