CA1041279A - Cambering attachment for truss assembly jig using canted roller press - Google Patents

Abstract

James D. Adams CAMBERING ATTACHMENT FOR TRUSS ASSEMBLY
JIG USING CANTED ROLLER PRESS

Abstract of the Disclosure Joist trusses, having generally parallel upper and lower chord members, are necessarily manufactured with a camber and pre-ferably upon an assembly jig having a longitudinally disposed, mov-able, endless belt-like support surface for supporting precut wooden members arranged into the shape of a joist truss. Clamping devices, mounted upon the support surface, hold the precut members in place and spiked, metal gusset plates are placed at opposite sides of each joint of the truss. Two pairs of opposing, transversely-disposed rolls, arranged as roller presses, are locat-ed at one end of the support surface, with a first pair of rolls being positioned to receive both the support surface and the assem-bled truss thereon, so as to partially impale the gusset plate spikes into the members. The second pair of rolls are positioned beyond the support surface to tightly press the gusset plates against the sides of the truss as it passes through these rollers.
The second pair of rolls are skewed, or angled from a normal trans-verse axial position to impart a predetermined camber into a truss as it moves through these rolls. :

Description

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CAMBERING ATTACHMENT FOR TRUSS ASSEMBLY
JIG USING CANTED ROLLER PRESS

Specification `:
The present invention relates to assembly jigs for form-ing assembled precut wood members into a structural joist truss, and more particularly to the manufacture of joist trusses upon such assembly jigs. The primary object of the present invention is to provide,~ in a truss assembly jig, a noveI, improved and s~mplified mode~of imparting a predetermined and accurat~ camber to a joist truss as i~ moves through the manufacturing jig.
A joist truss may be defined as having generally straight, parallel upper and lower chords with a zigzag array of web or diag-onal members between these chords, and including perpendicular ends.
Such trusses are comparatively shallo~ and the ratio of height to span may be as small as 1 to 20, in contrast with othex types of trusses whexe a desirable height-to-span ratio is more nearly 1 to 5~or more.~ Accordingly, joist trusses are used extansively for ~. ~
` supporting~floor~and roof decks~ ~n the past, some joist truss s have been manufactured of steel beams and rods, wood and steel, etc., but recently, some joist truss~s are being constructed of ~r: wood (generally 2 x 4'sj and have become very popular for use ~n lieu of scarce, more expensi~e ti~ber joists.
Other actors which have brought about an increased use ,~
of joist trusses, and also, various other types of timber trusses, are the development of improved truss components and methods for manufacturing the trusses. Spiked gusset plates, which are affixed to a truss at each side of each joint of the truss, have simplified the problems of holding the web and chord members together. Assem-bly jigs or truss forming machines have been developed to manufac-ture the trusses. One such an assembly jig generally comprii~As a s ~ ~

lQ~79 movable, table-like support surface, preferably an endless belted ~ -structure, whereon the upper and lower truss chords and the web members are positioned and held by ~amps in the form of the truss.
Gusset plates (spiked, metal plates) are then placed at each joint, and thereafter, movem~nt of the support surface passes the preas-sembled truss through upright pair of opposing rolls arranged as a roller press, to press the spikes of the gusset plates into the wood. Preferably (and the type of apparatus with which the present invention is concerned), two sets of rolls are used. The first rol-ler press set is at, and above and below the movable surface andfunctions to partially impale the gusset plate spikes into the wood-en members to hold the truss together. The second roller press set is beyond the movable surface and functions to press the gusset plates in pla e tightly against the sides of the truss and produce a-finishedi~truss.
Since timber is moderately elastic, a truss will deflect under load even when the components are tightly knit togethex at the joints by the gusset plates. This movement is pronounced as a joist truss is moved through the double roller press assembly.
~, 20 Such~deflection is not significant on an A-frame type truss, such as may be used for supporting a roof, but it becomes quite impor-tant in joist trusses which axe supporting a floor~ The floor must be flat and not sag at the center of the span when the trusses are supporting a loadO To avoid such a ~ag, it is a common practice to provide a predetermined camber in the joist trusses. Thus, once . ~, a group of cambered trusses are positioned across an open span and covered with a floor deck, they will deflect from an arched, cam-bered form to lie flatly or even have a slight upwaxd crown at the center of the span.
This practice of providing camber is well known and proper axchitectural specifications require that a joist truss be cambered~

A common procedure for forming a camber in a joist truss is to arch 7~
the truss when it is being formed upon the support suxface of an assembly jig, using the restraining clamps upon the table holding the truss in the cambered position until the gusset plates are af-fixed in place. However, it has been found that it is dificult to produce a consistent, predetermined camber in a truss even though each truss is arched the same amount, when such a truss is formed by the two roller press sets on the jig. There is a sub-stantial stress exerted on a truss as i~ passes through the roller presses, and a truss with its preformed camber genexally substan-tially changes, forming non-uniform trusses. In the manufacture of a large number of the same size of trusses, a number of the trusses must be rejected because of either insuf~icient camber or too much camber.
The present invention was conceived and developed with such considerations in view, and the invention comprises, in es-sence, a truss assembly jig having a movable support surface with `~ clamps thereon to hold precut wooden members in the form of a joist truss and with spiked gusset plates at the truss join'csl two pairs `~ of opposing rolls (forming two roller presses) in tandem at the discharge end of the support surface to receive one or two trusses and to press the gusset plate spikes into the wooden members in a two-step, single-pass operation, and an arrangement where the second pair of rolls is skewed, or angled slightly from a normal straight line traverse, axial alighment with respect to the movable surface, to impart a predetermined camber to~the truss. It was ascertained that the second, angled roller press set would not only impart a camber to the truss when it is laid out in a straight, longitudinal alignment upon the support surface, but also, it would cause the camber to be predictable and consistent for a large number of similar size of trusses being manufactured.
Thus, another object of the invention is to provide a truss assembly jig which is capable of manu~acturing cambered k ~4~Z79 joist trusses having a selected, specified camber which will be consistently the same in each of a large number of joist trusses manufactured in the jig, and minimize the number of trusses which have to be rejected.
Another object of the invention is to provide, in a truss assembly jig, an adjustably angled roller press for forming a pre-determined camber in a joist truss manufactured therein which does not require any significant modifications to a double roller press, truas assembly jig, nor require any extra steps in the formation of a predetermined, cambexed truss manufactured therein.
Another object of the invention is to provide a modified truss assembly jig to produce, accurately and consistently, camber in joist trusses manufactured therein which is simple, economical, reliable, rugged and durable.
j With the foregoing and other objects in view, all of which more fully hereinafter appearl my invention comprises certain constructions, combinations and arrangements of parts and eIements ~`` as hereina~ter described, defined in the appended claims and illus-trated, in a preerred embo~iment, in the accompanying drawings, in which:
Fig. 1 is a plan view of a truss assembly jig of a type ,, which manufactur~s two trusses at a time, and which is arranged ~1 with two sets of oppositely-skewed discharge rolls to impart cam-ber to trusses manufactured on the job, and with trusses being il-lustrated as passing through the rolls.
Fig. 2 is a side elevation view of the discharge end of the truss assembly jig as from the indicated line 2 2 at Fig. 1, but on an enlarged scale.
Fig. 3 is an enlarged, plan view of the discarge end of the truss viewed at Fig. 2, but without trusses in the apparatus.
Fig. 4 is a diagrammatic view of the two roller press arrangements and of a truss passing through the rolls to permit 7~
the first pair of rolls to partially impale the gusset plate spikes into the truss and the second pair to press the gusset plates against the truss members to complete the truss.
Fig. 5 is a fragmentary portion of a sectional plan view as taken -from the indicated line 5-5 at Fig. 2, but with some parts being removed to show constructions otherwise hidden from view Fig. 6 is a fragmentary sectional detail as taken from the indicated line 6-6 at Fig. 5.
Referring more particularly to the drawings, Fig. 1 illus- -trates a truss assembly jig 20 of a t~pe whereon either one or twojoist trusses A and B may be assembled at one tIme, as upon an end-less, assembly belt 21. This belt 2I constitutes the movable sup-port aurface for carrying preassembled trusses and for moving the trusses through rolls arranged in upright pairs as roller presses These rolls constitute a double roller press assembly 22 to press ; ~ spiked gussets G into the preassembIed truss members to complete a truss as it moves through the roIler press assembly, a~l as here-inafter fuxther described.
The assembly belt 21 is essentially a conventional unit -.~ 20 which may be construc~ed as a continuous web or as a longitudinally - extended array of slats 23 mounted on chains 24, as indicated at ~ Figs. 1 and 2. The chains of this assembly belt 2I are extended :
about end rolls or sprockets 25 which, in turn, are mounted on shafts 26. The sha~ts, in turn, are carried in bearings 27 sup-ported in an elongated structural framework 28 consisting of longi-tudinal members, transverse members and uprights in any suitable, essentially conventional organization.
The belt 21, whose upper face constitutes a movable sup-port surface whereon trusses are assembled, is driven by a motor 29 connected to the shaft 26 at the discharge end of the belt sur-face adjacent to the roller assembly 22, to operate in unison with - the operation of the roller assembly, as hereinafter described~ The ~L~34~Z~
belt 21 will include conventional components, not shown, such as take-up adjusting devices on the bearings 27. Suitable restrain-ing clamps 30 will be provided upon the surface of belt 21 as spaced arrays ex~ending along the longitudinal reach of the upper surface of the belt to hold the truss components in place when they ; are preassembled and before the truss components are fastened to-gether by the gusset plates G.
The roll assembly 22 includes a first roller press includ-ing a pair of opposir.g, upright rolls 31 and 3II which extend across i 10 the belt 21 near its discharge end. The roll assembly 22 also includes lefthand and righthand roller press assemblies including pairs of opposing, upright, finishing rolls 32R and 32R' and 32L
and 32L' located a short distance beyond the discharge end of the belt 21. These rolls may be carried in a common structural frame-~`1 work 33 consisting of longitudinal, transverse and upright members at both sides of the rolls in any suitable, convenient arrangement~
~ The framework 33 is integrated with and may be a continuation of -, the framework 28 of the beIt, heretofore described. This frame-work includes uprights at the rolls 31 and 31' and shelf members 33' in the uprights at each side of each roll 31 and 31' to carry bearings 34 to support the shafts of the rolls. The rolls 32R-32R' and 32L-32L' are carried in upright yokes 35R and 35L, respectively, which permit them to change alignment as hereinafter described and the upright members of these yokes include shelf members 35' to carry bearings 36 to support the shafts of the rolls.
The first set of rolls 31 and 31', located near the dis-charge end of the assembly belt 21, are positioned with the upper roll 31 being spaced above the surface of the assembly belt to per-mit truss components with gusset plates preassembled upon the as-sembly belt 21 to pass ~nderneath this roll. The lower roll 31' is underneath this belt 21 and supports the belt. The upper roll 31 is driven in synchronism with the movement of the belt 21 by a ~ 4~79 suit~ble motor 37 which is preferably an elec~rical-motor, gear-reducer combination. The lower roll 31', on the other hand, may j be an idler (also may be driven) and functions to support the as-sembly belt against pressures imposed by the upper roll whenever a truss pa ses underneath it. It may be of reduced diameter, if necessary, to fit between the upper and lower ~eaches of the belt, as best illustrated at Fig. 2. Since the lower roll 31' is posi-tioned to contact the underside of the upper reach of the belt 21, this roll will be formed with suitable circumferential slots, not shown, to provide clearance for belt chains 24 and it will be shortened, if necessary, to clear members of the framework 28.
The function of the first roller press set, including rolls 31 and 31', is to partially impale gusset plate spikes into the wooden truss components. The gussets G, which fasten the truss ~, members together, are flat metal plates 38. Each plate has spikes 39 outstanding from one face and preferably, these spikes 39 are ~, formed outstanding from one face and preferably, these spikes 39 are formed integrally with the plate 38 by punching and bending opera-tions~ cutting the spikes out of the surface of the plates. In the formation of a truss according to the invention, gusset plates are placed on both faces of the truss members at each joint when the truss members are preassembled on the belt 21 as best indicat-ed a~ Fig. 4. To hold a truss in its preassembled form, the re-straining clamps 30 upstand from the surface of the assembly belt 21 a distance sufficient to hold the wooden truss members when they ; are held above the belt surface by gusset plates underneath them.
These clamps are arranged in straight lines, spaced apart to hold a truss of the desired width.
The spikes 39 on a gusset plate may be as much as 1-3/4 inches long, and hence it is impractical to completely drive these spikes into the timber components by a single pair of rolls. Ac-cordingly, the gusset plate spikes are driven into the wooden components approximately half way as they pass through the first pair of rolls 31 and 31l. They are subsequently completely driven in place by a pair of finishing rolls 32R and 32R' or 32L and 32L'.
This partial impalement of the gusset plate spikes by rolls 31 and 31' does fasten the timber components of a truss ~ogether to such a degree as to make the truss rigid, so rigid, in fact, that the truss may then move from the support surface of the beIt 21 to cantilever the gap between the end of the belt 21 to move into a pair of finishing rolls, as in the manner indicated at Fig. 4.
However, there is a substantial stress on the trusses which may induce lateral movement imparting unwanted camber in the trusses.
The pairs of finishing rolls 32R and 32R' and 32~ and 32L' are thus positioned to receive a truss having its components held toge~her by partially impaled spikes of the gusset plates 38.
~he~rolls~of each pair are spaced apart a distance sufficient to tightly press these gusset plates against the sides of the truss ( ~
members as the truss moves through the rolls. These ~inishing rolls may be mounted in a rigid manner in the yoke frames, 35R and 35L as illustrated, or they may be spring mounted in any suitable manner to yield a small amount whenever a truss pas~es through them, to allow for the~gusset plate thickness and other variations in the thickness of the members. Each upper roll 32R and 32L is driven in synchronism with the movement of a truss moving from the first set of rolls 31 and 31', and from ~he belt 21, as by a suitable motor 40R and 40L, respecti~ely, and each motor is preferably an electri~al-motor, gear-reducer combination. The lower rolls 32R' and 32L' are idlers.
In accordance with the present invention, each pair of finishing rolls 32R-32R' and 32L-32L' is skewed or angled to place the roll axe~-at a small angle from a normal transverse~alignment with respect to the longitudinal axis of the apparatus. Such an angle may be from 2 to 10 degreesg from the normal to the longitudinal 27~
axis of the apparatus. This angling of the rolls produces a pre-determined camber in trusses being formed in the apparatus which is surprisingly consistent in the trusses. As a matter of conven-ience, righthand and lef~hand rolls are used to manufacture two trusses at a time, and each pair of rolls is skewed to turn a truss passing therethrough outwardly and away from the longitudinal axis ~..
of the apparatus, as best illustrated at Fig. 1, thus preventing ;~ any interference of one truss with another.
~ It is apparent that this angle of skew may need to be ~ 10 changed whenever different siæes of trusses are being manufactured or a different camber is necessary, a means for adjustment may be necessary. Accordingly, the two pairs of finishing rolls, 32R-32R
and 32L and 32L', are mounted upon shiftable ~rames, the aforemen-tisned yokes 35R and 35L. ~he upright arms 41 of each yoke frame ~ 35R and 35L, which carry the respective rolls, upstand from a flat `,! ~ crotch or b~ase 42. ~his base 42 of each yoke rests upon the frame-work 33 as hereinafter further described.
The width of each pair of finishing rolls 32L-32L' and ,. ~
32R-32R~ is such as to extend to the longitudinal central axis of the apparatus, and to avoid a problem of overlap, the pair of rolls , .
32R-3ZR' is placed ahead of the pair of rolls 32L-32L', and closer to the end ffl the belt 21~ as illustrated. It was ascertained that ~; this difference with respect to the distance from the end of the belt 21 will not significantly affect the results of the truss-forming and camber-producing operations and thus, the offsetting roll pattern is provided as a matter of convenience~
~ his offset pattern of the rolls requires an ofsetting frame portion to properly support the base 41 of each yoke 35R and 35L, as best illustrated at Figs. 3 and 5. The framework 33 thus includes a longitudinally spaced outward pad 43R and an inward pad 44R and 44L whereon the sides of the base 42 of the yoke 35R are mounted. While this yoke may be formed in various ways, a preferred 1~

~ _ 7: ' , ~ , structuxe is illustrated at Fig. 5 where the base 42 of each yoke combines an outward side crossarm 45 and an inner crossarm 46 which are spaced apart by a transverse center section 47 in the general orm of an "H" structure. The uprights 41 of each yoke upstand from these crossarms 45 and 46. The crossarms 45 and 46 res~ upon ~heir respective pads 43R and 43L and 44R and 44L. Each end of each crossarm 45 and 46 is formed with ears 45' and 46', respectively, for receiving tiedown bolts to secure the yokes 35R
and 35L to the framework pads.
The outward crossarm 45 of each yoke base is pivotally connected to its pad 43R or 43L as by a pivot bolt 48 at the cent-er of the crossarm. The inward crossarm 46 of each yoke is slidably carried upon its pad 44R or 44L by adjustment bolts 49 fitted in the ears 46' at each side of the crossarm. The bolts pass through holes in these ears and into radial slots 50 in the respective pads 44R or 44L. These slots are centered on the axis of the opposing bolt 48. To complete the arrangement, tiedown bolts 51 may be pro-ùided in the ears 45l of each outward crossarm 45 and these bolts are itted in slots 52 in the ears and in the outward pads 43R and 43L which are also centered on ~he axis of the respective bolts 48.
The operation of this apparatus is manifest from the fore-going description. Whenever a pair of trusses, or a single truss for that matter, is to be formed in the apparatus, the finishing rolls 32R-32R' and 32L-32L' are skewed from a longitudinal axial alignment of the apparatus by shifting the base of the yokes 35R
and 35L about the pivot bolt 48. The other bolts 49 and 51 are then tightened to secure the rolls in place at a selected angle of skew. Next, a truss is formed upon the belt 21 in a conventional manner and is allowed to move from the belt through the rolls 31 to partially impale gussets into the truss and thereafter, to move to the skewed, or angled, finishing roll. This angling of the roll then imposes a selected camber upon the truss through an action ~k~

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which, though observed, is not completely understood. Howevex, in a run of a large number of trusses of the same size, these rolls will be skewed at ~electsd angles, determined by experiment if necessary, and the camber in each and every truss will be consis-;
tently the s~me~ and to the point where the number of rejec~s be-cause of improper camber in the trusses, is absolutely-minimized.
I have now described my invention in considerable detail.
However, it is obvious that others skilled in the art can arrange `~
and devise alternate and equivalent constructions and operations which are nevertheless within the spirit and scope of my invention.
Hence, I desire that my prote`c~ion be limited, not by the construc-tions and operations illustrated and described, but only by the proper scope of the appended claims.

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Claims (7)

I claim:

1. In a truss assembly jig for forming a timber truss having parallel upper and lower chords and diagonal struts between the chords, with the truss members, the chords and the struts being fastened together by spiked gusset plates, the combination including:
(a) a movable support surface whereon the truss members are placed in preassembled, longitudinal position to be thereafter moved to and from a discharge end of the support surface;
(b) a pair of first roll means near the dis-charge end of the support surface including a roll spaced above the surface a distance sufficient to partially impale the gusset plates into the wood truss members as the truss moves thereunder towards the discharge end of the surface;
(c) a pair of finishing roll means a short distance beyond the discharge end of the surface to receive a truss as it moves from the support surface, said pair of finishing roll means having rolls spaced apart to press the gusset plates into and against the sides of the truss members to finish the truss; and the improvement wherein: the finishing roll means is skewed at an angle from the normal transverse axial alignment with respect to the longitudinal axis of the support surface whereby to impart a camber to a truss passing therethrough which is initially placed in longitudinal align-ment upon the support surface.

2. The apparatus defined in claim 1, wherein:
the skew angle is from 2 to 10 degrees.

3. The apparatus defined in claim 1, wherein:
said pair of finishing roll means is carried in an adjustable frame means adapted to permit the same to be rotatably shifted to provide the aforesaid skew position.

4. The apparatus defined in claim 1, wherein:
said pair of finishing roll means is carried in a yokelike frame, the base of which is rotatably shiftable whereby to permit the rolls to be set at a selected skew angle.

5. The apparatus defined in claim 4, including:
a second pair of finishing roll means, with one of said pair of finishing roll means being at one side of the apparatus, and the other pair of finishing roll means being at the other side of the apparatus, whereby to permit the simultaneous formation of a pair of joist trusses on the apparatus.

6. The apparatus defined in claim 5, wherein:
the second pair of finishing roll means is longitudinally offset from the first to permit each said pair of finishing roll means to extend to the center of the apparatus.

7. In the method of manufacturing a wooden joist truss, including longitudinal upper and lower wooden chords with wooden cross-bracing members, with a predetermined camber, which includes assembling wooden components, an assembly in the form of a joist truss with the upper and lower chords members in straight and parallel arrangement, placing toothed, metal gusset plates on each side of each joist, moving such assembly through a first roller press set at a normal angle to the longitudinal axis of the truss to partially embed the teeth of the gusset plates in the wooden members, and the improvement of passing the partially finished truss through a second roller press having the axis of its rolls set at a small angle to a normal position to the longitudinal axis of the truss passing through the first roller press to form a camber of predetermined dimensions in the truss.