Abstract:
A gun for dispensing pasty products which includes a piston seal member mounted between a cylinder and a cartridge and through which gas under pressure passes from the cylinder to a supply container in communication with the cartridge wherein the piston seal member includes a pair of annular lips of differing diameters and an inner skirt which provide for selective sealing between the cylinder and the cartridge whenever pressure is applied to the cylinder.

Description:
BACKGROUND OF THE INVENTION 
     1. History of the Related Art 
     It is known that pasty products such as lutes, glues, greases, etc. . . are stored in cartridges or in bags constituted by a supple envelope preferably made of aluminum foil. 
     European Pat. No. 0052 060 describes a gun intended for discharging the products in question. Such a gun comprises a bored piston disposed in an open cylinder connected to a source of pressurized gas and which in addition ensures tight closure of the base of the cartridge by a rounded peripheral contour. 
     It will be readily understood that, if the free end of the skirt of the cartridge is damaged, a seal is not ensured, so that an appreciable loss of pressure appears to the detriment of the good general functioning of the gun. 
     2. Object of the Invention 
     The improvements forming the subject matter of the present invention aim at overcoming the aforementioned drawback and at allowing production of a piston adapted to ensure tightness either with a cartridge even in the case of a defect in the free edge of its skirt, or with a tubular sleeve in which is placed a charge of pasty product enclosed in a supple envelope. 
     The invention also aims at providing a free piston which makes it possible to use the tubular sleeve simply by turning over after expulsion of the charge of pasty product. 
     Finally, the invention aims at a particular tubular structure which allows the use of bellows whose bottom actuates the piston of the cartridge or that of the sleeve in order to avoid any possibility of transfer of compressed gas towards the product to be discharged. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, given by way of example, will enable the invention, the characteristics that is presents and the advantages that it is capable of procuring, to be more readily understood. 
     FIG. 1 is a partial section of a gun according to the invention, using a commercially available cartridge. 
     FIG. 2 is a view similar to that of FIG.. 1, but illustrating the gun during use of a charge of pasty product enclosed in a supple envelope. 
     FIGS. 3 to 5 illustrate the way of eliminating the supple envelope of the charge of pasty product at the end of discharge of the product. 
     FIG. 6 shows how the tubular sleeve is turned over in order to use a new charge of pasty product. 
     FIG. 7 shows a particular structure allowing the use of bellows for the actuation of the piston of a cartridge or a tubular sleeve containing a charge enclosed in a supple envelope. 
     FIG. 8 is a detailed view showing the use of a ring sector for maintaining the base of a cartridge of pasty product. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates in a partial view a gun according to the invention comprising a reinforcement or base 1 provided with a handle (not shown) to which may be connected a source of pressurized gas. At the front of the reinforcement 1, there is provided a block 2 provided with a discharge spout 3 which contains a supple or flexible tube 4 capable of being deformed by a piston 5 urged downwardly by a spring 6 when the user presses on a trigger (not shown), which cuts off the admission of compressed gas to the head of the piston 5. This block is described in Applicants&#39; European Pat. No. 0052 060 and its functioning will not be described. 
     The European Patent also describes an open jack 7 (FIG. 1) located at the end of the reinforcement 1 opposite the block 2 and which comprises an open cylinder 8 containing a seal 9 which is movable as a piston and which is urged outwardly by a spring 10. A threaded shaft 11 prevents the piston seal 9 from leaving the cylinder 8. The piston seal 9 determines with the cylinder a chamber 12 placed under pressure when the user acts on the trigger (not shown), at the same time as the pressure supply to the piston 5 is eliminated. It will be observed that, according to the invention, the supply of pressurized gas is effected through a pressure reducing valve 13 making it possible to adjust the pressure prevailing in the chamber and which may be monitored by means of a pressure gauge 14. The pressure may thus be adjusted to the desired value. This pressure is transmitted outwardly via longitudinal holes 9a made in the piston seal 9. 
     In accordance with the invention, the piston seal comprises, from its outer end 9b at the level of which open exhaust holes 9a, two peripheral grooves 9c, 9d disposed in tandem, the one referenced 9c being disposed nearest the outer end 9b and defining therewith a first radial lip 9e, while, between the two grooves 9c, 9d is located a second lip 9f whose diameter is greater than that of 9e. The transverse wall of the second lip 9f is provided on the groove 9c side, with a shoulder 9g whose diameter is slightly smaller than that of the lip 9e in the free state, for reasons which will be better explained hereinbelow. The piston seal 9 comprises, opposite its outer end 9b, a divergent conical skirt 9h with cylindrical lateral wall 9i whose diameter is larger than that of the second lip 9f. Of course, the diameter of the bottom of the groove 9c is very clearly smaller than that of groove 9d. 
     In this way, when a cartridge 15 containing a pasty product (not shown) limited by a piston 16 which constitutes a movably bottom which is disposed in the open skirt of the cartridge 15 is placed as illustrated in FIG. 1, the first lip 9e is slightly compressed and is applied against the inner wall of the skirt and also cooperates with the periphery of the shoulder 9g, so that the groove 9c constitutes a tight chamber. When the pressure is applied in the cylinder 8, it prevails against the piston 16 of the cartridge 15 so that the latter penetrates little by little to cause discharge of the pasty product via the spout, as needed. The pressure prevailing between the piston seal 9 and the piston 16 applies the lip 9e firmly against the inner wall of the skirt of the cartridge 15 in order to produce an excellent seal, all the more so as the space constituted by the groove 9c is not under pressure, so that the pressure is more reliably maintained even if the cartridge tends to be deformed outwardly. 
     If it is desired to employ a pasty product disposed in a supple envelope 17 such as aluminum foil, this charge is disposed in a tubular sleeve 18 used as a cartridge and which contains a freely movable piston 19. The free piston lies at a certain distance from one of the ends of the sleeve 18, which may thus engage around the piston seal 9. Such cooperation is effected in manner similar to that of the skirt of cartridge 15, but, in that case, the inner wall of the tubular sleeve cooperates with the second lip 9f of base 9, while its free edge comes into abutment against the conical skirt 9h of piston seal 9. There again, when the compressed gas arrives at the front of the piston seal, it straightens the lip 9f against the inner wall of the tubular sleeve 18, the space constituted by groove 9d being tight. 
     The free piston 19 is formed by a web 19a provided with a peripheral seal 20 and presenting two concave end walls with each of which a star-shaped scraper 21, also provided to be concave, cooperates. 
     The displacement of the free piston 19 under the effect of the compressed gas brings about the flow of the pasty product contained in the envelope 17 after it has been cut at its end opposite the end cooperating with piston 19. Of course, the end of the tubular sleeve 18 opposite the one which cooperates with the piston seal 9 is closed by an endpiece 22 presenting a wall 22a which includes axial tabs 22b which penetrate in that part of the envelope 18 which engages the wall. 
     When all the product is expelled, as illustrated in FIG. 3, the envelope 17 is flattened and forms scrap 23 constituted by multiple folds. 
     As illustrated in FIG. 4, this scrap remains associated with the endpiece 22 thanks to the presence of the tabs 22b. It may therefore be easily extracted from the endpiece, as illustrated in FIG. 5, and eliminated. 
     If it is desired to place a fresh charge in the tubular sleeve 18, it suffices to turn the latter over as illustrated in FIG. 6, to place the charge in the direction of arrow F, to position the endpiece and to dispose this assembly in the gun, as illustrated in FIG. 2. 
     FIG. 7 illustrates a tubular structure which is constituted by a tube or cartridge member 24 of which one of the ends comprises an inner diameter equal to that of the cartridge 15, so that it cooperates with the first lip 9e and with the shoulder 9g. This tube 24 extends within in a spacer member 25 which comprises an inner flange 25a. In the spacer member 25 there have been previously disposed bellows 26 comprising an end wall 26a, while the other end wall is provided with a peripheral flange 26b which is sandwiched between the tube 24 and the flange 25a of the spacer member 25. That part of the spacer members opposite the one which receives the tube 24 presents a diameter such that it may receive for example a cartridge 15 provided with its piston 16. 
     In order to discharge the product contained in the cartridge 15, the piston 16 is displaced by bellows 26 which expands until the piston has accomplished its stroke. Thanks to the use of these bellows, the hermetic distribution of the product contained in a cartridge and comprising fine and hard grains such as quartz, is ensured. Such grains risk being interposed between the piston 16 and the skirt of the cartridge, provoking scratches, therefore admissions of gas in the product to be discharged. 
     Of course, a spacer member 25 may be provided of which the inner diameter is adapted to receive a tubular sleeve of type 18 for the extrusion of a product contained in a charge in a supple packing. 
     FIG. 8 illustrates a ring sector 27 adapted to clip on the end bead 8a of the cylinder 8 and of which the inner diameter corresponds to that of the cartridge 15 so as to prevent any outward deformation of the latter at the level of lip 9e with a view to ensuring perfect tightness at that spot. Of course, it is unnecessary to use such a ring with a tubular sleeve 18 or a tube 24 which may be provided, for example, to be metallic, so as to undergo no centrifugal deformation under the effect of the pressure. 
     It must, moreover, be understood that the foregoing description has been given only by way of example and that it in no way limits the domain of the invention which would not be exceeded by replacing the details of execution described by any other equivalents.