US3787799A

US3787799A - Multi-piece coil form assembly

Info

Publication number: US3787799A
Application number: US00180813A
Authority: US
Inventors: L Mcfarlane
Original assignee: COILFORM CO Inc
Current assignee: COILFORM CO Inc
Priority date: 1971-09-15
Filing date: 1971-09-15
Publication date: 1974-01-22
Anticipated expiration: 1991-01-22

Abstract

A coil form assembly of multi-piece construction which includes a tube of distortion resistant thermo-setting material to accommodate a coil wound thereabout, a thin washer of thermosetting material secured intermediate the ends of the tube, and, for some installations, mounting means on the washer for connecting the assembly, for instance, to a pierced circuit board. The preferred mounting means are a plurality of lugs arranged in a pattern about the washer, each lug being of resilient material and having a jaw or mouthpiece provided with teeth to receive and to grip the peripheral margin of the washer. The lugs have a portion which, when so mounted to the washer, extend as legs in a pattern below the coil form assembly and are adapted to be received in the openings of a companionate pattern of a circuit board. The arrangement of the lugs circumferentially about the washer may be varied to meet any of the omnifarious conditions met in electronic or appliance installations.

Description

United States Patent 91 McFarlane Jan. 22, 1974 MULTl-PIECE COIL FORM ASSEMBLY [73] Assignee: Coilform Company Inc., Geneva, 111.

[22] Filed: Sept. 15, 1971 [21] App1.No.: 180,813

Related US. Application Data [63] Continuation of Ser. No. 886,685, Dec. 19, 1969.

[52] US. Cl 339/214 R, 336/192, 339/220 C, 339/275 A [51] Int. Cl H01r 13/66 [58] Field of Search..... 339/17, 194, 196, 214, 217, 339/220, 221, 275 A, 276 C; 336/136, 192

Garlerding 339/220 R X Brown et a1. 336/192 X Primary Examiner-Richard E. Moore 5 7 ABSTRACT A coil form assembly of multi-piece construction which includes a tube of distortion resistant thermosetting material to accommodate a coil wound thereabout, a thin washer of thermo-setting material secured intermediate the ends of the tube, and, for some installations, mounting means on the washer for connecting the assembly, for instance, to a pierced circuit board. The preferred mounting means are a. plurality of lugs arranged in a pattern about the washer, each lug being of resilient material and having a jaw or mouthpiece provided with teeth to receive and to grip the peripheral margin of the washer. The lugs have a portion which, when so mounted to the washer, extend as legs in a pattern below the coil form assembly and are adapted to be received in the openings of a companionate pattern of a circuit board. The arrangement of the lugs circumferentially about the washer may be varied to meet any of the omnifarious conditions met in electronic or appliance installations.

4 Claims, 12 Drawing Figures 4 I l I l I l l 601 w: i 501 34 5 6 I I" w I I "MINNIE-Ill PATENIEBJANZZIHM SHEET 1 OF 2 INVENTOR. Le 1 w 5- 176F424 mug PATENIEUJANZZ I974 SHEET 2 '0? 2 INVENTOR. Le P0) F MCFHAL/QAJE MULTI-PIECE COIL FORM ASSEMBLY This is a continuation of application Ser. No. 886,685, filed Dec. 19, 1969.

In the past, coil forms for use in numerous applications have been known; for example, variable inductors as disclosed in U.S. Pat. No. 3,105,948. The present invention relates to improvements in coil forms.

Coil forms are generally cylindrical, tubular portions to accept windings of an electrically conductive wire, and often the coil form is provided with terminal posts for attachment of the lead wires of the coil. To adapt the coil and supporting coil form for some installations, for instance to an electronic circuit board, mounting lugs are often used. However, because very thin walled tubes are preferred, reinforcing collars have been employed in circumposed relation about the end of the coil form tube to provide a base for attachment of the lugs, i.e., a sleeve is fixed about the end of the tube to provide a reinforced zone for mounting the lugs so that they may be riveted or otherwise applied in a side surface attachment to the axial dimension of the reinforcement sleeve. The use of the end collar, however, increases the overall length of the coil form because the overlap of the reinforcement collar reduces the effective axial length of thin walled tube available to accept a coil. In other words, the axial dimension of the coil form assembly is increased by the use ofa collar on thin walled coil forms, but in the past has been accepted in order to gain the thin wall which is preferred for the main cylindrical coil form length.

The present coil form construction provides 'a thin walled tubular portion and a thin wafer or washer at the base or secured intermediate the ends of the tube which provides a mounting flange for the lugs. The resultant flange form coil, being of less axial length than the prior art collar, reduces the axial length of the coil form, which.is important in the miniaturizationprograms called for in many electronic applications. Also, for use with the improved coil form construction an improved clamping lug is provided which includes ajaw or mouthpiece for gripping engagement of the flange margin of the washer and for use in mounting the flange type coil form; also, the improved lugs include an upper and a lower terminal post.

It is a general object of this invention to provide an improved coil form structure and mounting means; it is also an object to provide a thin tube coil form assembly adapted for mounting in printed circuit boards which is of reduced coil height and of improved solderability which is not subject to thermal degradation of lug supporting material.

It is also an object of this invention to provide an improved coil multi-piece form assembly which includes a thin walled tube length and a washer element secured intermediate the ends thereof which is adapted to receive a plurality of mounting lugs in clamped engagement with the margin of the washer and arranged in any of the omnifarious pattern requirements of various electronic installations.

It is a further object of this invention to provide an improved multi-piece coil form construction of thermo-setting material, and an improved mounting means lug, which is described more fully hereinafter, which is simple and inexpensive to manufacture and assemble to a coil form.

It is a general object of this invention to provide an improved coil form which is simple and inexpensive to manufacture, is adapted to receive a mounting lug in clamping relation of a flange circumposed about the tube of the coil form which is useful in electronic and appliance installations, which is of a non-woven fabric impregnated with thermo-setting materials and which presents a thin tube wall for increased efficiency of inductors, for example.

In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a perspective view indicating a printed circuit board with pierced openings and coil forms;

FIG. 2 is a view in cross section ofa coil form having a single washer at one end thereof and indicating by dotted lines an optional location for the washer with respect to the tube;

FIG. 3 is a view similar to that of FIG. 2 indicating a washer at the opposite ends in flush relation with the tube face;

FIG. 4 is a view similar to that of FIG. 3 indicating a washer intermediate the ends with a washer at one of the ends in flush relation with the end face of the tube;

FIG. 5 is a view similar to that of FIG. 3 and illustrating a washer intermediate the end washers;

FIG. 6 is an enlarged view of the zone of juncture of the tube and washer of a preferred embodiment;

FIG. 7 is a somewhat modified arrangement of the zone of juncture of the washer and tube;

FIG. 8 is a perspective view of an improved mounting means for the coil form illustrated in the abovedescribed Figures;

FIG. 9 is a view of the assembly of the coil form and lug of FIG. 8;

FIG. 10 is a view ofa plurality ofinterconnected lugs;

FIG. 11 is a view of a washer having an eyelet mounted thereto; and

FIG. 12 is an enlarged view illustrating the gripping means of the lug of FIG. 8.

Referring to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, it is seen that two types of variable inductor coil form assemblies are depicted in FIG. 1. One is generally designated by the numeral 12, while the other is designated by the numeral 12'. Each is shown in relation to a mounting board indicated by the numeral 14 which conveniently may be provided with a pattern of pierced openings 16 for receiving a corresponding pattern of mounting lugs 18 on the coil form assembly. As indicated in FIG. 2, the variable or fixed inductor coil form is a multi-piece assembly which includes (a) a cylindrical tube or stack 20 of distortion resistant material, the outer surface 22 of which provides a form for a coil indicated by the numeral 24 in FIG. 1 carried thereon, and (b) a washer 26 intermediate the ends and sized for snug receipt in circumposed relation about the tube defining a generally axially-facing flange surface 28. The washer 26 is arranged at a predetermined location intermediate the

ends

30 and 32 of the tube and secured in position by suitable securing means 34 which may be composed of a thermo-setting adhesive.

As'indicated in FIG. 2, the washer or, as it may alternatively be termed, the wafer or flange form for the coil form, may be disposed at one end, as shown in FIG. 2, or in an axially-spaced disposition from the end, as indicated by the dotted line position 36. Alternatively, on

a given tube or stack, instead of one, a plurality of such flange forms may be employed; for instance, as indicated in FIG. 3, one in flush relation at each end, these washers being indicated by the

numerals

26 and 27.

One of the washers, i.e., washer 27, may be disposed intermediate the flush positions, that is, instead of as shown in FIG. 3, between the ends as indicated by the upper washer position in FIG. 4. The double flange form shown in FIG. 3 may be further modified to include the multi-flange arrangement shown in FIG. which is characterized by a washer 34 or several washers intermediate the tube ends or outer washers 30 and 31 which, as shown, are intermediate the ends and in flush relation with the end face of the tube of the coil form. As indicated in FIG. 1, the coil form may be of any convenient cross-section, ordinarily right circular,

square, or rectangular, but other suitable tubular or cylindrical configurations may be employed. Also, the wafer type washer may be of any suitable configuration as seen in plan.

Referring more in detail to the multi-piece coil form assembly or bobbin for use, for instance, in a variable inductor as illustrated in FIG. 1, the stack 22 is of distortion resistant material, that is, with shape retaining characteristics so as to resist fracture and deformation caused by mechanical stresses encountered as circuit elements in electrical appliances or electronic installations. A tube may be conveniently made of a carrier or underlying network such as paper, asbestos, cellulose fibers, or suitable stress-resisting material impregnated with a suitable thermo-setting material such as, for example, polyester, epoxy, melamine, phenolic and the like, to make it impervious to moisture. The main exterior surfaces of the coil form in the preferred embodiment are of thermo-setting material and the coil form is of a tube of alpha cellulose non-woven fabric, either spirally or convolutely wound and impregnated with suitable polymerizable material. The coil form tube may include at least one spirally arranged rib projecting into the column of the tube from its inside surface to define thread-engaging means for a threaded core, as is more fully described in US. Pat. No. 3,105,948. The winding of the coil may be of any suitable type, such as a pattern winding or a random winding used in solenoids or a bi-filar winding. In a preferred embodiment for use in commercial installations, the axial length of the tube is in the range of about onehalf inches to 2 inches in length; and the inside diameter is in a range in the order of about A inch to 2 inches, with the thickness of the wall of the tube being as thin as 0.006 inches and generally within the range of between 0.010 inches and 0.020 inches, the thickness being sufficient to provide for structural rigidity in the intended environment of use of the coil form in a variable inductor installation, for example. The tube is preferably made of alpha cellulose non-woven material impregnated with thermo-setting plastic materials to provide a thin wall throughout the effective length, and it is preferred that the outer surface be of thermosetting material so that brief exposure to heating when soldering the leads of a coil wound on the stack to terminal posts does not weaken the material on short duration application of such heat loads. 1

Referring more in detail to the washer 26 or washers intermediate the ends of the stack of the assembly, the same may be of the same configuration as the cross section of the tube; or they may be of somewhat different configuration, such as of square, rectangular or hexagonal form. One of the washers, flange forms or wafers may, as indicated above, be mounted to the tube in flush relation at one of the tube ends or two may be provided, one in flush relation at either end. Alternatively, whether in a plural or singular type washer assembly, the washer may be axially displaced with respect to the end face of the stack providing a gauge length extending from the outer axial face of the washer for bottoming the flange;'that is, it may be displaced axially from the end of the stack. In the preferred construction, the flange is of similar material to that of the stack and includes at least on the surface facing the main length of the stack in the preferred embodiment a thermo-setting material. The thickness of the washer may be substantially the same as or somewhat different than that of the stack, while the axial hole is sized to snugly receive the stack end in a press fit.'The radial dimension of the washer is such as to define an axially facing flange of about at least the radius of the stack in the commercial embodiment.

As seen in FIG. 6, the sides 42 of the hole 44 of the washer 26 may be tapered so as to diverge toward the surface 46 which in the preferred embodiment presents the face of thermo-setting material. The adjacent end of the tube 20 is, in this embodiment, characterized by 'an outer diameter slightly less than the diameter of the hole 44 at the face 46 and slightly more than the diameter at the outer end face 48 of the hole. It is thus seen that there is defined an annular space 50 thereabout when the leading end 52 of the stack is flush with the end face 48, for a purpose which will be described more fully hereinafter. As seen in FIG. 7, which is numbered correspondingly to that of FIG. 6, with the exception that prime designations are utilized for clarity, a similar annular space 50' is provided by an annular recess in the face 46 which is of a diameter slightly larger than the diameter of the end of the companionate tube, and this recess is of a relatively short, axial dimension. In assembly of the tube and washer, the nest defined by the

recess

50 or 50 tends to automatically guide and center the tube and the washer into cocylindrical relation, and, in addition, the recess defines an annular pocket to receive adhesive material for se curing the washer and tube in assembly.

As indicated in the preceding paragraph, means are provided to connect the washer means and an intermating tube of the assembly with the washer means at a predetermined axial position, the preferred connecting means comprising adhesive means securing the washer in position which maybe of any suitable material com patible with that of the washer means and tube. Preferably, the adhesive is of thermo-setting material and flowable in an untreated condition into an annular fillet zone of juncture at the intersection of the outer surface of the tube and the adjacent face of the washer, see FIG. 2. The fillet type zone of juncture, when the adhesive has been cured, resists penetration of the wire of a coil wound about the tube, which is often of very small diameter and is likely to become wedged or jammed in any space which exists between the washer and the stack. The radius of the fillet causes the lead end to be deflected onto the washer face where it is readily grasped for attachment to a terminal. The recess 50 and 50' when filled with adhesive tends to increase the structural rigidity of the assembly.

On the flange formed by the end washer 26, lugs are arranged in any of the omnifarious arrangements required by the installations of modern electronic and appliance technology. The lug construction of the preferred embodiment is illustrated in FIGS. 8-10 in which it is seen that by reason of the aforesaid assembly, they are adapted to be arranged and mounted at any suitable circumferential position on the flange, or, altematively, suitable eyelets may be so arranged; in the latter event, however, a suitable hole pattern is provided to accommodate the eyelets. In either embodiment, the

lugs of FIGS. 8-10 or the eyelet of FIG. 11, these connector means are adapted to accommodate the leads of a coil wound on the assembly, and the tube may be assembled to the washers and-kept in this condition for the mounting of suitable lugs or eyelets to the flange to meet the needs of any particular installation. In other words, the eyelets or lugs may be arranged in any desired pattern about the flange. To facilitate attachment of these mounting means, the washers may be provided with a slot in the periphery of the flange for use in orienting the washer in a predetermined attitude for convenient application by a machine of the lugs or eyelets to the flange in the required pattern.

Referring more in detail to the lug of FIG. 8, the lugs may be stamped from a sheet of resilient metal as indicated in FIG. 10 in which a plurality of the lugs is seen heldand maintained in a common orientation by the connector strip 25. Each of the mounting lugs 60, see FIG. 8, includes an upper portion 62 and a lower portion 64 with a mouthpiece portion 66 intermediate the upper-and lower portions. The mouthpiece portion defines a cavity 68 between an upper lip 70 anda lower lip 72 and a generally longitudinally-extending back wall 74 of the cavity which serves to space the lips and which lies opposite the opening into the cavity between the lips. The lower portion preferably includes detent means for use in mounting a coil form assembly to pierced openings of a printed circuit board, see FIG. 1. In the preferred embodiment, these detent means comprise a dogleg bend 74 intermediate the length of the lower portion and defining an apex or region generally beneath the cavity of the mouthpiece. The opening of the cavity between the lips is sized to snugly receive the axially thin margin of the radially-extending washer or flange form of the assembly. With respect to the upper portion 62 of the lug, it includes a headed upper end 76 and a shoulder portion 78 above the upper lip 70 with an intermediate neck portion 80 intermediate the head and shoulder for tying or wrapping the lead end of a coil wound on the tube. The lower portion of the lug may also be provided with a constricted neck zone intermediate the lower lip and the dogleg bend or detent means, the said neck zone being indicated by the numeral 82 and also comprising a terminal post means for connecting a conductor thereto. As seen in FIG. 9, the upper lip and the lower lip each include in the preferred embodiment confronting barbed elements extending into the cavity, the said elements being indicated by the

numerals

84 and 86 and defining a plane of entry therebetween of an axial dimension slightly greater than the thickness of the washer to which mounted to grip the surfaces thereof without piercing the same. The teeth on each lip are preferably in pairs at opposite sides of their respective lips at the cavity opening. In the preferred embodiment the teeth form is as indicated in FIG. 12, that is, with a long leg 88 and a shorter leg 90 converging depthwise into the pocket to a tooth apex 92 with the longer leg being on the opening side of the lip and the shorter leg being on the cavity side of the tooth. It is thus seen that in assembly when the lug is applied to the periphery of the flange of the washer, by compressing the lips to cause the teeth to grip the margin of the flange, there will be a slight tilting of the outer longer leg 88 toward the inner shorter leg 90 tilting the tooth tip 92 so as to resist withdrawal of the flange form from the bite of the mouthpiece to provide a sturdy gripping mounting means. It is seen that the lower portion includes a leg which includes the detent means and that the leg is enlarged intermediate the detent means and the lower lip defining a stop or shoulder 96 which limits penetration of the leg of the lower portion into a pierced opening of proper size and serves to locate the coil form or space the coil form slightly above the plane of a circuit board for properly bottoming it. In the preferred embodiment, the vertical dimension of the cavity is about 0.035 inches and the plane of passage defined by the distance between the teeth is about 0.015 inches. While the teeth may be opposite one another providing a four point main contact for each lug at the flange it is preferred that the lower lip be somewhat deeper than the upper lip. After assembly the upper portion 62 above the lower lip in the preferred embodiment is tilted slightly out of the plane of the leg and lower portion and in the direction in which the mouthpiece and detent means extend to provide a somewhat enlarged annular space between the upper portion and the tube to facilitate manipulation of a wire in connection of it to the upper terminal post.

What is claimed is:

1. An inductor comprising a coil form assembly including a a tube having an axially thin, radiallyextending flange portion, a mounting lug and terminal posts of resilient material comprising: an elongate body having an upper portion, a lower portion and a mouthpiece portion intermediate the upper and lower portions, said mouthpiece portion defining a cavity between an upper lip and a lower lip and a generally longitudinally-extending back wall spacing the lips and opposite the opening,

said lower portion comprising a lug depending at its proximal end from said lower lip at said opening and having a dogleg bend intermediate the length thus defining an apex on the same side of the lower portion as said mouthpiece, said dogleg bend comprising a detent means to engage in a pierced opening of a circuit board, the opening of said mouthpiece between said lips being sized to snugly receive the axially thin margin of the radiallyextending flange of the assembly,

said upper lip and said lower lip each including confronting barbed elements defining said mouth opening and a plane of entry for the axially thin flange of the assembly having an axial dimension slightly less than the axial dimension of said flange for gripping the marginal edge of said flange.

2. The device as set forth in claim 1 wherein the lower portion is provided with a constricted neck zone intermediate the lower lip and the dogleg bend comprising a terminal post.

3. The device as set forth in claim 2 wherein the upper portion includes a terminal post having a headed upper end, a shoulder portion above the upper lip and 5 an intermediate neck portion for tying the lead end of a coil on the tube.

relation from a circuit board.

Claims

1. An inductor comprising a coil form assembly including a a tube having an axially thin, radially-extending flange portion, a mounting lug and terminal posts of resilient material comprising: an elongate body having an upper portion, a lower portion and a mouthpiece portion intermediate the upper and lower portions, said mouthpiece portion defining a cavity between an upper lip and a lower lip and a generally longitudinally-extending back wall spacing the lips and opposite the opening, said lower portion comprising a lug depending at its proximal end from said lower lip at said opening and having a dogleg bend intermediate the length thus defining an apex on the same side of the lower portion as said mouthpiece, said dogleg bend comprising a detent means to engage in a pierced opening of a circuit board, the opening of said mouthpiece between said lips being sized to snugly receive the axially thin margin of the radially-extending flange of the assembly, said upper lip and said lower lip each including confronting barbed elements defining said mouth opening and a plane of entry for the axially thin flange of the assembly having an axial dimension slightly less than the axial dimension of said flange for gripping the marginal edge of said flange.

3. The device as set forth in claim 2 wherein the upper portion includes a terminal post having a headed upper end, a shoulder portion above the upper lip and an intermediate neck portion for tying the lead end of a coil on the tube.

4. The device as set forth in claim 1 wherein said lower portion is enlarged intermediate the lower lip and the dogleg bend defining a stop spaced from said lower lip for locating said flange of said assembly in spaced relation from a circuit board.