US2938480A - Assembly fixture for bar and long span joists - Google Patents

Description

y 1, 1960 M. IRWIN 2,938,480

ASSEMBLY FIXTURE FOR BAR AND LONG SPAN JOISTS Filed July 8, 1955 3 Sheets-Sheet 1 y 3 1 0 M. IRWIN 2,938,480

ASSEMBLY FIXTURE FOR BAR AND LONG SPAN JOISTS Filed July 8, 1955 3 Sheets-Sheet 2 May 31, 1960 IRWIN 2,93 80 ASSEMBLY FIXTURE FOR BAR AND LONG SPAN JOISTS Filed July 8, 1955 3 Sheets-Sheet 3 I f\; X7 HQ 60 INVENTOR.

L 1 7.? I 2 f0 I Z V a e 55 BY United States Patent ASSEMBLY FIXTURE FOR BAR AND LONG SPAN JOISTS Milton Irwin, Minneapolis, Minn., assignor to Qeneral Steel, Inc., Minneapolis, Minn., a corporation of Minnesota Filed July 8, 1955, Ser. No. 520,676

3 Claims. (Cl. 113-99) This invention relates to fabricating metal joists and more particularly to an assembly fixture for holding the members of bar and long span joists during welding thereof. There are two principle types of light fabricated metal joists currently used in the building industry. These types are popularly known as bar joists and long span joists. Bar joists are employed generally for spans which do not exceed forty feet and consists of longitudinal members or cords with continuous lengths of zig-zag round bars welded thereto. In a bar joist the top cord generally consists of a pair of angle irons welded to the uppermost apexes of the zig-zag bars and the bottom cord consists generally of either angle irons or round bars applied to the opposed series of apexes. The selection of sizes, thicknesses, angles, diameters of bars and so forth are engineering factors which are calculated for the specific span and loading to be carried .by the joist.

Long span joists are employed for extra heavy loads or for spans which exceed around forty feet. The long span joist is constructed of a pair 'of angle irons for both the upper and lower cord members and is generally provided with vertical struts constructed of pairs of angle irons extending across the upper and lower cords. Diagonal braces, generally constructed of-fiat metal bars, are placed between the pairs of angle irons constituting the upper and lower cords, all members preferably being welded together to form an integral unit.

Since the combination of factors in engineering and designing a joist to meet a specific purpose requires a wide variety of lengths, depths and designs, there has been, to the best of my knowledge, no simple and straight forward means developed in the prior art for producing .such joists. Because of the complexity of the problem,

it appears that engineers have not succeeded prior to my invention in developing a single apparatus with sumcient latitude to hold and support both bar and long span joists of various sizes and shapes during the fabrication thereof.

In conventional practice where a number of identical joists are to be fabricated, it is customary to set up blocks, studs and other devices to help position the various members of the joist so as to reduce the time consumed in measuring out the exact location of each member in consecutive runs. Table or framework members are generally provided and numerous clamps are then placed on the members to maintain them in correct position and to hold them in intimate contact until welded in place. During the conventional welding operation, it becomes necessary to employ a crane or other similar equipment to pick up the entire joist and move it to various positions so as to make the parts more accessible to the welders. After the joist is completely welded, all of the clamps must again be removed one by one and the joist must be pried out from between the studs. Since the welding heat tends to progressively distort the joists, they are often difiicult to remove and may even be dam- 2,938,480 7 Patented May 31, 1960 aged in the process. Because of the flexing and shifting of the members under thermal expansion, the individual conventional clamp members often become loosened or permit the members to misalign themselves with respect to other parts.

When a new run of identical joists is to be made under present practice, all of the positioning studs and blocks must again be laid out with considerable loss of time to the welders waiting to begin fabrication. In some instances, it is necessary for the fabricator to make a considerably greater number of joists than he has on order since the set up time is not economical for a short run. Even when an over-run of joists is made, the economic factor is not always satisfactorily adjusted since the fabricators warehousing space and capital for material willlbe tied up in the surplus production unless an immediate sale of the same could be made.

My invention contemplates overcoming, to a large measure, the above mentioned difficulties and it is an important object thereof to provide an apparatus for quickly and efficiently fabricating metal joists without employing crane equipment and the like and without requiring individually set up studs and blocks to hold the joist members in position during the welding operation.

Another object of the invention is to provide an as sembly fixture which can be adjusted to automatically provide a proper camber for any length of joist and to position all strut and bracing members prior to welding so as to eliminate the necessity of measuring during fabrication.

A further object of the invention is to provide a device for holding bar, and long span joist members for welding so that such members, after setting in position, will simultaneouslybe clamped firmly together and subsequent to the welding operation, will simultaneously unclarnp and free 'the'finished joist.

A still further object of the invention is to provide an assembly fixture of the class described which has a clamping rack capable of rotating the entire joist at any stage of thewelding operation without unclamping or without rmorting to a crane, yet which will position the partially completed joist for the greatest working efliciency.

These and other objects and advantages of my invention will more fully appear from the following description, made in connection with the accompanying drawings, in which like characters refer to the same parts throughout thesevenal views and in which:

Figure 1 is aplan view of my assembly fixture, an intermediate section thereof havingbeen cut away to avoid unnecessary duplication;

FigureZis, a side view ofthe assembly fixture similarly'sectioned; l ,Figure V3is a vertical section of my fixture taken on the line 3e3 of Figure 1, the clamping jaws being shown 1 n operative. position and the dotted line position indicating the retracted or inoperative condition thereof;

' Figure 4 is an enlarged detail view of a clamping elementvand strut support taken on the line 4-4 of Figure 3, some of the members being vertically sectioned and others cut away to better show the hidden parts;

Figure 5 isan enlarged fragmentary view of one set .of clamping jaws operatively holding a pair of chord members in a bar joist construction;

Figure 6 is a similar view to that shown in Figure 5 with the clamping jaws holding the angle irons in the chord of a long span joist structure;

Figure 7 is a somewhat diagrammatic view of a portion of a long span joist with several of the members vin clamped relation prior to welding thereof;

Figure 8 is a somewhat diagrammatic view of a portion of a barv joist in clamped relation prior to welding;

Figure 9 is an enlarged detail view of the adjustable. pivot bearing the upper clamping arm; and

Figure 10 is an enlarged view of the clamping element showing details of construction.

With continued'reference to the drawings, my assembly fixture consists generally in a rack structure 10 which is mounted on trunnions .11 disposed endwise of an axis running longitudinally of the rack structure and preferably slightly below the top surface thereof. The rack structure 10' has clamping elements 12 secured along each longitudinal edge in spaced relation as shown in Figs, 1 and 2. The rack structure 10 is so mounted in trunnions 11 that drive mechanism 13 can be employed to tilt the entire rack during operation, as will be set forth later in this specification.

The rack structure comprises principally a pair of rails 14 and 15, which are shown in cross section, in Fig. 3. The rail members may be formed of a pair of channel irons 16 on the outside and .17 on the inside. Rails 14 and are positioned and secured adjustably at intervals to cross braces 18, as shown in Fig. 3. The cross braces 18 may likewise constitute a pair of inwardly turned channel members 19 and 20, as shown in Fig. 4. The fastening means by which the rails 14 and 15 are secured to the cross braces .18 as shown in detail in Fig. 4, may constitute an upper bearing plate 21, a lower bearing plate 22, a guide plate 23, and a cap screw 24, which passes through plates 21 and 23 and is threadably received in lower plate 22. Lateral positioning of each of the rails 14 and 15 is thus determined by the secured position of the plate and screw memberswith respect to channels 19 and 20. The channels 19 and may be braced at their outer ends by angle irons 25, as shown in Fig. 3. Intermediate the ends of braces 18 is secured a tubular shaft 26, as shown in Fig. 3. The tubular shaft 26 is preferably welded at the midpoint of each of the braces 18 which, in turn, are spaced conveniently along the tubular shaft. Additional bracing such as the diagonal members 27 may be employed to reinforce the horizontal portion of the rack structure, and depending struts 28 may be secured as by welding to both the tubular shaft 26 as well as the horizontal frame portion of rack structure 10, defined by a plurality of the-cross braces 18. The upper ends of the depending struts 28 may be further reinforced by horizontal angle irons 29 which are also welded to tubular shaft 26, and by bracing angle irons30 secured to the ends of a plurality of the strut members 28, as shown in Figs. 2 and 3. j

The complete rack structure 10 provides a flat table which can be of any suitable length and composed of a plurality of frame sections as appears in Figs. 1 and 2. The rail members 14 and 15 are disposed longitudinally 'of the rack and preferably toward the outer ends of the cross braces 18 so that they are generally in spaced, parallel'relation and disposed to opposite sides of tubular shaft 26.

Trunnions 11' are constructed of suitable framing members 31 and have bearings 32 secured at an upper position thereon as by bolt fasteners 33 as shown in Figs. 1 and 2. The ends of tubular shaft 26 are secured to stub shafts 34 which, in turn, are journaled in bearings 32 and extend at least at one of the ends through a bearing 32 for mounting a pinion sprocket 35 thereon. Drive mechanism 13 comprises a motor 36 which is coupled through shafts 37 to a gear box 38, as shown in Figs. 1 and 2. Shaft 39 extends outwardly from gear box 38 and is provided with asprocket 40 which is aligned with the pinion 35 and drivably connected there- "with through chain 41. Control mechanism (not shown) is employed to start and stop the motor and to reverse the direction of drive so that the entire rack structure 10 can be oscillated to one side or the other in tilted position, or may be even rotated upside down, if desired. 1

Clamping elements 12 form an important part of my invention and these clamping elements are set forth in detail in Figs. 3 to 6, inclusive. It is preferred that the same number of clamps be disposed in spaced relation along rail 15 as are disposed along rail 16. The number of clamps employed and the spacing selected is, however, subject to the convenience of the operator. It is desirable to have a suflicient number of clamps for rigid clamping of the joist members while, at the same time, positioning them properly so as not to interfere with the strut or brace members of the joist when they are welded together and to the chord. Each clamping element has identical parts and, hence, only one of such elements will be described in detail. The powering connection may be to a common source of energy such as a hydraulic pressure line, which is not shown since the use thereof is commonly known in the prior art. The clamping element 1'2 is shown in opposed relation with another clamping element 12 in Fig. 3, and the direction of parts extending convergently toward those of an opposed clamping element will be treated as inward, while those directed divergently' will be spoken of as extending outwardly.

Clamping element 12 has an upstanding mount which is preferably in the form of a plate 42 which may be mounted at right angles to a rail 14 or 15 and is secured to a pair of angle irons 43 which, in turn, form a base 44 which overlies a trackway formed by the spaced channels 16 and 17. A guide plate 45 is positioned beneath the iron angle base 44 and is adapted to slide snugly in the pathway defined by the channels. A clamping plate 46 underlies the "guide plate 45 and also lies in contact with the upper inside surface 47, as shown in Fig; 3.

A bolt 49 passes through the base 44 at each side of plate 42 and is threadably received by the clamping plate 46, as shown. When the bolts 49 are drawn up tightly, the clamping plate 46 will securely position the clamping element 12 in its proper position longitudinally of the rack structure 10. The angle irons 43 extend inwardly of the plate 42 and are adapted to receive therebetween a chord supporting member 50, the member 50 being slidable inwardly and outwardly to vary the spaced relation between its inner edge 51 and the inwardly facing abutment edge 52 of plate 42. Adjustment may be made through nut and bolt members 53 which are adapted to be received in a horizontal slot 54 in the flange members 43, as shown in Figs. 3, 4 and 5. Handle 55 is secured to bolt fastener 53 so as to firmly clamp the chord support 50 in proper spacing with abutment edge 52.

Another adjustable plate 56 is positioned near the upper end of chord support 50 and comprises an edgewise horizontal bar having a guide slot 57 disposed medially thereof as shown in Fig. 5. The upper edge of plate 56 is cammed downwardly to form a rest 58, as shown in Fig. 5. Horizontal plate 56 rests on a rigid horizontal offset 59 which, in turn, is secured to the plate 50 and the upper straight edge of which provides a guiding surface for plate 56. Cap screw 60 may be tightened to secure the horizontal plate 56 in proper position relative to the plate 50 and to the abutment edge 52 as shown in Fig. 3. Use of the chord support and horizontal plate 56 will be described more fully under details of operation hereinafter given. It is to be pointed out that the upstanding plate 42 and its abutment edge 52 cooperatively forms with the chord support 50 and horizontal plates 56, when used, a general chord-positioning means in the setting up and holding of the joist parts prior to and during welding.

A pair of clamp arms or jaws, 61 in upper position and 62 in lower position, provide the force for clamping and holding the chord member in firm position during the welding operation. The clamp arm or jaw 61 is reversely in turn, is arcuately adjustable on the fixed pin 65a for moving the jaw 61 inwardly and outwardly withrespect to its position on mount 42, as shown in Figs. 3, 4 and 6. The pivot member alone is shown in Fig. 9. The opposed end portion 66 is pivotally mounted at 67 to a clevis 68 which, in turn, bears a connecting rod 69. The connecting rod, in turn, bears another clevis 70 which is pivotally secured at 71 to an equalizer bar 72.

Lower clamp arm or jaw 62 is preferably constructed with an upstanding and an inwardly formed end 73, as shown in Figs. 3, 5 and 6, end 73 having a slightly angulated outwardly facing abutment edge 74 for gripping rods or bars as will be described. The lower jaw 62 has an outwardly bent portion 75 which is pivotally secured at 76 to a clevis 77. A depending extension of arm or jaw 62 provides a pivotal connection at 78 with the base member 43, as shown in Figs. 4 and 6. A connecting rod 79 is fastened to the clevis 77 and extends outwardly to connect with anotherclevis 80 which, in turn, is pivotally connected at 81 to a lower position on the equalizer bar 72. Lower jaw 62 is limited in its inward movement by stop pin 62a. All of the clevis members can be threadably adjusted to vary the effective length of the connecting rods 69 and 79.

Intermediate the upper and lower ends of equalizer bar 72 is pivotally mounted a clevis 82 which is secured, in turn, to a piston rod 83, as shown in Fig. 3. Piston rod 83 terminates inwardly in a piston 84 which is slidably mounted within hydraulic cylinder 85. A cross bar 86 extends to the side of the piston rod 83 and is secured thereto. A tension spring 87 is connected between cross bar 86 and is anchored at 86a inwardly of the piston 85, as shown in Fig. 3. Hydraulic inlet port 88 is connected to a source of fluid (not shown) pressure, and a breather opening or vent 89 communicates with cylinder 85 rearwardly of piston 84.

Additional independent supports 90 may be provided along tracks 14 and 15 for supporting strut members in the welding operation. The strut supports 90 have an ofiset and notched upper end 91 and have an outwardly bent lower end 92 which is adapted to be clamped by set screws 93 to a shelf angle iron 94, which, in turn, is secured inwardly of the track 14 and 15.

In the use and operation of my assembly fixture, the rails 14 and 15 are adjusted to the desired spacing, and one of the rails 14 or 15 may be bowed in a parabolic curve from one end to the other of the rack structure. The pathway of the parabolic curvature can be measured with respect to straight edge member 25 and. is calculated according to the formula where c is the camber in inches and D is the distance from the center of the joist in feet. Thus, one track or rail can be fastened permanently in place, following this curve. The other track can then be positioned parallel to and at a preselected distance from the fixed track. When the center of the joist is made to coincide with the center of the track or rail, the resulting joist will have the correct camber, regardless of its length.

Having positioned the track or rail for a particular design of joist, the individual clamping elements 12 are adjusted in proper spaced relation along the rails 14 and 15. Strut supports 90 are likewise placed in their proper positions.

Presuming a bar joist is to be constructed, a dual chord member comprising a lower bar or rod 95 .is placed upon the beveled or cammed upper edge 58 of horizontal plate 56 with the support 50 adjustably retracted inwardly, as shown in Fig. 5. A zig-zag bracing element 96 is then placed upon rod 95 and upon such opposed chord member, as desired. The relationship of the bracing rod 96 with respect to the lower chord'member 95 is set forth in Fig. 5. An upper rod or bar 97 is then placed against abutment edge 52 and on top of the zig-zag rod 96. The procedure is repeated for each of the clamping elements 12 along both of the rails or tracks 14 and 15. During this setting up procedure the clamp arms or jaws are retracted to the dotted line position indicated in Fig. 3. Simultaneous hydraulic force is then supplied to all of the hydraulic inlets 88 which will simultaneously move the clamp arms or jaws 61 and 62 from their dotted line position to the full line position of Figs. 3 and 5. .The equalizer bar 72 will exert even pressure upon both of the arms and cause them to bear simultaneously upon the chord members and 97. The angulated abutment surface 74 of the lower arm 62 will prevent the rod 95 from springing upwardly. Likewise, the downward and outward pressure from the notched nose 63 in upper arm 61 will engage the upper rod member 97 of the dual chord and press it downwardly with relation to the lower rod 95 and zig-zag rod 96, as well as against the abutment edge 52. The joist is then ready for welding, and all of the joints may be worked upon at the most convenient location and angulation of the rack structure 10. Whenever it is desired to invert or tilt the rack or joist to another or more convenient angle, the motor 36 may be energized in the direction desired and stop when the proper position has been obtained.

When the entire bar joist has been completed, the hydraulic pressure may be relieved on all of the individual clamp elements 12 and tension springs 87 will cause the equalizer bar 72 -to move inwardly and thereby retract both of the jaws 61 and 62 simultaneously. The selection of pivot points is such that the greatest mechanical advantage is obtained at the clamping or locking position. During retraction, however, the mechanical advantage is lowered in favor of rapid movement. It will be noted that the particular curvature and configuration of each of the jaws is such as to accommodate a wide variety of chord members and yet will move completely out of the way to permit instantaneous removal of the completed joist when the hydraulic pressure is relieved upon the individual clamps.

Referring now to Fig. 6, when it is desired to make a long span joist, the same spacing and anchoring procedure is followed with respect to the individual clamps 12. The chord support, however, is now utilized to position the lower angle iron member 98 of the dual chord against the abutment edge 52, as well as to support it. The cammed horizontal plate 56 is retracted and not utilized where a long span angle iron joist is constructed. Strut member 100 is first laid in position following which lower angle iron 98 is placed thereover. Diagonal 99 is then placed over angle iron 98 and then strut 101 and angle iron 102 are laid in position. Before the strut 101 is positioned, however, the upper chord angle iron 102 is positioned against the abutment 52, as shown in Figs. 6 and 7. Fluid force is now applied to cylinders 85 of all the clamping elements 12 and jaws 61 and 62 will press convergently and outwardly to hold the joist members firmly against one another and against the abutment edge 52 of each of the clamping elements. It will be noted that the angulated abutment surface 74 of lower jaw 62 and the notch 64 of the upper jaw 61 are not utilized in the case of long span joists, but the ends of the jaws merely engage and press against the fillets of the respective dual angle iron chord members. In either case, however, the joist members are held firmly and simultaneously in clamp engagement without the necessity of individually measuring the positions and locations of the members. Furthermore, the proper camber can be automatically obtained by adjusting one of the rail or track elements with respect to a fixed, opposed rail or track which has been mathematically curved to give the correct camber for a wide variety of types and sizes of joists.

It will, of course, be understood that various changes may be made in the form, details, arrangement and prosecured on the cantilever outer ends of said frame elements, means rotatably supporting said rack on an axis extending longitudinally thereof and adjacent said transverse frame elements, a plurality of spaced clamping elements mounted on each of said tracks for adjustment therealong, each of said clamping elements having upstanding and rigid chord-positioning means spaced above the track for holding a doublechord member of a joist, and a pair of jaws swingable convergently, one of said jaws being swingable from one side of the chord-positioning means to hold one portion of said double chord in clamped engagement with the chord-positioning means,

"and the other swingable from the other side of the chordpositioning means for holding another portion of 'the double chord in clamped engagement with respect to the first mentioned chord portion, and drive means for ad justably turning said rack and joist mounted thereon, whereby to facilitate ready and easy access to the joist chords from a multiplicity of angles to permit complete welding of the chords while on the fixture.

2. An assembly fixture for bar and long span joists of the type including chords and bracing elements, comprising an elongated rack having a pair of spaced tracks secured thereon, means rotatably supporting said rack on an axis extending longitudinally between the tracks and therebelow, a plurality of upwardly facing chord supports and inwardly facing chord-positioning abutments adjacent each track and spaced thereabove, mounting means carrying said supports and abutments on the tracks for individual adjustment therealong, and clamping means on the mounting means and adjustable therewith along the track for securing the joist chords and bracing elements in predetermined relation with each other and with said chord supports and abutments, and drive means for adjustably turning said rack and joist mounted thereon about said axis, whereby to permit Welding of the joist chords from a multiplicity of angles to facilitate completion of the joist fabrication while on the fixture.

' 3. An assembly fixture for bar and long span joists, comprising a supporting structure, a pair of horizontally juxtaposed elongate tracks on the supporting structure, a plurality of joist chord supports adjacent each of the tracks, a plurality of chord-positioning abutments adjacent each track and above the chord supports and said abutments facing inwardly toward each other, mounting means carrying said supports and abutments on the tracks for adjustment therealong, the abutments defining an open and unobstructed area therebetween and above the supports, a plurality of movable and convergent upper and lower chord-clamping jaws on the mounting means and having outwardly facing chord-engaging surfaces inwardly of the abutments for clamping the chords outwardly thereagainst, each of said upper jaws being swingable upwardly and outwardly of the corresponding abutment to permit the joist, when assembled and welded to be lifted off the fixture.

References Cited in the file of this patent UNITED STATES PATENTS 842,007 Parker Ian. 22, 1907 1,303,596 Rifilard May 13, 1919 1,481,906 Jackson L. Jan. 29, 1924 4,615,335 Macomber Jan. 25, 192.7 1,822,270 Bunch Sept. 8, 1931 2,021,893 Mitchell Nov. 26, 1935 2,047,190 Blickman July 14, 1936 2,269,754 Bernhardt et al. I an. 13, 1942 2,384,148 Yeager Sept. 4, 1945 2,453,046 Sutton Nov. 2, 1948 2,537,350 -Hunt Jan. 9, 1951 2,546,458 Launder Nov. 27, 1951

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