Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2 [3~L7~7
AIR-OIL PRESSURE INTENSIFIER CYLINDER
F I ELD OF THE I NVENT I ON
This invention relates to air powered pressure intensifier
cylinders of th~ type which provides an operating ram pressure
applicator initially with a relatively low hydraulic oil operating
preqsure and, subsequently with a second higher and final operating
pressure, the first lower pressure being utilized to advance a ram
to which a tool is secured, for instance a punch, to contact a
workpiece and the second higher pressure being used to power the
ram to perform the actual work on the workpiece, which work may be
the piercing of the workpiece by the punch~
BACKGROUND OF TE~E I NVENT I ON
Pressure intensifier cylinders providing two distinct pressure
steps are known from United States patent 4,271,671 ~ G. G. F.
Smeets - issued June 9, 1981 wherein a two step pressure
intensifier system is described. ~~
In the arrangement, according to the patent, a ~irst piston, moved
by primary air pressure, continues to move, in the working stroke
direction, after the ram has been moved, initially, to contact a
workpiece, by the pro~Jision of a pressure bleed past a second
piston directly mechanically activated by the first piston and
applying pressure to the oil medium operable on the ram piston per
se. At a predetermined position in the working stroke direction
the pressure bleed is closed off and a stepped up pressure,
produced by a third piston, also mechanically activated by the
first piston, is applied to the oil medium to power the ram piston
to perform the final work function.
A disadvantage of the Smeets cylinder, described above, is the
fact that the stepped up pressure i5 applied at a fixed point in
the working stroke rather than at a point which may be varied. A
further disadvantage of the Smeets cylinder is that the time of a
Z ~ ~ ~ 7 ~ 7
working cycle is fixed and can only be changed by mechanically
changing the parameters of the components of the pressure
intensifier system.
A further United States patent 4,300,351 - A. Grullmeier -
issued November 17, 1981 discloses a pressure intensifying cylinder
in which a first air powered piston applies spring prescure to a
floating piston, which floating piston is in direct contact with an
oil medium by virtue of which pressur~ is applied to a ram
operating piston-cylinder arrangement. The initial portion of the
stroke is at a low pressure, applied throuyh the spring, which
increases with the distance travelled by the first air powered
piston. At a predetermined point in the working stroke direction a
third piston, directly operated by the first piston, becomes active
to provide a stepped up oil pressure to the ram operating piston
whereby the final work function, such as workpiece punching, is
performed.
OBJE~CTS OF THE INVENTION
It is a prime object of the present invention to provide an air
to oil pressure intensifier cylinder in which the length of the
~0 initial portion of the working stroke is automatically variable
dependent on the thickness of a workpiece.
It is a further object of the invention to provide an air to oil
pressure intensifier cylinder which will allow a choice between a
controlled cycle time and an automatically timed cycle of
operation.
It is a still further object of the invention to provide an air
to oil pressure intensifier cylinder which is simple and economical
to construct, utilizing a minimum number of parts and springs.
other objects and advantages of the invention will become
apparent in the detailed description of the invention provided
below.
.:
2~ 7~7
BRIEF DESCRIPTION OF~TEIE DRAWINGS
For a full understanding of the present invention reference
will be made to the figures of the drawings in which;
Figure 1 shows a detailed cross-section of the cylinder,
according to the invention, wherein the parts there~f are shown in
the position of rest or at the start point sf a working cycle
which, of course, will correspond to the end point of a working
cycle as well,
Figure 2 shows the cylinder of the invention in the initial low
pressure portion oE a work cycle thereof,
Figure 3 shows the cylinder of the invention in the final high
pressure operating portion of the work cycle,
Figures 4 shows an enlarged detail portion of a piston with a
ported valve system which is operative to switch the cylinder per
se between the low and high pressure operating portions of the
working cycle of the cylinder, and
Figure 5 shows a cross-sectional view of the piston shown in
Figure 4.
DETAILED DESCRIPTION OF THE INVEN~ION
Referring now to the figures of the drawing, Figure 1 shows a
cross-sectional view of the cylinder, according to the present
invention, at the start point of the working stroke thereof. The
cylinder comprises a hollow, main cylindrical ~ody housing 1
provided with a centrally apertured partition 2 and three primary
pressure ports 9, 10 an 11 to which air pressure can be applied by
valve means not shown, which valves can be mechanically or
electrically controlled to apply or release air pressure at these
ports.
In the upper portion of the cylinder housing there is provided
a first floating piston 6, fitted with one or more pressure seals
6s. Piston 6 is free to move in the axial direction of the
7~)7
cylinder between the positions shown in Figure 1 and Figure 3, for
instance. A second floating piston 7, also located in the upper
portion of the housing 1, is free to move between a limited upper
position and partition 2. The particular construction of piston 7
will be described subsequently in greater detail with reference to
Figures 3 and 4.
A ram piston 8, provided with pressure seal 8s, is incorporated
in the lower portion of the housing below partition 2. Piston 8 is
provided with an operable ram portion 5, in the form of a
cylindrical rod, which extends externally of the housing through an
aperture in the lower wall 4 of the housing. The aperture is
provided with sealing rings 4s. Piston 8 and ram 5 are hollowed
out cylindrically and axially thereof to provide accommodation for
a hollow cylindrical shaft member 12 to move downward thereinto.
be.r
C~}n&e~ 12 is provided with end flanges 12a and 12b wherein flange
12b retains the upper end of member 12 within the lower part of
piston 7 with freedom to move between the limiting positions
thereof shown in Figures 1 and 3 while lower flange 12a prevents
removal of the member 12 upward from the aperture in partition 2.
Appropriate seals for member 12, 12s in the upper flange of member
12 and seal 2s in partition 2 are provided. The interior space of
the housing between floating pistons 6 and 7 and the interior
spaces of hollow shaft 12 and ram 5 are filled with an oil medium,
i.e. hydraulic oil.
By means of ports 9, 10, 11 primary fluid (air~ pressure can be
applied to the upper side of piston 6 and the lower sides of
pistons 7 and 8 respectively.
Referring now to Figures 4 and 5, showing in greater detail the
construction of piston 7 and member 12, piston 7 is shown as having
a cover plate 7a secured to the main body part of piston 7 by means
of cap screws 14. The cover plate is provided with a number of
perforations 7b circularly arranged about a centrally located,
downward protruding cylindrical plug 17 which is sized ~o enter the
upper end of member 12 to seal off the communication, normally
provided for the oil medium, between the chamber above piston 7 and
the interior of member 12. Member 12, as shown best in Figure 1,
is effective, through the contact of its lower flange with the
lower side of partition 2 and the upper flange thereof with the
shoulder provided in piston 7 and shown clearly in Figure 5, to
limit the movement of piston 7 in an upward direction. A spring 13
10 is provided to assist in the seal ing of the upper end of member 12
which sealing takes place at the initiation of the high pressure
portion of the working cycle.
OPE~ON OF TH13 I NTE:N S I F I ER CYL I NDER
The operation of the cylinder, according to the present
invention, will be now described with reference to Figures 1,2 and
3. Figure 1 shows the position of the pistons and other elements
at the position of rest or the end of the return stroke of the
working cycle. During operation and at this point in the working
cycle port 9 is open and primary air pressure is applied to ports
10 and 11, as indicated by the arrows, and to the undersides of
pistons 7 and 8. This air pressure is effective to return ram 5
and floating pistons 7 and 8 to their starting positions. Piston
7, in returnin~ to this position, pulls member 12 up with it by
virtue of the top flange coupling 12b and the cooperating shoulder
2~ provided in piston 7. The lower flange 12a on member 12 limits the
upward movement of piston 7 and simultaneously removes protrusion
17 from the top end of member 12 so that communication is opened
between the top side of piston 8 and the lower side of piston 6.
Piston 8 continues to move upward and forces the oil medium into
the space between pistons 6 and 7 thus forcing piston 6 to return
to its uppermost or start position.
L7~t7
Referring now to Figure 2, which shows an intermediate point in
the working cycle, primary air pressure, as indicated hy the
arrows, i5 applied to ports 9 and 10. The pressure applied to
piston 6 via port 9 is effective to move that piston downward while
the pressure applied to the underside of piston 7 and the friction
of the sealing rings 7s are sufficient to prevent movement downward
of piston 7. The pressure difference across piston 7 is slightly
greater in the downward pushin~ direction due to the thickness of
the wall of cylindrical member 12 but is not sufficient to overcome
the friction of the sealing rings 7s. However the full pressure on
the oil medium, provided by piston 6, forces ram piston ~ downward
until ram 5 contacts a workpiece, not shown.
At this point in the cycle, referring now to Figure 3, primary
pressure is removed from port 10 and the pressure on the oil medium
is now effective to move piston 7 downward and, with the assistance
of spring 13, to seal the top end of member 12. Spring 13 is
preferably present and used to ensure proper sealing of member 12
since there is initially no back pressure on member 12 to assist in
the sealing.
At this point in the cycle full primary air pressure is applied
to piston 7, via the oil medium between pistons 6 and 7, and a step
up in the pressure applied to ram piston 8 occurs by virtue of the
fact that the ~ull pressure provided by piston 7 is applied to the
much smaller area encompassed by member 12, which smaller area, in
relationship to the full area of piston 7, when member 12 is sealed
off, is designed to be such that a punching or other operation on
the workpiece may be performed.
At the termination of the work function of the cylinder ram
primary air pressure is applied to ports lO and ll to move pistons
7 and 8 upward. The lower shoulder on member 12 nGw becomes
effective to limit the upward movement of that member so that
~ 7 07
continued movement of pi~ton 7, in the upward direction, removes
the sealing protrusion 17 from the upper end of member 12 thus
allowing piston 8 to return oil to the space between pistons 6 and
7 and fully return pistons 6 and 8 to their original start
positions as shown in Figure 1. The upward movement of piston 7
spri~g
continues until spring ~ag 13 is compressed. However, spring
13, on its own, is not sufficiently strong as to overcome the
friction, provided by the relevant seals, to return the protrusion
17 of piston 7 into the top end of member 12 to produce a seal when
primary air pressure is removed from ports 10 and 11.
Due to the fact that member 12 is not mechanically coupled to
ram piston 8 that piston can move the full length allowed by the
lower part of the housing during the initial part of the working
cycle and piston 6 is also free to move with respect to piston 7
with the result that a great variation in thickness of workpieces
can be accommodated when sufficient time is allowed in the initial
low pressure portion of the working stroke cycle before primary air
pressure is removed from port 10 to allow piston 7 to move to seal
off the upper end o~ member 12 and initiate the high pressure
portion of the cycle. The time of a complete cycle can be
controlled by the timing of the application to and the removal of
primary air pressure from ports 9, 10 and 11 as will now be
obvious. For instance, the high pressure portion of the working
cycle may be initiated by electrical switch means operablew when
ram 5 contacts a workpiece so that variations in workpiece
thickness are automatically taken care of.
It should be noted that the drawings have been simplified to
facilitate a clear understanding of a preferred embodiment of the
invention and that construction details can be varied and
controlled by tho~e skilled in such manufacturing without departing
from the spirit and scope of the invention. For instance, the
2~ 7~7
housing may be made in sections to facilitate assembly of a
complete working cylind0r. In addition it is not essential that the
ram piston be coaxial with pistons 6 and 7, i.e. the pressure in
the lower part of the housing may be piped to a remotely located
ram operating cylinder per se. Furthermore, such parts as the
flanges for member 12 may be in the form of threaded nuts which are
screwed onto the ends of member 12, which ends are provided with
the appropriate threading. Further modifications may be made which
are considered within the skill of those versed in the relevant art
and which do not depart from the spirit and scope of the invention
as defined in the appended claims.
