US3767061A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tower crane with load limiting apparatus
Assignee: Individual
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Filing: 1972-01-25
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Granted: 1973-10-23
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Expires: 1992-01-25
Abstract
Abstract The load limiting apparatus of a tower crane, which inactivates the load lifting winch when a predetermined load is exceeded, is controlled in such a manner that the maximum permissible load Lmax varies with the angle Alpha between the boom and the horizontal, and the corresponding horizontal spacing a between the projections of the boom pivot and of the depending load carrying cable in a manner to satisfy the equation Lmax L0max k1a wherein L0max is the value of Lmax when a is at a minimum, and k1 is a proportionality factor and constant for all practical purposes. Under these conditions, the maximum tensile stress developed in the boom is constant, at least for an optimum boom length, while a varies between amin and amax, and the structural strength of the material can be fully utilized under all conditions.
Inventors
- 👤 H Tax
- 👤 R Franke
- 👤 K Hosler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 23:00
CPC Classifications
B; B66; B66C; B66C23/00; B66C23/88; B66C23/90
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
234 words
A tower crane comprising: a. a base structure; b. an upright column upwardly extending from said base structure; c. a pivot on said column near the upper end of the column; d. an elongated boom having one longitudinal end portion secured to said column by said pivot for angular movement in a vertical plane; e. adjusting means for varying the angular position of said boom in said plane; f. a load lifting, elongated tension member depending from the other longitudinal end portion of said boom, whereby the spacing of said pivot and of said member projected into a horizontal plane, varies in response to the variation of said angular position between a minimum value and a maximum value; g. winch means for longitudinally raising and lowering said tension member and a load attached thereto; and h. load limiting means for inactivating said winch means when a load attached to said tension member exceeds a predetermined value, 1. said load limiting means including means for varying said predetermined value as a function of said projected spacing during said variation of the angular position of said boom to satisfy the equation Lmax LOmax - k1a wherein Lmax is said predetermined value of said attached load, a is said projected spacing, LOmax is the value of Lmax when a amin, amin being minimum value of said projected spacing, and k1 is a proportionality factor and substantially constant.
Claim 2
Dependent Claim
234 words
A tower crane comprising: a. a base structure; b. an upright column upwardly extending from said base structure; c. a pivot on said column near the upper end of the column; d. an elongated boom having one longitudinal end portion secured to said column by said pivot for angular movement in a vertical plane; e. adjusting means for varying the angular position of said boom in said plane; f. a load lifting, elongated tension member depending from the other longitudinal end portion of said boom, whereby the spacing of said pivot and of said member projected into a horizontal plane, varies in response to the variation of said angular position between a minimum value and a maximum value; g. winch means for longitudinally raising and lowering said tension member and a load attached thereto; and h. load limiting means for inactivating said winch means when a load attached to said tension member exceeds a predetermined value, 1. said load limiting means including means for varying said predetermined value as a function of said projected spacing during said variation of the angular position of said boom to satisfy the equation Lmax LOmax - k1a wherein Lmax is said predetermined value of said attached load, a is said projected spacing, LOmax is the value of Lmax when a amin, amin being minimum value of said projected spacing, and k1 is a proportionality factor and substantially constant.
Claim 3
Dependent Claim
46 words
A tower crane as set forth in claim 1, wherein the values of Lmax differ by not more than 10 percent from the values of Lmax defined by said equation when k1 is constant while a varies between amax and amin, amax being said maximum value.
Claim 4
Dependent Claim
46 words
A tower crane as set forth in claim 1, wherein the values of Lmax differ by not more than 5 percent from the values of Lmax defined by said equation when k1 is constant while a varies between amax and amin, amax being said maximum value.
Claim 5
Dependent Claim
42 words
A tower crane as set forth in claim 1, wherein the maximum tensile stress in said boom differs by not more than plus/minus 10 percent from a constant value while said a varies between amin and amax, amax being said maximum value.
Claim 6
Dependent Claim
42 words
A tower crane as set forth in claim 1, wherein the maximum tensile stress in said boom differs by not more than plus/minus 5 percent from a constant value while said a varies between amin and amax, amax being said maximum value.
Claim 7
Dependent Claim
62 words
A tower crane as set forth in claim 1, wherein said load limiting means include means responsive to said spacing a for generating a first force, means responsive to said attached load for generating a second force, and comparator means for generating an inactivating signal when the relationship of said forces exceeds a predetermined value, said winch means responding to said signal.
Claim 8
Dependent Claim
75 words
A tower crane as set forth in claim 6, wherein said comparator means include a switch and a movably mounted switch actuating member, a pulley member mounted on said switch actuating member, said load lifting member being trained over said pulley member, said pulley member and said tension member constituting elements of said means for generating said second force, and means transmitting said first force to said switch actuating member to resist said second force.
Claim 9
Dependent Claim
45 words
A tower crane as set forth in claim 7, wherein said means for generating a first force include a spring, first motion transmitting means interposed between said boom and said spring, and second motion transmitting means interposed between said switch actuating member and said spring.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-22 | 1977-04-23 | 1977-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-22 | 1981-04-23 | 1981-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-22 | 1985-04-23 | 1985-10-23 | $7700.00 | Window Closed / Lapsed |