US3410166A

US3410166A - All hydraulic cutter with spring knife return

Info

Publication number: US3410166A
Authority: US
Inventors: Thumim Carl
Original assignee: Miehle Goss Dexter Inc
Current assignee: Miehle Goss Dexter Inc
Priority date: 1966-03-10
Filing date: 1966-03-10
Publication date: 1968-11-12
Anticipated expiration: 1985-11-12

Description

Nov. 12, 1968 C. THUMIM 4 Sheets-Sheet ALL HYDRAULIC CUTTER WITH SPRING KNIFE RETURN Filed March l0, 1966 Nov. 12, 1968 c. THUMIM 3,410,155

ALL HYDRAULIC CUTTER WITH SPRING KNIFE RETURN Filed March lO, 1966 4 Sheets-Sheet 2 Nov. 12, 1968 C. THUMIM 3,410,166

ALL HYDRAULIC CUTTER WITH SPRING KNIFE RETURN Filed March l0, 1966 4 Sheets-Sheet 3 1N VEN TOR V7/FL THUM/M NOV. 12, THUMIM ALL HYDRAULIC CUTTER WITH SPRING KNIFE RETURN Filed March lO, 1966 4 Sheets-Sheet 4 United States Patent O 3,410,166 ALL HYDRAULIC CUTTER WITH SPRING KNIFE RETURN Carl Thumim, Chicago, Ill., assignor to Miehle-Goss- Dexter, Incorporated, Chicago, Ill., a corporation f Delaware Filed Mar. 10, 1966, Ser. No. 533,178 13 Claims. (Cl. 83-380) ABSTRACT 0F THE DISCLOSURE A cutting machine of the guillotine type which includes a clamp operated entirely by a hydraulic system, and a knife operative in its cutting stroke by hydraulic means but returned to its rest position by spring biasing means. The hydraulic system includes a large capacity and a small capacity pump which are cumulative in effect when the knife and clamp are being operated but requires only the small capacity pump to retain the clamp in its upward or rest position between cutting cycles.

This invention relates to guillotine-type paper cutters, and more particularly to a cutter in which knife return iS effected by a spring.

Among the objects of the invention are to provide a simplified hydraulic system and electric control circuitry for a hydraulic paper cutter; to provide for economy of operation by reducing the oil pressure and the quantity of oil circulating under pressure in the hydraulic system between cutting operations; to provide for operator safety in that two hands are required to effect actuation ofthe clamp and knife; to provide optionally for convenient operation in that once the knife has started moving the operator may free one hand; to provide an arrangement using a high capacity pump and low capacity pump in which both pumps provide pressure for actuating the clamp and the knife, thereby effecting a power saving and a simplicity of construction, but wherein only the low capacity pump is required to maintain the clamp in raised position.

Other objects and features of the invention will be apparent from the description that follows, a particular object being to provide a simple mechanism wherein a spring effects a return movement of the knife.

Referring to the drawings;

FIGURE 1 is a diagrammatic illustration of the mechanical arrangement utilizing hydraulic cylinders for operating the clamp and knife and showing the use of a spring for effecting knife return;

FIGURE 2 is a fragmentary illustration in elevation partially in section showing certain components of the knife actuating mechanism;

FIGURE 3 is an end view partially in section showing certain components illustrated in FIGURE 2;

FIGURE 4 is a plan view illustrating, partially in section, certain components shown in FIGURE 2;

FIGURE 5 is an electrical diagram showing circuitry control for the novel aspects of the invention; and

FIGURE 6 is a hydraulic circuit diagram illustrating the pump and valve arrangement to effect actuation of the knife and clamp.

Referring to FIGURE 1, a knife bar 10 is illustrated which will be understood to be reciprocal in a vertical plane being guide by fixed pins 12 acting in slots 15 of the knife bar in a conventional manner. The knife bar carries a knife 18 secured thereto and is actuated by a pull bar 22, all in a conventional manner.

A clamp 25 is illustrated which will be understood to be conventionally operated as by pull bars 28 acting through a link 32 and bellcranks 35 and 38 powered by a Patented Nov. 12, 1968 double ended hydraulic cylinder 40 connected to bellcrank 35 and having

pressure chambers

43 and 46.

The arrangement for effecting actuation of the knife pull bar 22 is believed to be unique and comprises a single ended hydraulic cylinder 50, having a pressure chamber 53 and a piston rod connected to a bellcrank lever 56 which is provided with three arms. Thus the arm 56A is connected to the piston rod while the arm 56B is connected to a rod 60 concentric within a compression spring 63 and arranged so that movement of the rod toward the right will compress the spring. The third arm 56C is connected to operate the knife bar linkage in a conventional manner but is disposed so that upon swinging counterclockwise when the cylinder 50 is put under pressure the end of the arm 56C will abut a dash pot 67 which serves as a cushion and motion limit stop at the end of the knife stroke, as indicated by the phantom lines illustrating the limit of downward movement of arm 56C. The rod 60 will be understood to be slidably supported in a fixed wall 70 which is part of the machine frame F indicated by the phantom line.

The outer end of rod 60 is disposed to abut a fixed rubber bumper pad 73 when the spring 63 is fully extended to serve as a cushion for limiting movement of the knife at top position.

In operation, the chamber 43 is filled with oil under pressure to cause the clamp to come down against a paper pile resting on a table 78, all in the usual manner. The nvention contemplates knife actuation only after a predetermined degree of pressure is brought to bear by the clamp on the paper pile, and this feature will be subsequently explained in connection with the hydraulic circuit. Upon predetermined pressure being applied by the clamp, the knife is actuated by pressure conducted to cylinder chamber 53 which rocks the bellcrank 56 counter-clockwise operating the knife bar linkage and at the same time compressing the spring 63 via arm 56B until the downward movement of the knife is stopped by arm 56C abutting dash pot 67. On the return stroke of the knife, pressure being exhausted from chamber 53, the spring 63 expands to rock the bellcrank lever 56 clockwise, moving the knife upwardly until the end of rod 60 abuts rubber bumper 73.

FIGURES 3, 4 and 5 show details of component construction and their relationship to each other insofar as essential elements are concerned. For example, in FIG- URE 2 the three-arm bellcrank 56 is illustrated as pivotal on a pin 82 which is carried at one end in a plate 85 (FIGURE 4) fastened to the machine frame F and has bearing in a journal 88 machined into a wall 90 of the frame, as seen in FIGURE 3. The spring 63 has its outer end abutting in a cup 92 suitably pinned by means of pins to the machine frame as generally illustrated in FIGURE 4. The rod 60 has a threaded end and bolt 98 thereon which abuts on the opposite side of cup 92 to limit spring expansion, it being understood that the rod is slidable in a bore through cup 92, which cup has ears 102 (FIGURE 3) through each of which passes the pins 10S to provide a pivotal mount for the spring between the

walls

90 and 108 of the machine frame.

The bellcrank lever S6 will be understood to be partially bifurca-ted so that the arm 56C is in actuality a pair of parallel arms between which the pull bar 22 is pivotally fastened as by pin 112 (FIGURE 3). The arm 56B is secured by pin 113 to a cap 116 to which the rod 60 is fastened, the cap having bifurcated walls 120 between which the lower end of the arm is disposed. The outer edges of walls about the rubber block 73 which has a metal facing 122 vulcanized to the rubber block in turn vulcanized to a metal block 125 carried in a bracket 128. Bracket 128 is part of the machine frame and metal block 125 may be adjusted axially relative to 3 rod 60 by means of a screw 132 carried inthe block and abutable with bracket 128 (FIGURE 4). A` positive stop adjustable screw 135 is carried in block 125 the end of which may be abutted by the lower end of arm 56B to effect a positive top position for the knife bar after the cushioning effect of rubber block 73.

The piston rod for cylinder 50 (FGURES 2 and 3) is pivotally secured between bifurcations of arms 56A as by a pin 140 with the outer end of the cylinder being pivoted between ears, such as 143, of the machine frame by means of a pin 146 having bearing support in

collars

149 and 152.

Referring to FIGURE 5, the electrical control circuitry is disclosed showing the main motor M to be controlled by the star-ting switch SW1 in a conventional manner, the power lines L1 and L2 being provided for actuation of the control circuitry for the motor and also foi solenoid valves which control the oil pressure cylinders. The control circuitry has left-hand and right-hand buttons, designated as LH and RH, wherein the buttons must be pressed by the operators two hands in order to actuate the clamp and knife. Solenoid SOL-1 controls a fourway valve for the clamp cylinder. Solenoid SOL-2 controls a valve for the knife cylinder and solenoid SOL-3 controls a two-way valve which provides for most of the oil being circulated in the hydraulic system under low pressure when not actuating the power cylinders, thereby effecting a power saving and reducing the heating effect of the circulating oil.

Various microswitches are disposed to be actuated by the knife and clamp, For example, MS-l is a normally open switch which is closed by the clamp when the clamp is in an upper position; MS-2 is a normally closed switch which is opened by the knife when the knife reaches its bottom position', MS-3 is a normally closed switch which is opened by the clamp in upper position and closes when the clamp starts to move. MS-4 is a normally closed switch opened by the knife at upper position which closes once the knife has started to move. MS-S is a normally closed switch opened by the knife when the knife reaches its bottom position. MS-6 is a normally closed switch opened when the knife starts its downward movement. MS-7 is a normally closed switch which is opened when the clamp reaches top position.

The securing of the several knife and clamp operated switches so as to be knife or clamp operated is well known as are switch `constructions and no mechanical d"- tails are necessary herein.

All switches are shown for the condition in which knife and clamp are at rest at stroke top.

The relay coil CR is normally energized via contacts of normally released button switches LH and RH when the clamp and knife are in raised position in order to condition SOL-1 and SOL-2 for energization via relay CR contacts. Relay CR is deenergized when the knife completes its cutting stroke due to opening of MS-2 and MS-S. Thus, the solenoids cannot operate again until the relay is reset by releasing button switches; LH and RH, and knife and clamp are in up positions, closing MS-2 and MS-l, respectively.

The main motor switch and starter system are shown at the top of FIGURE 5, being conventional in nature and having a contact R-l which connects the control circuitry to power when the main motor is started, as effected by relay R.

Assuming the main motor is running, the manually operable LH and RH buttons released being spring biased to the position shown and relay CR is normally energized through switches MS-l and MS-2 and contacts A. This closes all CR contacts CRI, CRS and CRi. Switches MS-l, MS-2 and MS-S are closed at this time since the clamp is in upper position as is the knife.

For operation, manual buttons LH and RH are pressed to complete a circuit through MS-Z, contacts Bfcontacts CRS and 4 and MS-S to energize the clamp control valve solenoid SOL-1. This opens a four-way valve 215 (FlGURE 6) to direct oil pressure to the chamber 43 of clamp cylinder 40 (FIGURES l and 6). After the clamp starts to move it releases switch MS-l which will not close again until the clamp returns to its top rest position. The A contacts of the pushbuttons LH and RH open to break the circuit to relay CR which, however, remains energized through MS2 and CRS. The clamp also releases MS-3 which then closes energizing control valve solenoid SOL-2 through MS-Z, contacts C, CR1, CR3 and MS-S.

Although the clamp is moving, the knife cannot move until the clamp pressure on the paper pile has reached a predetermined value, thus providing an interlock to prevent the knife from starting its motion before the paper pile is fully clamped. This is under non-electric hydraulic control as will be later described. Assuming the predetermined pressure has been built up by the clamp on the paper pile, and since SOL-2 is energized, it opens a four-way valve 22! (FGURE 6) to pressurize chamber 53 of knife cylinder 50. The knife commences moving downwardly thereby permitting closure of switch MS-4 which locks clamp solenoid SOL-1 in energized condition independently of relay CR Contact CR4, although the relay remains energized. Continued movement of the knife to bottom position opens switches MS-2 and MS-S to deenergize the relay CR and SOL-2. Accordingly, all CR contacts open, SOL-2 is deenergized and oil pressure ceases to chamber 53 of knife cylinder 50, but MS-4 remains closed, SOL-1 remains energized, the clamp maintains pressure.

The

valves

215 and 220 are of a commercial type which are moved in one direction by their solenoids but have internal springs (not shown) which move them in the opposite direction when their solenoids are deenergized.

Oil pressures ceasing to flow to cylinder 50 and it being understood that the valve 22) is then actuated to its alternate position by internal spring bias, exhaust of cylinder 5t) occurs through

valves

275 and 220 upon such deenergization of SOL-2. Spring 6) (FIGURE 1) which was compressed as the knife carne down, by virtue of the rocking of bellcrank 56, expands to move the knife to top position. At top position the knife opens switch MS-4 to deenergize clamp Valve solenoid SOL-1 thereby permitting reversal (due to its internal spring) of the four-way valve 215 which controls clamp movement. Such reversal effects movement of the valve to conduct oil under pressure to chamber 46 (FGURE 1) of cylinder 40 effecting raising of the clamp, chamber 43 exhausting. When the clamp reaches top position, relay CR could reset due to closing of IMS-1, but the knife cannot recycle since buttons LH and RH are being held depressed which there-by prevents energization of relay CR due to the open contacts A. Both hands must be removed from buttons LR and RH in order to reset the relay in energized condition. Thereafter, the machine can be recycled by pressing both buttons again.

The circuitry provides for a necessity that both hands of an operator start the cyciing of the machine but after being started one hand can maintain the cycling if so desired. In order to accomplish this the normally closed switch MS-6 may be disposed to be closed when the knife starts its ldownward movement and the switch shunts the Contact C of the LH button. The clamp solenoid SOL-1 remains energized through MS-4 after the knife starts down. The LH button may then be released. By maintaining the RH button depressed SOL-2 will remain energized to complete the knife cycling. Switch MS- is, of course, maintained open by the knife at top position so that two hands are required to start the cycle. If .MS-6 is not supplied, both hands must lbe kept on the buttons for full cuttings strokes.

The function of MSJ and SOL-3 is explained below in detail.

Referring to the hydraulic diagram of FIGURE 6, the system comprises a twin pump having a high capacity section P1 and low capacity section P2 wherein the high capacity section has a -discharge volume of approximately ten times that of the low capacity section. Flow from both sections are used in parallel Via outlet tube 221 for obtaining rapid action during machine cycling. However, P1 has its output shunted through a valve 222 to the tank, the valve 222 being normally open between cycling operations. At that time P2 maintains the clamp in top position through line 225, reducing valve 22d, check valve 232, four-way valve 215, line 236, and check valve 140. Two-way valve 222 is biased internally to open when SAL-3 (FIGURE 5) is deenergized upon opening of MS-7 when the clamp reaches top position. As the clamp starts down MS-'7 closes to close valve 222 via SOL-3 so that full pumping capacity of P1 and P2 is used in clamping and cutting.

The valve 228 is a pressure reducing valve which places a maximum limit on the outlet pressure of pumps P1 and P2 regardless of inlet pressure. In commercial practice such maximum pressure would be about 1200 pounds at the outlet even though pump pressure may rise to about 1500 pounds. Valve 228 can be adjusted for variable outlet pressures.

An auxiliary relief valve 243 is connected so as to control clamp pressure when the clamp is moving down but has no affect when the clamp is in top position.

When valve 215 is shifted by its internal spring (SOL-1 deenergized) pressure from pump P2 is maintained in chamber 46 of cylinder 40 to hold the clamp in its upper position and pump P1 is shunted to the tank as previously mentioned. Sufficient clamp holding pressure is provided by adjustment of a relief Valve 252 so that there is enough force exerted -by cylinder 40 to just maintain and balance the clamp weight at the top of its stroke. This has the affect of maintaining pump section P1 at a low pressure which effects a saving of power and minimum of temperature rise in the circulating oil.

Upon `energization of SOL-1, oil under pressure from valve 220 is conducted to chamber 43 to move the clamp down. The clamp drops initially of its own weight, oil being sucked into chamber 43 via the usual prefill valve 244. Speed of clamp drop can be regulated by the 110W control valve 248 which has a needle valve for adjustment, The check valve 232 prevents bounce of the clamp at each end of its stroke. The ow shunt to tank through valve 222 for pump 'P1 is closed by closing of MS-7 and energization of SOL-3.

Thus, when the clamp starts to move down, the combined capacity of the pumps sends a large flow of oil to the system. Oil from pump P1 goes through check valve 256 which otherwise prevents oil from pump P2 from shunting through valve 222 when the clamp is held in raised position.

A relief valve 260 insures the system against excessive pressure.

As previously mentioned, the valve 228 maintains a pressure to clamp control valve 215 within certain limits for operation of the clamp and a s-imilar valve 264 performs the same function for knife power. However, valve 264 is a so-called sequence valve which requires a predetermined pressure to be exerted on it before passing the oil through to the knife control valve 220. In commercial operation such pressure may be pre-set at about 1350 pounds. As was previously mentioned in connection with description of FIGURE 5, the energization of solenoid SOL-2 is without affect on control of valve 220 prior to a predetermined clamp pressure being brought to bear on the paper pile. The pipe connection 270 in FIG- URE 6 from pressure chamber 43 to a pilot piston with which valve 220 is conventionally provided effects the desired function. Thus, when the clamping pressure begins to build up in chamber 43 oil pressure for actuating the pilot piston of valve 220 can then pass from line 270 to actuate valve 220. Oil under pressure from line 22S-221 and valve 264 can then be directed to flow control valve 275278 to the cylinder chamber 53.

Valve 275 can be manually closed so that flow can take place to chamber 53 only through check valve 278, but oil will then not be able to return to the tank through valve 220. This serves the purpose of permitting the operator to adjust the knife. Thus, cylinder 50 will pull the knife down when the buttons LH and RH are pressed, but when released, oil cannot exhaust from chamber 53 through closed valve 275 back to valve 220, although valve 220 has shifted to exhause position due to de-energization of SOL-2 and the internal spring in valve 220. Accordingly, the knife will be hydraulically locked in place. When valve 275 is opened, spring 60 (FIGURE 1) will raise the knife forcing oil from chamber 53 through valve 275 and thus through valve 220 and ultimately back to the tank.

It will be seen from the above that the system provides a simplicity and a power saving over systems which use respective pumps for the clamp and for the knife. In the present system both pumps are working at all times when hydraulic power is required for clamping and cutting, but only the output of the smaller pump section P2 is required when the machine is idling.

When the clamp is in top position, a cam operated valve 300 opens the exhaust of relief valve 252 to the tank so that the low pressure (approximately p.s.i.) prevails when the clamp is up, thus further reducing the motor load and therefore the heating effect on the oil.

Alternatively, 300 may be omitted and the exhaust or' 252 piped to 301 where the operation of 222 will connect 252 to tank.

All switches of the control circuitry are of conventional construction and it will be understood that although they are described as separate switches, they may be of well known combined construction.

Likewise all valves are of well known conventional and commercially obtainable construction hence detailed deneription of their mechanical construction is not required.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to these skilled in the art. Therefore, this invention is to be limited, not by the specie disclosure herein, but only by the appending claims.

What is claimed is:

1. In a paper cutting machine of the guillotine type, a knife actuating mechanism comprising a single-ended power cylinder means, a knife bar lfor supporting a knife, linkage means connecting said single-ended cylinder means to said knife bar for actuating said knife bar in a cutting stroke when pressure is applied to said cylinder means, a spring means connected to said linkage means and adapted to be stressed thereby when said knife bar is performing a cutting stroke in order to effect a return movement of said knife bar when pressure is released from said cylinder means; said linkage means comprising a bellcrank having three arms and a fixed pivot therefor, one arm being connected to said cylinder means for effectlng pivotal action of said bellcrank lever when said cylinder means is provided with pressure, a second arm being connected for actuating said knife bar, and a third arm being disposed to stress said spring means.

2. In a machine as set forth in claim 1, and further including a dashpot disposed to be abutted by said second arm to limit downward movement of said knife bar.

3. In a machine as set forth in claim 1, said spring means being a compression spring, a rod through said spring, an end of said rod being connected to said third arm, said spring having an end abuttable by a portion of said rod to be compressively stressed thereby when said bellcrank lever is pivotally actuated by said cylinder, and a resilient bumper means disposed adjacent the third arm to be abutted thereby for effecting a stop position in upd ward movement of said knife bar as effected by said spring.

4. ln a machine as set forth in claim 1, including a dashpot disposed to be abutted by said second arm to limit downward movement of said knife bar, said spring means being a compression spring, a rod means through said spring, an end of said rod means being connected to said third arm, said spring having an end abuttable by a portion of said rod means to be compressed thereby when said bellcrank lever is pivotally actuated by said cylinder means and a resilient bumper means disposed adjacent the third arm to be abutted thereby for effecting a stop position in upward movement of said knife bar as effected by said spring.

5. A control circuit for a guillotine type paper cutter having a clamp and knife, comprising a knife control solenoid, a clam p control solenoid, a relay and respective contacts of said relay in series circuit with said solenoids and another contact of said relay in series circuit with said relay, a pair of manually operable switches each having a first contact element in series circuit with said relay, and having a second contact element in series circuit with said knife control solenoid, and having a third contact element in series circuit with said clamp control solenoid, said first contact element being normally closed, said second and third contact elements being normally open and requiring manual force to be held closed while said first contact element is being held open, clamp operated switch means, knife operated switch means, said switch means having switches connected in said circuit to said relay and said solenoids wherein said relay is energized when the clamp and knife are in raised position through said other contact of said relay and said first contact element of said manually operable switches; and wherein said solenoids are energized when said manually operable switches are manually operated and the circuit through said rst contact element of said manually operable switches is then broken; and wherein said relay and said solenoids are then energized through said clamp and knife operated switch means and said respective contacts.

6. The control circuit of claim 5, wherein energization of said knife control solenoid and said clamp control solenoid causes said knife and clamp, respectively, to move toward a cutting and clamping position, respectively, and de-energization of said respective solenoids causes said knife and clamp to return toward their resting positions; and wherein said respective contacts of said relay are normally open, and are only actuated to their closed circuit conditions in response to energization of said relay; whereby if said relay becomes de-energized, said respective contacts thereof will revert to their normally open condition to open the series circuits with said solenoids to cause de-energization thereof to effectuate the return movement of said knife and clamp.

7. A control circuit as set forth in claim 5, said knife operated switch means comprising a switch responsive to knife return movement and connected to de-energize said clamp control solenoid, and said knife operated switch means having a switch connected to de-energize said knife control solenoid when said knife reaches the end of a cutting stroke, said relay being cle-energized when said knife control solenoid is cle-energized, wherein said relay is again energize upon release of manual force on said manually operable switches.

S. A control circuit as set forth in claim 5, one of said switch means comprising a switch shunting a contact element of one of said manually operable switches and being operable upon initial cutting movement of said knife to shunt said contact element so that said one manually operated switch may be released.

9. A control circuit as set forth in claim 7, said knife operated switch means comprising a switch connected to shunt the second contact element of one of said manually operated switches after the knife starts a cutting movement so that said one manually operated switch may be released.

itl. A hydraulic system for operating a clamp of a paper cutter comprising a high volume pump and a low volume pump having separate outlets connected in parallel, a normally open shunt valve connected to conduct fluid to a tank from the outlet of said large volume pump, a check valve connected between the outlets of said pumps whereby outlet huid from said large volume pump only can pass to said shunt valve, an outlet means from said pumps, and valve means connecting said outlet means to conduct fluid pressure to and from clamp cylinder means, control means having elements responsive to initial clamp movement toward a paper pile from a rest position for closing said shunt valve whereby fluid pressure is supplied to said valve means from both pumps, said control means comprising said valve means whereby said clamp is maintained in said rest position by discharge from only said low volume pump through said valve means with outlet ow of said high lvolume pump being shunted through said shunt valve.

11. The hydraulic system of claim 1t), wherein said control means includes an energizable solenoid which closes said normally open shunt valve in response to energization thereof, said solenoid being energized in response to one of said elements being operated iu response to initial clamp movement toward a paper pile, whereby if said solenoid is fle-energized during operation of said clamp said shunt valve will revert to its normally open condition to conduct huid from the outlet of said large volume pump to said tank, whereby only outlet uid rom said low volume pump will he discharged through said outlet means to operate said clamp.

12. ln a paper cutting machine, a reciprocable clamp, hydraulic means for moving said clamp down and returning it to its starting top position, a reciprocable knife, hydraulic means for moving said knife down for cutting, spring means for returning said knife to its Starting top position and holding it there, pump means for supplying high pressure and volume of oil to move said clamp and knife downwardly and for supplying low volume to hold said clamp in its top position.

'13. ln a paper cutting machine as set forth in claim 12, said pump means including a high volume pump and a low volume pump having separate outlets connected in parallel, shut valve means for conducting fluid from said high volume pump to a tank when said clamp is in its top position, and control means for closing said shunt valve means when said clamp and said knife are to be moved downwardly whereby the combined output of said high Volume pump and low volume pump will be utilized to move said clamp and knife downwardly.

References Cited UNITED STATES PATENTS 2,400,996 5/1946 Iverson 83-639 X 2,664,860 l/l954 Levetus 83-639 X 3,118,338 1/1964 Barley 83-639 X 3,182,542 5/1965 Cochran 83--461 X 2,278,713 4/1942 Riddle 83-380 2,825,404 3/ 1958 Barley 83-390 3,173,327 3/1965 Rupp 83-588 3,272,050 9/1966 Barley 83-390 FOREIGN PATENTS 452,317 8/1936 Great Britain.

ANDREW R. JUHASZ, Primary Examiner.