Abstract:
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.

Description:
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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and further features of the invention will be apparent with reference to the following description and drawings, wherein: 
         FIG. 1A  is a front elevational view of an engine with a belt mounted around a series of drive, driven and idler tensioning pulleys; 
         FIG. 1B  is similar to  FIG. 1A , but showing the tension releasing device disposed over an automatic belt tensioning cylinder; 
         FIG. 2  is a front perspective view of the tension releasing device; 
         FIG. 3  is a rear perspective view of the tension releasing device; 
         FIG. 4  is a perspective view of a cylinder weldment; 
         FIG. 5  is a perspective view of a base weldment; 
         FIG. 6  is a front perspective view of the tension releasing device according to the present invention with the tensioning cylinder received in the jig and in a normal or extended condition, and with other portions of the engine removed for purposes of clarity; 
         FIG. 7  is similar to  FIG. 6 , but illustrates the tension releasing device in an activated condition and with the tensioning cylinder in a compressed condition to permit placement of the belt around the pulleys; 
         FIG. 8  schematically illustrates a pneumatic circuit of the tension releasing device of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1A and 1B , an engine  10  has a plurality of pulleys extending therefrom that are adapted to receive a belt  11 . These pulleys include a drive pulley  12 , one or more driven pulleys  14 , and one or more idler pulleys  16 . In the illustrated engine  10 , both idler pulleys are tensioning pulleys  16 , although this is not always the case. The tensioning pulleys  16  are mounted upon a mounting plate  18 , and the mounting plate  18  is pivotally moved by an automatic belt tensioning cylinder  20 . Normally, belt tension fluctuates during operation of the engine  10 , and the tensioning cylinder  20  moves the mounting plate in response to these changes in belt tension so as to maintain a fairly constant tension on the belt  11 , as is well known in the art. 
     The tensioning cylinder  20  has a first end  20   a  and a second end  20   b . The tensioning cylinder first end  20   a  is attached to the engine  10  and thus is held in a fixed position. The tensioning cylinder second end  20   b  is attached to the mounting plate  18  and thus is movable relative to the first end  20   a  and the engine  10 . A tension releasing device  22  of the present invention, described hereinafter, is adapted to compress or deactivate the tensioning cylinder  20  so as to ease installation of the belt  11  around the engine pulleys  12 ,  14 ,  16 . 
     With particular reference to  FIGS. 2-3 , the tension releasing device  22  of the present invention includes a double-acting pneumatic cylinder  24  and a jig  26 , with the jig  26  being adapted to receive the tensioning cylinder  20 . The jig  26  includes a cylinder weldment  28  ( FIG. 4 ), a base weldment  30  ( FIG. 5 ), a pusher block  32 , and a sensor  34 . As will be apparent from the following discussion, the jig  26  is integral with the pneumatic cylinder  24  in that the cylinder weldment  28  and base weldment  30  are secured to the pneumatic cylinder  24  and the pusher block  32  is secured to a free or distal end of a piston rod  36  extending from, and driven by, the pneumatic cylinder  24 . 
     The pneumatic cylinder  24  includes a framework or body that provides mounting locations for the various handles, guards, and valves, as illustrated and described hereinafter, and to which the jig  26  is secured. More specifically, a hanger member  37  and a first handle  38  are attached to a top of the pneumatic cylinder  24 , with the hanger member  37  extending upwardly from a first side of the pneumatic cylinder  24  and the first handle  38  extending rearwardly from a second side of the pneumatic cylinder  24 . Relatively beneath the first handle  38 , a toggle valve assembly  40  is mounted to a first vertical sidewall of the pneumatic cylinder  24 . 
     The toggle valve assembly  40  includes a toggle valve body  40   a  from which a toggle valve switch  40   b  extends. The toggle valve body  40   a  includes a plant air input  42 , first and second air outlets  44 ,  46 , and a toggle valve (not shown) that is actuated or manipulated by the toggle valve switch  40   b  so as to control communication of pressurized air to the pneumatic cylinder  24  so as to control operation (extension/retraction) of the device  22 . More particularly, the toggle valve controls communication of pressurized air from the plant air input  42  to the first and second air outlets  44 ,  46 . 
     As will be appreciated by those skilled in the art, when the toggle valve switch  40   b  is moved in a first direction from a neutral position, pressurized air supplied to the toggle valve body  40   a  via the plant air input  42  is directed through the first outlet  44 , the plunger valve  34 , and a first flow restrictor  45 , and is introduced into the pneumatic cylinder  24  on a first side of the piston and thereby drives the piston in a first direction (i.e., to extend the piston rod  36  and pusher block  32 ). On the other hand, when the toggle valve switch  40   b  is moved in a second direction from the neutral position, pressurized air supplied to the toggle valve body  40   a  via the plant air input  42  is directed through the second outlet  46  and a second flow restrictor  47  and is introduced into the pneumatic cylinder  24  on a second side of the piston and thereby drive the piston in a second direction (i.e., to retract the piston rod  36  and pusher block  32 ). 
     The first handle  38  includes a guard that helps to conceal and protect the toggle valve switch  40   b  so as to prevent unintended actuation thereof. A shield  48  is secured to the pneumatic cylinder  24  relatively beneath the first handle  38  and the toggle valve assembly  40  and serves to prevent tampering of the flow controls (i.e., the first and second flow restrictors  45 ,  47 ) mounted to the pneumatic cylinder  24 , as described hereinafter. 
     With reference to  FIG. 4 , the cylinder weldment  28  includes an upper plate  50 , a lower plate  52 , a series of supports  54  extending between the upper and lower plates  50 ,  52 , and a guide handle  56  extending outwardly from the lower plate  52 . The guide handle  56  is disposed below the shield  48  on the second side of the pneumatic cylinder  24 , and is directed outwardly and upwardly therefrom in spaced relation to the first handle  38 , as illustrated. 
     The cylinder weldment upper plate  50  has a generally rectangular periphery, and has a circular hole  50   a  formed in the center thereof through which the piston rod  36  extends. Fasteners extending through corners of the upper plate  50  connect the upper plate  50  to a lower end of the pneumatic cylinder  24  in a face-to-face fashion, as illustrated in  FIGS. 2-3 . 
     The cylinder weldment lower plate  52  is somewhat u-shaped, having a pair of sides or arms  52   a  that are interconnected by a base or leg  52   b  so as to define a u-shaped opening  52   c . The pusher block  32  secured to the free or distal end of the piston rod  36  is reciprocally movable within or through the u-shaped opening  52   c , as will be described hereafter. 
     The base weldment  30  includes a u-shaped upper wall  58 , a u-shaped lower wall  60 , and first and second sidewalls  62 ,  64  interconnecting the upper and lower walls  58 ,  60 . The base weldment upper wall  58  is mechanically affixed to the cylinder weldment lower plate  52  by a series of screws, as illustrated. It will be appreciated that the dimensions of the base weldment upper wall  58  are slightly smaller than the corresponding dimensions of the cylinder weldment lower plate  52 . 
     The base weldment&#39;s u-shaped upper wall  58  includes a first arm  58   a , a second arm  58   b , and an interconnecting base or leg  58   c . Similarly, the base weldment&#39;s u-shaped lower wall  60  has first and second arms  60   a ,  60   b  and an interconnecting base  60   c . The u-shaped lower wall  60  is slightly smaller than, and offset from, the u-shaped upper wall  58 , but the upper and lower u-shaped openings  58   d ,  60   d  provided by the u-shaped upper and lower walls  58 ,  60  are aligned with one another. The u-shaped lower wall  60  and, more specifically, the space within the base weldment  30 , is adapted to receive the tensioning cylinder  20  and, as such, may be considered a custom part. While the space between the upper and lower u-shaped walls  58 ,  60  is important (to permit the tensioning cylinder  20  to be received therebetween), the space between the first and second arms  60   a ,  60   b  of the u-shaped lower wall  60  is chosen such that a first portion of the tensioning cylinder  20  may extend therethrough while a second portion of the auto tensioning cylinder  20  will rest thereon, as will be apparent from the discussion to follow. As such, the particular size, dimensions, etc. of the base weldment  30  are illustrative of a preferred embodiment adapted to a particular automatic belt tensioning cylinder  20 , 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 sidewall  62  extends between, and is integrally affixed to, the first arms  58   a ,  60   a  of the u-shaped upper and lower walls  58 ,  60 . The first sidewall  62  includes a pair of lengthwise extending slots that permit adjustable securement of a wear pad  66  to an inner surface thereof. The second sidewall  64  extends between, and is integrally affixed to, the base or interconnecting leg  58   c ,  60   c  of the upper and lower u-shaped walls  58 ,  60 . The second sidewall  64  has a plurality of tapped openings formed therein to which a guide  68  and a guard  70  are attached. More specifically, an upper pair of tapped openings permit an upper L-shaped guide  68  to be secured to the second sidewall  64 , while the lower pair of tapped openings allow a lower L-shaped guard  70  to be secured thereto. It will be appreciated that the guide  68  and guard  70  have slotted openings that permit horizontal adjustment of the guide  68  and guard  70  relative to the base weldment second sidewall  64 . Relatively below the tapped openings, the second sidewall  64  has an enlarged opening  64   a  formed therein to which the sensor  34  is mounted. 
     The sensor  34 , which is sometimes called a plunger sensor or plunger valve, includes a body portion  72  having an air inlet  72   a  and an air outlet  72   b . Between the air inlet  72   a  and air outlet  72   b , the body  72  holds a valve (not shown) that is opened and closed by a spring-biased plunger  74  extending outwardly from the body portion  72 . The plunger  74  is biased away from the body portion  72   a  toward a valve-closed position. The plunger  74  extends through the enlarged opening  64   a  in the second sidewall  64  so as to project into the interior of the jig  26 . When a tensioning cylinder  20  is properly received within the interior of the jig  26 , the plunger  74  will be depressed, opening the valve and thereby allowing pressurized air to pass through the sensor body portion  72  (i.e., from the body portion air inlet  72   a  to the body portion air outlet  72   b ). 
     The pneumatic circuit for the tensioning releasing device  22  is fairly simple, and is schematically illustrated in  FIG. 8 , and will be discussed hereafter as it relates to operation of the device  22 . 
     Plant air is introduced into toggle valve body  40   a  via the inlet  42  and is directed toward one side or the other of the pneumatic cylinder  24 , depending upon the direction of actuation of the toggle valve switch  40   b , described previously. When the tensioning cylinder  20  is detected in the jig  26  by depression of the plunger sensor  34 , and the toggle valve switch  40   b  is moved in the first direction, pressurized air flows through the first flow restrictor  45  and is introduced into the pneumatic cylinder  24  via an extend port  24   a  so as to extend the piston rod  36  and the pusher block  32 . The first flow restrictor  45  is adjustable so as to selectively limit or adjust the pressurized air flow into the pneumatic cylinder  24  and thereby permit the cylinder extension speed to be adjusted. 
     It has been found that, in order to prevent damage to the tensioning cylinder  20 , it is important to not compress the tensioning cylinder too fast. In the present invention, the speed of movement of the pneumatic cylinder  24  is adjusted by the first flow restrictor  45  so 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 cylinder  24  is about 30 mm, with the maximum compression of the tensioning cylinder  20  being about 16 mm. The tensioning cylinder compression stroke takes at least 3 seconds. 
     Since the first end  20   a  of the tensioning cylinder  20  is immovably fixed to the engine  10 , when the pusher block  32  engages the first end  20   a  of the tensioning cylinder  20 , the jig  26  and the second end  20   b  of the tensioning cylinder  20  are drawn upwardly or toward the pneumatic cylinder  24 , compressing the tensioning cylinder  20  and pivoting the mounting plate  18 , and the tensioning pulleys  16  disposed thereon, into a position that eases placement of the belt  11  around the engine pulleys. Once the belt  11  is placed around the pulleys  12 ,  14 ,  16 , the toggle valve switch  40   b  is actuated in the opposite direction to direct pressurized air through the second flow restrictor  25  and into the pneumatic cylinder  24  via the retract port  24   b  so as to drive the piston rod  36  and pusher block  32  toward the pneumatic cylinder  24 , release the tensioning cylinder  20  from the jig  26 , and permit removal of the tension releasing device  22  from the tensioning cylinder  20 . The second flow restrictor  47  may be considered optional as it may not be necessary or desirable to reduce or limit the speed of decompression of the tensioning cylinder  20 . 
     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.