B42.25-0002-06
Framework
3 Discharge (exhaust)
11 Supply connection
21 Braking pressure (35.02)
22 Braking pressure (35.03)
41/42 Control mechanism drive pressures (13.02)
43 Control mechanism drive pressure (14.12)
a Piston
b Intake valve
d Orifice
and Discharge valve
h Orifice
i Spring
k Piston
m Spring
B42.25-0003-01
Operation:
I - Loading position
Without pressure, the control piston (a) is kept on the lower position due to the spring force action (i). During the filling of the air reservoir, the compressed air that gets to the port 11 of the 2/2 way valve, pressurizes the chamber (A) lifting the control piston (a) up against the spring force (i).
The compressed air coming from the port 11 flows from orifice (d) to the chamber (B) pressurizing the port 21 and consequently the trailer supply coupling head (35.02).
The same way, the compressed air in chamber (B), lifts the piston (k) up, opening the intake valve (b) and closing the discharge (e).
The chamber pressure (B) flows to chamber (C) pressurizing port 22 and, consequently, the signal coupling head to the trailer (35.03).
B42.25-0004-01
II - Running position (brake released)
With the vehicle moving, the chamber (D) referring to port 43 is pressurized due to the parking brake valve activation.
Chamber (D), when pressurized, pushes the control piston (k) down, closing the intake valve (b) and opening the discharge (e).
This way, the trailer brake is released due to the depressurization of port 22.
B42.25-0005-01
III - Service brake position applied:
With the action of the service brake (double circuit), the ports 41 and 42 are pressurized and, when the trailer brake valve is activated, only port 41 is pressurized.
When ports 41 and 42 are pressurized by the service brake, the pressure on chamber (E) or (G) pushes the control piston (l) down, closing the discharge (e) and opening the intake valve (b).
This way, the pressure in chamber (B), flows to chamber (C) below the piston (l) pressurizing port 22 that, in turn, is connected to the signal coupling head (35.03) to the trailer.
B42.25-0006-01
IV - Balance position:
A balance position happens when the pressures on chambers (C) and (E) or (G), reach a force balance. On this condition, the piston (l) moves up until the intake valve (e) closes. The pressure on chamber (C) remains constant in port 22.
Simultaneously, the compressed air on chambers (B) and (C) keeps the 2/2 way valve with no effect.
B42.25-0007-01
V - Exhaustion position (discharge):
On the discharge position, the compressed air in ports 41 and 42 is unloaded to the atmosphere. This way, the pressure in chamber (C) lifts the piston (l) up so that the inlet valve (b) closes and the discharge valve (e) opens. The compressed air in the trailer brake pipeline and in chamber (C) is unloaded to the atmosphere, through discharge (3).
B42.25-0008-01
VI - Operation of the 2/2 way valve with breakage of the trailer brake pipeline:
In case of breakage in the trailer brake pipeline (port 22), the pressure in chamber (C) decreases.
This way, when the service brake port 41 is applied, the chamber pressure (E) flows to chamber (P) moving the control piston (a) down against the spring force (m), restricting the passage orifice (h).
This restriction causes a quicker pressure drop in the “trailer supply pipeline” port 21, which is fed by port 11. Through this process, the trailer is immediately braked. After service release, the 2/2 way valve commutes again.