2. A mechanism according to claim 1, wherein said aligning means are arranged one adjacent each of four corners of said car, and said mechanism additionally includes means for substantially simultaneously extending said cam means into engagement with said stationary cam means.

3. A mechanism according to claim 1, wherein said cam means are fixed relative to said movable member for movement therewith along said path of travel of said car.

4. A mechanism according to claim 1, wherein said elevator car when stationary at said floor level serves to approximately place said members in horizontal alignment, and said cam and stationary cam means define generally horizontally and vertically disposed surfaces, said horizontally disposed surfaces cooperating to effect accurate vertical alignment of said members and said vertically disposed surfaces cooperating to effect accurate horizontal alignment of said members.

5. A mechanism according to claim 4, wherein said aligning means are arranged one adjacent each of four corners of said car, and said mechanism additionally includes means for substantially simultaneously extending said cam means into engagement with said stationary cam means, said extending means and said cam means are fixed relative to said movable member for movement therewith along said path of travel of said car.

6. A mechanism according to claim 1, wherein said aligning means are arranged one adjacent each of four corners of said car, each said cam means includes a bar member and means to mount said bar member for reciprocating movement tranversely of said path of travel between retracted and extended positions, said bar member having a vertically inclined cam surface disposed adjacent a free end thereof, each said stationary cam means includes a roller member and means to joUrnal said roller member for free rotational movement about a horizontally disposed axis, said roller member being engageable by said cam surface when said bar member is reciprocated into said extended position, and said mechanism additionally includes means for substantially simultaneously reciprocating said bar members into said extended position thereof.

7. A mechanism according to claim 6, wherein said aligning means are arranged in cooperating pairs of aligning means, said stationary cam means of each said pairs includes a pair of horizontally spaced vertically extending cam surfaces, said pair of cam surfaces being engageable by an associated pair of said bar members when reciprocated into said extended position thereof, whereby said pairs of cam surfaces and associated pairs of bar members are adapted to effect accurate horizontal alignment of said movable and stationary members.

8. A mechanism according to claim 1, wherein said system is an overhead conveyor system including a trolley, said stationary member is a stationary conveyor rail for transporting said trolley at said floor level, and said movable member is a transfer conveyor rail for supporting said trolley for vertical movement with said car between floor levels, said transfer and stationary rails when accurately aligned permitting transfer of said trolley therebetween.

9. A mechanism according to claim 8, wherein said car when stationary at said floor level serves to approximately place said members in horizontal alignment, and said cam and stationary cam means define generally horizontally and vertically disposed surfaces, said horizontally disposed surfaces cooperating to effect accurate vertical alignment of said rails, and said vertically disposed surfaces cooperating to effect accurate horizontal alignment of said rails.

10. A mechanism according to claim 8, wherein said cam means are fixed relative to said transfer rail for movement therewith along said path of travel of said car.

11. A mechanism according to claim 8, wherein said support means includes platform means and means to suspend said platform means from said car for limited vertical movement relative thereto, said transfer rail and said cam means being supported on said platform means for movement therewith.

12. A mechanism according to claim 8, wherein said support means includes platform means and means to support said platform means for limited vertical movement relative to said car, said transfer rail being fixably supported on said platform means for movement therewith, and said mechanism additionally includes in combination means to transfer said trolley between said transfer and stationary rails, said transfer means being fixably supported on said platform for movement therewith.

13. A mechanism according to claim 12, wherein said aligning means are arranged one adjacent each of four corners of said car and platform means, each of said cam means includes a bar member and means to mount said bar member on said platform means reciprocating movement transversely of said path of travel between retracted and extended positions, said bar member having vertically inclined cam surface disposed adjacent a free end thereof, each said stationary cam means is fixed relative to said stationary conveyor rail and includes a roller member and means to journal said roller member for free rotational movement about a horizontally disposed axis, said roller member being engageable by said cam surface when said bar member is reciprocated into said extended position, and said mechanism additionally includes means mounted on said platform means for substantially simultaneously reciprocating said bar members into said extended position thereof.

14. A mechanism according to claim 13, wherein said platform supporting means permits limited horizontal movement of said platform means relative to said car, said aligning means are arranged in cooperating pairs of aligning means straddling said transfer raiL, said stationary cam means of each said pairs including a pair of horizontally spaced, vertically extending cam surfaces, said pair of cam surfaces being engageable by an associated pair of said bar members when reciprocated into said extended position thereof, whereby said pairs of cam surfaces and said associated pairs of bar members are adapted to effect accurate horizontal alignment of said transfer and stationary rails.

15. A mechanism according to claim 12, wherein said transfer rail has input and output ends, said stationary conveyor rail arranged at said floor level being adapted to feed said trolley onto the inlet end of said transfer rail when said car is disposed at said floor level and at least another stationary conveyor rail is arranged at another floor level and adapted to receive said trolley from the outlet end of said transfer rail when said car is disposed at said other floor level, and said transfer means includes an endless conveyor, motor means to drive said endless conveyor in a given direction between a first trolley receiving condition and a second trolley carrying condition, said endless conveyor having means engageable with said trolley to move said trolley from adjacent said inlet end along said transfer rail into a predetermined trolley carry position when said motor is energized to drive said endless conveyor from said first to said second condition and to feed said trolley from said predetermined position off of said transfer rail and onto said other stationary rail when said motor is energized to drive said endless conveyor from said second to said first condition, means to control energization of said motor, and means carried by said platform for cooperation with said engaging means to removably lock said trolley in said predetermined position during movement of said car from said floor level to said other floor level.

16. A mechanism according to claim 15, wherein said other stationary rail is additionally adapted to feed said trolley onto the outlet end of said transfer rail, a second stationary rail is arranged at a second floor level and adapted to receive said trolley from the output end of said transfer rail when said car is disposed at said second floor level, said motor means is adapted to drive said endless conveyor in a direction opposite to said given direction between said first condition and a third condition and in said given direction between said third condition and said first condition, said endless conveyor includes additional means engageable with said trolley to move said trolley fed by said other stationary rail from adjacent said outlet end to a second predetermined trolley carry position when said motor is energized to drive said endless conveyor from said first to said third condition and to feed said trolly from said second predetermined trolley carry position onto said second stationary rail when said motor is energized to drive said endless conveyor from said third condition to said first condition and said platform carried means additionally cooperates with said additional engaging means to removably lock said trolley in said second predetermined position during movement of said car from said other floor level to said second floor level.