US746856A - Air or gas pump for refrigerating-machines. - Google Patents

Description

PATBNTEDDBG. 1.5, 1903.

P. N. MAGKAY. y AIR 0R GAS PUMP EUR REFRIGERATIN@ MACHINES.

APPLICATION YILED JUNE Z3, 1902.

5 SHEETS-SHEET 1.

NO MGDEL,

F. N. MACKY.

PATENTED DEC. l5, 1903.

AIR R GAS PUMP FOR REFRIGE'RATING MACHINES.

APPLICATION FILED JUNE 23, 1902.

HO MODEL.

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PATENTED DEC. l5, 1903.

NOQ 746.856.

F. NQMAGKAY. .l PUMP PDR REPBIGBRATING MACHINES. APPLIGATION FILED JUNE 23, '1802. I

AIR 0 3 GAS- v SHEETS-SHEET s.'

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PATENTED DBG. l5., l903.

P. N. MAGKAY. A1B 0R GAS PUMP FOR RBERIGERATING MAGHINES.

APPLIGATION FILED JUNE 23,1902.

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PATENTED DEG." l5, 1903.

, RN. MACKAY. f f AIR 0R GAS PUMP FOR RBPRIGERATING MACHINES.

APPLIOATIGN FILED JUNE 23, 1902.

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N0 MODEL.

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UNITED 'STATES Patented December 15, 1903l PATENT OFFICE. c

AIR R GAS PUMP Fon REFRlG-ERATINc-MAci-HNES.

SPECIICATION forming part of Letters Patent No. 746,856, dated December 15, 1903.

` Application ne@ Jute 23, 1902'. sena no. 112,885. in man.)

To all whom t may concern: i

Be it known that I, FREDERICK NOEL .MACKAR engineer, a citizen of England, re-

vented a certain new and useful Air or Gas Pump for Refrigerating-llfachines, (for which I have applied for apatent in Great Britain,

No. 24,04S,dated November 26, 1901,) of which the following is a specification.

This invention relates to an apparatus for utilizing the force produced by the expansion of vapors or gases condensed to a liquid or partly-liquid state in the condenser of an icemaking or refrigerating-machine as motive power for driving such part of the machine as may be best adapted to economically use the saine; and the object ofthe invention is to improve and simplify the construction of this class of apparatus generally.

Although all gases or vapors capable of being condensed to a liquid state are available for the purposes of this invention, I prefer to use carbon dioxid as the refrigerating medium, because this gas in expanding from the liquid state evaporates and expands tol a greater degree in cooling than perhaps any other gas or vapor used in ice-making machinery and' is consequently very Well adapt- .ed for doing economical work during expansion which is afterward utilized in compressing the gas from the expanded or gaseous to the liquid state.

` The apparatus which Iemploy for the above purpose may alsofbe employed for obtaining power from vapors or gases that have been condensed by other apparatus than that of an ice-making machine, as the chief-feature of my apparatus consists in the means adopted for expanding and exhausting the expanded gases in such manner as to insure the maximum amount of power being derived therefrom and also in the means adopted for preventing thelfreezing of the vapors in the passages in and about the valvesA or tappets employed-namely, by causing the incoming and the outgoing vapors to enter and leave the pump by one and the same channel or port, whereby any frozen matter formed by the expanding gases will be removed by the higher temperature of the compressed gases, the exhaust-valve being rendered free to open inward directly the expanded gas is reduced to the pressure of that already in the evaporator or cooler of the machine, so that excess of low temperature is thereby prevented. and thus the chance of freezing up due to excessive lowness ,of temperature is reduced to a minimum. Furthermore, the temperature of the expanding-cylinder is .by the construction of the apparatus prevented from becoming unduly lowered by the fact that while expansion takes place on the one side compression is eected on the other side of `one and the same piston. Also as the incoming gases or vapors from the evaporator are by preference made to' enter the compressor by passing through a hollow pistonrod in the expanding-cylinder a further interchange of temperature takes place, thus also preventing au undue lowness of temperature Within the expanding-cylinder.

It will be obvious that my hereindescribed apparatus can be operated with other refrigerating gases or vapors than carbon dioxid, though for the reason set forth I believe that the best results are obtained by using the ,gas speci lied.

I will proceed to describe, by way of example, a construction [of apparatus which is shown on the accompanying drawings, in which carbon dioxid is assumed to be the refrigerating medium employed.

` Figure l shows a vertical sectionfthrough the pump-cylinderand parts connected therewith on line 1 1, Fig. 5. Fig. 2 shows asoction on line 2 2, Fig. 1. Fig. 3 showsa section through the cylinder, taken at right angles to that at Fig. 1. Fig. Ltshows a section on line L 4, Fig. 5, which shows a cross-section on line 55, Fig. 3. Fig. 6 shows a front elevation, partly in section, of the entire machine. Fig. 7 shows a side view thereof. Figs. 8 and 9 show enlarged details of the several valve devices.

The compressor-cylinder l is made at the same time to constitute an expansion-cylinder in which the work or the expanding highly compressed and condensedgas or vapor is performed, the space above the piston 2 constitutingthe compressor-chamber, kWhile the space below the piston constitutes the expansion-cylinder into which the gas coming from the condenser issues, as will be pres- IDO ently described. Separated from the expansion-chamber by a suitable partition 3, with packing, through which the piston -rod 4 passes, is a lowei chamber 5, intowhich the fully-expanded gas coming from the cooler of the machine passes on its way tothe compressor-chamber. For this purpose the upper part 4 of the piston-rod 4 is enlarged and formed tubular and its upper open end is formed with a coned seating for a valve 6, which is held closed by aspring 7. At the lower end of the tubular part 4 is a lateral opening 8, which always communicates with the chamber 5, into which the fully-expanded gas passes, as will be present-ly described. Thus, on the downstroke of tl1`e piston 2 and consequent formation of a partial vacuum above it, the gas will pass from chamber 5 through opening Sinto the tubular piston-rod and forcing open the valve 6 will pass into the .-ylinder above the piston. On the upstroke it' the latter it will compress the charge of gas above it (valve 6 being 'then closed) and force it through the valve 9 into the chamber 10, communicating with the condenser, as will be presently explained.

In order to insure a perfect gas-tight working of the piston 2, it is preferably constructed, as shown-namely, with a cupleather packing 11, fitting the enlarged head of the piston, as shown-and secured by a screw-nut 12 and lock-nut 13, both screwed onto an external thread 14 on the piston-rod. It will be seen that the upper end of the piston with its valve is made to fit closely up to the under side of the valve 9`and its seat 47, just short of actual contact at the end of the upstroke, so that the whole of the charge com pressed by the piston will be forced through the valve 9 into chamber 10, thus preventing any opposition against the next upstroke of the piston and consequent Waste of power due to the rexpansion of any gas remainingin the cylinder on the downstrok Vof the piston.

To the side of the cylinder 1 is xed a double-valve apparatus 15, communicating therewith by a single passage 16. This doublevalve apparatus is constructed and operates as follows: The valve-chamber 17 communicates with the condenser of the machine by a pipe 18, from which the condensed gas passes vinto the chamber ata very high pressure, such as sixty atmospheres. In this chamber is an inlet-valve 19, closing an opening 20, leading, rst, into the upper end ot' the lower valvechamber 2l and thence through passage 16 into cylinder 1, so that when 19 is momentarily opened, as will be presently described, a certain quantity of the condensed gas will flow through 2O and 16 into the cylinder. The opening of the valve 19 is timed to take place when the piston 2 has just completed its downstroke, so that as the piston receives its upstroke from the crank-shaft of the machine the admitted chargeof gas in'expanding below it acts as motive power in assisting in eecting the upstroke of the piston for compressing the charge admitted above it, as described. The lower valve chamber 21, which, as before stated, also communicates with the cylinder through the passage 16, contains a valve 22, closing the communication between passage 16 and a pipe'23, leading to the cooler of the machine. When the piston 2 com mences its downstroke,valve 22 is opened, as will be presently described, and the partiallywexpanded gas below the piston which, however, is still at a pressure of, say, twenty atmospheres, escapes through 16, 22, and 23 to the cooler. The gases in expanding during the upstroke of the piston will of course be reduced in temperature, and although the fully expanded and comparatively warm gases passing in through chamber 5 and tubular piston-rod 4X will to a certain extent counteract such decrease of temperature, yet the gases passing o through passage 16 may still be sufliciently cold to freeze the particles of oil carried with them, and thus obstruct the passage. I prevent this, however, by causing the condensed gases, which are at a higher temperature', coming from chamber 17 to pass into the cylinder through the same passage 16 through which the expanded gases escape, so that the passage is warmed thereby and the deposit of any frozen oil particles in it from the escaping expanded gases will be prevented.

As the valve 19 is subject to considerable( downward pressure by the entering condensed gas, I relieve it to a certain extent of such pressure by forming it with an upward extension 19X, passing up through a gas-tight packing 24 into a chamber 25, that communicates by a passage 26 with the upper end of the lower valve-chamber 21, as shown at Fig. 2, so that the upper end surface of the valve-stem is only subject to the pressure in this valvechamber. The chamber 17 is divided by a partition 27, through which the valve-stem Works into an upper and lower compartment which communicate with each other by a passage 28, opening into the upper compartment at a point somewhat above the partition, so that the oil coming in with the condensed gas will leak down between the valvespindle and partition into the lower compartment, where it will lubricate the actuatf ing cam-spindle 29X, while the gas will pass down through the passage 28. The valve 19is openedby the revolving cam 29, whose spindle receives rotary motion through toothed gear 30 from the cam-spindle 31 of the discharge-valve 22, driven by a chain-wheel 32 and pitch-chain from the crank-shaft, so as to revolve synchronously therewith.

For enabling the supply of condensed gas to the cylinder 1 to be regulated to any degree required the cam 29 is made tapering, as shown at Fig. 2, and is capable of being movedlongitudinally relatively to the valvespindle by means of a hand screw-spindle 33, so as to increase or decrease the extent to IOO ICS

IIC

which` the valve is raised by the cam and the duration of its opening. As the packing 34 in thestufting-box of the cam-spindle is subject to the high 'pressure of the gas coming from the condenser, the packing is divided into two parts, as shown, between which is a lantern-piece 35, communicating, by means of a channel 36, with the channel 26, leading to the valvechamber 21, so that any gas and oil leaking 'past the inner part of the packing. 34 will find its ,Way through 36 and 26 into 21, and thus leakage through the outer part of the packing'34 will be prevented.

It will be seen from the above-described arrangement of the discharge-Valve 22 that should the condensed` gas admitted to the cylinder below the piston 2 in expanding become less in pressure than that within the cooler of the machine the said valve will open automatically and in allowing the gas to'pass from the cooler lo the cylinder 1 the pressure will be equalized, thereby preventing an undue lowness of temperature in the cylinder. The oil that comes over with the gas from the condensel will by thechlling of the expansion-cylinder 1 be caused to remain to a great extent in the latter and will lubricate thecup-leather packing of the piston 2 and that of the partition 3. This partition and packing is secured in position by a lantern 37, which in its turn is Vsecured by the gland 89 of the stuffing-box to be presently described. The piston-rod 4 Works through av cup-leather 39, held in the partition 3-by a ring 38, secured by screws 42.

r1`he lantern 37 isconnected to the stuihngbox vgland 89 by a rotatable connection consisting of a groove 40, in which'the thickened end 41 of the lantern' is held by grooves and pins 43.

In order to prevent an undue accumulation lof oil in the expansion-chamber of the cylin der, I provide a discharge-passage 44 just above the partition, through which the oil as it collects over the partition Hows into a chamber 45, formed; in the cylinder-casting.

I From this chamber the oil is allowed to pass Y inder, the gas'will thereby be made to take upsufcien't of thev oil to convey it `to thev compressor-chamber, and thereby lnbricate the partsthereof as described and make good the'quantity of oil discharged with the compressed gas. l

For readily ascertaining the amount of' oil in the chamber 5 thereis provided'at the lower part thereof a gage-'glass 52', which is fitted into a small chamber 53', formed at the side of the pum p-casting, with sight-holes 54. The ends of the gage-glass aretted With pump-cylinder due to expanded gas. vchamber 48 communicates atrophy the regu- `grooved plugs 55', fitting the-hereof chamber 53' and pressed tight onto the ends ofthe glass by the screw-capf. The-:plugs have a central passage l57',.communicating with, the interior of the glass and with aftransverseA passage 58', communicating Withthelcircular channel 59f, formed bythe grooveofthe plug,

which channel'spin` their turn communicate with the openings GOQleading into, t-hepumpconsists, tirst, of an outer glandgl),4 screwed into the neck of the cylinder and having a grooved flange 89X with packing for. making.

ages-tight joint against the ,end 0f -the cyling a tight joint against the piston; thirdly, a ring 91, screW-inginto the internal thread yof gland'89 for keepingthe cup-leather in position and. making a gas-tightjoint therewith;

inder-neck; secondly, a cup-leatherQ, makfourthly, a packing consisting,by preference,

of two rings of leather 92, between which are rings of elastic material; and, lastly, an

inner gland 94, screwed Ainto theonter gland. 39, so as to tighten upthe packing A92 93. vThis inner gland is loosened when the machineis working, because at that time the `gas-pressure causes thejcup-leather to make a gas-tight; fit against the piston-rod but when the machine is standing and the pressure isv comparatively small Vthe cupleather may not fit Asufficiently tight to prevent a leakage of gasgor oil between'it and th'e piston-rod, and to'vprevent any such leakage at that time the gland 94 is then screwed up, so as to tighten the packing 92 93 against f As shown in the section,atFig. 3,thecasting ofthe pump-cylinder 1 is formed with a suc-A tion-chamber 48 on one side thereof and with a discharge-chamber 49 onY the other side,

-these chambers being preferably formed in IOO rio

one casting with the cylinder in order to effect an interchange of temperature between themandconduct the heat of the compressed `gasfin chamber 49 to the pump-cylinder 1 to prevent the freezing of oil particles in said The lating-valve 5'0 .with therpipe 51- from the bottom of -the cooler and at bottom by the opening 52 with the bottom chamber 5 of the 'pump-cylinder, so that on the .piston 2 per`vr `forming its downstroke the expanded gas and oil vapor carried thereby will How down cham- ,ber 48 andthrongh opening 52 into chamber into the discharge-chamber 49, whence it lpasses vthrough opening 54 and regulating; 1valve 55 into, pipe 56, leadingto the condenser. l

In lorder to prevent the oil vapor carried by the gas from passing oi with the latter through the opening 54, a baille-plate 57 is xed in the chamber 49 between the openings 53 and 54, so that the oil vapor in striking against such plate is deflected thereby and descends to the lower part of the chamber 49, where it is condensed by the cold interchanged between the lower end of the pumpcylinder 1 and the lower end of said chamber 49, the gas freed from the oil passing up on the other side of the baille-plate and passes off through 54.

At the lower part of the discharge-chamber 49 is formed a small lateral opening 58, leading into the bottom chamber 5 of cylinder 1, which opening is closed by a stop-valve 59" of a construction -to be presently described, so that when required this valve is opened -and more or less of the oil accumulated in` chamber 49 is allowed to tlow back into the pu nip-chamber and thence into the suctionchamber 48.

The seat 47 of the compression-valve 9 is formed cup-shaped, as shown, so that a certain quantity of the oil passing up wit-h the gas will accumulate in it above the compression-valve and willv thus prevent any down- Vward leakage of the compressed gas through the valve when the piston performs its downstroke, while any leakage ot the oil-will not matter, as it will only pass down onto the piston 2 and serve to lubricate the packing l1 thereof, to facilitate which small passages 59 may be formed in the piston.v

At the one side of the pump-chamber is formed asmall chamber 60,having attached to it a screw hand-pump 6l for forcing oil into the pump-chamber from the outside (for making good any loss, such as oil that may have leaked through the gland) should the oil therein be deficient. The barrel 6l has for this purpose a screw-spindle 62 screwing'through its cup-shaped upper end 63, which is filled with the oil to be supplied. This oil finds its way down into the barrel 61 through longitudinal grooves 64, formed in the screwspindle, the lower end of which has rotatably attached to it a plunger 65, that lits the bore of the chamber 60, which has a lateral opening 66 leading into the pump-chamber and closed by a stop-valve 67. When it is required to supply oil to the pump-chamber, the screw-spindle 62 is first screwed upward, so as to withdraw the plunger from the bore of chamber 60, thereby causing the oil to liow down from the cup 63 into this chamber. On then unscrewingthe stop-valve 67, so as to open passage 66, and screwing the spindle 62 down again the plunger 64 will force the'oil into the pump-chamber, after which the stopvalve is closed again.

The stop-valve 67, as also all other stopvalves of the machine, is preferably constructed as follows-z A screw-threaded spindle 67 has its inner end formed with a central recess 68, so that it seats with an annular edge over the opening. This spindle screws through a gland 69, that is screwed into thev cylinder-casting, and is secured by a locknut 70, having an annular groove on its under side filled with packing material, so as to prevent leakage past the screw-thread. The outer end of gland 69a has a coned recess, into which fits a correspondingly-shaped block 71, of .suitable packing material, and on its outer screw-thread is screwed a socket-piece 72, so formed with a partition 73 as to press upon the packing 71 by means of a loose washer 74, and thereby form a gas-tight packing for the screw-valve 67. The stem of the latter extends through the partition'73 into the outer part of the socket-piece,which is closed by a screw-cap 75, having an annular groove lled with packing. It will be'seen thatv by this construction all leakage past the screw stop-valve 67 is efEectuall-y prevented,- first, by the packing 71, and, secondly, by the packed screw-cap 75. For opening or closing the screw-valve the cap 75 is temporarily removed. Fig. 8 shows the application of the same construction screw stop-valve tothe valves 50 and 55 for controlling the suction andv discharge to and from'the pump-cylinder 1. The only dierence'in this application is that the part 69a instead of being' screwed with its end into the cylinder communicatesv therewith by a lateral screwed branch 76 and has its other end connected by a gland with suitable packing to the pipe 51 or 56, leading in the one cas'e from the cooler and in the other case to the condenser. Fig. 9 shows the same construction of valve appliedas the expansion-valve 77, connecting' the pipe 23 from cylinder 1 to the cooler-coil'78, Fig. 6. In this case the screw-valve has a small plug 79 fixed in it, which fits into the small passage 80 of the pipe 23, leading from the discharge-valve.

Figs. 6 and 7 show the general arrangement of the above-described machine for compress-vv ing and expanding gases or vapors for refrigerating purposes. The cylinder lis mount ed on the top of a frame 91, at the bottom of lwhich are concentric-ally arranged the conup through the pipe 18 to the inlet-valvechamber 17 in order to do work in partially expanding in the cylinder, as before explained,the partially-expanded gas then passing from the discharge-valve chamber 21 through pipe 23 and expansion-valve 77 into4 the upper end of the cooler-coil 78.

The operation of theapp'aratus is briefly as follows: Expanded gas or vapor compressed by the piston in the cylinder 1 passes into the chamber 49. From the chamber 49 the compressed gas passes through the pipe 56 to the upper end of the condenser-coil 92, where its heat isexracterl and it is condensed hy a cooling medium surrounding said coil. The condensed or liquefied gas then passes from the lower end of the condenser-coil 92 by the to the upper end of the cooler-coil 7S, where From the lower end of the cooler-coil 78 the l expanded gas passes by the pipe 51 tothe upper end `of the chamber 48, then down through the chamber 48, and into the lower end of the hollow'piston, by which it is compressedand delivered tothe chamber 49. The operation continues in this cycle. v

It will be seen from the above-described arrangement that any of the sealing-oil that may pass from the pump into the condensercoil will be made to passup from the lower end of the latter through pipe 18 into the cylinder again, collecting in the oil-chamber 45, as described, and also any oil passing from the cylinder with the gas-through pipe l23 into the cooler-coil 78 will be drawn from the-bottom of the latter through pipe 5l to the suction-chamber of the compressor-cylin- 1 y f pauding gases or vapors for refrigerating pur- Y v der, so that by this means any accumulation otherwise.

of oil in the condenser-andcooler coils is effectually prevented. 1-

On the driving-shaft 93 of the machine is a chain-wheel 94, geared, by means of a pitchchain 95, with the chain-Wheel 32 on the camspindle 31, that works thevalves 19 and 22, as before described.

For charging the machine in the drst instance with carbon dioxid or other vapor from a convenient source, such as a CO2 cylmarked thermometer 98is fitted in the cap of the pump-chamber, so that by the increase or decrease of temperature lshown by the thermometer it will be seen whether the charge of gas in the machine is deficient or For facility of observation I prefer to mark the thermometer with a red line at the point 99 of the scale, where the rise Vof temperature would indicate that more gas is wanted in the machine or the expansioncock required to be opened to a greater extent The partially-expanded gas i chamber 49 are each provided with 'a pressure-gage 10i.

Having thus described the nature of this invention and the best means I know of carposes, a compressing-cylinder divided by a partition into an upper and lower chamber,

. a pistou Working in the upper chamber of the cylinder and having a piston-rod made partly tubularworking through the partition, a latl, eral opening communicating with the hollow of the piston-rod which extends through the I piston on the upper side of which it is closed by avalve held down by a spring, a valve E apparatus communicating with the upper 1 chamber of the cylinder below the piston andI adapted to supply the same with charges of;

lcondensed gas during the Working stroke of; :the piston, and todischarge the partly-ex` l panded gas during the return stroke of the pist-on, means for supplying fully-expanded ilowing'working stroke, substantially as and` forV the purpose described.

2. In machinery Afor compressing and eX- ;poses, thecombination of a compressing-cyl- LinderA 1, partition 3, piston 2, tubular pistonrod 4 4X, Working through the partition 3 Y and having an openingScommunicatingwith the lower chamber 5 of the cylinder, a Valve 6 closing the upper end of .the tubular pistonrod,a chamber 10 with valve 9 into which the compressed gas is forced by the piston, a chamber 48 communicating on the one hand with the discharge-pipe of the cooler-coil and on the other hand by an opening 52 with said lowercham ber 5 forsupplying fully-expanded gas thereto, a chamber 49 communicating with the chamber l0 and with a pipe lead- Aing tov the condensing-coil, valve apparatus 15 communicating with cylinder 1 by a passage 16, and containing firstly a chamber 17 with valve 19 operated by a cam device for admitting condensed gas to the cylinder through passage 16 and secondly Va chamber 21 with valve 22'operated by a cam device for discharging the partially-expanded gas from the cylinder through passage l'to the Vcooler-coil of the machine, substantially as and for thevpurposes described.

3. In an apparatus ior compressing gases or vapor for refrigeratin'g purposes, the combination of a cylinder, a partition in said cylinder,a piston ,working on the upper side of said partition, a hollow piston-rod passing through said partition, a'valve controlling the passage through said piston-rod, a passage communicating with said cylinder between said partition and said piston, means for supplying compressed gas or vapor to said pas- IIO sage, means for withdrawing said gas or vapor from said passage when it has become partially expanded beneath said piston, an inlet to said cylinder below said partition for expanded gas, and an outlet from said cylinder above said piston' for said gas.A l

4. In an apparatus for compressing gases or Vapor for refrigerating purposes, the combination of a cylinder, a partition in said cylinder, a piston Working on the upper side of said partition, a hollow piston-rod passing through said partition, a valve controlling the passage through said piston-rod, a passage communicating with said cylinder between said partition and pistona chamber for compressed gas or vapor communicating with said passage, a valve between said chamber and said passage, a second chamber communicating with said passage, a valve between said second chamber and said passage, an inlet to said cylinder below said partition for expanded gas, and an outlet from said cylinder above said piston for said gas.

5. In an apparatusfor compressing gases or vapor for refrigerating purposes, the combination of a cylinder, a partitionin said cylinder, a'chamber in the upper end of said cylinder provided with an upwardly-opening valve, a piston working on the upper side of,

said partition, a hollow pist-on-rod extending through said partition, an upwardly-opening Valve controlling the passage through said piston-rod, means for supplying gas or vapor to said cylinder between said piston and said partition, means for withdrawing said gas or vapor from said cylinder after it has become partially expanded beneath said piston, an inlet to said cylinder below said partition for expanded gas, and an inlet to the lower part 4ofsaid tubular piston-rod for said gas.

6. In an apparatus for compressing gases or vapor for refrigerating purposes, the combination with a condenser and a cooler; of a cylinder, a partition in said cylinder, a piston working in said cylinder above said partition, a hollow piston-rod extending through said partition, an upwardly-opening valve controlling the passage through said piston-rod, a passage leading from said condenser and entering said cylinder between said partition and said piston, a valve for controlling said passage, a passageleading from said cylinder between said partition andsaid piston to said cooler, a valve for controlling said last-mentioned passage, a passage leading from said cooler and entering said cylinder below said partition', a passage leading from the upper part of said cylinder above said piston to said condenser, and a valve for controlling said last-mentioned passage. y

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

FREDK. NOEL MACKAY.

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