US2624499A

US2624499A - Apparatus for plugging test tubes and the like

Info

Publication number: US2624499A
Application number: US122957A
Authority: US
Inventors: Gold William
Original assignee: Wisconsin Alumni Research Foundation
Current assignee: Wisconsin Alumni Research Foundation
Priority date: 1949-10-22
Filing date: 1949-10-22
Publication date: 1953-01-06
Anticipated expiration: 1970-01-06

Description

Jan. 6, 1953 w, GOLD 2,624,499

APPARATUS FOR PLUGGING TEST TUBES AND THE LIKE Filed Oct. 22, 1949 PLUGGER ammo/0 555055? 50LE/V0/l7 J] 50 44 a? FEEDER U N 5 LE INVENTOR.

Wz flz am Gold,

g By

57 FEEDER CUTTER PLUGGEF 5W/TCH 6W/TCH SWITCH Patented Jan. 6, 1953 ITED STATES ATENT OFFICE Claims. 1

This invention relates, generally, to plugging apparatus, and it has particular relation to apparatus for plugging test tubes and the like.

Among the objects of this invention are: To provide for plugging test tubes or the like with short lengths of cotton or like material in a simple, efficient, and economical manner; to employ a strip of material of indefinite length and to cut the same into the required lengths for each plug; to feed the strip automatically into cutting and plugging position; to withdraw the feeding mechanism in response to placing the test tube in position to receive the plug' to cut the strip in response to the withdrawal of the feeding mechanism; to insert the plug into the test tube in response to operation of the cutting mechanism; to hold the plug in the test tube while the plugging mechanism is being withdrawn; and to feed the strip into the cutting and plugging posi in response to the removal of the plugged test tube from its plug receiving position.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

This invention is disclosed in the embodiment thereof shown in the accompanying drawing, and it comprises the features of' construction, combi* nation of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention reference can be had to the following detailed description, taken together with the accompanying drawing, in which:

Figure 1 is a view, in side elevation, of a device for plugging test tubes and the like;

Figure 2 is a view in front elevation of the apparatus shown in Figure 1;

Figure 3 is a topplan View of the apparatus shown in the preceding figures; and

Figure 4 illustrates diagrammatically the circuit connections which can'be employed for energizing the solenoids shown in-the preceding figures.

Referring now particularlyto Figures 1, 2 and 3 of the drawing, it will be observed that the referense character it designates, generally, an automatic test tube pluggingfmachine. The machine it includes a frame that is indicated, generally, at H. The frame H includes-a base l2 which carries a transverse upright I3 from'which a shelf id projects rearwardly; The shelf It may be supported atits rear end by a support IS: The

. 2. transverse upright I3 carries a vertical base It. It will be understoodthat the frame H, as

desoribed and shown in the drawings, can be modified as desired and that the particular arrangement thereof is shown only for illustrative purposes.

A strip iii of material such as cotton and having an indefinite length maybe fed through a horizontal hollow guide 28 which is positioned along oneside of the shelf M. The forward end of the strip [9 is fed into a trough 2! which has outflared sides 22 and an opening 23 in the bottom under which a test tube 24 or like receiver may be positioned for receiving a' plug to close its upper end. If desired,- a" clip' 25' may be carried by the vertical base [6 and arranged to receive the test tube 24 for centering it properly underneath the opening 23.

The strip 19 is fed into the trough 21 by a resilient feeding tongue 26. As shown more clearly in Figure 3, the tongue 26 has forwardly inclined teeth 21 for gripping the forward end of the strip l9 and moving it into't-he trough 2 along one side of the'opening" or aperture 23. In order to hold the strip l9 in theposition to which it is fed by the tongue 26 forwardly inclined teeth 23 are provided along the sid'e'22 against which the strip I9 is held by the tongue 26. When the tongue 26 is retracted, the teeth 28serve to hold the strip is in the forward position.

The feeding tongue'2'6 isurged'to'move the strip is into the trough 2 l' by a coil tension spring 29. The tongue 26can be retracted'by a feeder armature 30 on' energization of a cooperating feeder solenoid 3 l.

With a view to cutting oif a plug 33, Figure 2, from the strip l9'for insertion into the upper end of the test tube 24, a cutter, shown generally at St; is provided and is'arranged tooperate between the forward end of the'hollow guide 2i} and the rear end of the trough- 2|, The cutter 34 comprises a stationary blade 35' which is fastened to the vertical base it; Cooperating with the stationaryblade 35- is a-movable bladetfi which is pivoted at 36' to the stationarybladetfi. A coil tension spring 3'1 serves to bias the movable blade 35 to the open positionl Foroper'ating the movable hlade'tt a flexible connection 3Y'S'is connected theretoand is trainedover a pulley 39; At its other end the flexibleconnection 38'is secured to a cutter'ar nature' tt whic'h'has a cutter solenoid ti tocooperate therewith. on energization of the cutter solenoid ll, thespring 311s tensioned andtheblaclett ismo v ed' to cutoff the plug 33 from the remainder of" the strip I 3;

With a view to carrying the plug 33 downwardly through the aperture 23 in the bottom of the trough 2| from its position along one side thereof, a plugger 44 is employed. As shown in the drawing, the plugger 44 is in the form of a flat blade and is carried at the lower end of an armature 45. A coil tension spring 46 is connected to the upper end of the armature 45 for retracting it and the plugger 44. The armature 45 and plugger 44 are moved downwardly by a solenoid 41 which is arranged to be energized in a manner to be described.

It is desirable that the plug 33 be held in the test tube 24 after it has been inserted therein by the plugger 44 while the latter is being withdrawn. For this purpose an inverted U-shaped guide and holding member 48 is slidably mounted on a shank portion 49 of the plugger 44 between it and the armature 45. The U-shaped guide and holding member 48 is loosely and slidably mounted on the shank portion 49 and is arranged to be moved downwardly by a coil compression spring 50 which is positioned, as shown more clearly in Figure 1, between the upper end of the guide 48 and the lower end of the armature 45. The guide 48 has lower elongated portions 5| for engaging and gripping more firmly the plug 33 after it has been inserted into the upper end of the test tube 24.

The energization of the feeder solenoid 3| is controlled by a feeder switch 54 which is arranged to be closed by a rod 55 that extends through the vertical base I6 and whose outer end is arranged to be engaged by the test tube 24 when it is positioned in the clip to receive the plug. As shown in Figure 4, the feeder switch 54 is arranged to connect the solenoid 3| for energization across energized terminals 53 which may be connected to a suitable current source as will be understood readily.

Also as illustrated in Figure 4, the cutter soleoid 4| is arranged to be engaged on closure of a cutter switch 58. As illustrated here the cutter switch 58 is arranged to be closed on energization of the feeder solenoid 3| and the movement of the feeder armature to a position where the resilient feeding tongue 26 is retracted out of the path of the movable blade of the cutter 34. The plugger solenoid 41 is arranged to be energized on closure of a plugger switch 59. It will be observed in Figure 4 that the plugger switch 59 is closed on energization of the cutter solenoid 4| and movement of the cutter armature to a position where the movable blade 36 has severed the plug 33 from the strip Is.

In operation it will be assumed that the strip |9 is positioned as shown in Figure 3 of the drawing and that the

terminals

56 and 51 are suitably energized. Fin'ther, it will be assumed that a test tube 24 to be plugged is placed in the clip 25 in the position shown in Figure 2. As a result of the positioning of the test tube 24 as described, the feeder switch 54 is closed and the feeder solenoid 3| is energized. The armature 30 is drawn into the solenoid 3|, the coil tension spring 29 is extended and the resilient feeding tongue 26 is retracted to a position out of the path of the movable blade 36. On completion of this movement by the feeder armature 30, cutter switch 58 is closed and cutter solenoid 4| is energized. The cutter armature 40 is attracted and the movable blade 36 is operated to cooperate with the stationary blade 35 and cut off the plug 33 from the strip I9. At the same time the spring 37 is tensioned. At the end of the forward stroke of the cutter armature 40, the plugger switch 59 is closed and the plugger solenoid 4'! is energized. The plugger armature 45 is moved downwardly and the spring 46 is extended. The plugger 44 engages the plug 33 intermediate its ends and moves the same through the aperture 23 downwardly into the test tube 24. At the same time the coil compression spring 55 causes the U-shaped guide and holding member 48 to be moved downwardly with the edges of the lower elongated portions 5| riding over the upper surfaces of the outflared sides 22 of the trough 2|. Further downward movement of the guide 48 is arrested when these edges engage the bottom of the trough 2|. By this time the flat blade plugger 44 has moved downwardly through the aperture 23 and has carried with it the doubled over plug 33. The plugger 44 continues to move downwardly while the guide 48 is held stationary in the trough 2|.

Now the pressure on the test tube 24 is relieved and the feeder switch 54 is opened. As a result the feeder solenoid 3| is deenergized and the spring 29 retracts the feeder armature 30 and, at the same time, the teeth 27 grip the forward end of the strip l9 and move it into the trough 2| preparatory to the next plugging operation. On deenergization of the feeder solenoid 3| and retraction of the feeder armature 30, the cutter switch 58 is opened and the cutter solenoid 4| is deenergized. The spring 31 promptly swings the movable blade 35 back to the position shown in Figure 2. Also the plugger switch 59 is opened and the plugger solenoid 41 is deenergized. The spring 46 retracts the armature 45 and the plugger 44 is withdrawn from the test tube 24. The U-shaped guide and holding member 48 is held in its lowermost position by the coil compression spring 50 while the plugger 44 is being withdrawn by the spring 46 from the test tube 24. In this manner the plug 33 is held in the plugged position and is prevented from being withdrawn together with the plugger 44. After the lower end of the plugger 44 has cleared the aperture 23, the guide 48 is picked up and moved to the position shown in Figure 2 in advance of the movement of the strip l9 into the trough 2|.

Since certain changes can be made in the foregoing construction and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawing and set forth hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

l. A plugging machine for test tubes or the like comprising, in combination, a stationary feeder trough having an aperture in the bottom through which a strip of plugging material can be fed into a test tube positioned generally normal to said trough and in register with said aperture. a feeding tongue movable endwise in said trough for feeding the strip into the same and across said aperture, means for plugging the strip intermediate its ends through said aperture into the test tube, and means for sequentially operating said feeding tongue and plugging means.

2. A plugging machine for test tubes or the like comprising, in combination, a stationary feeder trough having an aperture in the bottom through which a strip of plugging material can be fed into a test tube positioned generally normal to said trough and in register with said aperture, a feeding tongue movable endwise in said trough for feeding the strip into the same and across said aperture, means for cutting the strip to the required length, means for plugging the cut off portion of the strip intermediate its ends through said aperture into the test tube, and means for sequentially operating said feeding tongue and said cutting and plugging means.

3. A plugging machine for test tubes or the like comprising, in combination, a feeder trough having an aperture in the bottom through which a strip of plugging material can be fed into a test tube, means for feeding the strip into said trough, means for plugging the strip through said aperture into the test tube, means cooperating with said plugging means for holding the plugging material in the test tube while said plugging means is being withdrawn therefrom, and means for sequentially operating said feeding and plugging means.

4. A plugging machine fortest tubes or the like comprising, in combination, a feeder trough having an aperturev in the bottom through which a strip of plugging material can be fed into. a test tube positioned generally normal to said trough and in register with said aperture, means I for feeding the strip into. said trough and across said aperture, means in said trough for gripping the strip to hold the same along one side of said aperture in position to, bev fed therethrough, means for plugging the strip intermediate its ends through said aperture into the test tube, and means for sequentially operating said feeding and plugging means.

5.. A plugging machine for test, tubes or the like comprising, in combination, feeder trough 1 having an aperture in the bottom through which a strip of plugging material can be fed into. a test tube positioned generally normal to, said trough and in register with said aperture, means for feeding the strip into said trough and across said aperture, means, for plugging the strip, intermediate its ends. through said aperture, into the test tube, and means responsive-to the; placi o t st tube in positi n to, be; p u ged for que a op rat n said f eding: and plug in m n 6 A u n ma hine for test tubes, or the-like mpr nain c mb nat on. a eeder rough. having an aperture in the bottom through which a strip f p u i aterialcan be fedlinto, a, test t e osi i d enera y n rm l.- to said trou h d n r ister with said. ape tur means. f r ed n s p nto sa d ou h and across, aid aper m a s or utt n h strip; to the re.- quired e h, ansv o plu ng e. ut. ff por o e 1 1 2 n elim dih fi. 1 l1dS: h1Qu h sa d ap re o. h testtu e; and, mea s resoo -si e to a in o te t tube; in; position o p u d o s u n a lr o eratin emiraming, cutting and plugging means,

7. A plugging machineior; test tubes, or the like comprising, in combinatioma; fepdertrough having; an aperture inthe bottom throughwhich a strip f u gin mate ial an. e fed. into a test tube positioned: generally; normal: to said trough and in register with saidaperture, means for feeding thestrip into said trough and across saidaperture, means for-plugging the stripinter-mediate its ends through said apertureinto the test tube, means responsive to-- the-placing of a test tube in position to be plugged for operating said feeding means, and means responsive to the operation of said feeding means for operating said plugging means.

8. A plugging machine for test tubes or the like comprising, in combination, a feeder trough having an aperture in the bottom through which a strip of plugging material can be fed into a test tube positioned generally normal to said trough and in register with said aperture, means for feeding the strip into said trough and across said aperture, means for cutting the strip to the required length, means for plugging the cut off portion of the strip intermediate its ends through said aperture into the test tube, means responsive to the placing of a test tube in position to be plugged for operating said feeding means, means responsive to the operation of said feeding means for operating said cutting means, and means responsive to the operation of said cutting means for operating said plugging means.

9. A machine for pluggingtest tubes or the like with material such as cotton comprising, in combination, a feeder switch arranged to be closed on placing a test tube in position to be plugged, a guide for receiving a strip of plugging material and having an aperture in the bottom at one end through which a short length of the strip can be fed into a test tube, a feeding tongue movable endwise of said guide, a spring connected to said feeding tongue for moving the same along said guide to feed the strip forwardly, a feeder armature connected to said feedingtong-ue, a feeder solenoid for said feeder armature arranged to be energized on closure of said feeder switch to tension said spring and retract said feeding tongue, a cutter-switch operated to closed position bysaid feeder armature on energization of its solenoid", a cutter arranged to out off a predetermined length of the strip of plugging material near said one end ofsaid guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of'said cutter switch to operate said cutter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocablethrough said aperture in said guide for moving the cut off portion of the strip of plugging material therethroug-h into the test tube, a spring connected to said plugger forretracting the same, a plugger armature connected to said plugger, and a plugger solenoid for said plugger armature arrangedto be energized on closure of said plugger switch to operate said plugger;

10. A machine for plugging test tubes or the likewith material such as cotton comprising, in combination, a feeder switch arranged tobe closed by placing a test tube in positiontobe plugged, a horizontally extending guide; forreceiving a strip of plugging material and having an aperture in the bottom atone end through which a short length of thestrip can be fed into a; testtube; therebel'ow, a feeding tongue movable endwise of said: guide anrlhaving teeth forengaging the strip to griptheysame, a spring connected to said feeding; tongue for moving the same along said guide" to; feed the strip; forwardly, a feeder-- armature connected; tosaid feeding tongues afeeder solenoid for" saidfeeder armature arranged; to be energized-on-clbsure of said feeder switch to tensiorr said spring and re"- tract said feeding" tongue; acutter" switcl'r operated to closed position by said feeder armature on energization of its solenoid, a cutter arranged to cut off a predetermined length of the strip of plugging material near said one end of said guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of said cutter switch to operate said cutter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocable through said aperture in said guide for moving the cut off portion of the strip of plugging material therethrough into the test tube therebelow, a spring connected to said plugger for retracting the same, a plugger armature connected to said plugger, and a plugger solenoid for said plugger armature arranged to be energized on closure of said plugger switch to operate said plugger.

11. A machine for plugging test tubes or the like with material such as cotton comprising, in combination, a feeder switch arranged to be closed on placing a test tube in position to be plugged, a guide for receiving a strip of plugging material and having an aperture in the bottom at one end through which a short length of the strip can be fed into a test tube, teeth extending inwardly from said guide near said one end for engaging the strip to prevent backward movement thereof, a feeding tongue movable endwise of said guide and having teeth for engaging the strip to grip the same, a spring connected to said feeding tongue for moving the same along said guide to feed the strip forwardly, a feeder armature connected to said feeding tongue, a feeder solenoid for said feeder armature arranged to be energized on closure of said feeder switch to tension said spring and retract said feeding tongue while the strip is held stationary by said teeth in said guide, a cutter switch operated to closed position by said feeder armature on energization of its solenoid, a cutter arranged to cut off a predetermined length of the strip of plugging material near said one end of said guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of said cutter switch to operate said cutter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocable through said aperture in said guide for moving the cut off portion of the strip of plugging material therethrough into the test tube, a spring connected to said plugger for retracting the same, a plugger armature connected to said plugger, and a plugger solenoid for said plugger armature arranged to be energized on closure of said plugger switch to operate said plugger.

12. A machine for plugging test tubes or the like with material such as cotton comprising, in combination, a feeder switch arranged to be closed on placing a test tube in position to be plugged, a horizontally extending guide for receiving a strip of plugging material and having an aperture in the bottom at one end through which a short length of the strip can be fed into a test tube, said guide being provided with outwardly and upwardly inclined sides at said one end, a feeding tongue movable endwise of said guide, a spring connected to said feeding tongue for moving the same along said guide to feed the strip forwardly, a feeder armature connected to said feeding tongue, a feeder solenoid for said feeder armature arranged to be energized on closure of said feeder switch to tension said spring and retract said feeding tonque, a cutter switch operated to closed position by said feeder armature on energization of its solenoid, a cutter arranged to cut off a predetermined length of the strip of plugging material near said one end of said guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of said cutter switch to operate said out-- ter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocable through said aperture in said guide for moving the cut off portion of the strip of plugging material therethrough into the test tube, a spring connected to said plugger for retracting the same, a plugger armature connected to said plugger, a plugger solenoid for said plugger armature arranged to be energized on closure of said plugger switch to operate said plugger, and guide and holding means carried by said plugger and cooperating with said outwardly inclined sides of said guide for directing the cut off portion of the strip of plugging material through said aperture and for holding the same in the plugged position thereof while said plugger is being retracted by its spring.

13. A machine for plugging test tubes or the like with material such as cotton comprising, in combination, a feeder switch arranged to be closed on placing a test tube in position to be plugged, a horizontally extending guide for receiving a strip of plugging material and having an aperture in the bottom at one end through which a short length of the strip can be fed into a test tube, said guide being provided with outwardly and upwardly inclined sides at said one end, a feeding tongue movable endwise of said guide, a spring connected to said feeding tongue for moving the same along said guide to feed the strip forwardly, a feeder armature connected to said feeding tongue, a feeder solenoid for said feeder armature arranged to be energized on closure of said feeder switch to tension said spring and retract said feeding tongue, a cutter switch operated to closed position by said feeder armature on energization of its solenoid, a cutter arranged to cut off a predetermined length of the strip of plugging material near said one end of said guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of said cutter switch to operate said cutter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocable through said aperture in said guide for moving the cut off portion of the strip of plugging material therethrough into the test tube, a spring connected to said plugger for retracting the same, a plugger armature connected to said plugger, a plugger solenoid for said plugger armature arranged to be energized on closure of said plugger switch to operate said plugger, an inverted U-shaped guide and holding member slidably mounted on said plugger and biased toward its operating end and having outwardly biased arms the extremities of which engage and slide over said outwardly inclined sides of said guide for directing the cut off portion of the strip of plugging material through said aperture and for holding the same in the plugged 9 position thereof while said plugger is being retracted by its spring.

14. A machine for lugging test tubes or the like with material such as cotton comprising, in combination, a feeder switch arranged to be closed on placing a test tube in position to be plugged, a horizontally extending guide for receiving a strip of plugging material and having an aperture in the bottom at one end through which a short length of the strip can be fed into a test tube therebelow, said guide being provided with outwardly and upwardly inclined sides at said one end, teeth extending inwardly from said guide near said one end for engaging the strip to prevent backward movement thereof, a resilient feeding tongue movable endwise of said guide and having teeth for engaging the strip to grip the same, a spring connected to said feeding tongue for moving the same along said guide to feed the strip forwardly, a feeder armature connected to said feeding tongue, a feeder solenoid for said feeder armature arranged to be energized on closure of said feeder switch to tension said spring and retract said feeding tongue while the strip is held stationary by said teeth in said guide, a cutter switch operated to closed position by said feeder armature on energization of its solenoid, a cutter arranged to cut off a pre determined length of the strip of plugging material near said one end of said guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of said cutter switch to operate said cutter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocable through said aperture in said guide for moving the cut off portion of the strip of plugging material therethrough into the test tube therebelow, a spring connected to said plugger for retracting the same, a plugger armature connected to said plugger, a plugger solenoid for said plugger armature arranged to be energized on closure of said plugger switch to operate said plugger, and guide and holding means carried by said plugger and cooperating with said outwardly inclined sides of said guide for directing the cut off portion of the strip of plugging material through said aperture and for holding the same in the plugged position thereof while said plugger is being retracted by its spring.

15. A machine far plugging test tubes or the like with material such as cotton comprising, in combination, a feeder switch arranged to be closed on placing a test tube in position to be plugged, a horizontally extending guide for receiving a strip of plugging material and having an aperture in the bottom at one end through which a short length of the strip can be fed into ii) a test tube therebelow, said guide being provided with outwardly and upwardly inclined sides at said one end, teeth extending inwardly from said guide near said one end for engaging the strip to prevent backward movement thereof, a resilient feeding tongue movable endwise of said guide and having teeth for engaging the strip to grip the same, a spring connected to said feeding tongue for moving the same along said guide to feed the strip forwardly, a feeder armature connected to said feeding tongue, a feeder solenoid for said feeder armature arranged to be energized on closure of said feeder switch to tension said spring and retract said feeding tongue while the strip is held stationary by said teeth in said guide, a cutter switch operated to closed position by said feeder armature on energization of its solenoid, a cutter arranged to cut off a predetermined length of the strip of plugging material near said one end of said guide, a spring connected to said cutter for retracting the same, a cutter armature connected to said cutter, a cutter solenoid for said cutter armature arranged to be energized on closure of said cutter switch to operate said outter, a plugger switch operated to closed position by said cutter armature on energization of its solenoid, a plugger reciprocable through said aperture in said guide for moving the cut on portion of the strip of plugging material therethrough into the test tube therebelow, a spring connected to said plugger for retracting the same, a plugger armature connected to said plugger, a plugger solenoid for said plugger armature arranged to be energized on closure of said plugger switch to operate said plugger, and an inverted U-shaped guide and holding member slidably mounted on said plugger and biased toward its operating end and having outwardly biased arms the extremities of which engage and slide over said outwardly inclined sides of said guide for directing the cut ofi portion of the strip of plugging material through said aperture and for holding the same in the plugged position thereof while said plugger is being retracted by its spring.

WILLIAM GOLD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,171,572 Kelley Sept. 5, 1939 2,269,722 Lakso Jan. 13, 1942 2,304,932 Lakso Dec. 15, 1942 2,412,089 Kelley Dec. 3, 1946 FOREIGN PATENTS Number Country Date 334,107 Great Britain Aug. 28, 1930