GB1274574A - Drawbar assembly - Google Patents

Abstract

1,274,574. Drawbar. DEERE & CO. 27 Aug., 1970 [29 Aug., 1969], No. 41307/70. Heading A1P. A drawbar assembly 12 for attaching a single-axle semi-trailer to a tractor enables the draw-hook 62 to be equally visible to the driver in its raised and lowered positions since the lower position of the hook is rearward of the upper position. The assembly comprises a draw bar 42, having the draw-hook 62 at one end, which is pivoted on an axle 50 which also carries links 52, 54. The forward end of the draw bar is pivoted on an axle 60 which also carries the rods 34, 36 of rams 22, 24 which operate the draw bar. The rams are double-acting, interconnected and operated by valve 74. The locking pin 90 may be operated hydraulically (Fig. 5). A line 98, leading from port 80 of ram 24, connects with a chamber to the left of the head 92 of the pin 90. The left chamber is connected to the right by channels 102, 104, cross-flow being hindered by a sprung check-ball 106. When raising the draw bar the pressure in line 98 is not normally sufficient to overcome spring 108 but when the draw bar hook 62 contacts the stop 66 the pressure increases so that the chcek ball is displaced and the pin 90 moves to the right, due to the difference in areas of the two faces of head 92. To disengage the pin, line 98 is exhausted so that ball 106 is seated and ball 114 is displaced. The pin may be actuated instead by a manually operated mechanical linkage, by pneumatic means or by electromagnetic means. The arrangement of the draw bar is such that the pulling forces of the tractor are cushioned in the rams; opening.88 is elongate to give the pin 90 lost motion for this reason.