Clamp for holding sheet articles

An improved clamp apparatus for storing sheets, for example of paper or foil, including especially maps and drawings, the sheets being neither rolled nor folded so that they can be readily inspected, and a considerable number of sheets can be stored without interfering with each other. The sheets are held from above from any convenient rail, by being inserted, singly or multiply in a clamp that may be comparable in length with the sheet the pressure of the clamp being adjusted gradually by means of wing nuts on self locking bolts and being biased by leaf springs.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an improved clamp. In particular, it relates to a 
clamp for holding one or more sheet articles, such as drawings or maps. 
2. Description of the Prior Art 
Large sheet articles of paper, thin cardboard or plastics material such as 
maps, tracings, charts, prints or plans cannot easily be stored or mounted 
for reference. It is with this difficulty in mind that the present 
invention was devised. Known methods of storing large sheet articles 
commonly involve rolling the sheets, punching holes in the articles, or 
permanently affixing tabs or the like to the articles, which is often 
unsatisfactory as the articles cannot be folded and must be kept flat and 
in good condition. 
New Zealand Design Pat. No. 16,519, issued Dec. 12, 1980 to Planhorse 
International Limited of New Zealand, disclosed a clamp for holding one or 
more sheet articles comprising a pair of jaws, each jaw having an elongate 
gripping part and an elongate base part, one of said base parts being 
pivotable about the other base part, a closing means adapted to bring 
together, in use, the gripping parts in order to hold one or more sheet 
articles between the gripping parts by causing the pivotable base part to 
pivot about the other base part. This clap, however, had no biasing means 
to enable the gripping parts to be self-opening. Also, the adjustment bolt 
was not self locking. 
SUMMARY OF THE INVENTION 
The present invention consists in a number of significant improvements on 
our basic clamp, the most important of which comprises biasing means 
biased to urge the gripping parts apart. 
An L-shaped leaf spring which provides a biasing pressure against the 
opposing legs of the clamp is disclosed. Also disclosed in an improved 
assembly/adjustment bolt. 
One advantageous feature of the spring-biased clamp combination of the 
present invention is that the use of a thin flat leaf spring to bias the 
gripping legs of the clamp allows thin sheets of paper, which may number 
anywhere between one and one hundred sheets, to be inserted between the 
gripping legs without fouling their edges against the biasing means. In 
other words, the thin spring of the present invention presents no obstacle 
to the insertion of paper into the clamp. 
Another advantage of the present invention is that the spring is held in 
place by the same bolt which holds the two separate elongate jaws of the 
clamp. Attachment of the spring to the lower jaw by means of the bolt 
results in the bolt itself being tensioned against the lower jaw. This 
facilitates assembly by keeping the bolt from falling out of the lower jaw 
when the upper jaw is being put in place. Furthermore, should the wing 
nut, which holds the clamp jaws together and provides tensioning force, 
fall out in use, the bolt will not dislodge and become lost within the 
interior of the clamp mechanism. 
Another feature of the present invention is that the biasing spring is 
designed to be capable of retrofitting to existing prior art paper sheet 
clamps. A spring is disclosed which fits between the upper and lower bases 
of the two jaws of existing clamps and provides its outward biasing force 
by abutting against the inner wall of the gripping leg of the upper jaw. 
Furthermore, because the spring is adapted to be secured by the existing 
assembly bolts, it may be retrofitted to prior art sheet clamps while 
allowing such clamps to receive final assembly at only two places. The 
jaws of the clamp are assembled by holding them together, along with the 
springs, by means of the two assembly bolts. As discussed in detail below, 
the assembly bolts also serve to tension and adjust the clamping action of 
the clamp when in use. 
Yet another feature of the present invention is an improved head for the 
assembly bolt. In prior art paper sheet clamps of the type improved by the 
instant invention, the assembly bolts were round headed and the heads were 
so small as to not contact the projecting flange of the lower base of the 
clamp. For this reason, the prior art bolts tended to rotate along with 
the wing nut when a user attempted to tighten the wing nut. 
The improved head of the bolt of the instant invention has at least one 
flat surface on its otherwise circular circumference. Furthermore, the 
head is enlarged so that when used in combination with the lower jaw of 
the clamp the flat surface of the head abuts against a flange on the base, 
preventing the bolt from turning when the wing nut is tightened. 
Yet another feature of the instant invention is a flangeless stopper which 
allows the clamp to be removed from a support fitment by a tilting action, 
the clamp being supported on the fitment by only one flanged member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The clamp comprises a pair of elongate jaws 1,1a. Each jaw has an elongate 
base 2,2a and an elongate gripping leg 3,3a. The jaws 1,1a are typically 
made of strips of extruded anodized aluminum. The jaws may be of different 
lengths, depending on the application. 82.5 cm would be a typical length. 
One of the bases is pivotable about the other base. In FIG. 2, the upper 
base 2a is pivotable about the lower base 2. 
A closing means is provided which is adapted to bring together in use the 
gripping legs 3,3ato hold one or more sheet articles (not illustrated) 
between the gripping legs. The preferred closing means is a nut 4 which is 
provided with wings for ease of turning by hand. The nut 4 is threaded on 
a bolt 5 which has a head 6 and which passes through circular holes in the 
bases 2 and 2a. The hole in the pivotable upper base 2a should be larger 
than the diameter of the bolt 5 to allow for pivotal movement of that base 
about the bolt 5. 
The head 6 of the bolt 5 abuts a portion of the lower base 2 of jaw 1 so 
that the bolt 5 will not turn when the nut 4 is tightened. One edge of the 
head 6 can be flattened as shown in FIG. 3 to turning resist movement. In 
FIG. 2 the lower base 2 is shown provided with a flange 7 against which 
the bolt head 6 abuts. 
The clamp is provided with biasing means biased to urge the gripping legs 
apart. The biasing means is preferably a steel leaf spring 10 which is 
held in place by the bolt 5, which passes through a hole 23 in the spring 
10. A clip 24, such as a circlip or gripping washer, for example may also 
be included between the leaf spring 10 and upper base 2a in engaging 
relationship with the bolt to hold the bolt 5 and the spring 10 onto the 
lower base 2, particularly when nut 4 is very loose or removed. The spring 
10 acts against the upper jaw 1a so as to urge the gripping leg 3a away 
from the gripping leg 3. Preferably a biasing means is provided for each 
closing means. 
A handle 12 is attached at or near the center of the upper base 2a. This 
enables the clamp and retained sheets to be lifted and moved easily. In 
FIG. 1 the handle 12 may be formed by of a bent steel rod which is 
attached to the upper base 2a by screwing; but the handle may be 
constructed and attached in other ways. 
Attachment means 13,13a are also affixed to the upper base part 2a. These 
are typically formed of plastics material and are rivetted onto the upper 
base 2a. They are designed to enable the clamp to be attached to a fitment 
25, for instance on a rack, trolley or stand (not illustrated) on which a 
number of the clamps may be mounted. The attachment means 13 shown has an 
elevated projecting flange 14 which engages with a flange or flanges on 
the fitment and holds the clamp in place. Alternative forms of attachment 
means may be used, for instance, hooks or eyes. Stopper 13a prevents the 
clamp from slipping forward when attached to the fitment. This stopper 
could be a knob of cylindrical or other flangeless shape. To remove the 
clamp from the fitment, the clamp is tilted down at the leading end so the 
stopper drops underneath the rear of the fitment, and the clamp can be 
removed by moving in a reverse direction. 
As can be seen from FIG. 2 each jaw 1,1a in cross-section has a flange 7,7a 
depending from the base 2,2a. The gripping legs 3,3a also depend from the 
base, the gripping legs being substantially at right angles to the bases 
adjacent the bases, and inclining inwardly so that the far ends 15,15a of 
the gripping legs 3,3a are substantially underneath the middle of their 
respective bases 2,2a. The depending gripping leg 3a of upper jaw 1a is 
longer than the gripping leg 3 of lower jaw 1. Base 2a substantially 
overlaps base 2 and flange 7a contacts base 2, so that the far gripping 
ends 15 and 15a of the jaws can meet. 
In use, the closing means are operated using hand pressure by tightening 
the nuts 4,4a causing the pivotable upper base 2a to pivot about lower 
base 2; flange 7 a forming the pivot point. This operation is eased by 
nylon washer 11. The downward pressure provided by the tightening of nut 4 
thus causes pivoting leg 3a to approach and close on gripping leg 3 at far 
ends 15,15a. Hand tightening nuts 4,4a provides sufficient pressure 
between gripping legs 3,3a at their far ends 15,15a to hold one or more 
sheet articles between the jaws, so that the articles will not fall out 
under their own weight. 
To release the articles between the jaws, nut 4 is loosened, and the 
biasing means provided by the spring 10, which spring was deformed by 
gripping part 3a as jaw 1a closed on jaw 1, forces the jaws apart. 
It has been found expedient to increaase the depth of flange 7 over prior 
art flanges to provide a more satisfactory locking edge for head 6 of bolt 
5. The bolt 5 has been especially designed with a head 6 which has a long 
flat edge 20 to lock against flange 7. This prevents the bolt from 
rotating when the wing nut 4 is tightened. 
An especially designed leaf spring 10 has been made. It is to be secured to 
the bolt 5 where it penetrates the inner extrusion lower base 2. The leaf 
spring 10 fits snugly against the inner extrusion wall of leg 3a thus 
preventing snagging of paper sheets within the clamp. The leaf spring 10 
causes the pivoting upper jaw 1a to self-open as wing nut pressure is 
released. This is an important aspect when one wants to remove sheets from 
within clamps singly or multiply. In such cases, since one hand is needed 
to hold the sheets, only one hand is available to loosen the nut 4 and 
none is available to bias open the jaws 1,1a. The spring 10 operates to 
provide this bias. The spring also contributes to overall positive 
operation of the clamp when tightening. The distal end of spring 10 may be 
bent or rounded in order that it slide freely against the inner surface of 
gripping leg 3a. 
The leaf spring 10 is also designed to lock the bolt 5 in position so that 
the flat edge 20 of bolt head 6 abuts the extrusion flange 7. This 
facilitates assembly--otherwise the bolt 5 tends to drop out. 
The leaf spring 10, shown in FIG. 4, consists of a planar upper leaf 21 
from which depends a planar lower leaf 22. The lower leaf 22 is bent at an 
angle of about 140.degree. from the upper leaf 21 when the spring 10 is in 
its resting state of non-compression. As shown in FIG. 2, the spring 10 
may be compressed in use to an included angle of about 90.degree. without 
undergoing permanent deformation. The spring 10 is preferably made of 30 
gauge spring steel. 
A specially designed wing nut 4,4a is used. This provides a comfortable 
finger tightening shape so that maximum purchase can be applied to tighten 
the clamp jaws 1,1a fully without special tools. 
The above broadly describes the preferred embodiment of the present 
invention and its method of use, and gives some alternatives. However, 
many modifications can be made without departing from the scope of the 
invention as claimed. 
For example, the flange 7a may be attached to jaw 1, and the steel spring 
10 may be replaced by a coiled steel spring or an elastic substance. 
Furthermore, the nut 4 may be replaced by a toggle or cam arrangement 
connected to a lever or handle to provide the required downward force.