GB2511387A

GB2511387A - Accessory adaptor for a firearm

Info

Publication number: GB2511387A
Application number: GB1321503.3A
Authority: GB
Inventors: Gregory Felton
Original assignee: Law Enforcement International Ltd
Current assignee: Law Enforcement International Ltd
Priority date: 2013-12-05
Filing date: 2013-12-05
Publication date: 2014-09-03
Anticipated expiration: 2033-12-05
Also published as: GB201321503D0; GB2511387B

Abstract

An adaptor 1 for attaching an accessory part 7 to a firearm barrel in an axially-aligned configuration comprises a generally tubular body 2 arranged to connect, in use, to an end portion of the firearm barrel. The body 2 has a bore 9 with a threaded region 3 for engagement with a threaded end part 5 of the accessory part 7, and an engagement member 10 biased to protrude from an end face of the body, in use, for engagement with a recess 8 in an opposing engagement face of the accessory part 7 when the accessory part 7 is screwed into the adaptor 1 so as to resist unintentional unscrewing of the accessory part 7 from the adaptor 1. The engagement member 10 is configured to disengage from the recess 8 when an unscrewing torque is applied to the accessory part 7.

Description

ACCESSORY ADAPTOR FOR A FIREARM

[00lJ The present invention relates to an adaptor for a firearm having a barrel, and in particular an adaptor for a small arms weapon such as an assault rifle or machine gun for enabling an accessory or attachment to be mounted to the weapon.

[002J Accessories such as suppressors (silencers), bayonets, blank firing adaptors and grenade launchers may be attached to weapons for added functionality. In many cases, these accessories are not required to be permanently attached to the weapon and it is advantageous if the accessory can be easily removed to reduce the weight and size of the weapon in use. It is therefore desirable that such accessories can be quickly and easily attached to and detached from the weapon.

[003J A particular difficulty arises when the accessory must be mounted coaxially with the weapon's barrel, as is the case for suppressors, for example. In such cases, the speed of attachment and detachment of the accessory affects the effectiveness of the weapon since this action is often undertaken in a combat scenario.

[004J To attach and detach an accessory from a firearm barrel, it is known to use an adaptor that releasably mounts to an end section of the barrel. The adaptor provides a threaded sleeve portion at one end for attachment of an accessory, whilst the other end of the adaptor engages with the barrel by a fastening mechanism.

[005J In this respect, one known approach is to mount such an adaptor onto a flash hider provided at the end portion of the barrel. In this connection, most modern assault rifles and machine guns are provided with a flash hider, or alternatively one may be added to the weapon after market.

Flash hiders are by necessity accurately aligned with the bore of the weapon barrel, and present a shoulder formed where the flash hider meets the remainder of the barrel, or as a feature of the flash hider itself, which can be used as a fixa biuxi or anchor poixiL for blie adapber.

[006J One type of conventional adaptor comprises a tubular sleeve that fits annularly around and connects to an end portion of the barrel, such as a flash hider. The sleeve is a close clearance fit or sliding fit on the barrel to allow the adaptor to be easily slipped on or off the end of the barrel. A U-shaped gate is fitted through a slot in the adaptor to engage with a recess or shoulder formed in the barrel, in the flash hider, or where the flash hider meets a smaller-diameter portion of the barrel. Engagement of the gate with the shoulder stops the adaptor from slipping off the barrel. The bore of the adaptor is internally threaded over a portion towards its front end away from the barrel, to accept an externally threaded end part of an accessory.

[007j The action of screwing the accessory into the adaptor causes the end face of the accessory to contact the front end face of the barrel. As the accessory is screwed in further, the adaptor is pulled forward, towards the accessory, which clamps the gate against the shoulder formed by the frontmost face of the recess in the barrel. This causes the adaptor, together with the attached accessory, to become tightly secured to the barrel. To remove the accessory from the barrel, the accessory is partially unscrewed from the adaptor, releasing the clamped gate. The adaptor, with the accessory still attached, can then be slipped off the end of the barrel.

[008] Tn order to function correctly, the adaptor should fit relatively tightly to the flash hider, to thereby obtain a secure fit and provide good axial alignment with the weapon barrel. Similarly, the accessory should he attached to the adaptor tightly to obtain a secure fit and provide good axial alignment with the weapon barrel.

[009] A common problem that can affect axial alignment when using an adaptor of this type is that the accessory can unintentionally partially unscrew or come loose from the adaptor, for example by as a result of vibrations, thermal variations and mechanical shock during use of the weapon.

[0010] To address this problem, some conventional adaptors include a ratchet mechanism which allows one-way tightening of the accessory to lock the accessory in a fully-tight position. A spring-biased pawl protrudes from the end face of the adaptor to engage with one of a series of teeth arranged in a circular array on an opposing face of the accessory. As the accessory is screwed into the adaptor, the pawl engages with the teeth in turn so that unscrewing movement of the accessory is blocked by engagement of the pawl with the teeth.

[0011] The pawl is attached to a lever that is located on the outside of the sleeve, so that the pawl can ba manually retracted against the spring force by pulling the lever when removal of the accessory is required. This disengages the pawl from the teeth, allowing unscrewing movement of the accessory.

[0012] Accordingly, the removal of this type of adaptor is a two-handed operation, since it is necessary to hold the pawl in the retracted position with one hand whilst unscrewing the accessory with the other hand. This is time-consuming and cumbersome for the user, since it requires the weapon to be balanced awkwardly whilst both hands are engaged with the end of the weapon. Also, the lever can be difficult to operate when wearing gloves or in combat situations.

[0013] The present invention seeks to overoome or mitigate Lhe above problems associa bed wi Lii Llie prior ar L. [0014] According to an aspect of the present invention, there is provided an adaptor for attaching an accessory part to a firearm barrel in an axially-aligned configuration, the adaptor comprising: a generally tubular body arranged to connect to an end portion of the firearm barrel and having a bore with a threaded region for engagement with a threaded end part of the accessory part; and an engagement member biased to protrude from an end face of the body for engagement with a recess in an opposing engagement face of the accessory part when the accessory part is screwed into the adaptor so as to resist unintentional unscrewing of the accessory part from the adaptor; wherein the engagement member is configured to disengage from the recess when an unscrewing torque is applied to the accessory part.

[0015] 1'ith this arrangement, when the accessory part is screwed in and attached to the adaptor, the engagement member, which protrudes from the end face of the body, engages with a recess in the opposing engagement face of the accessory part. The engagement member is biased to resist disengagement from the recess with a sufficient force to guard against unintentional unscrewing movement of the accessory part. This prevents the accessory part from becoming unintentionally unscrewed or loosened from the adaptor, which would otherwise compromise the alignment between the adaptor and the acoessory part.

[0016] The engagement member may be arranged to disengage from the recess when the unscrewing torque applied to the accessory part is sufficient to overcome the biasing force acting on the engagement member. As such, this allows the user Lo a I leasL parLially unscrew Lhe accessory par L from the adaptor, guickly and easily, with a single action and with one hand.

[0017] Preferably, the engagement member comprises a part-spherical surface for engagement with the recess. In this way, the part-spherical surface allows for the engagement member to smoothly engage with and disengage from the recess as the accessory part is rotated in either direction with respect to the adaptor. For example, the engagement member may comprise a ball bearing or a ball plunger. When the engagement member comprises a ball bearing, the ball bearing can revolve as the engagement face of the accessory part passes over it, thus reducing wear and frictional resistance.

[0018] Preferably, the adaptor further comprises a biasing means to bias the engagement member to protrude from the second end face of the body. In this way, the biasing means assists the engagement member in remaining in contact with the opposing engagement face of the accessory part.

[0019] Preferably, the biasing means applies a biasing force of at least 3 Newtons to the engagement member. More preferably, the biasing means applies a biasing force of at least 5 Newtons. More preferably still, the biasing means applies applies a biasing force of at least 10 Newtons. By applying a sufficiently large biasing force, the engagement means remains engaged to resist rotation of the accessory part even when large vibrational or shock loads are applied to the firearm.

[0020] Preferably, the biasing means comprises a compression spring. The biasing means may be housed within the body, for example in a wall of the body. In this way, the biasing means is protected against environmental conditions. For example, in one embodimexi I, Ihe adapLor comprises a second bore extending in a wall of the body to house the biasing means.

[0021] Preferably, the second bore includes retaining means for retaining the engagement member against the force of the biasing means. In this way, the engagement member is prevented from being ejected from the second bore. For example, when the engagement member comprises a ball bearing, the retaining means may comprise a reduced diameter portion of the second bore, with a diameter less than the maximum diameter of the ball bearing. In one embodiment, the retaining means comprises a retaining formation formed integrally with the body. In another embodiment, the retaining means comprises a separate part that is fitted to the bore.

[0022] Preferably, the second bore extends from the end face of the body to an opposite back face of the body. In this way, the size of the biasing means that can be accommodated can be maximised. When the biasing means is a compression spring, a relatively powerful biasing means can therefore be provided.

[0023] Preferably, the adaptor further comprises closure means to close the second bore at the back face of the body.

In this way, the closure means may provide a surface for the biasing means to act against in order to bias the engagement member to protrude from the end face of the body.

[0024] Preferably, the engagement member is configured to successively engage with and disengage from a plurality of recesses in the engagement face of the accessory part as the accessory part is screwed into or unscrewed from the adaptor.

In this way, as the accessory part is screwed in, the exigagemexiL member engages and Lhexi disengages wi Lii Llie recesses in the opposing face of the accessory part incrementally until the accessory part is fully tight. Once tightened, the engagement member remains engaged with a particular recess, thereby resisting further rotation of the accessory part. The provision of multiple recesses allows for the accessory part to be securely attached to the adaptor whilst accommodating dimensional tolerances or wear in use.

[0025] Preferably, the bore is arranged to receive the end portion of the firearm barrel. The end portion of the firearm barrel is optionally a flash hider or a part thereof. The adaptor may comprise securing means for securing the adaptor to the firearm barrel.

[0026] In one embodiment, the bore is arranged to receive the end portion of the firearm barrel, and the securing means comprises a securing member arranged to extend into the bore for engagement with a shoulder in the firearm barrel. For example, the shoulder of the firearm barrel may be defined by a recess in the barrel, by an end surface of a flash hider, or by a groove or channel in the barrel or in a flash hider that forms the end pornion of the barrel. The recess may be annular.

[0027] Preferably, the securing member comprises a U-shaped gate having first and second arms to embrace the firearm barrel therebetween and to engage with the shoulder. In this way, the securing member is arranged to engage with the shoulder.

[0028] Preferably, the body comprises a slot for receiving the securing member.

[0029] According to a further aspect of the present ixivenbioxi, Lhere is provided an accessory sys bern for a firearm, comprising an adaptor according to any preceding claim and an accessory part for attachment to the adaptor, the accessory part comprising: a threaded end part for engagement with the threaded region of the bore of the adaptor; and an engagement face that opposes the end face of the body of the adaptor when the accessory part is attached to the adaptor, the engagement face comprising at least one recess for engagement with the engagement member of the adaptor.

[0030] Preferably, the engagement face of the accessory part comprises a plurality of recesses. In this way, the engagement member can engage incrementally with the recesses as the accessory part is screwed into the adaptor. This helps to secure the accessory part as it is screwed in, and also allows for variations in assembly angle and dimensional tolerances.

[0031] Preferably, the recesses are arranged in a generally circular array.

[0032] Preferably, the or each recess is generally part-spherical. In this way, the part-spherical surface of the recess allows for the engagement member to easily and smoothly engage with the recess and then disengage as the accessory part is unscrewed from the adaptor. In other embodiments, the recess or recesses may be generally cuboidal, generally pyramidal or generally wedge-shaped.

[0033] Preferably, the accessory part comprises a generally tubular body, and the engagement face comprises a shoulder of the body adjacent to the threaded end part of the accessory part.

[0034] The accessory part may be an integral part of an accessory, such as a suppressor. Alternatively, the accessory part may be attachable to a suppressor or other accessory.

For instance, the accessory part may be formed as one or more separate components for attachment to a body part of the accessory. For the purposes of this specification, the term "accessory part" is used to denote any component or part thereof that is suitable for engagement with an adaptor according to the invention.

[0035] Preferred and optionaL features of the first aspect of the invention may be used alone or in suitable combination with the second aspect of the invention also.

[0036] The invention will now be described, by way of illustration only, with reference to the accompanying drawings in which: Figure 1 shows a side cross-sectional view of an adaptor according to an embodiment of the invention, and an accessory part for attachment to the adaptor; Figure 2 shows a rear view of the accessory part of Figure 1; Figure 3 shows a front view of the adaptor of Figure 1; Figure 4 shows a side cross-sectional view of the adaptor and accessory part of Figure 1, fitted to a weapon and with the accessory part partially screwed in to the adaptor; and -1_c -Figure 5 shows a side cross-sectional view of the adaptor and accessory part of Figure 1, fitted to the weapon and with the accessory part fully screwed in to the adaptor.

[0037] Figure 1 shows an adaptor 1 according to an embodiment of the present invention, together with an accessory parL 7 for a S Lacimiexi S So She adap Sor 1. The adapLor 1 is arranged to attach the accessory part 7 to a firearm barrel (not shown in Figure 1) in an axially-aligned configuration. The accessory part 7 may be integrally formed with an accessory, such as a suppressor, or the accessory part 7 may be welded to or otherwise attached to an accessory. Figures 2 and 3 show end views of the accessory part 7 and the adaptor 1, respectively, viewed from the ends of the components that connect to one another in use.

[0038] The adaptor 1 comprises a generally tubular body or sleeve 2 having a bore 9 that extends from a back face 21 to a front end face 20 of the body 2. The back face 21 has a first opening 15 for admitting an end portion of a firearm barrel to the bore 9, and the front end face 20 has a second opening 4 for admitting an end part 5 of the accessory part 7 to the bore 9.

[0039] A region 3 of the bore 9 of the adaptor 1, adjacent to the front end face 20, is internally threaded to engage with a cooperating external thread provided on the end part of the accessory part 7. In this way, the accessory part 7 can be screwed into the adaptor 1 in use to attach the accessory part 7 to the adaptor 1 in an axially-aligned configuration.

[0040] To guard against accidental unscrewing of the accessory part 7 from the adaptor 1, for example due to vibration or mechanical shock, the adaptor 1 includes -1_i -engagement means that cooperate with the accessory part 7 in such a way that unscrewing movement of the accessory part 7 is possible only when an unscrewing torque is deliberately applied to the accessory part by a user. The engagement means therefore serves to resist unintentional unscrewing of the accessory part 7 from the adaptor 1, whilst allowing the accessory par L 7 Lo be manually unscrewed when required.

[0041] The engagement means comprises an engagement member in the form of a ball bearing 10, which is housed in a second bore 12 that extends longitudinally in a wall of the tubular body 2. The second bore 12 extends from the front end face 20 to the back face 21 of the body 2, and is closed at the back face 21 by a closure member or plug 14. The closure member 14 may be retained in the second bore 12 by threaded engagement or other mechanical fastening, or the closure member 14 may be welded, brazed, soldered or otherwise fixed in the second bore 12.

[0042] The ball 10 is retained in the second bore 12 by a retaining means or retaining formation. The retaining formation comprises a reduced-diameter end portion (not visible in figure 1) of the second bore 12, disposed adjacent to the front end face 20. The reduced-diameter end portion of the second bore 12 has a smaller diameter than the maximum diameter of the ball 10, so that the ball 10 is retained in the second bore 12.

[0043] A biasing means, comprising a compression spring 11, is housed within the second bore 12. The spring 11 acts between the closure member 14 and the ball 10 to bias the ball 10 towards the end of the second bore 12 that opens onto the front end face 20 of the adaptor.

[0044] Referring additionally to figure 3, the reduced-

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diameter end portion of the second bore 12 is sized so that, when the ball 10 is pressed against the end portion by the spring 11, part of the ball 10 protrudes from the front end face 20 of the body 2. In this way, the ball 10 presents a part-spherical surface for engagement with a corresponding recess in the accessory part, as will now be explained.

[0045] Referring again to figures 1 and 2, the accessory part 7 is generally tubular, and the threaded end part 5 of the accessory part 7 has a reduced external diameter compared to the remainder of the accessory part 7. The resulting shoulder, formed where the end part 5 joins the remainder of the accessory part 7, provides an engagement faoe 6 of the accessory part.

[0046] As shown most clearly in figure 2, a plurality of recesses 8 are arranged in a circular array on the engagement face 6. Each recess 8 is part-spherical, for cooperation with the hall 10. As will be explained in more detail later, when the accessory part 7 is screwed into the adaptor 1, the ball is biased to engage with one of the recesses 8. The force applied to the ball 10 by the spring 11 presses the ball 10 into the recess 8 to increase the torque required to rotate the accessory part 7 with respect to the adaptor 1. In this way, unintentional unscrewing of the accessory part 7 is resisted.

[0047] To secure the adaptor 1 to the barrel of a firearm, the adaptor 1 is provided with securing means in the form of a U-shaped gate 13 that is slidably received in a slot 22 in the body 2. The slot 22 is disposed towards the back face 21 of the body 2.

[0048] As shown most clearly in figure 3, the gate 13 comprises parallel first and second arms 24, 25 that extend -1_3 -from a cross member 23. When the gate 13 is in place in the slot 22, the arms extend into the bore 9 of the body 2 for engagement with the firearm barrel (not shown in figures 1 and 3).

[0049] Figure 4 shows the adaptor 1 fitted to the barrel 18 of a firearm, wi Lh Llie accessory parL 7 parbially screwed in to the adaptor 1. In this configuration, the front end face of the adaptor 1 and the engagement face 6 of the accessory part 7 are spaced apart so that the ball 10 is not in engagement with a recess 8.

[0050] An end part of the barrel 18 of the firearm includes a flash hider 17. Behind the flash hider 17, the barrel 18 includes an annular recess 19. Tn this way, the back surface of the flash hider 17 presents a shoulder 26 that forms one wall of the recess 19.

[0051] To connect the adaptor 1 to the barrel 18, the gate 13 is withdrawn from the slot 22 so that the arms 24, 25 are clear of the bore 9. The end part of the barrel 18 is then inserted in the bore 9 of the adaptor 1, by way of the first opening 15. The gate 13 is then pushed home so that the arms 24, 25 mate with the recess 19 behind the flash hider 17 and embrace the barrel 18 therebetween. The gate 13 is held in place by a suitable retaining mechanism or clip (not shown) [0052] With the gate in place, the shoulder 26 formed by the back surface of the flash hider 17 acts as a stop to limit axial movement of the adaptor 1 away from the body of the firearm. It will be appreciated from figure 4 that the gate 13 is a clearance fit in the recess 17 so that, in this configuration, the adaptor 1 is connected relatively loosely to the barrel 18. This makes the adaptor 1 easy to connect to the barrel 18.

-:I_4 - [0053] To prepare an accessory for use, the accessory part 7 is screwed further into the adaptor 1. In doing so, the adaptor 1 becomes tightly attached to the barrel 18.

[0054] As the accessory part 7 is screwed into the adaptor 1, Lhe end face 16 of Ihe accessory par L 7 (i.e. Llie rearmost end surface of the threaded end portion 5 of the accessory part 7) moves further into the bore 9, to the left in figure 4. Eventually, the end face 16 of the accessory part 7 comes into abutment with the opposing end face 27 of the flash hider 17, within the bore 9. Further screwing movement of the accessory part 7 draws the adaptor 1, and hence the gate 13, towards the accessory part 7 (to the right in figure 4) [0055] The accessory part 7 reaches a fully-tight or fully-home position when the gate 13 presses against the shoulder 26 formed by the back surface of the flash hider 17, as shown in figure 5, with the flash hider 17 firmly clamped between the gate 13 and the end face 16 of the accessory part 7. In this way the adaptor 1 and the accessory part 7 are tightly attached to and axially aligned with the firearm barrel 18 with substantially no free play.

[0056] As can be seen in figure 5, the components are dimensioned such that, when the accessory part 7 is fully tightened in the adaptor 1, the engagement face 6 of the accessory part 7 comes into ciLose proximity to the front end face 20 of the adaptor 1.

[0057] In this state, the ball 10 engages with one of the recess 8 in the engagement face 6 of the accessory part 7.

The ball 10 is biased into engagement with the recess 8 by the spring 11. In this way, the engagement member 10 acts in -1_S -combination with the recess 8 as a detent mechanism to physically resist rotation of the accessory part 7. This resistance makes unintentional or accidental unscrewing cf the accessory part 7 from the adaptor 1 much less likely, thereby reducing the risk of improper bore alignment or failure of the connection between the barrel 18, the adaptor 1 and blie accessory par b 7.

[0058] In order to detach the adaptor 1 and accessory part 7 from the barrel 18, a torque is applied by the user to the accessory part 7 in an unscrewing direction. This urges the recess 8 with which the ball 10 is engaged to rotate away from the position of the ball 10. Provided the unscrewing torque is sufficient, the resulting force acting on the ball 10 overcomes the force of the spring 11 so that the ball 10 is caused to retract into the bore 12, allowing the ball 10 to disengage from the recess 8.

[0059] With the ball 10 disengaged from the recess 8, the torque reguired to unscrew the accessory part 7 is reduced until the ball 10 engages with the next recess 10 on the engagement face 6 of the accessory part 7. Upon further or continued application of a sufficient unscrewing torque, the ball 10 is forced to retract again to disengage from each further recess 8 as unscrewing movement of the accessory part 7 continues, until the engagement face 6 of the accessory part 7 is spaced from the end face 20 of the adaptor 1 so that the protruding ball 10 no longer contacts the engagement face 6.

[0060] When the accessory part 7 has been unscrewed sufficiently so that its end face 16 loses contact with the end face of the flash hider 17, the clamping force applied to the shoulder of the flash hider 17 by the gate 13 is released, and the adaptor 1 becomes loose on the barrel 18.

-f6 -The U-shaped gate 13 can then be withdrawn from the slot 22 to allow the adaptor f to be slipped off the end portion of the barrel 18.

[0061] In this way, the accessory part 7 and the adaptor 1 can be detached from and attached to the barrel 18 as a single ciii L. Furblier uxiscrewi:ig of Lhe accessory parL 7 from the adaptor 1 will remove the accessory part 7 from the adaptor 1.

[0062] The adaptor of the present invention allows the accessory part 7 to be rotated both clockwise and counter-clockwise, relative to the firearm's operator, by the simple application of a suitable torque to the accessory part 7. In this way, the engagement means of the adaptor acts as a two-way ratchet mechanism to secure the accessory part 7 against undesired rotation. It is not necessary for the user to operate additional levers, catches or other mechanisms to screw in or unscrew the accessory part 7, hut the risk of unintentional unscrewing of the attachment 7 is substantially reduced.

[0063] It is desirable that the spring 11 is selected so that the biasing force acting to keep the ball 10 engaged with the recess 8 can be overcome when a positive, deliberate manual unscrewing action is applied to the accessory part 7.

However, the biasing force should be sufficient so that the ball 10 remains engaged with the recess under all expected operational loads, such as vibrations and mechanical shocks due to firing or handling of the firearm. This therefore requires a relatively high force, much greater than that applied in conventional ball bearing latches. In one example, a suitable spring 11 applies a biasing force of at least 3 Newtons, preferably at least 5 Newtons, and more preferably at least 10 Newtons, to the ball 10.

-1_7 - [0064] The biasing force that acts on the ball 10 tends to increases as the spring 11 is compressed when the bail 10 is pushed into the bore 9. Preferably, the spring 11 applies a minimum biasing force of approximately S Newtons to the ball when the spring 11 is at its maximum length in the bore 9 and, as blie spring]l is compressed, bhe biasing force applied to the ball 10 preferably increases to a maximum of at least 5 Newtons, and more preferably at least 10 Newtons.

[0065] It will be appreciated that, when the accessory part 7 is in its fully tight position, the engagement face 6 of the accessory part need not actually abut the front end face 20. Instead, a small clearance may be present, provided that the engagement face 6 is close enough to the front end face to allow the ball 10 to engage sufficiently with one of the recesses 8. The ball 10 may engage with rear and/or side surfaces of the recess 8, or the ball 10 may simply protrude into the recess 8.

[0066] It will be understood that the embodiment illustrated above shows an application of the invention only for the purposes of illustration. In practice the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

[0067] For example, the gate that contacts with the rear surface of the flash hider may instead be V-shaped or any other suitable shape for embracing or engaging with a generally tubular barrel. The gate may engage with any suitable shape of shoulder, recess or groove in the barrel or the flash hider.

[0068] The use of a ball, and in particular a ball bearing, -to -as the engagement member in the illustrated embodiment is advantageous, since the bali can roll across the engagement face as it passes into and out of each successive recess.

This reduces wear on the engagement face, the recesses, and the engagement member. It will be appreciated, however, that engagement members of different shapes could be used. For example, a ball p1 uxiger (i.e. a rod wi Lii a parL-splienical tip) could be used in place of the ball.

[0069] when a ball or a ball plunger are used, the engagement means presents a part-spherical surface for engagement with the recesses, to allow the engagement member to ride smoothly into and out of the recesses on the engagement surface.

[0070] It is also conceivable that engagement members with other shapes, and recesses with other shapes, could be used provided that, in combination, the shapes of the engagement member and recesses act together to allow two-way rotation of the accessory part with respect to the adaptor upon application of a sufficient torque to the accessory part.

[0071] In the illustrated embodiment of the invention, a plurality of recesses are provided in the engagement face of the accessory part, and the engagement member is configured to engage and disengage successively with adjacent recesses as the accessory part is screwed into the adaptor. By providing a plurality of recesses, the chances of one of the recesses being in alignment with the engagement means when the accessory part is in its fully home position are maximised, thereby allowing for variations in assembly geometry and manufacturing tolerances. It will be understood, however, that a variant having only one recess in the engagement face is also possible. In such a case, the recess would be positioned so that the engagement member comes into -1_9 -register with the recess when the accessory part is in its fully home position.

[0072] It will be appreciated that further modifications and variations of the invention are also possible without departing from the scope of the invention as set out in the appended claims.

Claims

-20 -CLAIMS1. An adaptor for attaohing an accessory part to a firearm barrel in an axially-aligned configuration, the adaptor comprising: a generally tubular body arranged to connect to an end por Lion of Lhe firearm barrel and having a bore wi Lii a threaded region for engagement with a threaded end part of the accessory part; and an engagement member biased to protrude from an end face of the body for engagement with a recess in an opposing engagement face of the accessory part when the accessory part is screwed into the adaptor so as fo resist unintentional unscrewing of the accessory part from the adaptor; wherein the engagement member is configured to disengage from the recess when an unscrewing torgue is applied to the accessory part.
2. An adaptor according to any preceding claim, wherein the engagement member comprises a part-spherical surface for engagement with the recess.
3. An adaptor according to claim 2, wherein the engagement member comprises a ball bearing or a ball plunger.
4. An adaptor according to any preceding claim, further comprising a biasing means to bias the engagement member to protrude from the end face of the body.
5. An adaptor according to claim 4, wherein the biasing means applies a biasing force of at least 3 Newtons to the engagement member.
6. An adaptor according to claim 4 or claim 5, wherein the biasing means comprises a compression spring.

-21 -
7. An adaptor according to any one of claims 4 to 6, wherein the biasing means is housed within the body.
8. An adaptor according to claim 7, comprising a second bore extending in a wall of the body to house the biasing means.
9. An adaptor according to claim 8, wherein the second bore includes retaining means for retaining the engagement member against the force of the biasing means.
10. An adaptor according to claim 8 or claim 9, wherein the second bore extends from the end face of the body to an opposite back face of the body.
11. An adaptor according to claim 10, further comprising closure means to close the second bore at the back face of the body.
12. An adaptor according to any preceding claim, wherein the engagement member is configured to successively engage with and disengage from a plurality of recesses in the engagement face of the accessory part as the accessory part is screwed into or unscrewed from the adaptor.
13. An adaptor according to any preceding claim, wherein the bore is arranged to receive the end portion of the firearm barrel.
14. An adaptor according to any preceding claim, comprising securing means for securing the adaptor to the firearm barrel.
15. An adaptor according to claim 14 when dependent on claim 13, wherein the securing means comprises a securing -22 -member arranged to extend into the bore for engagement with a shoulder in the firearm barrel.
16. An adaptor according to claim 15, wherein the securing member comprises a U-shaped gate having first and second arms to embrace the firearm barrel therebetween and Lo engage wi Lii Liie shoulder.
17. An adaptor according to claim 15 or claim 16, wherein the body comprises a slot for receiving the securing member.
18. An accessory system for firearm, comprising an adaptor according to any preceding claim and an accessory part for attachment to the adaptor, the accessory part comprising: a threaded end part for engagement with the threaded region of the bore of the adaptor; and an engagement face that opposes the end face of the body of the adaptor when the accessory part is attached to the adaptor, the engagement face comprising at least one recess for engagement with the engagement member of the adaptor.
19. An accessory system according to claim 18, wherein the face of the accessory part comprises a plurality of recesses.
20. An accessory system according to claim 19, wherein the recesses are arranged in a generally circular array.
21. An accessory system according to any one of claims 18 to 20, wherein the or each recess is generally part-spherical.
22. An accessory system according to any one of claims 18 -23 -to 21, wherein the accessory part comprises a generally tubular body, and wherein the engagement face comprises a shoulder of the body adjacent to the threaded end part of the accessory part.
23. An accessory system according to any one of claims 18 Lo 22, wherein Llie accessory par L is formed inLegrally wi Lii an accessory.
24. An accessory system according to any one of claims 18 to 22, wherein the aocessory part is attached or attachable to an accessory.
25. An accessory system according to claim 23 or claim 24, wherein the accessory comprises a suppressor.
26. An adaptor substantially as hereinbefore described with reference to figures 1, 3, 4 and 5 of the accompanying drawings.
27. An accessory system substantially as hereinbefore described with reference to figures 1, 4 and 5 of accompanying drawings.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:CLAIMS1. An adaptor for attaching an accessory part to a firearm barrel in an axially-aligned configuration, where the accessory part has a threaded end part and an engagement face with at least one recess, the adaptor comprising: a generally tubular body arranged to connect to an end portion of the firearm barrel and having a bore with a threaded region for engagement with the threaded end part of the accessory part; and an engagement member biased to protrude from an end face of the body for engagement with one of the at least one recesses in the opposing engagement face of the accessory part when the accessory part is screwed into the adaptor so as to resist unintentional unscrewing of the accessory part from the adaptor; wherein the engagement member is configured to disengage from the recess when an unscrewing torque is applied to the accessory part. (42. An adaptor according to any preceding claim, wherein the engagement member comprises a part-spherical surface for engagement with the recess.3. An adaptor according to claim 2, wherein the engagement member comprises a ball bearing or a ball plunger.4. An adaptor according to any preceding claim, further comprising a biasing means to bias the engagement member to protrude from the end face of the body.5. An adaptor according to claim 4, wherein ihe biasing means applies a biasing force of at least 3 Newtons to the engagement member.6. An adaptor according to claim 4 or claim 5, wherein the biasing means comprises a compression spring.7. An adaptor according to any one of claims 4 to 6, wherein the biasing means is housed within the body.8. An adaptor according to claim 7, comprising a second bore extending in a wall of the body to house the biasing means.9. An adaptor according to claim 8, wherein the second bore includes retaining means for retaining the engagement member against the force of the biasing means.10. An adaptor according to claim 8 or claim 9, wherein the second bore extends from the end face of the body to an opposite back face of the body.11. An adaptor according to claim 10, further comprising closure means to close the second bore at the back face of the body.12. An adaptor according to any preceding claim, wherein the engagement member is configured to suocessively engage with and disengage from a plurality of recesses in the engagement face of the accessory part as the accessory part is screwed into or unscrewed from the adaptor.13. An adaptor according to any preceding claim, wherein the bore is arranged to receive the end portion of the firearm barrel.14. An adaptor according to any preceding claim, comprising securing means for securing the adaptor to the firearm barrel.15. An adaptor according to claim 14 when dependent on claim 13, wherein the securing means comprises a securing member arranged to extend into the bore for engagement with a shoulder in the firearm barrel.16. An adaptor according to claim 15, wherein the securing member comprises a U-shaped gate having first and second arms to embrace the firearm barrel therebetween and to engage with the shoulder.17. An adaptor according to claim 15 or claim 16, wherein the body comprises a slot for receiving the securing member.18. An accessory system for firearm, comprising an adaptor according to any preceding claim and an acoessory part for attachment to the adaptor, the accessory part comprising: a threaded end part for engagement with the threaded region of the bore of the adaptor; and an engagement face that opposes the end face of the body of the adaptor when the accessory part is attached to the adaptor, the engagement face comprising at least one recess for engagement with the engagement member of the adaptor.19. An accessory system according to claim 18, wherein the face of the accessory part comprises a plurality of recesses.20. An accessory system according to claim 19, wherein the recesses are arranged in a generally circular array.21. An accessory system according to any one of claims 18 to 20, wherein the or each recess is generally part-spherical.22. An accessory system according to any one of claims 18 to 21, wherein the accessory part comprises a generaliy tubular body, and wherein the engagement face comprises a shoulder of the body adjacent to the threaded end part of the accessory part.23. An accessory system according to any one of claims 18 to 22, wherein the accessory part is formed integrally with an accessory.24. An accessory system according to any one of claims 18 to 22, wherein the accessory part is attached or attachable to an accessory.25. An accessory system acccrding to claim 23 or claim 24, wherein the accessory comprises a suppressor.26. An adaptor substantially as hereinbefore described with reference tc figures 1, 3, 4 and 5 of the accompanying drawings.27. An accessory system substantially as hereinbefore described with reference to figures 1, 4 and 5 of accompanying drawings.