US2064235A - Packing - Google Patents

Description

Dec. 15, 1936. WHEELER 2,064,235

PACKING Filed March 21, 1952 2 Sheets-Sheet l I N VEN TOR.

Dec. 15, 1936. H. T. WHEELVER 2,064,235

PACKIN? Filed March 21, 1932 2 sheetsgsheyz INVENTOR.

Patented Dec. 15, 1936 11 Claims.

My invention relates to porous packing rings to be used in closing off the passage of fluid. under pressure from around a moving part. It is adapted for use in stuffing boxes around the moving shaft or rod, and on pistons working within a cylinder or other similar situations where the passage of the pressure fluid between the moving parts is to be sealed on.

It is an object of the invention to provide a packing of the character noted which is selfadjustable and adapted to be expanded to take up the Wear by the action of the pressure fluid.

I desire to eliminate the necessity of tightening a gland against the packing so as to increase the frictional contact of the packing with the adjacent wall.

I is a further object to provide a packing wherein the pressure fluid serves as a lubricant to prevent excessive friction along the moving part and to allow lubrication thereof.

I aim to cause the seepage flow of pressure fluid more strongly toward the moving part whereby lubrication can be more effectively accomplished and the heating and deterioration of the packing eliminated.

It is a further object to provide a durable and effective packing which wil stand up under heavy duty for long periods of time before removal is necessary.

Obviously a porous structure, packing for example, when sealing pressure must have the pores and interstices so regulated as to reduce the pressure to a required lower level, and within a certain length or that structure. It should also be apparent that the de ree of porosity must be regulated in some manner to accomplish this pressure reduction. The usual manner is by packing gland adjustment in which the tightening of the gland increases the frictional contact of the packing with the surface to be sealed. It is a method of manual operation, which, being subject to the opinion of the operator, productive of a wide range of results uniformly unsatisfactory and has given rise to many forms of non-adjustable packings which in turn has introduced still other undesirable troubles inherent with the type considered.

In the drawings herewith I have shown how my invention may be carried out with various types of packing ring constructions.

Fig. 1 indicates the various shapes of packing rings discussed in this specification.

Fig. 2 shows the possible cross-sections of the laminations of a stuffing-box ring.

Fig. 3 shows the possible cross-sections of the laminations or" a piston ring.

Fig. 4 represents the helical wound method of forming packing rings from the cross-sections of Figs. 2 and 3.

Fig. 5 represents the accordion base method of forming packing rings from the cross-sections of Figs. 2 and 3.

Fig. 6 is my fiuxion chart for denoting saturation. 10

Fig. '7 is my internal-pressure chart for denoting pressure drop and thrust.

Fig. 8 is a representation of the planes of saturation as governed by porosity and density of the porous structure.

Fig. 9 represents the phasing of the seepage flow of the examples of Fig. 8.

Fig. 10 represents the saturation planes of a uniform density ring.

Fig. 11 illustrates the saturation planes and seepage flow of my plan; construction.

Fig. 12 illustrates the saturation planes of my multiple fold construction.

Fig. 13 shows diagrammatically the of saturation in Fig. 10.

Fig. 14 illustrates the two-phasing of the saturation of Fig. 11.

Fig. 15 similarly shows the three-phasing of the saturation of Fig. 12.

Unquestionably, the single most important need of any set of packing is to protect it from accidental or intended excessive compression. Experience shows that a fabric packing is the tightest, holds the highest pressure without leakage and is easiest and cheapest to replace. The essence of my research on ways and means to offset mechanical compression, or excessive com pression, is that saturation automatically controlled by the pressure is an all sufficient agent for the purpose.

The feature of a packing which will equalize excessive compression I have found to lie in the manner of construction and to be independent of the shape, the width of the annular space and the contact length of the set. That is to say, the creation of elasticity by pressure is a matter of porosity incorporated during construction.

Referring now to Fig. l, cross-sections of annular ring packings, named from the faces exposed to the source of pressure: square (0.); cupped (b); V-shaped (c); conical (d); concave-cone (e); convex-cone (f); concave-convex (g); and frusto-conical (h). The first four shapes a, b, c, d have frequently appeared on 55 phasing the market. The last four e, j, g and h, have been created during various phases of. my research on saturation. The shape controls the amount of friction when properly related to the width of the annular space. Shape has nothing to do with the relation of elasticity due to pressure when opposed to mechanical compression.

Another important factor in designing porous packing structures is that there is a great difference between the use of a ring for stuffing-boxes and for piston rings. That is, a stuffing-box ring has the movable contact on the inner surface while a piston ring contact is at the outer periphery.

There is a considerable difference between the correct width of a ring for stuffingeboxeszand'for pistons. As tothe subject matter of this specification, the automatic control of elasticityby the ring construction, it may now be stated that differences of construction must be referred to the difference of application, as before considered. This is shown by Figs. 2 and 3, the former being stuffing-box cross-sections, while the latter are those of piston rings. In both figures the plane r is the rod or movable contact surface, while 3 is the box wall, or stationary surface.

Referring now to Fig. 2, form 7 is a quadrilateral representing a strip of cloth or an annular ring, there being no difference as to box or piston ring application. Form 7c is my plait construction. It should be noted that the open ends contact with the movable plane surface r. Form Z is the double plait, or a dual-fold. Form m is the three-fold, or triple plait. Form 11. is the four-fold or quadruple plait. Form is the five-fold or quintuple plait. Forms k, m and 0 have one more plait enclosure facim the movable plane 1 than those facing the stationary surface 8. Forms Z and n have equal openings on both surfaces. It should be apparent that the number of folds may be increased beyond five (form 0), the alternation of open ends recurring in even and odd numbers.

In Fig. 3, piston ring type, forms 9", l and n are necessarily the same as 9', Z, and n of Fig. 2. It is also noted that 7c, m and o are the reverse of the same plait form of Fig. 2. Forms 1 and :i may be the cross-section of a strip or of an annular ring, forms 70 and k may be a plait wound from a strip, an annular ring processed into a continuous plait, or a tube processed into a plait. Forms m, n, o, and m, n and 0' may be multiple folded strips of tubing processed.

There are two forms of ring construction which may result from using a strip or a plait; helically wound and a radial wrap. An annular ring can be radial only. Referring now to Fig. 4, p is a helically wound strip being the cross-sectional forms or a" of Figs. 2 and 3. q is the helically wound plait using form 70 of Fig. 2, while t is the helically wound strip employing the form I or Z section. Forms m, n, and 0 may be similarly treated.

The form of packing ring shown in Fig. 4, which I call my helically wound plait, is one preferred form of the invention, particularly as to the embodiments q and t. In these two forms the strip of porous packing material is folded on itself as shown at k in Fig. 3. The packing strip is then wound into helical form and compressed, when thus wound, into a frusto-conical ring. It will be noted that the open ends of the fold are toward the inner side adjacent the rod so at the circulation of the pressure fluid will be more strongly toward the interior face of the packing adjacent the rod about which the seal is to be preserved.

In the embodiment shown at t the same general construction is shown, except that the packing strip is folded as shown at l in Fig. 3, making the packing ring available for use either in connection with a moving rod in a stuffingbox, or upon the outer surface of the moving part adjacent the wall of a cylinder or box, the arrangement of the open sides of the folds being presented uniformly in both directions.

Fig. shows radial lapped types, u being of .the cross-section m, while u is of the form 0.

It should be obvious that any section of Fig. 2 or '3 may be radially wound and lapped.

Great care is taken in manufacturing machinery to insure the uniformity of all of the materials except packing, apparently the belief being that packing is of little importance. Yet such a porous structure of a fragile composition stands more abuse in proportion to its strength than any other material.

From tests made upon various forms of pack ing, I have obtained data shown on the fluxion chart disclosed in Fig. 6, the abcissas being in terms of impressed pressure 0 to P of the pressure fluid, the ordinates in measured friction upon the moving part. The upper curve is an example of a 45 degree cone packing set, every ring alike in porosity. The initial set friction is the friction rising proportionally with the pressure along line e a then decreasing along line a d h, the friction increasing during pressure, the decrease being due to saturation. The value h f is hysteresis, or friction due to the time lag necessary for the fluid medium to drain out of the structure after the pressure is released. The relation 20 (1 over p e is the fiuxion value, being greater than unity and denoting reflux action.

The lower curve was obtained from the same packing arranged according to graduated porosities, the amount of friction being greatly reduced as evidenced by the moderate rise along line a: n b and the decrease b m 1/. Both the hysteresis y x and the fiuxion relation p m plus 10 n are less than those of the upper curve.

In Fig. 7 is shown an internal pressure chart compiled from data obtained from tests, the abcissas in length of the packing set, 0 to L,

the ordinates in internal pressure, P being the pressure impressed. The actual curves of an example packing are given as r, c, and s, at the movable surface, the center of a ring and the stationary surface respectively. At any point in the length, such as l, the ordinate intersects the three curves at three different internal pressures. As the internal pressure is governed by the rate of seepage flow which inturn is governed by the degree of porosity, it should therefore be obvious that at the same distance from the source of the impressed pressure, at various distances from the movable surface, the rate of seepage flow is shown by the internal pressure curves of Fig. 7. Therefore, when any point in the length is considered, the relations of seepage flow at various points in the annular space are termed phase relations or phasing.

Referring to Fig. 8 in the diagram :0 represents the laminations of a 45 degree cone, either a helical wind or a radial wrap, the greatest density at the smaller diameter, or movable surface r, the wall surface being 8. The density relation is represented by the varying crosshatching, close lines for greater density. As

before mentioned the seepage flow is inversely proportional to the degree of porosity, therefore adjacent to surface r the small dotted lines indicate the greatest flow and the least internal pressure. The field of flux, or the planes of seepage flow are present at all points of the annular space for all porosities greater than zero and will hereafter be represented by dotted lines in the direction of flow.

The flow across the laminations and in the direction of pressure is called straight-line flow and occurs under constant pressure. The hardest test for. packing occurs under intermittent impressed pressure which creates in addition to straight-line flow, a cross-flow, or drainage from the denser portions toward the lighter, as indicated by the heavy arrows between laminations not joined by folds. As the cross-flow is toward the outer diameter, the inner-density ring should be used for pistons only, the movable surface being the ring traveling against a cylinder wall.

The diagram 1 of Fig. 8 represents a uniform density ring, the seepage flow at surfaces 1 and s being equal, therefore the field of fiux is uniform as shown. Under intermittent pressure there is no cross-flow. This type may therefore be interchangeably used for pistons or stuffing-boxes.

The diagram 2 of Fig. 8 represents a 45 degree cone, my annular ring construction, be-

fore mentioned. In keeping with the distribution of porosity, this is properly denoted a stuffing-box ring, the movable surface 1 being the rod inside of the ring, the stationary surface s to the outside, or the box wall. The field of flux is densest at the inner diameter due to the greater degree of porosity. The cross-flow due to intermittent pressure is toward the inner surfaces.

The phasing of seepage flow affects the lubrication of the movable surface and furnishes fluid medium to maintain a seal against the wall, the requirements of the latter surface being much less than that of the movable. It is particularly desirable to cause a fiow of the seepage toward the moving surface for purposes of lubrication. The importance of phasing is further emphasized by the diagrams of Fig. 9. Diagram :13 corresponds to r of Fig. 8, the curve being the seepage fiow at plane 0 of the former figure, during a single impression of pressure. In like manner, the curves 1, a, b and .9 correspond to the planes so designated. The interpretation is, that at a point I of Fig. '7, the flow at r precedes that of c, and s is later than the latter. The method shown is diagrammatic, to no scale of actual flow or of the degree of porosity of the material.

Diagram 11' of Fig. 9 corresponds to y of Fig. 8. As the field of fiux is uniform the points r, c and s are in phase and their variations coincident.

Diagram 2' of Fig. 9, corresponding to z of Fig. 8 corresponds to a." in appearance but is oppositely interpreted due to the reversal of porosities. Curves 1' and a precede 0 under a single impression of pressure, while b and 8 follow 0.

In conclusion, a variable porosity causes flow relations out of phase in a degree in direct relation to the arrangement of the porosity.

Figs. 10, 11 and 12 are comparisons of uniform density packing with the fold of the plait form. Fig. 10 is a reiteration of diagram :1 of Fig. 8, the movable surface 1 being interchangeable with the stationary surface s.

Fig. 11 represents two sections of a helically wound or a radial wrapped plait, the open edges adjacent to the movable surface 1", the folds touching the stationary surface s. For simplicity all of the laminations adjacent to the folds are considered of uniform density. By the method of internal-pressure indications I have discovered that a fold of fabric joining two parallel laminations reduces the porosity to a high degree at the point of fold. The saturation at such a point is therefore high and causes a slow seep-.

age and a high local internal pressure. This I have discovered is the basis for perfecting packing rings of a high efliciency at the movable surface and for augmenting the available fluid medium at the stationary surface, referring especially to the pressure holding capability of the annular wedge ring as detailed in my application Serial Number 580,015, filed Dec. 10, 1931, now Patent No. 1,989,903, dated February 5, 1935.

The folded ring of frusto-conical shape is the form constituting my main improvement herein. In operation against intermittent pressure, the combination of a high saturation at the fold contiguous to the stationary surface, with open ends contacting with the movable surface is a considerable improvement, as the wall seal is maintained at a constant value, while the seepage may flow into and out of the folds from the movable surface as indicated by the two-way arrows. There is also a cross-flow between adjacent fold assemblies as indicated by the single arrows.

It is to be noted particularly with reference to Figs. 11 and 12, that the pressure fluid normally moves in a direction parallel to the shaft and along the surface 1. In engaging the inclined surface of the ring there is a component of the force which is perpendicular to! the surface of the packing material and another at right angles thereto and directed inwardly toward the shaft. Furthermore, pressure fluid engaging between the folds of each strip of packing material will find a partial exit around the open side of the fold adjacent the shaft or rod.

Also, the spaces between adjacent windings or rings of the packing material will be shut off on the folded portion of the packing ring more strongly than it is on the open side, and there will, therefore, be an obvious movement of the pressure fluid toward the side 1" of the packing in Fig. 11.

This circulation will provide a film of fluid adjacent the shaft 2 where the packing is employed to resist the passage of gas. I have found 1 that with this type of packing wear along the surface of the moving parts is largely eliminated, there being a very apparent lubrication of the packing strip adjacent the open side, and that instead of heating up as is done where friction is excessive, the packing remains comparatively cool and does not deteriorate. This same action is obtained in the Fig. 12 embodiment, as will be obvious on examination of that figure.

Fig. 12 is an example of the multiple plait, or accordion type of ring, the stationary surface 3 being contiguous to the greatest number of folds, the movable surface r being in contact with the greatest number of open ends. The field of flux by this arrangement causes a high local pressure at the wall, yet increases the available fluid medium at the movable surface, the greatest flow being through the center, as at c. This type, fittingly called the accordion, operates like a bellows, expanding and contracting against the ends of the stuffing-box and is very sensitive to change of pressure. The same comment may be made of the multiple plaits of Figs. 2 and 3, the number of folds and their relative positions determining their efficiency and the uses to which they should be put.

Fig. 13 illustrates the phasing of Fig. for two consecutive impressions of pressure, the curves 1", s and 0 being coincident, and in phase.

Fig. 14 illustrates the phasing of Fig. 11, the curves (0) 7 based on the same planes of the latter figure being in phase. However, curve 8 is retarded due to the highly saturated flux field in the folds.

Fig. illustrates the phasing of the multiple plait, or accordion, of Fig. 12, the curve 0, due tosuccessive impressions of pressure, corresponding to the same plane of the latter figure. Curve 1" is retarded due to the introduction of a fold at the movable surface while .9 is further retarded by the dually connected folds.

In the use of my packing it will be obvious that the same may be used to seal off the passage of fluid on the inner side of the ring or the outer side of the ring, and in either case the open side of the fold should be presented toward the surface along which movement takes place. When used in the stuffing-box about a rod or shaft, the open sides of the fold are presented inwardly. When used on a piston or other reciprocating member the open side of the fold is presented outwardly toward, the interior surface of the cylinder.

By using this type of packing member in the situation described, the seepage flow through the packing will have the effect of tending to straighten the packing ring into a radial position rather than in the inclined or frusto-conical form shown in Figs. 15 and 16. This will tend to tighten the packing against the moving part and the result will be an automatically expanding packing.

As wear occurs, the packing will still hold against the moving part and a seal will be maintained along that surface due to the seepage of pressure fluid toward the open side of the fold where the fluid tends to prevent excessive friction and acts as a lubricant.

I have, therefore. a packing which may be called a/ self-expanding packing which does not need adjustment after it has been placed in position, and it is to be observed that when adjusted in position the pressure of the gland or the sides of the box need not be heavy. The seal will be maintained largely in response to the pressure of the fluid against which the packing is to seal. The packing will be durable for long periods due to the absence of excessive friction, and to the lubrication maintained along the moving surface, due to the structure of the ring itself. i

The advantages of this construction will be obvious.

I claim:-

1. A packing ring comprising a strip of porous material folded longitudinally and formed into frusto-conical ring shape, one side of the folded strip being open and presented toward the source of fluid pressure.

2. A packing ring comprising a strip of porous material folded longitudinally, said material being compressed adjacent the fold, the side opposite the fold being open, said strip being formed into annular frusto-conical shape.

3. A packing ring comprising a strip of porous material folded longitudinally, said material being compressed adjacent the fold, the side opposite the fold being open, said strip being formed into annular frusto-conical shape with the folded edge of the strip presented away from the moving surface.

4. A packing ring comprising a strip of porous packing material folded longitudinally in folds of equal width and formed into annular shape with the majority of the folds opening toward the moving surface which is to be sealed.

5. A packing ring comprising a strip of porous packing material folded longitudinally and formed into annular frusto-conical shape with the majority, of the folds opening toward the moving surface which is to be sealed.

6. A ring for sealing off the space between moving and stationary cylindrical surfaces comprising a strip of porous material folded longitudinally to form folds of equal width and fitted into said space with the folds lying in planes inclined from the outer edge toward the source of pressure and with the open side of the fold presented toward the moving surface of contact.

'7. A ring for sealing off the space between moving and stationary cylindrical surfaces comprising a strip of porous material folded longitudinally and one edge of which is compressed more than the other, said compressed edge being presented away from the moving surface of contact.

8. A frusto-conical shaped packing ring, for sealing between a stationary and a moving member, made of porous material folded longitudinally and wound into helical shape with the adjacent sides of the folds in contact with each other, the space between the folds that open toward the moving member being presented to receive the pressure fluid to be sealed against.

9. A frusto-conical shaped packing ring, for sealing between a stationary and a moving member, made of porous material adapted to allow seepage therethrough, said material being folded longitudinally and wound into helical shape with the adjacent sides of the folds in contact with each other and the open portion of the fold being presented toward the moving surface.

10. A packing ring composed of an elongated parallelogram of flexible material folded once longitudinally midway of its Width and of frustoconical ring shape.

11. A self-adjusting packing ring comprising a strip of porous material folded longitudinally with the adjacent sides of the folds parallel and uncemented so as to receive fluid between said folds, said folded strip being formed into a ring of frusto-conical shape, the open sides'of said folds being presented toward the moving surface, the outer and inner edges of said folds lying in parallel cylindrical surfaces.

HARLEY T. WHEELER.

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