US2638986A

US2638986A - Portable punching machine

Info

Publication number: US2638986A
Authority: US
Inventors: Emmer Charles Edward
Original assignee: General Binding Corp
Current assignee: General Binding Corp
Priority date: 1947-08-29
Filing date: 1947-08-29
Publication date: 1953-05-19
Anticipated expiration: 1970-05-19

Description

y 1953 c. E. EMMER ,638,986

PORTABLE PUNCHING MACHINE Filed Au 29, 1947 a Sheets-Sheet 2 19,4953 E.. EMt llER 2,638,986

PORTABLE PUNCHING MACHINE f d l ZZZ-WI CA /was far/rep [IA/68 Patented May 19, 1953 2,638,986 PORTABLE PUNCHING MACHINE Charles Edward Emmer, Chicago, Ill., assignor to General Binding Corporation, Chicago, 111., a

corporation of Illinois Application August 29, 1947, Serial No. 771,161

14 Claims.

My invention relates to portable punching machines and more particularly to portable machines for punching a row or rows of holes in a stack of sheets to receive one or more ring binders.

In business offices it is frequently necessary to bind reports and other papers in neat attractive folders having the appearance of a manufactured product but without the use of specialized personnel and without the need for large or expensive machines. One method of achieving the requisite appearance is by the use of one or more ring type binders having plastic backbones from which a plurality of curved teeth extend. The teeth may be opened or bent back to receive the sheets and then released to form the complete binder or folder. However, to accomplish this result it is first necessary that the sheets be punched to receive the teeth of the binder. Moreover, since the binder or binders used for various types and numbers of sheets vary in size and location, it is necessary that the punch used for this purpose be capable of simple adjustment to produce a wide variety of holes and locations of the same. Furthermore, maximum utility of the punch can only be achieved if it is tures of construction, combination, and arrangement whereby simple construction, small size, and reliable operation are achieved, to the end that it may be of maximum utility in an ordinary business office.

A further object of the present invention is to provide an improved punch for punching a plurality of sheets to receive one or more ring binders and which utilizes separate gangs of punches each of which is capable of adjustment to place the separate groups of openings at different points in the sheets.

Another object of the present invention is to provide an improved punch for punching one or more gangs of holes in sheets and in which the punching elements for each gang of holes may easily be inserted or removed from the frame.

' Yet another object of the present invention is to provide an improved punch for punching a plurality of sheets to receive a ring binder and which may be adjusted to place the holes at various distances from'the edges of the sheets,

thus to accommodate various types of ring binders and different sheet sizes.

Still another object of the present invention is to provide an improved punch for punching a plurality of sheets to receive one or more ring binders and which is provided with indexing mechanisms to position the separate gangs of punches to place groups of holes in the sheets at predetermined distances apart and thus accommodate single ring binders with teeth inserted in the punches formed by two or more gangs of punches.

The novel features which I believe to be characteristic of my invention are set forth with particularity in. the appended claims. My invention itself, however, both-as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing.

On the drawing:

Figure 1 is a top plan view of an embodiment of the present invention showing two gangs of punches in place;

Figure 2 is a view along axis IIII, Figure 1, showing in elevation the punching elements and their engagement with the cam bar;

Figure 3 is a cross sectional view through the axis IIIIII, Figure 1, and showing the cam bar in three positions typical of the operation of the same;

Figure 4. is an enlarged cross sectional view along the axis IVIV, Figure 1, showing the construction of the feeler gage provided to index the holes relative to the edges of the sheets being punched;

Figure 5 is an enlarged cross sectional view through axis VV, Figure 1, showing the operating bar in the down position with the punching elements extending through the sheets and into the base of the punch gang;

Figure 6 is a cross sectional view like Figure 3 but showing how a gang of punches may be removed from the unit;

Figure 7 is an enlarged fragmentary top plan view of the punch with two gangs of punches adjacent to each other and with the feeler gage between them; and

Figure 8 is a view of a typical folder or binder obtained by placing ring binders in sheets punched by the use of the present invention.

As shown on the drawings:

Referring to the top, end, and side views of Figures 1, 2, and 3, the punch ofthe present invention comprises a frame F supported from a table or other surface by a plurality of feet It). A support bar S extends transversely across the frame F as shown in Figures 2 and 3 and is rigidly mounted on frame F by welding, bolts, or a similar method. A plate P is attached to the frame F by screws i2, Figure 3, and to the support bar S by the screws 54, Figure 1. As will be evident from the view of Figure 3, this plate is bent to form an end wall for the frame F and is then bent over backwardly to form a top Working surface therefor. It is this surface, indicated generally at It, Figure 3, upon which the sheets A are placed for punching.

A second support bar, T, Figure 3 extends transversely across the frame F and is rigidly mounted thereon by screws, welding or similar method. This bar cooperates with bar S to support the punch gangs 28 and and the feeler gage 8 I.

The frame F includes .a pair of upstanding ears 7 l8 and 26 located on opposite sides of the rearward portion thereof. An actuator comprising a cam bar 22 extends transversely across the frame and is pivotally supported from the ears i8 and 20 by

pins

24 and 26, respectively, so as to assume a position parallel to and generally above the support bar S. As will be evident from Figures 2 and 3, a U-shaped hand operating arm 28 is attached to the cam bar 22 to enable the latter to be rotated about the pivots 24 and 2E by suitable hand pressure from the operator of the machine. As will be described in further detail hereafter it is this pressure, causing the cam bar 22 to assume the various positions shown in the dotted lines of Figure 3, that causes the punch to operate and punch the desired holes in the sheets A. The stops 23 are provided to prevent swinging of cam bar 22 in the rearward direction beyond the point necessary for operation of the unit. Stops 39 prevent motion beyond a predetermined point in the opposite direction.

In .the illustrative embodiment of the present invention shown in the drawings, two groups or gangs of punches are shown positioned in the mechanism. These are indicated at 28 and 30, Figure 1. Each comprises a separate identical unit capable of punching five holes simultaneously in the sheets to be punched and may be shifted relative to the frame F to punch the holes at any desired point along the sheets. If desired, additional gangs may be provided to punch further groups of holes.

Inasmuch as each gang of punches comprises an identical unit, it is merely necessary to describe one gang in detail.

Eachgang of punches includes five substantially rectangular punching elements, identified as a, b, c, d, and e on punch gang 39, Figures 1 and 2. Each of these punch elements is provided with a collar 32, Figure 5, against which a compression spring '34 bears. This spring is bottomed on the stripper and guide member 36, Fig-ures 3 and 5, which extends the entire length of the punch gang as will be seen in Figure 1 and biases the punch element to an upper or retracted position. The stripper and guide member 36 is of U-shaped cross section to provide opposed upper and lower hor zontal sections 33 and 4B. The former, or upper, section operates as 'aguide for the punch elements and is provided with openings to accommodate and guide these elements. The latter, or lower, section acts as .a stripper section and for this purpose is provided with openings to fit exactly the cross section of the punch elements. The openings in sections 38 and 40 are aligned to position the punch ele ments along axes substantially normal to the surface it.

Each punch gang includes a base member 42 which extends underneath the U-shaped stripper and guide member 35 and is provided with openings aligned with the openings in the opposed sections of the stripper and guide member 36 to receive the punch elements as they pass through the sheets punched, thereby achieving the stripper action necessary for a clean punch. The portions of this base member directly underneath the punch elements are best seen in the enlarged cross sectional View of Figure 5.

In addition to forming a bottom stripper element, the base member 42 extends backwardly to support the punch gang and the stripper and guide member 3G. The latter support is derived from the upstanding flange member 44 to which the stripper and guide member is brazed or welded. The flange member M is formed by cutting out the opening 15, Figure l, in the base member 42 on the back and sides and then bending up the cut-out portion to the vertical position shown in Figures 3 and 5.

The constructions of the remaining portions of the base member t2 may best be understood by reference to Figure 3, which is a cross sectional view through the III-III, Figure 1, and Figure 6, which is a Six. iilar View showing removal of the punch gang As will be evident from these views, the base member 42 extends backwardly to the support bar T and is provided with downwardly extending flange or lip portions 46 and 41 to engage the forward and rear edges of that bar respectively. A thumb screw 58 rides in threaded engagement with the flange 48 to press flange 46 against the edge of bar T and rigidly sustain the punch gang in position. Thumb screw 50 also rides in the groove on the rear side of support bar T to provide vertical as Well as horizontal support for the base member 42.

The forward edge of base member 42 is provided with a cut-off portion 52, Figure 6, which is inserted in the notch formed by the similar cutout portion 53 of plate P as it rests on bar S. In addition, the stripper section 49 of stripper and guide member 38 extends forwardly of the upper section 38 and underneath the retainer bar 54 which extends across the frame F as seen in the View of Figure 2. This engagement, together with that of the cut-off portion 52 of the base member 42, fixes the forward ends of the punch gangs against vertical movement and coacts with the lateral support achieved by the flange members 46 and 48 to sustain the punch gangs in fixed positions on the frame F.

The retainer bar 54 is supported from the front portions of the ears it and 28 by thumb screws 56 and 58, respectively. These ride in the openings 68 and '82 of bar 54 so that the bar may readily be removed or swun up to free the punch gangs for removal from the unit. This is shown in the view of Figure 6 which shows retainer bar 54 in an upturned position about thumb screw 58 and the punch gang 28 raised ofif of the support bar T after unscrewing the screw 5E] out of the slot 5|. The gang 28 is thus slipped out from cut-out 53. This easy removal and replacement of the punch gangs makes the device very flexible and facilitates settings for different types of punching jobs. The openings 60 and 62 also provide adjustment of the position of the retainer bar 54 relative to the surface l6 of the frame.

Figure 3 shows the hand operating arm .28 in assuage 'reportbound by a pair of ring binders'as'might be. accomplished with'the punch of the present invention when adjusted as-shown' in Figure 1. In this folder, the sheets 94 are first punched by the machine of the present invention to provide the

separate groups

96 and 98 comprising holes each. Then the ring binders Hill and ill? are inserted into these holes, this operation being accomplished by opening the flexible fingers of each of the binders against the backbones and inserting the fingers through the groups of holes. The fingers are then released relative to the backbones to form the closed structures shown in Figure 8, thereby providing an effective and attractive binder for the sheets.

From the foregoing description it will be apparent that I have provided an improved portable punch of simple construction that may be operated in an ordinary business office by untrained .oince help but which nevertheless has a high degree of flexibility and range of adjustment. Any number of gangs of punches may, for example, be provided and they may be spaced any desired distances. Moreover, the distances between the edges of the sheets punched and the holes is readily adjustable and, when once selected, the spacing is assured by the bottoming action of the sheets'against the feeler gage. Thus the unit accommodates itself to various sheet sizes, numbers of ring binders, sizes of ring binders, etc. and

is of maximum usefulness without excessive expense or space requirements.

While I have shown a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto since many modifications both in the elements employed and their cooperative structure may be made without departing from the spirit and scope of my invention. I, of course, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

I claim as my invention:

1. A portable punch for punching sheets to receive a ring binder or the like comprising a having a substantially flat surface to support said sheets, a cam bar extending across said frame and pivotally supported therefrom, a plurality of punch gangs each having a plurality of equally spaced punching elements disposed to be engaged by said bar to punch holes in said sheets as said bar is rotated, means to bias said elements to retracted positions free of said sheets, said gangs being shiftable relative to said frame to adjust the positions of the holes punched in said sheets and said operating bar having a plurality of slots along the surface in engagement with said punching elements, said slots being spaced in accord with the spacing of said elements so that the positions of said gangs may be fixed relative to each other-by aligning said slots and said elements.

2. A portable punch for punching sheets to receive a ring binder or the like comprising a frame having a substantially fiat surface to support said sheets, a cam bar pivotally supported above said frame, a plurality of punch gangs each having a plurality of equally spaced punching elements disposed to be engaged by said bar to punch holes in said sheets as said bar is rotated, means to bias said elements to retracted positions free of said sheets, said gangs being shiftable relative to said frame to adjust the positions of the holes punched in said sheets and said cam bar hav mg a plurality of slots along the edge in engagement with said punching ele 'ments, said slots-being of width corresponding to the dimension of said punching elements indirecti-on ofthe axis of rotation of said bar and being spaced in accord with the spacing of said ele ments so that said .slots provide lateral support for said punching elements and permit indexing of said gangs relative to each other.

' '3. A portable. punch for punching sheets to receive a ring binder or the like .comprising a frame to support-said sheets, a cam bar pivotally supported above said frame, a plurality of punching elements disposed to be engaged by said bar to punch holes in said sheets as said bar is retated, means to bias said elements to retracted positions-free of said sheets, said operating bar having slots along the edge in engagement with said punching elements, said slots being of width corresponding to the dimension of said punching elements in the direction of the axis of rotation of said bar to provide a lateral support for said punching elements.

4. A punch gang forum in punching sheets tobe received in aring binder or the like comprising in combination a base, a member supported in spaced relation-to said base and having opposed portions in parallel relationship with said base, said base and said opposed portions of said member having'a plurality of equally spaced sets of aligned punch element receiving openings, and punch elements disposed in said openings, the distance between the end punch elements of said gang being less than half the distance between adjacent elements to permit insertion of a ieeler gage between two adjacent gangs while maintaining a uniform spacing between adjacent openings punched by the adjacent gangs.

5; A'porta'ble punch for punching .sheets to receive ring binders or the like comprising a frame having a substantially flat surface to support said sheets, said frame havinga first support bar along'one edge of said surface, a second support bar parallel to said first 'bar and substantially in the'p'lane of said surface and in spaced relation with said edge and a retainer bar disposed parallel to said first bar and spaced therefrom in direction normal to the plane of said surface, a plurality of punch gangs, each of said gangs having a base with flanges to ride .on said first bar and of length to ride on said second bar, a support member disposed in spaced relationship with said base and having opposed portions in parallel relationship with said base, one of said opposed portions extending under said retainer bar, said base and said opposed portions having a plurality of groups of aligned punch element receiving openings, and punch elements ,in said openings, whereby said bars sustain said gangs in position while permitting removal or shifting movements thereof.

'6. A portable punch for punching sheets to receive ring binders or the like comprising .a frame having a substantially fiat surface to support said sheets, a punch gang, said gang having a base positioned in the plane .ofsaid surface, a member disposed in spaced relationship with said base, said member and said base having a plurality of groups of aligned punch element rece'iv-ing openings, and punch elements in said openings, a bar .in the plane of .one end .of said surfaceiand in spaced relationship therewith .to support said punch gangs for shifting movement to: vary the positions or the openings punched in said sheets, a .cam .bar .to engage said punch elements to force them through the openings of the various positions assumed during the'punching operation. When the bar is in the position shown in the solid lines of that figure, the cam bar 22 is held by stop 23 and the punch elements are free of that bar and are biased to upward positions by the springs 34, Figure 5. In this condition, the punch elements are retracted and do not extend below the stripper portion 40 of the stripper and guide member 36, Figure 5. The sheets A may then be inserted in the punch to rest between members 36 and the bases 42 of the punch gangs. The operating arm 28 may then be pulled down to accomplish the punching action, first assuming the position shown by the uniformly dashed lines in Figure 3 and then the position shown by the alternate long and short dashed lines of that figure. In the former position the operating bar 22 just touches the tops of the punch elements and further motion of the hand operating arm causes the punch elements to be depressed against the biasing action of the springs 34. In the latter position, the operating bar 22 is rotated to the full downward position wherein the punch elements extend entirely through the sheets A and the base member 42 and stops 39, Figure 5, prevent further motion. When this condition is reached, the holes have been punched in the sheets A.

When the hand operating member is released from the downward position shown in Figure 5 and the alternate long and short dashed lines of Figure 3, the springs 34 bias the punch elements, and hence the operating bar 22, in the upward direction and return the unit to the position shown in the uniform dashed lines of Figure 3.

In order to index the positions of the punch gangs relative to the frame and to each other and to provide a further guide for the punch elements, the cam bar 22 is provided with a series of slots 64, Figures 1 and 2. These slots are located on the surface which engages the punch elements and are of width corresponding to the punch elements. They are spaced equal distances along the bar, the distances corresponding to the spacing of the separate punch elements in the punch gangs. Thus when a punch gang is removed for shifting along the frame F to punch holes at different points, it may be readily indexed with respect to all other punches of the unit by fitting the punch elements in the slots 64 of cam bar 22.

The indexing action achieved with the slots 64 of the cam bar 22 is particularly effective when a plurality of punch gangs are placed in side-byside relation to punch a continuous series of equally spaced holes. Such a condition is shown in the view of Figure 7. As will be evident from this view, the space between the adjacent punches a and e of the two

punch gangs

28 and 30 is made exactly equal to the space between adjacent punches in each gang by the fixed spacing of the slots 64. Thus each punch of both

gangs

28 and 30 seats in a slot 64 and the gangs are automatically spaced so that adjacent punches of each gang cannot be too close or too far apart.

It is the function of the guide 10, Figure 1, to position the sheets A in the lateral direction relative to the frame F. This guide includes a bar portion 12 to which is attached the support portion 14. The latter portion contains a lengthy slot 16 in which thumb screw 18 rides. A corresponding lengthy slot 80 is placed in the upper surface portion l6 of plate P to enable adjustment of the position of the guide relative to the frame F. The sheets are inserted against guide 10 so that the lateral position of the guide 10 fixes the position of the sheets to index the position of the punches relative to the sides of the sheets to assure a uniform bindin when ring binders are inserted in the holes.

The feeler gage, shown generally at 89, Fig.- ure 1, coacts with the guide to align the forward edges of the sheets relative to the punch elements. Enlarged side and top views of this gage are shown in Figures 4 and 7 respectively. As will be evident from these figures, the gage comprises a series of bars 82, B4, 86, and 88 pivotally supported from member 90. The latter member is C-shaped to fit about the support bar T located at the rear end of the frame F. The thumb screw 92 rides in a suitably threaded hole in the member 90 and fits in the slot 94 of the bar T, thereby permitting a rigid attachment of the member 98 to the bar T by suitable tightening of the screw 92. The pivot 8G,,which supports the

bars

82, 84, 86, and 88, is threaded and fits in a correspondingly shaped hole in the member 90. Thus pivot 85 may be loosened to permit any one of the bars to rest on support T, Figure 4, and thus permit selection of the position of the holes relative to the edge of the sheets A.

The

bars

82, 84, 3B, and 88 are bifurcated at their forward ends, the bottoms of the separate bifurcated portions being located at various distances from the pivot 9'5 in accord with the desired distances between the edges of the sheets punched and the holes. When it is desired to punch a group of sheets, the bar having a bifurcated portion of the desired depth is allowed to rest against the support 5, and the remaining bars are raised up at an angle to clear the sheets. Bar 82 is shown in the operative position in Figure 4 and bars 84, 85, and 88 are in the upturned position. By holding the sheets against the guide It, Figure l, and inserting them until they bottom on the selected

bar

82, 84, 86, or 88, the holes will be punched at a uniform distance from the edges of the sheet in the desired alignment with the edge thereof.

In accordance with one feature of the present invention, the outer end punches a and e of each gang of punches are spaced inward from the side edges 43 of the base members 5-2 of the punch gangs 28 and so a distance less than half of the distance between adjacent punches in each

gang

28 or 30. Thus if punches b and d are spaced one inch from their adjacent punches a, c and e the punches a and e will be less than inch inward from the adjacent edge 43. This feature makes possible the positioning of the punch gangs in side by side relation to punch a continuous series of equally spaced holes and yet leave a gap between the base members 42 of sufiicient width to receive a bar of the feeler gauge 8| as shown in Figure '7. This arrangement is desirable where the sheets being punched do not extend beyond the outer ends of the punch gangs a sumcient distance to coact with a gauge at these points. In Figure 7 the bar 82 is shown in a horizontal position to accomplish gaging action and the remaining bars are held upwardly by pressure from the screw 35.

It will be apparent to those skilled in the art that several feeler gages 89 may be provided to permit bottoming of the sheets against more than one point, thereby facilitating the positioning action secured therefrom and supplement ing the action of guide It! in aligning the edges of the sheets against the punch elements.

Figure 8 shows a top plan view of a folder or said base to punch sheets disposed between said member and said base, and a feeler gage slidably mounted on the first mentioned bar, said gage having a plurality of pivoted members having bifurcated ends bottomed at different distances from said pivot to permit selection of the distance of the punched holes from the edges of said sheets.

7. A punching machine comprising a frame, removable punch gangs slidably mounted on said frame, each of said gangs having a plurality of punches arranged to receive sheets for punching, a single actuator for simultaneously depressing all of the punches on said gangs, and a feeler gage adjustably mounted on said frame to limit the extent of infeed of work to said punch gangs, said gage fitting between said punch gangs to permit positioning of the punch gangs in sideby-side relation to form a continuous row of equally spaced holes.

8. A quickly adjusted punch for sheet material comprising a support for said sheet material, a gang shiftable along an edge of said support, a single punch actuating cam bar overlying the path of said gang and mounted for operating said gang and indexing indentations on said bar for receiving the punch elements.

9. A punching machine comprising a frame, a punch support movable longitudinally on said frame, a punch carried by said punch support, a punch-operating member on said frame, and a plurality of longitudinally spaced punch index means on said operating member, each of said punch index means comprising a pair of longitudinally spaced facing surface portions for embracing said punch on movement of said operating member in a punch-operating direction, so that the position of said punch on said frame may be fixed after movement of said punch support to a position in which said punch is aligned between a pair of facing surface portions of a selected punch index means.

10. A punching machine comprising a frame, a punch operating bar on said frame, a punch support carried on said frame for adjustable movement parallel to said bar, a punch carried by said support and operable by said bar, and a plurality of longitudinally spaced lateral slots in said bar, said punch being engageable within an aligned slot on operating movement of said bar so that the position of said punch may be fixed after adjusting the position of said punch to align said punch with a selected slot in said bar.

11. A portable punch for punching sheets to receive ring binders or the like comprising a frame having a substantially flat surface to sup-' port said sheets, said frame having a first support bar along one end of said surface, a second support bar parallel to said first bar and substantially in the plane of said surface and in spaced relation with said edge and a retainer bar disposed parallel to said first bar and spaced therefrom in a direction normal to the plane of said surface, a plurality of punch support means, each of said punch support means having a base with flanges to ride on said first bar and of length to ride on said second bar, a support member disposed in spaced relationship with said base and having opposed portions in parallel relationship with said base, one of said opposed portions extending under said retainer bar, said base and said opposed portions having aligned punch element-receiving openings, and a punch element in said openings, whereby said bars sustain said punch support means in position while 10 permitting removal or shifting movement thereof.

12. A punching machine comprising a frame having a substantially flat sheet-supporting surface, a punch, and means supporting said punch for adjustable movement along one edge of said surface, said means comprising a bar supported on said frame in a position parallel to and spaced from said edge, a support member slidably disposed on said bar for supporting said punch, a first flange on said support member for slidably engaging the outside surface of said bar, a second flange on said support member for slidably engaging the inside surface of said bar, and adjustable means on said first flange for lockingly engaging the outside surface of said bar.

13. A punching machine comprising a frame having a substantially fiat sheet-supporting surface, a punch, and means supporting said punch for adjustable movement along one edge of said surface, said means comprising a bar supported on said frame in a position parallel to and spaced from said edge, a support member slidably disposed on said bar for supporting said punch, a first right angled flange on said support member for slidably engaging the outside surface of said bar, a second right angled flange on said support member for slidably engaging the inside surface of said bar, said inside and outside surfaces being generally normal to said flat sheet-supporting surface, a 1ongitudina1 groove in the outside surface of said bar, and a screw on said first flange extendable into said groove.

14. In punching apparatus, a pair of spaced parallel bars positioned substantially in the plane of sheets to be punched, a punch gang slidably movable along said bars, and a feeler gauge movable independently from said punch gang and comprising: a support member slidably movable on the .bar most remote from said sheets, a plurality of arms each having a bifurcated end portion, and a pivot to support said arms from said support member, said pivot and said arms being positioned to permit any one of said arms to rest upon said second bar in position to receive sheets in the bifurcated portion thereof and said bifurcated portions having bottoms at various distances from said pivot to enable selection of the distance between the edges of the sheets and the holes punched by selection of the appropriate one of said bars.

CHARLES EDWARD E'MMER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 851,656 Dahly Apr. 30, 1907 926,261 Krag June 29, 1909 1,259,551 Parker Mar. 19, 1918 1,687,758 Glaeser Oct. 16, 1928 1,759,672 Tellier May 20, 1930 1,928,383 Lee Sept. 26, 1933 2,114,259 Trussell Apr. 12, 1938 2,244,320 Unger June 3, 1941 2,335,552 Unger Nov. 30, 1943 2,382,523 Unger Aug. 14, 1945 2,368,790 Unger Feb. 6, 1945 2,382,523 Unger Aug. 14, 1945 2,389,105 Kern Nov. 13, 1945 FOREIGN PATENTS Number Country Date 368,575 Germany Feb. 7, 1923