TRANSMITTER ARRANGEMENT

Abstract: Transmitter arrangement for rotatable shaft (1) comprising a rotor (2) in the form of a cog-wheel arrangement (7, 8) which is to be mounted on the shaft, and a stator (6a-6d) which is rigid relative to the rotable shaft and is adapted for connection to an AC voltage source for generating electrical signals which depend on the angular position of the rotor relative to the stator. The cog-wheel device comprises a folded cog band (7) of magnetic material which is attached to a carrying band (8) which is provided with means (11, 12, 13) for attachment of the cog-wheel device around the shaft and which is provided with radially extending tabs (9) on the surface facing the shaft, said tab means intended for guiding a hose (10) which can be filled with fluid and which is insertable between the guiding members. At filling with fluid the hose will expand both around the periphery of the shaft and towards the carrying band for fixed mounting and centering the cog-wheel device on the shaft. The transmitter arrangement is specifically suited for measuring angular differences between two cog-wheels (2, 3) which are fixedly mounted on the shaft, whereby voltage supplied stator elements in the form of segments are disposed around the periphery of the shaft and are rigid relative thereto each stator element being intended to cooperate with a cog band for generating electrical signals which depend on the angular position in space of the cog-wheel.

Description: TRANSMITTER ARRANGEMENT The present invention relates to a transmitter arrangement for a rotatable shaft comprising a rotor in the form of a cog-wheel device wh is to be mounted on the shaft and a stator which is rigid relative to t rotatable shaft and is adapted for connection to an AC voltage to gener electrical signals which depend on the angular position of the rotor relative to the stator. An arrangement of this kind is disclosed in for instance US-PS 3 505 862 and relates to a device for measuring angular differences bet ween two toothed wheels which are mounted on a rotatable shaft. Such an arrangement comprises two inductive transmitters, each of which cooperat with a toothed wheel to generate electrical signals which depend on the angular position in space of the toothed cog-wheel. A differentiaating device is connected to the two transmitters and is adapted to measure th difference between two signals generated by the transmitter. The measuri technique which is accomplished through the system according to the just mentioned US specification is consequently utilized in the transmitter arrangement according to the present invention. In the system according to the US specification the two wheels are massive and are mounted on the shaft by means of supporting rings which have to be carefully centered and fixed directly on the shaft by means o jaws. Such an installation is rather complicated and time-consuming whic has caused problems specifically if the installation has to be carried o on a ship's propeller shaft during the short time period when the ship i staying in harbour for loading or unloading of cargo. Consequently, demands have been made for an improved installation of the toothed wheel which can be carried out more rapidly and which does not unnecessarily prolong the ship's stay in harbour. The object of the present invention is to provide a transmitter arrangement for a rotatable shaft which has low weight and enables easy mounting and centering on the shaft and consequently can be installed in very short time. A transmitter arrangement according to the invention is substantia ly characterized in that the cog-wheel device comprises a folded cog ban of magnetic material which is attached to a carrying band provided with means for assembling the cog band device around the shaft, the carrying band being provided with radially extending guide members on the surface facing, the shaft, said guide members being arranged for axial guidance o a hose to be filled with a fluid, said hose being insertable between the / / * f Q MPi guide members and when filled with said fluid expanding both around the periphery of the shaft and against the carrying band to fix and centre t cog band device on the shaft. An embodiment of the invention will now be described in detail wit reference to the accompanying drawings on which Fig. 1 is a perspective view of a transmitter arrangement accordin to the invention to measure angular differences between two cog wheels, Fig. 2 is a perspective view of details in a cog-wheel device according to the invention, Fig. 3 is a plan view from below and a side view of the ends of a carrying band according to the invention, and Figs. 4 - 6 show different steps in mounting the cog-wheel device according to the invention on a shaft. A transmitter arrangement according to the invention can be used for measuring torque on a shaft 1. The arrangement thereby comprises a rotor which, according to Fig. 1, comprises two toothed wheels in the fo of cog-bands 2 and 3 which are mounted on the shaft 1 and two stators 4 and 5 which are rigid relative to the rotatable shaft and are adapted fo connection to an AC voltage source for generating electrical signals which depend on the angular position of the rotor relative to the stator as described in the above-mentioned US-PS 3 505 865. Each stator compris four stator segments 6a-6d which are arranged with the same angular spacing around the periphery of the shaft 1 and are disposed just opposi to the cog-wheels. The design of the cog-wheel device is shown on Fig. 2 and comprise a folded cog band 7 of magnetic material which is mounted on a carrying band 8. The cog band is preferably made of high quality magnetic materia and the carrying band is suitably made of a flexible material with high strength and toughness which makes it possible to shear the band. The carrying band is provided with radially extending tabs 9 on the surface facing the shaft. The tabs are stamped out of the carrying band and are consequently formed in one piece with the band. The tabs are stamped in two rows in the carrying band between which a flexible hose 10 is inserted. The two rows of. tabs 9 are consequently intended to axially guide the hose 10 and to prevent the hose from extending outside the ban at the mounting around the shaft. The hose 10 is to be filled with gas o liquid and a simple method is to fill the hose 10 with air by means of a common bicycle pump (not shown). When the hose 10 is filled with air it -βU'riEΛ O.MPI will expand both around the periphery of the shaft 1 and against the carrying band 8, whereby the cog-wheel device will be fixedly mounted a securely centered on the shaft 1. Fig. 2 shows a position of the carryi band 8 when it has been arranged around the shaft 1 and its ends are to assembled. For this purpose a joint plate 11 is provided with holes 12 corresponding to the tabs 9 formed in the inner surface of the carrying band.8. The joint plate 11 is fixed to one end of the carrying band 8 b means of clips 13 and in the Figure the position of the other end is sho immediately before it has been brought down against the joint plate and the tabs have been fitted in the corresponding holes. Fig. 3 shows a plan view of the joint plate 11 from beneath and a lateral view of the joint between the carrying band 8 and the ends of th cog-band 7. The joint plate 11 is thus provided with holes 12 correspond ing to the tabs 9 on the inner side of the carrying band. The holes are disposed in such a way that only a cog band with an odd number of cogs h tabs which correspond to the hole locations in the joint plate. This is due to the fact that in the manufacture of the cog wheel arrangement the cog band 7 and the carrying band 8 are accurately attached to one anothe so that each cog will exactly correspond to an inwardly projecting tab. Each cog band with an odd number of cogs will thus be terminated with an inwardly projecting tab 9a in the lower row of tabs which directly corresponds to the hole 12a in the joint plate in the embodiment shown i the Figure. If the number of cogs had been even the cog band would have been terminated with a cog which corresponds to the tab 9b in the upper row of tabs which thus will fit into the corresponding hole 12b. In this case, however, the joint plate 11 will not permit the ends of the cog ba to be assembled and this measure will therefore prevent that the cog ban by mistake is but off with an even number of cogs. By choosing an odd number of cogs it is possible to align the stator segments exactly relative to the cog band. If the cog band always has an odd number of cogs and the four stator segments are positioned around the shaft with an angular spacing of 90° the blocks will generate output voltages which are separated by an electrical angle which corresponds to 1/4 of the tooth pitch. It belongs to common knowledge that the difference of 1/4 tooth pitch corre ponds to an electrical angle of 90°. The segments will thus generate voltages with the following electrical angles: I Segment 6a 6b 6c 6d A ngle J?+90° ft+180° β+270° The voltage from the segments 6a and 6c can be combined to a voltage which is proportional to sin and the voltage from the segments 6b and 6d can be combined to a voltage proportional to cos μ . The above is applicable for all odd numbers. Thus, the shortening of the carrying band should always be made in steps of two cogs if the cog number has to be odd. This means that a certain clearance can occur between the inner diameter of the carrying band and the outer diameter of the shaft. The gap between the shaft 1 an the ends of the tabs 9 can in practice be about 2 mm if no other measure are taken. A gap of 2 mm can be difficult to bridge for instance in a glueing operation. In order to decrease the gap to a size of about 0.5 m the lengths of the tabs are shortened by shearing. The different steps of assembling the cog-wheel device on a shaft shown on Figs. 4-6. The folded cog band is thus put around the shaft 1 a is joined in the way described in connection with Figs. 2 and 3. One end of the flexible hose 10 is provided with a spigot 14 (see Fig. 2) wherea the other end is connected to a flexible tube 15 which in its turn is connected to a test section 16 which consists of a hose section which is equal to that inserted between the tabs 9 of the carrying band 8. The te section 16 is meant to indicate the degree of expansion of the flexible hose under the carrying band 8 since the latter is not visible and therefore cannot be controlled by the person filling the hose with air. Fig. 4 shows that the tabs 9 have such height that they are dispos around the periphery of the shaft 1 without considerable gap. The end of the test section 16 is connected to a pressure source which can be a usu bicycle pump. The hose is filled to a pressure which permits a certain axial movement of the carrying band on the shaft and is then displaced under the transmitter segments 6 and centered very accurately so that on end of the band will be completely aligned with one edge of the stator segment. When this alignment has been carried out and the two bands have been placed in correct position on the shaft relative to the two stators and 5 the pressure in the hose is increased whereby it is immovably fixe around the shaft. After a certain time the air pressure in the hose 10 i controlled in order to establish that it has not been decreased. The flexible tube 15 is then tied up in the way shown on Fig. 5 and a curing glue is applied to the hose on both sides thereof so that the tabs will also be embedded in the glue 17 in the way shown on Fig. 6. The end of flexible tube is then cut off and the tied-up end is put under the carrying band where it is fixed. Applying the glue outside the hose wil have the effect that if an air leakage occurs in the hose the glue will be compressed between the shaft and the carrying band which will furthe increase the strength of the glue joint.

Claims: G Claims 1. Transmitter arrangement for a rotatable shaft comprising a roto in the form of a cog-wheel device which is mounted on the shaft and a stator which is rigid relative to the rotatable shaft and is adapted for connection to an AC voltage source for generating electrical signals whi depend on the angular position of the rotor relative to the stator, characterized in that the cog-wheel device comprises a folded cog band of magnetic material which is attached to a carrying band provided with means for assembling the cog band device around the shaft, the carrying band being provided with radially extending guide members on the surface facing the shaft, said guide members being arranged for axial guidance o a hose to be filled with a fluid, said hose being insertable between the guide members and when filled with said fluid expanding both around the periphery of the shaft and against the carrying band to fix and centre t cog band device on the shaft. 2. An arrangement according to claim 1, characterized in that the radially extending guide members comprise two rows of tabs being stamped out of the carrying band, the hose being insertable between said rows of tabs which have such height that the inner diameter of the carrying band in assembled position around the shaft is substantially as great as the shaft diameter. 3. An arrangement according to claims 1 and 2, characterized in th the cog teeth and the tabs have the same pitch, and that the folded cog band is thus positioned on the carrying band that the pitch distances coincide along the periphery. 4. An arrangement according to claims 2 and 3, characterized in th the tabs in the two rows are mutually displaced a cog pitch whereby the distance between tabs in the same row will be two cog pitches. 5. An arrangement according to any of the preceding claims, characterized in that the folded cog band is provided with an odd number of cogs. 6. A transmitter arrangement for measuring angular differences bet ween two cog wheels which can be mounted on a shaft, comprising voltage supplied stator elements in the form of segments which are disposed arou the periphery of the shaft and are rigid relative to the shaft, each of which being intended to cooperate with a cog wheel for generating electrical signals which depend on the angular position in space of the OfttPI cog wheels, characterized in that each cog wheel comprises a folded cog band of magnetic material which is attached to a carrying band being provided with means for assembling the cog wheel device around the shaf said carrying band being provided with radially extending guiding membe on the surface facing the shaft and intended for axial guidance of a ho which can be filled with a fluid, said o-i≤e being insertable between th guide members and at filling with the fluid expanding both around the periphery of the shaft and against the carrying band for fixedly mounti and centering the cog-wheel on the shaft. OMPI

Inventors: BYSTROEM KARL, KARLSSON ERIK, KIHLBERG GUNNAR, REIT HENRY, BYSTROEM, KARL, KARLSSON, ERIK, KIHLBERG, GUNNAR, REIT, HENRY
Applicants: JUNGNER MARINE AB
Application year: 1984
Main classification: G01B7
IPC codes: G01B7, G01L3