STRAIN RELIEF PLUG FOR LEAD WIRES ON A PRINTED CIRCUIT BOARD

Abstract

A strain relief plug to restrict movement of wires on a printed circuit board, the strain relief plug having an elongated stem along a vertical axis of the strain relief plug. The strain relief plug has an in-board flange defined by the elongated stem, the in-board flange configured to seat in a bore defined by the printed circuit board. The strain relief plug has an anchor defined by a first end of the elongated stem configured to prevent the strain relief plug from releasing from the printed circuit board. The strain relief plug has a bar defined by a second end of the elongated stem and transverse the vertical axis, the bar forming wire channels. The strain relief plug provides strain relief for wires on the printed circuit board of an electric motor in a vertical dimension resembling the thickness of the printed circuit board.

Claims

1. A strain relief plug to restrict movement of one or more lead wires on a printed circuit board, the strain relief plug comprising: an elongated stem along a vertical axis of the strain relief plug; an in-board flange defined by the elongated stem, the in-board flange configured to seat in a bore defined by the printed circuit board; an anchor defined by a first end of the elongated stem configured to prevent the strain relief plug from releasing from the printed circuit board; and a bar defined by a second end of the elongated stem and transverse the vertical axis, the bar forming one or more lead wire channels to trap the one or more lead wires.

2. The strain relief plug of claim 1, wherein the bar has turned ends.

3. The strain relief plug of claim 1, wherein the anchor comprises one or more flexible barbs.

4. The strain relief plug of claim 1, wherein the anchor extends outwardly toward the bar to form a gap between the anchor and the bar, the gap sized relative to a thickness of the printed circuit board and the one or more lead wires.

5. The strain relief plug of claim 1, further comprising one or more brackets defined by the elongated stern and extending transverse the vertical axis, the one or more brackets joining the bar, wherein the anchor extends outwardly toward the one or more brackets to form a gap between the anchor and the one or more brackets, the gap sized relative to a thickness of the printed circuit board and the one or more lead wires.

6. The strain relief plug of claim 1, wherein the in-board flange includes a radial body having a tapered profile on an edge thereof to aid installation into the bore defined by the printed circuit board.

7. The strain relief plug of claim 1, further comprising a reinforcing spine affixed to bar.

8. The strain relief plug of claim 1, wherein the bar is configured to secure the one or more lead wires against the printed circuit board.

9. The strain relief plug of claim 1, wherein the strain relief plug relieves strain on one or more lead wires on a printed circuit board of an electric motor within a vertical dimension resembling the thickness of the printed circuit board and the one or more lead wires.

10. An electric motor with the strain relief plug of claim 1, wherein strain relief is accomplished within a vertical dimension resembling the thickness of the printed circuit board and the one or more lead wires.

11. A printed circuit board for use in an electric motor, the printed circuit board comprising: one or more lead wires soldered to the printed circuit board forming one or more solder joints; and a strain relief plug having an elongated stem along a vertical axis of the strain relief plug; an inboard flange defined by the elongated stem, the in-board flange configured to seat in a bore defined by the printed circuit board; an anchor defined by a first end of the elongated stem having one or more flexible barbs configured to prevent the strain relief plug from releasing from the printed circuit board; and a bar defined by a second end of the elongated stem and transverse the vertical axis, the bar having turned ends to form one or more lead wire channels to trap the one or more lead wires, wherein the one or more barbs extend outwardly toward the bar to form a gap between the one or more barbs and the turned ends, the gap sized relative to a thickness of the printed circuit board and the one or more lead wires.

12. The strain relief plug of claim 11, further comprising one or more brackets defined by the elongated stem and extending transverse the vertical axis. the one or more brackets joining the bar, wherein the anchor extends outwardly toward the one or more brackets to form a gap between the anchor and the one or mare brackets, the gap sized relative to a thickness of the printed circuit board and the one or more lead wires.

13. The strain relief plug of claim 11, wherein the in-board flange includes a radial body having a tapered profile on an edge thereof to aid installation into the bore defined by the printed circuit board.

14. The strain relief plug of claim 11, further comprising a reinforcing spine affixed to bar.

15. The strain relief plug of claim 11, wherein the bar is configured to secure the one or more lead wires against the printed circuit board.

16. The strain relief plug of claim 11, wherein the strain relief plug relieves strain on one or more lead wires on the printed circuit board of the electric motor within a vertical dimension resembling the thickness of the printed circuit board and the one or more lead wires.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various aspects of the present disclosure are discussed herein with reference to the accompanying Figures. It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements can be exaggerated relative to other elements for clarity or several physical components can be included in one functional block or element. Further, where considered appropriate, reference numerals can be repeated among the drawings to indicate corresponding or analogous elements. For purposes of clarity, however, not every component can be labeled in every drawing. The Figures are provided for the purposes of illustration and explanation and are not intended as a definition of the limits of the disclosure.

[0018] FIG. 1 is an isolated perspective view of a strain relief plug in accordance with the subject disclosure.

[0019] FIGS. 2a-2b are cross-sectional perspective views of the strain relief plug of FIG. 1 installed on a printed circuit board.

[0020] FIG. 3 is a perspective view of the strain relief plug of FIG. 1 installed on a printed circuit board, including one or more lead wires.

[0021] FIGS. 4a-4e are overhead perspective views of the strain relief plug of

[0022] FIG. 1 installed on a printed circuit board.

[0023] FIG. 5 is a side perspective view of the strain relief plug of FIG. 1 installed on a printed circuit board, showing a wire gap between one or more lead wires and the printed circuit board.

[0024] FIGS. 6a-6b are cross-sectional views of another implementation of a strain relief plug in accordance with the subject disclosure.

[0025] FIG. 7a is a top view of an electric motor armature with connections to a printed circuit board, wherein the strain relief plug of FIG. 1 is installed thereon, acting on sensor lead wires.

[0026] FIG. 7b-7c are perspective views of the electric motor armature of FIG. 7a.

[0027] FIG. 7d is a side view of the electric motor armature of FIG. 7a, displaying the profile height of the strain relief plug relative to the thickness of the sensor lead wires and printed circuit board thickness.

DETAILED DESCRIPTION

[0028] The subject technology overcomes many of the prior art problems associated with strain relief devices. The advantages, and other features of the technology disclosed herein, will become more readily apparent to those having ordinary skill in the art from the following detailed description of certain exemplary embodiments taken in combination with the drawings and wherein like reference numerals identify similar structural elements. It should be noted that directional indications such as vertical, horizontal, upward. downward, right. left and the like. are used with respect to the figures and not meant in a limiting manner.

[0029] Referring now to FIG. 1, a strain relief plug 100 is shown. The strain relief plug 100 may be readily installed to a printed circuit board or other installations to protect solder joints or other fragile secured wire connections from detrimental pulling forces, tension, stress, and the like. There is a great variety of electrical and solid state equipment including printed circuit boards or modules which are interconnected with other printed circuit boards or modules. This interconnection is enabled by securing interconnecting lead wires through the agency of relatively fragile bonds or solder joints on thin metallic solder pads. In all such instances, it is beneficial that these fragile connections be protected from any damaging mechanical forces encountered in assembling, using, maintaining, and servicing the equipment.

[0030] A coordinate system is used herein to help characterize implementations of the strain relief plug 100. For example, a vertical axis 104, a transverse axis 130, and an axial axis 146 are referenced. The vertical axis 104 defines a vertical direction of the strain relief plug 100, the transverse axis 130 is disposed at a 90 degree angle relative to the vertical axis 104 and defines a lateral direction of the strain relief plug 100, and an axial axis 146 is disposed at a 90 degree angle relative to the vertical axis 104 and the transverse axis 130 and defines an axial direction of the strain relief plug 100 and a lead wire direction.

[0031] Referring briefly to FIGS. 2a-2b for context, a cross-sectional view is illustrated of a conventional printed circuit board 202 with the strain relief plug 100 of FIG. 1 installed therein. The printed circuit board 202 may include one or more typical flat laminated composites made from non-conductive substrate materials with one or more layers of copper circuitry buried internally or on an external surface. The printed circuit board 202 may include a first surface 204 and an opposing second surface 206 with conventional conductors etched on either the first or second surfaces 204, 206. As referenced herein, the printed circuit board 202 includes a thickness t, shown in greater detail with reference to FIG. 2a. The thickness is defined by a height of a connecting surface 208 joining the first surface 204 and the second surface 206.

[0032] Referring to FIGS. 1, 2a, and 2b together, the strain relief plug 100 may be molded from a slightly resilient or flexible plastic. Alternatively, the strain relief plug 100 may include copper, silver, aluminum, gold, steel, or brass portions. The strain relief plug 100 is formed in the general configuration of a “T”, which includes an elongated stem 102. The elongated stem 102 runs parallel to a vertical axis 104 of the strain relief plug 100. As illustrated in FIG. 1, the elongated stem 102 terminates at a first end 106 thereof.

[0033] The first end 106 includes an anchor 108 defined thereby. The anchor 108 may include one or more flexible barbs 110 configured to prevent the strain relief plug 100 from releasing from the printed circuit board 202. The bore 210 of the printed circuit board 202 may force an inner surface 112 of the one or more flexible barbs 110 to associate with a peripheral surface 114 of the elongated stem 102 upon insertion. Once the first end 106 of the elongated stem 102 has cleared the bore 210 of the printed circuit board 202, the one or more barbs 110 may unassociate and broaden from the peripheral surface 114 such as to rivet, clamp, pin, screw, or otherwise fasten to the printed circuit board 202.

[0034] In other implementations, the anchor 108 may include an enlargement or a knob-like projection. In this regard, the anchor 108 may be removably coupled to the elongated stern 102. Upon installation of the strain relief plug 100 into the bore 210 of the printed circuit board 202, and once the first end 106 of the elongated stern 102 has cleared the bore 210 of the printed circuit board 202, the anchor 108 may thereafter be coupled to the first end 106 of the elongated stern 102 such as to rivet, clamp, pin, screw, or otherwise fasten to the printed circuit board 202.

[0035] Disposed between the first end 106 and a second end 116 of the elongated stern 102 is an in-board flange 118 defined by the elongated stem 102. The in-board flange 118 may include a radial body. In this regard, the in-board flange 118 may include a curvilinear geometric shape, such as that of a cylinder. The in-board flange 118 may include a first opposing surface 120, a second opposing surface (not shown) opposite thereto, and a lateral side 123 joining the first opposing surface 120 and the second opposing surface. The lateral side 123 may include a height 124 relative to the vertical axis 104 of the strain relief plug 100.

[0036] The height 124 of the lateral side 123 of the in-board flange 118 may resemble the thickness t of the printed circuit board 202. For example, the height 124 may be the same as the thickness t of the printed circuit board 202, slightly larger the thickness t of the printed circuit board 202, or slightly less than the thickness t of the printed circuit board 202. In the same respect, the in-board flange 118 may include a radius 126. The radius 126 may resemble a radius of the bore 210 defined by the printed circuit board 202, shown in greater detail with reference to FIG. 2a. For example, the radius 126 may be the same as the radius of the bore 210, slightly larger the radius of the bore 210, or slightly less than the radius of the bore 210.

[0037] The in-board flange 118 configured to seat in a bore 210 defined by the printed circuit board 202 restricts transverse 130 motion of the strain relief plug 100, does not restrict rotation of the plug 100, and allows for installation at an arbitrary angular position.

[0038] The in-board flange also does not over constrain an azimuthal orientation of the plug 100. This provides a range of angular position for the installation of the strain relief plug 100 to align with respect to various position of wires 212.

[0039] In FIGS. 2a-2b, the in-board flange 118 fits snug in the bore 210. Thus, the in-board flange 118 has a smaller radius 126 than the radius of the bore 210. The difference in radius may be miniscule to enable a close-fit between the two components.

[0040] The in-board flange 118 may include a beveled edge 122. The beveled edge 122 may have a tapered profile to aid installation of the strain relief plug 100 into the bore 210 defined by the printed circuit board 202. The beveled edge 122 may slope inwardly such that the first opposing surface 120 has a greater radius than the second opposing surface. As such, the beveled edge 122 may include a varying radius.

[0041] The second end 116 of the elongated stem 102 defines a bar 128. The bar 128 extends along a transverse axis 130 relative to the vertical axis 104 of the strain relief plug 100. In one implementation, the bar 128 may include a three-dimensional U-shape having a flat mounting surface 132 and one or more subjacent surfaces 134. In another implementation, the bar 128 may include a portion of a three-dimensional annular shape, torus shape. or ellipsoid shape. In yet another implementation, the bar 128 may include a three-dimensional rectangular shape having a flat mounting surface 132 and one or more flat subjacent surfaces 134.

[0042] In one implementation, the bar 128 may include a spine 150 mounted to the mounting surface 132. The spine 150 may extend along the transverse axis 130 and provide support to the U-shape structure of the bar 128.

[0043] The bar 128 may include turned ends 136. For example, the mounting surface 132 may extend along the transverse axis 130 to a mounting surface curve 138, and thereafter extend vertically along the vertical axis 104, parallel to the elongated stem 102, defining the turned ends 136. The mounting surface 132 may meet the one or more subjacent surfaces 134 at a turned end periphery 140 to form the three-dimensional U-shape mentioned.

[0044] The bar 128 and the anchor 108 form a gap g. For example, in one implementation, the turned end periphery 140 and a flexible barb periphery 148 may form the gap g. The one or more flexible barbs 110 and the turned ends 136 may each include a respective height relative to the vertical axis 104 to adjust the length, width, or height dimension of the gap g. In a preferred implementation, the one or more flexible barbs 110 and the turned ends 136 form a gap g having a vertical dimension resembling the thickness t of the printed circuit board 202 and one or more lead wires 212. For example, the gap g may have a vertical dimension equal to, slightly less than, or slightly larger than the thickness t of the printed circuit board 202.

[0045] To install, the strain relief plug 100 may be inserted into the bore 210 defined by the printed circuit board 202. The one or more flexible barbs 110 are configured to prevent the strain relief plug from releasing from the printed circuit board 202 as a flexible barb periphery 148 makes contact with the second surface 206 of the printed circuit board 202.

[0046] Once the strain relief plug 100 is installed in the bore 210 of the printed circuit board 202 as shown in FIGS. 2a-2b, the turned ends 136 and the one or more flexible barbs 110 make contact with opposite sides of the printed circuit board 202, restricting movement of the printed circuit board 202 relative to the vertical axis 104 of FIG. 1.

[0047] Additionally, the bar 128 forms one or more lead wire channels 142 to trap or restrict the one or more lead wires 212 on the printed circuit board 202. In one implementation, the turned ends 136 may include an outward ledge 144 to restrict movement of the one or more lead wires 212 along the transverse axis 130. In another implementation, the subjacent surface 134 of the bar 128 may restrict movement of the one or more lead wires 212 along the vertical axis 104. In yet another implementation, the subjacent surface 134 of the bar 128 may restrict movement of one or more lead wires 212 along a transverse axis 130 by pinning the one or more lead wires 212 against the printed circuit board 202. In yet another implementation, the subjacent surface 134 of the bar 128 may restrict movement of the one or more lead wires 212 along an axial axis 146 by pinning the one or more lead wires 212 against the printed circuit board 202. In yet another implementation, the turned ends 136, subjacent surface 134 of the bar 128, and the first opposing surface 120 of the in-board flange 118 form one or more lead wire channels 142 to trap the one or more lead wires 212 on the printed circuit board 202.

[0048] In FIGS. 2a-2b, the one or more lead wires are restricted in motion along the transverse axis 130 of FIG. 1 by the turned ends 136, while the one or more lead wires are restricted in motion along the vertical axis 104 of FIG. 1 by subjacent surface 134 of the bar 128 and the first surface 204 of the printed circuit board 202.

[0049] Though, the anchor 108 and in-board flange 118 do not constrain the angular orientation of the plug 100 and allow for variability in the directional alignment of the wires 212 on the printed circuit board 202.

[0050] Referring now to FIG. 3 and FIGS. 4a-4e, a perspective view and overhead views of the strain relief plug 100 installed in the bore 210 of the printed circuit board 202 are shown. The strain relief plug 100 restricts motion of the one or more lead wires 212 along the transverse axis 130 and/or vertical axis 104 shown in FIG. 1, with respect to solder joints 402. In turn, detrimental pulling forces, tension, stress, and the like are mitigated on the solder joints 402.

[0051] FIG. 5 shows a perspective view of the strain relief plug 100 installed in the bore 210 of the printed circuit board 202. In the implementation shown, the anchor 108 includes an enlargement or a knob-like projection. In this regard, the anchor 108 is removably coupled to the elongated stem 102. Upon installation of the strain relief plug 100 into the printed circuit board 202, the anchor 108 may thereafter be coupled to the first end 106 of the elongated stern 102 such as to rivet, clamp, pin, screw, or otherwise fasten to the printed circuit board 202.

[0052] FIG. 5 also shows a wire gap 502 between the one or more lead wires 212 and the circuit board 202. As such, the one or more lead wires 212 need not make contact with the first surface 204 of the circuit board 202 to restrict movement. Similarly the one or more lead wires 212 need not make contact with the turned ends 136 of the strain relief plug 100. Rather, in both scenarios, the first surface 204 or the turned ends 136 may provide a motion boundary in which the one or more lead wires can move along the vertical 104 and transverse axis 130.

[0053] FIGS. 6a-6b show another implementation of a strain relief plug 600, similar to the strain relief plug 100 of FIG. 1. The strain relief plug 600 of FIGS. 6a-6b is different from the strain relief plug 100 in that strain relief plug 600 includes one or more brackets 602. The one or more brackets 602 are defined by the elongated stem 102 and extend along the transverse axis 130 of FIGS. 6a-6b, that is, transverse the vertical axis 104. The one or more brackets 602 join the turned ends 136 to form one or more lead wire channels 142 that are enclosed, encapsulating at least a portion of the one or more lead wires 212. The one or more brackets 602 may form a bracket angle 604 or may curve in order to join the turned ends 136.

[0054] Additionally, the strain relief plug 600 is different from the strain relief plug 100 in that the bar 128 of strain relief plug 600 transitions into the turned ends 136 at a rigid angle as opposed to the strain relief plug 100 of FIG. 1. For example, the bar 128 may transition into turned ends 136 at a 90 degree angle. For example, the bar 128 may transition into turned ends 136 at an angle ranging from 1 to 179 degrees.

[0055] FIGS. 7a-7d show top, side, and axial views of an electric motor armature 700 with connections to a printed circuit board 202. The electric motor armature 700 carries alternating current. Armature windings conduct AC even on DC machines, due to commutator action (which periodically reverses current direction) or electronic commutation, as in brushless DC motors. The armature 700 can be on either the rotor (rotating part) or the stator (stationary part) of an electric motor, depending on the type of electric machine. The strain relief plug 100 of FIG. 1 is installed to the printed circuit board 202 of the electric motor armature 700. The strain relief plug 100 restricts motion of the one or more lead wires 212 along the transverse axis 130 and/or vertical axis 104 shown in FIG. 1, with respect to solder joints 402. In turn, detrimental pulling forces, tension, stress. and the like are mitigated on the solder joints 402.

[0056] Referring specifically to FIG. 7d, the strain relief plug 100 has a relatively low profile height compared to the thickness of the one or more lead wires 212 and printed circuit board 202 thickness. This low profile helps improve the electric motor assembly torque density.

[0057] As can be seen, the subject disclosure provides many improvements to strain relief devices. For example, without limitation, the use of the strain relief plug 100, 600 described herein provides strain relief in a vertical direction, resembling the thickness of one or more lead wires and the thickness of a printed circuit board, amounting to a reliable way to protect soldered joints and lead wires connected thereto. During assembly, testing, use, and maintenance of printed circuit boards having such connection, the lead wires are frequently pulled from modules and boards. Further, the subject technology can be adapted to any kind of solder joint, module, or board.

[0058] All of the features as described achieve strain relief for solder joints in a considerably low profile topology component compared to commercially available strain reliefs. That is, the strain relief plugs 100, 600 hold lead wires in a manner to prevent stress on a solder joint without adding substantial height to a printed circuit board.

[0059] As a further advantage, the strain relief plugs 100, 600 described herein accomplish strain relief of solder joints on electric motor connection printed circuit boards. Electric motor performance is commonly compared on the basis of torque per length or torque per volume. The low profile of strain relief plugs 100, 600 facilitates improvements in torque density on the order of 30% compared to existing products in the marketplace when used for strain relief of solder joints on an electric motor connection printed circuit board.

[0060] It will be appreciated by those of ordinary skill in the pertinent art that the functions of several elements can, in alternative embodiments, be carried out by fewer elements, or a single element. Similarly, in some embodiments, any functional element can perform fewer, or different, operations than those described with respect to the illustrated embodiment. Also, functional elements shown as distinct for purposes of illustration can be incorporated within other functional elements in a particular embodiment.

[0061] While the subject technology has been described with respect to various embodiments, those skilled in the art will readily appreciate that various changes and/or modifications can be made to the subject technology without departing from the scope of the present disclosure.