US2554579A - Feeding mechanism for printing presses - Google Patents

Description

May 29, 1951 J. R. LAUFFER FEEDING MECHANISM FOR PRINTING PRESSES 3 Sheets-Sheet 1 Filed Feb. 15, 1949 INVENTOR. M4605 P AAuF/Z'P May 29, 1951 J. R. LAUFFER v FEEDING MECHANISM FOR PRINTING PRESSES 3 Sheets-Sheet 2 Filed Feb. 15. 1949 P 5 F m; W

May 29, 1951 J. R. LAUFFER FEEDING MECHANISM FOR PRINTING PRESSES S Sheets-Sheet 5 Filed Feb. 15, 1949 INVENTOR.

L#605 A? LHUFFZ/P Patented May 29, 1951 FEEDING MECHANISM FOR PRINTING PRES SES Jacob Robert Lauffer, Valley Stream, N. Y., as-

signor to Miller-Laufier Printing Equipment Corporation, New York, N. Y., a corporation of New York Application February 15, 1949, Serial No. 76,597

Claims. 2

This invention relates to feedin mechanism for a rotary printing press designed to print upon pre-cut or pie-formed pieces of paper. For convenience the invention is here described in connection with a press for printing corner legends on pre-formed envelopes, more particularly a machine of the type in which envelopes are successively advanced at constant speed: through the printing position by means of carrier chains having lugs which engaged the envelope under each end of its flap. It is contemplated that the in vention may also be used for printing articles other than envelopes, such as flat sheets of paper or cut sheets afterwards to be folded into envelopes, in which case other forms of press or carrier would be used. The press and carrier here described form no part of the present invention. In the annexed drawings which form part of this specification:

Fig. l is a vertical longitudinal-section through approximately the center line of a machine made in accordance with my invention, in the plane !-i of Fig. 2.

Fig. 2 is a horizontal section in the plane 2-2 of Fig. 1.

Fig. 3 to a portion of the mechanism shown in Fig. 1, illustrating one embodiment of the machine when the envelopes have become closely packed adjacent the delivery end of the feed magazine.

Fig. 4 is similar to Fig. 3, but with the envelopes separated due to lag in the feed.

Fig. 5 is similar to Fig. 4, except that it shows a structure modification in which the sensing lever is applied at the bottom, instead of the top,

of the stack of envelopes.

A printing press with which my novel feeding mechanism may be employed is more fully described in my co-pending application Ser. No. 768,744, filed August 15, 1947, and is here shown merely diagrammatically. In this press two endless carrier chains II, I2 are rotated in parallel planes over a series of rollers i3, I4, !5, etc., journaled in frame 48. Suitably spaced links are provided with lugs I 6, 57, etc. The lugs of one chain project laterally thereof in a direction towards the other chain, and the chains are so arranged that, as they move at the same speed in their parallel planes, a lug on one chain remains in axial alinement with a 111g on the other chain. While the distanceseparating the planes in which the two chains operate is adjustable, depending upon the length of the envelope to be printed, the arrangement is such that each pair of axially alinedlugs (for example,- lugs I6--I6- shown in is a diagrammatic View, corresponding Fig. 2) is adapted to engage under the flap of an envelope at the opposite ends thereof and thus to convey the envelope forward from the pick-up position C to the printing position !8. Suitable guides (not shown) restrain the envelope from flying outwardly where the chains pass around a roller, for example roller I3, and elsewhere.

Suitably positioned with respect to the envelopes passing under control of. the chains are a printing roll it, bearing impression plates 20 and H, and. a series of inking and ink distributing rolls 22, 23 and 24 arranged in the usual manner to supply ink to the impression plate 2?], 2| An impression roll 25 is provided at the printing position I8 to afford a backing for each envelope at the moment or printing.

Beyond the printing position, in the direction of travel of chains II, I2, is suitable mechanism (not shown), such for example as that shown in my co-pending application above-mentioned, for removing envelopes from the chain and delivering them to a delivery hopper. The means disclosed for this purpose in my co-pending application is a pair of speed-up belts which engage the envelopes and advance them more rapidly than the chain, thereby disengaging their flaps from lugs I6, I'I, etc. Thereafter the chains II, I12 are brought back around suitable rollers (not shown) and power sprockets 2'! to the starting point. Power for the carrier, whatever its type, is supplied by a motor 28 geared or belted toshaft 26 on which are mounted sprocket wheels 21 whose teeth engage and drive the chains II, I2. Motor 28, as will be described below, also drives the secondary feed belts t0, 4!.

The foregoing describes one form of carrier (1. e., parallel endless chains) whereby envelopes are conveyed through the printing position, and one form of rotary printer. The invention which is the subject of the present application, while it may be inter-related as regards driving mechanism and speed with the above-mentioned carrier and printer, is not limited to the particular form of carrier or printer herein shown.

At the pick-up position C, lugs I6, IT, etc., of chains I I, I2 are moving either in a vertical plane or in a plane which isinclined at a small angle to a vertical plane. Hence, the envelope which momentarily occupies the pick-up position is ready, when the opposite ends of its flap are engaged by lugs It, to be lifted vertically or almost vertically for further traverse to the printing position. To assist inthis operation I provide a pneumatic jet fiI which is aimed to blow the flap outwardly and one or more rollers on fixed axles to hold the envelopes in the required alinement. The mechanisms described below perform the function of assuring a constant flow of envelopes to the pick-up position C, so that a fresh envelope will be presented at that position without fail as each successive pair of lugs It comes along.

Adjacent pick-up position C is a feed magazine designated generally by the reference numeral 29. Feed magazine includes adjustable side plates 33, 3| and two primary feed belts 32, 33 forming a support for envelopes resting on their lower edges and with their faces juxtaposed in a continuously moving stack in feed magazine 25. Said belts pass over drive rollers 34, 35, fixed on shaft 35, which support these belts at their ends nearest the carrier chains H, I2. The opposite ends of these belts 32, 33 are supported on idler rollers (not shown) which are at the remote end of feed magazine 25. Preferably the feed magazine should be of substantial length on the order of from 3 to 10 feet, i. e., sufficient to hold from several hundred to several thousand envelopes. It is contemplated that envelopes will be stacked by hand in feed magazine 25, with their flaps at the top, the flap side facing towards the carrier chains H, l2, and tilted slightly so that they lean forward in the direction of their travel.

Primary feed belts 32, 33 are advanced by power applied to shaft 35 (see Fig. 4) Fixed on shaft 35 is a pulley 37 over which is engaged a transmission belt 58 driven by motor 39. Thus the speed of movement of belts 32, 33 is governed by the speed of rotation of motor 39.

At that end of feed magazine 29 which is adjacent carrier chains H, l2 are a pair of secondary feed belts 35, ii passing over idler rollers 52, 33 and drive rollers M, 35. The upper surfaces of these belts are preferably in the same plane as the upper surfaces of belts 32, 53, and the axes of rollers 34, 35 and of idler rollers 42, G3 are preferably disposed in vertical planes separated a short distance from each other so that envelopes being delivered from the primary to the secondary feed belts will for a moment be in contact with both belts. A spacing and tensioning frame (shown only in Fig. 1) provides support for each idler roller 42, 43. Drive rollers 44, B5 are fixed to shaft I31 (see Fig. 2) which is journaled in supporting frame 48 and carries at one end a worm-drive connection with a shaft 49 which in turn is connected through a second worm drive with the shaft of motor 28 (see Fig. 1). Thus motor 28 drives both carrier chains l I, 12 and secondary feed belts 43, 4| and the latter therefore move in synchronism with (i. e., at

" a speed which is always proportional to the speed of preferably adapted to be pressed against the top of the stack of envelopes or, alternatively, adapted to be pressed against the bottom of the stack. Lever 59 rotates upon a fixed pivot 52 and its opposite end is tensioned by a spring 53 secured to the under side of frame member 54. In position to be engaged by lever is mounted an electrical switch 55 shown diagrammatically in Figs. 3, 4 and 5.

Power for motor 33 is derived from mains 56, 5! which are connected to the terminals of motor 39 across a resistance 58. Power is derived from the same mains for motor 28. A manual switch 59 when closed connects both motors to the mains. Main 56 is also connected through switch 55 with an intermediate point of resistance 58, whereby less resistance is interposed in the circuit to motor 39 when switch 55 is closed and consequently a higher voltage will be impressed upon that motor and it will run faster. The opening of switch 55 interposes all of resistance 58 in the circuit to motor 39 and consequently a lower voltage will be impressed upon that motor and it will run slower. Switch 55 does not affect the supply of current to motor 23.

In the form of device shown in Figs. 3 and 4, roller 5| of sensing lever 55 is arranged to be spring-tensioned against the upper surface of the stack of envelopes moving toward the carrier chains H, l2 under the influence of primary feed belts 32, 33 and secondary feed belts 35, 5!. Under ordinary conditions this stack of envelopes presents a comparatively solid appearance, the envelopes standing in close array with their upper surfaces forming a comparatively straight line as they move forward (see Fig. 3). However, at the point where the envelopes are delivered from the primary feed belts 32, 33 to the secondary feed belts 40, 4| there is a tendency under certain conditions for the stack of envelopes to become sepaarted and to form a break as described below. This occurs in the delivery zone.

The delivery zone is the zone or region in the moving stack of envelopes where individual envelopes are passing from the control of primary feed belts 32, 33 to the control of secondary feed belts 40, 4|. As previously set forth I prefer to arrange these belts so that envelopes being delivered from one pair of belts to the other will for a moment be in contact with both. In the drawings I have indicated by dotted lines A and B (which if extended would respectively pass through the axes of rollers 42, 33 and of rollers 34, 35) the approximate margins of the delivery zone. Since, however, there would nevertheless be a delivery zone even if the axes of all these rollers were in the same vertical plane, the showing is approximate only and is employed in this specification simply to point out that an ascertainable region exists where a break or separation in the moving stack of envelopes will occur if the supply of envelopes to the secondary feed belt is deficient, and thereby to show the correct positioning of roller 5: of the sensing lever 55.

Roller 5| is located at or immediately adjacent the delivery zone and in position to move toward the central axis of the envelope stack in the event of a diminution of the numb-er of envelopes passing through the delivery zone at a given instant.

Vertical alinement of those envelopes which are wholly under control of secondary feed belts 40, M is maintained by the pressure of envelopes behind, by the action of the belts themselves, and by the point of bearing of the leading envelope against chains ll, l2, the pneumatic jet 5| and rollers 65. Under ordinary operating conditions, the envelopes on the primary belts are stacked thereon so as to tip forward slightly in the direction of their travel. As they pass through the delivery zone and come under control of the secondary belts they assume a vertical alinement, largely due to the action of the secondary belts which, for this purpose, should preferably'be run faster than the primary belts. Under these conditions a slight break in the upper surface of the stack at the delivery zone is normal and denotes merely the point at which the envelopes become vertical.

However, when operating at speeds on the order of 50,000 to 100,000 impressions per hour, very slight differences between the delivery speed of the primary belts and the requirements of the y press, if long continued, tend to produce a cumulative efiect which ultimately becomes disastrous at the pick-up position C. If the primary belt oversupplies the secondary, the break in the upper surface of the stack, normally apparent in the delivery zone, disappears or moves to the left (as seen in Fig. 3) far from the delivery zone and the pressure on the envelopes resting on the secondary belt becomes so great that jamming occurs. This causes envelopes to be thrown out at the pick-up position C and requires that the press be slowed down or stopped altogether. On the other hand, if the primary belt undersupplies the secondary for any considerable length of time the envelopes on the primary belt become tipped forward at an increasingly sharp angle to the vertical and the break at the delivery zone deepens and becomes more pronounced and will in time move to the right (as seen in Fig. 3) This condition, if allowed to develop, ultimately causes envelopes to be presented almost horizontally to the carrier chains H, l2 and requires that the press be stopped altogether till the feed is straightened out.

According to my invention, I provide means for automatically and continually varying the speed of the primary belts in accordance with the condition of the envelopes in the moving stack at or immediately adjacent the delivery Zone. A means I may employ for this purpose includes the sensing lever and the connections thereof with the supply circuits for motor 39 described above.

If insufficient envelopes are being supplied to the secondary belts, two effects are observed at the delivery zone (a) the normally slight break in the upper surface of the moving stack deepens appreciably and (b) the weight or density of envelopes momentarily in the delivery zone at any given instant becomes markedly less.

I so position the roller 55 as to be adapted to move towards the axis of' the moving stack in response to either of these conditions. On the other hand, if an oversupply of envelopes is reaching the secondary belts, two other efiects are observed at the delivery zone(c) there is no longer any break in the upper surface of the moving stack at the delivery zone, and (d) the weight or density of envelopes momentarily in the delivery zone at any given instant becomes markedly greater. In response to either of these last named conditions roller 5! is pressed outwardly away from the axis of the moving stack.

In the modification of my invention shown in Figs. 3 and 4, roller 5| on the end of sensing lever 50 is spring-pressed so as to bear against the upper surface of the stack of envelopes adjacent the delivery zone and in such position as to be movable in response to a significant deepening of the break in the upper surface of the stack at that point. When the upper surface of the stack assumes substantially a straight line in the delivery zone (as in Fig. 3), roller 5| is pressed upwardly and switch 55 is opened. Under these conditions, as above described, the speed of motor 39, and. thus of primary feed belts 32, 33 is reduced. When, however, break 64 deepens markedly, roller 5| is spring pressed into the depression thus formed. and in consequence switch 55 is closed. This, as described above, cuts out a portion of the resistance in the motor circuit, increases the voltage to motor 38, and thereby increases its speed and that of primary feed belts 32, 33. Consequently, the supply of envelopes being delivered by primary feed belts 32, 33 to secondary feed belts 40, N is automatically and constantly varied in such manner as to compensate for underand over-supply at the delivery zone and thus assure a substantially constant feed of envelopes at the pick-up position 0.

In the modification shown in Fig. 5, roller 51 on the end of sensing lever 5a is spring-pressed so as to bear against the under surface of the stack of envelopes at or near the deliver zone in such position as to be movable in response to a lessening in the weight or density of envelopes momentarily at this point. To this end the tension of spring 58 (in Fig. 5) is adjusted with reference to the characteristics of the envelopes being handled. Upward movement of roller 5! causes (through the circuits previously described) an increase in the speed of motor 39 and of primary feed belts 32, 33.

While the linear speed of travel of the primary and secondary feed belts may be varied according to the thickness and weight of the envelopes being handled, and the speed of printing, the following is set forth as an example of belt speeds which have been employed in printing No. 10 envelopes at the rate of approximately 50,000 per hour:

Primary belts: Inches per minute It will be observed that, in the example given, the primary belts at their higher speed ran faster than the secondary belts. Because of continual opening and closing of switch 55, the average speed of the primary feed belts lay somewhere between the low and high speeds above indicated. This average speed represents the net speed of feed to the press, and it may be and preferably should be lower than the speed or" the secondary belts. It is therefore within the spirit of my invention to provide two different speeds for the primary belts, both of which will be less than the speed of the secondary belt. In such cases the slippage occurring between the secondary belts and the bottoms of the envelopes resting thereon equalizes the feed. Indeed this slippage probably occurs whatever the speeds of the primary belts and is relied on to assure that envelopes reaching the pick-up position C will be in proper vertical, or substantially, vertical alinement at that point as required by chains ll, !2.

According to this invention the speed of the primary feed belts 32, 33 is under control of mechanism responsive to the condition of the envelopes in the stack at or adjacent what I have called the delivery zone-the point where these envelopes pass from control of the variable-speed primary feed belts 32, 33 to t e control of constant-speed secondary feed belts it, 4!. At this point the stack exhibits a definite condition or phenomenon, namely a pronounced separation and tipping, which signals the for an increase in the speed of the primary feed belts when the secondary feed belts 7 plied. The mechanism I have described, namely a mechanical lever spring-pressed against the moving stack of envelopes, and having a small .roller at the end thereof which bears against the envelopes at or near the delivery zone, aifords a convenient means of efiecting the de-- sired automatic control of the speed of the primary feed belts. Preferably I apply this roller to the upper surface of the envelope stack to take advantage of the break, although it may also be applied to the lower surface to take advantage of reduced weight or density. It is my belief that other and equivalent means or instrumentalities may be employed, responsive to the separation, tipping, break, opening up or reduced weight or density of the envelope stack or adjacent the delivery point to vary the speed of motor 39, either mechanically or electrically. Consequently, while my claims herein are limited to the specific form of instrumentality which I have discovered and used, it is my intention that these claims shall be interpreted to embrace equivalent mechanisms producing the same result.

While I have sometimes referred herein to the speed of carrier chains ii, l2, and of the secondary feed belts All, 4!, as being constant, it is intended thereby to mean that their speed is, for a predetermined speed of printing, constant and not variable so long as the press is running at that speed of printing. It is of course contemplated that the speed of printing (under control of motor 28) may be varied at will.

In the foregoing I have shown and described for purposes of illustration one specific form of mechanism, involving primary and secondary feed belts, embodying my invention. It is to be understood, however, that the invention is not limited to the specific form of mechanism herein shown and described, but is to be taken as including other forms of mechanism, and portions or subcombinations thereof, comprehended with in the scope of the following claims.

I claim:

1. In a feed mechani m for delivering articles of paper such as envelopes and the like to a printing press, the combination of a feed belt adapted to advance towards the press a moving and normally unbroken stack of said articles resting on the belt with their faces juxtaposed, a variable-speed electric-powered drive for acivancing said belt at not less than two different feeding speeds one of which is fast enough to oversupply articles to the pres at ordinary press operating speeds, an electrical switch for controlling the speed of the drive, and a lever in sensing relation with the stack adjacent the point at which articles are delivered from the belt to the press and operable in response to reficiency in the sup-ply of articles at that point to actuate the switch in a direction causing the drive to advance the belt at a higher rate of speed so long as the deficiency persists.

2. In a feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, the combination of a feed belt adapted to advance towards the press a moving and normally unbroken stack of said articles resting on the belt with their faces juxtaposed, a variable-speed electric-powered drive for advancing said belt at not less than two different feeding speeds one of which is fast enough to oversupply articles to the press, and another of which is slow enough to under-supply articles to the press, at a given speed of operation of the said drive to advance the belt at the slower speed,

and a lever in sensing relation with the stack adjacent the point at which articles are to be delivered to the press and operable in response to a deficient supply of articles at that point to actuate the switch to that position in which the drive advances the belts at the faster speed and, in response to an excess supply of articles at that point, to actuate the switch to that position in which the drive advances the belts at the slower speed.

3. Feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising two alined feed belts adapted to advance said articles continuously from one belt to the other in a substantially unbroken stack with their lower edges resting successively upon first one and then the other of said belts and their faces juxtaposed, means to drive the belt nearest the press at a speed constant in relation thereto, an electrical drive and associated supply circuit for the other of said belts arranged to advance said other belt at a plurality of different feeding speeds including at least one speed which is less than that of the belt nearest the press, a pivoted sensing lever one end of which is adapted to engage the stack adjacent the point where said articles pass from the control of one to the other of said belts, and electrical switching mechanism controlled by said lever and interposed in the drive circuit adapted to increase the speed of said drive and of the belt actuated thereby in response to diminution in the number of articles in said stack at said point.

4. Feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising two alined feed belts adapted. to advance said articles continuously from one belt to the other in a substantially unbroken stack with their lower edges resting successively upon first one and then the other of said belts and their faces juxtaposed, means to drive the belt nearest the press at a speed constant in relation thereto, an electrical drive and associated supply circuit for the other of said belts arranged to advance said other belt at a plurality of different feeding speeds including one which is less and one which is greater than the speed of the belt nearest the press, a pivoted sensing lever one end of which is adapted to engage the stack adjacent the point Where said articles pass from the control of one to the other of said belts, and electrical switching mechanism controlled by said lever and interposed in the drive circuit adapted to cause said drive and the belt actuated thereby to advance at the higher of said speeds in response to diminution in the number of articles in said stack at said point.

5. Feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising two alined feed belts adapted to advance said articles continuously from one belt to the other in a substantially unbroken stack with their lower edges resting successively upon first one and then the other of said belts and their faces juxtaposed, means to drive the belt nearest the press at a speed constant in relation thereto, an electrical drive and associated supply circuit for the other of said belts arranged to advance said other belt at a plurality of different feeding speeds including at least one speed which is less than that of the belt nearest the press, a pivoted sensing lever one end of which is adapted to engage the stack adjacent the point where said articles pass from the control of one to the other of said belts, and electrical switching mechanism controlled by said lever and interposed in the drive circuit adapted to increase the speed of said drive and of the belt actuated thereby to a greater speed when the number of articles in said stack at said point becomes less than a predetermined number.

6. Feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising two alined feed belts adapted to advance said articles continuously from one belt to the other in a substantially unbroken stack with their lower edges resting successively upon first one and then the other of said belts and their faces juxtaposed, means to drive the belt nearest the press at a speed constant in relation thereto, an electrical drive and associated supply circuit for the other of said belts arranged to advance said other belt at a plurality of different feeding speeds including at least one speed which is less than that of the belt nearest the press, a sensing lever pivoted adjacent the point where said articles pass from the control of one to the other of said belts, one end of said lever being spring-pressed against the stack and biased to move towards the stack when the number of articles at said point becomes less than a predetermined number, and electrical switching mechanism interposed in said circuits and controlled by said lever adapted to increase the speed of said drive when said lever moves towards the stack.

'7. In a, feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising 'alined primary and secondary feed belts adapted to advance said articles on edge with their faces juxtaposed in a moving and normally substantially unbroken stack which is continuously delivered by the primary to the secondary belt in a delivery zone between them, the secondary belt delivering said articles to the press in suitable alinement for and at the speed required b the press, the combination of a variable speed electrical drive for advancing the primary belt at not less than two different feeding speeds at least one of which is fast enough to oversupply articles to the secondary belt, a supply circuit for said drive, a pivoted lever one end of which bears against the moving stack adjacent the delivery zone and is spring-biased so as to move towards said stack when the stack in said zone becomes broken, and an electrical switch controlling said supply circuit and responsive to the lever adapted to cause the primary belt to move at oversupply speed so long as said break in the stack persists.

8. In a feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising alined primary and secondary feed belts adapted to advance said articles on edge with their faces juxtaposed in a moving and normally substantially unbroken stack which is continuously delivered by the primary to the secondary belt in a delivery zone between them, the secondary belt delivering said articles to the press in suitable alinement for and at the speed required by the press, the combination of a variable speed electrical drive for advancing the primary belt at not less than two different feeding speeds at least one of which is fast enough to oversupply articles to the secondary belt, a supply circuit for said drive, a pivoted lever one end of which bears against the upper surface of the moving stack adjacent the delivery zone and is adapted to move downwardly towards the center of the stack when 'a substantial break occurs in such surface in that zone, and an electrical switch controlling said supply circuit and responsive to said movement of the lever adapted to cause the primary belt to move at oversupply speed so long as said break in the stack persists.

9. In a feed mechanism for delivering articles of paper such as envelopes and the like to a printing press, comprising alined primary and secondary feed belts adapted to advance said articles on edge with their faces juxtaposed in a moving and normally substantially unbroken stack which is continuously delivered by the primary to the secondary belt in a delivery zone between them, the secondary belt delivering said articles to the press in suitable alinement for and at the speed required by the press, the combination of a variable speed electrical drive for advancing the primary belt at not less than two different feeding speeds at least one of which is fast enough to oversupply articles to the secondary belt, a, supply circuit for said drive, a pivoted lever one end of which bears against the lower surface of the moving stack adjacent the delivery zone and is spring-biased upwardly to move toward the center of the stack when the number of articles above it becomes less than a predetermined number, and an electrical switch controlling said supply circuits and responsive to said movement of the lever adapted to cause the primary belt to move at oversupply speed so long as said number of articles remains less than the predetermined number.

10. In a feed mechanism for delivering articles of paper such as envelopes and the like to a, printing press, comprising alined primary and secondary feed belts adapted to advance said articles on edge with their faces juxtaposed in a, moving and normally substantially unbroken stack which is continuously delivered by the primary to the secondary belt in a delivery zone between them, the secondary belt delivering said articles to the press in suitable alinement for and at the speed required by the press, the combination of a variable speed electrical drive for advancing the primary belt at not less than two different feeding speeds at least one of which is fast enough to oversupply articles to the secondary belt, a supply circuit for said drive, a lever in sensing relation with the stack adjacent the delivery zone and operable in response to a deficiency in the supply of articles in that zone, and an electrical switch for controlling the supply circuit adapted to be actuated by the lever to cause the drive to advance the primary belt at oversupply speed so long as said deficiency persists.

JACOB ROBERT LAUFFER.

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

UNITED STATES PATENTS Number Name Date 2,180,601 Mitchell et al Nov. 21, 1939 2,267,784 Belluche Dec. 30, 1941 2,317,921 Leach Apr. 27, 1943

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