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Retractable stop assemblyRetractable stop assembly description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070170035, Retractable stop assembly. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to power operated retractable stop assemblies. [0003] 2. Background Art [0004] The use of industrial retractable stop products has become wide spread, due at least in part to high demands in the automotive and heavy equipment industries. Conventionally, a retractable stop is powered by a linear actuator such as an air or hydraulic cylinder, a solenoid actuator, or a rotary actuator with a linear worm gear. [0005] A power operated retractable stop assembly typically includes a reciprocatable rod member driven by the linear actuator, and an assembly body secured to the driving cylinder. Some of these existing assemblies, such as those described in U.S. Pat. No. 4,184,579, utilize a stop lever for stopping and releasing loads traveling on a conveyor. In such an assembly, a blocker leg is used to prevent pivoting of the stop arm causing an uncushioned hard stop of loads traveling on the conveyor when the blocker leg is in the blocking position. [0006] Other existing assemblies attempt to provide a cushioned stop by using cylinder pressure to hold the stop arm in the blocking position. However, assemblies such as these may be disadvantageous in that there is no guarantee of a stop, and a heavy load may deflect the stop lever against the biasing cylinder pressure and continue right past the retractable stop without stopping. Sometimes, assemblies utilize a first mechanism for actuating and deactuating the stop and utilize a separate shock absorber mechanism, such as the assembly described in U.S. Pat. No. 5,168,976. [0007] Other existing assemblies use a linear actuator rod interfering at a right angle with the direction of travel of the conveyor load. This has the disadvantage of side loading the actuator which is designed for the loads to be in line with the center line of the actuator. This creates excessive wear of the actuator. Also, excessive side load on a linear actuator can cause the actuator to bind and be unable to release without first releasing the load. [0008] Although the existing retractable stop assemblies that provide a hard stop and those assemblies that attempt to provide a cushioned stop by using cylinder pressure have been used in many applications that have been commercially successful, these assemblies have disadvantages. In some applications, it may be desirable to provide a cushioned stop, and assemblies providing a hard stop without any cushion may not be desired. Further, although a cushion may be desirable in some applications, because assemblies providing a cushioned stop cannot guarantee a stopping of the load after the cushion, these assemblies may also not be desired. Further, assemblies utilizing a separate shock absorber mechanism are complex and costly, so these assemblies may also not be desired. [0009] Power operated retractable stop assemblies with integral cushion and stopping mechanisms are described in U.S. Pat. No. 6,119,843. These power operated retractable stop assemblies provide a cushion when stopping a load and provide a hard stop at the end of the cushion zone. These existing retractable stop assemblies that provide integral cushion and stopping mechanisms have also been used in applications that have been commercially successful. [0010] There is an opportunity for improvement in integral cushion and stopping mechanisms in the situation where the stop arm remains near the locked position after the drive arm, which drives the stop arm, is driven to the unlocked position. That is, the stop arm balances near the locked position even though it has been released by the drive arm. If this situation occurs in a conveyor arrangement where there is cross-traffic, and the stop assembly is located at a cross-traffic point, the balanced stop arm may interfere with the cross-traffic. [0011] The balanced stop arm condition also makes it difficult for a worker to determine the position of the drive arm and the driving cylinder by visual inspection. When the worker sees the stop arm at the locked position, the worker may assume that the cylinder has been actuated to cause the drive arm to engage and drive the stop arm. However, this assumption is not correct in the case where the stop arm balances near the locked position after it has been released by the drive arm. [0012] Another opportunity for improvement in integral cushion and stopping mechanisms occurs when the retractable stop assembly is mounted in an inverted orientation. Because the assembly is in an inverted orientation, the stop arm may again balance near the locked position after the drive arm is driven to the unlocked position. Even if the stop arm has been pushed to the open position by a passing load, gravity will cause it to return to the locked position. That is, the stop arm hangs near the locked position even though it has been released. [0013] Although the existing power operated retractable stop assemblies with integral cushion and stopping mechanisms have advantages, there are still situations where these assemblies may have shortcomings. In particular, the potential for a balanced stop arm condition may make it undesirable to use these assemblies in certain conveyor applications and in certain applications requiring the assemblies to be mounted in inverted orientations. [0014] For the foregoing reasons, there is a need for an improved power operated retractable stop assembly. SUMMARY OF THE INVENTION [0015] It is an object of the invention to provide a power operated retractable stop assembly in which the stop arm and drive arm interact to cause the stop arm to automatically follow the drive arm and move to a released position, and avoid hanging or balancing near the locked position, when the drive arm is driven to the released or unlocked position. [0016] The invention involves a power operated retractable stop assembly. The assembly comprises a body, a reciprocatable member, a drive arm, and a stop arm. The reciprocatable member extends at least partially into the body and is adapted to engage a driving means such as a cylinder. The reciprocatable member is driveable between an extended position and a retracted position. The drive arm is pivotally mounted to the body and drivingly connected to the reciprocatable member such that the drive arm is pivoted about a drive axis. The drive arm is pivotable over a motion range between a pre-locked position and an unlocked position in response to movement of the reciprocatable member. The motion range includes a locked position between the pre-locked position and the unlocked position. The drive arm has a central axis passing through the drive axis to define a drive arm plane that pivots with the drive arm. [0017] The stop arm is pivotally mounted to the body such that the stop arm is pivotable about a stop axis. The stop arm has a front side for engaging a workpiece and a back side for engaging the drive arm. The stop arm is positioned to apply a reaction force to the drive arm in response to a force exerted on the stop arm front side by a workpiece. [0018] The stop arm back side is configured such that the reaction force has a component normal to the drive arm plane when the drive arm is between the pre-locked position and the locked position. The normal component of the reaction force urges the drive arm toward the locked position. Further, the stop arm back side is configured such that the reaction force is substantially coplanar with the drive arm plane when the drive arm is in the locked position to cause the drive arm to remain at the locked position. [0019] In accordance with the invention, when the drive arm is driven to the unlocked or released position, the stop arm and drive arm interact to cause the stop arm to automatically follow the drive arm to move to and stay in a released position. This interaction precludes the stop arm from balancing at the ready or locked position. [0020] It is appreciated that the interaction of the stop arm and drive arm may be achieved in various ways. In the preferred embodiment of the invention, the drive arm has an added leg below the drive arm pivot, and the stop arm has an added leg below the stop arm pivot. When the drive arm is driven to the drive arm unlocked or released position, the lower leg of the stop arm rides on the lower leg of the drive arm to cause the stop arm to automatically follow the drive arm and move to and be held in the stop arm released position, precluding the stop arm from balancing at the ready or locked position. [0021] In another aspect, the invention comprehends an apparatus comprising a body, a drive arm, and a stop arm. The drive arm is pivotally mounted to the body such that the drive arm is pivotable about a drive axis. The drive arm is pivotable over a motion range between a pre-locked position and an unlocked position. The motion range includes a locked position between the pre-locked position and the unlocked position. The stop arm is pivotally mounted to the body such that the stop arm is pivotable about a stop axis. The stop arm has a front side for engaging a workpiece and a back side for engaging the drive arm. When the drive arm is driven to the unlocked or released position, the stop arm and drive arm interact to cause the stop arm to automatically follow the drive arm to move to a released position. This interaction precludes the stop arm from balancing at the ready or locked position and may be achieved, for example, by a lower leg of the stop arm riding on a lower leg of the drive arm when the drive arm is driven to the drive arm unlocked or released position. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading about Retractable stop assembly... Full patent description for Retractable stop assembly Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Retractable stop assembly patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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