US3725948A

US3725948A - Scratch strain recorder

Info

Publication number: US3725948A
Application number: US00157187A
Authority: US
Inventors: R Prewitt; V Schmidt; E Schmidt
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-06-28
Filing date: 1971-06-28
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

A scratch strain gauge has an annular target guided into its recording position where it cooperates with a scratch element on a scratch arm to indicate strains of opposite senses. The gauge has a guide adjacent one edge of a plate on which rollers are mounted for rotatably mounting the target in cooperation with brushes. The guide cooperates with a groove in the periphery of the target to insure that the groove receives one of the rollers, then the brushes, and finally the other roller as the target is inserted into its recording position. Ears, which are disposed above the rollers and extend outwardly beyond the rollers to overlie portions of the target when the target is in its recording position, aid in insuring that the target is seated on the roller tongues when disposed in its recording position.

Description

- United States WEE? [1 1 Prewitt et al.

[54] SCRATCH STRAIN RECORDER 22 Filed: June 28,1971 21 Appl.No.: 157,187

[52] U.S. Cl. ...346/77, 346/124, 346/137 [51] Int. Cl. ..G01d 115/02 [58] Field of Search ..346/7, 77 R, 124, 137;

[56] References Cited UNITED STATES PATENTS Prewitt et al ....73/88 R 2/1969 Prewitt et al. ..346/7 51 Apr.3,1973

Primary Exa miner.loseph W. l-lartary AttorneyFrank C. Leach, Jr.

[57] ABSTRACT scratch element on a scratch arm to indicate strains of opposite senses. The gauge has a guide adjacent one edge of a plate on which rollers are mounted for rotatably mounting the target in cooperation with brushes. The guide cooperates with a groove in the periphery of the target to insure that the groove receives one of the rollers, then the brushes, and finally the other roller as the target is inserted into its recording position. Ears, which are disposed above the rollers and extend outwardly beyond the rollers to overlie portions of the target when the target is in its recording position, aid in insuring that the target is seated on the roller tongues when disposed in its recording position.

14 Claims, 4 Drawing Figures PATENTEDAPR3 1975 INVENTORS RICHARD H. PREWITT ERICH A. SCHMIDT VOLKER SCHMlDT ATTORNEY SCRATCH STRAIN RECORDER In U.S. Pat. No. 3,430,250 to Richard H. Prewitt et al, there is shown a scratch strain recorder or gauge in which the target is rotatably mounted on a pair of rollers and two brushes and is rotated in only one direction is response to strains of one sense of a work to which the gauge is attached at two spaced areas. Strains in each sense are recorded on the target by a scratch arm, which is mounted on a plate secured to a different area of work than a plate supporting the rollers.

Under certain conditions, difficulty is sometimes encountered in inserting the target so that a groove in the periphery of the target receives the wires of the two brushes and the rollers to rotatably mount the target. This problem is usually encountered when the gauge is mounted in a relatively inaccessible position so that the user cannot see the relationship of the target groove, roller, and brush wires during the insertion of the target into its recording position.

Therefore, when inserting the target, it is necessary for the groove to receive the rollers, a first group of wires, which form a brush to prevent rotation of the target in one direction, and a second group of wires, which form a brush to cause rotation of the target in the opposite direction in response to strains of one sense on the work. If these wires fail to enter the groove, the tar-' get may not rotate as desired even though the rollers are disposed in the groove.

Additionally, if the target is not properly positioned in its recording position so that the wires are unable to enter the groove of the target, the possibility exists that the wires may become separated from each other and damaged sufficiently. As a result, the first group of wires will not engage the base of the groove to prevent rotation of the target in one direction and can create excessive friction because of their friction against the periphery of the target, and the second group may not have sufficient force to advance the target in the opposite direction when thework is subjected to strains in one sense due to the reduced number of wires engaging the base of the groove and the additional drag from the displaced wires at the periphery of the target.

The scratch strain gauge of the present invention is an improvement of the scratch strain gauge of the aforesaid Prewitt et al patent by satisfactorily solving the foregoing problems whenever they occur. The present invention enables one to insert the target into its recording position without having to visibly view whether the groove of the target is disposed in a plane so as to receive the rollers. The present invention also satisfactorily solves the problem of the wires inadvertently not entering the groove in the target since the present invention insures that the groove in the target is positioned in a plane to initially receive one of the rollers and a target groove guide whereby it is positioned to receive the wires as the target is advanced to its recording position since the wires are in the same plane as the rollers and the target groove guide. The present invention also permits the replacement of the target in a cold climate where it is necessary to wear heavy gloves.

When the scratch strain gauge of the aforesaid Prewitt et al patent is disposed in an inaccessible position insofar as the user being able to view the position of the target, it is possible for the user to insert the target with sufficient force that he would displace the target beyond its recording position. To prevent this from occurring, the present invention employs a stop for preventing the target from being advanced beyond the recording position during insertion of the target.

Under some conditions such as when used on an aircraft, for example, the target of the scratch strain gauge of the aforesaid Prewitt et al patent may vibrate when in its recording position because of the vibrations of the work to which the gauge is attached. The present invention satisfactorily solves this problem by providing means to prevent vibration of the target when the target is disposed in its recording position.

When inserting the target into its recording position in the scratch strain gauge of the aforesaid Prewitt et al patent, the possibility exists that the scratch arms pointed element, which engages the upper surface of the target to form the scratches thereon, will scratch the upper surface of the target during insertion of the target into its recording position. Furthermore, the pointed element of the scratch arm may be damaged when it comes against the outer upper surface of the target during insertion of the target into its recording position. Accordingly, the present invention has a unique arrangement for preventing the pointed element of the scratch arm from engaging the upper surface of the target during insertion of the target into its recording position.

- With the present invention, the group of wires, which rotate the target when the work is subjected to strains of one sense, could be inadvertently withdrawn from a support, which holds the wires close together adjacent the target and is integral with the target groove guide, prior to mounting the gauge on the work, since the support is on one plate and the wires are connected to the other plate. The two plates of the scratch strain gauge are movable relative to each other until mounted on two spaced areas of the work that has strains which it is desired to record. The present invention prevents this from occurring by having means to limit the amount of relative longitudinal movement between the two plates when they are not attached to two spaced areas of the work. Accordingly, the group of wires, which rotate the target in response to strains of one sense on the work, cannot easily be removed to a position in which they would not be supported by the support. However, if desired, the two plates can be separated by rotating the plate, which has the rotating group of wires connected thereto, while moving the two plates relative to each other so that the limit means are rendered ineffective.

An object of this invention is to provide an improved scratch strain recorder.

Another object of this invention is to provide a scratch strain recorder in which the target is always properly inserted into its recording position.

A further object of this invention is to provide a scratch strain recorder'in which the target does not vibrate.

Still another object of this invention is to provide a scratch strain recorder in which the target is not scratched by the scratch means during insertion of the target to its recording position or removal of the target from its recording position.

A still further object of this invention is to permit target insertion without having to manually lift the scratch arm. r

Other objects of this invention will be readily perceived from the following description, claims, and drawing.

This invention relates to an improvement in a recording instrument comprising first and second support means with scratch means mounted on the first support means. A target, which records motions in opposite senses by scratches formed on the target due to movement of the scratch means, is rotatably mounted on the second support means. The target has a groove formed in its periphery with one of the opposite walls of the groove being engaged by rotatably mounted means, which are supported on the second support means, to rotatably support the target. The first support means has means connected thereto to engage the base of the groove to rotate the target, which is removably mounted on the rotatably mounted means, in response to motions in one of the senses only. The improvement includes means supported on the second support means and cooperating with the target during insertion of the target into its recording position to dispose the groove of the target to receive the rotatably mounted means and the base engaging means.

The attached drawing illustrates a preferred embodiment of the invention, in which:

FIG. 1 is a top plan view of the scratch strain recorder of the present invention;

FIG. 2 is a fragmentary plan view of a portion of the recorder of FIG. 1 with the target partially inserted;

FIG. 3 is a side elevational view of a portion of the scratch strain recorder of FIG. 1; and

FIG. 4 is a side elevational view of a guide utilized with the gauge of FIG. 1.

Referring to the drawing and particularly FIG; 1, there is shown a scratch strain gauge of the present invention having an elongated base plate and an end base'plate 11, which is spaced from the base plate 10. Each of the base plates 10 and 11 is relatively thin and may be formed of any suitable material.

The base plate 10 has a lip 12 on its end, which is remote from the end base plate 11. The lip 12 is adapted to be secured to an area of a work or part that is to have its :strains recorded by the scratch strain gauge of the present invention in the manner more particularly shown and described in the aforesaid Prewitt et al patent. The end base plate 11 is adapted to be secured to a second area of the same work or part in the manner more particularly shown and described in the aforesaid Prewitt et al patent. The two areas are longitudinally spaced from each other.

The elongated base plate 10 supports an annular member 16, which functions as the target of the scratch strain gauge of the present invention. The annular member 16- has a continuous groove 17 formed in its periphery to receive a pair. of rollers 18, which are rotatably mounted on the base plate 10 adjacent opposite edges thereof.

Each of the rollers 18 has an enlarged central portion 19 (see FIG. 3), which abuts against one of

opposite side walls

20 and 21 of the groove 17 in the annular I member 16. The periphery of the annular member 16 has an upper portion 22, which is above the groove 17, engaging an upper circular portion 23 of each of the rollers 18. The periphery of the annular member 16 also has a lower portion 24, which is below the groove 17, bearing against a lower circular portion 25 of each of the rollers 18.

The rollers 18 are mounted with respect to the annular member 16 so that the enlarged central portion 19 of the roller 18 does not extend into the groove 17 to engage its base or bottom 26. Thus, friction between the rollers 18 and the annular member 16 is reduced to permit easier rotation of the annular member 16. Furthermore, the engagement between the

circular portions

23 and 25 of each of the rollers 18 and the portions 22 and 24 of the periphery of the annular member 16 minimizes any friction on the upper or lower surface of the annular member 16 due to mounting thereof. Accordingly, the rotatable mounting of the annular member 16 by the rollers 18 is a substantially friction-free mounting.

Each of the rollers 18 is rotatably mounted on a shaft 27, which has its lower end fixed to the base plate 10. The upper end of each of the shafts 27 is fixed to an ear 28, which is formed by bending a portion of the base plate 10 adjacent the lip 12.

The annular member 16 is held against clockwise (as viewed in FIG. 1) rotation by a retaining or holding means. The retaining or holding means comprises one or more relatively thin members or elements 29, which are adapted to engage against the base or bottom 26 of the groove 17. The members 29 may be formed of any suitable material as long as the edges, which engage the bottom or base 26 of the groove 17 in the annular member 16, are sharp. As an example, the member 29 could be a wire formed of metal and have its end ground or could be formed of glass fiber and have its end broken to provide the sharp edge.

The members 29 pass through a tubular member 30, which is secured to the base plate 10, and are secured to a tubular member 31 intermediate the ends of the members 29. The members 29 also extend through a tubular member 32, which also is supported by the base plate 10.

If the members 29 are metal wires, they could be secured to the tubular member 31 by soldering or.

crimping, for example. If the members 29 are glass fiber, they could be secured to the tubular member 31 by a suitable adhesive or crimping, for example. The tubular members 30 and 32 are fixed to the upper surface of the base plate 10 by suitable means such as soldering or welding, for example.

The scratch means for forming the scratches on the upper surface of the annular member 16, which is the target, includes an am 33 having one end fixed to the end base plate 1 l. The arm 33 has a pointed element 34 at its end, which is remote from the end base plate 11, for forming the scratches on the upper surface of the annular member 16. The pointed element 34 extends downwardly from the lower surface of the arm 33, which overlies the annular member 16, and is urged downwardly against the annular member 16 due to the flexing force of the arm 33. g

Accordingly, each time that there is relative motion between the areas of the work, there is relative motion between the base plate 10 and the end base plate 11 so as to cause the pointed element 34 to form a scratch on the upper surface of the annular member 16. It should 34 must be capable of scratching the upper surface of the annular member 16. Furthermore, if the base plate l0 and the arm 33 are made of materials having the same rate of thermal expansion, they will not adversely affect final results when auxiliary plates of the same material as that of. the structure being recorded are added underneath the plates and 11 and attached thereto at the adjacent edges of the two plates 10 and The annular member 16 is rotated in a counterclockwise direction by a driving means. The driving means includes a plurality of relative thin members or elements 35, which have their edges sharpened to engage the bottom or base 26 of the groove 17 in the same manner as the members 29. The embers 35 are preferably formed of the same material as the members 29. It should be understood that the

members

29 and 35 are of a harder material than the annular member 16 so that the edges of the

members

29 and 35 bite into the bottom or base 26 of the groove 17 in the manner more particularly shown in the aforesaid Prewitt et al member31.

The members 35 extend through a curved tubular member 37, which is fixed to the upper surface of the base plate 10 by suitable means such as welding or soldering, for example. The ends of the members 35 extend through an opening 38 (see FIGS. 1 and 4) in a support 39. The support 39 includes a U-shaped member 40, which has one leg secured to the base plate 10 and its other leg held in spaced relation by a spacer 41 (see FIG. 4). The spacer 41 cooperates with a guide element 42 on the support 39 to form the opening 38 and has the members 35 bear thereagainst.

As a result, the 'members 35 are guided, in cooperation with the tubular member 37, so that they are retained in positive engagement withthe base or bottom 26 of the groove 17. The tubular member 37 serves to hold the members 35 in a close relation to each other while the edge of the spacer 41 insures that the members 35 have positive engagement with the base or bottom 26 of the groove 17. This insures that the annular member 16 rotates counterclockwise (as viewed in FIG. 1) during each movement of the end base plate 1 1 toward the base plate 10.

As shown in FIGS. 3 and 4, the guide element 42 has a protruding portion 43, which extends beyond the U- shaped member 40 and is thinner than the groove 17 in the annular member 16. The portion 43, which is slightly thicker than the remainder of the guide element 42, is disposed in the same plane as the enlarged central portion l9'of each of the rollers 18.

Each of the ears 28 extends beyond the enlarged central portion 19 of the rollers 18 as shown in FIG. 1. Each of the ears 28 has a sufficient length to overlie a portion of the annular member 16 when the annular 7 member 16 is in its recording position as shown in FIG. 1.

As shown in FIG. 3, the bottom surfaces of the ears 28 are so disposed with respect to the enlarged central portion 19 of each of the rollers 18 that the annular member 16 cannot be inserted between the roller 18 and the portion 43 of the guide element 42 without the groove 17 of the annular member 16 receiving the enlarged central portion. 19 of the roller 18 and the portion 43 of the guide element 42.

Accordingly, the portion 43 of the guide element 42 insures that the annular member 16 is raised sufficiently with respect to the base plate 10 so that the groove 17 of the annular member 16 can receive the enlarged central portion 19 of the roller 18, which is adjacent the edge of the base plate 10 over which the annular member 16 is passed in being inserted into its recording position. At the same time, the ear 28 insures that the annular member 16 cannot be disposed so high that the groove 17 of the annular member 16 will not receive the enlarged central portion 19 of the roller 18. Thus, the present invention insures that the annular member 16 cannot be inserted too high or too low with respect to the rollers 18 whereby the annular member 16 is disposed in its recording position and is rotatably mounted.

Because of the portion 43 of the guide element 42 raising the annular member 16 with respect to the base plate 10, the groove 17 is so positioned that it could engage the scratch arm 33. Accordingly, the scratch arm 33 has a raised portion or lip 43 for cooperation with the upper surface of the annular member 16 so. that the scratch arm 33 is lifted slightly as .the annular member 16 is advanced to its recording position. This camming of the scratch arm 33 by the annular member 16 prevents the scratch arm 33 from engaging the groove 17 of the annularmember 16.

As the annular member 16 is advanced to its recording position, the relative movement between the annular member 16 and the pointed element 34 of the arm 33 could result in scratches appearing on the upper surface of the annular member 16. This would result in a waste of a portion of the available recording surface of the annular member 16 or misleading information.

' Accordingly, the arm 33 has a protrusion 44 extending downwardly from its lower surface for engagement with the upper surface of the annular member 16 as the. annular member 16 is inserted into its recording position. As shown in FIG. 1, the protrusion 44 is supported on the arm 33 at a position in which it will not engage the annular member 16 when the annular member 16 is in its recording position. Thus, the pointed element 34 of the arm 33 engages the upper surface of the annular member 16 when the annular member '16 is in its recording position.

When the annular member 16 .is inserted into its recording position, the user could exert a sufficient force on the annular member 16 to push it beyond its recording position. This would primarily be whenever the scratch strain gauge is mounted in a position in which the user cannot view the scratch strain gauge.

Accordingly, the base plate 10 has a projection 45 extending upwardly therefrom by bending a portion of the base plate 10 upwardly. The projection 45 limits the amount of advancement of the annular member 16. When the annular member 16 is in its recording position, the annular member 16 is slightly spaced from the projection 45 as shown in FIG. 1. This is accomplished because of the forces of the members 35 and the members 29 on the annular member 16. These have sufficient resiliency to return the annular member 16 to the position of FIG. 1 if the annular member 16 should be advanced to the position in which it engages the projection 45 on the base plate 10.

As shown in FIGS. 1 and 4, the members 29 also extend through the opening 38 in the support 39 and bear against an inclined edge of the guide element 42. While the members 29 function to prevent rotation of the annular member 16 in a clockwise direction, the members 29 also may be employed to manually advance the antion 46 extending slightly upwardly from its upper surface. The projection 46 will not engage the bottom surface of the annular member 16 as long as there is no vibration of the work since the base plate is sufficiently spaced from the annular member 16. However, if vibration of the work is transmitted through the base plate 10, the projection '46 functions to prevent vibrations of the annular member 16. v

The arm 33 has an opening or window 47 (see FIG. 2) through which the user may view the members 29 and the members 35. This enables one to ascertain whetherthe

members

29 and 35 are in engagement with the annular member 16.

Since the base plate 10 and the end base plate 11 are movable relative tov each other until they are fixed to spaced areas of the work, the end base plate 11 could be moved sufficiently relative to the base plate 10 so that the members 35 could cease to be disposed within the opening 38. To prevent this, the arm 33 has an upwardly extending projection 48 for cooperation with an ear'49, which is formed by bending theportion of the base plate 10 at its end adjacent the end base plate 11. When the projection 48 engages the ear 49, no further longitudinal separation of the end base plate 11 from the base plate 10 can readilyoccur. With the projection 48 engaging the ear 49, the members 35 still extend through the opening 38. However, if desired, the end .base plate 11 can be separated from the base plate 10 by rotating the end base plate 11 counterclockwise while separating the two plates 10 and 11.

To insert the annular member 16 into its recording position, the annular'member 16 is advanced beneath the ear 28 so that the groove 17 of the annular member With the annular member 16 in the position of FIG. 2, the

members

29 and 35, which are held in the same plane as the portion 43 of the guide element 42, are disposed in the groove 17 in the annular member 16. Thus, the annular member 16 is positioned to receive the

members

29 and 35 in the groove 17.

As the annular member 16 continues to be advanced from the position of FIG. 2 to the position of FIG. 1, the lip 43 of the arm 33 and the protrusion 44 combine to lift the pointed element 34 of the arm 33 so that it does not engage the upper surface of the annular member 16 as the annular member 16 progresses to its recording position of FIG. 1. The spring forces of the members 29 and 35.cooperate to act against the bottom or base 26 of the groove 17 to push the annular member 16 to the recording position of FIG. 1. That is, the

members

29 and 35 urge the annular member 16 to the position of FIG. 1 in which the other of the rollers 18 has the enlarged central portion 19 also disposed within the groove 17 in the annular member 16.

As previously mentioned, if the user should exert too great a force on the annular member 16 as it is being inserted, the annular member 16 would advance until it engages the projection 45. Upon release of the annular member 16 by the person who is inserting the annular member 16, the forces of the

members

29 and 35 in combination with the forces exerted by the rollers 18 will move the annular member 16 to its recording position of FIG. 1.

The annular member 16 is removed from its recording position by moving the annular member 16 in the opposite direction to that in which it was inserted. As the annular member 16 is removed, the protrusion 44 on the arm 33 again lifts the pointed element 34 on the arm 33 so that scratching of the upper surface of the clockwise manually whenever-it is desired by merely moving the tubularmember 31 until it engages the tubular member 30. This will produce a slight counterclockwise rotation of theannular member 16.

It should be understood that this invention is suitable as a recording transducer for recording temperature, acceleration, pressure, and the like in the same manner as the recorder of the aforesaid Prewitt et al patent.

An advantage of this invention is that the target can be properly positioned at its recording position even when the user cannot see the gauge in which the target is to be disposed. Another advantage of thisjnvention is that there is no inadvertent scratching of the recording surface of the target during insertion of thetarget to its 16 receives the portion 43 of the guide element 42 and the enlarged central portion 19 of the roller 18 over which the ear 28 is positioned. Since the portion 43 of I the guide element 42 is spaced from the enlarged cenv groove 17 and lesser than the diameter of the annular member 16, the annular member 16 is easily positioned as shown in FIG. 2.

modifications in the arrangement and construction of A r the parts thereof may be resorted to without departing from the spirit and scope of the invention.

We claim:

1. A recording instrument comprising first and second support means, scratch means mounted on said first support means, a target for recording motions in opposite senses by scratches formed on said target due to movement of said scratch means, said target being rotatably mounted on said second support means, said target having a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including:

means supported on said second support means and cooperating with said target during insertion of said target into its recording position to dispose said groove of said target to receive said rotatably mounted means and said base engaging means, and said target cooperating means being disposed to cooperate with said target during insertion of .said target into its recording position and to not cooperate with said target when said target is in its recording position.

2. The improvement according to claim 1 in which said rotatably mounted means comprises a pair of rollers rotatably mounted on said second support means, each of said rollers engages one of the opposite walls of said groove to rotatably mount said target, said target in circular, said target cooperating means includes means positioned in substantially the same plane as the portion of each of said rollers that engages one of the opposite walls of said groove, and said positioned means is disposed from one of said rollers a distance greater than the diameter of said base of said groove and lesser than the diameter of said target.

3. The improvement according to claim 2 including means disposed above each of said rollers to cooperate with said target during its insertion into its recording position to prevent said groove of said target from being positioned above said positioned means.

4. The improvement according to claim 3 in which each of said disposed means includes a member extending beyond the periphery of said roller so as to overlie a having a guide disposed in the same plane as said rollers so that said guide enters said groove when said target is inserted between one of said rollers and said guide for disposition of said target in its recording position, and said guide being disposed from said one roller a distance greater than the diameter of said base of said groove and lesser than the diameter of said target.

6. The improvement according to claim 1 in which said base engaging means includes a'plurality of elements; first means cooperating with said elements to hold said'elements together; second means, separate from said first element cooperating means, cooperating with said elements to insure that said elements engage the base of said groove; and said first and second element cooperating means being supported on said second support means and said second element cooperating means being disposed adjacent said target and closer to said target than said first element cooperating means. I

7. The improvement according to claim 6 in which said second element cooperating means and said target cooperating means are integral.

8. The improvement according to claim 1 in which said target cooperating means includes means positioned in the same plane as said rotatably mounted means that engages one of 'the opposite walls of said groove.

9. The improvement according to claim 1 including means, separate from said target cooperating means, cooperating with said. target to prevent vibration thereof when said target is in its recording position and said first and second support means are secured to spaced areas of a work susceptible to motions in opposite senses.

10. The improvement according to claim 1 in which said scratch means has means to prevent said scratch means from forming scratches on said target during insertion of said target into its recording position or removal of said target from its recording position.-

11. The improvement according to claim 1 in which said scratch means has means cooperating with said target to automatically lift said scratch means above said target during insertion of said target into its target having a groove fonned in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including:

means cooperating with said target to prevent vibration thereof when said target is in its recording position and said first and second support means are secured to spaced areas of a work susceptible to motions in opposite senses.

13. A recording instrument comprising first and second support means, scratch means mounted on said first support means, a target for recording motions in opposite senses by scratches formed on said target due to movement of said scratch means, said target being rotatably mounted on said second support means, said target having a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected tosaid first support meansand engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the imtarget having'a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including:

said scratch means having means cooperating with said target to automatically lift said scratch means above said target during insertion of said target into its recording position.

Claims

1. A recording instrument comprising first and second support means, scratch means mounted on said first support means, a target for recording motions in opposite senses by scratches formed on said target due to movement of said scratch means, said target being rotatably mounted on said second support means, said target having a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including: means supported on said second support means and cooperating with said target during insertion of said target into its recording position to dispose said groove of said target to receive said rotatably mounted means and said base engaging means, and said target cooperating means being disposed to cooperate with said target during insertion of said target into its recording position and to not cooperate with said target when said target is in its recording position.

4. The improvement according to claim 3 in which each of said disposed means includes a member extending beyond the periphery of said roller so as to overlie a portion of said target when said target is in its recording position.

5. The improvement according to claim 1 in which said rotatably mounted means comprises a pair of rollers rotatably mounted on said second support means, each of said rollers engages one of the opposite walls of said groove to rotatably mount said target, said target is circular, said target cooperating means includes a member supported on said second support means and having a guide disposed in the same plane as said rollers so that said guide enters said groove when said target is inserted between one of said rollers and said guide for disposition of said target in its recording position, and said guide being disposed from said one roller a distance greater than the diameter of said base of said groove and lesser than the diameter of said target.

6. The improvement according to claim 1 in which said base engaging means includes a plurality of elements; first means cooperating with said elements to hold said elements together; second means, separate from said first element cooperating means, cooperating with said elements to insure that said elements engage the base of said groove; and said first and second element cooperating means being supported on said second support means and said second element cooperating means being disposed adjacent said target and closer to said target than said first element cooperating means.

8. The improvement according to claim 1 in which said target cooperating means includes means positioned in the same plane as said rotatably mounted means that engages one of the opposite walls of said groove.

9. The improvement according to claim 1 including means, separate from said target cooperating means, cooperating with said target to prevent vibration thereof when said target is in its recording position and said first and second support means are secured to spaced areas of a work susceptible to motions in opposite senses.

10. The improvement according to claim 1 in which said scratch means has means to prevent said scratch means from forming scratches on said target during insertion of said target into its recording position or removal of said target from its recording position.

11. The improvement according to claim 1 in which said scratch means has means cooperating with said target to automatically lift said scratch means above said target during insertion of said target into its recording position.

12. A recording instrument comprising first and second support means, scratch means mounted on said first support means, a target for recording motions in opposite senses by scratches formed on said target due to movement of said scratch means, said target being rotatably mounted on said second support means, said target having a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including: means cooperating with said target to prevent vibration thereof when said target is in its recording position and said first and second support means are secured to spaced areas of a work susceptible to motions in opposite senses.

13. A recording instrument comprising first and second support means, scratch means mounted on said first support means, a target for recording motions in opposite senses by scratches formed on said target due to movement of said scratch means, said target being rotatably mounted on said second support means, said target having a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including: said scratch means having means to prevent said scratch means from forming scratches on said target during insertion of said target into its recording position or removal of said target from its recording position.

14. A recording instrument comprising first and second support means, scratch means mounted on said first support means, a target for recording motions in opposite senses by scratches formed on said target due to movement of said scratch means, said target being rotatably mounted on said second support means, said target having a groove formed in its periphery, means rotatably mounted on said second support means and engaging one of the opposite walls of said groove to rotatably support said target, means connected to said first support means and engaging the base of said groove to rotate said target in response to motions in one of the senses only, said target being removably mounted on said rotatably mounted means, the improvement including: said scratch means having means cooperating with said target to automatically lift said scratch means above said target during insertion of said target into its recording posItion.