US2598200A

US2598200A - Hoisting apparatus

Info

Publication number: US2598200A
Application number: US34772A
Authority: US
Inventors: David A Wallace
Original assignee: WALCO Inc
Current assignee: WALCO Inc
Priority date: 1948-06-23
Filing date: 1948-06-23
Publication date: 1952-05-27
Anticipated expiration: 1969-05-27

Description

May 27, 1952 D. A. WALLACE 2,593,200

HOISTING APPARATUS Filed June 23, 1948 3 Sheets-Sheet -1 1 JNVENTORA.

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May 27, 1952 D. A. WALLACE HOISTING APPARATUS 3 Sheets-Sheet 2 Filed June 23. 1948 INVENTOR. )avz'i /$f lnZ/aae.

y 27, 1952 D. A. WALLACE 2,598,200

HOISTING APPARATUS Filed June 23, 1948 3 Sheets-Sheet 5 Patented May 27, 1952 UNITED STATES,

.ENT OFFICE" nois'riNo APPARATUS David A. Wallace, Grosse Pointe Farms, Mich.,

assig nor to Walco, 1110., Detroit, Mich., a corporation of- Michigan 21 Claims. 1

This invention relates to hoisting. apparatus and is an improvement in hoisting apparatus of. the character shown in my patent. application Serial No. 15,827, filed March 19, 1948,, and Patents Nos. 2,576,907, 2,576,908, and 2,576,158, issued November 27, 1951.

More specifically the invention relates to improvements in hoisting apparatus which is particularly adapted for hoisting vehicles.

In. my above applications there are disclosed various embodiments of hoisting apparatus. in which arev included a boom member that is shift,- able between substantially horizontal and substantially vertical positions by various actuating mechanisms each of which, includes a system of'l'evers which, in the horizontal position of the boom member, is more or less nested with, the boom member in order that the boom memher and lever assembly be accommodated Within a space of limited height when the boom member is in. its lower position. The lever systems of these hoisting apparatuses have upper ends pivoted directly to the boom member at locations intermediate their lengths, as in my Eat,- ents Nos. 2,576,907 and 2,576,158, or pivoted to fixed extensions similarly located on the boom members, as in my Patent No. 2,576,908 and application Serial No. 15,827. In all cases the boom members are raised and lowered by producing relative approaching and separatory movements respectively of the lower ends of the boom members.

One of the characteristics of a lever system and boom member assembly of this kind is that during initial raising of the boom member from its lowermost position, many times as much force is required than that which is required to produce the final increments of upward movement of the boom member to its substantially vertical position. This is because the angle between the boom member and the effective lever arm of the system of levers by which it is raised is not much less than 180 when the boom member is in its lowermost position and decreases gradually as the boom member is raised. As the angle between this eifective lever arm and the boom member decreases the mechanical advantage of the entire system increases. Thus the maximum force required during the starting phases of elevating a load determines the size and capacity of the power driving mechanism involved.

Some reduction in the force required to produce initial lifting of a load by hoisting apparatus of this character can be made, as illustrated in my Patent No. 2,576,908 and application Serial No. 15,827, byiixingextensions on the boom member which project upwardly from it when it, is in its lower position and then pivotally attaching the, boom lifting levers to the upper ends of such extensions. This reduction in the initial force requirement can be only limited, however, because excessive upward prof jection of such. extensions must be avoided in order to accommodate the hoisting apparatus in a space of limited height and to allow; clearance for accommodating driving of a vehicle over the hoisting apparatus toa position from which it may be lifted by it.

One of the main objects of this invention is to provide a system of levers in hoisting apparatus of this character which materially decreases the force required to initially lift a load andwhich is entirely accommodatable in a space having no greater height than that required for the boom' member when the latter is in its substantially horizontal position.

Another object of the invention is to provide in hoisting apparatus, a system of levers of this kind which accomplishes the above results while confining the upward and downward movements of a load on the apparatus to a course which does not depart significantly fr m a vertical path.

Another object of the invention is to provide a system of levers for raising and lowering the boom member of hoisting apparatus of this kind which may be nested in substantially parallelism with the boom member when the latter is in its horizontal position and shifted without elevating the boom member to a position relative to the boom member at which it has a more favorable mechanical advantage during initial boom raising operation.

A further object of the invention is to provide a system of levers of this kind which can be contracted into unobstructing relationship with respect to a vehicle being driven into position to be lifted.

A s i furt er object of th invention is t provi a boo m m controlling lever system of this kind which rigidifles the boom member.

Other objects of the invention are to provide a Combination of link and lever elements in a boom member controlling lever system of this kind which are adapted to be substantially aligned when the boom member is in its horizontal position, to provide resilient means which is energizable during lowering of the boom member for shifting the link and lever elements out of substantial alignment preparatory to initial raising of the boom member; to provide an abutment on the boom member which is engageable with the link element for holding the link against movement in one direction with respect thereto beyond a predetermined initial boom raising position; to provide an abutment on the lever element which is engageable with the link element when the boom member is in its substantially vertical position for limiting relative movement between the link and lever elements and rigidifying the lever system by tensioning all pivotal connections embodied therein.

Another object of the invention is to provide in screw type actuating mechanisms having an irreversible pitch for positively selectively raising and lowering the boom members of a multiple unit hoisting apparatus, an improved releasable nut member and control means therefor by which the screw element of the mechanism may be releasably coupled with a boom member for operating it.

Another object of the invention is to provide improved means for releasably fixing one hoisting unit of hoisting apparatus of this kind in a plurality of different positions with respect to another hoisting unit thereof in order to accommodate lifting of vehicles of diverse lengths and constructions.

An illustrative embodiment of the invention is shown in the accompanying drawings, in which:

Figure l is a perspective view showing hoisting apparatus, embodying the invention, in its elevated position.

Figure 2 is a fragmentary side elevational view showing one of the hoisting units of the apparatus of Figure 1, in its fully contracted lowermost position.

Figure 3 is a fragmentary side elevational view, similar to Figure 2, but showing the lever system of the hoisting unit shifted from its fully contracted position of Figure l, to a more favorable mechanical advantage position preparatory to a hoisting operation.

Figure 4 is a fragmentary side elevational view showing in full lines one of the hoisting units illustrated in Figure l, in its upper position and showing an intermediate position of said unit in dot and dash lines.

Figure 5 is a plan view of the hoisting unit illustrated at the right of Figure 1.

Figure 6 is a fragmentary longitudinal vertical sectional view taken on the line 66 of Figure 5.

Figure 7 is a transverse vertical sectional view taken on the line 1-1 of Figure 5.

Figure 8 is a vertical sectional view taken on line 8-8 of Figure 1.

Figure 9 is a transverse vertical sectional view taken on the line 99 of Figure 3.

Figure 10 is a transverse vertical sectional view taken on line I 0--l 0 of Figure 5.

In Figure l of the drawings is illustrated hoisting apparatus embodying the invention which comprises'hoisting units A and B each of which are substantially identical, the description of one of which will serve, in all but certain respects hereinafter specified, for the others. These hoisting units are particularly constructed to lift vehicles but may be readily adapted to the lifting of numerous other articles. They are preferably operatively mounted on a track comprising spaced rails l0 and II of channel-shaped cross section having inwardly facing upper flanges l2 and I3 and lower flanges l4 and I5. The rails 10 and ii may be mounted in a shallow groove formed in a platform structure (not shown) which may be disposed upon a floor structure or they may be mounted in a shallow groove (not shown) of a floor structure with the upper flanges l2 and i3 flush with the floor surface.

The hoisting units A and B each include a shiftable carriage, generally designated by the numeral I1, having a horizontal base plate It! and a vertically upstanding flange l9. Provided on each of the opposite ends of the shiftable carriage are wheels 20 and 2i which are received between the flanges l2 and I4 and I3 and 15 of the rails I9 and II, respectively. The wheels 2c and 2| are journalled on the outer end portions of trunnions 22 and 23, which are respectively mounted on and extend outwardly from end flanges 24 and 25 of the carriage H. The end flanges 24 and 25 may be welded to or formed integral with the base plate 18 and flange IQ of the carriage l1.

Each hoisting unit includes a boom member, generally designated by the numeral 29, which comprises a pair of channel members 30 and ill having outwardly facing web portions and provided with solid lower end portions 38 and 3|, respectively. The solid lower end 30' of the channel member 30 is apertured and journalled on the trunnion 22 at a location between the wheel 20 and end flange 24, as shown in Figure '7. The solid lower end 31' of the channel member 3| is apertured and journalled on the trunnion 23 at a location between the wheel 21 and the end flange 25.

A load receiving seat, generally designated by the numeral 36, is pivotally mounted on the upper ends of the channel members 30 and 31, as illustrated in Figures 1 and 4. The load receiving seat 36 comprises a bar 31 having upwardly extending notched flanges 38 provided on its opposite extremities for receiving a vehicle axle or other portion of a load to be lifted. Provided on the opposite side of the bar 37 are spaced downwardly extending ears 39 for receiving pins 48 by which the seat 36 is pivotally mounted on the upper ends of the channel members 30 and 3|.

When the boom member comprising the channel members 30 and 3| is in its upper most position, the lower side of the bar 37 seats upon the upper extremities of the channel members. During movement of the boom member 29 from its lower to its upper position the seat 36 is retained in a substantially horizontal position by parallelogram mechanism including link members 4i extending substantially parallel to the channel members 30 and 31 which are pivotally attached at their upper ends by a pin 42 to rigid arms 43 extending from the lower side of the bar 37 of the seat member, as shown in Figure 4. The lower ends of the links M are pivotally attached by pins 45 carried by ears 44' extending upwardly from the base portion l8 of the carriage H. The pivotal axes provided by the pins 42 and Mare equidistant from the pivotal axis of the seat 36 provided by the pins 40 and the pivotal axis of the boom member provided by the trunnions 22 and 23, respectively. This provides a parallelogram mechanism which retains and supports the seat 36 in horizontal load supporting position during movement of the boom member 29 between its lower and upper positions. When the boom member is in its upright position the seat 36 is supported in horizontal position by engagement of its lower side with the upper extremities of the channel members 30 and 3 I.

The boom member 29 is supported and guided tats; so and a": a: the stem memb r" 2st a s at petitions mien riiediat the lnthof them 5 at v M fi evided on the spanpa t' 46' of the oke ai e spaced teary" on which are jcurnalled the uppel end portions of a pan" of 1t'rs 50'. As shown in Fi fiie's 1 tot,- th levers 5i; ai 's sign; union out the frhajof portions of: then length but a e fiilovided with slightly? upwardly curved upper enq e 'rmqes. The Iowa ends or the levers 5c" are sadism" attached to a eigsta f 5 whicli exf tends between the fails l9 and ll of; the tiack stiuctui'e. This cross barf is proyided with upwardly extending shoes 52, one of which is engaged between the flanges l2 and hi of the rail and the other of which is engaged between the flanges l3 and [5 of the rail H. The cross baifl5l menses integral upwardly extending pairs of flanges 5 13 and 54 and a central bearing po rtion 55 havingf a bofe 56. The lower end of one lever 5!] is rec 'eived between the flanges 53 and pivotally attached thereto by a pin 51 2mg the loweif end of the othei lever is received between the flanges 5A and pivotally attached thereto by a pin 58. The cross bar 5] is .pi efei'ably i'eleasablji fixed to the side rails H1 and H by pins 59 or othel suitabl inans such as bolts, capsci ews and the like. The bai s stand 3 of the boom 23 afejadapted to be i c'eived between the shoes 52 and the adjacent flanges 53 and 55 respectively when the hoist is in lower position, v

The hoisting B is substantially identical to the' misting member A and similar parts are designated byfihe' samenumemi Howeve'i", the unit 13 has a slightly difie 'ent sieat generally designated by the nuinei'a'l 36' which includes a bar 31 having achan'nel in its uppei' side bounded by flanges 56 in which rests 6! are shif tably mounted. Each test s! has a notch 62 in its upper side for receiiiing a p'oiition of the load to be lifted. The lowei' ends of the levers 50 of the hoisting unit 13 are pivotally attached to a cross bat 5i which i's subs t 'antially warmth to the ci'oss bai- 5! of unit A Piovided on the cross bar 5! are pans of upstanding flanges {-33 and 65. The lowei end of one lever 59 is received between the flanges 63 and pi'votally attached thereto by a pin 65 and the lower" end of the other lei/ei- 59 is mated between the flanges 64 and pivotally attached thereto by a pin 66. The cioss bar 5? has an upstanding fian'g'e G? extending along its right side, as viewed in Figure 5; on the fight side Sl'ilfEiC 0f Whih is vi't-ialh shijft'ably lfibll-ntd a HIKE-Shaped lbking membi 68 Th locking member 58 has downwardly extndihg leg 156itibfis 69 slidably icitfe d in biaclits 1B. The miter end editions of the legs 69 are adapted to be -selectively positioned in aligned pairs of slots H formed in plates 72 which are rigidly liked to the Tails H] and H or ethe i 'suitable stationaiii supporting structure adjacent the'reto. By 'iaisihg theyokegsha-ped ioekinginefiibe'r 58 the ends a: thelegs 69 na'ay be disengaged from one et of a igned slats 1 i and the cities bai they be r'neir'ed relative to the rails and s emed against displacement fifbi'h its new positionebfi meta-3% lowering the locking in'einbei 68. In this way the ies 566th e e13 individua ly and sun afieous y osi-' ber, generally designated by the numeral 1 mg thfeads" 7'4 theieon' associated with; e the team nier'nbeis Z9, respective he s re'tv; member 13 pi'fe'i'ably co'r'r'ipfises" a piu'ra w of sections which aie eonnectjed togthef lorli= tud'ina'l alig ment by couplings'jfi. The lessee ti'iiely opposite end poftioris of the s cfe vtf membef 13 are journalled in hearinefj projvided in ma a er's'e' cfoss] man-pars; 1sand n which tween and ate fixed to the; ends of t and] I One or more intermediate erossniewe" 78 a'ls0' extends etween and is fixed to inter diate portions of the rails and is piotided Withbe'afings r'qr fotatively supporting the screw me pei at locations between its ends. Tli been inset of the cross b'a'i 4'8 also fotatiulfi 'supfioffs' an intermediate' portion of the screw member.

Each carfiage I! of the boom member's A and 13 includes a releasable nut meinbei', genefany' designatedby the numeral 19, which is adapted to be th 'eadably engaged with the scfej'w 13 in the I manner hereinafter set forth. The nut member 18 comprises separable internally threaded, semi-cylindrical nut sections 80 ema l are pro'i/idedwith oppositely extending same 8 1.

Each stem 8| is slidably mounted in a earing block 82 for movement transversely of the axis of the screw 13, as shown in Figui'e 7. The nut sections 80 may be simultaneously mated iiiwaidly and outwardly relative to each othef if: ordeito engage; and dis'ehg'ae the thiffads 6f the nut section and screw, respectively. This movementis produced by an ecen'tiic 33 which i' tatably mounted in an aperture; 84 formed in h stein 8| respectively. Each eccentiic' 83 is nonrotatabli fixed on 'a square section of a shaft 85 ivhichis journalled in spaced bearing blocks 8 6 for rotation about an axis substantially serene to the axis of the screw 13. Provided oneah shaft 85 isa sprocket 31. The sprockets 8'! ate connected together foi simultaneous fotation by an endless chain 88. A handle 89 is fixed on one of the shafts as fof' mating both eeeentnes which as illustrated in Figure '7 have opposite c a so are isengaged from the screw 13 the is permitted to turn while the teenage n mains at met. when the nut sections are e13 ages with the thr ads of the sdr w retation or the screw in opposite directions shifts the earriag'e i1 and lower end or the booth ine'xnbef which is pivctauy attae hed to it, longitudinally 6r therails in coffe'spondihgly opposite diiftions. It should be noted, that, as shown in Figures 1 and 7, the carriage n has a side Wall 90 on the eig teinal side of which are located the spioekets' a1 and chain 9' The end portions or the side Wall 90 of the carriage I! serve as abutm'ents' to limit the upward movement of the boom "memher to a substantially vertical position. Each basin ni einb'e'r ma thus be selectively coupled with and uncoupled item the drive sere'w T3.

The etisperatmg thieads of the screw meme? i3 and nut sections 80 have an irreversible than aiid therefore, While fot'ation of the screw si fives eaves the booin member 29 upwardlfii and downwardly, the weight of an elevated load supported on the boom member cannot rotate the screw member 73. Accordingly, the threaded enagement between the screw member 13 and the nut sections 80 serves as a lock to positively hold each boom member 29 in any selected position to which it is shifted by rotation of the screw member.

The screw member 13 is preferably driven thru suitable reduction gear mechanism 9|, which is in turn driven by a reversible electric motor 92. The details of the gear mechanism are fully disclosed in my pending application Serial No. 15,827. Any gear reduction mechanism may be used for this purpose.

The electric motor 92 may be provided with any suitable control circuit by which the motor 92 may be selectively driven in opposite directions, started and stopped under control of a portable switch 532, such for example as the control circuit shown in my above pending patent application. This circuit may, if desired, in clude suitable limit switches for interrupting the motor operation at predetermined upper and lower positions of the boom members 29, as shown in the above patent application.

In operation of the hoisting apparatus in lifting a vehicle, the vehicle is driven over the base structure including the rails l9 and H while the hoisting units are fully lowered and substantially completely nested between the rails Ii! and H with all but the load receiving seats 35 and 35' disposed below the plane of the upper extremities of the rails. The wheels of the vehicle may be supported by the floor in which the base structure is submerged. The vehicle may be brought to rest in such position as to cause the seat 3% of the hoisting unit A to register with and receive the rear axle of avehicle as the seat is alevated in the manner hereinafter set forth. The position of the vehicle relative to the seatpSS may be predetermined in any manner as for example, by providing a depression in the base structure adjacent the rails Ill and H, as illustrated in the above patent application. The seat 36' of the hoisting unit 13 may be so positioned as to move into registration with and receive any suitable structure at the front end of the vehicle by disengaging the threads of the nut sections 86 and screw 73 as heretofore set forth. The cross bar may be released for movement relative to the rails by lifting the lock member 68 to disengage its end portion 69 from the slotted plate 12. With the parts of the hoisting unit B in the above described condition, this hoisting unit may be manually shifted in either direction to properly position its seat 36' where desired. The nut sections 80 may be thereafter reengaged with the screw 13 and the lock member 68 may be returned to locked engagement with the plates 72 at a new position thereby placing the hoisting apparatus in condition for operation.

The hoisting unit may be mechanically shifted after the lock member 68 has been lifted from the plates 72, by allowing the nut sections 86 of hoisting unit B to remain engaged with the screw 13 and disengaging the nut sections 89 of the hoisting unit A from the screw. Rotation of the screw l3 in opposite directions by the motor 92 under these conditions will shift the hoisting unit B in corresponding opposite directions along the base structure While the locking member 68 is released.

The relative positions of each boom and its associated lever system in the fully lowered position of the boom is illustrated in Figures 2 and 6 in which is shown spring members 93 one of which is mounted on each side rail 30 and 3| of the boom member. Each spring 93 has a free end portion which is adapted-to engage one of the lever arms 41 of the yoke structure shown in Figure 9 when the lever system is moved to is lowermost position shown in Figure 2. Each spring 93 is adapted to be loaded by the last increment of downward movement of the yoke member from the position shown in Figure 3 to the position shown in Figure 2.

When the screw 13 is rotated in a forward direction each boom member is shifted in a substantially horizontal path to move the linkage system from the position shown in Figure 2 to the position shown in Figure 3. This change in the angularity of the lever elements 50 with respect to the boom member is brought about without lifting the load or engaging the seats 36 and 36' with it. Counter-clockwise rotation of the link arms ll from the position shown in Figure 2 to the position shown in Figure 3 is initially assisted by the springs 93 which serve to guard against locking of the lever elements 50 and link arms :31 in an aligned relationship. The left end portions of the lever elements 55 are slightly curved upwardly with respect to the main links thereof in order to further guard against aligning of the pivotal axes of the connections between the link arms and lever elements and between the yoke member and the boom member. This counter-clockwise rotation of the link arms 4'! is arrested when the link arms are substantially normal to the length of the boom member by engagement with stops 94 one of which is secured to each of the bars 39 and 3! of the boom member 29. When the lever elements 50 are angularly disposed with respect to the boom member, as shown in Figure 3, they are in position to exert a favorable mechanical advantage in initially elevating the load engaging seat of the hoisting unit into contact with the load during movement of the left end of the boom unit toward the fixed cross bar 5| by further forward rotation of the screws 13. By the time the seat 36 of the boom member engages the load the mechanical advantage of the lever system has been further increased. Therefore the force required to be applied by the screw 13 during initial lifting of the load is reduced by this system of levers and accordingly the capacity requirement of the motor 92 is reduced. As the boom member reaches its intermediate position shown in dot and dash lines in Figure 4 the link arms 4? swing into substantially aligned overlapping relationship with respect to the lever elements 59 and at this position each link arm engages a stop 95 provided on each of the lever elements 50 for limiting relative rotation of the link arms 47 and lever elements 58 beyond this relationship. Further movement of the lower end of the boom member toward the lower fixed ends of the lever elements '50 elevates the boom member to the full line position shown in Figure 4 while the link arms remain in substantially aligned overlapping relation to the lever elements. The need for an increased mechanical advantage in the lever system of a hoisting unit of this kind is illustrated in Figure 4 wherein it will be seen that approximately the last quarter of the upward movement of the seat 36 is produced during approximately the last half of the travel of the lower end of the boom member toward the lower ends of the lever elements 50, whereas the first half of the travel of the lower 11 base structure for shifting movement between generally vertical and generally horizontal positions and having a load support on one end; mechanism for shifting said boom member between said positions including a lever element, a link element pivoted at one end to an end portion of said lever element and at its opposite end to said boom member at a location intermediate the length of the latter, means for producing relative shifting movements in respectively opposite directions between the other end of said lever element and the other end of said boom member for respectively raising and lowering said boom member through the action of said link and lever elements, said means being adapted to releasably hold said link and lever elements in approaching alignment with each other and in substantially parallel relation to said boom member when the latter is in its generally horizontal position, and a resilient ele mechanism for shifting said boom member between said positions including a lever element, a link element pivoted at one end to an end portion of said lever element and at its opposite end to said boom member at a location intermediate the length of the latter, an abutment engageable by said link element for limiting pivotal movement thereof in one direction relative to said boom member to a position substantially normal to said boom member when the latter is spaced from its vertical position, a second abutment engageable by said link element when said boom member is substantially in its vertical position for limiting pivotal movement of said link element in an opposite direction, means for producing relative shifting movements in respectively opposite directions between the other end of said lever element and the other end of said boom member for respectively raising and lowering said boom member through the action of said link and lever elements, said means being adapted to releasably hold said link and lever elements in approaching alignment with each other and in substantially parallel relation to said boom member, and a resilient element energizable during movement of said link and lever into said aligned relationship for urging said elements toward angular relationship with respect to each other.

7. Hoisting apparatus comprising a base structure, a boom member mounted on said base structure for shifting movement between generally horizontal and generally vertical positions, said boom member having a load receiving seat on one end and the other end shiftably connected to said base structure for movement therealong, a link and lever assembly for shifting said boom member between said positions including means pivotally connecting one end of said link to said boom member at a point intermediate the ends thereof and means pivotally connecting the other end of said link to one end of said lever, means for pivotally connecting the other end of said lever to said base structure, said link and lever being adapted to substantially align longitudinally with each other and to be disposed in angular relationship with respect to each other while said boom member is in its generally horizontal position so as to produce a favorable mechanical advantage during initial movement of said boom member from its generally horizontal position, and mechanism for relatively shifting said other end of said lever and the other end of said boom member toward and away from each other for raising and lowering said boom member respectively, said mechanism being adapted to initially shift said boom member and link relative to each other while said boom member is in its generally horizontal position in order to move said link and lever into angular relationship before said boom member is started toward its generally vertical position.

8. Hoisting apparatus comprising spaced rails, a boom member disposed between said rails hav ing a load receiving seat pivotally mounted on one end thereof, means pivotally connecting one end of said boom member with said rails and adapted to hold said end of said boom member against vertical displacement relative to said rails while permitting longitudinal shift of said one end of said boom member along said rails, a link and lever assembly for controlling shifting of said boom member between generally horizontal and generally vertical positions including alink element pivoted at one end to said boom member and a lever element having one end pivotally connected to the other end of said link element, means for fixing the opposite end of said lever element against movement relative to said rails, said link and lever assembly being substantially alignable with each other and receivable between said rails when said boom member is in its horizontal position, and power actuated mechanism comprising a member operatively connected with said first mentioned means for initially shifting said boom member bodily only longitudinally of said rails to bring said link and lever elements into an angular relationship to produce a favorable mechanical advantage for subsequently shifting said one end of said boom member toward the fixed end of said lever element to move said boom member from its horizontal position toward its vertical position.

9. Hoisting apparatus comprising a base structure, a boom member mounted on said base structure for shifting movement between generally horizontal and generally vertical positions comprising laterally spaced bars, a load receiving seat connecting the upper ends of said bars, a carriage on said base structure shiftable longitudinally thereof and pivotally connecting the lower ends of said bars, an inwardly extending trunnion fixed to each of said bars respectively at horizontally aligned locations intermediate their ends, a rigid yoke member comprising arm elements journalled on said trunnions and a connecting span element having spaced bearing portions, a pair of levers each having one end journalled on a bearing portion of said span element respectively and adapted to substantially align with said yoke when said boom member is in a horizontal position, means pivotally connecting the opposite ends of said levers with said base structure, and means for shifting said carriage toward said last mentioned ends of said levers to initially bodily shift said boom member and bring said levers and yoke into angular relationship and to subsequently urge said boom member toward its vertical position under the control of said yoke and levers.

l0. Hoisting apparatus comprising a base structure, a boom member mounted on said base structure and a boom member including laterally spaced bars mounted on said base structure for shifting movement between generally vertical and generally horizontal positions and having a load receiving seat mounted on one end and means connecting the other end to said base structure for shiftable movement therealong; mechanism for shifting said boom member between said positions including a pair of lever elements, a

pair of link elements, each link element being pivoted at one end to one end of one of said lever elements respectively and pivotally connected at its opposite end to one of said bars respectively at a location intermediate the length of the latter, and-means for producing relative shifting movement between the other endsof said lever elements and the other end of said boom member for raising said boom member through the action of said link and lever elements.

17. Hoisting apparatus comprising a base structure and a boom member including laterally spaced bars mounted on said base structure for shifting movement between generally vertical and generally horizontal positions and having a load receiving seat mounted on one end and means connecting the other end to said base structure for shiftable movement therealong; mechanism for shifting said boom member between said positions including a pair of lever elements, a pair of link elements, each link element being pivoted at one end to one end of one of said lever elements respectively and pivotally connected at its opposite end to one of said bars respectively at a location intermediate the length of the latter, a bar extending transversely of said link and lever mechanism interconnecting the adjacent pivoted ends of said link and lever elements, and means for producing relative shifting movement between the other ends of said lever elements and the other end of said boom member for raising said boom member through the action of said link and lever elements.

18. In hoisting apparatus comprising a base structure and a boom member mounted on said base structure for shifting movement between generally vertical and generally horizontal positions and having a load receiving seat mounted on one end and means connecting the other end to said base structure for shiftable movement therealong; mechanism for shifting said boom member between said positions including a lever element, a link element pivoted at one end to one end of said lever element and at its opposite end to said boom member at a location intermediate the length of the latter, and means for producing relative shifting movement between the other end of said lever element and the other end of said boom member for raising said boom member through the relative movement of said link and lever elements.

19. Hoisting apparatus comprising a base structure, a rigid fixed length boom member mounted on said base structure for shifting movement between generally horizontal and generally vertical positions, said boom member having a otally connecting the other end of said lever to said base structure, said link and lever being adapted to substantially align longitudinally with each other and to be disposed in angular relationship with respect to each other while said boom member is in its generally horizontal position, means for producing relative shifting movements in respectively opposite directions between said other end of said lever and the other end of said boom member while the latter is in its horizontal position for respectively contracting said assembly vertically and bringing the link and lever into angular position to produce a favorable mechanical advantage during initial movement of said boom member from its generally horizontal position.

20. In hoisting apparatus comprising a base structure and a rigid fixed length boom member mounted on said base structure for shifting movement relative thereto between generally vertical and generally horizontal positions, said boom member having a load receiving seat pivoted on its upper end and having its lower end shiftably connected to said base structure for movement therealong; mechanism for shifting said boom member between said positions including a lever element pivotaily connected at one of its ends to said base structure and shiftable bodily relative to said boom member, a link element pivoted at one end to the other end of said lever element and having a fixed pivotal connection at its opposite end to said boom member at a location intermediate the length of the latter, and means for producing relative shifting movements in respectively opposite directions between said one end of said lever element and the lower end of said boom member for respectively raising and lowering said boom member through the action of said link and lever elements.

21. Hoisting apparatus comprising a base structure, a boom member mounted on said base structure for shifting movement between generally horizontal and upper positions, a load receiving seat on one end of said boom member, means bodily shiftably mounting the other end of said boom member on said base structure, and mechanism for shifting said boom member between said positions including an actuating means having an element operatively connected to said boom member and including a toggle acting lever system comprising link and lever elements pivotally connected together at their adjacent ends and having their spaced ends pivotally connected to said boom member and base structure respectively and adapted to nest in substantially aligned relation substantially between the horizontal bounding plane of said boom memher when the latter is in its horizontal position and to be projected from between said planes into angular relation with respect to each other while said boom member is still in its horizontal position for providing a favorable mechanical advantage during initial raising of said boom member from its horizontal position.

DAVID A. WALLACE.

REFERENCES CREEK) The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,025,377 Craig May 7, 1912 1,725,216 Seldomridge Aug. 20, 1929 2,533,980 Weaver Dec. 12, 1950