Abstract:
An improved and simplified balancing machine comprising upright supports devices to hold the workpiece to be balanced, a motor and mount to spin the workpiece, and a system to detect and measure imbalance in the workpiece when it is rotated at speed. Said machine configured to be attached to a machine tool or work table without losing functional integrity, thereby eliminating the need for a massive base. Specific preferred structural embodiments are disclosed.

Description:
FIELD OF THE INVENTION 
   The invention relates to a machine for detecting and measuring rotational imbalance of mechanical components. More particularly, this invention relates to an improvement in balancing machine technology through a more simplified design which eliminates the need of certain components. 
   DESCRIPTION OF THE PRIOR ART 
   Prior art in balancing machines consist of large free standing machines. They incorporate a massive base, support devices to hold the workpiece to be balanced, a motor mounted in said base to spin said workpiece, and a system to detect and measure imbalance in said workpiece when it is rotated at speed. One type of balancing machine requires that said workpiece be removed from the balancer in order that said workpiece be drilled, ground or otherwise brought into a dynamically balanced state. Other types of these machines are so large that a milling/drilling machine is mounted on said massive base, allowing said milling/drilling machine to be rolled into position over the point of imbalance thereby drilling said workpiece to remove material from the point of imbalance. In this example, said workpiece is not removed from the machine until the balancing is completed. This method works well. In order to achieve this, however, the machine was massive, expensive, and dedicated in its application. Many small businesses can afford neither the purchase price nor the dedicated floor space for these machines.  FIG. 9  of the appended drawings shows an example of this type of balancing machine. 
   A pre-examination search found the following United States patents which are illustrative of the types of prior art devices that have been known.
         U.S. Pat. No. 3,871,234; C. Langlois describes a dedicated balancing machine of rather complex mechanical nature requiring a special base.   U.S. Pat. No. 4,406,164; G. Hines describes a dedicated balancing machine requiring a massive base and the drive motor mounted in said base below the part to be balanced. This prior art is represented by  FIG. 6  of the appended drawings.   U.S. Pat. No. 4,556,346; G. Hines describes a dedicated balancing machine requiring a massive base and the drive motor mounted in said base below the part to be balanced. This patent claims the apparatus for mounting a drill press on said base. This prior art is represented by  FIG. 6  of the appended drawings.   U.S. Pat. No. 5,199,992; G. Hines describes a dedicated balancing machine with correction apparatus for applying and hardening a viscous material on the workpiece. This unit also requires a massive specially designed base.   U.S. Pat. No. 5,505,083; G. Hines describes a dedicated balancing machine with correction apparatus operating in a split station mode with a workpiece transport module. This unit also requires a massive specially designed base.       

   Des. 320,214 G. Hines claims a design patent on his massive dedicated base. 
   The foregoing prior art, which generally describe the current commercially available balancing machines clearly show a consistent use of large, heavy, dedicated machine bases. As can be seen from discussion of this prior art and the following disclosure this invention, the prior art has not provided a balancing machine having the features hereinafter described. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is the object of this invention to provide a new and improved device whose purpose is to detect and measure rotational imbalance in mechanical components, retaining all the functions of the prior art while eliminating certain features which require increased size, weight, and cost, thereby demonstrating that a relatively small, light weight, and lower cost machine can function equally as compared to the existing art in this field of application. The lower cost will increase the availability of these machines to smaller companies. The small size and lighter weight will allow shipment by parcel services rather than by motor freight thereby increasing the portability of the unit. 
   More particularly, it is the object of this invention to provide a balancing machine for automotive engine crankshafts and obviate the disadvantages of the prior art. 
   These and other objects will become apparent from the descriptive matter provided hereinafter, particularly when taken into conjunction with the appended drawings. 
   In accordance with this invention, there is provided a balancing machine comprising:
         A. support devices to hold the workpiece to be balanced;   B. a motor and mount to spin said workpiece;   C. a system to detect and measure imbalance in said workpiece when it is rotated at speed.       

   In my preferred embodiment, there is no massive base. This machine is configured as an attachment to the milling/drilling machine. The mass of the milling machine is used as the base for the balancer with portions of the balancing machine mounted to the machine table, specifically the support devices with sensors, the motor mount/belt tensioner unit, and the rotary position sensor. Rather than the method used in prior art, moving the milling/drilling machine to the location of imbalance and securing said machine in position for drilling or milling, the table of the milling machine is moved, usually with a hand crank, thereby positioning the workpiece under the spindle of the milling machine. The movement of the mill table with balancer and workpiece attached is simpler and more precise as compared to the method of operation in prior art. The new design also lends itself to computer controlled automation of the process where a computer controlled milling/drilling machine, with the attached invention, could be used for automatic positioning and drilling. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of the balancing machine with a workpiece in position to be spun and measured for dynamic balance. The cover plates are removed from this view of the upright supports in order to show the configuration of said upright supports and the linear displacement sensors. 
       FIG. 2  is an isometric view the invention configured as an attachment to a conventional vertical milling machine. It shows the balancing machine attached to the milling machine table. An automotive crankshaft with attached weights is in position on the balancer. A computer is connected to the balancing machine. 
       FIG. 3  is a combination of isometric views with orthographic top, front, left, and right sides showing the same configuration as  FIG. 1 . 
       FIG. 4  is a close up isometric view of the upright support. The cover plates are removed from this view of the upright support in order to show the configuration of said upright support and the linear displacement sensor. 
       FIG. 5  is a close up view of the optical sensor case and internal components. 
       FIG. 6  is a block diagram flow chart of the adapter card for personal computer. 
       FIG. 7  is a block diagram flow chart of the microprocessor program. 
       FIG. 8  is a block diagram flow chart of the software program for personal computer. 
       FIG. 9  is an isometric view of commercially available prior art. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   While it is to be borne in mind that this invention can be attached to different types of machine tools and configured for balancing many different mechanical components, one of the areas where it finds usefulness is in the balancing of automotive crankshafts. Many small engine shops can not afford the purchase price and the floor space required by the large units that are now commercially available. In the preferred embodiment, the invention is uniquely advantageous when configured as an attachment to a vertical milling machine of the type frequently already owned by these shops. If the purchase of a milling machine is necessary, the mill is not permanently dedicated to balancing. The balancing machine can be easily removed from the mill, leaving it fully functional for other work. It should also be noted that the combined purchase price of the milling machine and the balancing machine is less than the cost of a dedicated balancing machine as shown in  FIG. 6 . Accordingly, it is in this environment that this invention will be described hereinafter. 
   Referring to  FIG. 1 , the workpiece  33  to be measured for dynamic balance is supported in v-block bearings  39  of at least two upright supports  10  while rotated by motor  22  by means of a belt  32  communicating pulleys  38 ,  28 , and  29  and said workpiece  33 . Said motor  22  and motor controller assembly  23  are rigidly attached to motor plate  24  which pivotally attaches to hinge tabs  37  through hinge pin  25 . Said hinge tabs  37  being rigidly attached to motor base  11 . Pulleys  29  and  28  are positioned by axle shafts  30  and  27  being rigidly attached to said motor base  11  in such a way as to align said belt  32  substantially vertical as it engages the workpiece  33 . This pulley arrangement allows a front mounted motor  22  while not inducing horizontal thrust to said workpiece  33  during the application of torque for rotation. A belt tensioning arm  26  secures said motor  22  in position to assure proper tension of said belt  32 . During rotation at speed, typically 200 to 700 revolutions per minute, said workpiece  33  is restrained from vertical movement by the v-block bearings  34  and the tension of said belt  32 . The horizontal component of the dynamic imbalance thrust is transmitted from workpiece  33  through said v-block bearings  34  to the upper portion  41  of said upright support  10 . Said thrust causes flexing of the thin vertical area  40  resulting in a substantially horizontal movement of upper portion  41  relative to lower portion  42  of said upright support  10 , said lower portion  42  being rigidly affixed to a machine tool  50  ( FIG. 2 ). Relative horizontal deflection between said upper portion  41  and said lower portion  42  is detected and measured by a linear sensor  43  (commercially known as a Linear Variable Differential Transformer) mounted in upright support  10 . Details of this construction and function will be descried further in detailed descriptive matter hereinafter. Rotational data is created by an optical sensor assembly  12  comprising, optical sensor head  15  attached to mounting block  16 , slideably communicating with vertical rod  18  and secured at proper vertical location by hand screw  17 , said vertical rod  18  being rigidly affixed to block  19 , slideably communicating with horizontal rod  21  and secured at the proper horizontal position by hand screw  20 , said horizontal rod  21  being rigidly connected to upright support  10 . The optical sensor head  15  detects rotation of slotted sensor wheel  13 . The sensor wheel  13  is attached to workpiece  33  coaxially by adapter hub  14  and rotates as an assembly. Rotational data from sensor head  13  is sent to a computer  51  ( FIG. 2 ) and used for speed control and angular position location of workpiece  33 . When the data from rotary sensor head  15  and data from linear sensors  43  are analyzed by the computer  51  ( FIG. 2 ) the amount of imbalance, the position of said imbalance, and the required corrective drill depth/location can be determined. This, of course, requires the proper computer interface card and computer program as described in  FIG. 6 ,  FIG. 7 , and  FIG. 8 . Further referring to  FIG. 1 , there is also provided a means of limiting the axial movement of workpiece  33 . Adapter hub  14  is configured with a groove  35  around the circumference which engages with semi-flexible thrust control plate  34 . Said thrust control plate  34  is rigidly attached to block  16 . There is provided a slight running clearance between the sides of said groove  35  in adapter hub  14  and thrust control plate  34 . This configuration of thrust control results in substantially all frictional forces existing in the vertical direction, with almost no horizontal force component which would affect the output of said linear sensors  43 . It should also be noted that said optical sensor  15  does not contact sensor wheel  13 , thereby isolating any forces, frictional or otherwise, from the rotating workpiece to be measured for dynamic balance. 
   Referring to  FIG. 5 , the optical sensor head  15  comprising of upper and lower case halves  44  and  45 , two standard commercially available optical emitter/detector sensors  46  and  47  mounted on a custom printed circuit board  48  and a cable  49  which connects to the computer. Said sensors  46  and  47  and board  48  are affixed inside said upper and lower case halves  44  and  45  so that apertures  50  and  51  align optically with sensors  46  and  47  and provide a masking effect for the proper width of detection. The vertical spacing between sensors  46  and  47 , as further restrictively established by apertures  50  and  51 , equals one and three quarters the circumferential spacing of the slots  52  in sensor wheel  13 . This offset spacing allows for both finer resolution of rotational position and data for determining the direction of workpiece rotation as said sensors  46  and  47  detect the change of reflectivity during rotation of sensor wheel  13 , alternately exposing either polished metal of sensor wheel  13  or slots  52  to said sensors  46  and  47 . 
   Referring to  FIG. 4 , the linear sensor  43  consist of body  52 , core  53 , and cable  54 . Said body  52  is rigidly clamped onto lower portion  42  of upright support  10  by clamp  57  and clamp screw/nut  55 . Said core  53  is rigidly held in slotted protrusion  58  of upper portion  41  by threaded nuts  56 . 
   Said core  53  is axially aligned to body  52 . Cable  54  of sensor  43  is routed through passages in upright support  10 , exiting at the rear of said upright support  10  and connecting to computer  51  ( FIG. 2 ). As upper portion  41  of upright support  10  moves relative to lower portion  42  through the flexing of portions  40 , said core  53  is moved inside body  52  of linear sensor  43 . This change of position creates a change in the electrical output of said sensor  43  which can be deciphered by computer  51  ( FIG. 2 ) as a force of imbalance when combined with rotational data. 
   In operation, upon computer entered command, the computer causes the motor to accelerate at a controlled rate to a predetermined rotational speed. The workpiece to be measured for dynamic balance is, in turn rotated by a belt communicating workpiece and motor through pulleys. As the workpiece rotates, electronic sensors provide coordinated data of rotation position and linear displacement due to any imbalance. This data is filtered and analyzed by the computer hardware and software. The computer then outputs the rotational imbalance data in the form of a maximum amount with angular location for each upright support. A graph of all data is also computed an output to the screen. The computer also calculates and provides the suggested depth to spot drill the workpiece in order to bring said workpiece into dynamic balance. In some instances multiple operations of spinning, measuring, and drilling are necessary. 
   Although this invention has been described with a certain degree of particularity, specifically referencing crankshaft balancing as the application, this reference is given only as example and does not limit the application to a specific use. While the preferred embodiment was described as mounted to a vertical milling machine, the invention can be mounted to any suitable device, including a substantial table or workbench. The invention can be used for many applications and can be configured specifically for other applications without violating the theme of this invention. The invention can even be configured using a single upright with linear sensor in conjunction with a rigid non sensing second support or other bearing support system. While the preferred embodiment demonstrates v-block bearings, it will be evident to those skilled in the art that other bearing arrangements are possible, including roller bearings mounted to the upright supports. While the preferred embodiment also demonstrates linear variable differential transformers for horizontal measurement of forces due to dynamic imbalance, other sensing devices such as strain gauges and load cells can be utilized without deviating from the scope and spirit of this invention.