CA1072990A - Vacuum clamping fixture - Google Patents

Abstract

ABSTRACT
A clamping fixture in a vacuum system comprises a block (185) which has a flat bottom round which is provided a seal (188), a push button (196 ) controlling an on-off valve and a hose (193) which connects through the valve to the space beneath the block. Application of a vacuum to the hose (193) and through the on-off valve clamps the block (185) securely to a flat surface (197).

Description

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This i-nvention rela~es generally to clamping flxtures in a vaeuu~ systemO
The present invention is in a vacuum system including a vacuum pUmp9 a clamping ~ixture comprising a block having at least one sur~ac~ for gripping a component and a bottom surface, a eonnection to a supply of vacuum extending through said block, said connection including a portion extending to the bottom surface of said block, a seal extending about ! 10 the edges o~ said bottom surface, and an on-off valve i disposed in said connection for providing at will a j vacuum at said bottom surface.
Embo~iments o~ the present invention will now be described, by way of example, with reference to the accompanying drawings~ in which:-! Flg. 1 is a cross-sectional view of a ¦ preferred embodiment o~ a vacuum pump ~or use with the present invention;
Fig. 2 is a cross-sectional view of another vacuum pump for use with the present invention;
. Fig. 3 i~s a view in perspective of a pair of clamping blocks or fixtures according to the present inventlon for securely gripping a component . and which may be secured to a bench top by the action . of a vacuum;
Fig. 4 is a cross-sectional view taken on . llne 4-4 of Fig. ~ to illustrate particularly the seal provided ~or each of the clamping fixtures;
Fig~ 5 is a view in perspective of two 3 clamping blocks similar to those of Fig. 3 for gripping .~
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~072990 a component such as a circui-t board and which are secured to a bench top by a vacuum connection provided in the bènch top; and Fig. 6 is a cross-sectional view taken on line 6-6 of Fig. 5 to illustrate the clamping block, its seal and the vacuum connection to the bench top.
Referring now to the drawings wherein like elements are designated by the same reference numbers and particularly to Fig. 1, there is illustrated a preferred embodiment of a vacuum pump forming part o~
a vacuum system. The vacuum pump of Fig. 1 includes I a housing generally designated at 10 within which I moves a control element or plunger 11 and further including a venturi tube 12~ me housing 10 may, as illustrated, be made in three parts and may include a plunger cap 14, a plunger housing 15 and a muf~ler portion 16. The purpose of the vacuum pump of Fig. 1 is to utilize compressed air to generate a vacuum.
In addition, the compressed air having passed the ~enturi tube 12 is converted into a gas or air at a relatively low pressure so that both a vacuum and a low pressure gas are available.
The pump is so arranged that it will automatically block the supply of high pressure air when a ~acuum of predetermined pressure has been .
obtained. The pump is provided with an automatic control to apply compressed air again when the pressure in the vacuum reservoir has risen to another predetermined value. Therefore, the vacuum is maintained ` 30 between two limits by a demand action~ $he operation } :
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-~ ~OqZ990 may be described as a variable pulse width modulation system, that is a system where the time duration of the on and off operation ~aries in accordance with demand.
- Before further explaining the operation of the pump of the invention the structure of the pump of Fig. 1 will now be described in some detail.
The plunger housing 15 consists of a j generally cylindrical outer body ha~:ing, for example, ¦ 10 four outlets 17, 18, 20 and 21 connected to the interior which forms a plenum 22. The outlets 17, 18, 20 and 21 are each provided with an outer serrated nipple for connection to a suitable hose such as a ¦ hose 2~ to provide a vacuum at a desired work place.

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The hose 23 may consist of a suitable plastic material which is flexible. It need not necessarily be able to withstand atmospheric pressure and may be allowed to collapse due to the ambient air pressure~ It will, of course, be obvious that more or less than the four nipples 17, 18, 20 and 21 may be provided. The plunger housing 15 is also provided with an apertured conical inlet ~4 by means of which the high pressure air or gas may be supplied through a flexible hose 25. The hose 25 should be 1, 10 able to withstand the high pressure which may amount to 80 - 100 psi (lbs. per square inch). qhe conical end 24 may be threaded for receiving a coupler element 26 which ,~n turn is con~ected to the high pressure hose 25 and which may have a serrated nipple 27 to whicn the hose is secured.
The radially extending inlet 24 has a bore 30 which'is connected to an ax~al bore 31 in the plunger housing 15. The bore 30 is connected to the axial bore 31 through a reduc,ed portion 32 which interconnects the high pressure hose 25 to the bore 31 and whic~ can be opened and closed by the forward portion 33 of the plunger 11 which is ~ealed on either en~ by two 0-rings 34. The bore 31 connects to a conical opening 35 which has a much reduced central cylindrical opening 36 connected in turn to the ~enturi 12.
m e plung0r housing 15 may be provided at its rear end with ~uitable internal holes not shown in ~ig. 1, for receiving ~elf-tapping screws to secure the plunger cap 14 to the plunger housing 15. Finally, the plunger housing 15 is provided with recesses 38 which cooperate with oorresponding pro~ections 40 in the venturi 16 to provide a bayonet lock to lock the ~enturi or muffler housing 16 to the plunger , ,. ' . .....
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housing 15.
Tu~ing now to the description of the muffler and venturi housing 12, it will be seen *hat this housing portion consists of a forwardly open cylindrical p~rtion or manifold 42 provided with a slot or hole 4~ in its side wall, The open end of the cylinder 42 is closed by a muffler material 44 ~o dampen noise created by the intermittent operation of the pump. me slot 43 serves the purpose to receive a portion of the muffler material 44 so as to prevent its being blown out of the open cylinder 42. The manifold 42 may be connc,ted to the outside of a room t~ ventilate the fumes and the like which may be sucked up by the vacuum.
I This will keep the room clean and free of obnoxious gases.
The rear end of the muffler housing 16 is closed by :
,, a disk-like structure 45 which in turn carries the venturi Ii tube 12. The rearward end 46 of the venturi tube 12 is ,1 spaced from the front end 4~/ of the plunger housing 15 and ¦ from its ~ore ~6 to provide an opening 48 through which air j can escape from a bore 50 to the venturi tube 12, thus creating a vacuum in a manner well understood. In other words, the venturi tube 12 has a reduced portion or throat ¦ through which the compressed gas or air must flow at an ¦ ' ~ncreased speed and reduced pressure, This reduced pressure ¦ ln turn will cause air to flow through the opening 48 into ¦ the venturi tube 12 thus creating a vacuum in the bore 50.
¦ . me bore 50 in turn has an enlarged cylindr'ical l portion 51 in which is provided a check valve 52 which is I ¦. capable of sealing the bore 50 against a connector element ¦ 53 by means of the 0-ring 540 me connector element 53 snaps o~er the outwardly bulging ring 55 at the end of the ., .,': ' ' ' , "

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i~Z990 housing portion 16 and again has a serrated nipple 56 for connection to a hose 57. The hose 57 should also consist of a material capable of withstanding the air pressure.
Hence the hose 57 whould be relatively rigid to resist collapse due to the air pressure and to provide a fast response time. It serves the purpose to interconnect the plenum 22 with the bore 50 so as to create a vacuum in the plenum 22. It will be understood that the projections 40 at the rearward end of the muffler housing 16 which create 1~ -a bayonet lock, extend on both sides through a predetermined an~le so that the two parts can be connec~ed and locked by rotating one against the other.
After ~he high pressure air has passed the venturi tube 12 it has a relatively low pressure such as say 2 - 6 ps~. mis air may be obtained through an aperture 60 in Il the cylinder 42 which connects to a connector 61 which may ,~j be identical to the connector 53 and which is snapped over ¦ an outwardly bulging portion 62 of the housing 42, The connector 61 is provided with a hole 63 having an eccentric portion 64 which can be connected to the bore 60 by rotating ~ .
lt. m is will permit to control the size o~ the opening , between the ~nterior of the cylinder 42 and a flexible hose 6S ~rom which the low pressure air can be obtainedO This can bé stored in a reservoir 66 shown schematically. This !~ regulated output air can be utilized for many purposes.

I Hav~ng now described the three housing portions 14, 15, ~nd 16, the control piston or p,unger and its function Will now be described. As explained before, the plunger 11 has a forward or control portion 33 for either opening or , closing the opening 32 which connects to the compressed air . ' . ~.

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~oq~sso supply. The plunger 11 is provided with a cylindrical central sha~-t 63 which is i.ntegral with the control portion 33. The rearward portion 70 is provided with a small metal pin 71 which coop~rates ~ith a trip cam 72. Finally the plunger 11 has a disk-like portion 73 which slides within the cylindrical opening 74 of the plunger housing 15 and is sealed by an 0-ring 75. A main sprin~ 76 bears against one surface of the disk 73 and against the front wall 77 of the plunger housing 15. :
~i 10 The trip cam 72 is of fork-like construction and has ~, a generally U-shaped opening 78 in both of its end portions j in which the plunger shaft 71 can move. It is provided on ; its ~orward si~e with a semicircular detent &0 which helps . the snap action provided by the trip cam 72 and its spring i load 81. m e spring 81 is loaded in compression and disposed between the cylindrical wall 74 of the plunger cap ~4 and the ~¦ top portion of trip cam 72. The spring 81 is presse~l against ;1 a shoulder 82 in the plunger cap by a pro~ection or ~etaining leg 83 forming part of the plunger cap ~4 and which is secured to a semicircular disk 840 The disk 84 additionally , : ,~ has two rearwardly projecting retaining legs 85 spaced from :l . retaining leg 83 and through which extend outwardly pro~ecting pins 86 about which the trip cam 72 is capable of -~lpi~oting. -~he pins 86 preferably form-part of the trip cam 72 and are molded integral therewith.
~ ~ A foam-like filter 88 of annular shape may be provided .. in the ple~um 22 for retaining particles such as solder which ~ may have been sucked in by one of the hoses such as 23.
;~ By way of example, the muffler housing 16 may consist . 30 of a clear plastic such as a polycarbonat.e which is sold in -.,'`1 ~ . . - .

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the ~rade under tlle name Le~an. The connector 53 may consist of polyethylene. The plunger housing 15 need not be transparent and may consist of a self-lubricating plastic such as Delrin which is an acetal. The plun~er cap 14 may again consist of Lexan. The trip cc~m 72 may also consist of Delrin.
; If desirèd, a vacuum tank 90 may be connected to one of the vacuum hoses 23 as shown schematically and this in turn may be connected to various work areas, for example by ! 10 a hose 89.
Hexa~cnal bore holes 91 may be provided in the housings 15 and 16 for securing the pump to a fixed supportO
e op~ration of the pump of Fig. 1 will now be described. Initially the plunger 73 is in the position shown in Fig. 1. In other words, the pressure of spring 76 pushes the plunger disk 73 rearwardly thus keeping the opening 32 free. Accordingly, air pressure applied through ¦ hose 25 flows through bore 30, opening 32, conical portion t 35~ reduced open:ing 36 into venturi 12. This will cause a ; 20 reduced pressure at the point 48 thus opening check valve 52. The air is now capable of flowing from plenum 22 through hose 57 into the bore 50 and out of the venturi tube 12. The air at reduced pressure is aYailable from hose 65 and may be ~¦ ~8t~red in the low gas pressure-reservoir 66 which may also be provided with a suitable check valve such as shown at 52.
As the vacuum in t~e plenum 22 reaches a predetermined .low pressure9 the differential air pressure will be able to push the dîsk 73 of the plunger 11 fon~ardly, that is toward ¦! the right of Fig. 1 and the control portion 33 will block 30 opening 32 thus shutting off the air supply.
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Thi s motion of tlle plunger 11 is accelerated by the snap action created by spring 81 and trip cam 72. In other words, the initial motion of the plunger 68 will eventually cause the spring to reach near dead center so that subsequent forward motion, toward the right of Fig. 1 is accelerated by the toggle action of the spring and cam.
The orce of control spring 76 and the size of the disk 73 are so dimensioned that the plunger moves toward the right when a predetermined low air pressure has been reached in the plenum 22.
As the vacuum is used up by operation of the tools connected thereto or simply by leakage, the pressure in the 1~ plenum 22 increases again. ~7hen it has reached a ¦ predetermined upper value again determined by the force of spring 76 and the size of the disk ?3, the re~erse action takes place, that is the plunger 11 moves rearwardly, that ls toward the left of Fig. ~ because the air pressure ¦ differential has been reduced. Again the motion is accelerated by the snap action or toggle action of spring 81 and trip cam 72. The off action, that is the movement of the plunger 68 into the position of Fig. 1, is helped by the -!l provision of the semicircular recess 80 in the two legs of ,, the cam 72. This is so because the recess 80 tends-to retain the pin 71 on the plunger 11.
It will now be seen that the p~p of Fig~ 1 operates on demand and hence the compressed air is only used when it ; is needed. This helps to conserve the supply of compressed air and makes it possible for a person to carry a self-contained system including a compressed air supply and a pump.
m e pump will last for years. The system provides not only -.,' .
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~7Z~90 a vacuum but also a low gas pressure supply which may be used for o~her purposes. Since th~ system operates on demand the on and off times are variable; therefore the system becomes essentially a variable pulse width modulation control.
The snap action caused by spring 81 and trip cam 72 serves the purpose to prevent that the plunger 68 with its ~ontrol portion 33 keeps the opening 32 partially open and partially closed. mis would mean that the compressed air is wasted and that no positive control is obtained. There-fore, in order to ob'tain the on-off action of the vacuum pump of the invention the snap action is essential.
Having now described the construction and operation ¦ of the preferred vacuum pump of the invention, re~erence is now ~ade to Fig. 2 which shows a modified vacuum pump. This ¦ Yacuum pump has a different arrangement for providing the required snap action of the demand control plunger. The pump o~ Fig. 2 again may have a three-part housing including ! plunger housing cap 100, a plunger housing 101 and a muffler and venturi housing 102. mus the plunger cap 100 has a cylindrical portion 103 and may be open to atmosphere at a , reduced rearward portion 104. The plunger cap has a cylindrical radial extension 105 for housing a spring 106 w~ich urges a conical tip 10~ against the plunger 110. Its operation will be subsequently described.
The plunger housing 101 has an outer cylindrical portion 111 for receiving the plunger i10. It has a disk-like forward portion 112 against which bears a main spring 114. It also has a central cylindrical portion 115 for the plunger 110 and which has a reduced opening 116 for connection .' .

to a venturi. A bore 116 connects to the venturi.
The muffler portion 102 has a forward end 118 with external openings 120 and which serves as a muffler. It may be provided with sound deadening material not shown. Its main body 121 forms a ~enturi 119 in the manner previously explained and connects to the bore 116 o~ the pl~ger housing. It has a first outlet 122 from which the vacuum is available. A check valve 123 may be provided in a connector 124 similar to those previously described. me connector in turn connects to a hose 125 which interconnects the outlet 122 with the outletl117 forming a serra~ed nipple so as to create a vacuum in the plenum 126 formed in the cylindrical portion 111. ~ ~ilter 129 may be provided in the plenum 126. The compressed air is applied to the inlet 127.
e air at reduced pressure is available from an air outlet 128 which may be closed by a check valve 130.
;.j ;, The plunger 110 may be somewhat similar to tnat of F~g. 1 and again has a forward portion 131 sealed by two .' O-rings 132 for opening or closing the air inlet opening 133.
me forward portion 131 o~ the plunger 110 is made integral ~with a circular disk 134 sealed by an 0-ring 135 against the ~I
cylindrical portion 1~1 of the plunger housing. Its rear~Jard portion 136 has a disk-like termination 137 w~ich cooperates with the spring biased detent 107.
me pump of Fig. 2 differs primarily from that of ~ig. 1 by its different snap action provided by the detent 107 and the spring 106. Its operation may be described as ~ollows. Due to the force of sprlng 114 acting against the plunger disk 134 the plunger is initially in its rea~ard position, that is in the left~hand position as ~iewed in ,' . , ' ' .

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Fig. 2. ~hen compressed air having a pressure of say 80 ~ 100 ? pSi iS applied to the inlet 127 a vacuum is cre~ted at the outlet bore 122 in the manner previously described. This reduced pressure is applied by the hose 125 to the plen~m 126. At the same time air at reduced pressure is available from the outlet 128 as long as the check valve 130 is open.
Eventually the pressure in the plenum 126 decreases to a predetermined value. mis will now permit the disk 134 to move toward the right against the pressure of the main spring 114. The snap action is obtained by the enlarged I disk-like portion 137 of the plunger being forced past the detent 107. This will now permit the control portion 131 to Z seal off the bore 133 thus cutting of~ the air supply. At that time the check valve 130 closes so as to preserve the low pressure air which may be maintained in the reservoir similar to the one shown in 66 in Fig. 1. At the same time the check valve 123 closes. me regulated ~acuum output ~ line 140 may also be connected to a vacuum tank such as shown ! at 90 in Fig. 1. As the vacuum is used up the pressure in the plenum 126 will slowly rise until it reaches a predetermined value. This is again determined by the force of main spring 114, the size of the plunger disk 134 and the -force-of-the -spring biased detent 107. Eventually, however, ! the plunger 110 will be able to snap rearwardly, that is to the left of Fig. 2 thus opening the bore 133 and the previously described action repeats again.
~ It should be noted that the embodiment of Fig. 1 has i~ certain advantages over that of Fig. 2~ I~ other words, the i plunger 110 of the embodiment of Fig. 2 must overcome the relatively strong force of the spring biased detent 107 to .

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lV7'~990 move left or ~ight. 'mis additional ~orce is wasted, that is it requires an additional supply of compressed air. Otherwise, however 9 the operation of the vacuum pump of Fig. 2 is basically identical with that of Fig. 1. It is again controlled by demand and provides variable on and off periods analogous to a variable pulse width modulation system.
The parts of the pump of Fig. 2 may consist of the same materials as corresponding parts of the pump of Fig. 1.
Shown in Figs. 3 and 4, are two clamping fixtures or clamping blocks 185 and 186 which operate in the manner of a vise. The blocks 185 and 186 may, for example, consist o~ a plastic transparent material having a ~lat bottom 187 provided around its edges with a resilient seal 188 such as a resilient gasket material permanently fixed to the bottom surface 187.
I me clamping fixtures may ha~e a substantially ¦ triangular side view as shown in Fig. ~. The long vertical sides 190 may be provided with a substantially I triangular depression 191 for securely gripping or grasping a component illustrated by way of example at 192.
Each of the blocks 185 and 186 is provided with a hose 193 which connects to a vacuum pump. The hose 193 in turn is connected by a cylinder 194 extending through the block to a hose or tube 195 which extends through the bottom surface 187. An on-off valve ~ot shown and disposed in the cylinder 194 is controlled by the push button 196 for connecting the tube 195 to ~72g90 the vacuum or disco~necting it therefrom.
In order to secure one of the blocks such as 185 to a bench top 197 the push button 196 is pushed to connect the tube 195 to the source of vacuum.
The vacuum will then evacuate the air space between the bottom 187 of the block and the bench top 197 to press the block 185 against the bench top 197 due to the atmospheric pressure.
Th~ advantage of the clamping fixtures 185 and 186 are several. The clamping blocks may be put anywhere at convenience on the bench top. Further-more, they can be conveniently moved closer together or further apart to accommodate components of different sizes.
It will be realized that the clamping fixtures of Figs. 3 and 4 take the place of a ; conventional vise. However, a vise must be secured I to the bench top and cannot readily be moved about.
¦ Also it takes some time to open and close the vise jaws to receive components of different sizes. Therefore, it will be realizedlthat the use of the blocks 185 and , 186 will considerably speed up the work and make it more convenient. It will also be realized that components or parts may be clamped between the lateral surface 198 of the blocks rather than against the ~ertical end surface 190.
Referring now to Figs. 5 and 6, there are ¦ again shown the same two clamping blocks 185 and 186 previously discussed. However, the clamping blocks 185 1 30 and 1~6 may now be used in a different manner. Here :

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vacuum hoses 200 and 201 extend through an openillg or bore 202 in the bench top 197. Ther2fQre by d.isposing one of the blocks such as 185 over the opening 20~ a vacuum will be created under the bo~tom surface 187 so as to press the block 185 against the bench top and against the seal 188. me o~her block 185 may be similarly position~d over -the opening of the hose 201.
In this case a component such as a circuit board 204 . may be pressed against the lateral surfaces 1~8 of the two blocks 185 and 186.
This system has a certain disadvantage in that the position of the two blocks 185 and 186 is determined to some extent by the position of the holes or openings such as 202 in the bench top. It i~ still j possible to move the blocks somewhat as long as the opening 202 is below the bottom surface 187 of each blook.

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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. In a vacuum system including a vacuum pump, a clamping fixture comprising a block having at least one surface for gripping a component and a bottom surface, a connection to a supply of vacuum extending through said block, said connection including a portion extending to the bottom surface of said block, a seal extending about the edges of said bottom surface, and an on-off valve disposed in said connection for providing at will a vacuum at said bottom surface.

2. A clamping block as claimed in claim 1, wherein a push button is provided for said valve and extending from said block for operating said on-off valve.

3. In a vacuum system including a vacuum pump, two clamping fixtures for clamping a component therebetween, said clamping fixtures being adapted to co-operate with a bench top, each of said clamping board fixtures comprising a bottom surface, a sealing material attached to said bottom surface about the circumference thereof, a bench top having at least two openings therein, and means for connecting each of said openings with a supply of vacuum, whereby each of said blocks may be positioned with its bottom surface over one of said openings to create a vacuum therein and to secure each of said blocks to said bench top.