Device for coating a strand with a binding material

Abstract

An apparatus to be associated with a filament winding machine for applying an adhesive binder to a strand. The binder is contained within a trough and the strand is passed through the trough to coat the strand with the binder. After leaving the trough, the coated strand is passed through a small hole in a flexible disc-like membrane. The size of the hole in the membrane is substantially equal to the cross sectional area of the strand plus the desired binder coating. As the strand is drawn through the hole, the membrane flexes and the excess resin is wiped from the strand to provide a uniformly coated strand.

Description

BACKGROUND OF THE INVENTION

In a filament winding machine a resin coated strand is wound in a generally helical pattern about a mandrel in a number of superimposed layers to form a tubular article. Various types devices have been used in the past to apply a coating of liquid resin to the fibrous stand prior to winding the strand on the mandrel. One common form of resin applicator is a drum-type in which a drum is rotated within a bath of liquid resin to apply a film of resin to the drum surface, and the strand is passed over the resin coated drum surface to transfer the resin coating to the strand. In the drum-type applicator, a doctor blade is normally associated with the drum to doctor or meter a precise thickness of resin on the drum prior to transferring the resin coating to the strand. With the drum type of applicator, the resin is not thoroughly impregnated into the fibrous strand, thereby reducing the mechanical, chemical and electrical properties of the resulting wound article. As a further problem, when using polyester resins, the styrene content can change due to the increased exposure of the resin on the drum surface. This can result in the deterioration of the resin and can cause the resin to become more tacky, so that the fibrous strand may adhere to the drum surface. Because of these problems a drum-type of applicator imposes a limit on the speed of application.

A second common form of resin applicator, is the gate-type in which the end of the resin trough is provided with a vertically movable gate having an opening to receive the strand. As the fibrous strand passes through the opening in the gate, the excess resin is doctored from the strand. As the gate is a rigid member this system does not allow for changes in resin viscosity, fiber size, or joints in the fibrous strand and as a consequence, the fibers are frequently fractured and thus must be cleared from the opening. With the gate-type system, the speed of strand travel must be low, for excessive fiber deterioration and pile-up will occur at the opening in the gate. Furthermore, this type of system, normally requires a device to raise the gate to allow knots, joints or enlargements in the strand diameter to pass through and the adjustment mechanisms are costly and difficult to maintain.

A third common type of resin applicator is the squeegy type in which the strand, after passing through the resin trough, travels between a roller and a resilient pad bearing against the roller. The squeegy pad system does not permit close control of the resin content, nor is it able to achieve low resin contents at high speeds of travel of the strand. Thus, the resin content obtained at high speeds is substantially different from that obtained at low speeds and the resin-fiber ratio is greatly dependent on the resin viscosity.

As a further problem, the resin applicating systems used in the past have not been capable of varying the amount of resin applied to the strand. A greater resin-to-fiber ratio is usually desired on the first layer wound on the mandrel and similarly, a greater resin-to-fiber ratio is also desired on the outside layer of the winding to serve as a protector and to provide a smooth glossly outer surface. Normally, it is not possible to vary the resin-fiber ratios without stopping operation of the machine and replacing components, thereby making it impractical in most situations to vary the resin-fiber ratio in a given winding operation.

SUMMARY OF THE INVENTION

The invention relates to a device to be associated with a filament winding machine for applying a uniform coating of a resin binder to a fibrous strand. The resin binder is contained within a trough and one or more strands are passed through the trough and coated with resin. After leaving the trough each resin coated strand passes through a hole in a flexible, disc-like membrane formed of a rubber-like material. The hole has a size substantially equal to the cross-sectional area of the strand, plus the desired resin coating. As the strand passes through the hole the excess resin is wiped from the strand to produce a strand having a uniform resin coating that can subsequently be wound on a mandrel to form a tubular article.

In order to vary the thickness of the resin coating applied to the strand, a plate is mounted on the discharge or downstream side of the membrane and has an opening substantially greater in size than the hole in the membrane. By varying the spacing between the plate and the member the degree of flexing of the portion of the membrane bordering the hole can be varied to thereby regulate the thickness of the resin coating applied to the strand. To aid in threading the strand within the hole in the membrane, the membrane can be provided with a radially extending slit which extends from the hole to the outer periphery of the membrane.

As the membrane is formed of an elastic or resilient material, changes in the size of the fibrous strand can be accommodated without fiber deterioration or breakage of the strand.

As the membrane can be mounted in close proximity to the resin in the trough, evaporation of components of the resin system are minimized, thereby avoiding undue tackiness of the resin in the area of the membrane.

The flexible membrane enables a uniform coating of resin to be applied to the strand and is operable over a wide range of resin viscosities. Furthermore, the device will operate to apply a uniform coating of resin to the strand at both high and low strand speeds.

As a further advantage, the resin-fiber ratio can be conveniently varied by changing the spacing between the mounting plate and the flexible membrane, thereby enabling different resin-fiber ratios to be employed during a winding operation.

Other objects and advantages will appear in the course of the following description.

DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is a perspective view of a filament winding machine utilizing the resin applicator of the invention;

FIG. 2 is a perspective view of the resin applicator unit;

FIG. 3 is a vertical section taken along line 3--3 of FIG. 2;

FIG. 4 is an enlarged section with parts broken away taken along line 4--4 of FIG. 2;

FIG. 5 is a view similar to FIG. 2 and showing the variation in thickness of the resin coating achieved by movement of the mounting plate;

FIG. 6 is a plan view of a modified form of the membrane;

FIG. 7 is a section taken along line 7--7 of FIG. 6;

FIG. 8 is a plan view of a second modified form of the applicator; and

FIG. 9 is a view taken along line 9--9 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a filament winding machine including a supporting structure or housing 1, and a guide rail 2 extends horizontally from the housing. A generally cylindrical mandrel 3 is mounted on a shaft 4 and one end of the shaft is operably connected to a drive mechanism contained within the housing 1, while the opposite end of the shaft 4 is journaled within a tail stock 5 connected to the outer end of the guide rail 2.

A group of fibrous strands 6 are adapted to be individually coated with a resin binder and wound in a generally helical pattern in a series of superimposed layers on the mandrel 3 by means of a winding head indicated generally by 7. The winding head 7 includes a carriage 8 which is mounted for reciprocating travel on the guide rail 2, and the carriage carries a resin supply unit 9 which acts to coated the strands 6 with the resin binder prior to the strands being wound on the mandrel 3.

As best illustrated in FIGS. 2 and 3, the resin supply unit 9 includes a trough 10 which is adapted to contain a liqiud uncured resin 11. The trough 10 includes a bottom 12, a pair of spaced side walls 13 and a pair of sloping end walls 14 which extend upwardly from the bottom wall 12. As best illustrated in FIG. 2, the series of fibrous strands 6 are passed through the resin 11 contained within the trough to provide a resin coating on the individual strands.

The fibrous strands 6 can take the form of a substantially continuous unidirectional fibers, twisted fibers, braided tubing, or the like. The fibrous material can be mineral fibers, such as glass or asbestos; vegetable fibers such as cotton; animal fibers such as wool; synthetic fibers such as nylon or polyester; or metal fibers such as steel wire.

The resin 11 can be any type of binder or adhesive used in filament winding operations and can take the form of thermosetting resin such as epoxide or polyester resins.

To guide the strands in movement through the trough 10 a series of guide units 15, 16, 17 and 18 are utilized. Guide units 15 and 16 are located at the entry end of the trough, while the guide units 17 and 18 are located at the discharge end of the trough.

As shown in FIG. 1, each of the guide units 15-18 includes a generally horizontal rod 19 and a series of spaced vertical pins 20. The individual fibrous strands 6 are adapted to pass either over or under the horizontal rod 19 depending on the location of the guide unit and between the upstanding pins 20. Thus, the guide units serves to properly align and guide the strands in both a horizontal and vertical plane.

In addition to the guide units 15-18, the strands are guided by a series of horizontal rods 21 as the strand travel through the resin 11. The strands pass alternately over and under the rods 21, which serve not only to guide the strands in travel, but also aid in working the resin into the interior of the strands.

In accordance with the invention a uniform coating of resin is applied to the strands 6 by a wiper unit 22 which is located between the guide units 17 and 18, as best illustrated in FIG. 2. The wiper unit 22 includes a bar 23 which is mounted within slots 24 in the side walls 13 of the trough. Bar 23 is provided with a series of key hole shaped openings 25 through which strands 6 pass. A plate 26 is secured to the discharge side of the bar 23 by a series of screws 27, and the plate 26 is formed with a series of keyhole shaped openings 28 which are similar in shape and are aligned with the keyhole shaped openings 25 in the bar 23.

A thin, flexible, membrane 29 is secured between the bar 23 and the plate 26. Membrane 29 can be formed of any rubber-like, resilient material such as neoprene, polyurethane, or the like. The membrane 29 has a series of small holes 30 which are aligned with the circular portions of the keyhole openings 25 and 28 and have a substantially smaller diameter than the circular portions of the keyhole openings. The size or diameter of each hole 30 is substantially equal to the cross-sectional area of the strand 6 and the desired thickness of resin coating to be applied to the strand.

Each strand 6 is centered within the respective hole 30 in the membrane 29 by virtue of the horizontal rods 19 and vertical pins 20 of the guide units 17 and 18. As the strand 6 is drawn through the hole 30 the excess resin is wipe or doctored from the strand so that the strand emerging from the membrane 29 will have a uniform coating of resin applied thereto. As illustrated in FIG. 3, the membrane 29 will flex or bend in the direction of travel of the strand, and due to the inherent elasticity in the membrane, variations in diameter or cross section of the strand will be readily accommodated without undue abrasion of the strand and a uniform coating of resin can be obtained.

To aid in threading each strand 6 within the hole 30, the membrane is provided with a series of slits 31 which extend upwardly from each hole 30 to the periphery of the membrane. Each slit 31 is located in alignment with the stem or slot portion of the heyhole shaped opening 25 and 28. The peripheral edge of the membrane 29 is provided with a notch 32 which merges with the slit 31 to aid in inserting the strand 6 into the slit. With this construction, each strand 6 can be readily threaded within the hole 30 by merely pushing the strand downwardly through the slit 31.

In order to vary the thickness of the resin coating being applied to the strand 6, the plate 26 can be moved toward and away from the membrane 29 to thereby vary the degree of flexing of the portion of the membrane bordering the hole 30. As shown in FIG. 5, a shim 33, having a generally U-shape, is inserted between the membrane 29 and the plate 26. The resulting increase in spacing between the plate 26 and the membrane 29 will permit the portion of the membrane bordering the hole 30 to flex or deflect to a greater extent, as illustrated in FIG. 5, thereby permitting a greater thickness of resin to be applied to the strand. Thus, by inserting or removing shims 33, the thickness of the resin coating applied to the strand can be varied as desired for a given winding operation.

FIGS. 6 and 7 illustrate a modified form of the wiper unit 22 which includes a pair of clamping rings 34 that are secured to the peripheral edge of a flexible membrane 35, similar to membrane 29, of the first embodiment. The central portion of the membrane 35 is provided with a hole 36 which receives the fibrous strand 6. One or more of the wiper units, as shown in FIGS. 6 and 7, can be mounted at the discharge end of the resin trough 10 and as the resin coated strand passes through the hole 36, the excess resin will be wiped from the strand to provide a uniform coating on the strand.

While the structure shown in FIGS. 6 and 7 illustrates a membrane with a single hole for a single strand 6, it is contemplated that the membrane could be provided with a series of holes each of which would accommodate a separate strand.

FIGS. 8 and 9 illustrate a further modified form of the invention in which the wiper unit 22 includes a pair of clamping rings 37 which are secured to the peripheral edges of a membrane 38, similar to membrane 29. As shown in FIG. 8, the membrane 38 is provided with a central hole 39 which receives the strand 6, and a slit 40 extends from the hole 39 to a notch 41 located in the periphery of the membrane. As described with respect to the first embodiment, the notch 41 and slit 40 aid in threading the strand 6 into the hole 39. Clamping rings 37 are not continuous, but are provided with gaps or slots 42 aligned with the notch 41 so that the strand can be inserted into the slit 40.

As shown best in FIG. 9, additional rigidity is provided for the portion of the membrane 38 bordering the slit 40 by a pair of pivotable arms 43. The arms 43 are pivoted at pivots 44 to one of the clamping rings 37 at the discharge side of the membrane. During the winding operation, the arms 43 are in the position shown in FIG. 8, in which the ends of the arms extend across the slit 40 and prevent deformation of the portion of the membrane bordering the slit. By pivoting the arms 38 downwardly to the phantom position shown in FIG. 8, the strand can be threaded through the slit 40 and into the hole 39 without interference with the arms 43.

The invention provides a device for applying a uniform resin coating to a strand with a selected resin-to-fiber ratio. The device operates to provide a uniform coating of resin on the strand at both low and high strand speeds and changes in tension of the strand do not effect the resin-fiber ratio. A change in the resin-fiber ratio can be achieved either by utilizing a hole of different diameter in the membrane or by moving the backing plate toward and away from the membrane to thereby vary the degree of flexing of the portion of the membrane bordering the hole.

As a portion of the membrane bordering the central hole is flexible and elastic, fiber joints and variations in strand diameter are accommodated without undue abrasion of the fibers or breakage of the fibers.

While the above description has illustrated a filament winding machine in which a series of strands are coated with the resin, it is contemplated that the device can be utilized to coat either a single strand or a multiplicity of strands. Moreover, the device can be employed to coat a strand of generally circular cross-sectional area, or a strand in the form of a tape or band, or a strand of any other cross sectional configuration.

Claims

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention:

1. An apparatus for applying a liquid binder to a strand comprising means for moving the strand through a path of travel, binder applying means for applying a coating of a binder to the strand as it moves through its path of travel, a flexible membrane following the binder applying means in the direction of travel of said trand, said membrane having a hole to receive the strand, said hole having a size substantially equal to the cross sectional area of the strand and the desired thickness of resin coating to be applied to the strand, the annular portion of the membrane bordering the hole flexing in the direction of travel of the strand as the strand passes therethrough to thereby meter a uniform coating of said binder on said strand, and means for varying the amount of flexing of said annular portion to thereby vary the thickness of the coating of binder applied to said strand.

2. The apparatus of claim 1, wherein said binder applying means is a trough to contain a quantity of a liquid binder, said membrane being located above said trough.

3. The apparatus of claim 1, and including a support member located on the downstream side of said membrane, said support member having an opening aligned with said hole and said opening having a substantially greater area than the area of the hole, said means for varying the amount of flexing comprising means for varying the spacing between said support member and said membrane.

4. An apparatus for applying a liquid resin binder to a fibrous strand, comprising a trough to contain a liquid resin binder, means for passing a strand through the resin in said trough to coat the strand with said resin binder, a flexible thin resilient wiper member located downstream of said trough in the direction of movement of said strand, said wiper member having a hole to receive said strand, a support member mounted on the downstream side of said wiper member and having an opening disposed in alignment with said hole, said opening having a substantially greater area than the area of said hole, said strand passing through said hole and the excess resin coating being wiped from the strand to provide a uniform coating of resin on said strand, aligning means for centering said strand within said hole, said membrane having a slit which extends from said hole to the periphery of the membrane, said support member having a slot communicating with said opening and aligned with said slit whereby the strand can be threaded through said slot and said slit into said hole, and movable support means connected to said support member, said support means being movable from a first supporting position wherein said support means extends across said slit to prevent deformation of the membrane adjacent said slit to a second position wherein said support means is located at a location remote from said slit so that the strand can be inserted through said slit without interference from said support means.

5. The apparatus of claim 4, wherein said movable support means comprises an arm pivotally connected to the support member.