Patent Publication Number: US-2010117843-A1

Title: Heat pump type hot water supply apparatus

Description:
BACKGROUND OF THE INVENTION 
     (i) Field of the Invention 
     The present invention relates to, for example, a heat pump type hot water supply apparatus which displays an amount of remaining hot water in a hot water storage tank by a plurality of levels. 
     (ii) Description of the Related Art 
     Generally, as a hot water supply apparatus which displays the amount of remaining hot water in the hot water storage tank, a hot water storage type water heater is known to comprise a remaining calorific value detecting means for detecting a remaining calorific value Q in a hot water storage tank, a remaining hot water amount calculating means for converting the remaining calorific value Q to a remaining hot water amount q at a predetermined converting temperature Tc, a remaining hot water supply time calculating means for converting the remaining hot water amount q to a remaining hot water supply time t at a predetermined conversion flow rate fc, and a display part which displays the remaining hot water supply time t. The hot water storage type water heater clearly displays remaining hot water in the hot water storage tank. 
     Patent Document 1: Japanese Patent Publication 2004-144327 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention  
     On the other hand, with regard to the heat pump type hot water supply apparatus which displays remaining hot water in a hot water storage tank by a plurality of levels, for example, when remaining hot water is displayed by 5 levels, remaining hot water can be displayed by level  2  out of 5 levels even though hot water still remains half of the capacity of the storage tank. In this case, the amount of remaining hot water looks less than the actual amount and users become anxious about shortage of hot water. 
     An object of the present invention is to provide a heat pump type hot water supply apparatus which is capable of preventing users from being unnecessarily anxious about shortage of hot water. 
     Means for Solving the Problems  
     In order to achieve the above object, the present invention, a heat pump type hot water supply apparatus, is provided with a remaining hot water display for displaying the amount of remaining hot water in a hot water storage tank by a plurality of levels, a display control means for changing the remaining hot water display according to the amount of remaining hot water in the hot water storage tank. A change amount of hot water which changes the remaining hot water display from a predetermined level to the next level thereof by the display control means is larger than a change amount of hot water which changes the remaining hot water display from the other levels to the next level thereof by the display control means. 
     In this heat pump type hot water supply apparatus, the change amount of hot water which changes the remaining hot water display from the predetermined level to the next level thereof is larger than the change amount of hot water which changes the remaining hot water display from the other levels to the next level thereof. Thus, the remaining hot water display does not change from the predetermined level to the next level thereof, when the amount of hot water which changes the remaining hot water display from the other levels to the next level thereof is supplied from the hot water storage tank to the outside. 
     Advantages of the Invention  
     In this heat pump type hot water supply apparatus, the remaining hot water display does not change from the predetermined level to the next level thereof when the amount of hot water which changes the remaining hot water display from the other level to the next level thereof is supplied from the hot water storage tank to the outside. Hence, it is possible to make the amount of remaining hot water in the hot water storage tank at the predetermined level look larger compared to the other levels. Also, by appropriately setting up an amount of hot water which changes from the predetermined level to the next level thereof, it becomes possible to display the amount of remaining hot water which is not so different from the actual amount of hot water in the hot water storage tank. Therefore, it is possible to prevent users from being unnecessarily anxious about shortage of hot water. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an outline composition view of a heat pump type hot water supply apparatus; 
         FIG. 2  is a block diagram showing a control system composition of the heat pump type hot water supply apparatus shown in  FIG. 1 ; 
         FIG. 3  is an external front view of a remote controller shown in  FIG. 2 ; 
         FIG. 4 , is a diagram showing a relationship between remaining hot water in a hot water storage tank and a remaining hot water display; and 
         FIG. 5  is a diagram showing a relationship between remaining hot water in the hot water storage tank and the remaining hot water display. 
     
    
    
     DESCRIPTION OF THE SYMBOLS 
       22  . . . hot water storage tank,  29   a - 29   f  . . . stored hot water thermometers,  30  . . . display controller,  40  . . . remote controller,  41  . . . remaining hot water display,  41   a - 41   e  . . . scales. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 to 4  show the first embodiment of the present invention.  FIG. 1  is an outline composition view of a heat pump type hot water supply apparatus,  FIG. 2  is a block diagram showing a control system composition of the heat pump type hot water supply apparatus shown in  FIG. 1 ,  FIG. 3  is an external front view of a remote controller shown in  FIG. 2 ,  FIG. 4  is a diagram showing a relationship between remaining hot water in a hot water storage tank and a remaining hot water display. 
     First, the composition of the heat pump type hot water supply apparatus in accordance with one embodiment of the present invention is explained with reference to  FIG. 1 . 
     The heat pump type hot water supply apparatus includes a heat pump unit  10  and a hot water storage unit  20 . The heat pump unit has a refrigerant circuit  17  composed by sequentially connecting a compressor  12 , a water heat exchanger  13 , a pressure reducing valve  14 , and a heat exchanger  15  via refrigerant pipes  11 . Refrigerant, such as CO 2 , is sealed in the refrigerant circuit  17 . 
     The compressor  12  has a motor (not shown) as a driving source. The compressor  12  has a generally known composition so that the revolution thereof is variably controlled. The compressor  12  applies pressure to the refrigerant and circulates it in the refrigerant circuit  17 . 
     The water heat exchanger  13  conducts heat-exchange between a high temperature and pressured refrigerant which is discharged from the compressor  12  and flows in the refrigerant pipe  11  and water flows in a circulation pipe  21  which is described later. By this, the water heat exchanger  13  functions as a condenser so that water flowing in the later-described circulation pipe  21  is heated. 
     The pressure reducing valve  14  is a commonly known motor-operated valve. The pressure reducing valve  14  depressurizes the refrigerant from which heat is absorbed by the water heat exchanger  13  and changes the said refrigerant into a low-temperature and pressure one. 
     The heat exchanger  15  conducts heat-exchange between the refrigerant flowing in from the pressure reducing valve  14  and outside air supplied by a fan  16 . The refrigerant which went through the heat exchanger  15  flows into the compressor  12  via the refrigerant pipe  11 . By this, the heat exchanger  15  functions as an evaporator so the refrigerant is heated. 
     The hot water storage unit  20  has a circulation circuit  24  composed by sequentially connecting a hot water storage tank  22 , a circulation pump  23 , and the above mentioned water heat exchanger  13  via the circulation pipe  21 . Also, the hot water storage unit  20  has a water supply pipe  25 , a water temperature sensor  25   a,  a branch pipe  25   b,  hot water outlet pipe  26 , a mixing valve  27 , a hot water supply pipe  28 , a hot water temperature sensor  28   a,  a flowmeter  28   b,  and a stored hot water thermometers  29   a - 29   f.    
     The hot water storage tank  22  has a circulation inlet  22   a  and a hot water outlet  22   b  in the upper part thereof, and the hot water storage tank  22  has a circulation outlet  22   c  and a water inlet  22   d  in the lower part thereof. From the outside water source (not shown), water is supplied to the hot water storage tank  22  via the water supply pipe  25  and the water inlet  22   d.    
     The circulation pump  23  applies pressure to the water flowing out from the circulation outlet  22   c,  circulates the pressured water in the circulation circuit  24 , and flows the pressured water into the hot water tank  22  through the circulation inlet  22   a.  By this, water flowing out of the lower part of the hot water storage tank  22  is heated by the water heat exchanger  13  of the heat pump unit  10 , and the hot water at the predetermined temperature such as higher than 60° C. (hereinafter referred as hot water), is supplied to the hot water storage tank  22  from the upper part thereof. 
     A mixing valve  27  comprises a publicly known three way valve. The mixing valve  27  mixes hot water flowing in from the hot water outlet  22   b  via the hot water outlet pipe  26  together with water supplied through the branch pipe  25   b  which diverged from the water supply pipe  25 . The mixing valve  27  supplies hot water at a temperature set up by users to the outside through the hot water supply pipe  28 . 
     The water temperature sensor  25   a  provided to the water supply pipe  25  detects the temperature of water supplied to the hot water storage tank  22  and the mixing valve  27  from the water source (not shown). The hot water temperature sensor  28   a  and the flowmeter  28   b  provided to the hot water supply pipe  28  detect the temperature and flow rate of hot water supplied from the mixing valve  27  to the outside, respectively. 
     The stored hot water thermometers  29   a - 29   f  is placed in the hot water storage tank  22  so as to be located at different positions in the up-and-down direction mutually. The stored hot water thermometers  29   a - 29   f  respectively detects temperatures of hot water or water at their installed positions in the hot water storage tank  22 . By this, it becomes possible to detect the amount of hot water or water in the hot water storage tank  22  by the installed positions of the stored hot water thermometers  29   a - 29   f  detecting a predetermined temperature. 
     In this embodiment, the capacity of the hot water storage tank  22  is 370 liters. Also, the stored hot water thermometers  29   a - 29   f  are installed at positions corresponding to the amount of remaining hot water of 330 liters, 280 liters, 230 liters, 150 liters, 100 liters, and 50 liters in the hot water storage tank  22 , respectively. 
     Next, a control system composition for displaying the amount of remaining hot water in the hot water storage tank  22  is explained with reference to  FIGS. 2 and 3 . 
     As is shown in  FIG. 2 , a display controller  30  makes a remote controller  40  display the amount of hot water in the hot water storage tank  22  by a plurality of levels which are described below. The display controller  30  is comprised of a commonly known computer which has a memory such as RAM, ROM, and etc. and a CPU. Also, the display controller  30  is connected to the above referenced water temperature sensor  25   a,  hot water temperature sensor  28   a , flowmeter  28   b,  stored hot water thermometers  29   a - 29   f  and remote controller  40 . 
     The display controller  30  outputs an operate signal to the remote controller  40  in accordance a program stored in the memory of the display controller  30  itself, the water temperature sensor  25   a,  the hot water temperature sensor  28   a , flowmater  28   b,  and detected signals of the stored hot water thermometers  29   a - 29   f.    
     The remote controller  40  is for users to operate various settings of the heat pump type hot water supply apparatus. As is shown in  FIG. 3 , a display portion  40   b  for displaying a predetermined information and an operation portion  40   c  having a plurality of buttons are provided on a surface panel  40   a  of the remote controller  40 . The display portion  40   b  has a remaining hot water display  41  showing the amount of remaining hot water in the hot water storage tank  22 . And the remaining hot water display  41  has a plurality of scales  41   a - 41   e.    
     The remote controller  40  displays the amount of remaining hot water in the hot water storage tank  22  by letting the scales  41   a - 41   e  of the remaining hot water display  41  light, extinguish, or flicker in accordance with a control signal from the display controller  30 . In  FIG. 2 , the scale  41   a  of the remaining hot water display  41  is extinguished and the scales  41   b - 41   e  of the remaining hot water display  41  are lighted. 
     Next, a relationship between the amount of hot water in the hot water storage tank  22  and the remaining hot water display is explained with reference to  FIG. 4 . 
     After the heat pump unit  10  heats water in the hot water storage tank  22  and the hot water storage tank  22  is filled with hot water, when the hot water is supplied to the outside from the hot water storage tank  22  in accordance with demands from the users, and if the stored hot water thermometers  29   a - 29   f  respectively detects temperatures higher than 60° C. as is shown in  FIG. 4 , the amount of hot water in the hot water storage tank  22  is 330 liters or more, thus, the display controller  30  turns on all of the scales  41   a - 41   e  of the remaining hot water display  41 . When the stored hot water thermometers  29   b - 29   f  respectively detects temperatures higher than 60° C., the amount of hot water in the hot water storage tank  22  is more than 280 liters and less than 330 liters, hence, the display controller  30  turns off the scale  41   a  of the hot water display  41 . When the stored hot water thermometers  29   c - 29   e  respectively detects temperatures higher than 60° C., the amount of the hot water in the hot water tank  22  is more than 230 liters and less than 280 liters, therefore, the display controller  30  extinguishes the scale  41   b  of the remaining hot water display  41 . 
     When the stored hot water thermometers  29   d - 29   f  respectively detects temperatures higher than 60° C., the amount of hot water in the hot water storage tank  22  is more than 150 liters and less than 230 liters. If the display controller  30  turns off the scale  41   c  of the remaining hot water display  41 , only 2 scales  41   d,    41   e  out of 5 scales  41   a - 41   e  will be lightened. By this, it gives an impression to the users that the amount of remaining hot water in the hot water storage tank  22  is less than half the capacity of the tank, even if the actual amount of hot water in the hot water storage tank  22  is 229 liters. 
     The display controller  30  calculates a hot water ratio h when the scales  41   c - 41   e  of the remaining hot water display  41  is lightened and when the stored hot water thermometers  29   d - 29   f  respectively detects temperatures higher than 60° C. (when the stored hot water thermometer  29   c  detects temperature lower than 60° C.). The hot water ratio h is calculated in accordance with detected signals of a water supply temperature Ts from the water temperature sensor  25   a,  a hot water supply temperature Tt from the hot water temperature sensor  28   a , and a stored hot water temperature Tc from the stored hot water thermometer  29   f  and by using the formula (1) below. 
         h =( Tt−Ts )/( Tc−Ts )   (1) 
     Also, the display controller  30  calculates, in advance, a hot water supply amount R which was supplied to the outside after the hot water storage tank  22  is filled with hot water based on a detected flow rate of the flowmeter  28   b.  And, the display controller  30  calculates a remaining hot water amount Z by using the formula (2) below. 
         Z= 370− R×h    (2) 
     When the calculated remaining hot water amount Z is more than 185 liters and less than 230 liters, the display controller  30  keeps the 3 scales  41   c - 41   e  of the remaining hot water display  41  lighting. As such, a change amount of hot water which changes the level lighting the 3 scales  41   c - 41   e  of the remaining hot water display  41  to the next level thereof is larger than a change amount of hot water which changes the other levels, such as the level lighting the 4 scales  41   b - 41   e  of the remaining hot water display  41  to the next level thereof. In other word, when an amount of hot water which changes the remaining hot water display  41  from the level lighting the 4 scales  41   b - 41   e  of the remaining hot water display  41  to the next level thereof is supplied to the outside from the hot water storage tank  22 , the display controller keeps the same level lighting the 3 scales  41   c - 41   e  of the remaining hot water display  41  and does not change the level to the next level thereof. 
     When the calculated remaining hot water amount Z becomes less than 185 liters, the display controller  30  extinguishes the scales  41   a - 41   c  of the remaining hot water display  41 . As such, the display controller  30  changes the level lighting the 3 scales  41   c - 41   e  of the remaining hot water display  41  to the next level thereof according to the actual amount of hot water in the hot water storage tank  22 . 
     When the stored hot water thermometers  29   e  and  29   f  respectively detects temperatures higher than 60° C., the amount of hot water in the hot water storage tank  22  is more than 100 liters and less than 150 liters, therefore, the display controller  30  extinguishes the scale  41   d  of the remaining hot water display  41 . When the stored hot water thermometer  29   f  detects temperature higher than 60° C., the amount of hot water in the hot water storage tank  22  is more than 50 liters and less than 100 liters, hence, the display controller  30  makes the scale  41   e  of the remaining hot water display  41  flicker. When the stored hot water thermometer  29   f  detects temperature lower than 60° C., there is no hot water or less than 50 liters of hot water in the hot water storage tank  22 , therefore, the display controller  30  extinguishes the scale  41   e  of the remaining hot water display  41 . In the  FIG. 4 , the state of the scale  41   e  flickering is shown as the lighting number of 0.5. 
     In this embodiment, when hot water is supplied to the outside from the hot water storage tank  22 , the change amount of hot water which changes the remaining hot water display  41  from the predetermined level to the next level thereof is larger than the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof. On the other hand, when the heat pump unit  10  heats water in the hot water storage tank  22  and the hot water storage tank  22  is being filled up with hot water, the change amount of hot water which changes the remaining hot water display  41  from the predetermined level to the next level thereof can also be larger than the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof. However, it is preferable to make the change amount of hot water larger only when hot water is supplied to outside from the hot water storage tank  22 . By this, when the hot water storage tank  22  is being filled up with hot water, the change amount of hot water which changes the remaining hot water display  41  from the predetermined level to the next level thereof does not become larger than the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof. Hence, when the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof is supplied to the hot water storage tank  22  from the outside, the remaining hot water display  41  can be changed from the predetermined level to the next level thereof. 
     Also, in this embodiment, the remaining hot water amount Z is calculated when the display controller  30  turns on the scales  41   c - 41   e  of the remaining hot water display  41 , and when the stored hot water thermometer  29   c  detects temperature lower than 60° C. On the other hand, the remaining hot water amount Z can be calculated at any times regardless of the display status of the remaining hot water display  41  or the temperature detected by the stored hot water thermometers  29   a - 29   f.    
     In addition, in this embodiment, when the calculated remaining hot water amount Z becomes less than the predetermined amount, the remaining hot water display  41  will be changed from the predetermined level to the next level thereof. On the other hand, for example, when a predetermined time passes from a predetermined level, it is also possible to change the remaining hot water display  41  from the predetermined level to the next level thereof, so that the change amount of hot water which changes the remaining hot water display  41  from the predetermined level to the next level thereof becomes larger than the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof. 
     The remaining hot water display  41  with a plurality of scales  41   a - 41   e  is nothing but an example. As long as remaining hot water in the hot water storage tank  22  is displayed step by step, other ways are acceptable, such as by frequency of having bath or shower, duration of hot water supply time in kitchens, liters (for example, for every 10 liters), and etc. 
     As such, in this embodiment, the heat pump type hot water supply apparatus, the change amount of hot water which changes the level lighting the 3 scales  41   c - 41   e  of the remaining hot water display  41  to the next level thereof is larger than a change amount of hot water which changes the other levels, for example, the level lighting the 4 scales  41   b - 41   e  of the remaining hot water display  41  to the next level thereof. By this, even when the amount of hot water which changes the remaining hot water display  41  from the level lighting the 4 scales  41   b - 41   e  of the remaining hot water display  41  to the next level thereof is supplied to the outside from the hot water storage tank  22 , the level lighting the 3 scales  41   c - 41   e  of the remaining hot water display  41  does not change to the next level thereof. Hence, it becomes possible to let the amount of remaining hot water in the hot water storage tank  22  at the predetermined level display larger than the amount of remaining hot water at the other levels. Also, by setting an appropriate amount of hot water which changes the display from the predetermined level to the next level thereof, it becomes possible to display the amount of remaining hot water which is not so different from the actual amount of hot water in the hot water storage tank  22 . Accordingly, it becomes capable of preventing users from being unnecessarily anxious about shortage of hot water. 
     Also, the change amount of hot water which changes the remaining hot water display  41  from the predetermined level to the next level thereof becomes larger than the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof only when hot water is supplied to the outside form the hot water storage tank  22 . By this, when hot water is supplied to the hot water storage tank  22 , the change amount of hot water which changes the remaining hot water display  41  from the predetermined level to the next level thereof does not become larger than the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof. Thus, when the change amount of hot water which changes the remaining hot water display  41  from the other levels to the next level thereof is supplied to the hot water storage tank  22  from the outside, the remaining hot water display  41  can be changed from the predetermined level to the next level thereof. Accordingly, it can prevent users from becoming anxious that the amount of hot water in the hot water storage tank  22  is not increasing when water in the hot water storage tank  22  is heated by the heat pump unit  10 . 
     Moreover, when the calculated remaining hot water amount Z becomes less than 185 liters, the display controller  30  turns off the scale  41   c  of the remaining hot water display  41 . More specifically, according to the actual amount of hot water in the hot water storage tank  22 , the remaining hot water display  41  will be changed from the level lighting 3 scales  41   c - 41   e  to the next level thereof. By this, it becomes possible to display the amount of remaining hot water which is not so different from the actual amount of hot water in the hot water storage tank  22  and to prevent users from being unnecessarily anxious about shortage of hot water more effectively. 
     Next, the second embodiment of the present invention is explained in accordance with reference to  FIG. 5 . 
       FIG. 5  is a diagram showing a relationship between the remaining hot water in the hot water storage tank  22  and the remaining hot water display. 
     In the second embodiment, the remaining hot water display  41  is changed from the predetermined level to the next level thereof after a predetermined stored hot water thermometer detects the temperature lower than a predetermined temperature and before a stored hot water thermometer right under the said predetermined stored hot water thermometer detects the temperature lower than the predetermined temperature. This is different from the first embodiment of this invention. The compositions which are the same to the ones in the previously explained first embodiment are assigned the same symbols and not explained. 
     As is shown in  FIG. 5 , if the stored hot water thermometers  29   a - 29   f  respectively detects temperatures higher than 60° C. and the display controller  30  turns on all of the scales  41   a - 41   e  of the remaining hot water display  41 , when the stored hot water thermometer  29   a  detects temperature lower than 60° C., the display controller  30  does not extinguish the scale  41   a  of the remaining hot water display  41  promptly, but keeps the scales  41   a - 41   e  lighting. After that, before the stored hot water thermometer  29   b  detects temperature lower than 60° C., more specifically, when the stored hot water thermometer  29   b  detects temperature at 60° C. (when the amount of hot water in the hot water storage tank  22  is 280 liters), the display controller  30  extinguishes the scale  41   a  of the remaining hot water display  41 . If the stored hot water thermometers  29   c - 29   f  respectively detects temperatures higher than  60 ° C. and the display controller  30  turns on the scales  41   b - 41   e  of the remaining hot water display  41 , when the stored hot water thermometer  29   c  detects 60° C. (when the amount of hot water in the hot water storage tank  22  is 230 liters), the display controller  30  extinguishes the scale  41   b  of the remaining hot water display  41 . If the stored hot water thermometers  29   d - 29   f  respectively detects the temperatures higher than 60° C. and the display controller  30  turns on the scales  41   c - 41   e  of the remaining hot water display  41 , when the stored hot water thermometer  29   d  detects 60° C. (when the amount of hot water in the hot water storage tank  22  is 150 liters), the display controller  30  extinguishes the scale  41   c  of the remaining hot water display  41 . If the stored hot water thermometers  29   e  and  29   f  respectively detects temperatures higher than 60° C. and the display controller  30  turns on the scales  41   d  and  41   e  of the remaining hot water display  41 , when the stored hot water thermometer  29   e  detects 60° C. (when the amount of hot water in the hot water storage tank  22  is 100 liters), the display controller  30  extinguishes the scale  41   d  of the remaining hot water display  41 . If the stored hot water thermometer  29   f  detects temperature higher than 60° C. and the display controller  30  lights the scale  41   e  of the remaining hot water display  41 , when the stored hot water thermometer  29   f  detects 60° C. (when the amount of remaining hot water in the hot water storage tank  22  is 50 liters), the display controller  30  let the scale  41   e  of the remaining hot water display  41  flicker. As such, after the stored hot water thermometer  29   a  detects temperatures lower than 60° C., and before the stored hot water thermometer  29   b  right under the said stored hot water thermometer  29   a  detects temperature lower than 60° C., the display controller  30  extinguishes the scale  41   a  of the remaining hot water display  41 , and changes the level lighting all the 5 scales  41   a - 41   e  of the remaining hot water display  41  to the next level thereof. By this, the change amount of hot water which changes the level lighting the 5 scales  41   a - 41   e  of the remaining hot water display  41  to the next level thereof is larger than the other level, for example, the level lighting the 4 scales  41   b - 41   e  of the remaining hot water display  41  to the next level thereof. 
     As such, by this embodiment, the heat pump type hot water supply apparatus, after the stored hot water thermometer  29   a  detects temperature lower than 60° C., and before the stored hot water thermometer  29   b  right under the stored hot water thermometer  29   a  detects temperature lower than 60° C., the display controller  30  extinguishes the scale  41   a  of the remaining hot water display  41 . Thus, the level lighting the 5 scales  41   a - 41   e  of the remaining hot water display  41  will be changed to the next level thereof. By this, the change amount of hot water which changes the level lighting 5 scales  41   a - 41   e  of the remaining hot water display  41  to the next level thereof is larger than the other levels thereof (for example, the change amount of hot water which changes the level lighting 4 scales  41   b - 41   e  to the next level thereof), so it is possible to achieve the same effect of the first embodiment. 
     The preferred embodiments described in this specification are illustrative and not restrictive. The scope of invention is given by the appended claims, and all changes and modifications included in the meaning of claims are embraced in the present invention.