US2921421A - Protector mechanism for wrapping machine - Google Patents

Description

Jam. 19, 196@ c, QUELLETTE ETAL 2,921,421

PROTECTOR MECHANISM FOR WRAPPING MACHINE Filed June 17, 1957 2 Sheets-Sheet 1 INVENTORS CLARENCE P. OUELLETTE RICHARD T. NATHAN @0041 7 ATTORNE Jam, 19, 1960 c. P. OUELLETTE ET AL 2,921,421

PROTECTOR MECHANISM FOR WRAPPING MACHINE Filed June 17, 195'? g Y nm 2 Sheets-Sheet 2 INVENTORS CLARENCE F? OUELLETTE 3 RICHARD T NATHAN ATTORNEY United States Patent PROTECTOR MECHANISM FOR WRAPPING MACHINE Clarence P. Ouellette, East Longmeadow, and Richard T. Nathan, Sprmgheld, Mass, assignor's to Crompton & Knowles Corporation, Worcester, Mass., a corporation of Massachusetts 1 Application June 17, 1957, Serial No. 666,022

25 Claims. (Cl. 53-53) 1 wrapping head which includes a vertically reciprocating plunger which moves the package to be wrapped up against the wrapping paper or the like and then through a folder or former. Among the articles which can thus be wrapped are sliced food articles such as cheese or meat, and also other food articles such as ground meat patties. Food articles of this type are not ordinarily able to withstand the strain of the wrapping operation and it is customary to place the articles on thin supporting elements or pallets such as cardboard which receives the upward thrust of the plunger and reinforces the food articles and enables them to withstand the forces in voived in the wrapping operation.

The article supporting elements can be applied to the conveyor in any manner either mechanically or by hand and then the food articles are placed on top of the elements and the latter together with the articles on them are then moved by the conveyor to the wrapping head. If for any reason an element should fail to have an article on it the conveyor, operating according to former practice, will deliver the element to the wrapping head. The machine is controlled by a detector mechanism arranged along the conveyor and under these conditions will not deliver a wrapper sheet to the head, but the plunger will rise and since there is no wrapper to hold the cardboard element in place it is likely to fall into any one of a number of positions where it will interfere with subsequent operations of the wrapping head and may in fact damage the head.

It is an important object of the present invention to provide means for removing an empty element from the conveyor to prevent it from reaching the wrapping head where it might do damage to the mechanism. This means for removing the empty or unoccupied element includes an ejector arranged at one side of the conveyor and having drive connections with the machine which cause the ejector to attempt to remove an element each time the conveyor presents an element to the ejecting station. If the element carries an article the latter prevents removal by the ejector, but if the element is empty it is promptly removed by the ejector.

It is a further object of the invention to provide the ejector with an arm which makes a revolution at the ejecting station each time an element, with or without an article on it, is presented at the station by the conveyor and provide yielding controls for the arm which will enable it topass over an empty element but will enable an article on the element to change the normal angular position of the arm and prevent it from passing over the element.

veyor to a receiver.

It is a further object of the invention to provide a movable element supporting disc or the like a part of which is located under the path traversed by an element as it is moved by the conveyor. The disc cooperates with the arm to grip an empty element and move it from the con- It is a still further object of the invention to provide means by which the arm is lowered against an element to frictionally engage it preparatory to its removal. If an article is on the element the arm would frictionally engage the disc and be forced against the article to damage it unless some provision were made to prevent engage.- ment of the disc by the arm. This is accomplished by providing the disc with an opening into which the descending arm, if deflected by an article, can move to avoid contact with the disc;

It is another object of the invention to provide a carrier which rotates preferably about a vertical axis and has the aforesaid arm pivoted thereto about a second axis spaced from theaxis of rotation of the carrier. As the arm revolves about the carrier axis a fixed cam means acts to lower the arm so that it can perform the functions already mentioned. This carrier may also have the previouslyrnentioned disc fastened thereto and the opening in the disc may be in the form of a slot concentric with the second axis.

It is a further object of the invention to provide an ejector unit which can be applied to wrapping machines already in existence with very little change in their structure or mode of operation. The unit includes a stationary shaft, preferably vertical, around which the aforesaid disc, carrier and arm move. The previously mentioned downward motion of the arm is effected by a cam secured in angularly adjusted position on the upper end of the vertical shaft to vary the time of depression of the arm to adapt the latter to elements of different-sizes.

In the use of machines of the general type set forth herein it is customary to locate several employees along the conveyor whose duty it is to place food articles on the elements. In this way the machine can operate at higher speeds than would be possible with only one em} ployee. "In the past the person nearest thewrapping head has been charged with the responsibility of seeing that an article is on each-element and to remove empty elements. At times this involves stopping the machine by the employee and the otheremployees are temporarily idle. It is a further object of the invention to provide automatic means for removing an empty element so that the former periods of idleness can be avoided. The empty elements are removed in a manner which will not damage them so that they can be put back on the conveyor.

In order that the invention may be clearly understood reference is made to the accompanying drawings which illustrate by way of example the embodiments of the invention and in which: I j

Fig. 1 isa plan view, parts broken away and parts omitted, of the conveyor part of a wrapping machine having the present invention applied thereto,

Fig. 2 is a longitudinal vertical section on line 2-}2, Fig. 1,

Fig. 3 is .an enlarged vertical Fig. 1,

Fig. 4 is a horizontal section on line 4+4, Fig.2;

Fig. 5 is an enlarged detailed vertical section on, line 5'5,Fig.4, .f

Fig. 6 is a bottom plan view of the. cam showing the supporting shaft therefor in section, I.

Fig. 7 is a diagrammatic viewindicating part of. the wrapping head of the-machine.,,

section 'on line 33,

Figs. 8-11 inclusive are diagrammatic views illustrating the operation of the invention, and

Fig. 12 is a group view showing examples of three different forms of supporting elements or pallets which may be used with the invention.

Referring to Fig. 1, the runway or conveyor system for the wrapping machine has sides 1 and 2 connected by cross guide bars 3 which support adjustable guide rails 4 and 5. Two screw members 6 and 7 are journaled to rotate in the sides 1 and 2 and are operatively connect:d to the side rails 4 and 5. The screw 7 has a handle 8 secured thereto and a chain 9 is trained over sprockets i and 11 on the screws 7 and 6 respectively. By turning the handle 8 the guide rails 4 and may be caused to move apart or together, depending upon the direction of turning the handle to accommodate the conveyor to use with supporting elements of different widths. The supporting elements are shown at E and are made of flat, thin stifi material, such as cardboard.

The machine has a driving shaft 15 to which are secured sprockets 16 and 17 which operate the conveyor chains 18 and 19 respectively. These two conveyor chains move in unison and to the right as viewed in Fig. 1.

Beyond the right-hand end of Fig. 1 is located a wrapping head WH which has a plunger system 20 and a guide former 21 having an opening 22 slightly larger but of the same general shape as the article to be wrapped. The sheet wrapper W is supplied by mechanism not shown but well understood and moves over the plunger and is pushed through the opening 22 by an article on the plunger. Continued upward movement of the plunger folds the wrapper down along the sides of the article after which folders (not shown) push the draping sides of the wrapper under the article. The conveyor has advancers 23 located at spaced distances therealong to push the articles to be wrapped one at a time onto the plunger. These advancers are connected to the chains 18 and :19 and project up between stationary runs 24 on which the packages to be wrapped slide toward the wrapper head. The chains 18 and 19 and the advancers 23 may be considered collectively to provide the conveyor.

The plunger 20 operates at regularly timed intervals so long as the machine is in operation, but a wrapper will not be fed over the plunger unless there is a full package on the conveyor to be wrapped. Arranged along the conveyor will be a detector 25 which is normally down and when in that position will prevent feed of a wrapper mechanism, but whenever the detector is lifted by a full package as indicated in Fig. 7 a wrapper will be advanced to the position shown in Fig. 7. If the detector 25 remains down due to absence of a full package no wrapper is advanced but the plunger will nevertheless go through its usual operation and have an idle upward stroke.

The matter thus far described is of common construction and may operate in the usual manner, the advancers 23 moving the packages or articles to be wrapped one at a time to the plunger after which the article may be wrapped according to known procedures. It should be noted that if an element E not having an article thereon should pass under detector 25 the latter will not be lifted and no wrapper will be present to hold the element in place and it can fall off the plunger to positions where it can damage or interfere with subsequent operations of the plunger. The element could get caught, for instance, between the plunger and the guide 21. The matter thus far described is for illustrative purposes since the invention is not necessarily limited to the specific details alreadydescrib'ed. During operation of the machine, element E is being continuously moved by the conveyor.

The present invention is provided to protect the wrapper head by preventing empty elements E from reaching it, and in carrying the invention into effect one of the sides of the machine, the side 1 as shown herein, has secured thereto a unit support stand in which is jour- 4 naled a short shaft 31 the left end of which as shown in Fig. 3 is provided with a sprocket wheel 32 meshing with a chain 33. This chain is driven by a sprocket 34 on a shaft 35 to which is secured another sprocket wheel 36 meshing with a chain 37. The latter is trained over another sprocket wheel 38 secured to the driving shaft 15. The sprocket 34 is preferably smaller than the sprocket 36 and the sprocket 32 is larger than the sprocket 34. The sprockets 36 and 38 are preferably of the same size. The sprockets are of such size that shaft 31 makes one rotation each time an advancer approaches the ejector to be described.

The right-hand end of the short shaft 31 has secured thereto a mitre gear 40 by means of a key 41 and this mitre meshes with a second mitre gear 42 of the same size rotatable on a fixed shaft 43 the lower end of which is held in the unit stand 30 by a set screw 44. The shaft 43 has preferably a vertical axis, called the primary axis herein, and has a collar 45 thereon which supports the second mitre 42.

A carrier 50 has a bearing 51 which rotates on the vertical shaft 43- and is formed at its upper end with a flange 52 to the under side of which is secured a supporting disc 53 continuously rotating. Upward motion of the carrier with respect to the shaft 43 is prevented by a collar 54 held to the shaft 43 by a set screw 55.

Secured to the top of shaft 43 by a set screw 56 is a stationary cam member 57 the under surface of which has a cam face 58 part 59 of which is low and part 60 of which is high. The reason for this cam will appear presently.

A guide 65 having a vertical secondary axis which is preferably parallel to the axis of shaft 43 is secured to the carrier by a screw 66 which also passes through the disc 53 and serves to hold the disc, carrier and the guide fixed to each other. If desired a second screw 67 can be used to fasten the disc to the carrier. Slidable vertically on the guide 65 is the hub 68 of a lever or ejector arm designated generally at 69. A compression spring 70 interposed operatively between the carrier and the bottom of the hub 68 acts normally to hold the hub and the ejector arm in the raised position shown in Fig. 3. A force transmitter 71 is also slidable on the guide 65 and has a fork 72 which receives the shaft 43, see Fig. 4. The effect of the work is to require the transmitter to maintain a substantially fixed angular position with respect to the carrier as the latter rotates around shaft 43. Arm 69 rotates continuously and without interruption while the machine is in operation.

A roll 75 is rotatable on a pin 76 in the upper part of the force transmitter and the axis of the pin is substantially radial with respect to the shaft 43 to keep the roll properly related to the cam. The roll 75 bears against the previously described cam face 58 and the low part 59 of the cam depresses the transmitter 71 and the hub 68 against the action on spring 70, as will be explained.

The arm 69 has a short extending end 80, see Fig. 4, to which is attached one end of a tension spring 81, the other end of which is anchored as at 82 to the carrier. A stop 83 has preferably a nonmetallic sleeve 84 to engage the end and cooperates with the spring to hold the arm 69 in the normal angular position with respect to the carrier and disc 53 shown in Fig. 4.

The outer end of the arm has a vertical bearing 85 in which is slidably mounted a plunger 86 to the upper end of which is secured a collar 87. The lower end of the plunger is provided with a friction pad 88 which in the present instance is soft rubber and a compression spring 89 within the lower end of the bearing 85 presses the plunger down to hold the stop collar 87 against the top of the bearing 85 and hold the friction pad or foot 88 in its normal down position with respect to the arm 69.

When the arm 69 is in the normal position shown in Fig. 4 the friction pad will be over a solid part of the disc 53 but the latter is provided with an arcuate slot 91 which is concentric with the secondary axis, or axis of arm 69.

The disc 53 has the upper surface thereof substantially aligned with or no higher than the upper surfaces of the runs 24 on which the articles to be wrapped slide. The reason for this relation is to permit an article on the runs to move over a part of the disc as shown in Fig. 4. The run 24 near the disc may be cut away at 95 to make room for the disc.

In the operation of the ejector the reenforcing supporting elements or pallets E will be placed on the conveyor, one in front of each of the advancers 23.- After the elements have thus been located on the conveyor an article A will be placed on each element before the latter reaches the ejector station ES arranged along the conveyor at the site of the ejector. As each element reaches the ejector station the arm 69 will be about in the position shown in Fig. 1 so that continued counterclockwise rotation of the carrier Will tend to move the arm over the element. If there is an article A on the carrier, see Fig. 8, it will project upwardly far enough above the flat thin element E to engage the lower end of the bearing 85 and prevent the foot 88 from moving over the element.- Under this condition spring 81 will be stretched as the carrier continues to rotate. The spring 81 is weak and yields readily to permit change of the angular relation of arm 69 relative to the carrier to prevent the bearing 85 from deforming the article at the station. If, however, there is no article on the element the bearing 85 and foot 88 will move over the element as suggested in Fig. 9.

At about the time foot 88 would be over an empty element the low area 59 of the cam will depress the transmitter 71 and the arm 69 to push the friction foot 88 down. If at this time there is an article A on the element the foot will enter slot 91, but if the element is empty the foot will be moved down against it. At the time in the cycle of the ejector when the cam depresses the foot 88 part of the element will be supported by an underlying solid part of the disc 53. If the element is empty the foot will press the element down on the disc and continued turning of the disc and foot, having the element gripped between it and the moving foot, will move the element from the position shown in Fig. 9 to the position shown in Fig. 10, at which time the ejector arm is released by the cam and can move upwardly, after which the empty element moves intoa receptacle R located at the side of the conveyor. It should be noted that the guide wall 4 has a slot 96 in the lower end thereof adjacent to the ejector means through which the empty element can move. This slot is not high enough to permit an element and its article to pass off the conveyor should the arm 69 by any circumstance be able to establish a frictional grip on a protruding edge of the element. When ejected, the element will move in the direction of rotation of the ejector until released whereupon the element will enter receptacle R. The ejector is capable of moving in the opposite direction of said rotation when it is engaged by an article on the element to permit the latter to continue toward the wrapping head-WH.

Itwill be noted that if the arm 69 were depressed while foot 88 was over a solid part of the disc the latter due to frictional contact with the foot would force the bearing 85 against the article and deform it. This is avoided by having the disc continue to turn as the arm 69 is deflected to locate the slot 91 under the foot 88 before it is depressed.

From the foregoing it will be understood that an article must be present on an element arriving at the ejector station before the element can continue toward the wrapping head. The element is removed if no article is on it and is thus prevented from reaching the head Where it might damage or interfere with proper operation. of the wrapping mechanism. The ejector means is driven by the same mechanism which moves the conveyor and also the wrapping head so that it is at all times in proper timed relation with respect to these two latter parts. The bearing of the ejector arm isnorrnally in a high enough position to pass over an empty element and will normally be over a solid part of the disc 53 and after it has passed over some part of the empty element the cam 57 then acts to lower the ejector to present the foot 88 against the element. Under these conditions the foot 88 and the disc will be moved in unison and can grip the element between them to eject it through the slot 96 into the receiver R. Fig. 12 shows three different forms of elements, the element E being similar to that shown in Fig. 1 for instance, element Ea being circular and element Eb being oblong. With supporting elements of different shapes and sizes it may be desirable to adjust the time at which the arm 69 is depressed by the cam and for this purpose the screw 56 is provided to permit angular adjustment of the cam on the upper part of the stationary shaft 43. While the slot 91 has been shown as concentric with the secondary vertical axis this is not an essential feature but has been found convenient in the operationof the ejector. The cam 57 and the transmitter 71 can be considered to be one form of operating means for lowering the ejector arm and these parts need not necessarily be exactly as shown in the drawings. The invention also includes the ejector unit which is supported on the mounting means or stand 30, the unit including the parts associated with the vertical shaft '43 such as the carrier 50, the disc 53, the guide '65, the arm 69 and the friction foot 88 and its spring controlled plunger 86.

Moreover, the operation of the parts, i.e., the conveyor for the elements and the ejector means are continuous and ejection of an element or indication of the presence of material on an element is without opera tional interruption resulting in a high rate of production of wrapped articles.

Also, the invention provides automatic means for removing empty elements to avoid the temporary periods of idleness on the part of several employees such as occurs under the prevailing prior practice. The removed elements are not damaged and can be put back on the conveyor. I

Having now particularly described and ascertained the nature of the invention and in what manner the same is to be performed, what is claimed is:

1. In protectormechanism for the wrapping head of a wrapping machine provided with driving means, a conveyor moved by said driving means to transport thin flat support elements toward said head, each element normally provided with an article thereon to be wrapped therewith at said head but being capable of damaging the head if delivered thereto by the conveyor without an article thereon, and continuously rotating ejector means located along said conveyor operated by said driving means and effective without interruption of said rotation to remove from the conveyor an element not having an article thereon in the direction of rotation of said means but ineffective to remove an element having an article thereon by having a movement in the opposite direction' of said rotation when said means is engaged by said article.

2. The protector mechanism set forth in claim 1 wherein the conveyor has advancing members to move the elements continuously and without interruption one at a time to said ejector means and connection between the driving means and the ejecting means cause the latter while continuously moving angularly to attempt an ejecting operation each time a member moves an element in the path of said ejector means.

3. The protector mechanism set forth in claim 1 where in the ejector means includes a part which moves over "7 an element not having an article thereon while said part and said element are both moving, the part being prevented from moving over an element by engagement with an article on the element.

4. The protector mechanism set forth in claim 1 wherein the said ejector means includes a carrier rotated by said driving means, an arm moved by the carrier along a path part of which is normally over part of an element on the conveyor and another part of which extends in a direction away from the conveyor, and means cooperative with the arm due to movement thereof by the carrier to move the arm when in the first named part of said path toward the conveyor and into engagement with an element which does not have an article thereon to remove the element from the conveyor when the arm is moving along said other part of its path.

5. The protector mechanism set forth in claim 1 wherein the said ejector means includes a stationary cam and an arm moving angularly with respect thereto and also movable toward and from the conveyor and rotated by said driving means along a path part of which is normally over an element on the conveyor, the stationary cam and arm cooperating due to said rotation of said arm to move the latter into engagement with an element which does not have an article thereon when said arm is over the element.

6. The protector mechanism set forth in claim 1 wherein said ejector means includes a carrier rotated about a vertical axis by said driving means, a vertical guide on the carrier revolved by the carrier about said vertical axis, an arm pivoted on the guide and slidable thereon in a direction toward the conveyor, yielding means normally holding the arm in a given relative angular position with respect to the carrier but enabling the arm to move away from said given angular position relatively to the carrier, and means to move the arm toward the conveyor when the arm moves over the conveyor, an article on an element on the conveyor engaging and causing the arm to move away from said given angular position and the arm remaining in said given angular position when moving over an element without an article thereon.

7. In protector mechanism for the wrapping head of a wrapping machine provided with driving means, a conveyor moved continuously by said driving means to transport toward said head thin flat support elements each of which may be empty or have thereon an article to be wrapped therewith by the head, continuously moving element ejecting means located at an ejecting station located along the conveyor including an arm, means operatively connected to said driving means to swing said arm over an empty element at said station while said arm and element are both moving, and stationary means causing the arm to engage an empty element frictionally and remove it from the conveyor along part of the path of movement of said arm to prevent the element from reaching the head, an article if on an element at said station preventing said arm from removing the element from the conveyor by moving said arm in a direction opposite of said path.

8. In protector mechanism for the wrapping head of a wrapping machine provided with driving means, a conveyor moved constantly by said driving means to transport thin flat support elements toward said head, each element normally provided with an article thereon to be wrapped therewith at said head but being capable of damaging the head it delivered thereto by the conveyor without an article thereon, ejector means having continuous angular motion located at an ejector station'arranged along said conveyor having an operation effective to remove from the conveyor a continuously moving element not having an article thereon but the operation thereon, and stationary and movable operative connections between the drive means and ejector means causing the latter to have an operation each time the drive means causes the conveyor to move an element to said ejecting station.

9. An ejector unit for a wrapping machine provided with a horizontal conveyor and drive means therefor, said unit including a carrier to be rotated by the drive means about a primary vertical axis, guide means mounted on the carrier rotating therewith and having a secondary vertical axis spaced from the primary axis, an ejector arm slidable vertically on the guide means and pivoted thereon to swing about said secondary axis, yielding means normally maintaining a given angular relation between the carrier and arm but enabling the latter to change the angular relation thereof with respect to the carrier, and operating means effective due to rotation of the carrier about the primary axis to cause the ejector arm to move downwardly on said guide means.

10. The unit set forth in claim 9 wherein the guide means is a round vertical rod on which the ejector arm slides and turns and resilient means surrounding part of the rod acts to lift the arm after it has been moved down by said operating means.

11. The unit set forth in claim 9 wherein the guide means is a roundvertical rod on which the ejector arm slides and turns and the operating means includes a cam and a depressor for the arm operatively related to the cam and arm and slidable on the rod.

12. The unit set forth in claim 9 wherein the operating means includesa cam above the ejector arm and resilient means below the arm tends to move the latter toward the cam.

13. The unit set forth in claim 9 wherein the carrier rotates about a fixed vertical shaft and the operating means includes a cam fixed to the upper part of the shaft.

14. The unit set forth in claim 9 wherein the operating means includes a fixed cam and a force transmitter between the cam and the ejector arm slidable on the guide means.

15. The unit set forth in claim 9 wherein the carrier is rotatable about a fixed shaft and the operating means includes a cam fixed to the shaft and a force transmitter slidable on the guide means between the cam and arm, the transmitter having a roll to engage the cam, and a connection between the shaft and transmitter holds the axis of the roll substantially fixed with respect to the carrier.

16. The unit set forth in claim 9 wherein the arm has a plunger slidable thereon along an axis substantially parallel to said axes and a spring normally holds the plunger in down position but enables it to move upwardly with respect to the arm.

17. The unit set forth in claim 9 wherein the arm has a downwardly facing element engaging friction foot mounted thereon for upward movement relative to the arm against the action of a spring carried by the arm.

18. The unit set forth in claim 9 wherein the carrier supports a stop and a spring normally effective to maintain the arm against the stop in said given angular relation can yield to enable the arm to move away from said stop and change the angular relation thereof with respect to the carrier.

19. The ejector unit set forth in claim 9 wherein a support means rotates with the carrier under said ejector arm and cooperates with the latter to grip an element between the arm and support means.

20. The ejector unit set forth in claim 19' wherein the support means is a disc having a slot therein concentric with the secondary axis to receive a friction foot on the arm when the latter changes the angular relation thereof with respect to the carrier.

21. The ejector unit set forth in claim 20 wherein the disc'has a solid part thereof under the arm when the latter is in said given angular position and the disc has an opening therein over which the arm moves when 9 it changes the angular relation thereof with respect to the carrier.

22. In protector mechanism for the wrapping head of a wrapping machine provided with driving means, a conveyor moved by said driving means to transport thin fiat support elements toward said head, each element normally provided with an article thereon to be wrapped therewith at said head but being capable of damaging the head if delivered thereto by the conveyor without an article thereon, ejector means located along said conveyor operated by said driving means and effective to remove from the conveyor an-element not having an article thereon but ineffective to remove an element having an article thereon, and a support adjacent to the conveyor for an element over part of which support the element is moved by the conveyor, the support being moved by the driving means and cooperating with the ejector means to remove an element which does not have an article thereon.

23. The protection mechanism set forth in claim 22 wherein the support and ejector means are moved by the driving means about a common vertical axis and an element to be removed is gripped frictionally between the support and the ejector means.

24. The protector mechanism set forth in claim 22 wherein the ejector means has a foot thereon which moves down toward the support and when effective to remove an element from the conveyor is over a solid part of the support and when ineffective to remove an element is out of vertical alignment with the support.

25. In protector mechanism for the wrapping head of a wrapping machine provided with driving means, a conveyor moved by said driving means to transport toward said head thin flat support elements each of which may be empty or have thereon an article to be wrapped therewith by the head, element ejecting means located at an ejecting station located along the conveyor including an arm, means operatively connected to said driving means to swing said arm over an empty element at said station, means causing the arm to engage an empty element and remove it from the conveyor to prevent it from reaching the head, an article if on an element at said station preventing said arm from removing the element from the conveyor, and a supporting disc at said station for an element on the conveyor rotated by said driving means and cooperating with the arm to remove an empty element at said station.

References Cited in the file of this patent UNITED STATES PATENTS 2,160,319 Swartz May 30, 1939 2,496,877 Krueger Feb. 7, 1950 2,716,487 COX Aug. 30, 1955 2,765,606 Brown Oct. 9, 1956

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