US 2134324 A
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Description (OCR text may contain errors)
Oct. 25, 1938. NI BRACKETT 2,134,324
DRY GRAPHITE LUBRICATED FABRIC PACKING Filed D60. 14,1957
Patented Oct. 25, 1938 DRY GRAPHITE LUBRICATED FABRIC PACKING Newell Brackett, Philadelphia, Pa.
Application December 14, 1937, Serial No. 179,762
This invention relates to improvements in packing and more particularly to what may be called dry-graphite lubricated and metalized fabric and semi-metallic fabric packing.
Conventional fabric packings or semi-metallic fabric packings, as used commercially, generally consist of certain fabric fibers such as flax, jute,
cotton, asbestos and others, spun; twisted or Said packings, furthermore, are frequently armored or combined with various metals such as lead, copper, aluminum, etc., to further reduce friction and give a full metallic or semi-metallic wearing face on the moving parts. The method for combining the metal with the other ingredients usually involves a process of wrapping, twisting, or interbraiding the metal in the form of foil or wire, to produce the metallic or semimetallic wearing face.
The objection to such packings is that the greases or other lubricating compounds will, under certain conditions and low temperatures, soften or melt and run out.or be squeezed out of the packing under compression and under continued wear. Thus the packing "does not retain its original characteristics and after a certain interval becomes unsuited for its purpose.
One objectof the present invention is to provide an improved method and the product resulting therefrom, in which more or less of an antifriction metal and a dry lubricant are introduced into a packing, which lubricant will not melt, squeeze out or be forced out under compression and continued use.
In carrying out the invention the packing is impregnated -with graphite and anti-friction metal in finely divided form, together with a suitable binder. A small strand is used, preferably of flax, although jute, cotton, asbestos fiber and other suitable fabrics may be used.
As contributory to the general object, therefore, the invention has as a further object, the provision of a packing made up of flax strands or yarn or other fibrous strands, each of which is thoroughly coated and more or less-impregnated with graphite and powdered metal. small diameter of the strands, the amount of graphite and metal in the packing may be considerably greater than would be the case with strands of larger diameter, and, furthermore,
Due to the said graphite and metal is more uniformly distributed throughout the entire packing. In other words, the effect is that of a thorough impregnaby twisting, wrapping, braiding or weaving, the
pulverized metal that is used may be sprayed, forced or otherwise applied onto and between the fibers, in combination with a binder which permits the small particles to adhere to said fibers and form a metallic or semi-metallic wearing face in the finished packing. It is another ob ject of the invention to provide an improved product made in this manner.
An additional object is to provide in the combination, a suitable binder which may consist of a rubber compound, various types of cement of a compound of such ingredients, preferably one which can be vulcanized and produce a product suitable for use to seal against leakage of water, steam, air, gases, petroleum products,
Before describing apparatus suitable for car rying out the process, the latter is outlined briefly as follows. The flax, asbestos, or other strands are drawn off of suitable supports such as reels and have a binder and vulcanizing agent applied thereto, preferably while separated from each other, hereinafter described more in detail. The strands are then run through small particles of anti-friction metal such as lead and graphite i. e. atomized or powdered lead pre-mixed with graphite. Said strands are then preferably twisted to form a single multiple-ply roving after which the same are wound onbobbins and used in a braiding machine to form a braided product. The braiding operation builds up a packing of the desired cross-section, usually square, but in some cases round, after which said packing is then preferably passed through a receptacle, where an additional binder and an extra coating of graphite and powdered metal are applied to the surface. At this point the packing may be run through rollersto square it more accurately, which operation compresses it more or less a: may be desired. It is thereafter vulcanized. Following this step it may be given a final die or roller operation to insure an accurate'crosssectional outline. The packing may, if desired, be vulcanized before squaring it through rollers.
In the accompanying drawing there is' illustrated diagrammatically, apparatus for carrying out the above described process and illustrating also the product in more than one form.
Fig. 1 is a top plan view, somewhat diagram matic, of devices for successively performing the steps described;
Fig. 2 is an elevation of the same;
Fig. 3 is an elevation of a perforated plate;
Fig. 4 is a perspective view of the finished I packing in one form;
Fig. 5 is a perspective view of a length of said packing coiled for packing and shipment;
Fig. 6 is a side elevationof an individual ring or split ring out from a length of packing and bent to circular form; and
Fig.7 is a perspective view of a modification.
As shown in Figs. 1 and 2, a suitable rack or frame H is provided having a number of reels l2 mounted thereon. There may be anywhere from about ten to thirty-five such reels, although these limits may be varied and the number depends on the product desired. These flax strands or asbestos or other fibrous strands are drawn continuously past guides l3, into and through a container ll and under a roller 15, the latter being submerged in a suitable binder and vulcanizing agent which is preferably rubber, natural or synthetic, among which may be mentioned the commercial product Neoprene.
rawn through a receptacle I 4 in a separated or spread out arrangement, to insure a thorough impregnation thereof. As the strands leave said receptacle they pass adevice for wiping off or removing the surplus binder, as for example rollers I6, constituting a squeegee. Said strands then pass over a guide I! which keeps them separated, and down into and through a second receptacle l8 and under the roller [9 therein. Said receptacle contains a dry lubricant such as graphite and anti-friction metal in finely divided form. For example, the mixture may consist of atomized or powdered lead premixed .with graphite. The proportions in one instance might be one part of lead by volume to five parts or less of graphite. More or less lead may be used and in fact the lead content may be reduced or substantially eliminated in some cases, but it is preferable to use some lead as it seems to protect the flax or asbestos from wear, in addition to its other well known advantages as a friction reducing packing ingredient. The preliminary application of the binder causes the graphite and powdered metal to adhere satisfactorily to the strands. The latter, before leaving the receptacle, pass through a perforated plate" which evenly spaces the strands in a concentric arrangement whereby they may be later twisted together in an even manner andare then brought together by being passed through an opening 2| in the wall of said receptacle after which they passthrough a rotating, twisting device 22. By
passing said strands through the perforated plate and the small opening 2 I, the excess graphite and atomized lead are prevented from being shaken off or thrown off during the twisting operation and the result is that more of these ingredients are incorporated into the braid than would other wise be the case, and there is more metal on the face of the packing when it is finished. The twisted strands form a single multiple-ply rope, the number depending on the desired size of packing. For example, about fourteen or'fifteen flax strands would be twisted together to make each of the composite flax strands used in forming a ,4; inch square flax packing. For a one inch flax packing about thirty-five strands per rope would be used. braiding, have been twisted preferably two or Said strands are Said 'twisted strands, before three turns per foot and half of said strands are twisted in one direction and the other half in the other direction.
From the twisting device, the composite, twisted strands are wound on a suitable bobbin 23. The bobbins are those suitable for use in a braiding machine, indicated diagrammatically at 24. Eight bobbins are ordinarily used in such machines for a square product, in addition to providing a center and four corner cores. the bobbins have the strands on them twisted in one direction and the other four in the opposite "direction. The cores are formed by combining together some of the same strands mentioned above or other similar strands. The ropes or strands are braided about the corner cores 25 and the center core 26 in the conventional manner.
After braiding, the binder is again applied in a receptacle 2'], similar to the one previously described, and an extra coating of graphite and lead, preferably 50-50 by volume, is applied to the surface in a receptacle 28, similar in general to the one previously described. At this point the packing may be passed between rollers of conventional design (not shown) to square it more. accurately or change its cross-sectional dimensions, which step compresses it more or less, after which it is vulcanized in any conventional vulcanizing apparatus 29, using a suitable source of heat 30. The rubber compound used is such as to permit vulcanizing preferably at the lowest Four of possible temperature to prevent possible damage to fibers which char at low temperatures. Maximum heat resistance is alsogiven to the product as well as resistance to the deteriorating effects of oil.
As a final step the packing may be given a die .or roller operation to insure accurate dimennecessary to control the leakage if any exists. It
can readily be bent into coils such as shown at 32 in Fig. 5, or cut up and bent into rings 33, as shown in Fig. 6 and installed in the usual manner, although it is preferable and customary to coil braided packings as a flat spiral, known to the trade as a coil. A further important advantage is that packing rings when formed of this material return to their original size approximately, when compression thereon is relaxed. For example, where the packing is applied to propeller shafts on ships and on centrifugal pumps in service generally, a certain small leakage is desired to lubricate the packing. On shut downs, as where the ship is docked, leakage can be stopped by gland adjustment. Upon further operation, the glands are slackened off and thedesired leakage obtained without adversely affecting the packing. Y
Where conventional flax packings are used, the lubricants may consist of tallow, Japan wax, parafiin wax, lubricating oils, etc., which melt at low temperatures and run out of the box, making it necessary to adjust the glands to compensate for this loss. Packings th deficient} in lubrication cause unn Iric on and wear of the shafts, as the fiber itself without lubrication will score the shaft. It is also necessary in certain cases to add additional rings. The .improved packing described herein has the further advantage of preventing the fibers from slipping one on the other. Such slipping action would result in the fibers extruding beneath the gland, causing heating, and resulting in a loss of packing material. Although flax and asbestos are the preferred fibrous materials, any suitable fibrous material may be used, i. e. vegetable, (cotton, jute, hemp, etc.) mineral, (spun glass) or animal, i. e. wool.
The packing may be reinforced, if desired, by the use of a suitable, stifi core, to add longitudinal rigidity to it. Also, in the case of commercial" asbestos which usually contains a little cotton, the strands are preferably reinforced with fine, non-abrasive wires, particularly where high temperatures and high pressures are to be encountered.
Fig. 7 shows a packing, preferably round in form, which is madeby braiding the previously described material on a core 34, which core may be initially a small, round core made of a few strands of treated yarn, or made of non-abrasive metal or other suitable material; One or more concentric jackets 35, 36, may be braided over said core. In this construction also the packing has the dry lubrication and powdered metal distributed substantially uniformly throughout the cross-section thereof. It will be understood also that successive jackets may be braided over a packing having a square cross-section such as shown in Fig. 4. Where these concentric Jacket over jacket arrangements are used, the graphite and lead may be omitted from the inner jackets as it is more readily available in the outer Jackets. The vulcanizing material not only serves the purpose previously described but tends to insure against slippage of one concentric layer on another, i. e. it tends to prevent slippage of the inner layer with respect to the core, as well as slippage of any outside layers with respect to each other. Where the core is made of a small strip-of soft metal such as lead for example, the
packing which is braided about the core will, for
many purposes adhere thereto sufiiciently to prevent slippage. 'I-Iowever, when a ring such as 33, shown in Fig. 6, surrounds a rotating shaft there is a tendency for the ring to open and form a gap between its ends. This objectionable tendency may be offset by providing a core such as previously referred to and so constructing the packing that there is no slippage of the packing material with respect to said core.
1. A packing comprising small strands of fibrous material, each of which is impregnated with a heat treated binder and also coated and partially impregnated with graphite, said strands being twisted together and intertwined with other twisted strands in the form of an elongated packing lubricated throughout.
2. A packing comprising several strands of f1- brous material, twisted together to form strands of small diameter, each of said strands having a binder which holds a filling of powdered metal and dry lubricant interspersed throughout said packing, whereby the latter has an anti-friction, metalized face, is flexible and resilient, and retains its lubricant despite compression and wear.
.3. A packing as in the preceding claim in which the said strands are twisted together to form threads and aplurality of said threads are' then braided to a square cross-section.
4. A packing as in claim .1 in which the binder is a vulcanized rubber compound and in which the elongated packing has an additional outer coating of finely divided metal'and a dry-lubricant applied thereto.-