DE1938561A1 - Pneumatically driven cylinder with a small diameter piston - Google Patents

Description

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46 741

WARHEN CHIIDS BÜRGESS, JR.,

31922 Lake Road, Avon Lake. Ohio 44012 (USA)

Pneumatically driven cylinder with a small diameter piston

The invention relates to a pneumatically driven cylinder with a small diameter Pistons. Such cylinders are for pneumatically driven, vibration-generating devices with in the cylinder Free reciprocating piston used.

It has been found that pneumatically powered vibration generating devices containing a free reciprocating piston encounter a problem known as "pumping" when the ratio of the outer circumference of the piston to the face thereof is 4 or greater. The "pumping", ie an increase and decrease in the movement, becomes noticeable through a change in the oscillation frequency of the entire device, meaning that externally controllable parameters such as the air pressure or the amount of bodies to be vibrated would be changed. This "pumping" is very often sufficient to throw a device which is set in vibration by such a vibration device out of the syringe at the big frequency.

Why this l & @ quenzänderuiEg stattfisxdetj is very precise known «Si® can on a® change äea ¥ a

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haltes are returned in the gas, which in the cylinder containing the freely movable piston as Drive means is initiated. However, it can also be caused by the deposition of an oil film in the play between the surface the cylinder wall and the surface of the reciprocating piston are caused, this film increases the resistance exerted on the piston in opposition to the desired movement.

The problem outlined is particularly pronounced with pistons small diameter, where the ratio between the circumference to the cross-sectional area of the piston 4 or larger. The ratio of the perimeter to the area of a piston is 4. Beninern pistons with a diameter of 25.4 mm from 19 mm this ratio is already 5.33. For a piston with a diameter of 12.7 mm, the ratio is increased to 8. The smaller the piston diameter, the greater this ratio.

A particular problem with the changes in the vibration frequency referred to as "pumps" is that the devices to be driven, for example a vibratory conveyor container, act as a multiplier or amplifier of the irregularities caused by the changes in the frequency. This is particularly important when dealing with extremely small rushes. Vibration conveying devices, with which one can convey the smallest ropes and deliver them to certain points, use vibration generators with pistons with a small diameter that move freely in a cylinder. For example, pistons with a diameter of less than 19 mm are used. In such cases, the "pumping ⁿ " can cause a change in the vibration amplitude of the driven device, which is up to 3 to 10 times greater than

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the tolerances allowed for the equipment of the device 1st. This change may result in one or more parts of a device bypassing that device would normally have to be rejected so that they are not properly aligned or rejected for other reasons Parts are transported further. If such parts continue to run in a continuous operation, call they often show difficulties at the following points in the work direction. Such puncture errors must as far as possibly reduced or completely excluded.

As an example of a pneumatically driven, vibration-generating device with a freely reciprocating piston, in which, according to the present invention, the "pumping ^{11 is to be} controlled or completely switched off, the applicant's US Pat. No. 2,861,548 may be mentioned. Furthermore referred to the US Patent 3,023,738, in order to show a vibration wit generating device with freely movable to and from pistons in very effective manner may be used.

According to the invention it has been found that the so-called "Pumping" with pneumatically driven, free in one Cylinder reciprocating small diameter piston can be reduced or canceled entirely by one the piston surface which is at a minimal distance from the cylinder wall is reduced.

When producing pneumatically driven cylinders, there is play between the piston, which can move freely back and forth and the cylinder wall is usually the same as with plain bearings, for example between 0.001 to 0.003 mm per Mlllimeter diameter. For pistons with a small diameter, d. H. for those with a diameter of less than 2.5 cm, the tolerances are on the order of 0.05

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to 0.01? mm. It is therefore easy to see that if water or oil gets into the space between the inner wall of the cylinder and the outer wall of the piston with a clearance of this order of magnitude, a viscous pull is exerted on the moving piston, which leads to a change in frequency that lasts as long as until the described state is ended. If you want to achieve an optimal degree of efficiency of the door direction, the existing clearance between the piston and cylinder wall or the existing distance decreases as the diameter of the piston decreases. It must therefore be expected that the tension or other inhibition exerted on the piston due to viscous velocity profiles will increase much more rapidly or more strongly with temporary changes in the vapor or liquid content in the form of drops in the pressurized actuating gas, for example compressed air . The so-called "pumping * ^1" can be brought under control or completely eliminated by reducing the surface of the piston having a minimal distance from the inner wall of the cylinder.

In the drawing, an exemplary embodiment of the invention is a pneumatically driven cylinder with a free back and forth movable piston for generating vibrations or oscillations shown, namely shows

Fig. 1 shows a longitudinal section through the cylinder with piston arranged in it and

Pig. 2 shows a side view of an embodiment of a piston designed according to the invention in relation to Zig. 1 enlarged scale.

In flg. 1 a typical pneumatically driven cylinder with a freely movable to and fro is cut in one length Piston shown as a vibration generating device

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client and through a pressurized grass, for example Compressed air is driven · This gate direction possesses a housing 10 having an inlet 12 for pressurized gas and outlet ports 14 and 16. Inlet 12 is in FIG Arranged in the middle of the enclosed cylindrical free space located in the housing 10 and opens into one of the Housing wall circumferential groove 18. The ends of the cylindrical housing 10 are closed with plugs 20 and 22, which are preferably driven in with a press fit so that a cylinder is formed that is tightly closed at both ends.

In the housing 10 there is a piston 24 which can be moved freely to and fro arranged, its length to the distance between the outlet openings 14 and 16 is matched so that the piston closes both outlet openings when it is in his center dead center is located. Lines 26 and 28, which close to each other, extend through the piston 24 in the axial direction open the end faces 30 and 32 of the piston. The conduit 26 is at its inner end with a radially but outer surface of the piston 24 extending bore 34, while the inner end of the conduit 28 in a similar manner via a radial bore 36 with the lateral surface of the piston 34 is in connection. Each of the lines 26 and 28 is longer than half the piston length, so that the radial Bores 34 and 36 are arranged offset from one another. The radial bores 34 and 36 serve to alternately with the circumferential groove 18 when the piston is pushed back and forth 24 in the cylindrical housing 10 to connect and through this hat to take in drive agas. The operation of the piston located in the cylindrical housing 10 For the rest, 24 is in detail in the United States' patent 2 861 548 described »

The one in Pig. 2 has piston 24 'shown in side view geometrically speaking the 3? form of a hollow cylinder

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and has annular webs 38 and 40 at its ends, while a wider web 42 is located in its central area. The webs 38, 40 and 42 have an outer diameter which is equal to the "great" outer diameter of the Piston 24 is and is, for example, 12.46 + 0.01 mm. There are recesses between each of the outer webs 38 and 40 and the central web 42 located between these two in Porm of grooves 44 and * 46 provided. The piston 24 has an outside diameter in the area of these grooves of 12.34 + 0.05 mm.

Projections 48 and 50 are preferably provided on the ends of the piston 24 in order to effectively prevent damage to the piston to be avoided if the same e.g. against the End plug 20 and 22 should hit. The width of the the ends of the piston provided webs is, for example, 1.3 mm. The width of hats 44 and 46 is in measured in the axial direction, for example 5 mm, while the middle web 42 has a width of 11.4 mm, for example having. The center line of each of the radial bores 34 and 36 is 15.5 at the distal end of the piston 24 removed while the diameter of the radial bores and the axially extending lines 26 and 28 are preferably 2.4 mm. The piston 24 has, for example, a Total length of 26.2 mm.

The dimensions described above relate to a half inch piston " ^{carrying practically no" pumps 11.} If the half inch piston operates under the same conditions, however

has a smooth surface as in U.S. Patent 2,861,54By

is operated with compressed air containing moisture or oil, so-called "pumping" ¹¹ occurs from time to time.

By the simple precaution, the piston surface which has a minimal distance from the cylinder wall

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Grinding in the grooves 44 and 46 near the two ends of the piston will reduce "pumping" to a minimum reduced or even eliminated entirely.

Rather than having just one recess near each end of the piston as shown in Figure 2, one can have a minimal one Also reduce the distance from the cylinder wall expanding piston surface by providing a plurality of recesses or grooves so that the piston has a has a greater number of webs than shown in FIG. On the other hand, it is also possible to use helical grooves work into the piston surface, for example in the form of threads, since such grooves have the same effect to have. Thus, any suitable gate precaution can be taken to keep a minimum distance from the cylinder To reduce the piston surface lying on the inside wall of the housing in order to avoid the so-called "pumping" of pneumatically driven, to avoid vibration generators having a freely movable piston.

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Claims (6)

Patent application 1. Pneumatically driven cylinder with closed at both ends Cylinder housing and one in the same freely movable to and fro, practically at right angles cylindrical piston for generating vibrations, characterized in that, that the piston (24) on its outer circumference or jacket axially spaced apart recesses or depressions (4.4, 46) has a minimal distance from the • Keep the piston surface area of the cylinder wall as small as possible. 2. Apparatus according to claim 1, characterized in that the piston (24) has a wide web in the central region (42) full diameter and near both ends each a further web (38, 40) with full diameter has and that between each of the webs and the central web a portion (44, 46) with a smaller Diameter than the full diameter of the piston. . 3. Apparatus according to claim 2, characterized in that the sections lying between the webs (38, 40, 42) are circumferential grooves (44, 46). 4. Apparatus according to claim 1 or 3, characterized in that that the width, measured in the axial direction, of each of the webs (38, 40) provided at the end of the piston (24) between 1/2 to 1/10 as large as the width of the circumferential grooves (44, 46) measured in the axial direction. 5. Device according to one or more of claims 1 to 4, characterized in that the ratio between the circumference and the cross section of the piston (24), measured larger than 4 due to its full diameter. 009852/1362 - 2 - 6. Apparatus according to claim 5 »characterized in that the ratio between the circumference and cross-sectional area of the basket (24) is greater than 8. 009352 / 13S2 Blank it e