GB2138094A

GB2138094A - Device for converting uniform rotary motion into variable speed rotary motion

Info

Publication number: GB2138094A
Application number: GB08408506A
Authority: GB
Inventors: Luigi Pazzaglia
Original assignee: Cefin SpA
Current assignee: Cefin SpA
Priority date: 1983-04-12
Filing date: 1984-04-03
Publication date: 1984-10-17
Also published as: DE3411922A1; IT8303395A0; FR2544438A1; IT1168668B; GB8408506D0

Abstract

A coupling device able to convert uniform rotary motion into variable speed rotary motion in accordance with a non-harmonic law, is fitted between a driving shaft (2 or 3) rotating at a constant speed and a misaligned driven shaft (3 or 3) virtually parallel to the former. The device comprises an engaging element (6) fixed rigidly in an eccentric position to one extremity of one of the said two shafts, and a slot (8) that is located on the extremity of the other shaft and extends perpendicularly to the axis of this, the engaging element and the slot cooperating in such a way as to convert the uniform rotary motion of the drive shaft into variable motion for the driven shaft. <IMAGE>

Description

SPECIFICATION Device for converting uniform rotary motion into variable speed rotary motion The invention relates to a device for converting uniform rotary motion into variable speed rotary motion.

In particular, the invention relates to a device defined by a coupling especially suitable for machines on which it is necessary to carry from one operating station to the next, or between an operating station and a store where unfinished or finished products are warehoused, parts that have to be subjected to particular machining operations.

As is known, machines of the above mentioned type are generally provided with a chain conveyor or other similar means provided with teeth for picking up the parts, the speed of which is virtually constant.

On other types of machines, the conveypr means are constituted, instead of by chains and pick-up teeth, by slides operated by connecting rod-crank mechanisms.

When the foregoing is applicable, the motion of the conveyor means is substantially of simple harmonic type.

In certain situations, however, neither conveyor means provided with virtually constant speed nor ones whose speed is variable in a simple harmonic fashion are satisfactory. It can, in fact, be desirable for the conveyor means to run at variable speeds in a nonharmonic fashion. Such a requirement exists, for example, when a part has perforce to be withdrawn at a reduced speed, in such a way as to avoid damage or errors in positioning the part, and then the speed has to be increased so as to reduce as much as possible down time due to the displacements of the parts to be machined. Furthermore, it can also be necessary to reduce the speed at which a part is transferred from the conveyor means to a receiving station.

To cater for the foregoing, the technical task at the basis of the invention is to make available a device able to furnish variable speed rotary motion out of uniform rotary motion.

Within the framework of the technical task, one object of the invention is to make available a coupling able to convert uniform rotary motion into variable speed rotary motion which can, furthermore, be connected to means able to convert, when this is necessary, the variable speed rotary motion into variable speed linear motion.

A further object of the invention is to create a coupling that can be connected to means of the connecting rod-crank type so as to obtain linear reciprocating motion of substantially non uniform type.

Yet another object of the invention is to make available a coupling whose manufacturing costs are particularly low, in such a way as to render the use thereof in machinery of any type inexpensive and opportune.

The said technical task and the objects mentioned above, as well as others too many will become more apparent hereinafter, are attained by the device forming the subject of the invention designed to be fitted between a driving shaft rotating at a constant speed and a misaligned driven shaft parallel to the former, and characterized by the fact of having an engaging element fixed rigidly in an eccentric position to one extremity of one of the said shafts facing one extremity of the other shaft, and a slot provided in the said extremity of the latter and extending in a direction virtually perpendicular to the said last mentioned shaft, the said engaging element being inserted in the said slot in a way whereby it is able to slide so as to convert the uniform rotary motion of the said driving shaft into variable rotary motion for the said driven shaft.

Further characteristics and advantages of the invention will become more apparent from the description of one preferred, though not sole, embodiment for the device, given purely as an unlimited example with reference to the accompanying drawings, in which: Figure 1 shows the device forming the subject of the invention in a lateral view, partially in sectional form; Figure 2 shows, in a view perpendicular to that in Fig. 1, in a diagrammatic and functional way, the paths followed by the various components of the device.

With reference to Fig. 1, the device according to the invention is shown globally at 1.

Structurally a coupling, the device in question consists essentially of two shafts 2 and 3, the axes of which though parallel one with the other are not aligned, and between one and the other there is a spacing or eccentricity e.

Provided on the two extremities of the shafts 2 and 3 that face one another are two elements, for example discs, one per shaft, shown at 4 and 5, respectively.

Each of the said discs is coaxial to the shaft on the extremity of which it is placed and thus is staggered with respect to the other disc to the same extent as are the shafts 2 and 3, one with respect to the other.

Fixed to the side of the disc 4 turned towards the disc 5 is an engaging element 6, shaped in the form of a roller, supported by a spindle 7. The said engaging element or roller 6 is eccentric with respect to the disc 4 and the centre axis of the former is parallel to the axis of the shaft 2 to which the said disc 4 is fixed.

In disc 5, instead, is machined a slot 8 inside which fits the roller 6 in a way whereby it is able to slide.

A broken line in Fig. 2, shown at 9, indicates the path followed by the roller 6 wherein a constant radial distance apart corresponding to the radius R is maintained from the centre of the disc 4 integral with and concentric to the shaft 2.

The spacing of the said roller 6 from the centre of the disc 5 and of the corresponding coaxial shaft 3 varies, instead, from a minimum to a maximum, as exemplified in Fig. 2 with radii A, close to the minimum radius, and radius B, close to the maximum radius.

When describing the operation of the coupling according to the invention, it is supposed initially that the driving shaft be the shaft 2 and that the driven shaft be the shaft 3.

At the time the driving shaft 2 is carried in uniform rotary motion by suitable known means not illustrated herein, with it revolves the disc 4 and the roller 6 integral with the latter. The path 9 followed by the roller 6 is concentric with the shaft 2 and, therefore, with a contant radius of curvature R. On account of the constancy of the radius R and of the angular velocity of the shaft 2, the roller 6 moves at a constant tangent velocity.

The driven shaft 3 is, instead, made to rotate at a variable speed since the position of the roller 6 along the slot 8 varies, as does, therefore, the distance the said roller is away from the axis of the driven shaft 3.

As stated above, the tangent velocity of the roller 6 is constant and thus the variations in radius intercurrent between the path 9 and the axis of the driven shaft 3 become variations in the angular velocity of the latter, this being because of the known mathematical expression V = a.R intercurrent, as the radius R varies, between the tangent velocity V and the angular velocity a?.

A connection of this type can be particularly advantageous in machines provided with a system for moving from one station to the next, parts undergoing machining operations.

It can be usefully employed, for example, in an automatic metal container forming-welding machine, for withdrawing the formed containers at the exit of the rollers and displacing them towards the welding station.

In this, as in similar cases, all that has to be done is to key on to the shaft 3, a pinion that operates a chain or rack provided with transportation teeth interspaced by an amount corresponding to the pitch circle length of the pinion.

After one revolution of the shaft 3, the next tooth takes over, in this way, the position the preceding tooth occupied.

The movement of the chain and of the teeth takes place, in this instance, at a variable speed and the device can easily be designed in such a way that the tooth moves at a decreased speed at the time of withdrawing the part, and then accelerates during the travel towards the subsequent station.

Assuming now that the shaft 3 is utilized as the driving shaft operated at a constant speed and that the shaft 2 is the driven shaft operated at a variable speed, in this second possibility the slot 8 rotates at a constant angular velocity and the roller 6 is compelled to slide at an angular velocity that is always constant with respect to the centre of rotation of the driving shaft.

However, the distance the said roller is away from the centre of rotation varies constantly with the sliding motion thereof along the slot 8 and, therefore, the tangent velocity of the roller varies continuously. Since the said roller is integral, through the disc 4, with the driven shaft 2, the said constant variations in the tangent velocity become variations in the angular velocity of the driven shaft 2.

The said type of device can be gainfully employed in a press of the automatic type for, withdrawing the strips from where they are stored and transferring them underneath the moulds: the strips can, in fact, be displaced with a particularly gentle and advantageous movement since the press has to operate at a high speed Thus with the advice according to the invention, the proposed objects are indeed achieved.

It is stressed that by varying suitably the eccentricity between the shafts 2 and 3 and by selecting one or the other as the driving shaft, it is possible to obtain results that suit the most varied requirements. Furthermore, the structure of the device is very simple and easily realizable at a low cost.

The invention as described herein is liable to undergo numerous modifications and variants, all of which falling within the conceptual framework thereof.

In particular, the applications to which reference has been made are purely indicative and must not be taken as binding for this type of device, which can be adopted in a considerable variety of ways.

All parts may be substituted with others of technical equivalence.

In practice, the materials used, as also the shapes and sizes thereof, may be any depending on the requirements.

Claims

1. Device for converting uniform rotary motion into variable speed rotary motion, to be fitted between a driving shaft rotating at a constant speed and a misaligned driven shaft parallel to the former, and characterized by the fact of having an engaging element fixed rigidly in an eccentric position to one extremity of one of the said shafts facing one extremity of the other shaft, and a slot provided in the said extremity of the latter and extending in a direction virtually perpendicular to the said last mentioned shaft, the said engaging element being inserted in the said slot in a way whereby it is able to slide so as to convert the uniform rotary motion of the said driving shaft into variable rotary motion for the said driven shaft.

2. Device according to Claim 1, characterized by the fact that the said driving shaft and the said driven shaft each have, on the extremities thereof facing one another, a disc shaped element coaxial to the axis of the corresponding shaft, and wherein the said engaging element is fixed eccentrically to one of the said disc shaped elements, while the said slot is machined in the other disc shaped element.

3. Device according to Claim 2, characterized by the fact that the said engaging element is fixed to a disc shaped element integral with the said driving shaft, and that the said slot is machined in a disc shaped element integral with the said driven shaft.

4. Device according to Claim 2, characterized by the fact that the said engaging element is fixed to a disc shaped element attached to the said driven shaft, and wherein the said slot is machined in a disc shaped element attached to the said driving shaft.

5. Device for converting uniform rotary motion into variable speed rotary motion, substantially as hereinbefore described with reference to the accompanying drawings.