JPS5917301B2 - How to make stickers - Google Patents

Description

[Detailed description of the invention] Technical field The present invention relates to radial type fluid seals.

In particular, the present invention provides a hydrodynamic surface, preferably a polytetrafluoroethylene surface, with a dustproof lip.
The present invention relates to the formation of a resilient radial lip seal having in combination a bonded wear insert made of afluoroethylene.

Background Art 7') Polytetrafluoroethylene (i.e. PTFE) is an ideal dynamic sealant in many respects.

It has a low coefficient of friction, so it slides easily, generates very little heat, especially when used in dry conditions, and is abrasion resistant, so it does not wear out easily. Furthermore, PTFE is non-porous 1
6, is stable in that it does not react chemically or thermally, and is not permeated by liquids and is hardly affected by solvents, oils, etc. In addition to the aforementioned advantages, it is elastic over a very wide temperature range. However, the negative side of PTFE is that it has two properties that make it an extremely difficult material to create fluid seals that take advantage of the excellent properties mentioned above. First, PTFE cannot be formed into unusual shapes as can common elastic materials and plastics, such as thermoplastics and heat-set plastics. Practically speaking, PTFE
is consolidated and sintered from the powder state from which it is manufactured, in the same manner as powder metal parts are made. Even more important is the fact that it does not have a liquid phase like most plastics, and sublimes directly from the solid state to the gaseous state at temperatures above 3 degrees Celsius (288°C (550T)).
Second, PTFE does not easily soften and is not as elastic as the common materials from which seals are made, such as nitrile rubber, polyacrylic rubber, silicone rubber, etc.

So-called rubber, which is easily elastic, conforms and makes intimate contact with whatever surface it is pressed against. As such, the rubber can provide a positive seal that prevents the passage of fluids at the contact surfaces. On the other hand, PTFE is stiffer and tends to form bridges at elevated points on the pressed surface. (This creates a small groove through which it can migrate.) Even if a successful seal is made with materials that do not make intimate contact, the conditions described above will allow any fluid that has migrated or leaked to return to the oil side of the seal. This indicates that some kind of mechanism must be included.

This is facilitated by making the seal hydrodynamic, for example by providing a hydrodynamic flute in the sealing lip of the seal. As mentioned above, what is important is the fact that PTFE has no noticeable liquid phase. Therefore, it does not flow into oddly shaped molds as most elastic materials do. Instead,
No. 38,571, assigned to Assignee of the Invention
No. 56, No. 3,929,341, No. 3,939,551 and No. 3,985,487 must be machined and/or pressed into a useful shape, such as a sealing lip with a hydrodynamic flute, as shown in Must be. In the above-mentioned patent, a PTFE sealing lip with a hydrodynamic flute is formed by turning the entire piece or turning and pressing with a die before assembly into the seal. Of course, turning and heading operations are relatively complex and expensive. Another prior art attempt, as shown in DE 24 35 675, combines a radial lip seal made of elastic material with a PTFE wear surface on the seal lip. However, the latter technique does not suggest forming a PTFE wear insert with a hydrodynamic wear surface. As can be seen from the foregoing discussion, the prior art provides satisfactory fluid seals containing PTFE wear inserts that are economically and easily made such that the wear inserts have a hydrodynamic surface formed thereon by a simple molding process. And it could not be produced economically. Also, such prior art seals do not have a dust lip, and such seals will quickly wear out the shaft.

DISCLOSURE OF THE INVENTION Briefly, the present invention provides a solid, deformable; non-moldable seal lip or alternatively a seal lip wear insert for use in forming a fluid seal. Overcomes various drawbacks associated with previously known seals and processes.

The present invention also provides a method for forming another lip member constructed to act as a lip that can be used for sealing purposes. TECHNICAL FIELD This invention relates to radial type fluid seals.

In particular, the present invention provides a hydrodynamic surface, preferably with a dustproof lip, containing polytetrafluoroethylene (POlytetrafluoride).
The present invention relates to the formation of a resilient radial lip seal having in combination a bonded wear insert made of afluOrOethylene.

BACKGROUND OF THE INVENTION Polytetrafluoroethylene (i.e., PTFE) is an ideal dynamic seal material in many respects.

It has a low coefficient of friction, so it slides easily, generates very little heat, especially when used in dry conditions, and is abrasion resistant, so it does not wear out easily. Furthermore, PTFE is non-porous, stable in that it does not react chemically or thermally, and is not permeated by liquids and is almost unaffected by solvents, oils, and the like. In addition to the aforementioned advantages, it is elastic over a very wide temperature range. However, the negative side of PTFE is that it has two properties that make it an extremely difficult material to create fluid seals that take advantage of the excellent properties mentioned above. First, PTFE cannot be molded into unusual shapes as is possible with common elastic materials and plastics, such as thermoplastics and heat-set plastics. In practice, PTFE is consolidated and sintered from the powder state from which it is manufactured, much like making powder metal parts. More importantly, it does not have a liquid phase as most plastics do;
It is a fact that when the temperature exceeds 1='), the solid state directly sublimates into the gas state. Second, PTFE does not easily soften and is not as elastic as the common materials from which seals are made, such as nitrile rubber, polyacrylic rubber, silicone rubber, etc.

So-called rubber, which is easily elastic, conforms and makes intimate contact with whatever surface it is pressed against. As such, the rubber can provide a positive seal that prevents the passage of fluids at the contact surfaces. PTFE, on the other hand, is more rigid and tends to form bridges at elevated points on the pressed surface. This will create a small groove through which fluid will migrate in a static state with no relative movement between the seal and the sealing surface. The conditions described above may occur even if a successful seal is made with materials that do not make intimate contact.
This indicates that some type of mechanism must be included to direct any escaping or leaking fluid back to the oil side of the seal. This is facilitated by making the seal hydrodynamic, for example by providing a hydrodynamic flute in the sealing lip of the seal. As aforementioned,
Important is the fact that PTFE has no liquid phase. Therefore, it does not flow into oddly shaped molds as most elastic materials do. Instead, commonly assigned U.S. Pat. No. 3,857
No. 156, No. 3929341, No. 3939551
No. 3,985,487, it must be machined and/or pressed into a useful shape, such as a sealing lip with a hydrodynamic flute as shown in No. 3,985,487. In the aforementioned patents, a PTFE sealing lip with a hydrodynamic flute is formed by turning the entire lip or turning and pressing it in a die before assembly into the seal. Of course, turning and heading operations are relatively complex and expensive. Another prior art attempt, as shown in DE 24 35 675, combines a radial lip seal made of elastic material with a PTFE wear surface on the seal lip. However, the latter technique does not suggest forming a PTFE wear insert with a hydrodynamic wear surface. As can be seen from the foregoing discussion, the prior art provides satisfactory fluid seals containing PTFE wear inserts that are economically and easily made such that the wear inserts have a hydrodynamic surface formed thereon by a simple molding process. And it could not be produced economically. Also, such prior art seals do not have a dust lip, and such seals will quickly wear out the shaft.

DISCLOSURE OF THE INVENTION Briefly, the present invention relates to a conventionally known fluid seal used to form a fluid seal employing a solid, deformable, non-mouldable seal lip or alternatively a seal lip wear insert material. overcoming various drawbacks associated with seals and processes.

The present invention is also believed to be an improvement over known seals and processes used to form fluid seals having fluted hydrodynamic surfaces that can be used for sealing purposes. Broadly, in accordance with the spirit and scope of the present invention, a bonded, solid, deformable, non-mouldable material having a hydrodynamic surface located on the sealing lip is formed by heat and pressure molding. A new and improved method of forming resilient radial lips with wear inserts is provided.

This method assembles a recessed surface with a hydrodynamic flute shape in place and applies a suitable adhesive onto a preheated lower mold core forming part of the mold cavity. The process of positioning the coated seal case member and deforming it into a generally annular shape treated with an appropriate adhesive on the lower mold core so that the fluted surface is positioned close to the predetermined position provided. and placing a non-moldable solid material. In this method, a generally annular, uncured elastomeric material in an amount greater than the volume of the mold cavity when closed is positioned adjacent to a solid, deformable, non-mouldable annular material, and the elastomeric material is Then, the deformable, non-formable annular material and the seal case member are heated and compressed and wrapped together, and the aforementioned pressure is applied to the deformable annular material, and the elastic material is hardened. The hydrostatic pressure generated during the process is sufficient to force the mold into the recessed fluted surface on one side, so that the recessed surface of the mold and the overall corresponding protrusion are deformable and non-moldable. It is formed into an annular material.
In this method, the elastic annular material and adhesive are cured, and the molded elastic annular material is bonded to the seal case member.
and holding the pressure and temperature for a predetermined time to ensure the formation of an integrated radial lip seal bonding the deformable non-moldable ring to the molded elastic ring, and then The plan is to remove the radial lip seal from the mold cavity. In a preferred embodiment, polytetrafluoroethylene forms the insert material.
Additionally, the present invention may include a hydrodynamic resilient radial lip seal having a wear insert bonded to a resilient seal body at the seal lip, the seal body being axially spaced from the wear insert and in contact with the shaft. It is angularly formed and dimensioned to have an auxiliary dust lip adapted to engage.

[Brief explanation of the drawing]

1 is a sectional view of an open compression mold with the individual parts of a radial lip seal according to the invention in the position before the molding operation, and FIG. 2 is shown in FIG. 1 in the closed position during the molding operation. Figure 3 is a partial cross-sectional view of the seal according to the invention as it has been removed from the mold; Figure 4 shows the trim line;
5 is a partial cross-sectional view of a seal according to the invention mounted on a shaft, and FIG. 5 is a cross-sectional view of another embodiment of the invention in which the elastic body of the seal is extended to form an auxiliary dust lip. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows in cross section the relative position of a sealing member according to the invention placed in a compression mold before a molding operation. With the exceptions noted below, the compression molding used herein is performed in a standard manner with conventional components. Accordingly, the heat, pressure and time required for the process will vary according to methods well known in the art and do not form part of this invention. A lower mold or core 10 is held in place on the lower platen of a press (not shown) by a centrally located bolt 12. Similarly, the upper mold or ring 14 is held in place on the upper platen of a repress (not shown) by a centrally located bolt 16. The mold core 10 has a peripheral shoulder 18 whose function is to position a sealing case 20 made of a suitable metallic material and coated with a suitable adhesive in a conventional manner. The mold core 10 according to this embodiment includes a circumferential outer protrusion 24 located at the axially outer end of a profile 22 and fluted surface 23 that generally forms most of the inner surface of the seal. P
A TFE (polytetrafluoroethylene) wear insert 26 is fitted over the protrusion 24. The insert 26, like the case 20, has been pretreated with a suitable adhesive, for example by brushing, rolling, dotting or spraying. The mold is preferably preheated to the curing temperature of the elastic material used before positioning the sealed metal case 20. The projections 24 also enhance proper positioning of the wear insert. Such protrusions are not found in conventional compression molded parts. Additionally, it is within the spirit and scope of the present invention to contemplate the use of other solid, deformable, non-formable materials in addition to PTFE. It is recognized that such materials must be capable of deforming under the static pressures that occur due to hardening of the elastic material. Wear insert 2
The term "fit" is used to describe the positioning effect of the protrusion 24, which has a larger outer diameter than the inner diameter of the protrusion 6. The insert 26 has a hydrodynamic fluted surface 2
3, it must be spread out and over the protrusion 24. A projection 24 having a small outer circumference is formed on the mold 10 and is located at the outer end of the fluted surface 23 in the axial direction. The initial shape of the wear insert is a simple flat washer. During positioning, without substantially changing the outer diameter, the wear insert 26 expands its inner diameter, thereby deflecting what was originally a flat washer and bringing it closer to the hydrodynamically shaped surface 23 of the mold core 10. By the way, as shown in FIG. 1, it has an overall conical shape. When the wear insert 26 is further expanded, it covers the fluted surface 23 of the mold core 10. The hydrodynamically shaped surface 23 is shown in FIG. 1 as a unidirectional conical groove.・Due to illustration, this shape is used. The hydrodynamic shapes that can be stamped in the mold core can be any shape, whether left-handed, right-handed, unidirectional or bidirectional, with various shapes of flutes. Since it can be stamped, the invention is not limited to the particular shapes shown. Continuing to refer to FIG. 1, an uncured elastomeric material 27 is positioned around lower taper 28a and rests near wear insert 26. As shown in FIG. The amount of prepared elastic material is such that the upper ring 14 is larger than the lower core 1.
It is larger than the rest of the cavity that is formed inside the mold when it is closed onto the mold. As is well known in the art, this difference in volume creates a very high degree of hydrostatic pressure as the elastic material 27 heats up inside the closed mold and becomes semi-liquid. Whenever the mold is in the closed position shown in FIG. 2, this semi-liquid elastic material flows to every corner of the mold cavity and completely fills it. The extra semi-liquid elastic material 27 is attached to the core 10
The ring 14 is pinched between the male taper 28a of the ring 14 and the female taper 28b of the ring 14. These tapers are very precisely machined to fit perfectly into each other. The angle of taper is precise, uniform, and generally within the range of 0 to 4 degrees, measured relative to the base of each mold member 10 or 14, so that the angle between the molds as the mold is closed is The relative axial movement is greater than the radial closure when surface 28b approaches surface 28a. Due to this difference in closing speed, surface 28a and surface 2
Very high pressure is generated inside the mold as the passage between 8b is closed to essentially zero. In fact, this pressure has been found to be sufficient to permanently deform or stamp the PTFE wear insert 26 into intimate engagement with the hydrodynamically shaped surface 23 of the mold core 10. This pressure is maintained throughout the curing cycle of the elastic material. The profile 30 of the outer ring 14 defines the outer shape of the seal member. Bottom or closing surface 32 is constructed to clamp sealing metal case member 20 against mold cavity 10 shortly before tapered surfaces 28a and 28b are brought together. In that way, excess semi-liquid elastomeric material is prevented from escaping in the seal metal section before final pressure is applied. To finally close the tapered surfaces 28a and 28b, the uncured sheet metal 20 must be slightly rolled or stamped by the closing surface 32 of the die ring 14. FIG. 2 shows the mold ring 14 fully closed against the mold core 10 and squeezing the sheet metal 20 at position 40. At this stage, the elastic material 27 (seen in Figure 1) is semi-liquid and completely fills the mold cavity to create the new shape, as shown at 42. Internal pressure is accumulated inside the mold, and PT
The FE wear insert 26 is stamped against the hydrodynamic fluted surface 23 of the mold core 10 at position 44.
The so-called "pads" 46 of the seal are non-functional in that they are not part of the final seal shape shown in FIGS. 3-5. Regarding the molding of the elastic material that forms the pad,
It merely fills the portion between the mold members that do not contact each other, and is formed by forming a male taper 28a and a female taper 28b as shown in FIG.
This ensures complete mold closure at the interface between the drawing position 40 and the taper 28. A ring cavity 48 is provided in the mold to accommodate excess elastic material 27 that does not fit into the closed mold as shown in FIG. The extra is what is known as a pop-up and is 5
Indicated by 0. It is important that there is some overhang to ensure that there is sufficient elastic material 27 to fill the mold cavity and to generate the necessary pressure to mold the PTFE wear insert 26. The mold shown in FIG. 2 is held closed while maintaining heat and pressure against the elastic material 27. The heat and pressure chemically create cross-bonds within the elastic material and adhesive. Adhesive is supplied to the metal case 20 and the PTFE wear insert 26. This cross-bonding allows the elastic material and adhesive to harden, ensuring that all parts adhere to each other and are integral during removal from the mold. FIG. 3 is a sectional view showing details of the seal after it has been removed from the mold. The resilient body of the seal is bonded to the sheet metal case 20 at 60 and to a stamped PTFE wear insert having a fluted surface 44 at 62. The chain line 66-66 indicates that the extra rubber of the "pad" is the seal body part 4.
The part to be removed from 2 is shown. Spring groove 64 is optional and depends on the ultimate application for which the seal is to be used. If a garter spring 70 is used in the finished seal at spring groove 64, it will increase the radial pressure of the seal lip on shaft 72, as shown in FIG. Increased radial pressure increases friction and wear, which may be undesirable for the application. On the other hand, the hydrodynamic shape 44 of the wear insert tends to wall the shaft 72 and increase the hydrodynamic efficiency of the seal. FIG. 5 is a cross-sectional view of another embodiment similar to that shown in FIG. 74 is formed. In certain applications where the work environment is particularly dusty, this supplemental dust lip 74 can greatly extend the useful life of the seal. More precisely, it greatly extends the life of the other half of the seal, the shaft. This Toge〒-touge〈K.
'． Fujini Pass. . ;:NiyakuH:Niyaku ↑F+The heavy shaft 72 and dirt particles are soft, so such dirt particles get eaten by them. Therefore, dirt particles become embedded in the PTFE insert 26,
It will be taken away. When debris is removed in this way, it forms the surface of the seal lip.
Most trash contains sand particles, which are composed of a significant number of quartz crystals. Of course, since quartz is harder than steel, the wear insert 26 becomes a piece of sandpaper and rapidly erodes the steel shaft 72. Particles eroded from the shaft will also become embedded in the PTFE wear insert, thereby accelerating shaft wear. All of the above occurs during operation, as the debris is trapped on the PTFE wear insert, whose sharp edges slide on the rotating shaft. lip 7
Unprotected PTFE wear insert without 426
However, the exposed shaft will wear to the point where the seal can no longer function on the damaged shaft surface. The dust lip device 74 is therefore an important part of the seal, especially in relation to the sealing lip of the wear insert 26, since it covers the above-mentioned drawbacks caused by the absence of this lip. From the foregoing description it is clear that the invention can be used in the manufacture of seals. Although the invention has been described in connection with preferred embodiments, it is not intended to be limited to the particular forms described, but on the contrary, within the spirit and scope of the invention as defined by the appended claims. It also covers possible alternatives, modifications, and equivalents.

Claims (1)

Claims: 1. Formed by compression molding into an elastomeric lip seal with a solid, deformable, non-mouldable wear insert bonded thereto having a hydrodynamic surface located on the sealing lip. (a) a sealing case member so as to form part of a mold cavity with the first mold member over a first mold member having a recessed surface in a hydrodynamically fluted configuration in place; (b) placing a generally annular, deformable, non-moldable solid material over the first mold member so as to proximate the predetermined location having a fluted recessed surface; , (c) placing a generally annular uncured elastomer in an amount greater than the volume of the remainder of the mold cavity when the mold is closed so as to proximate the deformable non-moldable annular material; (d) deformable to the elastic material by compressive pressure and heating of a magnitude sufficient to force the non-moldable annular material portion into the recessed fluted surface by the fluid voltage generated when the elastic material hardens; By enclosing the non-moldable annular material and the sealing case member together, the protruding fluted surface, which generally corresponds to the recessed surface of the mold, can be deformed into a non-moldable annular material. form (e
) a deformable, non-moldable annular member is bonded to the molded elastomeric annular member such that the elastomeric annular member forms an integral radial lip seal bonded to the seal case member; Maintaining the pressure and heat for a predetermined period of time to ensure curing; and (f) removing the integrally molded seal from the cavity of the mold. Method. 2. The method of claim 1, wherein the insert is made of polytetrafluoroethylene and the first molding member is a lower mold core. 3. The method of claim 2, wherein the lower mold core has a circumferential protrusion above and near the recessed surface, the outer diameter being larger than the inner diameter of the annular wear insert. Pre-formed method. 4. The method according to claim 3, wherein the mold is preheated to the curing temperature of the elastic material. 5. The method according to claim 4, wherein the heating and pressurizing steps are maintained until the elastic material is cured. 6. A method as claimed in claim 5, wherein the seal is formed with a further lip member adapted to engage the shaft and act as a barrier to debris.