Board lock

A board lock includes a base section fixed to an electrical device, such as a connector, and an elastically diameter-contractible barrel section extending from the base section beyond a face of the electrical device. The barrel has an external threading. The barrel has a section of nominal diameter substantially equal to or greater than an inner diameter of a hole defined in a circuit board whereby the barrel is elastically contractible to be inserted into the hole which generates a spring-back force driving the external threading to engage with the inner diameter thereby securing the electrical device to the substrate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to a board lock for securing an 
electrical device, such as a connector, to a substrate, and in particular 
to a universal board lock which is capable of securing an electrical 
device to substrates of different thicknesses. 
2. The Prior Art 
An electrical circuit usually comprises a printed circuit board on which a 
plurality of electrical elements and devices are mounted. Some of the 
electrical elements are fixed to the circuit board by means of external 
fasteners or board locks before being soldered to the circuit board. 
Examples of board locks are shown in Taiwan Patent Application Nos. 
83112290 and 84101384. 
The conventional board locks comprise a plate-like base from which two 
resilient legs extend. The legs have barbs formed on free ends thereof 
opposite each other whereby when the legs are inserted into a hole defined 
in a substrate, the barbs extend beyond a bottom surface of the substrate 
and engage therewith. 
FIG. 1A of the attached drawings shows a conventional board lock 50. The 
board lock 50 comprises an enlarged plate-like base section 51 from which 
two resilient legs 52 extend. Each resilient leg 52 has a barb 53 formed 
on a free end thereof. The board lock 50 is received in a bore 71 defined 
in an electrical device 70, such as a connector, whereby the base section 
51 is supported on a shoulder 72 of the device 70 and the legs 52 extend 
through a narrow section of the bore 71. 
The legs 52 are received in a hole 61 defined in a circuit board 60. The 
free ends of the legs 52 extend through the hole 61 and the barbs 53 
engage with a bottom surface of the circuit board 60 thereby securing the 
electrical connector 70 to the circuit board 60. 
The securement of the electrical connector 70 to the circuit board 60 is 
basically provided by the engagement between the barbs 53 and the bottom 
surface of the circuit board 60. This implies that the axial dimension of 
the legs 52 has to substantially correspond to the thickness of the 
circuit board 60 in order to ensure an effective securement of the 
electrical connector 70 to the circuit board 60. 
As shown in FIG. 1B, if the legs 52 have a length substantially greater 
than the thickness of a circuit board 60' and extend through a hole 61' 
defined in the circuit board 60', then a distance exists between the barbs 
53 and the bottom surface of the circuit board 60'. This distance prevents 
the barbs 53 from securely engaging with the bottom surface of the circuit 
board 60' and the connector 70 is not soundly secured on the circuit board 
60'. 
Therefore, a disadvantage associated with such a conventional design is 
that different board locks must be used for circuit boards having 
different thicknesses. 
It is thus desirable to have a universal board lock which allows an 
electrical device to be effectively secured to substrates of different 
thicknesses. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a board lock 
which is capable of mounting an electrical device to circuit boards of 
different thicknesses. 
Another object of the present invention is to provide a board lock which is 
capable of engaging with a substrate through holes of different diameters 
defined therein. 
A further object of the present invention is to provide an electrical 
connection device which comprises an electrical connector secured to a 
circuit board by means of the board lock described above. 
To achieve the above objects, a board lock in accordance with the present 
invention comprises a base section fixed to an electrical device, such as 
a connector, and an elastically diameter-contractible barrel section 
extending from the base section beyond a face of the electrical device. 
The barrel has an external threading. The barrel has a section of nominal 
diameter substantially equal to or greater than an inner diameter of a 
hole defined in a circuit board whereby the barrel is elastically 
contractible to be inserted into the hole which generates a spring-back 
force driving the external threading to engage the inner diameter thereby 
securing the electrical device to the substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings and in particular to FIG. 2, a pair of board 
locks 20 constructed in accordance with the present invention are used to 
secure an electrical connector 1 to a circuit board 40 (FIG. 4A) or 40' 
(FIG. 4B). The connector 1 comprises an insulative casing 10 having a 
plurality of conductive terminals 30 received and fixed therein for 
electrical connection with a mating device (not shown). The casing 10 
defines a recessed section 12 in opposite ends thereof for fixedly 
receiving the board lock 20 therein respectively. 
Further referring to FIGS. 3A-3C, the board lock 20 of the present 
invention comprises a plate-like base section 21 from which a barrel-like 
section 22 extends. The base section 21 is received in the corresponding 
recessed section 12 of the casing 10 of the connector 1. The base section 
21 defines a central hole 24 through which a fastener 13 extends. The 
fastener 13 is fixed to the casing 10 thereby securing the board lock 20 
to the casing 10 of the connector 1. 
As shown in FIG. 3A, the barrel section 22 is preferably constructed by 
forming a flat plate 22' into a cylinder. The plate 22' is preferably 
connected to the base section 21 by a neck 211. Threading 23 may be formed 
on the plate 22' by a stamping procedure. 
The plate 22' defines a plurality of slits 222 substantially parallel to 
each other. The cylinder defines a gap 25 (FIG. 3B) between two opposite 
edges of the plate 22'. Therefore, the barrel section 22 constructed from 
the plate 22' comprises a plurality of axially-extending slits 222 which 
are circumferentially spaced. The slits 222 and the gap 25 divide the 
barrel section 22 into several resilient segments 221 (FIG. 3A) each 
having a portion of the threading 23 formed thereon. 
Preferably, the cylinder constructed from the plate 22' forms a central 
outward convex portion having an increased diameter. 
Referring back to FIG. 2, the recessed section 12 of the connector 1 may be 
provided with a notch 14 for receiving the neck 211n of he board lock 20. 
Due to the provision of the slits 222 and the gap 25, the segments 221 of 
the barrel section 22 are contractible when acted upon by a radial force 
thereby reducing the diameter of the barrel section 22. The contracted 
condition of the barrel section 22 allows the barrel section 22 to be 
readily fit into a hole 41 defined in a substrate 40 having a specific 
thickness "a" (FIG. 4A). The resiliency of the segments 221 of the barrel 
section 22 generates a spring-back force which causes the barrel section 
22 to resume its original diameter upon removal of the radial force. The 
threading 23 may be arranged to engage with an inner surface of the hole 
41 and a bottom surface of the substrate 40 to secure the connector 1 to 
the substrate 40. 
It is understood that the central convex portion of the barrel section 22 
allows a portion of the threading 23 to engage with a bottom surface of 
the substrate 40 thereby enhancing the securement of the connector 1 to 
the substrate 40. 
FIG. 4B shows that the board lock 20 secures a connector 1 to a substrate 
40' of a smaller thickness "b". The barrel section 22 is fit into a hole 
41' and engages with the substrate 40'. Due to the convex portion of the 
barrel section 22, the threading 23 engages with an inner surface of the 
hole 41' and a bottom surface of the substrate 40' to securely fix the 
connector 1 to the substrate 40'. 
It can be noted that because the invention provides a line/circumferential 
engagement between the board lock 20 and the substrate 40 instead of the 
traditional two opposite points engagement, the securement effect can be 
increased. By the way, in the invention through some proper arrangement of 
the lead angle and the pitch of the thread, and the angle of the convex 
portion of the barrel section 20, the threading 23 may engage both the 
inner surface of the hole 41 and the bottom surface of the substrate 40 to 
generate two directional retention forces, i.e., the horizontal lateral 
force derived from the engagement upon the inner surface of the hole and 
the vertical force derived from the engagement upon the bottom surface of 
the substrate around the hole. 
It should be noted that although an electrical connector is taken as an 
example to explain the present invention, the application of the present 
invention is not limited to the connector. The board lock of the present 
invention may be used to secure other devices or articles to a substrate. 
Although the present invention has been described with reference to a 
preferred embodiment thereof, it is apparent to those skilled in the art 
that a variety of modifications and changes may be made without departing 
from the scope of the present invention which is intended to be defined by 
the appended claims.