Cassette PTC semiconductor heating apparatus

A PTC semiconductor heating device includes: two half shells combinable for forming a housing of the semiconductor heating device, a plurality of linear arrays of PTC semiconductor heating elements parallelly mounted in the housing with each linear array containing a plurality of PTC semiconductor heating elements longitudinally disposed in a side-by-side linear arrangement in said housing and each linear array of PTC heating elements being sandwiched in between every two neighboring thermally and electrically conducting units respectively connected to two poles of a power source and longitudinally juxtapositionally mounted in the housing each thermally and electrically conducting unit including a corrugated fin plate formed with a plurality of continuous square waves and clamped by a pair of conducting plates, and a plurality of resilient embedding plates each embedding plate resiliently inserted in between every two neighboring thermally and electrically conducting units for firmly tensioning, packing and retaining all the PTC heating elements, the conducting units and the embedding plate in the housing to eliminate any welding or bonding joint processing for their assembly for saving production cost and enhancing heating efficiency thereof.

BACKGROUND OF THE INVENTION 
conventional dryer or heater for blowing heated air as shown in FIG. 7 is 
formed by binding each PTC semiconductor heating element H in between two 
aluminum-plate frames A by adhesive S, each aluminum frame A confining a 
corrugated fin F within each frame A with the fin F fixed to the frame A 
by adhesive S such as by silicon adhesive, and each pair of terminals T 
connected to a power source being electrically connected to two poles of 
each PTC semiconductor heating element H for passing current through each 
PTC element H for heating air blown through the PTC elements H for heating 
purpose. 
However, such a conventional dryer has the following drawbacks: 
1. Due to different coefficients of heat expansion of the aluminum frame A 
and PTC element H, and due to the exposure of the silicon adhesive under 
high temperature to cause curing, breakage and cleavage of the adhesive 
binding, a sparking gap may occur between each PTC heating element H and 
each aluminum plate A to cause sparking, short-circuit or explosion 
hazards. The conducting surface on each PTC heating element H, as 
influenced by the silicon adhesive subjected to thermal shock when heated 
and cooled, may be easily oxidized to produce high impedance which in turn 
may cause partial over-current and over-heating of the PTC element, 
shortening the service life of PTC element or even explosion hazard 
thereof. 
2. The binding of PTC element with aluminum plate A or aluminum plate A 
with fin F should be processed or welded from point to point to increase 
production cost and quality control problems. 
3. The fin S forms a "point" contact with the aluminum plate A rather than 
a "surface" contact to thereby reduce the heat-exchange area and decrease 
the heating efficiency. Meanwhile, the "point" contact between the 
corrugated fin F with the aluminum plate A may be accumulated with dusts 
and dirts to increase wind resistance and decrease heat-exchange 
efficiency therefore. 
4. The aluminum plate A contacted with the PTC element H is directly 
secured with a terminal T which is connected to power source without any 
fuse. Once a short-circuit and sparking accident is caused, the PTC heater 
may be burned. During the manufacturing of the PTC elements, the clearance 
of thinner PTC element may be loosened in the assembly of PTC elements to 
produce sparking gap which may cause fire or explosion hazard of the PTC 
heater when passing current therethrough. 
The present inventor has found the drawbacks of a conventional PTC dryer or 
heater, and invented the present cassette type PTC heating device. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a PTC semiconductor 
heating device including: two half shells combinable for forming a housing 
of the semiconductor heating device, a plurality of linear arrays of PTC 
semiconductor heating elements parallelly mounted in the housing with each 
linear array containing a plurality of PTC semiconductor heating elements 
longitudinally disposed in a side-by-side linear arrangement in said 
housing and each linear array of PTC heating elements being sandwiched in 
between every two neighbouring thermally and electrically conducting units 
respectively connected to two poles of a power source and longitudinally 
juxtapositionally mounted in the housing each thermally and electrically 
conducting unit including a corrugated fin plate formed with a plurality 
of continuous square waves and clamped by a pair of conducting plates, and 
a plurality of resilient embedding plates each embedding plate resiliently 
inserted in between every two neighbouring thermally and electrically 
conducting units for firmly tensioning, packing and retaining all the PTC 
heating elements, the conducting units and the embedding plate in the 
housing to eliminate any welding or bonding joint processing for their 
assembly for saving production cost and enhancing heating efficiency 
thereof.

DETAILED DESCRIPTION 
As shown in FIGS. 1-6, the present invention comprises: a first half shell 
1, a second half shell 2, a plurality of PTC semiconductor heating 
elements 3, a plurality of thermally and electrically conducting units 3a 
with every two conducting units 3a disposed on two opposite sides of each 
array of PTC semiconductor heating elements 3 with each conducting unit 3a 
containing a corrugated fin plate 5 disposed in between two metallic 
conducting plates 4, and a plurality of resilient embedding plates 6 each 
embedding plate 6 resiliently inserted in between every two neighbouring 
conducting units 3a; two respective thermally and electrically conducting 
units 3a disposed on two opposite sides of each PTC semiconductor heating 
element 3 for contacting two opposite electrode surfaces 31, 32 of each 
PTC semiconductor heating element 3, and respectively connected to two 
poles of a power source 7 through two fuses 73 each fuse 73 connected 
between each respective terminal plate 71 or 72 of each thermally and 
electrically conducting unit 3aand each respective pole of a power source 
7. 
As shown in FIG. 5, a fan 8 driven by a driving motor 81 is provided to 
blow air W through the PTC heating elements 3 for supplying heated air for 
drying purpose. 
The shapes of a housing 1a composed of the first and the second half shells 
1, 2 and the depth or length of the housing 1a for passing air 
therethrough are not limited in this invention. 
The first half shell I is made of heat resistant and electrically 
insulative materials and includes: a first base socket 11 recessed in a 
central portion of the first half shell 1 to form a first frame 18 
circumferentially disposed around the first base socket 11, a first 
grating 12 formed with crosslinking net structure secured to an outer edge 
portion of the first frame 18 having a plurality of first ventilation 
holes 13 formed in the grating 12, a plurality of first terminal slits 14 
longitudinally recessed in a side portion of the first frame 18 for 
engaging each terminal plate 71 or 72 connected to a power source 7, and a 
plurality of tenons 15 formed on the first frame 18. The first grating 12 
extrapolatively defines a plane generally perpendicular to an air flow 
direction W through the ventilation holes 13 in the first half shell 1. 
The first half shell 1 is formed with a plurality of pin holes 17 
engageable with a plurality of first coupling pins 101 of a first hood 
member 10 for securing the first hood member 10 with the first half shell 
1 for guiding air flow W as shown in FIG. 5 when combined with a second 
half shell 2. 
The second half shell 2 is made of heat resistant and electrically 
insulative materials and includes: a second base socket 21 recessed in a 
central portion of the second half shell 2 to form a second frame 28 
circumferentially disposed around the second base socket 21, a second 
grating 22 parallel to the first grating 12 formed with crosslinking net 
structure secured to an outer edge portion of the second frame 28 having a 
plurality of second ventilation holes 23 formed in the grating 22, a 
plurality of second terminal slits 24 longitudinally recessed in a side 
portion of the second frame 28 for engaging each terminal plate 71 or 72 
connected to a power source 7 in cooperation with the first terminal slits 
14 in the first half shell 1, and a plurality of tenon sockets 25 formed 
on the second frame 28 engageable with the tenons 15 of the first half 
shell 1 for combining the two half shells 1, 2 for forming a housing 1a. 
The second half shell 2 is formed with a plurality of pin holes 27 
engageable with a plurality of second coupling pins 201 of a second hood 
member 20 for securing the second hood member 20 with the second half 
shell 2 for guiding air flow W as shown in FIG. 5 when combined with the 
first half shell 1. 
The first and the second half shells 1, 2 may be formed with a plurality of 
bolt holes 16, 26 in the first and second frames 18, 28 for fixing the two 
shells 1, 2 on any mounting bracket, structure or fixture. 
The first half shell 1 once combined with the second half shell 2 to form a 
housing 1a will confine an air duct 1b within the first and the second 
base sockets 11, 21 having a housing axis 100 transversely defined in a 
center portion of the housing 1a and being parallel to an air flow 
direction W when blown by the fan 8 into the air duct 1b in the housing 
1a. 
Each grating 12, 22 may be tapered frontwardly to face the fan 8 in order 
to reduce wind resistance when operating the present invention. 
The hood members 10, 20 may also be integrally formed with the first and 
second half shells 1, 2 without providing any tenon and tenon holes as 
aforementioned. Also, the hood members 10, 20 may also be omitted. 
Two poles of the power source 7 are electrically connected to two terminal 
plates, i.e., a first electrode terminal plate 71 and a second electrode 
terminal plate 72 respectively connected through two fuses 73 to two 
thermally and electrically conducting units 3a disposed on two opposite 
sides of each PTC semiconductor heating element 3. Either terminal plate 
71 or 72 is inserted in each terminal slit 14, 24 respectively recessed in 
two half shells 1, 2 of a housing 1a. 
Each thermally and electrically conducting unit 3a includes: an elongated 
fin plate 5 corrugated and continuously wound with a plurality of square 
waves sandwiched in between two elongated conducting plates 4 which may be 
electrically conductive metallic plates to form a generally rectangular 
shape from a longitudinal side view of each thermally and electrically 
conducting unit 3a which is embedded in the base sockets 11, 21 in the 
housing 1a to be juxtapositional to each side of each PTC semiconductor 
heating element 3 and to be tangential to an air flow direction W parallel 
to the housing axis 100. 
One elongated conducting plate 4 contacted with a first electrode surface 
31 of one PTC semiconductor heating element 3 is formed with a bending 
edge portion 41 on one end portion of the conducting plate 4 to connect a 
fuse 73 which is connected to a first electrode terminal plate 71 
connectable with a first pole of a power source 7; while the other 
elongated conducting plate 4 connectable to a second electrode surface 32 
of the PTC semiconductor heating element 3 is also formed with a bending 
edge portion 41 on one end portion of the conducting plate 4 to connect 
another fuse which is connected to a second electrode terminal plate 72 
connected with a second pole of the power source 7, thereby directing 
electric current through two electrode surfaces 31, 32 of each PTC heating 
element for producing heat. 
The bending edge portion 41 of the conducting plate 4 may also be omitted 
in this invention. 
Each elongated fin plate 5 includes each latitudinal blade portion 51 
continuously integrally connected with each longitudinal blade portion 52 
to be perpendicular to each other, each latitudinal blade portion 51 
followed with each longitudinal blade portion 52 being repeatedly wound to 
form a plurality of continuous square-wave forms to form a plurality of 
ventilation passages 53 through the blade portions 51, 52 to be 
communicated with a plurality of ventilation holes 13, 23 formed in a 
first and a second half shells 1, 2 for passing air flow W therethrough 
(FIGS. 6, 3), with each longitudinal blade portion 52 planarly contacting 
each elongated conducting plate 4 abutting the fin plate 5 for a better 
heat transfer between the fin plate 5 and conducting plate 4. 
Each resilient embedding plate 6 is also made of electrically conductive 
and thermally conductive materials, such as stainless steel or steel 
plate, and includes: an elongated flat plate member 61 having a plurality 
of protrusions 62 directly transversely punched on the elongated flat 
plate member 61 to have a longitudinal projective view of the protrusions 
62 alternatively or sinuously protruded from the flat plate member 61 as 
shown in FIGS. 6, 3 for a balancing elastic insertion of each embedding 
plate 6 in between every two neighbouring thermally and electrically 
conducting units 3ato firmly retain all the PTC heating elements 3 and the 
conducting units 3ainto the sockets 11, 21 in the housing 1a as squeezed 
by the embedding plates 6 longitudinally juxtaposed in the sockets 11, 21 
of the housing 1a. 
As shown in FIG. 4, each protrusion 62 of the embedding plate member 61 has 
two taper portions 621 tapered transversely towards two side edge portions 
of the flat plate member 61 for an easy insertion of the embedding plate 6 
into an aperture between every two thermally and electrically conducting 
units 3awhen embedded in the sockets 11, 21 of the housing 1a. 
Each linear array of the PTC semiconductor heating elements 3 has a width 
slightly smaller than a width of each grating 12, 22 formed in each half 
shell 1, 2 so that each grating 12, 22 will shield each array of PTC 
heating elements 3 to preclude any intrusion of an external object 
(electrically conductive) into the sockets 11, 21 of the housing 1a to 
touch the PTC element 3 to prevent a short-circuit or sparking accident. 
When mounting and assembling the present invention, each conducting unit 3a 
and each array of the PTC heating elements 3 are subsequently 1a id into a 
first socket 11 of the first half shell 1 to pack all the PTC elements 3 
and the conducting units 3a including conducting plates 4 and fin plates 5 
into the sockets 11 of the first shell 1, and then a plurality of the 
embedding plates 6 are parallelly inserted into the arrays of the 
conducting units 3a for resiliently tensioning, packing, squeezing and 
holding all the elements into the socket 11 of the first shell 1 which is 
then covered with second shell 2 and further combined by fixing bolts (not 
shown) therebetween. 
Therefore, this invention provides a PTC heater having the following 
advantages superior to any prior arts: 
1. All the elements are embedded in the housing 1 without any welding 
processing for saving production cost. 
2. An adhesive used in a conventional PTC heater is now eliminated to 
thereby prevent any drawbacks such as curing, breakage, overcurrent, 
shortcircuit, sparking and explosion caused by the conventional PTC heater 
bonded with adhesive. 
3. The embedding plates 6 are provided to squeeze the insertion of all PTC 
elements 3, fin plates 5 and conducting plates 4 in the sockets 11, 21 of 
the housing 1a to thereby firmly closely pack all parts in the housing to 
enhance heat transfer and current conductance therebetween to increase 
heating efficiency and prevent accident of shortcircuit, sparking or even 
explosion. 
4. The fin plate 5 has the square-wave shaped blade portions 51, 52 to 
increase thermal contacting or conducting areas for better heat exchange 
operation to thereby increase an overall heating efficiency of the present 
invention. Meanwhile, the square-wave shaped fin plate will reduce those 
small acute-angle "corners"(C) easily accumulated with dirts and dusts as 
found in a conventional heater as shown in FIG. 7 to thereby reduce the 
wind resistance because the right-angle "corners"(C) of this invention 
will be clearly purged by the air flow W by comparing FIG. 6 (this 
invention) with FIG. 7 (the prior art).