Abstract
An electrical cartridge type heater (100) includes an outer metallic jacket (110) an electrical heating element (120, 121) arranged in an interior space (140) of the outer metallic jacket (110) and a device for monitoring the temperature (130), which is galvanically separated from the electrical heating element (120, 121) and is arranged in the interior space (140) of the outer metallic jacket (110). The device for monitoring the temperature (130) includes a wire or a tube, in addition to the electrical heating element (120, 121), made of a material that changes resistance with temperature change with a value of the temperature coefficient of the electrical resistance greater than 800 ppm/K, and especially preferably greater than 4,000 ppm/K between 20 C. and 105 C. The wire or the tube is directly embedded into an electrically non-conducting filler filling a remaining interior space (140) of the outer metallic jacket (110).
Claims
1. An electrical cartridge heater comprising: an outer jacket with an interior space; an electrical heating element arranged in said interior space of said outer jacket, said heating element being formed in a cylindrical shape, said electrical heating element being arranged in a meandering pattern with said meandering pattern being arranged on a circumferential surface of said cylindrical shape; a temperature monitoring device arranged in said interior space of said outer jacket, said temperature monitoring device comprising a wire or tube arranged in a meandering pattern, said temperature monitoring device in said meandering pattern being formed in a cylindrical shape with said meandering pattern being arranged on a circumferential surface of said cylindrical shape, said cylindrical shape of said temperature monitoring device being arranged coaxial with said cylindrical shape of said electrical heating element, said cylindrical shape of said temperature monitoring device being arranged radially inside said cylindrical shape of said electrical heating element, said wire or tube being made of a material that has an electrical resistance that increases with increased temperature, with a positive temperature coefficient, or that has an electrical resistance that decreases with increased temperature, with a negative temperature coefficient, an absolute value of the temperature coefficient of the electrical resistance being greater than 800 ppm/K, between 20 C. and 105 C.; an electrically non-conducting filler arranged between each of said outer jacket, said electrical heating element and said temperature monitoring device.
2. An electrical cartridge heater in accordance with claim 1, wherein the wire or the tube is made of a material, the resistance of which has a temperature coefficient, the value of which in the range between 20 C. and 105 C. is at least twice as high as the value of the temperature coefficient of the resistance of the electrical heating elements in the range between 20 C. and 105 C.
3. An electrical cartridge heater in accordance with claim 1, wherein the electrical cartridge type heater is compressed or crimped in at least some sections and the wire or the tube extends in at least one compressed or crimped section.
4. An electrical cartridge heater in accordance with claim 1, wherein the temperature monitoring device is configured as the tube and the tube is made of a material that has an electrical resistance that increases with increased temperature, with a positive temperature coefficient, or that has an electrical resistance that decreases with increased temperature, with a negative temperature coefficient, and that the electrical heating element is arranged in an interior space of the tube such that the tube forming the device for monitoring the temperature and the electrical heating element together form a coiled tube cartridge.
5. An electrical cartridge heater in accordance with claim 1, wherein the at least one electrical heating element comprises an alloy containing chromium and nickel or an alloy containing copper and nickel, and the wire or the tube is a pure metal comprised of nickel, refined nickel or highly refined nickel.
6. An electrical cartridge heater in accordance with claim 1, wherein the electrical resistance is greater than 4,000 ppm/K.
7. An electrical cartridge heater in accordance with claim 1, wherein: said electrical heating element is a wire; said meandering pattern of said electrical heating element, and said meandering pattern of said temperature monitoring device are aligned.
8. An electrical cartridge heater in accordance with claim 7, wherein: said temperature monitoring device is aligned with said electrical heating element for a majority of extent of said electrical heating element.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) In the drawings:
(2) FIG. 1a is a perspective view of a first electrical cartridge type heater;
(3) FIG. 1b is a section through the electrical cartridge type heater from FIG. 1a in a direction parallel to its direction of extension;
(4) FIG. 2a is a perspective view of a second electrical cartridge type heater;
(5) FIG. 2b is a section through the electrical cartridge type heater from FIG. 2a in a direction parallel to its direction of extension;
(6) FIG. 3 is a section through a third electrical cartridge type heater in a direction parallel to its direction of extension;
(7) FIG. 4a is a perspective view of a fourth electrical cartridge type heater;
(8) FIG. 4b is a section through the electrical cartridge type heater from FIG. 4a in a direction parallel to its direction of extension;
(9) FIG. 5a is a perspective view of a fifth electrical cartridge type heater;
(10) FIG. 5b is a section through the electrical cartridge type heater from FIG. 5a in a direction parallel to its direction of extension;
(11) FIG. 6a is a perspective view of a sixth electrical cartridge type heater;
(12) FIG. 6b is an exploded view of the electrical cartridge type heater from FIG. 6a;
(13) FIG. 6c is the electrical heating element from FIG. 6a in the unwound state;
(14) FIG. 6d is a cross section through the electrical cartridge type heater from FIG. 6a in a direction at right angles to its direction of extension;
(15) FIG. 7a is a section through a third electrical cartridge type heater in a direction parallel to its direction of extension;
(16) FIG. 7b is a first enlarged detail view from FIG. 7a;
(17) FIG. 7c is a second enlarged detail view from FIG. 7a; and
(18) FIG. 8 is a schematic perspective view an electrical heater.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(19) Referring to the drawings, FIG. 1a shows a first electrical cartridge type heater 100 with a metallic jacket 110 that is tubular in this example, with an oval cross section, which is closed on each end face by means of end caps 111, 112 that are each traversed by three connecting bolts 114-119. As the sectional view according to FIG. 1b shows, two electrical heating elements 120, 121, which are embodied as coiled hot wires, are arranged in the interior space 140 of the metallic jacket 110, preferably under mechanical tension, between the connecting bolts 114 and 115 or 118 and 119, while a device for monitoring the temperature 130 in the form of a coiled wire made of a cold-conducting material(PTC material)a material that has an electrical resistance that increases with increased temperatureor made of a heat-conducting material(NTC material)a material that has an electrical resistance that decreases with increased temperatureis arranged between the connecting bolts 116 and 117, preferably under mechanical tension, which device, to clarify that it is not a third electrical heating element and a different material forms the wire, is shown to be thinner than the electrical heating elements 120, 121, which, however, shall not be understood here as in all other figures to be an indication of a necessary difference with respect to the necessary dimensioning, especially with respect to the cross section.
(20) The preferably crimped insulating material, which may consist, e.g., of MgO powder or granules, actually filling the interior space 140 of the respective metallic jacket 110 is not shown in this figure as well as in all other figures for the sake of clarity.
(21) FIG. 2a shows a second electrical cartridge type heater 200 with a metallic jacket 210, which is tubular in this example, with an essentially rectangular cross section with rounded corners, which is closed on one side on the end face by a bottom 211. On the other end face, four connecting bolts 214-217 lead into the interior space 240 of the metallic jacket 210. As the sectional view according to FIG. 2b shows, an electrical heating element 220, which is embodied as a coiled hot wire and which runs in an approximately U-shaped manner through the interior space 240 of the metallic jacket 210, is arranged between the connecting bolts 214 and 215, while a device for monitoring the temperature 230 in the form of a coiled wire, which is made of a cold-conducting material or made of a heat-conducting material, is arranged between the connecting bolts 216 and 217, which device, to clarify that it is not a second electrical heating element and a different material forms the wire, is shown to be thinner than the electrical heating element 220 and likewise runs in an approximately U-shaped manner.
(22) In contrast to the electrical cartridge type heater 100 to be connected on both sides shown in FIGS. 1a and 1b, the electrical cartridge type heater 200 according to FIGS. 2a and 2b is thus a cartridge type heater 200 to be connected on one side; further, the electrical cartridge type heaters 100, 200 differ with respect to their cross section.
(23) The electrical cartridge type heater 300 shown in a sectional view in FIG. 3 includes a tubular metallic jacket 310, end caps 311, 312, which is embodied as a coiled, preferably self-supporting hot wire, which is arranged in the interior space 340 of the metallic jacket 310, an electrical heating element 320, which is arranged between the connecting bolts 314 and 315 and a device for monitoring the temperature 330 which is arranged in the interior space 340 of the metallic jacket 310 in the form of a coiled wire made of a cold-conducting material or made of a heat-conducting material, the ends of which lead directly out of the tubular metallic jacket 310 and are thus not provided with connecting bolts. The special feature of the embodiment according to FIG. 3 is that the device for monitoring the temperature 330 is arranged coaxially within the coils of the electrical heating element 320, which makes possible a very high sensitivity and an especially fast response of the device for monitoring the temperature 330 to a local failure of the electrical heating element 320.
(24) In the fourth electrical cartridge type heater 400 shown in FIG. 4a and FIG. 4b, the tubular metallic jacket 410 is cylindrical and closed with a bottom 411 formed in one piece with it as well as with an end cap 412. The electrical heating element 420, which is arranged in the interior space 440 of the tubular metallic jacket 410 and is embodied as a coiled hot wire wound onto a coil body 450, is passed through the end cap 412 with its ends 420a, 420b. The ends 430a, 430b of the device for monitoring the temperature 430, which is embodied here in the form of a U-shaped coiled wire made of a cold-conducting material or made of a heat-conducting material lying in a central plane of the coil body 450, are also passed through the end cap 412.
(25) In the fifth electrical cartridge type heater 500 shown in FIG. 5a and FIG. 5b, the tubular metallic jacket 510 is likewise cylindrical and closed with a bottom 511 as well as an end cap 512, the bottom 511 having a recess 511a as a positioning aid for a coil body 550. As in the electrical cartridge type heater 400 according to FIGS. 4a,b, the electrical heating element 550, which is arranged in the interior space 540 of the tubular metallic jacket 510 and which is embodied as a coiled hot wire wound onto a coil body 550, is passed through the end cap 512 with its ends 520a, 520b. Also passed through the end cap 512 are the ends 530a, 530b of the device for monitoring the temperature 530, which is embodied here in the form of a U-shaped, coiled wire made of a cold-conducting material or made of a heat-conducting material, lying in a central plane of the coil body 550, wherein the sections 530c, 530d of the device for monitoring the temperature 530 forming the two legs of the U are passed through holes in the coil body and thus are arranged radially within the turns or coils of the electrical heating element 520 wound onto the coil body 550.
(26) FIGS. 6a through 6d show a sixth exemplary embodiment of an electrical cartridge type heater 100. As is especially readily seen in the exploded view of FIG. 6b, the electrical cartridge type heater 600 has an electrical heating element 620, which is arranged between an outer metallic jacket 610 and an inner metallic jacket 660, which are connected to one another by means of a bottom surface 661 facing away from the viewer and hence not visible in FIG. 6a. As can be readily seen in FIG. 6a, the electrical heating element 620 is arranged in the interior space 640 of the outer metallic jacket 610 between an outer shaped ceramic part 670, which at the same time guarantees an electrical insulation to the outer metallic jacket 610, and a central shaped ceramic part 671, and is optionally additionally embedded in an electrically insulating material, not shown, e.g., MgO granules, which, however, is not shown in FIGS. 6a through 6c for the sake of clarity.
(27) In addition, a device for monitoring the temperature 630, which is embodied in the form of a wire made of a cold-conducting material or made of a heat-conducting material, is arranged between the central shaped ceramic part 671 and an inner shaped ceramic part 672, the wire likewise depicting a space curve, which can be obtained by winding a basic shape in a meandering pattern. It is preferred in this case when the space curve, which depicts the device for monitoring the temperature 630, can be converted, by scaling in the radial direction, into the space curve, which depicts the electrical heating element 620. Further, it is preferred when an alignment is present, in which points corresponding to one another in the same direction of curved arcs 628, 629 or 638, 639 of the meandering structures of the device for monitoring the temperature 630 or of the electrical heating element 620 lie each on a common radius r, as is shown by example in FIG. 6d. In this way, a section of the device for monitoring the temperature 630 is directly assigned to each section of the electrical heating element 620, which leads to especially reliable detection of temperature deviations.
(28) The end face of the electrical cartridge type heater 600, which can be seen by the viewer in FIG. 6a, is closed with a circular-ring-shaped cap 662 in the assembled state. The outer metallic jacket 610 and the inner metallic jacket 660 are each configured as a cylindrical tube and are arranged concentrically to one another. The direction of extension of the outer metallic jacket 610 and of the inner metallic jacket 660 is thus predefined by the cylinder axis.
(29) As can be especially readily seen in FIG. 6c, which shows the electrical heating element 620 in the wound or unwound state, i.e., not in the state, in which it is installed, the electrical heating element has a meandering shape with meandering loops. A connecting bolt 614, 615 each with a hole, which cannot be seen in FIG. 6c, into which an end section of the electrical heating element 620 is received and electrically contacted, is at both ends of the electrical heating element 620.
(30) In the electrical cartridge type heater 700 shown in FIGS. 7a through 7c, as can be especially readily seen in the detailed view of FIG. 7b, the electrical heating element 720 is arranged in the form of a hot wire centrally in the interior of a device for monitoring the temperature, which device is embodied as a tube made of a cold-conducting material or made of a heat-conducting material and is electrically insulated from same with magnesium oxide powder 735. Thus, the electrical heating element 720 and the device for monitoring the temperature together form a coiled tube cartridge, which is arranged in some sections coiled in the interior space 740 of a cup-shaped outer metallic jacket 710. The filling, consisting of a readily heat-conducting, preferably electrically non-conducting material, especially MgO powder or granulates, filling this interior space and ensuring the heat conduction to the cup-shaped metallic jacket 710, has been omitted for the sake of clarity. Contact plates 713, 714 and connecting bolts 721, 722 are provided for contacting the electrical heating element 720. The contacting of the device for monitoring the temperature 730 is carried out via contact plates 715, 716 and connecting wires 717, 718, as can be especially readily seen in FIG. 7c.
(31) The electrical heater 1000 shown in FIG. 8 has, besides an electrical cartridge type heater 200, as it was already described above on the basis of FIGS. 2a,b and which was hence identified in FIG. 8 with the same reference numbers as in FIGS. 2a,b, a power supply 1010 for energizing the at least one electrical heating element 220 and a device for determining the resistance 1020 of the wire present as a device for monitoring the temperature 230 and for assigning a temperature value to the determined resistance of the device for monitoring the temperature, which are both combined in a control device 1030 in this example. Accordingly, the power supply 1010 and the electrical heating element 220 are connected to one another by electrical lines 1011, 1012 via the connecting bolts 214, 215, and the device for determining the resistance 1020 and the device for monitoring the temperature 230 are connected to one another by electrical lines 1021, 1022 via the connecting bolts 216, 217.
(32) In addition, the device for determining the resistance 1020 of the device for monitoring the temperature 230 is in signal communication with the power supply 1010 via a signal line 1023, so that the energizing of the at least one electrical heating element 220 can be changed as a function of the temperature value assigned to the resistance value by the device for determining the resistance 1020.
(33) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
APPENDIX
List of Reference Characters
(34) 100, 200, 300, 400, 500, 600, 700 Electrical cartridge type heater 110, 210, 310, 410, 510, 610, 710 Outer metallic jacket 111, 112, 311, 312, 412, 512 End caps 114, 115, 116, 117, 118, 119, 214, 215, 216, 217, 314, 315, 721, 722 Connecting bolt 120, 121, 220, 320, 420, 520, 620, 720 Electrical heating element 130, 230, 330, 430, 530, 630, 730 Device for monitoring the temperature 140, 240, 340, 440, 540, 640, 740 Interior space 211, 411, 511 Bottom 420a, 420b, 520a, 520b End 430a, 430b, 530a, 530b End 450, 550 Coil body 511a Recess 530c, 530d Section 628, 629 Arc 638, 639 Arc 660 Inner metallic jacket 661 Bottom surface 670 Outer shaped ceramic part 671 Middle shaped ceramic part 672 Inner shaped ceramic part 713, 714, 715, 716 Contact plate 717, 718 Connection wire 735 Magnesium oxide powder 1000 Electrical heater 1010 Power supply 1011, 1012, 1021, 1022 Electrical line 1020 Device for determining the resistance 1023 Signal line 1030 Control device r Radius
