of dog teeth 65 fig8 the clutch 60 is keyed to the drive sleeve 30 by way of splines not shown to prevent relative rotation between the clutch 60 and the drive sleeve 30 in the illustrated embodiment the clicker 50 and the clutch 60 each extend approximately half the length of the drive sleeve 30 however it will be understood that other arrangements regarding the relative lengths of these parts are possible the clicker 50 and the clutch means 60 are normally engaged that is as shown in fig7 a dose dial sleeve 70 is provided outside of the clicker 50 and clutch means 60 and radially inward of the main housing 4 a helical groove 74 is provided about an outer surface of the dose dial sleeve 70 the main housing 4 is provided with a window 44 through which a part of the outer surface of the dose dial sleeve may be seen the main housing 4 is further provided with a helical rib 46 adapted to be seated in the helical groove 74 on the outer surface of the dose dial sleeve 70 the helical rib 46 extends for a single sweep of the inner surface of the main housing 4 a first stop 100 is provided between the splines 42 and the helical rib 46 fig1 a second stop 102 disposed at an angle of 180 u00b0 to the first stop 100 is formed by a frame surrounding the window 44 in the main housing 4 fig1 conveniently a visual indication of the dose that may be dialed for example reference numerals not shown is provided on the outer surface of the dose dial sleeve 70 the.