Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
1999-08-25
2001-12-04
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S266000, C318S466000, C318S468000, C049S352000, C049S026000
Reexamination Certificate
active
06326751
ABSTRACT:
TECHNICAL FIELD
Generally, the present invention relates to detecting and measuring the motion, speed and position of a garage door as it travels between open and closed positions. More particularly, the present invention relates to an internal entrapment system which employs a potentiometer to detect a position of the garage door and a pulse counter to detect the speed of the garage door, wherein the system compensates for changes in ambient temperature and wear of the mechanical components off the garage door. More specifically, the present invention relates to an internal entrapment system utilized with either an open-loop drive system or a closed-loop lift cable system.
BACKGROUND ART
As is well known, motorized garage door operators automatically open and close a garage door through a path that is defined by an upper limit and a lower limit. The lower limit is established by the floor upon which the garage door closes. The upper limit can be defined by the highest point the door will travel which can be limited by the operator, the counterbalance system, or the door track system's physical limits. The upper and lower limits are employed to prevent door damage resulting from the operator's attempt to move a door past its physical limits. Under normal operating conditions, the operator's limits may be set to match the door upper and lower physical limits. However, operator limits are normally set to a point less than the door's physical upper and lower limits.
Systems used to set operator limits are composed of switches used to terminate travel in the up and down directions. These mechanical switches are adjustable and can be used by the consumer or an installer to “fit” the door travel to a garage opening. These switches are mechanical and have a limited life span. Metal fatigue and corrosion are the most likely causes of switch failure. Another drawback of mechanical switches is that they can be wired in series with the motor which creates high current draw across the contacts of the switch causing the contacts to fail. A further limitation of limit switches is that the up and down limits, which must be set manually, can be improperly set or misadjusted.
Other limit systems employ pulse counters that set the upper and lower travel of the door by counting the revolutions of an operator's rotating component. These pulse counters are normally coupled to the shaft of the motor and provide a count to a microprocessor. The upper and lower limits are programmed into the microprocessor by the consumer or installer. As the door cycles, the pulse counter updates the count to the microprocessor. Once the proper count is reached, which corresponds to the count of the upper and lower limits programmed by the consumer or installer, the door stops. Unfortunately, pulse counters cannot accurately keep count. External factors such as power transients, electrical motor noise, and radio interference often disrupt the count allowing the door to over-travel or under-travel. The microprocessor may also lose count if power to the operator is lost or if the consumer manually moves the door while the power is off and the door is placed in a new position which does not match the original count.
Motorized garage door operators include internal entrapment protection systems designed to monitor door speed and applied force as the door travels in the opening and closing directions. During travel from the open to close and from close to open positions, the door maintains a relative constant speed. However, if the door encounters an obstacle during travel, the speed of the door slows down or stops depending upon the amount of negative force applied by the obstacle. Systems for detecting such a change in door speed and applied force are commonly referred to as “internal entrapment protection” systems. Once the internal entrapment protection is activated, the door may stop or stop and reverse direction.
Most residential operator systems are closed loop systems where the door is always driven by the operator in both the open to close to open directions. A closed loop system works well with the internal entrapment system wherein the operator is always connected to the door and exerting a force on the door when the door is in motion unless disconnected manually by the consumer. If an obstacle is encountered by the door, the direct connection to the operator allows for feedback to the internal entrapment device which signals the door to stop or stop and reverse. However, due to the inertia and speed of the door, and the tolerances in the door and track system, these internal entrapment systems are very slow to respond and some time passes after contacting an obstruction before the internal entrapment device is activated allowing the door to over-travel and exert very high forces on the object that is entrapped. Further, a closed loop operator system always has the capability of exerting a force greater that the weight of the door.
A method of internal entrapment protection on a closed loop system uses a pair of springs to balance a lever in a center position and a pair of switches to indicate that the lever is off-center signaling that an obstruction has been encountered. The lever is coupled to a drive belt or chain and balanced by a pair of springs adjusted to counterbalance the tension on the belt or chain so the lever stays centered. When an obstruction is encountered, the tension on the belt or chain overcomes the tension applied by the springs allowing the lever to shift off-center and contact a switch which generates an obstruction signal. Sensitivity of this system can be adjusted by applying more tension to the centering springs to force the lever to stay centered. This type of internal entrapment systems is slow to respond due to the inertia of the door, stretch in the drive belt or chain, and the components of the drive system.
Another method of the prior art on closed loop operator internal entrapment systems uses an adjustable clutch mechanism. The clutch is mounted on a drive component and allows slippage of the drive force to occur if an obstruction prevents the door from moving. The amount of slippage can be adjusted in the clutch so that a small amount of resistance to the movement of the door causes the clutch to slip. However, due to aging of the door system and environmental conditions that can change the force required to move the door, these systems are normally adjusted to the highest force condition anticipated by the installer or the consumer. Further, over time the clutch plates can corrode and freeze together preventing slippage if an obstruction is encountered. The drive systems on open loop operator systems are very efficient and can be back driven when the garage door is forced open as in a forced entry situation. Motor controls have been designed to use signals from the lower limit switch and the pulse counter to detect when this condition is occurring and start the motor to drive the door down again to its closed position. As mentioned before, the limit switches can fail and/or the pulse counter can miscount rendering this feature useless.
Another type of operator system is an open loop operator system wherein the door is not attached directly to the operator. In an open loop operator system when the door is moving from the closed to the open position, the door is lifted by the operator applying torque to the counterbalance system which reels in the cables attached to the door. When the door is moving from the open to closed position, the operator turns the counterbalance system to reel out the cables attached to the door and relies on gravity to move the door.
An open loop operator system has several advantages over a closed loop operator system. For example, the operator can never force the door to exert a downward force and any downward force can never be greater than the weight of the portion of the door that is in the vertical position. Further, vibrations from the operator and misalignments of the operator mountings will not affect movement of th
Kyle Donald B.
Mullet Willis J.
Rodriguez Yan
Leykin Rita
Nappi Robert E.
Renner Kenner Greive Bobak Taylor & Weber
Wayne-Dalton Corp.
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