Lifting tongs

Claim 2

Lifting tongs comprising a frame, a coupling on said frame, two crossed arms each pivotally secured at one end in the frame and at their other ends to the coupling, two crossed links pivotally secured at one end to each of the two arms at a position between the said one ends of these arms and the position at which they cross over, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the coupling being lifted.

Claim 3

Lifting tongs according to claim 1, comprising two rectilinear guideways in said frame, and wherein the links are pivotally secured to the jaws through pins which protrude into the frame and are accommodated in the said guideways.

Claim 4

Lifting tongs according to claim 2, comprising two arcuate guideways in said frame, and wherein the links are pivotally secured to the two arms through pins which protrude into the frame and are accommodated in the said arcuate guideways.

Claim 5

Lifting tongs comprising a frame, a beam, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.

Claim 6

Lifting tongs comprising a frame, a beam, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.

Claim 7

Lifting tongs according to claim 4, comprising two sets of arcuate guideways in said frame, and a plurality of pins by which the second arms are pivotally secured (a) to the first arms and (b) to the crossed links, respectively, one set of guideways accommodating the pins effecting connection (a) and the other set of guideways accommodating the pins effecting connection (b), a further set of guideways defining said rectilinear path, and a pair of pins by which the crossed links are pivotally secured to the two jaws, the further set of guideways accommodating the said pair of pins.

Claim 8

Lifting tongs comPrising a frame, a beam, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted, and locking means for automatically retaining the jaws of the tongs in an open posture after the beam has been lowered and the load set down.

Claim 9

Lifting tongs comPrising a frame, a beam, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted, and locking means for automatically retaining the jaws of the tongs in an open posture after the beam has been lowered and the load set down.

Claim 10

Lifting tongs according to claim 6, wherein the first arms are connected to said beam through a common pivot.

Claim 11

A lifting tongs assembly comprising a framework, two sets of lifting tongs mounted on and spaced apart by said framework, and a beam common to the two sets of tongs, each one of said sets of tongs comprising a frame, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.

Claim 12

A lifting tongs assembly comprising a framework, two sets of lifting tongs mounted on and spaced apart by said framework, and a beam common to the two sets of tongs, each one of said sets of tongs comprising a frame, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.

Claim 13

A lifting tongs assembly according to claim 8, comprising locking means secured to the beam, and including a pivotal hooked mechanism for automatically hooking around the framework after the beam has been lowered and the load set down whereby to constrain the jaws of the tongs to maintain their open posture, said mechanism being manually operable to unlock the jaws from their open posture.

Claim 14

A lifting tongs assembly according to claim 9, wherein each set of tongs comprises two rectilinear guideways in the said frame, and wherein the links are pivotally secured to the jaws through pins which protrude into the frame and are accommodated in the said guideways.