Component sealing system

Method for the removable sealing of a component housing, and apparatus to practice the method using an elastic or conformable sealing band. The present invention teaches a sealing band, preferably elastic, to apply a horizontal seal to the horizontal seam defined by vertically assembled component case elements. The seal is maintained in position over the seam by an alignment element disposed on at least one of the seal and the case. The sealing band is rendered electrically conductive by admixing therewith a conductive material, or by plating thereon a conductive coating. A retaining element may be further added to at least one of the sealing band and the case to minimize tampering with the sealing band once installed.

TECHNICAL FIELD
 The present invention relates to a methodology for removably sealing
 housing elements utilizing an elastic seal element. More particularly, the
 present invention teaches a removable elastic casing methodology
 applicable to precision electronic component cases and the apparatus to
 perform the methodology.
 BACKGROUND OF THE INVENTION
 In many engineering disciplines, one or more housing or case elements are
 mechanically conjoined to form a chamber wherein the functional components
 of a device are housed. It is often the case that one or more of the
 housing elements is itself a functional component of a device. One such
 example is the housing elements of a computer head disc assembly (HDA).
 Typically, in most current production HDAs, at least one of the case
 elements also serves as a mounting frame for mounting at least some of the
 HDA functional components thereto.
 It is often desirable that the housing elements, when mechanically
 conjoined, provide not only a stable mechanical, electrical, hydraulic,
 pneumatic or other platform in which the device's functional components
 operate, but that the housing elements unite to form a sealed environment
 for maintaining those functional components in some form of controlled
 environment. This environment may require the retention of a fluid or
 liquid within the sealed housing, the exclusion of fluids, liquids, or
 contaminants from without the sealed housing, or a combination of both
 requirements.
 Many HDAs in current production are sealed within two horizontally divided
 case halves. In a typical instance, a first case element has disposed upon
 it hard drive functional elements including, but not limited to, at least
 one magnetically recordable and readable hard disk, a motor to drive the
 disk, a read/write head mounted on an arm which may be in turn pivotably
 mounted on the case element, as well as other sundry electro-mechanical
 and electronic components. A second case element, which may or may not
 have additional functional elements disposed thereon, is then positioned
 over the first case element and mechanically secured in place with a
 plurality of mechanical fasteners, e.g. machine screws.
 The plurality of machine screws provide a vertical clamping pressure
 between the first and second horizontally separated case elements.
 Captured between the first and second case elements and forming a seal
 therebetween is often a conformable, or deformable, gasket element.
 Examples of currently utilized gaskets include but are not limited to
 die-cut sheet gaskets, cast resilient polymeric gaskets and O-rings. The
 first and second case elements in operative combination with the screws
 applying a vertical force to the gasket element seal the cavity formed
 within the first and second case elements. This has the effect of
 precluding the unwanted intrusion of contaminants from the ambient
 atmosphere into the case interior.
 Additionally, the case elements/screws/gasket element in operative
 combination often unite to provide an effective electromagnetic
 interference (EMI) barrier. EMI can be a significant problem in computer
 head disc assemblies in that excess levels of EMI can serve to apply an
 unwanted signal or noise to interior components of the HDA. Such noise can
 interfere with the proper read/write functionality of the HDA.
 The case sealing methodology previously outlined presents several problems
 during the manufacture of HDAs. First, in order to ensure an effective
 seal between the first and second case elements, a significant number of
 screws is often required to obtain the required screw clamping pressure
 about the periphery of the case elements as well as to obviate case
 deformation occasioned by that pressure.
 A second problem is that during the manufacturing process of HDAs, it is
 occasionally necessary to rework an HDA being built. This rework is often
 effected subsequent to a final quality assurance check conducted
 subsequent to the final assembly of the drive, which check reveals some
 malfunction. Accordingly, in order to rework a defective drive component
 after final assembly, it is generally necessary to remove the plurality of
 screws uniting the first and second case elements in operative combination
 and to separate those case elements. As the number of screws required to
 mechanically connect the case elements increases, so increases both the
 amount of time required to assemble and disassemble the drive, as well as
 the likelihood that the assembly or disassembly process will damage the
 screw threads of either the screw itself or of the case elements.
 Furthermore, it is often the case that a deformable gasket captured and
 clamped between a first and second case element is permanently deformed
 thereby or is damaged by the separation of the case elements,
 necessitating the replacement of the gasket during rework. Each of these
 factors adds to the time, expense and effort required to rework an HDA.
 One alternative to the use of vertically clamped gasket elements in HDA
 manufacturing technology has been the use of a metalized pressure
 sensitive adhesive tape applied to the seam between case elements
 subsequent to their being mechanically conjoined by a plurality of screws.
 The use of such tape can reduce the number of screws required to
 mechanically conjoin and seal the several case elements, and the metallic
 surface provides the requisite EMI barrier. By removing the requirement
 for an even clamping pressure across a broad horizontal surface, the
 number of screws required to join the case elements is reduced. Because
 the pressure sensitive adhesive tape is metalized, it further acts as an
 effective block to EMI.
 While the previously discussed use of pressure sensitive adhesive tape
 provides an advantage over vertically clamped gaskets, this solution
 presents a new set of problems to HDA designers. A first problem is
 occasioned by the fact that the removal of the tape and/or the adhesive
 residue therefrom during rework constitutes a further increase in labor
 costs during rework. Further, pieces of tape removed during rework may
 inadvertently be introduced into the case interior, requiring further
 effort. A third new problem is occasioned by the fact that adhesives in
 general, and pressure sensitive adhesives in particular, exhibit an
 out-gassing of volatile adhesive components, especially the adhesive's
 solvent or carrier. These volatile components, when admixed with the
 ambient atmosphere inside the HDA and dispersed therethrough can adversely
 effect critical electronic or magnetic components contained inside the
 HDA.
 What is needed is some means to quickly and securely seal and unseal HDA
 case elements. This sealing methodology should reduce the number of screws
 or other mechanical fasteners required to conjoin the case elements. The
 methodology should further minimize damage to the case elements in the
 event it becomes necessary to separate them during rework or repair. The
 seal should leave no appreciable residue behind on being removed, and
 should be easily sealed and unsealed. The seal should not introduce any
 appreciable levels of volatile solvents into the interior of the HDA. It
 would be additionally advantageous if the seal were reusable: failing
 that, its removal should not introduce any additional components into the
 HDA. Finally, the sealing methodology should reduce electromagnetic
 interference beneath an acceptable threshold level, or preclude it
 entirely. It would be further desirable if a sealing methodology could
 facilitate alignment of the several seal elements during construction, and
 optimally minimize unwanted opening of, or tampering with, the seal.
 DISCLOSURE OF INVENTION
 The present invention provides a method to quickly and securely seal and
 unseal HDA case elements, and an apparatus to practice the method. The
 present invention teaches a conformable, and preferably elastic, sealing
 band for applying a horizontally biased sealing pressure to the horizontal
 seam of vertically assembled case elements. An alignment element, disposed
 on at least one of the sealing band and the assembled case, aligns the
 band with case seam during assembly, and maintains the band in place once
 it is assembled to the case. A retaining element may be added to at least
 one of the case and the sealing band to further secure the band to the
 case. This retaining element not only aids in positioning the band, but
 also serves to resist tampering by unauthorized individuals.
 The sealing methodology taught herein has the advantage that it can serve
 to reduce the number of screws or other mechanical fasteners required to
 conjoin the case elements, as screw clamping pressure is not required to
 perfect and maintain the seal between case elements. Also, case distortion
 can be minimized for the same reasons. Further, as no adhesives are used,
 damage to the case elements is minimized should rework require their
 separation. The seal leaves no appreciable residue behind on being
 removed, presents no out-gassing problems, and is easily sealed and
 unsealed.
 The seal taught herein may be impregnated, plated or otherwise coated with
 electrically conductive material to reduce electromagnetic interference
 beneath an acceptable threshold level, or to preclude its intrusion into
 the case entirely. Finally, the methodology taught herein facilitates
 alignment of the several seal elements during construction, and can be
 used to minimize unwanted or accidental opening of the sealed case.
 Other features of the present invention are disclosed or apparent in the
 section entitled "BEST MODE OF CARRYING OUT THE INVENTION".

Reference numbers refer to the same or equivalent parts of the invention
 throughout the several figures of the drawing.
 BEST MODE OF CARRYING OUT THE INVENTION
 Having reference to FIG. 1, a first preferred embodiment for carrying out
 the principles of the present invention is shown. Having reference to that
 figure, case 1 is shown to comprise a pair of horizontally separated case
 elements, 10 and 11. When assembled together, upper case 11 and lower case
 10 define horizontal seam 12 therebetween. Case elements 10 and 11 are
 held and maintained in mechanical alignment by means of fasteners, for
 instance machine screws 13.
 According to this embodiment, upper and lower case elements 11 and 10
 respectively, when mechanically fastened and aligned, further define a
 horizontally annular alignment depression, 14 for receiving therein
 elastic sealing band 15. Accordingly, it is seen that case 1 comprises a
 pair of horizontally separated case elements 10 and 11 which are
 vertically fastened together by machine screws 13.
 In order to seal case elements 10 and 11 elastic sealing band 15 is
 provided. By way of illustration but not limitation, in a first preferred
 embodiment of the present invention, band 15 is formed of synthetic rubber
 having admixed therewith a sufficient quantity of electrically conductive
 powdered metal so as to render it substantially electrically conductive.
 Alternatively, sealing band 15 may be formed of any of several natural or
 synthetic elastic monomers or polymers well known to those of ordinary
 skill in the art. Another alternative consists of depositing a metallic or
 other conductive coating on sealing band 15 by plating, coating, painting,
 lamination, or other methodology well known to those of ordinary skill in
 art. As a further alternative, band 15 may be formed of a conformable
 material, or materials, which renders it conformable on a single-use basis
 to the region defined by depression 14. One such conformable material is
 the plastic "shrink-tubing" well-known in the electronic arts. This
 shrink-tubing contracts on application of heat.
 In a first preferred embodiment of the present invention, elastic sealing
 band 15 is sized such that its circumference at rest is somewhat smaller
 than the circumference, within depression 14, of case elements 10 and 11.
 The sizing of elastic sealing band 15 is further such that when band 15 is
 fitted to assembled case 1 it not only seals seam 12 but is substantially
 fully received within depression 14. As shown in FIG. 1, elastic seal band
 15 is at the point of being expanded to fit around case 1.
 Sealing band 15 is fitted to case 1 in the following manner: sealing band
 15 is first elastically expanded such that its circumference is greater
 than the circumference of case 1. Sealing band 15 is then positioned over
 depression 14 and allowed to contract. Where required, a pressure may be
 applied to sealing band 15 on a axis parallel to the seam and hence
 perpendicular to the assembly axis of case 1. This pressure is sufficient
 to elastically deform detent 17, thereby enabling the insertion of at
 least the detent, and preferably the detent and a portion of the alignment
 surface, into the interior of the case. Thereafter at least a portion of
 detent 17 is allowed to expand within the interior portion of case 1,
 whereby detent 17, returned to its substantial initial shape, serves to
 retain sealing band 15 within depression 14, and hence, case 1.
 Referring now to FIG. 3, a view of case 1 having elastic sealing band 15
 fitted thereto is shown. As seen in that figure, elastic sealing band 15
 not only seals seam 12 (covered by band 15 in this view) but is received
 into and substantially fills depression 14. Band 15 may take the form of
 any of several cross-sectional configurations. The simplest of which is an
 elastic ribbon, attached at either end to form a simple band. A
 cross-section of this implementation of the present invention is shown in
 FIG. 3C.
 A further alternative, embodying an alignment element disposed on sealing
 band 15 is shown as a second preferred embodiment in FIG. 2. Having
 reference to that figure, elastic sealing band 15 is further fitted with
 an alignment surface 16. As shown in FIG. 2A, alignment surface 16 may be
 implemented as a simple projection, protrusion or ridge 18 formed on an
 internal surface of band 15, and substantially perpendicular thereto.
 Another alternative to this implementation consists of the addition to
 alignment surface 16 of a barb, or detent, 17 to the free end thereof.
 Such a barbed alignment surface is shown in FIG. 2B.
 As a further alternative to the substantially continuous alignment surface
 16 or projection 18 shown in FIG. 2, an alternative embodiment may be
 formed wherein projection 16 is discontinuous. By way of illustration, but
 not limitation, such an implementation might be utilized where it is
 desirable for reasons of space or ease of installation to eliminate the
 projection 16 where it will be engaged at the corners of case 1.
 A third preferred embodiment of the present invention is shown at FIG. 4,
 wherein it is desirable to form the case without depression 14, not shown
 in this embodiment. In this implementation, elastic sealing band 15 is
 maintained in substantial alignment with case 1 by means of projection 16
 inserted into horizontal seam 12 (covered by band 15 in this view). In
 this instance, the alignment projection 16 of band 15 serves as the sole
 alignment methodology, and is shown in FIG. 4A. As before, a barb or other
 projection 17 may be added to projection 16 as shown in FIG. 4B to
 minimize tampering with the seal.
 The present invention has been particularly shown and described with
 respect to certain preferred embodiments of features thereof. However, it
 should be readily apparent to those of ordinary skill in the art that
 various changes and modifications in form and detail may be made without
 departing from the spirit and scope of the invention as set forth in the
 appended claims. In particular, differing materials, seal plans and
 cross-sections, electrical conducting methodologies, and mechanical
 fasteners may, with equal facility, be implemented without departing from
 the teachings set forth herein, and such alternatives are specifically
 contemplated by the principles of the present invention. Furthermore,
 while the discussion herein of the principles of the present invention has
 centered on an implementation on computer head disc assemblies, it will be
 apparent to those of ordinary skill in the art that the invention taught
 herein may, with equal facility, be implemented on a broad range of
 component sealing applications. All such implementations are specifically
 contemplated by the principles of the present invention. The invention
 disclosed herein may be practiced without any element which is not
 specifically disclosed herein.