NZ197990A - Bullet proof type screen:laminated front panel with film,and rear panel supported slidably against front panel - Google Patents

Description

m r PtmrlV.; D&l«(s}: . .U: : $9 , Cc-vr n: Cpeiificffition Fiied: r.r^.EO&Glloo* EOb&SliO ' ••■•••'••■>■■■23fr£Lg 1985■" •PuljHoation Data: ..J3£7. *v ?. Journal f-Jo: NEW ZEALAND PATENTS ACT, 1953 197990 No.: Date: COMPLETE SPECIFICATION » SAFETY SCREEN 142. P&Tm AUG 1981) RECEIVED XK/We, AECI LIMITED, 16th Floor, Office Tower, Carlton Centre, Commissioner Street, Johannesburg, Transvaal Province, Republic of South Africa, a South African Company hereby declare the invention for which ? / we pray that a patent may be granted tojnall/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - THIS INVENTION relates to a security screen. In particular the invention relates to a transparent security screen of the type used, for example in banks, to protect personnel from firearm attacks.

According to the invention a security screen comprises a front panel having a front pane of relatively hard, rigid and brittle material which is transparent and which has applied to at least one surface thereof an adherent film of transparent plastics or resinous material which, compared with the material of the front pane, is relatively flexible and tough; a rear panel having a rear pane of a transparent material which, compared with the material of the front pane, is relatively soft, flexible and tough; and supporting means supporting the panels in abutment with and in intimate face to face contact with each other, yet permitting the panels to slide relative to each other.

In this context "front" refers to the direction from which an attack or like cause of danger or damage is anticipated, and "rear" has the corresponding opposite meaning. • — - — : — 4W#- Furthermore, with reference to the material of the front and rear panes, the terms "hard" and "soft" are intended to have opposite meanings; "rigid" and "flexible" are intended to have opposite meanings; and "brittle" and "tough" are intended to have opposite meanings. Thus the rear pane is relatively less hard, less rigid and less brittle than the front pane; and with reference to the film, the terms flexible and tough have corresponding meanings.

The testing methods used to determine hardness/softness, rigidity/flexibility and brittleness/toughness for the purpose of this invention may respectively be American Society for Testing Materials, procedure numbered D 785 I (hardness/ softness), ASTM D747 (rigidity/flexibility) and ASTM D256 (brittleness/toughness), but other suitable testing methods may be used instead as bases for comparison.

In practice the screen of the invention, although intended to perform a broad protective function while being \ transparent in at least one direction, will be required to be capable of protecting personnel to the rear thereof from a firearm attack of at least a limited intensity, particularly a hand-gun attack.

During a firearm attack, the front pane is intended to function, when struck by a bullet, to deform the bullet, thereby to reduce the ability of the bullet to ir' 197990 the screen on which the bullet acts. In other words by flattening or spreading out the bullert, the front panel increases the area of the screen which must be penetrated to allow the bullet to pass through the screen, thereby reducing the likelihood that the bullet will in fact pass through the screen. For _th.is reason the front panel should be comparatively hard and rigid.

At the same time, the front pane functions by virtue of its brittleness by shattering and crumbling in the zone of impact, to become crushed or pulverized in this zone, thereby absorbing energy and momentum from the bullet, and again reducing the likelihood that it will penetrate the screen as a whole.

Suitable materials for the front pane are thus those of mineral or inorganic origin and having a high melting point, such as glass or the like, although such materials may include a proportion of organic constituents, provided they are sufficiently hard, rigid and brittle.

The film(s) on the front pane will adhere thereto and will by virtue of the flexibility and toughness and consequent shatter resistance of the material thereof function to prevent or reduce the likelihood of shattering and/or spalling of the front pane, to combat the collapse thereof into shards or fragments, upon ,** impact, particularly in the area surrounding the impact zone. The front pane, although possibly cracked, will thus tend to remain in place fronting the rear panel after impact, .except for the impact zone itself which will b^s pulverized, and the front pan^-will thus be in position to * continue its protective function in the event of succeeding impacts caused for example by further bullets.

% Although both sides or the front side alone of the front pane may be coated with the film, the film will generally, by virtue of its relatively soft and flexible nature compared with the material of the front pane, be more prone to surface damage and deterioration by scratching during cleaning, from cleaning chemicals and ordinary wear and tear. It is thus preferred to have a single film on the front pane, on the rear thereof, where it is protected by the rear panel. polyvinyl chloride, polyethylene, polypropylene, cellulose acetate or the like, but it is contemplated that polyester |p (polyethylene terephthalate) film will be preferred Suitable materials for the film include because of its ready availability and because the technology of its use in conjunction with glass (in the context of the production of shatter resistant laminated glass) is already widely practiced. 19799$'' Turning to the rear panel, this will typically be a sheet of a suitable plastics or resinous material having the required physical properties, sudh as polycarbonate or polymethyl methacrylate (acrylic), with acrylic being preferred for reasons of cost. The rear pane may also have either or both of its surfaces coated with a flexible and tough polymeric film, of the type described above with reference to the film on the front pane.

On the rear pane the film will have essentially the same function as on the front pane, but will be particularly important by virtue of its shatter resistance for the prevention or reduction of shattering and spalling behind a bullet impact zone, as the fragments arising from spalling can be projected violently from the rear side of an uncoated rear panel, and can cause danger to personnel in the vicinity, or damage to property. For this reason, and because scratch resistant grades of film material such as polyesters are available with greater surface durability than for example polycarbonates or acrylics, it is preferred to coat both faces of the rear pane with film, rather than merely the protected face as in the case of the front pane. The film on the front face of the rear:— pane will reinforce the action of the film on the rear face, to reduce the likelihood of shattering of the rear 55 O pane. For convenience the films on both the front and >o rear panes may be of the same material, and may be of the .t*. same thickness. I t 197RftG If desired, the rear pane may have its impact resistance, i.e. its resistance to cracking, breaking or shattering upon impact which resistance arises from its relative softness, flexibility, and tougfmess, improved by incorporating therein an impact modifier such as a suitable rubbery polymeric material e.g. methacrylate butadiene styrene or similar synthetic rubbers. The rear pane will thus be impact modified by mixing or polymerization of the polycarbonate, acrylic or the like with a rubbery material, selected so that the transparency of the panel remains adequate. Likewise the film material on the front and/or rear panes may be selected to provide for colouring of the screen as a whole, ultra violet absorption, one way characteristics (reflection in one direction and transparency in the other) or the like. The film may be self adhesively secured, e.g. by welding, to its associated pane, or it may be secured thereto by a separate adhesive, and the film, apart from holding together the underlying pane will also contribute to resisting impact and penetration of the screen by a bullet or the like.

The rear panel abuts the front panel to support it in the event of an impact on its front side, to prevent the area of the front panel surrounding the impact zone from moving physically or bodily rearwardly upon impact.

Such movement would tend to negate the function of the :v l-TI G4 O O r> H 3 oo z N TO m z H O Tl T1 O m ioi§§§^ film on the front pane and could lead to undesired shattering and collapse of the front pane. It is preferred that the front and rear panels be in abutment such that some sliding therebetween is possible, and not adhesively secured to or otherwise fast with each other. The reason for this is that laminating the panels together can give rise to various problems in the cutting and forming of the laminate, reduced transparency of the screen and the formation of bubbles at the interface, increased cost, stressing due to differential expansion between the panels, % crack propagation from one panel to the other, etc.

As regards thickness, clearly the thicker the panes and the films thereon, the more effective will be the screen as a whole in its protective function.

However, effectiveness must be balanced against considerations of cost, overall weight, transparency, and the like. The thicknesses of the panes and films, the numbers of films and the surfaces of the panes to which they are applied, the physical properties of the materials of the panes and films, etc, will thus be selected in combination for the particular specifications required for the screen, so that it will best perform its intended function at an acceptable cost. ruT.a* '-vH. t- vr» »^v; 1^1 197 O It is contemplated that for use against attacks by hand guns, a front pane thickness in the region of 3- » 10mm will be used, and a rear pane thickness in the region of 15-30mm, although some protection will be conferred with a front pane as thin as 3mm in combination with a rear pane as thin as 10mm, particularly if the screen is * inclined to the vertical to deflect bullets and promote ricochets (while at the same time avoiding undesireable reflections). This inclination may be of the order of about 15° to 30° to the vertical, e.g. about 20°, with the front pane preferably facing downwards.

In use, the panels may be clamped together in abutment by means of a suitable frame, provided with e.g. rubber gaskets to promote intimate crontact between the panels while permitting them to slide over each other to cater for differential thermal expansion and contraction. Allowance will typically be made for such expansion/contraction of the order of about 2-10% in all directions parallel to the plane of the screen.

The invention will now be described, by way of example, with reference to the accompanying single diagrarrmatic drawing, which shows a partial cross-sectional side elevation of a security screen according to the invention. u 7 patent Of fice 300CT1984 f (<p</ 197990 In the drawing reference numeral 10 generally designates a security screen in accordance with the invention. The screen 10 has a front 'side 12 facing in a direction from an attack e.g. with a hand gun is anticipated, and a rear side 14 to the rear of which personnel and property to be protected will be situated. The screen comprises a front pand. 16 and a rear panel 18 clamped together by a metal frame 20 via soft rubber gaskets 22 (10mm thick) extending along the periphery of the panels between the panels and the frame. A space 24 is provided between the edges of the panel 16, 18 and the frame 20 to provide for thermal expansion of the panels of the order of about 5% of their dimensions in a direction parallel thereto.

The rear side 16.1 of the pane 16 is coated with an adhesive film 26 and the front and rear sides respectively 18.1 and 18.2 of the pane 18 are coated with films 28 and 30. The outer surfaces of the films 26 and 28 are flat and are held in intimate face to face abutment flat against each other by the frame 20 and gaskets 22. The plane of the panels is set inclined at an angle "A" of 20° to the vertical, which is indicated by chain dotted line 32.

K.Z. PATEN'l ! A hand gun bullet 34 is shown immediately after impact with the front side 16.2 of the pane 16, having been fired in a direction normal to said pane.

* The pane 16 is of relatively hard, rigid and brittle glass, while the pane 18 is of relatively soft, flexible and tough acrylic available in South Africa as "Perspex" (Registered Trade Mark) frcm AECI Limited. The pane 16 is 6irm thick and the pane 18 is 25nro thick. The films 26, 28 and 30 are "Protekt" (unregistered Trade Mark) polyester films available in South Africa from Van Leer (South Africa) -fPrpprretary) Limited and are 0,.l75mm thick, although other V suitable polyester films ranging frcm 0.05 - 0.175 in thickness are available in South Africa from various suppliers.

In use, upon impact of the bullet 34 against the surface 16.2 of the pane 16, the bullet is deformed and flattened as at 34.1 by the impact, thereby increasing its area of contact with the screen and reducing the likelihood that it will penetrate the screen. The zone 16.3 (cross-hatched) of the pane underlying the bullet is pulverized by the bullet. The pane, by virtue of its inertia and strength, and by virtue of its crumbling in the zone 16.3, absorbs, at least in part, the energy and momentum of the bullet. The film 26 in turn acts to prevent fragments of the pane 16, formed by cracks in the pane 16 radiating from the zone 16.3, from falling out of their positions in the frame 20 in abutment with the pane 18. r 1 97 9 The pane 18 in turn acts to absorb and dissipate any residual energy and momentum of- the bullet 34, to prevent or at least resist and retard its penetration and passage through the screen 10.

The impact of the bullet 34 will tend to cause, * in a percussion cone or fracture zone 18.3 (broken lines) in the pane 18, spalling of the pane 18 and projection of shards of the pane 18 outwardly from its rear side 18.2, and may cause cracks to radiate from the zone 18.3 which can break the pane 18 into fragments. The films 2 8 and 30 act, in the fashion of film 26, to keep such fragments in position in the frame 20, abutting the pane 16.

The film 30, in particular, also acts to combat the projection of shards of the pane 18 from its rear surface 18.2, caused by spalling.

In this regard it will be appreciated that the films 26, 28 and 30, by holding fragments of the panes 16, 18 in position in the frame 20 after an impact by a bullet, perform the particularly advantageous function of keeping these fragments available for resisting further impacts by bullets, in the event of a sustained burst of gun fire. The formation of a substantial hole in the screen by the initial shot or shots, through which further shots can be fired, is thus resisted. f reogWl ..I r,n^wLM4bi JS*TrTTF.nJL«-v iVldlV^ Furthermore, by synergistically combining the s impact and penetration resistance properties of glass and n Perspex", a substantial reduction in expense can be achieved, when compared with laminated safety glass screens of the same effectiveness, while at the same time reducing the weight of the screen substantially, which is an advantage where limited floor loadings are permitted.

Various tests were carried out with various screens in accordance with the invention, together with various controls for the purpose of comparison. The screens in question were fired at in a tunnel from a distance of 2m with various firearms. Details of the screens, the firearms or weapons used and the results of the tests are set out in the following table. Unless otherwise specified the films, when used, were polyester films self-adhesively secured to the panes in question and were of "Protekt" polyester available in South Africa from Van Leer (South Africa) (Proprietary) Limited, the glass was commercial plate glass available from Pilkington Brothers (South Africa) (Proprietary) Limited or PG Glass Holdings (Proprietary) Limited and the acrylate was "Perspex" available in South Africa from AECI Limited. Unless otherwise specified the screens were vertical. The screens were arranged, when they had two panels in accordance with the invention, as shown in the drawing, so that the glass pane was struck by the bullet(s). When the glass pane had a polyester film, or 197 when the acrylate pane had a single film, this was always on the rear side of the pane, on its side remote from the firearm. When the acrylate pane had ,two films, this is indicated in the table, as are the thicknesses of the panes and films used. In tests 1 to 14 the paneJs were merely placed in flat face to face abutments as shown in the drawing, but without a frame, and supported against a * metal box. In tests 15 to 24, the panels were clamped together by a frame of the type shown in the drawing. The area of the screens was of the order of about 0,3m x 0,3m. In the table, the controls are marked with an asterisk, and unless otherwise specified the order of the panels listed from top to bottom in the table for a screen, specifies the order of the panels in the screen from front to rear. In tests 25 to 30 a single gasket was used in the frame to the rear of the panels.

PATENT OCT 1984 TEST WEAPON SCREEN OBSERVATIONS /tw° i 9 7~9 9 ( xl. 7,62 urn Tdkarev 25 mm "Perspex" xZ. 7,62 mm Tokarev 19 mm laminated glass 3. 7,62 mm Tokarev 4. 7,62 mm Tokarev . 7,62 mm Tokarev 6. 7,62 mm Tokarev x7. 7,62 rnn Tokarev x8. 7,62 mm Tokarev x9. 7,62 ran Tokarev xlO. 7,65 mm Walther PPK mm "Perspex" 3 ran glass/0,05 ran polyester 19 mm "Perspex" 3 mm glass/0,05 mm polyester 19 mm "Perspex" -4 mm glass/0,05 irm . polyester 2 x 19 mm "Perspex" 3 mm glass/0,05 mm polyester 19 mm "Perspex" 6 mm glass mm "Perspex" 6 ran glass 19 mm "Perspex" 10 mm laminated glass mm "Perspex" Total penetration through screen and some spal1ing.

Bullet did not penetrate screen but much spalling was obtained.

"Perspex" cracked by first bullet. No penetration obtained with second bullet, but screen collapsed.

No penetration obtained, but the "Perspex" cracked and collapsed.

No penetration, but "Perspex" cracked and collapsed.

No penetration;. Both first and second bullets cracked the first "Perspex" screen, but second remaind unaffected.

No penetration, but star crack caused "Perspex" to collapse.

No penetration, but star crack developed in "Perspex", which did not col lapse.

No penetration, but star crack developed in "Perspex" screen, which collapsed.

No penetration, but star crack developed with first bullet. Some spalling. Second bullet also cracked "Perspex", but no spalling obtainedQ -9MAY1984 f 197 990 11. 9 mm Star mm "Perspex" 3 mm glass/0,05 mm polyester 12. 9 mm Star 13. 9 mm Colt (magnum) 14. R1 rifle . 9^ Colt (magnum) xl6. 9 mm Colt (magnum) 17. 9 mm Colt (magnum) 18. 9 mm Colt (magnum) 19 mm "Perspex" 9 mm glass/0,05 mm polyester First bullet caused no damage to "Perspex". Second and third bullets damaged "Perspex" surface slightly, but no penetration and no spalling obtained.

No penetration of bullet, but "Perspex" cracked and collapsed. mm "Perspex" No penetration, but 2 x 3 mm glass/0,05. mm "Perspex" cracked and polyester collapsed. 2 x 25 mm "Perspex" 3 mm glass/0,05 mm polyester 6 mm glass/0,175 mm polyester mm "Perspex"/2 x 0,175 mm polyester Vertical No glass mm "Perspex"/2 x 0,175 mm polyester Vertical 6 mm glass/0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester Verti cal 2 x 6 mm glass/0,175 polyester 19 mm "Perspex"/2 x 0,175 mm polyester Vertical Total penetration by first bullet.

First bullet: no damage to "Perspex" Second bullet: no damage to "Perspex" Third bullet: star crack in "Perspex" but no penetration and no spalling Fourth bullet: star crack in "Perspex" but no spalling.

First bullet: total penetration but "Perspex" did not collapse.

First bullet: star crack in "Perspex" but no penetration Second bullet: star crack and some spalling. mm First bullet: star crack, no penetration and no spalling Second bullet: star crack, no penetration and no spalling.

Third bullet: star crack, no penetration and no spalling. 111110 197990 19. 9 nm Colt (magnum) . 9 nm Colt 21. AK 47 Rifle 2l. AK 47 Rifle (Test repeated) 23. AK 47 Rifle x24. 9 mm Colt (magnum) . AK 47 Rifle 2 x 3 mm glass/0,05 mm First bullet: star crack, polyester no penetration and 19 mm "Perspex'72 x no spalling. 0,175 mm.polyester Second bullet: no pene-Vertical ' - tration but some spalling. 6 ran glass/0,175 mm First bullet: no damage polyester to "Perspex" ram "Perspex" (no Second bullet: star crack polyester. no penetration but Vertical screen collapsed. 2 x 6 jren glass/0,175 mm First bullet: star crack polyester ' but no penetration mm "Perspex'72 x and no spalling. 0,175 mm polyester Second bullet: total angle penetration. 2 x 6mm glass/0,175 mm First bullet: star crack polyester but no penetration mm "Perspex"/0,175mm and no spalling polyester 20° angle. 6 mm glass/0,175 nm First bullet: no damage polyester to 25 mm "Perspex" 19 mm "Perspex"/0,175mm - pane polyester Second bullet: Rear 6 nm glass/0,175 mm "Perspex" pane polyester cracked but no mm "Perspex"/0,175mm penetration or polyester spalling.

Vertical 7 x 3 run glass/0,05 mm First bullet: total polyester penetration No "Perspex" Verti cal 6 mm glass/0,175 mm First bullet: no pene- polyester tration mm "Perspex'72 x Second bullet: : no pene- 0,175 nm polyester tration 6 mm glass/0,175 mm Third bullet: no pene- polyester tration nm "Perspex"/2 x Fourth bullet: : no pene- 0,175 mm polyester tration 6 ran glass/0,175 mm fifth bullet: No pene- polyester tration Vertical 197990 1 26. R1 Rifle 27. R1 Rifle 28.

Full length shotgun. SSG cartridge 29.

Full length shotgun. SG cartridge . R1 Rifle p n.Z. PATENT OFFICE 6 mm glass/0,175 ran polyster on front 25 nm "Perspex"/ 2x 0,175 mm polyester at back 6 ran glass/0,175 ran polyester at back 25 mm "Perspex"/2 x 0,175 ran polyester 6 mm glass/0,175 mm polyester at back Vertical 6 ran g.lass/0,175 mm polyester on front 25 mm "Perspex" /2 x 0,175 mm polyester 6 iron glass/0,175 mm polyester at back 25 mm "Perspex"/2 x 0,175 ran polyester No glass at rear of screen Verti cal 6 mm glass/0,175 mm polyester on front 19 mm "Perspex"/2 x 0,175 mm polyester 6mm glass/0,175 mm polyester at back 19 mm "Perspex"/2 x 0,175 mm polyester 2 mm polycarbonate Verti cal 6 mm glass/0,175 mm polyester on front 19 mm "Perspex"/2 x 0,175 mm polyester 2 mm polycarbonate Vertical 6 ran glass/0,175 mm polyester on front 25 mm "Perspex"/2 x 0,175 mm polyester at back mm "Perspex"/2 x 0,175 mm polyester 2 mm polycarbonate First bullet: no penetration or spalling Second bullet very close to first: penetration Third bullet: no penetration First bullet: no penetration or spalling Second bullet: no penetration or spalling but "Perspex" pane collapsed First shot: No penetration or spalling Second shot: No penetration or spalling Third shot: No penetration or spalling Fourth shot: No penetration or spal1ing First shot: No penetration or spalling Second shot very close to first: Penetration Third shot: No penetration or spalling Fourt shot: Penetration First bullet: No penetration or spalling Second bullet: no penetration or spalling Third bullet: no penetration or spalling Fourth bullet: No penetration or spalling, l<n <?<|o 197990 31. Shotgun L6 cartridge 32. AK 47 Rifle 33. AK 47 Rifle 34. AK 47 Rifle . AK 47 Rifle 6 ran qlass/0,175 mm polyester mm "Perspex" 6 mm glass/0,175 mm polyester Vertical 6 mm glass/0,175 mm polyester 19 mm "Perspex" 6 mm glass/0,175 ran polyester mm "Perspex" Vertical 6 mm glass/0,175 mm polyester mm "Perspex" 6 mm glass/0,175 mm polyester mm "Perspex" 6 nm glass/0,175 mm polyester Vertical 6 mm glass/0,175 ran polyester 19 mm "Perspex" 6 mm glass/0,175 mm polyester 6 mm glass/0,175 mm polyester Vertical 6 mm glass/0,175 mm polyester 19 mm "Perspex" 6 mm air gap 6 mm glass/0,175 mm polyester 19 mm "Perspex" 6 mm glass/0,175 mm polyester Vertical but small tear in polycarbonate.

Fifth bullet: no penetration or spal1ing but another small tear in polycarbonate Sixth bullet: no penetration or spalling in spite of increased size of tear in polycarbonate.

First shot: penetration First bullet: No penetration but star crack in 25 mm "Perspex" First bullet: no penetration, no spalling to first): Total pene-trati on Third bullet: No penetration, some spalling First bullet: No penetration, no spalling, but star crack in both "Perspex" panes Second bullet(close First bullet: no penetration, no spalling, but star crack in both "Perspex" panes r 197990 36. Shotgun SSG cartridge (1st shot) SG cartridge (2nd shot} 37. Shotgun SG cartridge 6 mm glass/0,175 mm polyester 6 mm glass/0,175 mm polyester mm "Perspex"/2 x 0,175mm polyester Vertical 6 mm glass/0,175 mm polyester 6 mm glass/0,175 nm polyester ran "Perspex"/2 x 0,175 ran polyester Verti cal first shot: no penetration and no damage to "Perspex" Second shot: star crack in "Perspex" and some penetration First shot: star crack in "Perspex" and some penetration 38. Shotgun SG cartridge 6 nm glass/0,175 mm polyester 19 ran "Perspex"/2 x 0,175 mm polyester 19 ran "Perspex/2 x 0,175 mm polyester Verti cal First shot: star crack in both panes of "Perspex", but no penetration. 39. Shotgun SG cartridge 6 mm glass/0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0,175 mm polyester nm "Perspex"/2 x 0,175 mm polyester Verti cal First shot: star crack in both panes of "Perspex", but no penetration Second shot: no penetration, but spalling from "Perspex" 40. Shotgun SG cartridge 6 ran glass/0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0,175 ran polyester Verti cal First shot: star cracks, no penetration. Second shot: star cracks, no penetration. 41. Shotgun SG cartridge N.Z. PATENT OFFICE 3 ©OCT 1984 6 mm glass/0,175 mm polyester mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0,175mm polyester Vertical First shot: small star crack, no penetration or spalling.

Second shot: total penetration f 197990 42. Shotgun SG cartridge 43. Shotgun SG cartridge 44. Shotgun AAA cartridge 45. Shotgun Solid slug 46. Shotgun Solid slug 47.

Shotgun Solid slug 48.

Sawn-off shotgun with choke SSG cartridge (18 pellets of 6,3 mm diameter) 6 nm glass/0,175 mm polyester 19 ran "Perspex"/2 x 0,175 mm polyester 6 iron glass/0,175 mm polyester Vertical 6 nm glass/0,175 mm polyester mm "Perspex"/2 x 0,175 mm polyester Vertical 6 mm glass/0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0,175 mm polyester Vertical. 6 mm glass/0,175 mm polyester 19 mm "Perspex"/ 2x 0,175 mm polyester 6 mm glass/0,175 mm polyester Vertical 6 mm glass/0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0.175 mm polyester Vertical 19 mm "Perspex"/2 x 0,175 mm polyester 19 mm "Perspex"/2 x 0,175 mm polyester 6 mm glass/0,175 mm polyester 6 mm glas.s/0,175 mm polyester mm "Perspex"/2 x 0,175 mm polyester Vertical First shot: total penetration First shot: no penetration, but some spalling.

First shot: star crack, but no penetration or spalling First shot: total penetration.

First shot: star crack in both panes of "Perspex", but no penetration through first pane of "Perspex" First shot: no penetration, but severe spalling of glass and "Perspex" First shot: total penetration r 1979Vcf?0 49. Sawn-off shotgun without choke. SSG cartridge (18 pellets of 6,3 mm diameter), 50. Sawn-off shotgun without choke SSG cartridge (18 pellets of 6,3 ircn diameter) 6 nm glass/0,175 mm polyester mm "Perspex'72 x 0,175 mm.polyester. Vertical 6 mm glass/0,175 rren polyester mm "Perspex" ° angle First shot: total penetration.

First shot: total penetration The test results demonstrate the superiority and effectiveness of the screens in accordance with the invention, and the synergism of the two panel when used together and with at * least one surface of the front pane coated with film, compared with the individual components or sub-combinations thereof. From the tests it can be seen that the invention contemplates using one or more front panels and/or one or more rear panels,to increase effectiveness if necessary or desirable. It will also be noted that in some of the tests a sandwich construction was used, with alternating glass and plastics panes. In such cases a front panel need not be the foremost pane, as long as it has a plastics rear panel immediately behind it, and the possibility of a glass panel sandwiched between two plastics panels is contemplated by the invention. Likewise, a rear pand. need not be the rearmost panel as long as it has a glass front panel immediately in front of it, and the possibility of a plastics panel sandwiched between two glass panels is also contemplated. In other N.Z> PATENT office 3 ©OCT 1984 r ( £('/ 197990 words, as long as the basic unit of a glass (ie front} pane with at least one film is'immediately in front of a plastics ( ie rear) panel, the addition of one or more further panes in front of and/or behind the unit in any order does not amount to a departure from the invention. 197 i)Wi

Claims (19)

WHAT WE CLAIM IS:

1. A security screen comprising: a front panel having a front pane of a relatively hard, rigid and brittle material which is transparent and which has applied to at least one surface thereof an adherent film of transparent plastics or resinous material which, compared with the material of the front pane, is relatively flexible and tough; a rear panel having a rear pane of a transparent material which, compared with the material of the front pane, is relatively soft, flexible and tough; and supporting means supporting the panels in abutment with and in intimate face to face contact with each other, yet permitting the panels to slide relative to each other.

2. A screen as claimed in claim 1, in which the major proportion by weight of the material of the front pane is inorganic.

3. A screen as claimed in claim 2, in which the material of the front pane is glass.

4. A screen as claimed in any one of claims 1 to 3 inclusive, in which the material of the film is selected from the group consisting of polyvinyl chloride, polyethylene, polypropylene, cellulose acetate and polyester materials. r I 97 9 -25-

5. A screen as claimed in any one of claims 1 to 4 inclusive, in which the Jrilm is applied to only one surface of the front pane, namely the" rear surface thereof.

6. A screen as claimed in any one of the preceding claims, in which the material of the rear pane is a plastics or resinous material".

}. A screen as claimed in claim 6, in which the material of the rear pane is selected from the group consisting in polycarbonate or acrylic materials.

8. A screen as claimed in any one of the preceding claims, in which at least one surface of the rear pane has applied thereto an adherent film of transparent plastics or resinous material.

9. A screen ^claimed in claim 8, in which the material of the film on the rear pane is selected from the group of materials consisting of polyvinyl chloride, polyethylene, polypropylene, cellulose acetate and polyester materials.

10. A screen as claimed in claim 8 or claim 9, in which the material of the film on the rear pane is more scratch resistant than the material of the rear pane. -a,-THar ~jfg 't'i 197 gi)V^0 -26-

11. A screen as claimed in any one of claims 8 to 10 inclusive, in which the ,film on the rear pane is applied to both surfaces thereof.

12. A screen as claimed in any one of the preceding claims, in which the front pane has a thickness of 3 to 10 mm and the rear pane 4*as a thickness of 15 to 30 mm.

*3. A screen as claimed in any one of the preceding claims, in which the supporting means by which the front and rear panels are held in abutment with each other is a frame.

14. A screen as claimed in claim 13, in which the frame permits relative sliding of the panels over each other in response to differential thermal expansion and contraction thereof.

15. a security screen substantially as described and as illustrated herein. . r ' ' ( c{ 't c(e{ 0 197990 -27-

16. A method of protecting personnel and/or property from an attack or. anticipated attack which comprises screening said personnel and property by means of a screen as claimed in any one of the preceding claims, the screen being mounted so that the front panel is on the side of the rear panel remote from said personnel and property.*

17. A method as claimed in claim 16, in which the screen is inclined to the vertical.

IS. A method as claimed in claim 17, in which the front panel faces downwardly and the screen is at an o o angle of from 15 to 30 to the vertical.

19. A method of protecting personnel and/or property, substantially as described and as illustrated herein. A. J. PARK & SON per AGENTS FOR THE APPLICANJS OFFICE