DIAL BORE GAGE

Abstract: An improved dial bore gage having an adjustment mechanism (16) associated therewith for adjusting the relative axial positions of the probe (14) and dial (12) portions of the gage, the probe (12) including spaced and opposed work engaging members (66, 68), the adjustment mechanism (16) enables an operator to easily and quickly zero in a setting on the dial indicator (40) to establish some desired preset probe diameter and includes a first member (30) operatively connected to the dial portion (12) of the gage having a first threaded portion (44) associated therewith of a predetermined thread pitch, a second member (50) operatively connected to the probe portion (14) of the gage having a second threaded portion (52) associated therewith of a different predetermined thread pitch, and an adjustment member (17) rotatably mounted to the first (30) and second (50) members, the adjustment member (17) having spaced threaded portions (46, 48) to correspond to and mate with the threaded portions (44, 52) on the first (30) and second (50) members whereby rotation of the adjustment member (17) will produce relative axial movement between the first (30) and second (50) members and this in turn will produce changes in the gage setting for each position thereof when the work engaging members (66, 68) on the probe portion (14) are maintained in fixed spaced relation to each other. The present dial bore gage also includes a mechanism (96, 98) for releasing pressure on the work engaging members (66, 68) of the gage to facilitate insertion and removal thereof into and out of a bore to be gaged and mechanisms (74) for providing both axial and angular backlash compensation between the probe (14) and dial (12) portions of the gage.

Description: The invention relates to a dial bore gage for gaging cylindrical work surfaces having spaced and connected dial and probe portions, said dial portion including a dial face and indicator means movable thereon for indicating a reading on said dial face, said probe portion having gaging means operatively connected to said indicator means and including at least two spaced opposed work engaging members for engaging opposite sides of a work surface to be gaged and biasing means for urging the work engaging members radially outwardly on said probe portion, adjustment means being provided for establishing a desired gage setting on said dial portion for a predetermined spacing between said work engaging members. Dial bore gages are specifically used to determine if the diameter and surface characteristics of cylindrical holes or bores are accurate to some known standard and such gages include gaging head members which gage the surfaces and have portions operatively connected to dial indicator means which indicate the condition and size of the hole or bore. Such dial bore gages are generally set and calibrated prior to usage based upon the final desired size or diameter of the bore to be gaged so that a user may quickly and accurately determine if the diameter and surface characteristics of such bore are of the desired size and finish, or if the diameter and surface finish is off by some amount, and if so, whether the bore is over or under size. This calibration is usually accomplished by placing the dial bore gage on a setting fixture, the setting fixture providing holding and supporting means for adjusting the alignment of the gaging contacts associated with the probe tip of a particular dial bore gage to the setting surfaces associated with the setting fixture. This procedure establishes the precise known distance between the gaging contacts and, based upon this known standard, the diameter and surface characteristics of a particular cylindrical hole or bore may be gaged. Typical of known setting fixtures is the fixture disclosed in Sunnen U.S. Patent No. 3,496,758 and the gage support means disclosed in co-pending Rutter et al U.S. patent application Serial No. 142,192, filed January 11, 1988. Once the gaging contacts associated with a particular dial bore gage have been set and calibrated, it is generally desired to reposition the movable pointers associated with the dial indicator to a zero setting to facilitate easy reading of the dial indicator to determine if the diameter and surface characteristics of the bore to be gaged are of the desired size and finish. If the gaging contacts are set to the desired finished size of the bore to be gaged as previously explained and the dial indicator reads zero, then, when the gage is positioned within the particular bore for the gaging thereof, the bore diameter will, if proper size, correspond to the desired finish diameter set between the gaging contacts. A reading other than zero on the dial indicator such as a plus or minus reading on the dial face indicates that the particular bore is either over or under size. Adjusting the movable pointers of the dial indicator to a zero reading has been accomplished in the past by using one of several known means. For example, zeroing of the dial indicator may be accomplished by either slidably or rotatably moving the dial indicator face so as to align the zero index marking on the dial with the dial pointer, or by otherwise moving the indicator stem associated with the particular gage to reposition the movable pointer over the zero index marking. It is an advantage to be able to zero the movable pointer associated with the dial indicator prior to usage for various reasons including for convenience purposes and for ease of reading the dial indicator during a gaging process. Typical of the known dial setting means are the means disclosed in U.S. Patent Nos. 4,045,877; 4,476,634 and 4,477,977. A dial bore gage of the generic kind which is shown in the DE-B-2 462 156 includes a dial portion which is fixed to a threaded pin by means of a knurled clamp nut. This clamp nut is screwed on a conical sleeve having a slot. The sleeve is provided with an inner and an outer thread. The threaded pin is screwed into the interior of the sleeve connected to the dial portion. Locking of this assembly is achieved by screwing the knurled clamp nut on the outer thread of the conical sleeve. With this assembly a variation of the axial position of the probe portion and the dial portion and locking of these portions in this position is possible. However, axial adjustment of the dial bore gage is very complicated and inaccurate as the assembly has to be locked after every adjustment. It is the problem underlying the invention to provide a dial bore gage which enables a user to make an appropriate accurate adjustement between the probe portion and the dial means in order to establish a desired relationship therebetween. Starting out from the dial bore gage of the generic kind this problem is solved in that the adjustment means includes a first member operatively connected to said dial portion and having a first threaded portion thereon of a predetermined pitch, a second member operatively connected to said probe portion and having a second threaded portion thereon of a different predetermined pitch, and an adjustable member rotatably mounted to said first and second members and having spaced threaded portions cooperatively engageable respectively with the first and second threaded portions of said first and second members, rotation of said adjustment member producing relative axial movement between said dial and probe portions so as to establish the desired gage setting on said dial portion. Since the spaced threaded portions are of different pitch, rotation of the adjustment member will produce relatively axial movement between the first and second member and this in turn will produce changes in the gage setting for each position thereof. Therefore, the dial gage of the present invention allows an appropriate accurate adjustment between the probe portion and the dial portion for establishing a desired relationship therebetween. A movable dial indicator face or other relatively complicated mechanisms for zeroing the movable dial pointers including means for locking the adjusted position against further movement are not needed. Still further, the present construction facilitates replacing probe tips or gaging heads of different ranges on the same gaging device. Advantageously relative rotational movement between said dial and probe portions is prevented by an elongated slot formed in one of said first and second members and engaging means in the other of said first and second members engageable with said slot. Conveniently the dial bore gage includes releasing means actuable to release the pressure exerted by said biasing means on said work engaging members so that the probe portion of the gage can be inserted into a bore to be gaged without any outward or radial force being applied to the gaging contacts or work engaging portions thereby minimizing the possibility for damage or wear on the work engaging members due to rubbing which is important to maintaining the accuracy and longevity of these members. This also reduces the possibility of damage to the internal bore surface due to scratching or otherwise by the probe assembly. These are important considerations when gaging relatively deep bores and bores that have interruptions such as bores having "O" ring grooves, retaining ring grooves, spaced groove portions and bores that have other types of interruptions. The releasing means preferably includes a lever mounted on said dial portion. The probe portion can include pairs of opposed gaging and centralizing elements. In a preferred embodiment said first member is biased axially relative to said second member to maintain axial pressure between the threaded portions on said adjustment member and the threaded portions engaged therewith on said first and second members. Thus, axial backlash compensation is achieved between the probe and dial portions. Advantageously said adjustment means establish a desired gage setting condition when said work engaging members are maintained in fixed relation to each other. Preferably the biasing means also bias the probe portion into engagement with said dial portion. In another preferred embodiment the biasing means includes tubular means extending between and connecting said dial and probe portions, a plunger biased towards the probe portion and having a first end operatively engageable with said work engaging members and an opposite end engageable with said dial portion. In conjunction with the accompanying drawings a preferred embodiment of the present invention is explained. Fig. 1 is a front elevational view of a dial bore gage embodying the improvements of the present invention; Fig. 2 is an enlarged fragmentary cross-sectional view taken along line 2-2 of Fig. 1; Fig. 3 is a side elevational view of the probe support means in the gage of Fig. 2 shown rotated 90° with respect thereto; Fig. 4 is an enlarged cross-sectional view taken along line 4-4 of Fig. 3; Fig. 5 is a partial side elevational view of the right end portion of the probe support means of Fig. 3 shown rotated 90° with respect thereto; Fig. 6 is an enlarged fragmentary cross-sectional view taken along line 6-6 of Fig. 2; and Fig. 7 is a further enlarged fragmentary cross-sectional view of the stem portion of the gage of Fig. 2 showing a modified form of the probe assembly associated therewith; The dial bore gage 10 of Fig. 1 and 2 and like measuring devices come in various sizes and shapes and generally include a dial portion 12 at one end thereof as shown in Fig. 1 for indicating a dimensional reading such as whether a bore diameter is over or under sized. This is determined by the gage reading when the gaging contacts of the device are in engagement with locations on a diameter of a bore being gaged. In this regard, the gage 10 also includes a gaging or probe portion 14 having spaced and opposed work engaging contacts 66 and 68 for engaging the work surface such as a bore surface that has been honed to some desired diameter. The gage 10 further includes an elongated connection or stem portion which extends between and connects the dial and probe portions 12 and 14, this connection portion of the gage including the present gage improvements and adjustment means 16. A probe pressure release lever 18 operatively connected to means for releasing pressure on the work engaging members is likewise provided to facilitate insertion and removal thereof into and out of a bore to be gaged as will be hereinafter further explained. The dial portion 12 of the present gage 10 includes a housing 20 which has an open-sided cavity 22 in which is positioned a rotatable dial assembly 24. The dial assembly 24 can be rotated in the cavity 22 and locked into any desired position by locking member 26. The provision of means for rotating the dial assembly 24 and means for locking the same represent a known means for zeroing the movable pointer associated with a particular dial indicator. Such features are obviated by the present gage adjustment means, and therefore may be eliminated from the gage. However, such features on a dial bore gage may be retained, if desired, to add further flexibility. It is mainly the construction and operation of the adjustment means 16 which are important to the present invention and represents the main novel features of the present gaging device. Referring to Fig. 2, the dial housing 20 is shown mounted on a tubular member 30 which extends therefrom towards the probe assembly 14. The member 30 is pinned or keyed to another tubular member 32 by pin 34, and the member 32 extends into the dial housing 20 and accommodates a dial assembly extension member 36 which is connected to the dial assembly 24. The extension member 36 in turn slidably accommodates a further extension member 38 which, in turn, extends into a counterbore 39A in a dial operator member 39. The operator member 39 is movable axially and geared to change the positions of the rotatable indicator pointers 40 and 42 as best shown in Fig. 1. The dial assembly 24 is mounted or attached to the dial housing 20 in a conventional manner such as illustrated in Rutter U.S. Patent No. 4,045,877. The tubular member 30 functions as a dial assembly support means and includes an external threaded portion 44 located adjacent the end portion thereof which extends towards the probe assembly 14. The adjustment means 16 includes an adjustment member 17 having spaced internally threaded portions 46 and 48 of slightly different thread pitch, the internal threads 46 associated with one end of the adjustment member 17 being cooperatively engageable with the external threads 44 on the member 30. Another tubular member 50 (Figs. 2 and 3) has an externally threaded portion 52 located intermediate the respective opposite ends thereof and is slidably receivable within the member 30 as best sown in Fig. 2. The internal threads 48 associated with the adjustment member 17 are cooperatively engageable with the external threads 52 on the member 50. Since the spaced threaded portions 46 and 48 (and 44 and 52) are of slightly different pitch, rotation of the threaded adjustment member 17 will produce some slight relative axial movement between the respective members 30 and 50 and this in turn will produce changes in the gage setting for each position thereof. This assumes that the members 30 and 50 and the parts fixedly attached thereto are not able to rotate relative to each other as is true and will be hereinafter explained. The tubular member 50 functions as support means for the probe assembly 14 and is constructed to receive the fixed probe portion 51 as shown in Fig. 2. The member 50 may be fixedly secured to the probe portion 54 by means such as set screw 56. The probe assembly 14 includes the elongated tubular member 54 which has a passageway or bore shown formed by communicating bore portions 58 and 60 which together extend therethrough from end-to-end. The bore portion 58 also receives a bushing 61 in its free end as shown. The bores 58 and 60 including the bushing 61 slidably receive a plunger assembly 62 which is positioned therein for axial movement. The plunger 62 includes a tapered forward end portion 64 adaptable for cooperatively engaging gaging and centralizing elements associated with the probe assembly 14 such as the ball-like gaging and centralizing members 66 and 68 shown in Fig. 1. Axial movements of the plunger 62 in a forward direction (away from the dial portion 12) will displace the members 66 and 68 radially outwardly during a gaging operation. It is important to the present invention that when the probe member 54 is fixedly secured to the probe support means 50, the end surface 70 of the plunger 62 engages and bears against the terminal end surface of a member 72 which is attached to the dial operator member 39 as shown in Fig. 2. Since the probe member 54 is fixedly secured to the probe support member 50, axial movement of the member 50 will produce a corresponding axial movement of the member 54. This means that when the adjustment member 17 is rotated in either direction about the respective threaded portions 44 and 52, the plunger 62 will move axially relative to the members 54 and 50. If the gaging balls 66 and 68 are in a bore or between the fixed contacts of a setting fixture, this means that they will operate through the members 64 and 62 against the end of the member 39 to change the position of the pointers 40 and 42. This therefore enables the operator to very accurately zero the dial indicator to any desired diameter as will be further hereinafter explained. Resilient means in the form of a compression spring member 74 is positioned about the members 38 and 39 between the respective ends of the members 32 and 50 as shown in Fig. 2. The spring member 74 is a fairly strong spring and applies constant pressure to urge the probe support means 50 away from the dial portion 12 of the gage 10. This arrangement forces the respective cooperatively engageable threaded portions 44 and 46 and 48 and 52 into predetermined engagement with each other in all positions of adjustment of the member 17 thereby eliminating any looseness or play between the respective engaged threads. This acts to provide axial backlash compensation between the members 17, 30 and 50 thereby improving the gage accuracy and response in all positions of adjustment. Other resilient means in the form of a relative weaker compression spring 76 is also provided to maintain the operator arm 39 engaged with the end surface 70 of the plunger assembly 62. The spring member 76 is positioned about overlapping ends of the members 30 and 39 (Fig. 2) such that one end portion thereof engages and bears against one end of the extension member 36 while the opposite end engages an annular flange or retaining ring 78 on the member 39. The spring 76 applies pressure to constantly urge the terminal end portion 72 of the operator arm 39 into engagement with the end surface 70. The spring member 76 is weaker than the spring member 74 and its main purpose is to maintain the members 39 and 62 engaged and to a much lesser extent may provide a small amount of backlash compensation. The probe support means 50 also includes a tapered or beveled elongated slot 80 located adjacent the end thereof nearest the dial portion 12 as best shown in Figs. 4 and 5. The slot 80 slidably receives a tapered portion 84 of a locking element or screw 82 as best shown in Fig. 6. The locking element 82 is threadedly engaged with opening 83 in the dial support member 30. This screw and slot arrangement between the members 30 and 50 substantially eliminates relative angular but not relative axial movement therebetween. However, there should be sufficient clearance between the tapered portion 84 of the set screw 82 and the elongated slot 80 in the member 50 to enable the members 30 and 50 to move axially relative to each other. The probe support member 50 also has a flat 86 machined on it adjacent the same end thereof as the slot 80 as best shown in Figs. 2 and 3. A set screw 88 having a flat inner surface 89 is able to pass through opening 90 formed in the housing 20 to be threadedly positioned in threaded opening 92 in the member 30. The set screw 88 is used to lock member 50 in relation to member 30 axially once the gage has been set to the correct reading. This prevents accidentally changing the reading by either moving member 17, or by accidentally bumping or dropping the gage. Once the gaging contacts associated with the probe assembly 14 are set between spaced setting surfaces on a setting fixture, or are engaged with opposite sides of a surface to be gaged, or are set by engagement with a ring gage or the like, and while maintaining the gaging contacts so engaged, the adjustment member 17 is rotated to move the aligned members 62 and 39 to reposition the movable pointers 40 and 42 to a zero setting on the dial face. This accurately zero sets the dimension being engaged by the gaging members 66 into the gage so that thereafter when the probe portion of the gage 10 is inserted into a bore it will indicate if the bore is of the desired diameter and if not how much it is over or under size. It is important to the present invention that the engaged threaded portions 44 and 46 be of slightly different pitch than the engaged threaded portions 48 and 52 because it is this difference in thread pitch that enables the members 30 and 50 to move axially relative to each other during adjustment. The amount of difference in pitch thread will determine the rate of relative axial movement and the range of such axial movement between the members 30 and 50. For example, if the pitch of the threaded portions 44 and 46 is 32 threads per inch and the pitch of the threaded portions 48 and 52 is 40 threads per inch, one complete rotation of the adjustment member 17 in either direction will produce a corresponding relative axial movement between the members 30 and 50 of about 0,16 mm (0.00625 inches). This means that the dial operator arm member 39 will move axially by this distance (assuming the gaging members 66 are held fixed) and this will produce rotation of the pointers 40 and 42 to establish a desired gage setting. The rate of change and the range of movement can be adjusted by selecting the thread pitches desired. The ability to precisely set the dial bore gage by zeroing the dial indicator to some desired reading in this manner prior to use allows the operator to achieve the full range of possible adjustment without moving the position of the dial portion of the gage as has been the practice with known dial bore gages. The adjustment member 17 is shown having a knurled outer surface 94 (Fig. 1) which the operator grips when making an adjustment. Once the movable pointers 40 and 42 are repositioned to align such pointers to a zero setting on the dial face of the gage portion 12 as explained, the gage 10 is ready for use. The gage 10 also includes means 18 operable to release pressure on the work engaging members 66 and 68 so that the probe portion 14 can be inserted into a bore to be gaged without any outward or radial force being applied to the gaging contacts or work engaging portions thereby minimizing the possibility for damage or wear on the work engaging members due to rubbing on the work surface. The probe release lever 18 is operatively connected by bell crank means (not shown) to the member 96 (Fig. 2) such that movements of the release lever 18 inwardly towards the dial housing 20 will cause axial movement of the member 96 in the direction of the dial portion 12. This causes a retractor member 98 fixedly secured to the member 96 adjacent the end thereof to also move. The member 98 is connected to the member 96 by fastener member 100 (Fig. 2) and extends through aligned openings 102 and 103 formed in the members 96 and 97. The retractor member 98 also extends through an oversized opening 104 (Fig. 2) formed in the member 30 and further extends trough a slot 106 formed in the member 50 (Figs. 2 and 4) such that its terminal end portion is in spaced axial alignment with or overlaps the annular flange 78 on the member 39. As the member 96 moves toward the dial portion 12 during a retraction operation, the retractor member 98 likewise moves in the same direction and will move against the annular member 78. Further movement of the retraction members 96 and 98 in the same direction will move the dial operating arm 39 in a direction away from the probe end portion 70 thereby releasing pressure on the plunger assembly 62 which in turn releases pressure exerted by the work engaging members 66 and 68 so that the probe assembly 14 can be inserted or removed from a work surface without rubbing thereagainst under pressure. The release of outward pressure of the work engaging members is important to the present invention for the reasons stated. This not only reduces the possibility of damage to the bore surface being gaged but also minimizes the possibility for damage or wear to the work engaging members. Fig. 7 is an enlarged fragmentary cross-sectional view of the central stem portion of the gage 10 of Fig. 2 illustrating in greater detail use of another embodiment 108 for the probe assembly. The probe assembly 108, like the probe assembly 14, is mounted in the probe support means 50 and includes a modified plunger assembly 110 as shown. Like the plunger assembly 62, the end portion 112 of the plunger 110 extends towards the dial portion 12 and engages the terminal end portion 72 of the dial operator arm 39. Operation of this embodiment is similar to that described above.

Claims: A dial bore gage for gaging cylindrical work surfaces having spaced and connected dial (12) and probe (14) portions, said dial portion (12) including a dial face and indicator means (40, 42) movable thereon for indicating a reading on said dial face, said probe portion (14) having gaging means operatively connected to said indicator means (40) and including at least two spaced opposed work engaging members (66, 68) for engaging opposite sides of a work surface to be gaged and biasing means (62, 64) for urging the work engaging members (66, 68) radially outwardly on said probe portion (14), adjustment means (16) being provided for establishing a desired gage setting on said dial portion (12) for a predetermined spacing between said work engaging members (66, 68), characterized in that said adjustment means includes a first member (30) operatively connected to said dial portion (12) and having a first threaded portion (44) thereon of a predetermined pitch, a second member (50) operatively connected to said probe portion (14) and having a second threaded portion (52) thereon of a different predetermined pitch, and an adjustable member (17) rotatably mounted to said first and second members (30, 50) and having spaced threaded portions (46, 48) cooperatively engageable respectively with the first and second threaded portions (44, 52) of said first and second members (30, 50), rotation of said adjustment member (17) producing relative axial movement between said dial and probe portions (12, 14) so as to establish the desired gage setting on said dial portion (12). A dial bore gage according to claim 1, characterized in that relative rotational movement between said dial and probe portions (12, 14) is prevented. A dial bore gage according to claim 2, characterized in that the relative rotational movement is prevented by an elongated slot (80) formed in one of said first and second members (30, 50) and engaging means (82) in the other of said first and second members (30, 50) engageable with said slot (80) A dial bore gage according to one of the preceding claims, characterized by releasing means (96, 98, 78) actuable to release the pressure exerted by said biasing means (62, 64) on said work engaging members (66, 68) to facilitate insertion and removal thereof into and out of a work surface to be engaged. A dial bore gage according to claim 4, characterized in that the releasing means (96, 98, 78) includes a lever (18) mounted on said dial portion (12). A dial bore gage according to one of the preceding claims, characterized in that said probe portion (14) includes pairs of opposed gaging (66) and centralizing (68) elements. A dial bore gage according to one of the preceding claims, characterized in that said first member (30) is biased axially relative to said second member (50) to maintain axial pressure between the threaded portions (46, 48) on said adjustment member (17) and the threaded portions (44, 52) engaged therewith on said first and second members (30, 50). A dial bore gage according to one of the preceding claims, characterized in that said adjustment means (16) establish a desired gage setting condition when said work engaging members (66, 68) are maintained in fixed relation to each other. A dial bore gage according to one of the preceding claims, characterized in that the biasing means (62, 64) also bias the probe portion (14) into engagement with said dial portion (12). A dial bore gage according to one of the preceding claims, characterized in that the biasing means includes tubular means (54) extending between and connecting said dial and probe portions (12, 14), a plunger (62) biased towards the probe portion (14) and having a first end operatively engageable with said work engaging members (66, 68) and an opposite end engageable with said dial portion (14).

Inventors: RUTTER, HAROLD T.
Applicants: SUNNEN PRODUCTS COMPANY
Application year: 1988
Main classification: G01B5
IPC codes: G01B5, G01B3