Patent Publication Number: US-6342684-B1

Title: Device for detecting objects moved downwardly to operate a switch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relates to and claims priority, under 35 U.S.C. §119, from Japanese Patent Application No. 11-206773 filed on Jul. 21, 1999, the entire contents of which are hereby incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a device for detecting objects which have been transferred to operate a switch. The device has a contact which comes into contact with a set position (for example, a terminal) of a different kinds of objects, such as a digital video cassette (DVC) and all other types of cassette, a FD and all other types of discs, and so on. The objects have been transferred to operate a switch and thereby, perform different electrical detecting operations. More particularly, the present invention provides a device for detecting objects which have been transferred to operate a switch, wherein the device includes a flexible spring part formed between a mounting plate part and a U-shaped spring part in a contact spring piece, made of a plate spring. The device further includes the mounting plate part, the U-shaped spring part, and a contact part so as to allow for making the spring span longer to equalize, with high precision, the required load for the contact spring piece (i.e., the contact pressure of the contact with the object) and at the same time, to drastically improve the durability of the contact spring piece. 
     2. Discussion of Background 
     A device for detecting an object transferred to operate a switch has been conventionally used, wherein a set position of the transferred object, such as a DVC, other types of cassettes, etc., comes into contact with a contact of a contact spring piece to operate the switch, thereby performing different electrical detecting operations. Two kinds of devices have been used for detecting the object transferred to operate the switch, namely, one in which a contact spring piece is made of wire, and another in which a contact spring piece is made of a narrow and long plate spring piece. 
     The device for detecting an object, which has been transferred to operate a switch and which uses the contact spring piece made of wire as described above, is prepared, for example, as shown in FIG.  9 . Referring to FIG. 9, a coil part  108  is shown as being elongatedly attached to the top of an upright mounting part  101 . A contact spring piece A 1  is elongatedly equipped with an angled contact part  103 . The angled contact part  103  is the lower part of the contact spring piece A 1 . An upright mounting part  101  is inserted into a hole or slit  106  of a back plate  105  of an L-shaped insulating stock  104  and is fixed in the hole of slit  106 . A lower end of the upright mounting part  101  extends outwardly past a lower end of a base  107  of the L-shaped insulating stock  104  to form a terminal  101   a . A shaft  111  is inserted into the coil part  108 . The angled contact part  103  extends outwardly in front of the back plate  105  of the L-shaped insulating stock  104 . A lower end of the angled contact part  103  presses against the front end of a slit  110  of the base  107  of the L-shaped insulating stock  104 . 
     Referring to FIG. 9, an object  109  is shown as being moved in a downward direction so as to contact an upper part of the angled contact part  103 . Once contact between the object  109  and the angled contact part  103  is established, the object  109  is then continued to be moved downwardly towards a contact or top  103   a  of the angled contact part  103 , while being in contact with the angled contact part  103 . The contact between the object  109  and the angled contact part  103  creates a downwardly-directed load L 1  and a cross-direction load L 2  on the angled contact part  103 . The downwardly-directed load L 1 , which moves the angled contact part  103  downwardly towards the bottom surface of the L-shaped insulating stock  104 , is added to the cross-direction load L 2 , which moves the angled contact part  103  backwardly in the direction of the front surface of the back plate  105 . The downwardly-directed load L 1  and cross-direction load L 2  act as a force for winding a coil of the coil part  108  so that a set position or terminal (not shown) of the object  109  contacts the contact or top  103   a  of the angled contact part  103 . A bending load P 5  is applied to the upper part of the contact spring piece A 1  to compress and bend the angled contact part  103  of the contact spring piece A 1  and the coil part  108  in cross-direction so as to operate the switch in order to perform detection of the object  109 . 
     However, the detecting device of FIG. 9 has disadvantages with respect to the contact spring piece A 1  which is made of wire and these disadvantages will be described in more detail, as follows: 
     (1). Since the coil part  108  is formed by three or four circular windings forming a coil, a certain amount of space is required, i.e., enough space for a shaft  111  of a predetermined diameter and for the width of the three or four circular windings of the coil. Therefore, further miniaturization of the detecting device is made more difficult to accomplish. 
     (2). Uniform and precise fabrication is not feasible because of the wire making up the contact spring piece A 1 . In other word, scatter occurs in every contact spring piece A 1 , particularly, in the spring constant. 
     (3). Since a shaft  111  should be inserted within the three or four windings of the coil of the coil part  108 , the efficiency of the assembly is poor. 
     (4). Gold-plating of the angled contact part  103  is necessary, but it is not possible to gold-plate only the angled contact part  103  of the contact spring piece A 1  because the wire material making up the contact spring piece is long and continuous and therefore, the overall length of the wire must be gold-plated with expensive gold, so that material costs are raised approximately two to three times what they would be if only the angled contact part  103  of the contact spring piece A 1  had to be gold-plated. 
     The disadvantage described in (4) above is the most significant disadvantage. 
     In spite of having the above-described disadvantages, a contact spring piece A 1  made of wire has the advantage of being very durable because the number of windings of the coil of the coil part  108  and the width of the coil can be adjusted. 
     A contact spring piece A 2  can be made of, for example, a long and narrow plate spring. Such a contact spring piece A 2  is shown in FIGS. 10 and 11. This type of contact spring piece A 2  is coming into wider use as compensating for the disadvantages (1)-(4) of the above-described conventional contact spring piece made of wire. 
     However, it has become clear that the contact spring piece A 2  made of a long and narrow plate spring is fatally poor in durability. A contact spring piece must have sufficient durability when it is subjected to a required load (i.e., contact pressure of the contact with an object). Thus, durability is the most important aspect of a contact spring piece. 
     This is true because it is the entire upright mounting plate part  101  (i.e., substantially up to a base of the U-shaped spring part  102  as shown in FIG. 10) that is inserted into the hole or slit  106  of the back plate  105  of the L-shaped insulating stock  104  and fixed to be immovable therein, when the contact spring piece A 2  is mounted. The contact spring piece A 2  includes the U-shaped spring part  102  and the angled contact part  103 . The U-shaped spring part  102  is attached to the upper end of the upright mounting plate part  101 . The angled contact part  103  is elongatedly attached to the lower part of the U-shaped spring part  102 . Referring to FIGS.  11 ( a ) and  11 ( b ), the U-shaped spring part  102  is shown as having a greater width than the contact spring part  103 , but a smaller width than the mounting plate part  101 . 
     Referring again to FIG. 10, an obliquely downward load P 1  is shown as acting on the upper portion of the angled contact piece  103  and a load P 2  is shown as action on a portion of the U-shaped spring part  102 . The load P 2  compresses and bends the U-shaped spring part  102  in a cross-direction, when an obliquely downward load P 1  is applied to the angled contact part  103  of the contact spring piece A 2 , by a synergistic action of the downwardly-directed load L 1  applied to the angled contact part  103  and cross-direction load L 2  due to contact of the object  109  with the angled contact part  103  and the further downward movement of the object  109  while being in contact with the contact part  103 . 
     That is to say, the U-shaped spring part  102  is compressed and bent by the load P 2  in the cross-direction. Thus, the U-shaped spring part  102  acts in a typical manner in that it is restored to its original state by a release of the load. Additionally, since the conventional contact spring piece A 2 , shown in FIGS. 10,  11 ( a ) and  11 ( b ), is not provided with the equivalent of the flexible spring part  8  of the present invention as shown in FIGS. 5,  6 ,  7 , and  8 ( a )-( d ), a flexible action does not occur when the object  109  moves downwardly toward the angled contact part  103  so as to frictionally contact the angled contact part  103 . Consequently, metal fatigue, caused by frequent application and release of the load P 2  on the relatively short span of the U-shaped spring part  102 , is entirely concentrated on the U-shaped spring part  102  at a top thereof, so that the U-shaped spring part has the drawback of often breaking in short-term service. 
     Furthermore, when the required load (i.e., the contact pressure of the angled contact part  103  and the object  109 ) is adjusted by adjusting the width (thickness) of the plate piece of the U-shaped spring part  102 , the load increases sharply by enlarging slightly the width (thickness) because the span between the upper end of the fixed upright mounting plate part  101  and the angled contact part  103  is short. Conversely, the load decreases sharply by diminishing slightly, thereby arising difficulty in adjustment. And, the width (thickness) of the U-shaped spring part  102  with a proper load obtained is extremely poor in durability. Accordingly, solutions to these problems are desirable. 
     SUMMARY OF THE INVENTION 
     The present invention improves the durability of the contact spring piece and solves the above-mentioned problems of the prior art contact spring pieces by providing a flexible spring part, being made of a plate spring piece and having predetermined dimensions, between the upright mounting plate part of the contact spring piece and the U-shaped spring part of the contact spring piece. The contact spring piece of the present invention, which is made of a plate spring piece, has performance superior to a contact spring piece made of wire, because the span between the upright mounting plate part and the angled contact part is lengthened and because the flexible spring part is provided so as to flex under the load of the contact pressure created when the object contacts the angled contact part. 
     That is to say, the present invention solves the above-described problems of the prior art by providing a detecting device, which detects when an object is moved downwardly to operate a switch. The detecting device includes a U-shaped spring part which is attached elongatedly to an upper end of an upright mounting plate part. The upright mounting plate part has a lower end which acts as a terminal. An angled contact part has a top or contact and the angled contact part is attached elongatedly to a lower end of the U-shaped spring part. Together the terminal, upright mounting plate part, U-shaped spring part, and angled contact part make up a contact spring piece. However, the different components of the contact spring piece have different widths. More particularly, the upright mounting plate part of the contact spring piece has a predetermined width, wherein the flexible spring piece has a width smaller than the upright mounting plate part, the U-shaped spring part has the same width as the flexible spring part, and the U-shaped spring part has a greater width than the angled contact part. The upright mounting plate part, of the contact spring piece, is inserted into a slit in a back plate of a L-shaped insulating stock and the upright mounting plate part is fixed therein. The upright mounting plate part has a terminal extending from a lower end thereof such that the terminal extends past a base of the L-shaped insulating stock. The angled contact part, attached to the U-shaped spring part, extends outwardly in front of the back plate of the L-shaped insulating stock. A lower end of the angled contact part is inserted into a slit in the base of the L-shaped insulating stock and a front of the angled contact part contacts a front end of the base of the L-shaped insulating stock. The present invention is characterized in that the contact spring piece has a flexible spring part of predetermined dimensions and the flexible spring part is located between the upright mounting plate part and the U-shaped spring part of the contact spring piece. Further, the upright mounting plate part has at least one contact spring piece and the upright mounting plate part is inserted into and fixed in a slit in the back plate of the L-shaped insulating stock such that a terminal extends from of lower part of the upright mounting plate part past a lower end of the base of the L-shaped insulating stock. The upper end of the U-shaped spring part is engaged with a stopping recess located at an upper end of the back plate of the L-shaped insulating stock. The angled contact part is located in front of the back plate of the L-shaped insulating stock, such that a lower end of the angled contact part is inserted into the slit in the base of the L-shaped insulating stock and is pressed to the front end of the base of the L-shaped insulating stock. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present invention may be had with reference to the following detailed explanations which are given in connection with the accompanying drawings, in which: 
     FIG. 1 is a front view of a working example of a device for detecting an object  9  moved downwardly to operate a switch of the present invention; 
     FIG. 2 is top plan view of detecting device of FIG. 1; 
     FIG. 3 is a right side elevational view of the detecting device of FIG. 1; 
     FIG. 4 is a left side elevational view of the detecting device of FIG. 1; 
     FIG. 5 is a cross-sectional view of the detecting device taken along line a  5 — 5  of FIG. 1; 
     FIG. 6 is a cross-sectional view showing operation of the detecting device of FIG. 5, wherein a top or contact  3   a  of the angled contact part  3  is in contact with a set position  9   a  (for example, a terminal) of an object  9  (for example, a DVC or other type of cassette or disk, etc.); 
     FIG. 7 is a cross-sectional view for explaining the operation of a contact spring piece A of the present invention; 
     FIGS.  8 ( a )-( d ) are a front view, plan view, right side view, and left side view, respectively, of a contact spring piece A of the present invention; 
     FIG. 9 is a cross-sectional view for explaining the operation of a conventional detecting device, wherein the contact spring piece A 1  is made of wire; 
     FIG. 10 is a cross-sectional view for explaining the operation of another conventional detecting device, wherein the contact spring piece A 2  is made of a plate spring; and 
     FIGS.  11 ( a ) and  11 ( b ) are a right side view and a left side view, respectively, of the contact spring piece A 2  of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1-8, working examples of the present invention will be described in more detail below. 
     A device for detecting an object moved downwardly to operate a switch is provided. The detecting device includes a U-shaped spring part  2  which is attached elongatedly to an upper end of an upright mounting plate part  1 . The upright mounting plate part has a lower end, which is made of a plate spring piece for acting as a terminal  1   a . An angled contact part  3  has a top or contact  3   a  which is attached to the lower end of the U-shaped spring part  2 . The upright mounting plate part  1 , the U-shaped spring part  2 , and the angled contact part  3  are all components of a contact spring piece A. The components forming the contact spring piece A are not all of the same width. For instance, the upright mounting plate part  1  has a width which is greater than the width of the U-shaped spring part  2  and the U-shaped spring part  2  has a width which is greater than the width of the angled contact part  3 , as can be clearly seen from FIGS.  8 ( b ) and  8 ( d ). 
     Referring to FIG. 5, it can be seen that the upright mounting plate part  1  is inserted into and fixed to a slit  6  in a back plate  5  of a L-shaped insulating stock  4 . The upright mounting plate part  1  has a contact spring piece extending from a first end thereof. The contact spring piece extending from the first end of the upright mounting plate part acts as a terminal  1   a  and extends past a lower end of the base  7  of the L-shaped insulating stock  4 . The angled contact part  3 , which is attached to the lower end of the U-shaped spring part  2 , extends in front of the back plate  5  of the L-shaped insulating stock  4 . The lower end of the angled contact part  3  is inserted into a slit  10  in the base  7  of the L-shaped insulating stock  4 . The angled contact part  3  is pressed towards a front end of the base of the L-shaped insulating stock  4 . 
     The present invention is characterized in that the contact spring piece A includes a flexible spring part  8 . The flexible spring part  8  has a predetermined dimension and functions as a contact spring piece between the upright mounting plate part  1  and the U-shaped spring part  2  as is clearly shown in FIGS.  8 ( a )-( d ). 
     The upper end of the U-shaped spring part  2  is engaged with a stopping recess  12 , which is formed on the upper end  11  of the back plate  5  of the L-shaped insulating stock  4 . 
     As stated above, the width of the U-shaped spring part  2  of the contact spring piece A is formed so as to be smaller than the width of the upright mounting plate part  1 . Because the spring constant increases when the width of the U-shaped spring part  2  of the contact spring piece A is the same as that of the upright mounting plate part  1 , the width of the angled contact part  3  attached to the U-shaped spring part  2  is formed so as to be smaller than the width of the U-shaped spring part, if necessary. This is because the load of the angled contact part  3 , which comes into contact directly with the object  9 , can be easily equalized. The load is reduced and mutual spaces between parallel and adjacent contact spring pieces A (i.e., four contact spring pieces A are shown in FIGS. 1 and 2) are widened, when the angled contact pieces  3  are in contact with the object  9 . 
     When the flexible spring part  8  is mounted between the upright mounting plate part  1  of the contact spring piece A and the U-shaped spring part  2  of the contact spring piece A as in the present invention and when the entire dimension of the contact spring piece A is not changed, then approximately one third (⅓) of the upper portion of the upright mounting plate part  1  is formed so as to have the same width as the width of the U-shaped spring part  2  and thus, the U-shaped spring part  2  and the angled contact part  3  are left as they are, which is the flexible spring part  8 . 
     The object  9  is moved downwardly to contact the top or contact  3   a  of the angled contact part  3  of the contact spring piece A. Then, as the object is continued to be moved downwardly, the object remains in contact with and moves along the top or contact  3   a  of the angled contact part  3  of the contact spring piece A so that the top or contact part  3   a  of the angled contact part  3  comes into contact with a set position  9   a  (for example, a terminal) of the object  9  in order to operate the switch to perform the detection function. 
     During the downward movement of the object  9  with respect to the angled contact part  3 , an oblique downward load P 1  is applied to the angled contact part  3  of the contact spring piece A by a synergistic action of a downwardly-directed load L 1 . The downwardly-directed load L 1  is applied in such a way that the flexible spring part  8  and the U-shaped spring part  2  are pulled downwardly by contact friction from the object  9  as the object  9  is being moved downwardly into contact with the upper portion of the angled contact part  3  of the contact spring piece A and moved further downwardly toward the top or contact  3   a  while the object  9  remains in contact with the upper portion of the angled contact part  3 . In addition, a cross-direction load L 2  is applied to the contact spring piece A so as to compress and bend the U-shaped spring part  2  toward the back plate  5  of the L-shaped insulating stock  4  while the object  9  is being moved downwardly to contact the angled contact part  3  and then is moved further downwardly towards the top or contact  3   a  of the angled contact part  3  while the object  9  remains in contact with the upper part of the angled contact part  3 . A load P 4 , which makes the flexible spring part  8  flex in the cross-direction, synergistically acts because the cross-direction load P 2 , for compressing and bending the U-shaped spring part  2  in the cross-direction, and the load P 3 , for making the flexible spring part  8  flex in forward-bent direction, are suppressed at the stopping recess  12 . 
     According to the present invention, the span between the upright mounting plate part  1  and the U-shaped spring part  2  can be lengthened by providing the flexible spring part  8  between the upright mounting plate part  1 , which is immovably fixed in the slit in the back plate of the L-shaped insulating stock, and the U-shaped spring part  2 . Therefore, when the downward load L 1  and the cross-direction load L 2  are applied synergistically on all of the components of the contact spring piece A, namely, the U-shaped spring part  2 , the flexible spring part  8 , and the angled contact part  3 , from the object  9  being moved downwardly into contact with the angled contact part  3  and being moved further downwardly toward the top or contact  3   a  of the angled contact part  3  while the object remains in contact with the upper part of the angled contact part  3 , the top or contact  3   a  of the angled contact part  3  comes into contact with the set position  9   a  of the object  9 , so that a spring action and a compression-bending action act synergistically. The spring action corresponds to the downwardly-directed load L 1  and the compression-bending action corresponds to the cross-direction load L 2 . Both of the spring action and the compression-bending action act synergistically, and accordingly, the flexible spring part  8  does not flex and the U-shaped spring part  2  is not compressed and bent. However, the flexible spring part  8  and the U-shaped spring part  2 , as a whole, are made to flex and are compressed and bent. As a result, the present invention makes it possible to improve the durability of the contact spring piece A in a different manner than conventional contact spring pieces. More particularly, conventional contact spring pieces, which are made of a plate spring, are broken in short-term service because only the U-shaped spring parts thereof (i.e., not the flexible spring parts, because conventional contact spring pieces made of plate springs do not have flexing spring parts) are strongly and repeatedly compressed and bent and restored to the original state so as to be susceptible to fatigue failure. 
     Similarly, since the span between the upright mounting plate part  1  and the U-shaped spring piece  2  can be set lengthened by providing the flexible spring part  8  of the present invention, the required loads (i.e., the contact pressure of the top of contact  3   a  of the angled contact part  3  on the set position  9   a  of the object  9 ) can be easily obtained, even if the width of the U-shaped spring part  2  and the angled contact part  3  is enlarged. Accordingly, a load adjustment range can be widely set and an adjustment can be made easily, thereby also improving the durability.