Switch biasing member providing tactile feel

Abstract: A switch biasing member (20) is provided that features substantially transverse apposed resilient arm pairs (A₁, A₂) and (B₁, B₂) that extend from a support member (5) to respective preferably arcuately shaped spaced-apart free-ends (14, 14′) and (16, 16′) that are operative to engage an actuator (2) and impose respective forces (F₁) and (F₂) that respectively increasingly and then decreasingly appose movement of actuator (2) axially between two positions such that the combination of forces (F₁) and (F₂) provide a tactile feel to operation of actuator (2).

Description: INTRODUCTION This invention relates generally to a biasing member that provides movement of a switch actuator with 5 a tactile feel and more particularly to a biasing member that is operative to provide first and second biasing forces that respectively initially increasingly and thence decreasingly appose movement of a switch actuator between first and second positions such that the combination thereof is operative to provide a tactile feel in moving the actuator therebetween. BACKGROUND OF THE INVENTION A variety of methods have been used in the past to provide movement of a switch actuator such as a button or the like with a tactile feel. A tactile feel has historically been provided by engaging the actuator with a biasing member that imparts a singular biasing force against the actuator that is operative to first increasingly resist and then decreasingly resist movement of the actuator between two positions, as disclosed in DE-A- 2 417 392. Examples of a single pair of apposed spring leaves that first resist and then snap to provide a singular biasing force that assists in moving an electrical switch between two positions are respectively disclosed in United States Patents 3,566,057: 3,983,351: and 3,999,025, the disclosures of which are incorporated herein by reference. An example of a double throw type snap action switch that utilizes a dome shaped biasing member to provide a singular biasing force that by reversing direction first resists and then snaps to assist movement of the switch is disclosed in United States Patents 4,438,304, the disclosure of which is incorporated herein by reference. FR-A-2 541 503 shows a snap action spring comprising four offset arms which extend in a plane parallel to the plane of a flat center portion, in such a manner that there are two pairs of opposed arms. As previously described, prior-art biasing members have been limited to providing a singular snap action for imparting a tactile feel to the operation of a switch or the like that is generally coarse in nature. In contrast to the above, the biasing member of the present invention is operative to provide a more subtle and tactile feel in moving an actuator between two positions by imparting a combination of two biasing forces against the actuator respectively initially increasingly and thence decreasingly apposing movement of the actuator between two positions to provide a tactile feel to its operation. SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a biasing member as defined in claims 1 and/or 7 divided into two parts with regard to the disclosure of FR-A-2 541 503. Preferred embodiment are shown in the independent claims. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of a preferred embodiment of the biasing member of the invention; FIGURES 2, 3 and 4 are respectively top, right side and front side elevation views of the biasing member of FIGURE 1; FIGURE 5 is a side elevation view of an embodiment of an actuator operative for use with the biasing member of FIGURES 1-4; FIGURE 6 is a partially schematic cross-sectional view through a first pair of resilient apposed arms of the biasing member of FIGURE 1 showing the force imposed thereby upon the actuator; FIGURE 7 is a cross-sectional view through a second pair of resilient apposed arms transverse to the first pair of FIGURE 6 showing the force imposed thereby upon the actuator; FIGURE 8 is a graph of the respective biasing forces imposed upon the actuator by the biasing member of FIGURE 2 as the actuator is moved between two positions; FIGURE 9 is a partial side elevation view of the biasing member of FIGURE 1 operative to provide a tactile feel to operation of an electrical switch; and FIGURE 10 is a partial side elevation view of the biasing member of FIGURE 1 operative to provide a tactile feel to actuator operative to control flow of a fluid medium. DESCRIPTION OF SOME PREFERRED EMBODIMENTS A preferred embodiment of a biasing member 20 made in accordance with the invention is shown in FIGURES 1-4. Biasing member 20 is preferably a one-piece construction stamped from a resilient material having a thickness suitable for the application involved that is preferably the same for the support portion and cantilever arm pairs hereinafter described with respect to FIGURE 2. Biasing member 20 preferably has a rectangular support portion 5 from which respectively extended apposed arm pairs A₁, A₂ and apposed second cantilever arm pairs B₁, B₂. As shown in FIGURE 2, biasing member 20 has a support portion S having a length L and a width "W". Cantilever arms A₁ and A₂ extend towards each other from opposite sides of portion S to apposed spaced-apart free-ends 14 and 14′ in overhanging relationship to portion S. Cantilever arms B₁ and B₂ are substantially transverse to arms A₁ and A₂ and extend from opposite sides of support portion S to apposed spaced-apart free-ends 16 and 16′ in overhanging relationship to portion S. Support portion S is preferably substantially flat with free-ends 14, 14′, 16 and 16′ preferably laying in a plane that is substantially parallel to support portion S. Free ends 14, 14′, 16 and 16′ are spaced-apart and preferably arcuately shaped to provide a substantially circular segmented opening 6 therebetween having a diameter D. The curvilinear length of free-ends 14 and 14′ is denoted as U and the curvilinear length of free-ends 16 and 16′ is denoted as R in FIGURE 2. Arms A₁ and A₂ are essentially mirror images of each other as are arms B₁ and B₂. Arms A₁, A₂, B₁ and B₂ preferably have a triangular shape provided by the four spaced-apart slots 8 extending radially from opening 6 as shown in FIGURE 2 with their respective bases adjacent support portion S. The width of the base of arms A₁ and A₂ is denoted by N and the width of the base of arms B₁ and B₂ is denoted by M in FIGURE 2. FIGURE 3 shows a view 3-3 from the right side of biasing member 20 shown in FIGURE 2 and FIGURE 4 shows a view 4-4 from the front side of biasing member 20 of FIGURE 2. FIGURE 5 shows an actuator 2 that is adapted to be inserted into circular opening 6 of biasing member 20 shown in FIGURE 2. Actuator 2 has a substantially cylindrical configuration having a diameter H at its lower end beneath a circumferential groove 7 having a breadth denoted as G and a diameter that is substantially the same as diameter D of opening 6. Diameter H is sufficiently larger than diameter D of opening 6 such that when the lower end of actuator 2 is inserted through opening 6, free-ends 14, 14′, 15 and 16′ will spread sufficiently to enable them to engage groove 7 and secure actuator 2 to biasing member 20. The breadth G of groove 7 is preferably slightly greater than the thickness of the arm pairs such as being about .25 millimeter when the thickness of the arm pairs is about 0.05 mm (.002 inch). Once secured to biasing member 20 in the manner described, actuator 2 is operative to move in a direction that is substantially orthogonal to the plane of support portion S. The effect of pressing actuator 2 downwardly upon arms A₁ and A₂ and upon arms B₁ and B₂ is respectively shown in FIGURES 6 and 7. In FIGURES 6 and 7, support portion S is restricted against movement relative movement of actuator 2 by securing it to a suitable fixed support. Support portion S has a neutral bending axis N.A. laying in a plane through support portion S. In FIGURE 5, as actuator 2 is pressed downwardly by a force P between a first and second position, not referenced, arms A₁ and A₂ exert an upwardly directed biasing force F₁ that initially increases and then decreases in resisting movement of actuator 2 between the two positions. Generally, position 1 is an initial "at rest" position and position 2 is an "actuated position" which may be either an engagement or disengagement function depending on how the actuator is being used. In FIGURE 7, pressing downwardly upon actuator 2 causes arms B₁ and B₂ to bend downwardly and exert an upwardly directed force F₂ that initially increases and then decreases in resisting movement of actuator 2 between the two positions. Neglecting the weight of actuator 2, the value of force P required to move actuator 2 downwardly is a function of the sum of forces F₁ and F₂ and is sufficiently greater than the sum to cause actuator 2 to move downwardly between the first and second positions to provide actuator 2 with a tactile feel in its operation. Additionally, the sum of forces F₁ and F₂ is sufficient to return actuator 2 to its initial position when force P is removed. The respective values of forces F₁ and F₂ in newtons when actuator 2 is moved for about 1.3 millimeters downwardly from a first position at which no bending force is exerted upon arms A₁, A₂, B₁ and B₂ is shown in graph form in FIGURE 8. The biasing member used to generate the data shown in FIGURE 8 was in the form of the preferred embodiment 20 shown in FIGURE 2 made from about 0.05 mm (.002 inch)thick type 301 stainless steel having dimensions referred to in FIGURE 1 shown in following Table I. In FIGURE 8, it can clearly be seen that force F₁, against downward movement of actuator 2 provided by arms A₁ and A₂ and force F₂ against downward movement of actuator 2 provided by arms B₁ and B₂ initially increases and then decreases as actuator 2 is moved downwardly about 1 millimeter from its initial position at rest. Preferably, actuator 2 is operative such that is does not bend free-ends 14, 14′, 16 and 16′ below neutral axis N.A. shown in FIGURES 6 and 7. FIGURES 9 and 10 show examples of applications for biasing members made in accordance with the invention. In FIGURE 9, member 20 is used to provide a tactile feel to actuator 2 for operation of an electrical contact 10 that is caused to move downwardly and make electrical contact with contact 12 by downward movement of actuator 2. The biasing member of the invention may be used in any type of electrical circuitry where it is desired to make or break one or more electrical circuits by movement of an actuator. Actuator 2 may for example be made from a conductive metal such that it itself is in electrical contact in the circuit rather than causing movement of a separate electrical contact. When made from an electrically conductive material, one or more of the arms may themselves operate to make and break one or more electrical circuits in response to movement of the actuator. The biasing member of the invention is also suitable for use in fluid control devices for which one example is shown in FIGURE 10 where member 20 is used to provide a tactile feel to movement of actuator 2 for controlling fluid flow through a fluid control device 18. Biasing members made in accordance with the invention may be made from any suitable plastic or metal or composites thereof having the resiliency required. Although preferably having a rectangular-shaped support portion having triangularly shaped arms as herein described providing forces F₁ and F₂ that are different from each other, the biasing member support portion as well as the arms may have any shape that utilizes separate apposed arm pairs that are operative to provide a tactile feel to operation of an actuator. The support portion of the biasing member may be square with the apposed arm pairs having substantially the same cantilever length resulting in the biasing forces of both being substantially the same. Although the free-ends of the respective arm pairs of the biasing member of the invention preferably lay in a single plane for engagement with the actuator at a single location such as a circumferential groove as herein described, the free-ends of the respective arm pairs may be offset from each other so they engage the actuator at different locations when such is desired. Likewise, the free-ends do not have to be arcuately shaped nor the actuator cylindrically shaped as described herein but may have any shape that cooperates to provide engagement with an actuator for which it is desired to provide a tactile feel. Although the support portion is preferably common to both arm pairs such as for the rectangular embodiment described herein, each arm pair may have its own separate support portion which may be secured at different locations provided that the result is two substantially transverse arm pairs that have respective free-ends that engage the actuator and provide a tactile feel to the operation thereof by exerting respective forces thereagainst whose combination initially increases and then decreases as the actuator is moved from a first to a second position.

Claims: A biasing member (20) adapted to provide an actuator moveable between a first position and a second position; said biasing member (20) having a support portion (5) secured against movement relative the actuator, and said biasing member (20) having; a first pair of apposed resilient cantilever arms (A₁,A₂) extending towards each other from opposite sides of support portion (5) to respective spaced-apart free-ends (14,14′) engaged with the actuator in overhanging relationship to support portion, a second pair of apposed resilient cantilever arms (B₁,B₂) extending from opposite sides of support portion (5) transversely to the first pair of resilient arms (A₁,A₂) to respective spaced-apart free-ends (16,16′) engaged with the actuator in overhanging relationship to support portion (5), characterized by said first pair resilient arms (A₁,A₂) adapted to impose a first biasing force (F₁) against the actuator that initially increasingly and thence decreasingly apposes movement thereof between the first and second positions, and said second pair of resilient arms (B₁,B₂) adapted to provide a second biasing force (F₂) against the actuator that initially increasingly and thence decreasingly apposes movement of the actuator between the first and second positions such that the combination of the first and second biasing forces (F₁,F₂) provides a tactile feel to movement of the actuator between the first and second positions, wherein the first biasing force (F₁) is always different from the second biasing force (F₂). The biasing member (20) of claim 1, wherein the biasing member (20) is a one-piece construction stamped from a resilient material. The biasing member (20) of claim 1 wherein the first pair of resilient arms (A₁, A₂) respectively have a prescribed cantilever length (X) extending from support portion (5) to the respective free-ends (14, 14′) thereof and the second pair of resilient arms (B₁, B₂) has a cantilever length (Y) extending from the support portion (5) to the respective free-ends (16, 16′) thereof that is less than the prescribed cantilever length (X) of the first pair of arms (A₁, A₂). The biasing member (20) of claim 1 wherein support portion (5) and first and second resilient arm pairs (A₁, A₂) and (B₁, B₂) have substantially the same thickness (t). The biasing member (20) of claim 1 wherein at least one of the first and second resilient arm pairs (A₁, A₂) and (B₁, B₂) respectively have a substantially triangular shape with the respective base (M) and (N) thereof adjacent support portion (5). The biasing member (20) of claim 1 wherein support portion (5) is oriented substantially orthogonal to the actuator axis defining a neutral bending axis (N.A) in a plane therethrough and the first and second positions are located such that the first and second pair resilient arm free-ends (14, 14′) and (16, 16′) do not pass the neutral axis (N.A.) during movement of the actuator from the first to the second position. A biasing member (20) adapted to provide an actuator moveable between a first and a second position; said biasing member (20) having a support portion (5) secured against movement relative to the actuator defining a first pair of resilient cantilever arms (A₁, A₂) extending towards each other from opposite sides of support position (5) for a prescribed cantilever length (X) to respective spaced-apart free-ends (14, 14′) engaged with the actuator in overhanging relationship to support portion (5), a second pair of apposed resilient cantilever arms (B₁, B₂) extending towards each other from opposite sides of support portion (5) substantially transversely to the first pair of resilient arms (A₁, A₂) for a cantilever length (Y) to respective free-ends engaged (16, 16′) with the actuator in overhanging relationship to support (5), characterized in that the support portion (5) defines a neutral bending axis (N.A.) in a plane therethrough that is substantially orthogonal to the actuator axis, the cantilever length (Y) of the second pair of arms is less than the prescribed cantilever length (X) of the first pair of arms, said first and second pair resilient arms (A₁, A₂) and (B₁, B₂) are adapted such that the respective free-ends (14, 14′ and 16, 16′) do pass the neutral bending axis (N.A.) during movement of the actuator between the first and second positions whereby said first resilient arm pair (A₁, A₂) imposes a first biasing force (F₁) against the actuator that initially increasingly and thence decreasingly apposes movement thereof between the first and second positions and the second resilient arm pair (B₁, B₂) imposes a second biasing force (F₂) against the actuator that initially increasingly and thence decreasingly apposes movement thereof between the first and second positions such that the combination of the first and second biasing forces (F₁) and (F₂) is operative to provide a tactile feel to movement of the actuator between the first and second positions. The biasing member (20) of claim 7 wherein at least one of the first and a second resilient arm pairs (A₁, A₂) and (B₁, B₂) have a substantially triangular shape with the respective base (M) and (N) thereof adjacent support portion (5). The biasing member (20) of claim 8 wherein both of the first and second resilient arm pairs (A₁, A₂) and (B₁, B₂) respectively have a substantially triangular shape with the respective base (M) and (N) thereof adjacent support portion (5). An electrical switch having an actuator engaged with the biasing member (20) of claim 1 or 7. A fluid control device having an actuator engaged with the biasing member (20) of claim 1 or 7.

Inventors: LAMBKE DAVID GERALD, LAMBKE, DAVID GERALD
Applicants: EATON CORP, EATON CORPORATION
Application year: 1988
Main classification: H01H13
IPC codes: H01H13