WO1988006273A1 - Electronic level - Google Patents

Abstract

An electronic instrument (1) for indicating angular inclinations. The level (1) has a substantially rectangular frame (2) having visual indicating means in the form of bubble vials (18, 19) and a visual light indicator (17). An optical encoder assembly (46) senses the angular inclination of the level (1). The optical encoder assembly includes a rotatable transparent disk (39) having a plurality of opaque, radial lines (9). A series of light emitting diodes (26) and corresponding photosensitive transistors (27) are positioned on each side of the disk. Affixed to the disk is a weight (42). When an opaque encoding line (9) passes between a light source (27) and phototransistor (26), the photosensitive transistor(26) undergoes change of state that activates an appropriate electronic circuit (500). The optical encoder assembly (46) activates indicating means including a speech synthesizer (24) which produces an audible word to correspond with the angular inclination of the instrument (1).

Description

ELECTRONIC LEVEL

Background of the Invention

Field of the Invention The present invention relates generally to angular measurement devices, such as protractor instruments and inclinometers. In particular, the present invention relates to an improved electronic slope indicating instrument which provides a verbal indication of an angular measurement.

This is a continuation-in-part of U.S. Serial No. 15,040, filed February 17, 1987.

Discussion of Related Technology The traditional instrument which has been available for indicating alignment with a horizontal or vertical axis is the bubble level. A bubble level usually consists of an elongated frame having a pair of parallel, flat longitudinal edges. Within the frame are mounted one or more bubble vials whose longitudinal axes are set at predetermined angles to the parallel edges of the frame member. The typical general purpose level has two vials, one being a "plumb vial" whose longitudinal axis is perpendicular to the frame edges, and the other a "level vial" whose longitudinal axis is parallel to the frame edges. More elaborate levels include three or more longitudinally spaced vials, including a 45 degree vial. In use, one of the parallel, longitudinal frame edges of the level is held flush against the working surface. If the working surface has achieved the desired alignment, such as horizontal, vertical, or 45 degrees, that position is indicated by the gas bubble of the appropriate vial being centered within a pair of transverse lines in the center of the vial. In each case, it is necessary that the user's eye be positioned in a location adjacent and opposite to the vial in order to determine, without parallax error, the existence of the desired alignment, and herein lies the major disadvantage of prior art levels. A traditional bubble level can be extremely time- consuming and inconvenient. Often the workpiece whose angular alignment is in question must be adjusted at some distance from the point of measurement, requiring the worker to travel repeatedly from the point of adjustment to the place where the level is located. The direct reading of the level is also difficult because it may be used in poorly lighted areas where the bubble cannot readily be seen.

One solution to these difficulties has been to create a level, usually electronic in nature, which gives an audio or visual indication that angular alignment has been achieved. Various .types of electronic levels have been proposed in the past. For example, U.S. Patent No. 3,172,212, issued to Pappas, discloses an electronic carpenter's level. The unit includes two mercury switches which are connected in appropriate electrical circuits in order to indicate a level condition. U.S. Patent No. 3,861,052, issued to Siegfried, discloses an electronic level which allows the measurement of any angular deviation. A visual indicator and buzzer are activated when the axis of the instrument corresponds with the axis to be measured.

U.S. Patent No. 4,079,521, issued to Uhorczak, discloses an electrically actuated level having light- emitting means to indicate when the level is in the desired _^horizontal or vertical orientation. However, the invention does not feature an audible indicator.

The devices just discussed have suffered from various problems, such as a lack of portability, relative crudeness in determining actual angular displacement, or a general fragility of construction which is unsuitable in the actual environment of the workplace. Summary of the Invention

The present invention is an instrument for indicating angular inclinations relative to the surface of the earth.

The instrument has a substantially rectangular frame with parallel edges, and the length of the level is substantially greater than the level's height. The frame is constructed of a non-deformable material to maintain the top and bottom edges in parallel relationship. The invention also includes sensing means for determining the angular inclination of the level, the sensing means having a rotatable disk with a weight thereon. The sensing means also includes electronic circuitry which detects the angular position of the weighted disk. Another element of the present invention is indicating means which produces a verbal word to correspond with the angular inclination of the instrument.

According to one aspect of the invention, the disk is substantially transparent, with a plurality of opaque radial lines. On one side of the disk is light-emitting means, and the opposite side of the disk has corresponding light-sensing means, so that the transparent portions of the disk permit a light beam to pass through the disk, whereas the opaque lines block passage of the light. When the opaque encoding lines on the disk pass between the light-emitting source and the light-sensing device, an appropriate electronic circuit is activated to give the desired audio indication. In the preferred embodiment, the instrument emits audible words at fifteen degree intervals of angular inclination. A preferred embodiment constructed according to the principles of the present invention utilizes light emitting diodes (LED's) as the light-emitting means and photosensitive transistors as the light-sensing means. The photosensitive transistors are biased to operate in a digital manner such that the photosensitive transistor's output is either a high voltage corresponding to a logical one or a low voltage corresponding to a logical zero. In this manner, a binary code of zero's and one's representing the level's angle of inclination are transmitted to a latching device which holds the binary code until the level achieves the desired angle. When the desired angle is achieved, the binary code is passed along to a multiplexer and a level detector. The multiplexer evaluates the binary code and provides a starting address for the memory location in a speech EPROM at which the speech corresponding to the binary code, and achieved angle, is stored. Simultaneously, the level detector triggers a start cycle circuit which in turn sets an RS Flip-Flop. When the RS Flip-Flop is set it provides a speech start signal to a speech generator circuit. The circuit utilizes the starting address provided by the multiplexer to find the correct speech to output to a small speaker located on the device. After the speech generator has completed communicating the speech, it provides a Word Finished reset signal to the RS Flip-Flop, thereby readying the circuit to communicate the speech corresponding to the next achieved inclination or the current angle of inclination if that angle is maintained. The instrument will repeat the speech at a rate of one word per second in the preferred embodiment.

Accordingly, the present invention provides a rugged, compact and highly accurate level that includes means for electronically generating an audible signal that verbally notifies the operator that the desired angular orientation has been achieved.

A unique aspect of the present invention resides in its use of a speech synthesizer such that the words "level", "forty-five", "ninety", etc., are actually- generated and communicated to the operator through a speaker. This type of audible signal gives a clear indication of the measured angle of inclination and minimizes errors in operation. The use of the speech synthesizer also eliminates the problems of prior art devices which generated a tone that was either difficult to distinguish from background noise or which was difficult to perceive by persons with certain hearing impairments.

Another feature of the present invention is the instrument's ability to sense the angle of inclination and provide an audible indication throughout the full three- hundred sixty (360) degrees of rotation. The construction of the sensing disk makes this feature possible by providing optical encoding lines around the entire circumference of the sensing disk, and by having a channel sized and configured to accommodate passage of the disk's weight through the channel. This feature allows the user to take continuous angular inclination readings without significantly repositioning the level.

The instrument of the present invention is also relatively lightweight and portable. The instrument is made of durable and non-deformable material, but is designed to be lightweight enough be easily carried and lifted by one person. In addition, the instrument features large handles which enhance its portability and make it less likely to be dropped.

The present invention is also advantageous in that it is highly accurate. The sensing disk of the present invention rides within a unique bearing arrangement which is substantially frictionless and allows the disk to be free-riding.

Another advantageous feature of the level of the present invention is that it is simple and uncomplicated in construction, resulting in a relatively simple manufacturing process and a relatively inexpensive unit. Yet another advantageous feature of the level is the manner in which the electronic circuitry provides for the finishing of one cycle of speech output when an angle of inclination has been achieved prior to beginning a new cycle. To provide for this feature, a three bit latch is used in connection with the light sensing means to store the achieved angle. The three bit latch is updated when the RS Flip-Flop is set by the light sensing means and reset by the speech generator. In operation, the light sensing means indicates that an angle of inclination has been achieved and sets the RS Flip-Flop to start a speech cycle. The stored three bit latch information is then transmitted to the speech generator to communicate the achieved angle. After completion of the speech cycle, the speech generator indicates that a cycle has been completed and resets the RS Flip-Flop. In this manner, the RS Flip- Flop will provide a signal to the speech generator to begin a new cycle and the three bit latch will store the next achieved angle information.

Another feature of the circuitry is in the manner in which the desired language and binary position code are analyzed to provide for the correct memory location of the speech EPROM to be accessed. A digital language selector switch is used in connection with a NOR gate, inverter and multiplexer to provide for the required four most significant address bits. The binary position code from the light sensing means is input to the NOR gate such that if at least one bit* is high, the output is low. This corresponds to providing a low most significant bit to the multiplexer for accessing a memory location which is in the lower half of the speech EPROM where the angles other than 0° are located. However if all bits of the binary position code are low, the NOR gate output is low. This provides a high most significant bit to the multiplexer for accessing a memory location in the upper half of the speech EPROM where the different languages for the word "level are stored. These and other features of the present invention will become apparent from a consideration of the following description of the invention and accompanying Drawings which form a part of this application.

Brief Description of the Drawings

In the Drawings, which form a part of the specification and are to be read in conjunction therewith. an optimum embodiment of the invention is shown and, in the various views, like numerals are employed to indicate like parts.

FIGURE 1 is a front elevational view of the electronic level constructed according to the present invention;

FIGURE 2 is a bottom view of the electronic level depicted in Fig. 1;

FIGURE 3 is a end view of the electronic level depicted in Fig. 1; FIGURE 4 is a perspective exploded view of the mid- section of the electronic level depicted in Fig. 1;

FIGURE 5 is a cross-sectional view of the electronic level taken along line 5-5 of Fig. 1;

FIGURE 6 is a cross-sectional view of the electronic level taken along line 6-6 of Fig. 1;

FIGURE 7 is a cross-sectional view of the electronic level taken along line 7-7 of Fig. 1;

FIGURE 8 is an enlarged fragmentary view of the radial disk of the present invention taken along line 8-8 of Fig. 7;

FIGURE 9 is a plan view, in section, of the level encoding disk assembly of the present invention;

FIGURE 10 is a front elevational view of the level encoding disk of the present invention; and FIGURE 11 is a block diagram illustrating functional elements of the electronics of a preferred embodiment electronic level; and

FIGURE 12 is a more detailed schematic diagram of several of the functional blocks illustrated in Fig. 11. Detailed Description of the Preferred Embodiments

Referring generally to Fig. 1, an electronic level constructed according to the principles of the present invention is shown generally at 1. The level 1 includes a rigid, substantially rectangular frame 2 which can be constructed of a variety of materials which resist bending, warping or other deformation about the longitudinal axis. For example, the frame 2 may be constructed of a metallic. wooden, or plastic-graphite material. The frame 2 can also be made of black poly-carbonate (10 - 15% glass-filled). A durable plastic material may also be used for the frame 2 of the level, with the use of a plastic material reducing the weight of the level 1. The most important property of frame 2 is the ability of the upper edge 3 to remain ^"parallel to the lower edge 4 throughout the life of the device 1.

The aspect ratio of the frame 2, that is, the ratio of the length of the level 10 to the width of the level 10, should be relatively large, perhaps on the order of 15 to 1. In any event, the use of the longest possible frame 2 will ensure that multiple sensing elements contained within the frame 2 can measure widely separated portions of the same surface, thereby ensuring reliability of the resultant measurement. The preferred length of the level 1 from end to end is approximately four feet (1.2 meters).

The device 1 is turned on by means of a push-button switch 30, with light-emitting diode 28 indicating that the device 1 is, in fact, "on". Another indicator light 17, which is present in a preferred embodiment, but which is optional, becomes actuated when the level is in a horizontal or vertical position. The indicator lights 17 and 28 are connected to the electrical circuit on the circuit board 8. The lights 17 and 28, when illuminated, are observable through transparent or translucent light covers.

In the preferred embodiment, a pair of bubble vials 18, 19 indicate when the level 1 is in a horizontal and vertical position, respectively.. The bubble vial 18 has a longitudinal axis perpendicular to th« frame edges 3, 4, and measures a vertical inclination, and the bubble vial 19 has a longitudinal axis parallel to the frame edges 3, 4 and indicates a horizontal inclination. The bubble vials 18, 19 are not connected with the electronic circuitry 500 of the level (described below) which is resident on circuit board 8. The bubble vials 18, 19 can be used as a visual indication of a horizontal or vertical level condition, and can also be used to check the operational accuracy of the electronic level 1.

The longitudinal edges 3, 4 and transverse edge 5 of the level may have stainless steel strips 6 affixed thereon. The strips 6 are durable, resist rusting, and minimize the potential for warping of the level 1. A pair of handles 20 enable the user to easily transport and adjust the position of the level 1. Thus, the handles 20 and relatively light weight of the instrument allow the level 1 to be highly portable.

The frame 2 contains two cavities, a small cavity 55 for housing the battery 7, and a relatively long cavity 21 for holding the sensing means which determines the angular inclination of the level 1. The electronic circuit 500 of the level 1 is powered by the battery 7, which is a single, nine volt battery in the preferred embodiment. The battery compartment 55 has a face plate 22 which is removable by means of fastening screws 23 to facilitate replacement of the battery 7 when a new battery is required by the unit.

The battery 7 is selectively connected to the electronic circuit 500 through the power switch 30 which is mounted on the front panel. A language selector switch 11, described below, is also contained in the battery compartment 55 in the preferred embodiment.

The large cavity 21 has a removable face plate 15 held onto the frame 2 with suitable fasteners 16. The circuit board 8 is attached to the back side of the face plate 15 by suitable peg fasteners 56. One novel aspect of the present invention resides in the unique sensing means or optical encoder assembly 46 utilized to determine when a level condition has been achieved. The optical encoder assembly 46 includes a level encoding disk 39 and corresponding electronic circuitry 500. The level encoding disk 39 of the present invention is illustrated in greater detail in Figs. 7, 8, 9. and 10. The interaction of the level encoding disk 39 with electronic circuit 500 is best seen in Fig. 11. The disk 39 is round in shape and approximately two and one-half (2-1/2) inches (6.3 centimeters) in diameter in the preferred embodiment. The disk 39 is mounted upon a shaft 45 so as to be substantially parallel to the front face plate 15. A mounting bracket (not shown) may be interconnected to the pivot point to provide additional stability to the disk assembly. As illustrated in Fig. 9, each end of the shaft 45 has a polished shaft point 48. In the preferred embodiment, each point 48 rotates within a jeweled bearing 47 which is mounted in a threaded screw 49. The two threaded screws 49 are located within a pair of holders 50, 51, described below.

The jeweled pivot bearing preferably consists of two small rubies 47, an upper and lower ruby. The rubies 47 are in the shape of a cylinder approximately 0.12 inch (3.0 millimeters in height) with a small hole in the center. The polished shaft points 48 ride in the thirty one- thousandths (30/1000) of an inch (0.76 millimeter) diameter hole in the center of the ruby in the preferred embodiment. The rubies are inserted within a one-sixteenth (1/16) of an inch (1.6 millimeters) diameter hole in a threaded screw 49, by utilizing a jewel press. The threaded screw 49 which contains the rubies 47 is used for tension adjustments and shaft point captivity. By utilizing two ruby jewel bearings 47, friction is substantially eliminated and the disk 39 may be rotated freely.

The disk 39 is preferably made of a transparent plastic material such as clear polycarbonate. Upon the disk 39 are a series .of opaque, radial lines 9. As shown in Fig. 10, there are a series of narrow lines 10 near the perimeter of the disk 39, and slightly wider radial lines 11 proximate the center 25 of the disk 39. The opaque lines 9 are applied to the disk 39 with a durable paint, such as black enamel. The width of the wider lines 11 is preferably approximately ten one-thousandths (10/1000) of an inch (0.25 millimeter). The opaque lines 9 correspond to various angles of inclination, with the 0° position corresponding to a horizontal or level condition.

A mass or weight 42 is affixed to disk 39, the locus of the mass 42 being on a radial line offset precisely 90 degrees from the opaque radial line 9 defined by "0°" or the level condition. The disk 39 is oriented so as to reside in a plane that is perpendicular to the surface of the earth, so that the mass 42 will be deflected by gravity in a radial direction toward the center of the earth. Preferably, the weight 42 is on both the front and back sides of the disk 39, as shown in Figs. 7 and 9, and is one-eighth (1/8) of an inch (3.2 millimeters) in diameter.

The mass 42 is made of steel or brass. The disk 39 may also have a damper (not shown) to minimize rotation of the disk 39 after the level 1 has been positioned at the desired angle of inclination.

The disk assembly 46 also includes optical encoder holders 50 and 51, one holder being on each side of the disk 39. Each of the holders 50 and 51 have a base portion proximate an outer edge of the disk 39, with a holder arm extending from the base portion toward the central shaft 45 of the disk 39. There is a holder arm 50, 51 on each side of the disk 39, and the holder arms 50, 51 are parallel and in alignment with each other. The holder 50 contains a series of light emitters 26, and the holder 51 contains a series of light sensors 27. As shown in Fig. 9, there are four light-emitting diodes (LED's) 26a, 26b, 26c and 26d, and four corresponding photosensitive transistors 27a, 27b, 27c, and 27d in the preferred embodiment. The LED's 26 emit a beam of light substantially parallel to the disk shaft 45 in a direction toward the disk 39. The photosensitive transistors 27 are mounted so that they are longitudinally aligned with the four LED's 26 along the path parallel to the shaft 45. In their "normal" state, the light passes through the clear disk 39 and is received by the photosensitive transistors 27. However, when an opaque encoding line 9 passes between an LED 26 and a photosensitive transistor 27, the photosensitive transistor 27 undergoes a change of state so that it activates an appropriate electronic circuit.

Referring now to Figs. 11 and 12a, illustrated at 46 there is a four-channel optical encoder assembly which reads the opaque encoding lines 9 present on the disk 39 in order to determine the angle of the level 1. As described, each of the four channels utilizes an LED 26a, 26b, 26c and 26d driven by current source 501. Current source 501 may be any number of well known devices, the simplest of which is merely a voltage potential source in series with a resistor. As best shown in Fig. 12a, LED 26a has its anode connected to voltage potential +V via resistor 502 and its cathode to ground/reference. Similarly, the anodes of the other three channel LED's 26b, 26c and 26d anodes are connected to voltage potential +V via resistors 503, 504 and 505 respectively and their cathodes are tied to a ground/reference level. For convenience, the voltage/reference level will be referred to as ground. The values of the resistors 502, 503, 504 and 505 depend upon the voltage potential chosen and the LED's 26 utilized as those skilled in the art will recognize.

Those skilled in the art will recognize that while not completely shown in the Figs, or described herein, all of the logical components are connected to appropriate voltage potentials, grounds and buses in order to enable them to operate in the manner intended. Further, while not shown it is to be understood that appropriate power regulation and filter means are provided to the electronic circuitry 500 to enable proper operation.

As discussed above, LED's 26 emit light through the clear disk 39 which is received by photosensitive transistors 27a, 27b, 27c, and 27d. In operation, when the unit is turned on, the LED's 26 emitted light provides base current to photosensitive transistors 27. The photosensitive transistors 27 have their collectors connected through pull-up resistors 506, 507, 508 and 509 respectively to a positive voltage potential +V and their emitters connected to ground. Therefore, when base energization is provided, the transistor turns on and the voltage across the photosensitive transistor's 27 collector and emitter goes low in the well known transistor manner. This low voltage corresponds to a logical "zero" when using positive logic.

When the clear disk 39 is in either a level position or at a designated angle, however, the light is blocked by the opaque lines 9 stopping the photosensitive transistors 27 energization. This turns the transistor off. In this state, the effected photosensitive transistor's 27 voltage at its collector rises. This high voltage corresponds to a logical "one" when using positive logic. The emitter and sensor farthest from the center 48 of the disk 39 and near the disk's edge are identified with the reference numerals 26a and 27a respectively. This emitter and sensor are regarded as the "first channel", with the remaining three pairs of LED's 26 and photosensitive transistors 27 being regarded as the second through fourth channels, or channels b, c and d, respectively.

The first channel LED 26a and sensor 27a are in their normal, light-transmitting and receiving state until a narrow opaque encoding line 10 near the outside perimeter of the disk blocks the light. In a preferred embodiment the lines 10 are approximately 0.2 inch (5.1 millimeters) radially. This tells the optical encoder assembly 46 that a predetermined angle of inclination has been reached. In the preferred embodiment, an audible indication is emitted from speaker 12 at fifteen degree intervals, so that blockage of the light beam by the line 10 signifies that one of the following angles of inclination has been reached: 0°, 15°, 30°, 45°, 60°, 75° and 90°. The optical encoder assembly 46 then determines the state of the remaining three channels to determine which particular angle has been reached. The first channel opaque lines 10 near the perimeter of the disk 39 are relatively narrow to provide more accuracy to the first channel. The remaining channels 2-4 correspond to relatively thicker lines 11, because the higher degree of accuracy associated with a narrower line is not needed for them. The line width for channels 2-4 may be of any width provided that the electronic circuit 500 can latch onto the corresponding code. As shown in Fig. 10, a particular combination of lines 9 corresponds to particular angles. The electronic circuit 500 reads the state of the four photosensitive transistors to determine the particular angle which has been reached. When the sensing means determines the particular angle of inclination, an appropriate audible word is enabled to identify the angle. The word is audibly transmitted by means of a speaker 12 and through an appropriate grill 13 in the front panel of the frame 2.

Fig. 10 and Table 1 illustrate the relationship of the second, third and fourth channels of disk assembly 46 to the angle of inclination. Table 1 is shown below:

TABLE 1

Hexadecimal Language Languac |e Channel

EPROM Selector Selection Switch b, c & d

Address Switch Binary Output Binary Output

Locations Speech Position S2S1S0 deb

0000-07FF — — * —

0800-0FFF Fifteen — —* 001

1000-17FF Thirty — —* 010

1800-1FFF Forty-five — —* 011

2000-27FF Sixty — —* 100

2800-2FFF Seventy-five — —* 101

3000-37FF Ninety — —* 110 1

4000-47FF Tone 7 000 000 Ul

1

4800-4FFF Level (Chinese) 6 001 000

5000-57FF Level (Japanese) 5 010 000

5800-5FFF Level (German) 4 011 000

6000-67FF Level (Italian) 3 100 000

6800-6FFF Level (Spanish) 2 101 000

7000-77FF Level (French) 1 110 000

7800-7FFF Level (English) 0 111 000

* These values are immaterial in the selection process for these achieved angles.

In Fig. 10, a blank space corresponds to a phototransistor 26 in an "on" or logical zero state (i.e. receiving light through disk 39), while a line corresponds to an "off" or logical one state (i.e. the light is blocked by an opaque line 9). In a preferred embodiment illustrated in Table 1, each angle of increasing magnitude equals a corresponding binary number. Therefore, while 0° equals binary output 0 (i.e. 000), 15° equals binary 1 (001), 30° equals binary 2 (010), and so on. In this manner, optical encoder assembly 46 determines the appropriate angle of inclination in increments of 15 degrees by producing binary output in channels b, c and d. It is to be understood that the increments between angles, as well as the angles to be read, can be varied within the scope of the present invention. It should be further understood that although positive logic is utilized in the preferred embodiment, use of negative logic is within the scope of the present invention. Another novel feature of the present invention is that the level does not emit a jumble of words when the level is being moved around quickly. Instead, the circuitry of the present invention stores the readings of channels b, c and d when an interruption in channel a is sensed. In a preferred embodiment illustrated in Figs. 11 and 12, the device latches onto the code of the four-channel disk assembly 46 by means of a binary position code latch device 580 (Fig. 11). The output signals from the photosensitive transistors 27b, 27c and 27d are first amplified by amplifier 530. Amplifier 530 can be of any configuration well known in the art and comprises, in the preferred embodiment, three NPN transistor amplifiers (530b, 530c and 530d) with emitter connected to ground and collectors connected to a positive voltage potential source through pull up resistors (535 536 and 537) and biased within their operable range. The amplifier 530 inverts the signals generated by the photosensitive transistors 27. The amplified signals are then sent to the latch 580. In the preferred embodiment, the latch is manufactured by Texas Instrument and designated 74HC175. The device operates in a well known D-flip flop manner, with each of channels b, c and d being the D inputs to three separate D flip flops. The clock pulse for the D flip-flop is provided by an RS Flip-Flop 590 which is set when level detector 540 is activated by the first channel 46a. RS Flip-Flop is later reset by the Word Finished clock 611. This Word Finished clock 611 provides a reset pulse after speech generator assembly 610 completes its speech generation cycle.

In operation, the first channel is sent from amplifier

530 to a level detector 540. Level detector 540 is a comparator op amp which compares the signal to a reference voltage level such that when the first channel goes to a logical one state, the level detector 540 is triggered.

When level detector 540 is triggered, it emits a signal which resets an automatic power off timer circuit 570 and provides a signal to start cycle circuit 550. Start cycle circuit 550 acts as a noise filter and a sensitivity damper. The circuit filters and slows the firing of the start cycle circuit 550 in order to avoid an improper pulse in the event of dust or other conditions which might become resident on disk 39 in a construction environment. The sensitivity is damped to avoid triggering a speech generation cycle when rapidly moving the level 1 through more than one achieved angle. Start cycle circuit 550 comprises, in the preferred embodiment, two filtering capacitors (not shown) tied to ground via a sensitivity adjusting resistor pot (not shown) and a comparator amp

(not shown). Start cycle circuit 550 in turn provides the set input to RS Flip-Flop 590. The other input to RS

Flip-Flop 590, as described, is provided by an output from speech generator assembly 610 which provides a reset signal

(designated "Word Finished" 611 on Fig. 11) when the speech generator has finished its output. This provides that a new cycle will not start until the previous speech generated has finished.

Therefore, in operation RS Flip-Flop 590 will not trigger until the "Word Finished" signal 611 has reset RS Flip-Flop 590 and subsequently the start cycle pulse from start cycle circuit 550 has gone high. At that time, both the signals designated "speech start" 612 and the "strobe" cycle 613 will go high thereby latching binary position code latch 580 with the correct three-bit binary code input from light sensors 27b, 27c and 27d and also prompt speech generator 610 to determine the appropriate output in order to start the speech cycle. To do so, speech generator 610 goes to the speech erasable programmable read only memory 620 (speech EPROM) to provide the necessary data to deliver to amp 630 and speaker 640. In the preferred embodiment, multiplexer 600 receives the latched binary position code from latch 580 and language switch 11 to determine the address corresponding to the appropriate speech which is stored in preset address locations in speech ROM 620. Table 1 illustrates the memory addresses, in hexadecimal, the speech stored at those locations, and the corresponding binary codes. The digitized speech information is programmed into the speech EPROM 580 before manufacture of the electrical circuit 500 in a manner well known in the _art. The speech information stored therein is sampled and digitized speech, as is well known in the art.

In the event that the photodetectors correspond to the three-bit binary code 000, corresponding to 0°, then multiplexer .600 looks to the upper half of the memory speech EPROM 620. The position of language switch 11 will then determine which language memory address will be accessed for output to amplifier 630 and speaker 640. Language switch 11 is a negative logic binary coded switch which provides for three outputs. Depending upon the switch's position, the values of the outputs will vary. Since it is negative logic, in the preferred embodiment. the switch position corresponds to its positive corresponding binary number after inverting each bit. As illustrated in Table 1, if the switch is set at its "0" position, the output will be 111 (corresponding to 000 positive logic). Continuing to position 1, the output is 110 and so on through position 7.

In the event that the three-bit binary code does not correspond to 0°, then the lower half of the memory addressed in speech EPROM 620 will be accessed. In the preferred embodiment, language switch 11 is then ignored as the language for the degrees, in the preferred embodiment, is provided only in English. However, language could easily be provided for the degrees as well, as those skilled in the art will appreciate. Once the starting memory address is provided to speech EPROM 620, speech generator 610 accesses the starting location, reads the speech generating data stored at those locations, and outputs the data to amplifier 630 and speaker 640. When speech generator 610 has finished accessing memory locations, a Word Finished 611 reset signal is provided to

RS Flip-Flop 590 in order to allow for a new cycle.

The emitter and sensor holders 50, 51 have a notch 52 formed in their holder arms, near the edge of the disk 39. The notches 52 are opposite each other and form a channel 52. The channel 52 is sized and configured to correspond with the size of the mass 42, so that the mass 42 can pass through the channel 52 freely as the disk 39 is rotating. This feature of the invention allows angles to be read as the level 1 rotates a full 360 degrees, without the necessity of the user turning the level 1 around to measure various angles.

Another feature of the present invention is an adjustment bracket 54 which allows preliminary adjustment of the level 1 before it is used by the consumer. The adjustment bracket 54 is located proximate the base portion of the holders 50, 51 and is interconnected to the electrical wires 55 leading to the sensors 27. The bracket 54 is preferably adjusted by turning a spring-loaded threaded bolt for alignment and adjustment of the sensors 27 and wires 55. The adjustment bracket 54 allows for the four sensors to be perfectly in line to improve the accuracy of the device 1.

As discussed, the language selector switch 11 is interconnected to the speaker 12 so that the word "level" can be heard in a variety of languages, or as a buzzer tone. Simple adjustment of the language switch 11 allows the user or the manufacturer to select the desired language or buzzer output sound.

The electric circuit 500 includes a speech generator circuit 600 which is activated by the first channel to emit the desired words. In the preferred embodiment, the device emits the words "level", "15", "30", "45", "60", "75", and "90". The number of degrees emitted corresponds to the angle of the level with respect to horizontal or the gravitational force of the center of the earth. The word emitted is perceived through the speaker 12 after amplification through amplifier 630. In the preferred embodiment, amplifier 630 is a standard audio amplifier which is connected to the speech synthesizer via a low pass filter (not shown), an AC coupling capacitor (not shown) and a voltage divider (not shown). As is well known in the art, the low pass filter eliminates digital noise, the voltage divider reduces the output level to the amplifier and the AC coupling capacitor disconnects the system from any DC levels present.

As best seen in Fig. 12b, channels 2, 3 and 4 of photosensitive transistors 27 are input to the binary position code latch 580. In the preferred embodiment, binary position code latch 580 is a device designated as a 74HC175 and manufactured by Texas Instruments. The three inputs b, c and d correspond to the outputs from amplifiers 530b, 530c, and 530d respectively. Operating in the well known D flip-flop manner, wherein the output (Q) of the D flip-flop corresponds to the input data (D) subsequent to an occurrence of a clock pulse. In the preferred embodiment, since the amplifier 530 has inverted the signals, rather than taking the output (Q), the inverted output signal (Q) is taken to provide for the appropriate input into multiplexer 600.

Still referring to Fig. 12b, multiplexer 600 consists of NOR gate 601, inverter 602, and multiplexer chip 603. In the preferred embodiment, multiplexer chip 603 is designated as a CD4519 and is manufactured by RCA. Output lines 581, 582, and 583 from binary position code latch 580 provide the input to NOR gate 601 and multiplexer chip 603 inputs e, f, and g. NOR gate 601 output will go low if any one of inputs 581, 582, or 583 are high. However, if those three inputs are low then the output of NOR gate 601 will be high. The output of NOR gate 601 is simultaneously delivered to input h on multiplexer chip 603 and to inverter 602. The output of inverter 602 is delivered to input i of multiplexer chip 603. This inverted signal is provided to Input i since the multiplexer chip 603 requires that an opposite polarity signal of input h be delivered to input i. Therefore, when multiplexer chip 603 receives a high signal at input h (corresponding to low input lines 581, 582, and 583), it indicates that the instrument 1 is at an inclination of zero degrees. In this event, the upper portion of the EPROM must be read. Therefore, multiplexer chip 603 must look to inputs j, k and 1 which are provided by binary coded language switch 11.

Language switch 11, as described above, provides inputs to multiplexer chip 603 in accordance with Table 1. However, if any one of input lines 581, 582, or 583 are high, then NOR gate 601 output is a zero wherein multiplexer chip 603 will read inputs e, f, and g. In this manner, multiplexer 600 in connection with language switch 11 is able to determine the angle of inclination which instrument 1 has achieved. This information is converted into a starting hexidecimal EPROM address location and delivered to speech EPROM 620 via lines m, n, and o. In order to provide a hexadecimal address, 15 binary input lines are required to EPROM 620. Address generator 611 provides the 11 least significant binary inputs. Multiplexer chip 603 provides the next three least significant binary inputs. NOR gate 601 provides the most significant bit to EPROM 620 via line 622. Address generator chip 611, which in the preferred embodiment is a CD 4040 chip manufactured by National Semiconductor, then provides an incrementing of the lower memory address bit positions to successively access each individual address location wherein digitized sampled speech is stored in speech EPROM 620. After accessing each memory location addressable by incrementing the least significant 11 bits, address generator 611 provides a reset, pulse via line 621 to RS Flip-Flop 590.

The information located at each successively accessed memory location in speech EPROM 620 is transmitted via lines aa-hh designated generally as "A" to byte converter 612. Byte converter 612 takes the 8 bit binary input and converts it into two 4-bit output messages. In the preferred embodiment, the byte converter is an RCA multiplexer designated CD 4019. The two 4-bit messages are delivered to speech generator 613 which is an OKI semiconductor speech chip. The implementation of the speech generator 613, byte converter 612, speech EPROM 620, timing, D-type flip-flops 618 and 619, and address generator 611 are fully described and disclosed further in the OKI semiconductor application note OKI Semiconductor, Speech Synthesis Using the OKI MSM 5205 ABPCM Speech Synthesizer Circuit (undated) . for the OKI semiconductor chip 5205 which is hereby incorporated by reference.

Another feature of the present invention is an adjustment pot (not shown) which sets the predetermined voltage level necessary to read an interruption, so that complete blockage of the light is not necessary. The adjustment pot allows for improved accuracy of the level 1 and is incorporated in the start cycle circuit 550 described above.

In operation of the unit, the power switch 30 is turned on. The instrument 1 is then positioned at the appropriate angle until an audible readout is produced. The working surface can then be placed against the level 1 so that the axis of the working surface is at the desired angle of inclination. Alternatively, the level 1 can be placed against the working surface, and the working surface can be rotated until the desired output is produced, e.g. the word "level" for a horizontal surface. When a horizontal or vertical angle of inclination is obtained, the indicator light 17 and the bubble vials 18, 19 will show that condition, as well as the audible output. The level 1 automatically shuts off after a desired number of seconds, thirty seconds in the preferred embodiment. In the preferred embodiment, the circuit which turns the unit off is an RC network (not shown) charged at the start of a cycle. The RC network decays to a voltage level at which time a comparator (not shown) which compares the voltage level of the RC network to a reference voltage level from the battery through a voltage divider. When the RC network decays to a certain value, the comparator turns the circuit 500 off.

It is to be understood that numerous and various modifications can be readily devised in accordance with the principles of the present invention by those skilled in the art without departing from the spirit and scope of the invention. Therefore, it is not desired to restrict the invention to the particular construction illustrated and described but to cover all .modifications that may fall within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS

1. An instrument for indicating angular inclinations relative to the surface of the earth, comprising:

(a) a frame, said frame being substantially rectangular and having a height and width, said width being substantially greater than said height, said frame having a first and second edge which are parallel, said frame being constructed of a non- deformable material so that the first parallel edge retains its spatial relationship to the second parallel edge;

(b) sensing means for determining the angular inclination of said frame with respect to the earth's surface, said sensing means including a rotatable disk having a first and second side and having a weight which is attracted to the earth's surface by gravity and including circuit means for detecting the rotatable position of said disk; and

(c) indicating means activated by said sensing means for producing an audible word which corresponds with the angular inclination of said frame.

2. The instrument of claim 1, wherein said disk is substantially transparent and includes a plurality of opaque radial lines; wherein said sensing means further includes a light-emitting source mounted adjacent said first side of said disk and a light-sensing receptor mounted adjacent said second side of said disk, said light-emitting source directing light toward said light- sensing receptor along a path substantially perpendicular to said disk; and wherein said disk is interposed between said light emitting source and light sensing receptor.

3. The instrument of claim 1, further comprising visual indicating means for providing a visual signal when said frame is disposed at a horizontal or vertical inclination with respect to the earth's surface.

4. The instrument of claim 1, wherein said disk is mounted upon a shaft, each end of said shaft being mounted within a jeweled bearing member.

5. The instrument of claim 2, wherein said indicating means is activated at fifteen degree intervals of said angular inclination.

6. The instrument of claim 2, wherein said light- emitting source is mounted within a first holder and said light-sensing receptor is mounted within a second holder, said first and second holders being parallel to each other and extending radially with respect to said disk, said holders defining a channel which is sized and configured to accommodate said weight.

7. The instrument of claim 2, wherein said light sensing receptor includes means for generating sensed signals responsive to said opaque radial lines.

8. The instrument of claim 7, wherein said circuit means comprises:

(a) first memory means cooperatively connected to said light sensing receptor for receiving and storing said signals generated by said light receptor means;

(b) logic means cooperatively connected to said first memory means and said indicating means, for determining and generating from said stored signals an output signal for said indicating means bearing information for producing that audible word corresponding with the angular inclination of said instrument.

9. The instrument of claim 8, wherein said indicating means includes means for generating a reset signal corresponding to completion of transmission of an audible word.

10. The instrument of claim 9, wherein said logic means include reset means, connected to receive a sensed signal from said light sensing receptor and to receive said reset signal from said indicating means for initiating transmission of said audible word and for instructing said first memory means to store said signals, whereby said. reset means is unable to reinitiate or reinstruct until receiving said reset signal.

11. The instrument of claim 10, wherein said reset means is an RS Flip-Flop.

12. The instrument of claim 10, wherein said logic means further comprises:

(a) gate means cooperatively connected to said first memory means for determining and generating from said stored signals the signal corresponding with the angular inclination of said instrument; and

(b) second memory means connected to said gate means and said indicating means for storing digital information corresponding to angles of inclination of the instrument, whereby said gate means provides a signal corresponding to said memory location and corresponding to said angle of inclination of said instrument.

13. An instrument for indicating angular inclinations relative to the surface of the earth, comprising: (a) sensing means for determining the angular inclination of said instrument with respect to the earth's surface, said sensing means including a rotatable disk having first and second sides and having a weight which is attracted to the earth's surface by gravity;

(b) circuit means responsive to said sensing means for detecting the rotatable position of said disk and generating a signal corresponding to said rotatable position of said disk; and (c) indicating means activated by said circuit means for producing an audible wcrd corresponding with the angular inclination of said instrument.

14. The instrument of claim 13, wherein said disk is substantially transparent and includes a plurality of opaque radial lines, said sensing means further including light emitting means mounted adjacent said first side of said disk and light sensing means mounted adjacent said second side of said disk, said light emitting means directing light toward said light sensing means along a path substantially perpendicular to said disk.

15. The instrument of claim 14, wherein said light sensing means includes means for generating sensed signals responsive to said opaque radial lines.

16. The instrument of claim 15, wherein said circuit means comprises:

(a) first memory means cooperatively connected to said light sensing means for receiving and storing said signals generated by said light sensing means; and

(b) logic means cooperatively connected to said first memory means and said indicating means, for determining and generating from said stored signals an output signal for said indicating means bearing information for producing that audible word corresponding with the angular inclination of said instrument.