Braking systems for pneumatic hoists
First Claim
1. A hoist system for lifting and lowering loads, the hoist system comprising:
- a winch drum configured to rotate to wind and unwind a length of cable;
an air motor coupled to the winch drum and operable to rotate the drum;
a brake coupled to the winch drum and operable to stop rotation of the winch drum; and
an over-speed sensing device configured to sense a speed of the winch drum, the over-speed sensing device including;
(i) a pneumatic switch operable to disconnect an air supply from the air motor and engage the brake to stop rotation of the winch drum; and
(ii) a centrifugal clutch coupled to the winch drum and configured to rotate at a rotational speed proportional to the speed of the winch drum, such that the clutch operates the pneumatic switch when the rotational speed of the centrifugal clutch reaches or exceeds a threshold rotational speed.
2 Assignments
0 Petitions
Accused Products
Abstract
Illustrative embodiments of apparatus and methods for braking a hoist system are disclosed. In one illustrative embodiment, a hoist system includes a winch drum and an air motor coupled to the winch drum. The hoist system further includes a brake coupled to the winch drum and operable to stop rotation of the winch drum and an over-speed sensing device configured to sense a speed of the winch drum. The over-speed sensing device includes a pneumatic switch operable to disconnect an air supply from the air motor and engage the brake to stop rotation of the winch drum and a centrifugal clutch coupled to the winch drum and configured to rotate at a rotational speed proportional to the speed of the winch drum. The centrifugal clutch operates the pneumatic switch when the rotational speed of the centrifugal clutch reaches or exceeds a threshold rotational speed.
22 Citations
20 Claims
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1. A hoist system for lifting and lowering loads, the hoist system comprising:
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a winch drum configured to rotate to wind and unwind a length of cable; an air motor coupled to the winch drum and operable to rotate the drum; a brake coupled to the winch drum and operable to stop rotation of the winch drum; and an over-speed sensing device configured to sense a speed of the winch drum, the over-speed sensing device including; (i) a pneumatic switch operable to disconnect an air supply from the air motor and engage the brake to stop rotation of the winch drum; and (ii) a centrifugal clutch coupled to the winch drum and configured to rotate at a rotational speed proportional to the speed of the winch drum, such that the clutch operates the pneumatic switch when the rotational speed of the centrifugal clutch reaches or exceeds a threshold rotational speed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A hoist system for lifting and lowering loads, the hoist system comprising:
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a winch drum configured to rotate to wind and unwind a length of cable; an air motor coupled to the winch drum and operable to rotate the drum; a brake coupled to the winch drum and operable to stop rotation of the winch drum; and an over-speed sensing device configured to sense a speed of the winch drum, the over-speed sensing device including; (i) a pneumatic switch operable to disconnect an air supply from the air motor and to engage the brake to stop rotation of the winch drum; and (ii) a centrifugal clutch coupled to the winch drum and configured to rotate at a rotational speed proportional to that of the winch drum, the centrifugal clutch including a mass biased toward a central hub of the centrifugal clutch and movable to a position away from the central hub to operate the pneumatic switch when the rotational speed of the centrifugal clutch reaches or exceeds a threshold rotational speed. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A method of braking a winch drum of a hoist system, wherein the winch drum is configured to rotate to wind and unwind a length of cable, an air motor being coupled to the winch drum to rotate the drum, and a brake coupled to the drum to stop rotation of the drum, the method comprising:
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positioning a first end of a rotatable input shaft adjacent a portion of the winch drum such that rotation of the winch drum is transferred to the input shaft; positioning a second end of the rotatable input shaft in engagement with a centrifugal clutch; and engaging the centrifugal clutch and, thereby, activating a pneumatic switch operable to disconnect an air supply from the air motor and to engage the brake to stop rotation of the winch drum. - View Dependent Claims (17, 18, 19, 20)
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Specification