WO2007012854A1

WO2007012854A1 - Canister-supported rotating ring count readout assembly for a metered dose inhaler

Info

Publication number: WO2007012854A1
Application number: PCT/GB2006/002798
Authority: WO
Inventors: Robert Owen Kivlin; Francis Dominic Lloyd-Lucas
Original assignee: Cambridge Consultants Limited
Priority date: 2005-07-27
Filing date: 2006-07-27
Publication date: 2007-02-01
Also published as: GB0515475D0; GB2429166A

Abstract

A dose counter assembly for use with an inhaler having a housing disposed about a longitudinal axis and a canister extending along a central axis. The canister is adapted to be received within the housing, whereby the central axis is substantially coaxial with the longitudinal axis and the canister is reciprocally moveable along said longitudinal axis of the housing. The dose counter assembly comprises a first ring rotatably mounted on the canister and having ratchet teeth thereon, a second ring rotatably mounted on the canister and having ratchet teeth thereon, activating means mounted on an outer surface of the first ring ,an inner surface of the housing, and a lever for operatively coupling the first ring so as to rotate the first ring in response to the movement of the canister along the longitudinal axis of the housing, and engaging means for operatively coupling the first ring with the ratchet teeth of the second ring so as to rotate the second ring in response to a predetermined amount of rotation of the first ring.

Description

CANISTER-SUPPORTED ROTATING RING COUNT READOUT ASSEMBLY FOR A METERED DOSE INHALER

FIELD OF THE INVENTION

[0001] This invention relates to a dose counter assembly, and in particular, to a dose counter assembly having an improved dosage indicator for indicating the number of metered dosages that have been dispensed from, or remain in, a canister. BACKGROUND OF THE DISCLOSURE

[0002] Patients having certain conditions, for example, asthma, can be treated with medicaments dispersed in an aerosol form and administered to that patient by inhalation. In one form, the aerosol and medicaments are contained in a canister, or container, and dispensed in metered or measured dosages from an inhalation device. In such an arrangement, it is important for the patient to be able to ascertain the number of metered doses remaining in the canister, either by an indication of the number remaining therein or by knowledge of the number already dispensed therefrom, such that the patient is not caught unaware with an empty canister when in need of the medicament. Thus, it is important for the inhalation device to provide an accurate indication of either the number of doses remaining in the canister, or the number of doses already dispensed therefrom.

[0003] Typically, a conventional aerosol canister includes a body and a valve stem extending from one end of the body to emit a metered dose of aerosol and medicament. The canister is usually supplied with a predetermined number of metered doses, generally between 100 and 200 doses of medicament although products outside of this range exist.

[0004] In many of the prior art inhalers, the aerosol canister is removable from the inhaler housing to permit effective cleaning of the structure defining the airflow path. In some inhalers, the housing is designed to accept a succession of user-introduced aerosol medicament canisters, as well as to provide for canister removal for cleaning.

[0005] In use of these devices, it is desirable that the user know whether the canister in, or about to be placed in, has an ample supply of doses of medicament for the near term, as well as for the long term. With that information, a user can know when to replace a given medicament canister.

[0006] U.S. Pat. No. 6,142,339 describes an inhalation device having a dose counter including a worm screw and a ratchet drive in a housing and an indicator having a circular gear thereon for engaging the worm screw. A canister is received within the housing and is reciprocally movable along a longitudinal axis of the housing. The reciprocal movement of the canister drives the ratchet and the worm to rotate, which in turn drives the indicator to advance and to count a dosage. The dose counter disclosed in the U.S. Pat. No. 6,142,339 is not linked to a specific canister or removable from the housing . If a user swap a new canister with the canister associated with the housing, the dosage on the dose indicator which is attached to the housing does not show the correct remaining dosage of the new canister.

[0007] U.S. Pat. No. 6,435,372 describes a dose counter also attached to the housing, but not to the canister. Again, the device presents a danger that the dose indicator may show incorrect remaining dosage of the canister if the canister has been swapped with another canister by the user.

[0008] Because the dose counters for metered dose inhalers available currently are vulnerable to unintentional misuse scenarios, for example inadvertent triggering, swapping of the canister and the housing, there is a need for an improved dose counter assembly that keeps an accurate record of the number of doses used or remained in the canister.

SUMMARY OF THE INVENTION

[0009] The present invention provides a dose counter assembly for use with a medicament dispensing device, preferably, a metered dose inhaler. The dose counter assembly is canister-supported and has a rotating ring count readout. The inhaler includes a housing disposed about a longitudinal axis with a mouthpiece section at one end, a canister extending along a central axis, and a dose counter assembly mounted on the canister.

[0010] The canister can be a known type of aerosol dispensing canister in the art, which generally has a cylindrical shape. A patient's inhalation at the mouthpiece or pressing downward at the cap causes the canister to move downward to an activated position, resulting in the release of a measured dose of medicament through a dispensing nozzle of the canister and into the mouthpiece at the same time as the patient breathes in. Thus the patient inhales air with a metered dose of medicament. The canister then returns to a rest position.

[0011] Typically, the canister is received within the housing, where the central axis of the canister is substantially coaxial with the longitudinal axis of the housing. The canister is reciprocally moveable along the longitudinal axis of the housing. [0012] In one preferred embodiment of the invention, the dose counter assembly for use with the inhaler includes a carrier, which has an annular shape and is mounted on an outer surface of the canister, a first ring rotatably mounted on the carrier about the central axis, a second ring rotatably mounted on the carrier about the central axis, engaging means pivotally mounted on the carrier, and activating means mounted on the outer surface of the first ring and an inner surface of the housing. The first ring has ratchet teeth on an outer circumference of the first ring. The second ring has ratchet teeth on an outer circumference of the second ring. The activating means is for operatively engaging the ratchet teeth of the first ring so as to rotate the first ring in response to the reciprocal movement of the canister along the longitudinal axis of the housing. The engaging means is for operatively engaging the first ring with the ratchet teeth of the second ring so as to rotate the second ring in response to a predetermined amount of rotation of the first ring. In one preferred embodiment of the invention, the canister can be formed to incorporate the carrier. [0013] In one preferred embodiment of the present invention, the first ring includes digits on its outer surface, and the second ring includes digits on its outer surface. For example, the first ring shows digits "0-9" and repeating thereon, and the second ring shows digits "0-20" thereon, wherein digit "0" on the second ring can be blank. The rings are oriented to permit a composite view of a multi-digit number formed by the digits of first ring and second ring. The present invention can employ other indication mechanism for indicating the dosage, such as a fuel gauge type indicator.

[0014] In a preferred embodiment, the ratchet teeth on the first ring are beveled with respect to the central axis of the canister and the activating means includes a set of multipoint teeth on an inner surface of the housing for engaging the beveled ratchet teeth of the first ring to rotate the first ring by one step when the canister is pressed downward along the longitudinal axis of the housing.

[0015] In one preferred form, the engaging means is a lever pivotally mounted on the carrier. The lever preferably includes a first pawl for engaging an engaging element on the outer surface of the first ring and a second pawl for engaging the ratchet teeth of the second ring, whereby the engaging element forces the lever to rotate, which in turn, forces the second ring to rotate by one step (one tooth). In a preferred embodiment, the first ring includes an array of engaging elements separated by a predetermined amount of distance on the outer surface of the first ring. For example, the engaging elements may occur at every tenth tooth of the first ring, which means that the second ring rotates one step (count one time) while the first ring rotates ten steps (count ten times).

[0016] In another preferred embodiment, the activating means includes a lever pivotally mounted on the outer surface of the carrier and a cam surface on the inner surface of the housing. As used herein, a "cam surface" may be a proud feature extending from an element or a recessed track extending into an element. A boss feature on the lever is guided by the cam feature when the canister is pressed downward, thereby causing the lever to move. In one preferred embodiment, the lever includes a pawl for engaging the ratchet teeth of the first ring, and the cam surface is adapted to force the lever to rotate about a pivot when the canister is pressed downward, whereby the pawl engages and rotates the first ring by one step. The engaging means may include a connector, which preferably includes an elongated element slideably mounted on an inner surface of the lever facing the canister. The elongated element includes a first pawl at one end for engaging at least one engaging elements on the outer surface of the first ring and a second pawl at the other end for engaging an array of engaging elements on the outer surface of the second ring. The connector is activated in response to a predetermined movement of the first ring, the predetermined movement being defined by the separation distance of the at least one engaging elements on the first ring. When the connector is activated, the connector contacts the second ring, such that the second ring rotates upon return of the activating lever to the neutral position. Alternatively, the connector of the engaging means is rotatably mounted on the inner surface of the lever. Preferably, the connector includes a first pawl for engaging an array of engaging elements (e.g., protrusions) extending from the outer surface of the first ring and a second pawl for engaging the ratchet teeth of the second ring or an array of engaging elements (e.g., protrusions) extending from the outer surface of the second ring.

[0017] The dose counter assembly preferably includes reverse rotation prevention means mounted on the carrier to cause the first ring and the second ring to rotate in predetermined directions and prevent the first ring and the second ring from rotating in directions opposite the predetermined directions.

[0018] According to another aspect of the present invention, the canister includes alignment means and the housing includes receiving means for receiving the alignment means, thereby maintaining the canister in a predetermined alignment within the housing and preventing the canister from rotary movement relative to the housing when the canister is received within the housing.

[0019] The forms of the invention may include the various ones of the above described features. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a fuller understanding of the nature and the objects of the invention, reference should be made to the following detailed description and the accompanying drawings in which like reference numerals refer to like elements and in which:

[0021] FIGS. IA and IB show two perspective views from different angles of the inhaler together with a dose counter assembly according to one preferred embodiment of the present invention;

[0022] FIG.2 shows a schematic view of a dose counter assembly according to one preferred embodiment of the present invention;

[0023] FIGS.3 A and 3B show schematic views of a dose counter assembly according to another preferred embodiment of the present invention;

[0024] FIG. 4 shows an exploded perspective view of the inhaler in FIGS. IA and IB; [0025] FIGS. 5 A - 5D illustrate schematic views of an exemplary dose counter assembly together with a canister from different angles according to one preferred embodiment of the present invention;

[0026] FIG. 6 illustrates a scale used in the dose counter assembly according to one preferred embodiment of the present invention; and [0027] FIG. 7 illustrates an indication mechanism for indicating the dosage according to yet another preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] An exemplary inhaler embodying the present invention is shown in FIGS. IA and IB. As shown in the figures, the inhaler 10 includes a housing 12 disposed about a longitudinal axis A with a mouthpiece section 14 at one end and an end cap 16 at the other end, a canister 20 extending along a central axis B, and a dose counter assembly 30 mounted on the canister 20. The canister 20 is received within the housing 12, where the central axis B of the canister 20 is substantially coaxial with the longitudinal axis A of the housing 12. The canister 20 is reciprocally moveable along the longitudinal axis A of the housing 12.

[0029] The canister 20 can be a known type of aerosol dispensing canister in the art, which generally has a cylindrical shape. The aerosol dispensing canister has a stem 21 which contains an aerosol dispensing valve (not shown). The inhaler 10 used with the present invention, can be a pressure actuation inhaler (pressing the canister to deliver the medicament), or a breath actuation inhaler. A patient's inhalation at the mouthpiece 14 or pressing downward the cap 16, causes the canister 20 to move downward to an activated position, and allows the release of a measured dose of medicament through the dispensing nozzle and into the mouthpiece 14 at the same time as the patient breathes in. Thus the patient inhales air with a metered dose of medicament. The canister 20 then returns to a rest position. Both actuation mechanisms can be used in the inhaler 10 embodying the present invention and both are known in the art, and are not described in detail in the present disclosure.

[0030] One preferred embodiment of the dose counter assembly 30 for use with the inhaler 10 is shown in FIG.2. The dose counter assembly 30 includes a carrier 24, which has an annular shape and is mounted on an outer surface of the canister 20 (or the canister 20 is formed to incorporate the carrier 24), a first ring 32 rotatably mounted on the carrier 24 about the central axis B, a second ring 36 rotatably mounted on the carrier 24 about the central axis B, engaging means 40 pivotally mounted on the carrier 24, and activating means 50 mounted on the outer surface of the first ring 32 and an inner surface of the housing 12. The first ring 32 has ratchet teeth 34 on an outer circumference of the first ring 32. The second ring 36 has ratchet teeth 38 on an outer circumference of the second ring 36. The activating means 50 is for operatively engaging the ratchet teeth 34 of the first ring 32 so as to rotate the first ring 32 in response to the reciprocal movement of the canister 20 along the longitudinal axis A of the housing 12 by a predetermined distance associated with delivery of a dose of medicament from the canister. The engaging mans 40 is for operatively engaging the first ring 32 with the ratchet teeth 38 of the second ring 36 so as to rotate the second ring 36 in response to a predetermined amount of rotation of the first ring 32.

[0031] In one preferred embodiment, the first ring 32 includes digits on the outer surface of the first ring 32, and the second ring 36 includes digits on an outer surface of the second ring 36. In another preferred embodiment, the carrier 24 includes a scale 22 thereon, and the scale 22 has dosage indicia as shown in FIG. 6. The second ring 36 includes a pointer 35 on the outer surface of the second ring 36 for registering against the scale 22 as shown in FIG.7. In yet another preferred embodiment, the scale 22 is on the housing 12. The present invention can employ other indication mechanisms for indicating the dosage. For example, the second ring 36 may include indicia thereon and the carrier, the canister or the housing includes a pointer for registering against the indicia on the second ring 36.

[0032] FIG.2 shows an opened view of the inhaler with a section of the canister 20 in the middle and a section of the housing 12 on the left. As shown in FIG.2, in a preferred embodiment, the ratchet teeth 34 on the first ring 32 are beveled with respect to the central axis B of the canister 20 and the activating means 50 includes a set of multipoint teeth 51 on the inner surface of the housing 12 for engaging the beveled ratchet teeth 34 of the first ring 32 to rotate the first ring 32 by one step when the canister 20 is pressed downward along the longitudinal axis A of the housing 12.

[0033] In one preferred form, the engaging means 40 is a lever (as indicated by reference number 40 in FIG.2) pivotally mounted on the carrier 24. The lever 40 preferably includes a first pawl 58 for engaging an engaging element 62 on the outer surface of the first ring 32 and a second pawl 60 for engaging the ratchet teeth 38 of the second ring 36, whereby the engaging element 62 forces the lever 40 to rotate, which in turn, forces the second ring 36 to rotate by one step (one tooth). Ih a preferred embodiment, the first ring 32 includes an array of engaging elements separated by a predetermined amount of distance on the outer surface of the first ring 32. For example, the engaging elements 62 may be placed at every tenth tooth of the first ring 32, which means that the second ring 36 rotates one step (count one time) while the first ring 32 rotates ten steps (count ten times).

[0034] In another preferred embodiment as shown in FIG. IB and FIGS.3A and FIG.3B, the activating means 50 includes a lever 64 pivotally mounted on the outer surface of the carrier 24, a boss 65 extending from a point at or near the bottom of the lever, and a cam surface 66 on the inner surface of the housing 12. In one preferred embodiment, the lever 64 includes a pawl 68 for engaging the ratchet teeth 34 of the first ring 32, and the cam surface 66 is adapted to force the boss 65 to move along the cam surface 66, thereby causing the lever 64 to rotate from an initial position about a pivot when the canister 20 is pressed downward, whereby the pawl 68 engages and rotates the first ring 32 by one step. As shown in FIG.3B. the engaging means 40 may include a connector 82, which preferably includes an elongated element slideably mounted on an inner surface of the lever 64 facing the carrier 24. The elongated element includes a first pawl 84 at one end and a second pawl 88 at the other end. Preferably the first ring 32 includes a step-like structure 92 defining at least one recess 94 for engaging the first pawl 84 of the connector 82. The second ring 36 includes a step-like structure 96 defining an array of recesses 98 for engaging the second pawl 88 of the connector 82. When the canister is pressed down, the lever 64 drives the first ring 32 to rotate. After a certain amount of rotation of the first ring 32, one recess 94 on the first ring 32 arrives at the location of the connector 82, and the first pawl 84 and the second pawl 88 respectively are driven into the recess 94 and recess 98, such that the second ring 36 is advanced by the activating lever 64 during return of the lever 64 to the initial position after movement of the canister 20 by the predetermined distance in one dispensing activity. For the next dispensing activity, the first pawl 84 is driven out of the recess 94 and the second ring 36 is disconnected from the activating lever 64. The connector 82 is activated in response to a predetermined amount of movement of the first ring 32, the predetermined movement being defined by the separation distance of the at least one recesses 94 on the first ring 32. [0035] Alternatively, the connector 82 of the engaging means 40 is rotatably mounted on the inner surface of the lever 64. Preferably, the connector 82 includes a first pawl 84 for engaging an array of engaging elements (e.g., protrusions) extending from the outer surface of the first ring 32 and a second pawl 88 for engaging the ratchet teeth of the second ring 36.

[0036] The dose counter assembly preferably includes reverse rotation prevention means mounted on the carrier 24 to allow the first ring 32 and the second ring 36 to rotate in predetermined directions and prevent the first ring 32 and the second ring 36 from rotating in directions opposite the predetermined directions. In one preferred form as shown in FIG.2 and FIG.3 A, the reverse rotation prevention means includes an elongated element 70 having a clip 72 near one end for engaging the ratchet teeth 34 of the first ring 32, allowing the first ring 32 to rotate in the direction A, and another clip 74 near the other end for engaging the ratchet teeth 38 of the second ring 36, allowing the second ring 36 to rotate in the direction B, which is opposite to direction A.

[0037] Preferably the canister 20 includes alignment means and the housing 12 includes receiving means for receiving the alignment means, thereby maintaining the canister 20 in a predetermined alignment within the housing 12 and preventing the canister 20 from rotary movement relative to the housing 12 when the canister 20 is received within the housing 12. In one preferred form, the alignment means is the elongated element 70 and the receiving means of the housing 12 is a slot defined on the inner surface of the housing 12 for receiving the elongated element 70.

[0038] The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

What is claimed is:

1. A dose counter assembly for use with a medicament dispensing device having a housing disposed about a longitudinal axis and a canister extending along a central axis, said canister being adapted to be received within said housing, whereby said central axis is substantially coaxial with said longitudinal axis and said canister is reciprocally movable along said longitudinal axis of said housing, said dose counter assembly comprising: a first ring rotatably mounted on the canister about said central axis, said first ring having ratchet teeth thereon; a second ring rotatably mounted on the canister about said central axis, said second ring having ratchet teeth thereon; activating means mounted on an outer surface of the canister for operatively engaging said ratchet teeth of said first ring so as to rotate said first ring in response to the movement of the canister along said longitudinal axis of the housing by a predetermined distance associated with delivery of a dose of medicament from said canister; and engaging means for operatively coupling said first ring with said ratchet teeth of said second ring so as to rotate said second ring in association with a predetermined amount of rotation of said first ring.

2. The dose counter assembly according to claim 1, wherein said first ring comprises digits on an outer surface of said first ring, and wherein said second ring comprises digits on an outer surface of said second ring.

3. The dose counter assembly according to claim 1, wherein said second ring comprises a pointer on an outer surface of said second ring, said pointer being adapted to register against a scale coupled to said canister, said scale having dosage indicia.

4. The dose counter assembly according to claim 1, wherein said second ring comprises a pointer on an outer surface of said second ring, said pointer being adapted to register against a scale on the housing, said scale having dosage indicia.

5. The dose counter assembly according to claim 1 further comprising reverse rotation prevention means mounted on said canister to allow said first ring and said second ring to rotate in predetermined directions and prevent said first ring and said second ring from rotating in directions opposite said predetermined directions.

6. The dose counter assembly according to claim 1, wherein said canister includes alignment means and said housing includes means for receiving said alignment means for maintaining said canister in a predetermined alignment within said housing and preventing said canister from rotary movement relative to said housing.

7. The dose counter assembly according to claim 1, wherein said activating means includes multipoint teeth on an inner surface of the housing for engaging said ratchet teeth of said first ring to rotate said first ring by one step when the canister is pressed downward along said longitudinal axis of the housing.

8. The dose counter assembly according to claim 1, wherein said activating means comprises a lever pivotally coupled to the canister, and a cam surface on an inner surface of the housing, said lever including a pawl for engaging said ratchet teeth of said first ring, wherein said cam surface is adapted to drive said lever to rotate from an initial position about a pivot when the canister is pressed downward, whereby said pawl rotates said first ring by one step.

9. The dose counter assembly according to claim 8, wherein said engaging means includes a connector moveably mounted on said lever, said connector is adapted to connect said second ring to said lever, whereby said connector is activated in response to a return of said lever to said initial position after movement of said canister by said predetermined distance.

10. The dose counter assembly according to claim 1, wherein said engaging means includes a lever coupled to the outer surface of the canister, said lever including a first pawl for engaging at least one engaging element on said first ring and a second pawl for engaging said ratchet teeth of said second ring, whereby said engaging element forces said lever to rotate, which in turn, drives said second ring to rotate.

11. The dose counter assembly according to claim 10, wherein said at least one engaging element includes an array of engaging elements separated by a predetermined amount of distance on said first ring.

12. The dose counter assembly according to claim 1 further comprising a carrier mounted on said canister, wherein said first and second rings, and said engaging means are mounted on said carrier, and wherein said carrier is adapted to be secured against rotation in said housing when said canister is installed in said housing.

13. An inhaler comprising: a housing disposed about a longitudinal axis; a canister extending along a central axis, said canister being adapted to be received within said housing, whereby said central axis is substantially coaxial with said longitudinal axis and said canister is reciprocally moveable along said longitudinal axis of said housing; a first ring rotatably mounted on the canister about said central axis, said first ring having ratchet teeth thereon; a second ring rotatably mounted on the canister about said central axis, said second ring having ratchet teeth thereon; activating means mounted on an outer surface of the canister and an inner surface of the housing for operatively engaging said ratchet teeth of said first ring so as to rotate said first ring in response to the movement of the canister along said longitudinal axis of the housing by a predetermined distance associated with delivery of a dose of medicament from said canister; and engaging means for operatively coupling said first ring with said ratchet teeth of said second ring so as to rotate said second ring in association with a predetermined amount of rotation of said first ring.

14. The inhaler according to claim 13, wherein said first ring comprises digits on an outer surface of said first ring, and wherein said second ring comprises digits on an outer surface of said second ring.

15. The inhaler according to claim 13, wherein said second ring comprises a pointer on an outer surface of said second ring, said pointer being adapted to register against a scale coupled to the canister, said scale having dosage indicia.

16. The inhaler according to claim 13, wherein said second ring comprises a pointer on an outer surface of said second ring, said pointer being adapted to register against a scale on the housing, said scale having dosage indicia.

17. The inhaler according to claim 13 further comprising reverse rotation prevention means mounted on said canister to allow said first ring and said second ring to rotate in predetermined directions and prevent said first ring and said second ring from rotating in directions opposite said predetermined directions.

18. The inhaler according to claim 13, wherein said canister includes alignment means and said housing includes means for receiving said alignment means for maintaining said canister in a predetermined alignment within said housing and preventing said canister from rotary movement relative to said housing.

19. The inhaler according to claim 18, wherein said activating means includes teeth on an inner surface of the housing for engaging said ratchet teeth of said first ring to rotate said first ring by one step when the canister is pressed downward along said longitudinal axis of the housing.

20. The inhaler according to claim 13, wherein said activating means comprises a lever pivotally coupled to the canister and a cam surface on an inner surface of the housing, said lever including a pawl for engaging said ratchet teeth of said first ring, wherein said cam surface is adapted to drive said lever to rotate from an initial position about a pivot when the canister is pressed downward, whereby said pawl rotates said first ring by one step.

21. The inhaler according to claim 20, wherein said engaging means includes a connector mounted on said lever, said connector is adapted to connect said second ring to said lever, whereby said connector is activated in response to a return of said lever to said initial position after movement of said canister by said predetermined distance.

22. The inhaler according to claim 13, wherein said engaging means includes a lever pivotally mounted on the outer surface of the canister, said lever including a first pawl for engaging at least one engaging element on said first ring and a second pawl for engaging said ratchet teeth of said second ring, whereby said engaging element forces said lever to rotate, which in turn, drives said second ring to rotate.

23. The inhaler according to claim 22, wherein said at least one engaging element includes an array of engaging elements separated by a predetermined amount of distance on said first ring.

24. The inhaler according to claim 13 further comprising a carrier mounted on said canister, wherein said first and second rings, and said engaging means are mounted on said carrier, and wherein said carrier is adapted to be secured against rotation in said housing when said canister is installed in said housing.