Abstract:
A time-out indicator is adapted for use in a pneumatic strapping tool for tensioning a strap around a load, adhering the strap onto itself, and cutting a feed end of the strap. The strapping tool has a cylinder housing, a piston disposed within a cylinder in the cylinder housing, a pneumatic weld motor operably connected to the piston, a vibrating weld element operably connected to the piston for contacting the strap and adhering the strap onto itself. A pneumatic module is mounted to the cylinder housing to provide compressed gas to the cylinder housing and the pneumatic weld motor. The time-out indicator includes a sleeve fitted into an opening in the module. The opening is disposed above and in communication with the cylinder. The sleeve defines a central, longitudinal opening. An indicator is biasedly mounted in the sleeve and disposed for contact with the piston. The indicator reciprocates between a retracted position and an extended position and indicates a cycle of the strapping tool as an in-cycle state in which the cylinder is under pressure, pressurizing the piston to urge the weld element into contact with the strap and a timed-out state in which the piston is not pressurized.

Description:
BACKGROUND OF THE INVENTION 
     The present invention pertains to an improved tool for tightening a strap around an object or load and adhering the strap onto itself. More particularly, the present invention is directed to a time-out indicator for a pneumatic motor tool for tensioning a strap around a load and welding or melt-adhering the strap onto itself. 
     Strapping tools are well-known in the art. These tools come in a wide variety of types, from fully manual tools to automatic, table-top tools. These tools are generally specifically designed for use with metal strapping or plastic/polymeric type strapping. 
     One well known type of strapping tool is a hand-held tool, that can be carried to and from a job-site. When such a tool is configured for use with plastic or polymeric strapping, a pneumatic system is used to vibrate contacting interfacial surfaces of overlapping plastic strap portions. The tool includes a clamping member for anchoring a strap free end portion, and a rotatable feed wheel cooperating with an anvil foot to engage a feed strap portion that is tensioned about the load. A clutch engagably couples the feed wheel to a pneumatic motor which also vibrates a jaw that welds the overlapping strap portions. 
     An exemplary tool, disclosed in U.S. Pat. No. 5,380,393 to Drabarek et al., also assigned commonly herewith and incorporated herein by reference, discloses a strapping tool having a pneumatic circuit for automatically controlling tool operation, including the timing and duration of strap welding and the cool down period. A pneumatically actuated ram extended after strap tensioning pivots a cam that moves a vibrating weld plate into contact with overlapping strap portions to form the weld. Vibration of the weld plate terminates after a time period controlled by the accumulation of air in a chamber. Air is subsequently bled from a cylinder that counter-pivots the ram to move the welding plate away from the welded strap portions after the cool down period. 
     As will be recognized by those skilled in the art, known pneumatic strapping tools require many system components that increase the size and weight of the tool. In addition, even though the pneumatic circuit of the above-mentioned U.S. Pat. No. 5,380,393 automates many strapping operations otherwise performed manually, controlling timing of the various tool operations as relatively and precise, and as a result inconsistent strap tension and welds may result. 
     An improved pneumatic strapping tool is disclosed in pending U.S. patent application Ser. No. 10/171,890, filed Jun. 14, 2002, entitled Dual Motor Strapper, which application is commonly assigned herewith, and the disclosure of which is incorporated herein by reference. In this improved tool, two unidirectional pneumatic motors, one motor for tensioning or feeding strap and another, separate motor for welding the strap material onto itself are provided. To provide flexibility as to operation and maintenance, a self contained modular pneumatic member or module includes pneumatically controlled timing circuits and is readily installed onto and removed from the body and motor portions of the tool. 
     In this tool, one timing circuit provides for properly timing the “welding” of the strap onto itself. That is, the timing circuit controls the time that the vibrating weld plate is maintained in contact with the overlapping strap portions to form the weld. The timing circuit works, in part, by accumulation of air in a chamber that halts vibration of the weld plate after a predetermined period of time. However, there is currently no indication of the changing state of the circuit. That is, there is no direct indication that the timing circuit has run its course. 
     Accordingly, there exists a needed for a timing indicator for the pneumatic circuit of a pneumatic strapping tool. Desirably, such an indicator is directly actuated by, e.g., operably connected to, the pneumatic circuit. More desirably, such an indicator provides readily visible indication of the state of the circuit and the weld cycle. 
     BRIEF SUMMARY OF THE INVENTION 
     A time-out indicator is configured for use in a pneumatic strapping tool. The toll tensions a strap around a load, adheres the strap onto itself, and cuts a feed end of the strap. The tool has a cylinder housing, a piston disposed within a cylinder in the cylinder housing, a pneumatic weld motor operably connected to the piston, a vibrating weld element operably connected to the piston for contacting the strap and adhering the strap onto itself, and a pneumatic module mounted to the cylinder housing. 
     The pneumatic module includes a compressed gas inlet, a plurality of valves and passageways between the inlet and the valves to provide compressed gas to the cylinder housing and the pneumatic weld motor. The module further includes at least one timer for operation of the weld motor and for providing pressure to the cylinder. The module further controls timing of the weld motor. 
     The time-out indicator includes a sleeve fitted into an opening in the module that is disposed above and in communication with the cylinder. The sleeve defines a central, longitudinal opening. 
     An indicator is biasedly mounted in the sleeve and is disposed for contact with the piston. The indicator reciprocates between a retracted position and an extended position. The indicator indicates a cycle of the strapping tool as an in-cycle state in which the cylinder is under pressure, pressurizing the piston to urge the weld element into contact with the strap and a timed-out state in which the piston is not pressurized. 
     Preferably, the indicator is in the retracted position when the strapper is in the in-cycle state and is in the extended position, by contact of the piston with the indicator, when the strapper is in the timed-out state. 
     A seal element is disposed along the stem for preventing the introduction or loss of compressed gas from the pneumatic module. In a current embodiment, the seal is positioned in a seal channel that is defined by a pair of spaced ring walls extending outwardly from the stem. 
     The sleeve can include an inwardly projecting lip at an upper end thereof. In this configuration, the stem includes an outwardly projecting wall adapted to contact the wall to retain the indicator within the sleeve. The outwardly projecting wall can be one of the ring walls. 
     A biasing element can be disposed in the sleeve for biasing the indicator to the retracted position. A retaining element is disposed to retain the biasing element in the sleeve. The retaining element can be a spring retaining clip that is received in a grooved formed in an inner wall of the sleeve. 
     A strapping tool can have the time-out indicator mounted in a pneumatic module for the tool. 
     These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a pneumatic strapper having a time-out indicator embodying the principles of the present invention, the tool being shown with a strap material positioned in the tool, and showing the direction of movement of the material; 
     FIG. 2 illustrates the tool positioned relative to a load being strapped and the direction of movement of the strap material during tensioning; 
     FIG. 3 is a partial exploded view of the pneumatic module showing the time-out indicator and position of the indicator relative to the weld piston cylinder and the weld piston; 
     FIG. 4 is a top view of the indicator; 
     FIG. 5 is a partial cross-sectional view of the indicator as positioned in the pneumatic module, and showing the indicator in the cycle timed-out position; 
     FIG. 6 is cross-sectional view taken along line  6 — 6  of FIG. 5; and 
     FIG. 7 is a pneumatic circuit for the exemplary strapping tool. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated. 
     It should be further understood that the title of this section of this specification, namely, “Detailed Description Of The Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein. 
     Referring now to the figures and in particular to FIGS. 1 and 2, there is shown a pneumatic strapper or strapping tool  10  having a time-out indicator assembly  12  embodying the principles of the present invention. The tool  10  is configured to tension a strap S around a load L, weld the strap material S onto itself and sever a feed end F of the strap S. For purposes of the present disclosure, the strap material S will be referred to as having a feed end F which is the supply end of the material and a free end R which is that end of the material that is fed around the load L and reinserted into the strapping tool  10 . 
     The tool  10  includes, generally, a body  14 , a foot  16 , a tensioning motor  18  and housing  20 , a weld motor  22 , a cylinder housing  24  and a pneumatic module  26 . The tool  10  can include a handle  28  and grip  30 , such as those shown for ease of handling and use. The pneumatic module  26 , as will be discussed in more detail below, is mounted to the cylinder housing  24  which is in turn mounted to the body  14  and provides pneumatic pathways between the module  26 , the cylinder housing  24  and the tensioning and weld motors  18 ,  22  for introducing and venting a compressed gas, such as compressed air, for operation of the tool  10  and to and from the motors  18 ,  22 . The module  26  is readily mounted to and removed from the housing  24  by a plurality of fasteners  32  such as bolts and the like. 
     Referring now to FIG. 1, in the exemplary tool  10 , the weld motor  22  is mounted to the body  14  in stationary relation so that the weld motor  22  and body  14  are fixed relative to one another. A weld motor shaft (not shown) extending from the motor  22  engages an eccentric element  34 . The eccentric element  34  is positioned in an elongated opening  36  in an arm  38  that is operably connected at one end to a weld element  40  and at an opposing end to a piston  42 . The piston  42  is positioned in a cylinder  44  in the cylinder housing  24 . 
     Upon actuation of the weld motor  22 , the shaft rotates which in turn rotates the eccentric element  34 . The eccentric  34  is fitted into the elongated opening  36  so that as the motor  22  rotates, it imparts vibrational movement to the weld element  40 . The upper and lower strap layers S U , S L  are positioned between the weld element  40  and a stationary weld pad  46  on the foot. The vibrational movement is transferred into the strap layers S U , S L  and welds the strap onto itself. The operation and construction of such vibrational weld elements and the various arrangements to impart vibrational energy will be recognized and understood by those skilled in the art and are within the scope and spirit of the present invention. 
     To assure that sufficient pressure is exerted by the weld element  40 , the piston  42  receives compressed gas (e.g., compressed air) at the top of the piston  42  in the cylinder  44  when the tool  10  is in the welding cycle. The gas forces the piston  42  downwardly to assure that the proper force is exerted on the strap S as the weld element  40  vibrates. 
     The foot  16  is likewise mounted to the body  14  so that foot  16  and body  14  are stationary relative to one another. The foot  16  has the weld pad  46  mounted thereto, against which the strap S is held for tensioning. As set forth above, the weld pad  45  is positioned on the foot  16  to maintain the lower section of the strap S L  stationary as the upper section of strap S U  is vibrated to effect the weld. 
     The tensioning motor  18  is mounted in fixed relation to the tensioning motor housing  20  which is in turn pivotally mounted to the body  14  by a pivot pin  48 . The pin  48  permits the motor housing  20  to pivot relative to the body  14 . A transmission (not shown) located within the housing  20  transfers the driving force from the motor  18  to a feed wheel shaft  50  on which a feed wheel (not shown) is mounted. As such, the feed wheel pivots along with the tensioning motor  18  and housing  20  relative to the body  14 . A detailed discussion of the weld and tensioning motors, as well as their operation within the overall strapper is provided in the aforementioned U.S. patent application Ser. No. 10/171,890. 
     Referring now to FIGS. 1 and 3, the pneumatic module  26  is removable mounted to the cylinder housing  24 . The module  26  includes a plurality of components (e.g., switches, valves, accumulators, shown schematically in FIG. 7) to control the overall operation of the strapper  10 . The module  26  is configured to readily mount to and be removed from the housing  24  by, for example, the exemplary bolts  32 . In this manner, in the event that maintenance is required on the pneumatic module  26 , the module  26  can be removed and a replacement module can be readily installed on the tool  10  for continued use. 
     Referring to FIG. 7, a pneumatic schematic is shown. Air enters the tool  10  through a compressed air supply  60  and enters a pilot valve  62 . The pilot valve  62  is a two position valve (on-off) that is biased to the on position (as shown). The on position routes air to a juncture  64  at which the air supply splits with one branch  66  routing air to a tension motor valve  68  and the other branch  70  routing air to a weld cycle valve  72 . 
     Depressing or actuating a tensioning motor switch  74  moves the tensioning motor valve  68  into the open position, routing air through a variable orifice  76  to the tensioning motor  18  and routing air to a tensioning piston  78 . The variable orifice  76  is adjustable to provide control of the tensioning motor  18  power output. (Note that the tensioning motor valve  68  is shown in the off or closed position.) The piston  78  extends downwardly from the cylinder housing  24  and applies a force against the tensioning motor housing  20  when the tensioning motor  18  is actuated. The piston  78  assists maintaining the tool  10  in the engaged position. A spring (not shown) is positioned above the piston  78  to bias the piston  78  downwardly against the motor housing  20 . Releasing the tensioning motor switch  74  closes the tensioning motor valve  68 , terminating the air feed to the tensioning motor  18  and to the piston  78 . 
     As set forth above, depressing the tensioning motor switch  74  actuates the tensioning motor  18  to tension the strap S. When a predetermined tension is reached, the motor  18  stalls. Releasing the switch  74  merely stops the feed of air to the motor  18 . The tensioning arrangement is such that the strap S will not “slip” back, nor will the strapper  10  rotate rearwardly to loosen the strap S. 
     A weld cycle switch  80  operates the weld cycle valve  72 . Depressing the switch  80  moves the valve  72  to the on position. (Note that the valve  72  is shown in the off or closed position.) The weld cycle valve  72  is a contact or maintain valve. In the on position, air is routed through the second line  70  branch to the valve  72 . Air enters the valve  72  and is routed to the weld motor  22 . A tee line  82  from the weld motor line is routed back to the weld cycle valve  72  to “hold” the valve  72  in the on position. The valve  72  is spring  84  biased to the closed position, however, the air pressure “holding” the valve  72  open is sufficiently high to overcome the spring  84  force. 
     At the same time that air is routed to the weld motor  22 , air is directed to a volume chamber or accumulator  86 , through a weld timer  88  and check valve  90  for weld timing. The weld timer  88  is a check valve  92  in parallel with a restriction device  94  such as the illustrated orifice. In this manner, air flow into the accumulator  86  is restricted (and thus timed) in that flow through the orifice  94  is limited or restricted. A line  96  from the accumulator  86  is routed to the pilot valve  62 , so that as the pressure in the accumulator  86  increases, air flows to the back side of pilot valve  62 . When the air in the accumulator  86  reaches a predetermined pressure, the pilot valve  62  closes, thus stopping air flow to the weld cycle valve  72 . This stops operation of the weld motor  22 . 
     When air flow is terminated to the weld cycle valve  72 , the pressure exerted to maintain the valve  72  open (through line  82 ) also drops, and the valve  72  returns to the closed position by action of the spring bias  84 . 
     Returning to the weld cycle, as air is provided to the weld motor  22 , air is also routed to the weld cylinder  4  (to the top of the piston  42 ) to maintain pressure on the piston  42  (which assures that sufficient pressure is applied by the weld element  40  on the strap S). The air is routed to the top of the cylinder  44  through a cool down timer  98 . As set forth above, after welding is complete, the strap S must be allowed sufficient time to cool to assure the integrity of the weld. Cool down is accomplish with pressure applied by the weld element  40  on the strap S (pressure on the piston  42 ), without vibrational motion of the element  40  being imparted. 
     The cool down timer  98  maintains pressure on the piston  42  without vibrational motion of the weld element  40 . When the air to the weld motor  22  is stopped, the weld element  40  ceases to vibrate. The air routed to the top of the weld  44  cylinder is slowly vented from the cylinder  44  by a restricted vent path from the top of the cylinder  44 . The cool down timer  98  is configured similar to the weld timer  88  and includes a check valve  100  in parallel with a restriction device  102  such as an orifice. In this manner, although the weld motor  22  has stopped, the pressure exerted by the (piston  42  and the) weld element  40  is maintained and is slowly released by timed venting from the cylinder  44 . 
     The time-out indicator assembly  12  is positioned on the pneumatic module  26 . The indicator assembly  12  is of the pop-up type and provides indication of the end of the cool down cycle following the weld cycle. The assembly  12  includes an indicator sleeve  106  that is mounted in an opening  108  in the pneumatic module  26 . The opening  108  opens into the weld piston cylinder  44 , above the piston  42 . 
     The sleeve  106  is fitted into the pneumatic module  26 , preferably by press-fitting. In a current embodiment, a groove  112  is formed in the inside surface  114  of the module  26  and the sleeve  106  has an outwardly extending flange  116  that fits into the groove  112 . An outside diameter of the sleeve  106  is slightly larger at the region that engages the inside wall of the opening  108  to assure a tight fit between the sleeve  106  and the module  26 . In this manner, the connection between the sleeve  106  and the module  26  is sufficiently tight to prevent the escape of compressed gas (air) from the cylinder  44  during operation of the strapper  10 . Because the sleeve  106  is fixed in the module  26  and does not move, the seal between the sleeve  106  and the module  26  is readily accomplished. The sleeve  106  further includes an inwardly turned lip  118  (defining an inner diameter d 118 ) at an upper end  120  and a groove  122  formed in an inner wall  124  of the sleeve  106  at a lower end  126 , adjacent the flange  116 . 
     An indicator  128  resides in the sleeve  106  and is configured for reciprocating (e.g., up and down) movement within the sleeve  106  between an “incycle” position and a “cycle timed-out” position. In the in-cycle position, the weld and cool down time has not yet elapsed and the strap S is not fully ready, that is not welded or fully cooled. 
     The indicator  128  includes a body or stem  130  having a relatively cylindrical profile that is divided by a ring channel  132 . The ring channel  132  is defined by inner and outer circumferentially outwardly extending ring walls  134 ,  136 , respectively, spaced from one another to define the channel  132 . As will be discussed below, the channel  132  is configured to receive a sealing element  138 . For purpose of the present disclosure, inner refers to that side of the sealing element, indicated generally at  140 , that is within the pressure boundary of the pneumatic module  26 , and conversely, outer refers to that side of the sealing element, indicated generally at  142 , that is outside of (i.e., the environs side of) the seal  138 . 
     The portion  142  of the indicator  128  above the outer ring wall  136  (i.e., on the environs side of the seal  138 ) has a slightly larger diameter than the portion  140  below the inner ring wall  134  (i.e., within the pressurized cylinder  44  region). At the far or free end of the environs side of the indicator body  130  (referred to as the indicating end), a head portion  144  tapers to a flat surface  146 . 
     In a current embodiment, an intermediate portion, as indicated generally at  148 , of the stem  130  and a portion of the tapered head  144 , such as by painting, with a readily visibly identifiable coating. This provides positive indication of the cycle timed out-state. A present indicator includes paint, preferably a bright, readily visible color, such as a white color, from about the outer ring channel  136  to about the mid-point of the indicating end head  144 . From the colored portion to the end of the head  144  (as indicated generally at  150 ), the indicator  128  is colored (painted) a dark color, such as black, preferably matching the color of the pneumatic module  26 . In this manner, when the strapper  10  is in the in-cycle mode and the indicator is retracted, no “color” is visible. When, on the other hand, the weld and cooling cycles have completed, and the strapper  10  is in the cycle timed-out mode, the indicator extends (or pops) and the color of the body or stem of the indicator  128  is readily visible. 
     During in-cycle mode, and when the strapper  10  is not in operation, it is preferred that the indicator  128  reside in the in-cycle position (i.e., retracted position) to prevent damage to the indicator  128 . To this end, the indicator  128  is biased to the in-cycle or retracted position. This is accomplished by a biasing element  152 , such as the illustrated coil spring that is positioned around the indicator stem  130  between the outer ring wall  136  and the sleeve lip  118 . The spring  152  thus biases the indicator  128  inward of the sleeve  106 , again to the retracted position. To retain the indicator  128  in the sleeve  106  and prevent it from inadvertently coming loose within the internal portions of the pneumatic module (e.g., falling into the cylinder  44 ), a clip  154 , such as the illustrated spring clip is positioned in the sleeve groove  122 . The clip  154  has an inner diameter d 154  that is less that the diameter d 134  of the inner ring wall  134 . As such, the clip  154  retains the indicator  128  and the spring  152  within the sleeve  106 , and thus maintains the indicator assembly  12  as a single, essentially integrated unit. 
     Because the bottom of the indicator  128  is positioned in the pressurized region of the strapper  10 , that is, in the weld cylinder  44 , and extends to an area external of the pneumatic module  26  (i.e., to the environs) it is necessary to provide a pressure barrier at the interface of the pressurized region and the environs. To this end, the sealing element  138  is provided between the indicator  128  and the sleeve  106 . In a present indicator, the seal  138  is an O-ring that is positioned in the ring channel  132 . As such, the seal  138  prevents the escape of compressed air from the pneumatic module  26 , and the channel  132  retains the seal  138  in place. 
     As will be appreciated from a study of the figures, the present indicator assembly  12  functions on a simple, contact principle, and does not rely on the application or use of pneumatic pressure to provide cycle indication. Rather, as the piston  42  rises in the cylinder  44 , it contacts the bottom portion of the indicator  128 . The upward force exerted by the piston  42  urges the indicator  128  up (that is outward of the sleeve  106 ), so that the painted (indicating) portion  148  of the indicator  128  extends above the sleeve lip  118  and becomes visible, providing indication that the cycle timed-out state has been reached. Upon movement of the piston  42  downward, the spring  152  force returns the indicator  128  to the retracted position, indicating the in-cycle state. 
     All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically do so within the text of this disclosure. 
     In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
     From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.