US3262517A

US3262517A - Bridge crane

Info

Publication number: US3262517A
Application number: US412000A
Authority: US
Inventors: Jerry P Malec
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-11-18
Filing date: 1964-11-18
Publication date: 1966-07-26
Anticipated expiration: 1983-07-26

Description

July 26, 1966 J. P. MALEC 3,262,517

BRIDGE CRANE Filed Nov. 18, 1964 4 Sheets-Sheet 1 IN VEN TOR.

J. P. MALEC BRIDGE CRANE July 26, 1966 4 Sheets-Sheet 2 Filed NOV. 18, 1964 INVENTOR. Jiffy 2 MALE! QM v 2% 147' 7" GPA E V6 J. P. MALEC BRIDGE CRANE July 26, 1966 INVENTOR. (/25)??? 1 MfiLL-C Filed Nov. 18, 1964 J. P. MALEC BRIDGE CRANE July 26, 1966 m rs/vroe Jiffy B MfiLfC 5y fi rQwy 4 Sheets-Sheet 4 A770/F/V Filed NOV. 1.8, 1964 United States Patent 3,262,517 BRIDGE CRANE Jerry P. Malec, 2930 N. 84th St., Omaha, Nebr. Filed Nov. 18, 1964, Ser. No. 412,000 Claims. (Cl. 182-2) This invention relates to a crane and in particular to a crane for movably supporting scaffolding.

The machine of this invention has many uses but one of its more important uses is in connection with inspection, repair and general maintenance of bridge-like structures. In a bridge for example, it is extremely difficult to provide a satisfactory working platform under the bridge. Heretofore, some areas under the bridge could not even be reached with conventional scaffolding equipment. It is important that the scaffolding equipment be easily moved from one position to another as is required in painting or sandblasting the under side of a bridge construction. The bridge scaffolding must be compact so that it may be moved on the streets and highways between work locations. Scaffolding equipment available heretoforehas not had these capabilities and therefore has been less than satisfactory.

Accordingly, it is one of the principal objects of this invention to provide a supporting means which may be readily positioned as desired to give access to out of the way hard to reach work areas on bridges or the like.

A related object of this invention is to provide a scaffolding construction which may be positioned directly under its supporting surface such as on a bridge.

Another object of this invention is to provide a supporting means for scaffolding which may be collapsed to form a compact unit which may be easily moved from one work location to another.

A still further object of this invention is to provide a scaffolding unit which is carried by a boom mounted on a truck wherein all components of the machine are interconnected during storage and during use thereby eliminating the need to assemble and disassemble the machine.

A still further object of this invention is to provide a bridge crane which carries a scaffolding platform which is accessible by use of an automatically extendable ladder connected to a boom on the crane wherein the boom may be readily moved to adjacent a landing for the workmen to reach the ladder.

Another object of this invention is to provide a crane having hydraulically operated components wherein the hydraulic'cables are maintained in a taut condition at all times regardless of the length of the boom being used.

A still further object of this invention is to provide a scaffolding platform for a bridge crane wherein the truss for the scaffolding is positioned on the lower side to thus eliminate any interference with the under structure of the bridge or the like.

A related object of this invention is to provide a scaffolding platform having selectively adjustable rail sections extending along the sides thereof.

Another object of this invention relating to the scaffolding platform is to provide a platform having means for receiving the rail sections which also may be used to receive the base end of a ladder.

Another object of this invention relating to the bridge scoffolding is to provide a platform on which a basket may be mounted at the outer end of the platform to reach remote inaccessible work areas.

Another object of this invention is to provide an outrigger which serves as a stabilizer assembly for the vehicle when carrying the boom and the scaffolding platform.

An object related to the outrigger or stabilizing unit is to provide a stabilizer unit which may be quickly moved 3 ,262 ,5 l 7 Patented July 26, 1966 into a position of use and retracted into a compact position on the vehicle.

Another related object to the stabilizing unit is that the stabilizing unit having the capability of maintaining the vehicle and thus the scaffolding platform at a constant elevation at all times as it is moved along the bridge or the like.

Thus another object of this invention is to provide a stabilizer unit for a vehicle which is responsive only to the general changes in contour of the roadbed rather than small indentations or projections.

Related to this object is the object that the stabilizer unit will incline from a vertical stabilizing or supporting position to accommodate the crown or high center construction found on most bridges.

Another related object to provide -a stabilizer unit which i has means to prevent its unintended forward or rearward movement relative to the vehicle.

A still further object of this invention is to provide a scaffolding platform or the like which is pivotally connected to the outer end of a crane boom wherein the scaffolding may be moved to a vertical position to permit dropping it through an arc to allow passage of the supporting means such as a truck around peers or pillars without moving either of the booms.

A further object of this invention is to provide a bridge crane which is simple in design, economical to manufacture and refined in appearance.

These and other objects will be apparent to those skilled in the art.

This invention consists in the construction, arrangements, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated in the accompanying drawings, in which:

FIG. 1 is a front elevation view of the bridge crane illustrating in particular two of an infinite number of positions to which the boom and the scaffolding platform may be moved;

FIG. 2 is a side elevation view of the bridge crane vehicle with the booms and scaffolding unit folded into the collapsed position on the vehicle for transporting and further illustrating the alternate positions during use and transporting for the stabilizer unit;

FIG. 3 is a perspective view showing only the scaffolding platform;

FIG. 4 is a fragmentary elevation view taken along line 4-4 in FIG. 3;

FIG. 5 is a fragmentary perspective view enlarged to show the adjustable fastener stop on a leg of a rail on the scaffolding platform;

FIG. 6 is a fragmentary perspective view of the outer end of the scaffolding platform being used to carry both a ladder and a basket;

FIG. 7 is a fragmentary elevational view from the forward end of the vehicle illustrating the stabilizer or outrigger unit taken along line 77 in FIG. 8;

FIG. 8 is a fragmentary elevational view taken at right angles to the view of FIG. 7 of the stabilizer unit;

FIG. 9 is a plan view taken along line 9-9 of FIG. 1 showing the extendable boom having the extendable ladder mounted thereon;

FIG. 10 is an elevational cross-sectional view taken along line 10-10 in FIG. 9 illustrating the supporting guide bracket connecting together the extendable sections of the ladder unit;

FIG. 11 is an elevational cross-sectional view taken along line 11-11 in FIG. 9;

FIG. 12 is an elevational view taken at right angles to the view of FIG. 11;

FIG. 13 is an exploded perspective view of the outer end of the stabilizer arm and the universal mounting bracket for connecting to the tandem wheel assembly;

FIG. 14 is a fragmentary perspective view of the extendable boom having the extendable ladders mounted thereon; and

FIG. 15 is a cross-sectional view of one of the spring loaded hydraulic hose reels carried on the extendable boom.

The bridge crane illustrated in the drawings is referred to generally in FIG. 1 by the reference numeral and is shown positioned on a bridge 12 having a railing 14 and under strengthening structure 14.

Referring to the bridge crane generally, a vehicle 16 is provided which carries on a rotatable vertical post 18 a pair of interconnected

boom sections

20 and 22. At the outer free end of the boom section 22 which is extendable a scaffolding platform 24 is mov-ably mounted. To maintain the truck and the scaffolding platform 24 at a constant elevation, a side rigger or stabilizer unit 26 is mounted on each side of the truck 16. To eliminate any slack in the hydraulic hoses, a spring loaded hose reel 28 is provided on the boom structure 22.

The vertical post 18 on which the boom 20 is mounted is rotatably positioned on the bed of the truck 16 and is operated by the cable assembly 30. A two-way hydraulically operated power cylinder 32 interconnects the boom 20 to a post mounting structure 34 which also is connected to the inner end of the boom 20. The outer boom 22 is connected inwardly of its inner end to the outer end 36 of the boom 20 and has its inner end connected to the piston of a two-way operated hydraulic power cylinder 38. The other end of the hydraulic cylinder 38 is connected to the boom 29 intermediate its ends.

The outer boom 22 includes an inner telescopic section 40 which receives an outer mating section 42. To extend and retract the

telescopic sections

40 and 42, a two-way operated cylinder 44 is mounted within the boom 22 and has its cylinder connected to the inner section 40 while the piston rod 46 is connected to the outer boom section 42.

An extend-able ladder assembly 48 is carried on the side of the extendable boom 22 as illustrated in FIG. 14. The ladder assembly includes overlapping or

telescoping sections

50 and 52 connected to the

boom sections

40 and 42 respectively. The connection between the

ladders

50 and 52 to the extendable boom 22 is made by a shaft 54 mounted through a gusset plate 56 to the side of the boom wherein the shaft 54 extends through a hollow rung 58 on the laddder sections as seen in FIGS.

9, 10, ll, 12 and 14. The

ladders

50 and 52 are easily removed from the hafts 54 by removing the key 60 extending through its outer end.

As best illustrated in FIGS. 9 and 10, the

ladders

50 and 52 are maintained in their overlapping telescoping relationship by a guide-supporting bracket 62 fixedly secured by screws or the like to the side channel legs of the ladder 50. As seen in FIG. 9 the brackets 62 are mounted opposite each other on each of the ladder legs. In FIG. 10 the bracket 62 is seen to have one end portion 64 which conforms to the configuration of the ladder leg and has an integral portion 66 extending downwardly and inwardly to provide a channel-like portion 68 for nestingly receiving a leg of the ladder 52. Thus, the ladder 52 is permitted to move longitudinally relative to the ladder 50 but cannot move laterally thereof. Since as seen in FIG. 14 the ladder 52 is connected to the outer boom section 42, the ladder 52 extends simultaneously with the extension of the boom section 42.

Just short of the outer end of the boom 22, a pair of ears 70 are provided for pivotal connection to the scaffolding 24. Outwardly on the outer tip end of the boom 22 a pair of finger elements 72 are provided for connection to a hydraulically operated cylinder 74 having its piston end 76 connected to the truss structure 4 78 provided under the scaffolding platform 24 as seen in FIG. 1.

The scaffolding construction is clearly shown in FIGS. 3, 4, 5 and 6 as well as in FIGS. 1 and 14.

The inner end of the scaffolding platform 24 is provided with an enlarged opening 80 which receives the ears 7:) on the boom section 42 and is connected together by a shaft 82 (FIG. 14) which is received in the sleeves 84 on the scaffolding 24. When the scaffolding 24 is in its normal horizontal position of use as illustrated in FIG. 3, the truss 78 is positioned underneath to thereby provide a completely fiat unobstructed top surface for the scaffolding.

A plurality of sleeve sockets 86 are fastened by weld or the like to the sides of the platform 24 to receive the legs 88 of rail units 90. The rail units 90 are formed of tubular construction and have a plurality of apertures 92 (FIG. 4) formed therein to receive locking pins 94 whereby the rails 90 may be positioned at any desired elevation between a fully vertically extended upwardly position to a completely down position as shown in FIG. 3. The pin elements 94 are adapted to abut against the top peripheral edge of the sleeve socket members 86 as illustrated in FIG. 4. As seen in FIG. 5, the pin 94 has a straight leg portion 96 and an arcuate leg portion 98 which conforms to the arcuate outer surface of the cylindrical leg 88 and therefore the pin 94 may be easily inserted into the hole 92 and removed therefrom by the spring leg 98 moving over the outer face of the leg 88.

If desired, a ladder 1119 may be secured to the platform 24 by positioning its legs 102 in the sockets S6.

Also, at the outer end of the platform 24 a basket 104 may be pivotally mounted on a pair of arms 106 extending outwardly from the channels forming the frame of the platform 24. The members 106 may have any desired length and may be locked in position by bolt elements 108.

As mentioned supra, the hydraulic hose reel 28 as for example shown in FIGS. 2, l4 and 15, serves to maintain the hydraulic hose line 110 in a taut condition. This hose as shown in FIG. 14 extends to the hydraulic cylinder 74 which provides for the pivotal movement of the platform 24 relative to the boom 22. Since the cylinder 74 is a two-way cylinder, it is therefore necessary that a pair of reel assemblies 28 be employed and theyv are each mounted side by side on the bottom side of the boom 22 as shown in FIG. 14 by a bracket 112 which is L-shaped. The bracket 112 is in turn connected to an elongated plate member 114 which is welded or the like to the exterior surface of the boom section 44.

An inlet hose portion 116 is connected to a passageway 118 extending through the hose reel frame 120. A coupling element 122 is rotatably connected to the outer end of the frame member to be in communication with the passageway 118. A hose portion 124 extends'therefrom and is wound around a reel 126 which is mounted on the frame 120 against a bearing unit 123. A snap ring 125 maintains the reel 126 on the frame member 120. In the interior of the reel 126 a conically shaped spring 128 is mounted on the frame member 120 and has one end 130 secured to the reel 126 with the other end 132 held stationary to the frame 120. Thereby, the reel 126 is wound tight against the action of the spring 128 until the desired tension in the hose 110 is obtained and normal extension of the boom section 42 is possible while when retracted the hose 110 is maintained in a tight condition.

The construction of the stabilizer outrigger 26 is very important as it has been found that a small two inch diameter obstruction using a single wheeled outrigger or a rigid double whee-led unit will cause the platform 24 (FIG. 1) to move upwardly several feet as the outrigger wheels pass over the obstruction. The platform tip end may be 64 feet away from the crane mast head 18 when the boom sections are fully extended. The construction of the stabilizer unit as illustrated in FIGS. 7, 8 and 13 in detail eliminates variations in elevational positioning of the platform 24.

An arm 136 is pivotally connected .at one end to the side of the truck bed (FIG. 1). The arm 136 includes a pair of U-shaped channel members 138 which are oriented to face each other and are secured together at their outer ends by a semi circular plate member 140. A pair of hydraulic cylinders 142 extend from the top of the vertical mast head 18 downwardly with their piston rods 144 being movably connected to the arms 136 through a pair of rollers 146 mounted on the cross-bar 148 mounted on the other end of the piston rod 144. Thus as the hydraulic cylinder 142 is extended the rollers 146 move in a track 150 formed by the channel members 138. In the extended position of the cylinder 142 the rollers 146 move to the outer end of the arm 136 and bear against the semi circular plate 140 to maintain the arm 136 in a rigid position. However, when the cylinder 142 is retracted, the arm 136 moves into overlapping relationship relative to the piston rod 144 since the rollers 146 move inwardly in thetrack 150 and accordingly the stab'lizer unit 26 is collapsed to the position shown by the unit on the left hand side of the truck 16 as viewed in FIG. 1.

A sleeve-like element 152 formed of plate metal is welded to the outer lower tip end of the plate member 140 and receives a bolt 154 which also extends through the parallel side walls 156 of a universal joint bracket 158. The universal joint 158 is thus permitted to rotate about a horizontal axis extending transversely of the arm 136. A second pair of ears or walls referred to by the numeral 160 are arranged at 90 degrees thus the opening 162 formed through the walls 160 are at right angles to the longitudinal axis of the plate sleeve 152.

A trolley 164 having a pair of mounting plates 166 are positioned in registering relationship with the ears 160 and are interconnected by a bolt member 168 whereby the tandem trolley 164 is permitted to pivot in two vertical planes each being normal to the other i.e. about the axis of the

bolts

154 and 168.

Stop means is provided to selectively position the tandem trolley 164 in the desired pivotal position about the longitudinal axis of the bolt 154. This means includes the parallel plate walls 156 forming the base portion of the T-shaped member 170 with the inner end thereof terminating in the cross portion 172. As seen in FIG. 7 the cross portion 172 is provided with a series of spaced apart holes 174 for selective registering with a hole in ears 176 formed on the bottom side of the arm 136. A :bolt 178 extends through the pair of cross bars 172 and the ears 176 as seen in FIG. 7. Accordingly, the tandem wheels 180 may be so positioned that their exterior surfaces conform to the incline of the bridge surface. It is seen that if one of the wheels 180 hits an obstruction the displacement thereof will not effect substantially the position of the stabilizing arm 136 since the trolley 164 will pivot about the axis of the opposite wheel 180 and thus tend to glide over the obstructions or depressions in the roadway. The tandem trolley 164 has a frame including a pairof parallel plates 184 which are interconnected at their ends by end plates 186 which in turn have eyelet elements 190 extending outwardly therefrom to receive one end of an anchor chain 192-as seen in FIGS. 1 and 2. The opposite end of the chains 192 extend inwardly towards the frame of the vehicle 16 and are secured thereto and thereby prevent the forward or rearward movement of the outer end of the stabilizer arm 136 relative to the truck 16 should the arm 136 inadvertently hit a post or the like.

Thus it is seen that through the use of the machine of this invention, it is possible to reach practically any remote work area under a bridge or the like as illustrated to the plate walls 156 and' in FIG. 1. Unlimited flexibility is permitted since the boom 20 may move upwardly and downwardly and around in a horizontal plane by its connection to the vertical mast head 18. The second boom 22 may pivot upwardly and downwardly and also be extended and retracted and moreover the platform 24 may be pivoted upwardly and downwardly relative to the boom 22. When it is desired to collapse the

extendible boom

20, 22 and 24 it is only necessary to retract the boom 22 and fully extend the cylinder 74 connected to the platform 24 thereby pivoting it onto the boom 22. The cylinder 38 is also fully extended to thereby collapse the boom 22 underneath the boom 20 as shown in FIG. 2. It is noted that the rails on the platform 24 are conveniently located even in the collapsed position of FIG. 2 as they straddle the

boom members

20 and 22. Regarding the stabilizer assembly 26 it is only necessary to retract the cylinder 142 thereby lifting the tandem wheel trolley 164 to the upward and inward position illustrated in FIGS. 1 and 2.

.When using the basket 104 as illustrated in FIG. 6 it is to be understood that the basket may be placed on the end of a boom section in lieu of the platform of FIG. 3. Thereby, a very versatile crane basket combination is provided which will have all of the flexibility of the crane being rotatable relative to its supporting means and extendible by virtue of the extendible telescopic boom and movable to various other positions by pivoting the boom sections relative to each other or relative to the supporting means. Similarly, the telescoping ladder may be mounted on the side of the telescoping boom section 22 as illustrated in FIG. 14 for use in climbing to the basket 104.

It is to be understood that the machine hereinabove described is not limited'to use on bridges or the like but may be used in any environment where it is desired to reach an otherwise unacces-sible work area.

Some changes may be made in the construction and arrangement of my bridge crane without departing from the real spirit and purpose 'of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim:

1. In a bridgework scaffold device,

a wheel supported vehicle adapted to move on the road surface of a bridge,

a boom structure movably mounted on said vehicle,

said boom structure including only first and second boom sections, with said first boom section being of fixed length and said second boom section being comprised of a first member, and a second member telescopically secured to said first member, whereby the length of said second boom section can be selectively varied,

said first boom section being pivotally connected to said vehicle by one of its ends and being pivotally connected at its outer end to one end of said first member of said second boom section,

a platform structure being movably secured to the outer end of said second member of said second boom section,

power means on said vehicle and said boom structure for independently moving said first boom section with respect to said vehicle; for moving said first member of said second boom section with respect to said first boom section; for moving the second member of said second boom section with respect to the first member thereof to vary the length of said second boom section; and for moving said platform structure with respect to said second member of said second boom section;

said first boom section normally assuming a substan tially horizontal position in its operative condition,

said second boom section normally assuming a sub stantially downwardly vertical position in its operative condition,

said platform structure normally assuming a substantially horizonal position substantially parallel to said first boom section when said platform structure is in its operative condition,

said first boom section and said platform structure normally extending in the same direction away from said second boom section when said boom structure is in its operative condition,

said platform and said first and second boom sections being adapted to be co-extensively folded upon themselves to form a compact package on said vehicle when said boom structure is not in use.

2. The device of claim 1 wherein an access ladder is secured to said second boom section, said ladder being comprised of separate sections telescopically secured together,

3. The device of claim 1 wherein a telescoping ladder means is secured to said second boom section, said ladder means comprising first and second ladder sections secured to said first and second members, respectively, of said second boom section, said ladder sections being telescopically secured to each other.

4. The device of claim 1 wherein a telescoping ladder means is secured to said second boom section, said ladder means comprises a first ladder section secured to said first member of said second boom section and a second ladder section telescopically connected to said first ladder section and connected to said second member of said second boom section, said first and second ladder sections being disposed in spaced parallel lateral relation to said second boom sections.

5. The structure of claim 1 wherein a plurality of shaft elements secured to the side of said first and second members of said second boom section and extending laterally outwardly thereof, a pair of telescopically movable ladder sections having hollow rungs, each of said shaft elements being received in one of said rungs.

6. The device of claim 1 wherein said power means includes a hydraulic power means having a cylinder and a piston interconnecting said platform structure and the second member of said second boom section to selectively pivot the same relative to said second member of said second boom section, a spring wound hose reel mounted on said first member of said second boom section, and at least one hydraulic hose extending from said cylinder and being wound around said reel whereby said hose is maintained in a taut condition by action of said spring tending to reel in said hose as said second member of said second boom section is moved inwardly and outwardly relative to said first member of said second boom section.

7. The device of claim 1 wherein said platform structure has an elongated walkway, said platform structure including a truss assembly to reinforce said walkway, said truss assembly being secured to the under side of said walkway to provide maximum. overhead clearance for said platform means when said walkway is disposed in a horizontal position.

8. The device of claim 1 wherein said power means.

includes means for moving said platform structure between a first position substantially parallel to said second boom section to a second operative position substantially perpendicular to said second boom section.

9. In a bridgework scafiold device, a supporting means adapted to move on the road surface of a bridge, a boom structure movably mounted on said vehicle, said boom structure being comprised of a plurality of movable boom sections, an elongated platform means on the outer end of said boom structure, said platform means having a walkway adapted to be disposed in a horizontal plane at times, said platform means including a truss assembly to reinforce said walkway, said truss assembly being secured to the under side of said walkway to provide maximum overhead clearance for said platform means when said walkway is disposed in a horizontal position, said truss assembly being pivotally connected at a point intermediate the length of said walkway to one end of an extendable power means having its other end pivotally connected to the outer tip end of said boom structure, said walkway having its end adjacent said boom structure pivotally connected thereto at a point inwardly of the tip end of said boom structure whereby said platform may be moved relative to said boom between positions substantially parallel to said boom to positions substantially perpendicular thereto. 10. The structure of claim 9 wherein the outer end of said platform is provided with a pair of outwardly extending arms and a bucket platform is pivotally connected therebetween.

References Cited by the Examiner UNITED STATES PATENTS 423,135 3/1890 Crippen 182-66 2,750,204 6/1956 Ohrmann 280-150 2,732,118 1/1957 Reinhardt 182-113 2,786,723 3/1957 Harsch 182-2 2,788,167 4/1957 Morrison 182-207 2,798,652 7/1957 Easton 182-113 2,907,534 10/1959 Benstein 242-86 3,015,497 1/1962 Aldred 280-150 3,056,510 10/1962 Garnett 182-2 3,072,215 1/1963 Rush 182-2 3,085,648 4/1963 Benedetto 182-2 3,145,801 8/1964 Callahan 182-63 FOREIGN PATENTS 846,399 8/1960 Great Britain.

REINALDO P. MACI-IADO, Primary Examiner.

Claims

9. IN A BRIDGEWORK SCAFFOLD DEVICE, A SUPPORTING MEANS ADAPTED TO MOVE ON THE ROAD SURFACE OF A BRIDGE, A BOOM STRUCTURE MOVABLY MOUNTED ON SAID VEHICLES, SAID BOOM STRUCTURE BEING COMPRISED OF A PLURALITY OF MOVABLE BOOM SECTIONS, AN ELONGATED PLATFORM MEANS ON THE OUTER END OF SAID BOOM STRUCTURE, SAID PLATFORM MEANS HAVING A WALKWAY ADAPTED TO BE DISPOSED IN A HORIZONTAL PLANE AT TIMES, SAID PLATFORM MEANS INCLUDING A TRUSS ASSEMBLY TO REINFORCE SAID WALKWAY, SAID TRUSS ASSEMBLY BEING SECURED TO THE UNDER SIDE OF SAID WALKWAY TO PROVIDE MAXIMUM OVERHEAD CLEARANCE FOR SAID PLATFORM MEANS WHEN SAID WALKWAY IS DISPOSED IN A HORIZONTAL POSITION, SAID TRUSS ASSEMBLY BEING PIVOTALLY CONNECTED AT A POINT INTERMEDIATE THE LENGTH OF SAISD WALKWAY TO ONE END OF AN EXTENDABLE POWER MEANS HAVING ITS OTHER END PIVOTALLY CONNECTED TO THE OUTER TIP END OF SAID BOOM STRUCTURE, SAID WALKWAY HAVING ITS END ADJACENT SAID BOOM STRUCTURE PIVOTALLY CONNECTED THERETO AT A POINT INWARDLY OF THE TIP END OF SAID BOOM STRUCTURE WHEREBY SAID PLATFORM MAY BE MOVED RELATIVE TO SAID BOOM BETWEEN POSITIONS SUBSTANTIALLY PARALLEL TO SAID BOOM TO POSITIONS SUBSTANTIALLY PERPENDICULAR THERETO.