US3521337A - Universal assembling machine for the manufacture of stacks of slats for venetian blinds - Google Patents

Description

July 21, 1970 v H. L. P. PE ETERS 3,521,337

UNIVERSAL'ASSEMBLING MACHINE FOR THE MANUFACTURE OF S'TACKS OF SLATS FOR VENETIAN BLINDS Filed Jan. 18, 1968 i 4 Sheets-Sheet 1 July-21,. 1970 H.- 1.. P. PEETERS 3,521

UNIVERSAL ASSEMBLING MACHINE FOR THE MANUFACTURE OF STACKS 0F SLATS FOR VENETIAN BLINDS Filed Jan, 18. 1968 4 Sheets-Sheet 2 July zl, 1970 H. L. P. PEETERS I 3,521,331

UNIVERSAL ASSEMBLING MACHINE FOR THE MANUFACTURE OF STACKS OF, SLATS FOR VENETIAN BLINDS 4 Sheets-Sheet 5 Filed Jan. 18. 1968 July 21-, 1970' H. L. P. PEETE RS 3,521,337

UNIVERSAL ASSEMBLINGYMACBINE FOR THE MANUFACTURE OF STACKS OE SLATS FOR VENETIAN BLINDS Filed Jan. 18. 1968 4 ShgetS-Sheet United States Patent ()ffice 3,521,337 Patented July 21, 1970 US. Cl. 2924.5 9 Claims ABSTRACT OF THE DISCLOSURE A universal assembling machine for the automatic assembling of Venetian blinds with slats carried by ladder means, said machine being adapted to be quickly readjustable for manufacturing blinds with different slat width, as well as with ladder tape or ladder cord according to choice. Also it may be adjusted for different mutual distance of the ladder carrier means along the blind and/or for different overlapping distance of the slats in a closed blind. This universality is obtained among others by the provision of a setting and regulating mechanism and of interchangeable or indexable units, elements, mechanisms etc.

This invention relates to an assembling machine for Venetian blinds. I

Existing assembling machines present the considerable drawback that they are only suitable for the manufacture of entirely or partly finished stacks of slats for one predetermined type of a Venetian blind. With these machines it is only possible to obtain a variation in length and height of one type of a Venetian blind only. This means that for each type of a Venetian blind a separate machine should be used. In order to remove this drawback the invention aims at providing a universal assembling machine on which Venetian blinds of different slat width, for example 25, 35 or 50 mm. may be manufactured, as well as ladder carrier means according to choice in the form of ladder tape or ladder cord with different mutual distance of the ladder carrier means along the Venetian blind and/or different overlapping distance of the slats in a lowered and closed Venetian blind.

For this purpose the invention provides a novel assembling machine for the manufacture of entirely or partly finished stacks of slats for Venetian blinds with slats and the like carried by ladder means, said machine comprising among other things fastening means for temporarily fastening said ladder means mutually spaced to the machine, a lifting device actuated by a driving mechanism for periodically raising one or more slats and/or the ladder means, tensioning and/ or guide means for the ladder means and, if necessary, guides for guiding the slats when being fed into the machine, said assembling machine being also provided with means for applying ladder cords and the like or ladder tapes and the like according to choice.

According to the invention it is preferred that the ladder cord tensioning and/or guiding mechanism and the ladder tape tensioning and/or guiding mechanism are interchangeable and the machine comprises at least one frame adapted to be moved and fixed relative to a stationary with fastening means for co-operation both with fastening means of the ladder cord tensioning and/or guiding mechanism and with fastening means of the ladder tape tensioning and/ or guiding mechanism.

The machine may be provided, according to the invention with an adjusting and regulating mechanism which co-operates with the driving mechanism of the lifting cle vice for adjusting the lift according to choice, as well as with operating means for said mechanism.

The invention will be further explained below with reference to the drawings showing by way of example an embodiment of the machine according to the invention.

FIG. 1 presents a diagrammatical front view of the machine.

FIG. 2 is a top plan view of the machine.

FIG. 3 is a front view of a ladder tape guiding and tensioning unit.

FIG. 3a presents a top plan view of a portion of the unit according to FIG. 3.

FIG. 4 shows the unit according to FIG. 3 in another position.

FIG. 5 shows a front view of a ladder tape guiding and tensioning unit, including a lift cord threading unit.

FIG. 5a presents a top plan view of a spacer.

FIG. 6 shows a unit according to FIG. 5 in another position.

FIG. 7 shows a front view in perspective and on an enlarged scale of the unit according to FIGS. 5 and 6 with the ladder cord unit removed.

The machine shown in FIGS. 1 and 2 comprises a frame 1 provided with supports 2, 3 with which the frame rests on the ground. The lifting device comprises a shaft 4 supported in bearings 5, 6 which by means of bearing bracket supports 7, 8 are secured to the frame 1.

At one end, to the right in FIGS. 1 and 2, the shaft 4 carries one half of an electro-magnetic clutch 9, 10 the other half 10 of which is fixedly secured to the shaft of an electromotor 11 mounted on the frame 1. The shaft 4 furthermore carries, distributed over its length, a number of pulleys 12, having as an example only four in the embodiment shown. The pulleys are slidable along the shaft 4, but they are mounted non-rotatably relative thereof in that the shaft 4 has a square.cross-section and in the pulleys 12 a corresponding square central aperture is provided. The slidability is desired in order to be able to change the position of guides for the slats and means for the provision of ladder means (to be described later on), from which the slats are suspended, along the slats.

Below each pulley 12 there is secured to the frame 1 a vertically extending guide plate 13 along which a lift plate 14 is guided in a vertically slidable manner. The lift plate 14 is connected with the pulley 12 by a tape 15 of spring steel one end of which is fastened to the lift plate 14 and the other end to a point on the circumference of the pulley 12. The lift plate 14 carries two forwardly projecting pins 16 by means of which a slat 17, horizontally fed into the machine, is supported and stays thereon after the slat has been entirely fed into the machine. By rotation of the shaft 4 in one direction the slat 17 is lifted.

On the shaft 4 there are fixedly arranged a set of cam discs 70,71, 72 which serve to control the lift of the lift plates 14 with pins 16. If three different slat widths are used, for example 25, 35 and 50 mm., three cam discs are provided as shown. To the cam discs there belongs a follower member in the form of a roller 73 connected to the switch arm of a micro switch 74. This micro switch is included in the energizing circuit of the electro-magnetical clutch 9, 10. The assembly operates such that when the motor 11 is started and a slat 17 has been entirely fed into the machine, said slat comes into contact with an end switch 75 operated by the slat, said switch being likewise included in the energizing circuit of the clutch. As a result of the operation of the switch 75 by the slat the clutch is energized and the motor 11 is connected to the shaft 4. When the roller 73, running on one of the cam discs, is actuated by the cam on said disc the switch 74 interrupts the current again so that the clutch is released. Thereafter in consequence of the weight of the lift plates 14 depending from the pulleys 12 the shaft 4 with the pulleys moves back again into its initial position.

The switch 74 is horizontally slidable on the frame 1. For example at the under side of the switch 74 a gear rack is provided engaging a pinion which is fixed on a shaft 77. At the front of the machine the shaft 77 projects from the frame 1 and there carries an operating knob 78 with an operating lever 79, said knob 78 being movable along a dial fixedly provided on the frame. Three positions are possible for the knob 78 with the operating lever 79 (corresponding with the slat widths of 25, 35 and 50' mm.), in each of which the follower roller 73 faces one of the discs 70, 71 or 72. The position of the cams on said discs is such that therewith each time a lift of the lift plates 14 is obtained which coresponds to the pitch of the ladder cross connections for the slat width in question. For one slat width various ladders may be used with mutually deviating pitch of the cross connections for special types of Venetian blinds. This may be met by adjusting the lift in question of the lift device corresponding to one slat width to the largest pitch so that the slightest ditferences in pitch are met and the slat is always sufficiently lifted.

The guide plate 13 movable along the frame (FIGS. 3 and 4) comprises at its top two upwardly projecting legs 18 which extend on either side of the pulley 12 and when being moved take along said pulley. By means of a fixing screw 13' the guide plate 13 may be fixed at any point along the frame 1.

On either side of the guide plate 13 there are provided U-shaped guides 19 for the slats 17 beside the pins 16. The guides 19 are connected to the guide plate 13 and are adjusted together with the adjusting of the guide plate 13. The guides 19 have in the legs of the U at some distance above the bottom side resilient stops 20. If a slat is moved upwards by means of the shaft 4 up to the stops 20, then said stops are pushed inwards into the legs of the U and after the passing of the slat they spring back so that they can support said slat. Each following slat is likewise pressed past the stops 20 so that finally the entire stack of slats rests on the stops 20.

The guides 19 are detachably fastened to the frame 1 or they are fixedly secured to a separate frame which is movable relative to frame 1 and they may be replaced by other similar guides with a different distance between the legs, depending on the slat width which will be used, for example 25, or 50 mm. It is also possible to make one of the legs of each guide adjustable relative to the other leg, for example slidable and fixable, for instance with an adjusting screw, and to provide openings or recesses in the part of the body of the U-shaped guide which is connected with the fixed guide leg, with which openings the adjusting screw engages for fixing the correct position of the adjustable leg.

It is also possible to provide a number, for example three guides (for the slat widths of 25, 35 or 50 mm. respectively) on an indexable plate rotatably conected to the frame 1 and in this arrangement the U-shaped guide, each time required, may be rotated into the operative position, if desired also with the plate being snapped in each of the three positions.

For providing the ladders in the stack of slats simultaneously with assembling said stack it is preferred to arrange such a ladder 21 (FIGURE 4) at each lift unit such that the first slat of a stack, when being fed into the machine, is positioned between two cross connections 22 situated at or near one end of the ladder 21. After a first slat has been moved through, the ladder 21 may be released and then depends substantially vertically from the uppermost of the cross connections in question. When the slat is lifted it also causes the ladder 21 to be lifted by means of said uppermost cross connection 22. The distance along which the lift is effected, therefore the distance between the pins 16 and the stops 20, is at least equal to the distance between two successive cross-connections 22 of the ladder 21. After a slat has been lifted a next slat is likewise pushed between two successive cross connections etc.

In order to render this possible the ladder must be maintained under tension in the longitudinal direction and besides both sides must be kept apart in the transverse direction so that the slat cannot be hindered when being moved forwards. For this purpose at the location of each lift unit, constituted by the guide plate 13, the lift plate 14 and the guides 19, a ladder tensioning means is interchangeably provided. FIGS. 3 and 4 show a ladder tensioning means 23 for ladder tape, consisting of a pair of tensioning elements 24. The tensioning elements 24 are U-shaped and made from sheet metal. Near one end of each element 24 a pivot shaft 25 is arranged through the legs of the U-shaped element on which the element 24 is rotatably mounted and which shaft 25 is fixedly secured to a plate connected to the frame 1. The legs of both elements 24 situated nearest to the frame 1 are each fixedly connected with a gear segment 26, both gear segments being in engagement with each other after elements 24 have been mounted to the frame. One of the segments 26 is connected at some distance from the pivot shaft 25 to one end of a tensioning spring 27 the other end of which is secured to the frame 1. Centrally relative to the unit 23 there is provided at the lower side of the frame 1 a U-shaped guide 29 having two legs projecting from the frame 1, the ladder tape 21 depending between these legs. Each element 24 is provided with one or more pairs of slots 30 for guiding the sides of ladder in question in the body of the U, said slots extending from the free end of the element in the longitudinal direction of the element.

The ladder tape unit is provided on the frame 1 such that it may be removed out of the operative position and that it may be replaced by a ladder cord unit (to be described later on) if Venetian blinds must be equipped with ladder cord instead of ladder tape. Both the ladder tape and ladder cord unit are placed on centering pins and on a bolt 81, all of them secured to the plate 13, after which on the bolt 81 a milled nut 82 is screwed (see also FIG. 7).

Venetian blinds with different slat widths may be manufactured with one and the same ladder tape or ladder cord unit, since for this purpose only a different lift of the lift units must be set, and also a tape or a cord with a different cross connection distance may be used. It is also possible to mount one tensioning unit for ladder tape and one tensioning unit for ladder cord on an indexable plate such that the units may be rotated according to choice into the operative position.

The above-described ladder tape tensioning means 23 operates as follows.

In the lowermost position of the lift plate the elements 24 are in the horizontal position, the free ends thereof facing each other with a small clearance. In this situation each side tape of the ladder tape 21, depending from slats already supported by the stops 20, projects into two slots 30 of the elements 24, said slots facing each other. The

elements 24 have been brought in this position by the tensioning spring 27 and by the co-operation of the gear segments 26. When the lift plate 14 is lifted the pins 16 move the slat resting thereon upwards, said slat exercising an upward pull on the ladder tape by means of the cross connection 22 situated above said slat. The side tapes may be moved upwards through the elements 24 as a result of the slots 30. If a cross connection 22 situated below the elements 24 abuts against the bodies of said elements 24, then said elements move apart, against the action of the tensioning spring 27, and pivot about the shafts 25 so that said cross connections 22 may pass the elements 24. Immediately after said passing the elements 24 return to their initial position under the influence of the spring 27.

If the Venetian blind to be manufactured must be provided with ladder cord instead of ladder tape a ladder cord tensioning unit is provided instead of a ladder tape tensioning unit. A first embodiment thereof is shown in FIGS. 5 and 6.

This unit consists of a plate 31 carrying at the lower side a holder 33 fixedly connected therewith in which two rollers 34, for example of a synthetic material, are rotatably mounted by means of journals 35. The journals 35 of one of the rollers project into slot-like openings 36 in the holder 33, and the journals of the rollers are interconnected on either side of the holder by the tensioning spring 37, said springs urging the rollers towards each other. When the ladder cord 38 is situated between the rollers 34 and a pull is exercised thereon by lifting a slat (corresponding with the situation in the case of a ladder tape), the rollers 34 ensure the necessary longitudinal tension in the ladder cord 38. Keeping the ladder cord open in the transverse direction is ensured by means of a spacer 39, consisting of a plate 41 pivotally connected about a shaft 40 to the plate 31, pairs of slots 42 being provided at the free end for accommodating the side cord of the ladder cord 38. The spacer 39 is biased under the influence of a tensioning spring 43 towards a position approximately parallel to the plane through the centre lines of the rollers 34, part of the free end of the plate 41 resting on a cross connection 44 of the ladder cord 38. In the rollers 34 there are provided peripheral grooves for correctly guiding and spreading the side cords.

The ladder cord tensioning unit too is provided on the frame 1 such that it may be removed, for example interchanged, out of the operative position and may be replaced by a ladder tape tensioning unit. If one wishes to use ladder cord for different slat widths, of which ladder cord not only the mutual distance but also the length of the cross connections is different, therefore the widths of the ladder cord, this is possible in a simple way by using the different pairs of slots 42 in the swing plate 41 as well as different pairs of slots in the rollers 34.

The operation of the ladder cord tensioning unit corresponds with the operation of the above-described ladder tape tensioning unit.

From FIG. 5 it is apparent that the guide plate 13 of each lifting device carries a column 53 with a guide bar 54 along which a holder 55 is vertically slidable, said holder carrying at the lower side a vertical threading needle 56. The threading needle 56 has at its lower end an eyelet 57, through which a lift cord 58 may be threaded. At the location of the threading needle 56 the slats of the stack are provided with an aperture, said apertures forming a vertical channel in the stacked package. The threading needle 56 projects through this channel. When the required number of slats have been added to the stack one may thread the lift cord 58 through the openings in the slats by moving the holder 55 with the threading needle 56 upwards. The cord 58 with the needle 56 may also be threaded from an upward position downwards through the channel formed by the openings when during the assembling of the stack the needle is situated in a position above said stack.

In order to prevent that in a completed Venetian blind at a possible inclined position of the blind or through other causes the slats with their lift cords show a deflection as a consequence of being shifted relative to the carrier means, i.e. the ladder tape or ladder cord, the lift cords of the ladder tape are threaded through slots in the centre of the cross tapes which are mostly provided double or in staggered position. In the case of ladder cord this is normally corrected by guiding the lift cord by hand alternately to the left and to the right past the successive cross cords. The invention also comprises a provision for automatically carrying out this weaving, which is explained with reference to FIGS. 5, 6 and 7. In this arrangement care is taken that the lift cord is alternatively situated to the left and to the right of the successive cross connections. This is accomplished by a rocking movement of the ladder cord tensioning unit. This unit is secured to a plate 31 construction as a rocking element, said plate being pivotally mounted about a journal 32 of a supporting plate 66, said supporting plate being secured to the frame.

At the rear of the rocking element 31 a pin 60 is secured and on the lift plate 14 a fixed guide 61 is provided consisting of a vertical slot downwardly widening into oppositely inclined portions 67 and underneath a triangular tipping guide piece 62 adapted to tip about a pivot pin 63 situated near the top angle of the tipping guide piece 62 and secured to the lift plate 14.

In order to explain the operation of this structure the lowest position of the lift plate 14 is selected as a starting point, in which position the pin 60 is situated in the top of the vertical slot of the fixed guide 61. It is thereby assumed that the tipping guide piece 62 has been tipped to the right.

When the life plate 14 is drawn upwards by the shaft 4 and the pulley 12 via the tape 15, a slot lying on the pins 16 is conveyed in upward direction, the upper side of the slat entraining the ladder cord. During this movement the slot of the fixed guide 61 moves upwards relative to the pin 60, as does the tipping piece 62 which is in a position tipped to the right. The tipping of the tipping piece 62 is limited in that downwardly projecting parts abut against a stop 65 (FIG. 7).

The tipping piece now comes with its left erect side into contact with the pin 60 which consequently is pushed away towards the left. Upon the pin 60 being pushed towards the left also the ladder cord tensioning unit and consequently the ladder cord are moved towards the left so that the next cross connection of this ladder cord assumes a position to the left of the threading needle 56 during the upwardly directed movement of said ladder cord relative to said threading needle.

Immediately after the pivot pin 63 has passed the pin 60 the tipping piece 62 is tipped to the left by the pressure exerted by the pin on the lower part of the tipping piece, the left erect side assuming an almost vertical position. Meanwhile the relative cross connection of the ladder cord has passed the end of the threading needle to the left.

At the subsequent downward movement of the lift plate 14 under the influence of the force of gravity the tipping piece moves along downwards in the position turned to the left. This is effected at such a speed that the pin 60 does not get a chance to push back the portion of the tipping piece situated above the pivot pin 63. Consequently the tipping piece remains in the position turned to the left and the pin 60 comes into contact with the left in clined portion 67 of the fixed guide 61 so that at a continued downward movement of the lift plate 14 the pin 60 is automatically guided in the vertical slot.

At the subsequent transport of the next slat by the renewed upward movement of the lift late 14 the right erect side of the tipping piece now comes into contact with the pin so that this pin is pushed towards the right and the next cross connection of the ladder cord therefore assumes a position to the right of the threading needle.

In this way the successive cross connections may therefore be brought alternately to the left and to the right hand side of the threading needle.

It is obvious that in the above-described embodiment of the machine many modifications may still be made within the scope of the invention.

With the aid of the machine according to the invention it is therefore possible to manufacture any slat as regards both the type (slat width, pitch of the slats, ladder tape or ladder cord) and dimensions (length and height) of the slat.

I claim:

1. An assembling machine for the manufacture of at least partly finished stacks of slats for Venetian blinds having slats carried by ladder means, said machine comprising: a lifting device actuated by a driving mechanism for periodically raising at least one slat; means for tensioning and guiding said ladder means; guide means for guiding the slats when being fed into the machine; said tensioning and guiding means comprising a device adaptable for applying according to choice either ladder cords or ladder tapes interchangeably, the device comprising at least one moveable frame adapted to be moved and fixed relative to the stationary frame of the machine, the moveable frame being provided with fastening means for co-operating both with fastening means of the ladder cord tensioning and guiding mechanism and with fastening means of the ladder tape tensioning and guiding mechanism.

2. An assembling machine for the manufacture of at least partly finished stacks of slats for Venetian blinds with slats carried by ladder means, said machine comprising a lifting device actuated by a driving mechanism for pcriodically raising at least one of the slats and the ladder means; tensioning and guide means for the ladder means, guide means for guiding the slats when being fed into the machine, said assembling machine being also provided with setting and regulating means for applying according to choice ladder cords or ladder tapes and the like of different dimensions and pitch of cross connections to assemble slats of different widths, preferably of slat widths of 25, 35 or 50 mm., said setting and regulating means comprising a setting and regulating mechanism which co-operates with the driving mechanism of the lifting device for adjusting the lift according to choice, as well as that of the operating means for said mechanism.

3. A machine according to claim 2 in which the setting and regulating mechanism and the operating means are set at a number of fixed lifts, corresponding to ladder cords or tapes for Venetian blinds having a slat width of 25, 35 or 50 mm.

4. An assembling machine for the manufacture of at least partly finished stacks of slats for Venetian blinds with slats and the like carried by ladder means, said machine comprising a lifting device actuated by a driving mechanism for periodically raising at least one of the slats and the ladder means, said driving mechanism consisting of a motor which is connected via a disconnectable clutch with the shaft of the lifting device operating a number of lift units, and a setting and regulating mechanism being connected with the disconnecting mech anism of the clutch for regulating the lift by disconnecting the clutch, tensioning and guide means for the ladder means, guide means for guiding the slats when being fed into the machine, said assembling machine being also provided with setting and regulating means for applying according to choice ladder cords and the like or ladder tapes and the like of different dimensions, width and pitch of the cross connections for assemblies of slats of different slat widths, preferably 25, 35 or 50 mm., said setting and regulating means comprising a mechanism which co-operates with the driving mechanism of the lifting device for adjusting the lift according to choice, said setting and regulating mechanism having a number of cam means on the shaft of the lifting device, each of them corresponding with a pre-determined 8 lift, and a switch means operated by said cam means and being adjustable relative to them for disconnecting the clutch, said switch means being connected with the operating means to bring said switch means according to choice into the path of one of the cam means.

5. A machine according to claim 4, wherein the clutch is an electromagnetic clutch and the adjustable switch means is a micro switch.

6. An assembling machine for the manufacture of at least partly finished stacks of slats for Venetian blinds With slats and the like carried by ladder means, said machine comprising a lifting device actuated by a driving mechanism for periodically raising at least one of the slats and the ladder means; tensioning and guide means for the ladder means, guide means for guiding the slats when being fed into the machine, said assembling machine being also provided with setting and regulating means for applying according to choice ladder cords and the like or ladder tapes and the like of different dimen sions and pitch of the cross connections for the assembling of slats of different slat width, preferably of slat widths of 25, 35 or 50 mm., said means comprising a mechanism which co-operates with the driving mechanism of the lifting device for adjusting the lift according to choice, as well as that of the operating means for said mechanism, said setting and regulating mechanism comprising a number of cam means provided on the shaft of the lifting device each of them corresponding with a predetermined lift, and a micro switch means to be operated by said cam means and being adjustable relative to them for disconnecting an electromagnetic clutch in the driving mechanism, said micro switch means being connected with the operating means for bringing it according to choice into the path of one of the cam means, wherein the operating means consist of a rotatable shaft and an operating knob provided thereon, the micro switch means being also provided adjacent said shaft.

7. An assembling machine for the manufacture of at least partly finished stacks of slats for Venetian blinds with slats and the like carried by ladder means, said machine comprising a lifting device actuated by a driving mechanism for periodically raising at least one of the slats and the ladder means; tensioning and guide means for the ladder means, guide means for guiding the slats when being fed into the machine, said assembling machine being also provided with means for applying according to choice ladder cords and the like or ladder tapes and the like of different dimensions, width and pitch of the cross connections for the assembling of slats of different slat width, said means for applying comprising differently spaced grooves, slots, guiding cams and the like provided on the tensioning and guide means for the ladder means.

8. An assembling machine for the manufacture of at least partly finished stacks of slats for Venetian blinds with slats and the like carried by ladder means, said machine comprising a lifting device actuated by a driving mechanism for periodically raising at least one of the slats and the ladder means; tensioning and guide means for the ladder means and one or more guide means for guiding slats of different widths when being fed into the machine and being lifted during operation of the machine, the guide means for the slats comprising a guide having upright legs and fastened to a frame, said guide ibeing provided with a mechanism for adjusting the mutual distance between the legs.

9. An assemblying machine for the manufacture of at least partly finished stacks of slats for Venetian blinds with slats and the like carried by ladder means, said machine comprising a lifting device actuated by a driving mechanism for periodically raising at least one of the slats and the ladder means; tensioning and guide means for the ladder means and one or more guide means for guiding slats of different widths when being fed into the machine and being lifted during operation of the machine,

the guide means comprising different guides provided 2,635,333 4/1953 Vodra 29-24.5 with upright legs, the distance between the legs differing 2,893,106 7/1959 Rosenbaum 29-245 for each guide, said guides being adapted to be brought into the operative position according to choice. JOHN CAMPBELL, 'y

References Cited 5 R. I. CRAIG, Assistant Examiner UNITED STATES PATENTS US. Cl. X. R. 2,489,467 11/1949 Sherwood 29-245 2,532,294 12/1950 Edwards et a1. 2924.5

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