Locking device for heat dissipating device

[0001] The present invention relates to a locking device, and particularly to a locking device which can conveniently mount a heat sink to an electronic component.

[0002] As computer technology continues to advance, electronic components such as central processing units (CPUs) of computers are made to provide faster operational speed and greater functional capabilities. When a CPU operates at a high speed in a computer enclosure, its temperature increases greatly and dramatically. It is desirable to dissipate the generated heat quickly, for example, by using a heat sink attached to the CPU in the enclosure. This allows the CPU and other electronic components in the enclosure to function within their normal operating temperature ranges, thereby assuring the quality of data management, storage and transfer. Generally, a locking device is required for mounting the heat sink to the CPU.

[0003] FIG. 5 shows a conventional locking device for mounting a heat sink 200 to a CPU 600. The CPU 600 is mounted on a printed circiut board 500 which defines mounting holes 502 about the CPU 600. The heat sink 200 forms a pair of extension arms 202 each of which defines a through hole 204 corresponding to one of the mounting holes 502 of the printed circuit board 500. The locking device comprises a pair of push-in pins 300 and a pair of springs 400 installed around the pins 300 respectively. In assembly, the pins 300 are inserted and extend sequentially through the respective springs 400, through holes 204 of the heat sink 200 and mounting holes 502. The bottom ends of the pins 300 are engaged with the printed circuit board 500 below the mounting holes 502. The springs 400 are compressed between the top ends of the pins 300 and the heat sink 200 to thereby exert downward force to the heat sink 200 to cause the heat sink 200 to intimately contact with the CPU 600.

[0004] However, it is difficult to detach the push-in pins 300 from the printed circuit board 500 in disassembly. Furthermore, the springs 400 are prone to fatigue after a long time using. As a result, the heat sink 200 is not capable of intimately contacting with the CPU 600 in an acceptably long-used period.

[0005] Accordingly, an object of the present invention is to provide a locking device which can firmly mount a heat sink to an electronic component for a long term and conveniently detach the heat sink from the electronic component.

[0006] To achieve the above-mentioned object, a locking device in accordance with a preferred embodiment of the present invention comprises a back plate mounted below a circuit board and comprising a plurality of fasteners extending upwardly beyond the circuit board, and a plurality of retainers. Each retainer comprises an operating member for resting on a heat sink, a locking member extending through the operating member, and a pushing member extending through the locking member. The locking member comprises a locking structure extending through the heat sink to engage with one of the fasteners. The pushing members are downward pushable to disengage the locking structure from the one of the fasteners.

[0007] Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which:

[0013] FIG. 1 shows a locking device in accordance with a preferred embodiment of the present invention for mounting a heat sink 1 to a printed circuit board 2. The printed circuit board 2 defines four through holes 22. An electronic component 24, such as a central processing unit (CPU), is installed on the printed circuit board 2, surrounded by the through holes 22. The heat sink 1 comprises a base 12 for contacting the CPU 70 and a plurality of fins 14 extending from the base 12. Four extension arms 16 extend from four corners of the base 12. Each arm 16 defines a through hole 18 corresponding to one of the through holes 22 of the printed circuit board 2.

[0014] The locking device comprises a back plate 3 and four retainers 4. The back plate 3 is for being mounted below the printed circuit board 2 and comprises a body 32 and four posts 34 extending upwardly from corners of the body 32. Each post 34 forms a barb 36 on a top end thereof to form a fastener. Each retainer 4 comprises a pushing member 42, a locking member 44, an operating member 46, a pair of first and second springs 47, 48.

[0015] Referring also to FIG. 2, the pushing member 42 comprises a head portion 422, a middle portion 424 extending downwardly from the head portion 422, and a bottom portion 426 formed at the bottom of the middle portion 424. The bottom portion 426 has a taper configuration and the transversely sectional diameter thereof increases gradually in a bottom-to-up direction.

[0016] The locking member 44 comprises a head 442 and a cylindric body 444 formed below the head 442. A through aperture 446 is defined in the locking member 44 extending through the head 442 and the body 444. The head 442 defines a pair of spaced semi-annular transverse grooves 448 in the bottom face thereof. The grooves 448 are concentric with each other along the axis of the head 442. Each groove 448 comprises a shallow end A and a deep end B opposing to end A. The depth of each groove 448 increases gradually from the shallow end A to the deep end B. The bottom end of the body 444 defines three longitudinal slots 450 to thereby form three spaced elastic plates 452 beside the three slots 450. Each elastic plate 452 forms a slanted portion 454 at the middle thereof corresponding to the taper bottom portion 426 of the pushing member 42. Each elastic plate 452 forms a hook 456 at the inner face of the distal end thereof. A longitudinal rib 458 is formed on the outer surface of each elastic plate 452. A pair of transverse flanges 459 is formed on the inner surfaces of two of the elastic plates 452.

[0017] The operating member 46 comprises a cylinder 462 with a through aperture 468 defined therein, and a handle 463 formed on the outer circumferential surface of the cylinder 462. A pair of poles 464 extends upwardly from the top surface of the cylinder 462 and is slidable in the respective grooves 448 of the locking member 44. A cavity 466 having a larger diameter than that of the through aperture 468 is defined in the lower portion of the cylinder 462 for receiving the second spring 48 therein.

[0018] In pre-assembly, the first spring 47 is disposed around the middle portion 424 of the pushing member 42. The pushing member 42 with the preset first spring 47 is inserted into and extends through the through aperture 446 of the locking member 44 to have the first spring 47 totally received in the through aperture 446 of the locking member 44 and the bottom portion 426 of the pushing member 42 extending beyond the locking member 44. The body 444 of the locking member 44 then is inserted into and extends through the cylinder 46 and the second spring 48 sequentially. The second spring 48 is received in the cavity 466 of the operating member 46 and firmly disposed around the ribs 458 of the locking member 44. The poles 464 of the operating member 46 are received in the corresponding grooves 448 of the locking member 44 and initially located at the deep ends B. Thus, the retainer 4 is pre-assembled.

[0019] Referring to FIGS. 3–4, in assembly, the back plate 3 is mounted below the printed circuit board 2 with the posts 34 extending through the respective through holes 22 of the heat sink 1. The heat sink 1 is placed on the CPU 24 with the through holes 18 of the heat sink 1 aligned with the respective through holes 22 of the printed circuit board 2. The retainers 4 are placed on the respective arms 16 of the heat sink 1. The bodies 444 of the locking members 44 extend through the corresponding through holes 18 of the heat sink 1 to cause the hooks 456 of the locking members 40 to interlock with the barbs 36 of the back plate 3. The operating members 46 are forced to rotate so as to cause the poles 464 thereof to move from deep ends B to shallow ends A in the grooves 448 of the locking members 44. The operating members 46 are therefore pushed downwardly by the locking members 44 until the operating members 46 firmly contact the corresponding arms 16 of the heat sink 1. The second springs 48 are thus compressed. The operating members 46 exert downward forces to the heat sink 1 whereby the heat sink 1 intimately contacts the CPU 24. Thus, the locking device firmly mounts the heat sink 1 to the CPU 24.

[0020] In disassembly, the pushing members 42 are downwardly pushed. The taper bottom portions 426 of the pushing members 42 push the elastic plates 452 of the locking members 44 outwardly after they contact the slanted portions 454 of the elastic plates 452. The hooks 456 of the locking members 44 therefore move outwardly to release from the barbs 36 of the back plate 3. The second springs 48 stretch toward their original states. The operating members 46 and the locking members 44 are therefore pushed upwardly by the second springs 48 to cause the hooks 456 of the locking members 44 to move away from the barbs 36 of the back plate 3. After that, the retainers 4 are readily detached from the printed circuit board 2.

[0021] In the preferred embodiment, the grooves 448 of the locking member 44 and the poles 464 of the operating member 46 constitute an actuating structure. Alternatively, the positions of the grooves and the poles can be exchanged, i.e., the grooves 448 are formed in the operating member 46 while the poles 464 are formed on the locking member 44. As another embodiment, the actuating structure comprises two pairs of annular wedgy blocks formed on the locking member 44 and the operating member 46 respectively. When one of the wedgy blocks is rotated relative to the other one of the wedgy blocks in a circumferential direction the one of the wedgy blocks is pushed to move relative to the other one of the wedgy blocks in an axis by the other one of the wedgy blocks.

[0022] It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment is to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.