US2918970A - Auto-tension felt stretcher - Google Patents

Description

Dec. 29, 1959 w. G. PRINTZ 2,918,970

AUTO-TENSION FELT STRETCHER Filed March 10, 1958 2 Sheets-Sheet 1 I N V EN TOR. 14/4455 61 Pgm/rz,

RTTO RNEYS.

Dec. 29, 1959 w. s. PRINTZ 2,918,970

AUTO-TENSION FELT STRETCHER Filed March 10. 1958 2 Sheets-Sheet 2 f 1 Jag-1" f2 6 33 I AUTO.

IN V EN TOR. M/ nv 6, p/guvrz,

' zm/w ATTORNEYS,

United States Patent AUTO-TENSION FELT STRETCHER Warren G. Printz, Middletown, Ohio, assignor to The Manchester Machine Co., Middletown, Ohio, :1 corporation of Ohio Application March 10, 1958, Serial No. 720,278

14 Claims. (Cl. 162-273) This invention relates to an automatic felt stretcher for use in conjunction with a paper making machine and more particularly to an automatically acting tensioning device by means of which the take-up of felts on a paper machine may be accurately controlled, the device incorporating automatic control means for maintaining uniform tension in the felts at all times.

A principal object of the invention is the provision of an improved felt tensioning device in which the tensioning of the felt is automatically maintained.

A further object of the invention is the provision of a felt tensioning or stretching device which is capable of both automatic and manual operation.

Still a further object of the invention is the provision of a tensioning device of the character described which can be controlled either automatically or manually and the unit, in either event, operated from an operators panel which can be remotely located at any convenient point in the machine room.

Still a further object of the invention is the provision of a tensioning or stretching device incorporating air diaphragms by means of which the tension rollers of the device may be raised and lowered, the air diaphragms serving to replace the conventional long stroke pistons and cylinders heretofore employed in tensioning devices of the character here under consideration.

Yet another object of the invention is the provision of a tensioning device incorporating air diaphragms in which the short stroke of the diaphragms is compensated for by means of adjustable sleeves mounting the tension roller, the arrangement of parts being such that the sleeves will be adjusted by means of motor driven threaded shafts controlled by limit switches when the degree of adjustment required is in excess of the stroke of the air diaphragms.

The foregoing together with other objects of the invention which will appear hereinafter or which will be apparent to the skilled worker in the art upon reading these specifications, I accomplish by that construction and arrangement of parts which I shall now describe an exemplary embodiment.

Reference is now made to the accompanying drawings wherein:

Figure l is an elevational view illustrating of the invention in conjunction with a paper making machine.

Figure 2 is a front elevational view of a tensioning device in accordance with the instant invention, with some of the parts shown broken away and others in section.

Figure 3 is a vertical sectional view taken along the line 3-3 of Figure 2.

Figure 4 is a side elevational view of the device illustrated in Figure 2.

Figure 5 is an enlarged fragmentary elevational view illustrating the details of the device.

Figure 6 is a wiring diagram illustrating the electrical controls for the device.

- Briefly, in the practice of the invention, each tensioning device is powered by screwjacks mounted on opposite sides of the felt or web to be tensioned, each screwjack being mounted within a hollow column and driven by an electric gear-motor mounted on the lower end of the column. A pneumatic diaphragm is mounted on a bracket positioned above the upper end of each column. Each screwjack--columngear motor assembly is mounted on movable clevis members at each end of the column so that the assembly may move a predetermined distance in either direction from a normal position. Movement of the assemblies is effected by the air diaphragm. If, however, the required movement is in excess of the stroke of the diaphragms, limit switches will be closed effective to actuate the gear motors and rotate the screwjacks until the required adjustment has been obtained.

For a more detailed understanding of the invention, reference is first made to Figure l of the drawings wherein the reference 1 indicates a felt passing around the various rollers 2 of the paper making machine. Front and back felt tensioning devices are indicated at 3 and 4, respectively; and their purpose is to maintain the felt 1 in stretched or tensioned condition. Each of the tensioning devices mounts a stretcher roller 5 which, as best seen in Figure 2, extends crosswise with respect to the felt and is journaled at each end in a bearing member 6 mounted on a sleeve 7 slidable axially along a hollow column 8. Since the mechanism at each end of the tension roller is identical, a description of one will suffice for both and like reference numerals have been employed to designate like parts.

At their upper ends the columns are each provided with a cap 9 which, as best seen in Figure 9, is pivotally secured to a yoke 10 which is in turn pivotally mounted to a supporting bracket 11 secured to a post or the like 12 forming a part of the machine frame. At their lower ends, the hollow columns 8 are each received in a bearing sleeve 13 which is also supported by a pivoted yoke 14 pivotally mounted to a bracket 15 also secured to the frame member 12.

On their outermost sides, and as best seen in Figure 4, each of the hollow columns 8 has an elongated slot 16 therein extending lengthwise of the column; and as best seen in the right-hand portion of Figure 2, an internally threaded inner sleeve 17 is disposed within the hollow column and fixedly secured to the external sleeve 7 by means of a mounting arm 18 which projects through the elongated slot 16. The internally threaded inner sleeve 17 receives a threaded shaft 19 extending lengthwise within the hollow column 8, the threaded shaft being rotatably secured at its upper end to the cap 9, as by means of perforated plate 20 and collars 21 seen in Figure 3. At its lower end the shaft 19 is keyed to a gear 22 which, through suitable additional gearing, is driven by motor 23 or hand wheel 24.

Axial movement of the column 8 and the treaded shaft '19 is controlled by means of an air diaphragm 25 fixedly secured to the bracket 11 and positioned to overlie the cap 9, the diaghragm having an arm or rod 26 connecting it to the cap 9. Air under pressure will be introduced into the diaphragm 25 through a conduit 27, the air entering a chamber 28 having a flexible wall portion 29 to which the upper end of arm 26 is secured, as by means of a circular plate 30. As the air enters the chamber 28, it will cause the flexible wall portion or diaphragm to expand, thereby exerting a downwardly directed force against the arm 26 which presses against the cap and pushes the column 8 and shaft 19 downwardly, the column moving downwardly by "reason of its pivotal mounting to the yokes 10 and 14.v As illustrated in Figures 3,4 and 5, the yoke 10 istpreferably provided with oppositely directed extensions 31 carrying adjustment screws 32 arranged to alternately contact the bracket '11, thereby limiting the extent of upward or downward movement of the assembly. In a preferred embodiment of the device now in commercial use, the stroke of the air diaphragm is approximately three inches and the set screws 32 are adjusted accordingly. The yoke 119 also mounts a finger 33 which, as best seen in Figure 5, is adapted to contact the switch arm 34 of two-way limit switch 35. As will be explained more fully hereinafter, movement of the hollow column 8 to its uppermost position will close the switch 35 in one direction and effect a starting circuit to the motor 23. Similarly, movement of the hollow column to its lowermost position will throw the switch 35 in the opposite direction and will effect a circuit to the motor 23 effective to operate it in the reverse direction.

In the operation of the device, air under a predetermined pressure, as for example 40 pounds per square inch, will be introduced into the diaphragm 25 through the conduit 20. This will force the diaphragm downwardly, the arm 26 pressing against the cap 9 and hence moving the entire unit downwardly, including the tension roller '5, until the felt is sufficiently taut to resist the downward thrust of the roller by what amounts to the applied force of the diaphragm, i.e. 40 pounds pressure. When the resistive force of the felt pulling upwardly against the roller 5 equals the applied pressure, the system will be in equilibrium and the roller 5 will remain stationary. Should the felt then tend to slacken, the force it exerts against the roller 5 will be reduced, i.e. fall below the arbitrary 40 pound pressure, and the greater pressure in the air diaphragm will force the hollow column 8 downwardly until the pressures are again equalized.

If, however, the air diaphragm reaches the bottom of its Stroke without having moved the roller 5 sufficiently far to offset the 40 pound air pressure, i.e. the upwardly directed force exerted on the roller by the felt is still less than the 40 pounds of air pressure, the limit switch 35 will be closed to form a circuit to motor 23 effective to start the motor and through it rotate gear 22 and shaft 19, the shaft being driven in a direction such that the internally threaded sleeves 17 will be moved downwardly along the threaded shaft. Since the mounting arm 18 connects the internally threaded sleeve 17 directly to the outer sleeve 7, which is slidable axially along the column 8, the sleeve 7 will move downwardly relative to the column carrying the tension roller with it and hence stretching or tightening the felt. The downward movement will continue until such time as the felt has been drawn sufficiently taut for the resistive force of the felt to slightly exceed the 40 pound pressure exerted by the diaphragm, whereupon the slightly greater force of the felt will act to push against the diaphragm causing it to move upwardly, i.e. the entire assembly including the column 8 and cap 9 will move upwardly tending to contract the diaphragm, and the upward movement of the cap will pivot the finger 33 in the opposite direction and cause the limit switch 35 to reopen, thereby shutting off the power to the motor 23. It will be understood that the upward movement of the column 8 will continue only until the force exerted by the felt against the roller 5 will have been relieved sufiiciently to equal the .air pressure in the diaphragm 25, whereupon the parts will again be in equilibrium.

Should the felt tend to contract during the operation of the machine, i.e. become taut to the extent that it places the roller 5 under more than the desired 40 pound tension, it will exert an upward force against the diaphragm 25 which will tend to contract under the excessive pressure. If the diaphragm travels to itsupper limit without relieving the excess pressure, the limit switch will be closed in the opposite direction, thereby forming a second circuit to the motor 23, this time causing it to ,run in the opposite direction and rotate the shaft 19 so as to cause the threaded sleeve '17 to move upwardlyfilld 8, 33

with it the outer sleeve 7. This upward movement will lift the tension roller 5 and hence relieve the taut condition of the felt. The upward movement will continue until the tension of the felt is relieved sufficiently for its effective force to drop below the 40 pound limit, whereupon the 40 pound pressure in the diaphragm will become dominant and will start the column to move downwardly. The downward movement will, as before, break the circuit to the motor by opening the limit switch, and the rotation of the shaft 19 will be stopped. The system will thus be balanced under the desired tension until the felt either tightens or loosens sufficiently to initiate correcting movement.

Figure 6 illustrates a control circuit for both automatic and manual operation of the device. When the master control switch 36 is in automatic position, circuits are formed to the two-way switches 35 for each of the motors 23, such switches being individually indicated at 35a, 35b, 35c and 35d. In the circuit diagram the limit switches are shown as separate units, as they are in Figure 2, although it will be understood that the sets of switches 35a, 35b and 35c, 35d may be components of a single two-way switch unit of the character illustrated in Figures 4 and 5. In either event, the sets of switches will be ale ternately operable to energize either the forward coils of the motors for the front and back tensioning devices or the reverse coils 38 of the motors, depending upon the condition of the felt, the opening and closing of the switches occurring automatically in the manner hereinbefore described.

For manual operation of the felt stretchers, the master control switch 36 is moved to the manual position which supplies power to switches 39, 40, 41 and 42. With this arrangement the front and back felt tension may be separately tightened by selectively closing switches 41 and 42. Similarly, the front and back felt tension may be slackened separately by closing switches 39 and 40.

Felt tension may be increased uniformally for both front and back tension rollers by closing switch 43 which starts both front and back motor coils in the forward direction. Similarly, uniform slackening of the felt may be accomplished by closing switch 44 which starts both front and back stretcher motor coils in the reverse direction. All switches excepting the master control switch 36 and the automatic switches 35 are spring loaded as a safety feature so that the operator must hold each one closed to either tighten or slacken the felt. The automatic switches 35 are by-passed by the manual control switches so that over control is possible when desired. By-passing the automatic switches allows the stretcher rolls to be positioned for installing and removing the felt. Thus, when felt is being installed or removed from the machine or when no felt tension is desired, the master control switch 36 will be moved to manual position so that the automatic switches are by-passed. This will maintain the tension rollers in the desired position whereas they would otherwise travel to either end of the posts depending upon which of the automatic switches were closed. Motor overload relays will be provided to protect the felt from being over stressed and afford protection for the motors when the tensioning rollers are in the extreme positions. Indicator lights 45 may be conveniently provided on the control panel to give the operator a visual indication of the operation of the device.

Modifications may, of course, be made in the invention without departing from the spirit of it. As has already been indicated, the switches 35 may be either two-way switches or they may be separate limit switches positioned above and beneath an actuating arm secured to the caps 9 at the upper end of each column. Similarly, the operating pressure of the device may be varied as desired; and it will be understood that the 40 pound pressure referred to herein is merely exemplary. While the device is intended primarily as a tensioning means for the felts in a pape making machin i i lh -.appa en t a i use is not so limited and that the device will have utility in any type of installation wherein tensioning control of a web or sheet is required.

Having thus described the invention in exemplary embodiment, what is desired to be protected by Letters Patent is:

1. In a tensioning device, a tubular column, means mounting said column for limited reciprocating movement, a sleeve movable axially along said column, means for journaling a tension roll to said sleeve for movement therewith, a threaded shaft within said column, means securing said shaft to said column for joint axial movement, with said shaft free for rotation relative to said column, drive means operatively connected to said shaft for rotating said shaft in both forward and reverse directions, means operatively connecting said sleeve to said shaft, whereby rotation of said shaft will effect axial movement of said sleeve relative to said column, means for applying predetermined pressure axially of said column in one direction in opposition to the force exerted by a web passing around the tension roller, whereby depending upon whether the force exerted by the web is greater or lesser than the applied pressure, said column will be caused to move axially either in the direction of the applied pressure or in the direction of the applied force, and switch means positioned to be actuated upon movement of said column in either direction to a predetermined limit, said switch means, when actuated, serving to energize said drive means to rotate said shaft in the direction which will cause said sleeve to travel along said column in the same direction as the direction in which said column was moved.

2. The device claimed in claim 1 wherein said means for applying pressure axially of said column comprises an air diaphragm operatively connected to said column.

3. The device claimed in claim 2 wherein the means for driving said shaft comprises a reversible motor, and wherein gear means operatively connect said motor to said threaded shaft.

4. The device claimed in claim 3 wherein said air diaphragm is operatively connected to one end of said column, and wherein said electric motor is at the opposite end of said column.

5. In a tensioning, device, a tubular column, means mounting said column for movement in the direction of its length, a shaft rotatably journaled within said column, drive means for rotating said shaft, an elongated slot in said column extending lengthwise thereof, means operatively connected to said shaft and movable axially there along upon rotation of said shaft, said means including an arm projecting through said slot, means on said arm for receiving the end of a tension roller, means for moving said column in the direction of its length under a predetermined applied force, means operative upon lengthwise movement of said column to actuate said drive means for said shaft, whereby to effect relative movement between said column and the means for receiving the end of the tension roller.

6. The device claimed in claim 5 wherein the force applying means for moving said column comprises an air diaphragm operatively connected to said column, and wherein means are provided to supply air to said diaphragm under predetermined pressure.

7. The device claimed in claim 6 wherein the drive means for rotating said shaft is mounted at one end of said column, and wherein said air diaphragm is operatively connected to the opposite end of said column.

8. In a tensioning device, a threaded shaft, means mounting said shaft for both axial and rotary movement, drive means for rotating said shaft, pressure applying means for effecting axial movement of said shaft, tension roller mounting means in threaded engagement with said shaft for axial movement relative thereto upon rotation of said shaft, and means operative upon predetermined axial movement of said shaft for actuating the drive means for rotating said shaft.

9. The device claimed in claim 8 wherein the means for driving said shaft comprises a reversible motor, and wherein the means for actuating said reversible motor comprises switch means effective to drive said motor in one direction upon axial movement of said shaft in a first direction and to drive said motor in the opposite direction upon axial movement of said shaft in the opposite direction.

10. The device claimed in claim 9 wherein the means for applying pressure to said shaft to effect axial movement thereof comprises an air diaphragm having a plunger operatively connected to said shaft, wherein said plunger has a predetermined stroke, and wherein the switch means for actuating said reversible motor is arranged to be closed when said plunger reaches substantially the end of its stroke.

11. In a tensioning device for a felt or like web wherein a tensioning roller is supported between a pair of supports lying beyond the opposite side edges of the felt, each of said supports including a vertically disposed threaded shaft, means mounting said shaft for limited axial movement both upwardly and downwardly relative to a normal position and for rotary movement about its longitudinal axis, drive means for rotating said shaft, pressure applying means for moving said shaft axially in one direction, mounting means in threaded engagement with said shaft for receiving the end of the tension roller, and means for actuating the drive means for rotating said shaft upon predetermined axial movement thereof in either direction.

12. The device claimed in claim 11 wherein the means for actuating said drive means comprises circuit means connected to said drive means, said circuit means including limit switches positioned to be actuated upon axial movement of said shaft.

13. The device claimed in claim 12 wherein the drive means for said shaft comprises a reversible motor, and wherein additional circuit means are provided for manually actuating said drive means, said last named circuit means acting to by-pass said limit switches.

14. The device claimed in claim 13 wherein a pair of said tensioning devices are provided to act upon said felt at spaced apart intervals, and wherein manually operated switch means are provided for concurrently controlling the actuating of said pair of devices.

References Cited in the file of this patent UNITED STATES PATENTS 813,288 Hancock Feb. 20, 1906 1,910,894 George et a1 May 23, 1933 2,244,033 Trempe June 3, 1941

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