Patent Publication Number: US-2020300597-A1

Title: Measuring device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 108109927, filed on Mar. 22, 2019. 
     FIELD 
     The disclosure relates to a measuring device, and more particularly to a measuring device for measuring a change of linear dimension of a shaft body. 
     BACKGROUND 
     In a conventional lathe manufacturing process, a workpiece is mounted to a rotary shaft of a lathe machine (e.g. a metal lathe machine). The rotary shaft is rotatably mounted to a shaft seat of the lathe machine, and is driven by electric power to rotate with the workpiece relative to the shaft seat such that various operations (e.g. cutting, sanding, drilling, etc.) may be performed on the workpiece. 
     During an operation, when the rotary shaft is running in high speed, friction between the rotary shaft and the shaft seat often causes the temperature of the rotary shaft to increase significantly, resulting in thermal expansion of the rotary shaft. Consequently, dimensional accuracy of a finished product may be affected by a change of linear dimension of the rotary shaft along its shaft axis due to the thermal expansion. 
     To recalibrate the rotary shaft, a conventional measuring device often used for measuring the change of linear dimension is a non-contact optical dilatometer. Once the linear dimension change is measured, a compensation can be made to improve accuracy of the operation. However, the non-contact optical dilatometer contributes to high manufacturing costs and thus, a comparable alternative with lower costs is highly anticipated. 
     SUMMARY 
     Therefore, the object of the disclosure is to provide a measuring device that can alleviate the drawback of the prior art. 
     According to the disclosure, a measuring device is adapted for measuring a change of linear dimension of a shaft body of a bearing device along an axis due to thermal expansion. 
     The measuring device includes a stationary seat and a strain unit. The strain unit includes an actuator and a strain member. 
     The actuator is adapted to be mounted to the shaft body, and is movable relative to the stationary seat along the axis as a result of the change of linear dimension of the shaft body. 
     The strain member is deformable, is secured to the stationary seat and is connected to the actuator such that movement of the actuator along the axis results in a force applied to the strain member which deforms the strain member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings, of which: 
         FIG. 1  is a fragmentary assembled perspective view of a first embodiment of a measuring device according to the disclosure mounted to a bearing device; 
         FIG. 2  is fragmentary partially exploded perspective view of the first embodiment and the bearing device; 
         FIG. 3  is a fragmentary sectional view of the first embodiment and the bearing device; 
         FIG. 4  is a view similar to  FIG. 3 , yet illustrating a second embodiment of the measuring device according to the disclosure; 
         FIG. 5  is a fragmentary assembled perspective view of a third embodiment of the measuring device according to the disclosure mounted to a bearing device; 
         FIG. 6  is fragmentary partially exploded perspective view of the third embodiment and the bearing device; 
         FIG. 7  is a fragmentary sectional view of the third embodiment and the bearing device; 
         FIG. 8  is another fragmentary sectional view of the third embodiment and the bearing device; 
         FIG. 9  is a fragmentary assembled perspective view of a fourth embodiment of the measuring device according to the disclosure mounted to the bearing device; 
         FIG. 10  is a fragmentary partially exploded perspective view of the fourth embodiment and the bearing device; 
         FIG. 11  is a fragmentary sectional view of the fourth embodiment and the bearing device; 
         FIG. 12  is a fragmentary assembled perspective view of a fifth embodiment of the measuring device according to the disclosure mounted to the bearing device; 
         FIG. 13  is a fragmentary partially exploded perspective view of the fifth embodiment and the bearing device; and 
         FIG. 14  is a fragmentary sectional view of the fifth embodiment and the bearing device. 
     
    
    
     DETAILED DESCRIPTION 
     Before the present disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
     Referring to  FIGS. 1 to 3 , a first embodiment of a measuring device according to the disclosure is adapted for use with a bearing device  1 . The bearing device  1  includes a hollow base seat  11 , a shaft body  12  and a bearing group  13 . The shaft body  12  extends through the base seat  11  and is rotatable about an axis (X) relative to the base seat  11 . The bearing group  13  is sleeved on the shaft body  12  and is mounted in the base seat  11 . 
     Specifically, the measuring device is adapted for measuring a change of linear dimension of the shaft body  12  along the axis (X) due to thermal expansion. The measuring device includes a stationary seat  2  and a strain unit  3 . 
     The stationary seat  2  is adapted to be fixedly mounted to the bearing device  1 , and includes a first seat body  21  and a second seat body  22 . The first seat body  21  is screwed to the base seat  11  of the bearing device  1 , and defines an installation space  210  that extends along the axis (X). The second seat body  22  is fixed to the first seat body  21 , and is provided with an internal thread. 
     The strain unit  3  includes an actuator  4 , a strain member  5  and a transmitting member  6 . 
     The actuator  4  is adapted to be mounted to the shaft body  12 , is disposed in the installation space  210 , and is movable relative to the stationary seat  2  along the axis (X) as a result of the change of linear dimension of the shaft body  12 . In the present embodiment, the actuator  4  is a thrust bearing and is sleeved on the shaft body  12 . 
     The strain member  5  is deformable, is secured to the stationary seat  2 , and is connected to the actuator  4  via the transmitting member  6 , such that movement of the actuator  4  along the axis (X) results in a force applied to the strain member  5  which deforms the strain member  5 . 
     Specifically, the strain member  5  is fixedly mounted between the transmitting member  6  and the second seat body  22  of the stationary seat  2 , and has a first face  51  that faces the transmitting member  6 , and a second face  52  that is opposite to the first face  51 . In the present embodiment, the strain member  5  is a strain gauge made of a conductive material. However, the strain member  5  may also be a piezoelectric sensor made of a piezoelectric material, or a linear variable differential transformer (LVDT), which is a type of electrical transformer used for measuring linear displacement, depending on actual needs. 
     The transmitting member  6  is connected between the actuator  4  and the strain member  5  and is co-movable with the actuator  4 , such that the movement of the actuator  4  drives the transmitting member  6  to push against the strain member  5 , resulting in the force applied to the strain member  5 . 
     Specifically, the transmitting member  6  has a large diameter portion  61 , a small diameter portion  62 , and a shoulder portion  63 . 
     The large diameter portion  61  surrounds the actuator  4 . The small diameter portion  62  is disposed between the large diameter portion  61  and the strain member  5 . The shoulder portion  63  interconnects the large and small diameter portions  61 ,  62 , and the actuator  4  abuts against the shoulder portion  63  of the transmitting member  6 . Each of the large diameter, small diameter and shoulder portions  61 ,  62 ,  63  has an outer surface, and those three outer surfaces cooperatively form an outer surface  64  of the transmitting member  6 . The outer surface  64  surrounds the axis (X), and is formed with two slide grooves  65  which are spaced apart from each other. Specifically, the slide grooves  65  are formed in the small diameter portion  62  of the transmitting member  6 . 
     The strain unit  3  further includes a guide sleeve  31 , two retaining pins  32 , a first threaded member  33  and a second threaded member  34 . 
     The guide sleeve  31  surrounds the small diameter portion  62  of the transmitting member  6  and a portion of the strain member  5 , and is disposed in and connected fixedly to the first seat body  21  of the stationary seat  2 . The retaining pins  32  are spaced apart from each other, are connected fixedly to the guide sleeve  32 , and extend transversely and respectively into the slide grooves  65  of the transmitting member  6 . A diameter of each of the retaining pins  32  is smaller than a length of each of the slide grooves  65  in a direction of the axis (X), such that movement of the transmitting member  6  along the axis (X) is guided and restricted by the retaining pins  32 . It should be noted that numbers of the retaining pins  32  and the slide grooves  65  are not limited to two; in variations of the present embodiment, there may be only one retaining pin  32  and one slide groove  65 . 
     The first threaded member  33  is disposed in the second seat body  22 , threadedly engages the internal thread of the second seat body  22 , and abuts against the second face  52  of the strain member  5 . In a similar manner, the second threaded member  34  is also disposed in the second seat body  22 , threadedly engages the internal thread of the second seat body  22 , and abuts against the first threaded member  33  opposite to the second face  52  of the strain member  5 . 
     By virtue of the abovementioned configuration, the strain member  5  is pressed by the first and second threaded member  33 ,  34  against the transmitting member  6 , with a predetermined force. Thus, a predetermined strain of the strain member  5  can be detected and measured as a reference value prior to an operation, where there are no change of linear dimension of the shaft body  12 . 
     During the operation, after the shaft body  12  of the bearing device  1  has been rotating for a period of time, the shaft body  12  of the bearing device  1  starts to expand in response to a change in temperature. The actuator  4 , which moved along the axis (X) as a result of the change of linear dimension of the shaft body  12 , drives the transmitting member  6  to push against and deform the strain member  5  (i.e., in the form of compression in the present embodiment). As a result, an electrical resistance of the strain member  5  is changed, and an electrical signal (e.g., voltage) corresponding to such change of electrical resistance can be measured. 
     It should be noted that, the strain member  5  may be electrically connected to a central control unit (e.g., a computer), such that the linear dimensional change of the shaft body  12  can be obtained after analyzing and processing the electrical signal. Alternatively, a database that compiles correspondence between numerical values of the electric signals and linear dimensional changes of the shaft body  12  can be established first, so that when a certain electrical signal is measured, the corresponding value of the linear dimensional change can be obtained by simply referring to the database. In addition, the strain member  5  may also be electrically connected to a cooling system. When the electrical signal output by the strain member  5  reaches a threshold value, which indicates that the shaft body  12  is experiencing a significant temperature increase (the higher the temperature, the greater the linear dimensional change), the cooling system is triggered, so that cooling water is injected into the bearing device  1  to lower the temperature. Furthermore, the electrical signals can be further used as compensation references for recalibrating the bearing device  1  to improve accuracy of the operation. 
     Referring to  FIG. 4 , a second embodiment of the measuring device according to the disclosure is similar to the first embodiment. The difference between the two embodiments resides in that, in the second embodiment, the actuator  4  includes two angular contact ball bearings, each of which includes an inner ring seat  41 , an outer ring seat  42 , and a plurality of bearing balls  43  (only one is visible in  FIG. 4 ) that are disposed between the inner and outer ring seats  41 ,  42 . When the shaft body  12  expands, the inner ring seats  41  of the angular contact ball bearings are moved, driving the outer ring seats  42  of the angular contact ball bearings to move therealong via the bearing balls  43  of the angular contact ball bearings, and to push against the shoulder portion  63  of the transmitting member  6 . 
     Referring to  FIGS. 5 to 8 , a third embodiment of the measuring device according to the disclosure is similar to the first embodiment. The differences between the two embodiments reside in that, in the third embodiment, the configuration of the stationary seat  2  is slightly different; the strain unit  3  further includes a support block  35 , a threaded rod  36 , two spring pins  37  and two springs  38 ; and the strain member  5  has a deflecting portion  53  and a linking portion  54 . In addition, in the present embodiment, the actuator  4  includes two ball bearings, which are the same as in the second embodiment. 
     Specifically, the stationary seat  2  in the present embodiment includes a surrounding wall  23  and two positioning walls  24 . The surrounding wall  23  is screwed to the base seat  11  of the bearing device  1 , and surrounds and extends along the axis (X). The positioning walls  24  are spaced apart from each other, and are connected to an end of the surrounding wall  23  opposite to the base seat  11 . 
     The support block  35  is secured to an outer surface of the surrounding wall  23  via screws (see  FIG. 8 ). The deflecting portion  53  of the strain member  5  is disposed at the end of the surrounding wall  23 , but is not fixed thereto. The linking portion  54  of the strain member  5  extends from the deflecting portion  53  and is fixed to the support block  35  via screws (see  FIG. 8 ). The threaded rod  36  threadedly extends through the deflecting portion  53  of the strain member  5  in a direction of the axis (X), and has a press end  361  abutting against the transmitting member  6 . A central axis of the threaded rod  36  coincides with the axis (X) (i.e., a central axis of the shaft body  12 ). The springs  38  are disposed between the transmitting member  6  and the stationary seat  2  for biasing the transmitting member  6  away from the stationary seat  2 , and for stabilizing movement of the transmitting member  6 . 
     In virtue of such configuration, the deflecting portion  53  of the strain member  5  is deflectable relative to the linking portion  54 , and the movement of the actuator  4  drives the transmitting member  6  to push the deflecting portion  53  via the threaded rod  36 . That is, deformation of the strain member  5  in the present embodiment (i.e., deflection) is different than that in the previous embodiments (i.e., compression), but still serves the purpose of measuring the change of linear dimension of the shaft body  12 . 
     Specifically, in the present embodiment, the transmitting member  6  has a push face  66  and two receiving grooves  67 . The push face  66  faces the strain member  5 , and the receiving grooves  67  are spaced apart from each other, and extend from the push face  66  into the transmitting member  6 . The spring pins  37  are received respectively in the receiving grooves  67 , and are connected respectively to the positioning walls  24  of the stationary seat  2 . Two circlips (i.e., C-clips)  371  are provided to be respectively secured to the spring pins  37 , which prevent the spring pins  37  from falling out of the receiving grooves  67  during assembling. The springs  38  are received respectively in the receiving grooves  67 , each having opposite ends that abut respectively against a respective one of the spring pins  37  and the transmitting member  6 , so that once the operation has been completed, the springs  38  are able to bias the transmitting member  6  back to its original position prior to the operation, which helps in securing connection between the transmitting member  6  and the actuator  4 . 
     Referring to  FIGS. 9 to 11 , a fourth embodiment of the measuring device according to the disclosure is similar to the third embodiment. The differences between the two embodiments reside in that, in the present embodiment, the actuator  4  includes a round plate washer that is sleeved on the shaft body  12 , and the strain unit  3  further includes a rolling wheel  39  that is connected to the press end  361  of the threaded rod  36  and that is in contact with the actuator  4 . The central axis of the threaded rod  36  is parallel to, but not coincides with, the axis (X). 
     When the shaft body  12  expands, the actuator  4  moves along the axis (X) and presses against the rolling wheel  39 , and deflects the strain member  5  via the rolling wheel  39  and the threaded rod  36 , resulting in a bending strain corresponding to the linear dimensional change of the shaft body  12 . 
     Referring to  FIGS. 12 to 14 , a fifth embodiment of the measuring device according to the disclosure is similar to the first embodiment. The differences between the two embodiments are described as follows. 
     In the present embodiment, the bearing device  1  further includes a bottom seat  14 . The bottom seat  14  includes a horizontal bottom wall  141 , and two side walls  142  that extend respectively and upwardly from two opposite lateral sides of the bottom wall  141 . The base seat  11 , the shaft body  12  and the bearing group  13  are disposed in a receiving space defined cooperatively by the bottom and side walls  141 ,  142  of the bottom seat  14 . 
     The stationary seat  2  is adapted to be spaced apart from the shaft body  12  along the axis (X), and is adapted to be fixed to the bottom wall  141  of the bottom seat  14  via screws (see  FIG. 14 ). The strain unit  3  includes the actuator  4 , the strain member  5  and the transmitting member  6 , and further includes two fastening members  30 . 
     The actuator  4  is adapted to be mounted to an end portion of the shaft body  12  that is proximate to the stationary seat  2 , and includes a combined type needle roller bearing, which is a combination of a thrust ball bearing and a needle roller bearing. The strain member  5  is mounted to a surface of the stationary seat  2  that faces the actuator  4  via screws (see  FIG. 14 ). 
     The transmitting member  6  has a coupling portion  68  coupled to the actuator  4 , and a rod portion  69  extending from the coupling portion  68  along the axis (X) through the strain member  5 . The fastening members  30  are configured as nuts engaged with the rod portion  69  of the transmitting member  6 , and abut against opposite ends of the strain member  5  such that the fastening members  30  apply a predetermined force onto the strain member  5 . 
     In virtue of such configuration, the rod portion  69  of the transmitting member  6  is fixed to the strain member  5  such that the change of linear dimension of the shaft body  12  drives the actuator  4  to push the coupling portion  68  of the transmitting member  6  along the axis (X), thereby resulting in the force applied to deform the strain member  5 . 
     In sum, the measuring device of the present disclosure is able to measure the change of linear dimension of the shaft body  12  via the strain member  5  in a contacting manner, providing an alternative to the non-contact optical dilatometer of the prior art with lower costs. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.