Patent Abstract:
A cartridge heater, especially a compressed cartridge heater ( 1 ) has at least one heating coil ( 8, 9 ), which is arranged exposed in a metallic tubular body ( 2 ) and is embedded in a granulated insulating material. The ends of heating coil portions ( 8, 9 ) are provided with terminals ( 7 ) projecting from the tubular body ( 2 ). To make it possible to manufacture such a cartridge heater with minimal effort in terms of labor and material, a flat insulating plate ( 10 ) coordinated in its width with the internal diameter of the tubular body ( 2 ) is provided as the carrier. The heating coils ( 8, 9 ) extend along the two flat sides of the insulating plate ( 10 ) and the two heating coils ( 8, 9 ) are connected to one another by a coil section (12, 12′), which is led around a deflecting edge ( 27 ) of the insulating plate ( 10 ).

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of priority under 35 U.S.C. § 119 of German Patent Application DE 20 2005 011 686.6 filed Jul. 26, 2005, the entire contents of which are incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention pertains to a compressed cartridge heater with at least one heating coil, which is arranged exposed in a metallic tubular body and is embedded in a granulated insulating material and whose ends are provided with terminals projecting from the tubular body. 
   BACKGROUND OF THE INVENTION 
   A compressed cartridge heater of this type is known, for example, from DE 70 31 974 U. A plurality of heating conductor coils with different wire thicknesses and different coil diameters are accommodated in this cartridge heater concentrically with one another, exposed in a cylindrical cartridge housing, which has a fixed front-side bottom at one end and whose other end is closed by a metal disk with wart-like holes. Instead of the otherwise usual terminal screws, strands provided with insulating jackets are connected to the ends of the heating conductors. These strands are led through the metal disk toward the inside with their insulating jackets, so that there is an insulation between the metal disk and the conductor wires of the strands. 
   DE 197 16 010 C1 discloses an electric jacket tube heater with integrated temperature sensor, in which the heating conductor coils are installed in a hairpin-like pattern in the jacket tube and the connection of the heating conductor is led out at one end of the jacket tube and of the connection temperature sensor at the other end of the jacket tube. The heating coil is embedded in compressed insulating material. 
   No support elements, which ensure that when the insulating granular material is filled in, the windings of the heating coil will not come into contact with the tube wall, are provided whatsoever for the heating coils within the metal tube in these prior-art cartridge heaters. It must rather be ensured when the granular material is filled in that the heating coils will not be bent out and are kept away in space from the tube jacket. 
   This makes it difficult to fill in the granular material and causes high manufacturing costs. 
   SUMMARY OF THE INVENTION 
   The basic object of the present invention is to create a compressed cartridge heater of the type mentioned in the introduction, which can be manufactured with minimal effort in terms of labor and material. 
   This object is accomplished according to the present invention by providing as the carrier for the heating coils a flat insulating plate, which is coordinated in its width with the internal diameter of the tubular body, wherein the heating coils extend along the two flat sides of the insulating plate and are connected to one another by a coil section that is led around a deflecting edge of the insulating plate. 
   Due to the arrangement according to the present invention and the provision of flat insulating plates as the carrier for the heating coil, it is substantially simpler to place heating coils within the tube such that they cannot come into contact with the wall of the tube, so that less care is needed when filling in the insulating granular material, and this filling in can be carried out substantially more rapidly and thus at a lower cost. The connecting coil section may consist of a short wire section or comprise one or more windings. 
   It is simplest to use the lower, narrow-side end edge of the insulating plate as the deflecting edge. 
   Another simple possibility of insulating the coil section led around this lower end edge against the bottom of the tubular body and of keeping it away from it is the deflecting edge being formed by the narrow-side end edge of the insulating plate and the coil section led around same being separated from the bottom of the tubular body by an insulating disk or a spacer ring. 
   Other advantageous possibilities of keeping the deflecting edge or the coil section led around it away from the bottom of the tubular body are presented herein. 
   Holding clamps may be provided that are distributed over the length of the heating coils, consist of insulating material, surround the said heating coils and are fastened at the longitudinal edges of the said insulating plate. 
   The holding clamps may be provided with clamping fingers, which mesh with said locking notches of the insulating plate. The holding clamps may comprise U-shaped flat bodies and have U-shaped recesses in which the heating coils ( 8 ,  9 ) are guided. These measures guarantee simple and reliable fastening of the holding clamps on the insulating plate and, moreover, sufficient fixation in space of the heating coils within the tubular body. 
   To also have the possibility of arranging two heating coils on each flat side of the insulating plate, the heating coils may be connected to one another in pairs that can be associated with different heating circuits on the two flat sides of the insulating plate. 
   Another advantageous embodiment of the cartridge heater according to the present invention presents the special advantages that the heating coils extending in parallel next to one another are mutually insulated by the insulating plates located in between. 
   Several possibilities of embodiment are available for designing the insulating plates. 
   Holding clamps, which prevent the individual heating coil strands from bending out radially, may be provided in case of greater overall length. 
   The present invention will be explained in greater detail below on the basis of the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  is a side view of a compressed cartridge heater; 
       FIG. 2  is a top view II from  FIG. 1 ; 
       FIG. 3  is a section III from  FIG. 2 ; 
       FIG. 3   a  is a sectional view of the lower section of the cartridge heater with another insulating plate; 
       FIG. 4  is a 3-D view of the cartridge heater with a cut-away sectioned tubular body; 
       FIG. 5  is a perspective showing an insulating plate as an individual part; 
       FIG. 5   a  is another embodiment of the insulating plate from  FIG. 5 ; 
       FIG. 6  is a holding clamp as an individual part; 
       FIG. 7  is an isometric view of a carrier plate with two heating coil pairs; 
       FIG. 7   a  an isometric view showing a variant of  FIG. 7 ; 
       FIG. 8  is a front view VIII from  FIG. 7  with the tubular body from  FIG. 4 ; 
       FIG. 9  is a perspective view showing the holding clamps from  FIG. 7  as individual parts; 
       FIG. 10  is an isometric side view of another cartridge heater; 
       FIG. 11  is a front view XI from  FIG. 10 ; 
       FIG. 12  is an isometric view of the carrier plates and heating coils arranged in the tubular body according to  FIGS. 10 and 11 ; 
       FIG. 13  is a perspective view showing the two insulating plates according to  FIG. 12  as individual parts; 
       FIG. 14  is a perspective view showing the closing disk from  FIG. 10  as an individual part; 
       FIG. 14   a  is a perspective view showing a variant of the closing disk of  FIG. 14 ; 
       FIG. 15  is a perspective view showing the holding clamps from  FIG. 12  as individual parts; 
       FIG. 16  is an isometric view of another embodiment of the intersecting insulating plates as individual parts; 
       FIG. 17  a perspective view showing the insulating plates from  FIG. 16  in the assembled state; 
       FIG. 18  is a partially cut-away, isometric view of insulating plates that are assembled according to the principle of  FIGS. 16 and 17 , but which have no recesses at the lower edge; 
       FIG. 18   a  is a sectional view of the lower section of the cartridge heater in the embodiment according to  FIG. 18 ; 
       FIG. 19  is partially cut-away, isometric view showing a variant of the embodiment according to  FIG. 18 ; 
       FIG. 20  is partially cut-away, isometric view showing a variant of the embodiment according to  FIG. 18 ; 
       FIG. 20   a  is a perspective view showing the insulating plates according to  FIG. 20  as individual parts; and 
       FIG. 20   b  of the lower section of the cartridge heater in the embodiment according to  FIG. 20 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the drawings in particular, the cartridge heater  1  comprises a cylindrical tubular body  2 , which has a fixed bottom  3  and whose upper, open end  4  is closed by a closing disk  5 . The tubular body  2  consists of metal, preferably stainless steel. It may also consist of brass, copper or the like. 
   The closing disk  5  consists of an insulating material and is provided with passage openings  6  for terminal screws  7  of two heating coils  8  and  9 . The two heating coils  8  and  9  extend on both sides of an insulating plate  10 , which is arranged centrally in the tubular body  2  and acts as a carrier for the heating coils  8  and  9 . 
   In the embodiment according to  FIGS. 1 through 3  as well as  FIGS. 4 and 5 , the insulating plate  10  is provided, in the area of its lower end, with a recess  11  shaped as a hole, through which a coil section  12  connecting the two heating coils  8  and  9  to one another is led. As is shown in  FIGS. 7 through 13 , the recess may also be designed as an open slot  11 ′. The deflecting edge, with which the coil section  12  is in contact, is located in the recess  11  or  11 ′ in these embodiments. 
   These recesses  11  and  11 ′ expediently have a size coordinated with the diameter of the heating coils  8  and  9 , so that one of the two heating coils  8 ,  9  can be easily lead through this recess  11  or  11 ′. 
   As is shown in  FIG. 3   a , it is also possible to use the lower end edge  27  of the insulating plate  10  as a deflecting edge and to lead the connecting coil section  12  directly around this end edge  27 . However, it is necessary for this to insulate the coil section  12  by an inserted insulating disk  26  against the bottom  3 . To achieve a certain fixation of the position for the coil section  12  in this case as well, the lower end edge of the insulating plate  10  may be provided with a notch, not shown. The notch is used as a deflecting edge for the coil section  12  in this embodiment. 
   As is shown by the example according to  FIGS. 18 through 20   b , it is also possible to establish an insulating distance from the bottom  3  by inserting a spacer ring  40  made of an insulating material, e.g., ceramic, on which the lower edge of the insulating plate  10  is seated. 
   The cavity of the tubular body  2  between the bottom  3  and the closing disk  5  is filled with an insulating material (granulated insulating material)  13 , which may consist of quartz sand or a metal oxide, especially magnesium oxide. A granular product consisting of heat-resistant plastic may also be used for this purpose. 
   It shall be pointed out here that the drawings show the cartridge heater  1  in the noncompressed state. 
   In case of relatively small overall lengths of the tubular body  2 , the two heating coils  8  and  9  are sufficiently guided within the tubular body  2  by the insulating plate  10  and the two terminal screws  7 , which are rigidly connected to the upper ends of the heating coils  8  and  9 , and are protected against bending out radially and thus against touching the wall of the tubular body. 
   If the cartridge heater has a greater overall length, it is useful to secure the heating coils  8  and  9  by holding clamps  14  arranged distributed over the length. These holding clamps  14  consist of U-shaped flat bodies made of insulating material and are provided with U-shaped recesses  15 , in which the heating coils  8  and  9  are guided. 
   In addition, these holding clamps have clamping fingers  16  and  17 , which engage locking notches  18  of the insulating plate  10  in a locking and positive-locking manner. These locking notches  18  are arranged in pairs opposite each other on the longitudinal edges  19  and  20  of the insulating plate  10 . With support surfaces  21  arranged on both sides of the U-shaped recess  15 , the holding clamps  14  are in contact with the respective flat sides of the insulating plate  10 . The insulating plate  10  may consist of micanite or ceramic or plastic. 
   Two heating coils  8  and  8 ′ and  9  and  9 ′ each are arranged on both sides of the insulating plate  10  in such a way that they extend in parallel to one another in the embodiment according to  FIGS. 7 and 8 . Their top ends are connected to the respective terminal screws  7  and  7 ′. The two heating coils  8  and  8 ′ are visible in  FIG. 8  only. 
   The insulating plate  10  is provided with two slot-like recesses  11 ′ at its lower end in this embodiment. These recesses could also be designed as holes. 
   To also support the two heating coils  8  and  8 ′ on one side and  9  and  9 ′ on the other side of the insulating plate  10  against bending out at the same time, holding clamps  14 ′, which are arranged distributed over the length, are equipped with two U-shaped recesses  15 ′ each, and by which a heating coil  8 ,  8 ′ and  9 ,  9 ′ each is guided, are provided. 
   These holding clamps  14 ′ are also provided with lateral clamping fingers  16  and  17 , which engage notches  18  of the insulating plate  10  in a positive-locking manner. Between the U-shaped recesses  15  and  15 ′, there is a support finger  22 , whose front surface  21  with the other two support surfaces  21  at the clamping fingers  17  and  18  is supportingly in contact with the flat side of the insulating plate  10 . 
   In the embodiment according to  FIGS. 7 and 8 , a closing disk  5 ′ ( FIG. 14 ) with four passage openings  6  is provided, through which the four terminal screws  7  and  7 ′ are led to the outside. 
   The embodiment according to  FIG. 7   a  provides for the terminal screws  7 ′ of the two heating coils  9  and  9 ′ ( FIG. 8 ) to be arranged at the lower end of the insulating plate  10  and thus to project from the tubular body  2  on the lower front side. Accordingly, the tubular body  2  is not equipped with a lower front wall  3  but, instead, likewise with a closing disk  5 ″ according to  FIG. 14   a , which is also used to close the upper end of the tubular body in this case. The passage openings  6  of this closing disk  5 ″ are arranged, corresponding to the terminal screws  7  and  7 ′, eccentrically, offset to one side in relation to the central plane  25 . 
   In the embodiment according to  FIGS. 10 through 15 , the cavity of the tubular body  2  is divided by two insulating plates  10 ′, which intersect centrally, into four space sectors  31 ,  32 ,  33  and  34  ( FIG. 11 ), in which a heating coil  8 ,  8 ′,  9 ,  9 ′ each is located. At least one of the insulating plates  10 ′ must be provided with two recesses  11 , through which a coil section  12  each extends, which connects two heating coils  8  and  8 ′ as well as  9  and  9 ′ extending on the two flat sides of the insulating plate  10 ′ to one another. 
   In the exemplary embodiment according to  FIG. 13 , both insulating plates  10 ′ are provided with two slot-like recesses  11 ′ each at both the top end and the lower end, so that these two can be pushed into the tubular body  2  in any desired position in a centrally crossing position, as is shown in  FIGS. 11 and 12 . Strictly speaking, this is only an insulating plate  10 ′ that is present in a pair, one of which is upside down. To make it possible to connect the two insulating plates  10 ′ to one another in a crossing position in a positive-locking manner, the two insulating plates  10 ′ are provided with insertion slots  35  each, which extend centrally and symmetrically to their longitudinal axis  35 . These insertion slots  35  have a width b 1  each, which corresponds to the thickness d of an insulating plate  10 ′. To make it possible to insert flush the two insulating plates  10 ′, which are of equal length and equal width and are also shaped identically otherwise, it is necessary for these insertion slots  35  to extend at least over half the length s. 
   These insulating plates  10 ′ are also provided with open slots  11 ′ ( FIG. 5   a ) instead of with holes  11 . 
   To support the heating coils  8 ,  8 ′,  9  and  9 ′, holding clamps  14 ″ made of insulating material, which have a U-shaped flat shape, are provided with two clamping fingers  16  and  17  and also have support surfaces  21 . The recesses  15  and  15 ′, which are designed without support fingers  22  in this case, are located between the support surfaces. A notch-like recess  15 / 1 , whose connection web  15 / 2  is accommodated by a notch  18  of the respective bridged-over insulating plate  10 ′ is provided between these recesses  15  and  15 ′. 
   The holding clamps  14 ″ are otherwise used in the same manner as the holding clamps  14 ′. 
   Other embodiments of insulating plates arranged crosswise are shown in  FIGS. 16 through 20   b . A first insulating plate  10 / 1  of the usual shape and with the locking notches  18  arranged at the longitudinal edges  19  and  20  is provided for fastening holding clamps  14 ″ according to  FIGS. 12 and 15 . 
   This insulating plate  10 / 1  has insertion slots  35 ′ each, extending symmetrically to its longitudinal axis  36 , in the area of its narrow-side end sections. These two insertion slots  35 ′ have a width b 2 , which corresponds to twice the thickness d second insulating plate  10 / 2 . In addition, these insertion slots  35 ′ have a longitudinal distance s 1 . This longitudinal distance s 1  corresponds to the length s 1  of a rectangular opening  35 / 1 , which the two second insulating plates  10 / 2 , which otherwise have an identical shape, have. The two remaining end sections  42  of these two second insulating plates  10 / 2  have the width b. 
   The width b 3  of the openings  35 / 1  corresponds to b/ 2 +d/ 2 . As a result, as is shown in  FIG. 17 , the end sections  42  can be introduced congruently into the insertion slots  35 ′ of the insulating plate  10 / 1  such that they project from these by equal amounts on both sides. 
   The upper and lower end sections  42  of the two second insulating plates  10 / 2  touch each other on their flat sides, as is shown in  FIG. 17 . The outer edges  20  of the second insulating plates  10 / 2  are likewise provided with locking notches  18 , which are used to receive holding clamps  14 ′ ( FIG. 15 ). 
   The upper and lower end sections  42  of the second insulating plates  10 / 2  are provided each with recesses  11 ′, which are arranged symmetrically to the first insulating plate  10 / 1  and are mutually flush with one another and through which coil sections  12  or windings  12 ′ of the heating coils  8 ,  9  can be led. 
   To make it possible to do away with such recesses  11 ′ and to use the lower, closed end edges  27  as deflecting edges for the coil section  12  or windings  12 ′, a spacer ring  40  each, which is seated on the bottom  3  and at the top edge  41  of which the insulating plates  10 / 1  and  10 / 2  are seated, is provided in the embodiments according to  FIGS. 18 through 20   b . As a result, the coil section  12  or the windings  12 ′ receive the proper distance from the bottom  3  of the tubular body  2 . 
   In the embodiment according to  FIGS. 19 and 20 , the first insulating plate  10 / 1  is provided with an extension  43  protruding into the spacer ring  40 . The insertion slot  35 ′ is not led up to the lower end of this extension  43  in this embodiment, but it rather ends at the level of a support shoulder  44 , with which the first insulating plate  10 / 1  is seated on the upper edge  41  of the spacer ring  40 . 
   This extension  43  is also present in the embodiment according to  FIG. 18   a . The two heating coils  8  and  9 , which are connected to one another in one piece, are led around the lower edges  27  of the two second insulating plates  10 / 2  with a plurality of windings  12 ′, which are shown in exemplary embodiment  3 . The extension  43  of the first insulating plate  10 / 1  protects the windings  12 ′ of the heating coils  8  and  9  extending on the two sides of the insulating plate  10 / 1 , which said windings  12 ′ are led around the lower edges  27  of the second insulating plates  10 / 2 , against mutually touching one another. 
   In  FIGS. 20 ,  20   a  and  20   b , the two second insulating plates  10 / 2  are provided with an extension  43 ′ each, which is arranged between two recesses  45 , which are open on the side and at the end. 
   The deflecting edges are formed by the horizontal sections  46  of the recesses  45  in this embodiment. As can be recognized from  FIG. 20 , a plurality of windings  12 ′ of the heating coils  8  and  9  can be led around these deflecting edges  46  and maintain the necessary distance from the bottom  3  in the case of the recesses  45  that are open both on the end and laterally. 
   The cartridge heater is assembled in all embodiments shown such that the heating coils  8 ,  8 ′,  9 ,  9 ′ are first mounted with the respective terminal screws  7  and  7 ′ fastened thereto on the insulating plates  10  and  10 ′ in the manner shown in the drawing and are secured by the holding clamps  14  and  14 ′ or  14 ″. This premounted component is then inserted into the tubular body  2  and the remaining cavity is filled with the granulated insulating material from the open upper side. The closing disk  5  and  5 ′ is then inserted into the upper end of the tubular body  2  and the tubular body is pressed radially from the outside such that not only does the granulated insulating material undergo intense compaction, but the passage openings  6  of the closing disk  5  and  5 ′ are also reduced in size such that they are tightly in contact with the terminal screws  7  and  7 ′. 
   Instead of the usual terminal screws  7 ,  7 ′, it is also possible to provide other terminals, as is known from DE 70 31 974 U, e.g., jacketed strands. 
   The closing disks  5 ,  5 ′ and  5 ″ consisting of insulating solids may also be replaced with other closing means. Depending on the nature of the insulating material filled into the tubular body, they may even be able to be omitted. 
   It is easy to imagine that the heating coils  8 ,  8 ′,  9 ,  9 ′ fastened to the insulating plate or plates  10  and  10 ′ do not run the risk of coming into contact with the wall of the tubular body  2 , especially because they are also secured by the holding clamps  14  and  14 ′ and  14 ″ against bending out radially. Since this granulated insulating material is a very fine-grained material, which has a high flowability, the filling into the tubular body can be carried out in a relatively problem-free manner such that no cavities, which can be reliably prevented from occurring by simple vibration, are left. 
   On the whole, the assembly of the heating coils  8  through  9 ′ and the filling in of the granulated insulating material are substantially simplified and thus also made less expensive by the use of the insulating plates  10  and  10 ′. 
   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.

Technology Classification (CPC): 7