US2665702A

US2665702A - Pulsator

Info

Publication number: US2665702A
Application number: US111935A
Authority: US
Inventors: Rawson Emanuel
Original assignee: Package Machinery Co
Current assignee: Package Machinery Co
Priority date: 1949-08-23
Filing date: 1949-08-23
Publication date: 1954-01-12
Anticipated expiration: 1971-01-12

Description

Jan. 12, 1954 E. RAwsoN 2,665,702

PULSATOR Filed Aug. 23, 1949 3 Sheets-Sheeil Jan. 12, 1954 E. RAwsoN 2,665,702

PULsAToR Filed Aug. 23. 1949 3 Sheejts-Sheet 2 45 INVENTOR. H ql Emanuel Rawson E. RAwsoN Jan. l2, 1954 PULSATOR Filed Aug. 25. 1949 3 Sheets-Sheet 5 FUE 10 INVENToR. Emanuel Rawson sation lines.

Patented Jan. 12, 1954 PULSATOR Emanuel Rawson, Chicago, Ill., assignor, by mesne assignments, to Package Machinery Company, a corporation of Massachusetts Application August Z3, 1949, Serial No. 111,935

18 Claims.

l This application is a continuation in part of my lcopending application, Serial No. 593,564, Vtiled May 14, 1945, now abandoned. l Thev present invention relates to vacuum type lmilking machine pulsators.

Pulsators of the type with which the present invention is primarily concerned consist of a block on which is mounted a reciprocating pulsation valve that applies vacuum and atmospheric pressure alternately to one or more pul- A timing or control valve on the valve block controls the frequency of the pulsations. Separate piston and cylinder combinations are controlled by and in turn operate the respective valves. The pulsator block of a pulsator of the above type has a number of air passageways therethrough forming parts of the vacuum and air circuits for the respective valves and cylinders.

It is-one of the objects of the present invention to provide a pulsator block that is simple and economical of manufacture and is well adapted for mass production. In accordance with the principles of the present invention the pulsator block is so constructed that the starting material for making the block consists of a flat metal disc of the required thickness. Such .discs may be economically formed by slicing the same from standard bar stock.

It is a further object of the present invention to provide a simple means for establishing vac* uum connections to a pulsator.

- It is a still further object of the present invention to provide a pulsator with a simple means for establishing vacuum connections to 1 the container on which the pulsator is mounted.

Another object of the present invention is the arrangement of the air passageways in the pulvsator block'in such a manner as to facilitate cleaning thereof.

It is another object of the' present invention to provide a pulsator of the above mentioned character with an improved means for regulating the frequency of the pulsations. This, in

resistance to the air ilow. The arrangement is such that the length of the air path may be increased or decreased at will, thereby altering the resistance to the air flow. thus altering the rate which the air can move into or from the cylinder wherein the control piston operates. This controls the rate oi.' operation of the control piston. In order to provide an exceedingly ne air passageway of variable length the arrangement is such that the air must pass through the limited helical space between the threads of a nely threaded screw and the tapped bore in which the screw is threaded. By advancing or retracting the screw in its bore the length of the passageway can be increased or decreased at will and thereby increase or decrease the total resistance to air flow.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawings form ing a part thereof.

In the drawings:

Figure 1 is a plan view of a pulsator of the present invention;

Figure 2 is a top view of the pulsator of the present invention with the cover thereof removed and with one of the cylinders shown in partial section;

Figure 3 is a section taken along the line 3-3 of Figure 2, with the pulsation valve shown in elevation;

Figure 4 is a view of the left side of Figure 2 with parts of the cover broken away and the timing valve shown in longitudinal section;

Figure 5 is a plan view of the pulsator block;

Figure 5a is a fractional end view of the pulsator block taken along the line 5a-5a of Figure 5;

Figure 6 is a horizontal sectional view taken along the line 6--6 of Figure 5a and looking in the direction of the arrows;

Figure 7 is a bottom view of the pulsation valve;

Figure 8 is a transverse sectional View of the pulsation valve taken along the line 8-8 of Figure 2 and looking in the direction of the arrows;

Figure 9 is a sectional View taken along the line 9 9 of Figure 8 and looking in the direction of the arrows;

Figure 10 is a fragmentary sectional view taken along the line I 0|0 of Figure '7;

Figure 11 is a bottom view of the control valve;

Figure 12 is a sectional view taken along the line I2-I2 of Figure 11; and

Figure 13 is a sectional View taken along the line I3-I3 of Figure 1.

Reference may now be had more particularly to the drawings'wherein like reference numerals designate like parts throughout.

The pulsator of the present invention comprises a pulsator block or body which is a brass disc that may have been sliced from round -bar stock. At its lower side it has a central circular bore forming a hollow chamber 3. The block has a circular top surface 5 that is ground and lapped to be perfectly dat. A vacuum line connector is adapted to Abe connected to the bottom of the block to establish vacuum connections to the chamber 3. The body i has on one side thereof four horizontally extending holes Ilia, |31), ic and ld, in each of which is a nipple each forl re- 1- ceiving a ilexible hose which extends to a teat cup in a manner known in the art. VThe holes I Qa, lb and are interconnectedV by a yboreV i2, the end of which is closed by a plug |211, and the holes liloA and ltd are interconnected 'by a bore i3. As a result all four holes illu., liib, lil'c and |Eld are interconnected. The hole ib is intersected by port holes l-i that are drilled vertically in the body from the top surface thereof. v-Adjacent the ports I there are formed a pair of communicating holes or ports |B which extend downwardly from the surface 5 to and intersect an inclined bore |8.that connects the ports le with the chamber 3.

A series of parallel air passages 2| 22, 23 and 25| are drilled from one side of the body in the cylindrical portion thereof. The outer end of each ofthe four passages is permanently closed by a plug 25, each plug consisting of a short length of wire that makes a snug nt inthe passageway and is soldered or otherwise permanently sealed therein with the vouter face of the wire terminating flush with the cylindrical surface of the block Two ports 2l and 2S are drilled from the top surface 5 to intersect the passage 2|. '

ports

29 and 3% are drilled from the surface 5 to intersect the passageway 22. Two other ports 3| 'and 32 extend from the surface 5 to and intersect 28, the passageway 22 connects the ports 2li-3e,

the passageway 23 connects the ports 3 |-32, and the passageway 2d connects the ports 35i-3d A vacuum port or passageway S6 extends from the surface 5 vto the chamber 3, as may be seen from Figures 3 and 5. n addition to the above the pulsator bodyhas a vacuum control port 37 that extends'downwardly from the surface 5 to and intersects a bore or passageway 33. The passageway 33 isclosed at oneend by a plug 39. A bore or passageway 4B connects the passageway 38 with a bore di which is internally threaded as at 42. A bore 43 connects the bore 4| with the vacuum chamber 3, as may be seen from Figures 5 and 6. The bore d@ is at such an angle that a drill following along the center line lid of the bore di! can be used, which drill enters through the bore 4|. As a result the passageway 4) may readily be cleaned as by passing a wire therethrough through the open end or the bore lil. The bore 4| is closed by a manually adjustable speed regulating screw 45 that has a knurled adjusting head 4S and may be locked in position by a lock nut el. A plurality of concentric grooves d8 are formed in the body i surrounding the bore el. A washer 49 of leather or the like, is compressed into the grooves d8 by the lock nut il and acts to tension the lock nut and thereby facilitates retaining of the regulating screw 45 in the `position .in which it is adjusted Four mountingposts 55 are mounted on thetop of the pulsator body, `as by threading the posts Two other into tapped openings 56 in the top of the pulsator body. These posts are adapted to receive and hold pistons that extend into cylinders, to be presently more fully described.

A pulsation Valve 6D and a timing or control valve 6| are positioned on the flat surface 5. Each of the valves has a at bottom surface adapted to slide along the surface. The pulsation valve 60 has, on the under side thereof', a rectangular recess 63 which is adapted to overlie the vacuum passageways It and connect them alternately with y the ports l5, depending upon the position of the pulsation valve. The pulsation valve 60 also has a pair of similar slots Gli- 65 on opposite sides of the recess 63 each of which slots is open at the base of the pulsation valve and at the side thereof. In addition the under surface of the pulsation valve ci) has an elongated recess 66 extending across the transverse center line of the valve, and a pair of separate shorter recesses Eil-68.

'Above the recesses 'and slots 63 through 68 the pulsation valve has two similar cylinder bores 'IIJ and ll formed therein separated by a Wall 12 which maintains the cylinder bores separate from one another. A port 'i3 is drilled from the underV side of the pulsation valve at the recess 61 and connects the recess with the interior of the cylinder 'il adjacent the dividing wall 12. A similar port or passageway 'It connects the recess 68 with the interior of the cylinder 10.

The control valve Gl has a at bottom surface in which are formed, respectively, a rectangular recess 'il which opens to the atmosphere at one side of the control valve, and a U-shaped recess i8 having arms 'IS- 19, and a pair of rectangular recesses iiD-8|. i Above the 'base of the control valve the valve is provided with two cylindersv 82-83 separated by a wall 84. A port or passageway t5 extends from the recess 8 into the cylinder 82 adjacent the wall 8d, and a similar port or passageway Se extends from the recess 8| into the cylinder 33 adjacent the partition wall 84.

`Similar pistons 9E) extend into each of the bores l2, 82 and 8S. EachV piston comprises a body 9| undercut at its forward end'to receive a cupshaped gland 92, of leather or the like, which is held in place by a screw 93 and a washer 94. A circular peripheral flange 96 on the piston limits the extent of insertion of the piston into the cylinder bore. On its rearward side the piston has a circular protuberance -93 Vwhich has a hole 94 therethrough to permit sliding of the piston onto one of the posts 55. The two pistons are assembled within the cylinder bores 82-33 and then the assembly is slipped over a pair of posts 55, the posts passing through the openings 9d in the pistons. -This xes the positions of the pistons and permits sliding movement of the control valve between the two posts 55.V The pulsation valve likewise has two pistons 9e similarly assembled therein and held each on one of the other two posts 55.

An explanation will now be given of the manner of operation of the mechanism thus far described. Assume that the parts are in the positions illustrated and that vacuum is applied through the connector 'i to the chamber 3. VThe vacuum connection extends by way of the holes or passagewaysV i6, thence by way of the recess 63. At this time the passageways I5 are overlaid by the recess 6d which, being open to atmosphere, applies atmospheric pressure to the ports l5 and the four nipples At the same time vacuum isapplied fromithe chamber 3 by way ofthe bore 43 (Fig. 6), thence. through the y Space between ',fiheffthreeds; @fifths ,regulating screw 45 and the threads of the bore 4|, thence by way of the

passageways

40 and 38 to the vacuum port 31 which is thus always connected to vacuum by way of the long spiral passageway between some of the threads of the regulating screw and the threads of the bore 4|. The port 31 is overlaid by the recess 66 which at this time 'extends to the port 33. Vacuum is thus extended to the port 33 and thence through the passageway 24 to the port 34. The port 34 is overlaid by the passageway 80 which, through the port 85, communicates with the interior of the cylinder 83. Vacuum is thus applied to the interior of the cylinder 83 thereby drawing the air out of that cylinder. At the same time the port 21 is under the slot 64 of the pulsa-tion valve so that atmospheric pressure is applied through theslot B4, port 21, passageway 2| and the-port 28, which is overlaid by the recess 8| that connects with the cylinder 82 through the passageway 86 in the control valve. Atmospheric pressure is thus applied to the cylinder 82. Since there is atmospheric pressure on one side of the dividing wall 84 and vacuum on the other side thereof the control valve 6I commences to move in a I direction downwardly as seen in Figure 2, to its alternate position. The rate of its movement is determined by the rate of air flow through the restricted passageway set by the regulating screw 45.

When the control valve has traveled to its alternate position abutting the flange 86 of the piston it establishes vacuum connections for operating the pulsation valve to its alternate position. These connections are as follows: Vacuum is applied from the passageway 36 and recess 18 tov one of the arms 19 thereof which is now over the port 30. This establishes vacuum connection from the port 36 by way of the passageway 18 to the port 38, thence by way of the passageway 22 to the port 29 which is overlaid by the recess 61 of the pulsation valve. The recess 61 communicates the vacuum connection to the cylinder 1| by way of the passageway 13. At the same time the atmosphere recess 11 of the control valve 6| is over the port 32, thus connecting atmospheric pressure via that port and passageway 23 to the port 3|, which port 3| is overlaid by the recess 68 in the pulsation valve, which, through the port 14, connects atmospheric pressure to the cylinder 10 of the pulsation valve. The cylinders of the pulsation valve thus have atmospheric pressure on the lower side of the wall 12 and vacuum on the opposite side thereof, as seen in Figure 2. The pulsa-tion valve now moves in a direction upwardly, as seen in Figure 2, to its alternate position. It moves to that position rapidly because the vacuum and atmospheric connections to the cylinders of the pulsation valve entirely by-pass the .restricting screw bore 4|. In its alternate position the recess 63 of the pulsation valve connects the vacuum ports |6 with the ports I5 thus applying vacuum to the nipples H. The port 33 is now open to the atmosphere, thereby applying atmospheric pressure through the passage 24 to the port 34 which is overlaid by the slot SI! of the control valve 6i. At this time the recess 66 connects the vacuum port 31 with the port 21 thus applying vacuum through the port 21 and passageway 2| to the port 28 which is overlaid by the recess 8| of the control valve, which recess 8| is connected to the cylinder 82 by passage 86. The control valve thus immediately `connnences to return to the position'illustratedy in'Figure-2 and, when it returns to that position, it establishes connections for immediately returning the pulsation valve to the position illustrated in Figure 2. It is thus apparent that by this arrangement when the pulsation valve reaches an extreme position it establishes vacuum and atmospheric connections for moving the control or timing valve from the position in which it is to its alternate position and that the control valve moves at a speed determined by the setting of the screw 45. When the control valve reaches its alternate position it then establishes vacuum connections for moving the pulsation valve to a position other than in which it is. The pulsation valve and the control valve thus reciprocate between the posts 55-55 alternately.

The pistons for each pair of cylinders are selfaligning because each piston is free to turn about the vertical axis of its mounting post 55. If there is any wear on the rubbing surfaces constituting the bottoms of the valves and the corresponding parts of the top 5 on which the valves slide this wear does not affect the seating of the valves because the pistons are free to slide downwardly on the mounting posts and thus vpermit the valves to be self-seating on the surface 5. Each valve, with its cylinder bores formed therein and with its associated pistons constitutes a pneumatic mechanism which may easily be removed from the pulsator block I by simply lifting the same along the posts 55, and may be replaced equally easily. rihis facilitates inspection and repair of the mechanism.

The pneumatic mechanisms are enclosed within a dome-shaped cover H0 the top of which has a circular opening I I, the surrounding metal of the cover being fiared downwardly and at an angle, as indicated at H2. A porous metal filter disc H3 rests on the seat H2 and is held in place by a cap I4 that has fingers I I5 bearing against the filter disc ||3 and spacing the cap I I4 therefrom to allow atmospheric air into the, space between the cap and the lter disc. The shank of a screw I I6 is welded to the under side of the cap H4 and makes a snug sliding f1tthrough the lter H3 and at its bottom is threaded into a tapped hole H1 at the top of the pulsator body.

An explanation will now be given of the-construction of the vacuum line connector 1 by which vacuum is connected to the pulsator block I. The vacuum line connector comprises a circular cup-shaped tting |30 the top of which is machined perfectly flat. 'Ihe top of the cupshaped tting |30 fits into a circular cavity at the back of the Apulsator block I and is secured to the block I by a screw |3| that threads into the block. The top of the tting |36 hasa cavity |32 that opens into the pulsator block chamber 3.. A gasket |33 over the top surface of the tting |30 makes an air tight sealing nt between the tting and the base of the chamber 3 of the pulsator block I. A metal pipe I 34 fits into a bore in the tting ISD being press itted therein and suitably sealed in any desired manner, as

.' by solder, and establishes communication with the cavity |32 through a circular bore |33. The pipe |34 has a handle |31 thereon to facilitate carrying of the pulsator. Beyond the handle the pipe 534 terminates in a hose-receiving nipple 38 which is adapted to receive the end of a vacuum line hose to extend vacuum to the pulsator via the pipe, |34.

The pulsator of the present invention is adapted to be positioned upon a milk receptacle and to establish vacuum connections to the receptacle.

7 To that eiect the pipe |34 has'a check valve |40 thereon which check valve is of a construction such as is shown more particularly in Figure 13. A hole |42 is formed on the under side of the pipe |34 and a vacuum fitting |44 is welded arounded the hole |42. The vacuum fitting is circular in horizontal cross section. A tubular valve body |45, of rubber or the like, is tensioned around the fitting |44. To facilitate retention of the valve body on the fitting |44 the fitting is outwardly flared downwardly from the pipe |34. The valve body |45 has a central opening |46 formed in a circular ledge |41 that constitutes a valve seat for a check valve stem |48. The check valve stem seats by gravity on the ledge |41 and closes the opening |46. The stem is adapted to be raised by a preponderance of pressure below the stem as compared to' the vacuum above thev stem. The rubber valve body |45 is adapted to be snapped over a fitting |54 at the top of the receptacle on which the pulsator is to be mounted, so that the ledge |41 seats on top of the fitting and the valve body |45 makes a vacuum tight seal around the fitting. The vacuum fitting |44 and the valve body |45 and the check valve stem |48 are all circular in cross section when viewed on a section taken in a plane at right angles to the longitudinal center line |54.

The pulsator block has a pulsator spring |58 secured to the under side thereof. rIhis spring merely extends downwardly to provide a leg for supporting the pulsator on the receptacle on which it is mounted. The pulsator is adapted to be positioned on a receptacle in the manner illustrated in my application for Letters Patent entitled, Suspended Milker, Ser. No. 111,934 filed of even date herewith, to which reference may be had. The pulsator spring |58 is hookshaped at its forward end so that the cover for the milk receptacle is suspended therefrom when the pulsator is lifted from the receptacle, all as shown in my above identified application.

When the pulsator is used and in operation the valve stem 48 is drawn upwardly by vacuum within the pipe |34 to apply vacuum to the valve body and the receptacle on which the pulsator is mounted. If the vacuum connection is thereafter released from the pipe |34 as, for instance, by disconnection from the main vacuum line, the check valve |43 will close and thereby prevent atmospheric air from rushing back through the pipe |34 into the milk receptacle on which the pulsator is mounted.

It is to be noted that the pulsator of the present invention lends itself readily to cleaning. To

that effect the screw |3| is unscrewed from the pulsator block, thereby permitting removal of the fitting |34 and its vacuum line connector 1 from the pulsator. This permits cleaning of the fitting since it is easy to insert a brush through the nipple |38 to clean the pipe |34. Any foreign matter that may have accumulated therein is easily removed through the bore |36v and the cavity |32. With reference to the pulsator block the cavity 3 is easily cleaned as may be seen. By removing the clean-out plug 39 and the speed regulating screw 45 it is a simple matter to insert a cleaning brush into the bore 38 and into the bore or passageway 4|. When the screw 45 has been removed it is possible to insert a cleaning brush into the bore 40, since the center line of this bore passes through the opening in the end of the bore 4|. It is further to be noted that the'pulsator block is of a very simple construction. The top and bottom surfaces of this block are fiat, thereby facilitating manufacture thereof, as well as facilitating cleaning thereof. As previously stated, this block may be formed from a round brass rod, of the necessary diameter, by slicing a piece of the requisite thickness from the rod stock. This greatly reduces the cost of manufacture of the same as compared to prior constructions wherein the pulsator block is of a shape that precluded use of bar stock as mentioned above. It is further to be noted that the same tapped hole that receives the cap holding screw I5 also receives at its opposite end the screw |3| for securing the fitting in place. As a result a single drilling and tapping operation provides threaded bores for both screws ||6 and |3|. In order to provide the necessary length of tapped bore a round projection |3|' is left at the bottom ofthe pulsator block in the machining of the bore 3. In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise construction here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

1. A vacuum typeV milking pulsator comprising a pulsator block, a fitting on the underside of the block, means securing the fitting to the block, the fitting and the block together having a chamber between them, a pipe secured to the fitting and opening into the chamber for extending Vvacuum connections thereto, air passageways extending from the chamber to the top of the block, a pulsation valve and a timing valve resting on the block and movable across different ones of the air passageways at the top of the block, and two separately movable pneumatic mechanisms for moving the respective valves and means forming operating air passageways extending from each valve to the pneumatic mechanism that operates the other valve so that each'valve controls the pneumatic mechanism that operates the other valve,

2. A vacuum type milking pulsator comprising a disc shaped pulsator block vhaving a flat upper surface and a recess in the lower' surface, a fitting closing the bottom of said recess and forming it into a chamber, means in addition to the fitting for securing the fitting and the block together, means for extendingV evacuating connections through the fitting to the chamber, air passageways in the block extending from the chamber to the top surface of the block, pneumatic operating means including a piston structure and a cooperating cylinder structure, the two structures being movable with respect to one another, means for holding one of said structures on the block as the other structure moves, and pulsator valve means constituting 'a-rigid part of the movable structure and movable across the air passageways at the top of the block.

3. A vacuum type pulsator comprising a disc shaped pulsator block having substantially fiat top and bottom surfaces, there being a recess formed in the bottom surface and constituting a vacuum chamber, an air passageway extending from said vacuum chamber to the top surface of the block, said air passageway comprising a series of communicating bores at least one of which extends to the periphery of thev block and is tapped, and anotherone of which intersectsthe tapped'bore at a location thereon which leaves at least 'some of the threaded' length ofI the tapped bore in the path of air flow through the communicating bores, and a screw threaded in said tapped bore, the threads of the screw and the threads of the tapped bore being of such relative sizes as to leave a spiral space between them, the space between the threads of the screw and the threads of the bore being part of said air passageway.

4. A vacuum type pulsator comprising a disc shaped pulsator block having substantially flat top and bottom surfaces, there being a recess formed in the bottom surface and constituting a vacuum chamber, an air passageway extending from said vacuum chamber to the top surface Aof the block, said air passageway comprising a series of communicating bores at least one of which extends to the periphery of the block and is tapped, and another one of which intersects the tapped bore at a location thereon which leaves at least some of the threaded length of the tapped bore in the path of air flow through the communicating bores, a screw threaded in said tapped bore, the threads of the screw and the threads of the tapped bore being of such relative sizes as to leave a spiral space between them, the space between the threads of the screw and the threads of the bore being part of said air passageway, another one of the bores extending also to the periphery of the block, a

removable closure plug for the outer end of said last named bore for facilitating cleaning thereof, and a third bore interconnecting the threaded bore and said other bore, said third bore being aligned with the opening of the threaded bore at the periphery of the block.

In a vacuum type milking machine pulsator, means for controlling the flow of air comprising a pulsation valve, mechanism for operating the valve, a pneumatic timing mechanism controlling the time intervals between operation of the valve, a structure having a fluid passageway extending vacuum to the timing mechanism, means inserted in the passageway providing a longl path through saidv passageway of relatively small cross sectional area, and adjustable means for lengthening and shortening the long path.

6. A milking machine pulsator including a valve block having an upper valve surface and a vacuum space below said surface, series connected passageways extending through the block and opening at one end at said valve surface and at the opposite end at said vacuum space, a valve s'lidable on said block over the opening in the valve surface, said series of passageways including a first passageway extending to the outside of the block anda second passageway at an angle to and intersecting the first passageway, said iirst passageway being screw threaded at a portion thereof through which air moves in flowing from the opening in the valve surface to the vacuum space by way of said series connected passageways, a regulating screw extending outside of the valve block and threaded into said threaded portion the threads of the screw and the threads of the tapped bore being of such relative sizes as to leave a spiral space between them so that air iiowing from the opening in said valve surface to said vacuum space by way of the series connected passageways must iiow through the restricted space between the threads of the screw and the threads of the threaded passageway, whereby the effective length of the restricted helical space through which the air ld mustv now may be adjusted by turning of the regulating screw.

7. A vacuum operated milking pulsator of the type having alternately operating pneumatic mechanisms including an actuatin' mechanism and a timing control mechanism for the actuating mechanism and having also a control air passageway leading to the pneumatically operated timing mechanism, characterized by the fact that said passageway is screw threaded at a portion thereof through which air flows and there is provided a closure threaded in said passageway, the threads of said closure and the threads cf the threaded passageway bei ig of such relative sizes as to leave a spiral clearing space between them thereby forming a closure for the passageway except for the clearance at the engaging threads which form a helical air path whereby upon threading the closure in the pas'- sageway the length of the helical air path is altered to alter he rate of iiow of air through the passageway to the timing mechanism.

8. A machine comprising a base structure, a mechanism on the base structure including means for controlling the fiow of atmospheric air through the base structure, a cover over the mechanism and resting on the base structure, said cover having an opening at the top, an air iilter disk closing said opening, a filter cap overlying the filter disk, there being means spacing the cap from the disk to permit the entrance oi atmospheric air between the two, and a cover screw extending through the filter disk and connected at one end to the base and at its other end pressing the cap towards the disk and the disk towards the cover.

9. A machine comprising a base structure, a,

vacuum operated mechanism on the base structure including means for controlling the iiow of atmospheric air through the base structure, a cover over the mechanism and resting on the base structure, said cover having an air inlet opening, an air filter disk closing said opening, a filter cap overlying the filter disk, there being means spacing the cap from the disk to permit the entrance of atmospheric air between Ithe two, and a cover screw extending through the lter disk and connected at one to the base and at its other end pressing the cap towards the disk and the disk towards the cover, said cover screw having means on the under side of the filter disk for engaging the disk upon upward retraction of the screw from the base to force the disk olf of the cover1 opening.

, 10. A pulsator cover having an opening therein, an air filter cap assembly closing said opening, said assembly comprising an air filter disk, a filter cap overlying the disk and spaced therefrom by a plurality of spaced projections to permit the entrance of atmospheric air between the two, a cover screw for mounting the cover, said cover screw extending through the filter disk and adapted to connect at one end to a structure on which the cover is mounted and at the other end to the lter cap.

ll. A lter cap assembly comprising an air filter disk having a cover screw longitudinally slidable therethrough, a iilter cap secured to one end of the screw on one side of the disk and overlying the disk and having means for spacing it from the disk and having air inlet openings to permit the entrance of atmospheric air between the disk and the cap, and means on the portion of the screw on the other side of the disk for limiting the extent of longitudinal slidand the screw with respect to crie the other end ing of the disk another, and mounting threads on of the screws.

12. In combination, a cover having an air inlet opening therethrough, a lter disk overlying the opening, and means for mounting the cover in position and mounting the disk on the cover. said means including a screw the shank of which extends through the disk and through the cover, said screw having screw threads on the side thereof that extends from the disk through the cover and having means on the opposite side thereof for pressing the disk towards the cover.

13. In combination, a cover having an air inlet opening therethrough, a filter disk overlying the opening, and means for mounting the cover in position and mounting the disk on the cover, said means including a screw the shank of which extends through the disk and through the cover, said screw having means at one end thereof for pressing the filter disk towards the cover and having means at the opposite end thereof for mounting the screw to hold the cover in place.

14. A dome-shaped cover having an opening in the dome portion thereof, a lter disk overlying said opening on the outside of the dome, a iilter cap overlying the disk but spaced therefrom to permit the flow of air from the atmosphere into the space between the disk and the cap, and means for securing the dome-shaped cover to a support that is to be covered thereby, said means comprising a screw extending through the lter disk and pressing the cap towards the disk and the disk towards the cover.

15. A dome-shaped cover having an opening in the dome portion thereof, a lter disk overlying said opening on the outside of the dome, a iilter cap overlying the disk but spaced therefrom to permit the flow of air from the atmosphere into the space between the disk and the cap, and means for securing the dome-shaped cover to a support that is to be covered thereby, said means comprising a screw extending through the lter disk and pressing the cap towards the disk and the disk towards the cover, said screw being freely rotatable with respect to the iilter disk and being secured to the cap so that turning of the cap results in turning of the screw.

16. A dome-shaped cover having an opening in the dome portion thereof, a lter disk overlying said opening on the outside of the dome, a filter cap overlying the disk but spaced therefrom to permit the ow of air from the atmosphere into the space between the disk and the cap, and means for securing the dome-shaped cover to a support that is to be covered thereby, said means comprising a screw extending through the filter disk and pressing the cap towards the disk and the disk towards the cover, said screw being freely rotatable with respect to the filter disk and being longitudinally slidable therein, and means on the screw for limiting the longitudinal sliding thereof through the filter disk.

1'?. A vacuum type milking pulsator comprising a pulsator block, air passageways'extending through the block to the top thereof, a pulsatlon valve mechanism and a timing valve mechanism resting on the top of the block and movable across diierent ones of the air passageways at the top of the block, a cover overthe mechanisms and resting on the block, said cover limiting the movement of the mechanisms in a direction away from the top of the pulsator block, said cover having a central opening over the mechanisms, an air filter disc closing said opening, and means pressing the air lter disc towards said cover and extending through the airy filter disc between the mechanisms and screw threaded into the pulsator block for holding the cover onto the block and thereby conning the mechanisms against movement in a direction away from the block.

18. A vacuum type pulsator comprising a pulsator block, a pneumatic timing mechanism carried by the block, an air passageway extending through the block to the timing mechanism, said air passageway comprising a series of communicating bores at least one of which extends to the periphery of the block and is tapped, and another one of which intersects the tapped bore at a location thereon which leaves at least some oi the threaded length of the tapped bore in the path of air ilow through the communicating bores, and a screw threaded in said tapped bore, the threads of the screw and the threads of the tapped bore being of such relative sizes as to leave a spiral space between them, the space between the threads of the screw and the threads of the bore being part of said air passageway.

EMANUEL RAWSON.

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