Securement for transformer core utilized in a transformer power supply module and method to assemble same

Information

  • Patent Grant
  • 6359542
  • Patent Number
    6,359,542
  • Date Filed
    Friday, August 25, 2000
    24 years ago
  • Date Issued
    Tuesday, March 19, 2002
    22 years ago
Abstract
An apparatus and method for releasable securement together of a transformer power supply assembly together which includes a stacked arrangement (20) of a first transformer core plate (28) positioned to overlie a circuit board (26), a second transformer core plate (24) positioned to underlie the first transformer core plate (28) and the circuit board (26) and a carrier member (22) positioned beneath the second transformer core plate (24), the first and second transformer core plates (28,24) contact one another through at least one opening positioned in the circuit board (26). The apparatus includes having a body positioned over the first transformer core plate (28) in which the body of the span member (32) extends over a surface of the first transformer core plate (28) and extends from a portion of a peripheral edge of the first transformer core plate (28) to another portion of the peripheral edge of the first transformer core plate (28). A cross member (42) connected to the span member extends in a direction transverse to the span member (32) and is interposed between the span member (32) and the first transformer core plate (28). At least two engagement leg members (38) are provided in which one engagement leg member (38) is connected to the span member (32) and extends in a direction transverse to the span member (32) for extending along a side of the stacked arrangement (20) and another engagement leg member (38) is connected to the span member (32) and is spaced apart from the one engagement leg member (38) and extends transverse to the span member (32) for extending along an opposing side of the stacked arrangement (20). At least two hook members (40) for engaging the carrier (22) in which one hook member (40) is connected to the one engagement leg member (38) and extends in a direction transverse to the one engagement leg (38) member and another hook member (40) is connected to the other engagement leg member (38) and extends in a direction transverse toward the other engagement leg member (38).
Description




FIELD OF THE INVENTION




The present invention relates generally to a transformer power supply module and, more particularly to securement of two piece transformer cores within a transformer power supply positioned on a circuit board.




BACKGROUND OF THE INVENTION




Transformer power supply modules are becoming more widely utilized for electronic communication devices such as high power radio bases, as well as for other electronic devices. These transformer power supply modules are mounted to a circuit board.




These transformer power supply modules include transformer core plates that are mounted to a circuit board, which typically carries electronic circuits. The transformer core plates are typically two metallic core plates often constructed of ferrite material. Each core plate is positioned one on each side of the dielectric or ceramic circuit board. The core plates are in contact with each other through an opening provided in the circuit board.




The circuit board in these assemblies is secured to a carrier such that one of the two metallic core plates is positioned interposed between the bottom side of the circuit board and the carrier. The other core plate is positioned overlying the circuit board. Thus, a sandwiched or stacked arrangement is created with a core plate, circuit board, a second core plate and a carrier. Additionally, a heat sink may be secured to the core plate in this stacked arrangement.




It is important that the transformer core plates are secured together to make good contact with one another in the stacked arrangement to insure optimum operation of the transformer. Additionally the core plates need to be maintained in alignment with one another and with the circuit board in a lateral direction. Thus, for proper operation of the transformer, the core plates need to be maintained with a compressive force and lateral restraint.




To secure these two core plates together, typically, a through hole is positioned in each element of the stacked arrangement of the power supply module, including the top core plate, the circuit board, the bottom core plate and the carrier. If a heat sink were positioned on the top core plate, a through hole would be positioned in the heat sink as well. With all of these components having a through hole positioned within them, the components are sandwiched together such that the through holes are in alignment. With the through holes in alignment, a screw or threaded bolt with a nut can be positioned through the through holes securing all of the components together. Alternatively, through holes may be positioned only in the carrier with bolts projecting upward through the holes. A metal clamp having through holes corresponding to the holes in the carrier is then positioned atop the sandwiched components, engaging the upwardly projecting bolts. Nuts may then be applied to the upper ends of the bolts and tightened to force the metal clamp against the sandwiched core plates and circuit board, thus securing these components to the carrier.




As can be appreciated, this bolted stacked arrangement or sandwiched assembly of this transformer power supply is awkward and time consuming to assemble. The core plates must be positioned on either side of the circuit board. The through holes of all of the components including the circuit board, the plates, the carrier and even possibly a heat sink, must be placed in registration with one another in order to engage the through holes of all of the components with a screw or bolt.




This construction makes it also difficult to test the core plates before they are installed into operation. The core plates which are positioned on either side of the circuit board are not easily maintained in alignment and secured contact with one another and must be temporarily secured together for testing prior to installation to a heat sink platform. Typically, a clamp, tape or glue would be needed to temporarily secure the top core plate, the circuit board and the bottom core plate together in order to test the core assembly. During testing, the components of the assembly must be maintained in lateral alignment and secured compressively together. After the testing, the assembly would have to be disassembled and the process of aligning and securing the components together would be repeated prior to operational use in the field.




Moreover, the individual pieces of this stacked arrangement of the power assembly module make it difficult for the field technicians to replace or install the assembly in the field. After the transformer plate cores have been removed from the circuit board, the field technician would find it awkward to position the two new core plates on opposing sides of the circuit board with the carrier heat sink platform positioned below the second plate and then align the all of these components including their respective through holes prior to securing them together with passing a screw or bolt through the through holes.




It is clear that, transformer power supply modules are awkward and difficult to assemble, test and utilize as a field replacement part. One generally needs to maintain the transformer core plates in alignment with one another on either side of the circuit board in alignment with the circuit board and maintain them in compressive contact with one another for optimal operation of the power supply module. In testing the core plates, the core plates likewise need to be compressively secured together on either side of a circuit board and maintained in lateral alignment for proper testing when testing them apart from an operational field unit. In addition, the core plates must be easily installed with compressive and lateral securement in the field for them to be used as replacement components in a field unit. Aligning through holes of multiple components can be tedious, time consuming and difficult, for assembling, testing and using as replacement components.




Additionally, the lateral alignment and restraint of the two core plates is critical when projections interposed between the core plates make electrical connection therebetween. With multiple projections involved, to make contact with the core plates, tolerances of fabrication are of concern in both plate constructions. Failure to make good contact with the other core plate will result in improper performance of the transformer. The inadequacies that may be created by inaccurate tolerances of the projections are not compensated for with a rigid securement of a clamp or screw or bolt used to connect the core plates together.




Thus, a need exists for an improved securement of the core plates of the transformer power transformer module. The improved securement must accommodate ease in assembly of the core plates to the circuit board, ease in testing the power module before sending it to the field and ease in installation for purposes of use in connection as a field replacement part. Moreover, the securement must assist in providing good contact between the core plates where the tolerances in the fabrication of the plates have not been precisely maintained.











BRIEF DESCRIPTION OF THE DRAWINGS




The foregoing objects and advantageous features of the invention will be explained in greater detail and others will be made apparent from the detailed description of the present invention, which is given reference to the several figures of the drawing, in which:





FIG. 1

is a top perspective view of the securement member of the present invention;





FIG. 2

is a bottom perspective view of the securement member shown in

FIG. 1

;





FIG. 3

is a side view of the securement member shown in

FIG. 1

;





FIG. 4

is an exploded perspective view of the stacked arrangement of the power transformer module showing the securement member of

FIG. 1

;





FIG. 5

is a side view of the power transformer module showing the module partially assembled, with the securement member positioned just above the circuit board;





FIG. 6

is a side view of

FIG. 5

with the engagement leg members deflected outward to provide clearance on opposing sides of the stacked arrangement of the power transformer module;





FIG. 7

is a cross-section view of the power transformer module along line


7





7


of

FIG. 4

showing the securement member resting on the top core plate of the stacked arrangement and positioned to engage the carrier;





FIG. 8

is a front view of the power transformer module of

FIG. 4

showing the securement member resting on the top core plate of the stacked arrangement and positioned to engage the carrier;





FIG. 9

is the view of

FIG. 7

showing the relationship between the securement member and the stacked arrangement prior to engagement of the securement member and the carrier; and





FIG. 10

is the view of

FIG. 7

with the securement member fully engaged to the stacked arrangement including the carrier of the power transformer module.











DETAILED DESCRIPTION OF THE DRAWINGS




Generally, the present invention encompasses a clamp securement member that exerts a compressive force between two transformer core plates enhancing contact between the two core plates, in a direction perpendicular to a plane generally formed by the two core plates or referred to as a “z” direction. In addition, the clamp securement member exerts a force against at least one of the core plates in at least one of two directions in the plane generally formed by the two core plates or referred to as “x” and “y” directions.





FIGS. 1 and 2

show, in detail, an embodiment of the securement member of the present invention. Securement member


30


comprises a span member


32


having a pair of opposite ends


34


, and an elongated body extending between opposite ends


34


. Span member


32


is constructed from a flexible resilient material. A finger pad


48


is located on span member


32


intermediate opposite ends


34


of the span member. An extension member


36


also projects from each end


34


of span member


32


generally along the plane defined by span member


32


. The utilization of extension members


36


and finger pad


48


will be discussed in more detail below in conjunction with grasping and securing securement member


30


to the transformer power supply module, as seen in

FIGS. 4-10

.




As seen in

FIGS. 1 and 2

, an engagement leg member


38


extends from a corresponding end


34


of span member


32


and may be integrally formed with span member


32


. Each of engagement leg members


38


terminates in a hook member


40


. Each hook member


40


may be integrally formed with its respective engagement leg member


38


. Also, each hook member


40


includes a hook member end


64


, hook member ends


64


projecting toward one another in a direction generally parallel to a plane defined by span member


32


.




A pair of cross members


42


, as seen in

FIGS. 1 and 2

, are connected to span member


32


along its body. Cross members


42


extend in a direction transverse to span member


32


. Each cross member


42


is constructed of a flexible resilient material. Cross members


42


, as shown, are integrally formed with span member


32


. Each cross member


42


has a pair of opposite ends


44


. A foot member


46


is located at each of cross member opposite ends


44


. Foot members


46


extend below the plane defined by span member


32


so as to be interposed between span member


32


and first transformer core plate


28


, as can be seen in

FIGS. 7-10

, effectively spacing span member


32


from first transformer core plate


28


.




Referring to

FIG. 3

, an engagement leg member


38


extends from each of a corresponding span member end


34


along a line in a predetermined direction. In the first embodiment, the directions of the lines “a” and “b” along which engagement leg members


38


extend are oriented so as to converge. Engagement leg members


38


may be integrally formed with span member


32


. As seen in

FIG. 3

, engagement leg members


38


are in a relaxed or undeflected state. In the relaxed state of engagement leg members


38


, hook member ends


64


are spaced apart at a distance D


1


. This relaxed or undeflected state of engagement leg members


38


will be discussed in more detail below.





FIG. 4

shows a stacked arrangement


20


of a transformer power supply module incorporating one embodiment of the securement member of the present invention. The stacked arrangement


20


of the transformer power supply module includes a first transformer core plate


28


, a circuit board


26


, a second transformer core plate


24


and a carrier


22


. All of these constituents of the stacked arrangement are secured to a carrier


22


by securement member


30


. First transformer core plate


28


has an axis of symmetry c-c′, while second transformer core plate


24


has an axis of symmetry d-d′. To assemble stacked arrangement


20


, second transformer core plate


24


is positioned on carrier


22


. Circuit board


26


is then positioned atop second transformer core plate


24


, and first transformer core plate


28


is positioned atop circuit board


26


. Securement member


30


is then positioned atop first transformer core plate


28


and secured to carrier


22


in a manner to be described. As seen in

FIG. 4

, a pair of leg member receiving cavities


50


are incorporated into carrier


22


for receiving insertion of engagement leg members


38


during operation of the securement member. Each leg member receiving cavity


50


incorporates a hook end receiving shoulder


52


for engaging one of hook member ends


64


when securement member


30


is applied to stacked arrangement


20


.




Referring to

FIG. 5

, securement member


30


is positioned over stacked arrangement


20


prior to engagement. Preferably, span member


32


is positioned to overlie an axis of symmetry c-c′ of first transformer core plate


28


, as seen in

FIG. 4

, as well as an axis of symmetry d-d′ of second transformer core plate


24


. Generally, axes of symmetry c-c′ and d-d′ are substantially aligned when core plates


24


,


28


are stacked over one another, as seen in FIG.


4


. Both core plates


24


,


28


are preferably of substantially the same dimensions and shape.




Operation of securement member


30


is shown in

FIGS. 6-10

. Referring to

FIG. 6

, securement member


30


is actuated by gripping the securement member between two opposed fingers of a user at extension members


36


residing at opposite ends


34


of span member


32


. The index finger of the user is then used to apply a force against finger pad


48


in the direction of arrow F. Application of this downward force while gripping the span member between opposed fingers at extension members


36


causes engagement leg members


38


to deflect outward as indicated by the arrows in FIG.


6


. With engagement leg members


38


deflected outward, securement member


30


is lowered toward stacked arrangement


20


.




Referring to

FIG. 7

, when engagement leg members


38


are deflected outward, the distance D


2


between hook member ends


64


increases until the distance separating hook member ends


64


exceeds the distance D


3


between opposite sides of stacked arrangement


20


. When the distance D


2


separating hook member ends


64


exceeds distance D


3


, adequate clearance exists between the opposite sides of stacked arrangement


20


and hook member ends


64


such that hook member ends


64


can be inserted past the opposing sides of stacked arrangement


20


into leg member receiving cavities


50


. As seen in

FIG. 7

, securement member


30


is lowered toward stacked arrangement


20


until foot members


46


rest on an upper surface


56


of first transformer core plate


28


. When foot members


46


rest on upper surface


56


, span member


32


is suspended above first transformer core plate


28


by its attachment to cross members


42


, which extend across span member


32


and which are supported at their ends by foot members


46


.




Referring to

FIG. 8

, additional pressure is then applied by the index finger of the user to finger pad


48


in the direction of arrow F, forcing span member


32


toward first transformer core plate


28


and causing portions of cross members


42


proximate span member


32


to deflect toward first transformer core plate


28


.




Referring to

FIG. 9

, as span member


32


is forced toward first transformer core plate


28


, engagement leg members


38


attached to span member ends


34


are forced farther into leg member receiving cavities


50


, bringing hook member ends


64


below the line “L” designating the level where hook end receiving shoulders


52


reside. When the forces applied by the opposing fingers of the user on extension members


36


are removed, engagement leg members


38


will tend toward their undeflected states as indicated by the arrows in

FIG. 9

, permitting hook member ends


64


to overlap hook end receiving shoulders


52


. However, after the forces on extension members


36


are removed, engagement leg members


38


do not return to a completely undeflected state, engagement leg members


38


instead coming to rest against the opposing sides of stacked arrangement


20


, effectively laterally biasing stacked arrangement


20


and, in this example, second core plate


28


in the direction of arrow E, toward one side of carrier


22


, while the opposing engagement leg member


38


biases in a direction of arrow G against carrier


22


. It can be appreciated that engagement leg member


38


against any number of the stacked arrangement


20


components depending on the particular design of the power transformer module. Moreover, it can be further appreciated that additional engagement leg members


38


can be added to securement member


30


in a direction transverse to the alignment of engagement leg members


38


shown in order to restrain and/or secure stacked arrangement


20


in both the “x” and “y” directions.




Referring to

FIG. 10

, after the forces on extension members


36


are removed, the pressure applied by the user's index finger on finger pad


48


is then removed, causing cross members


42


to tend toward their relaxed or undeflected states and tending to force span member


32


upward, away from first transformer core plate


28


until hook member ends


64


engage hook end receiving shoulders


52


. However, hook member ends


64


will engage hook end receiving shoulders


52


before cross members


42


have returned to their completely relaxed or undeflected states provided by the predetermined shortness in length of engagement leg members


38


. Thus, foot members


46


will remain biased against upper surface


56


of first transformer core plate


28


after pressure on finger pad


48


is removed and, in turn, pushes first core plate


28


into second core plate


24


and second core plate


24


into carrier


22


. At this point, securement member


30


is fully engaged to secure the components of stacked arrangement


20


together.




The biasing forces exerted by securement member


30


, both downward toward carrier


22


and laterally toward one side of carrier


22


, act to immobilize the elements of stacked arrangement


20


, helping to prevent relative movement between these elements which may lead to misalignment of the elements. Moreover, the resilient biasing by the construction of securement member


30


and, particularly, in the z direction, will assist in overcoming deficiencies in tolerances in the construction of core plates


24


,


28


.




To disengage securement member


30


, the procedure described above is reversed. Pressure is applied to finger pad


48


by the index finger of the user in the direction of arrow F (FIG.


8


), causing deflection of cross members


42


toward first core plate


28


, thereby moving engagement lag members


38


downward and enabling hook member ends


64


to disengage from hook end receiving shoulders


52


. Securement member


30


is then gripped between two opposing fingers of a user at extension members


36


. Extension members


36


are forced in a direction away from first transformer core plate


28


while pressure is maintained on finger pad


48


, causing leg members


38


and hook members


40


to deflect outward, away from the opposing sides of stacked arrangement


20


, thereby providing a clearance between each of hook member ends


64


and the corresponding sides of stacked arrangement


20


. Engagement leg members


38


can then be withdrawn from leg member receiving cavities


50


.




As seen from the description above, the securement member of the present invention provides important advantages over existing methods of securing transformer cores within a transformer power supply positioned on a circuit board. Installation and field replacement of the transformer power supply module using the securement member of the present invention is easier and less time consuming than when existing assembly methods are used. Also, testing of the transformer cores prior to installation for actual service is expedited by the relative ease with which the plates can be aligned and secured to one another. In addition, by enabling application of biasing forces in at least two planes, the securement member of the present invention aids in preventing misalignment between elements of the stacked arrangement after the stacked arrangement has been assembled and provides a biasing force to facilitate good contact between core plates which have not been constructed in an otherwise necessary tolerance.




While a detailed description of various embodiments of the present invention have been given, it should be appreciated that many variations can be made thereto without departing from the scope of the invention as set forth in the appended claims.



Claims
  • 1. A releasable securement apparatus for releasably securing a transformer power supply assembly together which includes a stacked arrangement of a first transformer core plate positioned to overlie a circuit board, a second transformer core plate positioned to underlie the first transformer core plate and the circuit board, and a carrier member positioned beneath the second transformer core plate, the first and second transformer core plates contact one another through at least one opening positioned in the circuit board, comprising:a span member having a body positioned over the first transformer core plate in which the body of the span member extends over a surface of the first transformer core plate and extends from a portion of a peripheral edge of the first transformer core plate to another portion of the peripheral edge of the first transformer core plate; a cross member connected to the span member in which the cross member extends in a direction transverse to the span member, the cross member is interposed between the span member and the first transformer core plate; at least two engagement leg members in which one engagement leg member is connected to the span member and extends in a direction transverse to the span member for extending along a side of the stacked arrangement and another engagement leg member is connected to the span member and is spaced apart from the one engagement member and extends transverse to the span member for extending along an opposing side of the stacked arrangement; and at least two hook members for engaging the carrier in which one hook member is connected to the one engagement leg member and extends in a direction transverse to the one engagement leg member, another hook member is connected to the other engagement leg member and extends in a direction transverse to the other engagement leg member.
  • 2. The releasable securement apparatus of claim 1 in which the body of the span member is elongated.
  • 3. The releasable securement apparatus of claim 1 in which the portion of the peripheral edge of the first transformer core plate is positioned on one side of the first transformer core plate and the other portion of the peripheral edge of the first transformer core plate is positioned on an opposite side of the first transformer core plate.
  • 4. The releasable securement apparatus of claim 1 in which the body of the span member generally overlies at least one axis of symmetry of the first transformer core plate.
  • 5. The releasable securement apparatus of claim 4 in which the second transformer core plate has another peripheral edge which defines substantially the same dimensions and shape as the peripheral edge of the first transformer core plate.
  • 6. The releasable securement apparatus of claim 4 in which the second transformer core plate has an at least one of another axis of symmetry which underlies and is generally in alignment with the at least one axis of symmetry of the first transformer core plate and the body of the span member.
  • 7. The releasable securement apparatus of claim 1 in which the span member is constructed of a flexible material.
  • 8. The releasable securement apparatus of claim 7 in which one of the two engagement leg members extends in a direction along a line and the other of the two engagement leg members extends in another direction along another line, in which the directions of the one and the other lines are oriented to converge.
  • 9. The releasable securement apparatus of claim 8 in which respective ends of the one and the other hook members are positioned at a distance apart from one another less than the distance between a side of the stacked arrangement.
  • 10. The releasable securement apparatus of claim 9 in which the body of the span member has an end and an opposing end upon which a force is applied to both the end and an opposing end of the span member enabling the span member to flex and increase a distance between the spaced apart one and another engagement leg members and enabling the one and other hook members to separate to a distance to exceed the distance between one side of the stacked arrangement and an opposing side of the stacked arrangement enabling the one and other hook members to have clearance along the side and the opposing side of the stacked arrangement.
  • 11. The releasable securement apparatus of claim 7 including an extension member positioned at the one end of the span member and another extension member positioned on an opposing end of the body of the span member enabling prehensile application of force at the one end and opposing end of the span member for flexing the span member.
  • 12. The releasable securement apparatus of claim 11 including a finger pad secured to the span member between the one and opposing ends of the span member for receiving a fingertip for applying a force to the span member.
  • 13. The releasable securement apparatus of claim 1 in which the cross member is constructed of a flexible material.
  • 14. The releasable securement apparatus of claim 1 in which the cross member includes an elongated body.
  • 15. The releasable securement apparatus of claim 1 in which the cross member extends generally within a plane containing the body of the span member.
  • 16. The releasable securement apparatus of claim 13 in which the cross member has one end positioned spaced apart from the body of the span member and another end spaced apart from the span member in which an one foot member is secured to one end of the cross member and another foot member is secured to the other end of the cross member in which the one foot member and the other foot member each extend in a direction transverse to the cross member for engaging the surface of the first transformer core positioning the span member spaced apart from the surface of the first transformer core plate.
  • 17. The releasable securement apparatus of claim 13 include s at least two cross members spaced apart from each other along the span member and extending generally in the same direction.
  • 18. The releasable securement apparatus of claim 16 in which at least one of the two engagement leg members with the respective hook member secured thereto extends short of the carrier of the stacked arrangement with each of the one and other foot members engaged with the surface of the first transformer core plate and the cross member unflexed relative to the span member.
  • 19. The releasable securement apparatus of claim 18 in which the one and other foot members are biased against the surface of the first transformer plate pushing the first transformer core plate against the second transformer core plate with the at least two hook members engaged to the carrier of the stacked arrangement and the cross member flexed relative to the span member.
  • 20. The releasable securement apparatus of claim 19 in which the distance between the respective ends of the two hook members engaged to the carrier of the stacked arrangement is greater than the distance between the hook members without the span member in an unflexed position biasing the two engagement leg members and hook members toward the stacked arrangement.
  • 21. The releasable securement apparatus of claim 1 in which the span member and the cross member are integrally formed.
  • 22. The releasable securement apparatus of claim 1 in which the at least two engagement leg members are integrally formed with the span member.
  • 23. The releasable securement apparatus of claim 1 in which one of the at least two hook members is integrally formed with one of the at least two engagement leg members and another of the at least two hook members is integrally formed with another of the at least two engagement leg members.
  • 24. A method for releasably securing a transformer power supply assembly together which includes a stacked arrangement of a first transformer core plate positioned to overlie a circuit board, a second transformer core plate positioned to underlie the first transformer core plate and the circuit board, and a carrier member positioned beneath the second transformer core plate, the first and second transformer core plates contact one another through at least one opening positioned in the circuit board, including the steps of:aligning a releasable securement apparatus with the stacked arrangement including positioning a span member of the apparatus to overlie the first transformer core plate and positioning each of at least two engagement leg members connected to opposing sides of the span member and which are in converging alignment with one another and in which a hook member is secured to each of the leg members in which the distance between the hook members is shorter than the distance between opposing sides of the stacked arrangement; applying a force to the span member flexing the span member and increasing the distance between the hook members providing clearance of the hook members along the opposing sides of the stacked arrangement; moving the engagement leg members along opposing sides of the stacked arrangement with at least one foot member secured to at least one cross member which is secured transverse to the span member and in which the at least one foot member is interposed between the span member and the surface of the top core plate member until the at least one foot member is positioned resting on the top core plate and the hook members are positioned short of an engagement position of the carrier; and applying another force to the span member flexing the cross member relative to the span member moving the leg engagement members further along the opposing sides of the stacked arrangement until the hook members reach the engagement position of the carrier; and releasing the application of the other force to the span member with the hook members engaging the engagement position of the carrier member maintaining the cross member in a flexed position biasing the at least one foot member against the top core plate and the second core plate with at least one of the leg engagement members biased against at least one of the opposing sides of the stacked arrangement.
  • 25. The method of claim 24 in which the step of applying the force to the span member includes grasping opposing ends of the span member and applying a force to each end moving the opposing ends closer together.
  • 26. The method of claim 25 in which the step of applying the force includes positioning a finger on a mid-portion of the span member to apply a force in an opposite direction than the force applied to the opposing ends of the span member.
  • 27. The method of claim 24 in which the step of applying another force to the span member includes pushing the span member towards the first transformer core plate.
  • 28. The method of claim 24 in which the reapplication of the force to the span member moves the leg engagement members further apart and increases the distance between the hook members allowing the hook members to disengage from the engagement position of the carrier.
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6015301 Brodsky et al. Jan 2000 A