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This application is a continuation of application Ser. No. 07/702,776 filed May 17, 1991 and now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates, generally, to motor control switches and, more specifically, to a limit switch mechanism for controlling the electric motor which powers an electric garage door opening and closing mechanism. There are many different types of so-called limit switches used in regulating and controlling the motor of a garage door opener. There are various safety requirements as well as installation problems associated with the varying structure and circumstances encountered at the site at which the garage door opener is to be installed. 
     Apart from the safety switches, which are necessary to control movement of the door when an object is encountered, it is also necessary to have controls which limit the movement of the garage door from between the fully raised and the fully closed positions. Because of the variations in door structures and the circumstances relating to the installation of the opener mechanism with its associated connections to the garage door, it is necessary that means be included in the limit switch mechanism to permit adjustment of the switching points so that they will be synchronized with the opened or closed position of the door. 
     In general the garage door switches have been complicated and difficult to install. The present invention involves a simple mechanism driven by the electric motor for the opener which has means for easily and simply adjusting the desired switch operating positions while leaving the limit switches themselves fixedly mounted with respect to their supporting frame. 
     2. Description of the Prior Art 
     The prior art includes a number of patents which disclose the broad idea of utilizing a motor driven threaded shaft with an axially translatable actuator to control other operations. Among this prior art is Fry U.S. Pat. No. 3,209,090, Hummel U.S. Pat. No. 1,788,302, and Hubers U.S. Pat. No. 1,457,367. The mechanisms disclosed in the above cited patents are relatively complex. The patent to Hubers discloses a split switch actuator which travels axially along a motor driven shaft and which may be repositioned by disengaging the switch actuator from the threaded shaft. Other prior art patents showing similar actuators travelling on motor driven shafts are Gibson et at. U.S. Pat. No. 2,504,018, Layer U.S. Pat. No. 4,838,403, and Layer et al. U.S. Pat. No. 4,721,196. These last cited patents disclose complex mechanisms for operating mechanical devices in general rather than switching applications of the kind herein involved. 
     SUMMARY OF THE INVENTION 
     The present invention provides a limit switch mechanism for use with a garage door opener which is driven by the door operating motor and includes a threaded shaft supporting one or more threaded switch actuators which are translated axially by rotation of the shaft. The switch actuators are restrained from rotating and guided in their translational movement by spring biased restraining means which is mounted for pivotal movement on a shaft parallel to the threaded shaft. The restraining means is formed with an edge which extends radially with respect to the threaded shaft and engages slots formed on the switch actuators. This engagement between the restraining means and the switch actuators prevents rotation of the actuators so that rotation of the threaded shaft causes the actuators to move axially thereon into engagement with the control means on one or more limit switches mounted in proximity to the threaded shaft. When it is desirable to adjust the point at which the limit switches will be actuated, the restraining means is simply pivoted out of engagement with the switch actuators and the actuators may be rotated to re-position them with respect to the threaded shaft. This provides a simple mechanism which may be mounted with the garage door opener and easily adjusted following the installation of the garage door opener. 
     Accordingly, it is an object of the present invention to provide a limit switch mechanism which is easily adjustable to control the operation of an electric motor over a selected range of movement. 
     It is a further object of the present invention to provide an improved limit switch mechanism including a motor driven threaded shaft having one or more switch actuator nuts mounted thereon selectively engageable by means for restraining rotary motion of said actuator nuts while they are translated axially on the threaded shaft. 
     Another object of the present invention is to provide improved limit switch mechanism for controlling two limit switches associated with a motor circuit using a motor driven threaded shaft having two switch actuating nuts which are moveable into and out of switch operating position as such actuator nuts are translated axially along the shaft while such nuts are being restrained from rotation by selectively engageable means. 
     Other objects and advantages of the present invention will be readily apparent from the following description of the various embodiments thereof taken in conjunction with the accompanying drawings: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plane view of a limit switch mechanism for a garage door opener embodying the invention; 
     FIG. 2 is a fragmentary sectional view taken on line 2--2 of FIG. 1; 
     FIG. 3 is a fragmentary enlarged perspective view of a portion of the limit switch mechanism of FIG. 1; 
     FIG. 4 is a schematic showing of a garage door opener including the limit switch mechanism of FIGS. 1-3; 
     FIG. 5 is an exploded perspective of an alternative embodiment of the invention; 
     FIG. 6 is an enlarged fragmentary elevational view of a portion of a limit switch mechanism of the embodiment shown in FIG. 5; and 
     FIG. 7 is a schematic diagram of a typical garage door opener circuit in which the limit switch mechanism of the instant invention is employed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, there is shown in FIG. 1 a limit switch mechanism which is designated generally by the reference numeral 10. The limit switch mechanism 10 includes a frame 12 having a bottom portion 12a and sidewalls 12b. Mounted on the bottom portion 12a are various electrical components including a transformer 14 and a capacitor 16, whichwill be discussed in greater detail in connection with the schematic diagram of FIG. 7 showing the operating circuit for a reversible drive motor 18. The motor 18 is drivingly connected to open a garage door 20, asshown in FIG. 4. The motor 18 has an output shaft 18a which drives a seriesof endless link chains designated generally by reference numeral 21. The motor 18 and the interconnecting link chains 21 provide a relatively low speed drive to an endless link chain 22 which is connected to a lever arm 24 to raise and lower the garage door 20 as the endless chain 22 is moved in one direction or the other. The specific arrangement of the motor 18 and the interconnecting means to raise and lower the garage door 20 form no part of the present invention, it being understood that the limit switch mechanism 10 of the present invention would be applicable to any type of motor operated garage door opener, whether employing a chain or worm type of drive or some other mechanism. 
     As shown in FIG. 4, the frame 12 is mounted adjacent to the motor 18 on a drive unit support 19, and there is provided an endless chain 26 which drives a shaft 28, which is a part of the limit switch mechanism 10. The chain 26 is driven from the output of the link chains 21, which also drives the chain 22. 
     Referring to FIG. 1, the shaft 28, which is driven by chain 26, is shown extending through the sidewalls 12b of the frame 12. Journal bearings 30 are provided in the sidewalls 12b to mount the shaft 28 for rotation. The shaft 28 includes unthreaded end portions 28a and a threaded central portion 28b. Received on the threaded portion 28b are switch actuators 32 and 34 which are substantially identical in size and shape, having centralhub portions 32a and 34a, respectively, which support peripheral portions 32b and 34b, respectively. The peripheral portions 32b and 34b are formed with radially extending slots 32c and 34c. 
     Mounted on the bottom portion 12a of the frame 12 adjacent the shaft 28 arelimit switches 36, 38, 40 and 42. The limit switches 36, 38, 40 and 42 are provided respectively with flexible control levers 36a, 38a, 40a and 42a, which actuate their respective limit switches in a manner known in the artwhen deflected. The control levers are positioned in the path of the switchactuators 32 and 43. 
     In order for the switch actuators 32 and 34 to engage the various switch control levers 36a, 38a, 40a and 42a at a selected point in time with respect to the travel of the endless chain 22, it is necessary to provide means for adjusting the point at which the switch actuators 32 and 34 engage the switch control levers. This adjustment is accomplished by rotating the switch actuators 32 and 34 with respect to the shaft 28, to move the switch actuators 32 and 34 axially along the shaft 28. Once the switch actuators 32 and 34 have been adjusted to the proper positions, it is necessary to provide means for limiting the rotation of the switch actuators 32 and 43 with respect to the shaft 28. This function of limiting the rotation of the actuators 32 and 34 is accomplished by a latch means 46 which includes a pivotally mounted plate 48 and a torsion spring 52 by a second shaft 50. This plate 48 includes a switch actuator restraining means or edge 48a  which is disposed along one edge of the plate 48 and extends generally radially with respect to the shaft 28, as best shown in FIG. 2. The restraining portion or edge 48a engages in one of the slots 32c and 34 c, to perform the function of restraining the switch actuators 32 and 34 from rotating with respect to the shaft 28. Theshaft 50 is supported in aligned openings in the sidewalls 12a of the frame 
     The plate 48 is formed along the edge remote from the restraining portion 48a with a tubular portion 48b which receives the shaft 50 and mounts the plate 48 for pivotal movement about the axis of shaft 50 which extends parallel to the axis of the shaft 28. 
     As best shown in FIG. 1, the torsion spring 52 is formed with a coiled portion 52a received on the shaft 50 and with ends 52b and 52c. End 52c engages the frame 12 and the end 52b extends beneath the plate 48, with the spring being tensioned to bias the plate 48 in a counterclockwise direction as seen in FIG. 2. Thus, the restraining portion 48a of the latch means 46 is normally biased into engagement with the switch actuators 32 and 34 to restrain relative rotation with respect to the shaft 28. If and when it becomes necessary to adjust the location of the switch actuators 32 and 34, the plate 48 is simply rotated clockwise by manual finger pressure from the position shown in FIG. 2 until the restraining portion 48a is disengaged from the slots 32c and 34c. After the adjustment has been accomplished, the plate 48 is allowed to return toits position with the restraining portion 48a engaged with the slots 32c and 34c. 
     With respect to the embodiment of FIGS. 1-3, it is noted that the four limit switches 36, 38, 40 and 42 are fixedly mounted on the bottom portion12a of the frame 12 by posts 43, which extend through clearance openings inthe plate 48. The switches 36 and 40 are the limit switches for the open and closed positions of the door 20. The switches 38 and 42 are typically used to disable the reversing function as the garage door 20 approaches the positions in which it is to remain open or closed until a further control signal is received. In many applications there is no need to adjust the relative positions of switch 38 with respect to switch 36 or switch 42 with respect to switch 40. Thus, in the embodiment of FIGS. 1-3 it is sufficient to adjust the switch actuators 32 and 34 with respect to limit switches 36 and 40 to set the proper door open and closed positions. 
     Referring now to the embodiment of FIGS. 4 and 5, there is shown a limit switch mechanism 60 which is generally similar to the embodiment of FIGS. 1-3, but includes some variations in the configuration of the latch and inthe mounting of the various limit switches. The limit switch mechanism 60 includes a threaded shaft 62 which corresponds in function to the shaft 28described in connection with the embodiment of FIGS. 1-3. Similarly, the limit switch mechanism 60 includes switch actuators 64 and 66 which correspond identically to the switch actuators 32 and 34 of the first embodiment. The threaded shaft 62 is mounted in a frame 68 having sidewalls 68a, in which journal bearings 70 are received to support threaded shaft 62 for rotation. A sprocket 72, keyed to the shaft 62, is driven by the above-described endless chain 26, which in turn is driven bythe motor 18. Although not shown, a similar drive sprocket would be utilized to drive shaft 28 by chain 26. 
     In the embodiment of FIGS. 1-3, the four limit switches 36, 38, 40 and 42 were fixedly mounted with respect to the frame 12. In the embodiment of FIGS. 4 and 5, two of the limit switches are fixedly mounted, whereas two are adjustably mounted with respect to the frame 68. More specifically, the limit switch mechanism 60 includes fixedly mounted limit switches 74 and 76, and adjustably mounted limit switches 78 and 80. The limit switches 74 and 76 include control levers 74a and 76a and are supported byelongated posts 82. Elongated bolts 84 extend through the limit switches 74and 76 and posts 82 into threaded engagement with the frame 68, to fixedly secure the switches 74 and 76 thereon. 
     The limit switches 78 and 80 are mounted on a transversely extending bracket 85 which is secured at its ends to the opposed walls 68a of the frame 68. As is best shown in FIG. 4, the bracket 85 is provided with slots 85a and 85b, through which assembly bolts 87 extend to secure the switches 78 and 80 with respect to the frame 68. The elongated slots 85a and 85b permit the limit switches 78 and 80 to be selectively positioned lengthwise of the shaft 62 and bracket 85 to adjust the relative positionsat which the switches 78 and 80 will be actuated. 
     In order to restrain the switch actuators 64 and 66 from rotating with respect to the threaded shaft 62, there is provided a latch means 86 whichperforms the same function as the latch means 46 described in connection with the embodiment of FIGS. 1-3. The latch means 86 includes a plate 88, which is mounted for pivotal movement on a shaft 90, and is biased into engagement with the switch actuators 64 and 66 by means of a torsion spring 92. The plate 88 is formed of extruded metal and includes, along one edge thereof, a cylindrical portion 88a which receives the shaft 90. The edge of the plate 88 remote from the cylindrical portion 88a is formedwith a manual actuating portion 88b. As is best shown in FIG. 5, the manualactuating portion 88b extends outwardly beyond the threaded shaft 62, permitting the operator or installer of the limit switch mechanism to apply a manual force downwardly on the plate 88 to disengage it from the switch actuators 64 and 66. 
     The plate 88 is formed intermediate the manual actuating portion 88b and the cylindrical bearing portion 88a with a restraining portion or edge 88c, which is adapted to insert into the slots in the switch actuators 64 and 66 in the same manner as the plate 48 engages the switch actuators 32 and 34 in connection with the embodiment of FIGS. 1-3. The torsion spring 92 is of similar configuration and function as the spring 52 described in the earlier embodiment. 
     Referring to the schematic circuit diagram of FIG. 7, there is shown the control circuit for a garage door opener which is typical of known prior art control circuits. The circuit itself forms no part of the present invention, the present invention being concerned solely with the limit switch mechanism which is mechanically driven by the motor 18, and which controls the electrical power to the motor. Typically, such a circuit includes a high voltage motor circuit 94 and a low voltage control circuit96 which is powered through a step-down transformer 14. The limit switches 36, 38, 40 and 42 are connected to a radio control circuit element 98 and relays 100 and 102 in the manner shown. The relay 100 includes a coil 100awhich cooperates switch contacts 100b by moving an armature 100c, while therelay 102 includes an operating coil 102a and switch contacts 102b operatedby moving an armature 102c. The limit switch 36 is opened by switch actuator 32 to de-energize the relay 100 and open the circuit to the winding of motor 18, causing the door 20 to stop in the open position. Theswitch 38 is operated prior to the switch 36 to prevent reversal of the motor 18 as the door approaches the open position. The limit switch 40 is actuated by the switch actuator 34 to de-energize the relay 102 and open the circuit to the winding of motor 18, causing the door 20 to stop in thefully closed position. The limit switch 42 is operated prior to the switch 40 to prevent reversal of the motor 18 as the door approaches the closed position. The circuit 96 also includes a manually operable switch having sets of switch contacts 104 for initiating opening of the door 20 and switch contacts 106 for initiating closing of the door 20. 
     It should be appreciated that the limit switch mechanism 10 or the alternative embodiment limit switch mechanism 60 provides complete flexibility in the adjustment of the time of actuation of the limit switches in synchronism with the opening and closing of the door 20 by themotor 18. The switch actuators of the limit switch mechanism are easily adjusted when the door 20 is in the open or closed position by disengagingthe latch means from the switch actuators and rotating them to reposition them axially on the threaded shaft to the switch actuating position. Such adjustment of the switch actuation positions may be accomplished by the unskilled non-professional who is often installing a garage door opener inhis own garage. It is sufficiently simple that no detailed instruction or special tools are required.

Summary:
An adjustable limit switch mechanism for controlling the operation of an electric motor of a garage door opener over a selected range of movement including a motor driven threaded shaft supporting at least one switch actuator which is adjustably positionable and restrained from rotary movement while being axially translated by rotation of the shaft. A limit switch is mounted adjacent the threaded shaft so as to be actuated as the switch actuator is translated axially on the shaft.