GB2117839A - Containers - Google Patents

Abstract

A dispensing gun suitable for dispensing elastomeric sealants, has a handwheel 50 operating a plunger 14 through a leadscrew 38 to dispense the product through a nozzle 8 at the front end, has a rigid end closure member 26 forming a bearing to restrain axial movement of the leadscrew 38 in both directions. A sealing disc 42 and a boss 44 are mounted on the rear end of the lead screw 38. A resilient rotary sealing member 52 is mounted on the boss 44, and is pressed into sealing engagement with the closure member 26 by the disc 42. <IMAGE>

Description

SPECIFICATION Containers This invention relates to dispensing containers in the form of a gun for flowable liquid-based products of high viscosity, of the kind comprising a hollow body shell; means closing a front end of the shell and having a dispensing nozzle; a threaded plunger-carrying rod mounted for free rotation in the rear end of the shell and extending coaxially along the shell; a plunger fitting closely in the shell and movable along it upon rotation of the plunger rod so as to push the flowable product towards the nozzle; and means at the rear end of the body shell for effecting the said rotation of the plunger rod. Such a dispensing gun will be called a "dispensing gun of the kind hereinbefore specified".

Such dispensing guns are well known for the purpose of containing and dispensing mastic products, particularly oil-based or water-based sealing compounds. The threaded plunger rod is rotated, and the sealing compound thus forced out through the nozzle, usually by a knurled wheel which forms the base of the pack. The nozzle is generally conical in shape, and the user cuts off a portion of it in order to obtain the required diameter of the slug of sealant extruded from the nozzle.

Dispensing guns of the kind hereinbefore specified have hitherto been confined in practice to use in connection with mastic products as mentioned above. The cylindrical body shell is typically of extruded plastics material, or a spiralwound laminated material comprising aluminium foil with a sulphite backing paper and a kraft paper lining layer, the front end being closed by a tinplate front end closure member crimped circumferentially to the front end of the body shell. The rear end is closed by another tinplate rear end closure member in the form of a cupshaped plug, having a circumferential flange crimped circumferentially to the rear end of the body shell, the plug having a plain central hole which supports a portion of the threaded rod extending through it to its attachment to the knurled handwheel which is arranged behind the rear end closure member.

The plunger or piston provides primary sealing towards the rear of the gun, whilst the circumferential crimped end seal of the front end closure member to the body shell provides primary sealing at the front end of the pack.

The above arrangements normally prove adequate to provide sealing for oil-based or water-based mastic products. However, dispensing guns of the kind described above as having been used hitherto are not suitable for use with certain other products, notably moisturesensitive products such as elastomeric sealants, products which contain volatile substances, and/or products having a substantially lower surface tension than those with which such guns are normally used. There is a need for improved sealing displaying improved vapour barrier properties against leakage of vapour from, or ingress of moisture into, the gun, if such other products are to be packed in the dispensing guns.

In addition, there is a need for the torque required to operate the gun not to be increased.

Since the types of products to be dispensed have a relatively high viscosity, the torque required to turn the threaded rod, so as to advance the plunger and force the product out through the nozzle, is in any case substantial, and any increase may render the gun difficult to use.

According to the invention, in a dispensing gun of the kind hereinbefore specified, the rear end of the body shell is closed by a rear end closure member secured to the body shell around its entire periphery and imperforate except for a central hole adapted to serve as a bearing for a journal of the threaded plunger rod, the threaded rod carrying a sealing disc having a rear-facing sealing face spaced forwardly of the rear end member, and a resilient rotary seal being interposed between the rear-facing sealing face and the rear end member so as to seal the bearing from the interior of the body shell forward of the seal.

The means closing the front end of the body shell preferably comprise a front end member, secured to the body shell around its entire periphery by a peripheral end seam and having the nozzle extending forwardly from a through hole therein, and a sealing diaphragm, secured behind the nozzle, extending over the entire crosssection of the body shell and having its periphery secured in the end seam between the body shell and the front end member.

The sealing diaphragm at the front end, incorporated so that it forms a part of the front end closure means, provides an improved primary seal at the front end, whilst secondary sealing at the rear end, in the zone most liable to leakage (viz. at the support bearing of the threaded rod in the rear end closure member) is improved by provision of the rotary seal and the sealing disc against which it bears.

Examples of products for which the dispensing gun of the invention is suitable, besides oil-based or water-based mastic products, include silicone-, polysulphide- and polyurethane-based elastomeric sealing compounds.

The sealing diaphragm at the front end is preferably of metallic foil laminated to a polymeric film, and it is preferably adhered to the rear face of the flange which is typically provided at the rear end of the nozzle behind the front end closure member, being extended beyond this flange into the end seam as beforementioned. The diaphragm is punctured through the nozzle prior to initial use of the dispensing gun.

The rotary seal is preferably of a material that is both flexible and has a relatively low coefficient of friction between the seal and the rear end closure member; one example of a suitable material is polyethylene.

One embodiment of a dispensing gun of the kind hereinbefore specified, according to the invention, will now be described, by way of example only, with reference to Figure 1 of the drawings thereof, in which: Figure 1 is a broken, diametral sectional elevation of the said dispensing gun according to the invention; and Figure 2 is a similar view showing, for purposes of comparison only, the rear end of a dispensing gun of a known kind.

Referring to Figure 1 , the dispensing gun shown therein is intended primarily for use with a product consisting of a moisture-initiated elastomeric sealant. The gun comprises a hollow cylindrical body shell 2; means 4 closing the front end 6 of the shell and having a dispensing nozzle 8; a threaded plunger-carrying rod 10 mounted for free rotation in the rear end 12 of the body shell 2, the threaded rod 10 extending coaxially along the latter; a plunger 14 fitting closely within the bore of the body shell 2 and movable along it upon rotation of the threaded rod 10 so as to push elastomeric sealant, contained in the portion of the body shell indicated at 16, ahead of the plunger 14 and towards the dispensing nozzle 8; and means at the rear end 12 of the body shell for effecting the said rotation of the threaded rod 10.

The body shell 2 is of extruded plastics tube or is spirally wound from a laminated material consisting of three layers, viz. fully-annealed aluminium foil, bleached sulphite backing paper, and a lining layer of kraft paper. The sprial winding is such as to give overlap between one turn and the next in each layer in a satisfactory manner as will be within the competance of a person skilled in the art; in particular, however, each turn of the kraft paper liner is overlapped over the next turn forward of it so that it is the overlapped portion of the rearward one of the two turns that is exposed in the bore of the body shell.

The front end closing means 4 comprise a front end closure member 18 made of tinplate, and a full sealing diaphragm 20, of aluminium foil laminated to polyethylene. The end closure member 1 8 has a central through hole in which the nozzle 8 is secured. The latter has a rear flange 22, over whose rear face the diaphragm 20 is heat sealed. The tinplate end closure member 1 8 has a circumferential curl within which the peripheral portion of the diaphragm 20 lies. The circumferential curl is crimped over the end of the body shell 2 to form a front end seal 24 in which the edge of the diaphragm 20 is trapped. The front end seam 24 serves as the primary seal, at the front of the dispensing container, against leakage of volatile substances from within the container, or ingress of moisture from outside.

The rear end 12 of the body shell 2 is closed by a rear end closure member 26, made of tinpiate and secured to the rear end of the body shell by a peripheral rear end seam 28 formed by crimping the circumferential curl of the closure member 26 around its entire periphery. The latter is imperforate except for a central hole 30. As seen in Figure 1 it is of the known kind having a cranked crosssection forming an annular flat shoulder 32 surrounding the central hole 30, the latter being formed with a short, axially-extending annular cylindrical flange 34, wherbey the hole is adapted to serve as a bearing for a journal portion 36 of the threaded rod 10.

The threaded plunger rod 10 is formed of a suitable robust plastics material in a single piece, and comprises the leadscrew portion 38 which extends forward from the remainder of the plunger rod unit, viz. (reading towards the rear end) a cylindrical boss 40; a sealing disc 42; a cylindrical seal-carrying boss 44 of smaller diameter than the sealing disc 42; the journal 36 (whose diameter is smaller than that of the seal- carrying boss 44); and a frusto-conical end portion 46.A handwheel 48, of conventional form having a knurled peripheral surface 50, is secured to the end portion 46 so that the front face of its hub co-operates with the rear end face of the seal-carrying boss portion 44 to trap the journal portion 36 within the bearing 34 of the rear end closure member, and to provide the necessary mechanical support for mounting the threaded plunger rod 10 in the rear end of the body shell 2.

In this connection, it will be observed that the annular rear face of the seal-carrying boss 44 engages against the annular flat shoulder 32 of the end closure member, whose inherent rigidity enables it to serve as a thrust bearing.

Surrounding the boss 44 is a resilient rotary sealing member 52, which is thereby interposed between the rearfacing sealing face 54 of the sealing disc 42, on the one hand, and on the other hand the front of the end closure member 26. The sealing member 52 is of a material such as lowdensity polyethylene.

Figure 2 shows an arrangement currently used in production, in which the one-piece plasticsplunger carrying rod 60 again has a handwheel 48, but is supported by means of an integral hub portion 62 in a simple through hole formed in the rear end closure member 66, which is again secured, by a crimped end seam indicated at 68, to the end of the body shell 2. The end closure member 66 is in the form of a cup and has substantially greater axial resilience than the rear end closure member 26 shown in Figure 1. The plunger-carrying rod 60 has an integral ring portion 64, of greater diameter than the hole in the end closure member 66, which bears against the front of the latter.

Sealing at the rear end of the dispensing gun is afforded by the end seam 68 and by the interface between the end closure member 66 and body shell 2. By contrast, in the dispensing gun shown in Figure 1 sealing around the plunger-carrying rod 10 at the rear end of the gun is provided by the sealing member 52 as primary seal, and, as secondary seal, by the interfaces between the plunger rod portions 44 and 36 with the rear end closure member 26.

In addition, the provision of the sealing diaphragm 20 trapped peripherally in the front end seam 24 (Figure 1) and extending over the entire cross-section of the body shell 2, provides improved sealing at the front end of the dispensing gun. In the dispensing gun described with reference to Figure 1, the leadscrew portion 38 is prevented from undergoing any significant axial movement in either direction.

In operation, the diaphragm 20 is punctured through the nozzle 8, and the handwheel 48 is turned to advance the plunger 14, which forces the product in the space 1 6 out through the nozzle.

Claims (1)

1. Claims

   1. A dispensing gun of the kind hereinbefore specified, wherein the rear end of the body shell is closed by a rear end closure member, secured to the body shell around its entire periphery and imperforate except for a central hole adapted to serve as a bearing for a journal of the threaded plunger rod, the threaded rod carrying a sealing disc having a rear-facing sealing face spaced forwardly of the rear end member, and a resilient rotary seal being interposed between the rearfacing sealing face and the rear end member so as to seal the bearing from the interior of the body shell forward of the seal.

   2. A dispensing gun according to Claim 1, wherein the means closing the front end of the body shell comprises a front end member, secured to the body shell around its entire periphery by a peripheral end seam and having the nozzle extending forwardly from a through hole therein, and a sealing diaphragm, secured behind the nozzle, extending over the entire crosssection of the body shell and having its periphery secured in the end seam between the body shell and the front end member.

   3. A dispensing gun according to Claim 2, wherein the sealing diaphragm is of metallic foil laminated to a polymeric film.

   4. A dispensing gun according to any one of the preceding claims, wherein the rotary seal is of polyethylene.

   5. A dispensing gun of the kind hereinbefore specified, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, Figure 1 of the drawings hereof.

   New claims or amendments to claims filed on 9/3/83 Superseded claims 1 New or amended claims:

   1. A dispensing gun of kind hereinbefore specified, wherein the rear end of the body shell is closed by a rear end closure member, secured to the body shell around its entire periphery and imperforate except for a central- hole adapted to serve as a bearing for a journal of the threaded plunger rod, the threaded rod carrying a sealing sleeve assembly whose rear end is of reduced diameter and in face to face contact with the end closure member around the central hole, the sealing sleeve assembly having a rear-facing sealing face spaced forwardly of the rear end closure member, and a separate, resilient rotary sealing member being interposed between the rear-facing sealing face and the rear end closure member, the rotary sealing member having a cuplike portion open towards the rear and presenting a circumferential terminal edge to form against the rear end member an annular face seal capable of resiling radially, whereby to seal the bearing from the interior of the body shell forward of the seal.