AU483473B2 - Lubricating means for gas-operated cylinders - Google Patents

Description

1 0,8 38 a This invention relates to fluid cylinders, piston- and, more specifically, to means for lubricating under pressure cylinder units of the type operated by gas

in a closed fluid system.

In metal die forming operations it is common of the die members practice to yieldably restrain movement

by means of fluid springs. Frequently such fluid springs

to a reservoir comprise piston-cylinder units connected ith such closed of gas under pressure, such as nitrogen. contain a lubri- pressure systems the gas itself does not piston-cylinder cant, as is the case with systems wherein by a com- units are operated by pressurized air supplied with lubricators. pressor and the air lines are equipped to which the Thus, in closed type systems of the type reduce wear and present invention relates, in order to are provided minimize service problems auxiliary means piston and to lubricate the surfaces of the cylinder,

piston rod which are in sliding contact. primary ob- The present invention has for its arrangement ject the provision of a novel lubricating by non-lubricated for such piston-cylinder units operated

gas under pressure.

483.473

10,8 38 M~ore specifically, the present invention con-

templates the provision of an air passageway to the

cylinder chamber on the side of the piston opposite that

to which gas under pressure is supplied and a lubricant-

impregnated material in said passageway through which the

air flows. When the piston moves in the cylinder in a

direction tending to create a negative pressure in said

cylinder chamber, air is drawn through the passageway

and lubricant becomes entrained therein so that the air!

lubricant mixture flowing into the cylinder provides

adequate lubrication for the surfaces of the piston,

piston rod and cylinder which are in sliding contact.

The arrangement of this invention also contemplates a.

means for prolonging the supply of lubricant to a

lubricant-impregnated piston ring, such as is conven-

tionally employed in such cylinders.

other objects and features of the present

invention will become apparent from the following 0f fw0 eA~C/6/o7, :ec2 description ~an~d accompanying drawings, re 14;e- e in which:

FIGURE 1 is a fragmentary vertical sectional

view of a fluid cylinder according to the present inven-

tion taken along the line 1-1 in FIG. 2 and illustrating

the manner in which it is utilized in a die assembly;

FIGURE 2 is a top view of the cylinder shown

in FIG. 1;

4 83.4 7 3

O8 38 j FIGURE 3 is a sectional view along the line 3-3

in FIG. 1;

FIGURE 4 -is a perspective view of the disc uti-

lized in the check valves employed in the c ylinder;

FIGURE 5 is a fragmentary sectional view illus-

trating on an enlarged scale a portion of the arrangement

shown in FIG. 1;

FIGURE 6 is a fragmentary sectional view taken

along the line 6-6 in FIG. 2;

FIGURE 7 is a fragmentary view, with parts

broken away, of the cylinder cap as viewed from the under

side thereof; and

FIGURE 8 is a sectional view along the line.8-8

in FIG. 1.

0-

Referring to FIG. 1, there is illustrated a

fluid spring generally designated 10 in the form of a

piston-cylinder unit according to the present invention

which is arranged between a vertically movable die member

12 and a fixed support 14, which in the illustrated ar-

rangement comprises a manifold plate. The overall ar-

rangement shown in FIG. 1 is generally similar to that

illustrated in m7y epending applieatien Serial Ne,. -6-7~84- .Lhepistoncylinder unit 10 comprises. a cylin-

der 16 which is mounted as by axially spaced rubber

483.4 73

1 0,8 3 8 j rings 18 in an outer cylindrical sleeve 20. Cylinder 16 is secured in sleeve 20 by means of a threaded clamping

ring 22 which urges a metal washer 24 downwardly against

the upper rubber ring 18. The two rings 18 are separated

by a flange 26 on cylinder 16 and the lower ring 18 is seated on a radially inwardly extending shoulder 28 on sleeve 20. Sleeve 20 is threaded, as at 30, into a bore

32 formed in manifold plate 14. A passageway 34 connects bore 32 and thus the lower opened end 36 of cylinder 16 with a reservoir 38 containing a.gas (such as nitrogen) under a predetermined high pressure. The arrangement of cylinder 16 in sleeve 20 permits the cylinder to tilt

slightly relative to the central vertical axis of sleeve

in the event that the direction of movement of die

member 12 is slightly inclined to the central axis of cylinder 16. This general arrangement is completely te 65. described in foresaid

Within cylinder 16 there is'arranged a piston

to which a rod 42 is fixedly connected. Rod 42 extends upwardly through a cylinder cap 44. Piston 40 divides the interior of the cylinder into a pressure chamber 46 and an atmosphere or idle chamber 48. Piston 40 is seal- ed in cylinder 16 by means of a conventional annular seal formed of an elastomer. The piston is also provided

with a fiber wear ring 52 and a lubricant-impregnated felt ring 54.

483,4 73

1 0,838 Cap 44 is preferably formed of a metal (such

as aluminum) which is a good conductor of heat. It is

secured to the upper end of cylinder 16 as by a plural-

ity of screws 56 (FIG. Around its periphery and on

the top side thereof cap 44 is formed with a plurality

of fins such as indicated at 58. Fins 58 assist in main-

taining the piston-cylinder unit at a desired low operat-

ing temperature. It will be observed that cap 44 extends

radially outwardly beyond and overhangs the upper end of

cylinder 16. The lower end of cap 44 is centrally bored

as at 60 so as to be telescopically received over the

upper end of cylinder 16. The upper portion of bore

is radially enlarged as at 62 to define an annular

passageway 64 between the outer periphery of cylinder 16

and the inner periphery of cap 44.

As is illustrated in FIGS. 1 and 5, passageway

64 is of generally rectangular cross section. A plural-

ity of radial openings 66 in cap 44 establish communica-

tion between annular passageway 64 and the surrounding

atmosphere. Openings 66 are located between a pair of

adjacent fins 58 so as to be generally shielded from oil,

dirt and other foreign matter which is usually present

around dies. Within passageway 64 there is arranged a

member 68 which is impregnated with a lubricant such as

oil. Member 68 preferably comprises a fibrous material

483,4 73

10,838n-6 (such as felt or the like) enclosed within a screen

cloth mesh. It will be noted that annular member 68

has a vertical dimension substantially less than that

of passageway 64. Furthermore, as shown in FIG. 3, the

oil-impregnated member 68 does not extend completely

around passageway 64; its opposed ends are spaced apart

circumferentially to provide an air space 70 therebetween

which is in communication with one of the radial openings

66.

ithin the upper end of cylinder 16 there is

arranged an inlet valve 72 and an outlet valve 74. These

valves are unidirectional check valves and are oppositely

oriented so that valve 72 only permits the ingress ofair

to chamber 48 and valve 74 only permits the egress of air

from chamber 48. Each of these valves are of similar

construction and include a light-weight movable valve

disc 76 of cruciform shape. A disc 76 is located at the

lower end of valve 72 and a similar disc 76 is located

at the upper end of valve 74. Discs 76 or equivalent

members are employed for unidirectional air flow through

the valves in the manner of a conventional check valve.

A clearance space 78 is machined on the underside of cap

44 adjacent inlet valve 72 so that the air in annular

passageway 64 above the lubricant-impregnated member can

flow into chamber 48 through valve 72. An opening 80 in

4 83.4 7 3

10,8 38 a passageway of cap 44 registers axially with the central from chamber 48. valve 74 to permit the exhaust of air in the cylinder The free end of piston rod 42 is guided sealing lip 84 by a nylon bushing 82 formed with a'wiper

at its upper end. In the arrangement illustrated, if

be omitted and air desired, exhaust check valve 74 ray through an axial permitted to escape from chamber 48

groove 86 in bushing 82 (FIG. 3).

with a Piston 40 and piston rod 42 are formed is threaded at central axially extending bore 82 which by a plug the free end of the piston rod and closed the plane of the Bore 88 extends downwardly to at least with the annular felt wiper ring 54 and communicates means of a pair of groove in which ring 54 is seated by 1 and Bore radially extending passageways 92 (FIGS. with an oil- 88 and radial passageways 92 are filled

impregnated fibrous wick material 94. illustrated The operation of the arrangement 42 abuts is clear. As shown, the free end of piston rod is urged upwardly the bottom face of die member 12 and pressure in cham- thereagainst by reason of the gaseous 34 with reservoir ber 46 which is connected by passageway

38. As-die member 12 descends it causes piston 40 to

increasing the pres- move downwardly in cylinder 16, thus evacuate chamber 48. sure in chamber 46 and tending to

4 8 3.4 73

1 0,8 3 8iz The tendency to create a negative pressure in chamber 48

causes air to be drawn into passageway 64 through open-

ings 66, The bulk of this air will flow upwardly through

the oil-impregnated member 68 and around passageway 64 to

inlet check valve 72. Since the pressure in chamber 48

is less than in passageway 64, disc 76 assumes the posi-

tion illustrated in FIGS. 1 and 5 to allow air from

passageway 64 to flow through valve 72 and into chamber

48. As this air flows upwardly through member 68 oil is

entrained therein and flows into chamber 48 along with

the air. The oil entrained in the air thus lubricates

and reduces wear on piston rod 42, the inner wall of

cylinder 16 and the bore of bushing 82. In turn.this, will assure concentricity of the piston and piston rod

within the cylinder.

As die member 12 moves upwardly the pressure

of the gas in chamber 46 causes piston 40 to move upward-

ly, thus ensmalling chamber 48 and causing the air to be

discharged therefrom through exhaust valve 74. Since at this time the pressure in chamber 48 is greater than at-

mospheric, valve disc 76 of valve 72 is urged upwardly to

block the passageway in valve 72 and the valve disc 76 of

valve 74 is urged upwardly to permit the escape of air

from chamber 48. As pointed out previously, if desired,

the air exhaust passageway from chamber 48 may be provided

4.8 3.4 73

1 0,8 3 8 a simply by the shallow groove 86 in bushing 82. In this event the sealing lip 84 at the upper end of bushing 82

will serve to prevent the ingress of a substantial amount

of air to chamber 48 through passageway 86 when piston

descends in the cylinder.

The air gap 70 illustrated in FIG. 3 (which is

defined by the space between the ends of member 68) is

provided as a precautionary measure to assure the free

flow of air into chamber 48 in the event that the oil-

impregnated member 68 should become clogged. However, it will be noted that the provision of cap 44 and the

location of passageway 64 and the inlet openings 66 are

designed to prevent oil, dirt, grease and other foreign

matter which are invariably present around dies from

being drawn into passageway 64. It will also be apparent

from the foregoing description that the oil-impregnated

wick member 94 provides a prolonged supply of oil to the

felt ring 54 which eliminates the necessity of frequent

servicing and replacement of ring 54. However, servicing

of cylinder 16 is relatively simple since the valves and

the oil-impregnated member 68 are readily accessible by

loosening screws 56 and removing cap 44 from the upper

end of the cylinder.

483.4 73

Claims (1)

1 0,8 3 8 j

The claims defining the invention are as follows:

i.

In combination a cylinder, a piston movable axially in the cylinder and'dividing the cylinder into a working chamber and an idle chamber which vary in- versely in size in accordance with movement of the piston axially in the cylinder, means for directing a pressurized gaseous medium into and out of said working chamber, a passageway for directing air from the sur- rounding atmosphere into said idle chamber, and air permeable means in said passageway impregnated with a lubricant, said air permeable means being disposed so- that air flowing through-said passageway is directed into intimate contact with said lubricant to entrain the lubricant in said air, whereby said piston and the internal walls of said idle chamber are lubricated by the lubricant entrained in the air flowing into said idle chamber.

2. The combination called for in claim 1 includ- ing a second passageway for exhausting air from said idle chamber.

483.4 73

1 0,8 3 8

3. The combination called for in claim 1 includ-

ing orifice means connecting and passageway and said idle chamber to permit the flow of air into said idle

chamber in response to a pressure differential in said

passageway resulting from enlarging of the idle chamber

as the piston moves toward the end of the cylinder constituting

the working chamber

4. The combination called for in claim 1 wherein said air permeable means comprises a porous wick.

The combination called for in claim 4 wherein

said wick is impregnated with oil.

6. The combination called for in claim 1 wherein

said passageway extends circumferentially around said

cylinder.

7. The combination called for in claim 6 including a

plurality of circumferentially spaced openings in said passageway communicating with the surrounding

atmosphere exteriorly of said cylinder.

483.4 73

1 0838

8.

The combination called for in claim 7 wherein

said air permeable means extends throughout at least a

major extent of the circumferentially extending portion

of the passageway.

9.

The combination called for in claim 8 wherein

said air permeable means has circumferentially spaced

parted ends, one of said openings registering with the

space between said parted ends, said space communicat-

ing directly with said idle chamber rather than through

said lubricant-impregnated means.

The combination called for in claim 1 includ-

ing a piston rod connected to said piston and extending

axially through said idle chamber, means defining a wall

adjacent the end of the idle chamber opposite the piston,

said end wall having a bore therein, said piston rod ex-

tending through said bore with a close fit whereby the

oil/air mixture in said idle chamber lubricates said

piston rod and bore.

48 3,4 73

10,8388 11.

The combination called for in claim 1 includ-

ing a unidirectional valve in said passageway for

admitting air to said idle chamber.

12.

The combination called for in claim 11 includ-

ing a second unidirectional valve for permitting air to

escape from said chamber in response to contraction in

size of the idle chamber as a result of axial movement

of said piston in said cylinder.

13.

The combination called for in claim 11 includ-

ing an exhaust passageway extending from said idle cham-

ber to the surrounding air, said exhaust passageway

being restricted to minimize the flow of air into said

idle chamber through said exhaust passageway.

14.

The combination called for in claim 10 includ-

ing a central bore extending axially in said piston rod,

a lubricant-impregnated material in said bore, said piston

having a lubricant-impregnated ring extending circumferen-

tially around the piston and engaging the side wall of the

cylinder, and means forming a radially extending passage-

way establishing communication betw.,en said central bore

and said ring.

483.4 73

1 0.838 a

The combination called for in claim 14 includ-

ing a lubricant-impregnated material in said radially extending passageway.

16.

The combination called for in claim 1 includ-

ing a piston rod connected to said piston and extending axially through said idle chamber and the adjacent end of the cylinder, an annular cap on said end of the cylin- der through which the piston rod-extends, said cap having a peripheral skirt which extends circumferentially around and overhangs the outer periphery of said cylinder at said one end thereof, said passageway being defined at least in part by said overhanging skirt.

17.

The combination called for in claim 16 wherein

said passageway extends circumferentially around the cylinder within the axial extent of the overhanging skirt.

48 3.4 73

1 0,838z6

18.

The combination called for in claim 17 wherein

the circumferentially extending portion of said passage-

way extends axially in a direction toward said end of

the cylinder, said passageway then extending radially in-

wardly beyond the inner periphery of the cylinder wall

and then axially toward said piston into said idle cham-

ber.

19.

The combination called,for in claim 18 wherein

said oil-impregnated material is disposed in the circum-

ferentially extending portion of said passageway.

Dated: 30th January, 1976 PHILLIPS ORI,.ONDE AIID FITZPATRICK Attorneys for: BERi'NARD JOSEPH UALLIS

16 4 8 3.4 7 3

1 0,8384o~

Fi&.I

483,4 73

1O0,838jz6

4 1

W6 Fie,. 4

4 8.3.4 7 3

10,8 38 fu

78 F

64

7Z

I, 4

91

21 483.4 73