Manually breakable sheet for cases of emergency

Abstract

 The sheet serves for cases of emergency. in particular for covering compartments containing emergency means, fire fighting means, alarm means and the like. The surface of the sheet comprises a lattice of linear incisions (10) of preferential fracture (11, 11'), each of which forms, in section, a recess which narrows towards the point of minimum level where it defines a preferential fracture line; said lattice of linear incisions defines a plurality of mutually adjacent closed sheet portions (20, 25) bounded by and separated from each other by the preferential fracture lines (11, 11'); according to the invention, at the nodal points, said preferential fracture lines (11, 11') join together in pairs to form chamfer lines (13, 13') bounding a closed nodal area (30) within which the thickness is much smaller than the overall thickness of the sheet. This overcomes the drawback caused by the fact that at the nodal points where the lines intersect, acute angles form along the fracture lines when the sheet is broken, and represent a danger to the person breaking the sheet, especially if using a hand to directly break the sheet.

Description

[0001] The present invention relates to a manually breakable sheet for cases of emergency, in particular for covering compartments containing emergency means, fire fighting means, alarm means, etc.

[0002] Boxes or other containers containing fire fighting means or alarm means are known having a door closed by a thin transparent sheet, usually of light-transparent synthetic resin, which in cases of emergency is intended to be broken manually, directly by a person's hand, to provide access to the means contained therein.

[0003] To facilitate their breakage, sheets are known provided with a lattice of rectilinear preferential fracture incisions extending in the vertical and horizontal directions, the incisions forming, in cross-section, a recess which narrows towards the point of minimum level to define a line along which the sheet inevitably separates (preferential fracture line). Said lattice of linear incisions defines a plurality of mutually adjacent closed sheet portions bounded by and separated from each other by the preferential fracture lines. As these sheet portions form acute angles at the nodal points where the lines intersect, sharp corners form at the nodal points along the preferential fracture lines when the sheet is broken, and represent a danger to the person breaking the sheet, especially if unable to use a hammer or other equivalent implement, and instead uses a hand to directly break the sheet.

[0004] An object of the present invention is to overcome said drawback by providing a sheet which, when broken, defines fracture edges which do not represent a danger to persons.

[0005] This and other objects are attained by the present invention as characterised in the claims.

[0006] The invention is described in detail hereinafter with the aid of the accompanying figures, which illustrate a non-exclusive embodiment thereof by way of example.

[0007] Figure 1 is a portion, of indeterminate area, of a first embodiment of the sheet according to the invention.

[0008] Figure 2 is an enlarged detail of Figure 1.

[0009] Figure 2A is a section on the plane A-A of Figure 2.

[0010] Figure 2B is a section on the plane B-B of Figure 2.

[0011] Figure 3 shows the same detail as Figure 2, broken along a possible separation line.

[0012] Figure 3A shows the same sheet portion as Figure 3, but broken along a different, improbable, separation line.

[0013] Figure 4 is a portion, of indeterminate area, of a second embodiment of the sheet according to the invention.

[0014] Figure 5 is an enlarged detail of Figure 4.

[0015] Figure 5A is a section on the plane A-A of Figure 5.

[0016] Figure 5B is a section on the plane B-B of Figure 5.

[0017] Figure 6 shows the same detail as Figure 4, broken along a possible separation line.

[0018] Figure 6A shows the same sheet portion as Figure 6, but broken along a different, improbable, separation line.

[0019] Figures from 1 to 3A show a first embodiment of the sheet (indicated overall by 1), of which a portion of indeterminate area is visible in Figure 1.

[0020] The surface of the sheet of the invention, indicated overall by 1 in the figures, comprises a lattice of linear preferential fracture incisions 10, each of which forms, in section, a recess 15 (see Figures 2A and 2B) the cross-section of which narrows in V-shape towards the point of minimum level where it defines a line 11 along which the sheet thickness assumes its minimum value to hence define a so-called preferential fracture line, i.e. a line along which the sheet breaks preferentially, and in practice always. In plan, each preferential fracture line 11 is contained between two close-together parallel lines 12, defined by the edges of the recess 15.

[0021] Said lattice of incisions 10 defines a plurality of mutually adjacent closed sheet portions 20, bounded and separated from each other by the preferential fracture lines 11.

[0022] According to the invention, at the nodal points (i.e. the points where the lines 11 tend to converge to mutually intersect), the lines join together in pairs to form chamfer lines 13 bounding a closed nodal area 30 having at least three vertices.

[0023] Thus the nodal area 30 shown on an enlarged scale in Figure 2 lies at the ideal point of convergence between a lower preferential fracture line 11a, a lower preferential fracture line 11b, and a vertical preferential fracture line 11c, where the corners of three portions 20a, 20b and 20c of the sheet 20 also converge. At these corners, each preferential fracture line 11 forks into two chamfer lines 13, each chamfer line 13 joining together two preferential fracture lines 11. In detail, the line 11a forks into the two chamfer lines 13a and 13c, the line 11b forks into the two chamfer lines 13a and 13b, and the line 11c forks into the two chamfer lines 13c and 13b. Consequently the line 13a chamfers the angle formed by the lines 11a and 11b, the line 13b chamfers the angle formed by the lines 11b and 11c, and the line 13c chamfers the angle formed by the lines 11a and 11c. Each nodal area 30 adjoins three sheet portions and has three acute angles positioned where the preferential fracture lines 11 fork into the chamfer lines.

[0024] When the sheet 1 is broken as a result of an impact substantially perpendicular to the sheet, the line of separation evidently follows the preferential fracture lines 11, whereas it has been found that in the nodal areas 30 the separation preferentially takes place along the chamfer line 13 which joins together two preferential fracture lines 11, hence in such a manner that the sheet portion 20 forming an acute angle has this angle chamfered.

[0025] For example (see Figure 3) if the breakage tends to separate the lower portion 20a from the other two portions 20b and 20c, the separation reliably takes place along the lines 11a and 11b adjoining the portion 20a, and when it reaches the nodal region it very probably takes place along a chamfer line 13a given that this directly connects the two lines 11a and 11b together. It is instead totally improbable that the separation will follow the chamfer lines 13c and 13b (as shown in Figure 3A) as this would require breakage along two chamfer lines (13c and 13b) instead of along the single line 13a, a happening which would require more energy and hence not representing a preferential path for the fracture.

[0026] According to the invention, said nodal area 30 presents a substantially constant thickness which is much smaller than the overall thickness of the sheet; in particular, this thickness is virtually equal to the thickness of the sheet 1 in correspondence with the preferential fracture lines 11 (as shown in Figures 2A and 2B).

[0027] By virtue of this characteristic, if the separation between the sheet portions 20 were to give rise to a nodal area 30 with a point projecting outwards (such as shown in Figure 3A), this point would however have a relatively very small thickness and would hence easily shatter against the body of the person breaking the sheet without causing damage thereto.

[0028] This aspect is very useful especially in the case in which the separation involves all the three preferential fracture lines which converge in the same nodal area 30, with the relevant nodal area hence giving rise to a pointed element.

[0029] The thickness of the sheet at the nodal area 30 could in fact be made zero by providing a nodal area in the form of a through aperture. In that case the breakage of the sheet would not give rise to any pointed element.

[0030] Figures 4-6A show a preferred embodiment of the sheet 1 which incorporates the aforedescribed innovative characteristics.

[0031] Again in this case, the surface of the sheet 1 comprises a lattice of linear preferential fracture incisions 10, each of which forms, in section, a recess 15 (see Figures 5A and 5B) the cross-section of which narrows towards the point of minimum level where it defines a line 11 along which the sheet thickness assumes its minimum value to hence define a so-called preferential fracture line. Again in this embodiment, said lattice of incisions 10 defines a plurality of mutually adjacent closed sheet portions 20, bounded and separated from each other by the preferential fracture lines 11.

[0032] However, this embodiment differs from the preceding in that in the regions in which three or more portions 20 converge, the incisions 10 define a like number of closed sheet portions 25 of smaller area than the major sheet portions 20, their plan profile being bounded partly by more or less rectilinear preferential fracture lines 11' which define the sides of the portion 25, each of these lines 11' separating the portion 25 from an adjacent major portion 20; moreover along the corners defined by these lines 11', the vertices of the portion 25 are rounded by chamfer lines 13'. In these corner regions there remain defined a like number of nodal areas 30, each bounded by a chamfer line 13' joining two sides 11' of the minor portion 25 together and by two chamfer lines 13 forking from the preferential fracture line 11 which divides the two major portions 20 adjacent to the minor portion 25 (see Figure 5).

[0033] Again in this nodal area the thickness is substantially constant and much smaller than the overall thickness of the sheet; in particular, it is equal to the thickness of the sheet 1 in correspondence with the preferential fracture lines 11 (as shown in Figures 5A and 5B), or could even be zero. This embodiment enables major portions 20 to be formed having more than four sides, where however the nodal areas 30 have three vertices, as indeed is desirable to reduce the possibility of forming pointed elements along a separation edge on breakage.

[0034] Numerous modifications of a practical and applicational nature can be made to the invention, but without leaving the scope of the inventive idea as claimed below.

Claims

1. A manually breakable sheet for cases of emergency. in particular for covering compartments containing emergency means, fire fighting means, alarm means and the like, the surface of which comprises a lattice of linear incisions (10) of preferential fracture (11, 11'), each of which forms, in section, a recess which narrows towards the point of minimum level where it defines a preferential fracture line, said lattice of linear incisions defining a plurality of mutually adjacent closed sheet portions (20, 25) bounded by and separated from each other by the preferential fracture lines (11, 11'), characterised in that at the nodal points, said preferential fracture lines (11, 11') join together in pairs to form chamfer lines (13, 13') bounding a closed nodal area (30) within which the thickness is much smaller than the overall thickness of the sheet.

2. A sheet as claimed in claim 1, characterised in that each nodal area (30) adjoins three sheet portions (20, 25) and has three vertices positioned where the line of paired contact between the sheet portions commences.

3. A sheet as claimed in claim 1, characterised in that the thickness of the nodal area (30) is virtually equal to the thickness of the sheet in correspondence with the preferential fracture lines (11, 11').

4. A sheet as claimed in claim 1, characterised in that the thickness of the nodal area (30) is zero.

5. A sheet as claimed in claim 1, characterised in that, in the regions in which three or more major portions (20) converge, the preferential fracture lines (11') define a like number of closed sheet portions (25) of smaller area, the plan profile of which partly follows the profile of the adjacent major portion and partly defines a chamfer in the region in which it penetrates between two major portions (20).

6. A sheet as claimed in claim 5, characterised in that, in the corner regions of the minor sheet portions (25), there remain defined a like number of said nodal areas (30), each bounded by a chamfer line (13') joining two sides (11') of the minor portion (25) together and by two chamfer lines (13) forking from the preferential fracture line (11) which divides the two major portions (20) adjacent to the minor portion (25).

Drawing