US3467217A - Aerial platform unit - Google Patents

Description

Sept. 16, 1969 D. H. zwlGHT AERIAL PLATFORM UNIT 5 Sheets-Sheet 1 Filed April 26. 19e? D. H. ZWIGHT AERIAL PLATFORM UNIT Sept. 16, 1969 DAME ZwlGHT BY I AT ORNE-Y Sept. 16, 1969 n. H. zwlGH'r AERIAL PLATFORM UNIT 5 Sheets-Sheet I5 Filed April 26, 1967 INVENTOR DANIEL ZWIGHT BY M ATTORNEY Sept. 16, 1969 n. H. zwIGHT I 3,467,211

AERIAL PLATFORM UNIT Filed April 26, 1967 5 Sheets-Sheet 4 BY @L ATTOR N EY Sept. 16, 1969 D. H. zwlGH'r AERIAL PLATFORM UNIT Filed April 26, 19.67

5 Sheets-Sheet s INVENTOR DANIEL H. ZwlGHT ATTORN EY United States Patent O U.S. Cl. 182-2 17 Claims ABSTRACT F THE DISCLOSURE An aerial platform unit includes a mast, a beam assembly including upper, intermediate, and lower beams telescopically mounted with respect to one another and supporting a basket at their upper ends; extension means interconnecting the lower and intermediate beams and having an extensible member adapted to move from a retracted position to an extended position; and connecting means interconnecting the upper and lower beams. The connecting means is responsive to the movement of the extensible member to cause the upper beam to move with respect to the lower beam a distance greater than tht extensible movement of the extensible member. A take-up reel assembly is located near the end of the lower beam and has a fluid conduit coiled around it. Leveling cylinders are connected to the mast, beams and basket for maintaining the basket level irrespective of the angular disposition of the beam assembly.

This invention relates in general to aerial platforms and, more particularly, to an aerial platform unit which employs telescopically mounted beams to carry a mansupporting platform aloft.

Many industrial organizations such as public utilities, which find it necessary to service overhead power lines, street fixtures, pole-mounted transformers, and the like, have found so-called aerial platform units ideally suited mast mounted on the bed of a truck and beams extending for their needs. These units generally employ a rotatable outwardly from the mast for supporting a basket-like work platform. Two dierent principles are utilized to operatively connect the beams so that the distance between the platform and mast can be varied at the option of the operator on the platform. One type of unit employs articulated beams, while in the other the beams are telescopically mounted with respect to one another. The latter type of unit is generally less expensive than the former and requires less skill to operate.

Telescopic beam units of current manufacture basically employ an inner beam journaled at one end in the mast, an outer or extensible beam telescopically tted Within the inner beam, and a hydraulic cylinder directly interconnecting the two. Consequently, the amount of extension of the outer beam is necessarily limited to the length of the stroke of the cylinder and this fact imposes a severe limitation on the usefulness of such aerial platform units. Moreover, to achieve maximum extension, either the piston rod or Ibarrel of the cylinder must be carried within the confines of the outer :beam and consequently the outer end of such a component is always located in close proximity to the basket-like work platform. As a result, such units are not safe for use around high voltage power lines for the danger of arcs spanning the short distance between the grounded cylinder and the basket is always present.

Inasmuch as aerial platform units are operated primarily from the platform itself a number of hydraulic fluid lines extend from the mast through the beams to the controls at the platform. Heretofore, these lines r' 3,467,217 Ice Patented Sept. 16, 1969 have been contained within a housing in a somewhat serpentine configuration when the upper beam is in its retracted position so that a suflicient length of hose is present as the beam extends. As a result of the extreme liextures associated with this type of hose containment, the hoses often unduly wear, rupture, and become entangled.

Whereas articulated beam units ideally lend themselves to parallel linkage arrangements for the purpose of maintaining the platform level irrespective of the angular positions of the beams, these linkages are not practical for use with telescopically mounted beams. Consequently, considerable diliiculty has been encountered in providing adequate leveling means for the ybaskets on such units. Heretofore, pairs of interconnected hydraulic cylinders connected to the mast and inner beam and to the outer beam and basket have been utilized to achieve this end. However, in time, the lines connecting the cylinders as well as the cylinders themselves leak slightly and this results in so-called free motion at the basket, that is the platform is unrestrained for a limited arcuate distance. The effects of thermal expansion and contraction further aggrevate this condition.

Among the several objects of the present invention may be noted the provision of an aerial platform unit which may be mounted on a truck or other mobile-platform; the provision of an aerial platform unit which is capable of vertical and horizontal swinging movement as well as extensible movement; the provision of an aerial platform unit which utilizes telescopic beams actuated by a hydaulic cylinder in such a manner that the relative movement of the beams is longer than the stroke of the cylinder; the provision of an aerial platform unit in which the hydraulic control lines are subject to relatively little fiexture and wear. thereby prolonging their life; the provision of an aerial platform unit wherein there is no free motion in the basket; the provision of an aerial platfom unit which is safe for use around high voltage power transmission lines; and the provision of an aerial platform which is rugged and durable in construction and economical to manufacture. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated:

FIG. l is a side elevational View of an aerial platform unit constructed in accordance with and embodying the present invention;

FIG. 2 is a rear elevational View of the platform unit;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2 and showing the beam assembly in its retracted position;

FIG. 4 is a longitudinal sectional view of the beam assembly showing it in its fully extended position;

FIG. 5 is a sectional view taken along line 5 5 of FIG. 2;

FIG. 6 is a s-ectional view taken along line 6 6 of FIG. 3;

FIG. 7 is a sectional view taken along line 77 of FIG. l;

FIG. 8 is a sectional view taken along line 8 8 of FIG. 7;

FIG. 9 is a schematic hydraulic circuit diagram of the hydraulic system forming part of the present invention; and

FIG. l0 is a longitudinal sectional view of a modified aerial platform unit also constructed in accordance with and embodying the present invention.

Corresponding reference characters indicate correponding parts throughout the several views of the drawings.

Referring now to the drawings, 2 designates an aerial platform unit including a pedestal 4 which is bolted, welded or otherwise securely attached at its lower end to the bed or frame 6 of a truck (not shown) or other suitable platform, forming no part of the present invention. Rigidly secured to pedestal 4 at its upper end is an annular mounting ring 8, and rotatably mounted on ring 8 is a mast 10 including a turret casting 12 and a pair of upstanding spaced side plates 14, 16. Turret casting 12 can be of any conventional design or it can be constructed in accordance with the teachings of copending application Ser. No. 491,295 now U.S. Patent No. 3,378,103, filed Sept. 29, 1965. It is, therefore, sufiicient for purposes of the present disclosure merely to note that turret casting 12 carries a hydraulic motor 18 which rotates mast 10 on annular ring 8. lournaled intermediate the extreme upper ends of side plates 14, 16, by means of a pin 22 is a boom or beam assembly 24 including a lower beam 26, an intermediate beam 28, and an upper beam 30, all of which are telescopically mounted with respect to one another.

Referring now to FIGS. 3 and 6, lower beam 26 consists of an elongated tubular member 32 preferably fabyricated from steel and having a rectangular cross-sectional shape. At its lower or inner end, tubular member 32 is fitted within an end casting 34 having a socketlike end portion 36 for reception of member 32 which is securely welded therein. End portion 36 integrally merges into a pair of spaced rearwardly extending ears 38, 40, which are provided with coaxial apertures for acceptance of pin 22 so that lower beam 26 can pivot thereon intermediate side plates 14, 16. Transversely connecting ears 38, 40, in forwardly spaced relation to pin 22 are integrally cast rear and forward cross partitions 44, 46. Journaled on pin 22 intermediate ears 38, 40, is a freely rotatable drum 48.

Welded to the side walls of tubular member 32 at its opposite or outer end are a pair of downwardly projecting apertured roller brackets 50 and journaled thereon is a roller 54. It should be noted that the extreme end portion of the bottom wall of tubular member 32 is cut away slightly so that a segment of roller 54 projects upwardly beyond the lower wall of member 32 into the interior of lower beam 26. Opposite roller 54 tubular member 32 is similarly provided with an upper roller 56 which is carried by a pair of roller brackets 60. A segment of roller 56 also projects into the interior of beam 26.

Intermediate its ends lower beam 26 is fitted with a downwardly projecting bifurcated bracket 62 and journaled thereto by means of a pin 64 is a piston rod 66 of a hydraulic elevation cylinder 68. Cylinder 68 also includes a barrel 70 which extends rearwardly between side plates 14, 16, of mast 10 where it is provided with outwardly projecting trunnions 71 which lit rotatably within mounting collars 72 attached to side plates 14, 16. Cylinder 68 raises and lowers lower beam 26 and it should be noted that trunnions 71 are located somewhat inwardly from the rear end of barrel 70 so as to achieve better leverage and to afford a greater arcuate traverse.

Also interconnecting mast 10 and lower beam 26 (FIG. is a lower leveling cylinder 74 including a barrel 75 which is journaled to side plate 16 by means of a pin 76. Fitted within barrel 75 for extensible movement beyond the end thereof is a piston rod 77 which is journaled on a stud 78 projecting laterally from end casting 34 in forwardly spaced relation to pin 22.

Intermediate beam 28 includes a tubular member 80 also formed from steel and having a rectangular crosssectional shape. Its upper and lower walls engage and ride upon rollers 54, 56, up to a limiting point defined by pairs of upwardly and downwardly extending roller brackets 82, 84, respectively, which prevent further inward longitudinal movement. Brackets 82, 84, are similarly welded to the side walls of tubular member 80 and carry upper and lower rollers 86, 88, which project slightly inwardly beyond the upper and lower walls, respectively, of tubular member 80 and into the interior of intermediate beam 28. At its extreme inner end intermediate beam 28 is provided with wear plates 90 which engage and ride upon the inwardly presented surfaces of lower beam 26.

Interconnecting lower and intermediate beams 26, 28, is a hydraulic extension cylinder 94 including a barrel 96 which is housed entirely within the confines of tubular member 80, being attached thereto by means of laterally projecting pins 98 which lit into socket fittings 100 secured to the inner end of tubular member 80. At its opposite or outer end barrel 96 is provided with a longitudinally projecting bifurcated bracket 102 which carries a freely rotatable sheave 104. Slidably fitted within barrel 96 for extensible movement beyond the end thereof is a piston rod 106 which rearwardly terminates at a diametrally enlarged flange 108 having a threaded end portion 110 projecting therefrom through rear cross-partition 44 of end casting 34, to which it is attached by means of a lock nut 112. From the foregoing description it is apparent that the movement of intermediate beam 28 corresponds to that of barrel 96 inasmuch as the two are connected directly to one another, and consequently the maximum extension of intermediate beam 28 beyond the end of lower beam 26 is no greater than the stroke of cylinder 94. Rigidly afxed to the bottom wall of tubular member 80 and projecting rearwardly therefrom is a sheave bracket 114 which carries a pin 116 having a sheave 118 journaled thereon, sheave 118 being disposed so that it rotates in a vertical plane with its axis of rotation located substantially coincident to the plane defined by the lower wall of member 80.

Telescopically fitted within intermediate beam 28 is upper beam 30 which consists of a tubular member 120 formed from a high tensile strength dielectric material such as fiber glass. Tubular member 120 furthermore possesses a rectangular cross-sectional shape of such size that its side walls slidably engage the side walls of intermediate beam 28 while its upper and lower walls engage and ride upon rollers 86, 88. At its extreme inner end tubular member 120 is provided with wear plates 121 which engage and ride upon the inwardly presented surfaces of intermediate beam 28. At its outer end, beyond the end of intermediate beam 28, tubular member 120 is fitted with a transversely extending bushing 122 having a pin 124 fitted therein. One end of pin 124 projects axially beyond bushing 122 where it is rigidly affixed to a steel or other suitable basket side plate 128.

Bolted to side plate 128 is a conventional man-supporting basket or work platform 130 which is also preferably molded or otherwise formed from a high dielectric material. Interconnecting basket side plate 128 and upper beam 30 is an upper leveling cylinder 132 including a barrel 134 which is journaled to side plate 128 in offset relation to pin 124 by means of a pin 136. Extending from barrel 134 is a piston rod 138 which is journaled to tubular member 120 in inwardly spaced relation to pin 124 by means of a stud 140.

Turning now to FIGS. 3 and 4, upper beam 30 is connected to and actuated by an extension chain 142 which is fastened at its one end to the inner or rear end of tubular member 120, chain 142 extending forwardly therefrom within the confines of tubular member 120 to sheave 104 over which itis trained. Chain 142 extends rearwardly from sheave l104 along the underside 0f barrel 96 and terminates at a threaded adjusting stud 144 which projects through forward cross-partition 46 of end casting 34. Stud 144 is tted with an adjusting nut 145 for adjusting the tension in chain 142. Also connected to the rear end of upper beam 30 is a retraction chain 148 which is trained around sheave 118 and thereafter extends forwardly along the bottom wall of tubular member 32, chain 148 being secured to that bottom wall in close proximity to the forward end of lower beam 26.

Mounted adjacent the rim of basket 130 on side plate 128 is a valve block 160 including three lever-operated remote controls 162, 164, 166, which for convenience of reference will be referred to as remote elevational, rotational, and extension controls, respectively. Also mounted at basket 130 on plate 128 are three plunger-operated controls 168, 170, 172, which will be referred to as remote stop, starter, and emergency power controls, respectively. Connected to valve block 160 and passing through upper beam 30 against the upper surface thereof, to which it is fastened by means of a plurality of clips, is an extruded multichannel flexible lluid conduit 174 having a substantially flat or band-like cross-sectional shape with the channels disposed in side-by-side relation (FIG. 6). Fluid conduit 174 further extends rearwardly through intermediate beam 28 and lower beam 26, passing between ears 38, 40, of the latter and over drum 48, beyond which it is coiled around and maintained under tension by a reel assembly 180.

As seen in FIGS. l, 7, and 8, reel assembly 180 includes a pair of mounting brackets 182 which are bolted to and project rearwardly from side plates \14, 16, beneath drum 48, and rigidly carried by brackets 182 is a collector spool 184 having cylindrical end portions 186, 188, which project laterally beyond brackets 182. Intermediate end portions 186, 188, spool 184 is turned down in the provision of a plurality of axially spaced annular collector grooves 190 and interposed between each collector groove 190 as well as between the two end collector grooves 190 and end portions 186, 188, are smaller seal grooves 192. Each seal groove 192, in turn, contains an O-ring seal 194. From each end, spool 184 is provided with a plurality of circumferentially spaced axial bores 196, each communicating at its inner end with a different collector groove 190 by means of a radial inner port 198. End portions 186, 188, are further provided with radial outer ports 200, 202, respectively, each of which, in turn, communicates with a different axial bore 196. The extreme outer ends of bores 196 are sealed by means of plugs 204.

Fitted over collector spool 184 for rotation thereon is a collector sleeve 210 having a cylindrical inner bore 212 which is snugly but rotatably engarged by O-ring seals 194 so as to prevent iluid from flowing between the various collector grooves 190. Extending radially through the wall of collector sleeve 210 are a plurality of axially spaced sleeve ports 214, each of which terminates at, and communicates with, a different collector groove 190. Consequently, each sleeve port 214 remains in communication with its respective collector groove 190 irrespective of the angular position of sleeve 210 or spool 184. Integrally formed on sleeve 210 is a diametrically enlarged central flange segment 216. The end of sleeve 210 adjacent end portion 188 is turned down slightly and a diametrally enlarged sprocket 220 is press-fitted theron.

Collector sleeve 210 further carries a takeup reel 222 including an arcuate drum segment 224 which is lltted on the outer periphery of ilange segment 216. Drum segment 224 is also of substantially the same circumferential dimension as flange segment 216 so that the cylindrical surface of collector sleeve 210 will be exposed through the opening in drum segment 224 across the entire width of reel 222. Welded to the arcuate side margins of drum segment 224 are diametrally enlarged annular side llanges 226 which are transversely connected intermediate the ends of drum segment 224 by a cross plate 228. The ends of cross plate 228 located beyond ilanges 226 are relieved in the provision of outwardly opening cutouts 230 having bolts 232 fitted therein. Bolts 232 extend inwardly where they are threaded into a locking bar 234 which is located in the space between the ends of flange segment 216.

Band-like tluid conduit 174, as previously noted, passes over drum 48 and thereafter is coiled around reel 222, the inner end of iluid conduit 174 being clamped between cross plate 228 and locking bar 234 by means of bolts 232. The extreme end portion of iluid conduit 174 passes beyond locking bar 234, and then turns inwardly toward the cylindrical surface of collector sleeve 210 where each channel thereor` is connected to a different preselected sleeve port 214.

Bolted to the inwardly presented surface of side plate 14 adjacent bracket 182 (FIG. 5) is a drum-like spring housing 236 having a conventional spiral spring (not shown) coiled therein. One end of the spring is secured to housing 236, while its opposite end is attached to a rotatable spring shaft 240 which projects outwardly from housing 236 where it is provided with a sprocket 242. Trained over sprocket 242 and sprocket 220 on collector sleeve 210 is a chain 244. By means of this construction a torque is continually maintained on collector sleeve 210 so that multichannel conduit 174 remains neatly coiled about reel 222 and under slight tension irrespective of the longitudinal position of beams 28, 30, with respect to lower beam 26.

Referring now to FIG. 9, aerial platform unit 2 includes a hydraulic control system 300 comprising a reservoir 302 and pump 304, both of which are mounted at some suitable location on the truck, the latter being preferably connected to the prime mover of the truck through a suitable clutch. Fitted axially within annular mounting ring 8 and turret casting 12 is a hydraulic collector assembly 306 including a spool and sleeve arrangement similar to that previously described in conjunction with reel assembly 180, but containing fewer grooves. It is, therefore, suilicient for purposes of the present disclosure to merely note that collector assembly 306 permits a pump line 308, a tank line 310, and a drain line 312 to pass through mounting ring 8 and turret casting 12 in such a manner that unlimited rotation of the latter on the former is not impeded. Drain line 312 and tank link 310 are connected beyond annular mounting ring 8 to reservoir 302 while pump line 308 is connected to pump 304. At their opposite ends lines 308, 310, 312, are connected to a pressureregulated valve 314. Mounted on the outwardly presented face of side pla-te 16 of mast 10 is a main valve block 316 having three lever controlled manually operated main valves which for convenience of reference will be designated as main elevational valve 318, main rotational valve 320, and main extension valve 322. Valve block 316 is of the sliding spool variety which is conventional and, therefore, will not be described in greater detail. It receives its supply of hydraulic iluid through a supply line 324 which interconnects it and pressure-regulated valve 314. Valve block 316 discharges its fluid into tank line 310. Elevational valve 318 is connected by a pair of hydraulic lines 326 to eleva-tion cylinder 68, while rotational valve 320 is connected to hydraulic motor 18 by a pair of hydraulic lines 328. Similarly interconnecting extension valve 322 and extension cylinder 94 are a pair of hydraulic lines 330. Connec-ted to the slidable spools of main control valves 318, 320, 322, are slave cylinders 332, 333, 334, which are connected to remote controls 162, 164, 166, respectively, of valve block 160 located at basket by pairs of hydraulic lines 335, 336, 337, each of which passes through reel assembly 180 and occupies two channels of flexible conduit 174. Valve block and its controls 162, 164, 166, are of the conventional power assist variety, being fed by means of a pressure line 338 and being drained by a return line 340, each of which also occupies a channel of ilexible conduit 174, and passes through reel assembly 180. Beyond reel assembly pressure line 338 is connected to pressureregulated valve 314, while return line 340 empties into tank line 310 prior to collector assembly 306.

Interconnecting lower and upper leveling cylinders 74, 132, and also passing through reel assembly 180 as well as occupying two channels of lexible conduit 174 are hydraulic leveling lines 342, 344. Lines 342, 344, are connected adjacent lower leveling cylinder 74 to a pair of feed lines 346, 348, having check valves 350 interposed therein which prevent reverse flow out of those lines. Feed lines 346, 348, are, in turn, connected to a common supply line 352 which is connected to tank line 310 adjacent valve block 316. Inasmuch as a back pressure exists within tank line 310 at its juncture with supply line 352 hydraulic leveling lines 342, 344, as well as cylinders 74, 132, will always remain charged with hydraulic fluid, thereby eliminating any possibility of free motion at basket 130.

Also interconnecting hydraulic leveling lines 342, 344, on one hand, and pressure line 338 and return line 340, on the other hand, is a valve cluster 354 including a fourway control valve 356 which is mounted on side plate 14 next to valve block 316, check valves 358, a pressure relief valve 360, another check valve 362, all connected as schematically illustrated in FIG. 9.

Plunger-operated controls 168, 170, 172, at basket 130 are connected by means of air lines 364, 366, 368, to pressure sensitive electric stop, starter, and emergency power switches 370, 372, 374, respectively, located beyond reel assembly 180. Lines 364, 366, 368, are in part located within flexible conduit 174 and are furthermore completely void of liquid hydraulic uid. Consequently, when plunger-operated stop control 168 is depressed the air pressure within line 364 will increase and thereby actuate stop switch 370. The same, of course, applies to starter and emergency power switches 372, 374.

It should be noted that the following fluid lines all occupy a channel of flexible conduit 174: hydraulic leveling lines 342, 344; pressure line 338; return line 340. pairs of hydraulic lines 337 terminating at remote extension control 166; pairs of hydraulic lines 336 terminating at remote rotational control 164; pairs of hydraulic lines 335 terminating at remote elevational control 162; air lines 364, 366, 368.

All of the foregoing fluid lines pass through one of collector grooves 190 in spool 184 forming part of reel assembly 180 and exit therefrom through one of radial outer ports 200, 202, which are connected by means of suitable fittings to the remaining portions of the fluid lines (FIG. 9).

In operation, pump 304 is first energized which, in turn, energizes hydraulic system 300. A workman then positions himself in basket 130 which can be lowered to an entry position in close proximity to the bed 6 of the truck or to the ground by manipulating valves 318, 320, and 322, of main valve block 316 located on mast 10. Once in basket 130 the workman can, merely by manipulating remote controls 162, 164, 166, maneuver into a comfortable working distance of selected elevated objects such as transformers, overhead power lines, light fixtures, and signboards, to name a few. More particularly, to elevate or depress beam assembly 24, the workman moves the lever of remote control valve 162 in the appropriate direction and this opens an internal poppet or valve which allows pressurized hydraulic fluid from pressure line 338 to pass through one of hydraulic lines 335 to slave cylinder 332 and return to control 162 through the other hydraulic line 335. This displacement of hydraulic fluid actuates the piston within slave cylinder 332 which, being attached to the spool of main elevational control valve 318, actuates it also. Control Valve 318, in turn, directs pressurized fluid from supply line 324 to barrel 70 of hydraulic elevation cylinder 68 through one of hydraulic lines 326, thereby causing piston rod 66 to either extend or retract and elevate or depress beam assembly 24. Hydraulic motor 18 which controls the horizontal angular disposition of beam assembly 24 and extension cylinder 94 which to a large extent controls the lateral disposition of basket 130 are similarly actuated from basket 130 by manipulating remote controls 164, 166, respectively. Similarly, the same degree of control is provided at mast through main valves 318, 320, 322, of valve block 316.

As beam assembly 24 elevates and depresses through the action of hydraulic elevation cylinder 68 piston rod 77 moves within barrel 75 of hydraulic leveling cylinder 74, thereby displacing hydraulic uid from barrel 75. This fluid passes through one of hydraulic leveling lines 342, 344, depending on the direction piston rod 77 moves and into barrel 134 of upper leveling cylinder 132, thereby displacing piston rod 138 thereof a corresponding distance. The location of pin 76 and stud 78 with respect to pin 22, and the location of pin 136 and stud 140 with respect to pin 124, as well as the size of the bores of cylinders 74, 132, are all such that basket 130 will remain level irrespective of the angular position of beam assembly 24. The fluid displaced from upper cylinder 132 returns to lower cylinder 74 through the opposite of hydraulic leveling lines 342, 344. Moreover, as previously noted a slight back pressure exists in tank line 310 as it exits from valve block 316, and this back pressure is applied to both leveling lines 342, 344, through supply line 352, feed lines 346, 348, and check valves 350. Consequently, any leakage is immediately replaced and any air pockets resulting from thermal contraction are filled so as to eliminate free motion at basket 130. Check valves 350 prevent hydraulic fluid from flowing reversely out of feed lines 346, 348, and into tank line 310. Nevertheless, leveling lines 342, 344, will not rupture nor will cylinders 74, 132, or their associated components become damaged due to the effects of thermal expansion or unauthorized forces applied to basket 130 because relief valve 360 will unload lines 342 or 344 at a predetermined pressure. Also basket 130 can be optionally tipped to drain water therefrom or to perform repairs by manipulating four-way control valve 356.

When either remote extension control 166 or main extension valve 322 is moved in the appropriate direction hydraulic fluid will be supplied through one of lines 330 to the outer end of barrel 96 forming part of hydraulic extension cylinder 94. Consequently, barrel 96 will move outwardly on piston rod 106 which is secured to end casting 34 of lower beam 26. Inasmuch as intermediate beam 28 is pinned directly to barrel 96 by laterally projecting pins 98, intermediate beam 28 will experience exactly the same extensible motion as barrel 96 (FIG. 4). Therefore, the maximum displacement of intermediate beam 28 beyond the end of lower beam 26 is equal to the stroke of cylinder 94. Upper beam 30, however, will experience a compound movement, its maximum displacement being twice the stroke of cylinder 94. As intermediate beam 28 and barrel 96 move outwardly chain 142 will ride over sheave 104 and inasmuch as one end of chain 142 is secured to lower beam 26 at end casting 34, its opposite end will traverse twice the distance as does barrel 96 and its sheave 104. Since this opposite end is fastened to upper beam 30, it too will experience twice the displacement of intermediate beam 28. Meanwhile, sheave 118 will ride forwardly with intermediate beam 28 so that chain 148 remains relaxed and does not in anyway interfere with the aforementioned movement. However, when intermediate beam 28 is retracted by directing hydraulic fluid to the opposite end of barrel 96, sheave 118 will ride over chain 148 and draw its movable end, that is the end fastened to the inner end of intermediate beam 28, rearwardly, Consequently, upper beam 30 again experiences compound movement, this time in a rearwardly or inwardly direction. Rollers 54, 56, and 86, 88, as well as wear plates and 121, enable beams 26, 28, 30, to move freely with respect to one another.

It is quite apparent from the foregoing that relatively long extensible movement is achieved without employing extremely long and expensive hydraulic extension cylinders. Furthermore, by utilizing three beams, a high degree of compactness is obtained when beams 28, 30, are fully retracted into their transport position. Obviously, when in the fully retracted position, beam assembly 24 is considerably shorter than conventional two-beam telescopic or articulated beam units which extend an equivalent distance. It is significant that when beam assembly 24 is in its extended positions, as illustrated in FIG. 4, the outer end of barrel 96 will be located a considerable distance from basket 130. Consequently, from an electrical standpoint, basket 130 is completely and safely isolated from the remaining portions of aerial unit 2 as well as from its truck.

As beams 28, 30, extend and retract with respect to lower beam 26, exible fluid conduit 174 rides over rotatable drum 48 and remains taut by virtue of the torque applied through reel assembly 180, so as not to become entangled in nearby components. Furthermore when beams 28, 30, are retracted, the surplus portion of conduit 174 remains neatly coiled around takeup reel 222. Consequently, harmful abrupt ilexures are eliminated and the life of conduit 174 is extended considerably.

Referring now to FIG. 9, it is possible to provide a modified aerial platform unit 400 which is very similar to unit 2 and includes a mast 402 and `a boom or beam assembly 404 journaled thereto by means of a pin 406. Beam assembly 404 includes a lower beam 408 and an extensible upper beam 410 which is telescopically mounted in lower beam 408 and is formed from a dielectric material. Lower beam 408 is swung about pin 406 by means of an elevation cylinder 412, while upper beam 410 is provided at its extreme outer end with a pin mounted basket 414.

Beam assembly 404 internally carries an extension cylinder 416 having a piston rod 418 which is secured at its outer end to lower beam 408 adjacent pin 406. Cylinder 416 also includes a movable barrel 420 which is carried by rod 418 and is located almost entirely within the confines of upper beam 410 when that beam is in its fully retracted position. At its outer end, barrel 420 is provided with a sheave 422 around which an extension chain 424 is trained. One end of extension 424 is secured to lower beam 408 in close proximity to pin 406 while its opposite end is fastened to a connecting link 426 which, in turn, is atiixed to the rear or inner end of upper beam 410. Pinned to the extreme inner end of barrel 420, that is the portion located rearwardly beyond upper beam 410, is a sheave 428 around which a retraction chain 430 is trained. One end of chain 430 is connected to the forward end of lower beam 408 while its opposite end is fastened to connecting link 426. Accordingly, when barrel 420 moves outwardly on piston rod 418, sheave 422 will place extension chain 424 under tension, and chain 424 will move upper beam 410 out of lower beam 408. By virtue of the chain and sheave arrangement, upper beam 410 will move twice the distance as barrel 420. As dielectric upper beam 410 extends, the distance between the end of barrel 420 and basket 414 becomes progressively greater. Thus, aerial unit 400 is entirely safe for use by workmen who have occasion to work on high voltage lines. The cylinder of a conventional unit, however, is located within the contines of the upper beam and moves in a one-to-one ratio therewith so that the basket and outer end of the cylinder are always located in close proximity to one another. When barrel 420 is retracted, sheave 428 will place retraction chain 430 under tension and it will draw upper beam 410 inwardly.

The hydraulic system for aerial unit 400 is similar to hydraulic control system 300. The hydraulic system includes a flexible conduit 432 which extends through beam assembly 404 to basket 414 as well as a leveling means 434.

The various extension and retraction chains 142, 148, 424, 430, described herein can be fabricated from any suitable exible material such as cable, rope, metal band, and the like, and will therefore be referred to hereinafter as bands.

Also, cylinders 94, 416i, preferably have their ports located at the ends of their respective piston rods 106, 41-8, so that the fluid lines leading thereto do not flex when barrels 96, 420, extend and retract. Such a cylinder is disclosed in copending application Ser. No. 587,826, filed Oct. 19, 1966 now U.S. Patent No. 3,396,852.

In view of the above it will be seen that the several objects of the invention are achieved and other advantageous results attained.

What is claimed is:

1. An aerial platform unit comprising a mast; a beam assembly including upper, intermediate, and lower beams having tubular construction and being telescopically mounted with respect to one another, the lower beam being swingably connected to the mast; extension means inside the beam assembly interconnecting the lower and intermediate beams, the extension means having an extensible member adapted to move from a retracted position to an extended position to move the intermediate beam with respect to the lower beam; and connecting means inside the beam assembly interconnecting the upper and lower beams, the connecting means being responsive to movement of the extensible member to cause the upper beam to move with respect to the lower beam a distance greater than the extensible movement of the extensible member.

2. An aerial platform unit according to claim 1 wherein the connecting means comprises a first arcuate surface carried on the extensible member of the extension means, an extension band connected at its one end to the lower beam and at its opposite end to the upper beam, the extension band being trained over the first arcuate surface intermediate its ends and doubling back upon itself at least once so that when the extensible member moves the arcuate surface against the extension band tension is induced therein, whereby for any given displacement of the extensible member in a direction which induces a tension in the extension band, the upper beam will displace a greater distance with respect to the lower beam.

3. An aerial platform unit according to claim 2 wherein the connecting means is further characterized by a second arcuate surface mounted in fixed longitudinally spaced relation to the first arcuate surface, and a retraction band connected at its one end to the upper beam and at its opposite end to the lower beam in longitudinally spaced relation to the point of securement of the extension band to the lower beam, the extension band being trained over the second arcuate surface intermediate its ends and doubling back upon itself at least once so that when the second arcuate surface moves against the retraction band tension will be induced therein, whereby when the extensible member moves in the opposite direction and thereby induces tension in the retraction band, the upper beam will be retracted with respect to the lower beam.

4. An aerial platform unit according to claim 1 wherein the extension means comprises a stationary member attached at its one end to the lower beam, and an extensible member slidably mounted with respect to the stationary member so that the stationary member projects longitudinally from one end of the extensible member; and wherein the connecting means comprises a first sheave mounted on the opposite end of the extensible member, an extension band connected at its one end to the lower beam and at its opposite end to the upper beam, the extension band being trained over the first sheave and doubling back upon itself at least once so that when the extensible member moves the first sheave against the extension band it will induce tension therein, whereby for any given displacement of the extensible member in a direction which induces a tension in the extension band, the upper beam will displace a greater distance with respect to the lower beam, a second sheave mounted in fixed longitudinally spaced relation to the first sheave, and a retraction band connected at its one end to the upper beam and at its opposite end to the lower beam in longitudinally spaced relation to the point of securement of the extension band to the lower beam, the extension band being trained over the second sheave inten mediate its ends and doubling back upon itself at least once so that when the second sheave moves against the retraction band tension will be induced therein, whereby when the extensible member moves in the opposite direction and thereby induces tension in the retraction band, the upper beam will be retracted with respect to the lower beam.

5. An aerial platform unit according to claim 2 in which the beam assembly is further characterized by the extensible member being attached directly to the intermediate beam so that the intermediate beam and extensible member experience simultaneous displacement of equal magnitude. I l

6. A beam assembly according to claim 4 in which the. extension and retraction bands double back upon themselves once so that when the extensible member extends the upper beam extends and vice-versa.

7. An aerial platform unit according to claim 4 in which the beam assembly is further characterized by the intermediate beam being slidably disposed within the lower beam and the upper beam being slidably disposed Within the intermediate beam; wherein the extensible member is disposed primarily within the confines of the upper beam when the beams are in their fully retracted position; wherein the extensible member is connected directly to the intermediate beam so that the intermediate beam and extensible member experience simultaneous displacement of equal magnitude.

8. An aerial platform unit comprising a mast, a beam assembly pivotally mounted at one end on the mast, a platform pivotally mounted at the outer end of the beam assembly, a lower leveling cylinder pivotally interconnecting the beam assembly and the mast in offset relation to the pivot-forming connection of the beam assembly and the mast, an upper leveling cylinder pivotally interconnecting the basket and the beam assembly in offset relation to the pivot-forming connection between the platform and beam assembly, first and second leveling fluid lines interconnecting the cylinders and emptying into their respective barrels on each side of their respective pistons, whereby the platform will remain horizontal irrespective of the angular disposition of the beam assembly, and means connected to the rst and second fluid lines for applying equal pressure to fluid therein, whereby free motion of the platform caused by thermal contraction of the fluid in or leakage of fluid from the fluid lines and cylinders is eliminated.

9. An aerial platform unit according to claim 8 in which the means for applying equal pressure to the fluid lines comprises first and second feed lines connected to the first and second leveling fluid lines, respectively, and to a source of pressurized fluid.

10. An aerial platform unit according to claim 9 and further characterized by check valves interposed in the feed lines so as to prevent reverse flow of fluid out of the feed lines toward the source of pressurized fluid, and a relief valve connected to the first and second leveling fluid lines so that iluid will be discharged from leveling lines at a predetermined pressure, whereby the possibility of injury to the fluid lines or cylinders through unauthorized forces applied to the platform or thermal expansion of the fluid is reduced.

11. An aerial unit comprising a mast; a lower beam swingably mounted on the mast; an upper beam shiftably mounted with respect to the lower beam for extensible movement therefrom; a reel assembly located near the end of the lower beam and including a rotatable reel; and a fluid conduit attached to the upper beam for extensible movement therewith; the fluid conduit termi- CII nating in a flexible end portion which extends outwardly from the lower beam beyond which it is coiled around the reel; the reel assembly being adapted to be connected to a stationary fluid line and including means connected to the fluid conduit and adapted to form communication between the fluid conduit and the stationary fluid line.

12. An aerial unit according to claim 11 in which the reel assembly is further characterized by means for applying a continual torque to the reel so that the flexible portion of the conduit will be wound around the reel when the upper beam retracts.

13. An aerial unit according to claim 12 in which the reel assembly is further characterized by a stationary spool having at least one annular collector groove, at least one axially extending bore in communication with the collector groove, and at least one outer port in communication with the bore, the outer port being adapted for attachment to a substantially stationary fluid line; a collector sleeve rotatably mounted on the spool and having a sleeve port which inwardly registers with and opens into the collector groove, the reel being secured to the sleeve for rotation therewith and the end of the flexible portion of the fluid conduit being connected to the sleeve port, whereby the fluid conduit communicates with the stationary fluid line.

14. An aerial unit according to claim 13 wherein the spool is provided with a plurality of axially spaced annular collector grooves and an equal number of axially extending bores, each bore internally communicating with a different groove and outwardly terminating at a different outer port; wherein the collector sleeve is provided with a plurality of axially spaced sleeve ports, each of which registers with and opens into a different collector groove; and wherein the fluid conduit is provided with a plurality of channels, each of which is connected to a different sleeve port, whereby a plurality of fluid lines pass through the upper and lower beams as well as through the reel assembly.

15. An aerial unit according to claim 14 wherein the reel assembly is carried by the mast; and wherein the unit is further characterized by a pin pivotally interconnecting the mast and lower beam and a freely rotatable drum mounted on the pin for rotational movement thereon, the flexible portion of the fluid conduit passing over the drum and then onto the reel.

16. An aerial unit according to claim 15 and further characterized by a man-supporting platform pivotally mounted at the outer end of the upper beam, a valve block mounted at the platform and having at least one control valve therein, the fluid conduit being connected to the valve block at its outer end.

17. An aerial unit according to claim 1 in which the upper beam is constructed from a dielectric material.

References Cited UNITED STATES PATENTS 2,571,858 10/1951 Garland 212-55 2,606,078 8/ 1952 Brock 182--2 2,786,723 3/1957 Harsch 182--2 2,787,278 4/1957 Mitchell 187-9 X 3,159,240 12/1964 Miller 182-46 3,212,604 10/1965 Garnett 182--2 3,305,220 2/ 1967 Nevulis 212-55 REINALDO P. MACHADO, Primary Examiner U.S. Cl. X.R. 182-46 UNITED STATES PATENT oFEICE CERTIFICATE OF CORRECTION Patent No. 3,467,217 September` 16, 196

Daniel H. Zwight It is certified that error' appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column l, lines 4l and 42, "mast mounted on the bed of a truck and beams extending for their needs. These units generally employ a rotatable" should read for their needs. These units generally employ a rotatable mast mounted on the bed of a truck and beams extending Column 2, line 5, "flextures" should read flexures line 23, "aggrevate" should read aggravate line 3S, "flexture" should read flexure Column 5, line 55, "diametrically" should read diametrally line 58, "theron" should read thereon line S9, "takeup" should read take-up Column 9, line l5, "takeup" should read take-up line 37, "extension 424" should read extension Chain 424 Signed and sealed this 5th day of May 1970.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR Attesting Officer Commissioner of Patents

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