AU699529B2 - Heat detector - Google Patents

Description

I Regulation 3.2 A UST RA LI A Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

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9* 9 9* *9 9 9999 o 9 9.0 9 9 99994' 9 Name of Applicant: Actual Inventor(s): Address for Service: Invention Title: ROBERT McCULLOCH ROBERT McCULLOCH SANDERCOCKS PATENT ATTORNEYS Suite 6, 50-54 Robinson Street, DANDENONG VIC 3175 HEAT DETECTOR Details of Associated Provisional Application(s): No(s): Australian Provisional Application No. PM8190/94 The following statement is a full description of this invention, including the best method of performing it known to me/us: 1- I- la- TITLE: HEAT DETECTOR 9.

a FIELD OF THE INVENTION 9 This invention relates to a heat detector construction and Srelates particularly but not exclusively to a heat detector which is capable of being disassembled to allow repair and/or adjustment if necessary.

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BACKGROUND OF THE INVENTION Heat detectors are in common use throughout the world.

They are generally associated with alarm systems and/or automatic systems for putting out fires.

Generally speaking they rely upon the principal of using -A"1/VrrTM JInH.CAP.1 I _I S0 _i II iip~sr---. 2 the differential expansion of the components of the heat detector to operate a switch when the ambient temperature rises beyond a predetermined value.

Whilst various heat detector constructions are available, they generally suffer a number of disadvantages such as difficulty in assembly, and quality control problems arising from various factors such as corrosion or unsatisfactory welding creating pin holes in the detector construction. Furthermore, the common detectors are not constructed in such a way that they can be demounted which means that they must be thrown away rather than be repaired if they are not functioning correctly.

Prior Art Two particular types of detectors are commonly available throughout the world.

20 A description of these detectors will be made with .9*9 reference to Figures 1 5 of the accompanying drawings.

Brief Description of the Views of the Drawings of the Prior Figure 1 represents a plan view of a first detector, Figure 2 represents an elevational view of the first detector, 9.9' Figure 3 represents a cross-section through an elevational S view of the first detector, Figure 4 represents an elevational view of a second detector, and Figure 5 represent a cross-section of an elevational view ie~ I -3 of the second detector.

Integer List with respect to the Prior Art 1. First detector 2. Shell 3. Tube 4. End Cap body 5. Screw thread 7. Hexagonal nut 8. Weld joints Bow assembly 11. Contacts 12. Leads 13. End piece 14. Screws Second detector 41. Shell 42. Tube 43. Body 44. End plug 45. Weld joint 46. Brazed joint 25 47. Coined keyway 48. Switching assembly *9 49. Screw 50. Locating piece 30 Detailed Description with Respect to the Drawings of the Prior Art e* SReferring to Figures 1 3, the first detector 1 comprises a shell 2 made up of a tube 3, an end cap 4 and a body The body is provided with a screw thread 6 and an integral hexagonal nut 7.

sI frl'a V7 r"s 1 -4- The body, tube and end cap are joined together by the weld joints 8.

A temperature sensitive switch is provided in the shell 2.

This comprises the bow assembly 10 provided with contacts 11.

Leads 12 extend from the contacts 11 and out of the detector.

The bow assembly 10 is provided with an end piece 13 which abuts against the screws 14 provided in the end cap 4.

The screws provide adjustment of the bow assembly by enabling pressure to be exerted on the end piece 13 thereby to set the switching mechanism defined by the contacts 11 on the bow assembly.

During manufacture, the bow assembly is located on the body 5 in the manner illustrated with the ends of the bow assembly being spot welded to the body **.Subsequently the tube 3 is welded to the body and finally the end cap 4 is welded to the tube.

During the various welding operations, inert gas needs to be pumped into the interior of the tube to avoid corrosion damage caused by the welding.

99C* 30 Once the whole detector has been assembled and welded together, adjustment can be achieved by rotation of the :99 screws 14 to abut against the end piece 13 in order to put pressure on the bow assembly and move the contacts out of electrical contact with each other.

In this last respect, rotation of the bow assembly 10 with respect to the body during adjustment is prevented by ar~s~ r. :"VAN I'M O- M9 0I1 welding as noted above.

When the detector is subjected to a temperature beyond a pre-determined level, the expansion of the tube 8 moves the end cap 4 upwards and hence the ends of the screws 14 no longer press upon the end piece 13 thereby relieving pressure on the bow assembly It should be noted that the bow assembly members are formed of a material which has a very low thermal co-efficient of expansion compared with that of the tube 3.

When pressure on the bow assembly is relieved, the contacts 11 come together thereby switching on whatever system is connected to the detector.

This type of detector suffers from the disadvantages that it requires intensive quality control in view of the need to create welds in the region of the bow assembly, and in particular is subject to corrosion by virtue of the welding operation. Furthermore, pinholing can cause problems and the difficulties associated with providing an atmosphere of inert gas during construction increase the manufacturing

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costs.

Finally, because the assembly is permanently welded 9 together, the detector can never be repaired.

Referring to Figures 4 and 5, the second detector 30 includes a shell 41, formed of a tube 42 and a body 43.

9 9 An end plug 44 is welded via weld joint 45 to the end of the tube 42 to seal off the tube.

The body 43 is secured to the tube 42 by means of a brazed joint 46.

6- A coined keyway 47 is provided in the tube and serves to hold and locate the switching assembly 48 provided in the shell. The keyway 47 and locating piece 50 serve to restrict the switching assembly 48 from rotating during adjustment.

Adjustment of the device is achieved by means of a screw 49 which serves to push the end piece of switching assembly up against the end plug 44.

The second detector is assembled by inserting the switching assembly 48 through the open end of the tube 42 in such a manner that the coined keyway interacts with the locating piece 50 provided on the switching assembly.

At the same time, care must be taken during assembly to ensure that the electrical leads and screw 49 line up with and protrud! through the bottom of the body 5 through the openings provided therein in the manner illustrated.

Thus, assembly can be intricate and there is the added difficulty that welding and brazing operations could affect product control.

9 25 In addition, once the device has been welded together, it cannot be repaired.

In this last respect, welding is likely to produce pinholes, cracking, distortion and structural, chemical and 30 metallurgical changes and these are not likely to be desirable.

SUMMARY OF THE INVENTION The present invention provides:a heat detector comprising Qrsfl12ansemmWe.OMCUtOc.(CAPA II M P I -7a shell, having an open end, a closed end, and securement means provided internally of the shell, said shell having a thermal expansion coefficient which enables it to expand under application of heat a pressure responsive switching assembly including a mounting assembly, and an end piece wherein, the construction is such that the pressure responsive switching assembly may be inserted through the open end of the shell to bring the securement means into engagement with the mounting assembly and the end piece into abutment with the closed end.

S: PREFERRED ASPECTS OF INVENTION '.opposite end, the bow members each being provided with complementary electrical contacts, the arrangement being such that the electrical contacts form an electrical connection between each other when there is no pressure exerted on the end piece by the 25 closed end and cease to form an electrical contact when the end piece is pressed against

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.t the closed end, In a preferred aspect, the securement means comprise a screw thread which is adapted to co-operate with a complementary screw thread in the mounting asg6mbly.

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2 In a preferred aspect, the mounswitching assembly includes a pair of elongate bow members 91013.63MCULAME7 connection between each other when there is no pressure exerted on the end piece by the 25 closed end and cease to form an electrical contact when the end piece is pressed against .the closed end.

:.In a preferred aspect, the securement means comprise a screw thread which is adapted to co-operate with a complementary screw thread in the mounting as ibly.

In a preferred aspect, the mounting assembly includes fine "f li) 981013.I63MCUL.AME7 -8- .odjustment means to facilitate adjustment of the switching assembly in the shell in order to bring the end piece into abutment with the closed end.

It is particularly preferred that the switching assembly is non-rotatable in normal use when the fine adjustment means is adjusted but nevertheless be removable from within the shell. Such removability may be desired for replacement or servicing.

In a preferr-q aspect, the shell is integrally formed from a single piece of metal or other suitable material.

in a preferred aspect, the mounting assembly, comprises an outer member, a hollow adjustment member and a movable member, wherein the outer member is tubular and includes an external screw thread adapted to co-operate with the screw thread of the 20 securement means, and an internal screw thread adapted to 0 t A co-operate with an external screw thread provided on the adjustment member, and the movable member extends into the hollow such that complementary screw threads provided on the adjustment member and movable member interengage, and rotation of the adjustable member serves to move the end piece into or out of abutment with the closed end.

30 Preferably the switching assembly is screwed into the shell too* to a torque, with respect to unscrewing, substantially greater than the torque that can be exerted on the 9: adjustment member by a human using a straight shanked tool without an offset handle and having a Phank end adapted to engage the adjustment member. That tool will usualj be a straight screwdriver with an appropriately shaped point or blade.

C'"I &~IIIf i fvu rAP it I 9 A specific embodiment of a heat detector in accordance with the present invention will now be described with the aid of the accompanying drawings.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS Figure 6 illustrates a cross-sectional elevational view of a detector constructed in accordance with the invention, Figure 7 illustrates a sectional elevational view of the shell of a detector constructed in accordance with the invention, Figure 8 shows an elevational view of a switching assembly for a detector constructed in accordance with the invention, Figure 9 shows an elevational view of the switching assembly shown in Figure 8 rotated 90° with respect to the 20 vertical axis, Figure 10 shows an elevational view of a detector constructed in accordance with the invention, and a 0 Figure 11 is a plan view of the detector shown in Figure 4 INTEGER LIST eaa*a 30 61. Detector 62. Shell 63. Open end 64. Closed end Screw thread 66. Hexagonal nut 67. Screw thread 68. Shoulder aYm17 v fm22 Ur m T rtru rAV 0 _Ix I d 10 81.

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Switching assembly Bow members Contacts Leads End piece Slot Mounting assembly Slot Outer member Slot Screw thread Conduits Screw thread Adjustment member Screw thread Hollow Screw thread Movable member Screw thread Pin ft 4 or a *0 '4,4 4 4*ft4 o *r f *4W4v DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS Referring to Figures 6 11 in the accompanying drawings, 25 the detector 61 comprises a shell 62 having an open end 63 and a closed end 64.

Screw threads 65 are provided on the external surface of the shell to facilitate securement of the detector in a mounting or similar situation and a hexagonal nut 66 forms part of the detector to assist with the mounting operation.

A screw thread 67 which extends to shoulder 68 is provided on the inner surface of the shell.

A switching assembly 80 is mounted within the shell 62.

95912Uupe3,MCCULLOCH.CA?,10 I" 'Ro 11 The switching assembly comprises bow members 81 which may be formed of any suitable low thermal expansion coefficient material. The bow members are provided with contacts 82 and leads 83.

An end piece 84 which receives and holds the ends of the bow members in a slot 85 is positioned so that it can abut ag~ainst the closed end 64 when the detector is adjusted to a particular temperature range.

The opposite ends of the switching assembly 80 are held in a slot 87 forming part of a mounting assembly 86.

The mounting assembly 86 comprises an outer member 89, having a slot 90, a screw thread 91 which is complementary to the screw thread 67 provided on the inside surface of the shell, and conduits 92 through which the leads 83 may project.

too:. 20 The outer member 89 is also provided with an internal screw a. at thread 93 which is adapted to co-operate with a corresponding screw thread 95 on the adjustment member 94 :provided within the outer member.

A lock nut is desirably provided on the adjustment member.

A hollow 96 extending down the centre of the adjustment member includes an internal screw thread 97 which is adapted to co-operate with a corresponding screw thread 101 formed on the end of the movable member 100 which extends into the hollow 96.

A pin 105 which f its in the slot 90 prevents the movable member 100 and hence the switching assembly 80, from turning when the adjustment member is turned.

Generally speaking, the materials of the shell and the M12xmupe=MCCULLOCH.CAP,11 I- 12 switching assembly are chosen so that a differential expansion between the two will act to operate the switching assembly.

Thus, the bow members 81 may be formed of material which has a low thermal expansion coefficient and the shell 62 may be formed of a material which has a higher thermal expansion coefficient, for example, stainless steel.

Typically, the shell may be turned from a billet of hexagonal cross-section stainless steel.

Assembly of the detector is quite simple as the switching assembly is simply inserted into the shell 62 and screwed in until the front end of the outer member 89 abuts against the shoulder 68.

The adjustment member 94 is then turned to bring the end piece 84 into contact with the closed end 64 of the shell 0o** 20 thereby exerting pressure on the bow members 81 and causing them to move apart and break the electrical contact between the two contacts 82.

o Because the pitch of the threads on the adjustment member 94 and movable member 100 can be adjusted to give a very fine rate of adjustment, the adjustment member 94 and movable member 100 effectively act in the manner of a micrometer screw gauge.

It is thus possible to carefully set the pressure against the end piece 84 to a predetermined level thereby adjusting the responsiveness of the detector to a particular temperature range.

It is to be noted that there is no welding or braising in the connection of the shell to the mounting assembly.

__12_AnOct IACCULLOCHCAP.l2 9--Y I -13further, the movable member is non-rotatable in normal use with respect to the outer member.

Further, the outer member is non-rotatable in normal use with respect to the shell. This last is achieved by screwing the outer member into the shell to a torque, with respect to unscrewing, substantially greater than the torque that can be exerted on the adjustment member by a straight shanked screwdriver having a blade shaped to engage in a slot in the adjustment member.

Nevertheless, the switching assembly can be unscrewed for replacement or service.

The claims, illustrations, photographs and drawings, if any, form part of the disclosure of this specification as does the description, claims, illustrations, photographs and drawings of any associated provisional or parent specification or of any priority document, if any, all of 20 which are imported hereinto as part of the record hereof.

Finally it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements or parts without departing from the spirit and ambit of the invention.

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Claims (3)

1. A heat detector comprising a shell, having an open end, a closed end, and securement means provided internally of the shell, said shell having a thermal expansion coefficient which enables it to expand under application of heat a pressure responsive switching assembly including a mounting assembly, and N\ an end piece wherein, 44*. a a 6 4l 6 a. h6 a 64

4. 4 4* C *tt a *9 6 the construction is such that the pressure responsive switching assembly may be inserted through the open end of the shell to bring the securement means into engagement with the mounting assembly and the end piece into abutment with the closed end. 2. A heat detector as claimed in Claim 1, wherein the switching assembly includes a pair of elongate bow members each attached to the end piece at one end, each secured to the mounting assembly at the opposite end, the bow members each being provided with complementary electrical contacts, the arrangement being such that the electrical contacts form an electrical connection between each other when there is no pressure exerted on the end piece by the closed end and cease to form an electrical contact when the end piece is pressed against the closed end. 3. A heat detector as claimed in Claim 1 or Claim 2, wherein the securement means

981013.163MCUL.AMEI4 OnU J -1(fi -1 EJL 15 comprise a screw thread which is adapted to co-operate with a complementary screw thread in the mounting assembly. 4. A heat detector as claimed in any preceding claim, wherein the mounting assembly includes fine adjustment means to facilitate adjustment of the switching assembly in the shell in order to bring the end piece into abutment with the closed end. A heat detector as claimed in Claim 4, wherein the switching assembly is non- rotatable in normal use when the fine adjustment means is adjusted but nevertheless be removable from within the shell. 6. A heat detector as claimed in any preceding claim, wherein the shell is integrally formed from a single piece of metal or other suitable material. 7. A heat detector as claimed in any preceding claim, wherein the mounting assembly comprises an outer member, a hollow adjustment member and a movable member, wherein 20 the outer member is tubular and includes an external screw thread adapted to co- operate with the screw thread of the securement means, and an internal screw i thread adapted to co-operate with an external screw thread provided on the adjustment member, and 25 the movable member extends into the hollow such that complementary screw threads provided on the adjustment member and movable member interengage, and rotation of the adjustable member serves to move the end piece into or out of abutment with the closed end. 8. A heat detector as claimed in Claim 7, wherein the switching assembly is screwed into the shell to a torque, with respect to unscrewing, substantially greater than I 981013,163MCULAMEIS II~BI1IIIC~JI~AII~ -I 16 the torque that can be exerted on the adjustment member by a human using a straight shanked tool without an offset handle and having a shank end adapted to engage the adjustment member. 9. A heat detector as claimed in Claim 8, wherein the switching assembly may be screwed out of the shell. A heat detector as claimed in Claim 7, wherein not one of the shell and switching assembly is welded or brazed to the other. 11. A heat detector, substantially as hereinbefore described with reference to any one of the accompanying drawings. Dated this 13th day of October, 1998 SANDERCOCK COWIE 4- PATENT ATTORNEYS FOR ROBERT McCULLOCH 4 4 i 981013,163MCUL.AME16 r 17 ABSTRACT A heat detector comprising a shell, having an open end, a closed end, and securement means provided internally of the shell, said shell having a thermal expansion coefficient which enables it to expand under application of heat a pressure responsive switching assembly including a mounting assembly, and an end piece wherein, 44* 4 4 4kr 44 4. 4' 4. 4 4 ft t 4 4 4 4 the construction is such that the pressure responsive switching assembly may be inserted through the open end of the shell to bring the securement means into engagement with 20 the mounting assembly and the end piece into abutment with the closed end. *4 04 I .4 4 4 i.r 4.44a 44 4 .4 4 4 *4r 4 44 444 4r 4 981013,163MCUL,.AMS7