Post retention arrangement

Abstract: An arrangement for securing a body (12) to a support (10) by means of a post (16) on the body which is inserted into an aperture (14) in the support. The post (16) is formed with a cavity into which there is inserted a resilient retaining member (34) having tapered barbs (42) extending outwardly of the post from opposite sides thereof. When the post (16) is thereafter inserted into the aperture (14), the retaining member (34) is compressed and the barbs (42) engage the interior walls of the aperture (14) to prevent subsequent removal of the post therefrom.

Description: This invention relates to the mounting of a body or member on a support by means of a post on the body which is adapted for insertion into an aperture in the support and, more particularly, to a device for retaining the post within the aperture. The present invention finds particular utility in the mounting of a connector receptacle block to a printed circuit board. In the past, such mounting has been effected by a variety of arrangements. For example, the connector receptacle block has often been formed with outwardly extending mounting ears having through-bores for accepting threaded mounting bolts which extend through appropriate positioned apertures in the circuit board for securement by nuts on the opposite side of the circuit board. Such an arrangement has an obvious disadvantage in that numerous small parts and a relatively complex assembly operation are required. Another mounting approach has involved the use of a barbed planar metal insert which extends through, and is captured in, a slot in the connector receptacle body and is then inserted through an appropriate aperture in the circuit board. This arrangement is disadvantageous in some applications because of its limited strength. A further mounting arrangement utilizes posts which are integrally molded to the plastic connector receptacle body and extend through appropriately located apertures in the circuit board. The ends of the posts extending through the other side of the circuit board are then heat staked to the circuit board. This arrangement is disadvantageous in that the heat required for the heat staking operation crystallizes and degrades the plastic material. It is therefore an object of the present invention to provide a securing arrangement or device of the type described which does not suffer from the disadvantages enumerated above. The invention consists in a securing device for securing a member to a support, comprising at least one post projecting from the member and including a cavity in which a retaining member is disposed, said post along with said retaining member being insertable into an aperture in the support to maintain said post within the aperture, characterized in that said cavity has a U-shape, said retaining member has a U-shape including a first leg portion, a second leg portion and a connecting portion disposed along corresponding leg and connecting portions of said cavity, and said first leg portion of said retaining member has outwardly extending portions extending beyond opposite sides of said post for engagement with the aperture wall. A securing device according to the preamble of claim 1 is, for example, known from GB-A-2 239 135. In one embodiment of the invention, the or each post has a major longitudinal axis and is formed with a generally planar cavity along a plane containing the axis, which cavity is open at both ends along a line transverse to the axis. The device further includes a generally planar resilient retaining member contained within the post cavity. The retaining member has a greater dimension than the width of the post at the outwardly extending portions so that the latter extend outwardly beyond opposite sides of the post. These outwardly extending portions are angled away from the post in a direction opposite to the direction of insertion of the post into an aperture and terminate in sharp corners. As the retaining member is larger than the internal dimension of the aperture, when the post is inserted into the aperture the retaining member is resiliently compressed and its outwardly extending sharp corners engage the walls of the aperture to prevent removal of the post therefrom. The retaining member may be formed with a notch between the sharp corners to allow compression of the retaining member substantially within its plane. Preferably both the cavity and the retaining member are generally U-shaped and are oriented sideways relative to the axis. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 is an exploded perspective view schematically showing how a connector receptacle block may be secured to a circuit board in accordance with the principles of this invention; FIGURE 2 is an elevational view showing the post of one embodiment of this invention; FIGURE 3 is a bottom plan view of the post of Figure 2; FIGURE 4 is a cross sectional view taken along the line 4-4 in Figure 2; FIGURE 5 is a cross sectional view taken along the line 5-5 in Figure 2; FIGURE 6 is an elevational view of a retaining member for use with the post of Figures 2 to 5; FIGURE 7 is a view similar to Figure 4 showing the retaining member of Figure 6 installed within the post of Figures 2-5; and FIGURE 8 is a view similar to Figure 7 showing the post and retaining member inserted in the aperture of the board shown in Figure 1. Referring now to the drawings, Figure 1 illustrates a printed circuit board 10 and a connector receptacle block 12 which is to be mounted to the board 10. While a printed circuit board 10 and a connector receptacle block 12 are specifically illustrated herein, it is understood that the principles of this invention are applicable to other types of supports and bodies or members. As shown in Figure 1, the board 10 is formed with a pair of apertures 14 and the block 12 is formed with a pair of posts 16. The spacing of the posts 16 matches the spacing of the apertures 14 so that the posts 16 may be inserted into respective ones of the apertures 14 for mounting the block 12 to the board 10. For ease of manufacture, the apertures 14 preferably are circular and the posts 16 are cylindrical, but other shapes are possible. Further, the block 12 and the posts 16 preferably are integrally molded of a plastic material. As shown in the drawings, each post 16 is formed with a cavity 18. The post 16 has a major longitudinal axis 20 and the cavity 18 is generally planar along a plane containing the axis 20. Preferably, the cavity 18 is generally U-shaped with a first leg portion 22, a second leg portion 24 and a central connecting portion 26, all within the plane. As shown, the U-shape of the cavity 18 is oriented sideways relative to the axis 20. The central connecting portion 26 is generally parallel to the axis 20 and is open along a wall 28 of the post 16. The first leg portion 22 of the cavity 18 extends through the post 16 across its width and is open at a wall 30 of the post 16 across the axis 20 from the central connecting portion 26. For reasons which will become apparent from the following description, the second leg portion 24 of the cavity 18 is preferably open at the end 32 of the post 16 which is remote from the block 12. Further, the central connecting portion 26 of the cavity 18 is formed to taper inwardly from the wall 28 of the post 16, as clearly shown in Figures 3 and 5. Finally, the post 16 is preferably tapered at its distal end 32 for ease of insertion into the aperture 14. In accordance with this invention, there is provided a retaining member 34, adapted for containment within the cavity 18. The retaining member 34 is generally planar and resilient and is preferably formed by being stamped from flat sheet stock metal. As shown in the drawings, the retaining member 34 is shaped complemental to the cavity 18. Thus, the retaining member 34 is preferably generally U-shaped with a first leg portion 36, a second leg portion 38 and a central connecting portion 40. The first leg portion 36 of the retaining member 34 is adapted for insertion into the first leg portion 22 of the cavity 18. Likewise, the second leg portion 38 of the retaining member 34 is adapted for insertion into the second leg portion 24 of the cavity 18. Finally, the central connecting portion 40 of the retaining member 34 is adapted for insertion into the central connecting portion 26 of the cavity 18. The taper of the central connecting portion 26 of the cavity 18 aids in the insertion of the retaining member 34 into the cavity 18. As is clear from Figure 7, the retaining member 34 is sized so that its first leg portion 36 has a maximum dimension along its length which is greater than the length of the first leg portion 22 of the cavity 18. That is, the length of the first leg portion 36 of the retaining member 34 is inserted into the cavity 18, the first leg portion 36 extends outwardly beyond the walls 28 and 30 of the post 16. The first leg portion 36 is formed so that those outwardly extending portions are angled away from the post 16 in a direction opposite to the direction in which the post 16 is inserted into the aperture 14, with the outwardly extending portions terminating in sharp corners 42. In effect, the outwardly extending portions of the retaining member 34 function as barbs. The retaining member 34 is further formed with a notch 44 in the first leg portion 36 between the sharp corners 42 thereby resulting in two segments 37 and 39 which are connected together at a resilient neck 41. This notch 44 and resilient neck 41 allow compression of the first leg portion 36 substantially within its plane. The retaining member 34 is dimensioned so that when it is inserted into the cavity 18, there is a tight fit around that part of the post 16 which is between the leg portions 22 and 24 of the cavity 18. Further, the facing edges 46 and 48 of the retaining member leg portions 36 and 38, respectively are tapered with a smaller spacing therebetween at the open end (the left when viewed in Figure 6) than at the closed end (the right when viewed in Figure 6) of the retaining member 34. Thus, when the retaining member 34 is inserted into the cavity 18, its leg portions 36 and 38 are spread apart slightly so that they exert a compressive force to that part of the post 16 which is between the cavity leg portions 22 and 24. Accordingly, when the post 16, having the retaining member 34 contained within the cavity 18, is inserted into the aperture 14, as shown in Figure 8 the leg portion 36 of the retaining member 34 is compressed due to the collapse of the notch 44. The resiliency of the metal forming the retaining member 34 opposes this compression and causes the sharp corners 42 to engage the walls of the aperture 14 so as to prevent removal of the post 16 therefrom. Should removal be attempted, the surface 45 of the post 16 urges the edge 46 upwardly causing the two sections 37 and 39 to tend to spread apart and pivot about the neck 41 so that the two corners 42 dig into the wall of the aperture 14. The greater the upward force of the surface 45, the greater the retention force caused by the corners 42. The aforedescribed arrangement can be used when the aperture 14 in the circuit board 10 is either a plain hole or a plated through-hole. If the aperture 14 is a plain hole, the sharp corners 42 perform the retention function. If the aperture 14 is a plated through-hole, the sharp corners 42 perform an initial retention function and then when wave soldering is performed to the underside of the circuit board 10, the lower leg portion 38 of the retaining member 34, which is exposed through the open cavity leg portion 24, acts to draw the solder upwardly so that the retaining member 34 becomes soldered to the plating on the interior wall of the aperture 14.

Claims: A securing device for securing a member (12) to a support (10) comprising at least one post (16) projecting from the member and including a cavity (18) in which a retaining member (34) is disposed, said post (16) along with said retaining member (34) being insertable into an aperture (14) in the support (10) to maintain said post within the aperture, characterized in that said cavity (18) has a U-shape, said retaining member (34) has a U-shape including a first leg portion (36), a second leg portion (38) and a connecting portion (40) disposed along corresponding leg and connecting portions (22,24,26) of said cavity (18), and said first leg portion (36) of said retaining member has outwardly extending portions (42) extending beyond opposite sides of said post (16) for engagement with the aperture wall. A securing device as claimed in claim 1, characterized in that said outwardly extending portions (42) are angled away from said post (16) in a direction opposite to the direction of insertion of the post into the aperture and terminate in sharp corners. A securing device as claimed in claim 2, characterized in that said retaining member (34) includes a notch (44) between the sharp corners (42) to allow compression of the retaining member within said cavity (18). A securing device as claimed in claim 1,2 or 3, characterized in that said retaining member is planar.

Inventors: BENDORF ROBERT LYNN, BENDORF, ROBERT LYNN
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1993
Main classification: H01R23
IPC codes: H05K3, F16B5, H05K13, H01R13, F16B17, F16B21, H01R12