US2101164A - Spray gun with pneumatic needle valve control - Google Patents

Description

Dec. 7, 1937. s. BRAMSEN ET AL 2,101,164

SPRAY GUN WITH PNEUMATIC NEEDLE VALVE CIONTROL Filed Nov. 27, 1955 y ZSheetS-Sheet l V Y M @QZMWW Dec. 7, 1937.

s. BRAMSEN ET Al.

-SPHAY GUN WITH PNEUMATIC NEEDLE VALVE CONTROL Filed Nov. 27, 1935 Patented Der.. 7; 1937 P'ATENTor-'Flcs s'raAY GUN wrrn rNaUMA'no NEEDLE vliLvrz Courson svena Bremen, ma Frm wahiln, Chrono. nl., unimore to Blnks Manufacturing Company, Chicago, Ill., a corporation of Delaware AAppliemnm November 21, 1935, sel-m No. 51.7164.

'zo calm. l (ci. a99-140.1)

O ur invention relates to a spray (or other spraylappliance allied thereto) of the class in which the material-discharge controlling valve,

. (or so-called needle valve) is continubusly urged toward its closure position `by a spring and is. opened by the pressure of air on a piston fastened to the needle valve, and lin general aims to provide la spray gun of the following characteristics:

1) A mechanism aording alspeedy, positive and full openingof the material valve, in re-` sponse to the retraction of the trigger which opens the air valve. (2) A mechanism of this kind which will require only a slight additional retracting pressure on the trigger, in addition'l to' that needed for opening the. air valve,'for admitting air to actuate the needle-valve retracting piston.

. (3) A mechanism for this purpose which will leave the entire part of the needle valve between o the usual forward guide for that valve and the pncumatically actuated piston free to flex, so as to avoid a cramping or binding of the needle valve. v

(4) A' mechanism oi this type whichwiil peri, mit, a ready adjusting of the eifective length of the needle valve, and thereby' of thefextent of the-opening movement of .this valve. without temptinga user to tamper with the adjustment.A

(5) A mechanism of thistype permittingthe auxiliary valve for controlling the admission of piston retracting air to' be coaxial with the needle v alve.

(c) A mechanism of this type which wm per;

mit a venting of air from in front yof the piston when the retracting pressure on the trigger is relaxed, and which will automatically annui the said venting before the4 opening of the auxiliary valve which controls the admission of -air for actuating thesaid piston. ('7) A spray gun .of the above recited characteristics which will not be materially heavier, more bulky or moreexpensive than a gun of the same operating capacity in which the needle valve is opened through the action of rigid members interposed between this .valve and the trigger oi the gun. Illustrative of the manner in which we accomplish the above recited objects, Fig. 1 is a central, longitudinal and vertical section of the major portions of a spray gun embodylngour invention, with both the air valve and the pneumatic needle valve control assembly shown. in elevation, showing the partsA as they appear when the trigger is not retracted.

Fig. 2 is an enlargement of pari'| of lillg. 1, with the air valve as well as the' pneumatic needle "i valve control mechanismshown in central and J vertical section.

l Fig. 3 is' a section similar to Fig. 2, but showing the parts as they appear when the valves have been fully opened in response to aI retraction of the trigger.

Fig. 4 is an enlargement of a portion of Fig. ii,

and Fig. 5 is an' enlargement vof the same portion showingvthe positions of the parts before the trigger was retracted.

Fig. 6 is an enlarged perspective view of the thrust member associated with the vent nipple. Fig. 1 is an enlarged perspective view vof the vent nipple, showing the longitudinal surface grooves on thisnipple. t

Fig. 8 is a still more enlarged and fragmentary front elevation of the vent nipple. j

' In the illustrated embodiment,.the .spray gun body isrof the two-part type disclosed in the The forward body part F supports a material nozzle N upon which a cap type air nozzle A is clamped by a retainer ring R threaded on the,

said forward body part, the discharge from the material nozzle being controlledby a needle valve I3 which extends rearwards axially into a bore l Y formed in the body tail part 2 which yconnects thefrear end of the stock S with the usual depending handle H. This bore'i has a diametrically contracted forward. end portion la connected to the main part of the said bore by a rearwardly facing annular shoulder 3. as shown in Figswi and 5 and a port P connects the for-` ward portion of the larger diametered part of the bore I with themain air'passage in th stocks. n Y,

The tail 2 also has a second bore 4 extending through it below and parallel to the bore I ior housing the tubular body I of an air valve which also includes -a movable valve member V fast on a valve stem 8' extending slidably `forward through the saidvalve body, the bore 4 being closed at itsfrear end by a cap C, and a compression spring 24 being interposed between the valve member V and the said cap. When the air valve is opened through `rearward pressure of the usual gun trigger T against the valve stem I. air iiows from an air supply passage 'I in the handle 1.11329 the lower bore 4 and the interior of the Cai tubular body 5 and issues from the latter through ports 8 into the part of the lower bore l which is forward from the seat 5a for the valve member V. This air then flows upward through a port 9 into the upper bore I and through the port P into the stock passage M.

Detachably socketed in the upper bore I is a tubular guide (generally designated as I) which has its rear end closed by a detachable cap 2li and which has a mid-length portion threaded (as at "Illa in Fig. 3) into the upper bore I. This guide has a cylindrical portion IIlb fitting the part of the said bore behind the said threaded connection, and also has a larger diametered rear part IIlc engaging the rear end of the tail 2 of the gun body.

The part ofthe said guide forward of its said threaded connection to'the gun body is generally shaped like a spool presenting a shank Ind, sufiiclently smaller in diameter than the part of the bore I which houses it, so that air can readily ow around this shank from the port 9 to the port P, and this spool-shaped part of the guide has an axial bore II, the main and medial portion of which shank Abore has a thrust tube I2 extending slidably through it.

` The rear endv portion IIa of the said shank bore II is enlarged in diameter and has one or more lateral ports I4 leading from it to the exterior of the said shank. This shank bore portion also has its extreme rear end flared to aiford an annular seat adapted to be engaged by the diametrically enlarged rear end portion I2a of the thrust tube (as in Fig. 2) so as to prevent air entering the lateral ports Il from reaching the part of the bore of the guide beh.nd the spool-like shank portion IIld of the said guide.

The forward portion of the bore of this shank Id is also enlarged diametrically for a considerable depth so as to house an annular packing I5 (which surrounds a part of the thrust tube I2) and also to house the rear portion of a tubular gland 46 which is threaded into the enlarged forward portion of the said bore and which gland clamps the packing I5 against the annular bottom of the said enlarged forward bore portion. This forward' shank portion also has its extreme forward end portion I 0b (Fig. 4) fitted into the frontal contracted portion Ia of the said upper bore I in the tail of the gun, and has a somewhat rnore rearward peripheral flange Illf which clamps an annular gasket g against the previously recited shoulder 3 when the said tubular guide is screwed into the tail bore I until the head end Illc of that member engages the rear of the body tail.

The more rearward exteriorly cylindrical' portion IIlb of the said guide has a cylindrical bore part slidably housing a piston through which the rearward portion of the needle valve I3 extends and to which that valve is adjustably fastened. This piston includes a metal stem I6 through which the needle valve is threaded, this stem'- having a peripheral flange I 6a .intermediate its ends, and the needle valvebeing locked to the said stem by a locknut I'l threaded on this valve behind the said stem.

Bearing rearwardly against the flange Ilia is a forwardly open cup-shaped piston ring 4I (of leather or the like) which has its annular cupbottom portion clamped against the forward face of the said flange by a ring I8 sleeved on the stem I6 behind a nut I9 threaded on the forward pcrtionof that stem. as shown in F18 2- The cap 20 which is threaded into the rear end of the said tubular member has a diametrically enlarged portion 20a bearing against -the rear end of the said member, to limit the extent to which the cap is screwed into that member, and this cap also has a vent bore 20h in its rear end 20c to permit the escape of any compressed air which might seep past the piston ring 4I into the interior of the cap. Moreover, the cap 20 is of such length that its forward end will engage the piston flange I6a to limit the rearward movement of the piston (as, shown in Fig. 3) and a compression spring 2| interposed between the piston flange I6a and the rear end 20c of the cap continually urges the piston forwardly.

With the bore of the slidable tube I2 considerably larger than the diameter of the needle valve I3, and with the wiper 28 made of flexible material, the needle valve is positively guided only by the usual guide bore 3 in the forward body part and by the piston, thusleaving the intervening major-part of the said valve free to flex, so as to prevent a cramping or binding of the needle valve in case this is not exactly straight axially. So also, by providing a wiper arrangement for effectively sealing the forward end of the said slidable tube we could prevent the-escape of air through the bore of that tube, from the cylinder space in front of the piston, when the gun is in operation. However, when the tube I2 is slid forward to shut oif the admission of further air into the piston cylinder through the ports Il, the residual compressed air in the cylinder in front of the piston, which could not issue through the tube past the wiper members, would act on the piston to prevent a speedy and complete forward movement of the piston for causing the needle valve to close the Idischarge port yof the material nozzle, if no means were provided for venting such air.

In the absence of a suitable venting provision, a releasing of the retracting pressure on the trigger, while allowing the spring 24 to close the air valve promptly, would permit material to be ejected for some time after; and this material would splash out unatomized so that some of it would harden on the front of the material nozzle and in the discharge port of that nozzle to gum the needle valve to this nozzle. To avoid these serious objections, we provide the following provisions for permitting residual compressed air in the piston cylinder to vent through the bore of the slidable tubef and for automatically annulling such venting as soon as the gun is again operated:

Threaded upon the forward end of the slidable tube I2 is a vent nipple 25 (Fig. 4) which is locked to that tube by a locknut n behind the said nut. 'I'his vent nipple 25 has a peripheral flange 25a on its forward end, and has longitudinal surface grooves 25h extending along its shank and opening through the said flange, (as shown in Fig. 7), and the forward portion of the vent nipple is housed by a stop nipple 26 threaded into the rearward portion of a rearwardly opening cap nut 21. This cap nut has its head 27a provided with an axial bore 2lb through which the needle valve I3 freely extends, and the stop nipple 26 has at its rear end an interior flange 26a disposed behind the peripheral flange 25a on the vent nut.

The cap nut 21 houses an annular wiper 28 (of leather or the like) which has its radially outer portion 28a bearing forwardly. against the axially perforated head 21a of the cap nut, and

der through the ports I4 almost instantly moves which wiper has its radially inner portion formed as a rearwardly tapering frustrum of a hollow cone fitted upon the portion of the needle valve I3 which extends axially'through the cap nut. Disposed behind this wiper is a presser member; a tubular shank 29 having an axial bore through which the needle valve freely extends, and which has at its forward end a peripheral flange 29, this being clamped against the cap nut head y21a by the shank of the stop nipple26.

This tubular shank 29 of the presser member has the forward portion 29h of its bore flaring forwardly to fitgagainst the hollow conical part 28 offthe Wiper, while theperipheral portion of the rear end of the said shank 29 tapers rearwardly and is adapted to fit against a forwardly flaring seat25c at the forward end of the bore` of the vent nipple 25. `Thus assembled, the cap` nut 21, the wiper and the presser member constitute a presser member through which rearward pressure of the trigger can be transmitted to the vent nipple 25 and hence to the tube I2, the rear end portion of which tube. controls the admission of compressed airthrough the po'rt I4 to the piston cylinder. n i

To complete the automatic venting provision, we interpose a compression spring 39 betweenthe flange 29a of the thrust member and the frontal flange 25a on the vent nipple 25, which spring continually tends to slide the said presser member forwardly; and a second and strong spring 3| (interposed between the lock nut u and an interior flange 46a on the gland 46) which spring 3| continually tends to slide the tube I2 forwardly toward the position of Fig. 2 in which the rear end portion of vthis tube prevents air from entering the piston cylinder. These springs 30 and 3| are each so light that their joint strength is c'onsiderably less than that of the spring 2| behind the piston. Moreover, the .just described assemblage is so proportioned inthe length of its parts (longitudinally of the needle valve) .thatthe head 21a ofthe cap-nut of the presser memb^r will be spaced rearwardly from the trigger T of the gun when the latter depends by gravity, and desirable even when the trigger first engages `the stemof the closed air valve asfshown in Figs. l and 2.

When our spray gun is not being-operated, the intermediate spring 3| holds; the sliding tube I2 in its forward position of Fig. 2,'so that the rear end portion of this tubeeffectively closes thev air ports I4 leading to the piston cylinder. At the same time, the lighter forward spring 30 holds the thrust member (namely the wiper and the parts supported by the latter) as far forward from the said tube as the engagement of the interior flange26a on the stop nipple 2E) with the flange 25a of the surface-grooved vent nipple 25 will permit; so that the grooves in the last named nipple, together with the spacing of that nipple from the thrust member 29 afford a free connection ofthe outer air to the bore of the tube I2.`

When the gun trigger is retracted, it first opens the air valve V and then must compress the (lightest) forward spring 30 sufficiently to permit the tubular shank part 29 of the said thrust member to engage the vent nipple 25 before the trigger starts tomove the tube rearwardly, thus affording a time interval (after air is supplied to the air passages of the gun) before air can be admitted to thepiston cylinder by a trigger retraction sumcient for compressing the stronger' intermediate spring 3| also. Then, as soon as the flaring rear end portion |2a of the slidable tube I2 leaves its seat, air admitted to the piston cylinthe piston rearwardly until thev piston flange I6a engages the forward end of the closure cap 20 behind the piston.A

By making-the joint strength of the springs 30 and 3| much` less than that of the spring 2l which continually urges thev piston forwardly, and also considerably less than that of the airvalve closing spring 24, we enable our spray gun to be operated with a quite .light digital pressure on the trigger. When this trigger pressure is released, the rear spring 2| immediatelyA slides the piston and needle valve forward. Theintermediatespring 3| likewise slides the tube I2 forward for effectively closing the air inlet' ports I4 leading to the piston cylinder; and the forward spring 30 slides the wiper 28 and the parts supported by the latter forward to their idle position of Fig. 5, vthus permitting residual compressed air in front of the piston to vent by fiowing alongthe arrow lines shown in that figure. i

With ourspray gun thus constructed, a detaching of the cap 20 from the pistoncylinder allows the piston and needle valve assembly to be slid rearwardly to expose the piston behind the said cylinder for adjusting the effective length of the needle valve without disassembllng any parts. And when the needle valve and piston assembly is thus detached, a detaching of the trigger from the gun body (in the well known usual manner) also permits a ready detaching of the cap nut 21 of the presser member for replacing the wiper 28 when the latter becomes worn.

By forming the tube guide IIld as an integral extension of the piston cylinder we allow air to enter `this cylinder through one or more quite short ports leading directly from the main air passage 9 of the gun; and by forming the guide IIJd for the control tube I2 as an integral extension of the said cylinder we simplify the construction and reduce the weight of the gun in comparison with the previously proposed use of a separately attached control cylinder. Moreover, most of the parts which together effect the automatic ventingV of the piston cylinder are simple and inexpensive screw machine products.

However, while we have heretofore described our invention in connection with a spray appliance having a' manually actuable trigger, and as including numerous desirable details of construction and arrangement, many changes might obviously be made without departing either from the spirit of our invention or from the appended claims.

We claim as our invention:

l. In a pneumatic spraying appliance of the class in which a rod-like needle valve is longitudinally moved rearwardly for opening the discharge of material, and in which the body of the appliance has a bore coaxialwith the needley valve: a rearwardlyi'closed cylindermounted in the saidbore and housingrthe rear end portion of the said valve, a piston fast upon the valve and slidable in the said cylinder, a springinterposed between the piston and therear end of the cylinder for continually urging thepiston forwardly; the cylinder having a tubular guide of relatively smaller bore coaxial with and extending forwardly from the cylinder and connected to the cylinder by an annular portion presenting a rearwardly facing annular valve seat; a tube longitudinally slidable in the said guide and through which tube a part vof the needle valve extends, the tube having a, rearward portion adapted to seat on the said valve seat; the said tube and guide being so formed as to affordv an annular space around a part of the tube forward of the said seat when the said 'tube part is thus seated;

the gun body having an air passage, and thel guide having an air port leading from the air passage to the said space.

2. A pneumatic spraying appliance as per claim 1, in which the bore of the said tube is considerably larger in diameter than the part. of thev needle .valve which extends through it, so as to permit air to vent through the tube from the part of the cylinder in front of the piston; the appliance also including means responsive to the position of the said tube with respect to .the said guide for controlling the said venting of air.

- -3. A pneumaticspraying applianceas per claim 1, vincluding spring ymeans operatively interposed between the said guide and tube, the said meansY continually urging the tube forwardly and being weaker than the said piston-urging spring.

'4. A pneumatic spraying appliance as per claim 1, including a rearwardly openable air valve controlling the admission of-air to the said passage and having a forwardly extending stem, an actu- .ating member movably supported by the appliance and extending in front of both the said ating member movably supported bythe appliance body and extending in front of and disposed for engaging both the said stem' and the said tube; thrust-transmitting means operatively interposed between the lforward end of the tube and the actuating member, through which means a rearward movement of the said member moves the tube rearwardly, the said means including a part slidably supported by the needle valve.

6. Vspray gun of the class in which a gun body supports 'a material nozzle, the discharge from which nozzle is controlled by a springclosed needle valve fastened to 'a pneumatic pis- -ton slidable in a cylinder supported by the gun body, in which the cylinder has an air port leading to its forward portion, and in which a movable trigger depends from the body in front of the said cylinder; the spray gun being characterized by including a generally tubular member extending slidably through the forward head of the cylinder, through which member the needle valve extends; the said member having a rearward part adapted simultaneously to engage the forward head of the cylinder for limiting the for- 'ward movement of the said tubular member and to shut ofi' the admission -of air to thecylinder through the said port; a thrust member slidably supported between the trigger and the tubular member for transmitting 4rearward movement of .the trigger to the tubular member; and spring means associated with the said tubular member 'for continuously urging the tube forwardly.

7. A sp'ray gun as per claim 6, including a compression spring interposed between the tubular member and the' thrust member for continually urging the thrust member forwardly, the said two members having portions thereof formed for affording a vpassageway between them through whichair in the said tube can vent out when the needle valve is spring-closed.

8. `A spray gun'of the class in which a rear- "wardly slidable. material-discharge controlling needle valve is fastened to a piston which slides in `a cylinder, in which the said cylinder has a port for admitting in front of the piston, in which an air valve controlling the supply of air to the said port is openable lby rearward movement. of, a movabletrigger through which the needle valve freely extends, and in which a spring continuallyurges the piston forwardly; the spray gun being characterized by also including a tube coaxial with the needle valve and extending slidably through an axialxbore in the forward head of the cylinder, the said tube having a rearward part adapted to seat inthe rear end of the said -bore for preventing 'the admission of air to the cylinder from the said port when the needle valve is notA slid rearward from its material discharge halting position; a second spring continually urging the tube-forwardly, and means slidable upon.

the needle valve and operatively interposed bet'ween the trigger and the tube for transmitting a rearward movement ofthe trigger to the tube. 9.- A spray gun as per claim 8,.'in which the .said interposed means' include provisions Vfor effectively closing the-forward end of the, tube v when the tube is moved rearwardV for permitting air to enter the cylinder through-the said port, the said provisions being arranged for permitting air to vent through ,the tube from the part of the cylinder in front ofthe piston when the tube is ina forward position in which the said rearward part of the tube prevents the flow of air from the said port to the cylinder.

10. A spray gun as per claim 8, in which the said interposed means include a trigger-thrust receiving member slidably supported by the needle valve, two'v annular elements respectively fast with respect to thetrigger-thrust receiving member and the said tube, and a compression spring interposed between the said two elements.

11.A A spray gun as per claim 8, in which the said interposed means comprise a rearwardly open cap-like trigger-thrust receiving member having its cap head provided with a central borethrough which the needle valve i'reely extends, an annular wiper housed by the said member and slidably fitted upon the needle valve, and mean clamping the wiper to the said member.

l2. A spray gun as per claim 8, in which the said second spring is suillciently weaker than the spring means whichurvge the tubeforward so that the rearward movement ofthe trigger will open the air valve before it begins to move the' tube rearwardly.

13. In a spray appliance in which a materialdischarge controlling needle valve is fastened' to a. piston slidable in a cylinder. in which a spring behind the piston continually urges the piston forward,and in which a movable trigger extends in front of the said cylinder: a cylinder having a smaller diametered sleeve coaxialwith and extending forwardly from the forward head of the front of `the-enlarged rear end of the tube, and

thesleeve having a portfor' admitting air to lthe, said chamber; a second spring, weaker than the piston-urging spring and operatively interposed between the ,said .sleeve and thetube for conmovement of the trigger uto the tube, the said means including an-annular wiper slidably fitted 1 upon the needle valve.

14. A spray appliance as per claim 13, including a third spring operatively interposed between the said .tube and the movement-transmitting means, and means operatively interposed between the tube and the movement-transmitting means for limiting the forward movement of the lsaid means'with respect to the said tube.

15. In a spray appliance in which a materialdischarge controlling needle valve is fastened to a piston which is continually urged forwardly by a spring. and which piston is slidable in a cylinder, a sleeve coaxial with and extending forwardlyvfrom the forward head of the cylinder and having a bore of smaller diameter than the cylinder; a tube extending slidably through the bore of the sleeve, the tube having a head at its rear end and the sleeve having a port for admitting air to the cylinder, which port is operatively controlled by the position of the said rear tube head, and the forward end portion of bore ofthe sleeve being enlarged in diameter; an annular packing sleeved upon the tube and engaging `the bottom of the said enlarged bore portion; a tubular gland threaded into the said enlarged bore portion and clamping the packing against the bottom of that bore portion; a compression spring bearing rearwardly against apart of the said gland; -an element fast on Athe tube and engaging the forward end of the said spring; a trigger movably supported forwardly of the said element, and 'means interposed between the said element and the trigger for transmitting rearward movement of the trigger to the tube.

16. Aspray appliance as per claim 15, in which the said interposed means comprise an annular element fast upon the forward end of the tube, a second annular element disposed. forward of the aforesaid member, a compression spring interposed between the said members, and means sealing the second annular element to the needle valve; the said' two elements having interengageable portions for limiting the movement of thesecond element forwardly away from the first named member, and also having annular interengageable portions disposed both for limiting the rearward movement of the first named element with respect to the said second member and for sealing the two elements to each other to cooperate with the sealing of the second element to the needle valve in preventing air in cylinder from venting forwardly through the bore of the tube; the said two elements also being relatively so formed as to permit air issuing from the bore of the tube to vent when the said annular interengageable portions are not engaging each other.

17. In a spray appliance in which a needle valve is moved in its opening direction by the rearward pressure of air on the piston. which is slidable in a cylinder, in which a, spring continually. urges the piston forwardly, 'in which air is admitted to a forward portion of a cylinder through a port leading from an air passage, and

in whlchthedsu-pply of air to .thisair passage is vcontrolled by an air-valve which ls openable by rearwardmovement:of a trigger throughwhich the needle` v alve freely extends, means whereby .thesaid rearward lmovement opens` the said port v.at .a time interval afterthe trigger has opened the air valve; the said meanslv comprising .a tube extending-slidably through the forward head of the cylinder, the, .tube having a .diametricallyr kenlarged rear end portion adapted .to seat on the said head for` limiting the forward sliding of the tube and halting the flow of air into the cylinder from the said port; spring means weaker than the said piston-urging spring and continually urging the tube forwardly; a thrust-transmitting instrumentality operatively interposed between the tube and the trigger and movable towards and away from the tube, and means associated with the tube and the said instrumentality for limiting the extent of the movement of the said instrumentality with respect to the tube in both directions longitudinal of the tube.

18. In a spray gun in which a needle valve is retractible by air pressing vrearwardly against a piston fastened to the said valve, and in which the needle valve extends freely through a trigger disposed forwardly of the piston, a longitudinally slidable tube coaxial with and freely housing a portion of the needle valve and disposed between the trigger and the piston, and means for transmitting a rearward movement of the trigger to the tube; the said means comprising: an annular member fast on the forward end of the tube and having a peripheral flange; a triggerthrust receiving member comprising a rearwardly open cap-like element having its cap top provided with a-n axial bore through which the needle valve extends; a nipple threaded into the said cap-like element and having an interior flange disposed behind the peripheral ange on theA said annular member; and a compression spring operatively interposed between the said annular member and the cap-bottom of the said cap-like member; the said annular member having longitudinal surface grooves to permit air to flow past both of the said anges when the said flanges' are in engagement with each other.

19. In a spray gun, an assemblage as per claim 18, including an annular wiper housed by the cap-like element, the wiper havingits radially outer portion bearing forwardly against the cap bottom of that member and having its bore engaging the needle valve, and an annular presser member bearing forwardly against the wiper, the wiper being clamped between the presser member and the cap bottom of the cap-like element by the said nipple, and the presser member having a rearwardly extending tubular shank'adapted to be moved into and out of engagementwith the said annular member respectively by rearward and forward movements of the presser member with respect to the said annular member.

20. In a spray gun in which a needle valve is fast upon a piston which slides in a cylinder, a tubular member coaxial with and freely housing a part of the needle valve and extending slidably through the forward head of the cylinder; the cylinder having a port associated with its forward head for admitting air in front of the piston; and the tubular membenhaving a rearward part adapted to engage the said cylinder head to limit the forward sliding of the tubular member and simultaneously therewith to halt the said admitting of air to the cylinder; the tubular member having depending in front of the said tube. through which trigger Athe needle vzelve freely extends:

and means Stor transmitting'rearward `movement of the trlerftothe said tubular member and 5 for controlling. venting ot alrfrom l,the cylinder through the said tube: the `said means comprising an annular trigger-*thrust-receiving member includinglan annular'wiper sleeved upon Ithe needle v valve, .axpresser member .disposed behind `and fast 10 with respect to the wiper and having a rearward ly extending vtubulin' stem, the rear end ot the said -stem'beingexteriorly instru-conical and adapted to seat against the forward end oi the bore oi' the said tubular member and a compression spring interposed between the presser.mem.

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