Abstract:
A mechanical latch relay started by a current pulse is disclosed which comprises an electromagnetic generating unit, a connecting mechanism and a mechanical locking mechanism, and which can maintain the existing operation state when the current pulse starting the relay disappears, and it changes its operation state when another current pulse is provided, and then it keeps the operation state even if the pulse disappears so that it can provide a stable operation state of current on/off unnecessary to be provided with a current for a long time, which enables to provide an effective control for current on/off.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a mechanical latch relay started by a latch current pulse, and more particularly, a relay having a mechanical locking means for keeping the operation states provided by the current pulse. 
     BACKGROUND OF THE INVENTION 
     At present, most of the commercial relays, when provided with an operation current, can change their output states, e.g. from “on” to “off” or from “off” to “on”, and will return to their original states when the current provided disappears. In order to maintain the changed states, the current must be provided constantly. An improved relay is on the market to overcome this drawback which needs only a single pulse to keep the changed state. The most relative prior art is the latch relay manufactured by COLE HERSEE CO., U.S.A., but it is complicated, large, and unstable in operation since it requires three springs. 
     SUMMARY OF THE INVENTION 
     The present invention provides at least a mechanical latch relay activated by a latch current pulse in which a mechanical locking means allows an operating current to maintain its present operating state of the latch relay when the latch current pulse is removed and changes its operating state of the latch relay when another latch current pulse is provided, and then keeps the new operating state when the latch current pulse is removed thereby eliminating the necessity to continuously provide the latch current pulse for a particular operating state. 
     The present invention further provides at least a mechanical latch relay started activated by a latch current pulse, which provides a stable operating state of on/off current for effective control of on/off current. 
     The present invention further provides at least a mechanical latch relay started by a very short latch current pulse. 
     The present invention further provides at least a mechanical latch relay which is convenient to operate, time and energy efficient, simple in structure, cheap to manufacture, and which may enable large current. 
     To achieve the above objects, the present invention provides a mechanical latch relay comprising a casing with two connecting holes on a side thereof for receiving a latch current pulse metal plates on a bottom thereof for connecting to an external circuit a cavity including at a center of the bottom side grooves and a cover on an upper end thereof; an electromagnetic generating unit, a connecting means and a locking means housed within said casing, said electromagnetic generating unit includes a coil assembly for generating an electromagnetic field including a central bore and a rotor spring positioned in said central bore; said connecting means includes a connecting plate having a bolt on one side of said connecting plate and a columnar rotor which is inserted into said rotor spring on the other side thereof, said locking means comprises a small spring positioned in said cavity a locking component placed on said small spring and a clamping part with clamping tabs; said locking component is a cylinder having teeth at one end thereof for engaging with said clamping tabs and a gear on the periphery thereof for engaging with side grooves of said cavity. 
     The advantages of the present invention lie in that it can provide a stable operating state for on/off current, and it enables an effective control for on/off current. Moreover, since the metal plate for connecting with an external circuit is made of special material, the range of output current is greatly extended, e.g. from 0 to 250 A. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present inventionl will described with the attached drawings, in which: 
     FIG. 1 is a perspective view of a latch relay according to the prior art; 
     FIG. 2 is a sectional view of the latch relay according to the prior art; 
     FIG. 3 is a schematic perspective view of a casing of a mechanical latch relay of the present invention; 
     FIG. 4 is an exploded view of an electromagnetic generating unit, a connecting means, a mechanical locking means, and a casing of a mechanical latch relay of the present invention; 
     FIG. 5A is an enlarged perspective view of a U-plate of the mechanical latch relay of the present invention; 
     FIG. 5B is a sectional view of the U-plate of the mechanical latch relay of the present invention illustrated in FIG. 5A taken along line  5 B— 5 B; 
     FIG. 6A is a top view of a connecting plate of the mechanical latch relay of the present invention; 
     FIG. 6B is a side view of the connecting plate of the mechanical latch relay of the present invention; 
     FIG. 7A is an enlarged perspective view of a clamping element of the mechanical latch relay of the present invention; 
     FIG. 7B is a bottom view of the clamping element of the mechanical latch relay of the present invention shown in FIG. 7A; 
     FIG. 8A is an enlarged perspective view of a locking component of the mechanical latch relay of the present invention; 
     FIG. 8B is a top view of the locking component of the mechanical latch relay of the present invention shown in FIG. 8A; 
     FIG. 9A is a sectional view of a locking cavity of the mechanical latch relay of the present invention; 
     FIG. 9B is a top view of the locking cavity of the mechanical latch relay of the present invention shown in FIG. 9A; 
     FIG. 10A is a sectional view of the mechanical latch relay of the present invention shown in FIG. 3 taken along line  10 A— 10 A in an output current “off” state; 
     FIG. 10B is a sectional view of the mechanical latch relay of the present invention shown in FIG. 10A taken along line  10 B— 10 B in an output current “off” state; 
     FIG. 11 is a sectional view of the mechanical latch relay of the present invention shown in FIG. 3 taken along line  11 — 11 , showing current “off” state turning the mechanical latch relay when a latch current pulse is provided; 
     FIG. 12A is a sectional view of the mechanical latch relay of the present invention shown in FIG. 3 taken along line  12 A— 12 A, in an output current “on” state; 
     FIG. 12B is a sectional view of the mechanical latch relay of the present invention shown in FIG. 12 A taken along line  12 B— 12 B, in an output current “on” state. 
    
    
     DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 show a latch relay according to the prior art, manufactured by COLE HERSEE CO., U.S.A., which has an external size 80 mm×85 mm×62 mm, and which has a large volume, a complicated structure and is unstable in operation since it requires three springs. 
     Referring to FIGS. 3 and 4, the mechanical latch relay of the present invention includes a casing  60  for containing an electromagnetic generating unit that produces a magnetic field, a connecting means and a locking means for maintaining a current on/off states (discussed in detail below). Two projecting metal plate  61  for connecting to an external circuit are provided on the bottom of the casing  60 , the metal plates  61  may be made of pure copper coated with tin. The other end of each metal plate  61  is inlaid on the bottom of casing  60  by a rivet made of silver alloy whose head  62  projects inwards from the bottom of the casing. Moreover, on the inside bottom of the casing  60 , in addition to the two rivet heads for connecting to an external circuit, there is a contact  69  providing a third contact point for contacting a connecting plate. The third contact point may also connect a detecting circuit so as to monitor the on/off state of the current to an external circuit. On the center of the bottom of casing  60  there is a cavity  70  which projects outwards and is provided with grooves in its interior wall for engaging with the locking component of the locking means. Two coil connecting holes  68  used for transmitting a latch current pulse to the coil assembly are installed on one side of casing  60 . On the other end of casing  60  is a cover  65 , both casing  60  and cover  65  are made of superior quality polyethylene through die casting, and are soldering sealed by ultrasonic technology. 
     FIG. 4 is a schematic view showing the interior parts of a mechanical latch relay of the present invention. The relay comprises a coil assembly  100  made of polyurethane insulated copper wire  13  wound about a reel  11  made of polysulfone through casting, both ends of copper wire  13  extending out connecting holes  68  in one side of the casing and connecting to a source of the latch current pulse. In the middle of reel  11  is an axle hole  12  in which a rotor spring  90  is positioned. Referring to FIGS. 4,  5 A and  5 B, a U-iron plate  80  presses upon an upper end of the coil assembly  100 , and on another end of the coil assembly  100  there is a magnetic field occlusor  10  which cooperates with U-iron plate  80  to enclose the coil assembly  100  so that a closed magnetic circuit is generated when a latch current pulse passes through the copper wire  13  which enhances the magnetic force. In the center of the U-iron plate  80  there is an inward projecting column  81  whose diameter and position are designed in such a way that the column  81  can complementarily engage the rotor spring  90 . An inward projecting conic groove  82  is provided at one end of column  81 , as shown in FIG.  5 B. The rotor spring  90  is made of superior quality steel coated with nickel. 
     The connecting means includes a magnetic field augment piece  21  and a connecting plate  20  secured to the augment piece  21 . A column is installed at the center of magnetic field augment piece  21  and connecting plate  20 . One end of the column is a columnar rotor  22  and the other end is a bolt  25  having a relative thickness less than the rotor  22 . One end of columnar rotor  22  is shaped as outer cone  27  matching the inward projecting conic groove  82  of column  81  mounted on the U-iron plate  80 . During installation columnar rotor  22  inserts through a hole  13  of magnetic field occlusor  10 , into the rotor spring  90  positioned in coil assembly  100  axle hole  12  with the inward projecting conic groove  82  of column  81  matching well with the outer cone  27  at the end of columnar rotor  22 . Thus, when the electromagnetic generating unit consisting of the U-iron plate  80 , coil assembly  100 , and magnetic field occlusor  10  generates a magnetic field and magnetic force upon receiving the latch current pulse the U-iron plate  80  and the magnetic field augment piece  21  press against the elastic force of the rotor spring  90  of coil assembly  100  under the magnetic force, with the inward projecting conic groove  82  of column  81  closely fitting with outer cone  27  at the end of the columnar rotor  22 . When the latch current pulse is removed, the magnetic force fades away concurrently, and the U-iron plate  80  and the magnetic field augment piece  21  move in the opposite direction due to the elastic force of the rotor spring  90 , thereby the inward projecting conic groove  82  of column  81  separates from the outer cone  27  at the end of the columnar rotor  22 . 
     Referring now to FIGS. 6A and 6B a shallow slot  26  is provided in one end of the connecting plate  20  on the same side of the bolt  25  for containing a metal slab  28  which has the features of high electric conductivity, high thermal conductivity, high resistance to electric arc, high mechanical stability, high hardness, and light weight, etc., so as to facilitate switching on larger current output. The metal slab  28  is made of silver-copper alloy, for example, 92.5% silver and 7.5% copper. When the metal slab  28  contacts a rivet head  62  at the internal end of the casing for securing the external circuit board, the external circuit is switched on. As illustrated in FIGS. 6A,  6 B, the connecting plate  20  may be made into a triangular shape so as to reduce its weight and volume. 
     The mechanical latch relay of the present invention is provided with a locking means which comprises a small spring  50  positioned in a locking cavity  70  of the casing  60 , a locking component  40  placed on the small spring  50 , and a clamping part  30 ; the clamping part  30  has columnar shape, at the center of one end of which is an inner hole  31  for receiving bolt  25 , and on the periphery of which are evenly distributed every 120° three clamping tabs  32  the bottom edges of the clamping tabs  32  form a slope  35 ; a small column head  33  is located at the center of the other end of the clamping part  30  for insertion into a hollow hole of the locking component  40 , as shown in detail in FIGS. 7A and 7B. The locking component  40  is a hollow cylinder, provided with teeth  41  at one end thereof whose shape and size match the slope  35  of the clamping tabs  32 , a bead  43  with a smaller diameter than the other end thereof, and a gear  42  on the periphery thereof, whose shape and size match the side grooves  72  on the interior wall of cavity  70  in casing  60 , as shown in detail in FIGS. 8A and 8B. The component  40  and the clamping part  30  are made of polyvinylacetate through casting which has good thermal stability, and the surface that engages with the cavity  70  is made of copper-nickel alloy, which may extend its service life. 
     FIGS. 9A,  9 B illustrate the locking cavity  70  of the casing  60  which includes interior circumstance wall having ribs  75  with end faces  73 , half grooves  71  and full grooves  72 . When the clamping tabs  32  are clamped in half grooves  71 , the metal slab  28  on the connecting plate  20  does not contact the rivet head  62  in the casing  60  and the external circuit is switched off. When the clamping tabs  32  are positioned in the bottom of full grooves  72 , the metal slab  28  on the connecting plate  20  contacts the rivet head  62  in the casing  60  and the external circuit is switched on. 
     Now the operating principle of the mechanical latch relay of the present invention will be explained with the attached drawings. 
     First referring to FIGS. 10A,  10 B, the metal slab  28  on the connecting plate  20  does not contact the rivet head  62  in the casing, and therefore the external circuit is in a “turn-off” state. At this time, the clamping tabs  32  of the clamping part  30  engage the half grooves  71  in the cavity  70  and the rotor spring  90  located between the magnetic field occlusor  10  and the U-iron plate  80  assumes a half-pressed status. An elastic force is transmitted to the clamping part  30  via the columnar rotor  22  and the bolt  25 . The small spring  50  also exerts a force to the clamping part  30  via the locking component  40  so as to enable the clamping tabs  32  to be firmly clamped on the half grooves  71  without rotation. 
     Referring to FIG. 11, now a latch current pulse is transmitted to the coil assembly  100  through coil connecting holes  68 , which generates a magnetic field with different polarities at both ends of the coil. Due to magnetic force attraction, the U-iron plate  80  and magnetic field augment piece  21  press onto the coil assembly  100  against the elastic force of the rotor spring  90 , and the inward projecting conic groove  82  of column  81  leading out from the U-iron plate  80  closely fits with the outer cone  27  at the end of the columnar rotor  22 . At the moment, the elastic force of the small spring  50  pushes the clamping tabs  32  out of the half grooves  71  in the cavity  70  through the locking component  40 . Due to the movement between the slope  35  of the clamping tabs  32  and the teeth  41  of the locking component  40  and the action of the rotor springs  90 , the clamping part  30  performs a tiny rotation, which enables an apex of the slope  35  to stick against the end face  73  of a rib, slide down along it and rotate (along the arrow direction in FIG.  10 B), until the clamping tabs  32  align with the full grooves  72 , referring also to FIG.  9 A. 
     Finally referring to FIGS. 12A and 12B, when a latch current pulse is removed, a repulsive force is generated upon magnetic field variation which, together with an elastic force of the rotor spring  90 , pushes the connecting plate  20  to the bottom. Since the clamping tabs  32  are already aligned with the full grooves  72  in the cavity  70 , it can move toward the bottom of the cavity  70  without resistance so as to enable the connecting plate  20  to contact with rivet head  62 , and the external circuit is switched on. 
     If another latch current pulse comes due to the magnetic force, the U-iron plate  80  and the magnetic field augment piece  21  press down on the coil assembly  100  again, the connecting plate  20  separates from the rivet head  62 , and the circuit is turned off. At that moment, the clamping tabs  32  are pushed out from the full grooves  72  in the cavity  70  by the elastic force of the small spring  50 . Similarly, due to the movement between the slope  35  of the clamping tabs  32  and the teeth  41  of the locking component  40  and the action of the rotor spring  90 , the clamping part  30  performs a tiny rotation, which enables an apex of slope  35  to stick against the end face  73  of another rib, slide down along it and rotate (along the arrow direction in FIG.  10 B), until the clamping tabs  32  are aligned with the half grooves  71 . When the latch pulse current pulse is removed due to the action of a magnetic field repulsive force and an elastic force of the rotor spring  90 , the clamping tabs  32  are pushed into the half grooves  71 . At that moment, the circuit maintains “off” state until the next pulse appears. 
     In summary, when a latch current pulse is input to the relay of the present invention, the state of the external circuit varies. Then, even if the latch pulse current pulse is removed, the status will be retained. A latch current pulse needs to be input again to change the status of the external circuit. Thus, a stable operating status of current on/off is provided, which enables an effective control for current on/off. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.