US2400486A - Safety device for fluid power operated presses - Google Patents

Description

May 21, 1946.

H. L. CARLYLE SAFETY DEVICE FOR FLUID POWER OPERATED PRESSES Filed Nov. 22, 1945 4! as 40 4o 45 I Patented May 21, 1945 SAFETY nnvrcn FOR FLUID rowan OPERATED PRESSES I Howard L. Carlyle, West Allis, Wis, assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a cornotation. of Delaware Application November 22, 1943, Serial No. 511,331 7 I 1 Claims.

This invention relates to a safety device for a fluid power operated press. 3

A primary object is to provide a simple and reliable safety control mechanism for a press of the aforementioned character."

Another object is to provide a safety device for such a press whereby the hands of the operator are left free to manipulate the work. material while positively insuring against to the hands of the operator during the power stroke of the press. I

Another object is to provide a press control system including a normally'open foot-operated switch whereby initiation and normal termination of the pressing operation may be effected.

Another object is to provide a press member having at least two relatively movable parts the arranged with respect to eachother and to the a press parts as to distinguish between normal and abnormal conditions in the operation of the press.

Another object is to provide for adjustment of certain of said switch elements to correspond to the thickness of the particular material being worked upon.

Another object is to provide for adjustment of the position of a switch element automatically in response to the thickness of the work material as an incident to the. initial operation of the press.

Another and more specific object is to provide for use of such a safety device in conjunction with a spot welding machine.

.Other objects and advantages of the will hereinafter appear.

The accompanying drawing illustrates someinvention what schematically and diagrammatically an embodiment .of the invention, it being understood that the embodiment illustrated is susceptible of modification in respect of certain structural details thereof without departing from the Scope of the appended claims.

In the drawing, the single figure illustrates a press having my novel safety control mechanism applied thereto.

Referring to the drawing the numeral 5 desi nates a fragment of a cylinder of a known type of press; said cylinder having therein a plunger (not shown) the movement of which towardits upper and lower extreme positions is effected by the application of fluid pressure to the lower and upper ends thereof respectively. The means for controlling the admission to, and release of fluid pressure from said opposite ends of the piston may comprise a suitable or known form of multi- 5 way valve (not shown). whichmay be housed within an auxiliary casing suchas that shown in dotted lines at 6., In practice said valve is biased to a position wherein the fluid pressure is controlled in a manner to force the aforem mentioned piston toits upper extreme position within cylinder 5, so that the parts associated with the piston will be in the normal positions thereof shownin thedrawing. I

More particularly, the sh ft 1 carried by and extending downwardly from the piston has rigidly attached thereto an L-shaped bracket 8; the latter in turn having attached thereto an inwardly extending contact member. or plate 9 which 'is insulated from bracket 8 as by means of an insulating spacer Ill. Plate 9 has attached thereto a pair of upwardly and downwardly facing contact tips II and I2, whichtips preferably consist of silver or a suitable composition includin silver. p

Shaft I is preferably provided with a portion I3 of reduced cross sectional dimensions and a head or end flange portion l4. Slidably mounted upon portions l3 and I4 is an auxiliary press member I5, the upper end portion [6 of which is recessed as shown at I! to accommodate the flange portion I4 and is provided with an opening II! to accommodate the aforementioned portion l3. The inwardly extending flange l9 cooperates with flange portion H to limit the degree of downward movement of auxiliary press member [5 with respect to shaft 1. In practice member I5 will assume its illustrated position with respect to shaft 1 by the force of gravity,

but I prefer to interpose between the lower wall I of recess l1 and the lower surface of flange portion l4 a relatively light coiled compression spring 20; a counterbore 2| being preferably provided in said lower surface of flange portion M to accommodate and center the upper end of said spring. Although I have shown more or less diagrammatically the lost motion interlocking connection between shaft I and auxiliary press member l5, it is to be understood that the arrangement is such as to prevent accidental complete separation of the latter from the former; whereas obviously suitable provision (such as means for removably attaching flange 19 to member l5) may be made for enabling separation of these parts at will.

The portion l6 of auxiliary press member l5 has attached thereto a laterally extending lug 22 which carries a contact plate 23 having a tip 24 of silver or a composition containing silver; plate 24 being suitably insulated from lug 22, as indicated at 25. The arrangement is such that in the illustrated normal or fully extended position of auxiliary member l with respect to shaft 1 the contact tip 24 will be engaged under suitable pressure with the aforementioned contact tip II. This presets an energizing circuit for the valve operating winding 26 for completion upon closure of a normally open foot-operated switch 21. Said circuit may be traced from line L through switch 21 (when closed), conductor 28 through winding 26, conductor 38 to plate 8. con tact tips II and 24, plate 23, and by conductor 3| to line L.

Winding 26 when thus energized efiects operation of the valve in a well known manner to release the fluid pressure applied to the lower end of the piston and to simultaneously apply the desired value of the fluid pressure to the upper end of the piston, whereby downward movement of shaft 1 is eflected. I

With the parts as thus far described the arrangement is such that during downward movement of auxiliary press member I5 (along with shaft 1) as an incident to closure of switch 21, as soon as the lower or working surface 32 of member [5 engages an obstruction, such as work material 33 interposed between the same and the upper surface of the lower or stationary die member 52, member l5 will remain stationary and shaft 1 will move downwardly with respect thereto. This will result in separation of contact tip II from tip 24 to interrupt the aforedescribed energizing circuit of winding 26, with consequent return of said parts to the initial positions thereof illustrated.

To avoid the effect, under normal conditions, of such operation of the aforedescribed parts, I provide a contact plate 34 which is initially positioned as shown in dotted lines, so that the contact tip 35 carried thereby will be engaged by contact tip [2 when the lower end or surface 32 of auxiliary press member I5 is a substantial distance above the work material 33. Such distance may in practice be greater than the thickness of a hand or finger of an operator, onlyduring the initial operation of the press, and is variable in accordance with the thickness of the particular work material, such as 33, to be operated upon. In this initial operation of the press, for each different thickness of material to be operated upon, it will be apparent that contact tip II will remain in engagement with contact tip 24 until after contact tip l2 has engaged contact tip 35. Such engagement of tip l2 with tip 35 provides an energizing circuit for winding 26, which circuit may be traced from plate 8 through contact tips l2 and 35 and plate 34, and through conductor 36 to line L It follows that the energizing circuit for winding 26 will be maintained notwithstanding disengagement of contact tip II from contact tip 24 due to engagement of auxiliary press member l5 with the work material 33.

As shown plate 34 is carried by but insulated, at 31, from a metal member 38 which is pivotally supported at 39 upon a member 48. Member 48 is provided with a forwardly extending portion between which and member 38 a coiled compression spring 42 is interposed to bias member 38 toward its upper extreme position with respect t member 48; the latter being provided with a laterally extending lug 43 overlying member 38 to limit such upward movement thereof. Portion 4| of member 48 is also provided with a lug 44 underlying plate 34 to limit downward movement of member 38 with respect to member 48, such downward movement of member 38 being effected against the aforementioned bias of spring 42.

Member 4815 pivotally supported at 45, and the same is manually moved-to its upper extreme position, shown in dotted lines, prior to the initial operation of the press. The pivotal portion of member 48 is provided with an enlargement having an arcuate edge portion 48 against which a friction-clutch member 41 is adapted to bear, said enlargement of member 48 having a shoulder 48 formed at the upper end of arcuate edge 46 for cooperation with member 41 to limit manual upward movement of said member 48. A coiled compression spring 49 is interposed between a suitable stationary abutment 58 and member 41 to provide for frictional retention of member 48 in any position to which it may be moved.

From the foregoing description it will be apparent that during the initial operation of the press (the member 48 and plate 34 being initially in the respective dotted line positions thereof illustrated) the full downward stroke of shaft 1 (as modified only by the thickness of the particular work material 33) will be insured. The corresponding downward movement of contact tip l2 will (by engagement thereof with contact tip 35) first take up the lost motion provided between members 38 and 48, and thereafter effect downward movement of the latter about its pivot 46 against the yieldable restraint afforded by friction clutch member 41. During such automatic downward movement of member 48 the shaft 1 willmove downwardly to eifect engagement of auxiliary member 15 with the work material 33 and to thereafter take up the lost motion provided between the lower end l4 of said shaft 1 and said auxiliary member I5. It follows that the final adjustment of member 48 thus automatically effected is definitely proportional to, or related to, the thickness of the particular work material 33.

More particularly, such automaticadjustment of the position of member 48 is such that when the press parts are returned to their normal or inactive positions illustrated by re-opening of foot-operated switch 21, the contact tip 35 will assume a position which is a distance beneath contact tip I2 only slightly less than the distance between the lowr end 32 of auxiliary member l5 and the upper surface of the work material 33. Thereafter if the operator's hand or finger i accidentally or otherwise interposed between the upper surface of the work material 33 and the lower end 32 of member l5 the downward movement of member 15 will be stopped and then upon a slight degree of further downward movement of shaft 1 relatively thereto contact tip .II will be disengaged from contact tip 24, thus immediately deenergizing winding 28 whose associated valve then moves to its normally biased position to not only prevent any further downward movement of shaft l8 under the action of the fluid pressure, but said valve when so permitted to return to its normal position insures return of shaft 1 and the parts associated therewith to the normal positions thereof illustrated.

In practice the initial operation of the press will be effected by the operator or by a supervisorwith extreme care to insure against injury to the hands or fingers; such initial operation 3 the latter, said contacts the press. I prefer to employ themethod of operation'flrst described whereby adjustment of member 40 is effected automatically by an initial operation of the press; such method being more positive and fool-proof in respect of insuring against injury to an operator. t 41 is preferably provided A shown member with a stud or projection 5| to fit withinvone end of spring 49 to insure maintenanceof said parts in proper relationship to each other.

The safety control device herein disclosed is well adapted for use with the electric spot welding machine, In such a machine the work-engaging press parts corresponding to those shown at 32 and 34 will preferably be in the form of points or cones, as is well understood in theart. Also, in such a spot weldpress parts of an ing machine it is usual to provide a normally open' switch responsive to the development of a predetermined degree of pressure of the welding electrodes (corresponding with members 32 and 33) against the work materialto effect closure of such switch for supplying the desired value of welding current to such electrodes.

Moreover, the voltage of the welding current normally employed with such electrodes, is so low as to prevent any possibility of substantial shock or other injury to an operator. I claim: I

1. In combination, a pair of relatively movable press members initially substantially spaced from each other, one of said member comprising two parts having a straight line lost motion connection'afiording a predetermined degreeof telescopic movement therebetween, one

of said parts being normally biased into an extended relationship to the other, fluid power operated means subject to manual control for initiating movement of said two-part member toward work material interposed between the same and the other member, associatednmeans responsive to relative movement of'said part of said two-part member due to the presencesof a foreign object of substantial thickness between the same and the work material to substantially instantaneously stop such movement of said twopart member, said last mentioned means including a set of electrical switch contacts carried by said two-part member and bodily movable with v being normally engaged with each other, and the same being disengageable as an incident to the aforementioned relative movement of said parts due to presence of such foreign object to effect interruption of an electric circuit controlled thereby, for the purpose set forth.

2. In combination, a pair of relatively movable press members initially substantially spaced from each other, one of said members comprising two parts having a straight line lost motion connection affording a predetermined degree of telescopic movement therebetween, spring means interposed between said parts to normally bias one of the same into an extended relationship to the other, fluid power operated Vmeanssubject to manual control for initiating movement of said two-part member toward work material interposed between the same and the other member, associated means responsive to relative movement of said parts or said two-part member due to the presence of a foreign object of substantial thickness between the same and the work material to substantially instantaneously stop such movement of said two-part member, said last mentioned means including a set of electrical contacts carried by the respective parts of said two-part member and bodily movable with the latter, said contacts being normally engaged with each other, the same being disengageable as an incident .to the aforementioned relative movement of said parts to effect interruption of an electric circuit controlled thereby, for the purpose set forth, and an additional contact associated with said set of contacts and'adapted to be engaged by one of the latter prior to separation of the contacts of said set in the normal operation of said press members, whereby said electric circuit is maintained notwithstanding separation of the contacts of I said set.

v 3. In combination, a pair of relatively movable press members initially substantially spaced from each other, one of said members comprising two parts having a straight line lost motion connection affording a predetermined degree of telescopic movement therebetween, one of said parts being normally biased into an extended relationship to the other, fluid power operated means subject to manual control for initiating movement of said two-part member toward work material interposed between the same and the other member, associated means responsive to relative movement of said parts of said two-part memberdue to the presence of a foreign object of substantial thickness betweenth'e same and the work material to substantially instantaneously stop such movement of said two-part member, said last mentioned means includinga set of electrical contacts carried by the respective parts of said twopart member and bodily movable with the latter, said contacts being normally engaged with each other, the same being disengageable as an incident to the aforementioned relative movement of said parts to effect interruption of an electric circuit controlled thereby, for the purpose set forth, an additional contact association with said set of contacts and adapted to be engaged by one of the latter prior to separation of the contacts of said set in the normal operation of said press members, whereby said electric circuit is maintained notwithstanding separation of the contacts of said set, and means including said oneof said set of contacts for automatically efiecting adjustment of the position of said additional contact in accordance with the thickness of the aforementioned interposed work material.

4. In combination, a pair of relatively movable press members, one of said members comprising at least two parts having a straight line lost motion connection affording a predetermined degree of telescopic movement therebetween, one of said parts being normally biased into an extended relationship to the other, fluid power operated means for effecting movement of said two-part member toward work material interposed between the same and the other member, electrical means including a foot-operated switch adapted when closed to render said power operated means effective, whereby the hands of an operator are freed for manipulation of the work material, associated means including a pair of normally closed electrical switch contacts carried by said twopart member and bodily movable with the latter, 5 said contacts being separable automatically upon telescopic movement of said one part with respect to the other against said bias due to the presence of the operator's hand between one of the press members and the work material, and said contacts when separated under such conditions acting to instantaneously render said power operated means inefl'ective, whereby further movement of said two-part member toward the work material is stopped.

5. In combination, a pair of relatively movable press members, one of said members comprising at least two parts having a straight line lost motion connection afiording a predetermined degree of telescopic movement therebetween, means in- Cllldlllg a relatively weak spring interposed between said parts to normally bias one of the same into an extended relationship to the other, fluid power operated means for effecting movement of said two-part member toward work material interposed between the same and the other member, electrical means including a foot-operated switch adapted when closed to render said power operated means efiective, whereby the hands of an operator are freed for manipulation of the work material, associated means including a pair of ment of said one part with respect to the other against said spring bias due to the presence of the operators hand between one of the press members and the work material, said contacts when separated under such conditions acting to instantaneously render said power operated means ineffective, whereby further movement of said two-part member toward the work material is stopped, and means including a third electrical contact cooperable with one contact of said pair to render the latter when separated ineffective for stopping ,such movement of said two-part member.

6. In combination, a pair of relatively movable press members, one of said members comprising at least two parts having a straight line lost motion connection affording a predetermined degree of telescopic movement therebetween, one of said closed to render said power operated means efi'ective, whereby the hands of an operator are freed for manipulation of the work material, as-

sociated means including a pair of normally closed to render the latter when separated inefiective for stopping such movement 01' said two-part member, said last mentioned contact being adjustable automatically by said one contact of said pair in accordance with the thickness of the work material as an incident to the initial normal cycle of operation of said press members with respect to the work material, whereby subsequent eflectiveness of said pair 01' contacts under the aforementioned abnormal conditions is insured.

7. In combination, a pair of relatively movable press members initially substantially spaced from each other, one of said members comprising two jointly movable parts having a straight line lost motion connection affording a predetermined degree of telescopic movement therebetween, one of said parts being normally biased into an extended relationship to the other, a pair of normally closed contacts carried by said two-part member and bodily movable with the latter, a normally open foot-operated switch included in a circuit in series with said contacts whereby said circuit is subject to control by said switch and said gagement thereof with work material interposed therebetween, said one of said parts when engaged with the work material being adapted to effect opening of said contacts, thereby tending to interrupt saidelectric circuit, for the purpose set forth, and a third contact cooperable with one contact of said pair to provide for maintaining said circuit under normal conditions, the position HOWARD L. CARLYLE.

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