US2530137A

US2530137A - Combined hoisting apparatus and automatic cover structure therefor

Info

Publication number: US2530137A
Application number: US88652A
Authority: US
Inventors: David A Wallace
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-04-20
Filing date: 1949-04-20
Publication date: 1950-11-14
Anticipated expiration: 1967-11-14

Description

Nov. i4, i950 D. A. WALLACE COMBINED HOTsTINC APPARATUS ANO AUTOMATIC COVER STRUCTURE THEREFOR 4 Sheets-Sheet 1 Filed April 20, 1949 IN VEN TOR.

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NOV- 14, 1950 D. A. WALLACE 2,530,137

COMBINED HOISTING APPARATUS AND AUTOMATIC COVER STRUCTURE THEREFOR Filed April 20, 1949 4 Sheets-Sheet 2 NVENTOR. ,ZBTI/a Hf WdZZqce.

Nomv. 14, 1950 D A WALLACE 2,530,137

COMBINED HOISTNG.- APPARATUS AND AUTOMATIC COVER STRUCTURE THEREFOR Filed April 20, 1949 4 Sheets-Sheet 5 NOV 14, 1950 D. A. WALLACE 2,530,137

COMBINED HOTSTTNG APPARATUS AND AUTOMATIC COVER STRUCTURE THEREFOR I Filed April 20, 1949 4 Sheets-Sheet 4 1N VEN TOR.

Patented Nov. 14, 1950 COMBINED HOISTING APPARATUS AND AUTOMATIC COVER STRUCTURE THERE- FOR Davia A. Wallace, Grosse Pointe Farms, Mich.

Application April 20, 1949, Serial No. 88,652

Claims. v 1 This invention relates to improved hoisting apparatus.

Y More particularly the invention pertains to improved cover mechanism for vehicle hoisting apparatus such as that set forth in my pending applications, Serial Nos. 15,827, 34,772 and 58,219.

One of the main objects of the invention is to provide fully automatic, self acting cover mechanism of -this kind which is adapted to substantially completely cover the recess or -chamber in a floor or other structure in which the boom members and operating means oi hoisting apparatus is received when the hoisting apparatus is in its lower position.

' Another object of the invention is to provide cover mechanism of this kind for such hoisting apparatus receiving recess or compartment which is automatically shifted from closed to open position during raising and lowering, respectively,

of the boom members and which is returned to l closed position when the boom'members reach their uppermost and lower positions, respectively, without requiring manipulation, adjustment or other attention of the operator.

A further object of the invention is to provide cover mechanism of this kind which can be .applied to the recesses in which are received multiple unit hoisting apparatus of the type in which the V respective hoisting units can be varably positioned to accommodate lifting of vehicles of diverse lengths.

Y. A still further object of the invention is'to provide a plurality Aof pivotally connected cover sections in cover mechanism of this kind which are shiftable relative to each other by the raising and lower movements of the respective parts of the .housing apparatus and in such timed relationship with respect to movements thereof as to lavoid obstructing interferences, free falling of cover sections from substantial heights and noisy operation.

.An additional object of the invention is to provide cover mechanism of this kind which performs Vits intended purpose while the hoisting units of lapparatus Vincluding a pair of such units are spaced at diverse distances from each other to accommodate lifting of vehicles of diiferent lengths.

An .illustrative embodiment of the invention is shown in the accompanying drawings, in which: f' Fig. 1 is a perspective view of hoisting apparatus provided with cover mechanism embodying the invention .showing portions of the cover structureremoved `to disclose the underlying hoisting sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a fragmentary plan of the central portion of the hoisting apparatus shown in longitudinal vertical section in Fig. 2.

Fig. 4 is a transverse, vertical sectional View takenon line 4--4 of Fig. 3.

Fig. 5 is a transverse, vertical sectional view taken on line 5 5 of Fig. v1.

Fig.6 is a perspective view of lhoisting apparatus provided with cover mechanism embodying the invention and showing the hoisting apparatus in its fully lowered condition.

Fig. 7 is a fragmentary, perspective view of the left end portion of the hoisting apparatus shown in Fig. fillustrating portions of the cover in their initial state of opening Aand last stages of closing movements which correspond with the first -increment of raising movement and last stage of lowering movement, respectively, of the hoisting apparatus.

Figs. 8, 9, l0, l1 and 12, show that portion of the hoisting apparatus, yand its cover mechanism, illustra-ted in Fig. 7, in successive stages of its upward movement, respectively, and which views, in reverse order, illustrate the positions of the 'cover mechanism at successive stages of lowering movement of the hoisting apparatus.

Fig. 13 is a fragmentary perspective View of the right end portion of the hoisting apparatus shown in Fig. 6, illustrating the cover removed to disclose the underlying construction.

Fig. 14 is a fragmentary-perspective view of the left end portion of the hoisting apparatus illus- 'trated in Fig. 6, showing the cover member of the apparatus in fully closed position.

Fig. 15 is a fragmentary side elevational View lshowing one of the hoisting units of the apparatus illustrated in Fig. l, in a position to which it is bodily shifted to obtain a favorable initial mechanical advantage during the first stages of operation-of the hoisting uni-t from its lowermost position.

Thehoisting apparatus of this Aapplication includes a pair vof hoisting units and is generally similar to that disclosed in my copending application, Serial No. 58,216, led November 4, 1948 and in some respects the apparatus is similar to the hoisting apparatus shown in my copending application, Serial No. 34,772, filed J-une 23, 1948. In this application. the hoisting apparatus is provided with an automatic, self-operating cover structure by lwhich it may be substantially completely enclosed within a chamber. The cover comprises a plurality of slidably and pivotally connected sections some of which uncovers the upper side of that portion of the chamber in which is received each of the hoisting units as they are either individually or simultaneously moved into and out of the chamber, and which covers the upper side of the chamber while either or both hoisting units are in their elevated and in their contracted positions respectively. The sections of the cover structure are so constructed and arranged and associated with respect to each other as to be operable to open and closed positions by engagement with respective portions of the boom structures and without the aid of complicated operating means in addition to that which is required for operation of the hoisting units.

In Fig. 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 respectshereinafter 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 and l! of channel shaped cross section having inwardly facing upper flanges l2 and I3 and lower flanges I4# and l5. The rails l0 and Hvmay 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 iiush with the floor surface.

The hoisting units A and Beach include a shiftable carriage, generally designated in Figs. 2 and 3 by the numeral Il, having a horizontal base plate I8 and a vertically upstanding flange |9. Provided on each of the opposite ends of the shiftable carriage are wheels 29 andrZl which are received between the flanges l2 and I4 and I3 and i5 of the rails l and respectively. The wheels 29 and 2| are journalled on the outer end portions of trunnions 22 and 23, which are respectively mounted on and extend outwardly from

end anges

24 and 25 of the carriage Il.

The

end flanges

24 and 25 may be welded to or y formed integral with the base plate I8 and flange i9 of the carriage Il.

Each hoisting unit includes a boom member, generally designated by the numeral 29, which comprises a pair of channel members 30| and 3| having outwardly facing web portions and provided with solid

lower end portions

30 and 3|', respectively. The solid lower end 30 of the channel 4member 30 is apertured and journalled on the trunnion 22 at a location between the wheel 2D and end flange 24, as shown in Fig. 4. The

. solid lower end 3|' of the channel member 3| is apertured and journalled on the trunnion 23 at a location between the wheel 2| and the end flange 25.

Hoisting unit A is provided with a load receiving seat, generally designated by the numeral 36, which includes a channel bar 3l on each of the opposite ends of which is pivotally mounted a rest 38 having a notch in its upper side for receiving the rear axle of a vehicle. Extending downwardly from the ends of the bar 31 are ears 39 by which the seat 35 is pivotally mounted on the channel members 3D and 3|, with the aid of pins 40.

A somewhat diiferent load receiving seat generally designated by the numeral 35', is pivotally mounted on the upper ends of the channel members 33 and 3| of the hoisting unit B, as illustrated in Fig. l. The load receiving seat 36' comprises a channel bar 31' on each of the opposite end portions of which is shiftably mounted for movement longitudinally and tranversely of the bar 3l', a rubber pad 38'. Provided on the 0pposite side of the bai` 3'." are spaced downwardly extending ears 33 for receiving pins 4G' by which the seat 35 is pivotally mounted on the upper ends of the

channel members

30 and 3|.

When kthe boom member of hoisting unit A comprising the channel members 33 and 3| is in its uppermost position, the lower side of the bar 3i seats upons the upper extremities of the channel members. During movement of the boom member 29 from its lower to its upper position the seat 35 is retained in a substantially hori- Zontal position by parallelogram mechanism including link members 4| extending substantially parallel to the channel members 3B and 3| which are pivotally attached at their upper ends by a pin 42 to rigid arms 43 extending from the lower sides of the bars 31 of the seat members, as shown in Fig, l. The lower ends of the links 4| are pivotally attached by pins 44 carried by ears 4' extending leftwardly from the flange portion E8 of the carriage The pivotal axis provided by the

pins

42 and 44 are equidistant from the pivotal axis of the seat 36 provided by the pins 49 and the pivotal axisof the boom member provided by the trunnions 2,2` and 23, respectively. This provides a parallelogramv mechanism which retains and Supports the seat 36 in horizontal load supporting position during movement of the boom member 23 between its lower and upper positions. When the boom member is in its upright position thefseat 36 is supported in horizontal position b y engagement of its lower side with the upper extremities of thev channel members 3i! and 3|. The same parallelogram mechanism is provided in hoisting unit B and designated by the same numerals.

The boom member 29 is supported and guided duringits movements by a lever system, generally designated by the numeral 45, which includes a rigid yoke element comprising an intermediate span part 46 and spaced rigidly connected link arms 4l. The span part 46 and link arms 4l may be integrally formed, welded or otherwise suitably rigidly connected. The free ends ofthe link arms 41 are journalled on trunnions 48 fixed to and extending inwardly from the

bars

30 and 3| of the boom member 2S at aligned locations intermediate the length of the

bars

30 and 3 I. Provided on the span part 46 of the yoke are spaced bearings on which are journalled the upper end portions of a pair of levers 50. As shown in Fig. 1 the levers 5B are straight throughout the major portions of their length but are provided with slightly upwardly curved upper end portions. The lower ends of the levers 50 are pivotally attached to a cross bar'5l which extends between the rails I0 and of the track structure. This cross bar is provided with upwardly extending shoes 52, one of which is engaged between the flanges I2 and I4 of the rail i3 and the other of which is engaged between the flanges I3 and |5 of the rail Il. The cross bar 5| includes integral upwardly extending pairs of flanges 53 and 54 and a central bearing portion 55 having a bore 56. The lower end of one lever 55 is received between. the flanges 53 and pivotally attached thereto by a pin 51 and the lower end ofithe other lever 501s receivedbetween the flanges 54 and pivotally attached thereto by a pin 58. The cross bar 5| is preferably releasably fixed to the side rails I and II by pins 59 or other suitable means such'as bolts, capscrews and the like. The bars 30 and 3l of the boom 29 are adapted to be received between the shoes 52 and the adjacent flanges 53 and 54 respectively when the hoist is in its lower position.

The hoisting unit B is substantially identical to the hoisting member A and similar parts are designated by the same numeral. However, the lower ends of the levers 50 of the hoisting unit .B are pivotally attached to a cross bar I shown in Fig. 3, which is substantially identical to the cross bar 5| of unit A. Provided on the cross bar 5| are pairs of upstanding iianges 63 and. B4. The lower end of one lever 50 is received between `the anges 63 and pivotally attached thereto by a pin 65 and the lower end of the other lever 50 is received between the anges 64 and pivotally attached thereto by a pin 66. The cross bar 5 I has an upstanding side flange 61 extending along its left side, as viewed in Fig. 3, on the left side surface of which is provided spaced pairs of ears 68. Between each pair of ears 58 is pivotally mounted a dog 69 which is engageable between teeth of a rack 10, one of which is stationarily mounted adjacent each rail I0 and I I, respectively. The dogs 69 are connected together by a bar 1| by which they may be simultaneously pivoted out of engagement with the rack when it is desired to release hoisting unit B for movement relative to hoisting unit A. In this way the apparatus may be conditioned for shifting loads of different lengths.

As each boom member 29 approaches its lower position, the links 50 and arms 41 reach the relative positions shown in Fig. 13 and further lowerlng movement brings these members into approaching alignment. A spring 93' is tensioned during movement of the levers 50 and links 41 towards an aligned condition. This spring, shown in Fig. 15, serves to shift the levers out of alignment when the boom members are raised.

The driving apparatus by which the boom members 29 of the hoisting units A and B may be simultaneously positively raised and lowered and by which only the boom member of the hoisting unit B may be operated if desired, comprises a pair of aligned

screw elements

13 and 14, associated with the hoisting units A and B, respectively. The screw element 13 is journaled at one end in the bore 56 of the bearing portion 55 on the `cross member 5| and it is held against axial movement by thrust resisting collars 15 fixed to the screw 13 which engage thrust bearings 1S mounted in opposite extremities of the bearing portion 55. The other end of the screw element 13 is journaled in a bore formed in a cross member 16 which extends between and is xed to the rails 'I0 'and II. 'The screw element 'I4 is journaled at one end in-a bearing 11 mounted on a cross member 18 which connects the rails I0 and II and at its other end in a bearing 19 mounted on a cross member 80 which joins the right end portions of .the rails Illand I I.

The adjacent ends of the

screw elements

13 and 14 are disengageably connected together by aIclutch, generally designated by the numeral 8 I', which includes a clutch element 82 fixed to the right vend of the :screw element .13, as viewed lin Figs. land 3, and a shiftable clutch element 83 which is splin'ed on the kleft end of the screw element :14. The clutch element `83 fis A'provided with an' operating lever y84 rwhich is pivotally 1mounted at 8.5.on the rail lfandoperatively con- 6, nected at its'in'termediate portion to the clutch element 83. The intermediate portion of the lever 84 is enlarged and 'provided with an opening in which the right .end portion of the clutch clement is received. The lever 84 is pivotally connected with a slit ring 84 seated in a groove 85 formed in the clutch element 83, by pins 86.' which loosely nts in apertures formed in the lever 84. The free end of the lever 84 extends through a slot in the rail I I and may be rotated manually in a clockwise direction, as viewed in Fig. 3, to engage the

clutch elements

82 and 83 and in a counterclockwise direction to disengage them. The carriage I1 of each hoisting'unit vA and B, respectively, is provided with a nut member 86 in which'one of the

screw elements

13 and 14 are threaded. The

screw elements

13 and 14 may be driven in respectively-opposite directions by a reversible motor 81 which is drivingly connected with the right end ofthe screw element 14, as viewed in Fig. 1. vThe motor and hoisting apparatus may be provided with a control circuit such as shown in Ymy application, Serial No. 58,219, if desired.

The motor B1 may bev driven in one direction to simultaneously raise the boom members of hoisting units A and B when the clutch 8| is engaged or to raise only the boom member of hoisting unit B when the clutch 8| is disengaged. The

motor 81 may be likewise driven in an opposite` direction to lower the boom members.

The'cover structure embodying the invention is shown in Fig. 6 in its closed position with both hoisting units A and B in their lower positions and only the load receiving seat structures 35 and 36' thereof remaining above the cover structure. As viewed in Fig. 6, the cover structure includes a plate |00, located at the left of the hoisting apparatus, which is provided with slots 101| in which are received the levers 50 of hoisting unit A when it is in its upper position. The plate `I 00 is preferably fixed by screws or other suitable means to the rails I0 and II and the next adjacent plate |02, appearing in Fig. 1, is seated upon the rails I0 and and fixed to the carriage I1 in order to travel therewith during its shifting movement. the plate |00 when the hoisting apparatusV is in its elevated position but is shifted rightwardly, as viewedin the drawings, as the boom members 29 are lowered. Immediately to the right of the position in which the plate |02 is disposed when the boom members are elevated, are three successive pivotally attached plates |03, |04 and |05, respectively. The adjacent ends of the plates |03 and |04 are pivotally connected together by hinges |05 and the adjacent ends of the plates |04 and |05 are pivotally connected together by hinges |01. The left end of the plate |03 is free and the right end of the plate |05 is guided for shi'ftable movement longitudinally of the track by cleats |08.

A plate |09 is disposed on the top of rails I0 and I'I with rits left end portion in overlapping relationship with respect to the right end portion of the plate |05 and it is guided by the cleats |08. The right end of the plate |09 is provided with :slots |1If0, .similar to the slots IOI, of the plate |00, for receiving the levers of the hoisting unit Bi. It will be seen in Fig. 1, that a plate III, similar to the plate |02, is iixed to the carriage I1 of the hoisting unit B and slidablyseated on v'thetop of the rails I0 and -I I. The right end portion of Athe plate III I is,l disposed Abeneath the The plate |02 is disposed adjacent' left end portion of a plate I |'2 which is pivotally attached at its right end to the next successive plate |I3 by hinges I |4 which is in turn pivotally attached to the second from the last rightward plate |I5 by hinges |I6. The last rightwardly positioned plate overlaps the main length of the plate |`|5 and is pivotally attached at its right end to the end of the track by hinges IIB. The longitudinal marginal portions of the last rightwardly positioned plate are provided with spaced apertures ||9 in which pins IZU, extending upwardly from the second from the last plate ||5 are receivable. The last plate ||7 is adapted to be pivoted upwardly about the hinges |`|8 to disengage the pins |20' from the holes H9 and while the plate is so held the hoisting unit B may be shifted relative to the hoisting unit A to adapt the hoisting apparatus for lifting vehicles of different lengths, which vehicles may be designated by dimensions or names, not shown, on the top side of the: plate in associated relationship to the holes IIB. The hoisting unit B may be shifted by power, as set forth in my copending application, Serial No. 58,219, this being accomplished by disengaging the clutch 8| and suitably propelling the screw 'i4 by the motor 87, while the hoisting units are in their lower positions.

Pivotally mounted on each carriage il of the respective hoisting units A and B, is a guide bar |2| which is connected to the carriage structure at its right end by a hinge |22. The guide bar |2| comprises a flat strip of metal and its free end portion extends beyond the yoke 4S and rests upon it. During initial stages of upward shifting action of the hoisting apparatus, the

link arms 41 and yoke 46 are shifted to the positions shown in Fig. 13 in which the links il are disposed vertically and at right angles to the levers 50 with whic'p` they are associated. A stop |23 on the bar 3| and 39 oi the boom structure limits pivotal movement of the link arms e?, as shown in Fig. 13. This upward movement o the levers 41 and yoke 46 rotates the guide bar |2i in a clockwise direction and elevates the hinged edges of the cover plates |83 and Hifi as illustrated in Fig. 7. During subsequent upward movement of the boom member, the guide bar |2| shifts the cover plates |93 and |134 upwardly through the progressive stages shown in Figs. 8 and 9. Further upward movement of the boom member allows the plates |63 and |04 to progressively slide downwardly upon the guide bar |2| through the stages shown in Figs. l0, 1l and l2 until they are returned to horizontal position upon the rails I I and I2 when the boom member is in its uppermost position as shown in Fig. 1. The reverse action of the plates |03 and |64 takes place during lowering of the boom member, the guide bar |2| serving to shift the plates |03 and |04 upwardly to uncover the space between the rails Il and I2 for receiving the boom member, and to guide the plates |03 and |94 back to their horizontal covering positions after the boom member is disposed in the space between the rails.

The same action takes place in the operation of the cover structure of hoisting unit B, in which case the guide bar |2| thereof operates the plates ||2 and ||3 in the same manner as the plates |03 and |04 are manipulated by the guide bar |2| of hoisting unit A. ln each case, when the yoke 4B is shifted by the link arms 4l to the various positions established by the stops |23 on the boom bars 30 and 3|, and stops |24 on the levers LII 50, the guide bar |2| follows the yoke 46 and remains in contact with it.

The foregoing cover structure therefore is automatically operable without attention of the operator and it covers the hoisting apparatus when it is in its lowered position and covers the chamber in which the hoisting apparatus is stored when the latter is elevated.

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:

l. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a boom member shiitable through said open top side portion from a lower position mainly within said recess to an elevated position exterior of said recess, and a cover normally closing said open top side portion of said recess comprising pivotally connected plates engageable by said boom member and swingable relative to each other by the raising and lowering action thereof to uncover said open top side portion of said recess during movement of said boom member both into and out of said recess.

2. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a boom member shiftable through said open top side portion from a lower position mainly within said recess to an elevated position exterior of said recess, a cover member for normally closing said open top side portion of said recess comprising pivotally connected plates, and guide means on said boom member engagea-ble with said plates for swingably shifting them by the lowering and raising actions of said boom member to uncover said open top side of said recess in timed relation to movement of said boom member both into and out of said recess respectively.

3. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a boom member shiitable through said open top side portion from a lower position mainly within said recess to an elevated position exterior of said recess, a lever system swingably connected with said boom member for guiding it to its upper and lower positions, said lever system being receivable in said recess and swingable through said open top side portion thereof to a position externally of said recess, and a cover member normally closing said open top side of said recess comprising cover sections shiftable relative to each other and to said base portion by the action of and in timed relationship with respect to the action of said boom member and lever system for uncovering said open top side portion of said recess during movement of said boom member both into and out of said recess respectively.

4. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a boom member shiftable through said open top side portion from a lower position mainly Within said recess to an elevated position exterior of said recess, a lever system swingably connected with said boom member for guiding it to its upper and lower positions, said lever system being receivable in said recess and swingable through said open top side portion thereof to a position externally of said recess, a cover member normally closing said open top sidefofsaid recess comprising'a xedendcover section, rst and second. cover sectionsr p1votally .connected together at their. adjacent extremities and swingable relative to eachother-to'accom- 'modate passage of said boom member-'and lever system into and out'of saidrecessv and a third cover section slidably mounted on said base portion and pivotally connectedY with the other extremity of said second cover section, and means onsaid base portion for guiding said third cover section. y l Y l 5.1 Hoistingapparatus comprising' a base portion having a recess therein providedwith an open top -side portion, a boom member shiftable through said 'open top side portion from a lower position mainly within said recess to an elevated position exterior of said recess, a lever system swingably connected with said boom member for guiding it to its upper and lower positions, said lever system being receivable in said recess and swingable through said open top side portion thereof to a position externally of said recess, a cover member normally closing said open top side of said recess comprising a xed end cover section, first and second cover sections pivotally connected together at their adjacent extremities and swingable relative to each other to accommodate passage of said boom member and lever system into and out of said recess and a third cover section slidably mounted on said base portion and pivotally connected with the other extremity of said second cover section, and a guide element on said boom member shiftable by the action of said lever system for controlling the relative pivotal movement of said rst and second pivoted cover sections to both cover and uncover said recess. Y

6. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a boom member shiftable through said open top side portion from a lower position mainly within said recess to an elevated position exterior of said recess, a lever system swingably connected with said boom member for guiding it to its upper and lower positions, said lever system being receivable in said recess and swingable through said open top side portion thereof to a position externally of said recess, a cover member normally closing said open top side of said recess comprising a fixed end cover section, iirst and second cover sections pivotally connected together at their adjacent extremities and swingable relative to each other to accommodate passage of said boom member and lever system into and out of said recess and a third cover section slidably mounted on said base portion and pivotally connected with the other extremity of said second cover section, a guide element on said boom member shiftable by the action of said lever system for controlling the relative pivotal movement of said rst and second pivoted cover sections to both cover and uncover said recess, and means on said base portion for guiding said third cover section.

7. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a pair of relatively shiftable hoisting units eachV comprising a boom member shiftable through saidopen top side portion from a lower position-mainly within said recess to an elevated position exterior of said recess, a cover member for normally closing said open top side portion of said recess comprising a pair of cover units one associated with each of said hoisting units respectively and each cover unit including a plurality of longitudinally aligned cover plates, adjacent end portions of the adjacent cover plates of said respective units being relativelyshiftably disposed in superimposed and overlapping relation for accommodating relative shifting of said hoisting units, hinge means pivotally connecting the adjacent end portionsY of the'successive cover plates of said cover units to each other, and means on each `of said hoisting units engageable with the pivotally connected cover plates of each cover unit respectively for shiftingV them to open position as said boom members are individually or simultaneously raised out of and into said recess respectively.

8. Hoisting apparatus comprising a base portionl Ahaving a recess therein provided with an open top side portion, apair of relatively shiftable hoisting units eac-h comprising a boom member shiftable through said open top sideportion from a lower position mainly Within said recess to an elevated position exterior of said recess, a cover member for normally closing said open top side portion of said recess comprising a pair of cover units one associated with each of said hoisting units respectively and each cover unit including a plurality of longitudinally aligned cover plates, adjacent end portions of the adjacent cover plates of said respective units being relatively shiftably disposed in superimposed and overlapping relation for accommodating relative shifting of said hoisting units, hinge means pivotally connecting the adjacent end portions of the successive cover plates of said cover units to each other, and means on each of said hoisting units engageable with the pivotally connected cover plates of each cover unit respectively for shifting them to open position as said boom members are individually or simultaneously raised out of and into said recess respectively, said last-mentioned means being so constructed and arranged as to guide said pivoted cover plates to their closed positions during the last stages of movement of said boom members toward their upper and lower positions respectively 9. Hoisting apparatus comprising a base portion having a recess therein provided with an open top side portion, a boom member shiftable through said open top side portion from a lower position mainly within said recess to an elevated position exterior of said recess, apparatus for shifting said boom member between said positions including a' lever element pivotally connected at one end to said base portion and a link member pivotally connected at one end to the other end of said lever and pivotally connected at its opposite end to said boom member, said link and lever members being angularly shiftable from an aligned relationship to an angular relationship while said boom member is disposed in said recess, a cover normally closing said open top side of said recess including a plurality of aligned pivotally connected plates, the pivotal connections between one pair of said plates being located adjacent said pivotally connected ends of said link and lever members for accommodating shifting of said link and lever members to said angular relationship, and a guide element on said boom member engageable with.

said pair of plates and shiftable by said link member for spacing said plates from said boom member during initial raising and nal lowering of said boom member, said guide member being adapted to guide said pair of plates to closed position during final upward and nal downward movements of said boom member respectively.

10.V Hoisting apparatus comprising abase por'- tion having av recess therein provided with an open top side portion, a boom member shiftable through said open top side portion from a lower position mainlywithin said recess to an elevated position exterior of said recess, load receiving seat structure on one end of said boom member, a carriage pivotally connected with the other end of said boom member and shiftably mounted on said base portion, apparatus for shifting said boom member between said positions including a lever element pivotally connected at one end to said base portion and a link member pivotally connected at one end to the other end of said lever and pivotally connected at its opposite end to said boom member, said link and lever members being angularly shiftable from an aligned relationship to an angular relationship while said boom member is disposed in said recess, a cover normally closing said open top side of said recess including a plurality of aligned pivotally connected plates, the pivotal connections between one pair of lsaid plates being located adjacent said pivotally connected ends of said link and lever members for accommodating shifting of said link and lever members to said angular relationship, and a guide member pivoted at one end on said carriage and having an opposite end portion engaged with and shiftable by said link member, said guide member being engageable with said pair of plates for spacing them from said boom member and guiding them to closed position during final upward and final downward movements of said boom member respectively.

DAVID A. WALLACE.

No references cited.