Patent Application
20080117600
The task of clamping one structure to another can be complicated by many factors. One such complication occurs when the structures must be clamped in an area that is difficult to access. Although the clamping of structures occurs in almost all industries, limited accessibility clamping is a large problem when dealing with the ever shrinking components in the electronics industry.
One structure in the electronics industry that commonly requires clamping is the heat sink of a circuit board. The heat sink facilitates conduction between the circuit board and a larger enclosure or chassis that contains the circuit board. To be effective, conduction requires a strong, solid contact between the two conducting surfaces. Thus, strong contact must be made between the heat sink and both the circuit board and the enclosure respectively. Contact between the heat sink and circuit board is often taken care of right during production as the heat sink is factory assembled to the circuit board. Once the circuit board arrives at its final destination, however, the entire circuit board assembly must then be mounted onto the enclosure in such a way that the heat sink makes strong contact with the enclosure. Ensuring strong contact between the heat sink and the enclosure can be difficult, however, because the circuit board is often much larger than the heat sink and there is often limited space around the circuit board in the enclosure.
Often, the only reasonable way to ensure strong contact with the enclosure is to clamp the heat sink. Screw attachment of the heat sink may be difficult, because heat sinks are often generically designed and may not have screw holes or tabs to match the enclosure. Additionally, once the heat sink has been assembled, modification of the heat sink is not a cost effective option. Since the heat sink and circuit board are typically factory assembled, the possibility of first mounting the heat sink to the enclosure and later mounting the circuit board on top is eliminated.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an apparatus that allows for clamping a structure down in an area with limited accessibility.
The present invention relates to a clamping system that includes at least one rigid clamp member. The rigid clamp member has an angled surface operable to hold a structure against a mounting surface, and the rigid clamp member is configured to be attached to the mounting surface. The clamping system also includes at least one adjustable clamp member. The adjustable clamp member has an angled adjustable surface operable to hold the structure against the mounting surface. Additionally, the adjustable clamp member is configured to be attached to the mounting surface.
The present invention can be more easily understood and further advantages and uses thereof are more readily apparent, when considered in view of the detailed description and the following figures in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Like reference characters denote like elements throughout the Figures and text of the detailed description.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that mechanical and structural changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.
The present clamping system provides an easy way to clamp a structure to a surface when the structure must be clamped in an area with limited accessibility. For example, such a structure can be a small heat sink located under a large circuit board and the heat sink must be clamped to an enclosure. The accessibility of a heat sink under a circuit board can be improved by placing the heat sink near the edge of the circuit board. Even this, however, usually allows access to only one side of the circuit board. The present system is designed, therefore, to securely clamp a structure, such as a heat sink, while requiring access to only one side of the structure.
The present clamping system comprises two or more clamp members. At least one clamp member is a rigid clamp member that is placed on the inaccessible side of the structure to be clamped. Also, at least one clamp member is an adjustable clamp member that is placed adjacent the structure and opposite of the rigid clamp member. The adjustable clamp member forces the structure downward and against the rigid clamp member. When pushed against the rigid clamp member, the structure receives a reactive force both lateral and downward to hold the structure in place. One use of the clamping system is to provide a downward clamp load sufficient to allow proper heat transfer from a heat sink to an enclosure surface.
The present system has many operational advantages. It can clamp many structures of varying shapes and sizes with no modification to the clamped structure. This is very beneficial for use with off the shelf heat sinks that lack custom mounting holes or small factor heat sinks with no space for such holes. The clamping system is also easy to use, as a single screw is sufficient to mount, support and adjust the adjustable clamp. In addition to its operational advantages, the present system has a cost-effective design that requires only two clamp members. Each clamp member uses only a single piece of sheet metal and requires no additional value added steps, e.g. welding, to maintain the structure. Finally, the clamp members are easily scalable to different sized structures and different clamping force needs. A simple change in the material of construction, or the size or thickness of the sheet metal changes the effective spring constant and accommodates different clamping requirements.
In one embodiment, circuit board assembly 104 comprises a heat sink 110, a first circuit board 112, a second circuit board 114, a third circuit board 116, and a carrier chassis 118. The circuit board assembly 104 can be fully assembled at a factory, with assembly 104 being sent to another location before mounting to enclosure 102. At the factory, assembly of circuit board assembly 104 begins by mounting heat sink 110 to first circuit board 112. The first circuit board 112 and heat sink 110 are then connected to second circuit board 114 and third circuit board 116. The resulting assembly of heat sink 110, first circuit board 112, second circuit board 114, and third circuit board 116 is mounted on carrier chassis 118. In one embodiment, carrier chassis 118 is composed of sheet metal and provides support to the circuit boards. The support of carrier chassis 118 is necessary to withstand the shock that occurs during transportation of circuit board assembly 104.
In another embodiment, heat sink 110 is mounted directly to a processor and the processor is on a single large circuit board. Alternatively, heat sink 110 could be mounted on a circuit board assembly of any size or containing any number of circuit boards as long as there is access to at least one side of heat sink 110. More detail regarding first clamp member 106 and second clamp member 108 is provided as follows by referring to
In one embodiment, first clamp member 106 has a generally triangular shaped cross-section such as an obtuse triangular shape. In this embodiment, first clamp member 106 has a bottom side 210, a contact side 212 and a support side 214. Bottom side 210 allows first clamp member to be easily mounted to enclosure 102. Contact side 212 extends from bottom side 210 and is angled generally downward to provide contact surface 202 with the proper angle 204. Support side 214 connects the far end of bottom side 210 with the far end of contact side 212. Support side 214 supports the contact side 212 and improves the ability of contact surface 202 to provide reactive force upon heat sink 110 as heat sink 110 is pushed against contact surface 202.
In one embodiment, first clamp member 106 can be attached to enclosure 102 by placing a pan head screw 216 through securing point 218. Securing point 218 extends outside the triangle of first clamp member 106 from the corner between support side 214 and bottom side 210. Pan head screw 216 is inserted through first clamp member 106 at securing point 218 and screwed into enclosure 102 at an aperture 220 to attach first clamp member 106 to mounting surface 103 of enclosure 102.
In one embodiment, first clamp member 106 is composed of a unitary piece of sheet metal. Constructing first clamp member 106 out of a single piece of sheet metal is cost effective, because clamp member 106 does not require many manufacturing steps. First clamp member 106 can be constructed by cutting a piece of sheet metal into a strip. The strip of sheet metal is then bent in three places to form the bottom side 210, contact side 212, support side 214, and securing point 218 of first clamp member 106. In one embodiment, before the strip of sheet metal is bent, one aperture is drilled at each end of the strip. When first clamp member 106 is bent to form its generally triangular cross-section each aperture is aligned to allow pan head screw 216 to be placed through the apertures and screwed into enclosure 102. In another embodiment, both apertures are drilled after bending first clamp member 106 into its triangular cross-section.
In another embodiment, first clamp member 106 is a solid structure, i.e. first clamp member 106 does not have a hollow cross-section as shown in
Referring now to
In one embodiment, seat portion 406 has three layers 412, each layer defining an aperture for load screw 310. Here, load screw 310 functions as a support mechanism by holding second clamp member 108 together as load screw 310 is placed through the three apertures in seat portion 404. Additionally, seat portion 404 supports the head of load screw 310 such that load screw 310 when inserted into aperture 312 will pull seat portion 404 towards mounting surface 103 of enclosure 102. Contact portion 406 has three sides, including one side having a contact surface 302 and two support sides 414. The contact surface 302 applies force to heat sink 110. Each support side 414, in one embodiment, is connected to contact surface 302 and also connected to one layer 412 of seat portion 404. Each support side 414 can also be positioned substantially normal to contact surface 302, such that support sides 414 in combination with the attached layers 412 of seat portion 404 can support contact surface 302 during application of force by contact surface 302.
Referring now to
Once heat sink 110 is in place, second clamp member 108 is placed adjacent heat sink 110 on the opposite side from first clamp member 106 (506). Second clamp member 108 is then attached to mounting surface 103 (508). For example, load screw 310 can be inserted through apertures in second clamp member 108 and into aperture 312 (shown in
Referring back to
As the force applied by second clamp member 108 increases, deflection may also occur at corner 416. Deflection at corner 416 will effectively reduce the force actually applied to heat sink 110. The force applied by second clamp member 108 can be increased by reducing the deflection at corner 416. In one embodiment, this defection can be reduced by increasing the thickness of the sheet metal used to construct second clamp member 106. Increasing the thickness of the sheet metal increases the effective spring constant of the second clamp member 108 and increases the amount of force transferred from the tightening of load screw 310. In another embodiment, the spring constant of second clamp member 108 is adjusted by using a different material, e.g. plastic. Alternatively, any material that is stiffer or more pliable can be used to change the spring constant accordingly.
In other embodiments, multiple clamp members can be used on each side of the clamped structure. For example, two or more first clamp members 106 can be located adjacent to one another on one side of heat sink 110. Two or more second clamp members 108 can also be located adjacent each other on the opposite side of heat sink 110 from first clamp members 106. Alternatively, clamp members could be placed on all sides of a structure as long as the positioning of the clamp members allows the structure to be slid up against the first clamp members 106 and clamped on the opposite side by at least one second clamp member 108. Each first clamp member 106 need not have an exactly matching second clamp member 108. For example, one second clamp member 108 could be used to clamp a circular structure with two first clamp members 106 located 120° away in each direction around the circular structure from the second clamp member 108. In another embodiment, the width of each of the clamp members is varied to, e.g., provide additional force, spread the force more evenly across the clamped structure, or avoid abnormalities of the structure.
One method of manufacturing an adjustable clamp member such as second clamp member 108 is shown in
Apertures 608 can be formed prior or after cutting elongated members 602, 604, 606. One aperture 608 is cut in the first elongated member 602 (708). Two apertures 608 are cut in the second elongated member 604 (710). Finally, one aperture 608 is cut in the third elongated member 606 (712).
In one embodiment, once body 600 has been formed, body 600 can be bent into second clamp member 108 (714). Body 600 is bent in areas 610 and intersections 612 between the dotted lines shown in
In another embodiment, first elongated member 602 is slightly longer than third elongated member 606 and accounts for the bottom layer of seat portion 404. In this embodiment, second elongated member 604 and third elongated member 606 account for the middle and top layers of seat portion 404 respectively. Alternatively, the lengths of elongated members 602, 604, 606 could be modified in any way to change the layers in seat portion 404. In yet another embodiment, elongated members 602, 604, 606 are rounded to provide a smoother contour for second clamp member 108 while the general shape of body 600 is retained.
Manufacturing the clamp members from a single piece of sheet metal is cost effective, simple, and adjustable. When constructing clamp members 106, 108, the width of the sheet metal can be selected based on the desired force to be applied to the clamped structure. Thicker sheet metal does not flex as easily, thus, thicker sheet metal can place a higher clamping load on the clamped structure. Likewise, thinner sheet metal gives more freely and could be used to place a lower clamping force on the clamped structure. Alternatively, the clamping force can be adjusted by changing the size of the clamp members 106, 108 or the material with which the clamp members 106, 108 are made. This effectively changes the spring constant of the clamp members 106, 108.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
