Air hoist with an overload protection device
AssigneeAtlas Copco Aktiebolag
InventorGunnar Christer Hannson
Life of this patent
Estimating the term…
Abstract
The pneumatic motor of an air hoist has a blow-off valve in its supply passage. When the blow-off valve is open to the atmosphere, the air pressure at the inlet of the motor is substantially reduced. The blow-off valve is held closed by a piston having a piston surface in an air chamber. The air chamber is supplied with compressed air through a restriction. The hoist has a hook by which it can be suspended and the hook is clamped to the housing of the hoist by means of a pre-loaded Belleville-spring. When the spring yields due to overload, a vent valve will open and vent said air chamber. As a result, the blow-off valve suddenly opens to limit the torque of the motor.
Claims24
An air hoist comprising:
- a rotatable drive wheel carrying a line which in turn is adapted to carry a work load,
- an air motor for rotating said drive wheel to retrieve said line,
- a supply conduit connected to an inlet of the motor for supplying motive air to the motor,
- a normally closed blow-off valve connected to said supply conduit so as to effect, when in an open position, a reduction of the motive air pressure at the inlet of said motor due to an increased pressure loss in said supply conduit and substantially located upstream of the blow-off valve, whereby to limit the power of the motor, and
- a load sensing device arranged to initiate the opening of the blow-off valve in response to the tension in the line reaching a predetermined magnitude.
An air hoist comprising:
- a housing,
- a suspension device by which the air hoist can be suspended, said suspension device being mounted to the housing,
- a rotatable drive wheel carrying a line for hoisting a workload,
- a rotary air motor for rotating said drive wheel to retrieve said line,
- a supply conduit connected to an inlet of the motor for supplying motive air to the motor,
- a normally closed blow-off valve connected to said supply conduit so as to effect, when in an open position, a reduction of the motive air pressure at said inlet of the motor due to an increased pressure loss in the supply conduit and substantially located upstream of the blow-off valve, and
- a pilot valve within said suspension device sensing the force transmitted through said suspension device and connected to initiate said blow-off valve to open when said sensed force reaches a predetermined magnitude.
An air hoist comprising:
- a rotatable drive wheel carrying a line which in turn is adapted to carry a work load,
- an air motor for rotating said drive wheel to retrieve said line,
- a supply conduit connected to an inlet of the motor and including a supply valve,
- a normally closed blow-off valve connected to the supply conduit between the supply valve and the inlet of the motor and adapted to open when the supply conduit is suddenly pressurized, whereby to reduce the motive air pressure at the motor inlet due to an increased pressure loss in the supply conduit and substantially located upstream of the blow-off valve, and
- means to provide for a slow closing of said blow-off valve to ensure a gentle start of said motor due to a slow pressure build-up at the motor inlet.
Dependencies are inferred from the claim text.