Lifting Tongs - A Brief Overview and Practical Advice

Transcription

1 Deals, `1,439,245 D. R, KNA PP., vhcusvmo MscHANlsM FlLeo MAY ` 2 sheets~sheet l '45 _ 6'/ +,.f5 7?. «/ l J5 674/: 70@,- _ Il _ gli ' 6/ ~

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3 ' ' État-entrati 19, lâzé, naze >otherimprovements as will hereinafter ap I" DAVID R. KNAPP, OF POTTSVILLE, PENNSYLVANIA. HOISTING MECHANISM., application filed May 27, Serial No. 384,578. To all fui/ 0m t may concern.' Be it known that Í, DAVID R. KNAPP, a citizenof the United States,`and a resident of Pottsville, county of Schuylkill, State of Pennsylvania, have invented certain new and useful lmprovementsin Hoisting Mech anism, of which the following is _a speci fication. ', - vsome of the objects of the present inven tion are to provide ain-apparatus for attach ing and releasing a hoisting mechanism to heavy material to be lifted or transported; to provide means operable independently of but in conjunction with a. hoisting mecha nism for causing a weight to be ~attached to or released from said hoisting mechanism; to providev an improved tongs for use «with hoisting apparatus; to provide means for opening and closing a tongs to engage or re lease material; to provide an electrically controlled tongs for use with al hoisting mechanism; to provide means for maintain ing an operating cable taut; and to provide pear. j*, j In the accompanying ' drawings, Figßl represents a side elevation of a lifting tongs embodying one form of the present inven tion; Fig. 2 represents an enlarged detail 1n plan of one form` of operating bars 'used in i the tong construction; and Fig. 3 represents - a side elevation of the parts shownin Fig. 2. Referring to the drawings, one form >of lifting tongs 10'comprises a pair of arms 11 and 12 pivotedat 13 and each consisting ofia downwardly curved jaw 14 and an up wardly curved lever 15, the respective pairs of jaws 14 and levers 15 extending in oppo site directions and substantially in parallel relation. ì The tong arms 11 and 12 are of generally heavy material and are suitably íí ulcrumed to produce the required gripping of the jaws 14,y and the weight of the parts,y j' in suspended operative position, is such as to draw and hold the levers 15 togetherl unless opposed by some greater force. In order: to gripa the material to he han- dled, such as an ingot 16 or any other mas sive weight, the jaws 14 are providedrespec tively with pointed gripping pins 17, 'which extend laterally from and in juxtaposed re lation upon the jaws 14. l Forsupporting the tongs 10 and also for raising and lowering them, the levers _15 are >respectively provided with ópenings 20 to which a bridle 21 of any suitable material is attached and has its upper end fixedto a block-22 in a manner to give an equal pull to the tong levers 15. rl he bloclr 22 is fixedly secured tothe extremitiesßof the hoisting j `cables 23 which extend yupward and, arei wound upon a> hoisting drum 24 ofthe usual type found on traveling cranes andwhich is arranged to be operated vby a hoisting'v motor 25 through a suitable gear reduction 26 and 27.» ln the'present instance the mo tor 25 is of the electric type though ob viously any other suitable power means may be employed tol operate the` drum for hoist ing operations. ' 70 For the purpose of operating thel levers 15 te open the jaws 14, a pair of bars 30 and 31 are provided, the bar 30 being pivoted to a pin 32 fixed> to the lever 15 of the-tong arm 11, and the bar 31 being~ pivoted to a pin 33 fixed to the lever löof the tong arm 12.l The pins 32 and 33 are respectively located at the same distance from the fulcrum pivot 13 and are normally horizontally opposite each other.v rllhe pivoted ends> of the re spective bars 30 and 31 are preferably-br furcated to straddle the levers 15 and form an effective connection between the parts. The end wall of the bifurcated portion may be beveled, as indicated at 34'to permit free swinging movement, vas 'will be understood. The free ends of the bars 30 and 31 a`re se `cured in pivotal relation by a pin 35 vand in order to provide for suitable interíitting of A the parts the meeting» ends of the respective bars 30. and 31 are reduced in> width respec tively and in right and left hand relation forming overlapping tongues 36 and 3i'. Thus the two bars 30 and 31 yin assembled >condition form a» sectional link yof uniform width throughout its >lengthand well suited _ "to distribute the operating strains and stresses. î._- i AS a means for limiting the downward movement of `the bars 30 and 31, the bar 30 is provided with an abutment 4()v having a face 41 juxtaposedrwith respect to a similar y face >'42 on an abutment 43 providedon the lbar" 31, the angle of these meeting faces 41 vand 42 being such as to permit free move lment of the bars y30 and 31> within an op erative range, but to ìlimit the distance the levers 15 can be drawn together. ' ' j ` j. As a means to prevent the bars 30 and 31 swinging across the> line of centers of the

4 _ 30 1,439,245 pins $532 and 253, or above the dotted line posi tion shown in Figcl, the bar is provided with angularly disposed abutment 'face 44 which is located in the path of movement of the tongue 37 to serve as a stop'` at the pre determined limit of motion, and the bar 31 is similarly provided with a like abutment face 45 in the path ot movement of the tongue 36. These two abutmenttaces 44 and 45 are arranged to be simultaneously engaged by the respective tongues 86 and >37 and thus form a rigid means to prevent further relative movement between the two bars 30 and 31. F or coi'itrolling the bars 30 and 31a yoke 46 is secured by the'pin 35 and has an eye bolt 47 or other securing means to"y which a cable 48 is made fast.v The opposite end of the cable 48 is :tast to a winding drum 50 and is wound thereon tor operation in the usual manner. The drum 50 is fast to a shalt 51 of a motor 52, which is here shown as an electric motor receiving current from the line conductors 53 and 54 leading from a suitable source of current. ~ 1n order to maintain the cable 48 taut at all times but without' placing sutiicient tension'thereon to overcome the tension of the hoisting cable 23, a relatively high re sistance 55 is inserted ina series with a lead 56 from one of the conductors, say conductor 54, so that, while current is supplied to the motor 52, the torque of the shaft 51 is insuh'i cient compared to the torque ot the drum 24. In consequence, under conditions otlifting or conveying, the motor 52 merely maintains the cable 48 taut, the shaft 51 turning only enough to take 'up slack. To cause the bars 30 and 31 to move rela tively and straighten out, as indicated in dotted lines in Fig. 1, to open the jaws 14 a commutator 60 is provided, the same being of any well known type having contactors and arranged to be manually operated to change its position; In the present instance three electrically connected contactors 61, 62 and 63 arearrangedìon the movable part of the commutator, the first 61 being positioned to engage a fixed contact 64 in one position of the commutator while the contacter 63 is continuous and engages a second fixed con tact 65. ~ ' The contact 64 is connected by a lead 66 and a low resistance 67 to the conductor 54, while the contact 65 is connected by a lead 68 with the lead 56. Thus when the commu tatcr 60 is turned to bring the contacter 61 into engagement with the contact 64 the re sistancesfööl and 67 will bein multiple and more current will flow to the motor 52, there by increasingv the torque and causing` the tongs 10 to, open to release or grip the ingot 16 or other load. The. total current is so ad jaisted thatl there will be. sufficient- torque ex»' erted to shift the operating bars' 30 and 31 to a position to open the tongs 10, but in sutiicient to raise them and interfere with the main hoisting mechanism. As long as the commutator 60 is in position to supply this additional current to the motor 52 the tongs 10 will remain open whether they are being raised or lowered by the cable 23. For emergency operation a third contact 70l is connected by> a lead 71 and a relatively low and the resistance arrangement 72 to the of the line commutator conductor is such that in the emergency position the three resistances55, 67 and 72 are in parallel with the motor insel-ies and the total resistance is adjusted so that the total current will not be vdetrimental to the motor 52. 'l he operation of the device takes place as follows :--Assuming the commutator or con troller 60 to be in the oit position, and current on, the circuit through the motor 52 by way. of the high resistance 55 will be closed thereby causing the motor 52 to exert a small torque which is suíiicient to take up the slack of the cable 48.y To open the tongs 10 the controller 60 is' turned 'to close contact between the contactor 61 and contact 64 so that the resistance 67 is thrown into the cir cuit whereby the motor torque is increased sufficiently to force the levers 15 apart and open the jaws 14. The main drum 24 is now operated to lower the tongs 1() over the ingot 16 or other material, land the control com mutator 60 again brought to the off posi tion and as the torque of the motor 52 is then insufñcient to sustain the weight, the tongs 10 collapse and the pins 17 grip the ingot The material can now be lifted, transported and placed inthe desired location where its weight is releasedl from the tongs and the controller or commutator 60 is then thrown again to its first position thereby opening the tongs so that the main hoisting drum 24 can raise the tongs in open position clear of the load which has been released. 1n case the pins 17 should bind to the material being lifted or moved so that the normal` operating torque is insuiiicient to open the tongs, the controller 60V is thrown to emergency posi tion and allows full current toy flow and` in crease the torque to maximum. In lifting tongs as heretofore usedr` par ticularly in steel mills where heavy red hot ingots are to be lifted and conveyed from one location to another, it hasbeennecessary to employ a number of operativesto place and securethe hoisting tongs in place upon Athe ingot or other material. The intense heat is not only detrimental to those re quired to perform this duty but causes con siderable, time to> be wasted: in getting the tongs properly adjusted. 4 By the, presentv invention the tongs, can be broughttoz-.position by the crane operator tomatically gripped Jfor lifting or transport and thenloweredover the'material and au

5 n BO 35 ing, thereby releasing the tong Setters for other work ami saving considerable time as 1,439,245 well.- ' ~ While but one ci the many forms in which the present invention may be embodied has been shown and described herein, it is to be understood that the invention is not limited to any specific construction bnt might be ap plied to various forms without departing from the spirit of the invention or the scope of the appended claims..» Having thus described my invention, I claim: l. In a hoisting mechanism, a tongs for gripping an object, a hoisting cable secured to said tongs, means for winding saidl cable to raise and lower said tongs, means for opening said tongs, means including an elec tric motor and an operating cable for con trolling said opening means, and means for causing said motor to exert a torque less than the weight of said tongs to maintain said ` operating cable constantly taut. 2. In a hoisting mechanism, a tongs` for gripping an object, a hoisting cable secured to said tongs, means for >winding said cable to raise and lower said tongs, means for opening said tongs, means including an elec tric motor and an operating cable for con trolling said opening means, means: for caus ing said motor to exert a torque less than the weight of said tongs to maintain said op erating cable constantly taut, and means to increase the torque of said motor to actuate said opening means. 3. In a hoisting mechanism, a tongs for gripping an object, operating barsfor actu ating said tongs, a motor operatively con nected to said bars, means to cause said mo tor to exert a permanent torque to hold said bars in a predetermined position, and means to increase said torque to canse said bars to operate said tongs. 4. In ia hoisting mechanism, a tongs for. gripping an object, operating bars for actu~ ating said tongs, a motor operatively con«nected to said bars, means to cause said mo tor to exert a permanent torque to hold said bars in a predetermined position, and means to increase said torque step by step to cause said bars to operate said tongs. _ 5. In a hoisting mechanism, a tongs for gripping an object, means for operating said tongs, an electric motor operatively connect ed to said means and having a constant torque insufficient to cause said means to op-, erate, and means to vary the resistance of said motor to increase the torque at will whereby said operating means is caused to operate. 6. In a hoisting mechanism, the combina tion of a device for supporting an _object to be lifted, operating means for causing said device to engage or release saida object, means including an electric motor and an operating cable for controlling said operating means, a current controlling means.for constantly subjecting said motor to a torque suiiicient to maintain said cable taut without causing said supporting device operating means to function, and a hoisting means operable in dependently of said device operating means for raising or lowering said supporting de vice. - Signed at Pottsville, in the county of Schuylkill, State of Penna., this 10th day of May, DAVID R. KNAPP