Machine element or mechanism – Mechanical movements – Oscillating to oscillating
Patent
1993-04-22
1995-05-16
Kwon, John T.
Machine element or mechanism
Mechanical movements
Oscillating to oscillating
49 49, 49200, F16H 2144
Patent
active
054150558
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a drive mechanism for a vertically rotating member, more especially for a vertically rotating beam or barrier of the kind intended for use in controlling the passage of vehicles or other traffic.
Barriers operating through vertical angles of about 90.degree. are well-known devices for controlling the flow of traffic to and from restricted areas. Such a barrier generally includes a drive mechanism comprising a member pivoted about an axis intended, in use, to be generally horizontal, a rotary element coupled to said member in such a manner that, with said axis horizontal, rotation of said element in a first direction is effective to raise a radially extending portion of said member relatively to said axis and rotation of said element in a reverse direction is effective to lower said portion of said member relatively to said axis, and a reversible drive means for driving said element.
Although the motion of such a barrier is relatively simple, the drive mechanism required to transmit movement to the barrier is subject to conflicting requirements that have hitherto been met only partially, and/or with the use of relatively complicated and expensive mechanisms. Thus, for example, it is required that the driving force applied to such a barrier during movement in the downward direction should be limited to provide safety for pedestrians and vehicles that may inadvertently enter the path of the barrier during its downward movement. On the other hand, the barrier and its associated drive mechanism should be resistant to attempts to force the barrier upward from its horizontal position to permit unauthorised entry to or exit from premises controlled by the barrier. The drive mechanism should be capable of accommodating varying loads placed on the barrier during movement in the upward direction, for example due to accumulation of ice or snow thereon, and also the mechanism should be capable of being released rapidly by an authorised person to enable emergency movement of the barrier by manual means without requiring complicated adjustment of the mechanism to enable resetting of the barrier for powered operation.
It is accordingly an object of the present invention to provide a drive mechanism capable of meeting one or more of the above requirements in an improved manner.
According to one aspect of the invention, a drive mechanism of the kind referred to above is characterised in that the reversible drive means includes a friction roller for engagement with a surface of said element extending circumferentially about the rotary axis thereof, said friction roller being supported for rotation upon a mounting pivoted relatively to the rotary axis of said element and biased in a direction such as to bring the friction roller into pressure contact with said surface, the arrangement being such that when said friction roller is driven to rotate the said element in said first direction reaction force tends to rotate said mounting to increase the pressure contact between said roller and said element, whereas when said friction roller is driven to rotate said element in the reverse direction, the corresponding reaction force tends to reduce such pressure contact.
In an arrangement in accordance with the invention the object is achieved that the force applied by the drive mechanism to move the pivoted member in a downward direction is reduced as the resistance to movement of the pivoted member is increased, for example by contact with an obstruction, whereas the force tending to drive the member in the upward direction is increased in response to an increase in the load thereon, for example if the weight of the member is increased by accumulated ice or snow.
In accordance with one embodiment of the invention the pivoted member comprises a beam or barrier having a generally horizontal rest position when in use, said rotary element is coupled to said pivoted member by way of a connecting rod and the arrangement is such that, during rotation of said element in said reverse direction a crankpin by way of whic
REFERENCES:
patent: 3153802 (1964-10-01), Howard
patent: 3196238 (1965-07-01), Freund et al.
patent: 3307583 (1967-03-01), Harter
patent: 4848175 (1989-07-01), Weiss
patent: 4897960 (1990-02-01), Barvinek et al.
patent: 4926707 (1990-05-01), Yamada
Kwon John T.
Sine Engineering Ltd.
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