US2732083A

US2732083A - smith

Info

Publication number: US2732083A
Authority: US
Publication date: 1956-01-24
Anticipated expiration: 1973-01-24

Description

Jan. 24, 1956 A. D. SMITH 2,732,083

ARTICLE HANDLER Filed Sept. 18, 1951 4 Sheets-Sheet 1 I INVENTOR. /}5RTHUR Din/v SMITH ATTORNEY Jan. 24, 1956 A. D. SMITH ARTICLE HANDLER 4 Sheets-Sheet 2 Filed Sept. 18, 1951 INVENTOR. ERTEH R EfiN MITH By Q 5 W NGHK T Wm ATTORNEY Jan. 24, 1956 A. D. SMITH ARTICLE HANDLER 4 Sheets-Sheet 3 Filed Sept. 18 1951 H An w W w mm W QW D AC m R U m. Ry A, 0% B N mN\ .w w wmiam Jan. 24, 1956 A. D. SMITH ,0

ARTICLE HANDLER Filed .Sept'. 18. 1951 '4 Sheets-Sheet 4 INVENTOR. is 'r u 1:32am SMITH BY 7 6 OTR/ ATTORNEY United States Patent ARTICLE HANDLER Arthur Dean Smith, Spokane, Wash, assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif, a corporation of Delaware Application September 18, 1951 Serial No. 247,143 5 Claims. (Cl. 214-1) This invention relates to hoisting and lifting tongs for picking up and transporting heavy articles from one location to another. More particularly, it is concerned with providing novel hoisting clamps or tongs for grasping and transporting coiled metal stock from one place to another.

The hoisting clamps or tongs, which have been employed in the past for graspng and transporting coiled metal stock from one place to another in rolling mills and the like, have not proven entirely satisfactory for one or more reasons.

These clamps or tongs'we're ordinarily suspended from a crane affixed to a trolley which travels along an overhead track in a rolling mill or factory. These clamps or article engaging tongs were usually of a toggle type and operated more or less on the same principle as ice tongs. Thus, when one of the tongs was brought into engagement with the outer surface of the coil and the other of the tongs brought into contact with the inner surface of the coil which was usually located in an upended position and a lifting force was applied to the tongs, they were forced together so as to grasp the coil of metal between them while simultaneously lifting the coil of metal to a predetermined height, after which it was carried by the crane and tongs to another location.

However, with these toggle type of clamping tongs, it was never possible to obtain a true, firm and solid grip on a coil of metal. While in this loose grip of the tongs, the several wraps of metal in the coil adjacent to the tongs were frequently pulled out of place, thereby scratching or scoring the surface of the metal and rendering that portion of the coil which had been scratched useless for 'certainpurposes.

This problem was particularly significant when these clamping tongs were used for transporting coils of aluminum in a rollng mill or factory, since the appearance of the aluminum is very important in the later fabricationof many aluminum products from such coiled stock. Accordingly, those portions of the aluminum coil which were scratched or scored during transport by the tongs ordinarily had to be relegated to the scrap heap. The amount 'of waste over a period of time through the use of such toggle type of tongs in hoisting and transporting metal coils, and particularly coils of aluminum, is 'ob- VlOllS.

It has been found, however, that by utilizing a novel clamping tong apparatus which will securely engage the coiled stock and not allow any slippage of the coil between the "clamping tongs that scoring or scratching of the metal coil during transport can be prevented effectively. In addition, this novel hoisting apparatus is so constructed that the clamping tongs cannot be elevated until the clamping tongs have vcompletely and securely clamped or gripped one or more coils. These clamping ton-gs are also so constructed that once the clamping tongs have been raised to a predetermined height, preferably by means ofa suitablehydraulic-hoisting cylinder, the weight of the coil and the tongs will cause a back pressure in the hoisting cylinder which in turn is transferred to a second hydraulic cylinder used to operate the clamping tongs themselves, thereby keeping the jaws clamped. In other words, the clamping jaws cannot be unclamped as long as there is a weight hanging on or suspended from the tongs.

These and other objects are accomplished by providing a hoisting apparatus comprised of a hoisting frame with a pair of clamping tongs dependingly attached thereto. One of the tongs is removably attached to the frame member at a fixed point thereon and the other of said tongs is arranged for reciprocatory movement toward and away from the first tong after the first tong has been removably attached to the frame at a'predetermined point thereon. Guide means are also provided for the reciprocating tong and a hydraulic cylinder and cooperating piston are preferably used for actuating the reciprocating tong.

A vertically disposed hydraulic cylinder and cooperating piston are attached to the hoisting frame member and these are adapted to lift and lower the frame. Common conduit means are utilized for supplying fluid to both of the aforesaid hydraulic cylinders. A fluid pressure operated valve is located in the conduit means and this valve operates to control the passage of fluid first to the cylinder adapted to actuate the reciprocating tong and then to the cylinder adapted to lift the hoisting frame. A second valve is also located in the conduit means and this second valve causes fluid to flow away from the hoisting cylinder through the conduit means and toward the reciprocating tong actuating cylinder, after the hoisting cylinder has been operated to lift the hoisting frame and the tongs attached thereto to a predetermined height.

Accordingly, it is an object of this invention to provide a novel hoisting device having article engaging and clamping tongs which are adapted to securely engage an article therebetween.

A further object of this invention is to provide a novel hoisting device having article engaging and clamping tongs which cannot be unclamped as long as an article is held in suspension by the clamping tongs. v Another object of this invention is to provide a novel hoisting device having article engaging and clamping tongs 'which cannot be elevated until the clamping tongs have first firmly gripped the article to be hoisted.

A further object of this invention is to provide a novel hoisting device'having article engaging and clamping tongs which can be adjusted so as to engage coils of metal stock of various sizes and/ or a plurality of coils at one and the same time.

Other objects and advantages of the instant invention Will become more apparent from a consideration of the following detailed description when taken in conjunction with the following drawingswherein:

Figure 1 is'a side elevational view partially broken of the hoisting apparatus of the instant invention;

Figure 2 is a plan view of the main frame of the hoisting apparatus when taken along lines 22 of Figure 1;

Figure 3 is a sectional view of the main frame of the hoisting apparatus and the clamping tongs carried thereby when taken along lines 3-3 of Figure 2 with the clamping tongs properly adjusted and the main frame properly balanced so that the apparatus can be .used to lift two coils of metal;

Figure 3a is a sectional view of the main frame of the hoisting apparatus and clamping tongs carried thereby with the clamping tongs adjusted and the frame properly balanced so as to'carr-y one coil;

Figure 4 is a cross-sectional view of the main frame and the clamping tongs carried thereby when taken along lines 4--4 of Figure 2; and

Figure is a schematic drawing of a suitable hydraulic system employed in the operation of the hoisting apparatus of the instant invention.

With further reference to the drawings and particularly Figures 1, 2 and 3, the hoisting apparatus is generally comprised of a main frame member 1. This frame member 1 in turn is roughly comprised of a pair of oppositely disposed, parallel and

elongated plates

2 and 2.

These plates are joined together by means of a suitable bridging member 3 which may be welded or otherwise secured to the anchoring plates 4, which are in turn bolted to the inside surfaces of plates 2 and 2'. Bridging member and plates 4 can also be formed from a single piece of metal as indicated in Figure 2. The

plates

2 and 2 are also secured together by means of the pivot pin 6 to which the clevis 5 is also attached.

The upper part of the clevis 5 is provided with a hollowed-out threaded portion 7 which is adapted to receive the externally threaded stud element 8 attached to the lower end of a piston rod 9 which is adapted to reciprocate in the hydraulic hosting cylinder 10, hydraulic cylinder 10 in turn being dependingly attached ot a travelling overhead trolley 11 by means of a suitable ball swivel mounting 12.

This trolley 11 is mounted on wheels 11' which engage the overhead tracks 9' and trolley 11 and may be driven by any suitable power means along these tracks 9. However, since this trolley does not form any part of the invention, it has neither been shown or described in detail.

The trolley 11 also has mounted thereon a vane type hydraulic pump 13 driven by a suitable motor 14. A fluid storage tank 15 is also located upon the trolley and the function and operation of pump 13, motor 14, and tank 15 will be hereinafter more fully described.

The clamping tongs or

jaws

17 and 18, which are carried by the main frame 1, are each cast from a separate piece of metal. Clamping tong 17 is so cast from a piece of metal as to be provided with a flat body portion 19. Body portion 19 has an elongated aperture or slot 20 located therein. One end of the body portion 19 terminates in a downwardly projecting arm 21, having an annular recessed portion 22 located in the inner marginal edge thereof.

An article gripping plate 24 is attached to arm 21 by means of a projecting lug or knob 23 formed integrally therewith, which lug is adapted to become lodged or seated within the recessed portion 22. This knob 23 can be secured to arm 21 by means of the anchoring plate 23 when this plate is bolted to one side of the arm 21 and one end of the plate 23 is inserted in a slot 24' in the knob 23. The outer surface of plate 24 is advantageously convex so as to be able to correctly engage the inner hollow center portion of a coil of metal, such as aluminum.

The other extremity of clamping tong 17 terminates in an upwardly projecting standard 25. Rigidly attached to the intermediate section of standard 25 by means of the nut 26 is the threaded extremity 27 of a piston rod 28, which is adapted to reciprocate in a hydraulic cylinder 29, threaded portion 27 being insertable through the hole 27 in standard 25.

This hydraulic cylinder 29 in turn is mounted upon and rigidly secured to the upper surface of the flat body portion 30 of the other clamping tong 18. This latter clamping tong is also cast from a single piece of metal in such a manner that in addition to being provided with a body portion 30, clamping tong 18 is also provided with a depending arm 31.

Arm 31 is also provided with a recessed portion 32, within which a projecting lug 33 on the article grasping plate 34 is adapted to be anchored in the same manner as plate 24 is aflixed to arm 21 on tong 17.

The other extremity of tong 18 is provided with an which abuts one end of the cylinder 29. A pair of side members 39 are formed integrally with backstop 36 and they are also provided with openings 40 through which a suitable bolt 41 may be inserted so as to rigidly anchor side members 39 and tong 18 to the plates 2 and 2' when this bolt has also been inserted in one of the

twin openings

38 and 38 in each side plate.

It will be observed by referring to Figures 2, 3, 3a and 4 that each of the

side plates

2 and 2 is so made as to be provided with a channel-shaped slot or keyway 44 in the bottom portion thereof, these channels being defined by the projecting and spaced rib portions 45 on the respective side plates. The body portion 19 of tong 17 and the body portion 30 of tong 18 are insertable in the several slots or keyways 44 of the side plates. They are placed one upon the other in such a way that arm 31 of tong 18 projects through the slot 20in tong 17, it being understood, of course, that plate 34 is attached to tong arm 31 only after the latter has first been inserted through slot 20 in tong 17.

From the above description it will be understood that once tong 13 is rigidly fixed or attached to the main frame, tong 17 is made movable with respect thereto by means of the piston 28 which is adapted to reciprocate in the cylinder 29 rigidly affixed to tong 18.

It will also be observed that the instant apparatus is adapted to lift and transport either one or two coils simultaneously. When it is employed to transport but one coil 100, tong 18 as indicated in Figure 3a is moved along slot 44 until it is located slightly to one side of the clevis 5 and pin 6, after which it is anchored rigidly to the frame 1 by means of the bolt 41 when this bolt is inserted in the hole 38 in each of the

side plates

2 and 2 and through the openings 40 in the side members 39 of the tong 18.

In order to balance the frame when the tong 18 is moved to the position indicated in Figure 3a, a counterbalancing weight 50 is then placed between

plates

2 and 2 at the other end of the main frame 1, weight 50 being secured to the side plates by means of the pins 51. At this time also pin 6 for the clevis 5 is inserted in the opening 37 in the side plates.

Whenever the device is employed to lift two coils and 100',.tong 18 is shifted in the opposite direction along keyway 44 until it reaches the position shown in Figure 3, at which time weight 50 is removed and pin 6 for clevis 5 is then removed from the openings 37 in the

side plates

2 and 2 and inserted in the openings 37 of the said side plates.

When the device is employed to hoist two coils, a suit able pinion gear 53 is located above cylinder 29 attached to tong 18, pinion gear 53 being held in the proper position by means of the upper and lower bridging members 54 and 54', which are suitably attached to

side plates

2 and 2 by means of the screws 55. Web members 54 and 54' both have aligned openings therein in which the shaft 53 of the gear 53 is inserted.

This pinion gear is adapted to mesh simultaneously with a rack 56 attached to the cylinder 29 and a second rack 57 rigidly affixed to standard 25 which forms part of tong 17. The purpose of

racks

56 and 57 and pinion gear 53 is to center the

tongs

17 and 18 and to keep them level, as well as to aid in properly balancing the hoisting device as a whole during its suspension from hoisting cylinder and piston 9 and 10, during the time the tongs are used to grasp and transport two coils of metal.

Suitable spacers 60 and 61 for the tongs may be In serted between and be removably attached to the side plates 2 and 2' at each of their ends, spacer 61 being removed when the device is used to hoist but one coil.

When one coil is grasped by the

tongs

17 and 18, one of the tongs is adapted to engage the inside of the coil while the other engages the outside of the coil so that the-coil may be firmly and securely clamped therebetween.

upstanding backstop 36 lNhen two coils are engaged each of the tongs engage the nside surface of a separate coil as indicated in Figure 3.

The arrangement and operation of the hydraulic circuit. for operating the hoisting cylinder and piston 9 and 10 and clamping tong cylinder and

piston

29 and 28 will now be described.

By referring to Figure 5 it will be observed that the hydraulic system includes a motor driven hydraulic pump 13, which pumps fluid out of tank through line 312) to the entry port 71 of a solenoid-operated 4-way valve One of the discharge ports of valve 72, namely port 73, is connected to tank 15 by means of the conduits or

lines

75 and 75, line 75 connecting the main exhaust port 74 of valve 72 directly to the tank 15. Another discharge port 77 of valve 72 is connected by means of

conduits

78 and 79 to a second solenoid-operated 4-way valve 80. Line 78 also connects with a sequence and pressure-operated valve 81.

The

discharge ports

83 and 82 of the second valve 80 are connected to the rod end and head end of the tong actuating cylinder 29 by means of the

conduits

84 and 85 respectively.

Valves

72 and 80 are advantageously electrically operated. Thus, when the

tongs

17 and 18 are in an unclamped position and are at rest about a coil to be hoisted, the pushing of a clamp button 86 of a suitable electric switch 80, also shown diagrammatically n gure wi l aus the ners za g of valve 72 in Sllch a manner that port 71 thereof will be connected with discharge port 77, thereby allowing fluid to pass through

conduits

78 and 79 to

valves

80 and 81. At this time also port 73 of valve 72 becomes connected to port 74. Valve 81 remains closed by a suitable spring mechanism until such time as pressure builds up in line '78 to the spring setting in valve 81. Initially, therefore, fluid is blocked from entering the hoisting cylinder 10 through line 38 which connects valve 81 with the hoisting cylinder. Instead fluid is first passed through line 79 to inlet port 90 in the valve 80, which valve is also adapted to be energized simultaneously with valve 72 by any suitable electrical device well known in the art when the clamp button 86 is pushed.

When in the clamp position discharge port 32. of valve 895 is connected with inlet port 90 and discharge port 83 of valve 80 is connected to exhaust port 1163 upon energization of valve 80. Fluid thus passes out of port 32 and through line 85 to the head end of the clamping cylinder 29 through the opening 29 therein, and out of rod end of cylinder 29 through line 84 to port 83 through valve 84} to port 110 through

lines

150 and 75 to tank 15, thereby actuating piston 28 and clamping tong or jaw 17 and drawing it closer to clamping tong or jaw 18 until both jaws securely engage thecoil between them, at which time pressure builds up in

lines

85 and 79 to a point where valve 81 opens, thus allowing fluid then to flow through line 88 to the lower part of the hoisting cylinder 10 which then operates to lift the clamping jaws and the article clamped thercbetween, such as a coil of aluminum.

Upon release of the clamp button 86 after the jaws or tongs have been raised to the desired height, solenoidoperated valve 72 operates to block the flow of fluid out of either

cylinder

29 or 10, while permitting a free flow of fluid from the pump discharge line 70 back through the return line 75 since at this time when the valve is deenergized or is in a neutral position the inlet port 71 of valve 72 is connected directly to the exhaust port 74 of the valve 72, thereby permitting fluid to flow freely from the inlet port 71 to the exhaust port 74 and thus unload.- ing the pump. Valve 30, however, stillremains energized.

In the meantime, the gravity Weight of the

jaws

17 and 18 and the coil and/or coils clamped therebetween causes a back pressure in the hoisting cylinder 10, and since the circuit remains open back pressure is also created in 6

lines

88 and 79 and then through the inlet port 90 and outlet port 82 of valve and through line 85. to the head end of the clamping cylinder 29, thereby creating a back pressure in this cylinder which acts to keep the tongs or jaws tightly clamped about the coil or coils.

The jaws remain in this clamped position about the coil until the lower push button 95 of switch 80' is depressed. Depressing the lower push button 95 causes valve 72 to be energized in such a manner that discharge port 77 becomes connected with exhaust port 74 while intake port 71 becomes connected to discharge port 73.

Fluid is then allowed to discharge out or" the hoisting cylinder 10 through valve 72 and back to the tank 15. Since port 71 is connected to port 73 and port 73 is connected to line 75 by means of auxiliary line 75, the pump continues to by-pass under no load during the lowering of the tongs or jaws with their load.

Releasing of the lower push button 95 when the tongs have been lowered the proper amount causes valve 72 to be actuated so that inlet port 71 is again connected directly to the exhaust port 74. During all of this time the position of valve 80 remains unchanged.

Thereafter the depressing of the unclamp push button 9.8 will cause valve 72 to be operated so that inlet port 71 becomes connected to discharge port 77, while discharge port 73 becomes connected to exhaust port '74. When push button 98 is pressed valve 80 is also simultaneously operated so that inlet port 99 becomes connected to discharge port 83, while discharge port 82 becomes connected to exhaust port 110. Fluid is thereby evacuated out of line and through line 150 to return line 75 and then back to the tank. Fluid in the meantime, of course, is also being pumped from inlet port and out through discharge port 83 and line 85} to the rod end of the cylinder 29 through port 28 so that the clamping jaws are forced apart and released from the coil. When the

jaws

17 and 18 reach their extreme open position, pressure builds up in

lines

84 and 79 to a point where valve 81 opens, thus allowing fluid to flow through line 88 to the lower part of the hoisting cylinder 10 which then operates to lift the unclamped tongs away from the article just released and in position to be lowered onto the next article, such as a coil of aluminum. It will be observed also that a suitable slot 175 may be located in one of the side plates to provide suitable clearance for port element 28' when the cylinder 29 is moved on the main frame as the apparatus is adjusted to pick up one coil or two coils. 9

Upon release of the unclamp button 98 after the jaws or tongs have been raised to the desired height, solenoidoperated valve 72 operates to block the flow of fluid out of either

cylinder

29 or 19, while permitting a free fiow of fluid from the pump discharge line 70 back through the return line 75 since at this time when the valve is deenergized or is in a neutral position the inlet port 71 of valve 72 is connected directly to the exhaust port 74 of the valve 72, thereby permitting fluid to flow freely from the inlet port 71 to the exhaust port 74 and thus unloading the pump. Valve 80, however, still remains energized. The jaws remain in this unclamped position suspended above another coil until lower push button of switch 89 is depressed. Depressing the lower push button 95 causes valve 72 to be energized in such a manner that discharge port 77 becomes connected with exhaust port 74 while intake port 71 becomes connected to discharge port 73.

Fluid is then allowed to discharge out of the hoisting cylinder 10 through valve 72 and back to the tank 15. Since port 71 is connected to port 73 and port 73 is connected to tine 75 by means of auxiliary line 75, the pump continues to by-pass under no load during the lowering of the tongs or jaws. This completes the cycle.

From the foregoing description it will be noted that

valves

72 and 80 are so constructed that depression of the clamp button 86 energizes the same solenoid in valve 72 as is energized when the unclamp button 98 is depressed, while depression of clamp button 86 shifts the solenoid valve 8% in an opposite direction to that obtained when the unclamp button 98 is pushed.

A pressure switch 91 is provided so that pushing of the wrong button on 80' will not energize valve 84). For example, if the coil is suspended in the tongs and the unclamp button 98 is pushed instead of the lower button 95, valve 72 will shift but valve 80 will remain unchanged. This shifting of valve 72 will cause the tongs to raise to a higher position as long as the button is held.

The hydraulic system may also be provided with

suitable chcck valves

200 and 201, a globe valve 202, and a relief valve 203, for protection of the system and to control the rate of flow in the system.

From the foregoing description it will also be observed that as long as there is a weight han ing from the tongs or jaws, such as a coil, it cannot be released from the jaws. The safety feature of the apparatus is therefore obvious. If a slow leak develops in any of the valves or hydraulic cylinders, the only thing that can happen while the coil is suspendid in the air is that the coil will be slowly lowered to the floor and then be released from the jaws. The only way in which a coil could be dropped would be by breaking a hose to the clamping cylinder 29. A hydraulic system is also preferably used to operate

cylinders

10 and 29. It will also be noted that the apparatus is simply constructed and can be easily repaired.

An advantageous embodiment of the invention has been herein described. It is obvious that various changes and modifications may be made therein without departing from the spirit and scope thereof as defined by the appended claims.

I claim:

1. In a hoisting apparatus of the type described which is adapted to securely engage and then transport a coil of metal or the like from one location to another, the combination of a hoisting frame member, a plurality of clamping tongs carried by said frame member, one of said clamping tongs being arranged for reciprocating movement toward and away from another of said tongs, hydraulic cylinder and piston means for actuating said reciprocating tong, a second hydraulic cylinder and piston means attached to the hoisting frame member for lifting and lowering the said frame member, pump means for supplying fluid under pressure to both of said cylinder and piston means, conduit means connecting said pump means to said first mentioned cylinder means, conduit means connecting said pump means to said second mentioned cylinder means, said second conduit means including a portion in common with said first mentioned conduit means, a fluid pressure operated valve located between the common portion of said first and second mentioned conduit means and said second mentioned cylinder and piston means for causing fluid to be passed first to the cylinder means adapted to actuate said reciprocating tong and then to said cylinder means adapted to lift said hoisting frame member, and valve means for cutting off the flow of fluid under pressure from said pump means to said common conduit means, whereby a back pressure will be exerted upon the piston of said tong actuating piston and cylinder means due to the weight imposed upon said second mentioned piston and cylinder means.

2. A hoisting apparatus of the type described in claim 1, including means for positioning one of the tongs at different points on the frame member, whereby the tongs may be adjusted so as to engage a plurality of coils.

3. In a hoisting apparatus of the type described which is adapted to securely engage and then transport a coil of. metal or the like from one location to another, the combination of a hoisting frame member, a pair of clamping tongs dependingly carried by the said frame member, one of said tongs being removably attached to said frame member, and the other of said tongs being arranged for reciprocatory movement toward and away from said first tong after the first tong has been removably attached to said frame member at a predetermined point thereon, hydraulic cylinder and piston means for actuating said reciprocating tong, a second hydraulic cylinder and piston means attached to the hoisting frame member for lifting and lowering the frame member, pump means for supplying fluid under pressure to both of said cylinder and piston means, conduit means connecting said pump means to said first mentioned cylinder means, conduit means connecting said pump means to said second mentioned cylinder means, said second conduit means including a portion in common with said first mentioned conduit means, a fluid pressure operated valve located between the common portion of said first and second mentioned conduit means and said second mentioned cylinder and piston means for causing fluid to be passed first to the cylinder means adapted to actuate said reciprocating tong and then to said cylinder means adapted to lift said hoisting frame member, and valve means for cutting off the fiow of fluid under pressure from said pump means to said common conduit means, whereby a back pressure will be exerted upon the piston of said tong actuating piston and cylinder means due to the weight of the load imposed on said second mentioned piston and cylinder means.

4. In a hoisting apparatus of the type described, the combination of a hoisting frame member, a pair of clamping tongs dependingly carried by said frame member, one of said tongs being attached to said frame member at a predetermined point thereon and the other of said clamping tongs being arranged for reciprocatory movement toward and away from said first tong, guide means for said reciprocating tong, hydraulic cylinder and piston means for actuating said reciprocating tong, a second hydraulic cylinder and piston means attached to the hoisting frame member for lifting and lowering the said frame member, pump means for supplying fluid under pressure to both of said cylinder and piston means, conduit means connecting said pump means to said first mentioned cylinder means, conduit means connecting said pump means to said second mentioned cylinder means, said second conduit means including a portion in common with said first mentioned conduit means, a fluid pressure operated valve located between the common portion of said first and second mentioned conduit means and said second mentioned cylinder and piston means for causing fluid to be passed first to the cylinder means adapted to actuate said reciprocating tong and then to said cylinder means adapted to lift said hoisting frame member, and valve means for cutting off the flow of fluid under pressure from said pump means to said common conduit means, whereby a back pressure will be exerted upon the piston of said tong actuating piston and cylinder means due to the load imposed upon said second piston and cylinder means.

5. In a hoisting apparatus of the type described, the combination of a hoisting frame member, a pair of clamping tongs dependingly carried by said frame member, one of said tongs being removably attached to said frame member and the other of said clamping tongs being arranged for reciprocatory movement toward and away from said first tong after said first mentioned tong has been attached to said frame member at a predetermined point thereon, guide means for said reciprocating tong, hydraulic cylinder and piston means for actuating said reciprocating tong, a second hydraulic cylinder and piston means attached to the hoisting frame member for lifting and lowering the said frame member, pump means for supplying fluid under pressure to both of said cylinder and piston means, conduit means connecting said pump means to said first mentioned cylinder means, conduit means connecting said pump means to said second mentioned cylinder means, said second conduit means including a portion in common with said first conduit means, a

fluid pressure operated valve located between the common portion of said first and second mentioned conduit means and said second mentioned cylinder and piston means for causing fluid under pressure to be passed first to the cylinder means adapted to actuate said reciproeating tong and then to said cylinder means adapted to lift said hoisting frame member, and valve means for cutting olf the flow of fluid under pressure from said pump means to said common conduit means, whereby a back pressure will be exerted upon the piston of said tong actuating piston and cylinder means due to the load imposed upon said second hydraulic piston and cylinder means.

References Cited in the file of this patent UNITED STATES PATENTS