Patent Publication Number: US-6341644-B1

Title: Heat sink assembly

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a heat sink assembly, and particularly to a heat sink assembly having a fixing device for readily and firmly attaching a fan to a heat sink. 
     2. The Related Art 
     Many electronic devices, such as Central Processing Units (CPUs), generate large amounts of heat during operation. This frequently deteriorates the operating stability of the electronic devices. Typically, a heat sink assembly with a fan is used to dissipate heat generated by an electronic device. 
     Referring to FIG. 5, a conventional heat sink assembly as disclosed in Taiwan Patent Application No. 86206427 includes a heat sink  70 , a fan  50  and a fixing device  60  which attaches the fan  50  to the heat sink  70 . The fan  50  is secured on the fixing device  60  with screws. Two arms  62  extend downwardly from opposite sides of the fixing device  60 . Each arm  62  forms a catch  622 . The fan  50  is attached to the heat sink  70  by the catches  622  engaging with apertures  72  defined in the heat sink  70 . 
     However, securing the fan  50  to the fixing device  60  with screws is cumbersome and time-consuming. Furthermore, the fixing device  60  is attached to the heat sink  70  by means of just two catches  622  engaging with two apertures  72 . This leaves the assembly prone to dislodgement when subjected to shock or vibration during normal operation. 
     An improved means of securing a fan to a heat sink, which overcomes the above problems, is desired. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a heat sink assembly having a fixing device which firmly and reliably attaches a fan to a heat sink. 
     Another object of the present invention is to provide a heat sink assembly which is readily assembled and disassembled. 
     To achieve the above-mentioned objects, a heat sink assembly in accordance with the present invention comprises a fan, a heat sink, and a fixing device which attaches the fan to the heat sink. The heat sink has a chassis and a plurality of fins extending upwardly from the chassis. Four catches are formed on respective outermost fins, two on each of two longitudinal sides of the heat sink. The fixing device has a base and four legs depending from respective corners of the base. Four poles extend upwardly from the base near respective corners of the base. A pair of protrusions depends from the base near respective opposite lateral sides of the base. Each leg defines an aperture for engaging with the corresponding catch of the heat sink. The fan defines four through holes for receiving the poles of the fixing device. The fan is thereby firmly securable to the heat sink. 
     Other objects, advantages and novel features of the present invention will be apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a heat sink assembly in accordance with the present invention; 
     FIG. 2 is a perspective view of a fixing device of FIG. 1, but now inverted; 
     FIG. 3 is a partly assembled view of FIG. 1, showing the fixing device with a portion cut away mounted on the heat sink; 
     FIG. 4 is a completely assembled view of FIG. 1; and 
     FIG. 5 is an exploded view of a conventional heat sink assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a heat sink assembly in accordance with the present invention comprises a fan  10 , a heat sink  40 , and a fixing device  20  which attaches the fan  10  to the heat sink  40 . 
     The fan  10  is configured to a shape of a rectangular box, and defines a vertical through hole  12  at each corner thereof. 
     The heat sink  40  has a chassis  42  and a plurality of longitudinal fins  44  extending upwardly from the chassis  42 . A plurality of grooves  46  is defined through the fins  44 . Four external catches  48  are respectively formed at upper portions of four outermost fins  44 , two on each of two longitudinal sides of the heat sink  40 . 
     The fixing device  20  has a rectangular base  22  with a bottom face  23 . The base  22  comprises a body  24  and a pair of shoulders  26  respectively formed on opposite lateral sides thereof. Top surfaces of the shoulder  26  are slightly higher than a top surface of the body  24 , thereby forming a recess (not labeled) for accommodating the fan  10 . The body  24  defines an opening  32  corresponding to a vent (not labeled) of the fan  10 , for providing air flow access for the fan  10 . Four poles  28  extend upwardly from four corners of the body  24  respectively. The poles  28  surround the opening  32 , and correspond to the four through holes  12  of the fan  10  respectively. Each pole  28  has a tapered spring head  30  with a vertical slit  31  defined in a top face thereof, for easily entering into and engaging with the corresponding through hole  12  of the fan  10 . A pair of legs  36  depends from opposite sides of each shoulder  26 . Each leg  36  defines an aperture  38  corresponding to the catch  48  of the heat sink  40 . An inclined resilient tab  34  is stamped downwardly from an outer middle portion of each shoulder  26  between the legs  36 . Also referring to FIG. 2, a pair of protrusions  33  is formed on respective opposite lateral sides of the bottom face  23  of the base  22 , between the resilient tabs  34 . 
     Referring to the FIGS. 3 and 4, in assembly, the fixing device  20  is pushed on top of the heat sink  40 . The protrusions  33  of the fixing device  20  are received in the corresponding grooves  46  of the heat sink  40 , and engage with corresponding side edges (not labeled) of the fins  44 . The aperture  38  of each leg  36  engages with the corresponding catch  48  of the fin  44 . The resilient tab  34  presses against corresponding top surfaces (not labeled) of the fins  44 . Thus the fixing device  20  is firmly attached to the heat sink  40 . Then the fan  10  is put into the recess (not labeled) of the fixing device  20 , with the poles  28  of the fixing device  20  extending into and engaging with the respective through holes  12  of the fan  10 . Thus the fan  10  is readily and firmly attached to the heat sink  40 . 
     It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.