Device for releasing tension from auto tensioning cylinder

An apparatus for compressing an automatic belt tensioning cylinder to permit a belt to be placed around, the engine pulleys, includes a pneumatic cylinder and a jig, the jib being adapted to hold the tensioning cylinder during compression thereof by the pneumatic cylinder. The jig holds a plunger sensor that is operable to detect the presence of the tensioning cylinder, and to control the flow of pressurizing fluid such that the pneumatic cylinder cannot be operated in an extension direction when the tensioning cylinder is absent from the jig.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to engine assembly techniques and, more particularly, toward devices and methods for easing installation of a belt around engine pulleys.

2. Description of Related Art

During the assembly of automobile engines, it is necessary to wrap one or more belts around the engine pulleys. Such pulleys include a drive pulley, one or more driven pulleys, and idler pulleys. One or more of the idler pulleys is a tensioning pulley that is adjustable to maintain the belt at a predetermined tension, so as to reduce belt slippage and wear. However, during a belt installation process, the tension placed on the belt by the tensioning assembly makes it difficult or impossible to wrap the belt around the pulleys. Therefore, it is necessary to reduce or relieve the belt tension in order to permit the belt to be wrapped around the pulley.

The belt tensioning devices typically include a spring-biased piston that is disposed within a cylinder. With this arrangement, the cylinder is secured to a pulley mounting plate, while the free end of the piston is secured to a fixed support on the engine. The cylinder and piston are urged away from each other by the spring, and the pulley mounting plate and the pulley disposed thereon are moved, with the cylinder, away from the piston fixed support, so as to place tension on the belt that is disposed around the engine pulley.

However, to permit the belt to be placed around the pulleys, the belt tensioning device must be compressed or otherwise de-activated. When the belt tensioning device is compressed, the associated idler pulley may be moved so as to permit the belt to be placed therearound. Thereafter, the belt tensioning device may be released to return the idler pulley to its normal position and place the desired tension on the belt.

Unfortunately, it is difficult to manually compress or deactivate the belt tensioning device. In the past, compression clips have been used to hold the belt tensioning device in a collapsed or deactivated condition, but such compression clips are not useful in all applications. Also, it is known to use a lever to force the idler pulley mounting bracket to rotate against the spring bias of the belt tensioning device, and thereby move the idler tensioning pulley into a position to permit the belt to be placed therearound. Unfortunately, moving the bracket in this way requires a lot of force, and is a difficult operation for the belt installer. Furthermore, the installer will have to hold the lever with one hand while positioning the belt with the other hand, which is awkward at best.

Therefore, there exists a need in the art for a device and method for releasing or compressing a belt tensioning device so as to ease installation of a belt around the engine pulleys.

SUMMARY OF THE INVENTION

The present invention is directed toward a device and method for compressing an automatic belt tensioning cylinder, and thereby easing installation of a belt around the engine pulleys.

In accordance with the present invention, a tension releasing device includes a double acting pneumatic cylinder having a jig secured thereto. The jig is adapted to receive the tensioning cylinder and to hold the tensioning cylinder during compression thereof by the pneumatic cylinder. The pneumatic cylinder has a piston rod extending therefrom, and is operated to extend/retract the piston rod relative to the pneumatic cylinder. A distal end of the piston rod holds a pusher block. The pusher block cooperates with the jig to receive and hold the tensioning cylinder.

In further accordance with the present invention, the jig includes a sensor that detects whether the tensioning cylinder is received within the jig. Operation of the pneumatic cylinder is prevented when a tensioning cylinder is not detected by the sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIGS. 1A and 1B, an engine10has a plurality of pulleys extending therefrom that are adapted to receive a belt11. These pulleys include a drive pulley12, one or more driven pulleys14, and one or more idler pulleys16. In the illustrated engine10, both idler pulleys are tensioning pulleys16, although this is not always the case. The tensioning pulleys16are mounted upon a mounting plate18, and the mounting plate18is pivotally moved by an automatic belt tensioning cylinder20. Normally, belt tension fluctuates during operation of the engine10, and the tensioning cylinder20moves the mounting plate in response to these changes in belt tension so as to maintain a fairly constant tension on the belt11, as is well known in the art.

The tensioning cylinder20has a first end20aand a second end20b. The tensioning cylinder first end20ais attached to the engine10and thus is held in a fixed position. The tensioning cylinder second end20bis attached to the mounting plate18and thus is movable relative to the first end20aand the engine10. A tension releasing device22of the present invention, described hereinafter, is adapted to compress or deactivate the tensioning cylinder20so as to ease installation of the belt11around the engine pulleys12,14,16.

With particular reference toFIGS. 2-3, the tension releasing device22of the present invention includes a double-acting pneumatic cylinder24and a jig26, with the jig26being adapted to receive the tensioning cylinder20. The jig26includes a cylinder weldment28(FIG. 4), a base weldment30(FIG. 5), a pusher block32, and a sensor34. As will be apparent from the following discussion, the jig26is integral with the pneumatic cylinder24in that the cylinder weldment28and base weldment30are secured to the pneumatic cylinder24and the pusher block32is secured to a free or distal end of a piston rod36extending from, and driven by, the pneumatic cylinder24.

The pneumatic cylinder24includes a framework or body that provides mounting locations for the various handles, guards, and valves, as illustrated and described hereinafter, and to which the jig26is secured. More specifically, a hanger member37and a first handle38are attached to a top of the pneumatic cylinder24, with the hanger member37extending upwardly from a first side of the pneumatic cylinder24and the first handle38extending rearwardly from a second side of the pneumatic cylinder24. Relatively beneath the first handle38, a toggle valve assembly40is mounted to a first vertical sidewall of the pneumatic cylinder24.

The toggle valve assembly40includes a toggle valve body40afrom which a toggle valve switch40bextends. The toggle valve body40aincludes a plant air input42, first and second air outlets44,46, and a toggle valve (not shown) that is actuated or manipulated by the toggle valve switch40bso as to control communication of pressurized air to the pneumatic cylinder24so as to control operation (extension/retraction) of the device22. More particularly, the toggle valve controls communication of pressurized air from the plant air input42to the first and second air outlets44,46.

As will be appreciated by those skilled in the art, when the toggle valve switch40bis moved in a first direction from a neutral position, pressurized air supplied to the toggle valve body40avia the plant air input42is directed through the first outlet44, the plunger valve34, and a first flow restrictor45, and is introduced into the pneumatic cylinder24on a first side of the piston and thereby drives the piston in a first direction (i.e., to extend the piston rod36and pusher block32). On the other hand, when the toggle valve switch40bis moved in a second direction from the neutral position, pressurized air supplied to the toggle valve body40avia the plant air input42is directed through the second outlet46and a second flow restrictor47and is introduced into the pneumatic cylinder24on a second side of the piston and thereby drive the piston in a second direction (i.e., to retract the piston rod36and pusher block32).

The first handle38includes a guard that helps to conceal and protect the toggle valve switch40bso as to prevent unintended actuation thereof. A shield48is secured to the pneumatic cylinder24relatively beneath the first handle38and the toggle valve assembly40and serves to prevent tampering of the flow controls (i.e., the first and second flow restrictors45,47) mounted to the pneumatic cylinder24, as described hereinafter.

With reference toFIG. 4, the cylinder weldment28includes an upper plate50, a lower plate52, a series of supports54extending between the upper and lower plates50,52, and a guide handle56extending outwardly from the lower plate52. The guide handle56is disposed below the shield48on the second side of the pneumatic cylinder24, and is directed outwardly and upwardly therefrom in spaced relation to the first handle38, as illustrated.

The cylinder weldment upper plate50has a generally rectangular periphery, and has a circular hole50aformed in the center thereof through which the piston rod36extends. Fasteners extending through corners of the upper plate50connect the upper plate50to a lower end of the pneumatic cylinder24in a face-to-face fashion, as illustrated inFIGS. 2-3.

The cylinder weldment lower plate52is somewhat u-shaped, having a pair of sides or arms52athat are interconnected by a base or leg52bso as to define a u-shaped opening52c. The pusher block32secured to the free or distal end of the piston rod36is reciprocally movable within or through the u-shaped opening52c, as will be described hereafter.

The base weldment30includes a u-shaped upper wall58, a u-shaped lower wall60, and first and second sidewalls62,64interconnecting the upper and lower walls58,60. The base weldment upper wall58is mechanically affixed to the cylinder weldment lower plate52by a series of screws, as illustrated. It will be appreciated that the dimensions of the base weldment upper wall58are slightly smaller than the corresponding dimensions of the cylinder weldment lower plate52.

The base weldment's u-shaped upper wall58includes a first arm58a, a second arm58b, and an interconnecting base or leg58c. Similarly, the base weldment's u-shaped lower wall60has first and second arms60a,60band an interconnecting base60c. The u-shaped lower wall60is slightly smaller than, and offset from, the u-shaped upper wall58, but the upper and lower u-shaped openings58d,60dprovided by the u-shaped upper and lower walls58,60are aligned with one another. The u-shaped lower wall60and, more specifically, the space within the base weldment30, is adapted to receive the tensioning cylinder20and, as such, may be considered a custom part. While the space between the upper and lower u-shaped walls58,60is important (to permit the tensioning cylinder20to be received therebetween), the space between the first and second arms60a,60bof the u-shaped lower wall60is chosen such that a first portion of the tensioning cylinder20may extend therethrough while a second portion of the auto tensioning cylinder20will rest thereon, as will be apparent from the discussion to follow. As such, the particular size, dimensions, etc. of the base weldment30are illustrative of a preferred embodiment adapted to a particular automatic belt tensioning cylinder20, and it is contemplated that at least these physical characteristics of the present invention will be modified to accommodate different auto tensioning cylinders.

The first sidewall62extends between, and is integrally affixed to, the first arms58a,60aof the u-shaped upper and lower walls58,60. The first sidewall62includes a pair of lengthwise extending slots that permit adjustable securement of a wear pad66to an inner surface thereof. The second sidewall64extends between, and is integrally affixed to, the base or interconnecting leg58c,60cof the upper and lower u-shaped walls58,60. The second sidewall64has a plurality of tapped openings formed therein to which a guide68and a guard70are attached. More specifically, an upper pair of tapped openings permit an upper L-shaped guide68to be secured to the second sidewall64, while the lower pair of tapped openings allow a lower L-shaped guard70to be secured thereto. It will be appreciated that the guide68and guard70have slotted openings that permit horizontal adjustment of the guide68and guard70relative to the base weldment second sidewall64. Relatively below the tapped openings, the second sidewall64has an enlarged opening64aformed therein to which the sensor34is mounted.

The sensor34, which is sometimes called a plunger sensor or plunger valve, includes a body portion72having an air inlet72aand an air outlet72b. Between the air inlet72aand air outlet72b, the body72holds a valve (not shown) that is opened and closed by a spring-biased plunger74extending outwardly from the body portion72. The plunger74is biased away from the body portion72atoward a valve-closed position. The plunger74extends through the enlarged opening64ain the second sidewall64so as to project into the interior of the jig26. When a tensioning cylinder20is properly received within the interior of the jig26, the plunger74will be depressed, opening the valve and thereby allowing pressurized air to pass through the sensor body portion72(i.e., from the body portion air inlet72ato the body portion air outlet72b).

The pneumatic circuit for the tensioning releasing device22is fairly simple, and is schematically illustrated inFIG. 8, and will be discussed hereafter as it relates to operation of the device22.

Plant air is introduced into toggle valve body40avia the inlet42and is directed toward one side or the other of the pneumatic cylinder24, depending upon the direction of actuation of the toggle valve switch40b, described previously. When the tensioning cylinder20is detected in the jig26by depression of the plunger sensor34, and the toggle valve switch40bis moved in the first direction, pressurized air flows through the first flow restrictor45and is introduced into the pneumatic cylinder24via an extend port24aso as to extend the piston rod36and the pusher block32. The first flow restrictor45is adjustable so as to selectively limit or adjust the pressurized air flow into the pneumatic cylinder24and thereby permit the cylinder extension speed to be adjusted.

It has been found that, in order to prevent damage to the tensioning cylinder20, it is important to not compress the tensioning cylinder too fast. In the present invention, the speed of movement of the pneumatic cylinder24is adjusted by the first flow restrictor45so that the tensioning cylinder rate of compression is adjusted so as to not damage the tensioning cylinder. In the illustrated embodiment, the maximum stroke of the pneumatic cylinder24is about 30 mm, with the maximum compression of the tensioning cylinder20being about 16 mm. The tensioning cylinder compression stroke takes at least 3 seconds.

Since the first end20aof the tensioning cylinder20is immovably fixed to the engine10, when the pusher block32engages the first end20aof the tensioning cylinder20, the jig26and the second end20bof the tensioning cylinder20are drawn upwardly or toward the pneumatic cylinder24, compressing the tensioning cylinder20and pivoting the mounting plate18, and the tensioning pulleys16disposed thereon, into a position that eases placement of the belt11around the engine pulleys. Once the belt11is placed around the pulleys12,14,16, the toggle valve switch40bis actuated in the opposite direction to direct pressurized air through the second flow restrictor25and into the pneumatic cylinder24via the retract port24bso as to drive the piston rod36and pusher block32toward the pneumatic cylinder24, release the tensioning cylinder20from the jig26, and permit removal of the tension releasing device22from the tensioning cylinder20. The second flow restrictor47may be considered optional as it may not be necessary or desirable to reduce or limit the speed of decompression of the tensioning cylinder20.

The preferred embodiment of the present invention has been described herein, but it is considered apparent that the invention is capable of numerous modifications or rearrangements of parts without departing from the spirit of the invention. Although the invention has been described herein as it relates to a drive device including the preferred pneumatic cylinder, it is considered apparent that the pneumatic (air) cylinder may be replaced by a hydraulic cylinder or an electric drive device (e.g., motor, gear reducer, transmission) without departing from the scope and spirit of the present invention. It is also contemplated that one skilled in the art may modify the pneumatic circuit to replace the flow restrictors with different means to adjust the speed of operation of the pneumatic cylinder, or that a single flow restrictor or means to adjust the speed of operation (i.e., in only the cylinder extension direction) may be desired. It is further considered apparent that the jig described herein is specially adapted to the particular tensioning cylinder used herein, and may be freely modified as necessary to accommodate different tensioning cylinders. Therefore, the present disclosure is not to be interpreted in a limitative fashion as the scope of the present invention is only defined by the claims appended hereto, which are to be given their broadest possible interpretation.