Energy supply device having a shaft rotatably supported on a polytetrafluoroethylene bearing surface

Abstract

An energy supply device such as a fan wheel generator for a mortar fuse or a battery which can be activated by a fan wheel. The energy supply device has a fast rotating fan wheel shaft which is supported in a housing body of the energy supply device. The fast-rotating fan wheel shaft and the housing body have a common bearing interface, wherein the bearing surface of the shaft or the bearing surface of the housing body is formed of a polytetrafluoroethylene material.

Description

[0001] This application claims priority under 35 U.S.C. §§ 119 and/or 365 to Patent Application Serial No. 100 45 684.7 filed in Germany on Sep. 15, 2000, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The invention relates to an energy supply device which comprises a fan wheel generator for a mortar fuse, e.g., for rotating a component of a mortar fuse, e.g., a detonator-carrying body or a battery charger. The generator includes a shaft which can be driven at high speed by a fan wheel. The shaft is rotatably supported in a housing body of the energy supply device.

[0003] In the case of mortar fuses or mortar fuse systems with integrated electrical functions, fan wheel generators are usually employed to provide the supply of energy. The nominal or operating rotary speed of fan wheel generators of that kind is very high, being for example 100,000 rpm. That nominal or operating speed has to be guaranteed during an operating period of the order of magnitude of 3 minutes. Hitherto the fan wheel shaft which rotates at high speed has been supported by high-speed ball bearings. The procurement price of such high-speed ball bearings is very high. Two such high-speed ball bearings are required to support the fan wheel shaft. This means that known energy supply devices of the above-indicated kind involve relatively high production costs.

[0004] The object of the present invention is to provide an energy supply device of the kind set forth in the opening part of this specification, the production costs of which are comparatively low, while at the same time mechanical strength and durability and resistance to heat are enhanced.

SUMMARY OF THE INVENTION

[0005] In accordance with the invention that object is attained by an energy supply device which includes a housing body, and a driven rotary shaft rotatably mounted in a bearing surface disposed in the body. The shaft includes an outer surface which engages the bearing surface. Either the outer surface or the bearing surface is comprised of polytetrafluoroethylene (PTFE), such as Teflon® or a Teflon® admixture.

[0006] Another aspect of the invention pertains to a mortar fuse which includes a housing, a body mounted in the housing for rotation and carrying a detonator, a rotary shaft to rotating the body, and a fan wheel mounted on the shaft for rotating the shaft. The shaft is rotatably mounted in a bearing surface disposed in the body. The shaft includes an outer surface which engages the bearing surface either the outer surface or the bearing surface is comprised of polytetrafluoroethylene (PTFE), such as Teflon® or a Teflon® admixture.

[0007] The fact that, in accordance with the invention, the fast-rotating fan wheel shaft and the housing body of the energy supply device (which is in particular a fan wheel generator for a mortar fuse or for a battery which can be activated by a fan wheel or the like) have a common bearing interface, wherein the bearing surface of the shaft or the bearing surface of the housing body is provided with a PTFE coating, provides a self-lubricating bearing arrangement for the shaft in the housing body. That bearing arrangement replaces the known high-speed ball bearings, thus resulting in enhanced mechanical durability and strength and a higher level of resistance to heat of the energy supply device according to the invention. In accordance with the invention the housing body can advantageously comprise a suitable plastic material. A major advantage lies in the great reduction in cost. The concept of the invention can be used for example in relation to simple AZ-mortar fuses with dual circuitry closure in accordance with MIL-STD 1316. The invention can also be employed in relation to mortar time fuses, mortar proximity fuses, multifunction mortar fuses and so forth.

[0008] In accordance with the invention the PTFE coating can be provided on a plain bearing insert of the housing body or on an injection moulding of the housing body.

[0009] The PTFE coating can comprise Teflon® or have a Teflon® admixture. Irrespective of the specific configuration involved, the above-mentioned advantages of relatively low production costs combined with enhanced mechanical durability and strength and increased resistance to heat are enjoyed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Further details, features and advantages are apparent from the description hereinafter of two embodiments of the energy supply device according to the invention, of which embodiments are shown in the drawing in which:

[0011] FIG. 1 is a view in longitudinal section showing a portion of a first embodiment of the energy supply device in the form of a fan wheel generator for a mortar fuse and,

[0012] FIG. 2 is a view in longitudinal section similar to FIG. 1 showing a portion of a second embodiment of the energy supply device in the form of a battery which can be activated by a fan wheel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0013] FIG. 1 shows an energy supply device 10 having a fan wheel 12 which is fixedly connected to a shaft 14. The apparatus can be of the type disclosed in U.S. application Ser. No. 09/754,208, filed Jan. 5, 2001, the disclosure of which is incorporated by reference herein. The shaft 14 drives a worm 30 which, in turn, rotates a body 32 that carries a detonator (not shown).

[0014] The shaft 14 is supported in a plain bearing insert 15 of PTFE (preferably Teflon® or a Teflon® admixture) which is provided in a housing body 16 of the energy supply device 10. For that purpose the plain bearing insert 15 is provided with a through hole 18 which forms a bearing surface 20 for the shaft 14. The bearing surface 20 is adapted with a sliding fit tolerance to a corresponding bearing surface 22 of the shaft 14.

[0015] The bearing surface 20 of the plain bearing insert 15 thus presents a PTFE coating 24 to the shaft 14. The PTFE coating 24 provides a self-lubricating bearing arrangement for the fan wheel shaft 14 which rotates at high speed during active operation, while affording a high level of mechanical durability and strength and a high degree of resistance to heat.

[0016] FIG. 2 shows a portion of an embodiment of the energy supply device 10 comprising a fan wheel 12 which is fixedly connected to a shaft 14. The fan wheel shaft 14 is rotatably supported in a housing body 16. The housing body 16 has two housing portions 26 and 28 which are fitted one into the other and each of which is provided with a through hole 18. The two through holes 18 of the housing portions 26 and 28 are adapted with a sliding fit tolerance to the two-part shaft 14 of the fan wheel 12, while there is a PTFE coating 24 between the through holes 18 and the shaft 14.

[0017] The fact that, in accordance with the invention, the bearing surface of the shaft or the bearing surface of the housing body is provided with a PTFE coating, provides a self-lubricating bearing arrangement for the shaft in the housing body, that bearing arrangement replacing the known high-speed ball bearings, thus resulting in enhanced mechanical durability and strength and a higher level of resistance to heat of the energy supply device according to the invention.

[0018] The housing body can advantageously comprise a suitable plastic material. A major advantage lies in the great reduction in cost. The concept of the invention can be used for example in relation to simple AX-mortar fuses with dual circuitry closure in accordance with MIL-STD 1316. The invention can also be employed in relation to mortar time fuses, mortar proximity fuses, multi-function mortar fuses and so forth.

[0019] The PTFE can comprise pure Teflon® or a Teflon® admixture within another material. Irrespective of the specific configuration involved, the above-mentioned advantages of relatively low production costs combined with enhanced mechanical durability and strength and increased resistance to heat are enjoyed.

[0020] Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, modifications, substitutions and deletions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An energy supply device comprising a housing body, a driven rotary shaft rotatably mounted in a bearing surface disposed in the body, the shaft including an outer surface engaging the bearing surface, one of the outer surface and the bearing surface comprises a polytetrafluoroethylene material.

2. The energy supply device according to claim 1 comprising a mortar fuse, and including a fan wheel connected to the shaft for rotating the shaft.

3. The energy supply device according to claim 1 including a hollow bearing insert mounted in the housing, the insert formed of a polytetrafluoroethylene material and forming the bearing surface.

4. The energy supply device according to claim 1 wherein the housing body is injection molded and forms the bearing surface which is coated with a polytetrafluoroethylene material.

5. The energy supply device according to claim 1 wherein the Teflon comprises a polytetrafluoroethylene material admixture.

6. A mortar fuse comprising: a housing; a body mounted in the housing for rotation and carrying a detonator; a rotary shaft for rotating the body; and a fan wheel mounted on the shaft for rotating the shaft; the shaft being rotatably mounted in a bearing surface disposed in the body, the shaft including an outer surface engaging the bearing surface, one of the outer surface and the bearing surface comprised of a polytetrafluoroethylene material.