US2653677A - Hoisting apparatus - Google Patents

Description

D. A. WALLACE HOISTING APPARATUS Sept. 29, 1953 3 Sheets-Sheet 1 Filed March 19, 1948 INVENTOR. jay 1i M aZ/azce ITTORA/IX Sept. 29, 1953 D. A. WALLACE HOISTING APPARATUS 5 Sheets-Sheet 2 Filed March 19, 1948 3 Sheets-Sheet 5 D. A. WALLACE HOISTING APPARATUS Q\ Tl: l' I q l hh'l lll M l l l l I l l II I .l l l I i J I .I: I. ll I I II'IHHI FWK Sept. 29, 1953 Filed March 19, 1948 Patented Sept. 29, 1953 HOISTING APPARATUS David A. Wallace, Grosse Pointe Farms, Mich.,

assignor to Walco, Inc., Detroit, Mich., a corporation of Michigan Application March 19, 1948, Serial No. 15,827

12 Claims.

This invention relates to hoisting apparatus and is an improvement in hoisting apparatus of the character shown in my patent applications Serial Nos. 653,385, 711,649 and 775,191 filed March 9, 1948; November 22, 1946 and September 20, 1947, respectively, now Patents Nos. 2,576,907, 2,576,153 and 2,576,908, respectively, dated November 27, 1951. Attention is also directed to my related copending applications which have issued as Patents Nos. 2,598,200 and 2,598,625 of May 27, 1952.

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

One of the main objects of the invention is to provide in hoisting apparatus having a plurality of independently and simultaneously operable hoisting units, a power driving mechanism which can be operatively engaged with one, all or a selected number of the hoisting units to positively elevate and positively lower the boom members thereof and which positively locks the hoisting units against unintended lowering from fully or partially raised positions.

Another object of the invention is to provide power driving mechanism in hoisting apparatus of this kind in which a single screw member serves to actuate all the hoisting units in their raising and lowering operations.

Another object of the invention is to provide improved reduction gear mechanism for driving a screw of this kind which accommodates extremely low positioning of the screw.

A further object of the invention is to provide driving mechanism for hoisting apparatus of this kind which can be conveniently controlled to raise and lower a load by any reversible prime mover,- such as a simple reversing electric motor.

A still further object of the invention is to provide mechanism for selectively coupling the boom members of the respective hoisting units to their common actuating screw.

Additional objects of the invention are to provide relatively shiftably mounted hoisting units in apparatus of this kind which can be conveniently variably spaced to accommodate loads of diiierent lengths, to provide relatively shiftable hoisting units which can be shifted with respect to each other by the same driving mechanism that is utilized to positively raise and lower the boom members of the units, to provide improved and conveniently manipulatable means for releasably holding the relatively shiftable hoisting units in a selected position, and to provide improved means for presetting the hoisting units for receiving spaced portions of a number of vehicles of difierent lengths and constructions in advance of placement of the vehicles upon the hoisting apparatus.

Another object of the invention is to provide mechanism for automatically interrupting operation of the power driving mechanism when the boom members of the hoisting units reach predetermined upper and lower positions respectively.

A further object of the invention is to provide screw operated hoisting apparatus which moves a load upwardly and downwardly in a path which does not excessively depart from a vertical course or require but a limited space at the opposite ends of the load to accommodate swinging thereof during the lifting and lowering operations.

Another object of the invention is to provide a system of levers in screw operated hoisting apparatus of this kind which does not require an excessively large starting torque in order to produce the initial load lifting action.

A further object of the invention is to provide screw operated hoisting apparatus of this kind which, when in its lower position, does not have its parts extending excessively above the floor level or base structure on which it is mounted or otherwise projecting into obstructing positions.

Another object of the invention is to provide improved hoisting apparatus of this character which can be disposed in a groove in a floor of relatively shallow depth or upon a fioor without requiring deep pits for its accommodation.

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

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

Fig. 2 is a fragmentary, end elevational View illustrating one manner in which the base structure of the hoisting apparatus may be installed to accommodate the driving of a vehicle into position to be lifted.

Fig. 3 is a fragmentary side elevational view of one of the hoisting units of the apparatus, illustrating in dotted lines various positions of the boom member of the unit during its lifting action.

Fig. 4 is a plan view of substantially the left half of the hoisting apparatus shown in Fig. 1, illustrating the left hoisting unit in its lowered position.

Fig. 5 is a plan view or substantially the right half of the hoisting apparatus shown in Fig. 1, illustrating the right hoisting unit in its lowered position.

Fig. 6 is a transverse sectional view taken on line 6-6 of Fig. 4.

Fig. '7 is a transverse sectional view taken on line 1-1 of Fig. 4.

Fig. 81s a side elevational view of the portion of the hoisting apparatus shown in Fig. 4, showing one "side rail thereof broken away and illustrating in dotted lines the raised position of the boom member of the hoisting unit.

Fig. 9 is a schematic wire diagram of an electrical control circuit for a hoist embodying the invention.

Fig. 10 is a vertical sectional view of the reduction gear mechanism of the driving apparatus shown in Fig. 1.

Fig. 11 is a side elevational view of a tool by which the hoisting units may be preset in position for receiving a vehicle of known length.

1 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 iirii'ts are particularly constructed to lift vehicles but may be readily adapted to the lifting of numerous other articles. 'Ihey are preferably operatively mounted on a track comprising spaced rails f and H of channel-shaped cross section having'lnwardly facing upper flanges l2 and I3 'andlower flanges and I5. The rails l0 and H may be mountedin a shallow groove formed in aplatform'str'ucture I6, illustrated in Fig. 2 which'is disposed upon a floor structure or they may be mounted in a shallow groove (not shown) of a floor structure with the upper flanges I2 and I3 flush with thefloorsurface.

:The hoisting units'A and B each includes a shiftable carriage, 'generally designated by the numeral I'Lhaving a horizontal base plate 18 and 'a lvertically upstanding flange l9. Provided on each of the opposite ends of the shiftable carriage are shoes20 and2| slidably mounted bet ween the flanges l2 and Hand the flanges nand l of the rails lfl'and rsepectively. 'The shoes'20 and 2| have recesses 22 and 23, respectively formed in their outer extremities for reducing "the areas of contact between the ex- "tremities of the shoes and the web portions of thera'ils l0 and I. An outer corner portion of the shoe ls'cut away to provide a passage 24' for accommodating an electrical wire I03, herelnal'ter referred to. The carriage l'i' includes "spaced flanges 21' and 28 disposed between and substantially parallel to the shoes and 2| and which are preferably formed integral with or welded to the base plate l8'a'nd upstanding flange l9, as illustrated in Fig. 4.

Each'hoisting 'unit'includes a boom member, generally designated by the numeral 29, which coinpri's'es'a pair of channel members 30 and 3|,

4 end 3| of the channel member 3| is received etween the shoe 28 and flange 28 of the carriage I! and is pivotally secured thereto by a pin 34, having a retaining collar 35 and which is received in apertures formed in the shoe 20 and flange 28 of the carriage IT, as shown in Fig. 7.

A load receiving seat, generally designated by the numeral 35 is pivotally mounted on the upper ends of the channel members '30 and 3|, as illustrated in Figs. 1 and 3. 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 31 are spaced downwardly extending ears 39 for receiving pins When the boom member comprising the channel members 39 and 3| is in its uppermost position, the lower side of the bar 31 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 "41 extending substantially parallel to the channel members 39 and 3| which are pivotally attached at their upper ends by a pin 42 to rigid arms 43 extending from the lower side of the baril of the seat member, as shown in Fig. 3. The lower ends of the links are pivotally attached by a pin 44 carried by and extending upwardly from the base portion l8 of the carriage IT. The

pivotal axes provided by the pins 42 and "44 are the boom member provided by the pins 82 and 34, respectively. This provides a parallelogram mechanism which retains and supports the' s'eat 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 35 is supported in horizontal position by engagement of its lower side with the upper eztre'mities'of the channel members 33 and 3|.

The boom member 29 is supported and guided during its movement by liriks45 each of which is pivotally attached at oneend to a plate 48 fixed to one channelmember respectively "of the boom. The plates 45 extend upwardly from'the lower position of the boom member, as illustrated in Fig. 4. The upper end of each link' 45" is pivotally attached toits associated plate 46 by pins 4'! and the links 45 are disposed adjacent the facing sides of the channel members 3D"and 3|. The lower ends of the links 45 are pivotally'attached toa cross bar 48 which extends between the rails I3 and H of the track structure. This cross 'bar'is provided with upwardly'extei'r' ding shoes 49 and 53 which are engaged between the flanges|2 and I4 of the rail Hi and the flanges i3 and I5 of the rail l The upper cornerfof the shoe 49 is cut'away to accommodate thewir'cs IN and I03. The cross bar 48 includes integral upwardly extending pairs of flanges 5| and 52 and a central bearing portion 53 having a bore v The lower end of one link is received between the flanges 52 and pivotally attached thereto by a pin 55 and the lower end of the other link 45 is received between the flanges 5| and pivotally attached thereto by a pin 56. :The cross bar 48 is preferably releasably fixed to the 5 side rails I8 and II by pins 51 or other suitable means. If desired this attachment may be made by the use of bolts or cap screws. The channel members 38 and 3| of the boom 29 are adapted to be received between the shoes 49 and 50 and the adjacent flanges SI and 52 respectively when the hoist is in its lower position.

The hoist member B is substantially identical to the hoist member A and similar parts are designated by the same numerals. The hoist member B however, has a slightly different seat generally designated by the numeral 36' which includes a bar 31 having a channel in its upper side bounded by flanges 58 in which rests 59 are shiftably mounted. Each rest 59 has a notch 60 in its upper side for receiving a portion of the load to be lifted.

The lower ends of the links 45 of the hoist B are pivotally attached to a cross bar GI which differs substantially from the cross bar 48 of the hoist A. The cross bar 6| has pinion segments 82 fixed on its opposite ends and provided with teeth 63 which are adapted to mesh with the teeth 65 of a rack 65 mounted on each of the lower flanges Ill and I5 of the rails I and II, respectively. The lower ends of the links 55 of the hoist B are pivotally attached by a pin 86 to each of the gear segments 62, respectively which are rigid with the cross bar 6|. The gear segments 62 fit between the upper and lower flanges of the rails I8 and II with suflicient clearance to permit the segments to be lifted out of engagement with the racks and selectively positioned in various locations along the racks 65. A handle 6i is provided for lifting the cross bar for this purpose. Any suitable means may be employed for detachably securing the cross bar 6i in a plurality of selected positions in order to vary the spacing of the hoisting units A and B to facilitate lifting of loads or vehicles of different lengths or constructions.

The driving apparatus by which the boom members 28 of the hoisting units A and B may be selectively individually and simultaneously positively raised and lowered comprises a screw member, generally designated by the numeral 68, having threads e9 thereon associated with each of the boom members 29, respectively. The screw member 68 preferably comprises a plurality of sections which are connected together in longitudinal alignment by couplings 10. The respectively opposite end portions of the screw member 38 are journalled in bearings provided in transverse cross members H and I2 which extend between and are fixed to the ends of the rails is and II. One or more intermediate cross member it also extends between and is fixed to intermediate portions of the rails and is provided with bearings for rotatively supporting the screw member at locations between its ends. The bearing 58 of the cross bar 48 also rotatively supports an intermediate portion of the screw member.

Each carriage ll of the boom members A and 33 includes a releasable nut member, generally designated by the numeral I4 which is adapted 'o be threadedly engaged with the screw member in the manner hereinafter set forth. The nut member 74 comprises separable internally threaded semi-cylindrical nut sections I5 and I8 integral with threaded stems I1 and i8 respectively, as shown in Fig. '7. The threaded stem l'i is axially shiftably mounted in aligned apertures 83 and 84 formed in spaced flanges 8I and 82, respectively which extend upwardly from and are formed integral with the base plate I8 of the carriage I1. The threaded stem 18 is axially shiftably mounted in aligned apertures I9 and formed in spaced flanges and 8'6 formed integral with and extending upwardly from the base plate I8 of the carriage I'I. Threaded on. the stems TI and I8 are adjusting nut elements 81 and 88 having handle elements 89 and 90, respectively which are receivable in notches 9I and 92 formed in the vertical flange I9 of the carriage H. The stems IT and 1'8 have threads 93 and 94, respectively of opposite pitch which is so predetermined as to separate the nut sections 15 and 18 sufficiently to disengage their threads from the screw member 68 when the nut elements 81 and 88 are rotated substantially one half turn relative to the threaded stems I1 and I8, respectively. When the handles 89 and are in the position shown in Figs. 4 and 5, the nut sections 15 and I6 are in threaded engagement with the screw member 68 and turning of the screw member in opposite directions shifts the carriage I1, and lower end of the boom member 29 which the carriage supports, longitudinally of the track toward and away from the lower ends of the links 45, respectively. When the handles 89 and 98 of the hoisting units A and B are in the positions shown in Figs. 1, 4 and 5 the boom member 29 of both hoisting units are simultaneously moved upwardly or downwardly depending upon the direction of rotation of the screw member 68. The handles 89 and 90 associated with both or either one of the hoisting units may be turned in a clockwise direction substantially 189 from the positions shown in Figs. 1, 4 and 5 to disengage the threads of the respective nut sections 15 and Hi from the threads of the screw 68, thereby permitting rotation of the screw 68 to shift the lower end of only one or the other of the boom members 29, or permitting rotation of the screw 68 without shifting either of the boom members 29, as desired.

The cooperating threads of the screw member 68 and nut sections 15 and 16 have an irreversible pitch and therefore while rotation of the screw positively drives the boom members 29 upwardly and downwardly, the weight of an elevated load supported on the boom member can not rotate the screw member 68. Accordingly the threaded engagement between the screw member 68 and the nut sections 15 and I6 serves as a lock to positively hold each boom member it in any selected position to which it is shifted by rotation of the screw member.

The screw member 68 is preferably driven through suitable reduction gear mechanism, generally designated by the numeral 95, which is in turn driven by a reversible electric motor The gear mechanism comprises a housing l2i1, having an opening I2I in its left end wall for receiving a shaft I22 which has a coupling 23 attached to the screw member 68, as shown in Fig. 10. The shaft 122 is journalled in bearings I24 and I25 which rotatably support it and resist thrust of it in both directions. The shaft 622 has a bevel gear 123 on its inner end which is meshed with a bevel gear I21 fixed to the end of a vertical shaft I28 which is journalled in bearings I30 and I8I mounted in the upper and lower walls of the housing I20, respectively. A large bevel gear I29 mounted on the shaft I28 is meshed with a bevel pinion I30 on the shaft I3I of the motor 96. The motor shaft I3I is journalled .in ,a bearing {I 32 which ,is :mounted in the end wall ,of the housing .I 20.

The bevel gears :and pinion are predetermined :in size to produce a desired vgear reduction, the final drive of which .is presented ,by .the shaft I22 at .a low level which accommodates .low ,positioning of the screw member 68 which ,itdrives.

The .electric motor 96 .is provided with a .control circuit, the wire .diagram of :which is schematically shown in 9.. The control circuit includes a portable switch unit -91, preferably having two push button switch elements '98 .and 99 of conventional construction which establish forward and reverse,drivingcircuitsof themotor .96. The switch elements 98 and 9,9 are preferably of the type which are spring urged to open positions and which have to be .manually held in closed positions. The switch unit 91 is connected onthe-endof a long cable I06 which .can be extended -.to positions adjacent the hoisting units A .and B to facilitate control by an attendant while standing close to either unit. The cable lfiflincludesthree wires I9I, I02 and I03. The center wire In is connected to one terminal of each of the switch elements .98 and .69 and the wire .-.IIII is-connected only to the switch element!!!) and the wire I03 isconneoted only to the switch element 9.8. Depression of the switch element 99 produces forward drive of the motor :96 .forraising the booms 29 and depression of :the :switchclement 98 produces reverse drive .of the :motor66 for lowering the boom elements.

Connected inseries in .the wire I03 is a conventional limit switch I04 shown in Figs 1 and 9 which is mounted onthe rail IQ and has a .rightwardly-spring urged plunger I which is engageable by'the carriage I! of the hoisting unit A when the carriage I'I reaches its extreme leftward position corresponding to the lower .position of the boom -,member 29. Opening of the limit switch IIi Lthus terminates the downward drive of screw 68. A limit switch I06 having a leftwardly spring urged plunger I01 is mounted onthe rail III at a location on the right of the boom member .29, as viewed in-Fig. 1. limit switch I66 isconnected in series in the wire IIII and serves tov open the forward driving .circuit of the motoriB when the boom member 29 reaches a predetermined upper position. It should be notedthat while the limit switches I04 and. I06 areshown associated only with the hoisting unit A which is fixed in position, similar limit switches. may be applied to the hoisting unit 15. However, ony one set of limit switches is required to safeguard each hoisting unit against excessive strain by urging of its boom member beyond either the'limiting upper or limiting lower positions thereof.

In operation of the hoisting apparatus in lifting a vehicle, the vehicleisdriven over the base structure including the rails I0 andII while the hoisting units are fully lowered-and-substantially completely nested between the rails -III and II with all but the load-receiving seats and 36' and insignificant portionsof theplates 46 and levers45;disposed-below the plane-of the upper extremities -of the rails. The wheels'of the vehiclemay be supported by the floor in which the base structure is submerged or if .a platform is employed, then the wheels of the vehicle are supported .on theplatform I6in which the rails II) and II..a-re-submerged, as, shown in 2. ...In either. case, ,d epr essions .I 09 are formed ;ad.iacent.the basestructure, in-either floor or the CPI '4 The center II2 carried by a block platform for receiving the rear wheels, for example, to position the rear axle of the vehicle in registering alignment with the seat 36 of the hoisting unit A so as to be engaged thereby when the boom member 29 is initially raised. The

,seat 316' of the hoisting unit B may be positioned to engage suitable structure at the front end portion of the'vehicle by disengaging the threads of the nut sections I5 and I6 from the thread of the screw 68 by operation of the handles 89 and 9 9 and thereafter the pinion segments 56 may be lifted out-of engagement with the racks .65 by lifting upon the handle 61. With the parts of the hoisting unit B in the above described condition, the hoisting unit may be manually shifted in either direction to properly position its seat 35 where desired. When the hoisting unit Bis thus adjustably positioned, the nut sections I5 and 16 may be reengaged with the screw 68 and the pinion segments 66 may be re- ;engaged with the rack 65 to condition the hoisting unit B for operation.

The hoisting unit B may be mechanically shifted after the pinion segments 66 have been lifted from the rack 65, by allowing the nut sections -I5 and I6 to remain engaged with the screw 68 and disengaging the nut sections of the hoisting unit A from the screw. Ro-

tation of the screw 58 in opposite directions by bers are in their lower positions.

The seats :36 and 35' may be preset in position in advance-of driving of a vehicle over the hoisting apparatus with the aid of a tool shown in Fig. 11. This tool comprises a bar IIII having a fixed center III at one end and a shiftable H3 shiftably mounted on the opposite-end. portion of the bar. The block II3 may be set by a screw H4 in an adjusted portion determined by applying the tool to thecenters of the hub caps of a vehicle or other structure thereof with which the seats 36 and 36 are desired to register, or the bar IIO may be provided with suitable marking (not shown) designating the proper positions of the shiftable center H2 for various makes and types of vehicles. When the centers III and I I2 are so located, one thereof may be placed in line with the notch of the seat ,35 of the hoisting unit A and the hoisting unit B may be shifted until the notch of its seat 36' is aligned with the other center.

When the vehicle is positioned relative to the hoisting units as above described and the forward drive control switch element 99 is depressed, the

.screwmember 68 is so rotated as to urge the carriages I! of both units rightwardly as viewed in Fig. 1. This action shifts the boom members 29 simultaneously upwardly, the movement of the seats 36 and 36 being so controlled, as illustrated in Fig. 3, by the links 45 as to confine each seat movement to a course which does not depart significantly from a vertical course.

The location of the pivots 41 of each unit above the plane defined by the pivotal axis of the lower endsof the links 45 and the pivotal axis of the .boom member thereof, prevents unintended locking of theboom member 29 and links 45 ,in an alignedrelationship and additionally provides a greater mechanical advantage during initial lifting of the load. Since the minimum mechanical advantage in the leverage system embodied in the above described hoisting apparatus occurs when the apparatus is fully contracted, increasing of the mechanical advantage at this end of its range of movement significantly reduces the maximum power requirements and size of the motor 96.

Lowering of the boom members 29 is accordingly produced by depression of the switch element 98 which causes reverse rotation of the screw 68.

Either one of the hoisting units A and B may be selectively rendered inoperative by disengaging its nut segments 15 and Hi from the screw member 68 so as to elevate only the boom member 29 of the other unit. In all instances of operation of the apparatus the boom members are positively driven upwardly and downwardly by the screw.

Although but one specific embodiment of the invention is herein shown and described, it will be understood that various changes in the details and construction thereof may be made without departing from the spirit and scope of my invention.

I claim:

1. Hoisting apparatus including a base structure, a pair of hoisting units mounted on said base structure each comprising a boom member and an operating lever pivotally attached at one end to an intermediate portion of each boom member respectively, one of said hoisting units being shiftable longitudinally of said base structure, means coacting with the other end of the lever of said latter hoisting unit for holding said latter hoisting unit against said shifting move- .ment, means mounting each of said boom members on one of said hoisting units respectively for shifting movement between generally horizontal and generally vertical positions, a common driving member for positively propelling each of said boom members from each of said positions to the other position, and mechanism for releasably effectively coupling each of said boom members independently to said common driving member, said shiftable hoisting unit being movable longitudinally of said base structure without affecting :said other unit by operation of said common driving means when said shiftable hoisting unit is coupled with said driving member and said holdting means is released and the boom member of the other hoisting unit is uncoupled from said common driving means, and apparatus for selectively operating said common driving member in respectively opposite directions.

2. Hoisting apparatus including a base structure, first and second hoisting units mounted on said base structure each comprising a boom member having a load receiving seat on one end, said second hoisting unit being shiftable longitudinally of said base structure, means mounting each of said boom members for shifting movement between generally horizontal and generally vertical positions including a lever element pivotally attached at one end to each boom member respectively, means pivotally fixing the other end of the lever element of said first hoisting unit to said base structure, detachable cooperating means on the other end of the lever element of said second hoisting unit and on said base structure respecstructure,a common driving member for positively driving each of said boom members from each of said positions to the other position, mechanism for releasably efiectively coupling the end of each boom member opposite its load receiving seat with said common driving member, said second hoisting unit being movable longitudinally of said base structure by operation of said common driving means when said cooperating means are detached and the boom member of said second hoisting unit is coupled with said common driving member, and apparatus for selectively operating said common driving member in respectively opposite directions.

3. Hoisting apparatus including a base structure comprising a track, a hoisting unit shiftably mounted on said track including a boom member having a load receiving seat on its upper end portion, means holding the lower end of said boom member against vertical displacement relative to said track and pivotally and shiftably supporting said boom member for movement longitudinally of said track, a, lever element pivotally attached at one end to an intermediate portion of said boom member for guiding it in its movement between said positions, releasable cooperating holding means on the other end of said lever element and on said base structure respectively for supporting the latter end of said lever element for pivotal movement relative to said base structure at a plurality of selected positions along said base structure, and a driving member operatively threadedly connected with the lower end portion of said boom member for shifting said lower end portion longitudinally of said track to raise and lower said load receiving seat, said hoisting unit being movable longitudinally of said base structure by operation of said driving member when said cooperating holding means are released.

4. Hoisting apparatus including a stationary base structure, a hoisting unit bodily shiftably mounted on said base structure comprising a boom member, means for releasably holding said hoisting unit against bodily shifting movement, means mounting said boom member on said hoisting unit for shifting movement between generally horizontal and generally vertical positions, a driving member extending longitudinally of and operatively mounted on said base structure in fixed location relative thereto, and means connecting said driving member with said boom member for positively propelling the latter from each of said positions to the other position, said hoisting unit being shiftable longitudinally of said base structure by operation of said driving member when said holding means is released.

5. Vehicle hoisting apparatus including a pair of hoisting units each having a rigid fixed length boom member, means mounting the boom member of each hoisting unit for shifting movement in the same direction between lower and upper positions, separate vehicle engaging members on the respective boom members of said units, a common driving member for positively propelling said boom members from each to the other of said positions comprising a rotatable screw element having threads of the same direction associated with each of said boom members, a nut element on each of said boom members in threaded engagement with said screw, said nut and screw elements having threads of irreversible pitch for effectively locking said boom elements in all positions in their paths of movement, and apparatus for selectively propelling said screw element in respectively opposite directions.

6. Hoisting apparatus comprising a base structure including spaced rails having a groove therebetween, a pair of hoisting units each having a boom member receivable substantially completely in said groove when in its lower position, means mounting each boom member for shifting movement between upper and lower positions, means for translatively shiftably supporting said units on said rails for movement longitudinally of said rails, said boom member mounting means and said unit supporting means being substantially completely receivable in said groove, and a common driving member in said groove connected with each boom member for positively driving them upwardly and downwardly.

7. Hoisting apparatus comprising a base structure, a hoisting unit, means bodily shiftably mounting said hoisting unit for movement longitudinally of said base structure including a carriage shiftably mounted on said base structure, said hoisting unit including a boom member shiftably mounted on said carriage for movement between generally horizontal and generally vertical positions, and mechanism for selectively bodily shifting said hoisting unit relative to said base structure and for positively selectively shifting said boom structure toward its generally horizontal and generally vertical positions respectively comprising a rotatable screw element on said base structure and a nut element in threaded engagement with said screw element and attached to said carriage.

8. Hoisting apparatus comprising a base structure, a hoisting unit, means bodily shiftably mounting said hoisting unit for movement longitudinally of said base structure including a carriage shiftably mounted on said base structure, said hoisting unit including a boom member having its lower end portion pivotally mounted on said carriage for movement between generally horizontal and generally vertical positions, mechanism for selectively bodily shifting said hoisting unit relative to said base structure and for positively selectively shifting said boom structure toward its generally horizontal and generally vertical positions respectively comprising a rotatable screw element on said base structure and a nut element on said carriage and adapted for releasable threaded engagement with said screw element, means for releasably holding said nut element in threaded engagement with said screw element and means for releasably holding said hoisting unit against shifting bodily relative to said base structure.

9. Hoisting apparatus comprising a base structure, a hoisting unit, means bodily shiftably mounting said hoisting unit for movement longitudinally of said base structure including a carriage shiftably mounted on said base structure, said hoisting unit including a boom member having an end portion shiftably mounted on said carriage for movement between generally horizontal and generally vertical positions, a rotatable screw element journalled on said base structure, a nut element in threaded engagement with said screw element, means holding said nut element against rotation with said screw element and operatively connecting it with said carriage for shifting said hoisting unit bodily linearly of said base structure and shifting said boom member toward its generally vertical and generally horizontal positions respectively in response to rotation of said screw element in respectively opposite directions, and reversable driving mechanism for selectively driving said screw element in respectively opposite directions.

10. Hoisting apparatus comprising a base structure, a hoisting unit, means shiftably mounting said hoisting unit for bodily movement relative to said base structure comprising a support means shiftably mounted on said base structure, said hoisting unit including a boom member having its lower end portion pivotally mounted on said support means for movement between generally horizontal and generally vertical positions, a rotatable screw element journalled on said base structure, a nut element comprising relatively shiftable sections adapted to be releasably engaged with said screw element, means for releasably holding said sections of said nut element in threaded engagement with said screw element, means operatively connecting said nut element with said support means and for holding it against rotation with said screw and against rotation with respect to said support means for shifting said hoisting unit bodily relative to said base structure and for shifting said boom member toward its generally vertical and generally horizontal positions respectively in response to rotation of said screw element in respectively opposite directions, and reversible drive mechanism for selectively driving said screw element in respectively opposite directions.

11. Hoisting apparatus comprising a base structure including a horizontal track member, a hoisting unit, means shiftably mounting said hoisting unit for bodily movement relative to said base structure including a carriage shiftably mounted on said track member having means coacting therewith for holding said carriage against movement transversely and vertically of said track member, said hoisting unit including a boom member pivotally mounted at one end on said carriage for shifting movement from a position substantially parallel to said track member to a substantially vertical position, a lever member pivotally mounted at one end for pivotal movement relative to said base structure and pivotally attached at its opposite end to said boom member at a location intermediate the ends of said boom member, a rotatable screw element journalled in and extending substantially parallel to said base structure, a nut element on said carriage in threaded engagement with said screw element for selectively shifting said hoisting unit bodily relative to said base structure and for shifting said carriage toward and away from said first mentioned pivoted end of said lever for respectively raising and lowering said boom member, and mechanism for selectively rotating said screw member in respectively opposite directions.

12. Hoisting apparatus including a stationary base structure, a hoisting unit bodily shiftably mounted on said base structure comprising a boom member, means for releasably holding said hoisting unit against bodily shifting movement, means mounting said boom member on said hoisting unit for shifting movement between generally horizontal and generally vertical positions, a driving member extending longitudinally of and operatively mounted on said base structure in fixed location relative thereto comprising a screw element journalled on said stationary base structure and a nut threaded on said screw element and attached to said boom member, and means connecting said driving member with said boom member for positively propelling the latter from each of said positions to the other position, said hoisting unit being shiftable longitudinally of said base structure by operation of said driving member when said holding means is released.

DAVID A. WALLACE.

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Prouty Feb. 19, 1907 Feix Mar. 15, 1910 10 Price June 14, 1921 Seldomridge Aug. 20, 1929 Martin Feb. 12, 1935 Weaver Sept. 24, 1935 Dement June 9, 1936 15 Number Number Name Date Meacham July 2, 1940 Weaver Dec. 12, 1950 Wallace Nov. 27, 1951 Wallace Nov. 27, 1951 Wallace Nov. 27, 1951 Wallace May 27, 1952 Wallace May 27, 1952 FOREIGN PATENTS Country Date Italy June 23, 1932 Great Britain Jan. 29, 1931 Great Britain May 27, 1935

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