US2983237A

US2983237A - Control means for electrically driven sewing machine

Info

Publication number: US2983237A
Application number: US701639A
Authority: US
Inventors: Lutz Friedrich; Daniel Hermann
Original assignee: Union Special GmbH
Current assignee: Union Special GmbH
Priority date: 1956-12-19
Filing date: 1957-12-09
Publication date: 1961-05-09
Anticipated expiration: 1978-05-09
Also published as: GB837652A; DE1085022B; FR1184936A

Description

F. LUTZ ETAL May 9, 1961 CONTROL MEANS FOR ELECTRICALLY DRIVEN SEWING MACHINE Filed D90. 9, 1957 5 Sheets-Sheet 1 F. LUTZ ET AL May 9, 1961 CONTROL MEANS FOR ELECTRICALLY DRIVEN SEWING MACHINE Filed Dec. 9, 1957 3 Sheets-Sheet 2 rl 1111 I IItHIlIIIII.

May 9, 1961 Lu z ETAL 2,983,237

CONTROL MEANS FOR ELECTRICALLY DRIVEN SEWING MACHINE Filed D60. 9, 1957 3 Sheets-Sheet 3 United States Patent Oifice 2,983,237 Patented May 9, 1961 CONTROL MEANS FOR ELECTRICALLY DRIVEN SEWING MACHINE Friedrich Lutz, Stuttgart-Degerlock, and Hermann Daniel,

Claims priority, application Germany Dec. 19, 1956 11 Claims. (Cl. 112-11) This invention relates to improvements in control means for starting and stopping the operation of an electric motor which serves to drive a sewing machine. It is particularly concerned with the provision of improved control means of the character indicated, applied to a portable bag sew- .ing machine of the type disclosed in applicants pending application Serial No. 535,316, filed September 20, 1955. .More particularly it is concerned with the provision of .improved means for starting and stopping the driving motor under the control of the work, such as filled bags, .being fed relative to the stitch forming point of the .sewing head of the unit.

In applicants pending application Serial No. 672,021, :filed on July 15, 1957, now Patent No. 2,932,266, granted .April 12, 1960, there is shown a control mechanism involving a feeler which serves the same general purposes :as the present invention. However, in that prior application, the feeler member which controls the closing of .a switch for the delivery of current to the motor is in the form of a lever which is arranged to swing about an axis coinciding with that about which rocks a needle carrying lever, an upper or outer feed dog carrying arm and a presser foot carrying arm. These latter devices, in said prior construction, are largely concealed and protected .by a hood secured to the frame or housing of the sewing head but the lever which carries [the feeler element is .mounted outside of said hood and is unprotected. As a .result of this arrangement the feeler member and its lever .are subject to being damaged in the course of the relatively rough handling to which machines of this char- ;acter are subjected. The dependability of the operation -of the 'feeler mechanism is thereby endangered. It has been found for example that when the machine does not function properly for some reason the operator will usualzly grasp the protective hood with his right hand and by :means of his fingers raise the lever arms which carry the outer feed dog and the presser foot to carry these :away from the bags or other work being stitched so that the latter may 'be removed from the machine. In the course of doing this the exposed feeler mechanism is frequently damaged. Also it has been found that the exposed feeler member of that construction is sometimes damaged when the operator puts the machine down during a pause in the sewing operations.

The foregoing disadvantages of the prior construction are eliminated in accordance with the present invention by the substantially complete enclosure of the feeler mechanism within the machine housing itself. Its construction is such as to readily enable this to be done. Moreover, the feeler mechanism is of very simple form and involves a work engaging feeler element secured to one end of a rod or bar which is mounted for simple sliding movement in guides or bearings provided in the machine housing or frame. At its opposite end the rod or bar extends outwardly of the enclosed housing of the sewing head and carries a cross head having a slot or opening adapted to receive a pin extending outwardly from the housing which serves to prevent turning or twisting of the rod or bar about its axis. Adjacent the cross head mentioned, on the side of the housing of the sewing head opposite to that at which stitch formation takes place, there is provided an electric switch having a protruding pin or plunger that is spring urged outwardly into engagement with the adjacent surface of the cross head. The pressure exerted by the spring is suflicient to cause shifting of the rod or 'bar, together with its feeler element, into its outermost position or against the Work being sewed. This arrangement is such that as the work moves relative to the throat plate or work supporting surface of the sewing head, it will serve to slide the feeler member and its supporting rod or bar to urge the pin or plunger of the switch against the action of its spring and thus close the switch. As the work advances beyond the feeler member the spring of the switch again .urges the plunger outwardly so that the switch is then opened and feeler member is restored to its normal position.

The improved arrangement is such that the electric switch is connected with a flange on the housing of the electric motor which is connected to the sewing head by a readily detachable coupling, prefer-ably of the bayonet type. Thus when the motor is disconnected from the sewing head, the electric switch and its electrical connections to the motor are carried by the motor and there is no need for any disturbance of the electrical connections. As the motor and sewing head are separated, the pin or plunger of the electric switch is simply disengaged from the end of, or a shoulder on, the rod or bar which carries the feeler member. In the improved construction the mounting and arrangement of the feeler member in relation to other parts of the sewing head are such that the feeler member will be properly operated even in the course of sewing relatively soft and flexible work such as soft linen bags, onion bags and the like. This is achieved by arranging the feeler member directly adjacent the toothed segmentor. the like of the lower or inner feed mechanism. Moreover, the arrangement is such that the feeler member and the toothed feed dog or segment pass in adjacent relationship through an opening in the throat plate of the sewing head and into an opening or cut away portion of the presser foot which is urged toward the throat plate. Also the arrangement is such that the feeler member shifts in a plane which is directly adjacent a toothed segment forming the work engaging portion of an upper or outer feed mechanism. As explained in said pending application Serial No. 535,316, the construction of the work feeding mechanism is such that the outer feed dog or segment and the presser foot are alternately brought against the outer face of the work in the course of operation of the machine. In accordance with the present invention the arrangement is such that the work is gripped firmly either between the two feed segments or between the presser foot and the throat platealong a line closely adjacent to the line along which the feeler member engages the work. Thus, the work is held taut in the immediate vicinity of the feeler so that the latter is reliably forced inwardly to cause closing of the switch as even very soft work is advanced relative to the throat plate in the switch forming region.

Another feature of the invention is the construction of the feeler member in such form that it has a portion which extends outwardly of the housing of the sewing machine at a point laterally of the stitch forming point and out of the path of movement of the work relative to the throat plate. This enables manual shifting of the feeler member to close the'electric switch whenever desired. The operator has access to the arm described so that he may, by the simple pressure of a'finger on the latter, bring about the closing of the switch. This is of particular advantage invarious situations. Thus, if it is found upon sewing extra soft material that the feeler member is not urged inwardly against the action of the spring in the switch and the inertia and frictional resistance to the sliding movement of the feeler member, the latter may be shifted laterally to start the operation of the machine and it will then remain in operation. It will be appreciated that once the feeler member and its corresponding rod or bar has been shifted into active position, the inertia and frictional resistance to movement of the feeler means will supplement the action of the work on the feeler to oppose the return of the latter by the spring. The arrangement of the manually operative arm of the feeler member is 'such that it may be readily engaged by the finger of the operator without danger of injury to the operator from the stitch forming and work feeding mechanisms.

Preferably in combination with the feeler operated switch described above, the system is provided with a manually'operated switch carried by the handle by which the unit is carried. 'This'switch, when operated, is retained in closed position by a spring latch which may be readily released by the operato'rthrou'gh a movement of the thumb or a finger of the hand which carries the sewing head and motdn' The switch carried by the handle is in series with the'fe'eler operated switch and provides a means for stopping the motor whenever any difliculty is encountered in the'operation of the sewing head while the work is passing through the stitching zone so that the feeler operated switch is closed.

i As a further special feature a cover plate is provided to protect the electric switch which is operated by the feeler member, this cover plate being on the side of the machine from which the Work is introduced. It thereby serves to prevent damage to the switch and its operating connections and also to prevent the work pieces from becoming caught on the switch or the associated parts, such as the cross head mentioned. Y 7

It will'be apparent from the foregoing that the novel feeler arrangement of the present invention has Various definite advantages including simplicity of construction, economical manufacture and dependable operation resulting from its particular construction and its substantially complete protection against damage in the course of use of the machine and its normal rough handling.

Further features and advantages of the new feeler arrangernent appear from the following detailed description of an illustrative embodiment of the same shown in the accomp anying drawings in which-- 1 is a side elevational View of the complete unit including the sewing head, the rigidly connected motor r us dju cts; Fig. 2 is a side elevational view of the lower portion of the main housing of the sewing head and related parts witha portion of the cover plate removed to show more clearly the feeler operated switch, this view being turned through 90 from the showing in Fig. 1;

'Fig. 3 is an elevational view of the parts shown in Fig. 2 as viewed from the left of the latter;

. Fig, 4 is a face view of a portion of the sewing head showing the throat plate and related parts;

Fig. 5 is a detail view, in perspective, showing the construction of the feeler member and its supporting rod or a Fig. 6 is a view smiliar to Fig. 4 but showing the presser foot in cooperation with the throat plate; and

Fig. 7 is a plan view of the presser foot employed in the illustrative embodiment of the invention.

Referring now to the drawings, the illustrative sewing unit comprises a sewing head having an enclosed frame or housing 1 in which is incorporated mechanism of the character disclosed in said pending application Serial No. 535,316. Rigidly connected with the housing \1 is a motor 2 preferably having a bayonet type connection with the sewing head housing, Whichpermits ready coupling and uncoupling of the motor in relag 4 v tion to the housing. A handle 3 secured to the motor serves as a means for suspending the entire unit from the hand of the operator who, in the use of the unit, will cause the sewing head to be carried across the top of a bag to be closed 'or along the; edge of other types of work to be stitched. Currentfor operating the motor i sup lie thmu h a ca le s whishsxtend into the handle 3 and has its wires. suitably connected with a switch carried by the handle adapted to be operated by depression of a spring arm or element 5 dog a plunger or button'extending upwa ly frorn the switch through the top of the handle. A spring elip 6 is provided to retain the spring arm 5 in its depressed position and hence the switch in its on position so that in the normal use of the unit the control over the operation of the'motor will be exercised by the feeler controlled switch to be described. In the normal use of the machine, when some difiiculty is encountered in a seaming operation the spring shifted toward the left (Fig. 1) bythe thumb or' finger of the operator to release the arm S and thus open the switch in the handle 3. A'second switch 7 provided in series with the switch in the handle, this second switch being controlled by the feeler member, as will be explained. It is arranged to extend along the forward side of the sewing head (Fig. 1) but is carried by means of a bracket 8 secured to a flange 9 which is connected with the housing of the motor 2 and forms part of the b yonet type coupling between the motor and the sewing head. This arrangement is such that when the motor is discon- "acted from h e fl hea ill? Swi h. 7 i carrie by the motor and all of the other partsof the electrical connections are so carried. Such connections include a cable 10 extending from the switch 7 to the handle 3 wherein a suitable circuit is provided to place the switch 7 in series with the switch in the handle tothe lines extending from the cable 4.

'Actuation of the switch 7 is accomplished by means of a feeler 11 the form of which is most clearly shown in Fig. 5 Its relation to other parts in thesewing head is indicated in most of the other views. The. stitch forming and work feeding devices of the sewing machine may, as previously indicated, suitablybe of the formand arrangement disclosed in the pending application Serial No. 535,316. For the purposes of the present disclosure it is sutiicient to point out that the stitch forming devices include a curved needle 12 and a reeiprocatory and oscillatory looper 13 which together serve to produce a two thread chain stitch. The work feeding devices of the machine include an outer or top, toothed feed dog or segment 14 and a lower or inner, toothed feed dog or segment 15. The latter is simply oscillated about a fixed axis while the outer feed dog 14, in addition to its swingi o l lfl m vem nt, is moved toward and away fromthe feed dog 15. Its movements toward and away from the feed dog 15 areaccompanied by opposite movements of a presser foot in relation to a :throat plate forming part of the sewing head structure,

As thework is introduced into the machine the leading edge of the work, such as the. topqof 'a filled bagto be sewed, is passed between the

opposedfeed dogs

14 and 15 and in doing so engages the feeler member '11. This is slightly in advance of the point at which theleading edge of the work will be grippedbetwe'en the two feed dogs. As best shown in Fig. 5,- the feeler member cornprises a slightly curved armll which is arranged to cooperate with the surface of they work, such asa bag to be closed, which slides along the. outer surface of the throat plate. This arm has an offset, integral cross member 11A ing of thesewing head. The opposite end of the bar 16 (its lower end as shown in Fig. 3) carries a cross head 19 which maybe suitably clamped upon the bar at a point outside of the enclosed housing of the sewing head. To prevent rotation of the cross head 19, bar 16 and feeler 11, andthus insure maintenance of the latter in the proper position for cooperation with the work, a slot or opening 20 is provided in the cross head to receive a pin 21 extending outwardly from the housing of the sewing head. 'Ihe lower surface of the cross head 19 (Figs. 2 and 3) is in contact with the upper end of a plunger or pin 22 which serves as the operating means for the switch 7. This. plunger or pin is normally urged outwardly or upwardly by a fiat spring 22a carried by a stud 23b, as shown in Fig. 3, into engagement with the cross head 19 and the spring is suificiently strong to shift the cross head, bar 16 and feeler 11 into its normal position in the path of the work. 'As explained, in the normal use of the machine it is disposed in the position indicated in Fig. 1 so that the bar 16 and the pin 22 extend horizontally. Therefore the spring acting on the pin 22 need not overcome the gravitational force acting on the feeler means. When the work engages the feeler arm 11 and urges this, together with bar 16 and cross head 19, toward the right in Fig. 1, the switch 7 will be closed by engagement of the flat spring 22a with a suitable contact.

When the switch 7 is closed, the switch in the handle 3 being previously closed, the sewing head will be driven by the motor and the teeth of the two feed dogs or

segments

14 and 15 will be caused to grip the work to be stitched and bring about the relative feeding movement between the work and the sewing head. Feeler 11 will remain in its switch closing position as the work advances along the feeler member to a point some distance beyond the stitching point, so that the switch will remain closed until the particular seaming operation has been completed and a suitable thread chain is provided beyond the trailing end of the work. It is only when the trailing end of the work passes beyond the free end of the feeler arm 11, which (Fig. 3) extends beyond the rearward end of the feed dog or segment 14 in the direction of feed, that the feeler is restored to its normal or inactive position under the action of the spring which urges the pin or plunger 22 outwardly to open the switch 7.

The arrangement of the feeler 11 in relation to the devices which support and grip the work is of particular importance. In order to insure proper actuation of the feeler 11, even in response to relative movement in the manner mentioned of work "formed of very soft material, the feeler arm 11 in accordance with the invention is arranged closely adjacent to the outermost branch of the feed dog 15, i.e., the lowermost branch in Fig. 1 and the one at the left in Fig. 2. This branch of the inner feed dog and also the feeler arm 11 extend into and through an opening 23 (Fig. 4) of a throat plate 24 across which the work is advanced in the course of seam formation. As best shown in Fig. 2, the feeler arm 11 extends outwardly beyond the contour of the feed dog 15 into a region adjacent the outer or top feed dog 14. To enable this the presser foot 25, as best shown in Fig. 2, is provided with a cutaway portion 25C into which or through which the feeler arm 11 may extend in the absence of any work being present between the presser foot and the throat plate. When the work has been introduced between the forward, divergently extending portions of the

feed dogs

14 and 15 as well as between presser foot 25 and the throat plate, and the feeler arm 11 is shifted to bring about closing of switch 7, the work will be grasped by the feed'dogs 14 and 15 in the course of operation of the machine and the feeler member will be held in its shifted position so that the switch 7 is held closed until the work passes beyond the rearward end of the feeler arm 11. It will be noted in this connection that as the

feed dogs

14 and 15 swing to advance the work in relation to the sewing head, the work is gripped closely adjacent to the feeler arm 11 so that suflicient rigidity is given to even relatively soft work to hold the feeler 11 in switch closing position in the manner described. As the feed dogs swing idly in the opposite direction, the outer feed dog 14 is in slightly elevated position so that this gripping action no longer takes place. However, at this time the presser foot 25 urges a portion of the work closely adjacent to the feeler arm 11 against a cooperating surface on the throat plate 24. The rearwardly extending branch 25A (Fig. 7) of the presser foot serves this purpose, as will be seen in Fig. 6. So also the portion 25B of the presser foot will press the work at the opposite side of feeler 11 against the throat plate. Thus, through out the entire seaming operation, the work being stitched will be gripped by one or another of the means described above along lines sufficiently close to the feeler member shifted position and the switch 7 in on position.

On occasion it may be found that very soft material entering the divergent passage between the

feed dogs

14 and 15 and the presser foot 25 and the cooperating throat plate, will not serve to shift the feeler in the manner explained, due to the necessity of not only overcoming the force of the spring in the switch 7 but also the frictional resistance to the sliding of the bar 16 as well as the inertia of the feeler mechanism as a whole. Provision is made for manual operation of the feeler member to close the switch 7 under these circumstances. This is accomplished by the arm 11B of the feeler member which, as shown in Figs. 1, 2, 3, 4 and 6, is beyond the path of movement of the work to be stitched. Thus, as is clear from Fig. 1, it is above the region in which the top of a filled bag to be closed will pass. Also it extends outwardly from the frame or housing of the sewing head to a certain extent. Therefore, it is readily adapted to be engaged by the finger of the operator to press it inwardly and cause the desired sliding movement of the feeler assembly as a whole to close the switch 7. This will begin the operation of the machine and the latter will continue until the seaming operation is completed since even the soft mate rial will serve to hold the feeler arm in shifted position once its inertia and frictional resistance have been overcome. At times it may be desirable to start the machine manually by inward pressing of the arm 11B, in the manner explained, even in Working upon relatively heavy and stifi bags or other work. This is to insure commencement of the operation of the machine before the

feed dogs

14 and 15 grip the work to advance it. Smooth operation of the machine throughout the stitching operation is thus insured.

In order to protect the switch 7 and the cross head 19 from possible damage or distortion, a cover plate 26 (Figs. 1, 2, 3, 4 and 6) is provided. This extends along the forward side surface of the sewing head in a plane transverse to the line of stitch formation outwardly of the point at which the work is introduced between the feed dogs and between the presser foot and throat plate. Plate 26 is secured to the housing of the sewing head by means of

screws

27 and 28. Provision of this plate insures against engagement or entanglement of the work with the switch 7 as the work is introduced into the machine. This protection is afforded for the cross head 19 and pin or plunger 22 as well.

While the invention has been disclosed in its application to a portable bag sewing machine of particular construction, it will be understood that it may advantageously be applied to other sewing machines which it is desired to start and stop under control of the work to be stitched. Various changes may be made in the particular construction and arrangement of the various parts within the scope of the appended claims.

What is claimed is:

1. A portable sewing unit comprising a sewing head having a frame provided with a throat plate relative to which work is advanced as it is being stitched and having stitch. forming and work feeding devices together with a I presser foot for urging the work against the throat plate, an electric motor directly connected with said sewing head for driving the same so long as the motor is operated,

a work advances as it is being stitched, and connections from said feeler member to said switch for closing the latter. t 2. A sewing unit of the character set forth in claim 1 m which said throat plate is provided with an opening through which a portion of said work feeding devices extends and said presser foot has a cut away portion aligned with said opening, said elongated arm of said feeler member having a work engaging portion normally extending through said opening in the throat plate from the side thereof opposite to that engaged by said presser foot and into said cut away portion of said presser foot. 3. A sewing unit of the character set forth in claim l in which said feeler member is carried by a bar extending from said member at a point laterally to one side of said elongated arm, said bar being slidably mounted in the throat plate carrying portion of said sewing head, said bar carryu'ng a cross head at the end thereof opposite to the point of connection with said feeler member arranged to engage said switch to operate the same, and means cooperating with said cross head for preventing turning of the latter and said feeler member. 4. A sewing unit of the character set forth in claim 2 1n which the connection between said feeler member and sald switch comprises a bar secured to said feeler member and a plunger in said switch engaged with said bar, said switch having a spring acting upon said plunger to urge the same and said bar in the direction in which said feeler member passes through said opening in the throat plate and into said cut away portion of the presser foot. 5. A sewing unit of the character set forth in claim 1 in which said motor has a flange adapted for rigid but releasable connection with said frame of the sewing head,

said switch being carried by said motor, and said connections from said feeler member to said switch comprising slidable parts which are in contact and arranged to move in unison, spring means for normally retaining said parts 1n contact, one of said pants being carried by said switch and the other by said sewing head'so that upon disconnection of said motor from said sewing head said slidable parts are disengaged.

6. A sewing unit of the character set forth in claim 2 in which said work feeding devices include a feed dog swingable in the direction of stitch formation and having an arcuate toothed surface, said work engaging portion of said feeler member extending through thetopening through which said feed dog extends and in closely spaced parallel relation thereto, the outer surface of a part of said work engaging portion being convex to conflorm substantially with the toothed surface of the feed g. 7 7. A sewing unit of the character set forth in claim 6 in which said presser foot has a portion extending along the opposite side of said opening through said throat plate from that through which said portion of said work feeding devices extends, said elongated arm being disposed between said feed dog and said portion of the presser foot, said portion of said presser foot cooperating with said throat plate to retain the work against the latter and being disposed closely adjacent to and parallel said work engaging portion of said feeler member. 8 A sewing unit of the character set forth in claim 1 in which saidv unit is provided with a handleattached to)- s'aid motor by which said "unit may be. supported and guided by the hand of the operator inthe courseof stitch formation, a manually operable switch carried by said unit adjacent said handle, means for retaining said manually operable switch in on position when operated, and,

and in alinement with the shank of said feeler-member,

and in which a protective cover is secured to said unit in advance of said switch to guard the sameand the connections from said feeler memher thereto, 7

10. A portable sewing unit comprising a sewing head having a frame provided with a throat plate relative to which work is advanced as it is being stitched and having stitch forming and work feeding devices together with a presser foot for urging the work against the throat plate, an electric motor connected with said sewing head for driving the same, means comprising a circuit for delivering current to said motor, a switch in said circuit, a feeler member in the path of movement of the work advancing along said throat plate, said feeler member having an elongated first arm along which the work slides and having a second arm disposed laterally of said elongated arm, said feeler member also having a shank mounted in said sewing head for simply sliding movement in a direction perpendicular to the plane along which the work advances as it is being stitched, and connections from said feeler member to said switch for closing the latter, said second arm of said feeler member projecting from the frame of said sewing head in an accessible position laterally removed from the path of movement of the work relative to said throat plate, thereby enabling manual sliding operation of said feeler member for closing said switch.

11. A portable sewing unit comprising a sewing head having a frame provided with a throat plate relative to which work is advanced as it is being stitched and having stitch forming and work feeding devices together with a presser foot for urging the work against the throat plate, an electric motor connected with said sewing head for driving the same, means comprising a circuit for delivering current to said motor, a switch in said circuit, a feeler member in the path of movement of the work advancing along said throat plate, said feeler member having an elongated arm along which the work slides and a shank which is mounted in said sewing head for simply sliding movement in a direction perpendicular to the plane along which the work advances as it is being 'stitched, and connections from said feeler member to said switch for closing the latter, said throat plate. being provided with an opening therethrough, said presser foot having a cutaway portion overlying said opening, said elongated'arm of said feeler member having a work engaging portion normally extending through said opening in the throat plate from the side thereof opposite to that engaged by said presser foot and into said cutaway portion of said presser foot, said work feeding devices including a first feed dog having a portion in closely spaced parallel relation to said elongated arm and arranged for swinging movement within said opening in the direction of stitch formation and having an arcuate toothed surface, said work feeding devices'also including a second feed dog swingable in the direction ofstitch formation and opposed to said first-mentioned feed dog to grip the work in advancing the same, said second feed dog being shiftable toward and away from the work, said presser foot being shiftable toward and away from, the throat plate to grip the work in alternate relation to said feed dogs, t e arrangement b n F2 th the aid tee 98 7 7 I 1 1 g or said presser foot and throat plate will grip the work at all times at a point adjacent said feeler member in the course of stitch formation, the outer surface of a part of said elongated arm being convex to conform substantially with the toothed surface of the first feed dog, said presser foot having a portion extending along the opposite side of said opening through said throat plate from that through which said portion of said first feed dog extends, said elongated arm of said feeler member being disposed between said feed dog and said portion of 10.

the presser foot, said portion of said presser foot cooperating with said throat plate to retain the work against the latter and being disposed closely adjacent to and parallel with said work engaging portion of said feeler member.

References Cited in the file of this patent UNITED STATES PATENTS 2,314,114 White Mar. 16, 1943 2,355,189 Tozier Aug. 8, 1944 2,472,968 Goldberg June 14, 1949 2,484,495 Fischbein Oct. 11, 1949 2,509,956 Benoit May 30, 1950 2,670,700 Kindseth Mar. 2, 1954 2,718,201 Kindseth et al. Sept. 20, 1955 2,779,445 Conord Ian. 29, 1957