Pushbutton Keyboard Switch Assembly With Improved Disc Spring Contact And Printed Circuit Structure

Abstract

A keyboard system particularly useful when a low profile is desirable as in miniature hand held calculators comprises an electrically insulative circuit board on which a plurality of sets of electrically conductive pads are arranged on one surface thereof. Aligned with each set is an actuating element and actuating button. The actuating element is supported on its peripheral edge on at least one pad of a set and upon actuation comes into bridging electrical contact with one or more pole pads of the set which are arranged near the peripheral edge of the actuating element. Certain of the pads are in electrical connection with electrical circuitry arranged on the reverse side of the board. In an alternative embodiment an electrical jumper is provided so that two circuits may cross one another while being maintained electrically separated from one another. For indefinite actuation of an on-off or a constant switch a sliding button switch is employed. The position of the sliding button controls the direction of force exerted by a coil spring and hence actuation of the switch. In another embodiment a double throw switch is shown.

Description

The present invention relates generally to keyboard systems and more particularly is directed to an improved push-button keyboard system for establishing electrical connections in response to actuation.

In recent years numerous types of keyboard systems have been developed for use in transmitting coded electrical information in various types of machines. Typically such keyboard systems utilize pushbutton members appropriately symbolized in a manner indicative of a numeric, alphabetic or mathematic function generated in response to depression of the pushbutton member to establish electrical connection between various conductive paths and various circuit elements coupled to the system in order to achieve a desired function. However, particularly as the cost of associated equipment has decreased dramatically in recent years coupled with an increase in the use and availability of various devices incorporating such systems the need has arisen for extremely inexpensive readily manufactured keyboard systems which may be economically and accurately produced on a mass production basis with a high degree of accurate repeatability. For example, the need of miniaturized electronic-calculators, units for addressing computer systems, credit card verifiers, telephone dialing and the like which necessarily require various types of keyboard arrangements has enormously increased in recent years requiring the provision of inexpensive, reliable and extremely durable keyboard systems which may be manufactured in a simple and economic manner on a relatively large volume basis. Particularly, in the computer field the need for durable, reliable yet inexpensive systems which can address electrical information either directly to a system or through a remote terminal or the like, while occupying a minimal amount of space, has become increasingly urgent. Such a system is disclosed and claimed in copending and coassigned application Ser. No. 148,503, filed June 1, 1971. In that application a plurality of spaced sets of conductive members including U and rivet shaped are arranged at a surface of a support in electrical communication with conductive paths on an opposite surface of the support. A plurality of actuatable conductive elements, one for each set of conductive members, are provided to establish bridging electrical connection between conductive members of a set application of a preselected deflecting force to the conductive elements. While this structure is very effective for many applications it is not readily adaptable to a two pole design which is required for binary encoding or for touch tone telephones, or in general to more complex circuitry. That is, if another U or rivet shaped conductive member were placed adjacent an actuatable conductive element it would be very difficult to assure that all the members of the set were bridged upon actuation. Thus reliability of actuation is deleteriously affected as soon as more than three portions are to be bridged.

Briefly, in accordance with this invention a plurality of discontinuous annular electrically conductive support pads are arranged on a surface of a support each supporting an actuatable conductive element in the form of a disc. A disc retainer maintains the discs in the desired location on the support pads. A plurality of electrically conductive pads are located within the annular pad adjacent to the discontinued portion. Each of the conductive pads are electrically connected to conductive paths on the reverse side of the support so that upon predetermined deflection of the discs bridging electrical connection is effected between the pads. For momentary actuation the discs are deflected by respective push buttons which are slidable in a direction perpendicular to the plane upon which the discs are supported. For extended actuation a disc is deflected by a button which is slidable in a direction parallel to the plane upon which the disc is supported which motion is translated to a perpendicular direction. This button has an at rest position in both the actuated and non-actuated positions.

It is therefore an object of the invention to provide a keyboard system having single or multiple pole switching action.

It is also an object to provide a single or double throw switching device usable in a keyboard system. It is another object of the invention to provide a keyboard system having an improved switch for extended actuation, such as an on-off switch.

It is yet another object of this invention to provide a reliable, durable, accurate yet inexpensive keyboard system which is conducive to mass production manufacturing techniques.

The above objects and still further objects of the invention will immediately become apparent to those skilled in the art after consideration of the following preferred embodiments which are provided by way of example and not of limitation.

In the accompanying drawings in which several preferred embodiments are illustrated;

FIG. 1 is a perspective view of a miniature hand held calculator incorporating the keyboard system of the invention;

FIG. 2 is a perspective view of the keyboard system used in the FIG. 1 calculator, the keyboard partly broken away to show the interrelationship of several of the component parts including an actuating element and electrically conductive pads;

FIG. 3 is an enlarged blow apart perspective view of an alternative set of electrically conductive pads with a retainer for the actuating elements partly broken away;

FIG. 4 is a cross section taken on lines 4--4 of FIG. 3;

FIG. 5 is a bottom plan view of a circuit board useful in the calculator of FIG. 1, the actuating elements for each station appearing in dashed lines;

FIG. 6 is a top plan view of a portion of a modified form of the circuit board;

FIG. 7 is a top plan view similar to FIG. 6 of a portion of another modified form of the circuit board;

FIG. 8 is a cross section taken on lines 7--7 of FIG. 2 showing a slide switch for extended actuation in the unactuated state;

FIG. 9 is the same view as FIG. 8 but showing the slide switch in the actuated state;

FIG. 10 is a cross sectional view of the slide button of the FIGS. 8 and 9 switch;

FIG. 11 is a bottom view of the FIG. 10 slide button;

FIG. 12 is a front view of the slide switch support shown in FIGS. 8 and 9;

FIG.13 is a bottom view of the support of FIG. 12.

FIG. 14 is a perspective view of a keyboard system useful in telephone dialing incorporating the instant invention;

FIG. 15 is a bottom plan view of a circuit board useful in the keyboard system of FIG. 14, the actuating elements for each station appearing in dashed lines; and

FIGS. 16 and 17 are top plan views of keyboard systems similar to that of the system shown in FIG. 14 but having modified keyboard arrangements.

Like reference characters indicate like elements throughout the several views of the drawings.

Numeral 10 in FIG. 1 indicates generally a miniature, hand held calculator which includes a digitial read out section 12 and a keyboard system 14. The keyboard system 14 is shown in FIG. 2 partly broken away and comprises escutcheon 16 mounting a plurality of manually depressable pushbutton members 18 on which are arranged characters symbolic of the operation effected by their actuation. It will be noted that the pushbutton members are provided with a shoulder 20 to limit outward movement. Aligned with each pushbutton 18 is an actuating element 22 and aligned with each actuating element is a set 24 of electrically conductive pads mounted on circuit board 26. Actuating elements are maintained in their proper location by means of retainer 28 preferably of a suitable electrically insulative material. A layer 30 of flexible material, such as polyethylene terephthalate is preferably placed over retainer 28 to seal each of the electrically conductive pad sets 24. Escutcheon 16 is spaced by any suitable means from layer 30 to permit movement of button 18 from an unactuated to an actuated position. FIG. 5 illustrates electrically conductive circuitry 50 of the reverse side of circuit board 26 to which the conductive pads are electrically connected as explained below.

Reference may be had to FIGS. 3 and 4 for details of an exemplary actuating station including a set of electrically conductive pads. It should be noted that set 24' of FIGS. 3 and 4 is a modified version of that shown in FIG. 2, two pole pads being shown rather than the single pole pad of FIG. 2. Circuit board 26 is composed of an electrically insulative material such as epoxy bonded glass cloth and may have a thickness of approximately 1/32 of an inch. An additional insulative support member 32 (shown only in FIGS. 3 and 4) may be provided beneath circuit board 26 if it is desirable to provide more rigidity and support for the associated electronic components, power supplies, display means and the like. Circuit board 26 has two generally parallel opposite planar surfaces 34, 36 with a plurality of sets of conductive pads 24 arranged on surface 34. As shown in FIGS. 3 and 4 a set 24' comprises a discontinuous annular or crescent shaped pad 38. Arc shaped pad portion 41 is aligned with the imaginary continuation of pad 38 but is separated therefrom. Aperture 40 extends through circuit board 26 as does conductive pad 38 which is electrically connected to a portion of electrically conductive circuit 50 on surface 36 of board 26. Pad 41 is not connected to circuit 50 but is used for support of the actuating element. Located adjacent pads 38 and 41 spaced slightly radially inwardly therefrom are pole pads 42, 44. Pads 42, 44 are aligned with respective apertures 46, 48 and extend through circuit board 26 from surface 34 to other portions of circuit 50 on surface 36. Received on pads 38 and 41 is actuating element 22 which may take the form of a disc having a non-developable surface to render it snap acting. That is upon depression of element 22 from that configuration shown in FIGS. 3 and 4, convex surface facing upwardly, force increases with distance travelled for a first distance which is followed by a second distance when force decreases with distance travelled. This negatively sloped portion of the force versus distance curve is referred to as the snap portion. In order for this to occur the central portion of the disc must travel beyond the plane on which the periphery of the disc rests. Thus pads 38 and 41 extend above the surface 34 a sufficient distance to permit snap action of disc 22. A disc which has been found to be satisfactory is a stainless steel disc 0.5 of an inch in diameter and the pads extend approximately 0.004 inches above surface 34. The height of pole pads 42, 44 is chosen to be approximately the same as that of pads 38, 41. Disc 22 is preferably gold plated on the bottom (as seen in FIG. 3) peripheral margin 23 forming a conductive berm. The peripheral edge of the disc 22 rests upon common pad 38 and arc shaped pad 41. As seen in FIG. 4 the edge is supported sufficiently above surface 34 of circuit board 26 so that any tendency of the disc to work its way beneath retainer 28 is avoided. Retainer 28 is chosen having a thickness appreciably more than the distance pads 38 and 41 extend above surface 34 to allow sufficient space to receive disc 22. Flexible sheet 30 is placed over the disc and is adhesively attached to retainer 28 to seal the sets of conductive pads from gross contaminants such as dust, dirt and even liquids. Spring 52 may be used to transmit force from the button to disc 22 and is captured in cavity 54 of button 18. Upon deflection of disc 22 to and beyond its over center position and the disc makes bridging electrical contact between common pad 38 and pole pads 42, 44 through berm 23. Pole pads are positioned so that disc 22 does not come into electrical contact therewith when the disc is in the unactuated state but does come into contact therewith with the disc 22 is in the actuated state. The pole pads thus are located near enough to the outer periphery of the disc when the disc is seated on common pad 38 to permit electrical contact with the disc in only the actuated state of the disc yet far enough away from the center of the disc to permit the disc to snap through center. It has been found that for satisfactory "feel" the pole pad must be located so that no portion of it is closer to the center of the disc than half the disc's radius. For optimum "feel" the pole pad must be positioned closely adjacent the outer periphery of the disc. For 0.5 inch diameter discs these pads are located so that the pad center is approximately 0.200 inches from the center of the disc. The outer radius of pad 38 is approximately 0.250 and is approximately 0.025 inches in width. Pole pads 42, 44 are approximately 0.050 inches in diameter. Preferably a clearance of at least 0.025 inches is provided between any two pads. A width of 0.075 inches of berm 23 for the above dimensions to insure proper bridging electrical connection has been found to be satisfactory. FIG. 15 illustrates electrically conductive circuitry 50 of a circuit board 26 in which the sets of conductive pads utilize the double pole pad embodiment of FIGS. 3 and 4. It will be understood that the particular number of actuating stations is one of choice determined by the desired design parameters of the unit into which the keyboard is used. It will be seen that depression of any disc 22, shown in phantom in FIG. 15, causes bridging electrical connection with two separate circuits. With the arrangement shown in copending application Ser. No. 148,503 this would be much more difficult to reliably achieve with a conductive member located to contact a central portion of the actuating disc. Further, in that application the outer conductive elements must extend a sufficient amount above the inner conductive element to provide proper actuation of the disc. While that structure is very effective for its intended use it requires precise handling and the circuitry with which it can be used is limited in its complexity. Structures made in accordance with the instant invention are not only conducive to mass manufacturing techniques but also can be used with more complex circuitry requiring multiple pole switching, double throw switching, means for jumping circuits and the like. A particular board made in accordance with this invention is preferably constructed by starting with electrically insulative board 26 having a layer of copper of two ounces per square foot on both sides 34 and 36. The required number of apertures are then formed as by drilling and another layer of copper of one ounce per square foot is added to both surfaces, as by plating. This results in a height of approximately 0.004 inches above the surface of the original substrate. A mask is then placed over the board and the copper is etched away from the board except for the desired configuration. Electrical connection is effected to those portions which are designed to carry current and a thin layer of oxidation resistant metal such as gold may be deposited thereon. This includes pads 38, 42, and 44 and circuitry 50.

FIG. 6 shows a second embodiment with an alternative set 24" of conductive pads. Common pad 38 and aperture 40 are the same as in FIGS. 3 and 4 as are pole pad 42 and aperture 46. However, in this embodiment two separated arc shaped pads 60 and 62 are located on the imaginary continuation of pad 38 and spaced therefrom. A jumper pad 64 is provided extending from apertures 66, 68, aperture 66 being adjacent and intermediate pads 60 and 62 while aperture 68 is adjacent and intermediate pads 62 and 38. As in the case of pad 42, the jumper pad 64 and apertures 66 and 68 are located slightly radially inwardly from pad 38 and the imaginary continuation thereof. This arrangement is particularly advantageous when the electrical circuitry on the reverse side is complex and it is desired to cross two circuits such as circuits 72 and 74 while maintaining them electrically separated from one another. Thus circuit 72 located on surface 36 of board 26 extends to aperture 68, across jumper 64 on surface 34 of board 26, back to circuit 72 on surface 36. Passing beneath jumper 64 on side 36 is circuit 74 electrically separated from circuit 72.

Another type of jumper is shown in FIG. 7 in which pad set 24'" comprises common pad 38' which is similar to common pad 38 of FIG. 6, aperture 40' corresponding to aperture 40 of pole pad 38, but with an additional aperture 43 so that circuits 70 and 71 can cross each other while being maintained electrically separated from one another. As seen in FIG. 7 circuit 70 on surface 36 leads to aperture 40', across a portion of pad 38' on surface 34 to aperture 43 and then back to circuit 70 on surface 36 so that circuit 79 passes beneath in electrical separation from that portion of pad 38' forming part of circuit 70.

Also shown in FIG. 7 is pad 75 which is located on the imaginary continuation of crescent shaped common pad 38'. Aperture 77 is provided in pad 75 electrically connecting pad 75 to circuit 79 on surface 36 of board 26. Pads 83 and 85 are provided spaced radially inwardly of the imaginary continuation of crescent shaped common pad 38' and are in electrical connection with circuit 73 through respective plated apertures 81, 87. Thus pad set 24'" comprises a double throw switch with pad 75, normally closed being bridged with comon pad 38' when the disc 22 is in the unactuated position. A light spring load caused by spring 52 helps to insure that this electrical connection is maintained when the disc is unactuated. Actuation of the disc will cause bridging of normally open pads 83, 85 with common pad 38' and separation of common pad 38' and pad 75. This switch may be useful for instance to shift from one memory to another.

With particular reference to FIGS. 8-13 a slide switch 80 is shown which is adapted for extended or indefinite actuation. The switch has two positions of rest, the actuated and the unactuated. Slide switch 80 comprises slide button 82 which slides parallel to the top surface of escutcheon 16. Button 82 is formed with two tabs 84 which extend transversely therefrom and which are captured beneath the escutcheon 16 to prevent button 82 from becoming dislodged. A knurled or serrated surface 86 may be provided on button 82 to facilitate actuation thereof. A protuberance 88 is formed on the bottom wall of the button and serves as a first spring seat. Protuberance 88 is formed near one end of the button for a purpose which will become obvious below. Located beneath button 82 is slide switch support 90 which is generally T shaped having a cross arm 92 which fits into a mating opening in escutcheon 16 and prevents support 90 from moving laterally. The main body portion 96 is adapted to fit within a channel 98 formed in button 82 thereby permitting relative sliding movement of button 82 and support 90. Located near the end of body 96 remote from the cross bar 92 is protuberance 100 which serves as a second spring seat. Coil spring 102 extends between the first and second spring seats. It will be seen that in the position of FIG. 8 in which the spring is in an at rest position essentially no force is exerted by spring 102. As the button is moved from the FIG. 8 to the FIG. 9 position the force exerted by spring 102 is initially primarily in a direction parallel to the surface of the escutcheon and the plane formed by the peripheral edge of the disc; the perpendicular moment being insufficient to cause actuation of disc 22; however, as the button approaches the position of FIG. 8 and rocks into the position shown and is placed in compression nearly all the force of the spring becomes perpendicular to the plane formed by the edge of the disc and hence forces knee 104 of support 90 downwardly thereby causing actuation of the disc and bridging electrical connection of the respective conductive pads. Protuberances 88, 100 are virtually aligned in this position with the axial centerline of the spring slightly over centered so that the moment of force parallel to the surface of the escutcheon is opposite to the button return direction so that button 82 remains in the actuated state until a sliding force is exerted against it to return it to the unactuated position. That is, as button 82 moves to the actuated position spring 102 reaches its maximum compression before reaching the position shown in FIG. 9. In the unactuated position the return force of disc 22 is sufficient to cause support 90 to return to its FIG. 8 position. Thus by means of coil spring 102 a horizontal motion is translated into a vertical force with spring 102 rocking back and forth within the confines of the cavities formed between button 82 and support 90.

FIG. 14 shows a keyboard system 110 including a plurality of keys 18' especially useful in telephone dialing apparatus. The circuit board shown in FIG. 15 may be used in the system of FIG. 14 and comprises a two pole arrangement as shown in FIGS. 3 and 4. FIGS. 16 and 17 show variations 112, 114 employing different keyboard arrangements, all of which are made in accordance with the invention.

Various changes and modifications in the above-described embodiments will be readily apparent to those skilled in the art and any of such changes or modifications are deemed to be within the spirit and scope of the present invention as set forth in the appended claims.

Claims

I claim:

1. A keyboard system comprising an electrically insulative substrate having generally planar opposed first and second surfaces, a plurality of sets of pads arranged on one of the first and second surfaces, an actuating element having a first at rest convex configuration and a second actuated concave configuration and having an outer peripheral margin circumscribed by an outer peripheral edge, a said element aligned with each set, an actuating button aligned with each actuating element and movable from an actuated to an unactuated position and back, each set of pads including a first crescent shaped pad of electrically conductive material having a top surface elevated above said one of the first and second surfaces, a second pad located radially inwardly of the first crescent shaped pad and radially outwardly from the center of said first crescent shaped pad and aligned with the actuating element so that bridging electrical connection is made between the pads upon actuation through contact with the outer peripheral margin of the element.

2. A keyboard system according to claim 1 in which the second pad has a top surface generally in the same plane as the top surface of the first pad.

3. A keyboard system according to claim 1 including electrical circuitry arranged on the other of said first and second surfaces and an aperture is formed through the board in alignment with each of the first and second pads on the said one surface and with a portion of the electrical circuitry on the said other surface, electrically conductive material located on the walls defining the apertures in electrical communication with respective pads and portions of electrical circuitry.

4. A keyboard system according to claim 3 in which each set of pads includes a third arc shaped pad located on the imaginary continuation of the crescent shaped pad and spaced from said pad, the arc shaped pad having a top surface generally in the same plane as that of the top surface of the crescent shaped pad.

5. A keyboard system according to claim 4 in which the second pad is intermediate the first and third pads adjacent one end of the crescent shaped pad and including a fourth pad intermediate the first and third pads adjacent another end of the crescent shaped pad but spaced therefrom and located slightly radially inwardly of the crescent shaped pad, an aperture through the substrate aligned with the fourth pad on said one surface and a portion of the circuitry on said second surface and electrically conductive material located on the wall of the aperture in electrical communication with the fourth pad and portion of the electrical circuitry.

6. A keyboard system according to claim 5 in which the second and fourth pads are generally cylindrical in shape.

7. A keyboard system according to claim 4 in which each set of pads includes a fourth pad located on the imaginary continuation of the crescent shaped pad and spaced from the third pad and said crescent shaped pad, the second pad is intermediate the first and third pads adjacent one end of the crescent shaped pad and including fifth and sixth pads located slightly radially inwardly of the first crescent shaped pad and adjacent opposite ends of said fourth pad and spaced therefrom, a respective aperture aligned with the fifth and sixth pads on said one surface and a portion of the electrical circuitry on the said second surface, electrically conductive material located on the walls defining the apertures in electrical communication with the respective fifth and sixth pads and portions of electrical circuitry, the fifth and sixth pads being joined electrically on the said first surface so that two portions of electrical circuitry can cross each other while being maintained electrically separated from one another.

8. A keyboard system comprising

an electrically insulative substrate having first and second planar, parallel surfaces,

a plurality of sets of apertures formed in the substrate extending from the first to the second surface,

electrical circuiry including a plurality of circuits arranged on the second surface aligned with the apertures,

a discontinuous annular common pad of electrically conductive material on the first surface aligned with one of said apertures in each set, the conductive material extending from the pad through the aperture to the electrical circuitry,

at least one pole pad of electrically conductive material on the first surface aligned with another of said apertures in each set, the conductive material extending from the pole pad through the said another aperture to the electrical circuitry, the pole pad located adjacent the imaginary continuation of the discontinuous annular pad but spaced therefrom radially inwardly, and

a generally circular shaped actuating element, having an electrically conductive berm along its outer periphery aligned with each set and movable into and out of bridging electrical connection with the common and the pole pad through its berm.

9. A keyboard system according to claim 8 in which two pole pads are provided in each set.

10. A keyboard system according to claim 8 in which one pad comprises two jumper apertures and an electrically conductive jumper arranged on the first surface extending from an electric circuit on the second surface through one jumper aperture along the first surface, through the second jumper aperture back to said electric circuit thereby forming a discontinuous portion of the said electric circuit on the second surface allowing another circuit to cross the said electric circuit on the second surface while being maintained electrically separated therefrom.

11. A keyboard system according to claim 8 in which the outer diameter of the annular pad is approximately 0.500 inches, the cylindrical pad is approximately 0.050 inches in diameter, the center line located 0.200 inches from the center of the annular pad, the pads having a top surface approximately 0.004 inches above the first surface, the top surface of the annular pad being approximately 0.025 inches in width, at least 0.025 inches of clearance provided between any two pads, and the actuating element is a snap acting disc measuring approximately 0.500 inches in diameter.

12. A keyboard system according to claim 8 further including an escutcheon for movably mounting buttons, a button mounted in the escutcheon for and in alignment with each set movable to an actuating and a non-actuating position, at least one of the buttons being slidable between first and second extremities on the escutcheon, a rockable support pivotably mounted on said escutcheon and disposed beneath the slidable button, a first spring seat formed in a bottom surface of the slidable button, a second spring seat formed in a top surface of the rockable support, a coil spring received between the first and second spring seat, the coil spring exerting a downward force on the rockable support causing it to rock with an end thereof moving toward the set in an actuating direction when the slidable button is at one extremity, the coil spring exerting no significant downward force on the rockable support when the slidable button is at the other extremity.

13. An actuating mechanism having two stable at rest positions in the actuated and the non-actuated states comprising a support, a button slidable on the support between two extremities, a first spring seat formed in a bottom surface of the button, a rockable member pivotably mounted on said support and located beneath the button, a second spring seat formed on a surface of the member in facing relation with the bottom surface of the button, a spring received on and extending between the first and second spring seats, a switch including an actuating element adapted to close an electrical circuit upon actuation, the actuating element aligned with a portion of the rockable member, when the button is at one extremity the spring applies a downward force on the member causing it to rock and actuate the actuating element, when the button is at the other extremity the spring exerting insufficient downward force to cause actuation of the actuating element.

14. An actuating mechanism according to claim 13 in which the rockable member is generally T-shaped having a main body portion with two ends, a cross bar formed at one end and the second spring seat formed at the other end.

15. An actuating mechanism according to claim 14 in which a stop wall contacts the support preventing sliding movement.

16. An actuating element according to claim 15 in which a channel is formed along a longitudinal axis of the sliding button, the channel in communication with the bottom wall of the sliding button, the main body portion of the rockable member received in the channel capturing the spring between the button and the rockable member.

17. An actuating element according to claim 16 including two tabs laterally extending from the sliding button, the tabs received beneath the support to prevent movement of the sliding button away from the support.

18. A keyboard system according to claim 1 in which at least one double throw switch is provided by further including in at least one set of pads another pad of electrically conductive material on said one surface aligned with one of said apertures, the conductive material extending from the said another pad through its respective aperture to the electrical circuitry, the and another pad is located on the imaginary continuation of the discontinuous crescent pad but spaced therefrom, and means providing a slight bias against the actuating element against the set of pads so that bridging electrical connection is effected between the crescent pad and the said another pad through the actuating element when unactuated, and when the actuating element is actuated bridging electrical connection is effected between the crescent pad and the second pad.