Abstract:
A linear measurement and control apparatus uses a press roll for directly engraving the surface of a linear control bar and then engaging the control bar which is attached to a machine element, to measure its linear motion and thereby identifying its position. As the machine element moves, the attached control bar transmits its motion to the press roll, inducing rotation. The press roll is attached to a measurement disk having a sensory pickup so that rotation of the press roll is sensed. Light transmission is used for sensing motion of a measurement disk and for counting pulses for determining position.

Description:
This application claims the filing date of a previously filed provisional application having serial No. 60/103,200 and an assigned filing date of Oct. 6, 1998 and which contains subject matter substantially the same as presented in the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to linear measurement tools, and more particularly to a linear measurement system that is inexpensive and highly accurate. 
     2. Description of Related Art 
     The following art defines the present state of this field: 
     Huber et al., U.S. Pat. No. 5,131,017 describes an evaluation device with an absolute value counter providing an incremental position measuring system which determines absolute position even in case of loss of the main power supply. The evaluation device is operated by means of an emergency power supply operated by means of an emergency power supply while the main power supply is out. Following the restoration of the main power supply, counting pulses are supplied to a follow-up counter by a pulse emitter, until the follow-up counter has reached the counter reading of the absolute value counter. Two rectangular signals, which are phase-shifted by 90 degrees in relation to each other, are formed as a function of the counting signals, which are present at the evaluation device in the form of output signals. 
     Hiramoto, U.S. Pat. No. 4,698,828 describes a system for sensing the position of an object such as a rotating member. The system provides a plurality of photo-couplers coupled with the interposition of a rotary disc having slits and rotating with the object. The system further has a position signal generating circuit for receiving signals produced by the photo-couplers and producing a series of component position signals differing in phase successively by a predetermined phase difference, a counting circuit having an up/down count for determining the position of the object by counting occurrences of a predetermined change recurring periodically in the component position signals, and a direction determining circuit for producing an up/down counter. Each time the predetermined change occurs in any one of he component position signal, the direction determining circuit determines the order in which the change occurs in two successive component position signals. 
     Burkhardt, U.S. Pat. No. 4,229,647 describes an improved electronic counter for use with an incremental measuring device. The counter includes two or more individual counters, a display unit, and a switch for selectively connecting any one of the individual counters with the display unit. Each of the individual counters may be individually set to a separate zero point so that each counter may be used to store a position value in a separate frame of reference. The position value stored in any one of the individual counters may be switched to the display unit without disturbing the contents of the other individual counters. In the preferred embodiment, the counter includes a circuit for automatically resetting a first individual counter to zero whenever the measuring device senses a predetermined reference mark, thereby automatically maintaining a calibrated zero point in that counter. The preferred embodiment also included a power fail circuit which generates a warning signal when the measuring device is operated following an interruption in the line voltage used to power the device. This warning signal is maintained until the first individual counter is automatically reset, and the device is again calibrated for use. 
     Renner et al. U.S. Pat. No. 3,965,340 describes an apparatus relating to an optical counting apparatus, which is employed in combination with an electronic hand-held calculator. The structure of this invention greatly expands the use of the hand-held calculator by permitting such to be employed as a measuring device and a unit counter. An optical device is activated by the difference between transmission of light and darkness. This activation is used as a counting apparatus or a measurer of distances with the accumulated count or the distance measure to be read on the display unit of the calculator 
     Ohtsuka, U.S. Pat. No. 3,886,542 describes a member, on which are marked scales having respective different pitches between their graduations, and is movable past a graduation detecting position at which there are plural graduation detectors each operatively associated with a different respective scale. One scale has fine or “unit” graduations arranged successively in groups of ten, and another scale extending parallel to the first scale has coarse of “tens” graduations each corresponding to a respective group of fine graduations. Each tenth fine graduation is relatively elongated. The detectors cooperate, respectively, with the fine graduations, with the elongated fine graduations and the coarse graduations. A counter has plural digit positions, with one digit position being a “units” position and a next higher digit position being a “tens” digit position. An electronic switching circuit connects the detectors to the counter and is operable, responsive to movement of the scale bearing member past the detecting position at a relatively low speed, to supply, to the low digit position of the counter, input signals from the detector operatively associated with the scale having the fine graduations. The electronic switching circuit is operable, responsive to movement of the scale bearing member past the detecting position at a relatively higher speed, to supply, to the next higher digit position of the counter, input signals from the detector operatively associated with the coarse graduation scale. Switching between the two digit positions of the counter, responsive to a change in the speed of movement of the scale bearing member past the graduation detecting position, is effected only responsive to simultaneous detection of a relatively elongated fine graduation and the corresponding coarse graduation. 
     Nelle, U.S. Pat. No. 4,101,764 describes an incremental measuring instrument having a series of fixed reference marks along one edge of a grid scale in which a series of movable magnets are located along the opposite edge of the grid scale so that a magnet may be associated with each reference mark which is needed for control purposes in the particular application in which the system is being used. The magnets are movable mounted so that reference marks not needed for control purposes in any specific application do not have magnets associated with them. An electric switch, preferably a magnetically actuated Reed switch, is also provided in the system&#39;s sensor head. Electrical impulses generated by the magnets and the switch are transmitted to an electronic comparator along with electric impulses generated when the sensor head passes over the reference marks. This electronic comparator is connected to the system&#39;s electronic control counter when and impulse is simultaneously fed to the comparator by the switch associated with the magnets. 
     Blanchard, U.S. Pat. No. 4,215,337 describes a form of shaft-position encoder employing “fast” and “slow” rotary selectors coupled by gearing to each other and to a shaft whose position is to be encoded. The selectors cooperate selectively with elements in respective “fast” and the “slow” circular series of elements. Two counters register the number of pulses in a train varying in accordance with the number of elements in each of the “fast” and the “slow” series between one end of the series and an element in cooperation with a related selector. The combined values registered in the counters represent the shaft position code. The inherent uncertainty in recognizing when the “slow” counter should register any particular value represented by the position of its selector along its series of elements could create significant ambiguity, which is here resolved through use of the value registered in the counter of the “fast” series of elements. 
     The prior art teaches a variety of encoders and measurement systems. However, the prior art does not teach that such a system may provide a press roll in compressive contact with a linear moving control bar wherein the control bar is engraved by the press roll during an initial linear pass and thereafter remains in sync therewith due to continued engagement of the engraving. The present invention fulfills these needs and provides further related advantages as described in the following summary. 
     SUMMARY OF THE INVENTION 
     The present invention teaches certain benefits in construction and use which give rise to the objectives described below. 
     The present invention provides a linear measurement and control apparatus using one or a pair of opposing press rolls for engraving and thereby meshing a linear control bar attached to a machine element for measuring its linear motion and thereby identifying its position. As the machine element moves, the attached control bar transmits its motion to the axle of a measurement disk having a sensory pickup feature so that rotation of the disk may be sensed. The axle presents an embossed surface to the surface of the control bar so that after an initial pass, the control bar is engraved by the axle and thereafter the axle and the bar are maintained in synchronization by the engravement. 
     A primary objective of the present invention is to provide a linear measurement apparatus having advantages not taught by the prior art. 
     Another objective is to provide such an apparatus having low manufacturing cost. 
     A further objective is to provide such an apparatus capable of measuring repetitive linear motion in two opposing directions. 
     A still further objective is to provide such an apparatus capable of measuring reversible linear motion without backlash through the use of an engraved pattern. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawings illustrate the present invention. In such drawings: 
     FIG. 1 is a perspective view of the preferred embodiment of the present invention; 
     FIG. 2 is a side elevational view thereof without an enclosure shown in FIG. 1; and 
     FIG. 3 is an enlarged front elevational view thereof showing the manner in which a control rod of the invention is embossed. 
    
    
     Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The above described drawing figures illustrate the invention, a linear measurement apparatus functionally comprised of a measurement wheel  10 , press roll assembly  20 ,  40  and linear motion control bar  60 . The disk shaped measurement wheel  10  is mounted for rotation about a first rotational axis  12  on an integral, first shaft  20  as shown in FIG. 1. A peripheral surface  14  of this first shaft  20  forms a first press roll and has a hardened, preferably very slightly concave, surface with texture embossment  30  as illustrated in FIGS. 1 and 2. A second press roll  40 , also has a hardened peripheral surface  42  and may be advantageously concave as well, and is mounted for rotation on second shaft  50  about a second rotational axis  52  that is parallel to the axis of rotation  12  of the first shaft  20  as shown in FIG.  1 . The hardened peripheral surfaces  14 ,  42  of the two press rolls  20 ,  40  respectively, are positioned in a spaced apart relationship. The measurement apparatus also includes a linear, elongated control bar  60  engaged in compressive contact between the peripheral surfaces of the first  20  and the second  40  press rolls, as illustrated in both FIGS. 1 and 2, such that linear axial motion, as defined by arrow  62  in FIG. 1, of the control bar  60  causes rotation of the press rolls  20 ,  40 . The external surface  64  of the control bar  60  is prepared for and capable of receiving an engraved impression  66  from the peripheral surface embossment  30  of the first press roll  20 . Thus, the control bar  60  must have a surface soft enough to receive the engraving, i.e., it must be softer than the surface  64 . This impression  66 , depicted from the side in FIG. 3, is accomplished during an initial linear axial motion of the control bar  20  as it is laterally pressed against first press roll  20  by second press roll  40 . After the initial engraving of the control bar  60  is complete, the engraved impression  66  on the control bar  60 , and the corresponding texture embossment  30  of the first press roll  20 , remain mutually engaged and thereafter provide for coordinated mutual synchronous movement with repeated control bar  60  linear motion. This control bar linear movement also causes the disk shaped measurement wheel  10  to rotate about the first axis  12 . As this wheel rotation occurs, the change in position is detected and measured by sensor devices designed and positioned for this purpose. 
     The present invention further provides for fully enclosing the measurement wheel  10  and press rolls  20  and  40 . This enclosure  70  may take the form as shown in FIG. 1, or any other enclosure shape as is well known in the art. The enclosure  70  provides two opposing walls  100  that comprise a pair of opposing coaxial apertures  110 , for frictionally engaging and positionally guiding the control bar  60 . These apertures  110 , preferably made of a soft teflon® or other compatible material, enable linear sliding motion of the control bar  60  through them but are in contact with the outer surface  64  of the control bar  60  so as to exclude dust and dirt from the interior of the enclosure  100 . 
     To accomplish the objective of accurately measuring the linear movement of the control bar  60 , the precise detection of changes in position of the measurement wheel  10  is required. The present invention teaches several alternative methods which are well known in the art and so will be described only briefly. The illustration of FIG. 1 provides an understanding of any one of the following methods. One method of measurement wheel  10  position sensing includes the use of a radially oriented inditia pattern  18  on an exterior surface  16  of the measurement wheel  10  in combination with a sensory means  120 . The inditia pattern  18  may use, for example, method (A) opaque lines, method (B) transparent lines or method (C) magnetic stripes used in conjunction with a light source  122  and receiver  124  for the former two approaches and a magnetic sensor for the later approach. Both the light sensor and magnetic sensor are fully represented by detector  124  in FIG.  2 . 
     FIG. 2 shows the method used with light beam source  122 , positioned on a first side of the measurement wheel  10 . This light beam source  122  directs a light beam, represented by the dashed line, through the measurement wheel  10 , assuming it to be transparent, and the beam is then received by detector  124  which is positioned in opposition to the light beam source  122 . Upon wheel rotation, the light beam is sequentially interrupted by the opaque inditia as it passes through the beam  130 . 
     Another method of measurement wheel position sensing includes the application of a radially oriented transparent inditia pattern on an opaque surface of the measurement wheel  10 . Illumination and detection is accomplished in the same manner as previously described. A further means of measurement wheel position sensing comprises the use of a radially oriented inditia that is composed of materials having magnetic characteristics. The movement of these magnetic inditia elements is detected by a magnetic sensor, also represented by the detector  124 , positioned on a first side of the measurement wheel  10 , and measures the moving magnetic field as the magnetic inditia elements pass by in close proximity during rotation of the measurement wheel  10 . 
     An additional means for measurement wheel position sensing is provided by a radially oriented reflective inditia that is fixed to a non-reflective surface of the measurement wheel  10  and the light beam source positioned on a first side of the measurement wheel  10  that directs the light scattered from the inditia&#39;s reflective surface. Then as the measurement wheel  10  rotates, the reflected light is sensed by detector  124  positioned for receiving reflected light from the reflective inditia surface. 
     One or more of he above described measurement wheel position sensing techniques may be combined to accomplish the desired measurement objectives depending upon the specific application. Detected light or magnetic pulses produced by at the detector  124  are electronically counted, as is well known in the art, with each count indicating one increment of rotation of the measurement wheel  10 . The incremental counts are typically counted by an electronic circuit of well known type for accurately representing the linear change in the position of the control bar. The precise and repeatable relationship that exists between the linear control bar  60  movement and radial movement of the measurement wheel  10  is insured by the continuous engagement of the engraving on the control bar surface and the press roll embossment  66 . Economically providing this capability is the objective of this invention. 
     Clearly, the present invention may use the well known technique of dual position sensing at the measurement wheel  10  in order to determine rotational direction. In this approach two or more sensors within sensory means  120 . Logic circuits for such use are well known. 
     While the invention has been described with reference to at least one preferred embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto. Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims.