US3248468A - Process of encapsulating coils - Google Patents

Description

April 26, 1966 K. A. ANDERSON PROCESS OF ENCAPSULATING COILS Original Filed May 23. 1960 4 Sheets-Sheet 1 F/GZ JNVENTOR. KARL. ALLEN ANDERSON Attorney April 26, 1966 ANDERSON 3,248,468

PROCESS OF ENCAPSULATING COILS Original Filed May 25, 1960 4 Sheets-Sheet 2 INVENTOR. G 4 KAR AM Anm-zas u Attorney April 26, 1966 K. A. ANDERSON PROCESS OF ENCAPSULATING COILS Original Filed May 2:5. 1960 4 Sheets-Sheet 8 INVENTOR. F/ K 1. ALL N Auoeasou Af'rorney April 6, 1966 K. A. ANDERSON 3,

PROCESS OF ENCAPSULATING COILS Original Filed May 23, 1960 4 Sheets-Sheet 4 INVENTOR. KARL ALLAN ANDERSON Attorney United States Patent 4 Claims. (Cl. 264-272) This is a division of my application Serial No. 31,151,

filed May 23, 1960, now abandoned. This invention relates to the process for encapsulating the space between the end portions of coils, particularly for mass production of encapsulated electrical coils.

Various types of molds have been designed for encapsulating electrical coils on a mass production scale as shown in my copending patent application Serial Number 840,653, now Patent No. 3,084,390 and in Patent No. 3,072,967 issued to Mathews et al., and assigned to the assignee of the patent application. These molds were designed for an assembly line type of operation wherein a plurality of molds are positioned on a conveyor and advanced ina step-by-step manner. This molds are opened or held open during one step and coils of the type set forth in copending application Serial No. 857,660 of Fred A Linn, filed on December 7, 1959 and assigned to the assigneee of the present application, now abandoned, are placed in the molds. The molds are closed in the next step of movement so that the flexible liner positioned within the jaws seals on the periphery of the end flanges ot the coil to form a cavity mold in cooperation with the coil bobbin. The resin which is used as the encapsulant is continuously mixed with a hardener immediately prior to using and is poured in the cavity formed by the mold and the flanges of the coil. After the resin and hardener have set, the mold is opened and the coil is removed.

Because of the extremely abrasive and adhesive nature of the encapsulating compounds, Teflon (tetrafluoroethylene) was selected for the liner in the mold. Even with this type liner, it was still necessary to treat the liner surface after each use to remove any of the encapsultant which had adhered to the liner surface. The liner also had to be replaced periodically because the surface became worn after long use.

The primary object of the present invention is to provide a lower cost process for encapsulating coils. v

Experiments showed the practicability of using a strip of paper, particularly a strip having a pressure sensitive adhesive backing, as a liner for a mold to prevent contact between the encapsulant and the mold. The adhesive backing achieved a dual advantage in that it provided a good seal between the preiphery of the flanges of the coil bobbin and the liner and also could be readily peeled from the encapsulated coil leaving a textured surface on the coil that prooved acceptable without any further working.

A further object of the present invention is to provide a process for preloading a mold at a minimum of time.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

FIG. 1 is a front elevation of the mold partly broken away to show the spring biasing means;

FIG. 2 is a side elevation of the mold;

FIG. 3 is a front elevation of the mold in an open position;

FIG. 4 is a side elevation of the loader with the mold in position;

FIG. 5 is a front elevation of the loader with the mold closed;

FIG. 6 is a view of the loader with the mold open and the coil moved part way down;

FIG. 7 is a view of the loader without the mold and the coil in an upper position;

FIG. 8 is a top view of the loader;

FIG. 9 is a back view of the loader; and

FIG. 10 is taken on line 10-10 of FIG. 9 showing the paper positioner.

In an effort to find a low cost molding process, the coil bobbin was wrapped with paper prior to molding and found successful. This was first tried in molds of the type disclosed in copending application Serial No. 840,-

653. Further experiments demonstrated that even better results could be achieved with adhesive backed paper such as masking tape because the paper adhered to the bobbin providing a seal and also served as an excellent agent for permitting the tape to be readily peeled from the encapsulated article while leaving an attractive textured finish. The adhesive paper was also tried with the mold above with success. It shortly became apparent that the cost of molds could be decreased and mold adaptability and flexibility increased in conjunction with the masking tape approach. The prior mold was designed to provide agood seal between the coil and liner and prevent leakage of the encapsulant on the mold. With the adhesive tape it is only necessary to insure that tape is stuck to the flanges of the coil thus eliminating the costly backing (Teflon) required previously.

In the mold disclosed herein, the articles to be encapsulated are placed in an adjustable sling with the article contacting only a contoured surface on the mold. The contoure dsurface provides a downward component of force pressing the coil against the sling, assuring that a good seal is provided between the coil flanges and the liner. The sling is presently made of Teflon impregnated fiber glass which can be easily cleaned in the event that some of the encapsulant spills on the sling. Plain paper could be used with this arrangement because the seal between the paper and coil is provided by the force of the contoured su1face of the mold pressing the coil against the sling. With adhesive type tape, a seal would be made between the coil flanges and the liner, whether the tape is wrapped on the coil mechanically by a loader described herein after or hand wound. The mold aids the seal between the flanges of the coil and the paper and locates the coil with respect to the conveyor when the mold is returned to the assembly line. While it may be feasible to wrap coils by hand, it is better to do it automatically on a coil loader of the type shown in FIGS. 41'0. In the prior patent application Serial No. 840,653, the coil was removed automatically while the mold remained on the assembly line. It has been found better to unload and load off the conveyor, with the above loader since the adhesive backing of the masking tape acts as an excellent agent for removing the tape from the encapsulated coil by peeling while leaving a smooth textured finish.

As seen in FIGS. 1 through 3, the mold includes a pair of brackets 10, 10 pivoted on rods 12, 12 which are secured to base 14. Replaceable jaws 16, 16 are secured to the brackets to bolts 20 and a flexible sling 21 is suspended between and secured to the jaws by clips 22 and screws 24. The brackets are biased towards each other by compressed springs 26 in holes 28 forcing caps 30 against the base. The mold is opened by the coil loader and a coil of the type mentioned above is wrapped with a paper liner and placed on the sling. The mold is closed and the interior surfaces 34 of the jaws engage the upper periphery of the flanges of the coil forcing it downward within the sling. This force can be varied by adjusting screws 32, which also serve to vary the gap between the jaws to accommodate different size coils. To set the mold for a specific coil, the coil should be placed in the sling and clips 22 loosened. The sling is then pulled so that the coil seats against the jaws and the clips tightened. Screws 32 can then be adjusted to provide the desired sealing pressure.

The mold is positioned manually on the coil loader in the closed position (FIG. with pins 38 on levers 39 projecting through holes 36. The mold is opened when crosshead 42 is moved upward by the actuation of double acting air cylinder (not shown) connected to bolt 44 on the crosshead. Cam 46 (FIG. 9) mounted on the back of the crosshead acts on cam rollers 50 on levers 52 to rotate shafts 41 in opposite directions and levers 39 mounted on shafts 41 move outward causing pins 38 to open the mold.

When the crosshead reaches the upper position, a coil 53 (shown dotted FIG. 7) is manually positioned on coil shaft 54 which is shaped to conform to the central opening in the coil bobbin. A paper tape 56 is pulled across platens 58 either manually or mechanically and placed between guide pins 60. As explained heretofore, the tape 56 can be of the type commonly known as masking tape. The tape is cut in a length suflicient to enclose the coil with its center located approximately below the axis of coil shaft 54. The crosshead is moved downward by I reversing the motion of the air cylinder pushing the coil with the paper downward between tape rollers 62. The tape rollers are mounted on rocker arms 64 which are pivoted on shafts 66 and are biased into engagement with the periphery of the flanges on the coil bobbin by spring 67 connected to levers 82 on shafts 66. The tape rollers wrap the paper around the periphery of the flanges of the coil as the coil is moved downward with the crosshead. When an adhesive type tape is used, the pressure of the rollers on the periphery of the flanges is suflicient to seal the tape to the coil. When plain paper is used to enclose the coil, the tape rollers hold the paper firmly in place around the coil while the crosshead is moving downward. Near the end of the downward movement of the crosshead, the corners of block 74 mounted on the crosshead will engage arms 64, rotating them outward until latch rods 70 biased by springs 68 snap into notches 76 in the rocker arms to hold the tape rollers in an outward position. Immediately before the crosshead reaches the end of its downward movement, the coil will engage the sling in the mold and at approximately the same time, the rollers 50 move inward on cam 46 allowing the mold to close on the coil.

The tape is cut in lengths longer than required to en close the coil to allow for any misalignment in centering the paper. The ends of the paper extending above the mold are folded back into clips 22 by actuating paper spreader 78, leaving an opening in the top of the mold for the admission of the encapsulant. As seen in FIGS. 9 and 10, the paper spreader includes a pair of plates 80 eccentrically mounted on shafts 82,, 84 which are operatively connected by gears 86, 86. Shaft 82 is extended (FIG. 10) to carry gear 90, which operativelyv engages rack 92. When the crosshead reaches the end of its downward movement, a switch (not shown) is tripped, either by the slider or manually, to actuate solenoid 94, pulling rack 92 upward and compressing spring 96. Gear 90 rotates shaft 82 clockwise (FIG. 9) and shaft 84 counterclockwise, moving plates 80 into a horizontal plane and pushing the ends of the tape into the clips on the mold. Since an adhesive tape would adhere to the flat surface of the plates, pins 96 are provided to engage the paper, thereby reducing the surface area engaging the tape so that the clips will hold the tape when the spreader is closed. Once the paper is secured in the clips, the solenoid is released, allowing spring 96 to pull the rack downward and rotate the plates 80 back to a vertical position. The clips will hold the ends of the paper clear of the opening in the top of the mold for the admission of the encapsulant.

The molds are then manually removed from the loader and another mold placed on the loader. The molds can be mounted in pairs on acommon base which requires a double coil loader to load the molds. When the base is positioned in the conveyor, the molds will be properly aligned with the encapsulant injectors. After encapsulation, the molds are removed from the conveyor and again placed on the loaders. The air cylinder is actuated moving the crosshead upward to open the mold as described above. The encapsulated coil is manually removed from the mold and a coil bobbin placed on the coil shaft. As described above, the tape rollers are held in an outward position by latch rods 70. It can be seen in FIG. 7 that if the latch rods were allowed to return to a closed position, after the crosshead has moved to a lower position, the tape spreader and coil shaft could not clear the rollers when the crosshead is moved upward. When the coil shaft has moved far enough upward to clear the rollers, the upper surface of block 74 will engage crosspiece 83 which is connected to latch rods 70 pulling the latch rods out of notches 76 in the rocker arms. Spring 67 will pull the tape rollers towards each other until latch rods 70 engage notches 77.

In the prior type molds, Teflon was used for the liner to provide a positive seal between the coil and the liner and because the encapsulated coil could be easily removed from the mold. In the present sling type mold, a disposable liner is used in place of the semi-permanent Teflon liner in order to reduce the cost. The sling acts only to support the coil and is made of Teflon impregnated fiber glass because of its tough and durable characteristics and because it requires very little maintenance. The sling also lends itself readily to a variety of shapes, increasing the over-all versatility of the mold. It is conceivable to use custom made tape having a specific trademark printed thereon which would be left on the surface of the coil after the tape has been removed.

The coils could be encapsulated by a manual process using the adhesive type tape. Wrapping the coil tightly with the tape will provide a completely sealed cavity into which the encapsulant is poured. The adhesion of the tape to the coil is sufficient to hold the encapsulant, since the encapsulant is only poured into the mold and no pressure is exerted against the liner. After the encapsulant has set, the tape can be easily peeled from the coil, leaving an attractive textured finish on the coil, which requires no reworking.

Although but a single embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. The method of encapsulating the portion of an article located between two sections of the article, comprising the steps of:

providing a flexible single-use liner having one side coated with a pressure sensitive adhesive and wrapping said article with said liner so that said adhesive coated side engages the two sections of the article to form a cavity having an opening at its top and being defined by the article, the two sections, and said adhesive coated side;

applying a force to said liner to press it against the two sections to thereby cause said adhesive coated side to sealingly engage the two sections;

filling said cavity through said opening with an encapsulant while maintaining said force on said liner; releasing said force and removing said liner from the encapsulated article after the encapsulant has set.

2. The method of encapsulating the portion of an electrical coil bobbin located between the end portions of the bobbin, comprising the steps of:

providing a flexible single-use liner having one side coated with a pressure sensitive adhesive and wrapping said article with said liner so that the said adhesive coated side sealingly engages the peripheries of the end portions to form a cavity which has an opening at its top and which is defined at two of its sides by said end portions and at two of its other sides and its bottom by said lines;

filling said cavity through said opening with an encapsulant;

removing said liner from the encapsulated article after the encapsulant has set. 3. The method of encapsulating the portion of an electrical coil bobbin located between end portions of the bobbin, comprising the steps of:

wrapping the bobbin with a flexible single-use liner having one side coated with pressure sensitive adhesive to form a cavity which has an opening at its top and which is defined at two of its sides by said end portions and at two of its other sides and its bottom by said adhesive coated side of said liner;

engaging the other side or" said liner by a flexible sling and tighening said sling to press said liner into sealing engagement with said end portions;

filling said cavity through said opening with an encapsulant;

loosening said sling and removing the bobbin and liner therefrom; and

removing said liner from the encapsulated bobbin after said encapsulant has set. 4. The method of encapsulating the portion of an electrical coil bobbin located between two end portions of the bobbin, comprising the steps of:

wrapping the bobbin with a flexible single-use liner having one side coated with a pressure sensitive adhesive to form a cavity which has an opening at its top and which is defined at two of its sides by the end portions and at two of its other sides and its bottom by said adhesive coated side of said liner;

applying a force to said liner to press its adhesive coated side against the peripheries of the end portions to thereby sealingly engage the liner therewith; and

filling said cavity through said opening with an encapsulant.

References Cited by the Examiner UNITED STATES PATENTS ROBERT F. WHITE, Primary Examiner.

Claims (1)

1. THE METHOD OF ENCAPSULATING THE PORTION OF AN ARTICLE LOCATED BETWEN TWO SECTIONS OF THE ARTICLE, COMPRISING THE STEPS OF: PROVIDING A FLEXIBLE SINGLE-USE LINER HAVING ONE SIDE COATED WITH A PRESSURE SENSITIVE ADHESIVE AND WRAPPING SAID ARTICLE WITH SAID LINER SO THAT SAID ADHESIVE COATED SIDE ENGAGES TO TWO SECTIONS OF THE ARTICLE TO FORM A CAVITY HAVING AN OPENING AT ITS TOP AND BEING DEFINED BY THE ARTICLE, THE TWO SECTIONS, AND SAID ADHESIVE COATED SIDE; APPLYING A FORCE TO SAID LINER TO PRESS IT AGAINST THE TWO SECTIONS TO THEREBY CAUSE SAID ADHESIVE COATED SIDE TO SEALINGLY ENGAGE THE TWO SECTIONS; FILLING SAID CAVITY THROUGH SAID OPENING WITH AN ENCAPSULANT WHILE MAINTAINING SAID FORCE ON SAID LINER; RELEASING SAID FORCE AND REMOVING SAID LINER FROM THE ENCAPSULATED ARTICLE AFTER THE ENCAPSULANT HAS SET.

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