[0001] This invention relates to a fluid-operated cylinder-piston unit having at least a
first operating chamber for alternate connection to a pressurized fluid feed and to
a discharge. A typical but not exclusive application is to a cylinder-piston unit
also having a second operating chamber opposing the first (double-acting).
[0002] As is well known, to operate fluid-operated cylinder-piston units a circuit has to
be provided connecting its operating chambers to a fluid feed and discharge and to
a distributor valve which, on command, connects one chamber to the feed while simultaneously
connecting the other chamber to discharge, and vice versa, depending on how the cylinder-piston
unit is required to operate.
[0003] All this requires not only plant elements and distributor valves of possibly high
cost, but also considerable personnel times for making said connections and installing
the plant. Moreover, if the cylinder-piston unit is some distance from the distributor
valve, long connection pipes are required, making the plant complicated.
[0004] An object of this invention is to provide a cylinder-piston unit which overcomes
said drawbacks.
[0005] This and further objects are attained by the invention as characterised in the claims.
[0006] The invention is characterised by comprising:
a pressurized fluid inlet to be connected to the feed, and provided within the body
of the headpiece to which the cylindrical wall laterally bounding the operating chamber
is connected;
a fluid outlet provided within the body of the headpiece;
at least a first conduit provided within the body of the headpiece and communicating
with an operating chamber of the cylinder-piston unit;
within the body of the headpiece, between the inlet and the conduit, a first passage
having in a lateral face of the body of the headpiece two spaced-apart ports, one
communicating with the inlet and the other with the conduit;
within the body of the headpiece, between the outlet and the conduit, a second passage
having in a lateral face of the body of the headpiece two spaced-apart ports, one
communicating with the outlet and the other with the conduit;
in each of said passages there being provided, covering said communication ports,
a lateral chamber formed in a cover positioned on the lateral face of the body of
the headpiece, and a free flexible membrane separating said ports from the lateral
chamber and being of such an area as to cover said communication ports, it being arranged
to assume a first position in which it adheres to the edge of the ports and a second
position in which it is raised from the edge of the ports;
thin pilot channels provided partly within the body of the headpiece and partly in
the cover, to feed into the lateral chamber a pilot fluid having a pressure such as
to urge the membrane into the first position and to press on it with a thrust sufficient
to prevent passage of fluid through the ports, against the thrust of the fluid present
in the ports;
a pilot valve means communicating with the fluid feed to distribute, when commanded,
pressurized pilot fluid to the lateral chambers via said pilot channels, to open the
first passage and close the second and vice versa.
[0007] The invention is described in detail hereinafter with the aid of the accompanying
figures which illustrate by way of non-exclusive example one embodiment thereof relative
to a double-acting cylinder-piston unit.
[0008] Figure 1 is a side view of the entire cylinder-piston unit.
[0009] Figure 2 is a section on the plane II-II of Figure 1.
[0010] Figure 3 is an enlarged detail of Figure 1 relating to the headpiece.
[0011] Figure 3A shows the detail of Figure 3 but without the cover which covers the visible
lateral face.
[0012] Figure 4 is a view of the other lateral face of the headpiece.
[0013] Figure 5 shows the detail of Figure 4 but without the cover which covers the visible
lateral face.
[0014] Figure 5 is a section on the central vertical plane V-V of Figure 6.
[0015] Figure 6b is a section on the plane VI-VI of Figure 5.
[0016] Figure 6A is an enlarged detail of Figure 6.
[0017] Figure 7 is a section on the plane VII-VII of Figure 3.
[0018] Figure 8 is a section on the plane VIII-VIII of Figure 5.
[0019] Figure 9 is a partial section on the series of planes IX-IX of Figure 3.
[0020] Figure 10 is a plan view from below of the headpiece shown without the pilot valve
40.
[0021] The cylinder-piston unit shown in the figures comprises a cylindrical wall 10 and
a piston 13 slidable in sealed contact with the inner surface of the wall 10, to move
an axial rod 14. The two ends of the wall 10 are closed, at the rear by a headpiece
20 and at the front by a front closure element (endpiece) 15, through which the rod
14 sealedly passes. The cylindrical wall 10 laterally bounds two opposing operating
chambers 11 and 12, separated from each other by the piston 13. When one of these
chambers expands the other contracts with the piston moving in a certain direction,
and vice versa.
[0022] The cylindrical wall 10 is joined to the headpiece 10 and to the endpiece 15 by screws
inserted in the direction of the axis of the cylinder-piston unit through holes 253
provided through the headpiece 20 and through holes (not shown) provided through the
endpiece 15. These screws engage corresponding threaded holes 101 provided at both
ends of the wall 10, in longitudinal protuberances 16 integral with the wall 10 and
projecting radially from it.
[0023] The headpiece 20 comprises a body 25, of substantially parallelepiped shape in the
figures, having a projection extending about it to define a square-perimeter flange
252 through which said holes 253 are formed.
[0024] Within the body 25 of the headpiece there are provided:
a pressurized fluid inlet 23, to be connected to the feed of the operating fluid for
the cylinder-piston unit;
an outlet 24 for connecting the fluid to discharge;
a first conduit 21 communicating with the first operating chamber 11 of the cylinder-piston
unit, and a second conduit 22 communicating with the second operating chamber 12 of
the cylinder-piston unit.
[0025] The first conduit 21 and the second conduit 22 consist of dead holes which open into
the front face of the headpiece body 25, they being positioned with their axes longitudinal
and mutually superposed, and lying in the longitudinal vertical plane of symmetry.
The inlet 23 comprises a cavity 231 of longitudinal axis, closed at both ends and
positioned below said conduits 21 and 22. The cavity 231 lies with its axis in the
vertical plane of symmetry, and communicates with the outside via an inclined lower
conduit 232 which opens into the lower face 25' of the body 25.
[0026] In one side of the body 25, namely the right side, there is provided a first passage
A between the inlet 23 and the first conduit 21 provided in the body 25. This passage
A has two spaced-apart ports 31a and 32a situated in the same right side face 26d
of the body 25. The port 31a communicates with the inlet 23 via a short horizontal
transverse channel 33a, the other port 32a communicating with the first conduit 21
via a short horizontal transverse channel 34a.
[0027] In the embodiment shown in the figures, each of said short channels 33a and 34a (and
the analogous channels 33b, 33c, 33d, 34b, 34c, 34d described below) is composed of
a pair of short channels, with their cross-section in the form of an elongate thin
slot, separated by a thin wall. Likewise, each of the ports 31a and 32a (and the analogous
ports 31b, 31c, 31d, 32b, 32c, 32d described below) is composed of two elongate narrow
ports separated by a thin strip. For greater ease of description, each said pair of
channels 33, 34 and ports 31, 32 is indicated herein as a single channel or single
port.
[0028] In the same side of the headpiece body 25, ie in its right side, there is also provided
a second passage B between the outlet 24 and the first conduit 21 provided within
the body 25. This passage B has two spaced-apart ports 31b and 32b situated in the
same right side face 26d of the body 25. The port 31b communicates with the first
conduit 21 via a short horizontal transverse channel 33b, the other port 32b communicating
with the outlet 24 via a short horizontal transverse channel 34b.
[0029] In the other side of the headpiece body 25, ie in its left side, there is provided
a third passage C between the inlet 23 and the second conduit 22 provided within the
body 25. This passage C has two spaced-apart ports 31c and 32c situated in the same
left side face 26s of the body 25. The port 31c communicates with the inlet 23 via
a short horizontal transverse channel 33c, the other port 32c communicating with the
second conduit 22 via a short horizontal transverse channel 34c.
[0030] In the same left side of the headpiece body 25, there is also provided a fourth passage
D between the outlet 24 and the second conduit 22 provided within the body 25. This
passage D has two spaced-apart ports 31d and 32d situated in the same left side face
26s of the body 25. The port 31d communicates with the second conduit 22 via a short
horizontal transverse channel 33d, the other port 32d communicating with the outlet
24 via a short horizontal transverse channel 34d.
[0031] In each of said passages A, B, C, D there is provided a respective lateral chamber
35a, 35b, 35c, 35d (hereinafter indicated generically by 35) which covers the communication
ports 31a, 31b, 31c, 31d and 32a, 32b, 32c, 32d (hereinafter indicated generically
by 31 and 32 respectively).
[0032] The lateral chamber 35 is provided in a cover positioned on the lateral face of the
headpiece body. Specifically, the chamber 35a of the first passage A and the chamber
35b of the second passage B are defined by respective recesses provided in the flat
inner surface of one and the same cover 27d, which is adheringly fixed to the right
face 26d of the body 25 to cover virtually the whole of this face. Likewise, the chamber
35c of the third passage C and the chamber 35d of the fourth passage D are defined
by respective recesses provided in the flat inner surface of another cover 27s, which
is adheringly fixed to the left face 26s to cover virtually the whole of this face.
[0033] In each of the passages A, B, C, D there is provided a fluid passage opening and
closure valve, comprising a free flexible membrane 36a, 36b, 36c, 36d respectively,
which separates the ports 31 and 32 of the lateral chamber 35. The membrane 36 has
an area such as to cover said ports 31 and 32, and is arranged to assume a first position
in which it lies adhering to the edge of the ports and a second position in which
it is raised from the edge of the ports.
[0034] The membrane 36a of the first passage A and the membrane 36b of the second passage
B are formed from a single thin, flexible, deformable sheet 37d, which is pressed
by the cover 27d against the face 26d, and has an area equal to that of the cover.
The sheet 37d is free to flex and deform in correspondence with the lateral chambers
35a and 35b, to define the respective membrane 36.
[0035] Likewise, the membrane 36c of the third passage C and the membrane 36d of the fourth
passage D are formed from a single thin, flexible, deformable sheet 37s, which is
pressed by the cover 27s against the face 26s, and has an area equal to that of the
cover 27s. The sheet 37s is free to flex and deform in correspondence with the lateral
chambers 35c and 35d, to define the respective membrane 36.
[0036] In detail, the two covers 27d and 27s are fixed to the body 25 by screws (not shown
in the figures) which pass through holes 71 and 72 provided in the covers 27d and
27s and in the headpiece body 25 respectively.
[0037] Figure 6A shows by way of example one of the passages A, B, C, D (specifically the
first passage A). The two ports 31 and 32 (specifically 31a and 32a) lie in one and
the same plane represented by the lateral face 26d, in this plane there lying the
membrane 36 (36a) which covers the ports 31 and 32, separating them from the lateral
chamber 35 (35a). By way of thin pilot channels (described in detail hereinafter)
provided partly within the headpiece body and partly within the cover, a pilot fluid
can be fed into the lateral chamber 35 at a pressure able to urge the membrane 36
into its first position, ie adhering to the edge of the ports 31 and/or 32 (as shown
by dashed and dotted lines in Figure 6A and with full lines in Figures 6-9), in order
to close these ports and hence prevent passage between the ports. The pilot fluid
pressure must be such as to press on the membrane 36 with a force sufficient to prevent
the force of the fluid present in the short channels 33 and 34, and hence in the ports
31 and 32, being able to separate the membrane 36 from the ports, ie sufficient to
prevent passage through these ports. In the embodiment shown in the figures, part
of the feed fluid, withdrawn from the inlet 23, is used as the pilot fluid (as described
hereinafter). This fluid, fed without relevant pressure drop, into the lateral chamber
35 has a pressure which is amply sufficient to maintain the membrane in its first
position even against the feed pressure present in the inlet 23. In contrast, on putting
the chamber 35 to discharge, the membrane 36 does not offer substantial resistance
to fluid passage and lifts from the ports 31 and 32 (as shown by the full line in
Figure 6A) to allow fluid to pass freely from one port 31 to the other port 32.
[0038] Consequently by means of the described shape of the ports 31 and 32, the presence
of the membrane 36 and the presence of the lateral chamber 35, there is formed in
correspondence with each passage 30 a valve piloted by a pilot fluid withdrawn from
the feed to the cylinder-piston unit, to open or close the passage for the operating
fluid of the cylinder-piston unit on command.
[0039] The pilot fluid is distributed to the passages A, B, C, D by a pilot valve 40 positioned
on the inner face 26' of the body 25. The valve 40 communicates with the fluid feed,
in particular the inlet 23, and is arranged to distribute the pilot fluid to the lateral
chambers 35 via the pilot channels on command.
[0040] The valve 40 is an electrically operated distributor valve. It can be a valve of
known type or of the type illustrated in Italian Patent Application No. RE99A000032
filed on 18 March 1999 by the present applicant.
[0041] In the embodiment shown in the figures, the cylindrical wall 10 comprises a longitudinally
extending channel 222 provided within the thickness of the wall (see Figure 2) and
connected at one end to the second conduit 22, its other end opening into the second
operating chamber 12 of the cylinder-piston unit.
[0042] In contrast the first conduit 21 communicates directly with the first operating chamber
11 of the cylinder-piston unit. The conduit 21 possesses a front axial portion 21'
communicating directly with the operating chamber 11 and a second axial portion 21"
to the rear of the first, which communicates with the first via an axial passage hole
212, on which there acts a conical piece 213 coaxial to the hole 212 and positioned
at a short (but adjustable) distance therefrom. The conical piece 213 defines together
with the hole 212 a valve which reduces the pressure of the fluid in passing from
the first portion 21' to the second portion 21". The channel 34a of the first passage
A opens into the front portion 21', the channel 33d of the fourth passage D opening
into the rear portion 21".
[0043] Within the body 25 and covers 27s and 27d there is provided a system of thin channels.
through which the pilot fluid flows and which open into two ports 51' and 52' located
in the lower face 26' of the body 25, for connection to the valve 40, they being aligned
in a transverse direction.
[0044] From the first port 51' there extends a duct 51 which, by avoiding the various cavities
provided within the body 25, leads both to the lateral chamber 35a of the first passage
A, and to the lateral chamber 35d of the fourth passage D.
[0045] From the second port 52' there extends a duct 52 which, by avoiding the various cavities
provided within the body 25, leads both to the lateral chamber 35b of the second passage
B, and to the lateral chamber 35c of the third passage C.
[0046] In detail, the duct 51 comprises (see Figure 9 in particular):
a first channel 511 extending from the port 51' and penetrating vertically into the
body 25,
followed by a second channel 512 which opens in a horizontal transverse direction
into the right face 26d,
followed by a third channel 513 extending at a right angle and provided in the face
26d as an open channel, it being closed frontwards by the cover 27d,
followed by a fourth channel 514 which is provided within the thickness of the cover
27d and, after traversing an appropriate hole provided in the sheet 37d, flanks the
lateral chamber 35a to then open into the centre thereof.
[0047] The duct 51 also comprises:
a fifth channel 515 extending from the upper end of the channel 513 and passing through
the body 25 from one side to the other in a transverse horizontal direction, to open
in the opposite lateral face 26s of the body 25,
followed by a sixth channel 516 which (in a manner similar to said fourth channel
514) is provided within the thickness of the cover 27s, passes through an appropriate
hole provided in the sheet 37s, flanks the lateral chamber 35d and finally opens into
the centre thereof.
[0048] In detail, the second duct 52 comprises:
a first channel 521 extending from the port 52' and penetrating vertically into the
body 25,
followed by a second channel 522 which opens in a horizontal transverse direction
into the left face 26s,
followed by a third channel 523 provided in the face 26s as an open channel and closed
frontwards by the cover 27s, its path extending upwards towards the right,
followed by a fourth channel 524 which is provided within the thickness of the cover
27s and, after traversing an appropriate hole provided in the sheet 37s, flanks the
lateral chamber 35c of the third passage C to then open into the centre thereof.
[0049] The duct 52 also comprises:
a fifth channel 525 extending from the upper end of the channel 523 and passing through
the body 25 from one side to the other in a transverse horizontal direction, to open
in the opposite lateral face 26d of the body 25,
followed by a sixth channel 526 which in a manner similar to said fourth channel 514
is provided within the thickness of the cover 27d, passes through an appropriate hole
provided in the sheet 37d, flanks the lateral chamber 35b of the second passage B
and finally opens into the centre thereof.
[0050] The pilot valve 40 comprises a port 41 and a port 42 positioned in correspondence
respectively with the port 51' and with the port 52' provided in the lower face 26'
of the body 25. The valve 40 also comprises an inlet 43 which communicates with the
inlet 23 via a channel 53 provided within the body 25 from its lower face 26'. Finally,
the valve 40 comprises an outlet 44 which discharges to atmosphere via a channel 54
provided in the lower face 26' of the body 25.
[0051] On electrically operating the valve 40, this assumes two configurations.
[0052] In a first configuration, the first pilot duct 51 is connected to the discharge outlet
44, whereas the second duct 52 is connected to the inlet 23.
[0053] Consequently, the lateral chamber 35a of the first passage A and the lateral chamber
35d of the fourth passage D are put to discharge, the respective membranes 36 consequently
allowing free passage of the operating fluid. Simultaneously, the lateral chamber
35b of the second passage B and the lateral chamber 35c of the third passage C are
put under pressure, the respective membranes 36 consequently being pressed against
the respective ports 31 and 32 to close passage for the operating fluid.
[0054] Hence the operating fluid passes from the inlet 23 to the first conduit 21 and from
there to the first operating chamber 11 of the cylinder-piston unit. Simultaneously,
the fluid present in the second operating chamber 12 of the cylinder-piston unit is
connected to discharge 24 via the second conduit 22.
[0055] In the second configuration of the valve 40, the first pilot duct 51 is connected
to the inlet 23, whereas the second duct 52 is connected to the discharge outlet 44.
[0056] Consequently, the lateral chamber 35a of the first passage A and the lateral chamber
35d of the fourth passage D are put under pressure, the respective membranes 36 consequently
being pressed against the respective ports 31 and 32 to close the passage for the
operating fluid. Simultaneously, the lateral chamber 35b of the second passage B and
the lateral chamber 35c of the third passage C are put to discharge with the result
that the respective membranes 36 leave the passage for the operating fluid free.
[0057] It follows that the operating fluid passes from the inlet 23 to the second conduit
22 via the third passage C, and from there to the second operating chamber 12 of the
cylinder-piston unit. Simultaneously, the fluid present in the first operating chamber
11 of the cylinder-piston unit is connected via the first conduit 21 to discharge
24 via the second passage B.
[0058] Hence by operating the valve 40 the required operation of the cylinder-piston unit
is achieved.
[0059] The headpiece 20 therefore comprises every means which, together with the valve 40,
enables the cylinder-piston unit to be operated. It is necessary merely to connect
the inlet 23 to a feed pipe for the pressurized operating fluid and connect the pilot
valve 40 to an electrical supply cable.
[0060] In a different embodiment (not shown in the figures) the cylinder-piston unit is
single-acting, ie it possesses only one operating chamber, for example the chamber
11, which is connected alternately to the feed and discharge via the headpiece 20.
[0061] In this case, compared with the embodiment illustrated in the figures, the headpiece
20 possesses only the first conduit 21, plus the inlet 23 and discharge 24. It also
possesses only the first passage A and the second passage B, together with a single
cover 27d. The first pilot duct 51 hence communicates only with the chamber 35a, and
the second pilot duct 52 communicates only with the chamber 35d of the second passage
B. The pilot valve 40 remains unmodified.
[0062] On setting the valve 40 into its first configuration, the first duct 51 is connected
to the discharge outlet 44, whereas the second duct 52 is connected to the inlet 23.
[0063] Consequently, the lateral chamber 35a of the first passage A is put to discharge
with the result that the respective membrane 36 leaves the passage for the operating
fluid free. Simultaneously, the lateral chamber 35b of the second passage B is put
under pressure, the respective membrane 36 consequently being pressed against the
ports 31 and 32 to close passage for the operating fluid.
[0064] Hence the operating fluid passes from the inlet 23 to the first conduit 21 and from
there to the first operating chamber 11 of the cylinder-piston unit.
[0065] In the second configuration of the valve 40, the first duct 51 is connected to the
inlet 23, whereas the second duct 52 is connected to the discharge outlet 44.
[0066] Consequently, the lateral chamber 35a of the first passage A is put under pressure,
the respective membrane 36 consequently being pressed against the ports 31 and 32
to close the passage for the operating fluid. Simultaneously, the lateral chamber
35b of the second passage B is put to discharge with the result that the respective
membrane 36 leaves the passage for the operating fluid free.
[0067] It follows that the first chamber 11 of the cylinder-piston unit is connected to
discharge 24 via the first conduit 21 and via the second passage B.
[0068] Numerous modifications of a practical and applicational nature can be made to the
invention concerned, but without leaving the scope of the inventive idea as claimed
below.
1. A fluid operated cylinder-piston unit having at least a first operating chamber for
alternate connection to a pressurized fluid feed and to a discharge, and having at
least one headpiece (20) to which the cylindrical wall (10) laterally bounding the
operating chamber is connected, characterised by comprising:
a pressurized fluid inlet (23) to be connected to the feed, and provided within the
body (25) of the headpiece;
a fluid outlet (24) provided within the body (25) of the headpiece;
at least one conduit (21) provided within the body (25) of the headpiece and communicating
with the first operating chamber;
within the body (25) of the headpiece, between the inlet (23) and the conduit (21),
a first passage (A) having in a lateral face of the body (25) of the headpiece two
spaced-apart ports (31a, 32a), one communicating with the inlet (23) and the other
with the conduit (21);
within the body (25) of the headpiece, between the outlet (24) and the conduit (21),
a second passage (B) having in a lateral face of the body of the headpiece two spaced-apart
ports (31b, 32b), one communicating with the outlet (24) and the other with the conduit
(21);
in each of said passages (A, B) there being provided a valve for opening or closing
the fluid passage, comprising a lateral chamber (35) covering said communication ports
(31, 32) and formed in a cover (27d, 27s) positioned on the lateral face of the body
of the headpiece, and a free flexible membrane (36) separating said ports (31, 32)
from the lateral chamber (35) and being of such an area as to cover said communication
ports (31, 32), it being arranged to assume a first position in which it adheres to
the edge of the ports (31, 32) and a second position in which it is raised from the
edge of the ports (31, 32);
pilot means able to feed into each lateral chamber (35) a pilot fluid having a pressure
such as to urge the membrane (36) into the first position and to press on it with
a thrust sufficient to prevent passage of fluid through the ports (31, 32), against
the thrust of the fluid present in the ports.
2. A cylinder-piston unit as claimed in claim 1, characterised by that said pilot means
comprise thin pilot channels (51, 52) provided partly within the body (25) of the
headpiece and partly in the cover (27d, 27s), which communicate with each lateral
chamber (35), and a pilot valve means (40) communicating with the fluid feed, to distribute,
when commanded, pressurized pilot fluid to the lateral chambers (35) via said pilot
channels (51, 52), to open the first passage (A) and close the second (B) and vice
versa.
3. A cylinder-piston unit as claimed in claim 1, also having a second operating chamber
(12) opposing the first (11), characterised by comprising:
a second conduit (22) provided within the body (25) of the headpiece and communicating
with the second operating chamber (12),
within the body (25) of the headpiece, between the inlet (23) and the second conduit
(22), a third passage (C) having in a lateral face (26s) of the body (25) of the headpiece
two spaced-apart ports (31c, 32c), one communicating with the inlet (23) and the other
with the second conduit (22);
within the body (25) of the headpiece, between the outlet (24) and the second conduit
(22), a fourth passage (D) having in a lateral face (26s) of the body (25) of the
headpiece two spaced-apart ports (31d, 32d), one communicating with the outlet (24)
and the other with the second conduit (22);
in each of said passages there being provided a lateral chamber (35) covering said
communication ports (31, 32) and formed in a cover (27d, 27s) positioned on the lateral
face (26d, 26s) of the body of the headpiece, and a free flexible membrane (36) separating
said ports (31, 32) from the lateral chamber (35) and being of such an area as to
cover said communication ports (31, 32), it being arranged to assume a first position
in which it in contact with the edge of the ports (31, 32) and a second position in
which it is raised from the edge of the ports (31, 32);
the pilot valve means (40) being arranged to distribute the pressurized pilot fluid
to the lateral chambers (35) in such a manner as to achieve a first configuration
in which the first passage (A) and the fourth passage (D) are
open whereas the second passage (B) and the third passage (C) are closed, and a second
configuration in which the second passage (8) and the third passage (C) are open whereas
the first passage (A) and the fourth passage (D) are closed.
4. A cylinder-piston unit as claimed in claim 3, characterised in that:
the first conduit (21) and the second conduit (22) are positioned with their axes
longitudinal and are mutually superposed;
the inlet (23) comprises a cavity (231) of longitudinal axis positioned below said
conduits (21, 22);
the first passage (A) and the second passage (B) are both positioned on one lateral
face (26d) of the body (25) of the head, the third passage (C) and the fourth passage
(D) being both positioned on the other lateral face (26s) of the body (25) of the
head.
5. A cylinder piston unit as claimed in claim 3, characterised in that the cylindrical
wall (10) laterally bounding the operating chambers (11, 12) comprises a longitudinal
channel (222) extending longitudinally within the thickness of the wall and connected
at one end to the second conduit (22), its other end opening into the second operating
chamber (12).
6. A cylinder-piston unit as claimed in claim 3, characterised in that within the body
(25) of the headpiece and within the covers (27s, and 27d) there is provided a system
of thin channels through which the pilot fluid flows, and which comprises:
a first duct (51) extending from a port (51') and leading both to the lateral chamber
(35a) of the first passage (A) and to the lateral chamber (35d) of the fourth passage
(D);
and a second duct (52) extending from a second port (52') and leading both to the
lateral chamber (35b) of the second passage (B) and to the lateral chamber (35c) of
the third passage (C);
said ports (51' and 52') being both provided in the face (26') of the body (25) and
being connected to the pilot valve (40).