US 3118189 A
Description (Le texte OCR peut contenir des erreurs.)
Jan. 21, 1964 R. L. DUGGER 3,118,189
AWB/aver R. L. DUGGER Jan. 21, 1964 DOOR 5 Sheets-Sheet 2 Filed June 25, 1959 Jan. 21, 1964 R. l.. DUGGER 3,118,189
Filed June 25, 1959 5 Sheets-Sheet 3 ZIE. 5
/VVENTOR RALPH L. buc.c1e&
www Jowwm R. L. DUGGER Jan. 21, 1964 DOOR 5 Sheets-Sheet 4 VvE/WDR Remy DUGGER Filed June 25, 1959 R. L. DUGGER 3,118,189
Jan. 21, 1964 DOOR Filed June 25, 1959 5 Sheets-Sheet 5 Q INVENTOR. Y mw x.. busen@ United States Patent O 3,118,189 DOOR Ralph Loring Dagger, BOX 73, Rte. 1, Hopkins, Minn. Filed .Inne 2S, 1959, Ser. No. 822,809 7 Claims. (Cl. 20-19) This invention relates to large doors for airplane hangars, equipment buildings, and structures where it is desired to provide a door which can be quickly opened and closed over a large door access opening. This application is a continuation-in-part of application Ser. No. 454,365, filed September 7, 1954, now Patent No. 2,937,- 415, and a continuation-in-part of application Ser. No. 556,198, iiled December 29, 1955, now abandoned. The disclosures of the aforesaid applications are incorporated herein by reference.
In the manufacture and rigging of doors of the aforementioned type, the door panel is unitary and is moved from the door-closed position to the door-open position by mechanisms as described in the aforesaid applications. The motion of the door is a compound motion whereby it is moved upward and while moving upward the plane of the door is rotated so that it is in a more or less horizontal position at an elevated location when the door is completely open. In this open position less than half of the lower portion of the door, preferably 20-40% of the vertical height of the door from the lower edge protrudes forwardly outside of the door opening, the balance of the door being contained within the connes of the building.
The mechanism for opening the door includes cables extending upwardly outside of the door and thence into the interior of the building by one or more patterns of novel arrangement, as set forth in the aforesaid applications. All of the cables are run along paths which, ultimately, are parallel and thence while running parallel pass over drum means by means of which the cables may simultaneously be drawn in or let out by equal increments of movement for all cables. After passing over the drum means the cables pass downwardly to counter-balancing weight means to which the cables are attached. According to my applications aforesaid, motivation of the door is preferably by mechanical power input to the shaft of the drum means, all as exemplified in my aforesaid applications. The power input, which can be manual or electric is Sudicient to operate the entire door through opening, closing, and latching movement.
The present invention provides certain improvements in the rigging of the door whereby the rigging is simpliiied and the cost reduced. Other improvements in the structure include the provision of an access door through the main door, and said access door being movable automatically to a non-interfering position by virtue of the movement of the main door during opening. Other improvements include improved bottom dashing of the main door.
It is an object of the present invention to provide an improved door having simplified rigging which may be provided at lower cost and added convenience. It is another object of the invention to provide an improved door structure wherein a large door is provided with an access door which is automatically movable during actuation of the main door to a non-interfering position. It is an- 3,118,189 Patented Jan. 2l, 1964 ICC other object of the invention to provide improved bottom ilashing for a large main door of the aforesaid type.
Other and further objects are those inherent in the apparatus illustrated, described, and claimed and will be apparent as the description proceeds.
To the accomplishment of the foregoing and related ends this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
The invention is illustrated with reference to the drawings wherein:
F'IGURE 1 is a front elevational view of a door constructed utilizing the principles of the present invention;
FIGURE 2 is a horizontal sectional view taken along the line and in the direction of arrows 2 2 of FIG- URE 1;
FIGURE 3 is a vertical sectional View taken along the line and in the direction of arrows 3 3 of FIGURE 2;
FIGURE 4 is an enlarged fragmentary vertical sectional view of the rigging of the door adjacent the head of the door, and corresponds to a portion of the apparatus shown in FIGURE 3;
FIGURE 5 is a fragmentary perspective View partially schematic of a portion of the rigging construction;
FIGURE 6 is a fragmentary horizontal sectional View taken along the line and in the direction of arrows 6 6 of FIGURE 1;
FIGURE 7 is a fragmentary enlarged vertical sectional view of the bottom edge of the door taken along the line and in the direction of arrows 7 7 of FIGURE 1;
FIGURE 8 is an enlarged fragmentary vertical sectional view taken in the direction of arrows 8 8 of FIGURE 2.
Referring to the drawings, the door generally designated D has a width W and a height H sufficient completely to close the door opening, except for side clearances SC SC, bottom clearance BC and top clearance TC. The building structure over the door opening is occupied by a truss having a height T and of course a truss length spanning the width of the opening. The door is a unitary flat panel which may be constructed according to accepted standards. According to my applications aforesaid, the door is sheeted by a vertical sheeting S preferably galvanized roof-decking and has a head flashing HF of sheet metal. Side ilashings are provided at SF SF. The door, while unitary in construction, may be considered as made up of a. plurality of theoretical panels P1-P4, which together constitute the width W of the door. These panels comprising the door are supported by the interior framing of the door, which consists of a plurality of vertically extending structural members, termed backbones 10 across which there are fastened horizontally extending purlins 11 spaced from the bottom to the top of the door as shown. The door framing (specifically the backbones 10) serves as a support for forwardly extending anchorages 13-16, see FIGURES 1 and 3.
Above the door there is arranged track means for translating the top of the door inwardly. This track means is here illustrated as composed of four tracks 17-20, one above each of the backbones 10, see FIGURE 2. Each track 1'7-20 contains a roller-hanger as illustrated at 21, FIGURE 4. To the roller-hanger there is attached a downwardly extending pendant suspension 22 which is pivotally attached at 23 to the upper end of the backbone 10. At least two tracks with roller-hangers and pivotal suspensions are provided across the width of the door and these can be placed wherever convenient, as on the sidewalls of the building opening or at spaced intervals across the opening. I prefer the latter mode of placement, as here illustrated.
The rear end of each of the tracks is supported from the roof structure of the building. The front end of each track structure is provided with a pair of upwardly extending suspension members 22-22 (see FIGURES 2 and 4) which at their lower ends are fastened to the track structure and at their upper ends are fastened together by a strong crosspiece 23 which is welded to the upper ends of the suspension members 22. The crosspiece 23 is apertured and upwardly through it extends a bolt 24 which passes through a horizontal outwardly extending perch 25 which is welded to the track and pulley support bracket (plate) generally designated 26. The bolt 24 extends upwardly well above the perch 25 and around the bolt there is provided a compression spring 27 the upper end of which is engaged by a washer and nut 28 on the upper end of the bolt. Accordingly, the front end of the track structure is resiliently supported and is permitted to move vertically within the limits of compression of the spring 27. The vertical movement of the track is denoted by the arrow 31. A pair of clips 32-32 are welded to the plate 26 so as to form a conned place where one of the members 22 can move vertically and through the clips extends a pin 34 which, passing over the face of the approximate tension member 22 keeps the latter from swinging outwardly from the plate 26, should it tend to do so. The clips 32 and pin 34 thus effectively prevent fore and aft movement of the track structure and movement away from plate 26. Accordingly, each of the tracks 17 through 20 or as many as may be used (minimum two), is supported at its rear end by suitable means such as structural member 17R extending upwardly to the building roof and resiliently supported from plate 26 at the front end by the suspension 22-23-24-27- 28 to bracket 25, as described. This permits a limited vertical movement of the front end of the track. This is advantageous in large door construction since it permits balancing the weight-loads of the tracks so that they all carry equal or nearly equal loads. It may be stated parenthetically that temperature changes in a building, or variations in roof loadings occasioned by snow, etc., will cause substantial deflections of long trusses and without the advantage of the resilient supports herein described, wide variations in loading of the tracks may result. When the door is in the raised and hence substantially horizontal position (when the roller-hangers are near the rear track suspensions 17R), the door is inherently flexible and permits equal distribution of the load on the tracks'. However, in a vertical plane the door is quite stiff and does not itself deflect sufficiently to permit equalization of loads on a plurality of tracks.
It will be noted from FIGURES 2 and 5 that the plates 26 upon which the pulleys 71-74 and tracks 17-20 are mounted are in each instance a ilat plate having its reverse side resting directly against the faces AF-AF of the angles A--A which constitute a part of the doorspan truss. These mounting plates are identical, except some may be right and some left, to iit the truss, and will be explained with reference to FIGURE 5. Bolts 36-36 pass through the plate 26 and through the space between the vertical angles A-A and are fastened to the truss. This serves to hold plate 26 firmly on the truss. A stub shaft 40 extends outwardly from the plate 26 to which it is attached and serves' as a spindle upon which the pulley 74 is adapted to rotate on anti-friction bearings contained within the pulley structure. The pulley 74 is held in place by cotter pin 42.
The single plate mounting 26 by which the pulleys 4 (7l-74) are mounted on stub shafts and the tracks 17-20 are resiliently supported from the same plate 26 offer distinct advantages in installation. It is only necessary to bolt the plate 26 in place. Then on the exposed face of the plate there may be mounted everything needed. This is a distinct time-saver.
Within the interior of the building there is provided a framing 45 upon which drum means 46 is journalled in suitable bearings, the drum shaft 47 is provided with a drive sprocket 4S at its forward end from which there downwardly extends a roller-chain 49 which goes around a sprocket 50 which is mounted on a stub shaft 51 on slide-plate 52 which is vertically slidably attached by suitable clips to the front face of the weight box shield 54. The weight box shield includes framing members 5555 on the exterior thereof and the slide-plate is provided at its lower end with a block 56 on its back side the block being threaded to receive a long set screw 57. The upper end of the setscrew engages the lower surface of the adjacent weight box frame member 55. This provides a ready downward adjustment for the slide-plate 52 for tightening the chain 49 during its service life. The sprocket 50 is provided with a crank 58 having a handle 59. By turning the crank it is thus possible to rotate the drum 46.
The position at which the weight box 60 and the drum 46 is mounted within the building may be varied to suit convenience as illustrated in my applications aforesaid.
Below the drum is a weight box 60 having a cross pin 61 therein. Along the centerline of the building there is a centerline wall CLW and a centerline tailbay truss CLT. The wall and the truss serve as convenient places for mounting for pulleys 62-65.
Referring to FIGURE 1, from each of the anchorages 13-16 which extend outwardly from the front of the door and fwhich are apertured to receive pins, at the level of the line 65-465, there are attached clevises 66 to each of which .in t-urn there is attached a suspension cable (67- 70). The run of these cables 67-70 are similar being in every instance upwardly from the anchorage (13-16) to the pulleys (7l-74) (see FIGURE l) which are mounted on the plates 26, thence directly around said pulleys and then substantially horizontal and normal to the plane of the door and into the building interior, thence around the redirecting pulleys (62-65) and along a parallel run to the drum y46, where all of the cables, which run parallel to each other at this point, pass one quarter turn around the drum and thence ydownwardly directly to and attached to the bar 61 which is a part of the weight box 60. The pulleys (162-65) are in all instances supported by brackets having a downwardly extending stub shaft such as shaft 65S, for pulley 65, see FIGURE 8. The shaft (of each pulley bracket -78) is a stub shaft and extends downwardly from a stiff bar (for example, bar 78, FIG-URE 8). tBar 78 (or 75-77) is attached to the lower face of any `convenient plate P which is in turn either a part of the building or is attached to the building or the truss work. Plates 7 5-7'8 are set at approximately 45 to the center line of the building. The criteria here is that the supporting brackets (7S-78) be above the pulleys (62-65) which are mounted on their downwardly extending stub shafts 'from each bracket (example 65S, bracket 65). A cotter pin at the lower end of the stub shafts (65S) is all that is required to hold the pulley in place on the `downwardly extending stub shaft. The brackets for the various pulleys to which reference was just made are shown in FIGURES 5 and 8. Thus the pulley 62 is supported from the bracket bar 75, the pulley 63 is supported from the bracket bar 76, the pulley 64 from the bracket bar 77, and the pulley 65 from the bracket bar 78. The objective is to have all or most of the bracket bars 7-5-78 above the pulleys and to have the bracket bars bolted or welded to the underside of a suitable part of the building structure itself. The cable 70 after making a quarter turn around the pulley 62 and running toward the drum 46, passes under the bracket 76 for pulley 63, Ibracket 77 for pulley 6'4 and the bracket 78 for pulley 65. Similarly, the cable 69 yafter it has turned around p-ulley `63 passes under the brackets 77 and 7 8 and the cable 68 after passing around pulley 64 passes under the bracket 78.
It is noted that the pulleys 71-74 are of a size such that they can extend outwardly through suitable apertures in the truss facing TF, see 'FIGURES 1, 3, and 5.
By the aforesaid rigging there is `gained a distinct advantage in respect to reduction of time and hence cost of construction, since it is only necessary to thread each cable upwardly in front of the door and thence through the aperture (in truss -facing TF) and over the Ifront pulleys 71-'74, and thence into the building.
Each cable is then attached to the -front bale 83 of a combined resilient link and cable length adjuster generally designated 80. Then an eye is made in one end of a fresh piece of cable and slipped over the rod 60 of the weight box. 'This cable is then brought up over the drum 46 `and (from the bottom) can be then looped up around through the groove of the appropriate one of the pulleys '62-65. The cable is then made fast to the rear bale -84 of unit 80. This avoids the necessity of Stringing the cables over and around intervening objects since everything below the bracket structures l5-7S is clear.
Referring to FIGURE 4, the unit 80 combines the function of length adjustment Ifor the cable and also provides a desired degree of resiliency in cable tensioning so that the loads on the cables can be adjusted and equalized. It is noted that pulleys 71-74 are not resiliently supported, being in every case on the stub shaft 41 on plate 26 bolted to the truss. As the truss moves vertically, some variation of cable tension would result were it not for the resilient function of unit 80. The unit 80 (see FIGURE 4) consists of a tube 81 having an apertured bottom S2 therein. To the left end of a tube S1 as shown in FIGURE 4 there is welded a bale 83 to which the adjacent part of the cable (67-70, '68 being illustrated) is attached. Another bale is provided at 84 which is attached to the plate 85. A long cap screw 87 is then provided. The head 87H of the cap screw rests against plate y85 and the shank of the cap screw extends through a hole in the plate 85 4in which the screw freely tur-ns. A nut 89 is welded to the cap screw 87 so as to provide convenient wrenchhold for turning the cap screw. The threaded end of the cap screw extends to the left as shown in `FIGURE 4 and threads into a nut 89 that is welded onto a washer 9i). The washer rests against the left end of spring 91, the right end of the spring resting against the washer S2 welded into the tube 81. As a :result a pull on cable 68 (right portion, FIGURE 4) is transmitted through the bale 84, plate 85 to the cap screw `87 then through the nut 89 and washer 99 to one end of the spring 91 which is hence placed in compression, since the other end of the spring is held by the washer 82 in the tube 81 which is in turn pulled by the bale 83. This provides resiliency in the suspension but with the spring in compression. lIt is only necessary to put a wrench on the wrenchhold S9 and the stud 87 can easily be turned to adjust the position of the stud Iwith reference to the element y89-90. This provides lengthwise adjustment of the cable.
As shown in FIGURE 2, on the inside of the door there are provided knuckles at 93 to which radius rods 94 are attached, the radius yrods extending upwardly at an angle (see IFIGURE 3) to pivots 95 on the walls of the hangar.
On the inside of the door adjacent the head `of the door are a plurality of latches -L as described in my applications previously referred to and `a plurality of latch bolts LB are operated by the latch release rod LR by means of the latch handle LH, which is normally held upward-ly by the 4spring LS, all as described in my applications aforementioned. The latches serve to hold the head of the door in a vmly closed position once the latch is snapped in place. All the latches may be simultaneously released by a Vdownward pull on the roll bar which pulls the latch handle LH downwardly.
Referring to FIGURES 1 and 6, there is provided in the main door D an access door 100, the bottom of which is at the level 101 (so as to be above snow). The door 190 is set in a suitable frame and is mounted by means of hinges 162 and swings outwardly. This is important. It will be noted that the hinges 102 are set on the side of the access door which is adjacent the nearest wall of the building and hence when the door 109 opens it tends to swing toward the adjacent wall of the hangar. The door is provided with a door closing mechanism 104 which is a standard article of commerce containing a bearing spring to effect closure and a self-contained air check cylinder. However, this closer 194 is set in a way which is not standard, namely, it is set so as to limit the opening of the door to an angle G which is less than The door closer 104 has a self-contained spring which tends to close the door.
The access door 141i) is provided with a latch at 106 of the snap type. It will be noted that the access door 19@ is thus mounted so that it swings outwardly with reference to the main door D and the swinging motion is in a direction toward the adjacent wall W. Also, the access door is provided with means, in this instance the door closer 1%4, which provides a closing bias and which is set so that the angle of maximum opening of the access door is less than 90 relative to the plane of the main door. The biasing means, which in this instance is a selfcontained spring within the door closer 104 diagrammatically illustrated at 1648, biases the movement of the axis door toward closed position. The effect of this arrangement is the following:
Should the access door 10i) be in an open condition, and in the event the spring 1048 is not suthcient to cause the access door to swing shut, the access door will still be in a position to fall shut as the main door D is opened since the opening angle of the access door is less than 90. If the opening angle were more than 90, it would be possible that the access door might fall open. It is an advantage to have the access door thus move to a closed position since in the raised position of the main door D, the access door, if open, would interfere with the opening movement of the main door. It is noted also that by mounting the access door so as to swing outwardly with reference to the main door, there is no possibility that the access door would swing open (hence, downwardly) as the main door D is opened (and hence moved to an elevated generally horizontal position). This also is an advantage since if the access door were mounted to swing inwardly and it should swing inwardly (hence, downwardly) when the main door is open and the access door would then be in a position to engage and damage the wings of a high-wing aircraft.
Referring to FIGURE 7 the bottom of the main door 1t) is provided with the purlin members 11-11 as previously mentioned which are mounted on the backbone 10. The'lowerrnost of these purlins and the sheeting on the outside of the door is set so as to be slightly above the level of the floor FR. The web of the lower purlin 11 is provided with apertures at intervals along the length of the purlin and beneath the purlin 11 is a metal flashing 120, the upper end of which is bent at 121 and thence downwardly at 122 to form a channel. Bolts 124 having heads 125 are situated in the channel (formed at 1Z0- 121-122), and the shank of the bolt extends upwardly and is held in place by a nut 126 which rests on washer 127 that in turn rests on a light spring 12S. The effect is as follows: The bolt spring washer nut assembly provides enough upward pull to hold the portion 121 against the web of the purlin 11 so long as the bottom edge 12GB of the flashing is not positively deflected, as by scraping the iloor. If any scraping is involved, the flashing will be tipped to one or the other of the dottedline position as shown and this will pull the bolt head downwardly a little against the action of the spring 128 which is light enough in its compression strength so that the cocking of the hashing 125) is readily permitted. The hashing 12@ is made of reasonably stiff metal so that even though the lower edge 120B should freeze down in an ice puddle, the opening of the door will yet be permitted. Under such conditions, the edge 120B would act as a pivot, as the lower portion of the door moves outwardly in the direction of arrow 130, during initial opening movement. This will crank the lower edge 120B loose from any ice in which it may have been frozen and as soon as the lower edge of the flashing is free from ice it will again come back to its normal position as shown in FIGURE 7, due to the influence of the springs 128. There is enough resiliency of portion 121 relative portion 120 to accommodate this motion upon opening. Accordingly, a reasonably tight hashing action can be achieved without the danger of the flashing being frozen down and torn at the next opening movement. Also, springs 127 keep flashing 120 in the plane of door when the latter is open, hence flashing 12@ does not droop down and reduce door clearance when the main door is open.
As many widely apparent different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein.
What I claim is:
l. A door for an opening in a building wall, the top of said opening being defined by structural members of the building, comprising a flat unitary widespan door in the form of a panel which in its Ivertical position closes the opening, rigging supporting the door including track means extending in a plane generally normal to the door opening and from a position over the door thence inlWardly into the building, roller-hangers for movement along said track means, said hangers being connected to the upper edge of the door for supporting a part of the door weight, said rigging also including cables, each extending from attachment points located on the outside of the door along a common substantially horizontal attachment point line transversely of the door at a level less than halfway up the door from its bottom edge, and thence upwardly outside -the door and over guide pulleys, located at a level above the upper edge of the door and thence inwardly to a common counterweight means and unitary Iload equalizing and cable length adjustment means in each of the cables along the length thereof, each such unitary means including spaced attachments connected to opposed spaced ends of the cable, said attachments being shaped to move in overlapping relation relative to each other in the direction of the cable run, said attachments being formed with opposed spring seats, a compression spring positioned between and engaged by said seats, at least one of said attachments being adjustable in length for taking in and letting out the cable, said attachments having relatively movable proximate parts serving to indicate the amount of compression of the spring for thereby gauging the cable tension.
2. A door for a buiiding opening, said opening being dened by structural members of the building, comprising a at unitary widespan door in the form of a panel which in its vertical position closes the opening, rigging for supporting the door including track means extending from a position adjacent the upper edge of the door and generally normal to the door and extending inwardly in respect to the building, roller hangers for movement along said track means, said hangers being connected to the upper edge of the door for supporting at least a part of the weight of the door, said rigging also including cables extending transversely of the door from a plurality of attachment points located on the outside of the door at a common substantially horizontal attachment point connection line at a level less than halfway up the door from the bottom edge, each of said cables extending upwardly therefrom and over a plurality of pulley means and thence along paths including a common parallel path of movement and thence over a common drum journalled from framing within the building and thence downwardly from the drum to a common counter-weight, said combination also including in each of the cables a combined cable length adjustment and resilient means comprising a pair of spaced bales to which adjacent ends of the cables are attached, a tension rod rotatably mounted with reference to one of the bales, said rod being screw threaded to a nut, said nut being formed so as to provide an abutment, a compression spring against said abutment and means extending from the other bale for engaging the opposite end of said compression spring for compressing it.
3. The combination of a doorspan truss framing, a iwidespan door across the space under said truss framing, a plurality of spaced parallel tracks above the upper edge of the door, -a roller hanger mounted for rolling movement on each of said tracks and having pivotal attachment to said upper edge of said door, and resilient load-equalizing means for supporting each of said tracks from the truss framing, a plurality of grooved pulleys pivotally mounted on the truss framing, each of said pulleys being mounted in a vertical plane and spaced from each other across the width of the door and with the groove of the pulley in front of the vertical plane of the door for receiving an upward run of cable, cables extending from a hitch point on the front of the door at a level above the bottom of the door and below the middle of the door, said cables each extending upwardly outside the door and thence each over a pulley and thence to counterweight means.
4. A combination as recited in claim 3 wherein each of said cables extends to a common counterweight means, and each of said cables includes load equalizing me-ans along the length thereof.
5. A Ilarge span door for aircraft hangar buildings and the like, said door comprising a unitary flat panel, a plurality of track means mounted within the building and extending generally normal to the door from a position above the door and inwardly in respect to the building, a plurality of bracket means supported above the edge of the door on the building structure alongside a respective one of said track means, said bracket means being fastened immovably with reference to the building structure, a spindle shaft mounted on each of said bracket means, a grooved pulley mounted on each spindle shaft, each pulley being thereby mounted in a fixed position relative to the building, each pulley being oriented so that a portion of the groove of said pulley is outwardly of the face of the door, resilient means on each of said bracket means for supporting therefrom that portion of the track means therealongside which is adjacent the upper edge of the door, and cable rigging extending from a level below the middle of the door upwardly and over said pulley means and into the rigging.
6. A door for a large building opening wherein the opening is defined by structural members of the building comprising a iiat unitary widespan main door in the form of a panel which in its vertical position closes the opening means mounted on the building structure for supporting the door for movement from a Vertical position in which it closes the door opening to an elevated position wherein it is generally horizontal and with a lower portion of the door extending outwardly through the upper part of the opening and an upper portion of the door extending into the building, the improvement comprising an access door in the main door, said access door being mounted on hinges on the main door for swinging movement about an axis perpendicular to the base of the main door outwardly beyond the plane of the main door, means for preventing swinging movement of the access door inwardly in respect to the main door, said access door being provided with means Afor limiting its outward swinging 9 movement to less than 90 with reference to the plane of the main door whereby said access door moves toward the closed position when Ithe main door is elevated.
7. The door as set forth in claim 6 further characterized in that combined means is provided for limiting the Outward swinging movement to less than 90 with reference to the plane of the main door and for biasing the access door towards closed position.
References Cited in the file of this patent UNITED STATES PATENTS 1,663,196 Gibbons Mar. 20, 1928 1G Kelly Feb. 14, Scott Sept. 5, Byrne Dec. 3, Casse Dec. 27, Jones Mar. 21, Byrne Oct. 31, Tucker Ian. 30, Siess et al. May 21, Vanditty May 15, Quinn June 22, Reid et al. Aug. 21,
Citations de brevets