1958 



MACHINERY 



MACHINERY 



In most pumps there is a narrow space left between 

 the piston and the inner wall of the chamber. This is 

 filled with some one of the many kinds of packing. One 

 of the cheapest of these is made of loosely rolled tow 

 strings and is sold as "candle-wicking." The best 

 kinds are combinations of canvas and rubber. It is 

 poor economy to buy cheap packing. The best does 

 not last very long and the time lost in replacing poor 

 packing would pay the slight extra cost of the better 

 grades many times over. 



No other part of the pump requires as frequent 

 attention as the packing, therefore it is important 

 that pumps should be so designed as to give ready 

 access to the packing and also that some means should 

 be provided for keeping it tight against the plunger. 



Considering the packing only, pumps may be divided 

 into two classes: outside-packed and inside-packed. 

 An outside-packed pump is one in which the packing 



1.50 



1.25 



1.00 



NOZZLE DISCHARGE 



| 



"Whirlpool"- small disc-opening 

 V - laree " 



.25 



Pounds Pressure 



2291. Diagram of the pressure and nozzle discharge. The amount of spray 

 discharged increases rapidly at low pressures but more slowly at higher pres- 

 sures. The amounts differ with different makes. 



is set on the inside of the pump-cylinder and presses 

 against the outside of the plunger (Fig. 2289, E). Such 

 packing may usually be reached without removing the 

 plunger. An inside-packed pump is one in which the 

 packing is on the face of the plunger and presses 

 against the inside of the pump-cylinder (Figs. 2289, F, 

 and 2290) thus necessitating the removal of the plunger 

 before it can be renewed. 



All parts, such as valves, plungers, and cylinder 

 lining, which come in contact with spray materials, 

 should be of brass, as this does not corrode so rapidly 

 as steel. For inside-packed pumps, a bored cylinder is 

 truer than a drawn tube and so pumps much easier 

 because of the decreased friction. 



A single-action pump is one which draws in the 

 liquid as the plunger moves in one direction and drives 

 it out as the plunger moves back. There are only two 

 valves on such a pump. When two single-acting cylin- 

 ders are used on the same pump it is called a two- 

 cylinder, or duplex pump; one with three such cylinders 

 is called a triplex pump. 



A double-action pump is one in which the plunger, as 

 it moves forward, pushes the liquid out ahead of it 



and at the same time draws in liquid back of it, then, 

 as the plunger moves back, this second amount of 

 liquid is pushed out and a new charge drawn in behind 

 the plunger. Thus, a complete forward and backward 

 movement of the plunger should discharge twice the 

 capacity of the cylinder. Such a pump requires four 

 valves and always has the packing on the face of the 

 plunger. 



Nozzles. 



Spray liquids were first applied in a solid stream, 

 though this was usually fine enough to be broken into 

 drops by the resistance of the air. The next step 

 forward was to place an obstruction at the end of the 

 nozzle so that the stream, striking against this, was 

 spattered out in fine drops. This method is still in use 

 in the bordeaux nozzle, a device that gives a fan-shaped 

 spray which at high pressures two hundred pounds or 

 more-yis mist-like. It is not adapted to 

 fungicides, but may be used in applying 

 poison sprays. 



In eddy-chamber nozzles, the liquid is 

 thrown into a whirling, or cyclonic, motion 

 in an eddy-chamber from which it is dis- 

 charged through a small opening. Particles 

 leave this opening in a direction tangent to 

 their previous rotation, thus producing a cone 

 of spray more or less uniformly filled. There 

 are two ways in which the rotating motion is 

 secured in the eddy-chamber: in one, the 

 liquid enters the chamber through openings 

 which have much the same pitch as the thread 

 of a screw; in the other, the liquid enters 

 through a passage tangent to the outer edge 

 of the eddy-chamber. The screw-thread noz- 

 zles are usually straight nozzles, that is, the 

 lines of entrance and exit are in the same 

 direction, and are best adapted to use in the 

 orchard. The tangent-entry nozzles are usu- 

 ally at right angles to the hose or spray-rod. 

 Some of them are well adapted to field- 

 spraying. 



At low pressures the quantity of liquid dis- 

 charged by a nozzle increases rapidly with 

 increases of pressure, but at higher pressures 

 the increase in discharge grows less as the 

 pressure increases (see Fig. 2291). As the 

 pressure increases, the size of the spray 

 particles decreases. 



The front face of all eddy-chambers is made 

 by a thin disc in the center of which there is 

 a round hole, called the discharge-disc open- 

 ing. The smaller this opening, the finer are 



the particles of spray and also the smaller the volume 

 discharged in any given tune. A change from a small 

 to a large opening may double or triple the discharge. 

 The wear of a week of spraying may so enlarge the 

 disc-opening as to increase the discharge from 50 to 

 100 per cent. 



With hand-pumps it is usually desirable to use the 

 lowest pressure which will give a good spray; therefore, 

 with such pumps, the nozzle-discs should frequently be 

 renewed and only those with small openings used. The 

 discs cost but a few cents. Even with the same size 

 of disc-opening, different makes of nozzles give a satis- 

 factory mist -spray at various minimum pressures, 

 ranging from as low as thirty to as high as one hundred 

 pounds; therefore a knowledge of the minimum pres- 

 sure at which a nozzle may be used is desirable when 

 one is using a hand-pump where the pressure may, at 

 times, run low. 



Sufficient emphasis has not been laid upon the impor- 

 tance of securing the nozzle best adapted to each pur- 

 pose. From what has been said above, it is readily 

 seen that no small part of the success of the spraying, 

 especially when hand-pumps are used, depends upon 



