Sensing Switch Construction

Abstract

Switch units designed for use with electrical apparatus for detecting discrete articles passing along a path of travel, wherein said units are engaged by the articles to energize or interrupt an energized circuit, thus producing a detectable signal. Each switch unit includes a pair of leaf spring arms having juxtaposed contacts on the respective ends thereof, and a pivotally mounted actuating element adapted to be engaged by articles passing along said path. The engagement of said actuating element results in the operation of said unit to produce said signal. The leaf spring arms are prepositioned such that during operation the respective contacts will slide relative to one another, thereby effecting a wiping action which keeps the contacts free of deposits and in good working order. In addition, novel dampening means are employed, which provide for improved accuracy and control.

Parent Case Text

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part, based upon United States application for Letters Patent, Ser. No. 797,171, filed Feb. 6, 1969, now abandoned, the benefit of which is claimed with regard to 35 USC 120.

Description

BACKGROUND OF THE INVENTION

The present invention relates to counting or monitoring apparatus, and more specifically, to novel switch means for use with said apparatus. Said switch means, in conjunction with said apparatus, is capable of providing accurate detailed signals upon being actuated by the passage of discrete articles along a selected path.

Farmers engaged in mechanized planting utilize planting machines which have a plurality of separate planting devices supplied with seed from a hopper so that a plurality of rows may be planted at one time. These planting machines are pulled behind a tractor which normally operates at a speed between 3 to 7 miles per hour. With the planting equipment heretofore in general use it has been difficult, if not impossible, for the farmer to determine the rate at which the seeds are being planted, or for that matter whether seeds are even being dispensed. Accordingly, to overcome these problems which arise when one or more hoppers become clogged or empty without the farmer knowing it, seed-monitoring systems have been proposed which are placed in association with the individual planting devices and are operable to warn the farmer when a failure occurs.

A particular system of the type mentioned above, and of the type to which the present invention is directed, forms the basis for the disclosure in U.S. Pat. application, Ser. No. 540,873, filed Apr. 7, 1966, now U.S. Pat. No. 3,527,928, issued Sept. 8, 1970. Briefly, with this system a switch unit is associated with each planting device so that as seeds are dispensed therefrom they will engage the actuator portion of said unit to operate the switch. The switch is placed in circuit with a control panel mounted for viewing by the farmer, so that each time said switch is operated a light will flash on said panel indicating to the farmer that seeds are being dispensed. On the other hand, an absence of flashing indicates to the farmer that a failure of the planting device has occurred. In addition, the system may be equipped with a counter and a timer so that the number of seeds dispensed in a given period of time may be counted.

While the system disclosed in the above-mentioned copending application has proven entirely satisfactory in service, certain problems have been encountered with the particular switch unit disclosed therein; the present invention providing improvements thereover. For example, sparking causes pitting of the contact points, as well as the buildup of deposits, all of which eventually lead to failure of the unit. Also, since the switch unit must be able to respond quickly and accurately to engagement by a constant, successive flow of articles, it is necessary to dampen the actuator member action in order to insure against bouncing or rebounding thereof after each engagement. If said bouncing occurs, the switch cannot accurately monitor the passage of seeds and errors will result, both from spurious signals and the failure to monitor properly a subsequent instance of seed passage.

In addition, the aforementioned system employed a switch arrangement of the normally closed variety; and while there will be disclosed hereinafter a modification of the present invention of this nature, it should be noted that switches of this type require complex, expensive monitoring apparatus. While the cost of such an arrangement is totally justified with respect to the sensitivity and accuracy of results achieved, there are, however, customers that do not desire such a refined system. Accordingly, the present invention also contemplates an improved switch construction capable of functioning in a system employing normally closed switch units, as will be detailed more fully hereinafter.

Accordingly, it is an object of the present invention to provide improved switch unit constructions adapted to be employed with seed monitoring systems of the general type described above to improve the sensitivity, accuracy and dependability thereof.

Another, more specific, object of the present invention is the provision of switch unit constructions wherein the respective contacts will move laterally with respect to each other during operation to effect a cleaning action which precludes pitting and the formation of microscopic welds, all of which detract from the operational life thereof.

Another object of the present invention is the provision of a switch unit having a pair of leaf spring contact arms that are positioned initially for joint, arcuate movement about different centers whereby the contact members on said arms will slide relative to each other.

A further object of the present invention is to provide a novel switch unit construction of the type described above having at least one said leaf spring contact arm canted, so that upon actuation, the wiping action will be enhanced to insure against pitting or the buildup of deposits thereon.

Still another object of the present invention is to provide a switch unit construction which employs damping means to positively insure against bouncing of the contact member after engagement by an article.

Another, somewhat more specific object of the present invention is the provision of a switch unit construction wherein the free, contact carrying portion, of leaf-springlike arms are canted with respect to the mounting portion to provide a preselected disposition when in a static position, which will achieve the desired wiping action during use.

Another object of this invention is to provide a novel switch unit of the normally open variety which will function to provide said desired wiping action.

A further object of the present invention is to provide a novel switch for monitoring apparatus of the type described which is of simple, rugged construction and adapted to be installed with the chute elements of various known seed planters now in use.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified side-elevational view showing a tractor pulling a seed planter of the type to which the present invention relates.

FIG. 2 is a partial perspective view illustrating the seed-monitoring system of the present invention, and showing one of the switch units associated with the chute portion of a seed feeder or dispenser.

FIG. 3 is an enlarged fragmentary sectional view of the leaf spring contact members of the switch structure of the present invention, with the contact members in the closed position.

FIG. 4 is an enlarged fragmentary sectional view similar to FIG. 3, but showing the actuator arm depressed and the contacts in the open position.

FIG. 5 is an enlarged elevational view of the switch structure of the present invention, with one-half of the housing removed.

FIG. 6 is a sectional view taken along the line 6--6 of FIG. 5, in the direction indicated.

FIG. 7 is a schematic wire diagram of a seed-monitoring system of the type to which the present invention relates.

FIG. 8 is a sectional view similar to FIG. 6, but illustrating a modified form of the invention; said switch unit illustrated being of the normally open variety.

FIG. 9 is a partial perspective view of the embodiment of FIG. 8, with the upper portion of the unit broken away, and the front portion of the unit housing removed to expose to view the disposition of the respective switch unit elements.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring now more specifically to the drawings, with regard to the embodiment of FIGS. 1-6 like parts are designated by the same reference numbers throughout the various figures; the corresponding parts or elements of the embodiment of FIGS. 8 and 9 being designated with the same numerals followed by the suffix a.

The seed-monitoring apparatus 10 shown in FIG. 2 is adapted to be installed in association with a planter 12 pulled by a tractor 14 as shown in FIG. 1. The planter 12 and tractor 14 may be of various known constructions and need not be described in detail. It suffices to state that the planter includes a plurality of planting units 16 mounted on a frame 18. In the particular embodiment shown for the purpose of illustrating one form of this invention, the seed-monitoring apparatus is constructed for association with a planter having four units 16. It is understood however that the monitoring apparatus may be adapted for association with planters having any desired number of planting units.

Each of the planting units 16 may also be of various known constructions and need not be described in detail. In general each planting unit comprises a hopper 19 for containing a supply of seed, a valve or feeding mechanism 20 at the lower end of the hopper for delivering seed into an upper end of a long trough 22 via a chute 23, shown in FIG. 2. The trough 22 is mounted in a depending hollow shank 24 of the planting unit for directing seed into a furrow prepared by a compaction seed runner 26 secured to the lower end of the shank 24.

As shown in FIGS. 1 and 2, the seed-monitoring apparatus 10 comprises a control or indicating panel unit 28 adapted to be mounted at a convenient location on the tractor, a seed-sensing switch unit 30 mounted in association with the chute 23, electrical cables 32 and 34 extending from the control unit 28 and switch 30 and a connector device 36 detachably connecting the cables 32 and 34. It is to be understood of course that the apparatus 10 includes a switch unit 30 in association with the chute 23 of each of the planter units 16, or in other words, for each row of seed to be planted. In the particular embodiment shown, it is contemplated that the apparatus 10 will include four associated switch units 30 and the electrical cables 32 and 34 are constructed for connecting the four individual switches to the control panel as will be discussed more fully below.

Each chute 23 is adapted by means of flange 37 to be disposed within a chute associated with the feed mechanism 20 of the planter unit. It is understood that the shape of the chute and the securing or fastening means therefor will vary in accordance with the particular make planting unit with which the monitoring apparatus is to be associated. In any event, each chute 23 comprises sidewalls defining a passageway 39 through which seeds must pass before entering trough 22 for planting. Passageway 39 has an open mouth or upper end 40 and a narrower throat portion 41 with a discharge opening 42. The switch unit 30 is mounted to one wall 44 of the chute and has an actuating or sensing element in the form of a blade 46 positioned adjacent portion 41 so as to be struck by seeds as they pass out of the chute 23 by way of said opening 42. Accordingly, seeds cannot pass through chute 23 without striking and depressing the blade element 46.

As shown in FIGS. 5 and 6, each switch unit 30 comprises housing members 52 and 54 secured together and to a mounting plate 45 connected to the wall 44 of the chute. A first electrical prong or strip 56 extends through an end of the housing or body member 52 and has apertures 53 so that it may be assembled over a pair of screws 58 and 60 positioned in apertures formed in housing member 52. A second terminal or conductor strip 62 extends into the housing between the members 52 and 54 and has apertures at 63 for assembly over the screws 58 and 60 and is separated from the terminal strip 56 by insulating blocks 64. The terminal strips are securely clamped against an abutment surface 66 of the body member 52 by the nuts 68 and 70 engaged with screws 58 and 60 and applying a clamping pressure through a washer 72 and an insulating spacer 74.

A first contact leaf spring member 76 carrying a contact or point element 78 is assembled over the screws 58 and 60 and is also clamped in electrical contact with the terminal strip 56. A second contact leaf spring member 80 carrying another point or contact element 82 is also assembled over the screws 58 and 60 and is clamped in electrical contact with the terminal strip 62. Accordingly, the respective leaf spring members 76 and 80 are free to move in arcuate paths about the points 81 and 81' as centers.

Turning first to FIG. 3, it can be seen that a pair of stop members are provided in the form of set screws 86 and 88 engaged in threaded apertures 89 and 87, respectively. The configuration of said leaf spring members 76 and 80 is such that the contact 78 bears against the opposing contact element 82, with said member reaching a statically balanced position as illustrated. For reference purposes the spring members 76 and 80 may be viewed as disposed at an acute angle with respect to a line perpendicular to a line drawn through points 81 and 81', with each spring member spaced from its associated stop member 86 or 88.

As is best seen in FIGS. 3 and 4, the leaf spring member 76 is canted or bent at 83 whereby the lower, contact carrying portion thereof is disposed at an angle with respect to the upper portion of said member, that portion clamped in engagement with the respective terminal strip, 56 or 62, by means of the nut and screw arrangements. Accordingly, with this arrangement the above noted disposition of said leaf spring members may be realized.

Before discussing in detail the mode of operation of switch 30, attention is invited to FIG. 5, wherein the structure for separation of contacts 78 and 82 is illustrated. Basically, the actuator blade or element 46 is mounted or carried by a pair of parallel, wirelike leg sections 96 and 98 of a frame member 100. The parallel leg sections 96 and 98 are bent, as can be seen in FIG. 6, to extend downwardly such that when said switch leg unit is affixed to wall 44 of chute 23, the pedal or actuator 46 will be properly positioned for engagement by seeds as they pass out of said chute through discharge opening 42. Wire element 100 also includes axially aligned pivot sections 104 and 106 which are pivotally mounted by the journals or bearings 108 and 110 formed integrally in one or both of the housing members 52 and 54. In addition, said wire element 100 includes an actuator section 112 which is joined to the pivot sections 104 and 106 by lever arm sections 114 and 116, whereby said section 112 is disposed between the respective leaf spring members 76 and 80, as can be seen in FIG. 6.

With the structural arrangement illustrated, it is believed clear that said wire element 100 and said blade 46 are supported for pivotal movement about a common axis defined by the wire sections 104 and 106. The weight of the blade or actuator member 46 biases the wire element 100 in a clockwise direction as viewed in FIG. 6 so that the actuating or lever section 112 is normally maintained in engagement with the contact leaf spring member 80. However, the combined weight of the panel member 46 and the wire sections 96 and 98 is insufficient to overcome the spring action of said leaf spring member so that the contact 82 remains in engagement with the oppositely disposed contact 78, viz, the disposition illustrated in FIG. 3.

When the actuator member 46 is struck or engaged by a seed passing out of the discharge opening 42 of chute 23, said panel member is depressed so that the lever or actuating section 112 of the wire element 100 is pivoted in a clockwise direction to bias the leaf spring elements 76 and 80 toward the right as viewed in FIGS. 3 and 4. Due to the spacing of leaf spring member 76 from its associated stop or set screw 86, initially both contacts 78 and 82 will move together until the lower portion of leaf spring member 80 strikes said set screw 86. However, due to the angular disposition of said springs 76 and 80 and especially due to the canted configuration of spring member 76, during said initial movement the contiguous surfaces 78' and 82' on said contacts will slide relative to each other, as indicated by arrow 117 in FIG. 4. This sliding movement effects a wiping action which will keep the contacts free from pitting and microscopic deposits that tend to buildup during use. Accordingly, after the leaf spring member 76 strikes the setscrew 86 the contacts 78 and 82 will separate with the leaf spring member 80 continuing until it strikes its associated setscrew or stop member 88, as seen in FIG. 4. As will be detailed more fully hereinafter, this separation may be employed to produce a detectable signal indicating that sensing member 46 has been struck by one or more seeds.

It will be appreciated that in order to monitor the passage of seeds through the chute 23 reliably and accurately, the actuator or sensing member 46 must be capable of operation at high speeds. In order to promote such operation which may, for example, be in the order of 1,500 cycles per minute, the switch unit is provided with means to minimize the inertial effects of the sensing member 46. That is to say, to prevent said member 46 from bouncing after being struck by a seed, whereby said sensing member will be correctly or properly positioned for engagement by subsequent seeds. The leaf spring members 76 and 80 are quite stiff so as partially to dampen any vibrations or oscillations of the actuator 46 transmitted thereto by means of the wire element 100.

To control positively the movement of the panel or actuator member 46, the switch unit of the present invention includes a damping means in the form of an elastomeric member 118. In the fabrication of member 118, it is desirable to use a butyl rubber composition although not absolutely necessary. The elastomeric member 118 is positioned between the mounting plate 45 and the switch unit housing section 54. The elastomeric member 118 is disposed inwardly of the opening 45' in said mounting plate 45, said opening having the parallel leg sections 96 and 98 extending therethrough. Accordingly, the lower end of said elastomeric member is disposed slightly above said leg sections 96 and 98, whereby after the actuator has been depressed and then moved upwardly, said leg sections 96 and 98 will engage the elastomeric member 118 positively to prevent further movement of said wire element 100 and its associated blade or actuator element 46.

At this point, it should be noted that the length of the lever arm provided by actuator element 46 and the associated parallel leg sections 96 and 98 is quite large as compared to the lever arms 114 and 116 which join the actuator section 112 of wire element 100 to the journaled wire sections 104 and 106. In practice, the former is about eight to 10 times as large as the latter, this feature thus promoting easy operation of the switch unit 30 and sensitivity to the application of a small force to the panel member 46.

As previously indicated, the switch units 30 associated with each of the planter devices 16 are connected by cables 32 and 34 with the control or indicating panel unit 28. As shown in FIG. 2 and in the schematic wiring diagram of FIG. 7, the unit 28 comprises a housing 119 in which indicating lights 120 are mounted. In the embodiment shown, the indicating lights 120 are numbered 1 through 4 and correspond to the number of rows of seeds to be planted. It is understood, of course, that the electrical circuit and number of indicating lights can be modified for association with planting apparatus having either a larger or smaller number of planting devices 16. The housing also contains a timer 122, a counter 124 and a gang switch 126 which may all be of known construction and need not be described in detail and which function in a manner described below. A light 128 is provided for indicating when the system is turned on and a test switch 130 is connected as described below for enabling an operator to test the circuit to insure operation of the lights.

Referring particularly to the wiring diagram shown in FIG. 7, the circuit of the apparatus is connected with a suitable source of energy such as a battery 132 of the type usually installed in a tractor. A wire 134 extends from one terminal of the battery to a terminal 136 of the timer 122, which terminal is connected by wire 138 with a blade or movable contact 140 of one side of the selector switch 126. As indicated heretofore, selector switch 126 may be of known construction and the movable contact 140 is mounted on a rotor for movement between an "off" position and a contact 142 at an "on" position. In addition, the blade 140 may be moved to contacts numbered 1 through 4 in FIG. 8 which correspond to the indicator lights 120 which are also numbered 1 through 4. The selector switch 126 has a second movable contact or blade 144 movable in unison with and electrically insulated from the blade 140. The blade 144 is adapted to be moved from an "off" to an "on" position and then for selective engagement with another series of contacts numbered 1 through 4 in FIG. 7. The blade 144 is connected by a wire 146 with the counter 124 which in turn is connected through wire 148 with a second terminal 150 of the timer.

The switch of the timer 122 is normally open so that the coil 152 of the counter 124 is normally deenergized. When the timer is activated, the terminal 150 is connected with the terminal 136 for energizing the coil of the counter and enabling the counter to respond to the passage of seeds as will be described below.

The first of the previously mentioned groups of contacts in the selector switch are connected by wires 154 and 156 to branch wires 158, 160, 162 and 164 which in turn are respectively connected to one side of the indicator lights numbered 1 through 4. The test switch 130 is connected in the wire 154 and the "on" light 128 is connected by wires 166 and 168 between the wires 154 and a wire 170 which in turn is connected with the battery. The indicator lights number 1 through 4 are respectively connected in series with the switches 30 also numbered 1 through 4 in FIG. 7 and to the wire 170. Thus, wires 172, 174, 176 and 178 extend from the lamps numbered 1 through 4 respectively to the connector 36 for connection to wires 180, 182, 184 and 186 which are respectively connected to one terminal of the switch units 30 numbered 1 through 4. Opposite terminals of the switch units are respectively connected by wires 188, 190, 192 and 194 with a common wire 196 which extends through the connector 36 to a wire 198. The wire 198 is connected with the battery by the wire 170. Rectifiers 200, 202, 204 and 206 are respectively connected in the wires 172 through 178 for enabling all indicator lights to light when the test switch is depressed. The circuitry is such that the indicating lights 120 flash on in response to the passage of seeds past the switch units 30 and thereby provide an operator with a visual indication of the seed flow.

The battery or power source 132 is now generally conventional in tractors and the like provides 12 volts. The circuits for the lights 120 are normally energized, but it is important to note that the lights 120 are fluorescent gas lights or glow discharge lamps such as small neon lights of a known type for which 12 volts is insufficient to cause lighting. Inductance coils or chokes 208, 210, 212 and 214 are respectively connected in parallel with the lights 120. When an individual light circuit is opened by the opening of its associated switch 30, its inductance coil discharges so as to apply a relatively high voltage to the light which is sufficient to cause the light to flash on. The discharge of the coil is accomplished almost instantly so that the light goes out almost instantly. In other words, the arrangement is such that each time a switch 30 is opened, the inductance coil associated therewith discharges and the light gives off one sharp, short flash.

The heretofore described seed-monitoring apparatus is adapted to operate in the following manner. When the selector switch 126 is turned to move the contact 140 from the "off" position to the "on" position, the circuits are completed through the normally closed switch units 30 and the indicator lights so that the light circuits are energized. Then upon operation of the planting devices 16, each individual seed or group of seeds dropping down through the chutes 22 will actuate, or in other words, open the contacts of the associated switch unit 30.

Upon opening of a switch 30, its associated indicating light circuit will be deenergized and the discharge of the coil will energize the light sufficiently to cause it to flash. The combination of the neon light with an inductance coil or choke connected in parallel therewith provides an extremely rapid and sharp response for obtaining a distinct and easily readable flashing of the light in accordance with the flow of the seed. This enables an operator to determine at a glance whether or not seeds are passing down any one or all of the chutes. Furthermore, an operator may determine the approximate rate at which seeds are being discharged by judging the rate at which the indicator light is flashing. In the event an indicator light for any one of the chutes remains steadily out or does not flash, the operator will know instantly that no seed is flowing through the chute.

When an operator wishes to obtain an accurate count of the seed population being planted through any chute, the selector switch 126 is first adjusted so as to move the contacts of blades 140 and 144 to the desired terminal associated with the chute to be checked. For example, the selector switch 126 may be adjusted so that the blades 140 and 144 respectively contact their associated terminals No. 1. Then when the timer 122 is actuated, the counter 124 is energized. As previously indicated, the arrangement is such that when the timer 122 is actuated, the coil of the counter is normally energized. Then when a seed passes through the chute for opening the associated switch unit 30, the circuit is opened so that the associated indicating light circuit is deenergized and the coil of the counter is deenergized. The inductance coil or choke connected in parallel with the light not only serves to actuate a readily discernable flashing of the light, but the circuit arrangement also promotes a rapid collapse of the magnetic field of the counter coil 152 for increasing the rate of response of the counter. As will be understood, each time the coil of the counter is deenergized and then reenergized in response to the passage of a seed past the associated switch unit 30, the seed is recorded on the counter dials 153.

The counter is of a known commercially available construction having a spring-biased shiftable element of magnetic material responsive to the magnetic field created when the coil is energized and adapted to actuate the counter dials 153 through a suitable mechanism. Such counters have heretofore been connected so that their coils are normally deenergized, but it has been found that, in the present apparatus, the counter can be made to function at a relatively higher rate by connecting it so that the coil 152 is normally energized as long as the timer is operating. Normally the counter continues to function for a predetermined time interval set by the timer 122 so that at the end of the interval, the rate at which the seeds are being planted may be determined by dividing the preset time into the total number of seeds recorded by the counter. However, the circuit may be provided with a manually or otherwise operable timer bypass for enabling the counter to be operated without a time limitation. Such a bypass may be provided separately by connecting a switch in a line bypassing the timer or it may be included in a timer device of known construction.

In FIGS. 8 and 9 a modified, or alternate form of the present invention is illustrated, which is adapted for use in a seed-monitoring system employing a normally open switch construction. Concerning this embodiment, it should be noted that parts or elements similar to those previously discussed are designated by like reference numbers, followed by the suffix a.

Before proceeding with the detailed description of the construction of switch unit 30a, it is believed desirable to set forth briefly the general nature of a system in which this form of the invention will be employed. Basically, the overall system is the same as that illustrated in FIG. 2. That is to say, switch 30a is placed in circuit with an indicating unit and mounted in relation to a seed planter chute, such that it will be actuated to provide a detectable signal each time a seed or group of seeds pass therethrough.

The primary difference between the construction of switch 30a, and the previously discussed unit 30, is that switch 30a operates on a normally open principle. That is, when the sensing element 46a is engaged, the switch is closed. Accordingly, with reference to FIG. 7, in the lighting circuit for switch 30a the discharge lamps 120 and the associated inductance coils 208-214 and rectifiers 200-206, are eliminated, with each switch 30a being connected in series with a simple incandescent lamp. Therefore, upon the actuation of a switch 30a, the circuit for an associated lamp will be closed and the lamp will light, to indicate the passage of a seed through the planter chute. However, subsequent to said instance of engagement, and prior to the next succeeding instance, switch 30a will open thus deenergizing or opening the lamp circuit.

Turning now to FIGS. 8 and 9, the construction of normally open switch unit 30a is illustrated in detail. Said switch 30a comprises housing members 52a and 54a secured together, with member 54a also being secured to a mounting plate 45a. Electrical terminals 56a and 62a extend from the upper portion of the housing assembly to provide for an electrical connection with the signaling apparatus. The terminals 56a and 62a are in conducting engagement with the upper portions of the leaf-springlike blade members 76a and 80a, respectively. The assembly of said terminals, 56a and 62a, and the leaf spring members, 76a and 80a, to the housing or body member 52a is effected in the same manner as described previously with regard to FIGS. 5 and 6, said description being incorporated herein by reference.

A contact element is carried on the free end of each said leaf spring member 76a and 80a, said elements being designated 78a and 82a, respectively. Accordingly, with the upper portion of each spring member being secured to the housing member 52a, the depending, contact-carrying portions are free to move in an arcuate path about the points 81a and 81'a.

As was the case with the previously discussed embodiment, the contact-carrying spring members 76a and 80a are canted or bent to achieve a desired equilibrium position that results in a wiping action upon actuation of the switch. In this regard, the members 76a and 80a are bent approximate the points 81a and 81'a, with the degree or severity of the bend being somewhat greater for member 76a than for member 80a. Accordingly, in the equilibrium position [not shown] the contacts will be engaged, with the free-depending portions of members 76a and 80a being disposed at an angle to their respective mounting portions which lie in parallel vertical datum planes.

With this arrangement, as illustrated in FIG. 8, it is possible to move or pivot the member 76a away from member 80a to separate the contacts 78a and 82a, without either of said members 76a and 80a passing through the vertical datum plane. To achieve the illustrated normally opened condition, setscrew 86a is employed to move member 76a against the force established by the initial bending thereof. Under these circumstances, spring member 80a will assume a disposition dictated by the initial bend applied thereto; or, as is illustrated, its position may be determined by engagement with section 112a of actuator 46a after the position of said actuator is preset, as will be detailed hereinafter. In either instance, the contacts 78a and 82a may be spaced, one from the other by means of setscrew 86a.

Turning now to FIG. 9, the construction of actuator 46a can be viewed in detail. Basically, the mounting arrangement for, and the general construction of, actuator 46a is similar to that previously discussed, with one exception. Said exception is that the lever arm sections 114a and 116a, which carry the spring-member-engaging portion 112a, depend downwardly, with the portion 112a, being disposed in back of member 80a, as compared to the positioning of portion 112 between the spring members in the previously discussed embodiment.

Accordingly, when the sensing element or actuator 46a is struck by a seed, the portion 112a will be pivoted in a clockwise direction to move spring member 80a also in a clockwise direction. As is clear from FIG. 9, this movement causes the contacts 78a and 82a to engage, thus closing momentarily the lamp circuit. The respective spring members 76a and 80a will now move jointly, in a clockwise direction, with the contacts 78a and 82a closed, until member 76a engages the stop provided by setscrew 85a. After this engagement, the spring members 76a, 80a move jointly in the counterclockwise direction, due to both the transfer of energy or rebounding occasioned by the engagement with stop 85a and the spring force stored in said members. Upon said counterclockwise movement, spring 76a will engage setscrew 86a to preclude further movement thereof, which results in the opening of contacts 78a, 82a, as the spring member 80a is free to move to the initial position. Accordingly, the switch unit 30a is now open, the lamp circuit is disengaged, and said switch is in condition to sense another, subsequent, instance of seed passage.

In a manner similar to that discussed previously, the initial canted disposition of the contact carrying portion of the spring members 76a and 80a provides for relative, sliding movement between the contacts 78a and 82a during the closing thereof. This relative movement effects a cleaning action, wherein pitting and the formation of harmful microscopic welds on the surfaces of said contacts is precluded, as indicated by arrow 117a.

Also, as will be recalled from the discussion of the embodiment of FIGS. 1-6, the attainment of accurate results requires that the movement of actuator 46a be dampened after each instance of engagement by a seed. To effect this dampening action novel bumper or dampener means 118a are employed, which in addition to precluding rebounding, serve as means to adjust the sensitivity of switch 30a, as will be explained.

The dampeners 118a are mounted to a sidewall of housing member 54a and are engaged, respectively, by the leg sections 96a and 98a of wire frame element 100a of the sensing means 46a. As can be seen in FIG. 9, dampeners 118a are of circular configuration, but are eccentrically mounted to the housing member 54a to provide a camlike arrangement. Thus, the initial or preengagement position of the leg section 96a and 98a, and correspondingly that of the actuator portion 112a, may be adjusted by rotation of the dampener means 118a about their eccentric mounting axes. While two dampener means 118a are illustrated, it is possible to employ only one, and still achieve the desired results.

The operation of dampeners 118a, in the precluding of actuator rebound is believed obvious in view of the previous discussion. However, the function of said dampeners with regard to the controlling of sensitivity via initial adjustment of the switch unit is believed worthy of further elaboration.

The sensitivity of a switch unit, be it unit 30 or 30a, is dependent upon several factors; for example, the spring constant of the spring member 76, 76a and 80, 80a, and the amount of actuator movement required to produce a detectable signal. It is this latter factor which lends itself to adjustment in the field; and which adjustment is facilitated by the novel dampener means 118a.

Turning to FIG. 8 and unit 30a, it can be seen that once setscrew 86a is adjusted, the preengagement position of spring member 80a determines the amount of actuator movement required to close contacts 78a and 82a. Also, it should be clear that this position of said spring 80a is or can be controlled by the disposition of the actuator portion 112a in conjunction with setscrew 88a, said disposition of portion 112a being easily adjusted by use of the camming action offered by dampener means 118a.

Concerning unit 30, the dampener means 118a may be employed to advantage here also, replacing elastomeric member 118. While the amount of actuator movement needed to separate contacts 78 and 82 can be controlled to a degree by the setscrews 86 and 88, this can also be achieved by adjusting the preengagement position of the portion 112 of actuator 46, an expedient readily accomplished with the eccentrically mounted dampener 118a.

While preferred embodiments of the present invention have been shown and described herein, it is contemplated that certain structural changes and substitutions may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims

1. A switch unit for use with electrical apparatus for monitoring seeds or the like passing along a prescribed path of travel, said unit being responsive to small pressures and capable of rapid successive operation and comprising: a support housing; first and second electrical contacts contained within said housing and adapted to be placed in circuit with electrical apparatus; a pair of leaf spring members contained within said housing and each having one end portion engaged with the support housing and a free end portion carrying one said contact, such that relative movement of said contacts from a first position to a second position may be effected by pivotal movement of said spring members; and actuating element operably associated with said spring members and adapted to project into said path, such that engagement of said actuating element by a seed will effect said relative movement of the contacts to said second position to produce a detectable signal when said switch unit is operably associated with said apparatus, said actuating element being pivotally mounted to a sidewall portion of said housing and including, an actuator section disposed within said housing and positioned for engagement with at least one of said spring members, at least one leg section disposed exteriorly of said housing, and a blade portion carried by said leg section and adapted to be engaged by seeds; and elastomeric dampening means carried exteriorly of said housing and disposed proximate said leg section and adapted to be engaged by said leg section upon deflection of said actuating element and thereby preventing excessive oscillations of said actuating element, said elastomeric dampening means comprise a camlike member mounted to said housing such that the relative position thereof can be employed to adjust the initial position of the leg section and correspondingly that of the actuator section and said leaf spring

2. A switch unit as defined in claim 1, including a pair of leg sections

3. A switch unit as defined in claim 1, wherein said camlike member comprises a rotatable disc element eccentrically mounted to the housing

4. A switch unit as defined in claim 1, wherein at least one of said spring members is canted such that in the first position said members are disposed so that pivotal movement thereof to the second position results in relative sliding movement between said contacts, effecting a wiping

5. A switch unit as defined in claim 4, wherein both said spring members

6. A switch unit as defined in claim 1, wherein said contacts are in engagement in the first position, thus constituting said unit a normally closed switch, said actuating section interposed between said spring members for effecting relative movement to the second position by

7. A switch unit as defined in claim 6, further including stop means for engaging one of said spring members, said stop means being adjustably spaced from said one spring member such that initially both said spring members will move jointly until said one spring member engages said stop means to effect separation of the contacts upon continued movement of the

8. A switch unit as defined in claim 1, further including adjustable stop means engaging one of said spring members to bias said member to a location wherein the respective contacts are spaced from each other, the resulting disposition of the spring members constituting said first position and said switch unit a normally open switch with said actuating section being engaged with the other of said spring members, such that upon engagement by a seed said other spring member is moved toward said one spring member to bring said contacts into engagement to close said switch, the resulting disposition of the spring members constituting said second position.