Fastener for fastening circuit card

Abstract

A fastener for fastening a circuit card assembly to a metal casting, the fastener comprising: a head having a first radius; a pin having a second radius less than the first radius, the pin extending from the head along the longitudinal axis, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature on the outer surface extending from the head toward a tip of the pin, the surface feature including: a helical knurl having a plurality of knurls extending from the head to the tip of the pin, the plurality of knurls form a helix, where each knurl of the plurality of knurls at least partially circumferentially surrounds the longitudinal axis.

Description

Technical Field

[0001] This specification generally relates to fasteners, and more particularly to fasteners for fastening a circuit card assembly to a metal casting. Background Art

[0002] In various manufacturing processes, screws are used to attach one component to another. When fastening components together, manufacturing using screws requires controlling the torque value. Controlling torque can be difficult to replicate and increases the time required for manufacturing. Additionally, over-tightening the screws can damage the components being attached together. Thus, alternative fasteners for attaching two components together are needed. Summary of the Invention

[0003] In one embodiment, a fastener for fastening a circuit card assembly to a metal casting, the fastener comprising: a head having a first radius; a pin having a second radius less than the first radius, the pin extending from the head along a longitudinal axis, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head toward the end of the pin, the surface feature comprising: a helical knurl having a plurality of knurls extending from the head to the end of the pin, the plurality of knurls forming a helix, wherein each of the plurality of knurls circumferentially surrounds the longitudinal axis at least partially.

[0004] In another embodiment, a fastener for fastening a circuit card assembly to a metal casting, the fastener comprising: a head having a first radius; a pin having a second radius less than the first radius, the pin extending from the head along a longitudinal axis, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head toward the end of the pin, the surface feature comprising: a plurality of barbs, each of the plurality of barbs circumferentially surrounding the longitudinal axis, and the plurality of barbs being spaced apart along the longitudinal axis.

[0005] In yet another embodiment, a circuit card assembly includes: a circuit card including a first opening; a metal casting including a second opening; and a fastener including a head and a pin extending from the head, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head toward the end of the pin, the surface feature being configured to couple the circuit card to the metal casting when the pin is positioned in the first opening and the second opening, and the fastener completing a ground path between the circuit card and the metal casting when positioned in the first opening and the second opening.

[0006] These features and additional features provided by the embodiments described herein will be more fully understood in conjunction with the accompanying drawings and according to the following detailed description. Brief Description of the Drawings

[0007] The embodiments illustrated in the drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of illustrative embodiments can be understood when read in conjunction with the following drawings, in which like structures are indicated with like reference numerals, and in which:

[0008] Figure 1 A cross-sectional side view of a fastener inserted into a circuit card assembly and a metal casting is depicted in accordance with one or more embodiments shown and described herein;

[0009] Figure 2 An example fastener for attaching a circuit card assembly to a metal casting is depicted in accordance with one or more embodiments shown and described herein; and

[0010] Figure 3 Another example fastener for attaching a circuit card assembly to a metal casting is depicted in accordance with one or more embodiments shown and described herein. Detailed Description

[0011] Referring initially to Figure 1 , a circuit card assembly 12 fastened to a metal casting 14 is depicted. The circuit card assembly 12 is fastened to the metal casting 14 by a fastener 10 through a press-fit engagement. The circuit card assembly 12 includes a first attachment opening 13 and a ground path 15 that extends from electronic components (e.g., capacitors, transistors, inductors, etc.) on the circuit card assembly 12 to or near the first attachment opening 13 such that when the fastener 10 is inserted into the first attachment opening 13, the head 16 of the fastener 10 contacts the ground path 15. It is also contemplated and possible that the ground path 15 extends into the opening 13 such that the pin 18 of the fastener 10 contacts the ground path 15. The metal casting 14 includes a second attachment opening 17 for receiving the fastener 10. Each of the first attachment opening 13 and the second attachment opening 17 may have an opening radius that is less than a second radius of the pin 18 of the fastener 10. The smaller radius of the attachment openings 13, 17 allows the pin 18 to engage the attachment openings 13, 17 in a press-fit engagement. The metal casting 14 can be any component made of metal, such as a heat sink, an electric motor housing, etc. The metal can be aluminum, steel, etc. that can be used to ground the circuit card assembly 12.

[0012] The fastener 10 extends into a first attachment opening 13 of the circuit card assembly 12 and a second attachment opening 17 of the metal casting 14 to couple the circuit card assembly 12 to the metal casting 14, wherein the fastener 10 completes a ground path 15 between the circuit card assembly 12 and the metal casting 14, thereby grounding the circuit card assembly 12. As shown by the dashed line, the fastener 10 can be inserted into the circuit card assembly 12 and the metal casting 14 along an insertion axis I that extends through the centers of the first attachment opening 13 and the second attachment opening 17 and along the length of the pin 18.

[0013] Now referring to Figure 2 , there is depicted Figure 1 a first embodiment of the fastener 10. The fastener 10 includes a head 16 and a pin 18 extending from the head 16 along a longitudinal axis 20. The head 16 has a first radius, while the pin 18 has a second radius that is less than the first radius. The pin 18 includes an outer surface 22 circumferentially surrounding the longitudinal axis 20 and surface features 24 on the outer surface 22 that extend from the head 16 toward the end 26 of the pin 18. The surface features 24 can be at least one of a plurality of barbs 32, a helical knurl 30, and a plurality of threads. Figure 2 The fastener 10 depicted in

[0014] The fastener 10 may include a chamfer 28 at the end 26 of the pin 18, the chamfer 28 having an angle between 25° and 40° relative to the longitudinal axis 20, or the fastener 10 may include a rounded corner. The fastener 10 may further include the length of the pin 18 that is positioned between the surface feature 24 and the end 26 of the pin 18 and that does not include the surface feature 24, wherein the length of the pin 18 that does not have the surface feature 24 extends from the surface feature 24 to the chamfer 28. The length of the portion of the pin 18 that does not have the surface feature 24 may be one-third (1 / 3) of the diameter of the portion of the pin 18 that does not have the surface feature 24. In other words, the ratio of the length to the diameter of the portion of the pin 18 that does not have the surface feature 24 is 1 / 3. The size of the opening 17 in the metal casting 14 may be determined to have the same radius or a slightly larger radius as the length of the portion of the pin 18 that does not have the surface feature 24. For example, the opening 17 may have a radius that is up to 0.03 mm larger than the radius of the length of the portion of the pin 18 that does not have the surface feature 24. The fastener 10 may include a zinc coating (or other coating that allows grounding) for preventing corrosion.

[0015] Now referring Figure 3 , another embodiment of a fastener 10' is depicted. In addition to the surface feature 24, the fastener 10' may include each of the features described above with reference Figure 2 . Thus, for the sake of brevity, like features will not be described again. The surface feature 24 of the fastener 10' may be a plurality of barbs 32, wherein each barb of the plurality of barbs 32 circumferentially surrounds the longitudinal axis 20, and the plurality of barbs 32 are spaced apart along the longitudinal axis 20. The plurality of barbs 32 are arranged sequentially along the longitudinal axis 20. The plurality of barbs 32 may include any operable number of barbs, including 1 barb, 20 barbs, or any number of barbs therebetween, and more specifically includes 12 barbs. The barbs 32 may each have a uniform thickness (e.g., a distance along the longitudinal axis 20) and a uniform spacing between the barbs along the longitudinal axis 20. The barbs 32 may have a radius that is 0.15 mm larger than the radius of the pin 18. The barbs 32 may be angled at at least 10 degrees with respect to an axis perpendicular to the axis 20. The barbs 32 may be angled to allow the pin 18 to be inserted into the opening 17.

[0016] It should be noted that the terms "substantially" and "about" may be used herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also used herein to represent the degree to which a quantitative representation may vary from the reference without causing a fundamental change in the basic function of the subject matter being discussed.

[0017] Although specific embodiments have been shown and described herein, it should be understood that various other changes and modifications can be made without departing from the spirit and scope of the claimed subject matter. Additionally, although various aspects of the claimed subject matter have been described herein, these aspects need not be used in combination. Accordingly, the appended claims are intended to cover all such changes and modifications that fall within the scope of the claimed subject matter.

Claims

1. A fastener for fastening a circuit card assembly to a metal casting, the fastener comprising: A head having a first radius; A pin having a second radius smaller than the first radius, the pin extending from the head along a longitudinal axis, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head towards the end of the pin, the surface feature comprising: A helical knurl having a plurality of knurls extending from the head towards the end of the pin, the plurality of knurls forming a helix, wherein each of the plurality of knurls circumferentially surrounds the longitudinal axis at least partially.

2. The fastener according to claim 1, further comprising a chamfer at the end of the pin, the chamfer having an angle between 25° and 40° relative to the longitudinal axis.

3. The fastener according to claim 1, further comprising a length of the pin that does not include the surface feature, the length being located between the surface feature and the end of the pin.

4. The fastener according to claim 1, wherein, The length of the surface feature is greater than the length of the portion of the pin that does not include the surface feature.

5. The fastener according to claim 1, wherein, The fastener is made of steel having a zinc coating.

6. The fastener according to claim 1, wherein, The plurality of knurls includes at least 10 knurls.

7. The fastener according to claim 1, wherein, At least one of the plurality of knurls is angled relative to the longitudinal axis, and the angle is between 25° and 40°.

8. A fastener for fastening a circuit card assembly to a metal casting, the fastener comprising: A head having a first radius; A pin having a second radius smaller than the first radius, the pin extending from the head along a longitudinal axis, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head towards the end of the pin, the surface feature comprising: A plurality of barbs, each of the plurality of barbs circumferentially surrounding the longitudinal axis, and the plurality of barbs being spaced apart along the longitudinal axis.

9. The fastener according to claim 8, wherein, The plurality of barbs are arranged sequentially along the longitudinal axis.

10. The fastener according to claim 8, further comprising a chamfer at the end of the pin, the chamfer having an angle between 25° and 40° relative to the longitudinal axis.

11. The fastener according to claim 8, further comprising a length of the portion of the pin that does not include the surface feature, the length being located between the surface feature and the end of the pin.

12. The fastener according to claim 8, wherein, The length of the surface feature is greater than the length of the portion of the pin that does not include the surface feature.

13. The fastener according to claim 8, wherein, The fastener is made of steel having a zinc coating.

14. The fastener according to claim 8, wherein, The plurality of barbs includes at least 10 barbs.

15. The fastener according to claim 8, wherein, The plurality of barbs are angled relative to the longitudinal axis, and the angle is between 25° and 40°.

16. A circuit card assembly, comprising: A circuit card including a first opening; A metal casting including a second opening; And A fastener, comprising a head and a pin extending from the head, the pin including an outer surface circumferentially surrounding the longitudinal axis and a surface feature extending on the outer surface from the head towards the end of the pin, the surface feature being configured to couple the circuit card to the metal casting when the pin is positioned in the first opening and the second opening, and the fastener completing a ground path between the circuit card and the metal casting when positioned in the first opening and the second opening.

17. The circuit card assembly according to claim 16, wherein, The surface feature includes: A helical knurl having a plurality of knurls extending from the head towards the end of the pin, the plurality of knurls forming a helix, wherein each of the plurality of knurls at least partially circumferentially surrounds the longitudinal axis.

18. The circuit card assembly according to claim 17, wherein, The plurality of knurls includes at least 10 knurls.

19. The circuit card assembly according to claim 17, wherein, The plurality of knurls are angled with respect to the longitudinal axis, and the angle is between 25° and 40°.

20. The circuit card assembly according to claim 16, wherein, The surface feature includes: A plurality of barbs, each of the plurality of barbs circumferentially surrounding the longitudinal axis, and the plurality of barbs being spaced apart along the longitudinal axis.

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