Flow Sense Sequencing
FLOW SENSE SEQUENCING:
Sequencing of hydraulic cylinders is traditionally done with pressure activated sequence valves. While in most instances this system works well there are a few limitations. It is not possible to use full pressure during cylinder movements or the sequence valves will "fire" early. Like wise if the equipment being sequenced is being moved around at the same time it is possible to get spurious pressure peaks that will also cause premature firing. A typical problem and solution is outlined below.
When ploughing the plough needs to
be turned over each time the tractor reaches
the end of the field. To make full use
of the timed control valve the turning
has to be controlled with one actuation
of the spool valve. Large ploughs can
weigh in excess of 2 tonnes making it
necessary to fold the plough before turning
to reduce the inertia.
To sequence a Turnover plough through
four Cylinder movements with one movement
of the spool valve.
Traditional sequencing using pressure
triggered sequence valves proved unreliable
as unexpected pressure peaks were experienced
due to uneven and sloping fields, (the
turnover takes place while the tractor
is turning round) and the erratic build
up of heavy soils on the plough bodies.
The Pressure system also requires 3 progressive
HAC developed with Dowdeswell Engineering
a valve that sequences by monitoring the
oil flows to and from the cylinders. When
each cylinder stops moving the next cylinder
movement is triggered. The Flow Sense
system has the advantage that full pressure
is available for each cylinder movement.
Call HAC to solve your next sequenced application.
Hydraulic Actuators & Controls (HAC),
10 Doman Road, York Town Industria Estate,
Tel: +44 (0)1276 670063
Fax: +44 (0)1276 27180
Check Valves - Relief Valves - Over Centre Valves - Combination
Valves - Motor Valves - Shuttle Valves
Berkshire - Hampshire - Surrey - Sussex - London - Middlesex
- Thames Valley - South