CA1053272A - Door operator with instant reverse feature - Google Patents

Abstract

A B S T R A C T
An improved garage door operator of the motor-driven chain-and-sprocket type comprising a molded plastic gear case assembly supporting an output shaft for rotation relative thereto. A molded plastic worm wheel is loosely disposed on the shaft for limited rotation relative thereto and is driven by a reversible electric motor through a worm. Up and down limits are established by means of a small threaded shaft which is driven off of the worm wheel and which procuces linear displacement of a limit switch actuator traveler. The traveler carries adjustable dogs which operate res-pective limit switches in a limit switch carrier which is mounted on the gear case.

Description

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This is a division of co-pending ~anadian Patent Application NoO
247,286 filed March 8th, 19760 This invention relates to power operators for garage doors and the like.
BACKGROUND OF THE INVENTION
Power operators for garage doors and the like generally comprise reversible electric motors connected to the garage door by means of a chain and pulley arrangement and provided with suitable controls to stop the motor at predefined limits of door travelO The typical operator comprises a case made out of stamped metal parts which are fastened together with machine screws, nuts and bolts, and the like, a small electric motor, a speed reducer, some kind of clutch, and a chain and sprocket or pulley drive system.
In one prior art system shown in United States Patent No.

2,672,582 the drive motor is caused to be shut-off at theup and down limits of door travel by sensing the fact that the door encounters a mechanical - obstacle; eOg., the floor of the garage or the top limit of the door carriage.
Motor shut-off is accomplished by means of a camming clutch arrangement on the motor output shaft which shifts a collar axially along the output shaft to trip a shut-off switch. More specifically, this is provided by means of a pair of collars having a ramp-like meshing combination of cam surfaces, one collar being fixed on the output shaft and the other being loosely disposed on the output shatO When the door encounters a mechanical obstacle, the motor continues to rotate the fixed collar, but the loose collar which is connected to the door begins to slip and the cams cause an axial shift of one collar relative to the other. When the free collar slides away from the fixed collar, a switch is thrown to stop the motorO
There are a number of disadvantages ~o this prior art system in-j .
;, cluding the fact that the clutch arrangement is operative for every half cycle of door travel and thus must be of extremely durable construction to avoid deterioration in an unacceptably short time~ Even with a durable -1- ~, ~, :~

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clutch, the operation of stopping the door by running it against a mechanical stop at ful 1 speed is bound to produce a good deal of wear on the door, the motor, and the various other components of the operatorO Perhaps most importantly is the fact that such a device has the capability of trapping a small child under the door until help arrives to restart the motor in the opposite direction. Finally, the prior art system described above fails to provide for the adjustment of the limit stopsO
A more practicable approach to the provision of limit stops is disclosed in Patent No. 2,951,920~ The system disclosed in that patent pro-vides for a small threaded shaft which is rotated in synchronism with the drive shaft of the operator and which is further provided with a pair of traveler nuts which are held against rotation and which thus travel linearly along the threaded shaft as the output shaft of the operator rotates. The system further comprises a pair of limit switches which are actuated by the fixed traveler nuts so as to stop the motor at each of adjustable up and down limits of travel. Thus the door is stopped by opening a motor control switch and not by running the door against a mechanical stop.
In addition, the feature of obstacle detection is best provided by means for causing an instant reversal of the direction of motor shaft rotation such that the motor does not merely stop, but actually backs away from the obstacle. This approach however, calls for a mechanism to disarm the instant reverse just before the door reaches bottom so that the ordinary closing function can not produce a reversalO
The invention of the disclosure herein relates to systems of the second type described above; io eO ~ a garage door operator of the type pro-viding adjustable limits along with an obstacle detector of the instant ' reverse type~
The invention provides in a garage door operator for powering a door between up and down limits, means for defining said limits and compris-ing: an operator body, a threaded shaft mounted on the body for rotation ,~

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relative thereto, means for driving the shaft according to the rotation of a power output shaft, a traveler slide on the body, a traveler member dis-posed on the slide for linear displacement and engaging said shaft whereby said linear displacement is related to rotation of said shaft, adjustable dog means carried on said traveler, and a carrier member mounted on the body adjacent said traveler slide and carrying limit switches to be actuated by . the dogs at selected linear positions of said travelerO
. As will be hereinafter described in greater detail the preferred embodiment of the invention comprises a number of components which are most ~ 10 advantageously constructed of molded plastic materialO For example, the .
preferred embodimnnt comprises a molded plastic gear case which provides support for a main drive shaft, a small threaded shaft which is involved in the limit stop assembly, and various other parts including limit switch carrier and limit switch actuator elementsO
Although the invention is described herein as being embodied in ` an operator having a chain and sprocket drive system it is equally applicable ~1 .
in many respects to screw drive operator systems; iOeO, those systems where the operator and the door are interconnected by an elongated screw shaft, ' the traveler for which comprises a fixed nut which is mechanically connected :f 20 to the door.

I The invention will further be described, by way of example only, .~ with reference to the accompanying drawings, wherein:-;i Figure 1 is a side view of a typical garage door power operator ~i installation;

~ Figure 2 is a side view, partly in section, of an operator embody-, ing the novel inventive features set forth herein;

Figure 3 is a side view, partly in section, of the drive train details of the operator of Figure 2 in the axially shifted configuration; ~

Figure 4 is a sectional view along section line 4-4 of Figure 3; ~ .

Figure 5 is a sectional view along section line 5-5 of Figure 3; ~
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Figure 6 is a perspective view of a limit switch carrier used in the assembly of Figure 2;
Figure 7 is a detailed view of a typical limit switch installation assembly;
Pigure 8 is a perspective view of a limit switch actuator dog and traveler assembly;

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FIGURE 9 is an exploded view of the operator of FIGURE 2 showing each of the various components of the oper-ator in a partially disassembled state;
- EIGURE 10 is a schematic diagram of the motor control circuit;
FIGURE 11 is a side view of a modification of the structure of FIGURE 2 having a manual operation feature; and, FIGURE 1~ is a plan view of a rolling curtain door having the operator of FIGURE 11 attached thereto.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODI~ENT
A. Power Drive and Instant Reverse FIGURE 1 shows a typical power garage door operator installation to comprise the power operator 10 suspended from a garage ceiling joist 12 and connected to a pivotal overhead door 14 by way of a drive chain 16. The door is typically ` mounted in a carriage having up and down limits of travel and is shown in the downlimit of travel wherein the bottom edge of the door is adjacent the garage floor (not shown). Chain 16 is engaged around sprocket 20 at the operator end, such 20 sprocket being mounted on the end of output shaft 18 driven by -. 7 a motor within the housing of operator 10. The other end of ~ chain 16 is engaged with an idler sprocket 22 on rail 24, the ¦ chain 16 being connected into a closed loop either by chain links or by a length of substantially inextensible cable.
! 25 To produce movement of the door 14 corresponding to movement of the chain 16, a linkage 26 connects the door 14 to a traveler unit 18 which is slidably mounted on the fixed rail 24 extending between the operator 10 and a point immediately adjacent and above the door opening as shown.
, 30 The traveler 28 is mechanically interconnected with the chain '~ - 5-- , .

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16 by means of a latch 30 such that traveler 28 moves back-and-forth in a shuttle~ e ~attern as the operator 10 is actuated in respective half cycles of operation.
FIGURES 2 through 9 illustrate details of the inter-nal mechanism of the operator 10, it being understood that thepoints of novelty in the subject invention lie in the improved construction of the operator 10 rather than in the overall assembly as has been described with reference to FIGURE 1.
Moreover, the invention is not dependent upon the specific nature of the drive system or the components thereof such as chain 16, the rail 24, the traveler 28, the linkase 26, the door 14, or any combination of these devices.
The device of FIGURES 2 through 9 comprises a motor drive operator 10 in which many of the major components, the counterparts of which have heretofore been manufactured from stamped metal, are most expeditiously fabricated from molded plastic. This construction offers considerable reduction in weight, ease of assembly, economy, long life and generally - improved operation and user satisfaction. In general, the oper-ator to be described is of the type comprising a rotatable out-put shaft 18 driven by a motor 50 to raise and lower the door 14 between open and closed limits of travel. It is to be understood that the terms "open", "closed", "up" and "down"
are arbitrarily chosen because of the specific embodiment disclosed. However, the term is not intended to limit the applicability of the invention, as sliding doors, gates and various other types of movable appliances may be equally amen-able to the application of the subject device. In addition, the operator 10 hereinafter described provides means for adjusting the up-and-down limits of travel and additional means '~ . .~., '~. , ' ' ' ' ' ' ' v~c~ 1053i~7Z
for sensing the fact that the door has cncountere~ an obstacle beyond which it cannot continue and from which it is necessary to reverse the direction of the door on a substantially in-staneous basis.
Looking to FIGURES 2 and 9 operator lO comprises a molded plastic body comprising an upper gear case 32 and a lower gear case 34 of complemental configuration and being joined with the upper gear case unit 32 by suitable fasteners such as small screws. The assembled gear case 32, 34 comprises and defines a normally vertically oriented cylindrical cavity 36 defining integrally molded bearing surfaces and extending ; through the gear case to support the output shaft 18 for rota-tion therein. The shaft 18 is of steel construction and extends above the gear case body to receive the sprocket 20 as shown, and below the gear case body to an adjustment knob 37 the function of which will be hereinafter described. The upper gear case 32 is molded to define a thrust bearing surface 38 .'1 .
which flares outwardly from the inner diameter of the cavity 36 to the wall 40 of a coaxial receptacle 40 which is of increased diameter. Disposed within the two-part interior ' volume of cavities 36 and 40 is a molded plastic worm wheel ~ 42 comprising a wheel portion having peripheral gear teeth 44 -~ and a hollow shaft portion 45 which terminates at the upper extremity thereof in a drive pinion 46 for purposes to be described. Peripheral teeth 44 of wheel 42 mesh with a worm 47 which is disposed within another interior volume 48 of the gear case 32, 34 also having axially spaced, molded-in bearing surfaces 51 and 53. Worm 47 is mounted for rotation with the output shaft 49 of the drive motor 50. Worm 47 is keyed onto the motor output shaft 49 in the conventional fashion. Accord-ingly, when motor 50 is actuated, worm gear 47 rotates and , , : - .

produces corresponding rotation of wheel 42.
A split ring bearing collar 66 is preferably dis-posed about the shaft portion 45 of wheel 42 t~ reside between the wheel 42 and the upper gear case 32 to provide a self-lubricating highly efficient bearing. The fact that the ring66 is split eliminates the need for a high precision injection molding operation.
Looking to FIGURE 4, the sectional view through the wheel 42, it can be seen that shaft 18 is provided along the lower length thereof with diametrically opposite flats 52 and the interior of the wheel 42, while generally of a cylindrical bore, is provided with radially inwardly projecting nibs 54.
In addition, the wheel 42 is loosely (non-drivingly) disposed about the shaft 18 such that there is typically no direct driving connection between wheel 42 and shaft 18, but rather an indirect connection via a molded plastic cam wheel 62 which is fixed on shaft 18 for movement therewith rotationally and free to move on the shaft axially~ The low-torque coupling - between wheel 42 and wheel 62 provides not only drive power, but a component of an instant-reverse system is hereinafter described.
Since the wheel 42 is loosely disposed about shaft 18, it is not the primary drive connection between the output shaft 49 of motor 50 and the output shaft 18 of the operator.
To provide this drive connection a low torque coupling is provided in the form of a first axially facing cam surface 56 formed integrally with the wheel 42 and comprising a continuous alternating configuration of lobes and troughs.
A second cam surface 58 is provided on the cylindrical portion 60 of the cam wheel 62 which is radially fixedly disposed on ., ~
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the lower end of the shaft 18 to rotate therewith under all conditions. The cam surface 58 on cam element 62 is also characterized by a continuous alternating combination of lobes and troughs and thus meshes complementally with the cam surface 56 on wheel 42 to provide a torque coupling which operates in a non-slip mode for all torques below a predetermined value;
i.e., value which is sufficient to move the aoor in the absence of an obstacle such as an automobile or a human body in the path of the door. However, the torque coupling provided by tne meshing cam surfaces 56 and 58 is insufficient to stall the motor 50, in the face of an obstacle, but rather causes realtive slip to occur between th~ motor driven wheel 42 and the cam wheel 60 which is secured on the shaft 18. The nibs 54 limit such slip to about 75.
FIGURE 2 shows the two cam elements under ordinary ` no-slip conditions while FIGURE 3 shows the cam elements 42 and 62 after considerable slip has occurred. It will be , apparent that the ramp-like configuration of the undulating i cam surfaces has caused the cam 62 to move axially away from 20 the gear case body 32, 34. Wheel 42 provides reaction force by pushing against the thrust bearing surface 38 previously , described. The cam surfaces 56 and 58 are normally urged into the meshing non-slip configuration by a coil spring 64 which is disposed between the bottom surface of cam wheel 62 and the adjustment knob 11.
, Summarizing the drive system as it has been thus J far described, reversible motor 50 drives worm wheel 42 by way of worm 47 meshing with peripheral teeth 44. As worm wheel 42 rotates within the gear case body 32, 34, torque is 30 coupled to the cam wheel 62 by way of the cam surfaces 56 and , t : 1 : 9 J
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i8, drivin~ shaft 18. Rotation of output shaft lB produces linear di~placement of the chain 16 and the traveler 28 which is mechanically connected to the door.
This description of operation of course assumes that the door 14 is free to move. If an obstacle prevents the door 14 from moving, shaft 18 is held fixed whereupon motor 50 continues to drive wheel 42 causing the cam surfaces 56 and 58 to slip relative to one another as shown in FIGUR2 3. Slip between the cam surfaces causes an axial shifting of cam member 62 and reversal of motor 50 as hereinafter described.
The axial shift of the cam element 62 on the shaft 18 triggers an "instant reverse" operation which prevents the door from continuing to bear against an obstacle such as a human being. To accomplish this a limit switch 68 is mounted 15 on the gear case 32, 34 with the actuator arm 70 thereof disposed against the annular collar 72 on the external surface of the cam wheel 62. The first quarter-inch or less of axial shift closes the limit switch 68 triggering the instantaneous reversal of motor 50 by means of the circuit illustrated in FIGURE 10.
This circuit is well known by way of s~rior art ~ devices and includes the instant reverse feature as well as -~ the limit switches 84 for stopping the motor 50 at the opposite limits of travel Thus, the axial shift of the cam wheel 62 signifies an overload condition caused by the door 14 encountering an obstacle. The result is to instantly reverse the direction of motor 50 to cause the door 14 to back away from the obstacle and prevent serious injury to persons or things which may be caught under the door.
As is also shown in FIGURES 2 and 3, the slope :, :

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of the cam lobes is not uniform or symmetrical relaLive to a centerline of a given lo~e but is steeper on the side which provides the reaction force while raising the door.
The result is a non-uniform or non-symmetrical torque coupling capability such that a lesser torque causes the slip condition while lowering the door and a higher torque causes the slip condition while raising tne door. The reason for this asym-metrical torque coupling capability is that raising the door require moving the door against its own weight and, moreover, it is far less likely that tne door will encounter an obstacle when being raised than when being lowered.
s. Limit Switch Apparatus The balance of the disclosure is directed toward the apparatus involved in establishing and adjusting the up and down limits of door travel.
As shown in FIGURES 2 and 9, gear case body 32, 34 provides a second hollow cylindrical cavity 70 with inte-;~ gral bearing holes to accommodate and support for rotation within the gear case a small threaded shaft 72 having a molded ., ~
plastic gear 74 secured to the upper end thereof for rotation i therewith. When disposed within the gear case 32, 34 in the manner shown in FIGURE 2, plastic gear 74 is coupled with the gear 46 formed on the upper end of the worm wheel 42 by means of an idler gear 76 which is carried between ~ertically spaced plastic panels providing integral, molded bearings on theupper end of the gear case 32 adjacent the shaft 18. Thus, the worm wheel 42 operates as the direct drive instrumentality to the threaded shaft 72 such that the shaft 72 rotates with the output shaft 49 of motor 50. In the preferred form the axis of shaft 72 is parallel and closely adjacent the axis of .~ .
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shaft 18 such that a sinyle idler gear interconnection may be emp]oyed.
Upper gear case element 32 has formed thereon adjacent the cavity 70 for shaft 72 a pair of spaced parallel mounting surfaces 78 which are grooved to precisely receive and locate the flanged mounting surfaces 80 of a limit switch carrier body 82 which is preferably molded of a suitable high-impact plastic material. Carrier body 82 is fastened to the gear case 32 by means of machine screws and houses in three parallel columns, a plurality of limit switches 84 which provide the various motor control function characteristics of a power garage door operator as is more fully described with reference to FIGURE 10. These include limit switches for stopping the motor 50 at the up and down limits o travel and various other switches for auxiliary functions such as turning lights on and offO When mounted in the carrier body 82 the limit switches 84 are fixed in position relative to the gear ~ case body 32, 34 where they may be actuated by a traveler ; assembly mounted on the shaft 72.
To operate the limit switches 84 a limit switch actuator traveler 86 having an integral molded plastic partial nut 88 is slidably mounted on the gear case 32 between the mounting surfaces 78 and threadedly engaging the shaft 72 as best shown in FIGURE 8. Flanges 89 bear against the gear case 32 to prevent traveler 86 from rotating witn the shaft sucn that rotation of the shaft 72 causes the slidable traveler 86 to move up and down the gear case body along an axis which 1 is parallel to the axis of shaft 72. Traveler 86 carries in '~1 adjustable relationship thereto molded plastic plates 91 and 90 having dogs 92, 94, 96 and 98 projecting toward the limit V~IC-12o lOS~7'~
switch banks to actuate the switches 84 at various lin~ar positions of ~raveler 86. Dog plate 91 is vertically adjustable relative to the traveler body 86 by means of adjustment screw 100 and dog plate 90 is similarly adjustable by means of screw 102. Both screws 100 and 102 pass through two axially spaced ribs in traveler 86 ana are locked in place by a flared flange on the shaft of each screw and a push nut 108 which is forced over the screw shaft end. The : threaded shaft is thus exposed between the ribs to receive the snap-on molded plastic partial nuts 104 and 106 of the dog plates as shown in FIGURE 9. Rotation of screw 100, for example, causes the dog plate 91 which is threadedly engaged with the threaded shank of the screw 100 to move up or down :
. thus to adjust the exact position of the traveler 86 along ` 15 shaft 72 at which actuation of one of the limit switches 84 is desired. Rotation of screw 102 produces a similar adjust-ment relative to dog plate 90. As shown in FIGURE 9 the nut portions 104 and 106 of the dog plates 91 and 90, respectively, are again partial such that they may be snapped on to the ~ 20 screws 100 and 102 during assembly.
il Because the dogs 92, 94, 96 and 98 on the dog plates 91 and 90 project toward the actuator elements of . the conventional limit switches 84, rotation of the shaft 72 produces linear displacement of the traveler 86 and J~
consequent operation of the limit switches at various oosi-tions of the door 14. In other wordq, as motor 50 rotates output shaft 18 through the aforementioned torque coupling comprising worm wheel 42 and cam wheel 62, it also rotates ~ shaft 72 through the gear drive comprising gears 46, 76, 74.
1~ 30 Thus, once calibrated, position of traveler 86 on shaft 72 is l~ -13-1: .
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~~ a mechanical analogy of and is proportional to the actual position of the door 14 between its limits of travel. Accord-ingly, a first limit switch may be established to stop the motor 50 at the down limit of travel and dog 98 may be employed to operate the stop feature actuator which in turn operates the down limit switch. Similarly dog 92 may be employed to operate the up limit switch which is disposed two columns over from the down limit switch in the limit switch carrier body 82 as previously described. The other limit switches are employed to turn the garage light on and off according to whether the door is opened or closed and to disarm the instant reverse feature just before the door reaches the bottom limit of travel.
Since each of the dog plates ~0 and 91 is independently adjust-able on the traveler body 86 an infinite number of up and down limits may be provided thus to adapt the subject operator to substantially any commonly encountered installation situation.
Since the shaft 72 is driven from the wheel 42 rather than directly from shaft 18, it is necessary to prevent a loss of synchronism between the actual position of the door ~ -14 and the rotational position of shaft 72 which represents door position. This is accomplished by means of the flats 52 on the shaft 18 and the nibs 54 on interior surface of the wheel 42 as previously described with reference to FIGURE 5.
In other words, the cam surfaces 56, 58 cannot travel over center and produce a continued rotation of shaft 72 even though , the door is actually stopped. Should this be allowed to occur it would be necessary to recalibrate the limit switch actuation assembly every time an obstacle of some type affected the operation of the door. It is of course possible to drive the shaft 72 directly from the shaft 18 thus to make the loss of .

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synchronism impossible but this req~ires a separate drive gear and some method of attaching it to the shaft.
Looking specifically to the limit switch carrier 82 as best shown in FIGURES 6 and 7 it can be seen that interior dividers 110 are provided for defining three parallel columns of receptacles for limit switches 84. Moreover, internally and integrally molded horizontal dividers 112 are placed in strategic locations ~o interfere with the actuator buttons and extender arms of the limit switches thus to prevent the switches from being inserted backwards or upside down as well as to prevent a limit switch of one type from being erroneously lnserted into the receptacle which is designed for a limit switch of another type. For example, the tab 112A positively prevents a limit switch having-an extender arm of the type shown at 84d from being inserted into the location for switch , 84c. The same tab 112A would interfere with the terminal of the switch 84c if an attempt were made to insert it backward.
Obviously the internal interfering divider configuration may be varied in accordance with the particular type of limit switch employed; the configuration shown in FIGURE 6 is designed to work with "Unimax" limit switches, Models 2 TM-4-W and having the specific actuator button and extender arm configuration shown. In the configuration of FIGURE 6, switch 84a is the down limit switch, switch 84b is the safety disarm switch, switch 84c is the up limit switch, and switch 84d is the light-on/off switch. Again the specific locations are given by way of illustration and are not intended to limit the flexibility of design which might be employed consistent with ~; the various implementations of the invention which are possible.
Looking to FIGURE 10, input terminals are connected .

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across a conventional household wiring outlet to provide po~er to the reversible P.S.C. (Permenant Split Capacitor) motor 50.
The input terminals are connected by the primary coil 130 of a small transformer; secondary coil 132 is connected in series with the coil of a bistable ratchet relay 134 and a spring biased manually actuable pushbutton 136. Pressing button 136 causes a surge of current throùgh relay 134 toggling two-position armature 138 between contacts 140 and 142. When on contact 140, the armature 138 directs current from the supply through the down limit switch 84c and motor 50. A second input phase to motor 50 by way of capacitor 144 to produce rotation in a direction to drive the door toward the down limit.
The next current surge caused by depressing button 136 causes relay 134 to toggle armature to contact 142 to complete a circuit to motor 50 through the up limit switch 84a. The direction of motor rotation is then reversed by reason of shifting the capacitive supply phase from 90 lead- -, ing the line phase to 90 lagging the line phase. Direction of motor rotation is reversed each time armature 138 is l~ toggled. The actual energization of motor 50, however, ~ depends on the condition of the limit switches 84a and 84c.
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The limit switches 84a and 84c are of the normally ~i~ closed type; i.e., they form a closed circuit connection unless the actuators thereof are depressed by the dogs of the plates 90 and 91 as traveler 86 moves along shaft 72.

The relay 134 may be purchased from the Ingraham Industries Division of McGraw Edison, Briston, Conn., their model ~o.

C6909A. There are many other sources.

A still further feature of the invention comprises , ~ . .. .

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~ the small three-sided ~Iastic el~méllt 114 w~ich is jam-fit bett~een a s~ring tab 116 formed integrally with the carrier body 82 and the down limit switch 84a as best shown in FIGURE
6. Tlle plastic element 114 is operated by dogs 94 and 98, and serves as a "memory device" to hold the actuator button of the down limit switch 84a in the depressed condition after reaching the down limit even though the door has started back up. During upward travel of the door, a second operation of the radio control or push button control will therefore merely stop the motor 50 rather than producing the instant reverse function; i.e., armature 138 toggles but switch 34a remains open circuited. Moreover, a third operation of the push button control or radio control will restart the door in the up direc-tion by toggling armature 138 back to contact 142. This permits the door to be partially opened to allow animals to go into or out of the garage, to-allow a breeze to pass under the garage door, or for various other reasons.
Element 114 is moved away from the position depress-ing the switch actuator by dog 94 just before the door reaches the up limit.
It is to be understood that the subject invention may be implemented in various ways and that the foregoing descrip-tion is not to be construed in a limiting sense.
C. Operation In a typical operation, the door is raised by pressing button 136 to start motor50 in the circuit including the up limit switch 84c. Rotation of wheel 42 on snaft 18 rotates shaft 72 until dog 92 reaches the actuator button of the up limit switch 84a. When the dog presses the button, the motor circuit is broken. Another depression of button 136 ,~:
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`- toqgles armature 138 and res~arts motor 50 through down limit switch 84a. If no obstacle is encountered, the door travels normally until dog 98 opens the down limit switch 84c. If an obstacle is encountered, overload cam (second cam element) shifts axially due to the ramp effect of the cam surfaces 56, 58 and trips switch 68 to recycle relay 134 to instantly re-- verse the door.
D. Disconnect for Manual Operation FIGURE 11 discloses a modified form of the operator assembly of FIGURES 1 and 2 wherei~n a disconnect feature for manual operation is provided. The apparatus of FIGURE 11 is designed to prevent a loss of limit switch synchronism during manual rotation of shaft 18 such as occurs when the door to which sprocket 20 is connected is raised or lowered by hand.
The apparatus of FIGURE 11 comprises the same shaft 18 and sprocket 20 as in the previously described embodiment.
`I However, here the worm wheel 42a and the pinion 46a which drives the limit switch shaft are non-integral. Moreover, wheel 42a has a cylindrical interior surface so as to be fully rotatable about shaft 18. Pinion 46a is fixed to shaft 18 to rotate therewith at all times. Cam member 62 is fixed to rotate with shaft 18 but may slide along the shaft as herein-after described.
Entirely new to the apparatus of FIGURE 11 is a bracket 500 carrying two plastic cam blocks 501 and 502; bracket 500 is bràced against the gear case body 32 so that it may ; ~ move axially along shaft 18 but it cannot rotate. A second stamped steel member 503 carries identical cam blocks 504 and 505 which engage blocks 501 and 502 to form a variable length , i .
,;~; 30 spacer. The ramp-like teeth of the four cam blocks provide a ',' ~ ' ~ -18-,; . , ! ~ ' .
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- mechanical spacer of ma~imum length betwe~n cam member 62 and stop 506 when engaged, and a spacer of minimum length when disengaged.
In normal operation, the cam block teeth are engaged such that cams 56 and 58 of elements 42a and 62 are fully engaged to provide torque transfer from wheel 42a to shaft 18 via member 62. In this condition, one cannot manually turn shaft 18 by raising or lowering the door since the mechanical advantage of the operator gear set works against you. To pro-vide manual operation, cam blocks 501, 502, 504, and 505 are disengaged by rotating bracket 503 to reduce the spacer length - and disconnect cams 56 and 58. ~ow the shaft need not turn ~ wheel 42a and the door is easily moved. Pinion 46a moves with -i shaft 18 to maintain correlation between door position and limit switch operation. ~lote that the instant reverse is ; eliminated.
FIGURE 12 shows the application of an operator 600 having the features of FIGURE 11 to a rolling curtain door 607. In such an operation, a mechanical disconnect in the drive link between operator and door is not conveniently provided; hence, the apparatus of FIGURE 11 is used to provide a disconnect between the operator motor and drive shaft 18.
In FIGURE 12, operator 600 is mounted with shaf~ 18 horizontal; sprocket 20 is linked to door roller sprocket 604 , 1 25 via chain 602. Sprocket 604 is connected to shaft 605 which extends through a roller housing 606 which receives articu-l~ lated door 607 as it is rolled up. Bracket 503 is provided with radial ears for connection to a pull rope 608 to discon-nect the cam blocks as previously described.
FIGURE 12 is representative of but one of several ~:

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possible applications of the operator of -this invention and FIGURE 11 is representative of but one variation in construe-tion. Various othex applieations and structural variations will oeeur to skilled persons and, hence, the specifie des-eriptions herein are not to be construed as limiting in effect.

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS;

1. In a garage door operator for powering a door between up and down limits, means for defining said limits and comprising: an operator body, a threaded shaft mounted on the body for rotation relative thereto, means for driving the shaft according to the rotation of a power output shaft, a traveler slide on the body, a traveler member disposed on the slide for linear displacement and engaging said shaft whereby said linear displacement is related to rotation of said shaft, adjustable dog means carried on said traveler, and a carrier member mounted on the body adjacent said traveler slide and carrying limit switches to be actuated by the dogs at selected linear positions of said traveler.

2. Apparatus as defined in claim 1 wherein a said carrier member comprises support means for receiving limit switch bodies in discrete posi-tions, and means for preventing the insertion of limit switch bodies other than in said discrete portions.

3. Apparatus as defined in claim 2 wherein the traveler, dog means and carrier are constructed of molded plastic.

4. Apparatus as defined in claim 3 including a friction member wedged between one of the limit switches and the carrier and engaging the limit switch actuates for holding the switch in a given state, the dog means associated with said one limit switch comprising first and second spaced portions, one portion operating to push the friction member toward the limit switch actuator and the other portion operating to push the friction member away from the limit switch actuator at approximately the opposite limits of travel.

5. Apparatus as defined in claim 1 wherein the traveler comprises an open, partial nut portion which can be snapped onto said threaded shaft.

6. Apparatus as defined in claim 5 wherein said dog means comprises at least a second threaded shaft on the traveler and a separate dog plate having an open, partial nut portion snapped onto said second threaded shaft so that rotation of said second threaded shaft causes linear displacement between the plate and traveler.