CA1050920A

CA1050920A - Indexing drive system

Info

Publication number: CA1050920A
Application number: CA249,341A
Authority: CA
Inventors: Stanley Howden
Original assignee: Canadian General Electric Co Ltd
Current assignee: General Electric Canada Co
Priority date: 1976-04-01
Filing date: 1976-04-01
Publication date: 1979-03-20

Abstract

ABSTRACT OF THE DISCLOSURE
A conveyor arrangement is provided wherein a chain or belt which conveys or serves to drive the conveyor is itself driven by accurately controlled repetitive steps through a rotary drive mechanism powered by a linear actuator. A simple interlock arrangement precludes backward motion. The arrangement is highly reliable, in requiring minimal maintenance or servicing while being suited for accurate operation in hazardous environments such as under heavy irradiation associated with handling of highly radioactive nuclear fuel.

Description

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This invention is directed to a positioning mechanism and is particular to a linear actuakion system suit-able for use in a nuclear environment.
The functional requirements for actuation system~
are largely affected by the need for reliability, the requisite accuracy of operation, and the demands imposed by environmental conditions.
In the case of nuclear fuel handling facilit;Les for the handling of u~ed fuel bundles, it is often desirab]Le for the fuel transporting appara~us to function under water, in an irradiated environment. m e placement of the ~uel carriers whilst recei~ing fuel requires considerable accuracy in view of the susceptibility o used nuclear fuel to damage, and the hazardous nature of the material involved, if relea~ed from the element sheaths.
Apparatus provided in accordance with the present disclosure comprises a conveying device having a linear acting prime mover pivotally connected in driving relation with a transmission output member of predetermined diameter, tension transmitting means engaging the output member in driven relation therewith, and indexing means regulating the extent o~ rotation of the output member in response to ~ working stroke of the actuator whereby a conveying step of predetarmined travel is imparted to the tension transmitting means on completion of a working stroke of the prime mover.
Certain embodiments o~ the invention are described, reference being made to the accompanying drawings, wherein:
Figure 1 i~ a part-sectioned elevation of the device taken at 1-1 of Figure 3, showing the actuator in the extended, end-of-stroke position;
Figure 2 is a view similar to Figure 1, with the actuator retracted to commence a new stroke, and . ..

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Figure 3 is an end elevational view of the device with ~he cylinder of the actuator the ratchet and the conveyor chains omitted.
Referring to the drawings, the apparatus 10 comprises a linear actuakor 12 in driving relation with a rotary assembly 14, to which a pair of chains 16 are connl-cted in driven relation, only one of the chains being shown, in Fig. 1. The chains 16 act in tension to drive a conveyor (not shown? and are referred to as tension transmitting means~
The actuator 12 is of the double acting hydraulic type. In the case of a nuclear spent-fuel installation wherein the actuator 12 may be positioned under water in a spent fuel bay, the water source might well comprise either make up water or filtered water recirculated from the bay by a suitable pres~ure pump, so that leakage past the actuator rod gland can be ignored. The actuator 12 has a casing 18, a piston rod 20 with a head 22 and a wrist pin 24. The casing 18 is pivotally mounted at 19 to accommodate to the pivoting mot~on, as indicated by the arc of travel 25 of the wrist pin ~4. The wrist pin 24 being free to rotate about its own axis serves as a bearing.
Referring to Figure 3, the rotary assembly 10 comprises a ~haft 31 ro-~atably supported on pedestals 32, having sprocket~
33, 33 keyed to the outer ends in the usual ~ashion, over which sprockets respective chains 16 are trained. A pair of cam plates 34 are located in k~yed relation on a mid-portion of the shaft 31, having the actuator head 22 secured therebetween by engagement of the opposed ends of the wri~t pin 24 within respective recessed cam track~ 36. The actuator heacl 22 fits snugly between the c>pposing faces of the cam plate~ 34, so as topreclude any twisting about the longitudinal axis of piston rod 20 and consequent canting of pin 24. ~he square arrangement of cam tracks 36 which are recessed into the surfac!e vE the ~ 2 --.

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respective cam plates 34 intersect at driving lobe rece3ses 37 into which the ends of wri~t pin 24 fit i.n driving engagement for a driving or expansion stroke, as shown in FigO 2, and from which the wrist pin 24 can be freely withdrawn along the cam track at the end of a driving stroke, shown in Fig. 1~
The peripheral outer surfaces a,f cam plates 34 also form cam surfaces, having straight portion~ 35, arcuate portions 38 and protruding step portions 39 located therebetween.
A resilient ratchet 42 comprising a plate spring engage~ the trailing abuttment face 41 of a step 39O
An abuttment or stop 40 s~ecured to the cylinder 18 engages a respectîve leading abuttment face 43 of a step portion 39 at the end of a working or expansion stroke of actuator 12, when the rod 20 is fully extended and in a horizontal position. In this po~ition the rotary asslembly 14 isl ma.intained secure in a loclced position by the wris~t pin 24 and by engagement o~ stop 40 with ~tep 39. Reversal of the application of hydraulic ~or pneumatic) pressure to the front face of the piston (nnt shown) of actuator 12 serves to with-draw the wrist pin 24 horizontally along the lowermos~t cam track 36, during which time, motion of the cam plate 34 in a clockwis~e sense is precluded :by the stop 40 and in a counter-clockwise slense by ratchek 42, each engaging a step 39O ~oweverO
at the end of the withdrawal stroke of actuator 12, the wriqt pin 24 drops downwardly or is moved by an external f~rce e.g. spring (not shown) into the recessed lob~ portions 37, -thereby displacing the outer or left hand end of actuator 12, so as to disengage the stop 40 from the cam plate 34n Upon application of fluid pressure to provide another expansion stroke of actuator 12, the cam plates 34 are driven through a further 90 of rotation~ cau ing a corres;pc)nding motion tc the chains 16, by way of s~prockets 33.

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It will be understood that the provision of a simple pressurized fluid supply with a 3-way control (not illustrated~
provides controlled operation of the device a5 desiredO
The diameter of the sprockets 33 determines the distance of travel of the conveyor chains 16 for each working stroke of the actuator 12.
It will be evident that more or less than four working strokes per revolution can be provided, by the provision of appropriately modified cam plates. m e cam plates sexve as a form of transmission indexing means and are referred to as such.
It is contemplated that alternative arrangements can be provided for the run of chains 16. Al~o tooth belts and equivalent may be substituted.
The use of gaseous as well as liquid pressure fluids in the actuator 12 is contemplated. In suitable environments solenoid actuators may also be employed.

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Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A discrete-step conveying device having a fluid pressure actuated linear acting prime mover actuator of predetermined stroke pivotally connected in substantially linear driving relation with a transmission output member of predetermined diameter, tension transmitting means engaging the output member for rotational displacement thereby, and indexing means including return restraint means regulating the extent of rotation of the output member in response to a working stroke of the actuator, whereby a conveying step of predetermined travel is imparted to the tension member means on completion of a working stroke of the prime mover.

2. The device as claimed in claim 1 wherein said prime mover is a piston and cylinder device operable by fluid pressure in an expansion mode and a contraction mode.

3. The device as claimed in claim 2, said indexing means including first stop means positioned by said prime mover in a first position to lock said conveying device in a sub-stantially immobilized condition, and withdrawable to a second, unlocked position.

4. The device as claimed in claim 3 wherein said first stop means are mounted on said prime mover for displacement therewith relative to said transmitting means.

5. The device as claimed in claim 2, said indexing means including second stop means having a ratchet to assure uni-directional rotation of said output member.