Improvements in or relating to Metal Strips or Clamps for Use in the Manufacture of Card-board Boxes and for similar Purposes.
Year: 1898

page_text: Date of Application, 7th Feb., 1898-Accepted, 17th Sept.,
1898
Improvements in or relating to Metal Strips or Clamps for Use in the
Manufacture of Card-board Boxes and for similar Purposes.
A communication from FRIEDRICH PARTZSCH, of Klienbauchlitz, near Dobeln,
Saxony, in the Empire of Germany, Builder.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
In the card-board and similar industries clamps (mostly in the form of strips)
are used for making boxes etc., of card-board or other material for securing or
strengthening the edges of the cardboard and for many other purposes. The
teeth of these clamps are produced by cutting out or indenting the edges of the
strip and bending down such edges.
The present invention on the contrary consists in the teeth on the edge of the
strip being produced by stamping only, that is to say, by pressing or stamping
certain portions of the strip from the plane of the back of the strip said portions
being attached to the back not by a straight line but by a curved or irregular line
or a line consisting of curved and straight portions and starting from the original
edge of the strip and returning to it. The tooth profile and the bend appear
therefore curved and the completed strip-even if it had before a smooth edge-
is thus provided with alternate recesses and projections.
By this means, 1) all punching or cutting can be completely avoided (when
clamp-strips with smooth edges are used) and the frequent difficult grinding of
the cutters is avoided which cutters are used to produce the necessary cuts for
very small teeth and are expensive and very often break. 2) when the blank
strip is formed of sheet metal by punching previous to stamping out the teeth
or when the operations take place simultaneously or when the strip is cut out at
the edges the use at least of very fine and sensitive cutters in the tools which are
employed to cut out the teeth is avoided (as explained under 1).
3). The teeth curved of the shape in cross section are much more rigid and
stronger when driven into the work than flat teeth the line of attachment of
which to the back is a straight line: the latter teeth having a small bending
resistance and the straight bend forming a bad or weak joint so that it easily
breaks whilst the strips being secured to the work, whereas the curved teeth are
very much stronger and the curved bend does not act as a joint or hinge.
4) In consequence of the property of the stamped out teeth mentioned under
paragraph 3, a thinner lighter less hard and rigid clamp strip may be used.
From what has been said under paragraph 2 it follows that beside stamping
in the manufacture of clamping strips punching, cutting and other operations may
he employed but the teeth are always produced only by stamping (without
cutting) certain portions of the edges in the above described manner, and this is
the characteristic feature of the present invention.

page_text: The stamping can take place so as to form teeth of different cross-section.
Figs. 13 to 15 of the accompanying drawings show in side-elevation, plan and
cross-section through the strip, a clamp stamped out from a smooth-edged metal
strip C (Fig. 8). The metal strip C having originally a smooth edge-the original
edges being shown dotted in Fig. 14-has a wavy or curved outline after having
been stamped. The projections remain in the plane of the strip but the recesses
or parts which originally filled the spaces between each curved section, are formed
into teeth e (Figs. 13 & 15) which are turned inwards and downwards and have an
approximately angular cross-section, that is to say similar to the recesses, the
outlines of which determine the shape of the bend between the back and the tooth.
Figs. 1 to 7 show in plan (similarly to Fig. 14) other suitable forms of strips, the
spaces between the projections indicating the shape of the bend or the cross-
section of the tooth, the dotted lines showing the original smooth edge. It must
not be forgotten that there must be intervals between individual teeth (as in
Fig. 13) otherwise the work would be cut through by the continuous edge of the
clamp. In other words, the strip must not have the form of a channel. It will
be seen in Figs. 13 to 15 that this requirement can be fulfilled when a smooth-
edged strip is used and otherwise a suitable shape in plan is chosen; but in case
of pointed projections (such as for instance Figs. 2, 4, 7) the recesses are smaller
than in cases where the projections are blunt or rounded. Blank strips with
smooth edges are shown in Figs. 8 to 11 from these as well as from that shown in
Fig. 2 it follows that other constructions than plain strip-shaped clamps can be
manufactured according to the present invention. Fig. 12 shows a toothed or saw
edged blank strip. Its projections are stamped into teeth according to the curvel
lines shown in the drawing.
The clamp shown in this figure when in its unfinished state i.e. as flat toothed
sheet metal strip, looks, in pian, similar to the well known clamps in plan when
in their finished state, that is to say when their teeth are bent. The essential
difference lies in the shape of the teeth and in the manner of producing them.
In ordinary clamps the teeth are simply bent, whereas according to this invention
the teeth are bent on a curved line as indicated in dotted lines. The tooth is
thus an arc of a circle when looked at in side view. While in other constructions
according to this invention the arc or tooth has its summit towards the back of the
clamp, said summit is turned outwards in the construction according to Figure 12.
From this it will be seen that teeth can be formed according to this invention not
only on strips with straight edges, but also on those with zig-zag or saw edges.
Cut teeth can be replaced by punched waved or curved edges so that the blank
strip has the appearance of the finished clamp in plan made out of a smooth edged
blank strip.
The accompanying drawings show some clamp strips only by way of example,
and many
details may be varied in the invention without departing from its
spirit.
A modified construction consists in the back of the clamp being depressed in
stamping relatively to the parts between the teeth.
This invention will be better understood by referring to the Figs. 16 to 19 in
which a
clamp produced according to the process described is shown and illus-
trates the action of blows upon it.
Fig. 16 is a vertical section of the clamp on the line y-y Fig. 17.
Fig. 17 is a plan of a portion of a clamp-strip connecting two parts A and B
adjoining each other and in the same plane.
Fig. 18 is a vertical section on the line y-y Fig. 17 and Fig. 19 shows in
vertical section the application of a clamp according to the present invention for
connecting the corners of a box or the like.
The teeth care stamped out of the edge of the strip C in the manner already
´described. In plan (Fig. 17) they appear to be notches in the edges, therefore
the intervening parts between the teeth appear to be projections beyond the back,
if the rectangular part between the lines - (Fig. 17) be considered as the back

page_text: of the strip. There are two different profiles the profile y-y and the pro-
file x-x.
The points or ends c¹ of the teeth are normal to the plane of the back
and of the intervening parts between the teeth and therefore penetrate into
the material A B or A¹ B in a direction at right angles to the surface of the
latter (Figs. 18 and 19). When the material is so thin (as compared to the depth
of the teeth) that the points of the teeth project on the lower side said points may
be bent or "jumped up' on some hard surface (anvil or the like).
indicated in Fig. 18 where the chain-line a-b shows the lower surface of a thin
material.
99
This is
Unless such jumping up or bending takes place, the clamp is held in place only
by friction. In many cases it is sufficient in other cases the teeth are made deeper
i.e. longer than the thickness of the material. But for stamping out very long
It may be also con-
teeth a specially tough or tensive material must be used.
sidered desirable to avoid the teeth projecting on the lower side of the material.
For this reason a clamp strip has been devised the teeth of which are driven
inwards by the action of blows that is to say with the points towards the back
with which they form sharp angles or not at right angles thereto the tooth thus
forming a kind of hook in the material. This is effected by the back (within the
lines) being depressed during stamping relatively to the projecting parts
between the teeth i.e. those parts outside the lines z-z.
Such a clamp is shown in Fig. 20 in vertical section on line y-y Fig. 22, in
Fig. 21 in vertical section through the material with the clamp in place Fig. 22
being a plan corresponding to Fig. 21.
the parts in eleva-
-r the back also
As in the previous
back but the root
In vertical section y-y this form of clamp is the same as those already described
but in vertical section -- which is represented in Fig. 20 by
tion outside the parts c¹¹, it is different. In this section
appears flat, but the parts outside the lines - are turned up.
forms the tooth point c¹ is at right angles to the plane of the
of the tooth extends in a curve from the line z- upwards and the side e³ extends
When such a clamp is
from the outer edge downwards to the point of the tooth.
struck to drive it in it does not act in the same manner as the forms previously
described. Firstly the hammer or stamp presses on the upwardly projecting edges
the point of the right angle between the back and at the point of the tooth
becomes the centre of rotation and the point of the tooth penetrates obliquely
downwards and inwards into the material, thereby engaging in it like a hook
(Fig. 21). Secondly the angle w (Fig. 20) must be reduced to the value to¹
(Fig. 21) and at the same time the curved surface of the part between the teeth
is pressed flat. But then obviously the material of the tooth-side no longer has
in the smaller angle w¹ the same room that it occupied in the larger angle .
Each side therefore becomes bent or curved laterally, that is to say, towards the
adjoining tooth the extent to which it bends being the greater the nearer the tooth
cross-section in question is situated to the point of the tooth. For at that point
the width of the tooth is the smallest and its resistance to bending the least.
the other hand the bending in the direction of the arrows (Fig. 22) will be
greater than the bending at the top, in the direction of the arrows for the top
or point of the tooth meets resistance along the whole extent of its length in
the material which has already been compressed owing to the oblique penetration
of the tooth. Whether this explanation be correct or not the tooth is made conical
and the result it that not only in the direction of the profile y y but also in any
other cross-section through a tooth side (for instance in the directions v ), the
material is grasped as by a hook. The shape of the tooth driven in will be substan-
tially that indicated by the dotted lines (Fig. 22).
•
On
It is clear that such a clamp even if it does not pass completely through the
material will have a better hold than a clamp such as first described.
According to this modification other clamp-shapes with similar and even better
action can be produced. While the obliquity of penetration of the point of the
tooth chiefly depends in the extent of the angle , the degree of the bulging or

page_text: curving of the sides of the tooth depends chiefly upon the extent of expansion of
the side of the tooth in the angle w. In the form described above the concave (if
viewed from the top) bending of the intervening part between the teeth Fig. 20
reduces the width of the side of the tooth when measured at a right angle to the
upper side of the angle w. The more however the side of the tooth projects beyond
the said side of the angle the more material there is available to bulge or curve
especially when the part between the teeth is bent into a convex shape. For the
rest the size and the shape of the curve is also determined by the cross-section of
the tooth. Thus the oblique position of the teeth driven in & the bulging or
curving of the sides of the teeth shown in Figs. 23 to 26 is sharper or more pro-
nounced than that of the teeth just described, and in the teeth in Figs. 27 to 29
it is still more pronounced. In both cases both actions are so strongly marked
that the tooth-point c¹ (Figs. 24 to 20) is bent inward stronger still in Fig. 20.
If it is also pointed out that the parts between the teeth according to Fig. 23,
are directed obliquely upwards from the flat back but in a straight line, and that
according to Fig. 27, they are bent so as to have a convex shape, these two con-
structions will not require any further description.
Another point which should be mentioned will be explained with reference to
Figs. 25 and 29. It is obvious that in the modified arrangement greater strain
is placed on the expansibility of the sheet metal, than in the first described forms,
as the relative motion of the molecules of metal beween the point and the root
of a tooth is considerably greater in the constructions shown in Figs. 20, 23
and 27, than in the construction shown in Fig. 16. If the material be very tough,
such movement of the molecules can take place, but if the material be brittle, the
tooth will split along the top c¹. In both, it does not matter if the tooth splits
only at the moment of completion or just before, then instead of one
$6 half-round
tooth, two teeth of arc-shape are obtained. If a clamp with broken teeth is
driven in, then the split increases when the clamp is driven in, and when the sides
of the tooth curve outwards and the edges of the split tooth form a sharp angle
as indicated in Fig. 29. Thus the splitting of the tooth is of no consequence. On
the contrary the halves of the tooth bend all the easier and the material will be
secured all the better.
"
If however a tooth splits when beginning to stamp clamps of the form shown in
Fig. 16, then the stamp, continuing to descend, bends the parts downward at a
right angle, but as a further expansion of the material does not take place, faulty
tooth halves are produced which of course do not hold so well in the work as
properly formed teeth. The modified form has therefore the advantage of render-
ing premature splitting of teeth harmless. If, for instance, the edge c¹ splits in
the stamping out stage indicated in Fig. 30, the tooth or, more correctly, the tooth
halves still penetrate properly into the material when stamped, and when the
convex shaped part between the teeth is pressed flat, the sides will curve outwards
equally well.
It follows, inversely, that under certain circumstances the tooth need not neces-
sarily be stamped out up to the normal position of the tooth-point if the tooth
be split after having been only partially stamped out-by means of a cutter
connected to the stamp, that is to say, if the unintentional result referred to is
produced intentionally. Such a clamp shown in Fig. 30 has, besides the advantage
already mentioned, also the following advantage. In all the clamps with teeth
at right angles to the back there is always the danger as regards their use for
securing corners (Fig. 26), that under the pressure of the hammer or stamp the
vertical teeth which are not normal to the surface of the material, may slide down
instead of penetrating it properly. This danger does not exist when clamps
according to Fig. 30 are used, as the back rests on the edge of the angle w of
the material from the very beginning, and the teeth are brought in contact with
the surface of the work only after the back has been bent, and then driven into
the material. Turning movements therefore take place about fixed points, so that
chance of sliding is prevented. This turning of the teeth takes place in clamps

page_text: of this shape even when they are driven in flat; moreover in this case, two pieces
of material forming a butt-point (such as for instance A B in Fig. 18, or A¹ B¹
in Fig. 19) are drawn together all the tighter. According to Fig. 30 the line rr
passing through the points of the teeth does not quite coincide with the back,
that is to say the edges of the slit portion between each half of a tooth form an
obtuse angle with the plane of the back, which angle can, however be one of 180°
without in any way affecting the property just explained of this shape of clamp.
Figs. 31 to 34 show another construction of the same kind. Here also the
points of the tooth-halves are stamped out only slightly beyond the plane of the
back, but nevertheless owing to the great projection of the tooth-point and to the
sharp convexity of the parts between the teeth, bent at an angle the gripping is
very secure and the tooth acts like a hook (Fig. 34).
The clamps might be first stamped out Hat and then altered to the form
described by one or more separate stamping operations. It is advisable however,
to manufacture them in one or more connected stamping operations.
Having now particularly described and ascertained the nature of this inven-
tion as communicated to me by my foreign correspondent and in what manner the
same is to be performed I declare that what I claim is:-
-
1. The method of forming metal clamps for use in the manufacture of card-
board boxes and for other purposes consisting in bending down portions of the
edges of a strip of metal to form teeth of curved or angular cross section substan-
tially as described.
2. The method of forming metal clamps for use in the manufacture of card-
board boxes or for other purposes consisting in bending down portions of the
edges of a strip or plate of metal to form the teeth of curved or angular cross
section the parts of the strip between the teeth being bent upwards relatively to
the back of the strip or plate substantially as described.
3. A modified method of forming metal clamps of the character described
consisting in bending down portions of the edges of a strip or plate of metal to
form the teeth and splitting the teeth centrally substantially as described.
4. Metal clamps for use in the manufacture of cardboard boxes and for other
purposes consisting of a strip or plate with downwardly extending teeth formed
by bending down portions of the edges of the metal thereby forming teeth having
a curved or angular cross section substantially as described.
5. Metal clamps for use in the manufacture of cardboard boxes and for other
purposes consisting of a strip or plate with downwardly extending teeth formed by
bending down portions of the edges of the metal to form teeth of curved or angular
cross section the portions of the edges between the teeth being bent upwards
relatively to the back of the strip or plate substantially as described.
6. A metal clamp for use in the manufacture of cardboard boxes and for other
purposes characterised by the teeth c c being produced solely by bending the edges
of the metal, said portions being on the one hand bounded by a smooth or wavy
edge and on the other hand by a curved line consisting of straight and curved
portions starting from the edge and returning to it, so that the tooth has a profile
corresponding to said limit, projections in the plane of the back of the clamp being
formed on the strip substantially as described.
7. Metal clamps of the character described substantially as described or illus-
trated in Figure 12 or in Figures 13 and 14 or in Figures 16 and 17 or in
Figures 20, 21, and 22 or in Figures 23, 24, and 25 or in Figures 27, 28 and 29,
or in Figure 30 or in Figures 3 to 32 of the accompanying drawings.
Datad this 7th day of February 1898.
BOULT & WADE,
Agents for the Applicant.