US3288977A

US3288977A - Apparatus for making girders

Info

Publication number: US3288977A
Application number: US411077A
Authority: US
Inventors: Keller Julius Georg Stefan
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-11-18
Filing date: 1964-11-13
Publication date: 1966-11-29
Anticipated expiration: 1983-11-29
Also published as: NL6413043A; DE1452714A1; NL146730B; CH431438A; GB1049600A; AT261368B

Description

Nov. 29, 1966 J-G.S.KELLER APPARATUS FOR MAKING GIRDERS 4 Sheets-Sheet 1 Filed Nov. 13, 1964 En I: 5 5 QN\ u& fim m N Irl' .IIF u g V DJ E l, 8 & a Q 3 U 7 my k T K 14 Q M q at 8 x a E 2 & Q, {Li 9 Q Q NQ mm EmFm Ii E mm mm w M N R 0 1966 J. G. s. KELLER APPARATUS FOR MAKING GIRDFJRS 4 Sheets-Sheet 2 Filed Nov. L3, 1964 /nvem0r. auuus Ra STEFAN KELLER BY z ATTORNEYS 1966 J. G. s. KELLER APPARATUS FOR MAKING GIRDERS 4 Sheets-Sheet 5 Filed Nov. 13, 1964 lnvemor: JULIUS EORG STEFPN Ell-ER BY A 7/ ATTORNEY Nov. 29, 1966 J. G. s. KELLER APPARATUS FOR MAKING GIRDERS 4 Sheets-Sheet 4 Filed Nov. 13, 1964 Q. Q Q my G 3 Q E 8 Iv E m? Q 3W $9. t 5

m cm 3 mm MN wm (lrllll.

mw mm mww Inventor: JULIUS Gsom srEFAN KELLER BY 7 ATTO RN E75 United States Patent 16 Claims. ((21. 219-49 The present invention relates to an apparatus for making girders, especially lattice girders of the type shown in my co-pending application Serial No. 275,670, filed April 25, 1963.

Such a girder is shown in FIGURES 2 and 3 of the accompanying drawings and comprises an upper chord made of two laterally spaced-apart angle members 1]" and 1' a lower chord made up of two further laterally spacedapart angle members 2 2'1, and the zigzag latticing of which FIGURE 3 shows the consecutive legs or reaches 3, 3, 4. The latticing is connected to the chords at the illustrated points of intersection, by welding.

The latticing is constituted by an iron strip or band. At the points at which the strip is secured to the chords, it is unprofiled and in an on-edge position and extends throughout its entire width, while throughout the diagonal reaches, i.e., throughout the lengths intermediate the juncture points the strip is profiled, i.e., stamped, bent or pressed, to have a generally channel-shaped configuration, as illustrated in cross section, at 5 in FIGURE 3. The purpose of this configuration is to impart buckling strength, it being apparent that the channel shape can be any V-shaped, U-shaped, C-shaped, semicircular or similar configuration which will provide the necessary rigidity to the girder.

By virtue of such an arrangement, a large moment of inertia or moment of resistance with respect to the Y-aXis is obtained, without it being necessary to provide wide, flanged or massive chords requiring a large amount of material. Instead, all that is necessary is a simple, sufficiently wide steel or iron strip which, at the points of intersection with the chords, is welded to the chords, the strip keeping the individual chord members spaced sufficiently far apart and to the right and left of the Y-axis, as shown in FIGURE 2. At the same time, the latticing is constituted by a strip which itself has an easily obtained configuration but which, thanks to its channel-shaped cross-sectional configuration in the reaches between the points of intersection, imparts substantial buckling strength to the girder as a whole.

It is the primary object of the present invention to provide an apparatus by which a girder of the above type can be produced fully automatically.

According to the present invention, such a girder is made by intermittently moving a plurality of strips in the same direction in a step-by-step manner, there being pauses between the movement. At least one of the strips has imparted to it a cross-sectional configuration which renders the strip resistant to buckling, this strip also being given the zigzag configuration, thereby to form the latticing. The remainder of the strips, that is to say, at least two strips which constitute the upper and lower chords, respectively, or, for example, two pairs of strips of which each constitutes a chord member, with two chord members together constituting one of the two chords, are then given the cross-sectional configuration of the upper and lower chords. The zig-zag latticing is placed against "ice the chords, and resistance Welded to the chords during the pauses.

The apparatus according to the present invention incorporates means forming a production line having at least three parallel paths for the upper and lower chords and the latticing, there being drum means arranged at the start of the production line for supplying at least three strips which are to constitute the upper and lower chords and the latticing, respectively, although if the girder being made is as shown in the mentioned application Serial No. 275,670, there will be five drums. Also provided are pulling means arranged at the delivery end of the production line 'for pulling the strips along their respective paths through the production line in a step-by-step manner, there being pauses between the steps. Means are arranged along the paths traversed by the strips which are to constitute the upper and lower 7 chords for continuously imparting thereto the shape of the upper and lower chords while the strips move along their respective paths, and means are arranged along the path traversed by the strip which is to constitute the latticing for imparting thereto, during the pauses, a channel-shaped transverse cross section as well as a zig-zag configuration, and for placing the zig-zag latticing of such cross section against the chords. Also, there are means for resistance welding the latticing to the chords in synchronism with the movement of the strips under the influence of the pulling means, these welding means preferably being operative during the pauses.

In accordance with the present invention, the means for imparting the channel-shaped transverse cross section and the zig-zag configuration to the latticing strip comprise a first device which imparts the channel-shaped transverse cross section to the latticing strip throughout lengths equal to the reaches of the zigzag, the strip being left flat at those regions where the same is to be secured to the chords of the girder. A second device is provided for imparting the zig-zag configuration to this strip, this second device being arranged at a point subsequent to the first device, considered in the direction of the production line, and comprises a stationary clamping unit and a movable clamping unit, the latter being movable toward and away from the stationary clamping unit in a direction coextensive with the direction of the production line. Means are provided for causing the clamping units to hold the latticing strip during the pauses and, after each two steps of the pulling means, for moving the movable clamping unit toward the stationary clamping unit, thereby to buckle the latticing strip into its zig-zag configuration; in the course of this, the latticing strip bends at three successive flat regions, which regions are brought into engagement with the strips which are to constitute the chords substantially along lines which represent the centers of gravity of the respective chords.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURES la and 1b are a diagrammatic illustration of the production line for producing the girders in accordance with the present invention. FIGURE 1a is the first half of the production line and FIGURE 1b is the second half, and the two figures will hereinafter be referred to, collectively, as FIGURE 1. For the sake of simplicity, FIGURE 1 shows only one longitudinal half of the production line, e.g., the half for producing the left half of the girder as viewed in FIGURE 2, there being suitable complementary components for producing the other half of the girder located on the other longitudinal side of the production line.

FIGURE 2, already referred to above, is a sectional view, on an enlarged scale, of a girder of the type which is produced in accordance with the present invention.

FIGURE 3 is a longitudinal view of a section of the girder of FIGURE 2.

FIGURE 4 is a sectional view showing the welding means.

FIGURES 5a, 5b and 50 show rollers by means of which one of the upper chord members is profiled, in three stages, to assume a partly finished configuration.

FIGURES 5d, 5e and 5f show rollers by means of which the chord member treated by the rollers of FIG- URES 5a, 5b and 5c is profiled further to assume its final configuration.

FIGURE 6 shows a junction of the latticing with one of the chords, on an enlarged scale.

FIGURE 7 is a schematic elevational view showing the device by means of which the strip which is to constitute the latticing is given its channel-shaped transverse cross section, hereinafter referred to as its profiled configuration. FIGURE 7 also shows punching means which perforate the strip at given points as well as rollers by means of which the strip is descaled and stretched prior to being fed through the punching means.

FIGURE 8 is a schematic elevational view showing the device by means of which the already profiled latticing strip is given its zig-zag configuration.

Referring now to FIGURE 1 of the drawing, the same shows a production line where the strips which will form the chord members If and 2 are unwound from supply drums R and R respectively. The material is here still in the form of a fiat band, and moves through

respective processing stations

5, 6, where the strips pass through

descaling rollers

55, 56, 57; 55a, 56a, 57a, respectively. The strips are then passed through the

roller pairs

7, 8, 9; 7a, 8a, 9a, where they are preliminarily profiled, to receive their final configuration at a later stage of the processing, by means of

roller pairs

10, 11, 12; 10a; 11a; 12a. The chord members 1') and 2') are similarly treated, so that a detailed illustration thereof is unnecessary.

FIGURES 5a through 5] show the various stages which the originally flat strips undergo, consecutively assuming the configurations 1a through 1 to assume their final shape. FIGURES 5a, 5b and 5c show the configurations assumed by the strips as the result of the treatment of the

roller pairs

7, 8, 9, while FIGURES 5d, 5e and 5 show the shape which is imparted to the strips by the

roller pairs

10, 11 and 12. In the production line shown in FIGURE 1, the

roller pairs

7, 8 and 9 act on the strip before the same is connected to the latticing, while the roller pairs 10, 11 and 12 act on the strips after the same have been welded to the latticing, as will be described below.

As shown in FIGURE 1, the strips which ultimately constitute the chord members are drawn by a pulling device 53, which, as will be explained below, moves the strips in a step-by-step manner, there being pauses between the movement. It will be noted that this is the only point at which a pulling force is exerted on the chord strips, this force being effective to unwind the strips from the drums and to pull them through the various rollers, the rollers themselves not being driven at all. That is to say, the roller pairs are freely rotatable in that they are not connected to any drive means.

The device 53 pulls the material through the production line in the direction of the arrow P. Arranged ahead of the

roller pairs

10, 11, 12, considered in the direction of the production line, are two welding devices incorporating

resistance welding electrodes

14, 14a, of which the former serves to weld the upper chord member and the other serves to weld the lower chord member to the latticing. The welding devices are shown in FIG- URE 4; this figure shows the two welding devices 14, 14',

4 which weld the two upper chord members to the latticing. It will be noted that at this point the chord members still have the configuration 10, 1'0, depicted in FIGURE 50.

FIGURE 6 shows the configuration of the latticing where the same is welded to the chord members, the latter being provided with

weld buckles

15, 16, 17, which are applied by means of the units shown at 51, 51a in FIG- URE 1. The

units

51, 51a press the chord members, at a point ahead of the welding stations, 14, 14a, where the chord members are to contact the edges of the latticing.

The latticing itself is taken off from a roller R where it is in strip form, as indicated at 18. As shown in FIG- URE 8, the strip then passes through a series of rollers 19 through 24, where the strip 18 is descaled and stretched. This is accomplished by repeatedly bending the strip 18 in opposite directions, while the only pulling force on the strip is that exerted from the delivery end of the production line. In this way, any bent or corrugated portions of the strip 18 will be corrected. It will be noted that the rollers 19 through 24 themselves are not driven, the rollers thus forming a stretching apparatus of the type disclosed and claimed in my co-pending application Serial No. 267,393, filed March 21, 1963.

For the sake of clarity, the rollers 19 through 24, as well as the roller 25 depicted in FIGURE 8, are not shown in FIGURE 1.

The strip 18, which ultimately is to constitute the latticing for the girder, is then subjected to two

punches

26 and 27 which are spaced from each other a distance equal to the diagonal length of one leg of the zig-zag latticing. The strip 18 then passes on ma device incorporating

presser jaws

28 and 29, shown in greater detail in FIGURE 8, where the strip 18 is given its U-shaped, V-shaped, C-shaped or other channel-shaped cross sectional configuration throughout a length which corresponds to two consecutive diagonal reaches. The

jaws

28 and 29 may be moved toward and away from each other by means of parallelogram-type linkages 30 to 33, the movement of the linkage pairs of the upper and lower jaws being effected by synchronously operating driving means 34, 35. The linkage pivots 30c, 31c, 32c, 330, are fixed, while the

pivots

30b, 31b, 32b, 33b, are mounted for movement in horizontal guides (not shown) while the

pivots

30a, 31a, 32a, 33a, are guided for movement in vertical guides (not shown). The jaw 29 is provided with a raised profile die 29a, while the other jaw 28 is provided with a correspondingly configured female die member. As shown in FIGURE 8, the

jaws

28 and 29 are not provided with raised or depressed portions in the regions of their

centers

28b, 29b, or in the regions of their ends, so that the strip 18 will not be deformed at the points 18a, whereat it was already perforated by the

punches

26 and 27. These are the points where the latticing is to receive its bends 37, 44, shown in FIGURE 7, and where it will be welded to the chord strips.

Referring once again to FIGURE 1, it will be seen that after the strip 18, which is ultimately to constitute the zig-zag latticing, has left the

jaws

28, 29, it is brought to a device which incorporates bending

devices

49 and 50, shown in greater detail in FIGURE 7. Here, the strip 18 is given its zig-zag configuration. This is brought about as follows: The lower bend 37 of the descending reach 3 of the section of the latticing which has been last produced, is clamped in place by means of a stationary clamping unit 38 having a clamping member 49, which is capable of clamping and releasing this strip. At the same time, a second clamping unit 42 having a clamping member 50 holds the other end of the length 39, 40 of the latticing. This clamping unit 42 is a movable one in that it is carried by a carriage 43 which can be moved toward and away from the stationary clamping unit 38, in the direction of the production line. The carriage is moved by means of a drive 41 and is moved toward the stationary clamping unit 38 such a distance that the center 44 of the reach 39, 40, is made to buckle upwardly so that the point 44 will rise a distance corresponding to the distance between the upper and lower chords of the lattice girder to be produced.

Shown at the left of FIGURE 7 are two stretches 3, 3', of the latticing after the same have been bent into the desired configuration.

The carriage 43 is provided with a bell crank lever having a short arm 45 and a long arm 47, the bell crank lever being pivotally mounted on the carriage 43 at 46. The free end of the longer arm 47 has an abutment 48, while the free end of the short arm 45 is connected to the driving means 41. Consequently, as the carriage 43'begins to move to the left under the influence of the driving means 41, the bell crank lever will be pivoted in clockwise direction so that the abutment 48 engages the underside of reach 40 of strip 18 and starts to press it upwardly. The bending process is then continued solely under the influence of the movement of the carriage 43 which carries the clamping unit 42. It will thus be seen that the bending is completed as a result of the relative movement-between the two clamping devices.

After the bending step has been completed, the clamping devices release the strip 18, and the carriage 43 is returned to its starting position. The

stationary clamping unit

38, 49, will swing out of the plane in which the bending took place, so that when the band 18 is pulled forward, it will be able to move past the clamping

unit

38, 49.

For the sake of clarity, FIGURE 1 shows the clamping units symbolically only, by the wedge-shaped

clamping members

49 and 50.

The holes punched into the strip 18 by the

punches

26, 27, can serve to receive the projecting lugs or mandrels carried by the clamping

units

38 and 42, so as to facilitate the holding effect of these units.

The

components

26, 27, 34, 35, 38, 41 and 42 will, in practice, he hydraulically actuated pistons which can be remote-controlled by electric valves.

It will be seen from the above that, according to the present invention, there is provided an apparatus and method for fully automatically producing endless lattice carriers. The automatic manufacture makes it possible to use resistance welding in lieu of the arc welding which is generally used in the manufacture of lattice girders. Moreover, the starting material for producing the girder is band-shaped, that is to say all that is needed for producing the lattice girder of the type shown in FIGURES 2 and 3 will be five drums which deliver the strip-shaped material. This material is then subjected to the various rollers and other units so as to subject it to the desired treatment and to give it the desired configuration. Should any one drum become exhausted, it is very simple to substitute a fresh drum whose band-shaped material can then readily be joined to the strip which has just left the spent drum.

It would also be seen that the present invention overcomes the problems inherent in any resistance welding process in which the parts to be welded to each other are joined at their'points of contact so that the material will flow into each other which, in turn, has as its result the fact that the relative position of the parts will be different after the welding than before the welding. This means that, but for the present invention, successive welding steps along the length of the chords would result in bending and pre-stressing of the chords themselves and, consequently, of the entire lattice girder. This inherent drawback, however, is avoided by the present invention in which, as described above, the manufacture occurs in a step-wise manner. Furthermore, the present invention readily allows the electrode pressure at each welding site to be held constant with sufliciently great accuracy.

It will also be seen from the above that there is provided a fully automatic method of producing endless lattice girders in such a manner that a plurality of endless strips made of a material suitable for the manufacture of the lattice girder, particularly iron or steel bands, are successively deformed during manufacturing steps which are interrupted by pauses. At least one of the bands is given the profile which will render the girder resistant to buckling, this strip being given the configuration of the continuous zig-zag lattice, while the other strips are rolled to assume the configuration of the upper and lower chord members, the process being further such that, in synchronism with the formation of the zigzag latticing while the material is at rest, the chords are welded to the zig-zag latticing by the electric resistance welding steps, thereby to form an endless lattice carrier.

It will also be seen that the apparatus for carrying out the above method comprises means forming a production line having parallel work paths for the upper and lower chords as well as for the zig-zag latticing. At the head of the path, there are drums for the individual strips which deliver the strips that constitute the starting material from which the chord members and the latticing are made. At the other or delivery end of the production line, there is a device which advances the aligned strips, step by step, by a distance equal to at least that between two successive bends of the zigzag, measured along one chord in the direction of the length of the finished lattice girder. The chord members are continuously profiled during the time while the strips which are to form the chord members are advanced. The strip which is to constitute the latticing, however, is profiled during the time intervals while the strips are at rest, this strip also beingbent to assume its zig-zag configuration while the other strips are at rest. Furthermore, there are electric welding devices which, in synchronism with the rate at which the material is advanced and preferably during the intervals while the girder is at rest, welds the latticing to the chords at those points at which the latticing is bent.

While, under certain circumstances, the chord members may be completely profiled either before or after they have been welded to the latticing, it is often of particular advantage that the upper and lower chords are profiled partly before and partly after they have been welded to the latticing, so that even in the case of very stiff chord members, the pressure at which the welding takes place can be adjusted very precisely, so as to make it possible to obtain a very good weld.

In any case, the chord members will be profiled by means of roller pairs which themselves are not powerdriven, so that the profiling takes place solely under the influence of the pulling force exerted at the delivery end of the production line.

The type of girder which may be produced by the present invention, as described above, particularly in conjunction with FIGURES 2 and 3, has a relatively large moment of resistance or section modulus, especially with respect to the Y-axis, without it being necessary to provide upper and lower chord members having broad lateral flanges. This, in turn, reduces the overall quantity of metal which is required to produce a lattice girder of given strength. This is due to the fact that the latticing is constituted by strip material which has a channelshaped cross section only at the points between the bends, while at the bend itself, which constitutes the junctions of the latticing with the chords, the latticing is flat. Consequently, the width of the latticing itself will serve to space the individual chord members apart. Furthermore, thanks to the fact that the buckling resistance of the latticing itself is at a minimum at the bends, the latticing can be bent without requiring special bending tools. Instead, the latticing can be given its desired zig-zag configuration by the upsetting or buckling process described above, which, in turn, greatly simplifies and reduces the costs of the production line as a whole.

Experience has shown that the present invention inherently possesses a number of surprising advantages, as will be described herewith.

For one thing, the production line makes use of steel strips which are readily available from commercial sources. The strip itself is wound on drums, where long lengths of the strip may be stored. The drums themselves can easily be delivered to the production line. If any one drum is spent, a new strip can readily be welded to the last end of the old strip, and this can readily be done, without providing any special means, if there is a loop between the supply drum and the point at which the strip is fed into the machine, so that a new strip may be welded to the old one during the time interval that the loop is taken up. This allows a new loop to be added without interrupting the manufacturing process.

Yet another advantage of the present invention is that, irrespective of whether the chord strips are profiled wholly or partly before or after being welded to the latticing, it will always be possible to weld the chord strips at such a point along the production line that the actual places at which they contact the latticing will still be flat and therefore relatively yielding. In any event, the point at which the chord strips are welded to the latticing will not have to be as stiff as the finished chord. This means that the pressure between the chord strips and the latticing can be kept very small so that, for all practical purposes, it does not enter into consideration insofar as the pressure of the welding rollers is concerned. In any event, pressure between the members will not exceed the welding pressure.

Insofar as the gripping means 53 are concerned, the same are constituted by gripper tongues or jaws which are mounted for reciprocatory movement to and fro in the direction of the production line, throughout a distance, or so-called stroke, which is equal to the spacing between consecutive points along a chord member at which the same is joined to the latticing. These grippers are operative to grip the already completed girder during the forward stroke, that is to say, movement in the direction of the arrow P shown in FIGURE 1, and to release the girder during the back stroke. Thus, as the grippers move back, they slide freely along the girder, the arrangement being such that they still provide a support for the girder even during their back stroke.

In practice, the gripper means will have tongues or jaws which will float, in the sense that they are so mounted as to have sufficient free vertical movement to enable the grippers to clear and allow for tolerances of the girder. In this way, they can adapt themselves to small variations of height in the girder and will therefore not tend to damage the same.

As for the welding devices shown in FIGURE 4, the same are provided with electrodes which are positioned against the outside of two similar and opposite chord members, i.e., the pair of chord members which together make up either the upper chord or the lower chord. The electrodes are energized during the pauses between the intermittent movement, thereby to weld the two chord members to the latticing; more particularly, the edges of the latticing will be welded to the inner surfaces of the chord members.

As explained above, the chords will preferably be provided with welding buckles, the purpose of which is to localize the heat of the welding. The reason for this is that the chords are more massive and have a cooling effect upon the welding operation which, in turn, raises the possibility that the latticing will be overheated. This is particularly so inasmuch as the cooling effect of a water cooling system with which the electrodes are usually provided will be primarily effective only on the outside of the chord members.

As explained above, the means for imparting the zigzag configuration to the latticing are subsequent to the means which profile this strip. The bending means comprise, as described above, a stationary and a movable clamping unit, the latter being movable in the direction of the length of the strip. The arrangement is such that the clamping units open and close in synchronism with the intermittent movement, with the movable clamping unit approaching the stationary one, after every two advancing steps, such that the strip which is to constitute the lat ticing will be bent at three consecutive and unprofiled places, with the finished bending points between the reaches of the latticing, coming to lie on the chords. In practice, the arrangement is such that the latticing will engage the chords along, or substantially along, straight lines, which represent the centers of gravity of the respective chords.

The above-mentioned bell crank lever in the movable clamping unit is intended to facilitate the bending step, particularly in its initial phase.

The purpose of the

punches

26 and 27 is to weaken the lattice strip at those points where it is to be bent, thereby to facilitate the bending process. Moreover, the fact that the lattice strip is punched at intervals which correspond to the length of a reach of the zig-zag latticing makes it possible to provide the

clamping elements

49, 50, themselves with projecting lugs or other means which engage and pass through the punched out holes, so as more reliably to hold and position the strip.

The purpose of the rollers 19 to 24 is to make sure that the girder manufacturing apparatus itself will be fed a properly descaled and stretched lattice strip. It has been found best to arrange these rollers ahead of the point at which the lattice strip is punched.

If desired, the descaling and stretching rollers may include at least two pairs of adjustable rollers, of the type shown in the above-mentioned application Serial No. 267,393.

If desired, the strips may be passed through at least one roller having lateral edge flanges, in order to correct for any laterally bent or corrugated portions.

Insofar as the profiling means are concerned, the same will, from the above description, be seen to impart the desired cross-sectional configuration to the latticing, while the same is at rest. The profiling is applied throughout the entire stretch of the latticing undergoing treatment in the profiling means, except at those points which ultimately constitute the bends, at which regions the lattice stripping will retain its entire width.

The use of the parallelogram type of linkages facilitates the use of synchronously operating drive means. Furthermore, thanks to the fact that both of the die means on opposite sides of the lattice strip are moved away from the same during the time that the lattice strip is pulled through the unit, unnecessary wear on the dies and matrices carried by the profiling device is prevented.

According to another feature of the present invention, each individual weld of the lattice girder can be tested by a hydraulic testing arrangement, to make sure that the weld is capable of withstanding a given tension or compression. Here, the testing means may come into operation between the individual steps, and may actuate an alarm signal if any one weld has been found to be inferior.

The testing means may operate, for example, as follows:

During the rest intervals, a force F is applied to one of the juncture points, for example, one of the juncture points on the upper chord, while a force of F/ 2 is applied to each of the adjacent two juncture points of the lower chord. If one of the welds tears, the upper chord will be slightly deformed, for example, a distance of 1.2 millimeters, which, in turn, makes it possible for a feeler to sense this deformation thereby to actuate the alarm signal.

In practice, the testing means will comprise hydraulic cylinders and grippers which, as the above-mentioned gripper jaws or tongues of the device 53, will float so as to afford suificient clearance for the strips while the same are moved past the testing means.

According to a further feature of the present invention, the endless girder coming from the delivery end of the machine will be fed to cutting means so that convenient lengths can be cut from the completed girder.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. Apparatus for making endless lattice girders having spaced-apart upper and lower chords and Zig-zag latticing of channel-shaped transverse cross section joining the chords, said apparatus comprising, in combination:

(a) means forming a production line having at least three parallel paths for the upper and lower chords and the latticing;

(b) drum means arranged at the start of the production line for supplying at least three strips which are to constitute the upper and lower chords and the latticing;

(c) pulling means arranged at the delivery end of the production line for pulling said strips along their respective paths through the production line in a step-by-step manner, there being pauses between the steps;

(d) means arranged along the paths traversed by the strips which are to constitute the upper and lower chords for continuously imparting thereto the shape of the upper and lower chords while the strips move along their respective paths;

(e) means arranged along the path traversed by the strip which is to constitute the latticing for imparting thereto, during said pauses, a channel-shaped transverse cross section as Well as a zig-Zag configuration, and for placing the zigzag lattice of channel-shaped transverse cross section against the chords, said lastmentioned means comprising (i) a first device for imparting said channel-shaped transverse cross section to the latticing strip throughout lengths equal to the reaches of the zigzag, the strip being left flat at those regions where the same is to be secured to the chords of the girder, and

(ii) a second device for imparting the zig-zag configuration to the last-mentioned strip, said second device being arranged at a point subsequent to said first device, considered in the direction of the production line, and comprising a stationary clamping unit and a movable clamping unit, the latter being movable toward and away from said stationary clamping 'unit in a direction coextensive with the direction of the production line, there being means for causing said clamping units to hold the latticing strip during the pauses and, after each two steps of said pulling means, for moving the movable clamping unit toward the stationary clamping unit for buckling the latticing strip into its Zigzag configuration with the latticing strip bending at three successive fiat regions, which regions are brought into engagement with the strips which are to constitute the chords substantially along lines which represent the centers of gravity of the respective chords; and

(f) means for resistance welding said latticing to said chords in synchronism with the movement of the strips under the influence of said pulling means.

2. An apparatus as defined in claim 1 wherein said Welding means are operative during said pauses.

3. An apparatus as defined in claim 1 wherein said means (d) are arranged at a point ahead of said welding means, considered in the direction of the production line.

4. An apparatus as defined in claim 1 wherein said means ((1) are arranged at a point subsequent to said Welding means, considered in the direction of the production line.

5. An apparatus as defined in claim 1 wherein said means (d) include preliminary profiling means arranged ahead of said welding means, considered in the direction of the production line, and final profiling means arranged subsequent to said Welding means, considered in the direction of the production line.

6. An apparatus as defined in claim 1 wherein said means (d) comprise profiling rollers which are mounted for free rotation, thereby to rotate solely under the influence of the movement of said strips while the same are being pulled through the production line by said pulling means.

7. An apparatus as defined in claim 1 wherein said pulling means comprise gripping means for engaging the lattice girder at points thereof Whereat the latticing is connected to the chords, said gripping means being mounted for reciprocatory movement to and fro in the direction of the production line and being operative to grip the girder when the same is to be pulled through the production line, said gripping means being floatingly mounted to afford clearance when the gripping means have released said girder and are moved back against the direction in which the girder is pulled through the production line.

8. An apparatus as defined in claim 1 for producing a girder each of whose chords is constituted by two parallel chord members which are positioned on opposite sides of the latticing, wherein said means forming the production line provide five parallel paths of which two pertain to the chord members constituting the upper chord, two pertain to the chord members constituting the lower chord, and one pertains to the latticing.

9. Apparatus as defined in claim 8 wherein said welding means comprise at least two electrodes arranged opposite each other and engaging the outside of the two chord members which constitute a respective chord of the girder and which have the latticing arranged between them, said electrodes operating during said pauses for welding the latticing to the two chord members.

10. An apparatus as defined in claim 1 wherein said device (i) comprises two coacting presser jaws for imparting the profiled configuration to a length of the latticing strip equal to the distance covered by two successive reaches of the zig-zag.

11. An apparatus as defined in claim 10 wherein said device (i) further comprises parallelogram linkage means for moving each of said presser jaws toward and away from the latticing strip.

12. An apparatus as defined in claim 1 wherein said movable clamping unit comprises a carriage carrying a bell-crank lever, the latter having a free end which presses against the latticing strip when said carriage moves toward said stationary clamping device, thereby at least to initiate the buckling of the latticing strip.

13. An apparatus as defined in claim 1, further com prising means arranged ahead of said device (ii) for punching holes into the latticing strip at intervals equal in length to the length of one reach of the zig-zag, the punched holes being located at the regions where the latticing is bent and connected to the chords of the girder.

14. An apparatus as defined in claim 13 wherein said clamping units of said device (ii) comprise means extending through the holes.

15. An apparatus as defined in claim 1, further comprising means arranged at a point ahead of said means (d), considered in the direction of the production line, for descaling and stretching the strip which is to constitute the latticing of the girder.

16. An apparatus as defined in claim 15, wherein said descaling and stretching means comprise at least two pairs 11 of adjustable descaling rollers which also allow the lattic- 2,939,206 ing strip to be stretched. 2,947,848 References Cited by the Examiner 3,004,666 UNITED STATES PATENTS 3129493 Keller 29155 Sciaky 219117 X Hack.

Grubb 29-155 RICHARD M. WOOD, Primary Examiner.

R. F. STAUBLY, A ssistant Examiner.

Claims

1. APPARATUS FOR MAKING ENDLESS LATTICE GIRDERS HAVING SPACED-APART UPPER AND LOWER CHORDS AND ZIG-ZAG LATTICING OF CHANNEL-SHAPED TRANSVERSE CROSS SECTION JOINING THE CHORDS, SAID APPARATUS COMPRISING, IN COMBINATION: (A) MEANS FORMING A PRODUCTION LINE HAVING AT LEAST THREE PARALLEL PATHS FOR THE UPPER AND LOWER CHORDS AND THE LATTICING; (B) DRUM MEANS ARRANGED AT THE START OF THE PRODUCTION LINE FOR SUPPLYING AT LEAST THREE STRIPS WHICH ARE TO CONSTITUTE THE UPPER AND LOWER CHORDS AND THE LATTICING; (C) PULLING MEANS ARRANGED AT THE DELIVERY END OF THE PRODUCTION LINE FOR PULLING SAID STRIPS ALONG THEIR RESPECTIVE PATHS THROUGH THE PRODUCTION LINE IN A STEP-BY-STEP MANNER, THERE BEING PAUSES BETWEEN THE STEPS; (D) MEANS ARRANGED ALONG THE PATHS TRAVERSED BY THE STRIPS WHICH ARE TO CONSTITUTE THE UPPER AND LOWER CHORDS FOR CONTINUOUSLY IMPARTING THERETO THE SHAPE OF THE UPPER AND LOWER CHORDS WHILE THE STRIPS MOVE ALONG THEIR RESPECTIVE PATHS; (E) MEANS ARRANGED ALONG THE PATH TRAVERSED BY THE STRIP WHICH IS TO CONSTITUTE THE LATTICING FOR IMPARTING THERETO, DURING SAID PAUSES, A CHANNEL-SHAPED TRANSVERSE CROSSS SECTION AS WELL AS A ZIG-ZAG CONFIGURATION, AND FOR PLACING THE ZIG-ZAG LATTICE OF CHANNEL-SHAPED TRANSVERSE CROSS SECTION AGAINST THE CHORDS, SAID LASTMENTIONED MEANS COMPRISING (I) A FIRST DEVICE FOR IMPARTING SAID CHANNEL-SHAPED TRANSVERSE CROSS SECTION TO THE LATTICING STRIP THROUGHOUT LENGTHS EQUAL TO THE REACHES OF THE ZIG-ZAG, THE STRIP BEING LEFT FLAT AT THOSE REGIONS WHERE THE SAME IS TO BE SECURED TO THE CHORDS OF THE GIRDER, AND (II) A SECOND DEVICE FOR IMPARTING THE ZIG-ZAG CONFIGURATION TO THE LAST-MENTIONED STRIP, SAID