US2624543A - Lifting device - Google Patents

Description

Jan. 6, 1953" A. E." JACKSON LIFTING DEVICE 5 Sheets-Sheet 1 Filed Jan. 26, 1950 INVENTOR. ALEXlS E. JACKSON ATTORNEYS A. E. JACKSON LIFTING DEVICE Jan. 6, 1953 3 Sheets-Sheet 2 Filed Jan. 26, 1950 O n Mm Kw N mm H m A R 1 N m C. m 7 2/ x VJ M w m A A S VIA w A. W N Q Q mm ww mm %v Jan. 6, 1953 A. E. JACKSON 2,624,543

LIFTING DEVICE Filed Jan. 26, 1950 5 Sheets-Sheet 3 PERCENTAGE OF F']G H 6 TOTAL RANGE ASSUM ED LOAD 10 295o# 34 5200* 21% .5592 .9940 L76 5200' 27 2900 34 4600 51 .5592 .0910 L60 4600 44 2900 30 4000 77 .5000 .7193 1.44 4040 52* 2740 25 5900 07 .4220 .6l57 1.41 3900 .01 2030 17 4400 96 -2924 .4040 1.00 4350 INVENTOR,

e7 2540 10 5600 100 .1794 .3907 2.10 5500 ALEXIS E. JACKSON mezauwmeanm FIG. IIA

ATTORNEYS Patented Jan. 6, 1953 UNHTED STATES AT NT OFFICE LIFTING DEVICE Delaware Application January 26, 1950, Serial No. 140,739

13 Claims.

This invention relates to lifting devices of the kind employed for raising automobiles and the like, and particularly this invention relates to such lifting apparatus of the kind wherein the lifting action is attained by means including a pivoted lifting frame that supports the load on the free end thereof and which effects lifting movement by upward pivotal movement of such frame.

In lifting devices of the aforesaid character, the upward pivotal movement is imparted. to the lifting frame in many different ways and through the uses of different sources and kinds of operating power, and it is an important object of the present invention to materially improve the way 1 in which the operating power is applied between the pivoted lifting frame and the supporting base upon which such lifting frame is mounted. More specifically, it is an object of the present invention to so relate the power driven operating 9 means to the base and the lifting frame in such a device that the application of the lifting power is not only accomplished in an efficient manner, but is effective in such a way that the device is particularly convenient and safe in its operation.

The operating power is in many instances applied to lifting devices of the aforesaid character in the form of compressed air, and since compressed air in every instance will expand until a balance is attained between the air pressure and the load that is being applied, it is well recognized that there may be instances where an excess of compressed air may be applied so as to cause a lifting device of this kind to go beyond the limit of movement that is desired. In this respect it should be observed that lifting devices of the kind to which the present invention relates are designed and adapted in each instance for operation through a predetermined maximum lifting range, and it is important to arrange such lifting devices so that the load will not be inadvertently lifted beyond such range, and to enable this to be accomplished in a simple and effective manner is another important object of the present invention. More specifically it is an object of this invention to apply the lifting power to the lifting frame in such a device in such a way that as the lifting frame approaches the upper limit of its normal operating range, the necessary force that must be applied to the lifting frame to support or move the load will be suddenly increased, thereby to guard against the inadvertent overthrow in the operation of the lifting device.

A primary object of my invention is to afford a lifting device for rai in n and of an object such as an automobile, or the like, in a novel and expeditious manner, and wherein the parts are so constituted and arranged that lifting of the object is accomplished efficiently and in a manner whereby the parts of the lifting device will not interfere with the efficient work of a repairman working on the automobile, or the like, supported on the device.

Another object of my invention is to construct a lifting device having pivotally mounted lifting arms and a motor constituted and arranged relative to each other in a novel and expeditious manner whereby the motor is connected in tention to the lifting arms and is effective during operation of the device to pivot the arms upwardly by pulling thereon.

A further object is to enable a novel lifting device of the aforementioned type to be constructed which embodies novel latching devices for positively, but releasably, holding the lifting arms of the device in raised position.

Yet another object of my invention is to construct a novel lifting device which embodies a supporting frame, lifting arms, a motor for raising the arms, and latching means for releasably holding the arms in raised position, constituted and arranged in a novel and expeditious manner, and which affords a novel, efii-cient, and practical lifting device which may be economically manufactured, and is efficient and practical in operation.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

In the drawings:

Fig. 1 is a longitudinal sectional view of a lifting device illustrating a preferred embodiment of my invention, the view being taken substantially along the line Il in Fig. 2;

Fig. 2 is a top plan view of the lifting device "shown in Fig. 1';

Fig. 4 is a detail sectional view taken substantially along the line 4-4 in Fig. 1;

Fig. 5 is a detail sectional view taken substantially along the line 5-5 in Fig. 1;

Fig. 6 is a detail sectional view taken substantially along the line 66 in Fig. 4;

Fig. '1 is a detail sectional view taken substantially along the line 1--1 in Fig. 4;

Fig. 8 is a detail sectional view of the latching mechanism shown in Fig. 1, showing the mechanism in a latched position;

Fig. 9 is a detail sectional view similar to Fig. 8, but showing the latching mechanism in released position;

Fig. 10 is a detail sectional view taken substantially along the line Ill-l0 in Fig. 1;

Fig. 11 is a schematic force diagram illustrating the forces required to operate the present lifting device in different operating positions; and

Fig. 11A is a table of values relating to the application of the operating forces.

For the purpose of illustrating a preferred embodiment of my invention, a lifting device is shown in the accompanying drawings which comprises, in general, Figs. 1, 2 and 3, a supporting frame 22, a lifting frame 24, a motor 26, and latching mechanism 28, the motor 26 being operable during an operation of my device to pivot the lifting frame 24 on the supporting frame 22 from the normal, lowered position shown in solid lines in Fig. 1 to the raised position shown in broken lines therein, and the latching mechanism 23 being operable to releasably, but positively, hold the lifting frame in such raised position, all of which will be discussed in greater detail presently.

The supporting frame 22, Figs. 1, 2 and 3, comprises two elongated side beams 3| and 32 preferably comprising two elongated, upwardly inclined channel members 34 and 35 having plates 3'! and 38 projecting from, and forming a longitudinal extension on the front ends thereof, respectively, and having two upwardly projecting posts 4| and 42 mounted on, and extending transversely across the rear end portions thereof. The posts 4| and 42 each comprise an outer plate Ma and 42a and an inner plate M27 and 4227, respectively, the plates 31, 38, Ma, 42a, M1) and 4212 being connected to the respective channels 34 and 35 by any suitable means such as welding.

As is best seen in Figs. 1 and 10, the lower end portion of the posts 4| and 42 are connected together by a rod 44 which extends through sleeves 48 and 49 mounted between and connected to the plates Ma and M1), and 42a and 421), respectively, two wheels 46 and 41 being journaled on the opposite end portions of the rod 44 for supporting the rear end portion of the supporting frame 22. A rod 5|, similar to the rod 44, is mounted in, and interconnects, the plates 35 and 31 on the front end portion of the side beams 3| and 32, and two wheels 53 and 54 are journaled on the outer end portions of the rod 5| to thereby afford supports for the front end portion of the supporting frame 22. The posts 4| and 42 are also interconnected at their upper end portions by another rod 55, Figs. 1 and 3, to thereby complete a relatively solid frame structure.

A handle 51 is mounted on the upper end portion of the posts 4| and 42, Fig. 1, and projects rearwardly therefrom to afford means for readily pushing or pulling the device 20 across a floor surface on the wheels 46, 41,, 53 and 54. A tray 53 may be mounted on the handle 51 for supporting tools and the like.

The lifting frame 24 comprises two lifting arms ti and 62 normally disposed in substantially horizontal position between the side beams 3| and 32 of the supporting frame 22, as shown in solid lines in Fig. 1, and having the front end portions thereof interconnected by a rod 84 rearwardly of the rod 5|. The other, or rear end portions of the arms 6| and 62 are welded to, or otherwise suitably secured to, a sleeve 66 rotatably mounted on the rod 44 between the collars 48 and 49, Figs. 2 and 10. Two axlereceiving hooks or forks 68 and 69 are mounted on the front end portions of the arms GI and 62 of the lifting frame 24, respectively, and are secured thereto by suitable means such as welding, the hooks 68 and 69 being adapted to supportingly engage an object such as, for example, the axle of an automobile, or the like.

In the operation of my novel device, the lifting frame 24 may be pivoted upwardly and downwardly on the rod 44 between the positions shown in solid lines and in broken lines in Fig. 1, to thereby raise and lower the hooks G3 and 65, and for this purpose I provide a motor such as the motor 26 which may be of any suitable type but which I prefer to be of the pneumatically operated type.

The motor 23 includes a cylinder 1| comprising a cylindrical-shaped side wall 13 and two end walls 15 and 16. The end walls 15 and 16 are clamped on the side wall 13 by studs 13, Figs. 1, 3 and 5, extending through the peripheral edge portions of the end walls 15 and 16 exteriorly of the side wall 13 and held therein by nuts 19.

A cylindrical-shaped guide sleeve 8| is mounted in the central portion of the lower end wall 16 of the cylinder 1| and projects therethrough to afford a guide for the piston rod 83 of a piston 85 having a piston head 86 reciprocably mounted in the cylinder 1| as will be discussed in greater detail presently. Two bosses 88 and 89 project laterally outwardly from the guide sleeve 8! in opposite directions and abut the lower face of the end wall 16 of the cylinder 1|, the bosses 88 and 89 being rotatably mounted on studs 01 and 99 projecting through sleeves 33 and mounted in the intermediate portions of the posts 4| and 42, respectively, Figs. 3 and 1. The posts 4| and 42 are preferably inclined forwardly from the vertical so that the studs 81 and 98 are disposed forwardly of the rod 44 for purposes which will be discussed in greater detail presently.

Two substantially L-shaped rods 9| and 92 extend through and are welded to the bosses 13-8 and 59 and have one leg 94 and 95, respectively, extending through the end wall 16 on opposite sides of the guide sleeve 8| and have the other legs, 91 and 98 abutting and welded to the outer face of the sleeve 8|. The upper end portions of the legs 94 and 95 of the rods 9| and 92 are welded to the end wall 16 of the cylinder Ti to thereby secure the rods 9| and $2 and the guide sleeve 8| in fixed position relative thereto.

The piston head 85 comprises a substantially circular shaped flat plate having suitable leathers ||l| mounted on the peripheral edge portion thereof by bolts I03 and nuts I04 in position to wipingly engage the inner surface of the side wall 13. The piston rod 83 comprises a rod member I05 having one externally threaded end portion I08 extending through the center of the head 86 in threaded engagement therewith and the other end portion I09, which is also externally threaded, screwed into a tapped opening III in a connecting 'block I I2 rotatably mounted between suitable spacing sleeves H and H3 on a shaft H4 extending between, and connected to, the lifting arms GI and 62 between the rods 44 and 64. A look nut H5 is mounted on the end I08 of the rod member I06 to hold the head 86 in threaded engagement therewith.

.A sleeve member H1, forming a part of the piston 85, and having an externally threaded end II 8 mounted in a threaded opening H9 in the block H2, is mounted on the rod I06 in spaced relation thereto and is slidably mounted in the guide sleeve 8I, suitable packing I2I and I22 is disposed in the opposite end portions of the guide sleeve 8| in engagement with the outer surface of the sleeve member H1. Bushings I24 and I25, and cotter pins I21 and I28, Figs. 4 and 5, afford means for retaining the packing I2I and I22 in position between the sleeves SI and H1. A suitable lubricant such as, for example, grease may be packed into the sleeve 8|, exteriorly of the sleeve I I1, between the bushings I24 and I25 to afford lubrication of the sleeve I I1 during reciprocation of the sleeve H1 and the sleeve 82 relative to each other.

As previously mentioned, it will be seen, Fig. 4, that the rod I06 is mounted in the sleeve H1 in spaced relation to the latter. By this construction, a certain amount of flexibility is imparted to the rod I06, the rod I06 being capable of movement laterally in the sleeve I I1 whereby the position of the rod I06 in the sleeve I I1 may be automatically adiusted to accommodate the piston head 86 in the cylinder 13 to eliminate side thrust between the piston head 86 and the cylinder 83 which might result from relatively minor irregularities in construction or assembly if the piston rod I06 were rigid in the sleeve I I1..

From the foregoing, it will be seen that movement of the piston 85 upwardly into the cylinder H, as viewed in Fig. l, is effective through the connecting rod 83 to apply tension between the studs 81 and 90 on the supporting frame 22 and the. rod H4 on the lifting frame 24 to thereby effect upward swinging movement of the lifting frame 24 around the rod 44 disposed at the lower rear end portion of the supporting frame 22. Upon such movement of the lifting frame 24, the motor 26 rotatestherewith on the studs 81 and 90 from the position shown in solid lines in Fig. 1 toward the position shown in broken lines therein, and it will be seen that the positioning of the studs 81 and 90 forwardly of the rod 44 so positions the motor 25 relative to the pivot point of the lifting frame 24 that efiicient lifting of the frame 24 is effected.

It will be seen, of course, that when it is desired to lower the lifting frame 24 from raised position, the piston 85 is moved outwardly in the cylinder II to thereby permit the frame 24 to pivot downwardly about the rod 44. Thus, it will be seen that reciprocation of the piston 85 into and out of the cylinder 1| is effective to pull the lifting frame 24 into raised position and to permit the frame 24 to be lowered from raised position, respectively.

For the purpose of reciprocating the piston 85 in the cylinder 1|, a suitable working fluid such as, for example, compressed air may be fed into and out of the cylinder II through suitable means such as a coupling member I3I and. a

flexible hose I32, Figs. 1 and 5, the fiowof the working fluid into and out of the cylinder 1|,

6, through thehose I32, being controlled by suitable valve means, not shown.

A latching mechanism I35, Figs. 1, 2, 8 and 9; which is releasably engageable with the legs 91 and 98 of the rods 9| and 92 is mounted on the rod I I4 and movable with the piston to thereby afiord a releasable, positive means for latching the lifting frame 24 in raised position to im sure against accidental or unintentional lowering of the-lifting frame 24.

The latching mechanism I35 comprises two elongated plates I31 and I38 pivotally mounted at one end on the rod H4 on opposite sides of the connecting block H2 and extending toward the head 85 of the piston 85. A plate I39 extends between, and is connected to the upper edge portions of the plates I31 and I38 and is adapted to normally rest on the upper surface of the piston sleeve H1, Fig. 1, to normally support the latching plates I31 and I38 in rearwardly extending position, in substantially parallel. alignment with the piston rod 85. A plurality of notches I4I, Figs. 1, 8 and 9, are formed in the lower edge portions of each of the, plates I31 and I38 and open toward the piston 85. The. notches I are complementary to the legs 91. and 98 of the rods 9| and 92, and the legs 91 and 98 are engageable therein during movement of the piston 85 into thev cylinder 11, the, notches. I41 each having a tapered wall I 4Ia under which, the legs 91 and 98 of the rods 9I and 92 will freely slide during inward movement, of the piston 85, and a concave wall I4Ib which is en-.- gageable with the legs 91 and 98 of the rods 91 and 92 when the latter are disposed in the slot [III to prevent outward movement of the Diston 85.

A release lever I43, Figs. 1, 2, 8 and 9, is embodied in the latching mechanism I35, the release lever I43 com rising a lifting plate I45 pivotally mounted between the plates I31 and I38 on a rod I41 journaled in the plates I31 and I38, and a handle I48 connected to the end of the rod projecting outwardly from the plate I 31. The lifting plate I45 is mounted between the piston rod 83 and the plate I39 of the latching mecha nism I35, and normally projects from the rod I41 toward the piston head 86 in substantially parallel alignment with the piston rod 83, in the position shown in Fig. 8, the handle I48 being weighted so as to tend to retain the plate I45 in that position. With the plate I45 disposed in this position, it will be seen that during movement of the piston into the cylinder H, the latching mechanism I35 slides upwardly over the legs 9! and 98 of the rods 9I and 92 with the tapered side walls I4Ia of the. successive notches MI in the plates I31 and I38 sliding freely over the, legs 91 and 98 of the rods BI and 92. Full movement of the piston 85 into the cylinder 1I disposes the rods 9I and 92 in the notches I4I closest to the connecting block H2 as shownin Fig. .8. Thus it will be seen that the latching mechanism is efiective to positively hold the piston 85 against accidental Withdrawal from the cylinder in any one of a plurality of positions wherein the rods 9!, and 92 are latchingly engaged in notches MI in the plates I31 and I38.

When it is desired to move the piston 85 outwardly from the cylinder H from a position such as that shown in Fig. 8 wherein the rods 4| and 42 are disposed in notches I4I, theoper ator may, first, feed a small additional amount of working fluid into theeylinder 1I to thereby move the piston 35 into the cylinder sufficiently 7" to move the tapered walls-141A out of engagement with the legs 91 and 98 and disposethe legs 91 and 98 in registration with the openings of the notches I4I, and then, the operator may turn the handle I48 ina counterclockwise direction,

as viewed in Fig. 8, to thereby swing the plate I45 down into camming'engagement with the guide sleeve 8| and thereby force the plates I3! and I38 to pivot in a clockwise direction into the released position shown in Fig. 9 wherein the plates I3! and I38 are disposed in raised position above the rods SI and 92, in which position the notches I4I are held out of latching engagement with the legs 9! and 98.

Thus, it will be seen that, in the operation of my novel device, the lifting device 28 with the lifting frame 22 thereof disposed in the normal, lowered position shown in solid lines in Fig. 1, may be moved on the wheels 45, 47, 53 and 5:;

into position wherein the hooks 53 and 69 are a disposed below an article to be lifted, such as the axle of an automobile. Compressed air or the like may then be fed through the hose I32 into the cylinder II to thereby cause the piston 85 to move into the cylinder H. Movement of the piston 85 into the cylinder H is effective to pull the lifting frame 22 upwardly around the rod 44 toward the position thereof shown in broken lines in Fig. l, to thereby raise the hooks 6B and 69 and, therefore, raise the article disposed thereon. It will be seen that, because of the manner in which the parts of my novel lifting device are constituted and arranged, a compact, practical and efficient lifting device is afforded wherein the lifting frame 22 is raised in a novel expeditious manner by the motor 26, tension being applied to the piston 85 to thereby effect raising movement of the lifting frame.

It will be remembered that during movement of the lifting frame 22 from the normal position shown in solid lines in Fig. 1 toward the raise-cl position shown in broken lines therein, the motor 26 pivots on the studs 31 and 90 from the solid line position toward the broken line position shown in Fig. 1. However, it will be seen that during a complete movement of the lifting frame 22 from the lowered to raised position, the latching plates I31 and I38, remain disposed in posi tion over the piston rod 83 so that they are urged by gravity toward the piston rod 83 in all operative positions of the motor so that they are always urged by gravity toward the position in which they may latchingly engage the rods BI and 92 when moved thereacross. Engagement of the latching mechanism I35 is effective to insure against accidental or unintentional lowering of the lifting frame 22, the latching plates I3! and I38 automatically riding into latching engagement with the rods 95 and 92 during movement of the piston 85 into the cylinder H. However, when it is desired to lower the lifting frame from raised position, this may readily be accomplished by, first, feeding a small additional amount of air into the cylinder II to thereby cause the piston 85 to move a slightly greater distance thereinto, and, then, actuating the handle I48 to thereby lift the plates I31 and I38 out of latching engagement with the rods SI and 92 and then, by permitting the air to escape from the cylinder II through the line I32, permitting the lifting frame 24 to move downwardly.

During the downward movement of the lifting frame 24, the plate I is retained in the angular position shown in Fig. 9 to thereby hold the plates I31 and I38 out of latching engagement with the legs El! and 98 of the rods SI and 92. However, as is best seen in Figs. 1, 8 and 9, a notch I45A is afforded in the top surface of the sleeve SI, adjacent the end thereof disposed closest to the connecting block H2, and is disposed in the path of travel of the free end of the plate I45 so that, as the lifting frame 24 nears its lowered position, the free edge of the plate I45 drops into the notch I45A and is stopped thereby, so that, during the remaining downward movement of the lifting frame 24, the plate I45 is forced around toward the position shown in Fig. 8 to thereby permit the plates I3! and I38 to drop down into operative position for engaging the rods 9| and 92 during the next raising actuation of the lifting frame 2 5. Thus, it will be seen that after having been actuated to lift the plates I37 and I38 out of engagement with the rods 9I and 92, the plate I45 is automatically restored to normal position during downward movement of the lifting frame 24 to thereby permit the plates I31 and I38 to be automatically restored to normal lowered position in preparation for the next raising movement of the lifting, frame 24.

Under and in accordance with the present invention, the power actuating means as afforded by the motor II and the piston rod 83 are associated with the base and the lifting frame 24 in such a way that the operation of the lifting apparatus is rendered unusually safe and advantageous in use. Thus, it will be observed that a lifting apparatus of the kind to which the present invention pertains is in every instance designed and intended for lifting movement throughout a predetermined range, and that when the load is approaching the maximum or highest position in this range, it is' important that the lifting action of the mechanism be controlled and controllable in an effective and safe manner. As shown in the following description, and the force calculations set forth therein, such a safe mode of operation is attained under the present invention.

In respect to one factor that enters in a minor way into the calculation of the forces involved in the present structure, it will be noted that where a pivoted lifting frame is utilized with upwardly extended load engaging arms 6859, as in the present instance, that as the lifting frame pivots from a generally horizontal relation and toward its maximum angle with respect to the horizontal, the effective load that must be overcome by the operating mechanism becomes gradually less, this effective reduction in the involved forces being brought about by reason of the angular relationship of the load engaging members 68 and 59 with respect to the lifting frame. In the present embodiment of the invention, the operating power is applied to the lifting frame at the cross shaft II4, which is located substantially midway between the mounting axis 44 and the center line of the load supporting seat that is afforded in the end of each of the load engaging arms 68 and 69. The load, of course, acts downwardly along a vertical line at all times, and this line intersects a continuation 224, Fig. 11, of a line that is extended through the axes of the shafts 44 and IN. This point of intersection is identified at 225 in Fig. 11, and this point of intersection 225 in each position of the lifting frame 24 determines the effective lever arm through which the load is applied about the mounting pivot 44.

Forillustrative purposes, the force diagram of 9 Fig. 11 has been constructed on the assumption that a 1500 lb. load is applied to the frame 24 at the load supporting end thereof, and the frame 24 has been shown in six different positions, numbered as positions 1 to 6 in Fig. 11. For each of these six positions, the vertical load L that is effective at the cross shaft H4 has been computed and is shown in the table of values that has been identified as Fig. 11A. The vertical force that is effective at each position of the cross shaft H4 has in each instance been plotted vertically as load vectors L1 to L-6, inclusive. In each instance the lower end of the load vector is located at the related position of the shaft 1 l4, while the upper end of the load vector constitutes the starting point of a second vector R l to Et -6, inclusive. The second vector R-l to R-fi is, in each instance, extended parallel to the longitudinal axis of the corresponding position of the lifting frame 24 and the second vector will thus, in each instance, intersect the axis of the piston rod 83, or an extension thereof. This point of intersection has been indicated in respect to the vector R-l by the reference character l3 5-l,,and the distance betweenthe point l35-l and the cross shaft H4 may then be scaled to indicate the amount of pulling force that must be exerted by the motor H to lift or support a load of 1500 lbs. in the particular location of the lifting frame 24. In the table that constitutes Fig. 11A, it will be evident that in position 1, as shown in Fig. 11, the pull that must be exerted is 5200 lbs.; in position 2, 4600 lbs.; in position 3, 4000 lbs.; and in position 4, 3980 lbs. In position 4, the load will have been lifted throughout a substantial portion of the verticalrange of the present lifting apparatus, or to be exact, 87 percent of the intended maximum range, and during this lifting movement, the amount of pressure required in the cylinder 1| will have been gradually reduced to some extent. To prevent overthrow, and insure proper control of the lifting apparatus as it moves beyond position 4 and into the final portion of its lifting range, the present apparatus air pressure or pull in the requires an increased '7 as this final movement of operating cylinder H the lifting frame 24 takes place, and it will be observed in this connection that in position 5 the pull required has increased to 4400 lbs.,.while at position 6 a relatively great increase has raised the required pull to 5600 lbs.

This advantageous mode of operation is attained under the present invention by so relating the pivot points 44, H4 and 81 that as the angle A between the lifting frame 24 andthe base gradually increases, the included angle B between the frame 24 and the piston rod 83 is reduced rather gradually until the load has reached what may be termed the final portion of the lifting range and so that this angle B becomes quite small and reduces quite rapidly as the load moves into and through this final or upper portion of the lifting range of the apparatus. Thus, in the table that forms Fig. 11A of the drawings, the included angles between the frame 24 and the piston rod 83 in the several selected position-s of the frame 24 are indicated as angles B-l to 13-6, inclusiveand it will be observed that; these angles B do not reduce very rapidly until the load-has entered the upper. or final portion of its movement.

In Fig. llthe pistonpullrequired for the assumed load in the various positions has been determined graphically but thismayalso be deter n d, ath matical y .since :this piston D11 Required piston pull L Thus, in Fig. 11A,.the sines of the various angles B and the e'osines of the anglesA are 'set forth together with the values ofthe required piston pull calculated according to the above formula, and while some differences maybe noted between the graphically and mathematically determined values, this is, of course,'due to the difficulty of determining the precise angular relationship of the elements.

The marked and con nued n eas in the tonpull that isgencountered the present apparatus when the liftingframe 24 enters the final or upper portion, of its lifting'rahge is due to the rapiddecrease in the angle 13 as this final portion of the lifting stroke is entered and traversed, and in attaining such reduction in t e angle B in this portion of the stroke, the location of the pivots! to the right of thfix ffirtioal plane of the pivot 44 is important, as is the location of the pivot 81 t a d s ance above the pivptfi h eh i e t the spacin of the vots .44 an If! other Q ds, it is important hat th p vo 01 e s 1, th when t e rame 24 i ab u fill h final r pper portion .of its ift n rang t pivot .81 will be spa ed but a shor di ant la e ally of the frame 24, .andtheangle B will be relati ly s l .I th s e ard. howeve t Pi .81 must in every instance be located a substantial distanceabove the horizontalplane of the pivot 44 s as to att in the require i tin a ti n on the. frame 2.4 throu ho t theen r an of mov ment of theframefZA.

Fromthe foreg in it wi .b. se n ha I ha afforded a novellifting device wherein liftingarms are moved upwardly in a novel and expeditious manner by a motor operatin under tension, and wh reinsa wefli i nt. and prac i a peratio of the device is insured 1 v thenov l a exp d manner in which the parts are constituted and arranged.

Hence, .while I have illustratedand described the preferred ernbodiments of my inventionit is to-be understood that these are'capable of .ivariation andmgdification and I therefore do ,not wish 0 b l mi d t thep fecise details set forth, but

. desiretoavailmyself of such changes and alterationsas .fallwithin th'efpurview of thefollowing claims:

Iclaim:

1. 1A lifting device comprising an elongated supporting frame, elongated arm's pivotallymounted at oneendto said frame and having means at the -other end thereof for 'supportin'g'an object, sup- .porting means on said frarne'andextending' upwardly above said onee'n'd'of said arms, a cylinder .pivotally mounted on said supporting means above ,saidoneend of said' arms, a" piston mounted in .said cylinder and pivotally connected -in tension .to said elongated arms betw'eenthe' ends thereof, said piston being movable into and out of said cylinder and operable upon movement into said cylinder to raise said"other'ends or said arms, .mearis'l projecting outwardly fr'dm said cylinder, and .a latching member pivotallymounted on'said piston and having .ab'utments thereon for engaging said last named means in latching engagee the ewith dur n such movement or said pi ton nto-sa l nde f h din sai pi ton a ainst .m vee gi o t dly dm s d c ind r.

2. A lifting device comprising an elongated supporting frame including upwardly extending sup porting means on one end portion thereof, elongated arms pivotally mounted at one end to said frame and having means at the other end thereof for supporting an object, cylinder means pivotally mounted on said supporting means, a piston mounted in said cylinder means, and pivotally connected in tension to said elongated arms between the ends thereof, said piston being movable into and out of said cylinder means and operable upon movement into said cylinder means to raise said other ends of said arms, means projecting outwardly from said cylinder means, a latching member pivotally mounted between said arms and movable into releasable latched engagement with said outwardly projecting means during such movement of said piston into said cylinder means to thereby positively hold said piston against outward movement relative to said cylinder means, and means mounted on said latching member and engageable with said cylinder means for moving said latching member from said engagement with said outwardly projectin means.

3. A lifting device comprising an elongated supporting frame comprising a pair of upwardly inclined elongated beams disposed in spaced parallel relation to each other, and a pair of upwardly extending posts mounted on the upper end portions of respective ones of said beams and having upper end portions extending thereabove, elongated arms pivotally mounted at one end to said frame and having means at the other end thereof for supporting an object, a cylinder pivotally mounted on said posts above said beams, a piston mounted in said cylinder and pivotally connected in tension to said elongated arms between the ends thereof, said piston being movable into and out of said cylinder and operable upon movement into said cylinder to raise said other ends of said arms, said cylinder including means projecting outwardly therefrom toward said arms and engaged with said piston for guiding the latter, abutment members projecting outwardly from said last named means transversely to said piston, and a latching member pivotally mounted on said piston and extending thereabove, said latching member having a plurality of recesses therein engageable with said abutment members during movement of said piston into said cylinder for holding said piston against outward movement relative thereto, and a lever carried by said latching member and engageable with said outwardly projecting means on said cylinder for moving said latching member out of said latchin engagement with said abutment members.

4. A lifting device comprising elongated supporting members, wheels mounted on the end portions of said members for supporting the latter, an elongated lifting frame pivotally mounted at one end to one end of said supporting members and having another end normally disposed adjacent to the other end of said supporting members, said other end of said lifting frame having means for supporting an object, two posts mounted on and extending upwardly from said one end of said supporting members in spaced relation to each other, a cylinder pivotally mounted between said posts above said supporting members, said cylinder including an elongated guide member projecting outwardly therefrom toward said lifting frame and having two rods projecting laterally outwardly therefrom in opposite directions, an elongated piston having one end portion extending through said guide member and slid- 12 able therethrough into and out of said cylinder, the other end portion of said piston being fixedly pivoted to said lifting frame between said two ends thereof, a latching member pivoted to said other end portion of said piston and extending thereabove, said latching member having a plurality of notches therein complementary to said rods and in which said rods are latchingly engageable during movement of said piston into said cylinder for holding said piston against outward movement relative to said cylinder, and a lever pivotally mounted on said latching member and manually engageable with said guide member for moving said latching member out of said latching engagement with said rods for freeing said piston for movement outwardly relative to said cylinder.

5. In a lifting apparatus, an elongated base, an elongated lifting frame having a mounting end pivoted on a first horizontal axis disposed transversely of said base adjacent one end of such base and said lifting frame having its other end formed with load engaging means to define a load end on said frame, said frame being shiftable about said first axis from a lower position wherein said frame is substantially horizontal through a limited lifting range'to thereby raise said load end of said frame, means affording a second horisontal axis parallel to and substantially above said first axis and spaced horizontally from said first axis toward the other end of said base, means affording a third pivotal axis disposed on and transversely of said lifting frame and intermediate the ends thereof and at a predetermined distance from said first pivotal axis, power operated force applying means connected between and pivoted at spaced points respectively on said second and third axes and operable to apply lifting forces in tension between said second and third axes to raise said lifting frame, said second axis being spaced vertically from said first axis in an amount substantially less than said predetermined dimension so that the included angle between said lifting frame and a line joining said second and third axes reduces rapidly and becomes relatively small when said frame approaches the upper limit of said lifting range.

6. In a lifting apparatus, an elongated base, an elongated lifting frame having a mounting end pivoted on a first horizontal axis disposed transversely of said base adjacent one end of such base and said lifting frame having its other end formed with load engaging means to define a load end on said frame, said frame being shiftable about said axis from a lower position wherein said frame is substantially horizontal through a limited lifting range to thereby raise said load end of said frame, an operating cylinder pivoted on a second horizontal axis parallel to and substantially above said first axis and spaced horizontally from said first axis toward the other end of said base, a piston in said cylinder, a piston rod connected between said piston and a third pivotal axis disposed on and transversely of said lifting frame and intermediate the ends thereof and at a predetermined distance from said first pivotal axis, said second axis being spaced vertically from said first axis in an amount substantially less than said predetermined dimension so that the included angle between said lifting frame and said piston decreases rapidly and becomes relatively small when said frame approaches the upper limit of said lifting range.

7. In a lifting apparatus, an elongated base, an elongated lifting frame having a mounting end pivoted on a first horizontal axis disposed transversely of said base adjacent one end of such base and said lifting frame having its other end formed with load engaging means to define a load end on said frame, said frame being shiftable about said axis from a lower position wherein said frame is substantially horizontal through a limited lifting range to thereby raise said load end of said frame, an operating piston and cylinder device including a piston, a piston rod element and a cylinder element, one of which elements is pivoted on a second horizontal axis parallel to and substantially above said first axis and spaced horizontally from said first axis toward the other end of said base, means connecting the other of said elements on a third pivotal axis disposed on and transversely of said liftingframe and intermediate the ends thereof and at a predetermined distance from said first pivotal axis, said second axis being spaced vertically from said first axis in an amount substantially. less than said predetermined dimension so that the included angle between said lifting frame and said piston decreases rapidly and becomes relatively small when said frame approaches the upper limit of said lifting range.

8. A lifting device comprising an elongated supporting frame including upwardly extending supporting means on one end portion thereof, elongated arms pivotally mounted at one end to said frame and having means at the other end thereof for supporting an object, cylinder means pivotally mounted on said supporting means, a piston mounted in said cylinder means and pivotally connected in tension to said elongated arms between the ends thereof, said piston being movable into and out of said cylinder means and operable upon movement into said cylinder mean to raise said other ends of said arms, means projecting outwardly from said cylinder means, a latching member pivotally mounted between said arms and movable into releasable latched engagement with said outwardly projecting means during such movement of said piston into said cylinder means to thereby positively hold said piston against outward movement relative to said cylinder means, a releasing member mounted on said latching member and operatively engageable with said cylinder means for moving said latching member from said engagement with said outwardly projecting means, and means comprising an abutment on said cylinder means and engageable with said releasing member during outward movement of said piston relative to said cylinder means for moving said releasing member out of said operative engagement with said cylinder means.

9. A lifting device comprising an elongated supporting frame, an elongated lifting frame pivotally mounted at one end to said supporting frame and having means at the other end for supporting an object, supporting means on said supporting frame and extending upwardly above said one end of aid lifting frame, a cylinder pivotally mounted on said supporting means above said one end of said lifting frame, said cylinder including an elongated guide member projecting outwardly therefrom toward said lifting frame, and an elongated piston having a head reciprocably mounted in said cylinder, and a, rod extending through said guide member and slidable therethrough into and out of said cylinder, said rod comprising an elongated sleeve having one end portion fixedly pivoted to said lifting frame and the other end portion slidably mounted in said guide member, and an elongated rod member mounted in and slidable with said sleeve in spaced relation thereto, said rod member having one end portion fixedly pivoted to said lifting frame and the other end portion connected to said head.

10. In a lifting device of the type comprising a supporting frame, an elongated lifting frame pivotally mounted at one end to said supporting frame and having means atthe other end for supporting an object, supporting means on said supporting frame and extending upwardly above said one end of said lifting frame, and a cylinder pivotally mounted on said supporting means above said one end'of said lifting frame, melon-- gated tubular guide member projecting out-- wardly from said cylinder toward said lifting: frame, bushing members mounted in oppositeends of said guide member, and an elongated: piston having a head reciprocably mounted i nn said cylinder, and a rod mounted in said bush-- ings extending through said guidemember and? slidable through said guide-member into and out. of said cylinder, said rod comprising an elongated sleeve having one end pivotally connected to said lifting frame and the other end projecting toward said head, and an elongated rod member laterally loosely mounted in said sleeve and reciprocable therewith, said rod member having one end pivotally connected to said lifting frame and the other end connected to said head for movement therewith.

11. A lifting device comprising an elongated supporting frame, arms pivotally mounted at one end to said frame and having means at the other end for supporting an object, posts on said frame and extending upwardly above said one end of said arms, a cylinder pivotally mounted on said posts on an axis located in a horizontal plane spaced above said pivot mounting of said one end of said arms and located in a vertical plane intermediate the ends of said arms, a latch member associated with said cylinder, a piston slidably mounted in said cylinder and pivotally connected in tension to said arms for raising the latter around said one end, and latch means connected to and movable with said piston and engageable with said latch member when the arms are in raised position to lock the piston to the cylinder against accidental displacement from a position corresponding to the raised position of said arms.

12. A lifting device comprising an elongated supporting frame, an elongated lifting frame pivotally mounted at one end to said supporting frame, the other end of said lifting frame having means for supporting an object, said supporting frame including elongated supporting means mounted on and extending upwardly from the lifting frame pivoting portion of said supporting frame, a motor pivotally mounted on said supporting frame above said one end of said lifting frame, the motor pivot axis being located in a vertical plane nearer said other end of said lifting frame than a vertical plane passing through, the pivotal mounting of said one end of said, lifting frame, said motor including a member fixed thereto and a reciprocating member, one end of which is movable upwardly relative to said supporting frame during an operation of said motor, said member being pivotally connected in tension to said lifting frame between the:

ends thereof and being operable upon such move-- ment upwardly relative to said supporting frame during operation of said motor to raise said other end of said lifting frame, and latch means mov-- able with said reciprocating member and en .gageable with the member fixed to the motor when the lifting frame is in raised position to lock said member against accidental displacement from a position corresponding to a raised position of said lifting frame.

13. A lifting device comprising an elongated supporting frame, an elongated lifting frame pivotally mounted at one end to one end of said supporting frame, the other end of said lifting frame being normally disposed adjacent to the other end of said supporting frame and having means thereon for supporting an object, elongated posts mounted on said first mentioned end of said supporting frame and extending upwardly from, and inclined toward, said other end of said supporting frame, power means including members pivotally and slidably mounted on said posts above said one end of said supporting frame and pivotally connected in tension to said lifting frame between the ends thereof for applying a predetermined tension to said lifting frame to thereby raise said other end of said lifting frame around said one end thereof, the pivotally mount- 16 ed power means member including a member fixed thereto, and latch means movable with said slidably mounted power means member and engageable with said member fixed to said pivotally mounted power means member when the lifting frame is in raised position to lock the slidably mounted power means member against accidental displacement from a position corresponding to a raised position of said lifting frame.

ALEIHS EUGENE JACKSON.

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

UNITED STATES PATENTS Number Name Date 2,552,965 Harris May 15, 1951 FOREIGN PATENTS Number Country Date 299,754 Great Britain Oct. 29, 1928

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