GB1582072A

GB1582072A - Position measuring instrument

Info

Publication number: GB1582072A
Application number: GB4037977A
Authority: GB
Original assignee: Teledyne Industries Inc
Current assignee: TDY Industries LLC
Priority date: 1976-12-22
Filing date: 1977-09-28
Publication date: 1980-12-31
Also published as: JPS6142201B2; DE2754500A1; DE2754500C2; JPS5380251A; GB1582073A

Description

(54) POSITION MEASURING INSTRUMENT (71) We, TELEDYNE INDUSTRIES, INC., a Corporation organized and existing under the laws of the State of California, United States of America, of 1901 Avenue of the Stars, Los Angeles, California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an instrument which measures the position of various points of interest in a three-dimensional space which includes a tube feeler which accommodates a range of different tube sizes.

U. S. patent to Eaton 3,944,798 discloses an apparatus for measuring the angles of a surface or axis of an object with respect to three reference planes. The apparatus includes a working head which may be engaged with the surface of the object being measured. The head is mounted through a series of five pivoted arms to a work table. Each joint between supporting arms has a sensor or resolver which measures the relative angular position of the arms to collectively define the position of the working head. A circuit processes the signals from the five sensors to calculate the relative position of the working head.

British patent 1,329,708, issued to McMurtry, describes a method for making a bent pipe from a master pipe based on measurements taken from the master pipe.

McMurtry shows a measuring apparatus having a sensing head for rectilinear movement in the X, Y and Z directions. McMurtry's apparatus has an arm upon which is mounted a carrier having an offset end portion. A sensing head having an outwardly opening U-shaped cross section is mounted on the offset end portion to receive the surface of the pipe. A projection of the axis of the arm intersects the axis of the sensing head at the centerline of the pipe when the surface of the pipe is in engagement with the sensing head. McMurtry obtains measurements of the centreline coordinates at two locations for each straight portion of the bent tube.

The coordinates of the point on the centerline of the straight portions of the pipe are utilized to calculate a bending program.

Eaton requires five analog sensors or resolvers to acquire sufficient information to develop a bending program. McMurtry must adjust the position of the offset end or change the axis of the sensing head to accomodate different tube diameters.

This invention provides an instrument for measuring the location of points along straight portions of a preformed tube positioned with respect to a reference point, comprising: means for providing movement along a work surface; a first arm having a first end and a second end, the first end of the first arm coupled to said means for providing movement; a second arm having a first end and a second end, the first end of the second arm coupled to the second end of the first arm; a carrier having an axis parallel to the axis of the second arm, said carrier mounted on said second arm to swivel about the second arm, said carrier having an end portion offset from the axis of the second arm;; tube feeler means mounted on the offset end portion of the carrier, the tube feeler means being movable about an axis thereof to engage the surface of a tube at opposite sides thereof so that an intersection of a projection of the axis of the second arm and the axis of the tube feeler means lies at the centerline of the tube when engaged; and means for determining the position of said intersection with respect to the reference point.

The tube feeler of the instrument preferably comprises a base, a pair of plates having tube-engaging surfaces; and means for mounting said plates on said base for movement toward and away from each other to bring said tube-engaging surfaces into contact with opposite sides of said tube, said base and plates being so related to each other that the engagement of said surfaces with the tube causes the centerline of the tube to lie at said intersection.

Embodiments to be described herein comprise tube feelers which may be mounted on the offset end portion of an apparatus for measuring points along straight portions of a preformed tube. One such tube feeler is capable of accommodating a range of tube diameters. The other such tube feeler is capable of accommodating various ranges of tube diameters. These tube feelers may be used in an instrument to be described herein or they could also be used with other types of apparatus such as that disclosed by Eaton or McMurtry, cited above.

In the instrument to be described herein, a preformed tube which is to be measured is placed on a work table. The measuring instrument has a carriage which moves linearly along an edge of the work table. A first sensor, coupled to the carriage, provides a signal indicative of the position of the carriage. A first and a second arm are coupled together and the first arm is coupled to the carriage, for pivotal movement of these arms in a vertical plane and a second and third sensor are located at the pivots.

The second and the third sensor provide signals representative of the angular position of the arms. A carrier having an offset end swivels about the axis of the second arm.

A tube feeler is mounted for rotation on the offset end portion of the carrier. A projection of the axis of the second arm and a projection of the axis of the tube feeler form an intersection. When the tube feeler is engaged with the surface of the tube, the intersection lies at a point on the center line of the tube. The intersection may be manually positioned at two points on each straight portion of the tube and the signals from the three resolvers are recorded for each point.

Two types of tube feelers may be coupled to the mount. One is a U-shaped member having two substantially parallel legs mounted for rotation on the offset end portion of the carrier to engage the surface of the tube.

The other has a pair of plates with opposed tube engaging surfaces. The plates are mounted on a base for movement toward and away from each other to contact opposite sides of the tube.

Each of the tube feelers to be described herein may be easily mounted on a variety of existing apparatus for measuring preformed tubes.

In the instrument to be described herein, each tube feeler is mounted so that the axis of the second arm intersects the axis of the tube feeler so that when the tube feeler engages the tube, the intersection of the axes lies on the centerline of the tube.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the instrument; Figure 2 is an enlarged perspective view of the instrument with a panel broken away to expose the carrier; Figure 3 is a sectional view of the instrument along line 3-3 of Figure 1; Figure 4 is an elevation of the tube feeler along line 4--4 of Figure 2; Figures 5 and 6 depict two sizes of one type of tube feeler; Figure 7 is a perspective view of the offset end portion of the apparatus shown in Figure 1 having another type of tube feeler mounted thereon; Figure 8 is an exploded perspective view of the tube feeler shown in Figure 7; Figure 9 is a cross-sectional view of the tube feeler shown in Figure 7; and Figure 10 is yet another cross-sectional view of the tube feeler shown in Figure 7.

Referring to Figure 1, the instrument 10 is shown positioned on table 12 where a preformed tube 14 is to be measured. A carriage 16, having a vertical column 18 and pivoted arms 20 and 22, moves linearly along work table 12 in housing 24. A linear sensor 25 (Figure 2) provides a signal indicative of the position of the carriage 16 along table 12. Rotary sensors 26 and 28 are mounted at the pivots of arms 20 and 22. The linear sensor 25 and the rotary sensors 26 and 28 collectively provide position information to the processor 30 by way of line 32. Carrier 34 is mounted on arm 22 for swiveling around the axis of arm 22.

The carrier 34 has an offset end portion 36 on which is rotatably mounted a U-shaped tube feeler 38. The tube feeler 38 may be rotated by knob 40 to engage selected points along tube 14. As will appear in more detail below, the axis of the arm 22 intersects the axis of the tube feeler 38, and when the tube feeler engages the surface of tube 14, the point of intersection is on the centerline of the tube. The output of the linear sensor and the two rotary sensors define the location of the intersection. Switch 44 is depressed to record signals from the sensors with which the position of the intersection is calculated.

A measuremtnt of the tube 14 will now be explained. Stands 46 and 48 support the tube 14 to provide access by the tube feeler 38. The stands are of a height sufficient to hold the tube 14 above the surface of table 12 so that the tube feeler 38 may be engaged at selected points along the tube surface.

Carrier 34 is manually positioned to the end of work table 12, and knob 40 is rotated so that the tube feeler 38 may be engaged with point 50 at the end of the tube. When the tube feeler 38 is suitably engaged with the tube 14 in a manner similar to the engagement shown in Figure 4, switch 44 is depressed and the position of the centerline of the tube is entered into processor 30. The tube feeler 38 is then moved from left to right, as shown in Figure 1, to point 52, which point is adjacent bend 54. The tube feeler 38 is again enaged against the surface of tube 14. The switch 44 is depressed for the second time to cause the recording of the position of the centerline of tube 14.

Thus, a vector representing a straight portion of the tube is established by the points 50 and 54. The tube feeler 38 is then disengaged from the surface of tube 14, repositioned and engaged at point 56, which point is adjacent bend 54. Switch 22 is depressed for a third time. The tube feeler 38 is manually positioned to the next point, point 58, along tube 14. Point 58 is adjacent bend 60. When the tube feeler 38 is suitably engaged with the surface of tube 14, switch 44 is then closed for a fourth time to enter the position of the centerline of the tube into processor 30. Manual positioning of instrument 10 is continued along the tube 14, and measurements are taken in a manner similar to that described until each straight portion of the tube 14 has been measured. The processor 30 accepts pairs of points which define the vectors that represent the straight portions of tube 14.A bending program may be established from the vector information, as in Eaton or McMurtry.

Referring to Figures 2 and 3, work table 12 is of sufficient size to accommodate various preformed tubes to be measured and has a housing 62 along the rear edge. Access to the housing may be obtained through a rear panel 64. The housing 62 encloses a track such as rails 66 and 68 which traverse the length of table 12. The rails have blocks 70 at their ends to stop the movement of carriage 72 and provide a reference for the calibration of sensor 25, as will be discussed below. Rack 74, also attached to the housing 62, extends the length of the table 12. Rack 74 engages gear 76 of linear sensor 25 causing the sensor to provide a signal indicative of the position of carriage 72 along table 12.

Column 18 is attached to the carriage 72 and projects through channel 78 of housing 62. Column 18 has an upper end 80 which receives rotary sensor 26 and arm 20. Arm 20 is pivotally attached to column 18 and provides for arcuate movement in a vertical plane, as best seen in Figure 3. Arm 20 swings in an arc 82 having a center 84. The other end of arm 20 receives a second arm 22. Arm 22 pivots about arm 20 in the same plane as arm 20 pivots with respect to column 18. Arm 22 swings in an arc 86 having a center 88 (Figure 3). Arm 22 terminates in an axially extending stud 90 having threads 92 at its end.

-Carrier 34 has an axis which is parallel to, and as shown in the figures may be coincident with, a projection of the axis of arm 22. Carrier 34 is coupled to arm 22 by stud 90. Specifically, stud 90 receives carrier 34 by collar 94 which is secured by nut 96.

The arrangement of the stud 90 and the nut 96, holding the collar 94, permits carrier 34 to swivel about the axis of arm 22. Collar 94 may include a stopping detent (not shown) to preclude rotation of carrier 34 about stud 90 in excess of 360". Carrier 34 has an offset end 36 which receives tube feeler 38. The amount of offset of carrier 34 must be sufficiently large to permit tube feeler 38 to lie within the projection of the axis of arm 22, as will be explained below.

Tube feeler 38 is coupled to the offset end 36 by shaft 98. Shaft 98 is attached to knob 40 and projects through bore 100 to receive a plate 102 on which tube feeler 38 may be mounted. Tube feeler 38 is rotatable about the axis of shaft 98 and is positioned by knob 40.

The tube feeler 38 is mounted on carrier 34 so that the projection of the axis of arm 22 intersects the axis of shaft 98. Opposing "V" recesses 104 and 106 in opposite sides of legs 108 and 110 are so located that a line between the vertices extends through the intersection of the projections of the axis of arm 22 and the axis of shaft 98. With the edges of the "V" recesses engaged with a straight portion of tube 14, the intersection lies on the tube centerline. The angle at which the sides of the "V" recesses are cut should be symmetrical with centerline 112, as shown in Figure 6. Although a variety of angles may be selected, a 45" angle frorn centerline 112 is desirable.

Tube feeler 38 may be detachably mounted on plate 102 by screws 114 and 116 through back 118. However, any suitable means of connecting tube feeler 38 to carrier 34 would be acceptable as long as the projection of shaft 98 intersects the projection of the axis of the second arm 22.

A single size tube feeler may accommodate a range of tube diameters. However, several different tube feeler sizes may be required to accommodate tube diameters of different ranges. Although the sizes of the various tube feelers may be different, each must provide for the intersection of the projection of the axis of arm 22 with the axis of shaft 98 at the centerline of the tube to be engaged. As long as this relationship is maintained, any particular size tube feeler may be employed.

To acquire an accurate bending program, it is important that sensors 25, 26 and 28 are calibrated before measurements of the tube are taken. The calibration of linear sensor 25 is effected when carriage 72 is positioned against stop 70. With the carriage in this position, the signal from sensor 25 is related to the reference position. Sensors 26 and 28 may be calibrated by engaging tube feeler 38 with reference bar 120. Specifically, tube feeler 38 may be engaged with reference bar 120, which is held in yoke 122. When tube feeler 38 is in this position, sensors 26 and 28 provide signals indicative of a reference position of arms 20 and 22. When each of the three sensors has been appropriately calibrated, the signals provided to processor 30, as collectively developed by sensors 25, 26 and 28, will denote the position of tube feeler 38.

Referring to Figure 7, another tube feeler to be employed in lieu of tube feeler 38 will now be considered. Pivot arm 20 is coupled to the vertical column (not shown) of the instrument 10 of the type shown in Figure 1. Pivoted arm 22 is coupled to arm 20, and rotary sensor 28 is mounted at the pivot.

Carrier 34 is mounted at the end of pivoted arm 22 so that it may swivel about its axis.

Carrier 34 has an offset end portion 38 of sufficient depth and length to accommodate rotatable tube feeler 124 which is shown engaging tube 14.

Tube feeler 124 is mounted for rotation on carrier 34 by shaft 126 which extends through the carrier and is retained by knob 128. Rotation of knob 128 controls the angular position of tube feeler 124 with respect to the carrier 34, as well as the position of plates 130 and 132 with respect to each other. A projection of the axis of arm 22 intersects the axis of tube feeler 124, and when plates 130 and 132 engage opposite sides of tube 14, the intersection of the axes is on the centerline of the tube 14. The outputs of the resolvers, as resolver 28, collectively define the location of the intersection and switch 44 is depressed to record the signals as described above.

The engagement of tube feeler 124 with tube 14 will now be explained. A point of interest on the tube is selected and pivot arms 20 and 22 are positioned near the point. Carrier 34 is rotated about pivot arm 22 so that the tube feeler 124 faces the tube with plates 130 and 132 spaced apart. Knob 128 is than rotated and the carrier 34 is positioned such that the tube lies between plates 130 and 132.

Base 134 of tube feeler 124 is manually restrained while knob 128 is rotated farther, thereby drawing plates 130 and 132 closer together. When plates 130 and 132 engage the opposite surface of tube 14, the base 134 no longer needs to be manually restrained. As knob 128 is rotated even farther, the plates tend to align themselves at right angles with the tube so that the edges of the plates lie flat against the opposing tube surfaces. When so engaged, the intersection of the projections of the axes of arm 22 and tube feeler 124 lies at the centerline of the tube.

Referring to Figures 8, 9 and 10, shaft 126 projects through hole 136 and offset end 36 of carrier 34. Knob 128 is attached to shaft 126 by threads 138. Disc 140 is mounted on shaft 126 so that its rear surface 142 is spaced outwardly, by a small amount, from the rear surface 144 of base 134. This spacing permits tube feeler 124 to rotate freely without interference from carrier 34. The front surface 146 of disc 140 is coincident with the inner surface 148 of base 134. Spur gear 150 is mounted against the front surface 146 of disc 140. The diameter of spur gear 150 is larger than the diameter of hole 136, so that its rear surface 152 is in engagement with inner surface 148 of base 134.

Gear teeth 154, around the perimeter of spur gear 150, engage gear teeth 156 on rack 158 and gear teeth 160 on rack 162.

Ring clamp 164 secures spur gear 150 to front surface 146 of disc 140 by screws 166 and 168 received in threaded bores 170 and 172. Shaft 126, which projects outwardly from the front surface 146 of disc 140 aligns spur gear 150 and ring clamp 164 concentric with the shaft axis. Ring clamp 164 has an outwardly extending bevel 174 around its perimeter, received in arcuate grooves 176 and 178 of retaining plates 180 and 182, respectively. Retaining plates 180 and 182 each have a spacer 184 and 186, respectively.

Retaining plates 180 and 182 are secured to inner surface 148 of base 134 by screws, as screw 188. When so secured to base 134, an upper channel 190 and a lower channel 192 are formed. The channels 190 and 192 are of sufficient width to accommodate gear teeth 156 and 160 on racks 158 and 162, respectively. The racks slide in their respective channels 190 and 192 in opposite directions as spur gear 150 rotates.

Plates 130 and 132 are coupled to racks 158 and 162 by screws 194 and 196, respectively. Plate 130 has a shank 198 and projecting therefrom is a finger 200 having a V-shaped recess 202. Similarly, plate 132 has a shank 204 and finger 206 having a V-shaped recess 208. V-shaped recesses 202 and 208 face each other. The length of shank 198 and the length of shank 204 are selected such that fingers 200 and 206 do not interfere with each other when plates 130 and 132 are drawn together, as best seen in Figure 9.

Fingers 200 and 206 must be sufficiently long to accommodate the wide range of tube diameters, and the vertices of V-shaped recesses 202 and 208 are positioned such that a line drawn between them is perpendicular to the projection of the axis of shaft 126. Although a particular angle of the V-shaped recess is not a requirement, an angle of 1200 is preferred. However, the angle of V-shaped recess 202 must be equal knob 40 or knob 128.

Various modifications to the invention will become apparent after a review of the specification. For example, the axis of the tube feeler need not be perpendicular to the axis of carrier 34. Carrier 34 could have a second offset to provide for improved access to knob or knob 128.

In our divisional application No. 21899/79 (Serial No. 1,582,073) we claim and describe an apparatus for measuring the location of a point along a straight portion of a preformed tube, said apparatus including means for mounting the tube in a known position, a member having an axis, means for positioning said member with respect to said tube, means for sensing the position of said member, and tube feeler means mounted on said member and having surfaces shaped to engage opposite sides of the tube upon positioning said member with respect to the tube and moving said tube feeler means about an axis thereof, which axis intersects a projection of said axis of said member to form an intersection therewith, wherein said intersection lies at the centerline of the tube when said surfaces engage said opposite sides of said tube.

WHAT WE CLAIM IS:- 1. An instrument for measuring the location of points along straight portions of a preformed tube positioned with respect to a reference point, comprising: means for providing movement along a work surface; a first arm having a first end and a second end, the first end of the first arm coupled to said means for providing movement; a second arm having a first end and a second end, the first end of the second arm coupled to the second end of the first arm; a carrier having an axis parallel to the axis of the second arm, said carrier mounted on said second arm to swivel about the second arm, said carrier having an end portion offset from the axis of the second arm;; tube feeler means mounted on the offset end portion of the carrier, the tube feeler means being movable about an axis thereof to engage the surface of a tube at opposite sides thereof so that an intersection of a projection of the axis of the second arm and the axis of the tube feeler means lies at the centerline of the tube when engaged; and means for determining the position of said intersection with respect to the reference point.

2. The instrument of claim 1 wherein the tube feeler means is an outwardly opening U-shaped member, rotatable about said axis of the tube feeler means and having a first and a second leg and "V" recesses on the first and second legs, a line between the vertices of the "V" recesses being intersected by the projections of the axis of the second arm and the axis of the tube feeler means.

3. The instrument of claim 1 wherein the tube feeler means includes: a base; a pair of plates having tube-engaging surfaces; and means for mounting said plates on said base for movement toward and away from each other to bring said tube-engaging surfaces into contact with opposite sides of said tube, said base and plates being so related to each other that the engagement of said surfaces with the tube causes the centerline of the tube to lie at said intersection.

4. The instrument of claim 3 further including: means for coordinating the movement of the pair of plates so that said intersection is always midway between tube-engaging surfaces.

5. The instrument of claim 3 further including: means for rotating said tube feeler means about the axis of the tube feeler means.

6. The instrument of claim 3 wherein the tube-engaging surfaces are V-shaped recesses in the pair of plates.

7. The instrument of claim 6 wherein a line drawn between the vertices of the V-shaped recesses intersects the intersection of the projection of the axes.

8. The instrument of claim 3 further including: a spur gear mounted for rotation in the base; and rack means mounted on the plates and engageable with the spur gear so that rotation of the spur gear relative to the rack means causes the plates to move.

9. The instrument of claim 8 wherein the spur gear is so positioned with respect to the rack means that rotation of the spur gear relative to the rack means causes the plates to move in equal and opposite directions.

10. The instrument of claim 8 wherein the tube-engaging surfaces of the pair of plates are substantially parallel to each other.

11. The instrument of claim 3 wherein the pair of plates is mounted perpendicular to the base.

12. The instrument of claim 1, substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Various modifications to the invention will become apparent after a review of the specification. For example, the axis of the tube feeler need not be perpendicular to the axis of carrier 34. Carrier 34 could have a second offset to provide for improved access to knob or knob 128. In our divisional application No. 21899/79 (Serial No. 1,582,073) we claim and describe an apparatus for measuring the location of a point along a straight portion of a preformed tube, said apparatus including means for mounting the tube in a known position, a member having an axis, means for positioning said member with respect to said tube, means for sensing the position of said member, and tube feeler means mounted on said member and having surfaces shaped to engage opposite sides of the tube upon positioning said member with respect to the tube and moving said tube feeler means about an axis thereof, which axis intersects a projection of said axis of said member to form an intersection therewith, wherein said intersection lies at the centerline of the tube when said surfaces engage said opposite sides of said tube. WHAT WE CLAIM IS:-

1. An instrument for measuring the location of points along straight portions of a preformed tube positioned with respect to a reference point, comprising: means for providing movement along a work surface; a first arm having a first end and a second end, the first end of the first arm coupled to said means for providing movement; a second arm having a first end and a second end, the first end of the second arm coupled to the second end of the first arm; a carrier having an axis parallel to the axis of the second arm, said carrier mounted on said second arm to swivel about the second arm, said carrier having an end portion offset from the axis of the second arm;; tube feeler means mounted on the offset end portion of the carrier, the tube feeler means being movable about an axis thereof to engage the surface of a tube at opposite sides thereof so that an intersection of a projection of the axis of the second arm and the axis of the tube feeler means lies at the centerline of the tube when engaged; and means for determining the position of said intersection with respect to the reference point.