US3601408A

US3601408A - Golf swing training apparatus

Info

Publication number: US3601408A
Application number: US865665A
Authority: US
Inventors: Kenneth K Wright
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-10-13
Filing date: 1969-10-13
Publication date: 1971-08-24
Anticipated expiration: 1988-08-24

Abstract

The time and position of a golf club head are sensed photoelectrically at selected stations along a practice swing, and corresponding characteristics of the swing and of the resulting ball flight are computed electronically and displayed to the player. The lateral club position is sensed accurately at spaced stations near the ball for computation of the swing direction. The clubhead attitude at impact is determined by two sensors spaced along the club face. Matrix circuitry computes the nature of ball flight from the club attitude and swing direction. Ball distance is computed by generating a pulse rate that varies with the ball flight characteristic, and counting the pulses during the portion of the swing between set points. The electronic computing system is reset during a backswing, and all computations are completed during the forward swing. The display is activated automatically as the swing is completed, and remains on until the ball is addressed for a new swing.

Description

United States Patent [72] Inventor Kenneth K. Wright 800 Rlrn Road, Pasadena, Calif. 91107 (21] Appl. No. 865,665 [22] Filed Oct. 13,1969 [45] Patented Aug. 24, 1971 {54] GOLF SWING TRAINING APPARATUS 17 Claims, 8 Drawing P1.

[52] U.S.C1. 273/l86 R, 273/185, 73/379 [51) Int. CL A631) 69/36 [50] Field 01 Search 273/183, 184, 185, 186; 73/379 [56] References Cited UNITED STATES PATENTS 2,399,668 5/1946 Francis 273/186 R 2,571,974 10/1951 Wa1ker...... 273/186 R 2,825,569 3/1958 Alvarez 273/186 R 3,020,049 2/1962 McNeill 273/186 R 3,117,451 1/1964 Verne Ray et a1. 73/379 Primary Examiner-George J. Marlo Attorney-Charlton M. Lewis ABSTRACT: The time and position of a golf club head are sensed photoelectrically at selected stations along a practice swing, and corresponding characteristics of the swing and of the resulting ball flight are computed electronically and displayed to the player. The lateral club position is sensed accurately at spaced stations near the ball for computation of the swing direction. The clubhead attitude at impact is deter mined by two sensors spaced along the club face. Matrix circuitry computes the nature of ball flight from the club attitude and swing direction. Ball distance is computed by generating a pulse rate that varies with the ball flight characteristic, and counting the pulses during the portion of the swing between set points. The electronic computing system is reset during a backswing, and all computations are completed during the forward swing. The display is activated automatically as the swing is completed, and remains on until the ball is addressed for a new swing.

PATENIEB' mama SHEET 1 OF 3 5. Q n .En

PATENIEU AuB24 IHYI mean 3 nr 3 a z @w f e P. g fi vIH h w J A 2 m: r w x a. m E a a $1 K P z T r T 6 H 0 7% 0M 0 if 4 m k 5 2 3 M M M e e 2 TV PW f l|| WM fl fwmmw f a Q a p. Q 2 a GOLF SWING TRAINING APPARATUS This invention concerns practice golf devices for detecting and indicating automatically the quality of individual golf swings.

FIELD OF THE INVENTION More particularly, the invention provides electronic means for measuring certain selected characteristics of a golf swing, for deriving from the resulting electrical signals information as to the ball flight that would normally result, for computing one or more overall evaluations of the swing, and for displaying the resulting data to the player.

The invention utilizes a captive or simulated ball, and obtains all necessary information by sensing the movement of the club head. Movement of the club head during a practice swing is measured by distinct groups of sensors, typically comprising photosensors which respond to the shadow of the club head formed by a single light source. Although the sensors of each group are suitably arranged to measure a particular feature of the swing or to perform a specific function, the output from each group is typically employed in the computation of more than one basis for swing evaluation.

Since no actual ball flight is required, the device may be extremely compact and may be made conveniently portable. In preferred form of the device, all operations are performed electronically. The substantial or complete absence of moving parts makes the machine economical to build and reliable in operation. Moreover, the device of the invention does not require a special club, but can be operated typically with any wooden driver, so that each player can use his own club.

THE PRIOR ART The practice device of the invention typically performs some of its functions in a conventional manner. Other features, however, are completely new, or utilize new principles of operation. In particular, US. Pat. No. 2,571,974 to John Walker employs light beams and photosensors for measuring club movement, but with only a one-to-one display of the light beams that are intercepted. Walker also includes a single sensor for supplying plate voltage to some of his vacuum tubes in response to the back swing of the club, thereby arming" the system. However, his mechanical relays are reset to idle condition after each swing by individual timing capacitors.

US. Pat. No. 3,020,049 to Alvin L. McNeill also uses photosensors and provides circuitry for computing the direction of swing. However, the photocells in each of his two rows l8 and 20 must be spaced apart widely enough so the club shadow will affect only one cell of each row. That requirement limits the accuracy with which the swing direction can be measured and prevents any effective measurement of swing direction close to the ball position.

SUMM ARY OF THE INVENTION The present system has the advantage of continuing to display the score for each swing until the display is automatically turned off as the player addresses the ball for the next swing. The display then remains off during normal small club movements or waggles and is turned on again only in response to the followthrough portion of the next swing. For each swing, the computing portion of the system is reset to zero condition in response to the backswing, and the new swing computation is carried out electronically during the course of the forward swing, and is ready when the display is turned on.

A further feature of the present invention permits accurate measurement of the swing direction essentially at the point of impact. That is accomplished by providing two spaced rows of sensors extending transversely of the swing direction, and deriving from the sensor outputs two signals that represent the positions at which the remote edge of the club shadow crosses the respective rows. With that technique of computation, the sensors of each row can be placed as close together as required to produce the desired accuracy.

The invention includes sensing mechanism for detecting the attitude of the club head essentially at the instant it strikes the ball, permitting evaluation of the swing in terms of square, open or closed attitude, for example.

The invention further utilizes the measurement of club attitude in combination with the measurement of swing direction for deriving an assessment of the flight characteristics of the ball. All three variables are preferably indicated to the player. Thus, the player is separately informed of the swing direction, the club attitude and the flight characteristic derived from them.

The invention further utilizes a distinctive method for com puting a probable distance of flight of the ball. The rate of swing of the club between predetermined points is timed by a clock that operates at variable pulse rate. The clock rate is automatically selected in accordance with the computed flight characteristic computed for that same swing. The clock rates are so selected that the resulting digital output is an appropriate measure of the distance in yards.

DESCRIPTION OF DRAWINGS A full understanding of the invention, and of its further objects and advantages, will be had from the following description of an illustrative system for carrying it out. That description is to be read in conjunction with the accompanying drawings, in which FIG. I is a somewhat schematic perspective representing an illustrative golf practice system in accordance with the invention;

FIG. 2 is a block diagram illustrating the system;

FIG. 3 is a schematic diagram representing typical circuitry for deriving swing and flight data;

FIG. 3A is a schematic diagram showing a portion of FIG. 3 in further detail;

FIG. 4 is a schematic fragmentary plan at enlarged scale. illustrating the measurement of different swing angles;

FIG. 5 is a schematic plan illustrating different swings having the same swing angle;

FIG. 6 is a schematic diagram representing typical circuitry for deriving club attitude data and for control of the display; and

FIG. 7 is a schematic diagram representing typical circuitry for the distance computation.

ILLUSTRATIVE EMBODIMENT OF THE INVENTION Referring first especially to FIG I, the present illustrative practice device is mounted on a flat base 10. The forward portion of base I0 provides the playing surface I9, which may be covered with artificial grass. A supplementary platform or ground surface is provided adjoining base edge II for the player to stand on. However, such a surface may be constructed integrally with base I0 if preferred.

Base 10 carries suitable indication of an aiming point or impact point for the golf swing, preferably in the form of a cap' tive or dummy ball, which may be of any conventional construction. As illustrated, the ball 12 is mounted on the flexible resilient arm 13, carried by the post 14. After each swing the ball is resiliently returned to its normal position, as shown in the drawing. Base 10 also carries an indication of the direction in which the ball is to be driven, thus defining the correct direction of swing. That direction may be shown only indirectly, as by the front edge 11 of base II], or by the ball or its support; or a line or arrow may be represented on the base surface, as indicated at IS.

The main instrument frame also includes the column 16, rigidly mounted on base 10 behind the ball as seen by the player. Column 16 is spaced far enough from the ball to be out of the way of the swing, but its upper end preferably projects toward the player, typically at about waist level. Column I6 carries the display panel 17, on which are displayed the various scores for each individual swing. Panel 17 forms the front face of a housing 20 for the computing circuitry and display lights.

Movement of the club head is detected by a plurality of photosensors which detect interruption of respective light beams that extend between selected points of base and of column I6. In the preferred structure shown in FIG. 1, the photosensors are mounted below the surface of base 10 and are all illuminated by the single light source 18, which is mounted on column 16 close to the axis about which the club head normally swings. The sensors are protected by windows, not explicitly shown, which may be formed as lenses for concentrating the light received from source 18.

It will be evident that separate light sources may be provided on column 16 for each group of sensors, or for each individual sensor, and suitable lenses at the source or sources may concentrate the light into relatively intense beams. Also, the light may be projected in the opposite direction, from individual sources mounted in base 10 to respective sensors on column 16. However, in the present description the lower ends of the light beams will be referred to for convenience as the sensors. Although the light paths may be made approximately or exactly vertical, it is generally preferred to group the upper ends of the light paths close together, and to take account of their different angles of inclination in the detailed placement of their lower ends and in the detailed design of the computing circuitry to be described.

The sensors 20 are arranged in several functional groups, typically including the reset sensors 21, the swing direction sensors comprising the two

sensor rows

22 and 23, the club face attitude sensors 24, and the display enabling and range sensors 25.

Reset sensors 2i and display sensors are arranged in respective rows extending transversely of the swing direction near the right and left edges of base 10, as seen by the player. The sensors of each row are spaced apart slightly less than the width of the shadow ofa typical club head, and each row contains enough sensors, shown illustratively as three, to insure that the club shadow will pass over at least one sensor of each row. At least sensors 25 are spaced far enough from the ball 12 to be clear of the club shadow during the preliminary movements of the club that a player usually performs prior to an actual swing.

The two groups of

swing direction sensors

22 and 23 comprise rows extending transversely of swing direction 15, initial row 22 being spaced appreciably ahead of ball 12 and final row 23 being closely adjacent the ball. The sensors of each row are arranged quite close together, typically of the order of half an inch or less, so that the club head shadow normally may cover several sensors of each row. The rows are so placed that during a normal swing about half of the sensors of each row are shaded momentarily by the club, the remaining sensors lying outside the shadow beyond the toe of the club.

Sensor group 24 comprises only two sensors, mutually spaced on a line close to the ball position and parallel to the leading edge of the club head shadow during a proper swing, so that the shadow then reaches both sensors simultaneously. However, if the club face is not strictly perpendicular to the ball in a horizontal plane, one sensor is shaded slightly ahead of the other. Sensors of

groups

22, 23 and 24 are shown at en larged scale in FIG. 4.

The functions of the several sensor groups will now be described, with special reference to the block diagram of FIG. 2. Electrical connections in that and other drawings are usually shown as single lines, but may comprise multiple wires.

Reset sensors 21 are connected in "or configuration, as indicated at 30, and are therefore all functionally equivalent. Momentary shading of any one of the sensors 21 produces in circuitry 31 one or more electrical reset pulses that are delivered to several points of the system via lines indicated only schematically in FIG. 2 at 32. The reset pulse or pulses release all memory devices within the system and return the various computing circuits to normal or zero condition. The system is thereby cleared of the previous swing and of the effects of any waggles that have been made, and is ready to receive new input signals from the forward swing.

Display and range sensors 25 are connected in or" configuration, as indicated at 34. The output on the line 35 from OR gate 34, in response to momentary shading of any one of the display sensors, operates the display control and memory circuit 36. One output from control circuit 36 on the line 37 energizes the display portion of the system, indicated generally at 60, for receiving and displaying on panel 17 (FIG. 1) a new set of output signals from the computing circuits. Since all computations are carried out electronically, final results are available when the club head reaches display enabling sensors 25. A second output signal is generated by display control circuitry 36 on the line 38. and is utilized to disable action by any sensors of

groups

23 and 24 that might be shaded momentarily by the ball I2 during its oscillations about support 14 after each swing. The negate signal may also be supplied if desired to sensors of

groups

21 and 22 to prevent disturbance of the display by accidental shading of such sensors by the club head or otherwise.

However, the negate signal is withheld from at least one sensor that is clear of the ball shadow and is in position to be shaded by the club head while addressing the ball. That sensor may be specially provided, but will be assumed for illustration to be the nearest sensor of the group 24. That sensor detects the club head when the player addresses the ball in preparation for the next practice swing and delivers a readiness signal via the line 39 to display control 36. That readiness signal resets the memory of control 36, deleting the output signals on

lines

37 and 38. The display is thereby turned off and the disabled sensors are restored to normal condition. The display then remains dark during preparation for the swing and during most of the swing itself. Practice waggles will be detected by the sensors, but the resulting spurious computations are not displayed and cause no problem since they are eliminated by the reset signal which is developed by sensors 2] first in response to the backswing and again during the downswingv The outputs from each of the swing direction sensors in

rows

22 and 23 are first stored in memory devices, indicated schematically at 40 and 42 of FIG. 2. The signals are then supplied to discriminating circuits 4i and 43, which develop for each row of sensors a signal that represents in digital form the position of the remote edge of the club head shadow as it crosses that row. That signal for each row may be arranged to represent the last sensor that lies within the club shadow, or the first sensor that escapes the shadow. The detailed correspondence is immaterial so long as the signals for the initial and

final rows

22 and 23 are suitably correlated. That processing technique permits effective determination of the club position to substantially any desired accuracy, limited only by the closeness of spacing of the sensors of each row.

The position signals for

sensor groups

22 and 23 are used to develop a signal representing the angular deviation of the ac tual club path from the normal or correct" direction, regardless of its transverse position. That angular deviation signal is derived effectively instantaneously by matrix circuitry indicated at 46 in FIG. 2, and is supplied via the line 47 to the swing direction readout portion 64 of display 60. The swing direction is typically displayed in the form of an appropriate designation such as straight, push, pull, hard push or hard pull.

The position signal for sensor group 23 also represents the transverse club position essentially at the moment of impact, and is therefore a measure of the horizontal point on the club face at which impact takes place. That signal is delivered from discriminating circuit 43 via the line 44 to circuitry for displaying the club face contact point, indicated at 62. That display typically comprises a portrayal ofa club face with an illu minated spot at the appropriate contact point.

The signals from the two club face attitude sensors 24 are supplied to logic circuitry 48, which may be designed to deter mine the club face angle at the moment of impact with any desired degree of precision and detail. In the present illustrative system, logic circuitry 48 has three primary alternative outputs, supplied as control signals via the line 52 to the flight matrix 50. One of those signals indicates substantially correct attitude of the club face, and the others show, if the club is not square, in which direction it is tilted. An auxiliary signal is responsive to the degree of that tilt, typically indicating whether it exceeds a selected threshold angle. All four output signals are supplied via the line 49 to the attitude readout device 61, where they typically appear as the appropriate one of the designations square, open, closed, wide open and wide closed.

The system also obtains information as to the velocity of the club head as it strikes the ball, presenting that information in terms of the distance the swing is likely to produce. The distance computation is performed by timing circuitry 54, which counts clock pulses during a period that is initiated by a signal on the line 56 from one of sensors 24 and is terminated by a signal on the line 57 from sensors 25. The number of counts is therefore inversely related to the speed of the club head. In addition, the clock rate is regulated under control of an output signal from the flight matrix 50 (see below), supplied via the line 53. That regulation takes appropriate account of the computed character of the swing. The resulting distance signal on the line 58 is therefore a realistic representation of the yards carried by the shot, and is supplied to the yards readout device 63 as a further criterion of swing quality.

In addition to the specific items of swing information outlined above, each of which constitutes a valid basis for swing evaluation and is therefore an item of interest to the player, the present invention computes from those items one or more general criteria for evaluation of the swing. Such criteria are typically indicated in terms of an appropriate brief description of the probable result of the measured swing, which description is displayed to the player in addition to the detailed components from which it was derived. Such display may be supplemented, if desired, by more elaborate indications, such as pictorial characterizations of the probable distance traveled by the ball.

For illustrative derivation of overall criteria, the output signals from swing matrix circuitry 46 and from club face attitude logic circuitry 48 are supplied via the respective lines 51 and 52 to computing circuitry of matrix form, designated in FIG. 2 as flight matrix 50. That matrix circuitry is designed in accordance with definite assumptions, based on golfing experience and the laws of physics, as to the type of ball flight that is produced by a golf swing having the club face attitude and the type of swing direction represented by the specified input signals. Like the input signals from which it is derived, the output from the flight matrix circuits can be designed to represent any desired degree of detail. The resulting flight signal is supplied via the line 53 to flight readout device 65, where it typically appears as an appropriate word or phrase, selected from an available assortment such as perfect, face, draw, push, pull, hook, slice, hard hook, hard slice, and bobble.

FIGS. 3 and 3A represent typical circuitry for instrumenting swing matrix 46 and flight matrix 50, together with circuits for developing input signals to the former. Throughout these and other circuit drawings the signal designations on various lines represent the signal that are present in normal or reset condition of the system, immediately prior to a forward swing. Those signals are always either a definitely positive potential, designated or "plus or a relatively negative potential, typically ground, designated or minus.

Initial row 22 of the swing direction sensors is shown illustratively as containing only two individual sensors, represented in FIG. 3 together with their preamplifier circuits at 221 and 22-2; and final sensor row 23 is shown with four sensors which are similarly indicated at 23-! through 23-4. As shown in FIG. 3A for a typical sensor, each of those circuit comprises a solid-state photovoltaic cell Pc connected with the indicated polarity in the base circuit of an amplifying NPN transistor ()1. The collector resistor R1 receives positive power via negate line 38 from a switchable control which is typically incorporated in display control 36, to be described (FIG. 6,), and which deletes power from the transistor during operation of the display. Accordingly, once a swing has been completed and the swing characteristics have been displayed, the display cannot be interfered with by further signals from photocell Fe.

The light from source 18 (FIG. I) normally maintains Fe in voltage generating or "011 condition, making 01 conductive. The transistor collector is thereby essentially grounded, producing the indicated normal negative signal on the output line 80. When covered by the clubhead shadow the photocell turns ofi', cutting off the transistor and supplying a positive signal from negate line 38 to line via the collector re sistance R1.

The particular logic or computing circuits to be described are selected somewhat arbitrarily from the very wide variety of available circuit techniques. An important criterion in the present illustrative design has been the convenient availability of integrated circuits comprising pairs of NPN transistors and load resistors connected to form NAND-NOR gates of conventional type. Each of those gates has two inputs and a single output. If either input is plus the gate output is minus. Only if both inputs are minus is the output plus. Such a gate circuit performs the NOR function when operating in positive logic, that is, when the plus voltage is considered the significant signal. When the minus voltage is considered the significant signal, as in some portions of the circuit of FIG. 3, the gate performs the NAND function. Such NAND-NOR gates are conveniently usable as simple inverting circuits, and may be combined to form flip-flops and other logic blocks. Such combinations are not always theoretically the simplest circuits for the present purpose, but have proved in practice to be highly convenient, economical and effective.

Memory circuits

40 and 42 of FIG. 3 comprise a bistable flip-flop FF for each sensor, each FF comprising two NOR gates A and B. Each memory FF normally produces a negative output signal on the line 82. That signal is changed to plus in response to a momentary plus signal on input line 80, and the output then remains plus until reset to negative by a positive reset pulse supplied via reset line 32.

Typical circuitry for each memory FF is shown in FIG. 3A. NOR gate A comprises the two NPN transistors 02 and 03, with their emitters grounded and their collectors connected together and via the resistance R2 to 3+. The two input signals for the gate are supplied to the respective transistor bases, and the gate output is taken from the collector junction. NOR gate B comprises the transistors Q4 and Q5, connected like gate A with collector resistance R3. The input signals to gate A with are taken from line 80 and via the line 84 from the output of gate B, respectively. The respective inputs to gate B are from the output line 83 of gate A and from reset line 32. The output from gate B is supplied as the FF output to line 82. In each gate, ifeither input signal is plus its transistor conducts and the gate output is negative. Only if both inputs are negative is the output plus.

In operation of the present illustrative memory circuit, a positive reset pulse on line 32 turns on Q5, resetting the FF output on line 82 to negative. That negative signal is coupled to Q3, cutting it off. Since O2 is also cut off by the normally negative input on line 80 the normal output of gate A is positive. That plus signal is coupled to O4, rendering it conductive and thereby maintaining the negative output signal from gate 8 after decay of the reset pulse cuts off 05. Thereafter, a momentary plus signal from line 80 turns on Q2, shifting the output of gate A to negative. Since both inputs to gate B are then negative, the output on line 82 is shifted to plus. That signal turns on Q3, holding the FF in active state after decay of the original signal on line 80.

Discriminating circuits 41 and 43 as already indicated, perform the primary function of producing a signal which represents the points of the

respective sensor rows

22 and 23 that were crossed by the edge of the clubhead shadow furthest from the player. The circuits shown comprise one NOR gate D and two inverting circuits C and E for each of the sensors of the row. The inverters E serve primarily to provide output signals of suitable polarity for the particular form of swing matrix circuitry 46, to be described, and might be omitted with different system design. Each of the NOR gates is typically identical in configuration and manner of operation to NOR gate A or B of FIG. 3A.

For each

sensor row

22 and 23, the memory output signal on line 82 for each sensor except the one farthest from the player is inverted at C and is then supplied as a normally plus input to NOR circuit D. The other input to D is taken via the line 92 directly from the memory output for the sensor next farthest from the player. The output from NOR circuit D is negative unless both inputs are negative, that is, unless the associated sensor was shaded by the clubhead swing and the sensor next farther from the player was not shaded. Under that condition the output is plus. After inversion at E, the final discriminator output signal to swing matrix 46 is negative only for the most remote sensor within the clubhead shadow. For other sensors within the shadow the final output continues positive; although the NOR gate receives a negative input from C, the input on line 91 is plus. And the final output for all sensors beyond the shadow naturally retains its normal value.

The discriminating circuitry for the sensor of each row farthest from the player is simply a direct connection from input line 82 to inverter E, since whenever that sensor is shaded it is assumed to be at the edge of the shadow. Similarly, if no sensor of a row is shaded, the shadow edge is assumed to be just inside the sensor nearest the player. An output signal corresponding to that condition is produced on the auxiliary output line 90-0 for sensor row 22 and on the line 91-0 for row 23. Those signals are developed by a NOR gate D which receives one input via line 92 from the first sensor of the row and the other input from a continuous source of negative signai, shown as a simple ground with current limiting series resistance R5. Since that NOR circuit D normally receives two negative inputs. its output is normally positive, but is inverted at E to negative, as indicated. If the first sensor of the row is shaded that final output shifts to positive.

Accordingly, the final output from each of the discriminating circuits 41 and 43 to swing matrix 46 comprises a negative signal on the

particular line

90 or 91 that corresponds to the most remote sensor within the clubhead shadow, all

other lines

90 and 91 carrying a plus signal. Since the significant signals are minus, the immediately following portion of the circuitry conforms to negative logic.

In addition to the output signal supplied from discriminator 43 to swing matrix 46, the same output signal may be utilized as an indication of the point on the clubface at which the ball was contacted. The signals for supply to club face readout device 62 (FIG. 2) are typically tapped from discriminator 43 just in advance of inverters E, as indicated by the output lines 44-0 through 44-4. Those lines then provide a positive significant signal for driving the display.

Before discussing swing matrix 46, it will be useful to consider FIG. 4, which indicates a club head 100 in a typical position about to strike ball 12, and with its remote edge 102 moving along the path 96. Five illustrative paths 94 through 98 correspond to respective swing angles that are denoted hard pull, pull, straight, push and hard push. All those lines pass between sensors 21-1 and 21-2 and therefore produce a signal from discriminator 41 on line 90-1. The corresponding signals from discriminator 43 are on the respective lines 91-0 through 91-4, as indicated in the figure. Each of the swing paths shown in FIG. 4 might be displaced laterally in either direction, leading to a different set of signals, but still representing the same swing angle. In the present system there are. in general. three different sets of discriminator signals which correspond to each swing angle, as represented in FIG. 5 at 97a, 97b and 97c for the typical case ofpush. Although only two such sets exist that uniquely represent hard pull and hard push, it is convenient to group with them the signal sets 90-2, 91-0 and 90-0, 91-4, corresponding to the still more extreme angular deviations in the respective directions.

Swing matrix 46, as shown in FIG. 3, comprises a plurality of gates F, each of which is typically identical in structure to NOR gate A or B of FIG. 3A, but which perform the function of NAND gates in view of the negative logic in which they operate. Each of those NAND gates receives one of its inputs from discriminator 41 and the other from discriminator 43, the wiring being such that each gate corresponds to a unique pair of discriminator signals. Each such signal pair corresponds to a definite swing direction, three signal pairs corresponding to each of the designated swing directions. The three NAND gates for each of those swing directions are grouped together in FIG. 3, and their outputs are supplied as inputs to a common gate G, which may be like NOR gate A or B of FIG. 3A but with three parallel transistors instead of two. The gates G operate in positive logic and function as NOR gates. They have respective outputs on the lines 51-1 through 51-5, all those outputs being plus except that the signal corresponding to the direction of the actual swing is minus. In normal or reset condition of the system as illustrated, the sig nificant minus output signal from matrix 46 is always on line 51-2. That is a coincidence, and results from the fact that discriminators 41 and 43 produce reset signals on lines -0 and 91-0, and that those signals happen to correspond to pull due to the geometry ofthe present sensors.

Flight matrix 50 of FIG. 3 will be described below, after considering clubface attitude logic 48.

FIG. 6 represents schematically illustrative circuitry for clubface attitude logic 48, which operates under control of the two photosensors 24-1 and 24-2. Those sensors are shaded simultaneously by the leading edge 104 ofclub head if the club attitude is correct (FIG. 4). If the club reaches the point of impact in open position sensor 24-1 is shaded first, if in closed" position 24-2 is shaded first. Those alternative conditions are discriminated by logic circuitry 48, producing a positive output signal to display 60 on the appropriate one of the three output lines 49-1, 49-2 and 49-3, and a negative output signal to flight matrix 50 on the corresponding output line 52-1, 52-2 or 52-3.

Each sensor is typically a photovoltaic cell connected in suitable preamplifying circuitry, which may be similar to that shown in FIG. 3A or may include additional stages of amplifcation. That circuitry includes signal inverters, if needed, to produce on the lines 112 of FIG. 4 respective signals that are negative when the sensors are illuminated and shift momentarily to positive when the clubhead shadow crosses them.

Those signals are supplied to the timing circuitry 114, comprising the capacitors Cl and C2 and the resistances R6, R7 and R8, R9 connected as shown. Circuits 114 differentiate the input signals and produce on the lines 113 positive output pulses of controlled duration corresponding to the leading edge of the clubhead shadow, as well as later negative pulses which correspond to the trailing edge and are not utilized. The positive pulses are inverted by the respective inverters J, produc ing negative signal pulses which are supplied to the NAND gate K. If both negative pulses arrive at K close enough in time to overlap, the gate output shifts momentarily from negative to positive, applying a positive pulse via the capacitor C3 to the flip-flop circuit FF2, The latter circuit is typically identical in configuration and operation to FF of FIG. 3A, and has normally negative output on line 52-1. The incoming positive pulse shifts that output to positive, indicating square" attitude of the clubhead. The flip-flop acts as a memory circuit to hold that output until reset by a positive pulse on reset line 32 from sensors 21 (FIG. 3). The angular tolerance allowed in the club head square attitude is readily determined by selection of the component values for timing circuits 114 to produce the desired degree of overlap of the signals reaching NAND gate K.

If desired, the circuitry for producing square signal on line 49-1, including timing circuits 114, flip-flop FF2 and their connecting circuits, may be duplicated one or more times with different timing relations in their respective circuits 114. Such a duplicate system is indicated schematically at 120, with output line 49- 4. If the circuits 114 of system 120 produce output pulses that are longer than those of system 110, for example, a signal will appear on line 49-4 whenever the club attitude satisfies a relatively lenient angular tolerance, while signals will appear on both lines 49-1 and 40-4 if the more strict tolerance of system 110 is met. The club attitude may thus be indicated to any desired degree of precision.

To indicate the direction of any deviation from square, the sensor signals on lines 112 are supplied also via the respective capacitors C5 and C6 to the two inputs of the flip-flop FF3. That FF typically comprises two NOR circuits of the same type as A and B of FIG. 3A, with their inputs and outputs connected as shown in FIG. 6, so that the flip-flop has two input lines and two output lines. FF3 has two stable conditions to which it is set by positive pulses on the respective input lines, and in which the corresponding output line is negative. In nor mal condition the circuit may be in either state, being shown illustratively with positive output corresponding to the input from sensor 24-2. In operation, whichever of the two input pulses arrives last determines the state of FF3. The output shown therefore represents open position of the club, in which sensor 24-1 is shaded before 24-2.

The circuit of FIG. 6 also includes means for disabling both open and closed signals in presence of a square signal on line 49-1. The two outputs from FF3 are supplied as inputs to the respective NOR circuits L, which receive their other inputs from the output of FFZ via the line 116 and the current limiting resistance R14. NOR gates L can produce a positive output signal only when the input from FF2 is negative, that is, in absence of a square signal. The presence of NOR gates L also inverts the outputs from FF3, so that the significant signal on output lines 49-2 and 49-3, like that on line 49-1, is the plus signal. Those signals are supplied directly to display 60 for controlling clubhead attitude readout 61 (FIG. 2), and are also Supplied, after inversion by the respective inverters M to flight matrix 50 (FIG. 3).

It is noted that the output on line 112-1 from sensor 24-1 may be amplified, shaped and otherwise modified, as required, to provide suitable control signals on the line 39 for turning the display off, and on line 56 for turning on the counter in distance computer 54 (FIG. 3). Circuitry for that purpose is indicated schematically in FIG. 6 as the amplifier 118. Sensor 24-1 receives power continuously, and is not disabled during operation of the display. Sensor 24-2, however, may receive power via negate line 38, as already described for

sensors

22 and 23, in order to desensitize the sensor to backlash oscillations of the ball 12.

Flight matrix 50, as shown in FIG. 3, comprises the fifteen gates H, which are typically constructed like NOR gates A and B of FIG. 3A, but function as NAND gates since they operate in negative logic. Each NAND gate H receives one input from an output line 51 from swing matrix 46 and the other input from a line 52 from clubface attitude logic 48 (FIG. 6), each gate receiving a unique pair ofinputs. The gate outputs on the respective lines 118-1 through 8-15 are normally minus. The single plus output indicates coincidence, for the swing in question, of the particular swing direction and the particular clubface attitude corresponding to the one activated gate.

In the present illustrative system, NAND gates H are required to cover all possible signal pairs, and all l5 possible signals might be displayed. However, it is generally preferred to reduce the variety of output signals by combining signals that represent generally similar results with respect to probable flight ofthe ball. Such generally equivalent signals are supplied to the OR gates I. The final outputs from flight matrix 50 then comprise the outputs from those OR gates and also the outputs from the lines 118 that are considered unique. FIG. 3 represents an illustrative selection of such outputs. comprising the lines 53-1 through 53-10. 'lhosc lines 53 are connected to display fill for driving flight rcadout 65 (FIG. 2). The significant positive signal typically illuminates on panel 17 (FIG. 1) a suitable flight designation, such as those shown in association with the respective lines in FIG. 3. The same output lines Ill 53 are also connected as control inputs to distance computer 54.

An illustrative form of distance computer 54 is shown in FIG. 7. A counting circuit, typically of conventional design, is indicated schematically at 130. Counter is set in operation by a pulse received on line 56 from sensor 24-] via amplifier 118 (FIG. 6), and is stopped by a pulse received on line 57 from sensors 25 via OR gate 34 (FIG. 2]. During its period of operation counter 130 counts positive pulses supplied via the line 132 from a source to be described. The resulting count controls an output signal on the line 58 for supply to distance readout device 63 (FIG. 2). Since the counting period varies inversely with the club speed, the distance readout is arranged to vary inversely with the count. In preferred form of the system, counter 130 is arranged to count down from an initial or reset value which corresponds to an assumed theoretical maximum distance. Each count then reduces the indicated distance by a selected interval. For example, with a binary counter having a capacity of 16 counts. the reset value may correspond to 400 yards, each pulse reducing that value by 25 yards. The display device then typically has 12 readout values from 25 to 300 yards and is made unresponsive to counts that would represent unrealistically high distances.

Pulses are supplied to counter 130 at various alternative rates, depending upon the output signal from flight matrix 50. That signal is supplied via the lines 53 and may control the rate of pulse development in any suitable manner. As shown in FIG. 7, the ten alternative signals on lines 53 are reduced to four signals on the lines 134 by combining signals that are cssentially equivalent for distance production. That is accomplished by the NOR gates P, which also invert the significant signals from plus to minus. Four distinct pulse rates are produced by the respective oscillators M1 through M4. All oscillators typically run continuously, delivering negative pulses at their respective rates f1 through f4 to the respective NAND gates 0. One of those pulse trains is selected by the NAND gate that also receives a minus control signal from its line 134. The selected train is delivered as positive pulses via OR gate R to the line 132 and thence to counter 130. The clock rate thus provided to the counter is higher the poorer the swing, so that, for any given speed of swing, an increasing distance is counted down from the assumed maximum.

The least effective types of swing, represented by a flight signal on line 53-], and designated bobble, typically produces essentially zero distance. With the system as so far described, an appropriate readout is readily obtained simply be leaving line 53-] open in FIG. 7. All oscillators M1 through M4 then remain cut off at their NAND gates Q, and counter 130 remains at its reset value, leaving the distance readout dark. The connection of line 53-1 shown in FIG. 7 is described below.

The distance-computing system, as so far described, may be modified as desired, for example to make the indicated distance dependent upon other characteristics of the swing, or to vary the relation between the speed of swing and the distance indicated. In particular, one or more additional pulse sources may be provided, which supply pulses at selected rates and under controlled conditions to counter 130. As an example of such modification, FIG. 7 shows a constantly running source Mo of negative pulses of frequencyfo. Those pulses are supplied as one input to a NAND gate S, the other input being a control signal derived via the line 138 and the OR gate T from counter 130. When that control signal is negative the pulses are delivered by gate S as positive pulscs via the line 137 to OR gate R, and thence to counter 130 along with the selected train of pulses already described. The control signal on line 138 is typically made responsive to counter 130 in such a way that it is normally minus and shifts to plus after a selected number of counts. Pulses from Mo are thereby supplied to counter 130 only during an initial counting period. after which they are cut off, decreasing the rate at which the indicated distance is reduced. Several such pulse sources may be provided in similar manner, having different rates and different periods of effectiveness.

if the pulse rate of auxiliary source M is sufficiently slow, the control signal from line 138 can be supplied directly to NAND gate S, and line 53l, representing bobble, may be left open as described above. However, it may be desirable to use a pulse rate from Mo that is high enough to produce a distance readout even for a bobble. That is prevented in the system of FIG. 7 by inserting the OR gate T in line 138 with its control signal taken from bobble line 53-1. A plus bobble signal on line 53-1 then makes the control signal at gate S plus, cutting off pulses from Mo regardless of the signal on line 138. Hence in presence of a bobble signal counter [30 receives no input pulses and the distance display remains dark.

Although selection of the correct pulse rate for a particular swing requires operation of sensors of

groups

22, 23 and 24 and of the circuits they control, including swing matrix 46, club face attitude logic 48 and flight matrix 50, the resulting delay in selection of a pulse rate is very slight and is found in practice to be only a negligible fraction of the entire counting time, which is essentially the time of travel of the club between

sensors

24 and 25.

FIG. 6 includes illustrative control circuitry 36 for turning display 60 on and off and for developing a negate signal on line 38 to desensitize the sensors during the display. That cir cuitry comprises the flip-flop FF4, formed of the two NOR gates A and B, typically as shown more fully in FIG. 3A. One input to FF4 is the line 142, which is normally minus but can receive a plus pulse via the OR gate U either from reset line 32 or via line 39 form sensor 24-1, as in response to a clubhead addressing the ball. The other input is the line 35, which is normally minus but can deliver a plus pulse from sensors 25 near the end of the swing. An input pulse from line 142 shifts FF4 to the condition shown, with output line 144 plus. The inverting amplifier 145 then delivers minus voltage to the line 146, idling the relay Ry. An input pulse from line 35 shifts FF4 to its other state, energizing Ry. The relay switch grounds the control line 37, providing a ground to the entire system of display 60 and enabling its various readout devices to be energized by positive signals on the respective control lines that have been described. The display remains so energized until FF4 is returned to normal condition by a reset pulse or by action of sensor 24l, Ground is then lifted, turning the display off.

A second output from FF4 normally supplies positive voltage to negate line 38 but opens that line during the periods that the display is on. That line supplies amplifying power to certain ofthe sensors, typically those of

groups

22, 23 and 24, but omitting sensor 24-l. As shown, negate line 38 receives its voltage via the inverting amplifier 147 from the output of NOR circuit A of FF4. Additional control functions, as for signal lamps and the like, can be performed via similar connections, or by providing additional switches or switch contacts on relay Ry.

I claim:

1 Golfpractice apparatus, comprising in combination structure defining a normal point of impact of a golf club head during a practice swing and a normal path direction at the point of impact,

two sensors for developing signals in response to passage of the club head leading edge essentially at the point of impact, the sensors being responsive to laterally spaced points ofthe leading edge,

timediscriminating circuit means receiving the signals and responsive to the mutual time relation in which the signals are received,

and display means controlled by the circuit means for representing angular relation of the club head leading edge with respect to the normal path direction.

2. Golf practice apparatus as defined in claim I, and in which said time discriminating circuit means comprise a flip-flop having two stable conditions to which it is shifted in response to the respective signals,

said display means being responsive to the condition of the ill 3. Golf practice apparatus as defined in claim 1, and in which said time-discriminating circuit means comprise a flip-flop having two stable conditions to which it is shifted in response to the respective signals,

and timing circuit means for producing a coincidence signal in response to substantial coincidence of said signals,

said display means being responsive to the coincidence signal and being normally responsive to the condition of the flip-flop,

and said apparatus including means responsive to the timing circuit means for rendering the display means unresponsive to the condition of the flip-flop in presence of the coincidence signal.

4. Golf practice apparatus as defined in claim 1, and in which said time-discriminating circuit means comprise circuit means responsive to said signals for developing respective electrical pulses of predetermined duration,

and coincidence circuit means for producing an output signal in response to coincidence of the pulses,

said display means being responsive to the output signal.

5. Golf practice apparatus as defined in claim 1, and in which said time discriminating circuit means comprise circuit means responsive to said signals for developing a first pair of electrical pulses having predetermined duration and having definite time relation to the respective signals,

circuit means responsive to said signals for developing a second pair of electrical pulses having predetermined duration longer than the duration of the first pair of pulses and having definite time relation to the respec tive signals,

coincidence circuit means for producing a first output signal in response to coincidence of the first pair of pulses and a second signal in response to coincidence of the second pair of pulses,

said display means including means responsive to both the output signals.

6. In golf practice apparatus which includes structure defining a normal path direction and a normal point of impact of a golf club head during a practice swing, mechanism for representing the lateral position of the swinging club head, comprising in combination an ordered series of sensing devices for developing respective signals in response to passage of a swinging clubhead at respective positions that are progressively spaced laterally of the club head path in mutually overlapping relation,

a discriminating circuit for receiving the signals from each pair of adjacent sensing devices and for producing an output signal only in response to combined presence of a signal from the sensing device that is nearer one end of the series and absence ofa signal from the sensing device that is nearer the other end of the series,

and output means for utilizing the output signal from any one of the discriminating circuits as a representation of the lateral position of the club head.

7. Mechanism as defined in claim 6, and including also a discriminating circuit for receiving the signal from the sensing device at said other end of the series, and for supplying to said output means an output signal as a representation that the clubhead is beyond said other end of the series of sensing devices.

8. Mechanism as defined in claim 6, and including also a discriminating circuit responsive to absence of any sensing device signal, for supplying to said output means an output signal as a representation that the club head is beyond said one end of the series of sensing devices.

9. In a golf practice apparatus which includes structure defining a normal path direction and a normal point of impact for a golf club head during a practice swing, swing direction indicating means comprising in combination two mechanisms as defined in claim 6 for representing the lateral position of the swinging club head, the sensing devices of the respective mechanisms being relatively spaced longitudinally of the club head path,

electronic circuit means responsive to the output means of both said mechanisms and acting to produce a final signal that represents the direction of movement of the clubhead between the sensing -devices of the respective mechanisms,

10. Golf practice apparatus, comprising in combination structure defining a normal direction and a normal point of impact of a golf club head during a practice swing,

first and second sets of signal lines, the signal lines of the respective sets corresponding to selected transverse positions of a swinging club head at first and second longitudinally spaced points of the swing,

means for sensing a swinging club head and for producing position signals on those signal lines of the respective sets that correspond to the actual club head positions,

a plurality of output terminals corresponding to respective directions of club head movement each of which directions corresponds to at least one pair of said selected transverse clubhead positions,

electronic circuit means including a matrix network of said sets of signal lines and responsive to the position signals thereon for energizing the output terminal that corresponds to the pair of club head positions represented by the position signals present on the lines,

and display means responsive to the energized terminal ll. Golf practice apparatus, comprising in combination structure defining a normal point of impact of a golf club head during a practice swing and a normal path direction at the point ofimpact,

first sensing and computing mechanism for sensing a swinging club head and producing a signal representing the angular deviation of a swinging club head from the normal path direction,

second sensing and computing mechanism for sensing a swinging club head and producing a signal representing the attitude of the club face substantially at the point of impact,

electronic circuit means including a matrix network responsive to both said signals for producing a third signal that represents a ball flight characteristic corresponding to the sensed swing,

and display means responsive to the third signal.

12. Golf practice apparatus, comprising in combination structure representing a golf ball and defining a normal path ofa golf club head during a practice swing,

a transducer responsive to a club head when addressing the ball prior to the swing,

a plurality of transducers normally responsive to a swinging club head,

electronic circuit means controlled by at least some of said transducers for producing a swing signal that represents a characteristic of the swing,

display mechanism having an active condition in which it is responsive to the swing signal for displaying said swing characteristic,

first circuit means responsive to the first said transducer for disabling the display mechanism prior to the swing,

and second circuit means responsive to at least one of said plurality of transducers for restoring the display mechanism to active condition.

13. Golf practice apparatus as defined in claim 12, and including also circuit means for disabling at least some of said plurality of transducers in response to said second circuit means and for restoring the disabled transducers to normal condition in response to said first circuit means.

14. Golf practice apparatus, comprising in combination structure defining a normal path of a golf club head during a practice swing,

a plurality of transducers for sensing a swinging club head and including transducers acting to produce first and second timing signals in response to presence of the club head at respective longitudinally spaced points of the path,

and timing circuit means responsive to the timing signals for producing a distance signal that represents a ball flight distance signal that varies inversely with the time interval between the timing signals,

said timing circuit means including means acting under control of the swing signal to modify the distance signal in ac cordance with said flight characteristic.

15. Golf practice apparatus as defined in claim 14 and in which said timing circuit means comprise clock means for producing a series of clock pulses,

control means for modifying the frequency of the clock pulses under control of the swing signal,

and counting means for counting clock pulses during the time interval between the timing signals.

16. Golf practice apparatus as defined in claim 14, and in which said timing circuit means comprise a plurality of oscillating circuits for producing respective series ofclock pulses at different pulse frequencies,

gating circuit means responsive to said swing signal for selecting one of said pulse series,

and counting means for counting the selected series of clock pulses during the time interval between the timing signals.

17. Golf practice apparatus as defined in claim 16, and including also means actuable to supply additional pulses at predetermined frequency to the counting means in addition to said selected pulse series,

and control means for actuating the last said means under control of the counting means.

Claims

1. Golf practice apparatus, comprising in combination structure defining a normal point of impact of a golf club head during a practice swing and a normal path direction at the point of impact, two sensors for developing signals in response to passage of the club head leading edge essentially at the point of impact, the sensors being responsive to laterally spaced points of the leading edge, time-discriminating circuit means receiving the signals and responsive to the mutual time relation in which the signals are received, and display means controlled by the circuit means for representing angular relation of the club head leading edge with respect to the normal path direction.

2. Golf practice apparatus as defined in claim 1, and in which said time discriminating circuit means comprise a flip-flop having two stable conditions to which it is shifted in response to the respective signals, said display means being responsive to the condition of the flip-flop.

3. Golf practice apparatus as defined in claim 1, and in which said time-discriminating circuit means comprise a flip-flop having two stable conditions to which it is shifted in response to the respective signals, and timing circuit means for producing a coincidence signal in response to substantial coincidence of said signals, said display means being responsive to the coincidence signal and being normally responsive to the condition of the flip-flop, and said apparatus including means responsive to the timing circuit means for rendering the display means unresponsive to the condition of the flip-flop in presence of the coincidence signal.

4. Golf practice apparatus as defined in claim 1, and in which said time-discriminating circuit means comprise circuit means responsive to said signals for developing respective electrical pulses of predetermined duration, and coincidence circuit means for producing an output signal in response to coincidence of the pulses, said display means being responsive to the output signal.

5. Golf practice apparatus as defined in claim 1, and in which said time discriminating circuit means comprise circuit means responsive to said signals for developing a first pair of electrical pulses having predetermined duration and having definite time relation to the respective signals, circuit means responsive to said signals for developing a second pair of electrical pulses having predetermined duration longer than the duration of the first pair of pulses and having definite time relation to the respective signals, coincidence circuit means for producing a first output signal in response to coincidence of the first pair of pulses and a second signal in response to coincidence of the second pair of pulses, said display means including means responsive to both the output signals.

6. In golf practice apparatus which includes structure defining a normal path direction and a normal point of impact of a golf club head during a practice swing, mechanism for representing the lateral position of the swinging club head, comprising in combination an ordered series of sensing devices for developing respective signals in response to passage of a swinging clubhead at respective positions that are progressively spaced laterally of the club head path in mutually overlapping relation, a discriminating circuit for receiving the signals from each pair of adjacent sensing devices and for producing an output signal only in response to combined presence of a signal from the sensing device that is nearer one end of the series and absence of a signal from the sensing device that is nearer the other end of the series, and output means for utilizing the output signal from any one of the discriminating circuits as a representation of the lateral position of the club head.

9. In a golf practice apparatus which includes structure defining a normal path direction and a normal point of impact for a golf club head during a practice swing, swing direction indicating means comprising in combination two mechanisms as defined in claim 6 for representing the lateral position of the swinging club head, the sensing devices of the respective mechanisms being relatively spaced longitudinally of the club head path, electronic circuit means responsive to the output means of both said mechanisms and acting to produce a final signal that represents the direction of movement of the clubhead between the sensing devices of the respective mechanisms.

10. Golf practice apparatus, comprising in combination structure defining a normal direction and a normal point of impact of a golf club head during a practice swing, first and second sets of signal lines, the signal lines of the respective sets corresponding to selected transverse positions of a swinging club head at first and second longitudinally spaced points of the swing, means for sensing a swinging club head and for producing position signals on those signal lines of the respective sets that correspond to the actual club head positions, a plurality of output terminals corresponding to respective directions of club head movement each of which directions corresponds to at least one pair of said selected transverse clubhead positions, electronic circuit means including a matrix network of said sets of signal lines and responsive to the position signals thereon for energizing the output terminal that corresponds to the pair of club head positions represented by the position signals present on the lines, and display means responsive to the energized terminal

11. Golf practice apparatus, comprising in combination structure defining a normal point of impact of a golf club head during a practice swing and a normal path direction at the point of impact, first sensing and computing mechanism for sensing a swinging club head and producing a signal representing the angular deviation of a swinging club head from the normal path direction, second sensing and computing mechanism for sensing a swinging club head and producing a signal representing the attitude of the club face substantially at the point of impact, electronic circuit means including a matrix network responsive to both said signals for producing a third signal that represents a ball flight characteristic corresponding to the sensed swing, and display means responsive to the third signal.

12. Golf practice apparatus, comprising in combination structure representing a golf ball and defining a normal path of a golf club head during a practice swing, a transducer responsive to a club head when addressing the ball prior to the swing, a plurality of transducers normally responsive to a swinging club head, electronic circuit means controlled by at least some of said transducers for producing a swing signal that represents a characteristic of the swing, display mechanism having an active condition in which it is responsive to the swing signal for displaying said swing characteristic, first circuit means responsive to the first said transducer for disabling the display mechanism prior to the swing, and second circuit means responsive to at least one of said plurality of transducers for restoring the display mechaNism to active condition.

14. Golf practice apparatus, comprising in combination structure defining a normal path of a golf club head during a practice swing, a plurality of transducers for sensing a swinging club head and including transducers acting to produce first and second timing signals in response to presence of the club head at respective longitudinally spaced points of the path, electronic circuit means controlled by at least some of said transducers for producing a swing signal that represents a characteristic of the swing, and timing circuit means responsive to the timing signals for producing a distance signal that represents a ball flight distance signal that varies inversely with the time interval between the timing signals, said timing circuit means including means acting under control of the swing signal to modify the distance signal in accordance with said flight characteristic.

15. Golf practice apparatus as defined in claim 14 and in which said timing circuit means comprise clock means for producing a series of clock pulses, control means for modifying the frequency of the clock pulses under control of the swing signal, and counting means for counting clock pulses during the time interval between the timing signals.

16. Golf practice apparatus as defined in claim 14, and in which said timing circuit means comprise a plurality of oscillating circuits for producing respective series of clock pulses at different pulse frequencies, gating circuit means responsive to said swing signal for selecting one of said pulse series, and counting means for counting the selected series of clock pulses during the time interval between the timing signals.

17. Golf practice apparatus as defined in claim 16, and including also means actuable to supply additional pulses at predetermined frequency to the counting means in addition to said selected pulse series, and control means for actuating the last-said means under control of the counting means.