CA1081504A - Grating welder clamping head with weld pool retaining means - Google Patents
Grating welder clamping head with weld pool retaining meansInfo
- Publication number
- CA1081504A CA1081504A CA290,171A CA290171A CA1081504A CA 1081504 A CA1081504 A CA 1081504A CA 290171 A CA290171 A CA 290171A CA 1081504 A CA1081504 A CA 1081504A
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- Prior art keywords
- clamping head
- weld
- grating
- dam
- slots
- Prior art date
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Abstract
ABSTRACT
A clamping head having an axial passageway receiving a welding gun, for accurately positioning the gun over a metallic grating structure for welding the intersections of the grating members. The head includes a plurality of replaceable chamfered dams which resiliently engage the corners formed by the grating member intersections to retain the molten weld pool during solidification and improve the integrity of the weld bead.
A clamping head having an axial passageway receiving a welding gun, for accurately positioning the gun over a metallic grating structure for welding the intersections of the grating members. The head includes a plurality of replaceable chamfered dams which resiliently engage the corners formed by the grating member intersections to retain the molten weld pool during solidification and improve the integrity of the weld bead.
Description
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This invention relates to clamping devices for positioning welding guns used in welding intersections of grating structures, and more particularly to a clamping head having a plurality of dams for retaining the molten weld pool during solidification.
Gratings fabricated from welded intersecting metal bars are well known and have found widespread use in many different applications. While such gratings have found application as loading docks, platforms and protective coverings for openings, by far the most important use of these structures has been for open bridge decks, where they have served to replace conventional concrete road beds in new and existing bridges. Such decks are generally con-structed of a high strength low alloy atmospheric corrosion resistant steel with good welding properties, such as Type CSA D 40.21 Gr50A.
These bridge decks are fabricated in panels which may measure eight feet wide by thirty feet long, and may be bolted or welded to the bridge span at the construction site.
Each panel comprises a grating made up of welded intersecting metal bars forming a grid-like structure. Slotted parallel spaced main bars provide the main bearing support for the deck panel, and will vary in size depending upon the expected load. Lying transverse the main bars and supported within slots spaced along the main bars are a plurality of parallel spaced cross bar members. Between the main bars and supported by slots in the upper edge of the cross bar members are a number of parallel spaced intermediate bars which determine the si~e of the openings in the bridge deck grating.
Serrations may be provided in the upper edges of some or 8~S~)~
all of the grating deck members to provide better traction for vehicular traffic passing thereover.
The interlocking deck members may be joined by a button weld formed at the intersections of the bar members. To facilitate this weld, the bars may be notched at the intersections to form a small recess for containing the button weld.
In the past, various fabrication problems have been encountered in forming this weld. For example, it has been found that in some cases, the molten weld metal will drain from the weld pool contained within the bar member intersection recess before the weld metal has solidified, resulting in welds of poor appearance and quality. The degree to which the molten weld metal will drain from the weld pool will depend upon such factors as welder voltage, amperage and weld time variations, as well as machining tolerances and fit up in the bar members and variations in quality of the weld metal wire. Final assembly of one bridge deck panel may require 1800-2000 welds per panel. It has been found that using prior art welding methods, 150-200 of these welds may be mechanically defective and require manual repair, significantly increasing the cost and time required to produce the bridge deck grating panels.
In contrast, the weld clamping head of the present invention retains the molten weld pool in the bar member intersection recess during solidification, practically eliminating the defective welds produced by prior art methods.
The present invention provides a weld clamping head for accurately positioning a welding gun to weld joints in metallic grating structures hav-ing parallel spaced lateral bar members and parallel spaced transverse bar members intersecting and supported by the lateral bar members to form the grating joints, said clamping head comprising: a) a body portion having an axial passageway therethrough for telescopically receiving the welding gun therein, one end of said body portion including locating slots spaced 90 apart for engaging the upper edges of the lateral and transverse bar members to position the head and the gun received therein over the grating joint; and ~ .
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b) clamping means positioned between said slots for resiliently engaging the corners of the bar intersections to retain the molten weld pool during solidification of the weld to form the weld bead of the grating joint.
The upper end of the body portion preferably contains a flanged skirt for attaching the head to suitable automatic indexing fabrication equipment. The locating slots preferably are tapered, and one pair of diametrically opposed slots is shallower than the other pair of diametrically opposed slots in order to exert a downward pressure on the appropriate bar to insure proper position and fit up of the bars during the welding opera-tion.
In the preferred embodiment, the clamping means comprise weld dams and spring means or urging the dams into the corners formed by the inter-secting bar members. The corner engaging ends of the dams are chamfered to abut the adjacent bar surfaces. The upper portion of the corner engaging end of each dam is also chamfered to shape and retain the molten weld pool.
The lower portion of the corner engaging end of each dam tapers rearwardly away from the corner engaging end of the dam to permit the dam to easily engage the corners of the bar intersection. In addition, each dam may include a lower wear block portion comprised of a hardened wear resisting material, and an upper backup block portion constructed of a material having a relatively high heat conductivity for supporting and cooling the weld pool during solidification. The backup block and wear block are removably attached to the end of the spring means, for easy maintenance and replacement.
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Reference is made to the accompanying drawings wherein:
FIGURE 1 is an exploded perspective view showing the clamping head of the present invention being lowered onto a bridge deck grating joint to be welded.
FIGURE 2 is a side elevation view of the clamping head of the present invention with the clamping means removed for clarity.
FIGURE 3 is a bottom plan view of the cla~mping head of Figure 2. --FIGURE 4 is a side elevation view of the clamping head of Figure 2 rotated 45 about its longitudinal axis.
FIGURE 5 is a side elevation view of one clamping means removed from the clamping head of the present invention.
FIGURE 6 is a front elevation view of the clamping means of Figure 4.
FIGURE 7 is a cross sectional view taken along section line 7-7 of Figure 3 with the clamping means in place.
FIGURE 8 is a fragmentary cross sectional plan view of the clamping head of the present invention illustra-ting the clamping means in place against the corners of `~
the grating bar members to shape and retain the weld pool.
FIGURE 9 is a fragmentary cross sectional elevational view of the clamping means of the clamping head of the present invention shown in place against the intersecting grating bar members to shape and retain the weld pool ?
taken along section line 9-9 of Figure 8.
.. . , ,, , ~-, .
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Figure 1 shows a perspective view of the clamping head of ~he present invention ! shown generally at 1, posi-tioned over the joint 2 of a typical bridge deck grating 3.
The grating 3 comprises at least two main bearing bars 4 containing a plurality of spaced slots, one of which is shown at 5, for receiving the parallel spaced cross bars, one of which is shown at 7, spanning the main support bars 4. Each cross bar 7 contains along its upper edge a plurality of spaced slots, one of which is illustrated at 8, for accepting and supporting a plurality of intermediate bars, one of which is shown at 9, such that intermediate bars 9 are sub-stantially parallel to main bearing bars 4. The interlocking structure formed by main bearing bars 4, cross bars 7 and intermediate bars 9 form the grid-like grating 3 which may comprise one panel of a completed bridge deck.
Each bar member may contain along its upper edge ; ;~
serrations, one of which is shown at 1 n, to provide a rough-ened surface for the grating and increased traction for vehicles or pedestrians moving thereon. Each bar may also contain a notch formed in the upper edge of the bar at its point of intersection with other bars to provide a shallow recess 11 in the upper surface of the grating joint 2 to aid in shaping and retaining the weld pool placed therein. It will also be understood that the other joints of grating 3 are constructed in a similar manner to joint 2.
Weld clamping head 1 is shown in greater detail, without the clamping means attached to the clamping head, in Figure 2 - Figure 4. Clamping head 1 is substantially s~
cylindrical-shaped and comprises a lower cylindrical portion 12 and an upper cylindrical portion 13 of smaller diameter than lower cylindrical portion 12. Cylindrical portions 12 and 13 are joined by skirt portion 14 which tapers outwardly from the lower edge of cylindrical portion 13 to the upper edge of cylindrical portion 12. Upper cylindrical portion 13 terminates at its upper edge in outwardly extending flange 48 which is adapted to engage suitably indexing apparatus, not shown.
An axial passageway 16 extends entirely through clamping head 1, opening into a generally circular aperture 17 in the upper surface of head 1. Passageway lZ extends through flange 48, upper cylindrical portion 13, skirt portion 14 and approximately the upper half of lower cylindrical portion 12 with substantially constant cross section. The lower end of this section of passageway 16 terminates in a flange 18 with inwardly tapering sides defining a substantially circular opening 19 therethrough.
The lower end of opening 19 opens into an axial bore 20.
Axial passageway 16 is so dimensioned as to accept a conventional gas or electric arc welding gun, not shown, such that the gun may be accurately positioned over the grating joint to be welded.
The lower or grate engaging end of clamping head 1 contains four locating slots, one of which is shown at 21, spaced 90 apart around the circumference of the lower edge of clamping head 1. Each slot tapers inwardly and upwardly from a lower bar engaging opening 22 to an upper bar member locating opening 23 dimensioned ~8~5~
slightly wider than the thickness of ~he grating bar members.
Locating slots 21 permit the entire head 1, together with the welding gun received therein, to be lowered onto the upper surface of a steel bridge deck grating 3 such that the upper ed~es of the intersecting bar members are recelved within tapered locating slots 21 and rest against the upper ends 23 of the slots, thus accurately positioning the welding gun over the center of the joint to be welded. Locating slots 21 also prevent lateral movement of the gun during the welding operation to improve the weld profile and mechanical proper-ties. The tapered shape of locating slot 21 permits the upper edges of the intersecting bar members to be guided into slot 21 as clamping head 1 is lowered onto the grating to compensate for slight misalignment of the head over the grating.
It will be observed that one pair of diametrically opposed slots is shallower than the other pair of diametri-cally opposed slots, as illustrated by slots 21a and 21b in FIG. 4. In this view, slot 21a and its diametrically opposed slot (not shown) are shallower than slot 21b and its diame-trically opposed slot (not shown). This arrangement permits the shallower slots to exert a downward pressure on the appropriate grating bar to insure proper position and fit up.
For example, if it be desired to weld the joints formed by the intersections of main bearing bars 4 and cross bars 7, head 1 is lowered onto the intersection such that the shallow slots 21a engage cross bar 7 and slots 21b engage main bearing bar 4. This forces cross bar 7 into the correct position in slot S of main bearing bar 4 before and during the welding operation. When this weld has been completed, head 1 is moved out of engagement with this intersection of bars 4 and 7, and moved to another main bearing bar - cross bar intersection where the positioning and welding operations are repeated.
When all main bearing bar - cross bar intersections have been welded, head 1 is rotated 90 and lowered over a cross bar - intermediate bar intersection, such that shallow slots 21a engage intermediate bar 9 and slots 21b engage cross bar 7. This orientation of head 1 applies a downward pressure to force intermediate bar 9 into proper engagement with cross bar 7. This intersection may then be welded, and the head indexed to a new position until all welds have been made.
The lower end of the clamping head 1 also contains four substantially rectangular dam retaining slots, one of which is shown at 24, extending upwardly from the lower edge of clamping head 1. Slots 24 are located 90 apart around the circumference of head 1, and intermediate locating slots 21a and 21b. Each of slots 24 retains a welding dam, as will be described hereinafter.
Spaced above each dam retaining slot 24 and adjacent the lower edge of skirt 14 is a tapped hole 15 adapted to accept a threaded fastener for attaching a leaf spring to the outer surface of clamping head 1, as will be described hereinafter. As is best shown in FIG. 4, the outer surface of clamping head 1 be-tween dam retaining slot 24 and threaded hole 15 is ground flat, as at 25, to provide a suitably flat seating surface for the leaf spring. Seating surface 25 also tapers inwardly toward the axial bore of clamping head 1, forming an angle ~15.l3~
of approximately 2 1/2 with the longitudinal axis of head 1. This taper permits the leaf spring to be preloaded to a tension of approximately five pounds to insure that the dams are perpendicular when in place over the grating joint, as will be explained hereinafter.
The clamping means used with the clamping head 1 of the present invention is illustrated generally at 26 in FIG. 5 and FIG, 6. Each clamping means comprises a block-like dam 27 attached at its rearmost surface to a leaf spring 28. Dam 27 comprises an upper back-up block portion 29 and a lower wear block portion 30. Block 29 contains a vertical tapped hole and block 30 contains a vertical clearance hole for accepting a flat head screw 31 to connect the blocks together. The lower sur~ace of wear block 30 may contain a counterbore 32 to insure that the head bf screw 31 is flush with the lower surface of wear block 30. The rearmost surface of wear block 30 contains a tapped hole 33 for accepting bolt 34 which passes through a suitable hole 35 in the lower end of leaf spring 28 to secure spring 28 to the rearmost surface of dam 27. The upper end of spring 28 contains a similar hole 36 dimensioned `;
to accept a fastener for securing spring 28 to seating surface 25 on the outer surface of head 1 as will be described hereinafter.
The lower portion of the forward or corner en-gaging end of wear block 30 tapers downwardly and rearwardly as at 37 to permit dam 27 to easily engage the corner of the grating bar intersection as the clamping head 1 is lowered over the grating joint to be welded. The upper portion of the forward or corner engaging end of back-up block 29 is chamfered at approximately a 60 angle,as at 38,to shape and retain the molten weld pool, as will be described hereinafter. The corners of the forward ends of back-upblock 29 and wear block 30 are chamfered at approximately a 45 angle to permit the dam 27 to fit into the corner formed by the intersecting bar members so that the chamfered portions, shown at 39 and 40 in FIG. 6,abut the adjacent bar surfaces.
Back-up block 29 supports the molten weld metal during solidification and prevents burn through. Block 29 may be constructed of any material having high heat conductivity, such as copper, and having sufficient mass to prevent it from being heated to its melting point which would result in contamination of the underside of the weld.
Wear block 30 is constructed of a hardened material to reduce wear on copper back-up block 29,as well as reduce the amount of material necessary to be used in the back-up block. Back-up block 29 may be easily replaced by removing flat head screw 31 securing back-up block 29 to wear block 30. In a like manner, wear block 30 may be replaced by removing bolt 34 securing wear block 30 to leaf spring 28. -~
Although back-up block 29 may be secured to wear block 30 in any suitable manner, it has been found advantageous to provide back-up block 29 with a ton~ue 41 projecting from the lower surface of back-up block 29 - which is received in a matching groove 42 positioned in 5~9~
the upper surface of wear block 30. This arrangement insures a good mechanical connection between backup block 29 and wear bloek 30 while at the same time providing an excel-lent heat eonduetion path between the two bloeks.
FIG. 7 is a cross sectional view of the clamping head 1 showing two of the four clamping means 26 secured to elampin~ head 1. Eaeh elampin~ means 26 is seeured to the seating surfaee portion 25 of head 1 by a bolt 43 whieh passes through aperture 36 in leaf spring 28 and is threadedly engaged in hole 15, sueh that the inner surface of leaf sprin~ 28 abuts the flattened portion 25 of head 1 and the axis of spring 28 is displaeed from the longitudinal axis of head 1 by approximately 2 1/2~. This displaeement permits dam 27 to be urged into the corner formed by the interseeting grating bar members with a foree of approximately five pounds to insure that the ehamfered surfaees 39 and 40 of baekup block 29 abuttingly contact the inner surfaces of the intersecting bar members of the joint to be welded. AS
shown in FIG. 7, dams 27 are slidably reeeived within slots 24 of head 1 to prevent lateral movement of the dams whieh eould result in damage to the baek-up bloek or wear bloek.
In operation, the elamping head is positioned over the joint to be welded, either manually or by means of an automatie positioner. As is well understood in the art, the positioner may contain as many clamping heads as necessary to perform simultaneous welding operations.
Limit switches in association with the automatic positioner may be used to guide the elamping heads, together with the welding guns eontained therein, over the grating intersections. The heads and guns may then be lowered into position and the welds made. Thereafter the heads and guns are raised and traversed or indexed to the next position as required.
~hen the head is lowered onto the grating inter-section, chamfered surfaces 37 of the clamping means 26 first make contact with the upper edges of the supporting bar members of the grating. As clamping head 1 descends, guided by the bar members received within locating slots 21a and 21b as described hereinabove, the upper surfaces of the bar members continue to exert a force against chamfered surfaces 37, thereby urging dams 27 outwardly. The downward motion of clamping head will containue until surfaces 23 of locating slots 21a and 21b rests against the upper surface of the grating bar members. At this point, leaf spring 28 is substantially parallel to the longitudinal axis of clamp-ing head 1 and exerts an inward force through dam 27 which tends to urge the corner engaging end of dam 27 into contact with the corner formed by the intersection of the bar members.
With clamping head 1 fully seated on the grating joint, the upper surface of back-up block 29 will lie slightly above the upper surface of the intersecting bar members. In addition, the lower edge of weld pool retaining chamfer 38 of backup block 29 will be positioned slightly below the lower edge of weld recess 11 formed by the intersections of the bar members. At this point, the welding gun received within the clamping head 1 may be activated to form the molten weld pool at the grating joint, as is best illustrated in FIG. 8 and FIG. 9.
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FIGURE 8 illustrates a cross sectional plan view of the welding head in position over the joint formed by the intersection of bar members 7 and 9, with dams or clamping means 45a-45d urged in~o the corners formed by the intersection of bar members 7 and 9. FIGURE 9 illustrates a frag-mentary cross sectional eleva~ional view of the grating joint showing dams or clamping means 45a and 45c positioned against the intersecting bar members.
During the welding operation, a pool of molten weld metal will be formed in recess 11 of the grating joint, depicted at 46 in FIGURE 8. In prior art clamping heads, there has been a tendency for the molten metal in weld pool 46 to drain from the corners of recess 11, thereby causing unsatisfactory welds. The addition of clamping means 45, and ln particular the chamfered portions 38 of back-up blocks 29, permit the molten weld metal which would otherwise be lost to collect in pyramid-shaped weld pools 47a-47d retained by the interior surface walls of intersecting bar members 7 and 9, as well as by chamfered portions 38 of back-up blocks 29. The weld pool is thus prevented from draining from the grating joint before it has a chance to ;
cool, providing a very satisfactorily welded joint. The high conductivity of back-up blocks 29 further chill the molten weld pool before it can drain from the recess ll and the dam pools 47a-47d. Hence adverse affects of weld wire straightness, incorrect bar member fitup, welder voltage, amperage and welding time variations, as well as variations in welding gun positioning, are eliminated.
It will be understood that var.ious changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principal and scope o the invention as expressed in the appended claims.
For example, the shape of the corner engaging endsand the chamfered portionsof the back-up blockfimay be varied depending on the weld profile desiredand welding para-meters, such as voltage, current and weld time, utilitzed. :~
This invention relates to clamping devices for positioning welding guns used in welding intersections of grating structures, and more particularly to a clamping head having a plurality of dams for retaining the molten weld pool during solidification.
Gratings fabricated from welded intersecting metal bars are well known and have found widespread use in many different applications. While such gratings have found application as loading docks, platforms and protective coverings for openings, by far the most important use of these structures has been for open bridge decks, where they have served to replace conventional concrete road beds in new and existing bridges. Such decks are generally con-structed of a high strength low alloy atmospheric corrosion resistant steel with good welding properties, such as Type CSA D 40.21 Gr50A.
These bridge decks are fabricated in panels which may measure eight feet wide by thirty feet long, and may be bolted or welded to the bridge span at the construction site.
Each panel comprises a grating made up of welded intersecting metal bars forming a grid-like structure. Slotted parallel spaced main bars provide the main bearing support for the deck panel, and will vary in size depending upon the expected load. Lying transverse the main bars and supported within slots spaced along the main bars are a plurality of parallel spaced cross bar members. Between the main bars and supported by slots in the upper edge of the cross bar members are a number of parallel spaced intermediate bars which determine the si~e of the openings in the bridge deck grating.
Serrations may be provided in the upper edges of some or 8~S~)~
all of the grating deck members to provide better traction for vehicular traffic passing thereover.
The interlocking deck members may be joined by a button weld formed at the intersections of the bar members. To facilitate this weld, the bars may be notched at the intersections to form a small recess for containing the button weld.
In the past, various fabrication problems have been encountered in forming this weld. For example, it has been found that in some cases, the molten weld metal will drain from the weld pool contained within the bar member intersection recess before the weld metal has solidified, resulting in welds of poor appearance and quality. The degree to which the molten weld metal will drain from the weld pool will depend upon such factors as welder voltage, amperage and weld time variations, as well as machining tolerances and fit up in the bar members and variations in quality of the weld metal wire. Final assembly of one bridge deck panel may require 1800-2000 welds per panel. It has been found that using prior art welding methods, 150-200 of these welds may be mechanically defective and require manual repair, significantly increasing the cost and time required to produce the bridge deck grating panels.
In contrast, the weld clamping head of the present invention retains the molten weld pool in the bar member intersection recess during solidification, practically eliminating the defective welds produced by prior art methods.
The present invention provides a weld clamping head for accurately positioning a welding gun to weld joints in metallic grating structures hav-ing parallel spaced lateral bar members and parallel spaced transverse bar members intersecting and supported by the lateral bar members to form the grating joints, said clamping head comprising: a) a body portion having an axial passageway therethrough for telescopically receiving the welding gun therein, one end of said body portion including locating slots spaced 90 apart for engaging the upper edges of the lateral and transverse bar members to position the head and the gun received therein over the grating joint; and ~ .
~8~5~
b) clamping means positioned between said slots for resiliently engaging the corners of the bar intersections to retain the molten weld pool during solidification of the weld to form the weld bead of the grating joint.
The upper end of the body portion preferably contains a flanged skirt for attaching the head to suitable automatic indexing fabrication equipment. The locating slots preferably are tapered, and one pair of diametrically opposed slots is shallower than the other pair of diametrically opposed slots in order to exert a downward pressure on the appropriate bar to insure proper position and fit up of the bars during the welding opera-tion.
In the preferred embodiment, the clamping means comprise weld dams and spring means or urging the dams into the corners formed by the inter-secting bar members. The corner engaging ends of the dams are chamfered to abut the adjacent bar surfaces. The upper portion of the corner engaging end of each dam is also chamfered to shape and retain the molten weld pool.
The lower portion of the corner engaging end of each dam tapers rearwardly away from the corner engaging end of the dam to permit the dam to easily engage the corners of the bar intersection. In addition, each dam may include a lower wear block portion comprised of a hardened wear resisting material, and an upper backup block portion constructed of a material having a relatively high heat conductivity for supporting and cooling the weld pool during solidification. The backup block and wear block are removably attached to the end of the spring means, for easy maintenance and replacement.
.5~
Reference is made to the accompanying drawings wherein:
FIGURE 1 is an exploded perspective view showing the clamping head of the present invention being lowered onto a bridge deck grating joint to be welded.
FIGURE 2 is a side elevation view of the clamping head of the present invention with the clamping means removed for clarity.
FIGURE 3 is a bottom plan view of the cla~mping head of Figure 2. --FIGURE 4 is a side elevation view of the clamping head of Figure 2 rotated 45 about its longitudinal axis.
FIGURE 5 is a side elevation view of one clamping means removed from the clamping head of the present invention.
FIGURE 6 is a front elevation view of the clamping means of Figure 4.
FIGURE 7 is a cross sectional view taken along section line 7-7 of Figure 3 with the clamping means in place.
FIGURE 8 is a fragmentary cross sectional plan view of the clamping head of the present invention illustra-ting the clamping means in place against the corners of `~
the grating bar members to shape and retain the weld pool.
FIGURE 9 is a fragmentary cross sectional elevational view of the clamping means of the clamping head of the present invention shown in place against the intersecting grating bar members to shape and retain the weld pool ?
taken along section line 9-9 of Figure 8.
.. . , ,, , ~-, .
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Figure 1 shows a perspective view of the clamping head of ~he present invention ! shown generally at 1, posi-tioned over the joint 2 of a typical bridge deck grating 3.
The grating 3 comprises at least two main bearing bars 4 containing a plurality of spaced slots, one of which is shown at 5, for receiving the parallel spaced cross bars, one of which is shown at 7, spanning the main support bars 4. Each cross bar 7 contains along its upper edge a plurality of spaced slots, one of which is illustrated at 8, for accepting and supporting a plurality of intermediate bars, one of which is shown at 9, such that intermediate bars 9 are sub-stantially parallel to main bearing bars 4. The interlocking structure formed by main bearing bars 4, cross bars 7 and intermediate bars 9 form the grid-like grating 3 which may comprise one panel of a completed bridge deck.
Each bar member may contain along its upper edge ; ;~
serrations, one of which is shown at 1 n, to provide a rough-ened surface for the grating and increased traction for vehicles or pedestrians moving thereon. Each bar may also contain a notch formed in the upper edge of the bar at its point of intersection with other bars to provide a shallow recess 11 in the upper surface of the grating joint 2 to aid in shaping and retaining the weld pool placed therein. It will also be understood that the other joints of grating 3 are constructed in a similar manner to joint 2.
Weld clamping head 1 is shown in greater detail, without the clamping means attached to the clamping head, in Figure 2 - Figure 4. Clamping head 1 is substantially s~
cylindrical-shaped and comprises a lower cylindrical portion 12 and an upper cylindrical portion 13 of smaller diameter than lower cylindrical portion 12. Cylindrical portions 12 and 13 are joined by skirt portion 14 which tapers outwardly from the lower edge of cylindrical portion 13 to the upper edge of cylindrical portion 12. Upper cylindrical portion 13 terminates at its upper edge in outwardly extending flange 48 which is adapted to engage suitably indexing apparatus, not shown.
An axial passageway 16 extends entirely through clamping head 1, opening into a generally circular aperture 17 in the upper surface of head 1. Passageway lZ extends through flange 48, upper cylindrical portion 13, skirt portion 14 and approximately the upper half of lower cylindrical portion 12 with substantially constant cross section. The lower end of this section of passageway 16 terminates in a flange 18 with inwardly tapering sides defining a substantially circular opening 19 therethrough.
The lower end of opening 19 opens into an axial bore 20.
Axial passageway 16 is so dimensioned as to accept a conventional gas or electric arc welding gun, not shown, such that the gun may be accurately positioned over the grating joint to be welded.
The lower or grate engaging end of clamping head 1 contains four locating slots, one of which is shown at 21, spaced 90 apart around the circumference of the lower edge of clamping head 1. Each slot tapers inwardly and upwardly from a lower bar engaging opening 22 to an upper bar member locating opening 23 dimensioned ~8~5~
slightly wider than the thickness of ~he grating bar members.
Locating slots 21 permit the entire head 1, together with the welding gun received therein, to be lowered onto the upper surface of a steel bridge deck grating 3 such that the upper ed~es of the intersecting bar members are recelved within tapered locating slots 21 and rest against the upper ends 23 of the slots, thus accurately positioning the welding gun over the center of the joint to be welded. Locating slots 21 also prevent lateral movement of the gun during the welding operation to improve the weld profile and mechanical proper-ties. The tapered shape of locating slot 21 permits the upper edges of the intersecting bar members to be guided into slot 21 as clamping head 1 is lowered onto the grating to compensate for slight misalignment of the head over the grating.
It will be observed that one pair of diametrically opposed slots is shallower than the other pair of diametri-cally opposed slots, as illustrated by slots 21a and 21b in FIG. 4. In this view, slot 21a and its diametrically opposed slot (not shown) are shallower than slot 21b and its diame-trically opposed slot (not shown). This arrangement permits the shallower slots to exert a downward pressure on the appropriate grating bar to insure proper position and fit up.
For example, if it be desired to weld the joints formed by the intersections of main bearing bars 4 and cross bars 7, head 1 is lowered onto the intersection such that the shallow slots 21a engage cross bar 7 and slots 21b engage main bearing bar 4. This forces cross bar 7 into the correct position in slot S of main bearing bar 4 before and during the welding operation. When this weld has been completed, head 1 is moved out of engagement with this intersection of bars 4 and 7, and moved to another main bearing bar - cross bar intersection where the positioning and welding operations are repeated.
When all main bearing bar - cross bar intersections have been welded, head 1 is rotated 90 and lowered over a cross bar - intermediate bar intersection, such that shallow slots 21a engage intermediate bar 9 and slots 21b engage cross bar 7. This orientation of head 1 applies a downward pressure to force intermediate bar 9 into proper engagement with cross bar 7. This intersection may then be welded, and the head indexed to a new position until all welds have been made.
The lower end of the clamping head 1 also contains four substantially rectangular dam retaining slots, one of which is shown at 24, extending upwardly from the lower edge of clamping head 1. Slots 24 are located 90 apart around the circumference of head 1, and intermediate locating slots 21a and 21b. Each of slots 24 retains a welding dam, as will be described hereinafter.
Spaced above each dam retaining slot 24 and adjacent the lower edge of skirt 14 is a tapped hole 15 adapted to accept a threaded fastener for attaching a leaf spring to the outer surface of clamping head 1, as will be described hereinafter. As is best shown in FIG. 4, the outer surface of clamping head 1 be-tween dam retaining slot 24 and threaded hole 15 is ground flat, as at 25, to provide a suitably flat seating surface for the leaf spring. Seating surface 25 also tapers inwardly toward the axial bore of clamping head 1, forming an angle ~15.l3~
of approximately 2 1/2 with the longitudinal axis of head 1. This taper permits the leaf spring to be preloaded to a tension of approximately five pounds to insure that the dams are perpendicular when in place over the grating joint, as will be explained hereinafter.
The clamping means used with the clamping head 1 of the present invention is illustrated generally at 26 in FIG. 5 and FIG, 6. Each clamping means comprises a block-like dam 27 attached at its rearmost surface to a leaf spring 28. Dam 27 comprises an upper back-up block portion 29 and a lower wear block portion 30. Block 29 contains a vertical tapped hole and block 30 contains a vertical clearance hole for accepting a flat head screw 31 to connect the blocks together. The lower sur~ace of wear block 30 may contain a counterbore 32 to insure that the head bf screw 31 is flush with the lower surface of wear block 30. The rearmost surface of wear block 30 contains a tapped hole 33 for accepting bolt 34 which passes through a suitable hole 35 in the lower end of leaf spring 28 to secure spring 28 to the rearmost surface of dam 27. The upper end of spring 28 contains a similar hole 36 dimensioned `;
to accept a fastener for securing spring 28 to seating surface 25 on the outer surface of head 1 as will be described hereinafter.
The lower portion of the forward or corner en-gaging end of wear block 30 tapers downwardly and rearwardly as at 37 to permit dam 27 to easily engage the corner of the grating bar intersection as the clamping head 1 is lowered over the grating joint to be welded. The upper portion of the forward or corner engaging end of back-up block 29 is chamfered at approximately a 60 angle,as at 38,to shape and retain the molten weld pool, as will be described hereinafter. The corners of the forward ends of back-upblock 29 and wear block 30 are chamfered at approximately a 45 angle to permit the dam 27 to fit into the corner formed by the intersecting bar members so that the chamfered portions, shown at 39 and 40 in FIG. 6,abut the adjacent bar surfaces.
Back-up block 29 supports the molten weld metal during solidification and prevents burn through. Block 29 may be constructed of any material having high heat conductivity, such as copper, and having sufficient mass to prevent it from being heated to its melting point which would result in contamination of the underside of the weld.
Wear block 30 is constructed of a hardened material to reduce wear on copper back-up block 29,as well as reduce the amount of material necessary to be used in the back-up block. Back-up block 29 may be easily replaced by removing flat head screw 31 securing back-up block 29 to wear block 30. In a like manner, wear block 30 may be replaced by removing bolt 34 securing wear block 30 to leaf spring 28. -~
Although back-up block 29 may be secured to wear block 30 in any suitable manner, it has been found advantageous to provide back-up block 29 with a ton~ue 41 projecting from the lower surface of back-up block 29 - which is received in a matching groove 42 positioned in 5~9~
the upper surface of wear block 30. This arrangement insures a good mechanical connection between backup block 29 and wear bloek 30 while at the same time providing an excel-lent heat eonduetion path between the two bloeks.
FIG. 7 is a cross sectional view of the clamping head 1 showing two of the four clamping means 26 secured to elampin~ head 1. Eaeh elampin~ means 26 is seeured to the seating surfaee portion 25 of head 1 by a bolt 43 whieh passes through aperture 36 in leaf spring 28 and is threadedly engaged in hole 15, sueh that the inner surface of leaf sprin~ 28 abuts the flattened portion 25 of head 1 and the axis of spring 28 is displaeed from the longitudinal axis of head 1 by approximately 2 1/2~. This displaeement permits dam 27 to be urged into the corner formed by the interseeting grating bar members with a foree of approximately five pounds to insure that the ehamfered surfaees 39 and 40 of baekup block 29 abuttingly contact the inner surfaces of the intersecting bar members of the joint to be welded. AS
shown in FIG. 7, dams 27 are slidably reeeived within slots 24 of head 1 to prevent lateral movement of the dams whieh eould result in damage to the baek-up bloek or wear bloek.
In operation, the elamping head is positioned over the joint to be welded, either manually or by means of an automatie positioner. As is well understood in the art, the positioner may contain as many clamping heads as necessary to perform simultaneous welding operations.
Limit switches in association with the automatic positioner may be used to guide the elamping heads, together with the welding guns eontained therein, over the grating intersections. The heads and guns may then be lowered into position and the welds made. Thereafter the heads and guns are raised and traversed or indexed to the next position as required.
~hen the head is lowered onto the grating inter-section, chamfered surfaces 37 of the clamping means 26 first make contact with the upper edges of the supporting bar members of the grating. As clamping head 1 descends, guided by the bar members received within locating slots 21a and 21b as described hereinabove, the upper surfaces of the bar members continue to exert a force against chamfered surfaces 37, thereby urging dams 27 outwardly. The downward motion of clamping head will containue until surfaces 23 of locating slots 21a and 21b rests against the upper surface of the grating bar members. At this point, leaf spring 28 is substantially parallel to the longitudinal axis of clamp-ing head 1 and exerts an inward force through dam 27 which tends to urge the corner engaging end of dam 27 into contact with the corner formed by the intersection of the bar members.
With clamping head 1 fully seated on the grating joint, the upper surface of back-up block 29 will lie slightly above the upper surface of the intersecting bar members. In addition, the lower edge of weld pool retaining chamfer 38 of backup block 29 will be positioned slightly below the lower edge of weld recess 11 formed by the intersections of the bar members. At this point, the welding gun received within the clamping head 1 may be activated to form the molten weld pool at the grating joint, as is best illustrated in FIG. 8 and FIG. 9.
~`
5~
FIGURE 8 illustrates a cross sectional plan view of the welding head in position over the joint formed by the intersection of bar members 7 and 9, with dams or clamping means 45a-45d urged in~o the corners formed by the intersection of bar members 7 and 9. FIGURE 9 illustrates a frag-mentary cross sectional eleva~ional view of the grating joint showing dams or clamping means 45a and 45c positioned against the intersecting bar members.
During the welding operation, a pool of molten weld metal will be formed in recess 11 of the grating joint, depicted at 46 in FIGURE 8. In prior art clamping heads, there has been a tendency for the molten metal in weld pool 46 to drain from the corners of recess 11, thereby causing unsatisfactory welds. The addition of clamping means 45, and ln particular the chamfered portions 38 of back-up blocks 29, permit the molten weld metal which would otherwise be lost to collect in pyramid-shaped weld pools 47a-47d retained by the interior surface walls of intersecting bar members 7 and 9, as well as by chamfered portions 38 of back-up blocks 29. The weld pool is thus prevented from draining from the grating joint before it has a chance to ;
cool, providing a very satisfactorily welded joint. The high conductivity of back-up blocks 29 further chill the molten weld pool before it can drain from the recess ll and the dam pools 47a-47d. Hence adverse affects of weld wire straightness, incorrect bar member fitup, welder voltage, amperage and welding time variations, as well as variations in welding gun positioning, are eliminated.
It will be understood that var.ious changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principal and scope o the invention as expressed in the appended claims.
For example, the shape of the corner engaging endsand the chamfered portionsof the back-up blockfimay be varied depending on the weld profile desiredand welding para-meters, such as voltage, current and weld time, utilitzed. :~
Claims (8)
1. A weld clamping head for accurately positioning a welding gun to weld joints in metallic grating structures having parallel spaced lateral bar members and parallel spaced transverse bar members intersecting and supported by the lateral bar members to form the grating joints, said clamping head comprising:
a) a body portion having an axial passageway therethrough for telescopically receiving the welding gun therein, one end of said body portion including locating slots spaced 90° apart for engaging the upper edges of the lateral and transverse bar members to position the head and the gun received therein over the grating joint; and b) clamping means positioned between said slots for resiliently engaging the corners of the bar inter-sections to retain the molten weld pool during solidification of the weld to form the weld bead of the grating joint.
a) a body portion having an axial passageway therethrough for telescopically receiving the welding gun therein, one end of said body portion including locating slots spaced 90° apart for engaging the upper edges of the lateral and transverse bar members to position the head and the gun received therein over the grating joint; and b) clamping means positioned between said slots for resiliently engaging the corners of the bar inter-sections to retain the molten weld pool during solidification of the weld to form the weld bead of the grating joint.
2. The clamping head according to claim 1 wherein the sides of said slots taper inwardly such that the bottom of each of said slots is wider than the top.
3. The clamping head according to claim 1 wherein said clamping means comprises a weld dam and spring means for urging said dam into the corners of the bar member intersections, the corner engaging end of said dam being chamfered to abut the adjacent bar surfaces.
4. The clamping head according to claim 3 wherein the upper portion of the corner engaging end of said dam is chamfered to shape and retain the molten weld pool.
5. The clamping head according to claim 3 wherein the lower portion of the corner engaging end of said dam tapers rearwardly away from the corner engaging end of said dam, said taper permitting said dam to easily engage the corners of the bar intersections.
6. The clamping head according to claim 3 wherein said dam includes a lower wear block portion and an upper back-up block portion, said wear block portion being adapted to engage the grating before said back-up block, said back-up block being constructed of a material having relatively high heat conductivity for supporting and cooling the weld during solidification.
7. The clamping head according to claim 6 wherein said back-up block is removably secured to said wear block and said wear block is removably secured to said spring means.
8. The clamping head according to claim 1 wherein said locating slots are arranged in pairs of diametrically opposed slots, the slots of one of said pairs being shallower than the slots of the other of said pairs for properly posi-tioning the lateral bar member with respect to the transverse bar members.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA290,171A CA1081504A (en) | 1977-11-03 | 1977-11-03 | Grating welder clamping head with weld pool retaining means |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA290,171A CA1081504A (en) | 1977-11-03 | 1977-11-03 | Grating welder clamping head with weld pool retaining means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081504A true CA1081504A (en) | 1980-07-15 |
Family
ID=4109940
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA290,171A Expired CA1081504A (en) | 1977-11-03 | 1977-11-03 | Grating welder clamping head with weld pool retaining means |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1081504A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114603279A (en) * | 2022-02-16 | 2022-06-10 | 山东高速铁建装备有限公司 | Automatic welding device for reinforcing mesh |
| CN116871764A (en) * | 2023-09-06 | 2023-10-13 | 无锡皮姆科技有限公司 | Welding fixture for new energy automobile battery rack |
-
1977
- 1977-11-03 CA CA290,171A patent/CA1081504A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114603279A (en) * | 2022-02-16 | 2022-06-10 | 山东高速铁建装备有限公司 | Automatic welding device for reinforcing mesh |
| CN116871764A (en) * | 2023-09-06 | 2023-10-13 | 无锡皮姆科技有限公司 | Welding fixture for new energy automobile battery rack |
| CN116871764B (en) * | 2023-09-06 | 2023-11-28 | 无锡皮姆科技有限公司 | Welding fixture for new energy automobile battery rack |
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