Gas separation: apparatus – Solid sorbent apparatus – Plural diverse separating means
Reexamination Certificate
2002-09-06
2004-03-30
Lawrence, Frank M. (Department: 1724)
Gas separation: apparatus
Solid sorbent apparatus
Plural diverse separating means
C096S139000, C055S385400, C055S385600, C360S097020
Reexamination Certificate
active
06712887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas adsorption filter that is provided at the breather hole for the pressure regulation of a semi airtight container that requires pressure regulation and has means for the elimination of chemical contaminants which enter through the breather hole.
2. Description of Related Art
Magnetic storage disk systems are extremely susceptible to chemical contamination. High molecular weight organic vapors are absorbed by the extremely smooth surfaces of the disk and the slider and, in addition, the characteristics of the fluid lubricants change. Other chemical contamination, for example, by SO
2
, causes the corrosion of the disk and head alloys and, especially, of magnetoresistive read-out elements. Previously, magnetic storage disk systems were made in a completely hermetically sealed form in order to prevent the entry of this kind of corrosive gas from outside. However, with the progressing changeover at the present time to stainless steel press molded plates for the top cover, the volume change distortion of completely hermetically sealed types due to temperature changes is great, producing problems such as head crashes, case deformation, and the like and it has become common to provide a breather hole so as to carry out pressure regulation. In addition, in order to prevent the entry of minute particles and the influx of corrosive gases, gas adsorption breather filters are often used that have a gas adsorbing agent and a particle filter combined in a single unit. With this filter, the entire breather hole is covered with an active carbon sheet or the like and the harmful gases that seek to enter are eliminated by passing the gases through the interior of the gas adsorbent material layer.
However, since air passes through the filter, nonwoven cloth type sheets, porous sheets, and the like having low permeability resistance are demanded. As a measure in response to that, schemes to reduce the permeability resistance such as decreasing the density and weight per unit area of the nonwoven cloth or increasing porosity have been employed. However, the resulting dilemma that is faced is that the packing density of the gas adsorbing agent is reduced and the adsorption effectiveness is lowered. Currently, in general, in contrast to breather filters that are not provided with a gas adsorbing agent, a tenfold pressure loss for gas adsorbent material sheets is common.
With the gas adsorption breather filter, a low pressure loss is demanded. In those cases where there is a high pressure loss, it is not possible for air to pass through to obtain satisfactory moderation with regard to the pressure changes in the magnetic storage disk system that accompany temperature changes when the system is turned on and off and with the high-speed rotation of the spindle motor. With this, air enters through those places where the sealing is weak rather than through the breather hole, bringing about an influx of contaminants. Because of this, an active carbon sheet such as an active carbon fiber woven fabric like Kynol is widely used for the gas adsorption breather filter. However, in the case of this woven fabric, the pressure loss is naturally low but the active carbon density per unit volume is low at 0.26 g/cc.
Incidentally, together with the currently increasing storage capacity of magnetic storage disk systems, their utilization environment is worsening due to a transition to higher rotation speeds and the spread of mobile type personal computer use and an increase in the amount of the activated carbon of the breather hole is desirable. In addition, because of the improvements that accompany higher hard disk drive (HDD) performance, the read heads of the HDD have come to be vulnerable with respect to contamination. Due to a transition to higher performance devices and use in environments other than a well-kept office environment, there has come to be a demand for not only the control of the influx of corrosive gases through the breather hole, but for much more stringent control of the gases and moisture generated by the motor and the like in the HDD. Because of this, there is always a demand that the amount of activated carbon that is enclosed in the filter be increased as much as possible.
However, when the amount of activated carbon is increased, the pressure loss for the filter increases and leakage problems such as those described before and the like are produced. Therefore, HDD manufacturers always are faced with the dilemma of the difficulty of achieving both the demanded reduction of filter pressure losses and the demanded increase in the amount of activated carbon at the same time.
A method has been proposed to resolve at one time the demand for an increase in the amount of activated carbon and the demand to reduce pressure losses as a method to resolve this dilemma (Japanese Laid-Open Patent Application Publication (Kokai) Number 2000-70649). With this, the contaminants are eliminated from the air that flows into a semi airtight container by having the air flow through the adsorbent material surface that is formed in the flow path and, since the air passes through a flow path having a low resistance, it is possible to keep the pressure loss low.
Incidentally, recently for HDDs, there has been an increasing demand for the rapid damping of pressure changes within the HDD, in other words, for breather filters with an extremely low resistance (pressure loss). The improvement of the damping performance of the breather filter is possible by relaxing the stringent specifications of the seal material. That is to say, if the pressure damping capability of the breather hole is satisfactorily increased even when the seal performance is low, the problem in which air flows other than through the breather hole does not occur. In addition, this makes it possible to relax the sealing specifications of not only the packing that fixes and seals the top cover but also the connector section for bringing in the electric power, inputting and outputting data and the like, as well as the portion for anchoring the motor and the like. By this means, it becomes permissible to use low-cost seal materials and, in addition, the simplification of the assembly process is possible. The result is that this makes a great contribution to reducing the total cost of the HDD.
In addition, the molding of the gas adsorbing agent as a protuberance which is formed in the space where the fluid that moves between the airtight container and the outside flows has been proposed as an improved plan (Japanese Laid-Open Patent Application Publication (Kokai) Number 2000-107543). This is done because the adsorbent material becomes a hindrance to the flow of the fluid and, as a result, the pressure drop is increased at the time of passing through the filter.
The methods that have been proposed here have as their aim solely the reduction of pressure losses by the filter and are proposed as measures to counteract that. However, two problems can be anticipated with these two methods.
(1) When the pressure loss becomes small, the air that is flowing through will quickly pass through the filter. In this case, the corrosive gases that are flowing through are not able to have satisfactory contact with the adsorbing agent and flow into the semi airtight container with a portion not adsorbed by the adsorbing agent. In other words, the corrosive gases that flow in without being captured adhere to the heads and media and there is a possibility that eventually the device will lapse into functional disorder. In other words, with these methods, the pressure loss is reduced but the measures they employ regarding gas adsorption performance are not satisfactory.
(2) These methods are effective in those cases where the influx of the air that flows through is from the center of the filter. However, in those cases where the breather hole is not in the center, in the same manner as in (1), as is to be expected, the air that flows through passes through the shortest distance and fl
Sasaki Yutaka
Ueki Takuya
Japan Gore-Tex Inc.
Lawrence Frank M.
Lewis White Carol A.
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