In a fork lift truck apparatus including vertically spaced, horizontally oriented, upper and lower truck carriage bars, each of said upper and lower truck carriage bars having upper and lower surfaces, a side shifter attachment movably mounted on said truck carriage bars, comprising:
- a pair of vertically spaced, horizontally oriented upper and lower shifter carriage bars and a pair of horizontally spaced, vertically oriented side bars connected to said upper and lower shifter carriage bars thereby forming a rectangular open frame;
- said upper shifter carriage bar including
- a first element having a downwardly open, elongated, rearwardly overhanging portion for mounting the side shifter attachment to the upper truck carriage bar,
- a second element having upper and lower surfaces, at least a portion of said upper surface including an upwardly projecting lip to supportingly receive lift forks thereon,
- said first element being connected to said second element on the upper rear surface of the latter, said lip being located forwardly of said first element,
- a pair of abutment means mounted on said second element of said upper shifter carriage bar near each end thereof for receiving a force to laterally move the side shifter attachment relative to said truck carriage bars;
- a fluid actuator disposed below the lower surface of said second element of said upper shifter carriage bar and horizontally forwardly of said upper truck carriage bar;
- means connected to said second element of said upper shifter carriage bar to protect said fluid actuator, said fluid actuator being disposed substantially within the horizontal projections of said upper and lower surfaces of said upper truck carriage bar, said fluid actuator comprising:
- a single cylinder;
- a partition centrally located in said cylinder, thereby dividing the cylinder into a first chamber and a second chamber;
- a cylindrical aperture disposed in said centrally located partition;
- a first piston mounted in said first chamber, thereby dividing said first chamber into first interior and exterior chamber portions;
- a second piston mounted in said second chamber, thereby dividing said second chamber into second interior and exterior chamber portions;
- a center rod disposed intermediate the first and second pistons and passing through the aperture in the centrally located partition;
- a first passage in the center rod for transmitting fluid under pressure from the first exterior chamber portion to the second interior chamber portion;
- a second passage in the center rod for transmitting fluid under pressure from the second exterior chamber portion to the first interior chamber portion;
- a passage in the first piston for transmitting fluid under pressure from the first exterior chamber portion to the first passage in the center rod;
- a passage in the second piston for transmitting fluid under pressure from the second exterior chamber portion to the second passage in the center rod;
- first and second rods each operatively associated with a respective piston, each of the rods including an inner and an outer end, the inner end of each respective rod being located in the exterior chamber portion of the respective first and second chambers, the respective outer ends of the rods extending exteriorly of the respective first and second chambers and operatively engaging said abutment means to exert a force thereon to laterally move the side shifter attachment relative to the truck carriage bars;
- first and second ports for introducing and releasing fluid under pressure into the exterior chamber portions of the first and second chambers;
- an elongated registration bar fixedly mounted on said upper truck carriage bar;
- and
- means for operatively mounting the ends of the cylinder to said registration bar,
- introduction of fluid under pressure into the first port and simultaneous release of fluid under pressure through the second port causing (1) the first piston to push on the center rod, transmitting force through the center rod to the second piston and the second rod located in the exterior chamber portion of the second chamber, and (2) the second piston to push independently on said second rod,
- said first and second pistons thereby acting in concert to cause said second rod to push on one of the pair of abutment means to shift the side shifter attachment laterally to one side of the truck carriage bar, and
- introduction of fluid under pressure into the second port and simultaneous release of fluid under pressure through the first port causing (1) the second piston to push on the center rod, transmitting force through the center rod to the first piston and the first rod located in the exterior chamber portion of the first chamber, and (2) the first piston to push independently on said first rod,
- said first and second pistons thereby acting in concert to cause said first rod to push on the other of the pair of abutment means to shift the side shifter attachment laterally to the other side of the truck carriage bar.