Shuttering mechanism for controlling translation of a longitudinally moveable component within a housing, the shuttering mechanism comprising at least one fixed shutter that can be or that is attached to or integrated with the housing and at least one moving shutter arm moveable between at least one locking position and at least one unlocking position, wherein the shuttering mechanism comprises at least one resilient arm which is associated with the longitudinally moveable component, the resilient arm having a dog resiliently biased towards the fixed shutter, wherein the moving shutter arm is arranged alongside the fixed shutter, wherein at least one fixed protrusion (3.1 to 3.n) is arranged on the fixed shutter at least one of the at least one fixed protrusion (3.1 to 3.n) arranged for engaging the dog so as to prevent translation of the longitudinally moveable component in a proximal direction, wherein at least one moving protrusion (7.1 to 7.n) is arranged on the moving shutter arm, at least one of the at least one moving protrusion (7.1 to 7.n) ramped in a manner to disengage the dog from the at least one of the fixed protrusions (3.1 to 3.n) and/or to prevent engagement of the dog to the fixed protrusion (3.1 to 3.n) when the moving shutter arm is in the unlocking position, wherein the moving shutter arm is arranged to allow engagement of the dog with the fixed protrusion (7.1 to 7.n) in the locking position, wherein the at least one fixed protrusion (3.1 to 3.n) comprises a set of consecutive fixed protrusions (3.1 to 3.n) spaced from each other, wherein the at least one moving protrusion (7.1 to 7.n) comprises a set of consecutive moving protrusions (7.1 to 7.n) spaced from each other, wherein both sets have the same pitch, wherein - the moving shutter arm is arranged to be rotated between its locking position and its unlocking position, and/or - a most distal moving protrusion (7.1) is ramped, wherein the other moving protrusions (7.2 to 7.n) are arranged as castellations or all fixed protrusions (3.1 to 3.n) are ramped with their ramps facing in the opposite direction of the moving protrusion's (7.1 to 7.n) ramps or the ramp of the most distal moving protrusion (7.1) is longer than the ramps of the other moving protrusions (7.2 to 7.n) or the ramp of the most distal moving protrusion (7.1) is steeper than the ramps of the other moving protrusions (7.2 to 7.n), and/or - at least two fixed shutters and at least two moving shutters are arranged as pairs with the pitches of the pairs out of phase with each other. wherein the shuttering mechanism comprises at least one resilient arm which is associated with the longitudinally moveable component, the resilient arm having a dog resiliently biased towards the fixed shutter, wherein the moving shutter arm is arranged alongside the fixed shutter, wherein at least one fixed protrusion (3.1 to 3.n) is arranged on the fixed shutter at least one of the at least one fixed protrusion (3.1 to 3.n) arranged for engaging the dog so as to prevent translation of the longitudinally moveable component in a proximal direction, wherein at least one moving protrusion (7.1 to 7.n) is arranged on the moving shutter arm, at least one of the at least one moving protrusion (7.1 to 7.n) ramped in a manner to disengage the dog from the at least one of the fixed protrusions (3.1 to 3.n) and/or to prevent engagement of the dog to the fixed protrusion (3.1 to 3.n) when the moving shutter arm is in the unlocking position, wherein the moving shutter arm is arranged to allow engagement of the dog with the fixed protrusion (7.1 to 7.n) in the locking position, wherein the at least one fixed protrusion (3.1 to 3.n) comprises a set of consecutive fixed protrusions (3.1 to 3.n) spaced from each other, wherein the at least one moving protrusion (7.1 to 7.n) comprises a set of consecutive moving protrusions (7.1 to 7.n) spaced from each other, wherein both sets have the same pitch, wherein - the moving shutter arm is arranged to be rotated between its locking position and its unlocking position, and/or - a most distal moving protrusion (7.1) is ramped, wherein the other moving protrusions (7.2 to 7.n) are arranged as castellations or all fixed protrusions (3.1 to 3.n) are ramped with their ramps facing in the opposite direction of the moving protrusion's (7.1 to 7.n) ramps or the ramp of the most distal moving protrusion (7.1) is longer than the ramps of the other moving protrusions (7.2 to 7.n) or the ramp of the most distal moving protrusion (7.1) is steeper than the ramps of the other moving protrusions (7.2 to 7.n), and/or - at least two fixed shutters and at least two moving shutters are arranged as pairs with the pitches of the pairs out of phase with each other. - the moving shutter arm is arranged to be rotated between its locking position and its unlocking position, and/or - a most distal moving protrusion (7.1) is ramped, wherein the other moving protrusions (7.2 to 7.n) are arranged as castellations or all fixed protrusions (3.1 to 3.n) are ramped with their ramps facing in the opposite direction of the moving protrusion's (7.1 to 7.n) ramps or the ramp of the most distal moving protrusion (7.1) is longer than the ramps of the other moving protrusions (7.2 to 7.n) or the ramp of the most distal moving protrusion (7.1) is steeper than the ramps of the other moving protrusions (7.2 to 7.n), and/or - at least two fixed shutters and at least two moving shutters are arranged as pairs with the pitches of the pairs out of phase with each other.