Gripper type linear motion device

Apparatus for axially moving a member comprising:

• a longitudinally extending shaft connected at one end to said member to be moved, said shaft having a plurality of longitudinally spaced laterally extending projections thereon, each of said projections having an upper surface and a lower surface and the minimum axial spacing between the lower surface of each of said projections and the upper surface of the next lower axially adjacent projection being of a first predetermined distance;
• a support means;
• first latching means supported on said support means and being adapted to be moved into an unlatched position, a coupled position, and a latched position with respect to said projections on said shaft, said first latching means when in said unlatched position being positioned in non-engagable relationship with said projections on said shaft, when in said latched position being positioned in engagable relationship with respect to said projections and being engaged with one of said projections to bear the load of said shaft, and when in said coupled position being positioned in engagable relationship with respect to said projectons but being positioned between adjacent projections so as not to be subject to the load of said shaft;
• first moving means for moving said first latching means longitudinally relative to said support means between a lower position and an upper position, the axial distance between said lower position and said upper position of said first latching means being of a second predetermined distance;
• second latching means supported on said support means and being adapted to be moved into an unlatched position, a coupled position and a latched position with respect to said projections on said shaft, said second latching means when in said unlatched position being positioned in non-engagable relationship with said projections on said shaft, when in said latched position being positioned in engagable relationship with respect to said projections and being engaged with one of said projections to bear the load of said shaft, and when in said coupled position being positioned in engagable relationship with respect to said projections but being positioned between adjacent projections so as not to be subject to the load of said shaft;
• second moving means for moving said second latching means longitudinally relative to said support means between a lower position and an upper position, the axial distance between said lower position and said upper position of said second latching means being of a third predetermined distance;
• and
• said first latching means and said second latching means being supported in spaced relationship on said support means and said predetermined distances being interrelated such that the following relationships exist:
• a. when said first latching means is in a latched position with respect to said projections and is in its upper position with respect to said support means, and when said second latching means is in a coupled position with respect to said projections and in its lower position with respect to said support means, one of said projections is a fourth predetermined distance above said second latching means;
• b. when said second latching means is in a latched position with respect to said projections and is in its upper position relative to said support means, and said first latching means is in a coupled position with respect to said projections and is in its lower position with respect to said support means, one of said projections is a fifth predetermined distance above said first latching means;
• and
• c. said first predetermined distance is greater than said second predetermined distance less said fourth predetermined distance and is also greater than said third predetermined distance less said fifth predetermined distance.