U.S. patent number 3,855,902 [Application Number 05/337,126] was granted by the patent office on 1974-12-24 for cylinder piston unit for a power operated revolving chuck.
This patent grant is currently assigned to Hofmann & Co. KG. Invention is credited to Rudi Kirst.
United States Patent |
3,855,902 |
Kirst |
December 24, 1974 |
CYLINDER PISTON UNIT FOR A POWER OPERATED REVOLVING CHUCK
Abstract
A pressurized fluid actuated cylinder piston unit for power
operated lathe chucks and the like in which safety means are
provided to prevent pressure drop in the pressurized cylinder
chamber in case of a pressure source failure, each cylinder chamber
being provided with a check valve as safety device, the valves
being resilient rings surrounding the piston rod bilaterally of the
piston and covering radial bores in communication with the pressure
source, the ring in the chamber to be vented being mechanically
expanded by a pressure responsive member.
Inventors: |
Kirst; Rudi (Hilden,
DT) |
Assignee: |
Hofmann & Co. KG (Haan,
DT)
|
Family
ID: |
5862283 |
Appl.
No.: |
05/337,126 |
Filed: |
March 1, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Nov 21, 1972 [DT] |
|
|
2256933 |
|
Current U.S.
Class: |
91/420; 251/900;
92/106; 279/4.02 |
Current CPC
Class: |
B23B
31/302 (20130101); Y10S 251/90 (20130101); Y10T
279/1208 (20150115) |
Current International
Class: |
B23B
31/02 (20060101); B23B 31/30 (20060101); F15b
011/08 (); F15b 013/04 () |
Field of
Search: |
;91/420 ;279/41,4
;92/106 ;251/DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Cohen; Irwin C.
Assistant Examiner: Hershkovitz; Abraham
Attorney, Agent or Firm: Palmatier; H. Dale
Claims
What I claim is:
1. A revolving pressurized fluid actuated operator for a chuck and
for use with fluid supply connections which are alternately
pressurized and vented, comprising:
a cylinder to confine a pressurized fluid,
a piston in the cylinder and dividing the cylinder into a pair of
fluid chambers, and the piston having a rod movable with the piston
and relative to the cylinder to operate the chuck, the piston rod
having an elongate hollow interior with opposite ends adjacent the
opposite sides of the piston,
fluid supply means attachable to such alternately pressurized and
vented fluid connections and including radial bores in the piston
rod at opposite sides of the piston to direct pressurized fluid to
the chambers and to vent the chambers alternately for controlling
the piston movement in the cylinder and including check valves for
each cylinder chamber to be opened and closed responsive to
pressure reversal in the fluid supply means, said check valves
comprising a pair of valve elements respectively disposed at
opposite sides of the piston and on the piston rod and in
obstructing relation with said radial bores to prevent release of
fluid pressure in the chambers, said fluid supply means including
duct means in the hollow piston rod defining and separating fluid
channels from each other, said channels respectively communicating
with opposite ends of the hollow interior of the piston rod to
alternately vent and pressurize the ends of the hollow interior and
bores,
operating means responsive to pressure reversal at such fluid
supply connections to selectively lift the valve elements out of
obstructing relation with the bores to alternately vent the
chambers and including radially movable actuating members in the
bores at both sides of the piston and acting on the valve elements
to lift the valve elements out of obstructing relation and said
actuating members also protruding into the hollow interior of the
piston rod, and an auxiliary fluid pressure-operated piston
slidable in the hollow interior of the piston rod and sealably
isolating said opposite ends of the hollow interior from each
other, said auxiliary piston being exposed to different fluid
pressures at opposite ends of the hollow interior of the piston rod
and being moved endwise in the piston rod by the fluid pressure
differentials, and said auxiliary piston being provided with cam
faces engaging said actuating members for radially moving the
actuating members in the bores.
2. A pressurized air actuated cylinder piston unit, comprising in
combination: a hollow cylinder having a cylinder head at each end,
a piston movable relative to said cylinder and mounted on a piston
rod extending through both cylinder heads, means sealing said
piston and piston rod against said cylinder, said piston rod having
a first and a second axially extending channel, a sleeve being
sealingly mounted about the piston rod end remote from said
cylinder and provided with first and second axially spaced radial
openings to be alternatively connected to a pressurized air source,
each opening communicating with an internal circumferential groove
within said sleeve, the first opening being via the respective
groove and a radial aperture in the piston rod in communication
with the first axially extending channel thereof and the second
opening being via its groove and a radial aperture in the piston
rod in communication with the second axially extending channel
thereof, said sleeve and the assembly consisting of piston rod,
piston, and cylinder being rotatable with respect to each other, a
first set of radial passages extending from the first of said
piston rod channels into a first cylinder chamber confined by the
cylinder, the piston, and the piston rod, a second set of radial
passages extending from said second piston rod channel into a
second chamber confined by the cylinder, piston, and piston rod
separated from the first chamber by the piston, radially resilient
ring means surrounding the piston rod at the position of said first
and second sets of radial passages closing the respective passages
to prevent pressure drop within the respective chamber, and
actuating means to radially expand the ring means and to render
communicating the respective chamber and channel in response to
pressure increase in the respective other channel, said actuating
means including radially movable plungers in said radial passages
to lift the resilient ring means out of obstructing relation with
the passages to release pressure in said cylinder chambers, said
actuating means also including a slidable operator movable along
the piston rod and having oblique cam surfaces engaging the
plungers in said first and second set of radial passages for
alternately opening said first and second passages as the operator
is moved endwise of the piston rod, and means slidably mounting
said operator within the piston rod between said first and second
axially extending channels to facilitate movement of the operator
under influence of the pressure reversal in said first and second
axially extending channels to release the pressure in said chambers
as the fluid pressure is reversed at the radial openings of the
sleeve.
3. A revolving pressurized fluid actuated operator for a chuck,
comprising:
a cylinder to confine pressurized fluid,
a piston in the cylinder and dividing the cylinder into a pair of
fluid chambers, and the piston having a rod movable with the piston
and relative to the cylinder to operate the chuck,
the piston rod being hollow,
fluid supply means including radial bores in the piston rod to
direct pressurized fluid to the chambers and to vent the chambers
alternately for controlling the piston movement in the cylinder and
including check valves for each cylinder chamber to be opened and
closed responsive to pressure reversal in the fluid supply means,
said check valves comprising a pair of deformable rings
respectively disposed at opposite sides of the piston and on the
piston rod and in obstructing relation with said radial bores, said
fluid supply means including a sleeve in the hollow piston rod and
defining and separating fluid channels from each other,
an actuation member movably mounted in one of said bores to lift
the check valve ring and provide venting of the respective cylinder
chamber, and
an auxiliary piston being slidably mounted on said sleeve and being
provided with cam faces engaging said actuating member for radially
moving the actuating member in the bore.
4. A fluid actuated operator as claimed in claim 3 wherein a
plurality of said actuation members are movably mounted in bores at
both sides of the piston to lift the deformable check valve rings
for venting alternate chambers, and said auxiliary piston having
tapered ends engaging said actuation members and alternately urge
said actuation members outwardly.
5. An operator as claimed in claim 4 wherein said actuation members
are plungers guided within said bores.
6. A revolving pressurized fluid actuated operator for a chuck,
comprising:
a cylinder to confine a pressurized fluid;
a piston in the cylinder and dividing the cylinder into a pair of
fluid chambers, and the piston having a piston rod movable with the
piston and relative to the cylinder to operate the chuck, the
piston rod having a longitudinally extending hollow interior
adjacent the piston defining a combined fluid passage and guideway,
said piston rod also having a plurality of radial bores extending
between said hollow interior and the exterior of the piston rod,
said bores being disposed in at least two locations along the
length of the piston rod adjacent each of said chambers so that
certain of said bores provide communication between the hollow
interior and one of the chambers, and the remaining bores provide
communication between the hollow interior and the other of the
chambers;
releasable valve means at the exterior of said piston rod and
obstructing said radial bores, and including a plurality of
plungers extending inwardly through said bores and protruding into
said hollow interior, said valve means being biased into
bore-obstructing position and being operable in response to outward
movement of said plungers to open the valve means and release
pressure from the chamber;
a fluid pressure operated slider in said hollow interior of the
piston rod which defines the slideway for the slider, said slider
traversing the hollow interior and sealing around the interior
periphery of the slideway to obstruct fluid communication
longitudinally along the hollow interior of the piston rod, said
slider having oblique camming surfaces bearing outwardly against
said plungers to restrain inward movement of the plungers and
produce radial outward movement of the plungers as the slider moves
longitudinally along the piston rod for operating said valve means,
said slider being moved along the interior of the piston rod by
fluid pressure differentials between opposite ends of the hollow
interior; and
said piston rod having a pair of separate fluid passages each
communicating with a respective end of the hollow interior of said
piston rod to facilitate control of the fluid pressure applied to
said bores and to the corresponding sides of the slider for
simultaneously pressurizing one of the cylinder chambers and
venting the other chamber as the fluid pressure moves the slider to
operate the plungers and valve means.
7. A revolving pressurized fluid actuated operator for a chuck,
comprising:
a cylinder to confine a pressurized fluid;
a piston in the cylinder and dividing the cylinder into a pair of
fluid chambers, and the piston having a piston rod movable with the
piston and relative to the cylinder to operate the chuck, the
piston rod having a hollow interior adjacent the piston defining a
combined fluid passage and guideway, said piston rod also having a
plurality of radial bores extending between said hollow interior
and the exterior of the piston rod, said bores being disposed in at
least two locations along the length of the piston rod adjacent
each of said chambers so that certain of said bores provide
communication between the hollow interior and one of the chambers,
and the remaining bores provide communication between the hollow
interior and the other of the chambers;
releasable valve means at the exterior of said piston rod and
obstructing said radial bores, and including a plurality of
plungers extending inwardly through said bores and protruding into
said hollow interior, said valve means being biased into
bore-obstructing position and being operable in response to outward
movement of said plungers to open the valve means and release
pressure from the chamber;
a plunger-operating slider in said hollow interior of the piston
rod which defines the slideway for the slider, said slider
traversing the hollow interior and sealing around the interior
periphery of the slideway to obstruct fluid communication
longitudinally along the hollow interior of the piston rod, said
slider having oblique camming surfaces bearing outwardly against
said plungers to restrain inward movement of the plungers and
produce radial outward movement of the plungers as the slider moves
longitudinally along the piston rod for operating said valve means;
and
said piston rod having a pair of separate fluid passages each
communicating with a respective end of the hollow interior of said
piston rod to facilitate control of the fluid pressure applied to
said bores and to the corresponding sides of the slider for
simultaneously pressurizing one of the cylinder chambers and
venting the other chamber as the slider operates the plungers and
valve means, wherein said piston rod includes a stationary tube
extending longitudinally through said hollow interior and being
connected to one of said fluid passages, and said slider being
annular and having an interior periphery mounted upon and sliding
along the exterior of said tube.
Description
BACKGROUND OF THE INVENTION
The invention relates to a pressurized fluid actuated rotating
cylinder piston unit for power operated chucks, in particular, for
lathes, milling machines, grinding machines and the like in which
the tool or the blank is held in a jaw chuck.
For safety reasons, check valves are provided to prevent pressure
drop in the actually pressurized cylinder chamber in case of the
pressure supply being shut down unintentionally, due to a pressure
tube defect or another leakage. When reversing the pressure under
normal operating condition, however, the respective chamber is to
be vented, i.e., the respective check valve must be disabled, or
rendered out of function.
German published patent specification German Offenlegungsschrift,
published Oct. 7, 1971, No. 2 011 996 shows certain aspects of such
a unit.
German Patent Specification 1 006 236 granted Oct. 10, 1957
discloses a cylinder piston unit for similar purposes and is
likewise provided with a radially movable actuating piston. In this
known design, the check valves are of the plug type with an
extension engaged by the piston. The non-symmetrical disposition of
the piston is a serious drawback because it may, under the effect
of centrifugal forces, unintentionally render the safety device out
of service. A further drawback is the complex shape of the
valves.
Similarly, the radially movable flap valves actuated by a radially
movable auxiliary piston as provided in the unit disclosed in
German published patent specification German Offenlegungsschrift
1,918,428 is extremely expensive to manufacture.
German utility model DT-GM 1 985 828 registered May 22, 1968
discloses a cylinder unit in which one of the valves is a disc
valve while the other is a flap valve. In this design which is
apparently quite expensive, an individual actuating piston is
provided for each valve. This unit, nevertheless, has the technical
advantage that all moving parts are disposed symmetrically with
respect to the unit axis; however, it is not possible to provide a
hollow machine spindle extending through the unit and serving as
blank supply channel for the check, as is often desired for
lathes.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a pressurized fluid
actuated cylinder piston unit for power operated chucks and the
like in which the advantages of the known units are maintained
while their drawbacks are avoided. In other words, the check valves
should have the form of simple O-rings, flat rings, quad rings or
the like because these require but a minimum of space within the
cylinder. Likewise, the actuating means are to be simple, small,
and should be insensitive against centrifugal forces. Finally, the
unit should permit hollow spindles to extend therethrough.
According to the invention, there is provided a cylinder piston
unit in which the fluid (preferably pressurized air) is supplied to
the cylinder chambers bilaterally of the piston via channels
extending axially through the piston rod and communicating each
with one of the chambers via series of bores extending radially
through the piston rod, each series being disposed at one side of
the piston. The bores open into a circumferential groove in which
an O-ring or other radially resilient ring is disposed. In case of
the pressure within the channel drops unintentionally, the ring
closes the bores and prevents rapid pressure drop within the
respective cylinder. In case of the pressure being intentionally
decreased or switched off, the other channel will be subjected to
pressure. This permits provision of an actuating member to lift or
radially expand the ring in response to pressure increase in the
other chamber. Preferably, the actuating means comprises plungers
slidingly received within some, but not all of the bores and pushed
outwardly by a slider or auxiliary piston moved under the pressure
which is supplied to the opposite chamber.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The accompanying drawings show in
FIG. 1, an axial section view of a cylinder piston unit according
to the invention; and
FIG. 2 is a detail section, partly broken away, and taken at line
2--2 in FIG. 1.
The drawings show a pneumatic cylinder unit but it will be
understood that the invention will be likewise applicable to
hydraulic cylinders.
In a cylinder 10, a piston rod 18 carrying a piston 20 is axially
movable and sealed against the cylinder by sealing rings 12, 14 and
16. The piston 20 separates the cylinder chambers 22 and 24.
The piston rod 18 has an elongate hollow interior 18.1, and a
central sleeve or tube 26 extends from the rod end remote from the
cylinder (lefthand in FIG. 1) to a point adjacent the front 28 of
the cylinder. It will be apparent to those skilled in the art that
the cylinder front 28 will be connected to a chuck body while the
piston rod extending therethrough will be connected to the jaw
actuating member mounted in said body; the chuck body and its
associated parts, however, are not shown in the drawing because
they do not form part of the invention nor do the connection means,
provided at the cylinder front 28 and the piston rod and not shown
either for the same reason.
The interior or duct 29 of sleeve or tube 26 communicates, via
axial bore 30 of the piston rod and a radial aperture 32 thereof
with a first supply opening 34 of a supply sleeve 36 and also
communicates with one end 18.1a of the hollow interior 18.1 of the
rod. Opening 34, aperture 32, bore 30 and the interior 29 of sleeve
26 define a first fluid medium channel.
A second channel leads from a second supply opening 38 of supply
sleeve 36 to a second radial aperture 40 of piston rod 18 to the
annular duct or passage 42 remaining between the outer
circumference of sleeve 26 and inner wall of bore 30, and then to
the other end 18.1b of the hollow interior 18.1 of the piston
rod.
It will be apparent to those skilled in the art that supply sleeve
36 will be fixed while the assembly consisting in the piston rod
with piston and cylinder may revolve relative thereto. Therefore,
in the interior of supply sleeve 36 circumferential grooves are
provided into which the apertures 32 and 40 open, the grooves
assuring permanent communication between the supply openings and
the aligned apertures. It is a matter of course that appropriate
sealing means are provided to prevent leakage or pressure short
circuit via the gap between members 18 and 36; these sealings,
however, are not shown in the drawing for sake of simplicity.
Finally, it will be understood that openings 34 and 38 are each
connected to one output of a fluid main valve (not shown) by which
either opening 34 or 38 is connected to a source of pressurized air
while simultaneously the other opening is vented to the atmosphere.
In case of a hydraulic cylinder, the other opening would be
connected to a fluid tank.
Returning again to the drawings, an auxiliary piston or actuating
slider 44 is slidably received between sleeve 26 and bore 30 about
at the axial position of the piston 20. The slider is sealed at its
interior and its exterior and has the shape of a double cone with a
central cylindrical portion.
On both sides of piston 20 circumferential grooves 45 are machined
in piston rod 18, and from the bottom of the grooves, bores 46
extend radially inwardly and open into axial bore 30 (see FIG. 2,
too). An O-ring 48 is disposed in each of the circumferential
grooves. In the embodiment shown, nine radial bores 46 are provided
for each grooves and the nine bores consist of three groups of
three bores each, the groups being equally angularly spaced. In the
central bore of each group, a plunger 50 is slidably received, the
outer end of each plunger abutting the inwardly facing side of the
O-ring while the inner plunger and engages the conical surface of
slider 44. It will be seen that each of the resilient O-rings
continuously biases the corresponding plungers 50 in a radially
inward direction so that the plungers 50 bear firmly against the
conical camming surfaces of the slider 44. The endwise facing
shoulders 52 on slider 44 alternately engage the plungers 50 so
that the axial sliding movement of slider 44 is restricted by the
plungers which are maintained in engagement with the slider by the
resilient O-rings 48. It will be seen in the drawings that as the
slider 44 moves in one direction, such as to the right in FIG. 1,
one set of the plungers 50 is urged radially outwardly as depicted
in FIG. 2 so as to urge the resilient O-ring 48 out of the groove
45 and allow the corresponding chamber 24 to be vented; and
simultaneously, the left hand group of plungers 50 are allowed to
move inwardly by the left hand conical camming surface of the
slider 44 and the plungers 50 are urged radially inwardly and
maintained in engagement with the slider 44 by the resilient O-ring
48 so as to allow the O-ring to seat into the groove 45 in a
valving action, thereby permitting substantial fluid pressure to be
confined in the chamber 22.
In order to explain the operation of the device, it may now be
assumed that chamber 24 is under pressure while chamber 22 is
vented and that the pressure supply be reversed. Thus, supply
opening 34 will be vented and opening 38 connected to the source of
pressurized air. Due to the pressure in channel 29, as compared to
the pressure in chamber 24 the sealing ring 48 for chamber 24 is
urged into the circumferential groove and prevents, at first,
venting of cylinder chamber 24 as it is expected to do.
Simultaneously, pressurized air will flow in passage 42 and into
chamber 22 lifting its O-ring 48 out of groove 45, and due to the
pressure differential across slider 44 the latter will move in a
direction toward chamber 24 and to the right in FIG. 1
substantially to the position illustrated so that its conical
surface urges the right hand plungers 50 outwardly toward chamber
24 for lifting sealing ring 48 in a cam-like action. This instant
is shown in FIG. 1, and FIG. 2 shows the deformation of the O-ring
under the action of the plungers 50. It will be seen that the empty
bores 46 adjacent each plunger are opened between passage 29 and
chamber 24. Thus, the check valve formed by the O-ring as the valve
member and groove 45 plus empty bores 46 as the valve seal has been
actuated to vent the respective cylinder chamber 24.
Because of the changed pressure conditions in the chambers 22 and
24, there is relative movement between the cylinder 10 and piston
rod 18 effectively enlarging chamber 22 and diminishing chamber 24
to produce desired movement between the chuck body and the jaw
actuating member of the power operated chuck. While pressure is
maintained in chamber 22, and chamber 24 is vented, the pressure
connections at ducts 34 and 38 may be reversed again so as to
pressurize the duct 34 and vent the duct 38. Application of
pressure at duct 34 causes pressure to be applied in the passage 29
and through the bores 46 and against the inside of the O-ring 48
which is disposed in the chamber 24, with the effect that the
pressurized air urges the O-ring 48 outwardly to allow the air
under pressure to be applied into chamber 24. Simultaneously, the
pressurized air from passage 29 is applied against the right hand
end of slider 44, tending to move the slider to the left.
Because duct 38 has been vented, passage 42 is also vented and the
air in passage 42 provides no resistance to the leftward movement
of slider 44, and, accordingly, the slider 44 moves to the left
until the slider is again stopped by the plungers 50. As the slider
moves to the left, the plungers 50, associated with the O-ring 48
of chamber 24, are urged radially inwardly toward tube 26 so as to
release the corresponding O-ring 48 and allow it to seat in the
groove 45 of chamber 24 whenever a sufficient buildup of pressure
in the chamber 24 stops the flow of air into this chamber. Because
of the leftward movement of slider 44, the plungers 50 associated
with chamber 22 and the corresponding O-ring 48 are urged radially
outwardly by the conical camming surface of the slider 44 so as to
release the air pressure in chamber 22 which has been trapped by
the valving action of the corresponding O-ring 48; and the air from
the chamber 22 is vented outwardly through passage 38. As the
pressure conditions in the chambers 22 and 24 are changing, with
the pressure increasing in chamber 24 and decreasing in chamber 22,
there will be relative movement between the cylinder 10 and the
piston rod 18 and an enlargement of the chamber 24 and a reduction
in the size of chamber 22 for operating the power chuck and
specifically the jaw actuating member thereof.
When this condition has occurred, then the pressure conditions at
ducts 34 and 38 may be reversed again to produce the operation
hereinbefore described when the duct 34 is vented and the duct 38
is pressurized.
It will be appreciated that the venting of either cylinder chamber
22 or 24 will be possible only in case no leakage has occurred in
the pressurized air supply conduits, because pressure in the
respective other channel will be required to actuate the slider 44.
If a pressure drop occurs due to a leakage, slider 44 will not be
moved and the sealing ring 48 subjected to the pressure in the
respective chamber will prevent venting thereof. Thus, even in case
of a sudden pressure drop there will be no risk that the chuck jaws
release the tool or blank during the operation of the machine.
In lieu of plungers 50, spheres or similar bodies may be used, and
the O-rings 48 may be replaced by other deformable resilient rings
such as flat rings, quad rings or sealing rings of other section
shape. An expert skilled in the art will readily be capable of
redesigning the axial support of the rings in accordance with the
section shape concerned.
The sliding motion of slider 44 is limited by a shoulder 52
bilaterally provided of the cylindrical central portion of the
slider, the shoulders serving as a stop means upon engagement at
the plungers. Other stop means, of course, may be provided, and
this will be compulsory if the plungers are replaced by
spheres.
It will be appreciated that the centrifugal force acting upon the
sealing rings will be negligible, and this will normally be assumed
for the plungers, too. In case of extremely high speed of the chuck
driven by the cylinder unit, the plungers may be replaced by link
systems in which the centrifugal force is counterbalanced; such
systems are known to experts skilled in the art.
It will be appreciated that a hollow spindle may readily be
disposed within the sleeve 26 extending through the entire length
of the cylinder unit, and this is a very desirable feature as
mentioned above. In such a design, the walls and diameters of the
piston rod would have to be adapted.
* * * * *