GB2307301A - Protective case for optical instruments - Google Patents

Abstract

A protective case 2 for optical instruments is described. The case comprises a transparent pouch 4 with a cut-out in the wall thereof, a lens 24 and an adaptor 22 for mounting the lens over the cut-out. The adaptor has a ring and a base with an aperture therein, the ring being securable to the base with the aperture aligned with the cut-out to clamp the portion of the wall around the cut-out therebetween in the plane of the wall. The adaptor may carry a lens cap 40 and the pouch may be formed as a bag with a closure 6. The case may be for a camera or video recorder and is for waterproofing.

Description

PROTECTIVE CASE FOR OPTICAL INSTRUMENTS This invention relates to a protective case for optical instruments and in particular, but not exclusively, to a waterproof case for carrying cameras, video recorders and other optical instruments.

Cases of the type to which the invention relates are typically used during water sports such as yachting, sailing and snorkling. Depending on the degree of waterproofing, they may also be used during diving. The case protects an optical instrument, typically a camera or video recorder, employed to take pictures whilst enjoying such pursuits. One known case of this type comprises a pouch with a closure for sealing its access opening. The bag is formed from relatively rigid plastic by blow moulding, and includes an upstanding boss on one face having an outer rim. A glass lens is held centred on the boss by an aluminium mount in the form of a split ring which is closed around the lens by a jubilee clip-type fastener.The boss is positioned so that when a camera is inserted in the bag the camera lens will be aligned with the glass lens carried on the boss so allowing clear photos to be taken.

The disadvantages of this known bag are that it is expensive to produce and proper sealing of the lens may not always be effected. These are consequences of the use of the split ring lens mount which is somewhat difficult to assemble, and therefore vulnerable to inaccurate lens positioning or insufficient tightening of the jubilee cliptype fastener. Further the metal mount adds to the cost of the bag.

Other bags for optical instruments are known which are simpler to produce and therefore less costly. In one known form, no lens is provided, whilst in another a flexible PVC lens is welded onto the bag. However, it has been found in use that neither arrangement allows the taking of fully clear pictures.

In another known form the bag is formed with a cut-out on a wall or at an end with the adjacent material moulded or manually formed into a tube extending up from the plane of the wall or bag end. A lens is secured by adhesive or other means to a mounting ring which is positioned within the tube with the lens aligned with the cut-out. A clamping ring is attached around the tube to clamp the tube therebetween. A disadvantage of this form is that it is sometimes difficult to maintain adequate clamping pressure on the bag material around the aperture with consequent risk of water ingress. In addition assembly of the lens onto the bag is a relatively slow operation and manual dexterity is required to get all the parts properly aligned.

A protective case for optical instruments in accordance with the invention comprises a ring and a base with an aperture therein, the ring being securable to the base with the aperture aligned with the cut-out to clamp the portion of the wall around the cut-out therebetween in the plane of the wall.

The advantage of this is that the pouch material does not adversely affect the operation of an optical instrument held in the case as the lens or other operative part of the optical instrument can be positioned directly adjacent the protective case lens. Proper sealing is however ensured because the clamping pressure is applied by an end of the ring as a line force onto the pouch material.

In a preferred embodiment, the lens is integrally formed with a lens mounting ring. The advantage of this is that it avoids the necessity to adhesively or otherwise secure the lens to a mount so saving costs and preventing the risk that the securement step may damage the lens. It has been found that more than adequate optical quality is achieved if the lens and mounting ring are formed by injection moulding from a suitable material such as acrylic or polycarbonate provided the portion of the mould against which the lens is formed is highly polished.

The lens mounting ring may be secured to either the adaptor base or the adaptor ring but preferably the latter through integral formation therewith. The number of parts required thereby reduced simply to two: the integral adaptor base, lens mounting ring and lens and the adaptor ring.

The adaptor ring is suitably secured to the base by a threaded connection between the ring and a collar upstanding from the base. In the embodiment where the lens mounting ring is integrally formed with the adaptor base, the lens mounting ring may act as a collar and be formed with external screw threads mating with internal screw threads formed on the adaptor ring.

Very preferably a clamping ring is provided which is held in use between the adaptor ring and the adaptor base. This has been found to be particularly advantageous when the adaptor ring is secured to the base by threaded connection as it minimises twisting and shearing of the material of the pouch adjacent the cut-out and thereby helps ensure good sealing.

The pouch is preferably formed from UV stabilised flexible laminate PVC.

The pouch will have an access opening for optical instruments and the case may include a closure for closing the access opening in watertight sealed fashion. A number of different closures are available on the market, but a particularly preferred one is that described and claimed in co-pending application No. 9517991.7.

The invention will now be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a protective case in accordance with the invention; Figure 2 is a schematic view illustrating formation of the protective case of Figure 1; Figure 3 is both a side view and an exploded partially sectional view of an adaptor and lens forming part of the protective case of Figure 1, and Figure 4 is a side view illustrating the welding operation carried out during formation of the protective case of Figure 1.

The protective case 2 of Figure 1 comprises a pouch 4 with an access opening closed by a closure 6. The closure 6 may take any suitable form. The preferred and illustrated form of the closure 6 is described in more detail in our copending application No. 9517991.7. In brief, it comprises two bars 8, 10 each of which is connected to a side of the access opening of the pouch 4 by a two-part attachment strip, the male part 12 of which only is shown. Each male strip 12 includes sprues 14 which are passed through apertures 16 in wings 18 at the access opening of the pouch 4, through holes in the female strip and into holes in the appropriate bars 8, 10 in which they form a friction fit.

One bar 8 includes a ridge and the other 10 a complementary groove in which the ridge is received when the bars 8, 10 are connected by the bayonet connectors, the ridge and groove being positioned such that the upper edges of the pouch 4 are clamped therebetween. The clamping pressure is applied along a single line which gives very good sealing.

The pouch 4 is formed with an aperture 20, see Figure 4, in one wall thereof. An adaptor 22 is secured in the aperture 20 to position a lens 24 over the aperture 20.

The adaptor 22 is shown in detail in Figure 3. It comprises a base 26 and a lens mounting ring 28 which are preferably and as shown formed integrally with each other and with the lens 24 to provide a lens ring 30. The adaptor 22 additionally includes an adaptor ring 32 which has an internal screw thread 34 dimensioned such that it will mate with an external screw thread 36 on the lens ring 30.

The adaptor 22 preferably additionally includes a clamping ring 38 which in use is positioned between the adaptor ring 32 and the adaptor base 26. As illustrated, a lens cap 40 may usefully be carried by the clamping ring through an integral strap 42.

To mount the lens 24 to the pouch 4 the lens ring 30 is positioned with the adaptor base portion 26 within the pouch 4 and the mounting ring 28 protruding through the aperture 20. The clamping ring 38 is located over the mounting ring 28 with the pouch material adjacent the aperture 20 positioned between a protruding circular bead 44 on the clamping ring 38 and a correspondingly shaped recess 46 on the upper face of the adaptor base 26. The adaptor ring 32 is then connected to the lens ring 30 by engaging threads 34 of the adaptor ring 32 with the threads 36 of the lens ring 30 to press the clamping ring 38 down against the adaptor base 26 and thereby to clamp the bag material around the aperture 20.

It will be appreciated that the form of the adaptor 22 makes the operation of attaching the lens 24 to the pouch 4 simple and easy. This is partially as a result of the small number of parts which may be reduced even further by dispensing with the clamping ring 38. The use of a clamping ring 38 is however preferred as it has been found this tends to prevent shearing and stretching of the pouch material as the adaptor ring 32 is screwed onto the lens ring 30 and therefore ensures that the clamping pressure is applied directly down on the pouch material as a line force. Good clamping is further ensured by the cooperation between the protruding bead 44 and corresponding recess 46.

The lens ring 30 may be made by injection moulding from any suitable material, preferred materials being acrylic and polycarbonate. Providing that the portion of the mould against which the lens 24 is formed is highly polished it has been found that sufficiently good optical quality results. The adaptor ring 32 and clamping ring 38 if provided may be formed from glass filled ABS, again by injection moulding.

The use of polycarbonate or acrylic for the lens 24 has the advantage that such materials are about six times stronger than glass and therefore the lens is less vulnerable to damage than with known cases where glass is nearly always used. Furthermore, if the lens 24 is scratched it can easily be replaced because of the form of the adaptor 22 without requiring any skilled personnel. Thus, adaptors 22 with integral lenses 24 may be sold separately for replacement in the field.

Figure 4 illustrates formation of the pouch 4. A single piece of plastic is formed in the illustrated shape and cut out to give holes 16, aperture 20 and, optionally, a viewfinder aperture 54. An ultra-clear PVC sheet polished on both sides to give good optical clarity is welded in the view finder aperture 54 to give good clear vision through the viewfinder of a camera with which the pouch 4 is used.

The plastic sheet is then folded along fold line 62 and a L-shaped weld formed along weld line 64. The weld is preferably a beadless weld to give the smallest possible seam. The bottom corners of the thus formed pouch 4 are welded off along weld lines 66. This opens-up the pouch to a 3-D shape suitable for a camera or the like as illustrated in Figure 1. The pouch is then fitted in a goose neck and a patch is attached at the closed end which covers the seam and provides some grip for a user of the pouch. As a result of the method of construction there is no seam along the side wall formed at fold line 62 which gives good access to the controls of a camera with which the pouch 4 is used.

The adaptor 22 and lens 24 are then fitted to the pouch 4 as described above.

The pouch 4 is preferably formed from UV stabilised PVC but other flexible plastic materials may be used, such as polypropylene, polyethylene, polyurethane and polyether urethane.

The protective case 2 is capable of protecting optical instruments, in particular cameras, from the elements but still allowing full use of the optical instrument. The lens 24 is readily mounted whilst at the same time being well sealed to the pouch and allowing good optical access to an instrument carried within the pouch. The case 2, particularly when a closure 6 of the illustrated for is employed, can be safely used under water without any risk of damage to an optical instrument carried in the pouch 4.

It is formed solely from plastics material which makes it cheaper and easier to produce than cases with metal components.

Claims (8)

1. A protective case for optical instruments comprising a transparent pouch with a cut-out in a wall thereof, a lens and an adaptor for mounting the lens over the cut-out, the adaptor comprising a ring and a base with an aperture therein, the ring being securable to the base with the aperture aligned with the cut-out to clamp the portion of the wall around the cut-out therebetween in the plane of the wall.

2. A protective case as claimed in Claim 1 wherein the lens is integrally formed with a mounting ring.

3. A protective case as claim in Claim 2 wherein the lens mounting ring is secured to either the adaptor base or the adaptor ring.

4. A protective case as claimed in Claim 3 wherein the lens mounting ring is secured to the adaptor base through integral formation therewith.

5. A protective case as claimed in any preceding claim wherein the adaptor ring is secured to the base by a threaded connection between the ring and a collar upstanding from the base.

6. A protective case as claimed in any preceding claim wherein a clamping ring is held between the adaptor ring and the adaptor base.

7. A protective case as claimed in any preceding claim wherein the lens is formed from polycarbonate or acrylic.

8. A protective case as claimed in any preceding claim wherein the adaptor is formed by injection moulding.