GB2187696A - Feed mechanism for workpieces - Google Patents

Abstract

A feed mechanism for workpieces 10 comprises an arm 12 having means e.g. suction gripper 13 engageable with the workpiece. The arm is movable so that the workpiece is conveyed from an arm loading position B to an arm unloading position A. Workpieces are moved to the position B by means of a belt 15 onto which the workpieces can be loaded by hand or from a magazine. The belt runs over the upper surface of a base plate 14 which carries adjustable guide plates 17. The base plate also mounts adjustable stop plates 16 which accurately locate the workpiece at the position B. The conveyor movement is halted when a workpiece arrives at position B. <IMAGE>

Description

SPECIFICATION Feed mechanism This invention relates to feed mechanism for workpieces and the like, for exampleforfeeding workpiecesto a machine tool.

The feeding ofworkpiecesto a machine tool for example a power press can be effected entirely by hand. In this case when the power stroke of the press has been completed the worked component or workpiece is removed from the tool and a new workpiece inserted following which a guard is closed and the press caused to partake of a power stroke after which the guard is raised or opened and the process repeated. The degree of effort expended by the operator is considerable even when the component is small. Moreover machinetime is lost inthe raising and lowering oftheguard and in spite of safety devices accidents can happen.

It has been proposed therefore to install feed mechanism for feeding the workpiece to the press.

The form ofthefeed mechanism depends upon the so-called production run oftheworkpiece. Some presses will be installed which are only intended to deal with one form of component and in this case the feed mechanism will be designed to deal only with thatworkpiece. In some cases the production run will only be a few hours in which case it is clearly uneconomic to design a feed mechanism which can only deal with one form of workpiece. Feed mechanisms have therefore been designed which can be altered fairly quickly to deal with different workpieces. Such alteration has generally required the replacement of one magazine by another, the magazine serving to hold a stack ofworkpieces to be worked.Although the magazines are comparatively simple structures they are in most cases of a construction which is peculiarto a particular workpiece. Moreover, since the workpieces are often taken from the top of the stack it is necessary to providesome sortofgate as an internal partofthe magazine which acts particularly in the case of flat workpieces,to ensure that only one workpiece at a time is fed to the press. In order to utilize the feed mechanism to feed another form ofworkpiece it is therefore necessary to utilize a different magazine.

The object of the present invention is to provide a feed mechanism for the purpose specified in a simple and convenient form.

According to the invention a feed mechanism for workpieces comprises a reciprocable arm, means carried by the arm engageable with aworkpiece which is located in use at an arm loading position, the arm being movable two an arm unloading position at which in use the workpiece is released following which the arm is returned to the arm loading position, conveyor means for delivering workpieces in turn to the arm loading position, a drive mechanism forthe conveyor means and means operable to halt the movement of the conveyor means when in use, a workpiece arrives at the arm loading position.

An example of a feed mechanism in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure lisa diagrammatic plan view of the feed mechanism, Figure2 is a side veiw of part of the mechanism of Figure 1 showing a modification foroneform of workpiece, Figure3is a viewsimilarto Figure 2 showing an alternative form of workpiece, and Figure4is a viewsimilarto Figure 2 showing a further modification.

In Figure 1 of the drawings the arrow A indicates the centre point of a press tool to which a workpiece 10, in this case a flat disc, has to be delivered. The workpieces are delivered one at a time to a position B by means of a conveyor means generally indicated at 11 and the workpieces are transferred one at a time from the position B to the press tool by means of a reciprocablearm 12 to which is attached in the particular example, a suction cup 13which engages the upper surface of a workpiece at position B. The cup can be replaced by a magnet with an air oerated release mechanism. When the power stroke ofthe press is completed the workpiece is ejectedfrom the press tool by an ejector mechanism (not shown) which may be actuated by the control system ofthe feed mechanism.Following ejection of the componentthe workpiece at position B is gripped by the suction cup, the arm 12 raised slightly to allow the workpiece to clear the sides of the conveyor means and then the arm is extended until the new workpiece lies over the press tool following which the arm is lowered, the suction cup released, the arm raised and returned to the position shown ready to grip a fresh workpiece when so required. To ensure release ofthe component the suction cup can be momentarily pressurized with air upon release of the vacuum.

The conveyor means 11 comprises a base plate 14 which is adapted to be secured relative to the press so that the upper surface ofthe plate is more or less at the same level as the upper surface ofthe lower part of the press tool. At opposite ends of the base plate apertures are provided in which are located pulleys aboutwhich is located an endless belt 1 Sthe upper run ofwhichslidesovertheuppersurfaceof the base plate. A drive mechanism not shown, is provided to drive the belt so that the upper run ofthe belt moves towards the position B. The belt is formed from a hard wearing material and the arrangement is such that a workpiece placed upon the belt will be moved by the belttowards position B.

The drive mechanism comprises a drive motor and a clutch which can be disengaged to stop the movement ofthe belt. Conveniently the clutch is a pneumatically operated dog clutch.

The movement of a workpiece when it arrives at position B is arrested by a stop which takes the form of a pair of mutually inclined upstanding stop plates 16. Each plate is conveniently formed by one limb of an "L" shaped member which can be secured to the base plate at any desired position. The mutual inclination of the plates 16 acts to locate the workpiece. For guiding the workpieces as they are moved overthe base plate towardsthe aforesaid stop plates 16, a pair of spaced guide plates 17 are located on opposite sides of the belt. These are formed in a similar mannerto the plates 16 and the base plate is slotted to aliow a wide range of adjustmentofthe plates.

In orderto minimisethe required vertical movement ofthe workpiece in orderto clearthe sides of the plates 17 the latter are of reduced height in the region of position B.

The arrival of a workpiece at position B is detected by means of a sensor 18 which includes a depending hinged arm the lower portion of which is engaged by the workpiece. The signal obtained from the sensor 18 is utilized to control the aforesaid clutch so that as soon as a workpiece arrives at position B the belt is halted. This releasesthe pressure exerted bythe following workpieces.

With the mechanism as described workpieces can be fed in turn onto the conveyor by an operatorwho is no longerinvolved in operating the guard of the press. The task of feeding the press isthereforemade much easier. If it is required to feed a different size of disc it is a simple matter two adjustthe distance between the plates 17 and also the positions ofthe stop plates 16 and sensor 18, the plates 16 requiring adjustment to ensure that the workpiece is correctly deposited in oron the press tool. Many shapes of workpieces can be fed and instead of flat plates they may have peripheral flanges, as long as the workpiece has a surface which can be engaged by the suction cup and can be located by the stop plates.

In the case of flat workpieces it may be more convenient to feed the workpieces from a stack. This can be achieved using the above described mechanism. In this case the guide plates 17 are utilized to engage opposite faces of the workpiece in the stack. The lowermostworkpiece rests on the belt and in orderto prevent the whole of the stack being moved by the belt, a stop bar 19 is provided and which and which extends transversely relative to the belt. The stop bar carries a depending stop member 20 (Figure 2) or members which engage an end surface or surfaces ofthe workpieces. The lower edge ofthe or each stop member is spaced from the upper surface of the belt by a distance about 1.5 times the thickness of the workpiece so that only one workpiece at a time can pass to position B.The use of the stop member is desirable even when workpieces are being fed by hand to the conveyor.

The base plate 14 is adapted to be secured to a mounting plate which is secured to the frame ofthe press, and which mounts the drive mechanism for the arm 12. Conveniently the mounting plate is carried on a hinge assembly which is in turn secured to the press. This allows the complete feed mechanism to be swung out of the way when it is required to change the press tool. The latter includes a first piston cylinder combination for reciprocating the arm and a second piston cylinder combination for raising and lowering the arm of a part thereof.

The operation ofthe first and second piston cylinder combinations, the operation ofthe suction cup and the operation of the ejector mechanism associated with the press is underthe control of a microprocessor based control system which receives signals from various sensors located about the mechanism.

In the previous description it has been assumed that the workpieces are flat. In practice workpieces are often not flat particularly where a workpiece is formed by a blanking operation from sheet material.

If the workpieces are thick and the total distortion is less than half the thickness of the workpiece then the mechanism as described can be used. However, if the total distortion is greater, then with the concave side down the workpiece will pass only partway beneath the stop member, and with the concave side up, theworkpiece will not pass beneath the stop member.

With reference to Figures 2 and 3 of the drawings the base plate of the feed mechanism is shown at 14 with the belt being shown at 15 and driven in the direction of the arrow. The stop bar is shown at 19 and its lower end it is provided with a stop member 20 engageable with the leading edge of a nominally flat workpiece 21. The workpieces are loaded as a stack, the stack being located in the transverse direction by means of adjustable side members (not shown) which are mounted on the base plate.

The edges of the workpieces remote from the stop member are supported on inclined surfaces 22 which are conveniently formed on support members 23 which are adjustably mounted on said side members. The surfaces 22 decline in the direction of movement of the belt and the support members 23 are spaced from the stop member 20 such thatthe smallest dimension between the surfaces 22 andthe stop member is less than the length of the workpieces. If workpieces are loaded with their concave surfaces uppermost as shown in Figure 2, the leading edges of the lowermostworkpiece considered in terms of the movement of the belt, will be held clear of the beltwhilstthe trailing edges i.e.

the edges adjacent the stop member, will be contact with the belt thereby providing three point support fortheworkpieces. The spacing of the stop member 20from the surface ofthe belt is about 1 .5timesthe thickness of the workpieces so thatworkpieces will pass beneath the stop member 20 one at a time, such movement being as a result of contact between the workpiece and the belt and by virtue of the inclination of the surfaces 22 which produces a reaction force on the workpiecestending to move them in the direction of movement of the belt.

Figure 3 shows the situation when the workpieces are loaded with their convex sides uppermost. In this case the trailing edges of the lowermostworkpiece will again be engaged with the belt but due to the curvature oftheworkpiece it may not pass beneath the stop member. The stop bar 19 and stop member 20 are therefore constructed so that they can move upwardly away from the belt as a workpiece moves underneath. The stop member will still be effective to prevent more than one workpiece being fed atthe same time.

The stop bar and stop memberforthe purpose of the aforesaid movement may be mounted on a pair of hinged armswhich hinge in thevicinity ofthe support members 23 on the aforesaid side members.

Alternativelytheycan be mou nted for vertica I movement and urged downwardly by gravity with assistance if required, buy a spring.

The form of the stop member 20 depends upon the shape of the trailing edge, as previously defined, of the workpiece and it is preferable to have a single stop member so that there is three point contactwith the workpieces. Some workpieces may have tags bent up from the general surfacethereof and in this case the stop member has to be shaped and positioned to avoid the tags and in some casestwo stop members may be required.

In some cases nominally flatworkpieces will have a substantial amount of fraze at their edges so much so as to prevent their being fed under the stop bar by the combined action ofthe belt and the inclined surfaces 22 on the support members 23. This porblem can be overcome by modifying the support members as shown in Figure 4 at 24. The support members 24 are movable by a piston cylinder combination 25 and have a short inclined surface 26 the upper portion of which leads into a substantially vertical step 27.In the retracted position of the support members the lowermostworkpiece of the stack of workpieces engages the surfaces 26 adjacent the stops 27 and the depth of the steps 27 is lessthan the thickness oftheworkpiecessothat when the support members 24 is moved towards the stop member 20 the lowermost workpiece will be positively driven beneath the stop member.

In addition to the clutch there may be located downstream of the stop member 20, a stop pin which is controlled by a further sensor which senses when aworkpiece passes beneath the stop member 20.

This allows the stop pin to fall onto the uppersurface ofthisworkpieceto preventafurtherworkpiece being fed until the first mentioned workpiece has moved to the loading position. The provision of the stop pin can be regarded as essential when dealing with thin workpieces because although the clutch will halt the belt when a workpiece arrives at the position B it is found thatthe following workpieces and even the belt do not stop immediately. Overlap of workpieces can therefore take place which can upset the operation of the suction cup. The same problem can occurwithworkpieceswhich have flanges extending outwardly from theworkpiece and spaced from the base.

In some cases the shape of the workpiece may be such as to allow the conveyor to move theworkpiece towards the position B but to prevent the use ofthe suction cup 13. For example, the workpiece may be of cup shaped form with the base of the cup engaging the conveyor belt.

In such a case the end ofthe arm 12 instead of having the suction cup may have an attachment which forms a three sided recess the open end of which faces the conveyor and into which the workpiece is pushed by the conveyor. In this case the plates 16 are not required. As the arm is moved towards position Athe next article on the conveyor engages the side of the arm to preventfurther movement. When the workpiece reaches position A the arm is raised to disengage the workpiece following which the arm is retracted. It is convenient to arrange that only the end portion of the arm which mounts the attachment is raised and this may be achieved using a piston cylinder combination mounted on the remaining portion ofthe arm. The use of an attachment defining a three sided recess means that only one size ofworkpiece can be properly located. This problem can be overcome and the need for pivotal movement eliminated by forming the attachment with a cut out which defines a stop surface extending transversely of the movement ofthe belt and a "V" shaped recess in the face of the cut out presented to position A. As the arm moves towards the position Atheworkpiece is located by the "V" shaped recess and in orderto ensure location during the initial movement ofthe arm, the surface of the base plate upon which the workpiece rests may be provided with a ridge over which the workpiece is pushed by the arm.

Claims (18)

1. Afeed mechanism forworkpieces comprising a reciprocable arm, means carried by the arm engageable with a workpiece which is located in use at an arm loading position, the arm being movable two an arm unloading position at which in use the workpiece is released following which the arm is returned to the loading position, conveyor means for delivering workpieces in turn to the arm loading position, a drive mechanism for the conveyor means and means operable to halt the movement of the conveyor means when in use, a workpiece arrives at the arm loading position.

2. Afeed mechanism according to Claim 1 in which said conveyor means comprises an endless belt, sensor means for controlling the operation of the drive mechanism, the workpieces being engaged bythe upper surface of the upper run of the beltto propel the workpieces towards the arm loading position, said sensor means being arranged so that the movement ofthe belt is halted when a workpiece is at the arm loading position.

3. Afeed mechanism according to Claim 2 in which the drive mechanism includes a clutch.

4. Afeed mechanism according to Claim 2 or Claim 3 in which the means carried by the arm is engageable with the upper surface oftheworkpiece at the arm loading position.

5. A feed mechanism according to Claim 4 in which said means comprises a suction cup.

6. Afeed mechanism according to any one ofthe preceding claims including a base plate over the upper surface of which the upper run ofthe belt is arranged to move, a pair of adjustable upstanding guide plates located adjacent opposite sides respectively ofthe upper run of the belt, the guide plates acting to guide the movement ofworkpieces towards the arm loading position, and means for locating a workpiece at the arm loading position.

7. Afeed mechanism according to Claim 6 in which the base plate is secured to a mounting plate which in use is hingedly supported in use on a press.

8. Afeed mechanism according to Claim 6 or Claim 7 in which the means for locating the workpiece at the arm loading position comprises a pair of mutually inclined stop plates which are adjustable mounted on the base plate.

9. Afeed mechanism according to any one ofthe preceding claims including a stop member positioned upstream considered in terms of movement ofthe upper run ofthe belt, of the arm loading position, said stop member being positioned above the uppersurface of the upper run ofthe belt and being spaced therefrom by a distance substantially equal to 1 1/2 times the thickness of the workpieces, said stop member acting to prevent more than one workpiece being delivered at the sametimetothe arm loading position.

10. Afeed mechanism according to Claim 9 including a pair of workpiece support members located upstream of said stop member and on opposite sides respectively ofthe upper run of said belt, said support members defining workpiece support surfaces which decline in the direction of movementofthe belt, said supportsurfaces providing two point support of the lowermost workpieces of a stack of workpieces, a third point of supportforthe lowermostworkpiece being provided by the belt

11. AfeedmechanismaccordingtoClaim 10in which said stop member is mounted for movement away from the belt.

12. Afeed mechanism according to Claim 11 in which said stop member is mounted upon a stop bar extending transversely ofthe belt, said stop bar being carried upon a pair of hinged arms.

13. Afeed mechanism according to Claim 10 in which said support surfaces lead at their upper ends into substantiallyvertical steps, said steps having a depth less than the thickness of a workpiece and said support members being movable towards said stop member whereby the lowermostworkpiece of a stack ofworkpieces will be positively displaced from the stack.

14. Afeed mechanism according to Claim 6 in which said guide plates in the vicinity of the arm loading position are of reduced height and said arm is hinged to enable the workpiece to be lifted overthe guide plate.

15. Afeed mechanism according to Claim 2 in which the arm mounts an attachment which is shaped to define a recess into which a workpiece is driven by the belt, the end portion of the arm being hinged to allowtheworkpieceto be disengaged from the attachment atthe workpiece unloading position.

16. Afeed mechanism according to Claim 2 including an attachment mounted at the end ofthe arm,the attachment defining a cut out which defines a stop surface extending transversely ofthe belt and a recess formed in the face of the cut out presented to the arm unloading position, said recess being shaped to locate a workpiece as the workpiece is moved towards the arm unloading position.

17. Afuel mechanism according to any one of the preceding claims including a stop pin and sensing meansforoperatingthestop pin, said stop acting to prevent movement of a workpiecetowards the arm loading position while a workpiece is at said position.

18. Afeed mechanismforworkpieces substantially as hereinbefore described with reference to the accompanying drawings.