Type: L16/24,L17/28/ L21/31, L23/30,L23/30H,  L27/38, L28/32H, L32/40

 This incorporates a ball-retaining plate with six ramped grooves for balls to roll along. A small spring pushes each of these balls to one side. A Belleville-type dished spring washer fits over these balls to form an upper race, which is supported on its outer edge by a spring-seat retainer. This retainer holds the whole assembly together and also provides a seat for the helical-coil valve springs. In the closed position of the valve, the dished washer is suspended between the spring-seat retainer and the ball-retainer, so that the balls move freely to the top of the ramp and abut against the end of the groove. During opening of the valve, the dished spring washer deflects with the increase in the compression load on the valve spring. The outer edge of the dished washer bears against the spring-seat retainer as before, but the inner part of the washer now bears against the six balls and hence pushes them down their ramps. The ramps are so shaped that, as contact with the washer is maintained, the spring-seat retainer is rotated and hence the poppet-valve is rotated by the same amount. As the valve closes, the washer comes back to its original position between the spring-seat retainer and the ball-retainer. This releases the load on the balls due to which the small bias springs now push the balls up their ramps and thereby bring the spring-seat retainer and the valve assembly back to its starting position.