Fluid-pressure and analogous brake systems – Automatic – Synchronizing
Patent
1981-07-08
1985-08-20
Reger, Duane A.
Fluid-pressure and analogous brake systems
Automatic
Synchronizing
303 82, B60T 1542
Patent
active
045360405
DESCRIPTION:
BRIEF SUMMARY
The invention refers to a service brake accelerator for indirect compressed-air brakes on railway vehicles, having pressure in the reference pressure chamber; predominant action by the pressure in the reference pressure chamber, and which is in a connection from the main airpipe to a piston chamber acted upon by an auxiliary pressure; case of predominant action by the pressure in the reference pressure chamber, and is in throttled connections from the main airpipe and from the piston chamber to atmosphere; and throttled via a further nozzle, from the reference pressure chamber to the atmosphere, where: by the force of a spring and the pressure in the piston chamber against the pressure in the reference pressure chamber, which with the air vent valve closed acts only upon a partial area; and where: arranged coaxially and the shutoff valve and the outlet valve system can be actuated by means of a valve stem connected to the control piston.
A service brake accelerator of that kind has become known from the South African Patent Application No. 77/6412. In the case of this service brake accelerator the outlet valve system from the main airpipe and from the piston chamber to atmosphere is combined into a single valve which in the case of predominant action upon the control piston by the pressure in the reference pressure chamber becomes opened in advance of the closing of the shutoff valve; hence the outlet valve system and the shutoff valve are opened simultaneously in a certain phase of operation of the known service brake accelerator. The valve piston is arranged at the side next to the control piston, whereby a structurally elaborate construction results. This known service brake accelerator is burdened with the defects that under certain conditions, for example, in the case of the pressure dropping slowly in the main airpipe as may be caused in the case of long trains and a large volume of air which has to be vented through the service brake accelerator from the main airpipe, the control piston gets stuck in its position with the outlet valve system already opened and the shutoff valve still open, and thus does not move further as far as closing of the shutoff valve. Thus it is not ensured that the service brake accelerator enters into the service function provided for it with pulsating tapping of air from the main airpipe to atmosphere, and hence there is uncertainty about the way of operation and the amount of compressed air tapped from the main airpipe in the case of the known service brake accelerator. Moreover, in the case of the known service brake accelerator it is not excluded that the further nozzle in the connection from the reference pressure chamber to atmosphere partially clogs, and thus upon opening the air vent valve a lowering of the pressure in the reference pressure chamber results which is too slow. In the known service brake accelerator, in the case of a disturbance of that kind from a trifling cause the control piston holds the shutoff valve which is inserted into the connection from the main airpipe to the outlet valve system, constantly closed so that the service brake accelerator cannot tap any air from the main airpipe and cannot exert any accelerating action to assist the drop in pressure in the main airpipe.
From the U.S. Pat. No. 3,988,044 a service brake accelerator of another construction has become known, in which by a mechanical dead stroke system between a control piston and a control rod which exhibits an auxiliary piston, a sequence of actuation of the individual valves is provided of such a kind that the defects described above cannot arise. But the dead stroke system of this service brake accelerator is costly and prone to wear and is only fully capable of operation in cooperation with certain frictions against the valve rod. But since the coefficients of friction can change in the course of service there is no guarantee of an always regular operation of this service brake accelerator.
The object of the present invention is to provide a service brake accelerator of the k
REFERENCES:
patent: 3988044 (1976-10-01), Hill
patent: 4145090 (1979-03-01), Hart
patent: 4175792 (1979-11-01), Hart
Knorr-Bremse GmbH
Reger Duane A.
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