Ice making machine

Abstract: Disclosed is a compact ice making machine, in which a multiplicity of freezing fingers (17) formed on the lower surface of a freezing base plate (18) are dipped in the water supplied to a freezing chamber (29) defined in a water tray (16) to carry out a freezing operation under agitation of the water by a rocking plate (54) disposed to the freezing chamber (29) and form inverted dome-shaped ice pieces (21) gradually around the freezing fingers (17), and the ice pieces (21) are designed to be released by tilting the water tray (16). In this ice making machine, a mechanism (33,37,36,AM) for tilting the water tray and a mechanism (38,59,RM) for rocking the rocking plate (54) are integrated into one unit and disposed to an inner cover (27) so as to enable efficient assembly of the machine and to facilitate maintenance and repair of the respective mechanisms. Further, since the freezing operation is carried out under agitation of the water to be frozen by the rocking plate (54), opacification of the ice pieces (21) to be formed around the freezing fingers (17) can effectively be prevented.

Description: BACKGROUND OF THE INVENTION This invention relates to an ice-making machine according to the preamble of claim 1. Various types of freezing systems have been proposed for automatic ice-making machines for making a number of ice pieces such as cubes continuously, and they are suitably employed depending on the applications. For example, the following systems are known: (1) a so-called closed cell system ice making machine having a multiplicity of freezing cells opening downward defined by a multiplicity of partitions crossing one another, to which water is injected upward to the respective freezing cells, which are cooled by an evaporator connected to a freezing system, from a water tray disposed below the freezing cells to form ice cubes gradually therein; (2) a so-called open cell system ice making machine having such freezing cells opening downward, in which water is sprayed upward directly into the freezing cells using no water tray to form ice cubes therein; and (3) a flow-down system ice making machine having a perpendicular freezing plate, in which water is supplied to flow down on one surface of the freezing plate to form a semicylindrical ice block on the corresponding surface. These three types of ice making machines all employ a forced circulation system and have a water tank for carrying therein a predetermined amount of water to be frozen, and the water in the tank is fed by a pump to the freezing cells or to the perpendicular freezing plate disposed in a freezing unit, while the unfrozen portion of the water is recovered into the tank to recirculate it to the freezing unit. Accordingly, incidental equipments such as a water tank and a pump for circulating the water to be frozen become necessary in such types of ice making machines. This causes not only complication of the structure of the machine but also production cost elevation and enlargement of the machine. Meanwhile, there has already been proposed a more simplified ice making machine, in which freezing fingers extending downward from the lower surface of a freezing base plate provided with an evaporator thereon are dipped in a predetermined level of water carried in a water tray to form ice pieces around the freezing fingers. This type of ice making machine requires no mechanism for circulating the water to be frozen between the water tray and the water tank during the freezing operation, so that the structure of the machine can be simplified, leading to production cost reduction and down-sizing of the machine, advantageously. As described above, in the last-mentioned type of ice making machine, in which ice pieces are designed to be formed around the freezing fingers merely by dipping them in the water carried in the water tray, the water need not be circulated during the freezing operation, as a matter of course, but maintained in a so-called "static state". Accordingly, the ice pieces gradually formed around the freezing fingers are opacified to white due to the influence of the air dissolved in the water. The opaque white ice pieces generally cause no problem if they are used for the original purposes such as cooling. However, such opaque white ice pieces, if served with drinks and the like in coffee shops or restaurants, look inferior to clear and transparent ice pieces and reduce as a whole the commercial value of the drinks, disadvantageously. From AU-B1-22730/77 an ice-making machine is known which comprises the features of the preamble of claim 1. The freezing fingers are fixedly provided in the compartment filled with water. In order to obtain clear ice, water is circulated through the water tank by means of a pump. This invention is proposed in view of the problems inherent in the conventional ice making machine, in which ice pieces are designed to be formed around the freezing fingers by dipping them into the water carried in the freezing chamber defined in a water tray, and with a view to overcoming them successfully. It is an object of this invention to provide an ice-making-machine for making non-opacified ice pieces which can be assembled in high efficiency and allow easy maintenance and repair of the mechanisms incorporated therein. The ice-making machine of this invention is defined by the features of claim 1. A multiplicity of freezing fingers formed on the lower surface of a freezing base plate are dipped in the water carried in the freezing chamber defined in a water tray to carry out a freezing operation under agitation of the water by a rocking plate disposed in the freezing chamber and form inverted dome-shaped ice pieces gradually around the freezing fingers, and the ice pieces thus formed are adapted to be released by tilting the water tray, wherein the water tray tilting mechanism and the rocking plate rocking mechanism are integrated into one unit and mounted onto an inner cover to allow assembling of the machine in high efficiency and to facilitate maintenance of the respective mechanisms. According to the ice making machine of this invention, the water tray tilting mechanism and the rocking plate rocking mechanism are mounted on the inner cover which is removably fitted to the opening of a box-like chamber, so that the operations of assembling the ice making machine can be facilitated. Meanwhile, this invention also enjoys advantages that the ice making machine can be down-sized and that maintenance and repair of the mechanisms can easily be carried out in a short time, since the tilting mechanism and the rocking mechanism are disposed at one position. Further, since the inner cover is designed to be positioned relative to the main frame by the engagement between protrusions and through holes, the time required for the positioning of the inner cover in the assembling operation can be reduced. Preferred developments of the ice making machine are given in the subclaims. Fig. 1 shows schematically in partially exploded perspective view a freezing unit in the ice making machine according to one embodiment of the invention. Fig. 2 shows schematically in vertical section the ice making machine according to the embodiment. Fig. 3 shows in front elevation an inner cover on which a water tray tilting mechanism, a rocking plate rocking mechanism and an ice discharging unit are mounted. Fig. 4 shows in exploded perspective view the major portions of the tilting mechanism and rocking mechanism. Fig. 5 shows in section the major portion of the freezing unit shown in Fig. 1. Fig. 6 shows schematically in perspective view the freezing unit disposed in an ice bin. Fig. 7 shows in front elevation the major portion of the ice bin from which the inner cover is removed. Fig. 8 shows in perspective view the appearance of the ice making machine. Fig. 9 shows in exploded perspective view how the ice making machine of the embodiment is assembled. Fig. 10 shows in vertical sectional side view a rectangular housing from which the mechanisms are all removed. Fig. 11 shows in front elevation the ice making machine from which the front panel and the inner cover are removed. Fig. 12 shows in rear elevation the ice making machine. Fig. 13 shows schematically in perspective view the ice making machine according to the embodiment, in which the front panel is separated from the main frame. Fig. 14 shows schematically in vertical sectional view the major portion of the front panel correlated with that of the machine chamber in the ice making machine. Fig. 15 shows schematically in horizontal sectional view the major portion of the front panel correlated with that of the machine chamber in the ice making machine. Fig. 16 shows in partially cut-away side view the freezing unit, in which a water tray is assuming a tilted posture. Fig. 17 shows a control circuit diagram of the ice making machine. Fig. 18 shows an explanatory view of the freezing unit under rocking of the rocking plate during the freezing operation and the rocking mechanism assuming a corresponding posture. Fig. 19 shows an explanatory view of the freezing unit after completion of the freezing operation and the rocking mechanism assuming a corresponding posture. Fig. 20 shows an explanatory view of the freezing unit after completion of the freezing operation and the rocking mechanism assuming a corresponding posture, where the rocking projection of a rocking member is retracted from the tilting orbit of the engagement piece of the rocking plate. Fig. 21 shows an explanatory view of the freezing unit after completion of the freezing operation, and the rocking mechanism and tilting mechanism assuming corresponding postures respectively. Fig. 22 shows an explanatory view of the freezing unit where the water tray is stopped in the tilted posture correlated with the position of the cam plate of the tilting mechanism assuming a corresponding posture and those of the second and fourth switches. Fig. 23 shows an explanatory view of the freezing unit where the water tray is resetting correlated with the positions of the cam plate of the tilting mechanism assuming a corresponding posture and of the second and fourth switches. Fig. 24 shows an explanatory view of the freezing unit where the water tray is counter-tilted over the horizontal posture correlated with the positions of the cam plate of the tilting mechanism assuming a corresponding posture and of the second and fourth switches. Fig. 25 shows an explanatory view of the motions of the rocking mechanism for the rocking plate, where the rocking protrusion of the rocking member is retracting from the tilting orbit of the engagement piece of the rocking plate after detection of completion of the freezing operation. Fig. 26 shows a control timing chart in the ice making machine. DESCRIPTION OF PREFERRED EMBODIMENT The ice making machine of this invention will be described below by way of a preferred embodiment referring to the attached drawings. For convenience's sake, it should be appreciated that the expressions "front", "rear", "right" and "left" referred to herein are with respect to the front view of the ice making machine. (General constitution of ice making machine) Figs. 2 and 8 each show schematically in vertical section and perspective view, respectively, an overall structure of the ice making machine according to a preferred embodiment of this invention. A rectangular housing 10 constituting the main body of the ice making machine basically has defined therein a lower machine chamber 12 in which the freezing system including a compressor CM and a condenser 11 are housed, a box-like ice bin 14, disposed above the lower machine chamber 12, surrounded with a heat insulating material 100 and having an ice chamber 83 defined therein, and a freezing unit 15 disposed in the ice bin 14 at an upper position thereof. As will be described later referring to Figs. 1 and 5, the freezing unit 15 has a water tray 16 in which a predetermined level of water to be frozen is carried and a freezing base plate 18 having freezing fingers 17 to be dipped in the water to be frozen, wherein the water tray 16 is tilted to a predetermined angle upon switching to the ice releasing operation to discharge the water remaining therein to the outside of the machine through a water collecting section 19 and drain pipe 20 as well as to release the ice pieces 21 into the ice chamber 83. Incidentally, an ice discharging mechanism 13 (to be described later) is disposed to the ice bin 14, and the ice pieces 21 stored in the ice chamber 83 are adapted to be discharged thereby to the outside of the machine. (Overall structure of rectangular housing) As shown in Figs. 8 to 13, the rectangular housing 10 consists of a supporting frame 101 on which the freezing system are mounted, a main frame 22 surrounding the freezing system mounted on the supporting frame 101 and the ice bin 14, and a front panel 23 disposed to the front surface of the main frame 22, and assumes as a whole a slim body having a very narrow transversal size. (Supporting frame) As shown in Fig. 9, the supporting frame 101 consists of a rectangular bottom 101a and a pair of vertical portions 101b,101c standing upright from the front and rear edges of the bottom 101a. The front vertical portion 101b and the rear vertical portion 101c have a plurality of tapped holes 103 and 104 respectively at predetermined positions, which are used for fixing the supporting frame 101 in position onto the main frame 22. Meanwhile, feet 102 are attached to the bottom 101a of the supporting frame 101 at the four corners, and the ice making machine is adapted to be set on an installation surface through these four feet 102. An air inlet (not shown) is defined in the bottom 101a of the supporting frame 101, while an air outlet is defined in the rear vertical portion 101c, so that the air introduced from the air inlet, by rotating the cooling fan (not shown) disposed in the machine chamber 12, is brought into contact with the condenser 11 housed in the machine chamber 12 to effect cooling thereof by heat exchange, and then the thus heated air is exhausted to the outside of the machine through an air outlet. Incidentally, a filter 26 covering the air inlet is removably applied to the lower surface of the bottom 101a, so that clean air filtered through the filter 26 can be introduced to the machine chamber 12 through the air inlet, whereby possible reduction in the cooling capacity of the condenser 11 due to clogging to be caused by the dust deposited thereon can be prevented. The filter 26 is also designed to be easily inserted to or drawn out from the front side of the rectangular housing 10. The front vertical portion 101b of the supporting frame 101 has a predetermined size of opening 101d, as shown in Fig. 13. This opening 101d can be opened by removing the front panel 23 from the main frame 22 so as to facilitate maintenance and repair of the freezing system housed in the machine chamber 12. Meanwhile, a heat insulating material 100 surrounding the ice bin 14 is disposed on the upper surface of the upper horizontal member 101e of the front vertical portion 101b over the full width thereof, so that the machine chamber 12 may be open to the front side through the opening 101d in the state where the front panel 23 is removed. (Ice bin) The ice bin 14 has a box-like form which is opening upward and forward and a plurality of fitting portions 14b are integrally formed on the upper opening end thereof, so that the freezing base plate 18 and the water tray 16 may be maintained horizontally by a pair of brackets 32 fixed to these fitting portions 14b (see Fig. 6). As shown in Figs. 7 and 9, the ice bin 14 also has formed integrally therewith on both sides of the front opening 79 thereof a pair of outward flanges 14c having a plurality of tapped holes 105 arranged vertically. These tapped holes 105 are used for securing the ice bin 14 onto the main frame 22 and for fitting an inner cover 27 (to be described later) to the ice bin 14. Meanwhile, a fitting panel 106 is fixed to the rear side of the ice bin 14. The fitting panel 106 has tapped holes 107 at predetermined positions, which are used for fastening the ice bin 14 to the main frame 22. As shown in Fig. 10, a predetermined size of outlet 14a is defined on the bottom of the ice bin 14 at a position adjacent to the front extremity thereof, so that the ice pieces 21 carried by the ice discharging unit 13 may be delivered through the outlet 14a to the outside of the machine. Incidentally, the outlet 14a is opening downward at a predetermined height above the upper end of the vertical portion 101b of the supporting frame 101 and at a position outer than the vertical portion 101b. The right and left flanges 14c of the ice bin 14 have protrusions 84 which are used for positioning the inner cover 27 on the flanges 14c. (Main frame) As shown in Fig. 9, the main frame 22 consists of a rectangular top plate 22a and a pair of side plates 22b extending downward from each side of the top plate 22a. The side plates 22b each have an inward flange 22c formed along the lower portion thereof. These flanges 22c each have tapped holes 108 at the positions corresponding to those of the tapped holes 103 formed in the front vertical portion 101b of the supporting frame 101. Meanwhile, the side plates 22b each have an inward tongue 22d at a position spaced upward with a predetermined distance from the flange 22c, and a tapped hole 109 is formed in each tongue 22d at the position corresponding to that of a certain one of the tapped hole 105 formed in the flange 14c of the ice bin 14. Further, an inward flange 22e is formed at the rear end of each side plate 22b, and each of these flanges 22e has tapped holes 110 and 111 at the positions corresponding to those of the tapped hole 104 formed in the rear vertical portion 101c of the supporting frame 101 and of the tapped hole 107 formed in the fitting panel 106 of the ice bin 14. More specifically, as shown in Figs. 11 and 12, the main frame 22 and the supporting frame 101 can be secured in position to each other by aligning each corresponding pair of tapped holes 108 and 103 (tapped holes 110 and 104) and fitting a screw 112 (113) therethrough. In this state, the top plate 22a of the main frame 22 is designed to be parallel to the bottom 101a of the supporting frame 101. Meanwhile, the main frame 22 and the ice bin 14 can be secured in position to each other by aligning each corresponding pair of tapped holes 109 and 105 (tapped holes 111 and 107) and fitting a screw 114 (115) therethrough. In this state, the top plate 22a of the main frame 22 is designed to be parallel to the upper opening edge of the ice bin 14 (see Fig. 10). Further, in the ice bin 14 disposed in the main frame 22, the bottom thereof (including the heat insulating material 100 and the lower end of the fitting panel 106) is designed to be brought into contact with or slightly spaced from the freezing system mounted on the supporting frame 101 or with the upper ends of the front and rear vertical portions 101b,101c (see Fig. 2), so that the position of the ice bin 14 may not be affected by the variations in the arrangement of the freezing system, heights of the vertical portions 101b,101c and the shape of the bottom of the ice bin 14. (Inner cover) As shown in Fig. 3, the inner cover 27 to be applied to the front opening 79 of the ice bin 14 has formed along both side edges 85 thereof through holes 85a and notches 85b at the positions corresponding to those of certain ones of the tapped holes 105 as well as protrusions 84 of the ice bin 14, and these two members 14 and 27 are adapted to be positioned by fitting the protrusions 84 into the corresponding through holes 85a (see Fig. 6), while these two members 14 and 27 can be secured to each other by fitting fasteners (not shown) such as screws through the rest of the through holes 85a or notches 85b and the corresponding tapped holes 105. Incidentally, the through holes 85a in which the protrusions 84 are to be fitted are elongated in the horizontal direction, allowing fine adjustment in the horizontal direction. As shown in Fig. 3, a tilting mechanism 33,37,36,AM for tilting the water tray 16, a rocking mechanism 38,59,RM for rocking a rocking plate 54 (to be described later), both in the freezing unit 15, and the ice discharging unit 13 are all mounted on the front surface of the inner cover 27, so that the inner cover 27 having mounted thereon these mechanisms and unit can be fixed to or removed from the ice bin 14. Accordingly, the respective mechanisms and unit can be mounted to the inner cover 27 beforehand in a separate line prior to starting assembly of the ice making machine, and the resulting inner cover 27 can be fitted on the front side of the ice bin 14, enabling to carry out the assembling operation efficiently in a short time. Meanwhile, maintenance service of these mechanisms and unit can easily be carried out, advantageously, from the front side by removing the front panel 23. (Front panel) As shown in Figs. 2 and 8, the front panel 23 has a bulge 23b enclosing therein the tilting mechanism 33,37,36,AM, rocking mechanism 38,59,RM and ice discharging unit 13 mounted on the front surface of the inner cover 27 and also has a recess 23c formed backward below the bulge 23b along the vertical axis thereof with a predetermined width. An opening 23a larger than the outlet 14a for discharging the ice pieces in the ice bin 14 is formed on the slope 23e continuing from the bulge 23b to the recess 23c, and the outlet 14a of the ice bin 14 is adapted to be surrounded by the opening 23a, when the front panel 23 is fitted to the main frame 22. Incidentally, the front panel 23 is formed, for example, using a synthetic resin. Meanwhile, a hollow table 24 is adapted to be removably fitted to the recess 23c locating below the opening 23a, on which a vessel such as a glass can be loaded whenever the ice pieces are to be delivered. This table 24 has on the upper surface thereof a multiplicity of slits 24a for draining the water drops dripping from the outlet 14a and the opening 23a and thus preventing splitting of the water drops around the machine. The bulge 23b has a power supply indication lamp L, a first switch SW 1 and a push button 25, and the ice discharging unit 13 is designed to be operated only while the push button 25 is depressed to turn on the first switch SW 1 . Namely, by depressing the push button 25 with a vessel loaded on the table 24, the ice pieces 21 carried by the screw of the ice discharging unit 13 are delivered through the outlet 14a and the opening 23a into the vessel. As shown in Figs. 13 and 14, the front panel 23 has formed therein a barrier 23d at the position corresponding to the location of the upper horizontal member 101e of the front vertical portion 101b of the supporting frame 101. This barrier 23d defines the inner space of the front panel 23 into an upper cavity and a lower cavity. The rear end of the barrier 23d is designed to be abutted against the front surface of the upper horizontal member 101e substantially over the full width thereof, when the front panel 23 is fitted to the main frame 22 (see Fig. 15), so that the lower machine chamber 12 is isolated from the opening 23a. Incidentally, the barrier 23d may be abutted against the heat insulating material 100. (Freezing unit) Fig. 5 shows minutely a vertical sectional view of the freezing unit 15, and the water tray 16, the structure of which is as shown in Fig. 1, is designed to carry a predetermined level of water to be frozen in the freezing chamber 29 defined therein. In other words, the freezing chamber 29 is defined by a rectangular bottom 16a of the water tray 16 and four walls 16b,16c,16d,16e standing upright from the four sides of the rectangular bottom 16a, respectively. A plurality of pintles 30, are integrally formed and aligned horizontally on the outer surface of the right wall 16e. These pintles 30 are pivotally fitted in the through holes 32a defined in the brackets 32 holding the freezing base plate 18 at an upper position in the ice bin 14, so that the water tray 16 can be pivoted sideways on the pintles 30 (see Fig. 6). Incidentally, a water supply pipe 49 for supplying water to be frozen is removably disposed to the freezing base plate 18 at an appropriate position, and a water valve WV is connected through a feed pipe 74 thereto. Thus, a predetermined amount of water to be frozen is designed to be supplied to the freezing chamber 29 by opening the water valve WV in accordance with the timing to be described later (see Fig. 26). Meanwhile, a square hole 30a is defined in the foremost pintle 30, in which a square shaft 33a protruding from the free end of a pivotal shaft 33 (to be described later) is fitted. The pivotal shaft 33 is pivotally supported on the inner cover 27, and thus the water tray 16 is designed to be tilted downward and reset upward on the pintles 30 with the rotation of the actuator motor AM mounted on the inner cover 27, as shown in Figs. 21 to 24. Such constitution of the water tray 16, which is designed to be tilted sideways, can reduce width of the ice making machine. (Water tray tilting mechanism) A cylindrical bearing 34 protruding forward is provided on the inner cover 27 applied to the ice bin 14 at a position corresponding to the location of the pintles 30 of the water tray 16, and the pivotal shaft 33 is pivotally supported in the through hole 34a defined in the bearing 34. The square shaft 33a formed on the other end of the pivotal shaft 33 is fitted in the square hole 30a of the pintle 30. A lever 33b is formed integrally with the pivotal shaft 33 to extend radially from the front end portion thereof, and a protrusion 33c is formed on the front surface of the lever 33b at the free end portion thereof. As shown in Figs. 1 and 4, a cam plate 36, which is a disc having a predetermined diameter and a notch on the circumference thereof, is disposed to the rotary shaft of the actuator motor AM, mounted to the inner cover 27 through a bracket 35, protruding forward through the bracket 35. A connection rod 37 is pivotally supported eccentrically at one end portion thereof onto the front surface of the cam plate 36, and the other end portion of the connection rod 37 has a slot 37a in which the protrusion 33c of the lever 33b formed integrally with the pivotal shaft 33 is slidably engaged. Accordingly, the pivotal shaft 33 can be pivoted reciprocatingly within a predetermined range of angle through the cam plate 36 and the connection rod 37 by rotating the actuator motor AM, whereby to tilt the water tray 16. Incidentally, an elliptic regulating piece 33d which can be inserted through the slot 37a of the connection rod 37 is disposed to the front end of the protrusion 33c, and this regulating piece 33d is elongated in the radial direction of the protrusion 33c, so that the connection rod 37 may not easily be disengaged from the protrusion 33c under engagement of the protrusion 33c with the slot 37a. Meanwhile, the lever 33b is designed to be shiftable within the allowance of the slot 37a relative to the connection rod 37 so as to tolerate any errors in the positions of the lever 33b and the connection rod 37 when the water tray 16 is stopped at the tilted posture. Further, an engagement piece 33e is formed on the rear side of the lever 33b, with which one end of a torsion spring 39 (to be described later) is designed to urge a fixture 38 (to be described later), on which the rocking motor (RM) is mounted, in a predetermined direction. (Water discharging mechanism of water tray) As shown in Figs. 5 and 16, the water tray 16 has a drainage for discharging the water remaining in the freezing chamber 29 whenever the water tray 16 is tilted. More specifically, an auxiliary chamber 46 is defined backward on the rear wall 16c of the water tray 16 at that end portion which can assume the lowest position when the water tray 16 is tilted, and a duct 47 having a predetermined length is connected to the outer (rear) wall surface of the auxiliary chamber 46. The water collecting section 19 for discharging the thus collected water to the outside of the machine defined at the rear side of the ice bin 14 locates below the duct 47. The auxiliary chamber 46 and the freezing chamber 29 are demarcated with a dam plate 48 which is lower than the wall 16c. Accordingly, the water to be frozen supplied to the water tray 16 is adapted to flow over the upper end of the dam plate 48 and to be discharged to the water collecting section 19 through the duct 47. In other words, the water to be frozen to be carried in the freezing chamber 29 can be maintained to a predetermined level by this dam plate 48. Upon switching to an ice releasing operation, the water tray 16 is tilted downward to discharge the water remaining therein through the duct 47, as shown in Fig. 16. With the water tray 16 stopping in this tilted posture, a part of the water to be frozen still remains therein due to the presence of the dam plate 48 (see Fig. 22) and combined with the water supplied afresh from the water supply pipe 49 for the next cycle of freezing operation to accelerate cooling of the water to be frozen. Incidentally, the duct 47 also serves as a stopper for the water tray 16, which is abutted against the upper edge defining the water collecting section 19 and the ice bin, when the water tray 16 is tilted downward. Since the protrusion 33c of the pivotal shaft 33 is designed to be shiftable in the slot 37a of the connection rod 37 in the tilting mechanism, any possible load to be applied to the tilting mechanism to be caused by the displacement between the stopping position of the tilted water tray 16 and the stopping position of the actuator motor AM can be obviated. As described above, the freezing base plate 18 is maintained horizontally at an upper position of the ice bin through a plurality of brackets 32, and an evaporator 31 led out of the freezing system housed in the machine chamber 12 is disposed zigzag on the upper surface of the freezing base plate 18. Meanwhile, a plurality of freezing fingers 17 protrude downward from the lower surface of the freezing base plate 18, and these freezing fingers 17 are adapted to be dipped in the water to be frozen carried in the water tray 16 during the freezing operation. As heat exchange with the cooling medium in the evaporator 31 is proceeded by operating the freezing system, the freezing fingers 17 are cooled and maintained at a temperature of 0°C or lower to allow ice pieces 21 to grow gradually around the freezing fingers 17, as shown in Fig. 20. Incidentally, the freezing base plate 18 has a plurality of through holes 18a which are formed for improving heat exchange efficiency as well as for reducing weight of the ice making machine (see Fig. 1). (Cam control mechanism) As shown in Fig. 3, a first cam 50 and a second cam 51 are formed on the rear surface of the cam plate 36 disposed to the actuator motor AM at radially staggered positions. Meanwhile, a second switch SW 2 and a fourth switch SW 4 are disposed to the bracket 35 at the positions corresponding to the locations of the first cam 50 and the second cam 51. By the cam actions to be added in accordance with predetermined timing to the rotation of the actuator motor AM, the following motions to be caused by the operation of the actuator motor AM are designed to be controlled: (1) tilting or resetting of the water try 16 and stopping it at such postures, as well as, opening of the hot gas valve HV; and (2) opening and closing of the water valve WV for supplying water to be frozen. More specifically, the first cam 50 and the second cam 51 each assume a form of arcuate ridge having a predetermined radius and protruding in the axial direction, and a lever 52 extending from the second switch SW 2 is designed to be abutted against the first cam 50 or spaced therefrom with a predetermined timing. The second switch SW 2 is turned on, upon contact of the lever 52 of the second switch SW 2 with the first cam 50. The second switch SW 2 is connected to a relay X 2 and the actuator motor AM, as shown in the control circuit diagram of Fig. 17, and controls tilting and resetting of the water tray 16 as well as stopping thereof at such postures by the actuator motor AM and also opening of the hot gas valve HV, as will be described later. Incidentally, the timing of actuating the second switch SW 2 by the first cam 50 is shown in the timing chart of Fig. 26. Meanwhile, the lever 53 extending from the fourth switch SW 4 is designed to be brought into contact with the second cam 51 and to be spaced therefrom in accordance with a predetermined timing. The fourth switch SW 4 is designed to be turned on upon contact of the lever 53 thereof with the second cam 51. As shown in Fig. 17, the fourth switch SW 4 is connected to the water valve WV to control opening thereof (as will be described later). The timing of the cam actions to be effected by the second cam 51 and the fourth switch SW 4 is as shown in the timing chart of Fig. 26. (Rocking plate and rocking mechanism) A rocking plate 54 is disposed in the freezing chamber 29 defined in the water tray 16 in such a way that it can be rocked freely therein. The rocking plate 54 has a rectangular bottom plate 54a and side walls 54b,54c,54d standing upright from the three side edges of the bottom plate 54a, except for the side edge opposing to the left wall 16d, which is to assume the lowest position when the water tray 16 is tilted and is designed to be rocked by the rotation of the rocking motor RM. A multiplicity of circular and/or square through holes 55 are defined at predetermined intervals on the bottom plate 54a and the right side wall 54b of the rocking plate 54. The circumferential size of the rocking plate 54 is designed to be slightly smaller than the inner circumferential size of the bottom 16a of the freezing chamber 29, and a pair of outward protrusions 56 formed on each longitudinal side of the side wall 54b are pivotally supported on the water tray 16 by a pair of pins 57. With the rocking plate 54 pivotally supported in the water tray 16, the rocking plate 54 is brought into intimate contact with the bottom of the freezing chamber 29, as shown in Fig. 5. Incidentally, the positions of the through holes 55 are designed to locate between every two adjacent freezing fingers 17. As shown in Fig. 4, an inverted L-shaped engagement piece 58 is integrally formed with the front side wall 54c of the rocking plate 54, and the upper horizontal portion 58a thereof extends outward beyond the wall 16b of the freezing chamber 29. Meanwhile, a vertically elongated opening 27a is defined in the inner cover 27 at the position corresponding to the location of the upper horizontal portion 58a, in which a rocking member 59 rotated by the rocking motor RM is slidably fitted. A rocking protrusion 59a is eccentrically formed on the rear side of the rocking member 59, which is designed to be engageable, on the rear side of the inner cover 27, with the lower surface of the upper horizontal portion 58a of the rocking plate 54. Accordingly, the rocking protrusion 59a is rotated under engagement with the upper horizontal portion 58a, as shown in Fig. 18, by rotating the rocking member 59 counterclockwise, to lift the rocking plate 54 to a predetermined height from the bottom of the freezing chamber 29, whereas upon disengagement of the rocking protrusion 59a from the upper horizontal surface 58a, to allow the rocking plate 54 to drop by its own weight onto the bottom of the freezing chamber 29. Namely, by rotating the rocking motor RM during the freezing operation, the rocking plate 54 repeats such rocking motion in the freezing chamber 29 on the pins 57, whereby the water to be frozen can constantly be agitated. Incidentally, since the rocking plate 54 has through holes 55, the water to be frozen flows through these through holes 55 upward and downward, whereby agitation of the water to be frozen can further be accelerated. While the rocking plate 54 is tilted as the water tray 16 is tilted upon switching to the ice releasing operation to be described later, a vertical member 60 extending upward over the height of the freezing base plate 18 is formed on the upper edge of the right side wall 54b of the rocking plate 54. By allowing the vertical member 60 to engage with the freezing base plate 18 on the way that the rocking plate 54 is tilted together with the water tray 16, the rocking plate 54 can be separated from the water tray 16 and can assume a fixed tilted posture as such (see Fig. 22). (Fitting structure of rocking motor RM) As shown in Figs. 3 and 4, one end portion of the planar fixture 38 is pivotally fitted on the bearing 34 protruding from the inner cover 27, and the rocking motor RM is disposed onto the front surface of the fixture 38 at a position spaced from the pivotally fitted portion thereof. The rocking motor RM is connected to the cam 59b protruding forward from the rocking member 59 through the through hole 27a. Meanwhile, a vertical member 38a is formed on the front side of the fixture 38 at a position between the pivotally fitted portion thereof and the rocking motor RM, and one end portion 39a of the torsion spring 39 is engaged with the lower end of the vertical member 38a. The engagement piece 33e formed on the lever 33b locates adjacent to the vertical member 38a, and the other end portion 39b of the torsion spring 39 is engaged with the upper end of the engagement piece 33e. In the state where the water tray 16 is maintaining the horizontal posture, the upper end of the engagement piece 33e extends upward over the upper end of the vertical member 38a of the fixture 38, as shown in Fig. 18. Accordingly, in this state, the fixture 38 is constantly urged to turn clockwise on the bearing 34 under the resilient action of the torsion spring 39. Upon application of a predetermined external force to the rocking motor RM, the fixture 38 is designed to be pivoted by a predetermined angle on the bearing 34. Namely, the torsion spring 39 functions to maintain the rocking protrusion 59a of the rocking member 59 at the operational position where it can be engaged with the engagement piece 58 of the rocking plate 54 while the water tray 16 is assuming a horizontal posture during the freezing operation. Meanwhile, when the water tray 16 is tilted upon switching from the freezing operation to the ice releasing operation, the upper end of the engagement piece 33e of the lever 33b is shifted to a position lower than the upper end of the vertical member 38a of the fixture 38, and the end portion 39b of the torsion spring 39 is engaged with the upper end of the vertical member 38a (see Fig. 25). Accordingly, the torsion spring 39 is adapted not to urge the fixture 38 while the water tray 16 is tilted. Incidentally, a vertical slot 38b is defined in the fixture 38 at the distal end portion spaced from the pivotally supported portion thereof, and a regulating pin 61 provided on the inner cover 27 at the corresponding position is slidably fitted therein. The regulating pin 61 functions to regulate the pivoting range of the fixture 38 so that the lower extremity of the slot 38b may be normally abutted against the regulating pin 61 under the resilient action of the torsion spring 39 to allow the rocking member 59 to be in the operational position (see Fig. 18). (Fifth switch SW 5 for detecting completion of ice formation and switch Th 1 for detecting completion of ice releasing operation) A fifth switch SW 5 such as a microswitch for detecting completion of ice formation is disposed on the front surface of the inner cover 27 through a bracket 70 with the lever 62 of the switch SW 5 being on the descending orbit of the cam 59b of the rocking member 59 so as to be able to be abutted against the cam 59b as the fixture 38 (rocking motor RM) is pivoted and operate the switch SW 5 . Namely, as will be described later referring to Fig. 19, when ice pieces 21 are formed around the freezing fingers 17 as the freezing operation proceeds, the rocking plate 54 is brought into contact with these ice pieces 21 in its upward stroke to exert a downward counterforce to the rocking motor RM through the engagement piece 58 and the rocking protrusion 59a. Accordingly, the fixture 38 having mounted thereon the rocking motor RM is pivoted counterclockwise on the bearing 34 and allows the cam 59b to depress the lever 62 of the fifth switch SW 5 in its pivoting process to change over the fifth switch SW 5 from the contact "a" to the contact "b", and thus completion of ice formation is detected. Incidentally, since the bracket 70 is disposed to the inner cover 27 to be adjustable in the vertical direction, the position of the lever 62 of the fifth switch SW 5 can be adjusted by adjusting vertically the position of the bracket 70. Thus, the size of the ice pieces 21 to be formed around the freezing fingers 17 can be changed. It should be noted here that, if the rocking motor RM is stopped upon changing over of the fifth switch SW 5 to the contact "b", the rocking protrusion 59a abutted against the engagement piece 58 of the rocking plate 54 interferes with the tilting motion of the rocking plate 54. Therefore, in this embodiment, a notch 59c is formed on the cam 59b of the rocking member 59, which can change over the fifth switch SW 5 to the contact "a" with the rocking motor RM being pivoted downward whereby to control the rocking protrusion 59a to deviate from the tilting orbit of the engagement piece 58. Meanwhile, this notch 59c is defined on the cam 59b in a positional relationship such that it may locate at a position corresponding to that of the lever 62 of the fifth switch SW 5 when the rocking protrusion 59a is spaced from the upper horizontal portion 58a of the engagement piece 58. In other words, the motor RM is designed: (1) to be rotated still after changing over of the fifth switch SW 5 for detecting completion of ice formation to the contact "b" by the pivoting of the rocking motor RM; and (2) to be stopped when the notch 59c is brought to the position corresponding to the location of the lever 62 of the switch SW 5 to change over the switch SW 5 to the contact "a". Thus, the rocking protrusion 59a is deviated from the tilting orbit of the engagement piece 58 of the rocking plate 54 and thus does not interfere with the tilting motion of the rocking plate 54. As shown in Fig. 5, a thermometal switch Th 1 for detecting completion of the ice releasing operation is disposed on the upper surface of the freezing base plate 18 in the freezing unit 15. This thermometal switch Th 1 is designed to be changed over to the contact "b" upon dropping of the temperature of the freezing base plate 18 to a predetermined level by the freezing operation, or changed back from the contact "b" to the contact "a" upon detection of the sudden temperature rise caused by dropping of the ice pieces 21 from the freezing fingers 17 by the ice releasing operation. Simultaneously, the hot gas valve HV is designed to be closed, as will be described later, and the actuator motor AM is also designed to be rotated. (Ice discharging unit and ice fullness detection switch) An ice discharging motor GM is disposed at the front lower position of the inner cover 27, and an screw 63 for carrying the ice pieces to be driven by the motor GM is disposed in the ice chamber 83. The screw 63 and the motor GM are connected to each other by engaging the pin (not shown) provided on the shaft of the motor GM with a groove (not shown) formed on the outer end portion of the shaft of the screw 63. Meanwhile, the inner end portion of the screw 63 is rotatably fitted in a recess 64 defined at the corresponding position of the ice bin 14, as shown in Fig. 2, so that the screw 63 can be rotated at a fixed position. The ice discharging motor GM is designed to be rotated only while the first switch SW 1 is turned on by depressing the push button 25 provided on the front panel 23 to carry the ice pieces 21 stored in the ice chamber 83 with the aid of the screw 63 to the outlet 14a. Incidentally, the screw 63 is positioned when the outer end thereof is connected to the motor GM after the inner cover 27 is fitted on the front surface of the ice bin 14 with the inner end portion thereof being fitted in the recess 64. As shown in Fig. 2, a regulating plate 65 is pivotally hanging from the rear side of the inner cover 27 at the position corresponding to the location of the screw 63 and inner than the position of the outlet 14a. This regulating plate 65 is designed to be pushed forward by the ice pieces 21 carried by the screw 63 to open the outlet 14a and allow delivery of the ice pieces 21 to the outside of the machine, as well as, to return to the initial position when the ice discharging unit 13 is stopped to close the outlet 14a and prevent the outer air from flowing into the ice chamber 83. Meanwhile, a separator 68 is disposed to the inner cover 27 at a position adjacent to the regulating plate 65, which functions to prevent the ice pieces 21 stored in the ice bin 14 from slipping out of the outlet 14a, as well as, to return some of the ice pieces carried by the screw 63 into the ice bin 14 and prevent clogging of the outlet 14a thereby. Incidentally, a drain pipe 69 is provided at the bottom of the ice bin 14 adjacent to the recess 64, so that the water melting from the ice pieces 21 can be discharged to the outside of the ice bin 14. A detection plate 66 is pivotally supported on the lower surface of the water tray 16, which is normally maintained in such a state that the open end side thereof may be spaced apart downward from the bottom of the water tray 16, as shown in Fig. 7. A third switch SW 3 for detecting ice fullness is disposed to the front surface of the water tray 16 with its lever 67 being normally urged by the protrusion 66a formed on the front side of the proximal end portion of the detection plate 66. When the detection plate 66 is abutted against the ice pieces 21 in the process of tilting of the water tray 16 to turn clockwise relative to the water tray 16, the protrusion 66a is designed to be spaced from the lever 67 to turn on the switch SW 3 , and thus ice fullness is detected. Incidentally, the protrusion 66a of the detection plate 66 is adapted to be abutted against the lever 67 of the third switch SW 3 under detection of no ice piece 21, so that the ice making machine can be stopped whenever the detection plate 66 happens to drop from the water tray 16 for some reason. Accordingly, no ice piece 21 is adapted to be formed under the condition where ice fullness is not detectable. Meanwhile, the free end portion of the detection plate 66 has a comb-like form, whereby the load to be applied to the detection plate 66 when it is abutted against the ice pieces 21 can be reduced. (Example of electric control circuit) Fig. 17 shows an electric control circuit in the ice making machine according to this embodiment, in which a fuse F is interposed between a power supply line R and a joint D, and a power supply indication lamp L is interposed between the joint D and a line T. Likewise, (1) the first switch SW 1 for ice discharging and the ice discharging motor GM; (2) the second switch SW 2 for the actuator motor AM, the third switch SW 3 for detecting ice fullness and a relay X 1 are interposed in series respectively between the joint D and the line T. Meanwhile, a normally closed contact X 1 -b 1 for the relay X 1 is interposed between a joint E and a joint K locating between the second switch SW 2 and the third switch SW 3 . Between the joint K and the line T are interposed in series respectively (1) a relay X 2 ; (2) the fourth switch SW 4 for supplying water to be frozen and the water valve WV; and (3) a normally open contact X 3 -a 1 for a relay X 3 and the actuator motor AM. Meanwhile, a normally closed contact X 2 -b 1 for the relay X 2 and a normally closed contact X 3 -b for the relay X 3 are interposed in series between the normally closed contact X 1 -b 2 of the relay X 1 connected in series to the fuse F and a joint N locating between the normally open contact X 3 -a 1 of the relay X 3 and the actuator motor AM. A fan motor FM for the condenser 11 is connected to the contact "a" of the thermometal switch Th 1 for detecting completion of the ice releasing operation connected in series to the normally open contact X 2 -a of the relay X 2 , while the hot gas valve HV for supplying a hot gas is connected to the contact "b" thereof. Further, between the normally closed contact X 1 -b 2 of the relay X 1 and the line T, are interposed in series respectively (1) a normally open contact X 3 -a 2 for the relay X 3 , the rocking motor RM and a normally closed contact X 2 -b 2 for the relay X 2 ; and (2) a relay SR and the compressor CM. The fifth switch SW 5 for detecting completion of ice formation is connected to a joint P locating between the normally open contact X 3 -a 2 of the relay X 3 and the rocking motor RM, and a protective thermometal cut-off Th 2 is connected to the contact "a" of the switch SW 5 , while the contact "b" thereof is connected to the joint D. Incidentally, the fan motor FM and the relay X 3 are connected in parallel. Next, the actions of the ice making machine according to this embodiment will be described. (Assembly of the ice making machine) First, the freezing system including the compressor CM and the condenser 11 is securely mounted on the supporting frame 101, while the freezing base plate 18 and the water tray 16 are disposed in the ice bin 14 through the brackets 32. The freezing base plate 18 and the water tray 16 can be maintained parallel to the upper opening face of the ice bin 14, if the brackets 32 are accurately fitted to the fitting portions 14b integrally formed on the ice bin 14. Next, after the ice bin 14 is temporarily set above the freezing system and the vertical portions 101b,101c, the main frame 22 is positioned to surround the freezing system and the ice bin 14. The tapped holes 108 formed on the flanges 22c of the main frame 22 are aligned with the corresponding tapped holes 103 formed on the front vertical portion 101b of the supporting frame 101, and a screw 112 is screwed into each pair of tapped holes 108 and 103 (see Fig. 11). Meanwhile, the tapped holes 110 formed on the flanges 22e of the main frame 22 are aligned with the corresponding tapped holes 104 formed on the rear vertical portion 101c of the supporting frame 101, and a screw 113 is screwed into each pair of tapped holes 110 and 104, whereby the main frame 22 and the supporting frame 101 are secured to each other in position (see Fig. 12). The main frame 22 and the supporting frame 101 can accurately be secured to each other in position such that the top plate 22a and the bottom 101a may be parallel to each other by forming the tapped holes 108,103,110,104 at accurate positions, respectively. Meanwhile, the tapped holes 109 formed on the tongues 22d of the main frame 22 are aligned with the corresponding tapped holes 105 formed on the flanges 14c of the ice bin 14, and a screw 114 is screwed into each pair of tapped holes 109 and 105 (see Fig. 11). Further, the tapped holes 111 formed on the flanges 22e of the main frame 22 are aligned with the corresponding tapped holes 107 of the fitting panel 106, and a screw 115 is screwed into each pair of tapped holes 111 and 107, whereby the main frame 22 and the ice bin 14 can be secured to each other in position (see Fig. 12). The main frame 22 and the ice bin 14 can accurately be secured to each other in position such that the top plate 22a and the upper opening face of the ice bin 14 may be parallel to each other by forming the tapped holes 109,105,111,107 at accurate positions, respectively. The ice bin 14 incorporated into the main frame 22, as described above, is positioned to be in contact with the vertical portions 101b,101c of the supporting frame 101 and the freezing system or to be spaced slightly therefrom (see Fig. 2). Namely, since the supporting frame 101 and the ice bin 14 are independently secured to the main frame 22 respectively in position, the horizontalness of the freezing unit 15 to be disposed in the ice bin 14 can be secured by accurately positioning each of these members. Accordingly, if the supporting frame 101 is set on a horizontal installation surface, the freezing unit 15 in the ice bin 14 can be positioned horizontally, and thus the freezing fingers 17 can be dipped in the water to be frozen carried in the water tray 16 at a fixed depth to allow formation of a uniform size of ice pieces around the freezing fingers 17. Meanwhile, when the water tray 16 is tilted after completion of ice formation, the water remaining therein can securely be discharged to the water collecting section 19. (Operation of ice making machine) Actions of the thus assembled ice making machine under operation will be described below referring to the timing chart shown in Fig. 26. Incidentally, by performing an initial running of the ice making machine prior to proceeding with the freezing operation, the water tray 16 is set in a horizontal posture, and a predetermined level of water is supplied to the freezing chamber 29 of the water tray 16. Meanwhile, the relay X 3 shown in Fig. 17 is self-held by the normally open contact X 3 -a 2 which interlocks therewith and the rocking motor RM is rotating being energized through this normally open contact X 3 -a 2 . (Freezing operation) A cooling medium is supplied to the evaporator 31 through a circulation pipe of the freezing system by a compressor CM powered by electricity, and cooling of the freezing fingers 17 provided on the freezing base plate 18 is started by the heat exchange action of the cooling medium. Since the freezing fingers 17 are dipped in the water to be frozen, the water starts to freeze around the freezing fingers 17 and grows gradually into inverted dome-shaped ice pieces 21. During such freezing operation, the rocking motor RM is continuously rotated. Accordingly, the rocking protrusion 59a of the rocking member 59 rotated by the motor RM is engaged with the engagement piece 58 provided on the side wall 54c to lift the rocking plate 54, as shown in Fig. 18. Upon disengagement of the rocking protrusion 59a from the engagement piece 58, the rocking plate 54 drops by its own weight and is abutted against the bottom 16a of the freezing chamber 29. Thus, the rocking plate 54 repeats such rocking motion in the water to be frozen in the freezing chamber 29 during the freezing operation to constantly agitate the water. Moreover, since through holes 55 are formed on the rocking plate 54, the water to be frozen flows through these through holes 55 as the rocking plate 54 is rocked to cause jet streams which accelerate the agitation of the water to be frozen. Since the water to be frozen is constantly maintained in a dynamic state, as described above, opacification to white of the ice pieces 21 to be formed around the freezing fingers 17 can be prevented, and transparent and clear ice pieces 21 can be obtained. (Ice releasing operation) As shown in Fig. 19, upon formation of inverted dome-like ice pieces 21 fully around the freezing fingers 17, the rocking plate 54 is brought into contact with the ice pieces 21 in its upward stroke and finally exerts a downward counterforce to the rocking motor RM through the engagement piece 58 and the rocking protrusion 59a. Accordingly, the fixture 38 having mounted thereon the rocking motor RM starts to make a counterclockwise turn on the bearing 34 to allow the cam 59b of the rocking member 59 to depress the lever 62 of the fifth switch SW 5 for detecting completion of ice formation to be changed over from the contact "a" to the contact "b", and thus completion of ice formation in the freezing unit 15 is detected. Whereupon the self-hold of the relay X 3 shown in Fig. 17 is released to close the normally closed contact X 3 -b which interlocks therewith and start rotation of the actuator motor AM. Thus, the cam plate 36 is turned counterclockwise to tilt counterclockwise the lever 33b of the pivotal shaft 33 engaged with the connection rod 37 connected eccentrically thereto, and thus the water tray 16 starts to be tilted downward. By this tilting motion of the water tray 16, the water remaining in the freezing chamber 29 flows over the dam plate 48 into the auxiliary chamber 46 and then discharged to the water collecting section 19. Incidentally, during the process that the water tray 16 is tilted, actuation of the fourth switch SW 4 by the second cam 51 of the cam late 36 rotated by the actuator motor AM is released (see Fig. 26). The rocking motor RM continues to rotate even after the fifth switch SW 5 for detecting completion of ice formation is changed over to the contact "b" when the lever 62 thereof is depressed by the cam 59b of the rocking member 59. Thus, the rocking protrusion 59a is spaced from the upper horizontal portion 58a to allow the fixture 38 to turn clockwise under the resilient action of the torsion spring 39, in turn, to change over the fifth switch SW 5 from the contact "b" to the contact "a" and stop temporarily the rocking motor RM. Accordingly, the upper end of the engagement piece 33e of the lever 33b is shifted to a position lower than the upper end of the vertical member 38a formed on the fixture 38 to allow the end 39b of the torsion spring 39 to be engaged with the upper end of the vertical member 38a, where the torsion spring 39 exerts no resilient action to the fixture 38 (see Fig. 25(b)). Whereupon, the fixture 38 starts to turn counterclockwise on the bearing 34 by its own weight to allow the cam 59b to change over the fifth switch SW 5 from the contact "a" to the contact "b" and start the rocking motor RM. The depression of the lever 62 is released when the notch 59c formed on the cam 59a comes to the position corresponding to the location of the lever 62 to change over the switch SW 5 from the contact "b" to the contact "a" and stop rotation of the rocking motor RM (see Fig. 25 (c)). Thus, the rocking protrusion 59a provided on the rocking member 59 stops at a position deviated from the tilting orbit of the engagement piece 58 of the rocking plate 54, where it does not interfere with the tilting of the rocking plate 54. Upon arrival of the first cam 50 provided on the cam plate 36 to the lever 52 of the second switch SW 2 , the switch SW 2 is turned on to actuate the relay X 2 and to open the normally closed contact X 2 -b 1 which interlocks therewith, as well as, to close the normally open contact X 2 -a. In this state, the thermometal switch Th 1 for detecting completion of the ice releasing operation is connected to the contact "b", since ice pieces 21 are formed fully around the freezing fingers 27. Accordingly, the relay X 3 is not actuated, and the rotation of the actuator motor AM is stopped to allow the water tray 16 to stop in a tilted posture at a predetermined angle, as shown in Fig. 22. In this state, while a portion of the water to be frozen remains in the freezing chamber 29 due to the presence of the dam plate 48, such residual water, fully cooled during the previous freezing operation, is mixed with another portion of water to be supplied afresh to cool effectively the thus combined water to be frozen. Meanwhile, the ice pieces 21 formed around the freezing fingers 17 are exposed as such by tilting the water tray 16. Further, in the process that the water tray 16 is tilted and stopped in the tilted posture, the vertical member 60 of the rocking plate 54 is abutted against the freezing base plate 18, so that the rocking plate 54 is allowed to locate diagonally above the bottom 16a of the freezing chamber 29 in the water tray 16 which stops later in the tilted posture. The rocking plate 54 also functions as a chute for guiding the ice pieces 21 dropping from the freezing fingers 17 into the ice bin 14. Simultaneously with the stopping of the actuator motor AM, the hot gas valve HV is opened to supply a hot gas, instead of the cooling medium, to the evaporator 31, as shown in the timing chart of Fig. 26, so that the freezing fingers 17 are rapidly heated through the freezing base plate 18. Accordingly, the bondage between the freezing fingers 17 and the ice pieces 21 is released, and the ice pieces 21 drop by their own weights, slide on the upper surface of the rocking plate 54 maintained in a predetermined tilted posture by the vertical member 60 and are guided into the ice chamber 83. The negative temperature load applied to the freezing base plate 18 is released by the dropping of the ice pieces 21, and the temperature of the freezing base plate 18 is suddenly elevated by the passage the hot gas through the evaporator 31. This temperature rise is detected by the thermometal switch Th 1 , which is immediately changed over to the contact "a" to actuate the relay X 3 , in turn, to close the normally open contact X 3 -a 1 which interlocks therewith and allows the actuator motor AM to resume rotation. Meanwhile, the hot gas valve HV is also closed to resume supplying of the cooling medium to the evaporator 31. The pivotal shaft 33 is turned clockwise under the actions of the cam plate 36, connection rod 37 and lever 33b by this rotation of the motor AM, and the water tray 16 is likewise turned clockwise to start resetting to the horizontal posture. Meanwhile, the second cam 51 of the cam plate 36 comes to the lever 53 of the fourth switch SW 4 as the motor AM resumes rotation to turn on the switch SW 4 , as shown in Fig. 23, whereby the water valve WV is opened to supply water to be frozen to the freezing chamber 29. Upon disengagement of the first cam 50 of the cam plate 36 from the lever 52 of the second switch SW 2 , actuation of the switch SW 2 is released to close the water valve WV and stop supplying of water to be frozen as well as to stop the actuator motor AM. This is because the relay X 3 is self-held to open the normally closed contact X 3 -b thereof. Thus, the water tray 16 is stopped in the horizontal posture. Incidentally, in the above embodiment, resetting of the water tray 16 is designed to be carried out by turning once the water tray 16 clockwise over the horizontal posture such that the free end portion thereof (the wall 16d) may be higher than the fixed end portion thereof and then turning counterclockwise to stop in the horizontal posture. Namely, if water to be frozen is supplied in a sufficient amount to the freezing chamber 29 with the dam plate 48 provided in the water tray 16 locating at a high level to let the water to flow over the dam plate 48, a necessary amount of water to be frozen is adapted to be securely supplied to the freezing chamber 29 when the water tray 16 is reset to the horizontal posture. Thus, possible troubles to be caused by the lack of water to be frozen can be prevented. Meanwhile, as the pivotal shaft 33 is turned clockwise, the upper end of the engagement piece 33e of the lever 33b shifts upward to a position higher than the upper end of the vertical member 38a of the fixture 38, so that the end portion 39b of the torsion spring 39 is engaged with the upper end of the engagement piece 33e (see Fig. 25(a)). Thus, the fixture 38 is turned clockwise on the pivotal shaft 33 by the resilience of the torsion spring 39, to allow the rocking protrusion 59a of the rocking member 59 to be in the operational position where it can be engaged with the engagement piece 58 of the rocking plate 54. Accordingly, upon releasing actuation of the relay X 2 by turning off the second switch SW 2 , the normally closed contact X 2 -b 2 is closed to rotate the rocking motor RM and allow the rocking plate 54 to resume and continue the rocking motion during the freezing operation. In the ice making machine, the cooling fan (fan motor FM) disposed in the lower machine chamber 12 is designed to be rotated during running thereof to suck the outer air and cool the condenser 11. In such constitution, if the opening 23a of the front panel 23 communicates to the machine chamber 12, the outer air is sucked into the machine chamber 12, and the dusts sucked through the opening 23a together with the air accumulate with time around the opening 23a to provide an insanitary condition. Therefore, in the ice making machine of the above embodiment, the rear end of the barrier 23d formed on the rear side of the front panel 23 is abutted against the front surface or the upper horizontal member 101e of the supporting frame 101 over the full width thereof so as to prevent the outer air from flowing through the opening 23a into the machine chamber 12. Namely, the outer air is sucked into the machine chamber 12 only through the inlet defined on the bottom 101a of the supporting frame 101 by rotating the cooling fan. The air sucked through the inlet is filtered through a filter 26 to remove completely the dusts therefrom, so that reduction in the heat exchange efficiency or troubles to be caused by overheat attributable to the dusts deposited on the condenser 11 can be prevented. In such constitution, the opening 23a of the front panel 23 and the outlet 14a of the ice bin 14 are isolated from the lower machine chamber 12 by the barrier 23d. Accordingly, no outer air is adapted to be sucked through the opening 23a into the machine chamber 12 to prevent deposition of dusts around the opening 23a. As a result, the ice pieces 21 to be discharged through the outlet 14a and the opening 13a from the ice bin 14 can be kept in a hygienic state. Moreover, since the cool air in the ice bin 14 is not sucked out by the rotation of the cooling fan, such temperature rise in the ice bin 14 as to be caused by the escape of the cool air therefrom can be prevented to inhibit melting of the ice pieces 21 stored in the ice chamber 83. Further, since the outer air is adapted to be sucked into the machine chamber 12 only through the filter 26, the dusts contained in the air is prevented from intruding into the machine chamber 12 and depositing on the condenser 11. If any maintenance service becomes necessary for the tilting mechanism for the water tray 16 or the rocking mechanism for the rocking plate 54 during running of the ice making machine, these mechanisms can be exposed to the front side by removing the front panel 23 shown in Fig. 2, so that such maintenance and repair for the respective mechanisms can very easily be carried out from the front side. On the other hand, if the inner cover 27 is removed from the ice bin 14, the tilting mechanism, the rocking mechanism and the ice releasing unit 13 can all be removed integrally therewith to enable such maintenance and repair or replacements of parts outside of the machine. Further, since the tilting mechanism, rocking mechanism and the ice releasing units 13 are all disposed on the inner cover 27, the working efficiency in assembling the ice making machine can also be improved.

Claims: An ice-making machine having a freezing unit (15) disposed in a box (14), said freezing unit consisting of an evaporator (31) connected to a freezing system including a compressor (CM) and condenser (11); a freezing base plate (18) having a multiplicity of freezing fingers (17) formed on the lower surface thereof, with said evaporator (31) being disposed on the upper surface thereof; a water tray (16) normally maintaining a horizontal posture and having defined therein a freezing chamber (29) for carrying water to be frozen in which said freezing fingers (17) are designed to be dipped; a tilting mechanism (33, 37, 36, AM) for tilting said water tray (16) downward upon formation of ice pieces (21) around said freezing fingers (17) to release the ice pieces (21) and then upward so that the water tray (16) resumes its horizontal posture; characterized in that said ice-making machine further has a rocking plate (54) disposed in said water tray (16); a rocking mechanism (38, 59, RM) for freely rocking said rocking plate (54); a removable inner cover (27) for closing an opening (79) of said box (14), said tilting mechanism (33, 37, 36, AM) and said rocking mechanism (38, 59, RM) being mounted on said inner cover (27); and a front panel (23) mounted on the front surface of the inner cover (27) and enclosing said tilting mechanism (33, 37, 36, AM) and said rocking mechanism (38, 59, RM). The ice making machine according to Claim 1, wherein said inner cover (27) has mounted thereon an ice discharging unit (13) for delivering the ice pieces (21) stored in said box (14). The ice making machine according to Claim 1 or 2, wherein said inner cover (27) and said box (14) are positioned to each other by the engagement between protrusions (84) and through holes (85a) formed, respectively, on the fitting portions of these members.

Inventors: SAKAI TADASHI, SANUKI MASAO, SAKAI, TADASHI, SANUKI, MASAO, Sakai, Tadashi, c/o Hoshizaki Denki Kabushiki K., Sanuki, Masao, c/o Hoshizaki Denki Kabushiki K.
Applicants: HOSHIZAKI ELECTRIC CO LTD, HOSHIZAKI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: F25C1
IPC codes: F25C1