GB1217540A - Improvements in or relating to hydrodynamic retarder systems for vehicles - Google Patents

Abstract

1,217,540. Hydrodynamic brakes. ALFRED TEVES G.m.b.H. 31 Oct., 1968 [13 Feb., 1968], No. 51602/68. Heading F2E. In a hydrodynamic retarder system for vehicles having a retarder casing enclosing a rotor driven by the vehicle wheels and a stator and supply and discharge lines for the liquid in it, a heat exchanger disposed in parallel with the retarder, a charging cylinder which is operated under control from a compressed air source, and an air line between the retarder and the charging cylinder, the air line contains a pilot valve which is closed when a pressure is applied to the charging cylinder, but can be opened by a predetermined differential pressure between the retarder and the charging cylinder, to equalize the pressure between the two last-mentioned members. As shown, a retarder 22, Fig. 1, may be filled with liquid by admission of compressed air to a charging cylinder 21 from a compressed air source 26 via a hand brake control valve 24 and rapid release valve 23. Between valve 24 and cylinder 21 a branch 32 extends to the control inlet 11 of a pilot valve 20, Fig. 2, disposed in a connecting air line 25 between the retarder 22 and charging cylinder 21. During idling, a valve tappet 33, Fig. 2, is forced open, to the position shown, against the force of a relatively-weak spring 27, by a piston 12 loaded by a relatively-strong spring 15. The air spaces of the retarder 22 and cylinder 21 thus communicate through the pilot-valve inlet 17 and outlet 18. During braking, liquid is forced through line 31 into the retarder in known manner. The pressure existing at this time in the main air line is communicated via branch 32 to the control inlet 11 of valve 20, thereby raising piston 12 against its spring 15 and permitting spring 27 to seat the tappet 33, thereby cutting off communication between connections 17 and 18. However, during filling, air escapes from above the liquid in the retarder through the connection 19 and along line 25. If the pressure is sufficient to overcome spring 27, poppet valve 33 is unseated, and the air passes to the charging cylinder 21, thus equalizing the pressures in the retarder and charging cylinder. Also, if the air pressure in the retarder should increase unduly as a result, e.g., of a rise in temperature therein, the poppet valve 33 may again be unseated, thus equalizing the pressure. Whilst pressure is being exerted at control inlet 11, thus removing the effect of piston 12 on poppet valve 33, the excess air pressure needed to open poppet valve 33 is determined by the strength of its spring 27. The operating liquid rises in the retarder until it is above the connection 19: no more air can then escape at 19, so the poppet valve closes. The air still in the retarder casing is compressed by the rising liquid. The height h, Fig. 1, of the connection 19 above the bottom of the casing may be varied by making the retarder casing pivotable around its axis 28. The retarder 22 is connected in parallel with a heat exchanger 29 cooled via lines 30 branching off from the vehicle cooling system.