US2768446A - Caliper - Google Patents

Description

W. O. GORR Oct. 30, 1956 CALIPER Filed Feb. 20, 1956 INVENTOR. III/ALTER a Geek,

United States Patent 9 'CALIPER Walter O. Gorr, Tujunga, Calif.

Application February 20, 1956, Serial No. 566,670

8 Claims. (Cl. 33-148) This invention relates to new and improved calipers, and more specifically to calipers utilizing a dial having a series of graduations marked thereon which are equally spaced from one another.

Any calipers, to be satisfactory for routine machine shop use, must be accurate and easy to use. Further, they must be capable of being manufactured by routine mass production techniques so as to be readily available at a comparatively low cost. Also, they must be of relatively small construction utilizing a minimum of externally exposed parts so as to avoid difficulties in handling and danger of damage to the exposed parts. A broad general object of this invention is to provide calipers having all of these characteristics,

A more specific object of this invention is to provide calipers of the class described having a fixed leg upon which there is pivotally mounted a movable leg so that, as the movable leg is moved with respect to the fixed leg, a small rack operatively attached to the movable leg within a dial is caused to actuate various readout means to indicate the distance between the ends of the two legs. Since, as the ends of a fixed and movable leg of this category are moved apart the distance between these two ends does not vary linearly with the amount of rotation, it is necessary with the calipers of this invention to pivotally mount the rack used in such a manner that the position of the rack during movement of the movable leg varies with respect to the movable leg so as to correspond to the amount of rotation of the movable leg if the device is to be linearly graduated.

This concept involved in this invention is difiicult to completely understand although it is comparatively simple. To illustrate it one may refer to the circumstance where two rods of equal length are placed together and pivotally connected between their ends in such a manner that they can be rotated. When the ends of such rods are moved apart the distance between these ends in effect constitutes a chord of a circle. From a consideration of basic geometry it will be realized that the length of such a chord is not linearly related to the amount of rotation of the two rods. However, it will also be noted from a consideration of the geometry involved that the distances between the two adjacent ends of the rods on either side of the pivot point remain proportional to one another at all times irregardless of the amount of rotation. This fact is made use of with this invention so as to permit the use of a uniformly graduated dial by employing a rack pivotally connected to a movable leg'as indicated in such a manner that this rack constantly is in a position corresponding to a chord which is proportional to the distance between the ends of a fixed and a movable leg.

By making a caliper of the general category indicated in p the preceding paragraphs it is possible to have a device which is relatively simple to manufacture and assemble and which is highly accurate, and yet which is compact and rugged enough to be generally acceptable.

Because of the nature of this invention it is not deemed desirable and necessary to set forth a long list of addi- 2,768,445 Patented Oct. 30, 1956 tional objects and advantages of it. Such items will be readily apparent to those skilled in the art to which this specification is directed from a detailed consideration of the remainder of this specification, the appended claims, and the accompanying drawings in which:

Fig. 1 is a top elevational view of a caliper of this invention, this view being partially in section;

Fig. 2 is a rear elevational view of part of the caliper shown in Fig. 1;

Fig. 3 is a cross sectional view taken at line 33 of Fig. 1 of the drawings;

Fig. 4 is a cross sectional view taken at line 4-4 of Fig. 3 of the drawings;

Fig. 5 is a cross sectional view taken at line 55 of Fig. 3 of the drawings;

Fig. 6 is a detailed, expanded view of part of the rack structure employed; and

Fig. 7 is a detailed, expanded view of the readout means utilized.

in all figures of the drawings like numerals are used to indicate like parts. While the accompanying drawings show an actual, preferred embodiment of the invention it is to be understood that the invention itself is not to be limited to the precise construction illustrated inasmuch as a number of different modifications may be made withoutdeparting from the essential features of the invention as defined by the appended claims.

These claims are considered to define the actual subject matter of this invention in detail. For purposes of understanding the invention it may be stated by way of summary that the invention concerns calipers, each of which employs a fixed leg, a movable leg pivotally attached to the fixed leg, a housing secured to the fixed leg at the point of attachment of the movable leg thereto, means attached to the movable leg so as to rotate Within said housing when the movable leg is rotated with respect to the fixed leg, a rack pivotally mounted within said housing on said means, and readout means including a uniformly graduated dial positioned within said housing so as to be engaged by said rack and actuated by said rack when the movable leg is rotated with respect to the fixed leg.

In the drawings there is shown a caliper 10 of this invention which includes a fixed leg 12 having a handle 14 extending therefrom at an obtuse angle. A movable leg 16, also having a handle 18 extending therefrom at an obtuse angle, is pivotally connected by means of a shaft 20 to the fixed leg 12 underneath a housing 22. Part of the handle 14 is carried on a support 24 on the bottom of the housing 22 in such a manner that the housing 22 is in effect fixed or secured to the fixed leg 12. The shaft 20 is constructed as indicated in Fig. 5 of the drawings so as to include a peripheral groove 26 within which the movable leg 16 is connected to this shaft 20. As will be noted the fixed leg 12 also passes through this groove 26.

The shaft 2% projects through a circular opening 28 in the housing 22, and is held in this position by an internal flange 30. From the shaft 20 there projects a small threaded stud 32 which is adapted to carry a cylindrical retainer 34 having an internal threaded opening 36 formed therein. This retainer is used to hold a generally V-shaped plate 33 against the end of the shaft 20 within the housing 22 so that whenever the movable leg 16 is rotated with respect to the fixed leg 12 this plate is rotated through an angle of the same number of degrees. The plate itself is formed with a hole 40 fitting over the stud 32 and with an upstanding projection 42 which is designed to engage one end of a strip 44 of spring steel. The other end of this strip is held against a brace 46, and the strip itself is bent around the retainer 34 so as to normally urge the plate 38 toward a and 16 are against one another.

In one end of the plate 38 there is formed a slot 48 as shown in Fig. 6 of the drawings. There is also formed in this end a threaded hole 50 which is designed to receive a small screw 52 in order to pivotally mount a rack 54 by engagement of this screw 52 with another threaded hole 56 on the rack. The rack 54 is positioned so as to pass through the slot 48. The rack itself is formed so that the hole 56 is located in a bent over end 58 with its center coincident with the pitch line of the teeth 60 of the rack proper, as the device is viewed from the front. The rear surface 62 of the rack 54 is slightly curved so that when the plate 38 is rotated this rear surface 62 is engaged by an eccentric adjustment pin 64 causing the rack teeth 60 to properly mesh at all times with a pinion gear 66. The pitch line of the pinion gear 66 contacts the pitch line at the teeth 60 when the pin 64 is properly adjusted.

The pinion gear 66 in turn is attached to a small shaft 68 carrying a spur gear 70 designed to engage and drive a second pinion gear 72. This second pinion gear is carried upon another shaft 74 projecting through the center of the housing 22. The various gears mentioned are carried by two gear housing plates 76 secured together through the use of spacers 78 and screws 80. Similar spacers and screws designated by the same numbers for convenience are used to support the gear housing plates 76 within the housing 22 above the plate 38 and the rack 54.

It will be seen from a consideration of Figs. 3 and 4 of the drawings that the rack 54 projects generally from one end of the plate 38 to the other end thereof; the rack 54 is pivotally attached to one end of the plate 38 and is slidably supported upon the other end of this plate. The tension holding the rack 54- against the pinion gear 66 can be readily regulated by adjusting the position of the pin 64 through the use of a screw 82.

Upon the housing 22 there is located a cover 84 having a transparent face plate 86 located therein. Beneath this face plate 86 so as to be spaced therefrom is a discshaped dial 88 having uniformly spaced graduations marked on the periphery thereof. This dial 88 is held by an internal flange 90 on the cover 84 against a dial plate 92 which in turn is mounted upon the one of the gear housing plates 76 closest to the cover 84 by means of screws 80 passing through holes 84 in a flange 96 on this dial plate. Within the center of the dial plate there is located an aperture 98 through which the shaft 74 projects. A hand 100 having a peripheral portion 102 shaped like a segment of a circle is attached to the shaft 74 so as to rotate around the dial 83 as the shaft 74 is turned. A small coil spring or hair spring 104 is secured at its center to a collar 106 held upon the shaft 74 and is secured at its end by means of a pin 108 to a projection 110 upon the gear housing plate 76 closest to the cover 84.

Adjacent to the slot 48 on the movable plate 38 there is formed a small upstanding support 112 which is adapted to carry a rigid strip 114 having a corresponding projection 116 formed thereon. The two projections 110 and 116 are conveniently held together by means of a screw 80. The strip 114 is located beneath an aperture 118 in the dial plate 92 and is provided with numbers 118 indicating the position of the movable plate 38 and the movable leg 16.

In using the caliper the handle 18 is moved toward the handle 14 causing the movable leg 16 to rotate away from the fixed leg 12. As this occurs the strip 114 will be moved so as to give an indication of the distance between the two legs 12 and 16 by looking through the aperture 118. Simultaneously the rack 54 will be moved causing the various gears previously described to be actuated turning the hand 100. These gears constitute what may be considered a gear train, and any slack in this gear train is taken up by the coil spring 104. A point 120 on the band 100, as this occurs, will indicate.

on the dial 88 in more detail the distance between the legs 12 and 16, and the graduations on the peripheral portion 102 when read in conjunction with the graduations on the dial 88 in the manner in which a common vernier is read will indicate with even greater accuracy the position of the legs 12 and 16. It will be realized that the graudations on the peripheral portion 102 must, for this to be the case, be proportioned with respect to the graduations on the dial 88 in the manner of a vernier scale.

Thus, with the invention three different readings can be obtained indicating with different accuracy the position of the legs 12 and 14. The last two readings so obtained are, in effect, fine adjustments and must be taken in conjunction with the initial reading taken through the aperture 118. Thus, the caliper 10 can be manufactured so as to indicate centimeters through the aperture 118, millimeters through the use of the point 120, and tenths of millimeters through the use of the peripheral portion 102.

I claim:

1. A device of the class described which comprises: a fixed leg; a movable leg pivotally attached to said fixed leg; a housing secured to the fixed leg at the point of attachment of the movable leg thereto; means attached to said movable leg so as to project into said housing, said means being capable of rotating when said movable leg is rotated with respect to said fixed leg; a rack having teeth pivotally mounted within said housing on said means at a point removed from the center of rotation of said means; and readout means including a uniformly graduated dial and a gear engaging said rack positioned within said dial so as to be actuated when said movable leg is rotated with respect to said fixed leg.

2. A device as defined in claim 1 wherein the pitch line of said gear contacts the pitch line of said teeth on said rack.

3. A device as defined in claim 1 wherein said rack has a rear surface and including means engaging said rear surface so as to hold said rack in engagement with said gear as said movable leg is rotated with respect to said fixed leg.

4. A device of the class described which includes: a fixed leg; a housing attached to said fixed leg; a shaft projecting into said housing from the exterior thereof; a movable leg secured to said shaft on the exterior of said housing; a plate secured to said shaft within said housing, said plate being capable of being rotated within said housing when said movable leg is rotated; spring means engaging said plate and said housing, said spring means serving to hold the ends of said fixed and movable legs against one another; a rack having gear teeth and a rear surface pivotally mounted on said plate with the center of rotation of said rack coincident with the pitch line of said teeth; a pinion gear rotatably mounted within said housing so as to engage said teeth of said rack; means engaging the rear surface of said rack so as to hold said rack in engagement with said pinion gear during movement of said plate and said rack so the pitch line of said pinion gear contacts the pitch line of said teeth during said movement; gear means mounted within the housing so as to be actuated by said pinion gear, said gear means including a shaft; a hand attached to said shaft; and a unif-ormly graduated dial positioned within said housing adjacent to said hand.

5. A device as defined in claim 4 wherein said hand includes a graduated peripheral portion shaped like a segment of a circle, and wherein the graduations on said portion are adapted to be read in conjunction with the graduations on said dial in the manner of a vernier.

6. A device of the class described which includes: a fixed leg; a housing attached to said fixed leg; a shaft projecting into said housing from the exterior thereof; a movable leg secured to said shaft on the exterior of said housing; a member secured to said shaft within said housing, said member being capable of being rotated within said housing when said movable leg is rotated; spring means engaging said member and said housing, said spring means serving to normally hold the ends of said fixed and movable legs against one another; a rack having gear teeth and a rear surface pivotally mounted on said member with the center of rotation of said rack with respect to said member coincident with the pitch line of said teeth; a pinion gear rotatably mounted within said housing so as to engage said teeth of said rack; means engaging the rear surface of said rack so as to hold said rack in engagement with said pinion gear during movement of said member and said rack so that the pitch line of said pinion gear contacts the pitch line of said teeth during said movement; a gear train including at least one shaft positioned within said housing so as to be actuated by said pinion gear; a hand attached to said shaft so as to project therefrom; a graduated dial positioned within said housing adjacent to said hand so that the center of said graduations corresponds to the axis of said shaft; and second spring means secured to said shaft and to said housing so as to take up any slack in said gear train,

7. A device as defined in claim 6 including: a graduated strip attached to said rack so as to move therewith; a plate having an aperture therein mounted within said housing adjacent to said strip whereby said graduations on said strip may be viewed through said aperture.

8. A device as defined in claim 7 wherein said hand includes a graduated peripheral portion shaped like a segment of a circle, and wherein the graduations on said peripheral portion are adapted to be read in conjunction with the graduations on said dial in the manner of a Vernier.

References Cited in the file of this patent UNITED STATES PATENTS 396,479 Green Jan. 22, 1887 1,621,778 Haglund Mar. 22, 1927 2,141,246 Jacobus et al. Dec. 27, 1938 2,421,517 Maerrnan June 3, 1947 FOREIGN PATENTS 254,565 Switzerland Dec. 16, 1948

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