NZ187230A - Production of nail plates with variable tooth spacing - Google Patents

Description

18133o/ NEW ZEALAND PATENTS ACT, 1953 No.: 187230/188916 Date: 10th May 1978/14th November 1978 COMPLETE SPECIFICATION RZ. PAT^STQFRCS - 3 MAY 1979 RECSVSD IMPROVEMENTS IN OR RELATING TO TOOTHED PLATE CONNECTORS Jt! We. GANG-NAILS N.Z. LIMITED, a company duly incorporated under the laws of New Zealand of 3-5 Zelanian Drive, East Tamaki, Auckland, New Zealand hereby declare the invention for which ✓?*/ we pray that a patent may be granted to p*€/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- ,872J0 U 188 This invention relates to toothed plate connectors.

It is an object of the present invention to provide a method of and apparatus for manufacturing a toothed plate connector and a toothed plate connector formed thereby 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) 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 in conjunction with said punch means and operatively connected to said feed rollers so as to rotate said feed rollers upon movement of said punch means away from said strip after a punching operation, said method 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 apparatus for manufacturing a toothed plate timber connector by rst fry OO punching rows of teeth out of a length of blank strip, M > said apparatus including, u™ § \ A I/) (a) punch means reciprocable toward and away from the line of feed of said strip to, in use, punch said rows i C 7 2 j 0 of teeth out of the plane of said strip, ' 88916 (b) feed rollers operative to advance said blank strip after a row of teeth have been punched, (c) connecting means reciprocable in conjunction with said punch means and operatively connected to said feed rollers so as to rotate said feed rollers upon movement of said punch means away from said strip 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 of 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; 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 187250 188916 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 incremental 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 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.

By use of this form of apparatus the incremental feeding steps between punching operations are varied so as to vary the spacing, in the direction of feed, 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. 187250 188916 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 mainshaft (not shown), the end 19 of the rod being mounted for rotation on the eccentric 18.

The opposite end 20 of the rod 15 pivotally receives the 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 187250 f 8 8 91 6 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.

In will be appreciated that the invention further envisages a method of forming a graded distribution toothed plate connector which method preferably involves the use of the apparatus hereinabove described.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 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. f '&7250 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 varied as the connector plate is progressively stamped out of the parent metal, using the apparatus described with reference to Fig. 1. Thus, the metal portions indicated by numeral 64" are less than the portions 65 which, in turn, are less than the portions 66 and again these are less than the metal portions 67.

The principle of operation can be applied to the case when two teeth are punched from the same slot (commonly termed air break in the industry) as shown in Fig. 3. 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 progressively increased as the spacings between adjacent rows of teeth are increased so '87230,., that increased steel area in the plate can be provided ' 889 5 6 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.

Accordingly a toothed plate connector may be formed which has less teeth and therefore a greater metal section at the point where loading which the plate will, in use, be subjected is the highest.

It will thus be 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. 187230

Claims (14)

WHAT WE CLAIM IS 1 88916

1. 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) 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 in conjunction with said punch means and operatively connected to said feed rollers so as to rotate said feed rollers upon movement of said punch means away from said strip after a punching operation, said method 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.

2. A method as claimed in Claim 1 further including counting the number of punching operations and at predetermined counts altering the operative connection between said connecting means and said feed rollers.

3. A method as claimed in Claim 1 or Claim 2 wherein: two feed rollers are provided geared for mutual rotation; and said connecting means is connected to variable stroke lever means pivotally mounted on the axis of one of said rollers and operable to rotate said one of said rollers -9- ! 87230 through a non-reversing mechanism; said method comprising altering the radius of a point of connection between said connecting means and said axis.

4. A method as claimed in Claim 3 wherein said point of connection is varied by actuation of pioton/cylinder apparatus.

5. A method as claimed in any one of the preceding claims wherein said operative connection is varied to increase the spacing between rows of teeth in said strip until said strip has been fed to the proposed mid-line of the connector and thereafter said operative connection is varied to reduce the spacing between rows of teeth until said strip has been fed by an amount corresponding to the length of said connector.

6. A method as claimed in Claim 5 wherein the operative connection is varied to produce a connector having teeth spaced symmetrically about said mid-line.

7. A method of manufacturing a toothed plate connector substantially as hereinbefore described with reference to the accompanying drawing.

8. 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 in conjunction w; said punch means and operatively connected to said feed -10- th 187230 18 rollers so as to rotate said feed rollers upon movement of said punch means away from said strip 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 of teeth.

9. Apparatus as claimed in Claim 8 wherein: two feed rollers are provided geared for mutual rotation; said connecting means comprising a connecting rod, reciprocable in conjunction with said punch means, connected to variable stroke lever means pivotally mounted on the axis of one of said rollers and operable to rotate said one of said rollers through a non-reversing mechanism; and said means to vary the operative connection between said feed rollers and said connecting means comprising means to alter the radius of a point of connection between said connecting rod and said axis

10. Apparatus as claimed in Claim 9 wherein said means to alter the radius of the point of connection between said connecting rod and said variable stroke lever comprises piston/cylinder apparatus.

11. Apparatus as claimed in Claim 10 further including a pre-programmed control system to set the extension of the piston in the cylinder.

12. Apparatus as claimed in Claim 12 wherein said preprogrammed control system is programmed to incrementally increase the stroke of said lever until a predetermined position is reached, and thereafter programmed to -11- '87230 188916 incrementally decrease said stroke in the same incremental steps.

13. Apparatus for manufacturing a toothed plate timber connector when constructed, arranged and operable substantially as hereinbefore described with reference to the accompanying drawings.

14. A toothed plate timber connector when made according to the method claimed in any one of Claims 1 to 7. -15^, A toothed plate timber connector when made by the apparatus claimed in any one of Claims 8 to 12. DATED THIS iDAY OF ft) oV<2,v\lo^ A. J. PARK & SON AGENTS FOR THE APPLICANT