Boom limit safety control circuit
First Claim
1. An extensible boom safety control circuit comprising:
- a. means for generating a coded boom angle word representing the boom angle of elevation comprising a voltage divider network including a pendulum potentiometer having a plurality of sequential swept contacts for providing discrete voltage levels representing boom angles; and
electrical contact means for contacting said swept contacts of said pendulum potentiometer;
an electrical bus connected to said electrical contact means;
a plurality of voltage comparators connected in parallel to said electrical bus for producing a parallel, coded word representing boom angle; and
a plurality of voltage dividers for providing reference potentials for said plurality of comparators;
b. means for generating a coded boom length word representing boom length, comprising a plurality of microswitches connected in parallel and means responsive to boom length for actuating said microswitches in a mutually exclusive fashion;
c. boom angle logic means responsive to said boom angle word and said boom length word for generating a boom extension control signal, wherein said boom angle logic means comprises a plurality of 3-input NAND gates each of which includes a first input electrically connected to one of said comparators, a second input electrically connected via an inverter to a different one of said comparators, and a third input electrically connected to one of said microswitches, and an inhibit function NAND gate including an input for each of said 3-input NAND gates, said 3-input NAND gates each connected to one of said inputs; and
d. boom length logic means responsive to said boom length word and said boom angle word for generating a boom lowering control signal;
e. boom extension inhibit means responsive to said boom extension control signal for preventing boom extension; and
f. boom down inhibit means responsive to said boom lowering control signal for preventing boom lowering.
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Accused Products
Abstract
A safety circuit for a lifting device extensible boom is presented wherein the boom angle of elevation and boom length are each converted into a parallel coded word. The two coded words, one representing boom angle and the other boom length, are processed in a digital logic network which provides inhibit functions that prevent boom extension or boom lowering when either of the two boom actions will place the boom in a position which will damage the boom or topple the machine. A plurality of switches are associated with the boom to generate and apply the boom length code word to a monitoring circuit, which responds thereto to provide a switch malfunction signal when one of the switches is defective, whereby boom extension or lowering are inhibited.
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Citations
18 Claims
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1. An extensible boom safety control circuit comprising:
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a. means for generating a coded boom angle word representing the boom angle of elevation comprising a voltage divider network including a pendulum potentiometer having a plurality of sequential swept contacts for providing discrete voltage levels representing boom angles; and
electrical contact means for contacting said swept contacts of said pendulum potentiometer;
an electrical bus connected to said electrical contact means;
a plurality of voltage comparators connected in parallel to said electrical bus for producing a parallel, coded word representing boom angle; and
a plurality of voltage dividers for providing reference potentials for said plurality of comparators;b. means for generating a coded boom length word representing boom length, comprising a plurality of microswitches connected in parallel and means responsive to boom length for actuating said microswitches in a mutually exclusive fashion; c. boom angle logic means responsive to said boom angle word and said boom length word for generating a boom extension control signal, wherein said boom angle logic means comprises a plurality of 3-input NAND gates each of which includes a first input electrically connected to one of said comparators, a second input electrically connected via an inverter to a different one of said comparators, and a third input electrically connected to one of said microswitches, and an inhibit function NAND gate including an input for each of said 3-input NAND gates, said 3-input NAND gates each connected to one of said inputs; and d. boom length logic means responsive to said boom length word and said boom angle word for generating a boom lowering control signal; e. boom extension inhibit means responsive to said boom extension control signal for preventing boom extension; and f. boom down inhibit means responsive to said boom lowering control signal for preventing boom lowering. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A safety control circuit for a variable length boom extensible in a rectilinear direction along its axis and pivotable between a down position and an up position, said safety control circuit comprising:
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first means for generating a first coded word indicative of the angle of elevation of the boom from its down position; second means for generating a second coded word indicative of the length of the boom; boom extension control means disposable to a first state for permitting boom extension and to a second state for preventing boom extension; boom lowering control means disposable to a first state for permitting boom lowering toward its down position and to a second state for preventing boom lowering to its down position; first control logic responsive to the first and second coded words as indicative of an unstable boom condition for disposing said boom extension control means to its second state; and
second control logic responsive to the first and second coded words as indicative of an unstable boom condition for disposing said boom lowering control means to its second state;monitoring means responsive to said second coded word for providing an inhibit signal if said second means is malfunctioning, and said boom lowering control means responsive to said inhibit signal to be disposed to its second state. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A safety control circuit for a variable length boom extensible in a rectilinear direction along its axis and pivotable between a down position and an up position, said safety control circuit comprising:
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(a) first means for generating a first manifestation indicative of the angle of elevation of the boom from its down position; (b) second means for generating a second manifestation indicative of the length of the boom; (c) boom extension control means disposable to a first state for permitting boom extension and to a second state for preventing boom extension; (d) boom lowering control means disposable to a first state for permitting boom lowering towards its down position and to a second state for preventing boom lowering towards its down position; (e) first control logic responsive to the first and second manifestations indicative of an unstable boom condition for disposing said boom extension control means to its second state; and (f) second control logic operating independently of said first control logic to respond to the first and second manifestations indicative of an unstable boom condition for disposing said boom lowering control means to its second state, whereby one of said boom extension control means and said boom lowering control means may be disposed to its first state while the other of said boom extension control means and said boom lowering control control means is disposed to its second state. .Iaddend. .Iadd. - View Dependent Claims (15)
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17. lowered but not extended. .Iaddend. .Iadd.21. A safety control circuit for a variable length boom extensible in a rectilinear direction along its axis and pivotable between a down position and an up position, said safety control circuit comprising:
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(a) first means for generating a first manifestation indicative of the angle of elevation of the boom from its down position; (b) second means for generating a second manifestation indicative of the length of the boom; (c) boom extension control means disposable to a first state for permitting boom extension and to a second state for preventing boom extension; (d) boom lowering control means disposable to a first state for permitting boom lowering toward its down position and to a second state for preventing boom lowering towards its down position; (e) first control logic responsive to the first and second manifestations indicative of an unstable boom condition for disposing said boom extension control means to its second state; and (f) second control logic operating independently of said first control logic to correspond to the first and second manifestations indicative of an unstable boom condition for disposing said boom lowering control means to its second state, whereby said boom extension control means and said boom lowering control means are operative independently of each other to inhibit the extension of and the lowering of the boom, respectively, said first control logic being responsive to a first manifestation indicative of boom elevation in a first range defined by a first, relatively high boom angle and a second, relatively low boom angle and including said first boom angle and to a second manifestation indicative of a first boom length for disposing said boom extension control means to its second state, and said second control logic being responsive to said first manifestation indicative of said first boom angle range and to said second manifestation indicative of said first boom length for disposing said boom lowering control means to its first state, whereby the boom may be lowered but not extended. .Iaddend. .Iadd.22. The safety control circuit as claimed in claim 21, wherein said second control logic is responsive to a first manifestation indicative of said second boom angle and to said second manifestation indicative of said first boom length for disposing said boom lowering control means to its second state, whereby the boom may not be lowered. .Iaddend. .Iadd.23. The safety control circuit as claimed in claim 22, wherein said second control logic is responsive to a first manifestation indicative of boom elevation in a second range defined by said second boom angle and a third boom angle lower than said second boom angle and including said second boom angle and to a second manifestation indicative of a second boom length less than said first boom length for disposing said boom lowering control means to its first state. .Iaddend. - View Dependent Claims (16)
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18. Iadd.24. The safety control circuit as claimed in claim 23, wherein said first control logic is responsive to said first manifestation indicative of boom elevation in said second range and to said second manifestation indicative of said second boom length for disposing said boom extension control means to its second state, whereby the boom may not be extended. .Iaddend.
Specification