Abstract:
An apparatus for situating a toroidal inductor having an inductor inner dimension, such as a ferrite bead, onto a rod having a diametral dimension. The apparatus comprises a flexible tubular supporter that has a first end, a second end, a support inner dimension substantially equal to the diametral dimension and a support outer dimension. The supporter flexes when installing the inductor to establish the support outer dimension at less than the inductor inner dimension to allow the inductor to surround the supporter and rod situated intermediate the first and second end with the supporter flexed to establish the support outer dimension at greater than the inductor inner dimension intermediate the inductor and the first and second end. Alternatively, the supporter may be a molded or snap-on cover substantially enclosing the inductor with apertures for frictionally fitting over a rod to secure the inductor in place.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is used for limiting electromagnetic interference (EMI) in electrical components as they are employed in electrical circuitry. One challenge for designing an electrical circuit is the reduction of electromagnetic interference (EMI) during operation of the circuit. One approach for effecting EMI reduction has been to design circuits in manners to confine components that are sources of EMI to restricted areas. Such an approach is marginally effective and contributes significantly to the time and talent required for circuit layout design. Increased time and talent in design contributes to the cost of circuit layout design, both in dollars and in time required. Many such early designs also proved difficult to manufacture on a production scale with acceptable manifested operating parameters. 
     Some of the earlier layout techniques included laying specified circuit traces atop one another in an effort to arrange for interlayer electromagnetic interference to cancel out. Another approach has been to place a ferrous bead on a wire connector (such as, for example a jumper wire), or on at least one lead of an electrical component (such as a transistor). Such ferrous beads provided a one-turn inductor. In using a ferrous bead, for example, in connection with a field effect transistor (FET), a bead may be installed on the source lead, on the drain lead, or on both the source lead and the drain lead. Such an addition of a one-turn inductor to the leads affects rise time or other operating characteristics of the FET in a manner that ameliorates the effects of high frequency noise on the FET. High frequency noise is a significant source of EMI. It is a characteristic of Fast Fourier Transform circuitry that a transform having a square shape involves a significant amount of high frequency noise. If the Fast Fourier Transform has the shape of a trapezoid (which would occur, for example, if rise times are affected), there are significantly fewer high frequency harmonics. Fewer high frequency harmonics means less EMI. 
     Ferrous beads employed on component leads also affect noise spikes. Ferrous beads installed encircling component leads absorb energy at high frequency and, therefore, suppress noise spikes. 
     The electrical benefits of ferrous beads in ameliorating effects of high frequency harmonics and noise spikes are evident and desirable. There is, however, a physical aspect of installation of the ferrous beads that has so far proven to be detrimental. The beads must be physically affixed in one place. If a bead is able to “rattle around” on a component lead, or a jumper wire or another bead-bearing structure, it will eventually increase the tendency of the bead-bearing structure to break. Indeed, vibration tests in which ferrous beads have become loose from their physically affixing restraint have yielded significant broken parts. One solution in the prior art has been to hot glue or otherwise adhesively affix a bead in place. Vibration tests yielded broken adhesive joints and subsequent broken bead-bearing structures. 
     There is a need for an apparatus for facilitating employment of ferrous beads to realize their electrical advantages without suffering the physical damage to a circuit in vibratory conditions. 
     SUMMARY OF THE INVENTION 
     An apparatus for affixing an inductive element in association with a rod within an electrical circuit is disclosed. The rod has a diametral dimension. In its preferred embodiment, the rod is a shaped rod with four or more sides. The inductive element has a generally toroidal shape with an inductive element inner dimension. The apparatus comprises a support member that is flexible to a plurality of orientations including an installing orientation and an installed orientation. The support member is substantially tubular with a first end, a second end and an inner wall defining a support member inner dimension and an outer wall defining a support member outer dimension. The support member inner dimension is substantially equal to the diametral dimension. The support member flexes to the installation orientation when installing the inductive element. The installation orientation establishes the support member outer dimension at less than the inductive element inner dimension appropriately to allow sliding installation of the inductive element about the support element and the rod to an installed position. The installed position is achieved when the inductive element surrounds the support member and the rod with the inductive element situated intermediate the first end and the second end with the support member flexed to the installed orientation. The installed orientation establishes the support member outer dimension at greater than the inductive element inner dimension intermediate the inductive element and at least at one end of the first end and the second end. A method for installing an inductive toroidal element upon a rod in an electrical device is also disclosed. The rod has a first longitudinal axis and a diametral dimension. The toroidal element presents an aperture having an inner toroid dimension. The method comprises the steps of: (a) providing a flexible insulative support member; the support member having a second longitudinal axis extending from a first end to a second end, an inner support dimension generally equal to the diametral dimension and an outer support dimension generally equal to the inner toroid dimension; (b) flexing the support element to situate the support element within the aperture with the toroidal element intermediate the first end and the second end to establish an assembly; (c) situating the assembly upon the rod with the first longitudinal axis generally aligned with the second longitudinal axis; and (d) slidingly positioning the assembly with respect to the rod to achieve an operational locus. 
     Prior art mounting of inductive elements, such as ferrous beads, on rods, such as component leads or jumper wires, in electrical circuits have not successfully affixed the beads in place. Normal vibration and other forces work the inductive elements loose during normal operation of the electrical circuits. As a consequence, broken leads, cracked beads and related problems have been experienced. 
     A further advantage of the present invention in each of its embodiments is that the support member absorbs shock forces that may be experienced by an inductor assembly according to the present invention, thereby reducing effects of forces upon the rod as well as upon the inductor member and reducing the risk of fracture or breaking of the rod, inductor member or joints associated with including the rod within an electrical circuit. 
     It is, therefore, an object of the present invention to provide an apparatus and method for affixing an inductive element with a rod in an electrical circuit that withstands dislodgment and shock forces during operation of the circuit. 
     Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective drawing illustrating the preferred embodiment of the present invention installed upon a component lead. 
     FIGS.  2 ( a )-( c ) are perspective drawings illustrating installation of an inductive element using the present invention. 
     FIG. 3 is a plan view of a preferred embodiment of one aspect of the apparatus of the present invention. 
     FIG. 4 is a partial section view illustrating the preferred embodiment of the present invention installed upon a rod. 
     FIG. 5 is a partial section view of a first alternate embodiment of the apparatus of the present invention. 
     FIG. 6 is an isometric view of a second alternate embodiment of the apparatus of the present invention. 
     FIG. 7 is an isometric view of a third alternate embodiment of the apparatus of the present invention. 
     FIG. 8 is a flow diagram illustrating the method of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a perspective drawing illustrating the preferred embodiment of the present invention installed upon a component lead. In FIG. 1, an electrical component  10  has component leads  12 ,  14 . Component leads  12 ,  14  are in the shape of rods, which may have a cross-section in the shape of a circle, an ellipse, a square, or any other polygon. Component leads  12 ,  14  have a diametral dimension which is measured at the maximum extremes of the polygonal rod cross-section in order to ascertain what clearance is necessary to fit the rod within a support member, as shall be described hereinbelow. An inductor assembly  16  constructed according to the present invention is associated with component leg  12 . Inductor assembly  16  is comprised of an inductor member  18  and a support member  20 . Support member  20  is in surrounding relation with component leg  12 . Inductor member  18  is in surrounding relation with support member  20  and component leg  12 . As will be described in greater detail hereinafter, clearances and dimensions among component leg  12 , support member  20  and inductor member  18  are appropriate to establish an interference fit, or a gripping relation among component leg  12 , support member  20  and inductor member  18  sufficient for inductor assembly  16  to withstand being dislodged from the installed position upon component leg  12  illustrated in FIG. 1 during operational employment of electrical component  10  and any shipping conditions that component  10  may experience. 
     FIGS.  2 ( a )-( c ) are perspective drawings illustrating installation of an inductive element using the present invention. In FIG.  2 ( a ), an inductor member  18  (illustrated in phantom in FIG. 2) is in an installing orientation with a support member  20 . In its preferred embodiment, support member  20  is constructed of flexible insulative material, such as a moldable plastic material. Inductor member  18  has an inner toroid dimension  21 . Support member  20  is illustrated in FIG. 2 in its preferred embodiment as a grommet having a tubular section  22  generally oriented about a rod  23  substantially coaxially with respect to a longitudinal axis  24 . Rod  23  may, for example, be a component lead or a jumper wire which may have a cross-section in the shape of a circle, an ellipse, a square, or any other polygon. Rod  23  has a diametral dimension  25 , which is measured at the maximum extremes of the polygonal rod cross-section in order to ascertain what clearance is necessary to fit rod  23  within support member  20 . At a first end  26  of support member  20 , tubular section  22  establishes a support member outer dimension  28  and a support member inner dimension  30 . In the installing orientation illustrated in FIG.  2 ( a ), support member inner dimension  30  is preferably substantially equal to or less than diametral dimension  25 , and support member outer dimension  28  is preferably substantially equal to or less than inner toroid dimension  21 . The relative dimensions are arranged to be “substantially equal to or less than” adjacent dimensions, as described briefly immediately above, in order to take advantage of the flexibility of the plastic material of which support member  20  is constructed. Specifically, when support member inner dimension  30  is substantially equal to diametral dimension  25 , rod  23  must necessarily flexibly displace some material of support member  20  as support member  20  is slidingly arranged on rod  23 . Such displacement of material enhances the desired tight fit, a gripping arrangement between support member  20  and rod  23 , when inductor assembly  16  is installed on rod  23  according to the present invention. Similarly, when support member outer dimension  28  is substantially equal to inner toroid dimension  21 , inductor member  18  must necessarily flexibly displace some material of support member  20  as inductor member  18  is slidingly arranged on support member  20 . Such displacement of material enhances the desired tight fit, a gripping arrangement between inductor member  18  and support member  20 , when inductor assembly  16  is installed on rod  23  according to the present invention. 
     At a second end  32  of support member  20 , a flange, or shoulder  34  is integrally formed with tubular section  22 . Shoulder  34  extends generally perpendicularly from longitudinal axis  24  to a shoulder dimension  36 . Preferably, shoulder dimension  36  is significantly greater than inner toroid dimension  21  to ensure that inductor member  18  will not disengage from support member  20  by sliding off at second end  32 . 
     In the preferred embodiment of the present invention illustrated in FIG. 2, shoulder  34  has an aperture  38  with an aperture dimension  40 . Tubular section  22  has a longitudinal aperture therethrough (not shown in detail in FIG. 2) substantially coaxial with axis  24  that is communicative with aperture  38  of shoulder  34  and receives rod  23 . Preferably, aperture dimension  40  is substantially equal to or less than diametral dimension  25  to further ensure a sturdy interference fit, or gripping relation, between support member  20  and rod  23 . 
     In FIG.  2 ( b ), installation of inductor member  18  has further progressed by sliding inductor member  18  further upon support member  20  toward shoulder  34 . In the interim installing position illustrated in FIG.  2 ( b ), first end  26  of tubular section  22  extends further from inductor member  18  than was the case in the initial installing position illustrated in FIG.  2 ( a ). Tubular section  22  is preferably manufactured with a set to it that establishes support member outer dimension  28  greater than inner toroid dimension  21 . Thus, when tubular section  22  sufficiently clears inductor member  18 , as in the interim installation position illustrated in FIG.  2 ( b ), first end  26  flexes to increase support member outer dimension  28  and support member inner dimension  30 . Support member outer dimension  28  preferably increases sufficiently to become greater than inner toroid dimension  21 . Thus, even in the interim installation position illustrated in FIG.  2 ( b ), inductor member  18  is captively contained between ends  26 ,  32  of support member  20 . Support member inner dimension  30  is still substantially equal to or less than diametral dimension  25  at a locus  35  displaced from first end  26 , so that a gripping relation between support member  20  and rod  23  is still maintained. 
     In FIG.  2 ( c ), inductor member  18  is fully installed upon support member  20  substantially abutting shoulder  34 . Tubular section  22  has assumed its “set” imposed during its manufacture to grippingly engage rod  23  at first end  26  and to establish a bulge  41  between first end  26  and inductor member  18  to a lateral dimension  42  that is greater than inner toroid dimension  21  (not visible in FIG.  2 ( c )). A gripping relation is also effected at least by aperture  38  in shoulder  34 , as previously described in connection with FIG.  2 ( a ). In the preferred embodiment of the present invention, tubular section  22  participates in effecting the gripping relation. 
     FIG. 3 is a plan view of a preferred embodiment of one aspect of the apparatus of the present invention. In FIG. 3, shoulder  34  is configured in a generally circular shape with a shoulder dimension  36 . The circular shape of shoulder  36  is representative only; shoulder  36  may just as well be in the shape of an ellipse, a square, or any other polygon and remain within the scope of the invention. The salient feature of shoulder  34  is that a maximum dimension (e.g., shoulder dimension  36 ) be greater than inner toroid dimension  21  in order to assure that shoulder  34  may perform as a stop to disengagement of inductor member  18  from support member  20  at second end  32 . Aperture  38  has an aperture dimension  40  configured to be substantially equal to or less than diametral dimension  25  of rod  23  in order to assure the desired gripping relation between shoulder and rod  23 . Aperture  38  is illustrated in the preferred embodiment of shoulder  34  illustrated in FIG. 3 as being rectangular in shape. Aperture  38  may be in the shape of an oval, a circle, a square or any other polygon and remain within the scope of the invention. It is a desired characteristic of aperture  40  that a minimum dimension (e.g., aperture dimension  40 ) be substantially equal to or less than diametral dimension  25  of rod  23  in order to assure the desired gripping relation between shoulder and rod  23 . In the preferred embodiment of the present invention, tubular section  22  participates in effecting the gripping relation. 
     FIG. 4 is a partial section view illustrating the preferred embodiment of the present invention installed upon a rod. In FIG. 4, installed inductor assembly  16  includes inductor member  18  installed with support member  20  upon rod  23 . Inductor member  18  substantially abuts shoulder  34 . Shoulder  34  grippingly engages rod  23  by aperture  38  having aperture dimension  40  substantially equal to or less than the diametral dimension  25  of rod  23 . Shoulder dimension  36  is greater than inner toroid dimension  21  to assure that inductor member  18  does not disengage from support member  20  at second end  32  of support member  20 . The intended “set” is taken by tubular section  22  of support member  20  to establish a lateral dimension  42  greater than inner toroid dimension  21  between inductor member  18  and first end  26  of support member  20 . By this lateral dimension  42  inductor member  18  is prevented from disengaging from support member  20  at first end  26 . Support member inner dimension  30  is substantially equal to or less than diametral dimension  25  and may provide a gripping relation between support member  20  and rod  23  at first end  26  of support member  20 . 
     FIG. 5 is a partial section view of a first alternate embodiment of the apparatus of the present invention. In FIG. 5, inductor assembly  16   a  includes inductor member  18  installed with support member  20   a  upon rod  23 . Tubular section  22   a  is substantially similar with tubular section  22  (FIGS. 1-4) adjacent first end  26 . Support member inner dimension  30  effects a gripping relation with rod  23  and lateral dimension  42  at bulge  41  prevents dislodgment of inductor member  18  from support member  22   a  at first end  26 . Inductor assembly  16   a  differs from inductor member  16  (FIGS. 1-4) in that inductor assembly  1   a  does not have an integrally formed shoulder at second end  32 . Instead, inductor assembly  16   a  is substantially symmetrical in its construction presenting a bulge  41   a  establishing a lateral dimension  42   a  greater than inner toroid dimension  21 . Lateral dimension  42   a  prevents dislodgment of inductor member  18  from support member  22   a  at second end  32 . Support member inner dimension  30   a  effects a gripping relation with rod  23  to assist maintaining inductor assembly  16   a  at its installed position on rod  23 . 
     Each of the embodiments of the present invention illustrated or discussed herein is depicted as comprising separate elements of inductor member (e.g., inductor member  18 , FIGS. 1,  2 ,  4 , and  5 ) and support member (e.g., support member  20 , FIGS. 1-4 support member  20   a , FIG.  5 ). The present invention may also be manufactured by molding an inductor member and a support member into a unitary piece for installation on a rod. The final product manifestation is within the scope of the present invention in so far as a flexible support member maintains an installed position upon a rod and holds an inductor member in an installed position on the rod. 
     FIG. 6 is an isometric view of a second alternate embodiment of the apparatus of the present invention. In FIG. 6, an inductor assembly  16   b  includes an inductor member  18   b  (shown in phantom in FIG. 6) and a support member  20   b . Support member  20   b  is applied to inductor member preferably by dipping, or by a similar process whereby inductor member  18   b  is substantially encased within support member  20   b . Inductor member  18   b  includes an aperture  38   b . Aperture  38   b  is at least partially filled by support member  20   b  present a reduced aperture  44  having dimensions reduced from the original dimensions presented by aperture  38   b . By such a structure inductor assembly  16   b  presents a yieldable reduced-dimension aperture (i.e., reduced aperture  44 ) for receiving a rod (such as rod  23 , FIGS. 1-5; not shown in FIG.  6 ). Reduced aperture  44  is preferably configured to yield to sliding insertion of a rod to establish a gripping relation between inductor assembly  16   b  and the inserted rod at reduced aperture  44 . Support member  20   b  provides the same benefits as other embodiments of the apparatus of the present invention described in connection with FIGS.  1 - 5 : captively affixing inductor member  18   b  on a rod (not shown in FIG.  6 ); cushioning impact of any physical forces on inductor member  18   b ; and reducing the risk of fracture or breaking of the rod, inductor member  18   b  or joints associated with including the rod within an electrical circuit. 
     FIG. 7 is an isometric view of a third alternate embodiment of the apparatus of the present invention. In FIG. 7, an inductor assembly  16   c  includes an inductor member  18   c  (shown in phantom) and a support member  20   c . Support member  20   c  preferably has physical dimensions substantially the same as the physical dimensions of shoulder  34  (FIGS. 2 and 3) and presents an aperture  38  for receiving a rod. Support member  20   c  is configured as a “snap-on” fixture. Support member  20   c  is sufficiently elastomeric to accommodate stretching appropriately for elastically receiving and holding inductor member  18   c  in the configuration illustrated in FIG.  7 . Another embodiment (not illustrated) contemplates assembling two facing support members  20   c  upon a single inductor member  18   c  to cooperate in elastically receiving and holding inductor member  18   c  in a substantially fully enclosed holding relation within two support members  20   c.    
     Aperture  38  is preferably configured to yield to sliding insertion of a rod to establish a gripping relation between inductor assembly  16   c  and the inserted rod at aperture  38 . Support member  20   c  provides the same benefits as other embodiments of the apparatus of the present invention described in connection with FIGS.  1 - 6 : captively affixing inductor member  18   c  on a rod (not shown in FIG.  7 ); cushioning impact of any physical forces on inductor member  18   c ; and reducing the risk of fracture or breaking of the rod, inductor member  18   c  or joints associated with including the rod within an electrical circuit. 
     FIG. 8 is a flow diagram illustrating the method of the present invention. In FIG. 8, the method for installing a toroidal element upon a rod in an electrical device begins, as indicated by a block  50 , with a rod having a first longitudinal axis and a diametral dimension. The toroidal element presents an aperture having an inner toroid dimension. 
     The method continues with providing a flexible insulative support member, as indicated by a block  52 . The support member has a second longitudinal axis extending from a first end to a second end, an inner support dimension generally equal to the diametral dimension of the rod and an outer support dimension generally equal to the inner toroid dimension of the toroidal element. 
     Continuing the method, as indicated by a block  54 , the support member is flexed to situate the support member within the aperture of the toroidal element with the toroidal element intermediate the first end and the second end of the support member. There is thereby formed an assembly including the inductive element and the support member. 
     The method continues, as indicated by a block  56 , situating the assembly upon the rod with the first longitudinal axis generally aligned with the second longitudinal axis. The final step of the method, as indicated by a block  58 , slidingly positions the assembly with respect to the rod to achieve a desired operational locus. 
     It is to be understood that, while the detailed drawings and specific examples given describe preferred embodiments of the invention, they are for the purpose of illustration only, that the apparatus and method of the invention are not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims: