a cylindrical rod having an outer and threaded peripheral surface; and a subassembly comprising:

a nut having an axial aperture with a threaded inner peripheral surface moveably engageable with the peripheral surface on the outer peripheral surface of said rod and having a peripheral gear surface;

a generally circular drive gear engaging the peripheral gear surface of said nut and having a central axis; and

a means for rotating said generally circular drive gear about the central axis, whereby said nut is moved along the outer peripheral surface of said rod;

wherein said peripheral gear surface of said nut is beveled;

wherein said peripheral gear is superimposed on a base cylindrical member having a peripheral groove;

wherein said generally circular drive gear has an axial aperture;

wherein a drive shaft extends through the axial aperture of said generally circular drive gear;

wherein there is a guide member having a top leg with an aperture and an end leg with parallel terminal fingers which is superimposed over said drive gear so that said drive shaft extends through the aperture in said top leg and said fingers in said end log engage the groove in said cylindrical gear base;

wherein a clip spring engages said rod.