US1810496A - Elevator door - Google Patents

Description

' R. S. PEELLE ELEVATOR DOOR June 16, 1931.

1926 4 Sheets-Sheet l Filed Dec.

-l/VVE/VTOR A ATTORNEY- R. S. PEELLE ELEVATOR DOOR- June 16, 1931,

Filed Deal 3, 1926 4 Sheets-Sheet 2 farm ATTORNEY;

June 16, 1931.

(R. s. PEELLE ELEVATOR DOOR 4 Sheets-Sheet 3 Filed Dec. 5, 1926 INVENTOR 5;; ATTORNEY,

R. s. PEEI LE ELEVATQR DOR June 16, 1931.

4 Sheets-Sheet 4 Filed Dec. 5, 1926 INVENTOR BY W M 1 ATTORNEY QZMXW anced doors in the shaft.

structure of such ClO01'S 1S mounted upon the Patented June 16, 1931 stars neianam s. PEELLE, or norms, New YORKqN. YyassIc-moa to.TH LEEELLE-QQM PANY, or snooza y'n; new Year, A coaroaarroner: YORK--" ELEVATOR noon Application filed December 3, 1926. Serial No. 152,362.

The invention relates to elevator doors, and more particularly to fullautomatic doors composed ofone or more section's/having movement in one direction for opening t the door and movement in the other direction for closing the door.

I The invention has particular applicability to doors of the telesooping'type which usuallv have two sections mounted uponoppo site guide rail structures each having parallel guides. With the actuation of such doors," which ordinarily have two sections only, the lower door section stops at the sill of a'door opening, and in the opening and i closing movement travels at twice the speed of the upper section. Such doors are commonly used under conditions where the avail'ablespacewithin an elevator shaft will not admit of the installation of counterbal- The guide rail wall of the elevator shaft upon the floorside. Under some conditions of use, instead of using two sections, a single panel is used, the dimensions of which are sufficient to completely close the door opening; Such panels have either a downward or an upward'sliding' movement.

in-the accompanying drawings, 1' have il-' lustrated the embodiment of the invention inconnection with both the telescoping type of doors and the single vertically movable panel type of doors.

.Doors' of the type above referred to are commonly used to close what'may be termed isolated door openings, such as the ground floor openings ofelevator' shafts or of build ings; 1n the upper floors of buildings,-counterbalanced or pass type counterbalanced 40 doors are commonly used, sincethere is usually space'for the installationof such doors in a shaft abovelthe ground fi'oor.- VVhi'le I have-referred to the use ofsuch doors in elevator shafts, it is obvious that they be used, in other connections, such as loading platform. openings, 'wharves or piers, churches, and in other connections where available space is a factor.

,The main objectof my present invention is'to provide doors ofthetype above-referred to, which will not only embody therein power operative means for imparting both opening and closing movement to the door, but an automatically actingmechanical limit stop'mecl'ianism includedlin this power actuated mechanism whicl'r will automatically stop the application of- .pow'erto thed'oors upon the completionvof either the opening c or, the closing movement thereof, irrespective ofa continuedactuation of the electric motor developing such power, Bysuch a construction, I not only secure ease in the movement of the door, but am enabled to provide a much simplified actuating mecha nism which is reliable in its operation and has remarkably low maintenance cost. The mechanism employed may also. be installed at a' relatively lower cost'than mecl'ianisms semi-automatic doors.

With the use of my invention indoors of the telescoping type, I am enabled to use a single. counterweight operative upon bothcommonly used in other types of full and.

the upperf and thelower section of the door but without interfering with the mechanicallimit stop movement, and without regardto the necessary differential i1itl'1e rateof travel of the flexible connectionsacted upon by the power mechanism and connected with both sections.

' The invention consists primarily in an-elevator'd'oor embodying" therein a vertically slidable panel, guides adj acent the opposite sides of a door opening, means upon. said panel co-operating withsaid guides, a counterweight, means V limiting the downward movement; of said counterweigl'it and saidpanel, flexible connections between xaidflc'ounr tel-weight; and said d'oor,,apinch groove pul-' ley about which said flexible connections'pass, a source of power, and operativeconnections between said source of power and; said puliley, whereby; the load of the doorand; said counterweight upon oppositefsides of said pull'y permits the applicationof power for eitherraising or lfowering thedoor, and'the relieving of said connections from the load of either said dooror said counterweight will prevent a further] application of'powelto thedoor; and in suchlot'her novel features;

of construction and combination of parts as are hereinafter set forth and described, and more particularly pointed out in the claims hereto appended.

Referring to the drawings,

Fig. 1 is a condensed view of a two-section telescoping elevator door embodying the invention;

Fig. 2 is a plan view thereof;

Fig. 3 is a perspective view showing the run of the flexible connections;

Fig. 4 is a detail horizontal section of one guide rail structure;

Fig. 5 is a cross-sectional view of the pinch groove pulley;

Fig. 6 is a condensed view of a single panel, upwardly movable door embodying the invention;

Fig. 7 is a plan view thereof; and p I Fig. 8 is a side .view thereof with the door in the opened position.

Like numerals refer to like parts throughout the several views In the embodiment of the invention, shown in Figs. 1 to 5 of the drawings, which discloses a telescoping type of door and a type having a much greater range of use than the single panel type, I have shown the wall of the building at 10, the sill of the door opening at 11, the lintel of the door opening at 12, and the side jambs at 13. As stated, this door opening may be in the wall of an elevator shaft or in any other location in a building.

Ordinarily upon the floor side of the wall and adjacent each jamb 13 is a guide rail structure consistingof vertically extending parallel guide rails 14 and 15 extending from adjacent the sill 11 to a height sufiicient to permitthe full opening of the door. There are various arrangements of rails now in use, any one of which may be employed.

Slidably mounted upon the guide rails 14 is an upper door section 16 having shoes 17 co-operating with said rails in a manner to bring this door section close to the wall of the shaft. (lo-operating with theguiderails 15 is a lower door section 18 having guide shoes 19 co-operating with said rails.

The rail structures substantially close the space upon opposite sides of the door, the upper door section substantially closes the space at the lintel of the door opening, and the lower door section engages the sill 11. which not only acts as means for stopping this section, but substantially closes the opening at this point; Any construction which will arrest downward movement of the upper door section 16 may be employed, it having been the common practice to employ hooks indicated in Fig.7 1 'ofthe drawingsat 20,-which cooperate with fittings 21 above the lintel of the door opening.

Aside from the fact that the invention is particularly applicable to large, heavy doors,

the detailed construction of the two sections of thedoor and the manner of mounting them is not diiferent from telescoping doors of the ordinary type.

It may be added that the doors illustrated in the drawings are approximately ten feet wide by fourteen feet high, and weigh be tween twelve and fifteen hundred pounds.

The door is provided with counterweighting means such as the hanging counterweights 22 and 23 in housings adjacent each guide rail structure, flexible connections 24 and 25 passing from said counterweights respectively to, and being connected with, the tops of the door section 16 and of the door section 18. In the embodiment of the invention shown, which is desirable by reason of its simplicity, the connections 24 consist. of a continuous cable, rope or other flexible means, one end of which is connected with the section 16 and the other end of which is connected with the section 18. At a point intermediate its ends, said connections 24 pass about a pulley 26 of the first class carried by the counterweight 22, and about parallel guide pulleys 27 and 28 for properly positioning said connections in relation to said pulley 26. Said connections also pass about parallel guide pulleys 29 and 30 for properly positioning them with relation to the door sections 16 and 18. V

Arranged in the length of the run of the connections 2 1 is a pinch pulley actuating mechanism, the arrangement of this mechanism being such as to cause the load of the doors to be applied to the connection at one side of the pulley, and the load of the counterweight to be applied to the connection at the other side of the pulley. Where two sections areto be actuated with a differential rate of travel, I employ in this mechanism two pinch groove pulleys 31 and 32, the diameter of one of which as 32 is greater than the diameter of the other pulley 31. In the form of the invention shown in the drawings, the pulley 31 is approximately one-half the diameter of the pulley 32, the construction of the sections 16 and 18 requiring the latter, which is actuated from the pulley 32to have twice the travel of the former, which is actuated from the pulley 31.

The connections 25 operate upon the other side of the sections 16 and 18 in the same manner as heretofore described with relation to the connections 24, the pulley upon the counterweight 23 being indicated at 33, the parallel guide pulleys positioning the connections 25 in relation tosaid pulley 33 being shown at 34 and 35, and the parallel guide pulleys for guiding the connections between the door sections being shown at 36 and 37. Mounted upon the same shaft 38 upon which the pinch groove pulleys 31 and 32 are mounted, are a pair of pinch groove pulleys 39 and 40 corresponding inarrangement and a release dimensions with the pulleys 31 and 32 and, having the function of imparting the same movement to' the side ofthe door with which the connections are connected, as is imparted to. the side of the door with. which the connections24are connected. To, secure this result, it is. necessary to. cross the flexible con nections 25,.intermediate the guide pulleys and pinch groove pulleys, as clearly shown in Fig. 3 of the drawings.

. The pinch groove pulleys 3'1 and 32] and 39. and 40 are driven from a motor 41 through any desired transmission mechanism 42, this motor 41 being a reversible source: of power.

With high doors, it is necessary to provide I clearancev fortheupward movement of both.

doorsections abovethelintel 12, which, in the formJofthe invention illustrated in the drawings, is done bymeans of a. slotor clearance way 43 formed in the floor above the opening closed by the door.

Referring to Figs (Ste, 8 of the drawings, I have here shown. an embodiment of the in,- vention employing but a 'single upwardly slidable panel. In this embodiment of the invention, this single panel. is. shown at 44, and co-operates with a door opening of the character heretofore described. With this construction, a single guide'rail 45 is used upon the wall ofthe shaft adjacent each jamb 13, the shoes 46 upon oppositeedges of the door section co-op'erating with this guide. A single counter-weight 47 is slidably mounted, in, a housing at one side-of the door'opening.

Extending-between. this counterweight and" the oppositesides of the doorpanel are flexible: connections 48, these connections having opposite ends connected with thetop of the door panel and passing at a pointintermo diat-e the ends; about a pulley 49 of the first class carried by the counterweight 47;. Said connections 48,1wh1ohmay be a metalcable,

a rope,or other flexible material, is-guided. in

relation, to one side of the door opening'by a guide pulley 50- and passes from this guide pulley SQ-tothe other side of the door and about one of two parallel pinch groove pulljeys 5L tothe pulley 49- and back over the other pulley 52, whichzlast named pulley thus.

acts in, addition tov its power transmission function, as a guide for the flexible connections, These pulleys 51 and 52 also serve as a, guide for the reaches of the-connections 48 passing to and from the equalizing pulley 49.

The pulleys 51 and; 52 ha-vepower applied- 7 thereto from a motor 53 through any desired;

. power transmission mechanism, 54. q

, The door,shown in Figs. 6to 8, is approaimately eighteen feet wide, and nine feet high, and weighs from 1500- pounds to a ton. Since the door must have arun of approximately nine feet to clear the door opening, a slot indicated at 55 is provided inthe floor above this door to permit the-necessary movement, and the, guide pulleys, and the is immediately above described.

actuating mechanism are positioned in. the x there is suflicient-head room for the full movementof the doorwithout'having it pass I through the floor above, this arrangement is a not required, although under conditions re quiring these large heavy dioors,it is usually necessary to employ an arrangement such as VVgith both. types of doors shown and described, and in other types of doors e1n bodying the invention, it is necessary to de termine the length, of the flexibleconnec tions 24and 25 and 4-8 with regard toithe necessary run of the door and of, the counterweight or counterweights, and to provide the necessary clearance for the full range of movement of these parts, required in the oporation of'the door. 1

While in connection with the. structures shown in Figs. 1 to 5 I have described the pulleys 26' and 33 as being of the first class, this is strictly true'only sojfar as the portion of the connections connected with the upper door section 16 is concerned, sinceso far as the portion of the connections secured to the section 18 is concerned, these pulleys are of the second class. I f e I I The movement of the counterweights in this form of the invention will equal three; fourths of the height of the door; By reason of the differential travel, of th e two door sec: tions, and the equalizing effect secured by said pulleys 26, and 3-3 withtheinovements seven andone-half feet, with a ten footopem ing'movement of the door, and clearance for this amount ofmovement only,-is; required below'the bottom of the c'ounterweights.

In the form, ofthe inventionfshown in Figs. 6 to 8, where there is no diflferentialin the. speed of movement of difierent parts ofthe connections;-thepulley 49 serves merelyas anequalizing pulley to ensure theapplication of thef load; .of the counterweight to both sides ofthe door andupon both pinch groove pulleys 5,1; and 52. Hence the run ofthe counterweight. will be substantially equal to thatof the run of th e door, and: ith

a nine foot door, ,clearancemust be provided below theqbott'om of; the counterweight of. nine feet, even though a, pocketfmust be formedloelowthe sill;.1;1;of the door opening.

In; both or s. of the nr tion, the sill-10f- 1 Ill ward movement of the upper section. The

bottom of the housing for the counterweights, in both forms of the invention,

' serves to stop. a downward movement of the counterweigthts.

' It is obvious, however, that other means may be provided for stopping the downward movement of the door and of the counterweight, if the'conditions of installation require. It is essential, however, that some positive stop be provided for both the door and the counterweight, so that upon the completion of both the closing and the opening movements, the connections between the door and the counterweight will be relieved of the load either of the door or of the counterweight in order to automatically and instantly stop the transmission of power through the pinch groove pulleys.

The operation of doors embodying the invention is as follows Referring more particularly to Figs. 1 to 5 of the drawings, when it is desired to open the door, power is applied to the motor ll to turn the pinch groove pulleys 313239-&O with a contra-clockwise movement. Since when the doors are closed the full load of the counterweight is upon the connections 24; and 25 upon one side or said pulleys, and the connections upon the other side are relieved from the load of the door, this turning movement of the pulleys will meet with resistance from the door suflicient to develop frictional resistance between said connections and the pulleys to cause the paying out of the connections toward the counterweight and the taking up of the connections with a lifting action, on towardthe doors. By using pulleys of different diameters arranged'as described,

not only will this action occur simultaneously as to opposite sides ofthe door, but the resulting movement of the door sections will have that diiierential in the speed of the two sections necessary to have both sections simulaneously reach substantially the same position with relation to the lintel 12 at the completion of the opening movement.

As heretofore described, the use of compensating' or equalizing pulleys upon the counterweight about which the flexible connections at each side of the door pass, en-

sections from the load of this counterweight and instantly making the pinch groove pulleys inoperative to impart further lifting movement to the door. The load of the doors, however, will still be applied to the portion of the connections between same and the pinch groove pulleys so that withthe reversal of the directionof the application of power to these pulleys, or with a clockwise movement thereof, the operation above described will be reversed, the doors being lowered and the counterweight being raised. Upon the completion of the'c'losing movement, the lower door section will be stopped by the sill, and the upper door section will be stopped by the hooks and lintel fittings,sothat the connections uponthe door side of the pinch groove pulleys will be relieved from the load of the door and make said pulleys inoperative to apply further power to the counterweight.

While with the completion of the opening movement of the door, the connections upon one side of the pinch groove pulleys will be relieved from the load of the counterweight, and with the completion of the closing movement of the door, the connections upon the other side of said pulleys will be relieved from the load of the door, and thus limit the operative effect of said pulleys to that required to either open or close the door, it is apparent that at all times, the door and the counterweight will have a balancing action as to each other, and when the pinch groove pulleys are at rest, the connections will be frictionally engaged therewith, so that with the starting of the rotation of said pulleys in either direction, according to the position of the'door, they will immediately be operative to cause movement of the door. It is also obvious that the door may be stopped in any position by merely interrupting the power to the motor actuating said pulleys.

Referring to the embodiment of the invention shown in Figs. 6 to 8, the weight of the door upon one side of the pinch groove pulleys 51 and 52 and of the counterweight 47 upon the other side of said pulleys, will develop that frictional resistance between the connections L8 and said pulleys, necessary to overcome the balanced condition between the counterweight and the door, and cause the movement of the door in either direction. Smce the connections upon opposite sides of the door will be taken up or paid out at the same rate, it is obvious that the movement of the counterweight 47 will be the same as that of the single panel, the equalizing de-,

with theengagement'of the panel 44; with the sill of the door-,the loadatone side or the other of said pinchgroove pulleys will be relieved to immediately interrupt the opera tion of these pulleys so 'far 'as' causing movement of the door is concerned. As with the telescoping type of door, there is always a "counterweighting action between the panel and the counterweight which, when the pulleys 51 and 52 are idle, will maintain that friction condition between sameand the connections 4L8, necessaryto ensure the turning of the pulleys resulting in-movement of the "door. 1

The action of a single panel door is similar to that of the lower door section in the form of the invention shown in Figs. l'to 5.

In both forms of the invention shown, not only will there be great ease of movement when starting the door inv either direction, but also withthe' continued run of the doors, the. operation ofthe doorrequires very littlepower because of the counterbalancing action of the door and the counterweight. p

' The mechanism for actuating the pinch groove pulleys is of a-well known standard construction embodying a stop mechanism therein which is made inoperativewith the application of power to thepulleys; This mechanism need not be employed, however, since with an approximate balancing of the door and the counterweight, there is no tendency of the loss of control ofthe door.

. In the accompanying drawings, I have shown how adoor' having asingle or a pluralityof panelsmovable upon vertically ex;

tending guides, may be constructed to secure the-desired modeof operation. While the run of the flexible' connections as shown in each instance,v has been found highly desirable in use, it is obviousthat there maybe changes in the details of'construction and opposite sides of a dooropening, means upon said panel co-operating with said guides, a counterweight, means-"limiting the down ward movement of said counterweight "and "said panel, fiekiblefconnectionsbetween said counterweight and said door, a pinch groove pulley about which saidflexible connections pass, a source of power, and operative connections between said'sour'ce of power a nd said pulley,- whereby the load of the door and v-said counterweight 'uponopposite'sides of said pulley permits the applicatiojn of power for either raising or" lowering the door, and the relieving of said connections fromthe load of'either said door "or said'counterweight to the door.

2. An elevator door embodying therein a plurality of panels vertically slidable in the same direction and "in parallel'planes, guides adjacent theopposite sides'of the door'ope'ning, means "upon said panels co-operating [will prevent a further application of power with said guides'respectively, counterweightin g means, means limiting the downward movement of said counterweightmg means and said panels respectively," flexible connections between said counterweighting means and each of said panels, plnch groove pulleys operative upon "different port-ions of said connections, said pulleys being of difierent diameters to impart simultaneous movement with 'a' difiere'ntial in speed, to said panels, guides for said connections between said pulleys andsaidf'p'anels respectively, and between said pulleysand said" counterweightin'g means, a source of power, and 0perative'connections between'said source of po er, and said'pulleys, whereby the load of thefdoor and said counterweight-mg means upon" opposite sidesfoi said pulleys permits the application ofpower for eitherraising or lowering the door, and the relieving-of said connections from theloard of either/said door or sa1d"coi1'nter\ve1ght1ng "meanswrll prevent a furtherapplication'of power to the doorf" 3. An elevator door embodying thereina plurality of panels vertically slidable, in' 't-he same direction andinparallel plane's, guides adj acent the opposite sidesfof the door opening, means upo'n -said 1 panels co-opera'ting with said guides respectively, counterweighting means, means limiting the downward movement of said coun terweighting means and said panels respectively, flexible connections, an equalizing device-carried bysaid c'o unterweifghting "me'ansabout which said connections pass, the opposite ends of said flexible connections being connectedwith said panels respectively, pinch groove pulleys operative upon different portions of said connections, said pulleys being'of different diametersto impart simultaneous movement with a differential speed, to" said panels, guides for said connections between saidtpulleys and said panels respectively', and betweensaid [pulleys and said counterweighting', means, a source of power, and operative; connections betw'een said source of power and said pulleys, whereby the load of the door andsaid counterweighti'ng means upon'opposite sides of said pulleys permits the "application of power for either raising 0rlowering the door, and the I an relieving of said connections from the load of either said door or said counterweighting means will prevent a further application of power to the door.

4. An elevator door embodying therein a plurality of panels, vertically slidable in the same direction and in parallel planes, guides adjacent the opposite sides of a door opening, means upon said anels co-operating with said guides respectively, a plurality of counterweights, means limiting the downward movement of each of said counterweights and each'of said panels, flexible connections between one of said counterweights and one of said panels, and between the other of said counterweights and the other of said panels, .two pinch groove pulleys operative upon each of said connections, the diameter of one of the pulleys operative upon each connection being greater than that of the other to impart simultaneous movement with a differential in speed to said panels, guides for each of said connections between said pulleys and said panels respectively, and between said pulleys and said counterweights, a source of power, and operative connections between said source of power and said pulleys, where by the load of thedoor' and said counterweights upon opposite sides of said pulleys permits the application of power for either raising or lowering the door, and the relieving of vsaid connections from the loadjof either said door or said counterweights will prevent a further application of power to the door.

5. An elevator door embodying therein a plurality of panels, vertically slidable in the same'direction and in parallel planes, guides adjacent the opposite sides of a door opening, means upon said panels co-operating with said guides respectively, a plurality of counterweights, means limiting the downward movement of each of said counterweights and each of said panels, flexible connections, equalizing devices upon said counterweights respectively about which said connections respectively pass,-the opposite ends of each of said' connections being secured to said panels respectively, two pinch groove pulleys operative upon eachof said connections, the diameter of one of the pulleys operative upon each connection being greater than that of the other to impart simultaneous movement with a differential in speed to said panel s, guides for each of said connections between said pulleys and said panels respectively, and between said pulleys and said counterweights, a source of power,

and operative connections between said source of power and said pulleys, whereby the load of the door and said counterweights upon opposite sides of said pulleys permits the application of power for either raising or lowering the door, and the relieving ofsaid or said counterweights will preventa further application of power to the door.

6. An elevator door embodying therein a plurality of panels, vertically slidable inthe same direction and in parallel planes, guides adjacent the opposite-sides of a door opening, means upon said panels co-operating with said guides respectively, a plurality of counterweights, means limiting the downward. movementof each of said counterweights and each of said panels, flexible connections between one of said counterweights and one of said panels, and between the other of said counterweights and the other of said panels two pinch groove pulleys operative upon each of said connections and arranged intermediate the sides of the door, the diameter of one of the pulleys operative upon each connection being greater than that of the other to impart simultaneous movement with a differential in speed to said panels, guides for each of said connections between said pulleys and said panels respectively, and between said pulleys and said counterweights, the flexible connections at one side of the door between said pinch groove pulleys and said guides being crossed to ensure similar movement of both sides of the door, asource of power, and operative connections between said source of power and said pulleys, where- 'by the load of theldoor and said 'counterweights upon opposite sides of said pulleys permits the application of power for either raising or lowering the door, and the relieving of said connections from the load of either said door or said counterweights will prevent a further application of power to the door.

7. An elevator door embodying therein a plurality of panels, vertically slidable in the same direction and in parallel planes, guides adjacent the opposite sides of a door opening, means upon said panels co-operating with said guides respectively, a plurality of counterweigh'is, means limiting the downward movement, of each of said counterweights and each of said panels, flexible connections, equalizing devices upon said counterweights respectively about which said connections respectively pass, the opposite ends or" each of said connections being secured to said panels respectively, two pinch groove pulleys operative upon each of said connections and arranged intermediate the sides of the door, the diameter of one of the pulleys operative upon each connection being greater c than that of the other to impart simultaneous movement with a differential in speed to said panels, guides for each of said connections between said pulleys and said panels respectively, and between said pulleys and said counterweights, the flexible connections at one side of the door between said pinch groove pulleys and said guides being crossed to ensure similar movement of both sides of the connections from the load'of either said door door, a source of power, and operative con nections between said source of power and said pulleys, whereby the load of the door and said. counterweights upon opposite sides of said pulleys permits the application of power for, either raising r lowering the door, and the relieving of said connections from the load of either said door or said counterweights will prevent a further application I of power to the door.

8. An elevator door embodying therein a.

plurality of panels, vertically slidable in the same direction and in parallel planes, guides adjacent the opposite sides of a door opening, means upon said panels co-operating with said guides respectively, a plurality of count-erweights, means limiting the down ward movement of each of said counterweights and each of said'panels, flexible connections, equalizing devices upon said counterweights respectively about which said 0011- nections respectively pass, the opposite ends of each of said connections being secured to said panels respectively, two pinch groove pulleys operative upon each of said connections and arranged intermediate the sides of the door, the diameter of one of the pulleys operative upon each connection being greater than that of the other to impart simultaneous movement with a differential in speed to said panels, guiding means for stud connections respectively, each comprising parallel guide pulleys between the pinch groove pulleys operativeupon the connections and a counterweight, and parallel guide pulleys over which each of said connections pass from the pinch groove pulleys operative thereon to said door sections respectively, the flexible connections at one side of the door between said pinch groove pulleys and said guides being crossed to ensure similar movement of both sides of the door, a source of power, and operative connections between said source of power and said pulleys, whereby the load of the door and said counterweights upon opposite sides of said pulleys permits the application of power for either raising or lowering the door, and the relieving of said connections from the load of either said door or said counterweights will prevent a. further application of power to the door.

In witness whereof I have hereunto aiiixed my signature this 20th day of November.

1926. ROBERT S. PEELLE.

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