WO2004080849A2

WO2004080849A2 - Pneumatic spinner drive tensioning assembly

Info

Publication number: WO2004080849A2
Application number: PCT/US2004/007517
Authority: WO
Inventors: Russell Varone; Michael Dietz
Original assignee: Graham Packaging Company, L.P.
Priority date: 2003-03-11
Filing date: 2004-03-11
Publication date: 2004-09-23
Also published as: WO2004080849A3; EP1603815A2

Abstract

An pneumatic tensioner apparatus includes: a main drive belt; a suspended chuck assembly, having a spinning member and a drive contact portion; a first frictional drive belt in a first track, the belt in contact with the drive contact portion operative to spin the chuck assembly, where the first track has a non-stick surface; a first tension adjusting device having a pneumatic tension adjustment member that applies pressure to the first frictional drive belt tangentially to the drive contact portion; a second frictional drive belt in a second track in contact with the drive contact portion and disposed on an opposite side of the chuck assembly to the first frictional drive belt and moving in a direction opposite the first frictional drive belt; and a second tension adjusting device having a tension adjustment member that applies pressure to the second frictional drive belt tangentially to the drive contact portion.

Description

Pneumatic Spinner Drive Tensioning Assembly Background of the Invention Field of the Invention

The present invention relates generally to a positive apparatus for, and method of, rotating bottle-holding chuck assemblies, particularly during coating application, to ensure correct container positioning during container finishing operations, for instance during exposure to coating application, to provide for coating application around the entire container circumference. Related Art In the container manufacturing industry, bottles move through various manufacturing steps suspended from chuck assemblies that are themselves moved by belt systems. One manufacturing step can include the application of a coating to a bottle. Such coatings can include resins to improve gas impermeability of the bottles, and coating to impart color to the bottle. Coatings can also be referred to generically as "paint." As the bottles are moved through coating application steps, the bottles are spun in order to achieve a uniform application of the coating around the entire bottle. A major defect results when a container fails to spin correctly during coating application. A misapplication of coating causes a container to be scrapped. Numerous parts of the machine for coating the bottles are also subject to deposits from the coating material and subsequent operational failure.

A linear belt drive, for example, one designed by Feco Engineered Systems, Ltd. of Cleveland, Ohio, U.S.A., uses a series of idler rollers to provide belt-to-chuck contact. The Feco assembly uses a single drive belt mounted on a single side of the chuck assembly with no counterbalancing force. The single- sided application of tensioning force leads to slipping belts, which can cause misalignment. For example, belt slippage can cause misalignment of a container with respect to an anticipated position of the container for coating application.

Conventional assemblies do not provide positive contact with the chuck assembly throughout the track length. Instead, conventional assemblies provide contact only at a series of tangent points along the track. Lack of continuous contact can cause uneven spinning of the bottles. Conventional assemblies also do not allow "on the fly" adjustments to the contact tension to compensate for variability in the bottles. Instead, a lengthy adjustment process must be done which is very operator dependent. What is needed then is an improved assembly that overcomes shortcomings of conventional solutions.

Summary of the Invention

In an exemplary embodiment of the present invention a pneumatic tensioner apparatus is disclosed. The pneumatic tensioner apparatus comprises: a main drive belt; a chuck assembly, suspended from the main drive belt, having a spinning member and a drive contact portion; a first frictional drive belt in a first track, the first frictional drive belt in contact with the drive contact portion operative to spin the chuck assembly, where the first track has a non-stick surface; a first tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure to the first frictional drive belt tangentially to the drive contact portion; a second frictional drive belt in a second track in contact with the drive contact portion and disposed on an opposite side of the chuck assembly to the first frictional drive belt and moving in a direction opposite the first frictional drive belt; and a second tension adjusting device having at least one tension adjustment member operative to apply pressure to the second frictional drive belt tangentially to the drive contact portion.

In another exemplary embodiment, the present invention can be a method of applying a coating to a container comprising: attaching a container to a chuck having a contact portion and a spinning member; contacting the contact portion with a frictional drive belt; applying pressure to the frictional drive belt with a pneumatic tensioner to increase contact with the contact portion; moving the chuck in a first direction at a first speed; moving the frictional drive belt in at least one of a second direction and a second speed in order to spin the chuck and the container; adjusting the pressure to the frictional drive belt with the pneumatic tensioner; and applying a coating to the spinning container. In another exemplary embodiment, the present invention can be a pneumatic tensioner apparatus comprising: a main drive belt; a chuck assembly, suspended from the main drive belt, having a spinning member and a drive contact portion; a first frictional drive belt in a first floating track, the first frictional drive belt in contact with the drive contact portion operative to spin the chuck assembly; a first tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure through the first floating track to the first frictional drive belt tangentially to the drive contact portion; a second frictional drive belt in a second floating track in contact with the drive contact portion and disposed on an opposite side of the chuck assembly to the first frictional drive belt and moving in a direction opposite the first frictional drive belt; and a second tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure through the second floating track to the second frictional drive belt tangentially to the drive contact portion; wherein the first and second pneumatic tension adjustment members each comprise a flexible elastic tube filled with a compressed substance, and wherein the pressure applied by the tube is adjusted by varying the amount of the compressed substance in the tube. In another exemplary embodiment the present invention can be a pneumatic tensioner apparatus comprising a main drive belt; a chuck assembly, suspended from the main drive belt, having a spuming member and a drive contact portion; a first track comprising a plurality of air holes; a first frictional drive belt in the first track in contact with the drive contact portion operative to spin the chuck assembly; a first tension adjusting device operative to apply pressure to the first frictional drive belt tangentially to the drive contact portion, the first tension adjusting device comprising a second track comprising a plenum through which air flows disposed on an opposite side of the first track from the first frictional drive belt, and coupled to the first track, where air from the plenum flows through the plurality of air holes and applies pressure to the first frictional drive belt; a second frictional drive belt disposed in at least one idler roller on an opposite side of the chuck assembly to the first frictional drive belt, the second frictional drive belt in contact with the drive contact portion; and a second tension adjusting device operative to apply pressure to the second frictional drive belt tangentially to the drive contact portion, the second tension adjusting device comprising: an adjustable shaft coupled to the at least one idler roller; a tension spring coupled to the adjustable shaft where the tension exerted by the tension spring on the adjustable shaft determines a position of the adjustable shaft; and an adjustment screw coupled to the tension spring and operative to adjust tension exerted by the tension spring; where the pressure applied by the second tension adjusting device on the drive contact portion is adjusted by adjusting the position of the adjustable shaft.

Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.

Brief Description of the Drawings

The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The left most digits in the corresponding reference number indicate the drawing in which an element first appears.

FIG. 1 shows an isometric view of an exemplary embodiment of the present invention;

FIG. 2 shows a cross-sectional view along line 2-2 of FIG. 1;

FIG. 3 shows a top view of the system of the present invention;

FIG. 4 shows a top view of the system of the present invention inside a spray booth; FIG. 5 shows an isometric view of another exemplary embodiment of the present invention; and

FIG. 6 shows a cross-sectional view along line 6-6 of FIG. 5.

Detailed Description of an Exemplary Embodiment of the Present

Invention A preferred embodiment of the invention is discussed in detail below.

While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention. h an exemplary embodiment of the present invention, a pneumatic tensioner provides a full length contact path on both sides of a chuck assembly and provides a positive, balanced frictional force to rotate the chuck assembly. The invention can be used for any application where a part suspended from a device having a circular contact portion requires even rotation. Such applications can include, for example, applying a coating or paint to the suspended parts, and drying or curing a suspended part.

FIG. 1 shows an isometric view 100 of an exemplary embodiment of a pneumatic tensioner system of the present invention. A pair of tracks 102, each holding one side of a frictional drive belt 104, holds between them a series of chuck assemblies 106. In an exemplary embodiment, tracks 102 are made of a non-stick surface such as, e.g. TEFLON™. Each chuck assembly 106 can hold a suspended container (not shown). The frictional drive belt 104, as it moves, imparts a spin to the chuck assemblies 106, and hence to the bottles. The chuck assemblies 106 are coupled, via a spindle shaft, to a third belt or chain (not shown), which imparts an overall forward motion to the line of bottles.

FIG. 2 shows a cross-sectional view 200 of the pneumatic tensioner system of the present invention along line 2-2 of FIG. 1. The track 102 is mounted on a floating bracket 222 via a support track 206, which together form an assembly.

The floating bracket 222 rests against a length of tube 208, which can be inflated, for example, by compressed air or some other substance. Tube 208 can be made of PVC or some other resilient material. The tube 208 is housed in a housing 202, to which is coupled the floating bracket 222 via fasteners 204. The tube 208 is flexible and elastically expandable and contractible. The tube 208 presses against the support track 206, floating bracket 222 and track 102 assembly, which in turn presses the frictional drive belt 104 against the chuck assembly 106. Controlling the pressure of the compressed substance in the tube 208 increases or decreases the tangential contact force of the frictional drive belt 104 against the chuck assembly 106. A pump or compressor (not shown) can be used to control the pressure of the compressed substance. Specifically, the frictional drive belt 104 presses against a drive contact portion 210, commonly referred to as a drive lug, which is coupled to a spindle body 212 and a cylindrical locking collar 216 of the chuck assembly 106. A spindle nose 214 of chuck assembly 106 can couple to a part being rotated, such as a container, to hold the part.

The chuck assembly 106 is coupled to a main drive belt 220, e.g. a carrier chain, via the cylindrical locking collar 216 and a carrier pin 218. The main drive belt 220 is the belt that provides the overall forward motion to the line of chuck assemblies. The main drive belt 220 is coupled to a bracket 224. The bracket 224 holds, in openings at each extremity, a shaft 225 to which are coupled two rollers 226. The rollers 226 roll on L-brackets 228 to move the chuck assembly 106 forward. The speed of the frictional drive belts 104 and the main drive belt 220 can be controlled by a controlled drive mechanism 304 (not shown in FIG. 2) such as, for example, a variable frequency drive motor and gearbox combination. The speed of motion of the frictional drive belt 104 can be, in an exemplary embodiment, operator selectable and programmed to provide a matched speed of rotation for both the main drive belt and the frictional drive belt 104. Speed matching is done by matching the contact speed of the each belt to the surface velocity of the part being rotated, for example, the chuck assembly 106. For example, to set the speed of the counter travel frictional drive belt, the relative velocity of the main drive belt 220 is subtracted from the rotational surface velocity of the chuck assembly 106. To set the speed of the relative travel frictional drive belt, the relative velocity of the main drive belt 220 is doubled and then added to the rotational surface velocity of the chuck assembly 106. The speed of motion of the frictional drive belt 104 can also be offset to compensate for forward relative motion of the main drive belt 220 and chuck assemblies 106 through the coating application area. It is important to set and maintain correct speed settings due to the frictional forces that are created by unbalanced speeds. An imbalance can cause inconsistencies in part rotation speed and increased wear.

In an exemplary embodiment of the present invention, a single side of a frictional drive belt can be used on one side of the contact portion of the chuck assembly. In order to maintain a continuous counter-balancing force, a series of idler rollers may be used on the opposite side of the chuck assembly. Alternatively, a non-pneumatic tensioning belt can be used on the opposite side of the contact portion from the frictional drive belt to provide the counter-balancing force to the frictional drive belt. The pneumatic tensioner system of this exemplary embodiment of the present invention provides one or more of the following advantages. First, the use of the air- filled tube 208 allows for remote adjustment of the running tension by changing the amount of the compressed substance, e.g. air, in the tubing. Second, the pneumatic tensioner system uses only four moving parts as opposed to more than fifty for a conventional system, which means less wear and tear on the apparatus and lower maintenance costs. An example of a conventional system is the rotational and retractable container holding device described in U.S. Patent No. 4,640,406, the contents of which are incorporated herein by reference in their entirety, and available from Feco Engineered Systems, Ltd. of Cleveland, Ohio, U.S.A. Third, the pneumatic tensioner system is more compact and has less exposure to coating contamination than conventional devices, again reducing maintenance costs. Fourth, the pneumatic tensioner system provides for a much more balanced frictional drive force, which provides an extremely low level of belt slippage. Limiting slippage greatly reduces the occurrence of container defects due to improper spin, which reduces scrap. Additionally, the pneumatic tensioner system is much less expensive to build than conventional systems, and is particularly well suited to low speed manufacturing and assembly lines. Other advantages will be apparent to persons skilled in the art.

FIG. 3 shows a top view 300 of an exemplary embodiment of a closed- loop system using the pneumatic tensioner system according to the present invention. The main drive belt 220 is driven by drive 304. An example drive 304 is described in U.S. Patent No. 5,769,476 to Lawn et al., filed September 16, 1996, entitled "Apparatus and Method for Handling and Processing Articles". As bottles suspended from the main drive belt 220 pass through spray booth 302, the bottles are spun by frictional drive belt 104 while coating is applied. The bottles proceed through ovens 306a and 306b where the coating dries. The dry, coated bottles are then unloaded from the main drive belt 220 at unloader 308 and can be taken away by a take-away conveyor indicated by arrow 310.

FIG. 4 shows a top view 400 of an exemplary embodiment of the pneumatic tensioner system of the present invention inside the spray booth 302. The frictional drive belt 104 is driven by spim er drive 402 in the direction indicated by arrows 404 and directed arc 410. At the end opposite the spinner drive 402, the frictional drive belt turns around the automatic take-up 408 as illustrated by directed arc 410. The main drive belt (not shown) moves in the direction indicated by arrow 406. FIG. 5 shows an isometric view 500 of another exemplary embodiment of a pneumatic tensioner system of the present invention. A track 102a holds an outer side of a frictional drive belt 104a. An inner side of the frictional drive belt 104a is in contact with a first side of a drive contact portion 210, also called a drive lug, of a chuck assembly 106. An inner side of frictional drive belt 104b is in contact with the opposite side of drive contact portion 210. Each chuck assembly can hold a suspended container (not shown) from a spindle shaft 212. The outer side of the frictional drive belt 104b is supported by idler rollers 504. The two inner sides of the frictional drive belts 104a and 104b move in opposite directions with respect to each other, imparting a spin to the chuck assemblies

106, and hence to the bottles. The chuck assemblies 106 are coupled, via a locking collar 216 on a spindle shaft, to a main drive belt (not shown), which imparts an overall forward motion to the line of bottles.

The track 102 is coupled to a second track 508. Either of the tracks 102 and 508 can be manufactured from a metal or other rigid material. Track 102 can include a smooth surface or a coating. The groove of track 102 may or may not include a coating such as, e.g. a non-stick coating, hi an exemplary embodiment, the track 102 can include, as shown, a semi-circular cylindrical concave groove (not labeled) for contacting frictional drive belt 104a. The track 508 forms an open plenum 502 behind the track 102 through which air can flow. The track 102 has air holes 506 through which air from the plenum can flow.

FIG. 6 shows a cross-sectional view 600 of the pneumatic tensioner system along line 6-6 of FIG. 5. The outer side of the frictional drive belt 104a moves through the groove in track 102. The air holes 506 allow the air from the plenum 502 to flow from the plenum and against the outer side of the frictional drive belt

104a. The air flowing through the holes 506 both applies pressure to the frictional drive belt 104a to keep the belt in tangential contact with the first side of the drive contact portion 210 of the chuck assembly 106, and also acts to lubricate the track 102 to keep the frictional drive belt 104a from sticking to the track 102. On the opposite side of the drive contact portion 210 is the inner side of the frictional drive belt 104b. The frictional drive belt 104b moves through a groove in the idler roller 504. The idler roller 504 is free to rotate and acts to apply pressure against the outer side of the frictional drive belt 104b, whose inner side in turn applies pressure against the drive contact portion 210. The idler roller 504 is coupled to a shaft 606, which is in turn coupled to a tension spring 604. The tension in the tension spring 604 can be varied by an adjusting screw 602. Varying the tension in the spring 604 causes the shaft 606 to move back and forth horizontally, changing the position of the idler roller 504 with respect to the chuck assembly 106. Bringing the idler roller 504 closer to the chuck assembly 106 increases the tangential pressure on the chuck assembly 106 from the frictional drive belt 104b, and moving the idler roller 504 further away reduces the pressure on the chuck assembly 106. The use of air through the plenum 502 and air holes 506 according to this second exemplary embodiment of the present invention provides an alternative to the use of pneumatic tubes, and does not require use of a low-friction track material. Pneumatic tubes and the low friction track material can need to be periodically replaced. In another exemplary embodiment, a low-friction track material may still be used. While the cost of constructing the apparatus of this embodiment may be higher than that of the apparatus of the first recited exemplary embodiment, this embodiment is better suited to higher speed operation. Additionally, this embodiment provides even greater control over the pressure exerted by the frictional drive belts 104 onto the chuck assemblies 106. While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should instead be defined only in accordance with the following claims and their equivalents.

Claims

WE CLAIM:

1. A pneumatic tensioner apparatus, comprising: a main drive belt; a chuck assembly, suspended from said main drive belt, having a spinning member and a drive contact portion; a first frictional drive belt in a first track, said first frictional drive belt in contact with said drive contact portion operative to spin said chuck assembly, wherein said first track has a non-stick surface; a first tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure to said first frictional drive belt tangentially to said drive contact portion; a second frictional drive belt in a second track in contact with said drive contact portion and disposed on an opposite side of said chuck assembly to said first frictional drive belt and moving in a direction opposite said first frictional drive belt; and a second tension adjusting device having at least one tension adjustment member operative to apply pressure to said second frictional drive belt tangentially to said drive contact portion.

2. The pneumatic tensioner apparatus of claim 1, wherein said first and second frictional drive belts are the same continuous belt.

3. The pneumatic tensioner apparatus of claim 1, wherein said at least one tension adjustment member comprises a flexible elastic tube filled with a compressed substance, and wherein said pressure applied by said tube is adjusted by varying the amount of said compressed substance in said tube.

4. The pneumatic tensioner apparatus of claim 3, wherein said compressed substance is air.

5. The pneumatic tensioner apparatus of claim 3, wherein said tube runs parallel to said first track.

6. The pneumatic tensioner apparatus of claim 1, wherein said main drive belt comprises a carrier chain.

7. The pneumatic tensioner apparatus of claim 1, wherein said first frictional drive belt moves in a direction opposite said main drive belt.

8. The pneumatic tensioner apparatus of claim 1, wherein said first track comprises a floating bracket.

9. The pneumatic tensioner apparatus of claim 1, wherein said first track is coupled to a support track.

10. The pneumatic tensioner apparatus of claim 9, wherein said support track is coupled to a floating bracket.

11. The pneumatic tensioner apparatus of claim 1 , wherein said first track comprises a plurality of air holes; wherein said first tension adjusting device comprises a third track comprising a plenum tlirough which air flows disposed on an opposite side of said first track from said first frictional drive belt, and coupled to said first track, wherein air from said plenum flows through said plurality of air holes and applies pressure to said first frictional drive belt; and wherein said second frictional drive belt is disposed in at least one idler roller on an opposite side of said chuck assembly to said first frictional drive belt, said second frictional drive belt in contact with said drive contact portion.

12. The pneumatic tensioner apparatus of claim 11, wherein said second tension adjusting device comprises an adjustable shaft coupled to said at least one idler roller, wherein the pressure applied by said second tension adjusting device on said drive contact portion is adjusted by adjusting the position of said shaft.

13. The pneumatic tensioner apparatus of claim 12, wherein said adjustable shaft is coupled to a tension spring, said tension spring coupled to an adjustment screw operative to adjust tension exerted by said tension spring, and wherein said tension exerted by said tension spring on said shaft determines a position of said shaft.

14. A method of applying a coating to a container comprising the steps of:

(a) attaching a container to a chuck having a contact portion and a spinning member; (b) contacting said contact portion with a frictional drive belt;

(c) applying pressure to said frictional drive belt with a pneumatic tensioner to increase contact with said contact portion;

(d) moving said chuck in a first direction at a first speed;

(e) moving said frictional drive belt in at least one of a second direction and a second speed in order to spin said chuck and said container;

(f) adjusting said pressure to said frictional drive belt with said pneumatic tensioner; and

(g) applying a coating to said spinning container.

15. The method of claim 14, wherein said pneumatic tensioner comprises an elastic and flexible tube containing compressed air, and wherein said step (f) comprises adjusting an amount of compressed air in said pneumatic tensioner.

16. The method of claim 14, wherein said frictional drive belt is one continuous belt and is disposed on opposite sides of said contact portion.

17. The method of claim 14, wherein: step (b) comprises contacting said contact portion with a first frictional drive belt disposed in a track having air holes; step (c) comprises blowing air through said air holes against said first frictional drive belt to increase contact of said frictional drive belt with said contact portion; and step (f) comprises applying pressure on an opposite side of said contact portion from said first frictional drive belt with a second frictional drive belt and adjusting said pressure to said first frictional drive belt by adjusting said blowing air.

18. The method of claim 17, wherein said first and second frictional drive belts are one continuous belt.

19. The method of claim 17, wherein said second frictional drive belt is supported by at least one idler roller.

20. The method of claim 19, wherein an adjustable shaft is coupled to said at least one idler roller, and wherein the pressure applied by said second frictional drive belt on said drive contact portion is adjusted by adjusting the position of said shaft.

21. The method of claim 20, wherein said adjustable shaft is coupled to a tension spring, said tension spring coupled to an adjustment screw operative to adjust tension exerted by said tension spring, and wherein said tension exerted by said tension spring on said shaft determines a position of said shaft.

22. An pneumatic tensioner apparatus comprising: a main drive belt; a chuck assembly, suspended from said main drive belt, having a spinning member and a drive contact portion; a first frictional drive belt in a first floating track, said first frictional drive belt in contact with said drive contact portion operative to spin said chuck assembly; a first tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure tlirough said first floating track to said first frictional drive belt tangentially to said drive contact portion; a second frictional drive belt in a second floating track in contact with said drive contact portion and disposed on an opposite side of said chuck assembly to said first frictional drive belt and moving in a direction opposite said first frictional drive belt; and a second tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure through said second floating track to said second frictional drive belt tangentially to said drive contact portion; wherein said first and second pneumatic tension adjustment members each comprise a flexible elastic tube filled with a compressed substance, and wherein said pressure applied by said tube is adjusted by varying the amount of said compressed substance in said tube.

23. The pneumatic tensioner apparatus of claim 22, wherein said first and second floating tracks have a non-stick surface.

24. The pneumatic tensioner apparatus of claim 22, wherein said first and second frictional drive belts are the same continuous belt.

25. The pneumatic tensioner apparatus of claim 22, wherein each of said first and second floating tracks is coupled to a separate support track; and wherein each of said support tracks is coupled to a separate floating bracket.

26. The pneumatic tensioner apparatus of claim 25, wherein each of said first and second frictional drive belts applies pressure to a different one of said separate floating brackets.

27. A pneumatic tensioner apparatus, comprising: a main drive belt; a chuck assembly, suspended from said main drive belt, having a spinning member and a drive contact portion; a first track comprising a plurality of air holes; a first frictional drive belt in said first track in contact with said drive contact portion operative to spin said chuck assembly; a first tension adjusting device operative to apply pressure to said first frictional drive belt tangentially to said drive contact portion, said first tension adjusting device comprising a second track comprising a plenum through which air flows disposed on an opposite side of said first track from said first frictional drive belt, and coupled to said first track, wherein air from said plenum flows through said plurality of air holes and applies pressure to said first frictional drive belt; a second frictional drive belt disposed in at least one idler roller on an opposite side of said chuck assembly to said first frictional drive belt, said second frictional drive belt in contact with said drive contact portion; and a second tension adjusting device operative to apply pressure to said second frictional drive belt tangentially to said drive contact portion, said second tension adjusting device comprising: an adjustable shaft coupled to said at least one idler roller; a tension spring coupled to said adjustable shaft wherein said tension exerted by said tension spring on said adjustable shaft determines a position of said adjustable shaft; and an adjustment screw coupled to said tension spring and operative to adjust tension exerted by said tension spring; wherein the pressure applied by said second tension adjusting device on said drive contact portion is adjusted by adjusting the position of said adjustable shaft.

28. The pneumatic tensioner apparatus of claim 27, wherein said first and second frictional drive belts are the same continuous belt.

29. The pneumatic tensioner apparatus of claim 27, wherein said first and second frictional drive belts move in opposite directions.

30. The pneumatic tensioner apparatus of claim 27, wherein said first frictional drive belt moves in a direction opposite said main drive belt.

31. The pneumatic tensioner apparatus of claim 27, wherein said main drive belt comprises a carrier chain.