Note: Descriptions are shown in the official language in which they were submitted.
llZ7525
1 This invention relates to toothed plate connectors.
It is an object of the present invention to provide a
method of and apparatus for manufacturing toothed plate
connectors which will at least provide the public with a useful
choice.
Accordingly, in one aspect, the invention consists in
a method of manufacturing a toothed plate timber connector
by punching rows of teeth out of a length of blank strip, using
a press having: (a) a punch means reciprocable toward and away
from the line of feed of said strip to punch said rows of teeth
out of the plane of said strip, (b) feed rollers operative
to advance said blank strip after a row of teeth have been
punched, (c) connecting means reciprocable with said punch
means and operatively connected to said feed rollers so as to
rotate said feed rollers upon withdrawal of said punch means
after a punching operation, said ~.ethod comprising the steps
of altering the operative connection between said connecting
means and said feed rollers between at least some successive
punch strokes to vary the amount of rotation of said feed
rollers during each press stroke and thus the spacing between
corresponding successive rows of teeth.
; In a further aspect the invention consists in an
apparatus for manufacturing a toothed plate timber connector
by punching rows of teeth out of a length of blank strip, said
apparatus including, (a) punch means reciprocable toward and
away from the line of feed of said strip to, in use, punch
said rows of teeth out of the plane of said strip, (b) feed
rollers operative to advance said blank strip after a row of
teeth have been punched, (c) connecting means reciprocable with
said punch means and operatively connected to said feed rollers
1~2~5~:S
1 so as to rotate said feed rollers upon withdrawal of said
punch means after a punching operation, (d) means operable during
actuation of said punch means to vary the operative connection
between said feed rollers and said connecting means in a manner
so as to vary the amount of rotation of said feed rollers
during each press stroke and thus the spacing between
corresponding successive rows to teeth.
To those skilled in the art to which this invention
relates many changes in construction and widely differing
embodiments and applications of the invention will suggest
themselves without departing from the scope of the invention
as defined in the appended claims. The disclosures and the
description herein are purely illustrative and are not intended
to be in any sense limiting.
One preferred form of the invention will now be
described with reference to the accompanying drawings in which:-
Fig. 1 shows a diagrammatic view of part of an
apparatus used for forming a graded distribution toothed plate
connector according to the invention; and
Figs. 2 and 3 show examples of graded distribution
toothed plate connectors formed in accordance with the invention.
The invention provides apparatus for manufacturing
toothed plate connector plates, the apparatus comprising
punch means including punch actuating means arranged to crack
teeth out of blank metal plate and feeding means operable to
move the plate between successive punching operations, the
feeding means being arranged and operable to vary the incre-
mental movement between at least some of the successive punching
operations, the end result being that a toothed plate connector
is formed having a graded distribution of teeth, the grading of
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112~5z5;
1 the tooth distribution being predetermined according to the
proposed in use stress demands to which the connector is to be
subjected.
One embodiment of apparatus is diagrammatically shown
in part in Fig. 1 for manufacturing a graded distribution toothed
plate connector according to the invention. According to this
form of apparatus the incremental feeding steps between punching
operations are varied so as to vary the spacing between rows
of teeth cracked out using a set punching sequence transverse to
the feed direction of the blank metal plate. Such connector
plates are shown in Figs. 2 and 3 and will be described in
greater detail hereinafter.
The apparatus for varying the feed between punch
strokes comprises a pair of feed rollers 10 and 11 which are
geared together for synchronous rotation. Drive is imparted
to the roller 11 by way of lever 12 which is pivotally mounted
with respect to the axis of roller 11 and transmits drive to
the roller 11 by a sprag clutch or ratchet mechanism comprising
pawls 13 mounted on the lever 12 and biased into engagement
with ratchet surface 14 mounted for rotation with the roller 11.
As shown in the drawings, each upward stroke of the
lever 12 imparts an increment of rotational movement to roller
11 and thus roller 10. The lever 12 is reciprocated through
a rod 15 and pin 16 which is mounted for reciprocation with
the rod 15, the pin 16 being received in a slot 17 provided
in the lever 12. Reciprocating motion is imparted to the rod
15 by an eccentric which is shown schematically at 18 in
Fig. 1 driven from the press main shaft (not shown), the end 19
of the rod being mounted for rotation on the eccentric 18.
The opposite end 20 of rod 15 pivotally receives the
~lZ75Z5
1 end of a piston rod 21 of a hydraulic or pneumatic piston and
cylinder arrangement 22. A pre-programmed control system (not
shown) is provided to actuate the piston and cylinder arrangement
and adjust the position of piston rod 21 which, it will be
appreciated, varies the position of pin 16 in slot 17 and thus
varies the arc through which lever 12 pivots which, of course,
has the effect of varying the increment through which roller 11
and thus roller 10 will be rotated.
The pre-programmed control system is preferably an
electronic system which counts the number of punching strokes
and, at predetermined counts, activates the piston and cylinder
arrangement 22 to alter the stroke of the lever 12. For the
manufacture of the connectors depicted in Figs. 2 and 3 the
counter is arranged to operate at five different counts, one
for each of the four different positions of the piston rod 21
(corresponding to the four alternative spacings between teeth
in the connector plate) and one to reset the piston/cylinder
arrangement and operate the connector severing apparatus (not
shown) at the completion of manufacture of any one plate.
It will be appreciated that the control system need
not be electronic but could be hydraulic, pneumatic, mechanical
or any other suitable form.
The remainder of the technology necessary to perform
the method of manufacture, i.e. the punching apparatus may
be of any conventional form so as to produce teeth of the
desired shape and configuration.
It will be appreciated that the invention further
envisages a method of forming a graded distribution toothed
plaie connector which method preferably involves the use of
the apparatus hereinabove described.
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1127525
1 By graded distribution toothed plate connector it is
meant a connector having different spacing between some of
the adjacent teeth on the plate. The intention of a graded
distribution toothed plate connector is to provide a toothed
plate connector in which the distribution of teeth is inversely
proportional to the, in use, stress at a particular point on
the plate.
In use, the centre of the plate typically lies over a
butt joint between two wooden members and thus the centre
receives the greatest stress. Accordingly a graded distribution
toothed plate has less teeth at the centre of the plate than
at the ends and thus a greater metal section is provided to
absorb the greater stress. In short, the available metal section
is more efficiently utilised.
The variable feed embodiment of apparatus described
with reference to Fig. 1 results in a form of connector plate
being formed which may be as depicted in Figs. 2 and 3.
Referring to Fig. 2 there is shown a toothed plate ~ -
connector in which a series of apertures 60 remain in the
parent metal 61 after teeth have been punched from the parent
metal and folded on the base of the triangle of the apertures 60.
It will be seen that rows of teeth 62 have the apices of the
triangle pointing to the left and such rows 62 alternate with
further rows 63 in which the apices of the apertures point
in the opposite direction. This is achieved by employing
two series of punching heads reversed with respect to one
another, the punching heads operating alternatively.
To achieve a varying tooth density and inversely
varying residual steel section the feed step is increased as the
connector plate is progressively stamped out of the parent
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~lZ'~5Z5
1 metal, preferably using the apparatus described with reference
to Fig. 1. Thus, the metal portions indicated by numeral 67 are
greater than the portions 66 which, in turn, are greater than
the portions 65 and again these are greater than the metal
portions 64. When the plate has been fed to the centre line
of the proposed connector the control system operates to
decrease the feed between successive punching operations to
form a plate symmetrical about its centre line.
The principle of operation can be applied to the case
where two teeth are punched from the same slot (commonly
termed air break in the industry) as shown in Fig. 7. In
this case the apertures 70 in one row alternate with apertures
71 in the next row and again in each row the end 72 of each
aperture is narrower than the end 73 giving a tapered side to
the aperture left after a small tooth positioned at end 72
and a large tooth positioned at end 73 are struck from the
parent metal. Again, the metal portions 74 and 75 are pro-
gressively increased as the spacings between adjacent rows of
teeth are increased so that increased steel area in the plate
can be provided toward the centre line 76 of the plate, being
the line on which, in use, two pieces of wood are centred in
making a joint. At the ends 77 of the plate an increase in
tooth density is provided, the tooth density between the centre
76 and the end 77 being graded to give a satisfactory increase
in steel area towards the centre 76 and an increase in tooth
number towards the end 77 which is the desired result.
According to the invention, therefore, a toothed plate
connector may be formed which has less teeth and therefore a
greater metal section at the point where the loading which the
plate will, in use, be subjected is the highest.
11275;~S
1 It will thus ~e appreciated that the present invention
provides methods of and apparatus for manufacturing toothed
nail connector plates which make far more efficient use of
a given volume of material used in its manufacture.
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