SECURITY COVER

Abstract: A security cover for a lockset door knob, of the kind having a keyhole in its outer face, includes; a rigid hollow body (12), preferably of frustoconical form, open at a first end but substantially closed by an end wall (14) at the oposite end, save for an aperture (16) dimensioned to permit key access through the end wall. Laterally projecting flange means (18) at the first end of the body is provided for engaging and fastening the body to a major surface of a door about a knob projecting from such major surface. The body (12) is dimensioned whereby, when it is so fastened, the body (12) extends about the sides of the door knob and the end wall (14) is disposed in front of the outer face of the knob sufficiently close thereto for a key to be passed through the aperture (16) operatively engaged with the keyhole, and manipulated from outside the body (12).

Description: "SECURITY COVER" TECHNICAL FIELD This invention relates to the securing of lockset door knobs of the kind having keyholes in their outer faces, and more especially to those in which insertion and rotation of the key will not only disengage the lock but also open the. door. BACKGROUND ART Locksets of the aforementioned kind are normally provided with a ' snib on the inside of the door which locks the outside knob against rotation. However, an established technique for breaching doors locked in this manner is to apply a heavy wrench to the outside door knob and forcably rotate it. The problem may not be overcome by employing locksets of the more complex * kind in which the outside knob is left freely rotating when the lock is snibbed from the inside, since the snibbing can be negated merely with the additional effort required to sufficiently deform the knob to grip the internal key release mechanism. DISCLOSURE OF THE INVENTION In accordance with this invention, it has been realised that the outside door knob of the aforementioned locksets may be advantageously further secured by the application of a cover which prevents access to the handle with a wrench or like tool but still permits the lock to be released and the door opened. For reasons which will become apparent, this principle is best applied to door knobs of the type in which rotation of the inserted key will effect opening of the door. The invention accordingly provides a security cover for a lockset door knob of the kind having a keyhole in its outer face, characterized by a rigid hollow body open at a first end but substantially closed by an end wall at the opposite end save for an aperture dimensioned to permit key access through the end wall; and laterally projecting flange means at the first end of said body for engaging and fastening said body to a major surface of a door about a knob of said * kind projecting from said surface; said body being dimensioned whereby, when the body is so fastened, the body extends about the sides of the door knob and said end wall is disposed in front of the outer face of the knob sufficiently close thereto for a key to be passed through said aperture, operatively engaged with ^ E said keyhole, and manipulated from outside the body. Said body is preferably of right frustoconical form broadest at said first end, thereby having a continuous tapered external surface, and said end wall adavantageously does not project laterally beyond this surface. The flange means may comprise a continuous flange about the larger end of the frustoconical body, or may comprise a plurality of circumferentially spaced tabs. The cover is, advantageously fashioned in metal, e.g., sheet steel. The invention also extends to the assembly of the aforesaid security cover with a door and lockset mounted in the door. Preferably, the cover is fastened to the door surface by fasteners which present a non grip head to the exterior of the door and are irrotationally received in complementary apertures in the flange means of the ■ cover. BRIEF DESCRIPTION OF THE DRAWINGS " The invention will be further described,by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a security cover in accordance with the invention; Figure 2 is an axial cross-section through the cover when fastened to a door about a lockset door knob; and Figure 3 is a front elevation of the assembly shown in Figure 2. BEST MODE FOR CARRYING OUT THE INVENTION The illustrated security cover 10 is integrally formed from strong metal sheet such as, e.g., 2mm gauge sheet steel. It includes a right hollow frustoconical body 12 which defines a continuous external frustoconical surface 13. Body 12 is open at its larger end but closed off at the opposite end by end wall 14, save for a central circular aperture 16 of a diameter sufficient to receive at least the shaft and stop of a standard domestic lockset key. At its larger end, the rim of body 12 merges with a laterally outwardly projecting surrounding flange 18 provided with four square bolt apertures 20 equiangularly spaced about the axis of body 12. It will be noted that flange 18 is continuous and defines a substantially smooth annular abutment. surface 19 (Figure 2) in a plane normal to the axis of body 12. Figures 2 and 3 show the security cover 10 fastened in abutment with the outside surface 7 of a door 6 about a knob 8 which projects from surface 7 and has a keyhole 5a in its outer face 5b. These drawings also demonstrate the selected dimensions of the cover: it will be noted that when the cover is . fastened to the door, abutment surface 19 is flat against door surface 7, while body 12 extends about the sides of the door knob " 5 - and near its smaller end is of only marginally greater internal diameter than the maximum external diameter of the knob. End wall 14 is disposed in front of outer face 5b of the knob sufficiently close for at least the shaft and stop of a key {indicated by broken lines at 11 in Figure 2) to be passed through aperture 16, operatively engaged with keyhole 5a and manipulated from outside body 12. In Figure 2, it will be seen that part of the head of the key also lies inwardly of aperture 16 and indeed the aperture may be made large enough (say 22mm or more in diameter) for a standard domestic lockset key to pass right through the .-aperture. This may be necessary if the cover is to be capable of application to knobs of widely varying sizes. It is believed that, in general, surface 13 is preferably of a diameter d, at its larger end between 70 and 120mm and a diameter d~ at its smaller end between 40 and 70mm. Its axial length £ is preferably between 50 and 90mm. The ratios l/ά. andd /d are preferably between 0.6 and 1.0 and between 0.5 and 0.8 respectively. The cover is fastened in place by means .of four fasteners 23 including bolts 24 (Figure 2) which each have a. round non-grip head 26 disposed to the exterior of the ' door, and, immediately under the head, a " short square-section shank portion 25 in irrotational engagement with a matching aperture 20. Nuts 28 applied from the inside of the door retain a ring 29 provided to prevent the bolts from being wrenched through the door. Roundhead female screws may be employed in place of nuts 28, while ring 29 may be either unitary or a multi-part element or may be dispensed with. It will be appreciated that a burglar or vandal endeavouring to gain access through the locked door shown in Figure 2 will not be able to employ the traditional technique of applying a wrench to the door knob. Any attempt to apply his wrench instead to the cover 10 will be frustrated by the cover's tapered surface. Destruction or removal of the cover could no doubt be achieved, but would require very considerable effort and time, with much attendant noise. It is therefore believed that the cover presents a very real deterrent to would-be intruders. On the other hand, the owner has no difficulty in achieving access as he may insert his key through aperture 16 to operative-ly engage keyhole 5a. The key can then be manipulated from outside the cover to release the lock previously set by inside snib 9, and open the door by withdrawing tongue 4. it will be appreciated that the illustrated cover is not readily applicable to locksets in which the key merely disengages the lock and opening of the door requires the knob to be gripped. However, the present invention renders the use of such more complex locksets unnecessary and indeed causes the simpler locksets to be favoured. OMPI

Claims: AMENDED CLAIMS (received by the International Bureau on 04 October 1982 (04.10.82)) 1. (Amended) A security cover for a lockset door knob of the kind having a keyhole in its outer face, comprising a rigid hollow body open at a first end but substantially closed by an end wall at the opposite end, save for an aperture dimensioned to permit key access through the end wall; and laterally projecting flange means at said first end of said body for engaging and fastening said body to a major surface of a door about a knob projecting from said surface; said body being dimensioned whereby, when the body is so fastened, the body extends about the sides of the door knob and said end wall is disposed in front of the. outer face of the knob sufficiently close thereto for a key to be passed through said aperture, operatively engaged with said keyhole, and manipulated from outside the body; characterized in that said body is of frustoconical form broadest at said first end, thereby having a continuous tapered external surface. 2. (Cancelled). 3. A security cover according to claim 2 further characterized in that said body is right frustoconical. . A security cover according to claim 2 or 3 further characterized in that the ratio of the diameters of -said body at said opposite and said first ends respectively' is between 0.5 and 0.8. 5. A security cover according to claim 2, 3 or 4 further characterized in that said flange means comprises a continuous flange about the first, larger, end of said body. 6. A security cover according to claim 3 further characterized in that said flange means comprises a continuous flange about the first, larger, end of said body, defining a substantially smooth annular abutment surface in a plane normal to the axis of said right frustoconical body. 7. A security cover according to any preceding claim further characterized in that the ratio of the separation of said ends of said body and the diameter of the body at said first end is between 0.6 and 1.0. ' 8. A security cover according to any preceding claim' further characterized in that said flange means has a plurality of apertures shaped for irrotational engagement with respective complementary shank portions of fasteners for fastening the cover to the door. 9. A security cover according to any preceding claim formed in metal sheet. 10. A security cover according to any preceding claim formed integrally from metal sheet. 11. In combination, a security cover according to any preceding claim and a door fitted with a lockset having a door knob of the said kind projecting from a surface of the door, the cover being fastened to the door about the knob so that the body extends about the sides of the knob and the end wall is disposed in front of the outer keyhole-containing face of the knob sufficiently close thereto for a key to be passed through said aperture, operatively engaged with the keyhole, and manipulated from outside the body. 12. The combination according to claim 11 wherein the cover -is fastened to the door by a plurality of fasteners having round heads at the outside of the door, and non-circular shank portions for irrotational engagement with respective complementary apertures in-the flange means of the cover. 13. The combination according to claim 12 further including a ring retained by said fasteners at the inside of the door. 14 (New) . The combination according to claim 12 wherein the cover is fastened to the door by a plurality of fasteners which extend through to the other side of the door.

Inventors: BEARDS BERTRAM MELVIN, BEARDS, BERTRAM, MELVIN
Applicants: AUSGLOBE PTY LTD, AUSGLOBE PTY. LTD.
Application year: 1982
Main classification: E05B17
IPC codes: E05B13