US 2765816 A
Description (OCR text may contain errors)
Oct. 9, 1956 Filed May 26, 1954 C. F. CARTER BAG FILLING MACHINE 5 Sheets-Sheet l 1 NVENT OR 6701211001. mfi w BY [44% waww ATTORNEYS Oct. 9, 1956 c. F. CARTER 2,765,816
BAG FILLING MACHINE Filed May 26, 1954 5 Sheets-Sheet 2 INVENTOR Warsaw}? Carir ATTORNEYS @ct. 9, 1956 c. F. CARTER BAG FILLING MACHINE 5 Shee ts-Sheet 3 Filed May 26. 1954 I N VE N T OR flarelzcel. Larier ATTORNEYS Oct. 9, 1956 c. F. CARTER BAG FILLING MACHINE 5 Shoets-Sheet 4 Filed May 26, 1954 ATTORNEYS Oct. 9, 1956 c. F. CARTER BAG FILLING MACHINE 5 Sheets-Sheet 5 Filed May 26, .1954
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ATTORNEYS United States Patent 2,765,81d BAG FILLING MACHINE Clarence F. Carter, Danville, Ill. Application May 26, 1954, Serial No. 432,419 Claims. (Cl. 141-65) This invention relates generally to a filling machine for dispensing particulate material into collapsible containers such as bags. More particularly the invention is directed to an apparatus adapted for filling valve bags wherein a chamber surrounding the bag to be filled is evacuated to draw the particulate material into the bag being filled.
The so-called valve bag, which is extensively used as a container for cement and many other particulate materials, is formed with a sewed or glued seam at the opposite ends of the bag with one corner of the bag being provided with an inwardly opening lateral aperture to permit the introduction of the material into the bag. Generally the material is introduced by means of a filling spout inserted through the lateral aperture at one corner of the bag. Particularly where'valve bags are filled with finely divided or powdered particulate material, it is a problem to keep down the amount of finely powdered material which seeps out around the filling nozzle during filling of the bag. Some of this powdered material becomes suspended in the atmosphere surrounding the bag filling machine to create an unhealthy atmosphere for the filling machine operators. Further, this seepage of finely divided particulate material makes frequent cleaning of the machine necessary to remove the accumulations of powdered material which collect around the machine and thus interfere with the elficient operation thereof.
The hereinafter described invention has been developed to overcome many of the objections existent in the use of prior bag filling machines. The filling apparatus of this invention is particularly adapted for use in the filling of valve bags with finely divided or powdered material although it will be readily recognized that it is capable of general utility in the filling of valve bags with any particulate material.
It is a principal object of this invention to provide a bag filling machine having a basket structure provided with a hinged portion to permit the bag to be introduced onto and removed from said basket structure and with the basket structure being enclosed within a shroud which is evacuated to effect filling of the bag, said shroud having a door therein to permit the bag to be introduced into and removed from the filling machine.
It is a further object of this invention to provide a bag filling apparatus having a basket structure providing a cavity generally conforming to the outer contour of the bag in its filled state-with a filling spout carried within the basket structure so as to extend into the lateral aperture of the valve bag to be filled and a selectively actuatable clamp assembly movable into engagement with the filling spout to retain a bagon said spout during filling, the basket structure being enclosed in a shroud which may be subjected to a vacuum to draw particulate material into the bag through the filling spout.
It. is an additional object; of this invention to provide in a bag filling machine a bag supporting basket structure having, an interior cavity generally conforming to the bag in its filled state with a filling spout and selectively actuatable clamping assembly mounted across the upper end of said basket structure to clamp the bag Within the basket structure, said filling spout and assembly being yieldably mounted relative to'the basket structure to accommodate changes in the contour ofthebag during the filling operation, the basket structure carrying the yieldably mounted 2,765,816 Patented Oct. 9, 1956 filling spout and assembly being adapted to be coupled to a weighing scales to register the weight of the material dispensed into the bag.
It is also an object of this invention to provide a valve bag filling machine wherein the bag to be filled is positioned during filling within an evacuated chamber and a filling spout positioned within the aperture of the bag is connected to a hopper containing particulate material to be dispensed, said filling spout having a material, feeding auger extending axially thereof and said hopper having a porous section adjacent the hopper outlet connectable to a source of low pressure air to distribute up along the sides of the hopper a layer of air to alleviate bridging or arching of the material within the hopper Various further and more specific objects, features and advantages of the instant invention will be apparent from the hereinafter detailed description given in connection with the accompanying drawings which form a part of this specification and illustrate, merely by way of example, a preferred form of the invention. The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the apparatus herein disclosed.
In the drawings:
Figure 1 is a vertical sectional view of the bag filling machine.
Figure 2 is a sectional view taken on line 22 of Figure 1.
Figure 3 is a sectional view taken on line 3-3 of Figure 1.
Figure 4 is a top plan view taken on line 4-4 of Figure 1.
Figure 5 is a detailed sectional view illustrating the filling spout and its associated clamping assembly in relation to a valve bag being filled.
Figure 6 is a detailed sectional view taken on line 6-6 of Figure 5.
Figure 7 is a detailed sectional view of a modified form of filling spout.
Referring to the drawings and more specifically to Figures 1 and 2, the bag filling machine of the instant invention has a shroud 10 which provides a chamber in which the bag is positioned during the filling operation. The shroud is suitably supported by legs 11 and has a conduit 12 communicating therewith adapted to be coupled to a suitable vacuum pump or other vacuum source (not shown) to permit the shroud to be evacuated to eifect the bag filling operation. As will be apparent from the description given hereinafter, conduit 12 is suitably controlled by a three-way valve (not shown) which is operable to alternately connect the shroud to the vacuum source or vent the shroud toatmosphere.
The shroud 10 is provided with a door 13 which in- I eludes one corner of the shroud and is suitably mounted on hinges 14 so as to permit opening of the shroud for the introduction of the bag to be filled and removal of the bag after it has been filled; The configuration of the door 13 in shroud 10 is more clearly shown in Figures 3 and 4, with Figure 4 illustrating the door 13 in its open position to permit the insertion and removal of the bag. Also, as shown in Figure 4, a pneumatic cylinder 15, pivotally mounted at 16 to the. top of the shroud 10, is effective upon the introduction of pressure thereinto to open the door 13. Actuating rod 17, extending outwardly from cylinder 15, is pivotally secured at 18 to the top of door 13 to enable the pneumatic cylinder to selectively open or close the door 13 of shroud 10. The door 13 has a resilient sealing strip 19 suitably secured along the edges thereof to insure that the door in its closed position will seal against the edge of the shroud 10 to preclude the leakage of air into the shroud during the filling operation when such shroud is-under vacuum.
Mounted above the shroud on supports 25 is a weighing scales 26 having its load responsive arm 27 extending downwardly therefrom through an aperture in the top of the shroud 10. A flexible bellows 28 is secured around the arm 27 and to the top of shroud 10 to permit axial movement of the arm while preventing leakage of air into the shroud where the arm enters the shroud. The scales 26 may be of any suitable construction and since its specific construction forms no part of this invention, it is not illustrated in detail on the drawings. As will become apparent from a description of the bag filling operation given below, it is preferred that the scales 26 be coupled to a suitable automatic control so that the scales which is responsive to the weight of material introduced into the bag being filled will be operable through such control to initiate actuation of the filling machine parts to terminate the filling at the desired point, release the vacuum from the shroud 10 and open the door 13 to permit removal of the filled bag and the introduction of a new bag to be filled.
Rearwardly of the shroud 1t? and the weighing scales 26 there is mounted a hopper 4% which serves to retain the particulate material which is to be dispensed into the bags. The hopper adjacent its lower end is provided with the usual tapered form which directs the material to a central dispensing pipe. Adjacent the lower end of hopper 40 there is inserted a porous ring 41 preferably made of a suitable porous metal which will permit air to be forced therethrough. An interiorly grooved sleeve 42 surrounds the ring 41 to provide an annular air chamber around the ring. A conduit 43 communicates with the chamber within sleeve 42 to permit the introduction of low pressure air thereinto. This air seeps through the porous ring 41 into the lower portion of the hopper so as to be distributed around the entire periphery of the exit portion of the hopper. The air so distributed, in traveling up the sides of the hopper, reduces the possibility of the finely divided particulate material therein from bridging or arching which would thus prevent free flow of material to the bag filling machine.
Below the ring 41 a conical delivery section 45 is provided to conduct the material downwardly to a pipe 46 which conducts the material into the filling machine. Intermediate conical section 45 and pipe 46 there is mounted a pneumatic valve 50. This pneumatic valve may take the form illustrated in my co-pending application, Serial No. 271,748 filed February 15, 1952. As shown on Figure 1, valve 50 consists of a cylindrical section connected between the lower end of conical section 45 and pipe 46. A resilient tubular member 51 having one end sealed and the other end connected with a suitable air pressure source by means of conduit 52 is centrally mounted within this tubular section. In the absence of pressure within tubular member 51, such member takes the shape shown in solid lines on Figure 1. Upon the introduction of pressure into the member by control of the flow through conduit 52 the resilient member expands to a position such as shown in dotted lines to close off the annular space between such member and the tubular section through which the particulate material flows to pipe 46.
The pipe 46 conveys the material into the shroud 10 wherein the pipe is connected to a filling spout 60. For reasons that will become apparent, the filling spout 66 is yieldably coupled to the end of pipe 46 by means of tube 62 interposed between pipe 46 and the shank of spout 60 and respectively connected thereto by a pair of flexible rubber sleeves 63. This form of connection of spout 60 to the pipe 46 which conducts the material from hopper 40 permits the spout to move relative to the stationary pipe 46 to accommodate changes in the bag contour which takes place as the bag is being filled. Also the provision of a yieldable mounting for spout 60 enables the weighing scales for the apparatus to register the weight of the bag contents without interference by the spouts being rigidly mounted, it being understood that during filling the spout extends into the valve opening of the bag to conduct the material into the bag.
As more clearly shown on Figures 5 and 6, the spout 60 is inserted into the lateral opening of the bag B adjacent the upper seam S of the bag. After the bag is filled and such bag removed from the filling spout 66, gusset F closes the bag aperture to prevent the exit of material from the bag. The gusset F thus acts as a valve, giving the designation valve bag to this type of bag.
To retain the bag on the spout 60 a clamping assembly cooperating with the spout is provided carried by a frame 70 secured to the shank of the filling spout. A pair of pneumatic cylinders 71 are secured to the frame with their respective actuating rods 72 extending downwardly and carrying at their lower ends a channel member 73. A plate 74 is attached to the outer ends of the flanges of channel member 73 with the underside of such plate providing a surface to engage the outer portion of the bag on the opposite sides of the seam S. Member 73 provides a longitudinal pocket 75 in which the sewed or glued seam S of the bag B is positioned when the bag is clamped in position for filling. A series of bars 76 are secured at spaced positions along the sides of channel member 73, these bars being downwardly curved as shown in Figure 6 to generally conform to the outer contour of the upper end of the bag B in its filled state.
A retracting bolt 77 is threaded to the channel member 73 and extends upwardly through an aperture in frame '70 with a retracting spring 78 mounted between the enlarged head of the bolt 77 of the frame 70 to serve as a spring bias to continuously urge member 73, plate 74 and the curved bars 76 upwardly as a unit away from the filling spout 60 to permit insertion of bag B for filling.
To provide a clamping surface to receive the seam S and portions of the bag adjacent such seam, the upper surface of spout 60, as shown in Figure 6, is provided with a built up section 80 which supports a resilient strip 81 beneath the seam of the bag. The strip 81, which is preferably made of rubber, is centrally provided with a ridge 82. This ridge during clamping of the bag on the filing spout extends up into the seam S to insure a more effective seal as the clamping assembly is urged downwardly into engagement with the spout 69 upon the introduction of air pressure into cylinders 71.
To additionally insure that the bag B, as clamped in position for filling, is sealed against the vacuum created in the shroud It the shank of the spout 69 is provided with an annular chamber 85 communicating with the exterior surface of the spout through a plurality of apertures which apertures are covered by a resilient sleeve 86. When the shroud 16 is evacuated during the filling operation, the air in annular chamber 85 expands to force resilient sleeve 86 outwardly to seal the bag opening against the exit of material at the point where the spout 6t) enters the bag.
With further reference to Figures 5 and 6, it will be seen that a material feed auger 90 is rotatably mounted Within the shank portion of the filling spout 6t) in a suitable bearing 91. A driving shaft 92 extending outwardly through a bearing 93 in pipe 46 is coupled to the end of auger 96 by means of a length of flexible shaft 94. The shaft 92 is preferably driven through a suitable magnetic clutch (not shown) which in the bag filling operation is selectively controlled in response to the action of the weighing scales 26. In other words, the rotation of auger 90 will be commenced subsequent to the clamping of bag B on the spout 6% to assist in propelling the material into the bag and will be terminated in response to a registration on the scales 26 indicating that the bag has been filled with the proper or desired Weight of material. The magnetic clutch is only one example of an effective and simple means to obtain selective rotation of auger 90.
Suspended from the lower end of the weight responsive arm 27 of scales 26 is a skeleton frame 100. This frame extends downwardly within the shroud 10 and has mounted therein a basket structure 110 which is made up a center slot 111 across the width of the basket structurewhich initially receives the lower seam. of the bag when.
the empty bag is placed on the spout 6d for filling. It will be readily recognized however, that as the bag is filled with material the lower portion of the bag will tend to balloon out and generally bridge across the slot 111 to be uniformly supported on the curved upwardly extending portions of the bars adjacent the slot 111.
The upper portion of the basket structure is formed by the series of downwardly extending curved bars 76 which, as described hereinabove, arecarried by the plate 74 and channel 73 to be selectively movable relative to spout 60 under control of pneumatic cylinders 71.
The bars making up the mid or central portion of the basket structure 110 complete the cavity which closely approximates the filled contour of the bag for which the machine is designed to fill. Two sections of the mid or central portion of the basket structure 110 are hingedly secured relative to the remainder of the basket structure so as to permit opening of the structure for the insertion and removal of the bag. The first section 120 is mounted on hinges 121 and the second section 122 is mounted on hinges 123; Figure 4 illustrates the position of the basket structure sections 120 and 122 in their open position in readiness to receive the bag to be filled.
A suitable clasp or latch 125 is mounted on the abutting edges of the basket structure sections 120 and 122 so as to enable the sections to be secured in their closed position while the bag is being filled. After filling of a bag the basket structure is opened by unhooking latch 125 and opening the sections 120 and 122 for removal of the filled bag and insertion of another empty bag.
The skeleton frame 100 within shroud 10 is provided with stabilizing links 130 pivotally connected to the top and bottom of such frame and at their outer ends to pintle means secured to the shroud It). in the illustrated embodiment 4, one pair of the stabilizing links are coupled to the rear of frame 160, as shown in Figure 1, and a second pair coupled to the left side, of frame 100, as shown in Figure 2.
In its initial empty state the bag is flat and of a length greater than that when the bag is filled, at which time the bag is ballooned out by the presence of the material therewithin. As pointed out above, the lower seam of the. bag is initially received in the slot 111 in the lower portion of the basket structure 110 and as the bag fills the bag bottom takes a configuration generally conforming to the concave saddle provided by the lower portion of the basket. At the same time as filling takes place the bag tends to shorten, placing weight on the spout 60 tending to pull it downward to accommodate this change in dimension of the bag during filling. To yield to this downward force, the filling spout together with its cooperating clamping assembly are supported on skeleton frame 101) by pairs of grooved wheels 140 and 141 engaging two parallel rails 143 connected to the frame. The pairs of wheels 1140 and 141 are rotatably mounted on the frame '76 which in the illustrated embodiment is secured to the shank of filling spout 6i); Coil springs 45 are secured between the upper ends of rails 143 andthe frame 70 to continuously urge the filling spout 6t) and. its associated clamping assembly upwardly. It will be appreciated that the flexible, interconnection between the spout 69 and the pipe 46 provided by cylinder 62 and sleeves 63 enables the spout 60 to move for a limited dis-- tance up and; down relativeto the-stationary structure of thefilling apparatus.
From the above set forth structure it will be clear that as the bag tends to shorten as it is being filled the major portion of the weight of the bag will be carried bythesaddle formed by the lower portion of the basket structure 110 since although the top of the bag and top seam are firmly secured to and sealed around the filling spout 60, such spout and its related clamping assembly will ield and move downwardly along rails 143 to accommodate the dimensional variations in the bag as it is filled.
Although a specific control system has not been illustrated on the drawings since any one of a variety of different manual or automatic controls might be employed in connection with the instant invention, it may be well to set forth by way of example one mode of operation employed in use of the bag filling machine of this invention. With the apparatus in readiness to commence bag filling and hopper 40 filled with the material to be dispensed into bags, low pressure air is imparted to the porous ring 41 through conduit 43 to insure against arching or bridging of the material in hopper 40 and pneumatic valve 50 is closed by air pressure being imparted thereto through conduit 52. At the same time the auger 90 stands idle and conduit 12 is cut off from communication with the vacuum pump or other vacuum source. Door 13 is open and the sections 120 and 122 of the basket structure are opened as shown in Figure 4 to receive an initial bag to be filled. Also the clamping assembly is raised by pneumatic cylinders 71 so that the bag to be filled may be freely inserted onto the spout 60.
The bag is positioned within the basket structure 110 with spout 60 inserted through the bag aperture. The clamping assembly is then actuated by the admission of air pressure to cylinders 71 to firmly clamp the empty bag on the spout 60 while the air in chamber expands sleeve 86 into sealing engagement with the bagv aperture. The sections of the basket structure 120 and 122 are closed and latched, and shroud door 13 then closed by appropriate manipulation of air pressure to cylinder 15.
With the bag so properly positioned, vacuum line 12 is opened and the shroud 10 thereby evacuated to draw into the bag through spout 69 the material from hopper 4'0. Pneumatic valve 50 is opened and auger 90 rotated to assist in feeding the material into the bag. As the bag fills with the material the spout 60 and its clamping assembly yields to the natural tendencies of the bag to assume the contour of the basket structure and thus moves downwardly. The weight of the contents dispensed into the bag is transmitted through arm 27 to weighing scales 26 and as the bag reaches the desired weight such as, for example, one hundred pounds, the scales effects control of the various bag filling elements to stop the rotation of anger 90, release the vacuum within shroud It) as by connecting conduit 12 to atmosphere, close pneumatic valve 50 and operate cylinders 71 to release the clamping assembly from the nozzle 60. The cylinder 15 then actuates door 13 to open the shroud for removal of the filled bag by the operator who unlatches the basket structure sections and 122 to open the structure for removal of the filled bag therefrom.
Figure 7 illustrates a modified form of filling spout which is particularly constructed for use in place of spout 60 when the bag filling machine is employed in the filling of vapor barrier bags, i. e., valve type bags wherein the bag material precludes the seepage of air of vapor therethrough.
Filling spout 160 possesses characteristics similar to spout 60 in that this modified spout has a built up upper portion supporting a resilient strip 181 longitudinally of the top thereof which, as in the previously described embodiment, has a central ridge which engages the underside of the bag seam when the clamping assembly is actuated to position the bag to be filled on the spout. Spout 160 also is provided with an annular chamber 185'pro- 7 vided with radially extending perforations communicating with the underside of a resilient sleeve 186 and is provided with a material feed auger 190 mounted centrally within the shank portion of the filling spout.
A housing 200 encases the shank of spout 160 providing a chamber 2-31 surrounding the shank and communicating with an annular duct 202 leading forwardly to the outer end of the spout. The outer end of spout 160 is provided in the wall forming one side of duct 202 with a plurality of small apertures 203 which, together with the outer open end of duct 202 permit air to be drawn into the duct by suitably connecting housing 200 to a source of vacuum.
The basic operation of the filling spout 160, when employed with the filling machine structure as described hereinabove is generally identical to the operation of the previously described spout 60. With the modified spout, however, as employed in filling vapor barrier type bags, the housing 200 is subjected to a vacuum greater than that prevailing in the shroud 10 so that any air trapped within the upper portion of the bag during filling may be withdrawn from the bag through duct 202. Thus, although the opening through which the spout extends into the bag is effectively sealed against the leakage of air and/ or material being dispensed into the bag, duet 202 in the modified spout enables withdrawal of air trapped Within the bag.
The provision of the large screen area, including the open end of duct 202 and the small apertures 203, in efiect precludes particulate material from being withdrawn through duct 202. Alternatively the arcuate underside of the filling spout may employ a screen-preferably of stainless steel and having a 100 to 150 mesh, instead of the multitude of apertures 203 on the underside of the filling spout visor. In the use of either of these structures, clogging of the forarninous screen area is avoided by successively subjecting chamber 291 to vacuum several times during a bag filling cycle. The vacuum release blows any material from the screen area perforations which may have lodged therein wh en vacuum in chamber 201 urged withdrawal of the air from within the bag.
Merely by way of example, it may be pointed out that in the filling operation, vacuums of upwards of twenty six inches of mercury may be employed in the shroud 10. This vacuum is the basic power source utilized in drawing the particulate material into the bag mounted on the filling spout and in opening the bag from its flattened condition to receive such material. At this time, as noted hereinabove, a slightly higher vacuum will be employed in a structure utilizing modified filling spout 169 to induce the small amount of air which may be entrapped in the bag to flow outwardly through duct 202.
Having thus described my invention, what I claim is: 1. In a bag filling machine, a frame adapted to be suspended from a weighing scales, a filling spout adapted to be inserted into the filling opening of a valve bag to conduct material thereinto, said spout being yieldably mounted relative to said frame, a clamping assembly carried by said spout including selectively actuatable means operable to clamp the bag on to said spout, a basket structure carried by said frame to provide a bag retaining cavity generally conforming to the outer contour of the bag in its filled state, said basket structure having a hinged portion to facilitate the introduction and removal of the bag being filled, a shroud enclosing said basket structure and having a door therein, and means for subjecting the interior of said shroud to a vacuum to draw the material into the bag through said filling spout.
2. In a bag filling machine as recited in claim 1 wherein said frame is restrained against undesirable lateral movement within said shroud by stabilizing links pivotally connected to said frame and to the surrounding shroud.
3. In a bag filling machine as recited in claim 1 wherein said yieldable mounting for said spout comprises a vertical guide rail secured to said frame and a pair of rollers rotatably carried by said spout at laterally and vertically spaced positions engaging opposite sides of said guide rail and spring means biasing said spout upwardly relative to said frame.
4. In a bag filling machine, a shroud having a door to permit the introduction thereinto of a bag to be filled, a basket structure mounted within said shroud having an interior cavity generally conforming to the outer contour of the bag in its filled state, a portion of said basket structure being hinged to facilitate the introduction of and removal of the bag being filled, a filling spout mounted adjacent the upper end of said basket structure to extend into the filling opening at the upper end of the bag positioned within said basket structure for conducting material into such bag, a clamping assembly mounted above and parallel to said spout including selectively actuatable means for moving said assembly downwardly into engagement with the top of said spout to clamp the bag to said spout, and means for evacuating said shroud to draw the material into the bag clamped on said spout.
5. In a bag filling machine as recited in claim 4 wherein said selectively actuatable means comprises a cylinder and piston connected to said assembly operable upon the introduction of pressure thereinto to urge said assembly into clamping engagement with said filling spout.
6. In a bag filling machine as recited in claim 4 wherein said basket structure is made up of a series of parallel spaced bars providing a perforate bag retaining cavity to confine the bag during filling.
7. In a bag filling machine as recited in claim 4 wherein a rotatable material feed auger is positioned within said filling spout to assist in propelling the particulate material to the bag being filled.
8. In a bag filling machine as recited in claim 4 wherein said door is operated by a pneumatic actuator pivotally connected between said door and said shroud.
9. In a bag filling machine as recited in claim 4 Wherein said filling spout has a duct extending between a point adjacent the material dispensing outlet of said spout and a chamber adapted to be selectively coupled to a source of vacuum, and a foraminous member interposed between said duct and the material dispensing outlet of said spout to preclude material from being drawn into said duct while permitting air entrapped within a bag being filled to be withdrawn therefrom.
10. In a bag filling machine, a filling spout adapted to be inserted into the opening of a valve bag to conduct material thereinto, a clamping assembly carried by said spout including an elongated channel member providing a longitudinal pocket to enclose the upper seam of the bag, selectively actuatable means for moving said channel member into clamping engagement with said spout, the upper edge of said spout being built up and carrying a resilient strip along the top thereof to provide a hearing surface for engagement with said channel, said resilient strip having a central upstanding ridge extending longitudinally thereof adapted to enter and seal the underside of the bag seam in clamping the bag on said spout.
References Cited in the file of this patent UNITED STATES PATENTS 1,029,273 Butler June 11, 1912 1,037,824 Fasting Sept. 3, 1912 1,579,006 Bates et al. Aug. 24, 1926 1,658,734 Nelson Feb. 7, 1928 1,861,443 Holzapfel June 7, 1932 1,971,852 Goebels Aug. 28, 1934 FOREIGN PATENTS 724,578 France Apr. 29, 1932 416,215 Great Britain Sept. 13, 1934