People are using conveyor belts to go up or down.
People having fun at work.
Use of conveyor belts for going up and down  does not necessarily mean that people have fun at work.
exists e1 p1 x1 x2 x3.(Theme(e1,p1) & Recipient(e1,x2) & Actor(e1,x1) & v_use(e1) & (exists e2 s1.(a_up(s1) & Manner(e2,s1) & Actor(e2,x1) & v_go(e2)) | exists e3 s2.(a_down(s2) & Manner(e3,s2) & Actor(e3,x1) & v_go(e3))) & n_belt(x2) & of(x2,x3) & n_conveyor(x3) & n_people(x1))
exists e1 x1 x2 x3 x4.(a_topic(x1) & at(e1,x4) & n_work(x4) & Theme(e1,x3) & Actor(e1,x2) & v_have(e1) & n_fun(x3) & (x1 = x2) & n_people(x1))