US2454226A

US2454226A - Drop table apparatus for use in servicing trucks and wheels of railway vehicles

Info

Publication number: US2454226A
Application number: US783415A
Authority: US
Inventors: Asa W Skinner
Original assignee: Whiting Corp
Current assignee: Whiting Corp
Priority date: 1947-10-31
Filing date: 1947-10-31
Publication date: 1948-11-16
Anticipated expiration: 1965-11-16

Description

Nov. 16, 1948. w, s m 2,454,226

v DRORTABLE APPARATUS FOR USE IN SERVICING I 'rnucxs ANDWHEELS 0F RAILWAY VEHICLES Filed 001;. 31, 1947 4 Sheets-Sheet 1 y. zarzWsi'llinner" Nov. 16, 19.48. A. w. SKINNER 2,454,

DROP TABLE APPARATUS FOR USE IN SERVICING TRUCKS AND WHEELS Q1: RAILWAY VEHICLES Filed Oct. 31, 1947 4 Sheets-Sheet 2 b BHI Hi Rt- *1 Nov. 16, 1948. A. w. SKINNER DROP TABLE APPARATUS FOR USE IN SERVICING TRUCKS AND WHEELS OF RAILWAY VEHICLES v 4 Sheets-Sheet 3 Filed Cat. 31, 1947 Nov. 16, 1948. A. w. SKINNER 2,454,226

DROP TABLE APPARAIUS FOR USE IN SERVICING TRUCKS AND WHEELS OF RAILWAY VEHICLES Filed Oct. 31, 1947 4 Sheets-Sheet 4 Patented Nov. 16, 1948 DROP TABLE APPARATUS FOR USE IN SERV- ICING TRUCKS AND WHEELS OF RAILWAY VEHICLES Asa W. Skinner, Riverdale Village, Ill., assignor to Whiting Corporation, Harvey, 111., a corporation of Illinois Application October 31, 1947, Serial No. 783,415

8 Claims. 1

The present invention relates generally to what is known in the art as drop table appa-- ratus. More particularly the invention relates to that type of drop table apparatus which serves as a medium or instrumentality for removing trucks or wheels of railway vehicles in connection with repair, servicing or replacement thereof and is adapted for use with a main railway track having an interruption therein and an elongated pit extending transversely of the main railway track at the interruption therein and having a longitudinal track along its bottom.

A standard or conventionaldrop table apparatus has heretofore consisted of a unitary elevator and transfer car which is mounted onthe track on the pit bottom to travel therealong and embodies a vertically movable table, and-a rail equippedvtop which is designedto be raised and lowered by the table, is adapted when the elevator and transfer car is disposed adjacent the main track and the table is raised to the proper extent to be brought into a working position wherein its rails bridge and complete the rails of the main track and are so disposed that the railway vehicle truck or wheels to be serviced may be propelled thereon preparatory to release from the vehicle. and subsequent lowering, and has mechanism whereby it may be locked in its operative or working position. In practice it has been found that a standard or conventional drop table apparatus of the last mentioned character effectively and efficiently fulfills its intended purpose, but it is subject to certain objections.

In the first place such an apparatus is costly to construct because of the numerous parts and elements of which it is composed. Secondly, because it embodies the rail equipped top in addition to the vertically movable table forming a part of'the elevator and transfer car its overall height is such that it necessitates the use of a comparatively deep and costly pit.

The primary object of the invention is to provide a drop table apparatus which is an improve ment upon and eliminates the objections to a standard'or conventional apparatus of the aforementioned character and is characterized by the fact that it not only embodies fewer parts and is hence less costly to manufacture, but also requires cr necessitates the use of a much more shallow pit. In general the improved apparatus comprises (1) a rectangular table which extends transversely across the pit, is vertically movable and has at its corners wheels for engaging the rails of the pit track when the table is lowered, (2) a plurality of' vertically extending struts which are so mounted with respect to the table that they and the table are relatively shiftable upwards and downwards, and (3) reversible power operated mechanism which is carried by the table, operates to eifect relative up and down shift of the struts and the table, is adapted when actuated in one direction while the lower ends of the struts are at rest adjacent the bottom of the pit to raise the table to the top of the pit, and is further adapted when reversely actuated first to lower the table with respect to the struts until it is supported by its wheels on the pit track and then to raise the struts relatively to the table inorder to release the latter so that it is free to be propelled along the pit track.

Another object of the invention is to provide a drop table apparatus of the last mentioned character in which the struts are four'in number, are located at the corners of the table and have at the lower ends thereof forked members for straddling the rails of the track along the pit bottom.

A further object of the invention is to provide a drop table apparatus of the type and character under consideration in which the four struts at the corners of the vertically movable table are in the form of screw shafts and the reversible power operated mechanism for effecting relative verticaI movement of the struts and the table comprises nuts which are mounted on the screw shafts and are carried at the corners of the table so that they are freely rotatable while at the same time they are held against vertical displacement with respect to the table.

A still further object of the invention is to provide a drop table apparatus of the character under consideration in which the fork forming members on the lower ends of the screw shafts constituting the vertically extending struts are downwardly tapered and are adapted, when the shafts are lowered preparatory to raising or elevating the table, to fit within socket equipped elements on the sides of the pit rails and to coact with such elements in such manner as to align the table with respect to the main railway track and also to hold the screw shafts together with the table against lateral displacement.

The invention also contemplates as one of its objects the provision of a drop table apparatus which is generally of new and improved construction, effectively and efficiently fulfills its intended purpose, and may be operated or manipulated with facility.

Other objects of the invention and the various advantages and characteristics of the present drop table apparatus will be apparent from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by'claims at'the conclusion hereof.

In the drawings which accompany and form a part of this specification or disclosure and in which like numerals of reference denote corresponding parts throughoutthe several views:

Figure l is a top plan view showing a drop table apparatus embodying the invention in operative relation with a mai'nrailway track with an interruption therein and an elongatedtrack equipped pit extending transversely of the main railway track at the interruption therein;

Figure 2 is an end elevation of the apparatus showing the table after it has been lowered 'so that the wheels thereof rest on the rails of the pit'track; r Figure 3 is an end elevation showing theapparatus after it'has been propelled along the'pit trackto another position within the pit and the table has been raised to a point adjacent the top'of the pit;'

Figure 4 is an enlarged vertical transverse section taken on the line S -40f Figure l and showing in' detail certain parts of the'reversible power operated mechanism for effecting relative vertical shift of the struts and the table;

T Figure'5 is an enlarged but fragmentary vertical transverse section taken on the line 55 -of-Figu're 1- and showing "in detail the motor driven mechanism for driving certain wheels of the table in order to effect propulsion of the apparatus alo'ng the pit track; :1" l 1. Figure 6 is an enlarged vertical transverse section taken on the line 6-6 ofFigure 1 and showing in detail the manner of mounting of the rotatable nuts-which are mounted on the'corners of the table and constitute parts of thereversible power actuated mechanism for effecting relative vertical shift of the struts and'the table; Figure '7- is' a vertical transverse section taken on'the line ll of Figure 6 and illustrating the construction and design of one of the fork formingmembers at "the lower ends of the screw shafts constituting thestruts of the apparatus;

and

Figure 8 is 'a-section similar to Figure '7 except that it shows the form forming member in its fully lowered position on the subiacent pit rail and in operative or interfitting "relation with the socket equippedelement that is associated therewith. I U

"The drop table apparatus which isshown in the drawing constitutes the preferred form or embodiment of the invention. It is adapted for use in connection with a main railway track 10 on a floor H and with'an interruption or cutout therein and an-elongated pit I2 and serves as a medium for effecting removal andreplacement of the truck or wheels of a railway vehicle on the track' Ill. As described more in detail hereafter the apparatus is brought into use when it is desired to remove, service and then remount the railwayvehicle truck or wheels, and is also used in connection with a so-called release track 13 on the floor. The'track lfl' is suitably anchored on the floor H and consists of-a'pairof laterally spaced, sectional rails M. The pit is formed in the floorll at the aforementioned cutout or interruption-in the track Ill.

It'is'" rectangi-ilar in cross section and extends transversely of the track 10 as shown in Figures 1, 2 and 3. Certain of the sections of the rails l4 constituting the track In lead to and terminate adjacent one side of the pit l2 and other sections of the rails l4 lead to and terminate adjacent the other side of the pit. The fioor H and the pit I2 are generally formed of concrete. The release track 13 is located at one side of the track [0, as shown in Figures 2 and 3. It is of the same gauge as the main railway track l0 andconsists-of a pair of laterally spaced sectional rails l5 whichlead to and terminate adjacent the top of, the pit i2. On the bottom of the pit I2 is a longitudinally extending track It; and this consists of a pair of laterally spaced rails I! of conventional design. The last mentioned rails are suitably anchored to the bottom of the pit and serve to support the drop table apparatus and to permit the latter to travel along the pit. As its principal components the apparatus comprises a rectangular table l8 and four struts in the form of screw shafts l9.

The table 8 of the apparatus extends transversely across the pit I2 and is adapted to be l raised and lowered in the pit as hereinafter de scribed. It is fabricated from structural steel and consists of a pair of laterally spaced, parallel, longitudinally extending I-beams 20, a pair of laterally spaced, parallel, longitudinally extending channel beams 2|, pairs of transversely extending channel beams 22 at the ends of the I-beams 20 and a pair of transversely extending channel beams 23 at the central portions of said I-beams. The aforementioned beams are welded or otherwise fixedly secured together so that the table l8 as a whole is rigid. The I-beams 20 are arranged so that the webs thereof extend vertically and are spaced apart a distance corresponding to the lateral spacing of the rails M as well as the rails l5. They are disposed inwards of, and in parallel relation with, the channel beams 2| and are so positioned and are of such length that the ends thereof terminate slightly inwards of the rails I! constituting the pit track [6. The channel beams 21 are arranged so that the webs thereof extend vertically and are so positioned and are of such length that the ends thereof project across the rails I1 and terminate adjacent the sides of the pit 12. The pairs of transversely extending channel beams 22 at the ends of the I-beams 20 are arranged so that the webs thereof extend vertically and consist of inner channel beams and outer channel beams in spaced relation with the inner channel beams. The inner channel beams 22 have the central or intermediate portions thereof connected to the ends of the I-beams 20 and their ends connected to the end portions of the longitudinally extending channel beams 2| at points inwards of the outer extremities of said end portions. The outer transversely extending channel beams 22 are arranged in parallelrelation with the inner channel beams 22 and have the ends thereof fixedly secured to the outer extremities of the end portions of the longitudinally extending channel beams. 2|. The transversely extending channel beams 23 adjacent the central portions of the I-beams 20 are spacedlaterally apart and are positioned in parallel relation. They are arranged so that the webs thereof extend vertically and underlie and extend across the central portions of the beams 2|] and 2!. The upsecured? to the lower flanges of the beams 20 and 2|. The; upper flanges of the Ibeams 20 have fixedly mountedthereon apair of laterally extending; rail sections. These extend throughout the length of theIebeams 29 and are adapted when the table I8 is raised 'tothe top of the Pit while in alignment with the main nailway track le to register with and bridge the rails l4 constituting the track l0. They; are also adapted when the apparatus is positioned as; shown in Figure 3 and the table thereof is raised sothat it is in alignment witht-he release t-rackl3; to register with and bridge the rails constituting the track l3. The: table I8 is provided with: four flanged wheels, 25" in order that, it may be propelled along the pit track l6 when it is loweredrto the bottomof' the pity l2. Thewheels 25 are located adjacent the corners of the table and are disposed between the inner and outer transversely extending channel beams 22., Theyare mounted on stub: shafts and-these arejournalled in bearings on the channel beams 22. The stub axles for-two opposed or aligned wheels are connected by a horizontally extending shaft 26. of the table andis located beneath and adjacent one of the horizontally extending I-beams 20. A reversible electric motor 21 and speed reducing gearing 28v constitute reversible power operated mechanism for efiecting propulsion of the apparatus in either direction along the pit track l6 when the table I8 is lowered so that the wheels 25; thereof rest. on the rails H. The electric motor 2'! is supported adjacent the central portions of the I-beams by way of a pair of horizontal, laterally spaced,- transversely extending channel beams 29. The latter are located outwards of one of the channel beams 23, as shown in Figure 1, underlie the I-beams 2B and have the, ends thereof suitably fixedly secured to the bottom flanges of said I-beams. The reversible electric motor 2! is so positioned that the armature. shaft thereof extends lengthwise of the table H3. The speed reducing gearing 23' between the motor 21 and the shaft 26 consists of a housed gear type speed. reducing unit 30, a chain and sprocket connection 3|, a shaft 32 and a chain and sprocket connection 33, (see Figure 5). The gear type speed reducing unit 30 is mounted on the central, portions of the channel beams 29 and has the casing of; the electric motor 21 fixed to its housing. One end of, the armature shaft of the motor 21 extends into the housing of the unit 30 and has one of the gears of the unit fixed to it. The chain and sprocket connection 3| extends between the driven gear of the unit wand one end of the shaft 32 and serves to drive the shaft 32 from the unit-30 in connection, with drive of. the electric motor 21. The shaft 32- extends lengthwise of the table l8 and is: journalled in a pair of bearings 34, one of which is mounted on one of the channel beams 29 and the other of which ismounted on. one of the channel beams 23. The chain and sprocket connection; 33 extends between the other end of; the shaft 32 and the central portion of the shaft 26 and serves to drive the last mentioned shaft in connection with drive of the first mentioned shaft. When the table I8 is lowered so that it is supported by the flanged wheels on the rails ll; of the :along; the pit track. Reverse drive of the electric The latter extends longitudinally motor 21: results in propulsion; of the apparatus in the opposite directionalong the pit track.

The screw shafts I9 extend; vertically and are located at thecorners of the table l8; They directly overlie the rails ll constituting the pit track l6 and'are disposed outwards of the flanged wheels 25 and between the outer ends of the pairs of transversely extending channel beams 2.2 As hereinafter described the screw shafts l9 and the table I 8 are movable or shiftable upwards and downwards relative to one another. The lower ends of the screw shafts are provided with fixed fork forming members 35 (see Figures 7 and 8) The latter are arranged in straddled relation with the heads of the pit rails IT and coact therewith to prevent turning or rotating of the screw shafts injeither direction. Eachof the fork forming' members consists of a pair of vertically extending laterally spaced plates 36'. The upper ends of such plates fit against flats on the lower ends of thescrewshafts l9 and are fixedly secured tothe screw shafts by horizontally extending bolts 31:, the shanks of which extend through aligned holes in the upper ends of the plates 36 and the lower ends of the screw shafts. The lower ends of the plates 36 are downwardly tapered and are adapted, when the screw shafts are lowered preparatory to raising or. elevating the table tothe top of thepit l2; to fit within either socket equipped elements 38 or socket equippedelements 39 on said pit rails I 5. The elements 38 areydisposed beneathv and slightly outwards of the rails [4 of the main railway track It). They are in the form of pairs of metallic blocks and these are riveted to opposite sides of the webs of the pitrails IT and have on the central portion's thereof upwardly and outwardly extending lugs 40. which. define outwards of the heads of the pit railsupwardly flared sockets 4|. The upward flare of they sockets 4| corresponds to the downward taper of the lower ends of the plates 36v constituting the fork forming members 35'. The socket equipped elements 38 are so positioned. on the rails of the pit track that when the screw shafts I 9 are disposed thereabove in connection with; proper positioning, of the drop table apparatus and, are then lowered preparatory to raising of the table I 8, the downwardly tapered lower ends of the plates 36 enter the sockets M as shown in Figure 8 and coact therewithv automatically to position the apparatus in such mannerxthat the rail sections 24 are in vertical alignment with the rails l 4 of the main railway track Hi. The coaction between the lower ends of the plates 36 and the lugs 49 that define the upwardly flared sockets 4| is, in effect, a cam action. When the fork forming members35 are positioned as shown in Figure 8 thelower ends of the screw shafts [9 rest on the heads of the pit rails I! and the lower ends of equipped elements 38 constitute aligning devices whereby when; the apparatus is propelled substantially into registry with the cutout or interruption in the main railway track 19 and the screw shafts H! are lowered the apparatus as a whole is cammed into true centered or registering relationwith the main railway track rails 14. The socket equipped elements 39 are constructed in; the same manner as, and function like, the elements 38. They are located in the pit beneath and slightly outwards of the rails l5 of the reentrees paratus is propelled into registry with the rails I and the screw shafts are lowered so that the -'lower ends rest on'the heads of the pit rails I! the lowerends of the plates 36.slide into the upwardly flared sockets 44 and coact with the lugs 43 properly to center the apparatus with respect to the release track rails and also to hold the apparatus against lateral displacement.

The upper ends of the screw shafts l9 extend through sectional gear boxes 45 at the corners of the table [8 and have nuts 46 mounted thereon. The gear boxes are four in number and are suitably fixedly secured within "cutouts 41 in the lower end corners of the transversely extending channel beams 22. They are preferably in the form of metallic castings and consist of inverted cupshaped upper sections 48 and plate like lower sections 49 (see Figure 6). The central portions of the upper sections '48 of the gear boxes are provided with integral, depending, open ended sleeves 50 and the central portions of the lower sections 49 are provided with integral, upwardly extending, open ended sleeves 5|. The latter are in coaxial relation with the depending sleeves 50. The outer margins of the lower sections 49 of the gear boxes are bolted or otherwise removably secured to the lower ends of the side walls of the upper sections 48. The screw shafts l9 extend through the sleeves 50 and 5|. The nuts 46 are disposed in the central portions of the interiors of the gear boxes and are interposed between the adjacent ends of the sleeves 50 and 5|. They are capable of rotating relatively to the gear boxes but are held against axial displacement relatively to said gear boxes. Roller type thrust bearings 52 are interposed between the upper ends of the nuts and the lower ends of the sleeves 50. When the nuts 46 are conjointly rotated in one direction while the table '18 is supported on the'pit' track'lB by the wheels 25 the screw shafts l9 are fed downwards until the lower ends thereof rest on the rails of the pit track. Thereafter the table is caused to be raised or shifted upwards towards the top of the pit. When the nuts 46 are conjointly rotated in the opposite direction the table I8 is caused to be lowered until the wheels 25 thereof rest' on the rails ofthe pit track. Thereafter the screw shafts are caused to moveupwards to a slight extent in order to cause the fork forming members 35 to be withdrawn from interfitting relation with the sockets of the socket equipped elements on the webs of the rails l1 and thus free the apparatus so that it is capable of being propelled in either direction "along the pit track I6.

In addition to the parts heretofore specifically described the drop table apparatus comprises reversible power actuated mechanism 53 for conjointly turning the nuts 46 in one direction or the other. Such mechanism consists of a reversible electric motor 54 and gearing between the motor and thenuts. The motor'54 is located at the central'p'ortion of the' table [8 and is suitably secured to acradle 55 which extends across, and is'secured to,'the central portions of thetransversely extending channel "beams 23. As best showh'iri Figure 1;"thmot0r'54- is positioned or arranged so that the armature shaft thereof extends transversely of the table. The gear'between the motor 54 and the nuts 46 consist of a pair of sectional shafts 56, a pair of gear type speed reducing units 51, four sectional shafts 58, four worms 59 and four worm gears 60. The speed reducing units 51 are mounted on the ends of the transversely extending channel beams 23 and, as shown in Figure 1, are positioned equidistantly between the gear boxes 45. The shafts 56' are horizontal and extend transversely of the table 18. They are positioned at opposite ends of the reversible electric motor 54 and have the inner ends thereof connected by flexible or universal couplings to the ends of the armature shaft of said motor. The outer ends of the shafts 56 extend into the speed reducing units 51 and are connected to certain gears (not shown) in such units. The shafts 58 are horizontal and extend lengthwise of the table. They are disposed directly inwards of,'and in parallel relation with, the longitudinally extending channel beams 2| of the table and extend between the speed reducing units 51 and the gear box 45. The inner ends of the shafts 58 are fixedly connected to certain of the driven gear-s of the speed reducing units and the outer ends of such shafts extend into the gear boxes 45 and have the worms 59 fixedly connected thereto. The worm gears 60 surround, and are fixedly secured to, the nuts 4Ban'd mesh with the'worms 59. The gearing between the reversible electric motor 54 and the nuts 46 is such that when the motor is driven in one direction it causes the nuts conjointly to rotate in one direction and when such electric motor is driven in reverse direction it operates or causes the'nuts conjointly to rotate in the opposite direction.

When it is desired to utilize the drop pit apparatus to service-a truck or a pair of wheels of a railway vehicle on the track ID the apparatus is first propel-led along the pit track until it is adjacent the cutout or interruption in the track -ll]. Propulsion of the apparatus is effected by driving the electric motor 21 in the proper direction. As soon as the apparatus is properly located or positioned the electric motor'54 is operated so that it, through the medium of the gearing inclllding the shafts 56, the speed reducing units 51, the shafts 58, the worms 59 and the worm gears 60, operates so to rotate the nuts 46 as to cause the screw shafts l9 to move downwards. As the screw shafts move downwards the lower ends of the plates 36 constituting the form forming members 35 enter the sockets 4| and coact with the lugs 40 of the elements 33 properly to effect centering or alignment of the apparatus. After the lower ends of the screw shafts H! are brought to rest on the heads of the rails I! of the pit track l6 continued operation of the electric motor 54 in the same direction effects raising of the table I8. Such motor is stopped when the table l8 reaches the top of the pit l2 and its rail sections 24 are in registry with and serve to bridge or form continuations of "the rails l4 of the main railway track [0. After the table is properly positioned at the top of the pit the railway vehicle is propelled along the track l0 until the truck or the wheels to be serviced are disposed on the rail sections 24 on the table. Thereafter release of the truck or wheel is effected. After such operation the electric motor 54 is reversely driven so as to cause conjoint reverse rotation of the nuts 46. Such rotation on the part of the'nuts first causes the table l8 to belowered until its wheels 25 rest on the pit rails I1 and then causes the screw shafts to be raised with respect tothe table. As soonas the screw shafts are raised to 'a slight extent so that the fork forming members 35 are disengaged from the socket equipped elements 39 the apparatus is propelled along the pit track l6 until it isadjacent the release track l3. After such propulsion on the part of the apparatus the motor 54 is operated in such direction that it operates through the medium of "the gearing between it and the nuts '46 first to lowerethe screw shafts Hand :then, after the screw shafts are i brought to rest on the pit rails H, to efiect raising of the table. When the table is at the top of the pit 12 with its [track section 24 in registry and bridging relation with the rails I5 of the release track the motor 54 is stopped. Thereafter the truck, for example, is propelled along .the' release track to the point where it is serviced or repaired. After repair the truck is propel-led back onto the rail section 24 and the table 18, by proper actuation of the mechanism 53, is lowered until its wheels 25*rest on the rails of the pit track 16. As soon as the table is lowered the apparatus is propelled back to its original position wherein it is adjacent the cutout or interruption in the main railway track III. Thereafter mechanism 53 is actuated so as to raise the table l8 into its workingposition wherein its rail sections bridge and serve to complete the rails 14 of the main railway track l0. At the conclusion of this operation the truck is connected to its railway vehicle and such vehicle is in condition to be propelled along the track Ill.

The herein described drop table apparatus is highly efiicient so far as operation is concerned and is characterized bythe fact that it consists of but a comparatively small number of parts and hence may be produced at a low cost. reason-of the fact that the wheels 25 aremounted directly on the table I8 and the raising and-lowering mechanism for the table includes screw shafts I9 the overall height of the apparatus is essentially small and as a result it is possible to make the pit l2 quite shallow so far as depth is concerned.

Whereas the apparatus has been described as having rail sections on the top Is it is to be understood that the top, instead of having rail sections, may be used to raise and lower a separable rail section equipped top having locking means for looking it at the top of the pit. It is also to be understood that the invention is not to be restricted to the details set forth since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is: a

1. A drop table apparatushaving associated therewith a main railway track with an interruption therein and an elongated pit extending transversely of the main track at said interruption and having a longitudinal track along its bottom, designed for use in removing and then replacing wheels on a railway vehicle on the main track, and comprising a table extending across the pit, adapted to be raised and lowered in the pit and when in its raised position while adjacent the main track to bridge the interruption and permit the wheels to be propelled thereover, and having mounted directly thereonwheels adapted when the table is iii-its lowered position 10 in the pit torest on the pit track 'andpermitthe tableto be'propelled therealong, a plurality of vertically extending struts connected to the table sothat they and said table are capable of relative raising and lowering movement, and reversible power operated mechanism mounted on the table, operative to effect relative "raisingand lowering movement of the struts and table, and so related to said struts that it is adapted when actuated in one direction after the lower ends of the struts aresupported at the pit bottomand the table is inits raised position first "to lower the table until the wheels thereof rest on the pit track and then to raise the struts relatively to the table and free the latter so that it is capable of being propelled 'along thepit'track, and is further:

adapted when actuated in the opposite direction first to lower the struts until the lower ends thereof are supported at the bottom of the pit a'n'dthen to-raise thetable.

2. A drop table apparatus having associated therewith a main railway track with an interruption therein and an elongated pit extending transversely of the main track at said interrupe tion and having a longitudinal track along its bottom and "in 'the form of a pair of laterally spaced r ails, designed for use in removing and then replacing wheels on a railway vehicle on the main track, and comprising a unitary recta'ngular table extending across the pit, adapted to be raised and lowered in the pit and when in its raised position while-adjacent the main track to bridge the interruption and permit the wheels to be propelled thereover, and having mounted directly thereon wheels adapted when the table is in its lowered position in the pit to 'rest on the rails of the pit track and permit the table to be propelled along the latter, four vertically extending struts positioned directly above the rails and connected to the corner portions of the table so that they and said table are capable of relative raising and lowering movement, and reversible power-operated mechanism mounted on-the table, operative to effect relative raising and lowering movement of the struts and table, and so related to the struts that it is adapted whenactuated in one direction after the lower ends of the struts are at rest on the rails and the table is in itsv raised position first to lower the table until the wheels thereof rest on the pit track and then to raise the struts relatively to the table and free the latter so that it is capable of being propelled along the pit track, and is further adapted when actuated in-the opposite direction first to lower the struts until the lower ends thereof rest on said rails and then to raise the table.

3. A drop table apparatus having associated therewith a main railway track with an interruption therein, and an elongated pit extending transversely of the main track at said interruption and having a longitudinal track along its on the rails of the pit track and permit the table to be :propelled therealong, four vertically extending struts "positioned directly above the rails QAMtQ Q and outwards of the wheels on the table andconnected to the table so that they and said table are capable of relative raising and lowering movement, and reversible power operated mechanism mounted on the table, operative to efiectrelative raising and lowering movement of the struts and table, and so related to the struts that it is adapted when actuated in one direction after the lower ends of the struts are at rest on the rails and the table is inits raisedposition first to lower the table until the wheels thereof rest on the pit track and then to raise the struts relatively to the table and free the latter so that it is capable of being propelled alongthepit track, and is further adapted when actuated in the p posite direction first to lower the struts until the lower ends thereof are at rest on said rails and then to raise the table. H

4 A drop table apparatus having associated therewith a main railway trackwith aninterruption therein and an elongated pit extending transversely of the main track at said interruption and having a longitudinal track along its bottom and in the form of a pair of laterally spaced rails, designed for use in removing and then replacing wheels on a railway vehicle on the main track, and comprising a rectangular table extending across the pit, adapted to be raised and lowered in the pit and when in its raised position while adjacent the main track to bridge the interruption and permit the wheels to be propelled thereover, and having mounted directly thereon wheels adapted when the table is in its lowered position in the pit to rest on the rails of the pit track and permit the table to be propelled along the latter, four vertically extending struts positioned directly above the rails, provided at their lower ends with forklike members for straddling said rails and connected to the corner portions of the table so that they and said table are capable of relative raising and lowering movement,v and reversible power operated mechanism mounted on the table, operative to efiect relative raising and lowering movement of the struts and table, and so related to the struts that it is adapted when actuated in one direction after the lower ends of the struts are at rest on the rails and the table is in its raised position first to lower the table untilthe wheels thereof rest on the pit track and then to raise the-struts relatively to the table and free the latter so that it is capable of being propelled along the pit track, and is further adapted when actuated in the opposite direction firstto lower the struts until the lower ends thereof rest on said rails and then to raise the table.

5. A drop table apparatus having associated therewith a main railway track with an interruption therein and an elongatedpit extending transversely of the main track at said interrup-. tion and having a longitudinal track along its bottom and in the form of a pair of laterally spaced rails designed for use in removing and then replacing wheels on a railway vehicle on the main track, and comprising a unitary rectangular table extending across the pit, adapted to be raised and lowered in the pit and when in its raised position while adjacent the main track to bridge the interruption and permit the wheels to be propelled thereover, and having mounted directly thereon wheelsadapted when the table is in its lowered position in the pit to rest on the rails of the pit track and permit-the. table to be propelled along the latter, four vertically extending struts positioned directly above the rails, provided at their lower ends with fork- I movement of the struts and table, and so related to the struts that it is adapted when ac' tuatedinone direction after the lower ends of the struts are at rest on the rails and the table is in its raised position first to lower the table until the wheels thereof rest on the pit track and then to raise the struts relatively to the table and free the latter so that it iscapablelof being propelled along the pit track, and.is.fur. ther adapted when actuated in the opposite di-v rection first to lower the struts until. the lower ends thereof rest on said rails and then to raise.

the table, and block-like elements secured to the rails at points adjacent the railway tracks and having upwardly flared sockets adapted when the table is propelled along the pitfltrack into a position under the interruption and the mechanism is initially actuated in said opposite direction for strut lowering purposes to receive the fork-like members and coact therewith in such manner as to hold the struts against lateral displacement.- I

;6."A drop table apparatus having associated therewith a main railway track with an inter ruption therein and an elongated pit extending transversely of the main track at said interruption and having a longitudinal track alongiits bottom, designed forq-use in removing: 'andathen replacing wheels ona railway vehicle -oniithe main track, andcomprising a unitalryt'abl'e tending across the pit,adapted to be raised and lowered in the pit and when in itsraisedposition while adjacent the main -trackto bridge-the interruption andpermit the wheels to 'be pro pelled thereover, and having -mounted directly thereon wheels adapted when'the table is in its" lowered position in the pit to rest fon the pit trackand I permit the "table uto be-J propelled-- thereon, a plurality of vertically extendiiig struts in the form of screw shaftsconnectdto the table so that they and said table are capable of relative raising and lowering "movementi reversible power operated mechanism'inounte'd on the table, operative to effect relative"raising and lowering movement of the-screw's'hafts- 'and table, so: related to the struts thatit is" adapted when actuated in onedirection afterth-lowr ends of the screw shafts are supported adjacen t the pit bottom and the table 'is'iin'it's' raised position first to lower the table until the wheels thereof'rest on the pittrack andfthen toraise the screw shafts memento th'o e tab leand free h a er einer t inc a Q i d l de g; he Pit tr de 3 2 i; ifl fi d ed when actuated in the opposite d rect 0 1 st to lower the screw shafts until'the l'oyve thereof aresupportd adj acentithe b'ottom pit and then to raise the table, and consist a reversible ,electric motor, t t mounted on the screw shafts; and held I table against axial displacerne t relativ'ely thereto; and gearing extending be'tween I tor and nuts and operative. con"ointl"- tomotat'i the nuts in v one direction Wh nfthe gfiotgr is driven in vone direci ;ion a he. nut the; ppn si egd rect ee' wh tor is reversely driven, and means associated with the struts for holding the latter against r0- tation relatively to the table.

7. A drop table apparatus having associated therewith a main railway track with an interruption therein and an elongated pit extending transversely of the main track at said interruption and having a longitudinal track along its bottom and in the form of a pair of laterally spaced rails, designed for use in removing and then replacing wheels on a railway vehicle on the main track, and comprising a unitary rectangular table extending across the pit, adapted to be raised and lowered in the pit and when in its raised position while adjacent the main track to bridge the interruption and permit the wheels to be propelled thereover, and having mounted directly thereon wheels adapted when the table is in its lowered position in the pit to rest on the rails of the pit track and permit the table to be propelled therealong, four vertically extending screw shafts positioned directly above the rails, connected to the corner portions of the table so that they and said table are capable of relative raising and lowering movement, reversible power operated mechanism mounted on the table, operative to effect relative raising and lowering movement of the screw shafts and table, so related to the struts that it is adapted when actuated in one direction after the lower ends of the screw shafts are at rest on the rails and the table is in its raised position first to lower the table until the wheels thereof rest on the pit track and then to raise the screw shafts relatively to the table and free the latter so that it is capable of being propelled along the pit track, and is further adapted when actuated in the opposite direction first to lower the screw shafts until the lower ends thereof are at rest on said rails and then to raise the table, and consisting of a reversible electric motor, nuts rotatably mounted on the screw shafts and held on the table against axial displacement relatively thereto, and gearing extending between the motor and nuts and operative conjointly to rotate the nuts in one direction when the motor is driven in one direction and conjointly to rotate the nuts in the opposite direction when the motor is reversely driven and means associated with the struts for holding the latter against rotation relatively to the table.

8. A drop tableapparatus having associated therewith a main railway track with an interruption therein, and an elongated pit extending transversely of the main track at the interruption and having a longitudinal track along its bottom, designed for use in removing and then replacing wheels on a railway vehicle on the main track, and comprising a unitary table extending across the pit, having rail sections on the top thereof, adapted to be raised and lowered in the pit and when in its raised position while adjacent the main track to have its rails bridge the interruption and permit the wheels to be propelled thereover, and having mounted directly thereon wheels adapted when the table is in its lowered position in the pit to rest on the pit track and permit the table to be propelled therealong, a plurality of vertically extending struts connected to the table so that they and said table are capable of relative raising and lowering movement, and reversible power operated mechanism mounted on the table, operative to effect relative raising and lowering movement of the struts and table, and so related to the struts that it is adapted when actuated in one direction after the lower ends of the struts are supported adjacent the pit bottom and the table is in its raised position first to lower the table until the wheels thereof rest on the pit track and then to raise the struts relatively to the table and free the latter so that it is capable of being propelled along the pit track, and is further adapted when actuated in the opposite direction first to lower the struts until the lower ends thereof are supported adjacent the bottom of the pit and then to raise the table.

ASA W. SKINNER.

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

UNITED STATES PATENTS Number Name Date 1,319,833 Bingaman Oct. 28, 1919 2,301,579 Plait et a1. July 30, 1941