US2554930A

US2554930A - Lift truck

Info

Publication number: US2554930A
Application number: US692465A
Authority: US
Inventors: Bronislaus I Ulinski
Original assignee: Yale and Towne Manufacturing Co
Current assignee: Yale and Towne Manufacturing Co
Priority date: 1946-08-15
Filing date: 1946-08-15
Publication date: 1951-05-29
Anticipated expiration: 1968-05-29

Description

May. 29, 1951 B. l. L lLlNSKl LIFT TRUCK sheets-sheet 1 Filed Aug. l5, 1946 INVENTOR BY /Wyfm ATTORNEY May 29, 1951 B. l. ULlNsKl 2,554,930

` LIFT TRUCK Filed Aug. 15,1946 4 sheets-sheet 2 INVENTOR @M l MVM TTORNEY B. l. ULINSKI May 29, 1951 LIFT TRUCK 4 Sheets-Sheet 3 Filed Aug. l5, 1946 wf l r INVENTOR Y A'TORNEY B. l. ULINSKI May 29, 1951 LIFT TRUCK l4 Sheets-Sheet 4 Filed Aug. l5, 1946 Mll; fl

Patented May "29, 195i UNITED STATES ATENT OFFICE 2,554,930 LIFT TRUCK Bronislaus 71. Ulinski, Chicago, Ill., assignor to' The Yale & Towne Manufacturing Company,

Stamford, Conn., a corporation of Gennecticut Application August 15, `i946, lSerial No. 692,465

l29 claims. (01.214-113) This invention relates to an industrial ltruck of the type in which a load elevating carriage is adapted to lift and lower a load. More particularly, my invention relates to a truck of `the particular class in whichV the carriage may not only be lifted and lowered, but may be tilted for effective manipulation of the load carried thereby,

Ain trucks kof the particular class described, it is customary to inunt -the elevating carriage for lifting movement 911 e reir Of Seggi-Mary uprights. The secondary uprights are in turn mounted -for lifting movement on rprimary uprights. For accomplishing this movement of the elevating carriage and lthe secondary uprights, it -is customary to use a hydraulic ram, the ram operating through a chain mechanism and thereby imparting lifting movement simultaneously to the carriage and `the .secondary uprights.

v As those slgilled in the art will fully appreciate, it is very important that the load elevating 4carriage be capable of some vlifting movement prior to the movement ofthe secondary uprights, ,so that the overall height of the truck shall not be increased When the carriage is lifted a limited amount. lThis arrangement is especially necessary where a truck is .to 4be used for moving loads in and out ofrlfreight cars, since there it .is :essential that .the overall height ofthe truck .be maintained a minimum, while the load elevating carriage is vraised to a considerable height to stack the load within Vthe freight .car ,or to remove it from Va stack within the car. It is .also necessary ,in trucks of the particular class that the elevating ram itself benot unduly exposed and that it shall not extend above .the primary or .secondary uprights during the lifting movement of the elevating carriage. v'

Inventors have attacked the particular problem .for many years, but no Very effective resuits have been obtained. One attemptedisolution of the problem is found in the Dunham Patent No. 2,178,370 dated October 31, l1939', Where the elevating ram is adapted .to raise the elevating carriage through means ,of a chain' mechanism, while adapted to elevate .thesecondary uprights through direct physical contact. ',Ihis direct physical contact is lnot made Iuntil after :the ram `moves a predetermined degree to lift the elevating carriage a short distance, from the ground. While the Dunham structure is eiective in maintaining .the secondary uprights in their lowered position while simultaneously lifting the V1elevating Acarriage somewhat, the amount of lif-t of the carriage thus obtained is naturally very limited. It, therefore, becomes impossible to utilize the carriage effectively fQr stacking loads within a freight car, because to obtainfaJ really considerable lift of the carriage, itis necessary to raise the secondary .uprights SplnWhat- I have conceived an effective solution ,of the problem` presented, and have actually "constucted a successfully operating and commercially desirable truck based on lthat conception. As a feature of my invention, I utilizetwo rams .with one ram adapted to lift the load elevating carriage relatively to the secondary uprights while the second ramlifts the secondary uprights relatively to the .primary uprights. As a further feature lof the invention, the'secdnd ram lifts both the secondary uprights .and the load elevating carriage.

As a still further feature ,of my invention, one ram extends between the Asecondary .uprights and the elevating carriage and is adapted to lift lthe elevating carriage, and while this may he ydone y directly, I prefer to utilize a flexible movement first ram for lifting the carriage.

It is a feature of this partof the invention that relatively small inexpensive rams may be utilized, as .each'ram is required to contribute relatively short movement to the mechanism actuated thereby. This is an exceedingly imprtantlcharacteristic .of my invention, as those' skilled in the art will appreciate.

As a further feature Vof my invention, the two rams areadapted to koperate `in sequence with the first ram lifting the load eleyating carriage to its Ifullect'ent before' any .Increment '.vvhats'oever is infiparted tothe 1secondary uprightsby the second ram. 1t is a `partirzular ir'nportal'nt feature of my invention thatthis sequential operation is inherent in my structure so thatboth rams may Abe direetlyfconnected .to la .single source of fluid pressure. rTheoperaticn `isinherent because .the nuid pressure Will first actuate .that ram having lthe lighter load with relation toits surface area, and will then :actu-atethe ramhaving the greater load with relation toits surface area.

For purposes ,of economy, lmy rams ,are duplicates, and Since one ram vis required to'lift merely the elevating carriage tvl'iilethe other ram is required to lift botn the carriage 'and secondary uprights, lit is ,obvious that the carriage willbe the rst load tobe lifted. For ,insuring `this sequential lift, those skilled in the art .may develop other structures based on my broad concept `o'f two sequentially actuatedlrams and it is naturally .important that .theclaims lgranted :ne shall he of Esufficient. scope `,to cover such'inodinfcatinsfof my invention'. 4As a 4matter of fact, `Ihavel already conueived the utilization of a larger ,area

ram to raise the load elevating carriage, thereby reducing the unit area pressure required to lift the carriage relatively to the unit area pressure required by the second ram, and thus insuring the operation of the first ram where friction or other factors may place unforeseen difculties on the carriage operation. Similarly, I have conceived the utilization of valving means, and even separate pressure sources and separate motors for those pressure sources, all designed to contribute the sequential lift I require, and all based on my broad concept of two rams.

As a further feature of my invention, the load elevating carriage and the secondary uprights are always maintained under the control of the hydraulic rams so that neither the carriage nor the secondary uprights may drop freely and cause damage. In the most successful structure of this type heretofore contributed, the secondary uprights may drop and cause considerable damage, and it has heretofore been possible only to limit this damage by limiting the amount of possible drop, and not to eliminate the difficulty. Those skilled in the art will appreciate greatly this particular phase of my invention and the considerable contributions made thereby to the art.

As still a further feature of the invention, I utilize a tilting ram for tilting the primary and secondary uprights together with the load elevating carriage relatively to the main frame of the truck. Insofar as the general arrangement of the tilting ram is concerned, there is no particular novelty therein to be claimed. However, the control of the tilting ram and the means whereby hydraulic pressure is directed thereto and therefrom, are of extreme importance and are herein to be described and claimed.

Thus, as a feature of my invention, the fluid pressure normally directed to the tilting ram will be directed to the lifting rams to augment the normal pressure applied to the lifting rams when the control for the tilting ram is in neutral position. As a particular feature of this part of the invention, the lifting rams and tilt ram are actuated from a single source of fluid pressure, in effect, with a part of the pressure going to the tilting ram and a part thereof going to the lifting rams, the arrangement being such that the fluid pressure will go entirely to the lifting rams if valve means are actuated for preventing the flow of fluid to either end of the tilting ram.

As a still further feature of my invention, I arrange for novel electrical controls for a motor utilized to develop a source of fluid pressure for the rams. Thus, it is possible to control the lift rams to lower the load without starting the motor, while at the same time, the actuation of the control means for the lift ram to lift the load, will start the motor, the starting of the motor being also accomplished upon movement of the control means for the tilt ram for tilting the load in either of opposed directions.

I have thus outlined rather broadly the more important features of my invention, in order that the detailed description thereof that follows may be better understood, and in order that my contribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate as I have already indicated, that the conception on which my disclosure is based, may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of my invention. It is important therefore that the claims to be granted me shall be of suincient breadth to prevent the appropriation of my invention by those skilled in the art.

Referring now to the drawings, Fig. 1 is a side elevation of an industrial truck of the general class described, illustrating my invention applied thereto. Fig. 2 is a forward end elevation of the truck of Fig. 1. Fig. 3 is a view of the uprights and the load elevating carriage with the carriage in its fully elevated position relatively to the secondary uprights. Fig. 4 is an end elevation of the parts in the position of Fig. 3. Fig. 5 is an elevation of the uprights and the elevating carriage showing both the carriage and secondary uprights in their fully lifted position. Fig. 5 is an end elevation of the parts of Fig. 5. Fig. is a perspective view showing the chains utilized for lifting the carriage and/or secondary uprights with the ram actuated sprockets in engagement therewith. Fig. 8 is a diagrammatic view showing the lift and tilt rams, the fluid pressure source, andA the valve mechanism and electrical mechanism for controlling the entire combination of elements.

Referring now more particularly to the drawings, the truck of my invention is of the general type well known in the art and having a load elevating carriage IIJ, a pair of secondary uprights II, and a pair of primary uprights I2. The primary uprights, together with the secondary uprights and the carriage I8, are adapted for tilting in a manner indicated by me in earlier patents, or as hereinafter set forth. While the traction of my truck is obtained electrically, the lifting cf the secondary uprights and load elevating carriage is obtained hydraulically.

Thus, the traction wheels I3 are driven in a conventional manner by an electric motor energized in the usual conventional manner, with the source of current being a battery contained in the battery compartment I4 of the truck illustrated. The operator of the truck will sit on the seat I5 and will steer the truck by means of the steering wheel I6. A pair of handles Il and I8 are pivoted on an axis I9 relatively to a forward standard 2li of the truck, the handle II actuating a control rod 2l and the handle I8 actuating a control rod 22, both rods being best illustrated in Fig. 8.

The source of uid pressure to which I have alluded is designated generally by the reference letter S in Fig. l, and is probably best illustrated in Fig. 8. It comprises an electric motor 23 driving through gearing 24 a pair of pumps 25, 26. The two pumps 25, 2t are functionally considered one source of fluid pressure, it being more economical for my purposes to utilize two pumps rather than a single large pump. Both pumps obtain their fluid from a reservoir R, and the ow of fluid is effectively controlled by a tilt control valve mechanism T and a lift control valve mechanism L, mechanism T being actuated and controlled in turn by handle I'i and shaft 2|, while mechanism L is controlled and actuated by handle I8 and shaft 22.

The load elevating carriage I8 is suitably secured to a vertically moving mounting member 27 that through opposed upper and

lower rollers

28 and 29 is adapted to move vertically in the bearing channels 38 of the secondary uprights II. The secondary uprights are in turn secured to a carrying member 3l that is equipped with upper and lower pairs of

rollers

32 and 33 moving in the channels 34 of primary uprights I2.`

lin this way the secondary uprights may move relatively to the primary uprights. The primary uprights may be mounted in any suitable way, as those skilled in the art will `iully appreciate, for tilting movement relatively to the truck. For the purposes of the present invention, I show at 35 stud shafts on which the uprights may tilt relatively to the truck main frame.

For accomplishing this tilting movement, I utilize a tilting ram designated generally by reierence numeral 36 and comprising a ram piston 3'! best illustrated in Fig. 8. This ram piston is pivoted at 3S to a lever llii that is in turn pivoted at il on the standard 2B of the truck. At i2 there is pivoted to the lever` lil a link i3 that is pivoted at liti to a bracket 45 forming an integral part of the primary uprights I2. It 1s now obvious that movement oi the ram piston 3l' will effect a tilting movement of the primary uprights I 2 and therefore a pivotal movement of the secondary uprights and load elevating carriage l.

For moving the load elevating carriage Iii and its mounting member 2 on rollers 2S and 29 relatively to the secondary uprights Il, utilize a ram designated generally by reference numeral i5 pivotally supported at l on the secondary uprights. Instead of the pivotal support 13'! the ram may simply be mounted in a universal cup-like bearing to be carried by `the secondary uprights H. The ram piston of the ram d8 is designated by reference numeral et.

and carries at its upper end a transverse bar se pivoted thereto at t, as best seen in Fig. 7. At each end of the bar 59 there is mounted a sprocket 5l, and the teeth of each sprocket are in engagement with a chain 52. Each oi the chains 52 is secured at one end to the carriage I (I through means of a bracket 53, and is secured at its other end to a bracket 5t carried by the secondary uprights II. It is, of course, obvious that upward movement of the ram piston i8 of ram 46 will effect a movement of the carriage Iii that will be double the movement of the ram piston 4S. The movement that may be imparted thus to the carriage It is best illustrated in Figs. 3 and 4. Y

For lifting the secondary uprights and the carriage Ed as a unit relatively to the primary uprights I2, there is utilized a second ram 55 pivoted at @la on the primary uprights I2, and having a ram piston 56. Ram piston 56 is connected at its upper end to a cross bar 5l that is a duplicate of the cross bar M3 actuated by the first ram piston lili. rlhrough suitable sprockets 58 secured at each end of the bar 51 a second pair of chains 59 is actuated, these chains being secured at one end to the secondary uprights at `Iii), and at the other end to the primary uprights at 6I. It is quite obvious that upward movement of the second ram piston 5t will contribute a double lift movement to the secondary uprights II in the same manner as a double lifting movement is contributed by the first ram piston 48 to the load elevating carriage it.

In Figs. 5 and 6 the secondary uprights are shown at their highest lifted point, and the load elevating carriage l@ is shown lifted to its highest degree relatively to the secondary uprights. A study of Figs. l, 3 and 4 illustrates the extremely high movement that may be imparted to the load elevating carriage prior to any 'movement of the secondary uprights. Thus, the dotted and dash line position of the forks 62 in Fig. 3 illustrates the height to which the lower rights I2, Il, and without any lifting of ther `secondary uprights I I. The other figures to which reference has been made illustrate very Well the extremely high lift possible when both the load elevating carriage and the secondary uprights have been fully lifted.

As is probably best illustrated in Fig. 8, the first ram t6 and the second ram 55 both receive their fluid from the pipe B5, so that fluid pressure will inherently be applied rst to that ram having the lightest load in proportion to its area. rhus, from the pipe 65 uid will ilow to the tting (it and thence through pipe til' to ram 5.5 or through pipe 63 to fitting and then pipe 'Ill to rain i. It will be understood that while I use the term pipe to designate the means through which the fluid ilows, it is actually desirable and even necessary to use flexible hose for conducting the iiuid. Now, since the second rain 5d must lift everything that the rst ram lifts, plus the first ram and the secondary uprights, it is obvious that with the rams both the same size, the pressure required to actuate ram d5 will be greater than the pressure required to actuate ram se.. Therefore, piston 68 Will be the rst to moveon the flow of fluid through pipe 65, and it Will, not be until ram t has first elevated load elevating carriage iii to the position of Figs. 3 and 4 that fluid will iiow into ram 55 for actuating that ram and for lifting the secondary uprights together with the load carriage to the position illustrated in Figs. 5 and 6.

I believe that with this explanation, taken together with the general discussion of my inn vention already set forth, this phase of the con-- tribution of my invention will be fully and clearly understood. l do wish to emphasize at this point, that both the elevating carriage and the secondary uprights are always under the control of the two rams so that it is never possible to have a free floating pair oi` uprights as in prior art constructions.

Referring now further `to Fig. 8, reference letter T, as already set forth, indicates the tilt control valve while reference letter L indicates generally the lift control valve. Referring first to the tilt control T, we dnd that it includes a chamber 'l0 in which slides a spool valve bodj,1 li controlled by a portion l2 of the rod 2l through the scalloped or bored abutments I3 and 'I4 on the said rod. We iind further in the tilt control T a spring loaded ball valve i5, with the pressure oi spring 'it thereof controlled by an adjusting mechanism "il, the purpose of which will be explained presently. In the upper portion of the tilt control we find a further chamber 'i8 within which floats a control piston 'F9 having a pair of opposed pins @t for controlling a right hand ball valve 3i and a left ball valve 82.

Each of these said ball valves Si, 82 is maintained within a bore formed in the end portion 83 of a regulator valve body designated generally by reference numeral 84. There is one regulator valve for each side of the tilt ram 3e, used for a purpose presently' to be described. A further bore 85 is formed in the body of each of the regulator valves, and mounted within each bore 85 is a compression spring 8S guided at o-ne end by a pin 8l and extending between the end 'of the bore 85 and a controlling sliding piston valve 83 whereby to maintain the said sliding piston` valve in its extreme right hand position illustrated in Fig. 8. The construction of the sliding piston valve 88 is such that pressure applied thereagainst through its flanged surface 99 surrounding its speed control passage 89a, will tend to move the piston valve against the force of the spring 86 and into a position obstructing bores 99, all for a purpose presently to be disclosed.

The rod 2E for controlling the spool valve 'II of the tilt valve control T is formed with a dwell 9| cooperating with a control pin 92 for closing a switch at 93 upon movement of the rod 2| to the right or -to the left from its position of Fig. 8.

I should now like to refer to the lift control valve L shown in Fig. 8. In the upper portion of this lift control valve L, there is shown a bore 94 within which is mounted a regulatingl valve 95 very similar in construction to the regulating valve shown in the tilt control T except that the end :portion 63 containing the ball valve 3| is not utilized, Thus, regulating valve 95 contains a sliding control piston 96 pressed to the extreme right position by a spring 9i and adapted to move against the force of the spring when fluid pressure is exerted against the flange 98 of the said sliding piston surrounding its speed control passage 99a.

A chamber 99 is formed in the control valve L, and is closed by a plug I 66. The plug |09 maintains in position a compression spring Il that presses a ball |02 into closing relation to a bore |03 formed in a moving control piece |94. Mounted for sliding movement also in the chamber 99, and relatively to the control piece |96, is a valve body |95.

The control rod 22 is formed with a long dwell |06 so that movement to the right thereof for a considerable distance will not move the switch operating pin |91 that controls a switch |98. Movement of the rod 22 to the left in Fig. 8 will, however, move the pin |61 to close the switch |99. An index ball |99 co-acts with three index notches in the rod 22 for indexing its three positions. Additional passages and means in the valve body L will be referred to later. It will be well now to disclose the operation of my invention under several conditions.

Let us rst assume that the operator wishes to lift the load, but not to tilt the load. I-Ie will, therefore, leave the valve control rod 2| and the handle Il in the neutral position illustrated in Fig. 8. He will move the handle I8 so as to move control rod 22 of control valve L to the left from the position of Fig. 8. This movement to the left will close a circuit at |68 and will excite the motor 23 which will immediately actuate pumps 25, 26. Simultaneously, the control surface ||i of rod 22 will move into position to close the right hand end of valve passage |I2. Fuid will now ilow from the reservoir through pump 25, pipe ||3, and passage ||4 to lift the ball valve II5. The flow will continue through passage I I6, passages II'|, IIS, H9 of the regulator valve 95, through the bore |29 and speed control passage 98a of the piston 96, and into pipe 65. From pipe 65 the fluid will flow first into the ram 66 to lift the elevating carriage, and thereafter will flow into the ram 55 to lift the secondary uprights and the carriage, all as has been previously described. Safety valve Illia will of course prevent the application of additional pressure upon full lifting of the rams as those skilled in the art will appreciate.

At the same time, fluid will flow from the reservoir R into the pump 25 and through the pipe I2I into passage |22 of control valve T. Be-

CJD

cause spool 1| is positioned to prevent the flow of fluid into the chamber 78 of control valve T, the fluid can then flow only into passage |33 and through the bore 'Ha of spool 'II about the stem l2 of rod 2| and into chamber 16. Thence, it will flow through passage lila and pipe |23 into pipe I I3 and join the output of the first pump 26 in the actuation of the two lift rams 46, 55. Thus, the entire output of fluid pressure source S is used to actuate the two lift rams.

Let us say that the load has been fully lifted and that the operator wishes to lower the load. In order to stop the operation of the pumps 25, 26, the operator need only restore control rod 22 to its position of Fig. 8. This will hold the load in any elevated position to which it has been moved, as fluid cannot flow past ball valve I|5. Thereafter, to lower the load he moves the rod 22 toward the right in Fig. 3 so that the pin |24 forming the end of the rod 22 unseats the ball |92. Once ball valve |92 is unseated, the pressures in the low pressure chamber |26 and in chamber 99 tend to become equalized. Therefore, the considerable pressure exerted by the fluid tending to flow from the

rams

46, 55 will be effective to move the control piece |54 and then the valve body |65 to the right from their positions in Fig. 8 to establish a flow of fluid past the valve seat |21 into the low pressure chamber |26. This allows fluid to flow from the lift rams through pipe 65, the speed control passage 98a and bore |26 of the control piston 96, and passages II9, H8, ||'I into bore ||6. The fluid then flows through port |25 and past valve seat |21 into chamber |26 and through pipe |28 back to the reservoir R. In this way, the fluid from the lift rams 55, i6 moves to the reservoir and the load is lowered, always under full control.

For controlling the lowering speed of movement. I utilize the control piston 96 within the regulator valve 95. Thus, should undue speed be developed in the rams, the considerable pressures will tend to operate against the flange 98 moving piston 96 to the left in Fig. 8. This movement will be against the pressure of the spring 91 and will tend to close the passages II9. This will immediately slow down the ram piston movements. It may, therefore, be said that the regulator valve effectively controls the speed of lowering movement of the elevating carriage and the secondary uprights. Incidentally, it will be well to emphasize here that the lifting speed is also controlled by regulator valve 95 through its passage 98a, as all uid to the rams must pass through passage 98a. Any excessive pressures wlill maturally be relieved by safety ball valve I 4a.

We have now seen that during the lifting movement both pumps operate together to contribute lifting action. We have also seen that during lowering movement of the lifting rams, no power is utilized, but control of the lowering speed is maintained. Let us now consider what happens when the load is tilted, and not lifted or lowered. In the event it is desired to tilt the load, but neither to lift nor lower, the control rod 22 is maintained in its position of Fig. 8. The control rod 2| is moved in one direction or the other depending upon the direction of the tilt desired. Let us say that it is desired to tilt in a direction in which the piston 3l of the ram 36 is moved upwardly in Fig. 8. For the particular purpose the rod 2| will then be moved to the right to align groove |30 of spool 1I with bore |29. This will 9 close the circuit at switch 93 and the motor 23 will be energized to actuate both pumps.

Fluid from pump 25 will move through pipe H3, bore H2, chamber 26 and pipe |28 back to the reservoir. The fluid from pump 25 will go through pipe |2l, bore |22, bore |29, the left groove |35 of spool 'll and into chamber l at the left side of piston 79. The fluid. will then move past the ball valve 82 and the regulator valve gli into pipe |3| and thence into ram 35 and against piston 3l. Movement of the piston 3l will, of course, tilt the load. Simultaneously, fluid will ilow from the other side of the piston 3l through pipe |32 into regulator valve 8d. The fluid will flow through the Valve il in the same manner as it was explained it ows through the regulator valve 95 of the lift valve control L. The application of pressure at the left side of the piston 'lil in chamber 'i3 has in the meantime forced the piston to the right from its neutral position of Fig. 8 so that its pin 8 has unseated ball valve 8|. Therefore, fluid may iiow through the regulator valve past the ball valve El into the right hand side of chamber 'E8 and thence through bore |33 and central borella of -spool 1|. From bore 'Ha fluid iiows through the scalloped or bored passages in abutment i4 to the left of said abutment and into chamber lli. From chamber 'le the fluid will flow through bore lila into pipe |23 and thence will join the output of the pump 26.

It is well to consider at this point that the ball valve l5 must be so loaded by spring 16 under adjustment mechanism Il that the iiuid from pump 25 will move through the bore |29 to actuate the tilt ram rather than to by-pass the tilt ram by unseating the ball valve l5. It is well to consider also that the speed control passages Sila will determine the speed of tilt with all excess pressures relieved by flow of fluid past ball valve 15.

Let us now consider what happens when it is desired both to lift the load and tilt it. For the particular purpose the control rod 22 is then moved toward the left to excite the motor 23 so that the pump 2t pumps fluid as earlier described into the two rams llt, 55. Simultaneously the pump 2li will direct fluid towards one or the other of two ends of the ram 35 under the control of the spool ll. The fluid returning from the other side of the ram 36 will be at suiliciently high pressure so as to move through the bore |33 of the spool and through the pipe |23 to the pressure side of The nature of my system is such that the pressure at each side of the ram 36 is quite great, with the differential relatively small because of the relatively light load moved by the tilt ram as compared to the load moved by the lift rams. Because of this relationship between the pressures at the two sides of the piston 3l, the pressure of the fluid owingfrom behind the moving piston 31 will be sufficient to allow the entry of the duid into the pressure side of the pump 2t? for movement therewith to actuate the rams 136, 55.

I believe that with this description of the operation and control of the hydraulic mechthose skilled in the art will fully appreciate and understand the basis of my contribution to the art.

I claim:

1. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a hydraulic ram interposed between said load carriage and secondary uprights, means whereby said hydraulic ram lifts said load carriage relatively to said secondary uprights and hold said carriage in an elevated position relatively to said secondary uprights, a second hydraulic ram interposed between said secondary uprights and primary uprights, and means whereby said secondary ram lifts said secondary uprights together with said load carriage relatively to said primary uprights while said iirst ram is conditioned to hold said load carriage elevated relatively to said secondary uprights.

2. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a ram for lifting said load carriage relatively to said secondary uprights extending between said secondary uprights and load carriage, and a second ram extending between said primary uprights and secondary uprights for lifting said secondary uprights relatively to said primary uprights.

3. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a ram for lifting said load carriage relatively to said secondary uprights supported on said secondary uprights, and a second ram for lifting said secondary uprights relatively to said primary uprights and therefore also said load carriage and first ram relatively to said primary uprights.

4. In a truck of the class described, primary uprights, secondary uprights, means mounting said sec-ondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for Vertical movement on said secondary uprights, a first ram supported on said secondary uprights, a Hexible member secured at one end to said load carriage and at its other end to said secondary uprights, means whereby said first ram actuates said exible member tc lift said load carriage, a second ram supported on. said primary uprights, and means whereby said second ram lifts said secondary uprights together with said rst ram and load carriage.

5. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement `relatively to said primary uprights, a load car- 'secured at one end to said secondary uprights and at its other end to said primary uprights, and means whereby said second ram actuates said flexible member to lift said secondary uprights together with said rst ram and load carriage relatively to said primary uprights.

6. In a truck of the class described, primary uprights, Secondary uprights, means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a hydraulic ram for lifting said load carriage relatively to said secondary uprights, a second hydraulic ram for lifting said secondary uprights relatively to said primary uprights, a source of hydraulic pressure, and the said rains being of such size as compared to the loads imposed thereon that the first of said rams is actuated from said source of hydraulic pressure automatically in advance of the second ram.

7. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement n said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a hydraulic ram for lifting said load carriage relatively to.

said secondary uprights, a second hydraulic ram for lifting said secondary uprights relatively to Vsaid primary uprights, a source of hydraulic pressure connected for the simultaneous flow of fluid to both rams, the said rams being of such size as compared to the loads imposed thereon that the fluid pressure required to actuate the first ram is less than that required to actuate the second ram whereby said first rain will lift said load carriage and thereafter the second ram will lift said secondary uprights.

8. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a hydraulic ram for lifting said load carriage relatively to said secondary uprights supported on said secondary uprights, a second hydraulic ram supported on said primary uprights for lifting said secondary uprights together with said load carriage and first ram relatively to said primary uprights, a source of hydraulic pressure, and the said rams being of such size as compared to the loads imposed thereon that the first of Said rams is actuated from said source of hydraulic pressure automatically in advance of the second ram.

9. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a hydraulic ram for lifting said load carriage relatively to said secondary uprights, a second hydraulic ram` for lifting said secondary uprights relatively to said primary uprights, and a source of hydraulic pressure connected to both said rams to actuate said rams in the order of the pressures required A to actuate said rams.

1Q. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement l2 secondary uprights together with said load cairiage and first ram relatively to said primary uprights, and a source of hydraulic pressure connected to both said rams to actuate said rams in the order of the pressures required to actuate said rams.

l1. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a iirst hydraulic ram supported on said secondary uprights, a flexible member secured at one end to said load carriage and at its other end to said secondary uprights, means whereby said iirst ram actuates said flexible member to lift said load carriage, a second hydraulic ram supported on said primary uprights, means whereby said second ram lifts said secondary uprights together with said first ram and load carriage, and a source of hydraulic pressure connected to both said rams to actuate said rains in the order of the pressures required to actuate said rams.

l2. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load cai*- riage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a hydraulic ram for lifting said load carriage relatively to said secondary uprights, a second hydraulic ram for lifting said secondaryV uprights relatively to said primary uprights, a source of hydraulic pressure connected to botli said rams to actuate said rams in the order of the pressures required to actuate said rams, the rst of said rams having a lighter load with relation to its surface area than the second ram to a degree sufclent to effect operation by said fluid iirst of said relatively lighter loaded ram and then of said relatively heavier loaded ram.

13. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a hydraulic ram for lifting said load carriage relatively to said secondary uprights supported on said secondary uprights, a second hydraulic ram supported on said primary uprights for lifting said secondary uprights together with said load carriage and first ram relatively to said primary uprights, a source of hydraulic pressure connected to both said rams to actuate said rams in the order of the pressures required to actuate said rams, the first of said rams having a lighter load with relation to its surface area than the second ram to a degree sufficient to effect operation by said fluid irst of said relatively lighter loaded ram and then of said relatively heavier loaded ram.

14. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, mgans mounting said load cairiage for vertical movement relatively to said secondary uprights, a rst hydraulic ram, a ileXible member secured at one end to said load carriage and at its other end to said secondary uprights, means whereby said first ram actuates said flexible member to lift said load carriage relatively to said secondary uprights, a second hydraulic ram, means whereby said second ram lifts said secondary uprights together with said `first ram and load carriage, a source of hydraulic pressure `connected to both said rams to actuate said rams in the order of the pressures required to actuate said rams, the first of said rams having a lighter load with relation to its surface area than the second ram to a degree sufficient to effect operation by said fluid first of said relatively lighter loaded ram and then of said relatively heavier loaded ram.

15. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for Vvertical movement relatively to said secondary uprights, a hydraulic ram, means whereby said ram lifts said load carriage relatively to said secondary uprights and holds said carriage in elevated relation to said secondary uprights, a second hydraulic ram, means whereby said second ram lifts said secondary uprights relatively to said primary uprights while said first ram holds said carriage fully elevated relatively to said secondary u prights, and a source of hydraulic pressure on said truck connected simultaneously to both said rams.

16. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a hydraulic ram for lifting said load carriage relatively to said secondary uprights supported on said secondary uprights, a second hydraulic ram supported on said primary uprights for lifting said secondary uprights together with said load carriage and first ramrelatively to said primary uprights, and a source of hydraulic pressure on said truck connected to said rams.

17. In a truck of the class described, a lift ram for lifting a load carrying member of said truck, a tilt ram for tilting said load carrying member, a source of fluid pressure, means of comm-unication between said source of fluid pressure and both ends of said tilt ram, means of communication between said source of huid pressure and said lift ram, a direction valve for directing fluid under pressure from said source of fluid pressure to one end or the other of said tilt ram, a fluid passage positioned between said direction valve and lift ram to permit the ow of fluid to said lift rain in by-pass relation to said tilt ram when said direction valve is positioned in neutral and preventing flow of fluid to either end of said tilt ram, and means in said direction valve whereby said fluid passage is in communication with one end of said tilt ram when said direction valve directs fluid to the other end of said tilt ram.

18. In a truck of the class described, a lift ram for lifting a load carrying member of said truck, a tilt ram for tilting said load carrying member, a source of fluid pressure, means of communication between said source of fluid pressure and both ends of saidtilt ram, a direction valve for directing fluid under pressure from said source of uid pressure to one end or the other of said tilt ram and against fiow to either end, andv means in said direction valve automatically opening a flow passage from the low pressure end of said tilt ram toward said lift ram when communication is made between' the high pressure side of said source of .iiuid pressure and the other end of said tilt ram.

i9. In a truck of the class' described, a lift ram for lifting a load carrying member of said truck, a tilt raml for tilting said load carrying member, a pair of pumps, means of communication between the first of said pumps and both ends of said tilt ram, means of communication between the second of said pumps and said lift ram, a direction valve for directing fluid under pressure from said first pump to one end or the other of said tilt ram, fluid passage means in by-pass relation to said direction valve to permit the flow of fluid in by-pass relation to said tilt ram when said direction valve is positioned in neutral and preventing iiow of fluid to either end of said tilt ram, means whereby said fluid passage means are in communication with one end of said tilt ram when said direction valve directs fiuid to the other end of said tilt ram, said fluid then flowing through said fluid passage means to said lift ram to augment the normal pressure flow to said lift ram, a control valve between said lift ram and said second pump communicating with said uid passage means, and means forming part of said control valve for directing fluid to said lift ram when in one position, whilev directing fluid `both from said first pump and from said fluid passage means back to the low pressure side of both said pumps when in a second position.

20. In a truck. of the class described, primary uprights, secondary uprights, bearing means mounting said secondary uprights for vertical movement on said primary uprights, a load carrage, bearing means mounting said load carriage for vertical movement on said secondary uprights, a pair of ram pistons, a source 0f hydraulic fluid pressure, means whereby fluid from said source is directed toward both ram pistons simultaneously, means whereby one of said ram pistons lifts said load carriage on said secondary uprights, and means whereby the other of said ram pistons lifts said secondary uprights on said primary uprights, the rst of said ram pistons having a lighter load with relation to its surface area than the second ram piston to a degree sufficient to effect operation by said fluid rst of said relatively lighter loaded ram piston and then of said relatively heavier loaded ram piston.

21. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to4 said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively7 to said secondary uprights, a pair of ram pistons, a source of hydraulic fluid pressure, means whereby fluid from said source is directed toward both ram pistons simultaneously, a chain through which one of said ram pistons lifts said load carriage relatively to said secondary uprghts, a second chain through which the other of said ram pistons lifts said secondary uprights and carriage together relatively to said primary uprights, the first of said ram pistons having a lighter load with relation to its surface area than the second ram piston to a degree sufcient to effect operation by said uid rst of said relatively lighter loaded ram piston and then of said relatively heavier loaded ram piston.

22. In a truck of the class described, primary uprights, secondary uprights, bearing means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, bearing means mounting said load carriage for vertical movement on said secondary uprights, a pair of ram pistons, means for directing fluid under pressure against said ram pistons, means whereby one of said ram pistons lifts said load carriage on said secondary uprights, and means whereby the other of said ram pistons lifts said secondary uprights on said primary uprights.

23. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a pair of ram pistons, means for directing duid under pressure against said ram pistons, means whereby one of said ram pistons lifts said load carriage relatively to said secondary uprights, and means whereby the other of said ram pistons lifts said secondary uprights relatively to said primary uprights.

24. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement on said primary uprights, a load carriage, means mounting said load carriage for vertical movement on said secondary uprights, a pair of ram pistons, a source of hydraulic fluid pressure, means whereby fluid from said source is directed toward both ram pistons simultaneously, a chain secured at one end to said load carriage and at its other end to said secondary uprights, means whereby one of said ram pistons acts on said chain to lift said load carriage on said secondary uprights, and means whereby the other of said ram pistons lifts said secondary uprights on said primary uprights, the first of said ram pistons having a lighter load with relation to its surface area than the second ram piston to a degree suincient to effect operation by said fluid rst of said relatively lighter loaded ram piston and then of said relatively heavier loaded ram piston.

25. An industrial truck` comprising a body, a tandem mast structure pivotally mounted on the forward end thereof, guideways in the masts, traveling members in the guideways, a hydraulic lift on each mast for actuating the traveling members, the outer mast being supported by the traveling member in the inner mast, and a loadsupporting fork supported by the traveling member in the outer mast.

26. In an industrial truck, a chassis, a first hydraulic lift comprising a mast supported on said chassis, supporting means associated with said mast, and a hydraulic motor for elevating said supporting means relative to said mast, a second hydraulic lift comprising a mast supported by said supporting means, a load-supporting platform, and a second hydraulic motor for elevating said platform relative to said second mast,

27. In a truck of the class described, primary uprights, secondary uprights, means mounting said secondary uprights for vertical movement relatively to said primary uprights, a load carriage, means mounting said load carriage for vertical movement relatively to said secondary uprights, a hydraulic ram interposed between said load carriage and secondary uprights, means whereby said hydraulic ram lifts said load carriage relatively to said secondary uprights and holds said carriage in all elevated positions relatively to said secondary uprights, a second hydraulic ram interposed between said secondary uprights and primary uprights, means whereby said secondary ram lifts said secondary uprights 16 together with said load carriage relatively to said primary uprights, and means for directing fluid simultaneously toward both said rams whereby to actuate said rams sequentially in the order of the pressures required to actuate said rams.

28. In a truck of the class described, a lift ram for lifting a load carrying member of said truck, a tilt ram for tilting said load carrying member, a source of fluid pressure, means of communication between said source of fluid pressure and both ends of said tilt ram, means whereby said lift ram is in communication with said source of fiuid pressure in by-pass relation to said tilt ram whereby all the fluid pressure is utilized to actuate said lift ram, a direction valve for direct-- ing fluid under pressure from said source of fluid pressure to one end or the other of said tilt ram and also against flow to either end, and means in said direction Valve automatically opening a flow passage from the low pressure end of said tilt ram toward said lift ram when communication is made between the high pressure side of said source of uid pressure and the other end of said tilt ram.

29. In a truck of the class described, a tilt ram for tilting a load carying member of said truck, a source of fluid pressure, means of communication between said source of fluid pressure and both ends of said tilt ram, a direction valve having direction `passages for directing uid under pressure from said source of fluid pressure to one end or the other of said tilt ram and against ilow to either end, means forming a part of said direction valve positioned in by-pass relation to said direction passages to permit the flow of uid in by-pass relation to said tilt ram when said direction valve is positioned in neutral and preventing flow of fluid to either end of said tilt ram, and said means automatically opening a passage from the low pressure end of said tilt ram to said means in by-pass relation to said direction passages when communication is made between the high pressure side of said source of uid pressure and the other end of said tilt ram through one of said direction passages.

BRON'ISLAUS I. ULINSKI.

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

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