US2712972A

US2712972A - Extension arm

Info

Publication number: US2712972A
Application number: US407964A
Authority: US
Inventors: Manson Morris; Hafekost Frederick
Original assignee: STEEL SLIDES Inc
Current assignee: STEEL SLIDES Inc
Priority date: 1954-02-03
Filing date: 1954-02-03
Publication date: 1955-07-12
Anticipated expiration: 1972-07-12

Description

July 12, 1955 M. MANsoN Erm.

EXTENSION ARM 2 Sheets-Sheet l Filed Feb. 3, 1954 July 12, 1955 M. MANsoN ETAL 2,712,972

EXTENSION ARM Filed Feb. 3, 1954 2 Sheets-Sheet 2 IIIIIIIIIIIIIIIII- 1N V EN TORS. MORE/5 MA N50/V BYFkEDER/CK H4 F15/(057.- LJAh-L, )un-L ,Mm i Onu.; g M Suma- ATTORNEYS'.

United States Patent O EXTENSION ARM Morris Manson, Brooklyn, N. Y., and Frederick Hafekost, Hopatceng, N. J., assignors, by mesue assignments, to Steel Slides, Inc., New Rochelle, N. Y., a corporation of New York Application February 3, 1954, Serial No. 407,964

11 Claims. (Cl. 311-71) by the combination of a pair of slide elements which are associated in longitudinally shiftable and nested relationship, each slide element comprising a main channel member having a ared outer portion which is adapted for engaging in nested relation with a base portion of the channel member of the next adjacent slide element, a transverse inner dimension of the ared portion being substantially equal to but slightly greater than the transverse outer dimension of said base portion whereby a satisfactory frictional Contact is obtained and a suitable load bearing function is achieved thereby. The channel members are held in nested relationship in a novel manner through the intermediary of a pair of oppositely and outwardly extending primary flanges for each slide element, each flange being secured longitudinally along its respective edge of the ared portion of the channel member and preferably integral therewith. Connected to each of such flanges and extending longitudinally therealong is a channel which is, by such connection, held in spaced and parallel relationship thereto. Such channel member has a mouth extending longitudinally of the slide element which opens inwardly toward the main channel member, there thus being two opposed subchannel members having longitudinally extending mouths which open toward one another. Such opposed subchannel members are constructed and ari ranged for receiving the primary flanges of the next adjacent element. this being made possible by virtue of the spaced relationship of each subchannel member to its respective ange. Such spaced relationship in efrect forms a pair of opposite and outwardly opening (ex- Y teriorly accessible) subchannel members into each of which there is received one side of the rst mentioned subchannel member. ln order for the primary subchannel members to receive the opposite edges of said flanges and thereby to be held to said main channel members in nested relationship, the dimension between the edges of said oppositely directed anges is slightly less than the dimension as measured between the bot toms of said primary subchannel members. The maximum dimension of each slide element as measured from opposite outer surfaces of said rst mentioned subchannel members is uniform with respect to all of the slide elements. Consequently a plurality of said elements in nested relationship can be associated with. for example, the under surface of a table, said slide elements being in a vertical attitude and the outer fold of each such subchannel member, if desired, engaging the under surface of the table.

One of the objects of the present invention is to provide an extension arm which is impervious to humidity and which will not become jammed or stick.

A further object is to provide an extension arm which ,i 2,712,9r2 Patented July 12, 1955 is of extraordinarily low cost and which is well adapted for mass production techniques, each slide element thereof being fabricatable from a single strip of metal by a relatively simple bending operation.

A further object is to provide an extension arm which is smoothly workable.

Another object is to provide such an extension arm which is of simple and light construction but with adequate rigidity in both horizontal and vertical planes. Another object is to provide such an extension arm which, when fully extended, has a little or negligible degree of sag.

A further object is to provide a device of this type particularly adapted for extension tables upon which a plurality of spare table leaves can be supported without sag and with easy registry of all leaves.

A further object is to provide an extension arm with a heretofore unattainable high range of extension commensurate with heretofore unattained low cost.

A further object is to provide a device of this character which eliminates complicated anti-friction struc'. tures, such as ball bearings.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not intended as a definition of the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawings:

Fig. l is a transverse cross sectional view of a single slide element embodying one form of the invention;

Fig. 2 is a plan view of the slide element shown in Fig. l;

Fig. 3 is a perspective view of a pair of the nestable slide elements shown in Fig. 1 in nested relationship and associated with, for example, one of the separable halves of a table top;

Fig. 4 is a perspective view of a pair of slide elements in nested relationship with one another, said elements embodying another but non-analogous form of the invention;

Fig. 5 is a transverse cross sectional view of one of the slide elements shown in Fig. 4; and

Fig. 6 is a fragmentary transverse cross sectional view of a feature of construction which may be employed in the embodiment of Fig. 4.

Referring to the drawings, with particular reference to Figs. 1-3, inclusive, the novel extension arm com-- prises a plurality of duplicate, nestable, slidably engageable slide elements, each of which may be fabricated with great ease and at low cost under mass production techniques from a single strip of sheet metal or other suitable sheet material.

The basic slide element of the invention is well shown in cross section in Fig. 1 and is designated by the nir-- meral 10 and consists, in this form of the invention, in a main channel member 11 having a depth 12. The main channel member 11 is constructed and arranged especially for nesting engagement with a corresponding channel memberV of the next adjacent element irl the manner well illustrated in Fig. 3. However, reverting again to Fig. 1, such channel member, in order to effect such nesting relationship, is formed in two portions, namely, a base portion 13 having a selected outer transverse dimension 14; and a top or ared portion 15 having a selected transverse inner dimension 16 which preferably is slightly greater than the dimen- Vsion 14, for example, the dimension 16 may be .01()

inch larger. Consequently, there is insured' a satisfactory frictional engagement 'between the opposed inner surfaces of Athe ilared `portion `1'5 Vwith the nesting or interitting outer areas of the next adjacent slide element corresponding'to the base portion 13.

The "ilare'd portion 15 of the main ichannel member 1'1 has a pair of 'opposite 1upper -lips 17 and '18 which comprise corners `from 'each of which there 'extends an outwardly directed primary flange. Consequently there are a pair of suchprimary anjges designated 19 and 20 which are respectively secured along the lips 1'7 'and "18 and which are outwardly directed with respect to the main `channel member 11. n

iSuch primary anges v19 and 20, together with their associated `means' to Vappear ;hereb`el0\v, comprise the means for holding the `several 'nested slide elements in nesting Vrelationship with one another .in such a way that a lnovel Lbearing Vassociation therebetween is effected.

Said vprimary ilanges `19 Vand V20 'are preferably but not necessarily substantially coplanar and are integral with the main channel 11.

Also the'slide elements arepre'ferably but not necessarily symmetrical withrespecVto Va central plane passing "longitudinally down `the middle of Vthe channel 11. Any asymmetrical characteristic -should be common Vto all slide elements to insure Vproper nesting and telescop'ic engagement.

VViewing the Vslide element 10 in 'a vh'orirontal Lattitude, that Vis with the primary yilanges 19 and 2t) Substantially horizontal, it is seen that there are secured to the respective outer edges `19aand 20a thereof a pair of

double subchannel members

21 and 22, respectively, Which are in transverse cross section respectively in the Vshape of a reverse 'S and an S, such reverse S and S conformation being substantially fiattened.

The -subchannel member 22 Vconsists of a peak Wall 'ewalls '24 and 25, together with their interconnecting fold or bend 27, deiine a subchannel 29 andthe vpeak and center -walls 23 and 24 define asubchannel 39.

The outer margin portion of `the lprimary 'ilange 2i), together withv the peak Wall 23, which'is adjacent thereto, forma double thicknessiwhich fis slightly less than the width of the channel 29. The 'reason 'for this is Y that fthe'channel 29 of the slide element Iii is designed for receiving such Aa double thickness of the next adjacent and nesting slide element, Vas is well shown in Fig. 3.

The conformation of the double subchannel member 21 is analogous to but reversed with respect to the subchannel member 22 above described Yin detail. Thusthe 'subchannel member '21 is provided Ywith a channel 31 formed between a center-'Wah 32 and a base Wallyand'also with a subchannel'34 formed Vbetween the 'center Wall'"32 and a peak wall '35.

`Referring nowto Fig. 3, there are shown 'the Vabovedescribed slide Lelement `10 yin telescopically engaged and lnesting relationV with .a v.duplicate Vslide element 36. In vthe opposed inturned channels 29 and'31 of 'the slide element 10, there are respectively received flanges 37 andY 38 Which are 'analogous respectively to vthe ilanges 20 and 19 (Fig. l), it being understood, of course, that the Vpeak walls analogous to'23 and 3S are also receivedl in channels 29 and'31,.-respectively, therebyvforrningithe above-mentioned double thickness.

Any desired number y.of such identical --nestableslde elements may be so associated with one another successively in the relationship shown in lFig. 3.

. the adjacent surface of the iiangeV 2i), that is, along a line designated by the point 26a. Consequently the primary [frange 20 protrudes sufciently from said connecting point or line tov provide a .flange which may be engaged by the channel 29 of the next adjacent slide element, it being, of course, understood that analogous but oppositely disposed structure Vis associated with the opposite side of the slide element.

'ln order to facilitate the proper nesting relationship of the several slide elements, the dimension 39 .is .slightly greater than the dimension 4@ (Fig. l). ample, dimension 39 maybe V54 of an inch and dimension 49 ljg. Y

By Way of example only, there are set forth on lFig. l a typical set of dimensions .for the various parts of the channel member, although Yit is, of course understood that the invention is not limited to these dimensions and that the latter are shown only for the Vpurpose of giving the relative sizes anddisposition of theparts.

ln order to limit the mot-ion'of one slide element, such as 36, with respect to another slide element, such as 1i), as viewed in Fig, 3, a pair of llimit-stop ears may be employed, one of which is shown at 41, formed in the iioor 11a of the Channel member 11. Such limit-stop ears 41 may be struck out oi thesurface oi floor of the channel member at opposite extremities of its length and there can cooperate with a limit-stop ear 42 which may be punched or strucktrom floor 43 of the neat adjacent slide element 36.

Referring again to Pig. l, reference is .made to relative dimensions 44 and i5 which respectively Yare the transverse dimension betweenthe outer lips of the primary flanges 19 and Ztl, and the transverse dimension between the opposite oors or bottoms of the opposite channels 29and .31. In order 'to insure aproper tit of such

primary lianges

19 and 21, together with the adjacent peak Walls 23 and 35, within their respective channels 29 and 3.1 ofthe next adjacent slide element, thc dimension d4 is sightly less than the dimension 45.

' The normal attitude for the slide elements, such as 1li .and 36 (Fig. 3) is Vsubstantially vertical, as shown, thereby to insure necessary rigidity, both in the vertical andhorizontal planes.

The upper edges of the folds le vand 45 are coplanar when such slide elements in the vertical attitude of Fig. 3 and thereby such top bends both are capable, if desired, of being placed extremeiy close to and, if desired, in trictional contact with the underside ot .a table top 46. Thus all of the slide elements, including as many more as desired vover and above those shown in Fig. 3, may be nestably associated therewith and all of their upper edges will be coplanar, thereby avoiding.probiemsV ofregistering the separable halves of table 47 of which the aforementioned top 46 is one oisuch halves.

The combination ofthe .several extension arms maybe secured to the table, as is .well shown in Fig. 3. For example, one of the slide elements, such as 1G, can be secured to a Wooden block til which is rigidly secured by suitable means to the under surface of the table top 46. The means for rigidly vsecuring the slide element 10 to suchV block 4S .may'comprise =a plurality of nut and bolt interconnections, one of which is shown at 49.V lt is, of course, understood that the slide Velement 35 or some Otherslide element nestablysecuredin azsuccession .of

By Way of ex-4 such elements, can be analogously secured t'o another wooden block analogous to 48 or secured to the coopera*- ing and extendable element of the piece of furniture in any suitable manner.

Referring to the embodiment shown in Figs. 4 and 5, an extension arm 5G is provided comprising aplurality of slide elements, for example, 51 and 52, each of which is substantially similar to the slide element above described with the exception that the main channel 11 has been omitted from each and in lieu thereof the primary anges thereof (analogous to 19 and 20, Fig. l) are associated without the aforementioned intervening channel member (11, Fig. l).

The basic element 51 of the extension arm 50 itself thus is in the form of a channel member having a floor or bottom 53 with sides 54 and 55 which have been partially collapsed, preferably by bending, to the form well shown in Pig. 5, the side 55 being collapsed in such a way that its `transverse cross section is in the shape of a tiattened S and wall 54 of a reverse S. Each of i the elements 54 and 5S have

peak Walls

56 and 57 which preferably but not necessarily are held in spaced relationship from the door 53 of the channel member.

Thus the embodiment or" Figs. 4 and 5 comprises also a series of duplicate nestable slide elements, the basic element of which comprises a channel member having sides 54 and SS shaped to form

inturned lips

5S, 59 and 60, 61. The inturned lips 59, 61 are each in the form of a channel having a mouth which opens outwardly of the overall channel member, that is, the inturned lips 59 and 61

form channels

62 and 62a respectively which are exteriorly accessible, viz., the mouths thereof open exteriorly of the slide element. The inturned lips 59 and 61 are disposed in the same relative positions on opposite sides of the slide element but pointing towards one another. The same is true of the inturned lips 5S and 69 which also are preferably but not necessarily coplanar.

As shown in Fig. 5, the edge 63 is closer to the axis 64 than the edge 65. The same relative disposition is true ot the edges 66, 67. The

edges

63 and 66, respectively, comprise the outer longitudinal edges of the oppositely disposed and outwardly protruding primary anges which are analogous to the primary flanges 26 and 19 (Fig. l). Such outwardly protruding flanges are received by the inwardly directed subchannel members 68 and 69 (Fig. 4) of the slide element 52.

The reason for the difference in the disposition of the

edges

63 and 65 with respect to the axis 64 is to permit the next slide element to nest easily thereupon and to permit each element to be a complete duplicate of all of the others.

Reverting to Fig. 3, it is seen that each slide element, such as 10, engages each next adjacent nested slide element, such as 36, along four longitudinally extending areas as follows:

(a) the outer edge of the bend or fold 53 (Fig. 3) engages the inner edge or bottom surface of the channel 31 formed by the center and base walls 34 and 33 interconnected by bend 33a;

(b) and (c) the opposite inner surfaces of the flared portion of each channel member 11 engages the outer surface of the restricted or base portion of the next adjacent channel member; and

(d) along the lower edge of the channel members shown (Fig. 3) there is an engagement analogous to that between the bend 53 and the bottom or inner surface of the channel 31.

If desired, face-to-face inner longitudinally extending edges of the base walls and 33 (Fig. l) may have beads secured thereto which may cooperate with and extend into a suitable passage formed in the channels 3 and 34 of the next adjacent slide element, such passages embracing the bead substantially throughout its periphery thereby providing a locking means for aiding in withstanding loads upon the extension arm when inI an extended condition.

There is thus provided a novel extension arm having a desirable and important characteristic in that the top edges of such elements when nested and vertically disposed are at a common level. This is of practical importance in the application of the extension arm, for eX- ample, to extension tables which have separable halves, because one side of the table must be secured to the extension arm at one level and the other side of the extension table must be secured to such extension arm at the same level. Otherwise, the primary halves of the table top could be at different levels but secured to the same extension arm, the latter being extended, and thence problems of placing the spare leaves in register would arise. In addition to the above, it is necessary to present a perfectly level top surface for the support of the spare leaves or cross bars of the table and this is accomplished by virtue of the common level of the top edges of the various slide elements.

Although only two modications of the invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may be made in the design and arrangement of the parts illustrated as will be apparent to those skilled in the art. For a detinition of the limits of the invention, reference will be had primarily to the appended claims.

What is claimed is:

l. A slide element including a pair of outwardly directed primary anges, a pair of exteriorly accessible subchannel members positioned next to and along respective of said anges, and a pair of interiorly accessible subchannel members positioned next to and along respective of said rst-mentioned subchannel members and conformed to receive in longitudinal sliding engagement the respective primary flanges of another such member.

2. In an extension arm element for nesting with a plurality of duplicates thereof, a channel member having a door and sides, said sides forming: a base portion, a ared portion adapted for nesting with the base portion of the next adjacent extension arm element, a pair of outwardly directed primary anges secured respectively along the opposite edges of said flared portion, a pair of exteriorly accessible subchannel members positioned next to and along respective of said anges, and a pair of interiorly accessible subchannel members positioned next to and along respective of said first-mentioned subchannel members and conformed to receive in longitudinal sliding engagement the respective primary ilanges of such next adjacent extension arm element.

3. In an extension arm element for nesting with a plurality of duplicates thereof, a channel member having a floor and sides, said sides forming: a base portion of relatively restricted outer dimension measured transversely thereof, a ared portion having an inner transverse dimension for nesting upon the outer sides of a next adjacent channel member of a duplicate extension arm element, a pair of opposite primary flanges along the opposite edges of said ared portion, a pair of exteriorly accessible subchannel members extending longitudinally along respective opposite edges of said primary flanges; and a pair of interiorly accessible and oppositely disposed subchannel members extending alongside respective of said first-mentioned subchannel members and conformed to receive the respective primary anges of such next adjacent extension arm element.

4. An extension arm comprising in combination: a pair of nestable duplicate slide elements, each of said elements including: a main channel member having a flared portiong for engaging in nested relationship with the channel member of the next adjacent slide element, a pair of primary anges extending outwardly of said channel member respectively along opposite edges of said ared portion, a pair of parallel subchannel members secured to respective of said opposite anges and extending longitudinally of said slide element and said lmain channel member, Lsaid subchannel `members vhaving longitudinally extending mouths vopening toward fone another, one side of -each of said subchannel members comprising an inturned secondary flange, said Yslide elements being associated with one another wherein said subchannel members on one slide clement receives said oppositely'directed anges on the'other islide element. Y Y

5. An extension arm including -a nestable :channel member adapted for cooperation with a plurality of identical channel members which slidably engage same, such 'channel -member having a primary portion with a preselected transverse outer Vdimems'ion at the bottom of such channel vmember and a secondary portion having va preselected transverse inner dimension"substantially equal'to but slightly greater than the aforementioned preselected transverse A'outer dimension whereby the secondary-por tion fmay 'slidably'fit in 'relatively close frictionalengagementV in nested relation overvthe Vprimary portion of a next adjacent and duplicate channel member, a pairof primary Viange` members extending routwardiy respectively from-the opposite Yedges Vof lsaid channel member, .said flange members'being integral with sm'd. channel member,

' a pair of double groove lmembers secured tothe outer lips respectively of said anges and 'extending longitudinally thereof, said double groove members being respectively transversely substantially S-shaped and reverse S-shaped, each double groove member having an inturned iange thereby to form with a midiiange of such double groove member a channel for receiving the primary flange of the next adjacent channel member.

6. An extension arm comprising in combination; a plurality of duplicate slide elements, .each slide element comprising a main channel member having a bottom portion Vwith a preselected uniform outer transverse dimension and a top Vportion having .a selected inner transverse uniform dimension substantially similar to but slightly .in excess vof said preselected outer dimension whereby the top portion ofone of such channel .members is .nestable with respect to the .bottom'portion of the channel of the next adjacent vslide element, .a pair of outwardly extending primary flanges integral with respective opposite edges of said channel member; a pair :of .secondaryiflanges parallel to saidprimary tianges and secured thereto, said Vsecondary flanges thereby forming with their respective primary flanges subchannelimembers which are substantially perpendicular to the first-'mentioned channel member; ia .pair of tertiary anges secured to .respective of said secondary flanges respectively along the outer edges thereof thereby forming 'anotherrzpairof subchannelmembers but having mouthsin .opposite and face-to-face relationship which .open .inwardly toward saidv first-mentioned channel member-as opposed to the mouths of the first-mentioned subchannel `whichopen outwardly with respect to the first-mentioned rmain channel member, a transverse dimensionasmeasured from opposite edges of said primary anges Vbeing less than the transverse dimension as measured `fromthe OPPO- site bottoms of said second-mentioned subchannel vmembers.

7. AA slide element for an extension arm comprising: a .main channel member having a base portion with a selected transverse outer dimension uniformly alon'gthe length thereof and a bell portion extending. longitudinally thereof having a vselected rinner dimension substantially equal to but slightly lgreater than that of the first-mentioned outer dimension, a; pair of primaryangesvextending .longitudinally on oppositeredges of saidbell channel portion ythroughout the -length of said slide element and having opposite parallel outer edges havingV a selected transverse distance between same; a pair of doublegroove members secured respectively to said-outeredges'of said flanges, said double groove members being in transverse Y cross -.-scction. substantially S fand; reverse S-shaped, the

peak of each S and .reverse .S being connected to the outeredge of said anges thereby to .form a pair of substantially 'coplanar subchannels with the mouths thereof Y theV floors of Vsaid last mentioned'channels.

8. An extension armcomprising in combination -a .pair of slide elements, each slide element including a channel member having an outer base transverse dimension :and Y a flared portion having an inner transverse dimension substantially equal to the Vaforementioned Vouter transverse dimension whereby said flared portion of one of said channel members is ncstable upon the base portion of 'the other channel member, `vsaid flared portion having a selected depth, a pair of `primary flanges secured rcspectively along therparallel edges of said ilared portion ofsaid-channel member and a pair of double subchannel members 'secured respectively along the outeraedges of said flange members, said double subchannel members being transversely substantially S and reverse S-shaped, respectively,.each being secured to its respective `ange by'a angeffoldand each having a peak fold and a baseV fold, said folds extending longitudinally of the slide element and being parallel with oneanother, thereby forming va pair of opposed inturned iianges along thebases respectively of said double subchannel members, whichv flanges, together with the mid-portion ofeach of isaid subchannel members, forma subchannel into which'the opposite primary kflanges extend `of the next adjacent slide element.

9. An .extension arm having in combination a pair of nestable slide elements, each slide element comprising: an integral folded sheet metalfmember having a center channel member having a ared outerportion conformed to nest upon a restricted .base portion of the center channelfmember of the .other slide element, .the transverse in ner Vdimension of said dared portion of-.one channelmernber being substantially equal to but slightly greater `than the transverse outer dimension of the .base .portion of-fsaid other 'channelmemberg a pair of opposed subchannel members extending longitudinally of .said Isli'de element each forming a subchannel which is substantiallyperpendicnlarto the first-mentioned center channel member, the mouths of said subchannel .members opening outwardly with respect-to said center channel member, ,eachiof said .subchannel members having a :primary lip, there being a selected distance between the opposed'primanl lips of said subchannel members, each of the latter having ,a secondary `lip extending Ilongitudinally thereof, fa'

pair of inwardly extending flanges secured respectively to said secondary lips thereby to form with respective of said `subchannel members another pair of subchannel members having opposed mout-hs in `face-to-face:relationship opening inwardly toward said center chann'elrmember, said other subchannel members being constructed and arranged to receive .opposed primary lips of the next adjacent-duplicate slide element, the .transverse `dimension between said primary lips being less than the transverse dimension'between the bottoms of said othersubchannels.

l0. An extension armv having in combinationz. a pair of duplicate nestable slide elements, each slide element comprising:A a main channel member having a flared outer portion for engaging in nested relation with a baseportion of the channel member of the nextadjacentfslide element, a pair of-subchannel members secured longitudinally along respective oppositeredges of said main channel member, said subchannel members Ahaving longitudinallyextending mouths opening outWardlywith -respect to said-main channel; another pair of subchannel and having a longitudinally extending mouth opening inwardly with respect to said main channel, said other subchannel members being constructed and arranged for receiving respectively oppositely extending sides of subchannel members of the next adjacent slide element; the transverse dimension between the opposed bottoms of said second-mentioned subchannel members being greater than the transverse dimension between the opposed edges of said irst-mentioned subchannel members, the depth of the flared portion of the main channel member being substantially equal to the transverse dimension of a first-mentioned subchannel member.

11. A slide element for an extension arm comprising: a main channel member having a bottom and two opposite sides, the transverse cross-section of each of such sides respectively being in the shape of a substantially attened S and reverse S, such sides being connected respectively to the outer edges of the aforementioned channel bottom thereby to form a pair of substantially coplanar subchannels with the mouths thereof opening outwardly of the extension arm and another pair of substantially coplanar subchannels with the mouths thereof in opposed face-to-face relation and thus facing inwardly of the main channel formed by said main channel member; the transverse dimension of said opposite outer edges being less than the transverse dimension between the opposite floors of said last-mentioned subchannels whereby a plurality of such extension arms in nested relationship have the outer edges of said second-mentioned coplanar subchannels in substantially a common plane.

References Cited in the le of this patent UNTED STATES PATENTS 889,284 Welterlin June 2, 1908 949,119 Gruender Feb. 15, 1910 978,730 Gaut Dec. 13, 1910 1,526,506 Schilling Feb. 17, 1925 1,531,810 Pelton Mar. 31, 1925