The present invention relates to manual guns for the spraying application of coating substances such as paints, chemicals and the like.
More in particular the invention relates to a spray gun of the type comprising a body having a union for the inflow of a substance to be sprayed, whereto is able to be connected a cup containing the substance to be sprayed and having an outflow union designed to be coupled with said inflow union through removable connecting means.
Traditionally, the removable coupling between the inflow union of the gun body and the outflow union of the cup is achieved by means of a screw-on system: more in particular, through an external thread whereof is provided the inflow union of the gun body whereon is screwed an internal thread of the outflow union of the cup or, alternatively, by means of an external thread of the outflow union of the cup which is screwed into an inner thread of the inflow union of the gun body.
This traditional connection system has essentially two problems.
In the first place, the screwing and unscrewing between the cup and the gun body require a relatively long and inconvenient operation.
In the second place, with this system, which is technologically simple and hence easily reproducible, there is the risk that the guns of a given manufacturer may be equipped with cups not produced by the same manufacturer, i.e. not original. In this case, it is possible that non original cups may induce an improper operation of the gun, and otherwise an operation that does not correspond with the use of the original cups for which the gun was designed.
To attempt to solve this second problem, international patent application
The object of the present invention is to provide a simple, economical and functional solution to both technical problems described above.
According to the invention, this object is achieved thanks to the features set forth in the characterizing portion of claim 1.
The invention will now be described in detail in reference to the accompanying drawings, provided purely by way of non limiting example, in which:
Initially referring to Figure 1, the number 1 designates the body of a gun for spray painting, provided posteriorly with a grip 2 and anteriorly with a generally conventional nebuliser nozzle 3.
In the upper part of the gun body 1 is formed a tubular boss 4 communicating with a feeding conduit, not shown, connected in known fashion to the atomising nozzle 3.
Into the boss 4 is permanently inserted, for example screwed, a tubular inflow union 5 adapted for the removable sealed connection of a cup 6 containing the substance to be sprayed by means of the gun 1. In the case of the illustrated example, the substance to be sprayed contained in the cup 6 is in use fed to the gun by gravity, placed in upside down position above the gun 1.
As shown in detail in Figures 2 and 3, the inflow union 5 has a cylindrical terminal portion 7, an intermediate portion with conical inner surface 8 and an initial cylindrical portion 9 with narrowed conformation, i.e. having reduced cross section with respect to that of the cylindrical terminal portion 7.
The edge of the free end of the narrowed initial portion 9 has an annular inner narrowing with conical surface 10.
The cylindrical terminal portion 7 is formed with a pair of diametrically opposite slits 11, each whereof has, as shown in detail in Figure 4, a general "L" shape with an axially directed upper segment 12 and an inclined or generally horizontal lower segment 13.
The reference 14 designates a ring nut which coaxially surrounds in rotatable fashion the cylindrical terminal portion 7 of the inflow union 5 and is axially movable relative thereto for a downwards travel, i.e. the initial narrowed portion 9, by an extend that is limited inferiorly by an arresting ring 15. As Figure 3 shows in detail, the ring nut 14 is formed on its inner wall with an annular groove 16 communicating with a pair of diametrically opposite axial grooves 17, whereof one is shown in Figure 3.
The cup 6 shown in Figure 1 is generally conventional and consists of a container of generally cylindrical shape, for example metallic or made of moulded plastic material, provided at an end with a removable lid 18 which may have an opening and aerial valve 19, and formed at the opposite end with a generally funnel shaped bottom 20 provided with an axial outflow union 22 able to be coupled in sealed, removable fashion with the inflow union 5 of the gun body 1, in the manner made more readily apparent below.
Referring now in greater detail to Figures 2 and 3, the outflow union 22 has a complementary shape to the inflow union 5: in detail, it comprises a broadened cylindrical initial portion 23, complementary to the final portion 7 of the inflow union 5, an intermediate portion with conical outer surface 34 complementary to the conical inner surface portion 8 of the inflow union 5, and a cylindrical terminal tang 24, complementary to the initial portion 9 of the inflow union 5.
The terminal tan 24 of the outflow union 22 has at its free end an externally enlarged annular edge 25 with a conical outer surface 26 complementary to the conical surface 10 of the inflow union 5.
As shall be described below, one or the other of the conical surfaces 10 or 26 can be provided with a circumferential throat for the insertion of a sealing O-ring made of elastomeric material, not shown in the drawings. However, said sealing O-ring is optional.
The reference number 27 designates a radial pin or stake which traverses the broadened cylindrical initial portion 23 of the outflow union 22 and whose opposite ends project externally thereto. It should be noted that the through pin 27 could be replaced with two distinct and separate pins, projecting outside two diametrically opposite areas of the initial cylindrical portion 23, in a wholly equivalent manner at the opposite ends of said through pin 27. It should also be noted that, instead of two diametrically opposite projecting pins, a single pin could also suffice, projecting radially outside the initial cylindrical portion 23. In this case, the cylindrical terminal portion 7 of the inflow union 5 may be provided with a single L shaped slit 11 and, similarly, the ring nut 14 may be provided with a single axial groove 17.
With the above described arrangement, the removable connection between the outflow union 22 of the cup 6 and the inflow union 5 of the gun is achieved, according to the peculiar characteristic of the invention, through a bayonet coupling with associated safety device for its reversible locking.
Said bayonet coupling is in practice constituted at one side by the opposite projecting end of the diametrical pin 27 of the outflow union 22, and at the other by the L shaped slits 11 of the inflow union 5, whilst the safety device is constituted by the rotatable and slidable ring nut 14.
To achieve the coupling between the cup 6 and the gun 1 it is simply necessary, starting from the configuration shown in Figure 1, to introduce axially the outflow union 22 into the inflow union 5, until the abutment between the conical surfaces 34 and 8 and 26 and 10, in the manner shown in Figure 2. During this manoeuvre, the projecting ends of the pin 27 are introduced into the axial portions 12 of the slits 11. Then, rotating the unions 22 and 5 relative to each other, the projecting ends of the pin 27 are made to slide along the portions 13 of the slits 11, until positioning themselves in correspondence with their terminal ends: the bayonet coupling between the unions 22 and 5 is thereby completed. The stability of said connection can be improved as a result of the yielding and of the consequence elastic reaction of the optional sealing O-ring inserted between the conical surfaces 10 and 26, or with the aid of possible additional elastic means. In any case, as explained above, the presence of the sealing ring is not strictly necessary, although it is preferable also for the purposes of a more secure hermetic seal between the unions 22 and 5.
To proceed with the positive locking of the bayonet coupling, it is therefore simply necessary axially to position the safety ring nut 14 engaging the projecting ends of the pin 27 into the axial grooves 17, and then to rotate said ring nut 14 to engage the ends of the pin 27 into the annular groove 16.
In this way, all risks of accidental or undesired disengagement between the cup 6 and the gun 1 are prevented.
To remove the cup 6, it will thus be sufficient to disengage the safety ring nut 14 from the projecting ends of the pin 27 and then disengage said ends of the pin 27, first by rotation and then axially, from the slits 11.
The bayonet coupling system with positive safety locking described above is applicable not only to conventional cups 6, but also to disposal cups, such as the one designated by the reference number 28 in Figure 4, in which parts that are identical or similar to those already described above are designated by the same numerical references.
According to said variant, the cup 28 comprises a disposable container 29, normally made of moulded plastic material, and the outflow union 22 is borne by a substantially funnel shaped bottom 30 separated from the container 29 and connected in removable fashion thereto by means of a ring nut 31. The arrangement of the cup 28 could be, for example, of the type described and illustrated in document
As an additional alternative, the funnel shaped bottom 30 can be disposable like the container 29: in this case, the outflow union 22 may also be, with the or with each projecting radial pin for the engagement of the or of each L-shaped slit 11, integrally formed by moulding of plastic material with said bottom 30.
Naturally, the construction details and the embodiments may vary widely from what is described and illustrated herein, without thereby departing from the scope of the present invention as defined in the appended claims.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.