Patent Grant
7753715
In a coil of conductive wire, such as a solenoid, the thinly insulated wire of the coil must be terminated at each end and joined to a source of electric power. Usually, this is accomplished by connecting each end of the coil wire to a connector which in turn connects to a larger heavily insulated power wire. Many methods exist for making the coil wire connection. Screw clamps, crimps, wire-wrapped pins, spring-loaded IDCs (Insulation Displacement Connectors), soldered joints, and welded joints, are among the most common.
When the coil wire is thick and robust, all of the above methods are satisfactory. But, when the coil wire is thin and fragile it must be handled gently and until now, soldering has been accepted as a practical low-cost industrial method for coil wires less than 35AWG (American Wire Gauge). However, soldering presents various problems.
Since July of 2006, products sold and used within the European Community have to comply with the Regulation of Hazardous Substances (RoHS) directive, which is legislation which aims to keep hazardous materials from being dumped into the environment. The element lead (Pb) is among the materials banned by this legislation.
Lead (Pb) has been used in tin/lead solder for many years and performs a stabilizing and melting-temperature-control function. The RoHS ban brought about a rush for compliance, in which “lead-free” alternative solders were developed for the electronic industry, where the use of solder is entrenched. Much study and debate continues addressing the economics and the reliability of the alternatives.
Those industries outside of the electronics industry have historically not been as wedded to the use of solder. However, where connections to coil wire below 35 AWG are sought, there has not historically been any alternative to the use of solder. In these other industries, the RoHS directive prompted lobbying for exemptions from the environmental directives banning the use of lead in solder.
Exemptions have been provided by the RoHS in recognition of the extreme difficulty of compliance with the new regulations with regard to certain applications of lead (Pb). One such exemption is where a solder must withstand a higher temperature than the melting point of the commonly used tin/lead solder or its lead-free alternatives. In these cases, high melting point solders with high lead (Pb) content are still allowed.
It is believed that the pursuit of exemptions may have been manipulated by reclassifying applications as “high temperature applications” to enable the lead-based solder to be used for high-melting-point solder. Paradoxically, this process may lead to more lead (Pb) being used than was the case prior to the imposition of the new rules. However, it is anticipated that the above-mentioned loopholes will be closed and secondly that the exemptions will in any case have a limited time span. It is anticipated that, eventually, lead-based solder will be completely banned.
Moreover, the RoHS directive is not the only impediment to using solder. Soldering is a dangerous and unpleasant task. The possibility of nasty burns is ever present and the fumes given off by the heated acid flux are unpleasant and unhealthy. Additionally, the intense study of solder that RoHS promoted exposed many failure modes, not fully recognized and understood before. Among these were such serious flaws as internal voids, age cracking, conductor corrosion, and an inconsistency of application. Perhaps the most frightening aspect is that these flaws are only discoverable by destructive examination or by x-ray. Even if the examination finds no flaws, doubt of reliability remains because of the inconsistency of soldering.
The cost and difficulty of pursuing exemptions from RoHS compliance and of the use of lead-free solder may be avoided by establishing connections with thin fragile coil wire without using solder. However, the solder-free methods of the prior art severely distorted, notched, squeezed and scraped the coil wire in order to break through the insulation and make a good connection. The use of this approach, which employs relatively high forces, incurs a limit when applied to fragile wires. This limit is defined by the point (force level) at which breakage of the wire occurs, which breakage renders the wire useless, and which therefore incurs considerably expense. Accordingly, there is a need in the art for an improved system and method for establishing conductive connections with wire, such as coil wire, without using solder, and without damaging the wire.
One or more embodiments of the system and method disclosed herein may include the wire wrapping of rectangular sectioned pins. Desirable results may be obtained by tightly winding the wire around the pin. Each time the wire is forced to bend around a corner of the pin, tight, intimate contact may be made. The use of plural wraps may establish plural corresponding points of conductive electrical contact.
If the corners of the pin are very sharp, such as are naturally formed on the die side during punch and die stamping, then such a wire wrapping method may be employed to penetrate coil wire insulation. However, current wire wrapping methods are limited to heavy gauge wires due to the fragility of fine wires. Wires below 36 AWG are susceptible to tension break due to the magnitude of the forces required to bend, notch, and penetrate the insulation together with the stress concentration effect of the notching.
Some embodiments of the present invention can be used on wire as fine as 42 AWG without breakage of the wire. In at least one aspect, the present invention includes the gentle skiving removal of the thin insulation of a coil wire by a sharp edge of a connector, thereby making electrical contact. This can be done on one wire when the wire is robust or on a plurality of load sharing fragile wires. Helically wrapping the wire presents one wire as if it were a plurality of wires from the vantage point of the connector.
In one aspect, a method of penetrating insulation includes scraping the insulation longitudinally along the wire. This scraping action may also scrape the conductor material of the wire to produce a good clean contact area. The foregoing step may be performed on only one side of the wire to avoid excessively reducing the wire diameter. Furthermore, this insulation removal and contact action may be applied to several locations along the wire, thereby creating many parallel electric paths. This action is conducive to adequate conductivity while spreading the scraping force loading over many points.
Another embodiment of the present invention may include a method of preparing the ends of the coil wires by wrapping the wires around structures incorporated within a bobbin molding. These structures support the wraps while providing access to the internal region of the wraps, or “wire loops”. Appendages on the subsequently introduced connectors then impinge, skive, and thereby make electrical contact with the coil wire conductor material. Various connector designs employing differing methods of deflecting the wire may be practiced.
In one or more embodiments, molded portions of the bobbin may be strategically located to anchor the wires. These anchoring structures allow the space available to receive wire loops to be filled before the connectors are assembled. Assembling the connector to the bobbin may include inserting a contact pin extending from the connector through a hollow in the bobbin that is configured to receive the contact pin. Insertion of the contact pin in this manner causes one or more edges of the contact pin to extend through the insulation material and thereby form conductive electrical contact with conductive wire in one or more of the wire loops that are wrapped around the bobbin.
One or more embodiments of the present invention may include converting the above-described temporary anchoring structures into permanent supports for the wire wraps that will be contacted by the later introduction of a connector.
There are at least two major avenues through which the systems and methods disclosed herein may be beneficially applied. These are defined by the order of assembly. In one avenue, the connector may be assembled into the coil bobbin after the coil is wound. In another, the connector may be assembled into the coil bobbin before the coil is wound. When the connector is assembled after winding the coil, the wire may be prepared for introduction of the connector by wrapping conductive wire around bobbin structures in preparation for introduction of the connector. When the connector is assembled before the coil is wound, the connector provides the structure around which the wire ends may be wrapped.
When the connector is assembled prior to coil winding, in one embodiment, an appendage of the starting connector is presented at an advantageous location so that the natural positioning of the wire guide of the coil winding machine can easily wrap the appendage with coil wire to anchor the coil wire at the start of the coil. Then, at the end of the coil winding, the coil wire is anchored and wrapped around a similar appendage of the finishing connector. This is presently done to present anchored wire ends for the prior art of soldering the wire to the connector.
In a further embodiment, the invention may include novel designs for specially shaped connector appendages. In some embodiments, the wire wraps on the appendages may be moved along the appendage to skive, scrape and make electrical contact between the wire and the connector, while not unduly stressing the wire. During such a wire moving (which may include pushing and/or pulling of one or more wire loops), the shape of the connector appendage may influence the changes in wire tension imparted to the various wire loops by the wire moving operation. For example, where the cross-sectional perimeter of the appendage increases in the direction in which the wire is moved, tension in the moved wire loops may increase with increasing travel of the wires. After the wire loops have been placed in a final desired location, the appendage and wire loops may then be protected, sealed, and/or locked in place by placing shrink wrap material about the appendage and wire loops.
Other aspects, features, advantages, etc. will become apparent to one skilled in the art when the description of the preferred embodiments of the invention herein is taken in conjunction with the accompanying drawings.
For the purposes of illustrating the various aspects of the invention, there are shown in the drawings forms that are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
An embodiment of the present invention provides an electrical connector that will adequately and consistently displace the insulation surrounding the magnet wire to make an effective, gas tight electrical connection between the conducting material of the wire and the material of the electrical connector. One or more embodiments provide a connector that may establish an effective, gas tight electrical connection over a large range of magnet wire sizes.
In the following description, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of one or more embodiments of the invention. It will be apparent, however, to one having ordinary skill in the art, that the invention may be practiced without these specific details. In some instances, well-known features may be omitted or simplified so as not to obscure the present invention. Furthermore, reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
Now referring to
Connector 100 may include connector pin 110 which may be stamped so as to include edges 112 thereon. Bobbin 200 may include anchor posts 210 and a groove 230 configured to receive connector pin 110. Wire 220 may be wrapped about bobbin post 210 to form a plurality of loops 224. Wire 220 may be coated with insulation 228. Bobbin 200 and bobbin post 210, may be made of plastic. However, materials may be employed for bobbin 200 and bobbin post 210 such as but not limited to metal (which may be insulated), ceramic, or other suitable materials known to those having ordinary skill in the art.
One or more embodiments of the present invention may provide electrical connector 100 for connecting two or more wires 220 together. Connector 100 may be quickly and efficiently produced with a stamping method using a progressive blanking die. This manufacturing method may be characterized by the occurrence, in the blanked part, of natural rounded edges on the punch entrance side of the part and sharp edges on the opposite (die) side. It is these sharp edges 112 that may be used to enable contact pin 110 to cut into the insulation 228 and thereby establish conductive electrical contact with the conducting material of the coil wire.
Now referring to
Wire 220 may be wound around bobbin 200 before or after the insertion of contact pin 110 into groove (or “hollow” or “hollow portion”) 230 of bobbin post 210. Attention is directed below to an embodiment in which wire 220 is wrapped about bobbin post 210 prior to the introduction of contact pin 110 into the groove 230. One wire 220 may be employed and wrapped to create a plurality of wire loops 224. Alternatively, a plurality of separate wires 220 may be employed and may each be wrapped one or more times to provide loops 224 that extend across groove or hollow portion 230 of bobbin post 210.
A method in accordance with one embodiment may include wrapping wire loops 224 about bobbin post 210. The wire loops 224 bridge across the groove 230, such that when the connector 100, which may include a wedge shaped pin 110, is later inserted into the groove 230 of the bobbin post 210, the combination of bobbin post 210 and wire loops 224 are suitably configured to receive contact pin 110. Once bobbin 200 is suitably configured as described, contact pin 110 may be inserted into the groove 230 (
In one embodiment, anchor posts 210 are used to anchor the beginning and the end of wire 220 of the coil by wrapping the wire around such posts 210. Anchor posts 210 are shown only in schematic form in
In one embodiment, the anchor posts 210 that anchor the two ends wire 220 are converted into small coil forms, (around which many turns of coil wire 220 are wound tightly), which may have grooves therein to allow the introduction of the insulation 228 cutting blades of the connector 110 to impinge against the inner portion of wire loops 224.
In at least one embodiment, means are provided to move the anchor posts 210 into the body of the bobbin 200 and to align anchor posts 210 into the proper path of the connector 110. Thus, otherwise stated, in this embodiment, the anchor posts 210 are incorporated within the body of the bobbin. One such embodiment may enclose within the body of the bobbin 200 all anchor posts 210 and wire 220 ends, so that no trimming of these parts is required. Another embodiment may provide a system and method in which the connection, sealing, taping and/or testing of a pin 110—bobbin 200 assembly are completed within a coiling machine, so that finished coils are completed in a cycle time corresponding to that of a coil winding operation, thereby enabling eliminating one or more further secondary operations.
With reference to
In one or more embodiments, when connector 100 is inserted toward bobbin 200, or other entity, so as to lead with the narrow tip of connector pin 110, the tip of pin 110 may impinge against a sloping surface (or “ramp”), that may be molded into the bobbin 200, which sloping surface may urge the lance 110 to deflect towards the inner part of the coil wire wrapping. Such a ramp is shown in connection with
This impinging action may cause the tapered sharp edges 112 to contact the wire 220 surface (which may include insulation 228). As the connector 100 is advanced with respect to bobbin 200, the lance 110 may be further deflected, thereby enabling lance 110 to apply a progressively increasing force against wire 220 insulation 228. Because of the movement of lance 110 and the force applied against the wire insulation 228, and because the sharp edges 112 of the lance 110 may be tapered, the insulation 228 on the wire loops 224 may peel in the insulation 228 region 604 (
Referring to
Variation of the taper angle 114 may be controlled to bring about desired effects in the process of inserting a connector pin 110 into one or more wire loops 224 to establish conductive electrical contact between the pin 110 and the wire loops 224. Moreover, taper angle 114 may be adjusted to suit the needs of different applications. In one embodiment, lance 110 may be designed to have a gentle taper (that is, with the edges 112 being disposed a relatively small acute angle with respect to the longitudinal axis of the pin 110) where it operates on thinner wires in a fine wire zone of a connector post and a wider taper angle when operating on thicker wires in a robust wire zone, thus producing longer peels on the robust wires. This can be achieved by providing lance edges 112 that have distinctly different taper angles 114, 116 at different points along their length, or by providing curved cutting edges 112. For example, in some embodiments, the taper angle (measured with respect to the longitudinal axis of the pin or lance 110) may be between five and seven degrees, and more specifically, about six degrees. In other embodiments, the taper angle may be between thirteen and seventeen degrees, and more specifically, about fifteen degrees. In still other embodiments, the taper angle could have any value above or below six degrees, and all such variations are intended to be included within the scope of the present invention.
Cutting edge serrations 502, 504 may be effective when dealing with tough insulation 228 material. The dimensions of the serrations and/or the length of the gaps separating successive serrations may be varied among different connector pins 110 based on the benefits that may be obtained therefrom in different applications. For example, in one embodiment, serrations 504 may be coarse near the tip of the lance 110 and fine near the root, thereby enabling pin 110 to impinge more aggressively on a wire when the wire is thicker.
One method of making serrations during stamping tool making may include simply speeding up the wire Electrical Discharge Machining (EDM) process. Speeding up the EDM process as described, may generate a coarse cut on pin 110, and may thereby produce a relatively rough edge 112 which may include the serrations 502, 504 sought in this embodiment of the invention.
The above-described devices for skiving wire 220 differently in different applications may be effective because the ramped groove in the bobbin or connector post 200 may allow the tip of the connector pin or lance 110 to clear the wire 220 in the delicate wire zone as the connector pin 110 is inserted. When suitable lance 110 geometry is established, the lance may be deflected so as to impinge against and skive the wires 220 with suitable cutting force and suitable insulation 228 removal, only when the lance 110 tip insertion proceeds beyond a delicate wire zone of a plurality of wire loops 224.
Referring to
The effects of lance 110 impingement on the surface and structure of wire 220 is now considered in greater detail with regard to
In addition to the effects of skiving on the outer surface of wire 220, skiving of wire 220 by lance 110 may in some cases cause wire 220 to be stretched and bent or kinked along its own longitudinal axis, as shown in
Experiments have demonstrated that the skiving of fine wire (i.e. below 36 AWG) may be conducted more effectively using a shorter peel distance. Conversely, the skiving of robust wire (i.e. above 30 AWG) may benefit from the use of a longer peel distance.
When establishing contact between connector pins 110 and fine wires 220, the skiving pressure (or “impingement force”), that is, the force compelling the wire 220 against the sharp edge of the connector pin 110, may have consequences for wire 220. If the impingement force is too high, the wires 220 may be excessively weakened or, in an extreme case, severed. If the impingement force is too low, the tension in the wire 220 may not be sufficient to maintain gas-tight contact with connector pin (lance) 110 during duty in a working environment. The impingement force may be affected by the tension in the wire 220 during wrapping of the wire 220 about the bobbin 200, and secondly by the dimensions of the bobbin 200 or connector post 210 and the connector pin 110.
In most cases, the wrapping tension used to wrap wire 220 may be close to the normal tension for coil winding. However, if this tension should prove not to be ideal, then the tension may be modified for a post-wrapping operation. Thereafter, the coil tension used in the pertinent coil wrapping machine may restored to its normal value. There are many means for making the tension adjustment including, but not limited to pneumatic dancers and wire straighteners, as will be apparent to those skilled in the art of wire handling.
One or more embodiments of the invention depicted in
Referring to
Upon impingement by lance 110 of connector 100, the fine wires may be pushed from their initial position 262 into a their final position 264. Similarly robust wires may be pushed from their initial position 266 into their final position 268.
Although the above methods of deflecting parts of the connector 100 by employing a cam 270 surface in the bobbin structure have proved effective, there is concern about the long term possible relaxation of the plastic parts (plastic creep) and a possible detrimental change that relaxes the contact pressure. Additional embodiments are depicted in
In these embodiments, a portion of the metal of the connector is stamped and retained and used as a wedge 130, which is urged into a narrowed opening between a pair of lances 110, thereby opening the lances 110 to impinge and scrape and make electrical contact with the coil wire wraps 224. The urging of the wedge 130 is accomplished by the action of inserting the connector 100 into the bobbin 200. The wedge impinges against a plastic surface of the bobbin and enters the space between the lances and reaches a point where it is beyond having any back reacting force. Plastic creep then has no effect.
Now referring to
Therefore, in instances where the conventional material is not strong and hard enough to perform the duties required in the foregoing embodiments, other embodiments are provided. In accordance with at least one embodiment, a method is provided for deflecting the connector elements that does not rely on the strength and hardness and long term stability of the bobbin 200 material.
In order to reduce the force needed to move the slugs 130 during assembly, with reference to
Attention is now directed to
In one or more embodiments, connector 900 may include connector pin 910 which may, in turn, include spring-loaded prongs (or “springs”) 920 and 930 and edges 912. Bobbin 1000 may include anchor post 1010 and may have wire 1020 wrapped thereabout to form plurality of wire loops 1024. Shrink wrap sleeve 1300 (
In an embodiment, when a plurality of loops 1024 of wire 1020 are wound before the connector 900 is assembled into the bobbin 1000, the wire 1020 may be anchored at each end of bobbin 1000 by wrapping wire 1020 around one or more bobbin 1000 structures. Once wire 1020 is suitably anchored, connector 900 may be inserted into the bobbin structure 1000, thereby causing sharp-edged features 912 of each connector pin 910 impinge on, skive and make electrical contact with the wire loops 1024 that are wrapped around the anchoring structures. See
With reference to
It is noted that while the above discussion is directed to embodiments in which pin 910 impinges on the interior surfaces of wire loops 1024 that are wrapped about bobbin 1000, in other embodiments, pin 910, or other structures may impinge on, skive, and establish conductive contact with other portions of wire loops 1024, including outer portions of loops 1024, whether along the exterior of the sides, top, or bottom of bobbin 1000.
In one or more embodiments, a bobbin, such as bobbin 1000, may include a surface that may be operable to push and deflect the contacting element of the connector 900 into impingement with the wire 1020. However, in contrast, one or more embodiments discussed below may involve having a preloaded element of the connector 910 being held back during assembly by a bobbin surface, possibly within bobbin groove 1030, and then released into spring-loaded contact with wire 1020 once the connector 900 is fully assembled. See
Now referring to
Note that the two sets of wire wraps shown in
During this movement, as the embodiment shown has a thicker root thickness, the wire wraps are compressed to be adjacent with each other and experience stretching, skiving and scraping contact with the connector appendage's sharp edges. The wire tension generally increases but, as the wrap initially at position 1430 moves further along the appendage to position 1440 than does the wrap initially at position 1432 which moves to position 1442, it is stretched more and therefore has more tensional stress. This produces a gradient tensile stress in the wire with the maximum stress being at the safest position most remote from the coil.
In accordance with at least one aspect of the present invention, contact may be established between appendage or “contact pin” 1400 and metal of wire 1420 in many places along the wire 1420. This approach may provide protective redundancy in that, if some appendage-wire contact areas fail, other contacts that are performing well, may serve as a backup.
However, with reference to
Herein, the term “coil” refers to a length of coil wire that is wound around a bobbin. This coil may contain many thousands of turns and serves to convert electrical energy into mechanical energy and movement, such as in a solenoid operating a valve or a power contactor.
A natural tension gradient may result from the magnitude of the linear gap or distance between neighboring wire loops 1424 on appendage 1400. In some embodiments, this fact may be beneficially exploited. The wire loops 1424 may be placed at a high end of the tension gradient, such as at 1902 in
Wire tension may be operable to apply the force that causes the devices of one or more embodiments of the present invention to function. However, the wire 1420 tension should preferably stay well below breaking tension. Therefore, suitably controlling the tension in wire 1420 may be beneficial for the operation of the embodiments disclosed herein.
The final resulting tension, or overall tension, in wire 1420 may be the result of at least four major contributions. The final resulting wire 1420 tension may be controlled by adjusting one or more of these four contributions.
A first contribution to the overall tension, is the initial tension with which wire 1420 is wound by a winding machine, in a fully automatic winding operation, or by the feel and skill of a human operator in a semi-automatic manual anchoring operation. A second contribution may arise from the helical pitch of the initial wrapping operations, as set by the action of a wire guide in a computer-controlled winding machine or by the operator in a manual anchoring operation. A third contribution may arise from the change in cross section of the appendage 1400 along which the wire loops 1424 are moved and compressed. The magnitude of this third contribution may fixed by the design of the appendage 1400. A fourth contribution to the final wire tension may be a function of the distance that the wire loops 1424 are moved along the length of the appendage 1400. This distance may be determined a design of the assembly process and/or of the assembly equipment.
It is noted that the shape of the appendage 1400 may be adjusted and fixed by the design and manufacture of the connector 1402, and may not be adjustable at the time of the winding operation. Therefore, the initial tension setting and the helical pitch adjustment may be the only variables that can be controlled at the time of the wire 1420 winding operation. After completing the winding (wire wrapping) operation, the length of the wrap pusher 1900 (
In some embodiments, one or more mechanisms for setting an initial tension for wire 1420 may be provided such as an adjustable spring, weight, and/or gas/fluid loaded dancer arm. This tension may be conveniently used for wrapping wire 1420 about the anchoring appendages.
In some cases, computer controls may be employed to increase or decrease the wire tension at one or more anchoring points. For example, the wire 1420 tension may be reduced when wrapping strain relief loops 1426, and may be increased upon wrapping the main, more tightly tensioned wire loops 1902, which are also denoted herein by reference numeral 1424.
The helical pitch of the wire loop 1424 contact wrapping may have the effect of reducing the final wire 1420 tension. A widely spaced helical pitch may produce a relatively low final wire 1420 wrap tension after the wire loops 1424 are pushed along the length of the appendage, since the wire loops 1424 may be loosened considerably by being forced closer together. In contrast, a closely spaced helical pitch may not cause the wire 1420 tension to decrease as the wire loops 1424 are pushed along appendage 1440 by wrap pusher 1900.
Once a suitable wire 1420 tension is in place, wire 1420 may then be moved relative to the sharp edges 1422 of the connector appendage 1400. The movement of the wire 1420 against the sharp edges 1422 of appendage 1400 may skive the insulation, thereby operating to establish conductive electrical contact between the conductor metal of wire 1420 and the appendage, or connector pin 1400. In one or more embodiments, such as where the wire loops 1424 are quite close together prior to the skiving action, the skiving action may be completed without significantly reducing the tension in wire 1420.
In
During the stamping of the connector 1402, the sharp edges 1422 may be produced by the sudden fracture of the material at the die side. There is typically a small burr protruding in the direction of the punch motion at a sharp edge 1422.
The selection of either a shape shown in
More robust wires, such as wires over 34AWG, do not normally require the tension control that the particular appendage 1400 shapes of
When using wires finer than 42 AWG, the tip 1414 (e.g.
Various other configurations of the appendage 1440 may enable penetrating the insulation of wire 1420 while moving wire 1420 along the length of the appendage 1400. All these possible configurations would be within the spirit and purpose of the present invention.
A method for manipulating the wire loops 1424 to make electrical contact between the wire 1420 and the appendage 1400 is described below. In some embodiments, the appendage 1400 and wire loops may be insulated, protected, and/or sealed to finish the connection and enable appendage 1400 with wire loops 1424 thereon to be effectively preserved.
Attention is directed to
The wire 1420 may then form various loops 1426 around a portion of the appendage 1400 at its root 1412, to provide strain relief. The wire 1420 may then be coupled 1428 onto the main winding of the coil. A portion at the tip 1414 of the appendage 1400 may not be wrapped. This portion may be used to guide the wrap pusher 1900 the operation of which is described below. A similar, but reversed wrapping scheme is used at the end of the coil winding. At the end of the winding, the wire first wraps around the strain relieving portion 1426 then around the contact portion 1902, ending towards the tip 1414 of appendage 1400.
In one or more embodiments, the above-discussed wire 1420 wrapping schemes, in combination with the selected particular shapes of the appendage 1400, may operate to stretch the wire loops 1424 that are farthest from the coil more than those near the coil. In this way, if a fracture occurs, it may be located at a harmless point, that is distant from the coil. Such a fracture may not defeat overall operation of the wound appendage 1400, as sufficient contact points may remain intact to enable sufficient current flow through wire loops 1424 that are still operational.
With reference to
A method of pushing the wire loops 1424 along the appendage 1400 in accordance with one or more embodiments of the invention is described in the following, with reference to
The slot 1910 may form a sliding fit with the appendage 1400. The wrap pusher 1900 may move towards the wire loops 1424 and may impinge against, or otherwise stated, press upon, the first wire loop. Continuing the motion of the wrap pusher 1900 with respect to the appendage 1400 may then compress the distribution of the wire loops 1424 into a confined space, until the loops 1424 are at least substantially adjacent to one another. Moreover, in addition to narrowing the distribution of the wire loops 1424, the wire loops as a whole may be pushed inward (that is, toward root 1412) along the appendage 1400.
In this way, insulation may be pierced and scraped from the wire 1420, thereby exposing the conducting material within wire 1420, as the wire is slightly stretched. Further motion may then press the conducting material of the wire 1420 to the appendage 1400, such as to corners 1422 of appendage 1400, thereby establishing conductive electrical contact between appendage 1400 and wire 1420. The motion of wire loops 1424 may then be stopped to avoid overstraining and/or breaking wire 1420.
Thereafter, with reference to
In one embodiment, the shrink wrap 2300 may not cover the few wire loops around the root 1412 of the appendage 1400. These uncovered wire loops 1426 may provide a strain relief which may support the relatively long span of unsupported wire from the appendage 1400 to the main coil winding and may prevent the vibration of this span from causing wire breakage at the stress-concentrating point where the wire 1420 enters the firm constraint of the encapsulation 2300. If the encapsulating material 2300 is soft and elastic than strain relief may not be required.
Another alternative is to use a resilient elastomer such as silicone rubber tube stretched over a form tube which is placed over the connector appendage 1400 and the wire loops 1424. The form tube may be removed while the rubber tube is stripped to compress tightly around the appendage 1400 and the wire loops 1424. This latter approach may present the advantage not needing heat. An adhesive and or a lubricant can be dispensed either onto the connector 1402 or into the tube as assembly takes place.
The shrink wrap 2300 method with the adhesive inner coating 2310 can have electrically conductive adhesive (not shown). This provides a back up so that in the event of a wire fracture that occurs within the adhesive 2310, the exposed ends of the wire 1402 may maintain contact through the conductive particles suspended in the adhesive 2310. Although the resistance of conductive adhesive may exceed that of metal, the conductive adhesive may still provide an effective current path when coils are wound with very fine wire. Such coils may have relatively high resistance and are operated at higher voltages. Thus, the extra resistance of the adhesive is not enough to significantly change the operation of the connector 1402.
With lower voltage coils, which may have more robust wire, the total coil resistance may be much lower, and the extra resistance of the conductive adhesive 2310 could cause significant alteration of the coil conditions and at some point not provide the protection sought. However this concern may be moot because since such wire is more robust, the wire is less likely to fracture and therefore may not need the protection afforded by conductive adhesive 2310. In view of the foregoing, coils with fine wires could be manufactured with shrink wraps 2300 that have conductive adhesive 2310, and coils with thicker wire could be manufactured with shrink wraps that employ non-conductive adhesive.
Another method of sealing the appendage 1400 with wire loops 1424 thereabout may involve omitting shrink wrap and applying adhesive directly to the wire 1420 that is wrapped around the connector appendage 1400 or the anchor post. As discussed above, such adhesive could be conductive or non-conductive in accordance with the gauge of the wire 1420, as discussed above.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.
This application claims the benefit of U.S. Provisional Patent applications Ser. No. 60/756,264, filed Jan. 4, 2006, 60/785,628 filed Mar. 24, 2006, 60/792,446 filed Apr. 17, 2006, 60/799,226 filed May 10, 2006, 60/813,643 filed Jun. 14, 2006, 60/836,159 filed Aug. 8, 2006; and 60/865,477 filed Nov. 13, 2006, the disclosures of which applications are incorporated in their entirety by reference herein.
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