Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1092488
The invention relates to a ram cylinder assembly
for operation by a liquid or gaseous pressure medium for con-
verting rectilinear motion into angular rotation. The ram
cylinder assembly according to the invention has a closed
internal operating chamber in which is located a piston
driven to move in alternating longitudinal motion by a
hydraulic or pneumatic medium. The piston is connected to
a shaft and at least one end of the shaft extends out of the
operating chamber.
In numerous fields of industry, agriculture
and commerce, it is frequently necessary to produce rotary
motion, including non-continuous rotation, e.g. an oscillating
rotary motion within a predetermined angular range. Often a
large torque is required, together with a small angular
velocity.
In mobile cranes and other loading machinery,
the mast frequently has to be rotatable in both directions
within an angular range of from 360 to 400. A similar
situation arises with crane-like earth moving machinery and
certain agricultural machines. An alternating angular
motion also has to be produced during the pivoting out and
supporting of support platforms of various apparatus, in
the movement of automatically opening vehicle doors and in
the operation of gear shifting, during control procedures
by automatic machines etc.
The object of the present invention is to pro-
vide an improved assembly for this purpose, to which end
the invention consists of a ram cylinder assembly comprising
(a) a cylinder defining at least one closed operating
chamber and having an lnner surface of polygonal cross-
section; (b) a piston having an outer surface of corresponding
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polygonal cross-section mounted in said cylinder for axial
movement therein in response to fluid pressure in said
chamber, said polygonal surfaces forming a first, sliding
connection; (c) a shaft rotatably mounted in the cylinder
to extend axially through the piston while having at least
one end extending to the exterior of the cylinder; (d) an
inner surface of the piston and an outer surface of the :
shaft having cross-sections forming a second, non-circular
connection; (e) at least one of said inner surface of the
cylinder and said outer surface of the shaft having its
cross-section twisted spirally whereby at least one of said --
connections becomes a driving connection that causes rotat-
ional movement of the shaft relative to the cylinder upon
axial movement of the piston.
Embodiments of the~invention are described in
more detail below with reference to the drawings.
Fig. 1 shows a longitudinal section through a
first embodiment of ram cylinder assembly according to the
invention;
Fig. 2 represents a longitudinal section of ~-
another embodiment;
Fig. 3 illustrates a longitudinal section through
a third embodiment;
Fig. 4 shows a sectional front view of a
connection among a cylinder, piston and shaft;
Fig. 5 illustrates the section V-V in Figure
4; and
Fig. 6 shows a longitudinal section of another
embodiment.
Fig. 1 represents a longitudinal section through
- an embodiment of ram cylinder assembly according to the
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109Z488
invention. In this embodiment, the cylinder 1 is formed by
a flanged tube which is open at both ends, and which is sealed
at both ends by covers 3, 3'. Sealing rings 51 and 52 are
arranged between the covers 3 and 3' and the cylinder 1. In
the interior of the cylinder 1 there is located a shaft 4
whose ends 14 and 15 projec-t from the operating chamber 12
formed between the cylinder 1 and the covers 3 and 3'. The
shaft 4 is arranged coaxially in the cylinder 1 and is ro-
tatably mounted about its own axis in the covers 3 and 3' by
means of bearings 16 and 17. The shaft 4 cannot move in the
axial direction in the embodiment shown in Fig. 1. In order
to seal the operating chamber 12 tight~ the ends of the shaft
4 which extend through the covers 3 and 3' are surrounded by
seals 5 and 5'.
The closed operating chamber 12 formed by the shaft 4
^ and the cylinder 1 is divided into two parts by a piston 6.
The piston 6 divides the operating chamber 12 in a tight
manner into a lower section 12' and an upper section 12",
the seal being provided by sealing rings 7a and 7b.
The inner surface la of the cylinder 1 and the outer ~ -
surface 6a of the piston 6 are each formed with polygonal
cross-sections ~Fig. 5) to provide a first sliding connection.
The inner sur~ace 6b of the piston 6 and the outer surface
4b of the shaft 4 also have non-circular, e.g. polygonal
cross-sections, to form a second sliding connection, with
the outer surface of the shaft having its cross-section
twisted spirally as shown diagrammatically by the helical
line 13. As a result, the piston 6 is able to move in an
axial direction in the operating chamber 12 under the
influence of a liquid or gaseous medium introduced into the
operating chamber under pressure through openings 8 and 8'
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in the side wall of the cylinder 1. The piston 6 slides in
the cylinder 1 without relative rotation, while the shaft 4
is forced to rotate within the piston 6.
The embodiment shown in Figure 2 substantially agrees
with the one shown in Figure 1, the difference lying in the
fact that only the upper end of the shaft 4 extends out of
the operating chamber 12. There is a fixed, e.g. welded,
connection or a screw connection between the lower cover 3'
and the cylinder 1. The openings 8 and 8' extend through the
covers 3 and 3'. The shaft 4 can perform a single rotation
about its axis, axial movement of the shaft being prevented
by its shoulders engaging in the covers. The bearings 16
and 17 are designed differently in this embodiment from those
shown in Figure 1.
Figure 3 shows another embodiment of ram cylinder assembly
according to the invention in which the part of the shaft 4
extending out of the operating chamber 12 can perform both
an axial and a rotational movement. The shaft 4 is cylind-
rical except for a non-circular, e.g. pentagonal, shoulder 18
on its lower part. The piston 6 has a similar, non-circular
inner surface fitting the profile of the shoulder 8 and is
rigidly connected to the lower end of the shaft 4 by means
of a screw 19. The piston 6 and the shaft 4 can therefore
alter neither their axial nor their angular positions
relative to each other. In this embodiment, the polygonal
inner surface of the cylinder 1 is designed spirally as
indicated by the line 13, so that the relative rotation
takes place between the piston 6 and the cylinder 1.
Figure 4 shows a sectional view in which only the
immediate surroundings of the piston 6 are shown. Figure 5
is a plan view of the detail shown in Figure 4. As already
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mentioned, the cylinder 1 has a polygonal, e.g. pentagonal,inner profile la and the outer surface 6a of the piston 6 is
adapted to this profile. The outer surface 4b of the shaft 4
is also designed to be non-circular, e.g. pentagonal, and the
inner surface 6b of the piston 6 is adapted to this shaft
profile. Generally speaking, a suitable seal can be achieved
between the piston and cylinder or between the piston and
shaft by means of conventional sealing rings when the profiles
are designed in the form of regular polygons.
Figure 6 shows several ram cylinder assemblies arranged
inside each other to form operating chambers which are
separated from each other or which communicate with each other
only via overflow openings. The external cylinder lA in the
arrangement is sealed tight by covers 3 and 3'. An internal
cylinder lB is arranged inside the external cylinder lA and
a first piston 61 is arranged between them. The outer sur-
face of the internal cylinder lB is to be considered as the
outer surface of a shaft, when viewed from the piston 61.
The inner shaft 4 is arranged inside the inner cylinder lB
and the operating chamber located between them is divided
into two parts by a second piston 62. The inner surface
of the inner cylinder lB guides the outer surface of the
second piston 62 whose inner surface embraces the outer sur-
face of the shaft 4. With regard to the hydraulic supply,
the external and internal operating chambers are connected
in parallel with each other by the openings 8, 8'. The
hydraulic medium flows in and out through ducts 24 and 25.
The various embodiments operate in the following manner:
If pressure medium is introduced into one of the sections of
the operating chamber 12 the piston 6 is shifted axially.
In the embodiments s~own in Figures 1 and 2, the outer profile
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of the shaft 4 follows the spiral path 13, so that axial
shifting of the piston 6 is therefore accompanied by rotation
of the shaft, the angular position of the piston 6 being
fixed relative to the cylinder 1. The connection between the
outer surface of the shaft and the inner surface of the piston
is~ then the "drivin~'connection. Of course, it is possible
to design not only the profile of the shaft spirally, but c
also the inner surface of the ram cylinder 1 in this way.
This possibility is illustrated in Figure 3. Here the piston
6 performs a composite movement, i.e. a rotational movement
about the axis and an advancing movement along the axis. In -
the embodiment shown in Figure 3, both the axial and rotary
motions are transferred from the piston 6 to the shaft 4,
and the connection between the outer surface of the piston
and the inner surface of the cylinder becomes the "driving "
connection. It is easy to see that, if there is no need to
extract the axial movement, the piston 6 could slide on the
shaft 4 and transfers only its twist to the shaft 4 ~since
no relative rotation between the piston and the shaft is
possible in this embodiment).
By cumulatively combining the arrangements shown
in Figures 1 and 3, both the inner surface of the cylinder
1 and the outer surface of the shaft 4 can be designed with
a spiral profile. As a result, for a given axial shifting
of the piston 6, the shaft 4 can perform a larger angular
twist.
In the double arrangement shown in Figure 6, the
inner surface of the external cylinder lA is designed
spirally, as in Fig. 3, so that axial shifting of the`first
piston 61 is accompanied by rotational movement of this
piston. This rotational movement of the first piston 61 is
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transferred to the internal cylinder lB. When the second
piston 62 shifts axially in the cylinder lB, the shaft 4 is
twisted relative to the internal cylinder lB so that the
shaft 4 performs an angular twist that is double that of the
internal cylinder relative to the external cylinder.
It is advantageous to select a regular polygon as the
profile configuration, because it is relatively simple to
release the seal in this casè. A polygonal form running
spirally along the axis can be produced by the known
technology for metal-cutting.
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