US1594422A - Automatic safety trap for refrigerating machines - Google Patents

Description

Aug. 3 1926. 1,594,422

A. T. MARSHALL AUTOMATIC SAFETY TRAP FOR REFRIGERATING MACHINES Filed Dec. 4, 1924 l I in n Gila/rs amp/1R4? sac/r P/rsnswrf snare/v 3 a q 7 r/ro/v EXPANSION 00/4 sou s r/PA P a 3 CG/VDEA/SEF? i To r lmmvslolv Wu v4 RECEIVER INVENTOR ALTIORNEYF Patented Aug. 3, l 926.'

UNITED STATES PATENT OFFICE.

ALBERT T. MARSHALL, OF JEARTFORD, CONNECTICUT, ASSIGNOR TO THE AUTOMATIC REFRIGERATING COMPANY OF HARTFORD, CONNECTICUT, A CORPORATION OF 7 NEW JERSEY.

AUTO MATIC SAFETY TRAP FOB REFBIGERATING MACHINES.

Application filed December 4, .1924. Serial No. 753,961.

This invention relates to refrigerating apparatus using a condensab'le vapor. In such apparatus trouble sometimes occurs from the.

passage over to, the compressor of slugs of liquid which mayresult-in the blowing out of the. cylinder head or other damage. Ordinarily, the smallscale trap that is interposed in 'the return line from the expansion coils is sufiicient to intercept such slugs of liquid and hold them until they re-evaporate I under the suction action of the compressor,

particularly if a choke diaphragm or equivalent device is interposed in the pipe between the trap and the compressor. At other times, the amount of'liquid coming over may be so great as to more than fill the scale trap.

The object of the present invention isto' provide means whereby such excessive amounts of liquid will be automaticall removed I from the suction conduits an returned to the liquid receiver, and in the event of the li uid coming over in an amount greater t an the return apparatus ,can take care of, I provide means whereby,

in such event the compressor is automatically stopped and again started when the liquid isdisposed of to a sufficient amount to make its operation safe. i

The inventioni' will be further described in connection with the accompanying drawings, in which a Figure 1 is a; diagram of refrigeratin apparatus to which my invention is appli Figure 2 is a detail mechanism. I

Figure 3 is a detail view of a modification of part of the apparatus in section.- I

' of the top part view of the switcli Figure 4 is an outside view of said modification. y

A receiver 1, containing a reservoir of condensed vapor, has a pipe 2 leading to an expansion valve which feeds the expansion or refrigerating coils. I Areturn pipe 3 from the expansion coils leads to the suction of a compressor 4 and a-pipe 5 takesthe compressed vapor from the compressor to the condenser 6t A scale trap,- 7' is inter .poseclin the suction line and. at '8 may be introduced a choke diaphragm in which the vapor is compelled to pass through an orifice very much smaller than the cross section of the pipe 3, with the result that any slugs of liqluld passing through will be heldup and on y so much allowed to pass as the com- 14 to, for example, the receiver 1.

pressor can take care of. A back pressure switch is shown at 9,-which serves the usual purpose of stopping the compressor when the pressure in the suction line falls below a certain limit, and restartingthe compressor when the said pressure-returns to a predetermined point. When larger amounts of liquid come over than the scale trap can take care of, I provide means whereby the surplus liquid can be automatically drained away as follows i A drain pipe 10 from the scale trap discharges the liquid from the scalev trap into a safety trap 11 which is of ample size to take care of such excessive amounts of liquid. A pipe 12 leads from the bottom of the safet trap. tov a pump 13 which pumps the liqui from the safety trap through safety trap 11 should be surrounded with' cork or other heat insulation 15 and is'shown mounted on the latform of a weighing scale 16, the weight I cam 17 of which has the usua adjusting weights 18 held on its outer end. Mounted on a stationary support is an electric switch 19 which may be of the usual quick-acting, snap over type. It is operated by a rod 20 which impinges against the scale beain 17, against whlch it is held either by its own weight or by weight assisted by the spring 21. Adjustable stops 22 onthe rod determine accurately at 'what point the said stops actuate the trig 23 that, :13; means of. spring 24, acts to t row the swi 19 either up against Contact 25 or down against rest 26. From contact 25 and switch 19, circuits lead to the motor driving the liquid pump 13. In addition to the adjustable weights 18 on-the scale beam, I provide an additional weight 27 held normally suspended on supports 28 from the frame. An adjustable piece 29 on the weight rod 30 is adapted to lift the weight 27 and transfer its weight'from supports 28 to the rod 30 when the weight of the liquid accumulated in the safety trap exceeds a certain amount. Before this occurs, the scale beam V value t at control electromal. tip the scale beam stil'l further member 29 to lift the weight on this occurs, the scale beam going up further, will lift 0 eratin rod 31 01 an additional switch 32. is swltch may be a quick-acting switch as is the switch 19. "When the rod 31 is thus pushed up by the scale beam, the switch 32 breaks the circuit of the motor driving compressor so that the compressor will be stopped before any damage from furtheraccumulation of liquid may occur. While I have shown these electric switches 19 and 32 as being placed directly in the circuits of the motors, they are, in practice, preferably of the relay type and onl operate circuits'of small current etic main switches in the motor circuits 1n a manner weli understood in the art. It is, of course, understood that pipes'lO and 12 supplying iiquid to and from the safety trap, will be flexible enough to permit the free vertical motion of the trap. As the total vertical mo vision in the pi e tion of the trap is a small fraction of an inch, this does not require any special proalthough such special provision may, 0 course, be made. The safety trap just described, thus serves to trap a certain amount of liquid, which may be rep evaporated by the suction of the pump with-- out actuating the weighing mechanism. Should it, however, accumulate faster than the compressor can take care of it, it will,

after arriving at a certain level, cause, by its weight, an lnitial movement of the scale-v beam whereby the weights 18 are lifted until ,the member 29 rests against the weight 27.

' cum'ulates.

started and ordinarily will safety trap.-' When the trap is sufficiently At this point, the liquid ump 13 will be soon empty the evacuated, the weight 18 will again descend, which will result in the opening of the circuit of the motor driving the liquid pump, thus causing a cessation of the operation of the pump until the liquid again achould, however, the accumulatron of liquid continue .at a rate that the small pump 13 is not able totake care of,

the added weight in the trap will cause a further movement of the scale-beam whereby .member 29 will be enabled to lift the wei ht 27 and this will cause theo ration 1e switch 32' and shut down tli: comressor. The, compressor maysubsequently started up aga n by the operator, or, if desired, the compressor may be automatically restarted by the closing Y in of the circuit of its driving motor w on the evacuat1on of the tra by the liquid pump brings the wei ht of iquid in the trap down to a point w ere it would be safe for the compressor to again start the suction.

In Fi re 3 I have shown another way of accomplishing the'same result. Here a stationary trap 34 has a float 35 which is supported on a spring 36. This float moves f other fol owing upon further accumulation of liquid, to stop the compressor. While I have shown two means of carryin my invention into effect, I do not wish to limited specifically thereto, as there are alter native means that could be equally applicable. The liquid pump could be started and stopped by mechanical means instead of electrical and the trapped liquid may be returned to any part of the system suitable to receive it. In some cases this might be part of the expansion side, like coils or cooler in large brine tank. For causing the weight of liquid in the trap to operate the switches, I have shown an ordinary form of platform weighin scale but the same re-v sult could be obtained if the trap were suspended by suitable levers that. would give the desired multiplied motion. The scale trap can be. omitted and safety trap serve the purpose of both.. The action of the ac cumulation of liquid in the trap 11 in operating the switches to start and stop the motors requires a certain amount of time.

In other words, it is necessary that the scale beam does not move quickly from one position to another but that its action be delayed in order that the-trap may have time to fill or em ty as the case may be, so as to not have t e starting and stopping of the motors occur more often than necessary. This de-' layed action may, for. example, be brought about by the tension of the springs 24 of the electric switches acting to hold .in restraint the rod 20 until the maximum and minimum weights in the trap are reached.

In the same way, the spring 24 of the switch- 32 will restrain the operatlon of rod 31 until the desired additional accumulation or reduction of liquidin the trap takes place. A spring 43 whose tension is adjustable by means .of an adjusting screw 44, may be used to regulate the resistance to the movement of the scale beam under the action of the liquid in the trap. In Figure 2 I have shown in a dotted" line diagram, means whereby the movement of the scale lever acting under the combined effect of the changeable weight of the liquid trap, the weig ts 18 and 27, and the spring 43, may act to close and open relay circuits from a source of electricity, shown at 45, whereby the compressor will ordinarily take care of further accumulations but the liquid pump will continue to operate until contact 46 reaches terminal 47 when the trap being a contact arm 46 will-contact with terminals 47 and 48 near the lower and upper limits of the motion of the scale beam,to operate a throw-over switch 49 by means of electromagnets 50. and. 51, to open the circuit of he liquid pump motor when the scale beam is near its lowermost position, and to close the same when the scale beam is near its uppermost position. It will be noted that such a switch operates only when the scale beam nears lts extreme posit on and 1s mactive at intermediate points.

vations of the scale beam, make contact with terminals 52 and 53, which, operating through electromagnets 54 and 55, will control a switch 56 that will operate at the proper times to close or open the circuits 33 of the motor driving the compressor. It

will beunderstood that with such switches, the scale control spring 43 will keep the.

scale resistance to the weight of the liquid in the" trap in. balance, which, in the ordinary operation of the plant, will mean that the liquid pump is not running and the compressor is running, the fluctuations of liquid in the trap, if any, being not sufii driving the liquid pump and thus start the evacuation of the trap, returning the liquidv therein to the receiver or'a-ny other suitable location. Ordinarily the operation of the liquid pump will prevent further accumulation of liquid in the trap and decrease the same until the trap is nearly or quite empty when contact 46 will touch terminal 47 and open the circuit ofthe liquid pump motor. If the operation of the pump is not suflicient to take care of the accumulation of liquid in the trap, the scale beam will lift the scale. beam consequent thereupon, the p st11l further and when contact 46 touches terminal 53, the magnet 55 will operate switch 56 to open the circuit 33 of the compressor motor, thus shuttin down the compressor before damage can done by overflow of liquid into the compressor cylinders. With the compressor thus shut down, the pump will be enabled to evacuate the trap and at some suitable point-in the descent of contact 46 will touch terminal 52 and restart the com ressor by the operation of magnet 54 closing switch 56. "From there on emptied, the pump motor will be stopped. It will be seen .from the above that I have Similarly,

. the contact 46 may at lower and higher eler provided means whereby abnormal accumulation of liquid in the trap will start a pump or other means which may, of course be a release valve to bring" about the reduction of the accumulation and that upon still further accumulation beyond the ability of such means to take: care of, still other means are provided for, in that event shutting down the compressor and that upon the reduction of the weight of 1i uid in the trap to a desired minimum, t ese operations are reversed.

I claim 1. The method of preventing excessiveamounts of liquid from entering the suction of the compressor of a refrigerating system, which consists in running such excessive liquid into a trap and causing the accumulation of weight of theliquid in the trap to operate electric switches to start a pump that will. evacuate the trap when the accumulation of liquid in the trap exceeds a certain amount and upon the further 110- cumulation of liquid in the trap to stop the compressor and a ai'n start the compressor when the liquid 1n the trap is reduced a predetermined amount.

2. In a refrigerating system using a condensable vapor, the combination comprisinga compressor having suction and delivery pipes, a trap for liquid in the suction pipe, means operated by the weight of accumulated liquid inthe trap to force the a liquid from the trap into the delivery pipe, and other means for stopping the compressor upon further accumulation of liquid in the trap. I

3. In a refrigerating system using a condensable vapor, the combination comprising a compressor having suction and delivery pipes, a trap for liquid in the suction pipe, means operated by the weight of accumulated liquid in the trap to force the li aid from the trap into the delivery pipe, other means for stopping the compressor upon further accumulation ofliquid in the.

trap, and means for restarting the compressor when the weight reduces.

. 4. In a refrigerating system using a condensable vapor, the combination comprising a compressor havingv suction and delivery pipes, atrap for liquid in the suction pipe, means operated by the weight of. ac cumulated liquid in the trap to force the li uid from the trap into the delivery pipe, other means for stopping the compressor upon further accumulation of liquid in the trap, and means for restarting the compressor when the weight reduces and stop pingthe liquid pump upon still further reduction 0 weight. 1 I

5. In a refrigerating system using a condensable vapor, the combination comprising a compressor having suction and delivery pipes, a trap for liquid in the suction pipe, means operated by the weight of accumulatedliquid in the trap to force the liquid fromthe trap, and means for opposing a cumulative resistance to the weight operated means to.delay the action of the said weight operated means until a desired maximum accumulation has been reached.

6. In a refrigerating system using a con densable vapor, the combination comprising a compressor having suction and delivery pipes, a trap for liquid in the suction pipe,

means operated by the weight of accumulated liquid in the trap to force the liquid from the trap, and adjustable means for opposing a cumulative resistance to the weight operated means to delay the action of the said Weight operated means until a desired maximum accumulation has been reached.

ALBERT T. MARSHALL.

Images