US2937819A

US2937819A - Constant web tension unwinding mechanism

Info

Publication number: US2937819A
Application number: US537855A
Authority: US
Inventors: Jr Richard Le Baron Bowen
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-09-30
Filing date: 1955-09-30
Publication date: 1960-05-24
Anticipated expiration: 1977-05-24

Description

y 1960 R. LE BARON BOWEN, JR 2,937,819

CONSTANT WEB TENSION UNWINDING MECHANISM 4 Sheets-Sheet 1 Filed Sept. 50, 1955 INVENTOR. RICHARD LEBARON BOWEN,JR.

BY .MMM $3M film ATTORNEY y 1960 R. LE BARON BOWEN, JR 2,937,819

CONSTANT WEB TENSION UNWINDING MECHANISM Filed Sept. 30, 1955 4 Sheets-Sheet 2 I62 /60 70 ii. a I43A /4 INVENTOR. RICHARD LEBARON BOWEN,JR.

ATTORNEY y 1960 R. LE BARON BOWEN, JR 2,937,819

CONSTANT WEB TENSION UNWINDING MECHANISM Filed Sept. 30, 1955 4 Sheets-Sheet 4 FIG. 6 V

l F 7 I50 INVENTOR. RICHARD LEBARON BOWEN,JR.

BY 322144;, jedefl z hhwk ATTORNEY United States Patent CONSTANT WEB TENSION UNWINDIN MECHANISM Richard Le Baron Bowen, Jr., 173 Columbus Ave., Pawtucket, RI.

Filed Sept. 30, 1955, Ser. No. 537,855

13 Claims. (Cl. 242-755) This invention relates to a constant web tension unwinding mechanism and more particularly to a mechanism for maintaining a constant speed on the web unwinding mechanism through a variable speed transmission responsive to the change in brake speed which reacts to control the speed of the brake.

One of the objects of the present invention is to provide a constant braking force in a web unwinding mechanism.

Another object of the present invention is to provide a braking force mechanism which inherently will permit the accurate duplication of the braking force.

Other objects of the present invention will be pointed out in part and become apparent in part in the following specification and claims.

The present application is a continuation-in-part of my copending application Serial No. 344,520, filed March 25, 1953, now Patent No. 2,781,178, dated February 12, 1957.

Uniform tension is a prerequisite to uniformity of product in many web processing machines used for textiles, paper, imitation leather, printing and the like. Especially is this true in coating machinery where the tension on the web effects the nature of the application of the coating being applied to the web, which may be paper, cloth, or plastic. When a supply roll of web material is placed in the machine the cloth is drawn off at a constant speed and at a given tension. As the diameter of the supply roll decreases the speed or linear travel of the cloth is maintained constant. However, the tension on the cloth increases as the drag on the supply roll increases. There fore, it is necessary to regulate the drag or friction onthe supply roll shaft if the tension on the cloth is to be maintained constant. Past devices have failed to automatically control the drag and thereby regulate the tension accurately in accordance with the changing tension produced as the supply roll decreases in diameter.

This failure was due in part to the nature of the braking mechanism, which consisted of the conventional arrangement of a brake drum and a shoe provided with a brake lining. Periodic adjustment was necessary to reduce the braking force as the rotational speed of the unwinding roll increased.

Referring to the drawings in which similar characters of reference indicate corresponding parts in all the figures:

Figure 1 shows an embodiment of the present invention in diagrammatic form, for the sake of clarity and simplicity, and presents the mechanism as applied to an unwinding device.

Figure 2 is a diagrammatic embodiment of a modified form of the mechanism illustrated in Figure 1.

Figure 3 is a diagrammatic form of an electric brake.

Figure 4 is a diagrammatic form of mechanism which is still another modification of the mechanism illustrated in Figure 1.

Figure 5 is a diagrammatic form of mechanism which is still another modification of the mechanism illustrated in Figure 1;

Figure 6 is a diagrammatic form of another modification of Figure 1. j a

Figure 7 is a modified form of Figure 6.

Referring to the drawings and particularly to Figure 1', a strip or web of material 11 is being withdrawn from a beam 12 by means of a drum 16. Beam 12 is secured to an axle 13 which has fixed to it bevel gear 14 which meshes with bevel gear 15 fixed to a shaft 20 of a continuously variable speed transmission, generally indicated by reference character 17. A second shaft 21 of variable speed transmission 17 is operatively connected to a brake generally indicated by reference character 150 through a shaft 36, sprocket 33 fixed to shaft 36, sprocket 32 fixed to shaft 21, and chain 34 connecting

sprockets

32, 33.

Fixed to the other end of shaft '36 is bevel gear 151 which meshes with bevel gear 152 fixed to brake drum 153 of brake 150. Brake drum 153is contacted by brake shoe 154 which is prevented from rotating as at point 155. Brake shoe 154 is compressed on drum 153 by means of adjusting screw 156. Loosening screw 156 permits drum 153 to rotate freely. Tightening screw 156 tends to restrain drum 153, and therefore also tends to restrain transmission 17 and roll 12 from rotating.

The variable speed transmission 17 comprises the pair of

shafts

20 and 21 which extend parallel to each other and are rotatably mounted in a housing 22. Each

shaft

20, 21 carries a pair of

coned disks

23, 24 respectively, forming expansive V pulleys which are splined to said shafts. Coned

disks

23, 24 are operatively connected through edge-active belt 25 and may be simultaneously and oppositely adjusted to provide variable speed by the simultaneous adjustment of

levers

26 and 27 which are operatively connected to coned

disks

23, 24 and pivotally separated by lever 28. The

levers

26, 27 are fixed at one end thereof to threaded shaft 30 by means of threaded

bearings

31, 132. The rotation of threaded shaft 30' through slip clutch 29 vsimultaneously and oppositely moves

disks

23, 24 on

shafts

20, 21 thereby varying the speed of rotation of shaft 20 relative to shaft 21. Threaded shaft 30 is controlled by a differential gear train generally indicated by reference character 58.

The differential gear train 58 comprises three shafts '60, 61, 62 rotatably mounted in housing 63.

Short stub shafts

64 and 64A project from block 62A fixed to shaft 62. Shafts 64 and 64A have rotatably mounted thereon

bevel gears

65 and 66 which are operatively connected to

bevel gears

67 and 68 rotatably mounted on shaft 62. A spur gear 70 fixed to bevel gear 67 meshes with spur gear 71 fixed to shaft 60. Sprocket 72 fixed to bevel gear 68 is operatively connected by means of chain 73 tosprocket 7.4 fixed to shaft 61. It is evident that shafts. 60, 61 when rotated in the same direction and at the. same speed cause shaft 62 to remain idle. However, any

difference in speed of shafts 60, 61 when turning in thesame direction, will cause shaft 62 to rotate, the speed of this rotation being proportional to the difference in the speeds of shafts 60, 61.

Shaft 61 of differential 58 is operatively connected with drum 16 through bevel gear 75 fixed to drum 16 which' meshes with bevel gear 76 fixed to shaft 77, on which isfixed sprocket 78 which is connected to sprocket 80 fixed; to shaft 61 by means of chain 81. Shaft 60 of differential 58 is operatively connected to shaft 21 of transmission 17 by means of

sprockets

82, 83 and chain 84 and has a handwheel 85 secured thereto. Shaft 62 of differential58 is operatively connected to threaded shaft 30 of trans-' mission 17 through a slip clutch 29 by means of

sprockets

46, 47 and chain 48, sprocket 47 being fastened toslip clutch 29.

is withdrawn at a constant linear velocity. When 'the system is at equilibrium, shafts 60, 61 of difierential 53 are revolving at the same speed and shaft 62 is motionless. Shaft 61 is driven at a constant speed by a driving connection with drum 16, which rotates at constant speed.

As beam 12 unwinds, its diameter decreases and its speed of rotation increases. This increase in speed is immediately transmitted to shaft 60 of difierential 58 from shaft 21 of transmission 17. As soon as there is a difference in speeds between shafts 60, 61 of direrential 58, shaft 62 commences to rotate, thereby changing the speed of transmission 17 and thus maintaining the speed of shaft 21 constant. Since the speed of shaft 21 is maintained constant, the speed of brake 150 is likewise maintained constant, and thus the power and tension applied to the web are also constant.

Figure 2 diagrammatically depicts a modified form of mechanism for controlling the variable speed transmission 17, and thus is a modified form of Figure 1. Here the, speed ratio of transmission 17 is changed by means of a hydraulic system rather than the mechanical screw used in Figure 1. The hydraulic control device consists of a fluid motor comprising a cylinder 140A connected to move with lever 26A, and a piston 141A reciprocally mounted in the cylinder 140A and operatively connected to lever 27A, together with valving means 142A for controlling the relative movement of cylinder 140A and piston 141A. Valve 142A is a four way bydraulic valve with a control lever 143A operatively connected to shaft 62 of differential 58 by means of bevel gear 160 fixed to shaft 62 meshing with bevel gear 161 which has fixed to it lever 162. Link 163 connects lever 162 to control lever 143A.

This piston type of hydraulic control is well known in the art and has been described by Clay in Patent No. 2,306,541. Oil is supplied to the control valve through line 144A, and oil is returned from the cylinder by line 146A. Hydraulic fluid is supplied to the system by means of hydraulic pump 164 which has a suction line 165 which connects with fluid reservoir 166. The construction of this type of four way hydraulic valve 142A has been well disclosed by Clay. Hydraulic pump 164 is driven by a constant speed power source, such as a motor not shown. Hydraulic pump 164 might well be driven from shaft 21 of transmission 17 which also turns at a. constant speed.

As previously described for Figure 1, when beam 12 unwinds,

shafts

20, 21 and brake 150 will tend to gradually increase in speed. This increase in speed is immediately transmitted from shaft 21 to shaft 60 to differential 58. As soon as there is a difference in speed between shafts 60, 61 shaft 62 commences to rotate thereby moving valve lever 143A and introducing oil to cylinder 140A causing the piston 141A to move cones 24 together and simultaneously move cones 23 apart, thereby. restoring the speed of the brake to its arbitrarily set initial value.

After the beam has been unwound, the transmission is at one limit. With the mechanism stopped, valve lever 143A is held from movement because differential shaft 62 has stopped. For starting another beam. of material the transmission should; be shifted back to the starting position. To accomplish this, handwheel is turned. This accomplishes two things. In the first place, since shaft 61 of differential 58 does not move, movement of shaft 60 produces motion in shaft 62 and thus moves valve lever 143A. Movement of

levers

26A, 27A would not shiftthe transmission unless the

sheeves

23, 24 were rotated. Rotation of handwheel 85 also rotates

sheeves

23, 24..

Figure4 diagrammatically depicts a modified form of mechanism for controlling the variable speed transmission 17, and thus is a modification of Figure 1. This comprises abell crank arm 100 pivotally mounted at 101 to a bracket 102 secured to housing 22 and having a follower roller 103 rotatably mounted at 104 which bears against the outside diameter of beam 12 to sense the decrease in the size of beam 12. A link 105 is pivotally mounted to hell crank arm 100 at 106 and to lever 27 at 107. A link 108 pivotally mounted to bell crank arm 100 at 110 connects to lever 26 at 111. A spring 112 is connected to bell crank lever 100 at 113 and to housing 22 at 114. The spring 112 causes the follower roller 103 to ride against beam 12.

In operation it is self evident that as the diameter of the beam 12 decreases, bell crank lever 100 will move

levers

26 and 27 thus changing the speed of the transmission 17. This movement will maintain the speed of shaft 21 essentially constant. Since the speed of shaft 21 is maintained constant, the power applied by brake 150 will likewise remain constant, thereby applying constant tension to the web 11.

Figure 5 diagrammatically depicts a modified form of mechanism for controlling the variable speed transmission 17, and thus is a modification of Figure 1. Here there is a governor generally indicated by which controls the current to an electric motor 44 which changes the speed of'the transmission.

Governor 120 consists of a rotatably mounted shaft 121 to which is fixed connector 122 and on which is slidably mounted flange 123. Arms 124 are pivotally mounted to connector 122, and links 125 connect arms 124 with flange 123. When flange 123 rises, it makes contact with switch 126 which connects with wire 54. Wire 51 contacts shaft 121 at 127. Shaft 121 is operatively connected to shaft 36 of brake by means of

sprockets

130, 131 and chain 132.

As previously described, when beam 12 unwinds,

shafts

20, 21, shaft 36 and brake 150 tend to increase in speed. Since shaft 121 of governor 120 is operatively connected to shaft 36, the governor will also increase its speed of rotation. As the speed increases, arms 124 are thrown outward by centrifugal force, and flange 123 rises to make contact with switch 126. This closes the electrical circuit and current is supplied to motor 44 through wires 50 and 51. To reset the mechanism after a beam has ben unwound, reversing switch 53 and handwheel 56 are used.

Motor 44 could be controlled by other electrical. switches responsive to changes in speed, such as other centrifugal switches or the speed responsive switch shown. by Butterworth et al. in Patent No. 2,392,226.

Figure 6 diagrammatically depicts a modified form of mechanism for controlling the variable speed transmission 17, and thus is a modification of Figure 1. This comprises gear pumps and 171 and hydraulic motor 172.

Pumps

170, 171 are connected to reservoir by

conduits

173 and 174.

Pumps

170, 171 are connected to each other by

conduits

176, 177. Motor 172 is connected to

conduits

176, 177 by conduit 178, and to reservoir 175 by conduit 180.

Pump 170 is driven from drum 16. Fixed to drum' 16 is bevel gear 75 which, meshes with bevel gear 76 fixed to shaft 77 which has sprocket 78 fixed to the other end. Sprocket 78 is operativelyconnected to sprocket S0 fixed to pump 170 by means of chain 81. Pump 171 is operatively connected to shaft 21 of transmission 17 by means of

sprockets

82, 83 and chain 84. Motor 172 is operatively connected to shaft 30 by means of

sprockets

46, 47 and chain 48. Sprocket 47 is fixed to slip clutch 29.

Pump 170 is driven at a constant speed from drum 16. When the system is in, equilibrium pump 171 travels at the samespeed as pump 170. When pumps 171,and 170* travel at the same speed they have the same volumetric displacement. When pumps 170, 171 travel at: thesame speed, fluidis drawn from reservoir 175.through conduit 173 by pump 171 and is passed through conduits 176,177

to the suction of pump 170. Thence the fluid goes through the conduit 174 to reservoir 175. As the beam 12 unwinds, the speed of rotation of shaft 21 increases, thereby increasing the speed of rotation of pump 171 relative to pump 170. This increase in the speed of pump 171 delivers more fluid than pump 170 can discharge. The excess fluid passes through conduit 178 and causes hydraulic motor 172 to revolve, turning speed changing screw 30. Fluid is returned to reservoir 175 through conduit 180.

When one beam has been unwound and removed, the unwinding mechanism must be reset for a new beam. To accomplish this, handwheel 56 is turned in a direction to cause pump 171 to discharge fluid through conduit 173. Conduit 176 becomes the suction line for pump 171. Since pump 170 is not free to rotate, fluid is drawn through conduit 178 thereby turning motor 172 and shifting screw 30 so that transmission 17 is shifted to the starting position.

Figure 7 shows how this same modification can be applied to the embodiment shown in Figure 2. Here the fluid motor takes the form of a cylinder and piston. Conduit 178 connects to one end of cylinder 181 and conduit 183 connects with reservoir 175. Piston 182 is operatively connected to control arm 143A of Figure 2.

In all the embodiments of the present invention a mechanical brake generally indicated by reference character 150 has been shown as the braking means for applying tension to the web of material. However, in all examples an electric brake such as shown by 190 in Figure 3 may be used. Electrical brakes are well known in the art and may be of electromagnetic nature, of eddy current design, or of the type known as the magnetic particle brake. All will perform equally well. The magnetic particle type of brake is particularly advantageous since the wear is virtually negligible.

Having shown and described preferred embodiments of the present invention, by way of example, it should be realized that structural changes could be made and other examples given without departing from either the spirit or scope of this invention.

What I claim is:

1. In a constant tension web unwinding mechanism, an axle, a beam carrying said web material, said beam being mounted on said axle, a brake comprising a rotatable drum and a brake shoe frictionally engaging said drum and held stationary, a variable speed transmission comprising two power transmitting shafts and a speed changing mechanism, a driving connection between said axle and one of said power transmitting shafts, a driving connection between said brake and the second of said power transmitting shafts, said transmission being driven by said axle, and means for automatically maintaining the speed of said brake constant, thereby compensating through said variable speed transmission for the variable speed of said axle to render the power applied to said axle constant, said brake being driven solely by the said second power transmitting shaft.

2. In a constant tension web unwinding mechanism, an axle, a beam carrying said web material, said beam being mounted on said axle, a brake comprising a rotatable drum and a brake shoe frictionally engaging said drum and held stationary, a variable speed transmission comprising two power transmitting shafts and a speed changing mechanism, a driving connection between said axle and one of said power transmitting shafts, a driving connection between said brake and the second of said power transmitting shafts, said transmission being driven by said axle, and means responsive to the rotation of said second shaft for maintaining the speed of said brake constant, said brake being driven solely by the said second power transmitting shaft.

3. In a constant tension web unwinding mechanism, a beam carrying the web, a drum operatively connected to said web and over which said web travels at a constant linear speed, said beam being rotated-by unwinding of the web therefrom, a variable speed transmission provided with a first shaft, a second shaft, and speed changing mechanism, said first shaft being driven by said beam, a brake comprising a rotatable drum and a brake shoe frictionally engaging said drum and held stationary, said second shaft driving said brake drum, and a differential gear train for maintaining the speed of rotation of said second shaft constant, said brake being driven solely by the said second shaft. 7

4. In a constant tension web unwinding mechanism, a beam carrying the web, a drum over which the web travels at a constant linear speed, a variable speed transmission comprising a first shaft, a second shaft, and a speed changing shaft, said first shaft being driven by said beam, a brake, said second shaft driving said brake, a differential gear train having three power transmitting elements, said second shaft driving one of said elements, a slip clutch, a drive connection between said speed changing shaft and a second of said three elements, said drive connection in eluding said slip clutch, and a shaft driven at a constant speed from said drum and connected to the third of said elements for driving the same.

5. In a constant tension web unwinding mechanism, a beam carrying the web, a drum rotated at a constant speed and over which the web travels at a constant linear speed, a variable speed transmission comprising a first shaft, a second shaft, and a speed changing shaft, said first shaft being driven by said beam, a brake comprising a rotatable drum and a brake shoe frictionally engaging said drum and held stationary, sa id second shaft driving said'brake drum, a differential gear train having three power transmitting elements, said second shaft driving one-of'saidelements, a shaft driven at a constant speed from said drum and connected with the second of said elements for driving the same, and means for operatively connecting the third of said elements with said speed changing shaft.

6. In a constant tension web unwinding mechanism, a beam carrying a web, said web being drawn from the beam at a constant linear speed, a variable speed transmission comprising a first shaft, a second shaft, and a speed changing mechanism, said first shaft being driven by said beam, a brake comprising a rotatable drum and a brake shoe frictionally engaging said drum and held stationary, said second shaft driving said brake drum,

and means connected to said speed changing mechanism responsive to changes in speed of said brake for operating said speed changing mechanism.

7. In a constant tension web unwinding mechanism, a beam carrying a web, a drum rotated at a constant speed and over which the web travels at a constant linear speed, a variable speed transmission comprising a first shaft, 8. second shaft, and a speed changing mechanism, said first shaft being driven by said beam, a brake, said second shaft driving said brake, a differential mechanism having three power transmitting elements, said second shaft driving one of said elements, a shaft driven at a constant speed from said drum and connected with the second of said elements for driving the same, and means for connecting the third of said elements with said speed changing mechanism.

8. In an apparatus for maintaining a constant tension on a traveling web, a rotatable beam carrying a roll of web material which is drawn therefrom at a constant linear speed, a variable speed transmission having an input shaft, an output shaft, and a speed adjusting means, said input shaft being connected to said beam and rotated thereby, a brake comprising a rotatable drum and a brake shoe-frictionally engaging said drum and held stationary, said brake being connected to said output shaft for applying a predetermined drag thereon at a predetermined speed of rotation of said output shaft, said drag tending to decrease the speed of rotation of said beam as the diameter of said roll decreases, and means connected to said speed adjusting means responsive to conditions affecting the speed of rotation of said input shaft for changing the speed ratio be- '7 tween said input and output shafts of said variable speed transmission so as to maintain the speed of rotation of said output shaft constant at said predetermined speed.

9. In an unwinding mechanism for web material, an axle, a beam for said material, said beam being mounted on said axle for rotation therewith and being rotated by unwinding web material therefrom, a rotatable brake, a complemental brake element for arresting said brake and held stationary relative thereto, a driving connection between said axle and brake including a variable speed transmission having input and output shafts, the input shaft of said transmission being. connected to said axle and rotated by unwinding material from said beam, said output shaft being connected to said brake, said brake being rotated solely by said transmission, and means for automatically maintaining the speed of rotation of said brake constant, said means adjustingsaid transmission.

10. ,An unwinding mechanism for web material as in claim 9 wherein the means for automatically maintaining speed of rotation of said brake constant comprises a differential gear train having one input thereof connected to said output shaft, the other input of said differential gear train being responsive to the linear speed of the unwinding web material, the output of said differential gear train being connected to a fluid motor means, said fiuid motor means adjusting said transmission.

11. An unwinding mechanism for web material as in claim 9 wherein the means for automatically maintaining speed of rotation of said brake constant comprises a pivotally mounted first class lever, one end of said lever contacting the surface of web material, the other end of said lever being operatively connected to adjust said transmission.

12. ,An unwinding mechanism for web material as in claim 9 wherein the means for automatically maintaining speed of rotation of said brake constant comprises a governor operatively connected to said output shaft, said governor being responsive to speed variations of said output shaft and having switch means operatively connected therewith, said switch means being responsive to speed variations above and below a preselected value, a source of electric power, a reversible electric motor, said switch means being in circuit with said motor and controlling direction of rotation of said motor in response to speed changes above and below the preselected value, the output of said electric motor adjusting said transmission.

13. An unwinding mechanism for web material as in claim 9 wherein the means for automatically maintaining speed for rotation of said brake constant comprises a fluid motor differential means, one input of said fluid motor differential means being connected to said output shaft, the other input of said fiuid motor differential means being responsive to the linear speed of the web material, the output of said fluid motor differential means adjusting said transmission.

References Cited in the file of this patent UNITED STATES PATENTS 2,168,071 Perry Aug. 1, 1939 2,346,903 Caftrey Apr. 18, 1944 2,392,226 Butterworth Jan. 1, 1946 2,470,125 Young May 17, 1949 2,582,966 Curtis Jan. 22, 1952