Source: https://patents.justia.com/patent/7578051
Timestamp: 2019-07-17 04:25:43
Document Index: 235672767

Matched Legal Cases: ['art 0', 'art 1', 'art 2', 'art 0', 'art 1', 'art 2']

US Patent for Machine for press fit assembly Patent (Patent # 7,578,051 issued August 25, 2009) - Justia Patents Search
Justia Patents With Control Means Energized In Response To Activator Stimulated By Condition SensorUS Patent for Machine for press fit assembly Patent (Patent # 7,578,051)
Dec 15, 2005 - Autocam Corporation
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A computer program listing appendix on one compact disc (labeled “Copy 1”) includes a file titled RSLogix 5000 Report (2) 12.02.04, created on Dec. 2, 2004, 473.022 bytes and an identical copy (labeled “Copy 2”) of the compact disc (labeled “Copy 1”) are attached hereto.
For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in FIG. 5. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
A press machine/apparatus 1 (FIG. 5) according to the present invention is utilized to press a torsion bar 20 into a cavity 11 of a power steering pinion gear 10 (FIG. 1). As discussed in detail below, press machine 1 initially first executes an “initial press” and presses first end 17 of torsion bar 20 partway into cavity 11 of gear 10. Machine 1 then measures the alignment of the torsion bar 20 relative to the gear 10. If the axis “B” of torsion bar 20 and the axis “A” of gear 10 are not aligned within a required tolerance, the machine 1 executes a “correction move” and rotates/tilts torsion bar 20 by tilting head assembly 8 (see also FIGS. 8 and 9) relative to gear 10 in a direction opposite the misalignment, and the torsion bar 20 is then pressed further into cavity 11 in a second press to complete the press fit operation. Rotation/tilting of torsion bar 20 relative to gear 10 during the correction move brings the final alignment of the torsion bar 20 relative to gear 10 within tolerance.
Power steering pinion gear 10 (FIGS. 1-4) is formed by forging and includes a cavity 11 having a generally cylindrical inner portion 12 and an enlarged outer portion 13. The cylindrical inner portion 12 includes a plurality of raised portions 14, each having a cylindrical surface portion 15 configured to fit closely against an outer surface 16 (FIG. 1) at a first end 17 of a torsion bar 20. The outer surface 16 is machined to a high tolerance cylindrical shape. In addition to the raised portions 14, pinion gear 10 also includes a plurality of raised portions 18 forming ridges extending parallel to an axis “A” of pinion gear 10. Each of the ridges 18 includes a relatively sharp edge 19, and the raised portions 14 and ridges 18 are arranged in a alternating manner around the cylindrical portion 12 of gear 10. The edges 19 define an imaginary cylinder having a diameter D1 (FIG. 4) that is smaller than the diameter of the cylindrical outer surface 16 of torsion bar 20. The cylindrical surface portions 15 of raised portions 14 define an imaginary cylinder having a diameter D2 that is substantially the same as the diameter of the outer surface 16 of torsion bar 20.
A camera 55 (FIGS. 7, 9) is mounted to a bracket 52 and precisely measures the horizontal position of the upper end 21 of a torsion bar 20 in holder 30 when the torsion bar 20 is press fit into gear 10. A plurality of data points forming a tolerance circle 105 (FIG. 9A) are programmed into camera 55 (or controller 28). Camera 55 forms a circular image of the perimeter of end surface 99 of torsion bar 20. If the torsion bar 20 is aligned exactly with gear 10, an image 106 of the end of torsion bar 20 will be centered within tolerance circle 105, and a uniform ring 107 equal to the allowable tolerance for the part will be formed between tolerance circle 105 and image 106. If the end surface of torsion bar 20 falls outside the tolerance circle 105, an image 108 of the end of torsion bar 20 will be formed. Controller 28 compares the data points forming image 108 to the data forming tolerance circle 105. If some of the data points of circle 108 are outside the data points forming tolerance circle 107, controller 28 determines that the alignment is not within tolerance, and calculates the distance or displacement “D” from the center Cl of tolerance circle 105 and the center C2 of an image 108 (end of the torsion bar 20). The controller also calculates the angle α between axis Y and the direction of displacement (arrow “A”) of the end of torsion bar 20. As discussed in more detail below, controller 28 utilizes the displacement D and angle α to calculate the required tilt angle correction of the torsion bar 20/head assembly 8 during a correction move. The vertical position of the camera 55 can be adjusted by turning a hand crank 51 of manually operable linear slide 50, such that the camera 55 can be positioned at the proper distance from end 21 of torsion bars 20 of different lengths. An opening 44 in upper member 38 provides clearance such that camera 55 is in optical communication with the end 21 of torsion bar 20.
The output members 22-24 of the linear actuators 5-7, respectively, are connected to ball joints 56, 57 and 58 (FIGS. 7 and 9), and the ball joints 56-58 are connected to a movable plate 60 via threaded connectors 61, 62 and 63, respectively. Linear actuators 5-7 are commercially available “Eliminator” model HD 404-12 units available from Axis Systems Corporation. Output members 22-24 of linear actuators 5-7 are movably mounted within housings 41, 42 and 43, respectively and extend through openings 34 in support member 38. Actuation of electric motors 25-27 causes output members 22-24 to extend and retract vertically from housings 41-43. The holder 30 for the torsion bar 20 is secured to the plate 60 and the ball joints 56-58 permit tilting of the plate 60 relative to its vertical axis to thereby tilt the torsion bar 20 during a correction move prior to completion of the press fit into gear 10.
At the start of the press fit operation, head 8 is in the fully raised position illustrated in FIG. 9 to provide clearance for insertion of torsion bar 20 in holder 30. Controller 28 is programmed to actuate electric actuators 5-7 at a relatively high rate (e.g., 150 mm/sec) at the start of the press fit operation to quickly bring end 17 of torsion bar 20 into close proximity to gear 10. As the plate 60 is brought downwardly and the first end 17 of torsion bar 20 comes into close proximity (e.g., 15 mm) with the cavity 11 of gear 10, controller 28 slows the rate of travel of head 8 to a slower speed (e.g., 5.0 mm/sec). After the end of torsion bar 20 contacts the sidewalls of cavity 12 of gear 10, controller 28 continues to actuate servos 5-7 at a slow rate such that head 8 travels at about 5.0 mm/sec. An arm 65 is pivotably mounted to the plate 60 to provide for sensing of the position of lower end 17 of torsion bar 20 relative to pinion gear 10. When the head 8 has press fit torsion bar 20 to within 0.15 mm of the full press depth, the end 66 of arm 65 contacts upper surface 67 of gear 10 causing the arm 65 to rotate, causing precision switch 68 to generate a signal to the controller 28. Controller 28 then stops translation of head 8, retracts slightly, and then determines if a tilt correction is required. If the alignment of the torsion bar 20 is within tolerance (i.e., image 106, FIG. 9A, falls within tolerance circle 105), controller 28 raises head 8 and the torsion bar 20/gear 10 assembly is removed from machine 1 without further press fit of torsion bar 20 into cavity 11. Because the tolerance for the depth of the press fit is greater than 0.15 mm, the torsion bar 20 does not need to be further press fit if the alignment is within tolerance. Alternately, if controller 28 determines that the torsion bar 20 is not aligned within tolerance (i.e., a portion of image 106, FIG. 9A, falls on or outside tolerance circle 105), controller 28 executes a correction move by tilting head 8 opposite the direction of displacement represented by arrow “A” (FIG. 9A). Controller 28 then translates head 8 downwardly at a slow speed (e.g., 5.0 mm/sec) an additional 0.15 mm.
Modified displacement = (Displacement + Adder) * Multiplier 1.0 Serve0 = Modified Displacement * Chart 0 1.1 Serve1 = Modified Displacement * Chart 1 1.2 Serve2 = Modified Displacement * Chart 2 1.3
FIG. 16A illustrates the Chart 0, Chart 1, and Chart 2 values utilized in the formulas for calculation of the input variables Serve0, Serve1, and Serve2. Serve0 is a numerical value corresponding to the amount of travel of rear servo 6, Serve1 is the amount of travel of the right servo 5, and Serve2 is the amount of travel of left servo 7. Modified Displacements for the servos 5-7, respectively. The Displacement variable in equation 1.0 is the distance (run out) “D” (FIG. 9A) that the end of the torsion bar 20 is displaced from center C1 measured/calculated by camera 55/controller 28. The Adder variable in equation 1.0 is a value that is added to the displacement D to compensate for lash in the tooling and flex in the torsion bar 20 and gear 10. The rotation angles of FIG. 16A is the angle α (FIG. 9A) defining the direction of misalignment of the end of the torsion bar 20 as measured by camera 55.
DESCRIPTION: Defines the name of the part. This value can be changed to correspond with the machine part number. The name will be displayed at the top of the Setup Screen next to the label “CURRENT PART”.
PART NUMBER: Number, 1 through 10, that is used to change from one part to another. Part number “0” has been established for testing, but could be used for a production part.
MULTIPLIER: This is the value in equation 1.0 that is applied to the displacement (run out) of the torsion bar 20 and the “ADDER”, and used in equation 1.0 to calculate the proper pitch angle and direction of the upper tooling head 8 during a correction move.
DISPLACEMENT: This title applies to the displacements (0.25 mm and 0.50 mm) at which forces DISP. #1 and DISP. #2 are applied. (The “DISPLACEMENT” values on the Correction Screen are not the Displacement variable of equation 1.0) define correction variables.
Step 1. To start, a dial indicator is used to check the parallelism of the upper tooling plate 60 to the bottom plate 39 of the machine 1. The start positions of servos 5-7 are adjusted and the machine 1 is adjusted or “homed” until the upper tooling plate 60 is parallel to lower plate 39.
The pressure move is set to “1” to limit the travel of the servos 5-7 during the correction move. This value should be set to ensure that the depth of the torsion bar 20 is within tolerance after the correction is complete.
The retry # is set to “1”.
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Patent Publication Number: 20060137546
Assignee: Autocam Corporation (Kentwood, MI)
Inventors: Edward W. Hekman (Alto, MI), John E. Swistak (Grandville, MI), David J. Ruthven (Wyoming, MI), David P. Deyoung (Zeeland, MI)
Application Number: 11/300,926
Current U.S. Class: With Control Means Energized In Response To Activator Stimulated By Condition Sensor (29/709); Including Position Sensor (29/712); Responsive To Work Or Work-related Machine Element (29/714); With Means To Fasten By Frictional Fitting (29/718); With Aligning, Guiding, Or Instruction (29/407.09); Assisting Assembly Or Disassembly (29/407.1)