US2890823A - Self-levelling ladder - Google Patents

Description

J. W. BENDICK SELF-LEVELLING LADDER Original Filed Jan. 21, 1954 June 16,1959

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June 16; 1959 I SELF-LEVELLiNG LADDER Original Filed" Jan. 21, 1954 J. w. BENDICK 5 Sheets-Sheet 2 INVSNTOK;

JACK w. BGN DICK Arrowevs June 16, 1959 J. w. BENDICK 2,890,823

I SELF-LEVELLING LADDER Original Filed Jan. 21, 1954 f s sheets-sheet 5 mvem'rok JACK w. BeN mcK BY ATTOKNGYS.

United States Patent 19, 1957. This application June 1, 1954, Serial No.

' Claims. (Cl. 228-29) This invention relates to a four legged structure such as stepladders, platform ladders, stairwell ladders, trestles and the like which are constructed so that the legs will automatically conform to an uneven surface within reasonable limits and thus be a self-levelling feature. The term ladder as used herein includes all of the foregoing devices.

This application is a continuation of my application Serial No. 405,424, filed January 21, 1954, now Patent No. 2,781,961, granted February 19, 1957, for a selflevelling stepladder as therein defined. That application described a construction in which the back legs or props and the front legs are connected together by means of a pin and slot construction to allow the front and back legs to cant or to shift angularly with respect to the front legs, the pins assuming different positions in their respective slots according to the unevenness in the floor on which the ladder is standing. Thus, by swinging one side of the back leg downwardly and toward the front of the ladder while the oposite side of the leg is moved upwardly and toward the back of the ladder, an offset in the level of the leg extremities of as much as one inch can be obtained. The front and back legs are each constructed to form a rigid unit so that they move as a unit. Therefore, the ladder levels itself at least as soon as any weight is placed upon the first step. In the said application, it will be seen that the levelling is effected by what may be termed a back and forth movement of the top end of the back leg structure relative to the front leg structure which has the effect of raising or lifting one leg of the pair of back legs and lowering the other. There will be the same relative movement of the front legs. In the present invention, the self-levelling of the device is obtained by a lateral movement of the back leg structure from side to side relative to the front leg structure or vice versa. By the term lateral I mean a movement in which the back leg structure moves in a substantially horizontal plane at right angles to the back and forth movements in my said prior application. I thus obtain a tilting action of the pair of back legs which has the efiect of raising one of said pair of back legs and lowering the other of saidpair.

In the present application, I have illustrated several modifications of my invention as applied to a conventional stepladder but its adaptation to other structures will be obvious to those skilled in the art.

ladder is adapted to be rested when the legs are in open position. The pins of said pin and slot interconnections are slidable within said slots, thereby permitting one of said pairs of legs to tilt laterally with respect to the other of said pairs of legs in accordance with irregularities in the surface of a floor upon which said ladder is rested with its legs in open position and supplemental means for limiting the spreading apart of said pairs of legs with respect to one another.

For an understanding of the invention, reference is to be had to the following description which describes several embodiments of the same as illustrated in the accompanying drawings in which:

Figure 1 is an elevation taken from the rear, of a stepladder embodying one modification of the present invention;

Figure 2 is a fragmentary perspective View of the top portion of the ladder shown in Figure 1;

Figure 3 is a cross sectional view on the line 3-3 Figure 1;

Figure 4 is a fragmentaryperspective view of the top end of a stepladder employing an alternative construction to that shown in Figure 1;

Figure 5 is a fragmentary perspective view illustrating another alternative construction;

Figure 6 is a cross sectional view on the line 66 Figure 5; H

Figure 7 is a fragmentary perspective view showing the topend of a stepladder embodying still another alternative construction of the self-levelling device;

Figure 8 is a rear view of the ladder constructed in accordance with the modification illustrated in Figure 7;

Figure 9 is a fragmentary view, on an enlarged scale, illustrating the pin and slot interconnection shown in Figures 7 and 8;

Figure 10 is a fragmentary rear view of the top end of the ladder illustrating a further modified form of the invention;

Figure 11 shows an alternative construction of a cross section taken on the line 11-41 Figure 12 of an alternative construction of a leg bracket;

Figure 12 is a side elevation of the leg bracket shown in Figure 11;

Figure 13 is a side view of the top end of a trestle with;

In one modification, the self-levelling ladder of the associating each leg of one pair with the corresponding leg of the other pair, the slots of said pin andslot interconnections being relatively elongated, and being angulated withrespect tothe plane ofa floor upon which said 14-14 Figure 13;

Figure 15 is an alternative construction of the leg bracket;

Figure 16 is a fragmentary view, on an enlarged scale, of a horn to show the notch construction.

Like characters of reference refer to like parts throughv out the specification and drawings.

Referring first to the construction illustrated in Figures 1-3, the ladder includes a pair of parallel front uprights or legs 100, 101 which may be made of wood or metal and rigidly interconnected one with the other to form a rigid front leg structure, a pair of rear legs 102, 103 rigidly interconnected with one another to form a rigid back leg stnucture, brackets 104, 105 suitably mounted on and secured to the upper ends of the front legs 100, 101 respectively, a platform 106 which is supported by the brackets 104, 105. Each of the brackets 104, 105 extend rearwardly from the front leg with i which it is associated and is then bent inwardly at right angles toform extensions 107, 108 respectively which underlies the rear or back edge of the platform 106.

The means by which the back legs are pivotally asso- .ciated with the front legs so as to have pivotal move Figure 14 is a fragmentary side view of the top portion of the trestle shown in Figure 13 taken on the line pin interconnection for associating-the front .leg structure andtheback leg structure totilt'as' hereinbefore mentioned, consists of angulated slots 111,112 formed. in the extensions 107, 108 .and. pins'fllf 114 ,attached to the crossmember .109 and slidingly fitted'into the slots 111, 112 respectively. The slots are arranged at an angle of between 45 to'6 .to the vertical centreline of theladder with the preferred angle being about 54. 7 In Figures 1"ancl2 the slots111,'112 are shown as being inclined upwardly and inwardly towards the centre line. However, the slots may incline downwardly. and inwardlyas illustrated in Figure 4. It will be .observed that in both constructions the slots converge towards each other arthe angles mentioned relative to the vertical centre line.

The back legs are maintained in a spread position at the correct angle relative to the front'legs'by a standard type of spreader.

.Figure 1 illustrates the ladder standing on an 'uneven surface with the result that the frontleg 101 is ata higher elevation than the front leg 1'00 and both the front legs are at a higher elevation than the rear legs 1'02, 1'03 respectively. The pinand slot construction hereinbefore.

described allows the-back leg structure to tilt or rotate laterally on its horizontal axis in a clockwiseor counterclockwise direction depending on the nature of unevenness of the floor. This movement of the pair "of back legs as a unit has the effect of causing the pm 113 to.

slide toward the toplimit of the slot 111 and the pm 114 to slide toward the bottom limit of the slot 112 which has the efliect of raising the leg 102 and lowering'the'leg 103 respectively. When the ladder has levelled itself, the

movement stops. This movement is accomplished by the simple expedient of at least the application of the-weight of a person stepping on the bottom step of the-ladder;

In some cases the weight'of the ladder alone will besufficient to cause the self-levelling action'to take place.

Pivotally mounted between the rear legs 1 02, 103 is a bucket rack 115. 'Placed between the side members of the rack and the'backlegsare wedge shaped inserts 116, 117 which are fastened to the back of the legs 102, 103, respectively, with the narrowportions pointing upwardly. The-bucket r-ack fits between these inserts which permit the front end of the side members of the bucket rack,

which-are cut somewhat at-an angle, to'bear against the top step of the ladder.

:Referring now to Figure 4, I' have therein illustrated a modified construction in which the pin'and 4 sions 107a, 10811 of the brackets are formed with holes 118, 119 through which the pins 120, 121 are inserted. These pins are not movable in the slots. The cross member 109a is formed with angulated slots 111a, 112a, similar to the slots 111 and 112 and disposed at an angle within the range of angles previously described.

Referring now to Figures 5 and, 6, I have therein illustrated another construction -of-my invention. In that construction, theladder comprises a pair of front legs 10% and 10117 which are formed into a rigid front leg structure and the pair of back legs -102b,103b formed into a rigid back leg structure. Securelyattachedtothe top 'end of the frontlegs 10011 and 101b are a'pairof brackets 122 and 123 which are turned inwardly at right angles thereto to form arms 124, 125 respectively lying immediately below the back edge of the platform 1061). Thus the brackets 122, 123 are substantially L-shaped and support the platform 10Gb. The rearwardly extend- 'i constructionjust described with reference to Figures 5 3 ing portions of brackets 122, 123 are each perforatedforthe purpose to be hereinafter explained, these perforations rbeing identified bythe numerals 126,127 respectively. .In punching the holes 126, 127, the material is not completely removed butsufiicient material is left to form a flange 138 to provide a bearing surface for the. back leg brackets hereinafter described with reference to Figures'S and '6. The top ends of the pair of rear legs 102b, 103b are rigidly secured together by a cross member-128. The pin construction in the present modification for connecting the back leg structure to the brackets 1'22 and 123 consist of a pair of back leg brackets 129, 130 which are substantially U-shaped. The back. leg brackets 129, 130 aresecurely attached, with the open .ends down, .to the cross member 128 so as to associate each-leg of the back leg structure'with the corresponding leg of the front leg structure. Each of the back .leg

brackets have an angulated portion which connect. the arms of each bracket. The angulated portions of the .. brackets 129, 130 are identified by the numerals 131,

132 respectively and disposed at an angle corresponding with the angle of the slots previously described. The

angulated portions 131, 132 are slidably fitted into the orifices 126, 127 to slide longitudinally therein. The

and 6 permits the back leg structure to tilt exactly the same as the construction previously described in conjunction with Figures 1 to 4 and to be hereafter describedwith reference to Figures 8 to 16 inclusive. In this construction there will be someslippage down the angulated por- I and 1010 and a pair ofback legs 102a and 1030, the legs. of each pair being interconnected to form a rigid front slot .interconnections'have their positionsreversed, that is the pins are carried by the brackets and the'slots are formed 'i-nthe cross member which is pivotally mounted on the-top endof the pair of rear legs. In this modification, brackets 104a, 105a, bent inwardly to form extensions 107a, 108a respectively which are similar in con- 7 the cross. member 109a by pivot pins l l 0a which are entered ;through holes 151 respectively formed in the top endof each leg and holes .152 for-med'in the inturned ends 15 3 of the member 109a. This means of pivotally connecting the back-legs to the cross member 109a is. the

me/as. that.s wa..in. .Fiaures 1.2 @913. tT e xt n us tion should the weight be concentrated on oneside of the ladder. Under ordinary circumstances where the weight on the ladder is more or less central there 'will be no slippage.

Referring now to Figures 7 to 10 inclusive, the modifications therein illustrated are basically similar tov the modification illustrated in Figures 5 and 6. i In this construction, the ladder comprises a pair of front legs a leg structure and a rigid back leg structure respectively. Mounted on the top end of the front legs 1000, 101c is a pair of brackets 133, 134 respectively which extend rearwardly relative to the front leg structure. Supported by the brackets is a platform 1060'. The rearward end of each of the brackets 133, 134 has. a round or oval straight punched hole 136, 137 respectively .so that the sidesof the hole are practically at right angles, the holes being provided to receive the ends .of the back leg brackets to be hereinafter described. The top ends of the legs 102e, 1030 forming the hack leg structure are rigidly connected together by means of a cross member 154. The

pin construction for connecting the' back legfstru'cture to the'brackets 133,134 consists of a pair of back leg brack- ' ets 139, 140. These'leg brackets'may 'besh'aped 'dif ferently as-shown inFi-gures'7 to ldinclusivelybuteach pair.of.leglaracketsiisprovidedwithangulated homslfl;

a 142 respectively, the horns 141, 142 lying at the same angle and converging towards each other in the same manner as the slots hereinbefore described.

Each horn is formed with a series of notches 138 upon which the brackets 133, 134 rest. The notches may be of various shape, but in the preferred construction, the notches have a substantially horizontal surface upon which the brackets rest. This is achieved by having the notches shaped like a wide V. As will be seen by reference to Figure 16 the notches 138 are arranged in a series to simulate steps of a stair with the portion 138a representing the tread which lies substantially in a horizontal plane with the front and rear leg spread apart. The riser portion of the step, indicated by the number 138b is inclined slightly away from the vertical so as to assist the bracket sliding up and down the horn during the self adjusting process. The notches act as steps and the bracket on one side is prevented from slipping off the notch by the bracket of the other side which must ride up the born before the first mentioned bracket slides off its notch. Once the ladder has been levelled and the brackets rest on the steps of the notches, there will be no slippage down the horn when weight is applied to one side of the ladder. In the levelling process the brackets slide up and down the respective horns until the proper notches have been reached, thus lengthening and shortening the respective legs so that the ladder will rest firmly on the uneven surface. The back leg brackets are preferably constructed from high tensile steels thereby permitting smaller dimensioned brackets to be used without detracting from their ability to withstand any and all pressures or forces that may be applied to them without bending in use. One of each of said pairs of leg brackets is secured to or mounted on the end of one of the pair forming the back leg structure. The horns 141, 142, ride in the perforations 136, 137 respectively whereby the legs work from side to side in levelling the ladder as hereinbefore described.

Figures l1, l2 and 15 illustrate an alternative construction of the leg bracket shown in Figures 7 to 10 inclusive. In each of these views only the top end of the front leg 1010 which carries the bracket 134 and platform 1060, the bracket being punched to form the hole 136 therethrough for receiving the horn 141, and the top end of one of the back legs namely back leg 102c is shown. The leg bracket 139 is secured in place by bolts 155, 156. The horn 141 in the construction illustrated is also formed with notches 138 previously described to provide steps on which the bracket 134 is supported to prevent slippage down the sloping horn when the weight on the ladder is shifted from side to side as is usually the case when a person is working from the ladder. When the selflevelling device is used on heavy duty ladders, it is recommended that the free end of each horn, as illustrated with reference to the horn 141, be supported by a sup port plate 158 which is secured to the upper end of the leg 102c by the bolt 155, the upper end of the plate 158 being perforated to receive the free end of the horn.

Referring now to Figure 15, the support plate 158 (Figure 11) is formed integrally with the prong so that there is provided a leg bracket 139 having an angulated horn 141a formed with notches 138, the horn having a downturned extension 159 which is secured to the upper end of the leg 102c by bolt 155.

4 Referring now to the construction of the trestle shown in Figures 13 and 14. The trestle therein illustrated comprises a front leg unit consisting of upright legs 200, 201, connected together into a unitary rigid front leg structure by spaced apart rungs 202 and a back leg structure consisting of the upright legs 203, 204 joined into a rigid back leg structure by spaced apart rungs 205. The top end of the front and rear leg structures are joined together in the manner hereinafter described. The legs are maintained in proper spread apart position by a pair of spreaders 221, 222, the spreader 221 being connected to the front and rear legs 200, 203, respectively, and the spreader 222 being connected to the front and rear legs 201, 204 respectively. Each spreader is formed of two parts pivotally connected in the centre to allow the spreader to told when the ladder is closed.

The preferred construction for pivotally associating the front leg structure and the rear leg structure to permit the leg structures to tilt relative to one another as Well as pivotally moving towards each other from operl to closed position, is similar to that hereinbefore described in connection with Figures 7 to 10 inclusive with such modifications as are necessary to adapt the same to the trestle and trestle extension hereinafter described.

Mounted on the top end of each of the front legs 200, 201 are brackets 206, 207 respectively. Each of the brackets are similar in construction and are L-shaped so as to provide each bracket with a rearwardly extending arm 208, 209 respectively. The arms 208, 209 allow the top ends of the front back leg structure to be spaced apart sufficient to allow the extension ladder unit consisting of legs 210, 211 which are connected together into a rigid extension ladder unit by rungs 212 to be mounted so as to be slidable vertically between the top ends of the front and back leg structure. Each of the arms 208, 209 are bent to form a guide channel 223 for guiding and supporting the legs 210, 211 of the extension unit the channels being completed by plates 213, 214 mounted on the upper ends of the legs 203, 204 respectively which, when the front and rear leg units are in spread apart or open position, bear against the legs 210, 211 respectively to increase the vertical stability of the extension unit. Pivotally mounted on each spreader 221, 222 and positioned thereon to be in vertical alignment with the guide channels 223 are U-shaped guide members 224, 225 respectively. The lower end of the extension unit legs 210, 211 ride in the guide members providing vertical stability to the extension unit. This construction also allows the trestle unit to be folded for convenience in transporting.

The means for connecting the rear leg structure to the front leg structure will now be described. This consists of a pair of leg brackets the same as leg brackets 139, mounted on the top end of the legs 203, 204 respectively. Due to the position of Figure 13, only the bracket 13% on the leg 203 is visible. Consequently only the leg bracket on top of the leg 203 will be described, it being understood that the description will apply, as well, to the leg bracket on top of the leg 204. The leg bracket 139 which is mounted on the top of the leg 203 is described in relation to Figure 9, and consists of an angulated horn 141 having stepped notches 138, the horn being inserted through the hole formed in the rear end of the arm 208. This construction permits the front leg structure and the rear leg structure to tilt relative to each other so as to take up unevenness in the floor level as well as allowing the front and back leg structures to be pivoted towards and away from each other to open and close position in the manner hereinbefore described. The structure for supporting the extension ladder structure in an adjusted vertical position consists of supports 219, 220 which are hingedly connected to the top end of the legs 200, 201 respectively. The supports 219, 220 have their upper ends concave to form a seat for the rungs 212. The hinged supports 219, 220 move out of position when raising or lowering the extension. To raise the extension, the pressure of the brackets 213, 214 is relieved by bringing the legs 203, 204 slightly in towards the front leg structure. The extension part is then raised to the desired height, after rungs 212 have passed the supports 219, 220, these supports fall back into position under the rung. The legs are then spread thereby applying pressure against the extension ladder through the brackets or plates 213, 214. To lower the extension piece, the reverse procedure is adopted.

"What I claim -as new and desire to Patent ofIthe .United-.States is: 1. ',A-self?levelling laddercomprising a pair of front legs permanently connected together forming a rigid frontleg unit, a pair of back-legs permanently connected together to form a rigid back leg unit and complemented parts including pin and slot interconnections respectively associating .each leg of one pair with the corresponding lcg-of'the other pair, the parts of said pinand slot inter- Connections being .slidable relative to each other, and one part heingangulated with respectto the planeof a floor upon which said ladder is adapted to be rested when the legs are .in open position andin a directionto permit one of said-leg units to have limited rotative movement in alateral direction relativeto the other leg unit to automatically change theelevation of one leg of one unit relative to the other legs of the ladder whereby the four legsof the ladder automatically adjust themselves to an uneven floor surface and automatically lock in the adjusted position when said ladder is under load with its legs .in open position, and supplemental means for limiting the spreading apart of said pairs of legs with respect to one another.

2. A self-levelling ladder according to claim 1 the additional feature of an extension ladder unit mounted perpendicularly between the front and rear leg units, and meanscarried by the-said brackets and the spreaders for maintaining the extension in a perpendicular position, and hingedtmenibers mounted-on thetop-of each leg of the front leg unit, said members engaging with a rung of said extension ladder unit thereby suppo'rtingsaid unit at a predetermined height.

3. A'self-levelling trestle comprising a pair of front legs interconnected to form a rigid front leg structure,

protect by Letters 3. pair ,of rear legs interconnected to form a rigidrearlegstructure, a bracket havinga .rearwardly extending arm mounted on the top-end of each front leg, each arm having perforations at the rear end thereof a leg bracket mounted on .the top end of each .rearleg, each leg brackethavingan angulatedhorn slidably fitted intothe-perforation of the adjacentarm, two of said brackets With related horns forminga pair, thehorns of the-pair being disposed atan angle ofbetween 45 and-65 to the vertical centre'line of the ladder when in open position, the said horns converging towards each other, fa

series of step-like: notches. formed in the-upper surface of each ho'rn, and a spreader connecting the front and rear leg units -to,-prevent the legs spreading beyond a predetennined limit.

4. A self-levelling trestle according-to claim 3 theadditional'feature of an extension ladder unit mounted perpendicularlybetween-the front and rear leg units, and means carried by the said brackets and the spreaders formaintainingtthe extension in a perpendicular position, andhinged members mounted on the "topofeaeh leg of the frontleg unit, said members engaging with a rung or said extension ladder unit thereby supporting said unitat a predetermined height.

"5. 'A self-levelling ladder comprisingapair of front legs permanently connected togetherlforming "a rigid frontleg unit, a pair of rear legs permanently connected together forming a rigid ba'ck 'l'eg structure, means .interconnecting the baCkand front leg structures at the upper ends'thereof to permit the leg structure to have limited 'rotative'nrovement in a lateral direction to automaticallyultlaterai'lyrelative"to one another in addition to-the pivotal moveinent'of-the leg str-ucturestowards and away from each other, said-means including a connecting-member associating each leg-of one pair withthe corresponding leg ofthe et-herpair-comprising-complemential parts,- -one-p'art being a slot and the other part being apinslidably mountdin said slot, one *ofsaid parts being-anghldr-ly --disposed relative to the other part and being angulated with respect to the-'planeof the floor upon which said ladder is adapted to rest when the legs are in-bpen position, said pin being ,Islidabledn; said slot to have relative movement with respect .thereto in accordance with the irregularities in the esu-rfaeertof'ihe floor upon"which the ladder 'is 'standing with thejlegs in spread apart position to automaticallychan'gevthe elevation 'ofone leg of one unit-relative to -the:;0th er leg unit of the ladder whereby the four tlegs sof-s the ladder automatically adjust -thernselves 1013.11 uneven floor surface and automatically lock in theadjusted position when said ladder is under load and-aspreadencon: nectin g the front-and backlegsto-prevent'the legs spreadingbeyonda pred'eterminedrlimit. t

v 6. A self-levelling ladder comprising a pair rof .-fro

legspermanently connectedvtogetherforming a-rigid front leg-unit, a pair of -rearlegs permanently-connectedsto gether to form a rigid back legstructure, meansjintep connecting the back leg unit and front leg uni-t at-the'upper ends thereof to permit the'leg structures to automatically tilt laterally relative to one another in addition :to ithe pivotal movement-ofthe leg structures towardsia-nd :away

from each other, said means including a connectinganem' berassociatnig each legof oneunitw-ith the correspond- 'ing leg of the other unit, said connecting members 300111- prising complementalparts,-one;part being 'a'bracketsand the other part being a pin slidably mounted ,inisaid bracket, said pinbeing angularly disposed relative do" the bracket and-being angulatedin a direction withnespect to thepla-ne of the" floor upon WhlChiSZi'ld ladder zisadeirted to'rest whenthe legs are in open-position:..to permitithe legunitsto tilt laterally relative to one another wherehy the Hfour legs of 'the ladder automatically adjust :themselves ,to an uneven :floorand automatically locktin the adjusted positionwhen said ladder is under: load,,iand';a' spreader, connecting thej'front and back legsto; prevent the legs spreading :beyond a predetermineddimit.

7. A self-levelling ladder, according to claim 6m the bracket is associated with and extended rearwardly from the'l'egs constituting one of the leg units, therearward'sex'tension of the bracket having an orificeiozteceive the .angtilarly tdisposed' pin associated with the correspondingleg' of the otherl'eg structure.

8. A-"self-levelling ladder comprising a pair 'of front legs, the legs in said pair being permanently connected together to term acriigid frontlegunit, a pair of back'ilegs' permanently connected together to form a back' leg unit, and means including pin and slot interconnect-ionsrespectively. associating each leg: of one unit with'the con esponding leg of the other unit, the pins of said pin and 1 slot interconnections being relativelyelongated, and being angnlated'with respect to-the plane ofa floor upon which said ladder is adapted to be rested, when the legs arein openposition, the pins of said pin and slot interconnec tions. being slidable within said slots thereby permitting -i'= one of said-leg units to tilt laterally'with respectto the other of saidleg unit in accordance with irregularities in the surface: of a-floor upon which saidladder is res-ted with its legs in open position, wherebythe tour-'legsoflthe two units automatically adjust themselves-to thesaid 'irreg-ul'a rities andautomatically lock in the adjusted position-during the time the said ladderis under -load', and supplemental means for limiting the spreading apart of said-pair's-oflegs with respect to one another.

9. A self-levelling ladder according to claim 8 in which eachpin -h-as-a--series of step-like notches formed-in upper surface, said pin being disposed at-an-angle of between 45 and to-thevertical eentre-l'in'e-of th'e ladder'When-in open position-to cause one braoket-toslideup the pin; with which it is associated-an'd the other bracket to slide down its pin until each bracket-is sup ported outhe notches with the bottom end of each leg res-tinglfirinly uponthe floor.

'10. -A self leve'lling ladder according to claim 8*inwhich the sa-idhorns converge towards each other, th'upper' ends being closer to each other'than the lower ends.

References Cited in the file of this patent 2,054,690 UNITED STATES PATENTS 5%?221 273,474 Dennis Mar. 6, 1883 355,095 Macnider Dec. 28, 1886 5 403,602 Neill May 21, 1889 519,535 Koehler May 8, 1894 5,433 522,444 Wright 1. July 3, 1894 126,132 1,087,286 Franklin Feb. 17, 1914 230,601

10 Barrett Sept. 15, 1936 Botinger et a1. Sept. 6, 1938 Nowick Nov. 12, 1940 FOREIGN PATENTS Australia Mar. 21, 1933 Switzerland June 1, 1928 Great Britain Mar. 19, 1925

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