GB2105813A

GB2105813A - Plug and socket coupling, especially for shells

Info

Publication number: GB2105813A
Application number: GB08218302A
Authority: GB
Inventors: Gerhard Grau; Walter Hanser
Original assignee: Buck Chemisch Technische Werke GmbH and Co
Current assignee: Buck Chemisch Technische Werke GmbH and Co
Priority date: 1981-07-23
Filing date: 1982-06-24
Publication date: 1983-03-30
Also published as: BE893905A; IT8248867A0; IT1148609B; ATA272582A; IL66153A; DE3129146C2; AT385118B; FR2510249A1; GB2105813B; DE3129146A1; FR2510249B1

Abstract

An adhesive connection is described for the two parts of a plug and socket coupling, especially for connecting the head or upper part with the tail or lower part in a shell, in particular, a mortar smoke shell. The coupling comprises a first part 1 having an interior substantially cylindrical surface and a second part having a collar 25 formed with an exterior substantially cylindrical surface adapted to fit within and mate with the substantially cylindrical surface of the first part, there being radially extending shear pins 26 passing through both mating surfaces to hold the parts together in their assembled state. The mating surface of the second part is formed with a thread which may lead at one or both ends into an annular groove 21,28 beyond which threadless fitting collars may be formed. The thread courses 18 of the thread situated on the collar and the annular grooves which may be present serve to receive adhesive 23 via inlet 22 and the thread crests 19 serve as mating surface. <IMAGE>

Description

SPECIFICATION Plug and socket coupling, especially for shells This invention relates in general to a plug and socket coupling and is concerned particularly, but not exclusively, with a plug and socket coupling for a shell, especially a mortar shell of the kind comprising a head or upper part and a tail or lower part formed with substantially cylindrical mating surfaces which can be assembled one within the other after the manner of a plug and socket coupling, there being radially extending shear pins passing through said surfaces to join the parts together in their assembled state. Such a shell will be hereinafter referred to as"a shell of the kind set forth".

A shell of the kind set forth is described, for example, in German Auslegungsschrift No. 1128478.

A shell of the kind set forth, such as a mortar shell, is composed of two parts, namely an upper part bearing a payload and an expulsion charge for the payload, and a lower part bearing a propelling charge. The parts are connected with each other by axially extending substantially cylindrical faces formed on their ends facing each other, and serving as mating surfaces which overlap each other when the two parts are joined in the manner of a plug and socket coupling. Radially extending shear pins penetrate the mating surfaces to hold the two parts together. The annular clearance between the mating and inner surface of the lower part which is in the form of a collar and the mouth of the upper part can not be designed as small as may be desired for reasons of manufacturing technique and costs. It is a maximum of 0.075 mm.This clearance may be filled with an adhesive, which only acts, however, as a packing and does not contribute to stability. The connection point between the upper and lower parts is therefor a critical point in such a shell.

The stability of such a connection is normally to be attributed solely to the shear pins, through which the collar of the lower part is cottered with the mouth of the upper part, since on dropping the cartridge in inclined position, the lower part and upper part tilt towards each other and may thereby break off the shear pins. This tilting is of course dependent on the width of said annular clearance. It decreases, the more the play is reduced and would be practically climinated, if there were in the extreme case, no play and consequently both parts fitted exactly into each other. However, this would entail considerable expense in manufacture, and would thereby lead to a corresponding increase in the cost of the shell. In such an instance, the lower part and the upper part would have to be matched in each case and numbered with respect to their correlation.

Even with such a drastic reduction of the annular clearance, however, there would only be stability and not one hundred percent tightness. The adhesive can never fill the annular clearance without gaps, and also is not sufficiently elastic to withstand a dropping test without the formation of cracks.

Also there is an optimum layer thickness for any particular adhesive, so that a particular adhesive only maintains its maximum stability and elasticity when applied as a layer of a particular thickness. The more highly viscose an adhesive is, the greater in general is its optimum thickness; however, thin jointing gaps can of course only be filled with an adhesive of low viscosity. It is therefore not possible, to introduce into such an annular clearance an adhesive of high viscosity, which after hardening automatically would also have a correspondingly high shear strength and elasticity.

With the conventional shells, such as mortar shells or particularly motar smoke shells, as a result of the above comments the clearance between the upper part and the lower part can fluctuate from 0 to 0.15 mm (= 2 x 0.075 mm). This difference exists not only within a number of shells, but also with a single shell, because the lower part and upper part are never able to be joined together so centered that the annular clearance for the adhesive is the same around the entire circumrerence. On the contrary, there always exists a certain eccentricity. The adhesive therefore always has differing strength and elasticity values distributed around the circumference of the annular clearance. As a result of the relatively narrow annular clearance, moreover, only adhesives of low viscosity can be used, as mentioned above.With this, automatically only an adhesive connection with a relatively low ultimate strength and elasticity results. Therefore, even with a simple jarring test an adhesive connection becomes loose and cracked, so that the connection between the ower part and upper part becomes unsound.

It has been proposed to overcome the problem of tightness by the provision of a sealing ring, as described in French Patent Specification 1,502,826.

The provision of sealing rings, however, requires that the material of the collar bearing the sealing ring should have a predetermined strength and requires the annular clearance to be enlarged so as not to damage the sealing ring on joining together. Such an enlargement of the annular clearance, however, again increases the risk of tilting, particularly with inclined impact of such cartridges, resulting in a shearing of the shear pins.

Finally, it would be possible to fill the annular slot, necessary for the attachment of a sealing ring, with adhesive instead of with a sealing ring. However, with this also it is not possible to achieve one hundred per cent tightness, because such an annular clearance can only be filled with adhesive completely and free from gaps with difficulty. Apart from that, the stability remains unaffected by this step.

With the known mortar shells, therefore, the problem exists that the connection point between the collar of the lower part and the mouth of the upper part is not able to be designed in such a way that, as regards stability and tightness, it withstands environmental influences during storage for years, and above all withstands the dropping test which is prescribed for such shells, particularly with inclined impact. This problem can also not be eliminated through the conceivable modifications, mentioned above, to the connection between the lower part and the upper part.

It is an object of the present invention to provide an adhesive connection between the two parts of a plug and socket coupling, especially the lower part and an upper part of a shell, in particular a mortar shell, which whilst maintaining the basic constructions of such a shell provides for an improvement in the stability and tightness at the connection, such that the shell is better able to withstand the dropping test even with inclined impact, and also better able to withstand other environmental influences during storage over a period of years.

According to the present invention there is provided a plug and socket coupling, wherein a first part of the coupling has an interior substantially cylindrical surface and a second part has a collar formed with an exterior substantially cylindrical surface adapted to fit within and mate with the substantially cylindrical surface of the first part, there being radially extending shear pins passing through both mating surfaces to hold the parts together in their assembled state, and wherein the substantially cylindrical surface of said second part is formed with a thread having a small pitch and/or flattened crests, the thread courses of which serve to receive an adhesive and the thread crests of which serve to mate with the interior surface of said first part.The first part being formed with a filling aperture leading into the region of said threaded courses for introducing an adhesive thereinto when the parts are assembled.

The present formation of the connection between the upper and lower parts of a mortar shell satisfies practical requirements.

The thread formed on the mating surface of the collar of the lower part has a small pitch and/or flattened crests, the pitch being small in relation to the axial extent of the thread. The thread courses are preferably approximately 2 mm. wide and approxi mately 0.25 mm. deep. The crests are preferably approximately 1 mm. wide and approximately 0.25 mm. high, and the play between the mating surface of the collar of the lower part, formed by the crests, and the sleeve mouth of the upper part preferably amounts to a maximum of approximately 0.075 mm.

In this way, a clean fit of the collar of the lower part in the sleeve mouth of the upper part is ensured and at the same time it is made possible for the thread courses situated on the collar of the lower part to be filled with an adhesive of high viscosity, for example a polyurethane adhesive, which, after hardening, produces an adhesive connection with a high degree of stability and elasticity.

The thread formed on the mating surface of the collar preferably opens out, at the end of the thread facing the shoulder of the collar of the lower part and/or at the beginning of the thread facing away from the shoulder of the collar of the lower part, into a lower annular groove and/or an upper annular groove, both a lower annular groove and an upper annular groove being preferably avoided. Both the upper annular groove and the lower annular groove communicate in each case with the thread courses of the thread situated on the mating surface of the collar of the lower part, so that both annular grooves likewise serve to receive adhesive. The annular grooves are generally deeper than the thread courses, and they preferably have a depth of approximately 0.5 to 1 mm.They can be the same or a different width, the lower annular groove being expediently approximately 6 mm. wide, which is of particular value if the filling aperture for the adhesive leads into it, so that this annular groove serves for filling the thread courses and the upper annular groove. The upper annular groove is expediently approximately 2 mm. wide. The arrangement of, respectively, an annular groove at the end of the thread, namely of a lower annular groove, and an annular groove at the beginning of the thread, namely of an upper annular groove, provides in combination with the thread courses, a particularly good adhesive connection between the collar of the lower part and the sleeve mouth of the upper part.

In order to seal the adhesive in the thread courses and, if applicable, in the annular grooves and to prevent discharge of the adhesive into the body of either part, a threadless lower fitting collar and/or a threadless upperfitting collar is preferably joined on to the thread end or the lower annular groove and/or to the beginning of the thread orthe upper annular groove. Preferably such a fitting collar is formed both at the end of the thread and at the beginning of the thread. In a particularly preferred embodiment, a lower annular groove and an upper annular groove are formed respectively at the end of the thread and at the beginning of the thread, onto which a lower fitting collar and an upper fitting collar are connected.This particularly preferred embodiment of the collar of the lower part, namely in the resulting sequence from the upper end of the collar, of upper fitting collar, upper annular groove, thread, lower annular groove and lower fitting collar, produces an adhesive connection of the mating surface of the collar of the lower part with the sleeve mouth of the upper part, which withstands most stresses. The maximum play between the upper fitting collar or the lower fitting collar and the sleeve mouth of the upper part amounts here likewise preferably to 0.075 mm. and therefore in turn corresponds to the maximum play between the crests of the thread situated on the collar of the lower part and the sleeve mouth of the upper part. The width and depth of the lower annular groove and the upper annular groove correspond preferably to the values already indicated above.

The upper fitting collar only needs to be a few mm.

wide and can therefore, for example, correspond to the preferred width of the thread course and of the upper annular groove, namely a width of approximately 2 mm.

The lower fitting collar is preferably wider than the upper fitting collar, since it preferably serves to receive the radial pins which the lower fitting collar of the lower part to the sleeve mouth of the upper part. It is therefore preferably approximately 15 mm.

wide, so that the length of this lower fitting collar up to the shoulder of the collar of the lower part in the sleeve mouth of the upper part is approximately 15 mm. This lower fitting collar of the mating surface of the collar of the lower part is then for example fixed with six to eight pins, preferably of brass, to the sleeve mouth of the upper part facing it, for which purpose the sleeve mouth is formed with bores and the lower fitting collar is formed with registering blind-end bores. The pins generally have a gauge of approximately 2 mm.

In addition a filling hole for the adhesive is formed in the sleeve mouth of the upper part, and leads into the region of the thread courses or the lower annular groove and/or the upper annular groove of the collar of the lower part. Preferably this filling hole for the adhesive leads into the lower annular groove, which according to the particularly preferred embodiment of the mating surface of the collar of the lower part, described above, is preferably widen than the upper annular groove, and has a width of approximately 6 mm.In order that the entire arrangement, and particularly the lower annular groove, can be filled easily and cleanly with adhesive, a control opening for the adhesive is formed in the sleeve mouth of the upper part so as to be coaxial with the filling hole for the adhesive leading into the lower annular groove, and therefore lying diametrically opposed to the filling hole, the control opening for the adhesive likewise leading into the lower annular groove. This substantially enables the lower annular groove to first of all be completely filled with adhesive, and then, after closing the control opening enables the thread courses and the upper annular groove of the mating surface of the collar of the lower part also to be cleanly filled with adhesive through the further addition of a precisely dosed quantity of adhesive.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example an embodiment thereof, and in which: Figure lisa longitudinal section through a motar smoke shell with an adhesive connection between an upper part and a lower part, and Figure2 is an enlarged detail of Figure 1, showing the upper part only in section.

Referring now to the drawings, there is shown a mortar smoke shell comprising a head or upper part 1 and a tail or lower part 2. At the head of the upper part 1 is a conventional fuse head 3 which is connected with an expulsion charge 4. A smoke cartridge 5 is situated in the interior of the upper part 1 and is filled with a conventional smoke charge 6.

An ignition charge 7 is fitted in the smoke charge 6 and is in operative connection with the expulsion charge 4 via an ignition delay element 8. The smoke cartridge 5 is formed with a central channel 9, which provides an operative connection between the expulsion charge 4 (and via the ignition delay element 8 also the ignition charge 7 for the smoke charge 6) and a frusto-conical pressure chamber 10 situated in the lower part 2. At the propellant charge 11 is mounted on the outside of the lower end of the lower part 2, and is in operative connection via ignition apertures 31 with an ignition charge 11, which, in turn, is in operative connection with a percussion primer cap 12. In addition, conventional flight stabilisers 13 are also attached to the end of the lower part 2.

As shown more clearly in Figure 2 the lower part 2 has at its upper end a shoulder 14, at which its collar 15 formed with a substantially cylindrical mating surface begins. This collar 15 of the lower part 2 engages into a sleeve mouth 16 of the upper part 1 and is connected with it substantially by means of an adhesive connection according to the invention. The collar 15 of the lower part 2 is formed externally with athread 17 having a small pitch, the thread courses 18 of this thread 17 being of flattened configuration as are the crests 19. At the end of the thread 20 facing the shoulder 14 of the collar 15 of the lower part 2, a lower annular groove 21 is formed into which a filling aperture 22 for an adhesive 23 leads, the aperture passing through the sleeve mouth 16 of the upper part 1.A control aperture 24 for the adhesive 23 is formed coaxially with the filling aperture 22 and leads out from the lower annular groove 21, through the sleeve mouth 16 of the upper part 1. A fitting collar 25 is formed at the lower end of the collar 15 of the lower part 2 directly beneath the lower annular groove 21 and is fixed by means of radial pins 26 to the sleeve mouth 16 of the upper part 1.

An upper annular groove 28 communicates with the beginning of the thread 27 of the collar 15 and is sealed from above by an upper fitting collar 29.

The cavities between the collar 15 of the lower part 2 and the sleeve mouth 16 of the upper part 1, which are formed by the lower annular groove 21, the thread courses 18 and the upper annular groove 28, are filled with adhesive 23, the upper annular groove 28 normally serving as an overflow groove, and then being only partially filled wituh surplus adhesive.

The smoke cartridge 5 is supported, via a projection 30, on the upper fitting collar 29 and then narrows in the trailing direction so that it is adapted to fit into the interior of the fitting collar 15 of the lower part 2, so that it extends fully there into. The cylindrical space bounded by the collar 15 of the lower part 2 is therefore completely filled by the smoke cartridge 5. Joined on to this cylindrical space filled by the smoke cartridge 5 is the pressure chamber 10 in the interior of the lower part 2, which, as already mentioned, is in operative connection via the central channel 9 of the smoke cartridge 5 with the expulsion charge 4 and with the fuse head 3.

The assembly of the mortar smoke shell shown in Figures 1 and 2 is carried out in the usual manner, the sleeve mouth 16 of the upper part 1 being cottered with the collar 15 of the lower part 2 in the manner shown by means of the pins 26, these usually being eight brass pins arranged around the circumference of the upper part 1.

After the assembly is completed, the shell is placed in a horizontal position and adhesive 23 is filled into the shell from below via the filling aperture 22 into the lower annular groove 21, until the adhesive appears at the control opening 24 which lies diametrically opposite the filling aperture 22.

The control aperture 24 is then closed and the mortar shell is placed in a vertical position on its tail, namely the lower part 2. Thereafter, the remaining quantity of adhesive is injected in a precisely pre-set dosage.

After the filling of the lower annular groove 21,the thread courses 18 of the collar 15 of the lower part 2 are completely filled with adhesive 23, without gaps, and any excess adhesive arising as a result of measurement tolerances, finally reaches the upper annular groove 28, which has the function of an overflow groove of the adhesive, and at the same time acts as a further sealing groove.

Finally, the filling aperture 22 for the adhesive 23 is closed and a mortar smoke shell is left to stand until the adhesive 23 has completely hardened.

Due to the design of the collar 15 of the lower part 2, namely the formation of the collar as a thread with annular groove 21 and 28 and fitting collars 25 and 29 joining on to it at both ends, both an increase in stability and in the tightness of the connection between the lower part 2 and the upper part 1 is achieved. The necessary stability is thereby ensured both through the crests 19 in connection with the fitting collars 25 and 29 and also through the adhesive 23 filling the thread course 18 and the annular grooves 21 and 28, whilst the tightness is produced solely through the adhesive connection.

The wall depth of the annular grooves 21 and 28 and of the thread courses 18 is adapted to the viscosity of the respective adhesive 23 to be used, and in the case of an adhesive of high viscosity, for example a polyurethane adhesive, it usually amounts to approximately 0.25 mm.

The thread crests normally have a tolerance of a maximum of 0.075 mm. which is still tenable in terms of production technique.

The adhesive connection which can be obtained leads to an increase in the stability of the connection between the collar 15 of the lower part 2 and the sleeve mouth 16 of the upper part 1, such that for the expulsion of the payload, in the present case of the smoke cartridge 5, namely a separation of the lower part 2 from the upper part 1, the quantity of expulsion charge 4 of generally approximately 15 g.

present in conventional mortar smoke shells, is not sufficient. The quantity of the expulsion charge 4 must therefore normally be somewhat increased in the present mortar smoke shell, so that for example it may amount to up to 50 g. Even such an increased quantity of expulsion charge 4, however, does not lead to any damage to the smoke cartridge 5, owing to the further particular construction of the interior of the upper part 1 and of the lower part 2 and of the construction of the smoke cartridge 5, this being for two reasons: a) the pressure chamber 10 adjoins the base of the smoke cartridge 5 in the region of the lower part 2 and is connected via the central channel 9 in the smoke cartridge 5 with the expulsion charge 4.This leads to the lower part 2 being predominantly separated from the upper part 1 via the gas pressure balancing itself through the central channel 9 and only to a slight extent via a compression load exerted by the smoke cartridge 5 onto the lower part 2.

b) the smoke cartridge 5 is supported via the projection 30 against the collar 15 of the lower part 2, so that a force transmission from the expulsion charge 4 optimally only takes place via the wall of the smoke cartridge 5. Deformation or damage to the smoke cartridge 5 is therefore practically ruled out.

Furthermore, the particular shaping of the smoke cartridge 5 also has the advantage that the interior of the mortar smoke shell is optimally used by the smoke charge 6.

The present adhesive connection is of course not only restricted to use with mortar smoke shells, mortar shells, or shells in general, but can of course be used where there is a comparable problem in the connection of two different sleeve-shaped parts with each other, namely an insufficient stability and tightness at the connection point with corresponding stress, for example a gravity and impact stress, which is brought about for example, in the dropping test or with inclined impact. The description of the invention with regard to shells, mortar shells or mortar smoke shells, is therefore not to be seen as a limitation as the invention is applicable to plug and socket couplings in general.

Claims

1. A plug and socket coupling, wherein a first part of the coupling has an interior substantially cylindrical surface and a second part has a collar formed with an exterior substantially cylindrical surface adapted to fit within and mate with the substantially cylindrical surface of the first part, there being radially extending shear pins passing through both mating surfaces to hold the parts together in their assembled state, and wherein the substantially cylindrical surface of said second part is formed with a thread having a small pitch and/or flattened crests, the thread courses of which serve to receive an adhesive and the thread crests of which serve to mate with the interior surface of said first part, the first part being formed with a filling aperture leading into the region of said thread courses for introducing an adhesive thereinto when the parts are assembled.

2. A coupling as claimed in Claim 1, wherein the collar of said second part is formed with an annular groove into which the thread opens at one or both ends of the thread.

3. A coupling as claimed in Claim 2, wherein the collar of said second part is formed with a threadless portion of substantially the same diameter as the thread at one or both ends of the thread.

4. A coupling as claimed in Claim 2 or 3, wherein the filling aperture for the adhesive leads into the annular groove nearer to a main body of the second part.

5. A coupling as claimed in Claim 4, wherein the first part is formed with a control aperture for the adhesive leading into said annular groove and coaxial with the filling aperture.

6. A coupling as claimed in any preceding claim, wherein the first part is the head of a shell and the second part is the tail of the shell.

7. A plug and socket coupling substantially as hereinbefore described with reference to the accompanying drawings.

8. A mortar shell substantially as hereinbefore described with reference to the accompanying drawings.