US2941654A

US2941654A - Mail handling apparatus

Info

Publication number: US2941654A
Application number: US684800A
Authority: US
Inventors: Falconer David Gray
Original assignee: Emerson Radio and Phonograph Corp
Current assignee: Emerson Radio Corp
Priority date: 1957-09-18
Filing date: 1957-09-18
Publication date: 1960-06-21
Anticipated expiration: 1977-06-21

Description

June 21, 1960 D. G. FALCONER 2,941,654

MAIL HANDLING APPARATUS Filed Sept. 18, 1957 5 Sheets-Sheet 1 ayww E 5 INVENTOR 217$ D G FALCONER WI, ATTORNEYS D. G. FALCONER MAIL HANDLING APPARATUS June 21, 1960 5 Sheets-Sheet 2 Filed Sept. 18, 1957 June 21, 1960 D. G. FALCONER 2,941,654

MAIL HANDLING APPARATUS Filed Sept. 18, 1957 5 Sheets-Sheet s INVENTOR 0.6 54160 75? ATTORNEYS June 21, '1960 D. G. FALCONER MAIL HANDLING APPARATUS 5 Sheets-Sheet 4 Filed Sept. 18, 1957 Q Q m3 m 3 III 3 5i 3 Q ull-I.

A "My N i... AM GWEN? INVENTOR D G FALCON 1? BY @4 5 +2 I;

ATTORNEYS June 21, 1960 I V D. G. FALCONER 2,941,654:

MAIL HANDLING APPARATUS Filed Sept. 18, 1957 5 Shets-Sheet 5 l fiQOOGOOOj join @ooooooo QGFALCO/VER INVENTOR ATTORNEYS Emerson Radio & Phonograph Corporation, Jersey City, N.J., a corporation of New York Fired Sept. 18, 1957, Ser'. No. 684,800 12 Claims. (Cl. 198-84) The present invention relates to apparatus and systems for handling and transporting flat light articles and es pecially letter mail.

In our current economy the expeditous handling and processing of mail has become vital to the eflicient conduct of business and communication. The volume of mail pieces has become so large as to encumber and literally swamp postal facilities especially at the larger metropoli tan post offices handling many millions of pieces of mail daily. The problems of conveying, cancelling and sorting this great volume of varied shapes and sizes of mail pieces have heretofore not been efi'iciently solved, resulting not only in delays of delivery of mail but also uneconomical utilization of space, equipment and manpower.

In solving this problem of mail handling the first step is to convert the irregular volume of bulk mail into a moving stream. Apparatus for accomplishing this function is described and claimed in the copending application of Milton A. Stovall, Serial No. 683,284, filed September 11, 1957, entitled Mail Handling Apparatus, and assigned to the same assignee as the present application. In that application an output stream of mail is provided which is of a high average speed and rate of flow but which is still irregular in having irregular spacings between letters and having possible multiple or overlapping letters.

The present invention is particularly concerned with apparatus for refining an irregular stream of mail such as supplied by the Stovall apparatus and to assure that its rate of flow is substantially uniform without overlapping or doubling the letters.

While the present invention is particularly described with reference to letter mail, it should be understood that it has general applicability to any fiat articles having relatively small mass-to-area ratio, and where mail pieces or letters are referred to herein,.such articles are included.

The present apparatus and system operate on the basic principle of successive attenuation and attrition of a stream of articles, accompanied by a general speed-up of such articles, so that, Without substantial change in average rate of flow, the individual articles are transported at successively higher speeds. Such a device may i be called a thinning unit, since it thins out the stream of articles.

According to another feature of the present invention, improved apparatus is provided for supplying such light flat articles or letter mail in a flow or stream of single pieces, by the provision of special means for preventing or avoiding overlapping or doubles.

By way of example, the present apparatus is adapted to receive letter mail at an irregular rate varying between 4 and 12 pieces per second, at an average of 8 /3 pieces per second, or 500 pieces per minute, including multiples up to say four in number at any one point in the stream, with preferably not more than half overlapping. The present apparatus is adapted to convert .thisiire'gula'r flow into a .uniformstream closely controlled 2,941,654 Patented June 21, 1960 to 83 pieces in any ten-second interval, with substantially no overlapping over multiples, and with a separation between successive letters, at illustrative longitudinal velocities of to inches per second. i

This apparatus accordingly supplies a feeder function which isolates the various letters by removing each from contact with its neighbors, and provides a proper interval between successive letters along the direction of motion, while continuing unchanged their original orientation. This apparatus in effect makes the rate of flow uniform as well as assuring uniform velocity for the individual pieces. It also provides an accumulation function with a form of storage for smoothing out input flow rate variations.

The present apparatus may also be used in connection with a shingling and feeder apparatus disclosed and claimed in copending application, Serial No. 696,393, entitled Mail Handling Apparatus, filed November 14, 1957, in the name of George Makrides and assigned to the same assignee as the present application, now Patent 2,905,309, issued September 22, 1959. In this Makrides application, in some situations it may be desirable to insert the mail stream thinning apparatus of the present invention in between the Makrides apparatus disclosed by Makrides and the input apparatus which may be sup; plying the stream of mail to be processed in that Makrides application.

These and other objects and advantages of the present invention will become more fully apparent from consideration of the following description of a preferred embodiment, taken in conjunction with the appended drawings, in which;

Fig. 1 is a top plan view of a thinning unit adapted to reduce the number of doubles or overlaps;

Fig. 2 is a side elevation view of the thinning unit of Fig. 1 viewed along line 2-2 thereof; r

Fig. 3 is a fragmentary cross-sectional elevation view of a portion of Fig. 1 taken along line3-3 thereof;

Fig. 4 is a top plan view of a modification of the device of Figs. 1 to 3; i

Fig 5 is a side elevational view of the apparatus of Fig. 4;

Fig. 6 is a fragmentary cross-sectional elevation view of Fig. 4 taken along line 66 thereof;

Fig. 7 is another fragmentary cross-sectional elevation view of Fig. 4 taken along line 77 thereof;

Fig. 8 is a top plan view of a portion of thedevice of Figs. 4 to 7 together with a subsequent unit;

Fig. 9 is a front elevation view of the device of Fig. 8;

Fig. 10, is a cross-sectional elevation view of Fig. 8 taken along line 1010 thereof;

Fig. 11 is a cross-sectional elevation view of Fig. 10.

taken along line 1111 thereof; and

Fig. 12 is another cross-sectional elevation view of Fig. 10 taken along line 1212 thereof. A

One form of thinning unit according to the invention is illustrated in Figs. .1, 2 and 3. The stream of mail of irregular velocity and irregular overlapping which appears between the guides 38,, illustratively derived from the output of said Stovall apparatus, or from any othersource, is suppliedto the thinning unit which essentially cornprises three separate moving friction belts. A first belt 21 is horizontal and is driven at a uniform speed by a suitable driving roller or drum 2?. continuously rotated by any suitable motive means such as motor 23 by suitable gearing or belting not shown. This horizontal conveyor belt 21 supports the lower longitudinal edges of the letter mail and conveys it in a vertical plane to the left as soon in Figs. 1 and 2. Two vertical continuously moving

belts

24 and 26 are also provided, belt 24 being a forward moving belt, while belt 26 is a rearward moving one. These may be driven also from motor 23 as for example .by way of pulley 27 driving a belt 28 engaging a pulley 29 coupled to a drivedrum or roller 31 for belt 26. Belt 28 also engages a pulley 32 of a speed-changing devlce 33 having an output drive belt 34 engaging a'pulley 36 coupled to the drive drum 'or roller 37 for vertical belt 24.

The function of the thinning unit is to feed letters to its output at a regular average rate. For this purpose the two

belts

24 and 26 are driven at different speeds. By means of the

speed change mechanism

32, 33, forward belt 24 is driven at a greater speed than rearward belt 26 and the spacing between these belts gradually diminishes as the letter mail proceeds from right to left as viewed in Fig. 1. The left gap 42 between the two belts may be adjusted by means of a roller 43 rotatable on an arm 44' which in turn is pivotally mounted on the frame at 46. The roller 43 may be pivoted in any position and clamped there in any suitable manner. In one flexible material or elements may be used. These chains 66 extend downward within the channel formed by guides 38 and conveyor belt 39 in the path of letters carried by the conveyor belt 39 so that the taller letters will hit the lower edges of the chains 66. These lower edges are not necessarily maintained at the upper limit of permissible width of letters (illustratively six inches) but may be placed closer to-the belt 39 than this distance. These chains 66 with their heavy inertia relative to that of the letters, serve to provide a toppling moment for the letters so that any of them which may be on end will thereby be rotated to have their long edges along the belt 39.

These chains however do not block the passage of the form anarcuate slot 47 may be formed in a bracket 48 and a suitable clamp 49 is provided to regulate the gap 42. In this way if letters should tend to pass in a bunched or grouped condition, the one letter which is in maximum area engagement with the forward moving belt 24 will be urged by frictional engagement therewith to pass through the gap 42 between the two belts. However all other letters will have frictional engagement only with the letters under them, which is considerably less friction thancompared to belt 24, and therefore less forward urging form. have a greater friction than normally exists between letters, so that it tends to wipe b'ac-k any overlapped or bunched letters, permitting only the letter closest to belt 24 to pass through the gap 42 between the belts. Thus overlapped letters are delayed until the letter directly against forward belt 24 passes on, when the next adjacent letter proceeds through gap 42, and the process is continued, converting a clump of mail into a stretched out stream. In effect, the thinning unit serves as a tempQ- rary accumulation point if the letters tend to bunch up.

letters, but will be urged aside upon impact of the letters which will then pass therethrough.

A further knockdown device 67, shown in Fig. 7, may be located downstream of the knockdown 63 to take care of any letters which may happen not to be completely orientedproperly. The knockdown device 67 is formed by a plurality of high mass flexible strips 68 pivotally mounted on a transversely extending rod 69 and serve the same function as the chains 66. These strips 68 7 may have greater clearance than chains 66, so as to act Furthermore, rearward belt 26 is made to 1 For further spacing of the letters as they leave the thinning unit, the flexibly fingered wheel 51 is continuously driven as by suitable shafting 52 and pulleys 53, 54, and belt 56, which are coupled to belt 34 as shown in Fig. 2. This fingered wheel 51 serves as a metering device to retard some of the letters which come out of the belt gap 42 along the guide 57 so that an interval is obtained between successive letters. These letters will therefore flow in a more nearly regular stream to the subsequent apparatus.

It will be understood that where desired this kind of thinning unit may .be cascaded with successively smaller gaps to assure that letters finally ejected therefrom are substantially entirely singles and not overlapped. v The output of this thinning unit'will go to some form of utilization device, such as a stacker, feeder, canceller or anothenthinning unit. .Desirably, the occurrence of a letter at a predetermined position of such a further device may be suitably sensed (for example, photo-electrically) and the signal thus produced may be used to cut off energization of the drive for the thinning unit so as to slow it down by allowing it to coast or so as to stop it entirely and thereby prevent undesired jamming of the further device.

Figs. 4 to 12 illustrate an alternative apparatus similar in' function to that of Figs. 1 to 3 which also serves the function of thinning out by bunching in the flow of letter mail, and thereby makes the stream more regular. in flow. In this instance, two successive thinning units 61 and. 62 are used.

The vertical letters are transported to the left in Figs.

'4 and 5 by the conveyor belt 39 between the guides 38.

In case any of the letters are not already lying on their longer sides, a' chain knockdown device 63 is provided which is shown more in detail in Fig. 6. This knockdown device 63 is formed by an arm 64 supporting a plurality of chains 66 illustrated as being of the bead chain type, although any other high mass, elongated,

only on letters which may have passed chains 66 without proper orienting. It will be understood that the

knockdowns

67 and 63 are interchangeable and either may be used alone or together with others of a similar or different type, as may be desired. Just downstream of the knockdown 63 is a feeler ele ment 111, shown in Figs. 4 and 6. This element 111 is normally positioned so as to leave a gap of predetermined size between it and the adjoining guide wall 38. Illustratively, this opening may be about one-half to five- ,eighths of an inch, which will offer no obstruction to bunches of mail of normal thickness, but causing the feeler v111 to be diverted only if an abnormally thick bunch appears. In such case the feeler element 111, which may be in the form of a vane as shown, will be pivoted as at 112 to actuate a microswitch 113, which will stop the preceding apparatus feeding conveyor belt 39, so as to interrupt the flow of mail pieces until the apparatus .of Fig. 4 has had a chance to pass and clear the cluimp of material which actuated the switch 113. Preferably an air dashpot 114 is also connected to the feeler element 111 so as to retard the return of feeler element 111 to its normal position, which is effected in response to a suitable restoring spring or resilient member, not shown. This dashpot 114 therefore assures that the energization of the preceding apparatus is interrupted for a sufficient period of time to allow the actuating clump of mail to proceed downstream so that'the apparatus will have time to separate the clump into single pieces and feed them onward.

A further feeler element 116 is provided downstream of the knockdown 67, and forward of belt 39, in the region of belt 121- This element may illustratively be in the form of a wire feeler 116 extending through a slot in the side wall of guide 38 and is allso illustrated in Fig. 7. Feeler 116 also hasa predetermined spacing from the opposite guide wall 38, which illustratively may be of the same order of magnitude as that for feeler 111. If the same clump which actuates feeler 111 should remain intact down to a position of feeler 116, or if a new clump should form prior to that stage, the feeler element 116 is displaced to actuate a microswitch 117 which not only interrupts the energization of the preceding apparatus, but additionally stops the conveyor belt 39. It will be noted that the feeler element 116 is downstream of the end of conveyor belt 39, so that any actuating clump of mail will continue forwardly through the subsequent thin.- ning unit despite stoppage of conveyor belt 39, which prevents a subsequent batch of letters from piling into the thinning unit before it clears the first clump.

From the conveyor belt 39 of Fig. 4, the mail pieces pass to aborizontal conveyor belt 121 which is in line "with the belt 39 but at a slightly lower level by an amount of the order 'of inch, which helps prevent a tendency of the mail pieces to upend to an improper orientation if this drop in level is not provided. Conveyor belt 121 operates in conjunction with a pair of

vertical belts

122 and 123 which have their operative surfaces converging to a gap 124 at the downstream end, which gap may be illustratively of the order of .195 inch. Vertical belt 122 operates in the forward direction at the gap 124 while vertical belt 123 operates in the reverse direction and at a lower speed. illustratively, belt 122 may have a linear speed of the order of 40 inches per second, while that of belt 123 may be of the order of 12 inches per second. Belt 123 passes around a pair of

rollers

126 and 127, one of which is a driving roller and the other an idler. Arms 128, shown in Fig. 5, hold the two

rollers

126, 127 in fixed relationship and permit the belt 123 and its rollers to be pivoted as a unit about the axis of drive roller 126. An adjustable stop arrangement 129 is provided to limit the amount by which rearward belt 123 can approach the forward belt 122 and thereby defines the gap 124. In the opposite sense, pivoting of the belt 123 is opposed by any suitable resilient means, such as spring 131. Illustratively, this spring may have a tension exerting a force of the order of 3 pounds to urge the belt unit against stop 129 so as to maintain the gap 124. However, if an extra thick batch of letters enters the gap 124, the belt 123 can pivot to permit their passage.

The forward belt 122 is similarly driven by a roller or drum 132 and passes over an idler roller 133. A guide 134 of low friction material maintains the working portion of rearward belt 123 in essentially a straight line between the

rollers

126, 127. Rearward belt 123 may have a high friction working surface, which may be increased by corrugations if desired. Forward belt 122 ;passes over a vacuum manifold 136 similar to that described in the abovementioned lviakrides application, and having several horizontal rows of ports 134, illustrated here as two in number. Belt 122 has similar rows of somewhat larger openings 135 extending completely therearound, each row being in registration with a corresponding row of openings 134 in the manifold 136. Vacuum pressure is applied continuously to manifold 136 by tube 137 and serves to positively hold to the belt 122 the letter most closely adjacent to it. As a result, belt 122 forcibly carries letters through the gap 124, while belt 123 tends to hold back and return any multiples overlapping the letter closest to the vaccum belt 122, until such time as the letter directly transported by the vacuum belt 122 has passed sufficiently downstream to expose manifold ports 134 through the belt ports 135, whereupon the next letter closest to the vacuum belt 122 will be attracted thereto and will be in turn positively transported.

The effect of these counteracting

belts

122, 123 in combination with the horizontal conveyor belt 121 is to stretch out any clumps or multiples which may occur, without interfering with the passage of single letters. Since the speed of these

belts

121, 122 and 123 is higher than that of the immediately preceding conveyor belt 39, the result is a speed-up and stretch-out of the letters. However, this arrangement, whileperforming a thinning function for the stack, may not positively assure the absence of multiples or overlaps, and accordingly a further thinning section 140, indicated in Figs. 8 to 13 may be used.

As shown most clearly in Fig. 9, the horizontal conveyor belt 121 is in alignment with a subsequent horizontal conveyor belt 141 which may also be at a slightly lower level if desired, although as the speed of transport of mail pieces increases, the necessity for such a dropdown diminishes. By way of example, the horizontal conveyor belt 141 illustratively may have a speed of the to the subsequentthinning unit 62 through the guides The thinning unit 62 is essentially the same as thin.- ning unit 61 except for differences in speed and dimensions. It includes a vertical'vacuum belt 142 running in the forward direction and a rearward acting belt 143; Illustratively vacuum belt 142 may have a speed of the same order as that of horizontal conveyor belt 141, such as 60 inches per second, while the rearward belt 143 illustratively may have a speed of the order of 25 inches per second.

A similar manifold 149 is provided for belt 142, and is continuously subjected to vacuum pressure. In this instance the ports 151 in the manifold and the openings 152 in the belt 142, which have a generally similar ar= rangement to that for vacuum belt 121, as are shown more in detail in Fig. 10, may be larger so as to exert a greater force on each piece, so that the vacuum belt will override the backward wiping tendency of the rearward belt 143 with greater positiveness.

The first thinning section forward vacuum belt 122 may be placed close to the second section belt 142 (Fig. 8) so that as soon as any letter is released by belt 122 it is picked up and accelerated by belt 142, thereby retaining positive control over the letters as they pass from one section to the next.

A similar stop arrangement 146 and spring arrangement 147 serve to maintain a gap 148 between the

belts

142 and 143 at their downstream end. Illustratively the spring 147 may provide a force of the order of 1% pounds in the direction of maintaining the gap 148 closed, the gap 148 being illustratively of the order of .09 inch wide at the exit end. Since the system is intended to accept letters of a thickness illustratively as high as A inch, preferably the separation of the two

belts

142 and 143 at the point Where the ports of the manifold 149 begin is at least this maximum letter thickness.

The output of the second thinning unit may be supplied to the shingling unit of the Makrides application, if desired. However, the accumulation function of the shingling unit is to a large extent accomplished by the thinnings units 61, 62, by their action in brushing back and retaining excess letters until the gaps 124, 148 are clear for their passage. Therefore the thinning unit output may be supplied directly to a feeder unit such as in the Makrides application, or to other utilization apparatus, as desired.

It will be seen that the use of elongated counter-rotating belts provides an advantageous accumulation function. As clumps or batches of mail pass down between the converging belts, the outer letters are continually urged in opposite directions by the two belts, while the clump is transported generally forward by the horizontal conveyor belt. Because of the elongated and converging nature of the belts, the thicker the clump the earlier the shearing back action starts, so the clump is essentially strung out into a line by the time its first piece arrives at the gap.

While two thinning units, like those of Figs. 1 to 3, 4 to 7 and 8 to 12 will generally provide a sufl-lcient separation of letter batches or an irregular into a regular and continuous stream, where desirable more of such units may be added in sequence, or but a single unit may be used.

The present invention has therefore provided apparatus effective to convert a random or irregular stream of mail pieces or the like into a uniform Indian file stream, with the output velocity of the pieces positively determined by the vacuum belt speed, and with the orientation of the pieces maintained unchanged.

While in general it is desirable that the horizontal bottom belt have the same speed as the forward belt, this is not essential, and the bottom belt may have a lesser speed.

While it is preferred to use vacuum forward belts, because of their high effective friction to letters or the tive than the vacuum belt arrangement.

like, theforward belt of Figs. 1 to 3 may. be formed to have a high-friction surface in any suitable manner, .and provides a'simpler apparatus though somewhat less effec- In either case; the rearward belt may also have a high-friction surface, as by waygof ribs, corrugations or cleats formed thereon or attached thereto.

i In an alternate form, the counter-rotating belts may be replaced by counter-rotating drums or rollers, with the rearward roller having a slower speed. The rollers may be spring or pneumatically biased for passage of letters or clumps thicker than the gaps between the rollers. 1

.It will be understood that the various dimensions and speeds; given herein are illustrative only, since they may be varied according to the requirements of each individual design. Since many variations in the foregoing description will be readily apparent to those skilled in the art, the invention herein is not to be deemed limited by this description of preferred embodiments, but is definedby the appended claims.

What is claimed is:

1. .Apparatus for smoothing an irregular flow of flat articles comprising a horizontal conveyor belt, forward and rearward horizontally moving vertical conveyor belts arranged above said horizontal belt, said vertical belts being converging in the direction of movement of said horizontal belt to provide an exit gap narrower than the entrance gap therebetween, said forward vertical belt having the same direction of movement as said horizontal belt and said rearward'vertical belt having an opposite direction of movement, said forward vertical belt having a greater speed than said other vertical belt, and having a greater effective coefficient of friction to said articles thansaid rearward vertical belt, means resiliently urging said vertical belts together to maintain said exit gap resiliently, and means feeding said irregular article flow onto said horizontal belt at said entrance gap with said .articles standing on edge, said exit gap having a width adaptedto pass freely articles of less than a predetermined width, whereby if overlapped articles attempt to pass said exit gap, said rearward moving vertical belt tends to wipe back all but the one article juxtaposed to said forward vertical belt to smooth said article flow thereby.

2. Apparatus as in claim 1 wherein said forward vertical belt comprises a vacuum transport belt arrangement.

3. Apparatus as in claim 1 wherein said horizontal belt has the same speed as said forward belt. .4. Apparatus as in claim l'further including means responsive to approach of an excessively thick clump of articles toward said entrance gap for interrupting said 7 feeding means.

5. Apparatus for smoothing an irregular flow of flat articles comprising the apparatus of claim 1 in'combination with a second similar apparatus having its entrance gap adjacent the first apparatus exit. gap and having higher belt speeds than said first apparatus.

6; Apparatus for smoothing an irregular flow of flat articles comprising a horizontal conveyor belt, forward and rearward horizontally moving vertical conveyor belts arranged above said horizontal belt, said vertical belts having the same direction of movement as said' horizontal belt and said rearward verticalbelt having an opposite direction of movement, and means feeding said irregular article flow onto said horizontal belt at said entrance gap with said articles standing on'edge, whereby-if overlapped articles attempt to pass said exit gap, said rearward movingvertical belt tends to wipe back all but the one article juxtaposed to said forward vertical belt to smooth said article flow thereby.

7. Apparatus as in claim 6 wherein'said forward vertical belt comprises a vacuum transport belt arrangement.

8. Apparatus for smoothing an irregular fiow of flat articles comprising forward and rearward horizontally moving vertical conveyor belts, said belts converging in the direction of movement of said forward belt to provide an exit gap narrower than the entrance gap therebetween, said exit gap having a predetermined width adapted to pass freely articles of lessthan a predetermined width, said belts having opposite directions of movement for their adjacent faces, and means feeding said irregular flow into said entrance gap with said articles standing on edge, whereby if overlapped. articles having an overall thickness greater than said width attempt to pass said exit gap said rearward belt tends to wipe back all but the one article juxtaposed to said forward belt to smooth said article flow thereby.

9. Apparatus as in claim 8, further including further means urging said articles from said entrance gap toward said exit gap.

10. Apparatus as in claim 6 further including means responsive to approach of an excessively thick group of articles towards said entrance gap for interrupting said feeding means. i

11. Apparatus for smoothing an irregular flow of flat articles comprising the apparatus of claim 6 in combination with a second similar apparatus having its entrance gap adjacent the first apparatus exit gap and having higher belt speeds than said first apparatus.

12. Apparatus for smoothing an irregular flow of flat articles comprising horizontal conveying means, a pair of horizontally moving vertically oriented conveying means in spaced apart relation arranged above said horizontal conveying means, said vertically oriented conveying means converging in the direction of movement of said horizontal conveying means to provide an exit gap narrower than the entrance gap therebetween, means for driving one of said vertically oriented conveying means in a forward direction and the other in a rearward direction, and means feeding said irregular article flow onto said horizontal conveying means at said entrance gap, whereby if over.-

1 lapped articles attempt to pass said exit gap' said rearward-moving conveying means tends to Wipe back all but the one article juxtaposed to said forward-moving conveying means to smooth said article flow thereby.

References Qitedin the file of this patent UNITED STATES PATENTS 2,224,137 Breman Dec. 10, 1940 2,541,300 Silva Feb. 13,1951 2,615,555 Carter Oct. 28, 1952 2,703,169 Beyer Mar. 1, 1955 2,738,051 Beyer Mar. 13, 1956 FOREIGN PATENTS i 7 512,940 Germany Nov. 25, 1930 UNITED STATES PATENT OFFICE CERTIFICATE OF CORBECTIQN Patent No 2 U 941 q 6541 June 21 1960 David Gray Falconer lt is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2 line 2 for "over" read or line 68 for "soon" read seen SEA L) Attest:

KARL H. AXLINE Attesting Officer ROBERT C. WATSGN Commissioner of Patents