A BLOCKING DEVICE FOR OBJECTS CONVEYED UPON A CONVEYOR TRACK

Abstract: An engageable and disengageable blocking device for objects (1) conveyed upon a conveyor track (2) incorporates a catch finger (4) displaceable at an oblique angle (α) to the normal of the conveyor track (2), whereby the acceleration of said finger at displacement to an release position can be bigger than the start acceleration of the object (1) after release thereof. It is thereby avoided that the catch finger due to sliding and friction against the object (1) will cause wear.

Description: A BLOCKING DEVICE FOR OBJECTS CONVEYED IJPON A CONVEYOR TRACK The invention refers to a blocking device of the type defined in the preamble of claim 1. When conveying objects along a conveyor track, e.g. a chain conveyor, it is often necessary in some positions and at certain times to stop the movement of the objects along the conveyor, whereas the propulsion of objects in other parts of the track is maintained. For this purpose it is earlier known to use movable stop lugs, which can be displaced into and out of the motion track of the objects. The lugs thereby are designed as pivotable rocker arms or axially displaceable catch fingers, which are movable perpendicularly to the motion direction of the conveyor track. Rocker arms incorporate several components and are therefore rather expensive and complex, whereas a catch finger, movable perpendicularly to the conveyor track, will cause wear to the arrested object, when the finger is displaced in order to release the object. and thereby engages a surface thereof. It is certainly possible to reduce the friction between the finger and the object. e.g. by providing the finger with a roller supported thereupon and contacting the object. but this step will make the device more expensive and complex. The purpose of the present invention is to provide a blocking device of the type mentioned in the preamble, which is simple and inexpensible to manufacture, which has a simple function and which will not subject the objects arrested to wear when the blocking device is moved to release position. According to the invention this is achieved thereby that the blocking device is made with the features defined in claim 1. Such a device can be made with one movable part only, which does not slide along the arrested object, when the catch is released. The invention is hereinafter further described with reference to the accompanying drawing, which shows a diagrammatic longitudinal section through a device according to one embodiment of the invention. An objet 1, e.q. a load carrier in a transport system, is An object 1 , e.g. a load carrier in a transport system, is arranged upon a conveyor track 2, e.g. a chain conveyor with driven chains, whereupon the object 1 rests. The object is thereby fed in the direction of the arrow. A blocking device is provided at a position along the conveyor track in order to control the feed of objects along the track The be blocking device incorporates a casing 3 which can be attached in a desired position to the conveyor and in which casing is arranged a catch finger 4 displaceable into and out of the motion track of the objects, said catch finger in arresting position contacting a forward end surface of the object, thus that this can not pass the blocking device but stops in a predetermined position, whereby the propulsion power e.g. from the friction force of the object against a driven chain will be absorbed by the catch finger 4 and the blocking device. The power thus absorbed is dependent of such factors as the weight of the object and the friction coefficient in the contact between the object and the chain. The catch finger is slidably supported in a recess in the casing 3 adapted to the shape of the be finger. When the object shall be released from the blocking device and be moved further, the catch finger must be removed from its arresting position, and this is achieved thereby that it is displaced in its longitudinal direction. In the embodiment shown the displacement is effected by introduction of a pressure medium through a conduit 5 arranged to extend through the casing 3 into a cylindric bore in which is displaceably arranged a plunge 6 which is connected to the catch finger 4. The plunge and thereby also the catch finger are thereby displaced against the action of a spring 7, which returns the catch finger to arresting position, when the supply of -pressure medium and the pressure upon the plunge ceases. If the catch finger EMI2.1 <tb> durin,tt <tb> displacement to release position moves perpendicularly to the conveying direction of the object, then sliding and therefor friction and wear will occur in the contact between the object and the catch finger. This can, according to the invention, be avoided if the catch finger is arranged thus that it is displaceable rectilinearly in a direction forming an oblique angle with the surface of the conveyor track in front of the blocking device, and the displacement to release position is effected with a movement component, pointing in the same direction as the direction of the object motion. The angle and the acceleration of the finger thereby can be adapted so that the acceleration component in the movement direction of the objects conveyed in the conveyor track will be bigger than the acceleration of an object which is momentarily released from a movement preventing catch. An object conveyed upon a chain conveyor when being released obtains an acceleration of the size p . g, where p = the friction coefficient at the contact between the chain and the object and g = the gravitational constant, whereby the acceleration component in the transport direction of the objects at the catch finger shall be bigger than this value, i.e. p . g < a sina wherein a = the angle formed by the finger against the normal of the surface of the conveyor track and a = the acceleration of the finger in the direction of movement at the releasing movement. During normal conditions to bring about this it is sufficient to connect the conduit 5 to a conventional pressure air duct, via a valve, which can be rapidly opened. If an extremely rapid acceleration is required it is possible e.g. to provide the outlet of the conduit 5 in the cylindric bore in the casing 3, which bore contains the plunger 6, with means which at a certain pressure will give a momentary pressure medium impact, whereby the elasticity and inertia depending on the valve and the volume of the conduit 5 are eliminated. The surface of the object 1 which contacts against the catch finger is generally arranged essentially perpendicularly to the extension of the track 2. It is therefor often more expedient if a portion of the catch finger has a surface intended for contact against the object 1 provided at the free end of the finger which surface extends perpendicularly to the motion direction of the object in the track This can most simply be obtained by providing the free end of the catch finger with a chamfer 8. A device according to the invention may have other designs and it can be used in other connections than those described hereintefore. The device may as an example be used at inclined conveyor devices, wherein the objects are driven by the attraction of gravity. The displacement of the catch finge-r can be effected with other than pressure medium based means, e.g. electro magnetical or mechanical. The shape of the catch finger can be adapted to objects of different types and it is preferably such that the finger is allowed to be axially displaced but is prevented from being rotated in the casing 3.

Claims: CLAIMS 1. Engageable and disengageable blocking device for arresting the motion of an object (1) conveyed on a conveyor track (2) and actuated by a continuous propulsion power, incorporating a catch finger (4) displaceable into and out of the motion track of the objects, which catch finger in an arresting position contacts a forward end surface of an object, characterizedtherein, that the catch finger is displaceable rectilinearly in a direction forming an oblique angle (a) with the surface of the conveyor track in front of the blocking device, the displacement to release position thereby taking place with a motion component pointing in the same direction as the direction of motion of the-objects.2. A blocking device as claimed in claim 1, characterized therein, that a portion (8) of the catch finger at the free end thereof has a surface extending mainly perpendicularly to the direction of motion of the object in the track.

Inventors: ADOLFSSON, RUNE
Applicants: SKF NOVA AB
Application year: 1986
Main classification: B65G47
IPC codes: B65G47