1. In a conveyor system comprising: a. an endless power-driven conveyor element having a plurality of driving dogs spaced from one another lengthwise of the element, b. a load-supporting track extending parallel to the path of travel of the conveyor element, c. a plurality of load carriers which run on the track, each load carrier comprising a trolley having a body mounted on wheels which run on said track, d. a first drive control element at the front end of each load carrier, e. a second drive control element at the rear end of each load carrier for co-operation with the first drIve control element of a following carrier when such following carrier comes into proximity with a preceding carrier, f. a supporting body supporting one of said drive control elements, spaced lengthwise of the track from the load carrier and mounted on wheels which run on the track, g. a connecting element articulately connecting said supporting body with said body of the load carrier, h. drive transmitting means associated with each load carrier for releasably engaging with a driving dog of the conveyor element to transmit drive from the conveyor element to the load carrier, said drive transmitting means being releasable from engagement with a driving dog of the conveyor element by cooperation of the first drive control element of the associated load carrier with the second drive control element of a preceding load carrier, the improvement wherein: i. said supporting body is spaced lengthwise of the track from the drive transmission means of the load carrier, j. said connecting element is contractable to permit relative movement of said supporting body and said body of the load carrier in a direction lengthwise of the track, k. said connecting element comprises two members relatively slidable in the fore and aft direction, l. one of said members is articulated to the supporting body, m. the other of said members is articulated to said body of the load carrier, and n. resilient damping means for damping said relative movement is interposed between said supporting body and said body of the load carrier, o. said resilient damping means comprises a helically coiled spring whereof opposite end portions are connected with respective ones of said members, whereby when a following load carrier carrying a load comes into proximity with a preceding, stationary, load carrier, a substantial part of the momentum of the load is absorbed by said damping means.

5. In a conveyor system comprising: a. an endless power-driven conveyor element having a plurality of driving dogs spaced from one another lengthwise of the conveyor element, b. a load-supporting track which extends parallel to the path of travel of said conveyor element, c. a plurality of load carriers which run on said track and each of which has drive transmitting means for releasable engagement with a driving dog of the conveyor element to transmit drive therefrom to the load carrier, d. each load carrier comprises a pair of load-supporting trolleys connected together in spaced relation in a direction lengthwise of the track, and a pair of drive control element-supporting trolleys spaced one forwardly of and one rearwardly of the pair of load-supporting trolleys, e. first and second drive control elements are mounted on respective ones of said drive control element-supporting trolleys, f. each load carrier further comprises a connecting element articulately connecting said first drive control element-supporting trolley to the adjacent load-supporting trolley and a further connecting element articulately connecting said second drive control element-supporting trolley to the adjacent load-supporting trolley, the improvement wherein: g. said drive transmitting means is mounted on said first drive control element-supporting trolley, h. said connecting element is of fixed length, whereby the distance between said first drive control element-supporting trolley and the adjacent load-supporting trolley is constant, and i. said further connecting element includes two tubes slidable one within the other telescopically and a coiled compression spring acting between the two tubes for biasing the tubes to a predetermined relative position.