portion which fits into an opening 107 in the housing that is open to the rear of groove 96a and opens radially inwardly to the channel 98 the opening also extends rearwardly beyond the channel and its circumferential dimension is greater than that of the groove 96a the latch radial inner portion fits into the opening 107 but is circumferentially wider than the groove 96a so that forward movement of the latch is limited by the channel wall adjacent the groove 96a the axial dimension of the latch is less than that of the opening 107 so that the latch can move rearwardly the radially outer portion of the latch is circumferentially larger than that of the opening 107 so the latch radial inward movement is limited by the radially outer portion engaging the exterior of the housing the latch spring 106 is positioned within an axially extending socket 105 in the housing 88 that opens to the opening 107 the pin 109 is also in the socket in front of the spring 106 and extends into a hole in the latch a shoulder on the pin engages the latch the spring 106 applies axial pressure to the latch pin.