Jack shaft garage door operator

Abstract

A jack shaft garage door operator for opening and closing a movable garage door has a drive containing an electric motor. A rotatable jack shaft is connected to the drive unit to be driven thereby. A pull-up cable drum is connected to and driven by the jack shaft. A pull-up cable extends from the drum about which it is wound and connects to a bottom part of the garage door to raise the door. A pivoting arm is mounted near the jack shaft and provides tension to the cable. A shaft lock hub mounted on the jack shaft is engaged and locked by the arm if the tension in the cable drops. A stop is mounted on the garage door for engagement by the movable arm in the event that the door is opened without the cable being drawn in the cable drum.

Description

[0001]This application is a continuation of application Ser. No. 08 / 456,874 filed Jun. 1, 1995, now abandoned.BACKGROUND OF THE INVENTION[0002]The invention relates in general to garage door operators and in particular to a jack shaft garage door operator having a pivoting arm for preventing cable associated with a pull-up cable drum from becoming slack during the operation of the door and for providing a positive door locking system.[0003]One of the problems associated with jack shaft garage door operators is that while they are compact and may be conveniently used in garages which have little overhead room, they may present problems to the owners of the garage in that the cable may be payed out allowing the door to close under its own weight and if the door stalls or if the cable pay out drum rotates too far, the tension in the cable will drop and the cable may come off the drum necessitating a visit from a repairman.[0004]In addition, the jack shaft garage door operator does not ...

AI Technical Summary

Benefits of technology

[0011]A jack shaft garage door operator is useful for opening aand closing a movable garage door. The jack shaft garage door operator embodying the present invention includes a drive unit having an electric motor therein for driving a jack shaft. The jack shaft is mounted above a door opening and usually has coupled to it a spring, or the like, for providing a restoring force to the jack shaft to help raise the door and to support a portion of the weight of the door that is not supported by the L-shaped rails that a door usually rides in. A pull-up cable drum is connected to the jack shaft to be rotated thereby and has a multi-strand steel pull-up cable connected thereto that may be payed out to lower a door or wound up to raise the door. The pull-up cable is typically connected to a bottom portion of the door and, when wound up, will cause the door to rise along vertical portions of L-shaped rails. A pivotable arm is mounted on the garage near the jack shaft and includes an arm extension having a rounded surface which may be a roller or may be fixed for engaging the multi-strand steel pull-up cable. The pivotable arm, including the cable engaging portion, is biased by a spring causing the cable engaging portion to maintain the cable under tension in the drum. In the event that the cable is inadvertently payed out, for instance, by the door having reached the bottom of its travel and the operator continuing to run, the pull-up arm is allowed to pivot upwardly by reduced tension in the cable and swings far enough upward that an operator arresting dog comes in contact with a toothed wheel mounted upon the jack shaft causing the garage door operator to stall. The garage door operator is otherwise a conventional garage door operator and when in a stalled condition, automatically reverses, causing the cable to be payed in and the door to be opened. Thus, the pivotable arm prevents the cable from coming off the cable drum. In addition, a stop or means for preventing the garage door from opening in the form of a metal plate is bolted on an upper panel of the garage door and, when in the closed position, is immediately beneath the pivoting arm of the cable when it is pulled downwardly by full tension on the cable. If the door is attempted to be breached, for instance by an intruder attempting to lift the door, the cable becomes slack allowing the pivoting arm to come out slightly so that it then engages compressionally the stop plate on the garage door thereby preventing further upward motion of the garage door.

Problems solved by technology

One of the problems associated with jack shaft garage door operators is that while they are compact and may be conveniently used in garages which have little overhead room, they may present problems to the owners of the garage in that the cable may be payed out allowing the door to close under its own weight and if the door stalls or if the cable pay out drum rotates too far, the tension in the cable will drop and the cable may come off the drum necessitating a visit from a repairman.

In addition, the jack shaft garage door operator does not provide any secure locking facility other than a lock at the bottom of the door, which may be tampered with by a burglar.

If the door is not locked by some other means, the bottom lock may be forced or damaged and the door can be lifted open and the garage entered by an intruder.

None of the aforementioned documents teach or disclose solutions for preventing a door from being opened or from stopping an operation of a garage door operator to cause it to reverse to take up cable which may have inadvertently been payed off a cable drum of a jack shaft door operator.

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