CA1127202A

CA1127202A - Pipe coupling

Info

Publication number: CA1127202A
Application number: CA341,596A
Authority: CA
Inventors: Reichi Makishima
Original assignee: Nitto Kohki Co Ltd
Current assignee: Nitto Kohki Co Ltd
Priority date: 1979-05-04
Filing date: 1979-12-11
Publication date: 1982-07-06
Also published as: DE2965478D1; JPS591912B2; JPS55149485A; US4331177A; AU5374679A; EP0018440A1; EP0018440B1; AU528663B2

Abstract

ABSTRACT OF THE DISCLOSURE

A pipe coupling made up of separably assembled plug and socket in which a latching piece is suspensibly held in the socket in latching engagement with the plug so that finger pressure on the latching piece drives it out of the latching engagement in order to enable easy disassembly of the pipe coupling. A flow rate adjuster piece may be incorporated into the socket so that its axial turning changes the extent of recession of a valve off a valve seat in the plug so that the flow rate can be adjusted whilst retaining the assembled state of the pipe coupling. Light, compact and cheap construc-tion is assured with simple operation and free flow rate adjustment.

Description

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Ii`l~ROVED PIPE ~OUP~ING

DESG~IP~ION O~ ~HE BACI~GROUND

~ he present i~venti.on relates to improved pipe coupling, and more particularly r~lates to impro~ed construction of a .
:~ plpe coupling made of a plug and socket separably assembled with each other.

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~ onventionally, metalli-c-materials are in general u.sed for.major elements of a pipe coupling and assembly o~ these ~ -elements is mostly based upon screw engagemen-ts or projection-lQ hollow engagemen~s. Such marlner of assembly requires applica-tion ~-., of delicate.machining after~initial shaping o~ the elenents in --~ man~facturing, and also r~quires complicated operation ~or assembly and disassembl~ of the pipe coupl~ng irl use.
- ' In practice, it is often required :o adjust flow rate of ~uid passing -through a piping system including the pipe coupling. ~onventionally, a separate cock is connected to the pipe coupling in order to enable-:s.uch adjustment of -the flow rat~. Addition of such a co~k irlevltably results in a oomplicated and enlarged construct1on o~ the pipe coupling , ., :

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and its related parts in the piping system.

SUMMARY OF THE INVENTION
The present invention seeks to provide a pipe coupling which can be manufactured very easily and -to provld~
a pipe coupling which can be very easily operated in use.
Further, the present invention seeks to provide a pipe coupling which enables free adjustment of flow rate despite its very simple, light and compact construction.
In one broad aspect, the inven~ion comprehends an improved pipe coupling which includes a plug and a socket separably assembled with each other. ~he plug includes a tubular nose section having a fore conduit, an annular latching groove formed in its outer surface, and an internal valve seat. A tubular tail section coupled liquid tight to the nose section has intermediate and rear conduits in communication with each other. A valve is arranged in the intermediate conduit of the tail section and has a front ex-tension slidably received in the fore conduit of the nose section, the front extension having at least one radial opening near its junction to the valve. Means resilien-tly urye the valve to pressure contact with the valve seat in the nose section, the fore, intermediate and rear conduits forming an axial flow passage through the plug. ~he socket includes a tubular main piece made of a resilient material and having a nose section adapted for receiving the nose section of the plug, a tail section extending rearwards from the nose section, ~' .

z~ z a tongue projecting forwards from the nose section, a center projection extending forwards from the nose section, and an axial through conduit opening in the center projection.
A tubular mantle piece is fixedly inserted over the nose section of the main piece, whilst leaving an annular yroove in front Or the nose sec-tion of the main piece, and has a radial opening. A la-tching piece has a tongue res-ting on the tongue of the main piece in -the radial opening of the main piece, and a ring section is normally partly received in the annular groove provided by the mantle piece. The ring section is fully sunk in the annular groove provided by the mantle piece when the tongue of the latching piece is depressed towards the axis of the pipe coupling, and the ring section is automatically placed in engagement with the latching groove in the plug due to resiliency of the tongue of the main piece in the assembled state of the pipe coupling.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional side view o~ one embodiment o~
the plug in accordance with the present invention, Fig. 2 is a sectional side view of one embodiment of the socket in accordance with the present invention, Fig. 3 is a section taken along a line III~III in Fig. 2, ~, . ., , :
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Fig. 4 is a perspec-tive view of the socket Shown in Fig. 2 in a disassemblecl state 7 Fig. 5 is a side sectional view of the pipe coupling made up of the plug in Fig. l and the socket in Fig. 2 in the firmly assembled state, Fig. 6 is a side view, partly in section, of the pipe ~- coupling in Figo 5 in the state ready for disassembly, Fig~ 7 is a slde sectional view of the o~her embodiment ol the socke-t in accordance wlth the present in~ention, !
, Fig. 8 is a section ~aken along a line VIII-VIII in Fig~ 7 ig. 9 i-s a section taken along a line TX-IX in Fig. 79 ~ ig. lO is a side vi w, partly i~ section, o~ the pipe coupling made up of the plug in Flg. l a~d the socket in Fig. 7 in one firmly assembled state in'-which the flow rate is highest~ -Fig ll is~a side view5 partly ln section, of the pipe coupling in ~ig. lO in another firmly assembled sta-te i-n which the flow rate is minimal~ more clearly naught, and Fig. 12 is an outer view n~ t'he soo~et sho~ in Figo 7 ~~
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L27Z~2 D3SCRIP~ION OF TH~ PREF~r~ED ~ODIr~E~TS

As briefly described already, the pi~e coupling of the present invention is made up of a plug and a ~ocl~et detachably asse~bled with each o-ther. In the follo~ing de~criptio~, the side o~ either of the element~ adapted for asse~bly with another of the ele~ent wlll be referred to with ~iords such as front and fore, and the oppisite side r~ith words suc~ as back and re2r.
., ' ' ' One embodiment of the plug in accordance wi-th the present invention is shorm in Fig. 1. ~ plug 10 i9 made up of a tubu-lar fore piece 14 and a tubular rear piece 18 fixedly Coupled~
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- preferably by fusion, to each other by ~eans of a seal ring 20.
~he piece~ 14 and 18 are both preferably made of a synthetic , resin. .- . - . - . .
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'~he ~ore piece 14 i~ provid~d wlth a nG~e SeCtion 12 to be insertea into a ~ocket when the plpe couplL~g is æs~embled~
Near the ~ron~ end, the no~e ~ection 12 i9 externally provided with 2 seal ring 22, a conical ~lange 24 and a~ annular latch-ing ~roove 26 formed just on $he bac~-slda of the flange 24.
~he fore piece 14 further internally define~ an ~xial fore conduit 38 for the ~luid flowing throu~h the pipe coupling.
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The rear piece 18 is provided with a tail section 16 adapted for connec-tion with any sui-table hose. The rear piece 18 i.s -fur-ther internall~J defines an a-~ial rear co~dui-~36 ~or -the ~luid flowing -through the pipe coupling, and an intermedia-te conduit 37 o-E a larger aiame~er.

A valve 30 having a co-nical head is arranged abou-t the junction between the pieces 14 and 18 with ltS seal ring 32 in pressure contact with a funnel-shaped seat 34 formed on the internal sur~ace of the~fore plece 14. ~his pressure con-10~ tact is caused by a helical compression spring 28 interposed between the valve 30 and -the rear end of the in-termediate con-duit 37. ~n axial projection 44 lS formed on the rear end o~
the intermediate conduit 37~in order to limit excessive rear-ward movement:of -the valve 30. ~he valve 30 is provided with -tùbular front extension 42 slidably recei~ed in the ore con-.
dui-t 38 of the fore piece 14~ ~he front extension 42 termi-nates -near the front.open1ng of the ~ore condult 38 and~ at a posi-tion near the conical head of the valve 30, is provided with at least one radia~ opening 40.

One embodiment of the socket ln accordance with the present in~ention is shov~ in Figs. 2, 3 and 4~ A socket 100 is made up o-~ a tubular main piece 110, a latching Piece 1209 a mantle piece 130 and a stop piece 140. ~hese pieces . .
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110 to 140 are all pre-erably made o-f a syntlne-tic resin. ~n par-ticular, at leas-t -the main piece 110 should be made of a synthe-tic resin sinc0 it is re~uired to be somewhat resilien~
as hereinafter described in more detail.

~ he main piece 110 is provided wi-th a front nose sec-tion 111 adapted fo-r accomomodating the nose section 12 of -the plug 10 and a tail section 112 adapted for connection with any hose.
The nose section 111 is~provided, near its periphery, with a tongue 113 projecting forwards, a~d~ nea~ its center, a center projection 114. ~he main-piece 110 internally defines an axial conduit 115 wh1ch opens in the center projection 114.

~ he ~antle piece 130 is internally designed so -that, when it is-inserted over and ixed to the nose section 111 o* the main piece llO, a~ annular groove 131 is le-f-t in front of the -front end of the nose section 111. ~ radial opening l32 is --formed in -the wall of the mantle piece 130~
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~ he latching piece 120 includes a ring section 121 and a tongue 122 extending rearwards from -the ~ing section 121 as best seen in Fi8. 4. In the assem-bled state of the socket 100 ~0 the ~top piece 140 is inserted over ~nd fixed to -the rear end por-tion of the nose sectian 111 o the main piece 110 in order to prevent falling of the mantle piece 130 inserted over the main piece 110. The tongue 122 of -the latching piece 120 ~. .

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rests on the tongue 113 of the main piece 110 so that -the latching piece 120 is su~pensibly he~d b~ the main piece 110.
In thisstate, the ring section 121 of' the latching pieoe 120 is received partly in the annular groove 131 provided by the mantle piece 130 as shown in ~ig. 2. ~urther~ the ton~ue 122 of the latching piece 120 appears in the radial opening 132.
of the mantle piece 130 with its outer suxface ~ubstantially flush ~ith that o~ the mantle piece 130~

Assembly of the pipe coupling using ~he plug 10 in ~ig. 1 and ~he ~ocket ioo in Fig. 2 is carried out as fOllo-llsr ' As the nose section.12 of..the plug 10 i9 inserted into the nose section 111 of the main piece 110 o~ the socket 100, the ring section 121 of the latching.piece 120 is depressed . . .
into the annular groove 131 due to pressure ~butment wi~h th~
conical. flange 24 of the plug lO and the tongue 122 of the latching piece 120 sink~ in the radlal opening 132 o~ the mantle piece 130 while bending tho resilient tongue 113 of the ~:
main piece 110. Due to the above-described pressure 2butmen~
wlth the conical flange 24 of the plug 10, the ring section 121 o~ the latching piece 120 is now fully plaoed in the an-nular groove 131 provided by ~he mantle piece 130 to allow further insertion o~ the plug 10 in~o the socket 100.

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As t~e latching groove 26 of the plug 10 arrives ~-t the position of ~he annula~ groove 131, the ~ing section 121 OL
the la~ching piece 120 automatically ~alls in-50 the l~tching groove 26 of tke plug~10 due to spring-back of the resilie~t tongue 113 which is no~r~ released from the pressure contact ith the tongue 122 o~ the latching piece 120. ~onsequently~
the plug 10 and the ocket 100 are now firmly assembled together as ~ho~n in ~ig. 5.

In tkis assem~led state J the front end of the center pro-jectio~ 114 o~ the socket 100 abuts against the front end ofthe front extension 42 of the valve 30 and pushes the valve 30 rear~ards off the seat 34 while overcoming the repulsion of the compression spring 28. Thus~ a continuous fl 0~7 pa~aage is established through the pipe coupling, v~ch includes the rear a~d intermediate con~uits 36 and 37, a clearance formed bet~een the conlcal he~d of the ~alve 30, the radial openi~gs 40 in the ~ront exten~ion 42, the interior of the front exten-sion ~2, and the conduit 115 of the socket 100.

Under tho condition sho~n in Fig. 6, the ton~ue 122 of the latching piece 120 i5 depressed by a finger ~ to-~ards the axis of the pipe coupling while bending the fle~ible ton~ue 113 of tne main piece. By this depression, the ring section 121 ~ brou~ht out of engagement with t~e latching groove 26 ~B . g ~lZ7Z~2 of the plug,10 and placed fully within ~lle a~ular groove 131 of the soc~et. Due to disappearance of the latching enyage~
ment, the plug 10 and the ~ocXet 100 can ea~ily be disa3sem-bled from each o-ther.
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In accordance with the present lnvention, at lea3t the main piece 110 of the socket 100, mor~ preferably bo~h the entire plug 10 and so~ket 100~ i~ made o~ a resilient materia such as synthetic resin. For example, the knovm pla9tic injec-tion moulding may be used for manufacturing the pipe COupling.
~his greatl~ simpli~ies manvfacturing of ~he pipe coupling whilst naturally cau3ing corresponding lowering in manufactur-ing cost. -- , . : . , : ,. . . . .
~he latching piece 120 is su~pe~s~bly held by the resili-ent tongue 113 of the socket 100 with it~ outer surface being .. .. : ............ . . .
substantially ~lush ~i-th that of the socket. This flu~h con-struction ~uccessfully a~oids accidental depression o~ ~he - : - - .
latching pi~o~ 12~, iJe. accidental disassembly of the pipe coupling, by application of any unexpected external force.
The flush con9truction ~urther provides a simple ou-ter de~ign of the pipe coupling.

Disassembly of the pipe coupling is carried out utili~ing the ~esilient nature of tha tongue 113 of the socket without :~ .
B - lo -, - 9 ~Z7;~2 .

requirement for provision of any addi~ional spring to -tha~
e,~fect. T~is al50 contributes to lo-~Jering in m~nuIacturing cost.

It ~ill be well unders~ood with the foregoing embodimen-t tha" ths flow rate of the fluid pa~sing throu~,~h the pipe coupl-ing in the a~sembled sta~e i~ detormined by the dimension O f the annular clearance formed around the conical head of the valve 30 in Fig. 5. In the cPse of the foregoing embodiment, ..
the dimension o~ thi~ clear~nce i8 fixed once ~he mechanical L0 desi~ o~'the pipe coupling i~ fixed.
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Another embodiment of the ~ocke~ shown in Fig. 7,enables - .adjustment o~ the flo~Y rate even with the fi~ed mechanica~
design o~ the pipe couplin~.
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. : . ; -A socke~ 50 in~ludc~ ~ main piece 52, a mantle piece 5~
. a latching piece 62, a ~lo~ rate adàuste~ piece 86 a~a a ~alve pressure piece 70. At least the ~ain piece 52 and the adjuster piece 86, more preferably all the piece3,' are mad~ of a resilient material such as synthe~ic resin~
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The ~ain piece 52 is prcvided ~lith a nose section 53 adap~ed for receiving ~he nose section lZ OI the plUg 10, and

2 tail section 56 adapted for connection with any hose. The main pie~e 52 further internally defines a fore conduit 54 of B ~

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a large diame-ter and a rear condul-t 55 of a small diame-ter in a~ial col~munication with each other. At a posi-'cion near the tail section 56, a srnall flange 84 ls ~'ormed on the main piece 52 for snap coupling with the adjuster piece 86. '~he no~e sec-tion 53 is provided with a tongue 69 projecting forrlards.guide slot 78 is ~ormed through the wall o~ the main piece 52, which extends spirally over a preseribed length. ~ flow ra-te indicafor band 98 is disposed to the outer surface of the main piece 52. ~his indicator band 9~ extends in the peripheral direction and includeS flow -rate indications. One example o-f such an indication is shown in ~ig. 12, in which ~I designates high flow rate.

~ he mantle piece 58 is fixedly lnæerted over the nose sec-tion 53 of the main piece 52 in an arrangement such -tha-t an annular groove 66 is left in front o the fore end of the .
nose sec~ion 53. A rad~al opening 59 is formed in the ~antle piece 58 in order -to receive the latching piece 62 as herein-a~ter described in ~f~re detail. An axial conduit 60 i~ formed in the mantle piece 58 in comm~lica~ion with the -ore conduit 54 o the main piece 52.

'~he latching piece 62 inclucles a ring section 64 receivec~
in the annular groove 66 provided by -the ma-rftle piece 587 and a tongue 68 e~-tendlng rearwards and located in -the radial open-- : ,, - .' : : ! ': .
~ '.~' ;.,` `:

2~2 ing 59 of -the man~le piece 58. Under the condition sho-;~ in the drawing~ t'ne tongu.e 6S of t~e latchin~ piece 62 res-t~ on the tongue 69 o~ -the main piece 52~ In other ~lords, t~e latiching piece 62 is suspensibly sup~orted by -the m~ln piece 52 in the m2ntle piece 58 as shown in Fig. 8. Here~ the e~iposed outer surface of -the latchin~ piece 62 is ~ub~tantially flusll :Yith that of the mantle piece 58.

~ he ~alve pressure piece 70 is slidably inserted into the -fore conduit 5~ of the m~in piece 52 by means o-E seal rings 72. ~he pressure piece 70 is provided with a center projection 74 e~tending for;/ards, and an axial conduit 71 opening in the center projection 74. This pressure piece 70 is provided, in its outer surface, with a recess 76.

The Llow rate adjuster piece 86 is inserted over the middle sec~ion of tke main piece 52 and internally deflnes a ~uide groove 88 extending in the axial d~rectlon. A guide pin 82 is inserted into the recess 76 of the pressure piece 70 via ~he ~uide s~ot 78 of the main piece 52 with its he~d 80 being receive~ in the guide grooV9 8S of the adjus-ter piece 86. The 2dauster piece 86 is desig~ed so that its inner surface is in ti~h~ pressure contact ~ith the head 80 o-f the guide pin 82.
~o-nse~uent~-~, as the zdjuster ~iece 86 is ~ lly ~urned about the l~ain piece 52, ~he guide pin 82 revolves helically about t~e a~is of the main piece 52 due to the helical arrangeme-n~
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of the guide slot 78 and this helical revolution oE the guide pin 82 causes axial movement of the pressure piece 70 by means of the engagement of the guide pin 82 with -the recess 76 in the pressure piece 70.

As best seen in Figs. 7 and 9, the adjuster piece 86 is further internally provided with a -tongue 90 which extends forward. Axially extending grooves 92a, 92b and so on are formed in the inner surface of the tongue 9Q at pre-scribed, preferably equal, intervals in the periphery direc-tion. A projection 94 is formed on the outer surface of the main piece 52, which is adapted for snap engagement wi-th any of the grooves 92aJ 92b and so on.

As an alternative, like grooves may be made in the outer surface of the main piece 52 and a like projection on the inner surface of the tongue 90.

At a position corresponding to the flow rate indi-cator band 98 on the main piece 52, a radial opening 96 is formed through the adjuster piece 86 so that each flow rate indication is visible from outsideO It will be well under-stood that the interval between adjacent grooves, e.g. 92aand 92b, should be equal to that between the adjacen-t flow rate indications.

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`~ 2~ 2 The socket 50 shown in Fig. 7 is adapted for assembly with the plug 10 shown in Fig. 1.

In order to assemble the pipe coupling, the nose section 12 of the plug 10 is inserted into -the fore condui-t 54 of the socket 50, the conical -flange 24 of the plug 10 depresses the ring sec-tion 64 of the latching piece 62 into -the annular groove 66 provided by the mantle piece 58 and the tongue 69 of the main piece 52 fle~es towards the axis of the pipe coupling being pressed by the latching piece 62.
This procedure is substantially the same as tha-t shown in Fig. 6, in which the latching piece 62 is depressed by the finger F.

Further insertion of the plug 10 brings the latching groove 26 in the plug 10 to the position of the annular groove 66. Then, the ring section 6~ of the latching piece 62 automatically slips into the latching groove 26 in the plug 10 due to the spring-back of the resilient tongue 69 of -the main piece 52. Thus, the plug 10 and the socket 50 are firmly assembled together as shown in Fig. 10 Under this condition, the flow rate is set to the highest level and the indication H appears in the radial opening 98 of the adjuster piece 86 as shown in Fig. 12.

The center projection 74 of the pressure piece 70 is in-serted into the ~ore conduit 38 of the plug 10 and pushes - : - : ~ . . ~ ,, ,. ' ' , '' '. ', ~Z72Q;Z:

the valve 30 rearwards off the valve seat 3~ by means o~ the front extension ~2 while overcoming the repulsion of the compression spring 28. Consequen-tly, a flow passage is established through the pipe coupling, which includes -the condui-ts 36, 37 and 38 o-f the plu~ 10, the clearance be~ween the conical head o~ -the valve 30 and -the valve seat 3~, the axial condui-t 71 of -the pressure piece 70, an~l the conduits 54 and 55 of the socket 50.

As described already, the flow rate of the fluid passing through the pipe coupling is set to the highest level in the situation shown in Fig. 10. Assuming that the groove 92a in Fig. 9 corresponds to the highest flow rate `
level, and the groove 92b the lowes-t flow level, i.e. the naught flow rate, the axial position of the pressure piece 70 changes as the adjuster piece 86 is axially turned about the main piece 52. That is, the pressure piece 70 moves rearward as the adjuster piece 86 is turned from the posi-tion shown in Figs. 9 and 10. With this turning of the adjuster piece 86, different flow rate indications appear in the radial opening 98 in the adjuster piece 96 so that an operator can recognize the flow rate to be selected. T~e above-described axial movement of the pressure piece 70 is caused by engagement of the guide pin 82 with the recess 76 in the pressure piece 70 by means of the helical guide slot 78 in the main piece 52, and by the pressure contact of the guide pin 82 with the adjuster piece 86.

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7Z~2 Under the condition shown in Fig. 11, the projec~
tion 94 on the main piece 52 is in engagement with the groove 92d in the -tongue 90 of -the adjus-ter piece 86 and -the flow rate is set -to naugh-t, Possibly an in~ication such as "L"
may appear in the radical opening 96 in the adjuster piece 86. In this situation, the pressure piece 70 is registered at the rearmost position and, despite the contact between the pressure piece center projection 74 and the valve front extension 42, the valve 30 remains in contact with the valve seat 34. In other words, passage of the fluid through the pipe coupling can be blocked even retaining the assembled state of the pipe coupling.

When the tongue 68 of the latching piece 62 is depressed by the operator's finger F under the condition shown in Fig. 11, the ring section 6~ of the latching piece ~ -62 is forced to fully sink in the annular groove 66 of the socke-t 50 off the latching engagement with the latching groove 26 in the plug 10 so that the pipe coupling can easily be disassembled.

For flow rate adjustment in the prior art, it is necessary to attach an additional flow rate adjuster such as a cock to the pipe coupling and -this caused a complicated ;
and enlarged construction of the pipe coupling and its re-lated parts in the piping system.

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In accordance with the present invention, the valve is provided with the dual functions, one blocking and open-ing of the ~low passage and -the other adjustment of the -flow rate. Such dual Eunctlons are provided by -the related mech-anism fully encased within the pipe coupling itself~ This greatly simplifies and minimizes the construction of the pipe coupling and its related parts in the piping system.

It should be well appreciated also that, in accord-ance with the present invention, the above-described flow rate adjustment is carried out whilst causing no disassembly of the pipe coupling. Only a simple finger action for axially turning the adjuster piece 86 enables such flow rate adjust-ment.

As the guide pin 82 is -tightly pressed by the inner surt'ace of the resilient adjuster piece 86, accidental move-ment of the guide pin 82 is well avoided. Further, frictional contact between the seal rings 72 on the pressure piece 70 and the well defining the fore conduit 54 of the socket 50 also hinders unexpected movement of -the guide pin 82. In other words, except for the intended finger action on the adjuster piece 86~ selected flow rate can be retained with-out any unexpected change.

Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. An improved pipe coupling comprising a plug and a socket separably assembled with each other;

said plug including a tubular nose section having a fore conduit, an annular latching groove formed in its outer surface, and an internal valve seat, a tubular tail section coupled liquid tight to said nose section and having intermediate and rear conduits in communication with each other, a valve arranged in said intermediate conduit of said tail section and having a front extension slidably received in said fore conduit of said nose section, said front extension having at least one radial opening near its junction to said valve, and means for resiliently urging said valve to pressure contact with said valve seat in said nose section, said fore, intermediate and rear conduits forming an axial flow passage through said plug;

said socket including a tubular main piece made of a resilient material and having a nose section adapted for receiving said nose section of said plug, a tail section extending rearward from said nose section, a tongue projecting forward from said nose section, a center projection extending forward from said nose section, and an axial through conduit opening in said center projection, a tubular mantle piece fixedly inserted over said nose section of said main piece whilst leaving an annular groove in front of said nose section of said main piece, and having a radial opening, and a latching piece having a tongue resting on said tongue of said main piece in said radial opening of said main piece, and a ring section normally partly received in said annular groove provided by said mantle piece;

said ring section being fully sunk in said annular groove provided by said mantle piece when said tongue of said latching piece is depressed towards the axis of said pipe coupling, and said ring section being automatically placed in engagement with said latching groove in said plug due to resiliency of said tongue of said main piece in the assem-bled state of said pipe coupling.

2. Improved pipe coupling as claimed in claim 1 in which said center projection of said main piece has a dimension such that, in the assembled state of said pipe coupling, said center projection is at least partly received in said fore conduit of said plug and moves said valve rear-ward of said pressure contact with said valve seat by means of said front extension.

3. An improved pipe coupling comprising a plug and a socket separably assembled with each other;

said plug including a tubular nose section having a fore conduit, an annular latching groove formed in its outer surface, and an internal valve seat, a tubular tail section coupled liquid tight to said nose section and having intermediate and rear conduits in communication with each other, a valve arranged in said intermediate conduit of said tail section and having a front extension slidably received in said fore conduit of said nose section, said front extension having at least one radial opening near its junction to said valve, and means for resiliently urging said valve to pressure contact with said valve seat in said nose section, said fore, intermediate and rear conduits forming an axial flow passage through said plug;
said socket including a tubular main piece made of a resilient material and having a nose section adapted for receiving said nose section of said plug, a tail section extending rearward from said nose section, a tongue projecting forward from said nose section, and fore and rear conduits in axial communi-cation with each other, a tubular valve pressure piece axially slidably arranged in said fore conduit of said main piece and having a center projection extending forward, means for registering said valve pressure piece at an axial position in said fore conduit of said main piece a tubular mantle piece fixedly inserted over said nose section of said main piece whilst leaving an annular groove in front of said nose section of said main piece, and having a radial opening, a latching piece having a tongue resting on said tongue of said main piece in said radial opening of said main piece, and a ring section normally partly received in said annular groove provided by said mantle piece, and means for changing said axial position of said valve pressure piece in accordance with the selected flow rate of the fluid passing through said pipe coupling;

said ring section being fully sunk in said annular groove provided by said mantle piece when said tongue of said latching piece is depressed towards the axis of said pipe coupling, and said ring section being automatically placed in engagement wih said latching groove in said plug due to resiliency of said tongue of said main piece in the assem-bled state of said pipe coupling.

4. Improved pipe coupling as claimed in claim 3 in which said center projection of said valve pressure piece has a dimension such that, in the assembled state of said pipe coupling, said center projection is at least partly received in said fore conduit of said plug and moves said valve rearward off said pressure contact with said valve seat by means of said front extension when said selected flow rate is other than naught.

5. Improved pipe coupling as claimed in claim 3 in which said registering means includes a guide pin inserted into a recess formed in said valve pressure piece via a guide slot formed through said main piece, and said guide slot extends over a prescribed distance helically about the axis of said socket.

6. Improved pipe coupling as claimed in claim 5 in which said changing means includes a tubular flow rate adjuster piece made of a resilient material and inserted over said main piece in the area of said guide pin in pres-sure contact with the head of said guide pin, said adjuster piece is axially turnable relative to said main piece, and said adjuster piece is provided with means for latching said adjuster piece to a selected angular position with respect to said main piece.

7. Improved pipe coupling as claimed in claim 6 in which said latching means includes a tongue extending axially from said adjuster piece and provided, in its surface facing said main piece, with a plurality of axial grooves arranged in parallel to each other, and an axial projection formed on the outer surface of said main piece and adapted for engagement with either one of said axial grooves in said tongue of said adjuster piece when said adjuster piece is turned about said main piece.

8. Improved coupling as claimed in claim 6 in which said latching means includes a tongue extending axially from said adjuster piece and provided with an axial projection on its surface facing said main piece, and said axial projection on the tongue is engageable with either one of axial grooves formed in the outer surface of said main piece in parallel to each other.

9. Improved pipe coupling as claimed in claim 6 further comprising means for indicating said selected flow rate in a fashion visible from outside.

10. Improved pipe couling as claimed in claim 6 in which said indicating means include a flow rate indictor band disposed on the outer surface of said main piece, and said adjuster piece is provided with a radial open-ing into which a part of said flow rate indicator band appears.

11. Improved pipe coupling as claimed in claim 1 or 3 in which the outer surface of said latching piece is substan-tially flush with that of said mantle piece when said latching piece is suspensibly held by said tongue of said main piece.

12. Improved pipe coupling as claimed in claim l or 3 in which said resilient material is synthetic resin.

13. Improved pipe coupling as claimed in claim 1 or 3 in which at least one of said plug and socket is entirely made of a resilient material.

14. Improved pipe coupling as claimed in claim 1 or 3, in which at least one of said plug and socket is entirely made of synthetic resin.