Bendix SV-1 SYNCHRO-SV-3 TRAILER RELEASE User Manual

®				SD-034020-
Bendix® SV-1™ Synchro Valve SV-3™ & SV-4™ Trailer Release Valve
	CONTROL		CONTROL
			EXHAUST
EXHAUST
	DELIVERY		DELIVERY
SUPPLY		SV-3™		SV-4™
1/4" P.T.		VALVE	SUPPLY	VALVE
			1/4" P.T.
CONTROL
			CONTROL
CAP NUT
		CAP NUT		O-RING
	O-RING
	O-RING	PISTON		O-RING
PISTON		PISTON SPRING
				O-RING
O-RING	PISTON			BODY
	SPRING	1/8" P.T.
1/8" P.T.
		EXHAUST		1/4" P.T.
EXHAUST	1/4" P.T.
				DELIVERY
	DELIVERY
BODY		SPRING
	VALVE			VALVE
		GUIDE
	SPRING
				VALVE
VALVE	O-RING	O-RING
				SPRING
SPRING	CAP NUT
				CAP NUT
GUIDE
1/4" P.T.			1/4" P.T.	DETAIL OF SV-3™
SUPPLY
			SUPPLY	VALVE
FIGURE 1 - SV-1™ SYNCHRO VALVE			CHECK VALVE
DESCRIPTION

	The SV-1™ synchro valve and the SV-3™ trailer release valve	DETAIL OF SV-4™
	are pilot operated, non-graduating pneumatic control valves.	VALVE
	These valves are used to control air from a remote supply,
		FIGURE 2 - SV-3™ & SV-4™ TRAILER RELEASE VALVE
	have set opening and closing pressures and can be used to
	delay or sequence the action of other pneumatic devices.	sequence various devices and events in the air brake system.
	GENERAL	These valves can be operated either in an automatic or
		manual mode using different air connection methods.
	The SV-1™ synchro valve (figure 1) and SV-3™ & SV-4™ trailer	Two .28 inch mounting holes are provided in the die cast
	release valves (figure 2) are air controlled, “On-Off” (non-	aluminum body for panel or frame mounting. Two hex cap
	graduating) control valves that are primarily used to delay or	nuts at the ends of the cylindrical valve body retain the internal

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components. The air connection ports for SV-1™, SV-3™ & SV-4™ valves are the same and are located in relatively the same position on each model.All connections are pipe thread. Lettering embossed in the valve body identifies two of the four connection ports in these valves. Refer to the chart below and figure one.

Air Connection	Body Ident.	Thread Size
Air Supply	SUP	1/4" PT
Delivery	DEL	1/4" PT
Control	None	1/4" PT
Exhaust	None	1/8" PT

IMPORTANT: An exhaust check valve should be installed in the threaded exhaust port of these valves when they are mounted outside the cab in unprotected environments.

SV-1™ Synchro Valve

1/8" PIPE THREAD

1/8" PIPE THREAD

Note: Either style may be installed in the

SV-1™, SV-3™ or SV-4™ valves

FIGURE 3 - EXHAUST CHECK VALVE STYLES

The SV-1™ valve is a general purpose valve used in a variety of applications on trucks, buses, tractors, trailers and converter dollies. The SV-1™ valve is the base valve from which both the SV-3™ and SV-4™ valves are derived. It is offered in a variety of pressure settings to accommodate applications where automatic operation is required. It is easily distinguished from the SV-3™ and SV-4™ valve by its smaller size.

SV-3™ Trailer Release Valve

While originally designed for automatic operation to accomplish brake release on trailers without spring brakes, the SV-3™ valve can be used in any installation where its single automatic pressure setting is advantageous. The SV-3™ valve is very similar in appearance to the SV-4™ valve but can be distinguished by measuring the length and diameter of the supply hex cap nut (1/4" PT supply port). See the comparison chart for the dimensions.

SV-4™ Trailer Release Valve

The SV-4™ valve was designed primarily for use on trailer converter dollies to minimize the possibility of false charging. Like the SV-3™ valve it can be used in other applications. The SV-4™ valve is the combination of two valves; an SV-3™ valve and a single check valve. A typical installation is illustrated in figure 4. The SV-4™ valve can be distinguished from the SV-3™ valve using the dimensions given in the comparison chart. In addition, the tip of the check valve contained in the SV-4™ valve is visible at the bottom of the ¼" PT supply port.

SV-3™/SV-4™ Valve Comparison

Supply Cap Nut Dimensions

Diameter Length

SV-3 .8125" 1.162"

SV-4 .94" 1.062"

OPERATION

GENERAL

The SV-1™, SV-3™, & SV-4™ valves all operate in a similar fashion. All can be connected in the air system so that other valves control them. When connected in this non-automatic mode the valve serves as a remote mounted, On-Off control. They can also be installed so that they function automatically or self actuate at a preset pressure. Automatic operation is the most common application. Regardless of how they are connected the internal valve operation is the same.

NON-AUTOMATIC (valve controlled remotely by another valve)

With no air pressure present at the control port, supply port air pressure and the inlet/exhaust valve spring hold the inlet valve on its seat in the body. The piston is held away from the inlet/exhaust valve by the piston spring, and the delivery line is vented to atmosphere through the hollow exhaust stem of the piston.

When sufficient air pressure is applied to the control port, the control piston moves against the resistance of its return spring. As the control piston moves, it contacts the exhaust valve portion of the inlet and exhaust valve which seals the hollow exhaust passage in the piston stem. Continued piston movement drives the inlet valve from its seat and allows supply air to flow through the body and out the delivery port.

When air pressure is removed from the control port, the piston return spring and delivery port air pressure move the piston away from the inlet/exhaust valve.As the piston moves, the inlet valve re-seats itself preventing air flow to the delivery port. Continued movement unseats the hollow exhaust passage in the piston stem allowing delivery air to flow through the stem and out the exhaust check valve.

SINGLE CHECK VALVE

SV-1™

SYNCHRO

Note: An SV-4™ valve can be used in place of the SV-1™ valve and single check valve shown here.

FIGURE 4 - TRAILER CONVERTER DOLLY

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