Enhanced panel latch

Details Enhanced panel latch Enhanced panel latch

1999-08-10

2001-09-04

Estremsky, Gary (Department: 3627)

Closure fasteners

Bolts

Spring arm

C411S508000, C024S453000

Reexamination Certificate

active

06283512

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an enhanced panel latch, and in particular, to a one-piece panel latch that is configured to minimize electromagnetic radiation emissions through a latch-receiving opening formed in a panel, for example.
2. Background Information
Frames or other enclosures are often used to house, for example, the various components of an electrical device, such as a computer. For example, circuit boards of the computer may be located within a metal frame to protect the circuit boards from being damaged, and to provide support for the circuit boards so that the circuit boards are properly positioned relative to each other.
In order to conceal the various inner workings of the computer, the frame may be provided with a cover, which may include one or more panels, formed from metal, for example. The installed panel provides a barrier between the internal electrical components of the computer and the user. The panel prevents the user from inadvertently coming in contact with a high-temperature or high-powered component located within the frame, thus protecting the user from accidental injury.
Further, panels help protect the components located within the frame from environmental damage, such as dust or liquid contamination. For example, should a user inadvertently spill a glass of water on the computer, the panel will provide a barrier that will help prevent the water from coming in contact with the internal components.
Additionally, panels provide sound barriers that help to muffle any noise generated by the components within the computer. For example, cooling blowers or fans are often used within the computer frame to cool the high-powered components located within the computer. These cooling blowers tend to generate a substantial amount of noise, which may be annoying to the user of the computer or to others working in the vicinity of the computer. The panel helps to contain this noise.
Furthermore, panels can serve as an electromagnetic shield. As is known, the electrical components located within the frame, when operated, generate emissions that include electromagnetic radiation. When this electromagnetic radiation influences the proper functioning of another device, the result is known as electromagnetic interference (also known as EMI).
In order to ensure that electromagnetic radiation is emitted only at acceptable levels, i.e., to prevent electromagnetic interference, various standards have been developed. For example, both the United States and Canada have determined acceptable electromagnetic radiation emission limits for electrical devices operating at set frequencies. If the electrical device exceeds the determined acceptable emission limits, the sale or use of the electrical device may be prohibited.
In order to reduce the emitted electromagnetic radiation, the panel can be configured to enclose the frame, and be formed of a metal, that, when grounded, will attenuate the electromagnetic radiation.
The panel is typically fastened directly to the underlying frame. For example, the panel may be permanently affixed to the frame by welding or gluing the panel to the frame. However, it may be desirable in certain situations to be able to remove the panel from the frame, for example, to allow for the easy replacement of components located within the frame. Thus, it is known to fasten the panel to the underlying frame using removable fasteners. This provides a secure connection between the panel and the frame and helps to prevent the panel from rattling against the frame. For example, a two-piece plastic fastener may be used, which includes a grommet snapped into an opening formed in a receiving part (such as an edge of the frame), and a movable plunger snapped into an opening formed in the removable panel. By engaging the plunger with the grommet, the removable panel can be secured to the receiving part. However, this arrangement requires two discrete components, thus increasing the risk that one of the components may become lost. Additionally, this arrangement requires a relatively precise alignment between the plunger and the grommet for their engagement. Moreover, this known fastener may not draw the removable panel up tight to the receiving part, thus allowing the removable panel to vibrate freely relative to the receiving part. Thus, there is a need for a one-piece panel latch that will hold a removable panel tightly in place, thus preventing a free vibration of the removable panel relative to the receiving part.
Alternatively, threaded fasteners, such as so-called thumbscrews, may be used to fix the removable panel to the frame. Threaded fasteners may provide for a more secure connection than the aforementioned two-piece plastic fastener. However, threaded fasteners require a threaded hole in the receiving part, which increases the cost of producing the receiving part. Moreover, installing and removing threaded fasteners requires numerous turns of the threaded fastener to fully draw the removable panel against the receiving part. Thus, installing and removing a threaded fastener is labor-intensive. Further, a threaded fastener may require the use of a special tool to fully secure the removable panel to the receiving part. Additionally, the threaded fastener is prone to cross-threading, causing damage to both the threaded fastener and the receiving part, thus leaving the threaded fastener, panel and receiving part, unusable. Thus, there is a need for a panel latch that does not require a threaded receiving hole, needs no tools to install, and which can be installed both quickly and easily.
The number of fasteners needed generally depends on the size of the panel, and the size of the fasteners. As will be appreciated, a large fastener may be capable of exerting a greater holding force than a small fastener. Thus, for ease of assembly, it may be desirable to utilize one large fastener, for example, rather than several small fasteners. However, with respect to the aforementioned two-piece plastic fastener, increasing the size of the grommet and movable plunger may require a similar increase in size in an opening formed in the removable panel, in order to accommodate the larger plunger. If the removable panel is used as an electromagnetic radiation shield, increasing the size of the opening in the removable panel disadvantageously allows for the passage of emitted electromagnetic radiation (in the form of electromagnetic radiation waves), thus raising the possibility of electrical magnetic interference.
It is known that an opening will attenuate electromagnetic radiation waves when the opening is less than ½ of the wavelength &lgr; to be attenuated (i.e., length of opening<½&lgr;). Moreover, the smaller the opening, the greater the attenuation of the electromagnetic radiation waves. The attenuation of electromagnetic radiation waves due to passage through an opening can be determined using the following formula:
S=20log(&lgr;/2L),
where
S=the shielding effectiveness of the opening (in decibels);
&lgr;=the wavelength of the electromagnetic radiation; and
L=the maximum linear length of the opening (in meters).
Moreover, the wavelength &lgr; can be determined by dividing the velocity of the electromagnetic radiation wave (i.e., the wave speed, which is approximately 3×10
8
m/sec) by the frequency of the electromagnetic radiation emissions.
Thus, as the operational frequency (and hence, speed) of an electrical device increases, the associated wavelengths become smaller, thus requiring smaller openings. Therefore, it is clear that the size of any opening in the removable panel must be considered, so as to not unnecessarily limit the speed (i.e., bandwidth) of the electrical components located in the frame.
Thus, there is a need for a panel latch that can securely hold a removable panel against a frame, and which does not require a large opening formed in the removable panel to accommodate the panel latch.
SUMMARY OF THE INVENTION
It is, therefore, a princip

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