US2377477A - Lifting device - Google Patents

Description

June 5, 1945. BLOCH 2,377,477

LIFTING DEVICE Filed Oct. 20, 1942 6 Sheets-Sheet l INVENTOR 56/09 5/- OCH ATTORNEY E. BLOCH I IFIING DEVICE June 5, 1945.

Filed Oct. 20, 1942 6 Sheets-Sheet 2 INVENTOR 56/0/ 52 OCH ATTORNEY June 5, 1945. E. BLOCH LIFTING DEVICE Filed Oct, 20, 1942 6 Sheets-Sheet 3 INVENTOR ATTORNEY E. BLOCH LIFTING DEVICE June 5, 1945.

6 Sheets-Sheet 4 Filed Oct. 20, 1942 ATTORN EY E. BLOCH LIFTING DEVICE June 5. 1945.

Filed Oct. 20; 1942 6 Sheets-Sheet 5 INVENTOR ch 54 OCH.

ATTORNEY ,June 5, 1945. E. BLOCH LIFTING DEVICE Filed 001;. 20, 1942 6 Sheets-Sheet 6 INVENTOR F/P/CH BLOC/1 ATTORNEY Patented June 5, 1945 LIFTIN G DEVICE Erich Bloch, New York, N. Y., assignor to Aeronautical Machinery Corporation, a corporation of New Jersey Application October 20, 1942, Serial No. 462,691

20 Claims.

This invention relates to lifting devices of the type in which pivoted arms which function as levers are raised and lowered and have the load supporting head on their free ends. The arms are coupled in the form of parallel linkage so as to keep the head horizontal in all positions.

The maximum angle of elevation of the arms depends upon the design of the particular device but such devices have the advantage that the supporting head or the load supporting saddle on it can be brought lower than is possible with screw jacks having a comparable maximum elevation. In other words the ratio of lift to the minimum height can be made considerably greater than is possible with screw jacks having telescopic sections.

The lever arms of such lifting devices are commonly cranked up and down through a reversible ratchet mechanism. While theoretically the maximum desired height of lift determines the length of the load or work arms of the levers, it is well known that there is a practical limit to that length which is determined by several factors among which are the feasible size of such devices, the possible length of the power arms, the power that can practically be applied to the crank, and the horizontal component of movement of the saddle.

It is the fact that the lifting head is carried on the end of a pivoted arm and therefore partakes of an arcuate movement which introduces the horizontal movement of the head as it is raised and lowered. Furthermore when the load is lifted at one end and is caused to pivot about a stationary line of support, the point at which it is engaged by the lifting device will for the same reason also have a horizontal component of movement. These two horizontal components of movement may be in different directions with the result that an undesirable force may be applied to the load. Since these horizontal components are a function of the angular movements of the lifting head and of the load, devices of this sort have heretofore been decidedly limited in their possible range of movement.

It is one of the principal objects of this invention to provide means for accommodating the horizontal component of movement of the supporting head arising from the angular movement of the arms.

Another object is to provide means to accommodate a horizontal component of movement of the load transverse to that of the head.

Another object is to provide these accommodations without increasing the effective minimum height of the head.

Another object is to provide a saddle construction which will reduce the minimum height practically to zero.

Another object is to provide a practical expedient for increasing the ratio of lift to the minimum height beyond that which can be attained merely by the rotation of the arms, and to an extent having no relation to the height of the saddle above the ground or other supporting surface in the lowermost position of the saddle.

Another object is to provide a construction which will increase the possible load capacity of such devices.

Other objects are facility of operation, dependability and reliability in use, and economy in size and construction.

To accommodate the relative horizontal components of movement the invention contemplates the provision of guide rails on the head or on members carried thereby which will afford freedom of relative movement to the saddle or load engaging member.

To increase the lifting range the invention contemplates a supplemental or extension jack that is pivoted to the under-side of the head so as to fold in parallel to the arms when the head is down without interfering with the bringing of the head down to the lowest position which the arms will permit, and this supplemental or extension jack assumes a, vertical attitude when the head i fully raised. The extension member of the jac then Wi e ge the saddle from the under-side and will continue to raise the load up to the full movement of the jack, which may be almost equal to that effected by the movement of the arms.

For strength and increased load capacity it is contemplated that the device may be mad in duplex form and it is so represented in the illustrated embodiment. The two duplicate structures are disposed side by side in a frame and they are operatively connected so as to synchronize in movement. The two heads will therefore move together and the two extension jacks move in unison.

The saddle in such construction may be between the heads on a member that rests upon and spans the two heads and is depressed or set back in the space between the heads so that the saddle does not extend substantially above the heads.

The invention comprehends other details of construction which will be hereinafter explained in connection with the description of the speciflc embodiment of the invention illustrated in the accompanying drawings.

Fig. 1 is a plan of such embodiment.

Fig. 2 is a side view of the same.

Fig. 3 is a sectional elevation with parts broken away, on the irregular plane represented by the line 3-3 of Fig. 1. v

Fig. 4 is a view similar to Fig. 2 showing the parts adjusted to elevate the supporting heads.

Fig. 5 is an elevation, partly in section, as viewed from the right in Fig. 4.

Fig. 6 is an enlarged sectional detail of one of the heads and immediately associated parts,

taken on the plane represented by the line 3-3 in Fig. 5.

Fig. 7 is a central longitudinal section of one of the extension Jacks and of its associated head.

Fig. 8 is a sectional detail of the upper end of the supplemental jack and associated head on a plane at right angles to that of Fig. 7, showing the extension sleeve protruded and the saddle and its supporting member lifted.

Fig. 9 is a sectional detail of the ratchet mechanism on line 3-9 of P18. '7.

Fig. 10 is a detail, partially in section and partially in elevation, of the two heads and of the upper ends of the extension jacks, showing a modified form of load supporting mechanism.

Fig. 11 is a plan of the same, partially in section, on line li--ll of Fig. 10.

Fig. 12 is a fragmentary plan of another modifled form of load supporting mechanism and of the immediately associated parts.

Fig. 13 is a side elevation of the same.

The lifting device has two supportingheads which are coupled together to move in unison, and each has its independent operating mechanism which is a duplicate of that of the other head, so that the device is in efl'ect a duplex mechanism.

The frame s a low structure having outer side plates I and 2 and two inner side plates 3 and 4. Plates I and 3 constitute the sub-frame for one lifting unit and plates 2 and 4 constitute the sub-frame for the other lifting unit. The four frame plates are united by transverse axle 5 at the rear end, and the two plates of each subframe are united by a transverse axle S at the front end. Wheels 1 are mounted on axle 3, and a wheel 3 is mounted upon each front axle 6, thus facilitating mobility. The outside plates have each an extension 3 either integral therewith, or, as shown, attached thereto, and these carry bearings for vertically adjustable screws it having operating handles II on their upper ends and universally jointed feet i2 on their lower ends. The purpose of these is to take the load and relieve the pneumatic tires on the wheels.

Draw arms I3 are attached to the extensions 9 and where they join they have an eye through which a pull bar l4 may be inserted for convenience in moving the device.

Each lifting head is supported and controlled by four pivoted arms. two arms, a front and back arm, being disposed adjacent to and just inside of each of the four frame plates. The arms have angular extensions at their pivot ends, making lbell cranks, and screw means are provided to crank the arms up and down.

The two heads are numbered I4 and II. The four arms of head II are shown in Figs. 2 and 3. Those on the outside are numbered l6 and i1 and those on the inside are numbered l3 and those for head it except that those on the outside are reversely shaped, the arms of the two p'airs being respectively right and left hand. Arms 20 and 2| correspond to arms l3 and II, respectively, and 22 and 23 (see Fig. 5) correspond to arms l3 and II, respectively.

Each pair of arms ispivoted to the respective head on their own side. They are also pivoted to the frame and the distance between pivots is the same. Thus they constitute a parallel linkage structure and maintain the heads horizontal in all positions of the arms. The arms l6, I3, 20 and 22 are pivoted upon a transverse pivot 24 passing through the four frame plates, and arms l1, l3, 2i and 23 are pivoted upon a transverse pivot .25 similarly passing through the four plates.

The angular extensions at the pivot ends of each pair of arms are coupled by an operating member that is moved back and forth under manual control to crank the arms up and down. There are four of such members which in the construction shown are plates or flat bars 23, 21, 23 and 23, respectively, having an upward bend at their rear ends and being pivoted to the ends of the angular extensions of the respective pairs of arms. Thus as the operating members are moved back and forth in a generally horizontal direction the arms are rocked about their pivots. The operating members 26 and 21 constitute one pair to operate the head I 4, and the operating members 28 and 29 constitute another pair to operate the head IS.

The screw mechanism for actuating the operating members includes a head that couples the outer ends of each pair of operating members, a traveling screw attached to the head and intended to be actuated through a reversible ratchet mechanism, and a nut fixed to the frame but pivoted on a transverse axis. The head 30 conit. The arms for the head [5 are identical with TI nects operating members 23 and 21, being pivoted to the ends thereof, and head 3| similarly connects operating members 23 and 23. Screw 32 is rotatably carried by head 30 and screw 33 is rotatably carried by head 3|. Screw 32 has a right-hand thread and screw 33 has a left-hand thread. The nut 34 for screw 32 is pivoted to plates i and 3 by pivot 35, and the nut 33 for screw 33 is pivoted to plates 2 and 4 by pivot 31. The angular movement of the nuts is necessary in order to accommodate the successive positions of the screws.

The two screws 32 and 33 are geared together. A transverse bearing sleeve 38 is supported by brackets 39 on operating members 21 and 23 and a shaft bearing therein has bevel gears 40 and II on its ends. A lbevel gear 42 meshing with bevel gear 40 is keyed on the outer end of screw 32, and bevel gear 43 keyed on the outer end of screw 33 meshes with bevel gear 4|. Thus rotation of one screw is transmitted to the other but in the opposite direction, and hence the screw threads on the two screws are respectively reversed.

Independent manually operated means are provided to actuate the two screws. The two means are identical and generally are of the well known reversible ratchet type controlled by a button to determine which way the ratcheting will operate the screws. The details of such a mechanism are shown in Fig. 9 which is a sectional view of similar ratchet construction applied to the supplemental or extension jack mechanism that will later be described.

Since the ratchet mechanisms applied to the two screws are identical, a description of one will sufiice for both. There is a casting 44 fully bearing upon the upper end of the screw and provided with a handle 45 and two sockets 46 to receive an operating bar 41. A pivoted dog 48 has a double detent portion, one on each side of the pivot, which selectively coacts with a ratchet 49 keyed on the screw. A sliding pin or button 50 through a yieldable plunger (see Fig. 9) determines by its position which way the dog is rocked on its pivot and hence which way it actuates the ratchet. In one position of the pin the dog will ride freely over the ratchet in a clockwise rotation of the casting and will catch into the ratchet teeth and rotate the screw in a counter-clockwise rotation of the casting, and in the other position of the pin the ratcheting will be in the opposite direction.

The ratcheting of the screws 32 and 33 moves the parts between the positions shown in Figs. 2 and 4. With the lifting mechanism down as shown in Fig. 2 the screws and all their operating attachments are in their outermost position. As the screws are turned and caused to move into their nuts 34 and 36, they carry the heads 30 and 3i and ratchet and transmitting mechanisms along with them. Their innermost position is shown in Fig. 4, in which position the bell cranks are rocked about their pivots and the arms are brought up to their greatest angle of elevation. The corresponding arms all have the same angular setting on their pivots and hence the two heads l4 and I are kept parallel in the same horizontal plane.

Frequently the conditions are such that it is not possible for the lifting device to roll toward and from a load to compensate fully for the horizontal components of movement, and therefore provision is made to let the work engaging member shift horizontally on the head as it goes up. This may be done in various ways. As shown, the heads are provided with tracks 5!, preferably having a stop lug 52 on each end, and in one form, the load engaging saddle 53 has rollers 54 runing on the tracks. head is thus provided with a load engaging saddle, there is a two point support which is desirable for some purposes.

Means are provided whereby the extension When each against vertical displacement while permitting relative horizontal adjustment.

Each tubular member has a telescopic internal sleeve and screw mechanism for actuating the sleeve, and each sleeve has a stud on its upper end which will pass up through the opening in the head as the sleeve is protruded and engage the socket and lift it and the saddle carried jacks will lift the saddles oil the heads, and this extension mechanism will now be described. Pivoted to each head is a tubular member the lower end of which is guided so as to cause it to fold in toward the horizontal as the arms are lowered and to approach a vertical position as the arms are raised until at the extreme upward position of the arms the tubular members depend from the heads in a vertical position.

The tubular member 55 is pivoted to the head It on trunnions 56 parallel to the pivots of the arms, and a similar tubular member 51 is similarly pivoted to the head l5 on trunnions 58. The heads are provided with central openings so that the tubular members are in line with those openings when the members hang vertically. Surrounding the opening on the top face of the head is a tapered annular boss, and a socket member 59 fits on this boss. The socket member has an integral horizontal guide plate 60 which extends between and parallel to the rails 5| When the socket is on the head. The saddle has inturned flanges 6| on its under side which engage under the edges of the plate 60 and so secure the saddle and socket together thereby off the head and thus provide an extension lift.

The sleeves in the tubular members 55 and 51 are numbered 62 and 63, respectively, and axially disposed in each sleeve is a screw substantially as long as the sleeve, the screw in sleeve 62 being numbered 64 and the screw in sleeve 63 being numbered 65. On the bottom end of the sleeve in each case is secured a nut 66 in which the screw engages, and secured on the bottom end of the screw is a bevel gear 61. The screw is secured against longitudinal movement by the gear engagement and the sleeve is secured against rotation by a key 68 on the inner face of the tubular member which engages in a spline in the sleeve. Therefore the rotation of the screw feeds the sleeve in and out. In the upper end of the sleeve is a stud 69 shaped to engage and fit in the socket 59.

The lower end of each tubular member is se cured in a casting 10 that makes a bearing head for the ratchet mechanism that actuates the sleeve. On the outside of each head is a ratchet mechanism similar to that shown and previously described for the crank actuatin screw 32 and 33. A bevel gear H meshes with bevel gear 61 and its hub bears in a sleeve 12 secured in a lateral hub portion of the casting l0 and a ratchet I3 is secured on the outer end of the hub of the bevel gear. A ratchet casting l4 loosely turns on the outer end of the hub about the ratchet. A dog 15 similar to dog 48 is pivoted in the casting in engaging relation with the ratchet, and a shift pin or button 16 carries the yieldable plunger 11 which rocks the do one way or the other on its pivot. A socket '18 receives an operating bar, as indicated by broken lines in Fig. 4.

Between the two bearing heads Ill extends a shaft 19 with a bevel gear on each end meshing with the bevel gear 61 on the end of the screw. Thus the actuation of either ratchet is transmitted to both screws. Simultaneously however the screws rotate in opposite directions and they are therefore given one a right-hand thread and the other a left-hand thread. As shown screw 65 has the right-hand thread.

In Figs. 4 and 8 the sleeve 63 is shown protruded. To retract the sleeve from the protruded postion shown in Fig. 8. the ratchet parts are in the position shown in Fig. 9. The gear wheel H will thus be ratcheted in a counter-clockwise direction as viewed from the right in Fig. 7, and this will turn the screw 65 to the right and feed the nut and sleeve down. At the same time the shaft 19 turns clockwise as viewed from the right in Fig. '7, and this will turn the gear wheel 61 on screw 64 to the left as viewed in Fig. 5. Therefore the screw 64 must have a left-hand thread. The ratcheting can of course be done from either side and the two sleeves 62 and 63 must move toether.

As shown, particularly in Fig. 8, the sleeve of the extension jack passes up through the opening in the head and the stud 69 enters the socket 59 and lifts the socket and the saddle oil the head and further raises the work, virtually doubling the lift.

The lower end of the extension jack is controlled by guides I ll of which there are two, one for each head IO, and pivoted to the inner faces of the inner frame plates 8 and 4. These guides are bars or narrow plates pivoted at their rear ends and provided with longitudinal guide grooves in which the shaft ll engages. At their outer ends the arms bend up making the groove at that end substantially vertical in thelifted position of the parts. Thus the lower ends of the extension members are captured and guided so that the members fold into the frame. The inner frame plates 3 and 4 have a cam portion ti on their upper edges which function to start the extension members pivoting into their folded position as the arms bring the head down so that the cross shaft 19 hits the cam. A pivoted latch H for each guide I" has a flange on its upper end overhanging the guide and limiting the guide from pivoting above the position in which the shaft 10 is in the outer ends of the grooves.

From the above it will be seen that ratcheting the screws 12 and 33 will raise the arms and heads from the lowermost position shown in Figs. 1, 2 and 3 to the elevated position shown in Fig. 4. This draws the extension members from their horizontal to their vertical positions, and then actuation of the ratchet 13 protrudes the sleeves and further lifts the saddles.

Instead of a two point lift the device may provide a one point lift by putting the saddle on a hanger or suspension member between the two heads. In such construction the saddle holdin portion between the heads may be depressed or set back so that the saddle is on the level of the heads and it does not add to the over-all height of the lifting member in its down position.

Such a construction is shown in Figs. 10 and 11. A suspension member 83 spans the heads and rests with its two ends upon the heads and is depressed in its mid portion between the heads. This suspension member, like the saddle in Fig. 5, has on each end wheels 84 that ride on the rails 5! of each head, and flanges 6| that cooperate with the guide plate 80 of socket member 59. As the sleeves of the extension members are protruded they engage in the sockets 59 on the two ends of the suspension member and raise it while maintaining it horizontal.

The saddle is carried by the depressed mid portion and hence, as shown, does not extend substantially above the level of the heads. The suspension member as a whole can slide back and forth on the rails Bi and thus to the desired extent compensate for the horizontal component of movement of the heads.

Some loads also pivot about any axis as they rise and the engaging point also has a horizontal component of movement. This is often at right angles to the horizontal component of movement of the heads. To compensate for this the invention contemplates giving the saddle a freedom of movement in a direction parallel to the pivotal axes of the arms, that is, transverse to the rails II. In the construction shown this is done by having transversely extending rails 84 on the mid portion of the suspension member I! on which the saddle 53 is free to slide.

To minimize the initial height of the lifting member that engages under the work, the invention contemplates a construction such as shown in Figs. 12 and 13. Here the mid portion of the lifting member II which spans the two heads and rests with its ends upon the heads loosely so as to be liftabletherefrom, is bent down substantially to the supporting surface. In other words the supporting member is made 2- shape with the one horizontal leg virtually to the ground or other supporting surface when the device is down.

Variou other modifications will readily occur to those skilled in the art, and. it will be understood that the illustrated constructions are not presented by way of limitation but that the invention comprehends all constructions coming within the scope of the appended claims.

I claim:

1. A lifting device comprising a frame, an arm pivoted at one end in the frame, means to rock the arm on its pivot and thus raise and lower its free end, a supporting head pivotally attached to the free end of the arm, a saddle loosely supported upon the head, a tubular member pivotally attached to the head and of a length to depend vertically therefrom when the head is in its elevated position, a telescopic sleeve in the tubular member adapted when protruded to engage and raise the saddle from the head. and screw mechanism for axially adjusting the sleeve relative to the tubular member.

2. A lifting device comprising a frame, an arm pivoted at one end in the frame, means to rock the arm on its pivot and thus raise and lower its free end, a supporting head pivotally attached to the free end of the arm, a saddle loosely supported upon the head, a tubular member pivotally attached to the head and of a length to depend vertically therefrom when the head is in its elevated position, a telescopic sleeve in the tubular member adapted when protruded to engage and raise thesaddle from the head. a nut fixed on the lower end of the sleeve, a screw in the sleeve engaging the nut, manual means for rotating the screw, and means for preventing rotation of the sleeve.

3. A lifting device comprising a frame having side plates and a support therefor, two arms pivotally mounted in the frame upon adjacent transverse pivots and having each an angular extension at the pivot end forming a bell crank, an operating member pivotally attached to both extensions and adjustable to raise and lower the arms together, a supporting head pivoted to the outer ends of the arms at equal distances from the mounting pivots, an extension jack pivotally attached to the underside of the head and of a length to depend vertically therefrom when the head is in elevated position, and a guide for the free end of the jack carried by the frame.

4. A lifting device comprising a frame having side plates and a support therefor, two arms pivotally mounted in the frame upon adjacent transverse pivots and having each an angular extension at the pivot end forming a bell crank, an operating member pivotally attached to both extensions and adjustable to raise and lower the arms together, a supporting head pivoted to the outer ends of the arms at equal distances from the mounting pivots, a saddle loosely supported upon the head, a tubular member pivotally attached to the underside of the head and of a length to depend vertically therefrom when the head is in elevated position and adapted to fold in the frame with the arms when the head is lowered, a telescopic sleeve in the tubular member adapted when protruded in vertical direction to engage and raise the saddlefrom the head, a nut fixed on the lower end of the sleeve, a screw in the sleeve engaging the nut, manual means for rotating the screw, and means for preventing rotation of the sleeve.

5. A lifting device comprising a frame having side plates and a support therefor, an arm pivoted at one end in the frame, means to rotate the arm on its pivot and thus raise and lower its free end, a supporting head pivoted on the free end of the arm, means to constrain the head at all times in a horizontal position, and a substantially Z-shape load engaging and lifting member detachably carried by and overhanging the head and proportioned so that the lower horizontal part is adjacent the supporting surface when the arm is in its lowermost position.

6. A lifting device comprising a frame having side plates and a support therefor, an arm pivoted at one end in the frame, means to rotate the arm on its pivot and thus raise and lower its free end, a supporting head pivoted on the free end of the arm, means to constrain the head at all times in a horizontal position, a tubular member pivotally attached to the underside of the head and of a length to depend vertically therefrom when the head is in elevated position, a telescopic sleeve in the tubular member having an axial stud on its upper end, screw means to adjust the sleeve in the tubular member, a carriage loosely supported upon the head and having a socket in line with the sleeve when the tubular member is vertical and having a track extending in a plane transverse to the pivotal axis of the arm, and a load engaging saddle on the carriage slidable upon the track.

7. A lifting device comprising a frame including two side plates and a support therefor, two pairs of arms mounted in the frame upon adjacent transverse pivots and disposed with one pair adjacent the inner face of each plate, each arm having an angular extension at the pivot end forming a bell crank, two operating members, one pivotally attached to the extensions of each pair of arms, a transverse head coupling the operating members, a screw carried by the head, a nut pivotally mounted in the frame and engaging the screw, means to rotate the screw and thereby cause the operating members to actuate the bell cranks and rotate the four arms on their pivots, a supporting head pivoted to the outer ends of the arms at equal distances from the mounting pivots, and an extension jack pivotally supported by the underside of the head upon an axis parallel to the pivot axes of the arms, whereby the jack will fold to a position in the frame between the two pairs of arms when the arms are down.

8. A lifting device comprising a frame including two side plates and a support therefor, two pairs of arms mounted in the frame upon adjacent transverse pivots and disposed with one pair adjacent the inner face of each plate, each arm having an angular extension at the pivot end forming a bell crank, two operating members, one pivotally attached to the extensions of each pair of arms, a transverse head coupling the operating members, a screw carried by the head, a nut pivotally mounted in the frame and engaging the screw, means to rotate the screw and thereby cause the operating members to actuate the bell cranks and rotate the four arms on their ivots, a supporting head pivoted to the outer ends of the arms at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of the head between the two pairs of arms upon an axis parallel to the pivot axes of the arms, whereby it will, fold in the frame when the arms are down and will depend from the head when the arms are up, a telescopic sleeve in the tubular member, screw means for adjusting the sleeve axially of the tubular member, and load engaging means on the head adapted to be engaged by the sleeve when it is protruded in vertical position and lifted above the head.

9. A lifting device comprising a frame including two side plates and a support therefor, two pairs of arms mounted in the frame upon adjacent transverse pivots and disposed with one pair adjacent the inner face of each plate, each arm having an angular extension at the pivot end forming a bell crank, two operating members, one pivotally attached to the extensions of each pair of arms, a transverse head coupling the operating members, a screw carried by the head, a nut pivotally mounted in the frame and engaging the screw, means to rotate the screw and thereby cause the operating members to actuate the bell cranks and rotate the four arms on their pivots, a supporting head pivoted to the outer ends of the arms at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of the head between the two pairs of arms upon an axis parallel to the pivot axes of the arms, whereby it will fold in the frame when the arms are down and will depend from the head when the arms are up, a telescopic sleeve in the tubular member, screw means for adjusting the sleeve axially of the tubular member, guide means on the frame engaging the free end of the tubular member and directing it as the pivoted end is raised and lowered, and load engaging means on the head adapted to be engaged by the sleeve when it is protruded in vertical position and lifted above the head.

10. A lifting device comprising a frame including two side plates and a support therefor, two pairs of arms mounted in the frame upon adjacent transverse pivots and disposed with one pair adjacent the inner face of each plate, each arm having an angular extension at the pivot end forming a bell crank, two operating members, one pivotally attached to the extensions of each pair of arms, a transverse head coupling the operating members, a screw carried by the head, a nut pivotally mounted in the frame and engaging the screw, means to rotate the screw and thereby cause the operating members to actuate the bell cranks and rotate the four arms on their pivots, a supporting head pivoted to the outer ends of the arms at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of the head between the two pairs of arms upon an axis parallel to the pivot axes of the arms, whereby it will fold in the frame when the arms are down and will depend from the head when the arms are up, a telescopic sleeve in the tubular member, screw means for adjusting the sleeve axially of the tubular member, an intermediate member loosely supported upon the head and adapted to be engaged by the sleeve and lifted above the head, and a load engaging saddle carried by the intermediate member and movable relative thereto.

11. A lifting device comprising a frame including two side plates and a support therefor, two pairs of arms mounted in the frame upon adjacent transverse pivots and disposed with one pair adjacent the inner face of each plate, each arm having an angular extension at the pivot end forming a bell crank, twooperating members, one pivotally attached to the extensions or each pair of arms, a transverse head coupling the operating members, a screw carried by the head, a nut pivotally mounted in the frame and engaging the screw, means to rotate the screw and thereby cause the operating members to actuate the bell cranks and rotate the four arms on their pivots, a supporting head pivoted to the outer ends or the armsat equal distances from the mounting pivots, a tubular member pivotally attached to the underside of the head between the two pairs of arms upon an axis parallel to the pivot axes of the arms, whereby it will fold in the frame when the arms are down and will depend from the head when the arms are up, a telescopic sleeve in the tubular member, screw means for adjusting the sleeve axially of the tubular member, guide means on the frame engaging the free end of the tubular member and directing it as the pivoted end is raised and lowered, an intermediate member loosely supported upon the head and adapted to be engaged by the sleeve and lifted above the head, and a load engaging saddle slidably supported upon the intermediate member.

12. A lifting device comprising a frame including side plates and a support therefor, two sets of lever arms arranged in spaced relation in the frame and each including two spaced pairs of arms mounted upon adjacent transverse pivots, each arm having an angular extension at the pivot end forming a bell crank, two pairs of operating members, one pair for each set or arms and one operating member being pivotally attached to the extensions of one pair of arms, two transverse heads, one coupling each pair of operating members, two screws, one carried by each head, two nuts pivotally mounted in the frame, one engaging each screw, gearing coupling the two screws to move them in unison, manual operating means attached to both screws, whereby the turning of either will operate both screws and move the two heads and thus rock all the arms in unison about their pivots, a supporting head pivoted to the outer ends of the arms of each set at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of each head between the two pairs of arms upon an axis parallel to the pivotal axes of the arms, a telescopic sleeve in each tubular member, and screw means for adjusting each sleeve axially of its tubular member.

13. A lifting device comprising a frame including side plates and a support therefor, two sets of lever arms arranged in spaced relation in the frame and each including two spaced pairs of arms mounted upon adjacent transverse pivots, each arm having an angular extension at the pivot end forming a bell crank, two pairs of operating members, one pair for each set of arms and one operating member being pivotally attached to the extensions of one pair of arms, two transverse heads, one coupling each pair of operating members, two screws, one carried by each head, two nuts pivotally mounted in the frame, one engaging each screw, gearing coupling the two screws to move them in unison, manual operating means attached to both screws, whereby the turning of either will operate both screws and move the two heads and thus rock all the arms in unison about their pivots, a supporting head pivoted to the outer ends of the arms of each set at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of each head between the two pairs of arms upon an axis parallel to the pivotal axes of the arms, a telescopic sleeve in each tubular member, screw means for adjusting each sleeve axially of its tubular member, connecting means between the two screw means to cause them to operate in unison, and manual operating means on each screw means.

, 14. A lifting device comprising a frame including side plates and a support therefor. two sets of lever arms arranged in spaced relation in the frame and each including two spaced pairs of arms mounted upon adjacent transverse pivots, each arm having an angular extension at the pivot end forming a bell crank, two pair of operating members, one pair for each set of arms and one operating member being pivotally attached to the extensions of one pair of arms, two transverse heads, one coupling each pair of operating members. two screws, one carried by each head, two nuts pivotally mounted in the frame, one engaging each screw, gearing coupling the two screws to move them in unison, manual operating means attached to both screws, whereby the turning of either will operate both screws and move the two heads and thus rock all the arms in unison about their pivots, a supporting head pivoted to the outer ends of the arms of each set at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of each head between the two pairs of arms upon an axis parallel to the pivotal axes of the arms, a telescopic sleeve in each tubular member, crew means for adjusting each sleeve axially of its tubular member, connecting means between the two screw means to cause them to operate in unison, manual operating means on each screwmeans, and a load engaging member loosely supported upon each head in position to be engaged by the respective sleeves and lifted from the heads as the sleeves are protruded.

15. A lifting device comprising a frame including side plates and a support therefor, two sets of lever arms arranged in spaced relation in the frame and each including two spaced pairs or arms mounted upon adjacent transverse pivots, each arm having an angular extension at the pivot end forming a bell crank, two pairs of operating members, one pair for each set of arms and one operating member being pivotally attached to the extensions of one pair of arms, two transverse heads, one coupling each pair of operating members, two screws, one carried by each head, two nuts pivotally mounted in the frame, one engaging each screw, gearing coupling the two screws to move them in unison, manual operating means attached to both screws, whereby the turning of either will operate both screws and move the two heads and thus rock all the arms in unison about their pivots, a supporting head pivoted to the outer ends of the arms of each set at equal distances from the mounting pivots, a tubular member pivotally attached to the underside of each head between the two pairs of arms upon an axis parallel to the pivotal axes of the arms, a telescopic sleeve in each tubular member, screw means for adjusting each sleeve axially of its tubular member, connecting means between the two screw means to cause them to operate in unison, manual operating means on each screw means, a suspension member spanning the two heads and resting loosely with its ends upon the heads in position to be engaged by the respective sleeves and lifted from the heads as the sleeves are protruded and having its intermediate portion inset below the level of'the heads and provided with a track transverse of the pivotal axes of the arms, and a load engaging saddle slidably disposed upon the intermediate portion of the suspension member.

16. A lifting device comprising a frame having side plates and a support therefor, an arm pivoted at one end in the frame, means to rotate the arm on its pivot and thus raise and lower its free end, a supporting head pivoted on the free end of the arm, means to constrain the head at all times in a horizontal position, a tubular member pivotally attached to the underside of the head and of a length to depend vertically therefrom when the head is in elevated position, a telescopic sleeve in the tubular member having an axial stud on its upper end, means to adjust the sleeve in the tubular member, a carriage loosely supported upon the head and having a socket in line with the sleeve when the tubular member is vertical and having a track extending in a plane transverse to the pivotal axis of the arm,'8nd a load elnagzkging saddle on the carriage slidable upon the t 1'7. In a lifting jack, the combination of a frame, an arm pivotally supported on the frame, a block mounted adjacent the free end of said am operating as a seat for the load in lifting the same, power-operated mean connected with said pivotally supp rted arm for swinging the same'upward on its pivotal support to an intermediate level, and power-operated means having pivoted at one e d in the fram e means to rock the arm on its pivot and thus radse and lower its free end, a supporting head pivotally attached to the free end of the arm, a tubular member pivotally supported by the arm and arranged to depend vertically below the head when the head is in it's elevated position, a plunger axially slidable in the tubular member and adapted when protruded to lift the load from the head, and means for protruding the plunger from the to bular member.

20. A lifting device comprising a frame, an an pivoted at one end in the frame, means to me the arm on its pivot and thus raise and lower ti free end, a supporting head pivotally attached t the free end of the arm, a saddle loosely sup ported upon the head, a tubular member pivotal! supported by the arm and arranged to depen vertically below the head when the head is in it elevated position, a plunger axially slidable i' the tubular member and adapted when protrude to lift the saddle from the head, and means it 30 protruding the plunger from the tubular membe ERICH BLOCH.

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