The present invention, the objective of which is to provide a push-button switch realized in a way to be held lightly with a small force at the position where the push button is pressed, and obtain a large returning force when the pressing force of the push button is released, is a push-button switch realized by slidably disposing the push button on the switch body and urging it with a return spring, comprising a hole formed in the push button in its pressing direction, a spring for balls inserted in said hole, a window opening on the side face of the push button in communication with the bottom of the hole, a ball for temporary fastening disposed at said window, a concavity, formed along the wall face on the switch body side on which the push button slides, in which to fit part of the ball for temporary fastening at the position where the push button is pressed, and an auxiliary push button, disposed at the top of the push button in a way to be pressed, by being urged by said spring for ball, for pressing the ball for temporary fastening to outside through the spring for ball with pressing, to fit part of the pushed out ball for temporary fastening in the concavity formed along the wall face on the switch body side.

BACKGROUND OF THE INVENTION
 The present invention relates to a push-button switch used for operating a
 crane or a hoist, more specifically a push-button switch realized in such
 a way that the push button can be held lightly at the current position
 when the push button of the push-button switch is pressed down.
 PRIOR ART
 As push-button switch provided with a clip mechanism for temporarily
 fastening the push button at the current position when the switch is
 pressed down, a type as shown in FIG. 10, has so far been widely used, for
 example.
 This push-button switch is realized by disposing steel balls 29 urged by a
 spring for steel ball 28 on a push button 27, and forming a stepped part
 for clip 31 in a way to face the steel balls 29 along the wall face of the
 switch body 30 on which the push button 27 slides, so as to clip the push
 button 27 at prescribed pressed down position by fastening the steel balls
 29 to this stepped part for clip 31 when the push button 27 is pressed
 down.
 By the way, a push-button switch used for operating a crane or a hoist
 allows the crane, etc. to work while the switch operation is made for a
 fairly long time when making a travelling motion. On this type of
 push-button switch is disposed a return spring for urging the push button
 in the direction opposite to the direction of the pressing down operation,
 to make the push button return to its initial position when the pressing
 down operation is released and, usually, a spring having a comparatively
 large spring constant is used as return spring, so that the push button
 may return accurately even when dust, etc. is bitten there.
 For that reason, the holding pressure of the push button inevitably
 increases, and said conventional type of push button had a problem of poor
 operability such as fatigue of the finger pressing the push button in the
 case of a long operating time.
 SUMMARY OF THE INVENTION
 The objective of the present invention is to provide, in view of the
 problem of said conventional type of push buttons, a push-button switch
 realized in a way to be held lightly with small force at the position
 where the push button is pressed, and obtain a large returning force when
 the pressing force of the push button is released.
 To achieve said object, the push-button switch according to the present
 invention is realized as a push-button switch slidably disposing the push
 button on the switch body and urging it along with a return spring,
 characterized in that it comprises a hole formed in the push button in its
 pressing direction, a spring for balls inserted in said hole, a window
 opening on the side face of the push button in communication with the
 bottom of the hole, a ball for temporarily fastening disposed at said
 window, a concavity, formed along the wall face on the switch body side on
 which the push button slides, in which to fit part of the ball for
 temporary fastening at the position where the push button is pressed, and
 an auxiliary push button, disposed at the top of the push button in a way
 to be pressed, by being urged by said spring for ball, for pressing the
 ball for temporary fastening to the outside through the spring for ball
 while pressing, to fit part of the pushed out ball for temporary fastening
 in the concavity formed along the wall face on the switch body side.
 This push-button switch presses the ball for temporary fastening to the
 outside through the spring for ball with the pressing made simultaneously
 with the pressing of the auxiliary push button.
 With this operation, part of the pushed out ball for temporary fastening is
 made to fit in the concavity formed along the wall face of the switch body
 side, and the push button is temporarily fixed at the current position by
 the resisting force produced by the fitting of this ball for temporary
 fastening in the concavity, making it possible to lightly hold the push
 button pressed against the return spring with a small force.
 Moreover, when releasing the pressing force on the push button, the
 pressing force pushing the ball for temporary fastening to the outside
 diminishes.
 As a result, the fitting of the ball for temporary fastening in the
 concavity formed along the wall face on the switch body side is
 disengaged, and the urging force of the return spring acts directly on the
 push button, thus obtaining a large return force.
 This makes it possible to provide a highly safe push-button switch with
 excellent operability, reducing the burden on the operating worker.
 In this case, it is possible to form a concavity in which to fit part of
 the ball for temporary fastening at the position where the push button is
 returned, along the wall face on the switch body side on which the push
 button slides.
 With this arrangement, part of the ball for temporary fastening is subject
 to a resisting force by being fit in the concavity formed at the position
 where the push button returns to at the start of the pressing of the
 auxiliary push button, and the push button is pressed at a stroke after
 accumulating a force until this ball for temporary fastening retreats and
 gets away from the concavity against the spring for ball. As a result, the
 contact of the switch body can be instantly connected.
 This helps improve the durability of the equipment by reducing electric
 exhaustion of the contact, and by preventing occurrence of troubles such
 as burning of motors, etc., especially with the improvement of operability
 of push-button switches with 2a contacts requiring opening and closing of
 2 contacts without any time lag.

DETAILED DESCRIPTION OF THE INVENTION
 Embodiments of the push-button switch according to the present invention
 will be explained hereafter based on drawings.
 FIG. 1 to FIG. 7 indicate the first embodiment of the push-button switch
 according to the present invention.
 This push-button switch is realized by slidably disposing left and right
 push buttons 2 on the switch body 1 by urging them with a return spring 3
 respectively, so that a fixed contact 4 of the switch body 1 may be
 connected with a mobile contact 5 with pressing down of the push button 2.
 And, this push-button switch is constructed by comprising a hole 6 formed
 in the push button 2 in its pressing direction, a spring for balls 7
 inserted in the hole 6, a window 8 opening on the side face of the push
 button 2 in communication with the bottom of the hole 6, a ball for
 temporary fastening 9 disposed at the window 8, a concavity 10, formed
 along the wall face on the switch body 1 side on which the push button 2
 slides, in which to fit part of the ball for temporary fastening 9 at the
 position where the push button 2 is pressed, a return side concavity 11,
 formed above this concavity 10, to fit part of the ball for temporary
 fastening 9 at the position where the push button 2 returned, and an
 auxiliary push button 12, disposed on the push button 2 in a way to be
 pressed, by being urged by the spring for ball 7, for pressing the ball
 for temporary fastening 9 to outside through the spring for ball 7 with
 pressing of the auxiliary push button 12.
 On the switch body 1 are formed longitudinal holes 13 in which the left and
 right push buttons 2 are slidably inserted respectively and transversal
 holes 14 through the longitudinal holes 13, and the fixed contact 4 is
 fixed to this transversal hole 14.
 Moreover, between the left and right longitudinal holes 13 is disposed an
 interlock 15, preventing the left and right push buttons 2 from being
 pressed simultaneously.
 The push button 2 is inserted in the longitudinal hole 13 of the switch
 body 1 through the return spring 3, and in a space 16 formed in the shaft
 are disposed a mobile contact 5 and a spring for mobile contact 17 which
 elastically fixes this mobile contact 5.
 The returning position of this push button 2, urged upward by the return
 spring 3, is determined as the mobile contact 5 gets in contact with the
 top of the transversal hole 14 in the switch body 1.
 On the other hand, the auxiliary push button 12, having a sliding shaft 18
 to be inserted in the hole 6 of the push button 2 and 2 hook-shaped claw
 members 20 to be engaged with U-shaped holes 19 at the top of the push
 button 2, is urged upward by the spring for ball 7 through the sliding
 shaft 18 and protected against falling by the claw member 20.
 Namely, as this auxiliary push button 12 is pushed down against the spring
 for ball 7, it is urged by the compressed spring for ball 7, to push the
 ball for temporary fastening 9 to outside.
 At the bottom of the spring for ball 7 is provided a pressing ball 21, so
 that the spring for ball 7 may rub the surface of the ball for temporary
 fastening 9 in the window 8 through the pressing ball 21, to smoothly
 press and push the ball for temporary fastening 9 to outside.
 The spring force of this spring for ball 7 is set fairly smaller compared
 with that of the return spring 3 of the push button 2.
 The window 8, formed adjacent to and obliquely below the hole 6 in a way to
 communicate with the bottom of the hole 6, is formed with a rather narrow
 space against the hole 6, to prevent the ball for temporary fastening 9 in
 the window 8 from moving into the hole 6.
 The window 8 is formed in a size sufficient for allowing free fitting of
 the ball for temporary fastening 9 to it.
 Furthermore, on the side face of the push button 2, a metallic or rigid
 resin plate 22 is fixed as wall face to the switch body 1, and in this
 plate 22 are formed a concavity 10 and a return side concavity 11 in which
 to selectively fit the ball for temporary fastening 9.
 The concavity 10 has a stepped part 10a in which to fasten the ball for
 temporary fastening 9 in the returning direction on the push-in side,
 while the return side concavity 11 has a stepped part Ha in which to
 fasten the ball for temporary fastening 9 on the return side.
 The ball for temporary fastening 9 and said pressing ball 21 to be engaged
 in those concavity 10 and return side concavity 11 are formed with either
 a metallic or a rigid resin material.
 Next, explanation will be made of the actions of the push-button switch
 having said construction.
 In the case where the push button 2 is pressed through the auxiliary push
 button 12, from the state in which the push button 2 is not pressed
 indicated in FIG. 1 and FIG. 2 (a), the push button 2 remains in the
 return position and only the auxiliary push button 12 is pushed down.
 With this pressing of the auxiliary push button 12, the ball for temporary
 fastening 9 is pushed to outside by the compressed spring for ball 7, and
 engaged in the state in which part of it is urged to the return side
 concavity 11 (FIG. 2(b)).
 With continued pressing of the auxiliary push button 12, the push button 2
 is pushed in, by being pressed by the bottom part of the auxiliary push
 button 12 (FIG. 2(c)).
 At that time, because part of the ball for temporary fastening 9 is engaged
 in the return side concavity 11, the push button 2 does not move until
 this ball for temporary fastening 9 gets away from the return side
 concavity 11 against the spring for ball 7, but is pushed in at a stroke
 after it accumulated a certain amount of force. This makes it possible to
 instantly connect the fixed contact 4 of the switch body 1 and prevent
 electric exhaustion, etc. of the contacts 4, 5.
 In this way, as the push button 2 is pushed in to the end through the
 auxiliary push button 12, part of the pressed ball for temporary fastening
 9 is engaged in the concavity 10 on the switch body 1 side, as shown in
 FIG. 2(c).
 And, because the ball for temporary fastening 9 is engaged in the concavity
 10, even in case the force pressing the push button 2 through the
 auxiliary push button 12 diminished, from the state indicated in FIG.
 2(c), the push button 2 is temporarily fixed at that position by the
 resisting force produced with the fastening of the ball for temporary
 fastening 9 in the stepped part 10a of the concavity 10, as shown in FIG.
 3(a), thereby making it possible to lightly hold the push button 2, pushed
 in against the strong return spring 3, with a small force.
 Next, in the case where the pressing force of the push button 2 applied
 through the auxiliary push button 12 is released, from the state indicated
 in FIG. 2(c) or FIG. 3(a), the auxiliary push button 12 returns in the
 first place, and the pressing force pushing the ball for temporary
 fastening 9 to outside with the auxiliary push button 12 diminishes (FIG.
 3(b)).
 As a result of the above action, the resisting force due to fastening of
 the ball for temporary fastening 9 to the stepped part 10a of the
 concavity 10 diminishes, and the ball for temporary fastening 9 is
 disengaged from the concavity 10, to apply the urging force of the return
 spring 3 directly to the push button 2, thus obtaining a large returning
 force.
 As described above, by releasing the pressing force of the push button 2
 exerted through the auxiliary push button 12, it becomes possible to make
 the push button 2 to return accurately (FIG. 3(c)) to its initial return
 position (FIG. 1 and FIG. 2(a)).
 At that time, since the push button 2 returns to the return position at a
 stroke, the connection between the fixed contact 4 of the switch body 1
 and the mobile contact 5 is instantly cut off, electric exhaustion, etc.
 of the contacts 4, 5 can be prevented.
 Next, FIGS. 8 and 9 indicate the second embodiment of the push-button
 switch according to the present invention.
 This push-button switch, realized by applying the construction of the
 present invention to a so-called 2a contact type push-button switch, which
 is constructed in such a way that 2 contacts are simultaneously opened and
 closed with pressing operation of the push button 2, comprises 2 pairs of
 space 16, mobile contact 5 and spring for mobile contact 17 against one
 push button 2, and is provided with 2 pairs of fixed contact 4 on the
 switch body 1.
 And, in this push-button switch, a storing hole 23 is formed in a way to
 intersect the shaft of the push button 2 about orthogonally, and in this
 storing hole 23 are inserted 2 clip balls 24 with a spring for clip ball
 25 interposed between the two.
 One clip ball 24 is engaged in the concavity for clip 26 formed below the
 concavity 10 of the plate 22, at the pressed position of the push button
 2, in the state urged by the spring for clip ball 25, and is engaged in
 the concavity 10 of the plate 22, at the return position of the push
 button 2.
 In addition, the other clip ball 24, urged toward the plate 22a fixed to
 the switch body 1 in a way to face the plate 22, is engaged in the
 concavity for clip 26 of the plate 22a, at the pressed position of the
 push button 2, and is engaged in the return side concavity 10a, at the
 return position of the push button 2.
 As described above, by providing clip balls 24, the distinction between the
 pressed position and the return position of the push button 2 becomes
 sensorially clear, and it becomes possible to prevent electric exhaustion
 of the contacts 4, 5 and trouble due to time lag of connection of a plural
 number of pairs of contacts, etc., by instantly connecting the fixed
 contact 4 of the switch body 1, in addition to the action of the ball for
 temporary fastening 9 and the return side concavity 11.
 As for other constructions of the push-button switch according to the
 present invention, explanation of the construction and actions will be
 omitted by just giving one same symbol to one same member, because they
 are the same as those of the push-button switch of said first embodiment.
 As an explanation has so far been given on embodiments of the present
 invention, the spring force of the spring for ball 7 can be set as
 required in a range weaker than that of the return spring 3, and the
 restrictive force at pressed position of the push button 2 can be adjusted
 with an adjustment of the depth of engagement of the ball for temporary
 fastening 9 in the concavity 10.