[0001] The present invention refers to an hydraulic force-multiplying actuator.
[0002] Different types of actuators are known in the art, both of the electromechanical
and of the hydraulic types. These latter ones have recently provided a better solution
from the point of view of increasing the force with variable multiplication ratios
upon their dimensioning. An example of a known actuator allows obtaining multiplication
ratios that vary from at least two up to a maximum of five times the recirculating
screw reaction. It is thereby possible to use screws into a constructive range of
standard sizes and loads and parking and operating brakes that are sized even only
for 1/5 of the maximum provided force. This type of electro-hydro-mechanical force-intensifying
actuator has the further advantage of being of a construction shape that is not unlike
the shape of an hydraulic cylinder and it is able to replace this latter one without
excessive modifications in the existing machine structures.
[0003] However, the above-described actuator has two substantial types of problems: first
of all, it is equipped with an actuating spring, which does not show a constant reaction
pressure, but rather a pressure accumulation and therefore does not perform a constant-force
stroke, and after a time tends to lose its own functionalities: moreover, its replacement,
in case of need, forces the whole actuator to be disassembled, with obvious problems
of times and costs. Secondly, such actuator allows realising multiplication ratios
that are not greater than five, which are of a limited application in the field of
existing machines.
[0004] Object of the present invention is solving the above prior-art problems, by providing
an hydraulic force-multiplying actuator that is not equipped with a spring but with
an air piston, that provides a constant reaction pressure and performs a constant
stroke; such arrangement with an adjustable pneumatic piston further allows doing
without the oleodynamic unit that was one of the limits of the previous actuator.
[0005] A further object of the present invention is providing an actuator of the above-mentioned
type that allows obtaining multiplication ratios that are up to 25, that are much
more suitable for nowadays applications on machines.
[0006] The above and other objects and advantages of the invention, as will appear from
the following description, are obtained by an hydraulic actuator as claimed in Claim
1. Preferred embodiments and non-trivial variations of the present invention are claimed
in the dependent Claims.
[0007] The present invention will be better described by some preferred embodiments thereof,
given as a non-limiting example, with reference to the enclosed drawings, in which
the single Figure 1 thereof shows a side cross-sectional view of the currently-preferred
embodiment of the multiplying actuator of the present invention. As shown in Fig.
1, the hydraulic actuator of the present invention substantially comprises, as its
major feature, adjustable pneumatic reaction means 60 that are composed of a compressed-air
piston supplied through a duct 52 and that operates on the actuator body in order
to exert a constant reaction pressure and to perform a constant-force stroke. Such
pneumatic piston 60 replaces the spring that was commonly used in known actuators
of this type.
[0008] The actuator of the invention is further equipped with a shoulder 50 in the working
area, such shoulder 50 allowing the operating oil (supplied through the duct 54) to
operate in a gradual increase in the working area in order to speed-up and improve
the actuator operability.
[0009] Moreover, the actuator of the invention can be equipped, differently from known actuators,
with at least one element 11 that is adapted to prevent the pad of the reaction means
60 from rotating: in practice, such elements 11 are two and are composed of rotation-preventing
studs.
[0010] As shown in detail in Fig. 1, the actuator then comprises, in a known way, normal
component parts that are, in detail, the following ones: a pad 1, a stem 2, an head
3, a liner 4, a liner flange 5, a pad support 6, a stem flange 7, a multiplying flange
8, a pneumatic liner 9, a pneumatic head 10, a spindle 12, a spacer 13, an internal
spacer 14, a lower spacer 15, a bearing capsule 16, a recirculation screw 18, a screw
spacer 19, a padded flange 20, a driven pulley 21, a "n-pur" 22, a "nipsl 310" 23,
a 4312 O-ring 24, a "pt1" 25, a "t 20" 26, an "oms - mr" 27, a guiding band 31, an
"omk-e" 32, a guiding band 33, an "omk-e" 34, a "pt1" 35, a "pu6" 36, a ring nut 37,
a corteco 38, a slanted bearing 39, a scroll 40, a tongue 41, a greaser 42, a slanted
bearing 43, a front ring nut 44, a 4762 TCEI - ISO screw 45, pitted bushes 47, screws
48 and a plug 49.
[0011] The actuator of the invention finds its most efficient application in the field of
pressings, and in particular in the field of material forming and cutting, without
having to use screws and toggles and allowing to perform both workings in a single
operation.
1. Hydraulic force-multiplying actuator, characterised in that it comprises adjustable pneumatic reaction means (60) adapted to exert a constant
reaction pressure and to perform a constant-force stroke, said reaction means (60)
being supplied by compressed-air supplying ducts (52).
2. Actuator according to Claim 1, characterised in that it is further equipped with a shoulder (50) in its working area, said shoulder (50)
allowing the operating oil to operate with a gradual increase in the working area.
3. Actuator according to Claim 1 or 2, characterised in that it is further equipped with at least one element (11) adapted to prevent the pad
of the reaction means (60) from rotating.
4. Actuator according to Claim 3, characterised in that said elements (11) are two and are composed of rotation-preventing studs.
