US3180671A - Reinforcing mat handling means - Google Patents

Description

A ril 27, 1965 v E. H. BACHMANN REINFORCING MAT HANDLING MEANS 5 Sheets-Sheet 1 Filed May 8, 1962 I '7zar F 5m,

April 27, 1965 E. H. BACHMANN REINFORCING MAT HANDLING MEANS 5 Sheets-Sheet 2 Filed May 8, 1962 fc \mw wh WW fnv/e'n for: Z'z'nar @ZLBacfi manrz C HM,M W M Wigs.

April 27, 1965 E. H. BACHMANN REINFORCING MAT HANDLING MEANS 5 Sheets-Sheet 3 Filed May 8, 1962 WWW en for: c Zffiacfimann Hawk} v April 27, 1965 E, H. BACHMANN REINFORCING MAT HANDLING MEANS 5 Sheets-Sheet 4 Filed May 8, 1962 en tor: Z'z'nar c 12 ,Bacmarzn Hm M M k LnN April 27, 1965 H. BACHMANN REINFORCING MAT HANDLING MEANS 5 Sheets-Sheet 5 Filed May a, 1962 United States Patent 3,189,671 REINFGRCING MAT HANDLING MEANS Einar H. Bachmann, 1515 Gregory St., Wilmette, Ill. Filed May 8, 1962, Ser. No. 193,228 Claims. (Cl. 294-81) This invention relates to novel means for grasping, lifting and manipulating steel reinforcing mats.

Steel reinforcing mats are embedded in the concrete are used in airport runways and superhighways weigh in excess of 700 pounds and are frequently 11% by 24 feet in size. Thus it is obvious that if mats such as those are to be manipulated manually, a number of men are necessary to handle them. And of course manual manipulation is necessarily slow and expensive.

The invention to be described herein obviates the necessity of having a large number of men available to remove reinforcing mats from trucks and other vehicles andto place them in their desired positions with respect to the ground base of concrete floors, roads and runways. It renders manipulation and handling of mats an easy,

inexpensive and rapid operation and enables a single operator to remove large mats from trucks and stacks and to place them in desired locations. It facilitates the positive removal of a single mat from stacks of such mats.

This invention contemplates the use of a lifting device suspendible from an overhead carriage such as a crane. The lifting device includes a plurality of depending individual gripping units each of which is adapted to grasp selectively a predetermined number of reinforcing mats at locations spaced from each other so that the predetermined number of mats may be lifted from a stack, may be suspended by the lifting device through the intermediary means of the gripping units, and may be moved to a desired location, at which time the individual gripper units are adapted to release the mats selectively grasped.

Therefore it is a principal object of this invention to provide novel means for manipulating steel reinforcing mats.

It is a further object of this invention to provide a novel lifting device suspendible from an overhead carriage means, said lifting device including a plurality of novel gripping units which are adapted to grip a reinforcing mat at a plurality of spaced locations so that the mat may be elevated and moved thereby.

A still further object is to provide a novel gripping device for gripping, holding and facilitating manipulationof steel reinforcing mats.

Further objects, advantages and purposes of this invention will become apparent from the following description and drawings of which:

FIGURE 1 is a perspective view of one embodiment of the lifting device of this invention; m

FIG. 2 is a plan view of the lifting device of FIG. 1 including certain details not shown in FIG. 1;

FIG. 3 is a side elevation of the lifting device of FIG. 2;

FIG. 4 is-an-enlarged side elevation of stop means taken substantially along the line 4-4 of FIG. 3;

FIG. 5 is an enlarged side elevation of one of the gripper: units of FIG. 1;

FIG. 6 is a front elevational view of the gripper unit of FIG. 5 looking at the unit from the right side of FIG. 5;

FIG. 7 is a detailed'view of the gripper unit of FIG. 5

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having one of the frame plates removed and showing the gripper unit adjacent a stack of reinforcing mats;

FIG. 8 shows the gripper unit of FIG. 7 in a mat gripping relationship to a stack of mats;

FIG. 9 shows the lifting device of FIGS. 2 and 3 in mat gripping relationship to a stack of reinforcing mats;

FIG. 10 shows the lifting device of FIG. 9 after it has removed a mat from the stack of mats;

FIG. 11 is a partial side elevational view of a modified suspension means for the individual gripper units; and

FIG. 12 is a partial plan view of the modification of FIG. 11.

Referring first to FIGURES 1 to 3 particularly, the lifting device 10 of this invention is seen to comprise a plurality of individual gripper units 12 mounted on frame 14 for gripping and lifting a reinforcing mat M. Mat M comprises spaced parallel longitudinal rods L and spaced parallel connecting rods C disposed perpendicular to rods L. Frame 14 includes a rectangular frame portion made up of sectional longitudinal frame members 16 joined by frame expansion members 18 connected to the longitudinal frame members by nuts and bolts Ztl which pass through suitable holes in members 16 and 18. The frame 14 also includes transverse frame members 24 and central reinforcing ribs 26. All of the frame members and the central reinforcing ribs may be of standard angle stock.

A central upstanding support column 28 is welded to the central reinforcing ribs. Tension reinforcing rods 30 are attached adjacent the top of column 28 by nuts and bolts 31. At their other ends tension rods 30 are attached near the ends of longitudinal frame members 16 by nuts and bolts 31. A pivotally mounted support hook 32 is located at the top of central support column 28. Support hook 32 is adapted to be engaged by a depending hook 34 which is suspended from a hoist line 36. The overhead carriage from which the hoist line depends is not shown.

Attached adjacent the center of one of the transverse frame members is a dragline eye-bolt 38. Dragl-ine eyebolt 38 is adapted to be engaged by a dragline hook 40 which in turn is connected to a dragline D also operable from the overhead carriage (not shown). Manipulation of the draglin-e enables more accurate angular orientation of lifting device it Each of the gripper units 12 is connected to the longitudinal frame members 15 by flexible connector members 42 which are attached thereto by nuts and bolts 44 which pass through suitable holes in longitudinal frame members 16.

As best seen in FIGS. 2 to 4-, each end of each of the transverse frame members 24 is provided with a bracket 46. Brackets 46 are attached to transverse frame members 24 by nuts and bolts 4-8 which pass through both the brackets and the frame members 24. Brackets 46 are proportioned and adapted to slidingly receive vertical stop members 50. Vertical stop members 5d are provided with a plurality of vertically spaced holes 52 for a purpose to be described. Nut and bolt means 54 which pass through frame members 24, brackets 46 and holes 52 serve to lock vertical stop members 5% to brackets 46 and thus maintain them in a fixed predetermined vertical relationship with respect to transverse frame members 24.

FIGURES 5 to 8 inclusive, show gripper units 12 in greater detail. Gripper units 12 include frame plates 6t) which terminate at their lower edges in outwardly extending flange portions 62 having slightly upwardly tapered forward and rearward edges. Frame plates 6% are maintained in a fixed predetermined parallel relati0nship by suitable spacing elements. 7

One of those spacing elements is upper pivot rod 64 reduced diameter end portions of which pass through vertically elongated openings in frame plates 69. The reduced diameter end portions are threaded. The elongated openings in frame plates 6% are sufficiently narrow so that only the reduced diameter portion may pass therethrough. Thus when bolts 65 are tightened on the threaded portions of the rod 64, frame plates 6% are immovably held between the shoulders of the larger diameter portion, that is the central portion, of rod 6 and bolts 65. Slidably mounted on upper pivot rod 6 are upper pivot rod sleeves 66 which serve to center, orient and minimize lateral movement of the gripper elements and the upper pivot arm, about which members more will be said.

Another of the spacing elements for maintaining frame plates 66 in their desired parallel orientation is lower pivot rod 68. Threaded reduced diameter ends of lower pivot rod also pass through elongated vertical openings in frame plates 643, bolts 69 serving to interconnect frame plates 69 in the same manner as described in connection with bolts 65. Sleeves similar to sleeves 66 may also be provided on lower pivot rod 68.

Frame plates 69 are adapted to support a solenoid between them. Mounting angles 76 are connected to frame plates 6% by bolts 72., and solenoid S is bolted to the mounting angles by bolts 73. Bolts 72 pass through vertical slots in plates 68 which permits a degree of vertical adjustment of solenoid S. When bolted securely, solenoid S and angles 7% also assist in spacing frame plates 60.

Solenoid S comprises a winding 74, a U-shaped magnetically permeable frame 76 which is constructed of a plurality of U-shaped stampings 'ffi held together by rivets (not shown), and a T-shaped plunger 84) assembled from a plurality of T shapcd stamp-ings held together by rivets (not shown). T-shaped plunger 89 includes a plunge-r section 82 and a head section 84. Conductors 86 leading to the winding 74 are connected to a suitable source of electrical current to operate solenoid S.

A first generally U-shaped pivot strap 90 is mounted to oscillate on lower pivot rod 68. Pivot strap 90 is connected by nuts and bolts 92. to a first gripper element 94.

On the upper pivot rod and between the upper pivot trod sleeves 66, there is oscillatably mounted an upper pivot arm 96. A second generally Uashaped pivot strap 98 is pivotally connected to the lower end of upper pivot arm 96 by a pivot pin 9%. Pivot strap 93 is connected by nuts and bolts 1% to a second gripper element 102. Gripper elements 94 and 162 are pivo-tally interconnected in their central regions by a hinge 1%. The arms of hinge 194 are welded to gripper elements 94 and 162.

Upper pivot $6 is provided with a vertically elongated slot 166 through which passes a solenoid plunger bolt 1%. Solenoid plunger bolt 1% is threading-1y received in head section 84 of plunger 89. Adjacent its enlarged end, plunger bolt 1538 contacts a washer 119 against which. bears one end of plunger compression spring 112. The other end bears against upper pivot arm 96 adjacent slot 166.

First and second gripper elements 94 and 102 are provided with axially spaced enlarged openings 114 and 116. Through these openings a compression bolt 118 passes. Concentricaliy mounted on bolt 113 are two gripper element compression springs 12%, two gripper washers 122 and finally compression bolt nut 124 which is threadingly received by bolt 1113. Nut 124 can be utilized to adjust the pressure exerted by springs 126. Gripper elements 94 and 102 terminate at their lower ends in hooks 126 and 123 having arcua te feet 13% and 132 respectively.

Flexible connectors 42 consist of chain links 134, and are attached to gripper units 12 by nut and bolt means 136.

FIGS. 11 and 12 show a modified means for supporting the gripper units of this invention from a frame mem- 4 ber 20% which might be one of the longitudinal frame embers 16 of FIG. 1.

A support bar 262 disposed normal to frame member iii-ll is welded thereto. Flexible connectors 2594 consisting of a plurality of chain links 266 are connected to frame member 266 and support bar 202 by nuts and bolts 2%. Connector plates 210 are welded to the upper edges of frame plates 2.12 of the gripper unit. Frame plates 212 terminate at their lower edges in flanges 214 having slightly tapered forward and rearward edges. Nuts and bolts 216 connect two of the flexible connectors 294 to connector plates 21! and nuts and bolts 218 connect frame plates 212 of gripper unit to the other two flexible connectors 204.

Operation The invention herein is adapted to handle reinforcing mats of varying lengths, widths and meshes. Thus, the frame 14 of FIG. 1 has been shown to be expandible in length by making use of expansion members 18 of different lengths. If for any reason it is necessary to increase the effective length of sectional longitudinal frame members 16, expansion members 18 may be removed and expansion members of greater lengths may be inserted. If that is done it will become necessary to increase the effective length of tension rods 30 also and to accomplish that, new tension rods of greater lengths may be substituted for the old. Of course it is possible to increase the effective length of tension rods 30 by severing them and inserting an expansion member in a manner similar to that shown for increasing the length of longitudinal frame members 16. It is to be understood, although -it is not shown, that the transverse frame members 24 as well as ribs 26 may he sectional to allow for increases in the width of frame 14.

The distance the gripper units are spaced apart may also be varied, if desired, consistent with the size of the mats to be handled, by providing additional holes in longi-tudinal frame members 16 through which gripper unit connecting nuts and bolts 44 may be attached to the ion-- gitudinal frame members.

All adjustments should take into consideration the fact that lifting device 10, when elevated, should lie in a generally horizontal plane.

The lifting device 10 of this invention may have a frame 7 by 17 feet which is a convenient size for handling reinforcing mats 11 /2 x 24 feet when the gripper units are spaced on seven foot centers. The mats M illustrated are of that size and are constructed of /2 steel longitudinal rods L spaced on three inch centers and are welded into a mesh by 7 steel connector rods C spaced on twelve inch centers.

When the frame and the gripper units have been ar-- ranged to handle mats" of the size to be manipulated, a crane or other suitable overhead support means is caused to engage support book 32, to elevate lifting device 10 thereby, and then to move the lifting device until it overhangs the mats. It is then lowered until each of the gripper units engages the top reinforcing mat of a stack of reinforcing mats. To mtaintainthe proper angular orientation, in a horizontal plane, of the lifting device, dragline D is connected to frame 14 by eyebolt 38 and dragline book 40. The dragline may be connected to and manipulatable from the overhead support means.

FIGURE 9 illustrates the lifting device in juxtaposition to a bowed stack of rnats which has been brought to the construction site on a truck T. Shown are the gripper units 12 in contact with the top mat. It should be observed that vertical stop members 50 are also in engagement with the top mat. The function of the vertical stop members 50 is to prevent frame 14 from descending far enough to allow the longitudinal frame members 16 to contact the tops of gripper unit frame plates 60. As best seen. in FIG. 4, vertical stop members 50 have taperedlower ends and are sufliciently wide so that they will not pass between longitudinal rods L when lowered into engagement with the mats, thereby preventing frame 14 from descending too far. The downward extent of stop members 50 will depend in large measure upon the length of flexible connectors 42 and the vertical extent of gripper units 12 and may be adjusted by making use of the holes 52 provided in stop member 50.

A study of FIG. 9 particularly will show why flexible connectors 42 are used. Since mats M very frequently are stacked in other than a true planar orientation, such as in the bowed configuration shown in FIGS. 9 and 10, or in other than a true horizontal plane, a certain degree of flexibility in the lifting device is desirable. For that reason flexible connectors 42 comprising links 134 are used, although it is apparent that cables or other means affording similar flexibility may be utilized. Although the flexible connectors 42 of FIG. 9 are all of the same length (see FIG. 10), certain of their effective lengths as seen in FIG. 9 vary. Thus, the flexible connectors 42 of the centermost gripper units are shown to have the shortest effective length, that is, the gripper units supported by them are closest to the frame 14. Also, the outermost flexible connectors of the outside gripper units have a somewhat greater effective length than the inside flexible connectors of the same gripper units, that is, the upper edge of the outermost frame plate 60 of the outside gripper-units is farther from the frame than is the upper edge of the innermost frame plate.

Referring now to FIG. 7, it will be observed that the feet 130 and 13,2 of hooks 126 and 128 are arcuate. That shape is provided so that if the hooks of a gripper unit descend into contact with a longitudinal rod L of mat M the hooks will be self-orienting. That is, they will tend to slide to one side or the other and as such will not remain on dead center. And too, as best seen in FIGS. 7 and 8, the frame plate flanges 62 are long enough to lie across several longitudinal rods L thereby acting as a self-stabilizing base on which the gripper units 12 will be seated on mats M. The upwardly tapered forward and rearward edges of frame plate flanges 62 facilitate smoothness and ease of seating of the gripper units 12.

When suitably seated on the mats, gripper units 12 are ready to be activated and caused to be moved from an inactive closed position shown in FIGS. 5 to 7 to the active open mat. gripping position of FIG. 8. As is seen in FIGS. 5 to 7, compression springs 120 normally maintain hooks 126 and 128 of gripper elements 94 and 102 in a closed adjacent inactive position.

When solenoid S is actuated plunger section 82 of T- shaped plunger 80 is drawn inwardly of winding 74 until head section 84 of plunger 80 stops that motion. As seen in FIG. 8, when plunger 80 moves to the left, upper pivot arm 96 moves in a clockwise direction pivoting on pivot rod 64. Sleeves 66 orient pivot arm 96, hence gripper elements 94 and 162, and prevent any substantial movement of pivot arm 96 axially of pivot rod 64. When pivot arm 96 moves in a clockwise direction that causes gripper elements 94 and 102 to pivot about lower pivot rod 68, pivot pin 99 and hinge 104, and forces hooks 126 and 128 downwardly and apart against the forces exerted by compression springs 120. Spring 112 serves to maintain positively the upper pivot arm 96 in either the inactive position of FIG. 7 or the active position of FIG. 8.

When in the active mat gripping position of FIG. 8, hooks 126 and 128 extend below the bottom surface of frame plate flanges 62 a distance sufficient to engage the longitudinal rods L of the top rnat but insufficient to grasp more than a single mat. That is accomplished by properly proportioning the various parts of the gripper units. It is to be noted that a certain degree of adjustment in the extent to which the hooks will move downwardly below frame plate flanges 62 is possible. The elongated vertical openings through which upper and lower pivot rods 64 and 68 extend permits upward and downward movement of the gripper elements 94 and 102. If such an adjustment is to be made it may also be necessary to adjust solenoid S vertically by moving mounting angles 70 either up or down. Very slight vertical adjustments in pivot rods 64 and 68 may not require movement of mounting angles 70 because of elongated vertical slot 106 in upper pivot arm 94. The provision of structure for effectuating vertical adjustment means that mats M having longitudinal or connecting rods of different diameters may be conveniently handled by the same gripping units and that any tendency of the gripper elements to bind in contacting the mats because the clearance is insufiicient may be compensated for.

It is to be noted that the vertical plane in which the axis of hinge 1G4- lies changes between the closed position of FIG. 7 andthe active mat gripping position of FIG. 8. To accomplish the desired gripping it may be necessary for the whole gripper unit 12 to be displaced slightly so that the axis of the hinge 104 can be oriented properly between the vertical planes in which lie the axes of the longitudinal rods L grasped. The flexible connectors 42, in addition to the earlier-mentioned functions, also serve to permit anysuch minor movement of the gripper units, as well as such other minor movements which might be necessary.

'A solenoid S is provided for each gripper unit. While each may be operated individually, it is preferable that they be operable simultaneously and remotely, such as from the cab of the overhead support device or crane from which hoist line 36 and dragline D are also operated. Electrical conductors 86 which carry the current to each solenoid winding 74 may be disposed adjacent flexible connectors 42, frame members 16 and 18, and 24, and then may be led up column 28 along hoist line 36, or instead may lie adjacent dragline D, thence to a suitable source of power 150 (see FIG. 7). Power source 150 is adapted to operate all of the solenoids S simultaneously by supplying current to all of them through conductors 86 simultaneously. Suitable switches are provided.

Once the solenoids S of gripper units 12 have been actuated and each of the gripper units has assumed the mat gripping disposition of FIG. 8, the lifting device may be elevated from the position shown in FIG. 9 to that of FIG. 10 wherein the mat lies in a substantially horizontal plane. Thus disposed, the mat may be moved by the overhead carriage means to the location where the mat is to be utilized, such as in the roadway, runway or the like, be placed in position, and then be released by deenergizing the solenoids. When de-energization occurs springs cause gripper elements 94 and 102 to return to the closed inactive position of FIGS. 5 to 7, thereby releasing the mat. The lifting device 11 may then be elevated and returned to grip and remove another mat M from a stack of mats.

As a safety feature, gripper units 12 may be constructed so that if de-energization of the solenoids S occurs while the mats gripped are suspended in the air, the mats will not be released. As seen in FIG. 8, when in mat gripping position, hooks 126 and 128 cradle the gripped longitudinal bars L. The compressive strength of springs 120 may be so regulated that the weight of mat M, when suspended from frame 14 by gripper units 12, is insufl'icient to overcome the efforts of the springs to cause gripper elements 94 and 192 to close. However, when all or a portion of the weight of the mat is removed from hooks 126 and 128, such as when the mat is lowered to the ground or into position in the roadway or the like, springs 120 will once again cause the gripper elements to close.

The modification of FIGS. 11 and 12 illustrates means for providing a more stable flexible connector system where such is found to be desirable. However, for general use it is contemplated that the two member flexible connector system illustrated in FIGS. 1 to 10 should provide ample stability and flexibility.

I do not intend to be limited to the embodiments disclosed and described herein, except insofar as may be necessary in view of the appended claims.

I claim:

1. In combination with at least one generally rectangular reinforcing mat comprised of a first plurality of spaced parallel coplanar elongated rods and a second plurality of spaced parallel coplanar elongated rods disposed at an angle to and interconnected with said first plurality of rods, said first and second plurality of rods defining an open meshwork comprising a plurality of openings, a device for lifting and suspending a predetermined number of said reinforcing mats at a plurality of widely spaced openings in said meshwork, said device comprising an enlarged :frame including means for suspending said frame from an overhead support structure, a plurality of gripper units suspended from said frame and disposed at said plurality of widely spaced openings in said meshwork, each of said gripper units including a housing, gripping means extending downwardly from said housing and into one of said widelly spaced openings in said rneshwork and means for moving said gripping means between an active rod supporting position to support and suspend said predetermined number of mats and an inactive position in which said gripping means do not support said predetermined number of mats, each of said gripper unit housings including means for seating and stabilizing said gripper unit upon the rods of a mat in said inactive position and being proportioned, together with said gripping means, to provide supporting engagement of said rods at one of said plurality of widely spaced openings in said meshwork by said gripping means to grip for suspension and support said predetermined number of mats.

2. The combination of claim 1 wherein said frame ineludes means connected thereto which limits the extent to which said frame may be moved downwardly from said overhead support structure into contact with a reinforcing mat.

3. The combination of claim 1 wherein each of said gripper units is independently suspended from said enlarged frame by flexible connector means and wherein each of said gripping means includes a pair of pivotally mounted gripper elements, the means for moving said gripping means of each of said gripper units being simultaneously actuatable.

4. Thecombination of claim 1 wherein each of said gripping means comprises a pair of hook elements, and

wherein said means for moving said gripping means to said active rod supporting position comprises a separate solenoid means in each of said gripper units, said hook elements being proportioned to maintain gripping contact with said mat when said mat is suspended therefrom and when said solenoids are de energized.

5. The combination of claim 1 wherein each of said gripper units is suspended from said frame by connector means comprising a pair of flexible connector elements connected at one end to said frame and at the other end to said gripper unit housings.

References Cited by the Examiner UNITED STATES PATENTS 3,064,855 11/62 Fischer 294-97 X 3,075,800 1/63 Rowekamp 294-88 3,078,115 2/63 Harlander 294-67 3,090,502 5/63 Gunzeirnann 294-63 X SAMUEL F. COLEMAN, Primary Examiner.

ANDRES H. NIELSEN, Examiner.

Claims (1)

1. IN COMBINATION WITH AT LEAST ONE GENERALLY RECTANGULAR REINFORCING MAT COMPRISING OF A FIRST PLURALITY OF SPACED PARALLEL COPLANAR ELONGATED RODS AND A SECOND PLURALITY OF SPACED PARALLEL COPLANAR ELONGATED RODS DISPOSED AT AN ANGLE TO AND INTERCONNECTED WITH SAID FIRST PLURALITY OF RODS, SAID FIRST AND SECOND PLURALITY OF RODS DEFINING AN OPEN MESHWORK COMPRISING A PLURALITY OF OPENINGS, A DEVICE FOR LIFTING AND SUSPENDING A PREDETERMINED NUMBER OF SAID REINFORCING MATS AT A PLURALITY OF WIDELY SPACED OPENINGS IN SAID MESHWORK, SAID DEVICE COMPRISING AN ENLARGED FRAME INCLUDING MEANS FOR SUSPENDING SAID FRAME FROM AN OVERHEAD SUPPORT STRUCTURE, A PLURALITY OF GRIPPER UNITS SUSPENDED FROM SAID FRAME AND DISPOSED AT SAID PLURALITY OF WIDELY SPACED OPENINGS IN SAID MESHWORK, EACH OF SAID GRIPPER UNITS INCLUDING A HOUSING, GRIPPING MEANS EXTENDING DOWNWARDLY FROM SAID HOUSING AND INTO ONE OF SAID WIDELY SPACED OPENINGS IN SAID MESHWORK AND MEANS FOR MOVING SAID GRIPPING MEANS BETWEEN AN ACTIVE ROD SUPPORTING POSITION TO SUPPORT AND SUSPEND SAID PREDETERMINED NUMBER OF MATS AND AN INACTIVE POSITION IN WHICH SAID GRIPPING MEANS DO NOT SUPPORT SAID PREDETERMINED NUMBER OF MATS, EACH OF SAID GRIPPER UNIT HOUSINGS INCLUDING MEANS FOR SEATING AND STABILIZING SAID GRIPPER UNIT UPON THE RODS OF A MAT IN SAID INACTIVE POSITION AND BEING PROPORTIONED, TOGETHER WITH SAID GRIPPING MEANS, TO PROVIDE SUPPORTING ENGAGEMENT OF SAID RODS AT ONE OF SAID PLURALITY OF WIDELY SPACED OPENINGS IN SAID MESHWORK BY SAID GRIPPING MEANS TO GRIP FOR SUSPENSION AND SUPPORT SAID PREDETERMINED NUMBER OF MATS.

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