Description - Rohm OVUSHH Instrucciones De Servicio

2. Hydraulic Double-Piston Cylinders Type OVUSHH,
OVUSSHH, OVUSSH, OVUSHHD
with independent piston movement, safety device and lifting control
Designations:
These cylinder types consist of two hydraulic cylinders
located beside each other, the force and movement of
which are transmitted independently of each other onto
the clamping device to be operated (chuck etc.), by
means of two draw elements (so-called draw tube or
draw bar) that are fixed with threads on one side of the
piston rod. This means that apart from the clamping
movement a further operation as for example of an
alignment jaw or a movable center, etc. is required.
Opposite of the cylinder, facing away from the spindle, a
multiple oil distributor with stationary maintenance-free
distributor housing is located. This distributor comprises
at least 4 connections for the operation of both cylinder
pistons. Each of such connections can be submitted to
an oil pressure within a range from 5 bars to a maxi-
mum of 50 bars, even under load.
The cylinders of the "OVU..." series may also be oper-
ated during rotation, as the safety valves are arranged
in such a way that they are not subject to centrifugal
force.
The type designation of "OVU..." describes an oil-oper-
ated cylinder with independent piston movement.
Safety devices:
The safety device prevents unintentional releasing of
the clamping means in case the pressure supply fails.
For this reason, both connections (hydraulic chambers)
of the relevant single cylinder are protected by means
of a hydraulic pilot controlled check valve. The control is
effected via the pressure of the opposite piston side and
ensures the exit of the pressureless oil.
Such cylinder thus corresponds to the test
principles of the employer's liability insurance
association.
The type designation "...S" or "...SS" indicates the num-
ber of safety devices available in the relevant double-
piston cylinder.
Example:
"OVUSHHD 120/80" --> safety device for one pistion
(= 2 hydraulic chambers, generally for the larger cylin-
der generating the main clamping force)
"OVUSSHH 140/80" --> safety device for both pistons
(= 4 hydraulic chambers).
Stroke control systems:
The movement of both pistons may be checked by
means of stroke control disks and inductive proximity
switches, via control cams or individual limit switches or
via stepless position sensoring systems like analog
position sensors, linear potentiometers, angular position
sensors or laser tracers.
The switches and sensors required for this must be
matched to the machine's control electronics and are
thus not delivered with the cylinder.
However, attention must be paid to the fact that the
costs for retrofitting the double-piston cylinder to a
different piston are rather high -- if such retrofit is
possible at all.
The type designation "...H" or "...HH" indicates the
number of the lift supervisions available in the relevant
double-piston cylinder. They do not indicate the quality
of the testing method.
Example:
"OVUSHHD 120/80" --> lift supervision for both pistons
"OVUSH 140/80" --> lift supervision for one piston
(usually for the larger piston generating the main
clamping force).
Additional rotation unions:
Basically, all double-piston cylinders are available with
an additional rotation union. They offer the possibility to
feed another medium (e.g. air, coolant, oil) up to a pres-
sure of 70 bars. For this purpose, an additional rotation
union is installed at the end of the piston rod, near the
4-way oil distributor. Attention must be paid to the fact
that the distributor housing of the feeding unit must also
be secured with an anti-twist device which moves
alongside the whole stroke of the smaller piston 2.
The type designation "...D" indicates if a further rotation
union device is installed.
Example:
"OVUSHHD 120/80" --> with additional rotation union
"OVUSHH 140/80" --> without additional rotation union
Piston diameter:
The two digits at the end of the type designation
(OVU...) indicate the outer diameter of the two piston
disks in mm. Piston 1 showing towards the spindle and
connected with the chuck via the draw tube is indicated
first, while piston 2 which faces away from the spindle
and is connected to the chuck via the draw bar is indi-
cated last.
Example:
"OVUSHHD 120/80" --> Diameter of piston 1: 120 mm,
diameter of piston 2: 80 mm
"OVUSHHD 140/80" --> Diameter of piston 1: 140 mm,
diameter of piston 2: 80 mm
Piston strokes:
The strokes of the two pistons in mm may be indicated,
too. As with the diameters, piston 1 is indicated first
(with draw tube), piston 2 follows (with draw bar).
Example:
"OVUSHHD 120/80 stroke 32/32" --> the stroke of both
(the larger) piston 1 and of (the smaller) piston 2 is 32
mm each.
"OVUSHHD 140/80 stroke 25/31" --> the stroke of pis-
ton 1 is 25 mm, that of piston 2 31 mm.
Oil distributor:
The distributor of the cylinder ensures a constant oil
flow. Maximum speed and pressure admissible for the
cylinder may come up at the same time. In this case,
the operating time is 100%.
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