Tensioning of flexible sheets across frames

In a display or the like device, a flexible sheet is supported in tension within a frame by means of tensioning devices secured to the frame. Each tensioning device includes a movable peg which is engaged in an aperture in the sheet. Each peg can be placed in a position nearer the middle of the space within the frame in which it is retained, or displaced away from the middle of this space, to tension the sheet, and when so displaced, the peg is urged resiliently away from the middle of this space by a spring within the respective tensioning device, to hold the sheet in tension. The tensioning devices thus constitute a simple and compact means of providing for ready interchangability of various display areas in the frame.

FIELD OF INVENTION 
This invention relates to the tensioning of flexible sheets across frames. 
The invention is particularly, but not exclusively, concerned with the 
tensioning, across display frames for use in showrooms, exhibitions, etc., 
of flexible sheets bearing, for example, printed advertising material or 
like, which sheets may, for example, comprise paper or card laminated with 
transparent plastics material. 
SUMMARY OF INVENTION 
It is an object of the invention, in one of its aspects, to privide an 
improved method of supporting a flexible sheet in tension within a space 
bounded by a peripheral frame. 
According to this aspect of the invention there is provided a method of 
supporting a flexible sheet in tension within a space bounded by a 
peripheral frame, the method including providing, on said frame, 
tensioning devices each including a sheet engaging element for engagement 
with a peripheral portion of the sheet, and means for moving said element 
towards and away from the middle of said space bounded by the frame, the 
method further comprising engaging said sheet with said sheet engaging 
elements whilst the latter are in their positions closest to the middle of 
said space and subsequently causing or allowing said sheet engaging 
elements to move away from the middle of said space towards the peripheral 
frame to tension the flexible sheet within the frame. 
It is an object of the invention, in another of its aspects, to provide an 
improved device, for example a display device, including a peripheral 
frame bounding a space and a flexible sheet extended across said space in 
tension. 
According to this aspect of the invention there is provided a device 
including a peripheral frame bounding a space, and a flexible sheet 
extended across said space and supported in a tensioned condition by means 
of tensioning devices carried by the frame, each tensioning device 
including a sheet engaging element engaged with a respective peripheral 
portion of the sheet, said element being movable towards and away from the 
middle of said space, the device including means urging said element in 
the direction away from the middle of said space, or holding said element 
against movement toward the middle of said space, to hold the sheet in 
tension. 
According to a yet further aspect of the invention there is provided a 
sheet tensioning device for use in supporting a flexible sheet in tension 
across a space bounded by a frame comprising an elongate member or members 
extending around the periphery of said space, the sheet tensioning device 
including a body having means for engaging such a peripheral member, and a 
sheet engaging element mounted in said body for movement towards and away 
from said means.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The display device shown in FIG. 1 comprises a base 10 in the form of a 
rectangular slab from which extend upwardly, and inclined forwardly, 
parallel side members 12 carrying at their upper ends an integral 
rectangular frame 14, the plane of which is inclined upwardly in the 
opposite sense from the frame members 12, the arrangement being such that 
the rectangular frame 14 is supported at such a level, and at such an 
angle that a sheet of advertising material or the like supported in the 
frame as explained below is disposed so as to be conveniently viewable by 
a person standing in front of the device. The device shown in FIG. 1 may, 
for example, be disposed in front of an exhibit at an exhibition or in 
front of an article, for example a motor vehicle, in a showroom or the 
like, the sheet supported in the frame 14 bearing, for example, material 
relating to the exhibit or article concerned. 
In the preferred embodiment shown, the frame 14 in fact carries two 
parallel sheets bearing display material, namely an upper sheet 16 and a 
lower sheet 18, the upper sheet 16, for purposes of illustration, being 
shown partly cut-away in FIG. 1. The sheets 16, 18 are conveniently of 
sheet or card laminated with transparent plastics material, i.e. having 
layers of transparent plastics material bonded to their faces and 
affording the surfaces of the sheet, and the sheets are held in a 
tensioned condition within the space bounded peripherally by the frame 14 
by tensioning devices to be described below. The members 12 and frame 14 
are, in the embodiment shown, made of round metal rod appropriately bent 
and welded to the form shown. 
FIG. 2 shows one of the upper corners of the frame 14, with the sheets 16, 
18 omitted, and shows a sheet-tensioning device 20 mounted in the corner 
of the frame. A corresponding device 20 is mounted in each of the other 
corners of the frame, the devices 20 serving to hold the sheets, 16, 18 in 
tension in the frame 14. 
The device 10 includes a hollow body 22, for example of synthetic plastics 
material affording, extending at right angles to one another, two sleeves 
24 through which extend, as a snug fit, respective ones of the two 
mutually perpendicular sides 14a, 14b of the frame which meet in the 
corner at which the device 20 is mounted, each sleeve 24 affording, as 
shown, a cylindrical bore through which extends the respective portion 
14a, 14b. The body 20 provides upper and lower terminal faces 26, 27 which 
extend approximately in the parallel planes which include respectively the 
upper and the lower edges of the rod portions defining the four sides of 
the frame 14. From the upper face 26 of the body 22 extends a cylindrical 
peg 28 forming part of a first sheet-tensioning element and from the lower 
face 27 of the body 22 extends a similar peg 28 of a further 
sheet-tensioning element. Each peg 28 has an outer cylindrical portion, a 
flange 29 engaging the respective face 26, 27 and a groove extending 
therearound between the flange 29 and the major cylindrical portion. 
Whilst this groove may have a simple circular annular form, so that the 
groove forms a reduced diameter portion of the peg, it is preferred that, 
as viewed in cross-section (not shown) through the peg, in the region of 
the groove, the peripheral surface of the groove has the form of two 
intersecting circular arcs, of equal radius of curvature, corresponding to 
the radius of the respective aperture (see below) in the sheet 16, 18 
through which the peg is to be extended, i.e. slightly greater than the 
radius of the major portion of the peg 28. The orientation of the 
intersecting circular arcs is such that when, as explained below, the 
respective peg is tensioned against the edge of the respective aperture in 
the sheet, the edge of the aperture bears uniformly over the part of the 
peripheral bottom surface of the groove which affords one of these 
circular arcs. Each sheet 16, 18 has, adjacent each of its four corners, a 
respective circular aperture therethrough which fits over the respective 
peg 28, the portion of the sheet affording the edge of said aperture being 
received in the groove 30. 
Each peg 28 is movable diagonally with respect to the frame under spring 
bias, i.e. along the arrow 32 in the case of the pegs 28 of the device 20 
shown in FIG. 2, so that the respective sheet 16, 18 is placed in tension. 
Referring to FIGS. 4 and 5, the device 20 effectively comprises two 
identical portions, on opposite sides of the median plane of the body 22, 
which is the plane of section indicated by the line IV--IV in FIG. 3. The 
device 20 may, in fact, be formed as two such identical parts engaging one 
another along planar faces lying in the median plane of the body 22, 
although other arrangements may be adopted. For example, the body 20 may 
be formed as two such identical parts which are, in effect, connected with 
one another via the wall of one sleeve, which wall is, for example when 
the body is formed by moulding, originally in an "unrolled" condition and 
which is bent around the respective limb 14a, 14b during fitting of the 
body to the frame. In any case, the two parts of the body are brought 
together on opposite faces of the frame to embrace the limbs 14a, 14b 
during fitting of the devices to the frame, the opposing parts of the body 
being held together by appropriate means, not shown, for example, by dowel 
arrangements, integral snap-fastening formations, or even by separately 
manufactured securing elements, none of which are shown. 
The upper and lower surfaces 26, 27 of the body 22 are afforded by 
respective major walls, which are spaced apart to define therebetween a 
chamber which accommodates parts of the tensioning mechanism to be 
described. Each major wall has a slot 40 formed therein extending along a 
diagonal line which bisects the angle between the sides 14a, 14b as shown 
in FIG. 2, and in this slot the respective sheet tensioning element is 
supported for sliding along the slot. As shown in FIG. 6, which is a 
fragmentary view in section along the line VI--VI in FIG. 2, each sheet 
tensioning element includes a stem portion 42 indicated in dotted lines in 
FIG. 2, which is approximately oblong as viewed in section parallel with 
the plane of FIG. 2. The stem 42 extends through the slot 40 with its 
longer dimension extending longitudinally of the slot, the cross sectional 
dimensions of the stem 42 being such that the stem 42 is freely slidable 
longitudinally of the slot but is non-rotatable therein. Within said 
chamber, the stem 42 carries an enlarged root portion 44 which is too 
large to pass through the slot 40, whereby the sheet engaging member is 
held captive. 
The enlarged root portion 44 has a circumferential groove 46 therein to 
receive an end portion 47 of a hairpin spring 48 which is fitted upon a 
boss 50 extending into the chamber from the respective major wall. The end 
portion 47 acts as a lever rotatable about an axis approximately 
corres-ponding with that of the boss 50 and bearing upon a cam surface 
provided by the bottom of the groove 46, the arrangement being such that 
in the position shown in FIG. 4, the portion 47 acts on the portion of 
this cam surface which faces toward one end of the slot 40 to urge the 
sheet-tensioning element along the slots 40 in the direction of the arrow 
32, whereas in the position shown in FIG. 5, the end portion 47 bears 
substantially on the side of the root portion 44 laterally of the slot 40, 
so that there is virtually no force urging the sheet tensioning element 
along the slot 40 so that the element will remain in the position shown in 
FIG. 5 untill displaced manually towards the opposite end of the slot 40, 
in the direction of the arrow 32. 
In use, the devices 20 are first attached to the frame 14 as shown, and the 
pegs 28 are initially displaced along the slots 40 towards the middle of 
the space defined within the frame so that the holes at the corners of the 
respective sheets 16, 18 can be fitted without difficulty over the pegs to 
engage in the grooves 30.The pegs 28 are then simply displaced manually 
away from the middle of the space bounded by the frame towards the 
respective corners so that they move into the regions of their respective 
slots where the respective springs 48 are effective to urge the pegs 28 
further towards the respective corners of the frame, whereby the springs 
48 tension the respective sheets 16, 18. The sheets 16, 18 are so formed 
that, as shown in FIG. 1, the corner portions thereof cover the bodies 22 
of the devices and conceal these bodies from view, only the pegs 28 
remaining visible on the outer sides of the sheets. 
It will be appreciated from FIGS. 4 and 5 that the boss 50 of one half of 
the tensioning device is positioned in the chamber entirely to one side of 
the diagonal along which slot 40 extends. The other half of the device 20, 
being identical, has its boss 50 lying in the chamber on the opposite side 
of this diagonal. The dimensions of the stems of the pegs 28 within the 
chamber, measured axially of the pegs, are such that interference between 
the two pegs is avoided. 
It will be noted that each slot 40 terminates, at its end further from the 
respective corner of the frame 14, in a transverse recess 41. This recess 
41 is simply to allow insertion of the enlarged root 44 of the sheet 
tensioning element (which is preferably formed integrally) during 
assembly. 
It will be appreciated that it is by no means necessary to have a sheet 16, 
18 on each side of the frame nor, consequently, a peg 28 on each side of 
each device 20, and, indeed, in a device such as shown in FIG. 1, only the 
upper sheet 16 would normally be used. However, the device may also be 
used in conjunction with vertical rectangular frames intended to be viewed 
from either side, in which case it may well be desirabe to have a separate 
sheet 16, 18 on either side of the vertical rectangular frame. Where only 
one sheet is to be used, pegs 28 may be fitted on only one side of the 
devices 20. 
In particular, the sheet-tensioning means may be used in conjunction with a 
panel system such as disclosed in our British Pat. No. 1,542,244, or Our 
patent application 8226563, in which adjacent panel-supporting rectangular 
frames may be coupled together hingedly with gear-toothed formations 
carried by the sides of such frames meshing during relative pivoting 
between such frames. It will be noted that the sleeves 24 have, 
externally, longitudinally projecting ribs 80 spaced apart 
circumferentially around each sleeve. These ribs 80 form rudimentary gear 
teeth so that adjoining sleeves 24 of adjoining devices on adjoining such 
rectangular frames may mesh together after the fashion of gear teeth 
during relative pivotal movement between the frames around the axes of the 
respective sleeves 24. 
A variant of the last-mentioned arrangement is shown in FIGS. 7 and 8. FIG. 
7 shows a panel system comprising a plurality of rectangular frames 60 
each having spaced apart parallel vertical side members connected by upper 
and lower parallel horizontal members. The upper ends of the side members 
of each frame 60 project upwardly above the upper horizontal member whilst 
the lower ends of the side members of each frame 60 project downwardly 
below the lower horizontal member. A plurality of frames 60 may be 
arranged in a common plane, one above the other, with their respective 
side members in vertical alignment, the vertically arrayed frames being 
interconnected by sockets 62 provided on the downwardly projecting parts 
of the side members of the frame above, receiving spigots 64 provided on 
the upwardly projecting parts of the side members of the frame below. 
Laterally adjacent frame members, which are transversely spaced somewhat 
in this arrangement, are held together by clips. 
In the arrangement of FIGS. 7 and 8, instead of the adjoining ribbed 
sleeves 24 on adjoining side members of adjoining frames meshing directly, 
each such sleeve has fitted thereover a fitting 66, preferably of 
resilient plastics having the peripheral form of a gear segment and having 
internally formations, not shown, to allow it to be retained firmly on the 
respective sleeve, and it is the respective fittings 66 on adjoining 
sleeves 24 which mesh together after the fashion of gear teeth during 
relative pivotal movement between the frames 60 around the axes of the 
respective sleeves 24. 
Whilst the devices shown are intended to be fitted in the corners of a 
rectangular frame, it will be appreciated that similar devices could be 
fitted, for example, midway along each side of the frame 14, in which case 
each sheet-tensioning device may have a body affording only a single 
rod-receiving sleeve and may have its sheet-tensioning element or elements 
slidable along corresponding slots extending in a direction perpendicular 
to the axis of the rod-receiving sleeve.