Patent Publication Number: US-2006010982-A1

Title: Method and apparatus for indicating an apparent error in the operation of a fluid-powered attachment

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a continuation-in-part of pending U.S. patent application Ser. No. 10/806,708, filed Mar. 23, 2004. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to a method and apparatus adapted for use in a cold-forming process (e.g., thread rolling, knurling, burnishing, etc.) for indicating an apparent error in the operation of a fluid-powered attachment mounted on a machine tool for controlled movement toward and away from a workpiece.  
     BACKGROUND ART  
      Various types of cold-forming processes are known. These processes include, but are not limited to, thread rolling, knurling, burnishing, etc. Some of these contemplate that a fluid-powered attachment be mounted on a machine tool for selective and controlled movement relative to a workpiece. In some devices, thread rolls are moved generally tangentially toward the workpiece. (See, e.g., U.S. Pats. No. 4,617,816, 4,766,750, 5,167,136 and 6,202,461, the aggregate disclosures of which are hereby incorporated by reference.) Alternatively, they may be initially moved to a radially-spaced position relative to the relatively-rotating workpiece, and then moved radially inwardly to roll a thread on the workpiece. (See, e.g., U.S. Pat. No. 6,508,095, the disclosure of which is hereby also incorporated by reference.)  
      In many cases, these devices and attachments are mounted on machine tools, and generally operate on a substantially unattended basis. Accordingly, it would be generally desirable to provide a means for automatically indicating that an error has apparently occurred during the cold-forming operation.  
     DISCLOSURE OF THE INVENTION  
      With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for purposes of illustration and not by way of limitation, the present invention broadly provides an improved method and apparatus for indicating an apparent error in the operation of a fluid-powered attachment (A) that is mounted on a machine tool (not shown) for controlled movement toward and away from a workpiece (W) upon which an operation is to be performed. Such an attachment may possibly be used in a cold-forming operation or process, such as thread rolling, knurling, burnishing, or the like. However, the invention is not limited to cold-forming processes, or to any of these specific operations. As used herein, the term “fluid” is intended to broadly include a liquid, a gas, or a mixture thereof.  
      The improved apparatus ( 60 ) may broadly include: a fluid-powered actuator ( 64 ) for selectively moving the attachment (A) relative to the workpiece (W) during an operational cycle; a sensor ( 73 ) operatively arranged to sense and monitor the value of at least one of the pressure of fluid within the actuator, and the time of operation, during at least a portion of the cycle, and to provide an output signal; and a programmable logic unit ( 75 ) provided with the sensor output signal, arranged to store minimum and maximum permissible values of said sensed pressure and/or time that the attachment is expected to encounter during the cycle, and operatively arranged to indicate an apparent error in the formation of a thread on the workpiece if the sensed value is not between these stored minimum and maximum values.  
      In the preferred embodiment, the sensor is arranged to continuously monitor the selected pressure and/or time.  
      The invention also provides an improved method of indicating an apparent error in the operation of a fluid-powered attachment (A) mounted on a machine tool (not shown) for controlled movement toward and away from a workpiece (W) upon which an operation is to be formed. This method may broadly include the steps of: providing a fluid-powered actuator ( 64 ) for selectively moving the attachment relative to the work-piece during an operational cycle; storing minimum and maximum permissible values of at least one of the fluid pressure within said actuator, and the time of operation, expected during said cycle; sensing the value of the selected pressure and/or time during at least a portion of said cycle, and providing an output signal; determining whether the sensed value is between said stored minimum and a maximum permissible values; and indicating an apparent error in the formation of a thread on the workpiece if the sensed value is not between the stored minimum and maximum values.  
      The method may further include the additional steps of: providing a programmable logic unit ( 75 ); supplying the programmable logic unit with the sensed value; storing the minimum and maximum permissible values in the programmable logic unit; and comparing the sensed value with the stored values.  
      Accordingly, the general object of the invention is to provide an improved apparatus for indicating an apparent error in the operation of a fluid-powered attachment.  
      Another object is to provide an improved method of indicating an apparent error in the operation of a fluid-powered attachment.  
      Still another object is to provide such an improved method in a device wherein an attachment is adapted to be mounted on a machine tool for controlled movement toward and away from a workpiece upon which a particular operation is to be formed during a cycle.  
      These and other objects and advantages will become apparent from the foregoing and ongoing written specification, the drawings, and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a simplified schematic of a prior art apparatus for operating a fluid-powered attachment.  
       FIG. 2  is a schematic, more detailed than  FIG. 1 , showing the improved apparatus according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.  
      Prior Art Arrangement ( FIG. 1 )  
       FIG. 1  is a schematic depicting a prior art arrangement for operating a thread-rolling attachment (A) on a machine tool (not shown). The circuit is generally indicated at  20 , and is shown as broadly including a filter/pressure regulator assembly  21 , a control valve  22 , an operator valve  23 , a flow control valve  24 , a fluid-powered actuator  25 , and a reset/return actuator  26 .  
      Compressed air is provided from a suitable source (not shown) through a line  28  as an inlet to filter/regulator  21 . This block incorporates a fluid filter and a pressure regulator, and provides an output flow through line  29 . The flow in line  29  is provided to control valve  22  via line  30 , and is also provided to line  31 , which contains a flow-control purge line  32  and a quick-disconnect plug  33 .  
      Control valve  22  is schematically shown as having a manually-operated valve spool that is slidably mounted within a body. The spool is biased toward its leftward position by a spring  34 . An input, indicated by arrow  35 , is arranged to selectively displace the spool rightwardly to the alternative position by overcoming the bias of spring  34 . When this occurs, fluid in lines  29  and  30  may flow through control valve  22  and line  36  to act on the left end face of a valve spool located within operator valve  23 . The right end face of this valve spool is provided with pressure from large-area chamber  38  of actuator  25  via line  39 , reset valve  26  and line  40 . Line  40  is also shown as containing a quick-disconnect  41 .  
      In the condition shown, flow in line  39  from the large-area actuator chamber  38  is initially blocked by virtue of reset valve  26  being in the position shown in  FIG. 1 . However, the right end chamber of operator valve  23  is vented to return via line  40  and the reset valve. Thus, when control valve  22  is displaced to the alternative position, line  36  is pressurized, and the spool of operator valve  23  is shifted rightwardly to the alternative position. Thus, compressed air may flow from line  29  through line  42 , the now-displaced operator valve  23  and line  43  to actuator large-diameter chamber  38 . Line  43  is shown as including a quick-disconnect  44 . At the same time, the fluid may flow from actuator small-diameter chamber  45  through line  46  and filter/regulator  24 , and line  48  to now-displaced operator valve  23 , and thence to exhaust. Filter/regulator assembly  24  is shown as having a variable orifice  49  and a check valve  50 . Line  46  is shown as having a quick-disconnect  51 . The actuator  25  is shown as having a piston  52  movable relative to a cylinder  53 , and having a rod  54  extending leftwardly from the piston and penetrating the left end wall of the cylinder. Thus, the piston has a large circular area facing rightwardly into chamber  38  and a smaller annular area facing leftwardly into chamber  45 .  
      When fluid pressure is provided to actuator chamber  38  and actuator chamber  45  is vented, the thread-rolling attachment is moved leftwardly toward the workpiece. At the end of its stroke, the thread-rolling attachment displaces a plunger  55  on the reset valve  26  so as to shift the reset valve to the alternative position. When so shifted, pressure in the large actuator chamber  38  is provided via conduits  39  and  40  to the operator valve right end chamber, and displaces its valve spool leftwardly and back to the position shown. This permits fluid in actuator chamber  38  to be vented to return via line  43 .  
      The arrangement indicated by  FIG. 1  is substantially automatic in that each time a thread is to be rolled, one need only to actuate the input device  35 , either manually or by some other means. This then causes the actuator to advance the thread rolls toward the workpiece. At the end of its intended stroke, the reset button is actuated, which causes the actuator to return to its initial position.  
      While this arrangement is functional to cause automatic operation of the device (i.e., to advance the thread-rolls to engage the workpiece, and then to automatically withdraw them at the end of their desired stroke), this arrangement did not have any type of mechanism for indicating whether an apparent error had occurred during operation of the device.  
      Improved Device ( FIG. 2 )  
      An improved device is generally indicated at  60  in  FIG. 2 .  
      Device  60  is arranged to be supplied with compressed air from a suitable source (not shown) via inlet  61 , and further contains a control valve  62 , an operator valve  63 , a fluid-powered actuator  64  upon which the thread-rolling attachment (A) is mounted, and an operating valve  67 . In the illustrated form, the attachment is used to roll a thread onto the workpiece. In other forms, the attachment might relate to another cold-forming process or operation, such as knurling or burnishing. However, the invention is not limited to such cold-forming processes or operations.  
      An outlet line is indicated at  65 , and a pilot line is indicated at  66 . Lines  65 ,  66 ,  68  and  69  are each provided to operator valve  63 . Pilot line  66  is connected to an end chamber of the pilot valve, and is operatively arranged to act on one end of the valve spool therein. The inlet  61  communicates with a line  70  which communicates with control valve  62  having an input  71 . Control valve  62  also communicates with the opposite end of the operator valve spool via line  72 .  
      In this form, a pressure sensor  73  is operatively arranged to monitor the pressure in line  72 , and to provide this a corresponding signal via line  74  to a programmable logic unit  75 .  
      Another pressure sensor  76  is mounted on actuator  64 , and provides a pressure-indicating signal via line  79  to the programmable logic unit. The logic unit is adapted to store two set points, these representing the minimum and maximum pressures (p min  and p max , respectively) expected during a normal thread-rolling cycle. So long as the pressure provided by sensor  73  is between the minimum and maximum pressures, the output signal from the programmable logic unit will indicate that the apparatus is operating normally. However, should the pressure exceed either limit, either by falling below the minimum, or by exceeding the maximum, the programmable logic unit will provide an error signal on output line  80  to indicate an apparent error in the thread-rolling operation. Pressure sensor  76  is used as an alternative to the reset arrangement shown in the prior art.  
      Alternatively, or in addition thereto, the apparatus may be arrange to sense or determine the time of operation during at least a portion of the cycle, and to provide an output signal; and to compare such sensed time with minimum and maximum permissible times of operation stored in the programmable logic unit  
      Thus, the present invention broadly provides an improved method and apparatus for indicating an apparent error in the operation of a fluid-powered attachment mounted on a machine tool for controlled movement toward and away from a workpiece upon which an operation is to be performed during an operational cycle. The improved apparatus may broadly include: a fluid-powered actuator for selectively moving the attachment relative to the workpiece during the cycle; a sensor operatively arranged to monitor the value of at least one of the pressure of fluid within the actuator, and the time of operation, during at least a portion of the cycle, and to provide an output signal; and a programmable logic unit provided with the sensor output signal, arranged to store minimum and maximum permissible values of said selected pressure and/or time of operation that the apparatus is expected to encounter during the thread-forming cycle, and operatively arranged to indicate an apparent error in the operation of the attachment on the workpiece if the sensed value is not between the stored minimum and maximum values.  
      The improved method broadly includes the steps of: providing a fluid-powered actuator for selectively moving the attachment relative to the workpiece during the cycle; storing minimum and maximum permissible values of at least one of the fluid pressure, and time of operation, expected during the cycle; sensing the value of at least one of the pressure within the actuator, and the time of operation, during at least a portion of the cycle, and providing an output signal; determining whether the sensed value is between the stored minimum and maximum permissible values; and indicating an apparent error in the operation of the attachment on the workpiece if the sensed value is not between the minimum and maximum stored values.  
      The apparent error signal, provided by programmable logic unit output  80 , may take any of a number of forms. For example, it may be in the form of a visual or audible indication, or it may be in the form of an automatic shut-down of the machine until such time as the apparent error may be investigated and the system reset. Other forms of error signals may be used as well.  
      Modifications  
      The present invention expressly contemplates that many changes and modifications may be made. For example, the method and apparatus is not limited to the specific form of the elements and circuitry shown in the accompanying drawings. Indeed, other types of apparatus may be substituted therefor. The pressure sensor may be electronic or pneumatic, as desired. Devices other than in the specific programmable logic unit, may be substituted therefor.  
      Therefore, while the presently-preferred form of the method and apparatus have been shown and described, and several modifications thereafter discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.